Method for detecting metal foreign matter in electrode active material
By dissolving the electrode active material to extract metal foreign matter in aqueous nitric acid solution and plating it on the electrode to determine, the problem of difficulty in detecting fine metal foreign matter in the prior art is solved, and quantitative analysis of a very small amount of metal foreign matter is achieved.
Patent Information
- Application Number
- CN202380077524.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-14
- Filing Date
- 2023-12-15
- Publication Date
- 2025-06-06
AI Technical Summary
It is difficult to detect and quantitatively analyze fine metal foreign matters with a particle size of less than 40 μm in electrode active materials, especially low-content metal foreign matters with a content of less than 1 ppm.
The amount of metal foreign matter plated by dissolving the electrode active material in aqueous nitric acid solution to form a metal foreign matter extraction solution, the metal foreign matter is plated on the electrode, and the amount of plated metal foreign matter is determined by ICP or anode dissolution voltammetry.
Quantitative detection of a very small amount of fine metal foreign matter in the electrode active material is achieved, the matrix effect of the metal component is reduced, and metal foreign matter with a particle size of less than 40 μm and a content of less than 1 ppm can be detected.
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for detecting metallic foreign matter in an electrode active material, and more particularly to a method for detecting fine metallic foreign matter of less than 40 μm which is difficult to remove in advance and quantitatively analyzing its content. Background Art
[0002] In secondary battery materials, metallic foreign matter contained in the electrode active material may precipitate on the negative electrode surface during charge and discharge, thereby forming an internal short circuit, which may cause capacity reduction, low voltage failure, and / or fire. Therefore, for the quality management of secondary batteries, it is necessary to measure and evaluate the amount of metallic foreign matter in the electrode active material.
[0003] Therefore, a method of removing metallic foreign matter from an electrode active material using a magnetic separator is generally used, or a method of measuring the amount of metallic foreign matter in an electrode active material by ICP analysis and managing the amount to keep it within a certain range is used. However, these conventional methods cannot detect metallic foreign matter of small particle size. Specifically, metallic foreign matter with a particle size of less than 40 μm is difficult to remove in advance using a magnetic separator, and low-content metallic foreign matter with a content of less than 1 ppm is difficult to measure by ICP analysis due to the significant influence of the matrix effect caused by the electrode active material components.
[0004] Therefore, in order to manage the amount of metallic foreign matter in electrode active materials, it is necessary to develop a method that can detect fine non-magnetic metallic foreign matter and quantitatively analyze its content. Summary of the invention
[0005] Technical issues
[0006] In order to solve the above-mentioned problems, one aspect of the present invention provides a detection method capable of quantitatively detecting a very small amount of fine metal foreign matter contained in an electrode active material.
[0007] Technical Solution
[0008] According to one aspect of the present invention, a method for detecting metal foreign matter in an electrode active material is provided, wherein the method comprises: a first step of dissolving the electrode active material in an aqueous nitric acid solution to form a metal foreign matter extraction solution; a second step of plating the metal foreign matter in the metal foreign matter extraction solution on an electrode; and a third step of determining the amount of metal foreign matter plated on the electrode.
[0009] In this case, the electrode active material may include metal foreign matter having a particle size of 40 μm or less, wherein the metal foreign matter may be Cu.
[0010] In addition, the electrode active material may be a positive electrode active material, wherein the D of the positive electrode active material50 It can be 1 to 40 μm.
[0011] On the other hand, the first step is preferably carried out under the condition that the solubility of the metal foreign matter is 80% or more and the solubility of the metal component of the electrode active material is 50% or less. Specifically, the first step can be carried out by dissolving the electrode active material in a nitric acid aqueous solution having a nitric acid concentration of 20 to 40% by weight, and then stirring the resulting product at room temperature for at least 20 hours.
[0012] On the other hand, the second step may be performed by immersing the electrode in the metallic foreign matter extraction solution and then applying a current so as to have a potential difference in which the metal component of the electrode active material is not reduced and the metallic foreign matter to be extracted is reduced, wherein the electrode may be a carbon electrode.
[0013] Thereafter, the third step may be performed by dissolving the metal foreign matter plated on the electrode using an acid and then measuring the amount of the dissolved metal foreign matter by inductively coupled plasma (ICP) or anodic stripping voltammetry.
[0014] When the ICP method is used, the acid may include hydrochloric acid, nitric acid, hydrogen peroxide, or a mixture thereof, and may preferably include at least one of hydrochloric acid and nitric acid and hydrogen peroxide.
[0015] Beneficial Effects
[0016] According to the detection method of the present invention, a nitric acid aqueous solution is used to selectively recover metal foreign matter in an electrode active material, the metal foreign matter is selectively plated on an electrode by an electrochemical method, thereby extracting the metal foreign matter from the electrode active material, and then the amount of the metal foreign matter plated on the electrode is measured, thereby minimizing the matrix effect of the metal components in the electrode active material, thereby quantitatively analyzing the amount of metal foreign matter with a particle size of less than 40 μm and a content of less than 1 ppm. DETAILED DESCRIPTION
[0017] The present invention will be described in detail below.
[0018] By repeatedly studying the management of metal foreign matter in electrode active materials that affects battery performance and safety, the present inventors have designed a method for selectively recovering metal foreign matter in electrode active materials using an aqueous nitric acid solution, plating the metal foreign matter on an electrode and then measuring the amount of metal foreign matter plated on the electrode, thereby minimizing the matrix effect of the metal component in the electrode active material, thereby quantitatively detecting the amount of metal foreign matter with a particle size of less than 40 μm and a content of less than 1 ppm, thereby completing the present invention.
[0019] Specifically, the method for detecting metal foreign matter in electrode active materials according to the present invention includes: a first step of dissolving the electrode active material in an aqueous nitric acid solution to form a metal foreign matter extraction solution; a second step of plating the metal foreign matter in the metal foreign matter extraction solution on an electrode; and a third step of measuring the amount of metal foreign matter plated on the electrode.
[0020] The following is a detailed description of the method for detecting metallic foreign matter in an electrode active material according to the present invention.
[0021] (1) Step 1: Dissolving Metal Foreign Matter
[0022] First, the electrode active material is dissolved in an aqueous nitric acid solution, and metallic foreign matter is dissolved out to form a metallic foreign matter extraction solution (first step).
[0023] In this case, the electrode active material may include a metal foreign substance having a particle size of 40 μm or less, and the metal foreign substance may be at least one selected from the group consisting of Cu, Zn, Ti, Sn, Pb, and alloys thereof, and may preferably be Cu.
[0024] The electrode active material may be a positive electrode active material or a negative electrode active material, and may preferably be a positive electrode active material. 50 It may be 1 to 40 μm, preferably 1 to 25 μm.
[0025] The first step is to selectively extract the metallic foreign matter contained in the positive electrode active material, using a nitric acid aqueous solution as an extraction solvent. Specifically, the first step can be performed in the following manner: adding the electrode active material to the nitric acid aqueous solution, and stirring the resulting product for a certain period of time, so that the metal in the electrode active material is dissolved.
[0026] In order to improve the extraction rate of metal foreign matter, the first step is preferably carried out under the condition that the solubility of the metal foreign matter is more than 80% and the solubility of the metal components constituting the electrode active material, such as Ni, Co, Mn, Al (for convenience, referred to as "metal components of electrode active materials") is less than 50%. The solubility of metal foreign matter and the solubility of the metal components of the electrode active material vary with the concentration of the nitric acid aqueous solution, the dissolution time and the dissolution temperature. Therefore, by appropriately controlling the concentration of the nitric acid aqueous solution used and the dissolution conditions of the metal ions according to the type of metal foreign matter to be detected, the solubility of the metal foreign matter and the solubility of the metal components of the electrode active material can be adjusted.
[0027] For example, when the metal foreign matter to be detected is copper (Cu), preferably, a nitric acid aqueous solution having a nitric acid concentration of 20 to 40% by weight is used. This is because, when the concentration of the nitric acid aqueous solution meets the above range, the solubility of copper increases and the solubility of transition metals becomes relatively low, resulting in an increase in the extraction rate of copper.
[0028] In addition, in the case where the metal foreign matter to be detected is copper (Cu), preferably, the electrode active material is dissolved in an aqueous nitric acid solution, and then stirred at room temperature, for example, at 10° C. to 30° C. for at least 1 hour, preferably for 1 hour to 30 hours, to dissolve the metal foreign matter. When the dissolution temperature and time meet the above ranges, the solubility of copper in the aqueous nitric acid solution will increase relative to the metal component of the electrode active material, and thus the copper ratio in the extraction solution can be increased.
[0029] However, when the type of metal foreign matter to be detected changes, the concentration of the nitric acid aqueous solution and the dissolution conditions may also change accordingly.
[0030] The metallic foreign matter in the electrode active material is extracted in the same manner as described above, and then the solution containing the metallic foreign matter is separated by a method such as centrifugation to obtain a metallic foreign matter extraction solution.
[0031] As in the present invention, when the difference between the solubility of the metal component of the electrode active material and the solubility of the metal foreign matter is used to dissolve the metal, the amount of the metal component of the electrode active material dissolved can be minimized. Specifically, using the above method, the content of the metal component of the electrode active material contained in the extraction solution can be reduced to a level of 1 / 2 to 1 / 3 or less relative to the content contained in the electrode active material.
[0032] (2) Step 2: Plating
[0033] Subsequently, the metallic foreign matter contained in the metallic foreign matter extraction solution obtained in the first step is plated on the electrode (second step).
[0034] The second step of selectively extracting the metallic foreign matter from the metallic foreign matter extraction solution may be performed, for example, by immersing an electrode in the metallic foreign matter extraction solution and applying a current to the electrode. In this case, the current may be applied so as to have a potential difference so that the metal component of the electrode active material is not reduced but the metallic foreign matter to be extracted is reduced, and the electrode may be a carbon electrode. In this case, the potential difference varies depending on the type of metallic foreign matter, and thus may be appropriately adjusted according to the type of metallic foreign matter to be detected.
[0035] The metallic foreign matter extraction solution obtained by the first step contains metallic foreign matter and also contains metal components of the electrode active material such as Ni, Co and Mn. Therefore, in order to accurately measure the amount of the metallic foreign matter, it is necessary to separate the metallic foreign matter to be detected from the metal components of the electrode active material.
[0036] Therefore, in the present invention, a current is applied to the extraction solution within a voltage range in which the metal foreign matter to be detected is reduced, and the metal foreign matter is reduced and precipitated on the electrode (positive electrode) to form a plating layer, thereby separating the metal foreign matter from the extraction solution. In the case of separating the metal foreign matter by electroplating, only the metal foreign matter is selectively reduced and precipitated in the plating layer, thereby forming an environment that is not affected by the matrix effect caused by the metal component of the electrode active material, and therefore, even a very small amount of metal foreign matter contained at the ppb level can be quantitatively determined.
[0037] (3) Step 3: Detection of metallic foreign matter
[0038] Thereafter, the amount of metallic foreign matter plated on the electrode is measured (third step). In this case, for example, the amount of metallic foreign matter can be measured by an electrochemical analysis method such as inductively coupled plasma (ICP) or anodic stripping voltammetry.
[0039] In this case, the determination of the amount of metallic foreign matter using inductively coupled plasma (ICP) can be performed in the following manner: the metallic foreign matter plated on the electrode is dissolved with an acid to prepare a sample solution, and then the amount of metallic foreign matter in the sample solution is determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), an inductively coupled plasma atomic emission spectrometer (ICP-AES), or an inductively coupled plasma mass spectrometer (ICP-MS).
[0040] In this case, the acid may include hydrochloric acid, nitric acid, hydrogen peroxide, or a mixture thereof, and preferably may include at least one of hydrochloric acid and nitric acid and hydrogen peroxide.
[0041] As described above, in the plating layer obtained by the second step, only metallic foreign matter is selectively reduced and precipitated, thereby forming an environment that is not affected by the matrix effect caused by the metal component of the electrode active material. Therefore, even a very small amount of metallic foreign matter contained at the ppb level can be analyzed by the ICP method.
[0042] On the other hand, the amount of metallic foreign matter can be determined using the anodic stripping voltammetry method in the following manner: a potential difference of opposite polarity to the potential difference applied in the second step is applied to the electrode plated with the metallic foreign matter, thereby ionizing the metallic foreign matter in the plated layer, and the amount of current generated in this process is measured to thereby determine the amount of metallic foreign matter.
[0043] As described above, when the content of metallic foreign matter is measured using an electrochemical method, the content can be simply measured without requiring a separate processing step for measuring the content.
[0044] Mode for carrying out the invention
[0045] The present invention will be described in more detail below in conjunction with specific implementation modes.
[0046] Example 1
[0047] 50 mL of a 20 wt % nitric acid aqueous solution was added to 10 g of the positive electrode active material (NCM811), stirred at 300 rpm for 24 hours at room temperature, and then centrifuged at 8000 rpm for 10 minutes to prepare a metallic foreign matter extraction solution A.
[0048] 8 ml of the metal foreign body extraction solution A was placed in an electrochemical cell to prepare a three-electrode system consisting of a glassy carbon electrode as a working electrode, a silver chloride electrode (Ag / AgCl) as a reference electrode, and a platinum wire (Pt wire) as a counter electrode.
[0049] Then, -0.2 V was applied to the glassy carbon electrode for 120 seconds to plate the metal in the metallic foreign matter extracting solution A. In this case, plating was performed while stirring the solution at 300 rpm for 60 seconds using a stirrer, and the stirrer was stopped for the remaining 60 seconds to allow the solution to reach equilibrium.
[0050] Example 2
[0051] A metallic foreign matter extraction solution B was prepared and plating was performed in the same procedure as in Example 1, except that 0.11 mg of copper particles was mixed with about 10 g of a positive electrode active material (NCM811).
[0052] Example 3
[0053] A metallic foreign matter extraction solution C was prepared and plating was performed in the same procedure as in Example 1, except that 0.13 mg of copper particles was mixed with about 10 g of a positive electrode active material (NCM811).
[0054] Experimental Example 1
[0055] 10 g of each of the metallic foreign matter extraction solutions A to C prepared in Examples 1 to 3 were taken, and then the Cu content was measured using an ICP-OES device. The measurement results are shown in Table 1.
[0056] Experimental Example 2
[0057] After plating in Examples 1 to 3, a voltage of 0.3 V was applied to oxidize the metal, and the stripping charge was measured (anodic stripping voltammetry, ASV). The measurement results are shown in Table 1 below.
[0058]
[0059] Table 1 shows that in the metal foreign matter extraction solution of Example 1 in which no additional metal foreign matter (Cu) is added, the content of metal foreign matter in the positive electrode active material is extremely small, so the amount of metal foreign matter cannot be measured using ICP-OES, but in the method of the present invention, quantification can be achieved when ASV is used for measurement after plating. On the other hand, in Examples 2 and 3, additional metal foreign matter (Cu) is added, thereby increasing the amount of metal foreign matter, so the amount of metal foreign matter can be measured using ICP-OES. As shown in Table 1, it can be seen that as the amount of metal foreign matter measured by ICP-OES increases, the charge value measured by ASV also increases. This shows that the charge value measured by ASV can represent the amount of metal foreign matter. Therefore, it can be seen that according to the method of the present invention, a very small amount of metal foreign matter that cannot be measured by ICP can be quantified.
Claims
1. A method for detecting metallic foreign matter in an electrode active material, the method comprising: include: In the first step, the electrode active material is dissolved in a nitric acid aqueous solution to form a metallic foreign matter extraction solution; The second step is to plate the metal foreign matter in the metal foreign matter extraction solution onto the electrode; and The third step is to measure the amount of metallic foreign matter plated on the electrode. 2 . The method according to claim 1 , wherein the electrode active material contains metallic foreign matter having a particle size of 40 μm or less. 3 . The method according to claim 2 , wherein the metallic foreign matter is at least one selected from the group consisting of Cu, Zn, Ti, Sn, Pb, and alloys thereof. 4 . The method according to claim 1 , wherein the first step is performed under the condition that the solubility of the metal foreign matter is 80% or more and the solubility of the metal component of the electrode active material is 50% or less. 5 . The method according to claim 1 , wherein the nitric acid concentration of the nitric acid aqueous solution is 20 to 40% by weight.
6. The method according to claim 1, wherein the first step is performed by dissolving the electrode active material in an aqueous nitric acid solution having a nitric acid concentration of 20 to 40 wt%, and then stirring the resulting product at room temperature for at least 20 hours.
7. The method according to claim 1, wherein the second step is performed by immersing the electrode in the metallic foreign matter extraction solution and then applying a current so as to have a potential difference in which the metal component of the electrode active material is not reduced and the metallic foreign matter to be extracted is reduced.
8. The method of claim 7, wherein the electrode is a carbon electrode.
9. The method according to claim 1, wherein the third step is performed by dissolving the metal foreign matter plated on the electrode using an acid and then measuring the amount of the dissolved metal foreign matter by inductively coupled plasma (ICP).
10. The method of claim 9, wherein the acid comprises hydrochloric acid, nitric acid, hydrogen peroxide, or a mixture thereof.
11. The method of claim 9, wherein the acid comprises at least one of hydrochloric acid and nitric acid and hydrogen peroxide.
12. The method according to claim 1, wherein the third step is performed by anodic stripping voltammetry.