Ring-Opening Polymerization Reconfigures Polyacrylonitrile Network for Ultra Stable Solid-State Lithium Metal Batteries

Abstract

Polyacrylonitrile (PAN) is a promising polymer for solid-state lithium (Li) metal batteries (SSLMBs). However, the low ionic conductivity of PAN-based solid polymer electrolytes (SPEs) and unstable Li/PAN interface hinder the applications of PAN in SSLMBs. Herein, a strategy of ring-opening polymerization is proposed to reconfigure the PAN-based SPE network. Triggered by the alkaline species from Li_6.4La₃Zr_1.4Ta_0.6O₁₂ nanoparticles, ethylene carbonate (EC) undergoes nucleophilic ring-opening reaction, and subsequently forms dipole–dipole interaction with the PAN chain. This polymerization process consequently reconfigures PAN segment, endowing the SPE with rapid Li⁺ transport channels and enhanced interfacial stability with Li metal. As a result, the designed PAN-based SPE demonstrates high ionic conductivity of 2.96 × 10⁻⁴ S cm⁻¹ and Li⁺ transference number of 0.56 at 25 °C. The Li/Li symmetric cells with the reconfigured PAN network deliver a high critical current density of 1.8 mA cm⁻² and maintain stable Li plating/stripping for 1200 h. A high-capacity retention of 90.1% after 1000 cycles at 2 C is achieved in LiFePO₄ (LFP)/Li solid-state cells with PAN-based SPEs. Moreover, the LFP/Li and LiNi_0.8Co_0.1Co_0.1O₂/Graphite pouch batteries both present good cycling and safety performances. This strategy provides new insights into designing high-performance PAN-based SPE for SSLMBs.