Polyoxymethylene-based solid polymer electrolyte for high-performance room-temperature all-solid-state lithium batteries

Abstract

Compared with flammable liquid electrolytes, solid state electrolytes show promising potential for lithium-ion batteries with high safety and high energy density simultaneously due to their high thermal stability, mechanical strength, excellent chemical and electrochemical stability. Solid polymer electrolytes are an attractive choice to achieve high energy density due to their thinness and good manufacturability. However, traditional solid polymer electrolytes typically need to operate at above 60 °C due to the insufficient room-temperature ionic conductivity, thereby limiting its practical application in common room temperature lithium-ion batteries. Here, we report a novel design of polyoxymethylene (POM)-based solid polymer electrolytes for high-performance room-temperature all-solid-state lithium batteries. This design includes POM and lithium bis(trifluoromethylsulfonyl)amine (LiTFSI), which offers the similar structure to polyethylene oxide based solid electrolyte while with shorter chain segments to achieve higher ionic conductivity (2.8 × 10⁻⁴S cm⁻¹) and mechanical strength at room temperature. As a result, lithium dendrites can be efficiently suppressed, and symmetrical Li-Li cells have demonstrated more than 300 h of cycling at 0.05 mA cm⁻². The wide electrochemical stability window of 4.75 V also enables broader application for full cells. All-solid-state lithium batteries fabricated with POM/LiTFSI exhibit excellent cycling stability for 150 cycles at 0.2 C rate at room temperature. The design breaks through the useable temperature limit of solid polymeric electrolytes and broaden their application in all-solid-state lithium batteries.