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