In-Situ Polymerized Polymer Electrolyte for Lithium-Ion Batteries

Abstract

A monomer for preparing a polymer electrolyte precursor composition capable of forming an in situ polymerized polymer electrolyte, the composition comprising, consisting essentially of, or consisting of A1) a first monomer and 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, a polymer electrolyte, and an electrochemical device.

Description

Technical Field

[0001] The present invention relates to a polymer electrolyte polymerized in situ using, for example, a cellulose separator for a lithium metal battery.

Background Art

[0002] Lithium-ion batteries (LIBs) are widely used in portable electronic devices, electric vehicles, hybrid electric vehicles, and energy storage systems. However, with the development and demand for various energy storage devices and systems, a high-energy density storage system is urgently needed. Lithium metal-based batteries (LMBs) are theoretically the most ideal anode candidates because they can provide the highest specific capacity (3860 mAh g -1 ) and the lowest redox potential (-3.04 V vs. standard hydrogen electrode). Unfortunately, the formation and growth of lithium dendrites and mossy metal deposits during the lithium plating / stripping process are not controlled, which may lead to potential safety problems, continuous decomposition of the electrolyte, continuous destruction / reconstruction of the solid electrolyte interface, and low Coulombic efficiency (CE). By replacing the liquid electrolyte with a polymer electrolyte or a solid polymer electrolyte, the growth of lithium dendrites can be effectively suppressed, and safety problems such as fire, explosion, and electrolyte leakage can be solved. However, solid polymer electrolytes have low ionic conductivity at room temperature, high interfacial resistance, and it is difficult to meet the requirements necessary for practical applications.

[0003] Polymer electrolytes that combine the advantages of liquid electrolytes and solid electrolytes have been shown to have ideal ionic conductivity, excellent electrochemical performance at room temperature, and no liquid leakage. More importantly, recent studies have shown that polymer electrolytes can suppress the growth of Li dendrites using a rigid backbone with good mechanical strength.

[0004] However, the conventional preparation process of polymer electrolytes is expensive and complex, consuming a large amount of solvents, which has become a serious obstacle to the development of polymer electrolytes. In-situ polymerization is a hot-press method that does not require solvents and is a simple and powerful technology for polymer electrolyte LMBs, avoiding solvent consumption and cumbersome preparation processes.

[0005] In-situ polymer electrolytes are thermally prepared from a precursor solution consisting of an organic solvent, a lithium salt, a polymerizable monomer, and a thermal initiator. Different monomers have different effects on the electrolyte system. Vinylene carbonate (VC) can polymerize into poly(vinylene carbonate) (PVCA) that is excellent in mechanical properties as a main component of the solid electrolyte interface (SEI), has a wide electrochemical stability window, and excellent interfacial compatibility with the electrode. Furthermore, the cross-linking agent can promote monomer polymerization at a low content. The combination of VC and the cross-linking agent forms an excellent polymer backbone. Furthermore, a cellulose membrane with a large number of micron pores and good mechanical strength and elasticity will have a wide range of applications in in-situ polymerization. The thinner the cellulose membrane, the better the battery performance, so an appropriate lithium ion permeation resistance can be obtained.

[0006] Non-Patent Document 1 clarified that the electrochemical stability window up to the poly(vinylene carbonate) (PVCA)-based solid polymer electrolyte is 4.5 V with respect to Li / Li+, and the ionic conductivity with respect to the LiCoO2 / Li battery is 9.82×10 -5 S cm -1 at 50°C. The LiCoO2 / Li battery only supplied a reversible capacity of about 97 mAh g -1 at a current density of 0.1C, which was due to the low ionic conductivity of PVCA-SPE and large polarization at 25°C.

[0007] Furthermore, Non-Patent Document 2 reported a capacity retention (88.7%) supplied after 1000 cycles at 1.0°C for a LiFe0.2 Mn0.8 PO4 / graphite lithium ion battery with an ionic conductivity of 5.59×10 -4 S cm -1and an electrochemical stability window of 4.8 V vs. Li + / Li, a PVCA-based polymer electrolyte was developed via a simple in-situ polymerization method. Here, graphite was used as the anode.

Prior Art Documents

Non-Patent Documents

[0008]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to develop a novel polymer electrolyte by in-situ polymerization.

Means for Solving the Problems

[0010] The present inventors have surprisingly found that different monomers, such as unsaturated carbonate ester monomers and trimethylolpropane ethoxylate triacrylate, can form excellent polymer skeletons for polymer electrolytes, showing excellent performance such as cycle performance and electrochemical stability window compared to commercially available liquid electrolytes when using lithium metal as the anode.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0012] The present invention provides a monomer (i.e., a monomer composition or a composition of monomers) for preparing a polymer electrolyte precursor composition capable of forming an in situ polymerized polymer electrolyte, wherein the composition comprises the following: A1) A first monomer, which is an unsaturated carbonate ester monomer, preferably of the following formula (I):

[0013]

Chemical formula

[0014]

Chemical formula

[0015] Using the monomer, a polymer electrolyte precursor composition can be prepared, and using it, an in-situ polymerized polymer electrolyte can be formed.

[0016] In some examples, the mass ratio of the first monomer to the second monomer is 20:0.5 to 20:10, such as 20:2 to 20:5, most preferably 20:3 to 20:5. The present invention further provides a polymer electrolyte precursor raw material composition for producing a polymer electrolyte precursor composition capable of forming an in-situ polymerized polymer electrolyte, comprising the following: A) the monomer of the present invention; and B) a free radical initiator for the thermal polymerization reaction of the monomer; A polymer electrolyte precursor raw material composition comprising, consisting essentially of, or consisting of is provided.

[0017] The present invention further provides a polymer electrolyte precursor composition capable of forming an in-situ polymerized polymer electrolyte, comprising the following: A) the monomer of the present invention; B) a free radical initiator for the thermal polymerization reaction of the monomer; C) a lithium salt, preferably lithium bis(trifluoromethanesulfonyl)imide; and D) optionally, an organic solvent, which is 0% to 70% by mass, preferably 10% to 60% by mass, more preferably 20% to 50% by mass, preferably ethylene carbonate / dimethyl carbonate, based on the total mass of the polymer electrolyte precursor composition; A polymer electrolyte precursor composition comprising, consisting essentially of, or consisting of is provided.

[0018] Preferably, the amount of the monomer is 5 to 80% by mass, for example, 10 to 80% by mass, 20 to 80% by mass. More preferably, it is 25 to 75% by mass based on the total mass of the polymer electrolyte precursor composition. Preferably, the mass ratio of the first monomer to the second monomer is 20:0.5 to 20:10, most preferably 20:3 to 20:5. Preferably, the polymer electrolyte precursor composition contains an organic solvent.

[0019] The method for preparing a polymer electrolyte precursor composition capable of forming the in-situ polymerized polymer electrolyte of the present invention may be a commonly used method, for example, a method including a step of mixing the components of the polymer electrolyte precursor composition.

[0020] The present invention further provides a method for preparing a polymer electrolyte in situ, comprising the following: 1) A step of injecting the polymer electrolyte precursor composition of the present invention into a battery case and then sealing it; and, 2) A step of in-situ polymerizing the polymer electrolyte precursor composition by heating; The present invention provides a method including these steps.

[0021] In one example, the reaction of the first monomer and the second monomer is as follows:

[0022]

Chemical formula

[0023] The present invention further provides a polymer electrolyte, particularly a gel polymer electrolyte, wherein the polymer electrolyte is formed by polymerizing a polymer electrolyte precursor composition containing the first monomer and the second monomer of the present invention, particularly the monomer of the present invention.

[0024] The present invention further provides a polymer electrolyte for a rechargeable battery, comprising a polymer that is a reaction product of the monomers of the present invention and includes a free radical initiator.

[0025] The present invention further provides a polymer electrolyte for a rechargeable battery, comprising the following: (i) a polymer that is a reaction product of the monomers of the present invention and comprises a free radical initiator, and (ii) an organic solvent containing an ionic salt in an amount effective to achieve an ionic conductivity of about 0.44 mS / cm or less. The present invention provides a polymer electrolyte comprising the above. In some examples, the ionic salt is a lithium salt.

[0026] In some examples, the amount of the monomer is 20 to 80% by mass, preferably 25 to 75% by mass, based on the total mass of the polymer electrolyte precursor composition.

[0027] When the amount of the lithium salt is about 25% by mass and the amount of the first monomer and the second monomer exceeds about 75% by mass based on the total mass of the polymer electrolyte precursor composition, the polymer electrolyte formed by the composition is in a completely solid state. However, when the amount of the first monomer and the second monomer is less than about 25% by mass, the polymerization of the monomer is incomplete and a good gel state cannot be formed. Therefore, preferably, based on the total mass of the polymer electrolyte precursor composition, the amount of the lithium salt is about 25% by mass, and the amount of the first monomer and the second monomer is 75% by mass or less and 25% by mass or more based on the total mass of the polymer electrolyte composition or the polymer electrolyte precursor composition.

[0028] The present invention further provides a polymer electrolyte prepared in situ by the polymer electrolyte precursor composition according to the present invention. The polymer electrolyte can be prepared according to conventional methods in the art.

[0029] The present invention further provides a rechargeable battery comprising an anode, a cathode, a microporous separator separating the anode and the cathode, and the gel polymer electrolyte of the present invention.

[0030] The present invention further provides a lithium-ion battery comprising a polymer electrolyte prepared in situ by the polymer electrolyte precursor composition according to the present invention.

[0031] The present invention further provides an electrochemical device comprising the polymer electrolyte according to the present invention. In some examples, the electrochemical device is a secondary battery.

[0032] The present invention further provides the following: A step of manufacturing a mounted battery case comprising an electrode assembly; A step of inserting the polymer electrolyte precursor composition of the present invention into the battery case and then sealing it; and, A step of polymerizing the polymer electrolyte precursor composition; provides an apparatus manufactured by: The polymerization can be carried out by heating.

[0033] The polymer electrolyte of the present invention may be in a gel state (i.e., a gel polymer electrolyte) or in a solid state (i.e., a solid polymer electrolyte). Preferably, the polymer electrolyte is in a gel state. In the case of the polymer electrolyte precursor composition of the present invention, 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 Examples 1 to 3, when the polymer electrolyte precursor composition does not contain an organic solvent, the obtained polymer electrolyte is solid, and when the polymer electrolyte precursor composition contains, for example, 10% to 70% by mass of an organic solvent, the obtained polymer electrolyte is in a gel state.

[0034] There is no particular limitation on the type of lithium-ion battery in which the electrolyte of the present invention can be used. In particular, the lithium-ion battery is an LMB.

[0035] The present invention further provides the use of the monomer of the present invention, or the polymer electrolyte precursor raw material composition of the present invention, or the in-situ polymerized polymer electrolyte or electrochemical device of the polymer electrolyte precursor composition of the present invention in the preparation.

[0036] A person skilled in the art can determine a suitable separator for a lithium-ion battery using the polymer electrolyte of the present invention. For example, the separator may be surface-modified or unmodified, may have a thickness of less than 30 μm, less than 20 μm, the porosity may exceed 70%, or further exceed 80%, and the material may be, for example, cellulose or polytetrafluoroethylene.

[0037] First monomer In some examples, the carbonate monomer is preferably vinylene carbonate with the chemical formula: C3H2O3 and the CAS login number 872 - 36 - 6.

[0038] Second monomer The second monomer is preferably trimethylolpropane ethoxylate triacrylate (ETPTA) or another monomer with a molecular structure similar to ETPTA such as trimethylolpropane triacrylate or pentaerythritol triacrylate. Trimethylolpropane ethoxylate triacrylate (ETPTA) has an average Mn of about 428 and the CAS login number N28961 - 43 - 5.

[0039] Free radical initiator The free radical initiator for the polymerization reaction of the monomer is for the thermal polymerization reaction of the monomer and may be those commonly used in the art.

[0040] Examples of the free radical initiator or polymerization initiator include azo compounds such as 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), 2,2'-azoisobutyronitrile (AIBN), and azobisdimethyl-valeronitrile (AMVN); peroxy compounds such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, cumyl peroxide, and hydrogen peroxide; and hydroperoxides. Preferably, AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile) (V65), di-(4-tert-butylcyclohexyl)-peroxydicarbonate (DBC), etc. can be used.

[0041] Preferably, the free radical initiator can be selected from azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), benzoyl peroxide (BPO), lauroyl peroxide (LPO), etc. More preferably, the free radical initiator is azobisisobutyronitrile.

[0042] The amount of the free radical initiator may be the one conventionally used. Preferably, the amount of the free radical initiator is 0.1 to 3% by mass, more preferably about 0.5% by mass, based on the total mass of the monomer.

[0043] The polymerization initiator can decompose at a constant temperature of 40 to 80°C to form radicals, and react with the monomer through free radical polymerization to form a gel polymer electrolyte. Generally, free radical polymerization is carried out by sequential reactions including initiation involving the formation of transient molecules with high reactivity or active sites, propagation involving the reformation of active sites at the chain ends by the addition of monomers to the active chain ends, chain transfer involving the transfer of active sites to other molecules, and termination involving the destruction of active chain centers.

[0044] Lithium salt The lithium salt is a substance that dissolves in the non-aqueous electrolyte to dissociate lithium ions.

[0045] The lithium salt may be those commonly used in the art. Non-limiting examples include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium difluorooxalate (LiODFB), LiAsF6, LiClO4, LiN(CF3SO2)2, LiBF4, LiSbF6, and LiCl, LiBr, LiI, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAlCl4, CH3SO3Li, (CF3SO3Li)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, and imide, and may be at least one selected therefrom. The lithium salt is preferably lithium bis(trifluoromethanesulfonyl)imide. These materials can be used alone or in any combination thereof.

[0046] The amount of the lithium salt may also be an amount commonly used, for example, 5 to 40% by mass. Most preferably, it is about 25% by mass based on the total mass of the polymer electrolyte precursor composition.

[0047] Organic solvent The organic solvent may be one commonly used in the relevant technical field. For example, the organic solvent may be N-methyl-2-pyrrolidinone, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate and ethyl propionate salt. These materials can be used alone or in any combination thereof.

[0048] In some examples, the organic solvent is selected from ethylene carbonate / dimethyl carbonate (EC / DMC), propylene carbonate (PC), triethylene glycol dimethyl ether, etc. In some examples, the organic solvent is preferably ethylene carbonate / dimethyl carbonate (EC / DMC, EC / DMC = 50 / 50 (v / v)).

[0049] The amount of the organic solvent may be an amount commonly used. For example, the amount of the organic solvent may be 0% to 70% by mass, such as 0% to 65% by mass, based on the total mass of the polymer electrolyte precursor composition. It may be 0 to 60% by mass, 0 to 55% by mass, 5 to 70% by mass, 5 to 65% by mass, 5 to 60% by mass, 5 to 55% by mass, preferably 10% to 70% by mass, 10 to 65% by mass, 10 to 60% by mass, 10 to 55% by mass, and more preferably 20% to 50% by mass. Furthermore, in order to improve charge and discharge characteristics and flame retardancy, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n - glyme, hexalene triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N - substituted oxazolidinone, N,N - substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2 - methoxyethanol, aluminum trichloride, etc. can be added to the electrolyte. If necessary, the electrolyte can further contain halogen - containing solvents such as carbon tetrachloride and vinylidene fluoride to impart flame retardancy.

[0050] An electrochemical device includes all kinds of devices that undergo an electrochemical reaction. Examples of electrochemical devices include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, capacitors, etc., preferably secondary batteries.

[0051] Generally, a secondary battery is manufactured by including an electrolyte in an electrode assembly composed of a cathode and an anode. The electrode assemblies face each other via a separator.

[0052] The cathode is manufactured, for example, by applying a mixture of a cathode active material, a conductive material, and a binder to a cathode current collector and then drying and compressing it. If necessary, a filler may be further added to the above mixture.

[0053] The cathode current collector is generally manufactured to have a thickness of 3 - 500 μm. There is no particular limitation on the material of the cathode current collector as long as there is no chemical change in the manufactured battery and the conductivity is high. Examples of the material of the cathode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, and aluminum or stainless steel surface - treated with carbon, nickel, titanium, or silver. The current collector may be manufactured to have fine irregularities on its surface so as to enhance the adhesiveness to the cathode active material. Furthermore, the current collector can take various forms including films, sheets, foils, nets, porous structures, foams, and non - woven fabrics.

[0054] Examples of cathode active materials that can be used in the present invention include the following: layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium manganese oxides, for example, the formula Li 1+× Mn 2-x O4 (0 ≦ x ≦ 0.33), compounds of LiMnO3, LiMn2O3 and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides, such as LiV3O8, V2O5 and Cu2V2O7; the formula LiNi 1-x M x O2 (M = Co, Mn, Al, Cu, Mg, B or Ga, and 0.01 ≦ x ≦ 0.3) lithium nickel oxide; lithium manganese composite oxides, the formula LiMn 2-x M x O2 (M = Co, Ni, Fe, Cr, Zn or Ta, and 0.01 ≦ x ≦ 0.1) or lithium manganese composite oxides of the formula Li2Mn3MO8 (M = Fe, Co, Ni) in which part of Li is substituted with alkaline earth metal ions, LiMn2O4, disulfide compounds, Fe2(MoO4)3, LiFe3O4, etc. can be mentioned, but are not limited thereto.

[0055] The conductive material is usually added in an amount of 1 to 50% by mass based on the total mass of the mixture containing the cathode active material. There is no particular limitation on the conductive material as long as there is no chemical change in the manufactured battery and the conductivity is high. Examples of the conductive material include graphite such as natural or artificial graphite; carbon black; acetylene black; ketjen black; channel black; furnace black; carbon black such as lamp black and thermal black; conductive fibers; metal powders such as carbon fibers and metal fibers; fluorocarbon powders; conductive whiskers such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials including polyphenylene derivatives.

[0056] The binder is a component that aids in the binding between the active material and the conductive material, as well as the binding with the current collector. The binder is usually added in an amount of 1 to 50% by mass based on the total mass of the mixture containing the cathode active material. Examples of binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0057] The filler may optionally be used as a component for suppressing cathode expansion. If there is no chemical change in the manufactured battery and the conductivity is high, there is no particular limitation on the filler. Examples of fillers that may be used include olefin polymers such as polyethylene and polypropylene, and fibrous materials such as glass fiber and carbon fiber. The anode is manufactured by applying the anode active material to the anode current collector and then drying it. Optionally, it can further include the other components described above.

[0058] The anode current collector is generally manufactured to have a thickness of 3 to 500 μm. If there is no chemical change in the manufactured battery and the conductivity is high, there is no particular limitation on the material of the anode current collector. Examples of materials for the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, stainless steel with a surface treated with copper or carbon, nickel, titanium or silver, and aluminum-cadmium alloy. Similar to the cathode current collector, in order to increase the adhesion strength to the anode active material, the anode current collector can also be treated to form fine irregularities on its surface. Furthermore, the anode current collector can be used in various forms including film, sheet, foil, net, porous structure, foam, and non-woven fabric.

[0059] Examples of anode active materials that can be used in the present invention include carbon such as non-graphitized carbon and graphite-based carbon; 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) and other metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO2, Pb2O3, Pb3O4, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; and Li-Co-Ni-based materials.

[0060] The secondary battery according to the present invention includes, for example, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, and the like. The secondary battery can be manufactured in various forms. For example, the electrode assembly can be configured as a jelly roll structure, a stack structure, a stack / folding structure, etc. The battery can be configured such that the electrode assembly is mounted in a battery case of a cylindrical can, a prismatic can, or a laminated sheet including a metal layer and a resin layer. Such a configuration of the battery is well known in the art.

[0061] In some examples, the present invention is a polymer electrolyte precursor composition capable of forming a polymer electrolyte, comprising the following: A) a monomer consisting of vinylene carbonate and trimethylolpropane ethoxylate triacrylate; B) a free radical initiator of 0.1 to 3% by mass based on the total mass of the vinylene carbonate and the trimethylolpropane ethoxylate triacrylate; C) lithium bis(trifluoromethanesulfonyl)imide; and, D) ethylene carbonate / dimethyl carbonate; comprising, consisting essentially of, or consisting of, wherein the amounts of the vinylene carbonate and the trimethylolpropane ethoxylate triacrylate are 25 to 75% by mass based on the total mass of the polymer electrolyte precursor composition, and the mass ratio of the vinylene carbonate to the trimethylolpropane ethoxylate triacrylate is about 20:2 to 20:5. A polymer electrolyte precursor composition is provided.

[0062] The amount of lithium bis(trifluoromethanesulfonyl)imide is preferably about 25% by mass based on the total mass of the polymer electrolyte precursor composition. The amount of ethylene carbonate / dimethyl carbonate is preferably 0% to 50% by mass based on the total mass of the polymer electrolyte precursor composition.

[0063] Accordingly, the present invention provides a novel polymer electrolyte obtained by in-situ polymerization of the polymer electrolyte precursor composition of the present invention. The polymer electrolyte can be prepared in-situ, and the thickness of the electrolyte can be conveniently controlled. Furthermore, the combination of monomers, for example, the first monomer and the second monomer, forms an excellent polymer backbone, has excellent cycle performance and a higher electrochemical stability window compared to commercially available liquid electrolytes. Furthermore, the polymer electrolyte is non-flammable and has been shown to be safer than conventional liquid electrolytes. Also, when using lithium metal as the anode, due to the excellent mechanical properties of the electrolyte as shown in FIG. 2, the formation of lithium dendrites is suppressed, and since it does not consume a large amount of the solvent of the lithium metal battery as in the conventional case, it is particularly suitable for use in LMB. Compared with conventional PEO-based polymer electrolytes, the polymer electrolyte of the present invention has excellent ionic conductivity, a wider electrochemical window, and better cycle performance. Other advantages of the present invention will be apparent to those skilled in the art from the description of the specification. In order to explain the content and effects of the present invention in detail, the present invention will be further described below by combining examples, comparative examples, and related drawings.

[0064] Preparation of lithium metal battery The lithium metal battery is as follows: Step a) Preparation of an electrolyte precursor composition solution; and, Step b) Assembly of the lithium metal battery and in-situ polymerization by heating; It was prepared by the method of. Steps a) and b) were carried out in a glove box filled with argon gas (H2O, O2 ≤ 0.5 ppm).

Example

[0065] 1) Preparation of the precursor electrolyte solution: 0.098 g of trimethylolpropane ethoxylate triacrylate (ETPTA, average Mn ~ 428), 0.652 g of vinylene carbonate (VC), 1.5 g of EC / DMC (EC / DMC = 50 / 50 (v / v)), 0.75 g of LiTFSI and 3.75 mg of AIBN were mixed and stirred at 25 °C for 0.5 h to obtain a precursor electrolyte solution.

[0066] 2) Cell assembly and in-situ polymerization by heating: The LiFePO4 (LFP) cathode was prepared as follows. LFP, acetylene black, and poly(vinylidene fluoride) in a mass ratio of 80:10:10 were mixed to form a viscous slurry. Next, a flat carbon-coated aluminum foil was coated with the viscous slurry by the doctor blade method. The carbon-coated aluminum foil coated with the viscous slurry was dried in an air circulation oven at 70 °C for 1 h and then further dried at 100 °C under high vacuum for 12 h to obtain a LiFePO4 cathode. The mass loading of the active material (LiFePO4) was 5.3 - 6.2 mg cm -2 It was. The precursor electrolyte solution was injected into a 2032 lithium battery equipped with a cellulose separator that separates the cathode and the anode (Li foil), and then the cell was heated at 60 °C for 8 h and then at 80 °C for 4 h. After the heating process, a gel-like polymer electrolyte without a flowing liquid phase between the anode and the cathode could be obtained. The gel state of the polymer electrolyte could be confirmed when the 2032 battery was disassembled. Furthermore, Fourier transform infrared spectroscopy (FTIR) was performed to analyze the chemical structure of the gel polymer electrolyte. As can be seen from Figure 1, after polymerization, the absorption peak at 3166 cm -1 disappeared, which was fully attributed to the chemical structure change from C=C double bond to C-C single bond.

Example

[0067] 1) Preparation of precursor electrolyte solution: 0.1956 g of trimethylolpropane ethoxylate triacrylate (ETPTA, average Mn~428), 1.3043 g of vinylene carbonate (VC), 0.75 g of EC / DMC, 0.75 g of LiTFSI, and 7.5 mg of AIBN were mixed and stirred at 25 °C for 0.5 h. 2) In the same manner as in Example 1, cell assembly and in-situ polymerization by heating were carried out. After the heating process, a gel-like polymer electrolyte without a flowing liquid phase between the anode and the cathode could be obtained. The gel state of the polymer electrolyte could be confirmed when the 2032 battery was decomposed.

Example

[0068] 1) Preparation of precursor electrolyte solution: 0.2935 g of trimethylolpropane ethoxylate triacrylate (ETPTA, average Mn~428), 1.9565 g of vinylene carbonate (VC), 0.75 g of LiTFSI, and 11.25 mg of AIBN were mixed and stirred at 25 °C for 0.5 h. 2) In the same manner as in Example 1, cell assembly and in-situ polymerization by heating were carried out. After heating, a solid-state polymer electrolyte was obtained. The solid state of the polymer electrolyte could be confirmed by the decomposition of the 2032 battery. 〔Comparative Example 1〕 Cell assembly: A commercially available liquid electrolyte 1 M LiPF6 in 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, where the cathode and the anode are the same as those in Example 1. Performance test 1. Cycle performance of the electrolyte Using LiFePO4 as the cathode and Li metal as the anode, the cycle performance of the battery was evaluated at room temperature using a Land battery test system (Wuhan King Electronic Co., Ltd., China). The cut-off voltages were 4.2 V vs. Li / Li+ for charging (Li extraction) and 2.4 V vs. Li / Li+ for discharging (Li insertion). All relevant cells were activated by a weak current before cycling. The C-rate for the entire electrochemical measurement was defined based on 1C = 160 mA g -1 . The test results are shown in Figure 3, where the solid dots represent the discharge capacity and the hollow dots represent the Coulomb efficiency in Figure 3.

[0069] In Figure 3, all cells were evaluated at 0.5 °C. The discharge capacity of the battery decreased rapidly after 100 cycles in Comparative Example 1, and the capacity retention rate was 77.9%, but the Coulomb efficiency of the electrolyte in Comparative Example 1 was less than 99% and decreased to 96.5% after 100 cycles. It is clear that the cycle performance with the polymer electrolytes of Example 1, Example 2, and Example 3 did not decrease as in Comparative Example 1, and they were clearly excellent in cycle performance. The capacity retention rates of Example 1, Example 2, and Example 3 were 93.97%, 98.7%, and 97.3% respectively, and the Coulomb efficiency was >99% as shown in Table 1. This means that the polymer electrolytes prepared in Example 1, Example 2, and Example 3 of the present invention have a significantly excellent effect on cycle performance. However, for the batteries with all solid polymer electrolytes prepared in Example 3, the discharge capacity was extremely low because of the low ionic conductivity.

[0070]

Table 1

[0071] Figure 4 shows the electrochemical stability windows of the polymer electrolyte and the liquid electrolyte. The liquid electrolyte of Comparative Example 1 showed an electrochemical stability window of about 4.6 V. Clearly, the electrochemical stability window of the polymer electrolyte was higher than that of the liquid electrolyte. The electrochemical stability windows of the polymer electrolytes of Example 1, Example 2, and Example 3 according to the present invention were extremely stable at about 5 V, whereby better electrochemical performance could be imparted. This extremely stable electrochemical stability window of about 5 V is extremely important, whereby the battery can use a novel high-nickel-containing cathode.

[0072] 3. Ionic conductivity AC (alternating current) impedance spectroscopy was measured with a CHI760e electrochemical workstation. The electronic conductivity of the gel-polymer electrolyte was measured using an SS / GPE / SS cell with an applied voltage of 5 mV, and the results are shown in Figure 5. The ionic conductivities of the examples were calculated based on Figure 5 and summarized in Table 2 below.

[0073] [Table 2] Poly(vinylene carbonate) (PVCA) with an ionic conductivity of 1.95×10 -5 S / cm is disclosed. Compared with the PVCA polymer electrolyte disclosed in Non-Patent Document 1, which represents the PVCA polymer electrolyte (PVCA), the ionic conductivity of the solid polymer electrolyte of the present invention (4.5×10 -5 S / cm of Example 3) was found to be higher. Also, the ionic conductivity was about 2.1×10 -6Much higher than the extremely low conventional PEO-based polymer electrolytes of S / cm (K.Wen et al. J.Mater.Chem.A, Vol.6 (2018), pp11631 - 11663). Furthermore, the ionic conductivities of the gel polymer electrolytes in Example 1 and Example 2 were equivalent to those of the PVCA-based gel polymer electrolytes of the prior art. (Non-Patent Document 2). 4. Inhibition of lithium dendrite formation After 200 cycles, the Li|GPE|LiFePO4 cell using the in-situ polymerized gel polymer electrolyte of Example 2 was disassembled in an argon glove box, and then the cycled Li foil was immersed in dimethoxyethane (DME) for about 2 hours to remove LiTFSI. For comparison, a Li foil (Comparative Example 1) that had been repeated 40 times in a commercial electrolyte was treated in the same manner as above. Next, the prepared Li foil samples were observed by SEM (Nova Nano SEM 230, FEI Company, U.S.A.).

[0074] As shown in Fig. 2(a), the Li foil cycled in the gel polymer electrolyte showed a dense paving stone structure with a particle size of 10 - 15 μm showing uniform lithium deposition during cycling, and no lithium dendrites were detected. After only 40 cycles in a commercial liquid electrolyte, as shown in Fig. 2(b), obvious Li dendrites were observed, and loose lithium deposition was observed as shown in the small image in the upper right corner of Fig. 2(b). Both Li dendrites and powdered Li are harmful to the battery. The results showed that the gel polymer electrolyte can effectively inhibit the formation of Li dendrites and suppress the pulverization of the lithium foil.

[0075] Therefore, when using a polymer electrolyte, due to the excellent mechanical properties of the electrolyte, the formation of lithium dendrites can be suppressed in LIBs having a lithium metal anode.

[0076] The term "comprising" etc. used in this specification is an open term meaning "including at least" unless otherwise specified. All references, tests, standards, documents, publications, etc. described in this specification are hereby incorporated by reference into this specification. When numerical limits or ranges are recited, endpoints are included. Also, all values and subranges within the numerical limits or ranges are specifically included as if expressly recited. The foregoing description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Accordingly, the invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. In this regard, particular embodiments within the invention do not represent all advantages of the invention and are not considered in a broad sense.

Claims

1. A monomer composition for preparing a polymer electrolyte precursor composition capable of forming a polymer electrolyte polymerized in situ, said monomer composition comprising the following: A1) A first monomer, an unsaturated carbonate ester monomer; and, A2) A second monomer having the following formula (II): 【Chemical 2】 (In the formula, R represents methyl, -CH ２ OH, ethyl, or -CH ２ CH ２ OH, and a, b, c are each independently 0, 1, 2, or 3, and a + b + c is 2 or more) represented by the monomer,; comprising or consisting of, monomer composition.

2. The first monomer has the following formula (I): 【Chemical 1】 (wherein R represents H, F, methyl or ethyl) The monomer composition according to claim 1, which is a monomer represented by the formula.

3. The first monomer is vinylene carbonate, and the monomer composition according to claim 1.

4. The second monomer is trimethylolpropane ethoxylate triacrylate, and the monomer composition according to claim 1.

5. The mass ratio of the first monomer to the second monomer is 20:0.5 to 20:10, and the monomer composition according to any one of claims 1 to 3.

6. The mass ratio of the first monomer to the second monomer is 20:2 to 20:5, and the monomer composition according to any one of claims 1 to 3.

7. The mass ratio of the first monomer to the second monomer is 20:3 to 20:5, and the monomer composition according to any one of claims 1 to 3.

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

9. A polymer electrolyte precursor composition capable of forming a polymer electrolyte polymerized in situ, comprising the following: A) The monomer composition according to any one of claims 1 to 7; B) A free radical initiator for the thermal polymerization reaction of the monomer composition; C) A lithium salt; and, D) Optionally, an organic solvent, wherein the organic solvent is 0% to 70% by mass based on the total mass of the polymer electrolyte precursor composition; comprising or consisting of, a polymer electrolyte precursor composition.

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

11. The polymer electrolyte precursor composition according to claim 9, wherein the organic solvent is 10% to 60% by mass.

12. The polymer electrolyte precursor composition according to claim 9, wherein the organic solvent is 20% to 50% by mass.

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

14. The polymer electrolyte precursor composition according to any one of claims 9 to 13, wherein the amount of the monomer composition is 5 to 80% by mass based on the total mass of the polymer electrolyte precursor composition.

15. The polymer electrolyte precursor composition according to any one of claims 9 to 13, wherein the amount of the monomer composition is 25 to 75% by mass based on the total mass of the polymer electrolyte precursor composition.

16. A method for preparing a polymer electrolyte in situ, comprising the following: 1) A step of injecting the polymer electrolyte precursor composition according to any one of claims 9 to 13 into a battery case equipped with an electrode assembly and then sealing it; and 2) A step of polymerizing the polymer electrolyte precursor composition in situ by heating. A method comprising the above steps.

17. A polymer electrolyte formed by the polymer electrolyte precursor composition according to any one of claims 9 to 13 or prepared according to the method of claim 16.

18. A polymer electrolyte for a rechargeable battery, comprising a polymer which is a reaction product of the monomer composition according to any one of claims 1 to 7 and includes a free radical initiator.

19. A polymer electrolyte for a rechargeable battery, comprising the following: (i) A polymer which is a reaction product of the monomer composition according to any one of claims 1 to 7 and includes a free radical initiator, and (ii) An organic solvent containing an ionic salt in an amount effective to achieve an ionic conductivity of 0.44 mS / cm or less. A polymer electrolyte comprising the above components.

20. A rechargeable battery, comprising an anode, a cathode, a microporous separator separating the anode and the cathode, and the polymer electrolyte according to any one of claims 17 to 19 which is a gel.

21. A lithium-ion battery comprising a polymer electrolyte prepared in-situ by the polymer electrolyte precursor composition according to any one of claims 9 to 13.

22. An electrochemical device comprising the polymer electrolyte according to any one of claims 17 to 19.

23. A mounted battery case provided with an electrode assembly and An apparatus comprising the polymer electrolyte precursor composition according to any one of claims 9 to 13, wherein the polymer electrolyte precursor composition is inserted into the battery case and sealed, Apparatus.

24. A polymer electrolyte precursor composition capable of forming a polymer electrolyte, comprising the following: A) Monomers consisting of vinylene carbonate and trimethylolpropane ethoxylate triacrylate; B) A free radical initiator in an amount of 0.1 to 3% by mass based on the total mass of the vinylene carbonate and the trimethylolpropane ethoxylate triacrylate; C) Lithium bis(trifluoromethanesulfonyl)imide; and, D) Ethylene carbonate / dimethyl carbonate; Containing, consisting essentially of, or consisting of Here, the amounts of the vinylene carbonate and the trimethylolpropane ethoxylate triacrylate are 25 to 75% by mass based on the total mass of the polymer electrolyte precursor composition, and the mass ratio of the vinylene carbonate to the trimethylolpropane ethoxylate triacrylate is 20:2 to 20:

5. Polymer electrolyte precursor composition.

25. Use of the monomer composition according to any one of claims 1 to 7, or the polymer electrolyte precursor raw material composition according to claim 8, or the polymer electrolyte precursor composition according to any one of claims 9 to 13, in the preparation of an in-situ polymerized polymer electrolyte or an electrochemical device.

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