ZnNixMnxCo2-2xO4 Spinel as a High-Voltage and High-Capacity Cathode Material for Nonaqueous Zn-Ion Batteries

Nonaqueous Zn-ion batteries are regarded as one alternative for Li-ion batteries. Such batteries not only afford attractive attributes of cost, but also embody the advantages of the high-specific capacities of Zn anodes, as well as the wide potential window of nonaqueous electrolytes. To fully exploit these advantages, improved cathode materials are highly desired. In this manuscript, a new series of spinels, ZnNixMnxCo2-2xO4, are reported as cathode materials for nonaqueous Zn-ion batteries. Full cells constructed using this new spinel (x = 1/2) as a cathode paired with a metal anode showed capacities over 200 cycles of 174 mAh g(-1) and an open circuit potential of 2.05 V. The battery exhibits an energy density of 305 Wh kg(-1), which is the highest energy density yet reported for a Zn-intercalation cathode. The data show that the Zn2+ ions reversibly intercalate into the spinel structure during the charge/discharge processes, a compositional transformation directly correlated with a multiply reversible conversion between Co4+/Co3+, Ni4+/Ni3+/Ni2+, and Mn4+/Mn3+ oxidation states within the lattice. The data suggest that Mn, Ni cosubstitution for Co in ZnCo2O4 is an efficient method to facilitate Zn-deintercalation and enhance discharge capacity, which may provide some guidelines for designing more attractive multivalent cathodes materials.