Sub-project 9.2

Recovery of Lithium using ball milling technique under controlled atmosphere

Theme 1 + 2

Based on prior analysis of recycling pathways, it was determined that lithium carbonate is the desired output material for lithium extraction processes. As a result, potential processes that could produce lithium carbonate were explored. One such theoretical approach is reactive milling, inspired by the initial step in previously studied lithium battery recycling methods. This process involves milling the battery sample in a carbon dioxide atmosphere to promote the formation of lithium carbonate.

If viable, this method could eliminate the need for strong acids, as used in Dolotko (2023, 2024), and bypass additional steps like selective solubility required to isolate lithium carbonate from more complex compounds. This would represent a significant advancement, offering environmental benefits through reduced use of harmful chemicals and shortened processing times. Such improvements could help address one of the major challenges of current lithium battery recycling methods: their limited cost-effectiveness.

Given that lithium carbonate is the desired output, brainstorming focused on how to directly synthesize this compound during milling. One idea was to create a carbon dioxide-rich environment using either pressurized CO₂ gas or dry ice (solid CO₂) during the milling process.

There is limited literature available in this emerging field of experimental recycling pathways. For instance, Wang (2021) studied a different type of battery—lithium cobalt oxide battery waste—whereas the sample provided by the University of Adelaide in this experiment is representative of current-generation lithium-ion batteries, such as lithium nickel manganese cobalt oxide (NMC) or lithium iron phosphate (LFP).

In Wang’s study, a purgeable planetary ball mill was used to remove air from the milling environment and maximize CO₂ concentration at a given pressure. Experiments were conducted at various speeds (100, 300, 500, and 700 rpm) and durations (0.5, 1, 1.5, 2.5, and 4 hours), with dry ice to sample mass ratios ranging from 1:1 to 20:1. For this earlier generation battery chemistry, the optimal lithium carbonate yield in terms of purity was achieved at 700 rpm for 1.5 hours with a 20:1 dry ice to sample ratio.

While previous research provides valuable insight into potential recycling approaches, there are notable limitations. For instance, Wang’s study emphasizes output purity (measured by weight percent) but does not fully address process scalability or applicability to newer battery chemistries.

A key constraint in replicating Wang’s method at the university is the lack of access to a purgeable planetary ball mill. Additionally, even if one were available, its maximum pressure capacity (400 kPa) falls short of achieving the CO₂ concentration seen in the 20:1 dry ice to sample ratio used by Wang. Another potential option would be to use the facilities at Gravitas Technologies, which possess a larger purgeable ball mill. However, this equipment requires a minimum sample size of 150 grams—more than what was provided for this experiment.