Dissociating high concentration lithium salts in LLZTO-based high dielectric polymer electrolytes for low temperature Li metal batteries†

Incorporating high concentrations of lithium salts into solid polymer electrolytes can enhance the electrochemical performance of Li metal batteries. However, this approach is often obstructed by the reduced mechanical properties and limited lithium salt dissociation capacity. To address these challenges, we coupled a rigid inorganic solid electrolyte, Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO), with a high-dielectric-constant polymer, polyvinylidene-trifluoroethylene-trifluoroethylene chloride. The resulting composite solid electrolyte (named PTCL-1.5) significantly improves Li⁺ transport at low temperatures. The assembled Li|PTCL-1.5|Li cell demonstrates remarkable cycling stability, operating for over 4350 hours at −20 °C and 0.1 mA cm⁻². The PTCL-1.5 electrolyte exhibits excellent compatibility with various cathodes. Specifically, the Li|PTCL-1.5|LiNi_0.8Co_0.1Mn_0.1O₂ cell achieves a capacity of 127.69 mA h g⁻¹ at −20 °C, while the Li|PTCL-1.5|LiFePO₄ cell shows exceptional cycle stability, exceeding 750 cycles. Our work offers a promising approach for developing solid-state electrolytes with high electrochemical stability at low temperatures.