H2O‐Boosted MgProton Collaborated Energy Storage for Rechargeable Mg‐Metal Batteries

Abstract Rechargeable magnesium batteries (RMBs) are a kind of energy storage system with high safety, low cost, and high volumetric energy density. In general perception, H 2 O will passivate the Mg‐metal anode. But herein, a coordination–hydrolysis strategy is developed, in which H 2 O can be used as an additive to produce dissociated H + . Moreover, MgH + energy storage mechanism is discovered on CuSe cathode, which helps the specific capacity and energy density enhance to 480 mAh g −1 and 413 Wh kg −1 , respectively. This coordination–hydrolysis strategy also promotes the conductivity and electron transfer ability of electrolyte. Consequently, the specific capacity can remain 247 mAh g −1 even at 2 A g −1 . MgH + energy storage route gets rid of massive cathode material, and protons have the smallest size and lightest weight, whose theoretical energy density can reach 4230 Wh kg −1 . The results elucidated here provide a new route for energy‐dense RMBs.