Abstract: Core-shell Mn₇C₃@C nanoparticles are synthesized successfully by a facile DC arc-discharge plasma method with CH₄ as carbon source and block metal Mn as manganese material, which are used as electrode materials for high-performance supercapacitors. The as-prepared Mn₇C₃@C mainly composes of spherical nanoparticles with a mean size of about 30-35 nm. Raman spectra provide enough evidence of high electrical conductivity of the graphitic carbon layers. The electrochemical performance of core-shell Mn₇C₃@C nanoparticles electrode material is tested by cyclic voltammograms, galvanostatic charge-discharge and electrochemical impedance spectroscopy, which shows an excellent electrochemical performance, such as high specific capacitance, rapid charge-discharge and so on. The specific capacitance reaches 185.8 F/g at the scan rate of 1 mV/s. Meanwhile, good cycle stability is obtained, where 88% of the initial specific capacitance is retained after 1 000 cycles at the scan rate of 100 mV/s, significantly improving the Mn₇C₃ nanoparticles performance (79%). The excellent electrochemical response is attributed to a well-defined core-shell structure, where a super-conductive, defect-enriched carbon layer that fastens the ion exchange and provides stability for the structure and the pseudocapacitive contribution from Mn₇C₃ core, which generates an optimal dual energy storage mechanism of double-layer capacitance and pseudocapacitance.

 http://dx.doi.org/10.7511/dllgxb201606003