Abstract The polycrystalline intermetallic vanadium carbide (V8C7) is successfully synthesized and investigated as an electrode material for electrochemical capacitors. The V8C7 electrode has a large specific capacitance of 161.7 F g−1 in 1.0 mol L−1 Na2SO4 at a specific current density of 1 A g−1 and remains 92.8% of this value after 10,000 cycles. 83.3% of the initial value can maintain even at a high current density of 10 A g−1. The outstanding electrochemical performance is attribute to the high electrical conductivity of V8C7 which can ensure fastly charge transfer. Combined with the analysis of specific capacitances and specific surface areas, the charge storage mechanism belongs to the sub-surface space pseudocapacitive mechanism. Moreover, the V8C7//activated carbon asymmetrical electrochemical capacitor owns a high energy density of 16.9 W h kg−1 at a power density of 8.7 kW kg−1.

中文翻译：

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金属间碳化钒的电化学电容

摘要 多晶金属间碳化钒（V8C7）被成功合成并作为电化学电容器的电极材料进行研究。V8C7 电极在 1 A g-1 的特定电流密度下在 1.0 mol L-1 Na2SO4 中具有 161.7 F g-1 的大比电容，并且在 10,000 次循环后保持该值的 92.8%。即使在 10 A g-1 的高电流密度下也能保持初始值的 83.3%。优异的电化学性能归功于 V8C7 的高导电性，可确保快速电荷转移。结合比电容和比表面积的分析，电荷存储机制属于次表面空间赝电容机制。此外，V8C7//活性炭非对称电化学电容器具有16的高能量密度。