The transport system is currently undergoing a transition to become fossil-free and sustainable. Electrification of vehicles is an important part of this transition. These vehicles must include batteries, whose health status will decrease during their lifetime. Batteries whose status no longer fulfill the requirements for use in vehicles can, however, still have a long remaining life-time if used in less-critical domains. It thus becomes necessary to facilitate the reuse and Second Life use of batteries. This presents both technological and business challenges. How can we ensure that adequate battery health data is collected and used to give a correct evaluation of the value of a battery that is being removed from a vehicle? What business models are needed? In this study, we present sustainable circularity models in the context of second-life batteries by analyzing the market scenarios, studying the processes and relationships between the stakeholders, and reviewing the enablers and ecosystems. We also discuss the opportunities, challenges and regulations in order to support a comprehensive understanding of the sustainable circularity process of retired electric vehicle batteries.