H2O-Boosted Mg-Proton Collaborated Energy Storage for Rechargeable Mg-Metal Batteries

Rechargeable magnesium batteries (RMBs) are a kind of energy storage system with high safety, low cost, and high volumetric energy density. In general perception, H2O will passivate the Mg-metal anode. But herein, a coordination-hydrolysis strategy is developed, in which H2O 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.