Precursor, preparation method therefor, positive electrode material, positive electrode sheet and lithium ion battery

Abstract

A preparation method for a precursor comprises the following steps: providing a plurality of first raw material components, the plurality of first raw material components comprising an iron source, a manganese source, a phosphorus source, an M source and hydrogen peroxide; mixing the plurality of first raw material components; and drying same to obtain a first precursor, the general formula of the first precursor being MnxFeyMzPO4•nH2O, wherein M is a metal element, x is 0.10-0.95, y is 0.10-0.95, z is 0.01-0.10, the sum of x, y and z are 0.95-1.06, and n is any integer from 0-10. Further provided are a positive electrode material prepared from the precursor, a positive electrode sheet and a lithium ion battery.

Description

Precursor and preparation method thereof, positive electrode material, positive electrode sheet and lithium ion battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 15, 2023, with application number 202311538600.9. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of electrode materials, and in particular to a precursor and a preparation method thereof, a positive electrode material, a positive electrode sheet and a lithium-ion battery. Background Art

[0003] Cathode materials significantly impact the performance of lithium-ion batteries and are a key constraint to improving battery performance. Lithium iron manganese phosphate (LiMnFePO4) is a new-generation cathode material for lithium-ion batteries. It boasts a stable structure during charge and discharge, high operating voltage, high energy density, and excellent safety.

[0004] In related technologies, the performance of lithium manganese iron phosphate materials is affected by their synthesis route, and there are problems such as poor cycle performance and low specific energy, which affect the application of the materials. Technical issues

[0005] The present application provides a precursor and a preparation method thereof, a positive electrode material, a positive electrode plate and a lithium-ion battery to solve the above technical problems. Technical Solutions

[0006] In a first aspect, the present invention provides a method for preparing a precursor, comprising the following steps:

[0007] Provide a plurality of first raw material components, the plurality of first raw material components including an iron source, a manganese source, a phosphorus source, an M source and hydrogen peroxide, mix the plurality of first raw material components, and dry them to obtain a first precursor, the general formula of the first precursor is Mn x Fe y M z PO4·nH2O;

[0008] Wherein, M is a metal element, x is 0.10 to 0.95, y is 0.10 to 0.95, z is 0.01 to 0.10, the sum of x, y and z is 0.95 to 1.06, and n is any integer from 0 to 10.

[0009] In a second aspect, an embodiment of the present application provides a precursor, wherein the precursor includes any one of a first precursor, a second precursor, and a third precursor:

[0010] The general formula of the first precursor is Mn x Fe y Mz PO4·nH2O;

[0011] The second precursor includes a general formula of Mn x Fe y M z The nucleus of PO4;

[0012] The third precursor includes a core and a carbon coating layer coated on the outer surface of the core. The material of the core includes a general formula of Li a Mn x Fe y M z PO4 materials;

[0013] Wherein, M is a metal element, x is 0.10 to 0.95, y is 0.10 to 0.95, z is 0.01 to 0.10, the sum of x, y and z is 0.95 to 1.06, a is 0.95 to 1.10, and n is any integer from 0 to 10.

[0014] In a third aspect, an embodiment of the present application provides a positive electrode material, which is prepared from a precursor, and the precursor includes the precursor prepared by the preparation method described above, or the precursor described above.

[0015] In a fourth aspect, an embodiment of the present application provides a positive electrode plate, comprising a positive electrode current collector and a coating disposed on one side of the positive electrode current collector, wherein the material of the coating comprises the positive electrode material described above.

[0016] In a fifth aspect, an embodiment of the present application provides a lithium-ion battery comprising the positive electrode sheet as described above. Beneficial effects

[0017] Beneficial effects of this application:

[0018] In an embodiment of the present application, a precursor for preparing a lithium iron manganese phosphate material is provided. By optimizing the element ratio of the precursor, the properties of the lithium iron manganese phosphate material can be better controlled, and the technical problems of low specific energy and poor cycle performance of the lithium iron manganese phosphate can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a schematic flow chart of a method for preparing a precursor provided in one embodiment of the present application;

[0020] FIG2 is a schematic flow chart of a method for preparing a precursor provided in another embodiment of the present application;

[0021] FIG3 is a schematic flow chart of a method for preparing a precursor according to another embodiment of the present application;

[0022] FIG4 is a schematic structural diagram of a lithium-ion battery provided in one embodiment of the present application;

[0023] FIG5 is a schematic structural diagram of the core package in FIG4 ;

[0024] FIG6 is a schematic structural diagram of the positive electrode sheet in FIG5 ;

[0025] Explanation of the accompanying reference numerals: 100 - positive electrode sheet; 10 - positive electrode current collector; 20 - coating; 200 - lithium-ion battery; 1 - outer shell; 11 - shell; 12 - shell cover; 2 - core pack; 3 - negative electrode sheet; 4 - diaphragm; 51 - positive electrode ear; 52 - positive electrode column; 53 - first connecting piece; 61 - negative electrode ear; 62 - negative electrode column; 63 - second connecting piece. Modes for Carrying Out the Invention

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art, and the materials and reagents used in the Examples and Comparative Examples of this application are commercially available. In addition, any methods and materials similar or equivalent to those described herein can be applied to this application. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0027] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. The various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0028] In the description of this application, the term "including" means "including but not limited to".

[0029] The terms "multiple", "multiple times" or similar expressions refer to two (times) or more than two (times), for example, it can be two (times), three (times), four (times), five (times), six (times), etc.

[0030] The selection scope of the term "and / or" includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, and the said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. For example, "A and / or B" includes three parallel solutions of A, B and A+B. For another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the four-item combination of A, B, C, and D (that is, the technical solution connected by "logical AND").

[0031] The term "solid content" refers to the ratio of the mass of solid matter in the slurry to the total mass of the slurry.

[0032] The present invention provides a precursor and a preparation method thereof. The precursor may be a first precursor Mn x Fe y M z PO4·nH2O can also be a second precursor, the second precursor includes a general formula of Mn x Fe y M z The core of PO4 can also be a third precursor, the third precursor includes a core and a carbon coating layer coated on the outer surface of the core, the material of the core includes a general formula of Li a Mn x Fe y M z PO4 material, the above-mentioned precursor can be used to prepare lithium manganese iron phosphate positive electrode material.

[0033] The Mn and Fe elements in the precursor uniformly form a solid solution, effectively avoiding element segregation, and the proportion of each element in the precursor is optimized and within a preferred ratio range. The precursor can be used to better control the properties of the lithium manganese iron phosphate positive electrode material, and to prepare a positive electrode material with a stable structure, smooth ion channels, high specific energy and long cycle life. The positive electrode material includes a core and a carbon coating layer coated on the outer surface of the core. The core has the following general formula: Li a Mn x Fe y M z PO4. The specific characteristics of the positive electrode material will be described in detail later and will not be mentioned here for the time being.

[0034] As shown in FIG1 , the present embodiment provides a method for preparing a first precursor, the method comprising the following steps:

[0035] S10, providing a plurality of first raw material components, the plurality of first raw material components including an iron source, a manganese source, a phosphorus source, an M source and hydrogen peroxide, mixing the plurality of first raw material components, and drying to obtain a first precursor, the general formula of the first precursor being Mn x Fe y M z PO4·nH2O.

[0036] As shown in FIG2 , the present embodiment provides a method for preparing a second precursor, which comprises the following steps:

[0037] S10, providing a plurality of first raw material components, the plurality of first raw material components including an iron source, a manganese source, a phosphorus source, an M source and hydrogen peroxide, mixing the plurality of first raw material components, and drying to obtain a first precursor, the general formula of the first precursor being Mn x Fe y M z PO4·nH2O.

[0038] S20, providing a calcined material, the calcined material including the first precursor, calcining the calcined material to obtain a second precursor, the second precursor including a general formula of Mn x Fe y M z The nucleus of PO4.

[0039] As shown in FIG3 , the present embodiment provides a method for preparing a third precursor, which comprises the following steps:

[0040] S10, providing a plurality of first raw material components, the plurality of first raw material components including an iron source, a manganese source, a phosphorus source, an M source and hydrogen peroxide, mixing the plurality of first raw material components, and drying to obtain a first precursor, the general formula of the first precursor being Mn x Fe y M z PO4·nH2O.

[0041] S20, providing a calcined material, the calcined material including the first precursor, calcining the calcined material to obtain a second precursor, the second precursor including a general formula of Mn x Fe y M z The nucleus of PO4.

[0042] S30, providing a plurality of second raw material components, the plurality of second raw material components including the second precursor, a lithium source and a surfactant, mixing the plurality of second raw material components, and drying to obtain a third precursor, the third precursor including a core and a carbon coating layer coated on the outer surface of the core, the material of the core including a general formula of Li a Mn x Fe y M z PO4 materials.

[0043] Based on step S10, a first precursor can be prepared. The general formula of the first precursor is Mn x Fe y M z PO4·nH2O. wherein x is 0.10 to 0.95, for example, 0.10, 0.12, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.91, 0.93, 0.95, and values ​​between any two of the above values; y is 0.10 to 0.95, for example, 0.10, 0.12, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.91, 0.93, 0.95, and values ​​between any two of the above values; and z is 0.01 to 0.10, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, and values ​​between any two of the above values. Furthermore, in some embodiments, the sum of x, y, and z satisfies a condition greater than or equal to 0.95 and less than or equal to 1.06; for example, x+y+z can be 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, or any value between any two of the above values. Wherein, n is any integer from 0 to 10, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0044] Furthermore, in some embodiments, x is between 0.40 and 0.70. Precisely controlling the molar ratio of the Mn element to meet the above conditions is beneficial for balancing the specific energy and cycle performance of the lithium manganese iron phosphate cathode material, thereby obtaining a cathode material with both high specific energy and high cycle performance. Furthermore, x is between 0.50 and 0.60, within this range, which helps further improve specific energy and cycle performance.

[0045] Furthermore, in some embodiments, y is between 0.30 and 0.60. Precisely controlling the molar ratio of the Fe element to meet the above conditions is beneficial for balancing the specific energy and cycle performance of the lithium manganese iron phosphate cathode material, thereby obtaining a cathode material with both high specific energy and high cycle performance. Furthermore, y is between 0.50 and 0.60, within this range, which helps further improve the cycle performance.

[0046] Furthermore, in some embodiments, when the ratio of x to y is 0.9 to 1.1, it helps to further improve the cycle performance.

[0047] Furthermore, in some embodiments, z is between 0.05 and 0.10. Precisely controlling the molar ratio of the M element to meet the above conditions is beneficial for balancing the specific energy and cycle performance of the lithium manganese iron phosphate cathode material, thereby obtaining a cathode material with both high specific energy and high cycle performance. Furthermore, z is between 0.05 and 0.07, within this range, which helps further improve specific energy and cycle performance.

[0048] Furthermore, in some embodiments, the sum of x, y, and z is 0.96 to 0.99. Precisely controlling the molar ratio of each element to meet the above conditions is beneficial for balancing the specific energy and cycle performance of the lithium manganese iron phosphate cathode material, thereby obtaining a cathode material with both high specific energy and high cycle performance.

[0049] In some embodiments, n is 0 or 1 or 2.

[0050] M represents a doping metal element. By doping with the M metal element, it helps to improve the lithium ion diffusion channel in the positive electrode material, thereby improving the conductivity of the positive electrode material. In addition, the doping metal element M can form a more stable lattice framework with oxygen, thereby enhancing the stability of the structure, helping to improve rate performance, cycle stability and energy density. In some embodiments, the M element includes but is not limited to one or more elements selected from magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum; it is understood that M can be one element, or two, three, or more elements. Among the metal elements contained in M, the phosphates of some of the metal elements have an olivine structure. For example, when M is nickel or cobalt, or when M is nickel and cobalt, the phosphate of M and manganese phosphate or iron phosphate are all configured into an olivine structure, thereby constituting a multi-component olivine-based positive electrode material. The charge and discharge curves and cycle performance curves of the multi-component olivine-based positive electrode material can be regarded as the linear superposition of the charge and discharge curves and cycle performance curves of the olivine structure composed of the phosphates of each metal element, thereby effectively improving the cycle performance of the positive electrode material.

[0051] Returning to step S10:

[0052] The iron source refers to a raw material compound for providing iron elements, and can be any compound containing iron elements commonly used in the preparation of positive electrode materials in the art, for example, it can include but is not limited to one or more of iron powder, inorganic iron salts and organic iron salts, wherein the inorganic iron salts include one or more of ferrous sulfate, ferric phosphate, ferrous hydrogen phosphate, and ferrous dihydrogen phosphate, and the organic iron salts include one or more of ferrous acetate, ferrous oxalate, ferrous tartrate, ferrous lactate, and ferrous formate.

[0053] The manganese source refers to a raw material compound for providing manganese elements, and can be any compound containing manganese elements that is commonly used in the preparation of positive electrode materials in the art, for example, it can include but is not limited to one or more of inorganic manganese salts and organic manganese salts, the inorganic manganese salts include one or more of manganese sulfate, manganese carbonate, manganese nitrate, manganese phosphate, and manganese hydrogen phosphate, and the organic manganese salts include one or more of manganese acetate and manganese oxalate.

[0054] The M source refers to a raw material compound for providing the M element, and can be any compound containing the M element commonly used in the art for preparing positive electrode materials. For example, it can include, but is not limited to, one or more of organic M salts and inorganic M salts. The organic M salts include one or more of the following: formate, acetate, glycolate, lactate, tartrate, and oxalate of the M element; the inorganic M salts include at least one of the following: phosphate, hydrogen phosphate, dihydrogen phosphate, carbonate, oxide, hydroxide, fluoride, chloride, nitrate, sulfate, and bromide of the M element. The M element includes one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum, and aluminum. It will be understood that the M source can contain one metal element or two or more elements.

[0055] The phosphorus source refers to a raw material compound used to provide phosphorus, including but not limited to one or both of phosphoric acid and ammonium dihydrogen phosphate. It is understood that in some embodiments, when the iron source, manganese source, M source, etc. used in the multiple first raw material components also contain phosphorus, such compound can also serve as a phosphorus source.

[0056] The iron source, manganese source, phosphorus source, M source and hydrogen peroxide are fully contacted by mixing to form a mixed phase.

[0057] In order to prepare a first precursor with a better element ratio, in some embodiments, the molar ratio of the manganese element in the manganese source, the iron element in the iron source, the M element in the M source, and the phosphorus element in the phosphorus source is (0.10-0.95): (0.10-0.95): (0.01-0.10): 1. In this way, the molar ratio of each element in the first precursor can be adjusted to obtain Mn x Fe y M z PO4·nH2O.

[0058] In some embodiments, the molar ratio of the hydrogen peroxide to the iron element in the iron source is (2-3):1, for example, it can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1 and values ​​between any two of the above values.

[0059] In some embodiments, the plurality of first raw material components further include a complexing agent, wherein the complexing agent includes one or more of HEDP (hydroxyethyl diphosphonic acid), ATMP (amino trimethylphosphonic acid), and DTPA (tetramethylenediamine diacetate). The added mass of the complexing agent is 0.1-1 wt% of the mass of the iron source, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, or values ​​between any two of the above values.

[0060] In some embodiments, the step of mixing the multiple first raw material components and drying them to obtain a first precursor includes: mixing the multiple first raw material components, heating them at a temperature of 60 to 95°C, then filtering the reaction product, and drying the solid phase at 100 to 150°C to obtain a first precursor.

[0061] The second precursor can be obtained by calcining the first precursor. The second precursor includes a general formula of Mn x Fe y M z A core of PO4, wherein M is a metal element, including but not limited to one or more elements selected from magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum; x is 0.10 to 0.95, y is 0.10 to 0.95, z is 0.01 to 0.10, and the sum of x, y and z is 0.95 to 1.06.

[0062] The second precursor may be a precursor material without a carbon layer. Specifically, the second precursor is a precursor material having a general formula of Mn x Fe y Mz PO4 material, the carbon content in the second precursor is 0; the second precursor can also be a precursor material having a carbon layer, specifically, the second precursor includes a core and a carbon layer attached to the surface of the core, the core includes a general formula of Mn x Fe y M z PO4 material, in the second precursor, the mass of the carbon layer accounts for a percentage of the mass of the second precursor that is less than or equal to 5%, for example, it can be a value greater than 0 and less than 0.01%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, and a value between any two of the above values. By attaching a carbon layer to the outer surface of the core and controlling its mass content within the above range, on the one hand, it can play a protective role in the process of preparing the positive electrode material, helping to prevent excessive oxidation of the material, reduce side reactions, and improve the purity of the product. On the other hand, it can also effectively regulate the crystal growth rate and reaction uniformity, so that the crystals grow uniformly everywhere, and inhibit crystal particle agglomeration or adhesion, which helps to obtain a product with more uniform size, higher ionic conductivity, and more stable performance. In addition, using the positive electrode material prepared from the second precursor to prepare a battery helps to improve the battery conductivity. It can be understood that the carbon layer refers to the carbon attached to the outer surface of the core, which can be a continuous film layer that completely covers the core, or a discontinuous film layer that only covers part of the surface of the core.

[0063] In step S20:

[0064] In some embodiments, the calcination temperature can be 550-750°C, for example, 550°C, 560°C, 580°C, 600°C, 620°C, 650°C, 670°C, 690°C, 700°C, 710°C, 730°C, 750°C and values ​​between any two of the above values.

[0065] In certain embodiments, the second precursor has a carbon layer. In order to form a carbon layer, it is necessary to provide a compound of carbon element, and the compound of the carbon element source of the carbon layer in the second precursor is named as the first carbon source by the application. The first carbon source includes one or more of an organometallic salt, an organic carbon source and an inorganic carbon source, and the organometallic salt includes one or more of an organic iron salt, an organic manganese salt, an organic M source, and the organic carbon source includes one or more of glucose, sucrose, lactose, starch, organic acid, vitamin, polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), hydroxyethyl diphosphonic acid, aminotrimethylphosphonic acid, diacetate tetramine and phenolic resin, and the inorganic carbon source includes one or more of graphene, carbon nanotube and graphite. Wherein, the organometallic salt is composed of a metal cation and an organic anion, and because the organic anion contains carbon element, it can also form a carbon layer when calcined under inert gas protection, so it can be used as a carbon source.

[0066] Specifically, step S20 can be implemented as follows: providing a calcined material, and calcining the calcined material under the protection of an inert gas to obtain a second precursor. The inert gas includes one or more of nitrogen, argon, and helium.

[0067] The first carbon source may be added separately in step S20, or may be introduced as an iron source, a manganese source or an M source in step S10.

[0068] When the multiple first raw material components for preparing the first precursor do not contain organic anions, that is, the multiple first raw material components include iron powder or inorganic iron salt, inorganic manganese salt and inorganic M salt, in step S20, the calcined material may also include a first carbon source, and the amount of the first carbon source added satisfies: the mass of the carbon element contained in the first carbon source accounts for a percentage of the total mass of the calcined material that is greater than 0 and less than or equal to 25%; for example, it can be a value less than 0.001%, 0.001%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 10%, 15%, 20%, 25% and a value between any two of the above values.

[0069] When the multiple first raw material components for preparing the first precursor contain organic anions, that is, the multiple first raw material components include one or more of organic iron salts, organic manganese salts and organic M salts, a carbon source may or may not be additionally added during the roasting in step S20.

[0070] In actual application, regardless of whether an additional carbon source is added, the amount of raw materials fed must meet the following requirements: the mass of the carbon element contained in the first carbon source accounts for a percentage of the total mass of the roasting material that is greater than 0 and less than or equal to 25%, wherein the mass of the carbon element contained in the first carbon source refers to the sum of the mass of the carbon element contained in multiple first raw material components and the mass of the carbon element in the additionally added carbon source.

[0071] The third precursor can be prepared from the second precursor. The third precursor includes a core and a carbon coating layer coated on the outer surface of the core, and the material of the core includes a general formula of Li a Mn x Fe y M z PO4 material, wherein M is a metal element, including but not limited to one or more elements selected from magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum; a is 0.95-1.10, x is 0.10-0.95, y is 0.10-0.95, z is 0.01-0.10, and the sum of x, y and z is 0.95-1.06. It can be understood that the carbon coating layer refers to a carbon layer coated on the outer surface of the core, which can be a continuous film layer that completely covers the core, or a discontinuous film layer that only covers part of the surface of the core. In the process of mixing the second precursor and the lithium source, the lithium source is fully in contact with the second precursor and gradually enters the core to form a mixed phase to obtain a third precursor.

[0072] In the third precursor, the mass of the carbon coating layer accounts for 1% to 5% of the mass of the third precursor, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% and values ​​between any two of the above values.

[0073] In step S30:

[0074] The lithium source includes but is not limited to one or more of lithium oxides, lithium hydroxide, organic lithium salts and inorganic lithium salts. Lithium oxides include but are not limited to Li2O. Inorganic lithium salts include but are not limited to one or more of lithium carbonate, lithium sulfate, lithium nitrate, lithium dihydrogen phosphate and lithium phosphate. Organic lithium salts include but are not limited to one or more of lithium acetate and lithium oxalate.

[0075] The surfactant includes but is not limited to one or both of PEG (polyethylene glycol) and ATMP (aminotrimethylphosphonic acid).

[0076] In some embodiments, the molar ratio of the lithium element in the lithium source to the iron element in the iron source is (0.95-1.10): (0.10-0.95).

[0077] In some embodiments, the added mass of the surfactant is 1 to 5 wt% of the mass of the iron source, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% and values ​​between any two of the above values.

[0078] In some embodiments, the plurality of second raw material components further include a phosphorus source, and the phosphorus source is added again to ensure an excess of the phosphorus source, thereby promoting sufficient reaction.

[0079] The third precursor has a carbon coating layer, and the carbon of the carbon coating layer is introduced when preparing the second precursor, and can also be introduced by a newly added carbon source. When preparing the third precursor, the newly introduced carbon source is named as the second carbon source in the present application. The second carbon source includes but is not limited to one or more of an organic metal salt, an organic carbon source and an inorganic carbon source, the organic metal salt includes one or more of an organic iron salt, an organic manganese salt, an organic M source, and an organic lithium source, the organic carbon source includes one or more of glucose, sucrose, lactose, starch, an organic acid, a vitamin, polyvinyl pyrrolidone, polyethylene glycol, hydroxyethyl diphosphonic acid, aminotrimethylphosphonic acid, diacetate tetramine and a phenolic resin, and the inorganic carbon source includes one or more of graphene, carbon nanotubes and graphite.

[0080] When the mass percentage of carbon elements contained in the second precursor is 0, the multiple second raw material components also include a second carbon source, and the mass of carbon elements in the multiple second carbon sources accounts for 1 to 25% of the total mass of the multiple second raw material components; for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 10%, 15%, 20%, 25% and values ​​between any two of the above values.

[0081] When the mass percentage of carbon elements contained in the second precursor is greater than 0 and less than or equal to 5%, the multiple second raw material components may include a second carbon source or may not include a second carbon source. When the second carbon source is added, the total mass of the carbon elements contained in the second precursor and the carbon elements contained in the second carbon source accounts for 1 to 25% of the total mass of the multiple second raw material components; for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 10%, 15%, 20%, 25% and values ​​between any two of the above values.

[0082] The present application further proposes a positive electrode material, which can be prepared from the above-mentioned precursor.

[0083] The positive electrode material includes a core and a carbon coating layer coated outside the core, and the material of the core includes a general formula of Li a Mn x Fe y M zPO4 material, wherein M is a metal element, including but not limited to one or more elements selected from magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum, and aluminum; a is 0.95-1.10, x is 0.10-0.95, y is 0.10-0.95, z is 0.01-0.10, and the sum of x, y, and z is 0.95-1.06. The mass of the carbon coating layer accounts for 1% to 2% of the mass of the positive electrode material; for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, and values ​​between any two of the above values. The positive electrode material has a high specific energy and excellent cycle performance.

[0084] The present invention also provides a method for preparing a positive electrode material, which comprises the following steps:

[0085] S100, providing a plurality of first raw material components, wherein the plurality of first raw material components include an iron source, a manganese source, a phosphorus source, an M source, and hydrogen peroxide, and mixing and drying the plurality of first raw material components to obtain a first precursor;

[0086] S200, providing a calcined material, wherein the calcined material includes the first precursor, and calcining the calcined material to obtain a second precursor;

[0087] S300, providing a plurality of second raw material components, wherein the plurality of second raw material components include the second precursor, a lithium source, and a surfactant, mixing the plurality of second raw material components, and drying to obtain a third precursor, the third precursor.

[0088] S400, calcining the third precursor under the protection of an inert gas to obtain a positive electrode material.

[0089] The general formula of the first precursor is Mn x Fe y M z PO4·nH2O; wherein x is 0.10 to 0.95, y is 0.10 to 0.95, z is 0.01 to 0.10, and the sum of x, y and z is greater than or equal to 0.95 and less than or equal to 1.06.

[0090] The second precursor includes a general formula of Mn x Fe y M zA PO4 core, wherein M is a metal element, including but not limited to one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum, and aluminum; x is 0.10 to 0.95, y is 0.10 to 0.95, and z is 0.01 to 0.10, with the sum of x, y, and z being 0.95 to 1.06. The second precursor may be a precursor material without or with a carbon layer, and the mass of the carbon layer in the second precursor is less than or equal to 5% of the mass of the second precursor.

[0091] The third precursor includes a core and a carbon coating layer coated on the outer surface of the core. The material of the core includes a general formula of Li a Mn x Fe y M z PO4 material, wherein M is a metal element including but not limited to one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum, and aluminum; a is 0.95-1.10, x is 0.10-0.95, y is 0.10-0.95, and z is 0.01-0.10, and the sum of x, y, and z is 0.95-1.06. In the third precursor, the mass of the carbon coating layer accounts for 1%-5% of the mass of the third precursor.

[0092] By preparing precursors at different stages in a graded manner and precisely controlling the structure of each precursor, it is possible to effectively prepare positive electrode materials with stable structures, unobstructed ion channels, high specific energy, and long cycles.

[0093] It is understood that, depending on the carbon content requirement of the precursor to be prepared, an additional carbon source may be added in step S200 or step S300. Specifically, steps S100, S200, and S300 may be implemented with reference to the aforementioned steps S10, S20, and S30, and are not described in detail here.

[0094] Specifically, step S400 may include: under inert gas protection, heating the third precursor to 600-950° C. at a heating rate of 2-10° C., keeping the temperature for 5-24 hours, and cooling to room temperature under an inert atmosphere to obtain a positive electrode material.

[0095] The room temperature mentioned in this application refers to 20 to 40°C.

[0096] The present application also provides a positive electrode sheet 100, as shown in FIG6 . The positive electrode sheet 10 includes a positive electrode current collector 10 and a coating 20 disposed on one side of the positive electrode current collector 10. The coating 20 is made of the positive electrode material described in any of the above embodiments. Specifically, the material of the positive electrode current collector 10 can be any common conductive metal material in the art, including but not limited to aluminum foil, platinum foil, or palladium foil, and this application does not impose any limitation on this.

[0097] The embodiments of the present application also provide a lithium-ion battery 100, including but not limited to button cells, soft-pack batteries, square lithium-ion batteries, cylindrical lithium-ion batteries, and the like. The lithium-ion battery includes a positive electrode sheet as described in any of the embodiments above. Specifically, referring to Figures 4 and 5, in some embodiments, the lithium-ion battery 200 includes an outer shell 1 and a core pack 2. The outer shell 1 is composed of a shell 11 and a shell cover 12. A receiving space is formed in the shell 11, and the core pack 2 is installed in the receiving space. The core pack 2 includes the positive electrode sheet 100, the separator 4, and the negative electrode sheet 3 stacked in sequence. In the positive electrode sheet 100, the positive current collector 10 is arranged close to the separator 4, and the coating 20 is arranged on the side of the positive current collector 10 facing away from the separator 4. In addition, in some embodiments, the core pack 2 also includes a positive electrode tab 51 connected to the positive electrode sheet 100 and a negative electrode tab 61 connected to the negative electrode sheet 3. The core pack 2 is filled with electrolyte. In addition, the lithium-ion battery 200 also includes a positive electrode column 52 and a negative electrode column 62 provided on the outer shell 1, wherein the positive electrode column 52 is provided corresponding to the positive electrode ear 51, and passes through the outer shell 1 and is connected to the positive electrode ear 51 through the first connecting piece 53, and the negative electrode column 62 is provided corresponding to the negative electrode ear 61, and passes through the outer shell 1 and is connected to the negative electrode ear 61 through the second connecting piece 63.

[0098] Example 1

[0099] This embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0100] The lithium manganese iron phosphate material of this embodiment is prepared by the following preparation method:

[0101] (1) Iron phosphate, phosphoric acid, manganese carbonate, and magnesium oxide were mixed, hydrogen peroxide and HEDP were slowly added, and then heated at 80°C. The reaction product was filtered and the solid phase was dried at 120°C to obtain the first precursor Mn 0.55 Fe 0.35 Mg 0.1PO4·nH2O, where n is 0. The molar ratio of manganese in manganese carbonate, iron in ferric phosphate, magnesium in magnesium oxide, and phosphorus in phosphoric acid is 0.55:0.35:0.1:1; the molar ratio of hydrogen peroxide to iron in ferric phosphate is 2.5:1; and the mass of HEDP added is 0.5 wt% of the mass of the ferric phosphate.

[0102] (2) Under nitrogen protection, the first precursor is calcined at 550-750 ° C to obtain the second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4, the second precursor, has a carbon content of 0%.

[0103] (3) The second precursor, sucrose, PEG, ATMP and lithium carbonate are mixed and ground to obtain the third precursor Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the third precursor, has a carbon content of 3.5%; among them, the mass of the carbon element in sucrose accounts for 10% of the total mass of the second precursor, sucrose, PEG, ATMP and lithium carbonate, the mass of the carbon element in PEG accounts for 2% of the total mass of the second precursor, sucrose, PEG, ATMP and lithium carbonate, the mass ratio of the lithium element in lithium carbonate to the iron element in iron phosphate is 1.04:0.35, and the added mass of ATMP is 3wt% of the mass of iron phosphate.

[0104] (4) Under the protection of inert gas, the third precursor was heated to 800°C at a heating rate of 8°C, kept at this temperature for 10 hours, and then cooled to room temperature under an inert atmosphere to obtain the positive electrode material Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C.

[0105] Example 2

[0106] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 The carbon content of the PO4@C cathode material is 1.4%. In this embodiment, iron phosphate is replaced by scrap iron, manganese carbonate is replaced by manganese dioxide, and sucrose is replaced by glucose. Other than that, all other parameters and steps remain unchanged.

[0107] Example 3

[0108] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn0.55 Fe 0.35 Mg 0.1 The carbon content of the PO4@C cathode material is 1.4%. In this embodiment, the iron phosphate is replaced by iron oxalate, the manganese dioxide is replaced by manganese oxalate, and hydrogen peroxide is not added. Other than this, all other parameters and steps remain unchanged.

[0109] Example 4

[0110] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.1 Fe 0.75 Mg 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate to iron in iron phosphate is changed to 0.1:0.75. Other than that, the other parameters and steps remain unchanged.

[0111] Example 5

[0112] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.95 Fe 0.1 Mg 0.01 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate, iron in ferric phosphate, and magnesium in magnesium oxide is changed to 0.95:0.1:0.01. Other than this, the other parameters and steps remain unchanged.

[0113] Example 6

[0114] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.1 Fe 0.95 Mg 0.01 The carbon content of the PO4@C cathode material is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate, iron in ferric phosphate, and magnesium in magnesium oxide is changed to 0.1:0.95:0.01. Other than this, the other parameters and steps remain unchanged.

[0115] Example 7

[0116] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.4 Mg 0.05The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate, iron in ferric phosphate, and magnesium in magnesium oxide is changed to 0.55:0.4:0.05. Other than this, the other parameters and steps remain unchanged.

[0117] Example 8

[0118] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.38 Fe 0.5 Mg 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate to iron in iron phosphate is changed to 0.38:0.5. Other than that, the other parameters and steps remain unchanged.

[0119] Example 9

[0120] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.7 Fe 0.3 Mg 0.05 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate, iron in ferric phosphate, and magnesium in magnesium oxide is changed to 0.7:0.3:0.05. Other than that, the other parameters and steps remain unchanged.

[0121] Example 10

[0122] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.57 Fe 0.3 Mg 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate to iron in iron phosphate is changed to 0.57:0.3. Other than that, the other parameters and steps remain unchanged.

[0123] Example 11

[0124] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.3 Fe 0.58 Mg 0.1The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate to iron in iron phosphate is changed to 0.3:0.58. Other than that, the other parameters and steps remain unchanged.

[0125] Example 12

[0126] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.39 Mg 0.05 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of the iron element in the iron phosphate to the magnesium element in the magnesium oxide is changed to 0.39:0.05. Other than that, the other parameters and steps remain unchanged.

[0127] Example 13

[0128] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.5 Fe 0.4 Mg 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of manganese in manganese carbonate to iron in iron phosphate is changed to 0.5:0.4. Other parameters and steps remain unchanged.

[0129] Example 14

[0130] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.37 Mg 0.04 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of the iron element in the iron phosphate to the magnesium element in the magnesium oxide is changed to 0.37:0.04. Other than that, the other parameters and steps remain unchanged.

[0131] Example 15

[0132] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.37 Mg 0.07The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, the molar ratio of the iron element in the iron phosphate to the magnesium element in the magnesium oxide is changed to 0.37:0.07. Other than that, the other parameters and steps remain unchanged.

[0133] Example 16

[0134] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 0.95 Mn 0.55 Fe 0.35 Mg 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (3) of this embodiment, the mass ratio of lithium in lithium carbonate to iron in iron phosphate is 0.95:0.35. Other than this, the other parameters and steps remain unchanged.

[0135] Example 17

[0136] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.1 Mn 0.55 Fe 0.35 Mg 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (3) of this embodiment, the mass ratio of lithium in lithium carbonate to iron in iron phosphate is 1.1:0.35. Other than this, the other parameters and steps remain unchanged.

[0137] Example 18

[0138] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Co 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, magnesium oxide is replaced by cobalt oxide. Other than that, the other parameters and steps remain unchanged.

[0139] Example 19

[0140] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Ca 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, magnesium oxide is replaced by calcium oxide. Other parameters and steps remain unchanged.

[0141] Example 20

[0142] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Sc 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, magnesium oxide is replaced by scandium oxide. Other than that, the other parameters and steps remain unchanged.

[0143] Example 21

[0144] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Cr 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, magnesium oxide is replaced by chromium oxide. Other parameters and steps remain unchanged.

[0145] Example 22

[0146] This embodiment is basically the same as embodiment 1, except that this embodiment provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 V 0.1 The carbon content of the positive electrode material PO4@C is 1.4%. In step (1) of this embodiment, magnesium oxide is replaced by vanadium oxide. Other parameters and steps remain unchanged.

[0147] Example 23

[0148] This embodiment is basically the same as embodiment 1, except that this embodiment provides a second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the second precursor, the carbon content is 1%, and the third precursor Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the third precursor, has a carbon content of 3%, and accordingly, lithium manganese iron phosphate material Li can be prepared. 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0149] In the preparation method of this embodiment, steps (2) and (3) are changed to:

[0150] (2) Under nitrogen protection, the first precursor and PEG were calcined at 550-750 ° C to obtain the second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4@C. The mass of the carbon element in PEG accounts for 4% of the total mass of the first precursor and PEG.

[0151] (3) The second precursor, sucrose, PEG, ATMP and lithium carbonate are mixed and ground to obtain the third precursor Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C; wherein, the added mass of sucrose accounts for 8% of the total mass of the second precursor, sucrose, PEG, and ATMP, the added mass of PEG accounts for 2% of the total mass of the second precursor, sucrose, PEG, and ATMP, the mass ratio of lithium element in lithium carbonate to iron element in iron phosphate is 1.04:0.35, and the added mass of ATMP is 3wt% of the mass of iron phosphate.

[0152] Example 24

[0153] This embodiment is basically the same as embodiment 1, except that this embodiment provides a second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the second precursor, the carbon content is 5%, and the third precursor Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the third precursor, has a carbon content of 3%, and accordingly, lithium manganese iron phosphate material Li can be prepared. 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the positive electrode material, has a carbon content of 2%.

[0154] In the preparation method of this embodiment, steps (2) and (3) are changed to:

[0155] (2) Under nitrogen protection, the first precursor and PEG were calcined at 550-750 ° C to obtain the second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4@C. The mass of the carbon element in PEG accounts for 5% of the total mass of the first precursor and PEG.

[0156] (3) The second precursor, ATMP and lithium carbonate are mixed and ground to obtain the third precursor Li 1.04 Mn 0.55Fe 0.35 Mg 0.1 PO4@C; wherein the mass ratio of lithium element in lithium carbonate to iron element in iron phosphate is 1.04:0.35, and the added mass of ATMP is 3wt% of the mass of iron phosphate.

[0157] Example 25

[0158] This embodiment is basically the same as embodiment 1, except that this embodiment provides a second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the second precursor, the carbon content is 5.5%, and the third precursor Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the third precursor, has a carbon content of 6%, and accordingly, lithium manganese iron phosphate material Li can be prepared. 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C, the positive electrode material, has a carbon content of 3%.

[0159] In the preparation method of this embodiment, steps (2) and (3) are changed to:

[0160] (2) Under nitrogen protection, the first precursor and PEG were calcined at 550-750 ° C to obtain the second precursor Mn 0.55 Fe 0.35 Mg 0.1 PO4@C. The mass of carbon in PEG accounts for 17% of the total mass of the first precursor and PEG.

[0161] (3) The second precursor, sucrose, PEG, ATMP and lithium carbonate are mixed and ground to obtain the third precursor Li 1.04 Mn 0.55 Fe 0.35 Mg 0.1 PO4@C; wherein the mass of the carbon element in sucrose accounts for 3% of the total mass of the second precursor, sucrose, PEG, and ATMP, the mass of the carbon element in PEG accounts for 1% of the total mass of the second precursor, sucrose, PEG, and ATMP, the mass ratio of the lithium element in lithium carbonate to the iron element in iron phosphate is 1.04:0.35, and the added mass of ATMP is 3wt% of the mass of the iron phosphate.

[0162] Comparative Example 1

[0163] This comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Mg0.1 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0164] The lithium manganese iron phosphate material of this comparative example was prepared by the following preparation method:

[0165] Lithium carbonate, manganese carbonate, iron phosphate, magnesium oxide, phosphoric acid, and graphite are mixed and ground, then calcined under nitrogen protection, and cooled to room temperature under an inert atmosphere to obtain a positive electrode material.

[0166] The molar ratio of lithium in lithium carbonate, manganese in manganese carbonate, iron in iron phosphate, magnesium in magnesium oxide, and phosphorus in phosphoric acid is 1.04:0.55:0.35:0.1:1, and the mass of graphite accounts for 3.0% of the total mass of lithium carbonate, manganese carbonate, iron phosphate, magnesium oxide, phosphoric acid and graphite.

[0167] Comparative Example 2

[0168] This comparative example is basically the same as comparative example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Co 0.1 The carbon content of the PO4@C cathode material is 1.4%. In this comparative example, magnesium oxide is replaced with cobalt oxide. Other parameters and steps remain unchanged.

[0169] Comparative Example 3

[0170] This comparative example is basically the same as comparative example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Ca 0.1 The carbon content of the PO4@C cathode material is 1.4%. In this comparative example, magnesium oxide is replaced by calcium oxide. Other parameters and steps remain unchanged.

[0171] Comparative Example 4

[0172] This comparative example is basically the same as comparative example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Sc 0.1 The carbon content of the PO4@C cathode material is 1.4%. In this comparative example, magnesium oxide is replaced with scandium oxide. Other parameters and steps remain unchanged.

[0173] Comparative Example 5

[0174] This comparative example is basically the same as comparative example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Cr 0.1 The carbon content of the PO4@C cathode material is 1.4%. In this comparative example, magnesium oxide is replaced by chromium oxide. Other parameters and steps remain unchanged.

[0175] Comparative Example 6

[0176] This comparative example is basically the same as comparative example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 V 0.1 The carbon content of the positive electrode material in PO4@C is 1.4%. In this comparative example, magnesium oxide is replaced by vanadium oxide. Other parameters and steps remain unchanged.

[0177] Comparative Example 7

[0178] This comparative example is basically the same as Example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.35 Mg 0.11 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0179] In the preparation method of this comparative example, the molar ratio of manganese element in manganese dioxide, iron element in scrap iron, magnesium element in magnesium oxide and phosphorus element in phosphoric acid is changed to 0.55:0.35:0.11:1.

[0180] Comparative Example 8

[0181] This comparative example is basically the same as Example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.55 Fe 0.45 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0182] In step (1) of the preparation method of this comparative example, magnesium oxide is not added.

[0183] Comparative Example 9

[0184] This comparative example is basically the same as Example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.96 Fe 0.1 Mg 0.01 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0185] In step (1) of the preparation method of this comparative example, the molar ratio of manganese in manganese dioxide, iron in scrap iron, magnesium in magnesium oxide, and phosphorus in phosphoric acid is changed to 0.96:0.1:0.01:1.

[0186] Comparative Example 10

[0187] This comparative example is basically the same as Example 1, except that this comparative example provides a lithium manganese iron phosphate material Li 1.04 Mn 0.1 Fe 0.96 Mg 0.01 PO4@C, the positive electrode material, has a carbon content of 1.4%.

[0188] In step (1) of the preparation method of this comparative example, the molar ratio of manganese in manganese dioxide, iron in scrap iron, magnesium in magnesium oxide, and phosphorus in phosphoric acid is changed to 0.1:0.96:0.01:1.

[0189] Experimental example

[0190] The lithium manganese iron phosphate materials prepared in the above examples and comparative examples were used to prepare batteries and perform performance tests.

[0191] The preparation methods of the lithium ion batteries of the embodiments and comparative examples are as follows:

[0192] (1) Preparation of negative electrode sheet: The negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber and the thickener sodium carboxymethyl cellulose are mixed in a weight ratio of graphite: acetylene black: styrene butadiene rubber: sodium carboxymethyl cellulose = 95:2:2:1, and an appropriate amount of deionized water is added and stirred thoroughly to form a uniform negative electrode slurry; the slurry is coated on the negative electrode current collector copper foil, dried and cold pressed to obtain a negative electrode sheet.

[0193] (2) Preparation of positive electrode sheets: The corresponding positive electrode active material (i.e., the lithium manganese iron phosphate material prepared in the examples and comparative examples), the conductive agent acetylene black, and the binder polyvinylidene fluoride were mixed in a weight ratio of 96:2:2, and N-methylpyrrolidone was used as a solvent. After thorough grinding and stirring, a uniform positive electrode slurry was formed; the slurry was coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

[0194] (3) Preparation of batteries: stack the positive electrode sheet, separator (PE / PP porous polymer film), and negative electrode sheet in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wind them to obtain a bare battery cell; place the bare battery cell in an outer packaging foil, inject a lithium ion electrolyte composed of organic solvents such as EC (ethylene carbonate) / EMC (methyl ethyl carbonate) and LiPF6 into the dried battery, and then obtain a lithium ion battery through vacuum packaging, standing, formation, shaping and other processes.

[0195] Performance testing method:

[0196] A battery cycle charge and discharge test was conducted using a constant temperature box battery test cabinet at a constant temperature of 25°C under 1C-1C charge and discharge conditions to test the 1C charge specific energy and 1C discharge specific energy of the batteries prepared using the lithium manganese iron phosphate materials of the above embodiment and the comparative example;

[0197] In a constant temperature environment of 25°C, the battery cycle charge and discharge life test was carried out under 1C-1C charge and discharge conditions. When the battery capacity dropped to 80% of the rated capacity, the number of cycles that the battery can achieve was recorded as 25°C 1C-1C cycle number @80%; in a constant temperature environment of 45°C, the battery cycle charge and discharge life test was carried out under 1C-1C charge and discharge conditions. When the battery capacity dropped to 80% of the rated capacity, the number of cycles that the battery can achieve was recorded as 45°C 1C-1C cycle number @80%.

[0198] The results are recorded in Table 1.

[0199] Table 1

[0200] From the table above we can see that:

[0201] Example 1 has a charge-discharge specific energy and a number of cycles that are better than those of Comparative Example 1, Example 18 has a charge-discharge specific energy and a number of cycles that are better than those of Comparative Example 2, Example 19 has a charge-discharge specific energy and a number of cycles that are better than those of Comparative Example 3, Example 20 has a charge-discharge specific energy and a number of cycles that are better than those of Comparative Example 4, Example 21 has a charge-discharge specific energy and a number of cycles that are better than those of Comparative Example 5, and Example 22 has a charge-discharge specific energy and a number of cycles that are better than those of Comparative Example 6. This shows that compared to the conventional pure solid-phase method, the present application adopts a liquid-solid phase method to synthesize materials and prepare precursors of different stages by graded preparation, and accurately controls the structure of each precursor, which can significantly improve the specific energy and cycle number of the positive electrode material;

[0202] Compared with Comparative Example 8, Example 1 has significantly higher charge-discharge specific energy and cycle number, indicating that the addition of doping metal elements into the positive electrode material in this application helps to improve the cycle performance and specific energy of the positive electrode material;

[0203] Comparing Comparative Example 7 with Example 1, Comparative Example 9 with Example 5, and Comparative Example 10 with Example 6, each example has significantly higher charge and discharge specific energy and cycle number, indicating that there is a specific molar ratio range between the elements in the precursor. When the molar ratio of each element is within this range, the prepared positive electrode material has good cycle performance and specific energy. Further optimizing the molar ratio of the elements to make it fall within the preferred range will help further improve the cycle performance and specific energy of the positive electrode material. When the molar ratio of one element exceeds the range, the cycle performance or specific energy of the material will decrease.

[0204] Among Examples 23 to 25, the batteries of Examples 23 and 24 have higher charge and discharge specific energy and cycle times, indicating that regulating the carbon content in the precursor helps to better regulate the performance of the positive electrode material. When the carbon content of the precursor exceeds the control range (carbon content is less than or equal to 5%), the material's cycle performance or specific energy will decrease.

Claims

1. A method for preparing a precursor, The following steps are involved: Provide a plurality of first raw material components, the plurality of first raw material components including an iron source, a manganese source, a phosphorus source, an M source and hydrogen peroxide, mix the plurality of first raw material components, and dry them to obtain a first precursor, wherein the general formula of the first precursor is Mn x Fe y M z PO 4 ·nH 2 O; Wherein, M is a metal element, x is 0.10 to 0.95, y is 0.10 to 0.95, z is 0.01 to 0.10, the sum of x, y and z is 0.95 to 1.06, and n is any integer from 0 to 10.

2. The preparation method according to claim 1, in, The molar ratio of the manganese element in the manganese source, the iron element in the iron source, the M element in the M source and the phosphorus element in the phosphorus source is (0.10-0.95):(0.10-0.95):(0.01-0.10):

1.

3. The preparation method according to claim 1, in, The M element includes one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum; and / or, The iron source includes one or more of iron powder, inorganic iron salt and organic iron salt, the inorganic iron salt includes one or more of ferrous sulfate, ferric phosphate, ferrous hydrogen phosphate and ferrous dihydrogen phosphate, the organic iron salt includes one or more of ferrous acetate, ferrous oxalate, ferrous tartrate, ferrous lactate and ferrous formate; and / or, The manganese source includes one or more of an inorganic manganese salt and an organic manganese salt, wherein the inorganic manganese salt includes one or more of manganese sulfate, manganese carbonate, manganese nitrate, manganese phosphate, and manganese hydrogen phosphate, and the organic manganese salt includes one or more of manganese acetate and manganese oxalate; and / or, The M source includes one or more of an organic M salt and an inorganic M salt. The organic M salt includes one or more of a formate of an M element, an acetate of an M element, a glycolate of an M element, a lactate of an M element, a tartrate of an M element, and an oxalate of an M element. The inorganic M salt includes a phosphate of an M element, a hydrogen phosphate of an M element, a dihydrogen phosphate of an M element, a carbonate of an M element, an oxide of an M element, a hydroxide of an M element, a fluoride of an M element, a chloride of an M element, At least one of nitrate of element M, sulfate of element M, bromide of element M; and / or, The phosphorus source includes one or both of phosphoric acid and diammonium phosphate.

4. The preparation method according to claim 1, in, The preparation method further comprises: providing a calcined material, wherein the calcined material comprises the first precursor, and calcining the calcined material to obtain a second precursor, wherein the second precursor comprises a general formula of Mn x Fe y M z PO 4 The nucleus.

5. The preparation method according to claim 4, in, The second precursor further includes a carbon layer attached to the surface of the core, and the mass of the carbon layer accounts for less than or equal to 5% of the mass of the second precursor.

6. The preparation method according to claim 5, in, The calcined material also includes a first carbon source, which includes one or more of an organic metal salt, an organic carbon source and an inorganic carbon source, the organic metal salt includes one or more of an organic iron salt, an organic manganese salt, and an organic M source, the organic carbon source includes one or more of glucose, sucrose, lactose, starch, an organic acid, a vitamin, polyvinyl pyrrolidone, polyethylene glycol, hydroxyethyl diphosphonic acid, aminotrimethylphosphonic acid, diacetate tetramine and a phenolic resin, and the inorganic carbon source includes one or more of graphene, carbon nanotubes and graphite.

7. The preparation method according to claim 5, in, The calcined material further includes a first carbon source, and the mass of the carbon element in the calcined material accounts for 0 to 25% of the total mass of the calcined material.

8. The preparation method according to any one of claims 4 to 7, in, The preparation method further comprises: providing a plurality of second raw material components, the plurality of second raw material components comprising the second precursor, a lithium source and a surfactant, mixing the plurality of second raw material components, and drying to obtain a third precursor, the third precursor comprising a core and a carbon coating layer coated on the outer surface of the core, the material of the core comprising a general formula of Li a Mn x Fe y M z PO 4 material, wherein a is 0.95 to 1.

10.

9. The preparation method according to claim 8, in, The molar ratio of the lithium element in the lithium source to the iron element in the iron source is (0.95-1.10): (0.10-0.95).

10. The preparation method according to claim 8, in, In the third precursor, the mass of the carbon coating layer accounts for 1% to 5% of the mass of the third precursor.

11. The preparation method according to claim 8, in, The plurality of second raw material components further include a second carbon source, and the mass percentage of carbon elements in the plurality of second raw material components to the total mass of the plurality of second raw material components is 1-25%.

12. The preparation method according to claim 8, in, The plurality of second raw material components further include a second carbon source, the second carbon source includes one or more of an organic metal salt, an organic carbon source and an inorganic carbon source, the organic metal salt includes one or more of an organic iron salt, an organic manganese salt, an organic M source and an organic lithium source, the organic carbon source includes one or more of glucose, sucrose, lactose, starch, an organic acid, a vitamin, polyvinyl pyrrolidone, polyethylene glycol, hydroxyethyl diphosphonic acid, aminotrimethylphosphonic acid, diacetate tetramine and a phenolic resin, and the inorganic carbon source includes one or more of graphene, carbon nanotubes and graphite; and / or, The lithium source includes one or more of lithium oxide, lithium hydroxide, organic lithium salt and inorganic lithium salt. The lithium oxide includes Li 2 O, the inorganic lithium salt includes one or more of lithium carbonate, lithium sulfate, lithium nitrate, lithium dihydrogen phosphate, and lithium phosphate, and the organic lithium salt includes one or more of lithium acetate and lithium oxalate.

13. A precursor, comprising any one of a first precursor, a second precursor and a third precursor: The general formula of the first precursor is Mn x Fe y M z PO 4 ·nH 2 O; The second precursor includes a general formula of Mn x Fe y M z PO 4 The nucleus; The third precursor includes a core and a carbon coating layer coated on the outer surface of the core. The material of the core includes a general formula of Li a Mn x Fe y M z PO 4 materials; in, M is a metal element, x is 0.10 to 0.95, y is 0.10 to 0.95, z is 0.01 to 0.10, the sum of x, y and z is 0.95 to 1.06, a is 0.95 to 1.10, and n is any integer from 0 to 10.

14. The precursor according to claim 13, in, M includes one or more elements of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum.

15. The precursor according to claim 13, in, The second precursor further includes a carbon layer attached to the surface of the core, and the mass of the carbon layer accounts for less than or equal to 5% of the mass of the second precursor.

16. The precursor according to claim 13, in, In the third precursor, the mass of the carbon coating layer accounts for 1% to 5% of the mass of the third precursor; and / or, x is 0.40 to 0.70; and / or, y is 0.30 to 0.60; and / or, z is 0.05 to 0.10; and / or, The sum of x, y and z is 0.96 to 0.

99.

17. A positive electrode material, wherein the positive electrode material is prepared from a precursor, wherein the precursor comprises a precursor prepared by the preparation method according to any one of claims 1 to 12, or a precursor according to any one of claims 13 to 16.

18. The positive electrode material according to claim 17, in, The positive electrode material comprises a core and a carbon coating layer coated on the outer surface of the core, and the core has the following general formula: Li a Mn x Fe y M z PO 4 ; Wherein, M is a metal element, a is 0.95-1.10, x is 0.10-0.95, y is 0.10-0.95, z is 0.01-0.10, the sum of x, y and z is 0.95-1.06, and in the positive electrode material, the mass percentage of the carbon coating layer is 1%-2%.

19. A positive electrode plate, comprising a positive electrode current collector and a coating disposed on one side of the positive electrode current collector, wherein the material of the coating comprises the positive electrode material according to claim 17 or 18.

20. A lithium ion battery comprising the positive electrode sheet according to claim 19.

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