Scalable Preparation of Polyimide Sandwiched Separator for Durable High‐Rate Lithium‐Metal Battery

Abstract The ever‐growing demands for efficient energy storage accelerate the development of high‐rate lithium‐metal battery (LMB) with desirable energy density, power density, and cycling stability. Nevertheless, the practical application of LMB is critically impeded by internal temperature rise and lithium dendrite growth, especially at high charge/discharge rates. It is highly desired but remains challenging to develop high‐performance thermotolerant separators that can provide favorable channels to enable fast Li+ transport for high‐rate operation and simultaneously homogenize the lithium deposition for dendrite inhibition. Polyimide‐based separators with superior thermal properties are promising candidate alternatives to the commercial polyolefin‐based separators, but previous strategies of designing either nanoporous or microporous channels in polyimide‐based separators often meet a dilemma. Here, a facile and scalable approach is reported to develop a polyimide fiber/aerogel (denoted as PIFA) separator with the microporous polyimide fiber membrane sandwiched between two nanoporous polyimide aerogel layers, which can enable LMBs with remarkable capacity retention of 97.2% after 1500 cycles at 10 C. The experimental and theoretical studies unravel that the sandwiched structure of PIFA can appreciably enhance the electrolyte adsorption and ionic conductivity; while, the aerogel coating can effectively inhibit dendrite growth to realize durable high‐rate LMBs.