Effect of lithium ion on the separation of electrode materials in spent lithium ion batteries using froth flotation

There is an urgent need to develop a recycling process for spent Lithium-Ion Batteries (LIBs). Amongst the various recycling technologies proposed, froth flotation is considered a cost-effective candidate for the separation of graphite from the lithium metal oxides due to the hydrophobic nature of graphite. However, experimental studies have identified that soluble lithium has a significant impact on the separation efficiency. Two series of experiments were undertaken to understand the influence of lithium ions. The first used a semi-synthetic mixture of spent anode and pure cathode material based on lithium nickel manganese cobalt oxide (LiNi0.33Mn0.33Co0.33O2) or NMC-111 cathode material. The second used mixed samples of spent lithium ion batteries of the same composition. Both the separation efficiency and the flotation kinetics are reported. The soluble lithium concentration is shown to have a significant impact on both. However, if the spent battery material is washed to reduce the lithium ion concentration, the flotation efficiency and kinetics are similar with the graphite recovery exceeding 90% and the graphite grade exceeding 84% in a single flotation stage. •The presence of soluble lithium comes mainly from the cathode materials (95%) .•Recoveries of 97.67% for anode and 11.09% for cathode material are achieved when washing prior to flotation.•Recovery of the cathode materials is controlled by water entrainment which is increased by soluble lithium.•Recovery of lithium from the flotation circuit is required to achieve good environmental and economic performance.