Boosting the Temperature Adaptability of Lithium Metal Batteries via a Moisture/Acid‐Purified, Ion‐Diffusion Accelerated Separator

Abstract The reliable operation of Li metal batteries suffers from cathode collapse due to high‐voltage cycling, interfacial reactivity of the Li deposits, self‐discharge at the elevated temperatures, as well as the power output deterioration in low‐temperature scenarios. In contrast to the individual electrode optimization, herein, a hetero‐layered separator with an asymmetric functional coating on polyethylene is proposed in response to the aforementioned issues: On the face‐to‐cathode side, the hybrid layer of the molecular sieve and sulfonated melamine formaldehyde can scavenge the hydrofluoric acid and moisture residues from the carbonate electrolyte, maintaining the cathode robustness in both the high‐voltage cycling or high‐temperature storage scenarios; while the pre‐coated Ag 2 S layer in situ generates the Li 10 Ag 3 ‐Li 2 S composite matrix in contact with the Li foil, promoting interfacial ion diffusion and isotropic Li deposition. The as‐constructed LiNi 0.8 Co 0.1 Mn 0.1 O 2 /Li pouch cell (3.2 Ah) with the hetero‐layered separator can achieve a high energy density of 400.6 Wh kg −1 on the cell level, as well as a wider temperature adaptability (0–75 °C). This asymmetric separator strategy enables facile energy‐dense cell prototyping with the commercial electrode/electrolyte.