A hybrid electrochemical capacitor (EC) with enhanced energy density is realized by integrating functionalized carbon nanotube (FCNT) electrodes with redox-active electrolyte that has a neutral pH value (1 M Na₂SO₄ and 0.5 M KBr mixed aqueous solution). The negative electrode shows an electric double layer capacitor-type behavior. On the positive electrode, highly reversible Br⁻/Br₃⁻ redox reactions take place, presenting a battery-type behavior, which contributes to increase the capacitance of the hybrid cell. The voltage window of the whole cell is extended up to 1.5 V because of the high over-potentials of oxygen and hydrogen evolution reactions in the neutral electrolyte. Compared with raw CNT, the FCNT has better wettability in the aqueous electrolyte and contributes to increase the electric double layer capacitance of the cell. As a result, the maximum energy density of 28.3 Wh kg⁻¹ is obtained from the hybrid EC at 0.5 A g⁻¹ without sacrificing its power density, which is around 4 times larger than that of the electrical double layer capacitor constructed by FCNT electrodes and 1 M Na₂SO₄ electrolyte. Moreover, the discharge capacity retained 86.3% of its initial performance after 10000 cycles of galvanostatic charge and discharge test (10 A/g), suggesting its long life cycle even at high current loading.

通过将功能化碳纳米管（FCNT）电极与具有中性pH值（1 M Na ₂ SO ₄和0.5 M KBr混合水溶液）的氧化还原活性电解质集成在一起，可以实现具有增强能量密度的混合电化学电容器（EC ）。负极显示出双电层电容器的行为。在正电极上，高度可逆溴^- /溴₃ ^-发生氧化还原反应，表现出电池类型的行为，这有助于增加混合电池的电容。由于中性电解质中氧气和氢气的放出反应具有很高的过电势，因此整个电池的电压窗口可扩展至1.5V。与原始CNT相比，FCNT在水性电解质中具有更好的润湿性，并有助于增加电池的双电层电容。结果，在不牺牲其功率密度的情况下，在不牺牲其功率密度的情况下，以0.5 A g ^-1从混合EC获得了28.3 Wh kg ^-1的最大能量密度，该能量密度是由FCNT电极构造的双电层电容器的功率密度的约4倍和1 M Na ₂ SO ₄电解质。此外，在经过10000次恒电流充放电测试（10 A / g）后，放电容量保持了其初始性能的86.3％，这表明即使在高电流负载下，其使用寿命也很长。