Epsilon Archive for Student Projects

Abstract

The use of electric vehicles has seen a rapid growth in the past decade as it is expected to have an important role in mitigating greenhouse gas emissions from the transport sector. The increased demand for electric vehicles has in turn amplified the demand for traction batteries, especially lithium-ion batteries. However, to avoid problem-shifting it is important to consider the life-cycleimpact from the transition to an electrified transport fleet, since lithium-ion batteries are associated with its own environmental problems. Previous life-cycle assessments have been conducted, however, many studies lack in traceability and transparency regarding both battery composition, raw material supply and the processes included in the system boundaries. This makes it hard to compare the results and prevents the field from reaching a consensus in the best approach in conducting lifecycle assessments. To enable future life-cycle assessments of lithium-ion batteries it is important to identify the key assumptions in the previous studies and understand why they differ to such large extent. This report will therefore assess how previous studies differ in two regards: 1. the methodological choices and 2. the environmental impact categories evaluated. By doing so, this report helps future studies identify how these choices affect the results and therefore aid in choosing the best options. The results of the study show that the processes with the largest contribution to the environmental impact is the mining of materials, cell assembly and the use-phase and should therefore be assessed further in detail in future studies in order to reduce uncertainties. The impact categories that are concerned the most is the global warming potential, human toxicity potential, acidification potential, eutrophication potential and abiotic depletion potential. A large contributor to several of these impact categories is the electricity used in both the production- and use-phase. Consequently, using an electricity mix with higher shares of renewables have been stated as an efficient measure to reduce the life-cycle impact from lithium-ion batteries. Furthermore, there is a need for future studies that conduct full cradle-to-grave life-cycle assessments with primary data from manufacturers, preferably representable of large-scale production and data that better represents the current industry practice end-of-life treatment. The best practice model to conduct future lifecycle assessment is dependent on the goal and scope
of the study. Both the functional unit and the system boundaries should reflect the goal of the assessment. Cradle-to-grave assessment is to be preferred if the goal is to compare the environmental impact between using batteries in electric vehicles to internal combustion vehicles. In that case, the functional unit should also include the performance of the battery, such as charge efficiency and lifetime, and therefore the unit kilometres driven is preferred. Also, in order to include the most common environmental impact categories that are concerned, five categories should be included:
the global warming potential, eutrophication potential, acidification potential, abiotic depletion potential and human toxicity potential.