Polymer electrolyte membrane and preparation method and application thereof

Abstract

The invention relates to the technical field of electrolyte membranes, and particularly discloses a polymer electrolyte membrane as well as a preparation method and application thereof. According to the preparation method, pre-lithiated cellulose grafted polyacrylic acid is taken as a core raw material, and the quasi-solid or semi-solid nonporous polymer electrolyte membrane is prepared through combination of constant-pressure differential shear fibrosis and a multi-roller continuous differential thinning process. The non-porous membrane structure is beneficial to uniform diffusion of current, promotes uniform deposition of lithium, effectively reduces growth of lithium dendrites, and remarkably improves the ion conduction efficiency and mechanical strength of the electrolyte membrane. Besides, the film has the decomposition temperature of 300 DEG C or above, the thermal runaway temperature of the battery is greatly increased, the safety of the battery in a high-temperature environment is enhanced, meanwhile, the preparation process is environmentally friendly, high in production efficiency and suitable for large-scale production, key technical support is provided for the lithium ion battery with high initial efficiency and good cycle performance, and the preparation method is suitable for industrial production. And the commercialized application process of the solid-state battery is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolyte membranes, in particular to a polymer electrolyte membrane and a preparation method and application thereof. BACKGROUND

[0002] At present, the new energy industry is booming, and lithium ion batteries are widely used in mobile electronic devices, new energy vehicles and energy storage systems due to their high energy density and long cycle life. Solid-state battery technology has become a research hotspot because it can inhibit lithium dendrite growth and adapt to high-capacity electrode materials to improve energy density. However, the high interfacial impedance between the solid-state electrolyte and the electrode, as well as the complex and expensive preparation process, seriously restricts its commercialization process.

[0003] Quasi-solid or semi-solid electrolyte membranes are mainly composed of a polymer matrix, electrolyte salt and a small amount of plasticizer or liquid electrolyte, and their phase state is between completely solid and liquid, combining the advantages of both. On the one hand, quasi-solid or semi-solid electrolyte membranes inherit the high ionic conductivity of liquid electrolyte, which can provide an efficient channel for lithium ion transmission in the battery, ensuring the charge and discharge efficiency of the battery; on the other hand, they also have the mechanical stability of solid-state electrolytes, which are less likely to leak than liquid electrolytes, effectively avoiding the risk of internal short circuit in the battery and significantly improving the safety of the battery. At the same time, its unique rheological properties enable it to closely adhere to the electrode surface under certain conditions, improving the interface contact and reducing the interfacial impedance, thereby improving the overall performance of the battery.

[0004] At present, solution casting is the most widely used method for industrial production of quasi-solid or semi-solid electrolyte membranes. This method dissolves the polymer, electrolyte salt and additives in an organic solvent to form a uniform solution, which is then cast on a substrate, and the solvent is removed by natural evaporation or heating to obtain an electrolyte membrane. It is simple to operate, has low equipment requirements and cost advantages. However, this method has obvious defects: during solvent evaporation, pores, cavities and other defects are easily generated in the membrane, which destroys the compactness of the membrane, reduces the mechanical strength, blocks the ion conduction path and reduces the ionic conductivity; the organic solvent used is flammable, explosive and toxic, which not only increases the cost of safety control and environmental protection treatment, but also poses a serious safety hazard; and the solution casting method has a long production cycle, the solvent evaporation takes a long time, and the production efficiency is difficult to meet the large-scale market demand. Therefore, it is crucial to develop a quasi-solid or semi-solid electrolyte membrane preparation method that has high ionic conductivity, good electrode compatibility, high production efficiency and is green and environmentally friendly, which is essential for the commercialization of solid-state batteries. SUMMARY

[0005] In view of the problems of poor film compactness, low ionic conductivity, long production cycle and safety hazards existing in the preparation method of the existing quasi-solid or semi-solid electrolyte membrane, the application provides a polymer electrolyte membrane and a preparation method and application thereof. The application is prepared by crushing the pre-lithiated cellulose grafted polyacrylic acid, a binder and a solvent after shearing fiberization under constant pressure, performing film formation and thinning on a differential speed multi-roll continuous thinning hot roller press, and obtaining a non-porous semi-solid or quasi-solid electrolyte membrane. The electrolyte membrane has high ionic conductivity, high film formation efficiency, is green and environmentally friendly, and can meet the needs of future commercial high-energy-density lithium battery production.

[0006] To solve the above technical problems, the technical scheme provided by the application is:

[0007] In a first aspect, the application provides a preparation method of a polymer electrolyte membrane, wherein the polymer electrolyte membrane is a semi-solid or quasi-solid polymer electrolyte membrane, and the preparation method comprises the following steps:

[0008] S1, uniformly mixing pre-lithiated cellulose grafted polyacrylic acid, a binder and a solvent to obtain a mixture; performing constant pressure differential shearing on the mixture by means of reverse rotating paddles to fiberize the mixture, crushing the mixture to obtain fiber powder;

[0009] S2, preheating the fiber powder, continuously differentially thinning the fiber powder by means of a multi-roll, drying the fiber powder to obtain a polymer electrolyte membrane.

[0010] Compared with the prior art, the preparation method of the polymer electrolyte membrane provided by the application uses lithium-modified cellulose grafted polyacrylic acid as a core raw material. Lithiation treatment has the effects of supplementing lithium ions, reducing the irreversible capacity loss in the first charge-discharge process of the battery, and improving the energy utilization efficiency of the battery. The grafting structure of cellulose and polyacrylic acid combines the high mechanical strength of cellulose and the good ionic conductivity of polyacrylic acid, which not only guarantees the excellent mechanical stability of the electrolyte membrane during battery operation, but also provides an efficient channel for lithium ion transmission. At the same time, the multi-hydroxyl and carboxyl structures in the raw material can effectively dissociate lithium salt to form conductive Li + complexes, greatly improving the ionic conductivity of the membrane and achieving a balance between high ionic conductivity and mechanical properties.

[0011] The electrolyte membrane microstructure is precisely controlled by the combination of constant pressure differential shearing fiberization of material extruded by counter-rotating blades and multi-roll continuous differential thinning process. During the constant pressure shearing fiberization process, the relative differential shearing of the blades and the increased friction of the binder particles under the constant pressure can quickly realize the depolymerization of the binder molecules and the fiber texture of the material, and promote the formation of a uniform and ordered fiber structure. During the multi-roll continuous differential thinning process, the shearing force and tensile force generated by the differential speed of the rollers make the fibers further orient and arrange, forming a dense and uniform non-porous membrane structure. The non-porous membrane structure enables uniform diffusion of electric current, promotes uniform deposition of lithium, effectively reduces the growth of lithium dendrites, and significantly improves the ion conduction efficiency and mechanical strength of the electrolyte membrane. In addition, the membrane has a decomposition temperature of above 300℃, which significantly increases the thermal runaway temperature of the battery and enhances the safety of the battery in high-temperature environments.

[0012] The electrolyte membrane structure formed by the above process has better rheological properties, can better adhere to the electrode surface, reduce the interfacial impedance between the electrolyte membrane and the electrode, enhance the compatibility of the two, and thus improve the charge-discharge performance and cycle stability of the battery, providing key technical support for the commercialization of solid-state batteries.

[0013] Further, in S1, the temperature of the uniform mixing is not more than 5℃.

[0014] Further, in S1, a constant pressure differential shearing mixer is used to mix and fiberize the material.

[0015] Further, in S1, the blades are inner helical blades, and the blade gap is 0.4mm-0.6mm.

[0016] It should be noted that the blade gap refers to the minimum distance between the two blades when extruding the material.

[0017] The commonly used airflow mill equipment using airflow shearing principle or high-speed shearing principle of blade type high-speed mixer equipment is only suitable for dry powder materials. The constant pressure differential shearing mixer used in the present application can adapt to a wide range of material forms and can also fiberize materials containing solvents.

[0018] Specifically, in S1, the pre-lithiated cellulose grafted polyacrylic acid, the binder, and the solvent are added to the constant pressure differential shearing mixer, the rotational speed of the relative rotating main stirring blades is set to 40r / min-60r / min, the differential speed ratio of the main blades and the slave blades is 1:(2-3), and the mixing time is 30min-120min.

[0019] Specifically, the constant pressure differential shearing mixer is GH-DBM-FK025 of Suzhou Guanhong Intelligent Equipment Co., Ltd.

[0020] Furthermore, in S1, the fiberization temperature is 70°C to 90°C, the pressure is 0.3MPa to 1.0MPa, the rotation speed of the main blade is 80r / min to 100r / min, the differential speed ratio between the main blade and the slave blade is 1:(2 to 3), and the fiberization time is 4min to 10min; the ratio of the linear speeds of the rollers at each stage increases gradually along the material conveying direction, the linear speeds of the last two rollers are the same, and the roller speed ratio of the primary roller to the final roller is 1:(1.5 to 1.6).

[0021] Specifically, the ratio of the linear speeds of the rollers at each stage increases with a gradient difference of 0.15 to 0.25.

[0022] The fiberization temperature is controlled at 70℃~90℃. This temperature range can put the material in an ideal viscous flow state. Shearing under a constant pressure of 0.3MPa~1.0MPa can effectively increase the friction between the binder particles, promote the rapid depolymerization of the binder molecules, accelerate the fiberization process of the material, and make the material more fully converted into a fiber network form, ensuring the uniformity and integrity of the fiber structure; at the same time, within the above-mentioned differential ratio range, it can generate efficient and moderate shear force, which can effectively stretch and orient the material molecular chain, promote it to form a uniform and orderly fiber structure, significantly increase the specific surface area, and create favorable conditions for the subsequent full infiltration of the electrolyte and the rapid diffusion of ions, thereby improving the ion conductivity performance of the electrolyte membrane.

[0023] Furthermore, in S1, the particle size of the fiber powder is ≤100 mesh.

[0024] Furthermore, in S1, the mass percentage of the pre-lithiated cellulose grafted polyacrylic acid in the mixture is 86% to 95%, the mass percentage of the binder is 2% to 6%, and the mass percentage of the solvent is 3% to 8%.

[0025] The optimal material ratio can ensure the smooth progress of the subsequent multi-roller continuous differential thinning process while ensuring the high mechanical strength and good ion conductivity of the electrolyte membrane, which is conducive to the final formation of a dense and uniform non-porous film structure.

[0026] Furthermore, in S1, the binder is polytetrafluoroethylene; and the solvent is one or more of diethyl carbonate, dimethyl carbonate, ethylene carbonate or ethyl methyl carbonate.

[0027] Furthermore, in S1, the preparation method of the pre-lithiated cellulose grafted polyacrylic acid comprises the following steps:

[0028] The cellulose-based derivative, polyacrylic acid and lithium salt are uniformly mixed, placed in a pressure reactor, reacted at 100-200° C. for 1-3 hours under an inert atmosphere, cooled and ground to obtain the pre-lithiated cellulose grafted polyacrylic acid.

[0029] Under high temperature and high pressure, -OH in cellulose and -COOH in polyacrylic acid will undergo esterification reaction to form ester group, and the adjacent carboxyl groups on the polyacrylic acid chain will form acid anhydride through dimerization condensation. The acid anhydride structure has a strong dipolarization adsorption effect on lithium salt anions, and the anions are firmly fixed on the condensed acid anhydride. Polyhydroxy cellulose, with its abundant hydroxyl sites, can react with Li + Tight complexation greatly improves the solid solubility of lithium salt in polymer and forms a stable lithium modified polymer structure. In this structure, the adsorption of anion by acid anhydride and the adsorption of Li by cellulose ether bond (-O-) + The dipole adsorption of the lithium-modified polymer synergizes with each other, not only enhancing the intrinsic diffusion coefficient of the lithium-modified polymer, but also further improving its conductivity. At the same time, the anions are fixed by the anhydride, and their movement within the polymer chain is greatly restricted, making the polymer a Li + As an excellent conductor of conduction, the number of lithium ion transference is greatly improved.

[0030] When a small amount of solvent is introduced into the solid electrolyte, the solvent molecules will quickly react with the Li + Solvation occurs to form solvated Li + These solvated Li + It has higher migration activity, further accelerating the ion conduction process, so that the ion conductivity of the electrolyte can reach about 10 -4 S / cm, meeting the stringent requirements of high-performance batteries for electrolyte conductivity.

[0031] Furthermore, the mass ratio of the cellulose-based derivative, polyacrylic acid and lithium salt is 100:100:(5-10).

[0032] Furthermore, the cellulose-based derivative includes at least one of cellulose, carboxyalkyl cellulose, cellulose ester, cellulose ether, cellulose salt or cellulose salt derivative.

[0033] Furthermore, the lithium salt includes at least one of LiClO4, LiTFSI, LiFSI, LiF, LiBF4 or LiPF6.

[0034] Furthermore, the molecular weight of the polyacrylic acid is 450,000 to 1,000,000.

[0035] Furthermore, the inert atmosphere is provided by an inert gas, which may be nitrogen, argon, helium, or the like conventional in the art.

[0036] Furthermore, in S2, the preheating temperature is 70°C to 90°C.

[0037] In S2, the temperature of the initial roll of the multi-roll continuous differential thinning is 100℃-120℃, the temperature of the subsequent rolls is increased by 5℃ / stage-20℃ / stage, the gap of the roll is decreased by 10um / level-30um / level, the initial roll gap is set to 60um, and the pressure of each roll is 3T-6T.

[0038] The preferred multi-roll continuous differential thinning process can ensure that the material is fully compacted during the rolling process, eliminate internal pores, further improve the density and film forming property of the film, ensure the uniformity of the film thickness, reduce the ion conduction resistance and mechanical property caused by uneven film thickness or internal defects, and also consider the production efficiency and process stability.

[0039] Specifically, the roll speed of the initial roll is 8m / min-12m / min.

[0040] Specifically, in S2, a differential multi-roll continuous thinning hot roller is used for thinning.

[0041] As a specific embodiment of the present application, a differential four-roll continuous thinning hot roller is used for thinning.

[0042] Specifically, the roll speed ratio of each stage is 1:(1.2-1.4):(1.4-1.6):(1.4-1.6). The roll speed ratio of the first stage to the third stage increases gradually, and the roll speed ratio of the third stage and the fourth stage is the same.

[0043] Specifically, the differential multi-roll continuous thinning hot roller is GH-DBM-AT030 of Suzhou Guanhong Intelligent Equipment Co., Ltd.

[0044] Further, in S2, the thickness of the polymer electrolyte membrane is 10um-50um.

[0045] Further, in S2, the drying is vacuum drying, the drying temperature is 60℃-100℃, and the drying time is 10h-24h.

[0046] The present application adopts a dry process, compared with the traditional solution casting method which needs to use a large amount of flammable and explosive organic solvent, without complex solvent volatilization process, reduces the safety hidden danger and environmental protection treatment cost. At the same time, the constant pressure differential shear and multi-roll continuous differential thinning process can realize continuous production, greatly shorten the production cycle, improve the production efficiency, and be more easily realized in large-scale industrial production. In addition, in the quasi-solid-state battery, the electrolyte film can realize no organic electrolyte, and in the semi-solid-state battery, the electrolyte amount can be reduced by 2 / 3, further reducing the battery production and use cost.

[0047] In a second aspect, the present application also provides a polymer electrolyte membrane prepared by the preparation method of the polymer electrolyte membrane.

[0048] The non-porous polymer electrolyte membrane prepared by the present invention has high ionic conductivity. Its unique non-porous structure can homogenize the lithium deposition current density, avoid the growth of lithium dendrites, improve the first efficiency of the battery, and ensure the stability and cycle life of the battery during the cycle. At the same time, the preparation method is simple and avoids the use of a large amount of solvents. It is a green and environmentally friendly solid electrolyte preparation process.

[0049] In a third aspect, the present invention further provides a lithium-ion battery comprising the above-mentioned polymer electrolyte membrane.

[0050] In a fourth aspect, the present invention further provides a battery module comprising the above-mentioned lithium-ion battery.

[0051] The present invention uses pre-lithiated cellulose grafted with polyacrylic acid as the core raw material, and prepares a quasi-solid or semi-solid non-porous polymer electrolyte membrane by combining constant pressure differential shear fiberization with a multi-roller continuous differential thinning process. The non-porous membrane structure is conducive to uniform current diffusion, promotes uniform lithium deposition, effectively reduces the growth of lithium dendrites, and significantly improves the ion conduction efficiency and mechanical strength of the electrolyte membrane. In addition, the membrane has a decomposition temperature of more than 300°C, which greatly increases the thermal runaway temperature of the battery and enhances the safety of the battery in high temperature environments. At the same time, the preparation process is green and environmentally friendly, has high production efficiency, and is suitable for large-scale production. It provides key technical support for the realization of lithium-ion batteries with high first efficiency and good cycle performance, which is conducive to promoting the commercial application process of solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is the FTIR image of the pre-lithiated cellulose grafted polyacrylic acid prepared in Example 1 of the present invention;

[0053] Figure 2 This is the XPS graph of the pre-lithiated cellulose grafted polyacrylic acid prepared in Example 1 of the present invention;

[0054] Figure 3 A physical picture of the quasi-solid polymer electrolyte membrane prepared in Example 2 of the present invention;

[0055] Figure 4 This is an SEM image of the quasi-solid-state polymer electrolyte membrane prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0057] In order to better illustrate the present invention, further examples are given below.

[0058] The constant pressure differential shear mixer used in the following examples is GH-DBM-FK025 manufactured by Suzhou Guanhong Intelligent Equipment Co., Ltd. The differential speed multi-roller continuous thinning hot roller press is GH-DBM-AT030 manufactured by Suzhou Guanhong Intelligent Equipment Co., Ltd.

[0059] Example 1

[0060] This embodiment provides a method for preparing a quasi-solid-state polymer electrolyte membrane, comprising the following steps:

[0061] The pre-lithiated cellulose grafted polyacrylic acid, polytetrafluoroethylene (PTFE) powder and dimethyl carbonate prepared above were added into a constant pressure differential shear mixer in a mass ratio of 90:4:6, the water bath circulation temperature was controlled to 3°C, the rotation speed of the relatively rotating main stirring blade was 50 r / min, the differential speed ratio of the master and slave blades was 1:2, and the mixing and kneading were carried out for 40 minutes. Then the water bath temperature was raised to 80°C, a constant pressure of 0.3 MPa was applied to the kneaded powder through the cover plate, the speed of the main blade was increased to 90 r / min, the differential speed ratio of the master and slave blades was 1:2, and the kneading was carried out for 6 minutes, and then the temperature was cooled to room temperature. The fiberized material was mechanically crushed by a V-type crusher and passed through a 100-mesh sieve to obtain fiber powder; the gap between the relative blades during the fiberization process was 0.5 mm;

[0062] The fiber powder was thinned into a film by a differential multi-roller continuous thinning hot roller press. The feed temperature was 80°C, the initial roller temperature was set at 100°C, the initial roller line speed was 10m / min, the roller speed ratio was 1:1.3:1.5:1.5, the temperature of subsequent rollers increased by 10°C step by step, and the roller gap decreased step by step to 60μm, 40μm, and 20μm respectively. The roller pressure was 5T. After four-stage roller pressing, a quasi-solid polymer electrolyte membrane with a thickness of 30μm was obtained.

[0063] The preparation method of the pre-lithiated cellulose grafted polyacrylic acid comprises the following steps:

[0064] Carboxymethyl cellulose, polyacrylic acid (M V =500000) and LiTFSI were uniformly mixed in a mass ratio of 100:100:5, then placed in a pressure reactor, filled with inert argon, heated to 150°C, reacted for 1 hour, and then cooled to room temperature. The product was crushed by a ball mill to obtain pre-lithiated cellulose grafted polyacrylic acid (CMC-PAA) with a D50 of 1 to 20 μm.

[0065] The FTIR and XRS of the pre-lithiated cellulose grafted polyacrylic acid prepared in this example are as follows: Figure 1 and Figure 2 shown.

[0066] from Figure 1It can be seen that the stretching vibration peak of the C=O bond in the ester group (COO) functional group of the condensation reaction between polyacrylic acid (PAA) and carboxymethyl cellulose (CMC) is 1712 cm -1 , and the characteristic band peak of dimer reaction anhydride at 1810 cm -1 .

[0067] Example 2

[0068] This embodiment provides a method for preparing a quasi-solid-state polymer electrolyte membrane, comprising the following steps:

[0069] The pre-lithiated cellulose grafted polyacrylic acid, polytetrafluoroethylene (PTFE) powder and ethylene carbonate prepared above were added into a constant pressure differential shear mixer in a mass ratio of 86:6:8, the water bath circulation temperature was controlled to 3°C, the rotation speed of the relatively rotating main stirring blade was 50 r / min, the differential speed ratio of the master and slave blades was 1:2, and the mixing and kneading were carried out for 40 minutes. Then, the water bath temperature was raised to 80°C, a constant pressure of 0.5 MPa was applied to the kneaded powder through the cover plate, the kneading speed was increased to 85 r / min, the differential speed ratio of the master and slave blades was 1:2, and the mixture was kneaded for 5 minutes. The mixture was cooled to room temperature, and the fiberized material was mechanically crushed by a V-type crusher and passed through a 100-mesh sieve to obtain fiber powder. The gap between the relative blades during the fiberization process was 0.5 mm.

[0070] The fiber powder was thinned into a film by a differential multi-roller continuous thinning hot roller press. The feed temperature was 80°C, the initial roller temperature was set at 100°C, the initial roller line speed was 10m / min, the roller speed ratio was 1:1.3:1.5:1.5, the temperature of subsequent rollers increased by 10°C step by step, and the roller gap decreased step by step to 60μm, 40μm, and 20μm respectively. The roller pressure was 5T. After four-stage roller pressing, a quasi-solid polymer electrolyte membrane with a thickness of 30μm was obtained.

[0071] The preparation method of the pre-lithiated cellulose grafted polyacrylic acid comprises the following steps:

[0072] Carboxymethyl cellulose, polyacrylic acid (M V =500000) and LiPF6 in a mass ratio of 100:100:8 were evenly mixed, then placed in a pressure reactor, filled with inert argon gas, heated to 200°C, reacted for 1 hour, and then cooled to room temperature. The product was crushed by a ball mill to obtain pre-lithiated cellulose grafted polyacrylic acid with a D50 of 1 to 20 μm.

[0073] The physical image and SEM image of the quasi-solid polymer electrolyte membrane prepared in this example are shown in Figure 2. Figure 3 and Figure 4 shown.

[0074] Example 3

[0075] This embodiment provides a method for preparing a quasi-solid-state polymer electrolyte membrane, comprising the following steps:

[0076] The pre-lithiated cellulose grafted polyacrylic acid, polytetrafluoroethylene (PTFE) powder and ethyl methyl carbonate prepared above were added to a constant pressure differential shear mixer in a mass ratio of 93:2:5, the water bath circulation temperature was controlled to 3°C, the rotation speed of the relatively rotating main stirring blade was 50 r / min, and the differential speed ratio of the master and slave blades was 1:2. Then, the water bath temperature was raised to 80°C, a constant pressure of 0.7 MPa was applied to the kneaded powder through the cover plate, the kneading speed was increased to 80 r / min, the differential speed ratio of the master and slave blades was 1:2, kneading for 4 minutes, and then cooled to room temperature. The fiberized material was mechanically crushed by a V-type crusher and passed through a 100-mesh sieve to obtain fiber powder; the gap relative to the blades during the fiberization process was 0.5 mm;

[0077] The fiber powder was thinned into a film by a differential multi-roller continuous thinning hot roller press. The feed temperature was 80°C, the initial roller temperature was set at 100°C, the initial roller line speed was 10m / min, the roller speed ratio was 1:1.3:1.5:1.5, the temperature of subsequent rollers increased by 10°C step by step, and the roller gap decreased step by step to 60μm, 40μm, and 20μm respectively. The roller pressure was 5T. After four-stage roller pressing, a quasi-solid polymer electrolyte membrane with a thickness of 30μm was obtained.

[0078] The preparation method of the pre-lithiated cellulose grafted polyacrylic acid comprises the following steps:

[0079] Cellulose, polyacrylic acid (M V =500000) and LiTFSI in a mass ratio of 100:100:7 were uniformly mixed, then placed in a pressure reactor, filled with inert argon, heated to 100°C, reacted for 3 hours, and then cooled to room temperature. The product was crushed by a ball mill to obtain pre-lithiated cellulose grafted polyacrylic acid with a D50 of 1 to 20 μm.

[0080] Example 4

[0081] This embodiment provides a method for preparing a quasi-solid-state polymer electrolyte membrane, comprising the following steps:

[0082] The pre-lithiated cellulose grafted polyacrylic acid, polytetrafluoroethylene (PTFE) powder and diethyl carbonate prepared above were added to a constant pressure differential shear mixer in a mass ratio of 93:4:3, the water bath circulation temperature was controlled to 3°C, the rotation speed of the relatively rotating main stirring blade was 50 r / min, the differential speed ratio of the master and slave blades was 1:2, and the mixing and kneading were carried out for 40 minutes. Then, the water bath temperature was raised to 80°C, a constant pressure of 1.0 MPa was applied to the kneaded powder through the cover plate, the kneading speed was increased to 100 r / min, the differential speed ratio of the master and slave blades was 1:2, and the mixture was kneaded for 4 minutes. The mixture was cooled to room temperature, and the fiberized material was mechanically crushed by a V-type crusher and passed through a 100-mesh sieve to obtain fiber powder. The gap between the relative blades during the fiberization process was 0.5 mm.

[0083] The fiber powder was thinned into a film using a differential multi-roller continuous thinning hot roller press. The initial roller temperature was set at 100°C, the initial roller line speed was 10 m / min, the roller speed ratio was 1:1.3:1.5:1.5, the subsequent roller temperatures were increased by 10°C step by step, and the roller gap was reduced step by step to 60 μm, 40 μm, and 20 μm, respectively. The roller pressure was 5T. After four stages of roller pressing, a quasi-solid polymer electrolyte membrane with a thickness of 30 μm was obtained.

[0084] The preparation method of the pre-lithiated cellulose grafted polyacrylic acid comprises the following steps:

[0085] Cellulose, polyacrylic acid (M V =500000) and LiPF6 were evenly mixed in a mass ratio of 100:100:6, and then placed in a pressure reactor, filled with inert argon gas, heated to 130°C, reacted for 2 hours, and then cooled to room temperature. The product was crushed by a ball mill to obtain pre-lithiated cellulose grafted polyacrylic acid (CMC-PAA) with a D50 of 1 to 20 μm.

[0086] The above embodiment may also adopt other cellulose-based derivatives and lithium salts, other raw material ratios, and reaction temperatures and times defined in the present invention. As long as they are within the range defined in the present invention, they can achieve technical effects equivalent to those of the pre-lithiated cellulose grafted polyacrylic acid prepared above.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing a quasi-solid-state polymer electrolyte membrane. The only difference from Example 1 is that the pre-lithiated carboxymethyl cellulose grafted polyacrylic acid is replaced with an equal amount of pre-lithiated carboxymethyl cellulose. The preparation steps of the pre-lithiated carboxymethyl cellulose are as follows:

[0089] Carboxymethyl cellulose and LiTFSI were mixed uniformly in a mass ratio of 100:5, then placed in a pressure reactor, heated to 150°C, reacted for 1 hour, and then cooled to room temperature. The product was crushed with a ball mill to obtain pre-lithiated carboxymethyl cellulose with a D50 of 1 to 20 μm.

[0090] The pre-lithiated carboxymethyl cellulose prepared above was used to prepare a quasi-solid-state polymer electrolyte membrane in exactly the same manner as in Example 1, which will not be described in detail here.

[0091] Comparative Example 2

[0092] This comparative example provides a method for preparing a quasi-solid-state polymer electrolyte membrane. The only difference from Example 1 is that the pre-lithiated carboxymethyl cellulose grafted polyacrylic acid is replaced with an equal amount of pre-lithiated polyacrylic acid. The preparation steps of the pre-lithiated polyacrylic acid are as follows:

[0093] Polyacrylic acid and LiTFSI were mixed uniformly in a mass ratio of 100:5, then placed in a pressure reactor, filled with inert argon, heated to 150°C, reacted for 1 hour, and then cooled to room temperature. The product was crushed in a ball mill to obtain pre-lithiated polyacrylic acid with a D50 of 1 to 20 μm.

[0094] The above-prepared pre-lithiated polyacrylic acid was used to prepare a quasi-solid-state polymer electrolyte membrane in exactly the same manner as in Example 1, which will not be described in detail here.

[0095] Comparative Example 3

[0096] This comparative example provides a method for preparing a quasi-solid-state polymer electrolyte membrane. The only difference from Example 1 is that the pre-lithiated carboxymethyl cellulose grafted polyacrylic acid is replaced with an equal amount of pre-lithiated carboxymethyl cellulose grafted polyphenylene sulfide. The preparation steps of the pre-lithiated carboxymethyl cellulose grafted polyphenylene sulfide are as follows:

[0097] Carboxymethyl cellulose, polyphenylene sulfide and LiTFSI were mixed uniformly in a mass ratio of 100:100:5, then placed in a pressure reactor, filled with inert argon, heated to 150°C, reacted for 1 hour, and then cooled to room temperature. The product was crushed with a ball mill to obtain pre-lithiated carboxymethyl cellulose grafted polyphenylene sulfide with a D50 of 1 to 20 μm.

[0098] The above-prepared pre-lithiated carboxymethyl cellulose grafted polyphenylene sulfide was used to prepare a quasi-solid-state polymer electrolyte membrane in exactly the same manner as in Example 1, which will not be described in detail here.

[0099] Application Examples

[0100] The quasi-solid polymer electrolyte membranes prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were assembled into CR2025 button-type half-cells for electrochemical performance testing. The specific steps are as follows:

[0101] The quasi-solid polymer electrolyte membrane obtained above was placed in a 60° C. oven and dried for 2 h. The membrane was cut into circular electrodes with a diameter of 19 mm using a cutting machine for later use.

[0102] A 15mm diameter, 1mm thick lithium metal sheet served as the counter electrode, and a 15mm diameter, 1mm thick lithium iron phosphate sheet served as the positive electrode. The sheets were dried in a vacuum oven at 100°C for 24 hours and then assembled in an argon glove box with strict oxygen and humidity control. The quasi-solid-state membrane was placed between the 15mm diameter lithium metal sheet and the positive electrode. A 1 mol / L solution of LiPF6 dissolved in ethylene carbonate and ethyl methyl carbonate (3:7 volume ratio) was used as the electrolyte. 5μL of this electrolyte was added to wet the electrode. The assembled button cell was left to rest for 12 hours before being charged to 3.6V at 0.1C (1C corresponds to a specific capacity of 170mAh / g) on ​​a LAND charge-discharge tester. Charging continued at a constant voltage of 3.6V until the charge current fell below 0.05C. After a 5-minute rest, the cell was discharged at 0.1C to 2.5V. The ratio of the discharge specific capacity to the charge specific capacity is the initial charge-discharge efficiency. The results are shown in Table 1.

[0103] CR2025 button cells were assembled in an argon glove box under strict oxygen and humidity control. A 19 mm diameter quasi-solid-state polymer electrolyte membrane disc was placed between polished 15 mm diameter stainless steel electrodes. The assembled button cells were subjected to electrochemical impedance spectroscopy (EIS) measurements using a PARSTAT electrochemical workstation with a frequency range of 1 MHz to 0.1 Hz and an amplitude of 10 mV. The membrane resistance was determined by analyzing the intersection of the high-frequency region of the Nyquist plot with the real axis. The test was performed at a strictly controlled temperature of 25°C and an assembly pressure of 0.5 MPa to eliminate the effects of temperature and poor interfacial contact. The bulk resistance of the membrane was calculated, combined with the membrane thickness and effective contact area, to calculate the ionic conductivity. The results are shown in Table 1.

[0104] Table 1

[0105] Discharge capacity (mAh / g) First charge and discharge efficiency (%) <![CDATA[电导率(S·cm -1 )]]> Example 1 165.0 97.5 2.0*10 -4 ]]> Example 2 160.3 97.2 <![CDATA[1.2*10 -4 ]]> Example 3 162.7 96.3 <![CDATA[1.8*10 -4 ]]> Example 4 158.6 96.1 <![CDATA[0.7*10 -4 ]]> Comparative Example 1 140.1 86.5 <![CDATA[1.1*10 -5 ]]> Comparative Example 2 142.2 87.8 <![CDATA[1.5*10 -5 ]]> Comparative Example 3 138.7 85.2 <![CDATA[7.8*10 -6 ]]>

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a polymer electrolyte membrane, wherein the polymer electrolyte membrane is a semi-solid or quasi-solid polymer electrolyte membrane, characterized in that: The preparation method comprises the following steps: S1, uniformly mixing pre-lithiated cellulose grafted polyacrylic acid, a binder, and a solvent to obtain a mixture; subjecting the mixture to constant pressure differential shearing by counter-rotating blades to fiberize and crush the mixture to obtain fiber powder; S2, preheating the fiber powder, and then thinning it with multiple rollers at a continuous differential speed, and drying it to obtain a polymer electrolyte membrane.

2. The method for preparing a polymer electrolyte membrane according to claim 1, wherein: In S1, the temperature of the mixing is not more than 5°C; and / or In S1, a constant pressure differential shear mixer is used to mix and fiberize the materials; and / or In S1, the blades are inner propeller blades, and the blade gap is 0.4 mm to 0.6 mm; and / or In S1, the fiberization temperature is 70° C. to 90° C., the pressure is 0.3 MPa to 1.0 MPa, the rotation speed of the main blade is 80 r / min to 100 r / min, and the differential speed ratio between the main blade and the slave blade is 1:(2 to 3); the ratio of the linear speeds of the rollers of each stage increases gradually along the material conveying direction, the linear speeds of the last two rollers are the same, and the roller speed ratio of the primary roller to the final roller is 1:(1.5 to 1.6); the fiberization time is 4 min to 10 min; and / or In S1, the particle size of the fiber powder is ≤100 mesh.

3. The method for preparing a polymer electrolyte membrane according to claim 1, wherein: In S1, the mass percentage of the pre-lithiated cellulose grafted polyacrylic acid in the mixture is 86% to 95%, the mass percentage of the binder is 2% to 6%, and the mass percentage of the solvent is 3% to 8%.

4. The method for preparing a polymer electrolyte membrane according to claim 1, wherein: In S1, the binder is polytetrafluoroethylene; and the solvent is one or more of diethyl carbonate, dimethyl carbonate, ethylene carbonate, or ethyl methyl carbonate.

5. The method for preparing a polymer electrolyte membrane according to claim 1, wherein: In S1, the preparation method of the pre-lithiated cellulose grafted polyacrylic acid comprises the following steps: The cellulose-based derivative, polyacrylic acid and lithium salt are uniformly mixed, placed in a pressure reactor, reacted at 100-200° C. for 1-3 hours under an inert atmosphere, cooled and ground to obtain the pre-lithiated cellulose grafted polyacrylic acid.

6. The method for preparing a polymer electrolyte membrane according to claim 5, wherein: The mass ratio of the cellulose-based derivative, polyacrylic acid and lithium salt is 100:100:(5-10); and / or The cellulose-based derivative comprises at least one of cellulose, carboxyalkyl cellulose, cellulose ester, cellulose ether, cellulose salt or cellulose salt derivative; and / or The lithium salt comprises at least one of LiClO4, LiTFSI, LiFSI, LiF, LiBF4 or LiPF6; and / or The molecular weight of the polyacrylic acid is 450,000 to 1,000,000.

7. The method for preparing a polymer electrolyte membrane according to claim 1, wherein: In S2, the preheating temperature is 70°C to 90°C; and / or In S2, the temperature of the initial roller of the multi-roller continuous differential thinning is 100°C to 120°C, the temperature of the subsequent rollers increases step by step at 5°C / step to 20°C / step, the roller gap decreases step by step at 10μm / step to 30μm / step, the primary roller gap is set to 60μm, and the pressure of each roller is 3T to 6T; the ratio of the linear speed of each roller increases gradually along the material conveying direction, the linear speed of the last two rollers is the same, and the gradient range of the roller speed ratio is 1:(1 to 1.6).

8. A polymer electrolyte membrane, characterized in that The polymer electrolyte membrane is prepared by the method for preparing the polymer electrolyte membrane according to any one of claims 1 to 7.

9. A lithium-ion battery, characterized in that: Comprising the polymer electrolyte membrane according to claim 8.

10. A battery module, characterized in that: Including the lithium ion battery according to claim 9.

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