Tin Electrodes Enhance Supercapacitor Efficiency and Sustainability

High-capacity, fast-charging supercapacitor energy storage devices have been limited by the composition of their electrodes — the connections responsible for managing the flow of electrons during charging and dispensing energy. Researchers have now developed a better material to improve connectivity while maintaining recyclability and low cost.

The team explored the connections in a micro-supercapacitor, which they use in their small, wearable sensors to monitor vital signs and more. Cobalt oxide — an abundant, inexpensive material that has a theoretically high capacity to quickly transfer energy charges — typically makes up the electrodes. However, the materials that mix with cobalt oxide to make an electrode can react poorly, resulting in a much lower energy capacity than theoretically possible.

The researchers ran simulations of materials from an atomic library to see if adding another material — also called doping — could amplify the desired characteristics of cobalt oxide as an electrode by providing extra electrons while minimizing, or entirely removing, the negative effects. They modeled various material species and levels to see how they would interact with cobalt oxide. Many of the possible materials were too expensive or toxic, so the team selected tin, which is widely available at a low cost and is not harmful to the environment.

In the simulations, the researchers found that by partially substituting some of the cobalt for tin and binding the material to a commercially available graphene film — a single-atom thick material that supports electronic materials without changing their properties — they could fabricate a low-cost, easy-to-develop electrode. Once the simulations were completed, the team conducted experiments to see if the simulation could be actualized.

The experimental results verified a significantly increased conductivity of the cobalt oxide structure after partial substitution by tin. The developed device is expected to have promising practical applications as the next-generation energy storage device.

Next, the team plans to use their own version of graphene film — a porous foam created by partially cutting and then breaking the material with lasers — to fabricate a flexible capacitor to allow for easy and fast conductivity. The supercapacitor is one key component. The team is also interested in combining with other mechanisms to serve as an energy harvester and a sensor.