Stabilized Molybdenum Trioxide Nanowires as Novel Ultrahigh‐Capacity Cathode for Rechargeable Zinc Ion Battery

Exploration of high‐performance cathode materials for rechargeable aqueous Zn ion batteries (ZIBs) is highly desirable. The potential of molybdenum trioxide (MoO 3 ) in other electrochemical energy storage devices has been revealed but held understudied in ZIBs. Herein, a demonstration of orthorhombic MoO 3 as an ultrahigh‐capacity cathode material in ZIBs is presented. The energy storage mechanism of the MoO 3 nanowires based on Zn 2+ intercalation/deintercalation and its electrochemical instability mechanism are particularly investigated and elucidated. The severe capacity decay of the MoO 3 nanowires during charging/discharging cycles arises from the dissolution and the structural collapse of MoO 3 in aqueous electrolyte. To this end, an effective strategy to stabilize MoO 3 nanowires by using a quasi‐solid‐state poly(vinyl alcohol)(PVA)/ZnCl 2 gel electrolyte to replace the aqueous electrolyte is developed. The capacity retention of the assembled ZIBs after 400 charge/discharge cycles at 6.0 A g −1 is significantly boosted, from 27.1% (in aqueous electrolyte) to 70.4% (in gel electrolyte). More remarkably, the stabilized quasi‐solid‐state ZIBs achieve an attracting areal capacity of 2.65 mAh cm −2 and a gravimetric capacity of 241.3 mAh g −1 at 0.4 A g −1 , outperforming most of recently reported ZIBs.