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.