Genuine divalent magnesium-ion storage and fast diffusion kinetics in metal oxides at room temperature

Rechargeable magnesium batteries represent a viable alternative to lithium-ion technology that can potentially overcome its safety, cost, and energy density limitations. Nevertheless, the development of a competitive room temperature magnesium battery has been hindered by the sluggish dissociation of electrolyte complexes and the low mobility of Mg²⁺ ions in solids, especially in metal oxides that are generally used in lithium-ion batteries. Herein, we introduce a generic proton-assisted method for the dissociation of the strong Mg-Cl bond to enable genuine Mg²⁺ intercalation into an oxide host lattice; meanwhile, the anisotropic Smoluchowski effect produced by titanium oxide lattices results in unusually fast Mg²⁺ diffusion kinetics along the atomic trough direction with a record high ion conductivity of 1.8 × 10^-4 S ⋅ cm^-1 on the same order as polymer electrolyte. The realization of genuine Mg²⁺ storage and fast diffusion kinetics enabled a rare high-power Mg-intercalation battery with inorganic oxides. The success of this work provides important information on engineering surface and interlayer chemistries of layered materials to tackle the sluggish intercalation kinetics of multivalent ions.