A Novel Asymmetric Diffusion Path for Superior Ion Dynamic in High-Voltage Mg-Based Hybrid Batteries.

Magnesium-based batteries have garnered significant attention due to their high energy density, excellent intrinsic safety, and low cost. However, the application process has been hindered by the high Mg ions diffusion barrier in solid-state structures and solid-liquid interphase. To address this issue, a hybrid battery technology based on Mg anode and Fe-based Prussian Blue Analogue cathode doped with functional transition metal ions and N═O bonds is proposed. Combined multiscale experimental characterizations with theoretical calculations, the subtle lattice distortion can create an asymmetric diffusion path for the active ions, which enables reversible extraction with significantly reduced diffusion barriers achieved by synergistic doping. The optimized cathode exhibits a working potential of 2.3 V and an initial discharge capacity of 152 mAh g at 50 mA g. With the preferred electrolyte combined with equivalent concentration [Mg(µ-Cl)(DME)][AlCl] and NaTFSI salt solution, the hybrid system demonstrates superior cycling performance over 200 cycles at a high current density of 200 mA g, maintaining ≈100% coulombic efficiency with superior ion dynamic. The findings are expected to be marked an important step in the further application of high-voltage cathodes for Mg-based hybrid batteries.