Metal‐Chelated Biomimetic Polyelectrolyte as a Powerful Binder for High‐Performance Micron Silicon Anodes

High‐capacity silicon anodes have attracted tremendous interest for next‐generation lithium‐ion batteries (LIBs). However, its further application is limited by the large volume expansion during cycling. Designing nanostructured silicon is an effective strategy to acquire high‐performance anodes, but it will face problems of high cost and poor coulombic efficiency. As a comparison, surface modification of micron silicon is more economically viable. Herein, a novel route is proposed to synthesize metal‐chelated biomimetic polyelectrolyte as a powerful binder, which wraps micron silicon particles in a thin Fe 3+ –polydopamine (PDA) layer with a thickness of 2–5 nm. The introduced Fe 3+ can form powerful metal‐chelated bonds with PDA at appropriate hydrothermal temperature (160 °C). As a result, the mechanical strength of the protective layer is enhanced and the electrochemical activity of micron silicon is improved. Meanwhile, the 3D crosslinking structure formed through the esterification between the elastic polymer layer and polyacrylic acid (PAA) further guarantees the structural stability of anodes. Batteries using Si@Fe 3+ –PDA–160/PAA anode exhibit excellent cycling performance with stable capacity of 2000 mAh g −1 over 200 cycles at 0.5 C and high capacity retention ratio of 80% after 100 cycles at 0.1 C.