Multifunctional structural composite battery
Creators: name: Shalouf, Salah M M
Publisher: name: RMIT University
Year: 2024

description: The overall aim of this PhD project is to advance the science and technology of multifunctional structural composite battery (MSCB) by performing an in-depth investigation into their mechanical and electrical properties, with a particular focus on the effect of mechanical deformation on the electric performances of rechargeable batteriesThis research focuses on two different MSCBs, embedded battery composites (EBC) and laminated composite batteries (LBC). The EBCs are fabricated by integrating thin liquid- and solid-electrolyte polymer batteries with a carbon fibre reinforced polymeric composite structure (CFRP). Extensive experiments are carried out to evaluate the electrical behaviour of the EBCs under various mechanical loadings that include bending, tension, and compression. The results show that the three modes of mechanical loading cause degradations to the energy capacity performance and increases in the electrical resistance of the energy cells. As measured by the percentage of applied load to strength, flexural deformation induces the most reduction in the electrical performance, followed by tension and compression. These new findings reveal that the mechanical strain relates strongly to the reduction in the storage energy capacity of the energy cells. A correlating relationship has been proposed to link the reduction in the electric performances to the applied mechanical deformation. Scanning electron microscope images of deformed separator show that mechanical deformation causes (i) the pores which are responsible for ion transportation in the battery to close up and (ii) the formation of cracks in the electrolyte region of the embedded solid electrolyte battery. These changes lead to an increase in the internal resistance of the energy cells and reduction in the energy storage capacity.<br><br>The second aim of this research is to investigate the possibility of utilizing the carbon fibre fabric as cathode and anode in the LCBs to store electrical energy and carry mechanical loads. Three types of LCBs, which are liquid, gel, and solid electrolyte batteries are manufactured and their electrical performances are tested through cycles of charging and discharging to characterise their electrical behaviour and the ability to store electrical energy. Investigations are also performed to improve the electrical conductivity performance of the cathode structure by incorporating carbon nano fibres in LCBs. Moreover, an investigation on the effect of mechanical loading on the electrical conductivity performance of its components is also conducted.<br><br>The results show that adding 10% of carbon nano fibre to the cathode structure improves its electrical conductivity performance by a factor of two over what can be accomplished by carbon black. The results also reveal that only a liquid electrolyte laminated composite battery could provide a reasonable voltage of 2 volts with charging storage capacity of 28mAh while the two other types produce very low voltages. Inspections of the electrical properties of the LCB components show that the low electrical conductivity of the cathode structure and possibly short circuiting between the cathode and anode are the main reasons for its low electrical performance. Recommendations of future research directions into the multifunctional structural composite battery (MSCB) are also briefly discussed.