The ultracapacitor developer, which has prior received funding from corporate-backed units Energy Technology Ventures and Aster Capital, has raised $21m in its latest round.

The International Finance Corporation (IFC), the investment arm of the World Bank Group, and the Westly Group, a venture capital firm based in California, have led a $21m series C round for ultracapacitor technology startup, Ioxus.

To date, Ioxus has now raised $57m in funding, including a $21m round in 2011 funded by Energy Technology Ventures, the joint venture formed by GE, NRG Energy and ConocoPhillips, and VC firm Aster Capital, which is sponsored by Alstom, Schneider Electric and Rhodia,…