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Published online: 26 November 2008 | doi:10.1038/nchina.2008.280

Supercapacitors: Foam success

Vicki Cleave

Introduction

© (2008) RSC

Electrochemical capacitors, also known as supercapacitors, are the topic of heated interest at the moment. Their high energy density and rapid charge–discharge capabilities make them the ideal for applications where batteries would be too slow to respond. As the world looks to improve the energy efficiency of cars, supercapacitors could therefore play a large part in storing captured energy in regenerative braking systems. Hulin Li, Cailing Xu and Guangwu Yang at Lanzhou University¹ have discovered an approach that could improve supercapacitors further. By coating a piece of nickel foam with an inexpensive electrode material, such as nickel hydroxide, the researchers achieved the highest-ever specific capacitance for an electrochemical capacitor.

Under the microscope, the nickel foam has a three-dimensional cross-linked structure, a wrinkly surface and high porosity. When nickel hydroxide is coated on the foam structure, it forms grains of 10-nm diameter that create a porous superstructure (pictured). The researchers explain that this high porosity is responsible for the high capacitance because the electrolyte is able to contact a large material surface area. The three-dimensional network also allows easy charge diffusion.

Although the capacitance is high, it degrades quickly over time, dropping to almost half after only 300 cycles. Given these promising results, the researchers' next objective is to improve the durability of the supercapacitor.

The authors of this work are from:
College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, China.

Reference

1. Yang, G. W., Xu, C. L. & Li, H. L. Electrodeposited nickel hydroxide on nickel foam with ultrahigh capacitance. Chem. Commun. doi:10.1039/b815647f (2008). | Article |