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Recycled Graphite for Sustainable Lithium-Ion Batteries
Abstract
Graphite – natural or synthetic – is the most dominant active material used for LIB anodes [1] . Natural graphite, however, is considered a critical material within the EU [2] , while synthetic graphite is obtained from coke [3] – a carbon precursor produced from coal or petroleum. Therefore, efficient recycling and reuse of graphite are essential towards sustainability and resource preservation [4] .
Herein, we report a novel and highly efficient process to recover high-quality graphite from spent LIBs. Following a comprehensive physicochemical characterization of the materials obtained, we conducted an extensive electrochemical characterization in half-cells and graphite‖NMC 532 full-cells and compared the results with the data obtained for half-cells and full-cells using pristine commercial graphite. In half-cells, the recycled graphite shows remarkably high reversible specific capacities (e.g., 350 mAh g ⁻ ¹ at C/20) and very stable cycling for several hundred cycles at 1C. The graphite‖NMC 532 full-cells also show excellent cycling stability, with a capacity retention of 80% after about 1,000 cycles. Particularly, the comparison with the pristine graphite comprising full-cells reveals very comparable performance, highlighting the great promise of recycled and reused graphite as a pivotal step towards truly sustainable LIBs and the great goal of a circular economy.
References
[1] J. Asenbauer, T. Eisenmann, M. Kuenzel, A. Kazzazi, Z. Chen, and D. Bresser, “The success story of graphite as a lithium-ion anode material – fundamentals, remaining challenges, and recent developments including silicon (oxide) composites,” Sustain. Energy Fuels , 2020.
[2] Comisión Europea, European Commission, Report on Critical Raw Materials and the Circular Economy, 2018 . 2018.
[3] S. Richard, W. Ralf, H. Gerhard, P. Tobias, and W. Martin, “Performance and cost of materials for lithium-based rechargeable automotive batteries,” Nat. Energy , vol. 3, no. Li, pp. 267–278, 2018.
[4] A. Vanderbruggen, E. Gugala, R. Blannin, K. Bachmann, R. Serna-Guerrero, and M. Rudolph, “Automated mineralogy as a novel approach for the compositional and textural characterization of spent lithium-ion batteries,” Miner. Eng. , vol. 169, p. 106924, 2021.
... Some studies have revealed that recovered GA could be regenerated as anode materials for energy storage devices after some retreatments. [103][104][105][106] Low-cost regeneration of GA from spent LIBs is of great significance to solve the problem of waste graphite utilization and pollution. Comparing with the fresh graphite, the directly recycled GA (with coating, SEI layer and other Impurities) exhibits lower initial discharge capacity, which are 354.2 and 298.7 mAh/g respectively. ...
There is growing production for lithium‐ion batteries (LIBs) to satisfy the booming development renewable energy storage systems. Meanwhile, amounts of spent LIBs have been generated and will become more soon. Therefore, the proper disposal of these spent LIBs is of significant importance. Graphite is the dominant anode in most commercial LIBs. This review specifically focuses on the recent advances in the recycling of graphite anode (GA) from spent LIBs. It covers the significance of GA recycling from spent LIBs, the introduction of the GA aging mechanisms in LIBs, the summary of the developed GA recovery strategies, and the highlight of reclaimed GA for potential applications. In addition, the prospect related to the future challenges of GA recycling is given at the end. It is expected that this review will provide practical guidance for researchers engaged in the field of spent LIBs recycling.
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... As a result, Western countries are actively searching for strategies to develop their own graphite supply chain for battery production, including plans to integrate recycled graphite. 7 During typical LIB recycling processes, a comminution stage is used as a first stage to separate electrode particles from their current collectors, producing foils in the coarse size fraction and active particles in the fine fraction. This is possible since electrode foils present a ductile behavior and, as reported by Schubert,8 ductile materials can be liberated through shear, cutting, and tearing stresses. ...
Recycling is a potential solution to narrow the gap between the supply and demand of raw materials for lithium-ion batteries (LIBs). However, the efficient separation of the active components and their recovery from battery waste remains a challenge. This paper evaluates the influence of three potential routes for the liberation of LIB components (namely mechanical, thermomechanical, and electrohydraulic fragmentation) on the recovery of lithium metal oxides (LMOs) and spheroidized graphite particles using froth flotation. The products of the three liberation routes were characterized using SEM-based automated image analysis. It was found that the mechanical process enabled the delamination of active materials from the foils, which remained intact at coarser sizes along with the casing and separator. However, binder preservation hinders active material liberation, as indicated by their aggregation. The electrohydraulic fragmentation route resulted in liberated active materials with a minor impact on morphology. The coarse fractions thus produced consist of the electrode foils, casing, and separator. Notwithstanding, it has the disadvantage of forming heterogeneous agglomerates containing liberated active particles. This was attributed to the dissolution of the anode binder and its rehardening after drying, capturing previously liberated particles. Finally, the thermomechanical process showed a preferential liberation of individual anode active particles and thus was considered the preferred upstream route for flotation. However, the thermal treatment oxidized Al foils, rendering them brittle and resulting in their distribution in all size fractions. Among the three, the thermomechanical black mass showed the highest flotation selectivity due to the removal of the binder, resulting in a product recovery of 94.4% graphite in the overflow and 89.4% LMOs in the underflow product.
... As a result, Western countries are actively searching for strategies to develop their own graphite supply chain for battery production, including plans to integrate recycled graphite. 7 During typical LIB recycling processes, a comminution stage is used as a first stage to separate electrode particles from their current collectors, producing foils in the coarse size fraction and active particles in the fine fraction. This is possible since electrode foils present a ductile behavior and, as reported by Schubert,8 ductile materials can be liberated through shear, cutting, and tearing stresses. ...
With the constant growth in portable electronic devices and the expected market growth for electric vehicles, the demand for lithium-ion batteries (LIBs) is booming. The raw materials production with a combination of mining and recycling will be essential and unavoidable to meet the upcoming demand for LIBs. Consequently, the European authority is updating the regulations demanding higher recovery efficiencies, 70 % by 2030. However, most of the state-of-the-art recycling technologies for LIBs focus on the recovery of components that have high economic value such as Co and Ni. The fine fraction resulting from the mechanical pre-treatment containing the lithium metal oxides (LMOs) and graphite particles, commonly referred to as "Black Mass" (BM), is generally used as a starting point for metals recovery by metallurgical means. Indeed, in industry, this BM is usually not further sorted and is directly fed to pyro- and/or hydrometallurgical processing routes to extract metals from LMOs, at the expense of graphite not being recovered. Recent studies, however, have convincingly illustrated that froth flotation can be applied to the BM to efficiently generate two valuable products, therefore increasing the overall efficiency of LIB recycling significantly. The work presented in this thesis aims to increase the overall materials recovery from LIBs by improving the BM beneficiation through froth flotation. The research work hereby presented offers a systematic study of the influence of the recycling pre-treatment processes on the liberation of the LIB components and the potential flotation mechanisms of active particles. The first part of this thesis is focused on the liberation analysis of the LIB components, which cannot be determined by conventional bulk characterization techniques such as X-ray fluorescence. In this thesis, a new approach for the BM characterization using automated mineralogy has been developed. With this particle-based technique, information on the chemical composition, morphology and degree of liberation of LIB components was acquired, helping to understand how the particles behaved during the process. The second part is focused on BM beneficiation on the basis of flotation. The use of flotation has recently gained interest as a method to separate LMOs and graphite particles. However, the flotation mechanisms of LMOs have not been paid sufficient attention. Therefore, this work provides the first fundamental study on the flotation mechanisms of active particles, with the aim of properly identifying the challenges to overcome in order to drive selectivity in flotation separation. To understand the flotation behavior, an industrial BM from pyrolyzed LIBs was compared to a model BM, comprising fully liberated LMOs and graphite particles. In addition, ultrafine hydrophilic particles were added to the flotation feed as an entrainment tracer, showing that the LMOs recovery in overflow products is a combination of entrainment and true flotation mechanisms. Ultimately, the findings of this thesis indicate the possibility of recovering and reusing graphite into new batteries.
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