Improved supercapacitors for better batteries, electric vehicles

Provides two times more energy and power compared to supercapacitors commercially available today
June 6, 2014

(a) Schematic illustration of the preparation process of RGM nanostructure foam. SEM images of (b–c) as-grown GM foam (d) Lightly loaded RGM, and (e) heavily loaded RGM. (Credit: UC Riverside)

Researchers at the University of California, Riverside have developed a new graphene-based nanoscale architecture that improves the performance of supercapacitors, a development that could mean faster acceleration in electric vehicles and longer battery life in portable electronics.

A supercapacitor is an energy storage device like a battery. The new design is based on ruthenium oxide anchored on a graphene foam electrode. It could deliver two times more energy and power compared to supercapacitors commercially available today.

The foam electrode was successfully cycled over 8,000 times with no fading in performance. The findings were outlined in the journal Nature Scientific Reports (open access).

Supercapacitors (also known as ultracapacitors) have ultra-high charge and discharge rate, excellent stability, long cycle life, and very high power density.

To achieve a higher power density, it is critical to have a large electrochemically accessible surface area, high electrical conductivity, short ion diffusion pathways, and excellent interfacial integrity, which are achieved by the new architecture.

These characteristics are desirable for many applications including electric vehicles and portable electronics. However, supercapacitors may only serve as standalone power sources in systems that require power delivery for less than 10 seconds because of their relatively low specific energy. Higher capacitance, or the ability to store an electrical charge, is critical to achieve higher energy density. This is also enabled by the new architecture.

Abstract of Scientific Report paper

In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO2) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO2 nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g−1, areal capacitance: 1.11 F cm−2) which leads to an exceptionally high energy density of 39.28 Wh kg−1 and power density of 128.01 kW kg−1. The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications.