Self-healing alginate–carboxymethyl chitosan porous scaffold as an effective binder for silicon anodes in lithium-ion batteries

Polymer binder plays a pivotal role in electrochemical performance of high-capacity silicon (Si) anode that usually suffers from severe capacity fading due to enormous substantial volume change of Si during cycling. In an effort to find efficient polymer binder that could mitigate such capacity fading, alginate–carboxymethyl chitosan (Alg–C-chitosan) composite polymer was investigated as a low-cost water-soluble binder for silicon anodes in lithium-ion batteries. The electrostatic interaction between carboxylate (–COO⁻) of Alg and protonated amines (–NH₃⁺) of C-chitosan forms a self-healing porous scaffold structure. Synergistic effect on the enhanced porous scaffold structure and self-healing electrostatic interaction of Alg–C-chitosan binder effectively can tolerate the tremendous volume change of Si and maintain an integrated electrode structure during cycling process. The Si nanopowder electrodes with Alg–C-chitosan composite binder exhibit an excellent cycling stability, with a capacity of 750 mAh·g⁻¹ remaining after 100th cycling. In addition, an extraordinary areal capacity of 3.76 mAh·cm⁻² is achieved for Si-based anodes with Alg–C-chitosan binder.