A novel hierarchical "ceramic in polymer - polymer in ceramic" structure composite solid-state electrolyte for safer lithium ion batteries

The development of advanced composite solid-state electrolytes (CSSEs) is considered to be one of the most promising solutions for technological breakthroughs in lithium ion batteries (LIBs). However, it is challenging to fabricate satisfied CSSEs that can meet requirements from mechanical, thermal, safety, and electrochemical perspectives at the same time. Herein, a novel CSSE with the "ceramic in polymer -polymer in ceramic (CIP-PIC)" hierarchical structure is introduced, which exhibits enhanced mechanical properties, safer thermal behavior, and better fire resistance compared to conventional Polyethylene oxide (PEO) solid-polymer electro-lytes (SPEs). The fabricated PMC10 CSSE shows a crystallinity of 15.2 %, a Young's modulus of 3.1 MPa, and an optimal ionic conductivity of 2.33 x 10-4 S cm- 1 at 50 degrees C. The compatible interface enables assembled sym-metrical Li cells stable plating/stripping galvanostatic cycles for 900 h at 0.2 mA cm-2. The LiFePO4|PMC10|Li cell shows an initial capacity density of 158.5 Ah kg -1, and a capacity retention of 80.3 % after 200 cycles. More importantly, compared to PEO SPE, a reduction of 33.4 % of the heat release capacity (HRC) verifies the enhanced fire safety performance of PMC10 CSSE. This work provides an effective approach for the development of CSSEs for the realization of fire-safer LIBs.