Solid-state polymer electrolyte based on block copolymer, method of preparation and use

Abstract

The present application relates to a kind of solid-state polymer electrolyte based on block copolymer, preparation method and application, solid-state polymer electrolyte includes: block copolymer, metal salt and porous base film;The mixture of block copolymer and metal salt is distributed in the pore of porous base film and on surface;The molecular weight of block copolymer is 200g / mol-2000000g / mol;The solid-state polymer electrolyte based on block copolymer provided by the embodiment of the present application has the advantages of high ionic conductivity, wide electrochemical window, good chemical stability and the like, and has good compatibility with base film.The solid-state polymer electrolyte based on block copolymer provided by the present application can not only match commonly used positive electrode material with narrow voltage range, but also can match high-voltage positive electrode material and metal negative electrode, and can effectively improve the cycle stability of battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a solid polymer electrolyte based on block copolymers, its preparation method, and its application. Background Technology

[0002] The commercialization of lithium-ion batteries has brought great convenience to our production and daily lives. However, safety issues related to the use of electrolytes and limitations in energy density remain unresolved. All-solid-state batteries (ASSBs), due to their high energy density and good safety, have become an important component of all-solid-state batteries.

[0003] Currently, commonly used solid electrolyte membranes can be broadly classified into three categories: inorganic solid electrolytes, polymer solid electrolytes, and hybrid solid electrolytes. Among them, inorganic solid electrolytes suffer from poor flexibility, making it difficult to achieve good interfacial compatibility. Furthermore, their high cost and low energy density limit their large-scale development. Of the polymer solid electrolytes, all-solid-state polymer electrolytes based on polyethylene oxide are the most widely studied, but their application is constrained by low room-temperature ionic conductivity and a narrow electrochemical window. Moreover, the large-scale application of new materials is hampered by cumbersome chemical synthesis steps. Hybrid solid electrolytes theoretically combine the advantages of the two types of electrolytes mentioned above, but they suffer from problems such as uneven dispersion of inorganic particles and difficulty in achieving ultra-thin designs to improve battery energy density.

[0004] Therefore, developing a novel polymer electrolyte material that can achieve high room temperature ionic conductivity and a wide electrochemical window, and is easy to prepare into an ultrathin electrolyte membrane, is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a solid polymer electrolyte based on block copolymers, its preparation method, and its application. A block copolymer of a specific molecular weight is obtained through ring-opening polymerization, and then combined with a porous matrix membrane to prepare a polymer solid electrolyte.

[0006] The block copolymer-based solid polymer electrolyte provided by this invention exhibits high ionic conductivity, enabling room temperature cycling of the battery. Furthermore, this block copolymer-based solid polymer electrolyte has a wide electrochemical window, allowing it to be matched with high-voltage cathode materials and metal anodes. Coin cells and pouch cells assembled using this material demonstrate excellent cycle stability.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a solid polymer electrolyte based on a block copolymer, the solid polymer electrolyte comprising: a block copolymer, a metal salt, and a porous base membrane.

[0008] The porous base membrane contains a mixture of the block copolymer and the metal salt distributed in its pores and on its surface.

[0009] The molecular weight of the block copolymer is 200 g / mol to 2,000,000 g / mol.

[0010] Preferably, the block copolymer is formed by ring-opening polymerization of organic monomers initiated by an initiator and / or catalyst.

[0011] The organic monomers include one or more of the following: conjugated diene organic compounds, non-conjugated diene organic compounds, cyclic monoesters, cyclic diesters, and subsequently functionalized cyclic esters.

[0012] The initiator includes one or more of the following: polyethylene glycol monomethyl ether, butyllithium, alkyllithium, alkylpotassium, diethylzinc, triethylaluminum, Green's reagent, aluminum isopropoxide, sodium alkoxide, potassium alkoxide, dimethoxydibutyltin, methoxytributyltin, ethoxydiethylaluminum, lithium tert-butoxide, and p-toluenesulfonic acid.

[0013] The catalyst includes one or more of the following: stannous octoate, aluminum triacetylacetonate, zinc oxide, metalloporphyrin, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), enzyme catalyst, and nickel catalyst.

[0014] More preferably, the organic monomer specifically includes one or more of the following: L-lactide, meso-lactide, glycolide, D-lactide, α-chloro-α-methyl-β-propiolactone, 3-methyl-5-isopropylpentanolactone, 1,4-dioxane-2-one, 3,3-dimethyloxetane-2-one, β-propiolactone, γ-butanolactone, δ-pentanolactone, ε-caprolactone, β-butanolactone, and δ-decanolactone.

[0015] Preferably, the metal salt comprises a sodium salt or a lithium salt; the mass of the metal salt accounts for 5% to 100% of the mass of the block copolymer.

[0016] The porous base membrane is made of one or more of the following materials: polyethylene (PE), polypropylene (PP), polyimide (PI), polyvinylidene fluoride (PVDF), cellulose, glass fiber, meta-aramid (PMIA), polyacrylonitrile (PAN), and polyethylene terephthalate (PET); the porosity of the porous base membrane is 10% to 70%; and the thickness of the porous base membrane is 5 μm to 100 μm.

[0017] The thickness of the solid polymer electrolyte is 5 μm to 150 μm.

[0018] More preferably, the sodium metal salt includes one or more of the following: sodium difluorooxalate borate, sodium bis(oxalate borate), sodium dioxo-borate, sodium difluorophosphate, sodium difluorosulfonamide, sodium bis(trifluoromethanesulfonamide), sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, and sodium perchlorate.

[0019] The lithium metal salt includes one or more of the following: lithium difluorooxalate borate, lithium dioxalate borate, lithium dioxalate borate, lithium dioxoacetic acid borate, lithium difluorophosphate, lithium difluorosulfonylimide, lithium bis(trifluoromethanesulfonylimide), lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium perchlorate.

[0020] Preferably, the solid polymer electrolyte further includes other compounds; the mass ratio of the other compounds to the block copolymer is 0% to 60%.

[0021] The other compounds are inorganic substances other than the metal salt.

[0022] Preferably, the inorganic material includes one or more of the following: aluminum oxide (Al2O3), silicon oxide (SiO2), NASICON solid electrolyte, LLZO solid electrolyte, and LLZTO solid electrolyte.

[0023] In a second aspect, the present invention provides a method for preparing the solid polymer electrolyte based on block copolymers as described in the first aspect, the method comprising:

[0024] Block copolymers were prepared by ring-opening polymerization.

[0025] The block copolymer is mixed with a metal salt, or with a metal salt and other compounds, in a solvent to obtain a polymer electrolyte mixed solution.

[0026] The polymer electrolyte mixture is cast onto a porous base membrane, allowing the polymer electrolyte mixture to wet and fill the pores of the porous base membrane and cover its surface, thus obtaining a composite membrane precursor.

[0027] The composite membrane precursor is subjected to hot pressing and then dried to remove the solvent, resulting in a solid polymer electrolyte based on block copolymer.

[0028] Preferably, the preparation of block copolymers via ring-opening polymerization specifically includes...

[0029] Organic monomers are added to a reaction flask, and after being evacuated to an anhydrous and oxygen-free state, the mixture is diluted with the first solvent. Then, it is placed in an oil bath at 60℃~150℃ and stirred until homogeneous to obtain the first mixture.

[0030] In another reaction flask, an initiator and / or catalyst are added, and the mixture is evacuated to an anhydrous and oxygen-free state. Then, a second solvent is added to dilute the mixture, and the mixture is placed in an oil bath at 30°C to 100°C and stirred until homogeneous to obtain a second mixture.

[0031] Take an appropriate amount of the second mixture and add it to the first mixture. Place the reaction flask containing the two mixtures in an oil bath at 60°C to 150°C and react for 1 hour to 36 hours to allow the organic monomers to undergo ring-opening polymerization to obtain a liquid polymer.

[0032] A terminator is added to the polymerized liquid after the reaction to terminate the reaction.

[0033] The polymeric reaction product liquid was purified to obtain a polymer precursor.

[0034] The polymer precursor was dried in a freeze dryer to remove residual solvent, resulting in a block copolymer.

[0035] The first solvent includes one or more of the following: deionized water, dichloromethane, methanol, ethanol, acetonitrile, acetone, cyclohexanone, diethyl ether, petroleum ether, N,N-dimethylformamide, N-methylpyrrolidone, toluenecyclohexanone, dimethyl sulfoxide, chloroform, tetrahydrofuran, benzene, toluene, xylene, cyclohexane, n-hexane, n-heptane, 1,4-dioxane, chlorobenzene, dichlorobenzene, phenol, pyridine, hexafluoroisopropanol, and ethyl acetate.

[0036] The second solvent includes one or more of the following: methanol, toluene, methyl methacrylate, ethanol, acetonitrile, ethylene glycol dimethacrylate, ethylene glycol phenyl ether acrylate, bisphenol A methacrylate diester, n-heptane, n-hexane, 1,3-dioxolane, dimethyl sulfoxide, dichloromethane, bis(trimethylolpropane)acrylate, chloroform, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetrahydrofuran, hexafluoroisopropanol, vinylene carbonate, methyl ethyl carbonate, ethyl acetate, ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethyl ether, (di, tri, tetra)ethylene glycol dimethyl ether, acetone, cyclohexane, 1,3-butanediol diacrylate, pentaerythritol tetraacrylate, γ-valerolactone, γ-butyrolactone, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethylene carbonate, and deionized water.

[0037] The terminating agents include: water, methanol, ethanol, isopropanol, C1-C6 alcohols, phenol and its derivatives, C4-C6 alcohols. 12One or more of the following: fatty acids, benzoic acid, tall oil fatty acids, trimethylchlorosilane, chlorosilane derivatives, hexamethyldisiloxane, vinyl ethyl ether, vinyl methacrylate, various aldehydes, non-protected thiols, glycerol, pentaerythritol, polyethylene polyamines, and carboxylates.

[0038] The purification process includes one or more of the following methods: filtration, recrystallization, column chromatography, dialysis, extraction, distillation, fractionation and sedimentation, dissolution and precipitation, salting out, gas washing, evaporation, and chromatography.

[0039] Preferably, the hot pressing process specifically includes: clamping the composite film precursor in a mold, then placing the entire mold on a tablet press, heating and holding the temperature for 1 to 5 minutes, then applying pressure, cooling to room temperature, removing the mold, taking it out, and drying it in an oven to obtain the solid polymer electrolyte based on the block copolymer.

[0040] The temperature at which the temperature is increased is lower than the decomposition temperature of the block copolymer.

[0041] The pressurized pressure is 1000 kg / cm². 2 -3000kg / cm 2 .

[0042] Thirdly, the present invention provides a secondary battery comprising the solid polymer electrolyte based on block copolymers as described in the first aspect.

[0043] The present invention provides a solid polymer electrolyte based on block copolymers, its preparation method and application, which have the following technical effects.

[0044] (1) The present invention provides a method for preparing a solid polymer electrolyte based on block copolymers. First, a block copolymer with controllable molecular weight (molecular weight range of 200 g / mol to 2000000 g / mol) is synthesized by ring-opening polymerization. Then, it is mixed with a metal salt to form a mixed solution, which is cast into a porous base membrane. After hot pressing and drying, a solid polymer electrolyte is obtained.

[0045] This preparation method is a non-in-situ preparation method. By controlling the molecular weight of the block copolymer to a low range, its mixture with the metal salt exhibits a low-viscosity liquid or flowable gel state at room temperature, which is beneficial for fully wetting the porous substrate membrane and achieving good interfacial contact between the solid electrolyte and the positive and negative electrodes after battery assembly.

[0046] Compared to existing in-situ polymerization methods, the non-in-situ preparation method of the present invention can pre-synthesize block copolymers with well-defined molecular weights and controllable distributions, avoiding problems such as uncontrollable molecular weights and increased side reactions caused by fluctuations in reaction conditions during in-situ polymerization, thereby improving the consistency of battery performance.

[0047] (2) When the solid polymer electrolyte based on block copolymers provided by this invention is applied to a secondary battery, due to the hydrogen bond interaction between the block copolymer molecules, they will spontaneously undergo anti-entropy aggregation, protecting the groups (-OH) that are not resistant to high voltage. This allows the solid polymer electrolyte to be matched with a high-voltage positive electrode, even though the block portion itself is not resistant to high voltage. The solid polymer electrolyte based on block copolymers provided by this invention has advantages such as high ionic conductivity, wide electrochemical window, and good chemical stability, and has good compatibility with the substrate membrane. The solid polymer electrolyte based on block copolymers can not only be matched with commonly used positive electrode materials with narrow voltage ranges, but also with high-voltage positive electrode materials and metal negative electrodes, which can effectively improve the cycle stability of the battery. Attached Figure Description

[0048] Figure 1 This is a flowchart of the preparation method of solid polymer electrolyte based on block copolymer provided in the embodiments of the present invention.

[0049] Figure 2 This is the 1H NMR spectrum of the block copolymer prepared in Example 1 of this invention.

[0050] Figure 3 This is a gel permeation chromatogram of the block copolymer prepared in Example 1 of the present invention.

[0051] Figure 4 This is the infrared spectrum of the block copolymer prepared in Example 1 of the present invention.

[0052] Figure 5 This is a scanning electron microscope (SEM) image of the block copolymer prepared in Example 1 of the present invention.

[0053] Figure 6 This is a scanning electron microscope (SEM) image of the solid polymer electrolyte prepared in Example 1 of this invention.

[0054] Figure 7 This is the X-ray diffraction (XRD) pattern of the solid polymer electrolyte and block copolymer prepared in Example 1 of this invention.

[0055] Figure 8 This is a graph showing the test results of the ionic conductivity of the solid polymer electrolyte prepared in Example 1 of this invention.

[0056] Figure 9 This is a test graph of the lithium-ion transference number of the solid polymer electrolyte prepared in Example 1 of the present invention.

[0057] Figure 10 This is a test graph of the redox potential of the solid polymer electrolyte prepared in Example 1 of the present invention.

[0058] Figure 11 This is a thermogravimetric analysis (TGA) chart of the solid polymer electrolyte prepared in Example 1 of this invention.

[0059] Figure 12 This is a charge-discharge curve of the battery prepared using LFP material in Embodiment 1 of the present invention.

[0060] Figure 13 This is a graph showing the capacity retention and coulombic efficiency of the battery prepared using LFP material in Example 1 of this invention.

[0061] Figure 14 This is a charge-discharge curve of the battery prepared using NCM622 material in Embodiment 1 of the present invention.

[0062] Figure 15 This is a graph showing the capacity retention and coulombic efficiency of the battery prepared using NCM622 material in Example 1 of this invention. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0064] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0065] To facilitate a better understanding of the present invention, some names or technical terms will be explained below.

[0066] The term "AEA-ASSPE-Li" is an abbreviation for the block copolymer-based solid polymer electrolyte prepared in Example 1 of this invention, referring to an anti-entropy aggregation all-solid-state polymer electrolyte for lithium metal batteries. This anti-entropy aggregation all-solid-state polymer electrolyte is composed of block copolymers, lithium metal salts, and a porous base membrane. The hydrogen bonding interactions between the block copolymer molecular chains drive their anti-entropy aggregation, effectively protecting high-voltage-sensitive groups (such as hydroxyl groups), thereby broadening the electrochemical window and achieving compatibility with high-voltage cathode materials.

[0067] The technical term "in-situ polymerization" refers to the polymerization of monomers in a polymer precursor inside and / or on the surface of an electrode using physical, chemical, or other methods to form a polymer electrolyte.

[0068] The technical term "hot pressing" includes, but is not limited to, molding and / or rolling at a certain temperature.

[0069] The technical term "all-solid-state battery" is defined in the group standard "All-solid-state battery judgment method" issued by the China Society of Automotive Engineers. It is a liquid content test method based on the weight loss rate. Specifically, the weight loss rate is tested by vacuum heating. When the sample is visually free of liquid and the weight loss rate is less than 1% after drying in a vacuum environment at 120°C for 6 hours, it is judged as an all-solid-state battery.

[0070] Next, based on the understanding of the above technical terms, the technical solution of the present invention will be further described in detail with reference to the accompanying drawings and embodiments.

[0071] This invention provides a solid polymer electrolyte based on block copolymers, comprising: block copolymers, metal salts, and porous base membranes.

[0072] The thickness of the solid polymer electrolyte based on block copolymers is 5 μm to 150 μm, and can be any value within this range, such as: 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 130 μm, 140 μm, 150 μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] The pores of the porous membrane are filled with a mixture of block copolymers and metal salts, and the surface of the porous membrane is also covered with a mixture of block copolymers and metal salts.

[0074] The molecular weight of the block copolymer is 200 g / mol to 2,000,000 g / mol, and can be any value within this range, such as: 200 g / mol, 350 g / mol, 500 g / mol, 2000 g / mol, 4000 g / mol, 6000 g / mol, 7000 g / mol, 8000 g / mol, 10000 g / mol, 20000 g / mol, 30000 g / mol, 40000 g / mol, 50000 g / mol, 100000 g / mol, 500000 g / mol, 1000000 g / mol, 2000000 g / mol, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. When the molecular weight is between 200 g / mol and 2000 g / mol, the block copolymer is in a liquid or waxy state and has insufficient mechanical strength. It needs to be combined with a porous base membrane to form a solid electrolyte membrane. The proportion of end groups that are not resistant to high voltage is relatively high, and intermolecular interactions are needed to broaden the electrochemical window. When the molecular weight is between 2000 g / mol and 2000000 g / mol, the polymer chain segments are severely entangled, and the chain segment mobility decreases, resulting in a significant decrease in room temperature ionic conductivity. At the same time, the viscosity increases after mixing with metal salts, making it difficult to fully wet the porous base membrane and electrode interface. Therefore, it is necessary to pre-dissolve the polymer in a solvent before wetting the base membrane, and then dry the solvent to obtain an all-solid polymer electrolyte membrane. The molecular weight of the block copolymer in this invention is controlled within the range of 200 g / mol to 2,000,000 g / mol. The mixture of the block copolymer and the metal salt presents a low-viscosity liquid, a flowable gel, or a solid state at room temperature. It is fully composited with the porous base membrane, resulting in a good electrode interface. At the same time, it obtains good mechanical strength with the support of the porous base membrane, thereby achieving a balance between high ionic conductivity, wide electrochemical window, and good processing performance.

[0075] Block copolymers are formed by ring-opening polymerization of organic monomers initiated by initiators and / or catalysts.

[0076] Initiators include one or more of the following: polyethylene glycol monomethyl ether, butyllithium, alkyllithium, alkylpotassium, diethylzinc, triethylaluminum, Green's reagent, aluminum isopropoxide, sodium alkoxide, potassium alkoxide, dimethoxydibutyltin, methoxytributyltin, ethoxydiethylaluminum, lithium tert-butoxide, and p-toluenesulfonic acid.

[0077] The catalysts include one or more of the following: stannous octoate, aluminum triacetylacetonate, zinc oxide, metalloporphyrin, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), enzyme catalysts, and nickel catalysts.

[0078] Organic monomers include one or more of the following: conjugated diene organic compounds, non-conjugated diene organic compounds, cyclic monoesters, cyclic diesters, and subsequently functionalized cyclic esters.

[0079] The organic monomers specifically include one or more of the following: L-lactide, meso-lactide, glycolide, D-lactide, α-chloro-α-methyl-β-propiolactone, 3-methyl-5-isopropylpentanolactone, 1,4-dioxane-2-one, 3,3-dimethyloxetane-2-one, β-propiolactone and its analogues, and δ-decanolactone; wherein β-propiolactone and its analogues include one or more of the following: β-propiolactone, γ-butanolactone, δ-pentanolactone, ε-caprolactone, and β-butanolactone; the structural formulas of these organic monomers are shown below: .

[0080] The metal salts include sodium metal salts or lithium metal salts; the mass of the metal salts accounts for 5% to 100% of the mass of the block copolymer. Specifically, the sodium metal salts include one or more of the following: sodium difluorooxalate borate, sodium bis(oxalate borate), sodium dioxoyl borate, sodium difluorophosphate, sodium difluorosulfonamide, sodium bis(trifluoromethanesulfonamide), sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, and sodium perchlorate; the lithium metal salts include one or more of the following: lithium difluorooxalate borate, lithium bis(oxalate borate), lithium bis(oxalate borate), lithium dioxoyl borate, lithium dioxoyl borate, lithium difluorophosphate, lithium difluorosulfonamide, lithium bis(trifluoromethanesulfonamide), lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium perchlorate.

[0081] The materials of porous base membranes include one or more of the following: polyethylene (PE), polypropylene (PP), polyimide (PI), polyvinylidene fluoride (PVDF), cellulose, glass fiber, meta-aramid (PMIA), polyacrylonitrile (PAN), and polyethylene terephthalate (PET).

[0082] The porosity of the porous base membrane is 10% to 70%, and can be any value within this range, such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] The thickness of the porous base film is 5μm to 100μm, and can be any value within this range, such as: 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] In optional embodiments, the solid polymer electrolyte also includes other compounds; the mass ratio of these other compounds to the block copolymer is 0%–60%. These other compounds are inorganic substances other than metal salts, specifically including one or more of the following: alumina (Al₂O₃), silicon oxide (SiO₂), NASICON solid electrolyte, lithium lanthanum zirconium oxide solid electrolyte (LLZO), and tantalum-doped lithium lanthanum zirconium oxide solid electrolyte (LLZTO). Preferably, the NASICON solid electrolyte is Na₃Zr₂Si₂PO₄. 12 LLZO is Li7La3Zr2O 12 LLZTO is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0085] This invention provides a method for preparing the above-mentioned block copolymer-based solid polymer electrolyte, such as... Figure 1 As shown, the specific steps include:

[0086] Step 110: Block copolymers are prepared by ring-opening polymerization.

[0087] Specifically, block copolymers are formed by ring-opening polymerization of organic monomers initiated by an initiator and / or catalyst, including the following steps.

[0088] Organic monomers are added to a reaction flask, and after being evacuated to an anhydrous and oxygen-free state, the mixture is diluted with the first solvent. Then, it is placed in an oil bath at 60℃~150℃ and stirred until homogeneous to obtain the first mixture.

[0089] In another reaction flask, an initiator and / or catalyst are added, and the mixture is evacuated to an anhydrous and oxygen-free state. Then, a second solvent is added to dilute the mixture, and the mixture is placed in an oil bath at 30°C to 100°C and stirred until homogeneous to obtain a second mixture.

[0090] Add an appropriate amount of the second mixture to the first mixture, place the reaction flask containing the two mixtures in an oil bath at 60℃~150℃, and react for 1 hour~36 hours to allow the organic monomers to undergo ring-opening polymerization to obtain the polymer liquid.

[0091] A terminator is added to the polymerized product liquid after the reaction to terminate the reaction; the terminator includes: water, methanol, ethanol, isopropanol, C1-C6 alcohols, phenol and its derivatives, C4-C6 alcohols, etc. 12 One or more of the following: fatty acids, benzoic acid, tall oil fatty acids, trimethylchlorosilane, chlorosilane derivatives, hexamethyldisiloxane, vinyl ethyl ether, vinyl methacrylate, various aldehydes, non-protected thiols, glycerol, pentaerythritol, polyethylene polyamines, and carboxylates.

[0092] The polymerization reaction product liquid is purified to obtain a polymer precursor; wherein the purification method includes one or more of the following methods: filtration, recrystallization, column chromatography, dialysis, extraction, distillation, fractionation sedimentation, dissolution precipitation, salting out, gas washing, evaporation, and chromatography.

[0093] The polymer precursor was dried in a freeze dryer to remove residual solvent, resulting in a block copolymer.

[0094] The initiators include one or more of the following: polyethylene glycol monomethyl ether, butyllithium, alkyllithium, alkylpotassium, diethylzinc, triethylaluminum, Green's reagent, aluminum isopropoxide, sodium alkoxide, potassium alkoxide, dimethoxydibutyltin, methoxytributyltin, ethoxydiethylaluminum, lithium tert-butoxide, and p-toluenesulfonic acid.

[0095] The catalysts include one or more of the following: stannous octoate, aluminum triacetylacetonate, zinc oxide, metalloporphyrin, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), enzyme catalysts, and nickel catalysts.

[0096] Organic monomers include one or more of the following: conjugated diene organic compounds, non-conjugated diene organic compounds, cyclic monoesters, cyclic diesters, and subsequently functionalized cyclic esters.

[0097] The organic monomers specifically include one or more of the following: L-lactide, meso-lactide, glycolide, D-lactide, α-chloro-α-methyl-β-propiolactone, 3-methyl-5-isopropylpentanolactone, 1,4-dioxane-2-one, 3,3-dimethyloxetane-2-one, β-propiolactone and its analogues, and δ-decanolactone; wherein, β-propiolactone and its analogues include one or more of the following: β-propiolactone, γ-butanolactone, δ-pentanolactone, ε-caprolactone, and β-butanolactone.

[0098] The first solvent includes one or more of the following: deionized water, dichloromethane, methanol, ethanol, acetonitrile, acetone, cyclohexanone, diethyl ether, petroleum ether, N,N-dimethylformamide, N-methylpyrrolidone, toluenecyclohexanone, dimethyl sulfoxide, chloroform, tetrahydrofuran, benzene, toluene, xylene, cyclohexane, n-hexane, n-heptane, 1,4-dioxane, chlorobenzene, dichlorobenzene, phenol, pyridine, hexafluoroisopropanol, and ethyl acetate.

[0099] The second solvent includes one or more of the following: methanol, toluene, methyl methacrylate, ethanol, acetonitrile, ethylene glycol dimethacrylate, ethylene glycol phenyl ether acrylate, bisphenol A methacrylate diester, n-heptane, n-hexane, 1,3-dioxolane, dimethyl sulfoxide, dichloromethane, bis(trimethylolpropane)acrylate, chloroform, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetrahydrofuran, hexafluoroisopropanol, vinylene carbonate, methyl ethyl carbonate, ethyl acetate, ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethyl ether, (di, tri, tetra)ethylene glycol dimethyl ether, acetone, cyclohexane, 1,3-butanediol diacrylate, pentaerythritol tetraacrylate, γ-valerolactone, γ-butyrolactone, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethylene carbonate, and deionized water.

[0100] The block copolymers prepared in this step have a molecular weight of 200 g / mol to 2,000,000 g / mol, and can be any value within this range, such as: 200 g / mol, 350 g / mol, 500 g / mol, 2000 g / mol, 4000 g / mol, 6000 g / mol, 7000 g / mol, 8000 g / mol, 10000 g / mol, 20000 g / mol, 30000 g / mol, 40000 g / mol, 50000 g / mol, 100000 g / mol, 500000 g / mol, 1000000 g / mol, 2000000 g / mol, etc., but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0101] In this invention, the molecular weight of the block copolymer is precisely controlled primarily by adjusting the molar ratio of initiator to monomer. In ring-opening polymerization, the number-average molecular weight is directly proportional to the monomer / initiator molar ratio and the monomer conversion rate. By designing suitable initiators and / or catalysts and their dosages, and strictly controlling the anhydrous and oxygen-free conditions of the reaction system to avoid chain transfer, the molecular weight of the block copolymer can be arbitrarily adjusted within the range of 200 g / mol to 2,000,000 g / mol. Reaction temperature and reaction time are indirect factors affecting the polymerization rate and conversion rate. The preferred reaction temperature in this invention is 60℃ to 150℃, and the reaction time is 1 hour to 36 hours. Under these conditions, the monomer can be fully converted, and side reactions are effectively suppressed, thereby achieving block copolymers with controllable molecular weight and narrow distribution. By controlling the molecular weight of the block copolymer, its mixture with metal salts can exhibit a low-viscosity liquid or flowable gel state at room temperature, which is beneficial for fully wetting the porous substrate and electrode interface, thereby improving the interfacial performance and cycle stability of the solid-state battery.

[0102] The block copolymers provided in this invention have hydrogen bond interactions between polar groups (such as hydroxyl groups -OH, carbonyl groups C=O, etc.) in their molecular chains, which promote the formation of specific aggregated structures in the polymer chains. Driven by hydrogen bonds, the block copolymer molecules undergo anti-entropic aggregation, that is, the molecular chains spontaneously arrange themselves in an ordered manner, protecting or shielding groups that are not resistant to high voltage (such as free hydroxyl groups) through the hydrogen bond network, thereby improving the electrochemical stability of the solid polymer electrolyte.

[0103] Step 120: The block copolymer is mixed with a metal salt, or with a metal salt and other compounds, in a solvent to obtain a polymer electrolyte mixed solution.

[0104] The metal salts include sodium or lithium salts; the metal salts constitute 5% to 100% of the mass of the block copolymer. Specifically, the sodium salts include one or more of the following: sodium difluorooxalate borate, sodium bis(oxalate borate), sodium dioxoyl borate, sodium difluorophosphate, sodium difluorosulfonamide, sodium bis(trifluoromethanesulfonamide), sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, and sodium perchlorate. The lithium salts include one or more of the following: lithium difluorooxalate borate, lithium bis(oxalate borate), lithium bis(oxalate borate), lithium dioxoyl borate, lithium dioxoyl borate, lithium difluorophosphate, lithium difluorosulfonamide, lithium bis(trifluoromethanesulfonamide), lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium perchlorate. The metal salts constitute 5% to 100% of the mass of the block copolymer.

[0105] In optional embodiments, the solid polymer electrolyte also includes other compounds; the mass ratio of these other compounds to the block copolymer is 0%–60%. These other compounds are inorganic substances other than metal salts, specifically including one or more of the following: alumina (Al₂O₃), silicon oxide (SiO₂), NASICON solid electrolyte, lithium lanthanum zirconium oxide solid electrolyte (LLZO), and tantalum-doped lithium lanthanum zirconium oxide solid electrolyte (LLZTO). Preferably, the NASICON solid electrolyte is Na₃Zr₂Si₂PO₄. 12 LLZO is Li7La3Zr2O 12 LLZTO is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The mass ratio of other compounds to block copolymers is 0% to 60%.

[0106] In this invention, the addition of other compounds can improve ionic conductivity by reducing crystallinity, construct multidimensional ion channels, enhance mechanical strength to suppress dendrites, and improve thermal stability and interfacial compatibility.

[0107] Step 130: The polymer electrolyte mixture is cast onto the porous base membrane, so that the polymer electrolyte mixture wets and fills the pores of the porous base membrane and covers the surface of the porous base membrane, thus obtaining the composite membrane precursor.

[0108] The porous base membrane is made of one or more of the following materials: polyethylene (PE), polypropylene (PP), polyimide (PI), polyvinylidene fluoride (PVDF), cellulose, glass fiber, meta-aramid (PMIA), polyacrylonitrile (PAN), and polyethylene terephthalate (PET).

[0109] The porosity of the porous base membrane is 10% to 70%, and can be any value within this range, such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0110] The thickness of the porous base film is 5μm to 100μm, and can be any value within this range, such as: 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0111] Step 140: The composite membrane precursor is subjected to hot pressing treatment, followed by drying to remove the solvent, to obtain a solid polymer electrolyte based on block copolymer.

[0112] The hot pressing process specifically includes: clamping the composite membrane precursor in a mold, then placing the entire mold on a tablet press, heating and holding it at that temperature for 1 to 5 minutes, then applying pressure, cooling to room temperature, removing the mold, and drying it in an oven to obtain a solid polymer electrolyte based on a block copolymer.

[0113] Specifically, the heating temperature is lower than the decomposition temperature of the block copolymer.

[0114] The drying temperature should be greater than or equal to the boiling point of the solvent, but lower than the decomposition temperature of the block copolymer and the metal salt.

[0115] The pressure applied is 1000 kg / cm². 2 ~3000kg / cm 2 It can be any value within this range, for example: 1000 kg / cm² 2 1500kg / cm 2 2000kg / cm 2 2500kg / cm 2 3000kg / cm 2 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0116] The solid polymer electrolyte based on block copolymers provided in this invention has advantages such as high ionic conductivity, wide electrochemical window, and good chemical stability, and has good compatibility with the substrate membrane.

[0117] The solid polymer electrolyte based on block copolymers provided in this invention does not contain any liquid plasticizers or free solvents. The mixture of block copolymers and lithium metal salts fills the pores and surface of the porous base membrane, forming a self-supporting solid electrolyte membrane with good mechanical strength.

[0118] The solid polymer electrolyte based on block copolymers provided in this invention can not only be matched with commonly used positive electrode materials with narrow voltage ranges, but also with high-voltage positive electrode materials and metal negative electrodes, which can effectively improve the cycle stability of the battery.

[0119] This invention provides a secondary battery, which is assembled from a positive electrode, the aforementioned block copolymer-based solid polymer electrolyte, and a negative electrode. This secondary battery is an all-solid-state battery, including but not limited to any one of all-solid-state lithium metal batteries and all-solid-state sodium metal batteries.

[0120] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the preparation process and characteristics of the solid polymer electrolyte based on block copolymers.

[0121] Example 1 This embodiment provides a preparation process for a solid polymer electrolyte based on block copolymers, as detailed below.

[0122] (1) Block copolymers were prepared by ring-opening polymerization, as follows.

[0123] Add 6 mmol of polyethylene glycol monomethyl ether (mPEG, molecular weight 2000 g / mol) and 135 mmol of L-lactide to a 500 ml three-necked flask. After pumping the solution three times to an anhydrous and oxygen-free state, add 300 ml of toluene to dilute it. Then place the flask in an oil bath at 100 °C and stir until the polyethylene glycol monomethyl ether and L-lactide are completely dissolved to obtain a mixed solution.

[0124] 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) was added to a 100ml single-necked flask. After being evacuated three times to an anhydrous and oxygen-free state, toluene was added to dilute the solution to prepare a 4.3mg / ml solution. The solution was then placed in an oil bath at 100℃ and stirred until homogeneous to obtain a toluene solution of TBD.

[0125] Add a toluene solution of TBD to a three-necked flask. The molar amount of TBD is 0.1% of L-lactide.

[0126] The three bottles were placed in an oil bath at 110°C for ring-opening polymerization for 24 hours.

[0127] After the reaction time is up, add 15 ml of 100 mg / ml benzoic acid solution. Benzoic acid can irreversibly destroy the active neutral, stop chain growth, and terminate the reaction, thereby achieving precise termination of the living polymerization reaction and precise control of the molecular weight of the final block copolymer.

[0128] After the solution in the three-necked flask cooled to room temperature, the solvent was removed by rotary evaporation, and then dissolved in dichloromethane. The solution was then added dropwise to n-hexane to dissolve the precipitate. This process was repeated three times to obtain the polymer precipitate. The polymer precipitate was then filtered to obtain the polymer precursor.

[0129] The polymer precursor was freeze-dried in a freeze dryer until no organic solvent residue remained, yielding a block copolymer (mPEG- b -PLA).

[0130] The block copolymer synthesis scheme in this embodiment is as follows: The prepared block copolymers were characterized and tested. The 1H NMR spectrum of the block copolymer prepared in this embodiment is shown in the appendix. Figure 2 The shifts in the corresponding characteristic peaks of the 1H NMR spectrum confirm the successful preparation of this block copolymer; all 1 H NMR spectra were acquired using a Bruker Avance NEO spectrometer at 400 MHz. Chemical shifts are expressed as ppm values ​​relative to tetramethylsilane (TMS). Figure 2 As can be seen, for mPEG and mPEG- b Proton nuclear magnetic resonance (1H NMR) spectral comparisons performed on PLA confirmed that polymer chain characteristics were incorporated into the resulting copolymer.

[0131] The gel permeation chromatogram of the block copolymer prepared in this embodiment is shown in the appendix. Figure 3 Through attachment Figure 3 Gel permeation chromatography (GPC) showed that the molecular weight of this block copolymer was 6593 g / mol. The figure shows that GPC analysis revealed mPEG- b The elution peaks of -PLA were symmetrical and narrow, indicating a uniform molecular weight. Compared with the GPC results of mPEG, mPEG- b -PLA shifts towards higher molecular weight regions, indicating that the PLA polymer sequence has been attached to the terminal hydroxyl groups of mPEG. The specific gel permeation chromatography (GPC) test method described above is as follows: the molecular weight and polydispersity of the polymer were determined by gel permeation chromatography (GPC) 220 (Polymer Laboratory, UK) equipped with two linear Mixed-B columns (300 mm × 7.5 mm) and a refractive index detector at 40 °C, using dichloromethane as the eluent at a flow rate of 1.0 mL / min, with polystyrene (PS) as the calibration standard.

[0132] The infrared spectrum of the block copolymer prepared in Example 1 of this invention is shown in the appendix. Figure 4 Through attachment Figure 4 Comparison of mPEG and mPEG- b -PLA revealed a blue shift and broadening of the hydroxyl stretching vibrations in the infrared spectrum, confirming the formation of hydrogen bonds (between C=O and -OH in the polylactic acid chain). The infrared spectra were obtained using Fourier transform infrared spectroscopy (FTIR) on a Thermo Fisher Scientific Nicolet iS20 spectrometer with a resolution of 4 cm⁻¹. -1(32 scans were collected). Samples were prepared by pressing potassium bromide tablets or by casting anhydrous dichloromethane solution at approximately 5.0 mg / ml onto a potassium bromide disk in air. The scanning range was 4000 cm⁻¹. -1 Up to 500cm -1 .

[0133] Scanning electron microscope (SEM) image of the prepared block copolymer, as follows: Figure 5 As shown, the block polymer exhibits a random distribution in all directions. The surface morphology and cross-section of the block polymer of this invention were tested using a scanning electron microscope (SEM, tested using a Zeiss GeminiSEM 300).

[0134] (2) The block copolymer prepared above is mixed with lithium bis(trifluoromethanesulfonyl)amine at a mass ratio, acetonitrile solvent is added, and the mixture is stirred evenly at 45°C to obtain a polymer electrolyte mixed solution. The mass of lithium bis(trifluoromethanesulfonyl)amine is 40% of the mass of the block copolymer.

[0135] (3) The polymer electrolyte mixture solution is injected into the porous base membrane (PP, thickness of 43 μm, porosity of about 30%) to wet and fill the porous base membrane, thus obtaining the composite membrane precursor. The precursor is placed in a glove box filled with argon gas to allow the acetonitrile to evaporate.

[0136] (4) The composite membrane precursor is subjected to hot pressing treatment at 60℃ and 2000 kg / cm². 2 After hot pressing for 10 minutes, the mixture was placed in a vacuum oven at 55°C for 24 hours to allow the acetonitrile to completely evaporate, resulting in a 60 μm thick solid polymer electrolyte based on block copolymer (abbreviated as AEA-ASSPE-Li).

[0137] The solid polymer electrolyte based on block copolymer prepared in this embodiment was tested: Scanning electron microscope images of the block copolymer-based solid polymer electrolyte are attached. Figure 6 As can be seen, the mixture of block polymer and salt has filled the pores and surface of the base film, and no pores were observed. The surface morphology and cross-section of the solid polymer electrolyte were measured by scanning electron microscopy (SEM, using a Zeiss GeminiSEM 300).

[0138] X-ray diffraction patterns of solid polymer electrolytes based on block copolymers are shown in the appendix. Figure 7 It can be seen in mPEG- bThe incorporation of lithium bis(trifluoromethanesulfonyl)imine (LiTFSI) into PLA significantly reduced the crystallinity of the resulting solid polymer electrolyte while increasing its ionic conductivity. Notably, bonding with the matrix film had almost no effect on crystallinity, confirming that the matrix film did not alter the inherent properties of the polymer electrolyte. The X-ray diffraction patterns of this invention were obtained by X-ray powder diffraction (XRD) analysis of the samples using a SmartLab SE diffractometer (employing copper Kα rays at a wavelength of 0.15418 nm) from Regma, with a scan rate of 20 degrees per minute and a test range of 10° to 80° 2θ values.

[0139] The electrochemical, mechanical, and thermal stability of the block copolymer-based solid polymer electrolyte prepared in Example 1 were tested: The ionic conductivity (σ) of the block copolymer-based solid polymer electrolyte prepared in this embodiment is tested, as shown in the appendix. Figure 8 It can be seen that the ionic conductivity of AEA-ASSPE-Li reaches 1.49 × 10⁻⁶ at 30 °C. -5 S / cm, this value is higher than the ionic conductivity of traditional polyethylene oxide polymer electrolytes at 30°C (10). -6 S / cm. The test method for the ionic conductivity of this invention is as follows: The σ value of AEA-ASSPE-Li was determined by electrochemical impedance spectroscopy (EIS) at open circuit potential using a 10mV perturbation signal (potential constant mode) within a frequency range of 4 MHz to 100 mHZ using a Zennium-Pro 43391 instrument in a temperature range of 30°C to 80°C (ESPEC MT3065, temperature accuracy less than 0.1°C). Using an SS|ASSPE|SS structure, the solid polymer electrolyte prepared in this embodiment was sandwiched between two stainless steel (SS, 16 mm) barrier electrodes. To form a stable contact, the coin cell was first heated at 80°C for 10 hours, and then held at each test temperature (from 80°C to 30°C) for 1 hour to reach thermal equilibrium.

[0140] The lithium-ion transference number of solid polymer electrolytes based on block copolymers is tested, see Appendix. Figure 9 As can be seen, the lithium-ion transport number at room temperature is approximately 0.2704. The method for testing the lithium-ion transport number in this invention involves combining AC impedance and DC polarization techniques. A symmetrical coin cell is obtained by sandwiching the solid polymer electrolyte prepared in this embodiment between two lithium sheets (Li|ASSPE|Li). The symmetrical coin cell is tested at 30°C, and the t-value of AEA-ASSPE-Li is obtained. Li+Values ​​were determined. To establish a stable interface between AEA-ASSPE-Li and the electrode, the coin cell was allowed to stand at 30°C for 10 hours prior to measurement. EIS data before and after polarization were obtained at an open-circuit potential (perturbation signal of 10 mV) using the same procedure as for ionic conductivity testing. Impedance data from 4 MHz to 8300 Hz were fitted and analyzed using electrochemical impedance spectroscopy software (Scribner Associates Inc.).

[0141] The redox potential of solid polymer electrolytes based on block copolymers was tested, see Appendix. Figure 10 As can be seen, by using the linear sweep voltammetry (LSV scan rate of 1E-4V s) -1 The reduction and oxidation stability of the conventional solid polymer electrolyte (mPEG-ASSPE-Li) and the solid polymer electrolyte (AEA-ASSPE-Li) prepared in this embodiment were compared at 70°C. The oxidation potential increased from 4V to 4.4V, while the reduction potential decreased from 1.44V to 1.35V. The redox potential of this invention was tested using a Chenhua CHI800D electrochemical workstation (Shanghai, China) to study the electrochemical stability of the solid polymer electrolyte. Electrochemical measurements were performed using a coin cell with a Li|ASSPE|SS structure within the forward potential range (from open circuit potential to 6.0V and from open circuit potential to 0.0V) at a scan rate of 0.1mV s. 1 The experiment was conducted at a temperature of 70°C.

[0142] Thermogravimetric analysis of solid polymer electrolytes based on block copolymers is shown in the appendix. Figure 11 The block polymer does not decompose below 120°C, meeting the requirements of battery cycling at room temperature and high temperature (70°C), and exhibits good thermal stability. The thermogravimetric analysis method of this invention involves using Netzsch TG 209 F3 at a nitrogen flow rate of 100 ml / min, with a heating rate of 5°C / min from 30°C to 800°C to determine thermal degradation.

[0143] The CR2032 button cell was assembled using a block copolymer-based solid polymer electrolyte prepared in this embodiment: the negative electrode material was lithium metal, and the positive electrode material was a ternary cathode material of lithium nickel cobalt manganese oxide (LiNi). 0.6 Co 0.2 Mn 0.2 O2 (NCM622) and lithium iron phosphate (LiFePO4, LFP). The assembled batteries were tested for electrochemical performance using a blue electrode tester.

[0144] For the LFP used as the positive electrode of the solid-state battery, Example 1 shows a coin cell assembled with a block copolymer-based solid polymer electrolyte as the solid electrolyte interlayer and lithium metal as the negative electrode. After two weeks of charge-discharge at 70°C at a rate of 0.1C, it was further cycled at 30°C at a rate of 0.1C for 200 cycles. The charge-discharge cutoff voltage range was 2.5V-4V. The charge-discharge curve of the all-solid-state lithium metal battery prepared under these conditions is shown in the appendix. Figure 12 As can be seen, within the first 90 cycles, the charge-discharge curves are normal with low polarization, and the capacity basically does not decay; the capacity retention and coulombic efficiency of the all-solid-state lithium metal battery prepared under these conditions are shown in the appendix. Figure 13 As can be seen, after 200 cycles at 30℃, the discharge capacity retention (DCR) is 94.93% and the coulombic efficiency (CE) is 99.96%.

[0145] For the coin cell battery assembled using the aforementioned NCM622 as the positive electrode of the solid-state battery, with the block copolymer-based solid polymer electrolyte prepared in Example 1 as the solid electrolyte interlayer and lithium metal as the negative electrode, after two weeks of charge-discharge at 70°C at a rate of 0.1C, it was further cycled at 30°C at a rate of 0.1C to 450 cycles. The charge-discharge cutoff voltage range was 2.8 V-4.3 V. The charge-discharge curve of the all-solid-state lithium metal battery prepared under these conditions is shown in the appendix. Figure 14 As can be seen, within the first 90 cycles, the charge-discharge curves are normal with low polarization, and the capacity basically does not decay; the capacity retention and coulombic efficiency of the all-solid-state lithium metal battery prepared under these conditions are shown in the appendix. Figure 15 As can be seen, after 450 cycles at 30℃, the discharge capacity retention rate (DCR) is 69.35% and the coulombic efficiency (CE) is 99.87%.

[0146] Example 2 This embodiment provides a preparation process for a solid polymer electrolyte based on block copolymers, as detailed below.

[0147] (1) The process of preparing block copolymers by ring-opening polymerization is exactly the same as in Example 1.

[0148] (2) The block copolymer prepared above is mixed with sodium bis(trifluoromethanesulfonyl)imide at a mass ratio, acetonitrile solvent is added, and the mixture is stirred evenly at 45°C to obtain a polymer electrolyte mixed solution. The mass of sodium bis(trifluoromethanesulfonyl)imide is 40% of the mass of the block copolymer.

[0149] (3) The polymer electrolyte mixture solution is injected into the porous base membrane (PP, thickness of 43 μm, porosity of about 30%) to wet and fill the porous base membrane, thus obtaining the composite membrane precursor. The precursor is placed in a glove box filled with argon gas to allow the acetonitrile to evaporate.

[0150] (4) The composite membrane precursor was hot-pressed (60°C for 10 min) and then placed in a vacuum oven at 55°C for 24 hours to allow the acetonitrile to evaporate completely, resulting in a solid polymer electrolyte based on block copolymer with a thickness of 60 μm.

[0151] The NNCFM all-solid-state sodium metal battery and the NVP all-solid-state sodium metal battery, which are assembled using solid polymer electrolytes based on block copolymer microphase separation prepared in this embodiment, are examples of such batteries.

[0152] The battery assembly process is as follows: the positive electrode active material is a sodium-containing layered oxide (NaNi). 2 / 9 Cu 1 / 9 Fe 1 / 3Mn 1 / 3 In Example 2, a solid polymer electrolyte based on a block copolymer, O2 (NNCFM) and sodium vanadium phosphate (Na3V2(PO4)3, NVP), were used as the solid electrolyte interlayer. Sodium metal was used as the negative electrode, and NNCFM and NVP all-solid-state sodium metal batteries were assembled using conventional methods. The electrochemical performance of the assembled batteries was tested using a blue electrochemical analyzer.

[0153] The NNCFM all-solid-state sodium metal battery was tested. After two weeks of charge-discharge at 70°C with a 0.1C rate, it was cycled at 30°C with a 0.1C rate for up to 200 cycles. The charge-discharge cutoff voltage range was 2.0 V-4.2 V. The cycle capacity retention rate and coulombic efficiency were measured. The test data are detailed in Table 1.

[0154] The NVP all-solid-state sodium metal battery was tested. After two weeks of charge-discharge at 70°C with a 0.1C rate, it was cycled at 30°C with a 0.1C rate for up to 250 cycles. The charge-discharge cutoff voltage range was 2.5 V-4.0 V. The cycle capacity retention and coulombic efficiency were measured. The test data are detailed in Table 1.

[0155] Example 3 This embodiment provides a preparation process for a solid polymer electrolyte based on block copolymers, as detailed below.

[0156] (1) The process of preparing block copolymers through ring-opening polymerization is as follows: Add 3 mmol of polyethylene glycol monomethyl ether (molecular weight 5000 g / mol) and 70 mmol of β-butyrolactone to a 500 ml three-necked flask. After pumping three times to an anhydrous and oxygen-free state, add 200 ml of toluene for dilution. Then place the flask in an oil bath at 80 °C and stir until the polyethylene glycol monomethyl ether and β-butyrolactone are completely dissolved to obtain a mixed solution.

[0157] Add stannous octoate (Sn(Oct)2) to a 100ml single-necked flask, evacuate three times until anhydrous and oxygen-free, then dilute with toluene to prepare a 1mg / ml solution. Place the solution in an oil bath at 80℃ and stir until homogeneous to obtain a toluene solution of stannous octoate (Sn(Oct)2).

[0158] Add a certain amount of toluene solution of stannous octoate to a three-necked flask.

[0159] Place the three bottles in an oil bath at 100°C and react for 15 hours.

[0160] After the reaction time is up, add 10 ml of 100 mg / ml benzoic acid solution to terminate the reaction. After the solution in the three-necked flask cooled to room temperature, the solvent was removed by rotary evaporation, and then dissolved in dichloromethane. The solution was then added dropwise to ice-cold ether to dissolve the precipitate. This process was repeated three times to obtain the polymer precipitate. The polymer precipitate was then filtered to obtain the polymer precursor.

[0161] The polymer precursor was vacuum dried overnight in a vacuum oven until no organic solvent residue remained, yielding a block copolymer with a molecular weight of 7000 g / mol.

[0162] (2) The block copolymer prepared above is mixed with lithium bis(trifluoromethanesulfonyl)amine at a mass ratio, acetonitrile solvent is added, and the mixture is stirred evenly at 45°C to obtain a polymer electrolyte mixed solution. The mass of lithium bis(trifluoromethanesulfonyl)amine is 40% of the mass of the block copolymer.

[0163] (3) The polymer electrolyte mixture solution is injected into the porous base membrane (PP, with a thickness of 43 micrometers and a porosity of about 30%) to wet and fill the porous base membrane, thus obtaining the composite membrane precursor. The precursor is placed in a glove box filled with argon gas to allow the acetonitrile to evaporate.

[0164] (4) The composite membrane precursor was subjected to hot pressing treatment (hot pressing at 55°C for 20 min), and then placed in a vacuum oven at 55°C for 24 hours to allow the acetonitrile to completely evaporate, resulting in a solid polymer electrolyte based on block copolymer with a thickness of 45 μm.

[0165] The CR2032 button cell was assembled using a block copolymer-based solid polymer electrolyte prepared in this embodiment: the negative electrode material was lithium metal, and the positive electrode material was a ternary cathode material of lithium nickel cobalt manganese oxide (LiNi). 0.6 Co 0.2 Mn 0.2 O2 (NCM622) and lithium iron phosphate (LiFePO4, LFP). The assembled batteries underwent cycle testing using the same methods as in Example 1, and the test data are detailed in Table 1.

[0166] To better illustrate the effects of the embodiments of the present invention, the following comparative examples are compared with the embodiments described above.

[0167] Comparative Example 1 This comparative example provides a preparation process for a solid polymer electrolyte, which differs from Example 1 in that the molecular weight of the prepared block copolymer is different, as detailed below.

[0168] (1) Block copolymers were prepared by ring-opening polymerization, as follows.

[0169] Add 70 mmol of polyethylene glycol monomethyl ether (molecular weight 20000 g / mol) and 350 mmol of L-lactide to a 500 ml three-necked flask. After pumping the solution three times to an anhydrous and oxygen-free state, add 300 ml of toluene to dilute it. Then place the flask in an oil bath at 100 °C and stir until the polyethylene glycol monomethyl ether and L-lactide are completely dissolved to obtain a mixed solution.

[0170] 1,5,7-triazabicyclodecene (TBD) was added to a 100ml single-necked flask, and the mixture was evacuated three times until it reached an anhydrous and oxygen-free state. Then, toluene was added to dilute the solution to prepare a 4.3mg / ml solution. The solution was then placed in an oil bath at 100℃ and stirred until homogeneous to obtain a toluene solution of TBD.

[0171] Add a toluene solution of TBD to a three-necked flask. The molar amount of TBD is 0.1% of L-lactide.

[0172] Place the three bottles in an oil bath at 150°C and react for 24 hours.

[0173] After the reaction time is up, add 15 ml of 100 mg / ml benzoic acid solution to terminate the reaction.

[0174] After the solution in the three-necked flask cooled to room temperature, the solvent was removed by rotary evaporation, and then dissolved in dichloromethane. The solution was then added dropwise to n-hexane to dissolve the precipitate. This process was repeated three times to obtain the polymer precipitate. The polymer precipitate was then filtered to obtain the polymer precursor.

[0175] The polymer precursor was freeze-dried in a freeze dryer until no organic solvent residue remained, to obtain a block copolymer with a molecular weight of 2,500,000 g / mol.

[0176] (2) The block copolymer prepared above is mixed with lithium bis(trifluoromethanesulfonyl)amine in a certain mass ratio, and a large amount of acetonitrile solvent is added. The mixture is stirred at 45°C until completely dissolved to obtain a polymer electrolyte mixed solution. The mass of lithium bis(trifluoromethanesulfonyl)amine is 30% of the mass of the block copolymer.

[0177] (3) The polymer electrolyte mixture solution is injected into the porous base membrane (PP, with a thickness of 43 micrometers and a porosity of about 30%) to wet and fill the porous base membrane, thus obtaining the composite membrane precursor. The precursor is placed in a glove box filled with argon gas to allow the acetonitrile to evaporate.

[0178] (4) The composite membrane precursor was hot-pressed at 80°C for 30 min and then placed in a vacuum oven at 55°C for 24 hours to allow the acetonitrile to completely evaporate, resulting in a solid polymer electrolyte based on block copolymer with a thickness of 150 μm.

[0179] The CR2032 button cell was assembled using a block copolymer-based solid polymer electrolyte prepared in this embodiment: the negative electrode material was lithium metal, and the positive electrode material was a ternary cathode material of lithium nickel cobalt manganese oxide (LiNi). 0.6 Co 0.2 Mn 0.2 O2 (NCM622) and lithium iron phosphate (LiFePO4, LFP). The assembled batteries underwent cycle testing using the same methods as in Example 1, and the test data are detailed in Table 1.

[0180] Comparative Example 2 This comparative example provides a preparation process for a solid polymer electrolyte. Unlike Example 1, this comparative example involves in-situ polymerization, as detailed below.

[0181] (1) Polyethylene glycol monomethyl ether (molecular weight 500 g / mol), L-lactide, lithium bis(trifluoromethanesulfonyl)amine, and stannous octoate were mixed in a certain mass ratio, wherein the molar ratio of L-lactide monomer to stannous octoate was 1000:1. The mixture was stirred at 40°C until completely dissolved to obtain a polymer electrolyte mixed solution. The mass of lithium bis(trifluoromethanesulfonyl)amine was 20% of the mass of the block copolymer.

[0182] (2) The above polymer electrolyte mixture solution is combined with a PP porous membrane to form an electrolyte membrane for battery assembly. CR2032 button cell: The negative electrode material is lithium metal, and the positive electrode material is a 622 type lithium nickel cobalt manganese oxide ternary positive electrode material (LiNi).0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622) and lithium iron phosphate (LiFePO4, LFP).

[0183] (3) The battery is placed at 70°C and left to stand for 5 hours for in-situ polymerization. The electrolyte membrane of the battery forms a solid electrolyte containing block copolymer in situ.

[0184] (4) After the battery was left to stand at room temperature for 5 hours, a cycle test was performed on the battery. The test method was the same as in Example 1. The test data are detailed in Table 1.

[0185] The test methods for the charge-discharge and cycle performance of the coin cells in the other examples and comparative examples other than Example 1 are the same as those in Example 1. When using different positive electrode materials, a voltage range that matches them is set. The test results are detailed in Table 1.

[0186] Table 1 summarizes the test data for Examples 1-3 and Comparative Examples 1-2.

[0187] As can be seen from the test data in Table 1, the coin cells prepared in Examples 1-3 can all cycle stably. After more than 200 cycles at low voltage, the capacity remains above 90%; after more than 200 cycles at high voltage, the capacity remains above 70%; and the coulombic efficiency is above 99%. This indicates that the coin cells prepared by the block copolymer-based solid polymer electrolyte preparation method provided by this invention have good cycle stability, normal capacity utilization, and slow capacity decay, exhibiting good scalability and process window adaptability.

[0188] Comparative Example 1 used a block polymer with a molecular weight of 2,500,000 g / mol. Due to its high molecular weight, a large amount of solvent was required for dilution during the preparation process to achieve composite with the porous base membrane. However, a large amount of solvent was difficult to remove completely, resulting in solvent residue. Furthermore, the obtained all-solid polymer electrolyte membrane had very high mechanical strength, making it difficult to wet the positive and negative electrode interfaces, leading to poor interfacial performance and thus reducing the cycle life of the battery. Regardless of whether it was a low-voltage LFP cathode or a high-voltage NCM622 cathode, the number of cycles was less than 100, and the capacity retention dropped to below 70%. This demonstrates that a suitable molecular weight is a key indicator for achieving this process.

[0189] In Comparative Example 2, the polymer electrolyte, produced via in-situ polymerization, maintained a capacity retention of 78.26% after 100 cycles for the low-voltage LFP cathode, indicating normal cycling performance. However, for the high-voltage NCM622 cathode, the capacity retention was only 40.67% after 100 cycles, showing rapid capacity decay and low coulombic efficiency. This is likely due to the uncontrollable molecular weight distribution resulting from in-situ polymerization and the presence of numerous side reactions. This demonstrates the necessity of ring-opening polymerization with controllable molecular weight.

[0190] This invention provides a method for preparing a solid polymer electrolyte based on block copolymers. Using a non-in-situ preparation method of ring-opening polymerization with controllable molecular weight, a mixture of block copolymers and metal salts is composited with a porous base membrane at room temperature. This achieves good interfacial contact between the solid electrolyte and the positive and negative electrodes after battery assembly, resulting in excellent battery performance. Furthermore, by designing the block copolymers, anti-entropy aggregation is achieved through hydrogen bonding interactions between molecules, broadening the electrochemical window. The solid polymer electrolyte based on block copolymers provided by this invention has advantages such as high ionic conductivity, a wide electrochemical window, and good chemical stability. It also exhibits good compatibility with the base membrane, and the assembled battery demonstrates excellent cycle performance.

[0191] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A solid polymer electrolyte based on block copolymers, characterized in that, The solid polymer electrolyte comprises: block copolymer, metal salt, and porous base membrane; The porous base membrane contains a mixture of the block copolymer and the metal salt distributed in its pores and on its surface. The molecular weight of the block copolymer is 200 g / mol to 2,000,000 g / mol.

2. The solid polymer electrolyte based on block copolymers according to claim 1, characterized in that, The block copolymer is formed by ring-opening polymerization of organic monomers initiated by an initiator and / or catalyst; The organic monomers include one or more of the following: conjugated diene organic compounds, non-conjugated diene organic compounds, cyclic monoesters, cyclic diesters, and subsequently functionalized cyclic esters; The initiator includes one or more of the following: polyethylene glycol monomethyl ether, butyllithium, alkyllithium, alkylpotassium, diethylzinc, triethylaluminum, Grignard reagent, aluminum isopropoxide, sodium alkoxide, potassium alkoxide, dimethoxydibutyltin, methoxytributyltin, ethoxydiethylaluminum, lithium tert-butoxide, and p-toluenesulfonic acid; The catalyst includes one or more of the following: stannous octoate, aluminum triacetylacetonate, zinc oxide, metalloporphyrin, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), enzyme catalyst, and nickel catalyst.

3. The solid polymer electrolyte based on block copolymers according to claim 2, characterized in that, The organic monomers specifically include one or more of the following: L-lactide, meso-lactide, glycolide, D-lactide, α-chloro-α-methyl-β-propiolactone, 3-methyl-5-isopropylpentanolactone, 1,4-dioxane-2-one, 3,3-dimethyloxetane-2-one, β-propiolactone, γ-butanolactone, δ-pentanolactone, ε-caprolactone, β-butanolactone, and δ-decanolactone.

4. The solid polymer electrolyte based on block copolymers according to claim 1, characterized in that, The metal salt includes sodium salt or lithium salt; the metal salt accounts for 5% to 100% of the mass of the block copolymer. The porous base membrane is made of one or more of the following materials: polyethylene (PE), polypropylene (PP), polyimide (PI), polyvinylidene fluoride (PVDF), cellulose, glass fiber, meta-aramid (PMIA), polyacrylonitrile (PAN), and polyethylene terephthalate (PET); the porosity of the porous base membrane is 10% to 70%; and the thickness of the porous base membrane is 5 μm to 100 μm. The thickness of the solid polymer electrolyte is 5 μm to 150 μm.

5. The solid polymer electrolyte based on block copolymers according to claim 4, characterized in that, The sodium metal salt includes one or more of the following: sodium difluorooxalate borate, sodium bis(oxalate borate), sodium dioxo-borate, sodium difluorophosphate, sodium difluorosulfonamide, sodium bis(trifluoromethanesulfonamide), sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, and sodium perchlorate. The lithium metal salt includes one or more of the following: lithium difluorooxalate borate, lithium dioxalate borate, lithium dioxalate borate, lithium dioxoacetic acid borate, lithium difluorophosphate, lithium difluorosulfonylimide, lithium bis(trifluoromethanesulfonylimide), lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, and lithium perchlorate.

6. The solid polymer electrolyte based on block copolymers according to claim 1, characterized in that, The solid polymer electrolyte also includes other compounds; the mass ratio of the other compounds to the block copolymer is 0% to 60%. The other compounds are inorganic substances other than the metal salt.

7. A method for preparing a solid polymer electrolyte based on a block copolymer as described in any one of claims 1-6, characterized in that, The preparation method includes: Block copolymers were prepared via ring-opening polymerization. The block copolymer is mixed with a metal salt, or with a metal salt and other compounds, in a solvent to obtain a polymer electrolyte mixed solution; The polymer electrolyte mixture is cast onto a porous base membrane, allowing the polymer electrolyte mixture to wet and fill the pores of the porous base membrane and cover its surface, thus obtaining a composite membrane precursor. The composite membrane precursor is subjected to hot pressing and then dried to remove the solvent, resulting in a solid polymer electrolyte based on block copolymer.

8. The preparation method according to claim 7, characterized in that, The preparation of block copolymers via ring-opening polymerization specifically includes: Organic monomers are added to a reaction flask, and after being pumped to an anhydrous and oxygen-free state, the first solvent is added for dilution. Then, the mixture is placed in an oil bath at 60℃~150℃ and stirred until homogeneous to obtain the first mixture. In another reaction flask, an initiator and / or catalyst are added, and the mixture is evacuated to an anhydrous and oxygen-free state. Then, a second solvent is added to dilute the mixture, and the mixture is placed in an oil bath at 30°C to 100°C and stirred until homogeneous to obtain a second mixture. Take an appropriate amount of the second mixture and add it to the first mixture. Place the reaction flask containing the two mixtures in an oil bath at 60°C to 150°C and react for 1 hour to 36 hours to allow the organic monomers to undergo ring-opening polymerization to obtain a polymer liquid. A terminator is added to the polymer liquid after the reaction to terminate the reaction; The polymeric reaction product liquid after the termination reaction is purified to obtain a polymer precursor; The polymer precursor was dried in a freeze dryer to remove residual solvent, yielding a block copolymer. The first solvent includes one or more of the following: deionized water, dichloromethane, methanol, ethanol, acetonitrile, acetone, cyclohexanone, diethyl ether, petroleum ether, N,N-dimethylformamide, N-methylpyrrolidone, toluenecyclohexanone, dimethyl sulfoxide, chloroform, tetrahydrofuran, benzene, toluene, xylene, cyclohexane, n-hexane, n-heptane, 1,4-dioxane, chlorobenzene, dichlorobenzene, phenol, pyridine, hexafluoroisopropanol, and ethyl acetate; The second solvent includes one or more of the following: methanol, toluene, methyl methacrylate, ethanol, acetonitrile, ethylene glycol dimethacrylate, ethylene glycol phenyl ether acrylate, bisphenol A methacrylate diester, n-heptane, n-hexane, 1,3-dioxolane, dimethyl sulfoxide, dichloromethane, bis(trimethylolpropane)acrylate, chloroform, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetrahydrofuran, hexafluoroisopropanol, vinylene carbonate, methyl ethyl carbonate, ethyl acetate, ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethyl ether, (di, tri, tetra)ethylene glycol dimethyl ether, acetone, cyclohexane, 1,3-butanediol diacrylate, pentaerythritol tetraacrylate, γ-valerolactone, γ-butyrolactone, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethylene carbonate, and deionized water. The terminating agents include: water, methanol, ethanol, isopropanol, C1-C6 alcohols, phenol and its derivatives, C4-C6 alcohols. 12 One or more of the following: fatty acids, benzoic acid, tall oil fatty acids, trimethylchlorosilane, chlorosilane derivatives, hexamethyldisiloxane, vinyl ethyl ether, vinyl methacrylate, various aldehydes, non-protected thiols, glycerol, pentaerythritol, polyethylene polyamines, and carboxylates; The purification process includes one or more of the following methods: filtration, recrystallization, column chromatography, dialysis, extraction, distillation, fractionation and sedimentation, dissolution and precipitation, salting out, gas washing, evaporation, and chromatography.

9. The preparation method according to claim 7, characterized in that, The hot pressing process specifically includes: clamping the composite film precursor in a mold, then placing the entire mold on a tablet press, heating and holding the temperature for 1 to 5 minutes, then applying pressure, cooling to room temperature, removing the mold, taking it out, and drying it in an oven to obtain the solid polymer electrolyte based on block copolymer. Wherein, the temperature at which the temperature is increased is lower than the decomposition temperature of the block copolymer; The pressurized pressure is 1000 kg / cm². 2 -3000kg / cm 2 .

10. A secondary battery, characterized in that, The secondary battery includes the solid polymer electrolyte based on block copolymers as described in any one of claims 1-6.

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