Crumpled Graphene Retains High Capacitance

Graphene’s intrinsically high conductivity and extreme thinness should make it outstanding for use in advanced electronics such as ultracapacitors, a type of charge storage device. In practice, those properties are often difficult to exploit when standard procedures are used to prepare bulk quantities of graphene from graphite powders. Those methods tend to cause ultrathin graphene flakes to aggregate and form stacks, greatly reducing the material’s surface area and electronic and ionic conductivity. A recently developed aerosol-based method to make crumpled graphene sheets can overcome those problems, because like wadded paper balls, crumpled graphene sheets resist aggregation and compression. Jiayan Luo, Hee Dong Jang, and Jiaxing Huang of Northwestern University prepared a series of capacitors with increasing mass of crumpled graphene. The capacitance values increased roughly linearly with mass, suggesting that the devices could be scaled up to meet the needs of various applications (ACS Nano, DOI: 10.1021/nn3052378). In contrast, increasing the loading of flat graphene leads to successively weaker capacitance per weight of graphene, as the increase in material causes greater aggregation, the team reports.