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, wherein 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, wherein the first-type particles and the second-type particles comprise a lithium-containing transition metal phosphate material. The primary particle size of the first-type particles is greater than 180 nm and less than 900 nm, and the primary particle size of the second-type particles is greater than or equal to 900 nm and less than or equal to 5 μm. The average value of the molar ratio of Mn of the second-type particles is less than that of the molar ratio of Mn of the first-type particles, wherein the average value of the molar ratio of Mn of primary particles of the positive electrode film layer is 0.4-0.8, and the molar ratio of Mn refers to the proportion of the mole number of Mn to the total mole number of Mn and Fe.

Description

Secondary battery and power consuming device

[0001] Cross-reference to related applications

[0002] This application is based on the Chinese Patent Application No. 202411034956.3 filed on July 30, 2024, entitled “Secondary battery and power consuming device”, which is incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of secondary batteries, in particular to a secondary battery and a power consuming device. BACKGROUND

[0004] Secondary batteries have the advantages of high energy density, high working voltage, low self-discharge rate, small volume, and light weight, and have a wide range of applications.

[0005] At present, with the rapid development of electric vehicles and mobile electronic devices, people have increasingly high requirements for the energy density of secondary batteries. How to improve the energy density of batteries is a technical problem to be solved in the current application field of secondary batteries. SUMMARY

[0006] The present application is made in view of the above-mentioned problems, and aims to provide a secondary battery and a power consuming device, the secondary battery having a high energy density.

[0007] A first aspect of the present application provides a secondary battery, the secondary battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte,

[0008] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector,

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

[0010] The first particles have a primary particle size greater than 180 nm and less than 900 nm, and the second particles have a primary particle size greater than or equal to 900 nm and less than or equal to 5 μm,

[0011] The average value of the Mn molar fraction of the second particles is less than the average value of the Mn molar fraction of the first particles,

[0012] The average value of the Mn molar fraction of the primary particles in the positive electrode film layer is 0.4-0.8,

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

[0014] The positive electrode active material includes two types of particles with different primary particle sizes, which can realize the purpose of filling gaps by mutual cooperation of large and small particles, so that the particle accumulation in the positive electrode active material is more compact, the compaction density of the electrode sheet is improved, and the energy density of the battery is improved. However, the second type of particles has a relatively large primary particle size, which makes the migration path of lithium ions in the particles longer, resulting in an increase in discharge polarization and a decrease in specific capacity of the second type of particles, affecting the specific capacity of the material, and further affecting the energy density of the battery. The Mn molar ratio of the particles affects the conductivity of the particles. By controlling the average value of the Mn molar ratio of the second type of particles with a relatively large primary particle size to be less than the average value of the Mn molar ratio of the first type of particles with a relatively small primary particle size, the conductivity of the second type of particles with a relatively large primary particle size can be improved, the discharge polarization of the second type of particles can be alleviated, the specific capacity of the material can be improved, and the energy density of the battery can be further improved. At the same time, the Mn molar ratio of the primary particles in the film layer is controlled within a suitable range, so that the material has a high voltage platform and good conductivity, which is beneficial to obtain a high-energy-density battery.

[0015] In summary, the present application forms a compact accumulation of two types of particles with different particle sizes, and controls the Mn molar ratio between the two types of particles with different particle sizes, which achieves the purposes of improving the powder compaction density and specific capacity of the material, and improving the energy density of the battery.

[0016] In any embodiment, the average value of the Mn molar ratio of the first type of particles is 0.5-0.7.

[0017] The average value of the Mn molar ratio of the first type of particles is controlled within a suitable range, so that the first type of particles has a high platform capacity, and at the same time, the first type of particles also has a certain electrical conductivity, which is beneficial to the first type of particles to exert its specific capacity, achieves the purpose that the first type of particles can contribute sufficient capacity, and further improves the energy density of the battery.

[0018] In any embodiment, the average value of the Mn molar ratio of the second type of particles is less than or equal to 0.35, which can be 0.02-0.30.

[0019] The average value of the Mn molar ratio of the second type of particles is controlled within a suitable range, which can improve the conductivity of the second type of particles, improve the conductivity of the overall material, and be beneficial to the material to exert its specific capacity, and improve the energy density of the battery.

[0020] In any embodiment, based on the total area of the primary particles of the positive electrode film layer, the area ratio of the first type of particles is 60%-80%, and / or the area ratio of the second type of particles is 15%-35%.

[0021] The area proportions of the first type of particles and the second type of particles are within a suitable range, which can realize the gradation of the large and small particles, improve the compaction density of the material, and also fully play the role of the first type of particles with relatively high manganese content to provide platform capacity, and the role of the second type of particles with suitable content and high compaction density to improve the powder compaction density of the material, and reduce the influence of the second type of particles with large particle size on the conductivity and the specific capacity of the material, which is beneficial to obtain a high-energy-density battery.

[0022] In any embodiment, the positive electrode film layer comprises third type of particles, the third type of particles comprise lithium-containing transition metal phosphate material, the primary particle size of the third type of particles is 50-180 nm, and the average value of the Mn molar proportion of the third type of particles is less than the average value of the Mn molar proportion of the first type of particles.

[0023] The area proportion 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 the primary particles of the positive electrode film layer.

[0024] The third type of particles with a suitable area proportion and a smaller primary particle size can be filled into the pores between the first type of particles and the second type of particles, so that the filling between the materials is more compact, which can further improve the powder compaction density of the material and the compaction density of the pole piece, and is beneficial to obtain a high-energy-density battery. At the same time, by controlling the average value of the Mn molar proportion of the third type of particles to be less than the average value of the Mn molar proportion of the first type of particles, the degree of side reaction and manganese dissolution of the third type of particles with the electrolyte can be reduced, the cycle performance of the battery can be improved, and the energy density of the battery can be improved.

[0025] In any embodiment, the average value of the Mn molar proportion of the third type of particles is less than or equal to 0.1, and can be 0.02-0.1.

[0026] Controlling the average value of the Mn molar proportion of the third type of particles within a suitable range can reduce the possibility of side reaction and manganese dissolution of the third type of particles with the electrolyte, improve the structural stability of the third type of particles, improve the cycle performance of the battery, and is beneficial to improve the energy density of the battery.

[0027] In any embodiment, the area proportion of the first type of particles is 45%-85%, the area proportion of the second type of particles is 10%-40%, and the area proportion of the third type of particles is 5%-15% based on the total area of the primary particles of the positive electrode film layer.

[0028] The area proportion of the particles of different particle sizes is controlled within a proper range, so that the first type of particles with high manganese content can achieve the purpose of contributing to the energy density of the flat pressure capacity and gram capacity, and the influence of the second type of particles with large particle size on the conductivity of the material and the influence of the third type of particles with small particle size on the stability of the material are reduced, which is beneficial to improve the energy density of the battery.

[0029] In any embodiment, 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 ,

[0030] wherein 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,

[0031] 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,

[0032] 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 ,

[0033] 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,

[0034] 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.

[0035] In any embodiment, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing transition metal phosphate material, and the positive electrode active material has a powder compaction density of 2.40 g / cm3 or more at a pressure of 29400 N. 3 -2.60 g / cm3 3 .

[0036] In any embodiment, the positive electrode active material has a gravimetric capacity of 140 mAh / g to 150 mAh / g at 40°C and a discharge rate of 1 / 3 C.

[0037] A second aspect of the present application provides a power consumption device comprising the secondary battery of the first aspect. BRIEF DESCRIPTION OF DRAWINGS

[0038] FIG. 1 is a schematic view of a longitudinal cross-section of a positive electrode sheet according to an embodiment of the present application;

[0039] FIG. 2 is a schematic view of a statistical distinguishing rule for primary particles in a transmission electron microscope image of particles according to an embodiment of the present application;

[0040] FIG. 3 is a schematic view of a secondary battery according to an embodiment of the present application;

[0041] FIG. 4 is an exploded view of the secondary battery according to an embodiment of the present application shown in FIG. 3;

[0042] FIG. 5 is a schematic view of a battery module according to an embodiment of the present application;

[0043] FIG. 6 is a schematic view of a battery pack according to an embodiment of the present application;

[0044] FIG. 7 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 6;

[0045] FIG. 8 is a schematic view of a power consumption device using the secondary battery according to an embodiment of the present application as a power source.

[0046] Reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 case; 52 electrode assembly; 53 cover plate; 10 positive electrode tab; 110 positive electrode current collector; 120 positive electrode film layer; 1210 first type of particle; 1220 second type of particle. DETAILED DESCRIPTION

[0047] Hereinafter, specific embodiments of the secondary battery and the electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters well known in the art, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0048] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing all the arbitrary real number combinations between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all the real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] If not specifically stated, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0050] If not specifically stated, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0051] If not specified otherwise, all of the steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method further comprising step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0052] If not specified otherwise, the terms "comprising" and "including" mentioned in the present application mean open-ended, and can also mean closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed can also be included, or can mean that only the listed components are included.

[0053] If not specified otherwise, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0054] The positive active material is one of the decisive factors of the performance of the secondary battery. At present, the common positive active materials mainly include lithium cobaltate, lithium manganate, nickel-cobalt-manganese ternary material, and lithium iron phosphate, etc. These materials each have advantages and disadvantages. For example, lithium cobaltate has a high energy density and voltage platform, but has a high cost and poor safety; lithium manganate has a low cost and good safety, but has a low energy density and voltage platform; the nickel-cobalt-manganese ternary material combines the advantages of the former two, but still has a high cost. Lithium iron phosphate has the advantages of low cost, high safety, long life, etc., and 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 tap density and low discharge capacity, which limit its application in high energy density batteries. Lithium manganese iron phosphate, as a new type of material developed from lithium iron phosphate, combines the advantages of manganese and iron elements, has two voltage platforms at 4.1V and 3.4V, respectively, can provide a certain platform capacity, and is expected to improve the disadvantages of lithium iron phosphate material. However, in the current research and application process, lithium manganese iron phosphate still has a low tap density and does not exhibit the potential advantage of high energy density. The presence of manganese elements also affects the conductivity of lithium manganese iron phosphate, affects the development of the material's specific capacity, affects the energy density of the battery, and cannot meet the practical needs. Therefore, how to improve the tap density and specific capacity of the positive active material powder and obtain a high energy density battery has become a key point of research.

[0055] [Secondary battery]

[0056] Based on this, the application provides a secondary battery, the secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte,

[0057] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector.

[0058] The positive electrode film layer comprises first type particles and second type particles, and the first type particles and the second type particles comprise lithium-containing transition metal phosphate materials.

[0059] The primary particle size of the first type particles is greater than 180 nm and less than 900 nm, and the primary particle size of the second type particles is greater than or equal to 900 nm and less than or equal to 5 μm.

[0060] The average value of the Mn molar ratio of the second type particles is less than the average value of the Mn molar ratio of the first type particles.

[0061] The average value of the Mn molar ratio of the primary particles in the positive electrode film layer is 0.4-0.8.

[0062] 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.

[0063] In some embodiments, the average value of the Mn molar ratio of the primary particles in the positive electrode film layer can be 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.

[0064] As shown in FIG. 1, the positive electrode sheet 10 comprises a positive electrode current collector 110 and a positive electrode film layer 120 arranged on at least one side of the positive electrode current collector, and the positive electrode film layer comprises first type particles 1210 and second type particles 1220.

[0065] In this document, the term “primary particle size” refers to the particle size of a primary particle.

[0066] Primary particles refer to the single particles that can be distinguished after the transmission electron microscopy (TEM) images of the particles are recognized by general professional software (for example, spectrum see; Avizo 3D) and confirmed, or that can be distinguished after artificial recognition or artificial aided calibration. Specifically, in order to determine the primary particles, the particles contained in the positive electrode film layer are subjected to enrichment and / or dispersion treatment, and then imaged under a transmission electron microscope. The imaged picture can be directly subjected to particle recognition by software (according to parameters such as gray scale and / or contrast / brightness), and the single particles that can be distinguished after recognition are primary particles. The imaged picture can also be directly subjected to artificial recognition, and the single particles that can be distinguished after recognition are primary particles. The imaged picture can also be directly subjected to software recognition combined with artificial aided calibration recognition, and the single particles that can be distinguished after recognition are primary particles. More specifically, the particles in the transmission electron microscope field of view form particles with clear boundaries that can be clearly distinguished from each other, and the single particles can be directly confirmed by software recognition or artificial recognition. However, some particles may be adhered and stacked to a certain extent in the transmission electron microscope field of view after dispersion treatment. For the adhered and stacked particles, the single particles that can be distinguished after recognition by software (according to parameters such as gray scale / contrast / brightness) are counted as primary particles. More accurately, for the particles that are adhered and stacked to a certain extent in the transmission electron microscope field of view, the single particles that can be distinguished after recognition by software according to parameters such as gray scale / contrast / brightness are subjected to artificial aided calibration according to certain rules by artificial recognition, and the single particles that can be distinguished after calibration are counted as primary particles. If the artificial calibration results are not uniform, the results obtained by 3 or 5 or 7 persons who are unaware of each other and separately calibrate the same imaging results according to the rules exemplified below are counted as the number of primary particles. The transmission electron microscopy images of the particles of the positive electrode film layer in Example 1 in FIG. 2 are taken as an example to further illustrate the distinction in the primary particle number and area statistical process. FIG. 2-a is the original transmission electron microscopy image, FIG. 2-b is the software recognition image of the image, and FIG. 2-c is an example of software recognition and / or artificial recognition of the independent particles, adhered particles and stacked particles in FIG. 2-a. The particles 1 and 2 in FIG. 2-c are distinguishable independent particles, which are primary particle 1 and primary particle 2, respectively. The particles 3 and 4 in FIG. 2-c are adhered, and the particles 5, 6 and 7 are adhered. After software recognition or artificial recognition, they are determined as primary particle 3, primary particle 4, primary particle 5, primary particle 6 and primary particle 7. The particles 8 and 9 stacked together are finally determined as primary particle 8 and primary particle 9, instead of being determined as one particle. FIG. 2-d is another example of software recognition and / or artificial recognition of the particles with stacking in FIG. 2-a. The particles 10-14 stacked together are finally determined as primary particle 10, 11, 12, 13 and primary particle 14, instead of being determined as one particle.In selecting the transmission electron microscope field of view, the number of stacked particles in the selected field of view accounts for less than 20% of the total number of particles (the total number of independent particles, adhered particles and stacked particles), more preferably the number of stacked particles in the selected field of view accounts for less than 15% of the total number of particles (the total number of independent particles, adhered particles and stacked particles), and further preferably the number of stacked particles in the selected field of view accounts for less than 10% of the total number of particles (the total number of independent particles, adhered particles and stacked particles).

[0067] The test method for the average value of the Mn molar percentage of the first type of particles and the average value of the Mn molar percentage of the second type of particles can be performed by methods and equipment known in the art, for example as follows: disassemble the battery to obtain a positive electrode sheet, peel off the positive electrode film layer of the positive electrode sheet, 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 a powder. 0.05 g of the uniformly mixed powder is dissolved in 40 ml of anhydrous ethanol, then an appropriate amount of dispersant is added, stirred uniformly to obtain a suspension, 2 ml of the suspension and 2 ml of anhydrous ethanol are mixed and then subjected to ultrasonic treatment, the ultrasonic power is 480 W, the ultrasonic time is 5 min, and a uniformly dispersed suspension is obtained, an appropriate amount of the middle layer suspension is subjected to transmission electron microscope testing, the projected area of each primary particle in the transmission electron microscope image is counted according to the definition of the primary particle, i.e. the cross-sectional area S of the primary particle, the equivalent circle diameter of the primary particle is obtained by the equivalent circle method, i.e. the primary particle size d of the primary particle, and in the above process of counting the primary particles and their primary particle sizes, the primary particles with a primary particle size less than 50 nm and greater than 5 μm are not included in the statistical range (i.e. the primary particles with a primary particle size greater than or equal to 50 nm and less than or equal to 5 μm are effective particles). The molar contents of Mn and Fe in each effective particle in the transmission electron microscope image can be tested by EDS point scanning, i.e. the molar percentage X of Mn in each effective particle can be calculated (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), and the test point is the middle part of the transmission surface of each particle. The transmission electron microscope and EDS test in different test areas are performed multiple times, at least 500 effective particles are tested for cross-sectional area S, primary particle size d and molar percentage X of Mn, then the effective particles obtained by testing are numbered 1, 2, 3, 4, 5…n according to the primary particle size from small to large, and the total number of particles is n. The mth is a particle with a primary particle size less than or equal to 180 nm, the m+1th is a particle with a primary particle size greater than 180 nm, the k-1th is a particle with a primary particle size less than 900 nm, and the kth is a particle with a primary particle size greater than or equal to 900 nm, then the m+1th to k-1th are the first type of particles, and the kth to nth are the second type of particles, when the primary particle size of the particle numbered 1 is greater than 180 nm, i.e. the particle numbered 1 to k-1 are the first type of particles, and the kth to nth are the second type of particles, at this time m is 0,

[0068] The average value of the mole fraction of Mn of the first type of particles is calculated by the formula:

[0069] The average value of the mole fraction of Mn of the second type of particles is calculated by the formula:

[0070] The average value of the mole fraction of Mn of the primary particles in the positive electrode film layer is calculated by the formula:

[0071] wherein Xi represents the mole fraction of Mn of the particle numbered i, and Si represents the cross-sectional area of the particle numbered i.

[0072] The positive electrode active material includes two types of particles with different primary particle sizes, which can achieve the purpose of filling gaps by mutual cooperation of large and small particles, so that the particles in the positive electrode active material are more densely packed, the powder compaction density of the material and the compaction density of the electrode sheet are improved, and the energy density of the battery is further improved. However, the second type of particles has a relatively large primary particle size, which makes the migration path of lithium ions in the particles longer, resulting in an increase in discharge polarization and a decrease in specific capacity of the second type of particles, affecting the performance of the material specific capacity, and further affecting the energy density of the battery. The mole fraction of Mn of the particles will affect the conductivity of the particles. By controlling the average value of the mole fraction of Mn of the second type of particles with a relatively large primary particle size to be less than the average value of the mole fraction of Mn of the first type of particles with a relatively small primary particle size, the conductivity of the second type of particles with a relatively large primary particle size can be improved, the discharge polarization of the second type of particles can be alleviated, the performance of the material specific capacity can be improved, and the energy density of the battery can be improved. At the same time, the mole fraction of Mn in the first type of particles with a relatively small primary particle size is relatively high, which can improve the platform capacity of the first type of particles while maintaining good conductivity of the particles, which is beneficial to improving the energy density of the battery. At the same time, the mole fraction of Mn of the primary particles in the film layer is controlled within a suitable range, so that the material has a high voltage platform and good conductivity, which is beneficial to obtaining a high energy density battery.

[0073] In summary, by using two types of particles with different particle sizes to form a tight packing, and controlling the mole fraction of Mn between the two types of particles with different particle sizes, the powder compaction density and specific capacity of the material can be improved, and the energy density of the battery can be improved.

[0074] In some embodiments, the average value of the mole fraction of Mn of the first type of particles is 0.5-0.7. In some embodiments, the average value of the mole fraction of Mn of the first type of particles can be selected from 0.4, 0.45, 0.50, 0.55, 0.6, 0.65, 0.7, or a range between any two of the above values.

[0075] The average value of the Mn molar ratio of the first type of particles is controlled to be within a suitable range, so that the first type of particles has a high platform capacity, while also ensuring that the first type of particles have a certain conductivity, which is conducive to the first type of particles to exert its gravimetric capacity and platform capacity, to achieve the purpose of the first type of particles to provide capacity, and to improve the energy density of the battery.

[0076] In some embodiments, the average value of the Mn molar ratio of the second type of particles is less than or equal to 0.35.

[0077] In some embodiments, the average value of the Mn molar ratio of the second type of particles can be 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, or a range between any two of the above values.

[0078] Controlling the average value of the Mn molar ratio of the second type of particles within a suitable range can improve the conductivity of the second type of particles and the overall material, which is conducive to the exertion of the gravimetric capacity of the material and improves the energy density of the battery.

[0079] In some embodiments, the average value of the Mn molar ratio of the second type of particles is 0.02-0.6, which can be 0.02-0.2, and more preferably 0.02.

[0080] In some embodiments, the average value of the Mn molar ratio of the second type of particles is 0.02-0.30.

[0081] In some embodiments, the average value of the Mn molar ratio of the second type of particles can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.30, or a range between any two of the above values.

[0082] Controlling the average value of the Mn molar ratio of the second type of particles within a suitable range can improve the conductivity of the second type of particles and the overall material, which is conducive to the exertion of the gravimetric capacity of the material and improves the energy density of the battery.

[0083] In some embodiments, the area ratio of the first type of particles is 60-80%, and / or the area ratio of the second type of particles is 15-35%, based on the total area of primary particles of the positive electrode film layer.

[0084] In some embodiments, the area ratio of the first type of particles is 60%, 65%, 70%, 75%, 80%, or a range between any two of the above values, based on the total area of primary particles of the positive electrode film layer.

[0085] In some embodiments, the area ratio of the second type of particles is 15%, 20%, 25%, 30%, 35%, or a range between any two of the above values, based on the total area of primary particles of the positive electrode film layer.

[0086] The testing method of the area ratio of the first type of particles and the area ratio of the second type of particles can be performed by methods and devices known in the art, for example, as follows: referring to the aforementioned testing method of the average value of the Mn molar ratio of the second type of particles, the cross-sectional area S of each particle is determined,

[0087] The calculation formula of the area ratio of the first type of particles is:

[0088] The calculation formula of the area ratio of the second type of particles is

[0089] wherein, Si and Sj represent the cross-sectional area of particles numbered i and j, respectively.

[0090] The area ratios of the first type of particles and the second type of particles within a suitable range can achieve the gradation of large and small particles, improve the powder compaction density of the material and the compaction density of the electrode sheet, and also fully exert the purpose of the first type of particles with relatively high manganese content to provide platform capacity, and reduce the influence of the second type of particles with large particle size on the conductivity and specific capacity of the material, which is beneficial to obtain a battery with high energy density.

[0091] In some embodiments, the positive electrode film layer comprises a third type of particles, the third type of particles comprise the lithium-containing transition metal phosphate material, the primary particle size of the third type of particles is 50-180 nm, and the average value of the Mn molar ratio of the third type of particles is less than the average value of the Mn molar ratio of the first type of particles,

[0092] wherein, the area ratio 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 of the positive electrode film layer.

[0093] The determination of the third type of particles and the test method of the area ratio thereof can be carried out by methods and devices known in the art, for example as follows: referring to the test method of the average value of the Mn molar ratio of the second type of particles defined as the first particle to the m-th particle, the calculation formula of the area ratio of the third type of particles is

[0094] wherein Si and Sj represent the cross-sectional area of the particle numbered i and j respectively.

[0095] In some embodiments, the area ratio of the third type of particles can be selected from 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 a range between any two of the above values, based on the total area of the primary particles of the positive electrode film layer.

[0096] The test method of the average value of the Mn molar ratio of the third type of particles refers to the test method of the average value of the Mn molar ratio of the second type of particles,

[0097] The calculation formula of the average value of the Mn molar ratio of the third type of particles is

[0098] wherein Xi represents the Mn molar ratio of the particle numbered i, and Si represents the cross-sectional area of the particle numbered i.

[0099] The third type of particles with a smaller primary particle size and a suitable area ratio can fill into the pores between the first type of particles and the second type of particles, making the filling between the materials more compact, further improving the powder compacting density of the material, improving the compacting density of the electrode sheet, and being beneficial to obtaining a high-energy-density battery. However, the third type of particles with an ultra-small particle size have a large specific surface area, and the surface activity increases significantly, which is more likely to contact the electrolyte and cause side reactions, exacerbate manganese dissolution, and thus affect the cycle performance and energy density of the battery. By controlling the average value of the Mn molar ratio of the third type of particles to be less than the average value of the Mn molar ratio of the first type of particles, the degree of side reactions and manganese dissolution of the third type of particles with the electrolyte is reduced, the cycle stability of the material is improved, the cycle performance of the battery is improved, and the energy density of the battery is further improved.

[0100] In summary, by forming a compact packing of three types of particles with different particle sizes and controlling the Mn molar ratio among the three types of particles with different particle sizes, the powder compacting density, the gravimetric capacity, and the structural stability of the material are improved, and the energy density of the battery is effectively improved.

[0101] In some embodiments, the average value of the mole fraction of Mn of the third type of particles is less than or equal to 0.1.

[0102] In some embodiments, the average value of the mole fraction of Mn of the third type of particles is 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, or a range between any two of the aforementioned values.

[0103] Controlling the average value of the mole fraction of Mn of the third type of particles within a suitable range can reduce the possibility of side reactions and manganese dissolution of the third type of particles with the electrolyte, improve the cycle stability of the third type of particles, improve the structural stability of the material, improve the cycle performance of the battery, and improve the energy density of the battery.

[0104] In some embodiments, the average value of the mole fraction of Mn of the third type of particles is 0.02-0.1.

[0105] In some embodiments, the average value of the mole fraction of Mn of the third type of particles is 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or a range between any two of the aforementioned values.

[0106] Controlling the average value of the mole fraction of Mn of the third type of particles within a suitable range can improve the structural stability of the third type of particles and the material, enable the third type of particles with excellent electrical conductivity to have a certain voltage plateau, fully exert the specific capacity of the third type of particles, and further improve the energy density of the battery.

[0107] In some embodiments, based on the total area of primary particles of the positive electrode film layer, the area fraction of the first type of particles is 45%-85%, the area fraction of the second type of particles is 10%-40%, and the area fraction of the third type of particles is 5%-15%.

[0108] In some embodiments, the area percentage of the first type of particles can be 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 a range between any two of the above values, based on the total area of primary particles of the positive electrode film layer.

[0109] In some embodiments, the area percentage of the second type of particles can be 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 a range between any two of the above values, based on the total area of primary particles of the positive electrode film layer.

[0110] In some embodiments, the area percentage of the third type of particles can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range between any two of the above values, based on the total area of primary particles of the positive electrode film layer.

[0111] Controlling the area percentage of particles of different particle sizes within a suitable range can achieve the purpose of contribution of the flat-press capacity of the first type of particles with high manganese content to the energy density, while also reducing the influence of the second type of particles with large particle size on the conductivity of the material and reducing the influence of the third type of particles with small particle size on the stability of the material, which is beneficial to improving the energy density of the battery.

[0112] In some embodiments, the composition general formula of the lithium-containing transition metal phosphate material of the first type of particles comprises Li m1 A1 a1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 ,

[0113] wherein 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,

[0114] 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,

[0115] 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 ,

[0116] 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,

[0117] wherein, A1, A2, A3 each independently includes one or more of Al, Na, K, Mg, M1, M2, M3 each independently includes one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, Q1, Q2, Q3 each independently includes one or more of B, S, Si, N, N1, N2, N3 each independently includes one or more of S, F, Cl, Br.

[0118] In some embodiments, m1, m2 and m3 each independently can 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 number in a range between any two of the above values.

[0119] In some embodiments, 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 defined by any two of the foregoing.

[0120] In some embodiments, 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 defined by any two of the foregoing.

[0121] In some embodiments, 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 defined by any two of the foregoing.

[0122] In some embodiments, 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 defined by any two of the foregoing.

[0123] The selection of appropriate modification elements M1, M2, M3 can improve the lattice change rate of the material during lithium extraction, improve the structural stability of the material, reduce the dissolution of manganese, and reduce the oxygen activity on the surface of the particles, thereby improving the specific capacity of the material, improving the energy density of the battery, and reducing the interface side reaction between the material and the electrolyte during use, thereby improving the cycle performance and storage performance of the material.

[0124] The selection of appropriate modification elements Q1, Q2, Q3 can help change the difficulty of the Mn-O bond length change, thereby improving the electronic conductivity and reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the rate performance of the secondary battery.

[0125] The selection of appropriate modification elements A1, A2, A3 can also improve the lattice change rate of the material and maintain the battery capacity of the material.

[0126] The modification elements N1, N2, N3 can help improve the interface side reaction between the material and the electrolyte, reduce the interface activity, thereby improving the cycle performance of the positive electrode active material, etc. In addition, the performance of the material in resisting acid corrosion such as HF can also be improved, thereby improving the cycle performance and storage life of the material.

[0127] In the present text, the modifying elements M1, M2, M3, Q1, Q2, Q3, A1, A2, A3, N1, N2, N3may be present in the lithium-containing transition metal phosphate material in the form of a doping element, but also in the form of a coating element in a coating layer of the material.

[0128] In some embodiments, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprising the lithium-containing transition metal phosphate material, the positive electrode active material having a powder compaction density at 29400 N pressure of 2.40 g / cm3 3 2.60 g / cm3 3 .

[0129] In some embodiments, the positive electrode active material has a powder compaction density at 29400 N pressure of 2.40 g / cm3 3 2.41 g / cm3 3 2.42 g / cm3 3 2.43 g / cm3 3 2.44 g / cm3 3 2.45 g / cm3 3 2.46 g / cm3 3 2.47 g / cm3 3 2.48 g / cm3 3 2.49 g / cm3 3 2.50 g / cm3 3 2.51 g / cm3 3 2.52 g / cm3 3 2.53 g / cm3 3 2.54 g / cm3 3 2.55 g / cm3 3 2.56 g / cm3 3 2.57 g / cm3 3 2.58 g / cm3 3 2.59 g / cm3 3 2.60 g / cm3 3 , or a range between any two of the above values.

[0130] The powder compaction density of the positive electrode active material under a pressure of 29400 N can be performed by methods and equipment known in the art, for example as follows: place the battery in a 25°C oven environment, stand for 2 h, and when the battery temperature is maintained at 25°C, discharge the battery at 1 / 3C constant current to 2.0V, disassemble the battery, obtain the positive electrode sheet, peel off the positive electrode film layer, and wash with acetone to remove the binder in the positive electrode film layer; dry to obtain powder for subsequent characterization tests. Subsequent characterization can be performed according to GB / T 24533-2009 using a compaction density instrument. Specifically, a certain amount of the above-prepared powder is placed on a compaction special mold (the mold diameter is known), and the mold has a metal disc on both the upper and lower hollow centers. The powder is placed between the metal discs, and a metal cylinder is placed on top. The mold is placed on the compaction density instrument, and the pressure is set to 29400 N. The thickness of the powder under a pressure of 29400 N can be read on the instrument, and the powder compaction density of the material is p = m / v, where v = (S x 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 equipment model of the compaction density instrument is UTM7305, and the equipment manufacturer is Systerm.

[0131] The greater the powder compaction density, the higher the mass of the powder material per unit volume. When the powder compaction density of the material is in an appropriate range, the positive electrode sheet has a higher compaction density during cold pressing, which is beneficial to further improving the volume energy density of the battery.

[0132] In some embodiments, the gram capacity of the positive electrode active material under a discharge rate of 1 / 3 at 40°C is 140-150 mAh / g. In some embodiments, the gram capacity of the positive electrode active material under a discharge rate of 1 / 3C at 40°C can be selected to be 140 mAh / g, 145 mAh / g, 150 mAh / g, or a range between any two of the above values.

[0133] The gram capacity of the positive electrode active material can be carried out by methods and devices known in the art, for example as follows: place the battery in a 40℃ oven environment, stand for 2h, and wait for the battery temperature to remain 40℃; then discharge the battery at 1 / 3C constant current to 2.0V; stand for 5min; after charging the battery to 4.1V at 1 / 3C constant current, charge to the cut-off current of 0.05C at 4.1V constant voltage; stand for 5min; discharge the battery at 1 / 3C constant current 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 to obtain a positive electrode sheet with an area of S2, separate the positive electrode film layer on the positive electrode sheet from the current collector, dissolve it in acetone, wash thoroughly to remove residual solvents and binders, etc., and then filter, dry to obtain a 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), and the gram capacity of the positive electrode active material = the discharge capacity C of the battery / the mass M1 of the positive electrode active material.

[0134] [Preparation method of positive electrode active material]

[0135] The application also provides a preparation method of a positive electrode active material:

[0136] mixing a first lithium-containing transition metal phosphate material and a second lithium-containing transition metal phosphate material to obtain a lithium-containing transition metal phosphate material,

[0137] The first lithium-containing transition metal phosphate material comprises a first inner core and a first carbon coating layer coated on the outer surface of the first inner core, and the second lithium-containing transition metal phosphate material comprises a second inner core and a second carbon coating layer coated on the outer surface of the second inner core,

[0138] The primary average particle size of the first lithium-containing transition metal phosphate material is smaller than the primary average particle size of the second lithium-containing transition metal phosphate material,

[0139] The Mn molar proportion of the second lithium-containing transition metal phosphate material is smaller than the Mn molar proportion of the first lithium-containing transition metal phosphate material,

[0140] The primary average particle size of the first lithium-containing transition metal phosphate material is 120nm-600nm,

[0141] The primary average particle size of the second lithium-containing transition metal phosphate material is 250nm-4000nm.

[0142] The method for testing the Mn molar ratio of the first lithium-containing transition metal phosphate material and the second lithium-containing transition metal phosphate material can be performed by a method and equipment known in the art, for example, as follows: referring to the method for chemical analysis of nano lithium iron phosphate in the national standard GB T33822-2017 to test the molar content of Mn element and Fe element, and then calculating the Mn molar ratio of the material.

[0143] The method for testing the primary average particle size of the first lithium-containing transition metal phosphate material and the second lithium-containing transition metal phosphate material can be performed by a method and equipment known in the art, for example, as follows: 0.05 g of the material to be tested is dissolved in 40 ml of anhydrous ethanol, and then an appropriate amount of dispersant is added, and the mixture is stirred uniformly to obtain a suspension, 2 ml of the suspension and 2 ml of anhydrous ethanol are mixed, and then ultrasonic treatment is performed, the ultrasonic power is 480 W, and the ultrasonic time is 5 min, to obtain a uniformly dispersed suspension, an appropriate amount of the middle layer of the suspension is taken for transmission electron microscopy testing, the projected area of each primary particle in the transmission electron microscopy image is counted according to the definition of the primary particle described above, that is, the cross-sectional area S of the primary particle, and the equivalent circle diameter of the primary particle is obtained by using the equivalent circle method, that is, the primary particle size d of the primary particle, in the above process of counting the primary particles and the primary particle sizes, the primary particles with a primary particle size less than 50 nm are not counted in the statistical range (that is, the primary particles with a primary particle size greater than or equal to 50 nm are effective particles). The cross-sectional area S and the primary particle size d of at least 500 effective particles are tested, and the primary average particle size of the material to be tested = the sum of the primary particle sizes of all primary particles / the number of all primary particles.

[0144] In some embodiments, the Mn molar ratio of the first lithium-containing transition metal phosphate material is 0.4-0.9, which can be 0.5-0.9.

[0145] In some embodiments, the Mn molar ratio of the second lithium-containing transition metal phosphate material is 0-0.6, which can be 0-0.4, and more preferably 0.

[0146] In some embodiments, the Mn molar ratio of the second lithium-containing transition metal phosphate material is 0.02-0.6, which can be 0.02-0.4, and more preferably 0.02.

[0147] In some embodiments, the Mn molar ratio of the second lithium-containing transition metal phosphate material is 0.2-0.6, which can be 0.2-0.4, and more preferably 0.2.

[0148] In some embodiments, the first lithium-containing transition metal phosphate material has a weight percentage of 50%-95%, optionally 65%-90%, more optionally 70%-80%, and the second lithium-containing transition metal phosphate material has a weight percentage of 5%-50%, optionally 10%-35%, more optionally 20%-30%, based on the total weight of the lithium-containing transition metal phosphate material.

[0149] In some embodiments, the method for preparing the positive active material comprises:

[0150] mixing a first lithium-containing transition metal phosphate material, a second lithium-containing transition metal phosphate material, and a third lithium-containing transition metal phosphate material to obtain the lithium-containing transition metal phosphate material,

[0151] wherein the first lithium-containing transition metal phosphate material comprises a first inner core and a first carbon coating layer coated on the outer surface of the first inner core, and the second lithium-containing transition metal phosphate material comprises a second inner core and a second carbon coating layer coated on the outer surface of the second inner core,

[0152] the primary average particle size of the first lithium-containing transition metal phosphate material is smaller than the primary average particle size of the second lithium-containing transition metal phosphate material,

[0153] the Mn molar percentage of the second lithium-containing transition metal phosphate material is smaller than the Mn molar percentage of the first lithium-containing transition metal phosphate material,

[0154] wherein the primary average particle size of the first lithium-containing transition metal phosphate material is 120 nm-600 nm,

[0155] the primary average particle size of the second lithium-containing transition metal phosphate material is 250 nm-4000 nm,

[0156] the third lithium-containing transition metal phosphate material comprises a third inner core and a third carbon coating layer coated on the outer surface of the third inner core,

[0157] the primary average particle size of the third lithium-containing transition metal phosphate material is smaller than the primary average particle size of the first lithium-containing transition metal phosphate material,

[0158] the Mn molar percentage of the third lithium-containing transition metal phosphate material is smaller than the Mn molar percentage of the first lithium-containing transition metal phosphate material,

[0159] wherein the primary average particle size of the third lithium-containing transition metal phosphate material is 50 nm-200 nm.

[0160] In some embodiments, the third lithium-containing transition metal phosphate material has a Mn molar fraction of 0-0.6, optionally 0-0.4, optionally 0-0.2, more optionally 0.

[0161] In some embodiments, the third lithium-containing transition metal phosphate material has a Mn molar fraction of 0.02-0.6, optionally 0.02-0.4, optionally 0.02-0.2, more optionally 0.02.

[0162] In some embodiments, the third lithium-containing transition metal phosphate material has a Mn molar fraction of 0.02-0.6, optionally 0.02-0.4, optionally 0.02-0.2, more optionally 0.02.

[0163] In some embodiments, the first lithium-containing transition metal phosphate material has a weight percentage of 60%-90%, optionally 65%-80%, more optionally 70%-80%, the second lithium-containing transition metal phosphate material has a weight percentage of 5%-30%, optionally 10%-30%, more optionally 20%-30%, and the third lithium-containing transition metal phosphate material has a weight percentage of 1%-10%, optionally 2%-8%, more optionally 3%-7%, based on the total weight of the lithium-containing transition metal phosphate material.

[0164] In some embodiments, the first inner core has a general formula of Li m4 A4 a4 Fe x4 Mn y4 M4 b4 P z4 Q4 c4 O n4 N4 d4 ,

[0165] wherein 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,

[0166] The second inner core has a general formula of Li m5 A5 a5 Fe x5 Mn y5 M5 b5 P z5 Q5 c5 O n5 N5 d50.8 < 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,

[0167] The general formula of the third core comprises Li m6 A6 a6 Fe x6 Mn y6 M6 b6 P z6 Q6 c6 O n6 N6 d6 ,

[0168] 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,

[0169] wherein A4, A5, A6 each independently comprises one or more of Al, Na, K, Mg, M4, M5, M6 each independently comprises one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, Q4, Q5, Q6 each independently comprises one or more of B, S, Si, N, N4, N5, N6 each independently comprises one or more of S, F, Cl, Br.

[0170] [positive electrode tab]

[0171] The positive electrode tab comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material.

[0172] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0173] In some embodiments, the positive electrode film layer further comprises a binder and a conductive agent.

[0174] In some embodiments, 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).

[0175] In some embodiments, the single-sided area density of the positive electrode film layer is 300 mg / 1540 mm 2 -580 mg / 1540 mm 2 .

[0176] The single-sided areal density of the positive electrode film layer can be tested using methods known in the art. As an example, the battery is placed in a 25°C oven environment and allowed to stand for 2 h, and when the battery temperature is maintained at 25°C, the battery is discharged at 1 / 3 C constant current to 2.0 V, the battery is disassembled to obtain the positive electrode sheet, the residual electrolyte is treated with dimethyl carbonate solvent, the sheet is dried, cut into a small disc with an area of 1540 mm 2 , weighed as M, then the positive electrode film layer of the above weighed sheet is wiped off, the weight of the current collector is weighed as N, and the single-sided coating weight is (M-N) / 2.

[0177] In some embodiments, the single-sided areal density of the positive electrode film layer is 300 mg / 1540 mm 2 , 340 mg / 1540 mm 2 , 380 mg / 1540 mm 2 , 420 mg / 1540 mm 2 , 460 mg / 1540 mm 2 , 500 mg / 1540 mm 2 , 540 mg / 1540 mm 2 , 580 mg / 1540 mm 2 , or a range between any two of the above values.

[0178] In some embodiments, the positive electrode film layer has a packing density of 2.25 g / cm 3 -2.75 g / cm 3 .

[0179] The packing density of the positive electrode film layer can be tested using methods known in the art. As an example, the battery is placed in a 25°C oven environment and allowed to stand for 2 h, and when the battery temperature is maintained at 25°C, the battery is discharged at 1 / 3 C constant current to 2.0 V, the battery is disassembled to obtain the positive electrode sheet, the residual electrolyte is treated with dimethyl carbonate solvent, the sheet is dried, cut into a small disc with an area of S, weighed as W1, and the thickness T1 of the positive electrode sheet is measured using a micrometer, then the positive electrode film layer of the above weighed sheet is wiped off, the weight of the current collector is weighed as W2, and the thickness T2 of the current collector is measured using a micrometer, and the packing density PD of the positive electrode film layer is (W1-W2) / [(T1-T2) x S].

[0180] In some embodiments, the packing density of the positive electrode film layer is 2.25 g / cm 3 , 2.35 g / cm 3 , 2.45 g / cm 3 , 2.55 g / cm 3 , 2.65 g / cm 3 , 2.75 g / cm 3or any value therebetween.

[0181] The compaction density of the positive electrode film layer is within a suitable range, and the battery has excellent volumetric energy density and rate performance.

[0182] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0183] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0184] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0185] In some embodiments, the positive electrode tab can be prepared by dispersing the above-described components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (for example, N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained.

[0186] [Negative electrode tab]

[0187] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0188] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0189] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0190] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0191] In some embodiments, the negative film layer can further optionally include a binder. The binder can 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).

[0192] In some embodiments, the negative film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0193] In some embodiments, the negative film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0194] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-described components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, coating the negative electrode slurry on a negative current collector, and drying, cold-pressing, etc.

[0195] [Electrolyte]

[0196] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application, and can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0197] In some embodiments, the electrolyte employs an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0198] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoroboric oxalate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate.

[0199] In some embodiments, the electrolytic solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive that improves certain properties of the battery, such as an additive that improves overcharge performance of the battery, an additive that improves high or low temperature performance of the battery, etc.

[0200] [Separator]

[0201] The separator of the present application employs the above-described separator. In addition, the separator of the present application can be used in combination with other separators commonly used in the art, as needed.

[0202] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly through a roll-pressing process or a stacking process.

[0203] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the above-described electrode assembly and electrolyte.

[0204] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0205] [Secondary battery]

[0206] In one embodiment of the present application, a secondary battery is provided, including a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, wherein the binder in the active material layer of the positive electrode sheet includes the polymer of any embodiment of the present application.

[0207] In some embodiments, the secondary battery is a lithium-ion battery or a sodium-ion battery. During the charging and discharging of the battery, active ions are inserted and de-inserted between the positive electrode sheet and the negative electrode sheet. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly serves to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0208] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to form an electrode assembly through a winding process or a stacking process.

[0209] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte described above.

[0210] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, or the like can be listed.

[0211] The shape of the secondary battery is not particularly limited in the present application, and the secondary battery can be cylindrical, square, or any other shape. For example, FIG. 3 is a secondary battery 5 in a square structure as an example.

[0212] In some embodiments, referring to FIG. 4, the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be used to form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be selected by a person skilled in the art according to specific actual needs.

[0213] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0214] FIG. 5 is a battery module 4 as an example. Referring to FIG. 5, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arrangements can also be used. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0215] Optionally, the battery module 4 can further include a case having an accommodation space, and the plurality of secondary batteries 5 can be accommodated in the accommodation space.

[0216] In some embodiments, the above-described battery module can be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0217] FIGS. 6 and 7 are a battery pack 1 as an example. Referring to FIGS. 5 and 6, the battery pack 1 can include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 can be disposed on the lower case 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0218] In addition, the present application also provides a power consuming device including at least one of the secondary battery, the battery module, or the battery pack provided by the present application. The secondary battery, the battery module, or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0219] As the power consuming device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0220] FIG. 8 is a power consuming device as an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the secondary battery for the power consuming device, the battery pack or the battery module can be used.

[0221] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thin and light, and the secondary battery can be used as a power source.

[0222] Embodiments

[0223] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are intended to explain the present application only, and should not be understood as limiting the present application. In the embodiments, the specific techniques or conditions not mentioned are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained on the market.

[0224] Table 1: Performance parameters and grades of the first lithium-containing transition metal phosphate material

[0225] Table 2: Performance parameters and grades of the second lithium-containing transition metal phosphate material

[0226] Table 3: Performance parameters and grades of the third lithium-containing transition metal phosphate material

[0227] I. Preparation method

[0228] Example 1

[0229] (1) Preparation of the positive electrode tab:

[0230] The first lithium-containing transition metal phosphate material A1 and the second lithium-containing transition metal phosphate material B1 were mixed at a mass ratio of 70:30 to obtain a positive electrode active material. The mixed positive electrode active material, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride were mixed at a weight percentage of 96:1.5:2.5, and N-methyl pyrrolidone was added. After sufficient mixing, stirring, and dispersion, a positive electrode slurry was prepared.

[0231] The viscosity of the slurry after uniform mixing and stirring was adjusted to 8000-20000 mPa.s until the slurry was not stratified. The slurry was coated on the surface of the substrate aluminum foil at 420 mg / 1540 mm 2 by a double-sided double-control coating device, and then dried, cold-pressed, cut, and tabbed to obtain a positive electrode tab.

[0232] (2) Preparation of the negative electrode tab:

[0233] The artificial graphite, the conductive agent conductive carbon black, the binder styrene-butadiene rubber (SBR), and the thickening agent sodium carboxymethyl cellulose (CMC) were mixed at a weight percentage of 95:1.0:2.0:2.0, and deionized water was added. After stirring and dispersion, a negative electrode slurry was obtained. The negative electrode slurry was coated on the substrate copper foil at 211 mg / 1540 mm 2 , and then dried, cold-pressed, cut, and tabbed to obtain a negative electrode tab.

[0234] (3) Separator

[0235] A polypropylene film was used as the isolation film.

[0236] (4) Electrolyte

[0237] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, fluoroethylene carbonate (FEC) were mixed uniformly according to a volume ratio of 1:1:1:1, LiPF6 was dissolved in the organic solvents and stirred uniformly to make the concentration of the electrolyte 1 mol / L, thereby obtaining the electrolyte of Example 1.

[0238] (5) Preparation of the battery:

[0239] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, the separator was capable of separating the cathode and the anode, a bare battery cell was obtained by winding, the bare battery cell was placed in an outer package, the electrolyte was injected, and the battery was finally obtained after packaging, formation, and degassing.

[0240] Examples 2-6 and Comparative Examples 1-2 were prepared in a manner similar to that of Example 1, except that the types of materials or the mass contents of the first lithium-containing transition metal phosphate material, the second lithium-containing transition metal phosphate material, and / or the third lithium-containing transition metal phosphate were adjusted, and the details are as follows:

[0241] Table 4

[0242] II. Test methods

[0243] 1. Volume energy density of the battery

[0244] Capacity test of the battery cell: The battery cell was placed at 40℃ for 2h to ensure that the temperature of the battery cell was 40℃, then the battery was discharged at 1 / 3C constant current to 2.0V; after standing for 5min, the battery cell was charged to 4.1V at 1 / 3C constant current, and then constant voltage charging was continued at 4.1V until the current was 0.05C, and the battery cell was discharged at 1 / 3 constant current to 2.0V, and the total discharge capacity C0 and the total discharge energy E0 of the battery cell were recorded, and the unit of the total discharge energy was Wh.

[0245] Volume measurement of the battery cell: The length, width, and height of the outer surface of the battery were measured using a caliper, and the volume V0 of the battery cell was calculated, and the unit was L.

[0246] Volume energy density calculation: The volume energy density of the battery cell was the discharge energy E0 of the battery cell divided by the volume V0 of the battery.

[0247] III. Analysis of test results of each example and comparative example

[0248] Secondary batteries of each example and comparative example were prepared according to the above method, and each parameter was measured, and the results are shown in the following table.

[0249] Table 5

[0250] The positive electrode film layer in embodiments 1-6 of the present application comprises first particles and second particles, the first particles and the second particles comprising lithium-containing transition metal phosphate materials, wherein the primary particle size of the first particles is greater than 180 nm and less than 900 nm, the primary particle size of the second particles is greater than or equal to 900 nm and less than or equal to 5 μm, the average value of the Mn molar fraction of the second particles is less than the average value of the Mn molar fraction of the first particles, and the average value of the Mn molar fraction of the primary particles in the positive electrode film layer is 0.4-0.8.

[0251] As can be seen from the comparison of embodiments 1-7 and comparative examples 1-2, by controlling the average value of the Mn molar fraction of the second particles to be less than the average value of the Mn molar fraction of the first particles, the powder compaction density and the gravimetric capacity of the material can be improved, and the energy density of the battery can be improved.

[0252] As can be seen from embodiment 1-4, by controlling the average value of the Mn molar fraction of the second particles to be less than or equal to 0.35, the battery has a high energy density. As can be seen from the comparison of embodiments 1, 3-4 and embodiment 2, by controlling the average value of the Mn molar fraction of the second particles to be 0.02-0.30, the gravimetric capacity of the material can be improved, and the energy density of the battery can be improved.

[0253] Table 6

[0254] As can be seen from the comparison of embodiments 5-6 and embodiment 1, the positive electrode film layer further comprises third particles with a primary particle size of 50 nm-180 nm, the third particles are primary particles, and the area fraction of the third 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.

[0255] As can be seen from embodiments 5-6, by controlling the Mn molar fraction of the third particles to be 0.02-0.1, the battery has a high energy density.

[0256] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery characterized by comprising: The positive electrode film layer comprises a first type of particles and a second type of particles, the first type of particles and the second type of particles comprise a lithium-containing transition metal phosphate material, wherein the primary particle size of the first type of particles is greater than 180 nm and less than 900 nm, and the primary particle size of the second type of particles is greater than or equal to 900 nm and less than or equal to 5 microns, the average value of the Mn molar fraction of the second type of particles is less than the average value of the Mn molar fraction of the first type of particles, the average value of the Mn molar fraction of the primary particles in the positive electrode film layer is 0.4-0.8, wherein the Mn molar fraction refers to the proportion of the number of moles of Mn to the total number of moles of Mn and Fe. The average value of the Mn molar fraction of the first type of particles is 0.5-0.

7. The average value of the Mn molar fraction of the second type of particles is less than or equal to 0.35, and can be 0.02-0.

30.

2. The secondary battery according to claim 1, characterized by The area fraction of the first type of particles is 60%-80%, and / or the area fraction of the second type of particles is 15%-35%, based on the total area of the primary particles of the positive electrode film layer.

3. The secondary battery according to claim 1 or 2, characterized by The positive electrode film layer comprises a third type of particles, the third type of particles comprise the lithium-containing transition metal phosphate material, the primary particle size of the third type of particles is 50 nm-180 nm, and the average value of the Mn molar fraction of the third type of particles is less than the average value of the Mn molar fraction of the first type of particles, 4. The secondary battery according to any one of claims 1 to 3, characterized by, wherein the area fraction 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 the primary particles of the positive electrode film layer.

5. The secondary battery according to any one of claims 1 to 4, characterized by The average value of the Mn molar fraction of the third type of particles is less than or equal to 0.1, and can be 0.02-0.

1. The area fraction of the first type of particles is 45%-85%, the area fraction of the second type of particles is 10%-40%, and the area fraction of the third type of particles is 5%-15%, based on the total area of the primary particles of the positive electrode film layer.

6. The secondary battery according to claim 5, characterized by 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, 7. The secondary battery according to claim 5 or 6, characterized by 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, 8. The secondary battery according to any one of claims 5 to 7, 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 , ​ 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 , ​ A1, A2, A3 each independently include one or more of Al, Na, K, Mg, M1, M2, M3 each independently include one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, Q1, Q2, Q3 each independently include one or more of B, S, Si, N, N1, N2, N3 each independently include one or more of S, F, Cl, Br.

9. The secondary battery according to any one of claims 1 to 8, 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 -2.60 g / cm 3 .

10. The secondary battery according to claim 9, characterized by The positive electrode active material has a gram capacity of 140 mAh / g-150 mAh / g at 40 DEG C and 1 / 3C discharge rate.

11. An electrical device, characterized by The power utilization device includes the secondary battery of any one of claims 1-10.

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