Unlocking Ultra‐Long Cycle Stability of Li Metal Electrode by Separators Modified by Porous Red Phosphorus Nanosheets

Abstract By surface‐decorating a conventional polypropylene separator with a porous red phosphorus nanosheet, it is demonstrated exceptional cycling performance of the Li metal electrode in both Li||Li symmetric cells, achieving over 9000 h of cycle life at 20 mA cm −2 and 10 mA h cm −2 , as well as in Li (20 µm)||LiFePO 4 full cells, which exhibited over 95% capacity retention after 400 cycles at a 2C rate. Experimental evidence and theoretical calculations attribute the ultra‐long cycle stability to the unique structural, chemical, and electronic features of red phosphorus, which facilitate rapid Li + transfer and promote the formation of an inorganic‐dominant solid electrolyte interphase (SEI) composition rich in LiF.