Life cycle assessment of electric vehicles' lithium-ion batteries reused for energy storage

Energy storage batteries are part of renewable energy generation applications to ensure their operation. At present, the primary energy storage batteries are lead-acid batteries (LABs), which have the problems of low energy density and short cycle lives. With the development of new energy vehicles, an increasing number of retired lithium-ion batteries need disposal urgently. Retired lithium-ion batteries still retain about 80 % of their capacity, which can be used in energy storage systems to avoid wasting energy. In this paper, lithium iron phosphate (LFP) batteries, lithium nickel cobalt manganese oxide (NCM) batteries, which are commonly used in electric vehicles, and lead-acid batteries, which are commonly used in energy storage systems were taken as the research objects. The environmental impacts of their full life cycles were compared, and the sensitivity analysis of the key parts in the battery production phase and the data with major contributions were carried out through the life cycle assessment (LCA) method. The results show that the environmental impacts of lithium-ion batteries in the production phase are higher than lead-acid batteries. However, they have lower environmental impacts in the use phase because of their higher charging and discharging efficiency. In general, the environmental performance of LFP batteries is better, especially in carbon emission, soil acidification, and abiotic resource depletion. Lead-acid batteries have more advantages in ozone loss, ecotoxicity, and eutrophication. The production phase contributes the most to various environmental impacts, which can be alleviated through recycling. The recycling of NCM batteries has better environmental benefits. The physical recycling technology of LFP batteries is better than hydrometallurgy in terms of ecotoxicity and eutrophication, but it has negative effects on some environmental indicators. Secondary utilization can avoid the high energy consumption and high emission process of battery production and achieve the purpose of environmental protection. According to the results, discarded lithium-ion batteries can be reused to maximize the value of batteries, which will also promote the development of clean electricity to a certain extent and further reduce the burden on the environment.