Crosslinked carboxymethyl cellulose-sodium borate hybrid binder for advanced silicon anodes in lithium-ion batteries

Silicon anodes have drawn ever-increasing attention in lithium-ion batteries (LIBs) owing to their extremely high theoretical capacity and abundance in the earth. Despite promising advantages, the wide use of silicon anodes in LIBs is highly hindered by their fast capacity fading and low Coulombic efficiency arising from their substantial volumetric variation (>300%). Herein, we report a novel aqueous hybrid gel binder for silicon anodes via crosslinking sodium carboxymethyl cellulose (NaCMC) by an inorganic crosslinker-sodium borate. Not only this gel polymer binder can chemically bond to silicon nanoparticle, but also the deformable framework of this crosslinked binder is capable of maintaining electrode integrity, thus buffering dramatic volume change of silicon. Consequently, the silicon anode with this gel binder exhibits good cycle life (1211.5 mAh/g after 600 cycles) and high initial Coulombic efficiency (88.95%).