Binder, preparation method thereof and application of binder in lithium ion battery

Abstract

The invention provides a binder, a preparation method thereof and an application of the binder in a lithium ion battery. In the past, a surface coating mode is mostly adopted for improving dissolutionof transition metal, but electrolyte still corrodes the surface, and the effect is not ideal; a polymeric monomer with a -COOH functional group or a -CHO functional group is introduced into the binder, and the chelating degree of the transition metal is ensured by controlling the addition amount of the polymeric monomer, so that the dissolution problem of the transition metal is solved to a greatextent, the high-temperature cyclic storage capacity of the battery is improved, and the service life of the battery is prolonged; and the polybutadiene block or the polyisoprene block in the binderhas very high cohesiveness, the stability of the positive electrode material can be ensured, the binder has a multi-arm structure, such as a star-shaped structure, and multi-arm branched chain polymers can be better intertwined, so that compared with a straight chain, the overall mechanical strength of the cathode can be improved.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a binder and a preparation method thereof, a positive electrode sheet including the binder, and a lithium ion battery. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, good rate performance, and long cycle life, and have been widely used in mobile phones, notebook computers, new energy vehicles and other fields. Cathode materials for lithium-ion batteries, such as LiCoO 2 、LiNi 1-x-y co x mn y o 2 (Ternary materials), etc. contain transition metals. During the use of the battery, especially at high temperature and high voltage, the transition metals are easy to dissolve from the positive electrode material, migrate through the electrolyte and deposit on the negative electrode, thereby causing battery performance. attenuation. Therefore, the research on the positive electrode of lithium-ion batteries is...

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Problems solved by technology

[0004] In view of the fact that the current positive electrode materials containing transition metals cannot effectively solve the problem of transition metal dissolution under high temperature and high pressure, and further improve the bonding effect of the binder in the positive electrode sheet, the present invention aims to develop a binder and its preparation method And in the application in lithium-ion battery, described binding agent comprises a kind of polymer, and the polybutadiene or polyisoprene block in described polymer can play a good role in positive electrode active material. Bonding effect, improving the cycle life of lithium-ion batteries and inhibiting process expansion. More importantly, the carboxyl or aldehyde-substituted vinyl blocks in the polymer can chelate the dissolved transition metal ions and inhibit the dissolution of transition metals to The electrolyte is finally deposited on the negative electrode, alleviating the capacity loss and internal resistance increase caused by it, and improving the service life of the battery

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