Titanium-doped lithium nickel manganese oxide cathode material, preparation method, application and lithium ion battery

Abstract

The application provides a titanium-doped lithium nickel-manganese oxide positive electrode material, a preparation method, application and lithium ion battery. The preparation method is as follows: (1) under stirring, titanium salt and a dispersion liquid containing a nickel-manganese precursor are mixed and reacted to obtain a precipitate containing nickel, manganese and titanium; the stirring speed is 150-900 r / min; the solvent in the dispersion liquid comprises alcohol, an alkaline solution and water; the volume ratio of water to alcohol is (0.05-5):100; the molar ratio of titanium salt to nickel-manganese precursor is (3-30):100; (2) the precipitate containing nickel, manganese and titanium obtained in step (1) is mixed with a lithium source to obtain an intermediate mixture which is calcined; the calcination temperature is 500-1000 DEG C; the calcination time is 8-20 h. The preparation method has the advantages of simple process, low cost and suitability for industrial production; and the lithium ion battery assembled by using the titanium-doped lithium nickel-manganese oxide positive electrode material has the advantages of high capacity, good rate performance and good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of new energy materials, specifically to a titanium-doped lithium nickel manganese oxide cathode material, its preparation method, applications, and lithium-ion batteries. Background Technology

[0002] Currently, lithium-ion rechargeable batteries are gradually becoming the core energy storage devices for various power equipment due to their advantages such as high energy density, no significant memory effect, low environmental pollution, and long cycle life. Developing lithium-ion rechargeable batteries with excellent electrochemical performance has become a key research focus. Among these, the cathode material is crucial for ensuring the superior performance of lithium-ion rechargeable batteries. Currently, commonly used cathode materials in lithium-ion rechargeable batteries, such as lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, are insufficient to meet market demands for high-performance lithium-ion batteries, including high energy density, excellent rate performance, and cycle performance. Therefore, researching and developing cathode materials with excellent electrochemical performance is of great significance.

[0003] Lithium nickel manganese oxide (LiMO) cathode materials have attracted much attention due to their advantages of high operating voltage, high energy density, and low cost. However, at high operating voltages, the lattice oxygen in the structure of LiMO materials is unstable. During repeated charge and discharge processes, it migrates to the surface, leading to the oxidative decomposition of the electrolyte. The decomposition product, hydrogen fluoride, corrodes the active material, causing a deterioration in capacity and cycle performance. Furthermore, after lattice oxygen is extracted from the bulk phase of the material, the stability of the oxygen framework and lithium-ion diffusion channels deteriorates, hindering rapid lithium-ion insertion and extraction and worsening rate performance.

[0004] Therefore, enhancing the stability of oxygen atoms in the crystal lattice is key to improving the electrochemical performance of lithium nickel manganese oxide cathode materials. Studies have shown that introducing titanium into the crystal structure of the material can effectively stabilize the lattice oxygen, thereby stabilizing the crystal structure and improving its electrochemical performance (J. Zhang, Q. Li, C. Ouyang, et al., Trace doping of multiple elements enables stable battery cycling of LiCoO2 at 4.6V, Nature Energy 2019, 4, 594-603). However, titanium ions have a low diffusion rate in cathode materials, and conventional doping modification methods easily form impurity phases on the surface of lithium nickel manganese oxide, which hinder the insertion and extraction of lithium ions, affecting the rate performance of the material.

[0005] For example, doping with titanium can improve the electrochemical performance of materials to a certain extent. However, although titanium is doped into the bulk phase, it also forms an impurity phase on the surface, which is not conducive to improving rate performance (D. Kong, et al., Ti-Gradient Doping to Stabilize Layered Surface Structure for High Performance High-Ni Oxide Cathode of Li-Ion Battery, Advanced Energy Materials, 2019, 1901756).

[0006] Therefore, finding effective modification methods to stabilize lattice oxygen by doping with titanium without introducing impurity phases on the surface has become a research challenge and hot topic. Furthermore, to further improve the electrochemical performance of lithium nickel manganese oxide cathode materials, a reasonable structural design is essential. Large-particle cathode materials are beneficial for increasing compaction density and mechanical strength, thereby enhancing the electrochemical performance of the cathode material. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the defects in the existing lithium nickel manganese oxide material structure, namely, the instability of lattice oxygen and the easy formation of impurity phases on the surface after the addition of titanium ions, resulting in poor rate performance. This invention provides a titanium-doped lithium nickel manganese oxide cathode material, its preparation method, applications, and lithium-ion batteries. The titanium-doped lithium nickel manganese oxide cathode material prepared by this invention effectively stabilizes lattice oxygen with titanium ions, improving crystal structure stability. Simultaneously, the low content or even absence of impurity phases on the surface facilitates rapid lithium ion insertion / extraction. When used in lithium-ion batteries, it exhibits high capacity, excellent cycle performance, and good rate performance. Its preparation method is simple and low-cost, enabling large-scale preparation of active materials and making it suitable for industrial production.

[0008] This invention achieves titanium ion doping of lithium nickel manganese oxide by uniformly depositing titanium salt on the surface of the precursor and combining it with high-temperature lithium intercalation calcination to incorporate titanium ions into the bulk phase of lithium nickel manganese oxide. This effectively stabilizes lattice oxygen without introducing surface impurities, ultimately yielding a titanium ion-doped lithium nickel manganese oxide cathode material.

[0009] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0010] This invention provides a method for preparing titanium-doped lithium nickel manganese oxide cathode material, which includes the following steps:

[0011] (1) Under stirring, titanium salt and a dispersion containing nickel-manganese precursor are mixed and reacted to obtain a precipitate containing nickel, manganese and titanium; the stirring speed is 150-900 r / min; the solvent in the dispersion includes alcohol, alkaline solution and water; the volume ratio of water to alcohol is (0.05-5):100; the molar ratio of titanium salt to nickel-manganese precursor is (3-30):100;

[0012] (2) The nickel, manganese and titanium precipitate obtained in step (1) is mixed with a lithium source to obtain an intermediate mixture and then calcined; the calcination temperature is 500-1000℃; the calcination time is 8-20h.

[0013] In step (1), the titanium salt can be conventional in the art, preferably tetrabutyl titanate or titanium tetrachloride.

[0014] In step (1), the molar ratio of the titanium salt to the nickel-manganese precursor can be (5-20):100, for example, 10.3:100.

[0015] In step (1), the mixing order can be conventional in the art, and preferably titanium salt is added to the dispersion containing nickel manganese precursor.

[0016] The titanium salt is preferably added drop by drop.

[0017] In step (1), the nickel-manganese precursor can be conventional in the art, and preferably prepared by the following method: dissolving nickel salt, manganese salt and precipitant in a solvent in stoichiometric ratio, and then reacting them with hydrothermal reaction.

[0018] The nickel salt can be a conventional inorganic or organic nickel salt in the art, such as nickel sulfate, nickel chloride, nickel nitrate, or nickel acetate.

[0019] The manganese salt can be a conventional inorganic or organic manganese salt in the art, such as manganese sulfate, manganese chloride, manganese nitrate, or manganese acetate.

[0020] The molar ratio of the nickel salt to the manganese salt can be 1:3.

[0021] The precipitant can be conventional in the art, preferably urea, hexamethylenetetramine or ammonium bicarbonate.

[0022] The amount of the precipitant used can be conventional in the art, generally not less than the sum of the molar numbers of the nickel salt and the manganese salt.

[0023] The solvent may be one or more of water, ethylene glycol, and glycerol.

[0024] The total mass concentration of the nickel salt, the manganese salt, and the precipitant can be 0.04–0.1 g / mL, preferably 0.05–0.08 g / mL, and more preferably 0.07 g / mL.

[0025] The temperature of the hydrothermal reaction can be 150-200℃, for example 180℃.

[0026] The hydrothermal reaction time can be 10 to 14 hours, for example, 12 hours.

[0027] In step (1), the molecular expression of the nickel-manganese precursor can be Ni x Mn 2-x (CO3)2, where 0.4≤x≤0.6.

[0028] In step (1), the concentration of the nickel-manganese precursor can be 0.5 to 2 mg / mL, preferably 0.8 to 1.2 mg / mL, for example 1 mg / mL.

[0029] In step (1), the alcohol can be conventional in the art, preferably ethanol or ethylene glycol.

[0030] In step (1), the volume ratio of the alcohol to the dispersion can be (90-99.9):100, preferably (95-99.9):100, for example 99.7:100.

[0031] In step (1), the alkaline solution can be conventional in the art, generally capable of controlling the pH value of the dispersion to be less than 12.5, such as ammonia or sodium hydroxide.

[0032] In step (1), the pH value of the dispersion containing the nickel-manganese precursor can be 8 to 12.5, for example 10.3, 10.7 or 12.1, preferably 9 to 11.5.

[0033] In step (1), the water can be conventional in the art, such as deionized water.

[0034] In step (1), the volume ratio of water to alcohol can be (0.1 to 1): 100, for example, 0.17: 100.

[0035] In step (1), the reaction temperature can be 60 to 90°C, for example 80°C.

[0036] In step (1), the reaction time can be 4 to 10 hours, for example, 4 hours.

[0037] In step (1), the stirring speed can be 150 r / min, 200 r / min, 500 r / min or 800 r / min, preferably 500-800 r / min.

[0038] In step (1), the precipitate containing nickel, manganese, and titanium can be Ni x Mn 2-x A mixture of (CO3)2 and TiO2.

[0039] In step (1), after the reaction is completed, the precipitate containing nickel, manganese and titanium generally needs to be filtered, washed and dried.

[0040] The washing operation and conditions are conventional in the art, generally using deionized water and ethanol alternately. The washing is generally performed three times.

[0041] The drying process can be conventional in the art, but vacuum drying is preferred.

[0042] The drying temperature can be conventional in the art, but is preferably 80°C.

[0043] In step (2), the lithium source can be conventional in the art, preferably lithium carbonate, lithium hydroxide, lithium acetate, lithium chloride or lithium nitrate.

[0044] In step (2), the molar ratio of the lithium source to the nickel, manganese and titanium precipitate can be 1.05:1 to 1.3:1, preferably 1.1:1 to 1.25:1, for example 1.1:1 or 1.25:1.

[0045] The nickel, manganese and titanium-containing precipitate is a mixture, and its main component is a nickel-manganese precursor. When calculating the amount of lithium source added, the entire nickel, manganese and titanium-containing precipitate can be regarded as a nickel-manganese precursor.

[0046] In step (2), the mixing can be conventional in the art, generally grinding and mixing.

[0047] In step (2), the calcination is generally carried out in a tubular furnace.

[0048] In step (2), the calcination atmosphere is generally an oxygen-containing atmosphere, such as air or oxygen.

[0049] In step (2), the calcination temperature can be 800-1000℃, preferably 850-1000℃, for example 800℃ or 900℃.

[0050] In step (2), the calcination time can be 9 to 20 hours, for example, 10 hours.

[0051] In step (2), the calcination is generally followed by natural cooling.

[0052] The present invention also provides a titanium-doped lithium nickel manganese oxide cathode material prepared by the preparation method described above.

[0053] This invention also provides a titanium-doped lithium nickel manganese oxide cathode material, the composition of which is LiNi x Mn 2-x-y Ti y O4; wherein, 0.4≤x≤0.6, 0.0005≤y≤0.01, the titanium is doped in the bulk phase of the lithium nickel manganese oxide material and there are basically no impurities on the surface of the lithium nickel manganese oxide material.

[0054] In this invention, the content of the impurity phase will not significantly alter the properties of the titanium-doped lithium nickel manganese oxide cathode material, for example, it will not cause the rate performance of the titanium-doped lithium nickel manganese oxide cathode material to be lower than that of Chinese patent document CN105280912 A.

[0055] In this invention, the titanium-doped lithium nickel manganese oxide cathode material can have a spinel structure.

[0056] In this invention, the impurity phase may be a titanium-containing phase different from spinel lithium nickel manganese titanate, such as TiMn2O4 or Li2TiO3.

[0057] In this invention, the titanium in the titanium-doped lithium nickel manganese oxide cathode material is in the tetravalent state.

[0058] In this invention, the titanium-doped lithium nickel manganese oxide cathode material can be a blocky particle with a maximum diameter in the range of 2 to 10 micrometers.

[0059] The present invention also provides an application of the titanium-doped nickel manganese oxide cathode material described above as a cathode material in lithium-ion batteries.

[0060] The present invention also provides a lithium-ion battery that uses the titanium-doped lithium nickel manganese oxide cathode material as described above.

[0061] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0062] The reagents and raw materials used in this invention are all commercially available.

[0063] The positive and progressive effects of this invention are as follows:

[0064] (1) By controlling the hydrolysis rate of titanium salt, a complete and uniform coating layer can be formed on the surface of nickel-manganese precursor;

[0065] (2) High temperature treatment allows titanium ions to diffuse fully into the bulk phase, resulting in titanium-doped lithium nickel manganese oxide cathode material with no impurity phase on the surface. Among them, titanium ions can effectively improve the stability of oxygen atoms in the lattice, inhibit their migration to the surface, and alleviate the occurrence of electrolyte decomposition side reactions. At the same time, the stable oxygen framework and the impurity-free surface enable the rapid insertion and extraction of lithium ions, improving the rate performance of the material.

[0066] (3) The large particle structure of titanium-doped lithium nickel manganese oxide cathode material can improve the compaction density, inhibit the cracking of the material during cycling, and significantly improve the electrochemical performance of titanium-doped lithium nickel manganese oxide cathode material.

[0067] (4) The method of combining liquid phase coating and high temperature calcination is simple and low-cost, and can realize the large-scale preparation of active materials, which is suitable for industrial production.

[0068] In a preferred embodiment, the titanium-doped nickel-manganese lithium cathode material of the present invention exhibits excellent electrochemical performance when assembled into a lithium-ion battery: the discharge specific capacity at 1C can reach as high as 133 mAh g⁻¹ within the voltage range of 3.5–5.0 V. -1 After 100 cycles at 1C, the capacity retention is 98%, and at a high current density of 10C, it can achieve a capacity of 90mAh g / L. -1 Specific capacity. Attached Figure Description

[0069] Figure 1 The X-ray diffraction pattern of the product of Example 1 is shown.

[0070] Figure 2 Here is an electron microscope image of the product from Example 1; Figure 2 a is a scanning electron microscope image of the product of Example 1; Figure 2 b is a transmission electron microscope image of the product of Example 1.

[0071] Figure 3 The results are the electrochemical performance test results of the cathode materials obtained in Example 1 and Comparative Example 4; Figure 3 a represents the rate performance test results of the cathode materials obtained in Example 1 and Comparative Example 4; Figure 3 b represents the cycle performance test results of the cathode materials obtained in Example 1 and Comparative Example 4. Detailed Implementation

[0072] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0073] Example 1

[0074] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. The precipitate (Ni) obtained by filtration was then collected. 0.5 Mn 1.5 The mixture of (CO3)2 and TiO2 was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80°C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni). 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.495 Ti 0.005 O4.

[0075] Example 2

[0076] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. The precipitate obtained by vacuum filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.25:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula Li. 1.15 Ni 0.5 Mn 1.495 Ti 0.005 O4.

[0077] Example 3

[0078] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethanol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.7. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. The precipitate obtained by filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.495 Ti 0.005 O4.

[0079] Example 4

[0080] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The solution was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of NaOH solution (1 M, pH = 14) and 1 mL of deionized water were added to form a dispersion with a pH of 12.1. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 r / min and reacted at 80 °C for 4 h. The precipitate obtained by vacuum filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.495 Ti 0.005 O4.

[0081] Example 5

[0082] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 150 r / min and reacted at 80 °C for 4 h. The precipitate obtained by vacuum filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.495 Ti 0.005 O4.

[0083] Example 6

[0084] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. The precipitate obtained by vacuum filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 800℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.495 Ti 0.005 O4.

[0085] Comparative Example 1

[0086] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 340 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. The precipitate obtained by vacuum filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.48 Ti 0.02 O4.

[0087] Comparative Example 2

[0088] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and subjected to a hydrothermal reaction at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. 600 mg of the precursor (Ni...) was then... 0.5 Mn 1.5 (CO3)2) The mixture was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. The precipitate obtained by vacuum filtration was washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C. The molar ratio of lithium carbonate to the dried precipitate was n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 6 hours in air. Upon cooling, titanium-doped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.495 Ti 0.005 O4.

[0089] Comparative Example 3

[0090] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and reacted hydrothermally at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. The precursor (Ni...) 0.5 Mn 1.5 (CO3)2) and lithium carbonate are in a molar ratio of n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air, and then cooled to obtain the lithium nickel manganese oxide cathode material LiNi. 0.5 Mn 1.5 O4. Take 430mg LiNi 0.5 Mn 1.5 O4 was ultrasonically dispersed in 600 mL of ethylene glycol, and 1 mL of ammonia and 1 mL of deionized water were added to form a dispersion with a pH of 10.3. 85 μL of tetrabutyl titanate was added dropwise to the dispersion, and the mixture was stirred thoroughly at 800 rpm and reacted at 80 °C for 4 h. After the reaction, the precipitate was obtained by filtration, washed three times alternately with deionized water and ethanol, and then dried under vacuum at 80 °C. After drying, the product was calcined in air at 400 °C for 10 h.

[0091] Comparative Example 4

[0092] 0.62 g of nickel acetate, 1.83 g of manganese acetate, and 1.2 g of urea were fully dissolved in 50 mL of ethylene glycol and reacted hydrothermally at 180 °C for 12 h. The resulting precipitate was filtered, washed, and dried to obtain the precursor. The precursor (Ni...) 0.5 Mn 1.5 (CO3)2) and lithium carbonate are in a molar ratio of n(Li):n(Ni) 0.5 Mn 1.5 After grinding and mixing (CO3)2 in a ratio of 1.1:1, the mixture is calcined at 900℃ for 10 hours in air. Upon cooling, undoped lithium nickel manganese oxide cathode material is obtained, with the molecular formula LiNi. 0.5 Mn 1.5 O4.

[0093] Example 1

[0094] 1. XRD

[0095] Figure 1 The image shows the X-ray diffraction pattern of the product from Example 1. As can be seen from the image, titanium ion doping modification did not damage the crystal structure of the lithium nickel manganese oxide cathode material and did not introduce impurity phases. The corresponding PDF card is 80-2162.

[0096] 2. SEM and TEM

[0097] Figure 2 Here is an electron microscope image of the product from Example 1; Figure 2 a is a scanning electron microscope image of the product of Example 1; Figure 2 b is a transmission electron microscope (TEM) image of the product from Example 1. The image shows that the titanium-doped lithium nickel manganese oxide cathode material exhibits a large-particle structure with no impurities on its surface.

[0098] 3. Electrochemical performance testing

[0099] The positive electrode materials obtained in Examples 1-6 and Comparative Examples 1-4 were used to assemble half-cells according to the following steps: The prepared materials were mixed with 10 wt% binder (4 wt% N-methylpyrrolidone (NMP) solution of polyvinylidene fluoride (PVDF)) and 8 wt% conductive agent (SuperP conductive carbon black), stirred evenly, coated onto aluminum foil, and dried in an oven at 60-80°C. Then, electrode sheets were formed using a punch with a diameter of 10-16 mm, dried in a vacuum oven at 60-120°C for 4-12 hours, and then transferred to an argon-filled glove box. Using metallic Li as the counter electrode and EC and DMC as the electrolyte, CR2032 coin cells were assembled. Constant current charge-discharge performance tests were performed on a LAND battery testing system (provided by Wuhan Jinno Electronics Co., Ltd.), and the charge-discharge cutoff voltage was compared with Li / Li + The voltage is 3.5-5.0V, and the current density is 1-10c, where 1c = 147mA / g.

[0100] The electrochemical performance data of Examples 1-6 and Comparative Examples 1-4 are shown in Table 1. In this invention, the specific capacity was obtained at 25°C.

[0101] Table 1

[0102]

[0103] Figure 3 The results are the electrochemical performance test results of the cathode materials obtained in Example 1 and Comparative Example 4; Figure 3 a represents the rate performance test results of the cathode materials obtained in Example 1 and Comparative Example 4; Figure 3 b shows the cycle performance test results of the cathode materials obtained in Example 1 and Comparative Example 4. Within the voltage range of 3.5–5.0 V, the cathode material prepared in Example 1 exhibits a discharge specific capacity as high as 133 mAh / g at 1C, a reversible specific capacity of 90 mAh / g at 10C, and a capacity retention rate of 98% after 100 cycles at 1C. In contrast, the cathode material prepared in Comparative Example 4 exhibits a discharge specific capacity of only 125 mAh / g at 1C, a reversible specific capacity of 30 mAh / g at 10C, and a capacity retention rate of only 74% after 100 cycles at 1C.

Claims

1. A method for preparing a titanium-doped lithium nickel manganese oxide cathode material, characterized in that, It includes the following steps: (1) Under stirring, titanium salt and a dispersion containing nickel-manganese precursor are mixed and reacted to obtain a precipitate containing nickel, manganese and titanium; the stirring speed is 150-900 r / min; the solvent in the dispersion includes alcohol, alkaline solution and water; the volume ratio of water to alcohol is (0.05-5):100, the pH value of the dispersion is less than 12.5; the molar ratio of titanium salt to nickel-manganese precursor is (5-20):100; (2) The nickel, manganese and titanium precipitate obtained in step (1) is mixed with a lithium source to obtain an intermediate mixture and then calcined; the calcination temperature is 500~1000 ℃; the calcination time is 8~20 h; the titanium is doped in the bulk phase of the lithium nickel manganese oxide material and there are no impurities on the surface of the lithium nickel manganese oxide material.

2. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The titanium salt is tetrabutyl titanate or titanium tetrachloride; And / or, the nickel-manganese precursor is prepared by dissolving nickel salt, manganese salt and precipitant in a solvent in stoichiometric proportions, followed by a hydrothermal reaction.

3. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The molar ratio of the titanium salt to the nickel-manganese precursor is 10.3:

100.

4. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The mixing sequence is as follows: titanium salt is added to a dispersion containing nickel-manganese precursor.

5. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The molecular formula of the nickel-manganese precursor is Ni x Mn 2-x (CO3)2, where 0.4 ≤ x ≤ 0.6; And / or, the concentration of the nickel-manganese precursor is 0.5~2 mg / mL; And / or, the alcohol is ethanol or ethylene glycol; And / or, the volume ratio of the alcohol to the dispersion is (90~99.9):100; And / or, the alkaline solution is ammonia or sodium hydroxide; And / or, the pH of the dispersion containing the nickel-manganese precursor is 8 to 12.5; And / or, the volume ratio of the water to the alcohol is (0.1~1):100; And / or, the temperature of the reaction is 60–90°C; And / or, the reaction time is 4 to 10 hours; And / or, the stirring speed is 150 r / min, 200 r / min, 500 r / min or 800 r / min; And / or, the nickel-, manganese-, and titanium-containing precipitate is Ni x Mn 2-x A mixture of (CO3)2 and TiO2.

6. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The concentration of the nickel-manganese precursor is 0.8~1.2 mg / mL; And / or, the volume ratio of the alcohol to the dispersion is (95~99.9):100; And / or, the pH of the dispersion containing the nickel-manganese precursor is 9 to 11.5; And / or, the volume ratio of water to alcohol is 0.17:100; And / or, the temperature of the reaction is 80°C; And / or, the reaction time is 4 hours; And / or, the stirring speed is 500-800 r / min.

7. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 6, characterized in that, The concentration of the nickel-manganese precursor was 1 mg / mL; And / or, the volume ratio of the alcohol to the dispersion is 99.7:100; And / or, the pH of the dispersion containing the nickel-manganese precursor is 10.3, 10.7 or 12.

1.

8. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 2, characterized in that, The nickel salt is an inorganic nickel salt or an organic nickel salt; And / or, the manganese salt is an inorganic manganese salt or an organic manganese salt; And / or, the molar ratio of the nickel salt to the manganese salt is 1:3; And / or, the precipitant is urea, hexamethylenetetramine, or ammonium bicarbonate; And / or, the amount of the precipitant used shall not be less than the sum of the molar numbers of the nickel salt and the manganese salt; And / or, the solvent is one or more of water, ethylene glycol, and glycerol; And / or, the total mass concentration of the nickel salt, the manganese salt, and the precipitant is 0.04~0.1 g / mL; And / or, the temperature of the hydrothermal reaction is 150~200℃; And / or, the hydrothermal reaction time is 10-14 h.

9. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 8, characterized in that, The nickel salt is nickel sulfate, nickel chloride, nickel nitrate, or nickel acetate; And / or, the manganese salt is manganese sulfate, manganese chloride, manganese nitrate, or manganese acetate; And / or, the total mass concentration of the nickel salt, the manganese salt, and the precipitant is 0.05~0.08 g / mL; And / or, the temperature of the hydrothermal reaction is 180°C; And / or, the hydrothermal reaction takes 12 hours.

10. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 9, characterized in that, The total mass concentration of the nickel salt, the manganese salt, and the precipitant is 0.07 g / mL.

11. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 1, characterized in that, The lithium source is lithium carbonate, lithium hydroxide, lithium acetate, lithium chloride, or lithium nitrate; And / or, the molar ratio of the lithium source to the nickel, manganese and titanium-containing precipitate is 1.05:1 to 1.3:1; And / or, the calcination temperature is 800~1000℃; And / or, the calcination time is 9~20 h.

12. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 11, characterized in that, The molar ratio of the lithium source to the nickel, manganese and titanium-containing precipitate is 1.1:1 to 1.25:1; And / or, the calcination temperature is 850~1000℃; And / or, the calcination time is 10 h.

13. The method for preparing titanium-doped lithium nickel manganese oxide cathode material as described in claim 12, characterized in that, The molar ratio of the lithium source to the nickel, manganese and titanium-containing precipitate is 1.1:1 or 1.25:1; And / or, the calcination temperature is 800°C or 900°C.

14. A titanium-doped lithium nickel manganese oxide cathode material, which is prepared according to the preparation method of titanium-doped lithium nickel manganese oxide cathode material according to any one of claims 1 to 13.

15. The titanium-doped lithium nickel manganese oxide cathode material as described in claim 14, characterized in that, The titanium-doped lithium nickel manganese oxide cathode material has a composition of LiNi x Mn 2-x-y Ti y O4; wherein, 0.4≤x≤0.6, 0.0005≤y≤0.01, and the titanium is doped in the bulk phase of the lithium nickel manganese oxide material and there are no impurity phases on the surface of the lithium nickel manganese oxide material.

16. The titanium-doped lithium nickel manganese oxide cathode material as described in claim 15, characterized in that, The titanium-doped lithium nickel manganese oxide cathode material has a spinel structure; And / or, the impurity phase is a titanium-containing phase different from that of spinel nickel manganese titanate lithium; And / or, in the titanium-doped lithium nickel manganese oxide cathode material, the titanium has a tetravalent valence state; And / or, the titanium-doped lithium nickel manganese oxide cathode material is a blocky particle with a maximum diameter in the range of 2 to 10 micrometers.

17. The titanium-doped lithium nickel manganese oxide cathode material as described in claim 16, characterized in that, The impurity phase is TiMn2O4 or Li2TiO3.

18. The application of the titanium-doped lithium nickel manganese oxide cathode material as described in any one of claims 14 to 17 as a cathode material in lithium-ion batteries.

19. A lithium-ion battery using the titanium-doped lithium nickel manganese oxide cathode material as described in any one of claims 14 to 17.

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