Secondary battery and electric device

Abstract

The present application provides a secondary battery and an electric device. The secondary battery comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector; the positive electrode film layer comprises first-type particles and second-type particles; the first-type particles and the second-type particles comprise lithium-containing transition metal phosphate materials; the Mn molar ratio of the first-type particles is greater than or equal to 0.5; the primary particle size of the second-type particles is greater than the average value of the primary particle sizes of the first-type particles; the average value of the Mn molar ratios of the second-type particles is less than the average value of the Mn molar ratios of the first-type particles; and the Mn molar ratio refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe.

Description

Secondary batteries and electrical appliances

[0001] Cross-references

[0002] This application incorporates Chinese Patent Application No. 202411035228.4, filed on July 30, 2024, entitled “Secondary Battery 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 more particularly to a secondary battery and an electrical device. Background Technology

[0004] Secondary batteries have advantages such as high energy density, high operating voltage, low self-discharge rate, small size, and light weight, and are widely used in the consumer electronics field.

[0005] With the rapid development of electric vehicles and mobile electronic devices, the requirements for the energy density and rate performance of rechargeable batteries are becoming increasingly stringent. How to improve battery energy density while simultaneously maintaining good rate performance is a pressing technical problem that needs to be solved in the current application of rechargeable batteries. Summary of the Invention

[0006] This application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery and an electrical device that combine high energy density and excellent rate performance.

[0007] The first aspect of this application provides a secondary battery, including a positive electrode, a negative electrode, and an electrolyte.

[0008] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector.

[0009] The positive electrode film layer comprises a first type of particles and a second type of particles, wherein the first type of particles and the second type of particles comprise lithium-containing transition metal phosphate materials.

[0010] The molar percentage of Mn in the first type of particles is greater than or equal to 0.5.

[0011] The primary particle size of the second type of particles is larger than the average primary particle size of the first type of particles.

[0012] The average molar percentage of Mn in the second type of particles is less than the average molar percentage of Mn in the first type of particles.

[0013] The molar percentage of Mn refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe.

[0014] The first type of particles has a high manganese molar ratio, contributing sufficient voltage plateau and specific capacity, which is beneficial to improving the energy density of the battery. Meanwhile, the primary particle size of the second type of particles is larger than the average primary particle size of the first type. Particles with different primary sizes can cooperate to fill gaps, resulting in a denser particle packing in the positive electrode active material, increasing the powder compaction density and electrode compaction density, thereby improving the battery's energy density. Furthermore, this application controls the second type of particles with relatively large primary particle sizes to be low-manganese or manganese-free, which can improve the conductivity of the relatively large primary particle size second type of particles, alleviate the discharge polarization of the second type of particles, and is beneficial to the material's specific capacity and kinetic performance. In addition to improving the powder compaction density and the battery's energy density, it also improves the material's conductivity and the battery's rate performance.

[0015] In any embodiment, the molar percentage of Mn in the first type of particles is 0.5-0.9.

[0016] By controlling the molar ratio of Mn in the first type of particles within a suitable range, the first type of particles can have a high plateau capacity, while also ensuring that the first type of particles have a certain conductivity. This is conducive to the first type of particles exerting their specific capacity, so that the first type of particles can contribute sufficient capacity, thereby improving the energy density of the battery.

[0017] In any embodiment, the average primary particle size of the first type of particles is 120 nm to 600 nm.

[0018] The average primary particle size of the first type of particles is within a suitable range, resulting in a shorter migration path for lithium ions within the particles, which is beneficial for lithium ion transport. The material has good conductivity, which is conducive to maximizing the specific capacity of the material and improving the energy density and rate performance of the battery. At the same time, the material also has certain cycle stability and storage stability, which is beneficial for improving the cycle stability and storage stability of the battery.

[0019] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

[0020] Controlling the molar percentage of Mn in the second type of particles within a suitable range can further improve the conductivity of the second type of particles, alleviate the discharge polarization of the second type of particles, and help to further improve the rate performance of the battery. At the same time, it is beneficial to concentrate sufficient manganese elements in the first type of particles with small primary particle size, so that the first type of particles contribute more plateau capacity, improve the energy density of the battery, and is suitable for high-rate and high-energy-density batteries.

[0021] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 5%-50%, optionally 5%-30%, more preferably 5%-10%, and even more preferably 5%.

[0022] Controlling the molar percentage of Mn in the second type of particles within a suitable range can improve the conductivity and kinetic properties of the material, while also allowing Mn in the second type of particles to contribute a certain amount of plateau capacity. It can also alleviate the impact of excessive Mn concentration in the first type of particles with relatively small particle size on the cycle performance and storage performance of the battery, making the battery more suitable for application scenarios with certain requirements for storage performance and / or cycle performance.

[0023] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 10%-50%, optionally 10%-30%, and more preferably 10%.

[0024] By controlling the molar percentage of Mn in the second type of particles within a suitable range, while ensuring good conductivity of the second type of particles, the effects of excessive Mn concentration in the relatively small first type of particles on the cycle performance and storage performance of the battery can be further mitigated. This makes the battery more suitable for applications with high requirements for storage performance and / or cycle performance.

[0025] In any embodiment, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles is 0-0.8, optionally 0-0.5, and more preferably 0.

[0026] By controlling the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles within a suitable range, the conductivity of the second type of particles can be improved while also taking into account the high platform capacity contributed by the first type of particles, thus comprehensively improving the energy density and rate performance of the battery.

[0027] In any embodiment, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles is 0.0003-0.8, optionally 0.0003-0.5, and more preferably 0.0003.

[0028] In any embodiment, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles is 0.002-0.8, optionally 0.002-0.5, and more preferably 0.002.

[0029] By controlling the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles within a suitable range, the battery can achieve excellent rate performance, cycle performance, and energy density.

[0030] In any embodiment, the average molar percentage of Mn in the first type of particles is 0.5-0.9, and can be optionally 0.6-0.9.

[0031] By controlling the average Mn molar ratio of the first type of particles within a suitable range, the first type of particles can have a high plateau capacity while also ensuring that the first type of particles have a certain conductivity. This is conducive to the first type of particles exerting their specific capacity, so that the first type of particles can contribute sufficient capacity, thereby improving the energy density of the battery.

[0032] In any embodiment, the average value of the Mn molar percentage of the second type of particles is greater than or equal to 0 and less than 0.5, and can be selected as greater than or equal to 0 and less than or equal to 0.3, or more preferably 0.

[0033] Controlling the average molar percentage of Mn in the second type of particles within a suitable range can improve the conductivity of the second type of particles, enhance the overall conductivity of the material, and improve the rate performance of the battery. At the same time, when the average molar percentage of Mn in the second type of particles is within a suitable range, the molar percentage of Mn in the material is also within a suitable range, which is beneficial to improving the storage performance and cycle performance of the battery.

[0034] In any embodiment, the average Mn molar percentage of the second type of particles is greater than or equal to 0.02 and less than 0.5, and can be selected as greater than or equal to 0.02 and less than or equal to 0.3, or more preferably 0.02.

[0035] In any embodiment, the average value of the Mn molar ratio of the second type of particles is greater than or equal to 0.1 and less than 0.3, and more preferably 0.1.

[0036] By controlling the average molar ratio of Mn in the second type of particles within a suitable range, the conductivity of the second type of particles and the material is improved, while also enabling the second type of particles to have a certain plateau capacity, thereby further improving the energy density of the battery.

[0037] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 20%-85%, optionally 20%-80%, and more preferably 50%-80%; and / or, the area ratio of the second type of particles is 15%-80%, optionally 20%-80%, and more preferably 20%-50%.

[0038] When the area ratio of the first type of particles and the second type of particles is within a suitable range, it can achieve particle size distribution, improve the compaction density of the material, and at the same time, it can give full play to the purpose of providing platform capacity for the first type of particles with relatively high manganese content. It can also achieve the purpose of improving the powder compaction density of the material by the second type of particles with appropriate content, and reduce the impact of large-diameter second type of particles on the conductivity of the material. This is conducive to obtaining batteries with high energy density and excellent rate performance.

[0039] In any embodiment, the positive electrode film layer includes a third type of particles, which includes the lithium-containing transition metal phosphate material.

[0040] Wherein, the primary particle size of the third type of particles is smaller than the average primary particle size of the first type of particles.

[0041] The average molar percentage of Mn in the third type of particles is less than the average molar percentage of Mn in the first type of particles.

[0042] Based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the third type of particles is greater than or equal to 5% and less than or equal to 30%.

[0043] The use of smaller, third-type particles with a suitable area ratio can fill the pores between the first and second-type particles, resulting in a denser material packing. This further increases the powder compaction density and electrode compaction density, which is beneficial for achieving high-energy-density batteries. Simultaneously, controlling the ultra-small particle size of the third-type particles to be low-manganese or manganese-free helps reduce side reactions between the particles and the electrolyte, as well as the degree of manganese dissolution. This not only improves the battery's energy density but also enhances its cycle performance and storage performance.

[0044] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

[0045] By controlling the molar percentage of Mn in the third type of particles within a suitable range, the possibility of side reactions between the third type of particles and the electrolyte and the phenomenon of manganese dissolution can be reduced, thereby improving the cycle performance of the battery and extending its service life.

[0046] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0.02%-12%, optionally 0.02%-8%, more preferably 0.02%-6%, and even more preferably 0.02%.

[0047] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0.2%-12%, optionally 0.2%-8%, more preferably 0.2%-6%, and even more preferably 0.2%.

[0048] By controlling the molar percentage of Mn in the third type of particles within a suitable range, the possibility of manganese leaching from the third type of particles is reduced, while also allowing the third type of particles with excellent conductivity to fully utilize their specific capacity and plateau capacity. This is beneficial for improving the energy density of the battery and makes it more suitable for application scenarios with high energy density requirements.

[0049] In any embodiment, the ratio of the average Mn molar percentage of the third type of particles to the average Mn molar percentage of the first type of particles is 0-0.8, optionally 0-0.4, and more preferably 0.

[0050] By controlling the ratio of the average Mn molar ratio of the third type of particles to the average Mn molar ratio of the first type of particles within a suitable range, the cycle stability of the third type of particles can be improved while also taking into account the high platform capacity of the first type of particles, thus comprehensively improving the energy density and storage performance of the battery.

[0051] In any embodiment, the ratio of the average Mn molar percentage of the third type of particles to the average Mn molar percentage of the first type of particles is 0.0003-0.8, optionally 0.0003-0.4, and more preferably 0.0003.

[0052] In any embodiment, the ratio of the average Mn molar percentage of the third type of particles to the average Mn molar percentage of the first type of particles is 0.002-0.8, optionally 0.002-0.4, and more preferably 0.002.

[0053] Controlling the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles within a suitable range is beneficial to further improve the energy density of the battery and makes it more suitable for application scenarios with high energy density requirements.

[0054] In any embodiment, the average value of the Mn molar ratio of the third type of particles is greater than or equal to 0 and less than 0.5, and can be selected as 0-0.2, or more preferably 0.

[0055] Controlling the average molar ratio of Mn in the third type of particles within a suitable range can reduce the possibility of side reactions between the third type of particles and the electrolyte, as well as the possibility of manganese dissolution, thereby improving the cycle stability and storage stability of the third type of particles and enhancing the cycle performance and storage performance of the battery.

[0056] In any embodiment, the average value of the Mn molar ratio of the third type of particles is greater than or equal to 0.02 and less than 0.3, and can be selected as 0.02-0.2, or more preferably 0.02.

[0057] In any embodiment, the average value of the Mn molar ratio of the third type of particles is greater than or equal to 0.1 and less than or equal to 0.2, and can be selected as 0.1.

[0058] By controlling the average molar ratio of Mn in the third type of particles within a suitable range, the cycle stability and storage stability of the third type of particles are improved, while also enabling the third type of particles to have a high specific capacity. The battery achieves a balance between good cycle performance, storage performance and high energy density.

[0059] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 45%-85%, the area ratio of the second type of particles is 10%-40%, and the area ratio of the third type of particles is 5%-15%.

[0060] By controlling the area ratio of particles of different sizes within a suitable range, the contribution of the first type of particles with high manganese content to the energy density in terms of both the average voltage and specific capacity can be achieved. At the same time, the impact of the second type of particles with large diameter on the rate performance of the battery and the impact of the third type of particles with small diameter on the cycle performance and storage performance of the battery can be reduced. The battery can achieve a balance of high energy density, good cycle performance, good storage performance and rate performance.

[0061] In any embodiment, the average molar percentage of Mn in the primary particles of the positive electrode film is 0.2-0.9, and can be selected as 0.3-0.8.

[0062] By controlling the average molar percentage of Mn in the overall particles within a suitable range, the material can have high plateau capacity, as well as excellent cycle stability and conductivity, which is beneficial for obtaining batteries with high energy density, excellent cycle performance, storage performance and rate performance.

[0063] In any embodiment, the general formula of the lithium transition metal phosphate material of the first type of particles includes Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 ,

[0064] 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,

[0065] The general formula for the lithium-containing transition metal phosphate materials of the second type of particles includes 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,

[0066] The general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 A3 a3 Fe x3 Mn y3 M3 b3 P z3 Q3 c3 O n3 N2 d3 ,

[0067] 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

[0068] 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.

[0069] In any embodiment, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises the lithium-containing transition metal phosphate material, and the powder compaction density of the positive electrode active material at a pressure of 29400N is 2.40 g / cm³. 3 -2.65g / cm 3 .

[0070] In any embodiment, the specific capacity of the positive electrode active material at 40°C and 1 / 3C discharge rate is 135mAh / g-150mAh / g.

[0071] In any embodiment, the positive electrode film layer further includes a binder and a conductive agent, wherein the mass ratio of the positive electrode active material, the binder, and the conductive agent in the positive electrode film layer is (92-99):(0.5-3):(0.5-3).

[0072] In any embodiment, the areal density of the positive electrode film is 300 mg / 1540 mm². 2 -580mg / 1540mm 2 .

[0073] In any embodiment, the compaction density of the positive electrode film is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0074] A second aspect of this application provides an electrical device comprising the secondary battery described in the first aspect. Attached Figure Description

[0075] 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;

[0076] Figure 2 is a schematic diagram of a secondary battery according to an embodiment of this application;

[0077] Figure 3 is an exploded view of the secondary battery according to an embodiment of this application shown in Figure 2;

[0078] Figure 4 is a schematic diagram of a battery module according to an embodiment of this application;

[0079] Figure 5 is a schematic diagram of a battery pack according to an embodiment of this application;

[0080] Figure 6 is an exploded view of the battery pack of one embodiment of this application shown in Figure 5;

[0081] 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.

[0082] Figure label:

[0083] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0084] The embodiments of the secondary battery and power-consuming device of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. 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 making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0085] 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.

[0086] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0087] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0088] 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.

[0089] 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.

[0090] 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).

[0091] 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 still suffers from low compaction density and has not yet demonstrated the potential advantage of high energy density. At the same time, the presence of manganese also affects the conductivity of lithium manganese iron phosphate, affecting the material's specific capacity and kinetic performance, as well as the rate performance and energy density of the battery. Therefore, how to improve the compaction density of lithium manganese iron phosphate, obtain high energy density batteries, and at the same time take into account the rate performance of the battery has become a key research point.

[0092] [Rechargeable Battery]

[0093] Based on this, this application proposes a secondary battery, including a positive electrode, a negative electrode, and an electrolyte.

[0094] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector.

[0095] The positive electrode film layer comprises a first type of particles and a second type of particles, wherein the first type of particles and the second type of particles comprise lithium-containing transition metal phosphate materials.

[0096] The molar percentage of Mn in the first type of particles is greater than or equal to 0.5.

[0097] The primary particle size of the second type of particles is larger than the average primary particle size of the first type of particles.

[0098] The average molar percentage of Mn in the second type of particles is less than the average molar percentage of Mn in the first type of particles.

[0099] The molar percentage of Mn refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe.

[0100] 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.

[0101] The average value of the Mn molar ratio of the first type of particles and the average value of the Mn molar ratio of the second type of particles can be tested using methods and equipment known in the art, for example as follows: Disassemble the battery to obtain the positive electrode sheet, peel off the positive electrode film layer of the positive electrode sheet, thoroughly wash the positive electrode film layer with acetone to remove the binder and dispersant in the positive electrode film layer, filter and dry to obtain powder. Take 0.05g of the uniformly mixed powder and dissolve it in 40ml of anhydrous ethanol. Then add an appropriate amount of dispersant and stir until a suspension is obtained. Take 2ml of the suspension and 2ml of anhydrous ethanol and mix them together. Then sonicate the mixture. The sonication power is 480W and the sonication time is 5min. Take an appropriate amount of the middle layer suspension for transmission electron microscopy (TEM). According to the definition of primary particles mentioned above, calculate the projection area of ​​each primary particle in the TEM image, which is the cross-sectional area S of the primary particle. Use the equivalent circle method to obtain the equivalent circle diameter of the primary particle, 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 50nm are not included in the statistical range (i.e., primary particles with a primary particle diameter greater than or equal to 50nm are valid particles). Simultaneously, EDS point scanning can be used to test the molar content of Mn and Fe in each effective particle in the transmission electron microscope (TEM) image. This allows calculation of the molar percentage of Mn (X) in each effective particle (the molar percentage of Mn refers to the content of the number of moles of Mn relative to the total number of moles of Mn and Fe). The test point is the middle part of the transmission surface of each particle. TEM and EDS tests are performed multiple times in different test areas, testing at least n (n ≥ 500) effective particles for their cross-sectional area S, primary particle size x, and molar percentage of Mn X. Particles with a molar percentage of Mn greater than or equal to 0.5 are selected and numbered A1, A2, A3, A4, A5…Am according to their primary particle size from smallest to largest. Particles numbered 1 to m are classified as the first type of particles, and the average primary particle size of the first type of particles is calculated. Among the remaining nm particles, those with a primary particle size greater than [missing value] will be [missing value]. The particles are selected and numbered B1, B2, B3, B4, B5…Bk according to their primary particle size from smallest to largest. Particles numbered B1 to Bk are classified as the second type of particles. In some cases, the sum of the number of particles in the first type (m) and the number of particles in the second type (k) is less than the number of valid particles (n), in which case a third type of particles exists. The remaining third type of particles are numbered C1, C2, C3, C4, C5…Cr according to their primary particle size from smallest to largest, where m + k + r = n. In some cases, the sum of the number of particles in the first type (m) and the number of particles in the second type (k) is equal to the number of valid particles (n), in which case r is 0, meaning that no third type of particles exists.

[0102] The formula for calculating the average molar percentage of Mn in the first type of particles is as follows:

[0103] The formula for calculating the average molar percentage of Mn in the second type of particles is as follows:

[0104] Where Xi represents the molar percentage of Mn in particle number i, and Si represents the cross-sectional area of ​​particle number i.

[0105] In this paper, the Mn molar ratio of the first type of particles being greater than or equal to 0.5 means that the Mn molar ratio of each particle in the first type of particles is greater than or equal to 0.5.

[0106] In some implementations, the molar percentage of Mn in the first type of particles is 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or any range between any two of the above values.

[0107] The first type of particles has a high manganese molar ratio, meaning they are high-manganese particles, which contribute sufficient plateau capacity and specific capacity, thus improving the battery's energy density. Meanwhile, the second type of particles has a primary particle size larger than the average primary particle size of the first type. These different primary particle sizes allow for particle-to-particle cooperation to fill gaps, resulting in a denser particle packing in the positive electrode active material. This increases the powder compaction density and electrode compaction density, thereby enhancing the battery's energy density. Furthermore, this application controls the second type of particles with relatively large primary particle sizes to be low-manganese or manganese-free, which improves their conductivity, alleviates discharge polarization, and facilitates the realization of the material's specific capacity and kinetic performance. In addition to improving the powder compaction density and battery energy density, this application also enhances the material's conductivity and improves the battery's rate performance.

[0108] In some embodiments, the molar percentage of Mn in the first type of particles is 0.5-0.9. In some embodiments, the molar percentage of Mn in the first type of particles is 0.5, 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.

[0109] By controlling the molar ratio of Mn in the first type of particles within a suitable range, the first type of particles can have a high plateau capacity, while also ensuring that the first type of particles have a certain conductivity. This is conducive to the first type of particles exerting their specific capacity, so that the first type of particles can contribute sufficient capacity, thereby improving the energy density of the battery.

[0110] In some embodiments, the average primary particle size of the first type of particles is 120 nm to 600 nm. In some embodiments, the average primary particle size of the first type of particles may be selected as 120 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, or any range between any two of the above values.

[0111] The average primary particle size of the first type of particles is within a suitable range, resulting in a shorter migration path for lithium ions within the particles, which is beneficial for lithium ion transport. The material has good conductivity, which is conducive to maximizing the specific capacity of the material and improving the energy density and rate performance of the battery. At the same time, the material also has a certain degree of structural stability, which is beneficial for improving the cycle stability and storage stability of the battery and extending its lifespan.

[0112] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

[0113] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the secondary particles can be tested using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for averaging the Mn molar percentage of the secondary particles, the cross-sectional area S and the molar percentage X of Mn for each particle are determined.

[0114] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the formula for calculating the molar percentage of Mn in the secondary particles is as follows:

[0115] Where Xi and Xj represent the molar percentage of Mn in particles numbered i and j, respectively, and Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0116] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles can be selected as 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, etc. 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any range between any two of the above values.

[0117] Controlling the molar percentage of Mn in the second type of particles within a suitable range can further improve the conductivity of the second type of particles, alleviate the discharge polarization of the second type of particles, and help to further improve the rate performance of the battery. At the same time, it is beneficial to concentrate sufficient manganese elements in the first type of particles with small primary particle size, so that the first type of particles contribute more plateau capacity, improve the energy density of the battery, and is suitable for high-rate and high-energy-density batteries.

[0118] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 5%-50%, optionally 5%-30%, more preferably 5%-10%, and even more preferably 5%.

[0119] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles can be selected as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any range between any two of the above values.

[0120] Distributing a small amount of Mn in the second type of particles can alleviate the impact of excessive Mn concentration in the relatively small first type of particles on the cycle performance and storage performance of the battery. While improving the energy density of the battery, it can also take into account certain cycle performance and / or storage performance, making the battery more suitable for application scenarios with certain requirements for cycle performance and / or storage performance.

[0121] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 10%-50%, optionally 10%-30%, and more preferably 10%.

[0122] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles can be selected as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any range between any two of the above values.

[0123] By controlling the molar percentage of Mn in the second type of particles within a suitable range, while ensuring good conductivity of the second type of particles, the effects of excessive Mn concentration in the relatively small first type of particles on the cycle performance and storage performance of the battery can be further mitigated. This makes the battery more suitable for applications with high requirements for storage performance and / or cycle performance.

[0124] In some embodiments, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles is 0-0.8, optionally 0-0.5, and more preferably 0.

[0125] In some embodiments, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles 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, or 0. 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, 0.65, 0.7, 0.75, 0.8, or a range between any two of the above values.

[0126] By controlling the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles within a suitable range, the conductivity of the second type of particles can be improved while achieving the goal of high platform capacity contribution from the first type of particles, thus comprehensively improving the energy density and rate performance of the battery.

[0127] In some embodiments, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles is 0.0003-0.8, optionally 0.0003-0.5, and more preferably 0.0003.

[0128] In some embodiments, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles can be selected as 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, or 0.00 7, 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, 0.65, 0.7, 0.75, 0.8, or a range between any two of the above values.

[0129] By controlling the average Mn molar ratio of the second type of particles to the average Mn molar ratio of the first type of particles within a suitable range, the second type of particles can have a certain amount of Mn content. The second type of particles can contribute a certain amount of platform capacity, which is beneficial to improving the energy density of the battery. At the same time, it can also alleviate the impact of excessive Mn concentration in the relatively small primary particle size of the first type of particles on the cycle performance and storage performance of the battery, making the battery more suitable for application scenarios with certain requirements for cycle performance and / or storage performance.

[0130] In any embodiment, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles is 0.002-0.8, optionally 0.002-0.5, and more preferably 0.002.

[0131] In some embodiments, the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles can be selected as 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, 0.65, 0.7, 0.75, 0.8, or any range between the above two values.

[0132] By controlling the ratio of the average molar percentage of Mn in the second type of particles to the average molar percentage of Mn in the first type of particles within a suitable range, the impact of excessive Mn concentration in the first type of particles with relatively small particle size on the cycle performance and storage performance of the battery can be further mitigated, making the battery more suitable for application scenarios with high requirements for storage performance and / or cycle performance.

[0133] In some implementations, the average molar percentage of Mn in the first type of particles is 0.5-0.9, and optionally 0.6-0.9.

[0134] In some embodiments, the average value of the molar percentage of Mn in the first type of particles can be selected as 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.

[0135] By controlling the average Mn molar ratio of the first type of particles within a suitable range, the first type of particles can have a high plateau capacity while also ensuring that the first type of particles have a certain conductivity. This is conducive to the first type of particles exerting their specific capacity and plateau capacity, achieving the purpose of providing capacity by the first type of particles, and improving the energy density of the battery.

[0136] In some embodiments, the average value of the Mn molar percentage of the second type of particles is greater than or equal to 0 and less than 0.5, which can be selected as greater than or equal to 0 and less than or equal to 0.3, or more preferably 0.

[0137] In some embodiments, the average value of the Mn molar ratio of the second type of particles 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, 0.49, 0.495, or a range between any two of the above values.

[0138] Controlling the average molar ratio of Mn in the second type of particles within a suitable range can improve the conductivity of the second type of particles, enhance the overall conductivity of the material, and improve the rate performance of the battery.

[0139] In some embodiments, the average Mn molar percentage of the second type of particles is greater than or equal to 0.02 and less than 0.5, and can be selected as greater than or equal to 0.02 and less than or equal to 0.3, or more preferably 0.02.

[0140] In some embodiments, the average value of the Mn molar ratio of the second type of particles 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, 0.49, 0.495, or a range between any two of the above values.

[0141] By controlling the average molar ratio of Mn in the second type of particles within a suitable range, the conductivity of the second type of particles and materials is improved, while also enabling the second type of particles to have a certain plateau capacity and high specific capacity, which can further improve the energy density of the battery.

[0142] In some embodiments, the average Mn molar ratio of the second type of particles is greater than or equal to 0.1 and less than 0.3, and more preferably 0.1.

[0143] By controlling the average Mn molar ratio of the second type of particles within a suitable range, the second type of particles not only have good conductivity, but also provide a relatively large voltage platform and specific capacity, which can further improve the energy density of the battery and is more suitable for application scenarios with high energy density requirements.

[0144] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the first type of particles is 20%-85%, optionally 20%-80%, and more preferably 50%-80%.

[0145] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the second type of particles is 15%-80%, optionally 20%-80%, and more preferably 20%-50%.

[0146] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or any range between any two of the above values.

[0147] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the second type of particles can be selected as 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any range between any two of the above values.

[0148] The method for testing the area ratio of the first type of particles and the area ratio of the second type of particles can be performed using methods and equipment known in the art, as exemplified below: Referring to the aforementioned method for testing the average value of the Mn molar ratio of the second type of particles, the cross-sectional area S of each particle is determined.

[0149] The formula for calculating the area ratio of the first type of particles is:

[0150] The formula for calculating the area ratio of the second type of particles is:

[0151] Where Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0152] When the area ratio of the first type of particles and the second type of particles is within a suitable range, it can achieve particle size distribution, improve the compaction density of the material, and at the same time, it can give full play to the purpose of providing platform capacity for the first type of particles with relatively high manganese content. It can also achieve the purpose of improving the powder compaction density of the material by the second type of particles with appropriate content, and reduce the impact of large-diameter second type of particles on the conductivity of the material. This is conducive to obtaining batteries with high energy density and excellent rate performance.

[0153] In some embodiments, the positive electrode film layer includes a third type of particles, which includes the lithium-containing transition metal phosphate material.

[0154] Wherein, the primary particle size of the third type of particles is smaller than the average primary particle size of the first type of particles.

[0155] The average molar percentage of Mn in the third type of particles is less than the average molar percentage of Mn in the first type of particles.

[0156] Based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the third type of particles is greater than or equal to 5% and less than or equal to 30%.

[0157] In this paper, the third type of particle is a primary particle.

[0158] The test method for the area ratio of the third type of particles can be performed using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for the average value of the Mn molar ratio of the second type of particles, the third type of particles are defined, and the formula for calculating the area ratio of the third type of particles is:

[0159] Where Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0160] The average Mn molar percentage of the third type of particles can be determined using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for testing the average Mn molar percentage of the second type of particles, the formula for calculating the average Mn molar percentage of the third type of particles is as follows:

[0161] Where Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0162] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the third type of particles can be selected as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any range between any two of the above values.

[0163] The use of smaller, third-type particles with a suitable area ratio can fill the pores between the first and second-type particles, resulting in a denser packing and further increasing the powder compaction density and electrode compaction density, which is beneficial for obtaining high-energy-density batteries. Simultaneously, controlling the ultra-small particle size of the third-type particles to be low-manganese or manganese-free helps reduce side reactions between the particles and the electrolyte, as well as the degree of manganese dissolution, improving the cycle stability and storage stability of the material. This not only increases the battery's energy density but also improves its cycle and storage performance.

[0164] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

[0165] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles can be optionally 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or a range between any two of the above values.

[0166] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the method for testing the molar percentage of Mn in the third type of particles can be performed using methods and equipment known in the art, as exemplified below: referring to the aforementioned method for testing the average molar percentage of Mn in the second type of particles, the cross-sectional area S and the molar percentage X of Mn for each particle are determined.

[0167] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the formula for calculating the molar percentage of Mn in the third type of particles is as follows:

[0168] Where Xi and Xj represent the molar percentage of Mn in particles numbered i and j, respectively, and Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0169] By controlling the molar percentage of Mn in the third type of particles within a suitable range, the possibility of side reactions between the third type of particles and the electrolyte and the phenomenon of manganese dissolution can be reduced, thereby improving the cycle performance and storage performance of the battery and extending the battery's lifespan and storage life.

[0170] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0.02%-12%, optionally 0.02%-8%, more preferably 0.02%-6%, and even more preferably 0.02%.

[0171] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles can be optionally 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or a range between any two of the above values.

[0172] Controlling the molar percentage of Mn in the third type of particles within a suitable range ensures that the small-diameter third type of particles contain a certain amount of Mn. This allows the highly conductive third type of particles to fully utilize their specific capacity, further improving the energy density of the battery. The battery is then more suitable for scenarios with specific energy density requirements.

[0173] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0.2%-12%, optionally 0.2%-8%, more preferably 0.2%-6%, and even more preferably 0.2%.

[0174] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles can be optionally 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or any range between any two of the above values.

[0175] Controlling the molar percentage of Mn in the third type of particles within a suitable range allows the small-diameter third type of particles to have a relatively large amount of Mn, which is beneficial for the highly conductive third type of particles to fully utilize their specific capacity, thereby further improving the energy density of the battery. This makes the battery more suitable for scenarios with high energy density requirements.

[0176] In some embodiments, the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles is 0-0.8, optionally 0-0.4, and more preferably 0.

[0177] In some embodiments, the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles 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, or 0. 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, 0.65, 0.7, 0.75, 0.8, or a range between any two of the above values.

[0178] By controlling the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles within an appropriate range, the cycle stability of the third type of particles can be improved while achieving the platform capacity contributed by the first type of particles, thus comprehensively improving the energy density and storage performance of the battery.

[0179] In some embodiments, the ratio of the average Mn molar percentage of the third type of particles to the average Mn molar percentage of the first type of particles is 0.0003-0.8, optionally 0.0003-0.4, and more preferably 0.0003.

[0180] In some embodiments, the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles can be selected as 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, or 0.00 7, 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, 0.65, 0.7, 0.75, 0.8, or a range between any two of the above values.

[0181] By controlling the average Mn molar ratio of the third type of particles to the average Mn molar ratio of the first type of particles within a suitable range, the third type of particles can have a certain amount of Mn content. The third type of particles with excellent conductivity can fully exert their specific capacity, which is beneficial to improving the energy density of the battery and making the battery more suitable for application scenarios with certain energy density requirements.

[0182] In some embodiments, the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles is 0.002-0.8, optionally 0.002-0.4, and more preferably 0.003.

[0183] In some embodiments, the ratio of the average molar percentage of Mn in the third type of particles to the average molar percentage of Mn in the first type of particles can be selected as 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, 0.65, 0.7, 0.75, 0.8, or any range between the above two values.

[0184] By controlling the average Mn molar ratio of the third type of particles to the average Mn molar ratio of the first type of particles within a suitable range, the third type of particles have a relatively high Mn content. The third type of particles with excellent conductivity can fully exert their specific capacity, which is beneficial to improving the energy density of the battery and making the battery more suitable for application scenarios with high energy density requirements.

[0185] In some embodiments, the average value of the Mn molar ratio of the third type of particles is greater than or equal to 0 and less than 0.5, optionally 0-0.2, and more preferably 0.

[0186] In some embodiments, the average value of the Mn molar ratio of the third type of particles 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, 0.49, 0.495, or a range between any two of the above values.

[0187] Controlling the average molar ratio of Mn in the third type of particles within a suitable range can reduce the possibility of side reactions between the third type of particles and the electrolyte, as well as the possibility of manganese dissolution. This can improve the cycle stability and storage stability of the third type of particles, enhance the cycle performance and storage performance of the battery, and extend the cycle life and storage life of the battery.

[0188] In some embodiments, the average value of the Mn molar ratio of the third type of particles is greater than or equal to 0.02 and less than 0.3, and can be selected as 0.02-0.2, or more preferably 0.02.

[0189] In some embodiments, the average value of the Mn molar ratio of the third type of particles 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, or a range between any two of the above values.

[0190] By controlling the average Mn molar ratio of the third type of particles within a suitable range, the cycle stability of the third type of particles is improved, and the third type of particles with excellent conductivity can fully exert their specific capacity, which can further improve the energy density of the battery and make the battery more suitable for application scenarios with certain energy density requirements.

[0191] In some embodiments, the average Mn molar ratio of the third type of particles is greater than or equal to 0.1 and less than or equal to 0.2, and can be selected as 0.1.

[0192] In some embodiments, the average value of the Mn molar ratio of the third type of particles can be selected as 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, or any range between any two of the above values.

[0193] By controlling the average Mn molar ratio of the third type of particles within a suitable range, the third type of particles with excellent conductivity can fully exert their specific capacity, which can further improve the energy density of the battery and make the battery more suitable for application scenarios with high energy density requirements.

[0194] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the first type of particles is 45%-85%, the area ratio of the second type of particles is 10%-40%, and the area ratio of the third type of particles is 5%-15%.

[0195] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles can be selected as 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any range between any two of the above values.

[0196] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the second type of particles can be selected as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or any range between any two of the above values.

[0197] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the third type of particles can be selected as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any range between any two of the above values.

[0198] By controlling the area ratio of particles of different sizes within a suitable range, the contribution of the first type of particles with high manganese content to the energy density in terms of both the average voltage capacity and the specific capacity can be achieved. At the same time, the impact of the second type of particles with large diameter on the rate performance of the battery and the impact of the third type of particles with small diameter on the cycle performance of the battery can be reduced. The battery can achieve a balance of high energy density, good cycle performance, and rate performance.

[0199] In some embodiments, the average molar percentage of Mn in the primary particles of the positive electrode film is 0.2-0.9, and optionally 0.3-0.8.

[0200] In some embodiments, the average value of the Mn molar ratio of the primary particles in the positive electrode film layer can be selected as 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.90, or any range between any two of the above values.

[0201] The average molar percentage of Mn in the primary particles of the positive electrode film can be determined using methods and equipment known in the art, as exemplified below: The cross-sectional area S and the molar percentage X of Mn for each particle are determined using the aforementioned test method for testing the average molar percentage of Mn in the second type of particles.

[0202] The formula for calculating the average molar percentage of Mn in the primary particles of the positive electrode film is as follows:

[0203] Where Xi represents the molar percentage of Mn in particle number i, and Si represents the cross-sectional area of ​​particle number i.

[0204] By controlling the average molar percentage of Mn in the overall particles within a suitable range, the material can have high plateau capacity, as well as excellent cycle stability and conductivity, which is beneficial for obtaining batteries with high energy density, excellent cycle performance and rate performance.

[0205] In some embodiments, the general formula of the lithium transition metal phosphate material of the first type of particles includes Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 ,

[0206] 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,

[0207] The general formula for the lithium-containing transition metal phosphate materials of the second type of particles includes 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,

[0208] The general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 A3a3 Fe x3 Mn y3 M3 b3 P z3 Q3 c3 O n3 N2 d3 ,

[0209] 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

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] Selecting appropriate modifying 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, reduce interfacial side reactions between the material and the electrolyte during use, and thus improve the cycle performance of the material.

[0217] Selecting appropriate modifying elements Q1, Q2, and Q3 can help change the ease with which the Mn-O bond length changes, thereby improving electronic conductivity, reducing the lithium-ion migration barrier, promoting lithium-ion migration, and improving the rate performance of secondary batteries.

[0218] Suitable modifying elements A1, A2, and A3 can also improve the lattice change rate of materials and maintain their cell capacity.

[0219] Modifying 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, doping at the O sites can enhance the material's resistance to acid corrosion such as HF, thereby improving its cycle performance and storage life.

[0220] In this paper, the modifying elements M1, M2, M3, Q1, Q2, Q3, A1, A2, A3, N1, N2, and N3 can exist in the lithium-containing transition metal phosphate material as doping elements, or in the coating layer of the material as coating elements.

[0221] In some embodiments, the positive electrode film layer comprises a positive electrode active material, which includes the lithium-containing transition metal phosphate material, and the powder compaction density of the positive electrode active material at a pressure of 29400 N is 2.40 g / cm³. 3 -2.65g / cm 3 .

[0222] In some embodiments, the compacted density of the positive electrode active material at a pressure of 29400 N is 2.40 g / cm³. 3 2.41 g / cm 3 2.42 g / cm 3 2.43 g / cm 3 2.44 g / cm 32.45g / cm 3 2.46 g / cm 3 2.47 g / cm 3 2.48 g / cm 3 2.49 g / cm 3 2.50g / cm 3 2.51g / cm 3 2.52g / cm 3 2.53g / cm 3 2.54 g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.59g / cm 3 2.60g / cm 3 2.61 g / cm 3 2.62 g / cm 3 2.63 g / cm 3 2.64 g / cm 3 2.65g / cm 3 , or the range between any two of the above values.

[0223] The compaction density of the positive electrode active material powder at 29400N pressure 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. Once the battery temperature remains at 40°C, it is discharged at a constant current of 1 / 3C to 2.0V. The battery is then disassembled to obtain the positive electrode sheet. The positive electrode film is peeled off and thoroughly washed with acetone to remove the binder from the positive electrode film. The powder is then dried for subsequent characterization testing. Subsequent characterization can be performed using a compaction density instrument, referring to GB / T 24533-2009. Specifically, a certain amount of the prepared powder is placed on a compaction mold (the mold diameter is known). The mold is hollow in the center and has a metal disc at the top and bottom. The powder is placed between metal discs, and a metal cylinder is placed on top. The mold is placed on a compaction density instrument, and the pressure is set to 29400N. The thickness of the powder under 29400N pressure can be read on the instrument. The compaction density of the material is then ρ = m / v, where v = (S × H), m is the mass of the powder, S is the bottom area of ​​the mold, and H is the thickness of the powder after compaction. The compaction density instrument model is UTM7305; the manufacturer is Sansi Zongheng.

[0224] The higher the powder compaction density, the higher the mass of powder material per unit volume. When the powder compaction density of the material is within a suitable range, the positive electrode sheet has a higher compaction density during cold pressing, which is beneficial to further improve the volumetric energy density of the battery.

[0225] 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-150 mAh / g. In some embodiments, the specific capacity of the positive electrode active material 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.

[0226] The specific capacity of the positive electrode active material can be determined using methods and equipment known in the art, for example as follows: Place the battery in a 40°C oven environment and let it stand for 2 hours to maintain the battery temperature at 40°C; then discharge the battery at a constant current of 1 / 3C to 2.0V; let it stand for 5 minutes; charge the battery at a constant current of 1 / 3C to 4.1V, and then charge it at a constant voltage of 4.1V until the cutoff current is 0.05C; let it stand for 5 minutes; and then discharge the battery at a constant current of 1 / 3C to 2.0V to obtain the discharge capacity C of the battery. Disassemble the battery to obtain a positive electrode sheet with a total area of ​​S1. Cut the positive electrode sheet to obtain a positive electrode sheet with an area of ​​S2. After peeling the positive electrode film layer on the positive electrode sheet from the current collector, dissolve it in acetone, wash thoroughly to remove residual solvent, binder, dispersant, etc., and then filter and dry to obtain sample powder. The weight of the sample powder is M2. Then the total mass M1 of the positive electrode active material of the battery is approximately M2*(S1 / S2). The specific capacity of the positive electrode active material = the discharge capacity C of the battery / the mass M1 of the positive electrode active material.

[0227] [Preparation method of positive electrode active material]

[0228] This application also provides a method for preparing a positive electrode active material:

[0229] A lithium-containing transition metal phosphate material is obtained by mixing a first lithium-containing transition metal phosphate material and a second lithium-containing transition metal phosphate material.

[0230] The first lithium-containing transition metal phosphate material comprises a first core and a first carbon coating layer covering the outer surface of the first core, and the second lithium-containing transition metal phosphate material comprises a second core and a second carbon coating layer covering the outer surface of the second core.

[0231] 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.

[0232] The molar percentage of Mn in the second lithium-containing transition metal phosphate material is less than that in the first lithium-containing transition metal phosphate material.

[0233] The primary average particle size of the first lithium-containing transition metal phosphate material is 120 nm-600 nm.

[0234] The primary average particle size of the second lithium-containing transition metal phosphate material is 250 nm to 4000 nm.

[0235] The test method for the molar content of Mn in the first lithium-containing transition metal phosphate material and the second lithium-containing transition metal phosphate material 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.

[0236] The method for testing the primary average particle size of the first and second lithium-containing transition metal phosphate materials can be carried out 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 and stirred evenly to obtain a suspension. 2 ml of the suspension and 2 ml of anhydrous ethanol are mixed and ultrasonically treated with an ultrasonic power of 480 W for 5 min to obtain a uniformly dispersed suspension. An appropriate amount of the intermediate suspension is then 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.

[0237] In some embodiments, the molar percentage of Mn in the first lithium-containing transition metal phosphate material is 0.5-0.9.

[0238] In some embodiments, the molar percentage of Mn in the second lithium-containing transition metal phosphate material is greater than or equal to 0 and less than 0.5, optionally greater than or equal to 0 and less than or equal to 0.4, more preferably greater than or equal to 0 and less than or equal to 0.2, and even more preferably 0.

[0239] In some embodiments, the molar percentage of Mn in the second lithium-containing transition metal phosphate material is greater than or equal to 0.02 and less than 0.5, optionally greater than or equal to 0.02 and less than or equal to 0.4, more preferably greater than or equal to 0.02 and less than or equal to 0.2, and even more preferably 0.02.

[0240] In some embodiments, the molar percentage of Mn in the second lithium-containing transition metal phosphate material is greater than or equal to 0.2 and less than 0.5, optionally greater than or equal to 0.2 and less than or equal to 0.4, and more preferably 0.2.

[0241] 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 is 10%-70%, optionally 30%-50%; and the weight percentage of the second lithium transition metal phosphate material is 30%-90%, optionally 50%-70%.

[0242] In some embodiments, the preparation method of the positive electrode active material is as follows:

[0243] A lithium-containing transition metal phosphate material is obtained by 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.

[0244] The first lithium-containing transition metal phosphate material comprises 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 comprises a second core and a second carbon coating layer covering the outer surface of the second core; and the third lithium-containing transition metal phosphate material comprises a third core and a third carbon coating layer covering the outer surface of the third core.

[0245] 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.

[0246] The primary average particle size of the third lithium-containing transition metal phosphate material is smaller than that of the first lithium-containing transition metal phosphate material.

[0247] The molar percentage of Mn in the second lithium-containing transition metal phosphate material is less than that in the first lithium-containing transition metal phosphate material.

[0248] The molar percentage of Mn in the third lithium-containing transition metal phosphate material is less than that in the first lithium-containing transition metal phosphate material.

[0249] The primary average particle size of the first lithium-containing transition metal phosphate material is 120 nm-600 nm.

[0250] The primary average particle size of the second lithium-containing transition metal phosphate material is 250 nm-4000 nm.

[0251] The primary average particle size of the third lithium-containing transition metal phosphate material is 50 nm to 200 nm.

[0252] In some embodiments, the Mn molar ratio of the third lithium-containing transition metal phosphate material is greater than or equal to 0 and less than 0.5, optionally greater than or equal to 0 and less than or equal to 0.4, more preferably greater than or equal to 0 and less than or equal to 0.2, and even more preferably 0.

[0253] In some embodiments, the Mn molar ratio of the third lithium-containing transition metal phosphate material is greater than or equal to 0.02 and less than 0.5, optionally greater than or equal to 0.02 and less than or equal to 0.4, more preferably greater than or equal to 0.02 and less than or equal to 0.2, and even more preferably 0.02.

[0254] In some embodiments, the molar percentage of Mn in the third lithium-containing transition metal phosphate material is greater than or equal to 0.2 and less than 0.5, optionally greater than or equal to 0.2 and less than or equal to 0.4, and more preferably 0.2.

[0255] 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 is 30%-65%, the weight percentage of the second lithium transition metal phosphate material is 25%-67%, and the weight percentage of the third lithium transition metal phosphate material is 3%-10%.

[0256] In some implementations, the general formula for the first kernel includes Li m4 A4 a4 Fe x4 Mn y4 M4 b4 P z4 Q4 c4 O n4 N4 d4 ,

[0257] Where 0.8≤m4≤1.2, x4≥0, y4>0, 0.9≤x4+y4≤1, 0.95≤z4≤1.1, 3.5≤n4≤4, 0≤a4≤0.1, 0≤b4≤0.1, 0≤c4≤0.1, 0≤d4≤0.1,

[0258] The general formula for the composition of the second kernel includes Li m5 A5 a5 Fe x5 Mn y5 M5 b5 P z5Q5 c5 O n5 N5 d5 , 0.8≤m5≤1.2, x5≥0, y5≥0, 0.9≤x5+y5≤1, 0.95≤z5≤1.1, 3.5≤n5≤4, 0≤a5≤0.1, 0≤b5≤0.1, 0≤c5≤0.1, 0≤d5≤0.1,

[0259] The general formula for the composition of the third kernel includes Li m6 A6 a6 Fe x6 Mn y6 M6 b6 P z6 Q6 c6 O n6 N6 d6 ,

[0260] 0.8≤m6≤1.2, x6≥0, y6≥0, 0.9≤x6+y6≤1, 0.95≤z6≤1.1, 3.5≤n6≤4, 0≤a6≤0.1, 0≤b6≤0.1, 0≤c6≤0.1, 0≤d6≤0.1

[0261] Among them, A4, A5, and A6 each independently include one or more of Al, Na, K, and Mg; M4, M5, and M6 each independently include one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti; Q4, Q5, and Q6 each independently include one or more of B, S, Si, and N; and N4, N5, and N6 each independently include one or more of S, F, Cl, and Br.

[0262] [Positive electrode plate]

[0263] 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.

[0264] 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.

[0265] In some embodiments, the positive electrode film layer further includes a binder and a conductive agent.

[0266] In some embodiments, the mass ratio of the positive electrode active material, binder, and conductive agent in the positive electrode film layer is (92-99):(0.5-3):(0.5-3).

[0267] In some embodiments, the areal density of the positive electrode film is 300 mg / 1540 mm². 2-580mg / 1540mm 2 .

[0268] The areal density of the positive electrode film can be tested using methods known in the art. An example is as follows: Place the battery in a 40°C oven and let it stand for 2 hours. Once the battery temperature remains at 40°C, discharge the battery at a constant current of 1 / 3C to 2.0V. Disassemble the battery to obtain the positive electrode sheet. Treat the residual electrolyte with dimethyl carbonate solvent, dry the electrode sheet, and cut it 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.

[0269] 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.

[0270] In some embodiments, the compaction density of the positive electrode film is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0271] The compaction density of the positive electrode film can be tested using methods known in the art. As an example, the battery is placed in a 40°C oven environment and left to stand for 2 hours. Once the battery temperature is maintained at 40°C, the battery is discharged at a constant current of 1 / 3C to 2.0V. The battery is then disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S. The weight is recorded as W1, and the thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the weighed electrode sheet is wiped off, and the weight of the current collector is recorded as W2. The thickness T2 of the current collector is measured using a micrometer. The compaction density of the positive electrode film layer is then PD = (W1-W2) / [(T1-T2)×S].

[0272] 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 32.65g / cm 3 2.75g / cm 3 Or any value in between.

[0273] When the compaction density of the positive electrode sheet is within a suitable range, the battery has a superior volumetric energy density.

[0274] 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.).

[0275] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0276] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0277] 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.

[0278] [Negative electrode plate]

[0279] 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.

[0280] 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.

[0281] 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.).

[0282] 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.

[0283] 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).

[0284] 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.

[0285] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0286] 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.

[0287] [Electrolytes]

[0288] 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.

[0289] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0290] 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.

[0291] 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.

[0292] [Isolation membrane]

[0293] The separator used in this application is the separator described above. Furthermore, the separator used in this application can be used in combination with other separators commonly used in the art, as needed.

[0294] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0295] 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.

[0296] 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.

[0297] [Rechargeable Battery]

[0298] In one embodiment of this application, a secondary battery is provided, including a positive electrode, a separator, a negative electrode, and an electrolyte, wherein the binder in the active material layer of the positive electrode includes polymers according to any embodiment of this application.

[0299] In some embodiments, the secondary battery is a lithium-ion battery or a sodium-ion battery. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. A separator is disposed between the positive and negative electrode plates, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing ions to pass through.

[0300] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0301] 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.

[0302] 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.

[0303] 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.

[0304] 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. The positive electrode, negative electrode, and separator may 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.

[0305] 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.

[0306] 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.

[0307] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0308] 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.

[0309] Figures 5 and 6 show a battery pack 1 as an example. Referring to Figures 4 and 5, 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.

[0310] 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 the power source of the electrical device or as the energy storage unit of 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.

[0311] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0312] 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.

[0313] 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.

[0314] Example

[0315] 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.

[0316] Table 1: Performance parameters and grades of the first lithium-containing transition metal phosphate materials

[0317] Table 2: Performance parameters and grades of the second lithium-containing transition metal phosphate material

[0318] Table 3: Performance parameters and grades of the third lithium-containing transition metal phosphate materials

[0319] I. Preparation Method

[0320] Example 1

[0321] (1) Preparation of the positive electrode sheet:

[0322] The first lithium-containing transition metal phosphate material A1 and the second lithium-containing transition metal phosphate material B1 are mixed at a mass ratio of 60%:40% 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 at a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone is added. After thorough mixing, stirring, and dispersion, a positive electrode slurry is prepared.

[0323] 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.

[0324] (2) Preparation of negative electrode sheet:

[0325] Artificial graphite, conductive carbon black, styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener were mixed evenly in a weight percentage 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 coated on a copper foil substrate at a concentration of 211 mg / 1540 mm2. After drying, cold pressing, slitting, and sheet forming, a negative electrode sheet was obtained.

[0326] (3) Diaphragm

[0327] Polypropylene film is used as the separator.

[0328] (4) Electrolyte

[0329] 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.

[0330] (5) Battery fabrication:

[0331] 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.

[0332] Examples 2-12 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, the second lithium-containing transition metal phosphate, and / or the third lithium-containing transition metal phosphate in the positive electrode active material are adjusted, as follows:

[0333] Table 4

[0334] II. Testing Methods

[0335] 1. Battery fast charging performance test

[0336] At 25°C, the battery was charged at a constant current of 4C to the charging cutoff voltage of 4.1V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0.

[0337] Then, the battery is sequentially charged at a constant current of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until the full battery charging cutoff voltage of 4.1V or the negative terminal cutoff potential of 0V (whichever comes first). After each charging, it is discharged at 1C0 until the full battery discharge cutoff voltage of 2.0V. The state of charge (SOC) is recorded at different charging rates until it reaches 10%, 20%, 30%...80%. By plotting the negative electrode potential corresponding to the state of charge (SOC), rate-negative electrode potential curves are generated for different SOC states. Linear fitting yields the charging rate corresponding to a negative electrode potential of 0V at each SOC state. This charging rate is the charging window for that SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC. The charging time T from 10% SOC to 80% SOC is calculated using the formula (60 / C20%SOC + 60 / C30%SOC + 60 / C40%SOC + 60 / C50%SOC + 60 / C60%SOC + 60 / C70%SOC + 60 / C80%SOC) × 10%. A shorter charging time T indicates better fast-charging performance of the secondary battery.

[0338] 2. Battery storage performance

[0339] Place the battery in a 40℃ oven and let it stand for 2 hours until the battery temperature reaches 40℃. 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 1 / 3C to 4.1V, and then charge it at a constant voltage of 4.1V to a current of 0.05C. After standing for 5 minutes, discharge the battery at a constant current of 1 / 3C to 2.0V. This is one charge-discharge cycle. Record the discharge capacity C1 of the first cycle. Then, fully charge the battery and place it in a 60℃ environment. Periodically take out the battery and test the remaining capacity at 40℃ until the discharge capacity of the secondary battery decays to 80%. Record the storage time at this point.

[0340] 3. Volumetric energy density of the battery

[0341] 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.

[0342] 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).

[0343] 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.

[0344] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0345] Secondary batteries for each embodiment and comparative example were prepared according to the above method, and various parameters were measured. The results are shown in the table below.

[0346] Table 5

[0347] The positive electrode film layer in Embodiments 1-12 of this application includes a first type of particles and a second type of particles. The molar percentage of Mn in the first type of particles is greater than or equal to 0.5. The primary particle size of the second type of particles is greater than the average primary particle size of the first type of particles. The average molar percentage of Mn in the second type of particles is less than the average molar percentage of Mn in the first type of particles.

[0348] As can be seen from the comparison between Examples 1-12 and Comparative Examples 1-2, the positive electrode film layer of this application contains two types of particles, which can improve the specific capacity of the material, shorten the charging time of the battery, and improve the energy density and rate performance of the battery.

[0349] Table 6

[0350] As can be seen from the comparison between Examples 8-9 and Example 10, controlling the molar percentage of Mn in the second type of particles to 0%-10% can further improve the specific capacity of the material, increase the energy density of the battery, shorten the charging time of the battery, and improve the rate performance of the battery.

[0351] As can be seen from the comparison between Examples 9-10 and Example 8, controlling the molar percentage of Mn in the second type of particles to be 5%-50% can extend the storage time of the battery and improve the storage performance of the battery.

[0352] As can be seen from the comparison between Example 10 and Examples 8-9, controlling the molar percentage of Mn in the second type of particles to be 10%-50% can further extend the storage time and lifespan of the battery.

[0353] As can be seen from the comparison between Examples 8-9 and Example 10, the average molar ratio of Mn in the first type of particles is 0.6-0.9, which can further improve the energy density of the battery.

[0354] A comparison of Examples 1-3 and Example 4 shows that the average Mn molar ratio of the second type of particles is greater than or equal to 0 and less than or equal to 0.3, which can shorten the battery charging time, increase the battery storage time, and improve the battery storage performance and rate performance.

[0355] A comparison of Examples 2-4 with Example 1 shows that the average Mn molar ratio of the second type of particles is greater than or equal to 0.02 and less than 0.5, which can improve the energy density of the battery. A comparison of Examples 2-3 with Examples 1 and 4 shows that the average Mn molar ratio of the second type of particles is greater than or equal to 0.02 and less than or equal to 0.3, which can improve the energy density of the battery while also achieving short charging time and long storage life, resulting in a battery that balances good rate performance and storage performance.

[0356] As can be seen from the comparison between Examples 2-3 and Examples 1 and 4, the average Mn molar ratio of the second type of particles is greater than or equal to 0.1 and less than 0.3, which can improve the energy density of the battery while taking into account the short charging time and long storage life. The battery has both good rate performance and storage performance.

[0357] As shown in Examples 5-7, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 20%-85%, and the area ratio of the second type of particles is 15%-80%. The positive electrode active material exhibits high powder compaction density and specific capacity, resulting in a battery with short charging time, long storage life, and high volumetric energy density. Comparing Examples 6-7 with Example 5, it is evident that, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 20%-80%, and the area ratio of the second type of particles is 20%-80%. This further improves the powder compaction density and specific capacity of the material, increases the battery's energy density, shortens the battery's charging time, extends the battery's storage life, and improves the battery's rate performance and storage performance.

[0358] Table 7

[0359] As can be seen from the comparison between Example 11 and Example 1, the positive electrode film layer also includes a third type of particles, and the primary particle size of the third type of particles is smaller than the average primary particle size of the first type of particles. The average Mn molar ratio of the third type of particles is smaller than the average Mn molar ratio of the first type of particles. Based on the total area of ​​the primary particles of the positive electrode film layer, the area ratio of the third type of particles is greater than or equal to 5% and less than or equal to 30%, which can further improve the powder compaction density of the active material and improve the energy density of the battery.

[0360] As can be seen from the comparison between Example 12 and Example 11, the average value of the Mn molar ratio of the third type of particles is greater than or equal to 0.1 and less than or equal to 0.2, which can improve the energy density of the battery.

[0361] 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 secondary battery characterized by comprising: The positive electrode film layer comprises first type particles and second type particles, the first type particles and the second type particles comprise lithium-containing transition metal phosphate materials, The Mn molar ratio of the first type particles is 0.5-0.

9. The average value of the primary particle size of the first type particles is 120 nm-600 nm. The average value of the Mn molar ratio of the second type particles is greater than or equal to 0 and less than 0.5, which is optionally greater than or equal to 0 and less than or equal to 0.3, and is more optionally 0. The average value of the Mn molar ratio of the second type particles is greater than or equal to 0.02 and less than 0.5, which is optionally greater than or equal to 0.02 and less than or equal to 0.3, and is more optionally 0.

02. The average value of the Mn molar ratio of the second type particles is greater than or equal to 0.1 and less than 0.3, and is more optionally 0.

1. ​ 2. The secondary battery according to claim 1, characterized by ​ 3. The secondary battery according to claim 1 or 2, characterized by ​ 4. The secondary battery according to any one of claims 1 to 3, characterized by, ​ 5. The secondary battery according to any one of claims 1 to 3, characterized by ​ 6. The secondary battery according to any one of claims 1 to 3, characterized by ​ 7. The secondary battery according to any one of claims 1 to 6, characterized by, ​ 8. The secondary battery according to any one of claims 1 to 6, characterized by, ​ 9. The secondary battery according to any one of claims 1 to 6, characterized by, ​ 10. The secondary battery according to any one of claims 1 to 9, characterized by ​ 11. The secondary battery according to any one of claims 1 to 10, characterized by ​ 12. The secondary battery according to any one of claims 1 to 10, characterized by ​ 13. The secondary battery according to any one of claims 1 to 10, characterized by ​ 14. The secondary battery according to any one of claims 1 to 13, characterized by, The area percentage of the first type of particles is 20%-85%, optionally 20%-80%, more optionally 50%-80%, based on the total area of primary particles in the positive electrode film layer; and / or, the area percentage of the second type of particles is 15%-80%, optionally 20%-80%, more optionally 20%-50%, based on the total area of primary particles in the positive electrode film layer.

15. The secondary battery according to any one of claims 1 to 13, characterized by The positive electrode film layer comprises a third type of particles, the third type of particles comprising the lithium-containing transition metal phosphate material, The average value of the Mn molar percentage of the third type of particles is greater than or equal to 0 and less than 0.5, optionally 0-0.2, more optionally 0. The average value of the Mn molar percentage of the third type of particles is greater than or equal to 0 and less than 0.5, optionally 0-0.2, more optionally 0. The average value of the Mn molar percentage of the third type of particles is greater than or equal to 0 and less than 0.5, optionally 0-0.2, more optionally 0.

16. The secondary battery according to claim 15, characterized by The area percentage of the third type of particles is greater than or equal to 5% and less than or equal to 30%, based on the total area of primary particles in the positive electrode film layer.

17. The secondary battery according to claim 15, characterized by The average value of the Mn molar percentage of the third type of particles is 0.2%-12%, optionally 0.2%-8%, more optionally 0.2%-6%, further optionally 0.2%, based on the total number of moles of Mn in the primary particles in the positive electrode film layer.

18. The secondary battery according to claim 15, characterized by The average value of the Mn molar percentage of the third type of particles is 0.2%-12%, optionally 0.2%-8%, more optionally 0.2%-6%, further optionally 0.2%, based on the total number of moles of Mn in the primary particles in the positive electrode film layer.

19. The secondary battery according to any one of claims 15 to 18, characterized by, The average value of the Mn molar percentage of the third type of particles is 0.2%-12%, optionally 0.2%-8%, more optionally 0.2%-6%, further optionally 0.2%, based on the total number of moles of Mn in the primary particles in the positive electrode film layer.

20. The secondary battery according to any one of claims 15 to 18, characterized by The ratio of the average value of the Mn molar percentage of the third type of particles to the average value of the Mn molar percentage of the first type of particles is 0-0.8, optionally 0-0.4, more optionally 0.

21. The secondary battery according to any one of claims 15 to 18, characterized by The ratio of the average value of the Mn molar percentage of the third type of particles to the average value of the Mn molar percentage of the first type of particles is 0.0003-0.8, optionally 0.0003-0.4, more optionally 0.0003.

22. The secondary battery according to any one of claims 15 to 21, characterized by The ratio of the average value of the Mn molar percentage of the third type of particles to the average value of the Mn molar percentage of the first type of particles is 0.002-0.8, optionally 0.002-0.4, more optionally 0.

002.

23. The secondary battery according to any one of claims 15 to 21, characterized by The average value of the Mn molar percentage of the third type of particles is greater than or equal to 0 and less than 0.5, optionally 0-0.2, more optionally 0.

24. The secondary battery according to any one of claims 15 to 21, characterized by, The average value of the Mn molar percentage of the third type of particles is greater than or equal to 0.02 and less than 0.3, optionally 0.02-0.2, more optionally 0.

02.

25. The secondary battery according to any one of claims 15 to 24, characterized by, The average value of the Mn molar percentage of the third type of particles is greater than or equal to 0.1 and less than or equal to 0.2, optionally 0.

1.

26. The secondary battery according to any one of claims 1 to 25, characterized by The area percentage of the first type of particles is 45%-85%, the area percentage of the second type of particles is 10%-40%, and the area percentage of the third type of particles is 5%-15%, based on the total area of primary particles in the positive electrode film layer. The average value of the Mn molar percentage of the primary particles in the positive electrode film layer is 0.2-0.9, optionally 0.3-0.

8.

27. The secondary battery according to any one of claims 15 to 26, characterized by The composition general formula of the lithium-containing transition metal phosphate material of the first type of particles includes Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 , 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, The composition general formula of the lithium-containing transition metal phosphate material of the second type of particles includes 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 composition general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 A3 a3 Fe x3 Mn y3 M3 b3 P z3 Q3 c3 O n3 N2 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.

28. The secondary battery according to any one of claims 1 to 27, characterized by The positive electrode film layer includes a positive electrode active material, the positive electrode active material includes the lithium-containing transition metal phosphate material, and the powder compaction density of the positive electrode active material under a pressure of 29400 N is 2.40 g / cm 3 -2.65 g / cm 3 .

29. The secondary battery of claim 28, wherein The gram capacity of the positive electrode active material at 40℃ and 1 / 3C discharge rate is 135mAh / g-150mAh / g.

30. The secondary battery according to claim 28 or 29, characterized by The positive electrode film layer further comprises 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 film layer is (92-99):(0.5-3):(0.5-3).

31. The secondary battery according to any one of claims 1 to 30, characterized by The single-sided areal density of the positive electrode film layer is 300 mg / 1540 mm 2 - 580 mg / 1540 mm 2 .

32. The secondary battery according to any one of claims 1 to 31, characterized by The compacted density of the positive electrode film layer is 2.25 g / cm 3 - 2.75 g / cm 3 .

33. An electrical device, comprising: The electric device comprises the secondary battery of any one of claims 1-32.

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