Novel rigid-flexible hydrogenated carboxyl nitrile rubber-guar gum binder for ultra-long cycle silicon anodes in lithium-ion batteries

Silicon (Si) is considered as one of the foremost attractive anode materials because of its excellent capacity. However, the severe volumetric fluctuation and unstable solid electrolyte interphase of Si anodes during repeating lithiation/delithiation will lead to a rapid capacity decay, which severely impedes the practical application and commercialization. Herein, a novel polymer network binder constructed by hydrogenated carboxyl nitrile rubber (HXNBR) and guar gum (GG) through chemical crosslinking is exploited to address the deteriorated volume expansion of Si anode. Remarkably, such a rigid-flexible binder (HX-GG) exhibits desirable electrochemical performance of a high discharge capacity of 1402 mAh g−1 for 500 cycles at 800 mA g−1 and Si@HX-GG//LiFePO4 full cell achieves an ultrastable capacity of 115 mAh g−1 for 2000 cycles at 2 C, which are superior to most of the polymer binders ever reported. The outstanding electrochemical performance is attributed to the buffer zone constructed by the elastic HXNBR and the rigid GG, the synergistic effect that effectively withstands the expansion of Si and maintains the conductive network of the electrodes as well as the mechanical integrity. This work opens a new route to discover potential binder of commercialization Si anode.