A polymer solid electrolyte monomer and its preparation method, as well as a secondary battery.

Abstract

This invention provides a polymer solid electrolyte monomer and its preparation method, as well as a secondary battery. The polymer solid electrolyte monomer provided by this invention has the structure shown in Formulas 1-4. The secondary battery provided by this invention introduces the polymer solid electrolyte monomer and a certain functional material solution, both of which are used on the positive electrode side. Simultaneously, an acrylate monomer is introduced on the negative electrode side. After battery assembly, heat treatment is performed to initiate gradient in-situ polymerization of the precursors on both the positive and negative electrode sides. Specifically, cationic polymerization initiates mild polymerization on the positive electrode side, free radical polymerization initiates high polymerization on the negative electrode side, and the two monomers interpenetrate at the separator to complete cross-linking copolymerization, thereby forming a gradient polymerization system with increasing polymerization degree from the positive to the negative electrode. The in-situ solid battery prepared using this method has lower internal resistance and faster Li + This improves the electrochemical performance of the battery by creating a transmission channel.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials, and particularly to a polymer solid electrolyte monomer and its preparation method, as well as a secondary battery. Background Technology

[0002] Lithium-ion rechargeable batteries, with their advantages of high energy density and long cycle life, are widely used in 3C products, power batteries, and storage. Rechargeable lithium-ion batteries using high-nickel ternary cathode materials offer even longer battery life and superior low-temperature performance. However, the stability and safety of high-nickel cathode materials still need improvement.

[0003] High-nickel ternary materials are strongly alkaline and readily react with water and carbon dioxide to form lithium carbonate and lithium hydroxide. Lithium carbonate, when operating at high temperatures, produces a large amount of CO2, causing battery swelling. Lithium hydroxide reacts with LiPF6 in the electrolyte to produce HF, a major cause of corrosion of the positive electrode's CEI and negative electrode's SEI by HF acid, ultimately leading to the dissolution of the positive electrode's transition metal and the generation of more carbon dioxide gas. This not only results in a loss of battery capacity but also severely impacts battery safety and stability. To stabilize the interface between the positive electrode and electrolyte and suppress the effects of moisture and HF acid on the high-nickel ternary positive electrode, common methods include: adding film-forming additives to the electrolyte or replacing lithium salts with materials like LiDFOB, which have shorter LUMO-HOMO gaps, to help form CEI on the positive electrode surface; coating the separator with oxide ceramic materials or other hygroscopic materials that can store water molecules; and seeking a transition to all-solid-state lithium batteries.

[0004] Among these factors, cathode film-forming additives, LiDFOB and its derivatives are expensive, and their large-scale use would increase the production cost of lithium secondary batteries and fail to suppress the decomposition of lithium carbonate at high temperatures, producing carbon dioxide. Membrane coating is a common method to improve the safety of high-nickel ternary lithium batteries, but it increases membrane thickness and battery internal resistance. Multi-layer coating requires multiple applications of polymer-based binders, which can lead to a decrease in the overall conductivity of the electrolyte and the risk of coating peeling. All-solid-state lithium batteries face challenges such as high interfacial impedance and low ionic conductivity. Therefore, finding a method to help high-nickel ternary cathodes achieve stable cycling is an urgent market demand.

[0005] CN115133222A discloses a method for coating both sides of a separator, comprising the following steps: Step 1: using a ceramic base membrane, PE base membrane, polypropylene / polyethylene / polypropylene multilayer base membrane, glass fiber base membrane, etc. as the base separator; Step 2: selecting a high molecular weight polymer with a molecular weight of 50,000 to 3 million as a binder, mixing the binder and functional material evenly, with a mass ratio of polymer binder to functional material of 1:2-20; Step 3: coating the base membrane on the positive electrode side, wherein the functional material used for coating is a hygroscopic material that can store water molecules; Step 4: coating the base membrane on the negative electrode side, wherein the functional material used for coating is an inorganic substance that can undergo chemical and alloying reactions with lithium, ultimately obtaining a double-sided coated composite separator.

[0006] CN201980098870.8 discloses a method for preparing an in-situ solid polymer electrolyte based on polyvinylidene fluoride hexafluoropropylene, comprising the following steps: Step 1, dissolving 2,478g of polyvinylidene fluoride hexafluoropropylene in 20ml of N,N-dimethylformamide, stirring and mixing evenly to obtain a mixture A; Step 2, using the mixture A obtained in Step 1 as an electrospinning solution, and obtaining a polymer membrane matrix by electrospinning, wherein the electrospinning voltage is 20kV, the rotation speed is 250rpm, the distance between the transmitter and the receiving substrate is 10cm, and the flow rate is 5mL / h; Step 3, using the polymer membrane obtained in Step 2... The membrane substrate was placed in a vacuum drying oven at 70°C for drying. Step 4: In a glove box under nitrogen atmosphere, 0.28g of neopentyl glycol diacrylate, 0.12g of ethylene ethylene carbonate, 0.561g of lithium bis(fluorosulfonyl)imide, 0.002g of azobisisobutyronitrile, and 4g of commercial electrolyte were mixed to obtain mixed solution B, and magnetically stirred for 2h. Step 5: The polymer membrane obtained in step 3 was placed in a battery case with electrode components, and then 40μL of mixed solution B obtained in step 4 was applied. The mixture was sealed and allowed to stand for 6h. Step 6: The battery obtained in step 5 was placed in an oven at 60°C for 12h. The electrolyte was finally obtained.

[0007] The modification methods described above carry the risks of separator coating peeling, increased battery internal resistance, and damage to the high-nickel ternary cathode structure. Using only acrylic monomers can ensure a wider electrochemical window and facilitate more uniform lithium metal deposition, but this also leads to increased internal resistance, particularly affecting lithium ion migration on the cathode side, thus impacting electrochemical performance. Summary of the Invention

[0008] In view of this, the present invention provides a polymer solid electrolyte monomer and its preparation method, as well as a secondary battery. The present invention can improve the stability of the interface between the high-nickel ternary cathode material and the electrolyte, reduce internal resistance, and improve safety.

[0009] This invention provides a polymer solid electrolyte monomer, wherein the polymer solid electrolyte monomer is selected from one or more of the structures shown in Formulas 1 to 4 below:

[0010]

[0011] The present invention also provides a method for preparing the polymer solid electrolyte monomer described in the above technical solution, comprising the following steps:

[0012] A1) Reactant 1 and reactant 2 are subjected to an esterification reaction to obtain a reaction solution;

[0013] A2) The reaction solution is post-treated to obtain the polymer solid electrolyte monomer;

[0014] in,

[0015] The reactant 1 is an alcohol compound containing at least two carboxyl groups at the end group;

[0016] Reactant 2 is vinylene sulfate.

[0017] Preferably, reactant 1 is selected from at least one of bis(trimethylolpropane), ethoxylated trimethylolpropane, pentaerythritol, triethylene glycol, diethylene glycol, tripropylene glycol, and dipropylene glycol.

[0018] Preferably, in step A1), the medium for the esterification reaction is methanesulfonic acid;

[0019] The molar ratio of reactant 1 to reactant 2 is (0.8-1.2):1; the molar ratio of reactant 1 to methanesulfonic acid is (3-6) mg:(150-400) mL.

[0020] Preferably, in step A1), the temperature of the esterification reaction is 80–110°C, and the time of the esterification reaction is 4–6 hours.

[0021] Preferably, in step A2), the post-processing specifically includes:

[0022] A2-1) The reaction solution is mixed with the polymerization inhibitor to obtain mixture 1;

[0023] A2-2) The mixture 1 is decolorized with activated carbon to obtain mixture 2;

[0024] A2-3) The mixture 2 is dried to obtain the polymer solid electrolyte monomer.

[0025] The present invention also provides a secondary battery, wherein the assembly steps of the secondary battery include:

[0026] B1) Mix monomer 1, initiator and base electrolyte to obtain mixed solution 1;

[0027] B2) Mix monomer 2 and the base electrolyte to obtain mixed solution 2;

[0028] B3) Apply the mixed solution 1 to the negative electrode side and the mixed solution 2 to the positive electrode side, press and seal with a separator to obtain a coin cell; then perform heat treatment on the coin cell;

[0029] in,

[0030] The monomer 1 is an acrylate compound;

[0031] The monomer 2 is the polymer solid electrolyte monomer of claim 1 or the polymer solid electrolyte monomer prepared by any one of claims 2 to 6.

[0032] Preferably, the method for preparing the positive electrode includes the following steps:

[0033] S1. Mix the positive electrode active material, conductive agent, binder and first solvent to obtain positive electrode slurry;

[0034] S2. Coat the positive electrode slurry onto the positive electrode current collector and dry it to obtain the basic positive electrode sheet;

[0035] S3. The functional material solution is coated onto the surface of the basic positive electrode sheet and then dried to obtain the positive electrode sheet.

[0036] Preferably, the functional material in the functional material solution is selected from at least one of Pd(Ac)2, La(Ac)3, Ar(Ac)4, Ce(Ac)3, Y(Ac)3, Pd(Ac)2 hydrate, La(Ac)3 hydrate, Zr(Ac)4 hydrate, Ce(Ac)3 hydrate and Y(Ac)3 hydrate;

[0037] The solvent of the functional material solution is selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, isopropanol, and anhydrous ethanol;

[0038] The functional material solution has a mass fraction of 1% to 5%.

[0039] Preferably, the positive electrode active material is a high-nickel positive electrode active material;

[0040] The first solvent is N-methylpyrrolidone;

[0041] The conductive agent is selected from conductive carbon materials;

[0042] The adhesive is selected from at least one of PVDF and PTFE.

[0043] Preferably, the monomer 1 is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, 2-methacrylate-2-epoxy ethyl ester, polyethylene glycol diglycidyl ether, di(trimethylolpropane)tetraacrylate, propylene glycol monomethyl ether acetate, methyl methacrylate, ethyl methacrylate, and triethylene glycol methacrylate.

[0044] Preferably, the base electrolyte comprises a lithium salt and a second solvent;

[0045] The lithium salt is selected from one of lithium hexafluorophosphate, lithium difluorooxalate borate, and lithium difluorosulfonylimide.

[0046] The second solvent is EC, PC, EMC, and DEC;

[0047] The concentration of the basic electrolyte is 1–1.2 mol / L.

[0048] Preferably, the base electrolyte further includes additives;

[0049] The additive is one or more of fluoroethylene carbonate, 1,3-propanesulfonate lactone, and 1,3-propenesulfonate lactone.

[0050] The additive has a mass fraction of 0.5% to 5% in the base electrolyte.

[0051] This invention provides a polymer solid electrolyte monomer and its preparation method, as well as a secondary battery. The invention provides specific thioester monomers (i.e., the polymer solid electrolyte monomers mentioned above), which are beneficial for improving the electrochemical performance of the battery. The secondary battery provided by this invention is essentially a method for modifying the interface of a high-nickel cathode material. The secondary battery provided by this invention introduces thioester monomers (i.e., the polymer solid electrolyte monomers mentioned above) and utilizes a certain functional material solution, both used on the positive electrode side. Simultaneously, acrylate monomers are introduced on the negative electrode side. After battery assembly, heat treatment is performed, using the functional material as an initiator to initiate gradient in-situ polymerization of the precursors on both the positive and negative electrode sides. Specifically, cationic polymerization initiates mild polymerization on the positive electrode side, free radical polymerization initiates high polymerization on the negative electrode side, and the two monomers interpenetrate at the separator to complete cross-linking copolymerization, thereby forming a gradient polymerization system with increasing polymerization degree from the positive to the negative electrode. The aforementioned gradient in-situ polymerization ensures the formation of high-mechanical-strength monomer polymerization on the negative electrode side to suppress lithium dendrite growth and protect the negative electrode Sei. Simultaneously, the low-polymerization-degree vinyl monomers ensure sufficient electrolyte wetting of the positive electrode active material on the positive electrode side, promoting the formation of positive electrode CEi and reducing excessive metal dissolution by HF. The cross-linking and copolymerization of the two types of monomers at the separator further enhances the separator's resistance to lithium dendrite penetration, improving battery safety. Furthermore, compared to single-monomer polymerization, cross-linking polymerization further improves mechanical strength while also being more beneficial for lithium-ion transport. The in-situ solid-state battery prepared using this method exhibits lower internal resistance and faster Li-ion transport. + This improves the electrochemical performance of the battery by creating a transmission channel.

[0052] Experimental results show that the solution of this invention enables the battery to achieve a specific capacity of 184 mAh g. -1 The initial coulomb efficiency reached over 89%, the capacity retention after 50 cycles reached over 97%, and the interface impedance R... SEI It exhibits excellent electrochemical performance below 299Ω. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of the assembly of the positive and negative electrodes when assembling a lithium-ion battery.

[0055] Figure 2 The graphs show the cycle performance and coulombic efficiency of the batteries obtained in each embodiment and comparative example.

[0056] Figure 3 The images show a comparison of EIS values ​​of the batteries obtained in each embodiment and comparative example at room temperature. Detailed Implementation

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0058] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0059] As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0060] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0061] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 80~110℃ means that the units for the left endpoint "80" and the right endpoint "110" are both in ℃.

[0062] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0063] This invention provides a polymer solid electrolyte monomer, wherein the polymer solid electrolyte monomer is selected from one or more of the structures shown in Formulas 1 to 4 below:

[0064]

[0065] The present invention also provides a method for preparing the polymer solid electrolyte monomer described in the above technical solution, comprising the following steps:

[0066] A1) Reactant 1 and reactant 2 are subjected to an esterification reaction to obtain a reaction solution;

[0067] A2) The reaction solution is post-treated to obtain the polymer solid electrolyte monomer;

[0068] in,

[0069] The reactant 1 is an alcohol compound containing at least two carboxyl groups at the end group;

[0070] Reactant 2 is vinylene sulfate.

[0071] [Regarding step A1]:

[0072] A1) Reactants 1 and 2 are subjected to esterification to obtain a reaction solution.

[0073] In this invention, reactant 1 is an alcohol compound containing at least two carboxyl groups at the end group, preferably at least one of bis(trimethylolpropane), ethoxylated trimethylolpropane, pentaerythritol, triethylene glycol, diethylene glycol, tripropylene glycol, and dipropylene glycol, more preferably bis(trimethylolpropane).

[0074] In this invention, reactant 2 is a thiomonomer material, specifically vinylene sulfate, with the following structure:

[0075]

[0076] In this invention, the molar ratio of reactant 1 to reactant 2 is preferably (0.8 to 1.2):1, specifically 0.8:1, 0.9:1, 1.0:1, 1.1:1, or 1.2:1.

[0077] In this invention, the esterification reaction is preferably carried out in a methanesulfonic acid medium. In this invention, the preferred ratio of reactant 1 to methanesulfonic acid is (3-6) mg : (150-400) mL.

[0078] In this invention, the preferred temperature for the esterification reaction is 80–110°C, specifically 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, or 110°C. The preferred reaction time is 4–6 hours, specifically 4 hours, 5 hours, or 6 hours. During the esterification reaction, stirring is preferably performed simultaneously to evaporate the water produced. The preferred stirring speed is 600–1000 rpm, specifically 600 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm. After the esterification reaction, a reaction solution is obtained.

[0079] [Regarding step A2]:

[0080] A2) The reaction solution is post-treated to obtain the polymer solid electrolyte monomer.

[0081] In this invention, the post-processing step A2) preferably includes:

[0082] A2-1) The reaction solution is mixed with the polymerization inhibitor to obtain mixture 1;

[0083] A2-2) The mixture 1 is decolorized with activated carbon to obtain mixture 2;

[0084] A2-3) The mixture 2 is dried to obtain the polymer solid electrolyte monomer.

[0085] Regarding step A2-1):

[0086] In this invention, it is preferable to first cool the reaction solution to room temperature before mixing it with the polymerization inhibitor. In this invention, the polymerization inhibitor is preferably at least one selected from p-hydroxyanisole, hydroquinone, and 2,6-di-tert-butyl-p-cresol. In this invention, based on the amount of the reaction solution used, the amount of polymerization inhibitor added is preferably 150-300 ppm, specifically 150 ppm, 200 ppm, 250 ppm, or 300 ppm. In this invention, the preferred method for mixing the reaction solution and the polymerization inhibitor is stirring. The preferred stirring speed is 600-1000 rpm, specifically 600 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm. The preferred stirring time is 4-6 hours, specifically 4 hours, 5 hours, or 6 hours. After the above mixing, mixture 1 is obtained.

[0087] Regarding step A2-2):

[0088] In this invention, the preferred method for decolorizing with activated carbon is to transfer the mixture 1 obtained in step A2-1) into an activated carbon filter column for decolorization. After the above treatment, mixture 2 is obtained.

[0089] Regarding steps A2-3):

[0090] In this invention, the drying process is preferably vacuum drying. The drying temperature is preferably 45–80°C, specifically 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. The drying time is preferably 8–12 hours, specifically 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. After the above drying treatment, the polymer solid electrolyte monomer (i.e., thioester monomer) is obtained.

[0091] In this invention, taking reactant 1 as bis(trimethylolpropane), ethoxylated trimethylolpropane, pentaerythritol, triethylene glycol, diethylene glycol, tripropylene glycol, or dipropylene glycol as an example, it undergoes an esterification reaction with reactant 2, vinylene sulfate, to obtain thioester monomers, namely bis(trimethylolpropane)tetravinylvinylsulfite, pentaerythritol tetravinylsulfite, triethylene glycol divinylsulfite, trimethylolpropane trivinylsulfite, and dipropylene glycol divinylsulfite. Specifically, taking reactant 1 as bis(trimethylolpropane), pentaerythritol, ethoxylated trimethylolpropane, or tri(ethylene glycol) as an example, the reaction routes for preparing thioester monomers (i.e., the polymer solid electrolyte monomers) by esterification with reactant 2, vinylene sulfate, are as follows (when reactant 1 is other substances mentioned above, the reaction routes are the same and will not be repeated):

[0092]

[0093] The present invention also provides a secondary battery, wherein the assembly steps of the secondary battery include:

[0094] B1) Mix monomer 1, initiator and base electrolyte to obtain mixed solution 1;

[0095] B2) Mix monomer 2 and the base electrolyte to obtain mixed solution 2;

[0096] B3) Apply the mixed solution 1 to the negative electrode side and the mixed solution 2 to the positive electrode side, press and seal with a separator to obtain a coin cell; then perform heat treatment on the coin cell;

[0097] in,

[0098] The monomer 1 is an acrylate compound;

[0099] The monomer 2 is the polymer solid electrolyte monomer described in the above technical solution or the polymer solid electrolyte monomer prepared by the preparation method described in the above technical solution.

[0100] [Regarding step B1]:

[0101] B1) Mix monomer 1, initiator and base electrolyte to obtain mixed solution 1.

[0102] In this invention, monomer 1 is an acrylate compound, preferably at least one selected from polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, ethyl 2-methacrylate-2-epoxyethylene ester, polyethylene glycol diglycidyl ether, di(trimethylolpropane)tetraacrylate propylene glycol monomethyl ether acetate, methyl methacrylate, ethyl methacrylate, and triethylene glycol methacrylate. In this invention, the amount of monomer 1 is preferably 0.5% to 5% of the mass of the basic electrolyte, specifically 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%.

[0103] In this invention, the initiator is preferably at least one selected from azobisisobutyronitrile (AIBN) and benzoyl peroxide. The amount of the initiator is preferably 0.1% to 0.5% of the mass of the base electrolyte, specifically 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%.

[0104] In this invention, the basic electrolyte is a lithium-ion battery electrolyte, generally comprising an electrolyte and a second solvent. The electrolyte is preferably a lithium salt electrolyte, more preferably LiPF6 (lithium hexafluorophosphate), LiDFOB (lithium difluorooxalate borate), and LiFSI (lithium bisfluorosulfonyl imide). The molar ratio of LiPF6, LiDFOB, and LiFSI is preferably (0.6–0.9):(0.05–0.2):(0.1–0.2), more preferably 0.6:0.2:0.2 or 0.9:0.05:0.1. The concentration of LiPF6 in the basic electrolyte is preferably 0.6–0.9 M. In some embodiments of this invention, the concentrations of LiPF6, LiDFOB, and LiFSI in the basic electrolyte are 0.6 M, 0.2 M, and 0.2 M, respectively; in other embodiments of this invention, the concentrations of LiPF6, LiDFOB, and LiFSI in the basic electrolyte are 0.9 M, 0.05 M, and 0.1 M, respectively. In this invention, the total concentration of the electrolyte in the base electrolyte solution is preferably 1–1.2 mol / L. In this invention, the second solvent is preferably a mixed solvent of EC (ethylene carbonate), PC (propylene carbonate), EMC (ethyl methyl carbonate), and DEC (diethyl carbonate). The volume ratio of EC, PC, EMC, and DEC is preferably 3:(1–4):(1–4):(1–3), more preferably 3:2:3:2. In this invention, the terms "first" and "second" in "first solvent" and "second solvent" do not have specific meanings; they are only used to distinguish whether they are used in different steps.

[0105] In this invention, the base electrolyte preferably further includes additives. Preferably, the additives are one or more of FEC (fluoroethylene carbonate), PS (1,3-propanesulfonate lactone), and PST (1,3-propenesulfonate lactone), more preferably FEC, PS, and PST. The mass fraction of the additives in the base electrolyte is preferably 0.5% to 5%. When the additive is a combination of the above three components, the mass fraction of FEC in the base electrolyte is preferably 0.5% to 5%, specifically 0.5%, 1%, 2%, 3%, 4%, or 5%; the mass fraction of PS in the base electrolyte is preferably 0.5% to 5%, specifically 0.5%, 1%, 2%, 3%, 4%, or 5%; and the mass fraction of PST in the base electrolyte is preferably 0.3% to 5%, specifically 0.3%, 0.5%, 1%, 2%, 3%, 4%, or 5%.

[0106] In this invention, the preferred method for mixing monomer 1, the initiator, and the basic electrolyte is stirring. The stirring speed is preferably 400–1000 rpm, specifically 400 rpm, 600 rpm, 800 rpm, or 1000 rpm. The stirring time is preferably 1–4 hours, specifically 1 hour, 2 hours, 2.5 hours, 3 hours, or 4 hours. After homogeneous mixing, mixed solution 1 is obtained.

[0107] [Regarding step B2]:

[0108] B2) Mix monomer 2 and the base electrolyte to obtain mixed solution 2.

[0109] In this invention, monomer 2 is the polymer solid electrolyte monomer described in the above technical solution or the polymer solid electrolyte monomer prepared by the preparation method described in the above technical solution. In this invention, the amount of monomer 2 is preferably 1% to 10% of the mass of the basic electrolyte, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0110] In this invention, the basic electrolyte is a lithium-ion battery electrolyte, generally comprising an electrolyte and a second solvent. The electrolyte is preferably a lithium salt electrolyte, more preferably LiPF6 (lithium hexafluorophosphate), LiDFOB (lithium difluorooxalate borate), and LiFSI (lithium bisfluorosulfonyl imide). The molar ratio of LiPF6, LiDFOB, and LiFSI is preferably (0.6–0.9):(0.05–0.2):(0.1–0.2), more preferably 0.6:0.2:0.2 or 0.9:0.05:0.1. The concentration of LiPF6 in the basic electrolyte is preferably 0.6–0.9 M. In some embodiments of this invention, the concentrations of LiPF6, LiDFOB, and LiFSI in the basic electrolyte are 0.6 M, 0.2 M, and 0.2 M, respectively; in other embodiments of this invention, the concentrations of LiPF6, LiDFOB, and LiFSI in the basic electrolyte are 0.9 M, 0.05 M, and 0.1 M, respectively. In this invention, the total concentration of the electrolyte in the base electrolyte solution is preferably 1–1.2 mol / L. In this invention, the second solvent is preferably a mixed solvent of EC (ethylene carbonate), PC (propylene carbonate), EMC (ethyl methyl carbonate), and DEC (diethyl carbonate). The volume ratio of EC, PC, EMC, and DEC is preferably 3:(1–4):(1–4):(1–3), more preferably 3:2:3:2. In this invention, the terms "first" and "second" in "first solvent" and "second solvent" do not have specific meanings; they are only used to distinguish whether they are used in different steps.

[0111] In this invention, the base electrolyte preferably further includes additives. Preferably, the additives are one or more of FEC (fluoroethylene carbonate), PS (1,3-propanesulfonate lactone), and PST (1,3-propenesulfonate lactone), more preferably FEC, PS, and PST. The mass fraction of the additives in the base electrolyte is preferably 0.5% to 5%. When the additive is a combination of the above three components, the mass fraction of FEC in the base electrolyte is preferably 0.5% to 5%, specifically 0.5%, 1%, 2%, 3%, 4%, or 5%; the mass fraction of PS in the base electrolyte is preferably 0.5% to 5%, specifically 0.5%, 1%, 2%, 3%, 4%, or 5%; and the mass fraction of PST in the base electrolyte is preferably 0.3% to 5%, specifically 0.3%, 0.5%, 1%, 2%, 3%, 4%, or 5%.

[0112] In this invention, more preferably, the base electrolyte used in step B2) is the same as the base electrolyte used in step B1).

[0113] In this invention, the preferred method for mixing monomer 2 and the basic electrolyte is stirring. The stirring speed is preferably 400–1000 rpm, specifically 400 rpm, 600 rpm, 800 rpm, or 1000 rpm. The stirring time is preferably 1–4 hours, specifically 1 hour, 2 hours, 2.5 hours, 3 hours, or 4 hours. After homogeneous mixing, mixed solution 2 is obtained.

[0114] [Regarding step B3]:

[0115] B3) Apply the mixed solution 1 to the negative electrode side and the mixed solution 2 to the positive electrode side, press and seal with the separator to obtain a coin cell; then perform heat treatment on the coin cell.

[0116] In this invention, the positive electrode sheet is preferably prepared by the following method:

[0117] S1. Mix the positive electrode active material, conductive agent, binder and first solvent to obtain positive electrode slurry;

[0118] S2. Coat the positive electrode slurry onto the positive electrode current collector and dry it to obtain the basic positive electrode sheet;

[0119] S3. The functional material solution is coated onto the surface of the basic positive electrode sheet and then dried to obtain the positive electrode sheet.

[0120] Regarding step S1:

[0121] S1. Mix the positive electrode active material, conductive agent, binder and first solvent to obtain positive electrode slurry.

[0122] In this invention, the positive electrode active material is preferably a high-nickel positive electrode active material, more preferably NCM811 (i.e., LiNi). 0.8 Co 0.1 Mn 0.1 O2).

[0123] In this invention, the conductive agent is preferably conductive carbon; the conductive carbon is preferably at least one of VGGTs (vapor-grown graphite tubes) and SuperP.

[0124] In this invention, the adhesive is preferably at least one of PVDF and PTFE.

[0125] In this invention, the preferred mass ratio of the positive electrode active material, conductive agent and binder is (8-9):(0.5-1):(0.5-1), more preferably 9:0.5:0.5 or 8:1:1.

[0126] In this invention, the first solvent is preferably N-methylpyrrolidone (NMP). In this invention, the preferred ratio of the positive electrode active material to the first solvent is (8-9) mg:(14-30) mL.

[0127] In this invention, there are no particular restrictions on the method of mixing the positive electrode active material, conductive agent, binder, and first solvent; any conventional mixing method in the art that can mix the substances evenly is acceptable, such as stirring in a homogenizer. After mixing, a positive electrode slurry is obtained.

[0128] Regarding step S2:

[0129] S2. Coat the positive electrode slurry onto the positive electrode current collector and dry it to obtain the basic positive electrode sheet.

[0130] In this invention, the positive current collector is preferably aluminum foil. The coating density is preferably 160–240 g / m³. 2 In this invention, after coating, the material is dried. The drying is preferably vacuum drying. The vacuum drying temperature is preferably 60–120°C, more preferably 80°C. The drying time is preferably 6–24 hours, more preferably 8 hours. In this invention, after the above drying, it is preferable to further perform roller pressing. The compaction density of the roller pressing is preferably 2.6–3.3 g / m³. 2 After rolling, a basic positive electrode sheet is obtained.

[0131] Regarding step S3:

[0132] S3. The functional material solution is coated onto the surface of the basic positive electrode sheet and then dried to obtain the positive electrode sheet.

[0133] In this invention, the functional material solution is a solution formed by dissolving the functional material in a solvent. The functional material is at least one selected from Pd(Ac)₂, La(Ac)₃, Ar(Ac)₄, Ce(Ac)₃, Y(Ac)₃, hydrates of Pd(Ac)₂, La(Ac)₃, Ar(Ac)₄, Ce(Ac)₃, and Y(Ac)₃. The solvent is preferably at least one selected from N-methylpyrrolidone (NMP), N,N-dimethylformamide, isopropanol, and anhydrous ethanol. In this invention, the mass fraction of the functional material solution is preferably 1% to 5%, specifically 1%, 2%, 3%, 4%, or 5%.

[0134] In this invention, the functional material solution is preferably obtained by mixing the functional material with a solvent to obtain the functional material solution. The mixing method is preferably stirring. The stirring speed is preferably 500–1000 rpm, specifically 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm. The stirring time is preferably 0.5–4 hours, more preferably 2 hours.

[0135] In this invention, the preferred method for coating the functional material solution onto the surface of the positive electrode sheet is spraying. Specifically, the functional material solution is transferred to a spray gun and sprayed uniformly onto the surface of the positive electrode sheet under a certain pressure. The spraying pressure is preferably 15–35 psi. In this invention, the functional material solution is coated on the side of the positive electrode sheet that has already been coated with the positive electrode slurry.

[0136] In this invention, after the above coating is applied, drying is performed. Preferably, the drying is vacuum drying. The vacuum drying temperature is preferably 80–130°C, more preferably 120°C. The vacuum drying time is preferably 8–24 hours, more preferably 12 hours. After drying, a functional material coating is formed, resulting in a positive electrode sheet with the functional material coating. In this invention, the thickness of the functional material coating is preferably 2–3 μm.

[0137] In this invention, the negative electrode is preferably a lithium metal electrode.

[0138] In this invention, the preferred method for applying the mixed solution 1 to the negative electrode side is dropwise addition. In this invention, when applying the mixed solution 1 to the negative electrode side, it can be applied to one side surface of the negative electrode sheet. Subsequently, during battery assembly, this surface with the mixed solution 1 applied is assembled opposite to the positive electrode sheet. In this invention, the preferred amount of the mixed solution 1 applied to the negative electrode side is 15–25 μL / cm. 2 Specifically, it can be 15 μL / cm 2 20μL / cm 2 25μL / cm 2 .

[0139] In this invention, the preferred method for applying the mixed solution 2 to the positive electrode side obtained in steps S1 to S3 is dropwise addition. In this invention, when applying the mixed solution 2 to the positive electrode side, it can be applied to one surface of the positive electrode. Subsequently, during battery assembly, this surface with the mixed solution 2 applied is assembled opposite to the negative electrode. In this invention, the preferred amount of the mixed solution 2 applied to the positive electrode side is 40–65 μL / cm. 2 Specifically, it can be 40 μL / cm 2 45μL / cm 2 50μL / cm 255μL / cm 2 60μL / cm 2 65μL / cm 2 .

[0140] In this invention, the diaphragm is preferably a PP diaphragm.

[0141] In this invention, there are no particular limitations on the method of assembling the battery by pressing and sealing the negative electrode, positive electrode, and separator; assembly can be performed according to conventional assembly methods in the art. The surface of the negative electrode to which the mixed solution 1 is applied faces the surface of the positive electrode to which the mixed solution 2 is applied, as shown below. Figure 1 As shown. In this invention, as with conventional battery assembly processes, an electrolyte needs to be added during battery assembly. The type of electrolyte used in this invention is preferably the same as the basic electrolyte in steps B1) and B2). In this invention, the above battery assembly process is preferably carried out in a glove box filled with argon gas. In this invention, after all components are assembled, a coin cell is obtained.

[0142] In this invention, after the battery is assembled, it undergoes heat treatment. The preferred temperature for this heat treatment is 45–60°C, specifically 45°C, 50°C, 55°C, or 60°C. The preferred heat treatment time is 6–12 hours, specifically 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. Through this heat treatment, the precursors on both the positive and negative electrode sides undergo gradient in-situ polymerization. Specifically, cationic polymerization initiates mild polymerization on the positive electrode side, free radical polymerization initiates high polymerization on the negative electrode side, and the two monomers at the separator interpenetrate to complete cross-linking copolymerization, thereby forming a gradient polymerization system with increasing polymerization degree from the positive to the negative electrode.

[0143] The following is an example illustrating the gradient in-situ aggregation described above:

[0144] On the positive electrode side, taking the monomer tri(ethylene glycol)divinylvinylsulfite as an example and the positive electrode coating using the functional material lanthanum acetate as an example, lanthanum acetate is diluted with a solvent and sprayed onto the positive electrode sheet. In the battery, it will come into full contact with the carbonate solvents of the electrolyte, causing the La... + The tri(ethylene glycol) divinyl sulfite on the positive electrode side will complete a certain coordination under the catalysis of the transition metal, thereby initiating a slight polymerization (as shown in formula (5) below). This polymerization will be terminated by factors such as moisture and HF, so the degree of polymerization is low.

[0145]

[0146] On the negative electrode side, acrylate monomers are used, taking ethoxylated trimethylolpropane triacrylate as an example, and free radical polymerization occurs under the action of an initiator, as shown in the following formula (6):

[0147]

[0148] At the diaphragm, the two types of monomers undergo cross-linking polymerization initiated by free radicals, as shown in equation (7):

[0149]

[0150] Thus, gradient in-situ polymerization is formed between the positive electrode, separator, and negative electrode, thereby achieving modification of the interface of the positive electrode material. When other types of monomers mentioned above are used on the positive and negative electrode sides, the same principle applies, and will not be elaborated further.

[0151] This invention provides a polymer solid electrolyte monomer and its preparation method, as well as a secondary battery. The invention provides specific thioester monomers (i.e., the polymer solid electrolyte monomers mentioned above), which are beneficial for improving the electrochemical performance of the battery. The secondary battery provided by this invention is essentially a method for modifying the interface of a high-nickel cathode material. The secondary battery provided by this invention introduces thioester monomers (i.e., the polymer solid electrolyte monomers mentioned above) and utilizes a certain functional material solution, both used on the positive electrode side. Simultaneously, acrylate monomers are introduced on the negative electrode side. After battery assembly, heat treatment is performed, using the functional material as an initiator to initiate gradient in-situ polymerization of the precursors on both the positive and negative electrode sides. Specifically, cationic polymerization initiates mild polymerization on the positive electrode side, free radical polymerization initiates high polymerization on the negative electrode side, and the two monomers interpenetrate at the separator to complete cross-linking copolymerization, thereby forming a gradient polymerization system with increasing polymerization degree from the positive to the negative electrode. The aforementioned gradient in-situ polymerization ensures the formation of high-mechanical-strength monomer polymerization on the negative electrode side to suppress lithium dendrite growth and protect the negative electrode Sei. Simultaneously, the low-polymerization-degree vinyl monomers ensure sufficient electrolyte wetting of the positive electrode active material on the positive electrode side, promoting the formation of positive electrode CEi and reducing excessive metal dissolution by HF. The cross-linking and copolymerization of the two types of monomers at the separator further enhances the separator's resistance to lithium dendrite penetration, improving battery safety. Furthermore, compared to single-monomer polymerization, cross-linking polymerization further improves mechanical strength while also being more beneficial for lithium-ion transport. The in-situ solid-state battery prepared using this method exhibits lower internal resistance and faster Li-ion transport. + This improves the electrochemical performance of the battery by creating a transmission channel.

[0152] Compared with the prior art, the present invention has the following beneficial effects:

[0153] 1. A novel thioester monomer was synthesized, which can effectively reduce the thickness of the SEI film during long-term cycling, reduce internal resistance, and promote the stability of long-term cycling. It also exhibits good compatibility with NCM.

[0154] 2. The positive electrode is coated by spraying, which ensures the uniformity of the coating and reduces the amount of adhesive used while lowering the risk of coating peeling.

[0155] 3. The synthesized multifunctional monomer contains ethoxy functional groups, which can increase the flexibility of the polymer and prevent the dry film from becoming brittle.

[0156] 4. The coating containing trace amounts of transition metal material applied to the positive electrode substrate can improve the delamination caused by solvent evaporation and particle sedimentation during the electrode drying process.

[0157] 5. Through gradient in-situ polymerization, the in-situ solid-state battery achieves lower internal resistance and faster Li-C / C polymerization. + This improves the electrochemical performance of the battery by creating a transmission channel.

[0158] Therefore, this invention solves the following problems: the need to use polymer binders for coating functional materials such as ceramics and molecular sieves on the separator, which leads to increased internal resistance and the risk of material peeling; the problem of high internal resistance in in-situ solid-state batteries; the problem of poor stability of the interface between high-nickel ternary cathode materials and electrolytes; and the safety problem caused by lithium dendrite growth in half-cells.

[0159] Experimental results show that the solution of this invention enables the battery to achieve a specific capacity of 184 mAh g. -1 The initial coulomb efficiency reached over 89%, the capacity retention after 50 cycles reached over 97%, and the interface impedance R... sei It exhibits excellent electrochemical performance below 299Ω.

[0160] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0161] Example 1

[0162] 1. Preparation of thioester monomers:

[0163] A1) Take 3 mg of bis(trimethylolpropane) and 7 mg of vinyl sulfite, add them to 200 mL of methanesulfonic acid, and carry out esterification reaction by stirring at 800 rpm for 5 h at 100 °C to obtain the reaction solution.

[0164] A2) Post-processing:

[0165] A2-1) Let the obtained reaction solution stand at room temperature, then add 0.05 mg of p-hydroxyanisole, and stir at 600 rpm for 4 h to obtain mixture 1.

[0166] A2-2) Transfer the mixture 1 to an activated carbon filter column for filtration and decolorization to obtain the mixture 2.

[0167] (A2-3) Place mixture 2 in a vacuum oven and let it stand at 80°C for 12 hours to obtain bis(trimethylolpropane)tetravinyl sulfite with a molecular weight of 546.26.

[0168] The reaction route for step A) is as follows:

[0169]

[0170] The NMR spectrum data of bis(trimethylolpropane)tetravinylvinylsulfite is as follows: 1 ¹H NMR (300MHz, CDCl₃) δ 3.79 (s, 4H), δ 1.69 (m, 4H), δ 0.83 (t, 6H), δ 3.39 (s, 8H), δ 5.07 (t, 4H), δ 5.34 (d, 4H), δ 5.09 (d, 4H). Mass spectrometry data are as follows: MALDI-TOF-MAS (m / z): calcd.for C 20 H 34 O9S4[M+1]+,546.11,found 546.26.

[0171] 2. Preparation of the positive electrode:

[0172] S1. Disperse the high-nickel positive electrode active material NCM811, conductive carbon VGGTs, and binder PVDF in NMP solvent at a mass ratio of 9:0.5:0.5 and mix them evenly to obtain the positive electrode slurry.

[0173] S2. Coat the positive electrode slurry onto the aluminum foil (coating density 120 g / m²). 2 The sample was dried in a vacuum oven at 80°C for 8 hours, and then rolled (compacted density 3.1 g / m³). 2 ), thus obtaining the basic positive electrode.

[0174] S3. Dissolve 5 mg of functional material Y(Ac)3·3H2O in 0.18 mL of N-methylpyrrolidone solvent and stir at 1000 rpm for 2 h to obtain a functional material solution. Transfer the functional material solution to a 0.5 mm nozzle spray gun and spray it onto the side of the base positive electrode sheet that has been coated with the positive electrode slurry under a pressure of 32 psi. Then quickly transfer it to a vacuum oven and dry it at 120 °C for 12 h to form a functional material coating (thickness of 2 μm), thus obtaining a positive electrode sheet with a functional coating material.

[0175] 3. Assemble the secondary battery:

[0176] Preparation: Dissolve the electrolytes LiPF6 + LiDFOB + LiFSI in a mixed solvent EC + PC + EMC + DEC (the volume ratio of the above components in the mixed solvent is 3:2:3:2), so that the concentrations of each electrolyte component are 0.09M LiPF6 + 0.05M LiDFOB + 0.1M LiFSI. Then add 3% FEC, 1% PS, and 0.3% PST to obtain the basic electrolyte solution.

[0177] B1) Add 3% polyethylene glycol methyl ether acrylate and 0.1% azobisisobutyronitrile to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 1.

[0178] B2) Add 2% of the thioester monomer obtained in step A) to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 2.

[0179] B3) Add mixed solution 1 (dropping volume 25 μL / cm) to the lithium metal anode. 2 Mixed solution 2 (55 μL / cm³) is added dropwise to the positive electrode side obtained in steps S1 to S3. 2 The separator is made of PP membrane, and the above-mentioned basic electrolyte is used as the battery electrolyte. After pressing and sealing, it is placed in a constant temperature oven at 60℃ for 8 hours to obtain button cell 1.

[0180] Example 2

[0181] 1. Preparation of thioester monomers:

[0182] A1) Take 3 mg pentaerythritol and 7.8 mg vinyl sulfite, add them to 200 mL methanesulfonic acid, and stir at 800 rpm for 5 h at 100 °C to carry out the esterification reaction to obtain the reaction solution.

[0183] A2) Post-processing:

[0184] A2-1) Let the obtained reaction solution stand at room temperature, then add 0.05 mg of p-hydroxyanisole, and stir at 600 rpm for 4 h to obtain mixture 1.

[0185] A2-2) Transfer the mixture 1 to an activated carbon filter column for filtration and decolorization to obtain the mixture 2.

[0186] (A2-3) Place mixture 2 in a vacuum oven and let it stand at 80°C for 12 hours to obtain pentaerythritol tetravinyl sulfite with a molecular weight of 496.32.

[0187] The reaction route for step A) is as follows:

[0188]

[0189] The NMR spectrum data of pentaerythritol tetravinyl sulfite is as follows: 1 ¹H NMR (300MHz, CDCl₃) δ 3.39 (s, 8H), δ 5.07 (t, 4H), δ 5.34 (d, 4H), δ 5.09 (d, 4H). Mass spectrometry data are as follows: MALDI-TOF-MAS (m / z): calcd.for C 13 H 20 O 12 S4[M+1]+,495.98, found 496.32.

[0190] 2. Preparation of the positive electrode:

[0191] S1, Same as Example 1.

[0192] S2, same as Example 1.

[0193] S3. Dissolve 5 mg of lanthanum acetate, a functional material, in 0.4 mL of NMP solvent and stir at 1000 rpm for 2 h to obtain a functional material solution. Transfer the functional material solution to a 0.5 mm nozzle spray gun and spray it onto the side of the base positive electrode sheet that has been coated with the positive electrode slurry under a pressure of 40 psi. Then quickly transfer it to a vacuum oven and dry it at 120 °C for 12 h to form a functional material coating (2 μm thick), thus obtaining a positive electrode sheet with a functional coating material.

[0194] 3. Assemble the secondary battery:

[0195] Preparation: Prepare the basic electrolyte according to Example 1.

[0196] B1) Add 3% pentaerythritol tetraacrylate and 0.1% azobisisobutyronitrile to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 1.

[0197] B2) Add 2% of the thioester monomer obtained in step A) to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 2.

[0198] B3) Using the above-mentioned mixed solution 1 and mixed solution 2, the battery was assembled and dried and heat-treated according to the process of Example 1 to obtain the button cell 2.

[0199] Example 3

[0200] 1. Preparation of thioester monomers:

[0201] A1) Take 3 mg of ethoxylated trimethylolpropane and 5.3 mg of vinyl sulfite, add them to 200 mL of methanesulfonic acid, and stir at 800 rpm for 5 h at 100 °C to carry out the esterification reaction, and obtain the reaction solution.

[0202] A2) Post-processing:

[0203] A2-1) Let the obtained reaction solution stand at room temperature, then add 0.05 mg of p-hydroxyanisole, and stir at 600 rpm for 4 h to obtain mixture 1.

[0204] A2-2) Transfer the mixture 1 to an activated carbon filter column for filtration and decolorization to obtain the mixture 2.

[0205] (A2-3) Place mixture 2 in a vacuum oven and let it stand at 80°C for 12 hours to obtain ethoxylated trimethylolpropane trivinyl sulfite with a molecular weight of 476.

[0206] The reaction route for step A) is as follows:

[0207]

[0208] The NMR spectra of ethoxylated trimethylolpropane trivinyl sulfite are as follows: ¹H NMR (300 MHz, CDCl₃) δ 3.79 (s, 6H), δ 1.69 (m, 2H), δ 0.83 (t, 3H), δ 3.54 (t, 6H), δ 3.7 (t, 6H), δ 5.07 (t, 3H), δ 5.34 (d, 3H), δ 5.09 (d, 3H). The mass spectrometry data are as follows: MALDI-TOF-MAS (m / z): calcd.forC 18 H 32 O 12 S3[M+1]+,536.11,found 536.22.

[0209] 2. Preparation of the positive electrode:

[0210] S1, Same as Example 1.

[0211] S2, same as Example 1.

[0212] S3. Dissolve 5 mg of cerium acetate, a functional material, in 0.5 mL of anhydrous ethanol and stir at 1000 rpm for 2 h to obtain a functional material solution. Transfer the functional material solution to a 0.5 mm nozzle spray gun and spray it onto the side of the base positive electrode sheet that has been coated with the positive electrode slurry at 45 psi pressure. Then quickly transfer it to a vacuum oven and dry it at 120 °C for 12 h to form a functional material coating (2 μm thick), thus obtaining a positive electrode sheet with a functional coating material.

[0213] 3. Assemble the secondary battery:

[0214] Preparation: Prepare the basic electrolyte according to Example 1.

[0215] B1) Add 3% ethoxylated trimethylolpropane triacrylate and 0.1% azobisisobutyronitrile to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 1.

[0216] B2) Add 2% of the thioester monomer obtained in step A) to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 2.

[0217] B3) Using the above-mentioned mixed solution 1 and mixed solution 2, the battery is assembled and dried and heat-treated according to the process of Example 1 to obtain the button cell 3.

[0218] Example 4

[0219] 1. Preparation of thioester monomers:

[0220] A1) Take 3 mg of triethylene glycol and 5.5 mg of vinyl sulfite, add them to 200 mL of methanesulfonic acid, and stir at 800 rpm for 5 h at 100 °C to carry out the esterification reaction, and obtain the reaction solution.

[0221] A2) Post-processing:

[0222] A2-1) Let the obtained reaction solution stand at room temperature, then add 0.05 mg of p-hydroxyanisole, and stir at 600 rpm for 4 h to obtain mixture 1.

[0223] A2-2) Transfer the mixture 1 to an activated carbon filter column for filtration and decolorization to obtain the mixture 2.

[0224] (A2-3) Place mixture 2 in a vacuum oven and let it stand at 80°C for 12 hours to obtain tri(ethylene glycol) divinyl sulfite with a molecular weight of 236.32.

[0225] The reaction route for step A) is as follows:

[0226]

[0227] The NMR spectrum data of tri(ethylene glycol) divinyl sulfite is as follows: 1 ¹H NMR (300MHz, CDCl₃) δ 3.52(t, 4H), δ 3.54(t, 4H), δ 3.7(t, 4H), δ 5.07(t, 2H), δ 5.34(d, 2H), δ 5.09(d, 2H). Mass spectrometry data are as follows: MALDI-TOF-MAS (m / z): calcd.for C 10 H 18 O8S2[M+1]+,330.04, found 330.16.

[0228] 2. Preparation of positive electrode sheet: Same as in Example 1.

[0229] 3. Assemble the secondary battery:

[0230] Preparation: Prepare the basic electrolyte according to Example 1.

[0231] B1) Add 3% tri(ethylene glycol) dimethacrylate and 0.1% azobisisobutyronitrile to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 1.

[0232] B2) Add 2% of the thioester monomer obtained in step A) to the basic electrolyte and stir at 600 rpm for 2 hours to obtain mixed solution 2.

[0233] B3) Using the above-mentioned mixed solution 1 and mixed solution 2, the battery is assembled and dried and heat-treated according to the process of Example 1 to obtain the button cell 4.

[0234] Comparative Example 1

[0235] 1. Preparation of positive electrode sheet:

[0236] The procedure was carried out as in Example 1, except that step S3, which involves preparing the functional material coating, was omitted.

[0237] 2. Assemble the secondary battery:

[0238] Preparation: Prepare the basic electrolyte according to Example 1.

[0239] B1) Add 3% polyethylene glycol methyl ether acrylate and 0.1% azobisisobutyronitrile to the basic electrolyte and stir at 600 rpm for 2 hours to obtain a mixed solution.

[0240] B3) The above mixed solution was added dropwise to both the negative electrode side and the positive electrode side of the lithium metal (the amount added was the same as in Example 1), and the battery was assembled and dried and heat-treated according to the process in Example 1.

[0241] Comparative Example 2

[0242] 1. Preparation of positive electrode sheet:

[0243] The procedure was carried out as in Example 1, except that step S3, which involves preparing the functional material coating, was omitted.

[0244] 2. Assemble the secondary battery:

[0245] Preparation: Prepare the basic electrolyte according to Example 1.

[0246] B1) Add 3% allyl isothiocyanate and 0.1% azobisisobutyronitrile to the basic electrolyte and stir at 600 rpm for 2 hours to obtain a mixed solution.

[0247] B3) The above mixed solution was added dropwise to both the negative electrode side and the positive electrode side of the lithium metal (the amount added was the same as in Example 1), and the battery was assembled and dried and heat-treated according to the process in Example 1.

[0248] Product Testing :

[0249] The batteries obtained in each embodiment and comparative example were subjected to constant current charge-discharge tests on a battery testing system, with a voltage range of 3-4.2V and a charge-discharge rate of 0.2C. See the results below. Figure 2-3 And Table 1.

[0250] Table 1: Test Results of Each Example and Comparative Example

[0251]

[0252] The test results show that the specific capacity of Examples 1-4 reaches 184 mAh g. -1 The initial coulomb efficiency reached over 89%, the capacity retention after 50 cycles reached over 97%, and the interface impedance R... sei Below 299 Ω, it exhibits excellent electrochemical performance; among them, the specific capacity of Example 1 is as high as 202.87 mAh g. -1 Furthermore, the initial efficiency reached 92.85%. Comparative Example 1, using a conventional in-situ solid-state process, performed poorly in terms of capacity utilization, capacity retention, and initial efficiency, and its interfacial impedance at the assembly point was significantly increased. For example, in Comparative Example 1, when only acrylic monomers such as polyethylene glycol methyl ether acrylate were used, the entire process was thermally initiated free radical polymerization. When the monomer ratio was slightly increased (≥3%), the degree of polymerization on the positive electrode side was too high, which was detrimental to lithium-ion extraction, resulting in a large interfacial impedance. Moreover, thermally initiated polymerization leads to uneven polymerization, resulting in uneven lithium deposition, especially severe in the battery, leading to lower initial efficiency and cycle performance. Comparative Example 2, using a conventional allyl isothiocyanate monomer, resulted in a decrease in the overall oxidative stability of the electrolyte, preventing normal battery cycling; therefore, specific capacity, initial coulombic efficiency, and capacity retention could not be tested, and its interfacial impedance after polymerization was also higher than all other examples. Examples 1-4, which use thiomonomers, only exhibit mild polymerization initiated by transition metals on the positive electrode side, which has a relatively small impact on the extraction of lithium ions from the positive electrode and can improve lithium deposition in in-situ solid-state batteries.

[0253] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A polymer solid-state electrolyte monomer, characterized by, The polymer solid electrolyte monomer is selected from one or more of the structures shown in the following formulas 1-4: Formula 1; Formula 2; Formula 3; Formula 4.

2. A method of preparing the polymer solid-state electrolyte monomer of claim 1, characterized by, The method comprises the following steps: A1) esterification of reactant 1 and reactant 2 to obtain a reaction solution; A2) post-treatment of the reaction solution to obtain the polymer solid electrolyte monomer; wherein, The reactant 1 is at least one of di(trimethylolpropane), ethoxylated trimethylolpropane, pentaerythritol, triethylene glycol; The reactant 2 is vinyl vinylene sulfate, and the structure is shown in the following formula: 。 3. The preparation method according to claim 2, characterized in that, In step A1), the medium of the esterification reaction is methane sulfonic acid; The molar ratio of the reactant 1 to the reactant 2 is (0.8-1.2):1; and the amount ratio of the reactant 1 to methane sulfonic acid is (3-6) mg:(150-400) mL.

4. The production method according to claim 2, characterized by, In step A1), the temperature of the esterification reaction is 80-110°C, and the time of the esterification reaction is 4-6h.

5. The preparation method according to claim 2, characterized in that, In step A2), the post-treatment specifically comprises: A2-1) mixing the reaction solution with a polymerization inhibitor to obtain a mixed solution 1; A2-2) decolorizing the mixed solution 1 with activated carbon to obtain a mixed solution 2; A2-3) drying the mixed solution 2 to obtain the polymer solid electrolyte monomer.

6. A secondary battery characterized by comprising: The assembling step of the secondary battery comprises: B1) mixing monomer 1, an initiator and a base electrolyte to obtain a mixed solution 1; B2) mixing monomer 2 and a base electrolyte to obtain a mixed solution 2; B3) applying the mixed solution 1 to the negative electrode side and the mixed solution 2 to the positive electrode sheet side, pressing and sealing with a separator to obtain a button cell; and then heat-treating the button cell; wherein, The monomer 1 is an acrylate compound; The monomer 2 is the polymer solid electrolyte monomer of claim 1 or the polymer solid electrolyte monomer prepared by the method of any one of claims 2-5.

7. The secondary battery according to claim 6, characterized by The preparation method of the positive electrode sheet comprises the following steps: S1, mixing a positive electrode active material, a conductive agent, a binder and a first solvent to obtain a positive electrode slurry; S2, coating the positive electrode slurry onto a positive electrode current collector and drying to obtain a base positive electrode sheet; S3, coating a functional material solution on the surface of the base positive electrode sheet and then drying to obtain a positive electrode sheet.

8. The secondary battery according to claim 7, characterized by The functional material in the functional material solution is selected from at least one of Pd(Ac)2, La(Ac)3, Ar(Ac)4, Ce(Ac)3, Y(Ac)3, a hydrate of Pd(Ac)2, a hydrate of La(Ac)3, a hydrate of Zr(Ac)4, a hydrate of Ce(Ac)3 and a hydrate of Y(Ac)3; The solvent of the functional material solution is selected from one or more of N-methyl pyrrolidone, N,N-dimethylformamide, isopropyl alcohol and anhydrous ethanol; The mass fraction of the functional material solution is 1%-5%.

9. The secondary battery according to claim 7, characterized by The positive electrode active material is a high-nickel positive electrode active material; The first solvent is N-methyl pyrrolidone; The conductive agent is selected from a conductive carbon material; The binder is selected from at least one of PVDF and PTFE.

10. The secondary battery according to claim 6, characterized by The monomer 1 is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, 2-methacrylic acid-2-oxirane ethyl ester, di (trihydroxymethyl propane) tetraacrylate, methyl methacrylate, ethyl methacrylate and triethylene glycol methacrylate.

11. The secondary battery according to claim 6, characterized by The base electrolyte comprises a lithium salt and a second solvent; The lithium salt is selected from one of lithium hexafluorophosphate, lithium difluoro (oxalato) borate and lithium bis (fluorosulfonyl) imide; The second solvent is ethylene carbonate, propylene carbonate, methyl ethyl carbonate and diethyl carbonate; The concentration of the base electrolyte is 1-1.2 mol / L.

12. The secondary battery according to claim 6, characterized by The base electrolyte further comprises an additive; The additive is one or more of fluoroethylene carbonate, 1,3-propane sulfone lactone and 1,3-propylene sulfone lactone; The mass fraction of the additive in the base electrolyte is 0.5%-5%.

Images