Joint MIT-Harvard SPECIAL LECTURE: Carbon Fiber Based Structural Battery Composites

Special lecture given by Professor Leif E. Asp

Structural battery composites are made from thin carbon fiber reinforced polymer composite electrodes. The negative electrode consists of carbon fibers in a spread tow. The positive electrode, the cathode, consists of lithium iron phosphate (LFP) coated onto carbon fibers, again in a spread tow [1,2]. The electrodes are set apart by an electrically insulating, ionically conductive, separator. The stacked layers are impregnated by a structural battery electrolyte, providing mechanical load transfer between fibers and plies as well as Li-ion migration between the electrodes.
This paper presents recent progress in carbon fiber based structural battery composites. In particular, the coupled electro-chemo-mechanical processes and their effect on the composite material and its constituents will be discussed. During electrochemical cycling, the elastic properties of the electrode materials, i.e., carbon fiber and lithium iron phosphate, swells/shrinks and undergoes changes in elastic moduli [3]. These changes to the composite’s constituents give rise to high internal stresses that may cause damage to the structural battery electrolyte or the fibers and thereby affect the multifunctional performance of the structural battery composite [4]. To conclude the presentation, a route towards damage tolerant structural batteries is discussed.