Ion transport regulation of polyimide separator for safe and durable Li-metal battery

Li-metal battery (LMB) gains enormous attentions because of its high energy and power density. However, the cycling stability of LMB is seriously harmed by the increase of internal temperature and Li-dendrite growth. The development of high-safety thermotolerant separators is urgently desired that can provide advantageous channels for rapid ion transport and simultaneously enable homogeneous Li+ fluxes to inhibit dendrite growth. With superior thermal and electrochemical stability, polyimide-based separator is a good alternative to commercial polyolefin-based separators, but prior design of either nanopores or micropores in polyimide-based separator usually met a dilemma. In this work, we report a polyimide sandwiched separator (denoted as s-PIF) with polyimide fiber (PIF) membrane coated by polyimide aerogels. Significant advancements in terms of mechanical property, electrolyte adsorption/retention and ion conductivity can be achieved for the s-PIF separator, compared with PIF separator. Moreover, the s-PIF separator can render a dendrite-free process of Li plating/ stripping for 1400 h. Consequently, the LMB with s-PIF separator shows a remarkable stability with 80 % of its capacity retention after 3000 cycles at 10C.