Self-healing composite solid electrolytes with enhanced Li+ transport and mechanical properties for safe lithium metal batteries

The Li dendrites introduced by the inhomogeneous Li-ion flux are the barriers to the commercialization of solid-state lithium metal batteries (LMBs). Increasing the Li+ transference number and homogenizing the Li+ flux are two effective strategies to solve the aforementioned issues. Herein, a flexible composite solid electrolyte (CSE) with an enhanced Li+ transference number, high ionic conductivity, and self-healing function was synthesized via a simple template method. Boron nitride (BN) nanosheets with high specific surface area and richly porous structure were used as the passive inorganic filler, homogenizing the Li+ flux and facilitating the Li+ transmission. The flexible and self-healing features of the CSE reduced the interface resistance and considerably prolonged their cycling life. By exploiting stress–strain curves before and after healing, along with physical characterizations, the self-healing efficiency was obtained and the dendrite suppress mechanisms at the electrode/CSE interface were discussed. Finally, the assembled LiFePO4/Li cell with optimized CSE exhibited impressive cycling performance and delivered a steady discharge capacity up to 152 mA h g−1 after 300 cycles at 0.1C. This universal strategy can be used in other emerging energy storage fields to boost high energy density and long cycling life.