Ultralong-life and high-capacity magnesium/sodium hybrid-ion battery using a ternary CoSe/NiSe 2 /CuSe 2 cathode and dual-ion electrolyte.

An ultrahigh-performance magnesium/sodium hybrid-ion battery (MNHB) is developed using ternary CoSe/NiSe 2 /CuSe 2 (CNCS) "micro-flowers" as cathode materials, working with a coordinative [Mg 2 Cl 2 ][AlCl 4 ] 2 and bis(trifluoroethylsulfonyl)imide anionic sodium salt in triglyme electrolyte. After 2000 cycles at 2.0 A g -1 , the MNHB shows a stable capacity of 115.5 mA h g -1 and a high Coulombic efficiency exceeding 99.8%. The battery shows very rapid charging, and good stability in extreme environments, providing new opportunities to develop other hybrid-ion systems.