Effect of copper to Selenium@Microporous carbon cathode for Mg–Se batteries with nucleophilic electrolyte

To enhance the electrochemical performance of Se cathode for high-energy-density magnesium-selenium (Mg–Se) batteries with easily prepared nucleophilic (PhMgCl) 2 -AlCl 3 +LiCl/THF (APC-based) hybrid electrolyte, Cu doped Se@MC composites (Cu–Se@MC) with different Cu content (0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) are prepared by impregnation reduction and melting selenization method. The composites are composed of a mixture of chain-structured Se and CuSe embedding in the microporous carbon, and the addition of Cu significantly improves reversibility and cycle life of the composites in the nucleophilic APC-based hybrid electrolyte. At the 0.25 Cu content, the cell exhibits 346.7mAhg −1 first discharge capacity and the specific capacity maintains at 112mAhg −1 after 200 cycles at a current density of 50 mA g −1 , which is superior to that with non-nucleophilic Mg(HMDS) 2 -(AlCl 3 ) 2 –MgCl 2 +LiTFSI/DME (HMDS-based) and MBA-(MgCl 2 ) 2 –(AlCl 3 ) 2 +LiCl/THF (MBA-based) hybrid electrolytes.