Carbon fibre composites as batteries, sensors, actuators and energy harvesting

Reduced mass for improvements in system performance has become a priority for a wide range of applications that requires electrical energy and includes load-bearing components. Use of lightweight materials has been identified as key for successful electrification of future transport solutions. Structure, energy storage and energy distribution are usually subsystems with the highest mass contributions but energy storage and energy distribution devices are structurally parasitic. One creative path forward is to develop composite materials that perform several functions at the same time – multifunctional materials. Combining functions in a single material entity will enable substantial weight savings on the systems level. One such concept is a structural battery, a material that simultaneously carry load and stores energy like a battery. Structural batteries employ carbon fibres as structural reinforcement and negative electrode and can also be used as current collectors to save additional weight. A number of new physical phenomena when using carbon fibres as battery electrodes have been found which allows for further multi-functionality. These are all based on the fact that carbon fibres intercalated lithium ions as an electrode material. The ion intercalation creates a reversible longitudinal expansion of the carbon fibres which could be used for actuation and morphing. A piezo electrochemical effect couples the electrical potential of the fibre to the strain acting on it, which can be used for sensing purposes. By combining the expansion and the piezo electrochemical effect one can convert mechanical energy to electrochemical energy, providing an energy harvesting function. The long-term vision of this work is to create a composite material that carries load, stores electrical energy, senses its own state, morphs and harvests energy.
QC 20191015