Olivine structured positive electrode material and preparation method thereof, lithium ion battery

Abstract

The present invention relates to the field of lithium ion battery technology, specifically to a positive electrode material having an olivine structure and a preparation method thereof, and a lithium ion battery, wherein the positive electrode material comprises a base and a carbon coating layer, and in Raman spectrum, the positive electrode material has a peak at 940-950 cm -1 , 1330-1350cm -1 , 1580-1610cm -1 and the positive electrode material satisfies the following conditions: 0.01≦the average value of [I(A) / I(C)]≦0.3 and 0.01≦the average value of [I(A) / I(B)]≦0.3. The positive electrode material according to the present invention has a uniform carbon coating, which gives the positive electrode material high stability, low specific surface area, low volume resistivity, and high-pressure compaction, and when used in a lithium-ion battery, the positive electrode material provides excellent electrochemical performance.

Description

[Technical Field]

[0001] The present invention relates to the field of lithium ion battery technology, and in particular to a cathode material having an olivine structure, a method for preparing a cathode material having an olivine structure, and a lithium ion battery including the cathode material having an olivine structure. [Background technology]

[0002] Lithium-ion batteries have the advantages of long cycle life, high energy density, and no memory effect, and are widely used in the fields of new energy vehicles, mobile electronics, new power batteries, and energy storage. As a key component, the cathode material plays an important role in the overall performance of lithium-ion batteries, and its electrochemical performance plays an important role in determining their overall performance.

[0003] Olivine structure cathode material (LiMePO4, Me = Fe, Mn, Fe x Mn (1-x) ) has the advantages of low cost, long cycle life, high safety performance, and environmental friendliness, and is widely used in the fields of power and energy storage. However, due to its inherent properties, the olivine structure cathode material has low electronic conductivity (LiFePO4=1.8×10 -8 S / cm, LiMnPO4<10 -10 S / cm) and low Li + Diffusion coefficient

number

[0004] CN115863596A discloses that the use of flexible cyclic carbonaceous materials with large specific surface areas is advantageous for achieving adhesion of lithium manganese iron phosphate, increasing the uniformity of the carbon layers and forming a continuous conductive network, thereby improving the conductivity and stability of the lithium manganese iron phosphate composite material. The preparation process of this cyclic carbonaceous material requires a long preparation cycle, requires large amounts of pure water for washing, and emits toxic gases such as methanol. The present invention employs a common organic carbon source that is mature for mass production, effectively reducing production costs.

[0005] In the above-mentioned prior art, the carbon-coated olivine structure positive electrode material usually contains I D / I G The graphitization degree of the coated carbon is characterized by the following: The processing temperature of the olivine structure cathode material is low (generally <900°C), and in the process of forming the inorganic carbon coating layer from the organic carbon source, as the graphitization degree deepens, the carbon sp 3 Mixed is sp 2 and I for the positive electrode material D / I G While the performance characterization effect of is relatively single, both the thickness of the carbon coating layer and the quality of the carbon formation affect the energy retention rate during the olivine structure cycling process. Summary of the Invention [Problem to be solved by the invention]

[0006] To overcome the above technical problems, the present invention provides a positive electrode material with an olivine structure, a preparation method thereof, and a lithium ion battery. The positive electrode material has a uniform carbon coating, which results in high stability, a low specific surface area, low volume resistivity, and high density. At the same time, when used in a lithium ion battery, the positive electrode material has excellent electrochemical performance and improves energy retention during cycling. [Means for solving the problem]

[0007] In order to achieve the above object, a first aspect of the present invention provides a positive electrode material having an olivine structure, the positive electrode material including a base and a carbon coating layer, and in a Raman spectrum, the positive electrode material has a peak at 940-950 cm -1 , 1330-1350cm -1 , 1580-1610cm -1 and the positive electrode material has a Raman response in a wavenumber range of 0.01≦the average value of [I(A) / I(C)]≦0.3 and 0.01≦the average value of [I(A) / I(B)]≦0.3.

[0008] In the present invention, unless otherwise specified, the positive electrode material having the olivine structure will be simply referred to as the positive electrode material.

[0009] The positive electrode material of the present invention has a Raman response within a specific wavenumber range, and the intensity ratio of the characteristic peaks is within a specific range, i.e., the average value of [I(A) / I(C)] is 0.01≦[I(A) / I(B)]≦0.3 and the average value of [I(A) / I(B)] is 0.3, with the standard deviation of [I(A) / I(C)] being ≦0.02 and the standard deviation of [I(A) / I(B)] being ≦0.02. The positive electrode material has good overall carbon coating uniformity, an appropriate carbon coating thickness, and the contents of disordered carbon and ordered carbon in the carbon coating within appropriate ranges, resulting in high compatibility with the base material. With the same carbon coating content, the uniform carbon coating of the present invention can effectively reduce the specific surface area and powder resistance of the positive electrode material.

[0010] A second aspect of the present invention provides a method for preparing a cathode material having an olivine structure according to the first aspect, the method comprising the steps of mixing a Mn source, an Fe source, an M source, a phosphorus source, a Li source, an organic carbon source, and water, and sequentially grinding, spray-drying, and sintering the resulting mixed slurry to provide a carbon coating layer on a surface of a base having Formula I, thereby obtaining a cathode material, wherein the sintering is carried out in an inert atmosphere; Here, the particle size D of the crushed 50 0.1μm≦D 50 ≦0.48 μm, preferably 0.15 μm≦D 50Controlled to satisfy ≦0.36 μm, where Li a Mn 1-x Fe x M b (PO4) c (I), M is selected from at least one of Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and 0.95≦a≦1.1, 0≦x≦1, 0≦b≦0.2, 1≦c≦1.1.

[0011] A third aspect of the present invention provides a lithium-ion battery comprising a cathode material according to the first aspect or a cathode material produced by the preparation method according to the second aspect.

[0012] Compared with the prior art, the present invention has the following advantages: (1) When the average values ​​and standard deviations of [I(A) / I(C)] and [I(A) / I(B)] of the positive electrode material according to the present invention are within appropriate ranges, the carbon coating of the positive electrode material is uniform throughout and has an appropriate thickness, the degree of graphitization of the carbon coating layer is high, and compatibility with the base is high. Under the condition that the carbon coating layer content is the same, the carbon coating layer of the present invention can effectively reduce the specific surface area and volume resistivity of the positive electrode material.

[0013] (2) The preparation method of the present invention is based on a solid-state process, and controls the grinding particle size range to prepare a cathode material with an olivine structure and a uniform carbon coating. In particular, the spray-drying particle size, sintering temperature, and type of organic carbon source can be adjusted to affect the carbon coating layer content and coating effect to a certain extent.

[0014] At the same time, this preparation method also adjusts and controls the addition method of the organic carbon source based on the existence and addition type of the main metal elements (Mn and Fe) other than Li in the positive electrode material, to obtain a positive electrode material with a uniform carbon coating.

[0015] (3) When the positive electrode material of the present invention is applied to a lithium ion battery, it can effectively improve the electrochemical performance of the lithium ion battery, especially the energy retention rate. At the same time, the present invention provides different carbon generation characteristics, and the positive electrode material with an olivine structure has different characteristics in Raman properties, which are reflected in the capacity retention of the lithium ion battery, and can better guide the preparation and process monitoring of the positive electrode material. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of the Raman spectrum of the positive electrode material S1 produced in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0017] The endpoints of ranges and any value disclosed herein should be understood to be not limited to such exact ranges or values, but to include values ​​close to those ranges or values. In the case of ranges of numerical values, values ​​between the endpoints of each range, between the endpoints of each range and any single point value, and between any single point value can be combined with each other to create one or more new numerical ranges, and these numerical ranges are considered to be specifically disclosed in the specification.

[0018] In the present invention, unless otherwise specified, the terms "first," "second," and "third" do not indicate priority or limit individual items or steps, but are used only to distinguish or explain that they are not the same items or steps. For example, the terms "first," "second," and "third" in "first slurry," "second slurry," and "third slurry" are used only to explain that they are not the same slurries, and similarly, the terms "first," "second," and "third" in "first sintering," "second sintering," and "third sintering" are used only to explain that they are not the same sintering.

[0019] A first aspect of the present invention provides a positive electrode material having an olivine structure, the positive electrode material comprising a base and a carbon coating layer, and in a Raman spectrum, the positive electrode material has a peak at 940-950 cm-1 , 1330-1350cm -1 , 1580-1610cm -1 and the positive electrode material has a Raman response in a wavenumber range of 0.01≦the average value of [I(A) / I(C)]≦0.3 and 0.01≦the average value of [I(A) / I(B)]≦0.3.

[0020] In the present invention, unless otherwise specified, the positive electrode material is subjected to a Raman test, and the measurement conditions include an excitation wavelength of 532 nm, a laser power of 0.1 mW, an objective lens magnification of 50X, a test range of 20 × 30 μm, and 600 measurement points.

[0021] In the present invention, unless otherwise specified, I(A), I(B) and I(C) are the Raman spectra of the positive electrode material at 940-950 cm -1 , 1330-1350cm -1 , 1580-1610cm -1 where I(A) / I(C) is the intensity ratio of the A peak to the C peak in the Raman spectrum of the positive electrode material, and similarly, I(A) / I(B) is the intensity ratio of the A peak to the B peak in the Raman spectrum of the positive electrode material.

[0022] In the Raman spectrum of the positive electrode material according to the present invention, 940-950 cm -1 The A peak in the wavenumber range is mainly due to the PO4 3- Due to 1330-1350cm -1 The B peak in the wavenumber range of 1580-1610 cm is mainly due to carbon D, i.e., disordered carbon in the carbon coating layer. -1 The C peak in the wavenumber range is mainly due to carbon G, i.e., ordered carbon / graphitized carbon in the carbon coating layer.

[0023] In the present invention, the average value of [I(A) / I(C)] indicates the average value of the I(A) / I(C) values ​​obtained at each measurement point during the measurement process, and the average value of [I(A) / I(B)] indicates the average value of the I(A) / I(B) values ​​obtained at each measurement point during the measurement process.

[0024] In some embodiments of the present invention, the positive electrode material has an average value of 0.01≦[I(A) / I(C)]≦0.3, for example, 0.01, 0.05, 0.06, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, and any value within a range consisting of any two numbers, preferably an average value of 0.05≦[I(A) / I(C)]≦0.25, and more preferably an average value of 0.1≦[I(A) / I(C)] ] ≦0.25, and 0.01 ≦ the average value of [I(A) / I(B)] ≦0.3, for example, 0.01, 0.05, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, and any value within a range consisting of any two numerical values ​​simultaneously, preferably 0.05 ≦ the average value of [I(A) / I(B)] ≦0.25, and more preferably 0.1 ≦ the average value of [I(A) / I(B)] ≦0.25.

[0025] In some embodiments of the present invention, the positive electrode material preferably further satisfies the standard deviation of [I(A) / I(C)]≦0.02, and preferably the positive electrode material further satisfies the standard deviation of [I(A) / I(B)]≦0.02. In the present invention, when the above standard deviation ranges of [I(A) / I(C)] and [I(A) / I(B)] are satisfied, the carbon coating layer of the positive electrode material has excellent overall uniformity and an appropriate thickness, a high degree of graphitization of the carbon coating layer, a low specific surface area and low volume resistance of the positive electrode material, and excellent performance.

[0026] In some embodiments of the present invention, the positive electrode material preferably also satisfies the average value of [I(B) / I(C)]≦1, more preferably the average value of [I(B) / I(C)]≦0.9, for example, 0.7, 0.75, 0.8, 0.85, 0.9, and any value within a range consisting of any two numbers. In the present invention, when the [I(B) / I(C)] of the carbon coating layer is within the above specified range, it indicates that the carbon coating layer has a high degree of graphitization.

[0027] In some embodiments of the present invention, the base preferably has the composition shown in Formula I, and a Mn 1-x Fe x M b (PO4) c (I), wherein M is selected from at least one of Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and 0.95≦a≦1.1, 0≦x≦1, 0≦b≦0.2, 1≦c≦1.1.

[0028] In the present invention, preferably, in formula I, M is selected from at least one of Ti, W, Co, V and Mg.

[0029] In the present invention, in formula I, 0.95≦a≦1.1, for example, 0.95, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.1, and any value within a range consisting of any two numbers, and preferably 1≦a≦1.05.

[0030] In the present invention, in formula I, 0≦x≦1, for example, 0, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value within a range consisting of any two numbers, preferably 0.3≦x≦1.

[0031] In the present invention, in formula I, 0≦b≦0.2, for example, 0, 0.1, 0.12, 0.15, 0.18, 0.2, and any value within a range consisting of any two numbers, preferably 0.1≦b≦0.2.

[0032] In the present invention, in formula I, 1≦c≦1.1, for example, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.08, 1.1, and any value within a range consisting of any two numbers, and preferably 1≦c≦1.05.

[0033] In the present invention, a, x, b, c, and M in Formula I are adjusted to control the value of a within a certain range, thereby affecting the proportion of Li in the positive electrode material, and thereby the capacity and compaction level of the positive electrode material. Adjusting the value of x affects the voltage platform of the positive electrode material. Adjusting the values ​​of b and M mainly affects the electrochemical kinetics and compaction density of the positive electrode material. Adjusting the value of c affects the proportion of P in the material, which in turn affects the capacity and compaction density of the material.

[0034] In some embodiments of the present invention, the content of the carbon coating layer is preferably 0.8-3 wt %, for example, 0.8 wt %, 1 wt %, 1.2 wt %, 1.5 wt %, 1.8 wt %, 2 wt %, 2.2 wt %, 2.5 wt %, 3 wt %, and any value within a range consisting of any two values, preferably 1-2.5 wt %, based on the total weight of the positive electrode material. In the present invention, the content parameter of the carbon coating layer is measured using a carbon-sulfur analyzer.

[0035] In some embodiments of the present invention, the thickness of the carbon coating layer is preferably 1-10 nm, for example, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, 8 nm, 10 nm, and any value within a range consisting of any two numerical values, preferably 1.5-5 nm. In the present invention, the thickness parameter of the carbon coating layer was measured by Raman spectroscopy and TEM photography.

[0036] In some embodiments of the present invention, the average particle size of the base is preferably 40-290 nm, for example, 40 nm, 70 nm, 90 nm, 100 nm, 150 nm, 200 nm, 230 nm, 290 nm, and any value within a range consisting of any two numbers, preferably 70-230 nm.

[0037] In some embodiments of the present invention, the average particle size of the positive electrode material is preferably 50-300 nm, for example, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 240 nm, 300 nm, and any value within a range consisting of any two numbers, preferably 80-240 nm. In the present invention, the average particle size of the positive electrode material = the average particle size of the base + the thickness of the coating layer.

[0038] In some embodiments of the present invention, the specific surface area BET of the positive electrode material is preferably 5-40 m 2 / g, e.g., 5m 2 / g, 8m 2 / g, 10m 2 / g, 15m 2 / g, 18m 2 / g, 20m 2 / g, 25m 2 / g, 40m 2 / g, and any value within the range consisting of any two numbers, preferably 8-25m 2 / g.

[0039] In some embodiments of the present invention, the volume resistivity of the positive electrode material is preferably 0-200 Ω·cm, for example, 0 Ω·cm, 5 Ω·cm, 10 Ω·cm, 20 Ω·cm, 30 Ω·cm, 50 Ω·cm, 60 Ω·cm, 80 Ω·cm, 100 Ω·cm, 150 Ω·cm, 200 Ω·cm, and any value within a range consisting of any two values, preferably 0-100 Ω·cm.

[0040] In some embodiments of the present invention, preferably, the compacted density of the positive electrode material is 2-2.7 g / m 3 , e.g., 2 g / m 3, 2.2g / m 3 , 2.3g / m 3 , 2.4g / m 3 , 2.5g / m 3 , 2.6g / m 3 , 2.7g / m 3 and any value within a range consisting of any two numbers, preferably 2.2-2.6 g / m 3 is.

[0041] In the present invention, unless otherwise specified, the specific surface area BET parameter is measured by the static adsorption method, the volume resistivity parameter is measured by the four-probe method, and the compaction density parameter is measured by the in situ static method.

[0042] A second aspect of the present invention provides a method for preparing a cathode material having an olivine structure according to the first aspect, the method comprising the steps of mixing a Mn source, an Fe source, an M source, a phosphorus source, a Li source, an organic carbon source, and water, and sequentially grinding, spray-drying, and sintering the resulting mixed slurry to provide a carbon coating layer on a surface of a base having Formula I, thereby obtaining a cathode material, wherein the sintering is carried out in an inert atmosphere; Here, the particle size D of the crushed 50 0.1μm≦D 50 ≦0.48 μm, preferably 0.15 μm≦D 50 Controlled to satisfy ≦0.36 μm, where Li a Mn 1-x Fe x M b (PO4) c (I), M is selected from at least one of Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and 0.95≦a≦1.1, 0≦x≦1, 0≦b≦0.2, 1≦c≦1.1.

[0043] The preparation method of the present invention uses a solid-state coating method to prepare a positive electrode material with an olivine structure, which has a high-quality carbon coating effect and provides the positive electrode material with high stability and good electrochemical performance. At the same time, the preparation method simplifies the process flow and facilitates product utilization. When used in lithium-ion batteries, it can effectively improve the energy retention rate during cycling.

[0044] In the present invention, the particle size D of the pulverized material 50 0.1μm≦D 50 ≦0.48 μm, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.36 μm, 0.4 μm, 0.48 μm, and any value within a range consisting of any two numerical values, preferably 0.15 μm≦D 50 In the present invention, the particle size D of the pulverized powder satisfies the condition of ≦0.36 μm. 50 and further control the size of the primary particles of the positive electrode material, thereby affecting the uniformity and thickness of the carbon coating layer, so that the positive electrode material satisfies the following conditions: 0.01≦average value of [I(A) / I(C)]≦0.3 and 0.01≦average value of [I(A) / I(B)]≦0.3.

[0045] In the present invention, unless otherwise specified, the grinding particle size D 50 Control the particle size D of the crushed material. 50 is 0.1μm≦D 50 ≦0.48 μm, and preferably 0.15 μm≦D 50 Similarly, the particle size D of the second grinding is controlled to satisfy ≦0.36 μm. 2 50 That is, the particle size D of the second grinding material is controlled. 2 50 and the particle size D' of the first coarse grinding is controlled. 1 50 That is, the particle size D' of the first coarsely pulverized material is controlled. 1 50 Control the particle size of the first fine grinding D 1 50 That is, the particle size D of the first pulverized material is controlled. 1 50 Controlling the particle size D'' of the first spray drying1 50 That is, the particle size D'' of the first spray-dried material is controlled. 1 50 and controlling the particle size D'' of the second spray drying. 2 50 That is, the particle size D'' of the second spray-dried material is controlled. 2 50 Control the particle size of the third grinding D 3 50 Control the particle size D of the third grinding material. 3 50 and controlling the particle size D'' of the third spray drying. 3 50 That is, the particle size D'' of the third spray-dried material is controlled. 3 50 Control.

[0046] In the present invention, unless otherwise specified, the inert atmosphere includes, but is not limited to, a nitrogen gas atmosphere, a helium gas atmosphere, an argon gas atmosphere, and the like.

[0047] In some embodiments of the present invention, the dosages of the Mn source, Fe source, M source, phosphorus source, and Li source, in elemental terms, preferably satisfy n(Mn):n(Fe):n(M):n(P):n(Li), where 0≦n(Mn)≦1, 0≦n(Fe)≦1, 0≦n(M)≦0.2, 1≦n(P)≦1.1, 0.95≦n(Li)≦1.1, and more preferably 0≦n(Mn)≦0.7, 0.3≦n(Fe)≦1, 0.1≦n(M)≦0.2, 1≦n(P)≦1.05, 1≦n(Li)≦1.05.

[0048] In some embodiments of the present invention, the M source is preferably selected from compounds containing Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and more preferably selected from compounds containing Ti, W, Co, V, and Mg.

[0049] In some embodiments of the present invention, the Li source is preferably selected from at least one of lithium dihydrogen phosphate, lithium carbonate, lithium oxalate, lithium oxide, lithium powder, and lithium phosphate.

[0050] In some embodiments of the present invention, the phosphorus source is preferably selected from at least one of lithium dihydrogen phosphate, iron manganese phosphate monohydrate, iron phosphate, and diphosphorus pentoxide.

[0051] In some embodiments of the present invention, the amount of the organic carbon source added preferably satisfies the requirement that the carbon coating layer content in the positive electrode material be 0.8-3 wt%, preferably 1-2.5 wt%. In the present invention, the amount of the organic carbon source added accounts for 5-40 wt% of the solid content in the mixed slurry, and can be adjusted according to the type of organic carbon source and the residual carbon rate, so that the carbon coating layer content in the positive electrode material be 0.8-3 wt%, preferably 1-2.5 wt%.

[0052] In some embodiments of the present invention, the organic carbon source is preferably selected from at least one of glucose, sucrose, starch, polyethylene, polyvinylpyrrolidone, tannic acid, and polydopamine, and more preferably selected from at least one of glucose, sucrose, and starch, and at least one of polyethylene, polyvinylpyrrolidone, tannic acid, and polydopamine. In the present invention, the weight-average molecular weight of polyethylene is 1500-6000 g / mol, the weight-average molecular weight of polyvinylpyrrolidone is 10000-40000 g / mol, and the weight-average molecular weight of polydopamine is 400-2000 g / mol.

[0053] In the present invention, when the above-mentioned specific type of organic carbon source is used, the inorganic carbon formed after sintering the organic carbon source is uniformly coated on the surface of the base having Formula I.

[0054] In the present invention, there is a wide range of choice for the amount of water to be added, as long as the solid content of the mixed slurry is 30-50 wt%, preferably 35-45 wt%.

[0055] In some embodiments of the present invention, preferably, the Mn source and the Fe source are each independently selected from at least one of an element, an oxide, a carbonate, an oxalate, and a phosphate.

[0056] In one specific embodiment of the present invention, the Mn source includes, but is not limited to, manganese powder, manganese dioxide, trimanganese tetroxide, manganese carbonate, manganese oxalate, manganese phosphate, iron manganese phosphate, iron manganese phosphate monohydrate, iron manganese carbonate, iron manganese oxalate, iron manganese hydroxide, iron manganese oxide, iron manganese oxyhydroxide, etc.

[0057] In one specific embodiment of the present invention, the Fe source includes, but is not limited to, iron powder, ferric oxide, ferric oxide, ferrous oxalate, iron phosphate, iron manganese phosphate, iron manganese phosphate monohydrate, iron manganese carbonate, iron manganese oxalate, iron manganese hydroxide, iron manganese oxide, iron manganese oxyhydroxide, and the like.

[0058] In a first specific embodiment of the present invention, the preparation method preferably includes the steps of: (I-1) mixing the Mn source, the Fe source, the M source, the phosphorus source, the Li source, a first carbon source, and water, and sequentially performing a first pulverization, a first spray drying, and a first sintering on the obtained first slurry to obtain a first sintered product; and (I-2) mixing the first sintered product and a second carbon source in water, and sequentially performing a second pulverization, a second spray drying, and a second sintering on the obtained second slurry to obtain a second sintered product as the positive electrode material, Here, the organic carbon source is divided into the first carbon source and the second carbon source, and the second crushed particle size D 2 50 is 0.1μm≦D 2 50 ≦0.48 μm, preferably 0.15 μm≦D 250 The first sintering and the second sintering are each independently performed in an inert atmosphere.

[0059] In some embodiments of the present invention, preferably, in step (I-1), the mass ratio of the first carbon source to the second carbon source is 0.1-1:1, such as 0.1:1, 0.15:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, 1:1, or any value within a range consisting of any two of these values, and preferably 0.15-0.8:1. In the present invention, satisfying the mass ratio in the above range effectively reduces the specific surface area of ​​the positive electrode material, increases the compaction density of the positive electrode material, and achieves a better degree of graphitization.

[0060] In some embodiments of the present invention, preferably, the first carbon source is selected from at least one of glucose, sucrose, starch, and polyethylene, and the second carbon source is selected from at least one of glucose, sucrose, and starch, and at least one of polyethylene, polyvinylpyrrolidone, tannic acid, and polydopamine.

[0061] In the present invention, the first pulverization refers to pulverizing particles in a first slurry having a solid content of 30-50 wt%. Preferably, the first pulverization includes a first coarse pulverization and a first fine pulverization, and the particle size D' of the first coarse pulverization is 1 50 is 0.3μm≦D' 1 50 The thickness D' is controlled to satisfy the condition of 0.5 μm≦D'≦10 μm, for example, 0.3 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, and any value within a range consisting of any two numerical values, and preferably 0.5 μm≦D' 1 50 ≦5 μm, and the particle size D of the first milling 1 50 is 0.1μm≦D 1 50≦0.5 μm, for example, 0.1 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.5 μm, and any value within a range consisting of any two numerical values, preferably 0.2 μm≦D 1 50 ≦0.4 μm.

[0062] In the present invention, the final particle size of the first grinding (i.e., the particle size D of the first fine grinding) 1 50 By adjusting and controlling the grinding speed, the components can be mixed more uniformly, which is beneficial to the purity of the positive electrode material phase. If the grinding speed is too coarse, it is unfavorable to homogenize the components. If the grinding speed is too fine, it becomes difficult to grind, which affects the size of the primary particles after sintering and further affects the compaction density and cycle stability of the positive electrode material. At the same time, the size of the first grinding particle size determines the uniformity of the carbon source in the first carbon supplementation process and affects the carbon distribution on the particle surface during the first sintering.

[0063] In some embodiments of the present invention, preferably the particle size D'' of the first spray drying 1 50 2μm≦D'' 1 50 The thickness D'' is controlled to satisfy the following condition: ≦30 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 30 μm, and any value within a range consisting of any two numerical values, and preferably 5 μm≦D'' 1 50 In the present invention, the first carbon source forms an effective coating on the surface of the spray material with the evaporation of water in the first slurry during the first spray drying process, but if the particle size of the spray material is too large, it will affect the evaporation of water from the particles, thereby affecting the uniform coating of the organic carbon source on the surface of the spray material.

[0064] In some embodiments of the present invention, the conditions for the first sintering preferably include: a temperature T1 of 350-650°C, preferably 400-600°C; a heating rate V1 of 0.5-10°C / min, preferably 1-5°C / min; and an isothermal time t1 of 0.5-6 h, preferably 1-3 h.

[0065] In the present invention, unless otherwise specified, the first sintered material obtained by the first sintering is an agglomerate, and the average particle size of the first sintered material is equal to or smaller than the particle size D'' of the first spray-dried material. 1 50 Preferably, the size of the primary particles of the first sintered material is 40-240 nm, preferably 60-180 nm.

[0066] In some embodiments of the present invention, in step (I-2), the particle size D 2 50 is 0.1μm≦D 2 50 ≦0.48 μm, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.36 μm, 0.4 μm, 0.48 μm, and any value within a range consisting of any two numerical values, preferably 0.15 μm≦D 2 50 In the present invention, the second crushed particle size D satisfies the condition of ≦0.36 μm. 2 50 By controlling the range of I(A) / I(C), a secondary carbon coating effect can be formed on the surface of the primary particles, resulting in specific I(A) / I(C) and I(A) / I(B).

[0067] In some embodiments of the present invention, preferably the second spray-dried particle size D'' 2 50 2μm≦D'' 2 50 The thickness D'' is controlled to satisfy the following condition: ≦30 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 30 μm, and any value within a range consisting of any two numerical values, and preferably 5 μm≦D'' 250 ≦20 μm. Too small a particle size of the second spray drying is unfavorable for improving production efficiency, while too large a particle size is unfavorable for volatilization of moisture and affects the uniform deposition of the second carbon source.

[0068] In some embodiments of the present invention, the conditions for the second sintering preferably include: a temperature T2 of 550-850°C, preferably 600-750°C; a heating rate V2 of 0.5-50°C / min, preferably 0.8-5°C / min; and an isothermal time t2 of 2-14 hours, preferably 6-12 hours.

[0069] In the present invention, if the second sintering temperature T2 is low, the degree of graphitization of the carbon coating layer of the positive electrode material will decrease, the carbon content will increase, and the corresponding [I(A) / I(C)] and [I(A) / I(B)] will decrease, the specific surface area will increase, the compaction density will decrease, and the resistance will increase, which will affect the electrochemical performance to some extent. If the second sintering temperature T2 is too high, the primary particles of the positive electrode material will grow abnormally and heterophases such as Fe2P will occur, which will affect the electrochemical performance of the positive electrode material.

[0070] In a second specific embodiment of the present invention, preferably, the preparation method includes the step of (II) mixing the Mn source, Fe source, M source, phosphorus source, Li source, organic carbon source, and water, and sequentially performing a third pulverization, a third spray drying, and a third sintering on the obtained third slurry to obtain a third sintered product, wherein the particle size D 3 50 is 0.1μm≦D 3 50 ≦0.48 μm, and preferably 0.15 μm≦D 3 50 ≦0.36 μm, and the third sintering is performed in an inert atmosphere; When the base represented by formula I simultaneously contains Mn and Fe, the Mn source and the Fe source are each independently selected from compounds containing both Mn and Fe, or when the base represented by formula I does not contain Mn or Fe, the Mn source is selected from manganese phosphate and the Fe source is selected from iron phosphate.

[0071] Comparing the above two preparation methods in the present invention, the first preparation method, i.e., adopts the technical means of two grinding steps, two spray drying steps, and two sintering steps, and the types of Mn and Fe sources in the raw materials are not limited in any way, i.e., all Mn and Fe sources applicable to the above limitations can be used. The second preparation method, i.e., adopts the technical means of one grinding step, one spray drying step, and one sintering step, and the types of Mn and Fe sources in the raw materials are limited.

[0072] At the same time, when a specific Mn source and Fe source are used as raw materials, instead of the technical means of two grinding processes, two spray drying processes, and two sintering processes, a technical means of one grinding process, one spray drying process, and one sintering process can be adopted, which not only allows a cathode material with a specific olivine structure to be obtained, but also simplifies the process flow and saves costs.

[0073] In the present invention, unless otherwise specified, "the base represented by formula I simultaneously contains Mn and Fe" means that in formula I, the subscript (1-x) of Mn and Fe and x are not equal to 0; "the Mn source and the Fe source are independently selected from compounds simultaneously containing Mn and Fe" means that the Mn source is selected from compounds containing Mn and Fe, and the Fe source is also selected from compounds containing Mn and Fe; and "the base represented by formula I does not simultaneously contain Mn and Fe" means that in formula I, the subscript (1-x) of Mn is equal to 0 and the subscript x of Fe is not equal to 0, or the subscript (1-x) of Mn is not equal to 0 and the subscript x of Fe is equal to 0.

[0074] In some embodiments of the present invention, when the base represented by Formula I simultaneously contains Mn and Fe, the Mn source and the Fe source are each independently selected from compounds simultaneously containing Mn and Fe. Preferably, the Mn source and the Fe source are each independently selected from at least one of manganese iron phosphate, manganese iron phosphate monohydrate, manganese iron carbonate, manganese iron oxalate, manganese iron hydroxide, manganese iron oxide, and manganese iron oxyhydroxide.

[0075] In some embodiments of the present invention, when the base represented by formula I does not simultaneously contain Mn and Fe, the Mn source is selected from manganese phosphates and the Fe source is selected from iron phosphates.

[0076] In some embodiments of the present invention, preferably, in step (II), the third pulverization includes a third coarse pulverization and a third fine pulverization, and the particle size D' of the third coarse pulverization 3 50 is 0.3μm≦D' 3 50 The thickness is controlled to satisfy the condition of 0.5 μm≦D′≦10 μm, for example, 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, and any value within a range consisting of any two numerical values, and preferably 0.5 μm≦D′ 3 50 ≦5 μm, and the particle size D of the third milling 3 50 is 0.1μm≦D 3 50 ≦0.48 μm, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.36 μm, 0.4 μm, 0.48 μm, and any value within a range consisting of any two numerical values, preferably 0.15 μm≦D 3 50 In the present invention, by satisfying the above particle size range, the carbon is uniformly coated on the surface of the positive electrode material, and the average values ​​of [I(A) / I(C)] and [I(A) / I(B)] are specific.

[0077] In some embodiments of the present invention, preferably the third spray-dried particle size D'' 3 50 2μm≦D'' 3 50 The thickness D'' is controlled to satisfy the following condition: ≦30 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 30 μm, and any value within a range consisting of any two numerical values, and preferably 5 μm≦D'' 3 50 ≦20 μm.

[0078] In some embodiments of the present invention, the third sintering conditions preferably include: a temperature T3 of 550-850°C, preferably 600-750°C; a heating rate V3 of 0.5-50°C / min, preferably 0.8-5°C / min; and a constant temperature time t3 of 2-14 hours, preferably 6-12 hours.

[0079] In the present invention, if the temperature T3 of the third sintering is low, the degree of graphitization of the carbon coating layer of the positive electrode material will decrease, the carbon content will increase, the corresponding [I(A) / I(C)] and [I(A) / I(B)] will decrease, the specific surface area BET will increase, the compaction density will decrease, and the resistance will increase, which will have a certain impact on the electrochemical performance. Conversely, if the temperature T3 of the third sintering is high, the content of the carbon coating layer of the positive electrode material will decrease, the average value of [I(B) / I(C)] will decrease, the degree of graphitization will increase, the primary particles will grow, the compaction density of the material will increase, and the specific surface area will decrease, which is beneficial to improving the electrochemical and processing performance.

[0080] A third aspect of the present invention provides a lithium-ion battery comprising a cathode material according to the first aspect or a cathode material produced by the preparation method according to the second aspect.

[0081] The present invention will be described in detail below with reference to examples. Table 1 shows the physical property parameters of the positive electrode materials produced in the examples and comparative examples.

[0082] Energy retention rate 80th Measurement method: (1) Assembling the battery: The positive electrode material to be measured, the conductive agent (acetylene black), and the adhesive (PVDF) were mixed with a solvent (NMP) in a mass ratio of 95:3:2 (temperature: 25°C, rotation speed: 1000 rpm, time: 40 min) to obtain a positive electrode slurry with a solid content of 40 wt%. The positive electrode slurry is applied to the surface of an aluminum foil, and the surface of the aluminum foil is coated with the positive electrode slurry. The coated surface is dried at 135°C, and then roll-pressed (at a pressure of 15T) using a roll press to form a positive electrode active material layer on the surface of the aluminum foil, thereby obtaining a positive electrode piece. The positive electrode pieces, separator, negative electrode pieces, and electrolyte were assembled into a 2025-type button battery in a gas glove box filled with argon gas, with the water and oxygen contents both less than 5 ppm, and allowed to stand for 6 hours. The negative electrode pieces were made of lithium metal sheet with a diameter of 16 mm and a thickness of 0.5 mm, the separator was a 25 μm thick polyethylene porous membrane (Celgard 2325), and the electrolyte was a mixture of equal parts ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol / L LiPF6.

[0083] (2) Measurement conditions: The charge / discharge voltage range was controlled to 2.5-4.35V, and at 25°C, the button battery was charged / discharged twice at 0.1C, and then charged / discharged 80 times at 1C. The first discharge specific capacity at 0.1C was the discharge specific capacity of the button battery at the first cycle, and the 80th discharge specific capacity at 1C was the discharge specific capacity of the button battery at the 80th cycle.

[0084] Here, the energy retention rate is 80 th = (discharge specific capacity at 80th cycle of button battery / discharge specific capacity at 1st cycle of button battery) x 100%.

[0085] Example 1 (1) A manganese source (manganese tetroxide), an iron source (iron phosphate), a lithium source (lithium dihydrogen phosphate, lithium carbonate), a phosphorus source (lithium dihydrogen phosphate, iron phosphate), an M source (titanium dioxide, tungsten oxide), and a first carbon source (glucose) are mixed in water to obtain a first slurry having a solid content of 40 wt %, and the element moles are represented by the chemical formula Li 1.04 Mn 0.65 Fe 0.35 Ti 0.05 W 0.05 (PO4) 1.01 Add with The first slurry is subjected to a first coarse pulverization, and the particle size D' of the first coarse pulverized material is obtained. 1 50 = 3.3 μm, and the first coarsely pulverized material is subjected to first fine pulverization, and the D 1 50 = 0.3 μm, The first pulverized material is subjected to a first spray drying, and D'' of the first spray-dried material is obtained. 1 50 = 10.2 μm, and BET = 7.2 m 2 / g, The first spray-dried material was subjected to first sintering in a nitrogen gas atmosphere, and the temperature was increased to T1=500°C at a temperature increase rate of V1=1.5°C / min and kept at that temperature for t1=3 hours. The first sintered material had an average particle size of 10.5 μm, a primary particle size of 80 nm, and a specific surface area of ​​7.3 m 2 / g, (2) Dispersing the first sintered material in water, and adding a second carbon source (glucose and PEG in a mass ratio of 5.6:4) to obtain a second slurry, wherein the mass ratio of the first carbon source to the second carbon source is 0.45:1, and the total amount of the first carbon source and the second carbon source is sufficient to ensure that the content of the carbon coating layer in the finished cathode material is 1.57 wt%; The second slurry is subjected to a second pulverization, and the D of the second pulverized material is 2 50 = 0.25 μm, The second ground material is subjected to a second spray drying, and D'' of the second spray-dried material is obtained. 2 50 = 8.0 μm, and BET = 8.8 m2 / g, The second spray-dried material was subjected to a second sintering process, in which the temperature was increased to T2 = 675 ° C at a temperature increase rate of V2 = 1.5 ° C / min, and the temperature was maintained for t2 = 10 hours to obtain a second sintered material. The second sintered material is crushed to obtain a positive electrode material S1 having an olivine structure.

[0086] Here, the Raman spectrum of the positive electrode material S1 is shown in FIG. 1. As can be seen from FIG. 1, the positive electrode material S1 has a peak at 950 cm -1 , 1350cm -1 and 1580cm -1 Peaks A, B, and C appear near the Raman displacements of 3- , which correspond to the characteristic peaks of carbon D and carbon G.

[0087] Example 2 According to the method of Example 1, In step (2), the mass ratio of glucose to PEG in the second carbon source is changed to 7:4; The mass ratio of the first carbon source to the second carbon source is changed to 0.39:1, and the total amount of the first carbon source and the second carbon source is such that the content of the carbon coating layer in the finished positive electrode material is 1.85 wt %; D of the second crushed material 2 50 = 0.25 μm, The second ground material is subjected to a second spray drying, and D'' of the second spray-dried material is obtained. 2 50 = 8.3 μm, and BET = 9.1 m 2 / g, Other conditions were the same to obtain a positive electrode material S2.

[0088] Example 3 According to the method of Example 1, In step (2), the mass ratio of glucose to PEG in the second carbon source is changed to 2.5:12; The mass ratio of the first carbon source to the second carbon source is changed to 0.3:1, and the total amount of the first carbon source and the second carbon source is such that the carbon coating layer content in the finished positive electrode material is 1.55 wt %; D of the second crushed material 2 50 = 0.25 μm, The second ground material is subjected to a second spray drying, and D'' of the second spray-dried material is obtained. 2 50 = 8.8 μm, and BET = 8.5 m 2 / g, Other conditions were the same, and positive electrode material S3 was obtained.

[0089] Example 4 A manganese source (iron manganese phosphate monohydrate), an iron source (iron manganese phosphate monohydrate), a lithium source (lithium dihydrogen phosphate, lithium carbonate), a phosphorus source (lithium dihydrogen phosphate, iron manganese phosphate monohydrate), an M source (titanium dioxide, tungsten oxide), and an organic carbon source (glucose, PEG) were mixed in water to obtain a third slurry with a solid content of 40 wt %, and the elemental moles were calculated according to the chemical formula Li 1.04 Mn 0.65 Fe 0.35 Ti 0.05 W 0.05 (PO4) 1.01 The amount of the organic carbon source added is such that the content of the carbon coating layer in the finished positive electrode material is 1.83 wt%; The third slurry is subjected to third coarse pulverization, and D' of the third coarse pulverized material is obtained. 3 50 = 2 μm, and the third coarsely pulverized material is subjected to a third fine pulverization, and the D of the third fine pulverized material is 3 50 = 0.3 μm, The third pulverized material is subjected to a third spray drying, and D'' of the third spray-dried material is obtained. 3 50 = 10.8 μm, BET = 30.1 μm, The third spray-dried material is subjected to a third sintering process, in which the temperature is increased to T3=650°C at a heating rate of V3=1.5°C / min, and the temperature is maintained for t3=10 hours. The resulting third sintered material is then crushed to obtain a positive electrode material S4 having an olivine structure.

[0090] Example 5 The iron source (iron phosphate), lithium source (lithium carbonate), phosphorus source (iron phosphate), M source (titanium dioxide, tungsten oxide), and organic carbon source (glucose, PEG) were mixed in water to obtain a third slurry with a solid content of 45 wt% and elemental moles of the chemical formula Li 1.04 FeTi 0.05 W 0.05 (PO4) 1.03 The amount of the organic carbon source added is such that the content of the carbon coating layer in the finished positive electrode material is 1.40 wt%; The third slurry is subjected to third coarse pulverization, and D' of the third coarse pulverized material is obtained. 3 50 = 2.8 μm, and the third coarsely pulverized material is subjected to a third fine pulverization, and the D of the third fine pulverized material is 3 50 = 0.35 μm, The third pulverized material is subjected to a third spray drying, and D'' of the third spray-dried material is obtained. 3 50 = 12.1 μm, and BET = 6.1 m 2 / g, The third spray-dried material is subjected to a third sintering process, in which the temperature is increased to T3=780°C at a heating rate of V3=3°C / min, and the temperature is maintained for t3=8 hours. The resulting third sintered material is then crushed to obtain a positive electrode material S5 having an olivine structure.

[0091] Example 6 In step (2), the procedure of Example 1 was repeated except that the temperature T2 of the second sintering was changed from 675°C to 650°C.

[0092] Other conditions are the same, and a positive electrode material S6 having an olivine structure is obtained. Example 7 In step (2), the mass ratio of the first carbon source to the second carbon source is 0.67:1, and the total amount of the first carbon source and the second carbon source is such that the content of the carbon coating layer in the finished cathode material is 1.67 wt%.

[0093] Other conditions are the same, and a positive electrode material S7 having an olivine structure is obtained. Comparative Example 1 Third fine grinding material D 3 50 The procedure of Example 4 is followed, except that the thickness is controlled so that the thickness is 0.5 μm.

[0094] Other conditions are the same, and an olivine structure positive electrode material DS1 is obtained. Comparative Example 2 In step (2), the D of the second crushed material 2 50 The procedure of Example 1 is followed except that the thickness is adjusted to 0.5 μm.

[0095] Other conditions are the same, and an olivine structure positive electrode material DS2 is obtained.

[0096] [Table 1-1]

[0097] [Table 1-2]

[0098] [Table 1-3]

[0099] From the data in Table 1, it can be seen that by combining Examples 1-7 and Comparative Examples 1-2, changing the preparation process, sintering temperature, grinding particle size, and type of organic carbon source of the positive electrode material with an olivine structure will affect the content and coating effect of the carbon coating layer to a certain extent.

[0100] By comparing Examples 1 and 2, it can be seen that as the content of the carbon coating layer of the positive electrode material increases, the average values ​​of [I(A) / I(C)] and [I(A) / I(B)] decrease, showing an inverse relationship with the thickness of the carbon coating layer, the average values ​​of [I(B) / I(C)] are at the same level, the degree of graphitization of the organic carbon source is more closely related to temperature, and when the carbon coating layer is uniformly coated, the content and thickness of the carbon coating layer show a positive correlation.

[0101] Comparing Example 1 and Example 3, it can be seen that by adjusting the amount of the second carbon source added, and controlling the mass ratio of the first carbon source to the second carbon source at the same sintering temperature and carbon coating layer content, the specific surface area of ​​the positive electrode material can be reduced, the compaction density can be improved, and a better degree of graphitization can be achieved.

[0102] A sample of the cathode material S3 prepared in Example 3 was measured at two laser intensities, 0.1 mW and 0.3 mW, respectively. When the 0.3 mW laser intensity was used, the average value and standard deviation of [I(A) / I(C)] were 0.31 and 0.03, respectively, the average value and standard deviation of [I(A) / I(B)] were 0.38 and 0.03, respectively, and the average value of [I(B) / I(C)] was 0.81. That is, when the 0.3 mW laser intensity was used, the average values ​​and standard deviations of [I(A) / I(C)] and [I(A) / I(B)] were both larger than when the 0.1 mW laser intensity was used. This indicates that the surface carbon coating was destroyed to some extent during the measurement process, resulting in an uneven and thin carbon coating, which enhanced the A signal and simultaneously increased the standard deviation. Therefore, a specific laser intensity must be specified for characterizing this characteristic of the material.

[0103] By comparing Example 2 and Example 4, the same olivine structure positive electrode material was prepared using different processes, and the average values ​​of [I(A) / I(C)] and [I(A) / I(B)] showed similar rules, which showed that the rules could effectively guide the preparation of positive electrode materials using different preparation processes.

[0104] By comparing Examples 4 and 5, two different cathode materials were prepared using the same process. Due to differences in sintering temperature, carbon loading, and grinding particle size, there are certain differences in the average values ​​of [I(A) / I(C)] and [I(A) / I(B)]. Therefore, this rule should guide the preparation of the same material.

[0105] By comparing Example 1 and Example 6, it can be seen that lowering the second sintering temperature reduces the degree of graphitization of the carbon coating layer of the positive electrode material, increases the content of the carbon coating layer, and correspondingly reduces the average values ​​of [I(A) / I(C)] and [I(A) / I(B)], increases the BET, reduces the compaction density, and increases the resistance, which to some extent affects the electrochemical performance.

[0106] Comparing Example 1 and Example 7, it can be seen that changing the carbon distribution method in the second sintering process increases the amount of residual carbon in the first sintering, and the uneven coating of inorganic carbon during the second grinding affects the quality of the carbon coating layer on the surface of the positive electrode material, resulting in abnormalities in both the average value and standard deviation of [I(A) / I(C)] and [I(A) / I(B)].

[0107] By comparing Example 4 with Comparative Example 1, and Example 1 with Comparative Example 2, it can be seen that after improving the grinding particle size, the sintering process is unfavorable for the carbon to uniformly coat the primary particles of the positive electrode material, and some primary particles may be exposed, resulting in an intensified A signal and abnormalities in both the average values ​​and standard deviations of [I(A) / I(C)] and [I(A) / I(B)].

[0108] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications of the technical means of the present invention can be implemented, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations shall also be regarded as the contents disclosed in the present invention and shall fall within the scope of protection of the present invention.

Claims

1. A positive electrode material having an olivine structure, the positive electrode material comprising a base and a carbon coating layer, and in a Raman spectrum, the positive electrode material has a peak at 940-950 cm －１ , 1330-1350cm －１ , 1580-1610cm －１ and a Raman response exists in a wavenumber range of 0.01≦the average value of [I(A) / I(C)]≦0.3 and a Raman response exists in a wavenumber range of 0.01≦the average value of [I(A) / I(B)]≦0.

3.

2. the positive electrode material satisfies the conditions: 0.05≦average value of [I(A) / I(C)]≦0.25 and 0.05≦average value of [I(A) / I(B)]≦0.25; More preferably, the positive electrode material also satisfies the following conditions: 0.1≦the average value of [I(A) / I(C)]≦0.25 and 0.1≦the average value of [I(A) / I(B)]≦0.25; and / or the positive electrode material also satisfies a standard deviation of [I(A) / I(C)] of ≦0.02; and / or the positive electrode material also satisfies a standard deviation of [I(A) / I(B)] of ≦0.02; and / or the positive electrode material also satisfies an average value of [I(B) / I(C)]≦1, preferably an average value of [I(B) / I(C)]≦0.

9.

3. The base has a composition shown in Formula I: Li ａ Mn １－ｘ Fe ｘ M ｂ (2O ４ ) ｃ (I), wherein M is selected from at least one of Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and 0.95≦a≦1.1, 0≦x≦1, 0≦b≦0.2, and 1≦c≦1.1; Preferably, in Formula I, M is selected from at least one of Ti, W, Co, V, and Mg, and 1≦a≦1.05, 0.3≦x≦1, 0.1≦b≦0.2, and 1≦c≦1.

05.

4. The content of the carbon coating layer is 0.8-3 wt %, preferably 1-2.5 wt %, based on the total weight of the positive electrode material; and / or the thickness of the carbon coating layer is 1-10 nm, preferably 1.5-5 nm; and / or the average particle size of the base is 40-290 nm, preferably 70-230 nm; And / or the cathode material according to any one of claims 1 to 3, wherein the average particle size of the cathode material is 50-300 nm, preferably 80-240 nm.

5. The specific surface area BET of the positive electrode material is 5-40 m ２ / g, preferably 8-25m ２ / g, and / or the volume resistivity of the positive electrode material is 0-200 Ω cm, preferably 0-100 Ω cm; and / or the compaction density of the positive electrode material is 2-2.7 g / m ３ and preferably 2.2-2.6 g / m ３ The positive electrode material according to any one of claims 1 to 4,

6. 6. A method for preparing a cathode material having an olivine structure according to claim 1, comprising: mixing a Mn source, an Fe source, an M source, a phosphorus source, a Li source, an organic carbon source, and water; and sequentially pulverizing, spray-drying, and sintering the resulting mixed slurry to form a carbon coating layer on a surface of a base having Formula I, thereby obtaining a cathode material; and performing the sintering in an inert atmosphere. Here, the particle size D of the pulverization ５０ is 0.1 μm≦D ５０ ≦0.48 μm, and preferably 0.15 μm≦D ５０ Controlled to satisfy ≦0.36 μm, Here, Li ａ Mn １－ｘ Fe ｘ M ｂ (P.O. ４ ) ｃ (I), M is selected from at least one of Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and 0.95≦a≦1.1, 0≦x≦1, 0≦b≦0.2, and 1≦c≦1.

1.

7. The dosages of the Mn source, Fe source, M source, phosphorus source and Li source satisfy n(Mn):n(Fe):n(M):n(P):n(Li), where 0≦n(Mn)≦1, 0≦n(Fe)≦1, 0≦n(M)≦0.2, 1≦n(P)≦1.1, 0.95≦n(Li)≦1.1, preferably 0≦n(Mn)≦0.7, 0.3≦n(Fe)≦1, 0.1≦n(M)≦0.2, 1≦n(P)≦1.05, 1≦n(Li)≦1.05; and / or the M source is selected from compounds containing Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, and Gd, and is preferably selected from compounds containing Ti, W, Co, V, and Mg; and / or the Li source is selected from at least one of lithium dihydrogen phosphate, lithium carbonate, lithium oxalate, lithium oxide, lithium powder, and lithium phosphate; and / or the phosphorus source is selected from at least one of lithium dihydrogen phosphate, iron manganese phosphate monohydrate, iron phosphate, diphosphorus pentoxide, and phosphoric acid; and / or the amount of the organic carbon source added satisfies that the content of the carbon coating layer in the positive electrode material is 0.8 to 3 wt %, preferably 1 to 2.5 wt %; and / or the organic carbon source is selected from at least one of glucose, sucrose, starch, polyethylene, polyvinylpyrrolidone, tannic acid and polydopamine, more preferably selected from at least one of glucose, sucrose and starch, and at least one of polyethylene, polyvinylpyrrolidone, tannic acid and polydopamine.

8. 8. The method according to claim 6 or 7, wherein the Mn source and the Fe source are each independently selected from at least one of an element, an oxide, a carbonate, an oxalate, and a phosphate.

9. The preparation method comprises: (I-1) mixing the Mn source, Fe source, M source, phosphorus source, Li source, first carbon source, and water, and sequentially subjecting the obtained first slurry to a first pulverization, a first spray drying, and a first sintering to obtain a first sintered product; and (I-2) mixing the first sintered product and a second carbon source in water, and sequentially subjecting the obtained second slurry to a second pulverization, a second spray drying, and a second sintering to obtain a second sintered product as the positive electrode material, The organic carbon source is divided into the first carbon source and the second carbon source, and the second crushing particle size D ２ ５０ is 0.1 μm≦D ２ ５０ ≦0.48 μm, and preferably 0.15 μm≦D ２ ５０ The method according to any one of claims 6 to 8, wherein the first sintering and the second sintering are independently carried out in an inert atmosphere.

10. In step (I-1), the mass ratio of the first carbon source to the second carbon source is 0.1-1:1, preferably 0.15-0.8:1; and / or the first carbon source is selected from at least one of glucose, sucrose, starch, and polyethylene; and the second carbon source is selected from at least one of glucose, sucrose, and starch, and at least one of polyethylene, polyvinylpyrrolidone, tannic acid, and polydopamine; and / or the first pulverization includes a first coarse pulverization and a first fine pulverization, and the particle size D' of the first coarse pulverization １ ５０ is 0.3 μm≦D′ １ ５０ The value is controlled to satisfy the condition of 0.5 μm≦D′≦10 μm, and preferably 0.5 μm≦D′. １ ５０ The particle size D of the first fine grinding is controlled to satisfy the following: １ ５０ is 0.1 μm≦D １ ５０ ≦0.5 μm, and preferably 0.2 μm≦D １ ５０ Controlled to satisfy ≦0.4 μm, and / or the particle size D″ of the first spray drying １ ５０ is 2 μm≦D″ １ ５０ ≦30 μm, and preferably 5 μm≦D″ １ ５０ Controlled to satisfy ≦20 μm, and / or the first sintering conditions include: a temperature T1 of 350-650°C, preferably 400-600°C; a heating rate V1 of 0.5-10°C / min, preferably 1-5°C / min; and a constant temperature time t1 of 0.5-6 hours, preferably 1-3 hours; And / or, in step (I-2), the particle size D'' of the second spray drying ２ ５０ is 2 μm≦D″ ２ ５０ ≦30 μm, and preferably 5 μm≦D″ ２ ５０ Controlled to satisfy ≦20 μm, and / or the second sintering conditions include: a temperature T2 of 550-850°C, preferably 600-750°C; a heating rate V2 of 0.5-50°C / min, preferably 0.8-5°C / min; and an isothermal time t2 of 2-14h, preferably 6-12h.

11. The preparation method comprises: (II) mixing the Mn source, Fe source, M source, phosphorus source, Li source, organic carbon source, and water, and sequentially subjecting the obtained third slurry to a third pulverization, a third spray drying, and a third sintering to obtain a third sintered product, wherein the particle size D of the third pulverization is ３ ５０ is 0.1 μm≦D ３ ５０ ≦0.48 μm, and preferably 0.15 μm≦D ３ ５０ ≦0.36 μm, and the third sintering is performed in an inert atmosphere; The method according to any one of claims 6 to 8, wherein when the base represented by formula I simultaneously contains Mn and Fe, the Mn source and the Fe source are each independently selected from compounds simultaneously containing Mn and Fe; or when the base represented by formula I does not simultaneously contain Mn and Fe, the Mn source is selected from manganese phosphate and the Fe source is selected from iron phosphate.

12. In step (II), The third pulverization includes a third coarse pulverization and a third fine pulverization, and the particle size D' of the third coarse pulverization ３ ５０ is 0.3 μm≦D′ ３ ５０ The value is controlled to satisfy the condition of 0.5 μm≦D′≦10 μm, and preferably 0.5 μm≦D′. ３ ５０ The particle size D of the third fine grinding is controlled to satisfy the following: ３ ５０ is 0.1 μm≦D ３ ５０ ≦0.48 μm, and preferably 0.15 μm≦D ３ ５０ Controlled to satisfy ≦0.36 μm, and / or the third spray-dried particle size D'' ３ ５０ is 2 μm≦D″ ３ ５０ ≦30 μm, and preferably 5 μm≦D″ ３ ５０ Controlled to satisfy ≦20 μm, and / or the third sintering conditions include: a temperature T3 of 550-850°C, preferably 600-750°C; a heating rate V3 of 0.5-50°C / min, preferably 0.8-5°C / min; and an isothermal time t3 of 2-14h, preferably 6-12h.

13. A lithium ion battery, characterized in that the lithium ion battery is selected from the cathode material according to any one of claims 1 to 5 or the cathode material produced by the preparation method according to any one of claims 6 to 12.

Images