Method for detecting residual alkali in sodium ion layered oxide positive electrode material

Abstract

The application discloses a kind of residual alkali detection methods in sodium ion layered oxide positive material, comprising the following steps: step 1, dispersing agent is added to sodium ion layered oxide positive material, stirring, extraction, suction filtration, and filtrate is collected;The dispersing agent is combined by polar organic reagent and water;Step 2, the pH value of filtrate is measured using potentiometric titration method, and the residual alkali in sodium ion layered oxide positive material is calculated.The application has the following beneficial effects: by adding an appropriate amount of polar organic reagent on the basis of using water as dispersant, the generation of NaOH in the material during testing and its influence on testing are inhibited, the testing interference caused by excessive organic solvent is avoided, the stability of the material during potentiometric titration is improved, and the sodium carbonate content detection result is more accurate and stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery detection, in particular to a method for detecting residual alkali in a sodium ion layered oxide positive electrode material. BACKGROUND

[0002] At present, lithium ion batteries have become the mainstream material in the battery industry due to their high capacity and long cycle life. However, due to the scarcity and uneven distribution of lithium resources, people have turned their attention to sodium, which has similar chemical properties to lithium. Compared with lithium ion batteries, sodium ion batteries have lower energy density, but sodium resources are widely distributed, have large reserves, are low in price and high in safety, and have very wide application scenarios (such as energy storage power stations, low-speed power fields and backup power sources, etc.). Therefore, people regard sodium ion battery technology as an effective supplement to lithium ion battery technology, and the research and production of sodium ion battery positive electrode materials have gradually become the focus of attention at home and abroad.

[0003] Common sodium ion battery positive electrode materials include transition metal oxides, prussian blue and prussian white and their derivatives, polyanion compounds and organic compounds, etc. The residual alkali content of these materials is one of the key factors affecting the performance of the battery. The residual alkali content can be used to guide the optimization of the preparation process of sodium ion battery positive electrode materials, and the sodium carbonate content is one of the residual alkali indicators, which is difficult to test.

[0004] Common sodium ion battery positive electrode materials include transition metal oxides, prussian blue and prussian white and their derivatives, polyanion compounds and organic compounds, etc. The residual alkali content of these materials is one of the key factors affecting the performance of the battery. The residual alkali content can be used to guide the optimization of the preparation process of sodium ion battery positive electrode materials, and the sodium carbonate content is one of the residual alkali indicators, which is difficult to test.

[0005] At present, the method for analyzing the residual alkali of the sodium ion battery positive electrode material is acid-base titration method, such as the sodium ion layered oxide positive electrode material PH test method disclosed by Chinese patent 202311196598.1. The sodium ion layered oxide positive electrode material PH test method of the application can detect the PH after stirring for 1 min, which is closer to the PH value of the residual alkali after completely dissolving in the solvent, can characterize the difference of the residual alkali, avoids the influence of the precipitation of sodium in the crystal on the accuracy of the PH test, and is closer to the true value than the traditional method. However, it is well known that during the residual alkali test of the sodium ion layered oxide positive electrode material, it is found that the replacement of Na in the material structure by hydrogen ions in water will cause the increase of NaOH content. Since the carbonate is insoluble in ethanol and other organic solvents, now NaOH is tested by extraction using ethanol as a dispersant, and sodium carbonate is still tested by extraction using pure water as a dispersant. However, excessive NaOH will affect the end point determination during potential titration, thereby affecting the test stability. Even if the new organic solvent such as ethylene glycol is used as a single dispersant, the result is not stable enough due to the non-similar solubility characteristics. SUMMARY

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a method for detecting residual alkali in a sodium ion layered oxide positive electrode material, which solves the problems of easy misjudgment of the titration end point and large error of the detection result during the detection of residual alkali in the existing sodium ion layered oxide positive electrode material.

[0007] To achieve the above-mentioned purposes and other related purposes, the present application provides a method for detecting residual alkali in a sodium ion layered oxide positive electrode material, characterized in that it comprises the following steps:

[0008] Step 1: adding a dispersant into the sodium ion layered oxide positive electrode material, stirring, extracting, suction filtering, and collecting the filtrate; the dispersant is composed of a polar organic reagent and water;

[0009] Step 2: measuring the pH value of the filtrate by using potential titration method, and calculating the residual alkali in the sodium ion layered oxide positive electrode material.

[0010] As a preferred embodiment of the present application, the chemical formula of the sodium ion layered oxide positive electrode material is Na x TMO2, 0 < x < 2, TM is selected from at least one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg and Zn.

[0011] As a preferred embodiment of the present application, the chemical formula of the sodium ion layered oxide positive electrode material is NaNiO2.

[0012] As a preferred embodiment of the present application, the mass ratio of the sodium-ion layered oxide positive electrode material to the dispersing agent is (1-5):60.

[0013] As a preferred embodiment of the present application, the mass ratio of the sodium-ion layered oxide positive electrode material to the dispersing agent is 1:20.

[0014] As a preferred embodiment of the present application, the polar organic reagent is an alcohol with a carbon atom number of 2-3.

[0015] As a preferred embodiment of the present application, the polar organic reagent is selected from at least one of ethanol, ethylene glycol, and propanol.

[0016] As a preferred embodiment of the present application, the mass ratio of the polar organic reagent to water is 1:10-10:1.

[0017] As a preferred embodiment of the present application, the mass ratio of the polar organic reagent to water is 7:3, 1:1, or 3:7.

[0018] As a preferred embodiment of the present application, the mass ratio of the polar organic reagent to water is 7:3.

[0019] As a preferred embodiment of the present application, the temperature for extraction in step 1 is 20-26℃, and the extraction time is 5-15 min.

[0020] As a preferred embodiment of the present application, the suction filtration in step 1 uses a sand core vacuum suction filtration device, and the filter membrane is a water-based filter membrane.

[0021] As a preferred embodiment of the present application, the electrode used for measuring the pH value of the filtrate by the potentiometric titration method in step 2 is a water-based pH electrode.

[0022] As a preferred embodiment of the present application, in step 2, the pH value of the filtrate is measured by the potentiometric titration method, and the residual alkali in the sodium-ion layered oxide positive electrode material is calculated by selecting the sodium carbonate test method.

[0023] The pH value of the filtrate is measured by the potentiometric titrator, and the titration end point determined by the potentiometric titration curve usually corresponds to the point of sudden change of the pH value, and the volume difference V mL of the standard hydrochloric acid solution consumed at the two sudden points is recorded.

[0024] The residual alkali content in the sample is calculated: the carbonate content A in the sample is:

[0025]

[0026] wherein 106 is the molecular weight of carbonate, C is the molar concentration of the prepared hydrochloric acid, mol / L; m is the mass of the sample weighed, g; V is the volume difference of the standard hydrochloric acid solution consumed at the two sudden points, mL.

[0027] The present application has the following beneficial effects: by adding a proper amount of polar organic reagent on the basis of using water as a dispersing agent, the generation of NaOH in the material during the test process and the influence on the test are inhibited, the test interference caused by too high organic solvent is avoided, the carbon sodium content detection result is more accurate and stable, and the stability of the material during the potential titration is improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Test potential titration graph for Example 1.

[0029] Figure 2 Test potential titration graph for Example 4.

[0030] Figure 3 Test potential titration graph for Example 5.

[0031] Figure 4 Test potential titration graph for Comparative Example 1.

[0032] Figure 5 Test potential titration graph for Comparative Example 2.

[0033] Figure 6 Test potential titration graph for Comparative Example 3. DETAILED DESCRIPTION

[0034] The present application will be described in greater detail by way of specific embodiments, from which the skilled person will readily appreciate other advantages and functionalities of the present application. The present application can also be carried out or applied in other different embodiments, and the details in the present description can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0035] It should be noted that the process equipment or devices not specifically mentioned in the following examples are all conventional equipment or devices in the art.

[0036] In addition, it should be understood that the one or more method steps mentioned in the present application do not exclude that there can be other method steps before and after the mentioned combination steps or other method steps can be inserted between the mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between the one or more devices mentioned in the present application does not exclude that there can be other devices before and after the mentioned combination devices or other devices can be inserted between the two mentioned devices, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the arrangement order of each method step or to limit the range of the present application, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also regarded as the scope of the present application.

[0037] Example 1

[0038] The present embodiment provides a preparation method of vanadium oxide nanosheet array, comprising the following steps:

[0039] Step 1, weigh 3g of sodium ion layered oxide positive electrode material NaNiO2 into a stoppered triangular conical flask (20℃, same below), and then add 42g of ethanol and 18g of pure water, respectively, and stir at 20℃ for 10min, and then filter, remove the extracted sodium carbonate, and collect the filtrate;

[0040] Step 2, measure the pH value of the filtrate by using the potential titration method, and calculate the residual alkali in the sodium ion layered oxide positive electrode material by selecting the sodium carbonate test method.

[0041] The specific calculation method is as follows:

[0042] The pH value of the filtrate is measured by using a 916 potential titrator and an aqueous pH electrode, and the titration end point determined by the potential titration curve usually corresponds to the sudden change point of the pH value, and the volume difference V of the standard hydrochloric acid solution consumed at the two sudden change points is recorded;

[0043] Calculate the residual alkali content in the sample: the carbonate content A in the sample is:

[0044]

[0045] Wherein, 106 is the molecular weight of carbonate, C is the molar concentration of the prepared hydrochloric acid, mol / L; m is the mass of the sample weighed, g; V is the volume difference of the standard hydrochloric acid solution consumed at the two sudden change points, mL.

[0046] The test results are shown in Table 1.

[0047] Example 2

[0048] The difference between the present embodiment and Example 1 is that the mass ratio of the sodium ion layered oxide positive electrode material to the dispersant is different, and in the present embodiment, the mass ratio of the sodium ion layered oxide positive electrode material to the dispersant is 1:60, and the rest of the process is exactly the same.

[0049] Example 3

[0050] The difference between the present embodiment and Example 1 is that the mass ratio of the sodium ion layered oxide positive electrode material to the dispersant is different, and in the present embodiment, the mass ratio of the sodium ion layered oxide positive electrode material to the dispersant is 5:60, and the rest of the process is exactly the same.

[0051] Example 4

[0052] The difference between this embodiment and embodiment 1 is that the mass ratio of the polar organic reagent to pure water in the dispersant is different, and in this embodiment, the dispersant is composed of 30 g of pure water and 30 g of ethanol, and the rest of the process is exactly the same.

[0053] Example 5

[0054] The difference between this embodiment and embodiment 1 is that the mass ratio of the polar organic reagent to pure water in the dispersant is different, and in this embodiment, the dispersant is composed of 18 g of ethanol and 42 g of pure water, and the rest of the process is exactly the same.

[0055] Example 6

[0056] The difference between this embodiment and embodiment 1 is that the mass ratio of the polar organic reagent to pure water in the dispersant is different, and in this embodiment, the dispersant is composed of 5.6 g of ethanol and 54.4 g of pure water, and the rest of the process is exactly the same.

[0057] Example 7

[0058] The difference between this embodiment and embodiment 1 is that the mass ratio of the polar organic reagent to pure water in the dispersant is different, and in this embodiment, the dispersant is composed of 54.5 g of ethanol and 5.5 g of pure water, and the rest of the process is exactly the same.

[0059] Example 8

[0060] The difference between this embodiment and embodiment 1 is that the type of dispersant is different, and in this embodiment, propanol is used instead of ethanol, and the rest of the process is exactly the same.

[0061] Example 9

[0062] The difference between this embodiment and embodiment 1 is that the type of dispersant is different, and in this embodiment, ethylene glycol is used instead of ethanol, and the rest of the process is exactly the same.

[0063] Example 10

[0064] The difference between this embodiment and embodiment 1 is that the type of dispersant is different, and in this embodiment, the dispersant is a mixture of ethanol, propanol and water with a mass ratio of 3.5:3.5:3, and the rest of the process is exactly the same.

[0065] Example 11

[0066] The difference between this embodiment and embodiment 1 is that the type of dispersant is different, and in this embodiment, the dispersant is a mixture of ethylene glycol, ethanol and water with a mass ratio of 3.5:3.5:3, and the rest of the process is exactly the same.

[0067] Comparative Example 1

[0068] The difference between this comparative example and embodiment 1 is that in this comparative example, pure water is used instead of the dispersant, and the rest of the process is exactly the same.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 1 is that ethylene glycol is used instead of dispersant in this comparative example, and the rest of the process is exactly the same.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is that ethanol is used instead of dispersant in this comparative example, and the rest of the process is exactly the same.

[0073] The method and results of calculating residual alkali in sodium ion layered oxide positive electrode material of Examples 2-11 and Comparative Examples 1-3 are comparable to those of Example 1, and will not be repeated here.

[0074] Table 1: Sodium carbonate test stability results measured by the method of Examples and Comparative Examples

[0075]

[0076]

[0077] As can be seen from Table 1, comparing Examples 1-11 with Comparative Examples 1-3, mixed dispersants generally have better stability than single dispersants. The stability of dispersants of ethanol + pure water is generally higher than that of other types of dispersants. Therefore, the dispersant of the present application is to add an appropriate amount of ethanol on the basis of using water as a dispersant, which can significantly inhibit the generation of NaOH in the material during the test and its impact on the test, making the sodium carbonate content detection result accurate and stable. Moreover, as the ethanol content increases, the X-axis titrant volume corresponding to EP1 decreases. However, when the mass ratio of ethanol and water is 7:3, the RSD is the smallest, 0.37%, indicating that under this ratio, the test result stability is the best, and it has the effect of accurately testing the sodium carbonate content in the residual alkali of sodium ion layered oxide positive electrode material.

[0078] The above examples are intended to illustrate the embodiments disclosed in the present application, and should not be construed as limiting the present application. In addition, various modifications listed herein and changes in the method and composition of the invention are obvious to those skilled in the art without departing from the scope and spirit of the present application. Although the present application has been specifically described in conjunction with various preferred embodiments thereof, it should be understood that the present application should not be limited to these specific embodiments. In fact, various modifications as described above to obtain the invention that are obvious to those skilled in the art should be included within the scope of the present application.

Claims

1. A method for detecting residual alkali in a sodium-ion layered oxide cathode material, characterized by, The method comprises the following steps: Step 1, adding a dispersing agent into a sodium ion layered oxide positive electrode material, stirring and extracting, filtering, and collecting the filtrate; the dispersing agent is combined by a polar organic reagent and pure water; the mass ratio of the sodium ion layered oxide positive electrode material to the dispersing agent is (1-5):60; the polar organic reagent is at least one selected from ethanol and ethylene glycol, and the mass ratio of the polar organic reagent to water is 7:3; Step 2, measuring the pH value of the filtrate by using a potential titration method to calculate the residual alkali in the sodium ion layered oxide positive electrode material; wherein, the method for calculating the residual alkali in the sodium ion layered oxide positive electrode material is as follows: The pH value of the filtrate is measured by using a potential titration instrument, and the titration end point determined by a potential titration curve usually corresponds to a sudden change point of pH value, and the volume difference V mL of the standard hydrochloric acid solution consumed at the two sudden change points is recorded; The residual alkali content in the sample is calculated: the carbonate content A in the sample is: Wherein, 106 is the molecular weight of carbonate, C is the molar concentration of the prepared hydrochloric acid, mol / L; m is the mass of the sample, g; V is the volume difference of the standard hydrochloric acid solution consumed at the two sudden change points, mL.

2. The method for detecting residual alkali in a sodium-ion layered oxide cathode material according to claim 1, characterized by: The sodium-ion layered oxide positive electrode material has a chemical formula of Na x TMO2, 0 < x < 2, TM is selected from at least one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, and Zn.

3. The method for detecting residual alkali in sodium ion layered oxide cathode material according to claim 1, characterized in that: The mass ratio of the sodium ion layered oxide positive electrode material to the dispersing agent is 3:

60.

4. The method for detecting residual alkali in sodium ion layered oxide cathode material according to claim 1, characterized in that: The electrode used in step 2 for measuring the pH value of the filtrate by using a potential titration method is a water-based pH electrode.

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