Phase-engineered MoO₃/MoO₂ heterostructures for enhanced Zn²⁺/H⁺ pseudocapacitive storage in aqueous zinc-ion...

MoO₃ is a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to its multi-electron redox capability, high proton conductivity, and low structural strain. However, its practical application is hindered by severe electrochemical dissolution and irreversible side reactions in acidic environments, leading to significant deterioration in cycling stability and rate performance. Here, we construct a MoO₃/MoO₂ heterostructure by phase engineering to enhance Zn²⁺ and H⁺ storage behavior at specific potential windows, thereby improving the chemical and electrochemical stability of MoO₃ electrode. This heterogeneous interface enhances ion transport, introduces abundant pseudocapacitive sites and achieves a transition H⁺ storage from intercalation to surface-dominated pseudocapacitive behavior at low potentials. Furthermore, the superior electrical conductivity and structural stability of the MoO₂ phase synergistically optimize the electronic structure of the MoO₃/MoO₂ heterostructures while effectively suppressing dissolution of active materials. As a result, the MoO₃/MoO₂ cathode exhibits outstanding rate performance (173 mAh g^-1 at 0.2 A g^-1, 98 mAh g^-1 at 10 A g^-1) and excellent cycling stability (101 mAh g^-1 after 2000 cycles at 5 A g^-1, 73 % capacity retention). This phase-modulated heterostructure strategy offers new insights into improving cycling stability and rate performance in AZIBs.