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

Rechargeable magnesium batteries (RMBs) suffer from low capacity and poor cyclability of cathode materials, which is due to the sluggish Mg 2+ diffusion kinetics and large lattice strain. Here, a layer-interweaving mechanism in lamellar cathode to simultaneously facilitate Mg 2+ diffusion and release Mg 2+ -insertion strain is reported. In the Cu 3 V 2 O 7 (OH) 2 ·2H 2 O (CVOH) cathode, Mg 2+ diffusion highways are generated by the vertical interweaving of CVOH layers and V 6 O 13 layers that nucleate in CVOH during discharging, which are switchable by Mg 2+ insertion/extraction. These highways enhance the Mg 2+ diffusion coefficient by three orders of magnitude and release 50% Mg 2+ -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.