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

• Published in: Journal of applied physics 2019-05, Vol.125 (17)
• Main Authors: Li, Zhong, Yuan, Daqing, Zhu, Shengyun, Fan, Ping, Ma, Hailiang, Zhang, Qiaoli, Wen, Ali, Zhu, Jiliang
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.5087981

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.