Improvement of leaching efficiency of cathode material of spent LiNixCoyMnzO2 lithium-ion battery by the in-situ thermal reduction

Abstract

Green cars and electronic products consume lots of lithium-ion batteries (LIBs), and massive spent LIBs are yielded due to performance degradation. This paper provides an economical and environmentally friendly approach to recover valuable metals from cathode materials of the spent LIBs. It combines the in-situ thermal reduction (self-reduction by polyvinylidene fluoride (PVDF) and residual electrolyte in cathode material) and sulfuric acid leaching. Elements of high valent are reduced by the binder (PVDF) and the residual electrolyte on the surface of NCM(LiNixCoyMn1-x-yO2) material at high temperatures. Moreover, the changes in substance type, element valency, and contents of cathode materials reduced with various terminal temperatures and retention time are analyzed by Xray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results show that the optimal terminal temperature for in-situ thermal reduction is 600 °C, and the optimum retention time is 120 min. Under the best in-situ thermal reduction conditions, the results from XRD confirm that part of Ni 2+ is converted to simple substance Ni, Co 3+ is reduced to Co, and Mn 4+ is reduced to Mn 2+ and elemental Mn, which are confirmed by XRD. Analyzed results by XPS indicate that the content of Ni 2+ decreases to 67.05%, and Co 3+ is completely reduced to Co. Mn 4+ is reduced to 91.41% of Mn 2+ and 8.59% of simple substance Mn. In-situ thermal reduction benefits the leaching processes of cathode materials. The leaching efficiencies of Ni, Co, and Mn increase from 53.39%, 51.95%, and 0.71% to 99.04%, 96.98%, and 97.52%, respectively.

Elucidating the charge-transfer and Li-ion-migration mechanisms in commercial lithium-ion batteries with advanced electron microscopy

“…XPS has also be used to analyze the content and charge-transfer in elements. For instance, in situ XRD and XPS have been used to analyze the changes in valence and contents of Ni, Co, and Mn in LiNi0.5Mn0.3Co0.2O2 (NMC 532) under heating [135]. Moreover, using in situ XRD and Ar-sputtering-assisted XPS, Si et al found that the NCM co-modified with titanium and fluorine formed an ultra-thin rock salt phase on the surface [136].…”

Analysis of Thermal Reduction of Mixture of Organic Components on Cathode Materials of Spent Ternary Lithium-Ion Battery

“…There is a significant dependence on foreign imports, leading to a prolonged period of high external dependence. The taste of valuable metals in waste lithium-ion batteries is higher than that of primary ores, , and the separation process is simpler than that of primary ores . In addition, compared with the direct synthesis of cathode materials from raw materials, the energy consumption of the cathode materials synthesized by metallurgical recycling is lower .…”

“…The leaching rates of Ni, Co, and Mn reached 99.04, 96.98, and 97.52%, respectively. 9 Zhang et al used organic binder, aluminum foil, and conductive agent acetylene black as reducing agents to conduct in situ thermal reduction of waste ternary lithium-ion batteries. In this process, the transition metals in the cathode materials were reduced to CoO, NiO, MnO, Ni, and Co. After acid leaching without a reducing agent, the recovery rates of Li, Ni, Co, and Mn were 81.26, 92.04, 93.01, and 92.21%, respectively.…”

Innovative Method to Recover Graphite from Spent Lithium-Ion Batteries

“…Data show that the number of spent lithium-ion batteries in the world will exceed 1.36 million tons by 2025 . On the one hand, spent lithium-ion batteries contain a large amount of valuable metals, such as Li, Ni, Co, Mn, Al, Cu, Fe, etc. , The metal content is much higher than the corresponding ore grade, and it is a veritable “urban mine” . On the other hand, if not handled properly, heavy metal substances in used lithium-ion batteries can cause environmental pollution and endanger human health. , Therefore, from the perspective of economy and environmental protection, the recycling of spent lithium-ion batteries is very necessary …”

“…11,12 The metal content is much higher than the corresponding ore grade, and it is a veritable "urban mine". 13 On the other hand, if not handled properly, heavy metal substances in used lithium-ion batteries can cause environmental pollution and endanger human health. 14,15 Therefore, from the perspective of economy and environmental protection, the recycling of spent lithium-ion batteries is very necessary.…”