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Gorji Pour Shafiee, Behzad

University of British Columbia

Hybrid electrolytes are the new type of electrolyte for electrochemical cells that were introduced recently by Suo et al. that have found their way to be used in supercapacitor devices in recent years. However, a critical evaluation of the hybrid electrolyte vs. commonly used organic electrolyte concerning the safety, cost, and electrochemical performance (such as capacitance and cyclic performance) is an important step to fully understanding the hybrid electrolyte’s potential. Here, first, the porosity of the carbon was optimized by changing the activation condition to become compatible with the organic and hybrid electrolytes to evaluate the performance of each electrolyte with different carbons having different porosities. The tuning of porosity of the carbon showed that there is a trade-off between capacitance (and energy density) and rate performance (and power density) as if the activation temperature is raised from 800 to 900 °C, the larger pores cause easier diffusion and better rate performance; however, the cell loses its capacitance as the carbon loses its macropores. Therefore, the carbon needs to be tuned based on the capacity (energy density) requirement or rate performance (power density). If higher energy is required, the carbon should be activated at a lower temperature, and if a better rate performance is needed, the activation should be conducted at a higher temperature. When it comes to the electrolyte, the organic electrolyte is the most commonly used electrolyte in commercial supercapacitors, but they suffer issues such as safety and high cost. Recently, a new type of electrolyte has been introduced to solve the organic electrolyte’s problems. The hybrid electrolyte solved the organic electrolyte’s problems, but these two electrolytes should be evaluated more meticulously and compared to have a clear view. For this purpose, the optimized activated carbons were used with the two electrolytes. The hybrid electrolyte solved the safety and cost issue; furthermore, in spite of operating at a lower potential, the hybrid electrolyte shows better capacitance (52.06 F.g-1 for APC-800-8-hyb vs 41.88 F.g-1 for APC-800-8-org), better power density (25.31 kW kgˉ¹ for APC-900-8-hyb vs 15.42 kW kgˉ¹ for APC-900-8-org), and better rate performance (89.34% for APC-900-8-hyb vs 66.09% for APC-900-8-org); however, the hybrid electrolyte showed lower cyclic performance after 20k cycles (82.91% for APC-900-8-hyb vs 95.33% for APC-900-8-org) and lower energy density (41.39 Wh.kg-1 for APC-800-8-hyb vs 42.15 Wh.kg-1 for APC-800-8-org).

Text

2023-04-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/81438

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/