Lithium-ion batteries are widely used for energy storage applications but are limited by low power density, slow charging capability and reliance on flammable organic solvents. A hybrid approach to electrochemical energy storage based on aqueous electrolytes is being advanced at Korea Advanced Institute of Science and Technology (KAIST) to overcome these constraints.

Conventional aqueous electrolyte-based energy storage systems suffer from low driving voltage and a shortageSwitching a wearable LED kit with two aqueous hybrid capacitors in series charged by a flexible photovoltaic cell. Source: KAIST of anode materials. New structures and materials designed by the researchers promote rapid energy exchange on electrode surfaces and minimize energy loss between the cathode and anode.

Graphene-based polymer chain materials were used to assemble the anodes. The web-like structure of graphene increases the surface area and results in higher capacitance. The team used metal oxide in sub-nanoscale structures for the cathodes to elevate atom-by-ion redox reactions. The design offers higher energy density and faster energy exchange while minimizing energy loss.

The device can be charged within 20 to 30 seconds using a low-power charging system, such as a USB switching charger or a flexible photovoltaic cell. The aqueous hybrid energy also shows more than 100-fold higher power density compared to conventional aqueous batteries and can be rapidly recharged. It also demonstrates high stability with its capacity maintained at 100 percent at a high charge/discharge current.

The research is published in Advanced Energy Materials.