Y.Y. Zhu, X. Ji, L.F. Yang, J. Jia, S. Cheng*, H.L. Chen, Z-S Wu, D. Passarello, M.L. Liu

Journal of Materials Chemistry A, 2020, 8, 7819-7827.

DOI: 10.1039/D0TA00697A [PDF]

Mo₂C is one of the few compounds that possess good electronic conductivity. Meanwhile, it possesses a natural 1D zigzag tunnel structure that is ideally suited for fast ion diffusion. Here, an effective approach is demonstrated for fabrication of structurally stable N-doped Mo₂C/C nanobelts. They demonstrate high and fast energy storage ability with initial capacitances of 1139 C g⁻¹at 1 mV s⁻¹, 151 C g⁻¹at an extremely high scan rate of 2000 mV s⁻¹and 208 C g⁻¹at a discharge current density of 200 A g⁻¹. After electrochemical activation of cycling, the capacity is continuously enhanced and much higher capacitances of 2523 C g⁻¹at 1 mV s⁻¹and 1403 C g⁻¹at 50 A g⁻¹are achieved after 15 000 cycles at 50 mV s⁻¹. Using the power law, it is evaluated that a surface-controlled capacitive process makes the main contribution to the capacity, which is over 90% when the scan rates are higher than 10 mV s⁻¹and still high as 73% at 1 mV s⁻¹. Fromin situsynchrotron XRD, it is found that there is a negligible change in the crystal structure and volume during charging/discharging, reflecting an insertion-type charge storage mechanism.