Effects of ion insertion on cycling performance of miniaturized electrochemical capacitor of carbon nanotubes array

Capacity degradation and ion insertion of a miniaturized electrochemical capacitor are studied using ionic liquid [EMI] [TFSI] as the electrolyte. This capacitor is featured with two comb-like electrodes of vertical carbon nanotubes, ∼70 μ m in height and 20 μ m in interelectrode gap. We quantify the levels of ion insertion damage with Raman spectroscopy after the electrode experiences 120 consecutive voltammetric cycles to various potential limits. Distinct structural damage emerges due to [EMI] when the negative potential reaches −1.7 V, and those due to [TFSI] arise when the positive potential reaches 1.7 V vs. RHE. Judging from the peak broadenings, [EMI] is more detrimental than [TFSI]. When the voltage window ΔU is set as less than or equal to 2.8 V, both electrode potentials are within the two intercalation limits, little or no decay is observed in 10 4 charge/discharge cycles. When ΔU is 3.4 V, the positive potential exceeds the upper l...

Dah-Shyang Tsai, Chuan-hua Chang, Wei-Wen Chiang, Kuei-Yi Lee and Ying-Sheng Huang

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