Secondary battery and preparation method therefor, and electric device

Abstract

A secondary battery and a preparation method therefor, and an electric device. The preparation method for the secondary battery comprises: preparing a positive electrode active material; mixing lithium-containing transition metal phosphate materials respectively having primary average particle sizes of 50-200 nm, 120-600 nm, and 250-4000 nm to obtain the positive electrode active material; controlling a Mn molar ratio in the lithium-containing transition metal phosphate material having the primary average particle size of 120-600 nm to be greater than a Mn molar ratio in the lithium-containing transition metal phosphate material having the primary average particle size of 50-200 nm and a Mn molar ratio in the lithium-containing transition metal phosphate material having the primary average particle size of 250-4000 nm; and in addition, controlling the particle size distribution of primary particles having a primary particle size of 50-180 nm in the lithium-containing transition metal phosphate material having the primary average particle size of 120-600 nm to be less than or equal to 10%, and controlling the number of primary particles having a primary particle size greater than or equal to 1200 nm to be less than or equal to 15 within a 250 μm2 region of a longitudinal section of an electrode sheet prepared from the primary particles.

Description

Secondary batteries, their preparation methods and electrical devices

[0001] Cross-referencing

[0002] This application incorporates Chinese Patent Application No. 202411035237.3, filed on July 30, 2024, entitled "Secondary Battery, Method of Preparation Thereof and Electrical Device", which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to the field of secondary battery technology, and in particular to a secondary battery, its preparation method and power supply device. Background Technology

[0004] In recent years, with the development of lithium-ion rechargeable battery technology, lithium-ion rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion rechargeable batteries, higher requirements have been placed on their cycle performance and energy density. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery that can improve the energy density and cycle performance of the battery.

[0006] The first aspect of this application provides a method for preparing a secondary battery, comprising the following steps:

[0007] Preparation of positive electrode active material: A first lithium-containing transition metal phosphate material, a second lithium-containing transition metal phosphate material, and a third lithium-containing transition metal phosphate material are mixed to obtain the positive electrode active material.

[0008] The primary average particle size of the first lithium-containing transition metal phosphate material is 50 nm-200 nm.

[0009] The primary average particle size of the second lithium-containing transition metal phosphate material is 120 nm-600 nm.

[0010] In the second lithium-containing transition metal phosphate material, the primary particles with a diameter of 50 nm to 180 nm account for less than or equal to 10% of the total particle size distribution.

[0011] Primary particles with a primary diameter greater than or equal to 1200 nm are used to prepare electrodes from lithium-containing transition metal phosphate materials, with a cross-section of 250 μm. 2 The number of particles in the area is less than or equal to 15;

[0012] The primary average particle size of the third lithium-containing transition metal phosphate material is 250 nm-4000 nm.

[0013] The primary average particle size of the first lithium-containing transition metal phosphate material is smaller than that of the second lithium-containing transition metal phosphate material.

[0014] The primary average particle size of the third lithium-containing transition metal phosphate material is greater than that of the second lithium-containing transition metal phosphate material.

[0015] The molar percentage of Mn in the first lithium-containing transition metal phosphate material is less than that in the second lithium-containing transition metal phosphate material.

[0016] The molar percentage of Mn in the third lithium-containing transition metal phosphate material is less than that in the second lithium-containing transition metal phosphate material.

[0017] Here, molar percentage refers to the ratio of the number of moles of an element to the total number of moles of Mn and Fe.

[0018] Preparation of positive electrode sheet: A positive electrode slurry containing positive electrode active material is coated on at least one surface of the positive electrode current collector to obtain a positive electrode sheet;

[0019] Preparation of secondary batteries: Assemble an electrode assembly containing a positive electrode, a negative electrode, and an electrolyte into a secondary battery.

[0020] On the one hand, the positive electrode active material includes three materials with different average particle sizes, which can achieve the purpose of filling the gaps by matching the size distribution of the materials, making the positive electrode active material more densely packed, increasing the powder compaction density, increasing the electrode compaction density, and thus improving the energy density of the battery. Controlling the small-particle-size first lithium-containing transition phosphate material to be low-manganese or manganese-free can reduce the possibility of manganese dissolution in the highly reactive first lithium-containing transition phosphate material, improving the cycle performance of the battery. Simultaneously, controlling the large-particle-size third lithium-containing transition metal phosphate material to be low-manganese or manganese-free can improve the conductivity of the large-particle-size third lithium-containing transition metal phosphate material, alleviate the discharge polarization of the material, and facilitate the utilization of the specific capacity and kinetic performance, further improving the energy density and rate performance of the battery. On the other hand, controlling the particle size distribution of primary particles with a diameter of 50nm-180nm in the second lithium-containing transition metal phosphate material to within 10% reduces the possibility of manganese dissolution caused by side reactions between the high-manganese small-diameter primary particles in the second lithium-containing transition metal phosphate material and the electrolyte, thereby improving the cycle stability of the material and extending the cycle life of the battery. At the same time, controlling the number of primary particles with a diameter greater than or equal to 1200nm in the second lithium-containing transition metal phosphate material within an appropriate range avoids the impact of excessive high-manganese large-diameter particles on the conductivity of the material, improves the overall conductivity of the material, and helps the second lithium-containing transition metal phosphate material to exert its specific capacity, so as to achieve the goal of the high-manganese second lithium-containing transition metal phosphate material contributing sufficient capacity, thereby improving the energy density of the battery.

[0021] In any embodiment, the primary particles with a primary diameter of 50 nm to 180 nm in the second lithium-containing transition metal phosphate material have a particle size distribution of 3% to 8.5% in the second lithium-containing transition metal phosphate material.

[0022] By controlling the number of small-diameter primary particles in the second lithium-containing transition metal phosphate material within a suitable range, the possibility of side reactions between the high-manganese second lithium-containing transition metal phosphate material and the electrolyte is reduced, the possibility of manganese dissolution during cycling is reduced, and the cycle performance of the battery is further improved.

[0023] In any embodiment, primary particles with a primary particle size greater than or equal to 1200 nm are 250 μm in diameter at the longitudinal section of the electrode prepared from the second lithium-containing transition metal phosphate material. 2 The number of particles in the region is 2-12.

[0024] Controlling the number of large-diameter particles in the second lithium-containing transition metal phosphate material within a suitable range reduces the impact of high-manganese large-diameter particles on the material's conductivity, allowing the high-manganese second lithium-containing transition metal phosphate material to achieve its specific capacity, which is beneficial for obtaining high-energy-density batteries.

[0025] In any embodiment, the particle size distribution index of the primary particles with a primary particle size greater than 180 nm and less than 1200 nm in the second lithium-containing transition metal phosphate material is less than or equal to 0.45, and can be selected as 0.3-0.36.

[0026] The second lithium-containing transition metal phosphate material has excellent particle size uniformity, which makes the discharge behavior of each particle tend to be consistent during battery cycling. This reduces the possibility of overcharging and over-discharging during charging and discharging, which helps to ensure the structural stability of the second lithium-containing transition metal phosphate material and the positive electrode active material, and improves the cycle performance of the battery.

[0027] In any embodiment, the second lithium-containing transition metal phosphate material satisfies at least one of (a1)-(d1):

[0028] (a1) The (Dv90-Dv10) / Dv50 ratio of the second lithium-containing transition metal phosphate material is 1-3;

[0029] (b1) The Dv50 of the second lithium-containing transition metal phosphate material is 0.35 μm-1.5 μm;

[0030] (c1) The Dv10 of the second lithium-containing transition metal phosphate material is 0.1 μm-0.4 μm;

[0031] (d1) The Dv90 of the second lithium-containing transition metal phosphate material is 2.5μm-6μm.

[0032] In any embodiment, the molar percentage of Mn in the first lithium-containing transition metal phosphate material is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

[0033] By controlling the molar ratio of Mn in the first lithium-containing transition metal phosphate material within a suitable range, the side reactions between small-particle materials and electrolytes and the degree of manganese dissolution can be further reduced, thereby further improving the cycle performance and storage performance of the battery. The battery is more suitable for application scenarios with high requirements for cycle life and / or storage life.

[0034] In any embodiment, the molar ratio of Mn in the first lithium-containing transition metal phosphate material is 0.02-0.6, optionally 0.02-0.4, more preferably 0.02-0.2, and even more preferably 0.02.

[0035] In any embodiment, the molar percentage of Mn in the first lithium-containing transition metal phosphate material is 0.2-0.6, optionally 0.2-0.4, and more preferably 0.2.

[0036] By controlling the average molar ratio of Mn in small-particle-size materials within a suitable range, the cycle stability of small-particle-size materials can be improved, while also allowing the highly conductive small-particle-size materials to fully utilize their specific capacity. This results in excellent cycle performance of the battery and further increases its energy density, making the battery more suitable for scenarios with high energy density requirements.

[0037] In any embodiment, the molar percentage of Mn in the second lithium-containing transition metal phosphate material is 0.4-0.9, and can be optionally 0.5-0.9.

[0038] By controlling the average Mn molar ratio of the second lithium-containing transition metal phosphate material within a suitable range, the second lithium-containing transition metal phosphate material can have a high plateau capacity, while also ensuring that the second lithium-containing transition metal phosphate material has a certain conductivity. This is conducive to the second lithium-containing transition metal phosphate material exerting its specific capacity, so as to achieve the goal of the second lithium-containing transition metal phosphate material contributing sufficient capacity, thereby improving the energy density of the battery.

[0039] In any embodiment, the molar percentage of Mn in the third lithium-containing transition metal phosphate material is 0-0.6, optionally 0-0.5, more preferably 0-0.1, and even more preferably 0.

[0040] Controlling the molar ratio of Mn in the third lithium-containing transition metal phosphate material within a suitable range can improve the cycle stability and conductivity of the third lithium-containing transition metal phosphate material, which is conducive to further exerting its specific capacity and improving the energy density and cycle life of the battery.

[0041] In any embodiment, the molar percentage of Mn in the third lithium-containing transition metal phosphate material is 0.02-0.6, optionally 0.02-0.5, more preferably 0.02-0.1, and even more preferably 0.02.

[0042] In any embodiment, the molar percentage of Mn in the third lithium-containing transition metal phosphate material is 0.2-0.6, optionally 0.2-0.5, and more preferably 0.2.

[0043] By controlling the molar ratio of Mn in the third lithium-containing transition metal phosphate material within a suitable range, the conductivity of the third lithium-containing transition metal phosphate material is improved, and the third lithium-containing transition metal phosphate material also has a certain plateau capacity, thereby further improving the energy density of the battery.

[0044] In any embodiment, based on the total mass of the positive electrode active material, the mass content of the first lithium transition metal phosphate material is 1%-10%, the mass content of the second lithium transition metal phosphate material is 60%-90%, and the mass content of the third lithium transition metal phosphate material is 5%-30%.

[0045] By controlling the mass ratio of materials with different particle sizes within a suitable range, the contribution of the high-manganese content second lithium-containing transition metal phosphate material to the energy density in terms of voltage rating and specific capacity can be achieved. At the same time, the impact of the large-particle-size third lithium-containing transition metal phosphate material on the rate performance of the battery and the impact of the small-particle-size first lithium-containing transition metal phosphate material on the cycle performance of the battery can be reduced. In addition, if the mass ratio of the three materials is within a suitable range, the molar ratio of Mn in the positive electrode active material can also be within a suitable range, which is conducive to obtaining a battery with high energy density, excellent rate performance and cycle performance.

[0046] In any embodiment, the first lithium-containing transition metal phosphate material includes a first core and a first carbon coating layer covering the outer surface of the first core; the second lithium-containing transition metal phosphate material includes a second core and a second carbon coating layer covering the outer surface of the second core; and the positive electrode active material further includes a third lithium-containing transition metal phosphate material, which includes a third core and a third carbon coating layer covering the outer surface of the third core.

[0047] The general formula for the first kernel includes Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 ,

[0048] Where 0.8≤m1≤1.2, x1≥0, y1≥0, 0.9≤x1+y1≤1, 0.95≤z1≤1.1, 3.5≤n1≤4, 0≤a1≤0.1, 0≤b1≤0.1, 0≤c1≤0.1, 0≤d1≤0.1,

[0049] The general formula for the composition of the second kernel includes Li m2 A2 a2 Fe x2 Mn y2 M2 b2 P z2 Q2 c2 O n2 N2 d2 ,

[0050] 0.8≤m2≤1.2, x2≥0, y2>0, 0.9≤x2+y2≤1, 0.95≤z2≤1.1, 3.5≤n2≤4, 0≤a2≤0.1, 0≤b2≤0.1, 0≤c2≤0.1, 0≤d2≤0.1,

[0051] The general formula for the composition of the third kernel includes Li m3 A3 a3 Fe x3 Mn y3 M3 b3 P z3 Q3 c3 O n3 N3 d3 ,

[0052] 0.8≤m³≤1.2, x³≥0, y³≥0, 0.9≤x³+y³≤1, 0.95≤z³≤1.1, 3.5≤n³≤4, 0≤a³≤0.1, 0≤b³≤0.1, 0≤c³≤0.1, 0≤d³≤0.1

[0053] Among them, A1, A2, and A3 each independently include one or more of Al, Na, K, and Mg; M1, M2, and M3 each independently include one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti; Q1, Q2, and Q3 each independently include one or more of B, S, Si, and N; and N1, N2, and N3 each independently include one or more of S, F, Cl, and Br.

[0054] In any embodiment, the positive electrode slurry further includes a binder and a conductive agent, and the mass ratio of the positive electrode active material, binder and conductive agent in the positive electrode slurry is (92-99):(0.5-3):(0.5-3).

[0055] In any embodiment, the areal density of the positive electrode sheet is 300 mg / 1540 mm². 2 -580mg / 1540mm 2 .

[0056] In any embodiment, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0057] The second aspect of this application provides a secondary battery prepared by the preparation method of the first aspect.

[0058] A third aspect of this application provides an electrical device comprising a secondary battery prepared by the method of the first aspect or a secondary battery of the second aspect. Attached Figure Description

[0059] Figure 1 is a schematic diagram of the statistical distinction rules of primary particles in the transmission electron microscope image of particles in this application;

[0060] Figure 2 is a schematic diagram of a secondary battery according to an embodiment of this application;

[0061] Figure 3 is an exploded view of the secondary battery according to an embodiment of this application shown in Figure 2;

[0062] Figure 4 is a schematic diagram of a battery module according to an embodiment of this application;

[0063] Figure 5 is a schematic diagram of a battery pack according to an embodiment of this application;

[0064] Figure 6 is an exploded view of the battery pack of one embodiment of this application shown in Figure 5;

[0065] Figure 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0066] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0067] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the secondary battery, its preparation method, and the power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0068] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0069] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0070] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0071] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0072] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0073] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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 both A and B are true (or exist).

[0074] The cathode active material is one of the decisive factors in the performance of secondary batteries. Currently, common cathode active materials mainly include lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, and lithium iron phosphate. Each of these materials has its advantages and disadvantages. For example, lithium cobalt oxide has high energy density and voltage plateau, but its cost is high and its safety is poor; lithium manganese oxide has lower cost and better safety, but its energy density and voltage plateau are lower; nickel-cobalt-manganese ternary materials combine the advantages of the former two, but their cost is still high. Lithium iron phosphate, on the other hand, has advantages such as low cost, high safety, and long lifespan, which can better meet the requirements of the new energy vehicle market for high safety and low cost of lithium-ion batteries. However, lithium iron phosphate also has some disadvantages, such as low compaction density and low discharge capacity, which limit its application in high-energy-density batteries. Lithium manganese iron phosphate, as a new material for the further development of lithium iron phosphate, combines the advantages of manganese and iron, and has two voltage plateaus at 4.1V and 3.4V respectively, which can provide a certain plateau capacity and is expected to improve the shortcomings of lithium iron phosphate materials. However, in current research and applications, lithium manganese iron phosphate (LFP) still suffers from low compaction density and has not yet demonstrated the potential advantage of high energy density. Furthermore, the trivalent manganese ions in LFP exhibit the Jan Taylor effect, transforming into tetravalent manganese ions. These highly reactive tetravalent manganese ions readily react with the electrolyte to become divalent manganese ions. These divalent manganese ions further dissolve in the electrolyte and are reduced and precipitated at the negative electrode, damaging the SEI film. This results in more active lithium being consumed during SEI film repair, thus affecting the battery's cycle life. Therefore, how to improve the compaction density of LFP to obtain high-energy-density batteries while simultaneously maintaining good cycle performance has become a key research focus.

[0075] [Preparation methods for secondary batteries]

[0076] This application provides a method for preparing a secondary battery, comprising the following steps:

[0077] Preparation of the positive electrode active material: A first lithium-containing transition metal phosphate material, a second lithium-containing transition metal phosphate material, and a third lithium-containing transition metal phosphate material are mixed to obtain the positive electrode active material.

[0078] The primary average particle size of the first lithium-containing transition metal phosphate material is 50 nanometers (nm) to 200 nm.

[0079] The primary average particle size of the second lithium-containing transition metal phosphate material is 120 nm-600 nm.

[0080] In the second lithium-containing transition metal phosphate material, the primary particles with a diameter of 50 nm to 180 nm account for less than or equal to 10% of the total particle size distribution.

[0081] Primary particles with a primary diameter greater than or equal to 1200 nm are used in the second lithium-containing transition metal phosphate material to prepare an electrode with a longitudinal cross-section of 250 square micrometers (μm). 2 The number of particles in the area is less than or equal to 15;

[0082] The primary average particle size of the third lithium-containing transition metal phosphate material is 250 nm to 4000 nm.

[0083] The primary average particle size of the first lithium-containing transition metal phosphate material is smaller than that of the second lithium-containing transition metal phosphate material.

[0084] The primary average particle size of the third lithium-containing transition metal phosphate material is greater than that of the second lithium-containing transition metal phosphate material.

[0085] The molar percentage of Mn in the first lithium-containing transition metal phosphate material is less than that in the second lithium-containing transition metal phosphate material.

[0086] The molar percentage of Mn in the third lithium-containing transition metal phosphate material is less than that in the second lithium-containing transition metal phosphate material.

[0087] Wherein, the molar percentage refers to the ratio of the number of moles of an element to the total number of moles of Mn and Fe.

[0088] Preparation of positive electrode sheet: A positive electrode slurry containing the positive electrode active material is coated on at least one surface of the positive electrode current collector to obtain a positive electrode sheet;

[0089] Preparation of secondary battery: Assemble the electrode assembly containing the positive electrode, negative electrode and electrolyte into a secondary battery.

[0090] The test method for the molar content of Mn in the first, second, and third lithium-containing transition metal phosphate materials can be carried out using methods and equipment known in the art. For example, the molar content of Mn and Fe elements can be tested by referring to the chemical analysis method for nano-lithium iron phosphate in national standard GB T33822-2017, and the molar content of Mn can be calculated.

[0091] In this paper, the term "primary particle size" refers to the particle size of a primary particle.

[0092] Primary particles refer to individual particles that can be distinguished after being identified by general-purpose software (e.g., SpectrumSee; Avizo 3D) in transmission electron microscopy (TEM) images, and / or individual particles that can be distinguished after manual identification or manual-assisted calibration. Specifically, in this paper, to identify primary particles, the particles contained in the positive electrode film were enriched and / or dispersed, and then imaged under a TEM. The resulting images can be directly identified using software (based on parameters such as grayscale and / or contrast / brightness), and the individual particles that are distinguished after identification are primary particles. Alternatively, the images can be directly identified manually, and the individual particles that are distinguished after identification are primary particles. Another method is to directly identify the images using a combination of software and manual calibration, and the individual particles that are identified and confirmed to be distinguishable are primary particles. More specifically, particles that form independent, clearly distinguishable boundaries in the TEM field of view can be directly identified as individual particles through software or manual identification. However, some particles, although dispersed, exhibit a certain degree of adhesion and stacking in the TEM field of view. For particles that are stuck together or stacked, those identified as individual particles by software (based on parameters such as grayscale / contrast / brightness) are counted as first-order particles. For more precise analysis, for particles that are stuck together or stacked to some extent under a transmission electron microscope (TEM) field of view, after being identified as individual particles by software based on parameters such as grayscale / contrast / brightness, potentially misidentified particles are manually calibrated according to certain rules. The calibrated, distinguishable individual particles are then counted as first-order particles. If there are inconsistencies in the manual calibration results, 3, 5, or 7 people, unaware of each other's knowledge of the same imaging result, can individually calibrate according to the rules illustrated below. The results are then statistically calculated, and the result obtained in this way is counted as the number of first-order particles. Figure 1 is a schematic diagram of the statistical distinction rules for primary particles in a transmission electron microscope (TEM) image. Figure 1-a is the original TEM image, Figure 1-b is the software-recognized image, and Figure 1-c shows examples of software and / or manual identification of independent, adhered, and stacked particles in Figure 1-a. Particles 1 and 2 are distinguishable independent particles, designated as primary particles 1 and 2, respectively. Particles 3 and 4 in Figure 1-c are adhered; particles 5, 6, and 7 are also adhered, and after software or manual identification, they are determined to be primary particles 3, 4, 5, 6, and 7, respectively. Particles 8 and 9, which are stacked together, are ultimately identified as primary particles 8 and 9, rather than being classified as a single particle. Figure 1-d is another example of software and / or manual identification of the stacked particles in Figure 1-a, where the stacked particles 10-14 are ultimately identified as primary particles 10, 11, 12, 13 and primary particle 14, rather than identifying the entire stack of particles as a single particle.When selecting the field of view for transmission electron microscopy, the field of view in which the number of stacked particles accounts for less than 20% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis. Alternatively, the field of view in which the number of stacked particles accounts for less than 15% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis. Furthermore, the field of view in which the number of stacked particles accounts for less than 10% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis.

[0093] The method for testing the primary average particle size of the first, second, and third lithium-containing transition metal phosphate materials can be performed using methods and equipment known in the art, as exemplified below: 0.05 g of the test material is dissolved in 40 ml of anhydrous ethanol, and then an appropriate amount of dispersant is added. The mixture is stirred until a suspension is obtained. 2 ml of the suspension is mixed with 2 ml of anhydrous ethanol and then subjected to ultrasonic treatment at a power of 480 W for 5 min. A uniformly dispersed suspension is obtained. An appropriate amount of the intermediate suspension is subjected to transmission electron microscopy (TEM). Referring to the aforementioned definition of primary particles, the projection area of ​​each primary particle in the TEM image is calculated, which is the cross-sectional area S of the primary particle. The equivalent circle diameter of the primary particle is obtained using the equivalent circle method, which is the primary particle diameter d. In the above statistical process of primary particles and their primary particle diameters, primary particles with a primary particle diameter less than 50 nm are not included in the statistical range (i.e., primary particles with a primary particle diameter greater than or equal to 50 nm are considered valid particles). The cross-sectional area S and primary particle size d of at least 500 effective particles are tested. The average primary particle size of the material under test is equal to the sum of the primary particle sizes of all primary particles and the total number of primary particles.

[0094] In some embodiments, the primary average particle size of the first lithium-containing transition metal phosphate material may be selected as 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, or any range between any two of the above values.

[0095] In some embodiments, the primary average particle size of the second lithium-containing transition metal phosphate material may be selected as 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, or any range between any two of the above values.

[0096] In some embodiments, the primary average particle size of the third lithium-containing transition metal phosphate material may be selected as 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 800nm, 900nm, 1000nm, 1200nm, 1300nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm, 4000nm, or a range between any two of the above values.

[0097] The term "particle size distribution" refers to the percentage of particles of a certain size or a certain size range in the total number of powder particles.

[0098] The particle size distribution of primary particles with a primary diameter of 50 nm to 180 nm in the second lithium-containing transition metal phosphate material can be tested using any method known in the art. Specifically: referring to the aforementioned method for measuring the average primary particle size of the second lithium-containing transition metal phosphate material, the primary particle size of each primary particle in the sample material is obtained using the aforementioned method for measuring the average primary particle size of the sample material. The number of primary particles with a primary diameter of 50 nm to 180 nm is denoted as M, and the total number of primary particles is N (including particles with a primary diameter greater than or equal to 50 nm). The particle size distribution of primary particles with a primary diameter of 50 nm to 180 nm in the material is M / N × 100%. During testing, 10 statistical regions can be randomly selected for testing, and then the average value is taken.

[0099] In some embodiments, the particle size distribution of primary particles with a primary diameter of 50 nm to 180 nm in the second lithium-containing transition metal phosphate material may be selected as less than or equal to 10%, less than or equal to 9.5%, less than or equal to 9%, less than or equal to 8.5%, less than or equal to 8%, less than or equal to 7%, less than or equal to 6%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, or less than or equal to 1%. Alternatively, the particle size distribution of primary particles with a primary diameter of 50 nm to 180 nm in the second lithium-containing transition metal phosphate material may be selected as 0.1% to 10%, 0.5% to 10%, 1% to 10%, 0.1% to 8%, 0.1% to 6%, 0.1% to 4%, 0.1% to 3%, 0.1% to 2%, 0.1% to 1%, 0.3% to 5%, 0.8% to 3%, or 0.1% to 1.5%.

[0100] Primary particles with a primary diameter greater than or equal to 1200 nm are used to prepare electrodes from lithium-containing transition metal phosphate materials, with a cross-section of 250 μm. 2The number of particles within the region can be tested using any method known in the art. An example is as follows: An electrode is prepared by mixing the test material with polyvinylidene fluoride binder at a mass ratio of 95:5. An argon ion beam is used to cut the electrode perpendicular to its large surface, exposing the entire longitudinal section. The entire longitudinal section is photographed using a scanning electron microscope. Using Avizo3D image processing software, the projection area of ​​each primary particle can be calculated, which is the cross-sectional area S of the primary particle. The equivalent circle diameter of the primary particle is obtained using the equivalent circle method. A particle with an area of ​​250 μm is randomly selected. 2 The number of primary particles with a diameter greater than or equal to 1200 nm within the test area is counted. During the test, 10 test areas can be randomly selected from different areas of the longitudinal section of the electrode for testing, and the average value is taken.

[0101] In some embodiments, primary particles with a primary diameter greater than or equal to 1200 nm are located at 250 μm in the longitudinal section of the electrode prepared from the second lithium-containing transition metal phosphate material. 2 The number of particles in the region is less than or equal to 15, and can be selected as 2-12.

[0102] In some embodiments, primary particles with a primary diameter greater than or equal to 1200 nm are located at 250 μm in the longitudinal section of the electrode prepared from the second lithium-containing transition metal phosphate material. 2 The number of particles in the region can be selected as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a value within a range of any two of the above values.

[0103] On the one hand, the positive electrode active material includes three materials with different average particle sizes, which can achieve the purpose of filling the gaps by matching the size distribution of the materials, making the positive electrode active material more densely packed, increasing the powder compaction density, increasing the electrode compaction density, and thus improving the energy density of the battery. Controlling the small-particle-size first lithium-containing transition phosphate material to be low-manganese or manganese-free can reduce the possibility of manganese dissolution in the highly reactive first lithium-containing transition phosphate material, improving the cycle performance of the battery. Simultaneously, controlling the large-particle-size third lithium-containing transition metal phosphate material to be low-manganese or manganese-free can improve the conductivity of the large-particle-size third lithium-containing transition metal phosphate material, alleviate the discharge polarization of the material, and facilitate the utilization of the specific capacity and kinetic performance, further improving the energy density and rate performance of the battery. On the other hand, controlling the particle size distribution of primary particles with a diameter of 50nm-180nm in the second lithium-containing transition metal phosphate material to within 10% reduces the possibility of manganese dissolution due to side reactions between the small-diameter primary particles and the electrolyte, thereby improving the cycle stability of the material and extending the cycle life of the battery. At the same time, controlling the number of primary particles with a diameter greater than or equal to 1200nm in the second lithium-containing transition metal phosphate material within an appropriate range avoids the impact of excessive large-diameter particles on the conductivity of the material, improves the overall conductivity of the material, and helps the second lithium-containing transition metal phosphate material to exert its specific capacity, so that the high-manganese second lithium-containing transition metal phosphate material can contribute sufficient capacity, thereby improving the energy density of the battery.

[0104] In some embodiments, the primary particles with a primary diameter of 50 nm to 180 nm in the second lithium-containing transition metal phosphate material have a particle size distribution of 3% to 8.5% in the second lithium-containing transition metal phosphate material.

[0105] In some embodiments, the particle size distribution of primary particles with a primary diameter of 50nm-180nm in the second lithium transition metal phosphate material can be selected as 3%, 4%, 5%, 6%, 7%, 8%, 8.5%, or a value within a range of any two of the above values.

[0106] By controlling the number of small-diameter primary particles in the second lithium-containing transition metal phosphate material within a suitable range, the possibility of side reactions between the high-manganese second lithium-containing transition metal phosphate material and the electrolyte is reduced, the possibility of manganese dissolution during cycling is reduced, and the cycle performance of the battery is further improved.

[0107] In some embodiments, primary particles with a primary diameter greater than or equal to 1200 nm are located at 250 μm in the longitudinal section of the electrode prepared from the second lithium-containing transition metal phosphate material. 2The number of particles in the region is 2-12.

[0108] In some embodiments, primary particles with a primary diameter greater than or equal to 1200 nm are located at 250 μm in the longitudinal section of the electrode prepared from the second lithium-containing transition metal phosphate material. 2 The number of particles in the region can be selected as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, or a value within a range of any two of the above values.

[0109] Controlling the number of large-diameter particles in the second lithium-containing transition metal phosphate material within a suitable range reduces the impact of high-manganese large-diameter particles on the material's conductivity, allowing the high-manganese second lithium-containing transition metal phosphate material to achieve its specific capacity, which is beneficial for obtaining high-energy-density batteries.

[0110] In some embodiments, the particle size distribution index of the primary particles with a primary particle size greater than 180 nm and less than 1200 nm in the second lithium-containing transition metal phosphate material is less than or equal to 0.45, and can be selected as 0.3-0.36.

[0111] In some embodiments, the particle size distribution index of the primary particles with a primary particle size greater than 180 nm and less than 1200 nm in the second lithium-containing transition metal phosphate material can be selected as 0.2, 0.25, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, or a value within a range consisting of any two of the above values.

[0112] The particle size distribution index (PDI) has a well-known meaning in the art and can be measured using well-known testing methods and instruments. The PDI is an important parameter for measuring particle size uniformity; the lower the PDI, the smaller the particle size deviation and the higher the particle size uniformity. As an example, the testing method is as follows: referring to the aforementioned method for testing the primary average particle size of the test material, the particle size of each primary particle of the second lithium-containing transition metal phosphate material is measured. Particles with a primary particle size greater than 180 nm and less than 1200 nm are defined as Class I particles. The primary particle size of each Class I particle is then measured.

[0113] In the second lithium-containing transition metal phosphate material, the particle size distribution index (PDI) for primary particles with a diameter greater than 180 nm and less than 1200 nm is the standard deviation of the particle size σ divided by the average particle size.

[0114] Where σ is the standard deviation of particle size, x i The particle size value is for the first type of particles. Let n be the average particle size of the first type of particles, and n be the total number of first type of particles. The average particle size is the total particle size of the first type of particles divided by the total number of first type of particles.

[0115] The second lithium-containing transition metal phosphate material has excellent particle size uniformity, which makes the discharge behavior of each particle tend to be consistent during battery cycling. This reduces the possibility of overcharging and over-discharging during charging and discharging, which helps to ensure the structural stability of the second lithium-containing transition metal phosphate material and the positive electrode active material, and improves the cycle performance of the battery.

[0116] In some embodiments, the (Dv90-Dv10) / Dv50 ratio of the second lithium-containing transition metal phosphate material is 1-3.

[0117] The particle size distribution of a material can be tested using any method known in the art. The volumetric distribution particle sizes Dv10, Dv50, and Dv90 are known in the art, representing the particle sizes corresponding to a cumulative volumetric distribution percentage of 10%, 50%, and 90%, respectively. These sizes can be determined using instruments and methods known in the art. For example, they can be conveniently determined using a laser particle size analyzer, referring to GB / T19077-2016, Particle Size Distribution Laser Diffraction Method. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0118] In some embodiments, the (Dv90-Dv10) / Dv50 of the second lithium-containing transition metal phosphate material can be selected as 2.9, 2.8, 2.6, 2.5, 2.4, 2.3, 2.2, 1.4, 1.5, 1.2, 1, or a value within the range of any two of the above values.

[0119] In some embodiments, the Dv50 of the second lithium-containing transition metal phosphate material is 0.35 micrometers (μm) to 1.5 μm. In some embodiments, the Dv50 of the second lithium-containing transition metal phosphate material may be selected from 0.35 μm, 0.45 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or any value within the range.

[0120] In some embodiments, the Dv10 of the second lithium-containing transition metal phosphate material is 0.1 μm-0.4 μm. In some embodiments, the Dv10 of the second lithium-containing transition metal phosphate material may be selected as 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, or any value within the range.

[0121] In some embodiments, the Dv90 of the second lithium-containing transition metal phosphate material is 2.5 μm-6 μm. In some embodiments, the Dv90 of the second lithium-containing transition metal phosphate material may be selected as 2.5 μm, 3.0 μm, 3.5 μm, 4 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, or any value within the range.

[0122] The second lithium-containing transition metal phosphate material has Dv90, Dv10, and Dv50 within a suitable range. The material has excellent particle size parameters, high specific capacity, and excellent cycle stability, providing a material basis for the preparation of batteries with high energy density and long cycle life.

[0123] In some embodiments, the molar percentage of Mn in the first lithium-containing transition metal phosphate material is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

[0124] In some embodiments, the molar ratio of Mn in the first lithium-containing transition metal phosphate material can be selected as 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or any range between any two of the above values.

[0125] Controlling the molar percentage of Mn in the first lithium-containing transition metal phosphate material within a suitable range can further reduce the side reactions between small-particle materials and the electrolyte, as well as the degree of manganese dissolution, thereby further improving the battery's cycle performance and storage performance. This makes the battery more suitable for applications with high requirements for cycle life and / or storage life.

[0126] In some embodiments, the molar ratio of Mn in the first lithium-containing transition metal phosphate material is 0.02-0.6, optionally 0.02-0.4, more preferably 0.02-0.2, and even more preferably 0.02.

[0127] In some embodiments, the molar percentage of Mn in the first lithium-containing transition metal phosphate material is 0.2-0.6, optionally 0.2-0.4, and more preferably 0.2.

[0128] In some embodiments, the molar ratio of Mn in the first lithium-containing transition metal phosphate material can be selected as 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or any range between any two of the above values.

[0129] By controlling the average molar ratio of Mn in small-particle-size materials within a suitable range, the cycle stability of small-particle-size materials can be improved, while also allowing the highly conductive small-particle-size materials to fully utilize their specific capacity. This results in excellent cycle performance of the battery and further increases its energy density, making the battery more suitable for scenarios with high energy density requirements.

[0130] In some embodiments, the molar percentage of Mn in the second lithium-containing transition metal phosphate material is 0.4-0.9, and optionally 0.5-0.9.

[0131] In some embodiments, the molar ratio of Mn in the second lithium-containing transition metal phosphate material can be selected as 0.4, 0.45, 0.50, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or any range between any two of the above values.

[0132] By controlling the average Mn molar ratio of the second lithium-containing transition metal phosphate material within a suitable range, the second lithium-containing transition metal phosphate material can have a high plateau capacity, while also ensuring that the second lithium-containing transition metal phosphate material has a certain conductivity. This is conducive to the second lithium-containing transition metal phosphate material exerting its specific capacity, so as to achieve the goal of the second lithium-containing transition metal phosphate material contributing sufficient capacity, thereby improving the energy density of the battery.

[0133] In some embodiments, the molar percentage of Mn in the third lithium-containing transition metal phosphate material is 0-0.6, optionally 0-0.5, more preferably 0-0.1, and even more preferably 0.

[0134] In some embodiments, the molar ratio of Mn in the third lithium-containing transition metal phosphate material can be selected as 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or a range between any two of the above values.

[0135] Controlling the molar ratio of Mn in the third lithium-containing transition metal phosphate material within a suitable range can improve the cycle stability and conductivity of the third lithium-containing transition metal phosphate material, which is conducive to further exerting its specific capacity and improving the energy density and cycle life of the battery.

[0136] In some embodiments, the molar ratio of Mn in the third lithium-containing transition metal phosphate material is 0.02-0.6, optionally 0.02-0.5, and more preferably 0.02.

[0137] In some embodiments, the molar percentage of Mn in the third lithium-containing transition metal phosphate material is 0.2-0.6, optionally 0.2-0.5, and more preferably 0.2.

[0138] In some embodiments, the molar ratio of Mn in the third lithium-containing transition metal phosphate material can be selected as 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or a range between any two of the above values.

[0139] By controlling the molar ratio of Mn in the third lithium-containing transition metal phosphate material within a suitable range, the conductivity of the third lithium-containing transition metal phosphate material is improved, and the third lithium-containing transition metal phosphate material also has a certain plateau capacity, thereby further improving the energy density of the battery.

[0140] In some embodiments, the weight percentage of the first lithium-containing transition metal phosphate material is 1%-10% based on the total weight of the lithium-containing transition metal phosphate material.

[0141] In some embodiments, based on the total weight of the lithium transition metal phosphate material, the weight percentage of the first lithium transition metal phosphate material can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of the above values.

[0142] In some embodiments, the weight percentage of the second lithium-containing transition metal phosphate material is 60%-90% based on the total weight of the lithium-containing transition metal phosphate material.

[0143] In some embodiments, based on the total weight of the lithium transition metal phosphate material, the weight percentage of the second lithium transition metal phosphate material can be selected as 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any range between any two of the above values.

[0144] In some embodiments, the third lithium-containing transition metal phosphate material accounts for 5%-30% of the total weight of the lithium-containing transition metal phosphate material.

[0145] In some embodiments, the weight percentage of the third lithium-containing transition metal phosphate material may be selected as 5%, 10%, 15%, 20%, 25%, 30%, or any range between any two of the above values, based on the total weight of the lithium-containing transition metal phosphate material.

[0146] Controlling the mass ratio of materials with different particle sizes within a suitable range is beneficial for achieving the goal of increasing the contribution of the high-manganese content second lithium-containing transition metal phosphate material to the voltage and specific capacity of the energy density. At the same time, it can reduce the impact of the large-particle-size third lithium-containing transition metal phosphate material on the specific capacity and rate performance of the battery, and reduce the impact of the small-particle-size first lithium-containing transition metal phosphate material on the cycle performance of the battery. In addition, keeping the mass ratio of the three materials within a suitable range also ensures that the molar ratio of Mn in the positive electrode active material is within a suitable range, which is beneficial for obtaining a battery with high energy density, excellent rate performance and cycle performance.

[0147] This application also provides a method for preparing a second lithium-containing transition metal phosphate material:

[0148] Compacting granulation: Compacting and granulating raw materials including lithium source, iron source, manganese source, phosphorus source, carbon source and molding aid to obtain compacted granules. Optionally, the raw materials may also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0149] Sintering: Filling and compacting the particles, and sintering the compacted particles to obtain a primary product;

[0150] Crushing: The primary product is crushed to obtain the second lithium-containing transition metal phosphate material.

[0151] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate, lithium oxide, lithium chloride, lithium nitrate, and lithium sulfate. Optionally, the lithium source includes lithium carbonate.

[0152] In some embodiments, the iron source includes at least one of ferric phosphate, ferrous hydroxide, ferrous nitrate, ferrous phosphate, ferrous pyrophosphate, ferrous carbonate, ferrous chloride, ferrous oxalate, ferric chloride, ferric hydroxide, ferric nitrate, ferric citrate, and ferric oxide. Optionally, the iron source includes ferric oxide.

[0153] In some embodiments, the manganese source includes at least one of manganese dioxide, manganese trioxide, manganese tetroxide, manganese oxalate, manganese acetate, or manganese nitrate.

[0154] In some embodiments, the phosphorus source includes at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, iron phosphate, lithium dihydrogen phosphate, and lithium phosphate. Optionally, the phosphorus source includes ammonium dihydrogen phosphate.

[0155] In some embodiments, the carbon source includes at least one of sucrose, glucose, citric acid, fructose, lactose, porous graphene, activated carbon, activated carbon fiber, mesoporous carbon, carbon nanotubes, carbon molecular sieves, pitch, and polyethylene glycol; optionally, the carbon source includes sucrose.

[0156] In some embodiments, the A2 source is selected from at least one of oxides, hydroxides, oxalates, acetates, chlorides, nitrates, or phosphates containing elements Al, Na, K, and Mg.

[0157] In some embodiments, the M2 source is selected from at least one of oxides, hydroxides, oxalates, acetates, chlorides, nitrates, or phosphates of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti. Optionally, the M2 source includes one or more of titanium dioxide, vanadium pentoxide, and niobium pentoxide.

[0158] In some embodiments, the Q2 source includes one or more of the following: silicic acid, metasilicic acid, silicon tetrachloride, silicon dioxide, tetraethyl orthosilicate, elemental boron, boric acid, boron trioxide, boron nitride, trimethyl borate, sodium tetraphenylborate, boron trichloride, ethylenediamine, melamine, benzylamine, acetonitrile, ammoniated sucrose, pyrrole, aniline, acrylonitrile, polyimide acid, nitrogen-containing aliphatic heterocyclic compounds, sulfur powder, sulfuric acid, sulfurous acid, ammonium sulfate, thiophene, thiazole, thiourea, dimethyl sulfoxide, thioacetamide, and thiols.

[0159] In some embodiments, the N2 source includes any one or more of the group consisting of sulfur powder, sulfuric acid, sulfurous acid, ammonium sulfate, thiophene, thiazole, thiourea, dimethyl sulfoxide, thioacetamide, thiol, hydrofluoric acid, ammonium fluoride, and fluorinated organic compounds, wherein the fluorinated organic compounds are selected from one or more of fluorinated alkanes, fluorinated alkenes, fluorinated aromatics, and fluorinated carboxylic acids.

[0160] The molding aid is selected from polymers that can be dissolved or dispersed in water or alcohol. In some embodiments, the molding aid includes at least one of polypropylene ester, starch, phenolic resin, polyurethane, melamine resin, polyethylene, stearic acid, PVC, polyacrylonitrile, natural rubber, styrene-butadiene rubber, and cis-butadiene rubber. Optionally, the molding aid includes starch.

[0161] In some embodiments, the grinding process involves raw materials including lithium, iron, manganese, phosphorus, carbon, and molding aids; optionally, the raw materials are ground to a Dv50 of 0.3-1.5 μm, 0.3-1.0 μm, 0.3-0.8 μm, 0.35-0.6 μm, or 0.35-0.9 μm. Grinding equipment, such as ball mills, sand mills, or mechanical mills, can be used to grind the raw materials.

[0162] In some embodiments, water, an alcohol solvent, or a homogeneous and stable mixture of both can be added, mixed evenly with the raw materials, and then ground. The alcohol solvent includes, but is not limited to, methanol, ethanol, and ethylene glycol, and can be one or more different alcohol solvents mixed together.

[0163] In some embodiments, the molding aids in the raw materials can be dissolved or dispersed in water, alcohol solvents, or a homogeneous and stable mixture of both, and mixed with other components in the raw materials upon the addition of the solvent or solution.

[0164] In some embodiments, the ground raw material is dried; alternatively, the ground raw material is spray-dried. In some embodiments, the microsphere particle size Dv50 formed by spray drying is 5-50 μm, optionally 5-40 μm, 8-30 μm, 10-25 μm, or 10-20 μm.

[0165] In some implementations, the spray-dried raw materials are compacted and granulated.

[0166] In some embodiments, the raw materials are compacted and granulated to obtain compacted particles with an average particle size of 3mm-30mm, optionally 5mm-25mm, 5mm-20mm, 5mm-15mm, 10mm-15mm, 10mm-20mm, or 10mm-25mm. The average particle size can also be selected from any value among 7.5mm, 12.5mm, 17.5mm, 22.5mm, and 27.5mm, or a range between any two values.

[0167] In some embodiments, the compacted granules obtained by compaction granulation have a compaction density of 1.0 g / cm³. 3 Above 1.2-3.0 g / cm³, optional. 3 In some embodiments, the compaction density of the compacted particles may be selected as 1.0 g / cm³. 3 1.2g / cm 3 1.4g / cm 3 1.6g / cm 3 1.8g / cm 3 2.0g / cm 3 2.2g / cm 3 2.4g / cm 3 2.6g / cm 3 2.8g / cm 3 3.0g / cm 3 Any value in the range, or the range between any two values.

[0168] In some embodiments, the preparation method includes: filling compacted granules to a filling height of 5 cm-30 cm, and sintering the compacted granules to obtain a primary product. Optionally, the filling height is 8 cm-30 cm, 8 cm-20 cm, 5 cm-25 cm, 5 cm-20 cm, 10 cm-30 cm, 10 cm-25 cm, or 10 cm-20 cm.

[0169] In some embodiments, the particles are sintered and compacted in an inert gas atmosphere, wherein the inert gas may include one or more of nitrogen, carbon dioxide, and helium, and optionally, the inert gas is selected from nitrogen.

[0170] In some embodiments, the compacted particles are sintered and compacted within a sintering temperature range of 600°C to 800°C. Optionally, the sintering temperature is selected from 650°C to 800°C, 680°C to 800°C, 700°C to 800°C, 600°C to 780°C, 600°C to 750°C, 620°C to 800°C, or 640°C to 720°C.

[0171] In some embodiments, the compacted particles are sintered and compacted in the sintering temperature range of 600°C-800°C for 2-12 hours. Optionally, the particles are sintered at the sintering temperature for 2-10 hours, 4-12 hours, 2-10 hours, 4-8 hours, 6-12 hours, 6-10 hours, or 6-8 hours.

[0172] In some embodiments, during the sintering process, the heating rate is controlled to reach the sintering temperature at a rate of 1°C-5°C / min. Optionally, the heating rate is selected from 2°C-5°C / min, 3°C-5°C / min, 2°C-4°C / min, or 2°C-3°C / min; or, the heating rate is selected from 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, or any range between two of the aforementioned values.

[0173] In some embodiments, the preparation method includes: pulverizing the primary product obtained after sintering to achieve a Dv50 of 0.35 μm-1.5 μm. Optionally, the Dv50 is selected from 0.5-1.5 μm, 0.8-1.5 μm, 0.7-1.5 μm, 1-1.5 μm, 0.45-1.3 μm, 0.45-1.0 μm, 0.5-1.0 μm, 0.6-1.5 μm, or 0.7-1.5 μm.

[0174] In some embodiments, the preparation method includes: pulverizing the primary product to satisfy the following particle size distribution: (Dv90-Dv10) / Dv50 is 1-3, optionally less than or equal to 2.9, 2.8, 2.6, 2.5, 2.4, 2.3, 2.2, 2, 1.8, 1.4, 1.2, or 1. Optionally, pulverizing the primary product to satisfy the following particle size distribution: 1≤(Dv90-Dv10) / Dv50≤3.

[0175] In some embodiments, the preparation method does not include multiple compaction granulation.

[0176] In some embodiments, the preparation method of the second lithium-containing transition metal phosphate material includes:

[0177] Raw materials including lithium source, iron source, manganese source, phosphorus source, carbon source and molding aid are mixed with water, alcohol or mixed solvent, ground, dried and compacted to obtain compacted granules. Optionally, the raw materials also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0178] The compacted granules are filled, sintered, and crushed to obtain a second lithium transition metal phosphate material.

[0179] In some embodiments, the preparation method of the second lithium-containing transition metal phosphate material includes:

[0180] Raw materials including lithium, iron, manganese, phosphorus, carbon and molding aids are mixed with water, alcohol or mixed solvent, ground, dried and compacted to obtain compacted granules with an average particle size control range of 3mm-30mm; optionally, the raw materials also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0181] The compacted granules are filled to a filling height of 5cm-30cm, with a porosity of 5%-20%, and then sintered.

[0182] The primary product obtained by pulverization and sintering has a Dv50 of 0.35μm-1.5μm and / or 1≤(Dv90-Dv10) / Dv50≤3, thus obtaining the second lithium-containing transition metal phosphate material.

[0183] In some embodiments, the preparation method of the second lithium-containing transition metal phosphate material includes:

[0184] Compacting and granulation: The raw materials, including lithium source, iron source, manganese source, phosphorus source, carbon source, molding aid and solvent, are ground to obtain a slurry; the slurry is dried and then compacted and granulated to obtain compacted granules. Optionally, the raw materials also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0185] Sintering: Filling and compacting the particles, and sintering the compacted particles to obtain a primary product;

[0186] Crushing: The primary product is crushed to obtain a second lithium-containing transition metal phosphate material.

[0187] In some embodiments, the preparation method of the second lithium-containing transition metal phosphate material includes:

[0188] Raw materials including lithium source, iron source, manganese source, phosphorus source, carbon source and molding aid are mixed with water, alcohol or mixed solvent, ground, dried and compacted to obtain compacted granules; the compacted granules are filled, sintered and crushed to obtain positive electrode active material. Optionally, the raw materials also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0189] The molding aids include at least one of polypropylene ester, starch, phenolic resin, polyurethane, melamine resin, polyethylene, stearic acid, PVC, polyacrylonitrile, natural rubber, styrene-butadiene rubber, and cis-butadiene rubber.

[0190] In some embodiments, the compaction and granulation step specifically includes:

[0191] (1-1) The initial reactants containing lithium source, iron source, manganese source, phosphorus source and carbon source are mixed evenly and then subjected to pre-sintering treatment to obtain the initial product. Optionally, the initial reactants also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0192] (1-2) The intermediate reactants containing the initial product, carbon source and molding aid are mixed and ground to obtain the intermediate product;

[0193] (2) Compact and granulate the intermediate product to obtain compacted granules.

[0194] The carbon source in step (1-1) has a mass content of 2%-5%, based on the total mass of the initial reactants.

[0195] In some embodiments, the preparation method of the second lithium-containing transition metal phosphate material includes:

[0196] (1-1) The initial reactants containing lithium source, iron source, manganese source, phosphorus source and carbon source are mixed evenly and then subjected to pre-sintering treatment to obtain the initial product. Optionally, the initial reactants also include one or more of A2 source, M2 source, Q2 source and N2 source.

[0197] (1-2) The intermediate reactants containing the initial product, carbon source and molding aid are mixed and ground to obtain the intermediate product;

[0198] (2) Compact and granulate the intermediate product to obtain compacted granules;

[0199] (3) The compacted granules are filled, sintered, and crushed to obtain a second lithium-containing transition metal phosphate material.

[0200] In step (1-1), the carbon source has a mass content of 2%-5%, based on the total mass of the initial reactants.

[0201] The molding aids include at least one of polypropylene ester, starch, phenolic resin, polyurethane, melamine resin, polyethylene, stearic acid, PVC, polyacrylonitrile, natural rubber, styrene-butadiene rubber, and cis-butadiene rubber.

[0202] In some embodiments, the intermediate product has a Dv50 of 0.45 μm to 1.25 μm and a DV10 of ≥0.15 μm.

[0203] In some implementations, the Dv50 of the intermediate product can be selected as any value among 0.45μm, 0.55μm, 0.65μm, 0.75μm, 0.85μm, 0.95μm, 1.05μm, 1.15μm, and 1.25μm, or a range between any two values.

[0204] In some implementations, the D of the intermediate product V 10 can be any one of the following: greater than or equal to 0.15 μm, greater than or equal to 0.16 μm, greater than or equal to 0.17 μm, greater than or equal to 0.18 μm, greater than or equal to 0.19 μm, or greater than or equal to 0.20 μm.

[0205] In some embodiments, the first lithium-containing transition metal phosphate material includes a first core and a first carbon coating layer covering the outer surface of the first core; the second lithium-containing transition metal phosphate material includes a second core and a second carbon coating layer covering the outer surface of the second core; and the positive electrode active material further includes a third lithium-containing transition metal phosphate material, which includes a third core and a third carbon coating layer covering the outer surface of the third core.

[0206] The general formula for the first kernel includes Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 ,

[0207] Where 0.8≤m1≤1.2, x1≥0, y1≥0, 0.9≤x1+y1≤1, 0.95≤z1≤1.1, 3.5≤n1≤4, 0≤a1≤0.1, 0≤b1≤0.1, 0≤c1≤0.1, 0≤d1≤0.1,

[0208] The general formula for the composition of the second kernel includes Li m2 A2 a2 Fe x2 Mn y2 M2 b2 P z2 Q2 c2 O n2 N2 d2 ,

[0209] 0.8≤m2≤1.2, x2≥0, y2>0, 0.9≤x2+y2≤1, 0.95≤z2≤1.1, 3.5≤n2≤4, 0≤a2≤0.1, 0≤b2≤0.1, 0≤c2≤0.1, 0≤d2≤0.1,

[0210] The general formula for the composition of the third kernel includes Li m3 A3 a3 Fe x3 Mn y3 M3 b3 Pz3 Q3 c3 O n3 N3 d3 ,

[0211] 0.8≤m³≤1.2, x³≥0, y³≥0, 0.9≤x³+y³≤1, 0.95≤z³≤1.1, 3.5≤n³≤4, 0≤a³≤0.1, 0≤b³≤0.1, 0≤c³≤0.1, 0≤d³≤0.1

[0212] Among them, A1, A2, and A3 each independently include one or more of Al, Na, K, and Mg; M1, M2, and M3 each independently include one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti; Q1, Q2, and Q3 each independently include one or more of B, S, Si, and N; and N1, N2, and N3 each independently include one or more of S, F, Cl, and Br.

[0213] Among them, A1, A2, and A3 each independently include one or more of Al, Na, K, and Mg; M1, M2, and M3 each independently include one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti; Q1, Q2, and Q3 each independently include one or more of B, S, Si, and N; and N1, N1, and N3 each independently include one or more of S, F, Cl, and Br.

[0214] In some implementations, m1, m2 and m3 can each independently be 0.8, 0.85, 0.9, 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15, 1.17, 1.2, or a value within a range of any two of the above values.

[0215] In some implementations, x1+y1, x2+y2, and x3+y3 can each independently be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or a value within a range consisting of any two of the above values.

[0216] In some implementations, z1, z2, or z3 can each independently be 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, or a value within a range of any two of the above values.

[0217] In some implementations, n1, n2, and n3 can each independently be 3.5, 3.6, 3.7, 3.8, 3.9, 4, or a value within a range consisting of any two of the above values.

[0218] In some implementations, a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, and d3 can each independently be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or a value within a range of any two of the above values.

[0219] Selecting doping elements M1, M2, and M3 can improve the lattice change rate of the material during lithium insertion / extraction, enhance the structural stability of the material, reduce manganese dissolution, and decrease oxygen activity on the particle surface. This can improve the specific capacity of the material and reduce interfacial side reactions between the material and the electrolyte during use, thereby improving the cycle performance of the material and the cycle performance of the battery.

[0220] Selecting doping elements Q1, Q2, and Q3 can help change the ease with which the Mn-O bond length changes, thereby improving electronic conductivity and reducing the lithium-ion migration barrier, promoting lithium-ion migration, and improving the rate performance of secondary batteries.

[0221] Appropriate elemental doping with Al, A2, and A3 can also improve the lattice change rate of the material and maintain its battery capacity.

[0222] Doping with elements N1, N2, and N3 can help improve interfacial side reactions between the material and the electrolyte, reduce interfacial activity, and thus improve the cycle performance of the positive electrode active material. Furthermore, it can enhance the material's resistance to acid corrosion such as HF, thereby improving cycle performance and lifespan, and extending battery life.

[0223] In some embodiments, the specific capacity of the positive electrode active material at 40°C and a 1 / 3C discharge rate is 135 mAh / g to 150 mAh / g. In some embodiments, the specific capacity of the positive electrode active material at 40°C and a 1 / 3C discharge rate can be selected as 135 mAh / g, 140 mAh / g, 145 mAh / g, 150 mAh / g, or any range between two of the above values.

[0224] The specific capacity of the positive electrode active material at 40°C and a discharge rate of 1 / 3C can be determined using methods and equipment known in the art, as exemplified below: The battery is placed in a 40°C oven and left to stand for 2 hours to maintain the battery temperature at 40°C; then, the battery is discharged at a constant current of 1 / 3C to 2.0V; left to stand for 5 minutes; the battery is then charged at a constant current of 1 / 3C to 4.1V, followed by constant voltage charging at 4.1V until the cutoff current is 0.05C; left to stand for 5 minutes; and finally, the battery is discharged at a constant current of 1 / 3C to 2.0V to obtain the discharge capacity C of the battery. The specific capacity of the positive electrode active material = the discharge capacity C of the battery / the mass M of the positive electrode active material.

[0225] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0226] In one embodiment of this application, a secondary battery is provided.

[0227] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0228] [Preparation of positive electrode sheet]

[0229] A positive electrode slurry containing the positive electrode active material is coated on at least one surface of the positive electrode current collector to obtain a positive electrode sheet.

[0230] In some embodiments, the positive electrode slurry further includes a binder and a conductive agent.

[0231] In some embodiments, the mass ratio of positive electrode active material, binder and conductive agent in the positive electrode slurry is (92-99):(0.5-3):(0.5-3).

[0232] In some embodiments, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0233] In some embodiments, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0234] In some embodiments, the positive current collector may be 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0235] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0236] [Positive electrode plate]

[0237] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0238] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0239] In some embodiments, the areal density of the positive electrode sheet is 300 mg / 1540 mm². 2 )-580mg / 1540mm 2 .

[0240] In some embodiments, the areal density of the positive electrode film is 300 mg / 1540 mm². 2 340mg / 1540mm 2 380mg / 1540mm 2 420mg / 1540mm 2 460mg / 1540mm 2 500mg / 1540mm 2 540mg / 1540mm 2 580mg / 1540mm 2 , or the range between any two of the above values.

[0241] The areal density of the positive electrode sheet can be tested using methods known in the art. An example is shown below: the positive electrode sheet is cut into pieces with an area of ​​1540 mm².2 The small circular sheet is weighed as M. Then, the positive electrode film layer of the weighed electrode sheet is wiped off, and the weight of the current collector is weighed and recorded as N. Then, the weight of the single-sided coating is (MN) / 2.

[0242] In some embodiments, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0243] The "compacted density of the positive electrode sheet" mentioned in this application refers to the "limited compacted density" of the positive electrode sheet, and its test method is as follows:

[0244] The double-coated electrode sheets were cold-pressed using a roller press, and the elongation of the cold-pressed electrode sheets was tested. At the same time, the flexibility of the cold-pressed electrode sheets was evaluated.

[0245] By increasing the pressure of the roller press, electrodes with different compaction densities can be obtained. As the pressure increases, the compaction density of the electrode increases, the elongation of the electrode increases, and the flexibility of the electrode decreases. Excessive elongation of the electrode can easily lead to warping, while insufficient flexibility can easily lead to brittle fracture. Therefore, the lower of the compaction density corresponding to an electrode elongation of 6‰ or an electrode flexibility folding number of 3 times is defined as the limiting compaction density.

[0246] The compaction density of the positive electrode sheet is calculated as the weight of a single positive electrode sheet divided by the volume of a single positive electrode sheet.

[0247] In some embodiments, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 2.35g / cm 3 2.45g / cm 3 2.55g / cm 3 2.65g / cm 3 2.75g / cm 3 Or any value in between.

[0248] When the compaction density of the positive electrode sheet is within a suitable range, the battery has a superior volumetric energy density.

[0249] [Negative electrode plate]

[0250] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0251] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0252] In some embodiments, the negative electrode current collector may be 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0253] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0254] In some embodiments, the negative electrode film layer may optionally include a binder. The binder 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).

[0255] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0256] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0257] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0258] [Electrolytes]

[0259] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0260] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0261] 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0262] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl 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.

[0263] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0264] [Isolation membrane]

[0265] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0266] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0267] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0268] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0269] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0270] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 shows a square-structured secondary battery 5 as an example.

[0271] In some embodiments, referring to FIG3, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0272] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0273] Figure 4 shows a battery module 4 as an example. Referring to Figure 4, in the battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can be fixed in place using fasteners.

[0274] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0275] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0276] Figures 5 and 6 show a battery pack 1 as an example. Referring to Figures 5 and 6, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0277] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical 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.

[0278] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0279] Figure 7 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0280] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0281] Example

[0282] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0283] The performance parameters and sources of the first lithium-containing transition metal phosphate material are shown in Table 1.

[0284] Table 1

[0285] The performance parameters and sources of the third lithium-containing transition metal phosphate material are shown in Table 2.

[0286] Table 2

[0287] The specific preparation method of the second lithium-containing transition metal phosphate material is as follows.

[0288] Preparation of the second lithium-containing transition metal phosphate material B1:

[0289] Lithium carbonate, ferric oxide, ammonium dihydrogen phosphate, and manganese tetroxide were weighed separately, with a molar ratio of Li:Fe:Mn:P of 1.01:0.4:0.6:1.02. Water was added and mixed thoroughly to obtain a slurry. Sucrose (8% by mass of all solid raw materials) and starch (1% by mass of all solid raw materials) were then added. The solid content of the slurry was 40%.

[0290] The slurry was ball-milled to a uniform consistency with a Dv50 of approximately 0.4 μm, and then spray-dried (using a high-speed spray dryer with a negative pressure of -650 to -200 Pa, an inlet temperature of 300℃ to 360℃, and an outlet temperature of 100℃ to 140℃). The spray-dried powder was then compacted and granulated using a granulator, resulting in an average particle size of approximately 10 mm and a compacted density of 1.2 g / cm³. 3 The granulated reactants were loaded into graphite crucibles to a depth of 12 cm. The crucibles were then placed in a kiln for sintering, with a heating rate controlled at 3 °C / min and a holding temperature of 720 °C for 10 hours. After cooling, the material was pulverized using an air jet mill or mechanical mill to a Dv50 of approximately 1.1 μm, yielding the second lithium transition metal phosphate material, B1.

[0291] Preparation of the second lithium-containing transition metal phosphate material B2:

[0292] (1) Weigh out lithium carbonate, ferric oxide, ammonium dihydrogen phosphate, and manganese tetroxide separately, so that the molar ratio of Li:Fe:Mn:P is 1.01:0.40:0.6:1.02. Add water and mix well to obtain a slurry. Add 2.5% by mass of sucrose from all solid raw materials. The solid content of the slurry is 40%. Grind the uniformly mixed slurry in a ball mill to a Dv50 of about 0.4 μm, and spray dry (the negative pressure of the high-speed spray dryer is -320 Pa, the inlet temperature is 320℃, and the outlet temperature is 110℃). Pack the dried material into a sagger and sinter it in a kiln. The heating rate is controlled at 5℃ / min, the holding temperature is controlled at 660℃, and the holding time is 6 hours.

[0293] (2) After cooling, the material is mechanically ground. The ground material, sucrose, and starch are mixed with water to obtain a slurry, wherein the mass fraction of sucrose is 5.5% and the mass fraction of starch is 1% based on the total mass of solid matter in the slurry. The slurry obtained above is ground using a ball mill until the Dv50 of the slurry (i.e., the intermediate product in Table 3) is 0.4 μm and the Dv10 is 0.12 μm. Then, it is spray-dried (the negative pressure of the high-speed spray dryer is -320 Pa, the inlet temperature is 320 °C, and the outlet temperature is 110 °C).

[0294] (3) The dried powder was compacted and granulated, with an average particle size of approximately 10 mm and a compacted density of 1.2 g / cm³. 3 .

[0295] Sintering: The granulated reactants are loaded into graphite saggers to a depth of 12 cm. The saggers filled with reactants are then placed in a kiln for sintering. The heating rate is controlled at 3℃ / min, the holding temperature is controlled at 720℃, and the holding time is 10 hours.

[0296] Crushing: After the material is cooled, it is pulverized by air jet mill or mechanical mill until Dv50 is 1μm to obtain the second lithium transition metal phosphate material B2.

[0297] The preparation method of the second lithium-containing transition metal phosphate material B3 is similar to that of the second lithium-containing transition metal phosphate material B3, but the types of raw materials are adjusted. Specifically, lithium carbonate, ferric oxide, ammonium dihydrogen phosphate, manganese tetroxide and titanium dioxide are weighed separately, so that the molar ratio of Li:Fe:Mn:Ti:P elements is 1.01:0.4:0.59:0.005:1.02, and the Dv10 of the intermediate product is 0.13 μm. The sintering temperature in the sintering step is adjusted to 660℃.

[0298] The preparation methods for the second lithium-containing transition metal phosphate materials B4-B7 are similar to those for the second lithium-containing transition metal phosphate material B3, the difference being that the Dv50 and Dv10 of the intermediate products or the sintering temperature in the sintering step are adjusted. Specific parameters are shown in Table 3.

[0299] Table 3

[0300] The performance parameters of the second lithium-containing transition metal phosphate material are shown in Table 4.

[0301] Table 4

[0302] Example 1

[0303] (1) Preparation of the positive electrode sheet:

[0304] The first lithium-containing transition metal phosphate material A1, the second lithium-containing transition metal phosphate material B1, and the third lithium-containing transition metal phosphate material C1 are mixed in a mass ratio of 5%:65%:30% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive agent conductive carbon black, and binder polyvinylidene fluoride are mixed in a weight percentage of 96:1.5:2.5:0.5 and N-methylpyrrolidone is added. After thorough mixing, stirring, and dispersion, a positive electrode slurry is prepared.

[0305] Adjust the viscosity of the thoroughly mixed slurry to 8000-20000 mPa·s until it no longer separates. Then, use a double-sided, double-control coating machine to apply the slurry at a rate of 420 mg / 1540 mm. 2 The coating is applied to the surface of the substrate aluminum foil, and then dried, cold-pressed, slit, and sheeted to finally obtain the positive electrode sheet.

[0306] (2) Preparation of negative electrode sheet:

[0307] Artificial graphite, conductive carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed evenly in a weight percentage ratio of 95:1.0:2.0:2.0, and deionized water was added. After stirring and dispersing, a negative electrode slurry was obtained. The negative electrode slurry was then mixed at a concentration of 211 mg / 1540 mm. 2 The negative electrode sheet is obtained by coating the substrate Cu foil, drying, cold pressing, slitting, and sheet forming.

[0308] (3) Diaphragm

[0309] Polypropylene film is used as the separator.

[0310] (4) Electrolyte

[0311] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and fluoroethylene carbonate (FEC) were mixed evenly in a volume ratio of 1:1:1:1. LiPF6 was then added and dissolved in the organic solvent and stirred evenly to achieve an electrolyte concentration of 1 mol / L, thus obtaining the electrolyte of Example 1.

[0312] (5) Battery fabrication:

[0313] The positive electrode, separator, and negative electrode are stacked in sequence. The separator must be able to isolate the anode and cathode. The bare cell is obtained by winding. The bare cell is placed in the outer packaging, electrolyte is injected, and after processes such as encapsulation, formation, and degassing, a lithium-ion battery is finally obtained.

[0314] Examples 2-11 and Comparative Examples 1-2 are prepared in a similar manner to Example 1, except that the types or mass contents of the first lithium-containing transition metal phosphate material, the second lithium-containing transition metal phosphate material and / or the third lithium-containing transition metal phosphate material in the positive electrode active material are adjusted, as shown in Table 5.

[0315] II. Battery Performance Testing

[0316] 1. Number of high-temperature cycles of the battery

[0317] Place the battery in a 60℃ oven and let it stand for 2 hours until the battery temperature reaches 60℃. Then, discharge the battery at a constant current of 1 / 3C to 2.0V. After standing for 5 minutes, charge the battery at a constant current of 1C to 4.1V, then charge it at a constant voltage of 4.1V to a current of 0.05C. After standing for 2 minutes, discharge the battery at a constant current of 1C to 2.0V. This completes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. Perform multiple charge-discharge cycles on the battery using the above method until the discharge capacity of the secondary battery decreases to 80%, and record the number of cycles.

[0318] 2. Volumetric energy density of the battery

[0319] Battery cell capacity test: The battery cell was left to stand at 40℃ for 2 hours to ensure the temperature of the battery cell was 40℃. Then the battery was discharged at a constant current of 1 / 3C to 2.0V. After standing for 5 minutes, the battery cell was charged at a constant current of 1 / 3C to 4.1V. The constant voltage charging at 4.1V continued until the current was 0.05C. After standing for 5 minutes, the battery cell was discharged at a constant current of 1 / 3 to 2.0V. The total discharge capacity C0 and the total discharge energy E0 of the battery cell were recorded. The unit of total discharge energy is Wh.

[0320] Battery cell volume measurement: Use calipers to measure the length, width, and height of the battery's outer surface, and calculate the cell volume V0 in liters (L).

[0321] Volumetric energy density calculation: The volumetric energy density of a battery cell is calculated as follows: Discharge energy of a single battery cell E0 / Battery volume V0.

[0322] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0323] The positive electrode active materials and secondary batteries of each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured.

[0324] Table 5

[0325] Based on the above results, the preparation method of the secondary battery in Examples 1-11 of this application, specifically the preparation method of the positive electrode active material, is as follows: A first lithium-containing transition metal phosphate material, a second lithium-containing transition metal phosphate material, and a third lithium-containing transition metal phosphate material are mixed to obtain the positive electrode active material. The primary average particle size of the first lithium-containing transition metal phosphate material is smaller than that of the second lithium-containing transition metal phosphate material, and the primary average particle size of the third lithium-containing transition metal phosphate material is larger than that of the second lithium-containing transition metal phosphate material. The molar percentage of Mn in the first lithium-containing transition metal phosphate material is smaller than that in the second lithium-containing transition metal phosphate material. The molar percentage of Mn in the first lithium-ion transition metal phosphate material is less than that in the second lithium-ion transition metal phosphate material. The average primary particle size of the first lithium-ion transition metal phosphate material is 50 nm-200 nm, that of the second lithium-ion transition metal phosphate material is 120 nm-600 nm, and that of the third lithium-ion transition metal phosphate material is 250 nm-4000 nm. In the second lithium-ion transition metal phosphate material, primary particles with a primary particle size of 50 nm-180 nm account for less than or equal to 10% of the total particle size distribution. Primary particles with a primary particle size greater than or equal to 1200 nm constitute 250 μm of the longitudinal section of the electrode prepared from the second lithium-ion transition metal phosphate material. 2 The number of particles in the area is less than or equal to 15.

[0326] As can be seen from the comparison between Examples 1-11 and Comparative Example 1, compared with the positive electrode active material containing only a single second lithium-containing transition metal phosphate material, the positive electrode active material of this application contains a first lithium-containing transition metal phosphate material, a second lithium-containing transition metal phosphate material and a third lithium-containing transition metal phosphate material, which can improve the powder compaction density of the material and improve the energy density and cycle number of the battery.

[0327] As can be seen from the comparison between Examples 1-11 and Comparative Example 2, controlling the molar percentage of Mn in the first lithium-containing transition metal phosphate material to be less than that in the second lithium-containing transition metal phosphate material, and controlling the molar percentage of Mn in the second lithium-containing transition metal phosphate material to be greater than that in the third lithium-containing transition metal phosphate material, can improve the specific capacity of the positive electrode active material, improve the energy density of the battery, increase the number of battery cycles, and extend the battery's service life.

[0328] A comparison of Examples 2-5 with Example 1 shows that controlling the particle size distribution index of the primary particles (greater than 180 nm and less than 1200 nm) in the second lithium-containing transition metal phosphate material to be less than or equal to 0.45 can further improve the battery cycle count and extend battery life. A comparison of Example 4 with Examples 2, 3, and 5 shows that controlling the particle size distribution index of the primary particles (greater than 180 nm and less than 1200 nm) in the second lithium-containing transition metal phosphate material to be 0.3-0.36 can further improve the battery cycle count and extend battery life.

[0329] A comparison of Examples 2 and 8 shows that the first lithium-containing transition metal phosphate material has a Mn molar ratio of 0-0.2, which can further improve the number of battery cycles and extend the battery's lifespan.

[0330] As can be seen from the comparison between Example 8 and Example 2, the first lithium-containing transition metal phosphate material has a Mn molar ratio of 0.02-0.6, which can improve the energy density of the battery.

[0331] A comparison of Examples 2 and 9 shows that the Mn molar ratio of the third lithium-containing transition metal phosphate material is 0-0.2, which can further improve the number of battery cycles and extend the battery's lifespan.

[0332] As can be seen from the comparison between Example 9 and Example 2, the molar ratio of Mn in the third lithium-containing transition metal phosphate material is 0.02-0.6, which can improve the energy density of the battery.

[0333] As can be seen from Examples 1 and 10-11, based on the total mass of the positive electrode active material, the mass content of the first lithium transition metal phosphate material is 1%-10%, the mass content of the second lithium transition metal phosphate material is 60%-90%, and the mass content of the third lithium transition metal phosphate material is 5%-30%. The positive electrode active material has high powder compaction density and specific capacity, and the battery has high energy density and long cycle life.

[0334] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for producing a secondary battery, characterized by, The method comprises the following steps: Preparation of a positive electrode active material: mixing a first lithium-containing transition metal phosphate material, a second lithium-containing transition metal phosphate material, and a third lithium-containing transition metal phosphate material to obtain the positive electrode active material, The first lithium-containing transition metal phosphate material has a primary average particle size of 50 nm-200 nm; The second lithium-containing transition metal phosphate material has a primary average particle size of 120 nm-600 nm, The second lithium-containing transition metal phosphate material has a particle size distribution of primary particles with a primary particle size of 50 nm-180 nm in the second lithium-containing transition metal phosphate material of less than or equal to 10%, Primary particles having a primary particle size of 1200 nm or greater in the second lithium-containing transition metal phosphate material prepared as a longitudinal cross-section of an electrode sheet 2 a particle number within the region of 15 or less; The third lithium-containing transition metal phosphate material has a primary average particle size of 250 nm-4000 nm; The first lithium-containing transition metal phosphate material has a primary average particle size smaller than that of the second lithium-containing transition metal phosphate material, The third lithium-containing transition metal phosphate material has a primary average particle size larger than that of the second lithium-containing transition metal phosphate material, The first lithium-containing transition metal phosphate material has a Mn molar proportion smaller than that of the second lithium-containing transition metal phosphate material, The third lithium-containing transition metal phosphate material has a Mn molar proportion smaller than that of the second lithium-containing transition metal phosphate material, The molar proportion refers to the proportion of the number of moles of an element relative to the total number of moles of Mn and Fe, Preparation of a positive electrode tab: coating a positive electrode slurry containing the positive electrode active material on at least one surface of a positive electrode current collector to obtain a positive electrode tab; Preparation of a secondary battery: assembling an electrode assembly containing the positive electrode tab, a negative electrode tab, and an electrolyte into a secondary battery.

2. The production method according to claim 1, characterized by, The second lithium-containing transition metal phosphate material has a particle size distribution of primary particles with a primary particle size of 50 nm-180 nm in the second lithium-containing transition metal phosphate material of 3%-8.5%.

3. The production method according to claim 1 or 2, characterized by, The primary particles having a primary particle size of 1200 nm or more are present in an amount of 0.1 to 10% by number in the second lithium-containing transition metal phosphate material 2 The number of particles in the region is 2-12.

4. The production method according to any one of claims 1 to 3, characterized by, The second lithium-containing transition metal phosphate material has a particle size distribution index of primary particles with a primary particle size of greater than 180 nm and less than 1200 nm of less than or equal to 0.45, which can be 0.3-0.

36.

5. The production method according to any one of claims 1 to 4, characterized by, The second lithium-containing transition metal phosphate material satisfies at least one of (a1)-(d1): (a1) The (Dv90-Dv10) / Dv50 of the second lithium-containing transition metal phosphate material is 1-3; (b1) The Dv50 of the second lithium-containing transition metal phosphate material is 0.35 μm-1.5 μm; (c1) The Dv10 of the second lithium-containing transition metal phosphate material is 0.1 μm-0.4 μm; (d1) The Dv90 of the second lithium-containing transition metal phosphate material is 2.5 μm-6 μm.

6. The production method according to any one of claims 1 to 5, characterized by, The Mn molar proportion of the first lithium-containing transition metal phosphate material is 0-0.6, which can be 0-0.4, more preferably 0-0.2, and further preferably 0.

7. The production method according to any one of claims 1 to 6, characterized by, The Mn molar proportion of the first lithium-containing transition metal phosphate material is 0.02-0.6, which can be 0.02-0.4, more preferably 0.02-0.2, and further preferably 0.

02.

8. The production method according to any one of claims 1 to 7, characterized by, The Mn molar fraction of the first lithium-containing transition metal phosphate material is 0.2-0.6, which can be 0.2-0.4, and more preferably 0.

2.

9. The production method according to any one of claims 1 to 8, characterized by, The Mn molar fraction of the second lithium-containing transition metal phosphate material is 0.4-0.9, which can be 0.5-0.

9.

10. The production method according to any one of claims 1 to 9, characterized by, The Mn molar fraction of the third lithium-containing transition metal phosphate material is 0-0.6, which can be 0-0.5, and more preferably 0-0.1, and further preferably 0.

11. The production method according to any one of claims 1 to 9, characterized by, The Mn molar fraction of the third lithium-containing transition metal phosphate material is 0.02-0.6, which can be 0.02-0.5, and more preferably 0.02-0.1, and further preferably 0.

02.

12. The production method according to any one of claims 1 to 9, characterized by, The Mn molar fraction of the third lithium-containing transition metal phosphate material is 0.2-0.6, which can be 0.2-0.5, and more preferably 0.

2.

13. The production method according to any one of claims 1 to 12, characterized by, The mass content of the first lithium-containing transition metal phosphate material is 1%-10%, the mass content of the second lithium-containing transition metal phosphate material is 60%-90%, and the mass content of the third lithium-containing transition metal phosphate material is 5%-30%, based on the total mass of the positive electrode active material.

14. The production method according to any one of claims 1 to 13, characterized by, The first lithium-containing transition metal phosphate material comprises a first inner core and a first carbon coating layer coated on the outer surface of the first inner core, the second lithium-containing transition metal phosphate material comprises a second inner core and a second carbon coating layer coated on the outer surface of the second inner core, and the positive electrode active material further comprises a third lithium-containing transition metal phosphate material, the third lithium-containing transition metal phosphate material comprises a third inner core and a third carbon coating layer coated on the outer surface of the third inner core, wherein the general formula of the first core comprises Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 , wherein 0.8≤m4≤1.2, x1≥0, y1≥0, 0.9≤x1+y1≤1, 0.95≤z1≤1.1, 3.5≤n1≤4, 0≤a1≤0.1, 0≤b1≤0.1, 0≤c1≤0.1, 0≤d1≤0.1, The general formula of the second inner core comprises Li m2 A2 a2 Fe x2 Mn y2 M2 b2 P z2 Q2 c2 O n2 N2 d2 , 0.8≤m2≤1.2, x2≥0, y2>0, 0.9≤x2+y2≤1, 0.95≤z2≤1.1, 3.5≤n2≤4, 0≤a2≤0.1, 0≤b2≤0.1, 0≤c2≤0.1, 0≤d2≤0.1, The general formula of the third core comprises Li m3 A3 a3 Fe x3 Mn y3 M3 b3 P z3 Q3 c3 O n3 N3 d3 , 0.8≤m3≤1.2, x3≥0, y3≥0, 0.9≤x3+y3≤1, 0.95≤z3≤1.1, 3.5≤n3≤4, 0≤a3≤0.1, 0≤b3≤0.1, 0≤c3≤0.1, 0≤d3≤0.1, wherein A1, A2, A3 each independently comprises one or more of Al, Na, K, Mg, M1, M2, M3 each independently comprises one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, Q1, Q2, Q3 each independently comprises one or more of B, S, Si, N, N1, N2, N3 each independently comprises one or more of S, F, Cl, Br.

15. The production method according to any one of claims 1 to 14, characterized by, The positive electrode slurry further includes a binder and a conductive agent, and the mass ratio of the positive electrode active material, the binder, and the conductive agent in the positive electrode slurry is (92-99):(0.5-3):(0.5-3).

16. The production method according to any one of claims 1 to 15, wherein the positive electrode active material has a capacity of 135 mAh / g to 150 mAh / g at 40°C and at a discharge rate of 1 / 3C.

17. The production method according to any one of claims 1 to 16, characterized by, The single surface area density of the positive electrode tab is 300 mg / 1540 mm 2 - 580 mg / 1540 mm 2 .

18. The production method according to any one of claims 1 to 17, characterized by, The compacted density of the positive electrode plate is 2.25 g / cm 3 - 2.75 g / cm 3 .

19. A secondary battery obtained by the production method according to any one of claims 1 to 18.

20. An electrical device, comprising: A secondary battery including a secondary battery obtained by the production method according to any one of claims 1 to 18 or the secondary battery according to claim 19.

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