Lithium (Li) is rapidly becoming a valuable commodity. In recent years, the industrial importance of Li has increased due to its use in Li-ion batteries. For example, large-sized Li-ion batteries are used as power supplies for electric vehicles and for storage of electricity in smart grids and smart houses. Therefore, a large amount of Li is required worldwide. Li reserves in the South American countries of Chile, Bolivia, and Argentina account for more than half of the world’s Li reserves; these countries have outstanding Li resources (brine water). Although Li extraction from chloride brine water is easy, the quantity of natural resources in these waters is limited. In contrast, the quantity of natural resources in sulfate brine water is large; however, the Li recovery technology from sulfate brine water has yet to be established.

    Thus, the extraction of Li from used Li-ion batteries would allow a large amount of Li to be inexpensively acquired. The technology for recycling cobalt (Co) and nickel (Ni) from used Li-ion batteries has already been established. On the contrary, the technology for recycling Li from used Li-ion batteries is not yet established, because the cost of Li recycling is higher than the import price of Li from South America. I have developed a method for the recovery of Li from seawater using a Li ionic superconductor functioning as a Li-ion separation membrane (LISM) [1]. Only Li ions were successfully recovered from seawater through the LISM; other ions in the seawater did not permeate the membrane. Therefore, I have developed an innovative new method for recycling Li from used Li-ion batteries using the LISM.

    Figure 1 shows the proposed Li recovery method. This innovative method involves the use of an LISM whereby only Li ions in a solution of used Li-ion batteries permeate from the positive electrode side to the negative electrode side during electrodialysis; the other ions, including Co, Al, and F, do not permeate the membrane. In this study, Li_0.29La_0.57TiO₃ was selected as the LISM because it exhibits high durability against water. The area and thickness of the LISM are 25 cm² (5.0 cm × 5.0 cm) and 0.5 mm, respectively. The positive side of the dialysis cell was filled with used Li-ion battery solution, supplied by DOWA ECO-SYSTEM Co., Ltd., Japan; the Li concentration of the solution was 2543.5 mg/L. Then the negative side was filled with distilled water. The applied dialysis voltage was 5 V, and the duration of dialysis was 72 h. The electrodes were Ti–Ir alloy on the positive electrode side and SUS316 on the negative electrode side, and electrode area was 16 cm².

    The calculation of the Li recovery ratios for this first of a kind electrodialysis technique with an LISM sheet was performed. The Li recovery ratio increased with electrodialysis time, reaching approximately 10% at 72 h of dialysis. The recovery ratios of Co, Al, and F were not calculated because the concentrations of Co, Al, and F were below the detection limit of inductively coupled plasma atomic emission spectrometry (ICP-AES). Moreover, the Li concentration dependency of the Li recovery amount was measured. These measurements showed that the amount of Li in the recovery solution increased with the Li concentration of the used Li-ion battery solution. This indicates that a used Li-ion battery solution with high Li concentration enables good Li recovery efficiency by this method.

    After electrodialysis, CO₂ gas was bubbled in the Li recovery water to produce lithium carbonate (Li₂CO₃) as a raw material for Li-ion batteries. The Li₂CO₃ deposition was easily generated by the reaction of CO₂ gas and the Li recovery solution as a lithium hydroxide (LiOH) solution.

    This new method for recycling Li-ion batteries shows good energy efficiency and is easily scalable. Furthermore, the estimated cost of 1 kg Li₂CO₃ produced by this method is approximately $3. This value is lower than the import price of Li ($5 to $8) from South America. Thus, this electrodialysis method is suitable for the recovery of Li from used Li-ion batteries.

Reference

[1] T. Hoshino, Innovative lithium recovery technique from seawater by using world-first dialysis with a lithium ionic superconductor, Desalination, 359 (2015) 59-63.