Life-cycle assessment (LCA) emphasizes obtaining primary data from an on-site process to reduce uncertainties. However, data of the upstream process from secondary sources also yield significant uncertainties, which have not been drawn enough attention. This study aims to explore the importance of primary data of the upstream process in LCAs. Here, we choose lithium, a key component of lithium-ion (Li-ion) battery, as a case to present a cradle-to-gate LCA for its production by rock-based technology (LRT). Then, we compare the environmental impacts of lithium by LRT with that by brine-based technology (LBT) and the Li-ion battery using lithium by the two methods. The result shows that the impacts of rock-based lithium production are dominated by the leaching process, which has the highest levels of impacts for 8 of 10 environmental categories. Besides, all 10 impact categories of lithium produced by LRT are much larger than that by LBT, with differences up to 60.4 -fold. We also find that the Li-ion battery pack by rock-based lithium offers a 17–32% increase in acidification and global warming potential relative to that by brine-based lithium. Our results contribute by providing the first mass-produced life-cycle inventory of rock-based lithium and showing the importance of primary data of the upstream process in LCAs.