In-situ polymerized hybrid polymer electrolyte for high voltage lithium batteries

Abstract

The present invention provides a monomer material for preparing a polymer electrolyte precursor composition capable of forming an in-situ polymerized polymer electrolyte, comprising, consisting essentially of, or consisting of: A1) a first monomer and, optionally, A2) a second monomer. Also provided are a polymer electrolyte precursor raw material composition, a polymer electrolyte precursor composition capable of forming a polymer electrolyte comprising the monomer material, a polymer electrolyte, and an electrochemical device.

Description

TECHNICAL FIELD

[0001] The present invention relates to the preparation and development of in-situ polymerized hybrid polymer electrolytes for high voltage lithium metal batteries. BACKGROUND

[0002] With the development and demand of various energy storage devices and systems, especially for electric vehicles, the conventional Li-ion batteries have not been able to meet the market demand and there is an urgent need for high energy / power density lithium batteries. Lithium batteries employing Li metal (-3.04 V vs. standard hydrogen electrode, 3860 mAh g -1 ) as anode and high voltage LiNi x Co y Mn 1-x-y (≥4.3 V vs. Li + / Li, ≥150 mAh g -1 ) as cathode are generally considered as the next generation lithium batteries. In addition to the electrode, which is one of the most important parts of lithium batteries, the electrolyte also plays a very important role in the prior art Li-based batteries. Unfortunately, the conventional organic liquid electrolytes using carbonate or ether-based solvents exhibit poor anode stability less than 4.3 V vs. Li / Li + , which makes them very unstable to the new high voltage cathode. In addition, the commercially available electrolytes contain a large amount of volatile and flammable organic components. Therefore, polymer electrolytes, especially solid polymer electrolytes (SPE) have attracted more attention due to their reduced safety risk, high anode stability and ability to suppress lithium dendrites.

[0003] PEO-based electrolytes are the most commonly studied among various known polymers and have a structure of low polyether (-CH2-CH2-O- n ) that can effectively dissolve Li salts. The transport motivation of Li + in PEO is attributed to the flexible ethylene oxide segment and ether oxygen atom. In most cases, PEO-based electrolytes have low ionic conductivity and exist ion clustering phenomenon due to their high crystallinity. Another problem of PEO-based electrolytes is the insufficient oxidation resistance (less than 4.2 V vs. Li / Li + ), which means that they are almost impossible to match with high voltage cathodes. In addition, non-in-situ PEO-based polymer electrolytes have poor wettability with cathodes, which can seriously affect their cycle performance.

[0004] In contrast to conventional non-in-situ PEO-based SPEs, in-situ polymerized SPEs are thermally prepared from a precursor solution consisting of a lithium salt, a polymerizable monomer, and a thermal initiator. Also, in-situ polymerized SPEs have good wettability with cathodes, which leads to better cycling performance. J. Chai et al. (J. Chai et al. Advance Science, Vol. 4 (2016), pp. 1600377) demonstrated that for LiCoO2 / Li batteries, in-situ polymerized poly(vinyl cylic carbonate) (PVCA)-based solid polymer electrolytes have an electrochemical stability window of up to 4.5 V and an ionic conductivity of 9.82 x 10 + S cm -5 at 50 °C, which is much better than the 0.1 x 10 -1 S cm -1 at 25 °C. LiCoO2 / Li batteries provide only about 97 mAh g SUMMARY

[0005] Therefore, it is an object of the present invention to develop a new hybrid solid / gel polymer electrolyte by in-situ polymerization.

[0006] The inventors surprisingly found that monomeric materials, such as an unsaturated cyclic carbonate monomer having a carbon-carbon double bond in the side chain and an optional multifunctional ester crosslinking agent such as ETPTA, can form an excellent polymer backbone for a solid or gel polymer electrolyte after in-situ polymerization. Such a polymer electrolyte shows excellent performance, such as cycling performance and electrochemical stability window, compared to a commercial liquid electrolyte. The resulting polymer electrolyte also exhibits a higher ionic conductivity at room temperature compared to conventional PEO-based electrolytes and compact PVCA-based electrolytes. The resulting polymer electrolyte also exhibits better flexibility than a PVCA solid polymer electrolyte, and thus a lithium ion battery with better flexibility can be manufactured. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 shows the ionic conductivity of the polymer electrolyte prepared in Example la.

[0008] Figure 2 shows the electrochemical stability window test results of the polymer electrolyte prepared in Example la.

[0009] Figure 3 shows the cycling performance of the electrolyte prepared in Example la with Li-NCM523 Figure 3 a) as the cathode and Example lb with Li-LiFPO4 Figure 3 b) as the cathode at a 0.2C rate.

[0010] Figure 4 shows the infrared test results demonstrating that VEC and ETPTA have reacted completely according to Example 2-1a.

[0011] Figure 5 shows the ionic conductivities of the polymer electrolytes prepared in Example 2-1a, Example 2-2, and Example 2-3.

[0012] Figure 6 shows the results of the electrochemical stability window test of the polymer electrolytes prepared in Example 2-1a Figure 6 a), Example 2-2 Figure 6 b), and Example 2-3 Figure 6 c).

[0013] Figure 7 shows the cycle performance at 0.2C rate of the polymer electrolytes prepared in Example 2-1a Figure 7 a), Example 2-2 Figure 7 b), and Example 2-3 Figure 7 c) with NCM523 as cathode, and Example 2-1b Figure 7 d) with LiFeP04 as cathode.

[0014] Figure 8 shows the ionic conductivities of the polymer electrolytes prepared in Example 3-1, Example 3-2, Example 3-3a, and Example 3-4.

[0015] Figure 9 shows the results of the electrochemical stability window test of the polymer electrolytes prepared in Example 3-1 Figure 9 a), Example 3-2 Figure 9 b), Example 3-3a Figure 9 c), and Example 3-4 Figure 9 d).

[0016] Figure 10 shows the cycle performance at 0.5C rate of the polymer electrolytes prepared in Example 3-1 Figure 10 a), Example 3-2 Figure 10 b), Example 3-3a Figure 10 c), and Example 3-4 Figure 10 d) with NCM523 as cathode, and Example 3-3b Figure 10 e) with LiFeP04 as cathode.

[0017] Figure 11 shows the electrochemical stability window of the Li-NCM523 battery prepared in Comparative Example 1Figure 11 a) and cycling performance Figure 11 b). DETAILED DESCRIPTION

[0019] The present invention provides a monomer material (i.e. monomer composition) for preparing a polymer electrolyte precursor composition capable of forming an in-situ polymerized polymer electrolyte, comprising, consisting essentially of, or consisting of:

[0020] A1) a first monomer represented by Formula (I), more preferably vinyl ethylene carbonate (VEC);

[0021]

[0022] wherein R represents H, F, methyl or ethyl; m represents 0, 1, 2 or 3; and optionally present

[0023] A2) a second monomer represented by Formula (II), preferably ethoxylated trimethylolpropane triacrylate (ETPTA);

[0024]

[0025] wherein R represents methyl, -CH2OH, ethyl or -CH2CH2OH, preferably R represents methyl, -CH2OH or ethyl; a, b and c each independently represent 0, 1, 2 or 3, and a+b+c > 2, preferably a+b+c > 3.

[0026] The first monomer represented by Formula (I) is an unsaturated cyclic carbonate monomer having a carbon-carbon double bond in the side chain.

[0027] Using the monomer material, a polymer electrolyte precursor composition can be prepared, which in turn can be used to form an in-situ polymerized polymer electrolyte.

[0028] In some examples, the mass ratio of the first monomer to the second monomer is 9.5:0.5-5:5, for example 9:1-6:4, more preferably 9.5:0.5-8:2, even more preferably 9:1-8:2.

[0029] The second monomer can act as a crosslinker. The use of the second monomer in the monomer material also helps to achieve a higher electrochemical stability window. However, the addition of a crosslinker in the monomer material will reduce the ionic conductivity of the polymer electrolyte. If the monomer material contains too much of the second monomer, the ionic conductivity of the prepared gel-polymer electrolyte will be low.

[0030] The present application further provides a polymer electrolyte precursor composition for making a polymer electrolyte capable of forming an in-situ polymerized polymer electrolyte, comprising, consisting essentially of, or consisting of:

[0031] A) the monomer material of the present application; and

[0032] B) a free radical initiator for the thermal polymerization reaction of the monomer material.

[0033] The present application further provides a polymer electrolyte precursor composition capable of forming an in-situ polymerized polymer electrolyte, comprising, consisting essentially of, or consisting of:

[0034] A) the monomer material of the present application; and

[0035] B) a free radical initiator for the thermal polymerization reaction of the monomer material; and

[0036] C) a lithium salt, preferably lithium bis(fluorosulfonyl)imide; and

[0037] D) an optional organic solvent, preferably a carbonate solvent, more preferably ethylene carbonate / dimethyl carbonate, the weight ratio of the monomer material to the organic solvent being 1 :0-1 :0.5, preferably 1 :0.1-1 :0.3, more preferably 1 :0.2-1 :0.3.

[0038] Preferably, the amount of the monomer material is 50-95 wt.%, for example 60-80 wt.%, 70-80 wt.%, more preferably 75-80 wt.%, based on the total weight of the polymer electrolyte precursor composition.

[0039] The method of making a polymer electrolyte precursor composition capable of forming an in-situ polymerized polymer electrolyte of the present application can be conventional, for example a method comprising the step of mixing the components of the polymer electrolyte precursor composition.

[0040] The present application further provides a method of in-situ making a polymer electrolyte, comprising the steps of:

[0041] 1) injecting the polymer electrolyte precursor composition of the present application into a battery case, followed by sealing; and

[0042] 2) in-situ polymerizing the polymer electrolyte precursor composition by heating.

[0043] In one example, the polymerization reaction of the first monomer can be schematically shown as follows,

[0044]

[0045] In another example, the reaction of the first monomer and the second monomer can be shown schematically as follows,

[0046]

[0047] The present application further provides a polymer electrolyte, in particular a gel or solid polymer electrolyte, wherein the polymer electrolyte is formed by (the polymerization of) a polymer electrolyte precursor composition comprising the monomeric material of the present application or is prepared according to the method of the present application.

[0048] The present application further provides a polymer electrolyte for a rechargeable battery comprising a polymer that is the reaction product of the monomeric material of the present application and a radical initiator.

[0049] The present application further provides a polymer electrolyte for a rechargeable battery comprising:

[0050] (i) a polymer that is the reaction product of the monomeric material of the present application and a radical initiator, and

[0051] (ii) an organic solvent containing an ionic salt in an amount effective to achieve an ionic conductivity of about 0.46 mS / cm or less.

[0052] In some examples, the ionic salt is a lithium salt.

[0053] The present application further provides a polymer electrolyte prepared in situ from a polymer electrolyte precursor composition according to the present application. The polymer electrolyte can be prepared according to conventional methods in the art.

[0054] The present application further provides a rechargeable battery comprising an anode, a cathode, a microporous separator separating the anode and the cathode, and a polymer electrolyte of the present application.

[0055] The present application further provides a lithium ion battery comprising a polymer electrolyte prepared in situ from (the polymerization of) a polymer electrolyte precursor composition according to the present application.

[0056] The present application further provides an electrochemical device comprising a polymer electrolyte according to the present application.

[0057] In some examples, the electrochemical device is a secondary battery.

[0058] The present application further provides a device manufactured by a method comprising:

[0059] preparing a battery case having an installed electrode assembly;

[0060] injecting a polymer electrolyte precursor composition of the present application into the battery case, followed by sealing; and

[0061] polymerizing the polymer electrolyte precursor composition.

[0062] The polymerization can be performed by heating.

[0063] The polymer electrolyte of the present application can be in a gel state (i.e., a gel polymer electrolyte) or a solid state (i.e., a solid polymer electrolyte), preferably, the polymer electrolyte is in a gel state. For the polymer electrolyte precursor composition of the present application, the gel or solid state of the polymer electrolyte can be adjusted by the amount of the organic solvent in the polymer electrolyte precursor composition. For example, as shown in Example 1 and Example 2, when the polymer electrolyte precursor composition does not comprise an organic solvent, the resulting polymer electrolyte is in a solid state; when the polymer electrolyte precursor composition comprises an organic solvent as shown in Example 3, the resulting polymer electrolyte is in a gel state.

[0064] There is no particular limitation on the type of lithium ion battery in which the electrolyte of the present application can be used. In some examples, the lithium ion battery is an LMB.

[0065] In some examples, the present application provides a polymer electrolyte precursor composition capable of forming a polymer electrolyte, the precursor composition comprising, consisting essentially of, or consisting of:

[0066] A) a monomer material consisting of vinylene carbonate and ethoxylated trimethylolpropane triacrylate;

[0067] B) a radical initiator;

[0068] C) a lithium salt, such as lithium bis(fluorosulfonyl)imide; and

[0069] D) an organic solvent, preferably a carbonate solvent, such as ethylene carbonate / dimethyl carbonate;

[0070] wherein the mass ratio of vinylene carbonate to ethoxylated trimethylolpropane triacrylate is 9.5:0.5-5:5, preferably 9.5:0.5-8:2, more preferably 9:1-8:2;

[0071] wherein the weight ratio of the monomer material to the organic solvent is 1:0-1:0.5, preferably 1:0.1-1:0.3, more preferably 1:0.2-1:0.3; and

[0072] wherein the amount of the monomer material is 50-95 wt.%, preferably 75-80 wt.%, based on the total weight of the polymer electrolyte precursor composition.

[0073] The amount of lithium bis(fluorosulfonyl)imide is preferably about 15 wt.%, based on the total weight of the polymer electrolyte precursor composition.

[0074] The present application further provides the use of the monomer material of the present application, or the polymer electrolyte precursor raw material composition of the present application, or the polymer electrolyte precursor composition of the present application in the preparation of an in-situ polymerized polymer electrolyte or an electrochemical device.

[0075] A person skilled in the art can determine a suitable separator for a lithium ion battery with the polymer electrolyte of the present application. For example, the separator can be surface-modified or unmodified; the separator can have a thickness of less than 30 pm, even less than 20 pm; the porosity of the separator can be higher than 70%, even higher than 80%; the material of the separator can be, for example, cellulose or polytetrafluoroethylene (PTFE).

[0076] First monomer

[0077] In certain examples, the carbonate monomer is preferably vinyl ethylene carbonate (VEC), which has the chemical formula: C5H6O3, CAS Registry Number 4427-96-7.

[0078] Second monomer

[0079] The second monomer is preferably ethoxylated trimethylolpropane triacrylate (ETPTA), or other monomers having a similar molecular structure to ETPTA, such as trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), and the like.

[0080] Ethoxylated trimethylolpropane triacrylate (ETPTA) can have an average Mn of about 428, CAS Registry Number 28961-43-5.

[0081] Radical initiator

[0082] The radical initiator for the polymerization reaction of the monomers is used for the thermal polymerization of the monomers, and can be those conventional in the art.

[0083] Examples of the radical initiator or polymerization initiator can include azo compounds such as 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), 2,2'-azoisobutyronitrile (AIBN), azobisdimethylvaleronitrile (AMVN), and the like, peroxide compounds such as benzoyl peroxide, acetyl peroxide, dilauroyl peroxide, di-t-butyl peroxide, cumyl peroxide, hydrogen peroxide, and the like, and hydroperoxides. Preferably, AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile) (V65), di-(4-t-butylcyclohexyl) peroxydicarbonate (DBC), and the like can also be used.

[0084] Preferably, the radical initiator can be selected from azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile (ABVN), benzoyl peroxide (BPO), lauroyl peroxide (LPO), and the like. More preferably, the radical initiator is azobisisobutyronitrile (AIBN).

[0085] The amount of radical initiator is conventional. Preferably, the amount of radical initiator is 0.1-3 wt.%, more preferably about 0.5 wt.%, based on the total weight of monomer material.

[0086] The polymerization initiator decomposes at a specific temperature of 40°C to 80°C to form radicals and can react with monomers via radical polymerization to form a gel polymer electrolyte. Generally, radical polymerization proceeds by sequential reactions consisting of initiation, which involves the formation of transient molecules with high reactivity or active sites; propagation, which involves the reformation of active sites at the end of the chain by the addition of monomers to the active chain end; chain transfer, which involves the transfer of active sites to other molecules; and termination, which involves the destruction of active chain centers.

[0087] Lithium salt

[0088] The lithium salt is a material that dissolves in the non-aqueous electrolyte thereby causing lithium ions to dissociate.

[0089] The lithium salt can be those conventionally used in the art, but which are thermally stable during in-situ polymerization (e.g. at 80°C), non-limiting examples can be selected from at least one of: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiODFB), LiAsF6, LiClO4, LiN(CF3SO2)2, LiBF4, LiSbF6, and LiCl, LiBr, LiI, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, chloroborane lithium, lithium lower aliphatic carboxylate, lithium tetraphenylborate, and lithium imide. The lithium salt is preferably selected from LiFSI, LiTFSI, and LiODFB. These materials can be used alone or in any combination thereof.

[0090] The amount of lithium salt is also conventional, for example 5-40 wt.%, most preferably about 15 wt.%, based on the total weight of the polymer electrolyte precursor composition.

[0091] Organic solvent

[0092] The organic solvent can be conventional in the art. For example, the organic solvent can be an aprotic organic solvent such as N-methyl-2-pyrrolidone, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone, dimethyl sulfoxide, methyl formate, methyl acetate, phosphoric acid triester, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, methyl propionate, and ethyl propionate. These materials can be used alone or in any combination thereof.

[0093] The organic solvent is preferably a carbonate solvent. The carbonate solvent can be preferably selected from the group consisting of ethylene carbonate / dimethyl carbonate (EC / DMC), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and γ-butyrolactone (GBL). In some examples, the organic solvent is preferably ethylene carbonate / dimethyl carbonate (EC / DMC, EC / DMC = 50 / 50 (v / v)).

[0094] The amount of the organic solvent is conventional as long as the polymer electrolyte is in a gel state. For example, if the amount of the organic solvent is extremely high and the weight ratio of the monomer material to the organic solvent is less than 1:0.5, a good gel state cannot be formed.

[0095] Further, in order to improve the charge / discharge characteristics and flame retardancy, for example, pyridine, triethyl phosphite, triethanolamine, ethylenediamine, n-glyme, triamide hexaphosphate, nitrobenzene derivatives, sulfur, quinonimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, and the like can be added to the electrolyte. If necessary, in order to impart non-flammability, the electrolyte can further include a halogen-containing solvent such as carbon tetrachloride and trifluoroethylene.

[0096] The electrochemical device includes all kinds of devices that perform electrochemical reactions. Examples of the electrochemical device include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, capacitors, and the like, preferably secondary batteries.

[0097] Generally, a secondary battery is manufactured by including an electrolyte in an electrode assembly composed of a cathode and an anode, which are opposed to each other with a separator therebetween.

[0098] For example, a cathode is manufactured by applying a mixture of a cathode active material, a conductive material, and a binder to a cathode current collector, followed by drying and pressing. If necessary, a filler can be further added to the above mixture.

[0099] Examples of cathode active materials that can be used in the present application can include, but are not limited to, layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals such as LiNi x Co y Mn 1-x-y (NCM); lithium manganese oxides, for example, compounds of formula Li 1+x Mn 2-x O4(0≤x≤0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; Ni-site type lithium nickel oxides of formula LiNi 1-x M x O2(M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and 0.01≤x≤0.3); lithium manganese composite oxides of formula LiMn 2-x M x O2(M = Co, Ni, Fe, Cr, Zn, or Ta, and 0.01≤x≤0.1) or formula Li2Mn3MO8(M = Fe, Co, Ni, Cu, or Zn); LiMn2O4, wherein a portion of Li is substituted with an alkaline earth metal ion; a disulfide compound; and Fe2(MoO4)3, LiFe3O4, etc. In some examples of the present application, LiNi5Co2Mn3 and LiFe3O4 are used as a cathode.

[0100] Since the polymer electrolyte of the present application exhibits a high electrochemical stability window (> 5 V), the polymer electrolyte is particularly suitable for use in NCM cathodes.

[0101] Examples of anode active materials that can be used in the present application include carbon, such as non-graphitized carbon and graphite-based carbon; metal composite oxides such as Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), and Sn x Me 1-x Me′ y O z(Me: Mn, Fe, Pb, or Ge; Me': Al, B, P, Si, Group I, II, and III elements of the Periodic Table, or halogen; 0 < x < 1; 1 < y < 3; and 1 < z < 8); lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; and Li-Co-Ni-based materials. In some examples of the present application, lithium metal is used as the anode.

[0102] The secondary battery according to the present application can be, for example, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, or the like. The secondary battery can be manufactured in various forms. For example, the electrode assembly can be constructed in a jelly-roll structure, a stacked structure, a stacked / folded structure, or the like. The battery can employ a construction in which the electrode assembly is mounted within a battery case of a cylindrical can, a prismatic can, or a laminate including a metal layer and a resin layer. Such a construction of the battery is well known in the art.

[0103] Accordingly, the present application provides a new polymer electrolyte by in-situ polymerization of the polymer electrolyte precursor composition of the present application. The polymer electrolyte can be prepared in-situ and the thickness of the electrolyte can be conveniently controlled. Further, the monomer materials, for example, the first monomer and the second monomer form an excellent polymer backbone upon polymerization, which shows excellent cycling performance and higher electrochemical stability window compared to the commercially available liquid electrolytes. Further, the polymer electrolyte is less flammable, indicating that it is safer than the conventional liquid electrolytes. Additionally, when lithium metal is used as the anode, the formation of lithium dendrites can be suppressed due to the excellent mechanical properties of the electrolyte. Further, the PVEC-based polymer electrolyte is substantially non-reactive with lithium foil during the polymerization process compared to PVC. This electrolyte also eliminates the consumption of large amounts of solvents in the conventional lithium metal batteries, and hence this electrolyte is particularly suitable for LMBs. The polymer electrolyte of the present application shows excellent ionic conductivity, wider electrochemical window, and better cycling performance compared to the conventional PEO-based polymer electrolytes.

[0104] Further, the monomer materials of the present application are chemically stable as the first monomer, particularly the VEC, does not react with Li. This is an important advantage compared to the monomer materials comprising vinylene carbonate (VC), which can adversely react with Li.

[0105] Other advantages of the present application will be clear to a person skilled in the art upon reading the description.

[0106] Preparation of lithium metal batteries

[0107] A lithium metal battery was prepared according to the following method:

[0108] Step a) Preparation of electrolyte precursor composition solution; and

[0109] Step b) Assembling the lithium metal battery and in-situ polymerization by heating.

[0110] Steps a) and b) were carried out in an argon (H2O, O2 < 0.5 ppm) filled glovebox.

[0111] To describe the content and effects of the present application in detail, the present application will be further described below in conjunction with examples and comparative examples and related drawings.

[0112] Unless otherwise specified, all tests in the examples were carried out at room temperature.

[0113] Example 1a (Li-NCM523)

[0114] 1) Preparation of precursor electrolyte solution:

[0115] 1 g of vinyl ethylene carbonate (VEC), 0.157 g of lithium bis(fluorosulfonyl)imide (LiFSI), and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0116] 2) Cell assembly and in-situ polymerization by heating:

[0117] LiNi5Co2Mn3(NCM523) cathode was prepared as follows. NCM523, acetylene black, and poly(vinylidene fluoride) were mixed in a weight ratio of 80:10:10 to form a viscous slurry. Then, the viscous slurry was coated on a flat carbon-coated aluminum foil by a doctor blade method. The carbon-coated aluminum foil coated with the viscous slurry was dried at 70 °C for 1 hour in an air-circulating oven and further dried at 100 °C under high vacuum for 12 hours to obtain an NCM523 cathode. The mass loading of the active material (LiNi5Co2Mn3) was 3-5 mg cm -2 The precursor electrolyte solution was injected into a 2032 lithium battery, which has a cellulose separator separating the cathode and anode (Li foil), and then the cell was heated at 80 °C for 24 hours.

[0118] After the heating process, a solid polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery was disassembled, the solid polymer electrolyte could be confirmed.

[0119] Example 1b (Li-LFP)

[0120] 1) Preparation of precursor electrolyte solution:

[0121] 1 g of vinyl ethylene carbonate (VEC), 0.157 g of lithium bis(fluorosulfonyl)imide (LiFSI), and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0122] 2) Cell assembly and in-situ polymerization by heating:

[0123] LiFeP04(LFP) cathode was prepared as follows. LFP, acetylene black, and poly(vinylidene fluoride) were mixed in a weight ratio of 80:10:10 to form a viscous slurry. Then, the viscous slurry was coated on a flat carbon-coated aluminum foil by a doctor blade method. The carbon-coated aluminum foil coated with the viscous slurry was dried at 70 °C for 1 hour in an air-circulating oven and further dried at 100 °C for 12 hours under high vacuum to obtain a LiFeP04cathode. The mass loading of the active material (LiFeP04) was 3-5 mg cm -2 The precursor electrolyte solution was injected into a 2032 lithium battery, which has a cellulose separator separating the cathode and anode (Li foil), and then the cell was heated at 80 °C for 24 hours.

[0124] After the heating process, a solid polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery was disassembled, the solid polymer electrolyte could be confirmed.

[0125] Example 2-1a (Li-NCM523)

[0126] 1) Preparation of precursor electrolyte solution:

[0127] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.157 g of LiFSI, and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0128] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0129] After the heating process, a solid polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery was disassembled, the solid polymer electrolyte could be confirmed.

[0130] Example 2-1b (Li-LFP)

[0131] 1) Preparation of precursor electrolyte solution:

[0132] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.157 g of LiFSI, and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0133] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1b.

[0134] After the heating process, a solid polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery is disassembled, the solid polymer electrolyte can be confirmed.

[0135] Example 2-2

[0136] 1) Preparation of a precursor electrolyte solution:

[0137] 0.8 g of vinyl ethylene carbonate (VEC), 0.2 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.157 g of LiFSI, and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0138] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0139] After the heating process, a solid polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery is disassembled, the solid polymer electrolyte can be confirmed.

[0140] Example 2-3

[0141] 1) Preparation of a precursor electrolyte solution:

[0142] 0.7 g of vinyl ethylene carbonate (VEC), 0.3 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.157 g of LiFSI, and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0143] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0144] After the heating process, a solid polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery is disassembled, the solid polymer electrolyte can be confirmed.

[0145] Example 3-1

[0146] 1) Preparation of precursor electrolyte solution:

[0147] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.1 g of EC / DMC, and 0.157 g of LiFSI and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0148] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0149] After the heating process, a gel polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery is disassembled, the gel polymer electrolyte can be confirmed.

[0150] Example 3-2

[0151] 1) Preparation of precursor electrolyte solution:

[0152] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.2 g of EC / DMC, and 0.157 g of LiFSI and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0153] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0154] After the heating process, a gel polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. When the 2032 battery is disassembled, the gel polymer electrolyte can be confirmed.

[0155] Example 3-3a (Li-NCM523)

[0156] 1) Preparation of precursor electrolyte solution:

[0157] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.3 g of EC / DMC, and 0.157 g of LiFSI and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0158] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0159] After the heating process, a gel polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. The gel polymer electrolyte can be confirmed when the 2032 battery is disassembled.

[0160] Example 3-3b (Li-LFP)

[0161] 1) Preparation of the precursor electrolyte solution:

[0162] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.3 g of EC / DMC, and 0.157 g of LiFSI and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0163] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1b.

[0164] After the heating process, a gel polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. The gel polymer electrolyte can be confirmed when the 2032 battery is disassembled.

[0165] Example 3-4

[0166] 1) Preparation of the precursor electrolyte solution:

[0167] 0.9 g of vinyl ethylene carbonate (VEC), 0.1 g of ethoxylated trimethylolpropane triacrylate (ETPTA, average Mn ~ 428), 0.3 g of EC / DMC, and 0.157 g of LiFSI and 3 mg of AIBN were mixed and stirred at 25 °C for 0.5 hours to obtain a precursor electrolyte solution.

[0168] 2) Cell assembly and in-situ polymerization by heating were performed according to the same method as Example 1a.

[0169] After the heating process, a gel polymer electrolyte without a flowable liquid phase between the anode and the cathode can be obtained. The gel polymer electrolyte can be confirmed when the 2032 battery is disassembled.

[0170] Comparative Example 1

[0171] Cell assembly:

[0172] A commercially available liquid electrolyte 1M LiPF6in EC / DMC (v / v 1 / 1) was injected into a 2032 lithium battery having a polypropylene (PP) separator that separates the cathode and the anode, wherein the cathode and the anode are the same as in Example 1a.

[0173] Characterization of the structure of the polymer electrolyte

[0174] Further Fourier transform infrared spectroscopy (FTIR) was performed to analyze the chemical structure of the solid polymer electrolyte prepared in Example 2-1a. From Figure 4 It can be seen that after polymerization, the absorption peaks of terminal double bond hydrogen (-C=CH2) at 2900 cm -1 , 2950 cm -1 , and -C=C- group at 915-905 cm -1 , 995-985 cm -1 disappeared, which is well attributed to the chemical structure change of C=C double bond to C-C single bond.

[0175] Performance test

[0176] 1. Cycle performance of electrolytes

[0177] The cycle performance of the batteries was evaluated on a LAND battery test system (Wuhan Kingnuo Electronics Co., Ltd., China) by using LiNi5Co2Mn3 or LiFePO4 as the cathode and Li metal as the anode at room temperature. The cutoff voltage was 4.3 V / 4.2 V vs. Li / Li + for charging (Li extraction) and 2.7 V / 2.4 V vs. Li / Li + for discharging (Li insertion). Prior to cycling, all relevant batteries were activated with a small current. The C rate was defined based on 1 C = 160 mA g -1 -1for all electrochemical measurements. The test results are shown in Figure 3 , Figure 7 , Figure 10 and Figure 11 . In each figure, the solid points represent the discharge capacity and the hollow points represent the coulombic efficiency.

[0178] For Figure 11 , the battery was evaluated at 0.2 C rate. Although it provided a higher discharge capacity in the first few cycles of the battery of Comparative Example 1, it decreased rapidly after 200 cycles with a capacity retention of 64.1%, and the coulombic efficiency of the electrolyte of Comparative Example 1 was >99%.

[0179] For Figure 3 and Figure 7The batteries were evaluated at 0.2C rate. The cycle performance of the solid polymer electrolytes of Example 1 and Example 2-(1-3) showed significantly more prominent cycle performance because their discharge capacity was not decreased as much as that of Comparative Example 1, and the capacity retention rates after 200 cycles of Example 1a and Example 2-(1-3) were 78.9%, 80.5%, 73.5%, 70.2% in the case of NCM523 as a cathode, and 85.5% and 86.8% in the case of LiFeP04 as a cathode, respectively. The coulombic efficiency of all batteries as shown in Table 1 was >99%, which means that the solid polymer electrolytes prepared in Example 1 and Example 2-(1-3) of the present application have a significant beneficial effect on cycle performance. Figure 3 and Example 2-1b Figure 7 The coulombic efficiency of all batteries as shown in Table 1 was >99%, which means that the solid polymer electrolytes prepared in Example 1 and Example 2-(1-3) of the present application have a significant beneficial effect on cycle performance.

[0180] For Figure 10 , the batteries were evaluated at 0.5C rate. The cycle performance of the gel polymer electrolytes of Example 3-(1-4) provided higher discharge capacity because their ionic conductivity was higher than that of the solid polymer electrolytes. The capacity retention rates of Example 3-(1-4) after 200 cycles were 73.2%, 79.0%, 85.4%, 77.1% in the case of NCM523 as a cathode, and 89.7% in the case of LiFeP04 as a cathode, respectively. Figure 10 The coulombic efficiency of all batteries as shown in Table 1 was >99%, which means that the solid polymer electrolytes prepared in Example 1 and Example 2-(1-3) of the present application have a significant beneficial effect on cycle performance.

[0181] Table 1

[0182]

[0183] However, the batteries including all solid-state polymer electrolytes showed lower specific capacity due to their lower ionic conductivity than that of gel polymer and liquid electrolytes.

[0184] 2. Electrochemical stability window

[0185] The electrochemical stability of the polymer electrolytes of the present application and the liquid electrolyte of Comparative Example 1 was evaluated by linear sweep voltammetry (LSV) which was performed from the open circuit voltage of each cell to 6V vs. Li+ / Li at a scan rate of 10 mV S-1 at room temperature in a CHI760e electrochemical workstation (Shanghai Chenhua Instruments Co., Ltd.) using SS (stainless steel) / gel-polymer electrolyte (GPE) / Li button cell. -1 The results obtained by the test are shown in + , Figure 2 , Figure 6 ,Figure 9 and Figure 11 in the middle.

[0186] Figure 2 , Figure 6 and Figure 9 shows the electrochemical stability window of the polymer electrolyte, Figure 11 shows the electrochemical stability window of the liquid electrolyte. The liquid electrolyte of Comparative Example 1 shows an electrochemical stability window of about 4.6 V. Apparently, the polymer electrolyte has a higher electrochemical stability window than the liquid electrolyte. The polymer electrolytes according to the present application show a more stable electrochemical stability window, for example, Example 1a (4.8 V), Example 2-(1-3) (5.2 V) and Example 3-(1-4) (5 V), which can contribute to better electrochemical performance. A very stable electrochemical stability window close to or above 5 V is very important, which makes it possible to use new high-nickel content cathodes in batteries.

[0187] 3. Ionic conductivity

[0188] The alternating current (AC) impedance spectra were measured in a CHI760e electrochemical workstation. The ionic conductivity of the polymer electrolytes was measured by SS / GPE / SS cell with an applied voltage of 5 mV, the results are shown in Figure 1 , Figure 5 and Figure 8 , and the ionic conductivities of the electrolytes in different examples were calculated based on Figure 1 , Figure 5 and Figure 8 and summarized in Table 2 below.

[0189] Table 2

[0190] Ion conductivity (10 -4 S / cm) Example 1a 0.696 Example 2-1a 0.434 Example 2-2 0.238 Example 2-3 0.143 Example 3-1 1.101 Example 3-2 1.553 Example 3-3a 2.626 Example 3-4 4.567 PVCA-SPE 0.195 PEO-SPE 0.021

[0191] Compared with the PVCA solid polymer electrolyte disclosed in J. Chai et al. (Advance Science, Vol. 4 (2016), pp. 1600377), which discloses a PVCA polymer electrolyte with an ionic conductivity of 1.95 x 10 -5 S / cm at room temperature, the ionic conductivity of the solid polymer electrolyte of the present application (6.96 x 10 -5 S / cm in Example 1a) is higher. In addition, the ionic conductivity is much higher than that of conventional PEO-based solid polymer electrolytes, which can only provide a very low ionic conductivity of about 2.1 x 10 -6 S / cm (K. Wen et al. J. Mater. Chem. A, Vol. 6 (2018), pp 11631-11663).

[0192] As used herein, the term such as "comprising" or the like, as used herein, unless otherwise specifically indicated, is meant to be an open term.

[0193] All references, tests, standards, literature, publications, etc., referred to herein are hereby incorporated by reference. In stating numerical limits or ranges, the endpoints are included. Likewise, all values and subranges within numerical limits or ranges are expressly included, as if explicitly written out.

[0194] The foregoing description is given for clearness of understanding only, and no unnecessary limitations are to be understood therefrom, since modifications will be obvious to and can be made by those skilled in the art without departing from the scope of the application. It is intended that claims to come within the purview of this application be interpreted under the broadest reasonable construction moving in the direction of additional claims permitted by law.

Claims

1. A monomer material for preparing a polymer electrolyte precursor composition capable of forming an in-situ polymerizable polymer electrolyte, consisting of: A1) a first monomer represented by Formula (I); wherein R represents H, F, methyl, or ethyl; m represents 0, 1, 2, or 3; and A2) a second monomer represented by Formula (II); wherein R represents methyl, -CH2OH, ethyl, or -CH2CH2OH; a, b, and c each independently represent 0, 1, 2, or 3, and a+b+c≥2, wherein the mass ratio of the first monomer to the second monomer is 9.5:0.5-5:

5.

2. The monomer material according to claim 1, wherein R in Formula (II) represents methyl, -CH2OH, or ethyl.

3. The monomer material according to claim 1, wherein a+b+c≥3.

4. The monomer material according to claim 1, wherein the first monomer is ethylene carbonate.

5. The monomer material according to claim 1, wherein the second monomer is ethoxylated trimethylolpropane triacrylate.

6. The monomer material according to claim 1, wherein the mass ratio of the first monomer to the second monomer is 9.5:0.5-8:

2.

7. The monomer material according to claim 1, wherein the mass ratio of the first monomer to the second monomer is 9:1-8:

2.

8. A polymer electrolyte precursor raw material composition for preparing a polymer electrolyte precursor composition capable of forming an in-situ polymerizable polymer electrolyte, consisting of: A) the monomer material according to any one of claims 1-7; and B) a radical initiator for a thermal polymerization reaction of the monomer material.

9. A polymer electrolyte precursor composition capable of forming an in-situ polymerizable polymer electrolyte, consisting of the following substances A), B), and C), or consisting of the following substances A), B), C), and D): A) the monomer material according to any one of claims 1-7; B) a radical initiator for a thermal polymerization reaction of the monomer material; and C) a lithium salt; and D) an organic solvent, the weight ratio of the monomer material to the organic solvent being 1:0-1:0.

5.

10. The polymer electrolyte precursor composition according to claim 9, wherein the lithium salt is lithium bis(fluorosulfonyl)imide.

11. The polymer electrolyte precursor composition according to claim 9, wherein the organic solvent is a carbonate solvent.

12. The polymer electrolyte precursor composition according to claim 9, wherein the organic solvent is ethylene carbonate / dimethyl carbonate.

13. The polymer electrolyte precursor composition according to claim 9, wherein the weight ratio of the monomer material to the organic solvent is 1:0.1-1:0.

3.

14. The polymer electrolyte precursor composition according to claim 9, wherein the weight ratio of the monomer material to the organic solvent is 1:0.2-1:0.

3. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 15. The polymer electrolyte precursor composition of any one of claims 9-14, wherein the amount of the monomeric material is 50-95 wt.%, based on the total weight of the polymer electrolyte precursor composition.

16. The polymer electrolyte precursor composition of claim 15, wherein the amount of the monomeric material is 60-80 wt.%, based on the total weight of the polymer electrolyte precursor composition.

17. The polymer electrolyte precursor composition of claim 15, wherein the amount of the monomeric material is 75-80 wt.%, based on the total weight of the polymer electrolyte precursor composition.

18. A method of in situ preparation of a polymer electrolyte comprising the steps of: 1) injecting the polymer electrolyte precursor composition of any one of claims 9-14 into a battery case having an electrode assembly, followed by sealing; and 2) polymerizing the polymer electrolyte precursor composition in situ by heating.

19. A polymer electrolyte, wherein the polymer electrolyte is formed from the polymer electrolyte precursor composition of any one of claims 9-14, or prepared according to the method of claim 18.

20. A polymer electrolyte for a rechargeable battery comprising a polymer that is a reaction product of the monomeric material of any one of claims 1-7 and a free radical initiator.

21. A polymer electrolyte for a rechargeable battery comprising: (i) a polymer that is a reaction product of the monomeric material of any one of claims 1-7 and a free radical initiator, and (ii) an organic solvent containing an ionic salt in an amount effective to achieve an ionic conductivity of about 0.46 mS / cm or less.

22. A rechargeable battery comprising an anode, a cathode, a microporous separator separating the anode and the cathode, and a polymer electrolyte according to any one of claims 19-21.

23. A lithium ion battery comprising a polymer electrolyte prepared in situ from the polymer electrolyte precursor composition of any one of claims 9-14.

24. An electrochemical device comprising a polymer electrolyte according to any one of claims 19-21.

25. A device made by a method comprising the steps of: preparing an installed battery case having an electrode assembly; injecting the polymer electrolyte precursor composition of any one of claims 9-14 into the battery case, followed by sealing; and polymerizing the polymer electrolyte precursor composition.

26. A polymer electrolyte precursor composition capable of forming a polymer electrolyte consisting of: A) a monomeric material consisting of ethylene carbonate and ethoxylated trimethylolpropane triacrylate; B) a free radical initiator; C) a lithium salt; and D) an organic solvent; wherein the mass ratio of ethylene carbonate to ethoxylated trimethylolpropane triacrylate is 9.5:0.5-5:5; wherein the weight ratio of the monomeric material to the organic solvent is 1:0-1:0.5; and wherein the amount of the monomeric material is 50-95 wt.%, based on the total weight of the polymer electrolyte precursor composition.

27. The polymer electrolyte precursor composition of claim 26, wherein the lithium salt is lithium bis(fluorosulfonyl)imide.

28. The polymer electrolyte precursor composition of claim 26, wherein the organic solvent is a carbonate solvent.

29. The polymer electrolyte precursor composition of claim 28, wherein the carbonate solvent is ethylene carbonate / dimethyl carbonate.

30. The polymer electrolyte precursor composition of claim 26, wherein the mass ratio of vinylene carbonate to ethoxylated trimethylolpropane triacrylate is 9.5:0.5-8:

2.

31. The polymer electrolyte precursor composition of claim 26, wherein the mass ratio of vinylene carbonate to ethoxylated trimethylolpropane triacrylate is 9:1-8:

2.

32. The polymer electrolyte precursor composition of claim 26, wherein the weight ratio of the monomer material to the organic solvent is 1:0.1-1:0.

3.

33. The polymer electrolyte precursor composition of claim 26, wherein the weight ratio of the monomer material to the organic solvent is 1:0.2-1:0.

3.

34. The polymer electrolyte precursor composition of claim 26, wherein the amount of the monomer material is 75-80 wt.%, based on the total weight of the polymer electrolyte precursor composition.

35. Use of the monomer material of any one of claims 1-7, or the polymer electrolyte precursor stock composition of claim 8, or the polymer electrolyte precursor composition of any one of claims 9-14, in the preparation of an in-situ polymerized polymer electrolyte or electrochemical device.

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