A bioinspired high-modulus mineral hydrogel binder for improving the cycling stability of microsized silicon particle-based lithium-ion battery

Silicon with high specific capacity is deemed an ideal anode material for lithium ion batteries, which, however suffers from low cycling life due to its dramatic volume changes. Water-soluble polymer binders recently gain increasing attention by providing an eco-friendly and low-cost way in improving the cycling stability of Si-based anodes. Herein, a novel bioinspired supramolecular mineral hydrogel binder consisting of polyacrylic acid (PAA) physically crosslinked with amorphous calcium carbonate (ACC) nanoparticles is designed for high-performance anodes made from low-cost microsized Si particles. Owing to its organic-inorganic hydrophilic nature, ACC-PAA hybrid binder exhibits the reported highest modulus (~ 22 GPa) for polymer binders in electrolyte, even higher than lithiated Si species (Li1₅Si₄, ~ 12 GPa). Together with its excellent adhesion and electrochemical stability, ACC-PAA binder can effectively suppress the pulverization of Si particles and maintain the mechanical integrity of electrodes during cycling. Therefore, even with a low binder content, the anode still shows an initial discharge capacity of 2, 973 mAh·g⁻¹ and Coulombic efficiency of 81.5%, and retains 75% at a current density of 600 mA·g⁻¹ after 100 cycles. The present organic-inorganic hybrid mineral binder may open a new approach for designing more effective polymer binders for Si-based lithium-ion batteries.