A lithium nickel manganese oxide cathode material, a preparation method and application thereof

Abstract

The application provides a lithium nickel manganese oxide positive electrode material and a preparation method and application thereof. The lithium nickel manganese oxide positive electrode material comprises an inner core and a cation and anion co-coating layer arranged on the surface of the inner core, and a phase of the lithium nickel manganese oxide positive electrode material comprises a spinel phase and a layered phase. The lithium nickel manganese oxide positive electrode material contains the spinel phase and the layered phase, the spinel phase and the layered phase have very good compatibility, the diffusion channel of Li is increased, and the lithium nickel manganese oxide positive electrode material has good rate performance and maintains high capacity.

Description

Technical Field

[0001] This application relates to the field of battery materials technology, such as a lithium nickel manganese oxide cathode material, its preparation method, and its application. Background Technology

[0002] Since Sony commercialized lithium-ion batteries in 1991, they have been widely used in consumer electronics and electric vehicles due to their high energy density, long cycle life, and environmental friendliness.

[0003] As a crucial component of lithium-ion batteries, cathode materials significantly impact their cost and performance. Commercially available ternary cathode materials, such as Li[Ni], are a prime example. x Co y Mn 1-x-y O2 (NCM) possesses advantages such as high discharge capacity and high energy density, making it a hot topic in the research and application of lithium-ion battery cathode materials. However, the increasing demand for ternary materials is accelerating the depletion of global cobalt reserves, and the tightening of the cobalt supply chain has significantly driven up cobalt prices. Adopting low-cost / cobalt-free cathodes can significantly reduce battery costs. This necessitates reducing dependence on cobalt while meeting the growing demand for lithium-ion batteries; therefore, low-cost / cobalt-free cathode materials are becoming the mainstream trend in the future development of the lithium battery industry.

[0004] CN102569776A discloses a method for preparing a spherical high-voltage cathode material for lithium-ion batteries. The method employs a hydrothermal-solid-phase two-step process to prepare the spherical high-voltage cathode material, spinel lithium nickel manganese oxide. First, a nickel source, a manganese source, and a solution of dopant compound are mixed uniformly with a sodium / ammonium carbonate solution. Then, a surfactant is added, and a near-spherical nickel-manganese carbonate co-precipitate is prepared under hydrothermal conditions. After washing and drying, sintering yields a spherical nickel-manganese oxide. The oxide is then mixed with a lithium source via liquid-phase ball milling, dried, and finally sintered to obtain the cathode active material.

[0005] CN101844817A discloses a method for preparing spinel-type lithium nickel manganese oxide, a positive electrode material for lithium-ion secondary batteries. The method uses nitrates or organic acid salts of lithium, nickel, and manganese elements to prepare the precursor of the product through a sol-gel-self-propagating combustion process, and then obtains the final product through a certain high-temperature treatment.

[0006] The lithium nickel manganese oxide prepared by the above method is difficult to balance capacity performance and cycle performance, which limits its practical application. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] This application provides a lithium nickel manganese oxide cathode material, its preparation method, and its application. The lithium nickel manganese oxide cathode material contains a spinel phase and a layered phase. The spinel phase and the layered phase have very good compatibility, which increases the diffusion channels of Li, resulting in good rate performance while maintaining high capacity.

[0009] In a first aspect, embodiments of this application provide a lithium nickel manganese oxide cathode material, the lithium nickel manganese oxide cathode material comprising a core and an anion-cation co-coating layer disposed on the surface of the core, the phases of the lithium nickel manganese oxide cathode material comprising a spinel phase and a layered phase.

[0010] The lithium nickel manganese oxide cathode material described in this application includes mutually compatible and disordered structures such as layered structure, nickel manganese spinel structure, and nickel-rich rock salt phase structure. Among them, the spinel structure has small lattice changes during charge and discharge, which can stabilize the crystal structure and provide additional three-dimensional ion diffusion channels to improve rate performance.

[0011] Preferably, the spinel phase comprises 20-90% lithiated spinel phase, which is a transitional state of spinel phase-layered phase.

[0012] Preferably, based on the mass of the spinel phase and the layered phase being 100%, the mass fraction of the spinel phase is 10% to 30%, for example: 10%, 15%, 20%, 25% or 30%, etc.

[0013] Preferably, the lithium nickel manganese oxide cathode material further includes nickel-rich salt rock facies.

[0014] Preferably, the molar ratio of nickel to manganese in the lithium nickel manganese oxide cathode material is (0.25 to 0.4):1, for example: 0.25:1, 0.3:1, 0.33:1, 0.35:1 or 0.4:1, etc.

[0015] Preferably, the ratio of the molar amount of lithium to the total molar amount of nickel and manganese in the lithium nickel manganese oxide cathode material is (0.95 to 1.15):1, for example: 0.95:1, 0.98:1, 1:1, 1.1:1 or 1.15:1, etc.

[0016] Secondly, embodiments of this application provide a method for preparing the lithium nickel manganese oxide cathode material as described in the first aspect, the preparation method comprising the following steps:

[0017] (1) Mix the nickel-manganese precursor, lithium source, flux and additives to obtain a mixture;

[0018] (2) The mixture is subjected to low-temperature sintering to obtain the lithium nickel manganese oxide cathode material;

[0019] The lithium source includes any two or at least three of lithium hydroxide, lithium sulfate, lithium acetate, or lithium iodide.

[0020] Preferably, the particle size of the nickel-manganese precursor in step (1) is 0.5 to 2 μm, for example: 0.5 μm, 0.8 μm, 1 μm, 3 μm or 5 μm, etc.

[0021] Preferably, the specific surface area of ​​the nickel-manganese precursor is 10–35 m². 2 / g, for example: 10m 2 / g, 15m 2 / g、20m 2 / g、30m 2 / g or 35m 2 / g etc.

[0022] Preferably, the flux in step (1) includes any one or a combination of at least two of LiF, Na2CO3, Na2SO4, K2CO3 or K2SO4.

[0023] Preferably, the molar ratio of the flux to the lithium source is (2-10):100, for example: 2:100, 4:100, 6:100, 8:100 or 10:100, etc.

[0024] Preferably, the additives in step (1) include anionic additives and cationic additives.

[0025] Preferably, the anionic additive includes any one or a combination of at least two of fluorides, sulfides, or chlorides.

[0026] Preferably, the amount of the anionic additive added is 1000 to 10000 ppm, for example: 1000 ppm, 2000 ppm, 5000 ppm, 8000 ppm or 10000 ppm, etc.

[0027] Preferably, the cationic additive includes any one or a combination of at least two of magnesium salts, aluminum salts, iron salts, titanium salts, tungsten salts, molybdenum salts, niobium salts, yttrium salts, or zirconium salts.

[0028] Preferably, the amount of the cationic additive added is 1000 to 5000 ppm, for example: 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm or 5000 ppm.

[0029] Preferably, the temperature of the low-temperature sintering treatment in step (2) is 360 to 390°C, for example: 360°C, 365°C, 370°C, 380°C or 390°C.

[0030] Preferably, the low-temperature sintering treatment time is 20 to 75 hours, for example: 20 hours, 30 hours, 40 hours, 50 hours or 75 hours.

[0031] Thirdly, embodiments of this application provide a positive electrode sheet, which comprises the lithium nickel manganese oxide positive electrode material as described in the first aspect.

[0032] Fourthly, embodiments of this application provide a lithium-ion battery, the lithium-ion battery comprising a positive electrode as described in the third aspect.

[0033] Compared with related technologies, the embodiments of this application have the following beneficial effects:

[0034] (1) The embodiments of this application can obtain a lithium nickel manganese oxide cathode material containing a mixture of spinel phase and layered phase containing lithiated spinel by selecting lithium source and low temperature sintering. The spinel phase and layered phase have very good compatibility, which increases the diffusion channels of Li and has good rate performance while maintaining high capacity.

[0035] (2) In this embodiment, suitable anions and cations are added in one sintering to take advantage of low temperature sintering and coating doping. Doping and coating can be completed in one sintering. Obvious element enrichment can be detected on the surface of the product. This is because the coated anions are difficult to enter the bulk phase at low temperature and will remain on the surface of the material to form a surface coating layer. These coating doping also significantly improve the electrical properties of the material.

[0036] (3) The battery made of the lithium nickel manganese oxide cathode material described in the embodiments of this application has a discharge specific capacity of more than 217.6 mAh / g at 0.1C, an initial efficiency of more than 97%, a discharge specific capacity of more than 206.2 mAh / g at 0.33C, a discharge specific capacity of more than 195.5 mAh / g at 1C, a specific capacity of more than 180.6 mAh / g after full battery formation, and a capacity retention rate of more than 91.5% after 50 cycles.

[0037] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0038] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0039] Figure 1 This is the XRD pattern of the lithium nickel manganese oxide cathode material prepared in Example 1.

[0040] Figure 2 This is a charge-discharge curve of the lithium nickel manganese oxide cathode material prepared in Example 1.

[0041] Figure 3 This is the EDS image of the lithium nickel manganese oxide cathode material prepared in Example 1. Detailed Implementation

[0042] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0043] Example 1

[0044] This embodiment provides a lithium nickel manganese oxide cathode material, which is prepared by the following method:

[0045] (1) Particles with a diameter of 4000 nm and a BET of 20 μm were used. 2 Nickel-manganese hydroxide with a nickel-manganese molar ratio of 0.33:1 and lithium source are mixed at Li / M = 1, wherein the lithium source is lithium hydroxide and lithium sulfate with a molar ratio of 1:1. The mixture is then mixed with lithium fluoride, wherein the molar amount of lithium fluoride is 5% of the molar amount of the lithium source. 8000 ppm of magnesium fluoride and 1000 ppm of titanium oxide are added and the mixture is stirred to obtain the mixture.

[0046] (1) The mixture is sintered at 375°C for 25 hours to obtain the lithium nickel manganese oxide cathode material. In the lithium nickel manganese oxide cathode material, the spinel phase accounts for 15% of the spinel phase and the layered phase, and the lithiated spinel accounts for 30% of the spinel phase.

[0047] The XRD pattern of the cathode material is as follows: Figure 1 As shown, by Figure 1 It can be seen that the lithium nickel manganese oxide cathode material described in this application contains a spinel phase and a layered phase.

[0048] The EDS image of the prepared lithium nickel manganese oxide cathode material is shown below. Figure 3 As shown, by Figure 3 It can be seen that the F and Mn elements are evenly distributed in the lithium nickel manganese oxide cathode material prepared by the method described in this application.

[0049] Example 2

[0050] (1) Particles with a diameter of 4000 nm and a BET of 10 μm were used. 2 Nickel-manganese hydroxide with a nickel-manganese molar ratio of 0.25:1 and a lithium source are mixed at Li / M = 0.95, wherein the lithium source is lithium hydroxide and lithium acetate with a molar ratio of 1:1. The mixture is then mixed with Na2SO4, wherein the molar amount of Na2SO4 is 2% of the molar amount of the lithium source. 1000ppm of tungsten chloride and 5000ppm of molybdenum oxide are added, and the mixture is stirred to obtain the final mixture.

[0051] (1) The mixture is sintered at 300°C for 75 hours to obtain the lithium nickel manganese oxide cathode material. In the lithium nickel manganese oxide cathode material, the ratio of spinel phase to spinel phase and layered phase is 1:6. In the spinel phase, the proportion of lithiated spinel is 20%.

[0052] Example 3

[0053] (1) Particles with a diameter of 4000 nm and a BET of 35 μm were used. 2 Nickel-manganese hydroxide with a nickel-manganese molar ratio of 0.4:1 and lithium source are mixed at Li / M = 1.15, wherein the lithium source is lithium hydroxide and lithium iodide with a molar ratio of 1:1. The mixture is then mixed with K2CO3, wherein the molar amount of K2CO3 is 10% of the molar amount of the lithium source. 10000ppm of tungsten chloride and 1000ppm of molybdenum oxide are added and the mixture is stirred to obtain the mixture.

[0054] (1) The mixture is sintered at 390°C for 20 hours to obtain the lithium nickel manganese oxide cathode material. In the lithium nickel manganese oxide cathode material, the ratio of spinel phase to spinel phase and layered phase is 1:7. In the spinel phase, the proportion of lithiated spinel is 50%.

[0055] Example 4

[0056] The only difference between this embodiment and Embodiment 1 is that the low-temperature sintering temperature is 350℃, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0057] Example 5

[0058] The only difference between this embodiment and Embodiment 1 is that the low-temperature sintering temperature is 400℃, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0059] Comparative Example 1

[0060] The only difference between this comparative example and Example 1 is that lithium hydroxide is used as the lithium source, while the other conditions and parameters are exactly the same as in Example 1.

[0061] Comparative Example 2

[0062] The only difference between this comparative example and Example 1 is that no flux is added; all other conditions and parameters are exactly the same as in Example 1.

[0063] Performance testing:

[0064] The positive electrode materials obtained in the examples and comparative examples were used to prepare coin cell half-cells with lithium negative electrodes, and the initial charge-discharge capacity at 2.5-4.65V was tested. The same materials and graphite negative electrodes were used to prepare coin cell full-cells, which were then formed and capacitated. The cycle retention rate at 25°C and 0.5C at 2.5-4.55V was tested. The test results are shown in Table 1.

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, and from Examples 1-3, the battery made of the lithium nickel manganese oxide cathode material described in this application can achieve a discharge specific capacity of over 217.6 mAh / g at 0.1C, an initial efficiency of over 97%, a discharge specific capacity of over 206.2 mAh / g at 0.33C, a discharge specific capacity of over 195.5 mAh / g at 1C, a specific capacity of over 180.6 mAh / g after full cell assembly, and a capacity retention rate of over 91.5% after 50 cycles.

[0068] A comparison of Examples 1 and 4-5 shows that during the preparation of the lithium nickel manganese oxide cathode material described in this application, the low-temperature sintering temperature has a significant impact on the phase composition of the material, which in turn affects the electrical properties of the material. Controlling the low-temperature sintering temperature at 360-390℃ yields lithium nickel manganese oxide cathode materials with better performance. If the low-temperature sintering temperature is too low, the material structure will not be formed and the capacity will be too low. If the low-temperature sintering temperature is too high, the layered structure will increase, which is not conducive to the capacity utilization.

[0069] As can be seen from the comparison between Example 1 and Comparative Example 1, this application uses at least two lithium compounds as lithium sources, which has a eutectic fluxing effect, can accelerate the reaction, and shorten the sintering time to an industrially applicable range. It is difficult to achieve the same effect using a single lithium source.

[0070] As can be seen from the comparison between Example 1 and Comparative Example 2, the main purpose of adding flux in this application is to reduce the sintering temperature and shorten the sintering time, so that the lithium source can react fully and form the desired structure as soon as possible. Among them, the lithium fluoride in Example 1 has a better fluxing effect.

[0071] The charge-discharge curve of the lithium nickel manganese oxide cathode material prepared in Example 1 of this application is shown in the figure below. Figure 2 As shown.

[0072] The EDS image of the lithium nickel manganese oxide cathode material prepared in Example 1 of this application is shown below. Figure 3 As shown, by Figure 1 It can be seen that the lithium nickel manganese oxide cathode material described in this application exhibits a high amount of fluorine (F) enrichment on its surface, indicating that F has indeed achieved surface enrichment, resulting in a coating modification effect. EDS surface scan results show no elemental segregation on the surface, confirming that the coating process achieved in a single sintering operation meets expectations.

[0073] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A lithium nickel manganese oxide cathode material, characterized in that, The lithium nickel manganese oxide cathode material includes a core and an anion-cation co-coating layer disposed on the surface of the core, and the phases of the material include a spinel phase and a layered phase. The lithium nickel manganese oxide cathode material is prepared by the following method, which includes the following steps: (1) Mix the nickel-manganese precursor, lithium source, flux and additives to obtain a mixture; (2) The mixture is subjected to low-temperature sintering to obtain the lithium nickel manganese oxide cathode material; The lithium source includes any two or at least three of lithium hydroxide, lithium sulfate, lithium acetate or lithium iodide. The additives mentioned in step (1) include anionic additives and cationic additives; The anionic additive includes any one or a combination of at least two of fluorides, sulfides, or chlorides; The cationic additive includes any one or a combination of at least two of magnesium salts, aluminum salts, iron salts, titanium salts, tungsten salts, molybdenum salts, niobium salts, yttrium salts, or zirconium salts; The temperature of the low-temperature sintering treatment in step (2) is 360~390℃; The low-temperature sintering treatment takes 20 to 75 hours.

2. The lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The spinel phase comprises 20-90% lithiated spinel phase.

3. The lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, With the mass of the spinel phase and the layered phase being 100%, the mass fraction of the spinel phase is 10-30%.

4. The lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The lithium nickel manganese oxide cathode material also includes nickel-rich salt rock facies.

5. The lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The molar ratio of nickel to manganese in the lithium nickel manganese oxide cathode material is (0.25~0.4):

1.

6. The lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The ratio of the molar amount of lithium to the total molar amount of nickel and manganese in the lithium nickel manganese oxide cathode material is (0.95~1.15):

1.

7. A method for preparing the lithium nickel manganese oxide cathode material as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Mix the nickel-manganese precursor, lithium source, flux and additives to obtain a mixture; (2) The mixture is subjected to low-temperature sintering to obtain the lithium nickel manganese oxide cathode material; The lithium source includes any two or at least three of lithium hydroxide, lithium sulfate, lithium acetate or lithium iodide. The additives mentioned in step (1) include anionic additives and cationic additives; The anionic additive includes any one or a combination of at least two of fluorides, sulfides, or chlorides; The cationic additive includes any one or a combination of at least two of magnesium salts, aluminum salts, iron salts, titanium salts, tungsten salts, molybdenum salts, niobium salts, yttrium salts, or zirconium salts; The temperature of the low-temperature sintering treatment in step (2) is 360~390℃; The low-temperature sintering treatment takes 20 to 75 hours.

8. The preparation method according to claim 7, characterized in that, The particle size of the nickel-manganese precursor in step (1) is 0.5~5μm.

9. The preparation method according to claim 7, characterized in that, The specific surface area of ​​the nickel-manganese precursor is 10~35m². 2 / g.

10. The preparation method according to claim 7, characterized in that, The flux in step (1) includes any one or a combination of at least two of LiF, Na2CO3, Na2SO4, K2CO3 or K2SO4.

11. The preparation method according to claim 7, characterized in that, The molar ratio of the flux to the lithium source is (2~10):

100.

12. The preparation method according to claim 7, characterized in that, The amount of the anionic additive added is 1000~10000ppm.

13. The preparation method according to claim 7, characterized in that, The amount of the cationic additive added is 1000~5000ppm.

14. A positive electrode plate, wherein, The positive electrode comprises the lithium nickel manganese oxide positive electrode material as described in any one of claims 1-6.

15. A lithium-ion battery, wherein, The lithium-ion battery includes the positive electrode as described in claim 14.

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