Electrolyte Solvation Manipulation Enables Unprecedented Room-Temperature Calcium Metal Batteries.

Calcium metal batteries (CMBs) provide a promising option for high-energy and cost-effective energy storage technology beyond current state-of-the-art lithium-ion batteries. Nevertheless, the development of room-temperature CMBs is significantly impeded by the poor reversibility and short lifespan of calcium metal anode. Herein we report a solvation manipulation strategy to improve the plating/stripping reversibility of calcium metal anode by enhancing the de-solvation kinetics of calcium ions in the electrolyte. The introduction of lithium salt greatly changes the electrolyte structure by reducing coordination number of calcium ions in the first solvation shell. As a result, an unprecedented Coulombic efficiency (CE) of calcium metal anode for galvanostatic plating/stripping is achieved up to 99.1%, accompanying with a very stable long-term cycling performance over 200 cycles at room temperature. This work may open up a new opportunity for developing practical calcium metal batteries.