In this paper the environmental performance of an advanced hybrid energy storage system, comprising high power and high energy lithium iron phosphate cells, is compared with a stand alone battery concept composed of lithium manganese oxide cells. The methodology used to analyse the environmental impacts is Life Cycle Assessment (LCA). The manufacturing, use phase and end-of-life of the battery packs are assessed for twelve impact categories. The functional unit is 1 km driven under European average conditions. The present study assesses the environmental performance of the two battery packs for two scenarios: scenario 1 with a vehicle total drive range of 150,000 km and scenario 2 with total driving range of the car of 300,000 km. The results of scenario 1 show that the increased efficiency of the hybrid system reduces, in general, the environmental impact during the use stage, although the manufacturing stage has higher impact than the benchmark. Scenario 2 shows how the extended lifetime of the hybrid system benefits the emissions per km driven. (C) 2014 Elsevier Ltd. All rights reserved.