Prof. Leif Asp

Structural Battery Composites for Mass-less Energy Storage

Chalmers University

Engineering materials that can store electric energy in structural load paths can revolutionise lightweight design across transport modes. Contemporary electric vehicles and aircraft use traditional lithium ion batteries for electrical energy storage. The battery is only providing an electrical energy storage function - adding weight to the system but does not contribute to its structural performance. Here we present research aimed at the development and demonstration of a multifunctional material that can simultaneously store electrical energy and carry mechanical loads. We have coined this material as the structural battery composite. Structural battery composite materials will allow radical weight savings for any electrically powered structural systems, from laptops to cars and aircraft. Over the last decade, Chalmers and KTH have performed research to realise structural battery composites. Current structural battery composites have demonstrated an energy density of 24 Wh/kg at a Young's modulus of 25 GPa. We are currently in the process of developing and demonstrating the second-generation structural battery composite with an anticipated energy density of at least 75 Wh/kg and a modulus of 75 GPa. The presentation is focused on research needed to take us to those levels. Structural battery composites are made from carbon fibres in a structural battery electrolyte (SBE) matrix material. Neat carbon fibres are used as a structural negative electrode, exploiting their high mechanical properties, excellent lithium insertion capacity and high electrical conductivity. Lithium iron phosphate coated carbon fibres are used as the structural positive electrode. Here, the lithium iron phosphate is the electrochemically active substance and the fibres carry mechanical loads and conduct electrons. The surrounding SBE is lithium ion conductive and transfers mechanical loads between fibres. With these constituents, structural battery cells are realised.