24M Technologies, a spin-out from US-listed renewable battery maker A123 Systems, has raised $10m from venture capital firms and a further $6m from a government grant.
Charles River Ventures and North Bridge Venture Partners, which also backed A123, are providing the $10m series A round.
A123 is retaining a seat on M24 and an equity stake after developing the technology alongside Yet-Ming Chiang, Professor of Ceramics at the Massachusetts Institute of Technology.
M24 is developing refuelable rather than rechargeable batteries by allowing a special liquid to be pour in to run an engine.