Trace Water‐induced Morphology Engineering and Oxygen Vacancy for Enhancing the Capacity of Bi2O3 Alkaline Battery‐Anode

Abstract Bi 2 O 3 is a theoretically high capacitive anode material; however, its low conductivity and deficient surface‐active sites lead to reduced practical capability compared to the theoretical one. Herein, a facile and environmentally benign strategy is developed to simultaneously tailor the morphology and create oxygen vacancies in Bi 2 O 3 by adding trace water in a solvothermal procedure. Here trace water serves as an intermediary agent to change the growth mechanism of Bi 2 O 3 and form a hierarchical structure with increased crystallinity. Electrochemical experiments reveal that the optimal tremella‐shaped Bi 2 O 3 delivers a higher specific capacity, approximately reaching 65 % of the theoretical one. Such satisfactory electrochemical performance is due to the regulated tremella shape and the created oxygen vacancies, which can expose more electrochemical active‐sites and promote ion diffusion. Moreover, the massive oxygen vacancies and increased crystallinity are also beneficial for electron transfer, thus enhancing the capacity. Eventually, a Bi 2 O 3 ‐6//AC asymmetric device is constructed and a superior energy density (40.8 Wh kg −1 ) is realized than the others Bi 2 O 3 ‐based peers. This study paves a facile way for exploring advanced Bi 2 O 3 ‐based alkaline battery anode materials through an environmentally benign method.