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

Abstract 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 TiNb 2 O 7 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.