Positive electrode active material and method for manufacturing the same, battery

Abstract

The present invention discloses a positive electrode active material, a method for manufacturing the same, and a battery. The positive electrode active material includes an inner core containing lithium metal phosphate, a first coating layer covering at least a portion of the surface of the inner core, and a second coating layer covering at least a portion of the surface of the first coating layer. The XRD diffraction peak intensity of the positive electrode active material in the range of diffraction angle 2θ being 35.5°-35.7° is S1. The XRD diffraction peak intensity of the positive electrode active material in the range of diffraction angle 2θ being 24.1°-25.4° is S2. S2 / S1 is (0.005-0.05):1. The XRD diffraction peak intensity of the positive electrode active material in the range of diffraction angle 2θ being 28.8°-29.2° is S3. S3 / S1 is (0.005-0.05):1.

Description

Technical Field

[0001] (Cross - reference to related applications) This application claims priority based on a Chinese patent application (application number 202410705712.7) filed in China on May 31, 2024, and incorporates the entire disclosure of this previous application herein for reference purposes.

[0002] The present invention relates to the technical field of batteries, particularly to cathode active materials and their manufacturing methods, and to batteries.

Background Art

[0003] As electric vehicles, and typical power batteries and energy storage batteries in the energy storage function market develop rapidly, people have put forward high requirements for the energy density, cycle life, and safety performance of current lithium - ion batteries. The performance of cathode active materials is an important factor affecting the performance of lithium - ion batteries. Among many cathode active material systems, cathode active materials represented by lithium metal phosphates have received wide attention. Taking lithium iron phosphate as an example, lithium iron phosphate has a theoretical specific capacity of 170 mAh / g, an operating voltage level of 3.4 V, and the corresponding theoretical specific energy is only 578 Wh / kg, which cannot meet the increasingly growing demand for battery energy density in the future power and energy storage markets. By adding doping elements, etc., it is possible to increase the theoretical capacity and operating voltage level of the cathode active material, but there are problems such as insufficient capacity utilization and poor cycle performance, and further improvement of the current cathode active material is expected.

Summary of the Invention

Means for Solving the Problems

[0004] In the first aspect of the present invention, a positive electrode active material is proposed. The positive electrode active material includes a core containing a lithium metal phosphate, a first coating layer covering at least a part of the surface of the core, and a second coating layer covering at least a part of the surface of the first coating layer. The XRD diffraction peak intensity of the positive electrode active material within the range of diffraction angle 2θ of 35.5° - 35.7° is S1. The XRD diffraction peak intensity of the positive electrode active material within the range of diffraction angle 2θ of 24.1° - 25.4° is S2. S2 / S1 is (0.005 - 0.05):1. The XRD diffraction peak intensity of the positive electrode active material within the range of diffraction angle 2θ of 28.8° - 29.2° is S3. S3 / S1 is (0.005 - 0.05):1. Thereby, the positive electrode active material has high gram capacity, excellent ion conductivity and electron conductivity, and excellent structural stability.

[0005] In some embodiments, S2 / S1 is (0.01 - 0.03):1, and / or S3 / S1 is (0.01 - 0.02):1.

[0006] In some embodiments, the first coating layer contains a hexagonal fast ion conductor, and / or the second coating layer contains an orthorhombic fast ion conductor and a carbon material. Thereby, the rate performance of the positive electrode active material is improved.

[0007] In some embodiments, the lithium metal phosphate has the general formula Li 1+a Fe x G y M 1 -x-y PO4C z satisfying -0.2 ≦ a ≦ 0.2, 0 < x < 1, 0 ≦ y ≦ 0.05, 0 ≦ z ≦ 0.1, M includes at least one of Mn, Co, V and Ni, and G includes at least one of Ga, Sn, V, Mo, Al, Mg, Ce, Ti, Zr, Nb, Si, W and In. Thereby, the positive electrode active material has a high operating voltage level and gram capacity.

[0008] In some embodiments, the hexagonal fast ion conductor has the general formula Li b M1 d M 2 e M 3 u (PO4) w1 (RO v ) w2 satisfies, where M 1 includes at least one of Mg, Na, and K, and M 2 includes at least one of Al, Ga, In, Y, and Sc, and M 3 includes at least one of Ti, Zr, and Ge, R includes at least one of Si, Cl, Br, S, Sb, Sn, F, and P, 0 ≦ b < 3, 0 ≦ d ≦ 0.1, 0 ≦ e ≦ 1, 0 ≦ u ≦ 1, 1 ≦ w1 ≦ 3, 0 ≦ v ≦ 4, 0 ≦ w2 ≦ 0.5. Thereby, the first coating layer effectively reduces the ion permeation resistance at the interface of the inner core.

[0009] In some embodiments, the orthorhombic high - speed ion conductor satisfies the general formula Li3M 4 t Ti 2-t (PO4)3, where M 4 includes at least one of Al, Ga, In, Y, and Sc, and 0 ≦ t ≦ 1. Thereby, the second coating layer plays a role in stabilizing the structure of the positive electrode active material and suppressing the elution of transition metals.

[0010] In some embodiments, the mass fraction of carbon in the lithium metal phosphate is 0.5% - 3%, and / or the mass fraction of carbon in the second coating layer is 1% - 5%. Thereby, the positive electrode active material has excellent electronic conductivity.

[0011] In some embodiments, the mass fraction of carbon in the positive electrode active material is 1% - 4%. Thereby, the positive electrode active material has a high gram capacity.

[0012] A second aspect of the present invention proposes a method for producing the positive electrode active material. The method includes the steps of: mixing a first lithium source with a first metal source and a first phosphorus source to obtain a first paste, and first sintering the first paste in an inactive atmosphere to obtain a core; mixing a second lithium source with a second metal source and a second phosphorus source to obtain a second paste, and second sintering the second paste in an oxygen atmosphere to obtain a powder for the first coating layer; and uniformly mixing the core with the powder for the first coating layer, and subsequently mixing it with a third lithium source, a titanium source, a third phosphorus source and a second carbon source to obtain a third paste, and third sintering the third paste in an inactive atmosphere to obtain a positive electrode active material. As a result, the positive electrode active material has a simple manufacturing method, is easy to control stably during the manufacturing process, and has low manufacturing costs.

[0013] In some embodiments, the first paste satisfies at least one of the following conditions: The first lithium source comprises at least one of lithium carbonate, lithium hydroxide, and lithium nitrate. The first metal source comprises at least one of an iron source, an M source, and a G source, wherein the iron source comprises at least one of iron phosphate, iron nitrate, and ferrous nitrate; the M source comprises at least one of a phosphate, nitrate, carbonate, and oxide corresponding to element M; and the G source comprises at least one of a nitrate, carbonate, and oxide corresponding to element G. The first phosphorus source comprises at least one of iron phosphate, iron manganese phosphate, phosphoric acid, hemiphosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxide. It further comprises a first carbon source, wherein the first carbon source comprises at least one of glucose, sucrose, starch, graphene, and carbon nanotubes. This allows for the production of the inner core in a fairly simple manner.

[0014] In some embodiments, the second paste satisfies at least one of the following conditions: The second lithium source comprises at least one of lithium carbonate and lithium hydroxide. The second phosphorus source comprises at least one of phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphorus oxide. The second metal source is M 1 Source, M. 2 Source and M3 Including at least one source, among which the M 1 The source is M 1 It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, and the M 2 The source is M 2 It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, and the M 3 The source is M 3 It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element. It further comprises an R source, the R source comprising at least one of the element, acid, and oxides corresponding to the R element. This allows for obtaining a first coating layer in a fairly simple manner.

[0015] In some embodiments, the third paste satisfies at least one of the following conditions: The third lithium source comprises at least one of lithium carbonate and lithium hydroxide. The titanium source comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element titanium. The third phosphorus source comprises at least one of phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides. The second carbon source comprises at least one of glucose, sucrose, starch, graphite, carbon nanotubes, and graphene. 4 The source further includes the M 4 The source is M 4 It contains at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element. This allows for the production of a cathode active material in a fairly simple manner.

[0016] In some implementations, the temperature of the first sintering is 600°C-800°C, the duration of the first sintering is 6h-12h, and / or the temperature of the second sintering is 700°C-900°C, the duration of the second sintering is 8h-12h, and / or the temperature of the third sintering is 300°C-600°C, the duration of the third sintering is 6h-12h. This increases the yield of the cathode active material.

[0017] In some embodiments, the solid content of the first paste, the second paste, and the third paste is independently 10 wt% to 70 wt%, and / or the average particle size of the first paste is 500 nm or less, and / or the average particle size of the second paste is 200 nm or less, and / or the average particle size of the third paste is 1 μm or less, and / or the solvent of the first paste, the second paste, and the third paste independently contains at least one of water, isopropanol, ethanol, and ethylene glycol. This improves the processing performance of the paste.

[0018] In a third aspect of the present invention, a battery is proposed. The battery comprises a positive electrode piece. The positive electrode piece contains the positive electrode active material. Therefore, since the battery possesses all the features and advantages of the positive electrode material and its manufacturing method, there is no need to repeat them here. [Effects of the Invention]

[0019] The above and / or additional aspects and advantages of the present invention will become clearer and easier to understand together with the description of the embodiments in conjunction with the following drawings. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic diagram of the structure of the positive electrode active material of one embodiment of the present invention. [Figure 2] This is a flowchart illustrating a method for producing a cathode active material according to one embodiment of the present invention. [Figure 3] This is a flowchart illustrating a method for producing a cathode active material according to another embodiment of the present invention. [Figure 4] These are the XRD patterns of the positive electrode active materials of Example 1 and Comparative Example 1 within the range of 10°-80° for 2θ. [Figure 5] These are the XRD patterns of the cathode active materials of Example 1 and Comparative Example 1 within the range of 2θ from 23° to 37°. [Figure 6]This is a charge / discharge curve diagram of the battery in Example 1 and Proportional 1. [Modes for carrying out the invention]

[0021] Next, embodiments of the present invention will be described in detail, and examples of these embodiments will be shown in the drawings, although unnecessary details may be omitted. For example, detailed explanations of already known matters or repeated explanations of the same structure may be omitted. This is to prevent the following explanation from being unnecessarily verbose and to facilitate understanding for those skilled in the art. In addition, the drawings and the following explanation are provided for those skilled in the art to fully understand the present invention and are not intended to limit the subject matter described in the claims.

[0022] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those commonly used in the art relating to this invention. The terms used in this invention are not limited to this invention solely for the purpose of describing specific embodiments. Unless otherwise specified, the values ​​of each parameter mentioned in this invention can be measured by various general measurement methods of the art (for example, by measuring according to the methods shown in the embodiments of this invention).

[0023] The terms "includes" and "has" in the description and claims of this invention, and any variation thereof, are non-excludable; that is, they include the contents described in this invention but do not exclude other contents.

[0024] Regardless of whether words such as "about" or "approximately" are used in the description of this invention, all figures mentioned herein are approximations. There may be differences of less than 10% in the numerical values ​​of each figure, or differences that would be considered reasonable to those skilled in the art, such as differences of 1%, 2%, 3%, 4%, or 5%.

[0025] In this invention, the order in which each step is described does not imply a strict order of execution, nor does it impose any limitations on the implementation process. The specific execution order of each step should be determined in accordance with its function and possible underlying logic. Unless otherwise specified, all steps of this invention may be performed sequentially or randomly, preferably in order. For example, if the method includes step (a) and step (b), the method may be performed sequentially in the order of step (a)-step (b), or in the order of step (b)-step (a). For example, if the method further includes step (c), the method may be performed sequentially in the order of step (a)-step (b)-step (c), or in the order of step (a)-step (c)-step (b).

[0026] Unless otherwise specified, all embodiments and optional embodiments of the present invention may be combined to form new technical means.

[0027] Unless otherwise specified, all technical features of the present invention, as well as the selectable technical features, may be combined with each other to form new technical means.

[0028] Taking lithium iron phosphate as an example of a cathode active material, adding doping elements, such as manganese doping iron, can improve the material's operating voltage level and gram capacity. However, this can lead to excessively low electronic and ionic conductivity, resulting in poor capacity utilization. Furthermore, the Kyō-Taylor effect of manganese ions impairs the structural stability of the cathode active material, leading to iron leaching. Coating the surface of the cathode active material with carbon does not effectively resolve problems such as the Kyō-Taylor effect caused by manganese ions and the leaching of transition metal iron, resulting in a reduced circulation performance of the cathode active material.

[0029] In this invention, by optimizing the material composition and crystal system structure, the problems of low electronic and ionic conductivity and easy elution of transition metals in current olivine-structured cathode active materials are effectively solved. Specifically, the X-ray diffraction peak of the cathode active material in the range of diffraction angle 2θ of 35.5°-35.7° corresponds to the diffraction peak of the inner core of the olivine structure and corresponds to the (311) crystal plane of the Pnma(62) space group of the olivine structure. The X-ray diffraction peak of the cathode active material in the range of diffraction angle 2θ of 24.1°-25.4° corresponds to the diffraction peak of a hexagonal fast ion conductor and corresponds to the (113) crystal plane of the hexagonal crystal system. The X-ray diffraction peak of the active material corresponds to the diffraction peak of an orthorhombic fast ion conductor and corresponds to the (024) crystal plane of the orthorhombic system. This allows the olivine core structure to be used to increase the operating voltage level of the positive electrode active material and increase its energy density. Furthermore, by building a protective layer of fast ion conductor on the surface of the core, direct exposure of the core to the electrolyte during the charge-discharge process can be effectively suppressed, stabilizing the structure, preventing the dissolution of transition metals, and significantly improving the circulation and safety performance of the positive electrode active material. Moreover, the intensity ratio of the characteristic X-ray diffraction peaks between the core and the coating layer can reflect the content ratio of the core to the coating layer. When S2 / S1 is (0.005-0.05) and S3 / S1 is (0.005-0.05):1, the first and second coating layers enhance the ionic and electronic conductivity of the cathode active material, suppressing the elution of transition metals from the cathode active material. Furthermore, because the coating layers occupy a relatively small proportion of the cathode active material, they have little effect on the gram capacity of the cathode active material, thus contributing to the full utilization of the high-capacity inner core.

[0030] The (113) crystal plane of the hexagonal system is the strongest diffraction peak of the first coating layer affected by X-ray radiation, and does not overlap with the diffraction peaks of the inner core and second coating layer affected by X-ray radiation.

[0031] The (024) crystal plane of the orthorhombic system is the third strongest peak among the diffraction peaks of the second coating layer related to X-ray radiation, and its standard peak intensity is 50% of the strongest peak, and it does not overlap with the diffraction peaks of the inner core and the first coating layer related to X-ray radiation.

[0032] In a first embodiment of the present invention, a positive electrode active material is proposed. As shown in Figure 1, the positive electrode active material includes an inner core 100 containing lithium metal phosphate, a first coating layer 210 covering at least a portion of the surface of the inner core 100, and a second coating layer 220 covering at least a portion of the surface of the first coating layer 210. The XRD diffraction peak intensity of the positive electrode active material in the range of diffraction angle 2θ being 35.5°-35.7° is S1. The XRD diffraction peak intensity of the positive electrode active material in the range of diffraction angle 2θ being 24.1°-25.4° is S2. S2 / S1 is (0.005-0.05):1. The XRD diffraction peak intensity of the positive electrode active material in the range of diffraction angle 2θ being 28.8°-29.2° is S3. S3 / S1 is (0.005-0.05):1. As a result, the positive electrode active material possesses high gram capacity, excellent ionic and electronic conductivity, and superior structural stability. This allows for improved magnification and circulation performance of batteries using this positive electrode active material.

[0033] For example, S2 / S1 could be 0.005:1, 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, 0.035:1, 0.04:1, 0.045:1, or 0.05:1.

[0034] For example, S3 / S1 could be 0.005:1, 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, 0.035:1, 0.04:1, 0.045:1, or 0.05:1.

[0035] In some implementations, S2 / S1 is (0.01-0.03):1 and / or S3 / S1 is (0.01-0.02):1.

[0036] In some implementations, the first coating layer 210 contains a hexagonal high-speed ionic conductor.

[0037] The first coating layer 210 is a solid electrolyte having a structure similar to NASICON (Na Superionic Conductor, a high-speed ion conductor). When the first coating layer has a hexagonal crystal structure, it has higher ionic conductivity and effectively reduces the ion permeation resistance of the inner core of the olivine structure at the interface.

[0038] In some implementations, the cathode active material exhibits diffraction peaks of hexagonal high-speed ion conductors related to X-rays within the range of diffraction angle 2θ of 28.8°-29.2°, which correspond to the (10⁴) crystal plane of the hexagonal system.

[0039] In some implementations, the second coating layer 220 includes an orthorhombic high-speed ionic conductor and a carbon material.

[0040] The second coating layer 220 contains a solid electrolyte and graphitized carbon material having a structure similar to NASICON (Na Superionic Conductor). The second coating layer 220 effectively suppresses direct exposure of the inner core 100 to the electrolyte during the charge-discharge process, stabilizing the structure and preventing the elution of transition metals. Furthermore, the second coating layer 220 has high electronic conductivity, effectively lowering the electron transmission resistance of the coated olivine structure's inner core at the interface, improving the material's circulation performance and safety performance.

[0041] In some implementations, the cathode active material exhibits diffraction peaks of orthorhombic high-speed ion conductors related to X-rays within the range of diffraction angle 2θ of 19.6°-19.8°, which correspond to the (10⁴) crystal plane of the orthorhombic system.

[0042] In some implementations, the mass ratio of the primary coating layer 210 to the inner core 100 is (1-3):100.

[0043] The core 100 is a material with an olivine structure having a high voltage and a high capacity. An appropriate amount of the first coating layer can improve the ion conductivity of the cathode active material. However, since the first coating layer cannot provide capacity, when the mass ratio of the first coating layer to the core is suppressed within the above range, the first coating layer 210 not only increases the ion conductivity of the cathode active material but also has a small impact on the gram capacity of the cathode active material.

[0044] In some embodiments, the mass ratio of the second coating layer 220 to the core 100 is (2-4):100. Thereby, the second coating layer 220 not only increases the electron conductivity of the cathode active material and suppresses the elution of transition metals in the cathode active material but also has a small impact on the gram capacity of the cathode active material.

[0045] The core 100 is a material with an olivine structure having a high voltage and a high capacity. An appropriate amount of the second coating layer can improve the electron-ion conductivity of the cathode active material and reduce the occurrence of side reactions between the core and the electrolyte. However, since the second coating layer cannot provide capacity, when the mass ratio of the second coating layer to the core is suppressed within the above range, the second coating layer 220 not only increases the electron-ion conductivity of the cathode active material and reduces the occurrence of side reactions but also has a small impact on the gram capacity of the cathode active material.

[0046] In some embodiments, the lithium metal phosphate has the general formula Li 1+a Fe x G y M 1-x-y PO4C z satisfies, in the formula, -0.2 ≦ a ≦ 0.2, 0 < x < 1, 0 ≦ y ≦ 0.05, 0 ≦ z ≦ 0.1, M includes at least one of Mn, Co, V, and Ni, and G includes at least one of Ga, Sn, V, Mo, Al, Mg, Ce, Ti, Zr, Nb, Si, W, and In. Thereby, the cathode active material has a high operating voltage level and gram capacity.

[0047] In some embodiments, -0.2 ≦ a ≦ 0.2, 0 < x < 1, 0.001 ≦ y ≦ 0.05, 0.001 ≦ z ≦ 0.1.

[0048] By comprehensively doping lithium iron phosphate with elements, the electronic conductivity of lithium iron phosphate is effectively increased, thereby forming a stable polyvalent anion structure in the core, exhibiting excellent circulatory stability, a voltage level higher than 3.4V during the charge-discharge process, and a significantly higher theoretical specific capacity compared to lithium iron phosphate.

[0049] In some implementations, it is possible to add a carbon source during the manufacturing process of lithium metal phosphate, thereby creating electron channels at the grain boundaries of the core and further increasing the electron conductivity of the core, which in turn causes the core of lithium metal phosphate to contain carbon.

[0050] During the charging and discharging process of a battery, situations such as the uninsertion and depletion of lithium, and the replenishment of lithium occur, resulting in different molar content of lithium in different discharge states. In the example related to the core in this invention, the molar content of lithium corresponds to the initial state of the material, that is, the state before raw material supply. When the positive electrode active material is applied to the battery system and undergoes a charging and discharging cycle, the molar content of lithium changes.

[0051] In some implementations, the hexagonal high-speed ionic conductor is a Li b M 1 d M 2 e M 3 u (PO4) w1 (RO v ) w2 The formula satisfies the condition, and the formula contains M 1 It contains at least one of Mg, Na, and K, M 2 It includes at least one of Al, Ga, In, Y, and Sc, and M 3 R contains at least one of Ti, Zr, and Ge, and R contains at least one of Si, Cl, Br, S, Sb, Sn, F, and P, with 0≦b<3, 0≦d≦0.1, 0≦e≦1, 0≦u≦1, 1≦w1≦3, 0≦v≦4, and 0≦w2≦0.5. Thus, the first coating layer 210 effectively reduces the ion permeation resistance at the interface of the inner core 100.

[0052] In some implementations, the conditions are 0.001≦b<3, 0.001≦d≦0.1, 0.001≦e≦1, 0.001≦u≦1, 1≦w1≦3, 0.001≦v≦4, and 0.001≦w2≦0.5.

[0053] When the first coating layer 210 is a high-speed ionic conductor having a hexagonal crystal structure that satisfies the above conditions, the first coating layer can stabilize the surface interface structure of the core material 100, thereby giving the core a capacity retention rate close to that of lithium iron phosphate crystals. Furthermore, because the first coating layer is a solid electrolyte with high ionic conductivity, the coated olivine-structured core has low ion permeation resistance at the interface and excellent magnification performance.

[0054] For example, since the core 100 is oxidizing, if a hexagonal high-speed ionic conductor contains tetravalent titanium ions, the hexagonal coating layer is less likely to oxidize after coming into contact with the core, and the first coating layer has high structural stability.

[0055] In some implementations, the orthorhombic high-speed ionic conductor has the general formula Li3M 4 t Ti 2-t (PO4)3 is satisfied, and in the formula, M 4 The material contains at least one of Al, Ga, In, Y, and Sc, and 0 ≤ t ≤ 1. Thus, the second coating layer 220 stabilizes the cathode active material structure and suppresses the elution of transition metals.

[0056] When the second coating layer 220 contains a high-speed ionic conductor having a tetragonal structure that satisfies the above conditions, the second coating layer can stabilize the surface interface structure of the core material 100, thereby giving the core a capacitance retention rate close to that of lithium iron phosphate. Furthermore, the high-speed ionic conductor having a tetragonal structure has high electronic conductivity after bonding with the graphitized carbon material, and the ion permeation resistance of the coated olivine structure core at the interface is low. Thus, the first and second coating layers achieve coating of the ion and electron mixed conductor of the core, giving the positive electrode active material excellent magnification performance.

[0057] For example, since the electrolyte has reducing properties and the core 100 has oxidizing properties, if the core comes into direct contact with the electrolyte, side reactions occur, causing adverse effects such as the dissolution of metal elements within the core. When the second coating layer 220 contains trivalent titanium ions, the second coating layer is less likely to be reduced after coming into contact with the electrolyte, thereby improving the chemical stability between the positive electrode active material and the electrolyte, and suppressing the reduction and dissolution of transition metal elements in the core 100 by the electrolyte.

[0058] For example, when an orthorhombic high-speed ionic conductor contains Li3Ti2(PO4)3, the anodic active material has two discharge levels at 4.0V and 3.5V during the 2.0V-4.25V charge-discharge process, as well as a discharge level at 2.8V corresponding to orthorhombic Li3Ti2(PO4)3.

[0059] In some implementations, the mass fraction of carbon in the lithium metal phosphate is 0.5%-3%.

[0060] To keep the mass fraction of carbon in lithium metal phosphate within the above range, a carbon source is added during the manufacturing process of lithium metal phosphate, and the grain boundaries and surface of the core are coated with carbon to create three-dimensional electron conduction channels and increase the electron conductivity of the core.

[0061] In some implementations, the mass fraction of carbon in the second coating layer is 1%-5%.

[0062] To keep the mass fraction of carbon in the second coating layer within the above range, three-dimensional electron conduction channels are constructed by coating the grain boundaries and surface of the inner core and the first coating layer with carbon, thereby increasing the electron conductivity of the cathode active material.

[0063] In some implementations, the mass fraction of carbon in the cathode active material is 1%-4%. This results in the cathode active material having a high gram capacity.

[0064] When the mass fraction of carbon in the cathode active material is kept within the above range, an appropriate amount of carbon element forms three-dimensional electron conduction channels, which not only increases the electron conductivity of the cathode active material but also has a small effect on the gram capacity of the cathode active material, thereby improving the discharge capacity and magnification performance of the cathode active material.

[0065] In some implementations, the average particle size Dv50 of the cathode active material can range from 0.5 μm to 20 μm. For example, the average particle size Dv50 of the cathode active material and the core may be measured using a laser particle size analyzer.

[0066] In a second aspect of the present invention, a method for producing the positive electrode active material is proposed. This method is simple, the manufacturing process is easy to control stably, the method for introducing doping elements and electron conduction channels is simple, the performance improvement effect is significant, and the manufacturing cost is low. Specifically, the method for producing the positive electrode active material includes the following steps.

[0067] S110, the first lithium source is mixed with the first metal source and the first phosphorus source to obtain the first paste.

[0068] In some implementations, in this step, the first lithium source, the first metal source, and the first phosphorus source are mixed with a solvent to obtain the first paste. Thus, the first paste can be sintered to obtain the core material.

[0069] In some embodiments, the first lithium source comprises at least one of lithium carbonate, lithium hydroxide, and lithium nitrate.

[0070] In some embodiments, the first metal source comprises at least one of an iron source, an M source, and a G source, wherein the iron source comprises at least one of iron phosphate, iron nitrate, and ferrous nitrate; the M source comprises at least one of a phosphate, nitrate, carbonate, and oxide corresponding to element M; and the G source comprises at least one of a nitrate, carbonate, and oxide corresponding to element G.

[0071] In some embodiments, the first phosphorus source includes at least one of iron phosphate, iron manganese phosphate, phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides.

[0072] In some implementations, referring to step S111 in Figure 3, a first lithium source, a first metal source, and a first phosphorus source are mixed with a solvent to obtain a first paste. Thus, the first paste can be sintered to obtain a core material. Specifically, the first carbon source includes at least one of glucose, sucrose, starch, graphene, and carbon nanotubes. By adding the first carbon source, electron channels can be built in the grain boundaries of the core, thereby increasing the electron conductivity of the core.

[0073] In some implementations, the solid content of the first paste is between 10 wt% and 70 wt%.

[0074] In some implementations, the average particle size of the first paste is 500 nm or less, for example, the average particle size of the first paste may be 5 nm-100 nm, 10 nm-200 nm, or 50 nm-500 nm.

[0075] In some embodiments, the solvent of the first paste comprises at least one of water, isopropanol, ethanol, and ethylene glycol.

[0076] Naturally, some of the primary carbon source is lost during the initial sintering process, and volatile substances such as carbon dioxide are generated. Therefore, the amount of primary carbon source added to the primary paste may be greater than the design value for the product.

[0077] S120, the first paste is initially sintered under an inactive atmosphere.

[0078] In some implementations, this step involves drying the first paste and then first sintering it under an inert atmosphere to obtain the inner core of the olivine structure.

[0079] In some implementations, the initial sintering temperature is 600°C-800°C, and the initial sintering time is 6h-12h.

[0080] When the temperature and time of the initial sintering are kept within the above range, the formation of the olivine core is promoted, the physical crystal system has high structural stability, there are few impurities, and the particle size of the formed core granules is appropriate.

[0081] In some implementations, the inert atmosphere includes nitrogen and / or argon.

[0082] In some implementations, the drying process satisfies the conditions of setting the drying temperature to 80°C–400°C, for example, 100°C–300°C, and the drying time to 0.1h–10h, for example, 0.5h–3h. Furthermore, the drying equipment includes at least one of a spray dryer, a fluidized bed dryer, a strip dryer, a flash evaporator dryer, and a multi-cavity polishing machine.

[0083] S210, the second lithium source is mixed with the second metal source and the second phosphorus source to obtain the second paste.

[0084] In some implementations, a second paste is obtained by mixing raw material compounds for forming the first coating layer with a solvent. Specifically, a second paste can be obtained by mixing a second lithium source, a second metal source, and a second phosphorus source. Thus, the powder material for the first coating layer can be obtained by sintering the second paste.

[0085] In some embodiments, the second lithium source comprises at least one of lithium carbonate and lithium hydroxide.

[0086] In some embodiments, the second phosphorus source includes at least one of phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides.

[0087] In some implementations, the second metal source is M 1 Source, M. 2 Source and M 3Including at least one source, among which the M 1 The source is M 1 It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, and the M 2 The source is M 2 It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, and the M 3 The source is M 3 It contains at least one of the following: an oxide, hydroxide, nitrate, oxalate, organic alcohol salt, and carbonate corresponding to an element.

[0088] In some implementations, referring to step S211 in Figure 3, in this step, a second lithium source, a second metal source, a second phosphorus source, and an R source are mixed with a solvent to obtain a second paste. The R source comprises at least one of the element, acid, and oxide corresponding to the R element.

[0089] In some implementations, the solid content of the second paste is 10 wt% to 70 wt%.

[0090] In some implementations, the average particle size of the second paste is 200 nm or less, and specifically, the average particle size of the second paste may be 5 nm-100 nm or 10 nm-200 nm, etc.

[0091] In some implementations, the solvent of the second paste comprises at least one of water, isopropanol, ethanol, and ethylene glycol.

[0092] S220, the second paste is sintered a second time under an oxygen atmosphere.

[0093] In some implementations, this step involves drying the second paste and sintering it a second time in an oxygen atmosphere to obtain a micrometer-sized powder material for the first coating layer, then nano-processing the powder material in a solvent to obtain a hexagonal nano-sized powder material for the first coating layer after drying.

[0094] In some implementations, the temperature of the second sintering is 700°C-900°C, and the duration of the second sintering is 8h-12h.

[0095] When the temperature and time of the second sintering are kept within the above range, the formation of the hexagonal first coating layer powder is promoted, and the stability of the physical crystal structure is high, with fewer impurities.

[0096] In some operational conditions, the oxygen atmosphere contains oxygen gas.

[0097] In some implementations, the drying process satisfies the conditions of setting the drying temperature to 80°C–400°C, for example, 100°C–300°C, and the drying time to 0.1h–10h, for example, 0.5h–3h. Furthermore, the drying equipment includes at least one of a spray dryer, a fluidized bed dryer, a strip dryer, a flash evaporator dryer, and a multi-cavity polishing machine.

[0098] Naturally, the order in which the nano-grade powder materials for the core and the first coating layer are manufactured does not matter; both can be manufactured before the second coating layer is formed. Those skilled in the art can choose the order according to the actual situation.

[0099] S310, the step of obtaining the powder of the first coating layer, uniformly mixing the inner core with the powder of the first coating layer, and then mixing it with a third lithium source, a titanium source, a third phosphorus source and a second carbon source to obtain a third paste.

[0100] In some implementations, in this step, the inner core of the olivine structure is uniformly mixed with the powder of the first coating layer, and then mixed with a third lithium source, a titanium source, a third phosphorus source, a second carbon source, and a solvent to obtain a third paste.

[0101] In some embodiments, the third lithium source includes at least one of lithium carbonate and lithium hydroxide.

[0102] In some embodiments, the titanium source comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element titanium.

[0103] In some embodiments, the third phosphorus source includes at least one of phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides.

[0104] In some implementations, the second carbon source includes at least one of glucose, sucrose, starch, graphite, carbon nanotubes, and graphene.

[0105] By adding a second carbon source, conductive channels can be built on the surface of the cathode active material, thereby increasing the electronic conductivity of the cathode active material.

[0106] In some implementations, refer to step S311 in Figure 3, in which the inner core is uniformly mixed with the powder of the first coating layer, and then the third lithium source, titanium source, third phosphorus source, second carbon source, M 4 The source and solvent are mixed to obtain a third paste. 4 The source is M 4 It contains at least one of the following: an oxide, hydroxide, nitrate, oxalate, organic alcohol salt, and carbonate corresponding to an element.

[0107] In some implementations, the solid content of the third paste is between 10 wt% and 70 wt%.

[0108] In some implementations, the average particle size of the third paste is 1 μm or less. For example, the average particle size of the third paste may be 5 nm-100 nm, 10 nm-200 nm, 50 nm-500 nm, or 200 nm-1 μm.

[0109] In some implementations, the solvent of the third paste comprises at least one of water, isopropanol, ethanol, and ethylene glycol.

[0110] Naturally, during the third sintering process, some of the second carbon source is lost, and volatile substances such as carbon dioxide are generated. Therefore, the amount of the second carbon source added to the third paste may be greater than the product's design value.

[0111] S320, the third paste is sintered for the third time in an inactive atmosphere.

[0112] In some implementations, the third paste is dried in this step and then sintered in an inert atmosphere to obtain the cathode active material.

[0113] In some implementations, the temperature of the third sintering is 300°C-600°C, and the duration of the third sintering is 6h-12h. This increases the yield of the cathode active material.

[0114] When the temperature and time of the third sintering are kept within the above range, the formation of the orthorhombic second coating layer is promoted, and the physical crystal structure is highly stable with fewer impurities.

[0115] In some implementations, the inert atmosphere includes nitrogen and / or argon.

[0116] In some implementations, the drying process satisfies the conditions of setting the drying temperature to 80°C–400°C, for example, 100°C–300°C, and the drying time to 0.1h–10h, for example, 0.5h–3h. Furthermore, the drying equipment includes at least one of a spray dryer, a fluidized bed dryer, a strip dryer, a flash evaporator dryer, and a multi-cavity polishing machine.

[0117] In some implementations, after the third sintering process, crushing may be performed to obtain cathode active material of appropriate particle size. Crushing equipment may include colloidal mills, mechanical polishers, jet mills, etc.

[0118] In a third aspect of the present invention, a battery is proposed. The battery comprises the positive electrode material. The positive electrode material includes the positive electrode active material. Therefore, since the battery possesses all the features and advantages of the positive electrode material and its manufacturing method, there is no need to repeat them here.

[0119] The technical means of the present invention will now be described through specific examples, but these examples are for illustrative purposes only and do not limit the scope of the invention. Any techniques or conditions not explicitly stated in the examples should be understood in accordance with the techniques or conditions described in the literature in the art or in the product descriptions. Unless the manufacturer is indicated on the required equipment or reagents, they are considered to be commercially available products.

[0120] Example 1 (1) Li:Fe:Mn:P:C (carbon source) = 1.03:0.3:0.7:1:1.16 Lithium carbonate, iron phosphate, manganese oxide, phosphoric acid, and glucose are mixed with pure water, and the mixture is ball-milled for 4 hours using zirconium oxide in a ball mill to obtain a first paste with an average particle size of less than 500 nm. The first paste is processed using a spray dryer to obtain a powder, and the powder is sintered at 700°C for 8 hours under a nitrogen atmosphere in a tube furnace. The sintered material is dissociated and sieved, and finally the composition of Li 1.03 Mn 0.7 Fe 0.3 PO4 / C 0.16 It acquires the following core.

[0121] (2) Li:Al:Ti:P = 1.3:0.3:1.7:3 is mixed with pure water, and the mixture is ball-milled using zirconium oxide for 4 hours to obtain a paste with an average particle size of less than 500 nm. The paste is then processed using a spray dryer to obtain a powder, and the powder is sintered at 700°C for 8 hours in an air atmosphere in a box furnace. The sintered material is ball-milled using zirconium oxide for 6 hours to obtain a second paste with an average particle size of less than 200 nm. The second paste is then processed using a spray dryer to obtain a powder, and the powder is dissociated and sieved to obtain the final Li 1.3 Al 0.3 Ti 1.7 A nano-grade powder is obtained for the first coating layer, which is (PO4)3.

[0122] (3) The inner core obtained in (1), the nano-grade powder of the first coating layer obtained in (2), lithium carbonate, titanium dioxide, ammonium dihydrogen phosphate, and glucose are mixed with pure water according to the molar ratio of Mn:Al:Li:Ti:P:C=70:0.3:3:2:3:16, and the ball milling is performed for 4 hours using zirconium oxide in a ball mill to obtain a third paste with an average particle size of less than 1 μm. The third paste is processed using a spray dryer to obtain a powder, and the powder is sintered at 500°C for 6 hours under a nitrogen atmosphere. Finally, the sintered material is crushed to obtain a cathode active material, and the composition of the second coating layer is graphitized carbon and Li3Ti2(PO4)3.

[0123] Example 2 Example 2 differs from Example 1 in that, in step (3), the nano-grade powders of the inner core obtained in (1), the first coating layer obtained in (2), lithium carbonate, titanium dioxide, ammonium dihydrogen phosphate, and glucose are mixed with pure water according to the molar ratio Mn:Al:Li:Ti:P:C=70:1.5:15:10:15:16, but is otherwise the same.

[0124] Example 3 Example 3 differs from Example 1 in that, in step (3), the nano-grade powders of the inner core obtained in (1), the first coating layer obtained in (2), lithium carbonate, titanium dioxide, ammonium dihydrogen phosphate, and glucose are mixed with pure water according to the molar ratio Mn:Al:Li:Ti:P:C=70:0.3:15:10:15:16, but is otherwise the same.

[0125] Example 4 Example 4 involves mixing lithium carbonate, titanium dioxide, iron phosphate, manganese oxide, phosphoric acid, and glucose with pure water in a molar ratio of Li:Ti:Fe:Mn:P:C (carbon source) = 1.03:0.01:0.3:0.699:1:1.16 in step (1), and then ball milling with zirconium oxide for 4 hours to obtain a first paste with an average particle size of less than 500 nm. The first paste is then processed using a spray dryer to obtain a powder, and the powder is sintered at 700°C for 8 hours under a nitrogen atmosphere in a tube furnace. The sintered material is then dissociated and sieved, and finally the composition of Li 1.03 Mn 0.699 Ti 0.01 Fe 0.3 PO4 / C 0.16 This example differs from Example 1 in that it acquires a core structure that is the same in all other respects.

[0126] Example 5 Example 5 involves mixing lithium carbonate, aluminum oxide, titanium oxide, ammonium dihydrogen phosphate, and silicic acid with pure water in a molar ratio of Li:Al:Ti:P:Si = 1.3:0.3:1.7:2.98:0.03 in step (2), and ball milling with zirconium oxide for 4 hours to obtain a paste with an average particle size of less than 500 nm. The paste is then processed using a spray dryer to obtain a powder, and the powder is sintered at 700°C for 8 hours in an air atmosphere in a box furnace. The sintered material is then ball milled with zirconium oxide for 6 hours to obtain a second paste with an average particle size of less than 200 nm. The second paste is then processed using a spray dryer to obtain a powder, which is then dissociated and sieved to obtain the final Li 1.3 Al 0.3 Ti1.7 (PO4) 2.98 (SiO3) 0.03 It is different from Example 1 in that nanoscale powder of the first coating layer is obtained, and the other points are the same.

[0127] Example 6 In Example 6, in step (3), the core obtained in (1), the nanoscale powder of the first coating layer obtained in (2), lithium carbonate, yttrium oxide, titanium oxide, ammonium dihydrogen phosphate and glucose are mixed with pure water according to the molar ratio of Mn:Al:Li:Y:Ti:P:C = 70:0.3:3:0.01:1.99:3:16, and ball milling is carried out for 4 hours using zirconium oxide in a ball mill to obtain a third paste with an average particle size of less than 1 μm. The third paste is processed using a spray dryer to obtain a powder, and the powder is sintered at 500 °C for 6 hours under a nitrogen atmosphere. Finally, the sintered material is crushed to obtain a cathode active material. The composition of the second coating layer is graphitized carbon and Li3Y 0.01 Ti 1.99 It is different from Example 1 in that it is (PO4)3, and the other points are the same.

[0128] Comparative Example 1 Comparative Example 1 is different from Example 1 in that the first coating layer and the second coating layer are not provided, and the other points are the same.

[0129] Comparative Example 2 Comparative Example 2 does not provide the second coating layer. Specifically, the core obtained in (1) and the nanoscale powder of the first coating layer obtained in (2) are mixed with pure water according to the molar ratio of Mn:Al = 70:0.3 related to the third paste to form a paste. The paste is processed using a spray dryer to obtain a powder, and the powder is dissociated and sieved. Finally, the Li 1.3 Al 0.3 Ti 1.7 It is different from Example 1 in that nanoscale powder of the first coating layer is obtained, and the other points are the same.

[0130] Comparative Example 3 Comparative Example 3 differs from Example 1 in that it does not have a second coating layer, specifically in that it does not add the nano-grade powder of the first coating layer to the third paste, but is otherwise the same.

[0131] Comparative Example 4 Comparative Example 4 differs from Example 1 in that, in relation to the third paste, the nano-grade powder of the inner core obtained in (1), the first coating layer obtained in (2), and glucose are mixed with pure water in a molar ratio of Mn:Al:C (carbon source) = 70:0.3:16, but is otherwise the same.

[0132] The configuration of the positive electrode active material in the above-described examples and proportionally is specifically shown in Table 1. [Table 1]

[0133] A button-type battery is assembled using the positive electrode active materials described in the above examples and comparative examples.

[0134] A paste is formed by mixing acetylene black and polyvinylidene fluoride (PVDF) according to a mass ratio of 90:5:5. This paste is applied to aluminum foil, dried, and then pressure-molded under a pressure of 100 MPa to produce a positive electrode piece with a diameter of 12 mm and a thickness of 120 μm. The positive electrode piece is placed in a vacuum drying box and dried at 120°C for 12 hours. A negative electrode piece is made from a Li metal piece with a diameter of 17 mm and a thickness of 1 mm. A diaphragm is made from a Celgard 2400 porous membrane with a thickness of 25 μm. The electrolyte is made from 1 mol / L LiPF6, and the solvent for the electrolyte is an equivolute mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). The 2025 type button cell is assembled using the positive electrode piece, diaphragm, negative electrode piece, and electrolyte in an argon-filled glove box with both moisture and oxygen content below 5 ppm.

[0135] Button-type batteries assembled with the positive electrode active materials described in the above examples and comparative examples were tested, and the test results are shown in Table 2.

[0136] Regarding the magnification performance, the battery was charged and discharged at a magnification of 0.1C and 1C within the range of 2.5V-4.3V at room temperature, and the discharge ratio capacity C at 0.1C was measured. 0.1C Discharge ratio capacity C at 1C 1C Compare with this. Magnification performance = C 1C / C 0.1C ×100%.

[0137] Regarding the circulating performance, the battery was subjected to 80 charge-discharge cycles under room temperature, 2.5V-4.3V, and 0.1C conditions. The discharge ratio capacity C0 in the first week was compared with the discharge ratio capacity C1 after the 80th week. Capacity retention rate = C1 / C0 × 100%.

[0138] Iron leaching is detected by the ICP method. Specifically, the battery is subjected to 80 charge-discharge cycles under conditions of 2.5V-4.3V and 0.1C at room temperature. After the cycles, the diaphragm and negative electrode piece are removed from the battery, dissolved in hydrochloric acid, and then placed in an ICP device to detect the Fe content. [Table 2]

[0139] Figure 5 shows the initial charge-discharge curves of the batteries in Example 1 and Comparative Example 1. Figures 4 and 5 show the XRD test results of the positive electrode active materials in Example 1 and Comparative Example 1. As shown in Figure 5, the positive electrode active material of Example 1 not only has a standard diffraction peak corresponding to LiFePO4, but also has a diffraction peak corresponding to the (113) crystal plane of the hexagonal first coating layer at 2θ = 24.5°, and a diffraction peak corresponding to the (024) crystal plane of the orthorhombic second coating layer near 2θ = 29.0°. The positive electrode active material of Comparative Example 1 has a standard diffraction peak corresponding to LiFePO4.

[0140] The battery performance of Examples 1-6 is superior to that of Comparative Examples 1-4. According to the test results, the first and second coating layers enhance the ionic and electronic conductivity of the positive electrode active material, suppressing the elution of transition metals from the positive electrode active material. Furthermore, because the coating layers occupy a relatively small proportion of the positive electrode active material, they have little effect on the charging capacity of the positive electrode active material, thus contributing to the full utilization of high-capacity nuclei.

[0141] In this description of the present invention, the terms "first" and "second" are used for descriptive purposes only and do not imply or indicate relative importance or the number of technical features. "First feature" and "second feature" may include one or more such features.

[0142] In the description of the present invention, the positioning of the first feature on the surface of the second feature means either that the first feature is in direct contact with the second feature, or that the first feature is not in direct contact with the second feature but is in contact with each other via another feature.

[0143] In the description of the present invention, "A and / or B" may include either A, B, or A and B, where A and B are merely examples and may be any technical features connected by "and / or" as described in the present invention.

[0144] The present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiment that has the same configuration as the essence of the technical concept and achieves the same effect within the scope of the technical means of the present invention is included in the technical scope of the present invention. Furthermore, various modifications of the embodiments that can be conceived by those skilled in the art, and other forms formed by combining some of the components of the embodiments, are also included in the scope of the present invention without departing from the spirit of the present invention. [Explanation of Symbols]

[0145] 100-inner core, 210-first covering layer, 220-second covering layer.

Claims

1. It comprises an inner core containing lithium metal phosphate, a first coating layer covering at least a portion of the surface of the inner core, and a second coating layer covering at least a portion of the surface of the first coating layer, The XRD diffraction peak intensity in the range of diffraction angle 2θ from 35.5° to 35.7° is S1, the XRD diffraction peak intensity in the range of diffraction angle 2θ from 24.1° to 25.4° is S2, and S2 / S1 is (0.005-0.05):1, and the XRD diffraction peak intensity in the range of diffraction angle 2θ from 28.8° to 29.2° is S3, and S3 / S1 is (0.005-0.05):

1. A cathode active material characterized by the following features.

2. The positive electrode active material according to claim 1, characterized in that S2 / S1 is (0.01-0.03):1 and / or S3 / S1 is (0.01-0.02):

1.

3. The first coating layer comprises a hexagonal high-speed ionic conductor, and / or the second coating layer comprises an orthorhombic high-speed ionic conductor and a carbon material. The cathode active material according to feature 1.

4. The lithium metal phosphate is of general formula Li １＋ａ Fe ｘ G ｙ M １－ｘ－ｙ PO ４ / C ｚ A positive electrode active material according to any one of claims 1-3, characterized in that the following conditions are met, where -0.2 ≤ a ≤ 0.2, 0 < x < 1, 0 ≤ y ≤ 0.05, 0 ≤ z ≤ 0.1, M comprises at least one of Mn, Co, V and Ni, and G comprises at least one of Ga, Sn, V, Mo, Al, Mg, Ce, Ti, Zr, Nb, Si, W and In.

5. The hexagonal fast ion conductor has the general formula Li ｂ M １ ｄ M ２ ｅ M ３ ｕ (PO ４ ) ｗ１ (RO ｖ ) ｗ２ satisfies, where M １ includes at least one of Mg, Na, and K, M ２ includes at least one of Al, Ga, In, Y, and Sc, M ３ includes at least one of Ti, Zr, and Ge, R includes at least one of Si, Cl, Br, S, Sb, Sn, F, and P, 0 ≦ b < 3, 0 ≦ d ≦ 0.1, 0 ≦ e ≦ 1, 0 ≦ u ≦ 1, 1 ≦ w1 ≦ 3, 0 ≦ v ≦ 4, 0 ≦ w2 ≦ 0.5, and the cathode active material according to claim 3, characterized in that.

6. The above orthorhombic high-speed ionic conductor is general formula Li ３ M ４ ｔ Ti ２－ｔ (PO ４ ) ３ Satisfying the condition, where M ４ The positive electrode active material according to claim 3, characterized in that it comprises at least one of Al, Ga, In, Y, and Sc, and 0 ≤ t ≤ 1.

7. The mass fraction of carbon in the lithium metal phosphate is 0.5%–3%, and / or the mass fraction of carbon in the second coating layer is 1%–5%. The cathode active material according to feature 3.

8. The positive electrode active material according to claim 7, characterized in that the mass fraction of carbon in the positive electrode active material is 1% to 4%.

9. The first step involves mixing a first lithium source with a first metal source and a first phosphorus source to obtain a first paste, and then performing an initial sintering of the first paste under an inactive atmosphere to obtain an inner core. The steps include: mixing a second lithium source with a second metal source and a second phosphorus source to obtain a second paste; sintering the second paste a second time under an oxygen atmosphere to obtain the powder for the first coating layer; The process includes the steps of uniformly mixing the inner core with the powder of the first coating layer, then mixing it with a third lithium source, a titanium source, a third phosphorus source, and a second carbon source to obtain a third paste, and sintering the third paste for a third time in an inactive atmosphere to obtain a positive electrode active material. A method for producing a positive electrode active material according to any one of claims 1 to 8.

10. The first paste mentioned above The first lithium source is provided to include at least one of lithium carbonate, lithium hydroxide, and lithium nitrate. The first metal source comprises at least one of an iron source, an M source, and a G source, wherein the iron source comprises at least one of iron phosphate, iron nitrate, and ferrous nitrate, the M source comprises at least one of a phosphate, nitrate, carbonate, and oxide corresponding to element M, and the G source comprises at least one of a nitrate, carbonate, and oxide corresponding to element G. The condition that the first phosphorus source includes at least one of iron phosphate, iron manganese phosphate, phosphoric acid, hemiphosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides, and The invention further comprises a first carbon source, wherein the first carbon source satisfies at least one of the following conditions: glucose, sucrose, starch, graphene, and carbon nanotubes. The manufacturing method according to claim 9.

11. The second paste, The condition that the second lithium source includes at least one of lithium carbonate and lithium hydroxide, The condition that the second phosphorus source includes at least one of phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides, The second metal source is M １ Source, M. ２ Source and M ３ Including at least one source, among which the M １ Gen is M １ It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, and the M ２ Gen is M ２ It comprises at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, and the M ３ Gen is M ３ The condition that it contains at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to the element, The invention further comprises an R source, satisfying at least one of the conditions that the R source comprises at least one element, acid, and oxide corresponding to the element R. The manufacturing method according to claim 9.

12. The third paste described above The condition that the third lithium source includes at least one of lithium carbonate and lithium hydroxide, The condition that the titanium source contains at least one of the following: an oxide, hydroxide, nitrate, oxalate, organic alcohol salt, and carbonate corresponding to the element titanium. The condition that the third phosphorus source includes at least one of phosphoric acid, heterophosphate, pyrophosphate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, and phosphoric acid oxides, The condition that the second carbon source contains at least one of glucose, sucrose, starch, graphite, carbon nanotubes, and graphene, M ４ The source further includes the M ４ Gen is M ４ Satisfying at least one of the conditions that it contains at least one of the oxides, hydroxides, nitrates, oxalates, organic alcohol salts, and carbonates corresponding to an element, The manufacturing method according to claim 9.

13. The temperature of the initial sintering is 600°C-800°C, the duration of the initial sintering is 6h-12h, and / or The temperature of the second sintering is 700°C–900°C, the duration of the second sintering is 8h–12h, and / or The temperature of the third sintering is 300°C to 600°C, and the duration of the third sintering is 6 hours to 12 hours. The manufacturing method according to any one of claims 9-12, characterized by...

14. The solid content of the first paste, the second paste, and the third paste is independently 10 wt% to 70 wt%, and / or The average particle size of the first paste is 500 nm or less, and / or The average particle size of the second paste is 200 nm or less, and / or The average particle size of the third paste is 1 μm or less, and / or The solvents of the first paste, the second paste, and the third paste each independently contain at least one of water, isopropanol, ethanol, and ethylene glycol. The manufacturing method according to any one of claims 9-12, characterized by...

15. A battery characterized by comprising a positive electrode piece containing the positive electrode active material described in any one of claims 1 to 8.

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