Silane-modified fluoroethyl ester polymer used as lithium battery binder and preparation method thereof

Abstract

The invention discloses a preparation method of a silane-modified fluoroethyl ester polymer used as a lithium battery binder, which comprises the following steps: 1) mixing perfluorovinyl ester compounds, silane compounds, 80%- Add 90% of the solvent into the container and stir, heat up to 60-80°C, dissolve the initiator in the remaining solvent and add it dropwise to the reaction solution. After the addition is complete, keep warm and continue the reaction for 10-12h; The solution was transferred to a rotary evaporator, the solvent was evaporated, the precipitate was washed with n-hexane, and the precipitate was dried to obtain the silane-modified fluoroethyl ester polymer. The fluorine atoms in the polymer prepared by the invention have a good binding force with lithium ions, which accelerates the transfer of lithium ions and improves the Coulombic efficiency of the battery; the silane structure enhances the adhesion between the polymer and the inorganic active silicon particles, and improves the battery life The cycle stability of the prepared polymers has excellent initial Coulombic efficiency and electrochemical stability.

Description

Technical field [0001] The present invention relates to the field of lithium-ion battery technology, specifically to a silane-modified fluoroethyl ester polymer used as a binder for lithium batteries and a preparation method thereof. Background [0002] At present, graphite is the main commercial lithium-ion battery anode active material, its theoretical specific capacity of 370mA·h / g, can not meet the needs of high energy storage equipment, and the theoretical specific capacity of the all-lithium silicon anode is 4200mA·h / g, which is more than 10 times the capacity of graphite, and the silicon element in nature is rich, which has aroused widespread concern among researchers. However, the silicon active material in the lithium embedded in the huge volume expansion, the expansion rate of 400%, after multiple charge and discharge cycle, silicon particles will rupture and powder, and gradually fall off the collector, resulting in a reduction in the content of electrode active substa...

AI Technical Summary

Problems solved by technology

The adhesion between silicon particles and current collectors is enhanced, and the specific capacity and cycle performance of lithium-ion batteries are improved, but the rate performance of silicon negative electrodes using this binder is poor

[0005] Patent CN108987753A discloses the use of silane coupling agent to modify the polymer binder of acrylic acid, which enhances the adhesion of the polymer. The initial specific capacity of the battery is 1883mAh / g, and the initial specific capacity is low, which cannot meet commercial needs.

Patent CN110247017A also discloses the use of silane coupling agent to modify acrylic acid and carboxymethyl cellulose polymer binder. The initial specific capacity of the battery is 3000mAh / g, but the capacity of the battery drops to 1500mAh / g after 30 cycles , the battery capacity loss is too fast, and the cycle performance is poor, which needs further improvement

[0006] Patent CN107863535A discloses that the composite binder of polyimide and conductive polymer polyaniline is used in the silicon negative electrode, which improves the cycle performance of the battery, but the high temperature resistance of the battery is poor, and the temperature of the system rises after repeated charging and discharging. There is a huge security risk

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