Oxygen Vacancy Engineering of TiNb2O7 Modified PE Separator Toward Dendrite‐Free Lithium Metal Battery

Lithium metal battery with high specific energy and high safety is crucial for the next-generation energy storage technologies. However, the poor thermal stability, lower mechanical performance, and poor electrochemical performance of the commercially available polyethylene (PE) separator hinders the development of high-specific lithium metal batteries. Herein, a functional PE separator is prepared by innovative coating the TiNb2O7 microspheres with oxygen vacancies on the surface of PE (denoted as TNO-x-PE). The porosity, contact angle, electrolyte uptake rate, thermal shrinkage rate, mechanical properties, conductivity as well as lithium ions transference number of the TNO-x modified PE separator are all improved. The favorable TNO-x is beneficial for facilitating fast Li+ migration and impeding anions transfer, guiding the uniform distribution of lithium-ion flux. Consequently, the lithium symmetric cells with TNO-x-PE separator can be stably cycled more than 1600 h at 1 mA cm-2, and the initial capacity of the LFP/Li cells with TNO-x-PE separator is as high as 139.8 mAh g-1, and after 500 cycles, the capacity retention rate is still 99.5%. This work may provide a new idea to construct a multi-functional separator with high safety and superior electrochemical performance and promote the development of LMBs.