Lattice expanding by Te-substitution to boost electrochemical Mg storage of Cu_7.2S₄ nanotube cathode

Cation-rich Cu_7.2S₄ 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 Cu_7.2S₄ nanotube cathode. Benefitting from lattice tailoring, the Te-substituted Cu_7.2S₄ 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 Cu_7.2S₄ 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.