Tailoring the microstructure of cathode materials

Abstract

A method for recycling lithium-ion (Li-ion) batteries involves selective leaching of charge material metals and subsequent control of impurities to create microstructures, such as pore volume and surface area, for optimal structural and charging performance. Particle characteristics with favorable effects on performance are associated with soluble impurities in the recycling leach solution formed from spent charge material in the battery recycling stream. A black mass of agitated and mixed cathode material, anode material, and current collector is obtained from spent batteries. Leaching of the black mass results in a recycled solution of charge material metals and impurities. Selective adjustment of these impurities by the addition and / or separation of soluble ions in the solution promotes the creation of internal voids, surface area, and pore volume in the resulting cathode material.

Description

[Background technology]

[0001] background Lithium-ion (Li-ion) batteries are one of the preferred chemistries for secondary (storage) batteries in high-discharge applications, such as electric vehicles (EVs) and power tools where electric motors are required for rapid acceleration. Li-ion batteries contain a charge material, conductive powder, and binder, which are coated or deposited on a current collector, typically a flat sheet of copper or aluminum. The charge material includes an anode material, typically graphite or carbon, and a cathode material containing predetermined ratios of metals such as lithium, nickel, manganese, cobalt, aluminum, iron, and phosphorus, which define the so-called "battery chemistry" of the Li-ion cell. Preferred battery chemistries vary between suppliers and applications, and efforts to recycle Li-ion batteries typically adhere to a defined molar ratio of battery chemistry in the recycled charge material product. Qualitative differences in charge material particles, such as the microstructure within and on the surface of the charge material particles, affect the performance of recycled battery cells based on the reclaimed charge material. Summary of the Invention [Problem to be solved by the invention]

[0002] overview A method for recycling lithium-ion (Li-ion) batteries involves selective leaching of charge material metals followed by control of impurities to shape the microstructure, such as pore volume and surface area, for optimal structural and charging performance. Particle characteristics with favorable effects on performance are associated with soluble ionic impurities in the recycling leach solution formed from spent charge material in the battery recycling stream. A black mass of agitated and mixed cathode material, anode material, and current collector is obtained from spent batteries. Leaching of the black mass yields a recycling solution of charge material metals and impurities. While some of these impurities are soluble and do not precipitate during the co-precipitation reaction, they affect the co-precipitation process and the microstructure of the precursor, and therefore the microstructure of the cathode material. Selective adjustment of these impurities by adding, diluting, and / or separating soluble ions in the solution promotes the formation of internal porosity, surface area, and pore volume in the resulting cathode material. [Means for solving the problem]

[0003] The present invention is based in part on the observation that the growing popularity of electric and hybrid electric vehicles (EVs / HVs) is generating large volumes of used Li-ion batteries containing chargeable materials such as NMC (Ni, Mn, Co) cathode materials. The recycling process for NMC chargeable materials involves leaching the used NMC chargeable materials, often augmented with a control (virgin) stock of Ni, Mn, Co salts to achieve a predetermined ratio of chargeable material metals that conforms to technical or customer specifications. Unfortunately, conventional NMC recycling methods suffer from the drawback that recycled NMC chargeable material particles may have undefined and / or undesirable microstructures, such as internal voids, pore volume, and porosity. Meeting customer specifications for performance and physical cathode material properties can be problematic when significant amounts of recycled cathode material are mixed into recycled products.

[0004] Thus, the configurations herein substantially overcome the drawbacks of conventional cathode material recycling by controlling impurities in the recycled leach solution to form desired or intended microfeatures or microstructures in the recycled cathode material. During recycling, small amounts of impurities remain in the leach solution, even after filtration and precipitation methods for removal. These impurities are in the form of soluble ions in the leach solution, and the configurations herein demonstrate beneficial performance effects by controlling the concentrations of impurities such as sodium and lithium, in addition to metal salts (e.g., Ni, Mn, Co) in the recycled cathode material.

[0005] More specifically, a method for forming microstructures in cathode material precursors in a battery recycling environment by adjusting the ratio of charge material metals from the black mass of depleted batteries to produce recycled charge material involves adjusting the concentration of soluble ions in the leach solution based on the intended or target microstructure to be formed in particles coprecipitated from the leach solution. Subsequent precipitation of the charge material precursor results in particles having the microstructure formed from the leach solution.

[0006] A method for producing a cathode material precursor from recycled batteries includes leaching black mass from spent lithium-ion batteries to obtain a leach solution containing a ratio of dissolved charge material metals and a concentration of soluble ionic impurities. Recycling includes adjusting the ratio of the charge material metals to a selected ratio with additional charge material metal salts. Further adjustment of the concentration of the soluble ionic impurities is performed. After adjusting the ratios and concentrations, a cathode material precursor is formed by co-precipitation of the charge material metal salts in the selected ratios and exhibiting a targeted and intended microstructure in the charge material particles.

[0007] BRIEF DESCRIPTION OF THE DRAWINGS These and other features will become apparent from the following description of specific embodiments disclosed herein, as illustrated 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. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a context diagram of a recycling environment suitable for use with the compositions herein. [Figure 2] 1 is a flow chart of the recycling method disclosed herein involving control of impurities during leaching of cathode material. [Figure 3A] 1 is an example of a microstructure including internal voids in charged material particles. [Figure 3B] 1 is an example of a microstructure including internal voids in charged material particles. [Figure 3C] 1 is an example of a microstructure including internal voids in charged material particles. [Figure 4] The cycle performance results for soluble ionic impurities obtained by the method of FIG. 2 are shown. DETAILED DESCRIPTION OF THE INVENTION

[0009] Detailed Description Representative methods and techniques for recycling batteries such as NMC batteries are described below. While the configurations herein use NMC battery chemistry as an example, the disclosed soluble ion techniques can be implemented with any suitable battery chemistry. Li-ion batteries use so-called battery chemistries that specify the types and ratios of metal ions used to form the cathode material; the anode material is most often a carbon or graphite blend. Specific ratios are set by the manufacturer, often accompanied by specifications for internal void space, porosity, and other physical characteristics. Charge material and charge material precursor suppliers provide charge material products that meet the manufacturer's specifications. Soluble ions that meet predetermined concentrations in the leaching solution are used to achieve the desired physical characteristics on the charge material particles.

[0010] FIG. 1 is a context diagram of a recycling environment suitable for use with the configurations herein. Referring to FIG. 1, a recycling scenario 100 begins with a Li-ion battery 102, typically deployed from an EV. The Li-ion battery 102 has a finite number of charge cycles before the charge material's ability to accept a sufficient charge substantially degrades. This is supplemented by batteries that have been prematurely terminated due to vehicle breakdown, collision damage, etc. The overall end-of-life recycling stream contributes a plentiful supply of spent cells and charge material 104, which are discharged, agitated, and physically crushed, crushed, and pulverized to obtain a granular mass. The leaching process accepts a black mass containing the charge material and any associated casings and copper and aluminum current collectors. The black mass, containing both the cathode material (metal salt) and the carbon and graphite anode material, is used to form a leach solution 106 with the charge material metals dissolved therein.

[0011] In one example configuration, the leach solution contains Ni, Mn, and Co in a sulfate solution from a sulfuric acid leach, although other charge material metals and / or leach acids can be used. The leach solution 106 has a molar ratio of Ni, Mn, and Co based on the composition of the components in the incoming recycle stream. This molar ratio is adjusted with additional sulfates of Ni, Mn, and Co (typically virgin or controlled forms of new material) to obtain a solution 108 adjusted to the target ratio.

[0012] The pH of the leach solution is adjusted to precipitate the desired ratio of charge material metals (charge materials) obtained above by a co-precipitation reaction 110 in one or more vessels. The NMC precipitates from the solution in granular form with sodium hydroxide or another strong base, and can be separated by filtration, typically as the hydroxide. This granular form precipitated by adjusting the pH of the leach solution is a cathode material precursor with the desired molar ratio for the target electrochemistry of the newly recycled battery. Sintering in a furnace 112 with lithium carbonate or another lithium salt forms the active cathode material 114 for the recycled Li-ion battery. In one example configuration, the active cathode material is LiNi x Mn y Co z O2, Ni x Mn y Co z NMC is synthesized by sintering (OH) and LiCO, where x, y, and z represent the respective molar ratios of Ni, Mn, and Co. In the example shown, the resulting recycled cathode material is NMC 111, which represents an equimolar composition of Ni, Mn, and Co. Other common chemistries include NMC 811, NMC 622, and NMC 532, although any suitable molar ratio can be achieved by adjusting the ratios in solution 106-108 and sintered. The recycled cathode material, when formed using soluble ions as further described below, performs better than the control material.

[0013] FIG. 2 is a flowchart 200 of a recycling method disclosed herein in which impurities are controlled in the formation of a cathode material precursor. Referring to FIGS. 1 and 2, a method for producing a cathode material precursor from a recycled battery stream based on soluble impurities includes, in step 201, leaching black mass from depleted lithium-ion batteries to obtain a leach solution containing a ratio of dissolved charge material metals and a concentration of soluble ionic impurities. The black mass generally contains mixed cathode and anode materials, as well as copper, iron, and aluminum obtained from the physical casing and current conductors of the recycled batteries. The leach solution 106 includes at least two charge material metals selected from the group consisting of Ni, Mn, Co, and Al, as shown in step 203. In the example herein, the ratios of Ni, Mn, and Co are confirmed by testing. While most impurities are removed by filtration, metal salts of Ni, Mn, and Co remain dissolved in the leach solution. In one embodiment, sulfuric acid is used as a leaching agent to form sulfate salts of the mixed charge material metals in solution.

[0014] Based on the results of the tested ratios, the ratio of charge material metals is adjusted to the selected ratio with additional charge material metal salts, as shown in step 205. In the particular example shown, the charge material metals are Ni, Mn, and Co, as shown in step 207. Minor amounts or impurities also remain in the adjusted leach solution. It has surprisingly been found that the microscopic features in the resulting precipitated charge material particles, such as internal voids, porosity, and pore volume, are affected by, and can be modified, shaped, or changed by, the amount of soluble ions of these impurities.

[0015] Therefore, the amount of soluble ionic impurities is examined and the concentration of the soluble ionic impurities is adjusted, as shown in step 209. The soluble ionic impurities include Li + , Na + , Mg 2+ , Ca 2+ , SO4 2- , NO3 -, PO4 3- , Cl - , K. + salts, or residual carbon, or other beneficial impurities that may be added or that may come from the source recycle stream. Different soluble ionic impurities can have different effects, and salts that appear to have beneficial performance effects include Li + , Na + , Mg 2+ , Ca 2+ , SO4 2- , or NO3 - In particular, Li + or Na + It is believed that the salts form internal voids and pore volume. It can be noted that the precursor charge material particles have not yet been sintered or mixed with significant amounts of Li, and therefore the Li in the precursor is considered a trace impurity.

[0016] The concentration of impurities to achieve beneficial results varies based on the source recycled material and the impurities added; generally, substantial impurity concentrations are on the order of 1-1000 ppm; beneficial effects may occur in narrower ranges such as 10-500 ppm, or even narrower ranges such as 15-350 ppm. Sodium and sulfur may also define other ranges.

[0017] As shown in step 213, the concentration of soluble ionic impurities can be increased by dissolving salts added to the leach solution having ions corresponding to those of the soluble ionic impurities. The beneficial effect of soluble ions can be achieved either through residual salts from the recycle stream and / or through salts added to the leach solution. Depending on the configuration, the adjustment of soluble ions can be performed before or after adjusting the charge material ratio. Conversely, as shown in step 215, the concentration of soluble ionic impurities can be reduced by diluting the leach solution with an aqueous solvent, i.e., water. Alternatively, or in addition, the concentration of soluble ionic impurities can be reduced by adding charge material metal salts having charge material metals corresponding to those of the leach solution while maintaining the charge material metal ratio. In this way, the amount of soluble ions relative to the charge material metal is reduced.

[0018] After adjusting the ratios (charge material metals) and concentrations (soluble ions), as disclosed in step 217, vessel 110 is used to co-precipitate the charge material metal salts to form a cathode material precursor having a selected ratio that benefits from increased soluble ions. In the example arrangement, this takes the form of charge material hydroxides precipitated from the leach solution, representing soluble ion impurities during co-precipitation in vessel 110. Determined by the soluble ion concentrations present or established (by addition / dilution), as shown in step 219, the cathode material precursor can have a target microstructure, meaning specific microstructural characteristics achieved by the type and concentration of soluble ions. In the example shown, as shown in step 221, the target microstructure includes at least one of a target particle pore size and a target porosity, and can be particularly affected by increasing the concentration of Li and / or Na to increase pore size and porosity, or decreasing Li and / or Na to decrease pore size or porosity.

[0019] 3A-3C are examples of microstructures including internal voids in charge material particles. The charge material precursor formed in vessel 110 of FIG. 1 is generally in particulate form and is used to form charge material particles 114 after sintering with Li in furnace 112. Referring to FIGS. 1-3C, FIGS. 3A-3C illustrate the difference in internal voids 316-1, 316-2, and 316-3 (collectively 316) in charge material precursor particles 314-1, 314-2, and 314-3 (collectively 314) obtained by increasing or decreasing the concentration of soluble ionic impurities in leach solution 106. FIG. 3A shows particle 314-1 formed when the concentration of soluble ionic impurities is increased to form a cathode material precursor having voids 316-1 of larger size and / or porosity than cathode material precursor formed without increasing the soluble ionic impurities. Conversely, Figure 3B shows particles 314-2 formed when the concentration of soluble impurities is reduced to form a cathode material precursor having voids 316-2 with a smaller size and / or porosity than a cathode material precursor formed without reducing the soluble ionic impurities. The concentration of soluble ions, particularly Li and Na, can be reduced by adding water or increased by adding control Li or Na (or other soluble ionic impurities different from the charge material metal ions, such as Ni, Mn, and Co). Figure 3C shows particles 314-C without discernible voids, also achieved by controlling the soluble ion concentration toward a desired microstructure.

[0020] It has been found that, in general, increasing the concentration of soluble impurities results in a larger target pore size or porosity, and decreasing the concentration of soluble impurities results in a smaller target pore size or porosity. Pore size, along with porosity, are properties that may be required by customer specifications for charge material precursors. As shown in Figures 4 and 5 below, adjusting or "steering" larger pore / void sizes, or generally the collective pore / void size of a batch of charge material precursor particles, can have beneficial performance effects.

[0021] Figure 4 shows the cycling performance results from soluble ionic impurities obtained with the method of Figure 2. Referring to Figures 1 and 4, a graph 400 of capacity retention 402 over the number of charging cycles 404 is shown. The recycled material 410 outperforms the control 412 or virgin (freshly decontaminated / purified) charged material.

[0022] The graph in Figure 4 shows the improvement in performance by adjusting the concentration of dissolved soluble ionic impurities. After adjusting the soluble ion concentrations, particularly Li and Na, a cathode material precursor exhibiting the intended microstructure of pore size and porosity is formed from the leach solution by co-precipitation of the charge material metals in the leach solution at 108.

[0023] While this disclosure provides exemplary methods and techniques for recycling batteries, such as spent NMC batteries, it is anticipated that these methods will also be applicable to the purification of Ni- and Co-containing ores. For example, various intermediate ore products, such as mixed sulfide precipitate (MSP), basic nickel carbonate (BCP), and mixed hydroxide product (MHP), are known in the art. Each contains Ni and Co, but is not fully purified to battery-grade nickel sulfate and cobalt sulfate due to the high cost and difficulty of separating the cobalt and nickel. However, using the methods disclosed herein, battery-grade cathode materials can be prepared from these ore materials at a much lower cost. Eliminating the energy and process steps required to separate the cobalt and nickel improves the efficiency of recycling steps similar to those shown in FIG. 1.

[0024] In particular, MSP, BCP, and MHP generally contain Mg and Ca as major impurities, which are also found in the black mass of recycled NMC batteries. The impurity levels in MHP are slightly higher than typical black mass. Furthermore, MHP has a nickel concentration of 30-40%, while black mass obtained from shredded NMC battery materials can also reach nickel concentrations within this range (over 30%). The handling characteristics of these ores are also similar to those of black mass. Therefore, these ore materials are expected to be usable in place of recycled battery black mass to produce battery-grade cathode materials.

[0025] Accordingly, the present disclosure further relates to a method for producing a cathode material precursor from an ore material, such as MSP, BCP, or MHP, having one or more charge materials. The method includes leaching the ore material to obtain a leach solution containing a ratio of dissolved charge material metal salts and a concentration of soluble ionic impurities. The method further includes adjusting the ratio of the charge material metal salts to a selected ratio with additional charge material metal salts and also adjusting the concentration of the soluble ionic impurities. After adjusting the ratios and concentrations, the charge material metal salts are co-precipitated to form a cathode material precursor. The cathode material precursor preferably has a target microstructure, including at least one of a target particle pore size and a target porosity.

[0026] While the systems and methods defined herein have been shown and described in detail with reference to embodiments thereof, those skilled in the art will understand that various changes in form and details may be made therein without departing from the scope of the invention as contained in the appended claims.

Claims

1. 1. A method for producing a cathode material precursor from a recycled battery stream, comprising: Leaching the black mass of a depleted lithium ion battery to obtain a leach solution containing a proportion of dissolved charge material metals and a concentration of soluble ionic impurities; adjusting the ratio of the charge material metals to a selected ratio with additional charge material metal salt; adjusting the concentration of soluble ionic impurities; After adjusting the ratio and the concentration, co-precipitating the charge material metal salts to form the cathode material precursor having the selected ratio; A method comprising:

2. 10. The method of claim 1, wherein the leaching solution comprises at least two charge material metals selected from the group consisting of Ni, Mn, Co, and Al.

3. 2. The method of claim 1, wherein the charge material metals are Ni, Mn, and Co.

4. The soluble ionic impurities are Li ＋ , Na ＋ , Mg ２＋ , Ca ２＋ , S.O. ４ ２－ , NO ３ － , P.O. ４ ３－ , Cl － , K. ＋ or a carbon residue.

5. The soluble ionic impurities are Li ＋ , Na ＋ , Mg ２＋ , Ca ２＋ , S.O. ４ ２－ , or NO ３ － 10. The method of claim 1, comprising a salt of

6. The soluble ionic impurities are Li ＋ or Na ＋ The method of claim 1, wherein the compound is a salt of

7. 10. The method of claim 1, wherein the concentration of soluble ionic impurities is increased by dissolving salts added to the leach solution having ions corresponding to the ions of the soluble ionic impurities.

8. 10. The method of claim 1, wherein the concentration of soluble ionic impurities is reduced by diluting the leach solution with an aqueous solvent.

9. The method of claim 8 , wherein the aqueous solvent is water.

10. 2. The method of claim 1, wherein the concentration of soluble ionic impurities is reduced by adding a charge material metal salt having a charge material metal corresponding to the charge material metal of the leach solution while maintaining the ratio of charge material metals.

11. The method of claim 1 , wherein the cathode material precursor has a target microstructure.

12. The method of claim 11 , wherein the target microstructure comprises at least one of a target particle void size and a target porosity.

13. 12. The method of claim 11, wherein the concentration of soluble ionic impurities is increased to form a cathode material precursor having a greater pore size or porosity than a cathode material precursor formed without the increased soluble ionic impurities.

14. 12. The method of claim 11, wherein the concentration of soluble ionic impurities is reduced to form a cathode material precursor having a smaller pore size or porosity than a cathode material precursor formed without reducing the soluble ionic impurities.

15. 12. The method of claim 11, wherein the target pore size or target porosity becomes larger when the concentration of the soluble impurities is increased.

16. 12. The method of claim 11, wherein the target pore size or target porosity becomes smaller when the concentration of the soluble impurities is decreased.

17. 1. A method for forming microstructures in a cathode material precursor from a recycled battery stream, comprising: measuring the concentration of soluble ionic impurities dissolved in a leachate solution obtained from the leaching of black mass of exhausted lithium-ion batteries; adjusting the concentration of dissolved soluble ionic impurities; After preparation, co-precipitating the charge material metals in the leach solution to form the cathode material precursor exhibiting the intended microstructure from the leach solution; A method comprising:

18. 20. The method of claim 17, wherein the concentration of soluble ionic impurities is increased to form a cathode material precursor having a greater pore size or porosity than a cathode material precursor formed without the increased soluble ionic impurities.

19. 20. The method of claim 17, wherein the concentration of soluble ionic impurities is reduced to form a cathode material precursor having a smaller pore size or porosity than a cathode material precursor formed without reducing the soluble ionic impurities.

20. 1. A method for forming microstructures in a cathode material precursor in a battery recycling environment to produce recycled charge material by adjusting the ratio of charge material metals from the black mass of a depleted battery, comprising: adjusting the concentration of soluble ions in the leach solution based on the microstructure formed in the particles coprecipitated from the leach solution; precipitating the formed microstructured charge material precursor particles from the leaching solution; A method comprising:

21. 10. The method of claim 1, wherein the soluble ionic impurities have a concentration of 1 to 1000 ppm (parts per million).

22. 10. The method of claim 1, wherein the soluble ionic impurities have a concentration of 10 to 500 ppm.

23. 10. The method of claim 1, wherein the soluble ionic impurities have a concentration of 15 to 350 ppm.

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