CoSe(OH)/Bi2O2Se heterostructure composites synthesized by one-step method as an anode material of high-performance alkaline supercapattery

Improving the energy storage capabilities of aqueous alkaline supercapatteries relies heavily on the development of high-performance anode materials. Here, we presented a one-step composite molten salts method for the preparation of cobalt selenium hydroxide and Bi 2 O 2 Se heterostructure composites (CoSe(OH)/Bi 2 O 2 Se). The composite capitalizes on the advantageous interlayer properties of two-dimensional (2D) layered Bi 2 O 2 Se, connected via weak Van der Waals forces, alongside the high theoretical specific capacity of cobalt hydroxide derived from cobalt selenium hydroxide. This synergy facilitates efficient ion transport, thus exhibiting remarkable electrochemical characteristics. Specifically, CoSe(OH)/Bi 2 O 2 Se demonstrates a great specific capacity of 313.6 mAh/g at 1 A/g, significantly outperforming pure Bi 2 O 2 Se nanosheets. Moreover, CoSe(OH)/Bi 2 O 2 Se exhibits remarkable rate capability with 63.8% capacitance retention at sufficiently high current density (20 A/g), and excellent cycle performance that the capacitance remains is 70.3% after 1000 cycles of GCD testing. Additionally, ex-situ XRD analysis of CoSe(OH)/Bi 2 O 2 Se at different charge and discharge stages provides further insights into its energy storage mechanism. Furthermore, the NiAl-Cl LDH// CoSe(OH)/Bi 2 O 2 Se device demonstrates high power density and energy density. These results validate the feasibility of enhancing the electrochemical performance of 2D Bi 2 O 2 Se layered materials through the incorporation of active and cost-effective transition metal oxides/hydroxides, highlighting the tremendous potential of CoSe(OH)/Bi 2 O 2 Se as a negative electrode material for aqueous alkaline supercapattery.