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

In next generation lithium-ion batteries (LIBs), silicon is a promising electrode material due to its surprisingly high specific capacity, but it suffers from serious volume changes during the lithiation/delithiation process which gradually lead to the destruction of the electrode structure. A novel fluorinated copolymer with three different polar groups was synthesized to overcome this problem: carboxylic acid, amide, and fluorinated groups on a single polymer backbone. Moreover, a dual cross-linked network binder was prepared by thermal polymerization of the fluorinated copolymer and sodium alginate. Unlike the common chemical cross-linked network with a gradual and nonreversible fracturing, the dual cross-linked network which combines chemical and physical cross-linking 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 density after 200 cycles) was achieved with this novel reversible cross-linked binder. Further research studies with regard to the influences of fluorine and acrylamide content were conducted to systematically evaluate the 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. This novel and unsophisticated design gives a result for fabrication of high-performance Si based electrodes and advancement of the realization of practical application.