Positive electrode plate and its manufacturing method, secondary battery and power consumption device

Abstract

The present application provides a positive electrode plate and a manufacturing method thereof, a secondary battery, and a power consumption device. The positive electrode plate includes a current collector and a positive electrode film layer located on at least one side of the current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a substrate and a carbon coating layer located on the surface of the substrate. The substrate has the general structural formula Li z Fe x Mn (1-x-y) M y PO4, wherein 1≦z≦1.1, 0.5≦x≦1, 0≦y≦0.1, and M element is selected from at least one of Ti, V, and Mg, at least a portion of the positive electrode active material contains primary particles, and the particle size distribution of the primary particles in the positive electrode active material having a primary particle diameter of 80 nm or more and 180 nm or less is 10% or less, and the particle size distribution of the primary particles having a primary particle diameter of 1500 nm or more is (250±5) μm in a cross section cut after the positive electrode active material is manufactured into an electrode plate. 2 The number of particles in the region does not exceed 15. The concentration of the primary particle size distribution of the positive electrode active material in the provided positive electrode plate is significantly improved, and the cycle performance of the battery is enhanced.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application incorporates by reference Chinese patent application No. 202310542575.5, filed on May 15, 2023, entitled "Positive electrode active material and manufacturing method thereof, positive electrode plate, secondary battery and power consumption device," which is incorporated herein by reference in its entirety. [Technical Field]

[0002] The present application relates to the field of secondary battery technology, and in particular to a positive electrode plate and a method for manufacturing the same, a secondary battery, and a power consuming device. [Background technology]

[0003] Olivine phosphate-based positive electrode materials have a stable structure and good cycle life, making them widely used as positive electrode active materials in secondary batteries. With the increasing demand for secondary battery performance in energy storage applications, how to improve the cycle performance of olivine phosphate-based positive electrode active materials is a scientific and technological problem that needs to be solved quickly in the current energy storage application field. One of the factors affecting the cycle performance of positive electrode active materials is the fine powder present in the positive electrode active material, which rapidly decays the cycle life, limiting further improvement of the cycle performance of positive electrode active materials.

[0004] Currently, most methods for improving fine powder in positive electrode active materials involve optimizing production processes and equipment to reduce the generation of fine particles during material mixing or transportation. This can reduce the generation of fine particles to some extent, but with little effect. Alternatively, cyclone separation equipment is used to remove fine particles from the material, but this is not very effective. In particular, it is difficult to achieve high-yield, effective separation for lithium iron phosphate or lithium manganese iron phosphate nanomaterials.

[0005] Furthermore, the ultra-large single crystal particles present in the positive electrode active material affect the mechanical integrity of the particles of the positive electrode active material, which also affects the cycle performance of the positive electrode active material.

[0006] Therefore, it is urgently necessary to improve the content of fine powder and ultra-large single crystal particles in the positive electrode active material, thereby improving the particle uniformity of the positive electrode active material. Summary of the Invention

[0007] The present application aims to solve at least one of the technical problems in the background art, and therefore, one of the objectives of the present application is to provide a positive electrode plate, which includes a phosphate-based positive electrode active material, which has a significantly different primary particle distribution compared with current conventional phosphate-based positive electrode active nanomaterials, a more uniform distribution, and a smaller ratio of fine particles to large particles, thereby improving the cycle and high-temperature storage performance of the phosphate-based positive electrode active material.

[0008] According to a first aspect of the present application, there is provided a positive electrode plate, the positive electrode plate including a current collector and a positive electrode film layer located on at least one side of the current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including a substrate and a carbon coating layer located on a surface of the substrate, the substrate having a structural general formula Li z Fe x Mn (1-x-y) M y PO4, where 0.5≦x≦1, 0≦y≦0.1, and 1≦z≦1.1; M is selected from at least one of Ti, V, and Mg; at least a portion of the positive electrode active material contains primary particles, and the particle size distribution of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less in the positive electrode active material is 10% or less.

[0009] The positive electrode active material in the positive electrode plate according to the present application has a primary particle diameter of 80 nm or more and 180 nm or less, and the particle size distribution of the positive electrode active material powder is controlled within an appropriate range, thereby reducing or slowing the decay of the cycle life of the small particle positive electrode active material in the positive electrode active material, slowing the rate of side reactions between the fine powder surface and the electrolyte, and further improving the cycle life of the positive electrode active material.

[0010] In some embodiments, the particle size distribution of primary particles in the positive electrode active material having a primary particle diameter of 80 nm or more and 180 nm or less is 8.5% or less, and optionally 8%, 6%, 5%, 2% or less.

[0011] In some embodiments, the primary particles of the positive electrode active material having a primary particle diameter of 1500 nm or more are essentially 250 μm in a cross section of the positive electrode plate. 2 The number of particles in the area does not exceed 15, and optionally, is essentially 250 μm 2 The number of particles in the area does not exceed 12, 8 or 6, and optionally, 250 μm 2 is 5 μm at the time of measurement. 2 Here, the region is selected from the cross-sectional end surface of the electrode plate, and the method for manufacturing the positive electrode active material as an electrode plate is known in the art.

[0012] Primary particles with a primary particle size of 1500 nm or larger are prone to particle crushing or pulverization during cycling, reducing the mechanical integrity of the particles and resulting in loss of active material. Controlling the particle size distribution of positive electrode active material powders with primary particles with a primary particle size of 1500 nm or larger within an appropriate range can improve the chemical and mechanical stability of the positive electrode active material, improving its electrochemical performance and thereby enhancing its cycling stability. If the primary particle size is too large, particles can be crushed during cycling, resulting in loss of electrical contact between the crushed particles, which is also a significant cause of capacity loss during battery use. The fresh interface created by crushing accelerates the elution of metal ions, resulting in a decrease in cycle life.

[0013] In some embodiments, the primary particle diameter of the positive electrode active material is 100 nm or more and 1500 nm or less, and the primary particle diameter of the positive electrode active material is (250±5) μm in a cross section cut after being manufactured into an electrode plate. 2 The particle size distribution index within this region is not greater than 0.45, and optionally not greater than 0.36, where the particle size distribution index is the ratio of the standard deviation of the primary particle sizes of the primary particles divided by the average primary particle size.

[0014] Primary particles with a primary particle diameter of 100 nm or more and 1500 nm or less have excellent particle diameter consistency, and the discharge behaviors of each particle in the battery cycle process tend to be consistent. Each particle can reduce the possibility of overcharge and overdischarge phenomena occurring during the charge and discharge process, ensure the structural stability of the positive electrode active material, and is beneficial to improving the normal temperature cycle performance and high temperature cycle performance of the battery.

[0015] In some embodiments, the positive electrode active material includes secondary particles, and the particle size distribution of the secondary particles satisfies (Dv90 - Dv10) / Dv50 ≤ 3.

[0016] In the positive electrode active material, the particle size distribution of the secondary particles being within an appropriate range helps to improve the particle size uniformity of the positive electrode active material.

[0017] In some embodiments, the Dv50 of the secondary particles is 0.45 - 1.5 μm, and optionally 0.6 - 1.5 μm.

[0018] In the positive electrode active material, the particle diameter of the secondary particles being within an appropriate range can eliminate or reduce the structural destruction of the secondary particles due to excessive lithium insertion and extraction during the charge and discharge process, or reduce the degree of polarization of the secondary particles during the charge and discharge process, and make the current density on the surface of the secondary particles more uniform, thereby helping to more fully exert the capacity of the positive electrode active material.

[0019] In some embodiments, in the general formula of the positive electrode active material according to the present application, 0.6 < x ≤ 1, 0 ≤ y < 0.1, 1 ≤ z ≤ 1.1, and optionally 0.8 ≤ x ≤ 1, 0.004 ≤ y ≤ 0.008, 1 ≤ z ≤ 1.08.

[0020] In some embodiments, in the positive electrode active material according to the present application, the mass content of the M element in the positive electrode active material is 1000 ppm - 6000 ppm, and optionally 1500 ppm - 5000 ppm.

[0021] The mass content of the M element in the positive electrode active material within an appropriate range helps to improve the structural stability of the positive electrode active material.

[0022] A second aspect of the present application provides a method for manufacturing a positive electrode plate, specifically, the method comprising: a compaction granulation step of compacting and granulating raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid to obtain compacted particles; a sintering step of packing the compacted particles and sintering the compacted particles to obtain secondary particles; a pulverization step of pulverizing the secondary particles to obtain a positive electrode active material; a coating step of coating at least one side of a current collector with a positive electrode slurry containing the positive electrode active material to form a positive electrode plate; Here, the positive electrode active material includes a substrate and a carbon coating layer located on the surface of the substrate, and the substrate has a structural general formula Li z Fe x Mn (1-x-y) M y PO4, wherein 0.5≦x≦1, 0≦y≦0.1, 1≦z≦1.1, and M element is selected from at least one of Ti, V, and Mg; at least a portion of the positive electrode active material contains primary particles, and the particle size distribution of the primary particles in the positive electrode active material having a primary particle diameter of 80 nm or more and 180 nm or less is 10% or less; (250±5) μm of primary particles having a primary particle diameter of 1500 nm or more in a cross section of the positive electrode plate 2 The number of particles in the region does not exceed 15.

[0023] Controlling the particle size distribution of the primary particle positive electrode active material powder having a primary particle diameter of 80 nm or more and 180 nm or less within the above range helps reduce or slow the decay of the cycle life of the small particle positive electrode active material in the positive electrode active material, and further improves the cycle life of the positive electrode active material.

[0024] In some embodiments, the particle size distribution of the positive electrode active material primary particles having a primary particle size of 80 nm or more and 180 nm or less is 8.5% or less, and optionally 8%, 6%, 5%, 4%, or 2% or less. A smaller particle size distribution of the positive electrode active material primary particles having a primary particle size of 80 nm or more and 180 nm or less is advantageous for improving the cycle life of the positive electrode active material and for maintaining the stability of the cycle life of the positive electrode active material.

[0025] In some embodiments, in the positive electrode active material in the positive electrode plate produced by the method, the primary particle diameter of the primary particles is 1500 nm or more, and the primary particle diameter of the primary particles is (250±5) μm in a cross section of the electrode plate. 2 The number of particles in the area does not exceed 15, and optionally, is essentially 250 μm 2 The number of particles in the area does not exceed 12, 8, or 6.

[0026] Controlling the particle size distribution of the positive electrode active material powder containing primary particles with a primary particle diameter of 1500 nm or more within the above range helps to improve the chemical and mechanical stability of the positive electrode active material and improve the electrochemical performance, thereby helping to improve the cycle stability of the positive electrode active material.

[0027] In some embodiments, the average particle size of the compacted particles in the compaction granulation step is 3 mm to 30 mm.

[0028] Compacted particles are suitable size The range helps to improve the uniformity of different raw materials inside the particles, and the voids between the particles allow the release of reducing gases generated by the decomposition of the carbon source during the manufacturing process. discharge It is advantageous to improve the uniformity of the carbon at different positions in the sintering device (e.g., sagger), and the carbon source precursor after compaction does not undergo obvious flow at high temperatures and does not cause stratification in height.

[0029] In some embodiments, the compacted particles have a compacted density of 1.0 g / cm 3or more, and optionally 1.2 to 3.0 g / cm 3 is.

[0030] Controlling the compaction density of the compacted particles within an appropriate range helps to increase the pot filling amount during the manufacturing process, thereby improving sintering production capacity.

[0031] In some embodiments, the method includes packing the compacted particles to a packing height of 5 cm to 30 cm, and sintering the compacted particles to obtain secondary particles; Optionally, the filling height is between 8 cm and 20 cm.

[0032] Ensuring that the filling height of the compacted particles during the sintering process is within an appropriate range helps to timely discharge reducing gases generated by the decomposition of the carbon source during the sintering process, thereby accelerating heat transfer and avoiding uneven decomposition of the carbon source in the compacted particles at different positions in the sintering device, thereby improving the consistency of particle growth and simultaneously achieving productivity.

[0033] In some embodiments, the method includes pulverizing the secondary particles so that their Dv50 is 0.45 μm to 1.5 μm, and optionally 0.6 μm to 1.5 μm. By pulverizing the secondary particles to a particle size within this range, the secondary particles eliminate or reduce structural destruction due to excessive lithium absorption / desorption during charge / discharge processes, or reduce the degree of polarization of the secondary particles during charge / discharge processes, thereby helping to fully utilize the capacity of the positive electrode active material.

[0034] In some embodiments, the method includes pulverizing the secondary particles so that the particle size distribution satisfies (Dv90-Dv10) / Dv50≦3, and optionally pulverizing the secondary particles so that the particle size distribution satisfies 1≦ ( and pulverizing the secondary particles so that Dv90-Dv10) / Dv50≦3. Pulverizing the secondary particles to bring their particle size distribution within the above range helps to improve the particle size uniformity of the positive electrode active material and the cycle stability of the positive electrode active material.

[0035] In some embodiments, the compaction step specifically comprises: The method includes the steps of grinding raw materials containing a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, M, a molding aid, and a solvent to obtain a slurry, drying the slurry, and then compacting and granulating it to obtain compacted particles.

[0036] First, the grinding process reduces the particle size of the ultra-large primary particles present in the raw materials, reducing the content of ultra-large primary particles in the raw materials and helping to reduce the particle size distribution of the ultra-large primary particles in the manufactured positive electrode active material, thereby reducing the particle sizes of the different raw materials and helping to obtain nano-level primary particles with more uniform particle sizes. At the same time, it improves the uniformity of the mixing of the different raw materials and helps to improve the uniformity of the different components in the manufactured positive electrode active material. The drying process also creates appropriate voids between the raw material particles, which helps to remove reducing gases generated by the decomposition of the carbon source during the sintering process.

[0037] In some embodiments, the sintering temperature in the sintering step is 600° C. to 800° C., and / or the constant temperature sintering time in the sintering step is 2 hours to 12 hours.

[0038] By controlling the sintering temperature and / or sintering time within an appropriate range, the compacted particles can be sintered sufficiently, and the positive electrode active material can have excellent structural parameters.

[0039] In some embodiments, the compaction step specifically comprises: A step (1-1) of uniformly mixing initial reactants including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, and an M source, followed by pre-sintering to obtain an initial product; A step (1-2) of mixing and grinding an intermediate reactant containing an initial product, a carbon source, and a molding aid to obtain an intermediate product; and (2) compacting and granulating the intermediate product to obtain compacted particles; Here, the mass content of the carbon source in the step (1-1) is 2% to 5% based on the total mass of the initial reactants.

[0040] The small amount of carbon source in the pre-sintering process plays a reducing role, allowing the initial reactants to be thoroughly mixed and reacted, improving the uniformity and completeness of the reaction, and resulting in a highly uniform particle size of the initial product. The pre-sintering process pre-reacts the ultrafine particles in the initial reactants, reducing the content of small particles in the raw materials and improving the particle size uniformity of the material. At the same time, the intermediate reactants containing the initial products, carbon source, and molding aids are further ground to refine the large particles and reduce the content of ultra-large primary particles in the raw materials, further improving the particle size uniformity of the material, providing a material basis for the subsequent production of a positive electrode active material with excellent particle size uniformity.

[0041] In summary, the pre-sintering treatment improves the particle size uniformity of the initial reactants, allowing the intermediate product to be compacted and granulated to have excellent particle size uniformity, which helps to improve the uniformity of different components in the produced positive electrode active material.

[0042] In some embodiments, the intermediate product has a Dv50 of 0.45 μm to 1.25 μm, and a DV10 of 0.15 μm or more.

[0043] Dv50 and D of the intermediate product V Controlling 10 within an appropriate range is advantageous for controlling the mass content of small particles in the positive electrode active material, which can improve the structural stability of the positive electrode active material and the cycle performance of the battery.

[0044] A third aspect of the present application provides a secondary battery, which includes a negative electrode plate and a positive electrode plate according to the first aspect of the present application or a positive electrode plate manufactured by the manufacturing method according to the second aspect.

[0045] A fourth aspect of the present application provides a power consuming device, the power consuming device including a secondary battery according to the third aspect of the present application.

[0046] The above description is merely a summary of the technical solution of the present application, which can be implemented in accordance with the content of the specification, so as to make the technical means of the present application more clearly understood, and to make the above and other objectives, features and advantages of the present application more apparent, the following particularly cites specific embodiments of the present application for description. [Brief explanation of the drawings]

[0047] In the drawings, unless otherwise specified, the same reference numerals throughout the several drawings represent the same or similar parts or elements. The drawings are not necessarily drawn to scale. It should be understood that the drawings depict only some embodiments disclosed in accordance with the present application and should not be considered as limiting the scope of the present application. [Figure 1] FIG. 2 is a schematic diagram of sintering of compacted particles in a sintering device according to the present application. [Figure 2] 1 is a scanning electron microscope (SEM) photograph of a positive electrode active material in Example 1 of the present application. [Figure 3] 3A and 3B are scanning electron microscope photographs of an argon ion beam cut cross section of the positive electrode active material in Example 1 of the present application after it has been manufactured into a positive electrode plate, the electron microscope scale in FIG. 3A being 2 μm, and the electron microscope scale in FIG. 3B being 500 nm. [Figure 4] 4A and 4B are scanning electron microscope photographs of an argon ion beam cut cross section after the positive electrode active material in Comparative Example 1 in the present application is manufactured into a positive electrode plate, the electron microscope scale in FIG. 4A is 1 μm, and the electron microscope scale in FIG. 4B is 200 nm. [Figure 5] 1 shows cycle performance test curves at 25° C. and 60° C. for secondary batteries in Example 1 and Comparative Example 1 of the present application. [Figure 6] 1 is a schematic diagram of a secondary battery cell according to an embodiment of the present application; [Figure 7] FIG. 7 is an exploded view of the secondary battery cell shown in FIG. 6 according to the embodiment of the present application. [Figure 8] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 9] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 10] FIG. 10 is an exploded view of the battery pack shown in FIG. 9 according to the embodiment of the present application. [Figure 11] 1 is a schematic diagram of a power consumption device in which a secondary battery according to an embodiment of the present application is used as a power source; [Figure 12] 1 is an SEM photograph of a cross section of an electrode plate in a secondary battery according to an embodiment of the present application. [Figure 13] 1 is a scanning electron microscope photograph of an argon ion beam cut cross section of a positive electrode plate of Example 15 in the present application. DETAILED DESCRIPTION OF THE INVENTION

[0048] The following describes in detail the embodiments of the technical solution of the present application in conjunction with the drawings. The following embodiments are only used to more clearly explain the technical solution of the present application, and are merely examples, which do not limit the protection scope of the present application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of this application, and the terms used herein are only for describing specific embodiments and are not intended to limit this application. The terms "comprises" and "having" and any variations thereof in the specification and claims of this application and the description of the drawings above are intended to cover a non-exclusive "comprise."

[0050] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. Appearances of this phrase in various locations throughout the specification do not necessarily all refer to the same embodiment, nor are they mutually exclusive, independent, or alternative embodiments. Those skilled in the art can explicitly or implicitly understand that the embodiments described herein can be combined with other embodiments.

[0051] In the description of the embodiments of this application, the term "and / or" is merely a relation that describes related objects and indicates that three relations may exist. For example, A and / or B may represent three cases: A alone, a combination of A and B, and B alone. In addition, the character " / " in this specification generally indicates that the related objects before and after are in an "or" relationship.

[0052] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and any combination is possible; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also possible. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all possible. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents that the present specification has already listed all real numbers between "0-5," and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0054] Unless otherwise specified, the terms "comprise" and "include" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "include" may further include or include other components not listed, or may include or include only the listed components.

[0055] positive electrode active material Several factors can affect the cycle performance of a positive electrode active material, such as the residual alkali content on the material surface, the perfection of the material's crystalline structure, the content of fine particles in the material, and the content of moisture adsorbed on the material surface. Here, the content of fine particles, i.e., the proportion of small particles in all particles, is an important factor that limits further improvement of the battery cycle performance. This is because, in the synthesis reaction of a positive electrode active material, the lithium ion embedding energy barrier in particles with a relatively small particle size is low, and the reaction activity is high, so that lithium ions can be easily embedded in the fine particles. Teli Thiol excessively This is because the Li content in the small particles of the fine powder is excessive, while the Li content in the particles with a larger particle size than the fine powder is insufficient, resulting in uneven lithium distribution. During charging, polarization causes the small particles to constantly release excess lithium, destroying their structure. Side reactions between the small particles in the charged state and the electrolyte become more intense, becoming more pronounced at higher temperatures, resulting in a rapid decline in the cycle life of the small particles. Therefore, controlling the content of the fine powder in the positive electrode active material is useful for improving the cycle performance of energy storage devices (e.g., secondary batteries).

[0056] The present application provides a carbon-coated (@C) phosphate-based cathode active material, having the general formula Li z Fe x Mn (1-x-y) M yPO4@C, where 0.5≦x≦1, 0≦y≦0.1, and 1≦z≦1.1; M element is selected from at least one of Ti, V, and Mg; at least a portion of the positive electrode active material includes primary particles, and the particle size distribution of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less in the positive electrode active material is 10% or less.

[0057] As used herein, the term "positive electrode active material" refers to "Li z Fe x Mn (1-x-y) M y It may also be expressed as "PO4@C".

[0058] As used herein, the term "positive electrode active material" refers to a material having the general formula Li z Fe x Mn (1-x-y) M y PO4@C” and the term “a positive electrode active material includes a substrate and a carbon coating layer located on a surface of the substrate, the substrate having a structural general formula Li z Fe x Mn (1-x-y) M y "Having PO4" is the same expression.

[0059] In some embodiments, the particle size distribution of the positive electrode active material having primary particles with a primary particle diameter of 80 nm or more and 180 nm or less is 9.5%, 9%, 8.5%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% or less, or the particle size distribution of the positive electrode active material having primary particles with a primary particle diameter of 80 nm or more and 180 nm or less is selected from 0.1% to 10%, 0.5% to 10%, 1% to 10%, 0.1% to 8%, 0.1% to 6%, 0.1% to 4%, 0.1% to 3%, 0.1% to 2%, 0.1% to 1%, 0.3% to 5%, 0.8% to 3%, or 0.1% to 1.5%.

[0060] The term "primary particle" is also called a single crystal particle, and generally refers to a single fine crystal grain. In some cases, even if the particle is amorphous, when original particles and aggregated particles exist, the original particles may be called primary particles.

[0061] The aggregate particles formed by aggregation between multiple original or primary particles are called "secondary particles." The force that causes aggregation between particles may be a physical bond (e.g., van der Waals force) or a chemical bond (e.g., bridging oxygen bond), and the method of forming aggregates between particles may be to assisted aggregation by external pressure or by another substance (e.g., a chemical substance with adhesive properties). The particle size of secondary particles is called "secondary particle size."

[0062] As used herein, the term "primary particle size" refers to the particle size of the primary particle.

[0063] In this application, the terms "fine powder", "small particles" and "fine powder small particles" have the same meaning and refer to particles with a particle size of 80 nm or more and 180 nm or less, including primary particles and secondary particles.

[0064] The term "particle size distribution" refers to the percentage of all powder particles that are within a certain particle size or particle size range.

[0065] The particle size distribution of powder particles can be measured using a detection method commonly used in the art, such as a laser particle size analyzer.

[0066] The particle size distribution can also be measured by a long diameter statistical method, which can measure the particle diameter of the active material in the electrode membrane. In some embodiments, an argon ion beam can be used to cut the electrode perpendicular to the electrode plane (e.g., a plane with a relatively large area), and the exposed cross section can be photographed using a scanning electron microscope. The equivalent circle diameter can then be calculated based on the cross-sectional area of ​​each particle. Particles smaller than 80 nm are difficult to distinguish individually when photographed using a scanning electron microscope. In such cases, particles smaller than 80 nm do not need to be counted when measuring the particle size distribution using the equivalent circle diameter statistical method.

[0067] In the positive electrode active material according to the present application, the particle size distribution of the positive electrode active material powder of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less is controlled to 10% or less, thereby reducing the number of fine powders whose structure is destroyed due to excessive lithium release during the charging process, reducing side reactions between the fine powder and the electrolyte, and delaying the decay of the cycle life of the positive electrode active material, which helps to improve the cycle life of the positive electrode active material.

[0068] As mentioned above, the high reactivity of the fine powder in the reaction leads to uneven lithium distribution in the positive electrode active material, which also affects the surface condition of the positive electrode active material. When the powder content is too high, the lithium content increases, strengthening the alkalinity of the positive electrode active material and increasing side reactions with the adhesive, which deteriorates the processing performance of the slurry, causing a rapid increase in the viscosity of the slurry and, in severe cases, gel formation. Controlling the particle size distribution of the fine powder within an appropriate range also helps improve the processing performance of the positive electrode active material.

[0069] In some embodiments, the particle size distribution of primary particles in the positive electrode active material having a primary particle diameter of 80 nm or more and 180 nm or less is 8.5% or less, and optionally 8%, 6%, 5%, 2% or less.

[0070] By controlling the particle size distribution of the positive electrode active material powder of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less to 8.5% or less, the possibility of side reactions between the fine powder and the electrolyte can be further reduced, and the room temperature cycle capacity retention rate and high temperature cycle capacity retention rate of the battery can be improved.

[0071] In some embodiments, the positive electrode active material has a primary particle size of 1500 nm or more, and the primary particle size is essentially 250 μm. 2 The number of particles in the area does not exceed 15, and optionally, is essentially 250 μm 2 The number of particles within the range of 12, 10, 9, 8, 7, 6, 5, 4, 3, or 2 does not exceed 12, 10, 9, 8, 7, 6, 5, 4, 3, or 2. "Basic" refers to the degree of measurement error or fluctuation during measurement, and is optionally 5 μm 2 Here, the "region" refers to a region in a cross section obtained by cutting the cathode active material after manufacturing it into an electrode plate, and the region is used to measure the number of large particles. The method for manufacturing the cathode active material into an electrode plate is known in the art.

[0072] In some embodiments, the positive electrode active material may be manufactured into a plate according to the method disclosed in Example 1. In some embodiments, the positive electrode active material powder and polyvinylidene fluoride (PVDF) adhesive are mixed in a mass ratio of 95:5, and N-methylpyrrolidone is used as a solvent to manufacture a plate, which has a compaction density of 2.2 g / cm. 3 It may be cold pressed up to

[0073] In some embodiments, the positive electrode active material has a primary particle diameter of 1500 nm or more, and the primary particle diameter is essentially 250 μm 2 The number of particles in the area does not exceed 0-2, 0-3, 1-2, 1-3, 2-3, 0-4, 2-4, 3-4, 0-5, 2-5, 0-6, 5-6, 6-8, 8-14.

[0074] In some embodiments, the positive electrode active material has a primary particle diameter of 1500 nm or more, and the primary particle diameter is essentially 250 μm 2The number of particles in the area does not exceed 0-2, 0-3, 1-2, 1-3, 2-3, 0-4, 2-4, 3-4, 0-5, 2-5, 0-6, 5-6, 6-8, 8-12.

[0075] The number of particles with a primary particle diameter of 1500 nm or more can be counted using a scanning electron microscope (SEM). For example, an argon ion beam is used to cut the electrode plate perpendicular to the large surface of the electrode plate to expose the edge, and the edge is photographed using an SEM. The particle diameters of the particles are then counted using the equivalent circle area statistical method. The number of large particles can be determined by a single measurement or by averaging multiple measurements.

[0076] Primary particles with a primary particle diameter of 1500 nm or greater are also referred to as "large particles," "ultra-large single-crystal particles," or "ultra-large primary particles." During cycling, cathode materials undergo a deformation process involving repeated expansion and contraction. The deformation of ultra-large primary particles during cycling can lead to grain boundary cracking and severe pulverization of the ultra-large primary particles. This severely reduces the mechanical integrity of the primary and secondary particles, impairs electrolyte penetration, and results in significant loss of the cathode active material (e.g., lithium ions). At the same time, the presence of grain boundary cracking can also lead to loss of electrical contact and exacerbate capacitance polarization loss. Accordingly, the continuous generation of new electrode / electrolyte interfaces can rapidly deteriorate the chemical and mechanical performance of the cathode active material during long cycling.

[0077] By controlling the particle size distribution of the positive electrode active material powder with a primary particle diameter of 1500 nm or more within an appropriate range, particle crushing can be effectively prevented, surface decomposition can be mitigated, and grain boundary cracking problems can be suppressed, thereby enhancing chemical and mechanical stability and improving electrochemical performance.Interface degradation and overall mechanical collapse effects can be suppressed, enhancing chemical and mechanical stability and improving the cycle stability of the positive electrode active material.

[0078] In some embodiments, the primary particle diameter of the positive electrode active material is 100 nm or more and 1500 nm or less, and the primary particle diameter of the positive electrode active material is (250±5) μm in a cross section cut after being manufactured into an electrode plate. 2 The particle size distribution index within this region is 0.45 or less, and the particle size distribution index is the ratio of the standard deviation of the primary particle sizes of the primary particles divided by the average primary particle size.

[0079] In some embodiments, the primary particle diameter of the positive electrode active material is 100 nm or more and 1500 nm or less, and the primary particle diameter of the positive electrode active material is (250±5) μm in a cross section cut after being manufactured into an electrode plate. 2 The particle size distribution index within the range is optionally any one of 0.45 or less, 0.40 or less, 0.35 or less, 0.3 or less, 0.25 or less, and 0.20 or less.

[0080] In some embodiments, the primary particle diameter of the positive electrode active material is 100 nm or more and 1500 nm or less, and the primary particle diameter of the positive electrode active material is (250±5) μm in a cross section cut after being manufactured into an electrode plate. 2 The particle size distribution index within this region is 0.36 or less, and the particle size distribution index is the ratio of the standard deviation of the primary particle sizes of the primary particles divided by the average primary particle size.

[0081] In some embodiments, the primary particle diameter of the positive electrode active material is 100 nm or more and 1500 nm or less, and the primary particle diameter of the positive electrode active material is (250±5) μm in a cross section cut after being manufactured into an electrode plate. 2 The particle size distribution index within the region is optionally any one of 0.36 or less, 0.3 or less, 0.25 or less, and 0.20 or less.

[0082] The particle size distribution index has a meaning known in the art and can be measured by known test methods and equipment. The particle size distribution index is an important parameter for measuring particle size uniformity, and the lower the particle size distribution index, the smaller the particle size deviation value and the higher the particle size uniformity. An exemplary test method involves using an argon ion beam to cut the electrode plate perpendicular to the major surface of the electrode plate to expose the cross section, photographing the cross section using a scanning electron microscope, and statistically analyzing the particle size of the positive electrode active material using the equivalent circle area statistical method. The particle size distribution index (PDI) is the standard deviation of particle size.

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[0083] Primary particles having a primary particle diameter of 100 nm or more and 1500 nm or less have excellent particle diameter uniformity, and the discharge behavior of each particle during the battery cycling process tends to be uniform. This reduces the possibility of overcharge and overdischarge phenomena occurring during the charging and discharging process, ensures the structural stability of the positive electrode active material, and is advantageous for improving the room temperature cycling performance and high temperature cycling performance of the battery.

[0084] In some embodiments, the cathode active material includes secondary particles, and the particle size distribution of the secondary particles satisfies (Dv90-Dv10) / Dv50≦3, optionally less than or equal to 2.9, 2.8, 2.6, 2.5, 2.4, 2.3, 2.2, 1.4, 1.5, or 1.2. Optionally, 1≦(Dv90-Dv10) / Dv50≦3.

[0085] In the positive electrode active material, the particle size distribution of the secondary particles is within an appropriate range, which helps to improve the particle size uniformity of the positive electrode active material and further enhance the cycle performance.

[0086] In some embodiments, the Dv50 of the secondary particles is 0.45-1.5 μm, optionally 0.5-1.5 μm, 0.8-1.5 μm, 0.7-1.5 μm, 1-1.5 μm, 0.45-1.3 μm, 0.45-1.0 μm, 0.5-1.0 μm, 0.6-1.5 μm, or 0.7-1.5 μm, or any value within said ranges.

[0087] In the positive electrode active material, when the particle diameter of the secondary particles is within an appropriate range, it eliminates or reduces the structural destruction of the secondary particles due to excessive lithium insertion and extraction during the charge-discharge process. Also, it helps to reduce the degree of polarization of the secondary particles during the charge-discharge process, and by making the current density on the surface of the secondary particles more uniform, it fully utilizes the capacity of the positive electrode active material and helps to improve the cycle performance.

[0088] In the positive electrode active material according to the present application, while reducing the fine powder and the large particle size distribution, the concentration degree of the particle size distribution of the positive electrode active material is significantly improved.

[0089] In some embodiments, the positive electrode active material may be one or more of lithium iron phosphate or lithium iron manganese phosphate having an olivine structure and its modified compounds, which can improve the cycle performance and storage performance of the battery while improving the rate performance of the battery. Since the operating voltage of the battery using these positive electrode active materials is not high, generally ≦ 4.35V, the cycle performance and storage performance of the battery can be further improved.

[0090] In some embodiments, in the positive electrode active material according to the present application, 0.6 < x ≦ 1, 0 ≦ y < 0.1, 1 ≦ z ≦ 1.1, and optionally, 0.8 ≦ x ≦ 1, 0.004 ≦ y ≦ 0.008, 1 ≦ z ≦ 1.08.

[0091] In some embodiments, in the positive electrode active material according to the present application, the mass content of the M element in the positive electrode active material is selected from 1000 ppm to 6000 ppm, and optionally, 1000 ppm to 5500 ppm, 1000 ppm to 5000 ppm, 1500 ppm to 60,00 ppm, 1500 ppm to 5000 ppm, 2000 ppm to 6000 ppm, 2500 ppm to 6000 ppm, or 2000 ppm to 5500 ppm, or any value within the range.

[0092] In some embodiments, the M element contains Ti. In some embodiments, the M element contains V. In some embodiments, the M element contains Mg.

[0093] The main body of the anion part of the positive electrode active material is a phosphate matrix, and the metal matrix is mainly composed of iron, manganese or a combination of both. By introducing divalent or polyvalent M cations, lithium ions are released in the matrix of the olivine structure composed of cations containing M and anions containing phosphoric acid, which helps to improve the structural stability of the positive electrode active material.

[0094] Method for manufacturing a positive electrode active material This application provides a method for manufacturing a carbon-coated (@C) phosphate-based positive electrode active material, and the positive electrode active material has the general formula Li z Fe x Mn (1-x-y) M y It contains at least one of the compounds shown in PO4@C, where 0.5 ≦ x ≦ 1, 0 ≦ y ≦ 0.1, 1 ≦ z ≦ 1.1, and the M element is selected from at least one of Ti, V, and Mg.

[0095] In the positive electrode active material of some embodiments, 0.6 < x ≦ 1, 0 ≦ y < 0.1, and optionally 0.8 ≦ x ≦ 1, 0.004 ≦ y ≦ 0.008, 1 ≦ z ≦ 1.08. In some embodiments, the M element is selected from Ti. In some embodiments, the M element is selected from V. In some embodiments, the M element is selected from Mg.

[0096] In the positive electrode active material of some embodiments, the mass content of the M element in the positive electrode active material is 1000 ppm to 6000 ppm, and optionally 1000 ppm to 5500 ppm, 1000 ppm to 5000 ppm, 1500 ppm to 6000 ppm, 1500 ppm to 5000 ppm, 200 ppm to 6000 ppm, 2500 ppm to 6000 ppm, or 2000 ppm to 5500 ppm, or any value within the range.

[0097] The anion portion of the positive electrode active material is mainly made of a phosphate matrix, and the metal matrix is ​​mainly composed of iron, manganese, or a combination of both. By introducing divalent or polyvalent M cations, lithium ions are released into the olivine structure matrix composed of M-containing cations and phosphate-containing anions, which helps to improve the structural stability of the positive electrode active material.

[0098] In some embodiments, the positive electrode active material may be one or more of olivine-structured lithium iron phosphate or lithium iron manganese phosphate and modified compounds thereof, which can improve the cycle performance and storage performance of the battery while also improving the battery's power rating. The operating voltage of batteries using these positive electrode active materials is not high, typically ≦4.35 V, further improving the cycle performance and storage performance of the battery.

[0099] The manufacturing method according to the present application comprises: The method includes a step of uniformly mixing raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid, followed by compacting and granulating the mixture to obtain compacted particles.

[0100] Generally speaking, compacted particles are actual particle groups consisting of particles that are not completely uniform in size and shape. Compared to a hypothetical particle group consisting of uniform spherical particles, if the total length of both particle diameters is the same, the diameter of the spherical particles is the average particle diameter of the actual particle group (compacted particles). While the spherical diameter is certainly the particle diameter of a spherical particle, in reality, true spherical particles do not exist, and the shapes of actual particles are very complex. For convenience, this application uses equivalent particle diameters to describe the particle size (particle size) or average particle diameter of irregular particles. As can be understood, when the physical properties or physical behavior of a particle are closest to those of a homogeneous sphere of a certain diameter, the diameter (or a combination) of this sphere is the equivalent particle diameter of the particle being measured.

[0101] The average particle size can be measured using a particle size measurement method or instrument commonly used in the art, including, but not limited to, a laser particle size analyzer and an ultrasonic particle size analyzer. The average particle size can be a linear average diameter, an area average diameter, a volume average diameter, a weight average diameter, or a specific surface average diameter, and the average particle size in this application refers to the volume average diameter. When particle size is described using an equivalent particle size, the average particle size in this application can also be the volume equivalent diameter.

[0102] In some embodiments, the lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate, lithium oxide, lithium chloride, lithium nitrate, and lithium sulfate; optionally, the lithium source comprises lithium carbonate.

[0103] In some embodiments, the iron source comprises at least one of ferrous phosphate, ferrous hydroxide, ferrous nitrate, ferrous phosphate, ferrous pyrophosphate, ferrous carbonate, ferrous chloride, ferrous oxalate, ferrous chloride, ferrous hydroxide, ferrous nitrate, ferrous citrate, and ferric oxide; optionally, the iron source comprises ferric oxide.

[0104] In some embodiments, the manganese source comprises at least one of manganese dioxide, dimanganese trioxide, trimanganese tetroxide, manganese oxalate, manganese acetate, or manganese nitrate.

[0105] In some embodiments, the phosphorus source comprises at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, iron phosphate, lithium dihydrogen phosphate, and lithium phosphate; optionally, the phosphorus source comprises ammonium dihydrogen phosphate.

[0106] In some embodiments, the carbon source comprises at least one of sucrose, glucose, citric acid, fructose, lactose, porous graphene, activated carbon, activated carbon fiber, mesoporous carbon, carbon nanotubes, carbon molecular sieves, asphalt, and polyethylene glycol; optionally, the carbon source comprises sucrose.

[0107] In some embodiments, the M source is selected from at least one of oxides, hydroxides, oxalates, acetates, chlorides, nitrates, or phosphates of Ti, V, and Mg elements, and optionally, the M source includes one or more of titanium dioxide, magnesium hydroxide, and vanadium pentoxide.

[0108] The molding aid is selected from polymeric substances that are soluble or dispersible in water or alcohol, and in some embodiments, the molding aid includes at least one of polyarylate, starch, phenolic resin, polyurethane, melamine resin, polyethylene, stearic acid, PVC, polyacrylonitrile, natural rubber, styrene butadiene rubber, and butadiene rubber, and optionally, the molding aid includes starch.

[0109] The molding aid can further improve the completeness of the sintering process of the particles after compaction, reinforce the mechanical stability of the compacted particles during the sintering process, and avoid structural collapse during the sintering process of the particles.

[0110] In some embodiments, a raw material containing a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid is ground, optionally until the raw material has a Dv50 of 0.3 to 1.5 μm, 0.3 to 1.0 μm, 0.3 to 0.8 μm, 0.35 to 0.6 μm, or 0.35 to 0.9 μm. The raw material can be ground using a grinding machine, such as a ball mill, a sand mill, or a mechanical mill.

[0111] In some embodiments, a homogeneous and stable mixture of water, an alcohol-based solvent, or both may be added and mixed with the raw material before polishing. The alcohol-based solvent may include, but is not limited to, methanol, ethanol, and ethylene glycol, and one or more different alcohol-based solvents may be mixed together before use.

[0112] In some embodiments, the forming aid in the raw material may be dissolved or dispersed in a homogeneous and stable mixture of water, an alcohol-based solvent, or both, and mixed with other components in the raw material upon addition of the solvent or solution.

[0113] After the grinding process, the particle size of the ultra-large primary particles present therein becomes smaller, which helps to reduce the content of ultra-large primary particles in the raw materials and reduce the particle size distribution of the ultra-large primary particles in the produced positive electrode active material, thereby reducing the particle sizes of the different raw materials and obtaining nano-level primary particles with more uniform particle sizes, and also helps to improve the mixing uniformity of the different raw materials and the uniformity of the different components in the produced positive electrode active material.

[0114] In some embodiments, the ground raw material is dried, and optionally the ground raw material is spray-dried. In some embodiments, the particle size Dv50 of the microspheres formed by spray drying is 5-50 μm, and optionally 5-40 μm, 8-30 μm, 10-25 μm, or 10-20 μm.

[0115] The spray-dried raw material exhibits a spherical shape with good fluidity, and the raw material particles have adequate voids between them, which are useful for discharging reducing gases generated by decomposition of the carbon source during the sintering process.

[0116] In some embodiments, the raw materials after the spray drying process are compacted and granulated.

[0117] In some embodiments, raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid are compacted and granulated to obtain compacted particles having an average particle size of 3 mm to 30 mm, optionally 5 mm to 25 mm, 5 mm to 20 mm, 5 mm to 15 mm, 10 mm to 15 mm, 10 mm to 20 mm, or 10 mm to 25 mm. The average particle size may be any value selected from 7.5 mm, 12.5 mm, 17.5 mm, 22.5 mm, and 27.5 mm, or a range between any two of these values.

[0118] When the average particle size of the compacted particles is less than 3 mm, the voids formed by the large bridges between the particles are relatively small, and the gas discharge If the average particle size of the compacted particles is larger than 30 mm, the uniformity of the nanoparticles within a single compacted particle cannot be guaranteed, and the exhaust capacity of a single compacted particle is significantly reduced. size The range helps to improve the uniformity of different raw materials inside the particles, and the voids between the particles allow the release of reducing gases generated by the decomposition of the carbon source during the manufacturing process. discharge It is advantageous to

[0119] In some embodiments, the compacted particles obtained by compaction have a compaction density of 1.0 g / cm 3 Above, selectively 1.2 to 3.0 g / cm 3 is.

[0120] Controlling the compaction density of the compacted particles within an appropriate range helps to increase the pot filling amount during the manufacturing process, thereby improving sintering production capacity.

[0121] In some embodiments, the method includes packing the compacted particles to a packing height of 5 cm to 30 cm and sintering the compacted particles to obtain secondary particles. Optionally, the packing height is 8 cm to 30 cm, 8 cm to 20 cm, 5 cm to 25 cm, 5 cm to 20 cm, 10 cm to 30 cm, 10 cm to 25 cm, or 10 cm to 20 cm.

[0122] Figure 1 shows the sintering of compacted particles. Device 1 shows a schematic diagram of a packed assembly, such as a sagger, used in sintering. Saggers 7 are typically made of graphite, and are filled with compacted particles 6. This allows voids to form between the compacted particles 6, allowing reducing gases and other gaseous substances generated by the decomposition of the carbon source during sintering to escape through the voids in the direction indicated by the arrows in FIG. 1. The rising gas transfers heat to the compacted particles 6 in the upper layer of the sagger 7. If the gas escapes improperly, uneven temperatures at various locations in the sagger 7 may occur, resulting in a high content of reducing gas in the upper layer of the sagger 7. Keeping the packed height of the compacted particles within an appropriate range helps ensure that reducing gases and other unwanted gases are expelled in a timely manner during sintering, accelerating heat transfer and preventing uneven decomposition of the carbon source among the compacted particles at different locations in the sintering device. This improves the consistency of particle growth and production capacity.

[0123] In some embodiments, after the compacted particles are packed, the porosity between the particles is between 5% and 20%, and optionally the porosity is selected from 5% to 15%, 10% to 20%, 10% to 15%, 8% to 20%, 12% to 20%, or 8% to 17%.

[0124] In some embodiments, the compacted particles are sintered in an inert gas atmosphere, which may include one or more of nitrogen gas, carbon dioxide, and helium gas, and optionally, the inert gas is selected from nitrogen gas.

[0125] In some embodiments, the compacted particles are sintered within a sintering temperature range of 600°C to 800°C, optionally with the sintering temperature selected from 650°C to 800°C, 680°C to 800°C, 700°C to 800°C, 600°C to 780°C, 600°C to 750°C, 620°C to 800°C, or 640°C to 720°C.

[0126] In some embodiments, the compacted particles are sintered within a sintering temperature range of 600°C to 800°C for 2 to 12 hours, optionally sintered at the sintering temperature for 2 to 10 hours, 4 to 12 hours, 2 to 10 hours, 4 to 8 hours, 6 to 12 hours, 6 to 10 hours, or 6 to 8 hours.

[0127] In some embodiments, during the sintering process, the heating rate to the sintering temperature is controlled to be 1°C to 5°C / min, and optionally the heating rate is selected from 2°C to 5°C / min, 3°C to 5°C / min, 2°C to 4°C / min, or 2°C to 3°C / min, or the heating rate is selected from 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, or a range between any two of the foregoing values.

[0128] In the manufacturing method of the present application, the raw material mixture is compacted and granulated before sintering, which allows the reducing gas from the decomposition of the carbon source to be released in a timely manner during the sintering process, preventing uneven decomposition of the carbon source at different positions in the sintering machine and promoting uniform heating of the compacted particles at different positions in the sintering machine. After sintering, the carbon contents of the surface, middle, and bottom particles tend to be at the same level, and the growth inhibition effect on the raw material particles during the sintering reduction process is basically consistent, improving the uniformity of the carbon content of the primary particle nanomaterials.

[0129] In some embodiments, the method includes grinding the secondary particles obtained after sintering to a Dv50 of 0.45 μm to 1.5 μm, optionally to a Dv50 selected from 0.5 to 1.5 μm, 0.8 to 1.5 μm, 0.7 to 1.5 μm, 1 to 1.5 μm, 0.45 to 1.3 μm, 0.45 to 1.0 μm, 0.5 to 1.0 μm, 0.6 to 1.5 μm, or 0.7 to 1.5 μm.

[0130] D V If 50 is too small, the overall particle size will be low and the proportion of small particles will increase, reducing the stability of the material surface and V If 50 is too large, the overall granularity Large This leads to an increase in the proportion of large particles and an increase in the crushing effect of particles during the cycling process, all of which are unfavorable to improving the stability of the material.

[0131] By grinding the secondary particles to an appropriate particle size range, structural destruction of the secondary particles due to excessive lithium absorption and desorption during charge and discharge is eliminated or reduced, which also helps to reduce the degree of polarization during charge and discharge of the secondary particles, making the current density on the secondary particle surface more uniform, and improving the stability of the material, thereby fully utilizing the capacity of the positive electrode active material and improving cycle performance.

[0132] In some embodiments, the method includes milling the secondary particles to have a particle size distribution that satisfies (Dv90-Dv10) / Dv50≦3, and optionally is less than or equal to 2.9, 2.8, 2.6, 2.5, 2.4, 2.3, 2.2, 2, 1.8, 1.4, 1.2, or 1.5. Optionally, milling the secondary particles to have a particle size distribution that satisfies 1≦(Dv90-Dv10) / Dv50≦3.

[0133] In the positive electrode active material, the particle size distribution of the secondary particles is within an appropriate range, which helps to improve the particle size uniformity of the positive electrode active material and further enhance the cycle performance.

[0134] In some embodiments, the production method includes pulverizing the sintered secondary particles so that at least a portion of the obtained positive electrode active material contains primary particles, and the particle size distribution of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less in the positive electrode active material is 10% or less.

[0135] In some embodiments, the particle size distribution of the positive electrode active material having primary particles with a primary particle diameter of 80 nm or more and 180 nm or less is 9.5%, 9%, 8.5%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% or less; or the particle size distribution of the positive electrode active material having primary particles with a primary particle diameter of 50 nm or more and 200 nm or less is selected from 0.1% to 10%, 0.5% to 10%, 1% to 10%, 0.1% to 8%, 0.1% to 6%, 0.1% to 4%, 0.1% to 3%, 0.1% to 2%, 0.1% to 1%, 0.3% to 5%, 0.8% to 3%, or 0.1% to 1.5%.

[0136] In the positive electrode active material produced by the production method of the present application, the particle size distribution of the fine powder is significantly reduced, side reactions between the fine powder and the electrolyte are reduced, the decay of the cycle life of the positive electrode active material is delayed, and the cycle life of the positive electrode active material is improved.

[0137] At the same time, the positive electrode active material produced by the above method has a narrow particle size distribution of fine powder, which reduces side reactions between the positive electrode active material and the adhesive, thereby improving the processability of the positive electrode active material.

[0138] In some embodiments, the resulting positive electrode active material has a primary particle size of 1500 nm or more, and the primary particle size is essentially 250 μm. 2 The secondary particles are crushed so that the number of particles in the region does not exceed 15, and selectively crushed to 250 μm 2 The number of particles within the area does not exceed 12, 10, 9, 8, 7, 6, 5, 4, 3, or 2.

[0139] The positive electrode active material prepared by this method has a significantly reduced particle size distribution of ultra-large primary particles, improved mechanical integrity of the primary particles and secondary particles, and delayed penetration of the positive electrode active material by the electrolyte and loss of the positive electrode active material (e.g., lithium ions) during cycling. At the same time, electrical contact failure and capacity polarization loss due to grain boundary cracking of the ultra-large primary particles are reduced, improving the chemical-mechanical and cycling performance of the positive electrode active material.

[0140] In some embodiments, the manufacturing method does not include multiple compaction granulations.

[0141] The manufacturing method of the present application has a simple process flow, high reproducibility, and relatively low cost, which is advantageous for industrial mass production.

[0142] In some embodiments, the method further comprises: The method includes the steps of mixing raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, and a molding aid with water, an alcohol, or a mixed solvent, grinding the mixture, drying the mixture, and compacting the mixture to obtain compacted particles, and packing, sintering, and pulverizing the compacted particles to obtain a positive electrode active material.

[0143] In some embodiments, the method further comprises: mixing raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, and a molding aid with water, an alcohol, or a mixed solvent, grinding, drying, and compacting to obtain compacted particles having an average particle size controlled in the range of 3 mm to 30 mm; The compacted particles are packed to a packing height of 5 cm to 30 cm and a porosity of 5% to 20%, and then sintered. and pulverizing the secondary particles obtained by sintering until Dv50 is 0.45 μm to 1.5 μm and / or 1≦(Dv90−Dv10) / Dv50≦3 to obtain a positive electrode active material.

[0144] In some embodiments, the method further comprises: a compaction granulation step of compacting and granulating raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid to obtain compacted particles; a sintering step of packing the compacted particles and sintering the compacted particles to obtain secondary particles; and a pulverization step of pulverizing the secondary particles to obtain a positive electrode active material.

[0145] In some embodiments, the method further comprises: a compaction granulation step of grinding raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, M, a molding aid, and a solvent to obtain a slurry, drying the slurry, and then compacting and granulating the slurry to obtain compacted particles; a sintering step of packing the compacted particles and sintering the compacted particles to obtain secondary particles; and a pulverization step of pulverizing the secondary particles to obtain a positive electrode active material.

[0146] First, the grinding process reduces the particle size of the ultra-large primary particles present in the raw materials, reducing the content of ultra-large primary particles in the raw materials and helping to reduce the particle size distribution of the ultra-large primary particles in the manufactured positive electrode active material, thereby reducing the particle sizes of the different raw materials and helping to obtain nano-level primary particles with more uniform particle sizes. At the same time, it improves the uniformity of the mixing of the different raw materials and helps to improve the uniformity of the different components in the manufactured positive electrode active material. The drying process also creates appropriate voids between the raw material particles, which helps to remove reducing gases generated by the decomposition of the carbon source during the sintering process.

[0147] In some embodiments, the compaction step specifically comprises: A step (1-1) of uniformly mixing initial reactants including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, and an M source, followed by pre-sintering to obtain an initial product; A step (1-2) of mixing and grinding an intermediate reactant containing an initial product, a carbon source, and a molding aid to obtain an intermediate product; and (2) compacting and granulating the intermediate product to obtain compacted particles; Here, the mass content of the carbon source in the step (1-1) is 2% to 5% based on the total mass of the initial reactants.

[0148] In some embodiments, the mass content of the carbon source in step (1-1) is optionally any value of 2%, 3%, 4%, 5%, or a range between any two of these values, based on the total mass of the initial reactants.

[0149] The small amount of carbon source in the pre-sintering process plays a reducing role, allowing the initial reactants to be thoroughly mixed and reacted, improving the uniformity and completeness of the reaction, and resulting in a highly uniform particle size of the initial product. The pre-sintering process pre-reacts the ultrafine particles in the initial reactants, reducing the content of small particles in the raw materials and improving the particle size uniformity of the material. At the same time, the intermediate reactants containing the initial products, carbon source, and molding aids are further ground to refine the large particles and reduce the content of ultra-large primary particles in the raw materials, further improving the particle size uniformity of the material, providing a material basis for the subsequent production of a positive electrode active material with excellent particle size uniformity.

[0150] In summary, the pre-sintering treatment improves the particle size uniformity of the initial reactants, allowing the intermediate product to be compacted and granulated to have excellent particle size uniformity, which helps to improve the uniformity of different components in the produced positive electrode active material.

[0151] In some embodiments, the intermediate product has a Dv50 of 0.45 μm to 1.25 μm, and a DV10 of 0.15 μm or more.

[0152] In some embodiments, the Dv50 of the intermediate product is optionally any value of 0.45 μm, 0.55 μm, 0.65 μm, 0.75 μm, 0.85 μm, 0.95 μm, 1.05 μm, 1.15 μm, 1.25 μm, or a range between any two of these values.

[0153] In some embodiments, the intermediate product D V 10 is optionally any one of 0.15 μm or more, 0.16 μm or more, 0.17 μm or more, 0.18 μm or more, 0.19 μm or more, and 0.20 μm or more.

[0154] Dv50 and D of the intermediate product VControlling 10 within an appropriate range is advantageous for controlling the mass content of small particles in the positive electrode active material, further improving the particle size uniformity of the positive electrode active material, improving the structural stability of the positive electrode active material, and improving the cycle performance of the battery.

[0155] The present application further provides a positive electrode active material produced by the method.

[0156] The present application further provides an application of the positive electrode active material prepared by the method in a secondary battery.

[0157] positive electrode plate The positive electrode plate of the present application includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and containing the positive electrode active material in any of the embodiments. For example, the positive electrode current collector has two surfaces facing each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0158] In the secondary battery of the present application, the positive electrode film layer generally includes a positive electrode active material, optionally an adhesive, and optionally a conductive agent. The positive electrode film layer is generally obtained by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing the positive electrode active material, optionally a conductive agent, optionally an adhesive, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The type and content of the conductive agent and adhesive are not specifically limited and can be selected according to actual needs. For example, the adhesive may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. By way of example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0159] In the secondary battery of the present application, the positive electrode current collector may be a metal foil sheet or a composite current collector. As an example of a metal foil sheet, the positive electrode current collector may be aluminum foil. The composite current collector may include a polymer base layer and a metal material layer formed on at least one surface of the polymer base layer. For example, the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.

[0160] Positive electrode plate manufacturing method The present application provides a method for manufacturing a positive electrode plate, specifically, the method for manufacturing the positive electrode plate includes: a compaction granulation step of compacting and granulating raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid to obtain compacted particles; a sintering step of packing the compacted particles and sintering the compacted particles to obtain secondary particles; a pulverization step of pulverizing the secondary particles to obtain a positive electrode active material; a coating step of coating at least one side of a current collector with a positive electrode slurry containing the positive electrode active material to form a positive electrode plate; Here, the positive electrode active material includes a substrate and a carbon coating layer located on the surface of the substrate, and the substrate has a structural general formula Li z Fe x Mn(1-xy)M y PO4, wherein 0.5≦x≦1, 0≦y≦0.1, 1≦z≦1.1, and M element is selected from at least one of Ti, V, and Mg; at least a portion of the positive electrode active material contains primary particles, and the particle size distribution of the primary particles in the positive electrode active material having a primary particle diameter of 80 nm or more and 180 nm or less is 10% or less; (250±5) μm of primary particles having a primary particle diameter of 1500 nm or more in a cross section of the positive electrode plate 2 The number of particles in the region does not exceed 15.

[0161] The positive electrode plate obtained by employing the above manufacturing method can improve the cycle stability of the positive electrode active material, improve the cycle stability of the positive electrode plate, and improve the room temperature and high temperature cycle performance of the battery by controlling the particle size distribution of the positive electrode active material primary particles having a primary particle diameter of 1500 nm or more and the primary particle diameter of 80 nm or more and 180 nm or less within an appropriate range.

[0162] In some embodiments, the average particle size of the compacted particles in the compaction granulation step is 3 mm to 30 mm. In some embodiments, the average particle size of the compacted particles in the compaction granulation step is optionally any value of 3 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, or a range between any two of these values.

[0163] Compacted particles are suitable size The range helps to improve the uniformity of different raw materials inside the particles, and the voids between the particles allow the release of reducing gases generated by the decomposition of the carbon source during the manufacturing process. discharge This is advantageous for increasing the uniformity of the carbon at different locations on the sintering device (e.g., sagger).

[0164] In some embodiments, the compacted particles have a compacted density of 1.0 g / cm 3 or more, or 1.2 to 3.0 g / cm 3 is.

[0165] In some embodiments, the compacted particles have a compacted density of, optionally, 1.0 g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 , 1.6g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 , 2.2g / cm 3 , 2.4g / cm 3 , 2.6g / cm 3 , 2.8g / cm 3 , 3.0g / cm 3 or a range between any two numbers.

[0166] Controlling the compaction density of the compacted particles within an appropriate range helps to increase the pot filling amount during the manufacturing process, thereby improving sintering production capacity.

[0167] In some embodiments, the sintering step specifically involves packing the compacted particles to a packing height of 5 cm to 30 cm, and sintering the compacted particles to obtain secondary particles.

[0168] In some embodiments, the sintering step specifically involves packing the compacted particles to a packing height of, selectively, 8 cm to 30 cm, 8 cm to 20 cm, 5 cm to 25 cm, 5 cm to 20 cm, 10 cm to 30 cm, 10 cm to 25 cm, or 10 cm to 20 cm.

[0169] Ensuring that the filling height of the compacted particles during the sintering process is within an appropriate range helps to timely discharge reducing gases generated by the decomposition of the carbon source during the sintering process, thereby accelerating heat transfer and avoiding uneven decomposition of the carbon source in the compacted particles at different positions in the sintering device, thereby improving the consistency of particle growth and simultaneously achieving productivity.

[0170] In some embodiments, the pulverization step specifically pulverizes the secondary particles so that their Dv50 is 0.45 μm to 1.5 μm, and the particle size distribution satisfies (Dv90-Dv10) / Dv50≦3.

[0171] In some embodiments, the milling step specifically mills the secondary particles to have a Dv50 of, optionally, any of 0.45 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.5 μm, or a range between any two of these values.

[0172] In some embodiments, the secondary particles are pulverized so that the particle size distribution satisfies any one of (Dv90-Dv10) / Dv50≦3, (Dv90-Dv10) / Dv50≦2.5, (Dv90-Dv10) / Dv50≦2, and (Dv90-Dv10) / Dv50≦1.5.

[0173] By pulverizing the secondary particles to have a particle size distribution within the above range, it is possible to improve the particle size uniformity of the positive electrode active material and the cycle stability of the positive electrode active material.

[0174] In some embodiments, the sintering temperature in the sintering step is 600° C. to 800° C., and / or the constant temperature sintering time in the sintering step is 2 hours to 12 hours.

[0175] In some embodiments, the sintering temperature is optionally any of 600°C, 650°C, 700°C, 750°C, 800°C, or a range between any two of these values.

[0176] In some embodiments, the sintering time is optionally any value of 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, or a range between any two of these values.

[0177] By controlling the sintering temperature and / or sintering time within an appropriate range, the compacted particles can be sintered sufficiently, and the positive electrode active material can have excellent structural parameters.

[0178] In some embodiments, the compaction step specifically comprises: The method includes a step (1) of grinding raw materials containing a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, M, a molding aid, and a solvent to obtain a slurry, drying the slurry, and then compacting and granulating it to obtain compacted particles.

[0179] First, the grinding process reduces the particle size of the ultra-large primary particles present in the raw materials, reducing the content of ultra-large primary particles in the raw materials and helping to reduce the particle size distribution of the ultra-large primary particles in the manufactured positive electrode active material, thereby reducing the particle sizes of the different raw materials and helping to obtain nano-level primary particles with more uniform particle sizes. At the same time, it improves the uniformity of the mixing of the different raw materials and helps to improve the uniformity of the different components in the manufactured positive electrode active material. The drying process also creates appropriate voids between the raw material particles, which helps to remove reducing gases generated by the decomposition of the carbon source during the sintering process.

[0180] In some embodiments, the compaction step specifically comprises: A step (1-1) of uniformly mixing initial reactants including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, and an M source, followed by pre-sintering to obtain an initial product; A step (1-2) of mixing and grinding an intermediate reactant containing an initial product, a carbon source, and a molding aid to obtain an intermediate product; and (2) compacting and granulating the intermediate product to obtain compacted particles; Here, the mass content of the carbon source in the step (1-1) is 2% to 5% based on the total mass of the initial reactants.

[0181] In some embodiments, the mass content of the carbon source in step (1-1) is optionally any value of 2%, 3%, 4%, 5%, or a range between any two of these values, based on the total mass of the initial reactants.

[0182] The small amount of carbon source in the pre-sintering process plays a reducing role, allowing the initial reactants to be thoroughly mixed and reacted, improving the uniformity and completeness of the reaction, and resulting in a highly uniform particle size of the initial product. The pre-sintering process pre-reacts the ultrafine particles in the initial reactants, reducing the content of small particles in the raw materials and improving the particle size uniformity of the material. At the same time, the intermediate reactants containing the initial products, carbon source, and molding aids are further ground to refine the large particles and reduce the content of ultra-large primary particles in the raw materials, further improving the particle size uniformity of the material, providing a material basis for the subsequent production of a positive electrode active material with excellent particle size uniformity.

[0183] In summary, the pre-sintering treatment improves the particle size uniformity of the initial reactants, allowing the intermediate product to be compacted and granulated to have excellent particle size uniformity, which helps to improve the uniformity of different components in the produced positive electrode active material.

[0184] In some embodiments, the intermediate product has a Dv50 of 0.45 μm to 1.25 μm, and a DV10 of 0.15 μm or more.

[0185] In some embodiments, the Dv50 of the intermediate product is optionally any value of 0.45 μm, 0.55 μm, 0.65 μm, 0.75 μm, 0.85 μm, 0.95 μm, 1.05 μm, 1.15 μm, 1.25 μm, or a range between any two of these values.

[0186] In some embodiments, the intermediate product D V 10 is optionally any one of 0.15 μm or more, 0.16 μm or more, 0.17 μm or more, 0.18 μm or more, 0.19 μm or more, and 0.20 μm or more.

[0187] Dv50 and D of the intermediate product V Controlling 10 within an appropriate range is advantageous for controlling the mass content of small particles in the positive electrode active material, further improving the particle size uniformity of the positive electrode active material, improving the structural stability of the positive electrode active material, and improving the cycle performance of the battery.

[0188] secondary battery The present application provides a secondary battery, which includes a positive electrode plate, a separator, a negative electrode plate, and an electrolyte in any embodiment.

[0189] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0190] In the secondary battery of the present application, the negative electrode film layer generally includes a negative electrode active material, optionally an adhesive, optionally a conductive agent, and optionally other auxiliary agents.

[0191] In some embodiments, the negative electrode active material comprises at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesocarbon microbeads, silicone-based materials, and tin-based materials.

[0192] The negative electrode film layer is typically formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, optionally a conductive agent, optionally an adhesive, and optionally other additives in a solvent and uniformly stirring the mixture. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. The type and content of the conductive agent and adhesive are not specifically limited and can be selected according to actual needs. For example, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., acetylene black, ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. For example, the adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). Other optional auxiliary agents may include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0193] In the secondary battery of the present application, the negative electrode film layer may be disposed on one side of the negative electrode current collector, or may be disposed on both sides of the negative electrode current collector simultaneously. For example, the negative electrode current collector has opposite sides in its thickness direction, and the negative electrode film layer is disposed on either one or both of the opposite sides of the negative electrode current collector.

[0194] In the secondary battery of the present application, the type of the negative electrode current collector is not specifically limited and can be selected according to actual needs.

[0195] In the secondary battery of the present application, the negative electrode current collector may be a metal foil sheet or a composite current collector. As an example of a metal foil sheet, the negative electrode current collector may be a copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0196] It should be noted that the negative electrode film layer parameters (e.g., thickness, compaction density, etc.) provided in this application refer to the parameters of the negative electrode film layer on a single side of the negative electrode current collector. When negative electrode film layers are installed on both sides of the negative electrode current collector, if the negative electrode film layer parameters on either side satisfy the requirements of this application, it is considered to fall within the scope of protection of this application. Furthermore, the ranges of negative electrode film layer thickness, compaction density, etc. described in this application refer to the parameters used to assemble the negative electrode film layer of a battery after compaction by cold pressing.

[0197] Furthermore, in the secondary battery of the present application, the negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the present application may further include a conductive undercoating (e.g., composed of a conductive agent and an adhesive) disposed between the negative electrode current collector and the negative electrode film layer. In other embodiments, the negative electrode plate described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0198] The electrolyte serves to conduct ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte may be liquid, gel, or all solid.

[0199] In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0200] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0201] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone.

[0202] In some embodiments, the electrolyte solution may further optionally contain additives, such as an additive for forming a negative electrode film or a positive electrode film, and may further include additives that can improve some battery performance, such as an additive for improving the overcharge performance of the battery or an additive for improving the high-temperature or low-temperature performance of the battery.

[0203] In the secondary battery of the present application, the type of separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability may be selected.

[0204] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitation.

[0205] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0206] The present application does not particularly limit the shape of the battery, which may be cylindrical, rectangular, or any other shape. For example, Fig. 6 shows a secondary battery 5 having a rectangular structure as an example.

[0207] In some embodiments, referring to FIG. 7 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select the number according to actual needs.

[0208] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by those skilled in the art depending on the application and capacity of the battery module.

[0209] Fig. 8 shows an example of a battery module 4. Referring to Fig. 8, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0210] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0211] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0212] 9 and 10 show an example of a battery pack 1. Referring to FIGS. 9 and 10, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0213] power consumption equipment The present application further provides a power consuming device, the power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0214] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0215] 11 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, which may employ a battery pack or a battery module to meet the demand for high power output and high energy density of secondary batteries.

[0216] Other examples of the device may be a mobile phone, a tablet computer, a notebook computer, etc. These devices are generally required to be thin, and may use a secondary battery as a power source.

[0217] Finally, it should be noted that the above examples are merely for the purpose of illustrating the technical solutions of the present application and are not intended to limit the same. Although the present application has been described in detail above with reference to the examples, those skilled in the art should understand that the technical solutions described in the examples may be modified or some or all of the technical features therein may be equivalently replaced, and such modifications or replacements will not substantially depart from the scope of the technical solutions of the examples of the present application, and all such modifications or replacements are within the scope of the claims and the description of the present application. In particular, the technical features described in the examples may be arbitrarily combined unless contradictory. The present application is not limited to the specific examples disclosed herein, but includes all technical solutions encompassed by the claims.

[0218] Example The following describes examples of the present application. The examples described below are illustrative and are intended to interpret the present application, but should not be understood as limitations on the present application. If no specific techniques or conditions are described in the examples, they are carried out according to the techniques, conditions, or product specifications described in documents within the field. If no manufacturer is specified for the reagents or equipment used, they are all ordinary products that are commercially available.

[0219] 1. Battery manufacturing Example 1 1) Manufacturing of positive electrode active material Lithium carbonate, ferric oxide, ammonium dihydrogen phosphate, and titanium dioxide were weighed out, with the mass ratio of Li:Fe:P being 1.01:0.99:1.01, and the mass ratio of titanium dioxide to lithium carbonate being 1:105. Water was added and the mixture was mixed uniformly to obtain a slurry, to which sucrose (8% by mass of all solid raw materials) and starch (1% by mass of all solid raw materials) were added. The solid content of the slurry was 40%.

[0220] The uniformly mixed slurry was ground in a ball mill until the Dv50 was approximately 0.5 μm, and then spray-dried (the negative pressure of the high-speed spray dryer was -650 to -200 Pa, the inlet temperature was 300 to 360 °C, and the outlet temperature was 100 to 140 °C). The powder obtained by spray-drying was compacted and granulated using a granulator to obtain a mean particle size of approximately 10 mm and a compacted particle density of 1.2 to 1.5 g / cm. 3 The granulated reactant was filled into a graphite sagger, with the filling depth of the material being 12 cm. The sagger filled with the reactant was placed in a kiln and sintered. The heating rate was controlled at 3°C / min, the temperature was kept at 750°C, and the heat-keeping time was set to 6 to 8 hours. After the material was cooled, it was pulverized using a jet mill or mechanical mill until the Dv50 was approximately 1.1 μm, yielding the positive electrode active material LiFe. 0.995 Ti 0.005 PO4@C is obtained, where the content of Ti element in the positive electrode active material is 1500 ppm.

[0221] 2) Manufacturing of positive electrode plates 2.0 wt% polyvinylidene fluoride adhesive was thoroughly dissolved in N-methylpyrrolidone (NMP), and then 1.0 wt% Super P, 0.5 wt% carbon nanotubes, and 96.5 wt% of the above positive electrode active material were added and stirred uniformly to obtain a positive electrode slurry. The slurry was evenly applied to the surface of an aluminum foil current collector and then transferred to a vacuum drying oven for complete drying. The dried electrode plate was rolled and punch-diced to obtain a positive electrode plate with a compaction density of 2.35 g / cm. 3 is.

[0222] 3) Manufacturing of negative electrode plates The active material, artificial graphite, the conductive agent, carbon black, the adhesive, styrene butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose (CMC-Na), were dissolved in deionized water as a solvent in a weight ratio of 96.7:1.3:0.8:1.2 and mixed uniformly to produce anode slurry. The cathode slurry was then uniformly coated onto anode current collector copper foil once or multiple times, followed by drying, cold pressing, and slitting to obtain anode plates.

[0223] 4) Electrolyte In an argon gas atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3:7, and LiPF6 lithium salt was dissolved in the organic solvent to prepare a solution with a mass content of 12.5%, thereby obtaining the electrolyte.

[0224] 5) Separator A polypropylene film was used as a separator.

[0225] 6) Battery manufacturing A positive electrode plate, a separator, and a negative electrode plate were stacked in this order, with a separator positioned between the positive and negative electrodes to provide isolation, and then wound to obtain an electrode assembly. The electrode assembly was placed in a battery case, dried, and then an electrolyte was injected. After further processes such as standing, hot and cold pressing, chemical forming, shaping, and capacity testing were performed, the lithium battery product of Example 1 was obtained.

[0226] Examples 2 to 10 are similar to the manufacturing method of Example 1, and specific parameter adjustments are as shown in Table 1.

[0227] Example 11 was produced using a method similar to that of Example 1, but magnesium hydroxide was used, and the mass ratio of magnesium hydroxide to lithium carbonate was adjusted to 0.73:105.

[0228] Example 12 was produced using a method similar to that of Example 1, except that vanadium pentoxide was used and the mass ratio of vanadium pentoxide to lithium carbonate was adjusted to 1.138:105.

[0229] The manufacturing method of Example 13 is similar to that of Example 1, but no doping elements are added to the raw materials, and the specific parameters are as shown in Table 1.

[0230] The manufacturing method of Example 14 is similar to that of Example 1, but the manufacturing process of the positive electrode active material is adjusted as follows.

[0231] 1) Manufacturing of positive electrode active material Compaction granulation: (1) Lithium carbonate, ferric oxide, ammonium dihydrogen phosphate, and titanium dioxide were weighed out separately, with a mass ratio of Li:Fe:P of 1.01:0.99:1.01, and a mass ratio of titanium dioxide to lithium carbonate of 1:105. Water was added and mixed uniformly to obtain a slurry. Sucrose was added at a mass fraction of 2% of all solid raw materials. The solid content of the slurry was 40%. The uniformly mixed slurry was ground in a ball mill until the Dv50 was approximately 0.5 μm and then spray-dried (the negative pressure of the high-speed spray dryer was -320 Pa, the inlet temperature was 320 °C, and the outlet temperature was 110 °C). The dried material was loaded into a sagger and placed in a kiln for sintering. The heating rate was controlled at 5 °C / min, the temperature was maintained at 750 °C, and the holding time was 6 hours.

[0232] (2) After cooling, the materials were milled using a mechanical mill. Water was added to the milled materials, sucrose, and starch to obtain a mixed slurry, in which the mass fraction of sucrose was 6% and the mass fraction of starch was 2%, based on the total mass of the solid matter in the slurry. The resulting slurry was milled using a ball mill until the slurry (i.e., the intermediate product in Table 1) had a Dv50 of 0.5 μm and a Dv10 of 0.12 μm, and was then spray-dried (the negative pressure of the high-speed spray dryer was -320 Pa, the inlet temperature was 320°C, and the outlet temperature was 110°C).

[0233] (3) The dried powder was compacted and granulated to obtain a powder with an average particle size of approximately 10 mm and a compacted particle density of 1.6 g / cm 3 is.

[0234] Sintering: The granulated reactant was filled into a graphite sagger, with the filling depth of the material set to 12 cm. The sagger filled with the reactant was placed in a kiln for sintering, with the heating rate controlled at 3°C / min, the temperature maintained at 750°C, and the heat retention time set to 6 hours.

[0235] Crushing: After cooling the material, crush it using a jet mill or mechanical mill until the Dv50 is 1 μm, and the positive electrode active material LiFe 0.995 Ti 0.005 PO4@C is obtained, where the content of Ti element in the positive electrode active material is 1500 ppm.

[0236] Examples 15 and 16 are similar to the manufacturing method of Example 14, and specific manufacturing parameters are shown in Table 1.

[0237] Comparative Example 1 The battery of Comparative Example 1 was manufactured in a similar manner to that of Example 1, except that no compaction molding was performed and no molding additives were added, and the sintering reaction was carried out directly after the spraying was completed.

[0238] Comparative Example 2 The battery of Comparative Example 2 was manufactured using a method similar to that of Example 1, except that no compaction additive was added.

[0239] Comparative Examples 3 to 6 are similar to the manufacturing method of Example 1, and specific parameter adjustments are as shown in Table 1.

[0240] The battery of Comparative Example 7 was manufactured using a method similar to that of Example 1, but the method of manufacturing the active material was adjusted as follows.

[0241] A) Anhydrous iron phosphate and lithium carbonate were weighed out in a molar ratio of 1:0.5, and 0.2 wt% titanium dioxide was mixed as an ion doping additive. Pure water was then added to prepare a slurry, which was then subjected to ball milling.

[0242] B) The slurry after ball milling is transferred to a sand mill and sand-polished. The particle diameter of the sand-polished product is D V 50 was controlled to 0.8 μm.

[0243] C) 5 wt% glucose was added to the sand-polished slurry as an organic carbon source, and the temperature of the slurry was maintained at 80°C to 85°C (specifically 80°C). After slowly stirring for 2 hours, the slurry was spray-dried to obtain a carbon-coated lithium iron phosphate precursor powder.

[0244] D) The precursor powder was transferred to a sintering furnace, where it was heated from room temperature to 380°C at a rate of 10°C / min in a nitrogen gas protective atmosphere, kept at that temperature for 4 hours, and then heated to 700°C at a rate of 10°C / min, sintered for 10 hours, and then naturally cooled to obtain a sintered powder.

[0245] E) The sintered material is pulverized in a jet mill to a pulverized particle size D V 10 range 0.41μm, D V 50 particle size range 1.08 μm, D V The particle size range of 90 was controlled to 3.3 μm, and the sieved material was passed through a sieve and iron was removed with an electric current to obtain a carbon-coated lithium iron phosphate positive electrode active material (the mass percentage of carbon coated on the surface of the lithium iron phosphate material was 1.35%).

[0246] 2. Performance test 1. Volume average particle size Dv10, Dv50, Dv90 test Instrument model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard flow: GB / T19077-2016 / ISO 13320:2009.

[0247] Specific test procedure: Take an appropriate amount of sample to be measured (sample concentration should be 8-12% light blocking), add 20ml of deionized water, and use ultrasonic waves for 5 minutes (53KHz / 120W) to completely disperse the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standards.

[0248] 2. Morphological examination The positive electrode active materials prepared in the examples and comparative examples were examined using a ZEISS sigma 300 scanning electron microscope to observe the morphology of the samples according to standard JY / T010-1996.

[0249] 3. Method for measuring primary particle size in positive electrode plate The electrode plate was cut perpendicular to the large surface of the electrode plate using an argon ion beam to expose the cross section, and the cross section was photographed using an SEM. The particle diameter of the particles was calculated using the equivalent circular area.

[0250] Taking FIG. 12 as an example, FIG. 12 shows an SEM image of the cross section of the electrode plate, and the double-headed arrow in the figure indicates the major axis of the primary particle in the positive electrode plate, and measurements and statistics were performed on the particle diameter of the primary particle.

[0251] The particle size in this patent is the area-equivalent circular diameter, and the area of ​​each particle is obtained by statistical analysis using graphics software.

[0252] 4. Primary particles with a diameter of 100 nm or more and 1500 nm or less are (250±5) μm in the cross section of the positive electrode plate. 2 Particle size distribution index within the region The electrode plate was cut perpendicular to the major surface of the electrode plate using an argon ion beam to expose the cross section, and the cross section was photographed using a scanning electron microscope. The particle size of the active material was statistically analyzed using the equivalent circular area statistical method, as shown in Figure 13.

[0253] The particle size distribution index (PDI) is calculated by multiplying the standard deviation σ of particle size by the average particle size.

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[0254] 5. Battery performance test 1) Capacity retention test at 25℃ The capacity retention test procedure was as follows: at 25°C, the fabricated battery was charged to 3.65 V at a constant current of 1 C, then further charged at a constant voltage of 3.65 V until the current decreased to 0.05 C, and then discharged to 2.5 V at 1 C. The resulting capacity was designated as the initial capacity (C0). The same battery was subjected to the same steps, and the discharge capacity (Cn) after the nth cycle was recorded. The battery capacity retention after each cycle was calculated as Pn = Cn / C0 × 100%. The capacity retention was measured after 1,000 cycles under the above conditions.

[0255] 2) Capacity retention test at 60℃ The capacity retention test process was as follows: the fabricated battery was charged at 60°C at a constant current of 1 C to 3.65 V, then further charged at a constant voltage of 3.65 V until the current decreased to 0.05 C, and then discharged at 1 C to 2.5 V, and the resulting capacity was designated as the initial capacity (C0). The above steps were repeated for the same battery, and the discharge capacity (Cn) of the battery after the nth cycle was simultaneously recorded. The battery capacity retention after each cycle was calculated as Pn = Cn / C0 × 100%, and the capacity retention after 1000 cycles under the above measurement conditions was measured.

[0256] 6. Measurement of the content of doping elements Ti, V, and Mg According to methods known in the art, a mixed acid of HF, HNO3, and HCl was prepared to dissolve the sample, and the titanium, vanadium, and Mg in the positive electrode material were sufficiently dissolved in the solution. Then, the Ti, V, and Mg elements were measured by inductively coupled plasma atomic emission spectroscopy.

[0257] 7. Evaluation of carbon distribution uniformity After sintering and cooling, the unpulverized material was taken and divided into three layers (top, middle and bottom) according to the height of the material packed in the graphite sagger. Samples were taken and the carbon content was measured in accordance with the carbon content measurement method (infrared carbon sulfur tester) in GB / T 33822-2017. The average carbon content of the top, middle and bottom three-layer material was calculated, and the extreme difference (i.e., the difference between the maximum and minimum values) was calculated based on the average carbon content of the top, middle and bottom three-layer material.

[0258] The material that was sintered, cooled, and pulverized was taken out, and the carbon content of the manufactured positive electrode active material was measured in accordance with the carbon content measurement method (infrared carbon sulfur tester) in GB / T 33822-2017.

[0259] When the ratio of the polarity difference to the carbon content of the positive electrode active material did not exceed 10%, the uniformity of the carbon distribution was determined to be relatively good; when the ratio of the two was greater than 10% but not greater than 20%, the uniformity of the carbon distribution was determined to be good; when the ratio of the two was greater than 20% but not greater than 30%, the uniformity of the carbon distribution was determined to be poor; and when the ratio of the two was greater than 30%, the uniformity of the carbon distribution was determined to be relatively poor.

[0260] 3. Analysis of the test results of each example and comparative example FIG. 2 shows an SEM image of the positive electrode active material prepared in Example 1. It was found that the primary particle size distribution of the positive electrode active material was very uniform, and the content of fine particles and large particles was low.

[0261] 3A and 3B show scanning electron micrographs of the argon ion beam cut cross section of the positive electrode plate prepared in Example 1. A uniform particle size distribution can be clearly observed. The content of fine particles and large particles in the positive electrode active material is extremely low. The proportion of nanoparticles with a diameter of less than 80 nm is 2% or less, and 250 μm of particles with a diameter of 1500 nm or more is 1500 μm. 2 The number inside is two.

[0262] 4A and 4B show scanning electron microscope photographs of the argon ion beam cut cross section of the positive electrode plate manufactured in Comparative Example 1, in which a relatively large amount of fine powder and ultra-large primary particles can be clearly observed.

[0263] FIG. 13 shows a scanning electron microscope photograph of an argon ion beam cut cross section of the positive electrode active material of Example 15 after it was manufactured into a positive electrode plate, and it was clearly observed that the particle diameter of the primary particles had good uniformity.

[0264] Table 1 shows the parameters of the positive electrode active materials and batteries manufactured in each Example and Comparative Example. Table 2 shows the particle diameter Dv50 (μm), particle size distribution concentration (Dv90-Dv10) / Dv50, particle size distribution of the fine powder (percentage of particle sizes of fine powder with particle diameters of 80-180 nm), and number of large particles (250 μm 2the number of primary particles with a particle diameter of 1500 nm or more within the area of ​​the positive electrode plate), particle size distribution index (the number of primary particles with a particle diameter of 100 nm or more and 1500 nm or less within a 250 μm 2 The graph shows the particle size distribution index within the range of 0.01 mm, the carbon distribution uniformity evaluation results, and the capacity retention test results for 1000 cycles of secondary batteries at 25°C and 60°C.

[0265] [Table 1] JPEG2026503803000050.jpg245170

[0266] [Table 2] JPEG2026503803000052.jpg245170

[0267] As can be seen from the above results, the particle size distribution of large and small particles in the positive electrode active materials of Examples 1 to 16 was reduced, and the uniformity of the charge / discharge reaction and cycle performance of the positive electrode active materials were significantly improved.

[0268] FIG. 5 shows the cycle curves of Example 1 and Comparative Example 1 at 25°C and 60°C (two samples were measured in parallel). It can be seen that the secondary battery manufactured in Example 1 has significantly improved cycle performance at room temperature and high temperature conditions compared to the secondary battery manufactured in Comparative Example 1.

[0269] The positive electrode plate in Examples 1 to 16 includes a current collector and a positive electrode film layer located on at least one side of the current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a substrate and a carbon coating layer located on a surface of the substrate, at least a portion of the positive electrode active material includes primary particles, the particle size distribution of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less in the positive electrode active material is 10% or less, and the particle size distribution of primary particles having a primary particle diameter of 1500 nm or more in the positive electrode active material is (250±5) μm 2The number of particles in this region did not exceed 15. In Examples 1 to 16, compared to Comparative Example 7 and the positive electrode active material of the prior art, the particle size distribution of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less was 35%, and the primary particle diameter of primary particles having a primary particle diameter of 1500 nm or more was (250±5) μm in the cross section of the positive electrode plate. 2 The number of particles in this region is 25. Compared to Comparative Example 7, by adopting the positive electrode active material and positive electrode plate of the present application, the cycle capacity retention rate of the battery at room temperature and high temperature was improved, and the cycle performance of the battery at room temperature and high temperature was improved. Compared to Comparative Examples 1 to 7, by adopting the positive electrode active material and positive electrode plate of the present application, Examples 1 to 16 were able to improve the room temperature cycle capacity retention rate and high temperature cycle capacity retention rate of the battery, and the room temperature and high temperature cycle performance of the battery.

[0270] As can be seen from a comparison between Examples 1, 3, 4, 8, 9, 11 to 16 and Examples 2, 5 to 7, and 10, the primary particle diameter of the positive electrode active material is 100 nm or more and 1500 nm or less, and the primary particle diameter of the positive electrode plate is (250±5) μm 2 The particle size distribution index within this region was 0.45 or less, and the room temperature cycle performance and high temperature cycle performance of the battery were further improved. As can be seen from a comparison of Examples 4, 15 to 16 with Examples 1 to 3, and 5 to 14, the primary particles in the positive electrode active material having a primary particle size of 100 nm or more and 1500 nm or less had a particle size distribution of (250±5) μm in the cross section of the positive electrode plate. 2 The particle size distribution index within this region was 0.36 or less, and the room temperature cycle capacity retention rate and high temperature cycle capacity retention rate of the battery were further improved.

[0271] In Examples 1 to 3, the average particle size of the compacted granules was adjusted, and compared to Comparative Examples 3 and 4, the average particle size of the compacted granules was in the range of 3 to 30 mm, which resulted in good air permeability during the sintering process of the material, uniform particle heating, good uniformity of the carbon content, and significantly improved battery cycle performance. If the average particle size of the compacted granules was too small or too large, it would be difficult to control the particle size distribution of the fine powder and the number of large particles.

[0272] In Examples 4 and 5, the packed height of the compacted particles during the sintering process was adjusted to a range of 5 to 30 cm, which ensured good air permeability during the sintering process, uniform particle heating, uniform carbon distribution, and good particle growth consistency, significantly improving the cycle performance of the battery and favoring good production capacity.

[0273] In Examples 6 to 8, the Dv50 value of the positive electrode active material after the pulverization treatment was adjusted, and compared with Comparative Example 6, the Dv50 value was within the range of 0.45 to 1.5 μm, the particle size of the positive electrode active material was fine, and at least some nano-level primary particles were included therein, which was advantageous for the release and embedding of lithium ions in the active material. In addition, the (Dv90-Dv10) / Dv50 of the obtained positive electrode active material powder was less than 3, and the particle size distribution concentration was high. If the Dv50 was too small or too high, it could lead to a deterioration in cycle performance. If the Dv50 was too small, the overall particle size would be low, the proportion of small particles would increase, and the stability of the material surface would be reduced. If the Dv50 was too large, the overall particle size would be Large This leads to an increase in the proportion of large particles and an increase in the crushing effect of particles during the cycling process, all of which are unfavorable to improving the stability of the material.

[0274] In Examples 9 and 10, the compaction density of the compacted granulation was adjusted to 1 to 2.5 g / cm. 3 This is advantageous for improving sintering production capacity. Compared with Comparative Example 1 and Comparative Example 2, if the compaction density is too low or no compaction molding process is performed, it is disadvantageous to the uniformity of particle size and carbon distribution.

[0275] In Examples 11 to 13, the doping element reactant was adjusted, demonstrating that the manufacturing method according to the present invention is applicable to phosphate-based positive electrode active materials containing different doping elements and those containing no doping elements. The doped phosphate-based positive electrode active materials manufactured using magnesium hydroxide and vanadium pentoxide had particle size distributions and electrical performances similar to those of the doped phosphate-based positive electrode active materials manufactured using titanium dioxide. The doped phosphate-based positive electrode active materials manufactured in the examples also had good particle size distributions and electrical performances.

[0276] In Examples 1 to 13, the positive electrode active materials produced without compaction granulation had low particle size distribution concentration and poor carbon content uniformity compared to Comparative Example 1. Compared to Comparative Example 5, adding a molding aid to the raw materials helped to improve the particle size distribution concentration and also helped to improve the chemical and mechanical performance, thereby improving the cycle performance of the battery.

[0277] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments and other methods that are configured by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0278] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate, 6 compacted particles, 7 sagger.

Claims

1. A positive electrode plate includes a current collector and a positive electrode film layer located on at least one side of the current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including a substrate and a carbon coating layer located on a surface of the substrate, the substrate having a structural general formula Li ｚ Fe ｘ Mn （１－ｘ－ｙ） M ｙ P.O. ４ wherein 1≦z≦1.1, 0.5≦x≦1, 0≦y≦0.1, and the M element is selected from at least one of Ti, V, and Mg; at least a portion of the positive electrode active material contains primary particles, and a particle size distribution of primary particles having a primary particle diameter of 80 nm or more and 180 nm or less in the positive electrode active material is 10% or less; (250±5) μm of primary particles having a primary particle diameter of 1500 nm or more in a cross section of the positive electrode plate ２ The number of particles in the region of (a) does not exceed 15.

2. 2. The positive electrode plate according to claim 1, wherein the particle size distribution of the positive electrode active material primary particles having a primary particle diameter of 80 nm or more and 180 nm or less is 8.5% or less.

3. In the positive electrode active material, primary particles having a primary particle diameter of 1500 nm or more are (250±5) μm in a cross section of the positive electrode plate. ２ 2. The positive electrode plate of claim 1, wherein the number of particles in the region of is not more than 12.

4. The primary particle diameter of the primary particles is 100 nm or more and 1500 nm or less, and the cross section of the positive electrode plate is (250±5) μm ２ the particle size distribution index within the region is 0.45 or less, and optionally 0.36 or less; 2. The positive electrode plate according to claim 1, wherein the particle size distribution index is a ratio obtained by dividing the standard deviation of the primary particle size of the primary particles by the average primary particle size.

5. The positive electrode plate according to claim 1, wherein the positive electrode active material contains secondary particles, and the particle size distribution of the secondary particles satisfies (Dv90-Dv10) / Dv50≦3.

6. The positive electrode plate according to claim 5, wherein the secondary particles have a Dv50 of 0.45 to 1.5 μm.

7. 0.6<x≦1, 0≦y<0.1, 1≦z≦1.1, 7. The positive electrode plate according to claim 1, wherein the mass content of the M element in the positive electrode active material is 1000 ppm to 6000 ppm.

8. A method for manufacturing a positive electrode plate, specifically, a compaction granulation step of compacting and granulating raw materials including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, an M source, and a molding aid to obtain compacted particles; a sintering step of packing the compacted particles and sintering the compacted particles to obtain secondary particles; a pulverization step of pulverizing the secondary particles to obtain a positive electrode active material; a coating step of coating at least one side of a current collector with a positive electrode slurry containing the positive electrode active material to form a positive electrode plate; Here, the positive electrode active material includes a substrate and a carbon coating layer located on the surface of the substrate, and the substrate has a structural general formula Li ｚ Fe ｘ Mn （１－ｘ－ｙ） M ｙ P.O. ４ wherein 0.5≦x≦1, 0≦y≦0.1, 1≦z≦1.1, and the M element is selected from at least one of Ti, V, and Mg; at least a portion of the positive electrode active material contains primary particles, and a particle size distribution of the primary particles in the positive electrode active material having a primary particle diameter of 80 nm or more and 180 nm or less is 10% or less; (250±5) μm of primary particles having a primary particle diameter of 1500 nm or more in a cross section of the positive electrode plate ２ The method for manufacturing a positive electrode plate, wherein the number of particles in the region does not exceed 15.

9. The method according to claim 8, wherein the average particle size of the compacted particles in the compaction granulation step is 3 mm to 30 mm.

10. The compaction density of the compacted particles is 1.0 g / cm ３ or more, or 1.2 to 3.0 g / cm ３ 9. The method according to claim 8, wherein

11. The manufacturing method according to claim 8, wherein the sintering step specifically comprises filling the compacted particles to a filling height of 5 cm to 30 cm, and sintering the compacted particles to obtain secondary particles.

12. Specifically, the pulverization step pulverizes the secondary particles so that their Dv50 is 0.45 μm to 1.5 μm, 9. The method according to claim 8, wherein the secondary particles are pulverized so that the particle size distribution satisfies (Dv90-Dv10) / Dv50≦3.

13. 9. The method according to claim 8, wherein the sintering temperature in the sintering step is 600° C. to 800° C., and / or the constant temperature sintering time in the sintering step is 2 hours to 12 hours.

14. Specifically, the compaction granulation step includes:

9. The method according to claim 8, comprising the steps of grinding raw materials containing a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, M, a molding aid, and a solvent to obtain a slurry, drying the slurry, and then compacting and granulating the dried slurry to obtain compacted particles.

15. Specifically, the compaction granulation step includes: A step (1-1) of uniformly mixing initial reactants including a lithium source, an iron source, a manganese source, a phosphorus source, a carbon source, and an M source, followed by pre-sintering to obtain an initial product; A step (1-2) of mixing and grinding an intermediate reactant containing an initial product, a carbon source, and a molding aid to obtain an intermediate product; (2) compacting and granulating the intermediate product to obtain compacted particles; The method according to any one of claims 8 to 13, wherein the mass content of the carbon source in step (1-1) is 2% to 5% based on the total mass of the initial reactants.

16. 16. The method of claim 15, wherein the intermediate product has a Dv50 of 0.45 μm to 1.25 μm and a DV10 of 0.15 μm or more.

17. A secondary battery comprising a negative electrode plate, a separator, an electrolyte, and the positive electrode plate according to any one of claims 1 to 7 or a positive electrode plate manufactured by the manufacturing method according to any one of claims 8 to 16.

18. A power consuming device comprising the secondary battery of claim 17.

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