Patent Application
20240332625
The present disclosure pertains to the field of lithium-ion battery technologies, relates to a battery, and specifically relates to a high-voltage lithium-ion battery having excellent high and low temperature performance.
In recent years, lithium-ion batteries have been widely used in a smartphone, a tablet computer, an intelligent wearing, an electric tool, an electric vehicle, and other fields. With increasing application of lithium-ion batteries, use environment and requirements of consumers for lithium-ion batteries are constantly improving. This requires that lithium-ion batteries have high safety while taking high and low temperature performance into account.
Currently, there is a potential safety hazard in a use process of lithium-ion batteries. For example, when a battery is in some extreme use cases such as a continuous high temperature, a serious safety accident such as a fire or even an explosion may occur. A main reason for the above problem is that a structure of a positive electrode material is unstable at high temperature and high voltage, metal ions are easily dissolved from the positive electrode and reduced and deposited on a surface of a negative electrode, thereby destroying an SEI film structure on the surface of the negative electrode, and resulting in an increasing negative electrode impedance and an increasing battery thickness. This makes a temperature of a cell continuously increase, and causes a safety accident when heat is continuously accumulated and cannot be released.
To resolve the above technical problem, currently, a flame retardant (such as trimethyl phosphate) is added to an electrolyte solution to improve high-temperature performance and safety performance of a battery. However, use of the above flame retardant often causes serious performance degradation of the battery.
Therefore, it is very important to develop a battery having both good high and low temperature performance and high safety performance.
To overcome defects in the conventional technology, the present disclosure aims to provide a battery. In the battery, an electrolyte solution cooperates with a positive electrode plate and a negative electrode plate to improve the high-temperature storage performance, low-temperature discharge performance, and safety performance of the battery, so that the battery is enabled to have both good high and low temperature performance and high safety performance.
To achieve the foregoing objective, the following technical solution is used in the present disclosure.
A battery is provided. The battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution, where the positive electrode plate includes a positive electrode active material; the negative electrode plate includes a negative electrode active material; the electrolyte solution includes an organic solvent, an additive and an electrolyte salt; and the electrolyte salt includes at least one compound represented by Formula 1 and/or at least one compound represented by Formula 2:
In an example, the compound represented by Formula 1 and the compound represented by Formula 2 are aluminum salt compounds.
In the present disclosure, the electrolyte solution of the battery contains the aluminum salt compound. The aluminum salt compound can sufficiently form a passivation coating protective layer that is rich in Al2O3 and AlF3 on a surface of a positive electrode, which can effectively protect the positive electrode active material, thereby inhibiting metal ions from dissolving out to catalyze side reaction decomposition of the electrolyte solution, and effectively improving the high-temperature storage performance and safety performance of the battery. In addition, the aluminum salt compound can also sufficiently reduce the surface tension of the electrolyte solution and inhibit the growth of lithium dendrites, thereby reducing a contact angle between the electrolyte solution and the negative electrode plate, and improving the infiltration of the electrolyte solution, the transmission rate of ions, and the low-temperature discharge performance of the battery. The aluminum salt compound can improve the interfacial compatibility of the battery, thereby effectively inhibiting a side reaction between an electrode and an electrolyte solution. This comprehensively improves the cell performance of the battery, thereby obtaining a battery that has not only high safety performance but also good high-temperature storage performance, high-temperature cycling performance and low-temperature discharge performance.
The battery may satisfy: a ratio of (A+B) to C ranges from 10 to 1000. For example, the ratio is 10, 50, 100, 150, 200, 250, 300, 400, 450, 500, 550, 600, 700, 800, 900, 1000, or a point value in a range formed by any two of the foregoing values. When the ratio of (A+B) to C ranges from 10 to 1000, the compound represented by Formula 1 and/or the compound represented by Formula 2 (namely, the aluminum salt compound) can more sufficiently form a passivation coating protective layer that is rich in Al2O3 and AlF3 on a surface of a positive electrode, which effectively protects the positive electrode active material, thereby inhibiting metal ions from dissolving out to catalyze side reaction decomposition of the electrolyte solution, and effectively improving the high-temperature storage performance and safety performance of the battery. Further, the compound represented by Formula 1 and/or the compound represented by Formula 2 can more sufficiently reduce the surface tension of the electrolyte solution and inhibit the growth of lithium dendrites, thereby reducing a contact angle between the electrolyte solution and the negative electrode plate, and improving the infiltration of the electrolyte solution, the transmission rate of ions, and the low-temperature discharge performance of the battery. When the ratio of (A+B) to C ranges from 10 to 1000, the compound represented by Formula 1 and/or the compound represented by Formula 2 can more sufficiently cooperate with the positive and negative electrode active materials to play a synergistic effect, thereby improving the interfacial compatibility of the battery, and effectively inhibiting a side reaction between an electrode and an electrolyte solution. This comprehensively improves the cell performance of the battery. Therefore, the battery has both good high and low temperature performance and high safety performance.
The percentage of the mass of the compound represented by Formula 1 and/or the compound represented by Formula 2 in the total mass of the electrolyte solution indicates that when the electrolyte solution includes only the compound represented by Formula 1 or the compound represented by Formula 2, C denotes a percentage of a mass of the compound represented by Formula 1 or the compound represented by Formula 2 in the total mass of the electrolyte solution, and that when the electrolyte solution includes both the compound represented by Formula 1 and the compound represented by Formula 2, C denotes a percentage of a total mass of the compound represented by Formula 1 and the compound represented by Formula 2 in the total mass of the electrolyte solution.
Beneficial effects of the present disclosure are as follows.
The present disclosure provides a battery. Inventors of the present disclosure find that the low-temperature performance, high-temperature cycling performance, high-temperature storage performance, and safety performance of the battery can be effectively improved due to the synergistic effect of the positive and negative electrode active materials and aluminum salt compounds (namely, the compound represented by Formula 1 and/or the compound represented by Formula 2) in the electrolyte solution.
The present disclosure is further described in detail below with reference to specific examples. It should be understood that the following examples are merely for the purposes of illustrating and explaining the present disclosure, and should not be construed as limiting the scope of protection of the present disclosure. Any technology implemented based on the foregoing contents of the present disclosure falls within the intended scope of protection of the present disclosure.
In an example, a specific surface area A of the positive electrode active material ranges from 0.05 m2/g to 1 m2/g. For example, A is 0.05 m2/g, 0.1 m2/g, 0.2 m2/g, 0.3 m2/g, 0.4 m2/g, 0.5 m2/g, 0.6 m2/g, 0.7 m2/g, 0.8 m2/g, 0.9 m2/g, or 1 m2/g. Preferably, A ranges from 0.1 m2/g to 0.4 m2/g. The specific surface area of the positive electrode active material can be tested by a conventional nitrogen adsorption method. For example, at a constant temperature (260° C.), changing a nitrogen pressure (ranging from 0.1 MPa to 0.15 MPa) until gas reaches an equilibrium state on a surface of a sample; and a adsorption isotherm is measured at a certain relative pressure range and a certain temperature, and a specific surface area of the sample is calculated based on a adsorption isotherm formula obtained by the adsorption isotherm.
In an example, a specific surface area B of the negative electrode active material ranges from 0.5 m2/g to 5 m2/g. For example, B is 0.5 m2/g, 0.6 m2/g, 0.7 m2/g, 0.8 m2/g, 0.9 m2/g, 1 m2/g, 1.5 m2/g, 1.8 m2/g, 2 m2/g, 2.5 m2/g, 3 m2/g, 3.5 m2/g, 4 m2/g, 4.5 m2/g, or 5 m2/g. Preferably, B ranges from 0.9 m2/g to 2 m2/g. The specific surface area of the negative electrode active material can be tested by a conventional nitrogen adsorption method. For example, at a constant temperature (260° C.), changing a nitrogen pressure (ranging from 0.1 MPa to 0.15 MPa) until gas reaches an equilibrium state on a surface of a sample; and a adsorption isotherm is measured at a certain relative pressure range and a certain temperature, and a specific surface area of the sample is calculated based on a adsorption isotherm formula obtained by the adsorption isotherm.
In an example, in Formula 1, R1, R2, R3, and R4 are the same as or different from each other, and are each independently selected from substituted or unsubstituted C1-6 alkyl; and the substituent is halogen, or halogen-substituted or unsubstituted C1-6 alkyl.
In an example, in Formula 1, R1, R2, R3, and R4 are the same as or different from each other, and are each independently selected from substituted or unsubstituted C1-3 alkyl; and the substituent is halogen, or halogen-substituted or unsubstituted C1-3 alkyl.
In an example, in Formula 1, R1, R2, R3, and R4 are the same as or different from each other, and are each independently selected from substituted methyl, substituted ethyl, or substituted propyl; and the substituent is fluorine, fluorine-substituted or unsubstituted methyl, or fluorine-substituted or unsubstituted ethyl.
In an example, in Formula 2, R5, R6, R7, and R8 are the same as or different from each other, and are each independently selected from —C(—O)—, or substituted or unsubstituted C1-6 alkylene; and the substituent is halogen, or halogen-substituted or unsubstituted C1-6 alkyl.
In an example, in Formula 2, R5, R6, R7, and R8 are the same as or different from each other, and are each independently selected from —C(═O)—, or substituted or unsubstituted C1-3 alkylene; and the substituent is halogen, or halogen-substituted or unsubstituted C1-3 alkyl.
In an example, in Formula 2, R5, R6, R7, and R8 are the same as or different from each other, and are each independently selected from —C(═O)—, substituted or unsubstituted methylene, or substituted or unsubstituted ethylidene; and the substituent is fluorine, fluorine-substituted or unsubstituted methyl, or fluorine-substituted or unsubstituted ethyl.
In an example, the compound represented by Formula 1 is selected from a compound represented by the following Formula T1:
In an example, the compound represented by Formula 2 is selected from at least one of compounds represented by the following formulas T2 to T4:
In an example, a mass of the compound represented by Formula 1 and/or the compound represented by Formula 2 accounts for 0.1 wt % to 16 wt % of the total mass of the electrolyte solution. For example, the percentage is 0.2 wt %, 0.5 wt %, 0.8 wt %, 1 wt %, 1.5 wt %, 2 wt %, 2.5 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, or 16 wt %. Preferably 0.2 wt % to 12 wt %.
In an example, a mass of the electrolyte salt accounts for 10 wt % to 20 wt % of the total mass of the electrolyte solution.
In an example, the electrolyte salt further includes a lithium salt.
In an example, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulphonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium hexafluorophosphate.
In an example, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer coated on a surface of either or both sides of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material is selected from lithium cobaltate oxide or lithium cobaltate oxide doped and coated with two or more elements in Al, Mg, Mn, Cr, Ti, or Zr. A chemical formula of the lithium cobaltate oxide doped and coated with two or more elements in Al, Mg, Mn, Cr, Ti, or Zr is LixCo1-y1-y2-y3-y4Ay1By2Cy3Dy4O2, where 0.95≤x≤1.05, 0.01≤y1≤0.1, 0.01≤y2≤0.1, 0≤y3≤0.1, 0≤y4≤0.1, and A, B, C, and D are selected from two or more elements in Al, Mg, Mn, Cr, Ti, or Zr.
In an example, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer coated on a surface of either or both sides of the negative electrode current collector. The negative electrode active material layer includes the negative electrode active material, a conductive agent, and a binder. The negative electrode active material is selected from one or more of artificial graphite, natural graphite, hard carbon, mesocarbon microbead, lithium titanate, silicon carbon, or silicon monoxide.
In an example, the electrolyte solution further includes 1-ethyl-3-methylimidazolium heptachlorodialuminate (CAS No.: 87587-77-7). 1-ethyl-3-methylimidazolium heptachlorodialuminate in the electrolyte solution may form a strong SEI film on a surface of a negative electrode, which can effectively inhibit reduction and decomposition of the electrolyte solution on the surface of the negative electrode, reduce a side reaction on an interface of the negative electrode, and improve the cycling performance of a cell. The positive electrode and the negative electrode are cooperatively combined with the electrolyte solution, which helps the cell have all of high-temperature storage performance, cycling performance, low-temperature discharge performance, and safety performance.
In an example, a percentage of a mass of 1-ethyl-3-methylimidazolium heptachlorodialuminate in the total mass of the electrolyte solution ranges from 0.1 wt % to 2 wt %. For example, the percentage is 0.1 wt %, 0.2 wt %, 0.3 wt %, 0.4 wt %, 0.5 wt %, 0.6 wt %, 0.7 wt %, 0.8 wt %, 0.9 wt %, 1.0 wt %, 1.1 wt %, 1.2 wt %, 1.3 wt %, 1.4 wt %, 1.5 wt %, 1.6 wt %, 1.7 wt %, 1.8 wt %, 1.9 wt %, or 2 wt %.
In an example, the electrolyte solution further includes one or more of a nitrile compound, a sulfur-containing compound, or a carbonate compound.
In an example, the additive includes one or more of a nitrile compound, a sulfur-containing compound, or a carbonate compound.
In an example, the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, glycerol trinitrile, ethoxy (pentafluoro)phosphazene, or 1,3,6-hexanetrionitrile.
In an example, the sulfur-containing compound is selected from one or more of 1,3-propane sultone, 1-propene 1,3-sultone, ethylene sulfate, or vinylene sulfate.
In an example, the carbonate compound is one or both of ethylene carbonate or vinylethylene carbonate.
In an example, a percentage of a mass of the additive in the total mass of the electrolyte solution ranges from 6 wt % to 20 wt %. For example, the percentage is 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, or 20 wt %.
In an example, the organic solvent is selected from at least one of carbonate, carboxylic acid ester, or fluorinated ether. The carbonate is selected from one or more combinations of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, or methyl propyl carbonate. The carboxylic acid ester is selected from one or more combinations of ethyl propionate or propyl propionate. The fluorinated ether is selected from 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
In an example, the separator is selected from polyethylene.
In an example, a charge cut-off voltage of the battery is 4.45 V or above.
Experimental methods used in the following examples are conventional methods, unless otherwise specified. Reagents, materials, and the like used in the following examples are all commercially available, unless otherwise specified.
Lithium-ion batteries in Comparative examples 1 to 3 and Examples 1 to 11 were prepared according to the following preparation method, and a difference lies only in that different positive and negative electrode active materials having different specific surface areas and different electrolyte solutions were selected. The difference is specifically shown in Table 1.
A positive electrode active material LiCoO2 (having a specific surface area shown in Table 1), a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black were mixed at a weight ratio of 98.2:1.1:0.7, and were added with N-methylpyrrolidone (NMP). The mixture was stirred under action of a vacuum mixer until a mixed system became a positive electrode slurry with uniform fluidity. The positive electrode slurry was evenly applied on aluminum foil having a thickness of 12 μm. The coated aluminum foil was baked in a five-stage oven with different temperatures and then dried in an oven at 120° C. for 8 hours, followed by rolling and cutting, to obtain different required positive electrode plates.
A negative electrode active material artificial graphite (having a specific surface area shown in Table 1) with a mass proportion of 96.5%, a conductive agent single-walled carbon nanotube (SWCNT) with a mass proportion of 0.2%, a conductive agent conductive carbon black (SP) with a mass proportion of 1%, a binder sodium carboxymethyl cellulose (CMC) with a mass proportion of 1%, and a binder styrene-butadiene rubber (SBR) with a mass proportion of 1.3% were made into a slurry by using a wet process. The slurry was applied on a surface of a negative electrode current collector with copper foil, and then drying (temperature: 85° C., time: 5 hours), rolling, and die cutting were carried out to obtain different required negative electrode plates.
In an argon-filled glove box (moisture<10 ppm, oxygen<1 ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), and ethyl propionate (EP) were evenly mixed at a mass ratio of 2:1:5:2; and lithium hexafluorophosphate, an aluminum salt compound (namely, the compound represented by formula 1 and/or the compound represented by formula 2), and 1-ethyl-3-methylimidazolium heptachlorodialuminate (specific amounts and selection thereof are shown in Table 1) were slowly added into the mixed solution. The mixture was stirred evenly to obtain the electrolyte solution.
A polyethylene separator with a thickness ranging from 7 μm to 9 μm was used.
The foregoing prepared positive electrode plate, separator, and negative electrode plate were wound to obtain an unfilled bare cell. The bare cell was placed in an outer packaging foil, the prepared electrolyte solution was injected into the dried bare cell, and after processes such as vacuum packaging, standing, forming, shaping, and sorting, the lithium-ion battery required was obtained.
The batteries obtained in the above comparative examples and examples were tested for electrochemical performance. The related descriptions are as follows:
(1) 45° C. cycling test: The batteries obtained in the above examples and comparative examples were placed in an environment of (45±2)° C. to stand for 2 to 3 hours. When the battery bodies reached (45±2° C.), the batteries were charged at a constant current of 1C, with a cut-off current of 0.05C. After the batteries were fully charged, the batteries were left aside for 5 minutes, and then discharged at a constant current of 0.7C to a cut-off voltage of 3.0 V. A highest discharge capacity for the first three cycles was recorded as an initial capacity Q. When the number of cycles reaches 500, the last discharge capacity of the battery was recorded as Q1. Recorded results are shown in Table 2.
The calculation formula used is as follows: Capacity retention rate (%)=Q1/Q×100%.
(2) 85° C. high temperature storage test for 8 hours: The batteries obtained in the above examples and comparative examples were charged and discharged three times at a charge and discharge rate of 0.5C at room temperature, and then charged to a fully charged state at a rate of 0.5C. A highest discharge capacity Q2 of the first three cycles at 0.5C was recorded. The batteries in a fully charged state were stored at 85° C. for 8 hours. After 4 hours, a 0.5C discharge capacity Q3 for each battery was recorded. Then, experimental data such as a capacity retention rate and whether gas is generated that are stored at a high temperature of each battery were obtained by means of calculation. Recorded results are shown in Table 2.
The calculation formula used is as follows:
(3) Overcharge test: The batteries obtained in the above examples and comparative examples were charged at a rate of 3C and a constant current to 5 V at an ambient temperature of (25±3° C.) A battery state was recorded. A test result is represented by “number of passed/number of tested”. For example, “2/5” indicates that two of five tests are passed. Recorded results are shown in Table 2.
(4) Low temperature discharge test: The batteries obtained in the above examples and comparative examples were first discharged at 0.2C to 3.0 V at an ambient temperature of (25±3)° C., and left aside for 5 minutes. The batteries were charged at 0.7C, and when a voltage at the cell terminals reached a charging limit voltage, the batteries began to be charged at a constant voltage. The charging was not stopped until a charging current is less than or equal to a cut-off current. The batteries were left aside for 5 minutes and then discharged at 0.2C to 3.0 V, and a discharge capacity in this case was recorded as a normal-temperature capacity Q4. Then, the cells were charged at 0.7C, and when a voltage at the cell terminals reached the charging limit voltage, the batteries began to be charged at a constant voltage. The charging was not stopped until a charging current is less than or equal to a cut-off current. The fully charged batteries were left aside at (−10±2° C.) for 4 hours, and then discharged at a current of 0.4C to a cut-off voltage of 3.0 V. A discharge capacity Q5 was recorded to calculate a low-temperature discharge capacity retention rate. Recorded results are shown in Table 2.
The calculation formula used is as follows: Low-temperature discharge capacity retention rate (%)=Q5/Q4×100%.
The following can be learned from the results in Table 2. It can be learned from the comparative examples and examples that the long cycle life, high-temperature storage performance, low-temperature discharge performance, and safety performance of the lithium-ion battery can be effectively improved due to the synergistic effect of the positive and negative electrode active materials and the aluminum salt compound in the electrolyte solution, and that after the additive 1-ethyl-3-methylimidazolium heptachlorodialuminate was added into the electrolyte solution, the long cycle life, high-temperature storage performance, low-temperature discharge performance, and safety performance of the battery may be further improved.
The implementations of the present disclosure are described above. However, the present disclosure is not limited to the foregoing implementations. Any modifications, equivalent replacements, improvements, and the like within the spirit and principle of the present disclosure shall fall within the scope of protection of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210519593.7 | May 2022 | CN | national |
The present disclosure is a continuation application of International Application No. PCT/CN2023/091652, filed on Apr. 28, 2023, which claim priority to Chinese Patent Application No. CN202210519593.7, filed on May 12, 2022. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2023/091652 | Apr 2023 | WO |
| Child | 18736266 | US |
