Comparative Life Cycle Assessment of Second Life NMC Batteries

Abstract

As the EV batteries reach their end of life, a large number of batteries will be available post 2030. One solution for retired batteries is to consider them for second life applications in Battery Energy Storage Systems (BESS). The viability of second life Nickel Manganese Cobalt (NMC) batteries, however, is a balancing act between their reliability due to fading performance and safety issues, costs and environmental impacts. This Master’s thesis investigates the viability by breaking it down into two research questions. Firstly, from the viewpoint of the impact categories energy demand and climate change, how the second life NMC battery compares to a new Lithium Iron Phosphate (LFP) battery for BESS applications. And secondly, regarding the material scarcity impact category, how beneficial it is to delay the recycling of the NMC battery by adding a second life. The first question is answered in a break- even analysis with LFP as a reference point by considering three different scenarios. The scenarios represent different allocations of environmental impacts between the first and second life of the NMC. Each scenario is further comprised of different recycling percentages. For the second question, the crustal scarcity indicator is used as a proxy to address the material scarcity hot-spots at the battery pack, cell and cathode level. Moreover, the supply risks and geopolitics surrounding the critical metals used in the battery chemistries are discussed. According to the break-even analysis, it is only when 0% of the energy requirement for production and recycling are allocated to the second life that a second-life NMC battery can outperform a new LFP battery in terms of energy use. This is mainly due to a lower efficiency of the aged battery. In terms of climate change, the second- life NMC battery can potentially be a viable choice for both 0% and 20% allocation, depending on the local electricity mix. The carbon intensity of the electricity mix in the BESS was indicated as the most significant parameter. Regarding materials scarcity it was observed that in some situations second life use of NMCs could aggravate supply risks of nickel and cobalt. However, this depends on the existence and efficiency of recycling infrastructure, and hence on the time horizon.