(180b) Recycling of Lithium Ion Batteries through Low-Temperature Calcination of a Novel Intermediate.

Lithium Ion Batteries (LIBs) have brought a monumental shift in energy storage and generation technologies as most countries aim to be environmentally friendly. It is widely used for energy storage in portable devices, electric vehicles, and storage due to their high specific energy density, high rated voltage, and low self-discharge rate. LIBs contain cathode-active materials, such as Lithium Cobalt Oxide (LiCoO₂) and lithium nickel manganese (LiNi_xMn_yCo_zO₂, x+y+z = 1), a graphite anode, a copper cathode, an aluminum cathode collector, PVDF binder, and the electrolyte. Recycling and disposal of LIBs pose a significant challenge for human health and the environment as they contain a high percentage of heavy metals and toxic electrolytes. In recent years, a lot of effort has been made to recover different components of the batteries, however, recovery of spent cathode material poses a significant future for the circular economy. The common method to extract the cathode metallic components (such as LiCoO₂, LCO) is pyrometallurgical, hydrometallurgical, mechanical, and mechano-chemical processes. Most of these processes are energy-intensive and involve high material and machinery costs, complex downstream processing, and loss of lithium in form slags. Thus, in the present study, a solvothermal method is proposed for novel precursor materials such as PM1 ([Li(C₂O₄)]₂[Co₅(OH)₈]) and PM2 [Li₂(Ni:Mn:Co)₅(OH)₈(C₂O₄)₂], for the recycling of battery cathode material. PM1 has a global structure of heterometallic layered double hydroxide visual representation can be made from Figure 1(a) which shows the AB layers containing lithium oxalate and cobalt hydroxide that are present in the PM1 structure. Additionally, cobalt can be octahedrally coordinated or tetrahedrally coordinated where systematic depilation takes place. Figure 1(b) presents a similar asymmetric unit structure of PM2 for the synthesis of NMC111 cathode material.

Lithium cobalt oxide and NMC111 contain a layered structure similar to what has been mentioned in the case of PM1 and PM2 respectively. This enables the recovery of the cathode material at much lower temperatures T <450ËšC compared to the conventional processes, making it more energetically favourable. The spent LCO from a battery waste is primarily digested in an organic acid (typically oxalic acid can be used) at elevated temperature (>80ËšC) resulting in Lithium oxalate and cobalt oxalate dihydrate. Later, by adjusting the stoichiometric ratio of cobalt and lithium oxalate to 1:1 in the pH range of 8-10, the PM1 can be synthesized in an aqueous medium at T = 80-100ËšC with 4 hrs standard reaction time. Powder X-ray diffraction indicates this new synthetic route is successful in synthesizing LCO with high phase purity at temperatures far below what has been reported previously. Thus, a novel technique was developed in which PM1 was calcined with a stoichiometric excess of lithium salt at T<450ËšC to provide layered LCO. This has been verified by quantitative Rietveld analysis using XRD data and also through Raman spectroscopy. To evaluate the electrochemical performance of the cathode material, discharge capacities, Cyclic Voltammetry, and Impedance data were measured and compared with the commercial LCO. Furthermore, the method has been demonstrated to be extendable to NMC chemistries using an analogous intermediate PM-2. A novel process utilizing these novel intermediates and associated plant designs is developed and compared with industrial processes to demonstrate their economic and industrial feasibility for lithium-ion battery recycling.