Effect of a buffer/iodide electrolyte on the performance of electrochemical capacitors
[ 1 ] Instytut Chemii i Elektrochemii Technicznej, Wydział Technologii Chemicznej, Politechnika Poznańska | [ SzD ] doctoral school student | [ P ] employee
PL Wpływ elektrolitu bufor/jodki na działanie kondensatorów elektrochemicznych
2024
scientific article
english
- buffer electrolyte
- iodide
- electrochemical capacitor
- activated carbon
- redox activity
EN One of the major problems affecting the energetic characteristics and cycle life of electrochemical capacitors (ECs) utilizing aqueous electrolytes is the narrow operating voltage range limited by the thermodynamic stability of water (1.23 V). Improvement of EC energy can be realized by capacitance and/or voltage increase. For that purpose, the redox additive of cost-effective and environmentally friendly iodides into aqueous electrolyte has been utilized. Moreover, buffer agents (acetate, citrate, phosphate) well-known for adjusting the pH of the electrolyte have been applied, which enabled ECs to reach 1.5 V stable operating voltage. After adding the iodide to the buffer system, the conductivity increased noteworthy, while pH values were nearly the same. Galvanostatic charge/discharge test (0.5 A g-1) of ECs operating in buffer electrolytes containing 0.2 mol L-1 NaI showed that this additive noticeably increases the specific capacitance values, from 91 to 149 F g-1 for acetate buffer, from 7 to 101 F g-1 for citrate buffer, and from 22 to 132 F g-1 for phosphate buffer. The long-time performance of ECs was investigated by accelerated potentiostatic floating. Electrochemical performance was studied with various activated carbons. During the floating ageing test, the YP50F-based EC working in acetate buffer with 0.2 mol L-1 NaI displayed the good long-term performance (310 h) as opposed to YP80F and BP2000 carbons, which exhibited 212 h and 126 h, respectively. The highly microporous YP50F carbon in acetate buffer/iodide electrolyte revealed the best wettability. Interestingly, citrate buffer/iodide EC system with YP50F demonstrated extremely long floating performance (1006 h). This study presents a new strategy to improve energetic metrics and cyclic performance of carbon-based ECs operating in the buffer electrolytes with an iodide redox pair.
09.05.2024
6684 - 6695
200
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