Boosting the cycling stability of rechargeable magnesium batteries by regulating the compatibility between nanostructural metal sulfide cathodes and non-nucleophilic electrolytes

Rechargeable magnesium batteries are attractive candidates for energy storage due to their high theoretical specific capacities, free of dendrite formation and natural abundance of magnesium. However, the development of magnesium secondary batteries is severely limited by the lack of high-performance cathode materials and the incompatibility of electrode materials with electrolytes. Herein, we report the application of CuS nanoflower cathode material based on the conversion reaction mechanism for highly reversible magnesium batteries with boosted electrochemical performances by adjusting the compatibility between the cathode and electrolyte. By applying non-nucleophilic electrolytes based on magnesium bis(hexamethyldisilazide) and magnesium chloride dissolved in the mixed solvent of tetrahydrofuran and N-butyl-N-methyl-piperidinium bis((trifluoromethyl)sulfonyl)imide (Mg(HMDS)₂-MgCl₂/THF-PP₁₄TFSI) or magnesium bis(trifluoromethanesulfonyl)imide, magnesium chloride and aluminium chloride dissolved in dimethoxyethane (Mg(TFSI)₂-MgCl₂-AlCl₃/DME), the magnesium batteries with CuS nanoflower cathode exhibit a high discharge capacity of ~207 mAh·g^–1 at 100 mA·g^–1 and a long life span of 1,000 cycles at 500 mA·g^–1. This work suggests that the rational regulation of compatibility between electrode and electrolyte plays a very important role in improving the performance of multi-valent ion secondary batteries.