Abstract
Mg-ion batteries (MIBs) are promising next-generation secondary batteries, but suffer from sluggish Mg(2+) migration kinetics and structural collapse of the cathode materials. Here, an H(2)O-Mg(2+) waltz-like shuttle mechanism in the lamellar cathode, which is realized by the coordination, adaptive rotation and flipping, and co-migration of lattice H(2)O molecules with inserted Mg(2+), leading to the fast Mg(2+) migration kinetics, is reported; after Mg(2+) extraction, the lattice H(2)O molecules rearrange to stabilize the lamellar structure, eliminating structural collapse of the cathode. Consequently, the demo cathode of Mg(0.75)V(10)O(24)·nH(2)O (MVOH) exhibits a high capacity of 350 mAh g(-1) at a current density of 50 mA g(-1) and maintains a capacity of 70 mAh g(-1) at 4 A g(-1). The full aqueous MIB based on MVOH delivers an ultralong lifespan of 5000 cycles The reported waltz-like shuttle mechanism of lattice H(2)O provides a novel strategy to develop high-performance cathodes for MIBs as well as other multivalent-ion batteries.