A kind of porous lithium ion pole piece with high energy density and its preparation method and lithium ion battery

Abstract

The invention provides a method for preparing porous lithium ion pole pieces with high energy density and a lithium ion battery. The preparation method includes the following steps: S1. Use N-methylpyrrolidone to dissolve a binder to prepare a glue liquid. Add active material and conductive agent to the liquid and mix them evenly to obtain a slurry; S2. Coat the mixed slurry on the current collector to prepare a pole piece; S3. Cold-press the coated pole piece, and then The surface of the cold-pressed pole piece is brushed with a pore-forming agent. The pore-forming agent is evenly coated on the surface of the cold-pressed pole piece with the help of a coating machine. It is dried while coating. The drying temperature is set to a temperature higher than that of the cold-pressed pole piece. The decomposition temperature of the porous agent is reduced to obtain porous lithium ion pole pieces with high energy density. In the present invention, thick electrodes with higher surface density are prepared, and a pore-forming agent is applied to the surface of the electrode piece after cold pressing, thereby improving the porosity of the thick electrode piece and improving the electrical performance.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a preparation method of a porous lithium ion pole piece with high energy density and a lithium ion battery. Background technique [0002] As a high-performance secondary battery, lithium-ion batteries are widely used in daily life due to their long cycle life and environmental friendliness, such as mobile phones, cameras, computers, electric bicycles, etc. [0003] In recent years, with the continuous expansion of its application range, especially in high-energy-consuming vehicles such as pure electric vehicles, plug-in hybrid vehicles, etc., the requirements for the energy density of lithium-ion batteries continue to increase. To improve the energy density of lithium-ion batteries, on the one hand, develop cathode materials with high capacity, such as lithium nickel manganese cobalt oxide (LiNi x CoyMn 1-x-y o 2 0.6<x<1, 0.3≤y≤1 / 3), lithium nickel cobal...

AI Technical Summary

Problems solved by technology

However, through practical use, it has been found that thick electrodes also have disadvantages. The increase in the thickness of the pole piece increases the energy density of lithium ions to a certain extent, but the increase in energy density is not proportional to the increase in the thickness of the pole piece. Coated active material is not fully functioning

After research, it is found that this is because during the rolling process of the pole piece, the upper surface pole piece is stressed first to reach the design compaction density, resulting in a structure with small porosity in the upper layer and large porosity in the bottom layer of the pole piece, which is not conducive to the electrolyte. Infiltration, which is not conducive to the extraction and insertion of Li+, and the increase of the thickness of the pole piece makes the migration of Li+ more difficult, which eventually leads to the lithium ion capacity density not up to the standard, the battery electrical performance deteriorates, restricting its practical use, and improving the porosity of thick electrodes , Improving the energy density of thick electrodes is imminent