Estimating the Dominant Life Phase Concerning the Effects of Battery Degradation on CO2 Emissions by Repetitive Cycle Applications: Case Study of an Industrial Battery System Installed in an Electric Bus

Many studies have evaluated CO2 emission from batteries. However, the impact of Li-ion battery (LiB) degradation on the CO2 emissions from the material through operation phases has not been sufficiently examined. This study aims to clarify the dominant CO2 emission phase and the impact of the degradation of general industrial LiBs from repetitive cycle applications. We developed a model common to general LiB composition and calculated CO2 emissions by the LCA method using the IDEA database. Our model simplifies the degradation process, including capacity decrease and internal resistance increase. We used it in a sensitivity analysis of the carbon intensity of electricity charged to a LiB. The loss mechanism was determined by experimental data for an electric bus with an industrial LiB. The results illustrate that the carbon intensity of electricity affects CO2 emissions dominance, the operation phase for mix (71.3%), and the material phase for renewables (70.9%), and that battery degradation over six years increases the total amount of CO2 emissions by 11.8% for mix and 3.9% for renewables equivalent. Although there are limitations regarding the assumed conditions, the present results will contribute to building a method for monitoring emissions and to standardizing degradation calculations.