Multi-walled carbon nanotubes and activated carbon composite material as electrodes for electrochemical capacitors

Abstract

We report on novel multi-walled carbon nanotubes (MWCNTs) and activated carbon (AC) composite material as electrode for electrochemical capacitors (ECs). Here MWCNTs work simultaneously as binder and additive for AC electrodes. MWCNTs were synthesised directly onto AC placed on nickel coated aluminium foils binding all of them. During MWCNT synthesis, nickel coated aluminium foils were converted on nickel aluminide alloy, which is extremely stable in neutral aqueous media and also permit welding in the case of large devices manufacturing or association.This novel material brings two significant features to ECs devices: (i) very low equivalent series resistance, and (ii) operational stability in aqueous based electrolytes. That is an excellent opportunity to explore because nonaqueous electrolytes itself and its handling to keep them humidity-free are ones of the most expensive part of ECs manufacturing. Replacing them using a better cost-effective and environmentally friendly electrolyte is desirable. Our approach is simple, fast, very reproducible, and low cost and in the end of the day devices showed large cell voltage of 1.5 V in aqueous electrolyte with specific capacitance of electrode material up to 105 F g−1 (e.g. very similar to several reports on literature using standard binders). Our cyclability test suggested a long service life with no significative lost on capacitance retention after 70 thousand cycles using a voltage range of 1.5 V at 25 A g-1. A detailed electrochemical analysis of device is also presented. On the Ragone plot, our devices fit between Li-ion capacitor and electrochemical capacitors.