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

NiCo 2 S 4 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 NiCo 2 S 4 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 NiCo 2 S 4 and optimize the electronic structure, thereby enhancing the crystal activity. Moreover, this process could also ensure the integrity of the NiCo 2 S 4 structure. Among them, NiCo 2 S 4 @0.1 with the highest Li content had a high specific capacitance (1 A g –1 @1048.6 F g –1 ) and an excellent rate performance (5 A g –1 @995 F g –1 ). Therefore, NiCo 2 S 4 as an electrode material for supercapacitors has great potential. To study the application value of NiCo 2 S 4 electrodes, NiCo 2 S 4 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.