Separation method and content determination method of titanium foreign matter in lithium battery positive electrode material

Abstract

The application provides a separation method and content determination method for titanium foreign matters in a lithium battery positive electrode material. Through the step design of material screening-metal titanium particle purification-metal titanium particle digestion-titanium content determination, with the aid of a specific mixed acid system, the digestion process is accurately controlled, the positive electrode material is effectively digested, and the metal titanium foreign matters are ensured not to be digested. Through the early passivation process, a dense oxide film mainly composed of titanium dioxide is rapidly formed on the surface of titanium, effectively preventing the internal titanium from continuing to react with nitric acid and hydrochloric acid, and the original form and content of the metal titanium foreign matters are maximally retained, so that the accurate determination of the content of the titanium foreign matters in the material is realized. Meanwhile, through the optimization of the sample pretreatment mode, the complex and high-cost operation steps are reduced, and the consumption of expensive reagents is reduced. The application provides a new detection idea and method, fills the gap in the related technical field, and promotes the development and application of the detection technology in the field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a method for separating and determining the content of titanium foreign matter in a lithium battery positive electrode material. BACKGROUND

[0002] Magnetic particles have gradually become a key safety indicator in the detection indicators of lithium battery positive electrode materials. The main introduction source is the friction between materials and stainless steel parts in production equipment. In order to reduce the introduction of magnetic particles, metal titanium parts are increasingly widely used in production equipment. However, normal wear and tear inevitably occurs in the long-term continuous operation of the equipment. This wear and tear can cause titanium elements to fall off in the form of small particles and mix into the materials being processed, thereby exposing the materials to the risk of contamination by titanium foreign matter.

[0003] Patent CN 115290416 A provides a method for testing the cleanliness of magnetic particles, which fully extracts the magnetic particles in the particles adsorbed by the magnetic rod wrapped in a thermoplastic bag. However, this method only detects particles with magnetism, and metal Ti particles do not have magnetism and cannot be separated by magnetic separation.

[0004] Patent CN 118437052 A provides a small particle size positive electrode material rapid screening device and screening method, which completes rapid screening of particles. However, in actual application, the sieve material will exist in the form of agglomeration of positive electrode, aluminum oxide debris, etc., with a proportion of 80-95%, resulting in a small amount of titanium particles, which cannot be quickly detected by energy spectrum, and in ICP detection, even if complete digestion, there is also the interference of the matrix, which is not conducive to detection.

[0005] Patent CN 117629974 A provides a method for determining aluminum and zirconium in a positive electrode material. The method provides a mixed acid digestion method, which can completely digest the tested positive electrode sample, so that there are no insoluble substances in the digested product, thereby improving the accuracy of the test results. However, this method cannot eliminate the water-based filter membrane after suction filtration, and the filter membrane residue may block the sampling system during constant volume.

[0006] Patent CN 117269154 A provides a method for detecting metal impurity elements in electrolyte, which provides an inorganic acid digestion scheme, which can dissolve metal impurities in the form of solid particles in electrolyte, so that metal impurities exist in the form of cations in the test solution, so as to be quantitatively measured. However, this scheme cannot effectively dissolve metal titanium particles, as a layer of oxide film will form on the surface of metal titanium, and the inorganic acid digestion system in the scheme cannot break through this oxide film.

[0007] Currently, the detection of metal particles mainly includes cleanliness test, energy spectrum test and ICP test. Since titanium metal has no magnetism, it cannot be separated by magnetic separation, but only by sieving method. However, even if sieving is completed, titanium foreign matter may still be mixed with larger particles of the material, which mainly come from the agglomeration of the material, alumina particles in the production tooling, etc., and it is difficult to accurately distinguish titanium particles, and the accuracy of the test is low. SUMMARY

[0008] The present application is carried out in view of the above-mentioned problems, and aims to provide a method for separating titanium foreign matter from a lithium battery positive electrode material and accurately determining the content of the titanium foreign matter, which effectively digests the positive electrode material while ensuring that the metal titanium foreign matter is not digested, thereby maximizing the retention of the original form and content of the metal titanium foreign matter, and eliminating the influence of the sample matrix component on the test results.

[0009] To achieve the above-mentioned purpose, the present application provides a method for separating titanium foreign matter from a lithium battery positive electrode material, comprising the following steps:

[0010] 1) Sample sieving: weigh the material, add sodium hexametaphosphate dispersant, put it into a roller shaft machine to mix the material and the dispersant thoroughly, sieve using a screen, then rinse the residual material on the screen into a beaker, and then perform suction filtration on the solution in the beaker to obtain a pretreated material;

[0011] 2) Passivation process: add concentrated nitric acid to the pretreated material and stir at room temperature for a period of time;

[0012] 3) Material impurity removal: under water bath environment, add hydrochloric acid to the passivated material and stir to cause oxidation-reduction reaction, digest the positive electrode material, and obtain metal titanium particles after reaction and suction filtration;

[0013] 4) Ti particle digestion: add ammonium fluoride and aqua regia to the suction-filtered filter membrane and metal titanium particles of step 3), and place them on a heating plate at 150-250°C for 15-60min to obtain soluble hexafluorotitanate complex ions.

[0014] In any embodiment, 5-10% of sodium hexametaphosphate dispersant by weight of the material is added in step 1); the sodium hexametaphosphate is completely dissolved in pure water with a concentration of 1-2%.

[0015] In any embodiment, the material and the dispersant are placed above the roller shaft of the roller shaft machine in step 1), and are treated by the roller shaft at 55-65r / min for 25-40min to mix the material and the dispersant thoroughly, and sieved using a seat-type screen.

[0016] In any embodiment, the screen is a seat-type screen with an area size of D60mm and a pore size of 500-800mesh.

[0017] In any embodiment, the ratio of concentrated nitric acid to material added in step 2) is 5-10 mL: 1 kg, and the reaction time is 5-10 min.

[0018] In any embodiment, the ratio of hydrochloric acid to material added in step 3) is 5-10 mL: 1 kg.

[0019] In any embodiment, the reaction temperature of the water bath in step 3) is 50-90°C, and the reaction time is 20-30 min.

[0020] In any embodiment, the concentration of the concentrated nitric acid is 65%-70%, and the concentration of the hydrochloric acid is 36%-38%; the ratio of ammonium hydrogen fluoride to material added in step 4) is 1-2 g: 1 kg, and the ratio of aqua regia to material is 8-16 mL: 1 kg.

[0021] In any embodiment, the stirring in steps 2) and 3) is magnetic stirring, and the stirring speed is 300-600 r / min.

[0022] A method for determining the content of titanium foreign matter in a lithium battery positive electrode material, the solution obtained by the above method is cooled, constant volume is performed, and ICP test is performed to obtain the content of titanium foreign matter in the lithium battery positive electrode material.

[0023] The beneficial effects of the present application are:

[0024] The present application surrounds the purification and determination method of metal titanium particles, through the steps of material screening, purification of metal titanium particles, digestion of metal titanium particles, and determination of titanium content, with the help of a specific mixed acid system, the digestion process is accurately controlled, the positive electrode material is effectively digested, and the metal titanium foreign matter is not digested. Through the early passivation process, a dense oxide film mainly composed of titanium dioxide will quickly form on the surface of titanium, which can effectively prevent the internal titanium from continuing to react with nitric acid and hydrochloric acid, thereby maximizing the preservation of the original form and content of the metal titanium foreign matter, avoiding the change of the chemical form and the loss of the content of the titanium foreign matter caused by the traditional pretreatment method, and eliminating the influence of the sample matrix composition on the detection result, thereby realizing the accurate determination of the content of the titanium foreign matter in the material. At the same time, by optimizing the sample pretreatment method, the complex and high-cost operation steps are reduced, and the consumption of expensive reagents is reduced. The present application provides a new detection idea and method, fills the gap in the related technical field, and promotes the development and application of detection technology in this field. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A comparison chart of the digestion conditions of the positive electrode material for the control experiment of different pretreatment stirring times set in Example 2. DETAILED DESCRIPTION

[0026] Hereinafter, specific embodiments of the method for separating titanium foreign matter in a lithium battery cathode material and the method for determining the content of titanium foreign matter according to the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there will be cases where detailed descriptions of matters well known in the art, repeated descriptions of substantially identical configurations are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0027] The ranges disclosed herein are defined by their lower and upper limits. Ranges that are given by selecting a lower limit and an upper limit define a particular range that is bounded by the lower and upper limits. Ranges defined by the lower and upper limits can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing all of the real combinations of a to b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all of the real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand way of describing these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0029] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0030] If not specified otherwise, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0031] If not specified otherwise, the terms "comprising" and "including" as used in the present application are meant to be interpreted open-ended. For example, the terms "comprising" and "including" can mean that other components not listed can also be included or can mean that only the listed components are included.

[0032] If not specified otherwise, the term "or" in the present application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0033] The present application precisely controls the digestion process by means of a specific mixed acid system, effectively digests the positive electrode material while ensuring that the metal titanium foreign matter is not digested. This not only maximizes the retention of the original form and content of the metal titanium foreign matter, but also completely digests the water-based filter membrane (to obtain the oversize material, the material needs to be sieved and then filtered) without leaving any residue, thereby avoiding the problems of traditional pretreatment methods: the traditional method causes the chemical form of the metal titanium foreign matter to change and the content to be lost, and since the filter membrane may contain residual material, the filter membrane needs to be treated together during digestion, and the filter membrane will form residue in the beaker during the digestion process. During subsequent sample volume testing, these filter membrane residues will enter the ICP liquid inlet tube, interfering with and blocking the sampling system, and affecting the accurate determination of the content of the metal titanium foreign matter in the material. Thus, the present application realizes the accurate determination of the content of the metal titanium foreign matter in the material. At the same time, by optimizing the sample pretreatment method, the complex and high-cost operation steps are reduced, and the consumption of expensive reagents is reduced. In terms of filling the technical gap, in view of the many shortcomings of existing ICP foreign matter titanium detection technology, and the lack of effective methods for determining the content of titanium foreign matter in lithium battery positive electrode materials, the present application provides a new detection idea and method, fills the gap in the related technical field, and promotes the development and application of detection technology in this field.

[0034] In one embodiment of the present application, the present application provides a method for separating titanium foreign matter in a lithium battery positive electrode material, comprising the following steps:

[0035] 1) Sample screening: weigh the material, add sodium hexametaphosphate dispersant, put it into a roller machine to mix the material and dispersant thoroughly, screen it with a screen, then rinse the residual material on the screen into a beaker, then perform suction filtration on the solution in the beaker to obtain the pretreated material;

[0036] The material to be separated and detected in the lithium battery positive electrode material of the present application is the content of impurity titanium particles mixed due to mechanical wear. The content of such impurity titanium particles in the material is relatively low, and a small amount of titanium particles may be mixed in several tons of material. Therefore, at least 1 kg of material is required in the pretreatment stage to ensure sufficient probability of capturing the target impurities. The 1 kg of material cannot be completely digested with acid, and the material must be first separated from the titanium particles. The role of sodium hexametaphosphate is to improve the dispersibility and flowability of the material, so that the material can pass through the screen more smoothly, and the separation efficiency of titanium particles and the material is improved. The screened material is usually less than 1 g, and the part of the material is then digested.

[0037] 2) Passivation process: add concentrated nitric acid to the pretreated material (screened material) and stir at room temperature for a period of time;

[0038] At room temperature, a dense oxide film mainly composed of titanium dioxide (TiO2) will quickly form on the surface of titanium. This oxide film can effectively prevent the internal titanium from continuing to react with nitric acid and hydrochloric acid.

[0039] 3) Material impurity removal: add hydrochloric acid to the passivated material under water bath environment and stir to cause oxidation-reduction reaction, digest the positive electrode material, and obtain metal titanium particles after reaction and suction filtration;

[0040] The main components in the positive electrode material will undergo oxidation-reduction reaction with chloride ions (Cl - ) in hydrochloric acid, thereby realizing digestion of the positive electrode material, and obtaining metal titanium (Ti) particles after reaction and suction filtration.

[0041] 4) Ti particle digestion: add ammonium fluoride and aqua regia to the filter membrane and metal titanium particles after suction filtration of step 3) to obtain soluble hexafluorotitanate complex ions.

[0042] Ammonium fluoride reacts with nitric acid, and nitric acid, as a strong acid, dissociates hydrogen ions (H + ), which can inhibit the hydrolysis of fluoride ions (F - ), thereby providing free F - for the reaction. F - can react with TiO2 on the surface of titanium to generate soluble hexafluorotitanate complex ions.

[0043] In any embodiment, 5-10% by weight of sodium hexametaphosphate dispersant is added in step 1); the sodium hexametaphosphate is completely dissolved in pure water with a concentration of 1-2%.

[0044] If the concentration is too low, the dispersion effect is poor and the material screening speed is slow; if the concentration is too high, the sodium hexametaphosphate particles aggregate and dissolve slowly, requiring high-temperature dissolution and high cost.

[0045] In any embodiment, the material and the dispersant in step 1) are placed above the rollers of the roller machine, and are treated at a speed of 55-65 r / min for 25-40 min to fully mix the material and the dispersant, and a seat-type screen is used for screening.

[0046] If the roller treatment time is too short, the material is not mixed sufficiently; if the time is too long, the efficiency is wasted; if the speed is too low, the mixture is not uniform; if the speed is too fast, the wear is increased, affecting the efficiency of the equipment; and the material and the dispersant are fully mixed.

[0047] In any embodiment, the screen is a seat-type screen with an area size of D60 mm and a pore size of 500-800 mesh.

[0048] The small area of the seat-type screen allows the oversize material to be collected quickly and efficiently, and the effect of complete collection is achieved.

[0049] In any embodiment, the ratio of concentrated nitric acid to material in step 2) is 5-10 mL: 1 kg, and the reaction time is 5-10 min.

[0050] If the amount is too much, resources are wasted, excess nitric acid does not participate in the formation of the oxidation film, TiO2 is stable and does not react with concentrated nitric acid, only increasing the cost and safety risk; if the amount is too little, the oxidation film is incomplete, and a thin oxidation film is formed on the titanium surface only, leaving a large number of exposed active sites; if the concentration is too low, the dilute nitric acid has weak oxidation ability and cannot rapidly oxidize Ti and form a dense oxidation film, and the protective property of the film layer is lost; if the reaction time is too short, the oxidation reaction is not complete and the TiO2 film only covers part of the active sites; and if the reaction time is too long, the time extension does not make the film layer denser, but rather causes a side reaction.

[0051] In any embodiment, the ratio of hydrochloric acid to material in step 3) is 5-10 mL: 1 kg.

[0052] If the amount is too little, the positive material is not completely digested and unreacted positive particles remain in the solution; if the amount is too much, the cost is increased and the safety risk is raised; if the concentration is too low, the low-concentration Cl - The reducing property is weak and the oxidation-reduction reaction driving force is insufficient, and the reaction time is prolonged.

[0053] In any embodiment, the water bath reaction temperature in step 3) is 50-90°C, and the reaction time is 20-30 min.

[0054] If the reaction temperature is too low, the nickel, cobalt, manganese and other metal elements in the positive electrode material are difficult to completely dissolve, which will cause a large amount of undigested solid particles to remain in the solution, and at the same time, the digestion solution is not completely reacted, which will prolong the overall processing cycle. If the temperature is too high, the digestion solution will be violently volatilized, which will cause the acid concentration in the system to rapidly decrease, thereby inhibiting the digestion reaction. When the acid amount is insufficient, the dissolution rate of the positive electrode material will decrease. In addition, high temperature may cause the originally stable titanium particles to be partially dissolved, affecting the accuracy of the detection.

[0055] Too short reaction time: incomplete digestion, a large amount of positive electrode material particles remain, too long reaction time: excessive volatilization of hydrochloric acid and increased energy consumption.

[0056] In any embodiment, the ratio of ammonium fluoride to the material in step 4) is 1-2 g: 1 kg, and the ratio of aqua regia to the material is 8-16 mL: 1 kg.

[0057] Too little amount: F - is not completely converted to [TiF6] on the surface of titanium, residual oxide film, too much amount: increased cost, increased safety risk. Too low concentration: unable to inhibit F 2- hydrolysis, effective F - concentration decreases, too short reaction time: incomplete digestion, too long reaction time: increased energy consumption. -

[0058] In any embodiment, the stirring in steps 2) and 3) is magnetic stirring, and the stirring speed is 300-600 r / min. The magnetic stirring is efficient and stable, so that the material and the reagent can fully react.

[0059] When the stirring speed is too low, the magnet rotates slowly and cannot fully drive the digestion solution to flow, which will cause uneven mixing of the system, large local acid concentration difference, easy settlement and aggregation of the positive electrode material particles, and difficulty in fully contacting with the digestion solution, thereby causing incomplete digestion. If the stirring speed is too high, high-speed stirring will make the digestion solution violently boil, even splash out of the container, causing material loss, and at the same time, causing the acid concentration to decrease, thereby affecting the digestion effect.

[0060] In addition, the application also provides a method for determining the content of titanium foreign matter in a lithium battery positive electrode material. The solution obtained by the above method is cooled, constant volume is performed, and ICP test is performed to obtain the content of titanium foreign matter in the lithium battery positive electrode material.

[0061] Embodiment

[0062] ​Hereinafter, the examples of the present application will be described. The examples described below are illustrative and are intended to be purely exemplary of the application and are not intended to limit the application. Unless otherwise indicated, technical or conditions not specified in the examples are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments used are not specified by the manufacturer, but are conventional products that can be obtained commercially.

[0063] Example 1

[0064] A method for separating and determining the content of titanium foreign matter in a lithium battery positive electrode material, comprising the steps of:

[0065] 1. Weigh 1 kg of the sample to be tested, add 2% sodium hexametaphosphate solution, shake uniformly, and place on the upper part of the roller machine. Set the roller parameters: 30 min, 60 r / min, so that the material and dispersant are fully mixed, and use a screen mesh to screen. Rinse the residual material on the screen into a beaker, and then perform suction filtration on the solution in the beaker.

[0066] 2. After suction filtration is completed, place a magnetic sub in the beaker, add 10 mL of nitric acid, stir at room temperature for 10 min, then add 10 mL of hydrochloric acid, and place in a 50°C water bath for 30 min. After stirring is completed, suction filter the material in the beaker.

[0067] 3. Place the filter membrane in a polytetrafluoroethylene beaker, add 2 g of ammonium fluoride, 6 mL of hydrochloric acid and 2 mL of nitric acid, and place on a 200°C hot plate for digestion for 15-60 min. After digestion is completed, clamp out the cooled and constant volume.

[0068] 4. After the sample pretreatment is completed, start the inductively coupled plasma optical emission spectrometer (ICP-OES) according to the instrument operation procedure. After the equipment is preheated and stabilized, the torch flame is normally ignited, and the parameters (radio frequency power, atomizing gas flow, auxiliary gas flow, etc.) reach the set standard, the ICP device is used to quantitatively test the content of the constant volume of the solution to be tested.

[0069]

[0070] Through the data comparison of the control experiment of multiple groups of different digestion times (15 min, 30 min, 45 min, 60 min) set in Example 1, it can be known that under the same mixed acid system (ammonium fluoride, concentrated nitric acid and hydrochloric acid), water bath temperature and stirring rate, when the digestion time is controlled to 45 min, the digestion effect of titanium (Ti) particles is significantly better than that of other groups. At this time, the titanium dioxide (TiO2) oxide film on the surface of the Ti particles is fully penetrated by free fluoride ions (F - ), and the generated soluble hexafluorotitanate complex ions ([TiF6] 2-) were uniformly dispersed in the solution. Based on the data and phenomena, it was found that a digestion time of 45 min could make the Ti particles more completely digested, and under the conditions of the experimental group, it was more conducive to realize efficient and deep digestion of Ti particles.

[0071] Example 2

[0072] A method for separating and determining the content of titanium foreign matter in a lithium battery positive electrode material, comprising the steps of:

[0073] 1. Weigh 1 kg of the sample to be tested, add 2% sodium hexametaphosphate solution, shake evenly, and place it on the upper part of the roller machine. Set the roller parameters: 30 min, 60 r / min) to make the material and dispersant fully mixed, and use a screen mesh to screen. Rinse the remaining material on the screen into a beaker, and then filter the solution in the beaker.

[0074] 2. After filtration, put a magnet into the beaker, add 10 mL of nitric acid, stir at room temperature for 10 min, then add 10 mL of hydrochloric acid, and place it in a 50°C water bath for 10-30 min. After stirring, filter the material in the beaker.

[0075] 3. Place the filter membrane in a polytetrafluoroethylene beaker, add 2g of ammonium fluoride, 6mL of hydrochloric acid and 2mL of nitric acid, and place it on a 200°C hot plate for 45 min. After digestion, cool and dilute to volume.

[0076] 4. After the sample pretreatment is completed, start the inductively coupled plasma optical emission spectrometer (ICP-OES) according to the instrument operation procedure. After the equipment is preheated and stabilized, the torch flame is normally ignited, and the parameters (radio frequency power, atomizing gas flow, auxiliary gas flow, etc.) reach the set standard, the ICP device is used to quantitatively test the content of the sample solution diluted to 50mL.

[0077] Comprehensive data comparison of multiple groups of experiments with different pretreatment stirring times (10 min, 20 min, 30 min) in Example 2 found (such as Figure 1 ): Under the same mixed acid system (ammonium fluoride, concentrated nitric acid and hydrochloric acid), water bath temperature and stirring rate, when the pretreatment stirring time is controlled at 30 min, the main components in the positive electrode material will react with the chloride ions (Cl - ) in hydrochloric acid, and the reaction time is more sufficient, so as to realize the digestion of the positive electrode material. After the reaction is completed, the titanium (Ti) particles can be obtained by filtration. Since the positive electrode material is more completely eliminated, the test interference is reduced, and the subsequent Ti particle content test is more efficient and accurate.

[0078] Example 3

[0079] A method for separating and determining the content of titanium foreign matter in a lithium battery positive electrode material, comprising the steps of:

[0080] 1. Weigh 1 kg of the sample to be tested, add 2% sodium hexametaphosphate solution, shake evenly, and place it on the upper part of the roller machine. Set the roller parameters: 30 min, 60 r / min) to fully mix the material and the dispersant. Use a screen mesh to screen the material. Rinse the remaining material on the screen into a beaker, and then filter the solution in the beaker.

[0081] 2. After the filtration is completed, put a magnet into the beaker, add 0-10 mL of nitric acid, stir at room temperature for 10 min, then add 10 mL of hydrochloric acid, and place it in a 50°C water bath for 30 min. After stirring is completed, filter the material in the beaker.

[0082] 3. Place the filter membrane in a polytetrafluoroethylene beaker, add 2 g of ammonium fluoride, 6 mL of hydrochloric acid and 2 mL of nitric acid, and place it on a 200°C hot plate for digestion for 45 min. After digestion is completed, clamp out the cooled and constant volume.

[0083] 4. After the sample pretreatment is completed, start the inductively coupled plasma optical emission spectrometer (ICP-OES) according to the instrument operation procedure. After the equipment is preheated and stabilized, the torch flame is normally ignited, and the parameters (radio frequency power, atomizing gas flow, auxiliary gas flow, etc.) reach the set standard, the ICP device is used to quantitatively test the content of the sample solution constant volume to 50 mL.

[0084]

[0085] After comparing and analyzing a plurality of experiments with different nitric acid contents (0 mL, 5 mL, 10 mL, 20 mL) set in Example 3, it is found that under the same conditions of mixed acid system (ammonium fluoride, concentrated nitric acid, hydrochloric acid), water bath temperature and stirring rate, the titanium particles surface rapidly undergoes oxidation reaction driven by the strong oxidizing property of nitric acid, which promotes the efficient combination of titanium (Ti) and oxygen to form a dense and uniform titanium dioxide (TiO2) passivation film. When the content of nitric acid is 10 mL, the integrity, density and stability of the passivation film on the surface of titanium particles reach the optimum, and the titanium particles pretreated in this way can prevent further reaction between titanium particles and hydrochloric acid during subsequent pretreatment and stirring, thereby ensuring the accuracy of subsequent titanium particle content measurement.

[0086] Example 4

[0087] A method for separating and determining the content of titanium foreign matter in a lithium battery positive electrode material, comprising the steps of:

[0088] 1. Weigh 1 kg of the sample to be tested, add 2% sodium hexametaphosphate solution, shake evenly and place on the upper part of the roller shaft machine. Set the roller shaft parameters: 30 min, 60 r / min) to mix the material and dispersant thoroughly. Use a screen mesh to screen the material. Rinse the residual material on the screen into a beaker, and then filter the solution in the beaker.

[0089] 2. After filtration, put a magnet in the beaker, add 10 mL of nitric acid, stir at room temperature for 10 min, then add 10 mL of hydrochloric acid, and place it in a 50°C water bath for 30 min. After stirring, filter the material in the beaker.

[0090] 3. Place the filter membrane in a polytetrafluoroethylene beaker, add 2 g of ammonium fluoride, 6 mL of hydrochloric acid and 2 mL of nitric acid, and place it on a 100-200°C hot plate for 45 min. After digestion, cool and dilute to volume.

[0091] 4. After sample pretreatment, start the inductively coupled plasma optical emission spectrometer (ICP-OES) according to the instrument operating procedures. After the equipment is preheated and stable, the torch flame is normally ignited, and the parameters (radio frequency power, atomizing gas flow, auxiliary gas flow, etc.) reach the set standard, the ICP device is used to quantitatively test the content of the sample solution diluted to 50 mL.

[0092]

[0093] After comparing and analyzing the experimental data of different digestion temperatures (100°C, 150°C, 200°C, 250°C) in Example 4, it can be clearly found that under the same mixed acid system (ammonium fluoride, concentrated nitric acid and hydrochloric acid), water bath temperature and stirring rate, when the digestion temperature is controlled at 200°C, the digestion effect of Ti particles shows a significant advantage compared to other temperature groups. The Ti content test data at this temperature is outstanding. Compared with 100°C, 150°C and other temperature groups, the Ti particle digestion degree is higher, the residue is less, and the Ti particle digestion can be more efficiently realized. However, at a higher temperature of 250°C, side reactions may be triggered or the system stability may be reduced due to the high temperature, affecting the digestion effect. Based on the data and phenomena, the digestion temperature of 200°C can make the Ti particle digestion more complete, and in the experimental condition system set in this group, it is more conducive to realizing efficient and deep digestion of Ti particles.

[0094] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art, without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A method for separating titanium foreign matter in a lithium battery cathode material, characterized in that, Includes the following steps: 1) Sample sieving: Weigh the material, add sodium hexametaphosphate dispersant, put it into the roller of the roller machine to make the material and dispersant fully mixed, use a sieve to sieve, then rinse the material remaining on the sieve into a beaker, and then filter the solution in the beaker to obtain the pretreated material; 2) Passivation process: Concentrated nitric acid is added to the pretreatment material, and the mixture is stirred at room temperature for a period of time; 3) Material removal: In a water bath environment, hydrochloric acid is added to the passivated material and stirred to cause an oxidation-reduction reaction, which digests the positive electrode material. After the reaction is completed, metallic titanium particles are obtained by suction filtration. 4) Digestion of Ti particles: Add ammonium bifluoride and aqua regia to the filter membrane and metallic titanium particles after filtration in step 3), and place them on a heating plate at 150-250℃ for 15-60 min to digest them and obtain soluble hexafluorotitanate complex ions.

2. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1, characterized in that, In step 1), add 5-10% by weight of sodium hexametaphosphate dispersant; the sodium hexametaphosphate is completely dissolved in pure water with a concentration of 1-2%.

3. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1, characterized in that, In step 1), the material and dispersant are placed above the rollers of the roller machine and processed by the rollers at 55-65 r / min for 25-40 min to ensure that the material and dispersant are fully mixed. Then, the mixture is sieved using a woven screen.

4. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1 or 3, characterized in that, The screen is a mat-type screen with a size of D60mm and an aperture of 500-800 mesh.

5. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1, characterized in that, In step 2), the ratio of concentrated nitric acid to material is 5-10 mL: 1 kg, and the reaction time is 5-10 min.

6. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1, characterized in that, In step 3), the ratio of hydrochloric acid to material is 5-10 mL: 1 kg.

7. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1, characterized in that, In step 3), the water bath reaction temperature is 50-90℃ and the reaction time is 20-30 min.

8. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1 or 5, characterized in that, The concentration of the concentrated nitric acid is 65%~70%, and the concentration of the hydrochloric acid is 36%~38%; in step 4), the ratio of ammonium bifluoride to the material is 1-2g:1kg, and the ratio of aqua regia to the material is 8-16mL:1kg.

9. The method for separating titanium foreign matter in lithium battery cathode material according to claim 1, characterized in that, In steps 2) and 3), the stirring is done with magnetic stirring at a speed of 300-600 r / min.

10. A method for determining the content of titanium impurities in a lithium battery cathode material, characterized in that, The solution obtained by the separation method according to any one of claims 1-9 is cooled and then brought to a constant volume. ICP testing is then performed to obtain the content of titanium foreign matter in the lithium battery cathode material.

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