Dual Supports by Cation Vacancies and Surface Optimization for CoNiSe2-Based Hybrid Supercapacitors with High Energy Density

Transition metal selenides as electrode materials for supercapacitors are becoming increasingly attractive, and effective modification strategies for improving their practical energy storage performance are highly desired. Herein, a dual modification strategy combined with surface laminating and introducing cation vacancies is utilized to optimize the polynary transition metal selenide CoNiSe2 in the surface and atomic levels. The as-obtained sample CNVS/rGO possesses well-developed surface chemical properties, optimized electron state, more exposed inner electroactive sites, and barrier-decreased kinetics. For the assembled asymmetric hybrid supercapacitor device, a high energy density of 106.2 Wh kg–1 at a power density of 0.77 KW kg–1 is achieved. Importantly, a pseudo-in-situ XPS test method and DFT calculations are conducted for better understanding of the modification mechanisms and electrochemical kinetics. This work presents a performance breakthrough; the corresponding modification strategy and kinetic studies are inspiring for the design of electrode materials in the related fields.