Repurposing and recycling of end-of-life batteries of electric vehicles : environmental perspective
Hayati Soloot, Hesam Edin (2024)
Diplomityö
2024
School of Energy Systems, Ympäristötekniikka
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2024052940956
https://urn.fi/URN:NBN:fi-fe2024052940956
Tiivistelmä
The electrifying road transport sector and its decarbonization have gained momentum in recent years. Electric vehicles (EVs) are one of the driving factors. However, EVs and batteries of electric vehicles (EVBs) reach their end of 1st life after 8 to 10 years. EVBs are considered to be at the end-of-life (EoL) stage while retaining nearly 80% of their original capacity or their state-of-charge (SoC≤80%). Owing to the steep increase in the global EV market and the criticality of raw materials within EVBs, there is growing concern about the waste management of EVBs at their EoL stage. At this stage, EVBs have reached the end of their 1st life and should not be considered waste batteries. Implementing suitable circular economy (CE) strategies with a hierarchical approach for EVBs can extend their lifetime and reduce their criticality by slowing down or closing the resource loop. In other words, they provide room for environmental benefit. One of the CE strategies is repurposing. Repurposing EVB means giving another life, 2nd or even 3rd life, to an EVB for a purpose other than the original one. Another strategy is recycling. However, the environmental performances of implementing these CE strategies are assessed through life cycle assessment (LCA).
This study was conducted as part of the REINFORCE project and focused on evaluating the environmental performance of EVBs at their EoL stage, which are repurposed and recycled during their lifespan. To this end, the study utilized a systematic literature review and included 24 intended LCA studies implementing these two strategies. In this way, it has found the top 10 environmental impact categories with a high frequency of appearance.
Moreover, the study considered four life cycle phases for EVBs: EVB production, 1st use as EV, repurposing, and recycling. In the case of global warming potential (GWP) as the most repeated impact category among the top 10 environmental impact categories, an EVB resulted in 0.22 to 0.25 kg CO2-eq/kWh during its entire life cycle. Here, kWh is the unit of the functional unit expansion. The functional unit expansion is utilized for the EVB due to the expansion of the system boundary in LCA, that considers both functions of the EVB during its lifespan: first, as the battery of EV and second, as a repurposed EVB in a stationary energy storage system (SESS). The EVB production and 1st use phases are the two main contributors to the total environmental impact of the EVB life cycle. For instance, in the case of the GWP impact of the EVB life cycle, their shares range from 32% to 40% and 31% to 61%, respectively. The repurposing phase accounts for 5-26% of the GWP impact. The considerable variations in the shares of these three phases back to excluding raw material extraction, considering electricity as the only needed energy, the role of the electricity mix, efficiency fading during 1st and 2nd life, capacity fading, the energy density of the considered EVB, cathode chemistry of lithium-ion batteries (LIBs), and the application scenario. Moreover, the role of the variation in the Goal and Scope definition of 24 LCA studies should not be forgotten. Repurposing and recycling EVBs would provide better environmental performance in all the top 10 impact categories than recycling after 1st life under the specified limitations for the performance indicators of EVBs. If the SoC of repurposed EVBs ranged from 66% to 85%, depth of discharge (DoD) was less than 50%, efficiency fading was less than 30%, degree of EVB component replacement was between 10% and 25%, and expected lifetime as repurposed EVB was a minimum of 5 years, repurposing EVB would have environmental benefits. These indicators are called the performance indicators of an EVB in its 2nd life. Recycling has an environmental benefit in most of the top 10 environmental impact categories. Recycling share in the total GWP impact ranges between 2% and 3%. Among the existing recycling methods, hydrometallurgy has a better environmental performance than pyrometallurgy and direct recycling for the Lithium Nickel Manganese Cobalt Oxide (NMC) and Lithium Iron Phosphate (LFP) chemistries of LIB. Among NMC and LFP chemistries of LIB cells for EVB, LFP has in total a lower environmental impact.
This study was conducted as part of the REINFORCE project and focused on evaluating the environmental performance of EVBs at their EoL stage, which are repurposed and recycled during their lifespan. To this end, the study utilized a systematic literature review and included 24 intended LCA studies implementing these two strategies. In this way, it has found the top 10 environmental impact categories with a high frequency of appearance.
Moreover, the study considered four life cycle phases for EVBs: EVB production, 1st use as EV, repurposing, and recycling. In the case of global warming potential (GWP) as the most repeated impact category among the top 10 environmental impact categories, an EVB resulted in 0.22 to 0.25 kg CO2-eq/kWh during its entire life cycle. Here, kWh is the unit of the functional unit expansion. The functional unit expansion is utilized for the EVB due to the expansion of the system boundary in LCA, that considers both functions of the EVB during its lifespan: first, as the battery of EV and second, as a repurposed EVB in a stationary energy storage system (SESS). The EVB production and 1st use phases are the two main contributors to the total environmental impact of the EVB life cycle. For instance, in the case of the GWP impact of the EVB life cycle, their shares range from 32% to 40% and 31% to 61%, respectively. The repurposing phase accounts for 5-26% of the GWP impact. The considerable variations in the shares of these three phases back to excluding raw material extraction, considering electricity as the only needed energy, the role of the electricity mix, efficiency fading during 1st and 2nd life, capacity fading, the energy density of the considered EVB, cathode chemistry of lithium-ion batteries (LIBs), and the application scenario. Moreover, the role of the variation in the Goal and Scope definition of 24 LCA studies should not be forgotten. Repurposing and recycling EVBs would provide better environmental performance in all the top 10 impact categories than recycling after 1st life under the specified limitations for the performance indicators of EVBs. If the SoC of repurposed EVBs ranged from 66% to 85%, depth of discharge (DoD) was less than 50%, efficiency fading was less than 30%, degree of EVB component replacement was between 10% and 25%, and expected lifetime as repurposed EVB was a minimum of 5 years, repurposing EVB would have environmental benefits. These indicators are called the performance indicators of an EVB in its 2nd life. Recycling has an environmental benefit in most of the top 10 environmental impact categories. Recycling share in the total GWP impact ranges between 2% and 3%. Among the existing recycling methods, hydrometallurgy has a better environmental performance than pyrometallurgy and direct recycling for the Lithium Nickel Manganese Cobalt Oxide (NMC) and Lithium Iron Phosphate (LFP) chemistries of LIB. Among NMC and LFP chemistries of LIB cells for EVB, LFP has in total a lower environmental impact.