An Aqueous Manganese-Ion Battery with NaV6O15/C Microrods as a Stable Mn²⁺ Storage Host

Manganese-ion batteries (MIBs) involving aqueous electrolytes are regarded as next-generation energy-storage systems for utilization in safe and non-flammable, grid-scale energy-storing appliances. For practical application, it is very important to establish a stable cathode with a high capacity and stable cycle life. In this respect, vanadium-based layered oxides have been well demonstrated as suitable cathodes for aqueous-electrolyte-based batteries due to their high theoretical capacity and adequate working voltage. However, the dissolution of vanadium in the aqueous electrolyte directly affects the cycle life of the vanadium-based layered oxides. In the present study, a carbon-coating approach is established to boost the rate capability and cycling stability of the NaV6O15 (NVO) cathode. When employed as a cathode for MIBs, the carbon-coated NaV6O15 (NVO/C) supplies a stable recoverable capacity of 149 mAh g−1 at 0.4 A g−1 after the 1600 consecutive cycles with 88 % capacity retention, along with a rapid Mn2+ storage ability of 6000 cycles at 3.0 A g−1 with 74 % capacity retention.