WO2024055510A1

WO2024055510A1 - Method for preparing lithium iron phosphate from nickel-rion alloy and use thereof

Info

Publication number: WO2024055510A1
Application number: PCT/CN2023/077137
Authority: WO
Inventors: 马阳婷; 李长东; 阮丁山; 唐玖平; 宁培超
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-09-15
Filing date: 2023-02-20
Publication date: 2024-03-21
Also published as: CN115448282A; CN115448282B

Abstract

Disclosed in the present invention are a method for preparing lithium iron phosphate from a nickel-iron alloy and the use thereof, which belong to the technical field of the preparation of a lithium iron phosphate material. In the present application, a nickel-iron alloy is leached using a combination of an organic acid and an oxidant, the reaction conditions are mild, the problems of high acidity, generation of a large amount of wastewater, great investment in equipment, high probability of releasing hydrogen ions, etc., existing in current leaching of a nickel-iron alloy with an inorganic acid are solved, and the leaching process produces no other impurities and is less corrosive to the equipment; and an iron salt and a nickel salt are precipitated in steps by using an organic precipitant, wherein an iron salt precipitate can be directly used in the preparation of lithium iron phosphate, and a nickel salt precipitate can be used as a nickel source for the subsequent preparation of a ternary positive electrode material. The preparation method of the present application reduces the recovery cost of a nickel-iron alloy, can produce certain economic benefits, and has prospects with regard to industrial application.

Description

A method and application of preparing lithium iron phosphate from nickel-iron alloy

Technical field

The embodiments of the present application relate to the technical field of preparing lithium iron phosphate materials, such as a method and application of preparing lithium iron phosphate from a nickel-iron alloy.

Background technique

Nickel oxide ore accounts for 70% of the nickel ores currently available for mining. Nickel oxide is mainly formed from nickel peridotite after large-scale, long-term weathering and metamorphism in tropical or subtropical areas, and also contains some iron, aluminum, silicon and other water-containing oxides, called laterite nickel ore; laterite nickel ore cannot be used directly, and usually requires fire or wet treatment. There are two fire processes: (1) reduction sulfur production smelting-blowing-high-sulfur nickel concentrate ore; (2) reduction of nickel iron smelting and blowing to obtain nickel iron; nickel iron can be further electrolyzed to obtain electric nickel; there are usually two wet processes: (1) selective reduction roasting-normal pressure ammonia leaching; (2) adding Pressure leaching. At present, nickel-iron alloys containing a large amount of nickel and iron are usually used directly as stainless steel materials with low added value. If nickel-iron alloys can be directly prepared into lithium iron phosphate and lithium nickel cobalt manganate, high added value of nickel iron will be achieved. High value-added industrial applications can realize huge economic benefits of nickel-iron alloys.

At present, most patents mainly use inorganic acid to leach nickel-iron alloy to prepare lithium iron phosphate and lithium nickel cobalt manganate. However, the inorganic acid system has problems such as strong acidity, large amounts of wastewater, large equipment investment, and large hydrogen production, and the subsequent preparation of phosphoric acid Lithium iron often adopts the route of preparing iron phosphate first and then lithium iron phosphate, and the reaction conditions are relatively harsh.

Therefore, developing a mild, simple, efficient, safe and environmentally friendly method for preparing lithium iron phosphate using nickel-iron alloy is a current research hotspot.

Contents of the invention

The following is an overview of the topics described in detail in this article. This summary is not intended to limit the scope of the claims.

The embodiments of the present application provide a method and application for preparing lithium iron phosphate from a nickel-iron alloy with mild reaction conditions, no impurity elements introduced, and a simple and efficient method.

The technical solutions adopted in the embodiments of this application are:

A method for preparing lithium iron phosphate from nickel-iron alloy, including the following steps:

S1. Crush and grind the nickel-iron alloy to obtain nickel-iron alloy powder;

S2. Mix nickel-iron alloy powder, organic acid and oxidant and sand grind;

S3. Sieve the mixed material after sanding in step S2;

S4. Add an organic precipitant to the screened undersize solution until a yellow iron salt precipitate is produced in the solution. After separating the iron salt precipitate, continue to add an organic precipitant to the undersize solution until a green nickel salt precipitate is produced. ;

S5. The iron salt precipitate obtained in step S4 is mixed with a phosphorus source, a lithium source, a carbon source, polyethylene glycol and water and sanded, and the mixture is pyrolyzed and sintered to obtain the lithium iron phosphate.

This application uses organic acids and oxidants to leach nickel-iron alloys, and the reaction conditions are relatively mild. It overcomes the problems of strong acidity, large amounts of wastewater generated, large equipment investment, and easy release of hydrogen ions existing in the current inorganic acid leaching of nickel-iron alloys. Moreover, the leaching process No other impurities are produced, and the corrosiveness to the equipment is small; this application also uses organic precipitants to precipitate iron salts and nickel salts in nickel-iron alloys step by step. The iron salt precipitation can be directly used to prepare lithium iron phosphate, and the nickel salt precipitation It can be used as a nickel source in the subsequent preparation process of ternary cathode materials, reducing the recycling cost of nickel-iron alloy.

Preferably, in step S1, the particle size of the nickel-iron alloy powder is 5-80 mesh. The applicant found through experiments that grinding the nickel-iron alloy powder to this particle size can be more fully mixed with other raw materials.

Preferably, in step S2, the mass ratio of nickel-iron alloy powder and organic acid is (0.25-2):1. The applicant found through experiments that when the amount of organic acid added is too small, it will lead to the final lithium iron phosphate. The ratio of Fe and P content exceeds the standard value of lithium iron phosphate. When the amount of organic acid added is too much, although it does not have a significant impact on the physical and chemical standards of lithium iron phosphate, the excess of organic acid will lead to increased costs in the preparation process. And easily cause environmental pollution.

Preferably, in step S2, the mass ratio of nickel-iron alloy powder and oxidant is (5-50):1. When the amount of oxidant added is too small, the ratio of Fe and P content in the final lithium iron phosphate will exceed that of phosphoric acid. For the standard value of lithium iron, when too much oxidant is added, although it does not have a significant impact on the physical and chemical standards of lithium iron phosphate, excess oxidant will lead to increased costs during the preparation process and may easily cause environmental pollution.

Preferably, in step S2, the organic acid is formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, adipic acid, oxalic acid, malonic acid, succinic acid, maleic acid, tartaric acid, benzoic acid, benzene At least one of acetic acid, phthalic acid, terephthalic acid, valeric acid, caproic acid, capric acid, stearic acid, palmitic acid, and acrylic acid.

More preferably, in step S2, the organic acid is formic acid. The applicant found through experiments that using formic acid As an organic acid, the acid can make the electrochemical performance of the finally prepared lithium iron phosphate better.

Preferably, in step S2, the oxidizing agent is ozone, hydrogen peroxide or hypochlorous acid.

More preferably, in step S2, the oxidant is hydrogen peroxide. Hypochlorous acid will introduce chloride ions during the preparation of lithium iron phosphate. Ozone can easily cause light pollution. Therefore, the applicant selected hydrogen peroxide as the oxidant in this application.

Preferably, in step S2, a sand mill is used to sand-mix the nickel-iron alloy powder, organic acid and oxidant.

More preferably, in step S2, the rotation speed of the sand mill is 300-1000 r/min, and the sand grinding time is 60-300 min. The sand mill can mix the raw materials more fully under these process conditions.

More preferably, in the step S2, the ball-to-material ratio during the sand grinding process is (5-50):1, the grinding concentration is 20%-70%, the filling rate is 30%-45%, and the ball-to-material ratio is between Within this range, the sanding efficiency is the highest and over-crushing is less likely to occur.

Preferably, in step S3, the mesh size of the sieve is 300-1000 mesh. The purpose of sieving is mainly to screen out the impurities in the nickel-iron alloy powder that have not reacted with organic acids and oxidants. The undersize solution can be directly Enter the next step of reaction, and the unreacted sieve material can be sanded and sieved again.

Preferably, in step S4, the organic precipitant is a weak acid and weak alkali salt, and ammonium oxalate is used in this application.

Preferably, in step S4, the pH when the iron salt is precipitated is 1.5-3.0, and the pH when the nickel salt is precipitated is 5.0-8.0; when ammonium oxalate with an acidic pH is added to the undersize solution in step S3. , the oxalate ions in the ammonium oxalate combine with the metal iron ions in the undersize solution to form iron oxalate precipitate. At this time, there are only a very small amount of ammonium ions in the mixed solution, so the overall solution is still acidic. When the iron is separated After salt precipitation, when ammonium oxalate is added to the solution, the oxalate ions in the ammonium oxalate combine with the metal nickel ions in the undersize solution to form nickel oxalate precipitate. At this time, a large number of ammonium oxalate ions in the ammonium oxalate are free in the mixed solution. This causes the pH of the solution to increase.

It should be noted that in step S4, after the nickel oxalate precipitate is generated, the nickel oxalate precipitated solid is separated, which can be used as a nickel source for subsequent ternary cathode materials.

Preferably, in step S5, the phosphorus source includes ammonium dihydrogen phosphate and ammonium monohydrogen phosphate, the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate, and the carbon source is glucose, sucrose, At least one of polyvinylidene fluoride (PVDF).

Preferably, in step S5, the mixture is mixed and sanded until the particle size is 0.1-0.6 μm. The applicant Through experiments, it was found that sanding the mixture to this particle size range is more conducive to subsequent processes.

Preferably, in step S5, the method used for pyrolysis is spray drying. The spray drying method used in this application can directly dry the polyethylene glycol and water in the mixed material, eliminating the evaporation of the solution and other processes.

More preferably, in step S5, the process parameters of spray drying are: inlet temperature is 150-250°C, feed speed is 300-650mL/h, inlet pressure is 0.1-0.5MPa, and outlet temperature is 120-150 ℃.

Preferably, in step S5, sintering is performed using a two-step sintering method.

More preferably, in step S5, the process parameters of the double sintering method are: the first sintering temperature is 400-500°C, the first sintering time is 5-8h; the second sintering temperature is 650-800 ℃, the second sintering time is 10-15h.

The embodiments of the present application also provide the application of the method for preparing lithium iron phosphate from nickel-iron alloy in the preparation of ternary cathode material precursor.

The beneficial effects of the embodiments of the present application are: the embodiments of the present application provide a method for preparing lithium iron phosphate from a nickel-iron alloy. The nickel-iron alloy is leached by using a combination of organic acids and oxidants. The reaction conditions are mild, which overcomes the current problem of leaching nickel by inorganic acids. Iron alloys have problems such as strong acidity, large amounts of wastewater, large equipment investment, and easy release of hydrogen ions. Moreover, the leaching process does not produce other impurities and is less corrosive to the equipment. By using organic precipitants, the nickel-iron alloys are precipitated step by step. The iron salt and nickel salt, the iron salt precipitation can be directly used to prepare lithium iron phosphate, and the nickel salt precipitation can be used as a nickel source for the subsequent preparation of ternary cathode materials; the method described in this application reduces the recycling cost of nickel-iron alloy and can create It produces certain economic benefits and has industrial application prospects.

Other aspects will be apparent after reading and understanding the drawings and detailed description.

Description of drawings

The accompanying drawings are used to provide a further understanding of the technical solutions herein, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solutions herein, and do not constitute a limitation of the technical solutions herein.

Figure 1 is a process flow chart for preparing lithium iron phosphate from nickel-iron alloy in an embodiment of the present application;

Figure 2 is an SEM image of lithium iron phosphate prepared in Example 2 of the present application;

Figure 3 is the discharge specific capacity curve of lithium iron phosphate prepared in Example 3 of the present application under 0.1C and nominal conditions.

Detailed ways

In order to better explain the purpose, technical solutions and advantages of the present application, the present application will be further described below in conjunction with specific embodiments.

Example 1

An embodiment of the method for preparing lithium iron phosphate from the nickel-iron alloy described in this application. The preparation method described in this embodiment includes the following steps:

S1. Crush and grind the nickel-iron alloy to a particle size of 5 mesh to obtain nickel-iron alloy powder;

S2. Mix 1kg of nickel-iron alloy powder, 2kg of formic acid, and 0.2kg of hydrogen peroxide and add it to the sand mill to grind at a speed of 300r/min for 60 minutes. The ball-to-material ratio is 5:1 and the grinding concentration is 31%. Fill The rate is 30%;

S3. Pass the mixture of step S2 through a 300-mesh screen and screen out unreacted nickel-iron alloy powder;

S4. Slowly add ammonium oxalate to the screened undersize solution. At this time, a yellow iron oxalate precipitate will gradually appear in the solution. Observe that when the yellow iron oxalate precipitate no longer forms in the solution, stop adding ammonium oxalate and test the solution with a pH meter. The pH is 1.5. After filtering the iron oxalate precipitate in the solution, continue to add ammonium oxalate to the mixed solution. Green nickel oxalate precipitate will form in the solution. Stop adding ammonium oxalate when no precipitate is formed in the solution. At this time, the pH of the solution is 5.0. ;

S5. Mix the ferric oxalate precipitate obtained in step S4 with ammonium dihydrogen phosphate, lithium carbonate, glucose, polyethylene glycol, and deionized water and sand-grind until the particle size of the mixture is 0.1 μm, and then spray-dry. The mixture is dried by the method, where the process parameters of spray drying are: inlet temperature is 150°C, feed rate is 300mL/h, inlet pressure is 0.1MPa, outlet temperature is 120°C; and the dried mixture is dried twice Sintering, the parameters of the two sinterings are: the first sintering temperature is 400°C, calcining for 5 hours, the second sintering temperature is 650°C, and the calcining is 10 hours. After the sintering is completed, the lithium iron phosphate is obtained.

The calculation formula of the grinding concentration in step S1 of this embodiment is shown in the following formula (1). The grinding concentration in this application adopts 2 decimal places.
Grinding concentration = m _{nickel-iron alloy powder} /(m _{nickel-iron alloy powder} + m _{organic acid} + m _oxidant )

Formula 1)

Example 2

The only difference between this embodiment and Embodiment 1 is that in step S1, the nickel-iron alloy is ground to a particle size of 60 mesh, in step S2, 1kg of nickel-iron alloy powder, 1kg of formic acid and 0.1kg of hydrogen peroxide are mixed and sanded for 150min at a sand mill speed of 500r/min, where the ball-to-material ratio is 30:1 and the grinding concentration is 48 %, filling rate 40%; in step S3, the mesh size of the screen is 600 mesh; in step S4, the pH when iron oxalate precipitate is generated is 1.8, and the pH when nickel oxalate precipitate is generated is 7.0; in step S5, you will get The iron oxalate precipitate is mixed with ammonium monohydrogen phosphate, lithium oxalate, sucrose, polyethylene glycol, and deionized water and sanded until the particle size of the mixture is 0.4 μm, and then the mixture is dried using a spray drying method, where , the process parameters of spray drying are: inlet temperature is 180°C, feed rate is 500mL/h, inlet pressure is 0.3MPa, outlet temperature is 130°C; then the dried mixture is sintered twice, and the parameters of the two sinterings are It is as follows: the primary sintering temperature is 450°C, calcined for 6 hours, the secondary sintering temperature is 700°C, and calcined for 13 hours. After the sintering is completed, the lithium iron phosphate is obtained. The size distribution of the lithium iron phosphate particles prepared in this example is relatively uniform, and its SEM The diagram is shown in Figure 2.

Example 3

The only difference between this embodiment and Example 1 is that: in step S1, the nickel-iron alloy is ground to a particle size of 80 mesh. In step S2, 1 kg of nickel-iron alloy powder, 0.5 kg of formic acid and 0.02 kg of hydrogen peroxide are mixed in a sand mill with a rotating speed of Mix and sand grind for 300 minutes under the condition of 1000r/min, in which the ball-to-material ratio is 50:1, the grinding concentration is 66%, and the filling rate is 45%; in step S3, the mesh number of the screen is 1000 mesh; in step S4, generate The pH when iron oxalate precipitates is 3.0, and the pH when nickel oxalate precipitates is generated is 8.0; in step S5, the obtained iron oxalate precipitate is mixed with ammonium dihydrogen phosphate, lithium carbonate, glucose, polyethylene glycol, and deionized water. Sand grind until the particle size of the mixture is 0.6 μm, and then use the spray drying method to dry the mixture. The process parameters of spray drying are: inlet temperature is 250°C, feed rate is 650mL/h, and air inlet pressure is 0.5MPa and the outlet temperature is 150℃; then the dried mixture is sintered twice. The parameters of the two sinterings are: the first sintering temperature is 500℃, calcining for 8h, the second sintering temperature is 800℃, calcining for 15h, and the sintering is completed. The lithium iron phosphate is then obtained. The discharge specific capacity curve of the lithium iron phosphate prepared in this example under 0.1C and nominal conditions is shown in Figure 3.

Example 4

The only difference between this embodiment and Example 1 is that in step S2, 1 kg of nickel-iron alloy powder, 4 kg of formic acid and 0.02 kg of hydrogen peroxide are mixed and sand-ground for 300 min, the grinding concentration is 20%, and the filling rate is 30%; the remaining steps are the same as Same as Example 1.

Example 5

The only difference between this embodiment and Example 1 is that in step S2, the organic acid is acetic acid, and the remaining steps are consistent with Example 1.

Comparative example 1

The only difference between this comparative example and Example 1 is that in step S2, 2 kg of nickel-iron alloy powder, 0.5 kg of formic acid and 0.4 kg of hydrogen peroxide were mixed and sanded for 300 min, and the grinding concentration was 69%. The remaining steps were consistent with Example 1.

Comparative example 2

The only difference between this comparative example and Example 1 is that in step S2, 0.2 kg of nickel-iron alloy powder, 1 kg of formic acid and 0.04 kg of hydrogen peroxide were mixed and sand-ground for 300 min. The grinding concentration was 16%. The remaining steps were consistent with Example 1.

Comparative example 3

The only difference between this comparative example and Example 1 is that in step S2, 0.5 kg of nickel-iron alloy powder, 1 kg of formic acid and 0.2 kg of hydrogen peroxide were mixed and sand-ground for 300 min. The grinding concentration was 29%. The remaining steps were consistent with Example 1.

Comparative example 4

The only difference between this comparative example and Example 1 is that in step S2, 1 kg of nickel-iron alloy powder, 2 kg of formic acid and 0.01 kg of hydrogen peroxide were mixed and sand-ground for 300 min. The grinding concentration was 33%. The remaining steps were consistent with Example 1.

Effect example

The finished lithium iron phosphate products prepared in Examples 1-5 and Comparative Examples 1-4 were tested for physical and chemical indicators and electrical properties. The test results are shown in Table 1 below.

Table 1

The results in Table 1 show that the physical and chemical indicators of the lithium iron phosphate prepared in Examples 1-4 using the method of the present application basically meet the standards of lithium iron phosphate cathode materials within the allowable error range, and the electrical properties are relatively excellent. The 0.1C discharge specific capacity is >154mAh/g; while in Example 5, because acetic acid is used as the organic acid, Fe/P does not meet the standard of lithium iron phosphate cathode material, the 0.1C discharge specific capacity is slightly lower than other examples. At the same time, the applicant's research found that in step S2, when other organic acids other than formic acid and acetic acid are used, the physical and chemical indicators and electrical properties of the prepared lithium iron phosphate are close to those of the lithium iron phosphate prepared in Example 5. In Comparative Examples 1 and 4, due to the small addition amount of organic acids and oxidants, the final Fe/P did not meet the standards for lithium iron phosphate cathode materials, and the 0.1C discharge specific capacity was <154mAh/g; in Comparative Examples 2 and 3, due to the organic acid . The amount of oxidant added exceeds the scope provided in this application. Although it has no significant impact on the physical and chemical indicators of lithium iron phosphate and has good electrical properties, excessive use of organic acids or oxidants has caused waste and environmental pollution. , does not conform to the concept of rational utilization of resources.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and do not limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art will understand that The technical solution of the present application may be modified or equivalently substituted without departing from the essence and scope of the technical solution of the present application.

Claims

A method for preparing lithium iron phosphate from nickel-iron alloy, which includes the following steps:

S1. Crush and grind the nickel-iron alloy to obtain nickel-iron alloy powder;

S2. Mix nickel-iron alloy powder, organic acid and oxidant and sand grind;

S3. Sieve the mixed material after sanding in step S2;

S4. Add an organic precipitant to the screened undersize solution until iron salt precipitation occurs in the solution, and the iron salt precipitate is separated; continue adding organic precipitant to the undersize solution until nickel salt precipitation occurs;

S5. The iron salt precipitate obtained in step S4 is mixed with a phosphorus source, a lithium source, a carbon source, polyethylene glycol and water and sanded, and the mixture is pyrolyzed and sintered to obtain the lithium iron phosphate.
The method for preparing lithium iron phosphate from nickel-iron alloy according to claim 1, wherein in step S2, the mass ratio of nickel-iron alloy powder and organic acid is (0.25-2):1.
The method for preparing lithium iron phosphate from nickel-iron alloy according to claim 1, wherein in step S2, the mass ratio of nickel-iron alloy powder and oxidant is (5-50):1.
The method for preparing lithium iron phosphate from a nickel-iron alloy according to claim 1, wherein in the step S2, the organic acid is formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, adipic acid, oxalic acid, malonic acid, At least one of succinic acid, maleic acid, tartaric acid, benzoic acid, phenylacetic acid, phthalic acid, terephthalic acid, valeric acid, caproic acid, capric acid, stearic acid, palmitic acid, and acrylic acid.
The method for preparing lithium iron phosphate from nickel-iron alloy according to claim 1, wherein in step S2, the oxidizing agent is ozone, hydrogen peroxide or hypochlorous acid.
The method for preparing lithium iron phosphate from nickel-iron alloy according to claim 1, wherein in step S3, the mesh size of the sieved sieve is 300-1000 mesh.
The method for preparing lithium iron phosphate from nickel-iron alloy according to claim 1, wherein in step S4, the organic precipitating agent is a weak acid and weak alkali salt.
The method for preparing lithium iron phosphate from nickel-iron alloy according to claim 1, wherein in step S4, the organic precipitating agent is ammonium oxalate.
The method for preparing lithium iron phosphate from a nickel-iron alloy according to claim 1, wherein in step S5, the method used for pyrolysis is a spray drying method.
Application of the method according to any one of claims 1 to 9 in preparing a cathode material precursor.