Grafting strategy achieving self-healing polymer/sulfide electrolyte for high-performance solid-state lithium–silicon batteries

Severe structural fractures and persistent side reactions at the interface with liquid electrolytes have hindered the commercialization of silicon (Si) anodes. Solid-state electrolytes present a promising solution to address these issues. However, the high interfacial resistance of rigid ceramic electrolytes and the limited ionic conductivity of polymer electrolytes remain significant challenges, further complicated by the substantial volume expansion of Si. In this work, we chemically grafted a flame-retardant, self-healing polyurethane-thiourea polymer onto Li₇P₃S₁₁ (SHPUSB-40%LPS) via nucleophilic addition, creating an electrolyte with exceptional ionic conductivity, high elasticity, and strong compatibility with Si anodes. We observed that FSI⁻ was strongly adsorbed onto the LPS surface through electrostatic interactions with sulfur vacancies, enhancing Li⁺ transport. Furthermore, SHPUSB-40%LPS exhibits dynamic covalent disulfide bonds and hydrogen bonds, enabling self-assembly of the electrolyte at the interface. This dynamic bonding provides a self-healing mechanism that mitigates structural changes during Si expansion and contraction cycles. As a result, the Si anode with SHPUSB-40%LPS presents excellent cycling stability, retaining nearly 53.5% of its capacity after 300 cycles. The practical applicability of this design was validated in a 2 Ah all-solid-state Si||LiNi_0.6Mn_0.2Co_0.2O₂ pouch cell, which maintained a stable Li-ion storage capacity retention of 76.3% after 350 cycles at 0.5C. This novel solid-state electrolyte with self-healing properties offers a promising strategy to address fundamental interfacial and performance challenges associated with Si anodes.