Stable Electrodeposition of Lithium Metal Driven by Interfacial Unsaturated Solvation Environments

The lithium (Li) dendrite and parasitic reactions are the two major challenges for the Li-metal anode, which is the most prominent anode for high-energy-density storage. However, in recent years, most studies have still focused on the increasingly complex design of electrolytes or solid electrolyte interfaces, and the essence of Li⁺ ion electrodeposition has been overlooked. Herein, we demonstrate a simple but useful strategy to control the Li solvation species in a classical electrolyte and promote its stable electrodeposition. In commonly used electrolytes consisting of ethylene carbonate (EC) and dimethyl carbonate, the first solvation shell of Li⁺ ions converts from EC-coordination-dominant to anion-diluent-dominant by simply reducing the EC content. Molecular simulations are performed to reveal that the latter solvation species could promote Li⁺ ions to become coordination-unsaturated in the electrical double layer and prefer to be reduced at the anode interface. Consequently, the simple tuning of local polarity around Li⁺ ions not only extends the cycling performance of the Li-metal anode significantly but also effectively suppresses Li-dendrite and parasitic reactions, which may inspire a rethinking of simple approaches for Li-metal anode challenges.