The innovation engine for new materials

Namrata Ramani

Namrata Ramani


University of California, Los Angeles


Materials Engineering

Site Abroad: 

Chalmers Institute of Technology, Gothenburg, Sweden


Qi Li
Mazharul Haque
Volodymyr Kuzmenko

Faculty Sponsor(s): 

Peter Enoksson

Project Title: 

Expanding the Voltage Window for Aqueous Electrolytes in Electrochemical Capacitors

Project Description: 

Electrochemical Capacitors, commonly known as supercapacitors, are emerging energy storage devices with high cyclability and power density. However, compared to battery-type devices, ECs are lacking in energy density, which can be increased by expanding their operational voltage window through advancement of electrolytes. Aqueous based electrolytes are preferable over organic electrolytes or ionic liquids for their low cost, stability in ambient conditions, and safety, but are typically limited by the decomposition voltage of H2O at 1.23 V. We investigated the effect of an aqueous salt electrolyte due to its high ionic conductivity, neutrality and the potential for anion redox activity. We performed electrochemical analysis on the EC with various concentrations of the electrolyte and activated carbon electrodes while ramping the voltage range of the device. We report a device that delivers a high specific energy density of 12 Wh kg-1 and high stability for over 20,000 cycles at voltages up to 1.8 V. The physicochemical properties suggest that neutral electrolytes show stability at higher voltages due to ion solvation effects and the equilibrium between hydronium and hydroxide ions. Cyclic voltammograms and galvanostatic charge/discharge tests on a two-electrode setup show conventional electrical double layer capacitive behavior, indicating there is minimal redox activity. Further studies of the electrolyte/electrode interface are necessary to rule out any redox contribution and to understand the mechanisms of charge storage. At the moment, this research highlights the expanded potential window of neutral electrolytes and introduces them as a promising energy storage solution for devices requiring a long cycle life.