A single-crystalline lithium-rich manganese-based cathode material with preferred orientation, a preparation method thereof, and a lithium-ion battery

Abstract

The present invention provides a single-crystalline lithium-rich manganese-based cathode material with preferred orientation, a preparation method thereof, and a lithium-ion battery, relating to the technical field of preparation of battery cathode materials. The lithium-rich manganese-based cathode material has a single-crystalline morphology. In the diffraction pattern obtained by using an XRD instrument with Cu Kα as the incident light source, the peak intensity ratio I(003) / I(104) of the (003) peak with 2θ located at 18.6±0.1° and the (104) peak with 2θ located at 44±0.5° is greater than 2. The present invention prepares a single-crystalline lithium-rich manganese-based material with preferred growth of a specific crystal plane. By regulating the synthesis process of the material to enable it to preferentially grow along the (003) crystal plane, the electrochemical performance of the material can be significantly improved, especially the stability under high-rate charge and discharge conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of cathode materials for batteries, and particularly to a single-crystalline lithium-rich manganese-based cathode material with preferred orientation, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] With the continuous growth of global energy demand and the increasing emphasis on environmental protection, lithium-ion batteries, as an efficient and environmentally friendly energy storage device, have received extensive attention and applications. Lithium-rich Mn-based cathode materials have gradually become a research hotspot due to their high capacity (the theoretical capacity exceeds 250 mAh / g), low cost, and good thermal stability. These materials can significantly improve the energy density of the battery through the transition state reaction of lithium ions and are suitable for the next generation of high-energy-density lithium-ion batteries. However, there are still some problems with lithium-rich Mn-based materials, such as low initial Coulomb efficiency, severe capacity decay, and poor rate performance, which limit their popularization in practical applications.

[0003] To solve these problems, in recent years, scientists have proposed to improve the electrochemical performance of lithium-rich Mn-based materials by means of structural design, doping modification, nanosizing, and single-crystallization. Among them, the research on single-crystallization has attracted extensive attention. Compared with polycrystalline materials, single-crystalline materials have better structural stability and electrochemical performance because they do not have grain boundaries, thus reducing the structural collapse and side reactions of the materials during charge and discharge. For example, Chinese Patent CN107834063B uses potassium chloride as an additive to obtain a single-crystalline one-dimensional structure of lithium-rich material, and Chinese Patent CN109537054A uses peracetic acid as an auxiliary agent to obtain a single-crystalline lithium-rich manganese-based cathode material. In addition, the single-crystalline structure shows better stability under high-rate cycling and can effectively reduce capacity decay. However, conventional single-crystalline synthesis methods can only utilize the structural advantages of single crystals and cannot fully exert the advantages of the preferred crystal plane. By designing the preferred crystal plane, the structural stress of the material during charge and discharge can be reduced, and the cycle stability and long life can be further improved.

[0004] Facetted growth preference refers to the process of preferentially exposing certain crystal planes during the synthesis of materials by controlling the crystal growth conditions, thereby improving the physical and chemical properties of the materials. Different crystal planes have a significant impact on the electrochemical behaviors of materials, such as ion migration, electron conduction, and surface reactions. For the cathode materials of lithium-ion batteries, facetted growth preference can effectively improve the diffusion path of lithium ions in the materials, reduce the charge transfer resistance, and thus enhance the rate performance and cycle stability of the materials. In the case of lithium-rich manganese-based cathode materials, it has been found that the (003) crystal plane has a significant impact on the electrochemical properties of the materials. The materials with exposed (003) crystal planes exhibit higher electronic conductivity, faster lithium-ion migration rate, and better cycle stability. Therefore, it is necessary to develop a preparation method for single-crystalline lithium-rich manganese-based materials that can achieve facetted growth preference along the (003) crystal plane, which can combine the structural advantages of single-crystalline materials and the electrochemical property advantages of facetted growth preference along the (003) crystal plane to obtain cathode materials for lithium-ion batteries with high energy density and long lifespan. Summary of the Invention

[0005] The present invention prepares single-crystalline lithium-rich manganese-based materials with specific facetted growth preference. By controlling the synthesis process of the materials, their facetted growth preference along the (003) crystal plane can be achieved, which can significantly improve the electrochemical properties of the materials, especially the stability under high-rate charge and discharge conditions.

[0006] One of the objectives of the present invention is to provide a single-crystalline lithium-rich manganese-based cathode material with preferred orientation.

[0007] Another objective of the present invention is to provide a preparation method for the single-crystalline lithium-rich manganese-based cathode material with preferred orientation.

[0008] A further objective of the present invention is to provide a lithium-ion battery including the single-crystalline lithium-rich manganese-based cathode material with preferred orientation.

[0009] In order to achieve the above objectives of the present invention, the following technical solutions are specifically adopted:

[0010] In the first aspect, the present invention provides a single-crystalline lithium-rich manganese-based cathode material with preferred orientation. The chemical formula of the lithium-rich manganese-based cathode material is Li[Li x M (1-x) O2, where M is at least one of Mn, Ni, or Co, and 0 < x < 1;

[0011] In the diffraction pattern obtained by an XRD instrument using Cu Kα as the incident light source, the peak intensity ratio I(003) / I(104) of the (003) peak at 2θ = 18.6 ± 0.1° and the (104) peak at 2θ = 44 ± 0.5° of the lithium-rich manganese-based cathode material is > 2, preferably I(003) / I(104) ≥ 3;

[0012] The lithium-rich manganese-based positive electrode material has a single crystal morphology and a layered structure of R-3m space group α-NaFeO2.

[0013] Preferably, the median particle size D50 of the single crystal lithium-rich manganese-based positive electrode material is 0.1 μm-10 μm, and the single crystal morphology is at least one of a cube, a cuboid, a hexahedron, a tetrahedron, and an octahedron.

[0014] Its (003) crystal plane proportion is significantly higher than that of conventional single crystal lithium-rich manganese-based materials.

[0015] The peak intensity ratio (I(003) / I(104)) is used to measure the degree of orientation of the (003) crystal plane in the material. The higher the peak intensity ratio, the stronger the preferred orientation of the (003) crystal plane relative to the (104) crystal plane, that is, during the crystal growth process, more (003) crystal planes are exposed on the surface of the material. This highly oriented (003) crystal plane can increase the migration rate and electronic conductivity of lithium ions in the material, thereby improving the electrochemical performance and cycle stability of the battery. Therefore, a high peak intensity ratio reflects that the material has better electrochemical performance in structure.

[0016] In a second aspect, the present invention provides a method for preparing a preferentially oriented single-crystal lithium-rich manganese-based positive electrode material, comprising the following steps:

[0017] (1) Mixing an aqueous solution A containing a metal salt and an aqueous solution B containing a precipitant and a complexing agent, performing a coprecipitation reaction at 45-75° C., controlling the pH value to be 10-13, washing, filtering, and drying the reaction product to obtain a cathode material precursor;

[0018] (2) The cathode material precursor obtained in step (1) is mixed evenly with a sodium source and a lithium source, and sintered to obtain a single crystal precursor P. The chemical formula of the single crystal precursor P is (Na x Li y M z )O2, wherein M is at least one of Mn, Ni or Co, 0.6≤x≤0.9, preferably 0.8≤x≤0.9, 0 <y≤0.3,0.7≤z<1,y+z=1;

[0019] (3) The single crystal precursor P is fully mixed with the molten salt and then sintered. The sintered product is washed, filtered, and dried to obtain the final product Li[Li x M (1-x) ]O2 (M is at least one of Mn, Ni or Co, 0 <x<1)。

[0020] In some embodiments, the metal salt in step (1) is at least one of sulfate, nitrate, oxalate or acetate, and the concentration of metal ions in aqueous solution A is 0.2 - 2 mol / L; the precipitating agent includes sodium hydroxide and / or potassium hydroxide, and the concentration of hydroxide ions in aqueous solution B is 1 - 3 mol / L; the complexing agent is ammonia water, and the concentration of ammonia water in aqueous solution B is 0.5 - 2 mol / L.

[0021] For example, according to the chemical formula, the metal salt is prepared with corresponding proportions of soluble nickel salt, soluble manganese salt and soluble cobalt salt. The soluble nickel salt includes any one or a combination of at least two of nickel sulfate, nickel acetate, nickel oxalate or nickel nitrate. The soluble manganese salt includes any one or a combination of at least two of manganese sulfate, manganese acetate, manganese oxalate or manganese nitrate. The soluble cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt acetate, cobalt oxalate or cobalt nitrate.

[0022] In some embodiments, the lithium source in step (2) is any one or a combination of at least two of lithium acetate, lithium nitrate, lithium carbonate, lithium oxalate, lithium hydroxide, and the sodium source is any one or a combination of at least two of sodium oxide, sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxalate.

[0023] In some embodiments, the sintering in step (2) includes: primary sintering and secondary sintering carried out in sequence. The temperature of the primary sintering is 400 - 700 °C and the time is 3 - 6 h. The temperature of the secondary sintering is 800 - 1100 °C and the time is 10 - 30 h.

[0024] In some embodiments, the molten salt in step (3) includes one or more of lithium chloride, lithium nitrate, lithium hydroxide; the molar ratio of lithium ions to sodium ions in the single crystal precursor P in the molten salt is greater than 3. Ion exchange occurs between lithium ions and sodium ions in the single crystal precursor P in the molten salt, and subsequent sodium is washed away.

[0025] In some embodiments, the sintering temperature in step (3) is 330 °C - 600 °C, and the sintering time is 1 - 20 h. The above lithium salt can form a molten salt at the sintering temperature.

[0026] In the third aspect, the present invention provides a lithium ion battery, including the above-mentioned single crystal lithium-rich manganese-based cathode material with preferred orientation.

[0027] Beneficial effects:

[0028] The inventors accidentally discovered that by precisely controlling the sintering conditions and the composition and sintering conditions (temperature) of the composite molten salt, the preferential growth of the (003) crystal plane of the lithium-rich manganese-based cathode material can be achieved, thereby significantly improving its electrochemical performance. Specifically, the sintering process includes primary sintering (temperature 400 - 700 °C, time 3 - 6 hours) and secondary sintering (temperature 800 - 1100 °C, time 10 - 30 hours), as well as composite molten salt sintering (temperature 330 °C - 600 °C, time 1 - 20 hours). These sintering conditions provide an appropriate thermodynamic environment for crystal growth, and at the same time, the liquid-phase environment formed by the composite molten salt during sintering promotes the rapid growth of crystals and the oriented arrangement of crystal planes. The control of sintering temperature and time provides appropriate thermodynamic conditions for crystal growth, while the liquid-phase environment of the composite molten salt provides a rapid mass transfer and nucleation process. This synergistic effect can significantly increase the crystal growth rate and the degree of oriented arrangement of crystal planes. By adjusting the composition ratio of the molten salt, the preferential growth effect of the crystal plane can be further optimized. This synergistic regulation mechanism not only improves the structural stability of the material but also significantly enhances the lithium-ion migration rate and electronic conductivity, providing a new technical path for the preparation of high-performance lithium-ion battery cathode materials.

[0029] The present invention prepares a single-crystal lithium-rich manganese-based material with preferential growth of a specific crystal plane, enabling it to preferentially grow along the (003) crystal plane, which can significantly improve the electrochemical performance of the material, especially the stability under high-rate charge and discharge conditions.

[0030] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art or the invention content or the following examples. Description of the Drawings

[0031] Figure 1 XRD pattern of Example 1;

[0032] Figure 2 SEM image of Example 1;

[0033] Figure 3 XRD pattern of Example 2;

[0034] Figure 4 SEM image of Example 2;

[0035] Figure 5 XRD pattern of Example 3;

[0036] Figure 6 SEM image of Example 3;

[0037] Figure 7 XRD pattern of Example 4;

[0038] Figure 8 SEM image of Example 4;

[0039] Figure 9 XRD pattern of Comparative Example 1;

[0040] Figure 10 SEM image of Comparative Example 1;

[0041] Figure 11 XRD pattern of Comparative Example 2;

[0042] Figure 12 SEM image of Comparative Example 2;

[0043] Figure 13 XRD pattern of Comparative Example 3;

[0044] Figure 14 SEM image of Comparative Example 3. Detailed implementation manners

[0045] The present invention will be further described below in conjunction with the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection required by the present invention.

[0046] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0047] XRD test: The material phase structure of the material was measured using an X-ray powder diffractometer (XRD), manufactured by Smart Lab 9 KW. The type of glass slide used was a special glass for XRD. Sample preparation: For each test, the sample was filled into the groove of the glass slide for testing. The scanning range of the test was 10-90°, the test rate was 10° / min, and the step size used was 0.02.

[0048] Specific surface area: Measured on a specific surface area analyzer of Guokangta Instrument Company, model QUADRASORB SI. The mass of the sample used was 3-5 g.

[0049] Compacted density: The compacted density was measured using a UTM7305 battery powder compacted density testing machine. The test conditions included weighing 2.0000 g of the sample, using a φ13 mm mold, compressing within a maximum test force of 300 kN, holding the pressure for 10 seconds, and obtaining the compacted density data by precisely controlling the pressure and time.

[0050] Example 1

[0051] (1) According to the molar ratio of Mn:Ni:Co of 0.68:0.16:0.16, weigh the corresponding mass of manganese sulfate monohydrate, nickel sulfate hexahydrate and cobalt sulfate heptahydrate, dissolve them in water, and prepare a metal salt solution A with a concentration of 2 mol / L. At the same time, weigh sodium hydroxide and dissolve it in water to prepare a solution with a concentration of 2 mol / L, and add ammonia water with a concentration of 1 mol / L as a complexing agent, stir evenly, and obtain solution B. Under the condition of stirring speed of 330 rpm, solution A and solution B are slowly added dropwise to a certain amount of deionized water. The drop rate of solution A is controlled to 0.4 L / h, and the drop rate of solution B is adjusted to maintain the pH value of the system at 12. The coprecipitation reaction is carried out at 50°C for 18 hours. After the reaction is completed, the product is washed, filtered and dried to finally obtain the positive electrode material precursor Mn 0.68 Ni 0.16 Co 0.16 (OH)2.

[0052] (2) The cathode material precursor obtained in step (1) was mixed with lithium carbonate and sodium carbonate in a molar ratio of 0.9:0.05:0.33, and then placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min and kept at this temperature for 4 hours, and then heated to 850°C at a heating rate of 5°C / min, sintered for 20 hours, and cooled to room temperature to obtain the precursor P-Na 0.66 Li 0.1 (Mn 0.68 Ni 0.16 Co 0.16 ) 0.9 O2.

[0053] (3) Precursor P and composite molten salt (lithium hydroxide: lithium chloride mass ratio = 37:63), with the molar ratio of lithium ions in the molten salt to sodium ions in the single crystal precursor P being 10:1, are fully mixed and placed in a crucible, sintered at 400°C for 4h, cooled to room temperature, washed, filtered, and dried.

[0054] The product was analyzed by XRD and had a crystal structure of α-NaFeO2 with R-3m space group and O3 phase. Figure 1 , characterized by a ratio of (003) peak intensity to (104) peak intensity of 3.89. The peak intensity ratio (I(003) / I(104)) is used to measure the degree of orientation of the (003) crystal plane in the material. The higher the peak intensity ratio, the more (003) crystal planes are exposed on the surface of the material. The SEM image of the product is shown in Figure 2 , which is characterized by single-crystalline particles with a size of approximately 2-5μm.

[0055] The prepared lithium-rich manganese-based cathode material with an oriented growth structure, acetylene black, polyvinylidene fluoride, and N-methylpyrrolidone were mixed to form a slurry, which was uniformly coated on the surface of an aluminum foil sheet to obtain a positive electrode sheet. Then, a lithium sheet was used as the negative electrode sheet, and a solution of 1 mol / L lithium hexafluorophosphate in ethylene carbonate (EC) and dimethyl carbonate (DMC) (the volume ratio of EC to DMC was 1:1) was used as the electrolyte, and the assembly was carried out in a glove box to obtain a lithium-ion battery.

[0056] The assembled lithium-ion battery was tested for its first-cycle charge-discharge performance and cycling performance using an electrochemical tester. The test temperature was 25 °C. At a current density of 0.1 C (1 C = 200 mAg -1 ), the first charge-discharge performance of the battery was tested under the condition of a charge-discharge voltage range of 2 - 4.8 V. After being activated for one week at 2.0 - 4.8 V and a current density of 0.1 C, the cycling performance of the battery was tested at a charge-discharge current density of 1 C and a voltage range of 2.0 - 4.8 V. Its first discharge specific capacity was 266.8 mAh / g, and the capacity retention rate after 200 cycles was 95.5%. The results are shown in Table 1.

[0057] Example 2

[0058] (1) The cathode material precursor obtained in step (1) of Example 1 was mixed evenly with lithium carbonate and sodium carbonate in a molar ratio of 0.9:0.05:0.43, and then placed in a muffle furnace and heated to 550 °C at a heating rate of 10 °C / min and held for 4 hours. Then, it was continuously heated to 850 °C at a heating rate of 10 °C / min and sintered for 20 h, and then cooled to room temperature in the furnace to obtain the precursor P-Na 0.86 Li 0.1 (Mn 0.68 Ni 0.16 Co 0.16 ) 0.9 O2.

[0059] (2) The precursor P was fully mixed with a composite molten salt (lithium hydroxide:lithium chloride = 37:63) and placed in a crucible, and sintered at 400 °C for 4 h. After cooling to room temperature, it was washed, filtered, and dried.

[0060] The product was analyzed by XRD and had an O3 phase, as shown in Figure 3 , and its characteristic was that the ratio of the intensity of the (003) peak to the intensity of the (104) peak reached 4.21. The SEM image of the product is shown in Figure 4 , and its characteristic was single crystal particles with a size of about 2 - 5 μm.

[0061] The electrochemical performance test method was the same as that in Example 1, and the results are shown in Table 1. Its first discharge specific capacity was 275.3 mAh / g, and the capacity retention rate after 200 cycles was 92.5%.

[0062] Example 3

[0063] (1) The cathode material precursor obtained in step (1) of Example 1 was mixed with lithium carbonate and sodium carbonate in a molar ratio of 0.9:0.05:0.43, and then placed in a muffle furnace and heated to 550°C at a heating rate of 10°C / min and kept at this temperature for 4 hours, and then heated to 850°C at a heating rate of 10°C / min, sintered for 20 hours, and cooled to room temperature to obtain the precursor P-Na 0.86 Li 0.1 (Mn 0.68 Ni 0.16 Co 0.16 ) 0.9 O2.

[0064] (2) The precursor P and the composite molten salt (lithium carbonate: lithium hydroxide = 74:26) were fully mixed and placed in a crucible. The mixture was sintered at 600 °C for 4 h. After cooling to room temperature, the mixture was washed, filtered and dried.

[0065] The product was analyzed by XRD and showed an O3 phase. Figure 5 , which is characterized by a ratio of (003) peak intensity to (104) peak intensity of 2.61. The SEM image of the product is shown in Figure 6 , which is characterized by single-crystalline particles with a size of approximately 2-5μm.

[0066] The electrochemical performance test method is the same as that of Example 1. The results are shown in Table 1. The initial discharge specific capacity is 259.4 mAh / g, and the 200-cycle capacity retention rate is 88.9%.

[0067] Example 4

[0068] (1) According to the molar ratio of Mn:Ni:Co of 0.65:0.3:0.05, weigh the corresponding mass of manganese sulfate monohydrate, nickel sulfate hexahydrate and cobalt sulfate heptahydrate, dissolve them in water, and prepare a metal salt solution A with a concentration of 2 mol / L. At the same time, weigh sodium hydroxide and dissolve it in water to prepare a solution with a concentration of 2 mol / L, and add ammonia water with a concentration of 1 mol / L as a complexing agent, stir evenly, and obtain solution B. Under the condition of stirring speed of 330 rpm, solution A and solution B are slowly added dropwise to a certain amount of deionized water. The drop rate of solution A is controlled to 0.4 L / h, and the drop rate of solution B is adjusted to maintain the pH value of the system at 12. The coprecipitation reaction is carried out at 50°C for 18 hours. After the reaction is completed, the product is washed, filtered and dried to finally obtain the positive electrode material precursor Mn 0.65 Ni 0.3 Co 0.05 (OH)2.

[0069] (2) Mix the cathode material precursor obtained in step (1) with lithium carbonate and sodium carbonate in a molar ratio of 0.9:0.05:0.33 evenly, then place it in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min and hold for 4 hours, continue to heat it to 850 °C at a heating rate of 5 °C / min, sinter for 20 h, and cool it to room temperature with the furnace to obtain the precursor P-Na 0.66 Li 0.1 (Mn 0.65 Ni 0.3 Co 0.05 ) 0.9 O2.

[0070] (3) Mix the precursor P with the composite molten salt (lithium hydroxide: lithium chloride = 37:63) evenly and place it in a crucible, sinter at 400 °C for 4 h, wash, filter and dry after cooling to room temperature.

[0071] The product was analyzed by XRD and has an O3 phase, see Figure 7 , and its characteristic is that the ratio of the intensity of the (003) peak to the intensity of the (104) peak reaches 2.98. The SEM image of the product is shown in Figure 8 , and its characteristic is single crystal particles with a size of about 2-5 μm.

[0072] The electrochemical performance test method is the same as that in Example 1, and the results are shown in Table 1. Its initial discharge specific capacity is 263.9 mAh / g, and the capacity retention rate after 200 cycles is 93.7%.

[0073] Comparative Example 1

[0074] Mix the precursor obtained in step (1) of Example 1 with lithium carbonate in a molar ratio of 1:1.15 evenly, then place it in a muffle furnace and heat it to 550 °C at a heating rate of 10 °C / min and hold for 4 hours, continue to heat it to 850 °C at a heating rate of 10 °C / min, sinter for 15 h, and cool it to room temperature with the furnace to obtain a lithium-rich manganese-based cathode material with a conventional spherical morphology.

[0075] The product was analyzed by XRD and has an O3 phase, see Figure 9 , and its characteristic is that the ratio of the intensity of the (003) peak to the intensity of the (104) peak is much lower than 2, only 1.2. The SEM image of the product is shown in Figure 10 , and its characteristic is polycrystalline particles (secondary particles) with a size of about 5 μm.

[0076] The electrochemical performance test method is the same as that in Example 1, and the results are shown in Table 1. Its initial discharge specific capacity is 262.5 mAh / g, and the capacity retention rate after 200 cycles is 87.6%.

[0077] Comparative Example 2

[0078] The precursor obtained in step (1) of Example 1, lithium carbonate, and potassium chloride were mixed evenly in a molar ratio of 1:1.15:4, and then placed in a muffle furnace. The temperature was raised to 550 °C at a heating rate of 10 °C / min and held for 4 hours. Then, the temperature was continuously raised to 950 °C at a heating rate of 10 °C / min, sintered for 20 h, and cooled to room temperature with the furnace. The product was washed, filtered, and dried to obtain a lithium-rich manganese-based cathode material with a conventional single-crystal morphology.

[0079] The product was analyzed by XRD and had an O3 phase, as shown in Figure 11 , and its characteristic was that the ratio of the intensity of the (003) peak to the intensity of the (104) peak reached 1.56. The SEM image of the product is shown in Figure 12 , and its characteristic was single-crystal particles with a size of about 5 μm.

[0080] The electrochemical performance test method was the same as that in Example 1, and the results are shown in Table 1. Its initial discharge specific capacity was 250.9 mAh / g, and the capacity retention rate after 200 cycles was 85.6%.

[0081] Comparative Example 3

[0082] (1) The cathode material precursor obtained in step (1) of Example 1, lithium carbonate, and sodium carbonate were mixed evenly in a molar ratio of 1:0.1:0.43, and then placed in a muffle furnace. The temperature was raised to 550 °C at a heating rate of 10 °C / min and held for 4 hours. Then, the temperature was continuously raised to 850 °C at a heating rate of 10 °C / min, sintered for 20 h, and cooled to room temperature with the furnace to obtain precursor P.

[0083] (2) Precursor P was fully mixed with a composite molten salt (lithium hydroxide: lithium carbonate = 76:24), placed in a crucible, and sintered at 700 °C for 4 h. After cooling to room temperature, it was washed, filtered, and dried.

[0084] The product was analyzed by XRD, as shown in Figure 13 , had an O3 phase, and the ratio of the intensity of the (003) peak to the intensity of the (104) peak was 1.45. The SEM image of the product is shown in Figure 14 , and its characteristic was single-crystal particles with a size of about 1 - 3 μm.

[0085] The electrochemical performance test method was the same as that in Example 1, and the results are shown in Table 1. Its initial discharge specific capacity was 187.7 mAh / g, and the capacity retention rate after 200 cycles was 64.5%.

[0086] Table 1

[0087]

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: within the scope not departing from the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and such modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A single-crystalline lithium-rich manganese-based cathode material with preferred orientation, characterized in that The chemical formula of the lithium-rich manganese-based cathode material is Li[Li x M (1-x) O2, where M is a combination of Mn, Ni, and Co, and 0 < x < 1; in the diffraction pattern obtained by an XRD instrument using Cu Kα as the incident light source, the peak intensity ratio I(003) / I(104) of the (003) peak with 2θ at 18.6 ± 0.1° and the (104) peak with 2θ at 44 ± 0.5° is ≥ 3; The lithium-rich manganese-based cathode material has a single-crystal morphology.

2. The preferred orientation single crystal lithium-rich manganese-based cathode material according to claim 1, characterized in that, The median particle size D50 of the single-crystal lithium-rich manganese-based cathode material is 0.1 μm - 10 μm, and the single-crystal morphology is at least one of a cube, a cuboid, a hexahedron, a tetrahedron, and an octahedron.

3. A method for preparing a single-crystalline lithium-rich manganese-based cathode material with preferred orientation as described in claim 1 or 2, characterized in that, It includes the following steps: (1) Mix an aqueous solution A containing a metal salt and an aqueous solution B containing a precipitant and a complexing agent, carry out a coprecipitation reaction at 45 - 75 °C, control the pH value to be 10 - 13, wash, filter, and dry the reaction product to obtain a cathode material precursor; (2) Mix the cathode material precursor obtained in step (1) uniformly with a sodium source and a lithium source, and sinter to obtain a single crystal precursor P. The chemical formula of the single crystal precursor P is (Na x Li y M z )O2, where M is at least one of Mn, Ni or Co, 0.6 ≤ x ≤ 0.9, 0 < y ≤ 0.3, 0.7 ≤ z < 1, and y + z = 1; The sintering in step (2) includes: primary sintering and secondary sintering carried out in sequence. The temperature of the primary sintering is 400 - 700 °C and the time is 3 - 6 h, and the temperature of the secondary sintering is 800 - 1100 °C and the time is 10 - 30 h; (3) Fully mix the single-crystal precursor P with a molten salt and sinter it, wash, filter, and dry the sintered product to obtain a final product; The molten salt in step (3) includes one or more of lithium chloride, lithium nitrate, and lithium hydroxide; the molar ratio of lithium ions to sodium ions in the molten salt to the single-crystal precursor P is greater than 3; The sintering temperature in step (3) is 330 °C - 600 °C, and the sintering time is 1 - 20 h.

4. The preparation method according to claim 3, characterized in that, The metal salt in step (1) is at least one of a sulfate, a nitrate, an oxalate, or an acetate, and the concentration of metal ions in the aqueous solution A is 0.2 - 2 mol / L.

5. The preparation method according to claim 3, characterized in that, The precipitant in step (1) includes sodium hydroxide and / or potassium hydroxide, and the concentration of hydroxide ions in the aqueous solution B is 1 - 3 mol / L; the complexing agent is ammonia water, and the concentration of ammonia water in the aqueous solution B is 0.5 - 2 mol / L.

6. The preparation method according to claim 3, characterized in that, The lithium source in step (2) is any one or a combination of at least two of lithium acetate, lithium nitrate, lithium carbonate, lithium oxalate, and lithium hydroxide, and the sodium source is any one or a combination of at least two of sodium oxide, sodium hydroxide, sodium carbonate, sodium nitrate, and sodium oxalate.

7. A lithium-ion battery, comprising the preferentially oriented single-crystal lithium-rich manganese-based cathode material described in claim 1 or 2 or the preferentially oriented single-crystal lithium-rich manganese-based cathode material prepared by the preparation method described in any one of claims 3 - 6.

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