Influence of carbonisation temperatures on multifunctional properties of carbon fibres for structural battery applications

Abstract Carbon fibres are multifunctional materials considered for the realisation of structural battery electrodes. Processing conditions affect the carbonaceous microstructure of carbon fibres. The microstructure dictates the fibre‘s mechanical properties, i. e. modulus and strength, as well as its electrochemical capacity. Here, carbon fibre processing conditions are investigated to identify the effect of carbonisation temperature on carbon fibre multifunctionality. Different thermal conditions during carbonisation are considered, while keeping the precursor material, applied tension, and oxidation temperature constant. The carbonaceous microstructure of fibres is investigated via wide‐angle x‐ray scattering (WAXS) and transmission electron microscopy (TEM) analyses to determine the effect of the carbonisation temperature. Mechanical and electrochemical tests are performed to characterise carbon fibre multifunctionality with respect to mechanical and electrochemical performance. A moderate trade‐off between mechanical and electrochemical performance is demonstrated, where the elastic modulus and strength decrease and the electrochemical capacity increase with reduced carbonisation temperature. Here, for the studied temperature interval, the elastic modulus and strength is found to drop up to 7 % with a 15 % increase in capacity. Thus, fibres customised for targeted multifunctionality within a limited design space can be realised by careful selection of the processing conditions in conventional carbon fibre manufacture.