From waste graphite fines to revalorized anode material for Li-ion batteries

• Published in: Carbon (New York) Vol. 209; p. 118004
• Main Authors: Abrego-Martinez, Juan Carlos, Wang, Youling, Vanpeene, Victor, Roué, Lionel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.06.2023
• Subjects: Li-ion battery; Natural graphite; Pitch coating; Re-agglomeration; Spheroidization by-product; Spray drying; Natural graphite; Spheroidization by-product; Spray drying; Re-agglomeration; Pitch coating; Li-ion battery
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2023.118004

A crucial step in the production of battery grade natural graphite for lithium-ion batteries is the spheroidization process. However, the spheroidization yield is typically only about 50%. The by-product consists of graphite fines that are not suitable for use in lithium-ion batteries due to their small particle size (<10 μm), therefore, graphite fines are discarded or sold at a loss. In this work, we report a method for graphite fines re-agglomeration and petroleum pitch coating that allows for revalorization and recycling of waste graphite from the spheroidization process. Re-agglomeration of graphite fines was achieved by spray drying technique using carboxymethyl cellulose as binder and citric acid as cross-linking agent to improve the mechanical strength of the agglomerate. The as-obtained particles were subjected to heat treatment in presence of petroleum pitch for simultaneous binder and pitch decomposition to obtain pitch-coated particles. Resulting agglomerate particles showed a median size comparable to a commercial battery grade natural graphite reference and proved structurally sound to withstand the electrode calendering process. Pitch-coated agglomerate particles exhibited lower surface area and improved stability in comparison with non-coated graphite agglomerate. The electrochemical performance of the coated material was comparable to a commercial graphite reference, particularly in terms of cumulative irreversible capacity. Analysis by X-ray nano-computed tomography provided further insight into morphological properties and dimensional changes after calendering and upon galvanostatic cycling. Overall, the material obtained through this method shows great potential for re-introduction in the production chain of battery grade natural graphite for lithium-ion batteries. [Display omitted] •Graphite fines are revalorized via re-agglomeration by spray drying.•Binder carbonization and pitch coating are performed simultaneously.•The re-agglomerated product can be used as anode in lithium-ion batteries.•Performance of pitch-coated agglomerate is comparable to a commercial reference.