A hybrid Mg²⁺/Li⁺ battery based on high-capacity conversion-type cobalt disulfide cathodes with ultralong cycle life and high energy density

Hybrid Mg²⁺/Li⁺ battery (MLIB) is an attractive energy storage system by coupling the advantages of Mg- and Li-rechargeable battery. Currently, conversion-type transitional metal sulfides (CTMS) have attracted attention for MLIB cathodes due to their large theoretical capacity. However, these cathodes suffer severe capacity fading because of huge volumetric change and dissolution of polysulfide intermediates during the process. Herein, a novel self-supported CoS₂/carbon composite nanotube arrays electrode derived from metal-organic framework is used as MLIB cathode. Benefiting from the homogeneous distribution of active nanoparticles in nanotube arrays, and the inhibition of the dissolution of polysulfide intermediates by N-doped amorphous carbon, as well as the appropriate work voltage range, the cathodes deliver a high specific capacity (697.2 mAh g⁻¹), impressive long cycling life (74% capacity retention at 1.0 A g⁻¹ after 2000 cycles), superior energy density (390.5 Wh Kg⁻¹) and good rate capability. Moreover, the conversion reaction mechanism and the reversibility of CoS₂ in MLIBs are analyzed by the ex-situ X-ray diffraction and transmission electron microscopy characterizations. The electrode design strategy in the present work paves a way to explore more CTMS electrodes with high capacity and long cyclic stability for MLIBs.