Iron phosphate material, preparation method thereof, positive electrode material, positive electrode sheet, and secondary battery

Abstract

The application provides a kind of iron phosphate material and its preparation method, positive electrode material, positive electrode sheet, secondary battery, wherein in the iron phosphate material, the ratio of the sum of the amount of substance of manganese element and iron element to the amount of substance of phosphorus element is (0.96~0.98):1, and the content of manganese element is 5200ppm~18100ppm.The iron phosphate material of the application has a high ratio of the sum of the amount of substance of manganese element and iron element to the amount of substance of phosphorus element, and the purity of the iron phosphate material is high, which is beneficial to improve the electrochemical performance of the positive electrode material prepared by using the iron phosphate material as raw material at low temperature.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to an iron phosphate material and its preparation method, a positive electrode material, a positive electrode sheet, and a secondary battery. Background Technology

[0002] Lithium iron phosphate (LiFePO4) materials are widely used in the new energy field, such as secondary batteries for new energy vehicles. Due to the limitations of its structure, the electrochemical performance of lithium iron phosphate, especially at low temperatures, is restricted. Doping lithium iron phosphate with manganese is one of the commonly used methods to improve its electrochemical performance (especially at low temperatures). Manganese-doped iron phosphate is a commonly used raw material for preparing manganese-doped lithium iron phosphate. However, existing methods for preparing manganese-doped iron phosphate tend to introduce impurities into the iron phosphate material, making it difficult to improve the purity of existing iron phosphate materials and consequently, the electrochemical performance of manganese-doped lithium iron phosphate materials obtained using existing iron phosphate materials is also difficult to improve.

[0003] Therefore, there is an urgent need to provide an iron phosphate material and its preparation method, cathode material, cathode electrode sheet, and secondary battery to solve the problem that the electrochemical performance of manganese-doped lithium iron phosphate materials at low temperatures needs to be improved due to the insufficient purity of existing iron phosphate materials. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides an iron phosphate material and its preparation method, a cathode material, a cathode electrode sheet, and a secondary battery, aiming to solve the technical problem that the low-temperature electrochemical performance of manganese-doped lithium iron phosphate materials needs to be improved due to the insufficient purity of existing iron phosphate materials.

[0005] In a first aspect, embodiments of this application provide an iron phosphate material, wherein the ratio of the sum of the amounts of manganese and iron to the amount of phosphorus in the iron phosphate material is (0.96~0.98):1, and the content of manganese in the iron phosphate material is 5200ppm~18100ppm.

[0006] In the technical solution of this application embodiment, the iron phosphate material has a high ratio of the sum of the amounts of manganese and iron to the amount of phosphorus, and the iron phosphate material has high purity, which is beneficial to improving the electrochemical performance of the cathode material prepared from the iron phosphate material at low temperature.

[0007] In some embodiments, the content of sulfur and other metallic elements besides manganese and iron in the iron phosphate material is less than or equal to 350 ppm; and / or, In the iron phosphate material, the molar ratio of iron to phosphorus is 0.91 to 0.96.

[0008] In the above embodiments, the iron phosphate material has low impurity content, high crystallinity, and uniform manganese doping, which is beneficial to improving the electrochemical performance of the cathode material prepared using this iron phosphate material as raw material.

[0009] Secondly, embodiments of this application provide a method for preparing an iron phosphate material, comprising: The ferrous source, the first phosphorus source, and the first oxidant undergo a first mixing process to obtain the first slurry; The first slurry undergoes a first purification process to obtain a first filter cake; The first filter cake is mixed with a manganese source, a second phosphorus source, and a second oxidant in a second process to obtain a second slurry; The second pulp is aged to obtain aged pulp; The aged slurry undergoes a second purification treatment to obtain a second filter cake; The second filter cake was calcined to obtain ferric phosphate material; The first slurry comprises amorphous iron phosphate, and the second slurry comprises manganese phosphate complex; the manganese content in the iron phosphate material is 5200ppm~18100ppm.

[0010] In the technical solution of this application embodiment, the ferrous source, the first phosphorus source, and the first oxidant undergo a first mixing treatment to obtain a first slurry with amorphous iron phosphate. The manganese source, the second phosphorus source, and the second oxidant undergo a second mixing treatment to form a manganese phosphate complex, which is then mixed with the amorphous iron phosphate in the first filter cake. After aging, a second purification treatment, and calcination, iron phosphate material is obtained. In the second mixing treatment, the manganese phosphate complex is formed and mixed evenly with the amorphous iron phosphate. In the subsequent aging treatment, since the decomplexing product of the manganese phosphate complex is consistent with the lattice structure of iron phosphate, it is easy to uniformly dope into iron phosphate to form a manganese-iron solid solution, thereby obtaining a high-purity iron phosphate material.

[0011] In some embodiments, the step of obtaining a first slurry by first mixing the ferrous source, the first phosphorus source, and the first oxidant includes: A ferrous solution and a first solution are provided, wherein the first solution comprises the first phosphorus source and the first oxidant; The first solution is mixed with the ferrous solution at a first mixing temperature and for a first mixing time to obtain a first mixture; The first mixture is reacted at a first reaction temperature and for a first reaction time to obtain the first slurry; Wherein, the first mixing temperature is 38℃~42℃, the first mixing time is 10min~30min, the first reaction temperature is 40℃~65℃, and the first reaction time is 40min~60min; The molar ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution is 1:(1.01~1.05):(0.58~0.7).

[0012] In the above embodiments, controlling the formation conditions of the first slurry and the molar ratio of iron, phosphorus, and the first oxidant is beneficial to the full reaction of the ferrous source, the first phosphorus source, and the first oxidant, thereby improving the purity of the amorphous iron phosphate obtained in this step.

[0013] In some embodiments, the step of subjecting the first filter cake to a second mixture with a manganese source, a second phosphorus source, and a second oxidant to obtain a second slurry includes: A second solution is provided, the second solution comprising the manganese source and the second phosphorus source; The second solution and the first filter cake are mixed at a second mixing temperature and for a second mixing time to obtain a second mixture; The second mixture and the second oxidant are mixed at a third mixing temperature and for a third mixing time to obtain a third mixture; The third mixture is dispersed at a dispersion temperature and for a dispersion time to obtain the second slurry; Wherein, the second mixing temperature is 20℃~30℃, the second mixing time is 8min~12min, the third mixing temperature is 20℃~30℃, the third mixing time is 5min~30min, the dispersion temperature is 20℃~30℃, and the dispersion time is 20min~30min; The molar ratio of manganese in the manganese source to iron in the ferrous source is greater than 0:1 and less than or equal to 0.1:0.9. The manganese element in the manganese source has a oxidation state of +2, and the amount of the second oxidant is 1 to 1.2 times the theoretical value required to oxidize the manganese element in the manganese source. The molar ratio of iron in the ferrous source to phosphorus in the second phosphorus source is 1:(0.15~0.3). In the above embodiments, controlling the formation conditions of the second slurry, as well as the amounts of manganese, phosphorus, and the second oxidant, is beneficial for the full formation of manganese phosphate complex. At the same time, controlling the molar ratio of manganese to iron in the ferrous source, and controlling the ratio of phosphorus in the second phosphorus source to iron in the ferrous source, is beneficial for controlling the amount of manganese doping in the iron phosphate material, thereby improving the electrochemical performance of the cathode material prepared using iron phosphate material as raw material.

[0014] In some embodiments, the step of aging the second slurry to obtain aged slurry includes: The second slurry is aged at an aging temperature and for an aging time to obtain an aged slurry; The aging temperature is 95℃~100℃, and the aging time is 1.5h~2.5h.

[0015] In the above embodiments, controlling the aging conditions is beneficial to the full decomposition of manganese phosphate complex and the full crystallization of iron phosphate, which in turn is beneficial to the uniform doping of manganese element into iron phosphate to form manganese-iron solid solution, thereby obtaining high-purity iron phosphate material.

[0016] In some embodiments, the step of calcining the second filter cake to obtain ferric phosphate material includes: The second filter cake is calcined at the specified temperature and for the specified time to obtain ferric phosphate material; The calcination temperature is 550℃~650℃, and the calcination time is 1.5h~2.5h.

[0017] In the above embodiments, controlling the calcination conditions is beneficial to the full calcination of the second filter cake, thereby improving the purity and crystallinity of the obtained iron phosphate material.

[0018] Thirdly, embodiments of this application provide a positive electrode material, which is prepared from the iron phosphate material as described above, or the positive electrode material is prepared from iron phosphate material prepared by the method described above.

[0019] In this embodiment, the positive electrode material is prepared from the iron phosphate material as described above or from the iron phosphate material prepared by the method described above, thus having the advantages of high purity and excellent electrochemical performance.

[0020] Fourthly, embodiments of this application provide a positive electrode sheet, including the positive electrode material as described above.

[0021] In this embodiment, the positive electrode sheet contains the above-mentioned positive electrode material, thus having the advantage of excellent electrochemical performance.

[0022] Fifthly, embodiments of this application provide a secondary battery, including the positive electrode sheet as described above.

[0023] In this embodiment, the secondary battery includes the aforementioned positive electrode sheet, thus possessing the advantage of excellent electrochemical performance.

[0024] Sixthly, embodiments of this application provide an electrical device including the secondary battery as described above.

[0025] In this embodiment, the electrical device includes the aforementioned secondary battery, thus possessing the advantage of excellent electrochemical performance.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0028] Figure 1 A schematic diagram of the process flow for the preparation method of the iron phosphate material provided in this application; Figure 2 The XRD result diagram of the iron phosphate material provided in Example 1 of this application; Figure 3 The image shows the SEM results of the iron phosphate material provided in Example 1 of this application. Detailed Implementation

[0029] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0031] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0034] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0035] In the description of the embodiments of this application, unless otherwise specified, "ppm" means the mass of the tested element, molecule or ion in parts per million of the sample mass.

[0036] In the description of the embodiments of this application, unless otherwise specified, "content" means the mass percentage of the tested element, molecule or ion in the sample.

[0037] In the description of the embodiments of this application, unless otherwise specified, the solvent used in the slurry and solution, as well as the washing water, are each independently selected from at least one of distilled water, deionized water, recycled water, pure water, and ultrapure water.

[0038] Existing methods for preparing ferric manganese phosphate tend to introduce impurities into the ferric phosphate material, making it difficult to improve the purity of the existing ferric phosphate material. Consequently, the electrochemical performance of manganese-doped lithium iron phosphate materials obtained using existing ferric phosphate materials as raw materials is also difficult to improve.

[0039] To address the technical problem of insufficient purity in existing iron phosphate materials leading to the need for improved electrochemical performance in manganese-doped lithium iron phosphate materials, this application provides an iron phosphate material, its preparation method, a cathode material, a cathode electrode, a secondary battery, and an electrical device. By increasing the ratio of the sum of the amounts of manganese and iron to the amount of phosphorus in the iron phosphate material, the purity of the iron phosphate material is improved, thereby enhancing the electrochemical performance of the cathode material prepared using this iron phosphate material as a raw material. Consequently, the electrochemical performance of the cathode electrode, the secondary battery, and the electrical device are also improved.

[0040] The electrical devices provided in this application embodiment can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0041] In a first aspect, embodiments of this application provide an iron phosphate material, wherein the ratio of the sum of the amounts of manganese and iron to the amount of phosphorus in the iron phosphate material is (0.96~0.98):1, and the content of manganese in the iron phosphate material is 5200ppm~18100ppm.

[0042] In the technical solution of this application embodiment, the iron phosphate material has a high ratio of the sum of the amounts of manganese and iron to the amount of phosphorus. The high purity of the iron phosphate material is beneficial to improving the electrochemical performance of the cathode material prepared using the iron phosphate material as raw material, especially the electrochemical performance of the cathode material at low temperature.

[0043] In some embodiments, the molar ratio of iron to phosphorus in the iron phosphate material is 0.855 to 0.960. The iron phosphate material has a high iron-to-phosphorus ratio, which is beneficial to improving the structural stability of the cathode material prepared from the iron phosphate material, thereby improving the electrochemical performance stability of the cathode material prepared from the iron phosphate material.

[0044] In some embodiments, the molar ratio of iron to phosphorus in the iron phosphate material is 0.947 to 0.951.

[0045] In some embodiments, the manganese content in the iron phosphate material is 5200 ppm to 18100 ppm. By controlling the manganese content in the iron phosphate, it is beneficial to maintain the structural stability of the iron phosphate material while improving the electrochemical performance of the cathode material prepared from the iron phosphate material, such as the electronic conductivity and ion diffusion rate, especially the electrochemical performance at low temperatures.

[0046] In some embodiments, the manganese content in the iron phosphate material is 7200ppm to 7600ppm.

[0047] In some embodiments, the content of sulfur and other metallic elements (excluding manganese and iron) in the iron phosphate material is less than or equal to 350 ppm. Further, the content of sulfur and other metallic elements (excluding manganese and iron) in the iron phosphate material is between 50 ppm and 350 ppm.

[0048] In some embodiments, the sulfur content in the iron phosphate material is 8 ppm to 20 ppm.

[0049] In some embodiments, the calcium content in the iron phosphate material is 1 ppm to 8.5 ppm. Further, the calcium content in the iron phosphate material is 1 ppm to 7.5 ppm.

[0050] In some embodiments, the cobalt content in the iron phosphate material is 0 ppm to 2.6 ppm.

[0051] In some embodiments, the potassium content in the iron phosphate material is 40 ppm to 380 ppm. Further, the potassium content in the iron phosphate material is 40 ppm to 300 ppm. Even further, the potassium content in the iron phosphate material is 40 ppm to 150 ppm.

[0052] In some embodiments, the magnesium content in the iron phosphate material is 0 ppm to 39 ppm.

[0053] In some embodiments, the magnesium content in the iron phosphate material is 0 ppm to 11 ppm. Further, the magnesium content in the iron phosphate material is 0 ppm to 8.5 ppm.

[0054] In some embodiments, the nickel content in the iron phosphate material is 0 ppm to 5 ppm.

[0055] In some embodiments, the zinc content in the iron phosphate material is 0 ppm to 5 ppm.

[0056] In some embodiments, the low content of impurity elements in the iron phosphate material indicates that the iron manganese phosphate material has high purity, which is beneficial to improving the electrochemical performance of the cathode material prepared from the iron phosphate material.

[0057] In some embodiments, when the cathode material prepared using the iron phosphate material is applied to a secondary battery, the discharge specific capacity at 0.1C rate is 148mAh / g to 160mAh / g at 25°C; further, the discharge specific capacity at 0.1C rate is 155mAh / g to 160mAh / g at 25°C.

[0058] In some embodiments, when the cathode material prepared using the iron phosphate material is applied to a secondary battery, the discharge specific capacity at a 0.1C rate is 115mAh / g to 129.5mAh / g at -20°C; further, the discharge specific capacity at a 0.1C rate is 120mAh / g to 129.5mAh / g at -20°C.

[0059] In some embodiments, when the cathode material prepared using the iron phosphate material is applied to a secondary battery, the discharge specific capacity retention rate at a 0.1C rate is 78%~81.5% at -20°C.

[0060] Please refer to Figure 1 Secondly, embodiments of this application provide a method for preparing an iron phosphate material, comprising: The ferrous source, the first phosphorus source, and the first oxidant undergo a first mixing process to obtain the first slurry; The first slurry undergoes a first purification process to obtain a first filter cake; The first filter cake is mixed with a manganese source, a second phosphorus source, and a second oxidant in a second process to obtain a second slurry; The second pulp is aged to obtain aged pulp; The aged slurry undergoes a second purification treatment to obtain a second filter cake; The second filter cake was calcined to obtain ferric phosphate material; The first slurry includes amorphous iron phosphate, and the second slurry includes manganese phosphate complex. The iron phosphate material contains 5200ppm to 18100ppm of manganese.

[0061] In the technical solution of this application embodiment, the ferrous source, the first phosphorus source, and the first oxidant undergo a first mixing treatment to obtain a first slurry with amorphous iron phosphate. The manganese source, the second phosphorus source, and the second oxidant undergo a second mixing treatment to form a manganese phosphate complex, which is then mixed with the amorphous iron phosphate in the first filter cake. After aging, a second purification treatment, and calcination, iron phosphate material is obtained. In the second mixing treatment, the manganese phosphate complex is formed and mixed evenly with the amorphous iron phosphate. In the subsequent aging treatment, since the decomplexing product of the manganese phosphate complex is consistent with the lattice structure of iron phosphate, it is easy to uniformly dope into iron phosphate to form a manganese-iron solid solution, thereby obtaining a high-purity iron phosphate material.

[0062] In some embodiments, the method for preparing iron phosphate material provided in this application is used to prepare the iron phosphate material as described above.

[0063] In some embodiments, the step of obtaining a first slurry by first mixing the ferrous source, the first phosphorus source, and the first oxidant includes: A ferrous solution and a first solution are provided, wherein the first solution comprises the first phosphorus source and the first oxidant; The first solution is mixed with the ferrous source at a first mixing temperature and for a first mixing time to obtain a first mixture; The first mixture is reacted at a first reaction temperature and for a first reaction time to obtain the first slurry.

[0064] In some embodiments, the first mixing temperature is 38°C to 42°C, the first mixing time is 10 min to 30 min, the first reaction temperature is 40°C to 65°C, and the first reaction time is 40 min to 60 min.

[0065] In some embodiments, the molar ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution is 1:(1.01~1.03):(0.55~0.65).

[0066] Controlling the formation conditions of the first slurry, as well as the molar ratio of iron, phosphorus, and the first oxidant, is beneficial to the full reaction of the ferrous source, the first phosphorus source, and the first oxidant, thereby improving the purity of the amorphous iron phosphate obtained in this step.

[0067] In some embodiments, the ferrous solution may be a ferrous salt solution, and the ferrous salt may be selected from at least one of ferrous salts such as anhydrous ferrous sulfate, ferrous chloride, ferrous nitrate, and ferrous sulfate heptahydrate.

[0068] In some embodiments, the first phosphorus source may be selected from phosphates, for example, it may be at least one of phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, and disodium hydrogen phosphate.

[0069] In some embodiments, the first oxidant may be selected from hydrogen peroxide. When the first oxidant is selected from hydrogen peroxide, the mass fraction of hydrogen peroxide in the hydrogen peroxide may be 26% to 29%, for example, 26%, 27%, 28%, 29%, etc.

[0070] The aforementioned ferrous salt, primary phosphorus source, and primary oxidant are inexpensive and widely available, which helps reduce the preparation cost of iron phosphate materials and facilitates large-scale industrial production.

[0071] In some embodiments, the concentration of ferrous ions in the ferrous solution can be 0.5 mol / L to 1.5 mol / L, for example, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, 1.5 mol / L, etc.

[0072] In some embodiments, the mass fraction of the first phosphorus source in the first solution can be 3% to 9%, for example, 3%, 4.5%, 5%, 6%, 7.5%, 9%, etc.

[0073] By controlling the concentration of ferrous ions in the ferrous solution and the mass fraction of the first phosphorus source in the first solution within the above-mentioned ranges, it is beneficial to adjust the ratio of the first solution to the ferrous solution involved in the mixing, which is conducive to the full reaction of iron and phosphorus elements, and to control the solid content of the obtained first slurry, so as to obtain a first slurry with suitable viscosity.

[0074] In some embodiments, the molar ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution is 1:(1.01~1.05):(0.58~0.7), where the first oxidant fully oxidizes the ferrous ions, thereby facilitating a full reaction between iron and phosphorus. For example, the molar ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution can be 1:1.01:0.58, 1:1.01:0.6, 1:1.01:0.65, 1:1.02:0.55, 1:1.02:0.6, 1:1.02:0.65, 1:1.03:0.55, 1:1.03:0.6, 1:1.03:0.65, 1:1.05:0.7, etc.

[0075] In some embodiments, in the step of mixing the first solution with the ferrous solution at a first mixing temperature and for a first mixing time to obtain a first mixture, the first solution is mixed with the ferrous solution under stirring, which is beneficial to the full mixing of the first solution and the ferrous solution and reduces the generation of impurities caused by local overconcentration of the first solution.

[0076] In some embodiments, the stirring speed of the ferrous solution is 400 r / min to 500 r / min, for example, it can be 400 r / min, 420 r / min, 450 r / min, 475 r / min, 500 r / min, etc.

[0077] In some embodiments, the first mixing temperature is 38°C to 42°C, and the first mixing time is 10 min to 30 min, which facilitates the thorough mixing of the first phosphorus source, the first oxidant in the first solution, and the ferrous ions in the ferrous solution. The first mixing temperature can be 38°C, 39°C, 40°C, 41°C, 42°C, etc., and the first mixing time can be 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0078] In some embodiments, the step of obtaining the first slurry from the first mixture at a first reaction temperature and after a first reaction time is carried out under stirring to ensure that the reaction occurs fully and uniformly. The stirring speed can be 400 r / min to 500 r / min, for example, 400 r / min, 420 r / min, 450 r / min, 475 r / min, or 500 r / min.

[0079] In some embodiments, the first reaction temperature is 40℃~65℃, and the first reaction time is 40min~60min, which facilitates the full reaction of ferrous ions in the ferrous salt solution, phosphate ions in the first solution, and the first oxidant in the first solution, thereby obtaining the first slurry. The first reaction temperature can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, etc., and the first reaction time can be 40min, 45min, 50min, 55min, 60min, etc.

[0080] In some embodiments, the first slurry is obtained by first mixing the ferrous source, the first phosphorus source, and the first oxidant, and the resulting first slurry contains amorphous ferric phosphate. The reaction equation is as follows: 2Fe 2+ +2H2PO4 - +H2O2+(X-1)H2O=2FePO4·XH2O↓+2H + By controlling the formation of the first slurry under the above conditions, it is beneficial to the full reaction of the ferrous source, the first phosphorus source, and the first oxidant, thereby improving the purity of the amorphous iron phosphate obtained in this step.

[0081] In some embodiments, the solid content of the first slurry is 12% to 20%, meaning the mass fraction of solid particles in the first slurry is 12% to 20%, which can be 12%, 15%, 16%, 18%, 20%, etc. A suitable solid content in the first slurry is beneficial for efficient reaction while avoiding excessive viscosity due to excessive solid content. This prevents problems such as material blockage that affect production.

[0082] In some embodiments, the step of obtaining a first filter cake by first purification treatment of the first slurry includes: The first slurry undergoes a first solid-liquid separation process to obtain a first solid material; The first solid material undergoes a first washing process to obtain a first washed material; The first washing material undergoes a second solid-liquid separation process to obtain a first filter cake.

[0083] In some embodiments, the first solid-liquid separation process and the second solid-liquid separation process are each independently selected from commonly used solid-liquid separation methods such as plate pressure filtration, atmospheric pressure filtration, pressure filtration, vacuum filtration, and centrifugation.

[0084] In some embodiments, the step of obtaining the first washed material by the first washing treatment of the first solid material includes: The first solid material is washed with a first washing liquid until the conductivity of the first washing liquid is less than or equal to 3.5 ms / cm, thus obtaining the first washed material.

[0085] In some embodiments, the moisture content of the first filter cake is less than or equal to 60% to 70%, for example, it can be 60%, 62%, 65%, 68%, 70%, etc.

[0086] In some embodiments, the step of subjecting the first filter cake to a second mixture with a manganese source, a second phosphorus source, and a second oxidant to obtain a second slurry includes: A second solution is provided, the second solution comprising the manganese source and the second phosphorus source; The second solution and the first filter cake are mixed at a second mixing temperature and for a second mixing time to obtain a second mixture; The second mixture and the second oxidant are mixed at a third mixing temperature and for a third mixing time to obtain a third mixture; The third mixture is dispersed at a dispersion temperature and for a dispersion time to obtain the second slurry.

[0087] In some embodiments, the manganese element in the manganese source has a oxidation state of +2, and the manganese source is selected from at least one of anhydrous manganese sulfate (II), anhydrous manganese chloride (II), manganese sulfate monohydrate (II), and manganese chloride tetrahydrate (II).

[0088] In some embodiments, the second phosphorus source is selected from phosphoric acid. Selecting phosphoric acid as the second phosphorus source is advantageous for controlling the pH of the third mixture within the range of 1.6 ± 0.15, and for controlling the dispersion of the third mixture within the pH range of 1.6 ± 0.15 by the dispersion temperature and dispersion time, thereby obtaining the second slurry. This helps reduce the precipitation of impurity elements and improves the purity of the final obtained iron phosphate material.

[0089] In some embodiments, the second oxidant is selected from at least one of potassium permanganate and ammonium persulfate.

[0090] The aforementioned manganese source, second phosphorus source, and second oxidant are inexpensive and widely available, which helps reduce the preparation cost of iron phosphate materials and facilitates large-scale industrial preparation.

[0091] In some embodiments, the manganese element in the manganese source has a oxidation state of +2, and the amount of the second oxidant is 1 to 1.2 times the theoretical value required to oxidize the manganese element in the manganese source. For example, it can be 1, 1.02, 1.05, 1.08, 1.1, 1.12, 1.15, 1.18, etc.

[0092] In some embodiments, when the second oxidant is selected from potassium permanganate, the disproportionation reaction of manganese is utilized, which is beneficial for obtaining manganese phosphate complexes and reducing the formation of other anions, thus saving the cost of treating the generation of other anions and reducing the preparation cost of iron phosphate materials. Specifically, when the second oxidant is selected from potassium permanganate, the reaction for generating manganese phosphate complexes is as follows: 8H + +MnO4 - +4Mn 2+ +10PO4 3- =5[Mn(PO4)2] 3- +4H2O In some embodiments, when the second oxidant is selected from ammonium persulfate, the step of mixing the second mixture with the second oxidant at a third mixing temperature and for a third mixing time to obtain a third mixture includes: The second mixture is mixed with the second oxidant and the catalyst at a third mixing temperature and for a third mixing time to obtain a third mixture.

[0093] In some embodiments, when the second oxidant is selected from ammonium persulfate, the catalyst can be a silver salt, for example, silver nitrate. Specifically, when the second oxidant is selected from ammonium persulfate and the catalyst is selected from silver nitrate, the reaction for forming the manganese phosphate complex is as follows: 5S2O8 2- +6Mn 2+ +20PO43- Ag+ == 10[Mn(PO4)2] 3- +10SO4 2- In some embodiments, the molar ratio of manganese in the manganese source to iron in the ferrous source is greater than 0:1 and less than or equal to 0.1:0.9. For example, the molar ratio of manganese in the manganese source to iron in the ferrous source can be 0.01:0.99, 0.02:0.98, 0.03:0.97, 0.04:0.96, 0.05:0.95, 0.06:0.94, 0.07:0.93, 0.08:0.92, 0.09:0.91, 0.1:0.9, etc.

[0094] In some embodiments, the molar ratio of iron in the ferrous source to phosphorus in the second phosphorus source is 1:(0.15~0.3). For example, the molar ratio of iron in the ferrous source to phosphorus in the second phosphorus source can be 1:0.15, 1:0.2, 1:0.25, 1:0.3, etc. Further, the molar ratio of iron in the ferrous source to phosphorus in the second phosphorus source is 1:(0.2~0.3).

[0095] By controlling the molar ratio of manganese in the manganese source to iron in the ferrous source, and the molar ratio of iron in the ferrous source to phosphorus in the second phosphorus source, it is beneficial for manganese to fully react with phosphorus in the second phosphorus source to form a manganese phosphate complex. At the same time, controlling the molar ratio of the formed manganese phosphate complex to amorphous iron phosphate in the first filter cake is beneficial for controlling the amount of manganese doped into the iron phosphate, which is conducive to improving the electrochemical performance of the cathode material obtained by using the prepared iron phosphate material as raw material.

[0096] In some embodiments, the molar ratio of manganese in the manganese source to the second oxidant is (4~6):(1~5.2). For example, the molar ratio of manganese in the manganese source to the second oxidant can be 4:1, 4:1.1, 4:1.2, 6:5, 6:5.1, 6:5.2, etc., which is beneficial for fully oxidizing the divalent manganese in the manganese source to the trivalent manganese in the manganese phosphate complex. Depending on the second oxidant, the molar ratio of manganese in the manganese source to the second oxidant varies. When the second oxidant is selected from potassium permanganate, the molar ratio of manganese in the manganese source to the second oxidant can be 4:(1~1.2), for example, 4:1, 4:1.1, 4:1.2, etc. When the second oxidant is selected from ammonium persulfate, the molar ratio of manganese in the manganese source to the second oxidant can be 6:(5~5.2), for example, 6:5, 6:5.1, 6:5.2.

[0097] In some embodiments, when the second oxidant is selected from ammonium persulfate and the catalyst is silver ions, the molar ratio of manganese in the manganese source, the second oxidant, and the silver ions in the catalyst can be 6:(5~5.2):(0.18~0.22), which is beneficial for the full oxidization of divalent manganese in the manganese source to trivalent manganese in the manganese phosphate complex. For example, the molar ratio of manganese in the manganese source, the second oxidant, and the silver ions in the catalyst can be 6:5:0.18, 6:5:0.2, 6:5:0.22, 6:5.1:0.18, 6:5.1:0.2, 6:5.1:0.22, 6:5.2:0.18, 6:5.2:0.2, 6:5.2:0.22, etc.

[0098] In some embodiments, the second mixing temperature is 20°C to 30°C, and the second mixing time is 8 min to 12 min.

[0099] In some embodiments, the third mixing temperature is 20°C to 30°C, and the third mixing time is 5 min to 30 min. For example, the third mixing temperature can be 20°C, 24°C, 25°C, 26°C, 28°C, 30°C, etc.; the third mixing time can be 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 24 min, 25 min, 28 min, 30 min, etc.

[0100] In some embodiments, the dispersion temperature is 20℃~30℃, and the dispersion time is 20min~30min. For example, the dispersion temperature can be 20℃, 24℃, 25℃, 26℃, 28℃, 30℃, etc.; the dispersion time can be 20min, 22min, 25min, 28min, 30min, etc.

[0101] In some embodiments, silver ions used as catalysts can be recovered using a cation exchange resin. Specifically, the filtrate containing silver ions and the wash water are collected, adsorbed by a strong acid cation exchange resin, and then countercurrently eluted with a 0.5 mol / L thiourea solution. The eluent containing silver ions is collected, and finally, the eluent is electrolyzed to obtain silver powder for recovery, thereby saving manufacturing costs.

[0102] In some embodiments, the steps of mixing the second solution with the first filter cake at a second mixing temperature and for a second mixing time to obtain a second mixture; mixing the second mixture with the second oxidant at a third mixing temperature and for a third mixing time to obtain a third mixture; and dispersing the third mixture at a dispersion temperature and for a dispersion time to obtain a second slurry are carried out independently under stirring conditions, with the stirring speed being 800 r / min to 1200 r / min, for example, 800 r / min, 850 r / min, 900 r / min, 950 r / min, 1000 r / min, 1050 r / min, 1100 r / min, 1150 r / min, 1200 r / min, etc.

[0103] By controlling the formation conditions of the second slurry, it is beneficial to fully form the manganese phosphate complex, and the formed manganese phosphate complex is also beneficial to fully and uniformly mix with the amorphous iron phosphate in the first filter cake.

[0104] In some embodiments, the step of aging the second slurry to obtain aged slurry includes: The second slurry is aged at an aging temperature and for an aging time to obtain an aged slurry.

[0105] In some embodiments, the aging temperature is 95℃~100℃, and the aging time is 1.5h~2.5h. For example, the aging temperature can be 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, etc., and the aging time can be 1.5h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.5h, etc.

[0106] In some embodiments, controlling the pH value within the range of 1.6 ± 0.15 during the aging process helps reduce the precipitation of impurity elements and improve the purity of the final obtained iron phosphate material.

[0107] During the aging process, the manganese phosphate complex fully de-complexes and precipitates homogeneously, combining with ferric phosphate to form ferric manganese phosphate. The reaction equation is shown below: 9FePO4·XH2O+1[Mn(PO4)2] 3- ==10Fe 0.9 Mn 0.1 PO4·2H2O+PO4 3- + (9X-2)H2O Controlling the aging process conditions is beneficial for the complete decomposition of manganese phosphate complexes and the complete crystallization of iron phosphate, which in turn facilitates the uniform doping of manganese into iron phosphate, forming a manganese-iron solid solution, thereby obtaining high-purity iron phosphate materials.

[0108] In some embodiments, the step of obtaining a second filter cake by second purification treatment of the aged slurry includes: The aged slurry undergoes a third solid-liquid separation process to obtain a second solid material; The second solid material undergoes a second washing process to obtain a second washed material; The second washing material undergoes a fourth solid-liquid separation process to obtain a second filter cake.

[0109] In some embodiments, the third and fourth solid-liquid separation processes are independently selected from common solid-liquid separation methods such as plate pressure filtration, atmospheric pressure filtration, pressure filtration, vacuum filtration, and centrifugation.

[0110] In some embodiments, the step of obtaining a second washed material by subjecting the second solid material to a second washing treatment includes: The second solid material is washed with a second washing liquid until the conductivity of the second washing liquid is less than or equal to 350 μs / cm, thus obtaining the second washed material.

[0111] In some embodiments, the moisture content of the second filter cake is less than or equal to 40% to 60%, for example, it can be 40%, 45%, 50%, 55%, 60%, etc.

[0112] In some embodiments, the step of calcining the second filter cake to obtain ferric phosphate material includes: The second filter cake is calcined at the specified temperature and for the specified time to obtain ferric phosphate material; In some embodiments, the calcination temperature is 550℃~650℃, and the calcination time is 1.5h~2.5h. For example, the calcination temperature can be 550℃, 575℃, 600℃, 625℃, 650℃, etc., and the calcination time can be 1.5h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.5h, etc.

[0113] Controlling the calcination conditions is beneficial for the complete calcination of the second filter cake, thereby improving the purity and crystallinity of the obtained ferric phosphate material.

[0114] In some embodiments, prior to the calcination of the second filter cake, the process further includes drying the second filter cake.

[0115] In some embodiments, the drying process can be carried out by methods such as atmospheric pressure drying or vacuum drying. When atmospheric pressure drying is used, the drying temperature can be 95℃~100℃, and the drying time can be 10h~14h. For example, the drying temperature can be 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, etc., and the drying time can be 10h, 11h, 12h, 13h, 14h, etc.

[0116] Drying the second filter cake helps reduce reaction byproducts generated during calcination and further improves the purity of the obtained iron phosphate material.

[0117] Thirdly, embodiments of this application provide a positive electrode material, which is prepared from the iron phosphate material as described above, or the positive electrode material is prepared from iron phosphate material prepared by the method described above.

[0118] In this embodiment, the positive electrode material is prepared from the iron phosphate material as described above or from the iron phosphate material prepared by the method described above, thus having the advantages of high purity and excellent electrochemical performance.

[0119] Fourthly, embodiments of this application provide a positive electrode sheet, including the positive electrode material as described above.

[0120] In this embodiment, the positive electrode sheet contains the above-mentioned positive electrode material, thus having the advantage of excellent electrochemical performance.

[0121] Fifthly, embodiments of this application provide a secondary battery, including the positive electrode sheet as described above.

[0122] In this embodiment, the secondary battery includes the aforementioned positive electrode sheet, thus possessing the advantage of excellent electrochemical performance.

[0123] Sixthly, embodiments of this application provide an electrical device including the secondary battery as described above.

[0124] In this embodiment, the electrical device includes the aforementioned secondary battery, thus possessing the advantage of excellent electrochemical performance.

[0125] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0126] I. Preparation Method Example 1 S100: Weigh ferrous sulfate and pure water to prepare a 1 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 7.0), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 27%) to prepare a 5% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.02:0.6, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 40℃, stirring speed of 500 r / min, and first mixing time of 20 min. Maintain stirring speed of 500 r / min, and at the first reaction temperature of 55℃ and first reaction time of 50 min, to obtain a first slurry with amorphous ferric phosphate.

[0127] S200: The first slurry is filtered through a plate press to obtain the first solid material. The first solid material in the chamber of the plate press is washed with pure water until the conductivity of the washing water is less than or equal to 3.5 ms / cm to obtain the first washed material. After the first washed material goes through the depressurization and feeding process, it is removed from the plate press to obtain the first filter cake.

[0128] S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source is 0.98:0.02, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source is 1:0.2. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution and the first filter cake are mixed at a second mixing temperature of 25°C and a stirring speed of 1000 r / min for a second mixing time of 10... After mixing for min, a second mixture is obtained; the second oxidant is weighed according to the molar ratio of manganese element in the manganese source to the second oxidant of 4:1.1, and the rotation speed is kept constant. The second mixture and the second oxidant are mixed at a third mixing temperature of 25℃ for a third mixing time of 20 min to obtain a third mixture. The pH value of the phosphoric acid system is controlled within the range of 1.6±0.15. The third mixture is dispersed at a dispersion temperature of 25℃ for a dispersion time of 20 min to obtain a second slurry.

[0129] S400: The second slurry is aged in a reactor. During the aging process, the pH value is controlled within the range of 1.6±0.15. The aging temperature is 98℃ and the aging time is 2h under stirring at a stirring speed of 500r / min. The manganese phosphate complex de-complexes and precipitates in a homogeneous phase to allow manganese to be incorporated into the iron phosphate. The precipitate color changes from yellow to blue-purple, and the aged slurry is obtained.

[0130] S500: The aged slurry is filtered through a plate press to obtain a second solid material. The second solid material in the chamber of the plate press is washed with pure water until the conductivity of the washing water is less than or equal to 350 μS / cm to obtain a second washed material. After the second washed material is depressurized and discharged, it is removed from the plate press to obtain a second filter cake.

[0131] S600: The second filter cake is dried under normal pressure at a temperature of 98°C for 12 hours to obtain dried material; the dried material is then calcined at 600°C for 2 hours to obtain iron phosphate material.

[0132] The XRD (X-ray diffraction) results of the iron phosphate material obtained in Example 1 are as follows: Figure 2 As shown, the SEM (scanning electron microscope) results are as follows: Figure 3 As shown.

[0133] Example 2 S100: Weigh ferrous sulfate and pure water to prepare a 0.5 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 6.8), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 26%) to prepare a 3% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.02:0.6, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 38℃, a stirring speed of 400 r / min, and a first mixing time of 10 min. Maintain stirring speed of 400 r / min, and at a first reaction temperature of 40℃ for a first reaction time of 40 min, to obtain a first slurry with amorphous ferric phosphate.

[0134] S200: The first slurry is filtered through a plate press to obtain the first solid material. The first solid material in the chamber of the plate press is washed with pure water until the conductivity of the washing water is less than or equal to 3.5 ms / cm to obtain the first washed material. After the first washed material goes through the depressurization and feeding process, it is removed from the plate press to obtain the first filter cake.

[0135] S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source is 0.98:0.2, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source is 1:0.2. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution is mixed with the first filter cake at a second mixing temperature of 20°C and a stirring speed of 800 r / min for a second mixing time of 8 min to obtain the second mixture. The second oxidant is weighed according to a molar ratio of manganese in the manganese source to the second oxidant of 4:1.1. Maintaining a constant stirring speed, the second mixture and the second oxidant are mixed at a third mixing temperature of 20°C for a third mixing time of 5 min to obtain the third mixture. The pH of the phosphoric acid system is controlled within the range of 1.6 ± 0.15. The third mixture is dispersed at a dispersion temperature of 20°C for a dispersion time of 20 min to obtain the second slurry.

[0136] S400: The second slurry is aged in a reactor. During the aging process, the pH value is controlled within the range of 1.6±0.15. The aging temperature is 95℃ and the aging time is 1.5h under stirring at a stirring speed of 500r / min. The manganese phosphate complex de-complexes and precipitates in a homogeneous phase to allow manganese to be incorporated into the iron phosphate. The precipitate color changes from yellow to blue-purple, resulting in the aged slurry.

[0137] S500: The aged slurry is filtered through a plate press to obtain a second solid material. The second solid material in the chamber of the plate press is washed with pure water until the conductivity of the washing water is less than or equal to 350 μS / cm to obtain a second washed material. After the second washed material is depressurized and discharged, it is removed from the plate press to obtain a second filter cake.

[0138] S600: The second filter cake is dried under normal pressure at a temperature of 95°C for 10 hours to obtain dried material; the dried material is then calcined at a temperature of 550°C for 1.5 hours to obtain ferric phosphate material.

[0139] Example 3 S100: Weigh ferrous sulfate and pure water to prepare a 1.5 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 7.2), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 29%) to prepare a 9% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.02:0.6, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 42℃, stirring speed of 450 r / min, and first mixing time of 30 min. Maintain stirring speed of 450 r / min, and at the first reaction temperature of 65℃ and first reaction time of 60 min, to obtain a first slurry with amorphous ferric phosphate.

[0140] S200: The first slurry is filtered through a plate press to obtain the first solid material. The first solid material in the chamber of the plate press is washed with pure water until the conductivity of the washing water is less than or equal to 3.5 ms / cm to obtain the first washed material. After the first washed material goes through the depressurization and feeding process, it is removed from the plate press to obtain the first filter cake.

[0141] S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source is 0.98:0.2, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source is 1:0.2. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution is mixed with the first filter cake at a second mixing temperature of 30°C and a stirring speed of 1200 r / min for a second mixing time of 12 min to obtain the second mixture. The second oxidant is weighed according to a molar ratio of manganese in the manganese source to the second oxidant of 4:1.1. Maintaining a constant stirring speed, the second mixture and the second oxidant are mixed at a third mixing temperature of 30°C for a third mixing time of 30 min to obtain the third mixture. The pH of the phosphoric acid system is controlled within the range of 1.6 ± 0.15. The third mixture is dispersed at a dispersion temperature of 30°C for a dispersion time of 30 min to obtain the second slurry.

[0142] S400: The second slurry is aged in a reactor. During the aging process, the pH value is controlled within the range of 1.6±0.15. The aging temperature is 100℃ and the aging time is 2.5h under stirring at a stirring speed of 500r / min. The manganese phosphate complex de-complexes and precipitates in a homogeneous phase to allow manganese to be incorporated into the iron phosphate. The precipitate color changes from yellow to blue-purple, and the aged slurry is obtained.

[0143] S500: The aged slurry is filtered through a plate press to obtain a second solid material. The second solid material in the chamber of the plate press is washed with pure water until the conductivity of the washing water is less than or equal to 350 μS / cm to obtain a second washed material. After the second washed material is depressurized and discharged, it is removed from the plate press to obtain a second filter cake.

[0144] S600: The second filter cake is dried under normal pressure at a temperature of 100℃ for 14 hours to obtain dried material; the dried material is then calcined at a temperature of 650℃ for 2.5 hours to obtain iron phosphate material.

[0145] Example 4 This embodiment is the same as or similar to Embodiment 1, except that: S100: Weigh ferrous sulfate and pure water to prepare a 1 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 7.0), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 27%) to prepare a 5% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.01:0.58, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 40℃, a stirring speed of 500 r / min, and a first mixing time of 20 min. Maintain stirring speed of 500 r / min and at a first reaction temperature of 55℃ for a first reaction time of 50 min to obtain a first slurry with amorphous ferric phosphate.

[0146] Example 5 This embodiment is the same as or similar to Embodiment 1, except that: S100: Weigh ferrous sulfate and pure water to prepare a 1 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 7.0), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 27%) to prepare a 5% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.03:0.65, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 40℃, stirring speed of 500 r / min, and first mixing time of 20 min. Maintain stirring speed of 500 r / min, and at the first reaction temperature of 55℃ and first reaction time of 50 min, to obtain a first slurry with amorphous ferric phosphate.

[0147] Example 6 This embodiment is the same as or similar to Embodiment 1, except that: S100: Weigh ferrous sulfate and pure water to prepare a 1 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 7.0), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 27%) to prepare a 5% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.00:0.5, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 40℃, a stirring speed of 500 r / min, and a first mixing time of 20 min. Maintain stirring speed of 500 r / min and at a first reaction temperature of 55℃ for a first reaction time of 50 min to obtain a first slurry with amorphous ferric phosphate.

[0148] Example 7 This embodiment is the same as or similar to Embodiment 1, except that: S100: Weigh ferrous sulfate and pure water to prepare a 1 mol / L ferrous sulfate solution (ferrous solution). Weigh phosphate salt (first phosphorus source, phosphate salt solution obtained by mixing ammonium dihydrogen phosphate solution and ammonia water, pH value 7.0), pure water, and hydrogen peroxide (first oxidant, hydrogen peroxide mass fraction of 27%) to prepare a 5% (based on the mass fraction of phosphorus) phosphate salt solution (first solution). With a molar ratio of ferrous sulfate: phosphate salt: hydrogen peroxide of 1:1.05:0.70, add the phosphate salt solution dropwise to the ferrous sulfate solution under the first mixing temperature of 40℃, stirring speed of 500 r / min, and first mixing time of 20 min. Maintain stirring speed of 500 r / min, and at the first reaction temperature of 550℃ and first reaction time of 50 min, to obtain a first slurry with amorphous ferric phosphate.

[0149] Example 8 This embodiment is the same as or similar to Embodiment 1, except that: S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution to manganese in the manganese source used in step S100 is 0.9:0.1, and the molar ratio of iron in the ferrous solution to phosphorus in the second phosphorus source used in step S100 is 1:0.15. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution and the first filter cake are mixed at a mixing temperature of 25°C and a stirring speed of 1000 r / min. After stirring and mixing for a second mixing time of 10 minutes, a second mixture is obtained. The second oxidant is weighed according to the molar ratio of manganese element in the manganese source to the second oxidant of 4:1.02. The rotation speed is kept constant. The second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 minutes to obtain a third mixture. The pH value of the phosphoric acid system is controlled within the range of 1.6±0.15. The third mixture is dispersed at a dispersion temperature of 25°C for a dispersion time of 20 minutes to obtain a second slurry.

[0150] Example 9 This embodiment is the same as or similar to Embodiment 1, except that: S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source is 0.9:0.1, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source is 1:0.25. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution is mixed with the first filter cake at a second mixing temperature of 25°C and a stirring speed of 1000 r / min for a second mixing time of 10 min to obtain the second mixture. The second oxidant is weighed according to a molar ratio of manganese in the manganese source to the second oxidant of 4:1.2. Maintaining a constant stirring speed, the second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 min to obtain the third mixture. The pH of the system is controlled within the range of 1.6 ± 0.15 using phosphoric acid. The third mixture is dispersed at a dispersion temperature of 25°C for a dispersion time of 20 min to obtain the second slurry.

[0151] Example 10 This embodiment is the same as or similar to Embodiment 1, except that: S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The manganese source and the second phosphorus source are weighed and dissolved in pure water to obtain a second solution, with the iron-to-manganese ratio in the ferrous solution used in step S100 being 0.9:0.1 and the iron-to-phosphorus ratio in the ferrous solution used in step S100 being 1:0.1. The second solution is then mixed with the first filter cake at a second mixing temperature of 25°C and a stirring speed of 1000 r / min for a second mixing time of 10 min to obtain a second mixture. The second oxidant is weighed according to a manganese-to-second oxidant ratio of 4:0.9. Maintaining a constant stirring speed, the second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 min to obtain a third mixture. The pH of the phosphoric acid system is controlled within the range of 1.6 ± 0.15. The third mixture is then dispersed at a dispersion temperature of 25°C for a dispersion time of 20 min to obtain a second slurry.

[0152] Example 11 This embodiment is the same as or similar to Embodiment 1, except that: S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source is 0.9:0.1, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source is 1:0.3. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution is mixed with the first filter cake at a second mixing temperature of 25°C and a stirring speed of 1000 r / min for a second mixing time of 10 min to obtain the second mixture. The second oxidant is weighed according to a molar ratio of manganese in the manganese source to the second oxidant of 4:1.3. Maintaining a constant stirring speed, the second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 min to obtain the third mixture. The pH of the system is controlled within the range of 1.6 ± 0.15 using phosphoric acid. The third mixture is dispersed at a dispersion temperature of 25°C for a dispersion time of 20 min to obtain the second slurry.

[0153] Example 12 This embodiment is the same as or similar to Embodiment 1, except that: S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. Following the molar ratio of iron in the ferrous solution to manganese in the manganese source used in step S100 (0.95:0.05) and the molar ratio of iron in the ferrous solution to phosphorus in the second phosphorus source used in step S100 (1:0.2), the manganese source and the second phosphorus source are weighed, dissolved in pure water, and stirred to form the second solution. The second solution and the first filter cake are mixed at a second mixing temperature of 25°C and a rotation speed of 1000 r / min. The mixture was stirred and mixed for a second mixing time of 10 minutes to obtain a second mixture. The second oxidant was weighed according to the molar ratio of manganese in the manganese source to the second oxidant of 4:1.1. The rotation speed was kept constant. The second mixture and the second oxidant were mixed at a third mixing temperature of 25°C for a third mixing time of 20 minutes to obtain a third mixture. The pH value of the phosphoric acid system was controlled within the range of 1.6±0.15. The third mixture was dispersed at a dispersion temperature of 25°C for a dispersion time of 20 minutes to obtain a second slurry.

[0154] Example 13 This embodiment is the same as or similar to Embodiment 1, except that: S400: The second slurry is aged in the reactor. During the aging process, the pH value is controlled within the range of 1.6±0.15, the aging temperature is 98℃, and the aging time is 1h. The manganese phosphate complex de-complexes and homogeneously precipitates to allow manganese to be incorporated into the iron phosphate. The precipitate color changes from yellow to blue-purple, and the aged slurry is obtained.

[0155] Example 14 This embodiment is the same as or similar to Embodiment 1, except that: S400: The second slurry is aged in the reactor. During the aging process, the pH value is controlled within the range of 1.6±0.15, the aging temperature is 98℃, and the aging time is 3h. The manganese phosphate complex de-complexes and precipitates in a homogeneous phase to allow manganese to be incorporated into the iron phosphate. The precipitate color changes from yellow to blue-purple, and the aged slurry is obtained.

[0156] Example 15 This embodiment is the same as or similar to Embodiment 1, except that: S600: The second filter cake is dried under normal pressure at a temperature of 98℃ for 12 hours to obtain dried material; the dried material is then calcined at a temperature of 550℃ for 1 hour to obtain iron phosphate material.

[0157] Example 16 This embodiment is the same as or similar to Embodiment 1, except that: S600: The second filter cake is dried under normal pressure at a temperature of 98°C for 12 hours to obtain dried material; the dried material is then calcined at 700°C for 3 hours to obtain iron phosphate material.

[0158] Example 17 This embodiment is the same as or similar to Embodiment 1, except that: Step S300: The manganese source is manganese sulfate, the second oxidant is ammonium persulfate, the catalyst is silver nitrate, and the second phosphorus source is phosphoric acid. Following the molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source being 0.9:0.1, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source being 1:0.2, the manganese source and the second phosphorus source are weighed, dissolved in pure water, and stirred to form the second solution. The second solution and the first filter cake are stirred at a mixing temperature of 25°C and a rotation speed of 1000 r / min. The mixture is then mixed for a second mixing time of 10 minutes to obtain a second mixture. The second oxidant and catalyst are weighed according to the molar ratio of manganese in the manganese source to the second oxidant and catalyst of 6:5.1:0.2. The rotation speed is kept constant. The second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 minutes to obtain a third mixture. The pH value of the phosphoric acid system is controlled within the range of 1.6±0.15. The third mixture is dispersed at a dispersion temperature of 25°C for a dispersion time of 20 minutes to obtain a second slurry.

[0159] Example 18 This embodiment is the same as or similar to Embodiment 18, except that: Step S300: The manganese source is manganese sulfate, the second oxidant is ammonium persulfate, the catalyst is silver nitrate, and the second phosphorus source is phosphoric acid. Following the molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source being 0.9:0.1, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source being 1:0.2, the manganese source and the second phosphorus source are weighed, dissolved in pure water, and stirred to form the second solution. The second solution and the first filter cake are stirred at a mixing temperature of 25°C and a rotation speed of 1000 r / min. The mixture is then mixed for 10 minutes to obtain a second mixture. The second oxidant and catalyst are weighed according to the molar ratio of manganese in the manganese source to the second oxidant and catalyst of 6:5:0.18. The rotation speed is kept constant. The second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for 20 minutes to obtain a third mixture. The pH value of the phosphoric acid system is controlled within the range of 1.6±0.15. The third mixture is dispersed at a dispersion temperature of 25°C for 20 minutes to obtain a second slurry.

[0160] Example 19 This embodiment is the same as or similar to Embodiment 18, except that: Step S300: The manganese source is manganese sulfate, the second oxidant is ammonium persulfate, the catalyst is silver nitrate, and the second phosphorus source is phosphoric acid. Following the molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source being 0.9:0.1, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source being 1:0.2, the manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution and the first filter cake are mixed at a second mixing temperature of 25°C and a stirring speed of 1000 r / min. A second mixture is obtained after mixing for a second mixing time of 10 minutes. The second oxidant and catalyst are weighed according to the molar ratio of manganese in the manganese source to the second oxidant and catalyst of 6:5.2:0.22. The rotation speed is kept constant. The second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 minutes to obtain a third mixture. The pH value of the phosphoric acid system is controlled within the range of 1.6±0.15. The third mixture is dispersed at a dispersion temperature of 25°C for a dispersion time of 20 minutes to obtain a second slurry.

[0161] Comparative Example 1 1. Synthesis of ferrous phosphate octahydrate: Weigh ferrous sulfate solution and pure water to prepare a 1 mol / L ferrous sulfate solution. Add manganese sulfate and phosphoric acid according to the molar ratio of manganese:iron:phosphorus = 0.02:0.98:0.7. Add ammonia water dropwise to the ferric phosphate solution to adjust the pH value of the solution to 6.5 to obtain manganese-doped ferrous phosphate octahydrate. Filter and rinse the obtained manganese phosphate octahydrate until the conductivity is ≤3.5 mS / cm. 2. Oxidation and aging: After washing the ferromanganese phosphate octahydrate into a slurry, phosphoric acid was added, and hydrogen peroxide was added dropwise for oxidation. The ratio of hydrogen peroxide to iron was 0.6:1. The slurry was then heated to 98℃ and aged for 2 hours. After filtration and rinsing until the conductivity was ≤350us / cm, white ferromanganese phosphate dihydrate was obtained. 3. Drying and calcination: Dry manganese ferric phosphate dihydrate at 98℃ for 12 hours, and then calcine at 600℃ for 2 hours to obtain manganese ferric phosphate.

[0162] Comparative Example 2 This embodiment is the same as or similar to Embodiment 1, except that: S300: The manganese source is manganese sulfate, the second oxidant is potassium permanganate, and the second phosphorus source is phosphoric acid. The molar ratio of iron in the ferrous solution used in step S100 to manganese in the manganese source is 0.88:0.12, and the molar ratio of iron in the ferrous solution used in step S100 to phosphorus in the second phosphorus source is 1:0.2. The manganese source and the second phosphorus source are weighed and dissolved in pure water to form the second solution. The second solution is mixed with the first filter cake at a second mixing temperature of 25°C and a stirring speed of 1000 r / min for a second mixing time of 10 min to obtain the second mixture. The second oxidant is weighed according to a molar ratio of manganese in the manganese source to the second oxidant of 4:1.1. Maintaining a constant stirring speed, the second mixture and the second oxidant are mixed at a third mixing temperature of 25°C for a third mixing time of 20 min to obtain the third mixture. The third mixture is dispersed at a dispersion temperature of 25°C for a dispersion time of 20 min to obtain the second slurry.

[0163] II. Testing Methods 1. In iron phosphate materials, the contents of manganese and iron are detected by redox titration, while other impurity elements are detected by inductively coupled plasma atomic emission spectrometry.

[0164] 2. The crystallinity of the iron phosphate material was obtained by X-ray diffraction.

[0165] 3. Electrochemical performance testing of cathode materials Preparation of positive electrode material: (1) The iron phosphate material, lithium carbonate and glucose prepared in the examples and comparative examples were mixed in a molar ratio of 1:1:0.05 and ground and mixed evenly. The D50 particle size of the mixed material was 0.65 μm. (2) The mixed material is spray-dried at an inlet air temperature of 250 ℃ and an outlet air temperature of 120 ℃ to obtain lithium iron phosphate precursor; (3) The lithium iron phosphate precursor is calcined in a nitrogen atmosphere at a temperature of 800 °C and a holding time of 12 h to obtain the lithium iron phosphate material, which is the cathode material.

[0166] Electrochemical performance testing: The positive electrode material prepared using the iron phosphate material in the examples and comparative examples as raw materials was mixed with conductive carbon black and PVDF binder at a mass ratio of 90:5:5, and coated onto a 12μm thick aluminum foil. The electrode was then dried in an oven at 110℃ for 10 hours. The dried electrode was then cut into 15mm diameter positive electrode discs and compacted to a density of 1.8g / cm³. 3The cells were rolled and pressed, with a 16mm diameter lithium sheet as the counter electrode. The electrolyte was obtained by dissolving 1mol / L LiPF6 in EC:EMC:DEC at a volume ratio of 1:1:1. The cells were assembled in an LG2400 / 1000TS glove box manufactured by Wig Gas Purification Technology (Suzhou) Co., Ltd., to obtain coin half-cells, and their rate performance was tested.

[0167] The battery performance testing system (model: CT3002A) of Wuhan Landian Electronics Technology Co., Ltd. was used for testing. The test temperature was 25℃ and -20℃, the voltage range was 2V~4.35V, and the test rate was 0.1C and 1C.

[0168] II. Analysis of Test Results for Each Embodiment and Comparative Example Table 1 Table 2 As shown in Table 1 above, the manganese-doped iron phosphate material obtained using the preparation method of the iron phosphate material provided in this application has significantly higher purity than the manganese-iron phosphate of Comparative Example 1. Consequently, the performance of the cathode material prepared using this method is also significantly better than that of the cathode material prepared using manganese-iron phosphate as raw material in Comparative Example 1. Specifically, as shown in Table 2, the cathode material prepared based on the iron phosphate material provided in this application exhibits significantly higher discharge specific capacity at 0.1C at 25℃ and -20℃, and a higher discharge capacity retention rate at 0.1C rate at -20℃ than the cathode material prepared using manganese-iron phosphate as raw material in Comparative Example 1.

[0169] As shown in Table 1 above, the preparation method of iron phosphate material provided in this application, compared with Comparative Example 2, controls the molar ratio of manganese in the manganese source to iron in the ferrous source, thereby obtaining an iron phosphate material with a manganese content of 5200ppm~18100ppm. The introduction of manganese improves the electrochemical performance of the cathode material prepared from iron phosphate material at room temperature and low temperature, while controlling the amount of manganese introduced avoids the reduction in discharge specific capacity caused by the John-Teller effect.

[0170] As shown in Table 1 above, compared to the ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution of Example 6 (1:1.00:0.5), the insufficient amount of the first oxidant resulted in incomplete precipitation of iron ions, a decrease in the iron-manganese ratio, and an increase in the manganese content. This led to incomplete utilization of raw materials, increased costs, and difficulty in controlling the stability of the finished product. The method for preparing iron phosphate material provided in this application controls the ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution to 1:(1.01~1.03):(0.58~0.7). The resulting iron phosphate material is more conducive to reducing costs and stably preparing cathode materials with significantly improved discharge performance at both room temperature and low temperature.

[0171] As can be seen from the results in Table 1 above, the method for preparing iron phosphate material provided in this application, which controls the amount of the second oxidant to be 1 to 1.2 times the theoretical value required for manganese element in manganese oxide source, results in iron phosphate material as raw material, which is more conducive to preparing cathode material with significantly improved discharge performance at both room temperature and low temperature.

[0172] As can be seen from the results in Table 1 above, the method for preparing iron phosphate material provided in this application, which controls the aging temperature to 95℃~100℃, the aging time to 1.5h~2.5h, and the calcination temperature to 550℃~650℃, and the calcination time to 1.5h~2.5h, yields iron phosphate material as raw material, which is more conducive to preparing cathode materials with significantly improved discharge performance at both room temperature and low temperature.

[0173] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing an iron phosphate material, characterized in that, include: The ferrous source, the first phosphorus source, and the first oxidant undergo a first mixing process to obtain the first slurry; The first slurry undergoes a first purification process to obtain a first filter cake; The first filter cake is mixed with a manganese source, a second phosphorus source, and a second oxidant in a second process to obtain a second slurry; The second pulp is aged to obtain aged pulp; The aged slurry undergoes a second purification treatment to obtain a second filter cake; The second filter cake was calcined to obtain ferric phosphate material; The first slurry comprises amorphous iron phosphate, and the second slurry comprises manganese phosphate complex; the iron phosphate material contains 5200ppm to 18100ppm of manganese; the iron phosphate material contains manganese in a molar ratio of (0.96 to 0.98) to phosphorus in a molar ratio of (0.96 to 0.98).

2. The method for preparing iron phosphate material according to claim 1, characterized in that, The step of obtaining a first slurry by first mixing of ferrous source, first phosphorus source, and first oxidant includes: A ferrous solution and a first solution are provided, wherein the first solution comprises the first phosphorus source and the first oxidant; The first solution is mixed with the ferrous solution at a first mixing temperature and for a first mixing time to obtain a first mixture; The first mixture is reacted at a first reaction temperature and for a first reaction time to obtain the first slurry; Wherein, the first mixing temperature is 38℃~42℃, the first mixing time is 10min~30min, the first reaction temperature is 40℃~65℃, and the first reaction time is 40min~60min; The molar ratio of iron in the ferrous solution, phosphorus in the first solution, and the first oxidant in the first solution is 1:(1.01~1.05):(0.58~0.7).

3. The method for preparing iron phosphate material according to claim 1, characterized in that, The step of obtaining a second slurry by second mixing treatment of the first filter cake with a manganese source, a second phosphorus source, and a second oxidant includes: A second solution is provided, the second solution comprising the manganese source and the second phosphorus source; The second solution and the first filter cake are mixed at a second mixing temperature and for a second mixing time to obtain a second mixture; The second mixture and the second oxidant are mixed at a third mixing temperature and for a third mixing time to obtain a third mixture; The third mixture is dispersed at a dispersion temperature and for a dispersion time to obtain the second slurry; Wherein, the second mixing temperature is 20℃~30℃, the second mixing time is 8min~12min, the third mixing temperature is 20℃~30℃, the third mixing time is 5min~30min, the dispersion temperature is 20℃~30℃, and the dispersion time is 20min~30min; The molar ratio of manganese in the manganese source to iron in the ferrous source is greater than 0:1 and less than or equal to 0.1:0.

9. The manganese element in the manganese source has a oxidation state of +2, and the amount of the second oxidant is 1 to 1.2 times the theoretical value required to oxidize the manganese element in the manganese source. The molar ratio of iron in the ferrous source to phosphorus in the second phosphorus source is 1:(0.15~0.3).

4. The method for preparing iron phosphate material according to claim 1, characterized in that, The steps for obtaining aged pulp by aging the second pulp include: The second slurry is aged at an aging temperature and for an aging time to obtain an aged slurry; The aging temperature is 95℃~100℃, and the aging time is 1.5h~2.5h.

5. The method for preparing iron phosphate material according to claim 1, characterized in that, The step of calcining the second filter cake to obtain ferric phosphate material includes: The second filter cake is calcined at the specified temperature and for the specified time to obtain ferric phosphate material; The calcination temperature is 550℃~650℃, and the calcination time is 1.5h~2.5h.

6. A type of iron phosphate material, characterized in that, It is prepared by the method for preparing iron phosphate material according to any one of claims 1 to 5.

7. The ferric acid material according to claim 6, characterized in that, In the iron phosphate material, the content of sulfur and other metallic elements besides manganese and iron is less than or equal to 350 ppm; and / or, In the iron phosphate material, the molar ratio of iron to phosphorus is 0.91 to 0.

96.

8. A positive electrode material, characterized in that, The positive electrode material is prepared from the iron phosphate material prepared by the method described in any one of claims 1 to 5, or the positive electrode material is prepared from the iron phosphate material described in any one of claims 6 to 7.

9. A positive electrode sheet, characterized in that, Including the cathode material as described in claim 8.

10. A secondary battery, characterized in that, Including the positive electrode sheet as described in claim 9.

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