Single-crystal lithium nickel manganese oxide positive electrode material, preparation method therefor and use thereof

Abstract

A single crystal nickel lithium manganese oxide positive electrode material for a lithium ion battery, a preparation method therefor and a use thereof. The method first prepares a spherical hydroxide precursor composed of nanosheet crystal grains, which is converted into a two-phase mixture of stable Mn2O3 and MnNiO3, which is mixed with a lithium source and sintered in an oxygen atmosphere at a temperature of 950-1100°C, to generate single crystal lithium nickel manganese oxide LiNixMn2-xO4, 0.3<x<0.6. The single crystal lithium nickel manganese oxide prepared by the present method has a square or octahedral structure, a grain size of 1-11 μm, a capacity of 134 mAh / g or higher, and excellent rate and cycle performance; the lithium nickel manganese oxide can simultaneously achieve high energy density and high power density, and has a long service life.

Description

A single crystal lithium nickel manganese oxide positive electrode material and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 14, 2023, with application number 202311722134.X and application name “A single crystal lithium nickel manganese oxide positive electrode material, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of lithium-ion battery materials, and relates to a single-crystal lithium nickel manganese oxide positive electrode material, a preparation method thereof, and an application thereof. Background Art

[0003] The power density of lithium-ion batteries is mainly determined by the discharge voltage platform and rate performance of the positive electrode material. Single-crystal spinel lithium nickel manganese oxide has a high tap density, which can improve the volume energy density. It also has a discharge voltage platform of 4.7V and excellent rate performance. It is a potential positive electrode material that can meet both high energy density and high power density.

[0004] Single crystal spinel lithium nickel manganese oxide is mainly prepared by conventional processes such as high temperature solid phase method, coprecipitation method, sol-gel method, etc. For example, patent CN113178566A discloses a method for preparing spinel single crystal cobalt-free high voltage lithium nickel manganese oxide positive electrode material, which includes the following steps: A) adding nickel source and manganese source under the action of precipitant, ammonia water and complexing agent to carry out coprecipitation reaction to obtain Ni 0.5 Mn 1.5 (OH)4 binary precursor; B) the Ni 0.5 Mn 1.5 The (OH)4 binary precursor is mixed with a lithium source, calcined at high temperature, then annealed at a low speed and kept warm, and finally cooled naturally to obtain a single crystal LiNi composed of a combination of regular octahedron and truncated octahedron. 0.5 Mn 1.5 O4 positive electrode material.

[0005] However, the single-crystal lithium nickel manganese oxide prepared by the conventional process is usually small in size, less than 5μm; the capacity is low, mostly below 130mAh / g; the rate and cycle performance are not high, and cannot meet the requirements of high energy density and long life.

[0006] Summary of the Invention

[0007] In view of the above problems existing in the prior art, one of the objectives of the present application is to provide a single crystal lithium nickel manganese oxide positive electrode material.

[0008] Another object of the present application is to provide a method for preparing a single-crystal lithium nickel manganese oxide cathode material. The method of the present application prepares a nanosheet hydroxide precursor through a coprecipitation reaction, and then performs lithium mixing and sintering to obtain a single-crystal lithium nickel manganese oxide material, which has excellent electrochemical performance.

[0009] Another object of the present application is to provide a lithium-ion battery.

[0010] To achieve the above object, the present application provides the following specific technical solutions.

[0011] The chemical formula of the single-crystal lithium nickel manganese oxide cathode material is LiNi x Mn 2-x O4, where 0.3 < x < 0.6, it is in a block shape or an octahedral structure, and the grain size is 1-11 μm.

[0012] Furthermore, 0.4 ≤ x ≤ 0.5.

[0013] A method for preparing a single-crystal lithium nickel manganese oxide cathode material includes the following steps:

[0014] (1) Under a protective atmosphere, a mixed solution of Ni salt and Mn salt, a precipitant solution, and a complexing agent solution are introduced into the bottom liquid of the reaction kettle and circulated for coprecipitation reaction; wherein, the molar ratio of Ni:Mn in the mixed solution of Ni salt and Mn salt = x / 2:1 - x / 2;

[0015] (2) When the D50 of the reaction slurry reaches the target value, the reaction is stopped, the reaction slurry is filtered, washed, and the solid phase is dried to obtain the precursor Ni x / 2 Mn 1-x / 2 (OH)2;

[0016] (3) Convert Ni x / 2 Mn 1-x / 2 (OH)2 into a biphasic mixture of Mn2O3 and MnNiO3;

[0017] (4) Mix the biphasic mixture of Mn2O3 and MnNiO3 with a lithium source evenly and sinter at 950-1100 °C in an oxygen atmosphere to obtain a single-crystal lithium nickel manganese oxide cathode material;

[0018] Where 0.3 < x < 0.6.

[0019] Furthermore, 0.4 ≤ x ≤ 0.5.

[0020] Furthermore, in step (1), the protective atmosphere is a nitrogen or argon atmosphere. The introduction of the protective gas can avoid the problems that Mn 2+ ions are easily oxidized during the coprecipitation of hydroxides and the particles are not easy to form spheres and grow;

[0021] Furthermore, in step (1), the total metal ion concentration in the mixed solution of Ni salt and Mn salt is 0.5-2 mol / L.

[0022] Furthermore, in step (1), the concentration of the precipitant solution is 1 to 8 mol / L. More preferably, the precipitant is a NaOH solution.

[0023] Furthermore, in step (1), the concentration of the complexing agent solution is 0.1 to 0.6 mol / L. More preferably, the complexing agent is NH3·H2O solution.

[0024] Furthermore, in step (1), the bottom liquid of the reaction kettle is 0.05-0.2 mol / L ammonia water.

[0025] Furthermore, in step (1), the feed rate of the mixed solution of Ni salt and Mn salt is 50 to 250 ml / h.

[0026] Furthermore, in step (1), the temperature of the reaction system is 50-60°C.

[0027] Furthermore, in step (1), the stirring speed is 300 to 800 rpm.

[0028] Furthermore, in step (1), the pH value of the reaction system is in the range of 9.5 to 12.0; further preferably, the pH value is controlled to fluctuate within the range of ±0.1 of a certain value during the reaction.

[0029] Furthermore, in step (2), when D50 of the reaction slurry is greater than 6 μm, the reaction is stopped.

[0030] Furthermore, in step (2), the drying method is low-temperature vacuum drying.

[0031] Because of Ni x / 2 Mn 1-x / 2 (OH)2 is unstable at room temperature and pressure and easily converts spontaneously into Mn3O4, forming Ni x / 2 Mn 1-x / 2 The mixture of (OH)2 and Mn3O4, and the inconsistent valence of Mn, is not conducive to the accurate calculation of the formation of single crystal lithium nickel manganese oxide LiNi x Mn 2-x The amount of lithium in O4. x / 2 Mn 1-x / 2 (OH)2 is converted into a stable and chemically simple two-phase mixture of Mn2O3 and MnNiO3.

[0032] Preferably, step (3) is specifically:

[0033] Nix / 2 Mn 1-x / 2 (OH)2 is dried at low temperature under vacuum conditions and then heated at 60-100°C under vacuum to convert into Ni x / 2 Mn 1-x / 2 OOH;

[0034] Ni x / 2 Mn 1-x / 2 (OH)2 and / or Ni x Mn 1-x / 2 OOH is sintered in an O2 atmosphere at a temperature of 650-750°C for 1-6 hours to be converted into a two-phase mixture of Mn2O3 and MnNiO3.

[0035] Preferably, step (3) is specifically:

[0036] Ni x / 2 Mn 1-x / 2 (OH)2 is sintered in an O2 atmosphere at a temperature of 650-750°C for 1-6 hours to be converted into a two-phase mixture of Mn2O3 and MnNiO3.

[0037] The present application describes the two-phase mixture as a single chemical formula (Ni x / 2 Mn 1-x / 2 )2O3 refers to, to facilitate the calculation of the amount of lithium. That is: the (Ni x / 2 Mn 1-x / 2 )2O3 is from Ni x / 2 Mn 1-x / 2 A two-phase mixture of Mn2O3 and MnNiO3 converted from (OH)2.

[0038] Furthermore, in step (4), the lithium source is LiOH.

[0039] Furthermore, in step (4), the amount of lithium source is added in a molar ratio of Li: (Ni + Mn) = 1.0 to 1.02: 2.0. Furthermore, in step (4), the sintering time is 10 to 30 hours;

[0040] Furthermore, in step (4), during the sintering process, the oxygen flow rate is 50 to 200 sccm;

[0041] Furthermore, in step (4), the heating rate is controlled at 3-6°C / min, and the cooling rate is controlled at 1-3°C / min.

[0042] The present application also discloses a lithium-ion battery, which includes the single-crystal lithium nickel manganese oxide positive electrode material.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] (1) The present invention prepares nanosheet hydroxide precursors by coprecipitation, and the unstable hydroxide precursor Ni x / 2 Mn 1-x / 2 (OH)2 is converted into a stable two-phase mixture of Mn2O3 and MnNiO3 as a precursor. The two-phase mixture can be converted into a stable two-phase mixture of Mn2O3 and MnNiO3 with a single chemical formula (Ni x / 2 Mn 1-x / 2 )2O3 refers to the ability to accurately prepare the Li content required for sintering, and sinter at a higher mixed lithium sintering temperature to obtain a single-crystal lithium nickel manganese oxide positive electrode material with a square or octahedral structure. The positive electrode material has a capacity of more than 134mAh / g, a grain size of 1 to 11μm, excellent rate and cycle performance, and can achieve high energy density and high power density at the same time, and a long service life.

[0045] (2) The method of the present application controls the pH fluctuation range of ±0.1 during the coprecipitation reaction to avoid the pH fluctuation affecting the nucleation and growth of the hydroxide precursor, thereby ensuring the growth of the precursor particles. By controlling the feed rate and regulating the growth rate of the precursor, a hydroxide precursor with a nanosheet structure can be generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 shows the Ni prepared in Example 1 0.25 Mn 0.75 OOH precursor morphology;

[0047] Figure 2 shows the LiNi prepared in Example 1. 0.5 Mn 1.5 O4 morphology;

[0048] Figure 3 shows (a)Ni prepared in Example 1 0.25 Mn 0.75 OOH and (b) LiNi 0.5 Mn 1.5 XRD pattern of the physical structure of O4. The inset of Figure (a) is the fitting diagram of the (002) peak;

[0049] Figure 4 shows the LiNi prepared in Example 1. 0.5 Mn 1.5 Electrochemical performance of O4: (a) 1C charge-discharge curve, (b) rate performance, (c) 2C charge-5C discharge cycle performance; 1C is calculated at 140 mA / g;

[0050] Figure 5 shows the Ni prepared in Example 2 0.25 Mn 0.75 OOH precursor morphology;

[0051] Figure 6 shows the LiNi prepared in Example 2 0.5 Mn 1.5 O4 morphology;

[0052] Figure 7 shows (a) Ni prepared in Example 2 0.25 Mn 0.75 OOH and (b) LiNi 0.5 Mn 1.5 XRD pattern of the physical structure of O4. The inset of Figure (a) is the fitting diagram of the (002) peak;

[0053] Figure 8 shows the LiNi prepared in Example 2 0.5 Mn 1.5 Electrochemical performance of O4: (a) 1C charge-discharge curve, (b) rate performance, (c) 2C charge-5C discharge cycle performance; 1C is calculated at 140 mA / g;

[0054] Figure 9 shows the Ni prepared in Example 3 0.2 Mn 0.8 OOH precursor morphology;

[0055] Figure 10 shows the LiNi prepared in Example 3. 0.4 Mn 1.6 O4 morphology;

[0056] Figure 11 shows (a) Ni prepared in Example 3 0.25 Mn 0.75 OOH and (b) LiNi 0.5 Mn 1.5 XRD pattern of the physical structure of O4. The inset of Figure (a) is the fitting diagram of the (002) peak;

[0057] Figure 12 shows the LiNi prepared in Example 3. 0.5 Mn 1.5 Electrochemical performance of O4: (a) 1C charge-discharge curve, (b) rate performance, (c) 2C charge-5C discharge cycle performance; 1C is calculated at 140 mA / g;

[0058] Figure 13 shows the LiNi prepared in Example 4. 0.4 Mn 1.6 O4 morphology;

[0059] Figure 14 shows the LiNi prepared in Example 5. 0.4 Mn 1.6 XRD pattern of the physical structure of O4;

[0060] Figure 15 LiNi prepared in Example 6 0.5 Mn 1.5 Electrochemical performance of O4: (a) 1C charge-discharge curve, (b) rate performance, (c) 2C charge-5C discharge cycle performance; 1C is calculated as 140 mA / g. DETAILED DESCRIPTION

[0061] To facilitate understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments or examples and are not intended to limit this application.

[0063] Example 1

[0064] This embodiment provides a method for preparing a single crystal lithium nickel manganese oxide positive electrode material, comprising the following steps:

[0065] (1) Prepare 1 L of a 2 mol / L mixed solution A of NiSO₄·6H₂O and MnSO₄·4H₂O with a molar ratio of Ni:Mn = 25:75, 1 L of a 4 mol / L NaOH solution B, and 1 L of a 0.25 mol / L ammonia solution C. Mix solutions B and C to form solution D.

[0066] (2) Add 5 L of 0.06 mol / L dilute ammonia solution to a 50 L reactor, raise the temperature to 55 °C and maintain it, introduce nitrogen gas to below the liquid level to remove the air in the reactor, and maintain the nitrogen flow rate at 500 sccm.

[0067] (3) Start stirring the reactor at 700 rpm. Control the feed rate of Solution A at 60 ml / h and the initial feed rate of Solution D at 120 ml / h. Fine-tune the feed rate of Solution D to maintain the pH of the reaction system at 9.7 within the reactor, with pH fluctuations within ±0.1.

[0068] (4) After 8 hours of reaction, when the D50 of the spherical particles in the kettle is greater than 10 μm and evenly distributed, the solution in the kettle is discharged, filtered, and washed with deionized water until the pH of the filtrate is less than 8, and then dried at 50 ° C in vacuum to obtain Ni 0.25 Mn 0.75 (OH)2.

[0069] (5) Ni 0.25 Mn 0.75 (OH)2 was heated at 60℃ under vacuum to obtain Ni 0.25 Mn 0.75 OOH;

[0070] Ni 0.25 Mn 0.75OOH was sintered at 700 °C for 5 h in an O2 atmosphere and converted into a two-phase mixture of Mn2O3 and MnNiO3, which was used as a precursor.

[0071] Here, the two-phase mixture of Mn2O3 and MnNiO3 is composed of Ni 0.25 Mn 0.75 OOH is converted and can be recorded as (Ni 0.25 Mn 0.75 )2O3, which is convenient for subsequent lithium addition.

[0072] (6) Prepare the above-mentioned precursor (Ni 0.25 Mn 0.75 )2O3 and LiOH were manually ground evenly, (Ni 0.25 Mn 0.75 )2O3 and LiOH were added in a molar ratio of Li:(Ni+Mn) of 1.01:2.0. Sintered at 950℃ for 20h in an oxygen atmosphere. The oxygen flow rate was 100sccm, the heating rate was controlled at 5℃ / min, and the cooling rate was controlled at 2℃ / min. After cooling to 300℃ and cooling in the furnace, the sample LiNi was taken out. 0.5 Mn 1.5 O4, vacuum storage for future use.

[0073] In this embodiment, the precursor Ni prepared in step (5) 0.25 Mn 0.75 The morphology of OOH is shown in Figure 1, which has a nanosheet structure. LiNi prepared in step (6) 0.5 Mn 1.5 As shown in Figure 2, O4 is generally an octahedral single crystal with a grain size of about 2μm. 0.25 Mn 0.75 OOH and LiNi 0.5 Mn 1.5 The XRD phase structure of O4 is shown in Figure 3. 0.25 Mn 0.75 OOH (002) peak, the thickness of the nanosheet is about 30nm, LiNi 0.5 Mn 1.5 O4 has a spinel structure.

[0074] 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground into a uniform mixture at a mass ratio of active material: carbon black: PVDF = 8:1:1. The mixture was passed through a 200# sieve and coated onto carbon-coated aluminum foil. The resulting pieces were dried, cut, weighed, and assembled into button cells. As shown in Figure 4, the discharge capacity at 1C charge and discharge was 134mAh / g, the discharge capacity at 15C was 121mAh / g, and the capacity retention after 200 cycles of 2C charge and 5C discharge was 96%.

[0075] Example 2

[0076] This embodiment is basically the same as embodiment 1, except that:

[0077] The C solution in step (1) is 0.5 mol / L ammonia water.

[0078] The base liquid in step (2) is 0.1 mol / L ammonia water.

[0079] In step (3), the feed rate of solution A was controlled at 120 ml / h, and the initial feed rate of solution D was controlled at 240 ml / h. The feed rate of solution D was fine-tuned to maintain the pH of the reaction system in the reactor at 10.1, with pH fluctuations controlled within ±0.1.

[0080] In this embodiment, the precursor Ni 0.25 Mn 0.75 The morphology of OOH is shown in Figure 5, which is a nanosheet structure. 0.5 Mn 1.5 As shown in FIG6 , O4 is generally an octahedral single crystal with a grain size of about 2 μm. 0.25 Mn 0.75 OOH and LiNi 0.5 Mn 1.5 The XRD phase structure of O4 is shown in Figure 7. 0.25 Mn 0.75 OOH (002) peak, the thickness of the nanosheet is about 50nm, LiNi 0.5 Mn 1.5 O4 has a spinel structure.

[0081] 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground into a uniform mixture at a mass ratio of active material: carbon black: PVDF = 8:1:1. The mixture was passed through a 200# sieve and coated onto carbon-coated aluminum foil. The resulting pieces were dried, cut, weighed, and assembled into button cells. As shown in Figure 8, the discharge capacity at 1C charge and discharge was 134mAh / g, the discharge capacity at 15C was 120mAh / g, and the capacity retention after 200 cycles of 2C charge and 5C discharge was 99%.

[0082] Example 3

[0083] This embodiment is basically the same as embodiment 2, except that:

[0084] In step (1), solution A is a 2 mol / L mixed solution of NiSO4·6H2O and MnSO4·4H2O with a molar ratio of Ni:Mn=0.2:0.8.

[0085] Precursor Ni prepared in Example 3 0.2 Mn 0.8 The morphology of OOH is shown in Figure 9, which is a nanosheet structure. 0.4 Mn 1.6 As shown in FIG10 , O4 is generally a block-shaped single crystal with a grain size of about 2 μm. 0.2 Mn 0.8 OOH and LiNi 0.4 Mn 1.6 The XRD phase structure of O4 is shown in Figure 11. 0.2 Mn 0.8 OOH (002) peak, the thickness of the nanosheet is about 50nm, LiNi 0.4 Mn 1.6 O4 has a spinel structure.

[0086] 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground into a uniform mixture at a mass ratio of active material: carbon black: PVDF = 8:1:1. The mixture was passed through a 200# sieve and coated onto carbon-coated aluminum foil. The resulting pieces were dried, cut, weighed, and assembled into button cells. As shown in Figure 12, the discharge capacity at 1C charge and discharge was 140 mAh / g, the discharge capacity at 15C was 129 mAh / g, and the capacity retention was 100% after 200 cycles of 2C charge and 5C discharge.

[0087] Example 4

[0088] This embodiment is basically the same as embodiment 3, except that:

[0089] (6) Prepare the above-prepared precursor Ni 0.2 Mn 0.8 OOH and LiOH were manually ground evenly, and Ni 0.2 Mn 0.8 OOH and LiOH were added in a molar ratio of Li: (Ni+Mn) of 1.01:2.0. The samples were sintered at 1050℃ for 20h in an oxygen atmosphere. The oxygen flow rate was 100sccm, the heating rate was controlled at 5℃ / min, and the cooling rate was controlled at 2℃ / min. After cooling to 300℃, the LiNi sample was taken out. 0.4 Mn 1.6 O4, vacuum storage for future use.

[0090] LiNi prepared in Example 4 0.4 Mn 1.6 As shown in FIG13 , O4 is generally an octahedral single crystal with a grain size of about 10 μm.0.4 Mn 1.6 The XRD phase structure of O4 is shown in Figure 14, which is a spinel structure.

[0091] 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground into a uniform mixture at a mass ratio of active material: carbon black: PVDF = 8:1:1. The mixture was passed through a 200# sieve and coated onto carbon-coated aluminum foil. The foil was dried, cut, weighed, and assembled into a coin cell. As shown in Figure 15, the discharge capacity at 1C charge and discharge was 140mAh / g, the discharge capacity at 15C was 125mAh / g, and the capacity retention after 200 cycles of 2C charge and 5C discharge was 99%.

[0092] Example 5

[0093] This embodiment is basically the same as embodiment 1, except that:

[0094] (6) Prepare the above-mentioned precursor (Ni 0.25 Mn 0.75 )2O3 and LiOH were manually ground evenly, (Ni 0.25 Mn 0.75 )2O3 and LiOH were added in a molar ratio of Li:(Ni+Mn) of 1.01:2.0. Sintered at 1000℃ for 25h in an oxygen atmosphere. The oxygen flow rate was 100sccm, the heating rate was controlled at 5℃ / min, and the cooling rate was controlled at 2℃ / min. After cooling to 300℃ and cooling in the furnace, the sample LiNi was taken out. 0.5 Mn 1.5 O4, vacuum storage for future use.

[0095] According to the mass ratio of active material: carbon black: PVDF = 8:1:1, 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground evenly, passed through a 200# sieve, and coated on a carbon-coated aluminum foil. The pieces were dried, cut, weighed, and assembled into button batteries.

[0096] After testing, the present embodiment was sintered at 1000℃, LiNi 0.5 Mn 1.5 The O4 morphology shows an octahedral single crystal, and the physical phase shows a spinel structure, with better rate performance and capacity.

[0097] Comparative Example 1

[0098] This embodiment is basically the same as embodiment 2, except that:

[0099] (6) Prepare the above-mentioned precursor (Ni 0.25 Mn 0.75)2O3 and LiOH were manually ground evenly, (Ni 0.25 Mn 0.75 )2O3 and LiOH were added in a molar ratio of Li:(Ni+Mn) of 1.01:2.0. Sintered at 900℃ for 20h in an oxygen atmosphere. The oxygen flow rate was 100sccm, the heating rate was controlled at 5℃ / min, and the cooling rate was controlled at 2℃ / min. After cooling to 300℃, the sample LiNi was taken out. 0.5 Mn 1.5 O4, vacuum storage for future use.

[0100] According to the mass ratio of active material: carbon black: PVDF = 8:1:1, 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground evenly, passed through a 200# sieve, and coated on a carbon-coated aluminum foil. The pieces were dried, cut, weighed, and assembled into button batteries.

[0101] After testing, it was found that the comparative example was sintered at a temperature of 900°C, which was too low and the crystallization was insufficient to form a single crystal, which seriously affected the rate performance and capacity.

[0102] Comparative Example 2

[0103] This embodiment is basically the same as embodiment 2, except that:

[0104] (6) Prepare the above-mentioned precursor (Ni 0.25 Mn 0.75 )2O3 and LiOH were manually ground evenly, (Ni 0.25 Mn 0.75 )2O3 and LiOH were added in a molar ratio of Li:(Ni+Mn) of 1.01:2.0. Sintered at 1200℃ for 20h in an oxygen atmosphere. The oxygen flow rate was 100sccm, the heating rate was controlled at 5℃ / min, and the cooling rate was controlled at 2℃ / min. After cooling to 300℃ and cooling in the furnace, the sample LiNi was taken out. 0.5 Mn 1.5 O4, vacuum storage for future use.

[0105] According to the mass ratio of active material: carbon black: PVDF = 8:1:1, 1.2g of the prepared sample, 0.15g of carbon black, and 3.75g of a 4% wt. PVDF solution in NMP were manually ground evenly, passed through a 200# sieve, and coated on a carbon-coated aluminum foil. The pieces were dried, cut, weighed, and assembled into button batteries.

[0106] After testing, it was found that the comparative example was sintered at a temperature of 1200°C, which was too high a temperature, resulting in excessively large grain size, affecting the rate performance and capacity.

[0107] Comparative Example 3

[0108] This comparative example is basically the same as Example 1, except that:

[0109] Step (5) is not set.

[0110] Specifically:

[0111] (1) Prepare 1 L of a 2 mol / L mixed solution A of NiSO₄·6H₂O and MnSO₄·4H₂O with a molar ratio of Ni:Mn = 25:75, 1 L of a 4 mol / L NaOH solution B, and 1 L of a 0.25 mol / L ammonia solution C. Mix solutions B and C to form solution D.

[0112] (2) Add 5 L of 0.06 mol / L dilute ammonia solution to a 50 L reactor, raise the temperature to 55 °C and maintain it, introduce nitrogen gas to below the liquid level to remove the air in the reactor, and maintain the nitrogen flow rate at 500 sccm.

[0113] (3) Start stirring the reactor at 700 rpm. Control the feed rate of Solution A at 60 ml / h and the initial feed rate of Solution D at 120 ml / h. Fine-tune the feed rate of Solution D to maintain the pH of the reaction system at 9.7 within the reactor, with pH fluctuations within ±0.1.

[0114] (4) After 8 hours of reaction, when the D50 of the spherical particles in the kettle is greater than 10 μm and evenly distributed, the solution in the kettle is discharged, filtered, and washed with deionized water until the pH of the filtrate is less than 8, and then dried at 50 ° C in vacuum to obtain Ni 0.25 Mn 0.75 (OH)2.

[0115] (5) Ni 0.25 Mn 0.75 (OH)2 and LiOH were manually ground evenly, Ni 0.25 Mn 0.75 (OH)2 and LiOH were added in a molar ratio of Li:(Ni+Mn) of 1.01:2.0. Sintered at 950℃ for 20h in an oxygen atmosphere. The oxygen flow rate was 100sccm, the heating rate was controlled at 5℃ / min, and the cooling rate was controlled at 2℃ / min. After cooling to 300℃ and cooling in the furnace, the sample LiNi was taken out. 0.5 Mn 1.5 O4, vacuum storage for future use.

[0116] Because of Ni 0.25 Mn 0.75 (OH)2 is unstable at room temperature and pressure and easily converts spontaneously into Mn3O4, forming Ni 0.25 Mn 0.75The mixture of (OH)2 and Mn3O4, that is, the precursor of this comparative example is composed of Ni 0.25 Mn 0.75 (OH)2 and Mn3O4, when calculating the amount of lithium, if the precursor is regarded as pure Ni 0.25 Mn 0.75 (OH)2, resulting in insufficient lithium and the inability to generate stoichiometric LiNi 0.5 Mn 1.5 O4. If lithium is added according to Mn3O4, there will be an excess of lithium, and the sintered product will be agglomerated and unusable. 0.25 Mn 0.75 (OH)2 will spontaneously convert to Mn3O4, making it impossible to estimate the lithium dosage within a reasonable range, resulting in inaccurate lithium dosing. In industrial mass production, this can lead to greater errors and poor consistency between batches, making it virtually impossible to obtain a consistent target product.

[0117] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A single crystal lithium nickel manganese oxide positive electrode material, wherein: The chemical formula of the single-crystal lithium nickel manganate cathode material is LiNi x Mn 2-x O4, where 0.3 < x < 0.6; it has a blocky or octahedral structure, and the grain size is 1-11 μm.

2. A method for preparing a single crystal lithium nickel manganese oxide positive electrode material, wherein: The following steps are involved: (1) Under a protective atmosphere, a mixed solution of Ni salt and Mn salt, a precipitant solution, and a complexing agent solution are introduced into the bottom liquid of a reaction kettle in parallel to perform a coprecipitation reaction; wherein the molar ratio of Ni:Mn in the mixed solution of Ni salt and Mn salt is x / 2:1-x / 2; (2) When the D50 of the reaction slurry reaches the target value, the reaction is stopped, the reaction slurry is filtered, and the solid phase is washed and dried to obtain the precursor Ni x / 2 Mn 1-x / 2 (OH)2; (3) Ni x / 2 Mn 1-x / 2 (OH)2 is converted into a two-phase mixture of Mn2O3 and MnNiO3; (4) mixing the two-phase mixture of Mn2O3 and MnNiO3 with a lithium source uniformly and sintering the mixture in an oxygen atmosphere at a temperature of 950 to 1100° C. to obtain a single crystal lithium nickel manganese oxide positive electrode material; Among them, 0.3 <x<0.6。 3. The preparation method according to claim 2, wherein 0.4≤x≤0.5。 4. The preparation method according to claim 2, wherein In step (1): the total metal ion concentration in the mixed solution of Ni salt and Mn salt is 0.5-2 mol / L.

5. The preparation method according to claim 2, wherein: In step (1), the concentration of the precipitant solution is 1 to 8 mol / L.

6. The preparation method according to claim 2, wherein: In step (1), the concentration of the complexing agent solution is 0.1 to 0.6 mol / L.

7. The preparation method according to claim 2, wherein: In step (1), the bottom liquid of the reaction kettle is 0.05-0.2 mol / L ammonia water.

8. The preparation method according to claim 2, wherein In step (1), the pH value of the reaction system is in the range of 9.5 to 12.

0.

9. The preparation method according to claim 2, wherein: In step (1), the pH value is controlled to fluctuate within a range of ±0.1 of a certain value during the reaction.

10. The preparation method according to claim 2, wherein: In step (1), the feed rate of the mixed solution of Ni salt and Mn salt is 50 to 250 ml / h.

11. The preparation method according to claim 2, wherein: In step (1), the temperature of the reaction system is 50-60°C.

12. The preparation method according to claim 2, wherein: In step (1), the stirring speed is 300 to 800 rpm.

13. The preparation method according to claim 2, wherein: In step (2), when D50 of the reaction slurry is greater than 6 μm, the reaction is stopped.

14. The preparation method according to claim 2, wherein: Step (3) is specifically as follows: Ni x / 2 Mn 1-x / 2 (OH)2 is dried at low temperature under vacuum conditions and then heated at 60-100°C in vacuum to convert into Ni x / 2 Mn 1-x / 2 OOH; Ni x / 2 Mn 1-x / 2 (OH)2 and / or Ni x / 2 Mn 1-x / 2 OOH is sintered in an O2 atmosphere at 650-750°C for 1-6 hours to be converted into a two-phase mixture of Mn2O3 and MnNiO3.

15. The preparation method according to claim 2, wherein: Step (3) is specifically as follows: Ni x / 2 Mn 1-x / 2 (OH)2 is sintered in an O2 atmosphere at 650-750°C for 1-6 hours to be converted into a two-phase mixture of Mn2O3 and MnNiO3.

16. The preparation method according to claim 2, wherein: In step (4): The lithium source is LiOH.

17. The preparation method according to claim 2, wherein: In step (4), the amount of lithium source is added in a molar ratio of Li:(Ni+Mn)=1.0-1.02:2.

0.

18. The preparation method according to claim 2, wherein: In step (4), the sintering time is 10 to 30 hours.

19. The preparation method according to claim 2, wherein: In step (4), during the sintering process, the oxygen flow rate is 50 to 200 sccm.

20. The preparation method according to claim 2, wherein: In step (4), the heating rate is controlled at 3-6°C / min, and the cooling rate is controlled at 1-3°C / min.

21. A lithium ion battery, wherein: It comprises a single crystal lithium nickel manganese oxide positive electrode material prepared by the preparation method according to any one of claims 2 to 9 or a single crystal lithium nickel manganese oxide positive electrode material according to claim 1.

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