Traction batteries are a key factor in the environmental sustainability of electric mobility and, therefore,it is necessary to evaluate their environmental performance to allow a comprehensive sustainabilityassessment of electric mobility. This article presents an environmental assessment of a lithium-iontraction battery for plug-in hybrid electric vehicles, characterized by a composite cathode material oflithium manganese oxide (LiMn2O4) and lithium nickel manganese cobalt oxide Li(NixCoyMn1-x-y)O2.Composite cathode material is an emerging technology that promises to combine the merits of severalactive materials into a hybrid electrode to optimize performance and reduce costs. In this study, theenvironmental assessment of one battery pack (with a nominal capacity of 11.4 kWh able to be used forabout 140,000 km of driving) is carried out by using the Life Cycle Assessment methodology consistentwith ISO 14040. The system boundaries are the battery production, the operation phase and recycling atthe end of life, including the recovery of various material fractions. The composite cathode technologyexamined besides a good compromise between the higher and the lower performance of NMC and LMOcathodes, can present good environmental performances.The results of the analysis show that the manufacturing phase is relevant to all assessed impact categories(contribution higher than 60%). With regard to electricity losses due to battery efficiency andbattery transport, the contribution to the use phase impact of battery efficiency is larger than that ofbattery transport. Recycling the battery pack contributes less than 11% to all of the assessed impactcategories, with the exception of freshwater ecotoxicity (60% of the life cycle impact). The environmentalcredits related to the recovery of valuable materials (e.g. cobalt and nickel sulphates) and other metalfractions (e.g. aluminium and steel) are particularly relevant to impact categories such as marineeutrophication, human toxicity and abiotic resource depletion.The main innovations of this article are that (1) it presents the first bill of materials of a lithium-ionbattery cell for plug-in hybrid electric vehicles with a composite cathode active material; (2) it describesone of the first applications of the life cycle assessment to a lithium-ion battery pack for plug-inhybrid electric vehicles with a composite cathode active material with the aim of identifying the “hotspots” of this technology and providing useful information to battery manufacturers on potentiallyimproving its environmental sustainability; (3) it evaluates the impacts associated with the use phasebased on primary data about the battery pack's lifetime, in terms of kilometres driven; and (4) it modelsthe end-of-life phase of the battery components through processes specifically created for or adapted tothe case study.