Dual Crosslinked Fluorinated Binder Network for High-Performance Silicon and Silicon Oxide Based Anodes in Lithium-Ion Batteries.

Silicon is a promising anode material for next generation lithium-ion batteries (LIBs) because of its surprisingly high theoretical capacity, but it suffers from severe volume changes during charge and discharge process which results in substantial deterioration of the electrode. A novel fluorinated copolymer with three different polar groups was synthesized to overcome this problem: carboxylic acid, amid and fluorinated groups on a single polymer backbone. Moreover, a dual crosslinked network binder was prepared by thermal polymerization of the fluorinated copolymer and sodium alginate. Unlike the common chemical crosslinked network with a gradual and nonreversible fracturing, the dual crosslinked network which combine chemical and physical crosslinking could effectively hold the silicon particles during the volume change process. As a result, excellent electrochemical performance (1557 mAh g-1 at a 4 A g-1 current destiny after 200 cycles) was achieved with this novel reversible crosslinked binder. Further researches in regard to the influences of fluorine and acrylamide content were conducted to systematically evaluate designed binder. Moreover, with the help of new binder, the silicon/graphite and silicon oxide/graphite electrode exhibit superb cycle performance with capacity fade rate of 0.1% and 0.025% per cycle over 200 and 700 cycles, respectively. Such a novel and facile design represents a resultful method manufacturing high-performance Si-based anodes and advancing the realization of practical application.