Multiple Network Binders via Dual Cross-Linking for Silicon Anodes of Lithium-Ion Batteries

Silicon has attracted much attention as a promising anode material in lithium-ion batteries owing to its high specific capacity. However, silicon anode suffers large volume expansion during periodical lithiation/delithiation processes, leading to particle pulverization and thus electrochemical performance degradation. Herein, we report a water-soluble three-dimensional network polymer binder for silicon anode in which the introduced poly(ethylene glycol) and divalent cation Ca 2+ can form chemical cross-linking and physical cross-linking with poly(acrylic acid), respectively. Poly(ethylene glycol) serves as a soft segment to regulate the mechanical properties of the polymer, and the divalent cation Ca 2+ acts as a physical cross-linking agent to form a dual network with poly(acrylic acid). The multiple network binder owns good mechanical strength, strain resistance ability, and strong adhesion with Si particles and Cu collector, thereby preserving the stability of the silicon electrode. Therefore, silicon anode with this rationally designed binder exhibits excellent electrochemical performance with a discharge capacity of 1596 mAh/g after 800 cycles at a current density of 2 A/g. This design can provide a way to alleviate the volume expansion of the silicon anode and other high-capacity alloy anodes with large volume change for advanced batteries.