Comparative life cycle assessment of different lithium-ion battery chemistries and lead-acid batteries for grid storage application

Abstract: With the rapid increase of renewable energy in the electricity grids, the need for energy storage continues to grow. One of the technologies that are gaining interest for utility-scale energy storage is lithium-ion battery energy storage systems. However, their environmental impact is inevitably put into question against lead-acid battery storage systems. Therefore, this study aims to conduct a comparative life cycle assessment (LCA) to contrast the environmental impact of utilizing lithium-ion batteries and lead-acid batteries for stationary applications, specifically grid storage. The main tools in this study include Microsoft Excel for the life cycle inventory and OpenLCA for life cycle modelling and sensitivity analysis. In this research, a cradle-to-grave LCA for three lithium-ion battery chemistries (i.e. lithium iron phosphate, nickel cobalt manganese, and nickel cobalt aluminium) is conducted. The impact categories are aligned with the Environmental Footprint impact assessment methodology described by the European Commission. The standby grid operation scenario is considered for estimating the environmental impacts, where the batteries would deliver 4,800 kWh of electric energy throughout 20 years. Consequently, the functional unit will be in per kWh energy delivered. The lead-acid battery system has the following environmental impact values (in per kWh energy delivered): 2 kg CO2-eq. for climate change, 33 MJ for fossil resource use, 0.02 mol H+-eq. for acidification, 10-7 disease incidence for particulate emission, and 8x10-4 kg Sb-eq. for minerals resource use. Going back to the lithium-ion batteries systems, for the climate change and fossil resource use impact categories, the best performer is found to be the nickel cobalt aluminium (NCA) lithium-ion battery, with 46% and 45% less impact than lead-acid for the respective categories. On the other hand, the nickel manganese cobalt (NMC) was the best for the acidification and particulate emission impact categories with respective 65% and 51% better performance compared to lead-acid batteries. Finally, for the minerals and metals resource use category, the lithium iron phosphate battery (LFP) is estimated to be the best performer, which is 94% less than lead-acid. To conclude, the life cycle stage determined to have the largest contribution for most of the impact categories was the use stage, which then becomes the subject to a sensitivity analysis. The sensitivity analysis was done by varying the renewable contribution of the electricity grids in the use phase. Overall, the lithium-ion batteries systems have less environmental impact than lead-acid batteries systems, for the observed impact categories. The findings of this thesis can be used as a reference to decide whether to replace lead-acid batteries with lithium-ion batteries for grid energy storage from an environmental impact perspective.