Fundamental Research on Green and Efficiency Recovery and Regeneration of Lithium Iron Phosphate Cathode Materials
Final Report Abstract
Clean energies of the future, in particular their use in electric vehicles, are leading to an increased use of lithium ion batteries (LIBs). While there are first commercial processes are available for LIBs that use cathode material wending cobalt, nickel and manganese, there is still a considerable need for research for batteries with LiFePO4 (LFP) as cathode material. The latter is characterized by long cycle life (2000+), a higher safety and low material cost. Within this project a green and efficient recovery and regeneration of LFP cathode material was investigated in joint research effort by Prof. Shili Zheng and Prof. Hao Du from the Institute of Process Engineering, Chinese Academy of Sciences (NSFC funded) and Prof. Weigand from the Technische Universität Dresden, Germany. In order to achieve a high material recovery yield and to prevent crosscontamination with the counter ions, phosphoric acid was use in the developed process. The evaluation for a recovery of the acid using liquid-liquid extraction as a low temperature process and powerful receptors for lithium recognition were subjects of the developments in the project. The spent cathode powder used in this study comprises of 6 wt.% carbon, 28.5 wt.% iron, 3.9 wt.% lithium and 20.4 wt.% phosphor. After a thermal treatment at 550 °C to reduce the carbon content a quantitative dissolution of the containing iron and lithium is achieved using 55 wt.% phosphoric acid at 40 °C for 120 min at an solid to liquid ration (S:L) of 1:4. After oxidation of residual iron in the oxidation state +II applying oxygen fine bubble technology, more than 99% of iron is removed in sufficient purity from the leach liquor as FePO4·2H2O by precipitation. For the recycling of the phosphoric acid the extractant mixture cyclohexanol and tri-butyl phosphate in Escaid 110 was developed. Hand tests revealed the sedimentation of LiH2PO4 as gelatinous precipitate after continuative extraction of the acid and prevent high recovery rates for phosphoric acid. However, with 77% of the phosphoric acid being transferred to the organic phase, a considerable amount of the acid was recovered a single extraction step. The resulting lithium rich liquor was treated with NaOH and Na2CO3 to facilitate the precipitation of Li3PO4. The reusability of the recovered materials, namely FePO4, Li3PO4 as well as the H3PO4 was demonstrated. The H3PO4 was employed in the leaching of spent cathode material and FePO4 and Li3PO4 were successfully used for the synthesis of LiFePO4/C as obtained. The receptors developed within the project are versatile and show great potential for various application. Simple oligo(ethylene oxide) ureas are powerful heteroditopic ligands and detailed proton NMR studies show an enhanced affinity towards anions in the presence of lithium ions. However, the high polarity of the polyethylene glycol moiety may hinder the transfer of the metal salts into the organic phase and prevents their use as reagents in liquid-liquid extraction. In contrast, the developed bis(guanidines) show clear differences in the solubility of different salts and prove their suitability for separation processes of anions. Of particular interest is the fact that large oxoanions such as ReO4- as well as chloridometalates such as HgCl4- are selectively crystallized form chloride media. Furthermore, 4-phosphorylpyrazolones were developed and show a very high affinity and extraction power towards lithium ions in the presence of the alkali metals Na+, K+ and Cs+ and renders them as new class of extraction agents. Single crystal X-ray analyses confirm the formation of multinuclear Li+ complexes in the solid state with the cocoordination of co-ligands such as trioctylphosphine oxide. Detailed NMR and MS studies reveal the presence of these polynuclear species in solution and provide a good example of the use of solid and solution studies for understanding the coordination mechanism in mixed-ligand systems. The Corona pandemic caused restrictions in laboratory operations and travel restrictions for a large part of the project duration resulting in challenges in the project work and administration. Consequently, the joint processing with intensive exchange of the participating junior scientists could only partly be realized as planned.
Publications
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Ammonium vanadate/ammonia precipitation for vanadium production from a high vanadate to sodium ratio solution obtained via membrane electrolysis method; J. Clean. Prod. 2020, 263, 121357
B. Pan, B. Liu, S. Wang, M. Wenzel, J. J. Weigand, M. Feng, H. Du, Y. Zhang
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Separation and recovery of rare earths by in situ selective electrochemical oxidation and extraction from spent fluid catalytic cracking (FCC) catalysts; Hydrometallurgy, 2020, 194, 105300
Y. Zhou, S. Schulz, L. F. Lindoy, H. Du, S. Zheng, M. Wenzel, J. J. Weigand
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4-Phosphoryl pyrazolones for highly selective lithium separation from alkali metal ions; Chem. Eur. J., 2021, 28, e202103640
J. Zhang, M. Wenzel, J. Steup, G. Schaper, F. Hennersdorf, H. Du, S. Zheng, L. F. Lindoy, J. J. Weigand
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A facile way to regenerate FePO4·2H2O precursor from spent lithium iron phosphate cathode powder: spontaneous precipitation and phase transformation in an acidic medium; J. Alloys Compd. 2021, 865, 158148
W. Lou, Y. Zhang, Y. Zhang, S. Zheng, P. Sun, X. Wang, S. Qiao J. Li, Y. Zhang, D. Liu. M. Wenzel, J. J. Weigand
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Leaching performance of Al-bearing spent LiFePO4 cathode powder in H2SO4 aqueous solution; Trans. Nonferrous Met. Soc. China 2021, 31, 817−831
W. Lou, Y. Zhang, Y. Zhang, S. Zheng, P. Sun, X. Wang, J. Li, S. Qiao, Y Zhang, M. Wenzel, J. J. Weigand
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Recovering valuable metals from spent hydrodesulfurization catalyst via blank roasting and alkaline leaching; J. Hazard. Mat. 2021, 416, 125849
J. Wang, S. Wang, A. Olayiwola, N. Yang, B. Liu, J. J. Weigand, M. Wenzel, H. Du
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Separation of Na3VO4 and Na2CrO4 from High Alkalinity Solutions by Solvent Extraction; Sep. Purif. Technol. 2021, 255, 117282
M. Feng, M. Wenzel, S. Wang, H. Du, Y. Zhang, J. J. Weigand
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Recent advances in guanidinium salt based receptors and functionalized materials for the recognition of anions; Chem. Lett. 2022, 51, 20– 29
M. Wenzel, J. Steup, K. Ohto, J. J. Weigand
