Multi‐Valent Cation Strategies for Controlling Interphase Chemistry at the Lithium Metal Anode

The effectiveness of a solid electrolyte interphase (SEI) in lithium metal batteries (LMBs) is crucial for the reversible deposition and dissolution of lithium (Li). Herein, a multi‐valent cation (MVC) is proposed approach to enable superior LMB performance without increasing conducting salt concentration, thus reducing the cost and environmental footprint of LMBs. In this approach, a minimal amount of magnesium carbonate (MgCO 3 ) of 0.05 m is added to a lithium hexafluorophosphate (LiPF 6 ) based electrolyte, which effectively scavenges hydrogen fluoride (HF) generated from hydrolysis of LiPF 6 . Concurrently, the HF scavenging process dissolves MgCO 3 microparticles and releases Mg 2+ cations. It is noteworthy that multivalent Mg 2+ cations, due to their high charge density, enrich the electric double layer with anions that preferentially decompose to form an anion‐derived SEI. Consequently, the MVC approach facilitates enhanced reversibility of Li metal deposition and dissolution, as well as stable galvanostatic cycling of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811)||Li cells. This approach provides a highly effective pathway for designing anion‐derived SEI, offering new insights into the control of Li metal interfaces.