Metal Selenide-Based Superstructure Nanoarrays with Ultrahigh Capacity for Alkaline Zn Batteries

Transition metal selenides (TMSs) have great potential as cathode materials for alkaline Zn batteries (AZBs) owing to their high theoretical capacity and metallic conductivity. However, achieving a high specific capacity remains a formidable challenge due to the low structural stability and sluggish reaction kinetics of single-phase TMS. Herein, a facile method for fabricating a robust CoSe₂@Ni₃Se₄@Ni(OH)₂ superstructure nanoarray (CNSNA) as an AZB cathode is presented. The sophisticated design enables structural stability and abundant active surface sites for efficient charge storage. Furthermore, the redox mediator K₃[Fe(CN)₆] is employed to expedite the reaction kinetics and introduce supplementary redox reactions, further enhancing the charge storage capability. Consequently, the CNSNA electrode delivers an exceptional specific capacitance (609.08 mAh g^-1 at 1 A g^-1), surpassing all previously reported selenide-based materials. High-rate capability (239.37 mAh g^-1 at 20 A g^-1) and long cycling stability have also been achieved. The comprehensive charge storage mechanism studies confirmed the structural integrity, kinetic improvement, and high reactivity of the CNSNA superstructure. Moreover, the corresponding AZB based on CNSNA demonstrates an extraordinarily high energy density of 516.58 Wh kg^-1. The work offers guidance in the construction of superstructure-based TMS electrode materials, paving the way for the development of high-performance AZBs.