Effects of gelation behavior of PPC-based electrolyte on electrochemical performance of solid state lithium battery

Abstract

Polypropylene carbonate (PPC)-based solid state electrolyte was fabricated by using a cellulose membrane as a skeleton. The gelation behavior of the PPC-based solid electrolytes in solid-state lithium batteries was found, and the effect of this behavior on battery performance was studied. It was found that the solute lithium salt in the matrix greatly promoted the gelation of the PPC-based solid electrolyte under heating conditions upon contact with metallic lithium. This behavior allows the room temperature conductivity of the electrolyte to be directly increased by two orders of magnitude, on the order of 10−3 S/cm, and also greatly improves the wettability of the electrode interface. The mechanism of in situ gelation allows the solid state battery to actually operate in a gel state. Since the actual electrochemical window of the electrolyte is only 3.8 V due to gelation, the electrolyte membrane continuously undergoes side reactions during the high voltage cycle, resulting in a continuous decrease in cycle efficiency.