Cathode material having an olivine structure and method for preparing the same, 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 more specifically to a cathode material having an olivine structure, a method for preparing a cathode material having an olivine structure, and a lithium-ion battery containing the cathode material having an olivine structure. [Background technology]

[0002] Lithium-ion batteries are widely used in new energy vehicles, mobile electronic devices, new power batteries, and energy storage due to their advantages of long cycle life, high energy density, and lack of memory effect. As a crucial component, the cathode material plays a vital role in the overall performance indicators of lithium-ion batteries, particularly in its electrochemical properties.

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

number

[0004] CN115863596A utilizes an annular carbon composition with flexibility and a large specific surface area, which is advantageous for realizing the adhesion of lithium iron manganese phosphate, enhancing the uniformity of the carbon layer, forming a continuous conductive network, and improving the conductivity and stability of the lithium iron manganese phosphate composite material. In the process of preparing the annular carbon composition, this technology has a long preparation cycle, requires washing with a large amount of pure water, and emits toxic gases such as methanol. The present invention adopts a common and mass-produced organic carbon source, which can effectively reduce the production cost.

[0005] In the above prior art, in the olivine-structured cathode material with carbon coating, usually, I D / I G is used to characterize the graphitization degree of the coated carbon. However, the treatment temperature of the olivine-structured cathode material is low (generally <900 °C). In the process of forming an inorganic carbon coating layer by the organic carbon source, as the graphitization degree deepens, the sp 3 hybridization converts to sp 2 , and the performance characterization effect of I D / I G on the cathode material is relatively single. At the same time, both the thickness of the carbon coating layer and the quality of carbon formation affect the energy retention rate in the olivine structure cycling process.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In order to overcome the above technical problems, the present invention aims to provide a cathode material having an olivine structure and its preparation method, and a lithium-ion battery. The cathode material has the characteristics of uniform carbon coating, and thus has high stability, low specific surface area, low volume resistance, and high tap density. At the same time, when the cathode material is used in a lithium-ion battery, it has excellent electrochemical performance and improves the energy retention rate in the cycling process.

Means for Solving the Problems

[0007] To achieve the above objective, a first aspect of the present invention provides a cathode material having an olivine structure, wherein the cathode material comprises a base and a carbon coating layer, and in the Raman spectrum, the cathode material has a wavelength of 940-950 cm⁻¹. -1 , 1330-1350cm -1 , 1580-1610cm -1 A Raman response exists in the wavenumber range, corresponding to three characteristic peaks A, B, and C, respectively, where the positive electrode material satisfies the following conditions: the mean value of 0.01 ≤ [I(A) / I(C)] ≤ 0.3 and the mean value of 0.01 ≤ [I(A) / I(B)] ≤ 0.3.

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

[0009] The positive electrode material according to the present invention exhibits a Raman response within a specific wavenumber range, and the intensity ratio of the characteristic peaks is within a specific range, i.e., the mean value of 0.01 ≤ [I(A) / I(C)] ≤ 0.3 and the mean value of 0.01 ≤ [I(A) / I(B)] ≤ 0.3, and in particular, the standard deviation of [I(A) / I(C)] ≤ 0.02 and the standard deviation of [I(A) / I(B)] ≤ 0.02 are further restricted, the overall uniformity of the carbon coating of the positive electrode material is good, the thickness of the carbon coating layer is appropriate, and the content of disordered carbon and ordered carbon in the carbon coating layer is within an appropriate range, resulting in high compatibility with the base. With the same carbon coating layer content, the uniform carbon coating layer in 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 preparation 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, sequentially grinding, spray-drying and sintering the resulting mixed slurry, supporting a carbon coating layer on the surface of a base having formula I, and obtaining a cathode material, wherein the sintering is carried out in an inert atmosphere. Here, the particle size D of the grinding process 50 For 0.1 μm ≤ D 50 Satisfying ≤0.48μm, preferably 0.15μm ≤D 50Controlled to satisfy ≤0.36μm, Here, 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, such that 0.95 ≤ a ≤ 1.1, 0 ≤ x ≤ 1, 0 ≤ b ≤ 0.2, and 1 ≤ c ≤ 1.1.

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

[0012] Compared to the prior art, the present invention has the following advantages. (1) The present invention demonstrates that, under the same conditions, the carbon coating of the positive electrode material is uniform and of appropriate thickness, the degree of graphitization of the carbon coating layer is high, the compatibility with the base is high, and the carbon coating layer content is the same, the carbon coating layer in the present invention can effectively reduce the specific surface area and volume resistivity of the positive electrode material.

[0013] (2) The preparation method according to the present invention is based on a solid-phase process, controls the particle size range of the grinding process, and prepares a cathode material having an olivine structure uniformly coated with carbon, and in particular adjusts and controls the spray drying particle size, sintering temperature and type of organic carbon source to some extent, which affects the carbon coating layer content and coating effect.

[0014] Simultaneously, the preparation method also adjusts and controls the addition method of the organic carbon source based on the presence and type of addition of main metal elements other than Li (Mn and Fe) in the cathode material, thereby obtaining a cathode material uniformly coated with carbon.

[0015] (3) When the cathode material according to the present invention is applied to a lithium-ion battery, the electrochemical performance of the lithium-ion battery, particularly the energy retention rate, can be effectively improved. At the same time, the present invention provides different carbon formation characteristics, and cathode materials having an olivine structure have different characteristics in Raman properties, which are reflected in the retention of lithium-ion battery capacity and can better guide the preparation and process monitoring of cathode materials. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram of the Raman spectrum of the positive electrode material S1 manufactured in Example 1. [Modes for carrying out the invention]

[0017] The endpoints and any values ​​of the ranges disclosed herein should be understood to include values ​​close to such exact ranges or values, and not to be limited to such exact ranges or values. In the case of numerical ranges, the intervals between the endpoint values ​​of each range, between the endpoint values ​​of each range and individual point values, and between individual point values ​​combine to obtain one or more new numerical ranges, and these numerical ranges shall be deemed to be specifically disclosed in the specification.

[0018] In the present invention, unless otherwise specified, "first," "second," and "third" are used not to indicate priority or to serve a limiting role to individual items or steps, but solely to distinguish or explain that they are not the same item or step. For example, "first," "second," and "third" in "first slurry," "second slurry," and "third slurry" are used solely to explain that they are not the same slurry, and similarly, "first," "second," and "third" in "first sintering," "second sintering," and "third sintering" are used solely to explain that they are not the same sintering.

[0019] A first aspect of the present invention provides a cathode material having an olivine structure, the cathode material comprising a base and a carbon coating layer, and in the Raman spectrum, the cathode material is 940-950 cm⁻¹-1 , 1330-1350cm -1 , 1580-1610cm -1 A Raman response exists in the wavenumber range, corresponding to three characteristic peaks A, B, and C, respectively, where the positive electrode material satisfies the following conditions: the mean value of 0.01 ≤ [I(A) / I(C)] ≤ 0.3 and the mean value of 0.01 ≤ [I(A) / I(B)] ≤ 0.3.

[0020] In the present invention, unless otherwise specified, a Raman test is performed on the cathode material, and the measurement conditions include an excitation wavelength of 532 nm, a laser power of 0.1 mW, an objective lens magnification of 50 X, 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 such that the cathode material has a Raman spectrum of 940-950 cm⁻¹, respectively. -1 , 1330-1350cm -1 , 1580-1610cm -1 These are the intensities of the A, B, and C peaks corresponding to the wavenumber range, where I(A) / I(C) represents the intensity ratio of the A and C peaks in the Raman spectrum of the positive electrode material, and similarly, I(A) / I(B) represents the intensity ratio of the A and B peaks in the Raman spectrum of the positive electrode material.

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

[0023] In this invention, the average value of [I(A) / I(C)] represents 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)] represents 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 satisfies the mean value of 0.01 ≤ [I(A) / I(C)] ≤ 0.3, for example, any value within the range of 0.01, 0.05, 0.06, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3 and any two numerical values, preferably the mean value of 0.05 ≤ [I(A) / I(C)] ≤ 0.25, and more preferably 0.1 ≤ [I(A) / I(C)] The mean value of ] is ≤ 0.25, and the mean value of 0.01 ≤ [I(A) / I(B)] is ≤ 0.3, for example, 0.01, 0.05, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, and any value within the range of any two numbers are simultaneously satisfied, preferably 0.05 ≤ the mean value of [I(A) / I(B)] is ≤ 0.25, and more preferably 0.1 ≤ the mean value of [I(A) / I(B)] is ≤ 0.25.

[0025] In some embodiments of the present invention, preferably, the positive electrode material 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 standard deviation ranges of [I(A) / I(C)] and [I(A) / I(B)] are satisfied, the overall uniformity of the carbon coating layer of the positive electrode material is excellent and the thickness is appropriate, the degree of graphitization of the carbon coating layer is high, the specific surface area of ​​the positive electrode material is low and the volume resistivity is low, resulting in excellent performance.

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

[0027] In some embodiments of the present invention, preferably, the base has the composition shown in formula I, and Li a Mn 1-x Fe x M b (PO4) c (I), where 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.

[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, any value within the range of 0.95, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.1 and any two numerical values, preferably 1 ≤ a ≤ 1.05.

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

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

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

[0033] In this invention, the values ​​of a, x, b, c, and M in Equation I are adjusted and controlled to control the value of a within a certain range, thereby affecting the capacitance and consolidation level of the cathode material by influencing the proportion of Li in the cathode material, adjusting the value of x affects the voltage platform of the cathode material, adjusting the values ​​of b and M mainly affects the electrochemical dynamics and consolidation density of the cathode material, and adjusting the value of c affects the proportion of P in the material, similarly affecting the capacitance and consolidation density of the material.

[0034] In some embodiments of the present invention, the carbon coating layer content is preferably 0.8-3 wt%, based on the total weight of the positive electrode material, and is any value within the range of 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 two numbers, preferably 1-2.5 wt%. In the present invention, the carbon coating layer content parameter was 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, any value within the range of 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, 8 nm, 10 nm, and any two values, and is 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, any value within the range of 40 nm, 70 nm, 90 nm, 100 nm, 150 nm, 200 nm, 230 nm, 290 nm, and any two numerical values, 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, any value within the range of 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 240 nm, 300 nm, and 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, preferably, the specific surface area BET of the positive electrode material is 5-40 m². 2 / g, for example, 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 of any two numbers, preferably 8-25m 2 It is / 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, any value within the range of 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 two numerical values, preferably 0-100 Ω·cm.

[0040] In some embodiments of the present invention, preferably, the compaction density of the positive electrode material is 2-2.7 g / m³. 3 For example, 2g / m 32.2g / m 3 2.3g / m 3 2.4g / m 3 2.5g / m 3 2.6g / m 3 2.7g / m 3 , and any two numbers within the range, preferably 2.2-2.6 g / m 3 That is the case.

[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 consolidation density parameter is measured by the insitu 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 preparation 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, sequentially grinding, spray-drying and sintering the resulting mixed slurry, supporting a carbon coating layer on the surface of a base having formula I, and obtaining a cathode material, wherein the sintering is carried out in an inert atmosphere. Here, the particle size D of the grinding process 50 For 0.1 μm ≤ D 50 Satisfying ≤0.48μm, preferably 0.15μm ≤D 50 Controlled to satisfy ≤0.36μm, Here, 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, such that 0.95 ≤ a ≤ 1.1, 0 ≤ x ≤ 1, 0 ≤ b ≤ 0.2, and 1 ≤ c ≤ 1.1.

[0043] The preparation method according to the present invention prepares a cathode material having an olivine structure by a solid-phase coating method, resulting in a high-quality carbon coating effect. The cathode material possesses high stability and good electrochemical performance. At the same time, the preparation method simplifies the process flow, facilitates the use of the product, and when used in lithium-ion batteries, it can effectively improve the energy retention rate during the cycle process.

[0044] In the present invention, the particle size D of the pulverization 50 For 0.1 μm ≤ D 50 The value is controlled to satisfy ≤0.48μm, for example, any value within the range of 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.36μm, 0.4μm, 0.48μm, and any two numerical values, preferably 0.15μm ≤ D 50 The particle size D of the grinding is satisfied by ≤0.36 μm. 50 By adjusting and controlling the size of the primary particles in the positive electrode material, the uniformity and thickness of the carbon coating layer are affected, and the positive electrode material satisfies the following conditions: the mean value of 0.01 ≤ [I(A) / I(C)] ≤ 0.3 and the mean value of 0.01 ≤ [I(A) / I(B)] ≤ 0.3.

[0045] In some embodiments of the present invention, preferably, the M source is one of the following: Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, Gd at least one of A compound containing is selected, and more preferably the M source is Ti, W, Co, V and Mg at least one of the following It is selected from compounds containing [the specified compound].

[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, or an argon gas atmosphere.

[0047] In some embodiments of the present invention, preferably, the doses of the elements 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, and more preferably, 0≦n(Mn)≦0.7, 0.3≦n(Fe)≦1, 0.1≦n(M)≦0.2, 1≦n(P)≦1.05, and 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, the M source is 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 monohydrate, iron phosphate, and phosphorus 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 is 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 is adjusted according to the type of organic carbon source and the residual carbon content to satisfy the requirement that the carbon coating layer content in the positive electrode material is 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, the organic carbon source is 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 the organic carbon source is sintered is uniformly coated onto the surface of the base having formula I.

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

[0055] In some embodiments of the present invention, preferably, the Mn source and the Fe source are metal elements, and each is independently selected from at least one of elemental elements, oxides, carbonates, oxalates, and phosphates.

[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 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 tetroxide, ferrous oxalate, iron phosphate, iron manganese phosphate, iron manganese monohydrate, iron manganese carbonate, iron manganese oxalate, iron manganese hydroxide, iron manganese oxide, iron manganese oxyhydroxide, etc.

[0058] In a first specific embodiment of the present invention, preferably the preparation method includes the steps of (I-1) mixing the Mn source, Fe source, M source, phosphorus source, Li source, first carbon source and water, and sequentially performing a first grinding, first spray drying, and 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 grinding, second spray drying, and second sintering on the obtained second slurry, and using the obtained 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 particle size D of the second grinding 2 50 0.1μm≦D 2 50 Satisfying ≤0.48μm, preferably 0.15μm ≤D 2 50 The process is controlled to satisfy ≤0.36 μm, and the first and second sintering processes are carried out independently 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, for example, any value within the range of 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, and any two numerical values, preferably 0.15-0.8:1. In the present invention, satisfying the mass ratio within the above range effectively reduces the specific surface area of ​​the positive electrode material, increases the compaction density of the positive electrode material, and results in 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 grinding refers to grinding particles in a first slurry having a solid content of 30-50 wt%. Preferably, the first grinding includes a first coarse grinding and a first fine grinding, wherein the particle size D' of the first coarse grinding is... 1 50 0.3μm≦D' 1 50 The value is controlled to satisfy ≤10μm, for example, any value within the range of 0.3μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 8μm, 10μm, and any two numbers, preferably 0.5μm ≤ D'. 1 50 The particle size D of the first fine grind is ≤5 μm. 1 50 0.1μm≦D 1 50 The value is controlled to satisfy ≤0.5μm, for example, any value within the range of 0.1μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.5μm, and any two numerical values, preferably 0.2μm ≤D 1 50 The size is ≤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 50By adjusting and controlling [[ID=]], each component is more uniformly mixed, which is beneficial to the purity of the cathode material phase. If it is too coarse, it is disadvantageous to the homogenization of the components. If it is too fine, the difficulty of grinding is high, which affects the size of the primary particles after sintering. Furthermore, it affects the tap density and cycle stability of the cathode 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 surface of the particles in the first sintering.

[0063] In some embodiments of the present invention, preferably, the particle size D'' of the first spray drying 1 50 satisfies 2μm ≦ D'' 1 50 ≦ 30μm, for example, 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 30μm, and any value within the range consisting of any two numerical values. Preferably, 5μm ≦ D'' 1 50 ≦ 20μm. In the present invention, the first carbon source forms an effective coating on the surface of the spraying material along with the volatilization of the moisture in the first slurry during the first spray drying process. If the particle size of the spraying material is too large, it will affect the evaporation of the moisture of the particles, thereby affecting the uniform coating of the organic carbon source on the surface of the spraying material.

[0064] In some embodiments of the present invention, preferably, the conditions of the first sintering include that the temperature T1 is 350 - 650 °C, preferably 400 - 600 °C, the heating rate V1 is 0.5 - 10 °C / min, preferably 1 - 5 °C / min, and the holding time t1 is 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 aggregate, and the average particle size of the first sintered material is related to 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 of the second grinding 2 50 is controlled to satisfy 0.1 μm ≤ 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 the range composed of any two numerical values, preferably, 0.15 μm ≤ D 2 50 ≤ 0.36 μm is satisfied. In the present invention, by controlling the above range of the second grinding particle size D 2 50 a second carbon coating effect can be formed on the surface of the primary particles, whereby having specific I(A) / I(C) and I(A) / I(B).

[0067] In some embodiments of the present invention, preferably, the particle size D'' of the second spray drying 2 50 is controlled to satisfy 2 μm ≤ D'' 2 50 ≤ 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 the range composed of any two numerical values, preferably 5 μm ≤ D'' 2 50 ≤ 20 μm. A particle size of the second spray drying that is too small is disadvantageous for improving production efficiency, and a particle size that is too large is disadvantageous for the volatilization of moisture and affects the uniform adhesion of the second carbon source.

[0068] In some embodiments of the present invention, preferably, the conditions of the second sintering include that the temperature T2 is 550 - 850 °C, preferably 600 - 750 °C, the heating rate V2 is 0.5 - 50 °C / min, preferably 0.8 - 5 °C / min, and the holding time t2 is 2 - 14 h, preferably 6 - 12 h.

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

[0070] In a second specific embodiment of the present invention, preferably the preparation method includes the steps of (II) mixing the Mn source, Fe source, M source, phosphorus source, Li source, organic carbon source and water, and sequentially performing a third grinding, a third spray drying, and a third sintering on the obtained third slurry to obtain a third sintered product, wherein the particle size D of the third grinding 3 50 0.1μm≦D 3 50 The size is controlled to satisfy ≤0.48 μm, preferably 0.15 μm ≤ D 3 50 The thickness satisfies ≤0.36 μm, and the third sintering is carried out in an inert atmosphere. Here, if the base represented by formula I contains both Mn and Fe, the Mn source and the Fe source are independently selected from compounds containing both Mn and Fe. Alternatively, if the base represented by formula I does not contain Mn and Fe, the Mn source is selected from manganese phosphate and the Fe source is selected from iron phosphate.

[0071] In the present invention, comparing the two preparation methods described above, the first preparation method employs the technical means of two grindings, two spray dryings, and two sinterings, and the types of Mn and Fe sources in the raw materials are not limited in any way, that is, all Mn and Fe sources applicable to the above limitation, while the second preparation method employs the technical means of one grinding, one spray drying, and one sintering, and the types of Mn and Fe sources in the raw materials are limited.

[0072] At the same time, instead of using specific Mn and Fe sources as raw materials and employing a technique of one grinding, one spray drying, and one sintering, it is also possible to obtain a cathode material having a specific olivine structure, simplify the process flow, and save costs.

[0073] In the present invention, unless otherwise specified, when a base represented by formula I contains both Mn and Fe, it means that in formula I, the subscripts (1-x) and x of Mn and Fe are not equal to 0; when the Mn source and Fe source are independently selected from compounds containing both Mn and Fe, it 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; when a base represented by formula I does not contain both Mn and Fe, it 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, the base represented by formula I contains both Mn and Fe, and the Mn source and Fe source are each independently selected from compounds that contain both Mn and Fe. Preferably, the Mn source and Fe source are each independently selected from at least one of iron manganese phosphate, manganese iron phosphate monohydrate, iron manganese carbonate, iron manganese oxalate, iron manganese hydroxide, iron manganese oxide, and iron manganese oxyhydroxide.

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

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

[0077] In some embodiments of the present invention, preferably the particle size D'' of the third spray drying. 3 50 2μm ≤ D'' 3 50 The value is controlled to satisfy ≤30μm, for example, any value within the range of 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 30μm, and any two numbers, preferably 5μm ≤ D''. 3 50 The size is ≤20μm.

[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 2-14h, preferably 6-12h.

[0079] In the present invention, when the third sintering temperature T3 is low, the degree of graphitization of the carbon coating layer of the positive electrode material decreases, the carbon content increases, the corresponding [I(A) / I(C)] and [I(A) / I(B)] decrease, the specific surface area BET improves, the compaction density decreases, the resistance increases, and to some extent the performance of electrochemical properties. When the third sintering temperature T3 is high, the carbon content of the carbon coating layer of the positive electrode material decreases, the average value of [I(B) / I(C)] decreases, the degree of graphitization improves, primary particles grow, the compaction density of the material improves, the specific surface area decreases, and it is advantageous for improving electrochemical and processing performance.

[0080] A third aspect of the present invention provides a lithium-ion battery, the lithium-ion battery containing a positive electrode material according to the first aspect, or a positive electrode material manufactured 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 properties of the cathode materials produced in both the examples and comparative examples.

[0082] Energy retention rate 80 th Measurement method: (1) The assembled battery, the positive electrode material to be measured, the conductive agent (acetylene black), and the adhesive (PVDF) are mixed with a solvent (NMP) in a mass ratio of 95:3:2 (at a temperature of 25°C, a rotation speed of 1000 rpm, and a time of 40 min) to obtain a positive electrode slurry with a solid content of 40 wt%. The above positive electrode slurry is applied to the surface of an aluminum foil, a positive electrode slurry coating is formed on the surface of the aluminum foil, and after drying at 135°C, it is roll-pressed (at a pressure of 15T) using a roll press machine to form a positive electrode active material layer on the surface of the aluminum foil, thereby obtaining a positive electrode piece. In a gas glove box filled with argon gas containing less than 5 ppm of both water and oxygen, the positive electrode, separator, negative electrode, and electrolyte were assembled into a 2025-type button cell and left to stand for 6 hours. In this test, a lithium metal sheet with a diameter of 16 mm and a thickness of 0.5 mm was used for the negative electrode, a polyethylene porous membrane (Celgard 2325) with a thickness of 25 μm was used for the separator, and the electrolyte was an equal mixture of 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 cell was subjected to two charge / discharge cycles at 0.1C, followed by 80 charge / discharge cycles at 1C. The initial discharge ratio capacity at 0.1C was the discharge ratio capacity of the button cell after the first cycle, and the discharge ratio capacity at 1C after the 80th cycle was the discharge ratio capacity of the button cell after the 80th cycle.

[0084] Here, the energy retention rate is 80 th = (Discharge ratio capacity of the button battery after 80 cycles / Discharge ratio capacity of the button battery after 1 cycle) × 100%.

[0085] Example 1 (1) A manganese source (trimanganese 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 with a solid content of 40 wt%, and the elemental moles are of 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 described above is subjected to a first coarse grinding, and the particle size D' of the first coarsely ground material is obtained. 1 50 =3.3μm, and the first coarsely ground material is subjected to the first fine grinding, and the D of the first finely ground material 1 50 = 0.3 μm, The first finely ground material is subjected to a first spray drying process, and the 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 described above was subjected to a first sintering process in a nitrogen gas atmosphere, heated to T1=500°C at a heating rate of V1=1.5°C / min, and held at t1=3h. The average particle size of the first sintered material was 10.5 μm, the primary particle size was 80 nm, and the specific surface area was 7.3 m². 2 / g (2) The first sintered material is dispersed in water, and a second carbon source (with a mass ratio of glucose to PEG of 5.6:4) is added 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 and second carbon sources added satisfies the requirement that the carbon coating layer content in the finished cathode material is 1.57 wt%. The second slurry described above is subjected to a second grinding process, and the second grinding material D 2 50 = 0.25 μm, The second pulverized material is subjected to a second spray drying process, and the D'' of the second spray-dried material is obtained. 2 50 = 8.0 μm, and BET = 8.8 m 2 / g The second spray-dried material described above is subjected to a second sintering process, where the temperature is raised to T2 = 675°C at a heating rate of V2 = 1.5°C / min, and the temperature is maintained for t2 = 10 hours to obtain the second sintered material. The second sintered material described above 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 Figure 1. As can be seen from Figure 1, the positive electrode material S1 has a Raman spectrum of 950 cm⁻¹. -1 , 1350cm -1 and 1580cm -1 Peaks A, B, and C appear near the Raman displacement, and peaks A, B, and C are each located within the PO4 in the base. 3- These 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 and second carbon sources added satisfies the requirement that the carbon coating layer content in the finished cathode material is 1.85 wt%. D of the second crushed material 2 50 = 0.25 μm, The second pulverized material is subjected to a second spray drying process, and the D'' of the second spray-dried material is obtained. 2 50 = 8.3 μm, and BET = 9.1 m 2 Other than being / g, Under similar conditions, the positive electrode material S2 is obtained.

[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 and second carbon sources added satisfies the requirement that the carbon coating layer content in the finished cathode material is 1.55 wt%. D of the second crushed material 2 50 = 0.25 μm, The second pulverized material is subjected to a second spray drying process, and the D'' of the second spray-dried material is obtained. 2 50 = 8.8 μm, and BET = 8.5 m 2 Other than being / g, Under similar conditions, the positive electrode material S3 is obtained.

[0089] Example 4 A manganese source (manganese iron phosphate monohydrate), an iron source (manganese iron phosphate monohydrate), a lithium source (lithium dihydrogen phosphate, lithium carbonate), a phosphorus source (lithium dihydrogen phosphate, manganese iron 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 determined to be Li 1.04 Mn 0.65 Fe 0.35 Ti 0.05 W 0.05 (PO4) 1.01 The amount of the above organic carbon source added is such that the carbon content of the carbon coating layer in the finished cathode material is 1.83 wt%. The third slurry described above is subjected to a third coarse grinding process, and the D' of the third coarsely ground material is obtained. 3 50 =2μm, and the third coarse pulverized material is subjected to a third fine pulverization, and the D of the third fine pulverized material 3 50 = 0.3 μm, The third finely ground material is subjected to a third spray drying process, and the D'' of the third spray-dried material is obtained. 3 50 = 10.8 μm, and BET = 30.1 μm, The third spray-dried material described above is subjected to a third sintering process, the temperature is raised 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 cathode material S4 having an olivine structure.

[0090] Example 5 An iron source (iron phosphate), a lithium source (lithium carbonate), a phosphorus source (iron phosphate), 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 45 wt%, and the elemental moles were of the chemical formula Li 1.04 Fe La 0.05 W 0.05 (PO4) 1.03 The amount of the above organic carbon source added is such that the carbon content of the carbon coating layer in the finished cathode material is 1.40 wt%. The third slurry described above is subjected to a third coarse grinding process, and the D' of the third coarsely ground material is obtained.3 50 = 2.8 μm, and the third coarse pulverized material is subjected to a third fine pulverization, and the D of the third fine pulverized material 3 50 = 0.35 μm, The third finely ground material is subjected to a third spray drying process, and the 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 described above is subjected to a third sintering process, the temperature is raised 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 cathode material S5 having an olivine structure.

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

[0092] Under similar conditions, a cathode 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 and second carbon sources added is in accordance with the method of Example 1, except that the carbon coating layer content in the finished cathode material is 1.67 wt%.

[0093] Under similar conditions, a cathode material S7 having an olivine structure is obtained. Comparative Example 1 Third finely ground material D 3 50 The procedure is carried out according to the method of Example 4, except that the thickness is controlled to be 0.5 μm.

[0094] Under similar conditions, the olivine structure cathode material DS1 is obtained. Comparative Example 2 In step (2), the second crushed material D 2 50 The procedure is carried out according to the method of Example 1, except that the particle size is adjusted to 0.5 μm.

[0095] Under similar conditions, we obtain the olivine structure cathode material DS2.

[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, and changing the preparation process, sintering temperature, grinding particle size, and type of organic carbon source for the cathode material having an olivine structure, the carbon coating layer content and coating effect can be affected to some extent.

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

[0101] By comparing Example 1 and Example 3, it can be seen that by adjusting the amount of the second carbon source added, the mass ratio of the first carbon source to the second carbon source can be adjusted and controlled at the same sintering temperature and carbon coating layer content, thereby reducing the specific surface area of ​​the cathode material, improving the compaction density, and achieving a better degree of graphitization.

[0102] Samples of the cathode material S3 manufactured in Example 3 were measured at two laser intensities, 0.1 mW and 0.3 mW. When the 0.3 mW laser intensity was used, the mean and standard deviation of [I(A) / I(C)] were 0.31 and 0.03, respectively, and the mean and standard deviation of [I(A) / I(B)] were 0.38 and 0.03, respectively, while the mean of [I(B) / I(C)] was 0.81. In other words, when the 0.3 mW laser intensity was used compared to the 0.1 mW laser intensity, both the mean and standard deviation of [I(A) / I(C)] and [I(A) / I(B)] increased. This is because the surface carbon coating layer is destroyed to some extent during the measurement process, resulting in a non-uniform and thin carbon coating layer, which enhances the A signal and simultaneously increases the standard deviation. Therefore, when characterizing this feature of the material, it is necessary to limit the laser intensity to a specific value.

[0103] By comparing Example 2 and Example 4, it can be seen that when the same olivine structure cathode material is prepared using different processes, the average values ​​of [I(A) / I(C)] and [I(A) / I(B)] show similar rules, indicating that these rules can effectively guide the preparation of cathode materials using different preparation processes.

[0104] By comparing Examples 4-5, it can be seen that when two different cathode materials are prepared using a similar process, a certain difference exists in the average values ​​of [I(A) / I(C)] and [I(A) / I(B)] due to differences in sintering temperature, carbon load, and grinding particle size. 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 carbon coating layer content, decreases the average values ​​of the corresponding [I(A) / I(C)] and [I(A) / I(B)], increases BET, decreases the compaction density, increases the resistance, and to some extent affects the performance of the electrochemical properties.

[0106] By 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 process affects the quality of the carbon coating layer on the surface of the positive electrode material, resulting in abnormalities in both the mean 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 pulverized particle size, the carbon is unfavorable to uniformly coat the primary particles of the positive electrode material during the sintering process, and some primary particles may be exposed, resulting in an enhancement of the A signal and abnormalities in both the mean and standard deviation of [I(A) / I(C)] and [I(A) / I(B)].

[0108] Preferred embodiments of the present invention have been described in detail above, but 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 to include various combinations of technical features in any other suitable manner, and these simple modifications and combinations shall likewise be considered to be within the scope of the disclosure of the present invention and shall be protected by the present invention.

Claims

1. A cathode material having an olivine structure, wherein the cathode material comprises a base and a carbon coating layer, and in a Raman spectral test with a laser power of 0.1 mW, the cathode material measures 940–950 cm⁻¹. －１ , 1330-1350cm －１ , 1580-1610cm －１ A Raman response exists in the wavenumber range, corresponding to three characteristic peaks A, B, and C, respectively, where the positive electrode material has an olivine structure characterized by satisfying the following conditions: 0.11 ≤ [I(A) / I(C)] mean < 0.3 and 0.01 ≤ [I(A) / I(B)] mean ≤ 0.

13. The base has the composition shown in formula I, Li a Mn 1-x Fe x M b (PO 4 ) c (I), Here, 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 is a positive electrode material with the following properties: 0.95 ≤ a ≤ 1.1, 0 < x ≤ 0.5, 0.1 ≤ b ≤ 0.2, and 1 ≤ c ≤ 1.

1.

2. The positive electrode material also satisfies the standard deviation of [I(A) / I(C)] ≤ 0.02, and / or, the positive electrode material also satisfies the standard deviation of [I(A) / I(B)] ≤ 0.02, and / or, the positive electrode material according to claim 1, wherein the positive electrode material also satisfies the mean value of [I(B) / I(C)] ≤ 1.

3. Based on the total weight of the positive electrode material, the carbon coating layer content is 0.8-3 wt%, and / or, the thickness of the carbon coating layer is 1-10 nm. and / or, the average particle size of the base is 40-290 nm, The cathode material according to claim 1, and / or, the average particle size of the cathode material is 50-300 nm.

4. The specific surface area BET of the aforementioned cathode material is 5-40 m². ２ / g, And / or, the volume resistivity of the positive electrode material is 0-200 Ω·cm. and / or, the compaction density of the positive electrode material is 2–2.7 g / m³ ３ The positive electrode material according to claim 1.

5. A method for preparing a cathode material having an olivine structure as described in claim 1, wherein the preparation method involves mixing a Mn source, an Fe source, an M source, a phosphorus source, a Li source, an organic carbon source and water, sequentially grinding, spray drying and sintering the resulting mixed slurry, supporting a carbon coating layer on the surface of a base having formula I to obtain a cathode material, and the sintering is carried out in an inert atmosphere. Here, the particle size D of the pulverization ５０ 0.1 μm ≤ D ５０ A method for preparing a positive electrode material, characterized by controlling the material to satisfy ≤0.48 μm.

6. The doses of the Mn source, Fe source, M source, phosphorus source, and Li source satisfy the following conditions: 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, and 0.95≦n(Li)≦1.

1. and / or, the M source is selected from compounds containing at least one of Ti, Mg, V, W, Nb, La, Cr, Mo, Ca, Zn, Y, Zr, Sm, Co, Ni, B, Cu, Gd, 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 monohydrate, iron phosphate, phosphorus pentoxide, and phosphoric acid. and / or, the amount of the organic carbon source added satisfies the requirement that the carbon coating layer content in the positive electrode material is 0.8-3 wt%, The preparation method according to claim 5, wherein the organic carbon source is selected from at least one of glucose, sucrose, starch, polyethylene, polyvinylpyrrolidone, tannic acid, and polydopamine.

7. The preparation method according to claim 5, wherein the metal element, the Mn source and the Fe source, are each independently selected from at least one of elemental form, oxide, carbonate, oxalate, and phosphate.

8. The aforementioned preparation method is (I-1) The steps include mixing the Mn source, Fe source, M source, phosphorus source, Li source, first carbon source and water, and sequentially performing a first grinding, first spray drying, and 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 grinding, second spray drying, and second sintering on the obtained second slurry, and using the obtained 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 particle size D of the second grinding ２ ５０ is controlled to satisfy 0.1 μm ≦ D ２ ５０ ≦ 0.48 μm, wherein the first sintering and the second sintering are each independently carried out in an inert atmosphere. The preparation method according to claim 5.

9. In step (I-1), the mass ratio of the first carbon source to the second carbon source is 0.1-1:

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 grinding comprises a first coarse grinding and a first fine grinding, wherein the particle size D' of the first coarse grinding is... １ ５０ 0.3 μm ≤ D' １ ５０ The particle size D of the first fine grinding is controlled to satisfy ≤10 μm. １ ５０ 0.1 μm ≤ D １ ５０ Controlled to satisfy ≤0.5 μm, and / or the particle size D'' of the first spray drying. １ ５０ 2 μm ≤ D'' １ ５０ Control to satisfy ≤30 μm, And / or, the first sintering conditions include a temperature T1 of 350-650°C, a heating rate V1 of 0.5-10°C / min, and a constant temperature time t1 of 0.5-6h. and / or, in step (I-2), the particle size D'' of the second spray drying ２ ５０ 2 μm ≤ D'' ２ ５０ Control to satisfy ≤30 μm, The preparation method according to claim 8, and / or the second sintering conditions comprising a temperature T2 of 550-850°C, a heating rate V2 of 0.5-50°C / min, and a constant temperature time t2 of 2-14h.

10. The aforementioned preparation method is (II) The process includes the steps of mixing the Mn source, Fe source, M source, phosphorus source, Li source, organic carbon source and water, and sequentially performing a third grinding, a third spray drying, and a third sintering on the obtained third slurry to obtain a third sintered product, wherein the particle size D of the third grinding ３ ５０ 0.1 μm ≤ D ３ ５０ The third sintering is performed in an inert atmosphere, with the particle size controlled to satisfy ≤0.48 μm. The preparation method according to claim 5, wherein, if the base represented by formula I contains both Mn and Fe, the Mn source and the Fe source are each independently selected from compounds containing both Mn and Fe, or, if the base represented by formula I does not contain both Mn and Fe, the Mn source is selected from manganese phosphate and the Fe source is selected from iron phosphate.

11. In step (II), The third grinding includes a third coarse grinding and a third fine grinding, wherein the particle size D' of the third coarse grinding is... ３ ５０ 0.3 μm ≤ D' ３ ５０ The particle size D of the third fine grind is controlled to satisfy ≤10 μm. ３ ５０ 0.1 μm ≤ D ３ ５０ Controlled to satisfy ≤0.48 μm, and / or the particle size D'' of the third spray drying. ３ ５０ 2 μm ≤ D'' ３ ５０ Control to satisfy ≤30 μm, The preparation method according to claim 10, and / or the third sintering condition comprising a temperature T3 of 550-850°C, a heating rate V3 of 0.5-50°C / min, and a constant temperature time t3 of 2-14h.

12. A lithium-ion battery, characterized in that the lithium-ion battery is selected from the positive electrode material described in any one of claims 1 to 4.

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