Aqueous energy storage device promises rapid charging of portable electronics

Researchers at Korea’s Advanced Institute of Science and Technology (KAIST) have developed a new type of aqueous energy storage device that they claim can be charged in less than half a minute.

aqueous energy storage
Schematic diagram for aqueous hybrid capacitors.

Employing aqueous electrolytes instead of flammable organic solvents, the device is claimed to enable a boosting charge with high energy density, potentially making it suitable for a range of portable electronic devices.

According to the group, which was headed up by Prof Jeung Ku Kang from the Graduate School of Energy, Environment, Water, and Sustainability the system owes its performance to a design that assembles fibre-like polymer chain anodes and sub-nanoscale metal oxide cathodes on graphene.

Conventional aqueous electrolyte-based energy storage devices have a limitation for boosting charges and high energy density due to low driving voltage and a shortage of anode materials.

Energy storage device capacity is determined by the two electrodes, and the balance between cathode and anode leads to high stability. In general, two electrodes show differences in electrical properties and differ in ion storage mechanism processes, resulting in poor storage and stability from the imbalance.

The research team came up with new structures and materials to facilitate rapid speed in energy exchange on the surfaces of the electrodes and minimise the energy loss between the two electrodes.

The team made anodes with graphene-based polymer chain materials. The web-like structure of graphene leads to a high surface area, thereby allowing higher capacitance.

For cathode materials, the team used metal oxide in sub-nanoscale structures to elevate atom-by-ion redox reactions. This method realised higher energy density and faster energy exchange while minimising 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.

Prof Kang said: “This eco-friendly technology can be easily manufactured and is highly applicable. In particular, its high capacity and high stability, compared to existing technologies, could contribute to the commercialisation of aqueous capacitors. The device can be rapidly charged using a low-power charging system, and thus can be applied to portable electronic device.”

The group’s aqueous energy storage work was reported in the journal Advanced Energy Materials