Secondary batteries and power consumption devices

Abstract

This application discloses a secondary battery and a power consumption device. Here, the secondary battery includes a battery case, and a positive electrode plate, a negative electrode plate, a separator, and an electrolyte disposed within the battery case. A separator is provided between the positive electrode plate and the negative electrode plate. Here, the positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material includes Li a Ni b Co c M 1d M 2e [[ID=ID=10]]O f R´ g and satisfies 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. The second positive electrode active material includes Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4 and satisfies -0.100 ≦ x ≦ 0.100, 0 ≦ n ≦ 1.1, 0.001 ≦ y ≦ 1, 0 ≦ z ≦ 0.100. A´ includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge. The secondary battery satisfies 【Equation 1】 TIFF2025528470000034.tif14168.

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and more particularly to 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 requirements for lithium-ion batteries are also increasing, including high energy density, good cycle performance, and safety. Increasing the battery pack margin is a common method for improving battery energy density. However, increasing the battery pack margin reduces the space available for expansion of the positive and negative plates inside the battery. Therefore, when a high-pack margin battery is charged, the winding core is subjected to a relatively large compressive force, which can severely extrude the electrolyte, causing problems such as lithium precipitation, which affect the battery's cycle performance and safety. Summary of the Invention

[0003] In view of the technical problems existing in the background art, the present application provides a secondary battery that aims to improve the cycle performance and safety performance of a high group margin battery.

[0004] In order to achieve the above object, a first aspect of the present application provides a secondary battery, the secondary battery including a battery case, and a positive electrode plate, a negative electrode plate, a separator, and an electrolyte disposed in the battery case, the separator being provided between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes 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 M2e O f R´ g including, 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 includes one or more elements selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb; R´ includes 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 including LiMnA´xPyEzO4, where -0.100 ≤ x ≤ 0.100, 0 ≤ n ≤ 1.1, 0.001 ≤ y ≤ 1, and 0 ≤ z ≤ 0.100; M3 includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; A´ includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; E includes one or more elements selected from B, Si, N, S, F, Cl, and Br. The secondary battery is

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[0005] Compared with the prior art, the secondary battery of the first aspect of the present application has at least the following beneficial effects: (1) Li a [ Nib Co c M 1d M 2e O f R´ g The positive electrode active material system has a small lattice shrinkage during the charging process, and when the battery group margin is relatively high, it cannot match the expansion of the negative electrode plate during the charging process, which is likely to cause serious extrusion of the electrolyte during the charging process, resulting in problems such as lithium precipitation and deterioration of battery performance, and Li a Ni b Co c M 1d M 2e O f R´ g The positive electrode active material Li has a relatively large lattice contraction during the charging process. 1+x M 3n Mn 1-y A´ y P 1-z E z By mixing O4, the lattice shrinkage of the positive electrode can be effectively improved and matched with the expansion of the negative electrode, thereby preventing the deterioration of battery performance at high packing margins and the occurrence of safety issues as much as possible. (2) The positive electrode active material Li a Ni b Co c M 1d M 2e O f R´ g contributes to improving the energy density of the battery, and the positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z Mixing O4 contributes to improving cycle performance, and by flexibly adjusting the relative amounts of the two used, it is possible to achieve both high energy density and good cycle performance in a high group margin battery. (3) By controlling the group margin of this battery within the above range, it is possible to obtain a high group margin while also further satisfying the flattening of the negative electrode and the long-term performance of the battery.

[0006] In some embodiments of the present application, the second active cathode material is: (i) y=1, n=0;1+x A'P 1-z E z O4, A' is Fe element, or A' is Fe element and one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; and (ii) 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 O4, and (iii) 0.001≦y≦0.500, 0.9≦n≦1.1, and the second positive electrode active material is Li 1+x M 3n Mn 1-y A´ y P 1-z E z and O4.

[0007] In some embodiments of the present application,

number

[0008] In some embodiments of the present application, 0.11 mm≦d 正極 ≦0.16 mm, and optionally, 0.12 mm≦d 正極 ≦0.14mm, and 0.15mm≦d 負極 ≦0.20 mm, and optionally, 0.16 mm≦d 負極 By controlling the thickness of the single-layer positive electrode plate and the single-layer negative electrode plate within the above-mentioned ranges, it is possible to simultaneously achieve high capacity, cycle performance, and rate performance of the secondary battery, which is advantageous in improving the discharge current and rapid charge performance of the battery.

[0009] In some embodiments of the present application, 0.009 mm≦d セパレータ≦0.014 mm, and optionally, 0.0011 mm≦d セパレータ By controlling the thickness of the single-layer separator within a certain range, it is possible to prevent short circuits between the positive and negative electrodes, as well as to avoid short circuits that can easily occur when the separator is punctured by burrs, particles, or dendrites, while also preventing the separator from being too thick and affecting the energy density of the battery.

[0010] In some embodiments of the present application, the positive electrode plate has an average lattice volume shrinkage of 2.7% or more of the positive electrode active material in a completely lithium-extracted state. By controlling the lattice volume shrinkage of the positive electrode active material within a predetermined range, deterioration of battery performance at high group margins and the occurrence of safety issues can be further avoided, which is advantageous for satisfying the long-term performance of the battery.

[0011] In some embodiments of the present application, the positive electrode plate has a lattice volume shrinkage rate of the second positive electrode active material of 2.7% to 6.9% in a completely lithium-deintercalated state. By controlling the lattice volume shrinkage rate of the second positive electrode active material within a predetermined range, it is possible to further improve both the cycle performance and rate performance of the secondary battery.

[0012] In some embodiments of the present application, the positive electrode plate has an average lattice volume shrinkage rate of the positive electrode active material of 2.7% to 4.2% in a completely lithium-extracted state. By controlling the lattice volume shrinkage rate of the positive electrode active material within a predetermined range, the cycle performance and rate performance of the secondary battery can be further improved.

[0013] In some embodiments of the present application, the compaction density of the active material layer of the positive electrode plate is 3.10 g / cm 3 ~3.50g / cm 3 and selectively 3.15 g / cm 3 ~3.40g / cm 3 and more selectively 3.15 g / cm 3 ~3.35g / cm 3By controlling the compaction density of the active material layer of the positive electrode plate within a predetermined range, it is possible to improve the polarization problem of the electrode plate and the cycle performance and long-term use performance of the high group margin battery.

[0014] In some embodiments of the present application, the compaction density of the active material layer of the negative electrode plate is 1.6 g / cm 3 ~1.70g / cm 3 and selectively 1.64 g / cm 3 ~1.69g / cm 3 Controlling the compaction density of the active material layer of the negative electrode plate within a predetermined range is advantageous in improving the cycle performance and long-term use performance of a high group margin battery.

[0015] In some embodiments of the present application, the secondary battery has a filling coefficient of 2.5 g / Ah to 3.0 g / Ah, optionally 2.62 g / Ah to 2.90 g / Ah, and more optionally 2.70 g / Ah to 2.90 g / Ah. Controlling the filling coefficient within a predetermined range not only ensures battery safety, but also favors sufficient infiltration of the electrode plates, ensuring battery performance.

[0016] In some embodiments of the present application, a first coating layer is provided on the 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. The provision of the first coating layer can reduce side reactions between the first positive electrode active material and the electrolyte, and improve the stability of the positive electrode active material structure, thereby improving cycle performance and safety.

[0017] In some embodiments of the present application, the thickness of the first coating layer is 20 nm to 150 nm.

[0018] In some embodiments of the present application, a second coating layer is provided on the surface of the second positive electrode active material, and optionally the second coating layer includes at least one of pyrophosphate, phosphate, and carbon. The provision of the second coating layer not only reduces 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, while simultaneously improving the structural stability, thereby improving cycle performance and safety.

[0019] In some embodiments of the present application, the second coating layer has a thickness of 10 nm to 50 nm.

[0020] 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, and / or the second positive electrode active material has a Dv50 particle size of 0.25 μm to 1.49 μm, and optionally 0.5 μm to 0.9 μm.

[0021] In some embodiments of the present application, in the second positive electrode active material, E includes one or more elements of B, Si, N, and S. Selecting the element E doped into phosphorus site from a predetermined range further contributes to changing the difficulty of changing the Mn-O bond length, promoting lithium ion migration and improving the rate performance of the secondary battery.

[0022] In some embodiments of the present application, in the second positive electrode active material, A' includes one or more elements of Fe, 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 secondary battery can be further improved.

[0023] In some embodiments of the present application, the second active cathode material is: (i) y=1, n=0; 1+x A'P 1-z E zO4, A' includes Fe element, or A' includes Fe element and one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; and (ii) 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 and O4.

[0024] In some embodiments of the present application, the first positive electrode active material and the second positive electrode active material are

number

number

number

number

[0025] In some embodiments of the present application,

number

[0026] In some embodiments of the present application,

number

[0027] In some embodiments of the present application, 0.001≦n (Ni) ≦0.0026, and optionally, 0.0014≦n (Ni) ≦0.002 and 0.00007≦n (A´) ≦0.00075, and optionally, 0.0001≦n (A´) ≦0.00032.

[0028] A second aspect of the present application provides a power consuming device including the secondary battery of the first aspect of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0029] 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.

[0030] 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.

[0031] 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. Unless otherwise specified, in this application, a numerical range, e.g., "10 to 50," represents a shorthand expression for any combination of real numbers between 10 and 50, where 10 and 50 are both 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 merely a shorthand expression for this combination of numbers.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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).

[0038] At present, improving the battery group margin is one of the common methods for improving the energy density of a battery. However, when the battery case group margin is improved, the space occupancy rate of the battery's winding core or stacking unit increases, that is, the number of layers of negative and positive electrode plates included in the winding core / stack unit increases, or the number of winding core / stack units increases, and the space available for the expansion of the positive and negative electrode plates inside the battery correspondingly decreases. Therefore, when a high group margin battery is charged, the winding core will have a relatively large pressing force, which will seriously extrude the electrolyte, causing problems such as lithium precipitation, and Li a Ni b Co c M 1d M 2e O f R´ g If the positive electrode active material system has small lattice contraction during charging and a relatively high battery pack margin, it cannot match the expansion of the negative electrode plate during charging, which can easily cause serious electrolyte extrusion during charging, resulting in problems such as lithium deposition and deteriorating battery performance. Lithium deposition not only reduces battery performance and significantly shortens cycle life, but also limits battery capacity, causes serious internal short circuits, and can cause catastrophic consequences such as combustion and explosion, creating safety issues.

[0039] In view of this, the first aspect of the present application provides a secondary battery, which includes a battery case, a positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution disposed within the battery case. A separator is provided between the positive electrode plate and the negative electrode plate. Here, the positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material includes 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, and f + g ≦ 3. M1 is an Mn element and / or an Al element. M2 includes one or more elements selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb. R´ includes one or more elements selected from N, F, S, and Cl. The second positive electrode active material includes 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 ≦ 1, and 0 ≦ z ≦ 0.100. M3 includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W. A´ includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge. E includes one or more elements selected from B, Si, N, S, F, Cl, and Br. The secondary battery satisfies

Number

[0040] The inventors have discovered that: a Ni b Co c M 1d M 2e O f R´ g The positive electrode active material Li has a relatively large lattice contraction during the charging process. 1+x M 3n Mn 1-y A´ y P 1-z E z By mixing O4, the lattice shrinkage of the positive electrode can be effectively improved and matched with the expansion of the negative electrode, thereby minimizing the deterioration of battery performance at high packing margins and the occurrence of safety issues. However, the following problem still exists: when the battery is charged, the lithium absorption rate and internal deposition state of the active material layer in different areas on the negative electrode plate are different, which causes different stresses in different areas of the negative electrode plate during charging, ultimately causing wrinkles in the plate (wrinkles affect the long-term performance of the battery). Generally, when the winding core or stacked unit is charged, it presses against the housing to flatten the negative electrode. However, if the battery packing margin is too low, Li 1+x M 3n Mn 1-y A´ y P 1-z E z Li using O4 a Ni b Co c M 1d M 2e O f R´ g If the shrinkage of the positive electrode grid is improved by mixing, the winding core or stacking unit is likely to be unable to contact the housing wall during charging, that is, the winding core or stacking unit cannot flatten itself under the external pressure, causing wrinkles in the negative electrode. If the battery group margin is too high, Li 1+xM 3n Mn 1-y A´ y P 1-z E z O4 to Li a Ni b Co c M 1d M 2e O f R´ g By mixing the two, the lattice shrinkage can be improved and the pressure on the winding core during charging can be reduced. However, as the battery usage time increases, side reactions inevitably occur on the surface of the negative electrode. These side reactions increase the thickness of the negative electrode plate, further increasing the battery group margin and causing Li 1+x M 3n Mn 1-y A´ y P 1-z E z If the O4 mixture exceeds its improvement capacity, it will ultimately deteriorate the battery performance. Therefore, it is necessary to control the group margin appropriately to ensure both the flattening of the negative electrode and the long-term performance of the battery. In the course of research, the inventor discovered the following: By controlling the battery group margin to satisfy the limited range (0.9 to 0.95) of the above formula, while at the same time 1+x M 3n Mn 1-y A´ y P 1-z E z Li using O4 a Ni b Co c M 1d M 2e O f R´ g When the lattice shrinkage of the positive electrode is improved by mixing, it is not only advantageous to flatten the negative electrode, but also can effectively match the expansion of the negative electrode, thereby avoiding the deterioration of battery performance at high group margin and the occurrence of safety issues as much as possible. In other words, it is possible to obtain high group margin while also satisfying the flattening of the negative electrode and the long-term performance of the battery. In addition, the positive electrode active material Li a Ni b Co c M 1d M 2e O f R´ g contributes to improving the energy density of the battery, and the positive electrode active material Li1+x M 3n Mn 1-y A´ y P 1-z E z Mixing O4 contributes to improving cycle performance. By flexibly adjusting the relative usage amounts of both, it is possible to further achieve both the high energy density and good cycle performance of the high-group margin battery. In short, this secondary battery is not only advantageous for flattening the negative electrode and meeting the long-term performance of the battery, but can further achieve both the high energy density and good cycle performance of the high-group margin battery, and improve the service life and safety of the secondary battery.

[0041] Furthermore, the inventors have intensively studied and found that, on the premise that the secondary battery of this application meets the above conditions, the performance of the secondary battery can be further improved by controlling the selection of the positive electrode active material, the thickness of the electrode plate and separator, the lattice shrinkage rate of the positive electrode active material, the compaction density of the active material layer of the electrode plate, the liquid injection coefficient, etc. That is, on the premise that the above conditions are met, one or more of the following conditions are selectively satisfied.

[0042] In some embodiments of this 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 be all 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 Lia Ni b Co c M 1d M 2e O f R´ g satisfies the above-mentioned predetermined range, which is more advantageous in that it combines a 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´ g In the above, taking a nickel-cobalt-manganese ternary cathode active material (i.e., NCM) system 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 and improve the safety and structural stability of the material. However, too much manganese content will destroy the layered structure of the material and reduce the specific capacity of the material. Cobalt can stabilize the layered structure of the material and improve the cycle and rate performance of the material, but too much cobalt content will reduce the actual capacity. By ensuring that the nickel-cobalt-manganese content satisfies the above specified range, the secondary battery can have relatively high energy density, good rate performance, and good cycle performance. Optionally, M1 can be Mn element, 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.

[0043] 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 M3n Mn 1-y TO y P 1-z AND 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 may include lithium sites, manganese sites, and Doping at least one of the phosphorus sites 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 doping element of the manganese site can further improve the particle morphology and the compaction density. In particular, a relatively high lattice contraction rate can reduce the lattice contraction rate during the charging process of the negative electrode. However, excessive lattice contraction of the cathode 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 lithium desorption, improving the structural stability of the cathode 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. It also reduces interfacial side reactions with the electrolyte during use, 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 the rate performance of secondary batteries. 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 will result in a decrease in the lithium content of the entire core system, which will affect the gram capacity of the material. The value of y limits the total amount of all doping elements and influences the manganese content in the system and the voltage plateau of the material.The E element is doped at the phosphorus site, and since the PO tetrahedron is relatively stable, a 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. In addition, by selecting the above doping element and the x, n, y, and z values, 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. Compared to materials such as lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate that are applicable to conventional high-voltage systems, this is advantageous for achieving good cycle performance and high-temperature stability, as well as a relatively large gram capacity and a relatively large compaction density. As can be seen, 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 replaced by 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 zO4 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.

[0044] 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. Selecting the element E doped into the phosphorus site from a predetermined range 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 of the secondary battery.

[0045] 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 of 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 secondary battery can be further improved.

[0046] 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 zIn 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 the cycle performance and safety performance of the secondary battery, but also promotes the adjustment of Mn-O bonds, lowers the lithium ion migration barrier, promotes lithium ion migration, and improves the rate performance of the secondary battery. Furthermore, by selectively simultaneously doping the lithium site, manganese site, and phosphorus site, significantly improved rate performance, improved cycle performance, and / or high-temperature stability can be further achieved.

[0047] 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 three conditions: (i) y = 1, n = 0, and the second positive electrode active material is Li 1+x A'P 1-z E z O4, and A' may be Fe, or A' may be Fe and may include one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge, i.e., the second positive electrode active material may include lithium iron phosphate or lithium iron phosphate doped at at least one of the iron site (the same as the manganese site) and the phosphorus site. (ii) 0.001≦y≦0.500, n=0, and in this case, the second positive electrode active material may include Li 1+x Mn 1-y A´ y P 1-z E zThe compound LiMnPO4 may be lithium manganese phosphate or lithium manganese phosphate doped at least one of the lithium site, manganese site, and phosphorus site. In this application, the lithium manganese phosphate is modified to significantly reduce the dissolution of elements at the manganese site and reduce the lattice change rate, which is advantageous for use in secondary batteries to improve the cycle performance, rate performance, and safety performance of the battery and to increase the capacity of the battery. For example, by doping specific elements in specific amounts 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 dissolution 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 (iii) 0.001≦y≦0.500, 0.9≦n≦1.1, and the second positive electrode active material may contain 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 y value 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 function. If y exceeds 0.5, the Mn content in the system will be 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 A'P 1-z Ez O4, Li 1+x Mn 1-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.

[0048] As a specific example, the second positive electrode active material is (i) y=1, n=0, and the second positive electrode active material is Li 1+x A'P 1-z E z O4, A' is Fe element, or A' is Fe element and one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; and (ii) 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 positive electrode active material may include a positive electrode active material having a chemical formula of Li 1+x A'P 1-z E z O4 and / or the formula Li 1+x Mn 1-y A´ y P 1-z E z In these two chemical formulas, the values ​​of x and z are independent, but both have the chemical formula Li 1+x M 3n Mn 1-y A´ y P 1-z Ez The stoichiometric numbers of x and z in O4 satisfy a limited numerical range.

[0049] 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 n The 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.

[0050] In some embodiments of the present application,

number

[0051] In some embodiments of the present application, in a secondary battery, the thickness d of a single layer positive electrode plate 正極 0.11mm≦d 正極 ≦0.16mm, for example, d 正極 The thickness d of the single-layer negative electrode plate may be 0.115 mm, 0.12 mm, 0.125 mm, 0.13 mm, 0.135 mm, 0.14 mm, 0.145 mm, 0.15 mm, or 0.155 mm, or may be in a range of any of the above values. 負極 0.15mm≦d 負極 ≦0.20mm, for example, d 負極may be 0.155 mm, 0.16 mm, 0.165 mm, 0.17 mm, 0.175 mm, 0.18 mm, 0.185 mm, 0.19 mm, or 0.195 mm, or may be in a range of any of the above values. Here, if the thickness of the positive / negative electrode plate is too small, it indicates that the active material coating on the electrode plate is too thin or the compaction density is too high, the former of which affects the energy density, and the latter of which affects the infiltration of the electrolyte into the electrode plate and deteriorates the cycle performance. If the thickness is too large, it indicates that the active material coating is too thick or the compaction density is too low, the former of which increases the polarization of the electrode plate and deteriorates the battery performance, and the latter of which increases the contact resistance between particles in the electrode plate and deteriorates the battery performance. In this application, by controlling the thickness of the single-layer positive electrode plate and the single-layer negative electrode plate within the above-mentioned predetermined ranges, it is possible to simultaneously achieve high capacity, cycle performance, and rate performance of the secondary battery, and it is advantageous to improve the discharge current and fast charging performance of the battery. Optionally, 0.12 mm≦d 正極 ≦0.14 mm, and further optionally, 0.16 mm≦d 負極 ≦0.18 mm, and by controlling the thicknesses of the single-layer positive electrode plate and the single-layer negative electrode plate within respective predetermined ranges, it is possible to further improve the compatibility of high capacity, cycle performance, and rate performance of the secondary battery. It should be noted that the method for measuring the thickness of the positive electrode plate and the negative electrode plate is not particularly limited and can be flexibly selected by those skilled in the art according to actual needs. Specifically, conventional testing methods in this field can be used, for example, a lithium battery plate thickness measuring instrument can be used to detect the thickness of the secondary battery plate.

[0052] In some embodiments of the present application, in a secondary battery, the thickness d of the single layer separator セパレータ 0.009mm≦d セパレータ ≦0.014mm, for example, セパレータThe thickness of the separator may be 0.01 mm, 0.011 mm, 0.012 mm, 0.013 mm, etc., or may be any range of the above values. Here, if the thickness of the separator is too large, it will increase the polarization of the battery, increase the difficulty of electrolyte penetration, and deteriorate the energy density of the battery. If the thickness of the separator is too small, it will affect the safety performance of the battery. In this application, by controlling the thickness of the single-layer separator within a predetermined range, it is possible to effectively ensure the insulation between the positive and negative electrodes and prevent contact short circuits between the positive and negative electrodes, as well as to provide the separator with a certain degree of tensile resistance, tear resistance, and puncture resistance, thereby preventing short circuits that are easily caused by punctures of the separator by burrs, particles, or dendrites. At the same time, by controlling the thickness of the single-layer separator within a predetermined range, it is possible to avoid the impact of an excessive separator thickness on the energy density of the battery. Optionally, 0.0011 mm≦d セパレータ ≦0.012 mm, which effectively prevents short circuits between the positive and negative electrodes and short circuits that are likely to occur when the separator is pierced by burrs, particles, or dendrites, and further reduces the adverse effect of the separator on the energy density of the secondary battery. Here, the thickness of the separator can be tested using conventional methods in this field, for example, by referring to GB / T 6672-2001.

[0053] In some embodiments of the present application, the positive electrode plate may have an average lattice volume shrinkage rate of the positive electrode active material of 2.7% or more in a completely lithium-deintercalated state, such as 2.8%, 3%, 3.2%, 3.5%, 4.0%, 2.7 to 7%, or any range of the above values. The lattice volume shrinkage is related to the lithiation state of the positive electrode material, i.e., the lithium desorption state of the positive electrode material (the positive electrode material is in a completely lithium-absorbed state at the beginning, and as the charging process progresses, lithium is desorbed from the positive electrode material, reaches the negative electrode, and is further absorbed). As charging progresses, the lithium content in the positive electrode material decreases, and the lattice volume shrinks (after lithium desorption, the valence state of some elements involved in the electrochemical reaction in the positive electrode material increases correspondingly, and at this time, their ionic radii become smaller, which macroscopically appears as lattice volume shrinkage). The degree of lattice volume shrinkage varies in different lithium desorption states. In this application, the completely lithium desorption state is taken as an example (i.e., from the completely lithium-absorbed state to the completely lithium desorption state), and the Li content in the first positive electrode active material is a Ni b Co c M 1d M 2e O f R´ g The lattice volume shrinkage of the mixed Li 1+x M 3n Mn 1-y A´ y P 1-z E zThe lattice volume shrinkage of O4 in the fully lithium-extracted state is relatively high. By controlling the lattice volume shrinkage of the mixed positive electrode active material in the fully lithium-extracted state within a predetermined range after mixing the first and second positive electrode active materials, the expansion of the electrode plate during charging can be more closely matched. This can prevent battery performance degradation and safety issues at high pack margins, which is beneficial for achieving satisfactory long-term battery performance. It should be noted that in this application, the average lattice volume shrinkage of the positive electrode active material refers to the lattice volume shrinkage of the composite positive electrode active material obtained by mixing the first and second positive electrode active materials in the fully lithium-extracted state. Given the difference in the lattice volume shrinkage of the first and second positive electrode active materials in the fully lithium-extracted state, the average lattice volume shrinkage is used herein to refer to the lattice volume shrinkage of the mixed composite positive electrode active material in the fully lithium-extracted state.

[0054] In some embodiments of the present application, in the positive electrode plate, in a completely lithium-deintercalated state, the lattice volume shrinkage rate of the second positive electrode active material may be 2.7% to 6.9%, for example, 2.9%, 3.3%, 3.6%, 4.1%, 4.5%, 4.8%, 5.2%, 5.6%, 6.0%, 6.4%, 6.8%, etc., or may be within a range of any of the above values. Here, a relatively high lattice shrinkage rate is advantageous in that it matches the volume expansion of the negative electrode during charging, but if the lattice shrinkage rate of the positive electrode material is too high, lithium will be deintercalated. However, by further controlling the lattice volume shrinkage rate of the second positive electrode active material in the fully lithium-extracted state within a predetermined range, the positive electrode active material obtained by mixing the second positive electrode material with the first positive electrode material can have a more appropriate volume shrinkage rate, which not only matches the volume expansion of the negative electrode during charging but also promotes lithium ion transport, further improving lithium ion mobility and achieving better compatibility between the cycle performance and rate performance of the secondary battery. Furthermore, the positive electrode plate may have an average lattice volume shrinkage rate of 2.7% to 4.2% in the fully lithium-extracted state. That is, the average lattice volume shrinkage rate of the positive electrode active material obtained by mixing the first positive electrode material with the second positive electrode material in the fully lithium-extracted state may be 2.7% to 4.2%, which not only matches the volume expansion of the negative electrode during charging but also ensures good lithium ion mobility, further improving the cycle performance and rate performance of the secondary battery.

[0055] In the present application, the lattice volume shrinkage rate of the positive electrode active material can be measured by a method known in the art, for example, by using a method such as X-ray diffraction pattern (XRD). As a specific example, an XRD test can be performed on a positive electrode active material in different lithium desorption states (points may be selected based on the charging curve of a button battery of the positive electrode material, and it is recommended to select one point every 5% SOC, where SOC = capacity when charged to a certain voltage / total charge capacity). The XRD test conditions are 12 to 40 degrees, and the sweep rate is The temperature was 0.02 degrees / min. The test data was processed using Jade software to obtain the lattice parameters a / b / c / β of the positive electrode material in this state, and the lattice volume in this state was calculated using the formula V = abc × sinβ. Similarly, the lattice volume of the positive electrode material in different lithium desorption states was obtained to calculate the lattice volume shrinkage rate, where lattice volume shrinkage rate in the fully delithiated state = (lattice volume (fully delithiated state) - lattice volume (non-delithiated state)) / lattice volume (non-delithiated state) × 100%. Positive electrode active materials in different lithium desorption states can be obtained as follows: The positive electrode active material is assembled into a button cell, and the button cell is charged to a selected voltage according to the method described above. The button cell is then disassembled in a glove box, the positive electrode plate is removed, and soaked in DMC solution for 6 hours, then washed with DMC solution 2-3 times, and then the plate is dried.

[0056] In some embodiments of the present application, the packed density of the active material layer of the positive electrode plate is 3.10 g / cm 3 ~3.50g / cm 3 For example, 3.15 g / cm 3 , 3.20g / cm 3 , 3.25g / cm 3 , 3.30g / cm 3 , 3.35g / cm 3 , 3.40g / cm 3 , 3.45g / cm 3or may be any range of values ​​above. Here, the packing density of the active material layer of the positive electrode plate can be measured in accordance with GB / T 24533-2009. If the packing density of the positive electrode active material layer in the positive electrode plate is too low, the contact between particles inside the plate is likely to loosen, increasing contact resistance. A positive electrode plate with a positive electrode active material layer with a too low packing density will be relatively thick and will have difficulty meeting the design requirement for high packing margin. However, if the packing density of the positive electrode active material layer in the positive electrode plate is too high, two problems will occur: first, some particles inside the plate will be prone to fracture / crack after cold pressing, and the fractured particles / cracks will likely react with the electrolyte, resulting in a decrease in battery performance; and during battery cycling, the internal pressure of the plate will be high, causing the particles to be pressed against each other and therefore prone to fracture. Second, the porosity of the plate will decrease, making it more difficult for the electrolyte to infiltrate, further reducing battery performance. In the present application, by controlling the packing density of the active material layer of the positive electrode plate within a predetermined range, it is possible to improve the polarization problem of the electrode plate and to advantageously improve the cycle performance and long-term use performance of the high-group margin battery. Optionally, the packing density of the active material layer of the positive electrode plate is 3.15 g / cm 3 ~3.40g / cm 3 and optionally 3.15 g / cm 3 ~3.35g / cm 3 This is further advantageous in improving the cycle performance and long-term use performance of the high group margin battery.

[0057] In some embodiments of the present application, the compaction density of the active material layer of the negative electrode plate is 1.6 g / cm 3 ~1.70g / cm 3 For example, 1.62 g / cm 3 , 1.64g / cm 3 , 1.66g / cm 3 , 1.68 / cm 3The density of the active material layer of the negative electrode plate can be measured in accordance with GB / T 24533-2009. If the density of the negative electrode active material layer in the negative electrode plate is too low, the contact between particles inside the plate will be loose, increasing contact resistance and hindering the design requirement for high group margin. If the density of the negative electrode active material layer is too high, battery performance will likely be attenuated. In the present application, controlling the density of the active material layer of the negative electrode plate within a predetermined range is advantageous not only for improving negative electrode performance but also for achieving a match between the lattice volume contraction rate of the positive electrode active material and the volume expansion during charging of the negative electrode, thereby further improving the cycle performance and long-term use performance of high group margin batteries. Optionally, the density of the active material layer of the negative electrode plate is 1.64 g / cm. 3 ~1.69g / cm 3 This is further advantageous in improving the cycle performance and long-term use performance of the high group margin battery.

[0058] In some embodiments of the present application, the injection coefficient of the secondary battery may be 2.5 g / Ah to 3.0 g / Ah, for example, 2.6 g / Ah, 2.65 g / Ah, 2.7 g / Ah, 2.75 g / Ah, 2.8 g / Ah, 2.85 g / Ah, 2.9 g / Ah, 2.95 g / Ah, etc., or may be in a range consisting of any of the above values. The inventors discovered that when the secondary battery pack capacity is high and the positive plate compaction density is relatively high, the corresponding difficulty of electrolyte infiltration is also relatively high. A too low injection coefficient results in a small amount of electrolyte, making it difficult to meet the infiltration demands of the plates and likely resulting in a rapid deterioration of battery performance. A too high injection coefficient further reduces the internal free space of the battery, which can lead to internal gas generation during battery use. This reduction in internal free space can increase the battery's internal pressure and affect battery safety. In this application, controlling the injection coefficient within the above specified range not only ensures battery safety, but also promotes sufficient infiltration of the plates and ensures battery performance. Alternatively, the injection coefficient of the secondary battery can be 2.62g / Ah to 2.90g / Ah, and more preferably 2.70g / Ah to 2.90g / Ah, thereby achieving a balance between battery safety and battery performance.

[0059] 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. The 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.

[0060] In some embodiments of the present application, the thickness of the first coating layer may be 20 nm to 150 nm, such as 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 foregoing values. If the thickness of the first coating layer is too thin, the possibility of rupture / deep damage to the positive electrode active material during use increases, significantly reducing the performance-enhancing and protective effect of the first positive electrode active material; if the thickness of the first coating layer is too thick, lithium ions will need a longer transport path from the electrolyte to the active material system, significantly affecting the performance of the active material; and when the coating layer sinters, the coating material will react with lithium in the internal material, reducing the available active lithium in the material and the corresponding gram capacity of the material. In the present 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 positive electrode active material can be effectively improved, and the surface structure of the material can be stabilized.

[0061] 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, and may be, for example, 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 range of the above values. 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 for preventing crushing or powdering during charge and discharge, thereby reducing capacity loss in the secondary battery and shortening the diffusion path of active ions, thereby increasing the electron conduction rate and improving the cycle performance of the secondary battery. At the same time, it also provides the active material with adequate active sites. A too small particle size results in a relatively large number of active sites, which increases side reactions during the material's cycle process and significantly adversely affects cycle performance. A too large particle size results in a relatively small number of active sites, which significantly adversely affects power performance. Furthermore, controlling the Dv50 particle size of the first positive electrode active material within a predetermined range based on the thickness of the first coating layer can further ensure that the secondary battery has a relatively high energy density. Optionally, the Dv50 particle size of the first positive electrode active material may be 3.5 μm to 4.9 μm, which further enhances the compatibility between high energy density and good cycle performance of the secondary battery.

[0062] 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 conductive performance and desolvation ability of the positive electrode active material. Carbon materials have good electronic conductivity. When applied to secondary 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 conductive properties 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.

[0063] 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 any range of the above values. 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, 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.

[0064] 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 enhance interparticle electron transport, 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 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 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 excessive coating thickness affecting the compaction density of the electrode plate when this sub-coating layer contains amorphous carbon can be avoided.

[0065] 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.

[0066] In some embodiments of the present application, the Dv50 particle size of the second positive electrode active material may be 0.25 μm to 1.49 μm, such as 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, or 1.4 μm, or may be any range of values ​​above. 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 the second positive electrode active material from being crushed or pulverized during charging and discharging, thereby not only reducing the capacity loss of the secondary battery but also shortening the diffusion path of active ions and increasing the electron conduction rate, which is advantageous in improving the cycle performance of the secondary battery. At the same time, the active material can have appropriate active sites, thereby achieving 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 and preventing relatively large voids between particles of the positive electrode active material. Furthermore, controlling the Dv50 particle size of the second positive electrode active material within a predetermined range based on the thickness of the second coating layer can further ensure that the secondary battery has a relatively high energy density. Furthermore, the lattice change rate of the second positive electrode active material and the elution of transition metals or doped elements can be reduced, thereby improving the high-temperature cycle stability and high-temperature storage performance of the secondary battery. Alternatively, the Dv50 particle size of the second positive electrode active material may be 0.5 μm to 0.9 μm, which further enables the secondary battery to achieve both high energy density and good cycle performance.

[0067] In some embodiments of the present application, the first and second positive electrode active materials are

number

number

number

number

[0068] Here, the second positive electrode active material Li 1+x M 3n Mn 1-y A´ y P 1-z E z O4, the first positive electrode active material Li a Ni b Co c M 1d M 2e O f R´ gAlthough the specific capacity of the first positive electrode active material is higher and the electrical conductivity is good, the lattice volume change rate after lithium deintercalation is relatively low, which is unfavorable for matching with the volume expansion of the negative electrode after lithium absorption. Furthermore, increasing the Ni content in the first positive electrode active material contributes to improving the energy density of the battery, but is unfavorable for lattice contraction of the composite positive electrode and may impair cycle performance. Doping other elements into the manganese site of the second positive electrode active material can improve the lattice contraction during the lithium deintercalation process and improve cycle performance, but excessive doping can impair the energy density of the battery. By selecting an appropriate doping amount, the energy density and cycle performance of the battery can be simultaneously ensured. For example, in one specific example, when manganese and iron elements are simultaneously contained in the manganese site, a high manganese to iron ratio can improve the voltage platform, which is advantageous for improving the energy density of the battery. However, if the manganese to iron ratio is too high, a large amount of trivalent manganese in the lithium desorbed state may destroy the solid solution structure, reducing the specific capacity and cycle capacity retention rate of the material, causing a decrease in cycle performance, and affecting the service life of the positive electrode. In this application, the Ni content in the positive electrode plate is provided by the first positive electrode active material,

number

number

[0069] Selectively,

number

number

number

[0070] In some embodiments of the present application, 0.001≦n (Ni) ≦0.0026, for example, n (Ni) may be 0.0011, 0.0011, 0.0013, 0.0015, 0.0017, 0.0019, 0.0021, 0.0023, 0.0025, etc., or may be in a range consisting of any of the above numerical values, where in the positive electrode active material after mixing, the Ni element is provided by the first positive electrode active material, and an increase in the Ni element content in the first positive electrode active material contributes to an improvement in battery energy density, but is detrimental to lattice contraction of the composite positive electrode, which may impair cycle performance, and in the present application, the Ni element content n in the positive electrode plate (Ni) By making n satisfy the above-mentioned predetermined range, the secondary battery can further have a relatively high energy density and good cycle performance. (Ni) When the ratio is ≦0.002, the secondary battery can further have a relatively high energy density and good cycle performance.

[0071] In some embodiments of the present application, 0.00007≦n (A´) ≦0.00075, for example, n(A´) may be 0.0001, 0.00015, 0.0002, 0.00025, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, or may be in a range of any of the above values. Doping another element into the manganese site of the second positive electrode active material can improve the lattice contraction during the lithium desorption process and improve the cycle performance, but if the doping amount is too large, the energy density of the battery may be impaired. In this application, the content n of the A' element in the positive electrode plate is (A´) By satisfying the above-mentioned predetermined range, the secondary battery can further have a relatively high energy density and good cycle performance. (A´) When the ρ is ≦0.00032, the battery can further have a relatively high energy density and good cycle performance.

[0072] In some embodiments of the present application, depending on the type of secondary battery, the battery case may be an aluminum plastic film or a metal case assembly, etc., and the metal case assembly may further include a prismatic case assembly and a cylindrical case assembly. When the battery case 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. Here, the composition of the negative electrode plate and the specific material or type of the separator may be materials or types commonly used in the art, and the composition of the electrolyte may also be a composition commonly used in the art. The selection of the positive electrode active material for the positive electrode plate has already been described in detail above and will not be described further here. However, the selection of the adhesive, conductive agent, thickness of the positive electrode active material layer, etc. can be flexibly selected by those skilled in the art according to actual needs.

[0073] 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. 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.

[0074] In some embodiments of the present application, the secondary 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.

[0075] 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.

[0076] The present application also provides a power consuming device including the secondary battery of the first aspect of the present application.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] Secondary battery manufacturing and testing methods: 1. Pouch laminated battery: (1) Manufacturing of positive electrode plates: 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.

[0083] (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.

[0084] (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.

[0085] 2. (a) Conduct a cycle test at 25°C on the pouch laminate battery manufactured in (a): The pouch laminated battery manufactured as above was charged at 0.5C0 from 2.5 to 4.4V in a constant temperature environment of 25°C, then charged at a constant voltage of 4.4V to a current of ≦0.05C0, left to stand for 5 minutes, and then discharged at 1C0 to 2.5V. The capacity was measured. n (n=1, 2, 3......) and repeat the above procedure. The capacity retention rate is C n Calculate the ratio of C / C3, nWhen / C3×100%=80%, the corresponding number of cycles is extracted and used as the test index for cycle capacity. After the cycle test is completed, the negative electrode plate is disassembled in a dry room or glove box to obtain it. The remaining lithium salt crystals on the surface of the electrode plate are washed with the main solvent of the battery electrolyte. A 1×2cm diameter area is then removed from the center of the electrode plate. 2 The sample was then cut and transferred to a vacuum transfer device or a protective inert atmosphere. A cross section was then prepared using an argon ion beam polishing (CP) machine at low temperature. After cutting, the sample was attached to a cross section sample holder with conductive tape and transferred to a SEM vacuum chamber for observation to obtain the cross section morphology of the sample. The deposition of lithium at the negative electrode interface was then observed.

[0086] Example 1 In pouch laminate batteries, (i) Positive electrode plate The number of layers of the positive electrode plate N1 is 15, and the thickness of a single layer of the positive electrode plate d 正極 is 0.13 mm, and the compaction density of the active material layer of the positive electrode plate is 3.10 g / cm 3 The first positive electrode active material is NCM523, the Dv50 particle size of the first positive electrode active material is 4.1 μm, 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 0.81 μm, and the first positive electrode active material and the second positive electrode active material are

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[0087] (ii) Negative electrode plate The number of layers of the negative electrode plate N2 is 16, and the thickness of a single layer of negative electrode plate d 負極 is 0.13 mm, and the compaction density of the active material layer of the negative electrode plate is 1.70 g / cm 3 is.

[0088] (iii) Separator The number of separator layers N3 is 16, and the thickness of a single separator d セパレータ is 0.011 mm, (iv) Thickness of the battery case cavity d ケース is 4.5 mm, (vi) The electrolyte filling coefficient of the secondary battery is 2.73 g / Ah; (v) Group margin is

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[0089] Examples 2 to 5 and Comparative Examples 1 to 3 The differences between Examples 2 to 5 and Comparative Examples 1 and 2 and Example 1 are that the thickness of the cavity in the battery case is different and the group margin of the secondary battery is different.

[0090] The difference between Comparative Example 3 and Example 1 is that the composition of the positive electrode active material is different; Comparative Example 3 does not contain the second positive electrode active material.

[0091] Examples 6 to 13 The difference between Examples 6 to 13 and Example 1 is that the injection coefficient of the secondary battery is different.

[0092] Examples 14-15 The difference between Examples 14 and 15 and Example 1 is that the composition of the second positive electrode active material is different, and details are shown in Table 1.

[0093] Examples 16 to 20 The difference between Examples 16 to 20 and Example 1 is that in the first positive electrode active material and the second positive electrode active material,

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[0094] Examples 21 to 24 The difference between Examples 21 to 24 and Example 1 is that the Dv50 particle size of the first positive electrode active material is different.

[0095] Examples 25 to 28 The difference between Examples 25 to 28 and Example 1 is that the Dv50 particle size of the second positive electrode active material is different.

[0096] The secondary batteries assembled in Examples 1 to 28 and Comparative Examples 1 to 3 were subjected to a cycle performance test. The test results are shown in Table 1.

[0097] [Table 1] TIFF2025528470000025.tif248161TIFF2025528470000026.tif248161TIFF2025528470000027.tif248161

[0098] Results and conclusions: As can be seen from the examples and comparative examples, adopting the battery design proposal of the present application can improve the cycle performance and safety of high-group margin batteries. Specifically, as can be seen from Examples 1-5 and Comparative Examples 1-3, by combining a nickel-cobalt-manganese ternary positive electrode active material with a lithium manganese iron phosphate positive electrode active material and controlling the group margin of the battery within the range of 0.9-0.95, the number of cycles at which the battery's capacity retention rate drops to 80% can be increased to 1,000 or more, and lithium precipitation problems do not occur. Furthermore, as can be seen from the data in Table 1, after combining a nickel-cobalt-manganese ternary positive electrode active material with a lithium manganese iron phosphate positive electrode active material, the group margin of the battery also affects the battery's cycle performance and safety. A group margin that is too high or too low is detrimental to improving the battery's cycle performance, and a group margin that is too high can cause lithium precipitation problems and affect battery safety. A group margin of 0.91-0.94 is preferred. As can be seen from Examples 1 and 6 to 13, for the battery designs of the above examples of the present application, the injection coefficient also has some influence on the cycle performance and safety of the battery, and with the increase of the injection coefficient, the range is preferably 2.5g / Ah to 3.0g / Ah, and more preferably 2.62g / Ah to 2.90g / Ah. As can be seen from Examples 1 and 14 to 20, for the battery designs in the above examples of the present application, the composition of the second positive electrode active material and the molar ratio of A' element to Ni element also have a certain effect on the cycle performance and safety of the battery. This is mainly because, when the second positive electrode active material changes, the improvement effect on the cycle performance and safety performance of the battery may also change after it is mixed with the nickel-cobalt-manganese ternary positive electrode active material. The molar ratio of A' element to Ni element limits the mixing ratio of the second positive electrode active material and the nickel-cobalt-manganese ternary positive electrode active material to a certain extent. If the mixing ratio of the two is different, the improvement effect on the cycle performance and safety performance of the battery may also change. Here, the molar ratio of A' element to Ni element is optionally 0.02 to 1.5, and more optionally 0.02 to 0.2.As can be seen from Examples 1 and 21 to 28, in the battery designs of the above examples of the present application, the particle size of the first positive electrode active material and the particle size of the second positive electrode active material also have some effect on the cycle performance and safety of the battery. This is mainly because changes in the particle size of the two materials affect the active sites, compaction density, and diffusion paths of active ions of the positive electrode active materials. Here, the Dv50 particle size of the first positive electrode active material is preferably 2.1 μm to 6.3 μm, and the Dv50 particle size of the second positive electrode active material is preferably 0.25 μm to 1.49 μm.

[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 secondary battery includes a battery case, and a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution disposed in the battery case, the separator being provided between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate includes a 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≦1, 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 secondary battery is [Equation 1] Fulfilling Here, d 正極 is the thickness of the single layer positive electrode plate, in mm, and d 負極 is the thickness of the single layer negative electrode plate, in mm, and d セパレータ is the thickness of the single layer separator, in mm, and d ケース is the thickness of the cavity of the battery case, in mm; N １ is the number of layers of the positive electrode plate in the battery case, and N ２ is the number of layers of the negative electrode plate in the battery case, and N ３ is the number of layers of the separator in the battery case.

2. The second positive electrode active material is (i) y = 1, n = 0, the second positive electrode active material is Li １＋ｘ A'P １－ｚ E ｚ O ４ and A' is Fe element, or A' is Fe element and one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; (ii) 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 (iii) 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 secondary battery according to claim 1 , comprising a positive electrode active material that satisfies at least one of the following conditions: 【Request 3】 【Number 2】 The secondary battery according to claim 1 or 2,

4. 0.11 mm≦d 正極 ≦0.16 mm, and optionally 0.12 mm≦d 正極 ≦0.14 mm, 0.15 mm≦d 負極 ≦0.20 mm, and optionally 0.16 mm≦d 負極 The secondary battery according to claim 1 , wherein the thickness is ≦0.18 mm.

5. 0.009 mm≦d セパレータ ≦0.014 mm, and optionally 0.0011 mm≦d セパレータ The secondary battery according to claim 1 , wherein the thickness is ≦0.012 mm.

6. The secondary battery according to claim 1 , wherein the positive electrode plate has an average lattice volume shrinkage rate of the positive electrode active material of 2.7% or more in a completely lithium-extracted state.

7. 7. The secondary battery according to claim 1, wherein the positive electrode plate has a lattice volume shrinkage rate of the second positive electrode active material of 2.7% to 6.9% in a completely lithium-deintercalated state.

8. 8. The secondary battery according to claim 1, wherein the positive electrode plate has an average lattice volume shrinkage rate of the positive electrode active material of 2.7% to 4.2% in a completely lithium-extracted state.

9. The compaction density of the active material layer of the positive electrode plate is 3.10 g / cm ３ ~3.50 g / cm ３ and optionally 3.15 g / cm ３ ~3.40 g / cm ３ and more preferably 3.15 g / cm ３ ~3.35g / cm ３ The secondary battery according to claim 1 , wherein

10. The compaction density of the active material layer of the negative electrode plate is 1.6 g / cm ３ ~1.70 g / cm ３ and optionally 1.64 g / cm ３ ~1.69 g / cm ３ The secondary battery according to claim 1 , wherein

11. The secondary battery has a liquid injection coefficient of 2.5 g / Ah to 3.0 g / Ah, optionally 2.62 g / Ah to 2.90 g / Ah, and further optionally 2.70 g / Ah to 2.90 g / Ah. The secondary battery according to any one of claims 1 to 10.

12. 12. The secondary battery according to claim 1, wherein a first coating layer is provided on a surface of the first positive electrode active material, and the first coating layer optionally contains one or more elements of Ti, Al, B, Nb, Zr, Si, and W.

13. 13. The secondary battery according to claim 12, wherein the first coating layer has a thickness of 20 nm to 150 nm.

14. 14. The secondary battery according to claim 1, wherein a second coating layer is provided on a surface of the second positive electrode active material, and optionally, the second coating layer contains at least one of pyrophosphate, phosphate, and carbon.

15. 15. The secondary battery according to claim 14, wherein the second coating layer has a thickness of 10 nm to 50 nm.

16. The Dv50 particle size of the first cathode active material is 2.1 μm to 6.3 μm, and optionally 3.5 μm to 4.9 μm; and / or 16. The secondary battery according to claim 1, wherein the Dv50 particle size of the second positive electrode active material is 0.25 μm to 1.49 μm, and optionally 0.5 μm to 0.9 μm.

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

18. The secondary battery according to claim 1 , wherein in the second positive electrode active material, A′ includes one or more elements of Fe, Ti, V, and Mg.

19. The second positive electrode active material is (i) y = 1, n = 0, the second positive electrode active material is Li １＋ｘ A'P １－ｚ E ｚ O ４ A' is an Fe element, or A' is an Fe element and one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ga, Sn, Sb, Nb, and Ge; (ii) 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 The secondary battery according to claim 1 , comprising a positive electrode active material that satisfies at least one of the following conditions:

20. The first positive electrode active material and the second positive electrode active material are [Equation 3] 、 [Equation 4] where n （Ｎｉ） is the molar amount of Ni in the positive electrode plate, and the unit is mol, and n （Ａ´） is the molar amount of A' in the positive electrode plate, and the unit is mol, and n （Ｐ） The secondary battery according to claim 1 , wherein ρ is the molar amount of P in the positive electrode plate, and the unit is mol. 【Request 21】 【Number 5】 The secondary battery according to claim 20, 【Request 22】 【Number 6】 The secondary battery according to claim 20 or 21,

23. 0.001≦n （Ｎｉ） ≦0.0026, and optionally 0.0014≦n （Ｎｉ） ≦0.002, 0.00007≦n （Ａ´） ≦0.00075, and optionally 0.0001≦n （Ａ´） 23. The secondary battery according to claim 20, wherein the ρ is ≦0.00032.

24. A power consuming device comprising a secondary battery according to any one of claims 1 to 23.

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