One-Step Synthesis of Trace Li ⁺ -Doped NiCo ₂ S ₄ Nanoparticles for High-Performance Asymmetric Supercapacitors

NiCo2S4 has rich redox reaction capabilities, but its electrical conductivity is poor, and the overall activity of the crystal is low. For this purpose, Li-doped NiCo2S4 nanoparticles for supercapacitors were prepared by a one-step solvothermal method. A series of samples were constructed by adjusting the amount of LiCl. The research results revealed that Li doping could increase the defect density of NiCo2S4 and optimize the electronic structure, thereby enhancing the crystal activity. Moreover, this process could also ensure the integrity of the NiCo2S4 structure. Among them, [email protected] with the highest Li content had a high specific capacitance (1 A g–[email protected] F g–1) and an excellent rate performance (5 A g–1@995 F g–1). Therefore, NiCo2S4 as an electrode material for supercapacitors has great potential. To study the application value of NiCo2S4 electrodes, NiCo2S4 and activated carbon were assembled into an aqueous asymmetric supercapacitor (ASC) device. At a power density of 400 W kg–1, it achieved an excellent energy density of 47.2 Wh kg–1. After cycling at a current density of 5 A g–1 for 5000 times, the capacitance retention rate was 92%. This work explored the correlation between crystal structure regulation and electrochemical activity and constructed a crystal phase structure regulation strategy for Li as a dopant, providing new ideas for the design of phase engineering of electrode materials in the field of supercapacitors.