Inhibiting irreversible Zn2+/H+ co-insertion chemistry in aqueous zinc-MoOx batteries for enhanced capacity stability

A polyaniline strategy is developed to inhibit the irreversible Zn 2+ /H + co-intercalation/extraction process in MoO 3 cathode for aqueous Zn batteries. This innovative approach delivers an unprecedented capacity and prolonged cycling stability. Rechargeable aqueous Zn-MoO x batteries are promising energy storage devices with high theoretical specific capacity and low cost. However, MoO 3 cathodes suffer drastic capacity decay during the initial discharging/charging process in conventional electrolytes, resulting in a short cycle life and challenging the development of Zn-MoO x batteries. Here we comprehensively investigate the dissolution mechanism of MoO 3 cathodes and innovatively introduce a polymer to inhibit the irreversible processes. Our findings reveal that this capacity decay originates from the irreversible Zn 2+ /H + co-intercalation/extraction process in aqueous electrolytes. Even worse, during Zn 2+ intercalation, the formed Zn x MoO 3− x intermediate phase with lower valence states (Mo 5+ /Mo 4+ ) experiences severe dissolution in aqueous environments. To address these challenges, we developed a first instance of coating a polyaniline (PANI) shell around the MoO 3 nanorod effectively inhibiting these irreversible processes and protecting structural integrity during long-term cycling. Detailed structural analysis and theoretical calculations indicate that =N– groups in PANI@MoO 3− x simultaneously weaken H + adsorption and enhance Zn 2+ adsorption, which endowed the PANI@MoO 3− x cathode with reversible Zn 2+ /H + intercalation/extraction. Consequently, the obtained PANI@MoO 3− x cathode delivers an excellent discharge capacity of 316.86 mA h g −1 at 0.1 A g −1 and prolonged cycling stability of 75.49% capacity retention after 1000 cycles at 5 A g −1 . This work addresses the critical issues associated with MoO 3 cathodes and significantly advances the understanding of competitive multi-ion energy storage mechanisms in aqueous Zn-MoO 3 batteries.