Valence modulation and morphological engineering of MoO3 as high-performance cathode for aqueous zinc ion batteries

Molybdenum trioxide (MoO3) has become the preferred choice of cathode materials for aqueous zinc ion batteries (AZIBs) because of their multivalency, high theoretical capacity, and unique layered structure. However, MoO3 suffers from low conductivity and poor cycling stability, which severely limits its practical application for commercialization. Here, we develop a morphological engineering couple valence modulation to remarkably enhance the Zn2+ storage capability of commercial MoO3 powder. Uniform MoO3 with low-valence-state Mo (denoted as MoO3−x) nanoparticles are readily manufactured through a simple solvothermal method with ethylene glycol as a reductant. Taking the merits of the increased electrical conductivity, Zn2+ diffusion rate and active sites, the Zn//MoO3−x battery achieves a boosted capacity of 144 mAh g−1 at 2 A g−1, substantially superior to the Zn//MoO3 one (only 17 mAh g−1). In addition, the Zn//MoO3−x battery exhibits an excellent energy density of 146 Wh kg−1 and good cycle stability with a capacity loss of only 0.07% per cycle over 500 cycles. This work provides an attractive approach to enhance the electrochemical properties of molybdenum-based materials and may open new idea to design advanced cathode material for AZIBs.