The Effects of Self-Discharge on the Performance of Symmetric Electric Double-Layer Capacitors and Active Electrolyte-Enhanced Supercapacitors: Insights from Modeling and Simulation

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• 作者：Innocent S. Ike ; Iakovos Sigalas ; Sunny E. Iyuke
• 关键词：Self ; discharge ; charge and energy loss ; mechanisms ; electric double ; layer ; symmetric ; active electrolyte ; enhanced supercapacitors
• 刊名：Journal of Electronic Materials
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：46
• 期：2
• 页码：1163-1189
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Optical and Electronic Materials; Characterization and Evaluation of Materials; Electronics and Microelectronics, Instrumentation; Solid State Physics;
• 出版者：Springer US
• ISSN：1543-186X
• 卷排序：46

文摘

The effects of self-discharge on the performance of symmetric electric double-layer capacitors (EDLCs) and active electrolyte-enhanced supercapacitors were examined by incorporating self-discharge into electrochemical capacitor models during charging and discharging. The sources of self-discharge in capacitors were side reactions or redox reactions and several impurities and electric double-layer (EDL) instability. The effects of self-discharge during capacitor storage was negligible since it took a fully charged capacitor a minimum of 14.0 days to be entirely discharged by self-discharge in all conditions studied, hence self-discharge in storage condition can be ignored. The first and second charge–discharge cycle energy efficiencies \( \eta_{{{\rm{E}}1}} \) and \( \eta_{{{\rm{E}}2}} \) of a capacitor of electrode effective conductivity \( \alpha_{1} \) = 0.05 S/cm with only EDL instability self-discharge with current density \( J_{\rm{VR}} \) = 1.25 × 10−3 A/cm2 were 72.33% and 72.34%, respectively. Also, energy efficiencies \( \eta_{{{\rm{E}}1}} \) and \( \eta_{{{\rm{E}}2}} \) of a similar capacitor with both side reactions and redox reactions and EDL instability self-discharges with current densities \( J_{\rm{VR}} \) = 0.00125 A/cm2 and \( J_{{{\rm{VR}}1}} \) = 0.0032 A/cm2 were 38.13% and 38.14% respectively, compared with 84.24% and 84.25% in a similar capacitor without self-discharge. A capacitor with only EDL instability self-discharge and that with both side reactions and redox reactions and EDL instability self-discharge lost 9.73 Wh and 28.38 Wh of energy, respectively, through self-discharge during charging and discharging. Hence, EDLCs charging and discharging time is significantly dependent on the self-discharge rate which are too large to be ignored.