Method of preparing a polymer solid-state electrolyte using a thermal latent catalyst composition and a solid-state battery

Abstract

The present application relates to a method for preparing a polymer solid-state electrolyte using a thermal latent catalyst composition, the method comprising forming the polymer solid-state electrolyte from an electrolyte precursor solution by in-situ thermal polymerization; components of the electrolyte precursor solution include polymerizable monomers, an alkali metal salt, a crosslinking agent, a thermal latent catalyst composition, and an organic solvent; the polymerizable monomers include thiol-based monomers, and the thermal latent catalyst composition includes DBU iso-octoate and DBU formate; the electrolyte precursor solution does not contain a thermal initiator that generates free radicals upon heating. The present application also relates to a solid-state battery comprising the polymer solid-state electrolyte prepared by the above method.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, and in particular to a method for preparing a polymer solid-state electrolyte using a thermally latent catalyst composition, and a solid-state battery comprising the polymer solid-state electrolyte. Background Technology

[0002] This section provides background information relevant to this application, which does not necessarily constitute prior art.

[0003] Existing solid electrolytes mainly include oxide solid electrolytes, sulfide solid electrolytes, and polymer solid electrolytes. Among them, polymer solid electrolytes have attracted widespread attention due to their good flexibility, ease of processing, and good contact with electrodes. However, polymer solid electrolytes generally suffer from technical problems such as low ionic conductivity, low thermal stability, and high interfacial impedance. To address these technical problems, existing technical solutions include preparing polymer electrolytes using in-situ polymerization processes. Specifically, a reactive electrolyte precursor solution is directly injected into the battery, and the electrolyte precursor solution contacts and wets the positive and negative electrodes. After the electrodes are fully wetted, polymerization is initiated by external stimuli such as heat, light, and electricity to obtain the polymer solid electrolyte, thereby constructing an integrated polymer solid electrolyte-electrode interface and reducing interfacial impedance.

[0004] Existing electrolyte precursor solutions include polymerizable monomers, alkali metal salts, crosslinking agents, initiators, and organic solvents. Among them, polymerizable monomers require initiators to generate primary free radicals to initiate chain reactions to obtain high molecular weight polymers. Too little initiator will lead to insufficient or failed electrolyte polymerization, while too much initiator will cause initiator residue, destroy the uniformity of electrolyte structure, cause interfacial side reactions, increase interfacial impedance, and ultimately affect the battery's ionic conductivity, cycle stability, and coulombic efficiency, thus deteriorating electrochemical performance.

[0005] Existing initiators mainly include photoinitiators (polymerization initiated by light) and thermal initiators (polymerization initiated by heating). Since in-situ polymerization requires injecting the electrolyte precursor solution into the battery, and the battery is an opaque, sealed structure, free radical polymerization cannot be initiated by photoinitiation. Therefore, most current in-situ polymerization technologies employ thermal initiation. Two common thermal initiators are azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO), with ten-hour half-lives of 65°C and 73°C, respectively, corresponding to typical thermosetting temperatures in actual preparation processes. However, according to the initiator decomposition formula: It can be seen that even at room temperature, the initiator will still decompose slowly. As a highly reactive system, free radical polymerization can trigger a chain reaction with a small amount of free radicals, leading to premature solidification and inability to inject the solution. This results in poor controllability of the polymerization system, posing a significant challenge to the storage and transportation of electrolyte precursor solutions. Summary of the Invention

[0006] This invention aims to provide a method for preparing polymer solid electrolytes using an electrolyte precursor solution. The electrolyte precursor solution uses a thermally latent catalyst composition instead of an existing thermal initiator. When the ambient temperature is lower than the predetermined polymerization initiation temperature, the electrolyte precursor solution will not undergo significant solidification. The thermally latent catalyst composition can significantly improve the storage stability of the electrolyte precursor solution over a wide temperature range. The thermally latent catalyst composition can achieve full polymerization of the electrolyte precursor solution while significantly reducing interfacial impedance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a polymer solid electrolyte using a thermally latent catalyst composition, the method comprising forming the polymer solid electrolyte by in-situ thermal polymerization of an electrolyte precursor solution, wherein the electrolyte precursor solution comprises a polymerizable monomer, an alkali metal salt, a crosslinking agent, a thermally latent catalyst composition, and an organic solvent, wherein the polymerizable monomer comprises a thiol monomer, and the electrolyte precursor solution does not contain a thermal initiator that generates free radicals upon heating.

[0008] The in-situ thermal polymerization of the electrolyte precursor solution is carried out in the presence of the thermally latent catalyst composition according to the invention, and can be implemented using any well-known polymerization technique, and in particular thermal polymerization (including induction and infrared heating) or radiation polymerization. Preferably, the in-situ thermal polymerization of the electrolyte precursor solution takes not less than 12 hours.

[0009] In one or more embodiments, the method for preparing the electrolyte precursor solution includes the following steps: Step 1: Mix the following components in molar amounts to obtain a mixture: 0.5-2 molar amounts of alkali metal salt, 10-15 molar amounts of organic solvent, 2-4 molar amounts of crosslinking agent, and 0.8-2.5 molar amounts of polymerizable monomer; Step 2: Add the thermally latent catalyst composition to the mixture and mix evenly to obtain an electrolyte precursor solution. The amount of thermally latent catalyst composition added is 0.05wt%-0.2wt% of the mass of the mixture (when the amount added is higher than 0.2wt%, there is a tendency to accelerate the polymerization reaction, which has a negative impact on the uniformity and density of the polymer solid electrolyte; when the amount added is lower than 0.05wt%, there is a tendency for incomplete solidification, which has a negative impact on the mechanical strength and other properties of the polymer solid electrolyte).

[0010] In one or more embodiments, a method for preparing a polymer solid electrolyte using an electrolyte precursor solution includes the following steps: Step 1: Mix the components, including polymerizable monomers, alkali metal salts, crosslinking agents, thermally latent catalyst compositions, and organic solvents, to prepare an electrolyte precursor solution; Step 2: Assemble a battery cell using a positive electrode, a separator (such as a porous membrane made of glass fiber, aramid, polyethylene, polypropylene, or polytetrafluoroethylene), and a negative electrode. During or after the battery cell assembly process, inject the electrolyte precursor solution into the battery cell. The injection process is carried out under an ambient moisture content of <20 ppm and a nitrogen atmosphere. Step 3: After allowing the electrolyte precursor solution to fully wet the positive and negative electrodes of the battery cell, the battery cell is placed in an oven and heat-treated under nitrogen atmosphere. The electrolyte precursor solution forms the polymer solid electrolyte through in-situ thermal polymerization. Preferably, the formed polymer solid electrolyte fully wets and penetrates into the separator and the interior of the electrodes, forming a solid electrolyte interface layer (i.e., SEI film) on the electrode surface.

[0011] The thermally latent catalyst composition comprises DBU isooctanoate as shown in Formula 1 and DBU formate as shown in Formula 2. The thermally latent catalyst composition is thermally activated; specifically, when heated to a predetermined polymerization initiation temperature, the thermally latent catalyst composition dissociates into a strong base, DBU, to catalyze the thiol-olefin click reaction via Michael addition, achieving efficient polymerization and solidification of the electrolyte precursor solution at the predetermined polymerization initiation temperature. In this invention, the thermally latent catalyst composition can be activated by heat and / or radiation.

[0012] Formula 1; Formula 2.

[0013] Both the DBU isooctanoate and the DBU formate are 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as shown in Formula 3, which forms a non-catalytically active DBU salt with an organic carboxylic acid at room temperature. The organic carboxylic acid acts as a blocker to prevent the DBU salt from reacting until it is activated by heating, which decomposes the DBU salt to regenerate DBU.

[0014] Formula 3.

[0015] The thermally latent catalyst composition is inactive at room temperature (e.g., 20-25°C) and only exhibits a significant reaction upon reaching its activation temperature, which is greater than or equal to 80°C. The thermally latent catalyst composition can synergistically enhance the stability of the electrolyte precursor solution during storage at room temperature.

[0016] The combination of DBU isooctanoate and DBU formate achieves a synergistic catalytic effect, significantly promoting the thermal polymerization reaction at lower concentrations, particularly suppressing side reactions during polymerization and improving the conversion rate. Preferably, the thermally latent catalyst composition contains 20 wt%-40 wt% DBU isooctanoate and 60 wt%-80 wt% DBU formate.

[0017] In one or more embodiments, the electrolyte precursor solution is subjected to heat treatment, specifically to induce the thermally latent catalyst composition in the electrolyte precursor solution to dissociate upon heating, releasing the strong base DBU to initiate in-situ polymerization, thereby obtaining a polymer solid electrolyte. The heat treatment temperature is 80-90°C, and the heat treatment time is 12-20 hours.

[0018] The thiol monomers mentioned herein are polythiol monomers. The term "polythiol monomer" as used in this invention should be understood as a compound containing at least two thiohydrogen (thiol) groups, such as dithiols, trithiols, and tetrathiols. Preferred polythiol monomers include aliphatic polythiols such as trimethylolpropanetrios(3-mercaptopropionate), trimethylolethanetrios(3-mercaptopropionate), pentaerythritol tetra(2-mercaptoacetate), pentaerythritol tetra(3-mercaptopropionate), 2,2'-thiobis[3-[(2-mercaptoethyl)thio]-1-propanethiol, 2,3-dithio(2-mercapto)-1-propanethiol, (R)-propane-1,2-dithiol, and propane-1,2,3-trithiol. Preferably, the polythiol has a viscosity of 1 Pa·s or less at 25°C.

[0019] It should be noted that, without affecting the technical effects described in this invention, the polymerizable monomer further includes at least one of vinyl monomers, allyl monomers (such as allylamine), and cyclic ether monomers (such as ethylene oxide, allyl glycidyl ether, etc.). Examples of vinyl monomers include acrylate monomers (such as methyl methacrylate, ethyl acrylate, butyl acrylate, ethylene glycol diacrylate, ethylene glycol dicyclopentenyl ether acrylate, ethylene glycol dicyclopentenyl ether methacrylate, etc.), acrylic acid, methacrylic acid, styrene, triethylene glycol divinyl ether, cyclopentene, dimercyclopentene, acrylonitrile, etc.

[0020] The crosslinking agent is selected from at least one of ethylene glycol diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, ethoxy pentaerythritol tetraacrylate, divinylbenzene, tetraethoxysilane, triallyl isocyanurate, and ammonium persulfate.

[0021] The alkali metal salt refers to an ionic compound formed by the combination of an alkali metal cation and anion through ionic bonds. The alkali metal cation is selected from at least one of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The anion is selected from inorganic anions and / or organic anions, and the inorganic anion may include, but is not limited to, hexafluorophosphate (PF6). - ), perchlorate (ClO4) - ), difluorophosphate (PO2F2) - ), tetrafluoroborate (BF4) - ), hexafluoroarsenate (AsF6) - ), aluminochloride (AlCl4) - The organic anions include, but are not limited to, trifluoromethanesulfonate (CF3SO3). - ), dioxalate borate (BOB) - ), bis(fluorosulfonyl)imide (FSI) - ), bis(trifluoromethanesulfonyl)imide (TFSI) - ).

[0022] The organic solvent is selected from cyclic carbonates (such as ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, ethylene ethylene carbonate, propylene carbonate, butene carbonate, etc.), chain carbonates (such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, etc.), carboxylic acid esters (such as methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, etc.), and lactones (such as γ- The following are listed as at least one of the following: valerol lactone, ethers (such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, polyethylene glycol, triethylene glycol dimethyl ether, fluorinated 1,4-dimethoxybutane, bis(2,2,2-trifluoroethyl) ether, tetraethylene glycol dimethyl ether, etc.), sulfones (such as sulfolane, cyclopentyl sulfone, dimethyl sulfone, ethylmethyl sulfone, diethyl sulfone, etc.), and silanes (such as tetramethylsilane, tetraethoxysilane, etc.).

[0023] It should be noted that, without affecting the technical effects described in this invention, the electrolyte precursor solution may also include functional additives, such as vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate, vinyl ethylene carbonate, vinyl sulfate, vinyl disulfate, methyl vinyl sulfate, propylene sulfate, vinyl sulfite, succinic anhydride, maleic anhydride, citrate anhydride, succinic nitrile, adiponitrile, glutaronitrile, hexanetrionitrile, tetravinylsilane, biphenyl, cyclohexylbenzene, fluorobenzene, p-fluorotoluene, p-fluoroanisole, tert-butylbenzene, and tert-amylbenzene. The additives include propylene sulfonate lactone, butane sulfonate lactone, methane disulfonate methylene ester, ethylene glycol bis(propionitrile) ether, glycerol trinitrile, glycerol tri(propionitrile) ether, hexamethyldisilazane (HMDS), heptamethyldisilazane, dicyclohexylcarbodiimide, diisopropylcarbodiimide, 2,6-di-tert-butyl-4-methylphenol, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphate, triphenyl phosphate, triphenyl phosphite, tri(trimethylsilyl)borate, tri(trimethylsilyl) phosphate, tri(trimethylsilyl) phosphite, tri(hexafluoroisopropyl) phosphate, (2,2-difluoroethyl) acetate, hexafluorocyclotriphosphazene, pentafluoroethoxycyclotriphosphazene, pentafluorophenoxycyclotriphosphazene, etc. Preferably, the amount of the functional additive added is 0.1wt%-4wt% of the total mass of the electrolyte precursor solution.

[0024] The present invention provides a method for preparing a polymer solid electrolyte by first mixing a polymerizable monomer, an alkali metal salt, a crosslinking agent, a thermally latent catalyst composition, and an organic solvent to prepare an electrolyte precursor solution, and then subjecting the electrolyte precursor solution to heat treatment. Upon heating, the thermally latent catalyst composition dissociates and releases the active base DBU, promoting in-situ thermal polymerization of the electrolyte precursor solution to form a polymer solid electrolyte. More specifically: (1) The thermally latent catalyst composition dissociates upon heating to release the active base DBU (pKa is about 13.5); (2) The strong basicity and weak nucleophilicity of DBU enable it to effectively abstract protons from thiols (RSH) to generate highly reactive thiolate anions (RS⁻) and protonated DBU. + ([DBU-H]) + RS⁻ is a nucleophile that attacks the β-carbon (electron-deficient carbon in the C=C double bond) of α,β-unsaturated carbonyl compounds (electrophiles), resulting in Michael addition (i.e., 1,4-conjugative addition) to form a new, stable carbon-sulfur bond (CS bond), extending the polymer chain. The protonated DBU⁺ regains protons from the reaction system or solvent, reverting to DBU, continuing the catalytic cycle, initiating a polymerization chain reaction, forming a three-dimensional network, and yielding a polymer solid electrolyte. (3) DBU will not react with electrophilic reagents, thus ensuring selectivity.

[0025] The method for preparing polymer solid electrolytes using a thermally latent catalyst composition provided by this invention has at least the following beneficial effects: By abandoning traditional thermal initiators that generate free radicals upon heating and instead using a thermally latent catalyst composition, the chain reaction rate was significantly suppressed within the temperature range from room temperature to the initiation temperature, and the thermal stability of the electrolyte precursor solution during storage and transportation was significantly improved. Furthermore, it was unexpectedly discovered that polymer solid electrolytes prepared by using a thermally latent catalyst composition instead of thermally radical-generating initiators can simultaneously achieve: (1) Improve the oxidation stability of polymer solid electrolytes, broaden the electrochemical window of electrolytes so that they can be matched with high-voltage cathode materials and improve battery safety; (2) It suppresses dendrite growth and gas generation, and can form good interfacial contact, improve the interfacial stability of polymer solid electrolyte and electrode, and enhance battery cycle stability. (3) Improve the ionic conductivity of polymer solid electrolyte, form a good ion transport channel, and improve the electrochemical performance of the battery.

[0026] On the other hand, the present invention also provides a solid-state battery, including a polymer solid-state electrolyte prepared by a method for preparing a polymer solid-state electrolyte using a thermally latent catalyst composition.

[0027] In one or more embodiments, the solid-state battery is a lithium-ion solid-state battery or a sodium-ion solid-state battery.

[0028] The following description is based on specific embodiments. Detailed Implementation

[0029] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] It should be noted that, unless otherwise specified, the components used in the embodiments and comparative examples of this invention are all commercially available products.

[0031] [DBU-formate] The preparation method of DBU-formate used in the embodiments and comparative examples of the present invention includes the following steps: Step 1, Solution preparation: Add 7.67 g DBU (0.05 mol) and 100 mL methanol to a two-necked flask, and stir until the DBU is fully dissolved; Step 2, neutralization reaction: Acid-base neutralization is an exothermic reaction. The double-necked flask needs to be placed in an ice-water bath (0-5 ℃). While stirring, add 1.90 mL (0.05 mol) of formic acid dropwise over 30 min. After the addition is complete, remove the double-necked flask from the ice-water bath and stir at room temperature for 12 h. Step 3, Evaporate the solvent: Transfer the solution in the double-necked flask to a rotary evaporator, set the water bath temperature to 45℃, the vacuum degree to 200 mbar, and the rotation speed to 100 rpm to remove the methanol solvent; Step 4, Vacuum drying: Transfer the solution from the rotary evaporator to a vacuum drying oven and heat at 50 °C for 12 h to obtain approximately 10 g of DBU-formate. [DBU-Isooctanoate] The preparation method of DBU-isooctanoate used in the embodiments and comparative examples of this invention includes the following steps: Step 1, Solution preparation: Add 5.13 g DBU (0.03 mol) and 100 mL methanol to a double-necked flask, and stir until the DBU is fully dissolved.

[0032] Step 2, neutralization reaction: Acid-base neutralization is an exothermic reaction, so the double-necked flask needs to be placed in an ice-water bath (0-5 ℃). While stirring, add 4.86 g of isooctanoic acid (0.03 mol) dropwise in small amounts over 30 min. After the addition is complete, remove the double-necked flask from the ice-water bath and stir at room temperature for 12 h.

[0033] Step 3, Evaporate the solvent: Transfer the solution in the double-necked flask to a rotary evaporator, set the water bath temperature to 45℃, the vacuum degree to 200 mbar, and the rotation speed to 100 rpm to remove the methanol solvent.

[0034] Step 4, vacuum drying: Transfer the solution from the rotary evaporator to a vacuum drying oven and heat at 50 °C for 12 h to obtain approximately 10 g of DBU-isooctanoate.

[0035] [Examples 1-4] Examples 1-4 each provide an electrolyte precursor solution.

[0036] The electrolyte precursor solution provided in Example 1 was prepared as follows: lithium hexafluorophosphate, ethylene carbonate, dimethyl carbonate, polyethylene glycol diacrylate, and pentaerythritol tetra-3-mercaptopropionate were mixed in a molar ratio of 0.5:5:5:2:0.8 to form a homogeneous 10g mixture; a thermally latent catalyst composition was added to the mixture and mixed evenly to obtain the electrolyte precursor solution. The amount of thermally latent catalyst composition added was 0.05wt% of the mass of the mixture. The thermally latent catalyst composition consisted of 20wt% DBU isooctanoate and 80wt% DBU formate.

[0037] The electrolyte precursor solution provided in Example 2 is prepared as follows: lithium hexafluorophosphate, ethylene carbonate, dimethyl carbonate, pentaerythritol tetraacrylate, and pentaerythritol tetra-3-mercaptopropionate are mixed in a molar ratio of 2:7.5:7.5:4:2.5 to form a homogeneous 10g mixture; a thermally latent catalyst composition is added to the mixture and mixed evenly to obtain the electrolyte precursor solution. The amount of thermally latent catalyst composition added is 0.2wt% of the mass of the mixture. The thermally latent catalyst composition consists of 40wt% DBU isooctanoate and 60wt% DBU formate.

[0038] The electrolyte precursor solution provided in Example 3 was prepared as follows: Lithium bis(trifluoromethanesulfonyl)imide, ethylene carbonate, dimethyl carbonate, polyethylene glycol diacrylate, and pentaerythritol tetra-3-mercaptopropionate were mixed in a molar ratio of 1:5.7:5.6:2.6:1.3 to form a homogeneous 10g mixture; a thermally latent catalyst composition was added to the mixture and mixed thoroughly to obtain the electrolyte precursor solution. The amount of thermally latent catalyst composition added was 0.15 wt% of the mass of the mixture. The thermally latent catalyst composition consisted of 30 wt% DBU isooctanoate and 70 wt% DBU formate.

[0039] The electrolyte precursor solution provided in Example 4 was prepared as follows: Lithium hexafluorophosphate, ethylene carbonate, dimethyl carbonate, polyethylene glycol diacrylate, and dipentaerythritol hexa(3-mercaptopropionic acid) ester were mixed in a molar ratio of 1:6.17:6.03:2.41:0.81 to form a homogeneous 10g mixture; a thermally latent catalyst composition was added to the mixture and mixed thoroughly to obtain the electrolyte precursor solution. The amount of thermally latent catalyst composition added was 0.1 wt% of the mass of the mixture. The thermally latent catalyst composition consisted of 35 wt% DBU isooctanoate and 65 wt% DBU formate.

[0040] [Comparative Examples 1-8] Comparative Examples 1-8 each provide an electrolyte precursor solution.

[0041] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 1 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 1, DBU isooctanoate was added to the mixture and mixed evenly to obtain the electrolyte precursor solution, and the amount of DBU isooctanoate added was 0.1 wt% of the mass of the mixture.

[0042] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 2 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 2, DBU formate is added to the mixture and mixed evenly to obtain the electrolyte precursor solution, and the amount of DBU formate added is 0.1 wt% of the mass of the mixture.

[0043] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 3 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 3, the thermally latent catalyst composition consists of 35 wt% DBU isooctanoate and 65 wt% DBU benzoate.

[0044] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 4 and the preparation method of the electrolyte precursor solution provided in Example 4 is that the thermally latent catalyst composition in Comparative Example 4 consists of 35 wt% DBU phthalate and 65 wt% DBU formate.

[0045] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 5 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 5, the thermally latent catalyst composition consists of 35 wt% DBU tartrate and 65 wt% DBU malonate.

[0046] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 6 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 6, triazine dione-DBU is added to the mixture and mixed evenly to obtain the electrolyte precursor solution. The amount of triazine dione-DBU added is 0.1 wt% of the mass of the mixture. Triazine dione-DBU is a latent catalyst obtained by the reaction of aryl isocyanate and DBU, which can reversibly regenerate the active form of the catalyst, namely DBU, upon heating.

[0047] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 7 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 7, azobisisobutyronitrile (AIBN) is added to the mixture and mixed evenly to obtain the electrolyte precursor solution, and the amount of AIBN added is 0.1 wt% of the mass of the mixture.

[0048] The only difference between the preparation method of the electrolyte precursor solution provided in Comparative Example 8 and the preparation method of the electrolyte precursor solution provided in Example 4 is that in Comparative Example 8, benzoyl peroxide is added to the mixture and mixed evenly to obtain the electrolyte precursor solution, and the amount of benzoyl peroxide added is 0.1 wt% of the mass of the mixture.

[0049] [Conversion Rate Test] The conversion rates of the electrolyte precursor solutions provided in Examples 1-4 and Comparative Examples 1-8 were tested respectively. The test procedures are as follows: Step 1: Take 20 mg of electrolyte precursor solution as the "initial sample", place the initial sample in an NMR sample tube, add about 0.5-0.7 mL of deuterated solvent, and then use nuclear magnetic resonance hydrogen spectroscopy to collect ¹H NMR spectrum to obtain the integrated area I0 of the characteristic peak before the reaction. Step 2: Take 20 mg of electrolyte precursor solution and place it in a reaction vessel. Place the reaction vessel in an oven and carry out a thermal polymerization reaction for 12 h under a nitrogen atmosphere (oxygen content <0.01 ppm, water content <0.01 ppm) and at a preset reaction temperature T to obtain the corresponding product. Step 2: After the thermal polymerization reaction is completed, the product is dissolved in a deuterated solvent (CDCl3) to obtain a mixture. The deuterated solvent can dissolve the residual monomers but not the cross-linked polymer network. Step 3: Place the mixture in a high-speed centrifuge and centrifuge at a speed of 10,000 rpm or higher for 10-20 minutes to precipitate the undissolved solid polymer. Take the supernatant (containing residual monomers) and then filter it through a 0.22 μm filter membrane to obtain a clear test solution. Step four: Transfer the test solution to an NMR sample tube, and then acquire a ¹H NMR spectrum using ¹H NMR spectroscopy to obtain the integrated area I of the characteristic peaks after the reaction. t The conversion rate is calculated using the following formula: Conversion Rate = (1 - I) t / I0)× 100%.

[0050] The conversion rates at different reaction temperatures T were tested, and the results are shown in Table 1 below.

[0051] Table 1

[0052] Based on the results in Table 1, we can conclude that: (1) Compared with Comparative Examples 7-8, the electrolyte precursor solutions provided in Examples 1-4, due to the addition of a combination of DBU isooctanoate and DBU formate, do not undergo significant solidification at temperatures below the predetermined initiation polymerization temperature (i.e. 80°C), and have excellent storage stability. (2) Compared with Comparative Examples 1-6, the combination of DBU isooctanoate and DBU formate in the electrolyte precursor solution provided in Examples 1-4 can achieve a synergistic catalytic effect. When the predetermined initiation polymerization temperature is reached, the "dissociation efficiency" and "catalytic activity" can be significantly improved, and the conversion rate of the polymerization reaction can be significantly increased.

[0053] [Examples 5-8] Examples 5-8 all provide a method for preparing a polymer solid electrolyte, comprising the following steps: Step 1: Mix and grind lithium iron phosphate powder, polyvinylidene fluoride, and conductive carbon black (super P) in a mass ratio of 8:1:1. Add N-methylpyrrolidone to make a positive electrode slurry. Coat the positive electrode slurry onto the surface of a carbon-coated aluminum foil substrate. After drying in a drying oven, a positive electrode active material layer is formed on the surface of the carbon-coated aluminum foil substrate. Cut the material into sheets with a length × width of 100mm × 80mm by a stamping machine. Step 2: Select a lithium metal sheet with a thickness of 400μm, slice it to prepare a lithium metal sheet with a length × width of 100mm × 80mm as the negative electrode sheet; Step 3: In a glove box filled with nitrogen (oxygen content <0.01ppm, water content <0.01ppm), a multi-layer stacked structure of "base film-negative electrode-base film-positive electrode-base film" is prepared by stacking the positive electrode sheet, high porosity PE base film and negative electrode sheet. The stacked multi-layer structure is then transferred into a punched aluminum-plastic film packaging bag. The top sealing equipment is used to heat seal the three sides of the aluminum-plastic film except for the liquid injection port to make a soft-pack battery cell with a pre-reserved liquid injection port. Step 4: Inject the electrolyte precursor solution into the pouch cell and let it stand for 48 hours to allow the electrolyte precursor solution to fully wet the cell. Step 5: After thorough impregnation, the battery cell is transferred into an oven and heated for polymerization under a nitrogen atmosphere (oxygen content <0.01ppm, water content <0.01ppm) to obtain a polymer solid electrolyte. Step six: Finally, a solid-state battery containing the polymer solid electrolyte is obtained through encapsulation.

[0054] The difference is: Example 5 uses the electrolyte precursor solution provided in Example 1 to prepare a polymer solid electrolyte. The process parameters for heating polymerization are: reaction at 85°C for 12 hours.

[0055] Example 6 uses the electrolyte precursor solution provided in Example 2 to prepare a polymer solid electrolyte. The process parameters for heating polymerization are: reaction at 80°C for 20 h.

[0056] Example 7 uses the electrolyte precursor solution provided in Example 3 to prepare a polymer solid electrolyte. The process parameters for heating polymerization are: reaction at 90°C for 12 hours.

[0057] Example 8 uses the electrolyte precursor solution provided in Example 4 to prepare a polymer solid electrolyte. The process parameters for heating polymerization are: reaction at 90°C for 20 h.

[0058] After the solid-state batteries provided in Examples 5-8 were formed and activated (at a temperature of 45°C, a uniform external pressure of 5 MPa was applied to the solid-state batteries, and three cycles of charge-discharge at a rate of 0.01C were performed at 2.0-4.0V), long-term charge-discharge tests were conducted at 25°C at a rate of 1C to test the cycle performance of the solid-state batteries. The test results showed that after 300 charge-discharge cycles, the capacity retention rate of the solid-state batteries provided in Examples 5-8 was not less than 88.5%, and the obtained solid-state batteries all had excellent cycle stability performance.

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing polymer solid electrolytes using a thermally latent catalyst composition, characterized in that, The method includes forming the polymer solid electrolyte from an electrolyte precursor solution by in-situ thermal polymerization; the electrolyte precursor solution comprises polymerizable monomers, alkali metal salts, crosslinking agents, thermally latent catalyst compositions, and organic solvents. The polymerizable monomers include thiol monomers, and the thermally latent catalyst composition includes DBU isooctanoate and DBU formate; The electrolyte precursor solution does not contain thermal initiators that generate free radicals upon heating.

2. The method according to claim 1, characterized in that, The method includes the following steps: Step 1: Mix the components including polymerizable monomers, alkali metal salts, crosslinking agents, thermally latent catalyst compositions, and organic solvents to prepare the electrolyte precursor solution; Step 2: Assemble a battery cell using a positive electrode, a separator, and a negative electrode. During or after the battery cell assembly process, inject the electrolyte precursor solution into the battery cell. The injection process is carried out under an ambient moisture content of <20 ppm and a nitrogen atmosphere. Step 3: After the electrolyte precursor solution has fully wetted the positive and negative electrode plates, the battery cell is placed in an oven and heat-treated under nitrogen atmosphere. The electrolyte precursor solution is then thermally polymerized in situ to form the polymer solid electrolyte.

3. The method according to claim 1, characterized in that, The preparation method of the electrolyte precursor solution includes the following steps: Step 1: Mix the following components in molar amounts to obtain a mixture: 0.5-2 molar amounts of alkali metal salt, 10-15 molar amounts of organic solvent, 2-4 molar amounts of crosslinking agent, and 0.8-2.5 molar amounts of polymerizable monomer; Step 2: Add the thermally latent catalyst composition to the mixture and mix evenly to obtain an electrolyte precursor solution. The amount of thermally latent catalyst composition added is 0.05wt%-0.2wt% of the mass of the mixture.

4. The method according to claim 1, characterized in that, The thiol monomers are polythiol monomers.

5. The method according to claim 1, characterized in that, The crosslinking agent is selected from at least one of ethylene glycol diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, ethoxy pentaerythritol tetraacrylate, divinylbenzene, tetraethoxysilane, triallyl isocyanurate, and ammonium persulfate.

6. The method according to claim 1, characterized in that, The organic solvent is selected from at least one of cyclic carbonates, chain carbonates, carboxylic esters, lactones, ethers, sulfones, silane-based silanes, etc.

7. The method according to claim 1, characterized in that, In the thermally latent catalyst composition, the content of DBU isooctanoate is 20wt%-40wt%, and the content of DBU formate is 60wt%-80wt%.

8. The method according to claim 1, characterized in that, The in-situ thermal polymerization satisfies the following conditions: the heat treatment temperature is 80-90℃, and the heat treatment time is 12-20h.

9. A solid-state battery, characterized in that, This includes polymer solid electrolytes prepared using the method described in any one of claims 1-8.

10. The solid-state battery according to claim 1, characterized in that, The solid-state battery is a lithium-ion solid-state battery or a sodium-ion solid-state battery.

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