Pretreatment method of lithium iron phosphate positive electrode material for ICP (Inductively Coupled Plasma) test

Abstract

The invention discloses a pretreatment method of a lithium iron phosphate positive electrode material for ICP (Inductively Coupled Plasma) test, which comprises the following steps: digesting the lithium iron phosphate positive electrode material and fixing the volume, dispersing the lithium iron phosphate positive electrode material in a dispersion medium before digesting, heating to 430-460 DEG C, carrying out oxidation reaction, and keeping for 1.5-3 hours. Comprising the following steps: S1, ultrasonic dispersion: weighing a lithium iron phosphate positive electrode material, and carrying out ultrasonic dispersion in a dispersion medium for 3-6 minutes to obtain a dispersion; s2, heating to remove carbon: heating the dispersion to generate oxidation reaction to obtain an oxidized sample; s3, acid digestion: mashing the oxidized sample into powder, and adding a digestion reagent until the solid is completely dissolved to obtain a digestion solution; and S4, constant volume: carrying out constant volume on the digestion solution by using pure water. The lithium iron phosphate is heated for 1.5-3 hours in an aerobic environment at the temperature of 430-460 DEG C, so that a carbon coating on the surface of the lithium iron phosphate can be effectively removed, and the content detection result of a main element Li is more accurate; concentrated hydrochloric acid is used for replacing mixed acid for digestion, so that waste gas is greatly reduced, and risks in safety and environmental protection are reduced.

Description

A pretreatment method for lithium iron phosphate cathode materials for ICP testing Technical Field

[0001] This invention relates to the field of lithium iron phosphate detection technology, and more specifically, to a pretreatment method for lithium iron phosphate cathode materials used in ICP testing. Background Technology

[0002] Lithium iron phosphate (LFP) cathode material is a widely researched and applied lithium-ion battery material. Compared with traditional lithium cobalt oxide (LiCO) materials, it has advantages such as lower toxicity, lower cost, longer cycle life, and better safety. LFP materials entered the industrialization stage in the 1990s and have been widely used in mobile phones, digital products, power tools, and electric vehicles. To ensure battery performance and safety, the main elements in LFP materials are typically tested during production, such as lithium (Li), iron (Fe), and phosphorus (P). Currently, the mainstream testing methods are spectrophotometry and ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry). ICP testing requires heating and digesting the sample with aqua regia before volume adjustment. For existing LFP cathode materials, the surface often has a carbon coating layer, making it difficult for aqua regia to completely dissolve the lithium iron phosphate portion. The long dissolution time also leads to the loss of the tested elements, resulting in lower test results for the main elements in the LFP cathode material. Furthermore, during volume adjustment, the dilution factor of the test solution increases, further amplifying the error.

[0003] Chinese patent application number CN201410428603.1 discloses a method for detecting the content of main elements in carbon-coated lithium iron phosphate or lithium manganese iron phosphate, including the following steps: (1) Sample pretreatment: the sample to be tested is digested with acid, transferred and diluted to a fixed volume, allowed to stand, and after the solution separates into layers, the clear middle part is taken as the test solution; (2) Plotting a standard curve: a series of mixed standard solutions are prepared according to the type of main element to be tested, and the standard curve is plotted using an inductively coupled plasma atomic emission spectrometer; (3) Determination of the content of main elements: the content of main elements in the test solution is determined using an inductively coupled plasma atomic emission spectrometer. This invention adopts a simple pretreatment method, and the analysis results are accurate. It can quickly, accurately, and quantitatively determine the content of main elements in carbon-coated lithium iron phosphate or lithium manganese iron phosphate, improve the product quality of lithium iron phosphate and lithium manganese iron phosphate, and provide a guarantee for controlling the intermediate process. However, the application only used a simple acid digestion process for the pretreatment of lithium iron phosphate. The modified carbon coating layer in the cathode material could not be removed well or the removal time was too long, which affected the ICP test results of the main elements, especially Li, Fe and P, after the volume was set.

[0004] Chinese Patent Application No. CN202310478280.6 discloses a digesting agent for carbon-coated lithium manganese iron phosphate and a method for detecting the content of major elements in carbon-coated lithium manganese iron phosphate. The digesting agent comprises a first digesting agent and a second digesting agent. The first digesting agent comprises a mixture of nitric acid solution and sulfuric acid solution, wherein the mass concentration of the nitric acid solution is ≥50 wt%, the mass concentration of the sulfuric acid solution is ≥80 wt%, and the volume ratio of the nitric acid solution to the sulfuric acid solution is not less than 0.3:1. The second digesting agent comprises a hydrochloric acid solution, wherein the mass concentration of the hydrochloric acid solution is ≥30 wt%, and the volume ratio of the hydrochloric acid solution to the sulfuric acid solution is not less than 1:1. This digesting agent can completely digest carbon-coated lithium iron phosphate, improving the accuracy and consistency of subsequent detection of the content of major elements in carbon-coated lithium iron phosphate. The application discloses a digestion agent, which is a combination of multiple reagents including hydrochloric acid, sulfuric acid, and nitric acid. It has a good digestion effect on carbon-coated lithium manganese iron phosphate. However, the use of multiple digestion agents not only makes the process complicated and increases the cost, but also releases a large amount of toxic and harmful gases from the nitric acid reaction, which will endanger experimental safety and pollute the testing environment.

[0005] Chinese Patent Application No. CN202211053973.2 discloses a method for detecting manganese in carbon-coated manganese iron lithium phosphate, relating to the field of manganese detection technology. The specific detection method is as follows: S1, ferrous ammonium sulfate standardization; S1-1, drying the working reagent potassium dichromate to constant weight using an electric drying oven at a temperature of 120℃±2℃; S1-2, weighing 0.1000±0.0004g of the working reagent potassium dichromate from the above steps and dissolving it in 25ml of ultrapure water; S1-3, adding 10ml of sulfuric acid mixed solution and 70ml of ultrapure water; S1-4, titrating with the prepared ferrous ammonium sulfate solution until the orange-yellow color disappears; S1-5, adding 2 drops of N-benzoic acid indicator and continuing titration until the solution changes from purple-red to bright green as the endpoint. This method for detecting manganese in carbon-coated lithium manganese iron phosphate (LMP) primarily avoids the impact of incomplete sample digestion on data accuracy. It employs manual titration to completely digest the LMP, improving detection stability and controlling the range within 0.2%. While the application proposes heating the sample in a graphite furnace (320°C) until completely dissolved (without black particles) and reacting it with perchloric acid to digest the carbon coating, this method involves pretreatment with perchloric acid in a 320°C graphite furnace to ensure complete dissolution of the carbon-coated LMP. The disposal of unreacted perchloric acid is difficult, and the waste liquid is corrosive and toxic. Furthermore, the high temperature may alter the valence state of metal ions (such as Mn and Fe) in LMP, affecting the accuracy of subsequent analyses. In addition, the mixing of perchloric acid with organic matter could potentially cause an explosion, endangering the safety of testing personnel.

[0006] In summary, when using ICP testing to determine the elemental content in battery materials, a pretreatment method is needed to digest the material due to the presence of a modified carbon layer. This digestion process eliminates the interference of carbon on the analytes, leading to more accurate results. Existing technologies suggest the selection of optimal digesting agents, commonly including hydrochloric acid, nitric acid, perchloric acid, and various acid combinations. However, firstly, carbon is insoluble in common acids, and prolonged dissolution time can cause loss of the analyte, resulting in lower data. Secondly, while perchloric acid can oxidize and decompose carbon, it can explode upon contact with organic matter, posing a certain hazard. Furthermore, using a combination of multiple strong acids as digesting agents increases safety risks and costs. Therefore, overcoming the interference of the carbon coating layer on the analytes during ICP testing, which leads to lower measured content, is a pressing technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] To address the problem that current ICP testing methods for elemental content in battery cathode materials often fail to effectively remove the carbon coating layer used for battery modification, leading to inaccurate element determination results due to carbon interference, this invention provides a pretreatment method for lithium iron phosphate cathode materials used in ICP testing. By designing an oxidation method, the influence of the carbon coating layer on the testing process is minimized, resulting in a more easily detectable precursor product and more accurate ICP test results.

[0008] This invention provides a pretreatment method for lithium iron phosphate cathode material for ICP testing, comprising: dispersing the lithium iron phosphate cathode material in a dispersion medium, then heating it to 430~460℃ and maintaining it for 1.5~3h to induce an oxidation reaction, and finally digesting and adjusting the volume.

[0009] Because lithium iron phosphate is coated with a carbon layer, the decomposition temperature of the surface carbon layer is above 400℃ in an aerobic environment. If the temperature is below 430℃, the carbon layer may not be completely decomposed, and if the temperature is above 460℃, elements such as Li and P in lithium iron phosphate may volatilize.

[0010] The method includes the following steps:

[0011] S1: Ultrasonic dispersion: Weigh the lithium iron phosphate cathode material and ultrasonically disperse it in the dispersion medium for 3-6 minutes to obtain the dispersion.

[0012] S2: Heating to remove carbon: The dispersion is heated to undergo an oxidation reaction to obtain an oxidized sample;

[0013] S3: Acid digestion: Crush the oxidized sample into powder, add digestion reagent until the solid is completely dissolved to obtain a digestion solution;

[0014] S4: Volume adjustment: The digestion solution is adjusted to volume with pure water.

[0015] In step S1, the dispersion medium is anhydrous ethanol or pure water; the liquid-to-solid ratio of the dispersion medium to the lithium iron phosphate cathode material is 5-12.5:1. In this step, the purpose of ultrasonic dispersion is to disperse the agglomerated material and ensure that the material can fully contact air for oxidation during the high-temperature process. Pure water or anhydrous ethanol is used as the dispersion medium to ensure no byproducts after dispersion. Pure water is low in cost, while ethanol has good dispersibility, is easily volatile at high temperatures, and does not introduce other impurities. The ultrasonic duration is controlled to be 3-6 minutes. Less than 3 minutes will result in poor dispersion and the material may still agglomerate. If it exceeds 6 minutes, the material is already completely dispersed, and continuing ultrasonication would waste testing resources.

[0016] In step S2, the carbon coating layer on the surface of the lithium iron phosphate cathode material is oxidized and removed. During this step, the carbon layer undergoes an oxidation reaction. Lithium iron phosphate also oxidizes in the presence of oxygen, with ferrous iron being oxidized to ferric iron, and the black lithium iron phosphate turning red. When the sample completely changes from black to red, it indicates that the carbon coating on the lithium iron phosphate surface has been completely removed.

[0017] In step S3, the digestion reagent is concentrated hydrochloric acid with a mass fraction of 36%; the mass ratio of the oxidized sample to the digestion reagent is 1:100-150; after adding the digestion reagent, the mixture is heated and stirred at 150-200℃. Maintaining the temperature at 150-200℃ in this step is to accelerate the reaction rate and better dissolve the sample. Below 150℃, the reaction rate decreases significantly, and the reaction between the oxidized sample and concentrated hydrochloric acid lacks the necessary high temperature to break the lattice energy, leading to reaction stagnation or only surface dissolution, resulting in incomplete dissolution of Fe. 3+ If not fully released, unreacted solids may remain in the solution or intermediate products (such as FeCl2) may be generated, affecting subsequent testing and analysis. Temperatures above 150℃ accelerate lattice disruption and ion diffusion, resulting in a rapid and complete reaction, suitable for industrial or high-efficiency experiments.

[0018] The volume adjustment includes a first volume adjustment and a second volume adjustment. In the first volume adjustment, 20-30 ml of the digestion solution is taken and diluted with pure water to a final volume of 100 ml. In the second volume adjustment, 5 ml of the first volume adjustment solution is taken and diluted with pure water to a final volume of 100 ml. In step S4, the sample is diluted twice. The first volume adjustment involves diluting all solutions to 100 ml. Then, 5 ml of the first volume adjustment solution is taken and diluted to 100 ml for the second volume adjustment, resulting in a final dilution factor of 5 * 20 = 100 times. ICP testing typically has certain accuracy requirements, necessitating dilution to a certain ratio. Diluting to too low or too high a ratio will prevent measurement. Appropriately reducing the dilution factor within the measurable range increases the representativeness of the measured sample, improves measurement accuracy, and reduces errors caused by uneven sample dilution during volume adjustment. This step involves two volume adjustments, gradually bringing the sample concentration to the instrument's optimal detection range through these two dilutions. This reduces the impact of single-shot errors on the results, improving accuracy and precision. It also avoids direct dilution that could lead to turbidity or uneven composition, ensuring the solubility and stability of the analyte.

[0019] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0020] 1. This invention uses high-temperature heating to react the carbon coating on the surface of lithium iron phosphate with oxygen, which can effectively remove the carbon coating on the surface of lithium iron phosphate. This overcomes the problem in the prior art where the carbon coating in lithium iron phosphate causes interference when testing lithium element, resulting in a lower lithium element value. At the same time, it shortens the acid digestion time and avoids the loss of lithium element due to excessive acid digestion time, which significantly improves the accuracy of lithium element testing in the main element test of lithium iron phosphate.

[0021] 2. This invention uses concentrated hydrochloric acid as a digestion reagent in the pretreatment process to replace mixed acid digestion, which can greatly reduce waste gas and lower safety and environmental risks.

[0022] 3. This invention can optimize the traditional testing process for lithium iron phosphate, reduce the acid removal step, decrease the pretreatment time for testing, and improve detection efficiency.

[0023] 4. This invention can prepare pre-test samples with a smaller dilution factor while ensuring the accuracy of the test results, thereby reducing the volume determination error caused by human error or a large dilution factor. Detailed Implementation

[0024] The embodiments of this application will now be described in more detail. This application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to provide a more thorough and complete understanding of the application. It should be understood that the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0025] Example 1: A pretreatment method for lithium iron phosphate cathode material used in ICP testing, comprising the following steps:

[0026] S1: Ultrasonic dispersion: Take a petri dish and a small beaker, wash and dry them, take 0.4g of lithium iron phosphate sample into the dried petri dish, measure 5ml of anhydrous ethanol into the petri dish with a graduated cylinder, and sonicate for 3min to obtain the dispersion;

[0027] S2: Decarbonization by heating: The obtained dispersion is placed in an environment of 430℃ and heated for 1.5h to remove carbon, and an oxidation reaction occurs to obtain an oxidized sample;

[0028] S3: Acid digestion: Gently crush the obtained oxidized sample into powder using a sampling spoon, weigh 0.2g of the powdered oxidized sample into a dry beaker, measure 20ml of 36% concentrated hydrochloric acid and pour it into the beaker, place the beaker on a graphite heating furnace at 150℃ and stir with a glass cup for 1h until completely dissolved to obtain the digestion solution;

[0029] S4: Volume Adjustment: First, transfer the cooled digestion solution to a 100ml volumetric flask rinsed with ultrapure water. Rinse the beaker with ultrapure water and pour the resulting washing solution into the volumetric flask. Use a dropper to adjust the volume to 100ml and shake well to complete the first volume adjustment. Then, use a pipette to draw 5ml from the 100ml solution adjusted in the first volume adjustment and transfer it to another 100ml volumetric flask. Adjust the volume to 100ml and shake well to complete the second volume adjustment.

[0030] The pre-test samples obtained by the above pretreatment method were subjected to ICP testing for main content.

[0031] Example 2: A pretreatment method for lithium iron phosphate cathode material used in ICP testing, the specific steps of which include:

[0032] S1: Ultrasonic dispersion: Take a petri dish and a small beaker, wash and dry them, take 0.4g of lithium iron phosphate sample into the dried petri dish, measure 5ml of anhydrous ethanol into the petri dish with a graduated cylinder, and sonicate for 5min to obtain the dispersion.

[0033] S2: Decarbonization by heating: The obtained dispersion is placed in an environment of 450℃ and heated for 1.5h to remove carbon, resulting in an oxidation reaction and an oxidized sample;

[0034] S3: Acid digestion: Gently crush the obtained oxidized sample into powder using a sampling spoon, weigh 0.2g of the powdered oxidized sample into a dry beaker, measure 20ml of 36% concentrated hydrochloric acid and pour it into the beaker, place the beaker on a graphite heating furnace at 150℃ and stir with a glass cup for 1h until completely dissolved to obtain the digestion solution;

[0035] S4: Volume Adjustment: First, transfer the cooled digestion solution to a 100ml volumetric flask rinsed with ultrapure water. Rinse the beaker with ultrapure water and pour the resulting washing solution into the volumetric flask. Use a dropper to adjust the volume to 100ml and shake well to complete the first volume adjustment. Then, use a pipette to draw 5ml from the 100ml solution adjusted in the first volume adjustment and transfer it to another 100ml volumetric flask. Adjust the volume to 100ml and shake well to complete the second volume adjustment.

[0036] The pre-test samples obtained by the above pretreatment method were subjected to ICP testing for main content.

[0037] Example 3: A pretreatment method for lithium iron phosphate cathode material used in ICP testing, the specific steps of which include:

[0038] S1: Ultrasonic dispersion: Take a petri dish and a small beaker, wash and dry them, take 0.4g of lithium iron phosphate sample into the dried petri dish, measure 5ml of anhydrous ethanol into the petri dish with a graduated cylinder, and sonicate for 6min to obtain the dispersion.

[0039] S2: Decarbonization by heating: The obtained dispersion is placed in an environment of 460℃ and heated for 1.5h to remove carbon, and an oxidation reaction occurs to obtain an oxidized sample;

[0040] S3: Acid digestion: Gently crush the obtained oxidized sample into powder using a sampling spoon, weigh 0.2g of the powdered oxidized sample into a dry beaker, measure 20ml of 36% concentrated hydrochloric acid and pour it into the beaker, place the beaker on a 200℃ graphite heating furnace and stir with a glass cup for 1h until completely dissolved to obtain the digestion solution;

[0041] S4: Volume Adjustment: First, transfer the cooled digestion solution to a 100ml volumetric flask rinsed with ultrapure water. Rinse the beaker with ultrapure water and pour the resulting washing solution into the volumetric flask. Use a dropper to adjust the volume to 100ml and shake well to complete the first volume adjustment. Then, use a pipette to draw 5ml from the 100ml solution adjusted in the first volume adjustment and transfer it to another 100ml volumetric flask. Adjust the volume to 100ml and shake well to complete the second volume adjustment.

[0042] The pre-test samples obtained by the above pretreatment method were subjected to ICP testing for main content.

[0043] Comparative Example 1: A pretreatment method for lithium iron phosphate cathode material used in ICP testing, comprising digestion using a mixed acid (nitric acid: hydrochloric acid), the specific steps of which include:

[0044] 1. Weigh 0.1±0.01g (accurate to 0.0001g) of lithium iron phosphate sample into the reaction vessel, add 15ml of mixed acid (nitric acid: hydrochloric acid = 3:2, nitric acid mass fraction is 65%, hydrochloric acid mass fraction is 36%), and perform external sterilization by heating to boiling for 2h.

[0045] 2. Place the digested solution into an acid removal apparatus and perform acid removal at 150°C in an open environment for 0.5 hours, until no more yellow fumes are emitted.

[0046] 3. After the acid removal is completed, transfer the sample to a beaker, then to a volumetric flask for the first volume adjustment to 100 ml. Use a pipette to transfer 1 mL to the 100 mL volumetric flask for a second volume adjustment, and then perform ICP testing.

[0047] Comparative Example 2: A pretreatment method for lithium iron phosphate cathode material used in ICP testing, comprising digestion using a mixed acid (nitric acid: hydrochloric acid), the specific steps of which include:

[0048] 1. Weigh 0.1±0.01g (accurate to 0.0001g) of lithium iron phosphate sample into the reaction vessel, add 15ml of mixed acid (nitric acid: hydrochloric acid = 3:2, nitric acid mass fraction is 65%, hydrochloric acid mass fraction is 36%), and perform external sterilization by heating to boiling for 2.5h.

[0049] 2. Place the digested solution into an acid removal apparatus and perform acid removal at 150°C in an open environment for 0.5 hours, until no more yellow fumes are emitted.

[0050] 3. After the acid removal is completed, transfer the sample to a beaker, then to a volumetric flask for the first volume adjustment to 100 ml. Use a pipette to transfer 1 mL to the 100 mL volumetric flask for a second volume adjustment, and then perform ICP testing.

[0051] Comparative Example 3: A pretreatment method for lithium iron phosphate cathode material used in ICP testing, comprising digestion using a mixed acid (nitric acid: hydrochloric acid), the specific steps of which include:

[0052] 1. Weigh 0.1±0.01g (accurate to 0.0001g) of lithium iron phosphate sample into the reaction vessel, add 15ml of mixed acid (nitric acid: hydrochloric acid = 3:2, nitric acid mass fraction is 65%, hydrochloric acid mass fraction is 36%), and perform external sterilization by heating to boiling for 3h.

[0053] 2. Place the digested solution into an acid removal apparatus and perform acid removal at 150°C in an open environment for 0.5 hours, until no more yellow fumes are emitted.

[0054] 3. After the acid removal is completed, transfer the sample to a beaker, then to a volumetric flask for the first volume adjustment to 100 ml. Use a pipette to transfer 1 mL to the 100 mL volumetric flask for a second volume adjustment, and then perform ICP testing.

[0055] The present invention performed main element detection on the samples obtained from Examples 1-3 and Comparative Examples 1-3, and the data are shown in Table 1 below. As can be seen from Table 1, compared with Comparative Examples 1-3, the Li element detected in the samples of Examples 1-3 showed a higher test value. According to the standard Li element ratio in lithium iron phosphate, it should be 4.40%. In actual industrial production, in order to improve product performance and reduce the impact of element loss, an excessive amount of Li element is added, reaching 4.4%-5.0% depending on the process.

[0056] Because of the excess lithium, the synthesis mechanism of lithium iron phosphate involves Li being released into FePO4. The excess lithium will remain on the surface of the material, and most of it will remain in the carbon coating. During the main element test, the carbon coating cannot be eliminated by external acid digestion. There are carbon-coated suspended matter in the solution that cannot be digested and the Li element cannot be released, thus affecting the accuracy of the Li element test.

[0057] In Examples 1-3, the Li detection results increased significantly after pretreatment, which is consistent with the case of excessive Li addition. Furthermore, the Fe and P elements in the main elements of lithium iron phosphate remained unchanged, indicating that the method can effectively remove the influence of carbon coating on the Li element test.

[0058] In this embodiment of the invention, the ultrasonic treatment takes 0.1 hours, the oxidation takes 1.5 hours, and the dissolution takes 1 hour, for a total pretreatment time of 2.6 hours. In the comparative example, the dissolution time is 2.5 hours and the acid removal time is 0.5 hours, for a total pretreatment time of 3 hours. This embodiment can reduce the pretreatment time by 0.5 hours, improve the detection efficiency, and eliminate the need for acid removal, thus reducing the pressure of waste gas treatment.

[0059] Table 1. Specific conditions and test results of the embodiments and comparative examples of the present invention.

[0060]

[0061] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A pretreatment method for lithium iron phosphate cathode material used in ICP testing, characterized in that, include: The lithium iron phosphate cathode material was digested and brought to a constant volume. Before digestion, the lithium iron phosphate cathode material was dispersed in a dispersion medium, and then heated to 430~460℃ to undergo an oxidation reaction, which was maintained for 1.5~3h.

2. The pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 1, characterized in that, Includes the following steps: S1: Ultrasonic dispersion: Weigh the lithium iron phosphate cathode material and ultrasonically disperse it in the dispersion medium for 3-6 minutes to obtain the dispersion. S2: Heating to remove carbon: The dispersion is heated to undergo an oxidation reaction to obtain an oxidized sample; S3: Acid digestion: The oxidized sample is crushed into powder, and a digestion reagent is added until the solid is completely dissolved to obtain a digestion solution; S4: Volume adjustment: The digestion solution is adjusted to volume with pure water.

3. The pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2, characterized in that, In step S1, the dispersion medium is anhydrous ethanol or pure water.

4. A pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2 or 3, characterized in that, In step S1, the liquid-to-solid ratio of the dispersion medium to the lithium iron phosphate cathode material is 5~12.5:

1.

5. The pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2, characterized in that, In the oxidation reaction of step S2, the carbon coating layer on the surface of the lithium iron phosphate cathode material is oxidized and removed.

6. The pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2, characterized in that, The digestion reagent in step S3 is concentrated hydrochloric acid with a mass fraction of 36%.

7. The pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2, characterized in that, In step S3, the mass ratio of the oxidized sample to the digestion reagent is 1:100~150.

8. A pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2, 6, or 7, characterized in that, In step S3, after adding the digestion reagent, the mixture is heated and stirred at 150~200℃.

9. A pretreatment method for lithium iron phosphate cathode material for ICP testing according to claim 2, characterized in that, The volume adjustment includes a first volume adjustment and a second volume adjustment; in the first volume adjustment, 20-30 ml of the digestion solution is taken and diluted with pure water to a volume of 100 ml; in the second volume adjustment, 5 ml of the first volume adjustment solution is taken and diluted with pure water to a volume of 100 ml.

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