CN-122025541-A - Lithium ion battery pole piece, preparation method thereof and lithium ion battery

CN122025541ACN 122025541 ACN122025541 ACN 122025541ACN-122025541-A

Abstract

The invention relates to a lithium ion battery pole piece, a preparation method thereof and a lithium ion battery. The lithium ion battery pole piece comprises a foil, a first layer of slurry and a second layer of slurry, wherein the bottom of the first layer of slurry is adhered to the foil, and the bottom of the second layer of slurry is adhered to the top of the first layer of slurry. The invention can enhance the cohesiveness between two layers of slurry and promote the permeation of electrolyte in the bottom layer of the thick electrode.

Inventors

LIAO SHIJIE
HUANG MING
CHEN LIXIA
HAN GAIGE
JIN MINGGANG

Assignees

杭州天丰电源股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260228

Claims (8)

1. The lithium ion battery pole piece comprises a foil, a first layer of slurry and a second layer of slurry, wherein the bottom of the first layer of slurry is adhered to the foil, the bottom of the second layer of slurry is adhered to the top of the first layer of slurry, the lithium ion battery pole piece is characterized in that a plurality of grooves are distributed on the top of the first layer of slurry, the cross section of each groove of the first layer of slurry is one or more than two of wedge-shaped, semicircular and square, the width of each groove of the first layer of slurry is 50 mu m to 1cm, the depth of each groove is 5 mu m to 100 mu m, the distance between every two adjacent grooves is 50 mu m to 1cm, a plurality of convex strips corresponding to the grooves positioned on the top of the first layer of slurry are distributed on the bottom of the second layer of slurry, and the convex strips at the bottom of the second layer of slurry are adhered to the grooves corresponding to the top of the first layer of slurry to form a mechanical interlocking structure.
2. A preparation method of a lithium ion battery pole piece according to claim 1 sequentially comprises the following steps of homogenizing, first layer coating, drying, primary rolling, secondary coating, drying and secondary rolling, and is characterized in that a special-shaped roller is adopted for rolling in the primary rolling, strip-shaped raised strips are uniformly distributed on the surface of the special-shaped roller, the raised strips are distributed along the axial direction or the radial direction, and after the special-shaped roller is rolled on first layer slurry after the first layer coating and drying, the raised strips on the special-shaped roller form uniformly distributed grooves on the first layer slurry.
3. The method of manufacturing a lithium ion battery pole piece according to claim 2, wherein the shape of the protruding strips of the profile roller is one or more of wedge-shaped, semicircular and square, the width of the protruding strips of the profile roller is 50 μm to 1cm, the height of the protruding strips of the profile roller is 5 μm to 100 μm, and the interval between two adjacent protruding strips on the profile roller on the circumference is 50 μm to 1cm.
4. A lithium ion battery comprises a positive electrode plate, a negative electrode plate, a separation film, a shell and electrolyte, and is characterized in that the positive electrode plate and the negative electrode plate adopt the structure of the lithium ion battery electrode plate as claimed in claim 1.
5. The lithium ion battery according to claim 4, wherein the negative electrode active material is one or more of graphite, hard carbon, soft carbon, lithium titanate, a silicon oxygen material and a silicon carbon material, and the positive electrode active material is one or more of a nickel cobalt manganese ternary material, a nickel cobalt aluminum ternary material, a lithium iron phosphate material, lithium cobaltate, lithium manganese ferrite, a lithium titanate layered oxide type sodium ion battery positive electrode material and a Prussian blue type sodium ion battery positive electrode material.
6. The lithium ion battery of claim 4, wherein the positive electrode sheet and the negative electrode sheet each have a thickness of 100 μm to 400. Mu.m.
7. The lithium ion battery of claim 4, wherein the positive electrode plate comprises, by mass, 95% -97.5% of positive electrode active materials, 1.5% -3% of conductive agents and 1% -2% of binders, the negative electrode plate comprises, by mass, 94% -97% of negative electrode active materials, 1% -3% of conductive agents and 1% -3% of binders, the binders are one or more than two of polytetrafluoroethylene, cellulose sodium and PAA, CMC, SBR, and the conductive agents are one or more than two of conductive graphite, conductive carbon black, carbon nanotubes and carbon nanofibers.
8. The lithium ion battery according to claim 4, wherein the positive electrode sheet has a foil of metal aluminum foil with a thickness of 8 μm to 15 μm, and the negative electrode sheet has a foil of metal copper foil with a thickness of 5 μm to 10 μm.

Description

Lithium ion battery pole piece, preparation method thereof and lithium ion battery Technical Field The invention relates to a lithium ion battery pole piece, a preparation method thereof and a lithium ion battery, and belongs to the field of lithium ion batteries. Background With the great development of new energy technologies, the demand of power batteries is gradually increased, so that the battery technologies gradually develop towards the directions of high energy density and quick charge, but the high energy density and the quick charge demand are often in conflict. Since the energy density of the battery is increased, it is common to increase the loading amount of the active material, but the polarization of the battery is increased due to the thick electrode structure of high loading, thereby affecting the quick charge performance of the battery cell. In order to balance the fast charge performance and high energy density requirements of the battery, the current methods for improving the poor wettability and high tortuosity of the electrolyte in the thick electrode and leading to large polarization of the battery mainly comprise the steps of adding pore-forming agents, pore-forming on the surface of a pole piece, improving the porosity of an upper layer and a lower layer through double-layer coating and the like. The transmission efficiency of lithium ions and electrons in the pole piece is improved by adding a pore-forming agent (such as the Chinese patent with publication number of CN113422005A, CN 111490225A), but the addition of the pore-forming agent can bring residual risks and energy consumption cost for removing the pore-forming agent, and the adhesive property of the pole piece can be influenced, so that the active substances are easy to fall off. In addition, mechanical pore-forming and template pore-forming (such as the chinese patent publication No. CN106531961 a) on the surface of the electrode are also a method for enhancing the lithium ion transmission rate of the thick electrode, but the wettability of the pore-forming on the bottom electrode is limited, and the stability of the electrode structure is affected by too deep pore-forming depth. The two-layer coating technology is a mainstream solution for ensuring both fast charging and energy density, but two-layer coating is divided into two types, one is that a two-layer coating die head performs two-layer coating, but the production line modification thereof requires cost, and the process has some problems to be solved, such as unstable coating caused by mixing of two slurries, for example, the influence of the difference of viscosity, surface tension and the like on the quality of the coating, and the like, so that the current large-scale adaptation application is not favored. The other is to use a traditional coater for secondary coating, and the aim of the secondary coating can be achieved on the basis of lowest possible transformation cost and process cost. The steps of secondary coating by using a traditional coating machine mainly comprise homogenization, primary coating, drying, rolling, secondary coating, drying and rolling (such as Chinese patent with publication number CN115528205A, CN 114156437A), or homogenization, primary coating, drying, secondary coating, drying and rolling (such as Chinese patent with publication number CN 111490225A). If the pole piece is not rolled after primary coating, the solvent of the secondary coating slurry can quickly permeate into the lower layer to cause the slurry to be less than leveling due to higher porosity after the pole piece is directly dried. Post-lamination coating may be preferable, but there are other problems such as a significant problem in that the surface of the first layer of slurry is smooth after lamination of the pole piece, resulting in poor adhesion between the two layers of slurry, and thus new methods are required to solve the adhesion problem of the two layers of slurry. The bonding between the adhesive and the foil is mainly formed by a chemical bond formed by a condensation reaction between a hydrogen bond formed by the group of the adhesive and the group on the surface of the copper foil, and after one-time coating and rolling, the bonding point of the second layer of slurry is mainly on the surface of the smoother and shiny active substance, and the main acting force is intermolecular acting force, so the bonding performance is poorer than that of the foil. Disclosure of Invention The invention aims to overcome the defects in the prior art and provide a lithium ion battery pole piece capable of enhancing the cohesiveness between two layers of slurry and improving the electrolyte permeation in a thick electrode bottom layer, a preparation method thereof and a lithium ion battery. The invention solves the problems by adopting the following technical scheme: the lithium ion battery pole piece comprises a foil, a first layer of slurry and a second layer of slurry,