Temperature and stress-resistant solid state electrolyte for stable lithium-metal batteries

Despite inherent good safety and high energy density, solid state batteries readily suffer from sudden capacity fading that stems from the structure deterioration under external/internal stress and temperature change. Herein, a temperature and stress-resistant solid-state battery is developed by utilizing a composite electrolyte, synthesized by chemically grafting a self-healing polyurethane-urea disulfide polymer (PUS) onto Li₇P₃S₁₁ via nucleophilic addition. In this way, Li₇P₃S₁₁ and PUS are kept in close contact ensuring their uniform distribution throughout the composite electrolyte. These chemically bound interfaces restrict PUS chain movement under cooling-heating cycling, and thus avoid phase separation in the composite electrolyte that often occurs in traditional systems. This ensures an unprecedented resilience of both capacity and conductivity (stable at 5 × 10⁻⁴ S cm⁻¹) to temperature fluctuations. Moreover, the dynamic S-S bond in PUS provides a fast self-healing rate of the composite electrolyte subjected to mechanical damage (100% current recovery within 3 min). The Li|PUS-LPS|LiFePO₄ full cell also displays super high post-damage capacity recovery of 95.1% and excellent cycling stability (95.4% capacity retention after 200 cycles).