A method for producing iron phosphate

Abstract

The application discloses a preparation method of iron phosphate and relates to the technical field of battery material preparation. The preparation method of the iron phosphate takes an iron-nickel dissolving solution as a preparation raw material, changes the crystal form surface of the prepared crude iron phosphate through appropriate heat treatment of the crude iron phosphate, and enables the nickel ions bound in the crystal to easily separate from the crystal. Then, the crude iron phosphate is washed, and the nickel content in the iron phosphate can be greatly reduced.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of battery material preparation, and particularly relates to a preparation method of iron phosphate. BACKGROUND

[0002] Lithium ion batteries have the advantages of high voltage, large energy density, good cycle performance, small self-discharge, no memory effect, wide working temperature range, etc., and are widely used in various fields. The positive electrode material is an important component of lithium ion batteries, and lithium iron phosphate is a common positive electrode material. Nickel iron can be used for the production of iron phosphate, and finally lithium iron phosphate is prepared.

[0003] In the related art, after the nickel iron dissolution solution is removed, iron phosphate can be synthesized by directly adding phosphoric acid. However, due to the high nickel content in the iron phosphate prepared by the nickel iron dissolution solution, the current washing process has poor nickel removal effect. Therefore, how to reduce the nickel content in the iron phosphate is a problem to be solved at present. SUMMARY

[0004] The present disclosure aims to at least solve one of the technical problems existing in the prior art. To this end, the present disclosure provides a preparation method of iron phosphate, which can greatly reduce the nickel content in the iron phosphate prepared by nickel iron.

[0005] According to the preparation method of iron phosphate provided by the first aspect of the present disclosure, the following steps are included:

[0006] S1, mixing and reacting the nickel iron dissolution solution, the phosphorus source and hydrogen peroxide, then aging treatment, solid-liquid separation, washing the first solid phase for the first time, and obtaining the crude iron phosphate;

[0007] S2, after the crude iron phosphate is heat treated, it is washed for the second time, solid-liquid separation, and the second solid phase is calcined, and the iron phosphate is obtained;

[0008] The temperature of the heat treatment is not less than 200 DEG C;

[0009] The time of the heat treatment is not less than 20 min;

[0010] The solid-liquid ratio of the second washing is not more than 1g:8mL.

[0011] According to the preparation method of the present disclosure, at least the following beneficial effects are achieved:

[0012] The preparation method of the embodiment changes the crystal form surface of the iron phosphate through appropriate heat treatment, so that the nickel ions and sulfate ions bound in the iron phosphate crystal are separated from the crystal, and then the iron phosphate is washed, which can greatly reduce the nickel content and the sulfur content in the iron phosphate.

[0013] According to some embodiments of the present disclosure, the preparation method of the ferronickel dissolution solution comprises the following steps:

[0014] The ferronickel is mixed with the acid solution to obtain the ferronickel dissolution solution.

[0015] Unless otherwise specified, "not higher than" in the present disclosure means less than or equal to, which should be understood as including the number.

[0016] Unless otherwise specified, "not lower than" in the present disclosure means greater than or equal to, which should be understood as including the number.

[0017] According to some embodiments of the present disclosure, the acid solution comprises at least one of sulfuric acid and hydrochloric acid.

[0018] According to some embodiments of the present disclosure, the content of nickel in the ferronickel dissolution solution is 35g / L-55g / L. For example, it can be specifically 35g / L, 38g / L, 40g / L, 42g / L, 45g / L, 48g / L, 50g / L, 52g / L or 55g / L.

[0019] According to some embodiments of the present disclosure, the content of iron in the ferronickel dissolution solution is 60g / L-80g / L. For example, it can be specifically 60g / L, 62g / L, 64g / L, 66g / L, 68g / L, 70g / L, 72g / L, 74g / L, 76g / L, 78g / L or 80g / L.

[0020] According to some embodiments of the present disclosure, the content of sulfur in the ferronickel dissolution solution is 60g / L-80g / L. For example, it can be specifically 60g / L, 62g / L, 64g / L, 66g / L, 68g / L, 70g / L, 72g / L, 74g / L, 76g / L, 78g / L or 80g / L.

[0021] According to some embodiments of the present disclosure, in the mixing reaction of step S1, the molar ratio of iron to phosphorus is 0.8-0.9:1. For example, it can be specifically 0.81:1, 0.82:1, 0.83:1, 0.84:1, 0.85:1, 0.86:1, 0.87:1, 0.88:1, 0.89:1 or 0.9:1.

[0022] According to some embodiments of the present disclosure, in the mixing reaction of step S1, the feed flow ratio of the hydrogen peroxide to the ferronickel dissolution solution is 1:(10-15). For example, it can be specifically 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15.

[0023] Unless otherwise specified, the "feed flow ratio" in the present disclosure is the volume flow ratio.

[0024] According to some embodiments of the present disclosure, in the mixing reaction of step S1, the mass concentration of the hydrogen peroxide is 27wt%-28wt%.

[0025] According to some embodiments of the present disclosure, in the mixing reaction of step S1, the reaction temperature is 85°C-90°C. For example, it can be specifically 85°C, 86°C, 87°C, 88°C, 89°C or 90°C.

[0026] According to some embodiments of the present disclosure, in the mixing reaction of step S1, the reaction time is 2h-4h. For example, it can be specifically 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h.

[0027] According to some embodiments of the present disclosure, the phosphorus source comprises at least one of phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0028] According to some embodiments of the present disclosure, in step S1, the temperature of the aging treatment is 60°C-80°C. For example, it can be specifically 60°C, 65°C, 70°C, 75°C or 80°C.

[0029] According to some embodiments of the present disclosure, in step S1, the time of the aging treatment is 9-10h. For example, it can be specifically 9h, 9.1h, 9.2h, 9.3h, 9.4h, 9.5h, 9.6h, 9.7h, 9.8h, 9.9h or 10h.

[0030] According to some embodiments of the present disclosure, the nickel content of the crude iron phosphate is 80ppm-100ppm. For example, it can be specifically 80ppm, 82ppm, 84ppm, 86ppm, 88ppm, 90ppm, 92ppm, 94ppm, 96ppm, 98ppm or 100ppm.

[0031] According to some embodiments of the present disclosure, the sulfur content of the crude iron phosphate is 150ppm-200ppm. For example, it can be specifically 150ppm, 155ppm, 160ppm, 165ppm, 170ppm, 175ppm, 180ppm, 185ppm, 190ppm, 195ppm or 200ppm.

[0032] According to some embodiments of the present disclosure, in step S2, the temperature of the heat treatment is 200°C-500°C. For example, it can be specifically 200°C, 225°C, 250°C, 275°C, 300°C, 325°C, 350°C, 375°C, 400°C, 425°C, 450°C, 475°C or 500°C.

[0033] According to some embodiments of the present disclosure, in step S2, the temperature of the heat treatment is 200-300℃.

[0034] According to some embodiments of the present disclosure, in step S2, the time of the heat treatment is 20-50 min. For example, it can be specifically 20 min, 25 min, 30 min, 35 min, 40 min, 45 min or 50 min.

[0035] According to some embodiments of the present disclosure, in step S2, the time of the heat treatment is 20-30 min.

[0036] According to some embodiments of the present disclosure, in step S2, the solid-liquid ratio of the second washing is 1 g:(8-11) mL. For example, it can be specifically 1:8, 1:8.5, 1:9, 1:9.5, 1:10, 1:10.5 or 1:11.

[0037] According to some embodiments of the present disclosure, in step S2, the time of the calcination is 1.5-2 h. For example, it can be specifically 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2 h.

[0038] According to some embodiments of the present disclosure, in step S2, the temperature of the calcination is 680-700℃. For example, it can be specifically 680℃, 685℃, 690℃, 695℃ or 700℃.

[0039] According to some embodiments of the present disclosure, the content of nickel in the iron phosphate is not higher than 20 ppm.

[0040] According to some embodiments of the present disclosure, the content of nickel in the iron phosphate is 15-20 ppm.

[0041] According to some embodiments of the present disclosure, the content of sulfur in the iron phosphate is not higher than 100 ppm.

[0042] According to some embodiments of the present disclosure, the content of sulfur in the iron phosphate is 50-100 ppm.

[0043] Other features and advantages of the present disclosure will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present disclosure. DETAILED DESCRIPTION

[0044] The concept and the technical effects of the present disclosure will be described below in conjunction with embodiments, so as to fully understand the purposes, features and effects of the present disclosure.

[0045] The reagents used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0046] In the description of the present disclosure, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0047] When a numerical range is disclosed in the present disclosure, the above range is considered to be continuous and includes the minimum value and the maximum value of the range, and each value between the minimum value and the maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed in the present disclosure should be understood to include any and all sub-ranges incorporated therein.

[0048] Unless otherwise specified, the nickel-iron dissolving solution used in the embodiments of the present disclosure is obtained by sulfuric acid leaching of nickel-iron; the nickel content is 40 g / L, the iron content is 60 g / L, and the sulfur content is 70 g / L.

[0049] Embodiment 1

[0050] The present example provides a preparation method of iron phosphate, the steps are as follows:

[0051] S1, mix the nickel-iron dissolving solution, phosphoric acid and 28wt% hydrogen peroxide at 85°C and pH 0.5 for 2h (the molar ratio of iron to phosphorus is 0.8:1, and the feeding flow ratio of 28wt% hydrogen peroxide to nickel-iron dissolving solution is 1:10), continue to age at 60°C for 9h, filter, and wash with pure water to obtain a crude iron phosphate product with a nickel content of 80ppm and a sulfur content of 150ppm.

[0052] S2, heat treat the crude iron phosphate at 200°C for 20min, wash with pure water (solid-liquid ratio 1g:8mL), separate the solid and liquid, and calcine at 680°C for 2h to obtain iron phosphate.

[0053] Embodiment 2

[0054] The present example provides a preparation method of iron phosphate, the steps are as follows:

[0055] S1, the nickel iron solution, sodium dihydrogen phosphate and 28wt% hydrogen peroxide were mixed at 87°C, pH 0.7 for 3h (the molar ratio of iron to phosphorus was 0.85:1, the feeding flow ratio of 28wt% hydrogen peroxide to nickel iron solution was 1:12), and then the aging treatment was continued at 70°C for 9.5h, pressure filtration, and pure water washing to obtain the crude iron phosphate with the nickel content of 90ppm and the sulfur content of 170ppm.

[0056] S2, the crude iron phosphate was heat treated at 200°C for 25min, then washed with pure water (the solid-liquid ratio was 1g:9mL), solid-liquid separated, and then calcined at 690°C for 2h to obtain the iron phosphate.

[0057] Example 3

[0058] The example provides a preparation method of iron phosphate, and the steps are as follows:

[0059] S1, the nickel iron solution, sodium dihydrogen phosphate and 28wt% hydrogen peroxide were mixed at 90°C, pH=0.9 for 3.8h (the molar ratio of iron to phosphorus was 0.87:1, the feeding flow ratio of 28wt% hydrogen peroxide to nickel iron solution was 1:13), and then the aging treatment was continued at 75°C for 9.7h, pressure filtration, and pure water washing to obtain the crude iron phosphate with the nickel content of 95ppm and the sulfur content of 180ppm.

[0060] S2, the crude iron phosphate was heat treated at 200°C for 28min, then washed with pure water (the solid-liquid ratio was 1g:9.5mL), solid-liquid separated, and then calcined at 695°C for 1.8h to obtain the iron phosphate.

[0061] Example 4

[0062] The example provides a preparation method of iron phosphate, and the steps are as follows:

[0063] S1, the nickel iron solution, sodium dihydrogen phosphate and 28wt% hydrogen peroxide were mixed at 90°C, pH=0.9 for 3.8h (the molar ratio of iron to phosphorus was 0.87:1, the feeding flow ratio of 28wt% hydrogen peroxide to nickel iron solution was 1:13), and then the aging treatment was continued at 75°C for 9.7h, pressure filtration, and pure water washing to obtain the crude iron phosphate with the nickel content of 95ppm and the sulfur content of 180ppm.

[0064] S2, the crude iron phosphate was heat treated at 200°C for 28min, then washed with pure water (the solid-liquid ratio was 1g:9.5mL), solid-liquid separated, and then calcined at 695°C for 1.8h to obtain the iron phosphate.

[0065] Example 5

[0066] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 4, except that the heat treatment temperature in step S2 is changed from 200°C to 300°C.

[0067] Example 6

[0068] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 4, except that the heat treatment temperature in step S2 is changed from 200°C to 400°C.

[0069] Example 7

[0070] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 4, except that the heat treatment temperature in step S2 is changed from 200°C to 500°C.

[0071] Example 8

[0072] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 4, except that the heat treatment temperature in step S2 is changed from 200°C to 500°C.

[0073] S1, mix the nickel-iron solution, sodium dihydrogen phosphate and 28wt% hydrogen peroxide at 90°C and pH=1.0 for 4h (the molar ratio of iron to phosphorus is 0.9:1, and the feed flow ratio of 28wt% hydrogen peroxide to nickel-iron solution is 1:14), continue to age at 80°C for 10h, filter, and wash with pure water to obtain a crude iron phosphate product with a nickel content of 100ppm and a sulfur content of 200ppm;

[0074] S2, heat treat the crude iron phosphate at 200°C for 20min, wash with pure water (solid-liquid ratio 1g:10mL), separate the solid and liquid, and calcine at 700°C for 1.5h to obtain iron phosphate.

[0075] Example 9

[0076] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 8, except that the heat treatment time in step S2 is changed from 20min to 30min.

[0077] Example 10

[0078] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 8, except that the heat treatment time in step S2 is changed from 20min to 40min.

[0079] Example 11

[0080] This example provides a method for preparing iron phosphate, which is basically the same as that of Example 8, except that the heat treatment time in step S2 is changed from 20min to 50min.

[0081] Example 12

[0082] The example provides a preparation method of iron phosphate, and the steps are as follows:

[0083] S1, the nickel-iron solution, phosphoric acid and 28wt% hydrogen peroxide are mixed and reacted at 85°C and pH 0.5 for 2h (the molar ratio of iron to phosphorus is 0.8:1, and the feeding flow ratio of 28wt% hydrogen peroxide to nickel-iron solution is 1:10), and then the aging treatment is continued at 60°C for 9h, pressure filtration and pure water washing are performed to obtain the crude iron phosphate with the nickel content of 80ppm and the sulfur content of 150ppm;

[0084] S2, the crude iron phosphate is heat treated at 200°C for 20min, washed with pure water (the solid-liquid ratio is 1g:8mL), solid-liquid separated, and roasted at 680°C for 2h to obtain the iron phosphate.

[0085] Example 13

[0086] The example provides a preparation method of iron phosphate, which is basically the same as that in example 12, and the difference is only that the solid-liquid ratio of washing in step S2 is replaced from 1g:8mL to 1g:9mL.

[0087] Example 14

[0088] The example provides a preparation method of iron phosphate, which is basically the same as that in example 12, and the difference is only that the solid-liquid ratio of washing in step S2 is replaced from 1g:8mL to 1g:10mL.

[0089] Example 15

[0090] The example provides a preparation method of iron phosphate, which is basically the same as that in example 12, and the difference is only that the solid-liquid ratio of washing in step S2 is replaced from 1g:8mL to 1g:11mL.

[0091] Comparative Example 1

[0092] The example provides a preparation method of iron phosphate, which is basically the same as that in example 4, and the difference is only that the heat treatment temperature in step S2 is replaced from 200°C to 100°C.

[0093] Comparative Example 2

[0094] The example provides a preparation method of iron phosphate, which is basically the same as that in example 9, and the difference is only that the heat treatment time in step S2 is replaced from 20min to 10min.

[0095] Comparative Example 3

[0096] The example provides a preparation method of iron phosphate, which is basically the same as that in example 12, and the difference is only that the solid-liquid ratio of washing in step S2 is replaced from 1g:8mL to 1g:7mL.

[0097] Detection Example

[0098] The nickel content and the sulfur content in the iron phosphate prepared in detection examples 1 to 15 and comparative examples 1 to 3 were detected.

[0099] The results are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] As can be seen from examples 4 to 7 and comparative example 1, the nickel content and the sulfur content in the iron phosphate gradually decrease with the increase of the heat treatment temperature. When the heat treatment temperature is 100℃, only the free water evaporates, and the crystal form of the iron phosphate does not change, the nickel ions and the sulfate radicals wrapped in the crystal cannot be effectively precipitated, and are difficult to be washed away.

[0104] As can be seen from examples 8 to 11 and comparative example 2, the nickel content and the sulfur content in the iron phosphate gradually decrease with the increase of the heat treatment time. When the heat treatment time is 10 min, the surface deformation of the crystal cannot be completed due to the too short heat treatment time, the nickel ions and the sulfate radicals wrapped in the crystal cannot be effectively precipitated, and are difficult to be washed away.

[0105] As can be seen from examples 12 to 15 and comparative example 3, the washing effect of the nickel ions and the sulfate radicals becomes poor when the amount of pure water is too small.

Claims

1. A method for preparing ferric phosphate, characterized in that, The steps are as follows: S1. After mixing and reacting the nickel-iron solution, phosphorus source and hydrogen peroxide, the mixture is aged, solid-liquid separation is performed, and the first solid phase is washed for the first time to obtain crude iron phosphate. The nickel content in the nickel-iron solution is 35 g / L to 55 g / L; the sulfur content in the nickel-iron solution is 60 g / L to 80 g / L. The aging process takes 9-10 hours and is carried out at a temperature of 60℃-80℃. S2. After heat treatment, the crude iron phosphate is washed a second time, and the solid and liquid phases are separated. The separated second solid phase is then calcined to obtain iron phosphate. The heat treatment temperature is 200℃~500℃; The heat treatment time is 20 min to 50 min; The solid-liquid ratio of the second wash is not higher than 1 g: 8 mL; The second washing is performed using pure water; The nickel content in the iron phosphate is not higher than 20 ppm; the sulfur content in the iron phosphate is not higher than 100 ppm.

2. The preparation method according to claim 1, characterized in that, The preparation method of the nickel-iron solution includes the following steps: The nickel-iron solution is mixed with acid to obtain the product.

3. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the heat treatment is 200℃~300℃.

4. The preparation method according to claim 1, characterized in that, In step S2, the heat treatment time is 20 min to 30 min.

5. The preparation method according to claim 1, characterized in that, In step S2, the solid-liquid ratio of the second wash is 1 g: 8 mL to 11 mL.

6. The preparation method according to claim 1, characterized in that, In the mixed reaction of step S1, the molar ratio of iron to phosphorus is 0.8~0.9:

1.

7. The preparation method according to claim 1, characterized in that, In the mixing reaction of step S1, the feed flow ratio of hydrogen peroxide to nickel-iron solution is 1:(10~15).

8. The preparation method according to claim 1, characterized in that, The phosphorus source includes at least one of phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

9. The preparation method according to claim 1, characterized in that, In the mixed reaction of step S1, the reaction temperature is 85℃~90℃.

10. The preparation method according to claim 1, characterized in that, In step S2, the roasting time is 1.5 h to 2 h.

11. The preparation method according to claim 1, characterized in that, In step S2, the calcination temperature is 680℃~700℃.

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