Reinforced bonding of Mo-doped MnO2 with ammonium-ion as cathodes for durable aqueous MnO2–Zn batteries

Abstract

Aqueous rechargeable Zn//MnO2 batteries have attracted extensive research interest owing to their low cost and high energy density. However, the slow reaction kinetics, the disproportionation of the MnO2 cathode, and the irreversible phase transition mechanism considerably restrict their development. Here, we chose Mo-doped α-MnO2 (Mo–MnO2) as the cathode material and proposed a stable N–H⋯O bond-reinforced interaction formed via NH4+ intercalation to stabilize the 2 × 2 tunnel structure of Mo–MnO2. Theoretical and experimental studies were conducted to demonstrate the performance of the cathode. Mn3+ dissolution was effectively inhibited, and lattice distortion did not occur during the proton insertion/removal process, which further improved the cyclic stability of the cathode. Specifically, at a current density of 100 mA g−1, the Mo–MnO2 cathode exhibited a specific capacity of 265.2 mA h g−1, the energy density was 364.3 W h kg−1, and the cathode exhibited excellent cyclic stability. At a current density of 2.0 A g−1, the specific capacity was 95.2% after 1000 cycles. This work provides further insight into the bond interaction between nonmetallic cations in the main materials of electrodes and contributes to the construction of aqueous-based zinc-ion batteries with high energy density and long-term cycling capability.