Sulfide-based inorganic solid electrolytes have been considered promising candidates for all-solid-state batteries owing to their high ionic conductivity. Compared with oxide-based inorganic solid electrolytes which require high-temperature sintering, the intrinsic deformability of sulfide electrolytes enables the fabrication of all-solid-state batteries by a simple cold pressing method. Nevertheless, the performance of sulfide-based all-solid-state batteries is still unsatisfactory, owing to the insufficient interfacial properties within the composite electrodes. Using cold pressing alone, it is challenging to form intimate contacts with rigid oxide-based cathode materials. Here, we demonstrate a mild-temperature pressing (MP) method for the fabrication of all-solid-state batteries. The mild temperature (85 °C) increases the deformability of the sulfide and therefore helps to form more enhanced interfacial contacts in the composite cathode without side reactions. Compared with the conventional cold pressing cell, the MP cell possesses more favorable contacts, resulting in higher capacity, cyclability, and rate capability. In addition, we demonstrate that the charge-transfer resistance in composite cathodes dominates the electrochemical performance of all-solid-state batteries.
Keywords: all-solid-state battery; deformability; interfacial contacts; mild temperature; sulfide solid electrolyte.