Lithium nickel manganese acid cathode active material, preparation method thereof, and secondary battery using the same

Abstract

The application provides a positive electrode active material of Li 1+x Ni y M z Mn 2‑x‑y‑z O 4‑k , -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti, in the first circle charging curve of the half cell of the positive electrode active material, the ratio of the charging capacity of 3.5V-4.4V to the charging capacity of 3.5V-4.95V is A, A satisfies 0.04≤A≤0.3, the product of k and A satisfies 0≤kA≤0.015, and the first circle charging curve is measured at a rate of 0.1C. The positive electrode active material of the application has high kinetic performance and high chemical stability, and the corresponding secondary battery has high rate discharge capacity and long-term storage stability.

Description

Technical Field

[0001] This application relates to a lithium nickel manganese oxide positive electrode active material for secondary batteries and its preparation method, as well as a secondary battery, battery module, battery pack and power device using the lithium nickel manganese oxide positive electrode active material. Background Technology

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace. Users have put forward higher requirements for their comprehensive performance, such as high-rate discharge capability and long-term storage stability.

[0003] The cathode active material is a key factor restricting the improvement of high-rate discharge capability and storage stability of secondary batteries. Therefore, it is urgent to develop a cathode active material with high kinetic performance and high chemical stability. Summary of the Invention

[0004] This application is made in view of the above-mentioned technical problems, and its purpose is to provide a spinel-structured lithium nickel manganese oxide cathode active material with high kinetic performance and high chemical stability, thereby improving both the high-rate discharge capability and long-term storage stability of secondary batteries using the lithium nickel manganese oxide cathode active material.

[0005] To achieve the above objectives, a first aspect of this application provides a lithium nickel manganese oxide cathode active material, wherein...

[0006] The positive electrode active material has the following composition: Li 1+x Ni y M z Mn 2-x-y-z O 4-k -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti.

[0007] In the first charge curve of the half-cell of the positive electrode active material, the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is A, where A satisfies 0.04≤A≤0.3, and the product of k and A satisfies 0≤kA≤0.015. The first charge curve is measured at a rate of 0.1C.

[0008] Thus, the obtained lithium nickel manganese oxide cathode active material has both high kinetic performance and high chemical stability, and the corresponding secondary battery has both high-rate discharge capability and long-term storage stability.

[0009] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0.11 ≤ k + A ≤ 0.18, optionally 0.11 ≤ k + A ≤ 0.15. This is because when the value of A is large, the Mn content in the corresponding spinel-structured lithium nickel manganese oxide cathode active material is... 3+ Higher content of manganese makes it easier for the transition metal to dissolve, thus reducing the chemical stability of the material. Therefore, a smaller k value is needed to improve the chemical stability of the material, so that the material has both good kinetic performance and chemical stability. The corresponding secondary battery has both excellent high-rate discharge capability and long-term storage stability.

[0010] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0.07 ≤ A ≤ 0.15. Therefore, the obtained lithium nickel manganese oxide cathode active material has further improved kinetic performance, corresponding to an increased high-rate discharge capability of the secondary battery.

[0011] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0 ≤ k ≤ 0.1, optionally 0 ≤ k ≤ 0.05, and more preferably 0 ≤ k ≤ 0.03. Therefore, the obtained lithium nickel manganese oxide cathode active material exhibits further improved chemical stability, corresponding to improved long-term storage stability of the secondary battery.

[0012] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0 < z ≤ 0.2, which can be selected as 0.001 ≤ z ≤ 0.15.

[0013] By controlling the content of element M within an appropriate range of 0 < z ≤ 0.2, it is easier to achieve comprehensive and uniform doping, thereby better balancing the material's kinetic properties and long-term stability. Further options include 0 < z ≤ 0.2, and even more options include 0.001 ≤ z ≤ 0.15.

[0014] In any embodiment, M is further selected from one or more of Nb, Ru, P, Ta, and Tl. This further reduces oxygen defect content, improves the chemical stability of the material, and enhances the long-term storage stability of secondary batteries using lithium nickel manganese oxide cathode active materials.

[0015] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies the following condition: the lithium nickel manganese oxide cathode active material is a single crystal and / or a near-single crystal particle. This further improves the chemical stability of the cathode active material, and consequently further enhances the long-term storage performance of the secondary battery using this cathode active material.

[0016] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies the following: the median volume diameter (D) of the particles. V50 ) satisfies 1μm≤D V50 ≤20μm, can be selected as 2μm≤D V50 ≤15μm. When the grains are larger, the exposed surface area is smaller, resulting in a smaller contact area with the electrolyte. This improves the stability of lithium nickel manganese oxide cathode active materials. However, excessively large grains can deteriorate their kinetic performance.

[0017] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0.06 ≤ (k + A) / (D) V50 0.3 If 0.12 is less than or equal to 0.06, then 0.06 ≤ (k + A) / (D) can be chosen. V50 0.3 )≤0.10, where (k+A) / (D V50 0.3 The unit is μm -0.3 By balancing k, A, and D using the relationships described above. V50 This is more conducive to the high-rate discharge performance and long-term storage stability of secondary batteries that use spinel-structured lithium nickel manganese oxide cathode active materials.

[0018] In any embodiment, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies the following condition: based on the total weight of the M element, in the radial direction from the surface of the cathode active material particle towards its geometric center, more than 80% of the M element is located within the first 50% volume of the cathode active material particle; optionally, it is within the first 30% volume. Therefore, by concentrating the dopant element on the surface, the surface stabilizing effect of the dopant element on the cathode active material can be further improved, the oxygen defect content can be further reduced, the surface stability of the material can be improved, and the long-term storage stability of the secondary battery using this cathode active material can be improved.

[0019] A second aspect of this application also provides a method for preparing a lithium nickel manganese oxide cathode active material, comprising the following steps:

[0020] S1: Provide a compound or mixture containing lithium, nickel, and manganese, optionally, the compound or mixture contains element M;

[0021] S2: The compound or mixture is heat-treated at 800℃~900℃ for 5h~20h in a furnace atmosphere where the gas pressure inside the furnace is positive relative to atmospheric pressure and the oxygen partial pressure is >50%, to obtain the positive electrode active material, wherein...

[0022] The positive electrode active material has the following composition: Li 1+x Ni y Mz Mn 2-x-y-z O 4-k -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti.

[0023] In the first charge curve of the half-cell of the positive electrode active material, the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is 0.04≤A≤0.3, and the product of k and A is 0≤k·A≤0.015, wherein the charging curve is measured at a rate of 0.1C.

[0024] In any embodiment, in S2, the oxygen partial pressure accounts for 80% to 100%.

[0025] In any embodiment, in S1, the lithium, nickel, and manganese-containing compound or mixture is heat-treated at 800°C to 1100°C for 5 to 50 hours in an oxygen-containing atmosphere.

[0026] In any embodiment, the nickel-manganese raw material in the lithium, nickel, and manganese mixture is selected from Ni y Mn 2-x-y-z (OH) 4-2x-2z Ni y Mn 2-x-y-z (CO3) 2-x-z Ni y Mn 2-x-y-z O 2-x-z Ni y Mn 2-x-y-z O 4-2x-2z 、(Ni y Mn 2-x-y-z )3O 4-2x-2z Ni y Mn 2-x-y-z [O(OH)] 2-x-z One or more of the following: -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2.

[0027] The spinel-structured lithium nickel manganese oxide cathode active material prepared by the above-described preparation method of this application has excellent kinetic properties and chemical stability.

[0028] A third aspect of this application also provides a secondary battery comprising the lithium nickel manganese oxide positive electrode active material of the first aspect or the lithium nickel manganese oxide positive electrode active material obtained by the preparation method of the second aspect, wherein the high-rate discharge capability and long-term storage stability of the secondary battery are significantly improved.

[0029] A fourth aspect of this application also provides a battery module comprising the secondary battery of the third aspect.

[0030] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0031] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application.

[0032] The battery module, battery pack, and power device of this application have the same advantages as the secondary battery cell of this application because they include the secondary battery cell of this application. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0034] Figure 2 yes Figure 1 The diagram shown is an exploded view of a secondary battery according to one embodiment of this application.

[0035] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0036] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0037] Figure 5 yes Figure 4 The diagram shown is an exploded view of a battery pack according to one embodiment of this application.

[0038] Figure 6 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0041] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the secondary battery, battery module, battery pack, and electrical 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.

[0042] 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.

[0043] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0044] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] Lithium nickel manganese oxide (NMO) cathode active materials, especially spinel-structured NMO cathode active materials, are excellent cathode active materials with high voltage characteristics and significant commercial value. Based on the current understanding of those skilled in the art, existing NMO cathode active materials have the following characteristics: spinel-structured NMO cathode active materials contain two space group structures: a disordered nickel-manganese phase Fd3m and an ordered nickel-manganese phase P4332. Due to the disorder of the Fd3m space group structure and the presence of a relatively large amount of +3 valent manganese, when the Fd3m structure has a higher proportion, the spinel-structured lithium manganese oxide material has stronger lithium-ion conductivity, resulting in stronger discharge capability at high rates. However, when the Fd3m structure has a high proportion, the spinel-structured NMO cathode active material has more surface oxygen defects. According to the current understanding of those skilled in the art, the more surface oxygen defects a spinel-structured lithium nickel manganese oxide cathode active material has, the more significant the side reactions between the lithium nickel manganese oxide cathode active material and the electrolyte (such as the dissolution of transition metal manganese, and the generation of gas by consuming electrolyte), which in turn leads to poor long-term storage performance of the secondary battery. In other words, existing spinel-structured lithium nickel manganese oxide cathode active materials have always been unable to simultaneously achieve high kinetic performance and high chemical stability.

[0049] Based on this, this application has developed a spinel-structured lithium nickel manganese oxide cathode active material with high kinetic performance and high chemical stability by reasonably controlling the preparation process, so that the secondary battery using the cathode active material has both high rate discharge capability and long-term storage stability.

[0050] [Positive electrode active material]

[0051] Based on this, the first aspect of the embodiments of this application proposes a lithium nickel manganese oxide positive electrode active material, wherein the positive electrode active material has the composition formula Li 1+x Ni y M z Mn 2-x-y-z O 4-k -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti.

[0052] In the first charge curve of the half-cell of the positive electrode active material, the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is A, where A satisfies 0.04≤A≤0.3, and the product of k and A satisfies 0≤kA≤0.015. The first charge curve is measured at a rate of 0.1C.

[0053] As mentioned above, when the proportion of Fd3m structure in spinel-structured lithium manganese oxide materials is relatively high, the spinel-structured lithium manganese oxide materials have stronger discharge capabilities at high rates. The spinel-structured lithium manganese oxide materials described in the first aspect of this application significantly increase the proportion of Fd3m structure, thereby significantly improving the lithium-ion conductivity of the spinel-structured lithium nickel manganese oxide cathode active material, significantly improving the kinetic performance of the spinel-structured lithium manganese oxide cathode active material, and thus significantly improving the high-rate discharge capability of the secondary battery prepared from the spinel-structured lithium nickel manganese oxide cathode active material.

[0054] In this application, the inventors have creatively discovered that the proportion of the Fd3m structure in the lithium nickel manganese oxide positive electrode active material can be represented by A. The method for determining A is as follows: in the first-cycle charging curve of the half-cell of the positive electrode active material, it is the ratio of the charging capacity from 3.5V to 4.4V to the charging capacity from 3.5V to 4.95V. Specifically, when testing the first-cycle charging curve, a coin cell half-cell is prepared using lithium as the negative electrode and the spinel-structured lithium nickel manganese oxide positive electrode active material of this application as the positive electrode. Then, it is charged at a rate of 0.1C to 4.95V to obtain the first-cycle charging curve. Using the obtained first-cycle charging curve, the charging capacity from 3.5V to 4.4V and the charging capacity from 3.5V to 4.95V are calculated. The value of A is the ratio of the charging capacity from 3.5V to 4.4V to the charging capacity from 3.5V to 4.95V.

[0055] The value of A can characterize the proportion of the Fd3m structure in the lithium nickel manganese oxide cathode active material for the following reasons: The Fd3m structure contains a relatively large amount of Mn. 3+ Therefore, during the charging process, in addition to the Ni oxidation that can occur in all lithium nickel manganese oxide cathode materials, 2+ / Ni 3+ / Ni 4+ In addition to the valence state change, the unique Mn content in Fd3m structure lithium nickel manganese oxide will also occur. 3+ / Mn 4+ The valence state changes of the element cause a voltage plateau in the charging curve in the range of 3.5V to 4.4V. Therefore, the ratio A of the charging capacity corresponding to the voltage plateau to the charging capacity corresponding to 3.5V to 4.95V can characterize the proportion of Fd3m structure in lithium nickel manganese oxide cathode active material.

[0056] Furthermore, the A value of the spinel-structured lithium nickel manganese oxide cathode active material of this application satisfies 0.04 ≤ A ≤ 0.3. When A satisfies 0.04 ≤ A ≤ 0.3, the spinel-structured lithium nickel manganese oxide cathode active material is almost entirely composed of Fd3m structures. The proportion of Fd3m structures in the spinel-structured lithium nickel manganese oxide cathode active material is increased, resulting in significantly improved kinetic performance. The high-rate discharge capability of the secondary battery prepared from the spinel-structured lithium nickel manganese oxide cathode active material is significantly enhanced.

[0057] The positive electrode active material of this application has Li 1+x Ni y M z Mn 2-x-y-z O 4-k The compositional formula is defined as follows: -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2. In the compositional formula, "1+x" represents the number of moles of lithium atoms, "y" represents the number of moles of nickel atoms, and "z" represents the number of moles of M atoms. "4-k" represents the number of moles of oxygen atoms.

[0058] Wherein, "k" represents the quantitative index of surface oxygen defects in lithium nickel manganese oxide with the spinel structure of the above composition. That is, the magnitude of k can characterize the chemical stability of the spinel structure lithium nickel manganese oxide cathode active material of this application, and further, can affect the long-term storage stability of the secondary battery prepared from the spinel structure lithium nickel manganese oxide cathode active material.

[0059] Furthermore, the k-value of the spinel-structured lithium nickel manganese oxide cathode active material of this application satisfies the following condition: the product of k and A satisfies 0 ≤ kA ≤ 0.015. The product kA can comprehensively characterize the overall performance of the spinel-structured lithium nickel manganese oxide cathode active material in terms of chemical stability and kinetic performance. Specifically, when A is large, it indicates that the proportion of Fd3m structure in the spinel-structured lithium nickel manganese oxide cathode active material is high, and the kinetic performance is good. However, if the k-value is too large, the corresponding spinel-structured lithium nickel manganese oxide cathode active material has many surface oxygen defects, resulting in poor chemical stability and an inability to comprehensively balance the material's kinetic performance and chemical stability. Through numerous experiments, when the spinel-structured lithium nickel manganese oxide cathode active material satisfies the relationship 0 ≤ kA ≤ 0.015, the spinel-structured lithium nickel manganese oxide cathode active material exhibits excellent overall performance, possessing both good kinetic performance and chemical stability. The secondary battery prepared in this way has excellent high-rate discharge performance and long-term storage stability.

[0060] In some embodiments, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0.11 ≤ k + A ≤ 0.18, optionally 0.11 ≤ k + A ≤ 0.15. This is because when the value of A is large, the Mn content in the corresponding spinel-structured lithium nickel manganese oxide cathode active material is... 3+ Higher content of manganese makes it easier for the transition metal to dissolve, thus reducing the chemical stability of the material. Therefore, a smaller k value is needed to improve the chemical stability of the material, so that the material has both good kinetic performance and chemical stability. The corresponding secondary battery has both excellent high-rate discharge capability and long-term storage stability.

[0061] In some embodiments, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0 ≤ k ≤ 0.1, optionally 0 ≤ k ≤ 0.05, optionally 0 ≤ k ≤ 0.03. The smaller the k value, the fewer oxygen defects on the surface of the spinel manganese oxide. By reducing oxygen defects, the chemical stability of the material can be significantly improved, the side reactions between the cathode material and the electrolyte can be mitigated, the dissolution of Mn and the consumption of electrolyte can be slowed down, and the long-term storage stability of the secondary battery can be improved.

[0062] In some implementations, when z is not 0, the spinel-structured lithium manganese oxide material contains a dopant element M. The dopant element M can form a strong bond with oxygen, which is not only beneficial for the synthesis of low oxygen defect Fd3m structure, but also can further improve the structural stability of the material. Thus, while taking into account high kinetic performance, it can better improve the stability of the secondary battery for long-term use.

[0063] Furthermore, by controlling the content of the aforementioned element M within an appropriate range of 0 < z ≤ 0.2, it is easier to achieve comprehensive and uniform doping, thereby better balancing the material's kinetic properties and long-term stability. Alternatively, the content can be 0.001 ≤ z ≤ 0.15.

[0064] In some embodiments, M is further selected from one or more of Nb, Ru, P, Ta, and Tl. This can further reduce oxygen defect content, improve material surface stability, and enhance the long-term storage stability of secondary batteries using lithium nickel manganese oxide cathode active materials.

[0065] In some embodiments, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies: 0.07≤A≤0.15.

[0066] As A increases, the spinel-structured lithium nickel manganese oxide cathode active material exhibits a higher proportion of Fd3m structure, improving the material's kinetic performance and thus enhancing the high-rate charge-discharge capability of the secondary battery. However, when A is excessively large, the proportion of Fd3m structure in the spinel-structured lithium nickel manganese oxide cathode active material becomes too high, leading to a decrease in the overall energy density of the secondary battery using this cathode active material.

[0067] In some embodiments, the lithium nickel manganese oxide cathode active material is a single crystal and / or a single crystal-like particle. "Single crystal-like" refers to a material with an aggregate-like morphology formed by several to a dozen grains. This type of single crystal-like material has advantages such as ease of synthesis and reduced grain boundaries of secondary spherical particles.

[0068] Because polycrystalline particles contain a large number of grain boundaries, these grain boundaries are prone to cracking under stress, thus exposing an unstable surface. This exacerbates side reactions with the electrolyte and leads to performance degradation. Therefore, monocrystalline or near-monocrystalline lithium nickel manganese oxide materials can effectively avoid or reduce these problems, thereby further improving the surface stability of the positive electrode active material and further improving the long-term storage performance of secondary batteries using this positive electrode active material.

[0069] In some implementations, from the viewpoint of more easily balancing a lower k-value and a higher A-value, the volume median particle size (D) of spinel-structured lithium nickel manganese oxide material particles is... V50 ) satisfies 1μm≤D V50 ≤20μm, can be selected as 2μm≤D V50 ≤15μm. When the grains are larger, the exposed surface area is smaller, resulting in a smaller contact area with the electrolyte. This improves the stability of lithium nickel manganese oxide cathode active materials. However, excessively large grains can deteriorate their kinetic performance.

[0070] In some embodiments, the spinel-structured lithium nickel manganese oxide cathode active material of this application further satisfies 0.06 ≤ (k+A) / (D) V50 0.3 If 0.12 is less than or equal to 0.06, then 0.06 ≤ (k + A) / (D) can be chosen. V50 0.3 )≤0.10, where (k+A) / (D V50 0.3 The unit is μm -0.3 Larger grains result in smaller exposed surfaces and a smaller contact area with the electrolyte, thus improving the stability of lithium nickel manganese oxide cathode active materials. However, excessively large grains can deteriorate their kinetic performance. Therefore, spinel-structured lithium nickel manganese oxide cathode active materials require a higher proportion of Fd3m structures. Furthermore, the presence of a small amount of oxygen vacancies (manifested as an increased k value) within the particles (not on the surface) can also improve overall kinetic performance. Experiments have shown that balancing k, A, and D using the relationships described above... V50 This is more conducive to the high-rate discharge performance and long-term storage stability of secondary batteries that use spinel-structured lithium nickel manganese oxide cathode active materials.

[0071] In some embodiments, the spinel-structured lithium nickel manganese oxide cathode active material of this application, based on the total weight of the M element, has more than 80% of the M element located within the first 50% volume of the cathode active material particles in the radial direction from the surface of the particles to their geometric center; optionally, it is within the first 30% volume.

[0072] Therefore, by concentrating the doping elements on the surface, the surface stabilizing effect of the doping elements on the positive electrode active material can be further improved, the oxygen defect content can be further reduced, the surface stability of the material can be improved, and the long-term storage stability of the secondary battery using the positive electrode active material can be improved.

[0073] In some embodiments, the grain shape of the lithium nickel manganese oxide cathode active material is octahedral, truncated octahedral, or a regular shape with sharpened edges. A truncated octahedral or a regular shape with sharpened edges refers to a shape where the apex of the octahedron is removed or the edges are flattened, but the main crystal orientations of the octahedron are retained. The octahedral or sharpened-edge grain shape indicates that the grain surface is a crystal face with optimal kinetic performance and greater stability, thereby improving the kinetic performance of the cathode active material and reducing surface side reactions, thus further improving the high-rate discharge capability of the secondary battery using this cathode active material.

[0074] Preparation methods for positive electrode active materials

[0075] The second aspect of the embodiments of this application provides a method for preparing lithium nickel manganese oxide positive electrode active material, which includes the following steps S1 and S2.

[0076] S1: Provide a compound or mixture containing lithium, nickel, and manganese, optionally, the compound or mixture contains element M;

[0077] S2: The compound or mixture is heat-treated at 800℃~900℃ for 5h~20h in a furnace atmosphere where the gas pressure inside the furnace is positive relative to atmospheric pressure and the oxygen partial pressure is >50%, to obtain the positive electrode active material, wherein...

[0078] The positive electrode active material has the following composition: Li 1+x Ni y M z Mn 2-x-y-z O 4-k -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti.

[0079] In the first charge curve of the half-cell of the positive electrode active material, the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is 0.04≤A≤0.3, and the product of k and A is 0≤kA≤0.015, wherein the charging curve is measured at a rate of 0.1C.

[0080] In step S1, "a compound of lithium, nickel and manganese" refers to a raw material that simultaneously contains lithium, nickel and manganese; "a mixture of lithium, nickel and manganese" refers to a mixed material that simultaneously contains lithium, nickel and manganese, formed by physically mixing raw materials containing lithium, nickel, manganese, or any two of the elements lithium, nickel and manganese.

[0081] In step S2, a higher heat treatment temperature is more conducive to the formation of Fd3m space group structure, but it is also more likely to form surface oxygen defects. Therefore, the heat treatment temperature is limited to 800℃~900℃ for 5h~20h. In addition, by performing heat treatment in a furnace atmosphere where the furnace pressure is positive relative to atmospheric pressure and the oxygen partial pressure ratio is >50%, the formation of surface oxygen defects can be minimized. Furthermore, by using an appropriate heat treatment time, a spinel structure lithium nickel manganese oxide cathode active material with a high Fd3m content but low surface oxygen defect content can be obtained.

[0082] In some embodiments, in step S1, powder containing an M source is further mixed, wherein M is one or more selected from Cr, Mo, Nb, Ru, P, S, Ta, W, Tl, and Ti. These M elements can form strong bonds with oxygen, which not only facilitates the synthesis of low-oxygen-deficient Fd3m structures but also further improves the structural stability of the material, thereby enhancing the long-term stability of the battery while maintaining kinetic performance. From the viewpoint of further reducing oxygen defect content, the M element is preferably selected from one or more of Nb, Ru, P, Ta, and Tl.

[0083] In some implementations, in order to better reduce oxygen defects, the oxygen partial pressure ratio in step S2 can be selected as 80% to 100%.

[0084] In some embodiments, step S1 includes a pre-firing process. A compound or mixture containing lithium, nickel, and manganese is heat-treated in an oxygen-containing atmosphere at 800°C–1100°C for 5–50 hours. Since step S2 requires precise control of temperature, atmosphere, and firing time, it may not be possible to achieve the target grain size, especially for large grains. Therefore, to obtain grains of the target size, a pre-firing process can be performed in an oxygen-containing atmosphere at 800°C–1100°C for 5–50 hours to first produce a product that meets the target grain size, and then the formal firing process can be carried out to obtain a lithium nickel manganese oxide cathode active material with low surface oxygen defect content and a high Fd3m structure ratio.

[0085] In some embodiments, before step S2, the lithium, nickel, and manganese-containing compounds or mixtures, or pre-calcined powders, can be crushed using a pulverizer to obtain crushed powders. The crushing process can reduce the particle size of the powder and improve its dispersibility, thereby dispersing near-single crystals into particles that are closer to single crystals.

[0086] In some embodiments, the nickel-manganese raw materials in the lithium, nickel, and manganese mixture are selected from Ni y Mn 2-x-y-z (OH) 4-2x-2z Ni y Mn 2-x-y-z (CO3) 2-x-z Ni y Mn 2-x-y-z O 2-x-z Ni y Mn 2-x-y-z O 4-2x-2z 、(Ni y Mn 2-x-y-z )3O 4-2x-2z Ni y Mn 2-x-y-z [O(OH)] 2-x-z One or more of the following: -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2.

[0087] Rechargeable batteries

[0088] In one embodiment of this application, a secondary battery is provided.

[0089] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, 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. This secondary battery can be a lithium-ion battery.

[0090] [Positive electrode plate]

[0091] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the spinel structure lithium nickel manganese oxide positive electrode active material described above or the spinel structure lithium nickel manganese oxide positive electrode active material prepared according to the above preparation method.

[0092] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0093] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0094] In some embodiments, the spinel-structured lithium nickel manganese oxide cathode active material of this application can also be used in combination with other cathode active materials known in the art for use in batteries to improve the electrical performance of the secondary battery. As an example, other cathode active materials may include any of the following materials: olivine-structured lithium phosphates, 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 battery cathode active materials may also be used. Examples of lithium transition metal oxides 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, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 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 Mn0.2 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) 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc. Examples of lithium phosphates with olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also known as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, etc.

[0095] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0096] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, lithium supplementing agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0098] [Negative electrode plate]

[0099] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0100] As an example, the negative electrode 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 electrode current collector.

[0101] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0102] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0103] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0104] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0106] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0107] [Electrolytes]

[0108] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[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 at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0111] In some embodiments, the solvent may be selected from non-fluorinated solvents and / or fluorinated solvents, wherein the non-fluorinated solvent comprises one or more of carbonates, carboxylic esters, sulfones, and ethers. The fluorinated solvent is one or more of fluorinated carbonates, fluorinated carboxylic esters, fluorinated sulfones, and fluorinated ethers. Specifically, it may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[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 may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or 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] 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.

[0118] 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.

[0119] 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 This is an example of a square-structured secondary battery 5.

[0120] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 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 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0121] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0122] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0123] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0124] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0125] Figure 4 and Figure 5This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0126] 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 a power source for the electrical device, or as an energy storage unit for 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.

[0127] As the electrical device, a 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. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, 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] 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.

[0131] Preparation and Parameter Testing of Spinel-Structured Lithium Nickel Manganese Oxide Cathode Active Material

[0132] Example 1

[0133] According to the target component Li 1.00 Ni 0.50 Mn 1.50 O 4-k Weigh out the corresponding stoichiometric amounts of Li₂CO₃ and Ni.0.5 Mn 1.5 (OH)4 powder is then mixed evenly to obtain a raw material mixture powder. The raw material mixture powder is pre-calcined in air at 1000℃ for 8 hours to obtain pre-calcined powder.

[0134] The pre-calcined powder was heated to 800°C and held for 10 hours under a positive pressure of 0.05 MPa relative to atmospheric pressure and a mixed atmosphere of oxygen and nitrogen containing 50% oxygen partial pressure to obtain the finished spinel lithium nickel manganese oxide.

[0135] Examples 2-10, Comparative Examples 1-3

[0136] Using the same pre-calcined powder obtained in Example 1 above, the calcination temperature and oxygen partial pressure were adjusted according to Table 1 in an oxygen + nitrogen mixed gas or air atmosphere at a positive pressure of 0.05 MPa relative to atmospheric pressure to obtain the finished spinel lithium nickel manganese oxide.

[0137] Examples 11-17

[0138] According to the target component Li shown in Table 1 1.00 Ni 0.50 M 0.05 Mn 1.45 O 4-k Weigh out the corresponding stoichiometric amounts of Li₂CO₃ and Ni. 0.5 Mn 1.45 (OH) 3.9 The raw material mixture powders were then mixed with Cr2O3, MoO3, Nb2O5, RuO2, NH4H2PO4, Ta2O5, and Tl2O3 until homogeneous to obtain a raw material mixture powder. The raw material mixture powder was then pre-calcined in air at 1000℃ for 8 hours to obtain a pre-calcined powder.

[0139] The pre-calcined powder was heated to 860°C and held for 10 hours in an oxygen + nitrogen mixed gas atmosphere with a positive pressure of 0.05 MPa relative to atmospheric pressure and an oxygen partial pressure of 80%, to obtain the finished spinel nickel manganese oxide products of each embodiment.

[0140] Examples 18-21, Comparative Example 4

[0141] According to the target component Li shown in Table 1 1.00 Ni 0.50 Nb z Mn 1.5-z O 4-k Weigh out the corresponding stoichiometric amounts of Li₂CO₃ and Ni. 0.5 Mn 1.5-z O 2-zThe raw material mixture powder is then mixed with Nb2O5 powder until homogeneous, resulting in a raw material mixture powder. This raw material mixture powder is then pre-calcined in air at 1000℃ for 8 hours to obtain the pre-calcined powder.

[0142] The pre-calcined powder was heated to 860°C and held for 10 hours in an oxygen + nitrogen mixed gas atmosphere with a positive pressure of 0.05 MPa relative to atmospheric pressure and an oxygen partial pressure of 80%, to obtain the finished spinel nickel manganese oxide products of each embodiment and comparative example.

[0143] Examples 22-25

[0144] According to the target component Li shown in Table 1 1+x Ni y Mn 2-x-y O 4-k Weigh out the corresponding stoichiometric amounts of Li₂CO₃ and Ni. y Mn 2-x-y (CO3) 2-x The powder is then mixed evenly to obtain a raw material mixture powder. The raw material mixture powder is pre-calcined in air at 1000℃ for 8 hours to obtain pre-calcined powder.

[0145] The pre-calcined powder was heated to 860°C and held for 10 hours in an oxygen + nitrogen mixed gas atmosphere with a positive pressure of 0.05 MPa relative to atmospheric pressure and an oxygen partial pressure of 80%, to obtain lithium nickel manganese oxide in each embodiment.

[0146] Examples 26-30

[0147] According to the target component Li shown in Table 1 1.00 Ni 0.50 Mn 1.50 O 4-k Weigh out the corresponding stoichiometric amounts of LiOH·H2O and Ni 0.5 Mn 1.5 (OH)4 powder was then mixed evenly to obtain a raw material mixture powder. Except for Example 26, in the other examples, the raw material mixture powder was pre-calcined in air at the temperatures shown in Table 1 for the corresponding time to obtain pre-calcined powder. In Examples 26-28, before calcination, the pre-calcined powder (Examples 27, 28) or the raw material mixture powder (Example 26) was crushed using an airflow mill to obtain crushed powder.

[0148] The pre-calcined powder (Examples 29, 30) or crushed powder (Examples 26-28) obtained were heated to the calcination temperature shown in Table 1 and held for the corresponding time in an oxygen + nitrogen mixed gas atmosphere with a positive pressure of 0.05 MPa relative to atmospheric pressure and an oxygen partial pressure of 80% to obtain the finished lithium nickel manganese oxide.

[0149] Example 31

[0150] According to the target component Li 1.03 Ni 0.51 Nb 0.03 Ru 0.02 Mn 1.41 O 4-k Weigh out the corresponding stoichiometric amounts of Li₂CO₃ and Ni. 0.51 Mn 1.41 (OH) 3.84 Nb2O5 and RuO2 powders were mixed evenly to obtain a raw material mixture powder. The raw material mixture powder was pre-calcined in air at 1000℃ for 8 hours to obtain pre-calcined powder.

[0151] In an atmosphere of oxygen + nitrogen mixture with a positive pressure of 0.05 MPa relative to atmospheric pressure and an oxygen partial pressure of 99%, the temperature was raised to 860℃ and held for 20 hours to obtain a spinel structure lithium nickel manganese oxide positive electrode active material.

[0152] Table 1. Preparation process parameters of lithium nickel manganese oxide cathode active material

[0153]

[0154] The physical and chemical parameters of each embodiment and comparative example were characterized by the following tests, and the results are summarized in Table 2.

[0155] (1) Referring to EPA 6010D-2014 Inductively Coupled Plasma Atomic Emission Spectrometry, the content of each element in the positive electrode active materials of each embodiment and comparative example was measured, and its k value was calculated. In addition, the element content, material structure, etc. can also be determined by XRD analysis, XRF analysis, etc.

[0156] (2) Referring to JY / T010-1996, the morphology of the positive electrode active materials of each embodiment and comparative example was observed using a ZEISS Sigma 300 scanning electron microscope, and their particle morphology was determined to be single crystal, near-single crystal, or polycrystalline. The powder particle morphology of the embodiments of the present invention is all single crystal or near-single crystal.

[0157] (3) Referring to GB / T 19077-2016 Particle Size Analysis by Laser Diffraction, the volume median particle size D of the positive electrode active material powder in each embodiment and comparative example was measured using a Mastersizer 3000 laser particle size analyzer. V50 .

[0158] (4) The positive electrode active materials obtained in each embodiment and comparative example were subjected to the following coin charge test to obtain the first charge curve and calculate the A value. The obtained A values ​​are shown in Table 2.

[0159] First, using a lithium sheet as the counter electrode, the spinel-structured lithium nickel manganese oxide positive electrode active materials of each embodiment or comparative example are assembled into a half-cell (button cell) according to the following steps:

[0160] • The lithium nickel manganese oxide positive electrode active material of each embodiment or comparative example was mixed with conductive carbon black and PVDF at a weight ratio of 90:5:5, and an appropriate amount of N-methylpyrrolidone was added. The mixture was stirred evenly to obtain a positive electrode slurry. The obtained positive electrode slurry was coated onto aluminum foil and dried to obtain a positive electrode sheet. The loading of lithium nickel manganese composite oxide on the positive electrode sheet was 0.015 g / cm³. 2 .

[0161] • A mixed solution containing 1 mol / L LiPF6 of carbonates, fluorocarbonates, fluoroethers, etc., was used as the electrolyte.

[0162] • A 12μm thick polypropylene film (φ16mm) is used as a separator. The lithium sheet, separator, and positive electrode are placed in sequence so that the separator is positioned between the metallic lithium sheet and the composite negative electrode to provide isolation.

[0163] • Inject electrolyte, assemble into CR2030 coin cell, let stand for 24 hours to obtain half cell.

[0164] Then, at 25°C, the coin cells prepared from the positive electrode active materials of each embodiment and comparative example were charged at a constant current of 0.1C to a voltage of 4.95V, and the charging capacity of 4.4V to 3.5V (C1) and the charging capacity of 4.95V to 3.5V (C2) were extracted from the original charging data.

[0165] Where A = C1 / C2.

[0166] Table 2. Product Parameters of Spinel-Structured Positive Electrode Active Materials

[0167]

[0168] *:P=(k+A) / (D V50 0.3 )

[0169] As can be seen from all the examples and comparative examples, by firing the raw material mixture that meets the conditions at a temperature of 800℃~900℃ and in a furnace atmosphere with positive pressure relative to atmospheric pressure and oxygen partial pressure ratio >50% for 5h~20h, a lithium nickel manganese oxide cathode active material with a density of 0.04≤A≤0.3 and 0≤kA≤0.015 can be obtained. The lithium nickel manganese oxide cathode active material has a high proportion of Fd3m space group structure and few oxygen defects.

[0170] As shown in Examples 1-6, by adjusting the firing temperature to 800℃~900℃ and matching it with a suitable oxygen partial pressure, the finished spinel nickel manganese oxide can be controlled to have suitable A value and kA value. That is, the spinel nickel manganese oxide has low oxygen defects and a suitable Fd3m content, and lithium-ion batteries using it can balance kinetic performance and long-term storage performance. When the firing temperature is outside the above range, it is impossible to achieve suitable A value and kA value. When the temperature is below 800℃, the A value decreases significantly. For example, in Comparative Example 1, the firing temperature was 670℃, and its A value was only 0.032, meaning that the Fd3m content was too low, which is not conducive to kinetic performance. When the temperature is too high, it is conducive to the generation of oxygen defects, so it is difficult to reduce the k value and kA value, which will aggravate the side reactions between the cathode material and the electrolyte and the dissolution of Mn, and reduce the battery life.

[0171] As can be seen from Examples 7-10 and Comparative Example 2, by extending the heat preservation time and increasing the oxygen partial pressure, the k value and kA value can be reduced while keeping the A value unchanged (the Fd3m structure content unchanged), which reduces oxygen defects and will benefit the structural stability of spinel nickel manganese oxide and the battery life.

[0172] As shown in Examples 11-17, doping with Cr, Mo, Nb, Ru, P, Ta, and Tl can further reduce the k value (reduce oxygen defects). This is because these elements can form strong bonds with oxygen, thus slowing down the oxygen release of spinel lithium nickel manganese oxide at high temperatures. The k values ​​in Examples 13-17 are even smaller, indicating that the doping elements Nb, Ru, P, Ta, and Tl have a more significant effect on suppressing oxygen defects.

[0173] As can be seen from Examples 18-21 and Comparative Example 3, by keeping the dopant content within a suitable range, it is possible to better balance the A value and kA value. However, when the dopant content is too high, i.e., z > 0.2, it no longer has a further effect on reducing oxygen defects, but the actual active material of the material is significantly reduced due to the excessive doping amount. This is because the spinel structure LiM2O4 corresponding to these dopants is almost inactive, affecting the charge and discharge capacity of the battery.

[0174] As shown in Examples 22-25, spinel lithium nickel manganese oxide with suitable A and kA values ​​can be obtained by appropriately adjusting the contents of Li, Ni, and Mn. This is because the Li, Ni, and Mn elements in spinel lithium nickel manganese oxide can partially substitute for each other in their respective positions.

[0175] As shown in Examples 26-30, the particle size can be controlled by adjusting the preparation process. With increasing maximum temperature and holding time during pre-firing and final firing in the preparation process, single crystals are more easily formed and grains are more likely to increase in size; the A value and kA value also change accordingly. Furthermore, the crushing process before final firing can reduce the particle size D. V50This improves dispersibility, thereby dispersing the quasi-single crystal into a quasi-single crystal or single crystal that is closer to a single crystal.

[0176] As shown in Example 31, by comprehensively adjusting the sintering process, doping modification, and the content of major elements (Li, Ni, Mn), it is possible to obtain a particle size with suitable k=0 (no oxygen defects), A value (A=0.109, kA=0), and suitable particle size (D). V50 Single-crystal spinel lithium nickel manganese oxide cathode active material (6.7 μm).

[0177] [Preparation and Performance Testing of Secondary Batteries]

[0178] The lithium nickel manganese oxide positive electrode active materials of each embodiment and comparative example were prepared into graphite negative electrode pouch batteries according to the following method. The discharge energy density E5C (Wh / Kg) at 5C rate and the full charge storage time ts (month) at room temperature were tested, and the results are shown in Table 3.

[0179] Fabrication of graphite anode soft-pack batteries:

[0180] (1) The lithium nickel manganese oxide positive electrode active materials of each embodiment and comparative example were mixed with conductive carbon black and PVDF at a weight ratio of 96:2.5:1.5, and an appropriate amount of N-methylpyrrolidone was added. The mixture was stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was coated onto aluminum foil and dried to obtain a positive electrode sheet. The loading of lithium nickel manganese composite oxide on the positive electrode sheet was 0.02 g / cm³. 2 .

[0181] (2) The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. The negative electrode slurry was uniformly coated onto the surface of the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet was obtained. The loading of the negative electrode active material on one side of the negative electrode current collector was 0.008 g / cm³. 2 .

[0182] (3) Use a mixed solution of carbonates, fluorocarbonates, fluoroethers, etc. containing 1 mol / L LiPF6 as the electrolyte.

[0183] (4) Using a 12μm thick polypropylene film (φ16mm) as the separator, the above-prepared positive electrode, separator, and negative electrode are arranged in sequence, with the separator positioned between the positive and negative electrodes to provide separation. The mixture is then wound into shape and packaged in an aluminum-plastic bag. Electrolyte is injected, and after encapsulation, the capacity is determined to produce a graphite negative electrode soft-pack battery.

[0184] Electrical performance testing of graphite negative electrode pouch batteries:

[0185] (1) Testing of the 5C discharge specific capacity and 5C discharge energy density of the positive electrode active material in a graphite negative electrode pouch cell:

[0186] At 25°C, the graphite negative electrode pouch cells of each embodiment or comparative example were charged at a constant current of 0.3C to a voltage of 4.9V, then charged at a constant voltage of 4.9V to a current of 0.05C. After standing for 5 minutes, the pouch cells were discharged at a constant current of 5C to a voltage of 3.5V. The corresponding discharge capacity and discharge energy were extracted to obtain the 5C discharge capacity and 5C discharge energy of the pouch cell. Dividing this capacity and energy by the mass (g) of the positive electrode active material in the battery yields the 5C discharge specific capacity and 5C discharge energy density of the positive electrode active material, as shown in Table 3. Compared to the conventional low-rate charge-discharge of 0.33C or 1C, 5C is a high-rate current, which better reflects the quality of the material and the dynamic performance of the battery. Therefore, the 5C discharge capacity and discharge energy density reflect the dynamic performance of the electrode material used in secondary batteries.

[0187] (2) Storage performance test of soft-pack secondary batteries at room temperature under full charge:

[0188] At 25°C, the graphite negative electrode pouch cells of each embodiment or comparative example were charged at a constant current of 0.3C to a voltage of 4.9V, and then charged at a constant voltage of 4.9V to a current of 0.05C. The secondary batteries were then placed at 25°C, and a full charge-discharge cycle was performed every 10 days. The discharge capacity value was extracted until the extracted discharge capacity decreased to 80% of the initial value, at which point storage was completed. The total storage time at 25°C after full charge is the room temperature full charge storage time ts, and is shown in Table 3. In this application, the room temperature full charge storage time ts represents the long-term stability of the material used in the secondary battery.

[0189] (3) Calculation of the comprehensive evaluation coefficient R of electrical performance:

[0190] Following the logic of "total lifespan = single-charge range × total lifespan", the comprehensive electrical performance evaluation coefficient R is set as (E5C-440)×(ts-12) / 100, where the two constants represent the energy density of 440Wh / kg and one year of full-charge storage, respectively, which are the basic conditions for the application value of the current material system. A negative R value is recorded as 0. This evaluation coefficient can intuitively and comprehensively evaluate the differences in battery performance. The comprehensive evaluation coefficient values ​​for each embodiment and comparative example are calculated, and the results are shown in Table 3.

[0191] Table 3. Performance Table of Secondary Batteries

[0192] Sample number 5C discharge energy density E / (Wh / Kg) Fully charged storage at room temperature (ts / (month)) Comprehensive evaluation coefficient R Comparative Example 1 443 25.1 0.4 Example 1 486 28.3 7.5 Example 2 497 27.2 8.7 Example 3 515 25.9 10.4 Example 4 532 23.4 10.5 Example 5 523 18.8 5.6 Example 6 521 16.5 3.6 Comparative Example 2 512 14.3 1.7 Comparative Example 3 531 11.6 0.0 Example 7 534 25.9 13.1 Example 8 545 24.8 13.4 Example 9 536 18.8 6.5 Example 10 533 16.2 3.9 Example 11 567 24.1 15.4 Example 12 541 27.8 15.9 Example 13 537 30.7 18.1 Example 14 541 31.2 19.4 Example 15 531 32.8 18.9 Example 16 523 33.7 18.0 Example 17 526 34.3 19.2 Example 18 533 26.8 13.8 Example 19 527 34.9 19.9 Example 20 498 35.8 13.8 Example 21 478 33.2 8.1 Comparative Example 4 405 31.5 0 Example 22 528 18.3 5.5 Example 23 502 27.9 9.9 Example 24 523 20.1 6.7 Example 25 508 27.4 10.5 Example 26 553 15.6 4.1 Example 27 545 18.1 6.4 Example 28 542 19.2 7.3 Example 29 518 21.0 7.0 Example 30 513 21.2 6.7 Example 31 537 37.8 25.0

[0193] Comparative examples and comparative cases show that the Li-Nickel Manganese Oxide positive electrode active material Li satisfies the following conditions: A value is 0.04 ≤ A ≤ 0.3, and 0 ≤ kA ≤ 0.015. 1+x Ni y M z Mn 2-x-y-z O 4-k The values ​​are 0.1≤x≤0.2, 0.4≤y≤0.6, and 0≤z≤0.2, which exhibit both good 5C discharge energy density and room-temperature full-charge storage performance. Comparative Example 1 shows that when A is less than 0.04, the 5C discharge energy density is low. Comparative Examples 2 and 3 show that when the value of kA is greater than 0.015, it is impossible to achieve both good 5C discharge energy density and room-temperature full-charge storage performance. Comparative Example 4 shows that when the content of dopant element M is too high, it is also impossible to achieve both good 5C discharge energy density and room-temperature full-charge storage performance.

[0194] Compared with Examples 1-10, when 0.11≤k≤0.22, the comprehensive evaluation coefficient R>5, which better balances good 5C discharge energy density and room temperature full charge storage performance; further, when 0.11≤k+A≤0.18, R>6, and the comprehensive performance is further improved.

[0195] Comparing Examples 1-3 with Examples 11-17, doping with M element improved the 5C discharge energy density and / or room temperature full-charge storage performance of the material, and improved the value of the comprehensive evaluation coefficient R; the modification effects of doping elements Nb, Ru, P, Ta and Tl were more significant.

[0196] Compared with Examples 13 and 18-21, the room temperature storage performance of lithium nickel manganese oxide with Nb doping content satisfying z≤0.2 was significantly improved, and the comprehensive evaluation coefficient R>8, which well balances good 5C discharge energy density and room temperature full charge storage performance; the comprehensive evaluation coefficient R>10 of lithium nickel manganese oxide with Nb doping content of 0.001≤z≤0.15 is even better, with superior overall performance.

[0197] Comparing Examples 4 and 26-30, the volume median particle size D V50 Satisfying 1μm≤D V50 Lithium nickel manganese oxide with a particle size ≤20μm has an R > 6, which effectively balances good 5C discharge energy density and room-temperature full-charge storage performance; lithium nickel manganese oxide with a particle size ≤20μm has a D > 6. V50 Lithium nickel manganese oxide cathode active materials with a diameter of ≤15μm have an R value of >7, resulting in superior overall performance.

[0198] Comparing Examples 1-10 and Examples 27-30, when P = (k + A) / (D) V50 0.3When 0.06≤P≤0.12 is satisfied, the comprehensive evaluation coefficient R>6, which takes into account both good 5C discharge energy density and room temperature full charge storage performance; further, when 0.06≤P≤0.10, R>7, and the comprehensive performance is further improved.

[0199] Compared with other embodiments, the lithium nickel manganese oxide active material with comprehensive control of A, kA, doping elements and doping amount, and particle size has both good 5C discharge energy density and room temperature full charge storage performance.

Claims

1. A lithium nickel manganese oxide positive electrode active material, characterized in that, The positive electrode active material has the following composition: Li 1+x Ni y M z Mn 2-x-y-z O 4-k -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti. In the first charge curve of the half-cell of the positive electrode active material, the ratio of the charging capacity of 3.5V~4.4V to the charging capacity of 3.5V~4.95V is A, where A satisfies 0.04≤A≤0.3, and the product of k and A satisfies 0≤kA≤0.

015. The first charge curve is measured at a rate of 0.1C. Wherein, A and k satisfy the following relationship: 0.11≤k+A≤0.

18.

2. The lithium nickel manganese oxide positive electrode active material according to claim 1, wherein, 0.07≤A≤0.15。 3. The lithium nickel manganese oxide positive electrode active material according to any one of claims 1-2, wherein, The k satisfies 0 ≤ k ≤ 0.

1.

4. The lithium nickel manganese oxide positive electrode active material according to any one of claims 1-2, wherein, The z satisfies the following relationship: 0＜z≤0.2。 5. The lithium nickel manganese oxide positive electrode active material according to any one of claims 1-2, wherein, M is selected from one or more of Nb, Ru, P, Ta and Tl.

6. The lithium nickel manganese oxide positive electrode active material according to any one of claims 1-2, wherein, The lithium nickel manganese oxide positive electrode active material is a single crystal and / or a single crystal-like particle.

7. The lithium nickel manganese oxide positive electrode active material according to any one of claims 1-2, wherein, The volume median particle size D of the positive electrode active material particles V50 Satisfying 1μm≤D V50 ≤20μm.

8. The lithium nickel manganese oxide positive electrode active material according to claim 7, wherein, 0.06≤(k+A) / (D V50 0.3 )≤0.12, where (k+A) / (D V50 0.3 The unit is μm -0.3 .

9. The lithium nickel manganese oxide positive electrode active material according to any one of claims 1-2, wherein, Based on the total weight of the M element, more than 80% of the M element is located in the first 50% of the volume of the particle along the radial direction from the surface of the positive electrode active material particle toward its geometric center.

10. A method for preparing a lithium nickel manganese oxide positive electrode active material, characterized in that, Includes the following steps, S1: Provide a compound or mixture containing lithium, nickel, and manganese, wherein the compound or mixture contains element M; S2: The compound or mixture is heat-treated at 800℃~900℃ for 5h~20h in a furnace atmosphere where the gas pressure inside the furnace is positive relative to atmospheric pressure and the oxygen partial pressure is >50%, to obtain the positive electrode active material, wherein... The positive electrode active material has the following composition: Li 1+x Ni y M z Mn 2-x-y-z O 4-k -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti. In the first charge curve of the half-cell of the positive electrode active material, the ratio A of the charging capacity of 3.5V~4.4V to the charging capacity of 3.5V~4.95V satisfies 0.04≤A≤0.3, and the product of k and A, kA, satisfies 0≤kA≤0.

015. The first charge curve is measured at a rate of 0.1C. Wherein, A and k satisfy the following relationship: 0.11≤k+A≤0.

18.

11. The preparation method according to claim 10, wherein, In S2, the oxygen partial pressure accounts for 80% to 100%.

12. The preparation method according to claim 11, wherein, In step S1, the compound or mixture containing lithium, nickel, and manganese is heat-treated at 800°C to 1100°C for 5 to 50 hours in an oxygen-containing atmosphere.

13. The preparation method according to any one of claims 10-12, wherein, The nickel and manganese raw materials in the lithium, nickel, and manganese mixture are selected from Ni y Mn 2-x-y-z (OH) 4-2x-2z Ni y Mn 2-x-y-z (CO3) 2-x-z Ni y Mn 2-x-y-z O 2-x-z Ni y Mn 2-x-y-z O 4-2x-2z 、(Ni y Mn 2-x-y-z )3O 4-2x-2z Ni y Mn 2-x-y-z [O(OH)] 2-x-z One or more of the following: -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.

2.

14. A secondary battery, characterized in that, The active material comprises lithium nickel manganese oxide cathode material according to any one of claims 1-9 or lithium nickel manganese oxide cathode material prepared by any one of claims 10-13.

15. A battery module, characterized in that, Includes the secondary battery as described in claim 14.

16. A battery pack, characterized in that, Includes the battery module as described in claim 15.

17. An electrical device, characterized in that, It includes at least one selected from the secondary battery of claim 14, the battery module of claim 15, or the battery pack of claim 16.

Images