Electrochemical Capacitor Performance in Aqueous Electrolytes
Summary
Electrochemical capacitors, also known as supercapacitors, store energy by adsorbing ions at the electrode–electrolyte interface and, in some designs, by surface redox reactions. In aqueous electrolytes, these devices benefit from high ionic conductivity, low cost and environmental compatibility, but face constraints imposed by the electrochemical stability window of water. Typical cell voltages are limited to around 1.0–1.8 V, beyond which hydrogen or oxygen evolution degrades performance. Advances in electrode materials, surface functionalisation and cell architecture have gradually expanded operating voltages and energy densities while preserving the inherently high power density and long cycle life that characterise these devices. Carbonaceous electrodes, including activated carbons, carbon nanotubes and graphene derivatives, remain the mainstay of commercial designs owing to their high surface area, tunable porosity and mechanical robustness. Incorporation of pseudocapacitive metal oxides or conductive polymers can further increase charge storage via fast faradaic processes, albeit at the expense of some rate capability. Asymmetric configurations, in which two different electrode materials operate within distinct potential windows, have emerged to maximise overall cell voltage and energy content. Practical applications span grid stabilisation, regenerative braking, pulse-power delivery in transport and back-up power for electronics. Continued optimisation of electrolyte composition, electrode thickness and interfacial chemistry is crucial to reconcile high energy and power demands while ensuring safety and durability across broad temperature ranges.
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Electrochemical Capacitor Performance in Aqueous Electrolytes publication trend
The graph below shows the total number of articles in electrochemical capacitor performance in aqueous electrolytes across all publications each year (not limited to Nature Index journals).
Technical terms
Electrochemical capacitor: A device that stores energy through rapid, reversible ion adsorption and, in some cases, surface redox reactions.
Aqueous electrolyte: A water-based ionic solution facilitating charge transport between electrodes.
Double-layer capacitance: Charge storage arising from the electrostatic separation of ions at the electrode–electrolyte interface.
Pseudocapacitance: Faradaic energy storage due to fast surface or near-surface redox processes.
Voltage window: The potential range within which the electrolyte remains electrochemically stable.
Specific capacitance: Capacitance normalised to the mass of active electrode material, indicating energy storage capacity per unit mass.
References
- Adjusting the electrode surface functionality to improve the cell voltage of aqueous electrolyte carbon/carbon supercapacitors. Carbon (2025).
- Synthesis and performance of binder-free porous carbon electrodes in electrochemical capacitors. Journal of Materials Chemistry A (2024).
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