The multi-structure NiCo₂S₄ prepared by solvothermal method for supercapacitor accompanied with positron annihilation study Available to Purchase

Fluffy spherical structure NiCo₂S₄ decorated with cubic phase hexagonal nanosheets was successfully synthesized through a two-step solvothermal method for energy storage. The electrochemical measurements reveal its good reversibility together with its high rate ability (1354 F g⁻¹ at 0.5 A g⁻¹ and 1128 F g⁻¹ at 10 A g⁻¹). Positron annihilation techniques (positron annihilation lifetime spectra and Doppler broadening spectra) were conducted to investigate the defects and the electronic structure of the two-step synthesized NiCo₂S₄. The results showed high S/W ratio, which is consistent with the electrochemical results. An asymmetric supercapacitor (ASC) was assembled in a button cell using the two-step synthesized NiCo₂S₄ as the positive electrode material and commercially activated carbon as the negative electrode material. The ASC presents a high energy density of 30.8 W kg⁻¹ at a power density of 352.2 W kg⁻¹ and 15.5 W kg⁻¹ at a power density of 6860 W kg⁻¹, with excellent cycling stability (89.3% capacitance retention after 3000 cycles) and nearly 100% Coulombic efficiency.