Method for detecting impurities in electrolyte, liquid salt or organic solvent by ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer)

Abstract

The invention discloses a method for detecting impurities in electrolyte, liquid salt or organic solvent by ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer). The method comprises the following steps: (1) preparing a mixed element standard solution with gradient concentration and containing impurity elements to be detected; a to-be-detected sample solution is taken and diluted with a diluent, and the diluent is ethyl alcohol of the electronic grade or above or a mixed solution of ethyl alcohol of the electronic grade or above and deionized water; and (2) respectively inputting the concentration value of the mixed element standard solution and the dilution multiple of the to-be-detected sample solution by adopting an inductively coupled plasma emission spectrometer, sequentially determining the analysis blank, the standard solution, the analysis blank and the to-be-detected sample solution, and determining the concentration of the mixed element standard solution by taking the diluent in the step (1) as the analysis blank and the curve of the determined standard solution as a standard curve. The content of to-be-detected elements in the to-be-detected sample solution is calculated by adopting an external standard method, the unit is ppm, and the to-be-detected impurity elements refer to at least one of K, Na, Fe, Ca, Pb, Cu, Cr, As, Al, Zn, Cd and Mn.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical chemistry and particularly relates to a method for detecting impurities in an electrolyte, a liquid salt or an organic solvent by ICP-OES. Technical Background

[0002] Liquid salt is the raw material for the electrolyte, a crucial component of batteries. It transfers charge between the positive and negative electrodes, significantly impacting battery performance, including operating temperature, cycle efficiency, and safety. The level of metal impurities in battery electrolytes plays a crucial role in determining battery performance. Therefore, the determination of metal impurities in battery electrolytes is extremely important. The primary method for determining metal impurities in battery electrolytes is inductively coupled plasma optical emission spectrometry (ICP-OES). Current ICP-OES methods suffer from complex pre-processing and unstable or inaccurate results.

[0003] Patent application CN109946366A discloses a method for determining metal impurities in lithium-ion battery electrolyte, wherein the metal impurities include K, Na, Fe, Ca, Pb, Cu, Cr, As, Al, Zn, Cd, and Mn. The method comprises the following steps: 1. preparing a standard solution containing the elements K, Na, Fe, Ca, Pb, Cu, Cr, As, Al, Zn, Cd, and Mn; 2. taking a sample solution to be tested and diluting the sample solution to be tested with a diluent solution; 3. using an inductively coupled plasma emission spectrometer, inputting the concentration value of the standard solution and the dilution multiple of the sample solution to be tested, and sequentially measuring an analytical blank, a standard solution, and a sample solution to be tested, using the diluent solution as the analytical blank and the curve of the measured standard solution as the standard curve, and using an external standard method to calculate the content (ppm) of K, Na, Fe, Ca, Pb, Cu, Cr, As, Al, Zn, Cd, and Mn in the sample solution to be tested. However, the patent application has the following disadvantages:

[0004] 1. There is no limit on the purity of ethanol. Ethanol or nitric acid below electronic grade will affect the blank of the standard solution curve, resulting in inaccurate results.

[0005] 2. Cannot detect lithium salts and sodium salts containing boron.

[0006] The purpose of the present invention is to provide a method for determining metal impurities in battery electrolytes, liquid salts and organic reagents with good accuracy, wide detection range and greater convenience. Summary of the Invention

[0007] The object of the present invention is to provide a method for detecting impurities in an electrolyte, a liquid salt or an organic solvent by using ICP-OES.

[0008] Based on the above objectives, the present invention adopts the following technical solutions:

[0009] A method for detecting impurities in an electrolyte, liquid salt or organic solvent by ICP-OES comprises the following steps:

[0010] (1) preparing a mixed element standard solution containing the impurity element to be tested with a gradient concentration; taking the sample solution to be tested, and diluting the sample solution to be tested with a diluent, wherein the diluent is electronic grade or higher ethanol or a mixed solution of electronic grade or higher ethanol and deionized water;

[0011] (2) using an inductively coupled plasma emission spectrometer, inputting the concentration value of the mixed element standard solution and the dilution multiple of the sample solution to be tested respectively, and sequentially measuring the analytical blank, the standard solution, the analytical blank, and the sample solution to be tested, using the diluent of step (1) as the analytical blank, and using the curve of the measured standard solution as the standard curve, and using the external standard method to calculate the content of the element to be tested in the sample solution to be tested, the unit is ppm, and the impurity element to be tested refers to at least one of K, Na, Fe, Ca, Pb, Cu, Cr, As, Al, Zn, Cd and Mn. When measuring Li salt, Li is not measured in the impurity elements to be tested, and when measuring Na salt, Li and Na are not measured in the impurity elements to be tested.

[0012] Furthermore, the dilution factor of the sample solution to be tested is ≥20 (high sample content will cause the instrument to stall).

[0013] Furthermore, the mixed element standard solution includes first, second, third and fourth mixed element standard solutions, and the concentration ranges of each element to be measured in the first, second, third and fourth mixed element standard solutions are: 0.025ppm~1ppm, 0.05ppm~2ppm, 0.25ppm~5ppm, 0.5ppm~10ppm respectively.

[0014] Specifically, the steps for preparing the mixed element standard solution are as follows: 1 g, 2 g, 5 g, and 10 g of a mixed standard solution containing the element to be measured with a concentration of 100 ppm are accurately weighed into four PFA plastic bottles on an electronic balance, and then the solutions in the four PFA plastic bottles are diluted to 100 g with a diluent to obtain the first, second, third, and fourth mixed element standard solutions with concentrations of 1 ppm, 2 ppm, 5 ppm, and 10 ppm of the element to be measured, respectively.

[0015] Furthermore, the electrolyte is a lithium salt electrolyte and / or a sodium salt electrolyte, the liquid salt is a lithium salt liquid salt and / or a sodium salt liquid salt, and the organic solvent is one or more carbonate solvents and carboxylate solvents.

[0016] Furthermore, the ethanol concentration in the diluent is 15v% to 100v%.

[0017] Furthermore, when detecting a sample containing boron or dichloromethane, 50v% to 100v% ethanol is used as a diluent, preferably, 50v% ethanol is used as a diluent; when detecting a sample that does not contain boron and does not contain dichloromethane, 15v% to 50v% ethanol is used as a diluent, preferably, 15v% ethanol is used as a diluent.

[0018] Furthermore, the lithium salt or sodium salt refers to at least one of lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, sodium lithium hexafluorophosphate, lithium difluorophosphate, sodium difluorophosphate, lithium tetrafluoroborate, sodium tetrafluoroborate, lithium difluorooxalatoborate (LiDFOB), sodium difluorooxalatoborate, lithium monooxalatobis(fluoroborate) (LiBF2C2O4), sodium monooxalatobis(fluoroborate), lithium bis(oxalatoborate) (LiBOB) and sodium bis(oxalatoborate).

[0019] Furthermore, the accuracy of the electronic balance is above 0.0001 g.

[0020] The advantages of the present invention are good accuracy, greater simplicity and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The standard curve diagram and standard curve equation for each impurity element when detecting lithium salt in an embodiment of the present invention;

[0022] Figure 2 The standard curve diagram and standard curve equation of each impurity element when detecting sodium salt in the embodiment of the present invention are shown. DETAILED DESCRIPTION

[0023] The following examples are intended only to provide those of ordinary skill in the art with a complete disclosure and description of how to make and evaluate the compounds, compositions, articles, devices and / or methods described and claimed herein, and are intended to be illustrative only and not to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperatures, etc.), but some errors and deviations should be accounted for.

[0024] Example 1

[0025] (1) The steps for preparing the mixed element standard solution are as follows: 1.0000 g, 2.0000 g, 5.0000 g, and 10.0000 g of a mixed element standard solution containing K, Na, Fe, As, Ca, Pb, Cu, Cr, Al, Zn, Cd, and Mn were accurately weighed into four 250 mL PFA plastic bottles on an electronic balance, respectively, with the concentration of each element being 100 ppm. Then, the solutions in the four PFA plastic bottles were diluted to 100 g with a diluent (15 v% electronic grade ethanol), thereby obtaining the first, second, third, and fourth mixed element standard solutions with the above-mentioned element concentrations of 1.0000 ppm, 2.0000 ppm, 5.0000 ppm, and 10.0000 ppm, respectively, hereinafter referred to as standard solution 1, standard solution 2, standard solution 3, and standard solution 4;

[0026] (2) Take about 2 g of lithium bis(fluorosulfonyl)imide liquid salt [lithium bis(fluorosulfonyl)imide is dissolved in EMC (ethyl methyl carbonate) to form a saturated solution] and dilute it to more than 40 g with a diluent (15 v% electronic grade ethanol). Record the sample weight and the weight of the diluted sample;

[0027] (3) Inductively coupled plasma atomic emission spectrometry was used to determine the spectral line intensity of each metal element in the standard solution at the analytical line of K, Na, Fe, As, Ca, Cu, Cr, Al, Zn, Pb, Cd, and Mn elements. A standard curve corresponding to each element was constructed according to the standard curve method, and the correlation of the standard curve was greater than 0.999. The standard curves and standard curve equations of each impurity element are as follows: Figure 1 As shown. Figure 1 It can be seen that the standard curve equations of each element are: Na: y = 2246000x-12166.4, K: y = 1035000x-5623.1, Cr: y = 333400x+162.0, Mn: y = 2831000x+3818.7, Cu: y = 541200x+354.9Zn: y = 63810x+53.1, Al: y = 463300x-216.9, Cd: y = 293100x+225.7, Fe: y = 331700x-1944.2, Pb: y = 16640x+19.0, Ca: y = 221200x+23.7, As: y = 5392x-0.7.

[0028] Detection limit requirements: As: 0.0529ppm; Zn: 0.0004ppm; Pb: 0.0314ppm; Fe: 0.0029ppm; Cd: 0.0017ppm; Mn: 0.0008ppm; Cr: 0.0009ppm; Cu: 0.0012ppm; Al: 0.0069ppm; Na: 0.0049ppm; K: 0.0075ppm; Ca: 0.0006ppm.

[0029] (3) Instrument sampling process: Using an inductively coupled plasma atomic emission spectrometer, the instrument must be turned on, stabilized, initialized, and cooled down. Then, the blank (15v% electronic grade ethanol), standard solution 1, standard solution 2, standard solution 3, standard solution 4, blank (15v% electronic grade ethanol), and the test solution are measured in sequence on the instrument software page;

[0030] (4) After the instrument detects the result, re-test the midpoint of the standard solution. If the deviation of the standard solution result is less than 10% of the midpoint of the standard solution, it indicates that the instrument test result is correct.

[0031] (5) The inductively coupled plasma atomic emission spectrometer is a 220MX model from PE Company, and the test conditions are as follows: atomizer flow rate: 0.6 L / min; power: 1150 W; radio frequency: 27.12 MHz; analytical pump speed: 45 r / min; argon outlet pressure: 0.5-0.6 MPa; oxygen outlet pressure: 15.0, cooling circulating water temperature 20°C-22°C; observation angle: radial observation;

[0032] (6) The cations in Table 1 are the average values ​​of ten ICP-OES detection results, and the cations in Table 2 are the average values ​​of ten ICP-OES detection results.

[0033] Table 1 The average value of the ten times of testing of the lithium bis(fluorosulfonyl)imide liquid salt sample prepared in Example 1

[0034] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.19 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0

[0035] Table 2 Results of ten tests on the lithium bis(fluorosulfonyl)imide liquid salt sample prepared in Example 1

[0036] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.19 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.19 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.18 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.19 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.19 0.70 0.25 0.34 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.19 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.19 0.72 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.20 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.20 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0 Element results (ppm) 0.19 0.71 0.25 0.33 0.21 0.02 0 0 0 0.03 0 0

[0037] The above results show that the method is stable for detecting lithium bis(fluorosulfonyl)imide liquid salt.

[0038] Example 2

[0039] (1) The steps for preparing the mixed element standard solution are as follows: 1.0000 g, 2.0000 g, 5.0000 g, and 10.0000 g of a mixed element standard solution containing K, Fe, As, Ca, Pb, Cu, Cr, Al, Zn, Cd, and Mn were accurately weighed into four 250 mL PFA plastic bottles on an electronic balance, respectively, with the concentration of each element being 100 ppm. Then, the solutions in the four PFA plastic bottles were diluted to 100 g with a diluent (15 v% electronic grade ethanol), thereby obtaining the first, second, third, and fourth mixed element standard solutions with the above-mentioned element concentrations of 1.0000 ppm, 2.0000 ppm, 5.0000 ppm, and 10.0000 ppm, respectively, hereinafter referred to as standard solution 1, standard solution 2, standard solution 3, and standard solution 4;

[0040] (2) Take 2 g of sodium bis(fluorosulfonyl)imide liquid salt [sodium bis(fluorosulfonyl)imide is dissolved in EMC (ethyl methyl carbonate) to form a saturated solution] and detect it using the method in Example 1; the standard curve and standard curve equation of each impurity element are as follows: Figure 2 As shown. Figure 2 It can be seen that the standard curve equations of each element are: K: y = 1002000x-5542.5, Cr: y = 365700x + 121.9, Mn: y = 3098000x + 1186.9, Cu: y = 545700x + 405.9, Zn: y = 73990x + 10.2, Al: y = 480400x-760.9, Cd: y = 325900x + 115.5, Fe: y = 362700x-1371.4, Pb: y = 18580x-50.8, Ca:

[0041] y=250100x+16.8, As: y=5661x-16.7.

[0042] (3) The cations in Table 3 are the average values ​​of ten ICP-OES detection results, and the cations in Table 4 are the average values ​​of ten ICP-OES detection results.

[0043] Table 3 The average results of ten tests of the sodium bis(fluorosulfonyl)imide liquid salt sample prepared in Example 2

[0044] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.30 0.41 0.31 0.11 0.02 0 0.02 0 0.03 0 0

[0045] Table 4 Results of ten tests on the sodium bis(fluorosulfonyl)imide liquid salt sample prepared in Example 2

[0046] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.30 0.41 0.31 0.10 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.31 0.42 0.31 0.11 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.30 0.41 0.31 0.10 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.30 0.41 0.31 0.13 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.30 0.43 0.31 0.13 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.31 0.40 0.31 0.11 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.30 0.41 0.31 0.11 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.30 0.41 0.31 0.10 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.30 0.40 0.31 0.10 0.02 0 0.02 0 0.03 0 0 Element results (ppm) 0.31 0.41 0.31 0.11 0.02 0 0.02 0 0.03 0 0

[0047] The above results show that the method is stable for detecting sodium bis(fluorosulfonyl)imide liquid salt.

[0048] Example 3

[0049] (1) Take 2 g of lithium hexafluorophosphate liquid salt [lithium hexafluorophosphate is dissolved in DMC (dimethyl carbonate) to form a saturated solution], establish a standard curve using the method in Example 1, and perform detection.

[0050] (2) The cations in Table 5 are the average values ​​of ten ICP-OES detection results, and the cations in Table 6 are the average values ​​of ten ICP-OES detection results.

[0051] Table 5 Average results of ten tests of the lithium hexafluorophosphate liquid salt sample prepared in Example 3

[0052] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.37 0.13 0.25 0.33 0.21 0.02 0 0 0.42 0.03 0.41 0

[0053] Table 6 Results of ten tests on the lithium hexafluorophosphate liquid salt sample prepared in Example 3

[0054] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.37 0.15 0.25 0.33 0.30 0.02 0 0 0.42 0.03 0.41 0 Element results (ppm) 0.36 0.13 0.25 0.32 0.33 0.02 0 0 0.44 0.03 0.41 0 Element results (ppm) 0.36 0.12 0.25 0.34 0.31 0.02 0 0 0.42 0.03 0.41 0 Element results (ppm) 0.37 0.11 0.25 0.32 0.29 0.02 0 0 0.41 0.03 0.41 0 Element results (ppm) 0.35 0.14 0.25 0.35 0.30 0.02 0 0 0.41 0.03 0.41 0 Element results (ppm) 0.37 0.12 0.25 0.33 0.29 0.02 0 0 0.43 0.03 0.41 0 Element results (ppm) 0.39 0.13 0.25 0.31 0.29 0.02 0 0 0.41 0.03 0.41 0 Element results (ppm) 0.39 0.13 0.25 0.35 0.29 0.02 0 0 0.41 0.03 0.41 0 Element results (ppm) 0.38 0.13 0.25 0.32 0.30 0.02 0 0 0.43 0.03 0.41 0 Element results (ppm) 0.37 0.15 0.25 0.33 0.30 0.02 0 0 0.41 0.03 0.41 0

[0055] The above results show that the method is stable for detecting lithium hexafluorophosphate liquid salt.

[0056] Example 4

[0057] (1) Take 2 g of sodium hexafluorophosphate liquid salt [sodium hexafluorophosphate is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and perform detection using the method in Example 2.

[0058] (2) The cations in Table 7 are the average values ​​of ten ICP-OES detection results, and the cations in Table 8 are the average values ​​of ten ICP-OES detection results.

[0059] Table 7 Average results of ten tests of the sodium hexafluorophosphate liquid salt sample prepared in Example 4

[0060] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.19 0.13 0.71 0.30 0 0 0.05 0.42 0.03 0.11 0

[0061] Table 8 Results of ten tests of the sodium hexafluorophosphate liquid salt sample prepared in Example 4

[0062]

[0063]

[0064] The above results show that the method is stable for detecting liquid sodium hexafluorophosphate.

[0065] Example 5

[0066] (1) Take 2 g of lithium difluorophosphate liquid salt [lithium difluorophosphate is dissolved in EA (ethyl acetate) to form a saturated solution] and test it using the method in Example 1.

[0067] (2) The cations in Table 9 are the average values ​​of ten ICP-OES detection results, and the cations in Table 10 are the average values ​​of ten ICP-OES detection results.

[0068] Table 9 Average results of ten tests of lithium difluorophosphate liquid salt samples prepared in Example 5

[0069] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.23 0.13 0.65 0.37 0.13 0.05 0 0 0.42 0 0.41 0

[0070] Table 10 Results of ten tests on the lithium difluorophosphate liquid salt sample prepared in Example 5

[0071] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.23 0.13 0.65 0.37 0.13 0.05 0 0 0.42 0 0.41 0 Element results (ppm) 0.23 0.14 0.65 0.37 0.14 0.05 0 0 0.44 0 0.41 0 Element results (ppm) 0.23 0.12 0.65 0.37 0.12 0.05 0 0 0.42 0 0.41 0 Element results (ppm) 0.24 0.13 0.62 0.36 0.13 0.04 0 0 0.41 0 0.41 0 Element results (ppm) 0.23 0.12 0.69 0.36 0.12 0.06 0 0 0.41 0 0.42 0 Element results (ppm) 0.25 0.13 0.65 0.37 0.13 0.05 0 0 0.43 0 0.41 0 Element results (ppm) 0.23 0.13 0.65 0.35 0.13 0.05 0 0 0.41 0 0.41 0 Element results (ppm) 0.24 0.12 0.65 0.37 0.12 0.05 0 0 0.41 0 0.41 0 Element results (ppm) 0.23 0.13 0.65 0.39 0.13 0.05 0 0 0.43 0 0.41 0 Element results (ppm) 0.23 0.14 0.65 0.39 0.14 0.05 0 0 0.41 0 0.41 0

[0072] The above results show that the method is stable for detecting lithium difluorophosphate liquid salt.

[0073] Example 6

[0074] (1) Take 2 g of sodium difluorophosphate liquid salt [sodium difluorophosphate is dissolved in EA (ethyl acetate) to form a saturated solution] and test it using the method in Example 2.

[0075] (2) The cations in Table 11 are the average values ​​of ten ICP-OES detection results, and the cations in Table 12 are the average values ​​of ten ICP-OES detection results.

[0076] Table 11 The average value of the sodium difluorophosphate liquid salt sample prepared in Example 6 tested ten times

[0077] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.19 0.13 0.81 0.30 0 0 0.05 0.41 0 0.11 0

[0078] Table 12 Results of ten tests of the sodium difluorophosphate liquid salt sample prepared in Example 6

[0079] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.20 0.15 0.81 0.30 0 0 0.05 0.41 0 0.10 0 Element results (ppm) 0.19 0.13 0.81 0.33 0 0 0.05 0.41 0 0.11 0 Element results (ppm) 0.18 0.13 0.81 0.31 0 0 0.05 0.41 0 0.10 0 Element results (ppm) 0.19 0.11 0.81 0.29 0 0 0.05 0.41 0 0.13 0 Element results (ppm) 0.19 0.14 0.81 0.30 0 0 0.05 0.42 0 0.13 0 Element results (ppm) 0.19 0.12 0.81 0.29 0 0 0.05 0.41 0 0.11 0 Element results (ppm) 0.19 0.13 0.81 0.29 0 0 0.05 0.41 0 0.11 0 Element results (ppm) 0.20 0.13 0.81 0.29 0 0 0.05 0.41 0 0.10 0 Element results (ppm) 0.20 0.13 0.81 0.30 0 0 0.05 0.41 0 0.10 0 Element results (ppm) 0.19 0.15 0.81 0.30 0 0 0.05 0.41 0 0.11 0

[0080] The above results show that the method is stable in detecting liquid sodium difluorophosphate.

[0081] Example 7

[0082] (1) The steps for preparing the mixed element standard solution are as follows: 1.0000 g, 2.0000 g, 5.0000 g, and 10.0000 g of a mixed element standard solution containing K, Na, Fe, As, Ca, Pb, Cu, Cr, Al, Zn, Cd, and Mn were accurately weighed into four 250 mL PFA plastic bottles on an electronic balance, respectively, with the concentration of each element being 100 ppm. Then, the solutions in the four PFA plastic bottles were diluted to 100 g with a diluent (50 v% electronic grade ethanol), thereby obtaining the first, second, third, and fourth mixed element standard solutions with the above-mentioned element concentrations of 1.0000 ppm, 2.0000 ppm, 5.0000 ppm, and 10.0000 ppm, respectively, hereinafter referred to as standard solution 1, standard solution 2, standard solution 3, and standard solution 4;

[0083] (2) Take 2 g of lithium tetrafluoroborate liquid salt [lithium tetrafluoroborate is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and dilute it to more than 40 g with a diluent (50% electronic grade ethanol). Record the sample weight and the weight of the diluted sample;

[0084] (3) Inductively coupled plasma atomic emission spectrometry was used to determine the spectral line intensity of each metal element in the standard solution at the analytical line of K, Na, Fe, Ca, Pb, Cu, Cr, Al, Zn, Pb, Cd, and Mn elements. A standard curve corresponding to each element was constructed according to the standard curve method, and the correlation of the standard curve was greater than 0.999.

[0085] (4) Instrument sampling process: Using an inductively coupled plasma atomic emission spectrometer, the instrument must be turned on, stabilized, initialized, and cooled down. Then, the blank (50v% electronic grade ethanol), standard solution 1, standard solution 2, standard solution 3, standard solution 4, blank (50v% electronic grade ethanol), and the test solution are measured in sequence on the instrument software page.

[0086] (5) After waiting for the instrument to detect the result, test the middle point of the standard solution again. If the deviation of the standard solution result is less than 10% of the middle point of the standard solution, it means that the instrument detection result is correct.

[0087] (6) The inductively coupled plasma atomic emission spectrometer is the 220MX model of PE Company, and the test conditions are as follows: atomizer flow rate: 0.6L / min; power: 1150W; radio frequency frequency: 27.12MHz; analysis pump speed: 45r / min; argon outlet pressure: 0.5-0.6MPa; oxygen outlet pressure: 15.0, cooling circulating water temperature 20℃-22℃; observation angle: radial observation.

[0088] (7) The cations in Table 13 are the average values ​​of ten ICP-OES detection results, and the cations in Table 14 are the average values ​​of ten ICP-OES detection results.

[0089] Table 13 Average results of ten tests of the lithium tetrafluoroborate liquid salt sample prepared in Example 7

[0090] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.37 0.42 1.81 0.65 0.13 0 0 0.13 0.42 0 0.41 0

[0091] Table 14 Results of ten tests on the lithium tetrafluoroborate liquid salt sample prepared in Example 7

[0092] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.37 0.42 1.81 0.65 0.13 0 0 0.13 0.42 0 0.41 0 Element results (ppm) 0.37 0.44 1.83 0.65 0.14 0 0 0.13 0.44 0 0.41 0 Element results (ppm) 0.37 0.42 1.81 0.65 0.12 0 0 0.15 0.42 0 0.41 0 Element results (ppm) 0.36 0.41 1.81 0.62 0.13 0 0 0.13 0.41 0 0.41 0 Element results (ppm) 0.36 0.41 1.82 0.69 0.12 0 0 0.12 0.41 0 0.42 0 Element results (ppm) 0.37 0.43 1.81 0.65 0.13 0 0 0.11 0.43 0 0.41 0 Element results (ppm) 0.35 0.41 1.80 0.65 0.13 0 0 0.14 0.41 0 0.41 0 Element results (ppm) 0.37 0.41 1.80 0.65 0.12 0 0 0.12 0.41 0 0.41 0 Element results (ppm) 0.39 0.43 1.79 0.65 0.13 0 0 0.13 0.43 0 0.41 0 Element results (ppm) 0.39 0.41 1.83 0.65 0.14 0 0 0.13 0.41 0 0.41 0

[0093] The above results show that the method is stable for detecting lithium tetrafluoroborate liquid salt.

[0094] Example 8

[0095] (1) The steps for preparing the mixed element standard solution are as follows: 1.0000 g, 2.0000 g, 5.0000 g, and 10.0000 g of a mixed element standard solution containing K, Fe, As, Ca, Pb, Cu, Cr, Al, Zn, Cd, and Mn were accurately weighed in four 250 mL PFA plastic bottles on an electronic balance, respectively, with the concentration of each element being 100 ppm. The solutions in the four PFA plastic bottles were then diluted to 100 g with a diluent (50 v% electronic grade ethanol), thereby obtaining the first, second, third, and fourth mixed element standard solutions with the above-mentioned element concentrations of 1.0000 ppm, 2.0000 ppm, 5.0000 ppm, and 10.0000 ppm, respectively, hereinafter referred to as standard solution 1, standard solution 2, standard solution 3, and standard solution 4.

[0096] (1) Take 2 g of sodium tetrafluoroborate liquid salt [sodium tetrafluoroborate is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and test it using the method in Example 7;

[0097] (2) The cations in Table 15 are the average values ​​of ten ICP-OES detection results, and the cations in Table 16 are the average values ​​of ten ICP-OES detection results.

[0098] Table 15 Average results of ten tests of the sodium tetrafluoroborate liquid salt sample prepared in Example 8

[0099] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.23 0.13 1.65 0.42 0 0 0.42 0.37 0 0.13 0

[0100] Table 16 Results of ten tests on the sodium tetrafluoroborate liquid salt sample prepared in Example 8

[0101] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.23 0.15 1.65 0.42 0 0 0.42 0.37 0 0.13 0 Element results (ppm) 0.23 0.13 1.65 0.41 0 0 0.44 0.37 0 0.14 0 Element results (ppm) 0.23 0.13 1.65 0.41 0 0 0.42 0.37 0 0.12 0 Element results (ppm) 0.24 0.11 1.62 0.43 0 0 0.41 0.36 0 0.13 0 Element results (ppm) 0.23 0.14 1.69 0.41 0 0 0.41 0.36 0 0.12 0 Element results (ppm) 0.25 0.12 1.65 0.41 0 0 0.43 0.37 0 0.13 0 Element results (ppm) 0.23 0.13 1.65 0.43 0 0 0.41 0.35 0 0.13 0 Element results (ppm) 0.24 0.13 1.65 0.41 0 0 0.41 0.37 0 0.12 0 Element results (ppm) 0.23 0.13 1.65 0.44 0 0 0.43 0.39 0 0.13 0 Element results (ppm) 0.23 0.15 1.65 0.42 0 0 0.41 0.39 0 0.14 0

[0102] The above results show that the method is stable for detecting liquid sodium tetrafluoroborate.

[0103] Example 9

[0104] (1) Take 2 g of lithium difluorooxalatoborate liquid salt [lithium difluorooxalatoborate is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and perform the test using the method in Example 7;

[0105] (2) The cations in Table 17 are the average values ​​of ten ICP-OES detection results, and the cations in Table 18 are the average values ​​of ten ICP-OES detection results.

[0106] Table 17 Average results of ten tests of lithium difluorooxalatoborate liquid salt samples prepared in Example 9

[0107] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.23 1.42 1.65 0.65 1.13 0 0 0.05 0 0.42 0.42 0

[0108] Table 18 Results of ten tests on the lithium difluorooxalatoborate liquid salt sample prepared in Example 9

[0109] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.23 1.42 1.65 0.65 1.13 0 0 0.05 0 0.42 0.42 0 Element results (ppm) 0.23 1.41 1.65 0.62 1.14 0 0 0.05 0 0.44 0.44 0 Element results (ppm) 0.23 1.41 1.65 0.69 1.12 0 0 0.05 0 0.42 0.42 0 Element results (ppm) 0.24 1.43 1.62 0.65 1.13 0 0 0.04 0 0.41 0.41 0 Element results (ppm) 0.23 1.41 1.69 0.65 1.12 0 0 0.06 0 0.41 0.41 0 Element results (ppm) 0.25 1.41 1.65 0.65 1.13 0 0 0.05 0 0.43 0.43 0 Element results (ppm) 0.23 1.43 1.65 0.65 1.13 0 0 0.05 0 0.41 0.41 0 Element results (ppm) 0.24 1.41 1.65 0.65 1.12 0 0 0.05 0 0.41 0.41 0 Element results (ppm) 0.23 1.44 1.65 0.65 1.13 0 0 0.05 0 0.43 0.43 0 Element results (ppm) 0.23 1.42 1.65 0.66 1.14 0 0 0.05 0 0.41 0.41 0

[0110] The above results show that the method is stable for detecting lithium bis(oxalatoborate) liquid salt.

[0111] Example 10

[0112] (1) Take 2 g of sodium difluorooxalatoborate liquid salt [sodium difluorooxalatoborate is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and test it using the method in Example 8;

[0113] (2) The cations in Table 19 are the average values ​​of ten ICP-OES detection results, and the cations in Table 20 are the average values ​​of ten ICP-OES detection results.

[0114] Table 19 Average results of ten tests of sodium difluorooxalatoborate liquid salt samples prepared in Example 10

[0115] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.42 1.81 1.13 0.42 0 0 0.42 0 0.30 0.13 0

[0116] Table 20 Results of ten tests on the sodium difluorooxalatoborate liquid salt sample prepared in Example 10

[0117]

[0118]

[0119] The above results show that the method is stable for detecting sodium difluorooxalatoborate liquid salt.

[0120] Example 11

[0121] (1) Take 2 g of lithium bis(oxalatoborate) liquid salt [lithium bis(oxalatoborate) is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and perform the test using the method in Example 7.

[0122] (2) The cations in Table 21 are the average values ​​of ten ICP-OES detection results, and the cations in Table 22 are the average values ​​of ten ICP-OES detection results.

[0123] Table 21 Average results of ten tests of lithium bis(oxalatoborate) liquid salt samples prepared in Example 11

[0124] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.37 2.81 1.42 1.81 0.41 0 0 0 0 0.42 0.30 0

[0125] Table 22 Results of ten tests on the lithium bis(oxalatoborate) liquid salt sample prepared in Example 11

[0126] Detection elements Fe As Na K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.37 2.81 1.42 1.81 0.41 0 0 0 0 0.42 0.30 0 Element results (ppm) 0.37 2.81 1.44 1.83 0.41 0 0 0 0 0.44 0.30 0 Element results (ppm) 0.37 2.81 1.42 1.81 0.42 0 0 0 0 0.42 0.30 0 Element results (ppm) 0.36 2.83 1.41 1.81 0.41 0 0 0 0 0.41 0.33 0 Element results (ppm) 0.36 2.81 1.41 1.82 0.41 0 0 0 0 0.41 0.31 0 Element results (ppm) 0.37 2.81 1.43 1.81 0.41 0 0 0 0 0.43 0.29 0 Element results (ppm) 0.35 2.82 1.41 1.80 0.41 0 0 0 0 0.41 0.30 0 Element results (ppm) 0.37 2.81 1.41 1.80 0.41 0 0 0 0 0.41 0.29 0 Element results (ppm) 0.39 2.80 1.43 1.79 0.40 0 0 0 0 0.43 0.30 0 Element results (ppm) 0.39 2.80 1.41 1.83 0.43 0 0 0 0 0.41 0.30 0

[0127] The above results show that the method is stable for detecting lithium bis(oxalatoborate) liquid salt.

[0128] Example 12

[0129] (1) Take 2 g of sodium bis(oxalatoborate) liquid salt [lithium sodium bis(oxalatoborate) is dissolved in DMC (dimethyl carbonate) to form a saturated solution] and test it using the method in Example 8.

[0130] (2) The cations in Table 23 are the average values ​​of ten ICP-OES detection results, and the cations in Table 24 are the average values ​​of ten ICP-OES detection results.

[0131] Table 23 Average results of ten tests of sodium bis(oxalatoborate) liquid salt samples prepared in Example 12

[0132] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.13 2.42 1.81 0.37 0 0 0.13 0 0 0.65 0

[0133] Table 24 Results of ten tests on the sodium bis(oxalatoborate) liquid salt sample prepared in Example 12

[0134] Detection elements Fe As K Ca Mn Pb Cr Cu Zn Al Cd Element results (ppm) 0.13 2.42 1.81 0.37 0 0 0.13 0 0 0.65 0 Element results (ppm) 0.14 2.44 1.83 0.37 0 0 0.14 0 0 0.65 0 Element results (ppm) 0.12 2.42 1.81 0.37 0 0 0.12 0 0 0.65 0 Element results (ppm) 0.13 2.41 1.81 0.36 0 0 0.13 0 0 0.62 0 Element results (ppm) 0.12 2.41 1.82 0.36 0 0 0.12 0 0 0.69 0 Element results (ppm) 0.13 2.43 1.81 0.37 0 0 0.13 0 0 0.65 0 Element results (ppm) 0.13 2.41 1.80 0.35 0 0 0.13 0 0 0.65 0 Element results (ppm) 0.12 2.41 1.80 0.37 0 0 0.12 0 0 0.65 0 Element results (ppm) 0.13 2.43 1.79 0.39 0 0 0.13 0 0 0.65 0 Element results (ppm) 0.14 2.41 1.83 0.39 0 0 0.13 0 0 0.65 0

[0135] The above results show that the method is stable for detecting sodium bis(oxalatoborate) liquid salt.

Claims

1. A method for detecting impurities in electrolyte, liquid salt or organic solvent by ICP-OES, characterized in that: The following steps are involved: (1) Prepare a mixed element standard solution containing the impurity element to be tested with gradient concentrations; take the sample solution to be tested and dilute it with a diluent, which is electronic grade or above ethanol or a mixed solution of electronic grade or above ethanol and deionized water; (2) Using an inductively coupled plasma emission spectrometer, input the concentration value of the mixed element standard solution and the dilution multiple of the sample solution to be tested respectively, and sequentially measure the analytical blank, standard solution, analytical blank, and sample solution to be tested. The diluent of step (1) is used as the analytical blank, and the curve of the measured standard solution is used as the standard curve. The content of the element to be tested in the sample solution to be tested is calculated by the external standard method, and the unit is ppm. The impurity element to be tested is at least one of K, Na, Fe, Ca, Pb, Cu, Cr, As, Al, Zn, Cd and Mn. When measuring Na salt, Na is not measured in the impurity elements to be tested.

2. The method according to claim 1, characterized in that The dilution factor of the sample solution to be tested is ≥20.

3. The method according to claim 1, characterized in that The mixed element standard solution includes first, second, third and fourth mixed element standard solutions, and the concentration ranges of the elements to be measured in the first, second, third and fourth mixed element standard solutions are respectively: 0.025ppm~1ppm, 0.05ppm~2ppm, 0.25ppm~5ppm, and 0.5ppm~10ppm.

4. The method according to claim 3, characterized in that The steps for preparing mixed element standard solutions are as follows: 1 g, 2 g, 5 g, and 10 g of a 100 ppm mixed standard solution containing the element to be measured are accurately weighed into four PFA plastic bottles on an electronic balance. Then, the solutions in each of the four PFA plastic bottles are diluted to 100 g with a diluent to obtain the first, second, third, and fourth mixed element standard solutions with concentrations of 1 ppm, 2 ppm, 5 ppm, and 10 ppm of the element to be measured, respectively.

5. The method according to claim 1, wherein The electrolyte is a lithium salt electrolyte and / or a sodium salt electrolyte, the liquid salt is a lithium salt liquid salt and / or a sodium salt liquid salt, and the organic solvent is one or more carbonate solvents and carboxylate solvents.

6. The method according to claim 1, characterized in that The ethanol concentration in the diluent is 15v%~100v%.

7. The method according to claim 6, characterized in that When testing samples containing boron or dichloromethane, use 50v%~100v% ethanol as the diluent. When testing samples that do not contain boron and dichloromethane, use 15v%~50v% ethanol as the diluent.

8. The method according to claim 5, characterized in that The lithium salt and sodium salt refer to at least one of lithium bisfluorosulfonyl imide, sodium bisfluorosulfonyl imide, lithium hexafluorophosphate, sodium lithium hexafluorophosphate, lithium difluorophosphate, sodium difluorophosphate, lithium tetrafluoroborate, sodium tetrafluoroborate, lithium difluorooxalatoborate, sodium difluorooxalatoborate, lithium monooxalatobisfluoroborate, sodium monooxalatobisfluoroborate, lithium bisoxalatoborate and sodium bisoxalatoborate.

9. The method according to claim 4, characterized in that The accuracy of the electronic balance is above 0.0001g.

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