Positive electrode plate, secondary battery and power consumption device

Abstract

This application discloses a positive electrode plate, a secondary battery, and an electric power consumption device. Here, the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material, and the first positive electrode active material contains Li a Ni b Co c M 1d M 2e O f R´ g and here, 0.75 ≦ a ≦ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≦ e ≦ 0.2, 1 ≦ f ≦ 2.5, 0 ≦ g ≦ 1, f + g ≦ 3, M1 is an Mn element and / or an Al element, and the second positive electrode active material contains Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, -0.100 ≦ x ≦ 0.100, 0 ≦ n ≦ 1.1, 0.001 ≦ y ≦ 0.500, 0 ≦ z ≦ 0.100, A´ contains one or more elements among Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge, and the positive electrode plate satisfies (I), where w (Mn) is the mass fraction of Mn in the positive electrode active material layer, d is the thickness of the positive electrode active material layer, the unit is mm, T is the weight of the positive electrode active material layer per unit area of the positive electrode plate, the unit is g / cm 2 , and R is the resistance of the positive electrode plate at 25°C, the unit is Ω. JPEG2025529291000062.jpg13170

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and more particularly to positive electrode plates, secondary batteries and power consuming devices. [Background technology]

[0002] Lithium-ion batteries are environmentally friendly, high-energy, and low-carbon. They are widely used in energy storage systems for hydroelectric, thermal, wind, and solar power plants, as well as in electric transportation tools such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. With the development of society, people's demands for lithium-ion batteries are increasing, and fast charging performance and long service life have become important performance indicators for lithium batteries. Currently, ternary layered positive electrode materials, such as nickel-cobalt-manganese (NCM)-based materials, are often used as the positive electrode material for lithium-ion batteries. However, traditional NCM-based materials have relatively poor rate-resistance limits at low voltages, which impact the fast charging capability and actual usable capacity of the battery. Summary of the Invention

[0003] In view of the technical problems existing in the background art, the present application provides a positive electrode plate that aims to expand the rate tolerance boundary at high and low voltage points of a positive electrode active material, improve fast charging capability, and at the same time ensure a long service life.

[0004] In order to achieve the above object, a first aspect of the present application provides a positive electrode plate, wherein the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer including a first positive electrode active material and a second positive electrode active material; The first positive electrode active material is Li a Ni b Co c M 1d M 2e O f R´ gcomprising, where 0.75 ≦ a ≦ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≦ e ≦ 0.2, 1 ≦ f ≦ 2.5, 0 ≦ g ≦ 1, and f + g ≦ 3; M1 is an Mn element and / or an Al element; M2 contains one or more elements selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb; R´ contains one or more elements selected from N, F, S, and Cl. The second positive electrode active material is Li 1+x M 3n Mn 1-y A´ y P 1-z E z contains O4, where -0.100 ≦ x ≦ 0.100, 0 ≦ n ≦ 1.1, 0.001 ≦ y ≦ 0.500, 0 ≦ z ≦ 0.100; M3 contains one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; A´ contains one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; E contains one or more elements selected from B, Si, N, S, F, Cl, and Br. The positive electrode plate

Number

[0005] Compared with the prior art, the positive electrode plate of the first aspect of the present application has at least the following beneficial effects: (1) Li a Ni b Co c M 1d M 2e O f R´g The positive electrode active material system has a relatively poor rate tolerance boundary at low SOC (state of charge, i.e., remaining capacity), and Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4 has a relatively poor rate tolerance boundary at high SOC. By using both in combination, the defects of the two systems can be simultaneously compensated for, widening the rate tolerance boundary at high and low SOC, thereby improving the fast charging capability. (2) Positive electrode active material Li a Ni b Co c M 1d M 2e O f R´ g and the positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, the battery can be endowed with both a relatively high energy density and relatively good cycle performance, and its service life can be extended. (3) Although the mechanism is unclear, the inventors have discovered that by controlling the Mn element content in the positive electrode active material layer, the thickness and areal density of the positive electrode active material layer, and the resistance of the positive electrode plate to satisfy the ranges defined by the above formula, it is possible to simultaneously ensure fast charging capability, energy density, and cycle performance, and obtain a fast charging positive electrode plate with good cycle life.

[0006] In some embodiments of the present application,

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number

number

[0007] In some embodiments of the present application, 0.01≦w (A´) ≦0.05.

[0008] In some embodiments of the present application, the second active cathode material comprises at least one of the following two active cathode materials: (i) 0.001≦y≦0.500, n=0, and the second active cathode material is Li 1+x Mn 1-y A´ y P 1-z E z O4, and (ii) 0.001≦y≦0.500, 0.9≦n≦1.1, the second positive electrode active material being Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, and optionally, the second cathode active material is (ii) Li 1+x Mn 1-y A´ y P 1-z E z It is O4.

[0009] In some embodiments of the present application, 0.032≦T≦0.043, and optionally 0.035≦T≦0.039. By controlling T within a predetermined range, improved fast charging performance and cycle life, and relatively high energy density can be further obtained.

[0010] In some embodiments of the present application, 0.11≦d≦0.16, and optionally 0.12≦d≦0.14. By controlling d within a predetermined range, improved fast charging performance and cycle life, and relatively high energy density can be further obtained.

[0011] In some embodiments of the present application, 0 < R ≤ 1.2, and optionally, 0 < R ≤ 1. By controlling R within a predetermined range, the internal resistance of the electrode plate can be further reduced, and the rapid charging performance and cycle performance can be improved.

[0012] In some embodiments of the present application, M1 is an Mn element.

[0013] In some embodiments of the present application,

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Number

Number

Number

[0014] In some embodiments of the present application, the Dv50 particle size of the second positive electrode active material is 0.21 μm to 1.53 μm, optionally 0.32 μm to 1.4 μm, further optionally 0.41 μm to 1.25 μm, also optionally 0.38 μm to 1.1 μm, and further optionally 0.47 μm to 0.91 μm.

[0015] In some embodiments of the present application, the specific surface area of the second positive electrode active material is 9.2 m 2 / g to 23.6 m 2 / g, optionally 10.5 m 2 / g to 19.6 m 2 / g, further optionally 12.0 m 2 / g to 16.2 m 2 / g and selectively 10.0m 2 / g~21.5m 2 / g and also selectively 10.9m 2 / g~17.6m 2 / g.

[0016] In some embodiments of the present application,

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number

number

[0017] In some embodiments of the present application, the first positive electrode active material has a Dv50 particle size of 2.1 μm to 6.3 μm, and optionally 3.5 μm to 4.9 μm.

[0018] In some embodiments of the present application, the specific surface area of ​​the first positive electrode active material is 0.3 m 2 / g~1.2m 2 / g, and selectively 0.5m 2 / g~0.9m 2 / g.

[0019] In some embodiments of the present application, a first coating layer is provided on a surface of the first positive electrode active material, and optionally, the first coating layer contains one or more elements of Ti, Al, B, Nb, Zr, Si, and W.

[0020] In some embodiments of the present application, the thickness of the first coating layer is 20 nm to 150 nm.

[0021] In some embodiments of the present application, a second coating layer is provided on a surface of the second positive electrode active material, and optionally, the second coating layer includes at least one of pyrophosphate, phosphate, and carbon.

[0022] In some embodiments of the present application, the second coating layer has a thickness of 10 nm to 50 nm.

[0023] In some embodiments of the present application, E includes one or more elements of B, Si, N, and S in the second positive electrode active material.

[0024] In some embodiments of the present application, in the second positive electrode active material, A′ includes one or more elements of Fe, Ti, V, Ni, Co, and Mg.

[0025] A second aspect of the present application provides a secondary battery including the positive electrode plate of the first aspect of the present application.

[0026] A third aspect of the present application provides a power consuming device including the positive electrode plate of the first aspect of the present application and / or the secondary battery according to the second aspect of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present application will be further described below in conjunction with the detailed description of the present invention. It should be understood that these specific embodiments are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0028] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. Appearances of this phrase in various locations throughout the specification do not necessarily refer to the same embodiment, nor are they mutually exclusive, independent, or alternative embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0029] The "ranges" disclosed in this application are defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit, and the selected lower and / or upper limit define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined; that is, any lower limit and any upper limit may be combined to form an unspecified range, any lower limit and any other lower limit may be combined to form an unspecified range, and similarly, any upper limit and any other upper limit may be combined to form an unspecified range. Furthermore, each point or single numerical value disclosed alone may itself be combined with any other point or single numerical value as a lower or upper limit, or with any other lower or upper limit, to form an unspecified range. For example, if a range of 150 or less is listed for a particular parameter, it is understood that ranges below 150, such as 10 to 140 and 20 to 120, are also contemplated. Note that if 2.1 and 3.5 are listed as minimum range values ​​and 4.9 and 6.3 are listed as maximum range values, then the ranges 2.1 to 6.3, 2.1 to 4.9, 3.5 to 6.3, and 3.5 to 4.9 are all possible ranges. In this application, unless otherwise specified, a numerical range, e.g., "10 to 50," represents a shorthand expression for any combination of real numbers between 10 and 50, where both 10 and 50 are real numbers. For example, the numerical range "20 to 30" represents that all real numbers between "20 and 30" have already been listed in this specification, and "20 to 30" is simply a shorthand expression for this combination of numbers.

[0030] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0031] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0032] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, a description of a method including steps S1 and S2 means that the method may include steps S1 and S2 performed in order, or steps S2 and S1 performed in order. For example, the above-mentioned method may further include step S3, indicating that step S3 can be added to the method in any order, e.g., the method may include steps S1, S2, and S3, or may include steps S1, S3, and S2, or may include steps S3, S1, and S2, etc.

[0033] Unless otherwise specified, the terms "comprise" and "include" used in this application may be open ended or closed ended. For example, the terms "comprise" and "include" may further include or include other components not listed, or may include or include only the listed components. Also, in this application, the terms "plurality" and "various" refer to two or more.

[0034] Unless otherwise specified, the term "and / or" in this application merely describes the relationship between related objects and indicates that three relationships may exist, for example, A and / or B may represent three cases: A alone, a combination of A and B, and B alone. In addition, the character " / " in this specification generally indicates that the related objects before and after are in an "or" relationship.

[0035] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art of this application. The terms used in this application are only for describing specific examples and are not intended to limit this application. The terms "comprises" and "having" and any variations thereof in the specification and claims of this application are intended to cover a non-exclusive "comprise." Unless otherwise specified, terms used in this application have the known meaning commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter mentioned in this application can be measured using various measurement methods commonly used in the art (for example, can be tested using the methods in the examples of this application).

[0036] Currently, fast charge performance and long service life have become important performance indicators for lithium batteries. Currently, positive electrodes are often manufactured using ternary layered positive electrode active materials (e.g., NCM). However, this type of positive electrode material can cause problems such as increased internal resistance and electrode polarization as the number of cycles and discharge times increase. Furthermore, this type of positive electrode material tends to prematurely reach the cutoff voltage, causing the discharge voltage to drop sharply at the end of the discharge curve, resulting in premature termination of discharge and affecting the actual usable capacity of the battery. That is, this type of positive electrode material has a relatively poor rate tolerance boundary at low SOC, which affects the fast charge and cycling performance of the battery. Furthermore, while ternary layered positive electrode active materials (e.g., NCM) have high energy density, their cycle life and fast charge performance are poor.

[0037] In view of this, a first aspect of the present application provides a positive electrode plate, wherein the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material, and the first positive electrode active material is Li a Ni b Co c M 1d M 2e O f R´ gcomprising, where 0.75 ≦ a ≦ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≦ e ≦ 0.2, 1 ≦ f ≦ 2.5, 0 ≦ g ≦ 1, and f + g ≦ 3, M1 is an Mn element and / or an Al element, M2 comprises one or more elements selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, R´ comprises one or more elements selected from N, F, S, Cl, and the second positive electrode active material is Li 1+x M 3n Mn 1-y A´ y P 1-z E z comprises Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, where -0.100 ≦ x ≦ 0.100, 0 ≦ n ≦ 1.1, 0.001 ≦ y ≦ 0.500, 0 ≦ z ≦ 0.100, M3 comprises one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W, A´ comprises one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge, E comprises one or more elements selected from B, Si, N, S, F, Cl, and Br, and the positive electrode plate [Number] satisfies where w (Mn) is the mass fraction of Mn in the positive electrode active material layer, d is the thickness of the positive electrode active material layer, with the unit of mm, T is the weight of the positive electrode active material layer per unit area of the positive electrode plate, with the unit of g / cm 2 and R is the Sheet resistance of the positive electrode plate at 25°C, with the unit of Ω. Here, the dimension of the "mass fraction" described in this application is 1 for all.

[0038] The inventor of this application discovered the following. The layered positive electrode active material system Li a Ni b Co c M 1d M 2e O f R´ g has a relatively poor rate tolerance boundary at low SOC locations, and the positive electrode active material Li 1+x M 3nMn 1-y A´ y P 1-z E z O4 has a low-voltage discharge plateau (generally 3.5 V or less) near the end of discharge, and by mixing it with the layered positive electrode active material, Li 1+x M 3n Mn 1-y A´ y P 1-z E z The discharge curve of the composite positive active material after mixing has a discharge plateau at the end of the entire discharge curve, and when the battery is discharged to this plateau, the change in the battery voltage with the capacity is relatively small. This is equivalent to a constant voltage discharge to a certain extent for the layered positive active material, which can mitigate the polarization effect in the discharge process at the previous low voltage point and improve the actual usable capacity. In addition, the positive active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4 is further limited by the problem of relatively poor rate tolerance boundary at high SOC, which is due to the layered cathode active material Li a Ni b Co c M 1d M 2e O f R´ g By using it in combination with Li, the defects of the two systems can be compensated for at the same time, and the rate tolerance boundary at high and low SOC points can be expanded, thereby improving the fast charging capability and achieving both cycle performance. a Ni b Co c M 1d M 2e O f R´ g The energy density of the positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E zO4 has higher cycle performance and safety. By combining the two, the electrode piece has both a relatively high energy density and a relatively good cycle performance, and the service life is extended. Furthermore, the positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z The lattice contraction rate of O4 during charging and discharging is relatively large, and mixing the two systems of positive active materials is advantageous for better matching the expansion of the battery negative plate, thereby improving the long-term performance of the battery.

[0039] Furthermore, the inventors discovered that Li a Ni b Co c M 1d M 2e O f R´ g and Li 1+x M 3n Mn 1-y A´ y P 1-z E z After mixing O4, we discovered that by controlling the Mn content in the positive electrode active material layer, the thickness and surface density of the positive electrode active material layer, and the resistance of the positive electrode plate to satisfy the ranges of the above formula, we could obtain a fast charging positive electrode plate that simultaneously guarantees fast charging capability, energy density, and cycle performance and has good cycle life. After analysis, we found that the possible cause was that the coating mass of the positive electrode active material was too low. a Ni b Co c M 1d M 2e O f R´ g and Li 1+x M 3n Mn 1-y A´ y P 1-z E z This may affect the mixing effect with O4, but is not limited to this. For example, if the coating mass of the positive electrode active material layer is too low, the polarization of the electrode plate will be significantly improved, and in this case, Li a Ni b Co c M 1d M2e O f R´ g Li 1+x M 3n Mn 1-y A´ y P 1-z E z The improvement effect of adding O4 is not significant, and if the coating mass of the active material layer is too high, the degree of polarization of the electrode plate increases. 1+x M 3n Mn 1-y A´ y P 1-z E z The areal density of the positive electrode active material layer is related to its thickness and compaction density. When the areal density is determined, a positive electrode active material layer that is too thin indicates that the coating on the positive electrode plate is too thin or the compaction density is too high. The former affects the energy density, and the latter affects the infiltration of the electrolyte into the plate, deteriorating cycle performance. A thickness that is too high indicates that the coating on the positive electrode plate is too thick or the compaction density is too low. The former increases polarization of the plate, deteriorating battery performance, and the latter increases contact resistance between particles within the plate, deteriorating battery performance. In addition, a positive electrode plate resistance R that is too high also affects power and cycle performance.

[0040] In the present application, the mass fraction w of each element (e.g., A' element, Mn element) in the positive electrode active material layer (A´)can be calculated after measuring the mass of the positive electrode active material layer and the mass of the A' element in the positive electrode active material layer, respectively. The mass of the positive electrode active material layer can be obtained by decomposition and weighing (accuracy up to 0.0001 g), and the mass of the A' element in the positive electrode active material layer can be obtained by ICP testing. For example, this can be done by the following procedure: about 0.4 g (accuracy up to 0.0001 g) of a dry positive electrode plate or 0.1 g (accuracy up to 0.0001 g) of a wet positive electrode plate is placed in a 30 ml decomposition tank, and one decomposition tank without sample is left as a blank sample. The decomposition tank containing the positive electrode plate sample is moved into a ventilation cabinet and 12 ml of reverse aqua regia is added. When adding reverse aqua regia, the reverse aqua regia is added along the inner wall of the decomposition tank, and the sample remaining on the inner wall flows to the bottom of the tank. Then, the top cover, insulating sleeve, gasket, microwave decomposition unit, and nut are installed in that order, and the nut is tightened with a wrench. Then, the microwave decomposition unit is started, and the The optical fiber sensor is inserted into the bottom of the digestion tank containing the assembled sample. The digestion tank is placed in a microwave digestion device to equilibrate, and the digestion begins (the digestion program is to heat to 120°C in 6 minutes and hold for 8 minutes, then heat to 160°C in 5 minutes and hold for 8 minutes, then heat to 180°C in 5 minutes and hold for 5 minutes). After completion, the digestion tank is cooled to room temperature and removed. The digestion tank is placed in a ventilation cabinet, the nuts are slowly loosened and ventilated, and the previously installed components are removed one by one. The solution in the digestion tank is transferred to a 100ml measuring flask through a funnel (which should be lined with filter paper). The digestion tank is then washed with ultrapure water, and the washings are also transferred to the measuring flask. 10ml of ultrapure water is used for each wash. The solution in the 100ml measuring flask is shaken evenly, and 1ml of the shaken solution is added to another 100ml measuring flask using a pipette. Ultrapure water is then added to the final volume (the solution reaches a total of 100ml). Finally, the sample solution is tested using ICP-OES.Here, when preparing reverse aqua regia, 1000 ml of ultrapure water can be poured into a 2500 ml glass bottle, followed by 750 ml of concentrated nitric acid and 250 ml of concentrated hydrochloric acid, and then stirred uniformly before use. The concentrated nitric acid can be a commercially available concentrated nitric acid solution with a mass fraction of 68%, and the concentrated hydrochloric acid can be a commercially available concentrated hydrochloric acid with a mass fraction of 68%. Alternatively, hydrogen chloride gas can be added to ultrapure water so that the mass occupancies of hydrogen chloride gas and ultrapure water are 68% and 32%, respectively, and the required concentrated hydrochloric acid can be obtained after complete dissolution.

[0041] In the present application, the coating mass T of the active material layer of the positive electrode plate can be measured using a weighing method, specifically, by weighing the positive electrode active material layer within a fixed area (with an accuracy of up to 0.0001 g).

[0042] In this application, the resistance of the positive plate is BER1300 at room temperature. Sheet The test can be performed using a resistance meter. The test steps can be as follows: (1) fabricate the electrode plate into a wafer with a diameter of 22 mm; (2) place the fabricated wafer on the test plate of the BER1300 instrument; (3) adjust the test pressure of the instrument to 0.4 tons, adjust the test time to 10 seconds, and start the test. The obtained resistance value is, Sheet It is resistance.

[0043] In the present application, the thickness d of the active material layer of the positive electrode plate can be measured by the following method: 2 An area is taken and transferred to a vacuum transfer device or an argon ion beam polishing (CP) device at a low temperature in an inert atmosphere protective environment until a cross section is produced. After cutting, the sample is attached to a cross section sample stage with conductive tape and transferred to an SEM vacuum chamber for observation. Appropriate parameters are adjusted until the cross section shape can be clearly observed, and the thickness of the active material layer is marked using scanning electron microscope software. Three areas are taken and marked, and the average value is taken as the thickness of the active material layer.

[0044] Furthermore, through intensive research, the inventor has discovered that, on the condition that the positive electrode plate of the present application meets the above conditions, the performance of the positive electrode plate can be further improved by further controlling the elemental mass fraction, the selection of the positive electrode active material, the plate resistance, the surface density and thickness of the positive electrode active material layer, etc. That is, on the condition of meeting the above conditions, one or more of the following conditions are further selectively satisfied.

[0045] In some embodiments of the present application, the first positive electrode active material may be partially Li a Ni b Co c M 1d M 2e O f R´ g or may all be Li a Ni b Co c M 1d M 2e O f R´ g where 0.75 ≦ a ≦ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≦ e ≦ 0.2, 1 ≦ f ≦ 2.5, 0 ≦ g ≦ 1, f + g ≦ 3, M1 is Mn element and / or Al element, M2 contains one or more elements of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, and R´ contains one or more elements of N, F, S, Cl. Optionally, 0.5 ≦ b < 1, 0 < c ≦ 0.5, 0 < d ≦ 0.5, and the positive electrode active material Li a Ni b Co c M 1d M 2e O f R´ g is made to meet the conditions within the above predetermined range, which is more advantageous for the plate and the battery to have relatively high energy density, good cycle performance and long cycle life, and the positive electrode active material Li a Ni b Co c M 1d M 2e O f R´ gTaking nickel-cobalt-manganese ternary cathode active material (i.e., NCM) as an example, increasing the nickel content can improve the volumetric energy density of the cathode material, and increasing the manganese content can reduce material costs, improve the safety and structural stability of the material, and improve cycle performance. However, too much manganese destroys the layered structure of the material and reduces the specific capacity of the material. Cobalt stabilizes the layered structure of the material and improves the cycle and rate performance of the material, but too much cobalt content can reduce the actual capacity. By ensuring that the nickel-cobalt-manganese content satisfies the above-mentioned specified range, it is advantageous for the electrode plate and battery to have relatively high energy density, good rate performance, and cycle performance. Optionally, M1 can be Mn, and the first cathode active material can be an NCM-based cathode active material, in which case the general formula is Li a Ni b Co c Mn d M 2e O f R´ g For example, it may be a nickel-cobalt-manganese ternary layered positive electrode active material.

[0046] In some embodiments of the present application, the second positive electrode active material is partially Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, all Li 1+x M 3n Mn 1-y A´ y P 1-z E zO4, wherein -0.100≦x≦0.100, 0≦n≦1.1, 0.001≦y≦1, 0≦z≦0.100, M3 includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W, A' includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge, E includes one or more elements of B, Si, N, S, F, Cl, and Br, and is selected from the group consisting of lithium site, manganese site, and phosphorus site. Doping at least one of the elements can help improve the performance of the positive electrode active material, for example, by improving the interfacial performance, reducing the interfacial side reaction with the electrolyte, reducing the antisite defect concentration, and improving the kinetic performance and gram capacity of the material. At the same time, adjusting the manganese site doping element can further improve the particle morphology and the compaction density. Specifically, the lattice volume change rate of the second positive electrode active material during the charge and discharge process is greater than that of the first positive electrode active material. However, a high lattice volume change rate of the positive electrode material is unfavorable for lithium ion transport. Selecting the element A' doped at the manganese site from the above-listed elements contributes to appropriately reducing the lattice change rate during the lithium release process of the material, improving the structural stability of the positive electrode material, reducing the elution of the manganese site element, and reducing the oxygen activity on the particle surface, further improving the gram capacity of the material, and reducing interfacial side reactions with the electrolyte during use, thereby further improving the cycling performance of the material. Selecting the element E doped at the phosphorus site from the above-listed elements also contributes to changing the difficulty of the Mn-O bond length, thereby improving electronic conductivity and lowering the lithium ion migration barrier, facilitating lithium ion migration, and improving rate performance and fast charging performance. Similarly, selecting the element M3 doped at the lithium site from the above-listed elements also contributes to improving the lattice change rate of the material and maintaining the capacity of the material. A too small value of x reduces the lithium content of the entire core system, affecting the gram capacity of the material.The value of y limits the total amount of all doping elements, affecting the manganese content in the system and the voltage plateau of the material. Since the E element is doped at the phosphorus site and the PO tetrahedron is relatively stable, a too large z value will affect the stability of the material. When x, y, and z are selected within the above ranges, the positive electrode active material can have better performance. Furthermore, by selecting the above doping elements and the values ​​of x, n, y, and z, Li can be obtained. 1+x M 3n Mn 1-y A´ y P 1-z E z O4 can maintain electrical neutrality, which can ensure that defects and heterophases in the positive electrode active material are minimized. Taking lithium manganese phosphate-based positive electrode active materials as an example, when excess transition metals (e.g., manganese) are present, the structure of the material system itself is relatively stable, so there is a high possibility that the excess transition metal will precipitate in a simple form or form a heterophase within the crystal lattice. Maintaining electrical neutrality can minimize such heterophases, and by ensuring the electrical neutrality of the system, lithium vacancies can be generated in the positive electrode active material in some cases, thereby improving the dynamic performance of the positive electrode active material. This is advantageous for achieving relatively good cycle performance and high-temperature stability, as well as a relatively large gram capacity and a relatively large compaction density, compared to materials such as lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate that are applicable to conventional high-voltage systems. As can be understood, in the "manganese site" doping described in this application, the manganese site is present in the positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z The value of y represents only the position of the manganese element or the A' element in the O4 crystal lattice, and does not necessarily indicate that the manganese element is present at the manganese site. The manganese element at the manganese site may be partially or completely substituted with the A' element. For example, when the value of y is 1, the second positive electrode active material Li 1+x M 3n Mn 1-y A´y P 1-z E z O4 does not contain manganese element, for example, it may contain iron element at the manganese site, or may contain iron element and other doping elements at the same time.

[0047] In some embodiments of the present application, the second positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z In O4, E may include one or more elements of B, Si, N, and S. By selecting the element E doped into phosphorus site from a predetermined range, it further contributes to changing the difficulty of changing the Mn-O bond length, thereby improving the electronic conductivity and lowering the lithium ion migration barrier, facilitating the lithium ion migration, and improving the rate performance and fast charging performance of the material.

[0048] In some embodiments of the present application, the second positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z In O4, A' may include one or more elements selected from Fe, Ti, V, and Mg. Optionally, A' may be Fe, or more optionally, A' may be at least two elements selected from Fe, Ti, V, and Mg, or even more optionally, A' may be Fe and one or more elements selected from Ti, V, and Mg. By selecting the element A' doped into the manganese site from a predetermined range, the structural stability, gram capacity, cycle performance, rate performance, etc. of the positive electrode material can be further improved, resulting in a positive electrode plate that combines relatively good cycle life and fast charging performance.

[0049] In some embodiments of the present application, the second positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z Ez In O4, the manganese site and phosphorus site can be simultaneously doped, which effectively reduces the elution of manganese site elements, further reduces the manganese site ions migrating to the negative electrode, reduces the amount of electrolyte consumed due to the decomposition of the SEI film, and not only improves cycle performance and safety performance, but also promotes the adjustment of Mn-O bonds, lowers the lithium ion migration barrier, promotes lithium ion migration, and improves rate performance and fast charging capability. Furthermore, selectively, simultaneous doping of the lithium site, manganese site, and phosphorus site can further achieve significantly improved rate performance, improved cycle performance, and / or high-temperature stability.

[0050] In the present application, the first positive electrode active material has the chemical formula Li a Ni b Co c M 1d M 2e O f R´ g and the second positive electrode active material has the chemical formula Li 1+x M 3n Mn 1-y A´ y P 1-z E z For O4, unless otherwise specified, when a doping site has two or more elements, the limitations on the numerical range of the stoichiometric number of the corresponding doping site element in the chemical formula are limitations on not only the stoichiometric number of each element in this site, but also the sum of the stoichiometric numbers of each element in this site. For example, for the second positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z Take the chemical formula of O4 as an example, A1' has two or more elements A1', A2'...A n If ', then A1', A2'...A n ´ each stoichiometric number y1, y2……y n are each within the numerical range defined for y in this application, and y1, y2...y nThe sum of M3 and E must also be within this range. Similarly, when M3 or E is two or more elements, the limitations on the range of the stoichiometric numbers of M3 and E in this application also have the same meanings as above.

[0051] In some embodiments of the present application,

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[0052] In some embodiments of the present application,

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[0053] In some embodiments of the present application, the mass fraction of the A′ element in the positive electrode active material layer is 0.01≦w (A´) ≦0.05, for example, w (A´) The value of may be 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, etc., or may be within any range of the above-mentioned numerical values. Increasing the content of the A' element in the second positive electrode active material contributes to improving the cycle performance, but if it is too high, it will impair the energy density. In the present application, by further controlling the mass fraction of A' in the positive electrode active material layer within a predetermined range, it is possible to further achieve both cycle performance and high energy density while improving the fast charging performance of the positive electrode plate, and to extend the service life.

[0054] In some embodiments of the present application, the second positive electrode active material is a lithium manganese phosphate-based, lithium iron phosphate-based, lithium manganese iron phosphate-based, or other lithium manganese iron phosphate-based material having the above general formula Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, for example, the second positive electrode active material may include a positive electrode active material that satisfies at least one of the following two conditions: (i) 0.001≦y≦0.500, n=0, in which case the second positive electrode active material is Li 1+x Mn1-y A´ y P 1-z E z Lithium manganese phosphate may be LiMnPO4, i.e., lithium manganese phosphate doped at least at the manganese site, wherein the present application modifies the lithium manganese phosphate to significantly reduce the elution of elements at the manganese site and reduce the lattice change rate, and when used in a secondary battery, it is advantageous to improve the cycle performance, rate performance, safety performance, and capacity of the battery. For example, by doping a specific element in a specific amount at the lithium site, manganese site, and phosphorus site of the compound LiMnPO4, improved rate performance can be obtained, and at the same time, the elution of Mn and doping elements at the Mn site can be reduced, improving cycle performance and / or high-temperature stability, and also improving the gram capacity and compaction density of the positive electrode active material. A specific example is Li 1+x Mn 1-y A´ y P 1-z E z O4 is Li 1+x Mn 1-y Fe y P 1-z E z O4, and compared to lithium iron phosphate, lithium manganese iron phosphate has a higher voltage plateau and, when the specific capacity is the same, it has a higher energy density; and (ii) 0.001≦y≦0.500, 0.9≦n≦1.1, in which case the second positive electrode active material is Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4. For the lithium manganese phosphate-based second positive electrode active material, the value of y limits the total amount of all doping elements. If y is too small, i.e., the doping amount is too small, the doping elements will not work. If y is greater than 0.5, the Mn content in the system will be relatively low, which will affect the voltage plateau of the material. The value of y is preferably in the range of 0.001 to 0.500, more preferably 0.25 to 0.5. It should be noted that the chemical formula Li 1+x Mn1-y A´ y P 1-z E z O4 and Li 1+x M 3n Mn 1-y A´ y P 1-z E z In O4, the stoichiometric numbers of elements located at the same site may be the same or different, but they all have the formula Li 1+x M 3n Mn 1-y A´ y P 1-z E z The stoichiometric number of each element in O4 satisfies a limited numerical range.

[0055] As a specific example, the second positive electrode active material satisfies 0.001≦y≦0.500, n=0, and the second positive electrode active material is Li 1+x Mn 1-y A´ y P 1-z E z Optionally, the second active cathode material may include a cathode active material having the formula Li 1+x Mn 1-y A´ y P 1-z E z Alternatively, A' may contain Fe element, for example, only Fe element.

[0056] In some embodiments of the present application, the weight T of the positive electrode active material layer per unit area of ​​the positive electrode plate (unit: g / cm 2(where T satisfies 0.032≦T≦0.043, for example, T may be 0.033, 0.034, 0.035, 0.036, 0.037, 0.038, 0.039, 0.040, 0.041, 0.042, etc., or may be within any range of the above values. The coating mass of the positive electrode active material layer not only affects the polarization of the electrode plate, but also the energy density of the electrode plate. In the present application, on the premise that the relationship between the content of the A′ element in the positive electrode active material layer, the thickness and areal density of the positive electrode active material layer, and the positive electrode plate resistance is satisfied, by further controlling the areal density T of the positive electrode active material layer within a predetermined range, improved fast charging performance and cycle life, as well as a relatively high energy density, can be simultaneously obtained, and the service life can be extended. Alternatively, 0.035≦T≦0.039, and by further controlling T within a predetermined range, the positive electrode plate can be made to have both good rapid charging capability and a long service life.

[0057] In some embodiments of the present application, the thickness d (unit: mm) of the positive electrode active material layer satisfies 0.11≦d≦0.16, for example, the value of d may be 0.115, 0.12, 0.125, 0.13, 0.135, 0.14, 0.145, 0.15, 0.155, etc., or may be within any range of the above values. The thickness of the positive electrode active material layer not only affects the energy density of the battery, but also its cycle performance and fast charge performance. In the present application, on the premise that the relationship between the content of element A′ in the positive electrode active material layer, the thickness and areal density of the positive electrode active material layer, and the positive electrode plate resistance is satisfied, the thickness d of the positive electrode active material layer can be further controlled within a predetermined range, thereby achieving improved fast charge performance, cycle life, and a relatively high energy density, and extending the service life. Alternatively, 0.12≦d≦0.14, and by controlling d within a predetermined range, the positive electrode plate can be made to have both good rapid charging capability and a long service life.

[0058] In some embodiments of the present application, the resistance R (unit: Ω) of the positive electrode plate satisfies 0 < R ≤ 1.2. For example, the value of R may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, etc., or may be within any range of any of the above numerical values. Considering that if the resistance of the positive electrode plate is too high, it will similarly affect the power performance and cycle performance of the battery, it is more advantageous to control the range of the value of R within a predetermined range, so that the electrode plate has relatively good rapid charging performance and cycle performance. Optionally, 0 < R ≤ 1, and by further controlling the range of the value of R within a predetermined range, the internal resistance of the electrode plate can be further reduced, and the rapid charging performance and cycle performance can be improved.

[0059] In some embodiments of the present application, the mass fractions of Mn element and A' element in the positive electrode active material layer are

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[0060] As a specific example, the first positive electrode active material is an NCM-based positive electrode active material Li a Ni b Co c Mn d M 2e O f R´ g It may also be, for example, Li a Ni b Co c Mn d O f R´ g The second positive electrode active material may be Li 1+x Mn 1-y A´ y P 1-z E z O4 (0.001≦y≦0.500), for example, Li 1+x Mn 1-y Fe y P 1-z E z In this case, it may be O4.

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[0061] In some embodiments of the present application, the positive plate comprises:

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[0062] In some embodiments of the present application, the Dv50 particle size of the first positive electrode active material is 2.1 μm to 6.3 μm, such as 2.4 μm, 2.7 μm, 3.0 μm, 3.3 μm, 3.6 μm, 3.9 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5.1 μm, 5.4 μm, 5.7 μm, 6.0 μm, or any of the above values ​​within a range. The Dv50 of the first positive electrode active material refers to the particle size corresponding to the cumulative volume distribution percentage of the first positive electrode active material reaching 50%. In the present application, the Dv50 particle size of the first positive electrode active material can be measured using laser diffraction particle size analysis, for example, by using a laser particle size analyzer (e.g., a Malvern Master Size 3000) according to standard GB / T 19077-2016. In the present application, controlling the Dv50 particle size of the first positive electrode active material within a predetermined range is beneficial to prevent crushing or powdering during charging and discharging, thereby reducing capacity loss and shortening the diffusion path of active ions, improving electron conduction rate, and improving cycle performance. At the same time, it also provides the active material with adequate active sites. A particle size that is too small results in a relatively large number of active sites, which increases side reactions during cycling and significantly impacts cycle performance. A particle size that is too large results in a relatively small number of active sites, significantly impacting power performance. Optionally, the Dv50 particle size of the first positive electrode active material may be 3.5 μm to 4.9 μm, which further achieves high energy density, relatively good power performance, and cycle performance, while improving fast charging capability and service life.

[0063] In some embodiments of the present application, the Dv50 particle size of the second positive electrode active material may be 0.21 μm to 1.53 μm, such as 0.25 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, or 1.5 μm, or may be within any of the above ranges. The Dv50 of the second positive electrode active material refers to the particle size corresponding to the cumulative volume distribution percentage of the second positive electrode active material reaching 50%. In the present application, the Dv50 particle size of the second positive electrode active material can be measured using laser diffraction particle size analysis, for example, by using a laser particle size analyzer (e.g., a Malvern Master Size 3000) according to standard GB / T 19077-2016. In the present application, controlling the Dv50 particle size of the second positive electrode active material within a predetermined range is advantageous in preventing crushing or powdering during charge and discharge, thereby reducing capacity loss and shortening the diffusion path of active ions, improving electron conduction rate, and improving cycle performance. At the same time, the active material has adequate active sites, allowing for both cycle performance and power performance. Furthermore, controlling the Dv50 particle size of the second positive electrode active material within a predetermined range is advantageous in achieving a desired compaction density in accordance with the Dv50 particle size range of the first positive electrode active material, thereby avoiding relatively large interparticle voids. Optionally, the Dv50 particle size of the second positive electrode active material may be 0.5 μm to 0.9 μm, which further improves high energy density, relatively good power performance, and cycle performance, as well as rapid charging capability and service life.

[0064] In some embodiments of the present application, the specific surface area of ​​the first positive electrode active material is 0.3 m 2 / g~1.2m 2 / g, for example 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m2 / g, 1.1m 2 / g, or any of the above numerical ranges. Optionally, the specific surface area of ​​the first positive electrode active material is 0.5 m 2 / g~0.9m 2 Further, the specific surface area of ​​the second positive electrode active material may be 9.2 m / g. 2 / g~23.6m 2 / g, for example 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14mg 2 / g, 15m 2 / g, 16m 2 / g, 17m 2 / g, 18m 2 / g, 19m 2 / g, 20m 2 / g, 21m 2 / g, 22m 2 / g, 23m 2 / g, or may be within a range of any value therein or therebetween, and optionally the specific surface area of ​​the second positive electrode active material may be 10.5 m 2 / g~19.6m 2 / g, and more selectively 12.0m 2 / g~16.2m 2 / g and selectively 10.0m 2 / g~21.5m 2 / g and also selectively 10.9m 2 / g~17.6m 2 / g. In the present application, the specific surface areas of the first and second positive electrode active materials can be measured using conventional methods in the art, such as nitrogen physical adsorption. Increasing the specific surface area contributes to an increase in the active sites of the positive electrode active material, which is advantageous for providing the material with relatively good power performance. However, these increased active sites also increase side reactions during the cycling process of the positive electrode active material, thereby causing a decline in the cycling performance of the material. In the present application, by controlling the specific surface areas of the first and second positive electrode active materials within a predetermined range, relatively good power performance and cycle life can be obtained, and fast charging capability and service life can be improved.

[0065] As a specific example, in the positive electrode active material layer

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[0066] In some embodiments of the present application, a first coating layer may be provided on the surface of the first positive electrode active material. Optionally, the first coating layer may contain one or more elements selected from the group consisting of Ti, Al, B, Nb, Zr, Si, and W. Providing a coating layer on the surface of the positive electrode active material not only prevents contact between the positive electrode active material and the electrolyte, but also reduces side reactions between the positive electrode active material and the electrolyte, improving the structural stability of the positive electrode active material and the cycle stability and safety of the material. The elements in the first coating layer may be provided in the form of oxides (e.g., Al2O3, ZrO2, TiO2, Nb2O3, etc.) or lithium compounds. The inclusion of the elements in the first coating layer in the above-described ranges improves the ionic conductivity of the material surface, improves the rate performance and gram capacity of the material, stabilizes the material structure, prevents direct contact between the material and the electrolyte, and improves cycle performance.

[0067] In some embodiments of the present application, the thickness of the first coating layer may be 20 nm to 150 nm, for example, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, etc., or any range of the above values. If the thickness of the first coating layer is too thin, the possibility of rupture / deep damage to the cathode active material during use increases, significantly reducing the performance-enhancing and protective effects of the first cathode active material. If the thickness of the first coating layer is too thick, lithium ions require a longer transport path from the electrolyte to the active material system, significantly affecting the performance of the active material. Furthermore, when the coating layer sinters, the coating material reacts with lithium in the internal material, reducing the available active lithium in the material and the corresponding gram capacity. In this application, by controlling the thickness of the first coating layer within the above-mentioned predetermined range, the above problems can be effectively avoided or reduced, the rate performance of the first cathode active material can be effectively improved, and the surface structure of the material can be stabilized. At the same time, controlling the thickness of the first coating layer within a predetermined range based on the Dv50 particle size of the first cathode active material is advantageous to further ensure a high energy density of the composite cathode.

[0068] In some embodiments of the present application, a second coating layer may be provided on the surface of the second positive electrode active material. The provision of the second coating layer not only prevents contact between the second positive electrode active material and the electrolyte, thereby reducing side reactions between the second positive electrode active material and the electrolyte, but also prevents or suppresses the leaching of transition metals or doping elements from the second positive electrode active material, improving its structural stability and further improving the cycle stability and safety of the positive electrode active material. Optionally, the second coating layer may include at least one of pyrophosphate, phosphate, and carbon. Metal ions are less likely to migrate in pyrophosphate. Selecting pyrophosphate as the coating layer material can effectively isolate the metal ions doped in the positive electrode material from the electrolyte. Furthermore, the pyrophosphate is preferably crystalline, which stabilizes the structure of the crystalline pyrophosphate and effectively suppresses the leaching of transition metals from the active material, improving cycle performance. The phosphate coating can improve the ion transport performance of the positive electrode material and is advantageous for promoting lithium ion transport. Furthermore, the phosphate can be a crystalline phosphate, which has a relatively high lattice match with crystalline pyrophosphate, and has high stability and excellent lithium ion conductivity. Coating the second positive electrode active material with this improves the stability of the positive electrode active material and effectively reduces interfacial side reactions with the electrolyte, thereby improving the high-temperature cycle and storage performance of the battery. The carbon coating can effectively improve the conductivity and desolvation ability of the positive electrode active material. Carbon materials have good electronic conductivity, and when applied to batteries, electrochemical reactions occur, requiring the participation of electrons. To increase electron transmission between particles and between different locations on the particles, carbon with excellent conductivity can be used to coat the positive electrode active material.As can be understood, when the second coating layer simultaneously contains pyrophosphate, phosphate, and carbon, the pyrophosphate, phosphate, and carbon may be located in the same coating layer or in at least two sub-coating layers. For example, a pyrophosphate coating layer, a phosphate coating layer, and a carbon coating layer may be formed in this order on the surface of the second positive electrode active material; a phosphate coating layer, a pyrophosphate coating layer, and a carbon coating layer may be formed in this order on the surface of the second positive electrode active material; or a composite coating layer of pyrophosphate and phosphate may be formed on the surface of the second positive electrode active material, and then a carbon coating layer may be formed on the surface of the composite coating layer.

[0069] In some embodiments of the present application, the thickness of the second coating layer may be 10 nm to 50 nm. For example, it may be 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, etc., or may be within any of the above numerical ranges. Controlling the thickness of the second coating layer within a predetermined range not only effectively inhibits the elution of transition metals or doping elements in the second positive electrode active material and reduces the lattice change rate of the second positive electrode active material, but also prevents an excessive coating thickness from affecting lithium ion migration and battery energy density, and further improves the dynamic performance, cycling performance, and safety of the battery without sacrificing the gram capacity of the second positive electrode active material.

[0070] As a specific example, the second coating layer may include a first sub-coating layer, a second sub-coating layer, and a third sub-coating layer, the first sub-coating layer may coat the second positive electrode active material and include a crystalline pyrophosphate, the second sub-coating layer may include a crystalline phosphate and coat the first sub-coating layer, and the third sub-coating layer may be carbon and coat the second sub-coating layer. The pyrophosphate, as the first sub-coating layer, can effectively isolate the metal ions doped in the second positive electrode active material from the electrolyte; the crystalline pyrophosphate coating can effectively inhibit the elution of transition metals in the second positive electrode active material and improve cycle performance; the crystalline phosphate, as the second sub-coating layer, has a relatively high lattice match with the crystalline pyrophosphate in the first sub-coating layer, is more stable than pyrophosphate, and has excellent lithium ion conductivity, which is advantageous for improving the stability of the positive electrode active material and reducing interfacial side reactions between the positive electrode active material and the electrolyte; and the third sub-coating layer can strengthen interparticle electron transmission, improve the electronic conductivity of the positive electrode active material, and effectively improve the conductive performance and desolvation ability of the positive electrode active material.Furthermore, the thickness of the first sub-coating layer may be 1 nm to 10 nm, for example, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, etc., or may be within any range of any of the above numerical values. When the thickness of the first sub-coating layer is within the predetermined range, it is possible to avoid the adverse effect on the dynamic performance of the positive electrode active material that may occur when the thickness of the first sub-coating layer is too thick, and it is possible to avoid the problem of not being able to effectively inhibit the migration of transition metal ions when the thickness is too thin. The thickness of the second sub-coating layer may be 2 nm to 15 nm, for example, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, etc., or may be within any range of any of the above numerical values. When the thickness of the second sub-coating layer is too large, it may affect the plateau voltage of the entire positive electrode active material. When the thickness of the second sub-coating layer is within a predetermined range, its surface structure is stable, side reactions with the electrolyte are small, and interfacial side reactions can be effectively reduced, thereby improving the high-temperature cycle performance and high-temperature storage performance of the battery. The thickness of the third sub-coating layer can be 2 nm to 25 nm, for example, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, etc., or can be any value within the above range. When the thickness of the third sub-coating layer is within the predetermined range, the conductivity of the positive electrode active material and the compaction density of the positive electrode plate can be improved, and at the same time, the problem of an excessively thick coating that affects the compaction density of the electrode plate when this sub-coating layer contains amorphous carbon can be avoided.

[0071] Here, in the present application, the thickness dimension test of the coating layer may be performed by FIB, and a specific method may include the following steps: randomly selecting a single particle from the positive electrode active material powder to be measured, cutting a thin slice with a thickness of about 100 nm from the middle position or near the middle position of the selected particle, and performing a TEM test on the thin slice to measure the thickness of the coating layer, measuring 3 to 5 points and taking an average value.

[0072] A second aspect of the present application provides a secondary battery including the positive electrode plate of the first aspect of the present application.

[0073] A secondary battery generally includes a case assembly, a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, with the positive electrode plate, negative electrode plate, separator, and electrolyte positioned within a cavity formed by the case assembly. Depending on the type of battery, the case assembly may be an aluminum plastic film or metal case assembly, and the metal case assembly may further include a prismatic case assembly or a cylindrical case assembly. When the case assembly is a metal case assembly, it generally includes a case with an opening on at least one side and a lid for sealing the opening. Any type of battery may be considered within the technical scope of the battery of the second aspect of the present application as long as its positive electrode plate includes the positive electrode plate of the first aspect of the present application. In addition to the aforementioned characteristics of the active material and the compaction density of the active material layer of the positive electrode plate, other structural characteristics or material selection of the positive electrode plate, and the selection of the negative electrode plate, separator, and electrolyte can all be selected according to common selection methods in the art, and those skilled in the art can flexibly select the appropriate materials according to their actual needs.

[0074] In some embodiments of the present application, the secondary battery may be a laminated battery or a wound battery, and the wound battery may be a prismatic battery or a cylindrical battery, or optionally, the battery may be a cylindrical battery. Depending on the type of battery, the positive electrode plate, the negative electrode plate, and the separator may be stacked to form a stacked unit, or may be stacked and then wound to form a wound body.

[0075] In some embodiments of the present application, the battery may be a single battery core or a battery module assembled with battery cores, and the number of battery cores included in the battery module may be multiple, and the specific number may be adjusted based on the application and capacity of the battery module. Furthermore, the battery module may further include a packaging assembly having an accommodating space, and the packaging assembly may include a bottom plate, a side plate, a cover plate, etc.

[0076] In some embodiments of the present application, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0077] The present application also provides a power consuming device including the positive electrode plate of the first aspect of the present application and / or the secondary battery of the second aspect of the present application.

[0078] The secondary battery, such as a battery core, a battery module, or a battery pack, may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. In one specific example, the power consuming device may be a vehicle.

[0079] The power consuming device can select a specific type of battery according to its usage needs, such as a battery core, a battery module, or a battery pack.

[0080] As an example, the power consuming device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, and a battery pack or battery module may be employed to meet the demand for high power output and high energy density of the battery of the power consuming device.

[0081] As another example, the power consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. The power consuming device generally requires a thin design and may employ a battery core as a power source.

[0082] The following examples of the present application are described. The examples described below are illustrative and are used only to interpret the present application and should not be understood as limitations on the present application. Unless specific techniques or conditions are specified in the examples, they are carried out according to the techniques or conditions described in literature in the field or according to the product instructions. Unless the manufacturer is specified, the reagents or equipment used are all commercially available products.

[0083] Secondary battery manufacturing and testing methods: 1. Pouch laminated battery: (1) Manufacturing of positive electrode plate: The positive electrode active material, polyvinylidene fluoride (PVDF), and conductive carbon were added to a certain amount of N-methylpyrrolidone (NMP) so that the mass ratio of positive electrode active material:polyvinylidene fluoride:conductive carbon was 90:5:5. The mixture was stirred in a drying chamber to produce a uniform slurry, and the viscosity was controlled to 3000-10000 mPa·S. The slurry was then applied to aluminum foil and dried to produce a positive electrode plate.

[0084] (2) Manufacturing of negative electrode plates: Graphite, sodium carboxymethylcellulose (CMC), styrene butadiene rubber (SBR), and conductive carbon were added to a certain amount of deionized water in a mass ratio of 90:2:3:5 (graphite:sodium carboxymethylcellulose:styrene butadiene rubber:conductive carbon). The mixture was stirred to produce a uniform slurry, the viscosity of which was controlled to 3000-10000 mPa·S. The slurry was then applied to copper foil and dried to produce a negative electrode plate.

[0085] (3) Pouch laminate battery manufacturing: The resulting positive and negative electrodes and separator (a polyethylene (PE) porous polymer film) are then stacked in a Z-shaped configuration to form a corresponding battery core. The battery core is then vacuum dried at 90°C for 12 hours. The positive and negative tabs are then ultrasonically welded together, with an aluminum tab for the positive electrode and a nickel tab for the negative electrode. The positive and negative tabs are located on the same side of the battery core. After the tabs are welded, the battery core is then placed in an appropriate-sized aluminum plastic film and top-packaged. The typical packaging temperature is 145°C. The electrolyte is then injected (1 mol / L LiPF6 / (ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate (DMC)) (volume ratio 1:1:1) + 5 wt.% fluoroethylene carbonate (FEC)). The battery is then allowed to stand, undergoes formation, aging, venting, secondary packaging, and capacity testing to produce a pouch-laminated battery.

[0086] 2. Conduct a cycle test at 25°C on the manufactured pouch laminate battery: The pouch laminate battery manufactured as above was charged at 0.5C0 from 2.5 to 4.4V in a constant temperature environment of 25°C up to 4.4V, then constant voltage charged at 4.4V until the current was ≦0.05C0, left to stand for 5 minutes, and then discharged at 1C0 down to 2.5V. The capacity was measured. n (n=1, 2, 3……) and repeat the above operation. The capacity retention rate is C n / C3 ratio, C n When / C3×100%=80%, extract the corresponding number of cycles and use it as the cycle capability assessment index. 3. Positive electrode plate Sheet Resistance test: Sheet Resistor: BER1300 Sheet The test was carried out using a resistance meter, and the test steps were as follows: (a) the electrode plate was fabricated into a wafer with a diameter of 22 mm; (b) the fabricated wafer was placed on the test plate of the BER1300 instrument; (c) the test pressure of the instrument was adjusted to 0.4 T, the test temperature to 25°C, and the test time to 10 seconds, and then the test was started. The obtained resistance value was: Sheet It is resistance.

[0087] 4. 10%~80% SOC charging time experiment: First, a capacity test was conducted on the pouch laminate battery. The procedure was as follows: constant current charging at 0.33C up to a full charge voltage V1, then switching to constant voltage charging. When the charging current decreased to 0.05C, the constant voltage charging ended, followed by discharging at 0.33C down to a full discharge voltage V2. This procedure was repeated three times, and the capacity result of the third test was used as the basis. At the same time, the gram capacity of the positive electrode was calculated using the third test result.

[0088] Different rates for pouch laminate batteries (C1 <C2<C3<C4<……<C n ) charging test, during which the charge rate must be increased from low to high, and the total electrical voltage of the pouch laminated battery and the negative electrode voltage of the pouch laminated battery must be monitored simultaneously during the charging process. The detailed process is as follows: the pouch laminated battery is charged at C1 until the full charge voltage V1 or the negative electrode voltage reaches 0V, and the battery SOC value at the end of charge is extracted. It is then discharged at 0.33C until the full discharge voltage V2 is reached. By repeating the above process, the SOC value at the end of charge can be obtained at different rates. A scatter plot of the SOC at the end of charge versus the rate is created and fitted to obtain the relationship between the SOC at the end of charge and the rate. 20%, 30%, 40%, 50%, 60%, 70%, and 80% are substituted into the relationship equation to obtain the corresponding rate (C 20% , C 30% , C 40% , C 50% , C60% , C 70% , C 80% After obtaining the value, the 10%~80% SOC charging time can be calculated, where 10%~80% SOC charging time = (60 / C 20% +60 / C 30% +……+60 / C 80% )×10%.

[0089] Example 1 In pouch laminate batteries, (i) Positive electrode plate: The number of layers of the positive electrode plate is 15, the thickness of the single-layer positive electrode plate is 0.13 mm, and the weight of the positive electrode active material layer per unit area of ​​the positive electrode plate is 0.038 g / cm 2 The first positive electrode active material is NCM523, the Dv50 particle size of the first positive electrode active material is 4.2 μm, and the specific surface area of ​​the first positive electrode active material is 0.5 m 2 / g, and the second positive electrode active material is LiMn 0.6 Fe 0.4 PO4, the Dv50 particle size of the second positive electrode active material is 0.8 μm, and the specific surface area of ​​the second positive electrode active material is 13.3 m 2 / g, and the positive electrode plate is

number

number

[0090] (ii) Negative electrode plate: The number of layers of the negative electrode plate is 16, the thickness of the single-layer negative electrode plate is 0.13 mm, and the weight of the negative electrode active material layer per unit area of ​​the negative electrode plate is 0.012 to 0.030 g / cm 2 is.

[0091] (iii) Separator: The number of layers of the separator is 16, and the thickness of the single-layer separator is 0.012 mm.

[0092] (iv) The thickness of the internal cavity of the battery case is 6.1 mm.

[0093] (v) The electrolyte filling coefficient of the secondary battery is 2.84 g / Ah.

[0094] Examples 2 to 15 and Comparative Examples 1 to 3 The difference between Examples 1 to 9 and Comparative Examples 1 to 3 and Example 1 is that the positive electrode plate

number

[0095] The difference between Examples 10 to 15 and Example 1 is that the type of the second positive electrode active material is different, as shown in Table 1 in detail.

[0096] The batteries assembled in Examples 1 to 15 and Comparative Examples 1 to 3 were tested, and the test results are shown in Table 1.

[0097] [Table 1-1] [Table 1-2]

[0098] Results and conclusions: As can be seen from the above examples and comparative examples, by adopting the battery design proposal of the present application, the battery's rapid charging performance and cycle performance can be improved. Specifically, as can be seen from Examples 1 to 9 and Comparative Examples 1 to 3, when the first and second positive electrode active materials are determined, the resistance of the positive electrode plate, the content of Mn element in the electrode plate, and the relative amounts of Mn element and A' element (Fe element in the above example) used, and

number

number

number

number

[0099] Finally, it should be noted that the above embodiments are merely for illustrating the technical solutions of the present application, and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications may still be made to the technical solutions described in the above embodiments, or equivalent substitutions may be made for some or all of the technical features therein. Such modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and should all be included in the scope of the claims and description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in the embodiments may be combined in any manner. The present application is not limited to the specific embodiments disclosed in the description, but includes all technical solutions included within the scope of the claims.

Claims

1. A positive electrode plate, wherein the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer including a first positive electrode active material and a second positive electrode active material; The first positive electrode active material is Li ａ Ni ｂ Co ｃ M １ｄ M ２ｅ O ｆ R' ｇ wherein 0.75≦a≦1.2, 0<b<1, 0<c<1, 0<d<1, 0≦e≦0.2, 1≦f≦2.5, 0≦g≦1, f+g≦3; and M １ is Mn element and / or Al element, M ２ R' includes one or more elements of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb; and R' includes one or more elements of N, F, S, and Cl; The second positive electrode active material is Li １＋ｘ M ３ｎ Mn １－ｙ A' ｙ P １－ｚ E ｚ O ４ where -0.100≦x≦0.100, 0≦n≦1.1, 0.001≦y≦0.500, 0≦z≦0.100, and M ３ comprises one or more elements of Zn, Al, Na, K, Mg, Nb, Mo and W; A' comprises one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb and Ge; E comprises one or more elements of B, Si, N, S, F, Cl and Br; The positive electrode plate is [Equation 1] Fulfilling where: w （Ｍｎ） is the mass fraction of Mn in the positive electrode active material layer, d is the thickness of the positive electrode active material layer, and the unit is mm. T is the weight of the positive electrode active material layer per unit area of ​​the positive electrode plate, and its unit is g / cm ２ and R is the sheet resistance of the positive electrode plate at 25°C, in Ω. 【Request Item 2】 【Number 2】 where w （Ａ´） is the mass fraction of A' in the positive electrode active material layer, and w （Ｐ） is the mass fraction of P in the positive electrode active material layer.

3. 0.01≦w （Ａ´） 2. The positive electrode plate of claim 1, wherein the ρ is ≦0.

05.

4. The second positive electrode active material includes at least one of the following two positive electrode active materials: (i) 0.001≦y≦0.500, n=0, the second positive electrode active material is Li １＋ｘ Mn １－ｙ A' ｙ P １－ｚ E ｚ O ４ and (ii) 0.001≦y≦0.500, 0.9≦n≦1.1, the second positive electrode active material is Li １＋ｘ M ３ｎ Mn １－ｙ A' ｙ P １－ｚ E ｚ O ４ The positive electrode plate according to claim 1 ,

5. 2. The positive electrode plate according to claim 1, wherein 0.032≦T≦0.

043.

6. The positive electrode plate according to claim 1 , wherein 0.11≦d≦0.

16.

7. The positive electrode plate according to claim 1 , wherein 0<R≦1.

2.

8. M １ The positive electrode plate according to claim 1 , wherein is Mn element.

9. Satisfy at least one of the following conditions: (i) [Equation 3] and (ii) the Dv50 particle size of the second positive electrode active material is 0.21 μm to 1.53 μm; (iii) The specific surface area of ​​the second positive electrode active material is 9.2 m ２ / g to 23.6m ２ The positive electrode plate according to claim 1, wherein the SiO2 content is 1 / g. [Request Item 10] [Number 4] and [Equation 5] The positive electrode plate according to claim 9 ,

11. The positive electrode plate according to claim 1, wherein the first positive electrode active material has a Dv50 particle size of 2.1 μm to 6.3 μm.

12. The specific surface area of ​​the first positive electrode active material is 0.3 m ２ / g to 1.2m ２ The positive electrode plate according to claim 1, wherein the SiO2 content is 1 / g.

13. The positive electrode plate according to claim 1 , wherein a first coating layer is provided on a surface of the first positive electrode active material.

14. The positive electrode plate according to claim 13, wherein the thickness of the first coating layer is 20 nm to 150 nm.

15. The positive electrode plate according to claim 1 , wherein a second coating layer is provided on a surface of the second positive electrode active material.

16. The positive electrode plate according to claim 15, wherein the second coating layer has a thickness of 10 nm to 50 nm.

17. The positive electrode plate according to claim 1 , wherein in the second positive electrode active material, E includes one or more elements of B, Si, N, and S.

18. 2. The positive electrode plate according to claim 1, wherein in the second positive electrode active material, A' includes one or more elements of Fe, Ti, V, Ni, Co, and Mg.

19. A secondary battery comprising the positive electrode plate according to claim 1.

20. 20. A power consuming device comprising the positive electrode plate according to any one of claims 1 to 18 and / or the secondary battery according to claim 19.

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