Patent Application
20220209301
The present invention relates to carbonate solvents for non-aqueous electrolytes for batteries. More specifically, the present invention is concerned with carbonate solvents for non-aqueous electrolytes that are characterized by their low corrosiveness against aluminum current collectors at voltages higher than 4.2 V vs. Li metal.
New technological solutions for telecommunications and especially electrification of transportation cells have been proposed for Li and Li-ion batteries. Their aim is to provide such batteries with the highest possible energy density in order to achieve higher voltage cathodes. This, however, requires high performance electrolytes which are resistant towards oxidation at the high potentials that occur during the operation of such a system. Also, other parasitic processes can cause deterioration and malfunctioning of the system. One such parasitic process is corrosion or electrolytic dissolution of the current collectors, which typically becomes significant at potentials beyond 4 V.
Conventional electrolytes used in most lithium and Li-ion battery systems, also in high voltage batteries, are based on LiPF6 salt, which has many good properties. For example, it passivates the majority of aluminum current collector materials, has good conductivity and it is relatively chew. However, it also has some disadvantages, most notably sensitivity to moisture, causing HF to form, which causes rapid deterioration of battery performance. Another weakness is its limited thermal stability, limited solubility in polymers and emission of toxic decomposition products. The solvents used for the preparation of conventional electrolytes are cheaply available C1-C2 dialkyl carbonates and lower cyclic carbonates, most notably ethylene carbonate and propylene carbonate.
In order to substitute the risky LiPF6 for safer alternatives, many salts have been proposed. One class of such salts are bissulfonyl amides; in fact, lithium bis(trifluoromethanesulfonyl)amide—LiTFSI, has been proposed as a salt for the preparation of electrolytes, including polymer electrolytes. In addition, other compounds of this class have been proposed. It has been discovered that LiTFSI produces serious anodic dissolution, erroneously called corrosion, of the aluminum current collector at voltages higher than 3.6 V. This means that the electrochemical charge that should be used for the charging of the battery is consumed for aluminum dissolution, such that the battery in fact cannot be charged. When this process occurs with a smaller rate (meaning only part of the charge is consumed by the corrosion process) the battery can be charged, but repeating the charging further dissolves the current collector. This slowly leads to diminished contact between the active electrode coating and the current collector, resulting in loss of capacity. This imposes a serious drawback for long-term operation, which entails many charges and discharges of the battery system.
For that reason, lithium bis(pentafluoroethanesulfonyl) amide—LiBETI was developed to overcome those problems, but its main disadvantages are its very high molecular weight, its high price and its accumulation in living organisms similar to all long chain perfluoroalkanes. On the other hand, two lighter salts have been proposed: lithium bis(fluorosulfonyl)amide—LiFSI and asymmetric lithium N-fluorosulfonyl-trifluoromethanesulfonyl amide—LiFTFSI. Other asymmetric bisfluorosulfonyl amides have also been suggested.
It has been stated that electrolytes containing LiFSI can support voltages up to 4.2V. However, it is not clear, and there is no experimental proof, that these electrolytes can support higher voltages.
Anodic dissolution of an aluminum current collector in sulfone-based solvents has been examined. As an alternative to molecular solvents, ionic liquids were reported as a good solvent for the suppression of anodic dissolution of aluminum. However, ionic liquids are not easily available, and their main drawback is their high price, which makes them less attractive for use in battery systems.
The influence of various solvents on anodic dissolution of aluminum collectors caused by LiTFSI has been examined. It has been found that collector corrosion depends on the electrolyte solvent, with strong corrosion in the presence of carbonates and lactones and minimal corrosion in the presence of nitriles. Such a conclusion discourages the utilisation of carbonate solvents for use with sulfonyl amide salts.
The inhibition of anodic dissolution of aluminum can be affected with fluoroborates, most effectively with lithium difluorooxalatoborate, LiDFOB; the drawback is the relatively high price of this additive.
Also, LiPF6 can be used as an aluminum anodic dissolution inhibitor. However, very high concentrations of LiPF6 are needed to effectively suppress the anodic dissolution of aluminum. In fact, due to the high concentrations, it would be more accurate to label such electrolytes as LiPF6 electrolytes, with LiFSI as an additive to the LiPF6.
Mother proposed solution is the use of highly concentrated electrolytes. However, there are several drawbacks, including the undesirable higher price of such a system and crystallisation problems at low temperatures.
There have also been more or less successful attempts to protect the aluminum current collector with a protective coating, but this increases the cost and weight of the battery. Furthermore, the most problematic point of this inhibition is that edges are not protected due to the cutting of electrodes to an appropriate size. Corrosion may propagate from the edges after many cycles, thus jeopardizing the long-term operation of such cells.
Possible solvents for lithium batteries have been discussed, but very little attention has been paid to unwanted proses on the current collectors. Most electrolytes used in the battery industry are based on the lower dialkyl carbonates: dimethyl, diethyl and ethylmethyl carbonate, mixed with additives, most notably ethylene carbonate. Syntheses of alkyl carbonates are very well developed, even on an industrial scale. Most suitable methods for their preparation in a laboratory are transesterifications.
Regarding high voltage applications, fluorinated carbonates have been proposed together with conventional LiPF6 salt. However, these solvents are very expensive and can represent a serious environmental risk, like all long chin fluorinated compounds. Insecticidal activity of some fluorinated carbonates has also been described.
The above solutions to inhibit aluminum corrosion do not represent an optimal solution to the problem of anodic aluminum dissolution and therefore they do not represent an optimal replacement for conventional solvents.
In accordance with the present invention, there is provided:
wherein:
In the appended drawings:
The present inventors have found that carbonate compounds of formula (I) can advantageously be used as solvents in non-aqueous electrolytes in batteries comprising a one cathode comprising an aluminum current collector because they are characterized by their low corrosiveness against aluminum, even at voltages of or higher than 4.2 V, even in electrolytes containing lithium sulfonylamide salts. Utilization of these lithium sulfonylamide salts with conventional solvents in such high voltage systems is typically not possible as anodic dissolution of aluminum becomes the preferred electrochemical reaction and the vast majority of the charge is consumed for this detrimental corrosion process.
While the low corrosiveness of the carbonate compounds of formula (I) is especially advantageous when lithium sulfonylamide salts are the main conducting salt, the person skilled in the art would recognize the potential of these solvents for achieving high voltage lithium and lithium ion batteries in connection with other conducting salts. The skilled person would also understand that the electrolyte can be used in different types of batteries, such as sodium, potassium, calcium, aluminum and magnesium-based batteries, and that when doing so, other salts can be dissolved in the solvents, for example sodium, potassium, calcium, aluminum and magnesium salts.
Indeed, the carbonate compounds of formula (I) are characterized by their capacity to suppress anodic dissolution of aluminum (e.g. in an aluminum current collector as well as any other aluminum member in the battery) when used as solvents in electrolytes in batteries, even at potentials higher than 4.2 V, as measured vs a lithium metal reference electrode. Such examples of batteries are a lithium or lithium-ion batteries. For clarity, unless specified otherwise, all electrode potentials in the present application are referenced to a Li metal anode.
Anodic dissolution of the aluminum current collector is defined as the dissolution of an aluminum current collector at a certain externally forced potential (the critical potential), which is higher than the open circuit potential. At the critical potential, the components of the electrolyte react with the surface of the collector and form soluble compounds, which in turn dissolve in the electrolyte and cause dissolution of the aluminum i.e. quasi corrosion. Significant dissolution of the aluminum can lead to malfunctioning of the battery system, if its operating voltage surpasses the critical potential. Accordingly, suppressing anodic dissolution enables safer and more powerful battery technologies, especially lithium-ion batteries. Herein, “suppressing” anodic dissolution means that anodic dissolution does not occur or that is reduced to such a level that it becomes non-deleterious to the battery.
This low corrosiveness of the carbonate compounds of formula (I) also enables the manufacture of batteries containing aluminum current collectors with extended operating voltages (in particular, operating voltages over 4.2 V vs a Li-metal reference electrode), even for electrolytes containing lithium sulfonylamide salts and lithium-ion batteries. This allows for the preparation of non-aqueous electrolytes containing lithium sulfonylamide salts that are free of corrosion inhibitors (while still maintaining said low corrosiveness against aluminum current collectors at voltages higher than 4.2 V).
Furthermore, when compared to conventional carbonate solvents (e.g. ethylene carbonate (EC), diethyl carbonate (DEC), and the like), the carbonate compounds of formula (I) have a wider operating temperature range, especially when used in lithium-ion batteries. Indeed, the temperature range in which the carbonate compounds of formula (I) are liquid (without crystallization) tends to be wider than that of these conventional carbonate solvents. For example, in embodiments, the carbonate compounds of formula (I) can have a melting point well below −10° C., and, in some cases, do not even have a melting point and thus stay liquid, without crystallizing, until they reach their glass transition point. Further, the melting point of the carbonate compounds tends to decrease with growing molecular mass to a certain point.
Further, the carbonate compounds of formula (I) have a higher boiling point than conventional carbonate solvents. For example, the boiling points of dimethyl carbonate, diethyl carbonate, dipropyl carbonate and dibutyl carbonate are 90, 126, 168 and 207° C., respectively. This indicates that electrolytes prepared from higher carbonates can be used at higher temperatures without the risk of rapid evaporation. These higher boiling points translates into improved safety properties for the batteries containing the electrolyte using the carbonate compounds of formula (I) as solvent.
Finally, the carbonate compounds of formula (I) are a very green, that is environmentally benign, group of solvents.
The inventors thus provide herein a metal or metal-ion battery comprising:
In embodiments, the upper potential limit of the cathode is preferably about 4.4 V or more, about 4.6 V or more, about 4.8 V or more, about 5.0 V or more, about 5.2 V or more, about 5.4 V or more, or about 5.5 V or more, vs a Li-metal reference electrode.
In embodiments, the upper potential limit of the cathode is preferably about 6.0 V or less, about 5.6 V or less, about 5.5 V or less, about 5.4 V or less, about 5.2 V or less, about 5.0 V or less, about 4.8 V or less, vs a Li-metal reference electrode.
In embodiments, the upper voltage limit of the battery is preferably about 4.4 V or more, about 4.6 V or more, about 4.8 V or more, about 5.0 V or more, about 5.2 V or more, about 5.4 V or more, or about 5.5 V or more.
In embodiments, the upper voltage limit of the battery is preferably about 6.0 V or less, about 5.6 V or less, about 5.5 V or less, about 5.4 V or less, about 5.2 V or less, about 5.0 V or less, about 4.8 V or less.
The lower potential limit of the cathode and the lower voltage limit of the battery are not substantially affected by using a carbonate compound of formula (I) as a solvent in the battery of the invention. Indeed, these lower limits are not critical to the invention since anodic dissolution occurs only at elevated potentials. Furthermore, the lower potential limit of cathode it typically not affected by the solvent used for the electrolyte. Therefore, these lower limits will be those found in corresponding conventional batteries that use other solvents.
Indeed, cathodes are characterized by a potential window that goes from a lower potential limit to an upper potential limit. The lower potential limit is the potential beyond which further discharge would harm the cathode. The upper potential limit is the potential beyond which further charge would harm the cathode. These potential values are always given referring to a certain reference. For example, for all lithium batteries, this reference is a Li-metal reference electrode. Herein, the potential values all refer to a Li-metal reference electrode, even when referring to other types of batteries (sodium-based, magnesium-based batteries, etc.).
Furthermore, batteries are characterized by an operating voltage window that goes from a lower voltage limit to an upper voltage limit. The lower voltage limit is the voltage at which a battery is considered fully discharged and beyond which further discharge would harm the battery (or its components). The upper potential limit is the voltage at which a battery is considered fully charged and beyond which further charge would harm the battery (or its components). Therefore, batteries are operated at voltages within their operating voltage window, i.e. they are charged/discharged so that their voltage falls within their operating voltage window, ideally as close as possible to the upper voltage limit when they are charged so as to provide a maximum of energy.
For note, a battery voltage is the difference between the potential of the cathode and that of the anode.
Battery voltage=(potential of the cathode)−(potential of the anode)
As such, no reference is needed when providing a battery voltage value.
When the anode of the battery is lithium metal, it has (all the time) a potential of 0V. Thus, in such cases, the upper and lower voltage limits of the battery are equal to the upper and lower potential limits of the cathode. In other cases, such as when the anode is made of graphite, the anode has a potential >0V. When the anode has a potential >0V, the upper and lower voltage limits of the battery are lower than the upper and lower potential limits of the cathode, respectively. For example, a graphite anode has (most of the time) a potential of about 0.1V, but this potential can nevertheless vary from about 2.5V to very close to 0V. An LTO anode has a potential of about 1.5V most of the time.
As noted above, anodic dissolution of aluminum in the aluminum current collector is suppressed during battery operation at voltages at least up to said upper voltage limit. Herein, the “suppression” of anodic dissolution mews that this phenomenon does not take place at all or that it is so limited that the battery can be charged up to said upper voltage without losing significant part of charge for anodic dissolution of aluminium. For example, less than 0.01%, preferably less than 0.001%, and more preferably less than 0.0001% of the charge is lost. In another scale, it is preferable that the corrosion current density be lower than about 1 microA/cm2. Indeed, when significant anodic dissolution occurs within the operating voltage window of a battery, significant amount of charge is lost, and significant amount of aluminium is dissolved and contact between the current collector and active material lost, further leading into loss of useful capacity. In the most catastrophic scenario, most of the charge is consumed by aluminium dissolution when first charging the battery, which means that the amount of charge stored by the battery (i.e. the amount of useful charge) is very small. In other words, the battery does not work. In particular, electrolytes comprising bis(sulfonylamide) salts (of e.g. lithium or of other metals in batteries based on other metals) can cause such catastrophic anodic dissolution of aluminium. In contrast, when such salts are dissolved in a carbonate compound of formula (I), as a solvent, the anodic dissolution is successfully suppressed.
In preferred embodiments, the battery is a lithium battery, a lithium-ion battery, sodium battery, a sodium-ion battery, a potassium battery, a potassium-ion battery, a magnesium battery, a magnesium-ion battery, an aluminum battery, or an aluminum ion battery. Preferably, the battery is a lithium battery, a lithium-ion battery, sodium battery, a sodium-ion battery, a potassium battery, a potassium-ion battery, a magnesium battery, a magnesium-ion battery. In more preferred embodiments, the battery of the present invention is a lithium battery or lithium-ion battery, even more preferably a lithium-ion battery.
More details on the various components of the battery of the invention are provided in the following sections.
There is also provided a method of manufacturing and/or operating a battery as describe above, said method comprising the step of charging the battery up to an upper voltage limit of about 4.2 V or more, preferably about 4.4 V or more, about 4.6 V or more, about 4.8 V or more, about 5.0 V or more, about 5.2 V or more, about 5.4 V or more, or about 5.5 V or more.
The carbonate compound of formula (I) is:
wherein
R1 represents a C3-C24 alkyl, a C3-C24 alkoxyalkyl, a C3-C24 ω-O-alkyl oligo(ethylene glycol), or a C4-C24 ω-O-alkyl oligo(propylene glycol), and
R2 represents a C1-C24 alkyl, a C1-C24 haloalkyl, a C2-C24 alkoxyalkyl, a C2-C24 alkyloyloxyalkyl, a C3-C24 alkoxycarbonylalkyl, a C1-C24 cyanoalkyl, a C1-C24 thiocyanatoalkyl, a C3-C24 trialkylsilyl, a C4-C24 trialkylsilylalkyl, a C4-C24 trialkylsilyloxyalkyl, a C3-C24 ω-O-alkyl oligo(ethylene glycol), a C4-C24 ω-O-alkyl oligo(propylene glycol), a C5-C24 ω-O-trialkylsilyl oligo(ethylene glycol), or a C6-C24 ω-O-trialkylsilyl oligo(propylene glycol).
In more preferred embodiments, R1 represents a C3-C24 alkyl or a C3-C24 ω-O-alkyl oligo(ethylene glycol). In more preferred embodiments, R1 represents a C3-C24 alkyl.
In more preferred embodiments, R2 represents a C1-C24 alkyl, a C2-C24 alkoxyalkyl, a C1-C24 cyanoalkyl, a C4-C24 trialkylsilyloxyalkyl, a C6-C24 ω-O-trialkylsilyl oligo(ethylene glycol), or a C3-C24 ω-O-alkyl oligo(ethylene glycol). In most preferred embodiments, R2 represents a C1-C24 alkyl.
Given that R1 and R2 as defined above contain at least 3 and 1 carbon atoms, respectively, the sum of the carbon atoms in R1 and R2 is at least 4. In preferred embodiments, the sum of the carbon atoms in R1 and R2 is:
Each of the alkyl and substituted alkyl in R1 and R2 are linear or branched.
Herein, “alkyl” has its usual meaning in the art. Specifically, it is a monovalent saturated aliphatic hydrocarbon radical of general formula —CnH2n+1.
Non-limiting examples of C3-C24 alkyl in R1 include propyl, isopropyl (2-propyl), butyl, 2-butyl, 3-butyl, isobutyl (3-methylpropyl), tertbutyl (2,2-dimethylethyl), 2-methylbutyl, 3-methylbutyl, 1-methyl-2-butyl, 2-methyl-2-butyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl, 3,3-dimethyl-2-butyl, 2,3-dimethyl-2-butyl, 2-ethylbutyl, 3-ethyl-2-butyl, 2-ethylhexyl, pentyl and its isomers (including 2-pentyl and 3-pentyl), hexyl and its isomers (including 2-hexyl and 3-hexyl), heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, undecyl and its isomers, and dodecyl and its isomers. In preferred embodiments, the C3-C24 alkyl in R1 is a C3-C18 alkyl, preferably a C3-C12 alkyl, preferably a C3-C11 alkyl, preferably a C3-C10 alkyl, preferably a C3-C3 alkyl, more preferably a C3-C8 alkyl, even more preferably a C3-C7 alkyl (yet more preferably a C4-C7 alkyl), yet more preferably a C3-C6 alkyl (yet more preferably a C4-C6 alkyl), more preferably a C3-C5 alkyl, and most preferably a C4-C5 alkyl.
Non-limiting examples of C1-C24 alkyl chain in R2 include the C3-C24 alkyls listed above with regard to R1, as well as methyl and ethyl. In preferred embodiments, R2 is a C1-C18 alkyl, preferably a C1-C12 alkyl, a C1-C9 alkyl, a C1-C8 alkyl, a C1-C7 alkyl, a C4-C7 alkyl, a C3-C7 alkyl (preferably a C4-C7 alkyl), a C3-C6 alkyl (preferably a C4-C6 alkyl), a C3-C5 alkyl, and most preferably a C4-C5 alkyl.
In preferred embodiments, both R1 and R2 are alkyl groups. In more preferred embodiments, R1 and R2 are the same alkyl groups. In alternative preferred embodiments, R1 and R2 are different alkyl groups.
Preferred C3 alkyls in R1 and R2 include propyl, and isopropyl (2-propyl).
Preferred C4 alkyls in R1 and R2 include butyl, 2-butyl, 3-butyl, isobutyl (3-methylpropyl), and tertbutyl (2,2-dimethylethyl).
Preferred C5 alkyls in R1 and R2 include pentyl and its isomers (including 2-pentyl and 3-pentyl), 2-methylbutyl, 3-methylbutyl, 1-methyl-2-butyl, and 2-methyl-2-butyl.
Preferred C5 alkyls in R1 and R2 include hexyl and its isomers (including 2-hexyl and 3-hexyl), 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl, 3,3-dimethyl-2-butyl, 2,3-dimethyl-2-butyl, 2-ethylbutyl, and 3-ethyl-2-butyl.
Preferred C7 alkyls in R1 and R2 include heptyl and its isomers.
Preferred C8 alkyls in R1 and R2 include 2-ethylhexyl.
Herein, a “haloalkyl” refers to an alkyl group in which one or more (or even all) of the hydrogen atoms are each replaced by a halogen atom, wherein the halogen atoms are the same or different from one another (when more than one halogen atoms are present). Halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Preferably, the halogen atom is fluorine. Non-limiting examples of C1-C24 haloalkyls in R2 include trifluoromethyl, pentafluoroethyl, heptafluoropropyl, nonafluorobutyl, 2,2,2-trifluoroethyl, and 1,1,1,3,3,3-hexafluoro-2-propyl.
Herein, an “alkoxyalkyl” refers to an alkyl group in which one or more, preferably one, of the hydrogen atoms are each replaced by an alkoxy group, wherein the alkoxy groups are the same or different from one another (when more than one alkoxy groups are present). In preferred embodiments, the alkoxyalkyl comprises only one alkoxy group. An alkoxy group is a radical of formula —O-alkyl, this alkyl being linear or branched, preferably linear. A C2-C24 alkoxyalkyl is alkoxyalkyl radical, wherein the sum of the number of carbon atoms contained in the alkyl and alkoxy groups is between 2 and 24. In preferred embodiments, the alkoxyalkyl is a (C1-C2)alkoxy(C2-C5)alkyl. Non-limiting examples of alkoxyalkyls in R2 or R1 include 2-methoxyethyl, 3-methoxypropyl, 2-methoxypropyl, 4-methoxybutyl, 4-ethoxybutyl, 5-methoxypentyl, 6-methoxyhexyl, and 2-isopropoxyethyl. In preferred embodiments, the alkoxyalkyl is 2-methoxyethyl or 2-isopropoxyethyl.
Herein, an “alkyloyloxyalkyl” refers to an alkyl group in which one or more, preferably one, of the hydrogen atoms are each replaced by an alkyloyloxy group, wherein the alkyloyloxy groups are the same or different when more than one alkyloyloxy groups are present). In preferred embodiments, the alkyloyloxyalkyl comprises only one alkyloyloxy group. An alkyloyloxy group is a radical of formula —O—C(═O)-alkyl, this alkyl being linear or branched. A C2-C24 alkyloyloxyalkyl is alkyloyloxyalkyl wherein the sum of the number of carbon atoms contained in the alkyl and alkyloyloxy groups is between 2 and 24. Non-limiting examples of C2-C24 alkyloyloxyalkyl in R2 include 2-acetoxyethyl, 3-acetoxypropyl, 2-acetoxypropyl, and 4-acetoxybutyl.
Herein, an “alkoxycarbonylalkyl” refers to an alkyl group in which one or more of the hydrogen atoms are each replaced by an alkoxycarbonyl group, wherein the alkoxycarbonyl groups are the same or different from one another (when more than one alkoxycarbonyl groups are present). In preferred embodiments, the alkoxycarbonylalkyl comprises only one alkoxycarbonyl group. An alkoxycarbonyl group is a radical of formula C(═O)—O-alkyl, this alkyl being linear or branched. A C2-C24 alkoxycarbonyl is an alkoxycarbonyl wherein the sum of the number of carbon atoms contained in the alkyl and alkoxycarbonyl groups is between 3 and 24. Non-limiting examples of C3-C24 alkoxycarbonylalkyl in R2 include 2-ethoxycarbonylethyl and 3-methoxycarbonylpropyl.
Herein, a “cyanoalkyl” refers to an alkyl group in which one or more of the hydrogen atoms are each replaced by a cyano (—C≡N) group. In preferred embodiments, the cyanoalkyl comprises only one cyano group. In preferred embodiments, the cyanoalkyl is a C1-C5 cyanoalkyl. Non-limiting examples of C1-C24 cyanoalkyls in R2 include cyanomethyl, 2-cyanoethyl, 3-cyanopropyl, 4-cyanobutyl, and 5-cyanopentyl. In preferred embodiments, the C1-C24 cyanoalkyl in R2 is 2-cyanoethyl.
Herein, a “thiocyanatoalkyl” refers to an alkyl group in which one or more of the hydrogen atoms are each replaced by a thiocyanato (—S—C≡N) group. In preferred embodiments, the thiocyanatoalkyl comprises only one thiocyanato group. Non-limiting examples of C1-C24 thiocyanatoalkyls in R2 include thiocyanatomethyl, 2-thiocyanatoethyl, 3-thiocyanatopropyl, 4-thiocyanatobutyl, 5-thiocyanatopentyl, and 6-thiocyanatohexyl.
Herein, a “trialkylsilyl” refers to a radical of formula (alkyl)3-Si—, wherein the alkyl groups are the same or different and are linear or brandied. A C3-C24 trialkylsilyl is a trialkylsilyl wherein the sum of the number of carbon atoms contained in all of the alkyl groups is between 3 and 24. In preferred embodiments, each of the alkyl groups in the trialkylsilyl is a C1-C4 alkyl group. In preferred embodiments, the three alkyl groups are the same. Non-limiting examples of C3-C24 trialkylsilyls in R2 include trimethylsilyl, ethyldimethylsilyl, diethylmethylsilyl, triethylsilyl, dimethylpropylsilyl, dimethylisopropylsilyl, triisopropylsilyl, butyldimethylsilyl, and tertbutyldimethylsilyl.
Herein, a “trialkylsilylalkyl” is an alkyl group in which one or more of the hydrogen atoms are each replaced by a trialkylsilyl group, wherein the trialkylsilyl are as defined above and are the same or different from one another (when more than one trialkylsilyl groups ae present). In a C4-C24 trialkylsilylalkyl, the sum of the number of carbon atoms contained in all four of the alkyl groups is between 4 and 24. Preferably, the trialkylsilylalkyl comprises only one trialkylsilyl group. In preferred embodiments, the C4-C24 trialkylsilylalkyl is a trialkylsilylalkyl(C1-C4)alkyl, preferably a trialkylsilylalkyl(C2-C4)alkyl. In preferred embodiments, the three alkyl groups attached to the Si atom are methyl groups. Non-limiting examples of C4-C24 trialkylsilylalkyl in R2 include trimethylsilylethyl, 2-trimethylsilylethyl, 3-trimethylsilylpropyl and 4-trimethylsilylbutyl.
Herein, a “trialkylsiyloxyalkyl” refers to an alkyl group in which one or more of the hydrogen atoms are each replaced by a trialkylsilyloxy group, wherein the trialkylsilyloxy groups are the same or different from one another (when more than one trialkylsilyloxy groups are present). Preferably, the trialkylsilyloxyalkyl comprises only one trialkylsilyloxy group. Herein, a “trialkylsilyloxy” is a radical of formula (alkyl)3-Si—O—, wherein the alkyl groups are the same or different from one another and are linear or branched. In a C4-C24 trialkylsilyloxyalkyl, the sum of the number of carbon atoms contained in all four of the alkyl groups is between 4 and 24. In preferred embodiments, the C4-C24 trialkylsilyloxyalkyl is a trialkylsilyloxy(C3-C4)alkyl. In preferred embodiments, the three alkyl groups attached to the Si atom are methyl groups. Non-limiting examples of C4-C24 trialkylsilyloxyalkyl in R2 include (2-trimethylsilyloxy)ethyl, 3-trimethylsilyloxypropyl and 4-trimethylsilyloxybutyl. In preferred embodiments, the C4-C24 trialkylsilyloxyalkyl in R2 is (2-trimethylsilyloxy)ethyl.
Herein an ω-O-alkyl oligo(ethylene glycol) is a radical of formula —(CH2—CH2—O—)n-alkyl, wherein n is 1 or more. In a C3-C24 ω-O-alkyl oligo(ethylene glycol), the sum of the number of carbon atoms contained in the alkyl and the (CH2—CH2—O—) repeating motif(s) is between 3 and 24. In preferred embodiments, n is an integer from 1 to 5. In preferred embodiments, the alkyl group is a C1-C4 alkyl. Non-limiting examples of ω-O-alkyl oligo(ethylene glycol) in R2 or R1 include 2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-isopropoxyethyl, 2-butyloxyethyl, 2-(2-methoxyethoxy)ethyl, 2-(2-butoxyethoxy)ethyl, 2-(2-ethoxyethoxy)ethyl, 2-[2-(2-methoxyethoxy)ethoxy]ethyl, 2-[2-(2-ethoxyethoxy)ethoxy]ethyl, 2,5,8,11-tetraoxatridecyl, 3,6,9,12-tetraoxatetradecyl, 2,5,8,11,14-pentaoxahexadecyl, or 3,6,9,12,15-pentaoxaheptadecyl. In preferred embodiments, the ω-O-alkyl oligo(ethylene glycol) of R2 or R1 is 2-methoxyethyl, 2-isopropoxyethyl, or 2-(2-methoxyethoxy)ethyl.
Herein an ω-O-alkyl oligo(propylene glycol) is a radical of formula —(CH2—CH2—CH2—O—)n-alkyl, wherein n is 1 or more. In a C4-C24 ω-O-alkyl oligo(propylene glycol), the sum of the number of carbon atoms contained in the alkyl and the (CH2—CH2—CH2—O—) repeating motif(s) is between 4 and 24. In preferred embodiments, n is 1. In preferred embodiments, the alkyl group is a C1-C4 alkyl. Non-limiting examples of ω-O-alkyl oligo(propylene glycol) in R2 or R1 include 2-methoxypropyl, 2-ethoxypropyl, 1-methoxy-2-propyl, 1-ethoxy-2-propyl, 1-propoxy-2-propyl, 1-isopropoxy-2-propyl, and 1-butoxy-2-propyl.
Herein an ω-O-trialkylsilyl oligo(ethylene glycol) is a radical of formula —(CH2—CH2—O—)n—Si-(alkyl)3, wherein the alkyl groups are the same or different and are linear or branched and wherein n is 1 or more. In a C5-C24 ω-O-trialkylsilyl oligo(ethylene glycol), the sum of the number of carbon atoms contained in the alkyl groups and the (CH2—CH2—O—) repeating motif(s) is between 5 and 24. In preferred embodiments, n is an integer from 1 to 5. In preferred embodiments, the three alkyl groups (attached to the Si atom) are methyl groups. Non-limiting examples of ω-O-trialkylsilyl oligo(ethylene glycol) in R2 include 2-trimethylsilyloxyethyl, 2-(2-trimethylsilyloxyethoxy)ethyl, 2-[2-(2-trimethylsilyloxyethoxy)-ethoxy]ethyl, 2-{2-[2-(2-trimethylsilyloxyethoxy)ethoxy]ethoxy}ethyl, and 2-(2-{2-[2-(2-trimethylsilyloxyethoxy)ethoxy]ethoxy}ethoxy)ethyl. In preferred embodiments, the ω-O-trialkylsiyl oligo(ethylene glycol) of R2 is 2-trimethylsilyloxyethyl.
Herein an ω-O-trialkylsilyl oligo(propylene glycol) is a radical of formula —(CH2—CH2—CH2—O—)n—Si-(alkyl)3, wherein the alkyl groups are the same or different and are linear or branched and wherein n is 1 or more. In a C6-C24 ω-O-trialkylsilyl oligo(ethylene glycol), the sum of the number of carbon atoms contained in the alkyl groups and the (CH2—CH2—CH2—O—) repeating motif(s) is between 6 and 24. In preferred embodiments, n is 1. In preferred embodiments, the three alkyl groups (attached to the Si atom) are methyl groups. Non-limiting examples of ω-O-trialkylsilyl oligo(propylene glycol) in R2 include 2-trimethylsiyloxypropyl, and 1-trimethylsilyloxy-2-propyl.
Preferably, the carbonate compound of formula (I) is: isopropyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl isopropyl carbonate, dipropyl carbonate, isopropyl propyl carbonate, diisopropyl carbonate, butyl methyl carbonate, butyl ethyl carbonate, butyl propyl carbonate, dibutyl carbonate, butyl isopropyl carbonate, 2-butyl methyl carbonate, 2-butyl ethyl carbonate, 2-butyl propyl carbonate, di(2-butyl) carbonate, 2-butyl isopropyl carbonate, isobutyl methyl carbonate, isobutyl ethyl carbonate, isobutyl propyl carbonate, diisobutyl carbonate, isobutyl isopropyl carbonate, 2-butyl isobutyl carbonate, 2-ethylbutyl methyl carbonate, di(2-ethylbutyl) carbonate, methyl pentyl carbonate, ethyl pentyl carbonate, pentyl propyl carbonate, butyl pentyl carbonate, dipentyl carbonate, isopropyl pentyl carbonate, 2-butyl pentyl carbonate, isobutyl pentyl carbonate, methyl 2-pentyl carbonate, ethyl 2-pentyl carbonate, 2-pentyl propyl carbonate, butyl 2-pentyl carbonate, di(2-pentyl) carbonate, isopropyl 2-pentyl carbonate, 2-butyl 2-pentyl carbonate, isobutyl 2-pentyl carbonate, methyl 3-pentyl carbonate, ethyl 3-pentyl carbonate, 3-pentyl propyl carbonate, butyl 3-pentyl carbonate, di(3-pentyl) carbonate, isopropyl 3-pentyl carbonate, 2-butyl 3-pentyl carbonate, isobutyl 3-pentyl carbonate, pentyl 2-pentyl carbonate, pentyl 3-pentyl carbonate, 2-pentyl 3-pentyl carbonate, methyl hexyl carbonate, ethyl hexyl carbonate, propyl hexyl carbonate, butyl hexyl carbonate, pentyl hexyl carbonate, dihexyl carbonate, isopropyl hexyl carbonate, isobutyl hexyl carbonate, di(2-ethylhexyl) carbonate, 2-ethylhexyl methyl carbonate, didodecyl carbonate, ethyl dodecyl carbonate, cyanomethyl propyl carbonate, butyl cyanomethyl carbonate, cyanomethyl isopropyl carbonate, 2-butyl cyanomethyl carbonate, isobutyl cyanomethyl carbonate, tertbutyl cyanomethyl carbonate, cyanomethyl pentyl carbonate, cyanomethyl 2-pentyl carbonate, cyanomethyl 3-pentyl carbonate, cyanomethyl hexyl carbonate, cyanomethyl heptyl carbonate, cyanomethyl octyl carbonate, cyanomethyl nonyl carbonate, cyanomethyl decyl carbonate, cyanomethyl undecyl carbonate, cyanomethyl dodecyl carbonate, cyanomethyl 2-ethylhexyl carbonate, 2-cyanoethyl propyl carbonate, butyl 2-cyanoethyl carbonate, 2-cyanoethyl isopropyl carbonate, 2-butyl 2-cyanoethyl carbonate, isobutyl 2-cyanoethyl carbonate, tertbutyl 2-cyanoethyl carbonate, 2-cyanoethyl pentyl carbonate, 2-cyanoethyl 2-pentyl carbonate, 2-cyanoethyl 3-pentyl carbonate, 2-cyanoethyl hexyl carbonate, 2-cyanoethyl heptyl carbonate, 2-cyanoethyl octyl carbonate, 2-cyanoethyl nonyl carbonate, 2-cyanoethyl decyl carbonate, 2-cyanoethyl undecyl carbonate, 2-cyanoethyl dodecyl carbonate, 2-cyanoethyl 2-ethylhexyl carbonate, 3-cyanopropyl propyl carbonate, butyl 3-cyanopropyl carbonate, 3-cyanopropyl isopropyl carbonate, 2-butyl 3-cyanopropyl carbonate, isobutyl 3-cyanopropyl carbonate, tertbutyl 3-cyanopropyl carbonate, 3-cyanopropyl pentyl carbonate, 3-cyanopropyl 2-pentyl carbonate, 3-cyanopropyl 3-pentyl carbonate, 3-cyanopropyl hexyl carbonate, 3-cyanopropyl heptyl carbonate, 3-cyanopropyl octyl carbonate, 3-cyanopropyl nonyl carbonate, 3-cyanopropyl decyl carbonate, 3-cyanopropyl undecyl carbonate, 3-cyanopropyl dodecyl carbonate, 3-cyanopropyl 2-ethylhexyl carbonate, 4-cyanobutyl propyl carbonate, butyl 4-cyanobutyl carbonate, 4-cyanobutyl isopropyl carbonate, 2-butyl 4-cyanobutyl carbonate, isobutyl 4-cyanobutyl carbonate, tertbutyl 4-cyanobutyl carbonate, 4-cyanobutyl pentyl carbonate, 4-cyanobutyl 2-pentyl carbonate, 4-cyanobutyl 3-pentyl carbonate, 4-cyanobutyl hexyl carbonate, 4-cyanobutyl heptyl carbonate, 4-cyanobutyl octyl carbonate, 4-cyanobutyl nonyl carbonate, 4-cyanobutyl decyl carbonate, 4-cyanobutyl undecyl carbonate, 4-cyanobutyl dodecyl carbonate, 4-cyanobutyl 2-ethylhexyl carbonate, propyl trimethylsilyl carbonate, butyl trimethylsilyl carbonate, isopropyl trimethylsilyl carbonate, 2-butyl trimethylsilyl carbonate, isobutyl trimethylsilyl carbonate, tertbutyl trimethylsilyl carbonate, pentyl trimethylsilyl carbonate, 2-pentyl trimethylsilyl carbonate, 3-pentyl trimethylsilyl carbonate, hexyl trimethylsilyl carbonate, heptyl trimethylsilyl carbonate, octyl trimethylsilyl carbonate, nonyl trimethylsilyl carbonate, decyl trimethylsilyl carbonate, trimethylsilyl undecyl carbonate, dodecyl trimethylsilyl carbonate, 2-ethylhexyl trimethylsilyl carbonate, ethyldimethylsilyl propyl carbonate, butyl ethyldimethylsilyl carbonate, ethyldimethylsilyl isopropyl carbonate, 2-butyl ethyldimethylsilyl carbonate, isobutyl ethyldimethylsilyl carbonate, tertbutyl ethyldimethylsilyl carbonate, ethyldimethylsilyl pentyl carbonate, ethyldimethylsilyl 2-pentyl carbonate, ethyldimethylsilyl 3-pentyl carbonate, ethyldimethylsilyl hexyl carbonate, ethyldimethylsilyl heptyl carbonate, ethyldimethylsilyl octyl carbonate, ethyldimethylsilyl nonyl carbonate, decyl ethyldimethylsilyl carbonate, ethyldimethylsilyl undecyl carbonate, dodecyl ethyldimethylsilyl carbonate, ethyldimethylsilyl 2-ethylhexyl carbonate, diethylmethylsilyl propyl carbonate, butyl diethylmethylsilyl carbonate, diethylmethylsilyl isopropyl carbonate, 2-butyl diethylmethylsilyl carbonate, isobutyl diethylmethylsilyl carbonate, tertbutyl diethylmethylsilyl carbonate, diethylmethylsilyl pentyl carbonate, diethylmethylsilyl 2-pentyl carbonate, diethylmethylsilyl 3-pentyl carbonate, diethylmethylsilyl hexyl carbonate, diethylmethylsilyl heptyl carbonate, diethylmethylsilyl octyl carbonate, diethyimethylsilyl nonyl carbonate, decyl diethylmethylsilyl carbonate, diethylmethylsilyl undecyl carbonate, diethylmethylsilyl dodecyl carbonate, 2-ethylhexyl diethylmethylsilyl carbonate, propyl triethylsilyl carbonate, butyl triethylsilyl carbonate, isopropyl triethylsilyl carbonate, 2-butyl triethylsilyl carbonate, isobutyl triethylsilyl carbonate, tertbutyl triethylsilyl carbonate, pentyl triethylsilyl carbonate, 2-pentyl triethylsilyl carbonate, 3-pentyl triethylsilyl carbonate, hexyl triethylsilyl carbonate, heptyl triethylsilyl carbonate, octyl triethylsilyl carbonate, nonyl triethylsilyl carbonate, decyl triethylsilyl carbonate, triethylsilyl undecyl carbonate, dodecyl triethylsilyl carbonate, 2-ethyihexyl triethylsilyl carbonate, dimethylisopropylsilyl propyl carbonate, butyl dimethylisopropylsilyl carbonate, dimethylisopropylsilyl isopropyl carbonate, 2-butyl dimethylisopropylsilyl carbonate, isobutyl dimethylisopropylsilyl carbonate, tertbutyl dimethylisopropylsilyl carbonate, dimethylisopropylsilyl pentyl carbonate, dimethylisopropylsilyl 2-pentyl carbonate, dimethylisopropylsilyl 3-pentyl carbonate, dimethylisopropylsilyl hexyl carbonate, dimethylisopropylsilyl heptyl carbonate, dimethylisopropylsilyl octyl carbonate, dimethylisopropylsilyl nonyl carbonate, decyl dimethylisopropylsilyl carbonate, dimethylisopropylsilyl undecyl carbonate, dimethylisopropylsilyl dodecyl carbonate, 2-ethylhexyl dimethylisopropylsilyl carbonate, propyl triisopropylsilyl carbonate, butyl triisopropylsilyl carbonate, isopropyl triisopropylsilyl carbonate, 2-butyl triisopropylsilyl carbonate, isobutyl triisopropylsilyl carbonate, tertbutyl triisopropylsilyl carbonate, pentyl triisopropylsilyl carbonate, 2-pentyl triisopropylsilyl carbonate, 3-pentyl triisopropylsilyl carbonate, hexyl triisopropylsilyl carbonate, heptyl triisopropylsilyl carbonate, octyl triisopropylsilyl carbonate, nonyl triisopropylsilyl carbonate, decyl triisopropylsilyl carbonate, triisopropylsilyl undecyl carbonate, dodecyl triisopropylsilyl carbonate, 2-ethylhexyl triisopropylsilyl carbonate, propyl tertbutyldimethylsilyl carbonate, butyl tertbutyldimethylsilyl carbonate, isopropyl tertbutyldimethylsilyl carbonate, 2-butyl tertbutyldimethylsilyl carbonate, isobutyl tertbutyldimethylsilyl carbonate, tertbutyl tertbutyldimethylsilyl carbonate, pentyl tertbutyldimethylsilyl carbonate, 2-pentyl tertbutyldimethylsilyl carbonate, 3-pentyl tertbutyldimethylsilyl carbonate, hexyl tertbutyldimethylsilyl carbonate, heptyl tertbutyldimethylsilyl carbonate, octyl tertbutyldimethylsilyl carbonate, nonyl tertbutyldimethylsilyl carbonate, decyl tertbutyldimethylsilyl carbonate, tertbutyldimethylsilyl undecyl carbonate, dodecyl tertbutyldimethylsilyl carbonate, 2-ethylhexyl tertbutyldimethylsilyl carbonate, propyl 2-trimethylsilylethyl carbonate, butyl 2-trimethylsilylethyl carbonate, isopropyl 2-trimethylsilylethyl carbonate, 2-butyl 2-trimethylsilylethyl carbonate, isobutyl 2-trimethylsilylethyl carbonate, tertbutyl 2-trimethylsilylethyl carbonate, pentyl 2-trimethylsilylethyl carbonate, 2-pentyl 2-trimethylsilylethyl carbonate, 3-pentyl 2-trimethylsilylethyl carbonate, hexyl 2-trimethylsilylethyl carbonate, heptyl 2-trimethylsilylethyl carbonate, octyl 2-trimethylsilylethyl carbonate, nonyl 2-trimethylsilylethyl carbonate, decyl 2-trimethylsilylethyl carbonate, 2-trimethylsilylethyl undecyl carbonate, dodecyl 2-trimethylsilylethyl carbonate, 2-ethylhexyl 2-trimethylsilylethyl carbonate, 2-methoxyethyl isobutyl carbonate, or (2-trimethylsilyloxy)ethyl butyl carbonate.
In more preferred embodiments, the carbonate compound of formula (I) is didodecyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl propyl carbonate, diisopropyl carbonate, isopropyl methyl carbonate, ethyl dodecyl carbonate, ethyl propyl carbonate, ethyl isopropyl carbonate, diisobutyl carbonate, isobutyl methyl carbonate, dipentyl carbonate, methyl pentyl carbonate, di(2-ethylhexyl) carbonate, 2-ethylhexyl methyl carbonate, methyl 2-pentyl carbonate, di(2-pentyl) carbonate, 2-butyl methyl carbonate, di(2-butyl) carbonate, 2-ethylbutyl methyl carbonate, di(2-ethylbutyl) carbonate, isobutyl isopropyl carbonate, 2-cyanoethyl butyl carbonate, 2-methoxyethyl isobutyl carbonate, (2-trimethylsilyloxy)ethyl butyl carbonate, di(2-methoxyethyl) carbonate, 2-isopropoxyethyl methyl carbonate, di(2-isopropoxyethyl) carbonate, or di(2-(2-methoxyethoxy)ethyl) carbonate.
In more preferred embodiments, the compound of formula (I) is didodecyl carbonate, dibutyl carbonate, 2-ethylbutyl methyl carbonate, di(2-ethylbutyl) carbonate, di(2-butyl) carbonate, di(2-ethylhexyl) carbonate, 2-ethylhexyl methyl carbonate, di(2-pentyl) carbonate, ethyl dodecyl carbonate, 2-cyanoethyl butyl carbonate, 2-methoxyethyl isobutyl carbonate, (2-trimethylsilyloxy)ethyl butyl carbonate, di(2-isopropoxyethyl) carbonate, or diisobutyl carbonate.
In even more preferred embodiments, the compound of formula (I) is didodecyl carbonate, di(2-ethylhexyl) carbonate, 2-ethylhexyl methyl carbonate, ethyl dodecyl carbonate, or diisobutyl carbonate.
In a most preferred embodiment, the carbonate compound of formula (I) is diisobutyl carbonate.
In another aspect of the invention, the invention provides all of the above carbonate compounds per se, including all preferred subgroups thereof, especially those wherein, when R2 is a C1-C9 alkyl, R1 is not a C3-C9 alkyl. Preferred such compounds include those in which, when R2 is a C1-C9 alkyl, R1 represents a C3-C24 alkoxyalkyl, a C3-C24 ω-O-alkyl oligo(ethylene glycol), or a C4-C24 ω-O-alkyl oligo(propylene glycol).
As noted above, the low-corrosiveness non-aqueous electrolyte comprises, as a solvent, the carbonate compound of formula (I) of the previous section as well as a conducting salt dissolved in said solvent.
In embodiments, mixtures of said carbonate compounds of formula (I) may be used as said solvent.
The electrolyte of the present invention can be prepared using any known technique in the art. For example, to prepare electrolytes from the carbonate solvents of the present invention, the skilled person would know that an appropriate conducting salt can be dissolved in said carbonate solvents in an appropriate concentration. Depending on the application of the electrolyte, a different salt can be chosen. For example, as described above, a lithium salt can be chosen when the electrolyte will be used in a lithium battery. However, for sodium, potassium, calcium, aluminum and magnesium based batteries, other salts can be dissolved in the solvents, for example sodium, potassium, calcium, aluminum and magnesium salts.
The voice of the conducting salt has an impact on anodic dissolution. For example, for an electrolyte containing less of the carbonate compound of formula (I) of the present invention, the addition of a passivating conducting salt will produce an electrolyte which nonetheless prevents anodic dissolution of aluminum. Some inorganic salts like LiPF6 passivate the surface of the aluminum, as they form insoluble compounds and thus do not cause anodic dissolution up to more than 5 V vs Li anodes. In contrast, some salts do not passivate aluminum, especially lower fluorinated sulfonyl amides, which cause a very strong dissolution of aluminum. As mentioned, this can lead to malfunctioning of the battery system if its operating voltage surpasses the critical potential. When such conducting salts are used, it is preferable to include more of the carbonate compound of formula (I) in the electrolyte so as to further prevent anodic dissolution.
The conducting salt can be chosen from: LiClO4; LiP(CN)αF6-α, where α is an integer from 0 to 6, preferably LiPF6; LiB(CN)βF4-β, where β is an integer from 0 to 4, preferably LiBF4; LiP(CnF2n+1)γF6_γ, where n is an integer from 1 to 20, and γ is an integer from 1 to 6; LiB(CnF2n+1)δF4-δ, where n is an integer from 1 to 20, and δ is an integer from 1 to 4; Li2Si(CnF2n+1)εF6-ε, where n is an integer from 1 to 20, and ε is an integer from 0 to 6; lithium bisoxalato borate; lithium difluorooxalatoborate; and compounds represented by the following general formulas:
wherein
R3 represents: Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Al, hydrogen, or an organic cation; and
R4, R5, R6, R7, R8 represent cyano, fluorine, chlorine, branched or linear alkyl radical with 1-24 carbon atoms, perfluorinated linear alkyl radical with 1-24 carbon atoms, aryl or heteroaryl radical, or perfluorinated aryl or heteroaryl radical;
and their derivatives.
In preferred embodiments, the conducting salt is a lithium salt. This is appropriate when, for example, the electrolyte will be used in a lithium or lithium-ion battery. Non-limiting examples of lithium salts include the above salts, preferably lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium sulfonyl amide salts (such as lithium bis(fluorosulfonyl)amide, lithium N-fluorosulfonyl-trifluoromethanesulfonyl amide (LiFTFSI), and lithium bis(trifluoromethanesulfonyl)amide) and their derivatives. In preferred embodiments, the conducting salt is a lithium sulfonylamide salt. In preferred embodiments, the lithium sulfonyl amide salt is lithium bis(fluorosulfonyl)amide (LiFSI), lithium bis(trifluoromethanesulfonyl)amide (LiTFSI), or lithium N-flurosulfonyl-trifluoromethanesulfonyl amide (LiFTFSI). In more preferred embodiments, the conducting salt is LiFSI. This is appropriate when, for example, the electrolyte is to be used in a lithium-ion battery. Indeed, an important advantage of the electrolyte of the present invention is that it enables use of lithium sulfonylamide salts in battery systems where the upper potential limit of the cathode is above 4.2 V vs Li metal.
In alternative embodiments, the salt is a sodium, a potassium, calcium, aluminum, or a magnesium salt such as those listed above. This is appropriate when, for example, the electrolyte is to be used in a sodium-, potassium-, calcium-, aluminum-, or magnesium-based battery.
The concentration of the conducting salt present in the electrolyte may vary; the skilled person would understand that the quantity of conducting salt should not severely negatively impact the efficacy of the electrolyte. The concentration of the conducting salt refers to the molarity of the conducting salt in the carbonate solvent and any other solvents (if present), disregarding the presence of additives. This can be represented by the following equation:
wherein the volume of the electrolyte is the final total volume of the carbonate compound of formula (I), the dissolved salt, and any liquid additive present
In embodiments, the concentration of the conducting salt is at least about 0.05 M and/or at most about 3 M. In embodiments, the concentration of the conducting salt is at least about 0.05 M, at least about 0.1 M, at least about 0.5 M, or at least about 1 M, and/or at most about 3 M, at most about 2 M, at most about 1.5 M, or at most about 1 M.
In preferred embodiments, the concentration of the conducting salt is 1 M.
Additives that Improve the Electrochemical Properties of the Electrolyte
In embodiments, the electrolyte further comprises one or more additives, which are used to improve the electrochemical properties of the electrolyte. Non-limiting examples of additives that improve the electrochemical properties of the electrolyte include:
It will be understood by the skilled person that one additive can have more than one specific technical effect on the electrolyte and thus may be cited in more than one of the above lists of exemplary additives with different preferred concentration ranges according to the effect desired of the additive.
Agents that improve solid electrolyte interphase and cycling properties are preferably present in the electrolyte. Non-limiting examples of agents that improve solid electrolyte interphase and cycling properties include ethylene carbonate, vinylene carbonate, fluorovinylene carbonate, succinic anhydride, malefic anhydride, fluoroethylene carbonate, difluoroethylene carbonate, methylene-ethylene carbonate, prop-1-ene-1,3-sultone, acrylamide, fumaronitrile, and triallyl phosphate. Preferred agents that improve solid electrolyte interphase and cycling properties include ethylene carbonate (EC) and fluoroethylene carbonate (FEC).
Unsaturated carbonates are optionally present in the electrolyte. Non-limiting examples of unsaturated carbonates that improve stability at high and low voltages include vinylene carbonate and derivatives of ethene (that is, vinyl compounds) like methyl vinyl carbonate, divinylcarbonate, and ethyl vinyl carbonate.
Organic solvents that diminish viscosity and increase conductivity are optionally present in the electrolyte. In preferred embodiments, such organic solvents are present Non-limiting examples of organic solvents that diminish viscosity and increase conductivity include polar solvents, preferably alkyl carbonates, alkyl ethers, and alkyl esters. For example, the organic solvent may be ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dimethoxyethane, diglyme (diethylene glycol dimethyl ether), triglyme (triethylene glycol dimethyl ether), tetraglyme ((tetraethylene glycol dimethyl ether), tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 1,4-dioxane, 1,3-dioxane, methoxypropionitril, propionitril, butyronitrile, succinonitrile, glutaronitrile, adiponitrile, esters of acetic acid, esters of propionic acid, cyclic esters like γ-butyrolactone, ε-caprolactone, esters of trifluoroacetic acid, sulfolane, dimethyl sulfone, ethyl methyl sulfone, or peralkylated sulfamides. In embodiments, ionic liquids could also be added in order to diminish flammability and to increase conductivity. Preferred organic solvents that diminish viscosity and increase conductivity include ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).
In embodiments, the agent(s) that improve solid electrolyte interphase (SEI) and cycling properties and the unsaturated carbonate(s), taken together, represents a total of at least about 0.1% and/or at most about 20% of the total mass of the electrolyte. In embodiments, the amount of these additives represents a total of at least about 0.1% w/w, at least 1% w/w, at least about 2% w/w, at least about 5% w/w, or at least about 7% w/w, and/or at most about 20% w/w, at most about 15% w/w, at most about 10% w/w, or at most about 7% w/w of the total weight of the electrolyte.
In embodiments, the organic solvents that diminish viscosity and increase conductivity represents a total of at least about 1% v/v and/or at most about 80% v/v of the total volume of the electrolyte. In embodiments, the f organic solvents represents a total of at least about 1% v/v, at least about 2% v/v, at least about 5% v/v, or at least about 7% v/v, and/or at most about 80% v/v, at most about 50% v/v, at most about 20% v/v, at most about 15% v/v, at most about 10% v/v, or at most about 7% v/v of the total volume of the electrolyte.
In preferred embodiments, the additives are fluoroethylene carbonate (FEC), ethylene carbonate (EC), diethyl carbonate (DEC), or a mixture thereof.
In more preferred embodiments, the additives are FEC, preferably about 2 w/w % of FEC, alone or together with EC, DEC or a mixture thereof, preferably alone or together with:
In embodiments, the volume ratio of ethylene carbonate (EC) to diethyl carbonate (DEC) in the mixture of EC and DEC is from about 1:10 to about 1:1, preferably this volume ratio is about 3:7.
In preferred embodiments, the additives are ethylene carbonate and fluoroethylene carbonate only (preferably in the above-mentioned quantities).
In more preferred embodiments, the additive is fluoroethylene carbonate only (preferably in the above-mentioned quantity).
In preferred embodiments, the electrolyte is free of corrosion inhibitors. Indeed, as noted above, one of the advantages of the carbonate compounds of formula (I) is that they are characterized by their low corrosiveness against aluminum current collectors, even at voltages higher than 4.2 V.
In alternative embodiments, the electrolyte further comprises one or more corrosion inhibitors. Non-limiting examples of corrosion inhibitors include LiPF6, lithium cyan fluorophosphates, lithium fluoro oxalatophosphates, LiDFOB, LiBF4, lithium fluoro cyanoborates, and LiBOB.
In embodiments, the corrosion inhibitors represent a total of at least about 1% and/or at most about 35% of the total weight of the electrolyte. In embodiments, the total amount of corrosion inhibitors represents at least about 1% w/w, at least about 2% w/w, at least about 5% w/w, or at least about 10% w/w, and/or at most about 35% w/w, at most about 25% w/w, at most about 20% w/w, at most about 15% w/w, at most about 10% w/w, or at most about 7% w/w of the total weight of the electrolyte.
The skilled person would understand that the concentration of carbonate compound of formula (I) in the electrolyte will be influenced by various factors, such as the desired concentration of the conducting salt, and the quantity of the above additives and corrosion inhibitors.
Nevertheless, the electrolyte of the present invention should contain the carbonate compound of formula (I) in a concentration sufficient to achieve a desired anodic dissolution suppression.
In practice, the concentration of carbonate compound of formula (I) necessary to achieve suppression of anodic dissolution will vary depending on various factors, such as the intended operating voltage and presence of corrosion inhibitors. Generally, when corrosion inhibitors are present, a lower concentration of the carbonate compound of formula (I) will be needed to achieve a desired suppression of anodic dissolution.
In preferred embodiments, the carbonate compound of formula (I) represents at least about 25% v/v, preferably at least about 50% v/v, more preferably at least about 75% v/v, yet more preferably at least about 85% v/v, even more preferably at least about 90% v/v, and most preferably at least about 95%, of the total volume of the electrolyte.
In alterative embodiments in which the electrolyte comprises one or more corrosion inhibitors as described in the previous section, the carbonate compound of formula (I) can be present at lower concentrations. For example at a concentration of at least about 10% v/v, preferably at least about 15% v/v, more preferably at least about 20% v/v, yet more preferably at least about 25% v/v, and most preferably at least about 30%, based on the volume of the electrolyte.
In preferred embodiments, the electrolyte of the invention is free of other solvents. In other words, the only solvent in the electrolyte is the carbonate compound of formula (I).
As noted above the battery of the present invention is comprised of:
(a) a cathode comprising an aluminum current collector,
(b) an anode,
(c) a separator membrane separating the anode and the cathode, and
(d) a low-corrosiveness non-aqueous electrolyte in contact with the anode and the cathode.
As noted above, this battery, in preferred embodiments, is a lithium battery, a lithium-ion battery, a sodium battery, a sodium-ion battery, a potassium battery, a potassium-ion battery, a magnesium battery, a magnesium-ion battery, an aluminum battery, or an aluminum ion battery.
The choice of non-aqueous solvent, anode, cathode, and separator membrane will vary depending on the type of battery. If the battery is a lithium-ion battery, it would be more appropriate to choose, for example, an electrolyte comprising lithium salt, such as a lithium sulfonyl amide salt as a conducting salt. However, if the battery is a sodium-based battery, it would be more appropriate to choose, for example, an electrolyte comprising a sodium salt as a conducting salt.
The non-aqueous electrolyte is the electrolyte defined in the previous section.
The anode can be any anode typically used for a battery.
In preferred embodiments, the anode is one that is suitable for a lithium or a lithium ion battery. Such anodes are usually made of Li metal, carbonaceous materials (graphite, coke, and hard carbon), silicon and its alloys, tin and its alloys, antimony and its alloys, and/or lithium titanate (Li4Ti5O12). These materials are usually mixed with a solvent, a polymer binder and electro-conductive additives—which include various forms of conductive carbon, such as carbon nanotubes and carbon black—and subsequently coated on a copper current collector in order to obtain the anode. In preferred embodiments, the anode is made of lithium metal or graphite.
As one advantage of using the electrolyte of the present invention is the prevention of anodic dissolution of aluminum current collectors, the cathode can be any cathode typically used for a battery that comprises an aluminum current collector.
In preferred embodiments, the cathode is one that is suitable for a lithium or a lithium ion battery. Such cathodes usually comprise lithium compounds. These lithium compounds are usually mixed with a solvent, polymer binder and electro-conductive additives—which include various forms of conductive carbon, such as carbon nanotubes and carbon black—and subsequently coated on an aluminum current collector in order to obtain the cathode. This aluminum current collector is susceptible to anodic dissolution at elevated potential, especially if the electrolyte contains non-passivating conducting salts. Such lithium compounds include lithiated oxides of transition metals like LCO (LiCoO2), LNO (LiNiO2), LMO (LiMn2O4), LiCoxNi1-xO2 wherein the x is from 0.1 to 0.9, LMN (LiMn3/2Ni1/2O4), LMC (LiMnCoO2), LiCuxMn2-xO4, NMC (LiNixMnyCozO2), NCA (LiNixCoyAlzO2), lithium compounds with transition metals and complex anions, LFP (LiFePO4), LNP (LiNiPO4), LMP (LiMnPO4), LCP (LiCoPO4), Li2FCoPO4; LiCoqFexNiyMnzPO4, and Li2MnSiO4.
In preferred embodiments, the cathode of the present invention is an LMN cathode or an LCO cathode.
In embodiments, the cathode comprises only the current collector.
In embodiments, the cathode is made by coating the current collector with the above described lithium compounds, preferably LMN or LCO. In preferred embodiments, the current collector is an aluminum current collector.
In order to prevent physical contact between electrodes, a separator membrane is usually placed between them. The separator membrane can be any separator membrane typically used for a battery.
In preferred embodiments, the separator membrane is one that is suitable for a lithium or a lithium ion battery. Mother function of such a separator membrane is to prevent lithium dendrite from causing a short-circuit between electrodes. Such separator membranes typically include (i) a polyolefin based porous polymer membrane, preferably made of polyethylene “PE”, polypropylene “PP”, or a combination of PE and PP, such as a trilayer PP/PE/PP membrane; (ii) heat-activatable microporous membranes; (iii) porous materials made of fabric including glass, ceramic or synthetic fabric (woven or non-woven fabric); (iv) porous membranes made of polymer materials such as polyvinyl alcohol), polyvinyl acetate), cellulose, and polyamide; (v) porous polymeric membranes provided with an additional ceramic layer in order to improve the performance at high potentials; and (vi) polymer electrolyte membranes. However, as mentioned, the separator membrane can also be any separator membrane typically used for a battery, preferably for a lithium or a lithium ion battery; for example Celgard 3501™ or Celgard Q20S1HX™.
Depending on the type of battery, a different cathode, anode, and separator membrane may be provided or prepared. Much like the electrolyte, the cathode, anode, and separator membrane can be prepared using any known technique in the art, and the battery can be prepared using any known technique in the art.
As noted above, the batteries of the present invention have a wide variety of applications that would be readily understood by the person of skill in the art. Such applications include electric vehicles, power tools, grid energy storage, medical devices and equipment, toys, hybrid electric vehicles, cell phones, laptops, and various military and aerospace applications.
In another aspect of the invention, a method for producing the above carbonate solvents and batteries is provided.
Each of the carbonate solvent, the electrolyte, and the battery of the present invention can be prepared using any known technique in the art.
For example, the carbonate solvents of the invention can be synthesised according to the following formula:
In the above formula, R6 represents both R1 and R2, defined above. Syntheses of alkyl carbonates are very well-developed processes. While the most convenient methods are discussed below, the skilled person would understand that other synthesis methods can be used.
Preparation of the carbonate solvents of the present invention in smaller scale is most conveniently accomplished by a base catalyzed transesterification of readily available dimethyl carbonate, diethyl carbonate, ethylene carbonate, or propylene with aliphatic alcohols in the presence of a suitable catalyst. The transesterification of carbonate esters obeys the same rules as transesterification of other esters, which is a typical equilibrium reaction, and can be easily controlled by the use of Le Chateliers' principle. The ratio between the alcohol and the carbonate ester determines the ratio of the products in a fully equilibrated reaction mixture. If a full substitution is desired, the excess of alcohol should be used. If the desired product is the mixed carbonate, the molar ratio should be close to 1, or a slight excess of starting carbonate should be used. During the reaction, it is desirable that the reaction products are steadily removed from the reaction mixture; this allows the reaction to proceed faster to completion. The separation is most conveniently done by fractional distillation of a lower alcohol. For this reason, the use of low carbonates is preferred over higher carbonates because the formed alcohol has a lower boiling point; however, attention must be paid to the formation of azeotropic mixtures which may complicate the separation.
The catalysts used for this transformation can be chosen from acids and from bases, but bases like alkali and earth alkali carbonates, oxides, hydroxides and alkoxides are preferred as they can be separated easily from the volatile products.
In a suitable reaction vessel equipped for a fractioning distillation, there is placed the appropriate amount of desired aliphatic alcohol and a certain amount of metallic sodium is added. The amount of sodium should be chosen so that it will react with the water present in the reactants and consume it all. In this way, a water free solvent can be isolated. The process of sodium dissolution can be accelerated by heating and stirring, which is necessary with all higher alcohols. A protective atmosphere of nitrogen or argon should be used to exclude the uptake of carbon dioxide and water from the atmosphere. When sodium is dissolved, the starting carbonate ester is added and the mixture is refluxed at such a temperature that the alcohol which is formed during the reaction distills from the reaction mixture, while all reactants remain in the reactor. After the reaction is finished, the components of the reaction mixture are separated by fractional distillation, under vacuum for higher alkyl carbonates. In this manner the solvents can be isolated in high purity if no azeotropes are formed.
However, the industrial preparation of symmetric carbonates can be performed by phosgenation of the corresponding alcohols.
When small amounts of mixed carbonate are desired, the most suitable method seems to be the reaction of an aliphatic alcohol with an aliphatic chloroformate in an aprotic solvent in the presence of a suitable base which binds the formed HCl. Even though this method is well established, it may sometimes give erroneous results.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or dearly contradicted by context.
The terms “comprising”, “having”, “including”, and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to”) unless otherwise noted.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All subsets of values within the ranges are also incorporated into the specification as if they were individually recited herein.
Similarly, herein a general chemical structure with various substituents and various radicals enumerated for these substituents is intended to serve as a shorthand method of referring individually to each and every molecule obtained by the combination of any of the radicals for any of the substituents. Each individual molecule is incorporated into the specification as if it were individually recited herein. Further, all subsets of molecules within the general chemical structures are also incorporated into the specification as if they were individually recited herein.
All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise dearly contradicted by context.
The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.
No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Herein, the term “about” has its ordinary mewing. In embodiments, it may mean plus or minus 10% or plus or minus 5% of the numerical value qualified.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the at to which this invention belongs.
For certainty, it should be noted that
Herein, the terms “alkyl” has its ordinary meaning in the art. It is to be noted that, unless otherwise specified, the hydrocarbon chain of the alkyl groups can be linear or branched.
Herein, the terms “aryl” has its ordinary meaning in the art. It is to be noted that, unless otherwise specified, the aryl groups can contain between 5 and 30 atoms, including carbon and heteroatoms, preferably without heteroatoms, more specifically between 5 and 10 atoms, or contain 5 or 6 atoms.
For clarity, the following abbreviations are used: EC—ethylene carbonate, PC—propylene carbonate, DEC—diethyl carbonate, EMC—ethyl methyl carbonate, DMC—methyl carbonate, FEC—fluoroethylene carbonate, VC—vinylene carbonate, LCO—LiCoO2-lithium cobaltate, LMN—LiMn3/2Ni1/2O4,
Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.
The present invention is illustrated in further details by the following non-limiting examples.
A brief summary of the nature of each Example is as follows:
Examples 1-4 involve the preparation of various carbonate solvents of the present invention.
Examples 5-7 are comparative examples wherein anodic dissolution is measured in button cells comprising conventional electrolytes.
Examples 8-10 measure anodic dissolution in button cells comprising electrolytes of the present invention.
Examples 11-54 involve measuring the starting potentials of anodic dissolution of various electrolytes of the present invention.
Examples 55 and 58 are comparative examples where charging and discharging of button cells comprising conventional electrolytes was measured.
Examples 56, 57, and 59 involve measuring the charging and discharging of button cells comprising electrolytes of the present invention.
Example 60 involves measuring the temperature range of an electrolyte of the present invention and a conventional electrolyte by performing a digital scanning calorimetry (DSC) experiment.
Example 61 involves measuring the discharge capacity of three cells versus cycle number; two of the cells comprise electrolytes of the present invention, while one comprises a conventional electrolyte.
In a 250 ml round bottom flask equipped with a Vigreux column is placed 128 g (1.73 mol) of isobutanol, in which 0.3 g sodium was dissolved at the baling pant and 59 g (0.66 mol) of dimethyl carbonate was added. The mixture was refluxed overnight with the separation of methanol formed. After the separation of the methanol ceased, the remainder was subjected to a fractional distillation, giving 120 g of diisobutyl carbonate as a colourless liquid. Unreacted isobutanol, dimethyl carbonate and isobutyl methyl carbonate were also detected in the preceding fraction. The structure of the products was confirmed by NMR (nuclear magnetic resonance spectroscopy), IR (infra-red spectroscopy) and GC/MS (gas chromatography with mass selective detector) analyses.
In a 250 ml round bottom flask equipped with a Vigreux column is placed 116 g (1316 mmol) of 2-pentanol, in which 1 g sodium was dissolved at 100° C. and 98 g (1088 mmol) of dimethyl carbonate was added. The mixture was refluxed over 48 h with the separation of methanol formed. After the separation of the methanol ceased, the remainder was subjected to a vacuum fractional distillation, giving a smaller fraction of 40 g containing pure methyl 2-pentyl carbonate and a main fraction of 70 g of di(2-pentyl) carbonate as a colourless liquid. Unreacted dimethyl carbonate, 2-pentanol and methanol were also detected in the preceding fractions. The structure of the products was confirmed by NMR, IR and GC/MS analyses.
In a 250 ml round bottom flask is placed 7.1 g (100 mmol) of 3-hydroxypropinonitril, 11 g of a freshly distilled triethyl amine, and 150 ml dry dichloromethane. The mixture was cooled under nitrogen in an ice water bath and a solution of 13.66 g (100 mmol) of butyl chloroformate in 30 ml of dichloromethane was added dropwise. After the addition, the mixture was stirred at room temperature for 2 h, after which water and sulfuric acid were added and the mixture was separated by means of a separation funnel. The organic phase was washed 4 times with water, and then dried with anhydrous magnesium sulfate, filtered, and evaporated. Distillation of the remaining clear oil gave pure product (13.1 g). Structure of the products was confirmed by NMR, IR and GC/MS analyses.
Other dialkylcarbonates were prepared similarly to the procedures in examples 1-3 and all are listed in the following table (Table 1) together with their 1H and 13C NMR spectroscopy data.
1H NMR (400 MHz,
29Si NMR (79 MHz,
In the following examples, anodic dissolution of an aluminum current collector was measured. Detection of anodic dissolution of an aluminum current collector can be realised by many electrochemical methods. One indicator of anodic dissolution is the current which appears between the reference electrode and the bae aluminum electrodes at a certain potential. Anodic dissolution is strongly dependent on the applied potential, so the variation of the potential during anodic dissolution probing is essential.
In light of the above, in the following Examples, anodic dissolution of an aluminum current collector was measured using chronoamperometry, CA. Chronoamperometry involves measuring the current at a given potential and is usually performed over a longer period of time; accordingly, even the slowest processes can be detected in that manner. For the following examples, chronoamperometry was used for 1 h at potentials between 4-5.5 V vs Li metal by 0.1 V steps (1 hour of CA at 4.0, 4.1, 4.2, etc., until 5.5 V). This enables relatively fast screening of the electrolytes.
The chronoamperometry results are shown in
In general, it was found that in electrolytes obtained by dissolution of LiFSI, LiFTFSI and LiTFSI in mixtures of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC), significant anodic dissolution appeared between 4.1 and 4.3 V vs Li metal, detected as a high current/current density between electrodes (
However, it was found that LiFSI, LiFTFSI and LiTFSI, when dissolved in higher, preferably branched, dialkyl carbonate, where the total number of carbon atoms was equal to or greater than 4, did not cause anodic dissolution of the aluminum current collector, in some cases even at potentials over 5 V vs Li metal (
1M solution of LiFSI (Nippon Shokubai) in a conventional industrial solvent mixture of ethylene carbonate and diethyl carbonate (EC/DEC), in volume ratio of 3:7, was prepared and 2 wt % of fluoroethylene carbonate was added.
A button cell was assembled using a disc of 16 mm diameter, with a 15 μm thickness of non-coated aluminum current collector, provided by UACJ as a cathode. Celgard 3501 was used as a separator membrane and the aforementioned LiFSI-EC-DEC electrolyte was also used. A 16 mm, 200 μm thick disc of lithium metal, provided by China Energy Lithium Co., LTD., was used as an anode. The cell was used for probing the anodic dissolution of the cathode during chronoamperometry for 1 h at potentials between 4 and 5.5 V vs Li metal at 0.1 V steps (1 hour of chronoamperometry at 4.0, 4.1, 4.2 . . . 5.5 V). The results of this experiment can be seen in
A button cell was assembled and tested according to example 5 but using a 1M solution of LiFTFSI in a conventional industrial solvent mixture of ethylene carbonate/diethyl carbonate, EC/DEC, in a volume ratio of 3:7, and 2 wt % of fluoroethylene carbonate, as an electrolyte. The results of this experiment can be seen in
A button cell was assembled and tested according to example 5 but using a 1M solution of LiTFSI (available from 3M™) in a conventional industrial solvent mixture of ethylene carbonate and diethyl carbonate, EC/DEC, in a volume ration of 3:7, and 2 wt % of fluoroethylene carbonate, as an electrolyte. The results of this experiment can be seen on
1M solution of LiFSI (Nippon Shokubai) in diisobutyl carbonate (Solvent no. 10 prepared according to Example 1) was prepared, to which 2 wt % of fluoroethylene carbonate was added.
A button cell was assembled and tested according to Example 5 but using the preceding LiFSI-diisobutyl carbonate electrolyte. The results of this experiment can be seen in
1M solution of LiFTFSI in diisobutyl carbonate (Solvent no. 10) was prepared according to example 1, to which 2 wt % of fluoroethylene carbonate was added.
A button cell was assembled and tested according to example 5 but using the preceding LiFTFSI-diisobutyl carbonate electrolyte. The results of this experiment can be seen in
1M solution of LiTFSI in diisobutyl carbonate (Solvent no. 10) was prepared according to example 1, to which 2 wt % of fluoroethylene carbonate was added.
A button cell was assembled and tested according to example 5 but using the preceding LiTFSI-diisobutyl carbonate electrolyte. The results of this experiment can be seen in
Button cells were assembled and tested according to example 5 but using each of the electrolytes listed in the following table (Table 2) with the previous results. The results of this experiment are presented as the potential where significant anodic dissolution of aluminum occurs and represents a safe use limit for said electrolyte. Several examples have been made in order to illustrate the mixing possibilities of different solvents in order to get an electrolyte with enhanced conductivity, while maintaining the effect of suppressing anodic dissolution.
In the table below, “EC/DEC (3:7 vol)” denotes an EC/DEC mixture in a 3:7 volume ratio.
An LCO cathode material was prepared using a mixture of LCO, VGCF (vapour grown carbon nanotubes), carbon black and polyvinylidene fluoride (PVDF) in a ratio 89:3:3:5 by weight in N-methyl-2-pyrrolidone (NMP). The mixture was then coated on a 15 μm thick non-coated aluminum current collector, provided by UACJ. The electrode material was calendered, cut into discs and dried at 120° C. in a vacuum oven for 12 h before use.
A button cell was assembled using one of the above-described discs (16 mm diameter) of LCO as a cathode, Celgard Q20S1HX as separator membrane, the electrolyte of comparative example 5, and a 16 mm, 200 μm thick disc of lithium metal, provided by China Energy Lithium Co., LTD., as an anode.
The cell was used for probing the charging and discharging between 3 and 4.5 V at C/24 rate. The results of this experiment can be seen in
A button cell was assembled using a disc of 16 mm diameter LCO as a cathode (prepared using the process described in Example 55), Celgard Q20S1HX as separator membrane, the electrolyte of example 8, and a 16 mm, 200 μm thick disc of lithium metal, provided by China Energy Lithium Co., LTD., as an anode.
The cell was used for probing the charging and discharging between 3 and 4.5 V at C/24 rate. The results of this experiment can be seen in
The electrolyte of example 33 (i.e. a 1M solution of LiFSI (Nippon Shokubai) in a 1:9 mixture by volume of ethylene carbonate (EC) and diisobutyl carbonate (solvent no. 10), respectively, to which 2% of fluoroethylene carbonate was added) was prepared. Note that this electrolyte is similar to the electrolyte of example 56 except that solvent no. 10 was replaced by a 1:9 mixture by volume of EC and solvent no. 10. In other words, EC is used as an additive herein.
A button cell was assembled using a disc of 16 mm diameter LCO coated on a 15 μm thick aluminum current collector (prepared using the process described in Example 55), provided by UACJ, as a cathode; Celgard Q20S1HX as a separator membrane; the preceding LiFSI-EC-diisobutyl carbonate electrolyte; and a 16 mm, 200 μm thick disc of lithium metal, provided by China Energy Lithium Co., LTD., as an anode.
The cell was used for probing the charging and discharging between 3 and 4.5 V at C/24 rate. The results of this experiment can be seen in
A LiMn3/2Ni1/2O4 (LMN) cathode material was prepared using a mixture of LMN, VGCF (vapour grown carbon nanotubes), carbon black and polyvinylidene fluoride (PVDF) in a ratio of 94:1.5:1.5:3 by weight in NMP. The mixture was then coated on a 15 μm thickness of non-coated aluminum current collector, provided by UACJ. The electrode material was calendered, cut into discs and dried at 120° C. in a vacuum oven for 12 h before use.
A button cell was assembled using a disc of 16 mm diameter LMN as a cathode, Celgard Q20S1HX as a separator membrane, the electrolyte of comparative example 5, and a 16 mm, 200 μm thick disc of lithium metal, provided by China Energy Lithium Co., LTD., as an anode.
The cell was used for probing the charging and discharging between 3.5 and 4.9 V at C/24 rate. The results of this experiment can be seen in
A button cell was assembled using a disc of 16 mm diameter LMN as a cathode (prepared using the process described in Example 58), Celgard Q20S1HX as separator membrane, the electrolyte of example 8, and a 16 mm, 200 μm thick disc of lithium metal, provided by China Energy Lithium Co., LTD., as an anode.
The cell was used for probing the charging and discharging between 3.5 and 4.9V at C/24 rate. The results of this experiment can be seen in
A digital scanning calorimetry experiment was performed on the electrolyte of example 33 and on the electrolyte of comparative example 5.
The electrolyte of comparative example 5 exhibited a melting pant of −10° C. and a glass transition point of −111° C. In contrast, the electrolyte of the invention showed no melting point and a glass transition point of 98° C. In other words, the electrolyte of example 33 stayed in liquid form and eventually in amorphous solid form, without crystallizing, until it reached its glass transition point of −98° C. This indicates that the electrolyte of the invention can be used at lower temperatures than conventional electrolytes without crystallisation.
Electrolytes from example 8 (LIFSI in diisobutyl carbonate, 2% of FEC) and example 33 (LiFSI in 90% diisobutyl carbonate:10% EC, 2% of FEC) and a conventional electrolyte of 1 M LiPF6 in EC/DEC (3:7 vol) with 2% of FEC were tested.
A graphite electrode was prepared by Cumstomcells Company by mixing 96% of modified graphite (SMG), 2% of water-based binder, and 2% of electronic conductivity enhancer in water; coating the mixture onto a 14 μm thick copper foil; drying it and calendering it. The resulting electrode material was cut into discs and dried at 120° C. in a vacuum oven for 12 h before use.
Li-ion button cells were assembled using a disc of 16 mm diameter LCO coated on 15 μm thick aluminum current collector (as in example 55), provided by UACJ, as a cathode; Celgard Q20S1HX as separator membrane; one of the above-listed electrolytes; and the above-prepared 16 mm disc of graphite electrode as an anode.
The cells were subjected to three formation cycles—the charging and discharging between 3 and 4.4 V at C/24 rate. After that, the cells were subjected to long term cycling with charging at C/4, followed by a 30 min float at 4.4 V and C/4 discharge. The results of this experiment—the discharge capacity of the cells versus cycle number—can be seen in
With this experiment, the utilisation electrolytes prepared of LIFSI in the solvents of the present invention in high voltage Li-ion batteries has been demonstrated, while the utilisation of LiFSI in conventional solvents is not possible for this battery system.
The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety. These documents include, but are not limited to, the following:
| Number | Date | Country | Kind |
|---|---|---|---|
| 1904075 | Apr 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/053563 | 4/15/2020 | WO | 00 |
