Method for measuring content of tricobalt tetraoxide in lithium cobalt oxide

Abstract

A method for measuring the content of tricobalt tetraoxide in lithium cobalt oxide, relating to the technical field of quantitative measurement of tricobalt tetraoxide. The method comprises the following steps: carrying out acid treatment on a lithium cobalt oxide sample to be tested to dissolve lithium cobalt oxide, and then carrying out solid-liquid separation, reacting the solid obtained by separation with a potassium permanganate solution and a sulfuric acid solution, adding a potassium iodide solution to end the reaction, and titrating to an end point with a sodium thiosulfate solution by taking starch as an indicator. By means of the method, a measurement result having high accuracy can be obtained.

Description

A method for determining the content of cobalt trioxide in lithium cobaltate Technical Field

[0001] The present disclosure relates to the technical field of quantitative detection of cobalt trioxide, and in particular to a method for determining the content of cobalt trioxide in lithium cobaltate. Background Art

[0002] With the rapid development of my country's new energy industry in recent years, the demand for lithium-ion batteries in power batteries, energy storage, smart devices, power tools and other fields has increased year by year. As a key component of lithium-ion batteries, the performance of cathode materials plays a vital role in the overall performance of the battery. As one of the earliest commercialized cathode materials, lithium cobalt oxide (LCO) has a high compaction density and a higher volumetric energy density than other commonly used cathode materials such as ternary, lithium iron phosphate, and lithium manganese oxide. Therefore, it holds an irreplaceable position in the 3C industry.

[0003] Currently, commercial lithium cobalt oxide is mainly prepared by mixing a lithium source, a cobalt source, and additives and then solid-phase sintering. However, due to uneven mixing and uneven temperature distribution during the sintering process, a portion of cobalt tetroxide that has not reacted with the lithium source exists in the finished product. Cobalt tetroxide does not exhibit electrochemical activity in the bulk phase of lithium cobalt oxide, and will result in a lower capacity and poor cycle stability of the lithium cobalt oxide material. Therefore, the content of residual cobalt tetroxide in the lithium cobalt oxide material is one of the key indicators for judging its performance.

[0004] However, there are currently few studies on the determination methods of residual cobalt tetroxide, and the accuracy of the determination results is low.

[0005] In view of this, the present disclosure is proposed.

[0006] Summary of the Invention

[0007] The present invention aims to provide a method for determining the content of cobalt trioxide in lithium cobaltate, which can obtain a highly accurate determination result.

[0008] The present disclosure can be implemented as follows:

[0009] The present disclosure provides a method for determining the content of cobalt trioxide in lithium cobaltate, which comprises the following steps: treating a lithium cobaltate sample to be tested with acid to dissolve the lithium cobaltate, followed by solid-liquid separation, reacting the separated solid with a potassium permanganate solution and a sulfuric acid solution, adding a potassium iodide solution to terminate the reaction, and titrating to an end point with a sodium thiosulfate solution using starch as an indicator.

[0010] In an alternative embodiment, the acid used for the acid treatment includes at least one of hydrochloric acid and nitric acid.

[0011] In an alternative embodiment, the acid used in the acid treatment is aqua regia.

[0012] In an optional embodiment, during the acid treatment, the ratio of the lithium cobalt oxide sample to be tested to the acid is (10 g:20 mL)-(10 g:30 mL).

[0013] In an alternative embodiment, the temperature of the acid treatment is 180°C-200°C.

[0014] In an optional embodiment, the acid treatment time is 25 min-35 min.

[0015] In an alternative embodiment, the reaction temperature is 20°C-30°C.

[0016] In an optional embodiment, the reaction time is 10 min-30 min.

[0017] In an optional embodiment, the concentration of the potassium permanganate solution is 0.008 mol / L-0.012 mol / L.

[0018] In an optional embodiment, 8 mL to 12 mL of potassium permanganate solution is used for every 10 g of lithium cobalt oxide sample to be tested.

[0019] In an optional embodiment, the concentration of the sulfuric acid solution is 0.8 mol / L-1.2 mol / L.

[0020] In an optional embodiment, 8 mL to 12 mL of sulfuric acid solution is used for every 10 g of lithium cobalt oxide sample to be tested.

[0021] In an optional embodiment, the concentration of the potassium iodide solution is 0.8 mol / L-1.2 mol / L.

[0022] In an optional embodiment, 4 mL to 6 mL of potassium iodide solution is used for every 10 g of lithium cobalt oxide sample to be tested.

[0023] In an optional embodiment, the concentration of the sodium thiosulfate solution is 0.04 mol / L-0.06 mol / L.

[0024] In an alternative embodiment, the concentration of the indicator is 4 wt%-6 wt%.

[0025] In an optional embodiment, 2 mL to 4 mL of the indicator is used for every 10 g of the lithium cobalt oxide sample to be tested.

[0026] In an alternative embodiment, the reaction endpoint is titration until the solution becomes clear.

[0027] In an optional embodiment, a blank sample is prepared without adding the lithium cobalt oxide sample to be tested, and the same potassium permanganate solution and sulfuric acid as used in the treatment process of the lithium cobalt oxide sample are directly used for the reaction. Potassium iodide solution is added to terminate the reaction, and starch is used as an indicator and titrated with sodium thiosulfate solution to the endpoint.

[0028] After the blank sample titration is completed, the content of cobalt trioxide in the lithium cobaltate sample to be tested is calculated according to the following formula:

[0029] Wherein, N1 is the mass percentage of cobalt trioxide in the lithium cobalt oxide sample to be tested, in %;

[0030] V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL;

[0031] V2 is the volume of sodium thiosulfate solution consumed by the lithium cobalt oxide sample to be tested, in mL;

[0032] c is the concentration of sodium thiosulfate solution, in mol / L;

[0033] m(Co3O4) is the amount of cobalt tetroxide in g / mol;

[0034] m0 is the weight of the lithium cobalt oxide sample to be tested, in g.

[0035] In an optional embodiment, the method further includes correcting the measured cobaltous oxide content N1 according to the following formula:

[0036] Wherein, N2 is the mass percentage of cobalt tetroxide in the lithium ion battery sample after correction, in %;

[0037] a is the correction parameter.

[0038] In an optional embodiment, the calculation formula of the correction parameter a is as follows:

[0039] Among them, N Co is the mass percentage of Co in any cobalt oxide sample measured by ICP method, in %;

[0040] m Co is the relative atomic mass of Co;

[0041] N0 is the mass percentage of cobalt tetroxide in the cobalt tetroxide sample measured by the same determination method as the cobalt tetroxide content N1 in the lithium cobaltate sample to be tested, and the unit is %.

[0042] The present invention dissolves only the lithium cobalt oxide in the lithium cobalt oxide sample by acid treatment, thereby separating the insoluble cobalt tetroxide, and then separating the low-valent Co in the cobalt tetroxide. 2+ The reducing properties of lithium cobalt oxide react with potassium permanganate, a strong oxidant, and the potassium permanganate consumed in the reaction is determined by titration. The cobalt oxide content in the lithium cobalt oxide sample is calculated based on the chemical formula ratio of cobalt oxide. This method has high accuracy. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0044] The method for determining the content of cobalt trioxide in lithium cobaltate provided by the present disclosure is described in detail below.

[0045] The present disclosure provides a method for determining the content of cobalt trioxide in lithium cobaltate, which comprises the following steps: subjecting a lithium cobaltate sample to acid treatment to dissolve the lithium cobaltate, followed by solid-liquid separation, reacting the separated solid with a potassium permanganate solution and a sulfuric acid solution, adding a potassium iodide solution to terminate the reaction, and titrating to an endpoint with a sodium thiosulfate solution using starch as an indicator.

[0046] In the above process, only the lithium cobalt oxide in the lithium cobalt oxide sample is dissolved by acid treatment, thereby separating the insoluble cobalt tetroxide, and then the low-valent Co in the cobalt tetroxide is separated. 2+ The reducing properties of lithium cobalt oxide react with potassium permanganate, a strong oxidant, and the potassium permanganate consumed in the reaction is determined by titration. The cobalt oxide content in the lithium cobalt oxide sample is calculated based on the chemical formula ratio of cobalt oxide. This method has high accuracy.

[0047] Specifically, the relevant chemical reaction equations involved in the above reaction and titration process include: 10Co3O4+48H2SO4+2KMnO4=15Co2(SO4)3+K2SO4+2MnSO4+48H2O, Formula 1; 2KMnO4+10KI+8H2SO4=2MnSO4+6K2SO4+5I2+8H2O, Formula 2; 2Na2S2O3+I2=2NaI+Na2S4O6, Formula 3;

[0048] Wherein, Formula 1 is the reaction equation of cobalt trioxide and acidic potassium permanganate; Formula 2 and Formula 3 are titration reaction equations.

[0049] For reference, the acid used in the above-mentioned acid treatment may include at least one of hydrochloric acid and nitric acid. For example, it may be only hydrochloric acid, only nitric acid, or aqua regia composed of concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 1:3.

[0050] When the acid used for the acid treatment is hydrochloric acid, the hydrochloric acid can be a standard hydrochloric acid solution, specifically a hydrochloric acid standard solution with a concentration of 1 mol / L to 1.5 mol / L. The standard hydrochloric acid solution used in this disclosure can be purchased directly or prepared by oneself with reference to GB / T 601 2016.

[0051] It should be noted that lithium cobaltate is insoluble in water but soluble in acid, while cobalt trioxide is only slightly soluble in hot sulfuric acid. Therefore, the above acid treatment can separate lithium cobaltate and cobalt trioxide in the lithium cobaltate test sample.

[0052] In the present disclosure, the ratio of the lithium cobalt oxide sample to be tested to the acid during the acid treatment process can be (10g:20mL)-(10g:30mL), such as 10g:20mL, 10g:22mL, 10g:25mL, 10g:28mL or 10g:30mL, etc., or it can be any other value within the range of (10g:20mL)-(10g:30mL).

[0053] The temperature of the acid treatment may be 180°C-200°C, such as 180°C, 185°C, 190°C, 195°C or 200°C, or any other value within the range of 180°C-200°C.

[0054] The acid treatment time can be 25 min-35 min, such as 25 min, 28 min, 30 min, 32 min or 35 min, or any other value within the range of 25 min-35 min.

[0055] By carrying out acid treatment under the above conditions, the lithium cobalt oxide in the lithium cobalt oxide sample to be tested can be substantially dissolved.

[0056] In the present disclosure, the reaction between cobalt trioxide and potassium permanganate solution is carried out in the presence of sulfuric acid, and the sulfuric acid provides an acidic environment to make potassium permanganate exhibit strong oxidizing properties.

[0057] It should be noted that the acid used to provide the acidic environment cannot be other than sulfuric acid. The reason is that among the commonly used inorganic acids, hydrochloric acid will react with potassium permanganate to produce chlorine gas; and nitric acid itself is oxidizing, which affects the titration results.

[0058] For reference, the reaction temperature may be 20° C.-30° C., such as 20° C., 22° C., 25° C., 28° C. or 30° C., or any other value within the range of 20° C.-30° C. In some specific embodiments, the reaction temperature may be understood to be room temperature.

[0059] After the separated solid has completely reacted with the potassium permanganate solution and the sulfuric acid solution, potassium iodide solution is added to terminate the reaction. For reference, the reaction time can be 10 min to 30 min, such as 10 min, 15 min, 20 min, 25 min, or 30 min, or any other value within the range of 10 min to 30 min.

[0060] By carrying out the reaction under the above-mentioned conditions, the cobalt trioxide and the potassium permanganate solution can be completely reacted.

[0061] For reference, the concentration of above-mentioned potassium permanganate solution can be 0.008mol / L-0.012mol / L, such as 0.008mol / L, 0.009mol / L, 0.010mol / L, 0.011mol / L or 0.012mol / L etc., or other arbitrary values ​​within the scope of 0.008mol / L-0.012mol / L. In some embodiments, potassium permanganate solution can adopt potassium permanganate standard solution, specifically can be the potassium permanganate standard solution that concentration is 0.01mol / L. It should be noted that the potassium permanganate standard solution used in the present disclosure can be directly purchased, and can also be prepared voluntarily with reference to 《 GB / T 601 2016 》.

[0062] In the present disclosure, 8 mL to 12 mL (eg, 8 mL, 9 mL, 10 mL, 11 mL, or 12 mL, etc.) of potassium permanganate solution may be used for every 10 g of the lithium cobalt oxide sample to be tested.

[0063] For reference, the concentration of the above-mentioned sulfuric acid solution can be 0.8mol / L-1.2mol / L, such as 0.8mol / L, 0.9mol / L, 1.0mol / L, 1.1mol / L or 1.2mol / L, or any other value within the range of 0.8mol / L-1.2mol / L. In some embodiments, the sulfuric acid solution can be a standard sulfuric acid solution, specifically a standard sulfuric acid solution with a concentration of 1mol / L. It should be noted that the high sulfuric acid standard solution used in the present disclosure can be purchased directly or prepared by oneself with reference to GB / T 601-2016.

[0064] In the present disclosure, 8 mL to 12 mL (eg, 8 mL, 9 mL, 10 mL, 11 mL, or 12 mL, etc.) of sulfuric acid solution may be used for every 10 g of the lithium cobalt oxide sample to be tested.

[0065] In some embodiments, for every 10 g of lithium cobalt oxide sample to be tested, the volumes of potassium permanganate solution and sulfuric acid solution used are equal.

[0066] For reference, the concentration of the potassium iodide solution can be 0.8mol / L-1.2mol / L, such as 0.8mol / L, 0.9mol / L, 1.0mol / L, 1.1mol / L or 1.2mol / L, or any other value within the range of 0.8mol / L-1.2mol / L. In some embodiments, the potassium iodide solution can be a standard potassium iodide solution, specifically a standard potassium iodide solution with a concentration of 1mol / L. It should be noted that the standard potassium iodide solution used in the present disclosure can be purchased directly or prepared by itself with reference to GB / T 601-2016.

[0067] In the present disclosure, 4 mL to 6 mL (eg, 4 mL, 4.5 mL, 5 mL, 5.5 mL, or 6 mL, etc.) of potassium iodide solution may be used for every 10 g of the lithium cobalt oxide sample to be tested.

[0068] It should be noted that after adding potassium iodide solution to terminate the reaction, try to avoid and reduce the volatilization of elemental iodine.

[0069] For reference, the concentration of the above-mentioned sodium thiosulfate solution can be 0.04mol / L-0.06mol / L, such as 0.04mol / L, 0.045mol / L, 0.05mol / L, 0.055mol / L or 0.06mol / L, etc., or any other value within the range of 0.04mol / L-0.06mol / L. In some embodiments, the sodium thiosulfate solution can adopt a sodium thiosulfate standard solution, specifically a sodium thiosulfate standard solution with a concentration of 0.05mol / L. It should be noted that the sodium thiosulfate standard solution used in the present disclosure can be purchased directly or prepared by itself with reference to GB / T 601 2016.

[0070] The concentration of the indicator can be 4wt%-6wt%, such as 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt%, or any other value within the range of 4wt%-6wt%. In some embodiments, the indicator can be a starch indicator, specifically a starch indicator with a concentration of 5wt%. It should be noted that the starch indicator used in the present disclosure can be purchased directly or prepared by oneself with reference to GB / T 601 2016.

[0071] In the present disclosure, 2 mL to 4 mL (eg, 2 mL, 2.5 mL, 3 mL, 3.5 mL, or 4 mL, etc.) of the indicator may be used for every 10 g of the lithium cobalt oxide sample to be tested.

[0072] In the present disclosure, the reaction endpoint is determined by titrating until the solution becomes clear. In some embodiments, when the sodium thiosulfate solution is titrated to near the titration endpoint, the starch indicator is added and the titration is continued until the solution becomes clear.

[0073] Furthermore, in the present disclosure, a blank sample is used without adding the lithium cobalt oxide sample to be tested. The same potassium permanganate solution and sulfuric acid as in the treatment process of the lithium cobalt oxide sample are directly used for the reaction. Potassium iodide solution is added to terminate the reaction. Starch is used as an indicator and sodium thiosulfate solution is used to titrate to the endpoint.

[0074] That is, the aforementioned lithium cobalt oxide test sample is used as the test sample treatment group, and the difference between the blank sample treatment group and the test sample treatment group is only that the lithium cobalt oxide test sample is not used in the treatment process of the blank sample treatment group, but is directly reacted with potassium permanganate solution and sulfuric acid of the same concentration and volume as in the test sample treatment group, and potassium iodide solution of the same concentration and volume as in the test sample treatment group is added to terminate the reaction, and then a starch indicator of the same concentration and volume as in the test sample treatment group is added, and sodium thiosulfate solution of the same concentration as in the test sample treatment group is titrated until the solution is clear.

[0075] After the blank sample titration is completed, the content of cobalt trioxide in the lithium cobaltate sample to be tested is calculated according to the following formula:

[0076] Wherein, N1 is the mass percentage of cobalt trioxide in the lithium cobalt oxide sample to be tested, in %;

[0077] V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL;

[0078] V2 is the volume of sodium thiosulfate solution consumed by the lithium cobalt oxide sample to be tested, in mL;

[0079] c is the concentration of sodium thiosulfate solution, in mol / L;

[0080] m(Co3O4) is the amount of cobalt tetroxide in g / mol;

[0081] m0 is the weight of the lithium cobalt oxide sample to be tested, in g.

[0082] The above m(Co3O4) is a fixed value, specifically:

[0083] 58.933×3+15.999×4=240.795.

[0084] As mentioned above, the present invention separates lithium cobaltate and cobalt tetroxide from the lithium cobaltate sample by acid solution, utilizes the reducing property of low-valent Co in cobalt tetroxide, and uses strong oxidizing potassium permanganate to react with it. In this process, lithium cobaltate and Co in cobalt tetroxide are 3+ They will not participate in the reaction, so even if lithium cobalt oxide is dissolved in sulfuric acid, it will not affect the titration results, greatly improving the accuracy of the measurement results.

[0085] Furthermore, the present disclosure also proposes to correct the measured cobalt tetroxide content N1 according to the following formula:

[0086] Wherein, N2 is the mass percentage of cobalt tetroxide in the lithium ion battery sample after correction, in %;

[0087] a is the correction parameter.

[0088] By adopting the correction parameter to correct the calculated value N1, different batches of materials can be measured based on the correction value, which is beneficial to improving the accuracy of the test and the test stability of different batches.

[0089] For example, the calculation formula of the correction parameter a can be referred to as follows:

[0090] Among them, N Co is the mass percentage of Co in any cobalt oxide sample measured by ICP method, in %;

[0091] m Co is the relative atomic mass of Co;

[0092] N0 is the mass percentage of cobalt tetroxide in the cobalt tetroxide sample measured by the same determination method as the cobalt tetroxide content N1 in the lithium cobaltate sample to be tested, and the unit is %.

[0093] That is, the aforementioned lithium cobalt oxide sample to be tested is used as the test sample processing group, and any cobalt oxide sample is used as the correction processing group. The only difference between the correction processing group and the test sample processing group is that the lithium cobalt oxide sample to be tested is replaced by any mass of cobalt oxide sample, and the other operating conditions are the same.

[0094] As mentioned above, the method for determining the content of cobalt trioxide in lithium cobaltate provided by the present disclosure has small error, high accuracy, high stability, and does not require multiple titrations.

[0095] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0096] Example 1

[0097] This embodiment provides a method for determining the content of cobalt trioxide in lithium cobaltate, comprising the following steps:

[0098] (1) Determination of test sample treatment group

[0099] A lithium cobalt oxide sintered product with a Li:Co molar ratio of 1.00 was selected as the lithium cobalt oxide sample to be tested. 10g of the lithium cobalt oxide sample was weighed and added to 30mL of a 1mol / L hydrochloric acid standard solution and heated at 200°C for 30min. After cooling, the residue was filtered and rinsed with deionized water. The solid residue was added with 100mL of deionized water and placed in a 500mL conical flask. Magnetic stirring was used to ensure uniform dispersion. 10mL of a 0.01mol / L potassium permanganate standard solution and 10mL of a 1mol / L sulfuric acid standard solution were mixed in a beaker and poured into the conical flask. The beaker was rinsed with 20mL of deionized water and the washing solution was transferred to the conical flask. The reaction was incubated at 25°C in a water bath for 20min. After the reaction was completed, 5mL of a 1mol / L potassium iodide standard solution was added to terminate the reaction and the glass dish was covered to prevent the volatilization of the iodine element. Use a 0.05 mol / L sodium thiosulfate standard solution for titration. Add 3 mL of 5 wt% starch indicator near the titration endpoint. Titrate until the color disappears and the solution becomes clear. Record the volume V2 of sodium thiosulfate consumed.

[0100] (2) Determination of blank sample treatment group

[0101] Measure 10mL of 0.01mol / L potassium permanganate standard solution and 10mL of 1mol / L sulfuric acid standard solution, mix in a beaker and pour into a conical flask equipped with 100ml of deionized water. Use 20mL of deionized water to rinse the beaker and transfer the washings to the conical flask. In a water bath, incubate at 25°C for 20min. After the reaction is completed, add 5mL of 1mol / L potassium iodide standard solution to terminate the reaction. Cover with a glass dish to prevent iodine from volatilizing. Use a 0.05mol / L sodium thiosulfate standard solution to titrate. When approaching the titration endpoint, add 3mL of 5wt% starch indicator. Titrate until the color disappears and the solution becomes clear. Record the volume V1 of sodium thiosulfate consumed.

[0102] (3) Calculate the content of cobalt trioxide in the lithium cobalt oxide sample to be tested according to the following formula:

[0103] Wherein, N1 is the mass percentage of cobalt trioxide in the lithium cobalt oxide sample to be tested, in %;

[0104] V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL;

[0105] V2 is the volume of sodium thiosulfate solution consumed by the lithium cobalt oxide sample to be tested, in mL;

[0106] c is the concentration of sodium thiosulfate solution, in mol / L;

[0107] m(Co3O4) is the amount of cobalt tetroxide in g / mol;

[0108] m0 is the weight of the lithium cobalt oxide sample to be tested, in g.

[0109] The titration data of the lithium cobalt oxide sample to be tested are shown in Table 1.

[0110] Table 1 Mass percentage of residual cobalt tetroxide in lithium cobalt oxide sample

[0111] Example 2

[0112] This embodiment provides a method for determining the content of cobalt trioxide in lithium cobaltate, comprising the following steps:

[0113] (1) Determination of test sample treatment group

[0114] A lithium cobalt oxide sintered product with a Li:Co molar ratio of 1.03 was selected as the lithium cobalt oxide sample to be tested. 10g of the lithium cobalt oxide sample was weighed and added to 30mL of a 1mol / L hydrochloric acid standard solution and heated at 200°C for 30min. After cooling, the residue was filtered and rinsed with deionized water. The solid residue was added with 100mL of deionized water and placed in a 500mL conical flask. Magnetic stirring was used to ensure uniform dispersion. 10mL of a 0.01mol / L potassium permanganate standard solution and 10mL of a 1mol / L sulfuric acid standard solution were mixed in a beaker and poured into the conical flask. The beaker was rinsed with 20mL of deionized water and the washing solution was transferred to the conical flask. The reaction was incubated at 25°C in a water bath for 20min. After the reaction was completed, 5mL of a 1mol / L potassium iodide standard solution was added to terminate the reaction and the glass dish was covered to prevent the volatilization of the iodine element. Use a 0.05 mol / L sodium thiosulfate standard solution for titration. Add 3 mL of 5 wt% starch indicator near the titration endpoint. Titrate until the color disappears and the solution becomes clear. Record the volume V2 of sodium thiosulfate consumed.

[0115] (2) Determination of blank sample treatment group

[0116] Measure 10mL of 0.01mol / L potassium permanganate standard solution and 10mL of 1mol / L sulfuric acid standard solution, mix in a beaker and pour into a conical flask equipped with 100ml of deionized water. Use 20mL of deionized water to rinse the beaker and transfer the washings to the conical flask. In a water bath, incubate at 25°C for 20min. After the reaction is completed, add 5mL of 1mol / L potassium iodide standard solution to terminate the reaction. Cover with a glass dish to prevent iodine from volatilizing. Use a 0.05mol / L sodium thiosulfate standard solution to titrate. When approaching the titration endpoint, add 3mL of 5wt% starch indicator. Titrate until the color disappears and the solution becomes clear. Record the volume V1 of sodium thiosulfate consumed.

[0117] (3) Calculate the content of cobalt trioxide in the lithium cobalt oxide sample to be tested according to the following formula:

[0118] Wherein, N1 is the mass percentage of cobalt trioxide in the lithium cobalt oxide sample to be tested, in %;

[0119] V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL;

[0120] V2 is the volume of sodium thiosulfate solution consumed by the lithium cobalt oxide sample to be tested, in mL;

[0121] c is the concentration of sodium thiosulfate solution, in mol / L;

[0122] m(Co3O4) is the amount of cobalt tetroxide in g / mol;

[0123] m0 is the weight of the lithium cobalt oxide sample to be tested, in g.

[0124] The titration data of the above-mentioned lithium cobalt oxide sample to be tested are shown in Table 2.

[0125] Table 2 Mass percentage of residual cobalt trioxide in lithium cobalt oxide sample

[0126] Example 3

[0127] This embodiment provides a method for determining the content of cobalt trioxide in lithium cobaltate, comprising the following steps:

[0128] (1) Determination of test sample treatment group

[0129] A lithium cobalt oxide sintered product with a Li:Co molar ratio of 1.06 was selected as the lithium cobalt oxide sample to be tested. 10g of the lithium cobalt oxide sample was weighed and added to 30mL of a 1mol / L hydrochloric acid standard solution and heated at 200°C for 30min. After cooling, the residue was filtered and rinsed with deionized water. The solid residue was added with 100mL of deionized water and placed in a 500mL conical flask. Magnetic stirring was used to ensure uniform dispersion. 10mL of a 0.01mol / L potassium permanganate standard solution and 10mL of a 1mol / L sulfuric acid standard solution were mixed in a beaker and poured into the conical flask. The beaker was rinsed with 20mL of deionized water and the washing solution was transferred to the conical flask. The reaction was incubated at 25°C in a water bath for 20min. After the reaction was completed, 5mL of a 1mol / L potassium iodide standard solution was added to terminate the reaction and the glass dish was covered to prevent the volatilization of the iodine element. Use a 0.05 mol / L sodium thiosulfate standard solution for titration. Add 3 mL of 5 wt% starch indicator near the titration endpoint. Titrate until the color disappears and the solution becomes clear. Record the volume V2 of sodium thiosulfate consumed.

[0130] (2) Determination of blank sample treatment group

[0131] Measuring 10mL of 0.01mol / L potassium permanganate standard solution and 10mL of 1mol / L sulfuric acid standard solution are mixed in a beaker and poured into a conical flask equipped with 100ml of deionized water. Use 20mL of deionized water to rinse the beaker and transfer the washings to the conical flask. In a water bath, incubate at 25°C for 20min at 4°C. Add 5mL of 1mol / L potassium iodide standard solution to terminate the reaction, and cover with a glassware to prevent iodine from volatilizing. Use a 0.05mol / L sodium thiosulfate standard solution to titrate. When approaching the titration endpoint, drip 3mL of 5wt% starch indicator, and titrate until the color disappears and the solution becomes clear. Record the sodium thiosulfate volume V2 consumed.

[0132] (3) Calculate the content of cobalt trioxide in the lithium cobalt oxide sample to be tested according to the following formula:

[0133] Wherein, N1 is the mass percentage of cobalt trioxide in the lithium cobalt oxide sample to be tested, in %;

[0134] V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL;

[0135] V2 is the volume of sodium thiosulfate solution consumed by the lithium cobalt oxide sample to be tested, in mL;

[0136] c is the concentration of sodium thiosulfate solution, in mol / L;

[0137] m(Co3O4) is the amount of cobalt tetroxide in g / mol;

[0138] m0 is the weight of the lithium cobalt oxide sample to be tested, in g.

[0139] The titration data of the above lithium cobalt oxide sample to be tested are shown in Table 3.

[0140] Table 3 Mass percentage of residual cobalt trioxide in lithium cobalt oxide sample

[0141] Example 4

[0142] The difference between this embodiment and embodiment 1 is that the acid used for the acid treatment is aqua regia composed of concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 1:3.

[0143] The titration data of the above lithium cobalt oxide sample to be tested are shown in Table 4.

[0144] Table 4 Mass percentage of residual cobalt trioxide in lithium cobalt oxide sample

[0145] By comparing Example 1 and Example 4, it can be seen that the cobalt tetroxide content (before correction) measured in Example 4 is lower than that measured in Example 1. The reason may be that the acid used in the acid treatment process in Example 4 causes a portion of cobalt tetroxide to be lost.

[0146] Example 5

[0147] This Example differs from Example 1 in that the concentration of the hydrochloric acid standard solution is 1.5 mol / L, and the ratio of the lithium cobalt oxide sample to the acid is 10 g:25 mL. The acid treatment is carried out at 180°C for 35 minutes. The concentration of the potassium permanganate standard solution is 0.008 mol / L, and the volume is 12 mL; the concentration of the sulfuric acid standard solution is 0.8 mol / L, and the volume is 12 mL. The reaction is carried out at 20°C for 30 minutes.

[0148] The titration data of the above lithium cobalt oxide sample to be tested are shown in Table 5.

[0149] Table 5 Mass percentage of residual cobalt trioxide in lithium cobalt oxide sample to be tested

[0150] By comparing Example 1 and Example 5, it can be seen that the cobalt trioxide content (before correction) measured in Example 5 is lower than the result measured in Example 1. The reason may be that Example 5 reduces the potassium permanganate concentration, resulting in a decrease in the reaction activity of the reaction system and a lower measured value.

[0151] Example 6

[0152] This example differs from Example 1 in that the concentration of the hydrochloric acid standard solution is 1.2 mol / L. The acid treatment is carried out at 190°C for 25 minutes. The concentration of the potassium permanganate standard solution is 0.012 mol / L, and the volume is 8 mL. The concentration of the sulfuric acid standard solution is 1.2 mol / L, and the volume is 8 mL. The reaction is carried out at 30°C for 10 minutes.

[0153] The titration data of the above lithium cobalt oxide sample to be tested are shown in Table 6.

[0154] Table 6 Mass percentage of residual cobalt trioxide in lithium cobalt oxide sample

[0155] By comparing Example 1 and Example 6, it can be seen that the cobalt trioxide content (before correction) measured in Example 6 is lower than the result measured in Example 1. The reason may be that: the hydrochloric acid pretreatment temperature is increased, and part of the cobalt trioxide is lost during the acid treatment stage, resulting in a lower measured value.

[0156] Example 7

[0157] This embodiment is based on Example 1, and the cobaltous oxide content N1 measured in Example 1 is corrected according to the following formula:

[0158] Wherein, N2 is the mass percentage of cobalt tetroxide in the lithium ion battery sample after correction, in %;

[0159] a is the correction parameter.

[0160] The calculation formula of the correction parameter a is as follows:

[0161] Among them, N Co is the mass percentage of Co in the known cobalt trioxide precursor sample measured by ICP method, in %;

[0162] m Co is the relative atomic mass of Co;

[0163] N0 is the mass percentage of cobalt tetroxide in the known cobalt tetroxide precursor sample measured by the same determination method as N1 for the cobalt tetroxide content in the lithium cobaltate sample to be tested in Example 1, in %.

[0164] Specifically, the mass percentage N0 of cobalt tetroxide in the cobalt tetroxide precursor sample is known and is determined by the following method:

[0165] (1) Determination of test sample treatment group

[0166] Weigh 0.1g of cobalt trioxide precursor sample and add it to 30mL of 1mol / L hydrochloric acid standard solution. Heat it at 200℃ for 30min. After cooling, filter to obtain the residue and rinse it with deionized water. The solid residue is used as the sample to be tested, add 100mL of deionized water and place it in a 500mL conical flask. Stir magnetically to ensure uniform dispersion. Measure 10mL of 0.01mol / L potassium permanganate standard solution and 10mL of 1mol / L sulfuric acid standard solution in a beaker, mix them, and pour them into the conical flask. Rinse the beaker with 20mL of deionized water and transfer the washing liquid to the conical flask. Incubate the reaction at 25℃ in a water bath for 20min. After the reaction is completed, add 5mL of 1mol / L potassium iodide standard solution to terminate the reaction and cover with a glass dish to prevent the volatilization of the iodine element. Use a 0.05 mol / L sodium thiosulfate standard solution for titration. Add 3 mL of 5 wt% starch indicator near the titration endpoint. Titrate until the color disappears and the solution becomes clear. Record the volume V2 of sodium thiosulfate consumed.

[0167] (2) Determination of blank sample treatment group

[0168] Measure 10mL of 0.01mol / L potassium permanganate standard solution and 10mL of 1mol / L sulfuric acid standard solution, mix in a beaker and pour into an Erlenmeyer flask. Use 20mL of deionized water to rinse the beaker and transfer the washings to an Erlenmeyer flask equipped with 100mL of deionized water. In a water bath, incubate at 25°C for 20min. After the reaction is completed, add 5mL of 1mol / L potassium iodide standard solution to terminate the reaction. Cover with a glass dish to prevent iodine from volatilizing. Titrate with 0.05mol / L sodium thiosulfate standard solution. When approaching the titration endpoint, drip 3mL of 5wt% starch indicator. Titrate until the color disappears and the solution becomes clear. Record the volume V1 of sodium thiosulfate consumed.

[0169] (3) Calculate the content of cobalt tetroxide in the cobalt tetroxide precursor sample according to the following formula:

[0170] Wherein, N0 is the mass percentage of cobalt tetroxide in the cobalt tetroxide precursor sample, in %;

[0171] V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL;

[0172] V3 is the volume of sodium thiosulfate solution consumed by the cobalt trioxide precursor sample, in mL;

[0173] c is the concentration of sodium thiosulfate solution, in mol / L;

[0174] m(Co3O4) is the amount of cobalt tetroxide in g / mol;

[0175] m1 is the weight of the cobalt trioxide precursor sample, in g.

[0176] The titration data of the above cobalt trioxide precursor sample are shown in Table 7.

[0177] Table 7 Cobalt Tetroxide Precursor Sample Titration Data

[0178] It should be noted that the actual content of cobalt tetroxide in the known cobalt tetroxide precursor sample used in this example is 98.10 wt %. Compared with the cobalt tetroxide content of 97.62 wt % measured by titration in Table 7, the result measured by the determination method provided in the present disclosure is close to the actual content result of the sample and has a high accuracy.

[0179] Furthermore, 0.1 g of the above-mentioned known cobalt tetroxide precursor sample was taken and reacted with 10 mL of 0.01 mol / L potassium permanganate standard solution and 10 mL of 1 mol / L sulfuric acid standard solution in a water bath at 25°C for 20 minutes. The reaction was then performed using ICP-AES. The results showed that the Co content was 72.20 wt%, the cobalt tetroxide accounted for 98.33 wt%, and the calculated correction parameter was a = -0.007 (rounded off).

[0180] Therefore, after correction, the cobaltous oxide content N2 measured in Example 1 is 0.2476 / (1-0.007)=0.2493.

[0181] In addition, the measured value N1 of Example 2-6 was corrected using the above correction parameters, and the results are shown in Table 8.

[0182] Table 8 Mass percentage of residual cobalt trioxide in lithium cobalt oxide sample to be tested

[0183] In summary, the method for determining the content of cobalt trioxide in lithium cobaltate provided by the present disclosure has small error, high accuracy, high stability, and does not require multiple titrations. Industrial Applicability

[0184] The present invention separates lithium cobalt oxide and cobalt tetroxide in the sample to be tested by using an acid solution, and uses the reducibility of low-valent Co in cobalt tetroxide to react with potassium permanganate with strong oxidizing property. In this process, Co in lithium cobalt oxide and cobalt tetroxide is reduced. 3+ It will not participate in the reaction, so even if lithium cobalt oxide is dissolved in sulfuric acid, it will not affect the titration results, which greatly improves the accuracy of the measurement results; by introducing a correction value, the test accuracy and the stability of different batches of tests are improved.

Claims

1. A method for determining the content of cobalt trioxide in lithium cobalt oxide, characterized in that: The following steps are involved: The lithium cobalt oxide sample is treated with acid to dissolve the lithium cobalt oxide, followed by solid-liquid separation, and the separated solid is reacted with potassium permanganate solution and sulfuric acid solution, potassium iodide solution is added to terminate the reaction, starch is used as an indicator and sodium thiosulfate solution is used to titrate to the end point.

2. The measuring method according to claim 1, characterized in that The acid used in the acid treatment includes at least one of hydrochloric acid and nitric acid.

3. The measuring method according to claim 2, characterized in that The acid used in the acid treatment is aqua regia.

4. The measuring method according to claim 2 or 3, characterized in that During the acid treatment process, the ratio of the lithium cobalt oxide sample to be tested to the acid is (10 g:20 mL)-(10 g:30 mL).

5. The assay method according to any one of claims 1 to 4, characterized in that The temperature of the acid treatment is 180°C-200°C.

6. The measuring method according to claim 5, characterized in that The acid treatment time is 25min-35min.

7. The assay method according to any one of claims 1 to 6, characterized in that The reaction temperature is 20℃-30℃.

8. The measuring method according to claim 7, characterized in that The reaction time is 10min-30min.

9. The determination method according to any one of claims 1 to 8, characterized in that The concentration of the potassium permanganate solution is 0.008 mol / L-0.012 mol / L.

10. The measuring method according to claim 9, characterized in that For every 10 g of the lithium cobalt oxide sample to be tested, 8 mL to 12 mL of the potassium permanganate solution is used.

11. The assay method according to any one of claims 1 to 10, characterized in that: The concentration of the sulfuric acid solution is 0.8 mol / L-1.2 mol / L.

12. The measuring method according to claim 11, characterized in that For every 10 g of the lithium cobalt oxide sample to be tested, 8 mL to 12 mL of the sulfuric acid solution is used.

13. The determination method according to any one of claims 1 to 12, characterized in that: The concentration of the potassium iodide solution is 0.8 mol / L-1.2 mol / L.

14. The measuring method according to claim 13, characterized in that For every 10 g of the lithium cobalt oxide sample to be tested, 4 mL to 6 mL of the potassium iodide solution is used.

15. The assay method according to any one of claims 1 to 14, characterized in that: The concentration of the sodium thiosulfate solution is 0.04 mol / L-0.06 mol / L.

16. The assay method according to any one of claims 1 to 15, characterized in that: The concentration of the indicator is 4wt%-6wt%.

17. The measuring method according to claim 16, characterized in that For every 10 g of the lithium cobalt oxide sample to be tested, 2 mL to 4 mL of the indicator is used.

18. The assay method according to any one of claims 1 to 17, characterized in that: The reaction endpoint is when the solution becomes clear.

19. The assay method according to any one of claims 1 to 18, characterized in that: A blank sample without adding lithium cobalt oxide to the sample to be tested is used as the blank sample, and the same potassium permanganate solution and sulfuric acid as in the treatment process of the lithium cobalt oxide sample are directly used for reaction, potassium iodide solution is added to terminate the reaction, starch is used as an indicator, and sodium thiosulfate solution is used to titrate to the end point; After the blank sample titration is completed, the content of cobalt tetroxide in the lithium cobalt oxide sample to be tested is calculated according to the following formula: Wherein, N1 is the mass percentage of cobalt tetroxide in the lithium cobalt oxide sample to be tested, in %; V1 is the volume of sodium thiosulfate solution consumed by the blank sample, in mL; V2 is the volume of sodium thiosulfate solution consumed by the lithium cobalt oxide sample to be tested, in mL; c is the concentration of sodium thiosulfate solution, in mol / L; m(Co3O4) is the amount of cobalt tetraoxide, in g / mol; m0 is the weight of the lithium cobalt oxide sample to be tested, in g.

20. The measuring method according to claim 19, characterized in that Also includes: Correct the measured cobalt tetroxide content N1 according to the following formula: Wherein, N2 is the mass percentage of cobalt tetroxide in the lithium oxide sample after correction, in %; a is the correction parameter.

21. The measuring method according to claim 20, characterized in that The calculation formula of the correction parameter a is as follows: Among them, N Co is the mass percentage of Co in any cobalt tetroxide sample measured by ICP method, in %; m Co is the relative atomic mass of Co; N0 is the mass percentage of cobalt tetroxide in the cobalt tetroxide sample measured by the same determination method as that of the cobalt tetroxide content N1 in the lithium cobalt oxide sample to be tested, and the unit is %.

Images