Lattice expanding by Te-substitution to boost electrochemical Mg storage of Cu7.2S4 nanotube cathode

Cation-rich Cu7.2S4 with high Cu2+ mobility has been researched as a promising cathode candidate for rechargeable magnesium batteries, yet suffers from large polarization and sluggish kinetics resulted from strong electrostatic interactions among host lattice and high-charge Mg2+. Herein, lattice expansion by in-situ anion-substitution with heavy element tellurium is presented to regulate the redox chemistry of Cu7.2S4 nanotube cathode. Benefitting from lattice tailoring, the Te-substituted Cu7.2S4 nanotube cathode delivers ultra-high discharge capacity of 354.1 mAh g−1 at 0.1 A g−1 and remarkable rate capability of 85.1 mAh g−1 at large current loading of 2.0 A g−1. The ultra-long cycling stability is achieved for 2000 cycles with 0.0277 % capacity decay per cycle. The significant improvement of Mg2+ storage performances of Te-substituted Cu7.2S4 nanotube can be attributed to the reinforced Te-substitution, that can generate lattice expansion and effectively adjust the Mg2+ storage reaction. The present lattice regulation strategy holds the great potential in electrode material modification for improving battery chemistry.