The Trade-Off between Extended Lifetime and Resource Utilization Efficiency - a Critical Analysis of Battery Second-Use Concepts Using Materials Flow Analysis
Authors: Sehnal Anne Christina Christina , Wesselkamper Jannis , Lux Simon , von Delft Stephan 
Published: February 2024

Sustainability and environmental concerns have recently led to heavy investment in the electrification of transport. A major implication of this transition is a surge in demand for batteries, the state-of-the-art energy technology for electric vehicles. While electric vehicles are locally free of emissions, battery production and end-of-life management still challenge its status as an economically, socially, and environmentally sustainable technology. Among these challenges are the globally unequal distribution of raw materials and associated geopolitical, supply and trade-related concerns as well as the high costs and environmental risks of batteries’ waste management. Furthermore, landscape disruption, biodiversity loss, and concerns over child labor and other human rights abuses haunt the mining of raw materials.
The circular economy promises to remedy many of these issues, by essentially allowing economic growth without the consumption of raw materials. It has enormous potential for the European Union in particular, as it has a growing trade deficit of raw materials due to a lack of resource deposits on the continent. Therefore, independence from them is expected to boost its international competitiveness. Besides reducing raw material dependence and thus supply risks, the circular economy promises to stimulate business model and product innovation, to meet the demands for recyclable and more durable products as well as recycling goals, further strengthening competitiveness.
In the case of electric vehicles, recycling processes have been established to allow the regeneration of battery-grade raw materials from batteries. Furthermore, models of extending the battery’s life cycle by applying it in a secondary application with less demanding energy and power requirements have recently been proposed, termed “second use”. This delays the point in time when a battery is recycled. Materials-break-even-points (BEP), the points in time at which an economy can achieve independence from raw materials and thus reach circularity, can be a tool of analysis for the overall effect of this delay. Second use increases the duration until the BEP, while at the same time reducing the annual demand for primary raw materials. Despite the shift in BEP, it is frequently argued that the extended battery lifetime and the reduction in primary materials demand improve resource utilization. We argue, however, that second use could have undesirable side effects. This is because due to the capacity and voltage fade occurring over a battery’s lifespan and the improvements in material efficiency through advances in research and development over time, the average amount of raw material required for the storage of one unit of energy increases relative to a scenario where the battery is recycled earlier. Hence, the overall amount of material invested in the circular economy would be larger in a scenario with second use compared to a scenario without second use. Depending on the battery technology in question and thus the materials involved, this trade-off between the amount of material invested in the economy and the use span of a battery could play out differently with respect to economic, social, and environmental effects.
In this work, this trade-off is investigated for a scenario involving different shares of LFP-based lithium-ion batteries, NCX-based lithium-ion batteries, and other technologies, with a focus on the raw materials Ni, Co and Li. Technology-specific scenarios are investigated, as different technologies require different raw materials, impacting the material flow rate over time. Furthermore, different technologies exhibit a varying degree of voltage and capacity fade over their lifetime, thus affecting the resource utilization efficiency in a second-use scenario. To this end, dynamic material flow analysis is applied, and the societal, economic, and ecological consequences of our findings are discussed from a critical perspective.
The insights provided by this analysis are first and foremost a contribution toward understanding the principles that determine the long-term resource efficiency of a battery circular economy. These principles are vital for policymakers when envisaging political goals and incentive schemes for the transition toward a circular economy. The findings are also vital for actors from the battery and automotive industry when developing end-of-life strategies for electric vehicle batteries, as ensuring the most efficient use of battery raw materials improves resource availability and minimizes their products' environmental and societal impact.