Robust NiWO₄ Hollow Hydrangea-Like Cathode with Boosted Electrochemical Performance for Aqueous Zinc-Ion Batteries

NiWO₄ shows promising application in the cathode material of aqueous zinc-ion batteries (AZIBs) due to its high capacity. Unfortunately, its practical application is limited by quick capacity fading. In this work, 3D hollow hydrangea-like NiWO₄, comprised of numerous nanoparticles, has been fabricated via a hydrothermal method followed with a calcination. The detailed characterizations are presented, including the structure, morphology, and Zn-storage performance. The William-Hall equation combined with the Scherrer equation gives the average crystal size of about 34.5-36.8 nm. As a cathode of a Zn half battery, 3D hollow hydrangea-like NiWO₄ gives rise to high capacity (361.7 mAh g^-1 at 0.1 A g^-1) and long cycling performance (retaining 98 mAh g^-1 after 2000 cycles at 5.0 A g^-1), which is better than that of the bulk one and can be regarded as a promising cathode candidate for AZIBs.