HO-Mg Waltz-Like Shuttle Enables High-Capacity and Ultralong-Life Magnesium-Ion Batteries.

Mg-ion batteries (MIBs) are promising next-generation secondary batteries, but suffer from sluggish Mg migration kinetics and structural collapse of the cathode materials. Here, an HO-Mg waltz-like shuttle mechanism in the lamellar cathode, which is realized by the coordination, adaptive rotation and flipping, and co-migration of lattice HO molecules with inserted Mg, leading to the fast Mg migration kinetics, is reported; after Mg extraction, the lattice HO molecules rearrange to stabilize the lamellar structure, eliminating structural collapse of the cathode. Consequently, the demo cathode of MgVO·nHO (MVOH) exhibits a high capacity of 350 mAh g at a current density of 50 mA g and maintains a capacity of 70 mAh g at 4 A g. The full aqueous MIB based on MVOH delivers an ultralong lifespan of 5000 cycles The reported waltz-like shuttle mechanism of lattice HO provides a novel strategy to develop high-performance cathodes for MIBs as well as other multivalent-ion batteries.