Electron-injection-engineering induced dual-phase MoO_2.8F_0.2/MoO_2.4F_0.6 heterostructure for magnesium storage

Rechargeable magnesium batteries (RMBs) have received increased attention due to their high volumetric capacity and safety. Nevertheless, the sluggish diffusion kinetics of highly polarized Mg²⁺ in host lattices severely hinders the development of RMBs. Herein, we report an electron injection strategy for modulating the Mo 4d-orbital splitting manner and first fabricate a dual-phase MoO_2.8F_0.2/MoO_2.4F_0.6 heterostructure to accelerate Mg²⁺ diffusion. The electron injection strategy triggers weak Jahn-Teller distortion in MoO₆ octahedra and reorganization of the Mo 4d-orbital, leading to a partial phase transition from orthorhombic phase MoO_2.8F_0.2 to cubic phase MoO_2.4F_0.6. As a result, the designed heterostructure generates a built-in electric field, simultaneously improving its electronic conductivity and ionic diffusivity by at least one order of magnitude compared to MoO_2.8F_0.2 and MoO_2.4F_0.6. Importantly, the assembled MoO_2.8F_0.2/MoO_2.4F_0.6//Mg full cell exhibits a remarkable reversible capacity of 172.5 mAh g^-1 at 0.1 A g^-1, pushing forward the orbital-scale manipulation for high-performance RMBs.