Patent Application
20240063433
The present invention relates to a polymer electrolyte suitable for use in lithium-ion secondary batteries.
Polymer electrolytes are interesting alternatives to liquid electrolytes in batteries. In that context, polyethylene oxide (PEO) based electrolytes have been extensively studied in the literature.
For examples, Ruoyuan Tao et al. in J. Appl. Electrochem. 35, 163-168 (2005) discloses a positive electrode comprising poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (Li(N(SO2CF3)2)), also called LiTFSI. PEO and LiTFSI were dissolved in acetonitrile in order to prepare an electrolyte solution. A positive electrode active material was added to the electrolyte solution.
U.S. Pat. No. 7,585,934 B2 discloses the use of EO/PO/AGE and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, Li(N(SO2CF3)2)) as a solid polymer electrolyte film. This document discloses in the working examples a copolymerization procedure of EO, PO, and AGE. In particular, LiTFSI was added as a Li salt to polyether polymer composition comprising said EO/PO/AGE copolymer, in an amount such that a ratio of (mol number of lithium atom in the electrolyte salt)/(mol number of oxygen atom in the polyether polymer) was 0.05.
Despite the recent advances in the field, capacity leak remains a problem when PEO based solid electrolytes are used in batteries. Capacity leak is a phenomenon according to which the electrolyte gains electronic conductivity which causes the electronic current to leak from the anode to the cathode.
There is thus a need for improved polymer electrolytes, particularly polymer electrolytes which cause reduced capacity leak when used in batteries.
The inventors have surprisingly found that that it is possible to provide an improved polymer electrolyte fulfilling the above mentioned needs.
Thus, the primary object of the present invention is a polymer electrolyte suitable for use in lithium-ion secondary batteries being obtained by reaction between:
wherein
wherein
The term “comprising”, as used herein and in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a composition comprising components A and B” should not be limited to compositions consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the composition are A and B. Accordingly, the terms “comprising” and “including” encompass the more restrictive terms “consisting essentially of” and “consisting of”.
As used herein, the terms “optional” or “optionally” means that a subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
The inventors have surprisingly found that when, the polymer electrolyte according to the present invention is used in a battery, in particular in solid-state lithium-ion batteries, capacity leaking is reduced which resulted in a battery with improved performance, as demonstrated in the working examples.
Within the context of the present invention, the expression “at least one polyether polymer [polymer (P), herein after)” is intended to denote one or more than one polymer (P). Similarly the expression “at least one polysiloxane compound having the formula (III)” is intended to denote one or more than one polysiloxane compound having the formula (III).
In the rest of the text, the expressions “polymer (P)” and “polysiloxane compound having the formula (III)” is understood, for the purposes of the present invention, both in the plural and the singular.
As used herein the term “alkyl” has the broadest meaning generally understood in the art, and may include a moiety which is linear or branched, or a combination thereof.
The term “alkyl”—alone or in combination means a straight or branched alkane-derived radical, for example, CF-G alkyl defines a straight or branched alkyl radical having from F to G carbon atoms, e.g. C1-4 alkyl defines a straight or branched alkyl radical having from 1 to 4 carbon atoms such as for example methyl, ethyl, 1-propyl, 2-propyl (isopropyl), 1-butyl, 2-butyl, 2-methyl-2-propyl (tert-butyl), 2-methyl-1-propyl (isobutyl).
The term “cycloalkyl”—alone or in combination means a cyclic alkane-derived radical, for example, CL-M cycloalkyl defines a cyclic alkyl radical having from L to M carbon atoms, e.g. C3-6 cycloalkyl defines a cyclic alkyl radical having from 3 to 6 carbon atoms such as for example cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.
The term “aryl”—alone or in combination means phenyl, naphthyl or anthracenyl optionally carbocyclic fused with a cycloalkyl or heterocyclyl of preferably 5-7, more preferably 5-6, ring members and/or optionally substituted with 1 to 5 groups or substituent. An aryl may be optionally substituted whereby the substituent is attached at one point to the aryl or whereby the substituent is attached at two points to the aryl to form a bicyclic system e.g. benzodioxole, benzodioxan, benzimidazole.
The term “heterocyclyl”—alone or in combination means a cyclic alkane-derived radical in which at least one carbon atom is replaced by a heteroatom independently selected from the group consisting of oxygen, nitrogen and sulphur, such as pyrrolidine, piperidine or morpholine and the like.
The term “alkoxy”—alone or in combination means a straight or branched alkane-derived radical in which the carbon atom bearing the radical is replaced by an oxygen atom. The alkoxy moiety has a —O—Rx structure wherein Rx is an alkyl.
The term “alkanediyl”—alone or in combination means a straight or branched alkyl derived divalent radical.
As said above, the polymer (P) comprises
wherein
Thus, at least 70.0% by moles of the recurring units of the polymer (P) are oxyethylene recurring units (EO), preferably, at least 80.0% by moles, preferably at least 85.0% by moles, preferably at least 90.0% by moles, more preferably at least 92.0% by moles, more preferably at least 94.0% by moles.
It is further understood that, at most 99.0% by moles of the recurring units of the polymer (P) are EO units, more preferably at most 98.5% by moles, more preferably at most 98.0% by moles.
In a preferred embodiment, said polymer (P) comprises at least 80.0% by moles and at most 99.0% by moles, preferably at least 90.0% and at most 98.5% by moles, preferably at least 92.0% and at most 98.5% by moles of EO units, preferably at least 94.0% and at most 98.5% by moles of EO units.
When oxypropylene recurring units (PO) are present in the polymer (P), at most 10.0% by moles of the recurring units of the polymer (P) are PO units, more preferably at most 6.0% by moles, even more preferably at most 5.0% by moles, even more preferably at most 4.0% by moles, even more preferably at most 3.0% by moles.
Advantageously, said polymer (P) comprises at least 0.1% by moles, or at least 0.5% by moles, or at least 1.0% by moles of PO units.
In a preferred embodiment, said polymer (P) comprises at least 0.5% by moles and at most 6.0% by moles, or least 0.5% by moles and at most 5.0% by moles, or at least 0.5% and at most 4.0% by moles, or at least 1.0% and at most 4.0% by moles, or at least 1.0% and at most 3.0% by moles of PO units.
The presence of PO units allows to reduce the crystallinity of the polymer (P), which improvise its ionic conductivity.
For the purpose of the present invention, the term oxypropylene (PO)” is intended to refer to the formula —O—CH2—CH2—CH2— or —O—CH2—CH(CH3)—, preferably —O—CH2—CH(CH3)—.
Preferably, at least 1.2% by moles of the recurring units of the polymer (P) are recurring units derived from the monomer (M) of general formula (I) or of general formula (II), as detailed above, or at least 1.5% by moles, or at least 1.8% by moles, or at least 2.2% by moles.
It is further understood that at most 4.0% by moles of the recurring units of the polymer (P) are recurring units derived from the monomer (M) of general formula (I) or of general formula (II), as detailed above, more preferably at most 3.5% by moles, even more preferably at most 3.0% by moles.
In a preferred embodiment, said polymer (P) comprises at least 1.2% by moles and at most 4.0% by moles, preferably at least 1.5% and at most 3.5% by moles, preferably at least 1.5% and at most 3.0% by moles of recurring units derived from the at least one monomer (M) of general formula (I) or of general formula (II), as detailed above.
When the recurring units in the polymer (P) are derived from the monomer (M) of general formula (II), it is understood that the recurring unit is the result of a ring opening polymerization of the epoxide moiety.
When the recurring units in the polymer (P) are derived from the monomer (M) of general formula (I) with X being an acylchloride or acylbromide, it is understood that the recurring unit can be the result of a reaction between said monomer (M) and terminal OH groups of an EO unit or PO unit, of for example, a dihydroxy terminated polyethylene oxide (or a PEO-co-PPO copolymer) thereby forming an ester moiety.
When the recurring units in the polymer (P) are derived from the monomer (M) of general formula (I) with X being trifluoromethanesulfonate, nonafluorobutanesulfonate, p-toluenesulfonate or methanesulfonate, the recurring unit can be the result of a Williamson type reaction between said monomer (M) and terminal OH groups of an EO unit or PO unit, of for example, a dihydroxy terminated polyethylene oxide (or a PEO-co-PPO copolymer) in the presence of strong base such as NaH thereby forming an ether moiety. via alkolate formation and subsequent substitution of the X moiety of the monomer (M).
These polymerization reactions are known in the art and notably described by H.-Q. Xie, J.-S. Guo, G.-Q. Yu, and J. Zu, in Journal of Applied Polymer Science 2001, 80, 2446.
Preferably, each of X in the monomer (M) of general formula (I) is a halide, more preferably a halide selected from the group consisting of chloride, bromide and iodide.
According to a preferred embodiment of the polymer electrolyte suitable for use in lithium-ion secondary batteries, the monomer (M) is of formula (II)
wherein
In another preferred embodiment of the polymer electrolyte suitable for use in lithium-ion secondary batteries, the monomer (M) according to the present invention is chosen among those of formulae (IA) to (IF) and (IIA) to (IIE):
wherein X is selected from the group consisting of halide, trifluoromethanesulfonate, nonafluorobutanesulfonate, p-toluenesulfonate and methanesulfonate, acylchoride, acylbromide. Preferably X is an halide, more preferably an halide selected from the group consisting of chloride, bromide, iodide. Even more preferably X is a bromide.
More preferably, the monomer (M) according to the present invention is a compound chosen among those of formulae (IA) to (IF).
Most preferably, said monomer (M) is a compound of formula (IA).
According to a preferred embodiment of the polymer electrolyte suitable for use in lithium-ion secondary batteries, the polymer (P) consist essentially of;
wherein each of R1 and R2, equal to or different from each other and at each occurrence, is a C1-2 alkanediyl and n is an integer 0 or 1, preferably n is 1. It is understood that chain defects, or very minor amounts of other units might be present, being understood that these latter do not substantially modify the properties of polymer (P).
Preferably, said polymer (P), as detailed above, has an Mw (weight average molecular weight) of at least 10 000 g/mol, more preferably at least 20 000 g/mol, even more preferably at least 40 000 g/mol, even more preferably at least 50 000 g/mol.
It is understood that said polymer (P), as detailed above, preferably has an Mw of at most 150 000 g/mol, more preferably at most 100 000 g/mol.
In a preferred embodiment, said polymer (P), as detailed above, has a Mw of at least 10 000 g/mol and at most 150 000 g/mol, preferably at least 20 000 g/mol and at most 150 000 g/mol, more preferably at least 40 000 g/mol and at most 100 000 g/mol, even more preferably at least 50 000 g/mol and at most 100 000 g/mol.
According to the present invention, the Mw is measured by GPC with a PEO standards calibration. Thus, the mentioned Mw are PEO equivalents.
Alternatively and even preferably, said polymer (P), as detailed above, has an Mn (number average molecular weight) of at least 10 000 g/mol, more preferably at least 20 000 g/mol, even more preferably at least 40 000 g/mol, even more preferably at least 50 000 g/mol.
It is understood that said polymer (P), as detailed above, preferably has an Mn of at most 150 000 g/mol, more preferably at most 100 000 g/mol.
In a preferred embodiment, said polymer (P), as detailed above, has a Mn of at least 10 000 g/mol and at most 150 000 g/mol, preferably at least 20 000 g/mol and at most 150 000 g/mol, more preferably at least 40 000 g/mol and at most 100 000 g/mol, even more preferably at least 50 000 g/mol and at most 100 000 g/mol.
According to the present invention, the Mn is measured by GPC with a PEO standards calibration. Thus, the mentioned Mn are PEO equivalents.
Preferably, the polymer (P) according to the invention is a random or a block copolymer, more preferably a random copolymer.
Preferably, the polymer (P) according to the invention is linear or branched, more preferably linear.
A particularly preferred polymer (P) is a linear random copolymer in which the backbone chain can be notably sketched according to formula (IV):
wherein the ratio of o to q (o/q) in the formula (IV) of the polymer (P) is between 25 and 100, or between 35 and 75, or between 40 and 60. The ratio of p to q (p/q) in the formula (IV) of the polymer (P) is advantageously between 0.05 and 1.50, preferably between 0.10 and 1.00, preferably between 0.20 and 0.60.
Such polymers (P) are notably commercially available from Meisei Chemical works ltd under the tradename Alkox® CP-A series.
As said, the polysiloxane compound having the formula (III),
wherein
Preferably, each of R3 and R4, equal to or different from each other and at each occurrence, is independently C1-6 alkyl, more preferably, each of R3 and R4, equal to or different from each other and at each occurrence, is methyl, ethyl, propyl, or isopropyl, even more preferably, each of R3 and R4, equal to or different from each other and at each occurrence, is methyl.
Preferably, each of R5 and R6, equal to or different from each other and at each occurrence, is independently selected from C1-4 alkyl or phenyl, wherein said C1-4 alkyl is optionally substituted with one or more substituents selected from halide, C1-4 alkyl, or CF3, more preferably, each of R5 and R6, equal to or different from each other and at each occurrence, is methyl, ethyl, propyl, or isopropyl, even more preferably, each of R5 and R6, equal to or different from each other and at each occurrence, is methyl.
Preferably, each of R7 is a C1-6 alkyl, more preferably, each of R7 is C1-4 alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or tert-butyl.
Preferably, m is an integer of at least 5, more preferably at least 7, even more preferably at least 8.
It is further understood that m is preferably an integer of at most 1000, more preferably at most 500, even more preferably at most 100, even more preferably at most 20, even more preferably at most 15.
In a preferred embodiment of the present invention, m is an integer of at least 5 and at most 1000, preferably at least 5 and at most 500, more preferably at least 5 and at most 100, eve more preferably at least 5 and at most 20, even more preferably at least 7 and at most 20, even more preferably at least 8 and at most 15.
Within the context of the present invention, it is understood that the —CH═CH2 moiety of monomer (M) is able to react with the H—Si moiety of the polysiloxane compound having the formula (III), as detailed above, so as to obtain a covalent bond between both moieties. Such reaction is in general referred to as a hydrosilylation reaction. It is further understood that said reaction may involve the formation of one or more intermediates including, metal complexes and sigma complexes.
For reacting, at least a fraction of the —CH═CH2 moiety of monomer (M), as detailed above, with the H-Si moiety of the polysiloxane compound having the formula (III), as detailed above, several techniques known in the art can be successfully used.
Polymer (P), as detailed above, and the polysiloxane having formula (III), as detailed above, can notably be reacted in the molten state; melt compounders such as extruders, melt kneaders or other devices can be advantageously used to this aim.
Polymer (P), as detailed above, and the polysiloxane having formula (III), as detailed above, can notably be reacted in solution; according to this embodiment polymer (P) and the polysiloxane having formula (III), as detailed above, are at least partially dissolved in a solvent. Dissolution can be obtained either at room temperature or preferably, upon heating to a temperature of at least 70° C., more preferably at least 80° C., even more preferably at the reflux temperature of the solvent. The selection of this solvent is not critical, provided that it efficiently solvates both polymer (P) and the polysiloxane having formula (III), as detailed above, and does not interfere with the hydrosilylation reaction. Generally, an organic solvent will be preferably selected. Among these organic solvents, mention can be notably made of benzene, toluene, xylene, cymene and the like.
Further, the polymer (P), as detailed above, and the polysiloxane having formula (III), as detailed above, can notably be reacted in the presence of a catalyst, in particular a hydrosilylation catalyst.
Such hydrosilylation catalysts are known in the art. Mention may be notably made of ruthenium, platinum, or rhodium based catalysts, such as notably a Karstedt's catalyst, Wilkinson catalyst, Speier catalyst and mixtures thereof.
Within the context of the present invention, the expression “through reaction of at least a fraction of the —CH═CH2 of monomer (M) with the H—Si moiety of the polysiloxane compound having the formula (III)” means that only a fraction or the totality of the —CH═CH2 of monomer (M) can react with the H—Si moiety of the polysiloxane compound having the formula (III).
Preferably, said polysiloxane compound having formula (III), as detailed above, is grafted to polymer (P), as detailed above, through reaction of at least 10% by moles, more preferably at least 15% by moles, even more preferably at least 20% by moles, even more preferably at least 25% by moles, even more preferably at least 30% by moles, even more preferably at least 35% by moles, even more preferably at least 40% by moles, even more preferably at least 45% by moles, of the —CH═CH2 moiety of monomer (M) with the H—Si moiety of the polysiloxane compound having the formula (III).
It is further understood that the polysiloxane compound having formula (III), as detailed above, can be grafted to polymer (P), as detailed above, through reaction of 100% by moles, preferably at most 95% by moles, more preferably at most 90% by moles, even more preferably at most 85% by moles, even more preferably at most 80% by moles, even more preferably at most 75% by moles, even more preferably at most 70% by moles, even more preferably at most 65% by moles, even more preferably at most 60% by moles, of the —CH═CH2 moiety of monomer (M) with the H—Si moiety of the polysiloxane compound having the formula (III).
In a preferred embodiment, said polysiloxane compound having formula (III), as detailed above, is grafted to polymer (P), as detailed above, through reaction of at least 10% and at most 90% by moles, more preferably at least 30% and at most 70% by moles, even more preferably at least 40% and at most 60% by moles, of the —CH═CH2 moiety of monomer (M) with the H—Si moiety of the polysiloxane compound having the formula (III).
The reaction can be monitored by using known analytical methods such as notably by using GPC or 1H-NMR methods, as illustrated in the experimental part.
Preferably, said polymer electrolyte is obtained by reaction between said at least one polymer (P) and at least 6 wt. % or at least 7 wt. % or at least 8 wt. % of said at least one polysiloxane compound, with regards to the total amount of said at least one polymer (P) and said at least one polysiloxane compound.
Preferably, said polymer electrolyte is obtained by reaction between said at least one polymer (P) and at most 27 wt. % or at most 25 wt. % or at most 22 wt. % of said at least one polysiloxane compound with regards to the total amount of said at least one polymer (P) and said at least one polysiloxane compound.
In a preferred embodiment, said polymer electrolyte is obtained by reaction between said at least one polymer (P) and at least 6 wt. % and at most 27 wt. % or at least 7 wt. % and at most 25 wt. % or at least 8 wt. % and most 22 wt. % of said at least one polysiloxane compound with regards to the total amount of said at least one polymer (P) and said at least one polysiloxane compound.
The following examples are intended to further clarify the present invention, and are not intended to limit the scope of the present invention.
Unless specified otherwise, the following materials were used as described hereafter.
The random polymer (P) was purchased from Meisei Chemical works ltd under the tradename CP series CP-A. Alternatively, the polymer (P) can be prepared by following the procedure disclosed in H.-Q. Xie, J.-S. Guo, G.-Q. Yu, and J. Zu, Journal of Applied Polymer Science 2001, 80, 2446.
The monohydride terminated polydimethylsiloxane (SiH-terminated PDMS, Mw=850 g/mol) was purchased from Gelest, Inc.
Silica-supported Karsted-type catalyst were prepared according to Q. J. Miao, Z.-P. Fang, and G. P. Cai, Catalysis Communications 2003, 4, 637-639.
LiTFSI (lithium bis(trifluoromethanesulfonyl)imide salt, 99.95% trace metals basis) was purchased from Sigma-Aldrich.
Acetonitrile anhydrous 99.8 wt. % was purchased from Sigma-Aldrich.
Timcal Super P is a conductive carbon black powder (CAS no 1333-86-4) manufactured by Imerys Graphite & Carbon.
Polyethylene oxide (PEO having a Mw of 1,000,000) was purchased from Alfa Aesar.
The 1H spectra were recorded at room temperature on a JEOL JNM ECZ 500 MHz NMR spectrometer. The polymer samples were dissolved in CDCl3 and the internal standard was optimized by using tetramethylsilane (TMS).
The inductively coupled plasma (ICP) measurements were carried out using an Agilent 720 ICP-OES (Agilent Technologies, https://www.agilent.com/cs/library/brochures/5990-6497EN%20720-725_ICP-OES_LR.pdf). 1 gram of powder sample is dissolved into 50 mL of high purity hydrochloric acid (at least 37 wt. % of HCl with respect to the total weight of solution) in an Erlenmeyer flask. The flask is covered by a watch glass and heated on a hot plate at 380° C. until the powder is completely dissolved. After being cooled to room temperature, the solution from the Erlenmeyer flask is poured into a first 250 mL volumetric flask. Afterwards, the first volumetric flask is filled with deionized water up to the 250 mL mark, followed by a complete homogenization process (1st dilution). An appropriate amount of the solution from the first volumetric flask is taken out by a pipette and transferred into a second 250 mL volumetric flask for the 2nd dilution, where the second volumetric flask is filled with an internal standard element and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this solution is used for ICP measurement.
A Polymer (P), a random linear copolymer which characteristics are shown in table 1, is reacted with a monohydride terminated polydimethylsiloxane (SiH-terminated PDMS) by hydrosilylation according to the following procedure:
A mixture containing 2.0 g of the polymer (P) and 0.36 g of SiH-terminated PDMS is added into 50 mL benzene containing 20 mg of silica-supported Karsted-type catalyst and heated at 90° C. for 48 hours under nitrogen atmosphere.
The heated mixture is filtered through celite to remove the solid catalyst, then placed under reduced pressure to remove the solvent. The PDMS was grafted to polymer (P) through reaction of 50% by moles of the —CH═CH2 of AGE units with the H—Si moiety of the PDMS.
The successful grafting was confirmed by 1H-NMR and by GPC (gel permeation chromatography).
Polymer (P): 1H-NMR (TMS, CDCl3, 500 MHz): δ (ppm) 1.2 (d, CH3 of PO units), 4 (m, —OCH2—CH═CH2 of the AGE units), 5.2 (m, CH2═CH— of AGE units), 5.8 (m, —CH═CH2 of AGE units).
Monohydride PDMS: 1H-NMR (TMS, CDCl3, 500 MHz): δ (ppm) 0.5 (m, —Si—CH2—CH2—), 0.9 (t, CH3—CH2—), 1.3 (br, —Si—CH2—CH2—CH2—CH3), 4.8 (m, H—Si—).
Polymer electrolyte: 1H-NMR (TMS, CDCl3, 500 MHz): δ (ppm): 0.5 (br, —Si—CH2—CH2— of PDMS), 0.9 (br, CH3—CH2— of PDMS), 1.1 (d, CH3 of PO units), 1.2 (br, —Si—CH2—CH2—CH2—CH3 of PDMS), 1.4 (br, —OCH2—CH2—CH2—Si—).
The presence of the broad peak at 1.4 ppm and the absence of a peak attributed to H—Si in the polyelectrolyte 1H-NMR spectrum are the confirmation of a successful hydrosilylation.
The lower elution time of the polymer electrolyte in comparison to the polymer (P), indicates that the polymer electrolyte has a higher molecular weight than the polymer (P) and thus that the PDMS was successfully grafted onto the polymer (P).
A lithium transition metal composite oxide having a general formula Li1.010(Ni0.621Mn0.224Co0.155)0.990O2.00 as measured by ICP is prepared as a positive electrode active material according to the following process:
A positive electrode comprising the positive electrode active material prepared according to section 1.3 and the polymer electrolyte prepared according to section 1.2, is prepared according to the following procedure:
A PEO-based solid polymer electrolyte (SPE) is prepared according to the process as follows:
The coin-type polymer cell is assembled in an argon-filled glovebox with an order from bottom to top: a 2032 coin cell can, a positive electrode prepared according to section 1.4, a SPE polymer electrolyte prepared according to section 1.5., a gasket, a Li anode, a spacer, a wave spring, and a cell cap. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.
A poly(ethylene oxide) (PEO) powder is purchased from Alfa Aesar (Mw of 1,000,000 g/mol) is used instead of the polymer electrolyte according to the present invention.
A positive electrode comprising the positive electrode active material prepared according to section 1.3 and the polymer electrolyte according to the section 2.1, is prepared according to the following procedure:
The coin-type polymer cell is assembled in an argon-filled glovebox with an order from bottom to top: a 2032 coin cell can, a positive electrode prepared from section 2.2, a SPE prepared from section 1.5, a gasket, a Li anode, a spacer, a wave spring, and a cell cap. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.
The capacity leaked (Qtotal) was measured for the coin cell prepared in section 2.3 and section 1.6. The coin cell prepared in section 2.3 comprises a polymer electrolyte according to the state of the art and the coin cell prepared in section 1.6 comprises a polymer electrolyte according to the invention.
Each coin-type polymer cell is cycled at 80° C. using a Toscat-3100 computer-controlled galvanostatic cycling stations (from Toyo,
http://www.toyosystem.com/image/menu3/toscat/TOSCAT-3100.pdf). The coin cell testing procedure uses a 1 C current definition of 160 mA/g in the 4.4-3.0 V/Li metal window range according to the schedule below:
Qtotal is defined as the total leaked capacity at the high voltage and high temperature in the Step 4) according to the described testing method. A low value of Qtotal indicates a high stability of the positive electrode active material powder during a high temperature operation.
Table 2 summarizes the Qtotal of the polymer batteries comprising positive electrodes as prepared in example 1 section 1.6 and comparative example section 2.3. According to Table 2, it is observed that the polymer battery comprising the polymer electrolyte according to the present invention (example 1) has a significantly lower Qtotal than the polymer battery comprising the polymer electrolyte according to example 2. This indicates that the use of the polymer electrolyte according to the present invention provides a better electrochemical performance than the use of PEO which is a conventional polymer electrolyte. A low value of Qtotal indicates a high stability for the lithium-ion secondary batteries in the high voltage application at a high temperature.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20217308.4 | Dec 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/087465 | 12/23/2021 | WO |
