A kind of preparation method of multilayer coating pole piece

Abstract

The invention discloses a method for preparing a multilayer coated pole piece. In the process of preparing a lithium-ion battery pole piece, the active material, conductive agent, binder, and dispersing solvent are prepared according to different proportions, and the content of the active material is gradually reduced. But slurry 1, slurry 2, and slurry 3 with increasing binder and conductive agent content. According to the sequence of slurry 1, slurry 2, and slurry 3, they are coated on the surface of the current collector, rolled and dried to obtain pole pieces. The pole piece prepared by the method has gradient distribution of active material, binder and conductive additive from the inside of the pole piece to the outside of the pole piece, so that the porosity of the pole piece gradually decreases and the electronic conductivity gradually increases from the inside to the outside of the pole piece. The pole piece prepared by the method can balance the electronic and ion conductivities, reduce the inhomogeneity of concentration polarization and electrochemical reaction rate, so that the pole piece can take into account high energy density and good electrochemical performance. Moreover, the preparation method is simple and easy, the manufacturing cost is low, and it is 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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