Cathode active material and method of manufacturing the same, positive plate, secondary battery and electric device

Abstract

As a positive electrode active material, the positive electrode active material comprises lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles, wherein the primary average particle size of the lithium iron phosphate particles is 500 to 3000 nm, the specific surface area BET of the lithium iron phosphate particles is 3 m² / g to 8 m² / g, and the specific surface area of ​​the lithium nickel cobalt manganese oxide particles is 0.4 m² / g to 2.0 m² / g. The positive electrode active material may have relatively excellent processing performance while also possessing a capacity per gram.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] The present application claims priority to Chinese patent application No. 202410026192.7, filed on January 8, 2024, titled "Cathode active material and method for manufacturing the same, cathode piece, secondary battery and electric device," and the said Chinese patent application is incorporated into the present application by reference.

[0003] The present application relates to the field of secondary battery technology, and in particular to a positive electrode active material and a method for manufacturing the same, a positive electrode piece, a secondary battery, and an electric device. Background Technology

[0004] Recently, lithium-ion batteries are being widely applied in various fields, including energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. The problem to be solved

[0005] Lithium nickel cobalt manganese oxide-based materials and lithium iron phosphate-based materials are commonly used lithium-ion cathode active materials. To lower the cost of lithium-ion batteries, lithium nickel cobalt manganese oxide-based materials and lithium iron phosphate-based materials can be used in combination, but there are a series of processing problems in the process of manufacturing a cathode slurry by mixing lithium nickel cobalt manganese oxide-based materials and lithium iron phosphate-based materials. means of solving the problem

[0006] This application has been made in consideration of the above-described problem and aims to solve at least one of the technical problems existing in the prior art. Accordingly, this application provides a positive electrode active material and a method for manufacturing the same, a positive electrode piece, a secondary battery, and an electric device. The positive electrode active material of this application may have relatively excellent processing performance while also possessing the capacity per gram of a secondary battery.

[0007] The first aspect of the present application provides a positive electrode active material, wherein the positive electrode active material comprises lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles, the primary average particle size of the lithium iron phosphate particles is 500 to 3000 nm, and the specific surface area BET of the lithium iron phosphate particles is 3 m 2 / g~8m 2 / g, and the specific surface area of ​​the lithium nickel cobalt manganese oxide particles is 0.4m 2 / g~2.0m 2 / g is.

[0008] To improve the electrochemical performance of lithium iron phosphate particles, they are generally nanosized to enhance their electron transport capabilities. However, nanosized lithium iron phosphate particles have an excessively large specific surface area, leading to severe moisture absorption. In actual applications, they are often mixed with lithium nickel cobalt manganese oxide particles to reduce costs; however, during the preparation of the mixed slurry, the lithium iron phosphate particles easily gel due to their high moisture absorption, resulting in a series of processing problems such as reduced solid content and decreased filtration performance. Furthermore, high molecular weight adhesives used in lithium nickel cobalt manganese oxide cathode slurries, such as polyvinylidene fluoride, exhibit poor compatibility with nanometer-sized lithium iron phosphate. In such adhesive systems, lithium iron phosphate particles easily aggregate, causing processing issues. The primary average particle size of the lithium iron phosphate particles in this application is 500–3000 nm, and the specific surface area is 3 m². 2 / g~8m 2 / g, and the specific surface area of ​​the lithium nickel cobalt manganese oxide particles is 0.4m 2 / g~2.0m 2 / g. A reduced specific surface area is advantageous for lowering the moisture absorption performance of the anode slurry, thereby reducing gelation and aggregation phenomena during the slurry processing process, and can also improve the drying speed and degree of drying of the electrode piece. At the same time, a relatively large primary average particle size is advantageous for better dispersing lithium iron phosphate particles in a high molecular weight adhesive system and further reducing the occurrence of aggregation phenomena. However, excessively large particle size and excessively low specific surface area affect kinetic performance and lower the capacity per gram. The anode active material of the present application increases the primary average particle size of lithium iron phosphate particles and lowers the specific surface area, controlling both within a reasonable range to obtain relatively excellent processing performance while also possessing the capacity per gram of the secondary battery.

[0009] In any embodiment, the lithium iron phosphate particles have the molecular formula Li m1 Fe x1 P y1 O z1 Q q1 having, where Q comprises at least one of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, and 0.95≤m1≤1.15, 0.9≤x1≤1, 0.95≤y1≤1, 3.5≤z1≤4, 0 <q1≤0.1이며, 및 / 또는

[0010] Lithium nickel cobalt manganese oxide particles have the molecular formula LiR x2 Ni y2 Co z2 Mn 1-x2-y2-z2 It has O2, where R includes at least one of Cr, Ti, V, Mg, Al, and Nb, and 0≤x2<1, 0 <y2<1, 0<z2<1, 0<x2+y2+z2<1이다.

[0011] Doping lithium iron phosphate particles and / or lithium nickel cobalt manganese oxide particles with the aforementioned elements helps to improve the ion transport capacity of the cathode active material. The aforementioned elements create vacancies in the crystal lattice of the particles or change the length of interatomic bonds, thereby allowing lithium ions to move easily within the crystal lattice, which can effectively improve the conductivity performance of the particles themselves and improve the kinetic performance of the cathode active material.

[0012] In any embodiment, the primary average particle size of the lithium iron phosphate particles is 650 to 2500 nm.

[0013] By controlling the primary average particle size of the lithium iron phosphate particles within a reasonable range, it helps to further improve the processing performance of the anode slurry while simultaneously increasing the capacity per gram of the secondary battery.

[0014] In any embodiment, the BET of the lithium iron phosphate particles is 4m 2 / g~7m 2 / g, and the BET of the lithium nickel cobalt manganese oxide particles is 0.6m 2 / g~2.0m 2 / g is.

[0015] If the BET of lithium iron phosphate particles and / or lithium nickel cobalt manganese oxide particles is too high, it increases the moisture absorption performance of the particles and affects the processing performance of the mixed cathode slurry. However, if the BET of lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles is too low, the capacity per gram and kinetic performance decrease. The BET of lithium iron phosphate particles is 4m 2 / g~7m 2 Controlled within / g, and the BET of lithium nickel cobalt manganese oxide particles is 0.6m 2 / g~2.0m 2 By controlling it within / g, it is advantageous to further balance the processing performance of the anode slurry and the capacity per gram of the secondary battery.

[0016] In any embodiment, when calculated based on the total weight of the lithium iron phosphate particles, the carbon content of the lithium iron phosphate particles is Cx weight%, and the ratio z of BET to Cx of the lithium iron phosphate particles satisfies 1.5≤z≤8.5, and in some embodiments, z satisfies 3≤z≤6.

[0017] In this application, the ratio z of the specific surface area BET and Cx of the lithium iron phosphate particles can characterize the degree of uniform density of the carbon contained in the lithium iron phosphate particles, and when the primary average particle size and carbon content of the lithium iron phosphate particles remain unchanged, the lower the ratio z, the more uniform and dense the carbon contained in the lithium iron phosphate particles becomes. Improving the degree of uniform density of the contained carbon is advantageous for further improving the kinetic performance and capacity per gram of the lithium iron phosphate particles, but if the carbon coating density is too high, it affects the insertion and extraction of lithium ions and has some effect on the kinetic performance and capacity per gram of the secondary battery. The range of the ratio z in the embodiments of this application is advantageous for improving the conductivity performance of the particle surface and for further improving the kinetic performance and capacity per gram of the secondary battery by ensuring that the carbon contained in the lithium iron phosphate particles has an appropriate uniform density.

[0018] In any embodiment, the carbon content of the lithium iron phosphate particles is 0.8 wt% to 2.0 wt% when calculated based on the total weight of the lithium iron phosphate particles, and in some embodiments, the carbon content of the lithium iron phosphate particles is 1.0 wt% to 1.6 wt% when calculated based on the total weight of the lithium iron phosphate particles.

[0019] Increasing the carbon content of lithium iron phosphate particles helps improve conductivity performance, thereby improving kinetic performance and capacity per gram; however, if the carbon content is too high, it affects the insertion and extraction of lithium ions and affects the capacity per gram of the secondary battery to some extent. The carbon content range of the present application helps to obtain relatively excellent kinetic performance and capacity per gram.

[0020] In any embodiment, Q comprises at least one of Ti, V, Mg, and Nb, and in some embodiments, Q is Ti;

[0021] When calculated based on the total weight of the lithium iron phosphate particles, the content of Q in the lithium iron phosphate particles is 1,000 to 10,000 ppm, and in some embodiments, when calculated based on the total mass of the lithium iron phosphate particles, the content of Q in the lithium iron phosphate particles is 2,500 to 6,000 ppm.

[0022] In conventional lithium iron phosphate particles, the content of doping elements is generally low or no doping elements are added. Increasing the content of Q element in lithium iron phosphate particles helps to further improve the bulk ion transport capacity of the lithium iron phosphate particles and enhance kinetic performance. However, as the content of Q element increases further, the bulk ion transport capacity may not increase continuously, and it may also occupy the positions of lithium ions, which may affect the expression of capacity per gram. The range of Q element in this application helps to obtain relatively excellent kinetic performance and capacity per gram.

[0023] In any embodiment, the ratio of the Dv50 of the lithium iron phosphate particles to the Dv50 of the lithium nickel cobalt manganese oxide particles is 1:(1 to 25), and in some embodiments, the ratio of the Dv50 value of the lithium iron phosphate particles to the Dv50 of the lithium nickel cobalt manganese oxide particles is 1:(1 to 20).

[0024] In any embodiment, the Dv50 of the lithium iron phosphate particles is 500 to 5000 nm, and in some embodiments, the Dv50 of the lithium iron phosphate particles is 700 to 2500 nm.

[0025] In any embodiment, the Dv50 of the lithium nickel cobalt manganese oxide particles is 1200 to 20000 nm, and in some embodiments, the Dv50 of the lithium nickel cobalt manganese oxide particles is 3000 to 15000 nm.

[0026] By controlling the Dv50 ratio range and value range of the lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles of the embodiment of the present application to within the above-described range, it is advantageous for the lithium iron phosphate particles to be uniformly and densely packed between the lithium nickel cobalt manganese oxide particles, it alleviates the aggregation phenomenon of single-component particles in the composite cathode active material, and improves the compression density of the cathode active material.

[0027] In any embodiment, the Dv50 of the lithium iron phosphate particles is 870 to 1500 nm, and the Dv50 of the lithium nickel cobalt manganese oxide particles is 1800 to 4200 nm.

[0028] In any embodiment, the mass percentage of lithium iron phosphate particles, calculated based on the total mass of the positive electrode active material, is 5% to 80%, and in some embodiments, 15% to 50%.

[0029] In any embodiment, when calculated based on the total mass of the positive electrode active material, the mass percentage of lithium nickel cobalt manganese oxide particles is 20% to 95%, and in some embodiments, 50% to 85%.

[0030] By controlling the mass percentage of lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles within the aforementioned range, it helps to further balance the electrical performance and cost of the cathode active material.

[0031] In any embodiment, the capacity ratio of the lithium iron phosphate particles is η≥88%, and η is:

[0032] A battery having lithium iron phosphate particles as the positive electrode active material is charged and discharged twice with a constant current at a rate limit of 0.1C within a voltage range of 2.0V to 3.75V, followed by a single charge and discharge with a rate limit of 1C. In a charge-discharge test with a rate limit of 1C, a capacity value at a discharge voltage of 3.2V is extracted as C1, and a capacity value discharged to 2.0V is extracted as C2, and η is defined as C1 / C2. Here, the charging process includes constant voltage charging, the constant voltage is 3.75V, and the constant voltage cutoff current is 50μA.

[0033] The capacity ratio η of lithium iron phosphate particles can represent kinetic performance and platform maintenance performance, and can be controlled by adjusting the primary average particle size, carbon content, ratio of carbon source to carbon film agent, and the modifier and its content. The η value of the lithium iron phosphate particles in the embodiments of this application is ≥ 88%, and they possess relatively excellent kinetic performance. At the same time, when the η value is relatively high, the secondary battery can still maintain relatively excellent output performance even when discharged at a low SOC (State of Charge); that is, when a battery with a high η value is discharged at a large current from a low electric charge, the voltage drop is relatively small. In the cathode active material of this application, during discharge, the voltage of the lithium nickel cobalt manganese oxide particles is high and participates in discharge first, and subsequently, the lithium iron phosphate particles participate in discharge. Since they must handle a relatively large current, polarization is prone to occur. As the lithium iron phosphate particles of the present application possess relatively high kinetic performance, they are advantageous for improving the discharge output performance of a secondary battery.

[0034] In any embodiment, the lithium iron phosphate particles satisfy at least one of (a) to (e):

[0035] a) Dv10≥200 nm of lithium iron phosphate particles;

[0036] b) Dv90≤10000nm of lithium iron phosphate particles;

[0037] c) Dv99≤12000nm of lithium iron phosphate particles;

[0038] d) Powder compression density of lithium iron phosphate at 3T pressure ≥ 2.25 g / cm³ 3 ;

[0039] e) The powder resistivity of lithium iron phosphate is less than 60 Ω·cm.

[0040] By ensuring that the lithium iron phosphate particles satisfy at least one of (a) to (e), the lithium iron phosphate particles can be made to better realize the technical effects of the present application.

[0041] A second aspect of the present application provides a method for manufacturing a positive electrode active material, the method comprising: a step of mixing lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles; and

[0042] Herein, the process for manufacturing lithium iron phosphate particles comprises: providing a raw material containing at least a lithium source, an iron source, a phosphorus source, an optional carbon source, an optional carbon film-forming agent, and an optional modifier, and sintering at least twice; wherein,

[0043] The primary sintering temperature is 500℃ to 760℃, and in some embodiments, 550℃ to 720℃;

[0044] The secondary sintering temperature is 700°C to 800°C, and in some embodiments, 720°C to 780°C.

[0045] Compared to traditional manufacturing methods that achieve particle growth using high temperatures, the lithium iron phosphate particles of the present application are sintered twice, and the sintering temperature is controlled twice, which is advantageous for producing lithium iron phosphate particles having the primary average particle size and specific surface area of ​​the present application. Furthermore, in a conventional high-temperature sintering process, the carbon coating layer on the particle surface easily cracks, thereby degrading the integrity of the carbon coating. The present application is advantageous for reducing suspended carbon and improving the consistency and uniformity of the surface carbon coating by performing large particle synthesis at low temperatures.

[0046] In any embodiment, lithium iron phosphate particles are obtained by a manufacturing method comprising providing a raw material containing at least: a lithium source, an iron source, a phosphorus source, a carbon source, a carbon film-forming agent, and a modifier, and sintering at least twice, wherein,

[0047] The carbon content of the material after the first sintering is 0.01 wt% to 0.79 wt%, and in some embodiments, 0.05 wt% to 0.4 wt%;

[0048] The carbon content of the material after secondary sintering is 0.8 wt% to 2.0 wt%, and in some embodiments, 1.0 wt% to 1.6 wt%.

[0049] By adding a carbon source before the first sintering, the trivalent iron in the raw material can be effectively reduced, thereby improving the purity and stability of the product. Furthermore, by adding a relatively low carbon source content during the first sintering process, the carbon layer is advantageous for lowering the blocking effect on the growth process of lithium iron phosphate particles, which is beneficial for crystal growth of the lithium iron phosphate particle precursor at a relatively low temperature. At the same time, the low carbon content in the first sintering process is also advantageous for the solid-state diffusion reaction between the modifier that can be added and the lithium iron phosphate material, which is beneficial for achieving a relatively high concentration of metal ion doping. By increasing the carbon content added during the second sintering, the uniformity and integrity of the coating are further improved, which is beneficial for obtaining lithium iron phosphate particles having the carbon content of the embodiments of the present application.

[0050] In any embodiment, the lithium iron phosphate particles contain at least one of the elements Ti, V, Mg and / or Nb, and when calculated based on the total weight of the lithium iron phosphate particles, the content of the elements is 1000 ppm to 10000 ppm, and in some embodiments, 2500 ppm to 6000 ppm.

[0051] In any embodiment, a first sintering is performed, followed by a first grinding, and a second sintering is performed, followed by a second grinding, wherein,

[0052] The Dv50 of the product after primary grinding is 300 nm to 1200 nm, and in some embodiments, 400 nm to 1100 nm;

[0053] The Dv50 of the product after secondary grinding is 500 nm to 5000 nm, and in some embodiments, 700 nm to 2500 nm.

[0054] By controlling the Dv50 of the product after the first grinding to within the aforementioned range, the added carbon source and the doping element that may be added are advantageous for lowering the blocking effect on the growth of the lithium iron phosphate particle precursor crystals, and help in producing micrometer-sized lithium iron phosphate particle precursors. By controlling the Dv50 value of the product after the second grinding to within the aforementioned range, it helps in obtaining lithium iron phosphate particles having the primary average particle size of the present application.

[0055] A third aspect of the present application provides a positive electrode, wherein the positive electrode comprises a positive electrode active material according to the present application or a positive electrode active material obtained through a manufacturing method according to the present application.

[0056] In any embodiment, the compressive density of the anode piece is 3.0 g / cm³ 3 ~3.5 g / cm 3 am.

[0057] A fourth aspect of the present application provides a secondary battery, wherein the secondary battery comprises a positive plate according to the present application.

[0058] A fifth aspect of the present application provides an electric device, and the electric device includes a secondary battery according to the present application.

[0059] The foregoing description is merely an overview of the technical method of the present application, and in order to more clearly understand the technical means of the present application, and to make the description and other purposes, features, and advantages of the present application more obvious and easy to understand, specific embodiments of the present application are specifically listed below. Brief explanation of the drawing

[0060] FIG. 1 is an anode section of Example 1 of the present application, FIG. 1a is an anode section under 5,000x magnification conditions and FIG. 1b is an anode section under 10,000x magnification conditions. Figure 2 is a scanning electron microscope image of lithium iron phosphate particles of Example 1 of the present application. FIG. 3 is a schematic diagram of a secondary battery of one embodiment of the present application. FIG. 4 is an exploded view of a secondary battery of one embodiment of the present application shown in FIG. 3. FIG. 5 is a schematic diagram of a battery module of one embodiment of the present application. FIG. 6 is a schematic diagram of a battery pack of one embodiment of the present application. FIG. 7 is an exploded view of a battery pack of one embodiment of the present application shown in FIG. 6. FIG. 8 is a schematic diagram of an electric device using a secondary battery as a power source according to one embodiment of the present application. FIG. 9 is a scanning electron microscope image of lithium iron phosphate particles showing the primary particle size of one embodiment of the present application. Specific details for implementing the invention

[0061] Hereinafter, embodiments specifically disclosed by the positive active material and method of manufacturing the same, positive plate, secondary battery, battery module, battery pack, and electrical device of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of known matters may be omitted, and repetitive descriptions of substantially identical structures may be omitted. This is intended to avoid making the following description unnecessarily long and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the contents described in the claims.

[0062] The “ranges” disclosed in this application are limited in the form of lower and upper limits, and a given range is limited by selecting one lower limit and one upper limit, and the selected lower limit and upper limit limit the boundaries of a particular range. A range limited in this way may or may not include end values ​​and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a single range. For example, if ranges 60–120 and 80–110 are listed for a specific parameter, it is expected to be understood as ranges 60–110 and 80–120. In addition, if minimum range values ​​1 and 2 are listed and maximum range values ​​3, 4, and 5 are listed, the following ranges 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5 may all be expected. In this application, unless otherwise stated, numeric ranges “a–b” represent a simplified expression of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" are listed in this document, and "0 to 5" is merely an abbreviated expression for such numerical combinations. Also, specifying that any parameter is an integer greater than 2 is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0063] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with one another to form a new technical solution.

[0064] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with one another to form a new technical solution.

[0065] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, and sequentially is preferred. For example, the statement that the method comprises steps (a) and (b) indicates that the method may comprise steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the expression stating that the method may also comprise step (c) indicates that step (c) may be added to the method in any order, and for example, the method may comprise steps (a), (b), and (c), steps (a), (c), and (b), or steps (c), (a), and (b).

[0066] Unless otherwise specified, the terms "comprehensive" and "include" as used in this application represent open expressions, which may also be closed expressions. For example, the "comprehensive" and "include" may also encompass or include other components not listed, or may only encompass or include the listed components.

[0067] Unless otherwise specified, the term “or” in this application is inclusive. For example, the expression “A or B” indicates “A, B or both A and B”. More specifically, any one of the following conditions all satisfy the “A or B” condition: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0068] To balance battery cost and electrical performance, a cathode active material can be manufactured by mixing lithium iron phosphate-based materials with lithium nickel cobalt manganese oxide-based materials. However, lithium iron phosphate particles have the problem of poor electrical performance. To improve the electrical performance of lithium iron phosphate particles, they are typically nanosized to enhance their electron transport capabilities. However, during the process of preparing a slurry by mixing lithium iron phosphate particles with lithium nickel cobalt manganese oxide particles, the cathode slurry easily forms a gel and exhibits severe aggregation, resulting in a series of processing problems such as low solid content, poor filtration performance, strong moisture absorption of the electrode pieces, and difficulty in drying. This application increases the primary average particle size of lithium iron phosphate particles, lowers the specific surface area, and controls it within a reasonable range, thereby achieving relatively excellent processing performance while also possessing the capacity per gram of the secondary battery. At the same time, lowering the BET of lithium iron phosphate particles and reducing moisture absorption performance is advantageous for reducing the occurrence of side reactions and improving the lifespan of battery cells.

[0069] [Cathode active material]

[0070] Based on this, the present application provides a positive electrode active material, wherein the positive electrode active material comprises lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles, the primary average particle size of the lithium iron phosphate particles is 500 to 3000 nanometers (nm), and the specific surface area BET of the lithium iron phosphate particles is 3 square meters / gram (m²). 2 / g)~8m 2 / g, and the specific surface area of ​​the lithium nickel cobalt manganese oxide particles is 0.4m 2 / g~2.0m 2 / g is.

[0071] In this application, the term "primary average particle size" refers to the average value of the primary particle size of all particles, wherein the primary particle size refers to the longest distance connecting two points at the edge in a cross-sectional view. In a specific embodiment, as shown in the scanning electron microscope image of the lithium iron phosphate particles in FIG. 9, the line segment indicated by the double arrow among the particles is the primary particle size defined in this application.

[0072] In this application, the terms "specific surface area" or "BET" refer to the total area of ​​a unit mass particle, and in this application, the BET of a lithium iron phosphate particle is related to factors such as the primary average particle size of the lithium iron phosphate particle, carbon content, the degree of density of the carbon coating, the degree of adhesion between the carbon and the particle, and the degree of porosity of the particle.

[0073] In some embodiments, the lithium iron phosphate particles are primary particles.

[0074] In this document, "primary particle" refers to a particle that lacks distinct aggregation interfaces in scanning electron microscope images but may contain fine pores and point or line defects, and is distinguished from powder particles of the smallest unit that lack structure, such as aggregation and planar connection.

[0075] In some embodiments, the lithium iron phosphate particles are single-crystal particles and / or polycrystalline particles.

[0076] In this document, the term "single crystal" refers to a crystal with a complete structure grown from a single crystal nucleus. The single crystal of this application is a single integrated body in the field of view of a transmission electron microscope, and there are no grain boundaries within the single crystal.

[0077] In some embodiments, the single crystal of the present application may have microscopic defects, for example, micropores, small amounts of dots and planes may be present internally, or small amounts of mutual adhesion of particles may be present on the surface of a particle.

[0078] In this document, the term "polycrystalline" refers to a crystal formed by combining small single-crystal particles in a random orientation, and grain boundaries exist within the polycrystalline structure.

[0079] In some embodiments, the number ratio of single-crystal particles is 90% or more based on the total number of lithium iron phosphate particles. By controlling the number ratio of single-crystal particles within the range described above, the proportion of single-crystal particles is relatively higher compared to polycrystalline and secondary aggregates, which is advantageous for lowering BET and improving processing performance.

[0080] The primary average particle size of lithium iron phosphate particles can be measured using methods and devices known in the art. For example, it can be tested using a scanning electron microscope and the Peret diameter statistical method. For instance, an electrode piece is cut perpendicular to the large surface of the anode piece using an argon ion beam to expose a cross-section, the cross-section is photographed using a scanning electron microscope, and the particle size of the lithium iron phosphate particles is statistically analyzed using the Peret diameter statistical method. Specifically, the total number of lithium iron phosphate particles with a primary particle size greater than 80 nm can be statistically determined from the electron microscope scanning image, and the sum of the primary particle sizes of lithium iron phosphate particles with a primary particle size greater than 80 nm can be statistically determined. The primary average particle size of the lithium iron phosphate particles = primary particle size of the lithium iron phosphate particles / total number of lithium iron phosphate particles. Here, in the statistical process of the primary particle size, particles with a primary particle size of 0 < primary particle size ≤ 80 nm are not included within the statistical range.

[0081] To improve the electrical performance of lithium iron phosphate particles, they are typically nanosized to enhance their electron transport capabilities. However, nanosized lithium iron phosphate particles have an excessively large specific surface area, leading to severe moisture absorption. Consequently, during the process of preparing a slurry by mixing them with lithium nickel cobalt manganese oxide particles, the high moisture absorption of the lithium iron phosphate particles causes gel formation, resulting in a series of processing problems such as reduced solid content and decreased filtration performance. Furthermore, high molecular weight adhesives, such as polyvinylidene fluoride, commonly used in the manufacture of nanometer-sized lithium iron phosphate particles and lithium nickel cobalt manganese oxide particle cathode active materials, present a problem of poor compatibility. In such adhesive systems, lithium iron phosphate particles easily aggregate, causing processing issues. The primary average particle size of the lithium iron phosphate particles in this application is 500–3000 nm, and the specific surface area of ​​the lithium iron phosphate particles is 3 m² 2 / g~8m 2 At / g, the specific surface area of ​​the lithium nickel cobalt manganese oxide particles is 0.4 m² 2 / g~2.0m 2 It is further adjusted to / g. A reduced specific surface area is advantageous for lowering the moisture absorption performance of the anode slurry, thereby reducing gelation and aggregation phenomena during the slurry processing process, and can also improve the drying speed and degree of drying of the slurry. At the same time, a relatively large primary average particle size is advantageous for better dispersing lithium iron phosphate particles in a high molecular weight adhesive system and further reducing the occurrence of aggregation phenomena. However, too large particle size and too low specific surface area lower the capacity per gram of the anode active material. The anode active material of the present application increases the primary average particle size of lithium iron phosphate particles and lowers the specific surface area, and lowers the specific surface area of ​​lithium nickel cobalt manganese oxide particles, controlling both within a reasonable range to obtain relatively excellent processing performance while also possessing the capacity per gram of the secondary battery.

[0082] In some embodiments, lithium iron phosphate particles have the molecular formula Li m1 Fe x1 P y1 O z1 Q q1 having, where Q comprises at least one of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, and 0.95≤m1≤1.15, 0.9≤x1≤1, 0.95≤y1≤1, 3.5≤z1≤4, 0 <q1≤0.1이며, 및 / 또는

[0083] Lithium nickel cobalt manganese oxide particles have the molecular formula LiR x2 Ni y2 Co z2 Mn 1-x2-y2-z2 It has O2, where R includes at least one of Cr, Ti, V, Mg, Al, and Nb, and 0≤x2<1, 0 <y2<1, 0<z2<1, 0<x2+y2+z2<1이다.

[0084] In some embodiments, lithium iron phosphate particles have the molecular formula Li m1 Fe x1 P y1 O z1 Q q1 It has, and m1 can be 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15, x1 can be 0.9, 1.0, y1 can be 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15, z1 can be 3.5, 3.6, 3.7, 3.8, 3.9, 4, and q1 can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1.

[0085] In some embodiments, lithium nickel cobalt manganese oxide particles have the molecular formula LiR x2 Ni y2 Co z2 Mn 1-x2-y2-z2It has O2, and R includes at least one of Ti, V, Mg, and Nb.

[0086] In some embodiments, lithium nickel cobalt manganese oxide particles have the molecular formula LiR x2 Ni y2 Co z2 Mn 1-x2-y2-z2 It has O2, and x2 can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.5, 0.7, 0.8, 0.9, y2 can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.5, 0.7, 0.8, 0.9, and z2 can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.5, 0.7, 0.8, 0.9. In some embodiments, the content ratio of lithium elements and oxygen elements in the lithium nickel cobalt manganese oxide particles fluctuates during the battery formation and circulation process.

[0087] Doping lithium iron phosphate particles and / or lithium nickel cobalt manganese oxide particles with the aforementioned elements helps to improve the ion transport capacity of the cathode active material. The aforementioned elements create vacancies in the crystal lattice of the particles or change the length of interatomic bonds, thereby allowing lithium ions to move easily within the crystal lattice, which can effectively improve the conductivity performance of the particles themselves and improve the kinetic performance of the cathode active material.

[0088] In some embodiments, the primary average particle size of the lithium iron phosphate particles is 650 to 2500 nm.

[0089] In some embodiments, the primary average particle size of the lithium iron phosphate particles may be a numeric value within a range consisting of 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 730 nm, 750 nm, 780 nm, 800 nm, 830 nm, 850 nm, 870 nm, 900 nm, 950 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 2000 nm, 2100 nm, 2200 nm, 2300 nm, 2400 nm, 2500 nm, 2600 nm, 2700 nm, 2800 nm, 2900 nm, 3000 nm, or any two of the primary average particle sizes described above.

[0090] By controlling the primary average particle size of the lithium iron phosphate particles within a reasonable range, it helps to further improve the processing performance of the anode slurry while simultaneously increasing the capacity per gram of the secondary battery.

[0091] In some embodiments, the BET of the lithium iron phosphate particles is 4m 2 / g~7m 2 / g, and the BET of the lithium nickel cobalt manganese oxide particles is 0.6m 2 / g~2.0m 2 / g is.

[0092] In some embodiments, the specific surface area BET of the lithium iron phosphate particles is 3 m 2 / g, 3.5m 2 / g, 4m 2 / g, 4.5m 2 / g, 5m 2 / g, 5.5m 2 / g, 6m 2 / g, 6.5m 2 / g, 7m 2 / g, 7.5m 2 / g, 8m 2 / g, or a value within the range consisting of the specific surface area BET of any two lithium iron phosphate particles described above.

[0093] In some embodiments, the specific surface area BET of the lithium nickel cobalt manganese oxide particles is 0.6 m2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.4m 2 / g, 1.6m 2 / g, 1.8m 2 / g, 2.0m 2 / g, or a value within the range consisting of the specific surface area BET of any two lithium nickel cobalt manganese oxide particles described above.

[0094] The specific surface area (BET) of a particle can be measured using methods and devices known in the art. For example, by referring to GB / T 19587-2017, it can be tested according to the gas adsorption method. For example, lithium iron phosphate particles are taken as a sample, placed in a sample tube, and the sample tube is immersed in liquid nitrogen at -196°C. The amount of nitrogen gas adsorbed on the solid surface is measured at different pressures with relative pressures of 0.05 to 0.30, and the specific surface area of ​​the sample is obtained by calculating the amount of monolayer adsorption of the sample based on the BET multilayer adsorption theory and its formula.

[0095] If the BET of lithium iron phosphate particles and / or lithium nickel cobalt manganese oxide particles is too high, it increases the moisture absorption performance of the particles and affects the processing performance of the mixed cathode slurry. If the BET of lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles is too low, the capacity per gram decreases. The BET of lithium iron phosphate particles is 4m 2 / g~7m 2 Controlled within / g, and the BET of lithium nickel cobalt manganese oxide particles is 0.6m 2 / g~2.0m 2 By controlling it within / g, it is advantageous to further balance the processing performance of the anode slurry and the capacity per gram of the secondary battery.

[0096] In some embodiments, when calculated based on the total weight of the lithium iron phosphate particles, the carbon content of the lithium iron phosphate particles is Cx weight%, and the ratio z of BET to Cx of the lithium iron phosphate particles satisfies 1.5≤z≤8.5.

[0097] In some embodiments, z satisfies 3≤z≤6.

[0098] In some embodiments, z may be a numeric value within a range consisting of 1.5, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.3, 4.5, 4.8, 5, 5.3, 5.5, 5.8, 6, 6.3, 6.5, 6.8, 7, 7.3, 7.5, 7.8, 8, 8.3, 8.5, or any two of the above-mentioned z values.

[0099] In this application, the ratio z of the specific surface area BET and Cx of the lithium iron phosphate particles can characterize the degree of uniform density of carbon contained in the lithium iron phosphate particles. When the primary average particle size and carbon content of the lithium iron phosphate particles remain unchanged, the lower the ratio z, the higher the carbon coating utilization rate in the particles, the less suspended carbon there is, and the more uniform and dense the carbon contained in the lithium iron phosphate particles becomes. Improving the degree of uniform density of the contained carbon is advantageous for improving the kinetic performance and capacity per gram of the lithium iron phosphate particles. However, if the carbon coating density is too high, it affects the insertion and extraction of lithium ions, which may have some effect on the kinetic performance and capacity per gram of the secondary battery. The range of the ratio z in the embodiments of this application is advantageous for improving the conductivity performance of the particle surface and further improving the kinetic performance and capacity per gram of the secondary battery by ensuring that the carbon contained in the lithium iron phosphate particles has an appropriate uniform density.

[0100] In some embodiments, when calculated based on the total weight of the lithium iron phosphate particles, the carbon content of the lithium iron phosphate particles is 0.8 wt% to 2.0 wt%.

[0101] In some embodiments, based on the total weight of the lithium iron phosphate particles, the carbon content of the lithium iron phosphate particles is 1.0 wt% to 1.6 wt%.

[0102] In some embodiments, when calculated based on the total weight of the lithium iron phosphate particles, the carbon content of the lithium iron phosphate particles is a value within the range consisting of 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, or any two of the carbon contents described above.

[0103] In some embodiments, the carbon contained in the lithium iron phosphate particles is coated on the surface of the particles. In some embodiments, the carbon contained in the lithium iron phosphate particles is embedded within the particles. In some embodiments, some of the carbon contained in the lithium iron phosphate particles is coated on the surface of the particles, and some is embedded within the particles.

[0104] The carbon content of iron phosphate particles can be measured using methods and devices known in the art. For example, it can be tested by referring to GB / T 20123-2006 / ISO 15350:2000.

[0105] Increasing the carbon content of lithium iron phosphate particles helps improve conductivity performance, thereby improving kinetic performance and capacity per gram; however, if the carbon content is too high, it affects the insertion and extraction of lithium ions and affects the capacity per gram of the secondary battery to some extent. The carbon content range of the embodiments of the present application helps to obtain relatively excellent kinetic performance and capacity per gram.

[0106] In some embodiments, Q comprises at least one of Ti, V, Mg, and Nb. In some embodiments, Q is Ti.

[0107] In some embodiments, when calculated based on the total weight of the lithium iron phosphate particles, the content of Q in the lithium iron phosphate particles is 1000 to 10000 parts per million (1000 to 10000 ppm).

[0108] In some embodiments, when calculated based on the total mass of the lithium iron phosphate particles, the content of Q in the lithium iron phosphate particles is 2500 to 6000 ppm.

[0109] In some embodiments, when calculated based on the total weight of the lithium iron phosphate particles, the content of Q in the lithium iron phosphate particles is a value within a range consisting of 1000 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm, 8500 ppm, 9000 ppm, 9500 ppm, 10000 ppm, or any two of the above-mentioned Q contents.

[0110] The content of Q, for example, the content of Ti, in lithium iron phosphate particles can be measured using methods and devices known in the art. For example, it can be tested by referring to GB / T 33822-2017.

[0111] In conventional lithium iron phosphate particles, the content of doping elements is generally low or no doping elements are added. Increasing the content of Q element in lithium iron phosphate particles helps to further improve the bulk ion transport capacity of the lithium iron phosphate particles and enhance kinetic performance. However, as the content of Q element increases further, the bulk ion transport capacity may not increase continuously, and it may also occupy the positions of lithium ions, which may affect the expression of capacity per gram. The range of Q element in this application helps to obtain relatively excellent kinetic performance and capacity per gram.

[0112] In some embodiments, the ratio of the Dv50 of the lithium iron phosphate particles to the Dv50 of the lithium nickel cobalt manganese oxide particles is 1:(1 to 25).

[0113] In some embodiments, the ratio of the Dv50 value of the lithium iron phosphate particles to the Dv50 of the lithium nickel cobalt manganese oxide particles is 1:(1 to 20).

[0114] In some embodiments, the ratio of the Dv50 of the lithium iron phosphate particles to the Dv50 of the lithium nickel cobalt manganese oxide particles may be a numeric value within a range consisting of 1:1, 1:3, 1:5, 1:7, 1:10, 1:13, 1:15, 1:20, 1:23, or 1:25, or the ratio of the Dv50 of any two of the lithium iron phosphate particles and the Dv50 of the lithium nickel cobalt manganese oxide particles described above.

[0115] In some embodiments, the Dv50 of the lithium iron phosphate particles is 500 to 5000 nm.

[0116] In some embodiments, the Dv50 of the lithium iron phosphate particles is 700 to 2500 nm.

[0117] In some embodiments, the Dv50 of the lithium iron phosphate particles is a numerical value within a range consisting of 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm, 2300 nm, 2500 nm, 2700 nm, 3000 nm, 3300 nm, 3500 nm, 3700 nm, 4000 nm, 4300 nm, 4500 nm, 4700 nm, 5000 nm, or the Dv50 between any two of the above-mentioned lithium iron phosphate particles.

[0118] In some embodiments, the Dv50 of the lithium nickel cobalt manganese oxide particles is 1200 to 20000 nm.

[0119] In some embodiments, the Dv50 of the lithium nickel cobalt manganese oxide particles is 3,000 to 15,000 nm.

[0120] In some embodiments, the Dv50 of the lithium nickel cobalt manganese oxide particles is 1200 nm, 1500 nm, 1700 nm, 2000 nm, 2300 nm, 2500 nm, 2700 nm, 3000 nm, 3300 nm, 3500 nm, 4000 nm, 4300 nm, 4500 nm, 4700 nm, 5000 nm, 6000 nm, 7000 nm, 8000 nm, 9000 nm, 10000 nm, 11000 nm, 12000 nm, 13000 nm, 14000 nm, 15000 nm, 16000 nm, 17000 nm, 18000 nm, 19000 nm, 20000 nm, or any of the above-mentioned wavelengths. It may be a value within the range consisting of the Dv50 of two lithium nickel cobalt manganese oxide particles.

[0121] In this application, the term "Dv50" refers to the particle size corresponding when the percentage of volume-cumulative particle size distribution among the particles reaches 50%.

[0122] The Dv50 of lithium iron phosphate particles and the Dv50 of lithium nickel cobalt manganese oxide particles can be measured using methods and devices known in the art. For example, with reference to GB / T19077.1-2016, it can be measured using a laser particle size analyzer (Malvern Master Size 3000).

[0123] By controlling the Dv50 ratio range and value range of the lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles of the embodiment of the present application to within the above-described range, it is advantageous for the lithium iron phosphate particles to be uniformly and densely packed between the lithium nickel cobalt manganese oxide particles, it alleviates the aggregation phenomenon of single-component particles in the composite cathode active material, and improves the compression density of the cathode active material.

[0124] In some embodiments, the Dv50 of the lithium iron phosphate particles is 870 to 1500 nm, and the Dv50 of the lithium nickel cobalt manganese oxide particles is 1800 to 4200 nm.

[0125] In some embodiments, the mass percentage of lithium iron phosphate particles is 5% to 80% when calculated based on the total mass of the positive electrode active material.

[0126] In some embodiments, the mass percentage of lithium iron phosphate particles is 15% to 50% when calculated based on the total mass of the positive electrode active material.

[0127] In some embodiments, when calculated based on the total mass of the positive electrode active material, the mass percentage of lithium iron phosphate particles may be a value within a range consisting of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any two of the aforementioned mass percentages of lithium iron phosphate particles.

[0128] In some embodiments, when calculated based on the total mass of the positive electrode active material, the mass percentage of lithium nickel cobalt manganese oxide particles is 20% to 95%.

[0129] In some embodiments, when calculated based on the total mass of the positive electrode active material, the mass percentage of lithium nickel cobalt manganese oxide particles is 50% to 85%.

[0130] In some embodiments, when calculated based on the total mass of the positive electrode active material, the mass percentage of lithium nickel cobalt manganese oxide particles may be a value within a range consisting of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any two of the aforementioned mass percentages of lithium nickel cobalt manganese oxide particles.

[0131] By controlling the mass percentage of lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles within the aforementioned range, it helps to further balance the electrical performance and cost of the cathode active material.

[0132] In some embodiments, the capacity ratio of lithium iron phosphate particles is η≥88%, and η is:

[0133] A battery having lithium iron phosphate particles as the positive electrode active material is charged and discharged twice with a constant current at a rate capability of 0.1 Cullon (C) within a voltage range of 2.0 volts (V) to 3.75 V, followed by a single charge and discharge with a constant current at a rate capability of 1 C. In the charge-discharge test with a rate capability of 1 C, a capacity value at a discharge voltage of 3.2 V is extracted as C1, and a capacity value discharged to 2.0 V is extracted as C2, and η is defined as C1 / C2. Here, the charging process includes constant voltage charging, the constant voltage is 3.75 V, and the constant voltage cutoff current is 50 microamperes (μA).

[0134] In some embodiments, η may be a numeric value within a range consisting of 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, or any two of the above-mentioned η values.

[0135] The η value of the lithium iron phosphate particles can be measured using methods and devices known in the art. For example, a button battery is first manufactured using lithium iron phosphate particles as the positive electrode active material, and the specific button battery manufacturing process is as follows: 2.0000 grams (g) of lithium iron phosphate particles are mixed with 0.1111 g of conductive carbon black and 0.1111 g of polyvinylidene fluoride, then added to 2.5 g of the organic solvent N-methylpyrrolidone and mixed sufficiently uniformly to form a slurry. The slurry is coated onto an aluminum foil with a coating thickness of 140 micrometers (μm), vacuum dried at 120 degrees Celsius (°C) for 2 hours (h), and then punched into a circular sheet with a diameter of 13 millimeters (mm) using a punching machine. Pressing is performed at 10 megapascals (Mpa) using a press machine, and vacuum-inserting is performed at 120°C for 12 hours to obtain a positive electrode. The weight of the positive electrode is weighed, wherein the loading amount of lithium iron phosphate particles is 11 to 12 milligrams (mg). A button battery is assembled in a glove box protected by an argon atmosphere, a metallic lithium sheet is used as the negative electrode, a mixed solvent of EC (ethylene carbonate) and DMC (1,2-dimethyl carbonate) with a volume ratio of 1:1 is used as the electrolyte, LiPF6 is used as the electrolyte, and a Celgard 2400 microporous polyethylene membrane is used as the separator.

[0136] The electrical performance of the manufactured button battery is tested using a LAND meter. Specifically, the button battery is charged and discharged twice with a constant current at a rate of 0.1C within a voltage range of 2.0V to 3.75V, followed by a single charge and discharge with a rate of 1C. In the charge-discharge test with a rate of 1C, the capacity value at a discharge voltage of 3.2V is extracted as C1, and the capacity value discharged to 2.0V is extracted as C2, where η = C1 / C2. Here, the charging process includes constant voltage charging, the constant voltage is 3.75V, and the constant voltage cutoff current is 50μA.

[0137] The capacity ratio η of the lithium iron phosphate particles can represent kinetic performance and platform maintenance performance, and can be controlled by adjusting the primary average particle size, carbon content, ratio of carbon source to carbon film agent, and the modifier and its content. The η value of the lithium iron phosphate particles in the embodiments of this application is ≥ 88%, and they possess relatively excellent kinetic performance. At the same time, when the η value is relatively high, the secondary battery can still maintain relatively excellent output performance even when discharged at a low SOC; that is, when a battery with a high η value is discharged at a large current from a low electric charge, the voltage drop is relatively small. In the cathode active material of the embodiments of this application, the lithium nickel cobalt manganese oxide particles have a high voltage and participate in the discharge first, and subsequently, the lithium iron phosphate particles participate in the discharge and must handle a relatively large current, so polarization is prone to occur. Since the lithium iron phosphate particles of this application possess relatively high kinetic performance, they are advantageous for improving the discharge output performance of the secondary battery.

[0138] In some embodiments, the lithium iron phosphate particles satisfy at least one of (a) to (e):

[0139] a) Dv10≥200 nm of lithium iron phosphate particles;

[0140] b) Dv90≤10000nm of lithium iron phosphate particles;

[0141] c) Dv99≤12000nm of lithium iron phosphate particles;

[0142] d) Powder compression density of lithium iron phosphate at 3T pressure ≥ 2.25 grams / square millimeter (g / cm³) 3 );

[0143] e) The powder resistivity of lithium iron phosphate is less than 60 ohm·centimeters (Ω·cm).

[0144] In this document, the term "Dv10" refers to the particle size corresponding when the percentage of the volumetric cumulative particle size distribution among the particles reaches 10%.

[0145] In this document, the term "Dv90" refers to the particle size corresponding when the percentage of volume-cumulative particle size distribution among particles reaches 90%.

[0146] In this document, the term "Dv99" refers to the particle size corresponding to when the percentage of volumetric cumulative particle size distribution among particles reaches 99%.

[0147] In this document, the term "powder compression density" refers to the density of a compact having a constant density and strength, formed during an external compression process in which, due to the movement and deformation of the powder, a relatively large gap is filled, the contact area between particles increases, attractive forces are generated between atoms, and the mechanical interlocking action between particles is strengthened; the unit is g / cm³ 3 am.

[0148] In some embodiments, Dv10 of lithium iron phosphate particles <Dv50이다.

[0149] In some embodiments, the Dv90 > Dv50 of the lithium iron phosphate particles.

[0150] The Dv10, Dv90, and Dv99 of lithium iron phosphate particles can be measured using methods and devices known in the art. For example, with reference to GB / T19077.1-2016, they can be measured using a laser particle size analyzer (Malvern Master Size 3000).

[0151] The powder compression density of lithium iron phosphate particles at different pressures can be measured using methods and devices known in the art. For example, with reference to GB / T 24533-2009, it can be measured using a compression density measuring instrument. Specifically, a certain amount of lithium iron phosphate particles is placed on a compression mold (the diameter of the mold is already known), and a metal circular sheet is provided at the top and bottom of the middle hollow of the mold. When the lithium iron phosphate particles are placed between the metal circular sheets, a metal circular column is placed at the top, the mold is placed on a compression density measuring instrument, and different pressures (e.g., 3T) are applied, the device can read the thickness of the lithium iron phosphate particles at different pressures, and the powder compression density of the lithium iron phosphate particles is given by ρ=m / v, where v=(SХH), m is the mass of the lithium iron phosphate particles, S is the bottom area of ​​the mold, and H is the thickness of the lithium iron phosphate particles after compression.

[0152] The powder resistivity of lithium iron phosphate particles can be measured using methods and devices known in the art. For example, with reference to GB / T 33822-2017, it can be measured using a powder resistivity meter (Suzhou Jingge, ST2722 type). Specifically, a certain amount of lithium iron phosphate particles (e.g., 1 g) is weighed and placed into the material chamber of the powder resistivity meter, and then a pressure of 8 MPa is applied to test the forward resistivity and reverse resistivity of the lithium iron phosphate particles, respectively, and the average value of both is taken as the powder resistivity of the lithium iron phosphate particles.

[0153] By ensuring that the lithium iron phosphate particles satisfy at least one of (a) to (e), the lithium iron phosphate particles can be made to better realize the technical effects of the present application.

[0154] The present application provides a method for manufacturing a positive electrode active material, wherein the method comprises the step of mixing lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles, and

[0155] Herein, the process for manufacturing lithium iron phosphate particles comprises: providing a raw material containing at least a lithium source, an iron source, a phosphorus source, an optional carbon source, an optional carbon film-forming agent, and an optional modifier, and sintering at least twice; wherein,

[0156] The primary sintering temperature is 500℃ to 760℃, and in some embodiments, 550℃ to 720℃;

[0157] The secondary sintering temperature is 700°C to 800°C, and in some embodiments, 720°C to 780°C.

[0158] In some embodiments, the primary sintering temperature may be a numeric value within a range consisting of 500°C, 530°C, 550°C, 580°C, 600°C, 630°C, 650°C, 680°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, or any two primary sintering temperatures described above; and the secondary sintering temperature may be a numeric value within a range consisting of 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, or any two secondary sintering temperatures described above.

[0159] In some embodiments, the temperature rise rate of the first sintering and the second sintering is independently 2 degrees Celsius / min (°C / min) to 20°C / min.

[0160] In some embodiments, the temperature rise rate during the first sintering and the second sintering is independently 2°C / min, 5°C / min, 7°C / min, 10°C / min, 13°C / min, 15°C / min, 17°C / min, or 20°C / min.

[0161] In some embodiments, the isothermal sintering time for the first sintering is 1 to 6 hours. In some embodiments, the isothermal sintering time for the first sintering may be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours.

[0162] In some embodiments, the isothermal sintering time for the second sintering is 2 to 12 hours. In some embodiments, the isothermal sintering time for the second sintering may be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, or 12 hours.

[0163] Compared to traditional manufacturing methods that achieve particle growth using high temperatures, the lithium iron phosphate particles of the present application are advantageous for producing lithium iron phosphate particles having the primary average particle size and specific surface area of ​​the present application by performing two sintering cycles and controlling the sintering temperatures twice. Furthermore, by controlling the temperature rise rate of the first and / or second sintering cycles, the sintering temperature, and the isothermal sintering time, it helps to reduce side reactions, thereby producing the lithium iron phosphate particles of the present application more effectively. Furthermore, in conventional high-temperature sintering processes, the carbon coating layer on the particle surface easily cracks, degrading the integrity of the carbon coating. The present application is advantageous for improving the consistency and uniformity of the surface carbon coating by performing large particle synthesis at low temperatures.

[0164] In some embodiments, lithium iron phosphate particles are obtained by a manufacturing method comprising: providing a raw material containing at least a lithium source, an iron source, a phosphorus source, a carbon source, a carbon film-forming agent, and a modifier, and sintering at least twice, wherein,

[0165] The carbon content of the material after the first sintering is 0.01 wt% to 0.79 wt%, and in some embodiments, 0.05 wt% to 0.4 wt%;

[0166] The carbon content of the material after secondary sintering is 0.8 wt% to 2.0 wt%, and in some embodiments, 1.0 wt% to 1.6 wt%.

[0167] In some embodiments, the carbon content of the material after the first sintering may be a value within a range consisting of 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.20 wt%, 0.25 wt%, 0.30 wt%, 0.35 wt%, 0.40 wt%, 0.45 wt%, 0.50 wt%, 0.55 wt%, 0.60 wt%, 0.65 wt%, 0.70 wt%, 0.75 wt%, 0.79 wt%, or any two of the carbon contents described above; The carbon content of the material after the second sintering may be a value within the range consisting of 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, or any two of the above-mentioned carbon contents.

[0168] By adding a carbon source before the first sintering, the trivalent iron in the raw material can be effectively reduced, thereby improving the purity and stability of the product. Furthermore, by adding a relatively low carbon source content during the first sintering process, the carbon layer is advantageous for lowering the blocking effect on the growth process of lithium iron phosphate particles, which is beneficial for crystal growth of the lithium iron phosphate particle precursor at a relatively low temperature. At the same time, the low carbon content in the first sintering process is also advantageous for the solid-state diffusion reaction between the modifier that can be added and the lithium iron phosphate material, which is beneficial for achieving a relatively high concentration of metal ion doping. By increasing the carbon content added during the second sintering, the uniformity and integrity of the coating are further improved, which is beneficial for obtaining lithium iron phosphate particles having the carbon content of the embodiments of the present application.

[0169] In some embodiments, at least a raw material containing a lithium source, an iron source, a phosphorus source, a carbon source, a modifier, and a carbon film-forming agent is provided and sintered at least twice.

[0170] In some embodiments, when calculated based on the atomic moles of each element, the mixing ratio of the lithium source, iron source, and phosphorus source satisfies Fe:P=(0.96~0.985):1 and Li:Fe=(1.0~0.95):1.1.

[0171] In some embodiments, when calculated based on the atomic moles of each element, the mixing ratio of iron source to phosphorus source satisfies Fe:P=0.96:1, Fe:P=0.965:1, Fe:P=0.97:1, Fe:P=0.975:1, Fe:P=0.98:1, or Fe:P=0.985:1.

[0172] In some embodiments, when calculated based on the atomic moles of each element, the mixing ratio of the lithium source and the iron source satisfies Li:Fe=1.0:1.1, Li:Fe=0.99:1.1, Li:Fe=0.98:1.1, Li:Fe=0.97:1.1, Li:Fe=0.96:1.1, or Li:Fe=0.95:1.1.

[0173] In some embodiments, the weight ratio of the carbon source to the carbon film agent is (9 to 0.25):1. In some embodiments, the weight ratio of the carbon source to the carbon film agent may be 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 0.8:1, 0.5:1, or 0.25:1.

[0174] In some embodiments, the lithium source is a compound containing lithium. In some embodiments, the lithium source comprises at least one of lithium dihydrogen phosphate, lithium oxalate, lithium carbonate, lithium oxide, lithium hydroxide, and lithium acetate. In some embodiments, the lithium source comprises lithium carbonate.

[0175] In some embodiments, the iron source is a compound containing iron. In some embodiments, the iron source comprises at least one of iron hydroxide, ferrous chloride, ferric trioxide, ferrous phosphate, ferrous pyrophosphate, ferrous oxalate, iron powder, ferrous nitrate, ferric tetroxide, and ferric oxyhydroxide. In some embodiments, the iron source comprises ferric trioxide.

[0176] In some embodiments, the phosphorus source is a phosphoric acid compound. In some embodiments, the phosphorus source comprises at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate. In some embodiments, the phosphorus source comprises phosphoric acid.

[0177] In some embodiments, the carbon source comprises at least one of citric acid, glucose, sucrose, starch, fructose, and lactose. In some embodiments, the carbon source comprises glucose.

[0178] In some embodiments, the carbon film-forming agent comprises at least one of polyethylene glycol, polyaniline, polyacrylonitrile, polyvinylpyrrolidone, and polyvinyl alcohol. In some embodiments, the carbon film-forming agent comprises polyaniline.

[0179] In some embodiments, the modifier comprises at least one of titanium dioxide, vanadium pentoxide, n-butyl titanate, ammonium metavanadate, niobium ethanolate, niobium oxalate, niobium pentoxide, magnesium hydroxide, and magnesium nitrate. In some embodiments, the modifier comprises titanium dioxide.

[0180] Using raw materials in the aforementioned ratio is advantageous for forming the lithium iron phosphate particles of the present application.

[0181] In some embodiments, the lithium iron phosphate particles contain at least one of the elements Ti, V, Mg and / or Nb, and when calculated based on the total weight of the lithium iron phosphate particles, the content of the elements is 1000 ppm to 10000 ppm, and in some embodiments, 2500 ppm to 6000 ppm.

[0182] In some embodiments, the content of the element is optionally 2500 ppm to 6000 ppm. Specifically, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, 3000ppm, 3100ppm, 3200ppm, 3300ppm, 3400ppm, 3500ppm, 3600ppm, 3700ppm, 3800ppm, 3900ppm, 4000ppm, 4100ppm, 4200ppm, 4300ppm, 4400ppm, 4500ppm, 4600ppm, 4700ppm, 4800ppm, 4900ppm, 5000ppm, 5100ppm, 5200ppm, 5300ppm, 5400ppm, 5500 ppm, 5600 ppm, 5700 ppm, 5800 ppm, 5900 ppm, or 6000 ppm, or a range between any two of the above values ​​can be selected.

[0183] By doping the lithium iron phosphate of the embodiment of the present application with one or more of the elements described above and ensuring that the content thereof is within the range described above, the metal bulk phase modification of the lithium iron phosphate particles can be better implemented under the premise of improving the primary average particle size of the lithium iron phosphate particles, the bulk phase ion transport capacity of the lithium iron phosphate particles can be further improved, and the kinetic performance and capacity per gram can be improved.

[0184] In some embodiments, a first grinding is performed after a first sintering, and a second grinding is performed after a second sintering, wherein,

[0185] The Dv50 of the product after primary grinding is 300 nm to 1200 nm, and in some embodiments, 400 nm to 1100 nm;

[0186] The Dv50 of the product after secondary grinding is 500 nm to 5000 nm, and in some embodiments, 700 nm to 2500 nm.

[0187] In some embodiments, the Dv50 of the product after primary grinding may be a numeric value within a range consisting of 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, or any two of the Dv50s of the products after primary grinding described above.

[0188] In some embodiments, the Dv50 of the product after secondary grinding is 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1700 nm, 1900 nm, 2000 nm, 2300 nm, 2500 nm, 2700 nm, 2900 nm, 3000 nm, 3200 nm, 3400 nm, 3600 nm, 3800 nm, 4000 nm, 4200 nm, 4400 nm, 4600 nm, 4800 nm, 5000 nm, or the Dv50 of any two of the products after secondary grinding described above. It can be a value within the configured range.

[0189] In some embodiments, crushing includes one or more of mechanical crushing, grinding, sanding, and air-flow crushing.

[0190] By controlling the Dv50 of the product after the first grinding to within the aforementioned range, the added carbon source and the doping element that may be added are advantageous for lowering the blocking effect on the growth of the lithium iron phosphate particle precursor crystals, and help in producing micrometer-sized lithium iron phosphate particle precursors. By controlling the Dv50 value of the product after the second grinding to within the aforementioned range, it helps in obtaining lithium iron phosphate particles having the primary average particle size of the present application.

[0191] [Polar Side]

[0192] The present application provides a positive electrode, wherein the positive electrode comprises a positive electrode active material described in the present application or a positive electrode active material obtained through a manufacturing method described in the present application.

[0193] In some embodiments, the compressive density of the anode is 3.0 g / cm³ 3 ~3.5 g / cm 3 am.

[0194] In some embodiments, the compressive density of the anode is 3.0 g / cm³ 3 , 3.1g / cm 3 , 3.2g / cm 3 , 3.3g / cm 3 , 3.4g / cm 3 , 3.5g / cm 3 Or it may be a numerical value within the range consisting of the compression densities of any two anode pieces described above.

[0195] The compressive density of the electrode piece can be tested using methods and devices known in the art. For example, when the electrode piece is single-sided coated, the compressive density of the film layer on one side of the electrode piece is m / (V1-V2), and when the electrode piece is double-sided coated, the compressive density of the film layer on one side of the electrode piece is m / [2×(V1-V2)], where m represents the weight of the film layer, V1 represents the volume of the electrode piece, and V2 represents the volume of the current collector. m can be obtained by subtracting the weight of the current collector from the weight of the electrode piece, the volume of the electrode piece (V1) is the product of the surface area of ​​the electrode piece and the thickness of the electrode piece, and V2 is the product of the surface area of ​​the electrode piece and the thickness of the current collector, and the thickness of the current collector and the thickness of the electrode piece are obtained by measuring the thickness of the empty foil in the electrode tab area using a micrometer.

[0196] The compression density of the positive active material in the embodiment of the present application is 3.0 g / cm³ 3 ~3.5g / cm 3 And, a relatively high compression density is advantageous for improving the energy density of secondary batteries.

[0197] In some embodiments, the positive plate comprises a positive current collector and a positive film layer installed on at least one surface of the positive current collector, the positive film layer comprises a positive active material, an adhesive and a conductor, and the positive active material is a positive active material according to an embodiment of the present application or a positive active material manufactured by a method of manufacturing an embodiment of the present application.

[0198] For example, the positive current collector has two surfaces facing each other in its thickness direction, and the positive film layer is installed on any one or both of the two surfaces facing each other of the positive current collector.

[0199] In some embodiments, the positive current collector may use a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0200] In some embodiments, the anode film layer may also optionally include an adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0201] In some embodiments, the anode film layer also optionally comprises a conductor. For example, the conductor may comprise at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0202] In some embodiments, an anode piece may be manufactured in the following manner: a positive slurry is formed by dispersing the components used in the above-described manufacturing of the anode piece, e.g., a positive active material, a conductor, an adhesive, and any other components, in a solvent (e.g., N-methylpyrrolidone); and the positive slurry is applied to a positive current collector and the anode piece is obtained through processes such as drying and cold pressing.

[0203] [Cathode]

[0204] The cathode piece comprises a cathode current collector and a cathode film layer installed on at least one surface of the cathode current collector, and the cathode film layer comprises a cathode active material.

[0205] For example, a cathode current collector has two surfaces facing each other in its thickness direction, and a cathode film layer is installed on any one or both of the two surfaces facing each other of the cathode current collector.

[0206] In some embodiments, the negative current collector may use a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0207] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of materials such as synthetic graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of single-element silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of single-element tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0208] In some embodiments, the cathode film layer also optionally comprises an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0209] In some embodiments, the cathode film layer also optionally comprises a conductor. The conductor may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0210] In some embodiments, the cathode film layer also optionally includes other auxiliary agents such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0211] In some embodiments, a cathode plate may be manufactured in the following manner: a cathode slurry is formed by dispersing the components used in the above-described cathode plate manufacturing, e.g., a cathode active material, a conductor, an adhesive, and any other components, in a solvent (e.g., deionized water); and the cathode plate may be obtained by applying the cathode slurry to a cathode current collector and undergoing processes such as drying and cold pressing.

[0212] [Electrolyte]

[0213] The electrolyte serves to conduct ions between the anode and the cathode. The present application has no specific limitations on the type of electrolyte and can be selected according to demand. For example, the electrolyte may be in a liquid state, a gel state, or a completely solid state.

[0214] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0215] 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 difluoro(bis-oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0216] 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, methyl ethyl sulfone, and diethyl sulfone.

[0217] In some embodiments, the electrolyte also optionally includes additives. For example, the additives may include a cathode film-forming additive and an anode film-forming additive, and may also include additives that can improve specific performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, etc.

[0218] [Separator]

[0219] In some embodiments, the secondary battery also includes a separator. The present application makes no particular limitation on the type of separator, and any known porous separator having good chemical and mechanical stability may be selected and used.

[0220] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and there are no particular limitations thereon. If the separator is a multilayer composite film, the material of each layer may be the same or different, and there are no particular limitations thereon.

[0221] In some embodiments, the anode, cathode, and separator can be manufactured into an electrode assembly through a winding process or a lamination process.

[0222] In some embodiments, the secondary battery may include an external packaging material. The external packaging material may be used to package the electrode assembly and electrolyte described above.

[0223] In some embodiments, the external packaging material of the secondary battery may be a rigid shell, such as a rigid plastic shell, an aluminum shell, a steel shell, etc. The external packaging material of the secondary battery may also be a soft pack, such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0224] [Secondary Battery]

[0225] The present application provides a secondary battery, and the secondary battery includes a positive plate of an embodiment of the present application.

[0226] In this application, there are no special restrictions on the shape of the secondary battery, and it may be cylindrical, square, or any other shape. For example, FIG. 3 is a secondary battery (5) with a square structure as an example.

[0227] In some embodiments, referring to FIG. 4, the outer packaging material may include a housing (51) and a cover plate (53). Here, the housing (51) may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving chamber. The housing (51) has an opening communicating with the receiving chamber, and the cover plate (53) is designed to cover the opening and install it so as to close the receiving chamber. The positive electrode, the negative electrode, and the separator may form an electrode assembly (52) through a winding process or a lamination process. The electrode assembly (52) is packaged within the receiving chamber. An electrolyte is infiltrated into the electrode assembly (52). The number of electrode assemblies (52) included in the secondary battery (5) may be one or more, and a person skilled in the art may select according to specific actual needs.

[0228] In some embodiments, the secondary battery may be assembled into a battery module, and the specific number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by a person skilled in the art according to the application and capacity of the battery module.

[0229] FIG. 5 is a battery module (4) as an example. Referring to FIG. 5, in the battery module (4), a plurality of secondary batteries (5) may be installed so as to be arranged sequentially along the length direction of the battery module (4). Of course, they may also be arranged in any other arbitrary way. Additionally, the plurality of secondary batteries (5) may be secured with fasteners.

[0230] In some embodiments, the battery module (4) may also include a housing having a receiving space, and a plurality of secondary batteries (5) are received in the receiving space.

[0231] In some embodiments, the battery module described above may be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number may be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0232] FIGS. 6 and 7 illustrate a battery pack (1) as an example. Referring to FIGS. 6 and 7, the battery pack (1) may include a battery case and a plurality of battery modules (4) installed in the battery case. The battery case includes an upper case (2) and a lower case (3), wherein the upper case (2) is installed over the lower case (3) and may form a closed space for accommodating the battery modules (4). The plurality of battery modules (4) may be arranged in any manner within the battery case.

[0233] [Electrical device]

[0234] Additionally, the present application also provides an electric device, and the electric device includes a secondary battery of an embodiment of the present application.

[0235] In some embodiments, the electric device according to the embodiments of the present application may also include at least one of a battery module or a battery pack. The secondary battery, battery module, or battery pack may be used as a power source for the electric device and may also be used as an energy storage unit for the electric device. The electric 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 and satellites, energy storage systems, etc.

[0236] As for the electrical device, a secondary battery, battery module, or battery pack can be selected depending on the usage demand.

[0237] FIG. 8 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the requirements for high power output and high energy density for the secondary battery of the electric device, a battery pack or battery module may be used.

[0238] Other examples of devices may include mobile phones, tablet computers, laptops, etc. These devices should generally be thin and light, and can use a secondary battery as a power source.

[0239] Examples

[0240] The following describes embodiments of the present application. The embodiments described below are illustrative and are intended only to interpret the present application and should not be construed as a limitation thereof. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature of the art or product descriptions. Where the manufacturer of the reagents or equipment used is not specified, they are all ordinary products available on the market.

[0241] Example 1

[0242] A. Manufacturing method

[0243] 1) Preparation of positive electrode active material

[0244] Preparation of lithium iron phosphate particles:

[0245] Lithium carbonate, diiron trioxide, phosphoric acid, glucose, titanium dioxide (based on the total weight of the lithium iron phosphate particles, the amount of titanium dioxide added satisfies the requirement that the titanium content in the manufactured lithium iron phosphate particles is 5000 ppm), and polyaniline were each weighed, wherein the weight ratio of the Li, Fe, and P elements satisfies Fe:P=0.968:1 and Li:Fe=1:0.98, and the weight ratio of glucose and polyaniline satisfies Glucose:Polyaniline=1:2. The amount of glucose and polyaniline added satisfies the requirement that the carbon content accounts for 0.15% of the weight of the lithium iron phosphate precursor after the completion of the first sintering. Water was added to the above-described materials to obtain a mixture slurry.

[0246] The mixture slurry was uniformly mixed using a ball mill and ground using a bead mill to obtain a slurry with a solid content of 38% and a Dv50 of 400 nm, after which it was spray-dried (the negative pressure of the high-speed spray dryer was -650 to -200 Pascals (Pa), the inlet temperature was 300°C to 360°C, and the outlet temperature was 100°C to 140°C). The dried reaction product was charged into a sintering furnace for primary sintering, with the temperature rise rate controlled at 5°C / min, the holding temperature controlled at 650°C, and the holding time set to 4 hours. After cooling the material, it was ground using a mechanical mill to obtain a powder.

[0247] The obtained powder, glucose, polyaniline, and water were mixed (based on the total weight of the lithium iron phosphate particles, the amount of glucose and polyaniline added satisfies the carbon content of the product after secondary sintering being 1.2%, and the weight ratio of glucose and polyaniline satisfies glucose:polyaniline = 1:2), and the solid content is 40%. After uniform mixing, the mixture was processed using ball milling and bead milling to obtain a slurry, the Dv50 of the insoluble matter in the slurry was 550 nm, and the slurry was spray-dried (the negative pressure of the high-speed spray dryer is -650~200 Pa, the inlet temperature is 300℃~360℃, and the outlet temperature is 100℃~140℃). The dried reaction product was loaded into a sintering furnace and subjected to secondary low-temperature sintering (controlled to a temperature rise rate of 5°C / min, a sintering temperature of 750°C, and a sintering time of 4 hours). After the material was cooled, it was subjected to secondary grinding until the primary average particle size reached 870 nm. After demagnetization, lithium iron phosphate particles were obtained with a carbon content of 1.2% and a Ti element content of 5000 ppm. The obtained lithium iron phosphate particles were placed under a scanning electron microscope and observed, and the results are shown in Figure 2.

[0248] Lithium nickel cobalt manganese oxide particles were purchased from Guangdong Brunp Recycling Technology Co., Ltd., model CPE-16, and BET and Dv50 values ​​are as shown in Table 1.

[0249] A positive electrode active material was obtained by mixing lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles according to the masses listed in Table 1.

[0250] 2) Manufacturing of the anode section

[0251] After sufficiently dissolving 2.0 wt% of polyvinylidene fluoride adhesive in N-methylpyrrolidone (NMP), 1.0 wt% of Super P, 0.5 wt% of carbon nanotubes, and 96.5 wt% of the above-described cathode material were added and uniformly mixed to obtain a cathode slurry.

[0252] Anode slurry 252 mg / 1540 mm 2 After uniformly applying the weight of a single surface to the surface of the aluminum foil of the current collector, it was transferred to a vacuum drying oven and completely dried. The dried electrode piece was rolled and punched to obtain an anode piece.

[0253] 3) Manufacturing of the cathode

[0254] Synthetic graphite as a cathode active material, carbon black as a conductor, carboxymethylcellulose as a thickener, and styrene-butadiene rubber as an adhesive were added to deionized water in a mass ratio of 0.9735:0.007:0.01:0.0095 and uniformly stirred to obtain a cathode slurry;

[0255] Then, the cathode slurry is 139 mg / 1540 mm 2 The cathode piece was obtained by uniformly coating a copper foil with a single-sided weight, and then drying, cold pressing, and slitting.

[0256] 4) Preparation of separator membrane

[0257] A polypropylene membrane was used as a separator.

[0258] 5) Battery manufacturing

[0259] The above-described positive electrode, separator, and negative electrode were sequentially stacked, and the separator was positioned between the positive electrode and the negative electrode to perform a separating function. Then, the assembly was wound to obtain a bare cell. Electrode tabs were welded to the bare cell, the bare cell was mounted in an aluminum shell, dried in a vacuum oven at 100°C for 8 hours, and then an electrolyte was injected and sealed to obtain an uncharged battery. Then, the uncharged battery was sequentially subjected to processes such as standing, cold pressing, formation, molding, and capacity testing to obtain the lithium-ion battery of Example 1.

[0260] The batteries of Examples 2 to 5 are similar to the manufacturing method of Example 1, but the primary average particle size value of the lithium iron phosphate particles was adjusted, specifically as shown in Table 1. The differences between the manufacturing methods of Examples 2 to 5 and Example 1 are as follows:

[0261] Example 2: The Dv50 of the mixed slurry after the first polishing was reduced to 350 nm;

[0262] Example 3: The Dv50 of the mixed slurry after the first polishing was increased to 1200 nm;

[0263] Example 4: The Dv50 of the mixed slurry after the first polishing was reduced to 450 nm;

[0264] Example 5: Increase the Dv50 of the mixed slurry after the first polishing to 1100 nm.

[0265] The batteries of Examples 6 and 7 are similar to the manufacturing method of Example 1, but the specific surface area value and carbon content of the lithium iron phosphate particles were adjusted, as specifically shown in Table 1. The differences between the manufacturing methods of Examples 6 and 7 and Example 1 are as follows:

[0266] Example 6: The carbon content of the secondary sintering process was adjusted to 0.8%;

[0267] Example 7: The carbon content of the secondary sintering process was adjusted to 1.4%.

[0268] The batteries of Examples 8 and 9 are similar to the manufacturing method of Example 1, but the specific surface area value of the lithium iron phosphate particles was adjusted, as specifically shown in Table 1. The differences between the manufacturing methods of Examples 8 and 9 and Example 1 are as follows:

[0269] Example 8: In the first sintering process, the weight ratio of glucose to polyaniline was set to 1:4;

[0270] Example 9: In the first sintering process, the weight ratio of glucose to polyaniline was set to 1:0.5.

[0271] The batteries of Examples 10 and 11 are manufactured using a method similar to that of Example 1, but the specific surface area value of the lithium nickel cobalt manganese oxide has been adjusted, as specifically shown in Table 1. The lithium nickel cobalt manganese oxide particles of Example 10 were purchased from Guangdong Brunp Recycling Technology Co., Ltd., and the model number is CPE17; the lithium nickel cobalt manganese oxide particles of Example 11 were purchased from Guangdong Brunp Recycling Technology Co., Ltd., and the model number is CPE18.

[0272] The batteries of Examples 12–14 are manufactured using a method similar to that of Example 1, but the doping amount of the Q element was adjusted, as specifically shown in Table 1. The differences from Example 1 in the process of manufacturing the lithium iron phosphate particles are as follows:

[0273] Example 12: The first sintering temperature was controlled to 590°C, the second sintering temperature to 720°C, and the Ti content to 0 ppm;

[0274] Example 13: The first sintering temperature was controlled to 620°C, the second sintering temperature to 740°C, and the Ti content to 2500 ppm;

[0275] Example 14: The first sintering temperature was controlled to 655°C, the second sintering temperature to 755°C, and the Ti content to 6000 ppm.

[0276] The batteries of Examples 15 to 18 are similar to the manufacturing method of Example 1, but the Dv50 values ​​of the lithium iron phosphate particles or lithium nickel cobalt manganese oxide particles were adjusted, specifically as shown in Table 1. The differences between the manufacturing methods of Examples 15 to 18 and Example 1 are as follows:

[0277] Example 15: Dv50 ground after secondary sintering was controlled to 870 nm;

[0278] Example 16: Dv50 ground after secondary sintering was controlled to 3500 nm;

[0279] The lithium nickel cobalt manganese oxide particles of Example 17 were purchased from Guangdong Brunp Recycling Technology Co., Ltd., and the model is CPE19;

[0280] The lithium nickel cobalt manganese oxide particles of Example 18 were purchased from Guangdong Brunp Recycling Technology Co., Ltd., and the model is CPE20.

[0281] The batteries of Examples 19 and 20 are manufactured using a method similar to that of Example 1, but the mixing ratio of lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles has been adjusted, as specifically shown in Table 1.

[0282] The battery of Comparative Example 1 is similar to the manufacturing method of Example 1, but the lithium iron phosphate particles used are different from those of Example 1, and the lithium iron phosphate particles used in Comparative Example 1 were purchased from Hunan Yuneng New Energy Battery Material Co., Ltd., model CPF-087-1, and specific parameters are referenced in Table 1.

[0283] The battery of Comparative Example 2 is manufactured using a method similar to that of Example 1, but the lithium iron phosphate particles used are different from those in Example 1. The lithium iron phosphate particles used in Comparative Example 2 were purchased from Hunan Yuneng New Energy Battery Material Co., Ltd., and the model is CPF-087-2. Specific parameters are indicated in Table 1.

[0284] The battery of Comparative Example 3 is similar to the manufacturing method of Example 1, but the primary average particle size and specific surface area of ​​the lithium iron phosphate particles were adjusted, as specifically shown in Table 1. The differences between the manufacturing method of Comparative Example 2 and Example 1 are as follows: Comparative Example 2 used only the primary sintering process, the sintering temperature was 750℃, and the carbon content of the product after sintering was 1.2%.

[0285] The battery of Comparative Example 4 is similar to the manufacturing method of Example 1, but the primary average particle size, specific surface area, and carbon content of the lithium iron phosphate particles were adjusted, as specifically shown in Table 1. The differences between the manufacturing method of Comparative Example 3 and Example 1 are as follows: Comparative Example 3 lowered the carbon content of the secondary sintering to 0.7%, and further adjusted the BET and primary average particle size.

[0286] B. Battery Performance Test

[0287] 1. Performance test of cathode active material

[0288] 1) Primary average particle size test method for lithium iron phosphate particles

[0289] Using an argon ion beam, the electrode piece is incised perpendicular to the large surface of the anode piece to expose the cross-section, the cross-section is photographed using a scanning electron microscope, and the particle size of lithium iron phosphate particles is statistically analyzed using the Peret diameter statistical method. Specifically, the total number of lithium iron phosphate particles with a primary particle size greater than 80 nm is statistically determined from the electron microscope scanning image, and the sum of the primary particle sizes of lithium iron phosphate particles with a primary particle size greater than 80 nm is statistically determined. The primary average particle size of lithium iron phosphate particles = sum of primary particle sizes of lithium iron phosphate particles / total number of lithium iron phosphate particles. Here, in the statistical process of primary particle size, particles with 0 < primary particle size ≤ 80 nm are not included within the statistical range.

[0290] 2) Test method for Dv50 value

[0291] Lithium iron phosphate particles: Referring to GB / T19077.1-2016, the Dv50 value of lithium iron phosphate particles can be measured using a laser particle size analyzer (Malvern Master Size 3000).

[0292] Lithium nickel cobalt manganese oxide particles: Referring to GB / T19077.1-2016, the Dv50 value of lithium nickel cobalt manganese oxide particles can be measured using a laser particle size analyzer (Malvern Master Size 3000).

[0293] 3) Specific Surface Area (BET) Test Method

[0294] In accordance with the GB / T19587-2017 test standard method, the specific surface area of ​​lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles was tested using the gas adsorption method. Specifically, lithium iron phosphate particles or lithium nickel cobalt manganese oxide particles were taken as samples, the sample tube was immersed in liquid nitrogen at -196°C, and the amount of nitrogen gas adsorbed on the solid surface was measured at different pressures with relative pressures of 0.05 to 0.30. The specific surface area of ​​the sample was calculated by calculating the amount of monolayer adsorption of the sample based on the BET multilayer adsorption theory and its formula.

[0295] 4) Test method for carbon content of lithium iron phosphate particles

[0296] After burning lithium iron phosphate particles using a high-frequency induction furnace, the carbon content was measured using the infrared absorption method, and the specific test procedure follows the standard GB / T 20123-2006 / ISO 15350:2000.

[0297] 5) Test method for the doping amount of Q element (e.g., Ti element) in lithium iron phosphate particles

[0298] The test method for the Q element content of lithium iron phosphate particles was performed by referring to GB / T 33822-2017.

[0299] 6) Test method for solid content of anode slurry

[0300] Electronic balance (precision 0.0001), oven, glass drying dish. Take an 8–10 g anode slurry sample and spread it uniformly onto a sample dish, and record the mass of the anode slurry before drying as A. Place the sample dish coated with the anode slurry sample into an oven and heat it at a heating temperature of 130°C for 5 hours. After drying and cooling, remove the sample and record the mass of the anode slurry after drying. Repeat the drying process several times, and record the mass when the mass of the anode slurry sample reached a constant weight as B. Solid content of the anode slurry = (A / B) × 100%.

[0301] 7) Test method for the filtration performance of anode slurry

[0302] A 200-mesh filter screen was folded into an inverted triangle and placed in a 500-milliliter (mL) beaker. Then, 500 mL of the prepared anode slurry (all poured in) was poured in. Time measurement was started when the slurry began to flow out from the end of the filter screen, and the filtration time was recorded until the slurry in the beaker reached 300 mL.

[0303] 8) Measurement of the η value of lithium iron phosphate particles

[0304] First, a button battery was manufactured using lithium iron phosphate particles as the positive electrode active material, and the specific button battery manufacturing process is as follows: 2.0000g of lithium iron phosphate particles were mixed with 0.1111g of conductive carbon black and 0.1111g of polyvinylidene fluoride, then added to 2.5g of the organic solvent N-methylpyrrolidone and mixed sufficiently and uniformly to form a slurry. The slurry was coated onto an aluminum foil with a coating thickness of 140μm, vacuum dried at 120°C for 2 hours, and punched into a circular sheet with a diameter of 13mm using a punching machine. Pressed at 10MPa using a press machine and vacuum held at 120°C for 12 hours to obtain a positive electrode piece. The weight of the positive electrode piece was weighed, wherein the loaded amount of lithium iron phosphate particles was 11–12mg. A button battery was assembled inside a glove box protected by an argon atmosphere, a metallic lithium sheet was used as the negative electrode, a mixed solvent of EC (ethylene carbonate) and DMC (1,2-dimethyl carbonate) with a volume ratio of 1:1 was used as the electrolyte, LiPF6 was used as the electrolyte, and a Celgard 2400 microporous polyethylene membrane was used as the separator.

[0305] The electrical performance of the manufactured button battery was tested using a LAND meter. Specifically, the button battery was charged and discharged twice with a constant current at a rate of 0.1C within a voltage range of 2.0V to 3.75V, followed by a single charge and discharge with a rate of 1C. In the charge-discharge test with a rate of 1C, the capacity value at a discharge voltage of 3.2V was extracted as C1, and the capacity value discharged to 2.0V was extracted as C2, where η = C1 / C2. Here, the charging process included constant voltage charging, the constant voltage was 3.75V, and the constant voltage cutoff current was 50μA.

[0306] 2. Battery performance testing

[0307] 1) Battery capacity per gram

[0308] The battery was placed in an oven environment at 25°C and left standing for 2 hours, ensuring the battery temperature was maintained at 25°C; the battery was discharged to 2.0V with a constant current of 1 / 3C; paused for 5 minutes; the battery was charged to 4.35V with a constant current of 1 / 3C, then charged to a constant voltage of 4.35V with a cutoff current of 0.05C; and paused for 5 minutes.

[0309] The battery is discharged to 2.0V with a constant current of 1 / 3C. This step is intended to test the capacity of the actual battery cell, and the capacity per gram of the battery can be calculated by combining it with the mass of the positive active material, where capacity per gram = capacity / mass of the positive active material.

[0310] 2) Compression density test method for anode specimens

[0311] When the electrode piece is single-sided coated, the compression density of the film layer on one side of the electrode piece is m / (V1-V2), and when the electrode piece is double-sided coated, the compression density of the film layer on one side of the electrode piece is m / [2×(V1-V2)], where m represents the weight of the film layer, V1 represents the volume of the electrode piece, and V2 represents the volume of the current collector. m can be obtained by subtracting the weight of the current collector from the weight of the electrode piece, the volume of the electrode piece (V1) is the product of the surface area of ​​the electrode piece and the thickness of the electrode piece, and V2 is the product of the surface area of ​​the electrode piece and the thickness of the current collector, and the thickness of the current collector and the thickness of the electrode piece are obtained by measuring the thickness of the empty foil in the electrode tab area using a micrometer.

[0312] C. Analysis of test results for each example and comparative example

[0313] Batteries of each example and comparative example were manufactured according to the method described above, and each performance parameter was measured. Refer to Table 1 for the parameter table of the positive electrode active material and refer to Table 2 for the performance test result table.

[0314]

[0315] number Solid content (%) of anode slurry 300mL anode slurry filtration time(s) Capacity per gram (milliampere-hour / gram mAh / g) Compressed density (g / cm³) 3 ) Example 1 65.0 150 171 3.35 Example 2 64.5 180 173 3.30 Example 3 68.0 130 165 3.25 Example 4 64.8 170 172 3.32 Example 5 67.5 150 167 3.28 Example 6 69.0 120 167 3.38 Example 7 63.5 195 172 3.34 Example 8 63.7 165 166 3.3 Example 9 66.4 145 165 3.35 Example 10 65.8 145 170 3.3 Example 11 61.0 170 173 3.25 Example 12 65.0 150 169 3.25 Example 13 65.0 150 170 3.25 Example 14 65.0 150 170 3.25 Example 15 64.0 178 172 3.25 Example 16 68.8 120 168 3.15 Example 17 60.0 190 174 3.1 Example 18 69.0 175 168 3.15 Example 19 70.5 100 183 3.42 Example 20 67.0 220 158 3.2 Comparative Example 1 58.0 300 158 3.05 Comparative Example 2 59.0 265 156 3.35 Comparative Example 3 70.5 120 156 3.15 Comparative Example 4 68.5 110 155 3.1

[0316] According to the results of the table above, as can be seen from Examples 1 to 20 and Comparative Example 1, increasing the primary average particle size of the lithium iron phosphate particles and lowering the specific surface area can improve the solid content and filtration performance of the anode slurry and is advantageous for improving processing problems. As can be seen from Examples 1 to 20 and Comparative Example 2, lowering the specific surface area of ​​the lithium iron phosphate particles is advantageous for improving the solid content and filtration performance of the anode slurry and is advantageous for improving processing problems. As can be seen from Examples 1 to 18 and Comparative Example 3, the primary average particle size of the lithium iron phosphate particles of the present application is advantageous for maintaining a relatively excellent capacity per gram. As can be seen from Examples 1 to 18 and Comparative Example 4, when the BET of the lithium iron phosphate particles is too small, the capacity per gram of the secondary battery decreases. In summary, the primary average particle size of the lithium iron phosphate particles is 500–3000 nm, and the specific surface area BET is 3 m² 2 / g~8m 2 / g, and the specific surface area BET of the lithium nickel cobalt manganese oxide particles is 0.4m 2 / g~2.0m 2 When / g, it is possible to improve the processing performance of the anode slurry while simultaneously achieving the capacity per gram of the secondary battery.

[0317] As can be seen from FIGS. 1a and 1b, lithium nickel cobalt manganese oxide particles are uniformly mixed with lithium iron phosphate particles, so that the lithium iron phosphate particles densely fill the pores of the lithium nickel cobalt manganese oxide particles. The scanning electron microscope image of FIG. 2 shows the micromorphism of the lithium iron phosphate particles of Example 1 of the present application, and as can be seen from the figure, the lithium iron phosphate of Example 1 of the present application exhibits a large single-crystal shape.

[0318] As can be seen from Examples 1 to 5, when the primary average particle size of the lithium iron phosphate particles is controlled to 500 to 3000 nm, the processing performance of the anode slurry can be improved, while the capacity per gram of the secondary battery can be achieved.

[0319] As can be seen from Examples 1, 6–7, and 10–11, the BET value of the lithium iron phosphate particles is 3m 2 / g~8m 2 Controlled at / g, the BET value of lithium nickel cobalt manganese oxide particles is 0.4m 2 / g~2.0m 2 When controlled at / g, it is possible to improve the processing performance of the anode slurry while simultaneously achieving the capacity per gram of the secondary battery.

[0320] As can be seen from Examples 1 and 8-9, increasing the proportion of the carbon source film-forming agent is advantageous for achieving a dense coating of the carbon layer, and the degree of carbon coating density of the present application is advantageous for further improving the kinetic performance and capacity per gram of the secondary battery.

[0321] As can be seen from Example 1 and Examples 12 to 14, the kinetic performance of the cathode active material can be improved by adding a metal element, such as titanium, to the lithium iron phosphate particles. Furthermore, increasing the content of the metal element within, for example, a range of 1,000 to 10,000 ppm is advantageous for further improving kinetic performance and minimizing the influence on the capacity per gram of the lithium iron phosphate particles.

[0322] As can be seen from Examples 1 and 15 to 18, when the Dv50 of the lithium iron phosphate particles is 500 to 5000 nm and the Dv50 of the lithium nickel cobalt manganese oxide particles is 1200 to 20000 nm and the ratio of the two is 1:(1 to 50), it is advantageous to improve the compression density of the anode.

[0323] As can be seen from Examples 1 and 19-20, when the mass percentages of lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles are controlled within an appropriate range, for example, when the mass percentage of lithium iron phosphate particles is controlled to 5% to 80% and the mass percentage of lithium nickel cobalt manganese oxide particles is controlled to 20% to 95%, it helps to better balance the processing performance, electrical performance, and cost of the cathode active material.

[0324] It should be noted that the present application is not limited to the embodiments described above. The embodiments described above are merely examples, and any embodiments having substantially the same configuration as the technical concept and exhibiting the same functional effects within the scope of the technical solution of the present application are included within the technical scope of the present application. Furthermore, other methods constructed by applying various modifications to the embodiments conceived by a person skilled in the art without departing from the spirit of the present application, and by combining parts of the components of the embodiments, are also included within the scope of the present application. Explanation of the symbols

[0325] 1: Battery pack; 2: Top case; 3: Bottom case; 4: Battery module; 5: Secondary battery, 51: Housing; 52: Electrode assembly; 53: Top cover assembly.

Claims

Claim 1 As a positive electrode active material, the positive electrode active material comprises lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles, wherein the primary average particle size of the lithium iron phosphate particles is 500 to 3000 nm and the specific surface area BET of the lithium iron phosphate particles is 3 m 2 / g~8m 2 / g, and the specific surface area BET of the lithium nickel cobalt manganese oxide particles is 0.4m 2 / g~2.0m 2 A positive active material characterized by being / g. Claim 2 In claim 1, the lithium iron phosphate particles have the molecular formula Li m1 Fe x1 P y1 O z1 Q q1 having, where Q comprises at least one of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, and 0.95≤m1≤1.15, 0.9≤x1≤1, 0.95≤y1≤1, 3.5≤z1≤4, 0 <q1≤0.1이며, 및 / 또는상기 리튬니켈코발트망간산화물 입자는 분자식 LiR x2 Ni y2 Co z2 Mn 1-x2-y2-z2 It has O2, wherein R comprises at least one of Cr, Ti, V, Mg, Al, and Nb, and 0≤x2<1, 0 <y2<1, 0<z2<1, 0<x2+y2+z2<1인 것을 특징으로 하는, 양극 활물질. Claim 3 A positive electrode active material according to claim 1 or 2, characterized in that the primary average particle size of the lithium iron phosphate particles is 650 to 2500 nm. Claim 4 In any one of claims 1 to 3, the BET of the lithium iron phosphate particles is 4m 2 / g~7m 2 / g, and the BET of the lithium nickel cobalt manganese oxide particles is 0.6m 2 / g~2.0m 2 A positive active material characterized by being / g. Claim 5 A positive electrode active material characterized in that, in any one of claims 1 to 4, the carbon content of the lithium iron phosphate particles is 0.8% by weight to 2.0% by weight when calculated based on the total weight of the lithium iron phosphate particles. Claim 6 A positive electrode active material characterized in that, in any one of claims 1 to 5, the carbon content of the lithium iron phosphate particles is 1.0% to 1.6% by weight when calculated based on the total weight of the lithium iron phosphate particles. Claim 7 A positive electrode active material characterized in that, in any one of claims 2 to 6, Q comprises at least one of Ti, V, Mg, and Nb; and when calculated based on the total weight of the lithium iron phosphate particles, the content of Q in the lithium iron phosphate particles is 1,000 to 10,000 ppm. Claim 8 A positive electrode active material characterized in that, in any one of claims 1 to 7, the Dv50 of the lithium iron phosphate particles is 500 to 5000 nm. Claim 9 A positive electrode active material characterized in that, in any one of claims 1 to 8, the Dv50 of the lithium nickel cobalt manganese oxide particles is 1200 to 20000 nm. Claim 10 A positive electrode active material according to any one of claims 1 to 9, characterized in that the Dv50 of the lithium iron phosphate particles is 870 to 1500 nm and the Dv50 of the lithium nickel cobalt manganese oxide particles is 1800 to 4200 nm. Claim 11 A positive electrode active material characterized in that, in any one of claims 1 to 10, the mass percentage of the lithium iron phosphate particles is 5% to 80% when calculated based on the total mass of the positive electrode active material. Claim 12 A positive electrode active material characterized in that, in any one of claims 1 to 11, the mass percentage of the lithium nickel cobalt manganese oxide particles is 20% to 95% when calculated based on the total mass of the positive electrode active material. Claim 13 A positive electrode active material according to any one of claims 1 to 12, wherein the capacity ratio of the lithium iron phosphate particles is η≥88%, and η is defined as follows: a battery having the lithium iron phosphate particles as a positive electrode active material is charged and discharged twice at a constant current with a rate limit of 0.1C within a voltage range of 2.0V to 3.75V, followed by charged and discharged once at a constant current with a rate limit of 1C; in a charge-discharge test with a rate limit of 1C, a capacity value at a discharge voltage of 3.2V is extracted as C1, a capacity value discharged to 2.0V is extracted as C2, and η=C1 / C2; wherein the charging process includes constant voltage charging, the constant voltage is 3.75V, and the constant voltage cutoff current is 50uA. Claim 14 In any one of claims 1 to 13, the lithium iron phosphate particles comprise: a) Dv10 ≥ 200 nm of the lithium iron phosphate particles; b) Dv90 ≤ 10000 nm of the lithium iron phosphate particles; c) Dv99 ≤ 12000 nm of the lithium iron phosphate particles; and d) powder compression density ≥ 2.25 g / cm³ of the lithium iron phosphate at a pressure of 3T. 3 ;e) A positive electrode active material characterized by satisfying at least one of (a) to (e) the powder resistivity of the lithium iron phosphate being less than 60 Ω·cm. Claim 15 A method for manufacturing a positive electrode active material, wherein the manufacturing method comprises the step of mixing lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles, and the manufacturing process of the lithium iron phosphate particles comprises the step of providing raw materials containing at least a lithium source, an iron source, and a phosphorus source, and sintering at least twice, wherein the first sintering temperature is 500℃ to 760℃; and the second sintering temperature is 700℃ to 800℃. Claim 16 A method of manufacturing according to claim 15, wherein the lithium iron phosphate particles are obtained by a method of manufacturing in which a raw material containing mainly: at least a lithium source, an iron source, a phosphorus source, a carbon source, a carbon film-forming agent, and a modifier is provided and sintered at least twice, wherein, the carbon content of the material after the first sintering is 0.01 wt% to 0.79 wt%; and the carbon content of the material after the second sintering is 0.8 wt% to 2.0 wt%. Claim 17 A method of manufacturing according to claim 15 or 16, wherein the lithium iron phosphate particles comprise at least one of the elements Ti, V, Mg and / or Nb, and the content of the element is 1,000 ppm to 10,000 ppm when calculated based on the total weight of the lithium iron phosphate particles. Claim 18 A manufacturing method according to any one of claims 15 to 17, wherein, after performing the first sintering, the first grinding is performed, and after performing the second sintering, the second grinding is performed, wherein, the Dv50 of the product after the first grinding is 300 nm to 1200 nm; and the Dv50 of the product after the second grinding is 500 nm to 5000 nm. Claim 19 A positive electrode, wherein the positive electrode comprises a positive active material according to any one of claims 1 to 14 or a positive active material obtained through a manufacturing method according to any one of claims 15 to 18. Claim 20 In claim 19, the compressive density of the anode piece is 3.0 g / cm³ 3 ~3.5g / cm 3 A positive plate characterized by being. Claim 21 A secondary battery characterized by including a positive plate according to claim 19 or 20. Claim 22 An electric device characterized by including a secondary battery according to claim 21.

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