A method for detecting the amount of manganese dissolved in lithium manganese iron phosphate positive electrode material

Abstract

The present invention provides a method for detecting the amount of manganese dissolved in a lithium iron manganese phosphate positive electrode material, prepares a certain Mn standard solution and uses an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element, and establishes a standard curve; and, uses water to treat the lithium iron manganese phosphate positive electrode material sample in combination with a certain treatment process to prepare a sample solution and a blank sample solution, and then uses an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element on the sample solution and the blank sample solution, and finally uses a computer to calculate the concentration of the Mn element in the sample solution in combination with the standard curve, thereby obtaining the amount of manganese dissolved in the lithium iron manganese phosphate positive electrode material. The detection method provided by the present invention can measure the content of manganese dissolved in the lithium iron manganese phosphate positive electrode material with high accuracy, and the detection method is simple, easy to operate, and has a detection period.

Description

Technical Field

[0001] The invention relates to the field of lithium ion batteries, and in particular to a method for detecting the amount of manganese dissolved in a lithium manganese iron phosphate positive electrode material. Background Art

[0002] Both LFP and LFP have olivine structures and theoretical capacities of 170 mAh / g. Therefore, LFP also has the advantages of high safety and high capacity. However, the operating voltage of LFP can reach 4.10 V (vsLi + / Li), while the working voltage of lithium iron phosphate is only 3.2V (vs Li + / Li), therefore, the energy density of lithium manganese iron phosphate can be increased by about 20% compared with the energy density of lithium iron phosphate.

[0003] However, as the ratio of manganese to iron in lithium manganese iron phosphate increases, a large number of defects and voids will appear in the material, and manganese and iron cannot completely form a unified solid solution. A large number of defects and pores are very likely to prolong the deintercalation and intercalation of lithium ions, which seriously affects the battery cycle life of lithium iron manganese phosphate during battery recycling. The manganese released from this solid solution can be characterized by manganese dissolution. The lower the manganese dissolution content (up to ppm level), the better the performance of the lithium iron manganese phosphate cathode material. Therefore, the detection of manganese dissolution in lithium iron manganese phosphate cathode materials can effectively evaluate the performance of lithium iron manganese phosphate.

[0004] Since lithium iron manganese phosphate is not widely used in the production of lithium-ion batteries, there is no public detection method for manganese dissolution detection of lithium iron manganese phosphate. If the content of manganese dissolution is too high, it will seriously affect the electrical properties of lithium iron manganese phosphate. Therefore, it is urgent to develop a detection method for manganese dissolution in lithium iron manganese phosphate positive electrode materials. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for detecting the amount of manganese dissolved in lithium manganese iron phosphate positive electrode material. The detection method provided by the present invention can measure the content of manganese dissolved in lithium manganese iron phosphate positive electrode material with high accuracy, and the detection method is simple, easy to operate, and has a short detection cycle.

[0006] The present invention provides a method for detecting the amount of manganese dissolved in a lithium manganese iron phosphate positive electrode material, comprising the following steps:

[0007] a) Take 10.00 mL of 1000 μg / mL Mn standard solution and place it in a 100 mL volumetric flask, add 2.00 mL of concentrated hydrochloric acid, add water to the mark, and shake well to obtain a stock standard solution with a Mn concentration of 100.00 μg / mL;

[0008] b) taking 0 mL, 0.50 mL, 1.00 mL, and 2.00 mL of the stock standard solution respectively into four 100 mL volumetric flasks, adding 2.00 mL of concentrated hydrochloric acid to each flask, and then adding water to the scale, shaking well, to obtain a series of standard solutions with Mn element concentrations of 0 μg / mL, 0.50 μg / mL, 1.00 μg / mL, and 2.00 μg / mL respectively;

[0009] c) using an inductively coupled plasma atomic emission spectrometer to respectively test the emission light intensity of the Mn element in the series of quasi-solutions; then, plotting a standard curve with the concentration of the Mn element in the series of quasi-solutions as the abscissa and the corresponding emission light intensity as the ordinate;

[0010] d) using an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the test sample solution and the blank sample solution respectively, and automatically calculating the concentration of the Mn element in the test sample solution from the standard curve by a computer, that is, the amount of manganese dissolved in the lithium manganese iron phosphate positive electrode material;

[0011] in,

[0012] In the step d), the sample solution is obtained by the following method:

[0013] S1. Take 5.00 g ± 0.05 g of lithium manganese iron phosphate positive electrode material and 100 mL of water into a beaker, stir and mix to obtain a mixed solution;

[0014] S2, keeping the mixed solution at 25° C. for 2 h to obtain a warm solution;

[0015] S3, filtering the insulation liquid with a microporous filter membrane with a pore size of 0.45 μm, and the obtained filtrate is the sample solution to be tested;

[0016] In the step d), the blank sample solution is prepared according to the above steps S1 to S3, except that lithium manganese iron phosphate positive electrode material is not added in step S1.

[0017] Preferably, in step c), the test conditions for testing the light emission intensity of the Mn element using an inductively coupled plasma atomic emission spectrometer are:

[0018] Wavelength: 257.610nm;

[0019] Plasma flow rate: 12L / min;

[0020] Auxiliary gas flow rate: 1.0L / min;

[0021] Atomizer flow rate: 0.7L / min;

[0022] RF power: 1200W;

[0023] Sample flow rate: 0.5L / min;

[0024] Measuring time: 5s;

[0025] Number of repetitions: 3 times;

[0026] Observation direction: radial.

[0027] Preferably, in step d), the test conditions for testing the light emission intensity of the Mn element using an inductively coupled plasma atomic emission spectrometer are:

[0028] Wavelength: 257.610nm;

[0029] Plasma flow rate: 12L / min;

[0030] Auxiliary gas flow rate: 1.0L / min;

[0031] Atomizer flow rate: 0.7L / min;

[0032] RF power: 1200W;

[0033] Sample flow rate: 0.5L / min;

[0034] Measuring time: 5s;

[0035] Number of repetitions: 3 times;

[0036] Observation direction: radial.

[0037] Preferably, in step c), the linear correlation coefficient of the standard curve is greater than 0.9995.

[0038] Preferably, in step a), the concentrated hydrochloric acid has a purity of premium grade.

[0039] Preferably, in the step b), the purity of the concentrated hydrochloric acid is premium grade.

[0040] Preferably, in step S1, the lithium manganese iron phosphate positive electrode material is weighed with an accuracy of 0.01 g.

[0041] Preferably, in step S1, the lithium iron manganese phosphate positive electrode material is a dried lithium iron manganese phosphate positive electrode material.

[0042] Preferably, the drying temperature is 110° C. and the drying time is 2 hours.

[0043] Preferably, in step S2, the insulation temperature is 25° C. and the time is 2 h;

[0044] The model of the inductively coupled plasma atomic emission spectrometer is Agilent 5110.

[0045] The detection method provided by the present invention is to prepare a certain Mn standard solution and use an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element to establish a standard curve; and, the water treatment of the lithium manganese iron phosphate positive electrode material sample is combined with a certain treatment process to prepare a sample solution and a blank sample solution, and then the inductively coupled plasma atomic emission spectrometer is used to test the Mn element emission light intensity of the sample solution and the blank sample solution, and finally the concentration of the Mn element in the sample solution is calculated by a computer in combination with the standard curve, thereby obtaining the manganese dissolution amount in the lithium manganese iron phosphate positive electrode material. The detection method provided by the present invention is simple, easy to operate and safe, can quickly detect the content of Mn dissolution, improve the work efficiency of manganese dissolution detection, and fill the lack of manganese dissolution detection methods in the industry for lithium manganese iron phosphate positive electrode materials. Moreover, the present invention has a low manganese dissolution content in lithium manganese iron phosphate, which is at the ppm level. In addition, the present invention uses an inductively coupled plasma atomic emission spectrometer to detect manganese dissolution, which is little affected by the sample matrix, so the reference sample does not need to be strictly matrix matched. At the same time, under normal circumstances, no internal standard is required, and no additives are required. Therefore, this method has good accuracy.

[0046] The experimental results show that the relative standard deviation of the detection method of the present invention is only 0.41%, and the accuracy of the Mn dissolution amount detected is relatively high. DETAILED DESCRIPTION

[0047] The present invention provides a method for detecting the amount of manganese dissolved in a lithium manganese iron phosphate positive electrode material, comprising the following steps:

[0048] a) Take 10.00 mL of 1000 μg / mL Mn standard solution and place it in a 100 mL volumetric flask, add 2.00 mL of concentrated hydrochloric acid, add water to the mark, and shake well to obtain a stock standard solution with a Mn concentration of 100.00 μg / mL;

[0049] b) taking 0 mL, 0.50 mL, 1.00 mL, and 2.00 mL of the stock standard solution respectively into four 100 mL volumetric flasks, adding 2.00 mL of concentrated hydrochloric acid to each flask, and then adding water to the scale, shaking well, to obtain a series of standard solutions with Mn element concentrations of 0 μg / mL, 0.50 μg / mL, 1.00 μg / mL, and 2.00 μg / mL respectively;

[0050] c) using an inductively coupled plasma atomic emission spectrometer to respectively test the emission light intensity of the Mn element in the series of quasi-solutions; then, plotting a standard curve with the concentration of the Mn element in the series of quasi-solutions as the abscissa and the corresponding emission light intensity as the ordinate;

[0051] d) using an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the test sample solution and the blank sample solution respectively, and automatically calculating the concentration of the Mn element in the test sample solution from the standard curve by a computer, that is, the amount of manganese dissolved in the lithium manganese iron phosphate positive electrode material;

[0052] in,

[0053] In the step d), the sample solution is obtained by the following method:

[0054] S1. Take 5.00 g ± 0.05 g of lithium manganese iron phosphate positive electrode material and 100 mL of water into a beaker, stir and mix to obtain a mixed solution;

[0055] S2, keeping the mixed solution at 25° C. for 2 h to obtain a warm solution;

[0056] S3, filtering the insulation liquid with a microporous filter membrane with a pore size of 0.45 μm, and the obtained filtrate is the sample solution to be tested;

[0057] In the step d), the blank sample solution is prepared according to the above steps S1 to S3, except that lithium manganese iron phosphate positive electrode material is not added in step S1.

[0058] The detection method provided by the present invention is to prepare a certain Mn standard solution and use an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element to establish a standard curve; and, use water treatment combined with a certain treatment process to prepare a sample solution and a blank sample solution, and then use an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element on the sample solution and the blank sample solution, and finally use a computer combined with the standard curve to calculate the concentration of the Mn element in the sample solution to be tested, thereby obtaining the manganese dissolution amount in the lithium manganese iron phosphate positive electrode material. The detection method provided by the present invention is simple, easy to operate and safe, and can quickly detect the content of Mn dissolution, thereby improving the work efficiency of manganese dissolution detection. Moreover, the present invention uses an inductively coupled plasma atomic emission spectrometer to detect Mn dissolution, and the plasma light source has good atomization, excitation and ionization capabilities. The detection method has a good detection limit, and its detection limit is generally 0.1ng / mL~100ng / mL, and the present invention has a low manganese dissolution content in lithium manganese iron phosphate, which can specifically reach the ppm level. In addition, the present invention uses an inductively coupled plasma atomic emission spectrometer to detect manganese dissolution, which is little affected by the sample matrix, so the reference sample does not need to be strictly matrix matched. At the same time, under normal circumstances, no internal standard is required, and no additives are required. Therefore, this method has good accuracy.

[0059] In the detection method provided by the present invention, a standard curve is first established through steps a) to c).

[0060] [About step a]:

[0061] a) Take 10.00mL of 1000μg / mL Mn standard solution and place it in a 100mL volumetric flask, add 2.00mL of concentrated hydrochloric acid, and then add water to the scale, shake well to obtain a stock standard solution with a Mn concentration of 100.00μg / mL.

[0062] In the present invention, the concentration of the Mn element standard solution is 1000 μg / mL, which is a national certified standard sample with a national number of GSB04-1736-2004. In the present invention, the concentrated hydrochloric acid is preferably high-grade pure concentrated hydrochloric acid, and its source is not particularly limited, and it can be a commercial product, with a concentration of 36% to 38%. In the present invention, the water is preferably pure water.

[0063] In the present invention, first measure 10.00mL of Mn element standard solution and place it in a 100mL volumetric flask, then add a small amount of concentrated hydrochloric acid 2.00mL, and then add water to make up the volume. After all the above materials are added, shake well. The temperature conditions of the above overall operation are not particularly limited and can be carried out at room temperature, specifically 20°C. After the above treatment, a reserve standard solution with a Mn element concentration of 100.00μg / mL is prepared.

[0064] [About step b]:

[0065] b) 0 mL, 0.50 mL, 1.00 mL, and 2.00 mL of the stock standard solution were respectively placed in four 100 mL volumetric flasks, 2.00 mL of concentrated hydrochloric acid was added to each flask, and water was added to the volume, and the solution was shaken to obtain a series of standard solutions with Mn element concentrations of 0 μg / mL, 0.50 μg / mL, 1.00 μg / mL, and 2.00 μg / mL, respectively.

[0066] Step b) of the present invention is to use the reserve standard solution obtained in step a) to prepare a series of standard solutions of different concentrations. Specifically, 0 mL, 0.50 mL, 1.00 mL, and 2.00 mL of the reserve standard solution are respectively measured and placed in 4 100 mL volumetric flasks, and then 2.00 mL of concentrated hydrochloric acid is added to each of the 4 volumetric flasks, and then water is added to each of the 4 volumetric flasks to make up to the scale. Among them, the concentrated hydrochloric acid is preferably a high-grade pure concentrated hydrochloric acid, and its source is not particularly limited, and it can be a commercial product with a concentration of 36% to 38%. The water is preferably pure water. After all the above materials are added, shake well. There is no special restriction on the temperature conditions of the above overall operation, and it can be carried out at room temperature, specifically 20°C. After the above treatment, a series of standard solutions with Mn element concentrations of 0 μg / mL, 0.50 μg / mL, 1.00 μg / mL, and 2.00 μg / mL are prepared.

[0067] [About step c]:

[0068] c) using an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the series of quasi-solutions respectively; then, plotting a standard curve with the concentration of the Mn element in the series of quasi-solutions as the abscissa and the corresponding emission light intensity as the ordinate.

[0069] After obtaining a series of standard solutions in step b), the present invention uses an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the obtained series of standard solutions. The model of the inductively coupled plasma atomic emission spectrometer used in the present invention is preferably Agilent 5110, which comes from Agilent Technologies Co., Ltd.

[0070] The test conditions for testing the light emission intensity of the Mn element using an inductively coupled plasma atomic emission spectrometer are preferably as follows:

[0071] Wavelength: 257.610nm;

[0072] Plasma flow rate: 12L / min;

[0073] Auxiliary gas flow rate: 1.0L / min;

[0074] Atomizer flow rate: 0.7L / min;

[0075] RF power: 1200W;

[0076] Sample flow rate: 0.5L / min;

[0077] Measuring time: 5s;

[0078] Number of repetitions: 3 times;

[0079] Observation direction: radial.

[0080] In the present invention, after measuring the emission light intensity of the Mn element in the series of standard solutions, the concentration of the Mn element in the series of quasi-solutions is used as the horizontal coordinate, and the corresponding emission light intensity is used as the vertical coordinate, and a standard curve is drawn one by one. In the present invention, the linear correlation coefficient of the standard curve is required to be greater than 0.9995. When the Mn dissolution content of the sample solution is subsequently tested in the present invention, its content is within the range of the above-mentioned standard curve.

[0081] [About step d]:

[0082] The emission light intensity of the Mn element in the test sample solution and the blank sample solution was tested by an inductively coupled plasma atomic emission spectrometer, and the concentration of the Mn element in the test sample solution was automatically calculated by a computer from the standard curve, which was the amount of manganese dissolved in the lithium manganese iron phosphate positive electrode material.

[0083] After obtaining the standard curve in step c), the present invention determines the manganese dissolution content in the lithium manganese iron phosphate positive electrode material in step d). Specifically, the present invention first uses an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the sample solution to be tested and the blank sample solution.

[0084] Wherein, the sample solution to be tested is obtained by the following method:

[0085] S1. Take 5.00 g ± 0.05 g of lithium manganese iron phosphate positive electrode material and 100 mL of water into a beaker, stir and mix to obtain a mixed solution;

[0086] S2, keeping the mixed solution at 25° C. for 2 h to obtain a warm solution;

[0087] S3. The insulation liquid is filtered using a microporous filter membrane with a pore size of 0.45 μm, and the obtained filtrate is the sample solution to be tested.

[0088] Regarding step S1:

[0089] The lithium manganese iron phosphate positive electrode material is preferably a dried lithium manganese iron phosphate positive electrode material. The drying temperature is preferably 110° C., and the drying time is preferably 2 hours. In the present invention, when weighing the lithium manganese iron phosphate positive electrode material sample, 5.00 g ± 0.05 g of the sample is measured, and the weighing accuracy is accurate to 0.01 g. The water is preferably pure water. The amount of water is 100 mL. The beaker is preferably a 250 mL beaker.

[0090] In the present invention, the step S1 preferably specifically includes:

[0091] Water-soluble: Measure 5.00g±0.05g of lithium manganese iron phosphate positive electrode material and place it in a beaker, then measure 100mL of water and pour it into the beaker, then seal the beaker with a sealing film and gently shake the beaker to disperse the sample;

[0092] Stirring: The beaker is placed on a magnetic therapy stirrer and stirred under the action of a magnetic stirrer to obtain a mixed solution. The stirring speed is preferably 300 r / min to 900 r / min, more preferably 800 r / min. The stirring time is preferably ≤ 60 min, more preferably 30 min. After stirring, a mixed solution is obtained.

[0093] The step S1 of the present invention mainly dissolves the lithium iron manganese phosphate positive electrode material in water, and transfers the manganese extracted from the lithium iron manganese phosphate positive electrode material into water, so as to facilitate the subsequent measurement of the manganese dissolution content. This step of the present invention uses water for treatment, and cannot use acid for treatment, otherwise the acid will destroy the structure of the lithium iron manganese phosphate, and the manganese dissolution content of the lithium iron manganese phosphate positive electrode material cannot be accurately measured.

[0094] Regarding step S2:

[0095] After the mixed solution is obtained in step S1, the mixed solution is kept warm, specifically, the beaker can be placed in a water bath for heat preservation. In the present invention, it is preferably kept warm at 10°C to 30°C, more preferably 25°C. The heat preservation time is preferably 0.5h to 4h, more preferably 2h. After the above-mentioned heat preservation treatment, a heat preservation liquid of the corresponding temperature is obtained. During the static heat preservation process, the mixed solution is gradually stratified, and the upper layer is a clear liquid.

[0096] Regarding step S3:

[0097] After the insulation liquid is obtained in step S2, it is filtered through a microporous filter membrane with a pore size of 0.45 μm, the upper clear liquid of the insulation liquid is filtered out and transferred to a clean beaker, which is the sample solution to be tested.

[0098] The present invention dissolves the deintercalated manganese of the lithium manganese iron phosphate positive electrode material to be tested through the above steps S1 to S3 to prepare a solution of the tested sample.

[0099] In the present invention, the preparation of the blank sample solution in step d) is carried out according to the above steps S1 to S3, except that no lithium manganese iron phosphate positive electrode material is added in step S1, thereby forming a blank control solution.

[0100] After obtaining the sample solution and the blank sample solution, the present invention uses an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the sample solution and the blank sample solution. The model of the inductively coupled plasma atomic emission spectrometer is consistent with that described above and will not be repeated here. The test conditions for testing the emission light intensity of the Mn element using the inductively coupled plasma atomic emission spectrometer are preferably as follows:

[0101] Wavelength: 257.610nm;

[0102] Plasma flow rate: 12L / min;

[0103] Auxiliary gas flow rate: 1.0L / min;

[0104] Atomizer flow rate: 0.7L / min;

[0105] RF power: 1200W;

[0106] Sample flow rate: 0.5L / min;

[0107] Measuring time: 5s;

[0108] Number of repetitions: 3 times;

[0109] Observation direction: radial.

[0110] The above test conditions of the present invention are the best conditions for determining manganese ions, which are conducive to ensuring the accuracy and precision of the test results. In the present invention, after measuring the emission light intensity of the Mn element in the sample solution and the blank sample solution, the computer automatically calculates the concentration of the Mn element in the sample solution in combination with the standard curve, thereby obtaining the manganese dissolution amount in the lithium manganese iron phosphate positive electrode material. In the present invention, the measured Mn element content unit is ppm.

[0111] The detection method provided by the present invention has the following beneficial effects:

[0112] 1. The detection method of the present invention is simple, easy to operate and safe, and can quickly detect the content of Mn dissolution, thereby improving the working efficiency of manganese dissolution detection.

[0113] 2. The present invention uses an inductively coupled plasma atomic emission spectrometer to detect Mn dissolution. The plasma light source has good atomization, excitation and ionization capabilities, and the detection method has a good detection limit, which is generally 0.1ng / mL to 100ng / mL. In addition, the present invention has a low manganese dissolution content in lithium manganese iron phosphate, which is at the ppm level.

[0114] 3. The present invention uses an inductively coupled plasma atomic emission spectrometer to detect manganese dissolution, which is little affected by the sample matrix, so the reference sample does not need to be strictly matrix matched. At the same time, under normal circumstances, no internal standard is required, and no additives are required. Therefore, this method has good accuracy.

[0115] The experimental results show that the relative standard deviation of the detection method of the present invention is only 0.41%, and the accuracy of the Mn dissolution amount detected is relatively high.

[0116] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0117] Example 1

[0118] a) Take 10.00mL of 1000μg / mL Mn standard solution and place it in a 100mL volumetric flask, add 2.00mL of concentrated hydrochloric acid (superior grade), then add water to the mark, shake well, and obtain a stock standard solution with a Mn concentration of 100.00μg / mL.

[0119] b) 0 mL, 0.50 mL, 1.00 mL, and 2.00 mL of the stock standard solution were respectively placed in four 100 mL volumetric flasks, 2.00 mL of concentrated hydrochloric acid (superior grade) was added to each flask, and water was added to the volume, and the solution was shaken to obtain a series of standard solutions with Mn element concentrations of 0 μg / mL, 0.50 μg / mL, 1.00 μg / mL, and 2.00 μg / mL, respectively.

[0120] c) using an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the series of quasi-solutions respectively; then, plotting a standard curve with the concentration of the Mn element in the series of quasi-solutions as the abscissa and the corresponding emission light intensity as the ordinate.

[0121] d) using an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the test sample solution and the blank sample solution respectively, and automatically calculating the concentration of the Mn element in the test sample solution from the standard curve by a computer, thereby obtaining the manganese dissolution amount in the lithium manganese iron phosphate positive electrode material;

[0122] The sample solution and the blank sample solution are obtained by the following method:

[0123] Take a dried lithium manganese iron phosphate powder sample, weigh it 5 times in sequence, weigh about 5.00g each time, accurate to 0.01g, put it in 5 250mL beakers, set a number (recorded as sample 1 to sample 5), and do a blank test with the sample; then use a 100mL measuring cylinder to accurately measure 100mL of pure water and pour it into the above 5 beakers and the blank sample beaker; immediately seal the beaker mouth with a sealing film, and gently shake the beaker to disperse the sample, then put all the beakers on a magnetic stirrer, add a magnetic stirrer, stir at 800r / min for 30min, and get a mixed solution (5 sample solutions and 1 blank solution). Then place the beaker in a 25℃ water bath and keep it warm for 2h. Then, the sealing film of the beaker was opened, and the supernatant in the beaker was filtered through a microporous filter membrane with a pore size of 0.45 μm on a suction filtration device, and transferred to a clean 100 mL beaker to obtain the test sample solution (a total of 5 portions) and the blank sample solution.

[0124] The model of the inductively coupled plasma atomic emission spectrometer used is Agilent 5110, and the test conditions for testing the emission light intensity of the Mn element are as follows:

[0125] Wavelength: 257.610nm;

[0126] Plasma flow rate: 12L / min;

[0127] Auxiliary gas flow rate: 1.0L / min;

[0128] Atomizer flow rate: 0.7L / min;

[0129] RF power: 1200W;

[0130] Sample flow rate: 0.5L / min;

[0131] Measuring time: 5s;

[0132] Number of repetitions: 3 times;

[0133] Observation direction: radial.

[0134] The five test sample solutions were all subjected to the tests of steps a) to d) to obtain the test results of five samples in total, as shown in Table 1.

[0135] Table 1: Test results

[0136]

[0137] It can be seen that the relative standard deviation of the sample is only 0.41%, and there is basically no significant difference in the manganese dissolution content results of multiple sampling tests of a sample. Therefore, the accuracy of the Mn dissolution amount detected by the present invention is relatively high.

[0138] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for detecting the amount of manganese dissolved in lithium manganese iron phosphate positive electrode material, characterized in that: The following steps are involved: a) Take 10.00mL of 1000μg / mL Mn standard solution and place it in a 100mL volumetric flask, add 2.00mL of concentrated hydrochloric acid, and then add water to the scale, shake well, and obtain a stock standard solution with a Mn concentration of 100.00μg / mL; b) Take 0 mL, 0.50 mL, 1.00 mL, and 2.00 mL of the stock standard solution respectively and place them in four 100 mL volumetric flasks, add 2.00 mL of concentrated hydrochloric acid to each flask, then add water to make up to the mark, shake well, and obtain a series of standard solutions with Mn element concentrations of 0 μg / mL, 0.50 μg / mL, 1.00 μg / mL, and 2.00 μg / mL respectively; c) using an inductively coupled plasma atomic emission spectrometer to respectively test the emission light intensity of the Mn element in the series of standard solutions; then, drawing a standard curve with the concentration of the Mn element in the series of standard solutions as the abscissa and the corresponding emission light intensity as the ordinate; d) using an inductively coupled plasma atomic emission spectrometer to test the emission light intensity of the Mn element in the test sample solution and the blank sample solution respectively, and automatically calculating the concentration of the Mn element in the test sample solution from the standard curve by a computer, that is, the amount of manganese dissolved in the lithium manganese iron phosphate positive electrode material; in, In the step d), the sample solution is obtained by the following method: S1. Take 5.00 g ± 0.05 g of lithium manganese iron phosphate positive electrode material and 100 mL of water into a beaker, stir and mix to obtain a mixed solution; The lithium iron manganese phosphate positive electrode material is a dried lithium iron manganese phosphate positive electrode material; S2, keeping the mixed solution at 25° C. for 2 h to obtain a warm solution; S3, filtering the insulation liquid with a microporous filter membrane with a pore size of 0.45 μm, and the obtained filtrate is the sample solution to be tested; Step S1 mainly involves dissolving the lithium manganese iron phosphate positive electrode material in water, and transferring the manganese extracted from the lithium manganese iron phosphate positive electrode material into water; In the step d), the blank sample solution is prepared according to the above steps S1 to S3, except that no lithium manganese iron phosphate positive electrode material is added in step S1.

2. The detection method according to claim 1, characterized in that: In the step c), the test conditions for testing the emission light intensity of the Mn element using an inductively coupled plasma atomic emission spectrometer are: Wavelength: 257.610 nm; Plasma flow rate: 12 L / min; Auxiliary gas flow rate: 1.0 L / min; Nebulizer flow rate: 0.7 L / min; RF power: 1200 W; Sample flow rate: 0.5 L / min; Measuring time: 5s; Number of repetitions: 3 times; Observation direction: radial.

3. The detection method according to claim 1, characterized in that: In the step d), the test conditions for testing the light emission intensity of the Mn element using an inductively coupled plasma atomic emission spectrometer are: Wavelength: 257.610 nm; Plasma flow rate: 12 L / min; Auxiliary gas flow rate: 1.0 L / min; Nebulizer flow rate: 0.7 L / min; RF power: 1200 W; Sample flow rate: 0.5 L / min; Measuring time: 5s; Number of repetitions: 3 times; Observation direction: radial.

4. The detection method according to claim 1, characterized in that: In the step c), the linear correlation coefficient of the standard curve is greater than 0.9995.

5. The detection method according to claim 1, characterized in that: In the step a), the purity of the concentrated hydrochloric acid is high purity.

6. The detection method according to claim 1, characterized in that: In the step b), the purity of the concentrated hydrochloric acid is high purity.

7. The detection method according to claim 1, characterized in that: In the step S1, the lithium manganese iron phosphate positive electrode material is weighed with an accuracy of 0.01 g.

8. The detection method according to claim 1, characterized in that: The drying temperature is 110° C. and the drying time is 2 hours.

9. The detection method according to claim 1, characterized in that: In step S2, the insulation temperature is 25°C and the time is 2h; The model of the inductively coupled plasma atomic emission spectrometer is Agilent 5110.

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