Polymer gel electrolyte membrane, preparation method thereof and battery

Abstract

The invention relates to the technical field of energy storage, in particular to a polymer gel electrolyte membrane, a preparation method of the polymer gel electrolyte membrane and a battery. The cross-linked polymer comprises a framework material, a grafting chain and a covalent bond, the framework material is connected with the grafting chain; a covalent bond is in bridge connection with the multiple grafting chains to form a covalent cross-linked network; the loofah sponge skeleton comprises purified loofah sponge; the framework material comprises cellulose and lignin; the grafting chain comprises at least one of-[-CH2-CH (COOH)-] n-,-[-CH2-C (CH3) (COOH)-] n-and-[-CH (COOH)-CH (COOH)-] n-; the covalent bond comprises a carbon-carbon double bond and / or an amide bond. When the polymer gel electrolyte membrane is applied to a battery, the ionic conductivity, the tensile strength and the elongation at break are remarkably improved, and the interface impedance is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, specifically to a polymer gel electrolyte membrane, its preparation method, and a battery. Background Technology

[0002] Currently, liquid electrolytes widely used in lithium-ion batteries pose safety hazards such as flammability and leakage, while solid polymer electrolytes, although highly safe, face the technical bottleneck of low ionic conductivity at room temperature (typically below 10⁻⁴ S / cm). Traditional gel polymer electrolytes (GPEs) can improve conductivity to the 10⁻³ S / cm range by introducing carbonate plasticizers, but they rely on non-renewable materials such as petroleum-based polymers like PVDF and PEO, and it is difficult to simultaneously achieve mechanical strength and interfacial stability. More importantly, existing GPE preparation processes often involve toxic organic solvents or high-temperature, high-pressure conditions, which are inconsistent with the trend of green chemistry development. Summary of the Invention

[0003] In view of this, the present invention aims to provide a polymer gel electrolyte membrane, its preparation method and battery, to solve the problems of complex process, high pollution and low mechanical strength and insufficient interface stability in the preparation methods of polymer electrolytes in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention is implemented as follows: A first aspect of the present invention provides a polymer gel electrolyte membrane, the polymer gel electrolyte membrane comprising a polymer crosslinker having a honeycomb structure; the polymer crosslinker having a honeycomb structure comprises a backbone material, graft chains, and covalent bonds; The skeleton material is connected to the grafted chain; the covalent bonds bridge multiple grafted chains to form a covalent cross-linked network; The skeletal material comprises cellulose and lignin; the grafted chain comprises -[-CH2-CH(COOH)-]. n -、-[-CH2-C(CH3)(COOH)-] n - -[-CH(COOH)-CH(COOH)-] n - At least one of the following, 1 ≤ n ≤ 3; the covalent bond includes carbon-carbon double bonds and / or amide bonds.

[0005] Optionally, the moisture content of the skeleton material is 4.5~5.5%; and / or, the pectin content in the skeleton material is ≤0.5wt%, and the hemicellulose content is ≤2wt%.

[0006] Optionally, the specific surface area of ​​the polymer gel electrolyte membrane is 400~500m². 2 / g; and / or, the porosity of the polymer gel electrolyte membrane is 60-90%; and / or, the average pore size of the polymer gel electrolyte membrane is 150-400 nm; and / or, the pore volume of the polymer gel electrolyte membrane is 0.85-1.35 cm³. 3 / g; and / or, the thickness of the polymer gel electrolyte membrane is 70~80μm.

[0007] Optionally, the polymer gel electrolyte membrane further contains a lithium salt; wherein, The polymer gel electrolyte membrane includes one or more of the following features (1) to (2): (1) Based on the total mass of the polymer gel electrolyte membrane, the lithium salt content is 10~20 wt%; (2) The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate and lithium dioxaborate.

[0008] A second aspect of the present invention provides a method for preparing a polymer gel electrolyte membrane, the method comprising the following steps: S1. The skeleton material, grafting agent and initiator are mixed to obtain a first mixture. The pH value of the first mixture is adjusted to 2.5~4.0 and a polymerization reaction is carried out to obtain a gel-like product. S2. The gel-like product is mixed with a first solvent to obtain a first solution; the first solution is mixed with a crosslinking curing agent and crosslinked and cured to obtain a second mixture; the second mixture is subjected to desolvation treatment to obtain a polymer gel electrolyte. S3. The polymer gel electrolyte is subjected to hot pressing treatment; The skeleton material includes cellulose and lignin.

[0009] Optionally, the step of mixing the skeleton material, grafting agent, and initiator includes: S11. After drying the loofah sponge, mix it with an alkaline solution and then subject it to ultrasonic treatment to obtain the third mixture. S12. Centrifuge the third mixture to obtain a precipitate; S13. The precipitate is washed until neutral and then vacuum dried to obtain a first framework material; the first framework material is then used as the framework material to undergo the mixing treatment with the grafting agent and the initiator; or... The precipitate is washed until neutral and then vacuum dried to obtain a first skeleton material; the first skeleton material is sulfonated and then washed and dried to obtain a modified skeleton material; the modified skeleton material is then used as the skeleton material and mixed with the grafting agent and the initiator.

[0010] Optionally, the sulfonation modification step includes: reacting the first framework material with a sulfurous acid solution in a high-pressure reactor at a high temperature, wherein the sulfurous acid solution includes at least one of NaHSO3 solution, KHSO3 solution and Na2SO3 solution, the ratio of the first framework material to the sulfurous acid solution is (50~70) g: (1~2) L, and the content of sulfite in the sulfurous acid solution is 1.5-2.5 wt%; the pressure of the high-pressure reactor is 0.4~0.8 MPa; the conditions for the high-temperature reaction include: a temperature of 100~140℃ and a time of 2~6 h.

[0011] Optionally, the alkaline solution includes at least one of NaOH solution, KOH solution, and Na2CO3 solution; the ratio of the dried loofah sponge to the alkaline solution is (100~150) g: (250~750) mL, the content of alkaline substances in the alkaline solution is 2~8 wt%, and / or, the conditions for ultrasonic treatment include: temperature of 50~70℃, power of 200~500W, frequency of 20~40KHz, and time of 1~3h; and / or, the conditions for centrifugation treatment include: rotation speed of 8000~10000rpm, and time of 8~12 min; and / or, the conditions for vacuum drying treatment include: pressure of 0.01~0.05Mpa, temperature of 50~70℃, and time of 10~14h.

[0012] Optionally, the mass ratio of the skeleton material, the grafting agent, and the initiator is 1:(0.67-1.2):(0.024-0.027); and / or, the ratio of the gel-like product to the first solvent is (2g~10g):100mL; and / or, the mass ratio of the gel-like product to the crosslinking curing agent in the first solution is 1:(0.075~0.25); and / or, the water content of the gel-like product is 50~70%; and / or, the grafting agent includes at least one of acrylic acid, methacrylic acid, and maleic acid; and / or, the initiator includes at least one of ammonium sulfate, potassium persulfate, and azobisisobutyronitrile; and / or, the crosslinking curing agent includes at least one of trimethylolpropane triacrylate, triethylenetetramine, and ethylene glycol dimethacrylate; and / or, the first solvent includes at least one of acetonitrile, γ-butyrolactone, and ethylene carbonate.

[0013] Optionally, in step S2, the mixing treatment includes ultrasonic dispersion treatment, wherein the conditions for ultrasonic dispersion treatment include: power of 200~800 W, frequency of 20~40 kHz, and time of 10~40 min; and / or, the polymerization reaction is carried out under an inert atmosphere, wherein the conditions for polymerization reaction include: temperature of 60~90℃ and time of 6~18 h; and / or, in step S3, the crosslinking curing is photocuring or thermocuring, wherein the conditions for photocuring include: wavelength of 300~400 nm and power of 100~300 mW / cm. 2 Alternatively, the thermosetting conditions include: a temperature of 60~120℃ and a time of 10~60 min; and / or, the desolvation treatment is a vacuum treatment, the vacuum treatment conditions include: a pressure of 0.05~0.2 Pa and a temperature of 40~60℃; and / or, in step S3, the hot pressing treatment conditions include: a temperature of 100~160℃, a pressure of 3~8 MPa, and a time of 5~15 min.

[0014] Optionally, the preparation method further includes: in step S2, mixing the first solution with lithium salt for ion exchange to obtain the first solution after ion exchange; mixing the first solution after ion exchange with the crosslinking curing agent and performing the crosslinking curing; wherein the conditions for ion exchange include: temperature of 20~40℃ and time of 12~36 h.

[0015] A third aspect of the present invention provides a battery comprising an electrolyte membrane, wherein the electrolyte membrane is the polymer gel electrolyte membrane described above and / or a polymer gel electrolyte membrane prepared according to the method described above.

[0016] The beneficial technical effects of the present invention through the above technical solution are as follows: (1) The polymer gel electrolyte membrane of the present invention comprises a polymer crosslinker with a honeycomb structure; the polymer crosslinker with a honeycomb structure comprises a backbone material, graft chains, and covalent bonds; wherein the graft chains are connected to the backbone material; the covalent bonds bridge multiple graft chains to form a covalent crosslinking network. The backbone material in the present invention comprises cellulose and lignin; cellulose forms a nanoscale scaffold from microfibrils, improving the tensile strength of the product, and its surface hydroxyl groups can form hydrogen bonds with water molecules, providing Li + Secondary transport path; the honeycomb pores of the skeleton material can provide Li +This invention provides multi-path diffusion channels, reducing ion migration resistance and improving conductivity; simultaneously, the high porosity of the honeycomb structure significantly reduces material density; the increased contact area between the honeycomb pores and the electrode reduces interfacial impedance; the covalently cross-linked network of the polymer gel electrolyte membrane of this invention can greatly improve the tensile strength and elongation at break of the product, fix the spatial position of the -SO3Li group, and increase the Li... + Migration number; This invention enables the construction of a biomimetic ion conductor by introducing graft chains: a rigid framework material provides mechanical support and a primary ion channel; flexible graft chains impart dynamic interface adaptability and secondary transport paths. When the polymer gel electrolyte membrane of this invention is applied to a battery, it exhibits significantly improved ionic conductivity, tensile strength, and elongation at break, as well as significantly reduced interfacial impedance.

[0017] (2) The preparation method of the polymer gel electrolyte membrane of the present invention solves the problem of the difficulty in achieving both high porosity and high strength of polymer gel electrolyte by using natural material structure design and multi-level process synergistic control. The dual-site lithium storage and pore-lithium salt synergistic optimization achieve a certain breakthrough in the lithium ion transport efficiency of polymer gel electrolyte. The triple protection of surface chemical passivation, physical strengthening and thermo-mechanical stability greatly improves the interface stability of the product. At the same time, the raw material cost of the present invention is low, which facilitates the application and promotion of the product.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0020] Figure 1 The image shown is a scanned image (SEM) of the polymer gel electrolyte membrane prepared in Example 1.

[0021] Figure 2 The Fourier transform infrared (FTIR) spectrum of the polymer gel electrolyte membrane prepared in Example 1 is shown.

[0022] Figure 3 A schematic diagram of the microstructure of a purified loofah sponge. Detailed Implementation

[0023] This invention discloses a polymer gel electrolyte membrane, its preparation method, and a battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0024] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0027] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0028] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0029] To address the problems of complex processes, high pollution, low mechanical strength, and insufficient interfacial stability in existing polymer electrolyte preparation methods, this invention adopts the following technical solution: A first aspect of the present invention provides a polymer gel electrolyte membrane, the polymer gel electrolyte membrane comprising a polymer crosslinker having a honeycomb structure; the polymer crosslinker having a honeycomb structure comprises a backbone material, graft chains, and covalent bonds; The skeleton material is connected to the grafted chain; the covalent bonds bridge multiple grafted chains to form a covalent cross-linked network; The skeletal material comprises cellulose and lignin; the grafted chain comprises -[-CH2-CH(COOH)-]. n -、-[-CH2-C(CH3)(COOH)-] n - -[-CH(COOH)-CH(COOH)-] n - At least one of the following, 1 ≤ n ≤ 3; the covalent bond includes carbon-carbon double bonds and / or amide bonds.

[0030] The polymer gel electrolyte membrane of the present invention comprises a polymer crosslinker with a honeycomb structure; the polymer crosslinker with a honeycomb structure comprises a backbone material, graft chains, and covalent bonds; wherein the graft chains are connected to the backbone material; and the covalent bonds bridge multiple graft chains to form a covalent crosslinked network. The backbone material provides mechanical support and forms a porous structure, promoting ion diffusion pathways and enhancing overall stability; the graft chains can introduce functional groups such as carboxyl groups, ionizing to form Li... + The conductive network enhances ionic conductivity and constructs secondary transport channels; covalent bonds bridge multiple graft chains, forming stable connections and ensuring structural integrity. The polymer crosslinks in this invention possess a honeycomb structure, which provides high-porosity channels, reduces ion migration resistance, increases the contact area with the electrode, and thus reduces interfacial impedance. The covalent crosslinking network formed by covalent bonds and graft chains fixes the positions of functional groups, significantly improving the mechanical strength of the membrane, such as tensile strength and elongation at break, and optimizing ion migration efficiency. The framework materials in this invention include cellulose and lignin; cellulose forms a nanoscale scaffold to enhance tensile strength and provides Li+ through hydrogen bonds formed between surface hydroxyl groups and water molecules. + The transport auxiliary path; lignin can participate in the framework construction, supporting the formation of honeycomb pores and jointly constituting a rigid main structure. In addition, lignin can passivate the lithium anode in situ to form a Li2O-rich SEI film, inhibiting lithium dendrite growth. When the polymer gel electrolyte membrane of the present invention is applied to a battery, it has significantly improved ionic conductivity, tensile strength and elongation at break, as well as significantly reduced interfacial impedance.

[0031] The purified loofah sponge in this invention, such as Figure 3 As shown, the moisture content of the skeleton material can be 4.5~5.5%, which can maintain the dynamic equilibrium of hydrogen bonds to protect the pores.

[0032] In one embodiment of the present invention, the pectin content in the skeleton material is ≤0.5wt%, and the hemicellulose content is ≤2.0wt%. In the skeleton material of the present invention, the content of pectin and hemicellulose needs to be controlled. If the pectin content is too high, the large number of carboxyl groups (-COOH) in the pectin will capture a large amount of Li. + Blocking ion transport channels leads to a decrease in ion conductivity, and the methoxy group (-OCH3) in pectin can hydrolyze to produce methanol, which can easily corrode the electrode interface. If the hemicellulose content is too high, the strong water absorption of hemicellulose will cause the membrane to swell excessively, decompose at high temperature to produce acid (acetic acid / formic acid), which will increase the swelling rate and cause the membrane structure to break. In addition, the acid will catalyze the decomposition of lithium salt, increasing the risk of perforation during hot pressing.

[0033] According to the present invention, if the specific surface area of ​​the polymer gel electrolyte membrane is too small, it may lead to insufficient ion adsorption sites, decreased conductivity, and reduced Li+ transport number; if the specific surface area of ​​the polymer gel electrolyte membrane is too large, it may lead to decreased mechanical strength, increased side reactions, and thickened SEI film. In the present invention, the specific surface area of ​​the polymer gel electrolyte membrane can be 400~500 m² / g. 2 / g. Exemplarily, the specific surface area of ​​the polymer gel electrolyte membrane can be 400 m². 2 / g、420 m 2 / g、440 m 2 / g、460 m 2 / g、480 m 2 / g and 500 m 2 Any value in / g or any value within the range formed by any two of the above values.

[0034] According to the present invention, if the porosity of the polymer gel electrolyte membrane is too low, it may lead to ion channel blockage, decreased conductivity, and increased susceptibility to cracking during hot pressing; if the porosity of the polymer gel electrolyte membrane is too high, it may lead to mechanical collapse and electrolyte leakage risk. In the present invention, the porosity of the polymer gel electrolyte membrane can be 60-90%. Exemplarily, the porosity of the polymer gel electrolyte membrane can be any value selected from 60%, 65%, 70%, 75%, 80%, and 90%, or any value within the range formed by any pair of the above values.

[0035] According to the present invention, if the average pore size of the polymer gel electrolyte membrane is too small, it may lead to Li +Increased migration resistance leads to a decrease in charging rate; if the average pore size of the polymer gel electrolyte membrane is too large, lithium dendrites may easily penetrate, increasing interfacial impedance. In this invention, the average pore size of the polymer gel electrolyte membrane can be 150~400 nm. Exemplarily, the average pore size of the polymer gel electrolyte membrane can be any value selected from 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, and 400 nm, or any value within the range formed by any two of the above values.

[0036] According to the present invention, if the pore volume of the polymer gel electrolyte membrane is too small, the electrolyte may not wet sufficiently, hindering the migration of interfacial ions; if the pore volume of the polymer gel electrolyte membrane is too large, the polymer gel electrolyte membrane may deform, resulting in large thickness deviations and increased expansion rate. The pore volume of the polymer gel electrolyte membrane can be 0.85~1.35 cm³. 3 / g. Exemplarily, the pore volume of the polymer gel electrolyte membrane can be 0.85 cm³. 3 / g, 1 cm 3 / g, 1.15 cm 3 / g, 1.25 cm 3 / g and 1.35 cm 3 Any value in / g or any value within the range formed by any two of the above values.

[0037] According to the present invention, if the polymer gel electrolyte membrane is too thin, its mechanical strength may be insufficient, resulting in a decrease in puncture strength; if the polymer gel electrolyte membrane is too thick, its internal resistance may increase, resulting in a decrease in volumetric energy density. In this invention, the thickness of the polymer gel electrolyte membrane can be 70-80 μm. Exemplarily, the pore volume of the polymer gel electrolyte membrane can be any value selected from 70 μm, 72 μm, 74 μm, 76 μm, 78 μm, and 80 μm, or any value within the range formed by any pair of the above values.

[0038] In a preferred embodiment of the present invention, the polymer gel electrolyte membrane further contains a lithium salt. In this invention, if the lithium salt content is too low, it may lead to the release of free Li. + Insufficient lithium content leads to decreased conductivity; excessive lithium salt content may cause lithium salt to crystallize and precipitate, blocking pores and accelerating interfacial side reactions. Optionally, the lithium salt content is 10-20 wt%, based on the total mass of the polymer gel electrolyte membrane.

[0039] For example, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), and lithium dioxolaneborate (LiBOB). Preferably, considering solubility and decomposition temperature, the lithium salt in this invention can be lithium bis(trifluoromethanesulfonyl)imide.

[0040] In this invention, at least a portion of the lithium salt forms an ion channel with the anionic group of the grafted chain, thereby enhancing ion transport and improving ion conductivity. In this invention, the portion of the lithium salt forming the ion channel may account for 20-30 wt% of the total lithium salt.

[0041] In this invention, the polymer gel electrolyte membrane further contains sulfonate groups. The introduction of sulfonate groups reduces the ion migration activation energy and significantly improves ionic conductivity. The sulfonate groups are distributed on the surface of the framework material, and at least a portion of the lithium salt forms ion clusters with the sulfonate groups; the portion of the lithium salt forming the ion clusters can account for 70-80 wt% of the total lithium salt. In this invention, the ion clusters can form penetrating lithium ion enrichment channels, increasing ionic conductivity; the Li in the ion clusters... + With multiple -SO3 - The strong coordination of the ions forms physical cross-linking points, enhancing the interchain forces in the polymer and increasing tensile strength, while simultaneously suppressing electrode expansion during cycling. The highly localized Li ion clusters... + Concentration at the Li interface + The uniform distribution eliminates uneven heat distribution on the electrode surface. Simultaneously, the strong coordination bonds of the ion clusters can withstand high temperatures, inhibiting lithium salt decomposition, increasing the thermal runaway initiation temperature, and mitigating thermal safety hazards.

[0042] In one embodiment of the present invention, lithium salt is distributed in the framework material, and sulfonic acid groups (-SO3) - The grafted chain is covalently anchored to the backbone (cellulose / lignin), forming fixed charge sites; while the carboxyl groups (-COO-) of the grafted chain are free to move. In this invention, the carboxyl groups (-COOH) of the grafted chain segment ionize to form -COO⁻ / Li + The -SO3Li groups, fixed on the rigid lignin framework, form a parallel conduction network; the sulfonic acid groups (-SO3H) undergo proton-lithium ion exchange with the lithium salt to form -SO3Li. Specifically, Li⁺ is preferentially captured by the high charge density sulfonic acid groups, resulting in a Li⁺ concentration on the framework surface that is approximately 3-5 times higher than that in the grafted chain region. The densely distributed sulfonic acid groups (-SO3H) on the framework surface... - Li is fixed by ion exchange + This forms a rigid, high-concentration lithium-ion enrichment layer. Compared to Li₂ dispersed in flexible polymer graft chains... + Li on the surface of the skeleton +The channel features a shorter ion hopping distance and a more stable transport path, reducing the activation energy for ion migration, increasing ion transport efficiency and conductivity, and also increasing the number of ions migrating. Simultaneously, the introduction of lithium salt can effectively suppress lithium dendrite growth and enhance interface stability; furthermore, Li... + It can form coordination crosslinking sites with the sulfonic acid groups of the backbone, enhancing the rigidity of the three-dimensional network and increasing tensile strength; high concentration of Li + Inhibit solvent penetration at the skeleton, reduce solvent swelling effect during cycling, and reduce thickness expansion.

[0043] A second aspect of the present invention provides a method for preparing a polymer gel electrolyte membrane, the method comprising the following steps: S1. The skeleton material, grafting agent and initiator are mixed to obtain a first mixture. The pH value of the first mixture is adjusted to 2.5~4.0 and a polymerization reaction is carried out to obtain a gel-like product. S1. The gel-like product is mixed with a first solvent to obtain a first solution; the first solution is mixed with a crosslinking curing agent and crosslinked and cured to obtain a second mixture; the second mixture is subjected to desolvation treatment to obtain a polymer gel electrolyte. S2. The polymer gel electrolyte is subjected to hot pressing treatment; The skeleton material includes cellulose and lignin.

[0044] The preparation method of the polymer gel electrolyte membrane of the present invention promotes the protonation of grafting agent monomers and improves the grafting rate by precisely controlling the pH at an acidic pH of 2.5-4; after cross-linking and curing, a covalent cross-linking network is constructed to lock the grafted chains with the backbone, thereby improving the tensile strength and elongation at break of the gel electrolyte; after hot pressing, internal defects are eliminated, interlayer contact is optimized, membrane density is improved, electron tunneling is blocked, and the ionic conductivity of the gel electrolyte is improved.

[0045] In one embodiment of the present invention, the step of mixing the skeleton material, grafting agent, and initiator includes: S11. After drying the loofah sponge, mix it with an alkaline solution and then subject it to ultrasonic treatment to obtain the third mixture. S12. Centrifuge the third mixture to obtain a precipitate; S13. The precipitate is washed until neutral and then vacuum dried to obtain a first skeleton material; the first skeleton material is used as the skeleton material and mixed with the grafting agent and the initiator.

[0046] This invention uses loofah sponge as the raw material for the skeleton material. After processing, the loofah sponge is purified to obtain loofah sponge (SL, i.e., the first skeleton material). Due to the high thermal decomposition temperature of lignin in loofah sponge, the prepared gel electrolyte has significantly improved heat resistance. At the same time, loofah sponge raw material has low cost and has advantages in terms of green low carbon and industrialization.

[0047] In a preferred embodiment of the present invention, the preparation method further includes: sulfonating and washing and drying the first skeleton material to obtain modified purified loofah sponge; and mixing the modified purified loofah sponge with the grafting agent and the initiator as the skeleton material.

[0048] The sulfonation reaction of this invention uses the hydroxyl group (-OH) in lignin as the nucleophilic site, reacting with sulfite (HSO3) ions. - The sulfonation reaction occurs, producing sulfonic acid groups (-SO3). - (The sulfonation reaction only partially converts the hydroxyl groups (50%-70%)). The reaction involved in the sulfonation reaction is: R-OH + HSO3 - →R-SO3 - + H2O.

[0049] This invention, through sulfonation, introduces sulfonic acid groups, subsequently forming a more hydrophilic honeycomb structure. Simultaneously, the enhanced hydrophilicity makes it easier for the sulfonated loofah sponge to form a uniform dispersion system with the solvent, preventing agglomeration and creating more regular honeycomb pores. Furthermore, the strongly acidic environment of the sulfonic acid groups can inhibit the decomposition of the electrolyte. In this invention, the sulfonated lignin (lignin sulfonate) transforms from an insulator into an ionic conductor, acting as a Li... + The main transport sites enhance the fracture energy of the product and inhibit crack propagation. Specifically, lignin sulfonate (L-SL) improves the electrochemical performance of lithium batteries through the following synergistic pathway: the aromatic phenolic hydroxyl groups undergo selective redox reactions with the lithium anode interface to generate a gradient passivation film with Li2O as the core and Li2CO3 / LiF as the outer layer, which can reduce the lithium deposition overpotential.

[0050] In this embodiment, the sulfonation modification step may include: reacting the purified loofah sponge with a sulfurous acid solution at high temperature in a high-pressure reactor. Optionally, the sulfurous acid solution includes at least one of NaHSO3 solution, KHSO3 solution, and Na2SO3 solution; preferably, the sulfurous acid solution is a NaHSO3 solution. NaHSO3 can dissociate to generate HSO3. - Its nucleophilicity is superior to that of SO3. 2- It is more likely to undergo nucleophilic substitution reactions with lignin hydroxyl groups to generate sulfonic acid groups; on the other hand, Na +It has no significant interference with the sulfonation reaction and is easily removed by water washing (Na). + (High solubility) to avoid residues affecting subsequent graft copolymerization reactions.

[0051] In this invention, an appropriate amount of sulfurous acid solution can provide ideal active sites for subsequent reactions. If too little sulfurous acid solution is added, the nucleophilic substitution reaction rate decreases, the amount of sulfonic acid groups introduced is insufficient, the proportion of residual hydroxyl groups increases, the number of active sites in the subsequent graft copolymerization reaction decreases, and the grafting rate decreases. If too much sulfurous acid solution is added, over-sulfonation leads to structural damage and exacerbates side reactions. According to this invention, the ratio of the purified loofah sponge to the sulfurous acid solution is (50~70) g: (1~2) L, and the content of sulfites in the sulfurous acid solution is 1.5-2.5 wt%.

[0052] In this embodiment, the pressure of the high-pressure reactor can be 0.4~0.8MPa; the conditions for the high-temperature reaction can include: a temperature of 100~140℃ and a time of 2~6 h.

[0053] The hydroxyl groups retained by the sulfonation reaction in this invention can be the active sites for graft copolymerization, thereby ensuring a grafting rate >70%.

[0054] The method for preparing the skeletal material of this invention can remove pectin and hemicellulose from loofah sponges. Pectin is a galacturonic acid polymer linked by α-1,4-glycosidic bonds; in an alkaline solution, the ester and glycosidic bonds are hydrolyzed to generate water-soluble sodium galacturonate and oligosaccharides. The β-1,4-glycosidic bonds of hemicellulose (mainly xylan) break in an alkaline environment, degrading into xylose monomers and oligosaccharides. Centrifugation separates the insoluble cellulose skeleton from the soluble degradation products, preserving the integrity of the fiber structure.

[0055] In this embodiment, the alkaline solution may include at least one of NaOH solution, KOH solution, and Na2CO3 solution. Since NaOH solution is both strongly alkaline and can rapidly hydrolyze pectin and hemicellulose in the loofah sponge, significantly improving storage efficiency, and its cost is lower than KOH and Na2CO3, the alkaline solution is preferably NaOH solution. In this invention, the ratio of the dried loofah sponge to the alkaline solution can be (100~150) g: (250~750) mL, and the content of alkaline substances in the alkaline solution can be 2~8 wt%.

[0056] In this embodiment, the conditions for ultrasonic treatment may include: a temperature of 50~70℃, a power of 200~500W, a frequency of 20~40KHz, and a time of 1~3h; and / or, the conditions for centrifugation treatment may include: a rotation speed of 8000~10000rpm and a time of 8~12min; and / or, the conditions for vacuum drying treatment may include: a pressure of 0.01~0.05Mpa, a temperature of 50~70℃, and a time of 10~14h.

[0057] According to the present invention, the mass ratio of the skeleton material, the grafting agent and the initiator can be 1:(0.67-1.2):(0.024-0.027).

[0058] According to the present invention, the ratio of the gel-like product to the first solvent can be (2g~10g):100mL.

[0059] According to the present invention, the mass ratio of the gel-like product to the crosslinking curing agent in the first solution can be 1:(0.075~0.25).

[0060] Optionally, the water content of the gel-like product is 50-70%.

[0061] For example, the grafting agent includes at least one of acrylic acid (AA), methacrylic acid (MAA), and maleic acid (MA).

[0062] The grafting agent of this invention undergoes a homopolymerization process during the polymerization reaction. Taking ammonium sulfate as an initiator as an example: when the grafting agent is acrylic acid, ammonium sulfate decomposes to form SO4. - • Free radicals attack the AA double bond to form AA·CH2-CH(COOH), the chain gradually grows, and AA·+nAA forms -[-CH2-CH(COOH)-]. n - When the grafting agent is methacrylic acid, free radical polymerization is initiated. Free radicals attack the MAA double bond to form ·CH2-C·C, chain growth occurs, and MAA·+nMAA forms -[-CH2-C(CH3)(COOH)-]. n - When maleic acid is used as the grafting agent, maleic acid undergoes ring-opening polymerization via free radicals to form polymaleic acid, which is then hydrolyzed to yield polymaleic acid chains -[-CH(COOH)-CH(COOH)-]. n - .

[0063] Preferably, the grafting agent is acrylic acid, whose linear structure can reduce steric hindrance, and its chain growth rate is superior to that of methacrylic acid and maleic acid.

[0064] For example, the initiator includes at least one of ammonium sulfate (APS), potassium persulfate (KPS), and azobisisobutyronitrile (AIBN). Preferably, the initiator is ammonium sulfate, which is stable under acidic conditions at pH 2.5-4, and its decomposition reaction continuously releases free radicals. Furthermore, the initiation efficiency of ammonium sulfate is significantly higher than that of potassium persulfate and azobisisobutyronitrile.

[0065] Exemplarily, the crosslinking curing agent includes at least one of trimethylolpropane triacrylate (TMPTA), triethylenetetramine (TEDA), and ethylene glycol dimethacrylate (EGDMA). Preferably, the crosslinking curing agent includes trimethylolpropane triacrylate. The three acrylic groups of trimethylolpropane triacrylate can undergo free radical polymerization with the C=C double bonds of the grafting agent to form a three-dimensional network structure (the grafted copolymerization residual double bonds are used for crosslinking and curing). Furthermore, in specific embodiments, trimethylolpropane triacrylate can complete crosslinking at 60-90°C for 6-18 hours, a shorter curing time than triethylenetetramine and ethylene glycol dimethacrylate.

[0066] For example, the first solvent includes at least one of acetonitrile, γ-butyrolactone (GVL), and ethylene carbonate (EC). Preferably, the first solvent is acetonitrile, which can effectively dissolve loofah sponge and graft copolymer to form a uniform dispersion system. At the same time, acetonitrile has better chemical stability than GVL and EC during crosslinking and curing.

[0067] In one embodiment of the present invention, in step S1, the mixing process includes ultrasonic dispersion, wherein the conditions for ultrasonic dispersion include: power of 200~800 W, frequency of 20~40 kHz, and time of 10~40 min; and / or, the polymerization reaction is carried out under an inert atmosphere, wherein the conditions for polymerization reaction include: temperature of 60~90℃ and time of 6~18 h.

[0068] In one embodiment of the present invention, in step S2, the crosslinking curing can be photocuring or thermal curing. Exemplarily, the photocuring conditions include: a wavelength of 300-400 nm and a power of 100-300 mW / cm². 2 Alternatively, the conditions for heat curing include: a temperature of 60~120℃ and a time of 10~60 min.

[0069] In this invention, the desolvation treatment can be a vacuum treatment, and the conditions of the vacuum treatment can include: a pressure of 0.05~0.2 Pa and a temperature of 40~60℃; and / or, in step S3, the conditions of the hot pressing treatment can include: a temperature of 100~160℃, a pressure of 3~8 MPa, and a time of 5~15 min.

[0070] In a preferred embodiment of the present invention, the preparation method further includes: in step S2, mixing the first solution with a lithium salt for ion exchange to obtain an ion-exchanged first solution; mixing the ion-exchanged first solution with the crosslinking curing agent and performing the crosslinking curing.

[0071] Optionally, the conditions for ion exchange may include: a temperature of 20~40℃ and a time of 12~36 h.

[0072] In this invention, through an ion exchange step, sulfonate (-SO3) can be... - The counterion of (e.g., Na) + ) by Li + Substitution forms Li-SL (not the removal of sulfonic acid groups).

[0073] A third aspect of the present invention provides a battery comprising an electrolyte membrane, wherein the electrolyte membrane is the polymer gel electrolyte membrane described above and / or a polymer gel electrolyte membrane prepared according to the method described above.

[0074] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0075] Example 1 (1) Pretreatment of loofah sponge: Take 125 g of dried loofah sponge, add 500 mL of 5 wt% NaOH solution (pH=13.5), and sonicate in a 60℃ water bath for 2 h. The sonication power is 200 W and the frequency is 40 kHz for 2 h to remove pectin and hemicellulose, and obtain the third mixture. Centrifuge the third mixture and collect the precipitate. The centrifugation speed is 9000 rpm and the time is 10 min. Wash the precipitate with deionized water until neutral (pH=7), and vacuum dry at 60℃ for 12 h to obtain purified loofah sponge powder.

[0076] (2) Take 60 g of purified loofah sponge and add it to 1.5 L of 2wt% NaHSO3 solution. Put the solution into a high-pressure reactor for sulfonation modification. The sulfonation modification temperature is 120℃ and the time is 4 h to obtain the modified product. Wash the modified product three times with an ethanol-water mixture (2:1, v / v) and dry it under vacuum at 60℃ for 12 h to obtain the modified purified loofah sponge powder (L-SL).

[0077] (3) Dissolve 2g of modified purified loofah powder, 1.5g of acrylic acid (AA) and 0.05g of ammonium persulfate (APS) in deionized water and ultrasonically disperse for 30 min to obtain the first mixture. The ultrasonic dispersion power is 500 W and the frequency is 30 kHz. After adjusting the pH of the first mixture to 3.2, transfer it to the reaction vessel and purge with nitrogen (flow rate 50 mL / min) for 30 min to remove oxygen. Then, keep the temperature constant at 80℃ for 12 h to obtain a transparent gel product.

[0078] (4) 30g of the transparent gel product was immersed in 500mL of 0.1mol / L LiTFSI solution for 24h for ion exchange to obtain the first solution after ion exchange. The first solution after ion exchange was mixed with 0.2g of trimethylolpropane triacrylate (TMPTA) and cured under ultraviolet light for 30min (wavelength 365 nm, power 200 mW / cm). 2 The second mixture was then subjected to a vacuum drying oven at 50°C to remove acetonitrile (0.1 Pa, 4 h) to obtain a polymer gel electrolyte.

[0079] (5) The polymer gel electrolyte was hot-pressed at 130℃ and 5 MPa for 10 min to obtain a polymer gel electrolyte membrane. The thickness of the polymer gel electrolyte membrane was controlled at 75±5 μm, and the thickness deviation was <5%.

[0080] Example 2 (1) Pretreatment of loofah sponge: Take 100 g of dried loofah sponge, add 250 mL of 2 wt% NaOH solution (pH=13), and sonicate in a 50℃ water bath for 1 h. The sonication power is 200 W and the frequency is 40 kHz for 2 h to remove pectin and hemicellulose, and obtain the third mixture. Centrifuge the third mixture and collect the precipitate. The centrifugation speed is 8000 rpm and the time is 8 min. Wash the precipitate with deionized water until pH=7.5, and vacuum dry at 70℃ for 14 h to obtain purified loofah sponge powder.

[0081] (2) Take 60 g of purified loofah sponge and add 1 L of 1.5 wt% NaHSO3 solution. Put the solution into a high-pressure reactor for sulfonation modification. The sulfonation modification temperature is 100℃ and the time is 2 h to obtain the modified product. Wash the modified product three times with an ethanol-water mixture (1:1, v / v) and dry it under vacuum at 60℃ for 12 h to obtain the modified purified loofah sponge powder (L-SL).

[0082] (3) Dissolve 1.5g of modified purified loofah powder, 1.2g of acrylic acid (AA), and 0.04g of ammonium persulfate (APS) in deionized water and ultrasonically disperse for 10 min to obtain the first mixture. The ultrasonic dispersion power is 200 W and the frequency is 20kHz. After adjusting the pH of the first mixture to 2.5, transfer it to the reaction vessel and purge with nitrogen (flow rate 40 mL / min) for 20 min to remove oxygen. Then, keep the temperature constant at 60℃ for 6 h to obtain a transparent gel product.

[0083] (4) 15g of the transparent gel product was immersed in 250mL of 0.1mol / L LiTFSI solution for 12h for ion exchange to obtain the first solution after ion exchange. The first solution after ion exchange was mixed with 0.2g of trimethylolpropane triacrylate (TMPTA) and cured under ultraviolet light for 30min (wavelength 300 nm, power 100 mW / cm). 2 The second mixture was then subjected to a vacuum drying oven at 60°C to remove acetonitrile (0.05 Pa, 4 h) to obtain a polymer gel electrolyte.

[0084] (5) The polymer gel electrolyte was hot-pressed at 160℃ and 3 MPa for 5 min to obtain a polymer gel electrolyte membrane. The thickness of the polymer gel electrolyte membrane was controlled at 70±5 μm, and the thickness deviation was <5%.

[0085] Example 3 (1) Pretreatment of loofah sponge: Take 150 g of dried loofah sponge, add 750 mL of 8 wt% NaOH solution (pH=14), and sonicate in a 70℃ water bath for 3 h. The sonication power is 200 W and the frequency is 40 kHz for 2 h to remove pectin and hemicellulose, and obtain the third mixture. Centrifuge the third mixture and collect the precipitate. The centrifugation speed is 10000 rpm and the time is 12 min. Wash the precipitate with deionized water until pH=6.5, and vacuum dry at 50℃ for 10 h to obtain purified loofah sponge powder.

[0086] (2) Take 50 g of purified loofah sponge and add it to 2 L of 2.5 wt% NaHSO3 solution. Put it into a high-pressure reactor for sulfonation modification. The sulfonation modification temperature is 140℃ and the time is 6 h to obtain the modified product. Wash the modified product three times with an ethanol-water mixture (3:1, v / v) and dry it under vacuum at 60℃ for 12 h to obtain the modified purified loofah sponge powder (L-SL).

[0087] (3) Dissolve 2.5g of modified purified loofah powder, 1.8g of acrylic acid (AA) and 0.04g of ammonium persulfate (APS) in deionized water and ultrasonically disperse for 40 min to obtain the first mixture. The ultrasonic dispersion power is 800 W and the frequency is 40kHz. After adjusting the pH of the first mixture to 4, transfer it to the reaction vessel and purge with nitrogen (flow rate 60 mL / min) for 40 min to remove oxygen. Then, keep the temperature constant at 90℃ for 18 h to obtain a transparent gel product.

[0088] (4) 45g of the transparent gel product was immersed in 750mL of 0.1mol / L LiTFSI solution for 26 h for ion exchange to obtain the first solution after ion exchange. The first solution after ion exchange was mixed with 0.25g of trimethylolpropane triacrylate (TMPTA) and cured under ultraviolet light for 30 min (wavelength 400 nm, power 300 mW / cm). 2 The second mixture was then dried in a vacuum drying oven at 40°C to remove acetonitrile (vacuum degree 2 Pa, 4 h) to obtain a polymer gel electrolyte.

[0089] (5) The polymer gel electrolyte is hot-pressed at 100℃ and 8MPa for 15min to obtain a polymer gel electrolyte membrane. The thickness of the polymer gel electrolyte membrane is controlled at 80±5 μm, and the thickness deviation is <5%.

[0090] Example 4 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as in Example 1, except that the alkaline solution used in the pretreatment of loofah sponge is KOH or Na2CO3 solution.

[0091] Example 5 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as in Example 1, except that the sulfonation reagent used is KHSO3 or Na2SO3.

[0092] Example 6 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as in Example 1, except that the carboxylic acid monomer used is MAA or MA.

[0093] Example 7 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as that in Example 1, except that the initiator used is KPS or AIBN.

[0094] Example 8 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as that in Example 1, except that the crosslinking agent used is TEDA or EGDMA.

[0095] Example 9 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as in Example 1, except that the lithium salt used is LiPF6 or LiBOB.

[0096] Example 10 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as in Example 1, except that the solvent used is GVL or EC.

[0097] Example 11 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as that in Embodiment 1, except that: thermosetting is used instead of ultraviolet curing, and the thermosetting temperature is 100°C and the time is 60 min.

[0098] Example 12 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as that in Example 1, except that: no sulfonation process is performed, and 2g of purified loofah powder, 1.5g of acrylic acid (AA), and 0.05g of ammonium persulfate (APS) are directly dissolved in deionized water and ultrasonically dispersed to obtain the first mixture.

[0099] Example 13 The preparation method of the polymer gel electrolyte membrane in this embodiment is the same as that in Example 1, except that: no ion exchange process is performed, and the transparent gel product is directly mixed with 0.2g of trimethylolpropane triacrylate (TMPTA) and cured with ultraviolet light.

[0100] Comparative Example 1 The preparation method of the polymer gel electrolyte membrane in this comparative example is the same as that in Example 1, except that there is no pretreatment process for the loofah sponge, and 60 g of dried loofah sponge is directly added to 1.5 L of NaHSO3 solution with a mass fraction of 2wt%.

[0101] Comparative Example 2 Preparation method: Polyvinylidene fluoride (PVDF) powder was added to dimethylformamide (DMF) and magnetically stirred (400 rpm) for 24 h until completely transparent (no particle residue). Heating to 60-80℃ can accelerate dissolution, but DMF volatilization should be avoided. Liquid electrolyte was slowly added dropwise to the PVDF solution, and stirring was continued for 2 h to ensure uniform dispersion. The mixed solution was poured into a clean glass plate and uniformly coated using a spatula (thickness controlled at 50-100 μm). The glass plate was placed in a vacuum drying oven (60℃, 0.1 MPa), and the temperature was gradually increased to 80℃ for 12 h until the solvent was completely removed. After drying, the film was peeled off to obtain a transparent gel electrolyte membrane.

[0102] Test Example 1 Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were performed on the polymer gel electrolyte membrane prepared in Example 1, as shown in the figure. Figure 1 and Figure 2 As shown.

[0103] in, Figure 1 SEM images of polymer gel electrolyte membranes. Figure 2 The image shows the FTIR spectrum of the polymer gel electrolyte membrane.

[0104] pass Figure 1 As can be seen, the polymer gel electrolyte membrane exhibits a honeycomb structure with a regularly arranged hexagonal pore network at the core. The honeycomb pores of the polymer gel electrolyte membrane in Example 1 can be Li + It provides multi-path diffusion channels, reduces ion migration resistance, and significantly improves conductivity; at the same time, the high porosity of the honeycomb structure can significantly reduce material density; the increased contact area between pores and electrodes can reduce interfacial impedance.

[0105] pass Figure 2 It can be seen that: Figure 2 At 3400 cm -1 The OH stretching vibration is observed at 3400 cm. -1 The main reason for this is the OH bond of the sulfonic acid group (-SO3H) and a small amount of residual lignin hydroxyl groups in the final product, confirming that the sulfonation modification successfully introduced strongly polar groups and provided a basis for Li + Transport constructs a hydrogen bond network. 1720 cm -1 The peak at this point exhibits C=O stretching vibration and appears after graft copolymerization. It corresponds to the carboxyl group (-COOH) in the grafted chain segment. Its formation mechanism is that the lignin hydroxyl group initiates the free radical graft polymerization of acrylic monomers to form the characteristic polyacrylic acid segment (-[-CH2-CH(COOH)-)). n - In the esterification reaction, the grafting agent copolymerizes with the lignin hydroxyl groups to form an ester structure, retaining the C=O double bond. The appearance of this peak proves that the copolymerization reaction between the grafting agent and the lignin hydroxyl groups was successfully completed. (1630 cm⁻¹) -1 The stretching vibration at point C=C represents the aryl ring skeletal vibration in lignin, the residual olefin in the grafted chain, and the residual TMPTA double bond crosslinking point. S=O stretching vibration (1240 cm⁻¹) -1 ) and COS stretching vibration (1040cm) -1 The asymmetric stretching vibration of S=O in sulfonic acid groups is typically between 1250 and 1280 cm⁻¹. -1 1240 cm -1 The peak at that position is a reasonable shift, corresponding to the sulfonic acid group (-SO3). -The S=O asymmetric stretching vibration of 1040 cm⁻¹. -1 The peak at that position is a result of the combined contribution of the COS bonds formed after sulfonation and the original ether bonds (C-O) of lignin, representing the sulfonic acid group -SO3. - The COS-symmetric stretching vibrations. The appearance of these two peaks indicates that the sulfonation modification was successful, and the sulfonic acid groups have been effectively introduced into the lignin system, while also suggesting the presence of Li. + The exchange is effective because the introduction of sulfonic acid groups provides the basis for ion exchange. Test Example 2 The electrolyte membranes prepared in Examples 1-13 and Comparative Examples 1-2 were used to fabricate batteries, and the performance of each group of batteries was tested; the test results are shown in Table 1. The performance of the electrolyte membranes prepared in Examples 1-13 and Comparative Examples 1-2 was tested; the test results are shown in Table 2.

[0106] The methods for preparing batteries include: (1) Preparation of positive electrode sheet Weigh NCM cathode material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP) solvent, and grind at high speed to obtain a uniform slurry (D50 particle size <10 μm). Coat the slurry uniformly onto a 12 μm aluminum foil surface, controlling the wet coating thickness to 15–25 μm (corresponding to a loading of 1–3 mg / cm²). 2 Remove solvent in an 80℃ vacuum drying oven for 12 hours, ensuring residual solvent <0.1wt%. Cold press to the target density (3.0~3.5 g / cm³). 3 Cut pieces for later use.

[0107] (2) Preparation of negative electrode sheet Mix the active material (graphite), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), add deionized water, and stir until the viscosity reaches 2000-3000 mPa·s. Coat the mixture onto an 8 μm copper foil surface (wet coating thickness 30-50 μm, corresponding to a loading of 2-5 mg / cm²). 2 Vacuum dried at 80℃ for 12 h. Cold pressed to a density of 1.6~1.8 g / cm³. 3 Cut to the same size as the positive electrode plate.

[0108] (3) Electrolyte membrane pretreatment Cut the polymer gel electrolyte membrane into a circular shape, with a diameter 1-2 mm larger than the electrode sheet, ensuring edge coverage. Clean the surface of the electrolyte membrane three times with acetonitrile using ultrasonic cleaning to remove residual solvent and particulate impurities.

[0109] (4) Battery assembly and packaging Assemble in the following order: outer shell (CR2032) → negative electrode sheet → gel electrolyte membrane → trace electrolyte (LiPF6 / EC-DMC) → positive electrode sheet → spacer → shrapnel → sealing cover.

[0110] Use a hydraulic press (pressure 50 MPa) for encapsulation to ensure that the interfacial impedance between electrodes < 100 Ω·cm 2 .

[0111] Battery performance tests include: 1. Ion conductivity (σ) test Steps: ① Sample preparation: Cut the electrolyte membrane into circular discs with a diameter of 10 mm, with a thickness measurement accuracy of ±1 μm, and place them in a drying oven (RH < 5%) for 24 h of equilibration. ② Test assembly:夹 the sample between two polished stainless steel electrodes, apply a pressure of 0.5 MPa to ensure tight contact, and place the whole in a constant temperature chamber at 25 °C. ③ EIS test: Apply a sine wave with an amplitude of 10 mV in the frequency range of 0.1 Hz - 1 MHz, and record the Nyquist plot. ④ Data processing: Fit the intercept of the high-frequency region with the real axis to obtain the bulk impedance Rb, and calculate: Ion conductivity = electrolyte membrane thickness / (bulk impedance × contact area) The contact area here = the area of the electrolyte membrane.

[0112] 2. Tensile strength & elongation at break test ① Sample preparation: Cut dumbbell-shaped specimens according to the GB / T 1040 standard (gauge section 20 × 4 mm, thickness uniform area ≥ 15 mm), with ≥ 5 parallel samples in each group. ② Pre-conditioning: Equilibrate in an environment of 23 °C / 50% RH for 48 h to eliminate the influence of temperature and humidity. ③ Mechanical test: The clamp spacing is 50 mm, and it is stretched at a constant speed of 10 mm / min until fracture, and the stress-strain curve is recorded synchronously. ④ Calculation: Tensile strength = maximum load / original cross-section (MPa) Elongation at break = (gauge length at fracture - original gauge length) / original gauge length × 100%.

[0113] 3. Interfacial impedance test ① Battery assembly: Stack Li foil (thickness 200 μm) - electrolyte membrane - Li foil in an argon glove box (H2O / O2 < 0.1 ppm), and encapsulate with a pressure of 0.5 MPa. ② Static activation: Let it stand at 25 °C for 12 h to allow the interface to fully contact. ③ EIS test: Test in the range of 100 kHz - 0.1 Hz, with an amplitude of 5 mV. ④ Data analysis: The diameter of the high-frequency semi-circle in the Nyquist plot is the interfacial impedance, and ΔR < 10% after 100 cycles is the qualified standard.

[0114] 4. Thermogravimetric test ① Pretreatment: Take 5±0.2mg of sample and pre-dry at 40℃ for 30min to remove free water. ② Heating program: N2 atmosphere (flow rate 50mL / min), increase from 25℃ to 800℃ at 10℃ / min. ③ Key parameters: Initial decomposition temperature Td5% (temperature corresponding to 5% weight loss), main decomposition peak temperature Tdmax (peak value of DTG curve), carbon residue at 800℃ (reflecting inorganic filler content). ④ Quality control: Use standard (such as Al2O3) to calibrate the temperature accuracy to ±1℃.

[0115] Electrolyte membrane performance testing includes: 1. Specific surface area & porosity testing ① Degassing treatment: The sample is degassed at 120℃ for 10 minutes. -3 ① Degassing under vacuum for 12 hours to remove adsorbate. ② N2 adsorption test: Adsorption-desorption isotherm tests were conducted in a liquid nitrogen environment (77K), with P / P0 ranging from 0.01 to 0.99. ③ Specific surface area: BET model (fitted to the relative pressure range of P / P0 = 0.05-0.30); Pore volume: adsorption amount converted to liquid volume when P / P0 = 0.99; Pore size distribution: desorption branch data analyzed by BJH method; Porosity determined by gas adsorption method.

[0116] 2. Method for testing the moisture content of the skeleton material: Take a 1g sample and place it in a 105℃ forced-air drying oven (take multiple parallel samples), and weigh it until the mass difference is <0.3mg; Moisture content = (initial mass - dried mass) / initial mass × 100% 3. Pectin content test method: Place the sample in 0.05mol / L HCl and water bath at 80℃ for 2h to release pectic acid. Then add 95% ethanol and 0.1mol / L CaCl2 to form calcium pectate precipitate. Ash the sample in a muffle furnace at 550℃ for 4h and determine the calcium content in the ash to infer the pectin content. Pectin content (%) = (ash mass × 0.92) / sample mass × 100% 4. Hemicellulose content test method: Multiple parallel samples were placed in 4% NaOH solution and extracted at 25℃ for 24h. The filter residue was cellulose + lignin, and the filtrate was dissolved hemicellulose. The filtrate was neutralized with acid and ethanol was added to precipitate the filtrate. The filtrate was then dried in an oven at 105℃ and weighed. Hemicellulose content (%) = (sample mass - filter residue mass) / sample mass × 100% - pectin content Table 1 Table 2 As can be seen from the data in Tables 1 and 2, the polymer gel electrolyte membranes prepared in the embodiments of the present invention exhibit excellent ionic conductivity, tensile strength and elongation at break. At the same time, the interfacial impedance of the polymer gel electrolyte membranes in each embodiment is significantly reduced.

[0117] Specifically, in Example 1, when all parameters are within their optimal range, the overall performance of the performance test results is the best.

[0118] In Example 2, the reduction of alkaline solution led to an increase in pectin residue, causing impurities to clog the network structure; the downsizing of sulfonation reaction parameters reduced the density of sulfonic acid groups, resulting in increased Li... + Reduced transport channels; insufficient cross-linking and curing; low sulfonic acid group density weakens intermolecular forces.

[0119] In Example 3, the increased alkaline solution leads to excessive removal of lignin; the increased sulfonation reaction parameters result in an increase in the density of sulfonic acid groups, which damages part of the loofah sponge structure; the increased cross-linking curing power leads to excessive cross-linking, thus causing a slight decrease in ionic conductivity and fluctuations in tensile strength.

[0120] Example 4 uses either KOH or Na2CO3 solution as the alkaline solution. KOH can more thoroughly remove pectin and hemicellulose, improving the efficiency of subsequent sulfonation. However, its high alkalinity leads to partial degradation of cellulose, which in turn affects ionic conductivity, tensile strength, and thermal stability. Na2CO3 solution is mildly alkaline, but it does not completely remove impurities, reducing sulfonation sites. This results in residual impurities clogging the pores, ultimately reducing ion transport efficiency and thus affecting ionic conductivity, tensile strength, and thermal stability.

[0121] Example 5 uses KHSO3 or Na2SO3 as the sulfonating agent. Among them, KHSO3 has low sulfonation efficiency and produces many byproducts. + Possibly interferes with Li + Migration, and incomplete sulfonation leading to -SO3 - The decrease in density affects ionic conductivity, tensile strength, and thermal stability; Na2SO3 has low reactivity and requires high-temperature activation, which further affects ionic conductivity, tensile strength, and thermal stability. Furthermore, during the reaction, SO3... 2- It needs to be converted to HSO3 first. - The sulfonation rate is slow, which reduces the porosity.

[0122] Example 6 uses methacrylic acid or maleic acid as a grafting agent. The flexible segments of MAA (methacrylic acid) improve elongation at break, while the single-carboxyl structure has weak ion conductivity and reduced carboxyl density. Li +The reduction in binding sites affects electrical conductivity and tensile strength. The dicarboxyl groups of MA (maleic acid) enhance ionic conductivity, while rigid segments reduce toughness. The rigid structure restricts segment movement, leading to increased brittleness, which in turn affects electrical conductivity and elongation at break.

[0123] Example 7 uses potassium persulfate or azobisisobutyronitrile (PS) as initiators. PS has good water solubility and is suitable for aqueous polymerization, but its initiation rate is too fast, resulting in a wide molecular weight distribution, an increase in short-chain polymers, and a decrease in ion channel continuity, thus affecting conductivity and tensile strength. AIBN (azobisisobutyronitrile) produces uniform free radicals, has a narrow molecular weight distribution, requires an organic solvent (such as DMF), and is close to optimal, with a moderate initiation rate and uniform polymer chain length.

[0124] Example 8 uses triethylenediamine or ethylene glycol dimethacrylate as a crosslinking agent. TEDA (triethylenediamine) is a multifunctional crosslinker with high steric hindrance, resulting in uneven crosslinking, disordered crosslinking point distribution, and hindering Li... + Migration affects electrical conductivity and tensile strength. EGDMA (ethylene glycol dimethacrylate) has uniform double bond crosslinking, but the crosslinking density may be too high. The crosslinking network is more regular, making it superior to TEDA overall, but its electrical conductivity and tensile strength are still somewhat reduced.

[0125] Example 9 uses LiPF6 or LiBOB (lithium bis(oxalatoborate)) as the lithium salt. LiPF6 has a high degree of dissociation, small anion volume, and poor thermal stability, while PF6... - It exhibits low migration resistance but is prone to decomposition at high temperatures, resulting in a decrease in electrical conductivity and tensile strength. LiBOB (lithium dioxolane borate) demonstrates good thermal stability, and its large anion (BOB) content is low. - Hindering migration, BOB - Large volume, reducing Li + The mobility is reduced, so the decrease in electrical conductivity and tensile strength is more significant.

[0126] Example 10 used GVL (γ-valerolactone) or EC (ethylene carbonate) as the first solvent. GVL (γ-valerolactone) has low toxicity, good biocompatibility, and a low dielectric constant (ε≈40), resulting in incomplete lithium salt dissociation and a lower ion concentration, thus reducing conductivity and tensile strength. EC (ethylene carbonate) has a high dielectric constant (ε=89.6) and higher volatility, promoting lithium salt dissociation, but solvent residue may affect mechanical properties; its conductivity is close to optimal, but its tensile strength is somewhat reduced.

[0127] Example 11 uses thermosetting instead of UV curing. Thermosetting (100°C) initiates homopolymerization of the crosslinking agent, forming a non-uniform network; while UV curing (365 nm) selectively activates TMPTA double bonds, resulting in more regular crosslinking. Therefore, in Example 11, the ionic conductivity, tensile strength, and elongation at break are all reduced.

[0128] In Example 12, without the sulfonation process, the hydrophilicity of the hydroxyl groups on the surface of the loofah sponge is weak and the dispersion is uneven, which leads to the collapse or blockage of the pore structure and a 14% decrease in specific surface area. At the same time, lithium ions need to overcome higher desolvation energy, which reduces the migration number and ionic conductivity. The number of grafting reaction sites is reduced and the crosslinking network is sparse, which reduces the tensile strength to 5.4 MPa.

[0129] Example 13 does not involve ion exchange; sulfonate ions retain Na+. + Or other counterions (such as H+) + Its coordination ability is weaker than that of Li. + This leads to a decrease in the binding force between sulfonic acid groups and lignin (binding energy reduced by 30-40%), resulting in a looser structure; without the introduction of LiTFSI, the residual Na2SO3 or H2SO3 is easily decomposed at high temperatures (e.g., Na2SO3 decomposition temperature <200℃), leading to a significant decrease in thermal stability (weight loss of 5% and temperature dropping to 210℃); Li + Uneven distribution leads to an increase in interfacial impedance to 47.3 Ω cm. 2 Local electric field distortion accelerates electrolyte decomposition, indirectly leading to a decrease in structural stability; the hydrophilicity of sulfonic acid groups has not been optimized, and the pore walls are prone to collapse during solvent evaporation, resulting in a further decrease in porosity (from 82% to 70%).

[0130] Comparative Example 1, without pretreatment of loofah sponge, showed a significant decrease in electrical conductivity and mechanical strength. Unremoved pectin / hemicellulose blocked the pores, reduced sulfonation sites, and increased interfacial impedance due to impurities.

[0131] Comparative Example 2 illustrates a conventional method for preparing polymer gel electrolyte membranes. While the β-crystal form of PVDF exhibits high mechanical strength, the crystalline regions hinder lithium-ion migration, resulting in low conductivity. DMF is difficult to completely remove during high-temperature drying, leading to increased interfacial resistance.

[0132] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polymer gel electrolyte membrane, characterized in that, The polymer gel electrolyte membrane comprises a polymer crosslinker with a honeycomb structure; the polymer crosslinker with a honeycomb structure comprises a backbone material, grafted chains, and covalent bonds. The skeleton material is connected to the grafted chain; the covalent bonds bridge multiple grafted chains to form a covalent cross-linked network; The skeletal material comprises cellulose and lignin; the grafted chain comprises -[-CH2-CH(COOH)-]. n -、-[-CH2-C(CH3)(COOH)-] n - -[-CH(COOH)-CH(COOH)-] n - At least one of the following, 1 ≤ n ≤ 3; the covalent bond includes carbon-carbon double bonds and / or amide bonds.

2. The polymer gel electrolyte membrane according to claim 1, characterized in that, The moisture content of the skeleton material is 4.5~5.5%; and / or, The pectin content in the skeleton material is ≤0.5wt%, and the hemicellulose content is ≤2.0wt%.

3. The polymer gel electrolyte membrane according to claim 1, characterized in that, The specific surface area of ​​the polymer gel electrolyte membrane is 400~500 m². 2 / g; and / or, The porosity of the polymer gel electrolyte membrane is 60-90%; and / or, The polymer gel electrolyte membrane has an average pore size of 150~400 nm; and / or, The polymer gel electrolyte membrane has a pore volume of 0.85~1.35 cm³. 3 / g; and / or, The thickness of the polymer gel electrolyte membrane is 70~80μm.

4. The polymer gel electrolyte membrane according to claim 1, characterized in that, The polymer gel electrolyte membrane also contains lithium salt; The polymer gel electrolyte membrane includes one or more of the following features (1) to (2): (1) Based on the total mass of the polymer gel electrolyte membrane, the lithium salt content is 10~20 wt%; (2) The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate and lithium dioxaborate.

5. A method for preparing a polymer gel electrolyte membrane, characterized in that, The preparation method includes the following steps: S1. The skeleton material, grafting agent and initiator are mixed to obtain a first mixture. The pH value of the first mixture is adjusted to 2.5~4.0 and a polymerization reaction is carried out to obtain a gel-like product. S2. The gel-like product is mixed with a first solvent to obtain a first solution; the first solution is mixed with a crosslinking curing agent and crosslinked and cured to obtain a second mixture; the second mixture is subjected to desolvation treatment to obtain a polymer gel electrolyte. S3. The polymer gel electrolyte is subjected to hot pressing treatment; The skeleton material includes cellulose and lignin.

6. The preparation method according to claim 5, characterized in that, The step of mixing the skeleton material, grafting agent, and initiator includes: S11. After drying the loofah sponge, mix it with an alkaline solution and then subject it to ultrasonic treatment to obtain the third mixture. S12. Centrifuge the third mixture to obtain a precipitate; S13. The precipitate is washed until neutral and then vacuum dried to obtain a first framework material; the first framework material is then used as the framework material to undergo the mixing treatment with the grafting agent and the initiator; or... The precipitate is washed until neutral and then vacuum dried to obtain a first skeleton material. The first skeleton material is then sulfonated, washed, and dried to obtain a modified skeleton material. The modified skeleton material is then used as the skeleton material and mixed with the grafting agent and the initiator.

7. The preparation method according to claim 5, characterized in that, The mass ratio of the skeleton material, the grafting agent, and the initiator is 1:(0.67-1.2):(0.024-0.027); and / or, The ratio of the gel-like product to the first solvent is (2g~10g):100mL; and / or, The mass ratio of the gel-like product to the crosslinking curing agent in the first solution is 1:(0.075~0.25); and / or, The water content of the gel-like product is 50-70%; and / or, The grafting agent includes at least one of acrylic acid, methacrylic acid, and maleic acid; and / or, The initiator includes at least one selected from ammonium sulfate, potassium persulfate, and azobisisobutyronitrile; and / or, The crosslinking curing agent includes at least one of trimethylolpropane triacrylate, triethylenetetramine, and ethylene glycol dimethacrylate; and / or, The first solvent includes at least one of acetonitrile, γ-butyrolactone, and ethylene carbonate.

8. The preparation method according to claim 5, characterized in that, In step S1, the mixing process includes ultrasonic dispersion, and the conditions for ultrasonic dispersion include: power of 200~800 W, frequency of 20~40 kHz, and time of 10~40 min. And / or, the polymerization reaction is carried out under an inert atmosphere, and the conditions of the polymerization reaction include: a temperature of 60~90℃ and a time of 6~18h; and / or, In step S2, the cross-linking curing is either photocuring or thermal curing, wherein the photocuring conditions include: wavelength of 300~400 nm and power of 100~300 mW / cm². 2 Alternatively, the thermosetting conditions include: a temperature of 60~120℃ and a time of 10~60 min; and / or, The desolvation treatment is a vacuum treatment, and the conditions of the vacuum treatment include: a pressure of 0.05~0.2 Pa and a temperature of 40~60℃; and / or, In step S3, the conditions for hot pressing include: temperature of 100~160℃, pressure of 3~8 MPa, and time of 5~15min.

9. The preparation method according to claim 5, characterized in that, The preparation method further includes: in step S2, mixing the first solution with lithium salt for ion exchange to obtain the first solution after ion exchange; mixing the first solution after ion exchange with the crosslinking curing agent and performing the crosslinking curing.

10. A battery, characterized in that, The battery includes an electrolyte membrane, which is a polymer gel electrolyte membrane according to any one of claims 1 to 4 and / or a polymer gel electrolyte membrane prepared by the method according to any one of claims 5 to 9.

Images