A Holistic Assessment Framework for Measuring Circularity of Second-Life Electric Vehicle Batteries : A Swedish Case Study in Frequency Containment ReserveApplications

Sammanfattning

As the electrification of transport accelerates, managing the growing volume of end-of-life electric vehicle (EV) batteries has become a critical challenge. While repurposing these batteries is a logical step, identifying the most valuable pathway requires a detailed analysis of battery degradation, market economics, environmental impacts, and resource supply-chain risks. This thesis addresses this by developing a novel, holistic assessment framework as a modular Python tool. The framework simulates battery degradation across defined first-and second-life stages to calculate integrated techno-economic, environmental, and resource security indicators, providing a quantitative foundation for strategic decision-making. The primary result of this work is the versatile assessment framework itself, a modular tool adaptable to different battery chemistries, applications, and market contexts. Its function is demonstrated through a specific Swedish case study of a 51 kWh lithium-iron phosphate (LFP) battery repurposed for Frequency Containment Reserve (FCR) services. For this case, the analysis reveals that maximizing total lifetime energy throughput is the most critical factor for optimizing value. This indicates that transitioning the battery to a high-throughput second life as early as is feasible is the most profitable and sustainable pathway, highlighting a market failure that could be addressed by "Battery-as-a-Service" models. These specific conclusions, however, are limited to the analyzed case and are derived from a simplified semi-empirical degradation model. The model's primary limitation is its definition of end-of-life by capacity fade alone, which omits other critical failure modes such as power fade from increasing internal resistance, potentially leading to optimistic lifespan predictions.