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Redox enhanced energy storage in an aqueous high-voltage electrochemical capacitor with a potassium bromide electrolyte

Qi Li (Institutionen för mikroteknologi och nanovetenskap, Elektronikmaterial och system ) ; Mohammad Mazharul Haque (Institutionen för mikroteknologi och nanovetenskap, Elektronikmaterial och system ) ; Volodymyr Kuzmenko (Institutionen för mikroteknologi och nanovetenskap, Elektronikmaterial och system ) ; Namrata Ramani ; Per Lundgren (Institutionen för mikroteknologi och nanovetenskap, Elektronikmaterial och system ) ; Anderson David Smith (Institutionen för mikroteknologi och nanovetenskap, Elektronikmaterial och system ) ; Peter Enoksson (Institutionen för mikroteknologi och nanovetenskap, Elektronikmaterial och system )
Journal of Power Sources (0378-7753). Vol. 348 (2017), p. 219-228.
[Artikel, refereegranskad vetenskaplig]

This paper reports a detailed electrochemical investigation of a symmetric carbon-carbon electrochemical device with a potassium bromide (KBr) electrolyte. Below 1.6 V, KBr gives electrochemical double layer behavior. At higher voltages the Br-/Br-3 redox reaction comes into effect and enhances the energy storage. The redox-enhanced device has a high energy density, excellent stability, as well as high coulombic and energy efficiencies even at 1.9 V. More importantly, the redox contribution can be “triggered” by pre-cycling at 1.9 V, and remains beneficial after switching to 1.6 V. The triggering operation leads to a 22% increase in stored energy with negligible sacrifice of power. The intriguing behavior is accompanied by a series of complex variations including the shifts of electrode potential limits and the shift of potential of zero voltage. The electro-oxidation of the positive electrode and kinetics of the Br-/Br-3 electrode reactions are proposed to be the main causes for the triggering phenomenon. These findings provide means to improve the design and operation of devices that contain bromine, or other redox species with a comparably high electrode potential.

Nyckelord: Redox-EDLC, aqueous supercapacitor, redox electrolyte, high voltage, electrode potential



Denna post skapades 2017-03-13. Senast ändrad 2017-06-12.
CPL Pubid: 248541

 

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