The effect of temperature on morphology and electrochemical properties of NiCo₂S₄ by hydrothermal synthesis

The hydrothermal method, using the template is a conspicuous way to change the morphology of the product, so it is used widely in many reports. The effect of temperature on morphology of NiCo₂S₄ by hydrothermal synthesis and its electrochemical properties is distinct as high-performance electrode materials for supercapacitors. With the help of the template (carbon sphere), different morphologies of NiCo₂S₄ under 90°C, 120°C and 180°C were obtained. They have different properties after electrochemical analysis. In order to build a hierarchical multi-level structure, two-step vulcanization was carried out at each temperature, resulting in the difference in the morphology and performance of the six sample of electrodes. The obtained NiCo₂S₄ electrodes exhibit 1000Fg-1 at the current density of 1Ag-1 in the second-step of the hydrothermal process under 120°C, which is superior to the microblocks NiCo₂S₄ electrode (90°C, 888Fg-1 at the current density of 1Ag-1) and microparticles NiCo₂S₄ electrode (180°C, 574Fg-1 at the same current density) in the second-step hydrothermal, which shows a high-rate capability (640Fg-1 at 20Ag-1). The obtained nanoparticles NiCo₂S₄ under 180°C in the first-step hydrothermal electrode had an excellent cycle retention rate (89.7%), although its specific capacitance was lower. At the same time, the specific capacitance of these sample electrodes obtained in the second-step hydrothermal process is superior to those from the first-step. It was mainly attributed to the fact that temperature can influence the morphology by controlling ion exchange. And our experiment aims to use the hydrothermal method and the template method to find a more suitable temperature range to provide more ideas.