Positive electrode active material, secondary battery, battery module, battery pack, and electric device

Abstract

A positive electrode active material, a secondary battery, a battery module, a battery pack, and a power using device. The positive electrode active material includes a spinel-type lithium-containing manganese composite oxide of a molecular formula of Li 1+x A a M b X c Mn 2‑a‑b‑c‑x O 4‑t , in the molecular formula, A is a manganese site doping element of the spinel-type lithium-containing manganese composite oxide, and A includes one or more of V, Nb, Ta, Mo, W, Ru, Rh, Sn, Sb, Te, Tl, Pd, Bi, and Po; M is used to form a second phase containing a polyoxoanion with O, and M includes one or more of B, C, N, Si, P, S, and Cl; X includes one or more of Mg, Al, Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn, and Zr, wherein -0.1≤x≤0.3, 0 The simultaneous doping of A and M in the positive electrode active material can simultaneously improve the cycle storage performance and cycle service life at high temperature.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to a positive electrode active material, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] Rechargeable batteries possess advantages such as small size, high energy density, high safety, low self-discharge, and long lifespan, and are widely used in various fields including energy storage, communications, electric vehicles, and aerospace. A battery comprises multiple secondary cells connected in series, parallel, or a combination thereof. The positive electrode active material, as a crucial component of the secondary battery, provides lithium ions that move back and forth between the positive and negative electrodes during the charging and discharging process; therefore, the positive electrode active material is vital to the battery's performance.

[0003] Spinel-type lithium-manganese composite oxides possess high theoretical capacity, but their poor cycling performance at high temperatures limits their application. Therefore, improving the high-temperature cycling performance of secondary batteries has become an urgent technical challenge. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode active material that can improve the cycle performance of a secondary battery, as well as a secondary battery, battery module, battery pack and power supply device made from the positive electrode active material.

[0005] To achieve the above objectives, the first aspect of this application provides a positive electrode active material, which comprises a material with the molecular formula Li 1+x A a M b X c Mn 2-a-b-c-x O 4-t The spinel-type lithium-manganese composite oxide, wherein in the molecular formula, A is the manganese site dopant element of the spinel-type lithium-manganese composite oxide, and A includes one or more of V, Nb, Ta, Mo, W, Ru, Rh, Sn, Sb, Te, Tl, Pd, Bi and Po; M is used to form a second phase containing multiple oxygen anions with O, and M includes one or more of B, C, N, Si, P, S and Cl; X includes one or more of Mg, Al, Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn and Zr, wherein -0.1≤x≤0.3, 0<a≤0.2, 0<b≤0.2, 0≤c≤0.7, 0≤t≤0.2.

[0006] Therefore, in this embodiment of the application, A and M are doped simultaneously in the positive electrode active material. While stabilizing the spinel structure, it also has the ability to capture HF in the electrolyte. The positive electrode active material after capturing HF can form a more stable fluorinated oxide containing A and M elements. That is, A and M elements work together to not only protect the structural stability of the positive electrode active material, but also protect the entire battery system, thereby improving the cycle storage performance and cycle life at high temperatures.

[0007] In some embodiments, A includes one or more of Nb, Ta, Mo, W, Ru, Te, and Tl.

[0008] In some embodiments, M includes one or more of Si, S, and Cl.

[0009] In some embodiments, X includes one or more of Al, Sc, Cr, Ni, Cu, Zn, and Ti; and / or 0.1 ≤ c ≤ 0.6.

[0010] Therefore, the X element in this embodiment can increase the average valence state of manganese and manganese site elements in the spinel structure, thereby making the average valence of manganese and manganese site elements greater than +3.5 valence during charging and discharging, reducing the risk of Jahn-Teller distortion in the spinel structure, and thus improving the structural stability and capacity characteristics of the positive electrode active material.

[0011] In some embodiments, the spinel-type lithium-manganese composite oxide includes a first region and a second region sequentially distributed from its core to its outer surface; based on the volume of the spinel-type lithium-manganese composite oxide, the volume percentage p of the second region is ≤ 50%; based on the total mass of element A in the spinel-type lithium-manganese composite oxide, the percentage of element A located in the second region is m; based on the total mass of element M in the spinel-type lithium-manganese composite oxide, the percentage of element M located in the second region is n, where m + n ≥ 70%; optionally, 10% ≤ p ≤ 30%, and / or 80% ≤ m + n ≤ 95%.

[0012] Therefore, in this embodiment, elements A and M are enriched in the second region. Through the synergistic effect of elements A and M, the surface of the spinel-type lithium manganese composite oxide is more fully protected, and the structural stability of its surface is improved. This improves the overall structural stability of the positive electrode active material and is conducive to the capacity utilization of the positive electrode active material, thereby improving the cycle performance and cycle life of the secondary battery using this positive electrode active material.

[0013] In some embodiments, in the molecular formula, -0.1 ≤ x ≤ 0.3 and / or 0 ≤ t ≤ 0.2. Therefore, the spinel-type lithium-manganese composite oxide of the present application embodiments has a more stable structure, which is more conducive to capacity utilization.

[0014] In some embodiments, in the molecular formula, 0.001≤a≤0.1 and / or 0.001≤b≤0.1; optionally, 0.005≤a+b≤0.1.

[0015] Therefore, when elements A and M in the embodiments of this application simultaneously satisfy the above-mentioned ranges, the synergistic effect of elements A and M can be fully utilized, which can improve the structural stability of the positive electrode active material and facilitate the capacity utilization of the positive electrode active material, thereby improving the cycle storage performance and cycle life of the positive electrode active material at high temperatures.

[0016] In some embodiments, the specific surface area of ​​the spinel-type lithium-manganese composite oxide is 0.01 m². 2 / g~1.5m 2 / g, can be selected as 0.1m 2 / g~1m 2 / g.

[0017] Therefore, the spinel-type lithium-manganese composite oxide of this application embodiment has a relatively small specific surface area, which can reduce the risk of surface side reactions and is beneficial to the long-term cycle stability of secondary batteries prepared using this spinel-type nickel-manganese-lithium composite oxide as the positive electrode active material. The surface of the spinel structure is easier to be fully covered and modified, thereby improving the overall structural stability of the spinel structure. In addition, the quality of the modification layer modifying the spinel structure is positively correlated with the specific surface area of ​​the spinel structure. The thickness of the modification layer in this application embodiment is not too thick, thereby ensuring the kinetic performance of the spinel structure.

[0018] In some embodiments, the average particle size D of the spinel-type lithium-manganese composite oxide V50 The range is 1μm to 20μm; it can be selected as 2μm to 15μm.

[0019] Therefore, the average particle size D of the spinel-type lithium-manganese composite oxide in the embodiments of this application is... V50 Within the aforementioned range, the crystal structure is relatively perfect, the grain surface is stable and the specific surface area is small. Furthermore, during the preparation process, it is convenient to dope the second region of the spinel-type lithium-manganese composite oxide, resulting in less loss of elements such as Li and O. At the same time, its processing performance during subsequent use is superior, thereby improving the overall performance of the material and the battery.

[0020] In some embodiments, a and b in the molecular formula are related to the average particle size D of the spinel-type lithium-manganese composite oxide. V50 The following condition must be met: 0.01 ≤ (a + b) × D V50 ≤1.

[0021] Therefore, the embodiments of this application simultaneously control the doping amounts of elements A and B, as well as the average particle size D of the spinel-type lithium-manganese composite oxide. V50 This allows for a balance between the structural stability and kinetic properties of spinel-type lithium-manganese composite oxides.

[0022] In some embodiments, the spinel-type lithium-manganese composite oxide has a single-crystal grain morphology or a near-single-crystal grain morphology.

[0023] Therefore, single-crystal or near-single-crystal particles have fewer internal grain boundaries, resulting in a lower probability of particle cracking during subsequent processing and rechargeable battery service. This structural stability is beneficial for improving the long-term stability of the rechargeable battery. Furthermore, single-crystal or near-single-crystal particles have better dispersion, making it easier to achieve uniform and comprehensive surface modification. In contrast, polycrystalline particles contain numerous grain boundaries, which make them prone to cracking during subsequent processing and use. This cracking exposes unmodified surfaces without an electrolyte interphase (CEI) film, ultimately degrading battery performance.

[0024] In some embodiments, the spinel-type lithium-manganese composite oxide has at least one of the following: octahedral grain shape, truncated octahedral grain shape, and regular polyhedral grain shape obtained by sharpening and removing the edges of an octahedron.

[0025] Therefore, the crystal surface of the spinel-type lithium manganese composite oxide is more stable and smaller, which helps to mitigate surface side reactions and thus improve the structural stability of the positive electrode active material.

[0026] The second aspect of this application provides a battery module including a secondary battery according to any embodiment of the first aspect of this application.

[0027] A third aspect of this application provides a battery pack that includes the battery module of the second aspect of this application.

[0028] A fourth aspect of this application provides an electrical device, including at least one of a secondary battery selected from any embodiment of the first aspect of this application, a battery module of the second aspect of this application, or a battery pack of the third aspect of this application. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0031] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0032] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0033] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0034] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0035] Figure 6 This is a schematic diagram of an electrical device according to one embodiment of this application;

[0036] Figure 7 This is a schematic diagram of the partitioning of the positive electrode active material particles in this application;

[0037] Figure 8 A morphology diagram of the positive electrode active material prepared in Example 51 is shown.

[0038] The reference numerals in the attached figures are explained as follows: 1. Secondary battery; 11. Outer packaging; 111. Top cover assembly; 112. Housing; 12. Electrode assembly; 121. First region; 122. Second region; 10. Battery module; 20. Battery pack; 21. Upper casing; 22. Lower casing; 30. Electrical appliances. Detailed Implementation

[0039] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the positive electrode active material, secondary battery, battery module, battery pack, and power supply 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.

[0040] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0042] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0043] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0044] 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.

[0045] 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).

[0046] [Positive electrode active material]

[0047] The lithium-manganese composite oxide (LMO) has a spinel structure. In this structure, oxygen atoms are arranged in a face-centered cubic configuration, occupying the 32e position in the crystal lattice. Lithium atoms are tetrahedral coordinated, while the transition metal manganese is octahedral coordinated. The spinel structure provides a good channel for lithium-ion insertion and extraction, which is beneficial for the charging and discharging of secondary batteries. In this paper, the lithium atom is located at the 8a position of the tetrahedron, hence the 8a position of the tetrahedron is referred to as the "lithium site"; the manganese atom is located at the 16d position of the octahedron, hence the 16d position of the octahedron is referred to as the "manganese site".

[0048] Manganese exists in many valence states. In spinel lithium manganese oxide, the average valence state of manganese is +3.5, and some manganese exists in the +3 form. However, trivalent manganese is unstable and easily undergoes disproportionation reactions to generate divalent and tetravalent manganese.

[0049] The inventors discovered that when using spinel-type lithium manganese composite oxide (LMO) as the positive electrode active material in a secondary battery, side reactions (oxygen loss, hydrogen ion generation, H+) easily occur on the surface of the positive electrode active material during the charging process, especially after charging to high voltage. + Transition metal ions such as Mn 2+ (dissolution), especially Mn 2+ Dissolving in the electrolyte disrupts the structure of the positive electrode active material, leading to structural instability during cycling and consequently decreased cycle performance. Simultaneously, the presence of small amounts of water in the electrolyte can react with electrolyte salts to form hydrofluoric acid (HF). The presence of HF further promotes manganese dissolution, creating a vicious cycle.

[0050] In addition, H + Diffusion to the negative electrode plate results in reduction to H2 and Mn. 2+ This diffusion extends to the negative electrode deposition and reduces the ionic conductivity of the solid electrolyte interface (SEI) film, leading to the risk of gas buildup during high-temperature storage and cycling of the secondary battery. It also results in rapid capacity decay and poor long-term stability under high temperature and high voltage conditions, thereby shortening the lifespan of the secondary battery.

[0051] Therefore, in this application, the inventors added doping elements, such as A, M and X elements, to the positive electrode active material to modify the positive electrode active material, hoping to improve the storage performance and cycle performance of the secondary battery using the positive electrode active material at high temperature.

[0052] This application provides a positive electrode active material comprising a molecular formula of Li. 1+x A a M b X c Mn 2-a-b-c-x O 4-t The spinel-type lithium-manganese composite oxide, wherein in the molecular formula, A is the manganese site dopant element of the spinel-type lithium-manganese composite oxide, and A includes one or more of V, Nb, Ta, Mo, W, Ru, Rh, Sn, Sb, Te, Tl, Pd, Bi and Po; M is used to form a second phase containing multiple oxygen anions with O, and M includes one or more of B, C, N, Si, P, S and Cl; X includes one or more of Mg, Al, Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn and Zr, wherein -0.1≤x≤0.3, 0<a≤0.2, 0<b≤0.2, 0≤c≤0.7, 0≤t≤0.2.

[0053] A may include subgroup elements and / or main group elements. For example, A includes one or more of V, Nb, Ta, Mo, W, Ru, Rh, Sn, Sb, Te, Tl, Pd, Bi, and Po; optionally, A includes one or more of Nb, Ta, Mo, W, Ru, Te, and Tl.

[0054] A element can be incorporated into the spinel structure, mainly replacing some manganese ions at manganese sites. A element can form strong interactions with multiple surrounding oxygen atoms, significantly stabilizing oxygen atoms, thereby reducing side reactions (such as oxygen loss) on the surface of the positive electrode active material under high voltage, thus improving the structural stability of the positive electrode active material.

[0055] M is used to form a second phase containing multiple oxygen anions with oxygen atoms. It can absorb hydrofluoric acid HF generated in the electrolyte under high voltage, and the generated fluorinated anions have high stability in the electrolyte. Exemplarily, M includes one or more of B, C, N, Si, P, S, and Cl; optionally, M includes one or more of Si, S, and Cl.

[0056] In this embodiment, A and M are simultaneously doped into the positive electrode active material. While stabilizing the spinel structure, it also has the ability to capture HF in the electrolyte. The positive electrode active material after capturing HF can form a more stable fluorinated oxide containing A and M elements. That is, A and M elements work together to not only protect the structural stability of the positive electrode active material, but also protect the entire battery system, thereby improving the cycle storage performance and cycle life at high temperatures.

[0057] In some embodiments, the positive electrode active material may not be doped with element X. In this case, c = 0, and the molecular formula of the spinel-type lithium-manganese composite oxide is Li. 1+x A a M b Mn 2-a-b-x O 4-t Through the synergistic effect of A and M, the performance of the positive electrode active material is improved.

[0058] In some embodiments, the positive electrode active material is further doped with element X, in which case 0 < c ≤ 0.7, optionally 0.1 ≤ c ≤ 0.6, and exemplaryly, c can be 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6.

[0059] X includes one or more of Mg, Al, Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn, and Zr. Optionally, X includes one or more of Al, Sc, Cr, Ni, Cu, Zn, and Ti.

[0060] Element X can increase the average valence state of manganese and manganese-site elements in the spinel structure, thereby ensuring that the average valence state of manganese and manganese-site elements is greater than +3.5 during charge and discharge. This reduces the risk of Jahn-Teller distortion in the spinel structure, thus improving the structural stability and capacity characteristics of the cathode active material. In particular, when X includes one or more of Al, Sc, Cr, Ni, Cu, Zn, and Ti, and 0.1 ≤ c ≤ 0.6, element X can significantly improve the structural stability of the cathode active material and can synergistically work with element M, such as phosphorus (P), to jointly improve the performance of the cathode active material.

[0061] In some embodiments, the spinel-type lithium-manganese composite oxide includes a first region and a second region sequentially distributed from its core to its outer surface; based on the volume of the spinel-type lithium-manganese composite oxide, the volume percentage p of the second region is ≤ 50%; based on the total mass of element A in the spinel-type lithium-manganese composite oxide, the percentage of element A located in the second region is m; based on the total mass of element M in the spinel-type lithium-manganese composite oxide, the percentage of element M located in the second region is n, wherein m + n ≥ 70%; optionally, 10% ≤ p ≤ 30%, and / or 80% ≤ m + n ≤ 95%.

[0062] Based on volume ratio, the positive electrode active material particles are divided into a first region and a second region. The first region is located in the core part of the particle, and the second region is located in the part of the particle away from the core. However, the first region and the second region are continuous parts with no obvious interface between them. The division of the positive electrode active material particles into different regions is only for the convenience of calculation and does not mean to limit the spinel structure of this application.

[0063] The volume percentage of the second region is p ≤ 50%, optionally 10% ≤ p ≤ 30%, and for example, p can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, or 30%. The relatively small volume percentage of the second region indicates that the second region is mainly located in the outer layer of the spinel structure.

[0064] Based on the total mass of A in the spinel-type lithium manganese composite oxide, the percentage of element A located in the second region is m. Based on the total mass of M in the spinel-type lithium manganese composite oxide, the percentage of element M located in the second region is n, where m+n≥70%, optionally 80%≤m+n≤95%, and exemplaryly, m+n can be 70%, 75%, 80%, 85%, 88%, 90%, 92%, or 95%. In this document, the percentage of element A located in the second region refers to the ratio of the mass of element A located in the second region to the total mass of element A in the spinel-type lithium manganese composite oxide. The percentage of element M located in the second region refers to the ratio of the mass of element M located in the second region to the total mass of element M in the spinel-type lithium manganese composite oxide.

[0065] Elements A and M are enriched in the second region. Through the synergistic effect of elements A and M, the surface of the spinel-type lithium manganese composite oxide is more fully protected, and the structural stability of its surface is improved. This improves the overall structural stability of the positive electrode active material and is conducive to the capacity utilization of the positive electrode active material. In turn, it improves the cycle performance and cycle life of the secondary battery using this positive electrode active material.

[0066] In some embodiments, in the molecular formula, -0.1 ≤ x ≤ 0.3. Exemplarily, x can be -0.1, 0, 0.1, 0.15, 0.2, or 0.3. Within this range, x ensures sufficient Li to guarantee capacity and improve the kinetic properties and structural stability of the material, while also maintaining a good spinel structure.

[0067] In some embodiments, in the molecular formula, 0 ≤ t ≤ 0.2. Exemplarily, t can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.18, or 0.2. When t satisfies the above range, oxygen defects in the structure of the positive electrode active material can be reduced, thereby reducing the risk of side reactions on the surface of the positive electrode active material.

[0068] In some embodiments, in the molecular formula, -0.1≤x≤0.3, 0≤t≤0.2. The ratio of lithium to oxygen is simultaneously adjusted to regulate the performance of spinel-type lithium-manganese composite oxides.

[0069] In some embodiments, in the molecular formula, 0.001 ≤ a ≤ 0.1. For example, a can be 0.001, 0.002, 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1. When the content of element A meets the above range, the improvement effect of element A replacing manganese sites is good.

[0070] In some embodiments, in the molecular formula, 0.001 ≤ b ≤ 0.1. For example, b can be 0.001, 0.002, 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1. When the content of element M meets the above range, the polyoxoanion formed by M and oxygen can fully absorb the hydrofluoric acid HF generated in the electrolyte and generate fluorinated anions with high stability in the electrolyte.

[0071] In some embodiments, in the molecular formula, 0.001≤a≤0.1 and 0.001≤b≤0.1. When elements A and M simultaneously satisfy the above ranges, the synergistic effect of elements A and M can be fully utilized, which can improve the structural stability of the positive electrode active material and facilitate the capacity utilization of the positive electrode active material, thereby improving the cycle storage performance and cycle life of the positive electrode active material at high temperatures.

[0072] In some embodiments, in the molecular formula, 0.005 ≤ a + b ≤ 0.1. For example, a + b can be 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1. When elements A and M simultaneously satisfy the above ranges, the synergistic effect of elements A and M can be fully utilized, which can improve the structural stability of the positive electrode active material and facilitate the capacity utilization of the positive electrode active material, thereby improving the cycle storage performance and cycle life of the positive electrode active material at high temperatures.

[0073] In some embodiments, the specific surface area of ​​the spinel-type lithium-manganese composite oxide is 0.01 m². 2 / g~1.5m 2 / g, can be selected as 0.1m 2 / g~1m 2 / g, for example, the specific surface area of ​​spinel-type lithium-manganese composite oxide can be 0.01m². 2 / g, 0.05m 2 / g, 0.1m 2 / g, 0.12m 2 / g, 0.15m 2 / g, 0.2m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.4m 2 / g or 1.5m 2 / g.

[0074] Spinel-type lithium-manganese composite oxides have a relatively small specific surface area, which reduces the risk of surface side reactions and is beneficial to the long-term cycle stability of secondary batteries prepared using this spinel-type nickel-manganese-lithium composite oxide as the positive electrode active material. Furthermore, the relatively small specific surface area facilitates uniform and comprehensive surface modification of the spinel material particles, thereby improving the overall structural stability of the spinel structure.

[0075] In some embodiments, the average particle size D of spinel-type lithium-manganese composite oxides V50 The thickness is 1μm to 20μm; optionally, it is 2μm to 15μm. For example, D V50It can be 1μm, 1.5μm, 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm.

[0076] The average particle size D of the spinel-type lithium-manganese composite oxide in the embodiments of this application is... V50 Within the aforementioned range, the crystal structure is relatively perfect, the grain surface is stable, and the specific surface area is small. Furthermore, during the preparation process, it facilitates doping of the second region of the spinel-type lithium-manganese composite oxide, and its subsequent processing performance is superior. During the doping process, the loss of elements such as Li and O in the spinel-type lithium-manganese composite oxide is minimal, thereby improving the overall performance of the material and the battery.

[0077] In some embodiments, a and b in the molecular formula are related to the average particle size D of the spinel-type lithium-manganese composite oxide. V50 The following condition must be met: 0.01 ≤ (a + b) × D V 50≤1, for example, (a+b)×D V 50 can be 0.01, 0.02, 0.03, 0.05, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

[0078] With the increase of A and M element content and average particle size D V50 The changes in these three elements (A, M, and D) exhibit a similar performance pattern, and their synergistic effect can further enhance the performance of the cathode active material. For example, when the contents of A and M are low, the improvement effect on the cathode active material is not strong; however, if D is also present, the improvement effect can be significant. V50 If the content of elements A and M is also relatively small, the improving effect will be further weakened. High content of elements A and M may deteriorate some properties of the positive electrode active material; if D is also present... V50 The particle size is also relatively large, which may further degrade the performance of this part of the positive electrode active material. Therefore, the embodiments of this application will simultaneously control the doping amounts of elements A and M, as well as the average particle size D of the spinel-type lithium-manganese composite oxide. V50 This allows for a balance between the structural stability and kinetic properties of spinel-type lithium-manganese composite oxides.

[0079] In some embodiments, the spinel-type lithium-manganese composite oxide has a single-crystal grain morphology or a near-single-crystal grain morphology.

[0080] The positive electrode active material with the above morphology has fewer internal grain boundaries, resulting in a lower probability of particle cracking during subsequent processing and secondary battery service. This structural stability is beneficial for improving the long-term stability of the secondary battery. Furthermore, single-crystal or near-single-crystal particles exhibit better dispersion, facilitating uniform and comprehensive surface modification. In contrast, polycrystalline particles contain numerous grain boundaries, making them prone to cracking at these boundaries during subsequent processing and use. This cracking exposes unmodified surfaces without an electrolyte interphase (CEI) film, ultimately degrading battery performance.

[0081] In some embodiments, the spinel-type lithium-manganese composite oxide has at least one of the following: octahedral grain shape, truncated octahedral grain shape, and regular polyhedral grain shape obtained by sharpening and removing the edges of an octahedron.

[0082] The crystal faces of grains with the above morphology are more stable and smaller, which helps to mitigate side reactions on the surface and thus improves the structural stability of the positive electrode active material.

[0083] [Preparation method of positive electrode active material]

[0084] The method for preparing the positive electrode active material provided in this application may include the following steps:

[0085] Weigh out the lithium source, manganese source, A source, M source, and X source in the corresponding stoichiometric ratio according to the target components, and then mix them evenly to obtain a raw material mixture powder. The lithium source, manganese source, A source, M source, and X source can be different or a mixture of multiple sources. Examples include lithium hydroxide, lithium carbonate, lithium nitrate, oxalic acid, manganese oxide, nickel oxide, nickel manganese hydroxide, oxides, hydroxides, and carbonates of at least one of A, M, and X.

[0086] The above-mentioned mixture powder is heated to 800-1100℃ and held for 2-50 hours in an oxygen-containing atmosphere to obtain the positive electrode active material.

[0087] In some embodiments, to reduce the t-value, when the sintering temperature is above 900°C, the temperature can be maintained at 550°C to 850°C for 5 to 30 hours. Specifically, after high-temperature sintering, the temperature can be lowered to this range and maintained; or after high-temperature sintering, the temperature can be lowered to room temperature, subjected to ball milling or other treatments, and then raised to this range and maintained.

[0088] [Rechargeable Battery]

[0089] This application also provides a secondary battery comprising the positive electrode active material as described in any of the above embodiments, thereby enabling the secondary battery to exhibit good long-term stability under high temperature and high voltage, especially high-temperature full-charge storage performance. This secondary battery can be a lithium-ion secondary battery, a sodium-ion secondary battery, a lithium-sodium secondary battery, etc.

[0090] A secondary battery may include a positive electrode, a negative electrode, an electrolyte, and a separator. During charging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0091] [Positive electrode plate]

[0092] The positive electrode includes a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector and comprising a positive active material. As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film is disposed on either or both of the two opposite surfaces of the positive current collector.

[0093] The positive current collector can be made of a material with good conductivity and mechanical strength. In some embodiments, the positive current collector can be aluminum foil.

[0094] In the secondary battery provided in this application, the positive electrode active material on the positive electrode sheet contains Li, which has the molecular formula provided in this application. 1+x A a M b X c Mn 2-a-b-c-x O 4-t A spinel-type nickel-manganese lithium composite oxide. This spinel-structured nickel-manganese lithium composite oxide material has good structural stability, especially surface structural stability. When used as the active material of the positive electrode sheet of a secondary battery, it can greatly enhance the battery system performance under high temperature and high voltage conditions, such as reducing gas expansion and slowing capacity decay, achieving long-term stability under high temperature and high voltage conditions, especially high-temperature full-charge storage performance, thereby significantly extending the service life and safety performance of the secondary battery.

[0095] In some embodiments, the positive electrode active material, in addition to containing the molecular formula Li provided in this application, 1+ x A a M b X c Mn 2-a-b-c-x O 4-tIn addition to spinel-type nickel-manganese-lithium composite oxides, the battery may also contain other cathode active materials known in the art for use in batteries. For example, other cathode active materials may also include at least one of the following: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as cathode active materials for batteries may also be used. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.80 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0096] In some embodiments, the positive electrode membrane may optionally include an adhesive. There is no specific limitation on the type of adhesive, and those skilled in the art can select one according to actual needs. As an example, the adhesive used for the positive electrode membrane may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0097] In some embodiments, the positive electrode membrane may optionally include a conductive agent. There is no specific limitation on the type of conductive agent, and those skilled in the art can select it according to actual needs. As an example, the conductive agent used for the positive electrode membrane may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0098] In some embodiments, the step of preparing a positive electrode sheet using a positive active material may include: dispersing the positive active material, a binder, and an optional conductive agent in a solvent, which may be N-methylpyrrolidone, and stirring the mixture uniformly under the action of a vacuum stirrer to obtain a positive slurry; uniformly coating the positive slurry onto a positive current collector aluminum foil, drying it at room temperature, transferring it to an oven for drying, and then cold pressing and slitting to obtain a positive electrode sheet.

[0099] [Negative electrode plate]

[0100] The negative electrode includes a negative current collector and a negative electrode film disposed on at least one surface of the negative current collector. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0101] The negative electrode current collector can be made of a material with good conductivity and mechanical strength, serving both as a conductor and a current collector. In some embodiments, the negative electrode current collector can be made of copper foil.

[0102] The negative electrode film includes a negative electrode active material. The steps for preparing a negative electrode sheet using the negative electrode active material may include: dispersing the negative electrode active material, binder, and optional thickener and conductive agent in a solvent, which may be deionized water, to form a uniform negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0103] In some embodiments, this application does not specifically limit the type of negative electrode active material, and the negative electrode sheet may optionally include negative electrode active materials that can be used as negative electrodes in secondary batteries. The negative electrode active material may be one or more of graphite materials (such as artificial graphite and natural graphite), mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon-based materials, and tin-based materials.

[0104] In some embodiments, the adhesive may be selected from one or more of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0105] In some embodiments, the thickener may be sodium carboxymethyl cellulose (CMC-Na).

[0106] In some embodiments, the conductive agent used for the negative electrode sheet may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] [Electrolytes]

[0108] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0109] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0110] In some embodiments, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).

[0111] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0112] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0113] [Isolation membrane]

[0114] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0115] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0116] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0117] [Outer Packaging]

[0118] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0119] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0120] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 and Figure 2 This is an example of a square-structured secondary battery 1.

[0121] In some embodiments, the secondary battery 1 includes an outer packaging 11. The outer packaging 11 includes a top cover assembly 111 and a housing 112. A positive electrode, a negative electrode, and a separator constitute an electrode assembly 12 housed within the housing 112, which also contains an electrolyte. The positive or negative electrode includes tabs. During the charging and discharging process of the secondary battery 1, active ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of ions between the positive and negative electrode. The separator is disposed between the positive and negative electrode, primarily to prevent short circuits between the positive and negative electrodes, while allowing active ions to pass through. Specifically, the secondary battery 1 can be a wound or stacked battery, such as a lithium-ion battery or a sodium-ion battery, but is not limited to these.

[0122] Optionally, the housing 112 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 112 has an opening communicating with the receiving cavity, and a top cover assembly 111 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to specific practical needs.

[0123] In some embodiments, the secondary battery 1 can be assembled into a battery. The battery can be a battery module or a battery component. For example, the number of secondary batteries 1 contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0124] Figure 3 This is battery module 10 as an example. (See reference...) Figure 3 In the battery module 10, multiple secondary batteries 1 can be arranged sequentially along the length of the battery module 10. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 1 can be fixed by fasteners. Optionally, the battery module 10 may also include a housing with a receiving space in which the multiple secondary batteries 1 are received.

[0125] In some embodiments, the battery module 10 described above can also be assembled into a battery pack. The battery pack may contain one or more battery modules 10, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack. Of course, the battery pack may also be directly composed of multiple secondary batteries 1.

[0126] Figure 4 and Figure 5 This is a sample battery pack 20. (See reference) Figure 4 and Figure 5 The battery pack 20 may include a battery box and multiple battery modules 10 disposed within the battery box. The battery box includes an upper box 21 and a lower box 22, with the upper box 21 covering the lower box 22 to form a closed space for accommodating the battery modules 10. The multiple battery modules 10 may be arranged in any manner within the battery box.

[0127] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. As an electrical device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0128] Figure 6 This is an example of an electrical device 30. This electrical device 30 can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device 30, a battery pack or battery module can be used.

[0129] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0130] Example

[0131] 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.

[0132] Example 1

[0133] 1. Preparation of positive electrode sheet

[0134] 1.1 Preparation of positive electrode active material, wherein the doping elements in the positive electrode active material are shown in Tables 1 to 3.

[0135] Weigh out the corresponding stoichiometric amounts of lithium carbonate, manganese tetroxide, source A, source M, and source X according to the components in Tables 1 to 3, and then mix them evenly to obtain a raw material mixture powder. Heat the above mixture powder to 900°C in air and keep it at that temperature for 20 hours to obtain the positive electrode active material.

[0136] 1.2 Preparation of the positive electrode sheet

[0137] An 8μm thick aluminum foil was used as the positive electrode current collector.

[0138] The positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) prepared above are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 95:2:3 to form a uniform positive electrode slurry. The positive electrode slurry is coated on the surface of the positive electrode current collector, and after drying and other processes, a positive electrode sheet is obtained.

[0139] 2. Preparation of negative electrode sheet

[0140] The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber latex (SBR) are thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 96:1:1:2 to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto the negative electrode current collector, and after drying and other processes, the negative electrode sheet is obtained.

[0141] 3. Preparation of electrolyte

[0142] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0143] 4. Preparation of lithium-ion batteries

[0144] The positive electrode, separator (PP / PE / PP composite film), and negative electrode are stacked in sequence, then wound into a cell and packaged in a casing. The electrolyte is injected into the cell, and then the cell undergoes sealing, settling, hot and cold pressing, and formation processes to obtain a lithium-ion battery.

[0145] Examples 2 to 5

[0146] The type of dopant element A is the same as in Example 1, but the mass content of A is different.

[0147] Examples 6 to 11

[0148] Unlike Example 1, the type of dopant element A is different.

[0149] Examples 12 to 15

[0150] The type of dopant element M is the same as in Example 1, but the mass content of M is different.

[0151] Example 16

[0152] The types of doping elements A and M are the same as in Example 1, but the mass content of A and M is different.

[0153] Examples 17 to 21

[0154] Unlike Example 12, the type of doped M source is different.

[0155] Examples 22 to 31

[0156] Unlike Example 12, the dopant element X is different in Example 30; the type of dopant element M is different.

[0157] Examples 32 to 41

[0158] Unlike Example 12, the enrichment levels of doped A and M elements in the second region are different.

[0159] Examples 42 to 58

[0160] Unlike Example 12, at least one of the doped elements A and M is different, and / or at least one of the particle size, specific surface area, and grain shape is different by adjusting the sintering process.

[0161] Comparative Example 1

[0162] Unlike Example 12, this example is doped with element A but not with element M.

[0163] Comparative Example 2

[0164] Unlike Example 12, this one is not doped with element A, but with element M.

[0165] Comparative Example 3

[0166] Unlike Example 12, it is not doped with element A, not doped with element M, but doped with element X.

[0167] Comparative Example 4

[0168] Unlike Example 12, it is not doped with element A, element M, or element X.

[0169] Table 1: Elemental content of positive electrode active materials prepared in Examples 1-31 and Comparative Examples 1 to 4

[0170] In Table 1, element A comes from oxides containing element A (A source). For example, if element A is Nb, the A source can be Nb2O5. Element M comes from oxides containing element M (M source). For example, if element M is B, the M source can be B2O3. Element X comes from oxides containing element X (X source). For example, if element X is Mg, the X source can be MgO.

[0171] Table 2: Elemental distribution of the positive electrode active materials prepared in Examples 12, 32 to 41

[0172] In Table 2, element A comes from oxides containing element A (A source). For example, if element A is Nb, the A source can be Nb2O5. Element M comes from oxides containing element M (M source). For example, if element M is B, the M source can be B2O3.

[0173] Table 3: Physicochemical properties of the positive electrode active materials prepared in Examples 12, 42 to 58

[0174] In Table 3, element A comes from oxides containing element A (A source). For example, if element A is Nb, the A source can be Nb2O5. Element M comes from oxides containing element M (M source). For example, if element M is B, the M source can be B2O3.

[0175] Performance testing:

[0176] 1. Initial discharge specific capacity test of spinel LMO in secondary batteries

[0177] The prepared secondary battery was used as the test object.

[0178] At 25°C, the secondary battery is charged at a constant current of 0.3C to the upper limit cutoff voltage V. max (V of conventional spinel LMO and trace-doped spinel LMO) max =4.3V), then with V max Charge the battery at a constant voltage until the current reaches 0.05C, let it stand for 5 minutes, and then discharge it at a constant current of 0.33C until the lower cutoff voltage V. min (V of conventional spinel LMO and trace-doped spinel LMO) min =2.5V), and the initial discharge capacity of spinel LMO in a secondary battery is C0 (mAh / g) when the discharge capacity is divided by the mass of the positive electrode active material spinel LMO.

[0179] Initial discharge specific capacity is the most basic performance parameter of positive electrode active materials. When the specific capacity C0 of spinel LMO is less than the standard value of 100 mAh / g, its use value is limited.

[0180] 2. High-Temperature Full-Charge Storage Performance Test of Secondary Batteries

[0181] The prepared secondary battery was used as the test object.

[0182] At 25°C, the secondary battery was charged at a constant current of 0.3C to a voltage of Vmax, and then charged at a constant voltage of Vmax to a current of 0.05C. The secondary battery was then placed at 45°C, fully discharged every month, followed by a full charge-discharge cycle at 25°C. The discharge capacity value C was then extracted. n Then fully charge again and continue storage at 45°C until the discharge capacity C... n Storage ends when the decay reaches 80% of the initial value C0. The total storage time at 45°C after full charge is the high-temperature full-charge storage time ts (months, meters).

[0183] 3. High-temperature cycle performance test of secondary batteries

[0184] The prepared secondary battery was used as the test object.

[0185] At 45℃, the secondary battery was charged at a constant current of 0.3C to a voltage of Vmax, then charged at a constant voltage of Vmax to a current of 0.05C. After resting for 5 minutes, the secondary battery was discharged at a constant current of 0.33C to a voltage of Vmin. This constitutes one charging cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. After the full battery was cycle-charged using the above method, the remaining reversible discharge capacity was recorded until the reversible discharge capacity decayed to 80% of the initial value. The total number of cycles, tc (×10 cycles, 10cls), was recorded.

[0186] This application comprehensively considers the capacity, storage and cycle performance of secondary batteries. Therefore, the overall coefficient E for evaluating the electrical performance of secondary batteries is defined to satisfy the following formula: E=(C0 / 100)×(ts / 36+tc / 100).

[0187] Taking a vehicle as an example, the performance of a secondary battery in a vehicle is reflected in its range and total mileage. Range can be measured by initial capacity, while total mileage is the product of range per unit lifespan and total lifespan. Total lifespan can be measured as the sum of cycle life and storage lifespan. The numbers in the above formulas represent the overall performance and applicable standards of spinel LMO. In (C0 / 100), 100 indicates an initial capacity of 100 mAh / g, 36 indicates a high-temperature full-charge storage life of 3 years, and 100 in tc / 100 indicates 1000 cls of high-temperature cycling. Clearly, under the applicable standard performance indicators, E = 2.

[0188] 4. Element content test in positive electrode active material

[0189] The content of each element in the positive electrode active material was measured according to EPA 6010D-2014 inductively coupled plasma atomic emission spectrometry.

[0190] 5. Average particle size D of the positive electrode active material V50(Volume median particle size D) V50 )test

[0191] Referring to GB / T 19077-2016 Particle Size Analysis by Laser Diffraction, the volume median particle size D of the positive electrode active material was measured using a Mastersizer 3000 laser particle size analyzer. V50 , which represents the particle size corresponding to a cumulative volume distribution percentage of 50% for the material.

[0192] 6. Specific surface area test of positive electrode active material

[0193] The specific surface area of ​​the positive electrode active material powder was measured according to GB / T 19587-2004, which describes the determination of the specific surface area of ​​solid materials by gas adsorption BET method.

[0194] 7. Scanning electron microscopy testing of positive electrode active materials

[0195] Referring to JY / T010-1996, the morphology of the positive electrode active material powder was observed using a field emission scanning electron microscope (Zeiss Sigma 300). In the scanning electron microscope images, a powder particle is called a single-crystal particle when it contains only one crystallite or when one crystallite occupies more than half the volume of the powder particle; a powder particle containing no more than 10 crystallites of similar size is called a near-single-crystal particle; and a powder particle containing more than 10 crystallites is called a polycrystalline particle.

[0196] Performance test results

[0197] Table 4: Performance of batteries prepared in Examples 1-31 and Comparative Examples 1 to 4

[0198] Compared to Comparative Example 4, the positive electrode active material was doped in Comparative Examples 1 to 3, which improved the structural stability of the positive electrode active material to a certain extent and improved the storage performance and cycle performance of the secondary battery at high temperature. However, E < 2, which is still quite different from the performance required for application.

[0199] Compared to Comparative Examples 1 to 3, Examples 1 to 31 doped the manganese sites of the positive electrode active material with elements that could form polyoxoanions with oxygen, thereby significantly improving the structural stability and thermal stability of the positive electrode active material, and thus significantly improving the storage performance and cycle performance of the secondary battery.

[0200] Compared to Example 2, Examples 6 to 11 use different A elements, such as Ru and Ta, for doping, which can improve the storage performance and cycle performance of the secondary battery at high temperatures.

[0201] Compared to Example 12, Examples 16 to 20 use different M elements, such as C, P, Si, S, etc., for doping, which can form multiple oxygen anions with oxygen, thereby improving the structural stability of the secondary battery and thus enhancing its performance.

[0202] Compared to Example 12, Examples 21 to 31 further include X element doping. X element can reduce the risk of Jahn-Teller distortion in the spinel structure, thereby improving the structural stability and capacity characteristics of the positive electrode active material.

[0203] As shown in Examples 1 to 5, the doping content of element A has a certain impact on the performance of the secondary battery. When 0.001 ≤ a ≤ 0.1, the performance of the secondary battery is relatively good. In particular, when 0.005 ≤ a + b ≤ 0.1, the storage performance and cycle performance of the secondary battery at high temperature are even better.

[0204] As can be seen from Examples 12 to 16, the doping content of element M has a certain impact on the performance of the secondary battery. When 0.001≤b≤0.1, the performance of the secondary battery is relatively good.

[0205] Table 5: Battery performance in Examples 12, 32 to 41

[0206] As can be seen from Examples 12, 32 to 41 in Table 5, while keeping m+n constant, within a certain range, as the volume percentage p of the second region decreases, more A and M elements can be enriched in the surface layer of the positive electrode active material, thereby further improving the surface properties of the positive electrode active material and enhancing the structural stability of the surface of the positive electrode active material. Figure 7 The diagram shows the distribution of the first region 121 and the second region 122 of the positive electrode active material.

[0207] As can be seen from Examples 36 to 41, the higher the content of m+n, the more A and M elements are enriched on the surface of the positive electrode active material, thereby further improving the structural stability of the surface of the positive electrode active material.

[0208] Table 6: Battery performance in Examples 12, 42 to 58

[0209] Table 6 shows that the performance of the secondary battery can be effectively adjusted by controlling the particle size, specific surface area (BET), and grain structure of the positive electrode active material. In particular, 0.01 ≤ (a+b)×D V50When the value is ≤1, the changes in electrical performance due to doping and variations in various physicochemical parameters can be well balanced, effectively avoiding the difficulty of sacrificing one aspect for another and maximizing the overall performance of the cathode active material. In particular, Examples 56-58, through multi-element doping combined with physicochemical parameter control, achieved excellent high capacity and long lifetime. Figure 8 A morphology diagram of the positive electrode active material of Example 51 is shown.

[0210] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode active material, comprising a molecular formula of Li 1+x A a M b X c Mn 2-a-b-c-x O 4-t Spinel-type lithium-manganese composite oxide, wherein the molecular formula is: A is a manganese site doping element in spinel-type lithium-manganese composite oxides, and A includes one or more of V, Nb, Ta, Mo, W, Ru, Rh, Sn, Sb, Te, Tl, Pd, Bi and Po; M is used to form a second phase containing multiple oxygen anions with O, and M includes one or more of B, C, N, Si, P, S and Cl; X includes one or more of Mg, Al, Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn, and Zr. in, -0.1≤x≤0.3, 0<a≤0.2, 0<b≤0.2, 0≤c≤0.7, 0≤t≤0.2, The spinel-type lithium-manganese composite oxide includes a first region and a second region distributed sequentially from its core to its outer surface; based on the volume of the spinel-type lithium-manganese composite oxide, the volume percentage p of the second region is ≤50%; Based on the total mass of element A in the spinel-type lithium-manganese composite oxide, the percentage of element A located in the second region is m; Based on the total mass of M in the spinel-type lithium manganese composite oxide, the percentage of M element located in the second region is n, where 70%≤m+n≤95%.

2. The positive electrode active material according to claim 1, wherein, A includes one or more of Nb, Ta, Mo, W, Ru, Te, and Tl.

3. The positive electrode active material according to claim 1 or 2, wherein, M includes one or more of Si, S, and Cl.

4. The positive electrode active material according to claim 1, wherein, X includes one or more of Al, Sc, Cr, Ni, Cu, Zn, and Ti; and / or 0.1 ≤ c ≤ 0.

6.

5. The positive electrode active material according to claim 1, wherein, 10%≤p≤30%。 6. The positive electrode active material according to claim 1, wherein, 80%≤m+n≤95%.

7. The positive electrode active material according to claim 1, wherein, In the molecular formula, 0.001≤a≤0.1 and / or 0.001≤b≤0.

1.

8. The positive electrode active material according to claim 1, wherein, 0.005≤a+b≤0.

1.

9. The positive electrode active material according to claim 1, wherein, The specific surface area of ​​the spinel-type lithium-manganese composite oxide is 0.01 m². 2 / g~1.5m 2 / g.

10. The positive electrode active material according to claim 9, wherein, The specific surface area of ​​the spinel-type lithium-manganese composite oxide is 0.1 m². 2 / g ~1m 2 / g.

11. The positive electrode active material according to claim 1, wherein, The average particle size D of the spinel-type lithium-manganese composite oxide V50 The range is from 1µm to 20µm.

12. The positive electrode active material according to claim 11, wherein, The average particle size D of the spinel-type lithium-manganese composite oxide V50 The range is 2µm to 15µm.

13. The positive electrode active material according to claim 1, wherein, The molecules a and b in the molecular formula and the average particle size D of the spinel-type lithium-manganese composite oxide V50 The following condition must be met: 0.01 ≤ (a + b) × D V50 ≤1.

14. The positive electrode active material according to claim 1, wherein, The spinel-type lithium-manganese composite oxide has a single-crystal grain morphology or a near-single-crystal grain morphology; and / or The spinel-type lithium-manganese composite oxide has at least one of the following: octahedral grain shape, truncated octahedral grain shape, and octahedral grain shape with sharpened edges.

15. A secondary battery comprising the positive electrode active material as described in any one of claims 1 to 14.

16. A battery module comprising the secondary battery as described in claim 15.

17. A battery pack comprising the battery module as claimed in claim 16.

18. An electrical device comprising at least one of the secondary battery as claimed in claim 15, the battery module as claimed in claim 16, or the battery pack as claimed in claim 17.

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