Investigating Diffusion and Aging Mechanisms in Lithium-ion Batteries

Abstract

As lithium-ion batteries become ubiquitous in electric vehicles and grid energy storage, low cost and sustainable materials must be used to meet the world’s energy demands in the equitable transition to renewable energy. The impact of transitioning to cobalt-free positive electrode materials is investigated in the context of lithium diffusivity measurements in Ni-rich layered oxides. Using microcalorimetry, the reactivity of graphite negative electrodes with electrolyte is investigated at different states of charge, and with various amounts of manganese deposited on the graphite from a LiMn2O4 positive electrode. LiFePO4 (LFP)/graphite cells were cycled over different operating windows, where higher average states of charge were found to cause more degradation in a variety of conditions. Finally, crosstalk reactions between LFP and graphite electrodes were investigated using microcalorimetry. The future work focuses on chemical mechanisms in liquid electrolytes, specifically how lithium alkoxide species affect transition metal dissolution and how to quantify these species.