Abstract
Lithium carbonate (Li2CO3) is a critical precursor for lithium-ion batteries, yet its production remains chemically intensive and environmentally burdensome. While CO₂-based precipitation has emerged as a promising alternative to conventional Na2CO3-based routes, yet its environmental performance has not been fully assessed. This study presents a comparative ex-ante life cycle assessment of four Li2CO3 precipitation pathways, Na2CO3-based, NaOH/CO2-based, direct CO2-based, and ultrasound-assisted CO2-based, using primary experimental data scaled to a 1000 L industrial process via a transparent scale-up framework. Baseline GWP ranges from 53.10 to 60.40 kg CO2-eq per kg Li2CO3, with the ultrasound-assisted CO2 route achieving the lowest impact (12% lower than the highest-impact NaOH/CO2-based route), driven mainly by its higher lithium yield rather than precipitation chemistry. Ethanol used in product washing dominates most impact categories (80-92% of total GWP), while CO2 supply, KCl, and the precipitation reagents (Na2CO3 or NaOH) act as secondary contributors. This dominance reflects not only the intrinsic environmental burden of ethanol production but also the harmonised modelling choice to apply a uniform washing requirement across all routes, which amplifies ethanol's contribution relative to other inputs. Scenario analysis indicates that single-lever decarbonisation (low-carbon CO2 or fermentation-derived ethanol alone) achieves only modest reductions, while combined substitution achieves up to 17% reduction, particularly in the CO₂-based and ultrasound-assisted routes. Prioritising high-efficiency ethanol recovery, low-carbon ethanol and CO2 sourcing, and integrated process design emerge, within this gate-to-gate assessment, as the most influential levers for reducing the environmental footprint of the Li2CO3 precipitation stage under the modelled conditions.