Charge materials synthesized from recycled lithium-ion batteries

Abstract

Lithium-ion battery (LIB) recycling is considered an important component of industrial sustainability. A large amount of LIBs in portable electronics, electric vehicles and grid storage will eventually become waste, causing serious economic and environmental problems. Therefore, great efforts have been made to improve the hydrometallurgical recycling process, which is the most promising option for processing scrapped LIBs due to its wide applicability, low cost and high productivity. Despite these advantages, some additional elements (Al, Fe, C, F, etc.) are retained as impurities during the removal process and remain in the solution, which poses a challenge to obtaining high-quality cathode materials. The present method demonstrates improved electrochemical performance by adding potential impurities in the leaching solution.

Description

[0001] Related Applications

[0002] This patent application is related to U.S. Patent Application No. 15 / 358,862, filed on November 22, 2016, entitled “METHOD AND APPARATUS FOR RECYCLING LITHIUM-ION BATTERIES,” now U.S. Patent No. 10,522,884, which is incorporated herein by reference in its entirety. Background Art

[0003] Lithium-ion batteries (LIBs) are widely used in automobiles, personal electronics, and industrial applications. The waste stream of recycled batteries usually consists of indiscriminate mixing (crushing and shredding) of entire battery pieces, resulting in a blended mixture of cathode, anode, separator, and casing materials. The mainstream cathode materials used in LIBs (such as NCM) are composed of heavy metals such as nickel and cobalt, which are not only toxic but also expensive and limited. Undoubtedly, the cumulative burden of battery waste is likely to pose environmental and economic challenges unless there is a practical solution to manage end-of-life LIBs. Recycling technologies mainly fall into three categories, including pyrometallurgical recycling, hydrometallurgical recycling, and direct physical recycling. Hydrometallurgical processes have been widely adopted as a promising battery recycling method in research and industry due to their high recovery efficiency, large-scale production capabilities, and low energy cost.

[0004] Lithium-ion battery (LIB) recycling is considered an important component of industrial sustainability. A large amount of LIB in portable electronics, electric vehicles and grid storage will eventually become waste, causing serious economic and environmental problems. Therefore, great efforts have been made to improve the hydrometallurgical recycling process, which is the most promising option for processing scrapped LIBs due to its wide applicability, low cost and high productivity. Despite these advantages, foreign elements (Al, Fe, C, F, etc.) are usually retained as impurities during the removal process and remain in the solution, which poses a challenge to obtaining high-quality cathode materials. Summary of the invention

[0005] The configurations herein demonstrate the beneficial enhancement caused by fluorine impurities or doping in NCM cathode materials obtained by hydrometallurgical co-precipitation. 2+ Ratio, up to 5at% fluorine impurities can have a positive impact on the recycled material. In addition, the presence of fluorine ions during the coprecipitation process leads to the formation of pores in the cathode particles, which significantly improves the rate capability and cycling performance. Compared with the original charge material, NCM622 (LiNi 0.6 Co 0.2Mn 0.2 O 2 ) material showed an increase in capacity by about 8% (167.7 mAh / g), with a remarkable capacity retention of 98.0% after 100 cycles at 0.33C. In addition, the cathode material with 0.2 at% fluorine impurities exhibited much better rate performance than the original material, especially at high rates (increase of about 7% at 5C). These results indicate that electrochemical performance is improved by the addition of potential impurities to the leaching solution, and more specifically, low concentrations of fluorine impurities are desirable during hydrometallurgical recycling, especially for NCM formulations. The disclosed method demonstrates the beneficial implications in the design of high performance NCM622 cathode materials produced by co-precipitation with ion doping.

[0006] The configurations herein are based in part on the observation that the recycling stream of Li-ion batteries tends to introduce additional materials, commonly viewed as "impurities". Physical disassembly of previously used batteries introduces structural and circuit aspects into the recycling stream, such as the physical housing, current collectors, and internal circuitry. Pre-existing impurities may also be present in the depleted / spent charge material. Unfortunately, conventional methods have the disadvantage of being difficult to completely remove impurities, and often result in a balance problem of removing enough impurities without removing valuable charge material compounds. The configurations herein substantially overcome the disadvantages of conventional methods by identifying impurities that actually have a beneficial effect on the properties of the resulting charge material.

[0007] The battery recycling method identifies small or trace compounds in the leach solution generated by the recycling stream of disassembled batteries. Battery performance is based on the ability of the charge material to produce electron flow by transferring electrons between ions in the charge material. The active charge material includes particles that are clustered or aggregated together to form a molecular crystal or network. The oxidation state of each molecule, especially the oxidation state on the surface of the particles, affects the performance of the battery in terms of charge capacity, discharge rate and charge cycle life. The inclusion of certain additional trace elements, either through accidental inclusion from the recycling stream or from addition to the leach solution, or "doping", can have a beneficial effect on the performance of the resulting recycled battery. In particular, small amounts of halides (such as fluorine) have the ability to help nickel and cobalt be in the +2 oxidation state. The increase in +2 atoms relative to atoms with a +3 oxidation state on the surface of the particles has a beneficial effect on performance.

[0008] In the above-referenced application, a highly efficient closed-loop hydrometallurgical recycling method for recycling end-of-life LIBs has been developed. In this method, spent LIBs are disassembled, crushed and sieved. The resulting mixed powder undergoes a leaching and subsequent purification process. Afterwards, the purified solution is adjusted to the desired concentration ratio of the target charge material for subsequent co-precipitation to produce a precursor. The final recovered cathode material is obtained by high-temperature sintering of the precursor. This novel recycling method has a high recovery efficiency (about 90%) and is applicable to a wide range of cathode materials (LiNi x Co y Mn z O 2 , x+y+z=1). Most importantly, the recovered cathode products have similar or even better electrochemical properties than their commercial counterparts. However, impurities caused by incomplete purification remain a potential problem for hydrometallurgical techniques. In fact, due to the similar properties of all impurity elements (such as Al, Fe and Cu), it is difficult to separate them from the useful transition metals in solution. The beneficial effects of impurities on recycled cathodes have attracted much attention among researchers. For example, it was demonstrated that metal ions (such as Al) can be removed only when the impurity levels are very low. 3 + , Fe 3+ , and Cu 2+ ) will have a positive impact on the final recycled cathode. In particular, these cations can replace transition metal ions within the cathode crystals by forming precipitates during the synthesis process.

[0009] The disclosed method describes the improved performance of NCM, and in particular NCM622 materials, recovered under the influence of fluorine impurities by hydrometallurgical synthesis. The disclosed method is also applicable to other NCM chemicals. Before the coprecipitation reaction, an additional fluorine source NaF with a content of 0.2at%, 1at% to 5at% (relative atomic percentage of total transition metals, Ni+Co+Mn=1) is added to the metal sulfate leaching solution as an impurity involved in the recycling process. NCM622 original material (denoted as VNCM) and materials affected by fluorine impurities (denoted as 0.2FNCM, 1FNCM and 5FNCM) are proposed. It is revealed that fluoride ions cause pores to be generated inside the precursor particles during the coprecipitation process. After sintering, it was found that fluoride ions occupied oxygen sites in the cathode crystals and mainly formed bonds with Ni ions (NiF 2 ), which significantly increases the Ni 2+ / Ni 3+ratio. In addition, when the fluorine impurity level is not excessive, the volume diffusion rate is improved due to the smaller lattice expansion and well-ordered structure. Both 0.2FNCM and 1FNCM samples show an excellent discharge capacity of about 167mAh / g (about 8% better than VNCM) and an excellent capacity retention of about 98% after 100 cycles at 0.33C (VNCM 94.8%). In addition, all FNCM cathodes have excellent rate performance compared to the original materials, especially at high rates. In fact, the pores in the cathode particles, the high surface Ni 2+ The positive aspects of fluorine impurities in hydrometallurgical recycling are demonstrated by the high content and improved bulk lithium diffusion rate. In addition, if excessive fluoride is introduced into the NCM622 lattice, the cobalt oxidation state on the cathode surface will be affected. High Co was detected on the 5FNCM cathode surface. 2+ concentration, resulting in poor cation ordering and structural stability, and inferior electrochemical performance to other F-doped NCM622. The results show that the balance of fluorine impurities has a beneficial effect in battery hydrometallurgical recycling, but it will disappear when the fluoride ion content level is high (>1at%) and should be prevented in this process. In addition, the disclosed method demonstrates the feasibility of large-scale production of "enhanced" NCM622 cathodes using hydrometallurgical methods with the help of fluoride additives.

[0010] In a particular configuration, the disclosed method of producing a charge material precursor having a preferred oxidation state for a secondary battery charge material includes forming a leach solution including a target charge material by leaching a target charge material obtained from a recycle stream in a leach solution, and controlling the pH of the leach solution to dissolve the target charge material in the leach solution. A battery chemistry of particular interest includes a charge material (NMC or NCM) of nickel, manganese, and cobalt. The method establishes a predetermined percentage of a halide, such as a halide from fluorine, in the leach solution based on the oxidation state of one or more target charge materials, such as a ratio of +2 and +3 oxidation states produced by a doping substance. The recycled material is obtained by adding a strong base to the leach solution to precipitate charge material particles. The charge material particles include the target charge material in the form of a charge material precursor for subsequent sintering with a Li compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other features will be apparent from the following description of specific embodiments disclosed herein as shown in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

[0012] Figure 1 is an environmental diagram suitable for a hydrometallurgical recycling method to be used with the configuration herein;

[0013] Figure 2 The morphology of the precursors at different times is shown, where the average particle size and sphericity increase;

[0014] Figure 3 shows the SEM image of the NCM622 sample synthesized from the precursor;

[0015] Figures 4A-4D The phase and structure of the prepared material are shown by pattern analysis by powder X-ray diffraction;

[0016] Figures 5A-5D Shows Figures 4A-4D Refinement curves of VNCM, 0.2FNCM, 1FNCM and 5FNCM cathodes of the materials;

[0017] Figures 6A-6C A surface scanning spectrum of the cathode material is shown;

[0018] Figures 7A-7D Deconvoluted scans and percentages of Ni and Co surface ions on cathode material particles are shown;

[0019] Figures 8A-8C Shown is a fitted line plot of peak current (Ip2) versus scan rate (ν);

[0020] Fig. 9 shows the Li ion diffusion within different cathode crystal structures; and

[0021] Figures 10A-10C is a schematic diagram showing pore formation based on doping / impurities. DETAILED DESCRIPTION

[0022] An exemplary method and apparatus for recycling batteries such as lithium-ion batteries is described below. The proposed method is an example and is applicable to other lithium and non-lithium batteries for recycling spent batteries and recovering active cathode materials suitable for use in new batteries.

[0023] Figure 1 is an environmental diagram of a hydrometallurgical recycling method suitable for use with the configuration herein. Cathode materials widely used in commercial lithium-ion batteries include LiCoO 2 、LiMn 2 O 4 、LiNiO 2 、LiNi x Co y Al z O 2 、LiNi x Mn y Co z O 2 and LiFePO4 . In order to effectively recycle lithium-ion batteries, it is beneficial to consider all of the various battery chemistries. Therefore, it would be beneficial to develop a simpler and environmentally acceptable recycling method that is generally applicable to a variety of widely used LIBs. The configuration disclosed herein provides an example of extracting compounds of desirable elements including Co, Ni, Mn, and Li from a mixed cathode material and utilizing the recycled material to produce active materials for a battery. Alternative chemistries can be recycled using the disclosed method.

[0024] refer to Figure 1 In step 1, the discharged Li-ion batteries are crushed / shredded. Mechanical separation methods are used as a pre-treatment to separate the shell and casing and plastic parts, as shown in step 1a. The recycling stream is a mixed material, including at least some of the charge materials, such as Ni, Mn, Co of the target charge material, meaning the battery chemistry and ratio of the intended recycled battery, such as NMC 622, NMC 532, NMC 111 or NMC 811.

[0025] The sieved cathode powder is passed through 4-5 M sulfuric acid (H 2 SO 4 ) and a reducing agent (such as 29%-32% hydrogen peroxide) for about 2-3 hours, as shown in step 2. Other concentrations of leaching acid may also be used, as well as alternative reducing agents. In an alternative arrangement, the leaching solution may be formed by a leaching acid that includes one or more of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, and perchloric acid. Adding hydrogen peroxide H 2 O 2 Not only Fe2+ is changed to Fe3+, but also other metal ions Mn, Ni, Co are changed to 2+, resulting in the separation of iron by controlling the pH of the solution in step 3. After filtration, the residual LiFeO4 and carbon can be separated by centrifugation, as shown in step 2a. Other impurities are also removed from the surface of the solution, as shown in step 2b.

[0026] The metal element of interest is transferred to an aqueous solution as the crushed raw cathode material forms a particulate mass used to produce a solution of aggregated battery material from spent batteries, as shown in step 3. This includes target charge materials of Co (cobalt), Ni (nickel), Mn (manganese); other target charge materials can be used with alternative battery chemistries using the methods of the present invention. The pH is adjusted to extract Fe(OH) 3 、Cu(OH) 2 and Al(OH) 3This involves adjusting the pH to a range between 3.0-7.0. Therefore, NaOH solution is added to adjust the pH to precipitate Fe(OH) 3 , Cu(OH)2 and Al(OH) 3 , and Mn 2+ 、Co 2+ 、Ni 2+ Keep in solution and then separate Fe(OH) by filtration 3 , Cu(OH)2 and Al(OH)3. It should be noted that the above method includes maintaining the solution at a temperature between 40°C and 80°C, thereby avoiding the high heat required in conventional methods.

[0027] The pH adjustment for removing impurities is usually based on the specific impurities sought to be removed to adjust the pH. For example, a pH range of about 3-5 can cause iron to precipitate from the solution. Copper tends to precipitate at a pH of about 5-7. Depending on the amount and type of impurities in the recirculation stream, the impurity removal stage can be directed to different pH ranges. Once the charge material metal (Ni, Mn, Co) dissolves, the pH will be reduced to about 1-3, depending on the amount and concentration of the acid leaching product. Before increasing the pH to precipitate the NCM in pure form, impurities can be precipitated, optionally by adding a reducing agent, which is further discussed below. In other words, while adding sodium hydroxide or other strong bases to increase the pH, impurities are precipitated at a lower pH, and then NCM hydroxides are precipitated at a higher pH. The strong base can also include a precipitant, such as a mixture of sodium hydroxide or potassium hydroxide.

[0028] The target charge material is now dissolved in the solution. Based on a predetermined target ratio of the target charge materials, the solution is adjusted so as to achieve the predetermined ratio of the target charge materials. In the exemplary method, this is a 6:2:2 combination of nickel, cobalt and manganese, but any suitable ratio may be used. Thus, adjusting the solution includes identifying a desired ratio of charge materials for use in the recycled cathode material produced from the generated solution, and adding raw materials to achieve the desired ratio. Adding raw materials includes adding additional amounts of target charge materials for achieving the desired ratio without separating individual target charge materials that are already in solution form, so that the mixed target charge materials (Co, Mn, Ni) do not need to be individually drawn out or extracted as in conventional methods, which typically involve high heat in order to break the molecular bonds of the compounds.

[0029] In other words, the pH is first raised to extract elements that are considered "impurities", meaning elements other than the charge materials. In NCM chemistry, this would include Fe, Cu, Al, and other trace materials. In practice, Al may be part of the battery chemistry in other battery formulations. Once the impurities are extracted, the pH is further increased to precipitate the target charge material. In the configuration herein, the halide (such as fluorine) is formed from residual amounts from a recycle stream and / or additional materials added as dopants.

[0030] To achieve the desired chemical properties or the ratio of the target charge material, the Mn 2+ 、Co 2+ 、Ni 2+ concentration, and with additional CoSO 4 、NiSO 4 、MnSO 4 Their ratio is adjusted to 6:2:2 or other suitable ratios. NaOH solution is added to increase the pH to about 11, typically in the range of 10.0-13, thereby adjusting the pH of the solution so that the target charge material for the new (recycled) charge material is precipitated. Ni 1 / 3 Mn 1 / 3 Co 1 / 3 (OH) 2 or Ni 1 / 3 Mn 1 / 3 Co 1 / 3 O(OH) or a mixture thereof can be co-precipitated such that the corresponding molar ratio is 1:1:1, as shown in step 4. Ni with different ratios of x, y and z can also be precipitated. x Mn y Co z (OH) 2 or Ni x Mn y Co z O(OH) or a mixture. Add Na 2 CO 3 To deposit Li 2 CO 3 , as shown in step 5. Finally, the recovered Ni 1 / 3 Mn 1 / 3 Co 1 / 3 (OH) 2 and Li 2 CO 3 Sintering is performed to produce the cathode material.

[0031] In an exemplary arrangement, the target charge material includes manganese (Mn), cobalt (Co) and nickel (Ni) extracted from the charge material of spent batteries, where these target charge materials are still admixed in solution during the precipitation process. Adjusting the pH includes adding a substance such as NaOH (sodium hydroxide, also known as lye or caustic soda) to increase the pH so that the target charge material is precipitated, however any suitable substance for increasing the pH may be used. The end result is that adjusting the pH includes adding sodium hydroxide to increase the pH so as to allow precipitation of the target charge material used as a cathode precursor material without the need to separately precipitate a separate compound defining the target charge material. The intermediate or precursor form will be in the presence of lithium carbonate Li 2 CO 3 After sintering together, lithium oxide forms are produced.

[0032] Adding Na to the solution 2 CO 3 In order to deposit Li at about 40 °C 2 CO 3 After filtration, Li 2 CO 3 Can be recycled as starting material to synthesize active cathode material LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 , as shown in steps 5 and 5a. Thus, the method adds lithium back to the precipitated target charge material to form an active cathode material suitable for use in a new battery, and precipitates the target charge material at a predetermined ratio to form a charge material for a new battery.

[0033] Li to M (M = Ni 1 / 3 Mn 1 / 3 Co 1 / 3 ) of the coprecipitated material Ni at a molar ratio of 1.1 1 / 3 Mn 1 / 3 Co 1 / 3 (OH) 2 or Ni 1 / 3 Mn 1 / 3 Co 1 / 3 O(OH) or their mixture and recovered Li 2 CO 3 With another Li 2 CO 3 Mix and grind in a mortar as shown in step 6. The mixture can be reconstituted by any suitable processing to form the active cathode material 134 for the new battery 140. In this exemplary method, the mixture is sintered at 900°C for 15 hours. The reaction product can be ground into a powder for subsequent distribution and reformation into the new battery 140. 1 / 3Mn 1 / 3 Co 1 / 3 O 2 The sintering was carried out by high temperature solid phase method at 900°C for 15 hours.

[0034] Extensions Figure 1 The cathode material is synthesized by a coprecipitation reaction and a post-sintering process, wherein the transition metal ion M 2+ (M=Ni, Co, Mn) are co-precipitated in alkaline solution to form Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 precursor, and then sintering the mixture of the dried precursor and lithium salt to obtain LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) as the final cathode sample. The following example illustrates a leaching solution containing a target charge material to produce a 622NMC charge material precursor, and the halide consists of a predetermined percentage of fluoride substantially about 1.0at%. Additional configurations can establish a predetermined percentage of halide in the leaching solution based on the oxidation state of one or more target charge materials, as expected to be formed on the resulting charge material particles. The halide is based on the electronegativity of the halogen and another atom. Other suitable halides can be used, including some of the more common ions: chloride (Cl-), bromide (Br-), iodide (I-), and astatide (At-).

[0035] Metal sulfate hydrate NiSO 4 6H 2 O. CoSO 4 7H 2 O and MnSO 4 ·H 2 O was added to deionized (DI) water in a stoichiometric ratio of 6:2:2 to obtain a 2M metal sulfate solution. For sample preparation containing impurities, NaF salt was mixed into the metal sulfate solution at concentrations of 0.2at%, 1at%, and 5at%, respectively, and are hereinafter named 0.2FNCM, 1FNCM, and 5FNCM, respectively. Before starting, 0.5M NH 3 ·H 2O was filled into a 5 L continuous stirred tank reactor (CSTR) as a complexing agent. Then, metal sulfate solution and ammonia solution were pumped into the reactor at controlled flow rates. Meanwhile, 7.5 M NaOH solution was added to the reactor via a peristaltic pump to maintain the reaction at the desired pH condition. The coprecipitation reaction was continuously carried out for 12 h under nitrogen protection at stable conditions of pH = 11 and T = 55 °C. After the reaction, the synthesized precursor was filtered and washed with deionized water to remove residues until the pH dropped to 7, and then the precursor powder was dried overnight in an oven at 130 °C. To obtain the cathode materials, the precursor was mixed with Li 2 CO 3 in a mortar at a stoichiometric ratio of 1:1.05 (using 5% excess lithium salt to compensate for the loss of lithium ions during the sintering process). Next, the mixture underwent a two-step sintering process: (Ⅰ) heating to 450 °C for 5 h and then cooling to room temperature, (Ⅱ) heating to 850 °C for 18 h and then using the same cooling method (the ramp rate was fixed at 2 °C / min). Finally, four cathode materials were obtained: LiNi 0.6 Co 0.2 Mn 0.2 O 2 (VNCM) and LiNi 0.6 Co 0.2 Mn 0.2 F x O 2-x (x = 0.002, 0.01, and 0.05, named 0.2FNCM, 1FNCM, and 5FNCM respectively).

[0036] The particle morphology and microstructure were observed by scanning electron microscopy (SEM, JEOL JSM - 7000F) combined with energy-dispersive spectroscopy (EDS) to analyze the elemental composition. The precise concentrations of all metal elements in the cathode were measured using inductively coupled plasma mass spectrometry (ICP-MS). The phase of each sample was identified by powder X-ray diffraction (XRD, PANalytical Empyrean), using Cu Kα (λ = 1.54) and a step size of 0.02° per scan. To obtain the lattice parameters, the following Rietveld refinement was performed through FullProf software, and LiNi 0.6 Co 0.2 Mn 0.2 O 2The powder structure of (PDF#00-066-0854) was used as a reference model. X-ray photoelectron spectroscopy (XPS) data of all cathodes were acquired using a PHI 5000 VersaProbe II system (Physical Electronics) to study the elemental composition and oxidation states of transition metals. The X-ray source was operated at 25 W and equipped with a monochromator Al Kα (hυ=1486.6 eV) set to Ar + Ion and electron beam sample neutralization, fixed analyzer transmission mode. XPS spectra were calibrated against CC at 284.8 eV before subsequent deconvolution simulations (fitting spectra to multiple Gaussian-Lorentzian peaks) processed on XPSpeak software.

[0037] CR-2032 button cells (consisting of a cathode electrode, a separator, an electrolyte, and lithium metal as an anode) were assembled in an argon-filled glove box (H 2 O, O 2 <1ppm) to study the electrochemical performance. The electrodes were prepared by mixing the active material (cathode powder, 80wt%), conductive carbon (C65, 10wt%) and polyvinylidene fluoride binder (PVDF, 10wt%) in N-methyl-2-pyrrolidone (NMP) solvent to form a slurry. The mixed slurry was then cast on aluminum foil by a doctor blade (MTI) and dried at 60°C overnight. Circular electrodes (Φ=12mm) were calendered and punched from the dried electrode sheets to obtain a final thickness of about 40μm with an active mass loading of 3.5-4.0mg / cm 2 The electrode samples were further dried in a vacuum oven at 120 °C overnight to remove residual NMP and moisture. Three layers of polypropylene-polyethylene-polypropylene film (Φ=16 mm) and 1 M LiPF in ethylene carbonate / ethyl methyl carbonate (EC / EMC, 3:7, by wt%) were prepared. 6 The electrochemical performance was between 3.0 V and 4.3 V (vs. Li / Li) on a Land battery test system (LAND, CT2001A). + ) test. Specifically, the battery was measured at current densities of 0.33C and 5C in the cycle test, while the current density was set from 0.1C to 5C (1C = 175 mAh / g) in the rate performance test. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests were performed on an electrochemical analyzer (Bio-Logic SAS, VMP3) using the EC-Lab program. In the CV test, the scanning potential was set between 3.0V and 4.5V (relative to Li / Li) at a rate of 0.1mV / s. + ). In the EIS test, the battery before and after cycling was measured in the frequency range of 100kHz to 10mHz with an amplitude of 10mV.

[0038] To monitor the morphology of the hydroxide precursor during the synthesis, samples were collected every 3 h and then analyzed by SEM. Figure 2 Precursor morphology at different times is shown, wherein the average particle size and sphericity increase as the reaction time increases. At each specified time, no significant difference was observed between the samples of 0.2FNCM (row 201), 1FNCM (row 202) and 5FNCM (row 203), indicating that the fluoride ions present in the alkaline environment during the coprecipitation process do not form additional precipitates to inhibit particle growth and hinder particle sphericity. Particle morphology is closely related to its physical properties, such as powder tap density. In Table I, the tap density also increases as the reaction proceeds, and all FNCM samples have similar density levels in each time period. It is worth noting that, compared with FNCM, the original material group has a lower powder tap density at 3 hours (column 211), 6 hours (column 212) and 9 hours (column 213), which is about 77%, 79% and 89% of the average value of the precursor affected by fluorine impurities. However, when the precipitation process ended at 12 h (214), all samples were close to similar density levels (about 1.90 g / ml). This phenomenon suggests that fluorine impurities affect the coprecipitation process due to faster nucleation and particle growth in its early stages, resulting in an increase in the powder tap density, while when the reaction reaches a steady state, there is no significant change in particle morphology and tap density.

[0039] sample 3 hours 6 hours 9 hours 12 hours VNCM 0.68 1.15 1.52 1.85 0.2FNCM 0.94 1.47 1.73 1.93 1FNCM 0.92 1..47 1.72 1.93 5FNCM 0.78 1.41 1.65 1.88

[0040] Table I

[0041] Figure 3 The SEM image of NCM622 sample synthesized from the precursor is shown. Figure 3In the figure, SEM images (scale bar 10 μm) of 0.2FNCM (row 301), 1FNCM (row 302) and 5FNCM (row 303) of the precursor (column 211), cathode (column 312) and cathode cross section (column 313) are shown. (Inset: image at higher magnification, scale bar 2 μm). Typical nearly spherical secondary particles composed of many tiny flake-like primary particles are observed in column 311. Primary particles are the most basic structural units of synthetic materials. During the reaction, the growth, attachment and aggregation of primary particles produce spherical secondary particles. For all cathodes shown in column 312, the shape of the primary particles changes from flake to polygonal after sintering of the high-temperature precursor. Both the precursor and the cathode have consistent surface morphology and secondary particle size (about 8 μm), which means that the effect of fluorine impurities on the final cathode morphology is negligible. However, the interior of the particles is completely different. According to the cross-sectional images given in column 313, pores (marked with circles and yellow arrows) were found inside the FNCM cathode particles. In addition, as the impurity concentration increased from 0.2at% to 5at%, the pore formation within the cathode particles also increased. This suggests that fluorine impurities are a key factor in the formation of pores in the cathode particles, and this beneficial feature can promote the improvement of electrochemical performance.

[0042] The SEM-EDS spectra of the prepared cathode showed that the transition metal elements Ni, Co and Mn were uniformly distributed throughout the particles. The exact composition of each element in the NCM622 cathode at different impurity levels was measured by ICP-MS. As shown in Table II, the atomic ratios of Ni, Co and Mn in all samples are close to the theoretical value (6:2:2). Specifically, for VNCM, 0.2FNCM, 1FNCM and 5FNCM, the exact atomic ratios between NCMs were calculated to be 6:2.05:2.00, 6:2.11:2.01, 6:2.10:2.00 and 6:2.15:2.05 (Ni=6), respectively. In addition, the lithium composition remains stable regardless of changes in impurity concentrations. Therefore, it can be concluded that fluoride ions do not occupy the site of cations during the synthesis process, but replace oxygen in the cathode crystals.

[0043] sample Li(%) Ni(%) Mn(%) Co(%) Na(%) VNCM 103.6 59.7 19.9 20.4 0 0.2FNCM 102.8 59.3 19.9 20.9 0 1FNCM 102.6 59.4 19.8 20.8 0 5FNCM 103.6 58.8 20.1 21.1 0

[0044] Table II

[0045] A typical mechanism for the synthesis of dense and spherical hydroxide particles by coprecipitation can be performed. There are two steps in the formation of the precipitate: the transition metal ion first coordinates with the ammonia complexing agent (1) and then slowly precipitates out from the alkaline solution (2). The relevant two-step reaction is as follows:

[0046] M 2+ +nNH 3 →[M(NH 3 )n ] 2+ (1)

[0047] [M(NH 3 ) n ] 2+ +2OH - →M(OH) 2 ↓+nNH 3 (2)

[0048] In the initial stage, the relatively abundant fluoride ions may lead to the reaction:

[0049] [M(NH 3 ) n ] 2+ +2F - →MF 2 +nNH 3 (3)

[0050] It consumes complex ions [M(NH 3 ) n ] 2+ and pushes the equilibrium of reaction (2) to the left. In this case, the rate of dissolution of the primary particles exceeds the rate of recrystallization, creating pores in the precursor.

[0051] Figures 4A-4D The phase and structure of the prepared material are shown in a pattern analysis by powder X-ray diffraction. Figures 4A-4D Shown in Figure 4A , 4B X-ray diffraction patterns of the precursor with (001) plane extension in Figure 4C and 4D X-ray diffraction pattern of the cathode with (003) plane extension. Figures 5A-5D Refinement curves for VNCM, 0.2FNCM, 1FNCM, and 5FNCM cathodes are shown. Figure 4A-4B All patterns in the figure have the same diffraction peak, corresponding to β-Ni(OH) 2 (PDF#00-059-0462), which is a layered metal hydroxide. Figure 4C-4D There are nine obvious diffraction peaks in the XRD spectra of all cathodes, which completely match the LiNi 0.6 Co 0.2 Mn 0.2 O 2 (PDF#00-066-0854), which refers to typical layered transition metal oxides. No additional phase or structural changes were found in both the precursor and cathode patterns. Meanwhile, pure phase and well-stratified cathode materials were maintained. Nevertheless, due to the reduction of primary particle size, the (001) peak of the FNCM precursor was slightly broadened, as shown in Figure 4AIn addition, due to the expansion of the c-axis in the lattice, all FNCM cathodes ( Figure 4C-4D ) is slightly shifted to a lower angle. Notably, 5FNCM has the lowest I (003 ) / I (104 ) ratio (1.59), while the other cathodes VNCM (1.81), 0.2FNCM (1.80), and 1FNCM (1.76) have much higher values. (003) / I (104) The value indicates that the lower Li + / Ni 2+ Therefore, the recycled cathode may be unlikely to be competitive compared to other cathodes under the influence of high concentration of fluorine impurities (5at%).

[0052] In order to obtain more detailed lattice information of the recycled cathode, the structural parameters were calculated using Rietveld refinement and the space group was The rhombohedral crystal system of is used as the standard. Figures 5-5D show the fitted XRD patterns of all cathode materials, and Table III lists the refined crystallographic data, showing the Rietveld refinement results of the example NCM622 cathode. Figures 5A-5D As shown, satisfactory agreement is achieved between the calculated and observed patterns. VNCM is shown in 5A, and 0.2FNCM, 1FCNM and 5FCNM are shown in Figures 5B-5D In addition, each fitting operation obtains a relatively small χ 2 (Table III), which guarantees the high quality of all the precise results in this work. It is clear that the expansion of the c-axis is associated with the increase in the level of fluorine impurities, which is consistent with previous studies. In fact, for 5FNCM, the interplate distance of VNCM expanded by about 0..03% to At the same time, the battery volume expanded by about 0.13%. It should be clarified that this expanded lattice not only reduces the resistance to Li diffusion, but also reduces the interlayer cation exchange (Li + / Ni 2+ ) energy barrier. Obviously, 5FNCM has less cation mixing (4.41%) compared with 0.2FNCM and 1FNCM due to its excessive lattice expansion, while other cathodes with smaller changes in the crystal structure remain in good condition. - Replace O 2- It is believed to be the cause of the apparent change in the lattice parameters of NCMs. It is reported that the inclusion of fluorine leads to the reduction of TM ions for charge compensation. Since TM ions with lower oxidation states have larger radii, when more and more O2 -Be F - When replaced (this is O 晶格 The decrease in the value of ) further proves that the presence of more and larger TM ions is consistent with a larger lattice expansion. These results suggest that fluorine impurities (<1at%) can enhance the Li diffusion rate in the cathode through optimized lattice modification, while the well-ordered structure may be destroyed when excessive impurities (>5at%) are included.

[0053]

[0054] Table III

[0055] Figures 6A-6C The surface scanning spectrum of the cathode material is shown. XPS testing is used to study the material composition and element valence state in the prepared cathode. Fig. 6A The Na 1s full spectrum scan in the HPLC-MS / MS showed no signal in all samples. This ensured that no Na-related species were present in the final recovered material. Figure 6B and 6C The surface and bulk F1s spectra of all cathode samples are shown. A strong peak is observed in the surface spectrum of the FNCM cathode. In contrast, Figure 6C There is no fluorine signal at all. This means that the fluoride ions are mainly concentrated on the surface of the cathode particles rather than inside. In addition, Figure 6B The peak in (about 685 eV) is similar to that in metal fluorides (such as LiF and TMF 2 (TM = Ni, Co or Mn)) are very consistent. In addition, as the impurity concentration increases from 0.2at% to 5at%, the peak intensity increases relatively. Therefore, XPS analysis confirms that fluoride is included in the cathode material by replacing oxygen, and more importantly, fluoride ions are present in large quantities near the particle surface, forming a layer with an increased level of low-valent (+2) TM ions.

[0056] In the claimed method, a predetermined percentage of fluoride is introduced by adding fluorine to the leaching solution, or simply from the residual quantity, before the precipitation of the charge material. The result is that after subsequent sintering, on the surface of the charge material, Ni 2+ and / or Co 2+ Ion ratio corresponding to Ni 3+ and Co 3+ Other ions may also achieve a preferred surface distribution based on the particle crystal structure.

[0057] Figures 7A-7D Deconvoluted scans and percentages of Ni and Co surface ions on cathode material particles are shown. 2+ / Ni 3+ and Co 2+ / Co3+ The relevant content of 2p 3 / 2 The spectra in the peak regions were deconvoluted to calculate the exact percentages of the different TM ions. Fig. 7A The Ni 2p 3 / 2 The fitted spectrum shows that the Ni 2+ and Ni 3+ In this example, the leaching solution has a fluoride content in the range of 0.2-5 at% and increases the percentage of Ni2+ ions on the surface of the charge material particles to between 40.1% and 43.8% before the charge material is precipitated. Thus, fluorine is effective in increasing at least the percentage of Ni and Co (Ni2+) ions on the particle surface having a 2+ oxidation state. 2+ ,Co 2+ ) has a quantifiable effect. As described above, when the leaching solution has a fluoride content in the range of 0.2-5 at% and the Ni on the surface of the charge material particles is removed before the charge material is precipitated, the leaching solution has a fluoride content in the range of 0.2-5 at% and the Ni on the surface of the charge material particles is removed. 2+ ions to between 40.1% and 43.8%. Similarly, when the leaching solution has a fluoride content in the range of 0.2-5 at% prior to precipitation of the charge material and the Co 2+ The percentage of Ni 2p ions increases to between 13.0% and 35.2%. Based on halide doping, other ions can also be distributed favorably. As shown above, Ni 2p 3 / 2 The peaks can be divided into Ni 2+ (854.7eV) and Ni 3+ (856.5 eV). Similarly, Figure 7B As shown, Co 2p 3 / 2 The peaks can be divided into Co 2+ (782.1eV) and Co 3+ (780.2eV). Figure 7C For all FNCM cathodes, the Ni 2+ The ratio increased from 40.1% (VNCM) to an average of 43.8%, an increase of about 4%. 2+ The content of Ni is almost unaffected by the additional fluorine impurities, with the maximum ratio changing by less than 1% between VNCM and 5FNCM. This further confirms the fact that there is more Ni near the surface of the FNCM cathode. 2+ ions, which may contribute to higher reversible capacity during cycling. Fig.7D Only a small amount of Co is shown 2+ Appear on the original cathode surface. For 0.2FNCM and 1FNCM, the surface Co 2+The percentage increases to about 13% and for 5FNCM, this percentage is as high as 35.2%. It can be inferred that the reduction of cobalt ions also occurs on the particle surface, especially in the case of high levels of fluoride incorporation (5at%) into the cathode particles. It should be noted that Li + With Co 3+ The large size and charge difference between the Co and C ensures good cation order, which is essential for the fast diffusion of lithium ions in the cathode. 3+ At very low concentrations, it is not surprising that 5FNCM has poor cation mixing, as previously revealed by XRD analysis. For all samples, Co 2+ The ratio remained stable (about 36%).

[0058] Figures 8A-8C Shown are fitted line plots between peak current (Ip2) versus scan rate (ν) from CV curves of (8A) the anode side and (8B) the cathode side; and (8C) the calculated Li ion diffusion coefficient. Fig. 9 The Li ion diffusion within different cathode crystal structures is shown. Figure 8A-9 The Li diffusion coefficient (D) was determined using a series of cyclic voltammetry (CV) tests at different scan rates using the Randles-Sevcik equation. Li ):

[0059]

[0060] Where n is the number of electrons transferred in the redox reaction (n = 1); A is the electrode surface area (1.13 cm 2 ); C is the theoretical molar concentration of Li ions in NCM crystals (0.05 mol / cm 3 ), and D Li is the Li diffusion coefficient. The square of the peak current (I p 2 ) to the scan rate (υ) and the lithium ion diffusion rate (D Li ) are proportional to each other. p 2 Relative to υ), the linear relationship between Figures 8A-8B As shown in Figure 2, the slope of the fitting line directly reflects the diffusion rate of Li ions in the NCM material. Then, the slope value is substituted into the Randles-Sevcik equation to calculate D Li And the relevant data is Figure 8C Given in. Fig. 8A , 8BThe anodic and cathodic slopes shown confirm the strong correlation between the anodic and cathodic diffusivities representing Li diffusion during delithiation and lithiation, respectively. Li Calculated to be 1.57×10 -10 cm 2 / s (anode) and 4.24×10 -11 cm 2 / s (cathode), which is consistent with recent reports.

[0061] According to the slope, 0.2FNCM and 1FNCM have larger D compared with the original standard. Li The Li diffusion condition in 5FNCM is the worst. In particular, 0.2FNCM has the largest Li diffusion coefficient of 2.04×10 -10 cm 2 / s (anode) and 4.83×10 -11 cm 2 / s (cathode), which are about 30% and 14% higher than the original standard, indicating that 0.2FNCM has the best electrochemical performance among all prepared samples. Fig. 9 The lattice images in Figure 1 show the effect of different levels of fluoride inclusion in NCM crystals on ion diffusion. It should be noted that the octahedral sites between the closely packed oxygen ions (marked with red x) are used for Li ion diffusion within the layer. When a small amount of fluoride substitution occurs (<1 at%), the diffusion path will still be viable. ) compared to the fluoride ion, which has a smaller ionic radius (approx. ) and charge number, so this substitution may lead to gap enlargement and lower energy barrier, which is the reason for the increase of Li ion diffusivity. However, excessive fluoride inclusion (>5at%) will trigger a significant deterioration of cation order. Therefore, more diffusion paths will be occupied by mismatched Ni 2+ Ion blocking, which leads to reduced diffusion efficiency.

[0062] Figures 10A-10C is a schematic diagram showing pore formation based on doping / impurity to illustrate the positive impact of fluorine impurities on recycled NCM622 cathodes. The addition of small amounts of halides such as fluoride creates pores in the precipitated charge material particles. The intra-particle charge and forces associated with the pores increase the ratio of the 2+ to 3+ oxidation states of the charge material precursor. By introducing a fluorine reaction equilibrium during the co-precipitation process, the fluoride ions promote the dissolution of the primary particles and lead to the formation of cavities or pores in the precursor.

[0063] Fig. 10A The conventional raw material is shown exhibiting solid particles 101 without pores. Fig. 10B shows a fluorine content of about 1%, which has a bond to Ni 2+Negative F of ions 1- ions, including hole 102, and in Fig. 10C With a 5% increase in F 1- The ion density also surrounds the hole 103 .

[0064] Thus, after precursor sintering, cathode particles with a hollow structure defined by pores were obtained in the FNCM material. The definition of the particle structure containing pores has a positive impact on the cathode rate performance and cycling stability, because the presence of pores reduces the overall Li diffusion distance and can improve particle stability by suppressing volume changes during cycling. In addition, Ni 2+ The ratio of the surface layer increases, which greatly increases the reversible capacity of the material. 3+ The amount of fluorine enhances the ability to maintain surface stability. In addition, the Li diffusion coefficient will be improved in FNCM cathodes (<1at%), where a small portion of the lattice oxygen is replaced by fluoride ions, resulting in better structure and energy levels for ion transport in the lithium layer. Despite all these positive effects, an undesirably high level of cation disorder was found in the 5FNCM cathode, which in turn had a negative impact on Li diffusion. Moderate levels of fluorine impurities or doping benefit recycled NCM622 cathodes obtained by hydrometallurgical processes. Similar benefits extend to at least other NMC chemistries. Overall, these results confirm the advantages of fluorine impurities for NMC622 cathode materials.

[0065] While the systems and methods defined herein have been particularly shown and described with reference to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention as encompassed by the following claims.

Claims

1. A method for producing a charge material precursor having a preferred oxidation state for a secondary battery charge material, the method include: forming a leach solution comprising the target charge material by leaching the target charge material from the recirculating stream in the leach solution; controlling the pH of the leaching solution to dissolve the target charge material in the leaching solution; adding a halide material as a dopant to the leach solution to establish a predetermined percentage of halide in the leach solution; as well as Adding a strong base to the leaching solution to precipitate charge material particles; the charge material particles include the target charge material in the form of a charge material precursor for subsequent sintering with a Li compound; wherein the halide comprises fluoride; the halide creates pores in the precipitated charge material particles, the pores increasing the ratio of 2+ to 3+ oxidation states of the charge material precursor; and prior to precipitation of the charge material, the leaching solution has a fluoride in the range of 0.2-5 at %.

2. The method according to claim 1, in, The target charge material includes a compound of at least one of Ni, Mn, Co, and Al.

3. The method according to claim 1, in, Prior to precipitation of the charge material, a predetermined percentage of fluoride obtained by adding fluorine to the leaching solution increases the Ni content on the surface of the charge material after subsequent sintering. 2+ Ions relative to Ni 3+ The percentage of ions.

4. The method according to claim 1, in, The addition of fluorine to the leaching solution prior to precipitation of the charge material to obtain a predetermined percentage of fluoride increases the Co content on the surface of the charge material particles after subsequent sintering. 2+ ions relative to Co 3+ The percentage of ions.

5. The method according to claim 1, in, Prior to precipitation of the charge material, the leaching solution has a fluoride content ranging from 0.2 to 5 at% to remove Ni 2+ The percentage of ions increased to between 40.1% and 43.8%.

6. The method according to claim 1, in, Prior to precipitation of the charge material, the leaching solution has a fluoride content ranging from 0.2 to 5 at% to remove the Co 2+ The percentage of ions increased to between 13.0% and 35.2%.

7. The method of claim 1, further comprising forming the leaching solution to include the target charge material to produce a NCM622 charge material precursor, and the halide consists of a predetermined percentage of fluoride.

8. The method of claim 1, further comprising forming the leaching solution from a leaching acid selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, and perchloric acid.

9. The method according to claim 1, in, The strong base includes a precipitating agent selected from the group consisting of sodium hydroxide or potassium hydroxide.

10. The method of claim 1, further comprising determining a predetermined percentage of halide in the leaching solution to achieve an oxidation state of one or more of the target charge materials.

11. A charge material precursor, comprising: Nickel, manganese and cobalt in precursor form, referred to as NMC, particles that respond to sintering with a lithium compound to form an active charge material; between 0.2 at% and 5.0 at% fluorine impurities in the NMC particles; pores in the particles created by the fluorine impurities; and Each particle of the structure is defined to have a surface, the surface having nickel ions, at least 40.1% of the Ni surface ions having an oxidation state of +2; in, The surface has cobalt ions, at least 13% of the cobalt surface ions having an oxidation state of +2; The fluorine impurities make Ni 2+ Ions relative to Ni 3+ The ratio of ions increased by 10%; The fluorine impurity increases the ratio of Co 2+ ions to 35.2%.

12. A method of controlling the oxidation state in a recycled secondary battery charge material, the method include: leaching NMC charge material from the recycle stream in a leach solution; controlling the pH of the leaching solution by adding a leaching acid to dissolve the charge material in the leaching solution, wherein the leaching solution has a certain pH; adjusting the pH to a pH range that precipitates impurities, including iron and copper, thereby removing them while leaving the charged material in solution; After removing the impurities, adding a halide material as a dopant to the leaching solution to establish a predetermined percentage of fluoride; as well as adding a strong base to precipitate charge material particles; the charge material particles comprising the NMC in the form of a charge material precursor for subsequent sintering with a Li compound, the precipitated charge material having an oxidation state based on the predetermined percentage; wherein the halide comprises fluoride; the halide creates pores in the precipitated charge material particles, the pores increasing the ratio of 2+ to 3+ oxidation states of the charge material precursor; and prior to precipitation of the charge material, the leaching solution has a fluoride in the range of 0.2-5 at %.

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