Recovery of anodes in regenerated batteries

Abstract

A method for regenerating anode material from a mixed regeneration stream obtained from a depleted Li-ion battery includes receiving a residual deposit from the cathode regeneration stream. This deposit is composed almost exclusively of graphite, which is used for the anode material in the regenerated battery. This deposit is obtained by acid leaching charge material from the lithium battery regeneration stream. A strong acid is added to the deposit to remove residual cathode and separator material, and the mixture is heated. The strong acid removes residual aluminum oxide from the separator by converting it to aluminum sulfate. The acid-treated deposit is washed to remove water-soluble contaminants, such as aluminum sulfate, which reacts with the aluminum oxide and sulfuric acid to produce substantially pure graphite. Any residual material remaining from the cathode regeneration step is also removed.

Description

[Background technology]

[0001] background In lithium-ion (Li-ion) batteries, which are widely used in automotive, consumer electronics, and industrial applications, cathode material recovery has become a key focus. However, the waste stream of reclaimed batteries typically involves indiscriminate agitation (crushing and shredding) of complete battery assemblies, resulting in a mixed mixture of cathode, anode, separator, and housing materials. In reclaimation procedures aimed at recovering cathode material, significant amounts of anode material are often unused and / or discarded. Summary of the Invention [Means for solving the problem]

[0002] overview Anode material regeneration processes recover secondary streams from the acid leaching of cathode material. Anode material regeneration involves collecting solid particulate residues from the acid leaching of cathode material from the mixed regeneration stream of disassembled batteries, which is rich in both cathode and anode material. Regeneration of charge materials from used or depleted batteries, such as that disclosed in U.S. Pat. No. 9,834,827 (incorporated herein by reference), tends to focus on cathode material due to the economics of collecting new material. However, anode materials such as graphite also have value as regenerated materials.

[0003] The configurations herein are based in part on the recognition that the modern trend toward the production of electric vehicles (EVs) will create a substantial demand for secondary (rechargeable) batteries, which correspondingly need to be disposed of or refurbished at the end of their useful life. Unfortunately, anode materials composed primarily of inexpensive graphite and / or carbon have not been found to be as feasible for large-scale refurbishment as their cathode materials. Accordingly, the configurations herein substantially overcome the drawbacks of anode refurbishment by receiving anode materials in conjunction with a complementary cathode refurbishment process, purifying already refined graphite and using it as the refurbished anode material. Because the graphite has already undergone much of the processing and refining involved in producing battery-grade graphite, refurbishment from used material can be more efficient than refining new graphite.

[0004] A method for regenerating anode material from a mixed regeneration stream obtained from a depleted Li-ion battery involves receiving a residual precipitate from the cathode regeneration stream through a membrane filter press. The precipitate contains approximately 6-7% by weight of alumina and 4-5% by weight of metal sulfate impurities. The remainder of the precipitate is almost exclusively graphite, which is used as the anode material in the regenerated battery. This precipitate is obtained by acid leaching the charge material from the lithium battery regeneration stream. A strong acid, such as 98% H2SO4, is added to the precipitate to remove residual cathode and separator material, and the mixture is heated to approximately 300°C. Once the cathode material, typically nickel, manganese, and cobalt, has been leached, aluminum oxide, which served as the separator material between the cathode and anode sides of the battery, is often left behind. The strong acid removes the aluminum oxide from the separator by converting it to aluminum sulfate. The acid-treated precipitate is then washed to remove water-soluble contaminants, such as aluminum sulfate, which has reacted with the aluminum oxide and sulfuric acid, producing substantially pure graphite. Also, any NMC (Ni, Mg, Co) remaining from the cathode regeneration step is removed.

[0005] Anode materials have received little attention in traditional regeneration due to the lower value of the raw material (graphite) compared to cathode materials. Traditional anode treatments also pose significant safety risks due to the use of hydrogen fluoride (HF) at very high temperatures. The approach proposed herein allows for cost-effective anode regeneration by using safer materials at much lower temperatures. Furthermore, the raw anode material for regeneration can be derived from the cathode regeneration approach disclosed in the '827 patent, as discussed above.

[0006] Further characterization includes the qualitative separation and classification of graphite types. Battery manufacturers use specified ratios of natural and synthetic graphite and further distinguish between different particle sizes due to the "flake" structure of natural graphite. The composition ratio of natural and synthetic graphite obtained in lithium battery regeneration streams is determined by testing or identifying the composition of the known source from which the regenerated batteries originate. The resulting pure graphite is sorted or labeled to maintain a composition ratio of synthetic graphite to natural graphite in the resulting substantially pure graphite, typically about 60 / 40% or 55 / 45%. The resulting harvested and purified graphite is approximately 98.5% pure, depending on several factors listed below.

[0007] Anode regeneration techniques that are substantially directed at recovering graphite from battery regeneration streams therefore benefit from the prior treatment and purity of the graphite used in first generation batteries. Anode material from depleted batteries is generally subjected to impurity treatment before use in first generation batteries. Any impurities in this anode material are confined to the surface of the graphite particles in the anode material.

[0008] Identifying reclaimed streams from EVs (electric vehicles) is further organized according to known vendors (automobile manufacturers) and the chemical composition of the Li-ion batteries used by each manufacturer. By maintaining a reclaimed stream sourced from batteries from a specific manufacturer, the composition of the incoming anode material can be known. By maintaining a homogeneous stream, this known composition can be reflected in the resulting pure graphite. In other words, incoming batteries from the same manufacturer, split 60 / 40% with a specific size composition of flake graphite, will be reclaimed to a similar composition of pure graphite if the incoming stream is limited to a known vendor.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the present invention will become apparent from the following description of specific embodiments of the invention 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]

[0010] [Figure 1] FIG. 1 is a flow diagram of the anode material regeneration process disclosed herein. [Figure 2A] 2 is a SEM (scanning electron microscope) graph of the regenerated charge material from the flow diagram of FIG. 1. [Figure 2B] 2 is a SEM (scanning electron microscope) graph of the regenerated charge material from the flow diagram of FIG. 1. [Figure 3] 2 is a graph showing charging characteristics using the charging material of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Detailed Description Electrochemical energy storage, typically implemented in the form of batteries, is becoming increasingly popular with the advent of electric and hybrid vehicles. The configurations described below are useful for regenerating aged or depleted charge-up materials from discarded batteries to recover active charge-up materials having specific NMC molar ratios, designated Ni:Mn:Co. More common types of cathode materials are 60%:20%:20% (622), 80%:10%:10% (811), 50%:30%:20% (532), and 33.3%:33.3%:33.3% (111). Cathode charge-up material precursors are derived from sulfate forms of Ni, Mn, and Co as defined in U.S. patents and U.S. patent applications, including U.S. Patent No. 9,834,827, U.S. Patent No. 10,522,884, U.S. Patent No. 10,741,890, and U.S. Patent Application Publication No. 16 / 164,952.

[0012] While elements of the cathode material tend to be more favorable for regeneration, recovery also generates anode charge material, composed primarily of graphite and carbon. Subsequent processing can also recover this anode charge material. Leaching of the cathode materials, such as nickel, manganese, and cobalt, and chemical and physical removal of incidental components, such as current collector metals and encapsulation materials, leaves graphite / carbon and approximately 15% alumina and sulfate materials. Subsequent treatment with strong acid and moderate heating can produce substantially pure graphite, as further described below.

[0013] FIG. 1 is a flow diagram of the anode material regeneration process disclosed herein. Referring to FIG. 1, in step 110, a graphite-containing precipitate is received as a by-product or waste stream from a battery cathode material regeneration operation. As outlined above, conventional approaches do not seek to recover the anode material (substantially graphite), whereas the approach herein regenerates the graphite as a complementary process to cathode regeneration. Thus, the received precipitate is charge material remaining from a regeneration stream of battery charge material previously acid-leached in regeneration. While any suitable regeneration or other process can be used to obtain the graphite precipitate, in certain configurations, the precipitate is obtained from previously leached charge material sourced from the NMC (nickel, manganese, cobalt) regeneration stream, typically representing previously used charge material used in charging cells from electric vehicles. One specific approach includes acid leaching according to the U.S. patent referenced above. EVs have batteries of considerable size and will continue to generate regeneration streams parallel to the vehicle's lifespan. More specifically, these NMC batteries are lithium-ion batteries (LIBs), which are widely applied in millions of electric vehicles (EVs) and plug-in electric vehicles.

[0014] Graphite in anode materials has morphology, or shape characteristics, that define the batch or quantity of bulk graphite. Natural graphite generally has flake characteristics and corresponding sizing, as further described below in Table II. Synthetic graphite is more expensive and generally has a powder or particulate texture. To produce anode materials from natural flake graphite, processing is required. Historically, this process yielded one ton of anode-grade graphite for every three tons of flake graphite concentrate. Even with modern production efficiencies, losses associated with graphite upgrading range from 30 to 50% before final purification. Described herein is a configuration for recycling electric vehicle lithium-ion batteries to recover high-purity graphite with morphologies and blends (natural and synthetic) specifically designed for electric vehicle applications. Because the graphite has already been upgraded for battery use, recovery efficiencies are on the order of 98%.

[0015] Traditionally, to bring graphite to final anode material specifications, anode companies upgrade the graphite from approximately 94% total graphitic carbon (Cg) to 99.95% Cg using treatment with hydrogen fluoride (HF) or inert high-temperature baking. The use of such expensive and environmentally unfriendly chemical and thermal processes is necessary to remove impurities from deep within the core of the material. However, the impurities found in BR graphite are on the surface of the graphite and are therefore more easily removed using cheaper, more environmentally friendly methods.

[0016] Because the graphite has been pre-processed for use in the battery, it is already refined and does not need to undergo the same treatments that first-generation natural and synthetic graphite must endure for initial deployment. Furthermore, because the approximate composition is known from the battery's construction, undesirable components can be identified by type and amount. Generally, the deposit from the regeneration stream has less than 11% impurities. More specifically, the deposit typically has less than 7% alumina and less than 5% metal sulfates. These parameters are known from the battery's construction and the cathode regeneration that precedes and provides for anode regeneration.

[0017] A method for regenerating anode material from a mixed regeneration stream of depleted Li-ion batteries includes, in step 112, washing the precipitate resulting from acid leaching of charge material from the regeneration stream of a lithium Li-ion battery. This removes any water-soluble components remaining from the NMC regeneration / leaching. An alternative approach involves separating the alumina via a frothing flotation process, based on alumina, which has a lower density than graphite, as disclosed in step 115. Aluminum is often used in current collectors in typical processes, and therefore can be expected to be approximately 7% of the precipitate.

[0018] As depicted in step 116, a strong acid, such as sulfuric acid 114, is added to the precipitate to remove residual cathode and separator material. This involves heating the mixture of strong acid and residual cathode and separator material to a temperature based on the expected purity of the resulting anode material. Given that there is remaining precipitate from a previous acid leaching of the cathode material, the strong acid will therefore be stronger (have a lower pH) than the acid used to acid leach the precipitate from the regeneration stream. Sulfuric acid is particularly suitable for leaching both the cathode and anode, and in a particular example, the strong acid is sulfuric acid at a concentration of at least 98%. Generally, increasing the temperature and heating time increases purity. Specific combinations to achieve the expected purity are shown in Table I.

[0019] [Table 1]

[0020] Other acids can be used. For example, a strong acid can be formed by combining sulfuric acid with one or more other acids based on the acid strength of the combined acids. A particular arrangement involves forming the strong acid from a mixture of about 80% sulfuric acid and 20% nitric acid. However, any suitable mineral acid or mixture of mineral acids can be used to produce the purified anode material as described above, for example, hydrochloric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid, and / or hydroiodic acid.

[0021] Regeneration of sulfuric acid may be carried out in a repeated manner for successive regeneration batches to recover sulfuric acid, as shown in step 118.

[0022] A further optional step includes performing a secondary leaching following the heating step to increase the purity of the produced graphite, as shown in step 120. The secondary leaching can be performed using one of dilute hydrochloric acid or dilute sulfuric acid.

[0023] Based on the information in Table I or alternative temperature and time parameters, further washing of the precipitate is performed to remove water-soluble contaminants to produce graphite of the expected purity, as shown in step 122. This removes water-soluble aluminum compounds.

[0024] As shown in step 126, sizing of the now refined deposit is performed to concentrate the material for a new reclaimed battery. Generally, this involves identifying the composition ratio of natural graphite and synthetic graphite obtained from the lithium battery reclaim stream used in the deposit and maintaining that composition ratio in the resulting substantially pure anode material. In other words, maintaining the morphology of the deposit as known from the incoming reclaim stream. Graphite morphology is provided in further detail in Table II.

[0025] [Table 2]

[0026] Synthetic graphite is a preferred material for lithium-ion batteries due to its purity, performance, and consistency. As an anode material, synthetic graphite allows for better cycling stability, faster charging, more consistent quality, and rapid production scalability. The chart also shows that synthetic graphite offers substantial cost advantages. Consequently, battery manufacturers, often driven by the receiving automobile manufacturers, specify the composition of their batteries. By identifying this composition (based on the morphology of the graphite in the battery) and maintaining it through remanufacturing, the battery can be resold to manufacturers that specify the specific composition.

[0027] High-quality synthetic graphite is synthesized from needle coke. The global market for needle coke is highly fragmented and dominated by a few large manufacturers, but is constrained by the technical requirements of crude oil, the by-product of which needle coke is refining. Increasing demand for needle coke in the steel and lithium-ion battery industries, as well as tightening environmental regulations, appear to be creating strong price headwinds.

[0028] Natural graphite is sourced from mines around the world, but purity and flake size vary widely. Converting natural graphite into the size-selected, ultra-pure, spheroidized material required for battery applications requires rigorous selection of starting materials to ensure long-term consistency and stability. Graphite is a widely distributed mineral on Earth, but not all mines produce the consistent, large flake material needed as a starting point to economically produce the desired product specifications. Therefore, it is typically preferable to produce substantially pure graphite with a morphology based on the specified morphology of natural graphite. The resulting product is substantially pure graphite, as depicted in step 128.

[0029] Figures 2A-2B are SEM (scanning electron microscope) graphs of the recycled charge material from the flow diagram in Figure 1. Referring to Figures 2A and 2B, the impact of the purification process is also illustrated by SEM. Figure 2A shows an SEM image of the original graphite from a used lithium-ion battery, and Figure 2B shows the graphite purified according to the process in Figure 1. As shown in Figure 2A, the graphite exhibits severe agglomeration and many residues. However, after the purification process, Figure 2B shows that the agglomeration and residues have been reduced or even disappeared, indicating better refined single-particle quality in the graphite. This indicates that the regeneration process effectively removed impurities. The lack of significant changes in the morphology of the graphite particles indicates that the morphology of the graphite was not destroyed during the purification process. In addition, the surface of the recycled graphite is smoother and more transparent than the original graphite, indicating that impurities have been significantly reduced.

[0030] Figure 3 is a graph of the charging characteristics using the charging material of Figure 1. Figure 3 shows the rate performance of the recovered graphite anode. The discharge capacity of the regenerated graphite was 377.3 mAh / g at 0.1 C, which is quite comparable to that of commercial graphite.

[0031] 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 can be made therein without departing from the scope of the invention as encompassed by the appended claims.

Claims

1. Cleaning deposits resulting from acid leaching of charge material from a regeneration stream of a Li-ion battery; adding a strong acid to the deposit to remove residual cathode and separator material to form a mixture; heating the mixture of the precipitate, the strong acid, the residual cathode, and the separator material to 250°C to 350°C; washing the precipitate of the mixture to remove water soluble contaminants to produce purified graphite; 1. A method for regenerating anode material from a mixed regeneration stream of a depleted Li-ion battery, comprising:

2. 10. The method of claim 1, further comprising separating alumina based on alumina having a lower density than said graphite via a froth flotation process.

3. The method described in claim 1, wherein the regeneration flow of the Li-ion battery is a regeneration flow of NMC (nickel, manganese, cobalt).

4. 10. The method of claim 1, wherein the strong acid has a lower pH than the acid used in the acid leaching of the precipitate from the regeneration stream.

5. 5. The method of claim 4, wherein the strong acid is sulfuric acid at a concentration of at least 98%.

6. Identifying the composition ratio of natural graphite and synthetic graphite obtained from the regeneration process of the Li-ion battery; maintaining said composition ratio in the produced substantially pure anode material; and The method of claim 1 further comprising:

7. 10. The method of claim 1, further comprising performing a secondary leaching following the step of heating to increase the purity of the produced graphite.

8. 8. The method of claim 7, wherein the secondary leaching is carried out with one of dilute hydrochloric acid or dilute sulfuric acid.

9. 10. The method of claim 1, further comprising forming the strong acid from a mixture of about 80% sulfuric acid and 20% nitric acid.

10. 10. The method of claim 1, wherein the strong acid is a mineral acid or mixture of mineral acids comprising an acid selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid, and hydroiodic acid.

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