Polymer electrolyte monomer, method for preparing the same, and secondary battery

Abstract

The application relates to the technical field of batteries, in particular to a polymer electrolyte monomer, a preparation method thereof and a secondary battery. The polymer electrolyte monomer provided by the application has the following structural formula: wherein R1 is a C3-C6 alkyl group, and R2 and R3 are each independently a C2-C4 alkenyl group. The polymer electrolyte monomer has a structure including a carbonate group, a fluorine-containing group and a phosphate group; shows excellent lithium ion transference number, high lithium ion conductivity, a wide electrochemical stability window and excellent flame retardant properties; and solves the problems of low lithium ion conductivity, a narrow electrochemical window and hidden safety hazards of existing gel-state polymer electrolytes.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a polymer electrolyte monomer, its preparation method, and a secondary battery. Background Technology

[0002] With the rapid development of the new energy industry, lithium-ion batteries are widely used in various fields due to their advantages such as high energy density, good charge / discharge rate performance, and long cycle life. However, with product upgrades and iterations, higher requirements are being placed on the energy density and safety of lithium-ion batteries.

[0003] In recent years, lithium metal anodes and high-voltage cathode materials have attracted widespread attention due to their ability to provide higher energy densities compared to traditional lithium-ion batteries. However, continuing to use existing commercial liquid electrolytes often leads to persistent side reactions at the electrode-electrolyte interface, inducing lithium dendrite growth, resulting in rapid battery capacity decay and even serious safety issues. Therefore, developing polymer electrolytes with high safety and compatibility with high-voltage cathodes has become one approach to address these problems.

[0004] To address the aforementioned issues, polycarbonate-based polymer electrolytes have become a focus of attention due to their superior oxidative stability compared to ether-based systems, good compatibility with high-voltage cathodes, and low crystallinity. However, these electrolytes still suffer from low lithium-ion transference numbers, difficulty in lithium salt dissociation, and the severe flammability of hydrocarbons, hindering their further development and application. Therefore, developing a polymer electrolyte that simultaneously achieves high pressure resistance, strong ion dissociation capability, and excellent flame retardant properties remains a significant challenge.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The first objective of this invention is to provide a polymer electrolyte monomer, wherein the polymer electrolyte prepared therefrom has high pressure resistance, high ionic conductivity, strong ion dissociation ability, thermal stability and flame retardancy.

[0007] A second objective of the present invention is to provide a method for preparing the above-mentioned polymer electrolyte monomer.

[0008] A third objective of this invention is to provide a secondary battery.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a polymer electrolyte monomer having the following structural formula: ; In this case, R1 is a C3~C6 alkyl group, and R2 and R3 are each independently a C2~C4 alkenyl group.

[0010] Furthermore, the polymer electrolyte monomer has the following structural formula: .

[0011] The present invention also provides a method for preparing the polymer electrolyte monomer as described above, comprising the following steps: S1, difluoromethanediol, compound A and catalyst react in a solvent to give compound I; The structural formula of the difluoromethanediol is as follows: The general structural formula of compound A is: The general structural formula of compound I is: R1 is a C3~C6 alkyl group; S2. Compound I, compound B, and organic amine are reacted in a solvent to obtain the polymer electrolyte monomer; Wherein, the general structural formula of compound B is R2 and R3 are each independently C2~C4 alkenyl groups.

[0012] Further, in step S1, the structural formula of compound A is as follows: The structural formula of compound I is as follows: ; And / or, in step S1, the reaction includes: reacting at 10~30°C for 20~30 h.

[0013] Furthermore, in step S2, the structural formula of compound B is as follows: ; And / or, in step S2, the reaction includes: adding compound B dropwise to a mixture of compound I, organic amine and solvent at 0~10°C; after the addition is complete, reacting at 10~30°C for 10~15 h.

[0014] The present invention also provides a secondary battery comprising a polymer electrolyte mainly formed by monomer polymerization; said monomer includes the polymer electrolyte monomer as described above.

[0015] Furthermore, the monomer also includes acrylate compounds.

[0016] Preferably, the mass ratio of the acrylate compound to the polymer electrolyte monomer is (6~8):(2~4).

[0017] Furthermore, the secondary battery includes electrodes, a separator, and the polymer electrolyte; the polymer electrolyte is mainly obtained by polymerizing a polymer electrolyte precursor solution; the polymer electrolyte precursor solution includes the monomer, lithium salt, initiator, and solvent.

[0018] Furthermore, it includes at least one of the following features (1) to (3); (1) The monomer content in the polymer electrolyte precursor solution is 1wt%~30wt%; (2) The lithium salt content in the polymer electrolyte precursor solution is 5wt%~25wt%; (3) The mass of the initiator is 0.01% to 5% of the mass of the monomer; (4) The polymer electrolyte precursor solution also includes additives.

[0019] Furthermore, the secondary battery includes electrodes, a separator, and a liquid electrolyte; The electrode comprises an electrode active material, a conductive agent, a binder, an oxide solid electrolyte, and the polymer electrolyte, which is mainly obtained by polymerization of the monomer and the initiator.

[0020] Preferably, the mass of the monomer is 1% to 8% of the total mass of the electrode active material, the conductive agent, the binder, and the oxide solid electrolyte.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The polymer electrolyte monomer of the present invention comprises carbonate groups, fluorinated groups, and phosphate groups in its structure. The phosphate groups can optimize the coordination environment of lithium ions through a competitive effect, accelerating the interfacial transport kinetics of lithium ions. Furthermore, the high phosphate content effectively enhances the thermal stability of the polymer matrix and its ability to capture flammable free radicals, thus significantly improving the thermal stability of the polymer electrolyte. The introduced fluorinated groups effectively promote the formation of a "fluorine-oxygen co-coordination" structure, relaxing and decoupling ion conduction from the polymer chain segments, enabling the construction of a more efficient lithium electrolyte along the polymer chain and surrounding solvent molecules. + Transmission channel, and achieve uniform Li at the anode interface + Deposition. The carbonate groups can effectively dissociate lithium salts, contributing to high ionic conductivity.

[0022] 2. The secondary battery of the present invention uses a polymer electrolyte formed by polymerizing the above-mentioned polymer electrolyte monomers, which has excellent electrochemical performance. The polymer electrolyte is a gel-state polymer electrolyte, exhibiting excellent lithium-ion transference number, high lithium-ion conductivity, a wide electrochemical stability window, and excellent flame retardant properties. It solves the problems of low lithium-ion conductivity, narrow electrochemical window, and safety hazards faced by existing gel-state polymer electrolytes.

[0023] 3. In the secondary battery of the present invention, the polymer electrolyte formed by polymerizing the above-mentioned polymer electrolyte monomers is added to the electrode, such as the positive electrode, which can significantly improve its cycle performance and is beneficial to improving the long-term cycle stability of the battery. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is the 1H NMR spectrum of compound I from Example 1 of the present invention.

[0026] Figure 2 This is the 1H NMR spectrum of the polymer electrolyte monomer of Example 1 of the present invention.

[0027] Figure 3 The cycle capacity retention rate of the secondary batteries in Embodiment 3, Comparative Example 3, and Comparative Example 4 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0029] In some embodiments of the present invention, a polymeric electrolyte monomer is provided having the following structural formula: ; Wherein, R1 is a C3~C6 alkyl group, and R2 and R3 are each independently a C2~C4 alkenyl group; for example, R1 is a C3~C6 straight-chain alkyl group, such as -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2- or -CH2CH2CH2CH2CH2CH2-; R2 and R3 are each independently -CH=CH2, -CH2-CH=CH2, -CH=CHCH3 or -CH=CHCH2CH3.

[0030] The polymer electrolyte monomer of the present invention comprises carbonate groups, fluorinated groups (-CF2- groups), and phosphate groups. The carbonate groups enable efficient lithium-ion transport and offer high-voltage compatibility compared to ether groups. Furthermore, to address the flammability of carbonates and their incompatibility with lithium metal anodes, fluorinated groups (-CF2- groups) and phosphorus-rich phosphate groups are introduced. This not only improves high-voltage resistance but also promotes lithium salt dissociation, restricts the migration of lithium salt anion groups, and significantly enhances the flame-retardant properties of the polymer electrolyte, ensuring the high safety of the high-voltage battery.

[0031] The polymer electrolyte monomer is a two-site phosphate ester-based monomer, forming a polymer electrolyte suitable for high-voltage cathodes and exhibiting strong flame retardancy. Centered on the phosphate ester, it optimizes the lithium-ion coordination environment through a competitive effect, accelerating lithium-ion interfacial transport kinetics. Furthermore, the phosphate ester content effectively enhances the thermal stability of the polymer matrix and its ability to capture flammable free radicals, significantly improving the thermal stability of the polymer electrolyte. The introduced fluorine-containing groups (-CF2- groups) effectively promote the formation of a "fluorine-oxygen co-coordination" structure, loosening and decoupling ion conduction from the polymer chain segments. This allows for the construction of a more efficient Li-ion system along the polymer chain and surrounding solvent molecules. + Transmission channel, and achieve uniform Li at the anode interface + Deposition. The carbonate groups can effectively dissociate lithium salts, contributing to high ionic conductivity.

[0032] In some embodiments of the present invention, the polymer electrolyte monomer has the following structural formula: It is named divinyl difluoro{[1-oxo-5-(2-oxo-1,3-dioxacyclopentan-4-yl)pentyl]oxy}methyl phosphate.

[0033] The polymer electrolyte monomer of this invention, when used to form a polymer electrolyte, exhibits a wide electrochemical window, which can be attributed to the combined effect of fluorine-containing groups (-CF2- groups) and phosphate groups; it also possesses high ionic conductivity, which can be attributed to the effective ion dissociation capability of the carbonate groups; and it has a high ion transference number, forming a highly efficient lithium-ion transport channel; and the use of phosphate ester as the polymer backbone provides strong thermal stability and flame retardant properties. This invention solves the problems of low ionic conductivity, narrow electrochemical window, and safety hazards caused by flammability faced by existing polymer electrolytes.

[0034] The introduction of fluorine-containing groups (-CF2- groups) into the polymer electrolyte monomer can effectively promote the formation of a "fluorine-oxygen co-coordination" structure, thereby relaxing and decoupling ion conduction from polymer segments and constructing a more efficient Li... +The transport channel is facilitated by the introduced carbonate, which effectively dissociates the lithium salt, significantly improving ionic conductivity. Using phosphate groups as the polymer backbone effectively enhances the thermal stability of the polymer matrix and its ability to capture flammable free radicals, thus greatly improving safety performance.

[0035] In some embodiments of the present invention, a method for preparing the above-mentioned polymer electrolyte monomer is also provided, comprising the following steps: S1, difluoromethanediol, compound A and catalyst react in a solvent to give compound I; The structural formula of difluoromethanediol is: The general structural formula of compound A is: The general structural formula of compound I is: R1 is a C3~C6 alkyl group; S2, compound I, compound B and organic amine react in a solvent to obtain a polymer electrolyte monomer; The general structural formula of compound B is: R2 and R3 are each independently C2~C4 alkenyl groups.

[0036] In some embodiments of the present invention, in step S1, the structural formula of compound A is as follows: It was named methyl 1,3-dioxolane-4-pentanoate; the structural formula of compound I is... It is named 5-(2-oxoylide-1,3-dioxacyclopentan-4-yl)valerate difluoro(hydroxy)methyl ester; preferably, the molar ratio of difluoromethanediol to compound A is (1~1.2):1.

[0037] In some embodiments of the present invention, in step S1, the catalyst includes, but is not limited to, tetraisopropyl titanate (Ti(OiPr)4); the solvent includes, but is not limited to, tetrahydrofuran (THF); preferably, the molar ratio of compound A to catalyst is 1:(0.05~0.1).

[0038] In some embodiments of the present invention, step S1 includes reacting at 10~30°C for 20~30 hours.

[0039] In some embodiments of the present invention, in step S2, the structural formula of compound B is as follows: It is named dienyl ethyl chlorophosphate; preferably, the molar ratio of compound I to compound B is 1:(1~1.2).

[0040] In some embodiments of the present invention, in step S2, the organic amine includes, but is not limited to, triethylamine (TEA); the solvent includes, but is not limited to, tetrahydrofuran (THF); preferably, the molar ratio of compound I to organic amine is 1:(1~1.3).

[0041] In some embodiments of the present invention, step S2 includes: adding compound B dropwise to a mixture of compound I, organic amine and solvent at 0-10°C; and reacting at 10-30°C for 10-15 hours after the addition is complete.

[0042] In some embodiments of the present invention, a secondary battery is also provided, comprising a polymer electrolyte mainly formed by monomer polymerization; the monomer includes the aforementioned polymer electrolyte monomer; preferably, the secondary battery comprises a lithium-ion battery.

[0043] In some embodiments of the present invention, the monomer further includes acrylate compounds; preferably, the acrylate compounds include, but are not limited to, methyl methacrylate; the acrylate compounds may also be replaced with other compounds, simple compounds that can cause polymerization or condensation reactions to synthesize polymers, and low-molecular-weight raw materials used to synthesize polymers.

[0044] In some embodiments of the invention, the mass ratio of acrylate compound to polymer electrolyte monomer is (6-8):(2-4); typically, but not limitingly, for example, the mass ratio of acrylate compound to polymer electrolyte monomer can be 6:4, 7:3, 8:2, and any value between any two thereof.

[0045] The addition of acrylate is to reduce steric hindrance, better polymerize with polymer electrolyte monomers to form high molecular weight products, and achieve complete coating of the electrolyte.

[0046] Excessive use of polymer electrolyte monomers will result in excessive impedance, thus affecting electrical performance; insufficient use will prevent the rapid transport of lithium ions, high voltage resistance, and excellent safety performance.

[0047] In some embodiments of the present invention, the polymerization temperature is 50~70°C and the polymerization time is 10~20h; preferably, the polymerization temperature is 60°C and the time is 12h.

[0048] The polymer electrolyte monomer of the present invention is used in secondary batteries, and the polymer electrolyte formed by its polymerization can be used as a solid electrolyte or for electrode mixing; it can improve the cycle stability and safety performance of secondary batteries.

[0049] In some embodiments of the present invention, the secondary battery includes electrodes, a separator, and a polymer electrolyte; the polymer electrolyte is mainly obtained by polymerizing a polymer electrolyte precursor solution; the polymer electrolyte precursor solution includes monomers, lithium salts, initiators, and solvents; preferably, the electrodes include electrode active materials, conductive agents, and binders; the electrodes include positive electrodes or negative electrodes; the electrode active materials include positive electrode active materials or negative electrode active materials.

[0050] In some embodiments of the present invention, the polymer electrolyte obtained mainly by polymer electrolyte precursor solution polymerization is a gel-state polymer electrolyte.

[0051] Gel-state polymer electrolytes offer advantages such as good flexibility, the ability to form tight in-situ contact between the electrode and electrolyte, significantly reduced electrolyte leakage risk, and compatibility with existing lithium-ion battery manufacturing processes, effectively improving battery energy density and preventing electrolyte leakage. However, the ion migration in existing gel-state polymer electrolytes mainly relies on the local movement of polymer chain segments, resulting in a high activation energy required for lithium-ion migration and consequently low ionic conductivity. The electrochemical window of gel-state polymer electrolytes is limited, particularly at high voltages (>4.3V vs. Li). + Under conditions of low permeability ( / Li), oxidative decomposition can occur, leading to interfacial side reactions and decreased cycle stability. Gel-state polymer electrolytes encapsulate a large amount of flammable organic liquid, making them highly susceptible to combustion under abusive conditions such as high temperatures and overcharging, potentially even triggering battery thermal runaway and posing safety hazards. Therefore, gel-state polymer electrolytes still face challenges such as low ionic conductivity at room temperature, low lithium-ion transference number, insufficient high-voltage resistance, and flammability, severely limiting their practical applications.

[0052] The gel polymer electrolyte formed by monomer polymerization according to the present invention has excellent electrochemical performance; it exhibits excellent lithium-ion transference number, high lithium-ion conductivity, wide electrochemical stability window and excellent flame retardant properties; it solves the problems of low lithium-ion conductivity, narrow electrochemical window and safety hazards faced by existing gel polymer electrolytes.

[0053] In some embodiments of the present invention, the monomer content in the polymer electrolyte precursor solution is 1 wt% to 30 wt%; typically, but not limitingly, for example, the monomer content in the polymer electrolyte precursor solution can be 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, and any value between any two thereof; preferably 10 wt% to 15 wt%.

[0054] In some embodiments of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(oxaloyl)borate (LiBOB), lithium difluorooxaloyl borate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0055] In some embodiments of the present invention, the lithium salt content in the polymer electrolyte precursor solution is 5 wt% to 25 wt%; typically, but not limitingly, for example, the lithium salt content in the polymer electrolyte precursor solution can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and any value between any two thereof; preferably 10 wt% to 15 wt%.

[0056] In some embodiments of the present invention, the initiator includes a thermal initiator and / or a photoinitiator; preferably, the thermal initiator includes at least one of benzoyl peroxide (BPO), dodecyl peroxide (LPO), tert-butyl peroxide (TBPB), dicumyl peroxide (DCP), di(2-ethylhexyl) percarbonate (EHP), azobisisobutyronitrile (AIBN), and azobisisoheptanenitrile (ABVN / AMVN); the photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), benzophenone (BP), benzoyl dimethyl ether (BDK), 4-chlorobenzophenone (CBP), and ethyl 4-dimethylaminobenzoate (EDB).

[0057] In some embodiments of the invention, the mass of the initiator is 0.01% to 5% of the monomer mass; typically, but not limitingly, for example, the mass of the initiator is 0.01%, 0.5%, 1%, 2%, 3%, 4%, 5% of the monomer mass and any value between any two thereof; preferably 0.5% to 1.5%.

[0058] In some embodiments of the present invention, the solvent includes at least one selected from ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethyl acetate (EA), methyl acetate (MA), propylene sulfite (PS), ethylene sulfate (DTD), and fluoroethylene carbonate (FEC).

[0059] In some embodiments of the present invention, the solvent content in the polymer electrolyte precursor solution is 50wt% to 85wt%; typically, but not limitingly, for example, the solvent content in the polymer electrolyte precursor solution can be 50wt%, 60wt%, 70wt%, 80wt%, 85wt%, and any value between any two thereof; preferably 60wt% to 80wt%.

[0060] In some embodiments of the present invention, the polymer electrolyte precursor solution further includes additives; preferably, the additives include at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfate (DTD), ethylene sulfate (DTD), triallyl phosphate, dimethyl methylphosphonate, dimethyl sulfate (DMS), trimethyl phosphate (TMP), dimethyl methyl phosphate (DMMP), biphenyl (BP), and cyclohexylbenzene (CHB).

[0061] In some embodiments of the present invention, the content of additives in the polymer electrolyte precursor solution is 3wt% to 5wt%; typically, but not limitingly, for example, the content of additives in the polymer electrolyte precursor solution can be 3wt%, 4wt%, 5wt%, and any value between any two thereof.

[0062] In some embodiments of the present invention, the preparation of the polymer electrolyte precursor solution includes: mixing the components.

[0063] In some embodiments of the present invention, the preparation of a secondary battery includes: assembling electrodes, a separator, and a polymer electrolyte precursor solution into a battery, and then allowing it to stand at 50-70°C for 10-20 hours.

[0064] The properties of the gel-state polymer electrolyte formed by monomer polymerization according to the present invention are as follows: using linear sweep voltammetry (LSV), its electrochemical window can reach 4.9V, which can be attributed to the combined effect of fluorine-rich and phosphorus-rich segments; using electrochemical impedance spectroscopy (EIS), its ionic conductivity can reach 0.7mS / cm, which can be attributed to the effective ion dissociation ability of carbonate groups; using electrochemical impedance spectroscopy and steady-state current method (it), its lithium-ion transference number can reach 0.6, indicating that it forms a highly efficient lithium-ion transport channel.

[0065] The secondary battery made with gel polymer electrolyte has excellent electrochemical and safety performance; it can maintain more than 94% capacity retention after 300 cycles at room temperature, and has good cycle stability; its safety performance is verified by hot box test and nail penetration test, and it can successfully pass the 190℃ hot box test and nail penetration test.

[0066] In some embodiments of the present invention, the secondary battery includes electrodes, a separator, and a liquid electrolyte; The electrode comprises an electrode active material, a conductive agent, a binder, an oxide solid electrolyte, and a polymer electrolyte, wherein the polymer electrolyte is mainly obtained by polymerization of monomers and an initiator; preferably, the electrode is a positive electrode or a negative electrode; the electrode active material is a positive electrode active material or a negative electrode active material. For example, the positive electrode comprises a positive electrode active material, a conductive agent, a binder, an oxide solid electrolyte, and a polymer electrolyte; the negative electrode comprises a negative electrode active material, a conductive agent, and a binder.

[0067] Using the polymer electrolyte of the present invention in the preparation of electrodes for secondary batteries can significantly improve their cycle performance and is beneficial to improving the long-term cycle stability of the battery.

[0068] In some embodiments of the present invention, the mass of the monomer is 1% to 8% of the total mass of the electrode active material, conductive agent, binder and oxide solid electrolyte; typically, but not limitingly, for example, the mass of the monomer is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% of the total mass of the electrode active material, conductive agent, binder and oxide solid electrolyte and any value between any two thereof; preferably 1.5% to 2.5%.

[0069] In some embodiments of the present invention, the initiator includes a thermal initiator and / or a photoinitiator; preferably, the thermal initiator includes at least one of benzoyl peroxide (BPO), dodecyl peroxide (LPO), tert-butyl peroxide (TBPB), dicumyl peroxide (DCP), di(2-ethylhexyl) percarbonate (EHP), azobisisobutyronitrile (AIBN), and azobisisoheptanenitrile (ABVN / AMVN); the photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), benzophenone (BP), benzoyl dimethyl ether (BDK), 4-chlorobenzophenone (CBP), and ethyl 4-dimethylaminobenzoate (EDB).

[0070] In some embodiments of the invention, the mass of the initiator is 0.01% to 5% of the monomer mass; typically, but not limitingly, for example, the mass of the initiator is 0.01%, 0.5%, 1%, 2%, 3%, 4%, 5% of the monomer mass and any value between any two thereof; preferably 0.05% to 0.15%.

[0071] In some embodiments of the present invention, the oxide solid electrolyte includes Li7La3Zr2O. 12 (LLZO), LLZTO, LLNOF, Li 3x La 2 / 3-x TiO3 (LLTO), Li 1+x Al x Ti2-x (PO4)3 (LATP) and Li 1+x Al x Ge 2-x At least one of (PO4)3 (LAGP).

[0072] In some embodiments of the present invention, the mass of the oxide solid electrolyte is 0.1% to 10% of the total mass of the electrode active material, conductive agent, binder and oxide solid electrolyte, preferably 0.5% to 1.5%.

[0073] In some embodiments of the present invention, the preparation of a secondary battery includes: coating a positive electrode slurry containing a positive electrode active material, a conductive agent, a binder, an oxide solid electrolyte, and a polymer electrolyte onto a current collector, drying it at 50-70°C for 10-20 hours, preferably at 60°C for 12 hours; then baking and rolling it sequentially to obtain a positive electrode; and assembling the positive electrode, negative electrode, separator, and electrolyte into a battery.

[0074] In some embodiments of the present invention, the positive electrode active material includes lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), and ternary positive electrode material (LiNi). x Co y Mn z O2, x+y+z=1), lithium nickel cobalt aluminum oxide (NCA) and lithium-rich manganese-based cathode materials; are high-voltage cathode materials.

[0075] In some embodiments of the present invention, the negative electrode active material includes at least one of natural graphite (NG), artificial graphite (AG), hard carbon, soft carbon, and silicon carbide (SiC); preferably SiC.

[0076] In some embodiments of the present invention, the diaphragm includes at least one of polyethylene (PE), polypropylene (PP), ceramic diaphragm, and adhesive-backed diaphragm.

[0077] The polymer electrolyte monomer of the present invention can be used in secondary batteries to prepare gel polymer electrolytes and to blend electrodes (positive and / or negative electrodes); it can also be used to coat the surface of electrodes or separators, or to immerse electrodes or separators in monomer solutions; the above-mentioned oxide solid electrolytes can also be used as separator coatings, current collector top coatings or bottom coatings, which also fall within this scope.

[0078] Example 1 The preparation method of the polymer electrolyte monomer provided in this embodiment has the following synthetic route: ; .

[0079] Specifically, the following steps are included: S1. Mix THF with molecular sieve, stir and reflux for 2-4 hours, distill, collect anhydrous THF, and store in a nitrogen atmosphere; Argon gas was continuously introduced for 30 min. Then, under the protection of dry nitrogen, methyl 1,3-dioxo-4-pentanoate (0.056 mol, 11.312 g), Ti(OiPr)4 (0.003 mol, 0.796 g), anhydrous THF (20 mL) and difluoromethanediol (0.067 mol, 5.645 g) were added to the round-bottom flask. The round-bottom flask was equipped with a condenser with a drying tube to prevent moisture from entering the air and to condense and reflux. The reaction was stirred at room temperature (25 °C) for 24 h. After the reaction, saturated brine was added to quench the reaction, and solid impurities were removed by filtration. THF was added for extraction and separation three times. The organic phases were combined and washed multiple times with saturated brine to remove water-soluble impurities such as difluoromethane glycol, catalyst Ti(OiPr)4, and byproduct methanol. The organic phase was dried with a drying agent (anhydrous Na2SO4 or MgSO4) for 30 min, and the drying agent was removed by filtration. The product was concentrated under reduced pressure using a rotary evaporator to obtain an oily crude product. The crude product was dissolved in anhydrous THF, and petroleum ether and ethyl acetate (volume ratio 3:1) were used as eluents. Column chromatography yielded a pale yellow transparent liquid (9.672 g, yield 68%), which was compound I (difluoro(hydroxy)methyl ester of 5-(2-oxoylide-1,3-dioxacyclopentan-4-yl)valerate). Compound I was analyzed using nuclear magnetic resonance (NMR), and its proton NMR spectrum is shown below. Figure 1 As shown; S2. Mix THF with molecular sieve, stir and reflux for 2-4 hours, distill, collect anhydrous THF, and store in a nitrogen atmosphere; Argon gas was continuously introduced for 30 min. Then, under the protection of dry nitrogen, compound I (0.036 mol, 9.144 g), triethylamine (0.043 mol, 4.372 g), and tetrahydrofuran (20 mL) were added to a Schlenk flask. A magnetic stir bar was added, and a condenser with a drying tube was installed. The flask was cooled to 0 °C in an ice bath. Divinyl chlorophosphate (0.042 mol, 7.077 g) was slowly added dropwise using a syringe at a rate of 1-2 drops / second, while maintaining the temperature at 0-5 °C. After the addition was complete, the ice bath was removed, and the flask was allowed to return to room temperature (25 °C) naturally. The reaction was stirred for 12 h to obtain the reaction solution. The reaction solution was transferred to a separatory funnel and extracted three times with saturated sodium bicarbonate (NaHCO3) solution to neutralize residual acid and remove triethylamine hydrochloride. The organic phase was dried with anhydrous Na2SO4 or MgSO4 for 30 min, filtered to remove the desiccant, and concentrated under reduced pressure using a rotary evaporator. To prevent the decomposition of double bonds or phosphate esters, the temperature was controlled below 40°C to obtain an oily crude product. Petroleum ether and ethyl acetate (volume ratio 3:1) were used as eluents, and column chromatography was performed to obtain a pale yellow transparent liquid (10.005 g, yield 72%), which was the polymer electrolyte monomer. The polymer electrolyte monomer was analyzed using nuclear magnetic resonance (NMR), and its proton NMR spectrum is shown below. Figure 2 As shown.

[0080] Example 2 The method for preparing the polymer electrolyte precursor solution provided in this embodiment includes the following steps: 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate in a volume ratio of 2:3 to obtain a mixture. Monomers (methyl methacrylate and polymer electrolyte monomers from Example 1 in a mass ratio of 7:3) were added to the mixture in sequence, with the monomers accounting for 15 wt% of the mixture. Then, AIBN accounting for 1 wt% of the monomers was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution.

[0081] Example 3 The method for preparing a secondary battery provided in this embodiment includes the following steps: 5 wt% PVDF was pre-dissolved in NMP for gelation treatment, with the stirring speed set to 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. NCM811, SP, and PVDF were mixed in a mixing tank at a mass ratio of 90:5:5, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil, and the areal density on one side was adjusted to 0.158 mg / mm². 2 The aluminum foil containing the positive electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 3.4 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the positive electrode; 5 wt% PVDF was pre-dissolved in NMP for gelling treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. SiC, SP, and PVDF were mixed in a stirring tank at a mass ratio of 95:1:4, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil, and the areal density on one side was adjusted to 0.104 mg / mm². 2 The copper foil containing the negative electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 1.55 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the negative electrode; 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate at a volume ratio of 2:3 to obtain a mixture. Monomers (methyl methacrylate and the polymer electrolyte monomer of Example 1 at a mass ratio of 7:3) were added to the mixture in sequence, with the monomers accounting for 15 wt% of the mixture. Then, AIBN accounting for 1 wt% of the monomers was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution. A PP separator is used to separate the positive and negative electrodes; the positive electrode, negative electrode, separator and polymer electrolyte precursor solution are assembled into a battery; the assembled battery is placed in a 60℃ oven and left to stand for 12 hours to initiate in-situ polymerization to obtain a secondary battery.

[0082] Example 4 The method for preparing a secondary battery provided in this embodiment includes the following steps: 5 wt% PVDF was pre-dissolved in NMP for gelation treatment, with the stirring speed set to 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. NCM811, SP, PVDF, and LLNOF oxide solid electrolyte were mixed in a stirred tank at a mass ratio of 89:5:5:1, and 2 wt% monomer (methyl methacrylate and the polymer electrolyte monomer from Example 1 in a mass ratio of 6:4) and 0.1 wt% AIBN were added. The stirring tank was set to 2500 rpm and stirred for 60 min to obtain the positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil, and the areal density on one side was adjusted to 0.158 mg / mm². 2 The aluminum foil containing the positive electrode slurry was first placed in a 60℃ oven for 30 minutes to initiate polymerization, and then placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 3.4 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the positive electrode; 5 wt% PVDF was pre-dissolved in NMP for gelling treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. SiC, SP, and PVDF were mixed in a stirring tank at a mass ratio of 95:1:4, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil, and the areal density on one side was adjusted to 0.104 mg / mm². 2 The copper foil containing the negative electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 1.55 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the negative electrode.

[0083] 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate in a volume ratio of 2:3 to obtain a mixed solution; the mixed solution was stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the liquid electrolyte. A PP separator is used to separate the positive and negative electrodes; the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain a secondary battery.

[0084] Comparative Example 1 The method for preparing the polymer electrolyte precursor solution provided in this comparative example includes the following steps: 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate at a volume ratio of 2:3 to obtain a mixture. A monomer (methyl methacrylate) was added to the mixture, with the monomer accounting for 15 wt%. Then, AIBN accounting for 1 wt% of the monomer was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution.

[0085] Comparative Example 2 The method for preparing the polymer electrolyte precursor solution provided in this comparative example includes the following steps: 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate at a volume ratio of 2:3 to obtain a mixture. The monomer (trifluoroethyl acrylate) was added to the mixture, with the monomer accounting for 15 wt%. Then, AIBN accounting for 1 wt% of the monomer was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution.

[0086] Comparative Example 3 The method for preparing the polymer electrolyte precursor solution provided in this comparative example includes the following steps: 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate at a volume ratio of 2:3 to obtain a mixture. The monomer (ethylene ethylene carbonate) was added to the mixture, with the monomer accounting for 15 wt%. Then, AIBN accounting for 1 wt% of the monomer was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution.

[0087] Comparative Example 4 The method for preparing the polymer electrolyte precursor solution provided in this comparative example includes the following steps: 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate at a volume ratio of 2:3 to obtain a mixture. The monomer (triallyl phosphate) was added to the mixture, with the monomer accounting for 15 wt%. Then, AIBN accounting for 1 wt% of the monomer was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution.

[0088] Comparative Example 5 The method for preparing the liquid electrolyte provided in this comparative example includes the following steps: 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate in a volume ratio of 2:3 to obtain a mixed solution. The mixed solution was stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the liquid electrolyte.

[0089] Comparative Example 6 The method for preparing a secondary battery provided in this comparative example includes the following steps: 5 wt% PVDF was pre-dissolved in NMP for gelation treatment, with the stirring speed set to 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. NCM811, SP, and PVDF were mixed in a mixing tank at a mass ratio of 90:5:5, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil, and the areal density on one side was adjusted to 0.158 mg / mm². 2 The aluminum foil containing the positive electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 3.4 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the positive electrode; 5 wt% PVDF was pre-dissolved in NMP for gelling treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. SiC, SP, and PVDF were mixed in a stirring tank at a mass ratio of 95:1:4, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil, and the areal density on one side was adjusted to 0.104 mg / mm². 2 The copper foil containing the negative electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 1.55 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the negative electrode; 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate at a volume ratio of 2:3 to obtain a mixture. A monomer (methyl methacrylate) was added to the mixture, with the monomer accounting for 15 wt%. Then, AIBN accounting for 1 wt% of the monomer was added. The mixture was then stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the polymer electrolyte precursor solution. A PP separator is used to separate the positive and negative electrodes; the positive electrode, negative electrode, separator and polymer electrolyte precursor solution are assembled into a battery; the assembled battery is placed in a 60℃ oven and left to stand for 12 hours to initiate in-situ polymerization to obtain a secondary battery.

[0090] Comparative Example 7 The method for preparing a secondary battery provided in this comparative example includes the following steps: 5 wt% PVDF was pre-dissolved in NMP for gelation treatment, with the stirring speed set to 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. NCM811, SP, and PVDF were mixed in a mixing tank at a mass ratio of 90:5:5, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil, and the areal density on one side was adjusted to 0.158 mg / mm². 2 The aluminum foil containing the positive electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 3.4 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the positive electrode; 5 wt% PVDF was pre-dissolved in NMP for gelling treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. SiC, SP, and PVDF were mixed in a stirring tank at a mass ratio of 95:1:4, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil, and the areal density on one side was adjusted to 0.104 mg / mm². 2 The copper foil containing the negative electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 1.55 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the negative electrode; 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate in a volume ratio of 2:3 to obtain a mixed solution; the mixed solution was stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the liquid electrolyte. A PP separator is used to separate the positive and negative electrodes; the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain a secondary battery.

[0091] Comparative Example 8 The method for preparing a secondary battery provided in this comparative example includes the following steps: 5 wt% PVDF was pre-dissolved in NMP for gelation treatment, with the stirring speed set to 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. NCM811, SP, PVDF, and LLNOF oxide solid electrolyte were mixed in a stirred tank at a mass ratio of 89:5:5:1, and 2 wt% monomer (methyl methacrylate) and 0.1 wt% AIBN were added. The stirring tank was set to 2500 rpm and stirred for 60 minutes to obtain the positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil, and the areal density on one side was adjusted to 0.158 mg / mm². 2 The aluminum foil containing the positive electrode slurry was first placed in a 60℃ oven for 30 minutes to initiate polymerization, and then placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 3.4 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the positive electrode; 5 wt% PVDF was pre-dissolved in NMP for gelling treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. SiC, SP, and PVDF were mixed in a stirring tank at a mass ratio of 95:1:4, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil, and the areal density on one side was adjusted to 0.104 mg / mm².2 The copper foil containing the negative electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 1.55 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the negative electrode.

[0092] 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate in a volume ratio of 2:3 to obtain a mixture. The mixture was stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the liquid electrolyte. A PP separator is used to separate the positive and negative electrodes; the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain a secondary battery.

[0093] Comparative Example 9 The method for preparing a secondary battery provided in this comparative example includes the following steps: 5 wt% PVDF was pre-dissolved in NMP for gelation treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. NCM811, SP, PVDF, and LLNOF oxide solid electrolyte were mixed in a stirring tank at a mass ratio of 89:5:5:1. The stirring speed was set to 2500 rpm, and stirring was carried out for 60 minutes to obtain the positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil, and the areal density on one side was adjusted to 0.158 mg / mm². 2 The aluminum foil containing the positive electrode slurry was first placed in a 60℃ oven for 30 minutes to initiate polymerization, and then placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 3.4 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the positive electrode; 5 wt% PVDF was pre-dissolved in NMP for gelling treatment, with a stirring speed of 800-900 rpm, and stirred until the PVDF was completely dissolved in the NMP. SiC, SP, and PVDF were mixed in a stirring tank at a mass ratio of 95:1:4, and the stirring speed was set to 2500 rpm for 60 minutes to obtain the negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil, and the areal density on one side was adjusted to 0.104 mg / mm². 2 The copper foil containing the negative electrode paste was placed in a 90℃ oven for electrode baking. The resulting electrode was then rolled to a compaction density of 1.55 g / cm³. 3 The rolled electrode sheet is then die-cut to obtain the negative electrode.

[0094] 1M lithium bis(trifluoromethanesulfonyl)imide was dissolved in ethylene carbonate and ethyl methyl carbonate in a volume ratio of 2:3 to obtain a mixture. The mixture was stirred at room temperature (25°C) until a transparent homogeneous liquid was obtained, which is the liquid electrolyte. A PP separator is used to separate the positive and negative electrodes; the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain a secondary battery.

[0095] Test case Electrochemical performance tests of the polymer electrolyte were conducted by assembling coin cells (Clude CR2032). The coin cells assembled with the polymer electrolyte precursor solutions in Examples 2 and Comparative Examples 1-4 required in-situ polymerization in a 60°C oven for 12 hours before electrochemical performance testing. The coin cell assembled with the liquid electrolyte in Comparative Example 5 could be tested directly. The measured electrochemical window, lithium-ion conductivity, and lithium-ion transference number are shown in Table 1.

[0096] Test method: 1. Electrochemical Window Test: A coin cell with a lithium-ion negative electrode, a steel plate positive electrode, and a 16-micron PP separator was assembled for electrochemical window testing. The specific assembly procedure was as follows: First, the lithium-ion electrode was placed in the negative electrode shell. 40 μL of electrolyte was added to the lithium-ion electrode using a pipette. Then, the separator was added, and another 40 μL of electrolyte was added to the separator using a pipette. The steel plate was added, and finally, the gasket and positive electrode shell were added. The coin cell was then sealed using a coin cell packaging machine, and excess electrolyte on the surface of the coin cell was wiped away with lint-free paper or a lint-free cloth. The electrochemical window of the coin cell was tested using a linear sweep voltammetry (LSV) curve on an electrochemical workstation. The test voltage range was 2–6 V, the voltage scan rate was 1 mV / s, and the sampling interval was 0.1 s.

[0097] 2. Ion Conductivity Test: The ionic conductivity of coin cells with steel sheets for both positive and negative electrodes and 16-micron PP separators was tested. The assembly procedure was as follows: First, the steel sheet was placed in the negative electrode shell. 40 μL of electrolyte was added to the steel sheet using a pipette. Then, the separator was added, and another 40 μL of electrolyte was added to the separator using a pipette. The steel sheet was then added, followed by the gasket and positive electrode shell. The cells were then sealed using a coin cell packaging machine, and excess electrolyte was wiped off the surface of the coin cells with lint-free paper or cloth. The ionic conductivity of the coin cells was tested using electrochemical impedance spectroscopy (EIS) on an electrochemical workstation. The AC voltage perturbation was set to 5 mV, the frequency range was 0.1~100000 Hz, and the sampling interval was 2 s. The calculation formula is σ=L / (SR), where L is the distance between the positive and negative electrodes, S is the area of ​​the positive and negative electrode sheets, and R is the initial impedance.

[0098] 3. Ion Transport Number Test: The ionic conductivity of coin cells with lithium-ion electrodes (both positive and negative) and a 16-micron PP separator was tested. The assembly procedure was as follows: First, the lithium-ion electrode was placed in the negative electrode shell. 40 μL of electrolyte was added to the lithium-ion electrode using a pipette. Then, the separator was added, and another 40 μL of electrolyte was added to the separator using a pipette. The lithium-ion electrode was then added, followed by the gasket and the positive electrode shell. The coin cell was then sealed using a coin cell packaging machine, and excess electrolyte on the surface was wiped away with lint-free paper or a lint-free cloth. The initial impedance (R0) of the coin cell was measured using electrochemical impedance spectroscopy (EIS) on an electrochemical workstation. The AC voltage perturbation was set to 5 mV, the frequency range was 0.1–100,000 Hz, and the sampling interval was 2 seconds. After the test, a constant voltage of 10mV was applied to the coin cell using the steady-state current method (it) for 3000s with a sampling interval of 0.1s. The initial current and steady-state current were i0 and is, respectively. The stabilized impedance (Rs) was then measured again using electrochemical impedance spectroscopy (EIS). The calculation formula is: lithium-ion transport number = (is / i0) × [( V-i0×R0) / ( V-is×Rs)], V is the test voltage.

[0099] Table 1

[0100] Table 1 shows that the gel polymer electrolyte prepared using polymer electrolyte monomers has a wider electrochemical window than gel polymer electrolytes prepared without polymer electrolyte monomers and liquid electrolytes; it also has a higher lithium-ion conductivity and a higher lithium-ion transference number than gel polymer electrolytes prepared without polymer electrolyte monomers and liquid electrolytes. Furthermore, it is superior to gel polymer electrolytes formed from monomers containing fluorine, carbonate, and phosphate groups, respectively.

[0101] The performance of the secondary batteries prepared in Example 3, Comparative Example 6, and Comparative Example 7 was tested, and the cycle test results of the secondary batteries are as follows: Figure 3 As shown in Table 2, the runaway temperature of the thermal shock test is shown in Table 3, and the results of the needle penetration test are shown in Table 3.

[0102] Test method: Cyclic testing standard: The charge and discharge process is conducted in a constant temperature chamber at an ambient temperature of 25℃±2℃, with a charge / discharge rate of 1C and a voltage range of 2.75~4.2V. Capacity calibration is performed before cycling: First, discharge at 1C to the lower cutoff voltage of 2.75V and rest for 10 minutes; then charge at 1C to the upper cutoff voltage of 4.2V. Once the upper cutoff voltage is reached, switch to constant voltage charging at 4.2V until the current is less than or equal to the given cutoff current of 0.05C, and rest for 10 minutes; then discharge at 1C to the lower cutoff voltage of 2.75V and rest for 10 minutes. This cycle is repeated three times. After calibrating the capacity, the cell is subjected to a 25℃ cyclic test with a cycle rate of 1C / 1C.

[0103] Thermal runaway test: After fully charging the test cell at a 1C rate with constant current and constant voltage, it is left to stand for 1 hour. Its OCV and internal resistance are measured, and then it is placed in a test chamber. The temperature chamber is heated to 130±2℃ at a rate of 5℃ / min, held for 30 minutes, and then stopped. It is left to stand for another 1 hour, and its OCV and internal resistance are measured again. The passing standard is no fire or explosion. If no explosion or fire occurs, the temperature is continued (using a 10℃ temperature gradient) until fire or explosion occurs.

[0104] Needle penetration test: After fully charging the test cell at a 1C rate with constant current and constant voltage, let it rest for 1 hour. Measure its OCV and internal resistance, then place the battery in a test chamber. Use a high-temperature resistant steel needle with a diameter of 5-8mm to penetrate the geometric center of the battery plates at a speed of 25±5mm. The needle remains inside the battery. Let it rest for 1 hour, then measure its OCV and internal resistance. Passing the test means no fire or explosion.

[0105] Table 2

[0106] Table 3

[0107] Depend on Figure 3 As shown in Tables 2 and 3, the pouch cell prepared using the polymer electrolyte monomer of this invention can maintain a capacity retention of 94.2% after 300 cycles. This is attributed to the introduction of fluorine-containing groups (-CF2- groups), which effectively promote the formation of a "fluorine-oxygen co-coordination" structure, thereby relaxing and decoupling ion conduction from polymer segments and constructing a more efficient Li... + The transport channel is optimized. The introduced carbonate effectively dissociates the lithium salt, significantly improving ionic conductivity. Furthermore, hot box and needle penetration results demonstrate that using phosphate groups as the polymer backbone effectively enhances the thermal stability of the polymer matrix and its ability to capture flammable free radicals, thus greatly improving safety performance.

[0108] The electrochemical performance of the secondary batteries of Example 4, Comparative Example 8 and Comparative Example 9 was tested, and the results are shown in Table 4.

[0109] Test Method: Tested according to the cycle test standard. The formula for calculating the initial efficiency (%) is: Initial Efficiency (%) = (Initial Discharge Capacity / Initial Charge Capacity) × 100%; the formula for calculating the capacity retention rate is: Capacity Retention Rate (%) = (Discharge Capacity of Current Cycle / Initial Discharge Capacity of Cell) × 100%. The ACR test is based on electrochemical impedance spectroscopy (EIS) technology. A small-amplitude sinusoidal AC voltage or current signal is applied to the battery, and the corresponding current or voltage response is measured to calculate the battery's complex impedance.

[0110] Table 4

[0111] As shown in Table 4, although the impedance of the polymer electrolyte monomer of the present invention increases when used in the preparation of solid-state electrode sheets, it can significantly improve their cycle performance and is beneficial to the long-term cycle stability of the battery cell.

[0112] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A polymer electrolyte monomer, characterized in that, It has the following structure: ； In this case, R1 is a C3~C6 alkyl group, and R2 and R3 are each independently a C2~C4 alkenyl group.

2. The polymer electrolyte monomer according to claim 1, characterized in that, It has the following structure: 。 3. The method for preparing the polymer electrolyte monomer as described in claim 1 or 2, characterized in that, Includes the following steps: S1, difluoromethanediol, compound A and catalyst react in a solvent to give compound I; The structural formula of the difluoromethanediol is as follows: The general structural formula of compound A is: The general structural formula of compound I is: R1 is a C3~C6 alkyl group; S2. Compound I, compound B, and organic amine are reacted in a solvent to obtain the polymer electrolyte monomer; Wherein, the general structural formula of compound B is R2 and R3 are each independently C2~C4 alkenyl groups.

4. The method for preparing the polymer electrolyte monomer according to claim 3, characterized in that, In step S1, the structural formula of compound A is: The structural formula of compound I is as follows: ; And / or, in step S1, the reaction includes: reacting at 10~30°C for 20~30 h.

5. The method for preparing the polymer electrolyte monomer according to claim 3, characterized in that, In step S2, the structural formula of compound B is: ; And / or, in step S2, the reaction includes: adding compound B dropwise to a mixture of compound I, organic amine and solvent at 0~10°C; after the addition is complete, reacting at 10~30°C for 10~15 h.

6. A secondary battery, characterized in that, It includes polymer electrolytes mainly formed by the polymerization of monomers; said monomers include the polymer electrolyte monomers of claim 1 or 2.

7. The secondary battery according to claim 6, characterized in that, The monomers also include acrylate compounds; Preferably, the mass ratio of the acrylate compound to the polymer electrolyte monomer is (6~8):(2~4).

8. The secondary battery according to claim 7, characterized in that, The secondary battery includes electrodes, a separator, and the polymer electrolyte; the polymer electrolyte is mainly obtained by polymerizing a polymer electrolyte precursor solution; the polymer electrolyte precursor solution includes the monomer, lithium salt, initiator, and solvent.

9. The secondary battery according to claim 8, characterized in that, Includes at least one of the following features (1) to (3); (1) The monomer content in the polymer electrolyte precursor solution is 1wt%~30wt%; (2) The lithium salt content in the polymer electrolyte precursor solution is 5wt%~25wt%; (3) The mass of the initiator is 0.01% to 5% of the mass of the monomer; (4) The polymer electrolyte precursor solution also includes additives.

10. The secondary battery according to claim 7, characterized in that, The secondary battery includes electrodes, a separator, and a liquid electrolyte; The electrode comprises an electrode active material, a conductive agent, a binder, an oxide solid electrolyte, and the polymer electrolyte, wherein the polymer electrolyte is mainly obtained by polymerization of the monomer and an initiator; Preferably, the mass of the monomer is 1% to 8% of the total mass of the electrode active material, the conductive agent, the binder, and the oxide solid electrolyte.

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