Purpose <p>A standardised life cycle assessment (LCA) approach for electric vehicle batteries is needed to meet reporting requirements, allow fair comparisons and to support LCA-driven development processes. As part of the standardised approach, guidance is needed for different multifunctionality situations, system boundaries, and consideration of other sectors and products. Especially, implementing different circular economy strategies such as reuse, repurpose and recycling, introduce new multifunctionality situations. Already developed guidance either does not apply to all multifunctionalities in different scopes and LCA purposes or is so generic that it leaves too much room for interpretation.</p> Method <p>Existing guidance and case studies for the handling of different multifunctionality situations in the life cycle of an EV battery are analysed. Based on this analysis, a hierarchy is developed to handle all potential multifunctionality situations across different scopes and purposes of the LCA. This hierarchy is translated into a decision tree, which supports the implementation of the hierarchy by guiding the LCA practitioner through the process for resolving multifunctionality. Furthermore, the documentation required to ensure transparency and reproducibility is discussed, along with potential formats for documentation. The proposed methodology is compared to existing approaches, especially those under development by or on behalf of the European Commission for the EU Batteries Regulation.</p> Results + discussion <p>Based on the analysis of the multifunctionality situations in all life cycle stages and under consideration of upcoming circular economy strategies, a situation-specific guidance for all LCA scopes and purposes was developed which includes a multifunctionality hierarchy, as commonly used in guidelines, and a specific recommendation for the End-of-Life allocation. The implementation of the different steps in the hierarchy is linked to safeguards, which reflect that some of the steps are only applicable for certain scopes or under specific circumstances. To support the implementation by the LCA practitioner, the hierarchy with all safeguards is translated into a decision tree which can be applied to solve each multifunctionality situation. As the decision tree can only capture one multifunctionality at a time, consistency checks are introduced at both the product and macro system level. To support transparency, standardised documentation formats are suggested, highlighting the key information to be shared.</p> Conclusion <p>The developed decision tree, along with necessary consistency checks and documentation, can guide the LCA practitioner in solving all multifunctionalities and foster transparency in the results. The proposed approach applies to multifunctionalities across different life cycle stages and various system boundaries of the LCA and therefore provides specific guidance for a more holistic scope than the already existing guidelines. It may not be entirely aligned with all guidelines under development by or on behalf of the European Commission; therefore, some adaptations may be necessary in the future.</p>