The electrochemical capacitor (EC) is a key enabler for the miniaturized self-powered systems expected to become ubiquitous with the advent of the internet-of-things (IoT). Vertically aligned carbon nanotubes (VACNTs) on graphite holds promise as electrodes for compact and low-loss ECs. However, as with all ECs, the operating voltage is low, and miniaturization of higher voltage devices necessitates a bipolar design. In this paper, we demonstrate a bipolar EC using graphite/VACNTs electrodes fabricated using a joule heating chemical vapor deposition (CVD) setup. The constructed EC contains one layer of double-sided VACNTs on graphite as bipolar electrode. Compared to a series connection of two individual devices, the bipolar EC has 22% boost in volumetric energy density. More significant boost is envisaged for stacking more bipolar electrode layers. The energy enhancement is achieved without aggravating self-discharge (71.2% retention after 1 h), and at no sacrifice of cycling stability (96.7% over 50000 cycles) owing to uniform growth of VACNTs and thus eliminating cell imbalance problems.

电化学电容器（EC）是微型自供电系统的关键推动力，随着物联网（IoT）的到来，微型自供电系统有望普及。石墨上垂直排列的碳纳米管（VACNT）有望作为紧凑型和低损耗EC的电极。但是，与所有EC一样，工作电压很低，并且更高电压设备的小型化需要双极性设计。在本文中，我们演示了使用焦耳热化学气相沉积（CVD）装置制造的使用石墨/ VACNTs电极的双极EC。构造的EC在石墨上包含一层双面VACNT，作为双极电极。与两个单独设备的串联连接相比，双极性EC的体积能量密度提高了22％。为了堆叠更多的双极电极层，设想了更大的提升。由于VACNTs的均匀生长，在不增加自放电（1小时后保留率71.2％）且不牺牲循环稳定性（50000次循环为96.7％）的情况下实现了能量增强。