A method for separating and detecting metal particles in a battery material

Abstract

The application belongs to the technical field of batteries, and discloses a separation method and a detection method for metal particles in battery materials. The method comprises the following steps: immersing a battery material to be detected in first pure water to obtain a first mixed solution; screening the first mixed solution to obtain oversize materials; immersing the oversize materials in a first ethanol aqueous solution to obtain a second mixed solution; configuring a double-solvent system composed of a second ethanol aqueous solution and second pure water; mixing the second mixed solution with the ethanol aqueous solution layer of the double-solvent system and performing layered sedimentation; and collecting a sediment in the pure water layer of the double-solvent system, wherein the sediment contains the metal particles. The application uses a double-solvent system of an ethanol aqueous solution and pure water, and utilizes the principle of layered sedimentation to realize physical separation of battery materials and metal particles. The separated metal particles can maintain the original morphology, and through qualitative and quantitative detection, data support is provided for the tracing of the metal particles.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a method for separating and detecting metal particles in battery materials. Background Technology

[0002] During battery manufacturing, materials come into contact with components such as copper, iron, zinc, and stainless steel. Wear and tear on these metal components can result in the presence of small amounts of elemental copper, iron, zinc, stainless steel, and metal oxides within the battery material. Small amounts of stainless steel and iron particles in the cell may puncture the separator, potentially causing thermal runaway. Small amounts of copper particles in the cell will gradually dissolve into copper ions during aging through charge-discharge cycles, migrating from the positive electrode to the negative electrode surface and reverting to elemental copper. Upon further aging, these ions can form copper dendrites, leading to mild self-discharge and capacity decay, or in severe cases, puncturing the separator and causing thermal runaway. Therefore, metal particles pose a significant safety risk, necessitating their separation and detection in battery materials. Summary of the Invention

[0003] In view of the problems existing in the background art, the purpose of the present invention is to provide a method for separating and detecting metal particles in battery materials.

[0004] To achieve the above objectives, the present invention adopts the following approach.

[0005] A method for separating metal particles in battery materials, comprising the following steps:

[0006] The battery material to be tested was immersed in a first pure water to obtain a first mixed solution;

[0007] The first mixed solution is sieved to obtain the residue on the sieve.

[0008] The sieve residue is immersed in a first aqueous ethanol solution to obtain a second mixed solution;

[0009] A dual-solvent system consisting of a second aqueous ethanol solution and a second pure water was prepared.

[0010] The second mixed solution is mixed with the ethanol-water aqueous layer of the dual-solvent system, and then subjected to stratification and sedimentation.

[0011] Sediment containing the metal particles is collected in the pure water layer of the dual-solvent system.

[0012] Optionally, the volume fraction of ethanol in the first and second aqueous ethanol solutions is 50% to 80%.

[0013] Optionally, the volume fraction of ethanol in the first and second aqueous ethanol solutions is 60% to 70%.

[0014] Optionally, the powder particle density of the battery material is less than 4 g / cm³. 3 The particle size Dv50 is less than 10 μm.

[0015] Optionally, the battery material includes one or more of lithium iron phosphate cathode material, conductive carbon, and polyvinylidene fluoride.

[0016] Optionally, a dispersant may be added to the first pure water, the dispersant including one or more of X-3204, PVP, D300, and TMN-6.

[0017] A method for detecting metal particles in battery materials, comprising detecting the sediment obtained by the above separation method.

[0018] Optionally, before testing the sediment, the method further includes the following step: immersing the sediment in a weak oxidizing acid solution containing antioxidants and corrosion inhibitors for reaction.

[0019] Optionally, the reaction conditions are a water bath reaction at 40–80°C for 0.5–2 hours.

[0020] Optionally, the weak oxidizing acid includes one or more of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0021] Optionally, the sulfuric acid solution has a mass fraction of 10% to 30%, the hydrochloric acid solution has a mass fraction of 5% to 20%, and the phosphoric acid solution has a mass fraction of 15% to 30%.

[0022] Optionally, the antioxidants include ascorbic acid, tea polyphenols, acetaldehyde oxime, acetone oxime, hydrazine hydrate, H2O2, and N. a2 One or more of S2O3, Na2SO3, NaHSO3, and FeSO4.

[0023] Optionally, the corrosion inhibitor includes one or more of the following: benzotriazoles such as benzotriazole, 5-methyl-1H-benzotriazole, ethylbenzotriazole, propylbenzotriazole, and butylbenzotriazole; imidazoles such as benzimidazole and thiabendazole; and thiazoles such as 2-methylbenzothiazole and 2-mercaptobenzothiazole.

[0024] Optionally, the mass concentration of the corrosion inhibitor is 5% to 15%.

[0025] Optionally, the sediment can be detected using scanning electron microscopy combined with energy dispersive spectroscopy.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] This invention uses a dual solvent system of ethanol aqueous solution and pure water, and utilizes the principle of stratification sedimentation to achieve physical separation of battery materials and metal particles.

[0028] The battery material and metal particles of this invention are physically separated, so the metal particles can maintain their original morphology. Qualitative and quantitative detection provides data support for tracing the origin of the metal particles.

[0029] This invention uses a combination of low-concentration acid, corrosion inhibitor, and antioxidant to remove zinc and zinc oxide, iron and iron oxide, copper oxide, etc. from metal particles, while retaining elemental copper and stainless steel, thus enabling targeted detection of elemental copper and stainless steel. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram illustrating the sedimentation effect of the dual-solvent system with different concentrations according to the present invention;

[0032] Figure 2 This is a schematic diagram of the separation device of the present invention.

[0033] In the diagram, 1 is a glass tube; 2 is a metal particle collection port; and 3 is a central discharge port. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0036] An embodiment of the present invention provides a method for separating metal particles in battery materials, comprising the following steps:

[0037] S1: Immerse the battery material to be tested in a first pure water to obtain a first mixed solution;

[0038] S2: Sieve the first mixed solution to obtain the residue on the sieve;

[0039] S3: Immerse the sieve residue in a first aqueous ethanol solution to obtain a second mixed solution;

[0040] S4: Prepare a dual-solvent system consisting of a second aqueous ethanol solution and a second pure water;

[0041] S5: Mix the second mixed solution with the ethanol-water solution layer of the dual-solvent system and allow it to settle in layers;

[0042] S6: Collect sediment in the pure water layer of the dual solvent system, the sediment containing the metal particles.

[0043] In steps S3 to S6, the dual-solvent system consists of a second ethanol aqueous solution and a second pure water, with the second ethanol aqueous solution on the upper layer and the second pure water on the lower layer, and a transition layer between them. When the second mixed solution is transferred to the ethanol aqueous solution layer of the dual-solvent system, the second mixed solution and the second ethanol aqueous solution are miscible. At this time, the ethanol aqueous solution layer of the dual-solvent system contains the sieve residue.

[0044] In the sieve residue, battery materials, with their lower density and smaller powder size, are essentially suspended in the ethanol-water solution layer due to buoyancy and Brownian motion, making it difficult for them to penetrate the transition layer. Conversely, metal particles such as copper, zinc, iron, and stainless steel, with their larger density and particle size, easily pass through the ethanol-water solution layer and the transition layer, settling to the bottom of the pure water layer. Utilizing the difference in settling velocities between battery materials and metal particles allows for effective physical separation of the two.

[0045] Optionally, the volume fraction of ethanol in the first and second aqueous ethanol solutions is 50% to 80%.

[0046] In ethanol-water solutions with a volume fraction of 80% or higher and in pure water, the interfacial tension is relatively high, causing metal particles to easily aggregate at the interface layer, resulting in poor stratification and sedimentation. In ethanol-water solutions with a volume fraction of less than 50% and in pure water, the concentration difference is small, resulting in a small difference in the sedimentation velocity between battery material powder and metal particles, also leading to poor stratification and sedimentation.

[0047] Optionally, the volume fraction of ethanol in the first and second aqueous ethanol solutions is 60% to 70%.

[0048] Actual measurements showed that the stratification and sedimentation effect of the ethanol aqueous solution and pure water was best when the volume fraction of ethanol in the first and second ethanol aqueous solutions was 60% to 70%.

[0049] Optionally, the particle density of the battery material powder is less than 4 g / cm³. 3The particle size Dv50 is less than 10 μm.

[0050] The suspension of powder particles is influenced by a combination of factors, including gravity, buoyancy, and the interaction forces between particles and between particles and the solvent (essentially driven by polar and non-polar functional groups). The lower the particle density and size, the greater the influence of Brownian motion and other interaction forces, resulting in suspension in an ethanol-water solution. Conversely, if the particle density or size is larger, the influence of Brownian motion and other interaction forces is less pronounced, with gravity and buoyancy being the primary factors. If gravity is greater than buoyancy, the particles will sink; if gravity is less than buoyancy, the particles will float; and if gravity and buoyancy are roughly equal, the particles will remain suspended.

[0051] When the particle density and particle size of the battery material powder are both small, its settling velocity in the ethanol aqueous solution is significantly lower than that of metal particles, and it is difficult for it to penetrate the interface formed by the ethanol aqueous solution and pure water. Therefore, effective physical separation of battery materials and metal particles can be achieved.

[0052] Generally speaking, the higher the particle density and the larger the particle size of the metal particles, the better the separation effect of the battery material powder from them.

[0053] The particle density of battery materials is the density obtained by dividing the particle mass by the particle volume. It can be determined by methods such as the Archimedes method or the He gas displacement method.

[0054] The particle size Dv50 of the battery material can be measured using a laser diffraction particle size distribution measuring instrument (Mastersizer3000) according to the particle size distribution laser diffraction method (see GB / T19077-2016 for details). The average particle size is represented by the median value Dv50 of the volume distribution.

[0055] Optionally, the battery material includes one or more of lithium iron phosphate cathode material, conductive carbon, and polyvinylidene fluoride.

[0056] Taking lithium iron phosphate cathode material as an example, its particle density is 3.6 g / cm³. 3 The particle density of lithium iron phosphate is smaller than that of metal particles. When the particle size of lithium iron phosphate is smaller than or equal to that of metal particles, its settling velocity in an ethanol-water solution is lower than that of metal particles, thus enabling separation between lithium iron phosphate and metal particles.

[0057] Optionally, a dispersant may be added to the first pure water.

[0058] Since battery materials are insoluble in pure water, adding a dispersant to pure water can make the battery material powder mix more evenly with the pure water.

[0059] Optionally, the dispersant includes one or more of X-3204, PVP, D300, and TMN-6.

[0060] An embodiment of the present invention provides a method for detecting metal particles in battery materials, comprising the following steps:

[0061] S1: Immerse the battery material to be tested in a first pure water to obtain a first mixed solution;

[0062] S2: Sieve the first mixed solution to obtain the residue on the sieve;

[0063] S3: Immerse the sieve residue in a first aqueous ethanol solution to obtain a second mixed solution;

[0064] S4: Prepare a dual-solvent system consisting of a second aqueous ethanol solution and a second pure water;

[0065] S5: Mix the second mixed solution with the ethanol-water solution layer of the dual-solvent system and allow it to settle in layers;

[0066] S6: Collect sediment in the pure water layer of the dual solvent system, wherein the sediment contains the metal particles;

[0067] S7: Detect the sediment.

[0068] In step S7, since the metal particles have been physically separated and the separated metal particles can maintain their original morphology, they can be qualitatively and quantitatively detected as needed using existing detection tools.

[0069] Optionally, the sediment can be detected using scanning electron microscopy combined with energy dispersive spectroscopy.

[0070] The use of scanning electron microscopy combined with energy dispersive spectroscopy enables qualitative and quantitative detection of metal particles, overcoming the challenge of ICP detection when the number of metal particles is small. It also enables the characterization of the particle size and morphology of metal particles, providing data support for tracing the source of metal particle introduction.

[0071] Optionally, prior to step S7, the sediment is immersed in a weak oxidizing acid solution containing antioxidants and corrosion inhibitors for reaction.

[0072] Zinc and its oxides, iron and its oxides, and copper oxides are easily dissolved and removed in acidic environments. Stainless steel is acid-resistant and does not easily corrode. Antioxidants can remove some oxygen, inhibiting the oxidative dissolution of copper particles. Corrosion inhibitors can form covalent and coordinate bonds with copper atoms, alternating to form chain-like polymers, thus forming a multi-layered protective film on the surface of copper particles, preventing the oxidation of copper and its reaction with acids, and inhibiting the dissolution of copper. By immersing the sediment in a weakly oxidizing acid solution containing antioxidants and corrosion inhibitors, targeted detection of copper and stainless steel can be achieved.

[0073] Optionally, the reaction conditions are a water bath reaction at 40–80°C for 0.5–2 hours.

[0074] Optionally, the weak oxidizing acid includes one or more of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0075] Optionally, the sulfuric acid solution has a mass fraction of 10%–30%, the hydrochloric acid solution has a mass fraction of 5%–20%, and the phosphoric acid solution has a mass fraction of 15%–30%.

[0076] Optionally, the antioxidant includes one or more of ascorbic acid, tea polyphenols, acetaldehyde oxime, acetone oxime, hydrazine hydrate, H2O2, Na2S2O3, Na2SO3, NaHSO3, and FeSO4.

[0077] Optionally, the corrosion inhibitor includes one or more of the following: benzotriazoles such as benzotriazole, 5-methyl-1H-benzotriazole, ethylbenzotriazole, propylbenzotriazole, and butylbenzotriazole; imidazoles such as benzimidazole and thiabendazole; and thiazoles such as 2-methylbenzothiazole and 2-mercaptobenzothiazole.

[0078] Optionally, the concentration of the corrosion inhibitor is 5% to 15% by mass.

[0079] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0080] Example 1

[0081] Operating steps:

[0082] (1) Weigh 1 kg of lithium iron phosphate powder to be tested, add 10 L of pure water and 10 g of dispersant X-3204, and stir and mix thoroughly.

[0083] (2) Use a wet sieve to sieve the material and repeat the operation until all materials are sieved. Wash the remaining powder and metal particles on the sieve with water into a beaker, vacuum filter the material onto the filter membrane, and then rinse and dry it.

[0084] (3) Add the dried sieve residue to 50 mL of 65% ethanol aqueous solution, sonicate and stir until homogeneous.

[0085] (4) The mixture of sieve residues is transferred to a dual solvent system consisting of 65% ethanol aqueous solution and water for stratification and sedimentation.

[0086] (5) Use vacuum filtration to collect metal particles at the bottom of the aqueous solution onto the filter membrane.

[0087] Example 2

[0088] Example 2 is largely the same as Example 1, except that step (6) is added:

[0089] (6) Rinse and dry the filter membrane, and place it under a scanning electron microscope and energy dispersive spectroscopy instrument to scan and count the metal particles.

[0090] Example 3

[0091] Example 3 is largely the same as Example 2, except that step (6) is:

[0092] (6) The filter membrane enriched with metal particles was transferred to a 20% sulfuric acid solution containing 5g of antioxidant ascorbic acid and 8mL of corrosion inhibitor benzotriazole. The mixture was reacted in a water bath at 60°C for 1 hour. The mixture was then filtered onto the filter membrane and dried. The metal particles were then scanned and counted under a scanning electron microscope and an energy dispersive spectroscopy instrument.

[0093] Example 4

[0094] To investigate the applicability of this invention to ethanol-water solutions of different concentrations in a dual-solvent system, lithium iron phosphate was used as an example. 0.5 g of lithium iron phosphate powder was weighed, and a certain number of copper particles were added. Ethanol-water solutions of different concentrations were then added, and physical separation was performed using a sedimentation method. The separation results are as follows: Figure 1 As shown.

[0095] Figure 1 In the sedimentation column, the upper layer is an ethanol-water solution, and the lower layer is pure water, forming an interface layer. The powder and elemental copper are shown as small circles in the figure. It can be observed that the stratification and sedimentation effects are poor when the ethanol-water solution volume fraction is below 50% or above 80% and pure water is used; sedimentation is slow, and a large number of metal particles accumulate in the interface layer. The stratification and sedimentation effects are best when using 60%, 65%, and 70% ethanol-water solutions and pure water, with no significant difference between the three. Metal particles settle quickly, and there is no large accumulation of metal particles in the interface layer; after 5–15 minutes, only a small number of metal particles remain suspended in the ethanol layer.

[0096] Example 5

[0097] To investigate the applicability of this invention to different metal particles in powder systems, lithium iron phosphate was used as an example. 0.5g of lithium iron phosphate powder was weighed and a certain number of Cu and CuO, Zn and ZnO, Fe and Fe2O3, and 304 stainless steel particles were added to it. Physical separation was performed by layer sedimentation, and the metal particles were collected by filtration. The particles were classified and counted using scanning electron microscopy and energy dispersive spectroscopy. The results are shown in Table 1.

[0098] Table 1

[0099]

[0100] It can be seen that the stratified sedimentation method in this invention can effectively separate various types of metal particles in lithium iron phosphate powder.

[0101] Example 6

[0102] To examine the applicability and effectiveness of this invention for the directional detection of elemental copper or stainless steel, the metal particles Cu and CuO, Zn and ZnO, Fe and Fe2O3, and 304 stainless steel collected in Example 4 were transferred to a mixed solution system of low-concentration H2SO4 solution, ascorbic acid, and corrosion inhibitor. The mixture was allowed to stand in a water bath at 50°C for 1–2 hours. The particles were then collected by filtration and classified and counted using scanning electron microscopy and energy dispersive spectroscopy. The results are shown in Table 2.

[0103] Table 2

[0104]

[0105] It can be found that the reaction system of low-concentration H2SO4 solution, antioxidant and corrosion inhibitor can completely remove metal oxides after standing in a water bath at 50℃ for 1 to 2 hours, and can be used for targeted detection of elemental copper or stainless steel.

[0106] like Figure 2 As shown, this invention enables the separation of powder and metal particles from the oversize material in a stratified sedimentation column. 1- Glass tube, 53cm long, 3cm in diameter. 2- Metal particle collection port, consisting of a conical bottom and a water outlet; the cone has an opening angle of 30-60°; the water outlet is 2cm long and 5mm in diameter. 3- Central discharge port, located in the middle of the glass tube, mainly used for discharging the upper layer of powder after metal particle separation; 3cm long and 5mm in diameter.

[0107] The foregoing has provided a detailed description of a method for separating and detecting metal particles in battery materials provided by the present invention. Specific embodiments have been used to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for separating metal particles in battery materials, comprising the following steps: The battery material to be tested was immersed in a first pure water to obtain a first mixed solution; The first mixed solution is sieved to obtain the residue on the sieve. The sieve residue is immersed in a first aqueous ethanol solution to obtain a second mixed solution; Prepare a dual-solvent system consisting of a second aqueous ethanol solution and a second pure water; The second mixed solution is mixed with the ethanol-water aqueous layer of the dual-solvent system, and then subjected to stratification and sedimentation. Sediment containing metal particles is collected in the pure water layer of the dual-solvent system. The powder particle density of the battery material is less than 4 g / cm³. 3 The volume fraction of ethanol in the first and second aqueous ethanol solutions is 50% to 80%.

2. The separation method according to claim 1, characterized in that, The volume fraction of ethanol in the first and second aqueous ethanol solutions is 60% to 70%.

3. The separation method according to claim 1, characterized in that, The particle size Dv50 of the battery material is less than 10 μm.

4. The separation method according to claim 3, characterized in that, The battery materials include one or more of lithium iron phosphate cathode materials, conductive carbon, and polyvinylidene fluoride.

5. The separation method according to any one of claims 1-4, characterized in that, A dispersant is added to the first pure water, wherein the dispersant includes one or more of X-3204, PVP, D300, and TMN-6.

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