Enhancing lithium metal battery safety and performance: a thermally stable poly(aryl ether benzimidazole) separator with 2D-functionalized boron nitride for 3000 hours lithium plating/stripping

Traditional polyolefin separators tend to shrink and melt under high-temperature conditions, posing a series of safety risks for lithium metal batteries (LMBs). Moreover, the disordered growth of lithium dendrites on the anode surface of LMBs using polyolefin separators has always been a prevalent issue. In this study, we have successfully prepared an excellent heat-resistant separator using functionalized boron nitride (f-BN) and poly(aryl ether benzimidazole) (OPBI). It is worth mentioning that the excellent compatibility of f-BN with OPBI, along with its amino groups and imidazole groups, aids in regulating the cross-sectional pore structure of the separator. This contributes to achieving uniform Li⁺ deposition and effectively inhibits the irregular dendrite growth on the lithium anode. The Li/OPBI@f-BN/Li cell maintained long-term stability for 3000 hours, which is one of the longest cycling durations to date. In addition, the cell assembled with the OPBI@f-BN separator exhibited excellent charge–discharge performance, achieving 153.98 mA h g⁻¹ and retaining 93.3% of its capacity after 200 cycles at 0.5C. Importantly, the capacity of the cell assembled with OPBI@f-BN separators remains relatively stable at 90 °C even after 50 cycles.