Resynthesized Electrode Materials from Chemically and Biologically Recycled Li-Ion Batteries

Recently, a dynamic increase of interest in the possibilities of recycling and reuse of materials from lithium-ion batteries was observed. Along with the ever-increasing number of Li-ion cells powering new electric and electronic devices, the management of waste batteries and materials contained within them has become a more and more urgent problem to be solved. Due to the growing environmental awareness more stringent legislative means to control the matter are introduced. This includes the latest European Union directive on batteries which states that no less than 35% of Li and 90% of cobalt, nickel and manganese will need to be recovered from waste Li-ion cells. Based on those regulations, the new batteries produced after 2030 will need to contain, for example, at least 6% of recycled lithium. Although large-scale, proper processing of waste batteries is still an economical challenge, the changing global supply and demand dynamics, geopolitical events, technological advancements, and the aforementioned environmental regulations force stakeholders in the battery market to consider battery recycling not only necessary, but also potentially financially viable and sustainable practice.<br/><br/>The battery recycling process should be characterized by high efficiency and the lowest possible impact on the environment, and as such, needs to be optimized for every type of electrode material. For the purposes of this study lithiated nickel-manganese-cobalt oxide 6:2:2 (NMC622) material was chosen, due to its high energy and power density, relatively high resistance to subsequent cell charge/discharge cycles, as well as favorable economic and environmental parameters associated with decreased cobalt content. The electrode material, synthesized from supplier grade new substrates was subsequently recycled in a series of steps, including hydrometallurgical recovery of lithium, and transition metal ions recovery as (hydr)oxides. The leachates were further processed chemically and biologically, by means of selected bacterial consortia, to increase the yield of recycled materials and to lower the concentration of dissolved ions. The use of biological processes in the recycling of waste electrode material reduces the costs of the process, especially at low concentrations – where the load of the leachate is too low for effective and economic chemical recovery, but still to great for safe discharge of the effluents to ground waters. With the use of microorganisms, nearly complete removal of nickel, cobalt and manganese ions from the leachates can be obtained, and the resultant technical-grade waters may be reused in the cycle. Effective lithium recovery, however, still remains a challenge.<br/><br/>The obtained recovered lithium and transition metals were further used to resynthesize electrode materials. Crystallographic measurements were performed proving the structure and purity of the obtained recycled materials. The resynthesized NMC622 electrode material with 0 to 100% of recycled materials content were structurally and electrochemically investigated and compared with the "original” material. It was shown that the electrode materials made of recycled materials may perform in a comparable manner with the "original” materials. However, their endurance and stability in charge/discharge cycles is greatly affected by the purity of the recycled substrates.<br/><br/>Recovery of metals from waste batteries is important for economic and ecological reasons. The presented results indicate that optimization of the recycling process, though challenging, is promising, and the resynthesized materials may be a good additive or even an alternative for commercial ones.