Optimisation of Mo doping to form NiCoMo ternary sulphides for high performance charge storage

Abstract

Multi-component synergy and the rational design of structures are effective methods for preparing electrode materials for high-performance energy storage devices. Transition metal-based hydroxides offer advantages such as a large specific surface area, large interlayer spacing, multiple redox states, and high theoretical capacity, making them commonly used as positive materials for supercapacitors. However, challenges like low conductivity and severe agglomeration limit their practical application. This study focuses on the preparation of Ni, Co, and Mo ternary transition metal hydroxides by incorporating the Mo element to optimize their structure. Furthermore, sulfide ions were utilized in an ion exchange process to replace hydroxides, resulting in the formation of NiCoMo ternary sulfide electrode materials. By adjusting the amount of Mo added, a spherical nanoneedle-shaped N₂C₁MS_0.2-2 electrode material was successfully synthesized. This electrode exhibited a specific capacity of 2094 F g⁻¹ at a current density of 1 A g⁻¹. In addition, an asymmetric supercapacitor was assembled with activated carbon as the negative electrode and N₂C₁MS_0.2-2 as the positive electrode, which had an energy density of 46.2 W h kg⁻¹ at a power density of 800 W kg⁻¹, a capacity retention of 89.7% and a coulombic efficiency of 97.8% after 10 000 cycles. This study provides a reference for the design and preparation of ternary sulphide electrode materials.