Pyrolysis and physical separation for the recovery of spent LiFePO4 batteries

Review of lithium-ion batteries' supply-chain in Europe: Material flow analysis and environmental assessment

European legislation stated that electric vehicles' sale must increase to 35% of circulating vehicles by 2030, and concern is associated to the batteries' supply chain. This review aims at analysing the impacts (about material flows and CO2 eq emissions) of Lithium-Ion Batteries' (LIBs) recycling at full-scale in Europe in 2030 on the European LIBs' supply-chain. Literature review provided the recycling technologies' (e.g., pyro- and hydrometallurgy) efficiencies, and an inventory of existing LIBs' production and recycling plants in Europe. European production plants exhibit production capacity adequate for the expected 2030 needs. The key critical issues associated to recycling regard pre-treatments and the high costs and environmental impacts of metallurgical processes. Then, according to different LIBs' composition and market shares in 2020, and assuming a 10-year battery lifetime, the Material Flow Analysis (MFA) of the metals embodied in End of Life (EoL) LIBs forecasted in Europe in 2030 was modelled, and the related CO2 eq emissions calculated. In 2030 the European LIBs' recycling structure is expected to receive 664 t of Al, 530 t of Co, 1308 t of Cu, 219 t of Fe, 175 t of Li, 287 t of Mn and 486 t of Ni. Of these, 99% Al, 86% Co, 96% Cu, 88% Mn and 98% Ni will be potentially recovered by pyrometallurgy, and 71% Al, 92% Co, 92% Fe, 96% Li, 88 % Mn and 90% Ni by hydrometallurgy. However, even if the recycling efficiencies of the technologies applied at full-scale are high, the treatment capacity of European recycling plants could supply as recycled metals only 2%-wt of the materials required for European LIBs' production in 2030 (specifically 278 t of Al, 468 t of Co, 531 t of Cu, 114 t of Fe, 95 t of Li, 250 t of Mn and 428 t of Ni). Nevertheless, including recycled metals in the production of new LIBs could cut up 28% of CO2 eq emissions, compared to the use of virgin raw materials, and support the European batteries' value chain.

Opportunity and challenges in recovering and functionalizing anode graphite from spent lithium-ion batteries: A review

Recent concerns have emerged regarding the improper disposal of spent lithium-ion batteries (LIBs), which has garnered widespread societal attention. Graphite materials accounted for 12-21 wt % of LIBs' mass, typically contain heavy metals, binders, and residual electrolytes. Regenerating spent graphite not only alleviated the shortage of plumbago, but also contributed to the supports environmental protection as well as national carbon peak and neutrality ("dual carbon" goals). Despite significant advancements in recycling spent LIBs had been made, a comprehensive overview of the processes for pretreatment, regeneration, and functionalization of spent graphite from retired LIBs, along with the associated technical standards and industry regulations enabling their smooth implementation still needed to be mentioned. Hence, we conducted the following research work. Firstly, the pre-treatment process of spent graphite, including discharging, crushing, and screening was summed up. Next,. Subsequently, graphite recovery methods, such as acid leaching, pyrometallurgy, and combined methods were summarized. Moreover, the modification and doping approach was used to enhance the electrochemical properties of graphite. Afterwards, we reviewed the functionalization of anode graphite from an economically and environmentally friendly view. Meanwhile, the technical standards and industry regulations of spent LIBs in domestic and oversea industries were described. Finally, we provided an overview of the technical challenges and development bottlenecks in graphite recycling, along with future prospects Overall, this study outlined the opportunities and challenges in recovering and functionalizing of anode materials via a efficient and sustainable processes.

A clean and sustainable method for recycling of lithium from spent lithium iron phosphate battery powder by using formic acid and oxygen

With the widespread adoption of lithium iron phosphate (LiFePO4) batteries, the imperative recycling of LiFePO4 batteries waste presents formidable challenges in resource recovery, environmental preservation, and socio-economic advancement. Given the current overall lithium recovery rate in LiFePO4 batteries is below 1 %, there is a compelling demand for an eco-friendly, cost-efficient, and sustainable solution. This study introduces a green and sustainable recycling method that employs environmentally benign formic acid and readily available oxygen as reaction agents for selectively leaching lithium from discarded lithium iron phosphate powder. Formic acid was employed as the leaching agent, and oxygen served as the oxidizing agent. Utilizing a single-factor variable approach, various factors including formic acid concentration, oxygen flow rate, leaching time, liquid-to-solid ratio, and reaction temperature were individually investigated. Moreover, the feasibility of this method was explored mechanistically by analyzing E-pH diagrams of the Li-Fe-P-H2O system. Results demonstrate that under conditions of 2.5 mol/L formic acid concentration, 0.12 L/min oxygen flow rate, 25 mL/g liquid-to-solid ratio, 70 °C reaction temperature, and 3 h reaction time, lithium leaching efficiency exceeds 99.9 %, with iron leaching efficiency only at 1.7 %. Moreover, we also explored using air instead of oxygen as the oxidant and get the excellent lithium leaching rate (97.81 %) and low iron leaching rate (4.81 %), which shows the outstanding selectivity. Furthermore, the environmentally benign composition of the chemical reagents, comprising only C, H, and O elements, establishes it as a genuinely green and sustainable technology for secondary resource recovery. It can be considered as a highly environmentally friendly, cost-effective, and efficient approach. Nevertheless, in the current context of carbon neutrality and sustainable development, this method undoubtedly holds excellent prospects for industrialization.

Applications of Plasma Technologies in Recycling Processes

Plasmas are reactive ionised gases, which enable the creation of unique reaction fields. This allows plasmas to be widely used for a variety of chemical processes for materials, recycling among others. Because of the increase in urgency to find more sustainable methods of waste management, plasmas have been enthusiastically applied to recycling processes. This review presents recent developments of plasma technologies for recycling linked to economical models of circular economy and waste management hierarchies, exemplifying the thermal decomposition of organic components or substances, the recovery of inorganic materials like metals, the treatment of paper, wind turbine waste, and electronic waste. It is discovered that thermal plasmas are most applicable to thermal processes, whereas nonthermal plasmas are often applied in different contexts which utilise their chemical selectivity. Most applications of plasmas in recycling are successful, but there is room for advancements in applications. Additionally, further perspectives are discussed.

A review on the recycling of spent lithium iron phosphate batteries

Lithium iron phosphate (LFP) batteries have gained widespread recognition for their exceptional thermal stability, remarkable cycling performance, non-toxic attributes, and cost-effectiveness. However, the increased adoption of LFP batteries has led to a surge in spent LFP battery disposal. Improper handling of waste LFP batteries could result in adverse consequences, including environmental degradation and the mismanagement of valuable secondary resources. This paper presents a comprehensive examination of waste LFP battery treatment methods, encompassing a holistic analysis of their recycling impact across five dimensions: resources, energy, environment, economy, and society. The recycling of waste LFP batteries is not only crucial for reducing the environmental pollution caused by hazardous components but also enables the valuable components to be efficiently recycled, promoting resource utilization. This, in turn, benefits the sustainable development of the energy industry, contributes to economic gains, stimulates social development, and enhances employment rates. Therefore, the recycling of discarded LFP batteries is both essential and inevitable. In addition, the roles and responsibilities of various stakeholders, including governments, corporations, and communities, in the realm of waste LFP battery recycling are also scrutinized, underscoring their pivotal engagement and collaboration. Notably, this paper concentrates on surveying the current research status and technological advancements within the waste LFP battery lifecycle, and juxtaposes their respective merits and drawbacks, thus furnishing a comprehensive evaluation and foresight for future progress.

The Foreseeable Future of Spent Lithium-Ion Batteries: Advanced Upcycling for Toxic Electrolyte, Cathode, and Anode from Environmental and Technological Perspectives

With the rise of the new energy vehicle industry represented by Tesla and BYD, the need for lithium-ion batteries (LIBs) grows rapidly. However, owing to the limited service life of LIBs, the large-scale retirement tide of LIBs has come. The recycling of spent LIBs has become an inevitable trend of resource recovery, environmental protection, and social demand. The low added value recovery of previous LIBs mostly used traditional metal extraction, which caused environmental damage and had high cost. Beyond metal extraction, the upcycling of spent LIBs came into being. In this work, we have outlined and particularly focus on sustainable upcycling technologies of toxic electrolyte, cathode, and anode from spent LIBs. For electrolyte, whether electrolyte extraction or decomposition, restoring the original electrolyte components or decomposing them into low-carbon energy conversion is the goal of electrolyte upcycling. Direct regeneration and preparation of advanced materials are the best strategies for cathodic upcycling with the advantages of cost and energy consumption, but challenges remain in industrial practice. The regeneration of advanced graphite-based materials and battery-grade graphite shows us the prospect of regeneration of anode. Furthermore, the challenges and future development of spent LIBs upcycling are summarized and discussed from technological and environmental perspectives.

Shearing-enhanced mechanical exfoliation with mild-temperature pretreatment for cathode active material recovery from spent LIBs

The conventional approaches for recovering valuable metals from spent lithium-ion batteries (LIBs) suffer from heavy dependence on chemical reagents, high energy consumption, and low recovery efficiencies. In this study, we developed a shearing-enhanced mechanical exfoliation combined with mild-temperature pretreatment (SMEMP) method. The method achieves high-efficiency exfoliation of the cathode active materials that remain strongly adhered to polyvinylidene fluoride after it melts during mild pretreatment. The pretreatment temperature was decreased from 500-550 °C to 250 °C, the duration was decreased to 1/4-1/6 of the traditional pretreatment duration, and the exfoliation efficiency and product purity reached 96.88% and 99.93%, respectively. Despite the weakening thermal stress, the cathode materials could be exfoliated by strengthened shear forces. Compared with other traditional methods, the superiority of this method in temperature reduction and energy saving was established. The proposed SMEMP method is environmentally friendly and economical, and it offers a new route for the recovery of cathode active materials from spent LIBs.

Recycling Hazardous and Valuable Electrolyte in Spent Lithium-Ion Batteries: Urgency, Progress, Challenge, and Viable Approach

Recycling spent lithium-ion batteries (LIBs) is becoming a hot global issue due to the huge amount of scrap, hazardous, and valuable materials associated with end-of-life LIBs. The electrolyte, accounting for 10-15 wt % of spent LIBs, is the most hazardous substance involved in recycling spent LIBs. Meanwhile, the valuable components, especially Li-based salts, make recycling economically beneficial. However, studies of electrolyte recycling still account for only a small fraction of the number of spent LIB recycling papers. On the other hand, many more studies about electrolyte recycling have been published in Chinese but are not well-known worldwide due to the limitations of language. To build a bridge between Chinese and Western academic achievements on electrolyte treatments, this Review first illustrates the urgency and importance of electrolyte recycling and analyzes the reason for its neglect. Then, we introduce the principles and processes of the electrolyte collection methods including mechanical processing, distillation and freezing, solvent extraction, and supercritical carbon dioxide. We also discuss electrolyte separation and regeneration with an emphasis on methods for recovering lithium salts. We discuss the advantages, disadvantages, and challenges of recycling processes. Moreover, we propose five viable approaches for industrialized applications to efficiently recycle electrolytes that combine different processing steps, ranging from mechanical processing with heat distillation to mechanochemistry and in situ catalysis, and to discharging and supercritical carbon dioxide extraction. We conclude with a discussion of future directions for electrolyte recycling. This Review will contribute to electrolyte recycling more efficiently, environmentally friendly, and economically.

In-situ pyrolysis based on alkaline medium removes fluorine-containing contaminants from spent lithium-ion batteries

Pyrolysis is an effective method for removing organic contaminants (e.g. electrolytes, solid electrolyte interface (SEI), and polyvinylidene fluoride (PVDF) binders) from spent lithium-ion batteries (LIBs). However, during pyrolysis, the metal oxides in black mass (BM) readily react with fluorine-containing contaminants, resulting in a high content of dissociable fluorine in pyrolyzed BM and fluorine-containing wastewater in subsequent hydrometallurgical processes. Herein, an in-situ pyrolysis process is proposed to control the transition pathway of fluorine species in BM using Ca(OH)₂-based materials. Results show that the designed fluorine removal additives (FRA@Ca(OH)₂) can effectively scavenge SEI components (Li_xPOF_y) and PVDF binders from BM. During the in-situ pyrolysis, potential fluorine species (e.g. HF, PF₅, and POF₃) are adsorbed and converted to CaF₂ on the surface of FRA@Ca(OH)₂ additives, thereby inhibiting the fluorination reaction with electrode materials. Under the optimal experimental conditions (temperature = 400 °C, BM: FRA@Ca(OH)₂ = 1: 4, holding time = 1.0 h), the dissociable fluorine content in BM was reduced from 3.84 wt% to 2.54 wt%. The inherent metal fluorides in BM feedstock hinder the further removal of fluorine with pyrolysis treatment. This study provides a potential strategy for source control of fluorine-containing contaminants in the recycling process of spent LIBs.

The Recycling of Spent Lithium-Ion Batteries: Crucial Flotation for the Separation of Cathode and Anode Materials

The recycling of spent lithium-ion batteries (LIBs) has attracted great attention, mainly because of its significant impact on resource recycling and environmental protection. Currently, the processes involved in recovering valuable metals from spent LIBs have shown remarkable progress, but little attention has been paid to the effective separation of spent cathode and anode materials. Significantly, it not only can reduce the difficulty in the subsequent processing of spent cathode materials, but also contribute to the recovery of graphite. Considering the difference in their chemical properties on the surface, flotation is an effective method to separate materials, owing to its low-cost and eco-friendly characteristics. In this paper, the chemical principles of flotation separation for spent cathodes and materials from spent LIBs is summarized first. Then, the research progress in flotation separation of various spent cathode materials (LiCoO₂, LiNi_xCo_yMn_zO₂, and LiFePO₄) and graphite is summarized. Given this, the work is expected to offer the significant reviews and insights about the flotation separation for high-value recycling of spent LIBs.

Ultra-fast recovery of cathode materials from spent LiFePO4 lithium-ion batteries by novel electromagnetic separation technology

The separation of electrode materials from current collectors plays a significant role in determining the leaching efficiency of different metals from spent lithium-ion batteries (LIBs). In the presented research, a highly efficient, environmentally sustainable, and cost-effective cathode materials separation strategy was proposed for spent LiFePO₄ batteries. Based on the difference in the thermal expansion coefficient of the binder and aluminum foil, the electromagnetic induction system was examined to harvest cathode materials for the first time, which could provide a high heating rate to erase the mechanical interlocking force between Al foil and coated material, and breaking the chemical bond or Van der Waals forces of the binder. The process avoids the usage of any chemicals such as acids and alkalis, thus eliminating the emission of wastewater. Our system shows ultra-fast separation (3 min) and achieves high-purity of recovered electrode materials and Al foils (99.6% and 99.2%). Furthermore, the morphology and crystalline structure of delaminated electrode materials remain almost the same compared with the pristine materials, which provides a previously unexplored technology to realize sustainable spent battery recycling.

Mechanochemical upcycling of spent LiCoO2 to new LiNi0.80Co0.15Al0.05O2 battery: An atom economy strategy

The use of strong acids and low atom efficiency in conventional hydrometallurgical recycling of spent lithium-ion batteries (LIBs) results in significant secondary wastes and CO2 emissions. Herein, we utilize the waste metal current collectors in spent LIBs to promote atom economy and reduce chemicals consumption in a conversion process of spent Li1-xCoO2 (LCO) → new LiNi0.80Co0.15Al0.05O2 (NCA) cathode. Mechanochemical activation is employed to achieve moderate valence reduction of transition metal oxides (Co3+→Co2+,3+) and efficient oxidation of current collector fragments (Al0→Al3+, Cu0→Cu1+,2+), and then due to stored internal energy from ball-milling, the leaching rates of Li, Co, Al, and Cu in the ≤4 mm crushed products uniformly approach 100% with just weak acetic acid. Instead of corrosive precipitation reagents, larger Al fragments (≥4 mm) are used to control the oxidation/reduction potential (ORP) in the aqueous leachate and induce the targeted removal of impurity ions (Cu, Fe). After the upcycling of NCA precursor solution to NCA cathode powders, we demonstrate excellent electrochemical performance of the regenerated NCA cathode and improved environmental impact. Through life cycle assessments, the profit margin of this green upcycling path reaches about 18%, while reducing greenhouse gas emissions by 45%.

Research on the high-efficiency crushing, sorting and recycling process of column-shaped waste lithium batteries

The efficient and environmentally friendly recycling technology of waste lithium batteries has become a research hotspot, in which mechanical crushing is an important part of the recycling process. Through experimental methods, the compressive and impact properties of columnar lithium batteries were studied, and the crushing product characteristics and crushing efficiency of the single tear crushing method, single hammer crushing method, and two-step crushing method were investigated. The study shows that the two-step crushing method could achieve 100 % dissociation of all battery components, and the crushed products can be recycled according to their particle size distribution characteristics. The power consumption of the two-step crushing method was only 23.59 % of that of a single hammer crusher, and the reduction of carbon dust emission in the crushing process was as high as 76.29 %. The high crushing efficiency and environmentally friendly of the two-step crushing method are of great practical significance for the subsequent industrial promotion of waste battery recycling.

Challenges in Recycling Spent Lithium-Ion Batteries: Spotlight on Polyvinylidene Fluoride Removal

In the recycling of retired lithium-ion batteries (LIBs), the cathode materials containing valuable metals should be first separated from the current collector aluminum foil to decrease the difficulty and complexity in the subsequent metal extraction. However, strong the binding force of organic binder polyvinylidene fluoride (PVDF) prevents effective separation of cathode materials and Al foil, thus affecting metal recycling. This paper reviews the composition, property, function, and binding mechanism of PVDF, and elaborates on the separation technologies of cathode material and Al foil (e.g., physical separation, solid-phase thermochemistry, solution chemistry, and solvent chemistry) as well as the corresponding reaction behavior and transformation mechanisms of PVDF. Due to the characteristic variation of the reaction systems, the dissolution, swelling, melting, and degradation processes and mechanisms of PVDF exhibit considerable differences, posing new challenges to efficient recycling of spent LIBs worldwide. It is critical to separate cathode materials and Al foil and recycle PVDF to reduce environmental risks from the recovery of retired LIBs resources. Developing fluorine-free alternative materials and solid-state electrolytes is a potential way to mitigate PVDF pollution in the recycling of spent LIBs in the EV era.

Facile separation and regeneration of LiFePO4 from spent lithium-ion batteries via effective pyrolysis and flotation: An economical and eco-friendly approach

The facile recycling of spent lithium-ion batteries (LIBs) has attracted much attention because of its great significance to the environmental protection and resource utilization. Hydrometallurgical process is the most common method for recycling spent LIBs, but it is difficult to economically recover spent LiFePO₄ batteries, because of the complicated metal separation process and low added value of its products. Herein, a novel and facile approach has been developed to achieve the direct regeneration of LiFePO₄ from spent LIBs. By employing a flotation process after effective pyrolysis, it is found that 91.57% of LiFePO₄ can be recovered from spent LIBs. Different surface hydrophobicity of cathode and anode active materials could be achieved via the selective adsorption of causticized soluble starch on the surfaces of spent LiFePO₄, which effectively enhances the separation performance in flotation process. The recovered LiFePO₄ barely contains metal impurities, which can be directly regenerated as new LiFePO₄ materials with the first discharge capacity of 161.37 mAh/g, and their capacity retention is as high as 97.53% after 100 cycles at 0.2C. A technology assessment and economic evaluation indicate the developed regeneration approach of LiFePO₄ is environmentally and economically feasible, which avoids the complex element separation process and achieves the facile recycling of spent LiFePO₄.

Kinetics study and recycling strategies in different stages of full-component pyrolysis of spent LiNixCoyMnzO2 lithium-ion batteries

Full-component pyrolysis has been proven to be a prospective method for the disposal of organic matters and the cathode material reduction of spent LiNi_xCo_yMn_zO₂ (NCM) lithium-ion batteries (LIBs). However, the kinetics of the full-component pyrolysis of spent NCM LIBs is still unclear. This work represents the first attempt to study the kinetics of different stages of full-component pyrolysis of NCM LIBs based on isoconversional method to guide the recycling of spent LIBs. Pyrolysis process was divided into four stages in accordance to the main weight loss temperature ranges and the classical Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa kinetics models were employed to calculate the activation energy (E) in each stage. The main physicochemical reactions were clarified though in situ analysis, and the average E in the four stages was determined: (I) The volatilization of electrolytes occurred in the temperature range of 100-200 °C with the E of 98.6 kJ/mol. (II) The decomposition of organic matters and the preliminary reduction of cathode material transpired in the temperature range of 400-500 °C with the E of 227.2 kJ/mol. (III) The further reduction of NiO and CoO occurred from 650 to 800 °C with the E of 258.8 kJ/mol. (Ⅳ) The reduction of MnO took place from 850 to 1000 °C with the E of 334.9 kJ/mol. The recycling strategies based on full-component pyrolysis of spent NCM LIBs was accordingly proposed. During pyrolysis, the cathode material was gradually reduced and the pyrolytic products can be controlled through temperature regulation.

Repurposing of spent lithium-ion battery separator as a green reductant for efficiently refining the cathode metals

Developing green and high-efficient pyrometallurgy processes to recycle precious metals from spent lithium-ion batteries (LIBs) is of great importance for resource sustainability and environmental protection. Herein, a novel reduction roasting approach relying on spent LIB separator to refine the spent cathode is proposed. The efficiency of repurposing separator as a reductant for roasting the spent LiCoO₂ cathode and the underlying mechanisms were investigated. After the separator-mediated roasting at 500 °C for 2 h, Li⁺ leaching efficiency of the cathode reached 93.2 %, >2.6 times higher than those after roasting without reductant (25.2 %) or with benchmark reductant graphite (26.1 %). Under the separator-added roasting condition, the cathode was converted to the desired products, CoO and Li₂CO₃. Based on the analysis of in-situ reaction using thermogravimetric/differential scanning calorimetry and pyrolysis gas species identification, the separator-mediated reduction roasting of cathode was composed of two stages, i.e., reducing gas generation due to separator pyrolysis, followed by the reducing gas mediated LiCoO₂ reduction. During the process, the generated C₂H₄ and CO dominated the reduction. The use of co-existing separator to recover precious metals from spent LIBs is an effective and sustainable strategy to maximize the utilization of spent LIBs.

Spent LiFePO4: An old but vigorous peroxymonosulfate activator for degradation of organic pollutants in water

Iron-based catalysts have been demonstrated to activate peroxymonosulfate (PMS) to generate reactive radicals, which is however limited by their complex preparation process, high costs and inefficiency for practical applications. Herein we obtain spent LiFePO₄ (SLFP), with powerful catalytic capacity by a simple one-step treatment of the retired LiFePO₄ cathode material, for PMS activation to decontaminate organic pollutants. Lithium defects and oxygen vacancies in SLFP play critical roles for PMS utilization, further confirmed by density functional theory (DFT) calculations. SLFP materials rapidly adsorb PMS, and the surface PMS is activated by Fe(II) to generate radicals, with ^•OH playing a major role for the degradation of organics after multi-step reactions. The SLFP/PMS process is finally validated for ability to remove organic contaminants and potential environmental application.

Advances and challenges in anode graphite recycling from spent lithium-ion batteries

Spent lithium-ion batteries (LIBs) have been one of the fast-growing and largest quantities of solid waste in the world. Spent graphite anode, accounting for 12-21 wt% of batteries, contains metals, binders, toxic, and flammable electrolytes. The efficient recovery of spent graphite is urgently needed for environmental protection and resource sustainability. Recently, more and more studies have been focused on spent graphite recycling, while the advance and challenges are rarely summarized. Hence, this study made a comprehensive review of graphite recycling including separation, regeneration, and synthesis of functional materials. Firstly, the pretreatment of graphite separation was overviewed. Then, the spent graphite regeneration methods such as leaching, pyrometallurgy, their integration processes, etc. were systematically introduced. Furthermore, the modification strategies to enhance the electrochemical performance were discussed. Subsequently, we reviewed in detail the synthesis of functional materials using spent graphite for energy and environmental applications including graphene, adsorbents, catalysts, capacitors, and graphite/polymer composites. Meanwhile, we briefly compared the economic and environmental benefits of graphite regeneration and other functional materials production. Finally, the technical bottlenecks and challenges for spent graphite recycling were summarized and some future research directions were proposed. This review contributes to spent LIBs recycling more efficiently and profitably in the future.

Transformation and migration mechanism of fluorine-containing pollutants in the pyrolysis process of spent lithium-ion battery

Pyrolysis is an effective method to remove organics (e.g. electrolytes and binders) from spent lithium-ion battery (LIB). In this study, the co-pyrolysis characteristics of fluorine-containing substances and active materials from LIB were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), infrared spectroscopy (IR), and mass spectrometry (MS) analysis. Associated with the pyrolysis, active materials adsorb the residues of electrolyte on the surface and into the pores (20-200 °C), while polyvinylidene fluoride (PVDF) forms a liquid film to cover the local surface of active materials (400-500 °C). These interactions prevent deep removal of organics, leaving fluorine-containing contaminants in active materials. The barrier effect of PVDF liquid mesophase on the removal of organics with secondary liquidous phase formation during pyrolysis was confirmed by in situ optical observation. The migration behavior of fluorine element during the pyrolysis of black mass (BM) from spent LIB was also investigated. With pyrolysis temperature increasing from 100 °C to 600 °C, the dissociable fluorine content in pyrolyzed BM increased from 1.4 wt% to 3.7 wt%. The fluorine-containing contaminants in BM cannot be removed completely by simply increasing pyrolysis temperature. This study provides a better understanding on the transformation of fluorine-containing pollutants during the pyrolysis of BM.

Complex gas formation during combined mechanical and thermal treatments of spent lithium-ion-battery cells

Spent lithium-ion batteries (LIB) contain volatile and reactive chemicals possibly generating toxic and/or flammable gases during the related recycling. In this study, two types of spent LIB cells were subjected to combined mechanical and thermal treatments at the constant temperatures of 20 °C, 120 °C, 200 °C, and 400 °C under a nitrogen atmosphere. A total of 46 gaseous species, including electrolyte components, oxygenated hydrocarbons, hydrocarbons, and others, were qualitatively and quantitatively analyzed by mass spectrometry. At higher process temperatures, the concentration or volume of the formed gases increased accordingly. Additionally, at and below 120 °C, the formed gaseous species slightly differed depending on the cell type, whereas they were analogous at 400 °C. The formation of different gas species involved the activity of electrolyte volatilization, electrolyte degradation/decomposition, and pyrolysis of the organic separator and binder, followed by complex radical reactions among the species formed by the physicochemical reactions. Possible strategies to mitigate the risks that may arise associated with the gas formation during recycling are presented.

Detailed Microparticle Analyses Providing Process Relevant Chemical and Microtextural Insights into the Black Mass

Eramet uses a combination of physical and hydrometallurgical treatment to recycle lithium-ion batteries. Before hydrometallurgical processing, mechanical treatment is applied to recover the Black Mass which contains nickel, cobalt, manganese and lithium as valuable elements as well as graphite, solvent, plastics, aluminium and copper. To evaluate the suitability for hydrometallurgical recycling, it is essential to analyse the Black Mass chemically but also with respect to size, shape and composition of particles in the Black Mass. The Black Mass of various battery recyclers was investigated by using a combination of SEM/QEMSCAN® analyses. This specific QEMSCAN® database contains 260 subgroups, which comprise major and minor chemical variations of phases. The database was created using millions of point analyses. Major observations are: (1) particles can be micro-texturally characterised and classified with respect to chemical element contents; (2) important textural and chemical particle variations exist in the Black Mass from several origins leading to different levels of quality; (3) elements deleterious to hydrometallurgical processing (i.g. Si, Ca, Ti, Al, Cu and others) are present in well liberated particles; (4) components can be quantified and cathodes active material compositions (LCO, different NMC, NCA, LFP, etc.) that are specific for each battery type can be identified; (5) simulation of further physical mineral processing can optimise Black Mass purity in valuable elements.

Efficient separation of aluminum foil from mixed-type spent lithium-ion power batteries

The disposal of spent lithium-ion power batteries (LIBs) has become an important research topic owing to the booming market for electric vehicles. However, the recovery efficiency of the alkaline solution and organic solvent methods currently used to separate Al foil from cathode materials still has room for improvement. The insufficient separation of Al foil and complexity of the battery types present obstacles to the extraction of valuable metals using simple processes. In this study, an efficient approach is developed to separate the Al foil in mixed-type spent LIBs (M-LIBs), namely, LiNi_xCo_yMn_zO₂ (NCM), LiFePO₄ (LFP), and LiMn₂O₄ (LMO) LIBs, by controlled pyrolysis. Hundred percent of the Al foil was recovered at the temperature of 450 °C, holding time of 60 min, and heating rate of 10 °C/min. The purity of Al in the recovered foil was 99.41 %, 99.83 % and 99.92 %, and the recovery efficiency of the active cathode materials was 96.01 %, 99.80 % and 99.15 % for NCM, LFP and LMO, respectively, without the loss of active cathode materials. The obtained active cathode materials exhibited a favorable crystalline structure, and the average particle diameter was reduced from 300.497 to 24.316 μm with a smaller and looser morphology. The process could be well fitted with the Friedman differential equation, and the correlation coefficients were higher than 0.99. The efficient separation could be attributed to the complete rupture of long chain -(CH₂CF₂)-_n bonds in the poly (vinylidene difluoride) (PVDF) binder, which resulted in the formation of HF, trifluorobenzene, alkanes, and gaseous single molecule CH₂CF₂. Therefore, this work potentially provides an alternative approach for the efficient separation of Al foil in M-LIBs, thereby simplifying the process and achieving lower cost, reduced loss of valuable metals, and higher recovery efficiency.

A novel pulsated pneumatic separation with variable-diameter structure and its application in the recycling spent lithium-ion batteries

In recycling of the spent lithium iron phosphorus (LiFePO₄) batteries, the mechanical pretreatment is critical for relieving the pressure of the subsequent recycling process and reducing the cost of whole recycling process. In order to achieve the separation and concentration of the cathode materials, anode materials, copper and aluminum foils from spent LiFePO₄ batteries, a novel pneumatic separation combined with froth flotation is designed in this research. A pulsated pneumatic separation with variable-diameter structure separator is used, through which 92.08% of copper and 96.68% of aluminum were recovered. In the pneumatic separation the movement of the copper and aluminum flakes can be described by an improved equivalent diameter method, based on the force analysis of the flaky particles. The froth flotation is utilized to recover the cathode materials and anode materials with the recovery of 92.86% and 83.21%, respectively. A mass balance and a technological route of the recycling process are provided finally. The present work provides a green and high-efficiency recycling process in which copper, aluminum, anode and cathode materials in lithium-ion batteries can be recovered respectively only by physical methods.

Recycling of electrode materials from spent lithium-ion power batteries via thermal and mechanical treatments

This study developed a physical separation process that recovers active cathode materials from current collectors in spent lithium-ion power batteries (LIBs). The physical separation process, implemented via thermal and mechanical treatments, was examined based on cohesive zone models (CZMs) and verified by physical separation experiments. The most efficient condition was determined by optimising the key parameters (temperature and time) of selective heating. Among several mechanical separation methods, high-speed shearing best separates positive electrode materials into active cathode materials (LiFePO₄) and current collectors (Al fragments). The separation effect was verified by computing the dissociation rate and microscopic observation of the separated materials. The feasibility and efficiency of the above process were assessed in a work-of-force analysis, flow field simulation, high-speed crushing experiment and material property analysis. The above analyses realised a feasible, efficient and environmentally friendly separation route without changing the chemical structure and properties of the electrode materials. Under non-high (energy-conserving) temperature conditions, the LiFePO₄ dissociation rate stabilises at 80-85%. Under high-speed crushing, the LiFePO₄ dissociation rate reaches 85% at 32,000-r/min crushing and a maximum shearing velocity of the blade edge v ≈ 500 m/s. This approach can effectively recycle electrode materials, gain valuable resources and can be used to recycle and utilise spent LIBs, thus addressing two grave issues - environmental pollution and resource wastage to achieve the sustainable development of LIBs and electric vehicle industry.

Recent advances in pretreating technology for recycling valuable metals from spent lithium-ion batteries

In recent years, the amount of spent lithium-ion batteries (LIBs) increase sharply due to the promotion of new energy vehicles and the limited service life. Recycling of spent LIBs has attracted much attention because of the serious environmental pollution and high economic value. Although some established techniques have been presented in spent LIBs recycling process, but most of them focus on cathode material recycling due to its high economic value. Therefore, preparation of high purity cathode material by a proper pretreating technology is an important procedure. In this paper, the technologies used in the pretreating process of spent LIBs are summarized systematically from three main points of discharging procedure, liberation, and separation. The collaborative application of multi-technologies is the key to realize efficient pretreating process, which can lay the foundation for the subsequent metallurgical process. In addition, an alternative pretreating flowchart of spent LIBs is proposed based on the multi-process collaboration. Pretreating procedures in this process are mainly based on the physical property difference, and they include "Discharging-Shredding-Crushing-Sieving-Separation".

Pneumatic separation for crushed spent lithium-ion batteries

Pneumatic separation was used to separate the valuable current collectors and harmful separators in spent lithium-ion batteries (LIBs) to avoid the plastic pollution caused by the separators in this study. Theoretical calculations for suspension velocities of the current collectors and separators indicate that they could be separated under special conditions. Furthermore, a special Z-shaped pneumatic separator was used to separate the current collectors and separators for the first time. Experiments for manually cut samples indicate that the efficiency of pneumatic separation is approximately 100% with the sizes and airflow velocities in the range of 3-4 cm and 6.96-7.8 m/s, respectively. Furthermore, industrial experiments of pneumatic separation indicate that the recoveries of the current collectors and separators are approximately 99.23% and 98.64%, respectively. Computer simulations of the separation process indicate that the turbulence and the changes in high-speed zones in the pneumatic separator benefit the separation of current collectors and separators. In conclusion, pneumatic separation is a promising technology to separate crushed current collectors and separators.

A Combined Pyro- and Hydrometallurgical Approach to Recycle Pyrolyzed Lithium-Ion Battery Black Mass Part 2: Lithium Recovery from Li Enriched Slag—Thermodynamic Study, Kinetic Study, and Dry Digestion

Due to the increasing demand for battery raw materials, such as cobalt, nickel, manganese, and lithium, the extraction of these metals, not only from primary, but also from secondary sources, is becoming increasingly important. Spent lithium-ion batteries (LIBs) represent a potential source of raw materials. One possible approach for an optimized recovery of valuable metals from spent LIBs is a combined pyro- and hydrometallurgical process. The generation of mixed cobalt, nickel, and copper alloy and lithium slag as intermediate products in an electric arc furnace is investigated in part 1. Hydrometallurgical recovery of lithium from the Li slag is investigated in part 2 of this article. Kinetic study has shown that the leaching of slag in H2SO4 takes place according to the 3-dimensional diffusion model and the activation energy is 22–24 kJ/mol. Leaching of the silicon from slag is causing formation of gels, which complicates filtration and further recovery of lithium from solutions. The thermodynamic study presented in the work describes the reasons for the formation of gels and the possibilities of their prevention by SiO2 precipitation. Based on these findings, the Li slag was treated by the dry digestion (DD) method followed by dissolution in water. The silicon leaching efficiency was significantly reduced from 50% in the direct leaching experiment to 5% in the DD experiment followed by dissolution, while the high leaching efficiency of lithium was maintained. The study takes into account the preparation of solutions for the future trouble-free acquisition of marketable products from solutions.

A Combined Pyro- and Hydrometallurgical Approach to Recycle Pyrolyzed Lithium-Ion Battery Black Mass Part 1: Production of Lithium Concentrates in an Electric Arc Furnace

Due to the increasing demand for battery raw materials such as cobalt, nickel, manganese, and lithium, the extraction of these metals not only from primary, but also from secondary sources like spent lithium-ion batteries (LIBs) is becoming increasingly important. One possible approach for an optimized recovery of valuable metals from spent LIBs is a combined pyro- and hydrometallurgical process. According to the pyrometallurgical process route, in this paper, a suitable slag design for the generation of slag enriched by lithium and mixed cobalt, nickel, and copper alloy as intermediate products in a laboratory electric arc furnace was investigated. Smelting experiments were carried out using pyrolyzed pelletized black mass, copper(II) oxide, and different quartz additions as a flux to investigate the influence on lithium-slagging. With the proposed smelting operation, lithium could be enriched with a maximum yield of 82.4% in the slag, whereas the yield for cobalt, nickel, and copper in the metal alloy was 81.6%, 93.3%, and 90.7% respectively. The slag obtained from the melting process is investigated by chemical and mineralogical characterization techniques. Hydrometallurgical treatment to recover lithium is carried out with the slag and presented in part 2.

Efficient process for recovery of waste LiMn2O4 cathode material: Low-temperature (NH4)2SO4 calcination mechanisms and water-leaching characteristics

An efficient process for recycling waste LiMn₂O₄ cathode material is proposed in this research. This report constitutes low-temperature (NH₄)₂SO₄ calcination mechanisms and water-leaching characteristics of the calcined samples. A calcination temperature range of 420.65-634.12 °C is determined by analysis of the TG-DSC curve under the conditions of heating from 25 to 1000 °C, with a molar ratio of n(2Li + Mn):n(NH₄)₂SO₄ = 1:1 in air atmosphere. The sample calcined at 600 °C for 45 min when the excess coefficient of the (NH₄)₂SO₄ was 1.1 exhibits optimal water-leaching efficiencies of the Li and Mn elements, which are approximately 100% and 96.73%, respectively. The macro-reaction mechanism of the waste LiMn₂O₄ cathode material calcined with (NH₄)₂SO₄ is determined as the liquid-solid reaction by analysing the apparent morphologies of the calcined samples and their water-leaching residues under different calcination conditions. Moreover, the micro-reaction mechanism is investigated by analysing the phases of the calcined samples and their water-leaching residues under different calcination conditions. The free high-energy H⁺ released by the decomposition of the NH₄⁺ generated by the molten (NH₄)₂SO₄ play a key role in the entire calcination process. The spinel structure of the LiMn₂O₄ is broken and Li⁺ is released owing to the H⁺ bombarding the MnO bonds. Finally, the LiMn₂O₄ is converted into soluble sulphate salts, such as Li₂Mn₂(SO₄)₃ and MnSO₄.

Progress and Status of Hydrometallurgical and Direct Recycling of Li-Ion Batteries and Beyond

An exponential market growth of Li-ion batteries (LIBs) has been observed in the past 20 years; approximately 670,000 tons of LIBs have been sold in 2017 alone. This trend will continue owing to the growing interest of consumers for electric vehicles, recent engagement of car manufacturers to produce them, recent developments in energy storage facilities, and commitment of governments for the electrification of transportation. Although some limited recycling processes were developed earlier after the commercialization of LIBs, these are inadequate in the context of sustainable development. Therefore, significant efforts have been made to replace the commonly employed pyrometallurgical recycling method with a less detrimental approach, such as hydrometallurgical, in particular sulfate-based leaching, or direct recycling. Sulfate-based leaching is the only large-scale hydrometallurgical method currently used for recycling LIBs and serves as baseline for several pilot or demonstration projects currently under development. Conversely, most project and processes focus only on the recovery of Ni, Co, Mn, and less Li, and are wasting the iron phosphate originating from lithium iron phosphate (LFP) batteries. Although this battery type does not dominate the LIB market, its presence in the waste stream of LIBs causes some technical concerns that affect the profitability of current recycling processes. This review explores the current processes and alternative solutions to pyrometallurgy, including novel selective leaching processes or direct recycling approaches.

Regeneration and characterization of LiNi0.8Co0.15Al0.05O2 cathode material from spent power lithium-ion batteries

The use and scrap of lithium ion batteries, especially power lithium ion batteries in China, are increasing every year. Regeneration of spent battery materials is not only important for environmental protection and resource saving, but also for the production of high value-added materials. In this research, spent power lithium-ion battery cathode material LiNi_1-xCo_xO₂ was acid-leached and a polymetallic leaching solution containing Li, Ni, Co, Al and Cu was obtained. Cu was extracted from the leachate by using CP-150 (2-hydroxy-5-nonyl salicylaldehyde oxime). The optimal conditions were found to be organic: aqueous phase ratio (O/A) = 2:1, extraction agent concentration of 30%, and pH = 3. The precursor was prepared by coprecipitation of the leachate after Cu removal. Then, cathode material of lithium nickel cobalt aluminate LiNi_0.8Co_0.15Al_0.05O₂ was synthesized under the optimal conditions of n (precursor): n (lithium carbonate) = 1:1.1, calcination temperature of 800 °C for 15 h. The regenerated LiNi_0.8Co_0.15Al_0.05O₂ product prepared under the optimized conditions was in a pure phase with a layered structure and a smooth surface morphology. The first charge specific capacity was 248.7 mAh/g, and the discharge specific capacity was 162 mAh/g. The interfacial impedance was 119 Ω. The 50th-cycle discharge specific capacity was 149.1 mAh/g, and the capacity retention rate was high as 92%. Therefore, the regenerated cathode material exhibited good performance.