阅读说明：本技术 一种凝胶复合负极片及其制备方法和应用 (Gel composite negative plate and preparation method and application thereof ) 是由 李峥 冯玉川 何泓材 周柯 王丹丹 杨帆 于 2020-04-17 设计创作，主要内容包括：本发明提供了一种凝胶复合负极片及其制备方法和应用,所述凝胶复合负极片的制备方法包括如下步骤：(1)将金属锂负极极片浸入含第一聚合单体的酯类电解液中进行浸泡,得到含有保护层的金属锂负极极片；(2)将步骤(1)得到的含有保护层的金属锂负极极片表面涂布含第二聚合单体的凝胶电解液,加热使得凝胶电解液聚合交联,得到所述凝胶复合负极片；通过在酯类电解液中增加第一聚合单体,使得凝胶电解液中的第二聚合单体在发生原位聚合之外,还会与保护层中的第一聚合单体发生弱聚合发硬,提高了保护层与凝胶电解质层之间的界面性能,从而提高凝胶电解质电池的首次效率和循环性能。(The invention provides a gel composite negative plate and a preparation method and application thereof, wherein the preparation method of the gel composite negative plate comprises the following steps: (1) soaking the metal lithium negative electrode piece in an ester electrolyte containing a first polymerization monomer to obtain a metal lithium negative electrode piece containing a protective layer; (2) coating gel electrolyte containing a second polymerization monomer on the surface of the metal lithium negative electrode piece containing the protective layer obtained in the step (1), and heating to polymerize and crosslink the gel electrolyte to obtain the gel composite negative electrode piece; by adding the first polymerized monomer into the ester electrolyte, the second polymerized monomer in the gel electrolyte can be weakly polymerized and hardened with the first polymerized monomer in the protective layer besides being subjected to in-situ polymerization, so that the interface performance between the protective layer and the gel electrolyte layer is improved, and the first efficiency and the cycle performance of the gel electrolyte battery are improved.)

1. The preparation method of the gel composite negative plate is characterized by comprising the following steps of:

(1) soaking the metal lithium negative electrode piece in an ester electrolyte containing a first polymerization monomer to obtain a metal lithium negative electrode piece containing a protective layer;

(2) and (2) coating the surface of the metal lithium negative electrode piece containing the protective layer obtained in the step (1) with gel electrolyte containing a second polymerization monomer, and heating to polymerize and crosslink the gel electrolyte to obtain the gel composite negative electrode piece.

2. The preparation method of the gel composite negative electrode sheet according to claim 1, wherein the ester electrolyte containing the first polymeric monomer in the step (1) comprises a solute, a solvent and the first polymeric monomer;

preferably, the solute comprises L iNO₃、KNO₃Or NaNO₃Any one or a combination of at least two of;

preferably, the solvent comprises any one of diethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate or a combination of at least two of the two;

preferably, the first polymeric monomer is an acrylate;

preferably, the content of the first polymeric monomer in the ester electrolyte containing the first polymeric monomer in the step (1) is 1-5%;

preferably, the solute concentration of the ester electrolyte containing the first polymeric monomer in the step (1) is 1-10 mol/L.

3. The preparation method of the gel composite negative electrode sheet according to claim 1 or 2, wherein the soaking time in the step (1) is 1-48 h;

preferably, the step (1) further comprises: after soaking the metal lithium negative pole piece, drying the metal lithium negative pole piece;

preferably, the drying is drying in a glove box;

preferably, the temperature of the drying is 60-80 ℃.

4. The preparation method of the gel composite negative electrode sheet according to any one of claims 1 to 3, wherein the coating of the gel electrolyte containing the second polymeric monomer and the number of polymerization crosslinking in step (2) are both n times, and n is greater than or equal to 1;

preferably, n is more than or equal to 2, and the compositions of the gel electrolyte coated for n times are the same or different;

preferably, n is more than or equal to 2, and the step (2) comprises the following steps: coating 1 layer of gel electrolyte containing a second polymerization monomer on the surface of the metal lithium negative pole piece containing the protective layer, heating to enable the gel electrolyte to be polymerized and crosslinked to obtain a negative pole piece with 1 layer of gel electrolyte layer, and repeating the steps for n-1 times to obtain the gel composite negative pole piece;

preferably, the n-times coated gel electrolytes each independently include a solute, a solvent, and a second polymeric monomer;

preferably, n is more than or equal to 2, and the concentration of the second polymeric monomer in the gel electrolyte close to the metal lithium negative electrode piece is lower than that of the second polymeric monomer in the gel electrolyte far away from the metal lithium negative electrode piece;

preferably, the solute comprises L iNO₃、LiPF₆、LiClO₄Or L iFSI, or a combination of at least two thereof;

preferably, the concentration of the solute in the gel electrolyte is 1-10 mol/L;

preferably, the solvent comprises any one of diethylene glycol dimethyl ether, dimethyl carbonate or ethyl methyl carbonate or a combination of at least two thereof;

preferably, the second polymeric monomer comprises any one of acrylate, ethylene oxide, propylene oxide or butylene oxide or a combination of at least two thereof, preferably a combination of acrylate and ethylene oxide;

preferably, the molar ratio of acrylate to ethylene oxide is (1-5: 1, preferably 3: 1;

preferably, the gel electrolyte in step (2) further comprises an initiator, wherein the initiator is azobisisobutyronitrile;

preferably, the content of the initiator is 1-5 wt% of the total mass of the gel electrolyte;

preferably, the gel electrolyte in step (2) further comprises an additive, wherein the additive comprises any one or a combination of at least two of vinylene carbonate, propylene sulfite or NaODFB.

5. The preparation method of the gel composite negative electrode sheet according to any one of claims 1 to 4, wherein the heating temperature in the step (2) is 50 to 100 ℃;

preferably, the heating time of the step (2) is 2-5 h.

6. The preparation method of the gel composite negative electrode sheet according to any one of claims 1 to 5, wherein when n is 1, the preparation method of the gel composite negative electrode sheet comprises the following steps:

(1) immersing the metal lithium negative electrode piece into ester electrolyte containing a first polymerization monomer with solute concentration of 1-10 mol/L for soaking for 1-48h, and drying in a glove box at 60-80 ℃ to obtain the metal lithium negative electrode piece containing a protective layer;

(2) coating the surface of the metal lithium negative electrode piece containing the protective layer obtained in the step (1) with gel electrolyte containing a second polymerization monomer, and heating at 50-100 ℃ to enable the gel electrolyte to be polymerized and crosslinked for 2-5 hours to obtain a gel composite negative electrode piece;

when n is more than or equal to 2, the preparation method of the gel composite negative plate further comprises the following steps: and (3) repeating the process of the step (2) for n-1 times on the metal lithium negative electrode piece with 1 gel electrolyte layer obtained by coating and crosslinking for 1 time in the step (2), so as to obtain the gel composite negative electrode piece.

7. The preparation method of the gel composite negative electrode sheet according to any one of claims 1 to 6, thereby obtaining the gel composite negative electrode sheet.

8. The gel composite negative plate according to claim 7, wherein the gel composite negative plate comprises metallic lithium, a protective layer and a gel electrolyte layer from bottom to top, the number of the gel electrolyte layer is n, wherein n is more than or equal to 1;

preferably, the protective layer and the gel electrolyte layer are connected by a chemical bond.

9. A gel electrolyte battery comprising a positive electrode sheet, a separator and the gel composite negative electrode sheet according to claim 7 or 8.

10. Use of the gel electrolyte battery according to claim 9 in electric vehicles or electronic products.

Technical Field

The invention belongs to the field of batteries, and relates to a gel composite negative plate and a preparation method and application thereof.

Background

The lithium ion battery as a new generation clean energy has the advantages of high output voltage, large energy density, small self-discharge, long cycle life, no memory effect, quick charge and discharge, environmental protection and the like, and is widely applied to various fields. The reason is that the lithium metal cathode has a good high energy density (3800mAh/g), and the selection of the corresponding cathode material is wide, so that the lithium ion battery industry chain has formed an industry chain system with high specialization degree and clear division of labor through the development of the last two decades.

Compared with the traditional graphite cathode, the lithium metal has the advantage of high energy density, but the lithium metal cathode has very high reactivity and can react with the electrolyte and the components in the electrolyte to generate loss; meanwhile, the lithium metal negative electrode may also generate powdering and dead lithium due to its unstable SEI film. The solid electrolyte is considered to have good matching property with the lithium metal negative electrode, but the problems of the fragile and unstable SEI film on the surface of the lithium metal negative electrode still cannot be completely solved.

Therefore, it is necessary to provide a composite negative electrode sheet which can protect the metal lithium, suppress the dendrite of the negative electrode lithium, and improve the battery performance.

Disclosure of Invention

The invention aims to provide a gel composite negative plate and a preparation method and application thereof, and the gel composite negative plate is characterized in that a first polymeric monomer is added into an ester electrolyte, so that a second polymeric monomer in the gel electrolyte can perform weak polymerization reaction with the first polymeric monomer in the ester electrolyte besides in-situ polymerization, the interface performance between a protective layer and a gel electrolyte layer is improved, in addition, the components in the gel electrolyte are mixed more uniformly by a repeated coating-crosslinking mode when the gel electrolyte layer is formed, the possibility of forming pits or unevenness between the gel electrolyte layer and the protective layer due to interface compatibility is reduced, and the electrochemical performance of a gel electrolyte battery is further improved; the gel electrolyte battery prepared by the gel composite negative plate has high first-effect efficiency and good cycle performance.

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

one of the purposes of the invention is to provide a preparation method of a gel composite negative plate, which comprises the following steps:

(1) soaking the metal lithium negative electrode piece in an ester electrolyte containing a first polymerization monomer to obtain a metal lithium negative electrode piece containing a protective layer;

(2) and (2) coating the surface of the metal lithium negative electrode piece containing the protective layer obtained in the step (1) with gel electrolyte containing a second polymerization monomer, and heating to polymerize and crosslink the gel electrolyte to obtain the gel composite negative electrode piece.

According to the invention, the metal lithium negative pole piece is immersed in the ester electrolyte containing the first polymeric monomer for immersion, so that on one hand, metal lithium is passivated, an inorganic layer and an organic layer can be sequentially generated on the surface of the metal lithium negative pole piece, the reaction of the metal lithium and the electrolyte can be reduced, and the growth of lithium dendrites can be inhibited, on the other hand, the first polymeric monomer in the ester electrolyte can perform weak polymerization reaction with the second polymeric monomer in the gel electrolyte, the interface performance between the protective layer and the gel electrolyte layer is improved, and the cycle performance of the gel electrolyte battery can be improved when the lithium negative pole piece is used in the gel electrolyte battery.

According to the invention, the electrolyte layer is formed on the metal lithium negative electrode plate containing the protective layer in a coating-crosslinking manner, so that the components in the gel electrolyte are mixed more uniformly, the possibility of forming pits and unevenness between the gel electrolyte and the negative electrode protective layer due to interface compatibility is reduced, and the overall performance of the battery is further improved.

According to the invention, the protective layer and the gel electrolyte layer are cooperatively used, so that the gel electrolyte battery prepared from the composite negative plate has higher first efficiency and better cycle performance.

In the invention, the ester electrolyte containing the first polymeric monomer in the step (1) comprises a solute, a solvent and the first polymeric monomer.

In the present invention, the solute includes L iNO₃、KNO₃Or NaNO₃Any one or a combination of at least two of them.

In the present invention, the solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate, or a combination of at least two thereof.

In the present invention, the first polymerized monomer is acrylate, preferably methacrylate and/or ethyl acrylate.

In the present invention, the content of the first polymeric monomer in the ester electrolyte containing the first polymeric monomer in step (1) is 1 to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.; when the content of the first polymer monomer is too low, effective weak crosslinking with the gel electrolyte layer cannot be formed, so that the interaction between the protective layer and the gel electrolyte layer is weakened, and the interface performance is deteriorated.

In the invention, the solute concentration in the ester electrolyte containing the first polymeric monomer in the step (1) is 1-10 mol/L, such as 1 mol/L, 2 mol/L0, 3 mol/L, 4 mol/L, 5 mol/L, 6 mol/L, 7 mol/L, 8 mol/L, 9 mol/L, 10 mol/L, and the like.

In the invention, the soaking time in the step (1) is 1-48h, such as 1h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 24h, 25h, 28h, 30h, 32h, 35h, 38h, 40h, 42h, 45h, 48h and the like; when the soaking time is too short, the formed protective layer is thin, so that the protective layer cannot play a good protection role on the lithium metal, and when the soaking time is too long, the formed protective layer is too thick, so that the performance of the final battery is influenced.

In the present invention, the step (1) further comprises: and after soaking the metal lithium negative pole piece, drying the metal lithium negative pole piece.

In the present invention, the drying is performed in a glove box.

In the present invention, the drying temperature is 60 to 80 ℃, for example, 60 ℃, 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 77 ℃, 80 ℃ and the like.

In the invention, the times of coating the gel electrolyte containing the second polymeric monomer and the polymerization crosslinking in the step (2) are both n times, and n is more than or equal to 1.

In the invention, when n is more than or equal to 2, the compositions of the gel electrolyte coated for n times are the same or different.

In the invention, when n is more than or equal to 2, the step (2) comprises the following steps: coating 1 layer of gel electrolyte containing a second polymerization monomer on the surface of the metal lithium negative pole piece containing the protective layer, heating to enable the gel electrolyte to be polymerized and crosslinked to obtain the metal lithium negative pole piece with 1 layer of gel electrolyte layer, and repeating the steps for n-1 times to obtain the gel composite negative pole piece.

According to the invention, when the multi-layer gel electrolyte layer is formed, the multi-layer gel electrolyte layer is realized by a repeated coating-crosslinking mode instead of one-time coating and then crosslinking, so that on one hand, all components in the gel electrolyte can be mixed more uniformly, and meanwhile, the possibility of forming pits and unevenness between the gel electrolyte and a protective layer due to interface compatibility can be reduced, and the first efficiency and the cycle performance of the gel electrolyte battery are further improved.

In the present invention, the n-times coated gel electrolytes each independently include a solute, a solvent, and a second polymeric monomer.

In the invention, when n is more than or equal to 2, the concentration of the second polymeric monomer in the gel electrolyte close to the metal lithium negative electrode piece is lower than that of the second polymeric monomer in the gel electrolyte far away from the metal lithium negative electrode piece.

In the invention, the concentration of the second polymer monomer in each gel electrolyte layer can be adjusted according to the actual effect in the gel electrolyte layer, and only a small amount of monomer concentration is needed to perform weak crosslinking with the polymer monomer in the ester protective layer on the side close to the lithium metal negative pole piece, so that the interface performance between the protective layer and the gel electrolyte layer is improved.

Preferably, the solute comprises L iNO₃、LiPF₆、LiClO₄Or L iFSI.

In the invention, the concentration of the solute in the gel electrolyte is 1-10 mol/L, such as 1 mol/L, 2 mol/L0, 3 mol/L, 4 mol/L, 5 mol/L, 6 mol/L, 7 mol/L, 8 mol/L, 9 mol/L and 10 mol/L.

Preferably, the solvent comprises any one of diethylene glycol dimethyl ether, dimethyl carbonate or ethyl methyl carbonate or a combination of at least two thereof.

Preferably, the second polymeric monomer comprises any one of acrylate, ethylene oxide, propylene oxide or butylene oxide or a combination of at least two thereof, preferably a combination of acrylate and ethylene oxide.

Preferably, the molar ratio of acrylate to ethylene oxide is (1-5: 1, e.g., 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc., preferably 3: 1; when the molar ratio of the protective layer to the gel electrolyte layer is too low, the content of the polymer with a long-chain structure is too low, which affects the battery performance, and when the molar ratio of the protective layer to the gel electrolyte layer is too high, the bonding strength between the protective layer and the gel electrolyte layer is too low.

Preferably, the gel electrolyte in step (2) further comprises an initiator, and the initiator is azobisisobutyronitrile.

Preferably, the initiator is present in an amount of 1 to 5 wt%, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc., of the total mass of the gel electrolyte.

Preferably, the gel electrolyte in step (2) further comprises an additive, wherein the additive comprises any one or a combination of at least two of Vinylene Carbonate (VC), Propylene Sulfite (PS) or NaODFB.

In the present invention, the heating temperature in the step (2) is 50 to 100 ℃, for example, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃ and the like.

Preferably, the heating time in step (2) is 2-5h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc.

As a preferred technical scheme of the present invention, when n is 1, the preparation method of the gel composite negative electrode sheet comprises the following steps:

(1) immersing the metal lithium negative electrode piece into ester electrolyte containing a first polymerization monomer with solute concentration of 1-10 mol/L for soaking for 1-48h, and drying in a glove box at 60-80 ℃ to obtain the metal lithium negative electrode piece containing a protective layer;

(2) coating the surface of the metal lithium negative electrode piece containing the protective layer obtained in the step (1) with gel electrolyte containing a second polymerization monomer, and heating at 50-100 ℃ to enable the gel electrolyte to be polymerized and crosslinked for 2-5 hours to obtain a gel composite negative electrode piece;

and (3) when n is more than or equal to 2, repeating the process of the step (2) for n-1 times on the metal lithium negative electrode piece with 1 gel electrolyte layer obtained by coating and crosslinking the step (2) for 1 time to obtain the gel composite negative electrode piece.

The invention also aims to provide the gel composite negative electrode sheet prepared by the preparation method of the gel composite negative electrode sheet.

In the invention, the gel composite negative plate comprises metallic lithium, a protective layer and a gel electrolyte layer from bottom to top, wherein the number of the gel electrolyte layer is n, n is more than or equal to 1, for example, n is 1, 2, 3, 4, 5, 6, 7, 8, 9 and the like.

Preferably, the protective layer and the gel electrolyte layer are connected by a chemical bond.

The third purpose of the invention is to provide a gel electrolyte battery, which comprises a positive pole piece, a diaphragm and the gel composite negative pole piece.

The fourth purpose of the invention is to provide the application of the gel electrolyte battery as the third purpose in electric vehicles or electronic products.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the first polymeric monomer is added into the ester electrolyte, so that the second polymeric monomer in the gel electrolyte can generate weak polymerization reaction with the first polymeric monomer in the ester electrolyte besides in-situ polymerization, the interface performance between the protective layer and the gel electrolyte layer is improved, in addition, the components in the gel electrolyte are mixed more uniformly by a repeated coating-crosslinking mode when the gel electrolyte layer is formed, the possibility of forming pits or unevenness between the gel electrolyte layer and the protective layer due to interface compatibility is reduced, and the electrochemical performance of the gel electrolyte battery is further improved; the gel electrolyte battery prepared by the gel composite negative plate has high first-effect efficiency and good cycle performance.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.