How will retired electric vehicle batteries perform in grid-based second-life applications? A comparative techno-economic evaluation of used batteries in different scenarios

The adoption of electric vehicles is increasing in a global trend toward decarbonization, yet the overall sustainability of these vehicles still poses many questions. The sourcing of many critical raw materials in battery production and their poorly-defined end-of-life management are among the underlined environmental challenges. The sustainability of battery placement in the transportation system in this sense needs to be supported by circular end-of-life strategies. While battery recycling for a secondary supply can be more favourable for producers, reuse disposition is regarded as being more environmentally attractive from a holistic lifecycle perspective. Cascading the life of batteries as such to reduce the environmental burdens is considered by both regulatory and industrial bodies. However, the uncertainties in cost breakdown and reliability of repurposed batteries reflected in naïve second-life market alignment and financial justification are barriers to current reuse policies and practices. For batteries with a variable lifetime subject to technical constraints in every application, the financial dynamics which underpin the choices of how and where to deploy them are challenging to investigate. While present studies make static assumptions about battery lifetime and operating costs, this work develops a dynamic investigation by incorporating battery degradation in hosts of different second-life applications into the financial analysis. This goal is approached by estimating the lifetime of the batteries in cascaded applications, and further evaluating their second-life contribution to energy and non-energy services in power systems. Findings indicate that settling on a lower purchase price for retired batteries and reducing the number of energy trading results in a justifiable return-on-investment. For batteries in early-failure vehicles such as 4-years-old, this arrangement is equally profitable compared to new ones when going below 26% of the original battery cell price, yet for older batteries such as 10-year-olds, the best performance is expected when contributing to grid services while keeping the investment value below 15%.