Recycling and upcycling of lithium-ion batteries through refinement and regeneration integrated materials engineering (PRIME)

Abstract

A process for directly recycling Li-ion battery cathode materials involves hydrothermally treating cathode black mass (CBM) in an alkaline solution to decompose polyvinylidene fluoride (PVDF) and remove electrolyte salts; rinsing the treated CBM in deionized water to remove excess alkaline solution, conductive carbon, degraded PVDF, and impurities; and annealing the washed material to restore the crystalline structure and remove residual carbon.

Description

[Technical Field]

[0001] Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 430,301, filed December 5, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to the recycling, recovery, and reclamation of electrode scrap, cell scrap, and materials from spent lithium ion batteries. [Background technology]

[0003] In recent decades, lithium-ion batteries (LIBs) have proliferated in consumer electronics applications, raising concerns about handling the resulting large volume of end-of-life (EoL) batteries to avoid adverse environmental impacts. Demand for LIBs in electric vehicles is growing even more rapidly, which is also straining the supply chain of critical materials. Shortages of these critical materials, especially transition metals like Ni and Co, could become a bottleneck in expanding the global transition to battery-powered vehicles in the near future. This rapid transformation creates opportunities to promote the "waste-to-wealth" aspect of battery recycling, along with environmental considerations, by establishing regional secondary supply chains for these materials. Direct recycling is one of the most promising solutions for obtaining maximum value from EoL batteries. This is because it allows for the direct revival of cathode active materials (CAMs) while preserving the targeted value products, while also enabling low energy consumption and net greenhouse gas (GHG) emission reductions. Many efforts have been made to scale up and simplify this technology to make it comparable to already industrially established hydrometallurgical and pyrometallurgical techniques. Direct recycling faces several major technical challenges, including rigorous pretreatment to remove impurities such as binders, conductive carbon, aluminum flakes, and electrolyte salts, as well as the need to regenerate a highly pure crystalline structure to meet industrial standards, which hinder its industrial application.

[0004] Direct recycling of cathode materials has been demonstrated at the laboratory scale, where small amounts of cathodes (a few grams) are processed. Various pretreatment methods are commonly used for purification. Cathode materials obtained from end-of-life batteries typically contain various impurities, including electrolyte salts (typically LiPF), conductive carbons (typically SuperP65 / P45), aluminum flakes, and binders (typically polyvinylidene fluoride (PVDF)), which are sometimes referred to as "cathode black mass" (CBM). The impurity removal process is often referred to as "purification." While heating and solvent washing have both proven effective for impurity removal, they also have drawbacks. During the heating process, PVDF, conductive carbon, and LiPF6 introduce fluorine and carbon into the reaction, compromising the quality of the resulting cathode material. For example, combustion of surface carbon creates a CO2 environment, which reacts with active surface oxygen anions, ultimately leading to the formation of Li2CO3 and irreversible lithium loss in the bulk. PVDF is known to be a low-temperature fluorination reagent for metal oxides and should therefore be avoided. Fluorine compounds (PVDF and LiPF6) generate HF during heating, which acts as a dopant within the cathode material, substituting oxygen to form MF2 (M = transition metal), or forms LiF on the surface, resulting in irreversible Li loss. Li loss is to be avoided, as used NMC-based materials, already Li-deficient, become even more vulnerable to oxygen loss. This promotes the formation of rock salt phases, which cause high impedance at the cell level. LiF is also quite insoluble in water and its evaporation temperature is very high. Once formed, it is very difficult to remove from the cathode surface and has low ionic conductivity (10 -9 S / cm), which increases the impedance.

[0005] Solvent washing, an alternative impurity removal process, is effective in removing various impurities. Electrodes can be immersed in dimethyl carbonate or other organic solvents to remove residual electrolyte salts. Conductive carbon and PVDF can be removed en bloc by dissolving the PVDF in toxic organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAC), which releases the conductive carbon and active material into the solvent. While solvent treatment provides high separation yields, large-scale use of organic solvents poses significant environmental concerns and is subject to strict government regulations, making it difficult to scale up. Other green solvents, such as triethyl phosphate and cyrene, have also been proposed, but excess solvent can introduce additional residues onto the cathode surface, ultimately requiring removal. Furthermore, mechanical methods are commonly used in the recycling industry to separate CBM from aluminum foil, which can leave traces of aluminum flakes within the CBM. Aluminum flakes have also been shown to act as dopants in CAMs, improving electrochemical performance. However, controlling the upper limit of dopant content (0.4 wt%) would be difficult on a large scale.

[0006] Therefore, there remains a need for sustainable and environmentally sound battery recycling processes that can be scaled up to industrial levels, which is required to support the large-scale global transition to batteries as a mainstream energy source. Summary of the Invention

[0007] The present method addresses the rapidly growing problem of battery waste accumulation by integrating the CBM purification and relithiation processes, providing a more environmentally friendly, cost-effective, and scalable recycling technology. By purifying CBM from unwanted binders, residual electrolyte, aluminum flakes, and conductive carbon, the resulting purified product can be integrated with existing relithiation and sintering steps. The present process successfully regenerated a 100g batch of CBM (NCM111) to virgin condition without the need for organic solvents. By using steps derived and designed from existing hydrothermal and sintering techniques used in cathode synthesis, the present process is safe and easily scalable to industrial levels. This process can be extended to NCM622, NCM811 (or higher nickel contents up to 99% by weight), NCA, NCMA, and mixed CBMs in various states, while simultaneously maximizing process efficiency by reusing chemical solutions. The present method solves one of the key challenges in scaling up direct recycling in an environmentally friendly and economical manner, making it suitable for future industrial applications.

[0008] The methodology of the present invention, called "Purification and Regenerating Integrated Materials Engineering" or "PRIME," is used to develop materials such as LiCoO2 (LCO), LiNi x Co y Mn z O2(x+y+z=1)(NCM or NMC), LiNi x Co y Al z O2(NCA), LiMn2O4(LMO), LiFePO4(LFP), LiMn x Fe yThe present invention provides a complete recycling capability, including the recovery and reclamation of materials from electrode scrap, cell scrap, and used batteries containing cathode active materials (CAMs) with different chemistries, such as PO4 (LMFP). Despite the fact that these various cathode materials may contain different amounts of dopants and may have surface coating layers, the recycled CAMs produced by the present method can be used to fabricate new batteries with electrochemical properties equivalent to those of the originals.

[0009] Direct recycling methods often involve multiple complex steps, increasing both the sophistication and cost of processing spent batteries, making the process less economically viable and more difficult to scale up. Compared to other direct recycling methods, the approach of the present invention dramatically reduces the number of required physical and chemical processing steps and provides an integrated process for recycling positive electrode materials, combining purification and regeneration into a single step.

[0010] In one aspect, a method for directly recycling Li-ion battery cathode materials includes hydrothermally treating cathode black mass (CBM) in a lithium ion-containing solution to decompose polyvinylidene fluoride (PVDF) and remove electrolyte salt; washing the treated CBM in a washing solution to remove excess lithium ion-containing solution, conductive carbon, degraded PVDF, and impurities; and annealing the washed material to restore the crystalline structure and remove residual carbon, recovering cathode active material (CAM), which can be used to fabricate new batteries. In some embodiments, the lithium ion-containing solution can be one or a combination of LiOH, NaOH, KOH, an alkali metal hydroxide solution, an aqueous lithium salt, and an electrolyte salt. The lithium ion-containing solution can be an alkali metal hydroxide solution containing one or a combination of Li2CO3, Li acetate, and Li2SO4. The lithium ion-containing solution may include an electrolyte salt including one or a combination of LiPF, LiBF, LiClO, lithium bis(oxalato)borate (CBLiO), and lithium difluoro(oxalato)borate (CBFLiO). The lithium ion-containing solution may have a lithium concentration at 25°C ranging from 0.1 to saturation. In some embodiments, the lithium ion-containing solution may be 0.1 to 5.34 M LiOH. The hydrothermal treating step includes subjecting the CBM in the lithium ion-containing solution to a temperature ranging from 50 to 300°C for a period ranging from 1 to 10 hours. The washing step may include mechanically agitating the CBM in the washing solution. In some embodiments, the lithium ion-containing solution may be a solution recovered and reused from one or more prior hydrothermal treatments. The CBM may be one or more of NCM111, NCM622, NCM811, NCA, NCMA, and mixed CBM.

[0011] In another aspect, a method for directly recycling Li-ion battery cathode materials includes hydrothermally treating cathode black mass (CBM) in a treatment solution containing an alkaline solution to decompose polyvinylidene fluoride (PVDF) and remove electrolyte salt and lithium ion solution to relithiate the CBM; washing the treated CBM in a washing solution to remove excess treatment solution, conductive carbon, degraded PVDF, and impurities; and annealing the washed material to restore the crystalline structure and remove residual carbon to recover cathode active material (CAM), which can be used to fabricate new batteries. In some embodiments, the treatment solution may be one or a combination of LiOH, NaOH, KOH, an alkali metal hydroxide solution, a water-soluble lithium salt, and an electrolyte salt. The treatment solution may be an alkali metal hydroxide solution containing one or a combination of Li2CO3, Li acetate, and Li2SO4. The treatment solution may include an electrolyte salt including one or a combination of LiPF, LiBF, LiClO, lithium bis(oxalato)borate (CBLiO), and lithium difluoro(oxalato)borate (CBFLiO). The treatment solution may have a lithium concentration ranging from 0.1 to saturation at 25°C. In some embodiments, the lithium ion-containing solution may be 0.1 to 5.34 M LiOH. The hydrothermal treating step includes subjecting the CBM in the treatment solution to a temperature ranging from 50 to 300°C for a period ranging from 1 to 10 hours. The washing step may include mechanically agitating the CBM in the washing solution. In some embodiments, the treatment solution may be a solution recovered and reused from one or more prior hydrothermal treatments. The CBM may be one or more of NCM111, NCM622, NCM811, NCA, NCMA, and mixed CBM.

[0012] Direct recycling of active materials from spent batteries or manufacturing scrap is highly desirable for battery recycling, where the cathode mixture is maintained intact. Several challenges, including impurity removal, batch uniformity, and scalability (ease of large-scale production), hinder the development and scale-up of direct recycling to be economically viable. Regarding impurity removal, the binder in the cathode black mass (CBM) is one of the biggest challenges. Polyvinylidene fluoride (PVDF) is the most commonly used binder in cathode manufacturing, essentially holding the active cathode material and conductive carbon together. Conventional purification steps for direct recycling involve dissolution or decomposition to remove PVDF, which is uneconomical or removes little of the fluorine impurity (LiF). Because different single-cell cathode materials typically have different SOC states after long-term cycling, batch uniformity is another challenge. The amount of lithium replenishment must be properly controlled. Finally, direct recycling still faces the issue of scalability. PRIME uses an innovative approach that bridges the gap between lab-scale direct recycling and current industrial recycling methods. PRIME is compatible with both used batteries and manufacturing scrap. PRIME removes impurities, dissolving some components and decomposing others. PRIME relithiates cathode materials with different lithium contents to their original lithium ratios. Most importantly, PRIME is scalable to ton-scale cathode recovery volumes. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram of one embodiment of the process of the present invention showing scalable regeneration of CAM through multi-stage integrated direct recycling. [Figure 2A] FIG. 1 is a schematic diagram of the mechanism of binder decomposition and active substance release. [Figure 2B] FTIR spectra plot showing chemical degradation of PVDF. [Figure 2C]1 is a plot of thermogravimetric analysis (TGA) results comparing CBM (NCM111) and cathode material recovered using the process of the present invention to estimate binder and carbon content. [Figure 3A] This is an SEM image of pCAM. [Figure 3B] This is an SEM image of CBM. [Figure 3C] This is an SEM image of rCAM. [Figure 3D] This is a wide-angle SEM image of rCAM. [Figure 3E] Comparison of XRD with pCAM, CBM, and rCAM, showing bulk relithiation of recovered materials. [Figure 3F] Fluorine XPS spectra of pCAM, CBM, and rCAM are compared. [Figure 3G] DTA and DSC data for CBM and rCAM are provided. [Figure 3H] This is a comparison of XPS data for oxygen. [Figure 3I] This is a comparison of XPS data for carbon. [Figure 4A] 1 is a plot of elemental analysis comparing the carbon content of pCAM and rCAM. [Figure 4B] The results of EDS analysis for aluminum tracing are provided. [Figure 5A] Electrochemical performance of the regenerated cathode material is shown, showing the voltage profile during the first cycle. [Figure 5B] 1 shows the electrochemical performance of the regenerated cathode material, plotting the cycling stability in half cells. [Figure 5C] The electrochemical performance of the regenerated cathode material is shown, demonstrating the extended cycling stability of the regenerated cathode as demonstrated in half cells. [Figure 5D] 1 shows the electrochemical performance of the regenerated cathode material, plotting the rate performance of the regenerated cathode compared to a virgin one. [Figure 5E]1 shows the electrochemical performance of the regenerated cathode material, plotting the cycling stability in a full cell. [Figure 6A] 1 provides a schematic diagram of the reuse of the LiOH auxiliary solution in the hydrothermal step. [Figure 6B] 10 shows the voltage profile of NCM111 (rCAM) recovered in recycled LiOH auxiliary solution during the first cycle. [Figure 6C] Comparison of (003) XRD peak data for different samples. [Figure 6D] 1 shows the first cycle voltage profile for recovered NCM622 (rCAM 622) using the process of the present invention. [Figure 7A] Initial cycles of unused NCM811 (pCAM NCM811) and recovered NCM811 (rCAM NCM811) are shown. [Figure 7B] Provides results for NCA materials. [Figure 7C] Provide results for NCMA materials. DETAILED DESCRIPTION OF THE INVENTION

[0014] The cathode recycling process of the present invention, shown diagrammatically in Figure 1, involves three major steps: (Step 102) hydrothermal ("HT") relithiation, which involves decomposition of PVDF and removal of electrolyte salts; (Step 104) washing to remove excess alkaline solution, conductive carbon, degraded PVDF, and other impurities; and (Step 106) annealing to restore the crystalline structure and remove residual carbon. By comparison, a typical lab-scale direct recycling process involves multiple purification steps (sometimes using sonication to expedite) using toxic organic solvents such as N-methyl-2-pyrrolidone (NMP) or dimethyl carbonate (DMC) to dissolve the PVDF binder and release the cathode material, as well as a centrifugation step to separate the conductive carbon from the cathode active material (CAM), making the overall process time-consuming. Positive electrodes typically contain PVDF and carbon black as key inert materials, but such materials are generally undesirable in recycling / upcycling processes.

[0015] The mechanism of the release of cathode materials occurring in steps 102 and 104 is shown diagrammatically in Figure 2A. To clarify the mechanism of PVDF degradation during the HT process, a pure PVDF membrane was prepared by coating PVDF on a glass plate, drying it, and then peeling it off. This transparent membrane was then subjected to the HT reaction in an alkaline solution (e.g., 0.1–4 M LiOH solution) at 220 °C for 4 h under the same conditions commonly used for cathode HT relithiation. After the reaction, the transparent PVDF membrane decomposed into a black, brittle membrane. The decomposed membrane product crumbled into powder during washing and completely lost its mechanical integrity. Referring to Figure 2B, Fourier transform infrared (FTIR) spectroscopy of the dried decomposed membrane revealed the absence of the characteristic fluorocarbon peaks (1000–1250 cm) observed in the original PVDF membrane. -1 ) disappears, while the broad peak of the double bond carbon appears at 1600 cm -1This result is consistent with previous studies suggesting that PVDF membranes undergo defluorination in alkaline environments. This result confirmed two important points: first, PVDF can be defluorinated / decomposed under the same HT conditions used for the relithiation of cathodes; and second, the decomposition products lose their mechanical integrity so much that they are easily broken down by gentle agitation during washing.

[0016] Variations in HT treatments are known in the art to be effective for relithiation, including different combinations of temperature, time, pressure, and atmosphere. For example, PCT Publication WO 2023 / 164073, incorporated herein by reference, discloses a low-temperature HT process for relithiation. Therefore, the specific temperatures and times cited herein are provided as examples of HT treatments, with the primary objective being to decompose the PVDF and substantially remove other impurities using alkaline solvents used in the HT process and subsequent washes. Furthermore, the HT treatment is not limited to LiOH; a variety of different treatment solutions may be used to perform the relithiation and electrolyte salt removal steps. The treatment solution may include LiOH, NaOH, KOH, alkali metal hydroxide solutions (e.g., one or a combination of Li2CO3, Li acetate, Li2SO4), water-soluble lithium salts, and electrolyte salts (e.g., one or a combination of LiPF6, LiBF4, LiClO4, lithium bis(oxalato)borate (CBLiO8), and lithium difluoro(oxalato)borate (CBF2LiO4)).

[0017] In this field, cathode regeneration based on hydrothermal relithiation followed by a short post-annealing step has been widely reported. Several researchers have regenerated used LiCoO2 (LCO), LiNi 0.33 Co 0.33 Mn 0.33 O2(NCM111), LiNi0.5Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co0.2 Mn 0.2 It has been confirmed that the morphology, composition, and crystalline structure of the cathodes of O2 (NCM622) and LiFePO4 (LFP) can be effectively reconstructed, resulting in electrochemical performance equivalent to that of virgin materials. For example, E. Gratz, et al., "A closed loop process for recycling spent lithium ion batteries," Journal of Power Sources 262 (2014) 255-262, Y. Shi, et al., "Ambient-Pressure Relithiation of Degraded Lithium x Ni 0.5 Co 0.2 Mn 0.3See “O2(0 < x < 1) via Eutectic Solutions for Direct Regeneration of Lithium Ion Battery Cathodes”, Adv. Energy Mater. 9 (2019) 1900454, S. Sloop, et al., “A direct recycling case study from a lithium-ion battery recall”, Sustainable Materials and Technologies 25 (2020) e00152, L. Brueckner, et al., “Industrial Recycling of Lithium-Ion Batteries - A Critical Review of Metallurgical Process Routes”, Metals 10 (2020) 1107, Y. Shi, et al., “Effective regeneration of LiCoO2 from spent lithium-ion batteries: A direct approach towards high-performance active particles”, Green Chem. 20 (2018) 851 - 862, and P. Xu, et al., “Efficient Direct Recycling of Lithium-Ion Battery Cathodes by Targeted Healing”, Joule 4 (2020) 2609 - 2626. The described methods are characterized by simple operation and low energy consumption, and utilize a hydrothermal relithiation process to restore the cathode composition without concern for variations in Li loss in different degraded LIB feedstocks. These processes also utilize a short sintering process to restore the microstructure of the cathode with the desired stoichiometric composition and crystallinity.

[0018] HT relithiation in an alkaline environment has been shown to be an essential step in the regeneration of cathode materials. The efficiency of the relithiation conditions can be further enhanced in this respect by using hydroxides in solution to react with the PVDF binder. The resulting CBM (NCM111) contained 3 wt. % PVDF (as suggested by thermogravimetric analysis (TGA) shown in Figure 2C) and was directly subjected to the same HT relithiation conditions for further processing. A post-hydrothermal wash with deionized water (DI) (step 104) was performed to remove decomposed PVDF, alkali, and carbon impurities. In some embodiments, other wash solutions, such as low-concentration alkaline solutions, may be used, and weak inorganic / organic acid solutions may be used instead of or in addition to DI water.

[0019] The majority of carbon impurities are removed after the cleaning process, which is advantageous for the subsequent annealing process. For direct comparison, Figures 3A–3C are backscattered mode scanning electron microscopy (SEM) images of virgin CAM (pCAM), CBM, and recovered CAM (rCAM), respectively. The CBM shown in Figure 3B clearly shows that binder and carbon cover most of the positive electrode surface. This observation is consistent with the TGA data plotted in Figure 2C, which indicates that approximately 9 wt% of binder and conductive carbon are present in total. The corresponding differential thermal analysis (DTA) and differential scanning calorimetry (DSC) data are shown in Figure 3G. The rCAM seen in Figure 3C exhibits a very clean surface, suggesting a successful purification process. Meanwhile, the secondary spherical shape is well preserved, which may help maintain packing density after electrode application.

[0020] To verify the effectiveness of the relithiation process, both X-ray diffraction patterns (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) were performed. Figure 3E shows the XRD patterns of pCAM, CBM, and rCAM. All samples were

number

[0021] X-ray photoelectron spectroscopy (XPS) was performed to track the surface fluorine. As shown in Figure 3F, a clear signal from F in the binder energy range of 680-690 eV was observed in the CBM, indicating the presence of both C-F bonds and metal-F bonds in the CBM, as well as the presence of both the binder and the cathode electrolyte interfacial layer (CEI). In the rCAM, as in the pCAM, no fluorine signal was detected, suggesting that elemental fluorine had been successfully removed from the CBM. Figures 3H and 3I show XPS data for oxygen and carbon, respectively, confirming the removal of the cathode electrolyte interfacial layer from the recovered cathode. In Figure 3H, the O1s from the treated CBM had a clear TM-O peak near 528 eV and no peak near 533 eV, further indicating the removal of the CEI. For the C1s, the C-F bond disappeared near 290 eV in the rCAM sample, which also confirmed the removal of PVDF.

[0022] The leaching of transition metals (TMs) is a possible cause of the degradation of LIBs. To identify the CBMs before and after the recovery process, ICP-MS was performed to verify the ratio of Ni / Co / Mn, and the relevant results are shown in Table 1. [Table 1] As can be seen in the table, the TM ratios are the same for both virgin and reclaimed samples, remaining constant as in virgin material. Therefore, the reclaimed process of the present invention maintains TM stoichiometry and avoids any leaching. To further evaluate the residual carbon in the samples, combustion elemental analysis was performed to quantify the carbon from pCAM and rCAM. The results are shown in Figure 4A. The weight ratio of residual carbon in rCAM was comparable to that of pCAM, further confirming the efficiency of carbon removal. EDS was also performed to track aluminum impurities. The results are shown in Figure 4B. The aluminum signal present in CBM disappeared in rCAM, indicating efficient removal of aluminum impurities.

[0023] After confirming the impurity removal and quality of rCAM, its electrochemical performance was evaluated using half-cell and full-cell configurations. The relevant results are shown in Figures 5A–5E. Figure 5A shows the first-cycle voltage profiles at a C / 10 rate, showing a discharge capacity of 155 mAh / g for rCAM and 154 mAh / g for pCAM, providing a comparison of the two. The initial coulombic efficiency (ICE%) of rCAM (89%) is very similar to that of pCAM (88%), and the curves are virtually indistinguishable. Half-cell cycling at a C / 3 rate showed 98% discharge capacity retention after 100 cycles for rCAM, which virtually overlaps with the results for pCAM, as shown in Figure 5B. Longer half-cell cycling for rCAM is shown in Figure 5C, with a discharge capacity retention of 90% for over 400 cycles. This result is indistinguishable from that of pCAM, further highlighting the remarkable quality of rCAM. Rate performance was evaluated using a half-cell configuration, and the data are shown in Figure 5D, showing complete overlap of the curves for both samples. The close agreement in performance between pCAM and rCAM confirmed the validity of the direct recycling process. Finally, full cells were assembled using graphite as the anode. Figure 5E shows a similar trend for pCAM and rCAM, with capacity retention at 1C rate of over 94% after 100 cycles. Therefore, it is clear that rCAM exhibits comparable electrochemical performance to pCAM in all respects.

[0024] To demonstrate the sustainability feature of the present approach, the HT auxiliary solution was collected as the supernatant after a single process to regenerate a new CBM batch.

[0025] Referring to the process schematic shown in Figure 6A, the auxiliary alkaline solution, 4 M LiOH, used in the hydrothermal treatment of a 100 g batch of CBM (NCM111) was saved. The same solution was used for the hydrothermal treatment of another batch of CBM (referred to as "batch 2"). The post-HT CBM was washed with copious amounts of DI water to remove surface alkali, decomposed PVDF, and carbonaceous impurities. The second batch was dried overnight in a convection oven at 80 °C, then mixed with 5 mol% Li2CO3 and annealed in a box furnace at 850 °C for 4 h (heating rate: 5 °C per minute, natural cooling after annealing). The resulting product was designated "rCAM-G2 (or rCAM produced in twice-used LiOH)." The same procedure using the same auxiliary solution yielded another product, "rCAM-G3 (or rCAM produced in three-used LiOH)." The resulting product was used for electrode coating.

[0026] The relithiated sample from the spent solution was further processed using the same steps. Figure 6B shows the voltage profile of the first cycle performed at a C / 10 rate in a half-cell configuration. Interestingly, the capacity obtained for this sample (155 mAh / g) was nearly identical to that of virgin material, as was the case for CBM regenerated with fresh solution. The same LiOH solution was reused multiple times, demonstrating robustness. The associated XRD analysis and electrochemical performance results indicate that regeneration of the material was achieved, with only a negligible impact of observed impurity accumulation on the quality of the final product. Corresponding energy efficiency comparisons between pCAM, rCAM, rCAM-G2, and rCAM-G3 also showed negligible differences between the samples.

[0027] In real-world use, CBMs obtained from EoL cells with various performance retention states have different Li deficiencies. To demonstrate the versatility of our process for processing such CBM mixtures, we mixed NCM111 CBMs from two different cells, i.e., CBM#1 and CBM#2, in a 1:1 ratio (mixed black mass, MBM) and evaluated them. To verify the different Li deficiencies, we compared the XRD patterns of CBM#1 and CBM#2 with those of rCAM. As seen in Figure 6C, the difference in the (003) peak shift indicated the difference in Li deficiency between CBM#1 and CBM#2. After our recovery process, the rCAM-MBM showed a fully recovered Li composition, and the 003 peak shifted to match that of virgin NCM111. Furthermore, to confirm the quality of the obtained product, we also analyzed its electrochemical performance, showing that the capacity was consistent with that of rCAM over several cycles.

[0028] A similar direct recycling process was also applied to NCM622 CBM (CBM622). CBM 622 obtained from the cycled cell was analyzed by ICP-MS, TGA, and XRD, yielding the black mass shown in Table 1. CBM 622 was found to be lithium-deficient by ICP-MS and XRD, and TGA suggested it contained 6.5 wt% PVDF and carbon impurities. CBM 622 was treated with the same process as NCM111 CBM, except for the annealing step, which was performed under pure oxygen flow rather than air flow. Ni-rich NCM cathodes are favored by nickel, which is the preferred Ni. 2+An oxygen atmosphere is an important factor for annealing Ni-rich NCM cathodes because of their tendency to form rock salt phases due to their oxidized state and oxygen deficiency. CBM622 washed in NMP was used as a control for this material. Figure 6D compares the first-cycle voltage profiles of a recovered NCM622 cathode (rCAM622) and a half-cell fabricated from the control CBM622 washed in NMP. The NCM622 CBM half-cell had an ICE of 79%, likely due to impurities, and a discharge capacity of only 119 mAh / g. ICP-MS and XRD confirmed the lithium deficiency and distorted bulk phase, as shown in Table 1. In contrast, the half-cell fabricated from rCAM622 exhibited an ICE of 82% and a discharge capacity of 176 mAh / g, which is in good agreement with commercial-grade NCM622. Long-term cycling data for the half-cell showed a capacity retention of 94% after 200 cycles, demonstrating the high quality of the regenerated cathode material. Figure 7A shows the initial cycle of virgin NCM811 (pCAM NCM811) and recovered NCM811 (rCAM NCM811), with nearly identical curves indicating successful regeneration. Figure 7B and Figure 7C provide similar results for NCA and NCMA materials, respectively.

[0029] From a technical perspective, our process bridges the gap between laboratory-scale direct recycling and industrial-scale recycling, taking into account both economic and ecological considerations. Using the Everbatt model developed by Argonne National Laboratory, we compared various recycling routes and determined the economic and ecological impacts of organic solvents on the direct recycling process. While many processes have been reported that use NMP (or similar toxic organics) as a solvent to remove PVDF, others use DMC. A comparison of older pyrometallurgical processes, currently pursued hydrometallurgical processes, current laboratory-scale direct recycling methods (using NMP and DMC), and our organic-free direct recycling method reveals several economic advantages. Avoiding the use of expensive NMP and DMC organics reduces processing material costs by approximately $5 per kg of cells. Not only does this reduce the initial material cost of these organic liquids, but it also reduces the general and plant overhead costs resulting from their use, including labor, supervision, administration, and maintenance, by approximately $2.16 per kg of cells. Direct recycling processes that rely on organic solvents on an industrial scale are likely to be even less profitable than current pyrotechnologies and hydrotechnologies. Organic solvent-dependent processes involve large amounts of toxic materials, increasing the risk of accidents and environmental damage at every stage, including handling, storage, disposal, and transportation, making them even more impractical for scaling recycling operations. Therefore, the effectiveness of the present approach, which circumvents these economic and environmental barriers, is not only practically suitable for scaling environmental protection, but also beneficial for business. [Example]

[0030] The following examples provide details of the procedures used during the processing and evaluation of the processes of the present invention.

[0031] Example 1 Collection of cathode black mass: End-of-life prismatic cells (20 Ah) were manually disassembled in a fume hood, and the long cathode strips were carefully separated and cut into approximately 5 x 5 inch pieces. After disassembly, the cathode strips were stored in a fume hood for 2 days and then placed in a vacuum oven at 80 °C overnight to dry. As starting material, these cathode strips were scraped with a blade to obtain 100 g of CBM for NCM111. Cathode strips for NCM622 were obtained from Argonne National Lab and scraped with a blade using a similar process to obtain black mass. Unused NCM111 (Toda Kogyo Corp., Japan) or pCAM and NCM622 or "pCAM622" (Targray, Montreal, CA) were used as controls.

[0032] Example 2 Regeneration of the cathode active material: 100 g of NMC111CBM was directly charged into a 500 mL autoclave reactor along with 300 mL of 4 M LiOH solution and heated at 220 °C for 4 hours (optimized conditions were taken from P. Xu, et al., ACS Sustain. Chem. Eng. 2021, 9, 4543, which is incorporated herein by reference). After hydrothermal heating, the supernatant was decanted and saved for later reuse. DI water was added to the precipitate, and mechanical stirring was performed at 500 rpm for 30 minutes. After stirring in DI water, the product was vacuum filtered and further washed with copious amounts of water. The product was recovered from the filter and dried overnight in a convection oven at 80 °C. The yield to this point was 91 wt% based on the CAM weight. The product was then ground with 5 mol% excess Li2CO3 and annealed in a box furnace for 4 hours at 5 °C / min to 850 °C, followed by natural cooling. NCM622 CBM batches were also processed using the same process up to the annealing step, which was performed in a tube furnace under oxygen flow.

[0033] Example 3 Mechanism Testing: A 5 wt% PVDF (KYNAR 2800) binder solution was prepared by stirring the components overnight in NMP as the solvent. This solution was then applied to a glass substrate using a doctor blade to form a thin PVDF film approximately 50 μm thick. After drying, the transparent film was easily peeled off using tweezers. A 50 mg portion of the PVDF film was cut out and placed in a 4 M LiOH solution and subjected to hydrothermal heating at 220 °C for 4 hours. (As previously mentioned, the HT parameters are variable.) After the HT treatment, the film turned black and crumbled into powder. The film was washed with DI water to remove the LiOH and subjected to FTIR spectroscopy using a Thermo Scientific Nicolet 6700 FTIR instrument equipped with a Smart iTR diamond ATR fixture. A portion of the film was also retained as a control for FTIR analysis.

[0034] Example 4 Characterization of the black mass and recycled material: Both CBMs were used for TGA, DTA, and DSC. They were heated to 1000 °C at 10 °C / min in air using an SDT650 setup. SEM images were obtained using an FEI Apreo SEM (Thermo Scientific) in backscattering mode. The voltage and current were set to 1 kV and 0.1 nA, respectively. Bulk crystal structure analysis of the powder samples was performed using a Rigaku Miniflex XRD setup. Stoichiometry and ratios were calculated using the iCAP RQ model of an ICP-MS (Thermo Scientific). XPS was performed on a Kratos Supra with an Al anode source at 15 kV under a vacuum of 10-8 Torr, with a step size of 1.0 eV for survey scans and 0.1 eV for high-resolution scans. The C 1s peak at 284.6 eV was used for calibration.

[0035] Example 5 Electrochemical Analysis: For comparison with the regenerated samples, virgin NCM111 was used as a control. Typically, the cathode powder was mixed with PVDF (KYNAR 2800) and carbon black (Super P65) in NMP (Sigma-Aldrich, anhydrous 99.5%) in a mass ratio of 8:1:1 to form a homogeneous slurry. The slurry was applied with a doctor blade and then dried overnight at 120 °C under vacuum. 12 mm cathode disks were cut, calendered, and used to assemble CR2032 coin cells with Li metal as the anode in an argon-environment glove box. The electrolyte used was a battery-grade lithium hexafluorophosphate (LiFP6) solution in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with a composition of EC / EMC = 30 / 70 (vol / vol) and 1.0 M LiPF6 (2nd generation, Gotion, USA). The mass loading was 4–5 mg / cm. 2 For the anode of the full cell, graphite (Superior Graphite) was substituted for the cathode powder following the same procedure of mixing PVDF and NMP in a mass ratio of 8:1:1. The graphite anode disk was cut to a size of 13 mm (active material loading of 4–5 mg / cm). 2 ), which were prelithiated by direct contact with Li metal for 10 minutes to compensate for future lithium loss during cycling. After resting the cells for 8 hours, they were subjected to four activation cycles at a rate of C / 10 (1C = 155mA / g) using a Neware battery cycler between the voltage window of 3 and 4.3V, followed by galvanostatic cycling at C / 3 for half cells and 1C for full cells with long-term cycling.

[0036] The inventive method described herein is highly effective for directly recycling cycled CAM from cathode black mass. It successfully removes all impurities, including PVDF binder, conductive carbon, electrolyte salt, and aluminum flakes. Hydrothermal and washing steps completely remove fluorine, aluminum, and most residual conductive carbon, while an annealing step helps restore the CAM phase and remove residual trace carbon. This process fully restores the electrochemical performance of cycled CAM and reproduces the performance metrics of pCAM. Direct recycling of active materials from spent batteries and manufacturing waste is essential for battery recycling. Previous challenges have hindered the development and scale-up of direct recycling.

[0037] The present PRIME process bridges the gap between laboratory-scale direct recycling and current industrial recycling methods. PRIME is compatible with both spent batteries and manufacturing scrap. PRIME removes impurities and relithiates cathode materials with different lithium contents, returning them to the same virgin lithium ratio. Importantly, PRIME is capable of scaling to ton-scale cathode recovery yields.

Claims

1. 1. A method for directly recycling a Li-ion battery cathode material, the method comprising: hydrothermally treating the cathode black mass (CBM) in a lithium ion-containing solution to decompose the polyvinylidene fluoride (PVDF) and remove the electrolyte salt; Washing the treated CBM in a washing solution to remove excess lithium ion-containing solution, conductive carbon, degraded PVDF, and impurities; and annealing the cleaned material to restore the crystalline structure and remove residual carbon, recovering the cathode active material (CAM), which can be used to fabricate new batteries. method.

2. 10. The method of claim 1, wherein the lithium ion-containing solution comprises one or a combination of LiOH, NaOH, KOH, an alkali metal hydroxide solution, a water-soluble lithium salt, and an electrolyte salt.

3. The lithium ion-containing solution is Li ２ CO ３ , Li acetate, Li ２ SO ４ 10. The method of claim 1, wherein the alkali metal hydroxide solution comprises one or a combination of:

4. The lithium ion-containing solution is LiPF ６ , LiBF ４ , LiClO ４ , lithium bis(oxalato)borate (C ４ BLiO ８ ), and lithium difluoro(oxalato)borate (C ２ BF ２ LiO ４ 10. The method of claim 1, wherein the electrolyte salt comprises one or a combination of:

5. 10. The method of claim 1, wherein the lithium ion-containing solution has a lithium concentration at 25° C. in the range of 0.1 to saturation.

6. 10. The method of claim 1, wherein the lithium ion-containing solution comprises 0.1 to 5.34 M LiOH.

7. 10. The method of claim 1, wherein hydrothermally treating comprises subjecting the CBM in the lithium ion-containing solution to a temperature in the range of 50 to 300° C. for a period in the range of 1 to 10 hours.

8. The method of claim 1 , wherein the washing comprises mechanically agitating the CBM in the washing solution.

9. 10. The method of claim 1, wherein the lithium ion-containing solution comprises a solution recovered and recycled from one or more prior hydrothermal treatments.

10. 2. The method of claim 1, wherein the CBM is one or more of NCM111, NCM622, NCM811, NCA, NCMA, and a mixed CBM.

11. 1. A method for directly recycling a Li-ion battery cathode material, the method comprising: hydrothermally treating the cathode black mass (CBM) in a treatment solution including an alkaline solution to decompose the polyvinylidene fluoride (PVDF) and remove the electrolyte salt and lithium ion solution to relithiate the CBM; washing the treated CBM in a washing solution to remove excess treatment solution, conductive carbon, degraded PVDF, and impurities; and annealing the cleaned material to restore the crystalline structure and remove residual carbon, restoring the cathode active material (CAM).

12. 12. The method of claim 11, wherein the treatment solution comprises one or a combination of LiOH, NaOH, KOH, an alkali metal hydroxide solution, a water-soluble lithium salt, and an electrolyte salt.

13. The treatment solution contains Li ２ CO ３ , Li acetate, Li ２ SO ４ 12. The method of claim 11, wherein the alkali metal hydroxide solution comprises one or a combination of:

14. The treatment solution is LiPF ６ , LiBF ４ , LiClO ４ , lithium bis(oxalato)borate (C ４ BLiO ８ ), and lithium difluoro(oxalato)borate (C ２ BF ２ LiO ４ 12. The method of claim 11 , wherein the electrolyte salt comprises one or a combination of:

15. 12. The method of claim 11, wherein the treatment solution has a lithium concentration in the range of 0.1 to saturation at 25°C.

16. The method of claim 11, wherein the treatment solution comprises 0.1 to 5.34 M LiOH.

17. 12. The method of claim 11, wherein hydrothermally treating comprises subjecting the CBM in the treatment solution to a temperature in the range of 50 to 300° C. for a period in the range of 1 to 10 hours.

18. The method of claim 11 , wherein the washing comprises mechanically agitating the CBM in the washing solution.

19. 12. The method of claim 11, wherein the treatment solution comprises recovered and recycled solution from one or more prior hydrothermal treatments.

20. 12. The method of claim 11, wherein the CBM is one or more of NCM111, NCM622, NCM811, NCA, NCMA, and a mixed CBM.

Images