Studying The Impact of Electrolyte, Li Excess, NMC Blending, and Cycling Conditions on The Lifetime and Degradation of LMO/AG Cells Using UHPC Cycling, XRF, and Isothermal Microcalorimetry
Ahmed Eldesoky, Nicole Kowalski, Haoqi Ni, E. R. Logan, Eniko Zsoldos, Animesh Dutta, Nian Zhang, J. R. Dahn
Abstract
The impact of electrolyte, Li excess, NMC blending, and cycling conditions on the performance of Li 1+x Mn 2-x O 4 (LMO)/Artificial Graphite (AG) cells was studied using ultra-high precision coulometry (UHPC), X-ray fluorescence (XRF), and isothermal microcalorimetry (IMC). Decreasing the Li excess resulted in severe capacity fade which was greatly improved by blending LMO with NMC622. The known synergy between NMC and LMO is electrolyte-dependant and was more significant at elevated temperatures. We showed with XRF that Mn deposition on the negative electrode occurs primarily during the early cycles and is reduced by increasing the Li excess in LMO or by blending with NMC622. IMC experiments demonstrates a correlation between parasitic heat flow and Mn loading on the negative electrode and gas generation. Finally, LiFSI co-salts were examined to suppress Al corrosion while retaining the beneficial role of LiFSI in improving cell performance.