Dissolution method and determination method of aluminum-doped cobaltosic oxide

Abstract

The invention discloses a dissolution method and a determination method of aluminum-doped cobaltosic oxide, and the dissolution method comprises the following steps: step 1, adding aluminum-doped cobaltosic oxide into a container, adding mixed acid to form a solid-liquid mixture, and covering the container with a container cover; and 2, heating the container until the solid-liquid mixture starts to slightly boil, and continuously heating until the aluminum-doped cobaltosic oxide is completely dissolved. Compared with the prior art, the dissolving method provided by the invention can completely dissolve the sample, is low in cost, short in time consumption and simple and convenient to operate, and can be used as a matching means for sample dissolving treatment before chemical analysis; according to the dissolving method disclosed by the invention, the Al-doped cobaltosic oxide sample can be rapidly and completely dissolved, and the detection efficiency of the contents of Al and Co elements in the sample and the accuracy of a detection result are improved.

Description

Technical Field

[0001] The invention relates to the technical field of element detection, in particular to a dissolution method and a determination method of aluminum-doped cobalt tetroxide. Background Art

[0002] Lithium cobalt oxide materials have always occupied a major position in the 3C market due to their high volume energy density and good cycle stability. In recent years, with the rapid development of products such as smartphones, tablets, and drones, the volume energy density of batteries has become increasingly demanded. The solution is to increase the volume energy density of lithium cobalt oxide batteries by increasing the cut-off voltage. At present, high-voltage lithium cobalt oxide is mainly made from aluminum-doped cobalt tetroxide as raw material. A certain amount of aluminum in cobalt tetroxide can stabilize the crystal phase structure of lithium cobalt oxide during high-voltage charging and discharging, and improve cycle performance.

[0003] Since the chemical bonds between aluminum, cobalt and oxygen in aluminum-doped cobalt tetroxide are relatively stable, aluminum-doped cobalt tetroxide is difficult to completely dissolve under general digestion conditions (hydrochloric acid, sulfuric acid, nitric acid, aqua regia, etc.), resulting in large errors in the detection results of the cobalt element and the aluminum doping amount in aluminum-doped cobalt tetroxide.

[0004] In order to completely dissolve cobalt tetroxide, Chinese patent CN200710130544.X proposes to first heat the cobalt tetroxide sample to 100℃~1100℃ at a rate of 10℃ / min~100℃ / min, and keep it for 1min~20min, and finally stir it with hydrochloric acid / nitric acid for 30min to obtain a completely dissolved solution. However, the sample pretreatment temperature is high, the operation is cumbersome, and it takes a long time; Chinese patent CN202211336329.6 proposes to use mixed acid to treat alumina fibers in a graphite digestion furnace for 5h~7h to obtain a completely dissolved aluminum-containing solution. This method can achieve complete digestion of the sample and improve the accuracy of the measurement results, but the use of a graphite digestion furnace is costly, cumbersome, and time-consuming.

[0005] In view of the above-mentioned defects in the dissolution of cobalt tetroxide, and the difficulty of dissolving aluminum-doped cobalt tetroxide is greater than that of ordinary cobalt tetroxide. The method provided by Chinese patent CN200710130544.X is used to dissolve aluminum-doped cobalt tetroxide. Experiments have confirmed that although this method can dissolve cobalt tetroxide, it cannot dissolve aluminum-doped cobalt tetroxide. Therefore, it is necessary to provide a technical solution to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a method for dissolving aluminum-doped cobalt tetroxide, which can also dissolve cobalt tetroxide. The patent of the present invention can completely dissolve the sample. The dissolution method is low in cost, short in time, and simple to operate. It can be used as a matching means for chemical analysis, such as metal content titration or instrumental analysis.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for dissolving aluminum-doped cobalt oxide comprises the following steps:

[0009] Step 1: Place aluminum-doped cobalt oxide in a container, add mixed acid to form a solid-liquid mixture, and cover the container with a lid;

[0010] Step 2: After the container is heated, the solid-liquid mixture begins to boil slightly. The aluminum-doped cobalt tetroxide can be completely dissolved by continuing to heat the container to obtain a clear solution.

[0011] In step 1, the mixed acid includes hydrochloric acid, perchloric acid, acetic acid, etc. Preferably, the mixed acid includes hydrochloric acid and perchloric acid.

[0012] The volume ratio of the hydrochloric acid to the perchloric acid is (0.1-4): 1. Preferably, the volume ratio of the hydrochloric acid to the perchloric acid is (2-4): 1.

[0013] The mass concentration of the hydrochloric acid is 32% to 38%, preferably, the mass concentration of the hydrochloric acid is 36% to 38%.

[0014] The mass concentration of the perchloric acid is 65% to 72%. Preferably, the mass concentration of the perchloric acid is 70% to 72%.

[0015] In the step 1, the ratio of the aluminum-doped cobalt oxide to the mixed acid is 0.1 g: 3 ml to 10 ml. Preferably, the ratio of the aluminum-doped cobalt oxide to the mixed acid is 0.1 g: 3 ml to 5 ml.

[0016] In the step 2, the heating temperature is 180°C to 300°C, and the heating time is 20min to 90min. Preferably, the heating temperature is 180°C to 250°C, and the heating time is 20min to 40min.

[0017] In the step 1, preferably, the container is a silicon dioxide reactor such as a crucible, a beaker, an evaporating dish, etc.

[0018] In the step 2, preferably, the heating method is heating using an electric heating plate.

[0019] The present invention also provides a method for determining the content of cobalt, aluminum and other impurity elements in aluminum-doped cobalt tetroxide, the method comprising dissolving the aluminum-doped cobalt tetroxide and performing chemical titration analysis and atomic emission spectrum testing, the dissolution method of the aluminum-doped cobalt tetroxide being the above-mentioned dissolution method.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for dissolving aluminum-doped cobalt tetroxide, and the method can obtain a completely dissolved sample by thermal dissolution at a relatively low temperature (≤250°C) and a relatively short time (≤40min), and the method is simple to operate and highly efficient, and can be used as a method for dissolving and treating aluminum oxide-containing samples; in the dissolution method of the present invention, the device required for the dissolution process is simple, the time consumption is short, and the complete dissolution of the sample is achieved, thereby improving the detection efficiency of the element content in the aluminum-doped cobalt tetroxide and the accuracy of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a photograph of comparative example 1 of the present invention after the aluminum-doped cobalt tetroxide could not be completely dissolved.

[0022] Figure 2 This is a photograph of the solution after the aluminum-doped cobalt tetroxide in Example 1 of the present invention is dissolved. DETAILED DESCRIPTION

[0023] In order to make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] According to a first aspect of the present invention, the present invention provides a method for dissolving aluminum-doped cobalt oxide, comprising the following steps:

[0025] Step 1: Place aluminum-doped cobalt oxide in a container, add mixed acid, and cover the container;

[0026] Step 2: Heat the container, and then the mixed acid begins to boil slightly, and then stops boiling slightly to produce acid mist. After continuing heating for 20min to 40min, the aluminum-doped cobalt tetroxide can be completely dissolved. When maintaining a slight boil, the aluminum-doped cobalt tetroxide and the mixed acid are in a dynamic stirring state, which strengthens mass transfer and heat transfer and accelerates the dissolution reaction. If the temperature is insufficient and the mixed acid does not reach a boiling state, the sample cannot be completely dissolved within the heating time. The generation of acid mist indicates that the temperature of the mixed acid system is further increased at this time, and the sample dissolution is accelerated at this time.

[0027] In one embodiment of the present invention, in step 1, the mixed acid includes hydrochloric acid and perchloric acid.

[0028] The present invention has found through experimental research that hydrochloric acid and perchloric acid are used because chloride ions have a strong ability to complex with metal ions. They preferentially adsorb and complex with metal ions and remove oxygen from the surface of metal oxides. Chloride ions and oxygen compete for adsorption points on the surface of metal oxides and form soluble chlorides with metals, which accelerates the corrosion of metal oxides; chloride ions have a destructive effect on oxide films and can penetrate the oxide films of Al and Co. This trend is more likely to occur under strong acidic and strong oxidizing conditions.

[0029] The reaction equation of mixed acid and sample is as follows:

[0030] Co3O4+8HCl=3CoCl2+4H2O+Cl2↑

[0031] Co3O4+8HClO4=3Co(ClO4)2+4H2O+Cl2↑+4O2↑

[0032] Al2O3+6HClO4=2Al(ClO4)3+3H2O

[0033] The Co(ClO4)2 containing crystal water obtained by the reaction is red crystals, and the Al(ClO4)3 is colorless crystals, both of which are easily soluble in water, so the dissolution method provided by the present invention can completely dissolve the sample.

[0034] In one embodiment of the present invention, the volume ratio of hydrochloric acid to perchloric acid is (0.5-4):1, preferably (2-4):1. The ratio range of hydrochloric acid to perchloric acid is obtained through experiments and can be 2:1, 3:1, 4:1. The appropriate proportion of perchloric acid in the mixed acid can ensure that the mixed acid takes into account the dissolution capacity and dissolution rate of aluminum-doped cobalt tetroxide and the safety of the experimental process.

[0035] In one embodiment of the present invention, the mass concentration of hydrochloric acid is 36% to 38%, for example, it can be 36%, 36.5%, 37%, 37.5%, 38%; the concentration range of hydrochloric acid should be selected within this concentration range, which is the highest concentration of hydrochloric acid commonly used in laboratories. If the concentration range of hydrochloric acid is too low, the acidity is weakened, which is not conducive to the dissolution of the sample; the mass concentration of perchloric acid is 70% to 72%, for example, it can be 70%, 70.5%, 71%, 71.5%, 72%; the concentration of perchloric acid should be selected within the aforementioned concentration range, which is the highest concentration of perchloric acid commonly used in laboratories. If the concentration range of perchloric acid is too low, its oxidizing property is weakened, which is not conducive to the dissolution of the sample.

[0036] In one embodiment of the present invention, in step 1, the ratio of the aluminum-doped cobalt oxide to the mixed acid is 0.1g:3ml~10ml, and is preferably 0.1g:3ml~5ml. For example, it can be 0.1g:3ml, 0.1g:4ml, 0.1g:5ml. Here, the ratio range of the sample to the amount of mixed acid used takes into account the overall dissolution capacity of the mixed acid on the sample and the economy of the amount of mixed acid used. If the amount of mixed acid is insufficient, the sample cannot be completely dissolved. If the amount of mixed acid is too much, the cost will increase and the subsequent detection equipment will be damaged.

[0037] In one embodiment of the present invention, in step 2, the heating temperature is 180°C to 250°C, for example, 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 189°C, 190°C, 191°C, 192°C, 193°C, 194°C, 195°C, 196°C, 197°C, 198°C, 199°C, 200°C, 201°C, 202°C, 203°C, 204°C, 205°C, 206°C , 207℃, 208℃, 209℃, 210℃, 211℃, 212℃, 213℃, 214℃, 215℃, 216℃, 217℃, 218℃, 219℃, 220℃, 221℃, 222℃, 223℃, 224℃, 225℃, 226℃, 227℃, 228℃, 229℃, 230℃, 231℃, 232℃, 233℃, 234℃, 235℃, 236℃, 237℃, 238℃, 239℃, 240℃, 241℃, 242℃ The temperature should be adjusted within this range during heating to make the mixed acid reach a slightly boiling state; if the heating temperature is insufficient, the sample cannot be completely dissolved within the dissolution time; if the heating temperature is too high, the mixed acid will become violently boiling, and an explosion may occur due to the presence of concentrated perchloric acid; the heating time is 20min to 40min, for example, 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min, 40min; if the heating time is insufficient, the sample cannot be completely dissolved, and if the temperature is too high, there is a safety hazard and resources will be wasted. The sample has been completely dissolved within the time range of the present invention and does not need to be heated further.

[0038] Preferably, in step 2, the heating method is to use an electric heating plate for heating, which is simple to operate and low in cost.

[0039] In one embodiment of the present invention, in step 1, the container is a silicon dioxide material reactor such as a crucible, a beaker, an evaporating dish, etc., which are chemical instruments commonly used in chemical experiments.

[0040] According to the second aspect of the present invention, a method for determining the content of cobalt, aluminum and other impurity elements in aluminum-doped cobalt tetroxide is also provided. Specifically, the method comprises dissolving aluminum-doped cobalt tetroxide using the above-mentioned dissolution method to obtain a solution, and using the solution as a test solution for chemical titration analysis and atomic emission spectroscopy test.

[0041] The present invention will be further described below by means of specific examples.

[0042] Example 1

[0043] Step 1: Weigh 0.1000 g (accurate to 0.0001 g) of aluminum-doped cobalt tetroxide into a quartz crucible, add 3 ml of hydrochloric acid and 1 ml of perchloric acid, and cover the crucible;

[0044] Step 2: Place the quartz crucible on a 220°C electric heating plate. After heating for 5 minutes, the mixed acid can be seen to be slightly boiling, and then the mixed acid stops slightly boiling and produces acid mist. After heating for 30 minutes, the sample can be completely dissolved.

[0045] Step 3: Accurately dilute the completely dissolved sample into a 50mL volumetric flask and shake well for testing the Al element; due to the high content of Co in the sample, the stock solution is generally diluted 100 times for testing the Co element;

[0046] Step 4: Turn on the inductively coupled plasma emission spectrometer, ignite the plasma flame and preheat for at least 10 minutes, open the Al element and Co element test worksheets respectively to enter the sample weight, volume, and dilution multiple, and after establishing the standard curve, you can add liquid to collect relevant data.

[0047] The experimental conditions of Examples 1 to 9 and Comparative Examples 1 to 6 are shown in Table 1, and the rest are the same as Example 1 and will not be repeated here.

[0048] Table 1

[0049]

[0050]

[0051] The samples were subjected to dissolution experiments according to the experimental parameters of Examples 1 to 9 and Comparative Examples 1 to 6. Whether the samples were completely dissolved is shown in Table 1. From the dissolution results recorded in Table 1, it can be seen that Examples 1 to 9 can completely dissolve aluminum-doped cobalt tetroxide (the photo of the solution after dissolution of Example 1 is shown in Table 1). Figure 2); Comparative Example 1 Since the amount of hydrochloric acid and perchloric acid used is lower than the range of this experiment (2.5ml: 0.1g), the sample cannot be completely dissolved (see Figure 1 ); in comparative example 2, the mixed acid is excessive, and the sample can be completely dissolved, but acid will be wasted, cost will be increased, and subsequent detection equipment will be damaged; in comparative example 3, the mixed acid cannot be heated to a slightly boiling state due to insufficient heating temperature, and the sample cannot be completely dissolved within this heating time; in comparative example 4, although the sample can be completely dissolved due to excessive heating temperature, the acid mist pressure generated is too high, which will open the container cover and easily cause safety accidents; in comparative example 5, the sample cannot be completely dissolved due to insufficient heating time; in comparative example 6, the heating time is too long, and although the sample is dissolved, time is wasted and cost is increased.

[0052] Table 2 is the test results of element contents in samples of Examples 1 to 4, 6 and Comparative Example 2

[0053] Co(mass%) Al(ppm) Example 1 72.44％ 4482 Example 2 72.42％ 4493 Example 3 72.52％ 4479 Example 4 72.62％ 4439 Example 6 72.54％ 4463 Comparative Example 2 72.64％ 4430

[0054] The instruments / equipment involved in the present invention are shown in Table 3.

[0055] Table 3

[0056]

[0057] The main instrument testing method of the present invention is as follows:

[0058] The composition analysis was carried out using the method in the national standard for lithium cobalt oxide (GB / T 20252-2014), and the contents of all metal elements (including cobalt) were determined by inductively coupled plasma emission spectrometry.

[0059] The main raw materials / auxiliary materials involved in the invention are as follows in Table 4:

[0060] Table 4

[0061]

[0062] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for dissolving aluminum-doped cobalt oxide, characterized in that: The following steps are involved: Step 1: Place aluminum-doped cobalt oxide in a container, add mixed acid to obtain a solid-liquid mixture, and cover the container with a lid; Step 2: The container is placed on a hot plate and heated for 20 to 40 minutes at a temperature of 180° C. to 250° C. The mixed acid begins to boil slightly, then stops boiling slightly and produces acid mist. Continuing heating can completely dissolve the aluminum-doped cobalt tetroxide to obtain a clear solution.

2. The method for dissolving aluminum-doped cobalt tetroxide according to claim 1, characterized in that: In the step 1, the mixed acid includes hydrochloric acid and perchloric acid.

3. The method for dissolving aluminum-doped cobalt tetroxide according to claim 2, characterized in that: The volume ratio of the hydrochloric acid to the perchloric acid is (2-4):

1.

4. The method for dissolving aluminum-doped cobalt tetroxide according to claim 2, characterized in that: The mass concentration of the hydrochloric acid is 36% to 38%, and the mass concentration of the perchloric acid is 70% to 72%.

5. The method for dissolving aluminum-doped cobalt tetroxide according to claim 1, characterized in that: In the step 1, the ratio of the aluminum-doped cobalt tetroxide to the mixed acid is 0.1 g: 3 ml to 5 ml.

6. The method for dissolving aluminum-doped cobalt tetroxide according to claim 1, characterized in that: In the step 2, the heating temperature is 180° C. to 250° C., and the heating time is 20 min to 40 min.

7. The method for dissolving aluminum-doped cobalt tetroxide according to claim 1, characterized in that: In the step 1, the container is selected from a crucible, a beaker and an evaporating dish.

8. A method for determining the content of cobalt, aluminum and other impurity elements in aluminum-doped cobalt tetroxide, the method comprising dissolving aluminum-doped cobalt tetroxide and performing chemical titration analysis and atomic emission spectroscopy test, characterized in that: The dissolution method of aluminum-doped cobalt oxide is the dissolution method of claim 1.

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