The increasing presence of Li-Ion batteries (LIB) in mobile and stationary energy storage applications has triggered a growing interest in the environmental impacts associated with their production. Numerous studies on the potential environmental impacts of LIB production and LIB-based electric mobility are available, but these are very heterogeneous and the results are therefore difficult to compare. Furthermore, the source of inventory data, which is key to the outcome of any study, is often difficult to trace back. This paper provides a review of LCA studies on Li-Ion batteries, with a focus on the battery production process. All available original studies that explicitly assess LIB production are summarized, the sources of inventory data are traced back and the main assumptions are extracted in order to provide a quick overview of the technical key parameters used in each study. These key parameters are then compared with actual battery data from industry and research institutions. Based on the results from the reviewed studies, average values for the environmental impacts of LIB production are calculated and the relevance of different assumptions for the outcomes of the different studies is pointed out. On average, producing 1Wh of storage capacity is associated with a cumulative energy demand of 328Wh and causes greenhouse gas (GHG) emissions of 110 gCO2eq. Although the majority of existing studies focus on GHG emissions or energy demand, it can be shown that impacts in other categories such as toxicity might be even more important. Taking into account the importance of key parameters for the environmental performance of Li-Ion batteries, research efforts should not only focus on energy density but also on maximizing cycle life and charge-discharge efficiency.