A composite modified spinel-type lithium nickel manganate cathode material, its preparation method and application

Abstract

The present invention provides a composite modified spinel-type lithium nickel manganate cathode material, a preparation method thereof, and an application thereof, relating to the technical field of cathode materials. The chemical formula of the cathode material of the present invention is LiNi 0.5 Re x Mn 1.5‑x O 4‑y F y , wherein 0

Description

Technical Field

[0001] The present invention provides a composite modified spinel-type lithium nickel manganate cathode material, a preparation method thereof and an application thereof, relating to the technical field of cathode materials. Background Art

[0002] At present, several types of lithium-ion battery cathode materials have been developed and commercialized, mainly including olivine-type LiFePO4, layered LiCoO2, layered nickel-cobalt-manganese ternary materials (LiNi x Co y Mn z O2) and spinel LiMn2O4. Among them, olivine-type LiFePO4 can provide the best long-cycle stability. However, its energy density (~495 Wh kg -1 ) is relatively low, and the preparation process is complex. Cobalt-based layered LiCoO2 (~518 Wh kg -1 ) and LiNi x Co y Mn z O2 (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, ~576 Whkg -1 ) have higher energy densities. However, cobalt is a rare and expensive metal, resulting in high production costs of cobalt-based layered oxides, thus limiting their large-scale application. The LiMn2O4 cathode material has the advantages of easy preparation and low production cost, but its inherent defects of low energy density (440 Wh kg -1 ) and poor cycle stability limit its large-scale application.

[0003] Researchers have found that introducing nickel ions into spinel-type LiMn2O4 can significantly improve the electrochemical performance of LiMn2O4. For example, the composition LiNi 0.5 Mn 1.5 O4 has an ultra-high discharge plateau of 4.7 V (vs. Li / Li + ) and a high energy density (650 Wh kg -1 ), which are 1.31 times and 1.63 times that of LiFePO4 and LiMn2O4 respectively. In addition to its high theoretical specific capacity and working voltage, due to its easy preparation and low cost, it is a promising lithium-ion battery cathode material. However, there are still Mn 0.5 Mn 1.5 ions in LiNi 3+ O4. During the charging process, Mn 3+ ions are prone to disproportionation reactions (Jahn–Teller effect), resulting in unstable material structure and rapid capacity decline.

[0004] In order to overcome the inherent defects of LiNi 0.5 Mn 1.5 O4 and improve its cycling stability, researchers have conducted a large number of studies on the modification of LiNi 0.5 Mn 1.5 O4. This includes doping with cations (Co 3+ 、Ce 4+ 、Mg 2+ 、V 5+ 、Cr 3+ 、Al 3+ 、B 3+ and W 6+ ), doping with anions (Cl – 、F – and S 2– ), and surface modification of particles. Cation or anion doping mainly serves to reduce the content of Mn 3+ ions, thereby enhancing the structural stability of LiNi 0.5 Mn 1.5 O4, while surface modification inhibits the decomposition of the electrolyte. In addition, it has been found that the strategy of co-doping cations and anions combined with particle surface modification has a synergistic effect on improving the structural stability and electrochemical performance of LiNi 0.5 Mn 1.5 O4. Therefore, the composite modification strategy is considered an effective method for improving the electrochemical performance of spinel-type lithium nickel manganate. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a simple room-temperature solid-state reaction method, combined with subsequent high-temperature calcination, to co-dope rare earth and fluorine into the phase structure of spinel-type lithium nickel manganate and simultaneously construct a rare earth-manganese-based perovskite-type oxide (ReMnO3) coating layer on its surface. The co-doping of rare earth and fluorine can significantly reduce the content of Mn 3+ ions and enhance the structural stability of LiNi 0.5 Mn 1.5 O4, while the ReMnO3 coating layer can effectively improve the stability of the cathode material / electrolyte interface.

[0006] The present invention is achieved by the following technical solutions:

[0007] A composite-modified spinel-type lithium nickel manganate cathode material, the chemical formula of the cathode material is as follows: LiNi 0.5 Re x Mn 1.5-x O 4-y F y , where 0 < x ≤ 0.08, 0 < y ≤ 0.06, and Re is a rare earth element.

[0008] Preferably, the positive electrode material has a core-shell structure, wherein the core layer is spinel-type lithium nickel manganate with a space group of Fd-3m(227), and the shell layer is a perovskite-type ReMnO3 coating layer.

[0009] Preferably, the rare earth is at least one of La, Ce, Pr, and Nd.

[0010] A method for preparing a composite-modified spinel-type lithium nickel manganate positive electrode material according to the present invention comprises the following steps:

[0011] (1) According to the stoichiometric ratio of the chemical formula, nickel salt, manganese salt, rare earth salt, and reactant are placed in a ball milling tank, and after adding water, ball milling reaction treatment is carried out at room temperature to obtain mixture A, wherein the ball milling time is 1-5 h and the rotation speed is 350-450 revolutions per minute;

[0012] (2) The mixture A is washed with water to remove soluble inorganic salts to obtain mixture B;

[0013] (3) According to the stoichiometric ratio of the chemical formula, the mixture B, lithium salt, and fluoride are placed in a ball milling tank, a dispersant is added, and after ball milling evenly at room temperature and drying, a doped lithium nickel manganate precursor C is obtained. The ball milling time is 1-5 h and the rotation speed is 350-450 revolutions per minute;

[0014] (4) The doped lithium nickel manganate precursor C is calcined at 800-950 °C in an air atmosphere for 2-13 h, then naturally cooled to room temperature, pulverized, and sieved to obtain a composite-modified spinel-type lithium nickel manganate positive electrode material.

[0015] Preferably, the lithium salt is selected from one or a combination of several of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate; the nickel salt is selected from one or a combination of several of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate; the manganese salt is selected from one or a combination of several of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate; the reactant is selected from one or a combination of sodium oxalate and sodium carbonate; the rare earth salt is selected from one or a combination of several of rare earth sulfates, rare earth chlorides, and rare earth nitrates; the fluoride is selected from one or a combination of lithium fluoride and ammonium fluoride.

[0016] Preferably, the dispersant in step (3) is at least one of water, ethanol, and acetone.

[0017] Preferably, the drying temperature in step (3) is 90-110 °C.

[0018] Compared with the prior art, the present invention prepares a spinel-type lithium nickel manganate cathode material coated with perovskite-type ReMnO3 co-doped with rare earth and fluorine through a room-temperature solid-phase reaction assisted by high-temperature calcination. During the heating process of the raw materials, rare earth and fluorine enter the transition metal sites and oxygen sites in the spinel-type lithium nickel manganate, respectively. Compared with nickel and manganese elements, rare earth elements have relatively low "solubility" in the spinel phase. With the increase of the calcination temperature, the increased positive charge causes rare earth elements to precipitate on the surface of the spinel phase to form ReMnO3. The present invention can simultaneously regulate the bulk structure and surface properties of the spinel-type lithium nickel manganate, effectively improving the electrochemical reversibility of the spinel-type lithium nickel manganate during charge and discharge. The method of the present invention is simple to operate, the reaction conditions are easy to control, and the cost is low. Description of the Drawings

[0019] Figure 1 XRD pattern of LiNi 0.5 Mn 1.5 O4 prepared in Example 1 of the present invention.

[0020] Figure 2 XRD pattern of LiNi 0.5 Mn 1.5 O4 prepared in Example 1 of the present invention.

[0021] Figure 3 Charge-discharge curve of the lithium-ion half-cell when LiNi 0.5 Mn 1.5 O4 prepared in Example 1 of the present invention is used as the cathode material at a current density of 20 mA g -1 -1.

[0022] Figure 4 Cycling performance of the lithium-ion half-cell when LiNi 0.5 Mn 1.5 O4 prepared in Example 1 of the present invention is used as the cathode material at a current density of 100 mA g -1 -1.

[0023] Figure 5 XRD pattern of LiNi 0.5 La 0.01 Mn 1.49 O4 prepared in Example 2 of the present invention.

[0024] Figure 6 XRD pattern of LiNi 0.5 La 0.01 Mn 1.49 O4 prepared in Example 2 of the present invention.

[0025] Figure 7 The charge-discharge curves of the lithium-ion half-cell when LiNi 0.5 La 0.01 Mn 1.49 O4 prepared in Example 2 of the present invention is used as the cathode material at a current density of 20 mA g -1 .

[0026] Figure 8 The charge-discharge curves of the lithium-ion half-cell when LiNi 0.5 La 0.01 Mn 1.49 O4 prepared in Example 2 of the present invention is used as the cathode material at a current density of 100 mA g -1 .

[0027] Figure 9 The X-ray diffraction (XRD) pattern of LiNi 0.5 Mn 1.5 O 3.97 F 0.03 prepared in Example 3 of the present invention.

[0028] Figure 10 The scanning electron microscope (SEM) image of LiNi 0.5 Mn 1.5 O 3.97 F 0.03 prepared in Example 3 of the present invention.

[0029] Figure 11 The charge-discharge curves of the lithium-ion half-cell when LiNi 0.5 Mn 1.5 O 3.97 F 0.03 prepared in Example 3 of the present invention is used as the cathode material at a current density of 20 mA g -1 .

[0030] Figure 12 The charge-discharge curves of the lithium-ion half-cell when LiNi 0.5 Mn 1.5 O 3.97 F 0.03 prepared in Example 3 of the present invention is used as the cathode material at a current density of 100 mA g -1 .

[0031] Figure 13 The X-ray diffraction (XRD) pattern of LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 prepared in Example 4 of the present invention.

[0032] Figure 14 The scanning electron microscope (SEM) image of LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 prepared in Example 4 of the present invention.

[0033] Figure 15 The charge-discharge curve of the lithium-ion half-cell when LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 prepared in Example 4 of the present invention is used as the cathode material at a current density of 20 mA g -1 .

[0034] Figure 16 The cycling performance of the lithium-ion half-cell when LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 prepared in Example 4 of the present invention is used as the cathode material at a current density of 100 mA g -1 . Detailed implementation manners

[0035] To make the objectives, technical solutions and advantages of the present invention clearer, the preferred implementation manners of the present invention will be further described in detail below with reference to the examples. All other examples obtained by those of ordinary skill in the art based on the examples in this application without creative efforts shall fall within the scope of protection of this application.

[0036] Example 1

[0037] A preparation method of a spinel-type lithium nickel manganate cathode material LiNi 0.5 Mn 1.5 O4 is as follows:

[0038] 7.3689 g of 0.055 mol (10% in excess) of Na2C2O4, 3.2856 g of 0.0125 mol of NiSO4∙6H2O, and 6.3383 g of 0.0375 mol of MnSO4∙H2O powders were placed in a ball milling jar, 10.0 mL of water was added as a dispersant, and the raw materials were ball milled and mixed for 1.5 h at a rotation speed of 400 revolutions per minute for solid-state reaction at room temperature. The soluble inorganic salts in the reaction mixture were washed away with water and the precipitate was collected by filtration to obtain a mixture of nickel and manganese oxalates. Then, the mixture of nickel and manganese oxalates and 1.1015 g of 0.02625 mol of LiOH∙H2O were placed in a ball milling jar, 10.0 mL of ethanol was added as a dispersant, and after ball milling at room temperature for 1.5 h, it was dried at 100 o °C for 2 h to obtain a precursor of LiNi 0.5 Mn 1.5 O4. Finally, the precursor of LiNi 0.5 Mn 1.5 O4 was placed in a muffle furnace and calcined at 850 °C for 12 h. After the calcined product was naturally cooled to about 40 °C, it was ground into powder to obtain spinel-type LiNi 0.5 Mn 1.5 O4.

[0039] The XRD pattern of the LiNi 0.5 Mn 1.5 O4 sample obtained in this example is as shown in Figure 1 . It can be seen from Figure 1 that the characteristic diffraction peaks of the spinel phase (space group Fd-3m(227)) and a weak layered Li o Ni 0.49 O2 diffraction peak at 2θ = 43.6 1.01 °. Figure 2 shows the scanning electron microscope (SEM) image of the LiNi 0.5 Mn 1.5 O4 sample. It can be seen from Figure 2 that the LiNi 0.5 Mn 1.5 O4 particles are in the shape of irregular polyhedra, and the particle size ranges from 500 nm to 7 μm. Figure 3 shows the charge-discharge curves of the half-cell with LiNi 0.5 Mn 1.5 O4 as the cathode material in the voltage range of 3.5 - 4.9 V and at a current density of 20 mA g -1 . The discharge specific capacities of the first cycle and the 10th cycle are 105.9 mAh g -1 and 114.8 mAh g -1 , respectively. Figure 4 shows LiNi 0.5Mn 1.5 The first-cycle discharge specific capacity and the discharge specific capacity after 100 cycles of the Mn -1 -1 O4 sample at a voltage range of 3.5 - 4.9 V and a current density of 100 mA g -1 are 118.0 mAh g -1 and 101.2 mAh g

[0040] Example 2

[0041] A preparation method of a spinel-type lithium nickel manganese oxide cathode material LiNi 0.5 La 0.01 Mn 1.49 O4 is as follows:

[0042] Put 7.3886 g of 0.05514 mol (10% in excess) of Na2C2O4, 3.2856 g of 0.0125 mol of NiSO4∙6H2O, 6.3383 g of 0.03725 mol of MnSO4∙H2O, and 0.0108 g of 0.00025 mol of La(NO4)3∙6H2O powders into a ball milling jar, add 10.0 mL of water as a dispersant, ball mill and mix the raw materials at a rotation speed of 400 revolutions per minute for 1.5 h for room temperature solid-phase reaction, then wash away the soluble inorganic salts in the reaction mixture with water and filter to collect the precipitate to obtain a mixture of nickel, manganese, and lanthanum oxalates. Then put the mixture of nickel, manganese, and lanthanum oxalates and 1.1015 g of 0.02625 mol of LiOH∙H2O into the ball milling jar, add 10.0 mL of ethanol as a dispersant, ball mill at room temperature for 1.5 h, and then dry at 100 o °C for 2 h to obtain the precursor of LiNi 0.5 La 0.01 Mn 1.49 O4. Finally, place the precursor of LiNi 0.5 La 0.01 Mn 1.49 O4 in a muffle furnace and calcine at 850 °C for 12 h. After the calcined product naturally cools to about 40 °C, grind it into powder to obtain spinel-type LiNi 0.5 La 0.01 Mn 1.49 O4.

[0043] The XRD pattern of the LiNi 0.5 La 0.01 Mn 1.49 O4 sample obtained in this example is as shown in Figure 5 . It can be seen from Figure 5 the characteristic diffraction peaks of the spinel phase (space group Fd-3m(227)) and a weak layered Li at 2θ = 43.6 o ​0.49 Ni 1.01 diffraction peaks of O2 and a weak perovskite-type LaMnO3 diffraction peak at 2θ = 33.0 o Figure 6 showed LiNi 0.5 La 0.01 Mn 1.49 Scanning electron microscope (SEM) image of the O4 sample, from which Figure 6 it can be seen that the LiNi 0.5 La 0.01 Mn 1.49 O4 particles are in the shape of irregular polyhedra, and the particle size ranges from 500 nm to 7 μm. Figure 7 showed LiNi 0.5 La 0.01 Mn 1.49 Charge-discharge curves of the half-cell with LiNi -1 La -1 Mn -1 O4 as the cathode material in the voltage range of 3.5 - 4.9 V and at a current density of 20 mA g Figure 8 showed LiNi 0.5 La 0.01 Mn 1.49 Discharge specific capacities of the O4 sample in the voltage range of 3.5 - 4.9 V and at a current density of 100 mA g -1 for the first cycle and after 100 cycles are 114.3 mAh g -1 and 102.6 mAh g -1

[0044] Example 3

[0045] Preparation method of a spinel-type lithium nickel manganate cathode material LiNi 0.5 Mn 1.5 O 3.97 F 0.03 is as follows:

[0046] ​​7.3689 g of 0.055 mol (10% in excess) of Na2C2O4, 3.2856 g of 0.0125 mol of NiSO4∙6H2O, and 6.3383 g of 0.0375 mol of MnSO4∙H2O powders were placed in a ball milling jar, 10.0 mL of water was added as a dispersant, and the raw materials were ball milled and mixed at a rotation speed of 400 revolutions per minute for 1.5 h for solid-state reaction at room temperature. The soluble inorganic salts in the reaction mixture were washed away with water and the precipitate was collected by filtration to obtain a mixture of nickel and manganese oxalates. Then, the mixture of nickel and manganese oxalates, 1.1015 g of 0.02625 mol of LiOH∙H2O, and 0.01945 g of 0.00075 mol of LiF were placed in a ball milling jar, 10.0 mL of ethanol was added as a dispersant, and after ball milling at room temperature for 1.5 h, it was dried at 100 o °C for 2 h to obtain a precursor of LiNi 0.5 Mn 1.5 O 3.97 F 0.03 . Finally, the precursor of LiNi 0.5 Mn 1.5 O 3.97 F 0.03 was placed in a muffle furnace and calcined at 850 °C for 12 h. After the calcined product was naturally cooled to about 40 °C, it was ground into powder to obtain spinel-type LiNi 0.5 Mn 1.5 O 3.97 F 0.03 .

[0047] The XRD pattern of the LiNi 0.5 Mn 1.5 O4 sample obtained in this example is as shown in Figure 9 . It can be seen from Figure 9 that the characteristic diffraction peaks of the spinel phase (space group Fd-3m(227)) and a weak layered Li o Ni 0.49 O2 diffraction peak at 2θ = 43.6 1.01 . Figure 10 shows the scanning electron microscope (SEM) image of the LiNi 0.5 Mn 1.5 O 3.97 F 0.03 sample. It can be seen from Figure 2 that the LiNi 0.5 Mn 1.5 O 3.97 F 0.03 particles are in the shape of irregular polyhedrons, and the particle size ranges from 500 nm to 7 μm. Figure 11 shows the LiNi 0.5 Mn 1.5 O3.97 F 0.03 The charge-discharge curves of the half-cell using this as the positive electrode material within the voltage range of 3.5 - 4.9 V and at a current density of 20 mA g -1 show that the discharge specific capacities in the first cycle and the 10th cycle are 105.9 mAh g -1 and 111.6 mAh g -1 . Figure 12 It shows that the discharge specific capacities of the LiNi 0.5 Mn 1.5 O 3.97 F 0.03 sample within the voltage range of 3.5 - 4.9 V and at a current density of 100 mA g -1 in the first cycle and after 100 cycles are 108.8 mAh g -1 and 102.3 mAh g -1 .

[0048] Example 4

[0049] A preparation method of a spinel-type lithium nickel manganate positive electrode material LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 is as follows:

[0050] Put 7.3886 g of 0.05514 mol (10% in excess) of Na2C2O4, 3.2856 g of 0.0125 mol of NiSO4∙6H2O, 6.2960 g of 0.03725 mol of MnSO4∙H2O, and 0.1083 g of 0.00025 mol of La(NO4)3∙6H2O powders into a ball milling tank, add 10.0 mL of water as a dispersant, ball mill and mix the raw materials at a rotation speed of 400 revolutions per minute for 1.5 h for solid-phase reaction at room temperature, then wash away the soluble inorganic salts in the reaction mixture with water and filter to collect the precipitate to obtain a mixture of nickel, manganese, and lanthanum oxalates. Then, put the mixture of nickel, manganese, and lanthanum oxalates, 1.0701 g of 0.0255 mol of LiOH∙H2O, and 0.01945 g of 0.00075 mol of LiF into a ball milling tank, add 10.0 mL of ethanol as a dispersant, ball mill at room temperature for 1.5 h, and then dry at 100 o °C for 2 h to obtain the precursor of LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 . Finally, put LiNi 0.5 La 0.01 Mn 1.49 O3.97 F 0.03 The precursor was placed in a muffle furnace and calcined at 850 ° C for 12 h. The calcined product was naturally cooled to about 40 ° C and then ground into powder to obtain spinel LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 .

[0051] The LiNi obtained in this example 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 The XRD pattern of the sample is as follows Figure 13 As shown, from Figure 13 The characteristic diffraction peaks of the spinel phase (space group Fd-3m(227)) and a peak at 2θ=43.6 o Weak layered Li 0.49 Ni 1.01 The O2 diffraction peak and one at 2θ=33.0 o Weak perovskite LaMnO3 diffraction peak. Figure 14 Shows LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 Scanning electron microscope (SEM) images of the samples. Figure 14 LiNi can be seen in 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 The particles are irregular polyhedral in shape and the particle size ranges from 500nm to 7μm. Figure 15 Shows LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 As a half-cell cathode material, the voltage range is 3.5 to 4.9 V, 20 mA g -1 The charge and discharge curves under the current density are shown in Figure 1. The discharge capacity of the first and 10th cycles are 109.1 mAh g -1 and 116.4mAh g -1 . Figure 16 Shows LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 The sample was in the voltage range of 3.5~4.9V and 100mA g -1The initial discharge specific capacity at a current density and the discharge specific capacity after 100 cycles are 112.2 mAh g -1 and 105.6 mAh g -1 .

[0052] Example 5

[0053] A preparation method of a spinel-type lithium nickel manganate cathode material LiNi 0.5 La 0.015 Mn 1.485 O 3.98 F 0.02 is as follows:

[0054] Put 7.3980 g of 0.05521 mol (10% excess) Na2C2O4, 3.2856 g of 0.0125 mol NiSO4∙6H2O, 6.2749 g of 0.03713 mol MnSO4∙H2O, and 0.16238 g of 0.000375 mol La(NO4)3∙6H2O powders into a ball milling jar, add 10.0 mL of water as a dispersant, and ball mill and mix the raw materials at a rotation speed of 400 revolutions per minute for 1.5 h for a room temperature solid-phase reaction. Then, wash away the soluble inorganic salts in the reaction mixture with water and filter to collect the precipitate to obtain a mixture of nickel, manganese, and lanthanum oxalates. Next, put the mixture of nickel, manganese, and lanthanum oxalates, 1.08055 g of 0.02575 mol LiOH∙H2O, and 0.01297 g of 0.0005 mol LiF into a ball milling jar, add 10.0 mL of water as a dispersant, ball mill at room temperature for 2 h, and then dry at 100 o °C for 2 h to obtain the precursor of LiNi 0.5 La 0.015 Mn 1.485 O 3.98 F 0.02 . Finally, place the precursor of LiNi 0.5 La 0.015 Mn 1.485 O 3.98 F 0.02 in a muffle furnace and calcine at 900 °C for 3.5 h. After the calcined product naturally cools to about 40 °C, grind it into powder to obtain spinel-type LiNi 0.5 La 0.015 Mn 1.485 O 3.98 F 0.02 .

[0055] Put LiNi 0.5 La 0.015 Mn 1.485 O 3.98 F 0.02The half-cell using this as the positive electrode material has a charge-discharge curve within a voltage range of 3.5 - 4.9 V and a current density of 20 mA g -1 The discharge specific capacities of the first cycle and the 10th cycle are 108.9 mAh g -1 and 116.0 mAh g -1 respectively. For the LiNi 0.5 La 0.015 Mn 1.485 O 3.98 F 0.02 sample, within a voltage range of 3.5 - 4.9 V and a current density of 100 mA g -1 the discharge specific capacities of the first cycle and after 100 cycles are 112.0 mAh g -1 and 105.0 mAh g -1 respectively.

[0056] Example 6

[0057] A preparation method of a spinel-type lithium nickel manganate positive electrode material LiNi 0.5 La 0.04 Mn 1.46 O 3.96 F 0.04 is as follows:

[0058] Put 7.4436 g of 0.05555 mol (10% in excess) of Na2C2O4, 3.2856 g of 0.0125 mol of NiSO4∙6H2O, 6.1692 g of 0.0365 mol of MnSO4∙H2O, and 0.4330 g of 0.001 mol of La(NO4)3∙6H2O powders into a ball milling tank, add 10.0 mL of water as a dispersant, ball mill and mix the raw materials at a rotation speed of 400 revolutions per minute for 1.5 h for a room temperature solid-phase reaction, then wash away the soluble inorganic salts in the reaction mixture with water and filter to collect the precipitate to obtain a mixture of nickel, manganese, and lanthanum oxalates. Then, put the mixture of nickel, manganese, and lanthanum oxalates, 1.0596 g of 0.02525 mol of LiOH∙H2O, and 0.0259 g of 0.001 mol of LiF into a ball milling tank, add 10.0 mL of water as a dispersant, ball mill at room temperature for 3 h and then dry at 100 o °C for 2 h to obtain the precursor of LiNi 0.5 La 0.04 Mn 1.46 O 3.96 F 0.04 Finally, heat the precursor of LiNi 0.5 La 0.04 Mn 1.46 O 3.96 F 0.04The precursor was placed in a muffle furnace and calcined at 900 °C for 3 h. After the calcined product was naturally cooled to about 40 °C, it was ground into powder to obtain spinel-type LiNi 0.5 La 0.04 Mn 1.46 O 3.96 F 0.04 。

[0059] The charge-discharge curves of the half-cell using LiNi 0.5 La 0.04 Mn 1.46 O 3.96 F 0.04 as the cathode material within the voltage range of 3.5 - 4.9 V and at a current density of 20 mA g -1 show that the discharge specific capacities in the first cycle and the 10th cycle are 108.8 mAh g -1 and 115.9 mAh g -1 respectively. The discharge specific capacities of the LiNi 0.5 La 0.04 Mn 1.46 O 3.96 F 0.04 sample within the voltage range of 3.5 - 4.9 V and at a current density of 100 mA g -1 in the first cycle and after 100 cycles are 111.8 mAh g -1 and 104.3 mAh g -1 respectively.

[0060] Example 7

[0061] A preparation method of a spinel-type lithium nickel manganate cathode material LiNi 0.5 La 0.05 Mn 1.45 O 3.95 F 0.05 is as follows:

[0062] 7.4624 g of 0.05569 mol (10% in excess) of Na2C2O4, 3.2856 g of 0.0125 mol of NiSO4∙6H2O, 6.1270 g of 0.03625 mol of MnSO4∙H2O, and 0.5413 g of 0.00125 mol of La(NO4)3∙6H2O powders were placed in a ball milling jar, and 10.0 mL of water was added as a dispersant. The raw materials were ball milled and mixed at a rotation speed of 400 revolutions per minute for 1.5 h for room temperature solid-phase reaction. Then, the soluble inorganic salts in the reaction mixture were washed away with water and the precipitate was collected by filtration to obtain a mixture of nickel, manganese, and lanthanum oxalates. Next, the mixture of nickel, manganese, and lanthanum oxalates, 1.0491 g of 0.025 mol of LiOH∙H2O, and 0.0324 g of 0.00125 mol of LiF were placed in a ball milling jar, and 10.0 mL of ethanol was added as a dispersant. After ball milling at room temperature for 2 h, it was dried at 100 o °C for 2 h to obtain a precursor of LiNi 0.5 La 0.05 Mn 1.45 O 3.95 F 0.05 . Finally, the precursor of LiNi 0.5 La 0.05 Mn 1.45 O 3.95 F 0.05 was placed in a muffle furnace and calcined at 900 °C for 4 h. After the calcined product was naturally cooled to about 40 °C, it was ground into powder to obtain spinel-type LiNi 0.5 La 0.05 Mn 1.45 O 3.95 F 0.05 .

[0063] The charge-discharge curves of the half-cell with LiNi 0.5 La 0.05 Mn 1.45 O 3.95 F 0.05 as the cathode material in the voltage range of 3.5 - 4.9 V and at a current density of 20 mA g -1 . The discharge specific capacities of the first cycle and the 10th cycle are 108.4 mAh g -1 and 115.5 mAh g -1 , respectively. The LiNi 0.5 La 0.05 Mn 1.45 O 3.95 F 0.05 sample in the voltage range of 3.5 - 4.9 V and at a current density of 100 mA g -1The initial discharge specific capacity and the discharge specific capacity after 100 cycles at a current density are 111.3 mAh g -1 and 104.0 mAh g -1 .

[0064] Example 8

[0065] A preparation method of a spinel-type lithium nickel manganese fluoride cathode material LiNi 0.5 La 0.01 Mn 1.49 O 3.96 F 0.04 is as follows:

[0066] Put 5.8440 g of 0.05514 mol (10% in excess) of Na2CO3, 3.6349 g of 0.0125 mol of Ni(NO3)2∙6H2O, 9.3501 g of 0.03725 mol of Mn(NO3)2∙4H2O, and 0.1083 g of 0.00025 mol of La(NO3)3∙6H2O powders into a ball milling jar, add 15.0 mL of water as a dispersant, and ball mill and mix the raw materials at a rotation speed of 420 revolutions per minute for 2.0 h for room temperature solid-phase reaction. Then, wash away the soluble inorganic salts in the reaction mixture with water and filter to collect the precipitate to obtain a mixture of nickel, manganese, and lanthanum oxalates. Next, put the mixture of nickel, manganese, and lanthanum carbonates, 0.9329 g of 0.01263 mol of Li2CO3, and 0.0259 g of 0.001 mol of LiF into a ball milling jar, add 10.0 mL of ethanol as a dispersant, ball mill at room temperature for 2 h, and then dry at 100 o °C for 2 h to obtain the precursor of LiNi 0.5 La 0.01 Mn 1.49 O 3.96 F 0.04 . Finally, place the precursor of LiNi 0.5 La 0.01 Mn 1.49 O 3.96 F 0.04 in a muffle furnace and calcine at 890 °C for 5 h. After the calcined product naturally cools to about 40 °C, grind it into powder to obtain the spinel-type LiNi 0.5 La 0.01 Mn 1.49 O 3.96 F 0.04 .

[0067] Put LiNi 0.5 La 0.01 Mn 1.49 O 3.96 F 0.04The charge-discharge curves of the half-cell using this as the cathode material within the voltage range of 3.5 - 4.9 V and at a current density of 20 mA g -1 show that the discharge specific capacities in the first cycle and the 10th cycle are 108.7 mAh g -1 and 115.7 mAh g -1 respectively. For the LiNi 0.5 La 0.01 Mn 1.49 O 3.96 F 0.04 sample, within the voltage range of 3.5 - 4.9 V and at a current density of 100 mA g -1 the discharge specific capacities in the first cycle and after 100 cycles are 111.9 mAh g -1 and 104.9 mAh g -1 respectively.

[0068]

[0069] From the lithium storage performance of spinel-type lithium nickel manganate prepared under different technical conditions in Table 1, it can be seen that the lithium storage performance of spinel-type lithium nickel manganate mainly depends on its composition. Among them, the spinel-type lithium nickel manganate with the composition of LiNi 0.5 La 0.01 Mn 1.49 O 3.97 F 0.03 has a relatively high discharge specific capacity in the first cycle, cycling stability and discharge voltage platform. Therefore, the spinel-type lithium nickel manganate with this composition has a relatively large output power. In addition, a relatively high lanthanum doping amount will reduce the discharge specific capacity of this material because the molar mass of lanthanum is much larger than that of nickel and manganese. This method directly uses nickel salts and manganese salts, which are the raw materials for producing nickel oxide and manganese oxide, as the raw materials for preparing lithium nickel manganate, so the cost of the material can be significantly reduced.

[0070] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

Claims

1. A preparation method of a composite modified spinel-type lithium nickel manganate cathode material, characterized in that The chemical formula of the positive electrode material is as follows: LiNi 0.5 Re x Mn 1.5-x O 4-y F y , where 0 < x ≤ 0.08, 0 < y ≤ 0.06, and Re is a rare earth element; the positive electrode material has a core-shell structure, where the core layer is spinel-type lithium nickel manganate with a space group of Fd-3m(227), and the shell layer is a perovskite-type ReMnO3 coating layer; The preparation method of the positive electrode material comprises the following steps: (1) According to the stoichiometric ratio of the chemical formula, nickel salt, manganese salt, rare earth salt and reactant are placed in a ball milling tank, and after adding water, ball milling reaction treatment is carried out at room temperature to obtain mixture A, wherein the ball milling time is 1 - 5 h and the rotation speed is 350 - 450 revolutions per minute; (2) Wash the mixture A with water to remove soluble inorganic salts to obtain mixture B; (3) According to the stoichiometric ratio of the chemical formula, place the mixture B, lithium salt and fluoride in a ball milling tank, add a dispersant, ball mill evenly at room temperature and then dry to obtain a doped lithium nickel manganate precursor C, the ball milling time is 1 - 5 h and the rotation speed is 350 - 450 revolutions per minute; (4) Calcinate the doped lithium nickel manganate precursor C at 800 - 950 °C in an air atmosphere for 2 - 13 h, then naturally cool to room temperature, pulverize, and sieve to obtain a composite modified spinel - type lithium nickel manganate positive electrode material; During the calcination heating process, the raw materials experience the entry of rare earth and fluorine into the transition metal site and oxygen site of spinel - type lithium nickel manganate respectively. Compared with nickel and manganese elements, the "solubility" of rare earth elements in the spinel phase is relatively low. With the increase of the calcination temperature, the increased positive charge causes the rare earth elements to precipitate on the surface of the spinel phase to form ReMnO3.

2. The preparation method of a composite modified spinel-type lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The rare earth is at least one of La, Ce, Pr, and Nd.

3. The preparation method of a composite modified spinel-type lithium nickel manganate cathode material according to claim 1, characterized in that, The lithium salt is selected from one or a combination of several of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate; the nickel salt is selected from one or a combination of several of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate; the manganese salt is selected from one or a combination of several of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate; the reactant is selected from one or a combination of sodium oxalate and sodium carbonate; the rare earth salt is selected from one or a combination of several of rare earth sulfate, rare earth chloride, and rare earth nitrate; the fluoride is selected from one or a combination of lithium fluoride and ammonium fluoride.

4. The preparation method of a composite modified spinel-type lithium nickel manganate cathode material as described in claim 1, characterized in that, The dispersant in step (3) is at least one of water, ethanol, and acetone.

5. The preparation method of a composite modified spinel-type lithium nickel manganate cathode material as described in claim 1, characterized in that, The drying temperature in step (3) is 90 - 110 °C.

6. Application of the composite modified spinel - type lithium nickel manganate positive electrode material obtained by the preparation method according to any one of claims 1 - 5 in a lithium - ion battery.

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