Preparation of nickel cobalt hydroxide with oxygen vacancies by intercalation of oxidizing anions as a high-performance electrode for supercapacitors

Abstract

Layered double hydroxides (LDHs) are a class of two-dimensional lamellar intercalation materials with significant potential for advanced supercapacitor applications. However, their limited electrical conductivity restricts their performance. In this study, a series of NiCoLDH-X materials intercalated with HPO₄²⁻, SO₄²⁻, ClO₃⁻, BrO₃⁻, and IO₃⁻ anions were successfully synthesized, leading to an increase in interlayer spacing from 0.782 nm to 0.798 nm. This structural modification facilitated higher ionic transport and increased the number of electrochemically active sites, thereby enhancing electrochemical efficiency. Density functional theory (DFT) calculations for NiCoLDH-ClO₃⁻ further supported these findings. Additionally, the oxidizing properties of ClO₃⁻, BrO₃⁻, and IO₃⁻ not only enabled anionic intercalation but also contributed to the formation of oxygen vacancies, significantly improving electrical conductivity. Among the investigated materials, NiCoLDH-ClO₃⁻ exhibited the highest electrochemical energy storage performance, achieving a peak specific capacity of 229.1mAh g⁻¹ at 1 A g⁻¹. Furthermore, the assembled hybrid supercapacitor demonstrated a high specific energy density of 15.06 Wh kg⁻¹ at a power density of 1.91 kW kg⁻¹. Both experimental and theoretical analyses confirmed that the synergistic effect of anionic intercalation and oxygen vacancy formation substantially enhanced the electrochemical properties of NiCoLDH. This strategy provides new insights into the design of high-performance supercapacitors (SCs) and contributes to the development of next-generation energy storage systems.