Preparation method of multi-layer coating pole piece

Abstract

The invention discloses a preparation method of a multi-layer coated pole piece, which comprises the following steps: in the process of preparing a lithium ion battery pole piece, preparing slurry 1,slurry 2 and slurry 3 of which the active substance content is gradually reduced and the binder content and the conductive agent content are gradually increased from an active substance, a conductiveagent, a binder and a dispersing solvent according to different proportions; and sequentially coating the slurry 1, the slurry 2 and the slurry 3 on the surface of a current collector, rolling and drying to obtain the pole piece. According to the pole piece prepared by the method, the active substance, the binder and the conductive additive are distributed in a gradient manner from the inner sideof the pole piece to the outer side of the pole piece, so that the purposes that the porosity of the pole piece is gradually reduced from inside to outside and the electronic conductivity is graduallyincreased are achieved. The pole piece prepared by the method can balance electron and ion conductivity and reduce concentration polarization and non-uniformity of electrochemical reaction rate, so that the pole piece has both high energy density and good electrochemical performance. The preparation method is simple and easy to implement, low in manufacturing cost and suitable for industrial production and application.

Description

technical field [0001] The invention relates to the technical field of preparation of lithium-ion battery pole pieces, in particular to a preparation method of a multilayer coated pole piece. Background technique [0002] Energy density is an unavoidable performance index for lithium-ion batteries. Increasing the thickness of the pole piece and increasing the proportion of active materials are effective means to increase the energy density of the battery. However, thick pole pieces also bring a series of problems. The electrolyte has a poor wetting effect on the inner pole piece (near the current collector side), so that lithium ions cannot reach the bottom of the pole piece smoothly and quickly during the charging and discharging process, forming a large concentration polarization; while the outer pole piece ( away from the current collector side) further weakens the electronic conductivity on the outside of the pole piece due to being away from the current collector. The...

AI Technical Summary

Problems solved by technology

However, since most of the active materials are concentrated in the middle layer, the wettability of the electrolyte inside the pole piece is worse than that of ordinary batteries.

During the charge and discharge process, lithium ions cannot reach the bottom of the pole piece smoothly and quickly, forming a large concentration polarization, which affects the performance of the battery

[0005] When charging and discharging a lithium-ion battery, the concentration of lithium ions in the electrolyte gradually decreases from the outside of the pole piece to the inside of the pole piece, resulting in concentration polarization; the electronic conductivity gradually decreases from the inside of the pole piece to the outside of the pole piece, thus limit the speed of electron transfer

These two effects are especially significant for thick electrodes, which can easily lead to non-uniform distribution of electrochemical reaction rates, resulting in the failure of the capacity of some areas to function normally, while some areas are in a deep discharge state.

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