Iodine-rich lithium argyrodite with enhanced ionic conductivity for solid-state batteries

Large-scale applications of Li6PS5I electrolytes have been limited due to their low ionic conductivities. This work demonstrated the conductivity enhancement of Li6PS5I via introducing more iodine in the structure. Li5.5PS4.5I1.5 electrolyte synthesized by the mechanical milling route exhibits high ionic conductivity of 0.31 mS/cm at room temperature, which is double times higher than the pristine material. Symmetric cell and half-cell tests confirm that Li5.5PS4.5I1.5 suffers from poor chemical/electrochemical stability towards the high-voltage cathode and high activation energy for lithium-ions transport in cathode/electrolyte interface. The introduction of Li3InCl6 ionic additive in the cathode can improve compatibility with LiNi0.7Co0.1Mn0.2O2 cathode, yielding better electrochemical performances. Li5.5PS4.5I1.5-based solid-state battery using Se0.05S0.95@pPAN displays a high initial discharge capacity and a capacity of 728 mAh/g after 30 cycles. This work provides a new route to explore iodine-based solid electrolytes with higher ionic conductivity for solid-state batteries.