Chitosan-grafted-Gallic Acid as a Nature-Inspired Multifunctional Binder for High-Performance Silicon Anodes in Lithium-Ion Batteries

Due to its high theoretical specific capacity and natural abundance, silicon (Si) and its composites are considered to be pivotal anode materials for high-energy-density next-generation lithium-ion batteries (LIBs). However, the significant volume changes during the repeated lithiation/delithiation process cause the loss of electrical contact and the continuous formation of a solid electrolyte interface (SEI), hindering Si’s practical applications. The rational design of the polymer binder is an efficient approach to preserve the electrode’s structure from large Si volume changes, thereby enhancing the cycle performance in lithium-ion batteries. We developed an aqueous binder using a plant-inspired adhesive phenolic moiety, gallic acid (3,4,5-trihydroxybenzoic acid, GA), grafted onto the marine-based polymer, chitosan (CS) by a simple radical reaction. The chitosan-grafted-gallic acid, CS-g-GA, not only improves the water solubility of CS but also achieves enhanced binding properties onto Si, hence contributing to better accommodating the volume expansion of Si during the repeated cycling and also maintaining the structural integrity of the Si electrode electronic made from the CS-g-GA as a binder. Si@CS-GA-100 exhibits excellent high-rate capability and long cycling stability, delivering a high reversible specific capacity of 1868 mAh g–1 with a capacity retention of 67% at a rate of 0.5 C after 350 cycles.