CN113328203B

CN113328203B - Gel electrolyte diaphragm, preparation method thereof and lithium ion battery

Info

Publication number: CN113328203B
Application number: CN202110431130.0A
Authority: CN
Inventors: 余津福; 符宽; 谢才兴; 甘婷; 赵云龙; 于子龙; 陈杰
Original assignee: Huizhou Liwinon Energy Technology Co Ltd
Current assignee: Huizhou Liwinon Energy Technology Co Ltd
Priority date: 2021-04-21
Filing date: 2021-04-21
Publication date: 2023-01-31
Anticipated expiration: 2041-04-21
Also published as: CN113328203A

Abstract

The invention provides a gel electrolyte diaphragm, a preparation method and a lithium ion battery, which comprise the following raw materials, by weight, 0.5-1 part of lignocellulose, 2-4 parts of polyethylene oxide and 0.5-1 part of polyacrylic acid. The preparation method comprises the following steps: step (A): grinding lignocellulose in a solvent to obtain a first solution; step (B): putting polyoxyethylene into a solvent to obtain a second solution; a step (C): adding polyacrylic acid into a solvent to obtain a third solution; step (D): mixing and stirring the first solution and the second solution to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; step (F): and soaking the polymer-based membrane in an electrolyte to obtain the gel electrolyte membrane. The prepared gel electrolyte diaphragm has excellent electrochemical performance, excellent liquid absorption rate and liquid retention rate and obvious inhibition effect on lithium dendrites.

Description

Gel electrolyte diaphragm, preparation method thereof and lithium ion battery

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a gel electrolyte diaphragm, a preparation method of the gel electrolyte diaphragm and a lithium ion battery.

Background

Currently, many materials with high energy density and power density are difficult to apply due to the use of liquid organic electrolytes in lithium ion batteries. In addition, since a liquid electrolyte is used, the battery is liable to generate heat accumulation in the event of short circuit or local overheating, or even to cause explosion. Therefore, the development of a safer battery system is urgently needed.

At this time, gel electrolytes and solid electrolytes have been proposed again for research. Among them, the solid polymer electrolyte has a long way to be used in industrial applications because the ionic conductivity of the battery is still not ideal when used in a room temperature environment. Furthermore, the problem of the interface between the solid polymer electrolyte and the electrode is in need of solution. Gel electrolytes have the advantages of good ionic conductivity of liquid electrolytes and excellent safety of solid electrolytes, and are now the focus of research by researchers. The gel electrolyte is a gel-state membrane formed by dissolving salt in a high molecular weight polymer matrix, and is widely applied to electrochemical devices such as lithium ion batteries. The ionic conductive phase in the gel electrolyte has the transmission property equivalent to that of certain liquid ionic solution, and has the advantages of transparency, no solvent, light weight, good flexibility, strong film forming capability, easy processing and the like.

For the research on gel-state polymer membranes, various attempts have been made, such as blending modification of different polymers, addition of inorganic particles to a single-ion conductive polymer, or addition of ionic liquid to a polymer to improve the ionic conductivity of the polymer, but gel electrolyte membranes still have the phenomena of poor electrochemical performance, easy occurrence of lithium dendrites, and the like, and thus a technical solution for solving the above problems is urgently needed.

Disclosure of Invention

The invention aims to: aiming at the defects of the prior art, the gel electrolyte diaphragm is provided, has excellent electrochemical performance, is green and environment-friendly, and has good inhibition effect on lithium dendrites.

In order to achieve the purpose, the invention adopts the following technical scheme:

a gel electrolyte diaphragm comprises the following raw materials, by weight, 0.5-1 part of lignocellulose, 2-4 parts of polyethylene oxide and 0.5-1 part of polyacrylic acid. By setting the mass ratio of the lignocellulose to the polyoxyethylene to the polyacrylic acid, the prepared gel electrolyte diaphragm has better and more complete electrochemical performance, lithium dendrite inhibition effect and film forming property.

The invention also aims to provide a preparation method of the gel electrolyte membrane, which utilizes polyacrylic acid with rich carboxyl functional groups to be capable of interacting with polyethylene oxide containing hydroxyl functional groups, firstly adds the polyethylene oxide into the cellulose with rich hydroxyl and carboxyl after grinding, then adds the polyacrylic acid to enable the three to be mutually crosslinked, locks part of the polyethylene oxide, increases the amorphous phase of the polyethylene oxide, is beneficial to the transfer of interchain and intrachain ions, and inhibits the piercing of lithium dendrites.

a method for preparing a gel electrolyte separator, comprising the steps of: step (A): putting the lignocellulose in parts by weight into a solvent for grinding treatment to obtain a first solution; step (B): putting the polyethylene oxide with the weight parts into a solvent to obtain a second solution; step (C): putting the polyacrylic acid in parts by weight into a solvent to obtain a third solution; step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane.

Wood fiberThe vitamin is an organic fiber substance obtained by chemical treatment and mechanical processing of natural renewable wood, and has no toxicity, odor, pollution and radioactivity. Polyethylene oxide (PEO), also known as polyethylene oxide, is a crystalline, thermoplastic polymer. The molecular weight of the industrial products can vary within a wide range. Products with a relative molecular mass of 200 to 20000 are called polyethylene glycols (PEG), which are viscous liquids or waxy solids: molecular relative mass 1x10 ⁵ ～1x10 ⁶ The product of (a) is called polyethylene oxide as a white powder. Polyacrylic acid is a water-soluble polymer, namely acrylic acid homopolymer with the chemical formula [ C ₃ H ₄ O ₂ ]n is weakly acidic and contains abundant carboxyl functional groups. The molecular formula of the polyoxyethylene is- (-O-CH ₂ -CH ₂ -) n-with ether linkage as the main functional group at 1100cm ^-1 Has obvious characteristic peaks. As shown in FIG. 2, unlike the PEO curve, the polyethylene oxide-polyacrylic acid-lignocellulose polymer was at 1730cm ^-1 There is a strong characteristic absorption peak, which is the characteristic absorption peak of the ester group, indicating that the-COOR functional group exists in the system polymer. It is demonstrated that the addition of PAA forms a related complex with PEO. As shown in fig. 3, the properties of the formed complex are different from those of any original substance, including crystallinity, thermal stability, morphology of precipitate, and the like, wherein the presence of cellulose reduces the crystallinity of the polymer electrolyte, facilitating lithium ion transport.

As an improvement of the preparation method of the gel electrolyte membrane, the lignocellulose is needle-leaved lignocellulose. The wood fiber includes needle wood fiber, broad leaf wood fiber, and grass wood fiber. The needle-leaf wood fiber has long fiber, tight tissue structure, less content of foreign cells, and loss of the foreign cells in the chemical pulp during washing, so the pulp has good quality and the formed paper has strong mechanical property. We have chosen softwood fibres as the support layer for the membrane, thus ensuring the complete structure of the membrane.

As an improvement of the preparation method of the gel electrolyte membrane of the present invention, the solvent is deionized water. The deionized water is used as a solvent, so that other groups can be avoided, and the reaction is ensured to be carried out.

As an improvement of the preparation method of the gel electrolyte membrane, the grinding treatment in the step (A) is that the lignocellulose and the solvent are put into a ball milling tank to be ball milled for 0.5 to 2 hours at the ball-to-material ratio of 40 to 60 and the rotating speed of 1000 to 1200 r/min. The fiber membrane is acted by a certain force through ball milling, so that the cellulose with abundant carboxyl and carboxyl functional groups is obtained. As shown in FIG. 4, it can be clearly observed under an electron microscope that the softwood fibers are densely and compactly arranged, and after ball milling, the softwood fibers have different lengths and are intertwined with each other, and the finest fibers are only about dozens of nanometers.

As an improvement of the preparation method of the gel electrolyte membrane according to the present invention, the curing in the step (E) is specifically to heat the liquid while stirring the bottom of the liquid. The liquid is heated to evaporate water, and the bottom of the liquid is stirred, so that the generation of bubbles and the influence on the integrity of a formed film can be avoided.

As an improvement of the preparation method of the gel electrolyte membrane, the heating temperature is 40-60 ℃. The film is easy to be pasted and damaged due to overhigh temperature; the film forming effect is affected by too low temperature and too slow film forming speed.

As an improvement of the preparation method of the gel electrolyte membrane, the step (F) is also preceded by a drying treatment, wherein the drying treatment is to dry the polymer-based membrane on a drying table at 90-100 ℃ for 1-3h. The drying treatment enables the polymer base film to remove residual moisture, and the moisture is easy to influence the combination of the subsequent electrolyte and the battery diaphragm and influence the liquid absorption rate and the liquid holding rate.

As an improvement of the preparation method of a gel electrolyte membrane according to the present invention, the soaking time in the step (F) is 0.5 to 2 hours. The soaking time is controlled, so that the electrolyte is fully combined with the diaphragm, and the high liquid absorption rate is ensured. As shown in fig. 5, the polymer sheet after soaking the polyethylene oxide-polyacrylic acid-lignocellulose polymer in the electrolyte for 1h was sufficiently wet and the electrolyte was full.

Still another object of the present invention is to: provided is a lithium electronic battery which can suppress lithium dendrites, has a long service life, and satisfies daily requirements.

a lithium ion battery comprises a positive plate, a negative plate and the gel electrolyte membrane, wherein the gel electrolyte membrane is arranged between the positive plate and the negative plate.

Compared with the prior art, the beneficial effects of the invention include but are not limited to:

(1) According to the invention, polyacrylic acid, polyoxyethylene and wood fiber are mutually crosslinked, part of polyoxyethylene is locked, the amorphous phase of polyoxyethylene is increased, the transfer of interchain and intrachain ions is facilitated, and the penetration of lithium dendrite is inhibited;

(2) The gel electrolyte membrane provided by the invention uses lignocellulose as a supporting layer, so that the complete structure of the membrane is ensured, and the membrane has excellent film forming property and dimensional stability;

(3) The gel electrolyte membrane has high liquid absorption rate (281.2 percent) and high liquid retention rate, and can still maintain about 120 percent of liquid absorption rate after standing for 24 hours at room temperature.

(4) The gel electrolyte diaphragm has excellent electrochemical performance in the charge-discharge process, and the specific cyclic discharge capacity under the 1C multiplying power is about 141 mAh/g.

(5) The gel electrolyte membrane has obvious inhibition effect on lithium dendrite. At a current density of 2mA/cm ² At around 78h in the liquid electrolyte battery, the polarization voltage has reached 0.4V or more, indicating that the separator has been pierced by lithium dendrites. And when the gel electrolyte battery is circulated for 1200h, the polarization voltage of the gel electrolyte battery is always 0.004V loitering without great change.

Drawings

Fig. 1 is a schematic structural view of a gel electrolyte separator prepared in example 1 of the present invention after being soaked in a lithium ion solution.

FIG. 2 is a graph of Fourier infrared reflectance spectra of polyethylene oxide and polyethylene oxide-polyacrylic acid-lignocellulosic polymers.

FIG. 3 is a graph comparing the X-ray diffraction patterns of polyethylene oxide and a polyethylene oxide acetylene-polyacrylic acid-lignocellulose polymer.

FIG. 4 is a scanning electron microscope image of lignocellulose after ball milling for one hour.

Fig. 5 is an optical diagram of a polyoxyethylene-polyacrylic acid-lignocellulose polymer after soaking in an electrolyte for one hour.

Fig. 6 is a graph comparing the cycle charge and discharge efficiency at 1C rate of the battery prepared in comparative example 1 and the battery prepared in example 1.

Fig. 7 is a voltage-time graph of the battery prepared in comparative example 1 and the battery prepared in example 1.

Fig. 8 is a schematic flow diagram of the present invention for making a polymer-based film.

Fig. 9 is a schematic flow chart of the preparation of a gel electrolyte separator based on a polymer-based membrane according to the present invention.

Detailed Description

1. A method for preparing a gel electrolyte separator, comprising the steps of: step (A): putting lignocellulose into a solvent for grinding treatment to obtain a first solution; step (B): putting polyoxyethylene into a solvent to obtain a second solution; a step (C): adding polyacrylic acid into a solvent to obtain a third solution; step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; a step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane. As shown in fig. 1, an interconnected structure formed by mutually crosslinking polyethylene oxide-polyacrylic acid-lignocellulose is distributed in the gel electrolyte membrane, and lithium ions are embedded in the interconnected structure. As shown in fig. 8, the flow chart of the preparation of polymer-based film by gathering together ethylene oxide, polypropylene and lignocellulose is shown. Fig. 9 is a schematic view showing a process for preparing a gel electrolyte separator from a polymer base film.

A method for preparing gel electrolyte diaphragm includes adding polyethylene oxide to ground cellulose with rich hydroxyl and carboxyl, adding polyacrylic acid to make three cross-linked, locking part of polyethylene oxide, increasing amorphous phase of polyethylene oxide, benefiting to transfer of ions between chains and in chains and suppressing piercing of lithium dendritic crystal.

Further, the lignocellulose is coniferous lignocellulose. The wood fiber includes needle wood fiber, broad leaf wood fiber, and grass wood fiber. The needle-leaf wood fiber has long fiber, tight tissue structure, less content of foreign cells, and loss of the foreign cells in the chemical pulp during washing, so the pulp has good quality and the formed paper has strong mechanical property. We have chosen softwood fibres as the support layer for the membrane, thus ensuring the complete structure of the membrane.

Further, the solvent is deionized water. The water is used as a solvent, so that other groups can be introduced, and the reaction is ensured to be carried out.

Further, the grinding treatment in the step (A) is that the lignocellulose and the solvent are put into a ball milling tank to be ball milled for 0.5 to 2 hours at the ball-to-material ratio of 40 to 60 and the rotating speed of 1000 to 1200 r/min. The fiber membrane is acted by a certain force through ball milling, so that the cellulose with abundant carboxyl and carboxyl functional groups is obtained. As shown in FIG. 4, it can be clearly observed under electron microscope that the softwood fibers are densely and compactly arranged, and after ball milling, the softwood fibers have different lengths and are intertwined with each other, and the finest fibers are only about tens of nanometers.

Further, the mass ratio of the lignocellulose to the polyethylene oxide to the polyacrylic acid is 0.5-1:2-4:0.5-1. By setting the mass ratio of the wood cellulose, the polyoxyethylene and the polyacrylic acid, the prepared gel electrolyte diaphragm has better film forming property and is more complete.

Further, the solidifying in the step (E) is specifically to heat the liquid while stirring the bottom of the liquid. The heating makes the liquid evaporate water, stirs the liquid bottom and can avoid having the bubble to produce, influences the integrality of filming.

Further, the heating temperature is 40-60 ℃. The film is easy to be pasted and damaged due to overhigh temperature; the film forming effect is affected by too low temperature and too slow film forming speed.

Further, the step (F) is preceded by a drying treatment, wherein the drying treatment is to dry the polymer-based film on a drying table at 90-100 ℃ for 1-3h. The drying treatment enables the polymer base membrane to remove residual moisture, and the moisture is easy to influence the combination of subsequent electrolyte and a battery diaphragm and influence the liquid absorption rate and the liquid holding rate.

Further, the soaking time in the step (F) is 0.5-2h. The soaking time is controlled, so that the electrolyte and the diaphragm are fully combined, and the high liquid absorption rate is ensured.

2. A gel electrolyte membrane has high liquid absorption rate and high liquid retention rate, excellent electrochemical performance and obvious inhibition effect on lithium dendrite. As shown in fig. 1, the structure diagram of the gel electrolyte membrane shows that polyacrylic acid, polyethylene oxide and wood fiber are cross-linked to form an interconnected structure, and lithium ions can be fully inserted into the interconnected structure.

The gel electrolyte diaphragm is prepared by the preparation method of the gel electrolyte diaphragm.

According to the invention, polyacrylic acid, polyoxyethylene and wood fiber are mutually crosslinked, part of polyoxyethylene is locked, the amorphous phase of polyoxyethylene is increased, the transfer of interchain and intrachain ions is facilitated, and the penetration of lithium dendrite is inhibited;

the gel electrolyte membrane provided by the invention uses lignocellulose as a supporting layer, so that the complete structure of the membrane is ensured, and the membrane has excellent film forming property and dimensional stability;

the gel electrolyte membrane has high liquid absorption rate (281.2 percent) and high liquid retention rate, and can still maintain about 120 percent of liquid absorption rate after standing for 24 hours at room temperature.

The gel electrolyte membrane has obvious inhibition effect on lithium dendrite. At a current density of 2mA/cm2, the polarization voltage of the liquid electrolyte battery reached 0.4V or more at around 78h, indicating that the separator had been pierced by lithium dendrites. And the polarization voltage of the gel electrolyte battery is always 0.004V loitering when the gel electrolyte battery is circulated for 1200h, and the change is not too large.

3. A lithium ion battery comprises a positive plate, a negative plate and a gel electrolyte diaphragm arranged between the positive plate and the negative plate, wherein the gel electrolyte diaphragm is any one of the gel electrolyte diaphragms.

The active material layer coated on the current collector of the positive plate can be, but is not limited to, an active material of a chemical formula such as Li _a Ni _x Co _y M _z O _2-b N _b (wherein 0.95. Ltoreq. A.ltoreq.1.2>0,y ≧ 0, z ≧ 0, and x + y + z =1,0 ≦ b ≦ 1, M is selected from one or more of Mn, al in combination, N is selected from one or more of F, P, S in combination), the positive electrode active material may also be a combination including but not limited to LiCoO ₂ 、LiNiO ₂ 、LiVO ₂ 、LiCrO ₂ 、LiMn ₂ O ₄ 、LiCoMnO ₄ 、Li ₂ NiMn ₃ O ₈ 、LiNi _0.5 Mn _1.5 O ₄ 、LiCoPO ₄ 、LiMnPO ₄ 、LiFePO ₄ 、LiNiPO ₄ 、LiCoFSO ₄ 、CuS ₂ 、FeS ₂ 、MoS ₂ 、NiS、TiS ₂ And the like. The positive electrode active material may also be modified, and the method of modifying the positive electrode active material should be known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, etc., and the material used in the modification process may be one or more of Al, B, P, zr, si, ti, ge, sn, mg, ce, W, etc. And the positive electrode current collector is generally a structure or a part for collecting current, and the positive electrode current collector may be any material suitable for use as a positive electrode current collector of a lithium ion battery in the art, for example, the positive electrode current collector may include, but is not limited to, a metal foil and the like, and more specifically, may include, but is not limited to, an aluminum foil and the like.

The active material layer coated on the current collector of the negative plate can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector is generally a structure or a part for collecting current, and the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.

The electrolyte includes an organic solvent, an electrolyte lithium salt, and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte ₆ And/or LiBOB; or LiBF used in low-temperature electrolyte ₄ 、LiBOB、LiPF ₆ At least one of; also can be LiBF adopted in anti-overcharging electrolyte ₄ 、LiBOB、LiPF ₆ At least one of, liTFSI; may also be LiClO ₄ 、LiAsF ₆ 、LiCF ₃ SO ₃ 、LiN(CF ₃ SO ₂ ) ₂ At least one of (1). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte ₂ At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.

The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.

Example 1:

a lithium ion battery comprises a positive plate, a negative plate and a gel electrolyte diaphragm arranged between the positive plate and the negative plate;

(1) Preparation of gel electrolyte separator

A method for preparing a gel electrolyte separator, comprising the steps of: step (A): putting lignocellulose into a solvent for grinding treatment to obtain a first solution; step (B): putting polyoxyethylene into a solvent to obtain a second solution; a step (C): putting polyacrylic acid into a solvent to obtain a third solution; a step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; a step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane.

Specifically, the lignocellulose is coniferous lignocellulose.

Specifically, the solvent is deionized water.

Specifically, the grinding treatment in the step (a) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 1h at a ball-material ratio of 50.

Specifically, the mass ratio of lignocellulose, polyethylene oxide and polyacrylic acid is 1:4:1.

Specifically, the curing in the step (E) is to heat the liquid while stirring the bottom of the liquid.

Specifically, the heating temperature is 50 ℃.

Specifically, the step (F) is preceded by a drying treatment, wherein the drying treatment is to dry the polymer-based film on a drying table at 100 ℃ for 2h.

Specifically, the soaking time in the step (F) is 1h. The soaking time is controlled, so that the electrolyte is fully combined with the diaphragm, and the high liquid absorption rate is ensured.

(2) Preparation of positive plate

Uniformly mixing an NCM811 positive active material, a conductive agent, superconducting carbon, a carbon tube and a binder, namely polyvinylidene fluoride according to a mass ratio of 96.0 to 0.8; and (5) performing edge cutting, sheet cutting and strip dividing, and then manufacturing the lithium ion battery positive plate after strip dividing.

(3) Preparation of negative plate

Preparing a silicon-carbon negative electrode active substance, a conductive agent, namely superconducting carbon, a thickening agent, namely sodium carboxymethyl cellulose, and a binder, namely styrene butadiene rubber, into negative electrode slurry according to a mass ratio of 96.5; and cutting edges, cutting pieces, slitting, and slitting to obtain the lithium ion battery negative plate.

(4) Preparation of the Battery

And winding the positive plate, the gel electrolyte diaphragm and the negative plate into a battery cell, wherein the battery cell capacity is about 5Ah. The diaphragm is positioned between the adjacent positive plate and negative plate, the positive electrode is led out by aluminum tab spot welding, and the negative electrode is led out by nickel tab spot welding; then the electric core is placed in an aluminum-plastic packaging bag, the electrolyte is injected after baking, and finally the lithium ion battery is manufactured after the processes of packaging, formation, capacity grading and the like.

Example 2:

a method for preparing a gel electrolyte separator, comprising the steps of: step (A): putting lignocellulose into a solvent for grinding treatment to obtain a first solution; step (B): putting polyoxyethylene into a solvent to obtain a second solution; step (C): putting polyacrylic acid into a solvent to obtain a third solution; step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane.

Specifically, the lignocellulose is coniferous lignocellulose.

Specifically, the solvent is deionized water.

Specifically, the grinding treatment in the step (a) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 0.5h at a ball-to-material ratio of 40:0.5 and a rotation speed of 1000 r/min.

Specifically, the mass ratio of lignocellulose, polyethylene oxide and polyacrylic acid is 0.5:2:1.

Specifically, the heating temperature is 40 ℃.

Specifically, the step (F) is also preceded by a drying treatment, wherein the drying treatment is to dry the polymer base film for 2 hours on a drying table at 900 ℃.

Specifically, the soaking time in the step (F) is 2h. The soaking time is controlled, so that the electrolyte and the diaphragm are fully combined, and the high liquid absorption rate is ensured.

Example 3:

a method for preparing a gel electrolyte membrane, comprising the steps of: a step (A): putting lignocellulose into a solvent for grinding treatment to obtain a first solution; step (B): putting polyoxyethylene into a solvent to obtain a second solution; step (C): adding polyacrylic acid into a solvent to obtain a third solution; a step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; a step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane.

Specifically, the lignocellulose is coniferous lignocellulose.

Specifically, the solvent is deionized water.

Specifically, the grinding treatment in the step (a) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 1h at a ball-material ratio of 60.

Specifically, the mass ratio of lignocellulose, polyethylene oxide and polyacrylic acid is 0.5:4:0.5.

Specifically, the heating temperature is 60 ℃.

Specifically, the step (F) is also preceded by a drying treatment, wherein the drying treatment is to dry the polymer-based film for 3 hours on a drying table at 100 ℃.

Specifically, the soaking time in the step (F) is 0.5h. The soaking time is controlled, so that the electrolyte and the diaphragm are fully combined, and the high liquid absorption rate is ensured.

Example 4:

a method for preparing a gel electrolyte separator, comprising the steps of: a step (A): putting lignocellulose into a solvent for grinding treatment to obtain a first solution; a step (B): putting polyoxyethylene into a solvent to obtain a second solution; a step (C): adding polyacrylic acid into a solvent to obtain a third solution; step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane.

Specifically, the lignocellulose is coniferous lignocellulose.

Specifically, the solvent is water.

Specifically, the grinding treatment in the step (a) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 0.5h at a ball-to-material ratio of 50.

Specifically, the mass ratio of lignocellulose, polyethylene oxide and polyacrylic acid is 0.5:3:1.

Specifically, the temperature of the heating is 55 ℃.

Specifically, the step (F) is also preceded by a drying treatment, wherein the drying treatment is to dry the polymer-based film for 1.5 hours on a drying table at 98 ℃.

Specifically, the soaking time in the step (F) is 1.2h. The soaking time is controlled, so that the electrolyte is fully combined with the diaphragm, and the high liquid absorption rate is ensured.

Example 5:

a method for preparing a gel electrolyte membrane, comprising the steps of: a step (A): putting lignocellulose into a solvent for grinding treatment to obtain a first solution; step (B): putting polyoxyethylene into a solvent to obtain a second solution; step (C): adding polyacrylic acid into a solvent to obtain a third solution; step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution; a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane; step (F): and (E) soaking the polymer-based membrane in the step (E) in an electrolyte to obtain the gel electrolyte membrane.

Specifically, the lignocellulose is coniferous lignocellulose.

Specifically, the solvent is deionized water.

Specifically, the grinding treatment in the step (a) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 1h at a ball-material ratio of 45.5 and a rotation speed of 1000 r/min.

Specifically, the mass ratio of lignocellulose, polyethylene oxide and polyacrylic acid is 0.5:4:1.

Specifically, the temperature of the heating is 45 ℃.

Specifically, the step (F) is further preceded by a drying treatment, wherein the drying treatment is to dry the polymer-based film on a drying table at 95 ℃ for 2.5h.

Example 6:

the difference from the embodiment 1 is that:

the grinding treatment in the step (A) is that the lignocellulose and the solvent are put into a ball milling tank to be ball milled for 1h at the ball-material ratio of 50 and the rotating speed of 1100 r/min; the mass ratio of the lignocellulose to the polyoxyethylene to the polyacrylic acid is 1: 2; the drying treatment is to dry the polymer-based film for 1h on a drying table at the temperature of 95 ℃; the soaking time in the step (F) is 2h.

The rest is the same as embodiment 1, and the description is omitted here.

Example 7:

the difference from the embodiment 1 is that:

the grinding treatment in the step (A) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 1h at a ball-material ratio of 60; the mass ratio of the lignocellulose to the polyethylene oxide to the polyacrylic acid is 0.5: 4; the drying treatment is to dry the polymer-based film for 2.5 hours on a drying table at the temperature of 95 ℃; the soaking time in the step (F) is 2h.

The rest is the same as embodiment 1, and the description is omitted here.

Example 8:

the difference from the example 1 is that:

the grinding treatment in the step (A) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 1h at a ball-material ratio of 60; the mass ratio of the lignocellulose to the polyoxyethylene to the polyacrylic acid is 1: 4; the drying treatment is to dry the polymer-based film for 2.5 hours on a drying table at the temperature of 95 ℃; the soaking time in the step (F) is 2h.

The rest is the same as embodiment 1, and the description is omitted here.

Example 9:

the difference from the embodiment 1 is that:

the grinding treatment in the step (A) is to put the lignocellulose and the solvent into a ball milling tank to perform ball milling for 1h at a ball-material ratio of 60.5 and a rotation speed of 1200 r/min; the mass ratio of the lignocellulose to the polyoxyethylene to the polyacrylic acid is 1: 4; the drying treatment is to dry the polymer-based film for 2.5 hours on a drying table at the temperature of 90 ℃; the soaking time in the step (F) is 2h.

The rest is the same as embodiment 1, and the description is omitted here.

Example 10:

the difference from the embodiment 1 is that:

the grinding treatment in the step (A) is that the lignocellulose and the solvent are put into a ball milling tank to be ball milled for 1h at the ball-material ratio of 50; the mass ratio of the lignocellulose to the polyethylene oxide to the polyacrylic acid is 1: 4; the drying treatment is to dry the polymer-based film for 2.5 hours on a drying table at the temperature of 95 ℃; the soaking time in the step (F) is 2h.

The rest is the same as embodiment 1, and the description is omitted here.

And (4) performance testing:

1. the separators prepared in examples 1 to 10 were soaked in the electrolyte solution with a commercial PP-based membrane (as comparative example 1) for 1 hour at a liquid absorption rate as shown in table 1; and the liquid holdup after soaking in the electrolyte for 1h, 2h, 4h, 6h, 8h, 24h and 48h is shown in the table 2.

TABLE 1

Sample (I)	As received mass (mg)	Mass (mg) after 1h of imbibition	Liquid absorption Rate (%)
				Example 1	8	30.5	281.25
Example 2	8.1	29.4	262.96
				Example 3	7.9	30.1	281.01
Example 4	7.4	30.1	306.76
				Example 5	7.8	30.2	287.18
Example 6	8	29.4	267.50
				Example 7	8.1	28.1	246.91
Example 8	8	28.9	261.25
				Example 9	8.1	29.6	265.43
Example 10	8	29.3	266.25
				Comparative example 1	4	6.7	67.50

TABLE 2

1h

2h

4h

8h

24h

48h

Example 1

188.8％

188.0％

185.0％

170.0％

118.8％

92.5％

Example 2

187.9％

187.2％

185.6％

170.1％

116.8％

90.1％

Example 3

187.8％

187.6％

185.5％

170.1％

114.8％

89.9％

Example 4

188.1％

188.0％

185.3％

171.1％

119.4％

89.9％

Example 5

186.7％

186.1％

186.4％

171.2％

118.2％

89.7％

Example 6

184.3％

182.7％

180.5％

168.2％

118.4％

90.4％

Example 7

188.2％

187.7％

185.8％

169.5％

118.9％

90.1％

Example 8

186.7％

186.4％

185.3％

169.4％

117.5％

91.7％

Example 9

186.4％

185.7％

184.6％

169.3％

117.6％

91.2％

Example 10

187.9％

187.4％

185.2％

168.5％

117.8％

92.4％

Comparative example 1

5.0％

2.5％

As can be seen from table 1, the gel electrolyte membrane of the present invention has a very high imbibition rate for the electrolyte, can sufficiently absorb the electrolyte, enables lithium ions to smoothly transfer in the membrane, and has good ionic conductivity, while comparative example 1 uses a conventional commercial PP-based membrane, has a very low imbibition rate for the electrolyte, is difficult to ensure free movement of lithium ions, and has poor ionic conductivity. Meanwhile, as can be seen from the table 2, the gel electrolyte membrane of the present invention has not only a high liquid absorption rate but also a high liquid holding rate, and can still maintain 89% after standing still for 48 hours at room temperature, with stable performance.

Second, the battery prepared in example 1 and the battery prepared in comparative example 1 using the PP separator were subjected to cycle charging at a rate of 1C. As shown in fig. 6, the gel electrolyte membrane of the present invention has excellent electrochemical properties during charging and discharging, and has a specific cyclic discharge capacity of about 141mAh/g at a 1C rate, which is higher than that of comparative example 1.

3. The battery prepared in example 1 and the battery prepared in comparative example 1 using the PP separator were used at a current density of 2mA/cm ² Next, the change in voltage with time is monitored. As shown in fig. 7, in comparative example 1 using the liquid electrolyte battery, the polarization voltage reached 0.4V or more at around 78h, indicating that the separator had been pierced by lithium dendrites. And when the gel electrolyte battery is circulated for 1200h, the polarization voltage of the gel electrolyte battery is always 0.004V loitering, and the change is not too large, which shows that the gel electrolyte diaphragm disclosed by the invention has an obvious inhibiting effect on lithium dendrites, so that the battery has a good service life.

In addition, as can be seen from comparison of examples 1 to 10, the performance of the gel electrolyte membrane of the present invention is affected by the mass ratio of each substance, the ball-to-material ratio at the time of grinding, the grinding rotational speed, the grinding time, the heating temperature, the baking time, the baking temperature, the soaking time, and the like, and the performance of the gel electrolyte membrane is more excellent when the mass ratio of each substance, the ball-to-material ratio at the time of grinding, the grinding rotational speed, the grinding time, the heating temperature, the baking time, the baking temperature, and the soaking time are adjusted. As in example 1, when the mass ratio of each substance is 1.

Variations and modifications to the above-described embodiments may become apparent to those skilled in the art to which the invention pertains based upon the disclosure and teachings of the above specification. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for preparing a gel electrolyte membrane is characterized in that: the method comprises the following steps:

step (A): putting 0.5-1 part by weight of lignocellulose into a solvent for grinding treatment to obtain a first solution;

step (B): putting 2-4 parts by weight of polyoxyethylene into a solvent to obtain a second solution;

a step (C): adding 0.5-1 part by weight of polyacrylic acid into a solvent to obtain a third solution;

a step (D): mixing and stirring the first solution and the second solution uniformly to obtain a mixed solution;

a step (E): adding the third solution into the mixed solution obtained in the step (D), uniformly stirring, and curing to form a polymer-based membrane;

step (F): soaking the polymer-based membrane in the step (E) in an electrolyte to obtain a gel electrolyte membrane;

the grinding treatment in the step (A) is that the lignocellulose and the solvent are put into a ball milling tank to be ball milled for 0.5 to 2 hours at the ball-material ratio of 40 to 60 and the rotating speed of 1000 to 1200 r/min;

wherein, the solidification in the step (E) is to heat the liquid and stir the bottom of the liquid at the same time, and the heating temperature is 40-60 ℃;

wherein, the step (F) is also preceded by a drying treatment, and the drying treatment is to dry the polymer-based film for 1 to 3 hours on a drying table at 90 to 100 ℃.

2. The method of preparing a gel electrolyte membrane according to claim 1, wherein: the lignocellulose is needle leaf lignocellulose.

3. The method of preparing a gel electrolyte membrane according to claim 1, wherein: the solvent is deionized water.

4. The method of preparing a gel electrolyte membrane according to claim 1, wherein: the soaking time in the step (F) is 0.5-2h.