Switchable and Strain-Releasable Mg-Ion Diffusion Nanohighway Enables High-Capacity and Long-Life Pyrovanadate...

Rechargeable magnesium batteries (RMBs) suffer from low capacity and poor cyclability of cathode materials, which is due to the sluggish Mg²⁺ diffusion kinetics and large lattice strain. Here, a layer-interweaving mechanism in lamellar cathode to simultaneously facilitate Mg²⁺ diffusion and release Mg²⁺ -insertion strain is reported. In the Cu₃ V₂ O₇ (OH)₂ ·2H₂ O (CVOH) cathode, Mg²⁺ diffusion highways are generated by the vertical interweaving of CVOH layers and V₆ O₁₃ layers that nucleate in CVOH during discharging, which are switchable by Mg²⁺ insertion/extraction. These highways enhance the Mg²⁺ diffusion coefficient by three orders of magnitude and release 50% Mg²⁺ -insertion strain. This enables CVOH to exhibit a high capacity of 262 mAh g^-1 at high current density of 250 mA g^-1 in aqua, and extremely low capacity loss of 0.0004% per cycle in the activated carbon//CVOH cell. This work inspires designing the magnesiation phase transformation of electrodes to resolve both kinetic and strain issues for high-performance RMBs.