Cathode material, preparation method thereof, cathode sheet, secondary battery and electric device

Abstract

The application discloses a positive electrode material and a preparation method thereof, a positive electrode sheet, a secondary battery and an electric device, and relates to the field of batteries. x Co y Mn z O2, x is greater than or equal to 0.8, y is less than or equal to 0.12, and x+y+z is equal to 1; and the modification element comprises a rare earth element and / or a refractory metal element. The application can improve the cycle stability of the positive electrode material by modifying the high-nickel ternary particle through the rare earth element and / or the refractory metal element.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a positive electrode material and its preparation method, a positive electrode sheet, a secondary battery, and an electrical device. Background Technology

[0002] With the goal of carbon neutrality being set, developing abundant and low-cost cathode materials to obtain high-energy-density batteries remains a significant challenge in meeting the ever-increasing range demands of electrical devices such as long-range electric vehicles. High-nickel layered materials, with their advantages of high capacity and low cost, are considered one of the most promising cathode materials for lithium-ion batteries. Currently, widely used polycrystalline high-nickel cathodes generally suffer from poor cycle stability during deep charge-discharge processes, severely limiting their commercial application. Summary of the Invention

[0003] This application provides a cathode material and its preparation method, a cathode electrode sheet, a secondary battery, and an electrical device, which can improve the cycle stability of the cathode material.

[0004] In a first aspect, this application proposes a cathode material, said cathode material comprising cathode material particles, said cathode material particles comprising a matrix and modifying elements, wherein:

[0005] The matrix includes LiNi x Co y Mn z O2, x≥0.8, y≤0.12, x+y+z=1;

[0006] The modifying elements include rare earth elements and / or refractory metal elements.

[0007] In the technical solution of this application embodiment, the high-nickel ternary particles are modified using the aforementioned rare earth elements and / or refractory metal elements. Rare earth metal atoms (hereinafter referred to as element A) can enter the surface structure of the cathode material, forming a fast-ion conductor network rich in A on the surface of the high-nickel ternary particles. This isolates the electrolyte, reduces side reactions, and thus improves cycle performance. Refractory metal elements (hereinafter referred to as element B) can enter the high-nickel cathode phase, forming a stable structure with strong bond energy, reducing the formation of impurity phases such as rock salt under high pressure, and improving cycle performance. Therefore, by modifying the high-nickel ternary particles with the aforementioned rare earth elements and / or refractory metal elements, the cycle stability of the cathode material can be improved.

[0008] In some embodiments, the rare earth elements are at least partially located on the surface of the matrix. When the high-nickel ternary particles are modified using the rare earth elements, at least some rare earth metal atoms (hereinafter referred to as element A) can enter the surface structure of the cathode material, forming an A-rich fast ion conductor network on the surface of the high-nickel ternary particles. This network isolates the electrolyte, reduces side reactions, and thus improves cycle performance.

[0009] In some embodiments, the refractory metal element is at least partially located within the matrix. When the high-nickel ternary particles are modified using the refractory metal element, at least a portion of the refractory metal element will enter the high-nickel cathode phase, forming a stable structure with strong bond energy, reducing the formation of impurity phases such as rock salt phase under high pressure, thereby improving cycle performance.

[0010] In some embodiments, the rare earth element includes at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Modifying high-nickel ternary particles with the above-mentioned rare earth elements can significantly improve the cycle performance of high-nickel ternary particles as electrode cathode materials.

[0011] In some embodiments, the rare earth element is lanthanum. Using lanthanum to modify high-nickel ternary particles significantly improves their cycle performance as cathode materials, and the modification process is easy to implement.

[0012] In some embodiments, the refractory metal element includes at least one selected from titanium, zirconium, niobium, vanadium, molybdenum, and tungsten. Modifying high-nickel ternary particles using the aforementioned refractory metal elements can significantly improve the cycle performance of high-nickel ternary particles as electrode cathode materials.

[0013] In some embodiments, the refractory metal element is niobium. Using niobium to modify high-nickel ternary particles significantly improves their cycle performance as cathode materials, and the modification process is easy to implement.

[0014] In some embodiments, the modifying element is bonded to the matrix through doping. By bonding the modifying element to the matrix through doping, the bonding effect between the modifying element and the matrix can be improved, the possibility of the modifying element detaching from the matrix can be reduced, and the modification effect on high-nickel ternary particles can be guaranteed.

[0015] In some embodiments, the doping mass of the modifying element is 1-10% based on 100% of the mass of the cathode material. Controlling the doping mass of the modifying element within the range of 1-10% results in better modification of high-nickel ternary particles and makes it easier to control costs.

[0016] In some embodiments, the doping mass of the modifying element is 3-5% based on 100% of the mass of the cathode material. Controlling the modifying element within this doping range results in a more significant modification effect on the high-nickel ternary particles.

[0017] In some embodiments, the LiNi x Co y Mn z O2 is a single-crystal particle. By selecting single-crystal high-nickel ternary particles, their non-porous and high-strength characteristics help to improve the compaction density of the cathode material, thereby increasing the energy density of the battery; at the same time, it is also beneficial to improve the structural stability and cycle performance of the cathode material, and has better stability under high pressure.

[0018] In some embodiments, the LiNi x Co y Mn z The Dv50 of O2 is ≥4μm. By limiting the Dv50 of the high-nickel ternary particles to ≥4μm, the breakage rate of the particles during cycling can be reduced, which is beneficial to obtaining a better compaction density, thereby obtaining a cathode material with better structural stability and cycling performance.

[0019] In some embodiments, the LiNi x Co y Mn z The SPAN of O2 is ≥1.6. By limiting the SPAN of the high-nickel ternary particles to ≥1.6, the breakage rate of the particles during cycling can be reduced, which is beneficial to obtaining a better compaction density, thereby obtaining a cathode material with better structural stability and cycling performance.

[0020] Secondly, this application proposes a method for preparing a cathode material, comprising the following steps:

[0021] Modifier and LiNi x Co y Mn z O2 is mixed and then calcined to obtain the positive electrode material; among which...

[0022] The LiNi x Co y Mn z In O2, x≥0.8, y≤0.12, x+y+z=1;

[0023] The modifier includes rare earth elements and / or refractory metal elements.

[0024] In the technical solution of this application embodiment, LiNi is modified by using a modifier including the rare earth elements and / or refractory metal elements. x Co y Mn zO2 mixed calcination can produce high-nickel ternary particles modified with rare earth elements and / or refractory metal elements, which effectively improves the structural stability and cycle performance of high-nickel ternary particles as battery cathode materials.

[0025] In some embodiments, the modifier includes Li X A Y B Z O (X+3Y+5Z) / 2 Li X A Y O (X+3Y) / 2 Or Li X B Z O (X+5Z) / 2 X≥5, Y≥3, Z≥2, A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten.

[0026] By using Li X A Y B Z O (X+3Y+5Z) / 2 Li a A b O (a+3b) / 2 Or Li a B c O (a+5c) / 2 As a modifier, with LiNi x Co y Mn z O2 mixed calcination can respectively produce high-nickel ternary particles modified with rare earth elements and refractory metal elements, high-nickel ternary particles modified with rare earth elements, and high-nickel ternary particles modified with refractory metal elements. All three methods can effectively improve the structural stability and cycle performance of high-nickel ternary particles as battery cathode materials.

[0027] In some embodiments, the calcination temperature is 600–800°C and the calcination time is 1–3 hours. Under these calcination conditions, the preparation efficiency of the cathode material is high.

[0028] Thirdly, this application proposes a positive electrode sheet, including the positive electrode material in the above embodiments or the positive electrode material prepared in the above embodiments.

[0029] Fourthly, this application proposes a secondary battery, including the positive electrode sheet in the above embodiments.

[0030] Fifthly, this application proposes an electrical device including the secondary battery described in the above embodiments. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 Schematic diagrams of some embodiments of the cathode material provided in this application.

[0033] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode material, its preparation method, the positive electrode sheet, the secondary battery, and the power application device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0038] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0040] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] Currently, judging from market trends, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of power battery applications, market demand is also constantly increasing.

[0042] With the goal of carbon neutrality being set, developing abundant and low-cost cathode materials to obtain high-energy-density batteries remains a significant challenge in meeting the ever-increasing range demands of electrical devices such as long-range electric vehicles. High-nickel layered materials, with their advantages of high capacity and low cost, are considered one of the most promising cathode materials for lithium-ion batteries. However, the widely used polycrystalline high-nickel cathodes generally suffer from poor cycle stability during deep charge-discharge processes, severely limiting their commercial application.

[0043] Based on the above considerations, in order to solve the problem that the poor cycle performance of high-nickel cathode materials limits their practical application, the inventors, after in-depth research, designed a scheme to modify high-nickel cathode materials by ion doping to improve their cycle performance.

[0044] Specifically, in some embodiments of this application, the cathode material includes cathode material particles, which in turn include a matrix and modifying elements, wherein the matrix includes LiNi. x Co y Mn z O2, x≥0.8, y≤0.12, x+y+z=1; Modifying elements include rare earth elements and / or refractory metal elements.

[0045] In the technical solution of this application embodiment, rare earth elements and / or refractory metal elements are used to modify high-nickel ternary particles. Rare earth elements (hereinafter referred to as element A) can enter the surface structure of the positive electrode, forming a fast-ion conductor network rich in A, which can isolate the electrolyte and reduce side reactions, thereby improving cycle performance. Refractory metal elements (hereinafter referred to as element B) can enter the high-nickel positive electrode phase, forming a stable structure with strong bond energy, reducing the formation of impurity phases such as rock salt under high pressure, and improving cycle performance. Therefore, modifying high-nickel ternary particles with rare earth elements and / or refractory metal elements can improve the cycle stability of the positive electrode material. Furthermore, modifying high-nickel ternary particles with both rare earth elements and refractory metal elements simultaneously, as shown by relevant performance tests, is more effective than modifying with a single rare earth element or a single refractory metal element, especially in terms of superior cycle life and storage time.

[0046] Rare earth elements are a collective term for 17 elements, including the lanthanides (La), scandium (Sc), and yttrium (Y). The lanthanides specifically refer to the 15 elements from lanthanum (element 57) to lutetium (element 71) in the periodic table. Theoretically, all rare earth elements can effectively modify the high-nickel ternary particles described in this application. In some embodiments of this application, the rare earth elements are lanthanides, specifically including at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Using these rare earth elements to modify the high-nickel ternary particles can significantly improve their cycle performance as a cathode material.

[0047] In some embodiments of this application, the rare earth element is lanthanum. Using lanthanum to modify high-nickel ternary particles significantly improves their cycle performance as cathode materials, and the modification process is easy to implement.

[0048] Typical refractory metals include tungsten, tantalum, molybdenum, niobium, hafnium, chromium, vanadium, zirconium, and titanium. Theoretically, all of these metal elements can effectively modify the high-nickel ternary particles described in this application. In some embodiments of this application, the refractory metal element includes at least one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten. Using the aforementioned refractory metal elements to modify the high-nickel ternary particles can significantly improve their cycle performance as an electrode cathode material.

[0049] In some embodiments of this application, the refractory metal element is niobium. Using niobium to modify high-nickel ternary particles significantly improves their cycle performance as cathode materials, and the modification process is easy to implement.

[0050] In some embodiments of this application, rare earth elements are at least partially located on the surface of the matrix. When high-nickel ternary particles are modified with rare earth elements, at least some rare earth metal atoms can enter the surface structure of the cathode material, forming an A-rich fast ion conductor network on the surface of the high-nickel ternary particles. This network isolates the electrolyte, reduces side reactions, and thus improves cycle performance.

[0051] In some embodiments of this application, the refractory metal elements are at least partially located inside the matrix. When high-nickel ternary particles are modified using refractory metal elements, at least some of the refractory metal elements will enter the high-nickel cathode phase, forming a stable structure with strong bond energy, reducing the formation of impurity phases such as rock salt phase under high pressure, thereby improving cycle performance.

[0052] In some embodiments, the modifying element is bonded to the matrix through doping. By bonding the modifying element to the matrix through doping, the bonding effect between the modifying element and the matrix can be improved, the possibility of the modifying element detaching from the matrix can be reduced, and the modification effect on high-nickel ternary particles can be guaranteed. Specifically, the above-mentioned doping methods include surface doping and / or bulk doping. When rare earth elements are used as modifying elements, it is surface doping, which is usually coated on the surface of the matrix. When refractory metal elements are used as modifying elements, it is bulk doping, which is usually inserted into the bulk phase of the matrix. In some embodiments of the present invention, both surface doping and bulk doping can be achieved by mixing and calcining the substance containing the modifying element with the matrix.

[0053] In some specific embodiments of this application, the modifying elements include lanthanides, and the lanthanides are at least partially located on the surface of the high-nickel ternary particles. This can be considered as modifying the surface layer of the high-nickel ternary particles. A atoms enter the surface structure of the cathode material, forming an A-rich fast-ion conductor network, which can isolate the electrolyte, reduce side reactions, and thus improve cycle performance. One way to modify high-nickel ternary particles using lanthanides is, for example, by using Li... X A YO (X+3Y) / 2 (X≥5, Y≥3, where X and Y are both integers, and A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium) and LiNi x Co y Mn z O2 high-nickel ternary particles mixed and calcined.

[0054] In some specific embodiments of this invention, the modifying element includes at least one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten, and it is at least partially located inside the high-nickel ternary particles. This can be considered as modifying the inner layer of the high-nickel ternary particles. The modifying element B enters the high-nickel cathode phase, forming a stable structure with strong bond energy, reducing the formation of impurity phases such as rock salt phase under high pressure, thereby improving cycle performance. One way to modify the high-nickel ternary particles using at least one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten is, for example, to use Li... X B Z O (X+5Z) / 2 (X≥5, Z≥2, where X and Z are both integers, and B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten) and LiNi x Co y Mn z O2 mixed and calcined.

[0055] In some specific embodiments of this application, see [reference]. Figure 1 As shown, the modifying elements include lanthanides and refractory metals. Lanthanides are at least partially located on the surface of the high-nickel ternary particles. To modify the surface layer of the high-nickel ternary particles, alpha atoms enter the cathode surface structure, forming an alpha-rich fast-ion conductor network, which can isolate the electrolyte and reduce side reactions, thereby improving cycle performance. Refractory metals are at least partially located inside the high-nickel ternary particles. To modify the inner layer of the high-nickel ternary particles, modifying element B enters the high-nickel cathode phase, forming a stable structure with strong bond energy, reducing the formation of impurity phases such as rock salt under high pressure, thereby improving cycle performance. Thus, through the combined modifying effect of lanthanides and refractory metals, the overall structure of the high-nickel cathode material is more stable, and its cycle performance is also more stable. The implementation of modifying elements including lanthanides and refractory metals can be achieved, for example, by using Li... X A Y B Z O (X+3Y+5Z) / 2 (X≥5, Y≥3, Z≥2, where X, Y, and Z are all integers; A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten) and LiNi x Co y Mn z O2 mixed and calcined.

[0056] For LiNi x Co y Mn z SEM and EDS tests were performed on the high-nickel ternary particles before and after O2 modification. It was found that element A was concentrated on the surface of the high-nickel ternary particles with shallow element deposition, while element B was incorporated into the bulk phase of the particles with more obvious element deposition. This shows that the modification method provided in this application can successfully achieve the effects of surface modification, inner layer modification or surface / bulk phase co-doping modification.

[0057] Furthermore, in some embodiments, the doping mass of the modifying element is 1-10% based on 100% of the cathode material mass. Controlling the doping mass of the modifying element within the range of 1-10% provides better modification effect for high-nickel ternary particles and makes it easier to control costs. It is understood that when the modifying element includes element A or element B, the doping amount of the modifying element refers to the doping amount of element A or element B in the high-nickel ternary particles; when the modifying element includes both element A and element B, the doping amount of the modifying element refers to the total doping amount of elements A and B.

[0058] In some embodiments, the doping mass of the modifying element is 3-5% based on 100% of the cathode material. Controlling the modifying element within this doping range results in a more significant modification effect on the high-nickel ternary particles and better cycle performance.

[0059] In some embodiments of this application, LiNi x Co y Mn z O2 is a single-crystal particle. By selecting single-crystal high-nickel ternary particles, their non-porous and high-strength characteristics help to improve the compaction density of high-nickel cathode materials, thereby increasing the energy density of the battery. At the same time, it is also beneficial to improve the structural stability and cycle performance of high-nickel cathode materials, and single-crystal high-nickel ternary materials have better high-voltage stability, with an upper limit voltage ≥4.3V. Under high voltage of 4.3V, the cell volume shrinkage of polycrystalline high-nickel is caused by the irreversible phase transition evolution of H2-H3, which inevitably leads to the formation of nanocracks in a highly delithiated state. In addition, the cathode surface inevitably comes into contact with the electrolyte, resulting in severe interfacial reactions. In this application, ion doping can accelerate electron / ion conduction and stabilize the internal lattice structure. Doping elements with strong metal-oxygen (MO) bond energy can suppress the migration of transition metal ions (TMs), reduce structural degradation, and promote Li+ diffusion. In addition, the fast ion conductor network formed by rare earth element modification in this application can improve low SOC kinetics and improve the power performance of the power battery.

[0060] When high-nickel materials are used as the positive electrode material of batteries, the particle size of the high-nickel materials will also have some impact on the relevant performance of the battery. Table 1 below shows the relevant performance parameters for different particle sizes.

[0061] Table 1. LiNi with different particle sizes x Co y Mn z O2 performance parameters

[0062]

[0063] As can be seen from Table 1, LiNi x Co y Mn z The increased particle size of O2 slightly reduces energy density, while significantly improving DCR, cycling and storage performance. Furthermore, the large single crystal particles are less prone to cracking and exhibit good high-voltage stability.

[0064] In some embodiments of this application, LiNi x Co y Mn z O2 has a Dv50 ≥ 4 μm. Here, Dv50 ≥ 4 μm refers to the particle size corresponding to 50% of the particle volume distribution being ≥ 4 μm. Thus, by limiting the Dv50 of high-nickel ternary particles to ≥ 4 μm, the particles of different sizes are tightly packed, avoiding excessive local stress in large particle packing that could lead to breakage. This reduces the breakage rate of high-nickel ternary particles during cycling, resulting in better compaction density and thus a cathode material with better structural stability and cycle performance. Furthermore, in practical applications, based on Dv50 ≥ 4 μm, a more specific particle size range can be selected according to the specific performance parameters required by the battery.

[0065] In some embodiments of this application, LiNi x Co y Mn z The SPAN of O2 is ≥1.6. Here, SPAN = (Dv90 - Dv10) / Dv50, where Dv90 is the particle size corresponding to 90% of the particle volume distribution, Dv10 is the particle size corresponding to 10% of the particle volume distribution, and Dv50 is the particle size corresponding to 50% of the particle volume distribution. By limiting the SPAN of high-nickel ternary particles to ≥1.6, the particles of different sizes are tightly packed, which avoids excessive local stress in large particle packing, making them more prone to breakage. This reduces the breakage rate of particles during cycling, resulting in better compaction density and thus a cathode material with better structural stability and cycling performance.

[0066] Secondly, this application proposes a method for preparing the positive electrode material in the above embodiments. Specifically, the method for preparing the positive electrode material includes the following steps:

[0067] Modifier and LiNi x Co y Mnz O2 is mixed and calcined to obtain the cathode material; among which, LiNi x Co y Mn z In O2, x≥0.8, y≤0.12, x+y+z=1; the modifiers include rare earth elements and / or refractory metal elements.

[0068] In the technical solution of this application embodiment, LiNi is modified by using a modifier including rare earth elements (A) and / or refractory metal elements (B). x Co y Mn z O2 mixing and calcination can cause the rare earth elements and / or refractory metal elements to be doped with the LiNi in a doping manner. x Co y Mn z By combining O2, high-nickel ternary particles modified with rare earth elements and / or refractory metal elements are produced, which effectively improves the structural stability and cycle performance of high-nickel ternary particles as battery cathode materials.

[0069] In some embodiments of this application, rare earth elements include lanthanides, specifically at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Refractory metal elements include at least one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten. Correspondingly, the modifier includes Li. X A Y B Z O (X+3Y+5Z) / 2 Li X A Y O (X+3Y) / 2 Or Li X B Z O (X+5Z) / 2 X≥5, Y≥3, Z≥2, and X, Y, and Z are all integers. A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten.

[0070] By using Li X A Y B Z O (X+3Y+5Z) / 2 Li a A b O (a+3b) / 2 Or Li a B c O (a+5c) / 2 As a modifier, with LiNi x Co y Mn zO2 mixed calcination can respectively produce high-nickel ternary particles with lanthanide elements modifying the surface of high-nickel ternary particles, high-nickel ternary particles with refractory metal elements modifying the interior of high-nickel ternary particles, and high-nickel ternary particles with rare earth elements modifying the surface of high-nickel ternary particles and simultaneously with refractory metal elements modifying the interior of high-nickel ternary particles. All three methods can effectively improve the structural stability and cycle performance of high-nickel ternary particles as battery cathode materials.

[0071] In some embodiments of this application, the modifier is Li X A Y O (X+3Y) / 2 (X≥5, Y≥3, where X and Y are both integers, and A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium), and LiNi x Co y Mn z O2 mixed calcination modifies the surface layer of high-nickel materials, allowing A atoms to enter the surface structure of the cathode material and form an A-rich fast-ion conductor network. This network isolates the electrolyte, reduces side reactions, and thus improves cycle performance.

[0072] In some embodiments of this application, the modifier is Li X B Z O (X+5Z) / 2 (X≥5, Z≥2, where X and Z are both integers, and B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten), and LiNi x Co y Mn z O2 mixed calcination modifies the inner layer of high-nickel materials, allowing boron to enter the high-nickel cathode phase and form a stable structure with strong bond energy. This reduces the formation of impurity phases such as rock salt under high pressure, thereby improving cycle performance.

[0073] In some embodiments of this application, the modifier is Li X A Y B Z O (X+3Y+5Z) / 2 (X≥5, Y≥3, Z≥2, and X, Y, and Z are all integers; A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten), and LiNi x Co y Mn zO2 mixed calcination enables simultaneous modification of the surface and inner layers of high-nickel materials. Through the co-doping of lanthanide metals and boron, the overall structural stability and cycle stability of high-nickel materials are further improved. At the same time, the surface layer of A and Li forms a fast ion conductor network, providing a fast diffusion channel for lithium-ion transport, which can further improve the power performance of the battery.

[0074] In some embodiments of this application, the calcination temperature is 600–800°C and the calcination time is 1–3 hours. Under these calcination conditions, the preparation efficiency of the cathode material is high.

[0075] In addition, single-crystal LiNi is also provided in some embodiments of this application. x Co y Mn z The preparation method of O2 is as follows: First, soluble sulfates of nickel, cobalt, and manganese are prepared into a solution with a total metal ion molar concentration of 1.0–2.2 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (e.g., 83:12:5). Then, a certain concentration of sodium hydroxide solution (4–8 mol / L) and ammonia water (0.1–0.5 mol / L) are added sequentially and stirred. A co-precipitation reaction is carried out under a nitrogen atmosphere, with the pH value of the co-precipitation reaction controlled at 9–12 and the reaction temperature at 40–60℃, to obtain a hydroxide precursor containing nickel, cobalt, and manganese. The obtained precursor is washed and dried, and LiOH and KCl flux are added. It is first sintered at 300–500℃ for 5–7 h, then calcined at 700–900℃ for 12–18 h, and then annealed in oxygen at 400–600℃ for 2–4 h to obtain single crystal LiNi. x Co y Mn z O2 (x≥0.8, y≤0.12, x+y+z=1) high-nickel ternary material powder.

[0076] Furthermore, in some embodiments of this application, Li is used. X A Y B Z O (X+3Y+5Z) / 2 (X≥5, Y≥3, Z≥2, A is lanthanum, B is niobium) for LiNi x Co y Mn z Taking O2 modification as an example, a more specific method for preparing cathode materials is also provided, with the following steps: using stoichiometric amounts of LiNO3, La(CH3COO)3, and C4H4NNbO9·nH2O as the raw materials for preparing Li X A Y B Z O (X+3Y+5Z) / 2The material is added to ethanol, and single-crystal ternary powder is added. The solution is then stirred at 45–60°C until the solvent is completely evaporated. The resulting mixture is then calcined at 600–800°C for 1–3 hours to obtain Li. X A Y B Z O (X+3Y+5Z) / 2 Modified high-nickel materials.

[0077] Thirdly, this application proposes a positive electrode sheet, including the positive electrode material in the above embodiments.

[0078] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive electrode coating coated on the positive current collector. The positive electrode coating is formed from a positive electrode slurry. The positive electrode slurry includes a positive electrode active material, a binder, and a conductive material. The binder includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc., which are not limited herein. The conductive material includes carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivatives, etc., which are not limited herein.

[0079] In some embodiments of this application, a method for preparing a positive electrode sheet is also provided, comprising the following steps: dissolving the positive electrode active material (the modified high-nickel ternary material provided in this application), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in a weight ratio of 96.5:1.5:2 in the solvent N-methylpyrrolidone (NMP), and mixing thoroughly to obtain a positive electrode slurry; then uniformly coating the positive electrode slurry onto a positive electrode current collector with a primer, and then drying, cold pressing, and slitting to obtain a positive electrode sheet.

[0080] The positive electrode sheet proposed in this application embodiment has all the beneficial effects of the positive electrode material in the above embodiments, which will not be repeated here.

[0081] Fourthly, this application provides a secondary battery, including the positive electrode sheet in the above embodiments.

[0082] The secondary battery includes a positive electrode as described in the above embodiments, as well as a negative electrode, a separator, and an electrolyte. The secondary battery can be a single battery cell; taking a lithium-ion battery as an example, a lithium-ion battery cell mainly relies on the movement of lithium ions between the positive and negative electrode cells to function. In a cylindrical battery cell, the three-layer thin-film structure is wound into a cylindrical electrode assembly, while in a cuboid battery cell, the thin-film structure is wound or stacked into an electrode assembly with a roughly cuboid shape.

[0083] In a typical battery cell structure, a battery cell includes a casing, electrode assemblies, and electrolyte. The electrode assemblies are housed within the casing and include a positive electrode, a negative electrode, and a separator. The casing includes a housing and end caps. The casing includes a receiving cavity formed by multiple walls and an opening. The end caps are positioned at the openings to close the receiving cavities. In addition to the electrode assemblies, the receiving cavities also contain the electrolyte. The positive and negative electrode assemblies in the electrode assemblies include tabs. To ensure that large currents can pass through without melting, multiple positive tabs and multiple negative tabs are stacked together. The tabs are electrically connected to electrode terminals located outside the battery cell via connecting members. The electrode terminals generally include positive and negative electrode terminals. For cuboid battery cells, the electrode terminals are generally located in the end cap portion. Multiple battery cells are connected in series and / or parallel via electrode terminals for various applications.

[0084] A battery composed of cells assembled in a wound manner is called a wound battery. Wound batteries are also known as cells, or "wound cores" by battery industry professionals. Compared to flat-plate batteries, wound batteries are made by high-voltage winding of plates only about 1mm thick. Through special processes, these batteries possess many characteristics: superior high-rate discharge capability (maximum discharge rate 18C–30C); excellent high and low temperature performance (operating from -55℃ to 150℃); stable high output voltage and higher energy density; robust structure with excellent shock resistance; no free electrolyte (e.g., using colloidal acid), allowing for placement in any orientation; fast charging capability (reaching over 95% charge in 40 minutes (1C charging); ultra-long lifespan (designed float charge life of over 8 years); and extremely high tolerance for deep discharge at low currents.

[0085] The electrolyte used in this application may be an electrolyte known in the prior art, including organic solvents, lithium salts and additives; the separator used in this application may be a separator known in the prior art.

[0086] The secondary battery proposed in this application possesses all the beneficial effects of the aforementioned cathode materials, which will not be elaborated upon here.

[0087] A secondary battery can be a battery module. A battery module is formed by electrically connecting a certain number of secondary batteries together and placing them in a frame to protect the individual battery cells from external impacts, heat, vibration, etc. A common battery module generally includes two end plates, with multiple battery cells (secondary batteries) arranged between the two end plates. The end plate with the battery module's output terminal is also called the output end plate, and the end plate without the battery module's output terminal is also called the non-output end plate.

[0088] Secondary batteries can also be battery packs. In some battery manufacturing and processing technologies, multiple individual battery cells are first integrated into battery modules, and then the battery modules are packaged in a battery casing to form a battery pack. A battery pack can contain multiple battery modules in one row, or multiple rows of multiple battery modules. The arrangement of multiple rows of multiple battery modules can be double-row multi-column, multi-row double-column, multi-row multi-column, etc. Taking a battery pack containing double-row multi-column battery modules as an example, the first end plate of each column is generally the head output terminal plate, the two adjacent end plates between two rows of battery modules are the middle non-output terminal plates, and the last end plate of each column is the tail non-output terminal plate. The head output terminal plate and one of the middle non-output terminal plates belong to the first row of battery modules, and one of the middle non-output terminal plates and the tail output terminal plate belong to the second row of battery modules.

[0089] Fifthly, this application provides an electrical device including the secondary battery described in the above embodiments.

[0090] The electrical devices proposed in this application include, but are not limited to: mobile phones, portable devices, laptops, electric vehicles, electric cars, ships, spacecraft, electric toys, and power tools, etc. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0091] The electrical device proposed in this application possesses all the beneficial effects of the aforementioned positive electrode material, which will not be elaborated upon here.

[0092] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0093] Example 1

[0094] (1) Single-crystal LiNi x Co y Mn zPreparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.5 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (83:12:5). Then, a certain concentration of sodium hydroxide solution (6 mol / L) and ammonia water (0.3 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH controlled at 10 and the reaction temperature at 55℃, to obtain the hydroxide precursor (Ni...). 0.83 Co 0.12 Mn 0.05 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 500℃ for 6 h, then calcined at 800℃ for 15 h, and finally annealed in oxygen at 600℃ for 3 h to obtain single-crystal LiNi. 0.83 Co 0.12 Mn 0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0095] (2) Preparation of modified high-nickel materials: LiNO3, La(CH3COO)3 and C4H4NNbO9·nH2O in stoichiometric ratios were used to prepare Li5La3Nb2O 12 The material was added to ethanol, and single-crystal ternary powder was added, controlling the total doping mass of lanthanum and niobium to be 1%. The solution was then stirred at 55°C until the solvent was completely evaporated. The resulting mixture was then calcined at 700°C for 3 hours to obtain 1wt% Li5La3Nb2O. 12 (Referring to LABO) Modified high-nickel material.

[0096] Example 2

[0097] The steps are basically the same as in Example 1, except that in step (2), the total doping mass of lanthanum and niobium is controlled to be 3%.

[0098] Example 3

[0099] The steps are basically the same as in Example 1, except that in step (2), the total doping mass of lanthanum and niobium is controlled to be 5%.

[0100] Example 4

[0101] The steps are basically the same as in Example 1, except that in step (2), the total doping mass of lanthanum and niobium is controlled to be 10%.

[0102] Example 5

[0103] (1) Single-crystal LiNi x Co y Mn zPreparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.0 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (85:10:5). Then, a certain concentration of sodium hydroxide solution (4 mol / L) and ammonia water (0.1 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH value controlled at 9 and the reaction temperature at 40℃, to obtain the hydroxide precursor (Ni...). 0.85 Co 0.10 Mn 0.05 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 500℃ for 6 h, then calcined at 800℃ for 15 h, and finally annealed in oxygen at 600℃ for 3 h to obtain single-crystal LiNi. 0.85 Co 0.10 Mn 0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0104] (2) Preparation of modified high-nickel material: LiNO3 and C4H4NNbO9·nH2O in stoichiometric ratio were used as materials for preparing Li6Nb2O8. They were added to ethanol and single-crystal ternary powder was added. The niobium doping mass was controlled to be 3%. The solution was stirred at 55°C until the solvent was completely evaporated. The resulting mixture was then calcined at 700°C for 3 hours to obtain 3wt% Li6Nb2O8 (denoted as LBO) modified high-nickel material.

[0105] Example 6

[0106] (1) Single-crystal LiNi x Co y Mn z Preparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.0 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (84:12:4). Then, a certain concentration of sodium hydroxide solution (4 mol / L) and ammonia water (0.1 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH value controlled at 9 and the reaction temperature at 40℃, to obtain the hydroxide precursor (Ni...). 0.84 Co 0.12 Mn 0.04 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 500℃ for 6 h, then calcined at 800℃ for 15 h, and finally annealed in oxygen at 600℃ for 3 h to obtain single-crystal LiNi. 0.84 Co 0.12 Mn0.04 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0107] (2) Preparation of modified high-nickel material: LiNO3 and C4H4NNbO9·nH2O in stoichiometric ratio were used as materials for preparing Li5La3O7. They were added to ethanol and single-crystal ternary powder was added. The doping mass of lanthanum was controlled to be 3%. The solution was stirred at 55°C until the solvent was completely evaporated. The resulting mixture was then calcined at 700°C for 3 hours to obtain 3wt% Li5La3O7 (denoted as LAO) modified high-nickel material.

[0108] Example 7

[0109] (1) Single-crystal LiNi x Co y Mn z Preparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.5 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (83:12:5). Then, a certain concentration of sodium hydroxide solution (6 mol / L) and ammonia water (0.3 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH controlled at 10 and the reaction temperature at 55℃, to obtain the hydroxide precursor (Ni...). 0.83 Co 0.12 Mn 0.05 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 300℃ for 7 h, then calcined at 850℃ for 16 h, and finally annealed in oxygen at 400℃ for 4 h to obtain single-crystal LiNi. 0.83 Co 0.12 Mn 0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0110] (2) Preparation of modified high-nickel material: LiNO3 and C4H4NTiO9·nH2O in stoichiometric ratio were used as materials for preparing Li6Ti2O8. They were added to ethanol and single-crystal ternary powder was added. The doping mass of titanium was controlled to be 3%. The solution was stirred at 45°C until the solvent was completely evaporated. The resulting mixture was then calcined at 600°C for 3 hours to obtain 3wt% Li6Ti2O8 (denoted as LBO) modified high-nickel material.

[0111] Example 8

[0112] (1) Single-crystal LiNi x Co y Mn zPreparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.5 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (83:12:5). Then, a certain concentration of sodium hydroxide solution (6 mol / L) and ammonia water (0.3 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH controlled at 10 and the reaction temperature at 55℃, to obtain the hydroxide precursor (Ni...). 0.83 Co 0.12 Mn 0.05 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 350℃ for 6 h, then calcined at 750℃ for 14 h, and finally annealed in oxygen at 450℃ for 4 h to obtain single-crystal LiNi. 0.83 Co 0.12 Mn 0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0113] (2) Preparation of modified high-nickel material: LiNO3 and Pr(CH3COO)3 in stoichiometric ratio were used as materials for preparing Li5Pr3O7. They were added to ethanol and single-crystal ternary powder was added. The doping mass of praseodymium was controlled to be 3%. The solution was stirred at 50°C until the solvent was completely evaporated. The resulting mixture was then calcined at 650°C for 2 hours to obtain 3wt% Li5Pr3O7 (denoted as LAO) modified high-nickel material.

[0114] Example 9

[0115] (1) Single-crystal LiNi x Co y Mn z Preparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.5 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (83:12:5). Then, a certain concentration of sodium hydroxide solution (6 mol / L) and ammonia water (0.3 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH controlled at 10 and the reaction temperature at 55℃, to obtain the hydroxide precursor (Ni...). 0.83 Co 0.12 Mn 0.05 (OH)2; The obtained hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 400℃ for 5 h, then calcined at 700℃ for 18 h, and finally annealed in oxygen at 550℃ for 3 h to obtain single-crystal LiNi. 0.83 Co 0.12 Mn0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0116] (2) Preparation of modified high-nickel materials: LiNO3, Ce(CH3COO)3 and C4H4NZrO9·nH2O in stoichiometric ratios were used to prepare Li5Ce3Zr2O 12 The material was added to ethanol, and single-crystal ternary powder was added, controlling the total doping mass of cerium and zirconium to be 3%. The solution was then stirred at 60°C until the solvent was completely evaporated. The resulting mixture was then calcined at 750°C for 2 hours to obtain 3wt% Li5Ce3Zr2O. 12 (Referring to LABO) Modified high-nickel material.

[0117] Example 10

[0118] (1) Single-crystal LiNi x Co y Mn z Preparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.5 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (83:12:5). Then, a certain concentration of sodium hydroxide solution (6 mol / L) and ammonia water (0.3 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH controlled at 10 and the reaction temperature at 55℃, to obtain the hydroxide precursor (Ni...). 0.83 Co 0.12 Mn 0.05 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 450℃ for 5 h, then calcined at 900℃ for 12 h, and finally annealed in oxygen at 600℃ for 2 h to obtain single-crystal LiNi. 0.83 Co 0.12 Mn 0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0119] (2) Preparation of modified high-nickel materials: LiNO3, Yb(CH3COO)3 and C4H4NMoO9·nH2O in stoichiometric ratios were used to prepare Li5Yb3Mo2O 12 A material with (X≥5, Y≥3, Z≥2, and X, Y, and Z are all integers, A is ytterbium, and B is molybdenum) was added to ethanol, along with single-crystal ternary powder. The total doping mass of ytterbium and molybdenum was controlled to be 3%. The solution was then stirred at 50°C until the solvent was completely evaporated. The resulting mixture was then calcined at 800°C for 1 hour to obtain 3wt% Li5Yb3Mo2O. 12(Referring to LABO) Modified high-nickel material.

[0120] Comparative Example 1

[0121] Single-crystal LiNi x Co y Mn z Preparation of O2: Soluble sulfates of nickel, cobalt, and manganese were prepared into a solution with a total metal ion molar concentration of 1.5 mol / L according to a certain molar ratio of nickel, cobalt, and manganese ions (83:12:5). Then, a certain concentration of sodium hydroxide solution (6 mol / L) and ammonia water (0.3 mol / L) were added sequentially and stirred. A co-precipitation reaction was carried out under a nitrogen atmosphere, with the pH controlled at 10 and the reaction temperature at 55℃, to obtain the hydroxide precursor (Ni...). 0.83 Co 0.12 Mn 0.05 (OH)2; The prepared hydroxide precursor was washed and dried, and LiOH and KCl flux were added. The mixture was first sintered at 500℃ for 6 h, then calcined at 800℃ for 15 h, and finally annealed in oxygen at 600℃ for 3 h to obtain single-crystal LiNi. 0.83 Co 0.12 Mn 0.05 O2 high-nickel ternary material powder, Dv50≥4μm, SPAN≥1.6.

[0122] The modified high-nickel materials obtained in Examples 1-10 and the high-nickel material obtained in Comparative Example 1 were used to prepare positive electrode sheets, which were then further assembled into lithium-ion batteries. The relevant performance was tested. The specific methods and results are as follows:

[0123] (1) Preparation of negative electrode sheet:

[0124] Active material graphite, silicon, conductive agent acetylene black, polymer, and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water in a weight ratio of 90:5:2:2:1 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is coated on copper foil, dried, and then cold-pressed and slit to obtain the negative electrode sheet.

[0125] (2) Preparation of the positive electrode sheet:

[0126] The positive electrode active material (high nickel material prepared in Examples 1-10 and Comparative Example 1), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 96.5:1.5:2. After thorough stirring and mixing, a positive electrode slurry was obtained. The positive electrode slurry was uniformly coated onto a positive electrode current collector with a primer, and then dried, cold-pressed, and slit to obtain a positive electrode sheet.

[0127] (3) Separating membrane:

[0128] The diaphragm is a PE diaphragm with a PVDF and alumina coating on the surface to improve adhesion and heat resistance.

[0129] (4) Electrolyte:

[0130] The electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then uniformly dissolving LiPF6:LiFSI (2:8) in the mixture. The concentration of lithium salt in the electrolyte was 1 mol / L.

[0131] (5) Lithium-ion battery assembly:

[0132] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product.

[0133] (6) Performance testing:

[0134] 1. Capacity test:

[0135] ① Let stand for 30 minutes;

[0136] ② Charge at a rate of 1 / 3C to 4.25V, then charge at a constant voltage of 4.25V to 0.05C to finish;

[0137] ③ Let stand for 30 minutes;

[0138] ④ Discharge to 2.8V at a rate of 1 / 3C to obtain the capacity C0;

[0139] The energy obtained is the battery energy, and the gravimetric energy density = energy / battery weight.

[0140] 2. DCR Test:

[0141] The prepared secondary battery was left to stand at 25°C for 30 minutes, then charged at a rate of 1 / 3C to 4.25V, and kept constant at 0.05C. After standing for 10 minutes, it was discharged at a rate of 1 / 3C0 until the cell's charge was 10% of its full charge, which was called 10% SOC. After standing for 60 minutes, it was discharged at a rate of 4C0 for 10 seconds, and the cell's DCR value was recorded.

[0142] 3. Storage test:

[0143] ① Let fresh battery cells stand at room temperature for 30 minutes;

[0144] ② Charge at a rate of 1 / 3C to 4.25V, then charge at a constant voltage of 4.25V to 0.05C to finish;

[0145] ③ Let stand for 30 minutes;

[0146] ④ Discharge to 2.8V at a rate of 1 / 3C to obtain the capacity C0;

[0147] ⑤ Store at 60℃ and 97% SOC, and take it out to test the capacity every 10 days. This capacity is Cn. Continue until Cn decays to 80% C0 to obtain the corresponding number of storage days.

[0148] 4. Element doping level test: Analyzed by inductively coupled plasma (ICP) spectroscopy, referring to relevant testing standards YS / T 1006.2-2014, GB / T 23367.2-2009 or YS / T 1028.5-2015.

[0149] 5. Loop testing:

[0150] ① Adjust the temperature to 25℃ and keep it warm for 2 hours;

[0151] ② Let stand for 5 minutes;

[0152] ③ Charge at a rate of 1 / 3C to 4.3V, then charge at a constant voltage of 4.3V to 0.05C to finish;

[0153] ④ Let stand for 5 minutes;

[0154] ⑤ Discharge to 2.8V at a rate of 1 / 2C0;

[0155] ⑥ Let stand for 5 minutes;

[0156] ⑦ Repeat steps ③, ④, ⑤, and ⑥ until the capacity fading is ≤ 80%, and obtain the corresponding number of cycle lifetimes.

[0157] The test results are shown in Table 2 below.

[0158] In Table 2, the energy density gradient range is defined as: moderate 258-260 Wh / kg, slightly high 260-262 Wh / kg, and high 262-264 Wh / kg;

[0159] In Table 2, the DCR step range is defined as follows: low 0.8 to 1.0 mΩ, moderate 1.0 to 1.2 mΩ, slightly high 1.2 to 1.4 mΩ, and high 1.4 to 1.6 mΩ.

[0160] Table 2 Performance tests of each embodiment and comparative example

[0161]

[0162]

[0163] As shown in Table 2, doping with lanthanide element La in Example 6 improves kinetics, reduces DCR, enhances structural stability, and improves cycling and storage performance. Doping with metallic Nb in Example 5 improves bulk structural stability and enhances cycling and storage performance. However, compared with co-doping with two metal elements in Example 4, co-doping is more advantageous. In Examples 7-10, replacing the lanthanide element La with other metal elements within the same range, and / or replacing metallic Nb with other metal elements within the same range, can all improve cycling and storage performance.

[0164] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the patent protection scope of this application.

Claims

1. A positive electrode material, characterized in that, The cathode material comprises cathode material particles, and the cathode material particles comprise a matrix and modifying elements, wherein: The matrix includes LiNi x Co y Mn z O2, x≥0.8, y≤0.12, x+y+z=1; The modifying elements include rare earth elements and / or refractory metal elements; The LiNi x Co y Mn z O2 is a single crystal particle; The LiNi x Co y Mn z O2 has a Dv50 ≥ 4 μm.

2. The cathode material as described in claim 1, characterized in that, The rare earth element is at least partially located on the surface of the matrix; and / or The refractory metal element is located at least partially inside the matrix.

3. The positive electrode material as described in claim 1, characterized in that, The rare earth elements include at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; and / or, The refractory metal element includes at least one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten.

4. The positive electrode material as described in claim 1, characterized in that, The rare earth element is lanthanum; and / or, The refractory metal element is niobium.

5. The positive electrode material as described in claim 1, characterized in that, The modified elements are incorporated into the matrix through doping.

6. The positive electrode material as described in claim 1, characterized in that, Based on the mass of the cathode material being 100%, the doping mass of the modified element is 1~10%.

7. The positive electrode material as described in claim 1, characterized in that, Based on the mass of the cathode material being 100%, the doping mass of the modified element is 3-5%.

8. The cathode material as described in claim 1, characterized in that, The LiNi x Co y Mn z O2 SPAN ≥ 1.

6.

9. A method for preparing a positive electrode material as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Modifier and LiNi x Co y Mn z O2 is mixed and then calcined to obtain the positive electrode material; among which... The LiNi x Co y Mn z In O2, x≥0.8, y≤0.12, x+y+z=1; The modifier includes rare earth elements and / or refractory metal elements.

10. The method for preparing the cathode material as described in claim 9, characterized in that, The modifier includes Li X A Y B Z O (X+3Y+5Z) / 2 Li X A Y O (X+3Y) / 2 Or Li X B Z O (X+5Z) / 2 X≥5, Y≥3, Z≥2, and X, Y, and Z are all integers. A is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. B is any one of titanium, zirconium, niobium, vanadium, molybdenum, and tungsten.

11. The method for preparing the cathode material as described in claim 9, characterized in that, The calcination temperature is 600~800℃ and the calcination time is 1~3h.

12. A positive electrode plate, characterized in that, The positive electrode sheet includes the positive electrode material as described in any one of claims 1 to 8.

13. A secondary battery, characterized in that, The secondary battery includes the positive electrode as described in claim 12.

14. An electrical appliance, characterized in that, The electrical device includes the secondary battery as described in claim 13.

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