High-voltage lithium nickel manganese oxide positive electrode material and preparation method thereof, battery positive electrode and battery

Abstract

The invention discloses a high-voltage lithium nickel manganese oxide positive electrode material and a preparation method thereof, a battery positive electrode and a battery, and belongs to the technical field of lithium ion battery materials. Comprising an inner core composed of a lithium-containing compound, the inner core is coated with a shell composed of tungstate, and a transition layer is arranged between the inner core and the shell. The tungstate has good chemical and thermodynamic stability, can prevent erosion of HF in the electrolyte, inhibit dissolution of transition metal, reduce the shuttle effect, and can greatly improve the capacity retention rate of the battery. The preparation method is simple in process steps and convenient for large-scale preparation. Meanwhile, the cathode material coated with magnesium tungstate, calcium tungstate or bismuth tungstate has good dynamic performance, the capacity and the rate capability are remarkably improved, meanwhile, the stability of the material is also remarkably improved, and a good application way is provided for application of the high-voltage type lithium nickel manganese oxide cathode.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and relates to a high-voltage lithium nickel manganese oxide positive electrode material and a preparation method thereof, a battery positive electrode, and a battery. Background Art

[0002] Lithium-ion batteries are considered the most suitable energy source for the new energy industry due to their excellent performance. Currently, the main battery materials that have been commercially applied are layered materials (including ternary materials and lithium cobalt oxide), olivine materials (lithium iron phosphate), and spinel materials (lithium manganese oxide). With the rapid development of the new energy industry, people have higher requirements for the range of electric vehicles, so high capacity and high voltage are the new trends in the development of new generation materials. High-voltage lithium nickel manganese oxide is considered to be the most promising next-generation cathode material due to its high average voltage, excellent kinetic performance, low cost, and environmental protection.

[0003] Currently, lithium iron phosphate (LFP) remains the most widely used cathode material in the power battery and energy storage industries due to its low cost. High-voltage LMNCO cathodes, however, boast high lithium ion utilization efficiency, an average voltage 1.4-1.5 times that of LFP, a compaction density 1.2-1.3 times that of LFP, and a volumetric energy density 1.6-1.7 times that of LFP. Furthermore, their watt-hour cost is 0.8-0.9 times that of LFP. Therefore, high-voltage LMNCO is considered the most likely replacement for current LFP cathodes.

[0004] High-voltage lithium nickel manganese oxide has the advantages of high energy density and low cost, and its advantages are mainly due to its operating voltage of 4.7V. A higher operating voltage means higher energy density and lower cost at the same capacity. At the same time, high voltage also has many problems. For example, for high-voltage materials, the battery system needs to be reasonably matched, and high-voltage electrolyte is an important part of the application of high-voltage positive electrode materials. Because the voltage of the positive electrode material is too high, the positive electrode interface oxidation ability is very strong, especially at high temperatures, it is very easy to cause the positive electrode to oxidize and decompose the electrolyte, which in turn leads to problems such as battery gas production, increased interface impedance, and capacity attenuation. Therefore, it is necessary to provide a new high-voltage lithium nickel manganese oxide positive electrode material and a preparation method thereof. Summary of the Invention

[0005] The present invention aims to provide a high-voltage lithium nickel manganese oxide cathode material, its preparation method, battery cathode, and battery, which exhibit stable surface and interfacial structures, excellent kinetics, and high stability at high temperatures. This material inhibits oxidative decomposition of the electrolyte and corrosion and dissolution of transition metals under the harsh conditions of high delithiation and high temperature, thereby improving charge and discharge coulombic efficiency, cycle capacity retention, storage gas production, and charge retention.

[0006] The first technical solution adopted by the present invention is a high-voltage lithium nickel manganese oxide positive electrode material, which includes a core composed of a lithium-containing compound, a shell composed of tungstate coated on the core, and a transition layer between the core and the shell.

[0007] The characteristics of this technical solution are:

[0008] The chemical formula of the lithium-containing compound in the core is LiNi 0.5-a Mn 1.5-b M c W e N f O 4-d , among which: -0.2≤a≤0.2, -0.2≤b≤0.2, 0≤c≤0.1, -0.3≤d≤0.3, 0≤e≤0.1, 0≤f≤0.1.

[0009] The chemical formula of the tungstate shell is N x W y O z , wherein N is selected from one or more elements of Ca, Mg, and Bi.

[0010] The tungstate of the shell is CaWO4, MgWO4 and Bi2 W3O 12 At least one of .

[0011] The chemical formula of the transition layer is LiNi m Mn n M l W g N h O i , wherein M is selected from one or more elements of Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si, 0.3≤m≤0.55, 1.3≤n≤1.55, 0<l≤0.1, 0<g≤0.1, 0<h≤0.1, 3.7≤i≤4.1.

[0012] The second technical solution adopted by the present invention is a method for preparing a high-voltage lithium nickel manganese oxide positive electrode material, which is specifically implemented according to the following steps:

[0013] Step 1: uniformly mixing a precursor, a lithium-containing compound, and an additive to obtain a primary mixture powder; wherein the additive is doped with one or more elements selected from the group consisting of Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F, and Si;

[0014] Step 2: Sintering the mixture powder at high temperature in an air atmosphere, followed by crushing and sieving to obtain a primary sintered material;

[0015] Step 3: Evenly mix the primary sintered material with tungstate to obtain a secondary mixture powder; wherein the tungstate is doped with one or more elements of Ca, Mg, and Bi;

[0016] Step 4: Sinter the secondary mixture powder in an air atmosphere, and then crush and sieve it to obtain a secondary sintered material, which is a high-voltage lithium nickel manganese oxide positive electrode material.

[0017] The characteristics of this technical solution are:

[0018] In step 1, the D50 of the precursor is 3 μm to 12 μm.

[0019] In step 2, the sintering temperature is 700° C. to 1000° C., the sintering time is 6 h to 10 h, and the D50 of the primary sintered material is 3 μm to 12 μm.

[0020] In step 3, the D50 of tungstate is 50 nm to 200 nm.

[0021] In step 4, the heating and cooling rate of sintering is 1°C / min to 5°C / min, and the mixed sintering is carried out at 300°C to 800°C for 4h to 8h. The D50 of the secondary sintered material is 3um to 12um.

[0022] The third technical solution adopted by the present invention is a lithium-ion secondary battery positive electrode, including a current collector on which the above-mentioned high-voltage lithium nickel manganese oxide positive electrode material is loaded.

[0023] The fourth technical solution adopted by the present invention is a lithium-ion secondary battery, which includes a separator, an electrolyte, a negative electrode and the above-mentioned lithium-ion secondary battery positive electrode.

[0024] The high-voltage lithium nickel manganese oxide positive electrode material provided by the present invention has a coating layer of magnesium tungstate, calcium tungstate or bismuth tungstate. Due to the strong tungsten-oxygen bond energy and high stability, the high oxidizability of the surface of the positive electrode material is not easy to oxidize and decompose the tungstate coating layer, and at the same time, it also has an insulating and protective effect on the electrolyte, inhibiting its decomposition and gas production. On the other hand, tungstate has good chemical and thermodynamic stability, which can prevent the corrosion of HF in the electrolyte, inhibit the dissolution of transition metals, reduce the shuttle effect, and greatly improve the capacity retention rate of the battery. In addition, bismuth tungstate has a high dielectric constant and good capacitance performance, generally with higher capacity and rate performance. Calcium tungstate has good electrochemical properties, and nano magnesium tungstate and calcium tungstate have good specific surface area and good charge transfer performance. At the same time, when compounded with conductive polymers, they have excellent energy storage performance, so there will be higher material specific capacity and cycle stability. Among them, especially magnesium tungstate, the magnesium element can diffuse into the lithium nickel manganese oxide material matrix during the coating process, further enhancing the stability of the material and significantly increasing the material cycle performance, especially the cycle performance of the material at high temperature.

[0025] The method for preparing high-voltage positive electrode active materials features simple process steps and is convenient for large-scale production. Furthermore, the positive electrode materials coated with magnesium tungstate, calcium tungstate, or bismuth tungstate exhibit excellent kinetic properties, significantly improved capacity and rate performance, and significantly improved material stability, providing a promising application path for high-voltage lithium nickel manganese oxide positive electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of the high-voltage lithium nickel manganese oxide positive electrode material of the present invention;

[0027] Figure 2 This is the SEM of the primary sintered material in Example 1 of the present invention;

[0028] Figure 3 This is the SEM of the secondary sintered material in Example 1 of the present invention.

[0029] In the figure, 1, inner core; 2, transition layer; 3, outer shell. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Due to its extremely high operating voltage (4.7V), high-voltage lithium nickel manganese oxide has a strong oxidizing ability on the surface of the positive electrode material, which easily leads to the decomposition of carbonate solvents in the electrolyte, thereby causing interfacial problems such as gas production. On the other hand, trace amounts of water in the material and the electrolyte lead to the generation of HF, which further corrodes the surface of the positive electrode material, causing the dissolution of transition metals, and thus causing the attenuation of the positive electrode material. Based on this, the present invention provides a high-voltage lithium nickel manganese oxide positive electrode material. The details are as follows:

[0032] like Figure 1 As shown, the high voltage lithium nickel manganese oxide positive electrode material of the present invention is composed of a core 1, a transition layer 2 and a shell 3 from the inside to the outside. 0.5-a Mn 1.5-b M c W e N f O 4-d A lithium-containing compound, wherein M is selected from one or more doping elements of Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si, -0.1≤a≤0.1, -0.2≤b≤0.2, 0≤c≤0.1, -0.3≤d≤0.3, 0≤e≤0.1, and 0≤f≤0.1.

[0033] Shell 3 is a tungstate coating layer N x W y Oz , wherein N is selected from one or more elements of Ca, Mg, and Bi. Specifically, it can be CaWO4, MgWO4, and Bi2 W3O 12 At least one of;

[0034] There is a transition layer 2 between the core 1 and the shell 3. The transition layer 2 is LiNi m Mn n M l W g N h O i , wherein M is selected from one or more elements of Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si, wherein N is selected from one or more elements of Ca, Mg, Bi, 0.3≤m≤0.55, 1.3≤n≤1.55, 0<l≤0.1, 0<g≤0.1, 0<h≤0.1, 3.7≤i≤4.1.

[0035] The high-voltage lithium nickel manganese oxide positive electrode material provided by the present invention has a coating layer of magnesium tungstate, calcium tungstate or bismuth tungstate. Due to the strong tungsten-oxygen bond energy and high stability, the high oxidizability of the surface of the positive electrode material is not easy to oxidize and decompose the tungstate coating layer, and it also has an isolating and protective effect on the electrolyte, inhibiting its decomposition and gas production. On the other hand, tungstate has good chemical and thermodynamic stability, which can prevent the corrosion of HF in the electrolyte, inhibit the dissolution of transition metals, reduce the shuttle effect, and can greatly improve the capacity retention rate of the battery. In addition, bismuth tungstate has a higher dielectric constant, good capacitance performance, and generally has higher capacity and rate performance. Magnesium tungstate and calcium tungstate also have good electrochemical properties. Nano magnesium tungstate and calcium tungstate have a good specific surface area and good charge transfer performance. At the same time, when compounded with conductive polymers, they have excellent energy storage performance, so there will be higher material gram capacity and cycle stability. For further explanation, the following comparative examples are provided:

[0036] Comparative Example 1

[0037] Weigh 100 g of nickel manganese hydroxide precursor and 21.46 g of lithium carbonate, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0038] Comparative Example 2

[0039] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of sodium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0040] Comparative Example 3

[0041] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of strontium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0042] Comparative Example 4

[0043] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of cobalt oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0044] Comparative Example 5

[0045] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate and 0.50g of iron oxide, put them into a small mixer and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace and calcine it at 900°C for 10 hours. The primary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0046] Comparative Example 6

[0047] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of cerium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0048] Comparative Example 7

[0049] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of aluminum oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0050] Comparative Example 8

[0051] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate and 0.50g of zirconium oxide, put them into a small mixer and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace and calcine it at 900°C for 10 hours. The primary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0052] Comparative Example 9

[0053] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of titanium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0054] Comparative Example 10

[0055] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of antimony oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0056] Comparative Example 11

[0057] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of rubidium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0058] Comparative Example 12

[0059] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate and 0.50g of lithium sulfide, put them into a small mixer and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace and calcine it at 900°C for 10 hours. The primary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0060] Comparative Example 13

[0061] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of ammonium dihydrogen phosphate, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0062] Comparative Example 14

[0063] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of boron oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0064] Comparative Example 15

[0065] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of lithium fluoride, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0066] Comparative Example 16

[0067] Weigh 100 g of nickel manganese hydroxide precursor, 21.46 g of lithium carbonate, and 0.50 g of silicon oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0068] Comparative Example 17

[0069] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.25g of antimony oxide and 0.25g of aluminum oxide, put them into a small mixer and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace and calcine it at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0070] Comparative Example 18

[0071] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.25g of antimony oxide, and 0.25g of cobalt oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0072] Comparative Example 19

[0073] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0074] In the above comparative examples, one or more elements selected from Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si were not added to comparative example 1, and one or more elements selected from Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si were added to comparative examples 2-19. In order to verify the effect of adding the corresponding oxides, physical and chemical tests and battery tests were carried out on the primary sintered materials in each comparative example, wherein the particle size, specific surface area and pH value were tested according to industry standard methods. The battery was subjected to 0.1C gram capacity and 1C100 high temperature 45°C cycle tests, wherein the active material loading was 95%, the surface density was controlled at 8-10 mg / cm2, and the electrochemical window was 3.5-4.95V. The test data are shown in Table 1.

[0075] Table 1 Physical and chemical and battery test data of the primary sintered materials in the comparative example

[0076]

[0077]

[0078] It can be seen that with the increase of sintering time, the particle size of the material becomes slightly larger, and after adding oxides doped with Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si, the capacity and high-temperature cycle retention rate are improved to varying degrees. This is mainly because after the doping of metal oxides, the lithium ion channel of the high-voltage lithium nickel manganese oxide is further broadened, and lithium ions are easier to transfer; and the doping of non-metallic elements enhances the bond energy, the material structure is more stable, and the stability of the samples doped with anions and cations is significantly better.

[0079] To further illustrate the preparation method of a high-voltage lithium nickel manganese oxide positive electrode material of the present invention, the following specific examples are provided for illustration.

[0080] Example 1

[0081] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0082] 100g of the primary sintered material was mixed evenly with 0.05g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 500°C for 6 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0083] Example 2

[0084] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0085] 100g of the primary sintered material was mixed evenly with 0.20g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 500°C for 6 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0086] Example 3

[0087] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0088] 100g of the primary sintered material was mixed evenly with 0.50g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 500°C for 6 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0089] Example 4

[0090] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0091] 100g of the primary sintered material was mixed evenly with 2.00g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 500°C for 6 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0092] Example 5

[0093] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0094] 100g of the primary sintered material was mixed evenly with 5.00g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 500°C for 6 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0095] The high-voltage lithium nickel manganese oxide cathode materials prepared in Examples 1-5 were subjected to physical, chemical, and battery testing. Particle size, specific surface area, and pH were measured according to industry standard methods. Cycling tests were conducted at 0.1C gram capacity and 1C for 100 cycles at 45°C. The active material loading was 95%, the areal density was controlled between 8-10 mg / cm², and the electrochemical window was 3.5-4.95V. The results are shown in Table 2.

[0096] Table 2 Physical and chemical properties and battery test data of the positive electrode materials prepared in the examples

[0097] Example D50 / um BET / m2 / g pH 0.1C gram capacity First effect / % 100 times retention rate 1 5.36 0.7055 8.47 133.93 88.28 97.28 2 5.77 0.8147 8.88 134.88 89.95 98.45 3 5.69 0.7795 9.15 135.06 89.69 98.39 4 5.28 0.8961 9.20 134.19 88.42 98.29 5 5.19 0.8744 9.12 132.27 89.10 97.73

[0098] It can be seen from Table 2 that after the experiment with different coating amounts of bismuth tungstate, its BET is significantly improved. At the same time, the primary sintered material and the secondary sintered material in Example 1 were scanned by electron microscope, and the SEM results were as follows: Figure 2 and Figure 3 As shown. It can be seen that the surface of the primary sintered material is smooth, while the surface of the secondary sintered material after coating is uniformly coated with nano-bismuth tungstate, so the BET is improved. At the same time, the nano-coating agent also significantly improves the kinetic performance of the high-voltage lithium nickel manganese oxide positive electrode material, with the capacity increased by more than 1.5mAh / g; as the coating amount increases, its capacity and retention rate also gradually increase. However, when the additive dosage exceeds 2%, its performance remains basically unchanged or deteriorates. This is because the coating layer becomes thicker, resulting in limited lithium ion transmission.

[0099] Example 6

[0100] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0101] 100g of the primary sintered material was mixed evenly with 0.20g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 300°C for 4 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0102] Example 7

[0103] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0104] 100g of the primary sintered material was mixed evenly with 0.20g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 450°C for 6 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0105] Example 8

[0106] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0107] 100g of the primary sintered material was mixed evenly with 0.20g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at 600°C for 8 hours at a heating and cooling rate of 2°C / min. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0108] Example 9

[0109] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0110] 100g of the primary sintered material was mixed evenly with 0.20g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at 700°C for 7 hours at a heating and cooling rate of 2°C / min. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0111] Example 10

[0112] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0113] 100g of the primary sintered material was mixed evenly with 0.20g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 800°C for 5 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0114] The high-voltage lithium nickel manganese oxide cathode materials prepared in Examples 6-10 were subjected to physical, chemical, and battery testing. Particle size, specific surface area, and pH were measured according to industry standard methods. Cycling tests were conducted at 0.1C gram capacity and 100 cycles at 1C at 45°C. The active material loading was 95%, the areal density was controlled between 8-10 mg / cm², and the electrochemical window was 3.5-4.95V. The results are shown in Table 3.

[0115] Table 3 Physical and chemical properties and battery test data of the positive electrode materials prepared in the examples

[0116] Example D50 / um BET / m2 / g pH 0.1C gram capacity First effect / % 100 times retention rate 6 5.52 0.8043 8.72 133.82 89.18 97.40 7 5.41 0.8247 8.45 134.18 88.99 97.54 8 5.19 0.7995 8.70 135.33 89.34 98.39 9 5.27 0.7317 8.89 134.36 88.82 98.18 10 5.37 0.7052 8.81 133.47 89.41 96.92

[0117] Table 3 shows that different temperatures and sintering times have varying effects on the coating effect of bismuth tungstate. As the temperature increases, the nanocoating agent gradually diffuses into the material interface, reducing its BET value. Furthermore, a sintering temperature of 600-700°C and a holding time of 7-8 hours are optimal. This process achieves excellent material capacity and stability.

[0118] Example 11

[0119] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0120] 100g of the primary sintered material was mixed evenly with 0.30g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at 700°C for 7 hours at a heating and cooling rate of 2°C / min. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0121] Example 12

[0122] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0123] 100g of the primary sintered material was mixed evenly with 0.30g of calcium tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 700°C for 7 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0124] Example 13

[0125] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0126] 100g of the primary sintered material was mixed evenly with 0.30g of magnesium tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at 700°C for 7 hours at a heating and cooling rate of 2°C / min. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0127] Example 14

[0128] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0129] 100g of the primary sintered material was mixed evenly with 0.15g of magnesium tungstate and 0.15g of bismuth tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 700°C for 7 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0130] Example 15

[0131] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0132] 100g of the primary sintered material was mixed evenly with 0.15g of magnesium tungstate and 0.15g of calcium tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 700°C for 7 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0133] Example 16

[0134] Weigh 100g of nickel manganese hydroxide precursor, 21.46g of lithium carbonate, 0.17g of diammonium dihydrogen phosphate, 0.17g of cobalt oxide, and 0.17g of zirconium oxide, put them into a small mixer, and stir for 30 minutes to obtain a primary mixture powder; then, place the primary mixture powder in a box furnace, calcine at 900°C for 10 hours, and obtain a primary sintered material by crushing and passing through a 325-mesh sieve.

[0135] 100g of the primary sintered material was mixed evenly with 0.10g of magnesium tungstate, 0.10g of bismuth tungstate, and 0.10g of calcium tungstate to obtain a secondary mixture powder. The secondary mixture powder was then sintered in an air atmosphere in a box furnace at a heating and cooling rate of 2°C / min at 700°C for 7 hours. The mixture was then crushed and passed through a 325-mesh sieve to obtain the secondary sintered material, which is the high-voltage lithium nickel manganese oxide cathode material.

[0136] The high-voltage lithium nickel manganese oxide cathode materials prepared in Examples 11-16 were subjected to physical, chemical, and battery testing. Particle size, specific surface area, and pH were measured according to industry standard methods. Cycling tests were conducted at 0.1C gram capacity and 1C for 100 cycles at 45°C. The active material loading was 95%, the areal density was controlled between 8-10 mg / cm², and the electrochemical window was 3.5-4.95V. The results are shown in Table 4.

[0137] Table 4 Physical and chemical properties and battery test data of the positive electrode materials prepared in the examples

[0138] Example D50 / um BET / m2 / g pH 0.1C gram capacity First effect / % 100 times retention rate 11 5.15 0.7518 8.43 134.36 89.28 98.28 12 5.29 0.7334 8.49 134.42 89.79 97.48 13 4.99 0.7982 8.18 134.41 89.25 97.66 14 5.72 0.7529 8.94 134.83 88.99 98.25 15 5.38 0.7052 8.39 134.47 89.16 98.95 16 5.51 0.7283 8.47 134.92 88.41 98.73

[0139] As can be seen in Table 4, different tungstate coatings have different effects. The high-temperature cycling performance of the cathode material coated with bismuth tungstate is slightly better than that of magnesium tungstate and calcium tungstate. Coordinated coating with multiple tungstates can further improve the capacity and high-temperature cycling retention of the cathode. Coating with magnesium tungstate and calcium tungstate significantly improves the capacity, initial efficiency, and retention of lithium nickel manganese oxide. This is because the higher dielectric constant of bismuth tungstate can improve capacity and rate performance, while magnesium tungstate and calcium tungstate have good electrochemical and thermodynamic stability, which can increase the material capacity and improve the high-temperature stability of the cathode material.

[0140] In addition, the present invention also relates to a lithium-ion secondary battery positive electrode, which includes a current collector on which the above-mentioned high-voltage lithium nickel manganese oxide positive electrode active material is loaded; and also relates to a lithium-ion secondary battery, which includes a diaphragm, an electrolyte, a negative electrode and the above-mentioned lithium-ion secondary battery positive electrode.

[0141] According to the disclosure and teachings of the above description, those skilled in the art to which the present invention belongs may also change and modify the above-mentioned embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention. As described in the above-mentioned embodiments of the present invention, other materials, preparation methods, and applications obtained by the same or similar methods and components are all within the scope of protection of the present invention.

Claims

1. A high voltage lithium nickel manganese oxide positive electrode material, characterized in that: The invention comprises a core (1) composed of a lithium-containing compound, the core (1) is coated with an outer shell (3) composed of tungstate, and a transition layer (2) is provided between the core (1) and the outer shell (3).

2. A high voltage lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The lithium-containing compound of the core (1) has the chemical formula LiNi 0.5-a Mn 1.5-b M c W e N f O 4-d , among which: -0.2≤a≤0.2, -0.2≤b≤0.2, 0≤c≤0.1, -0.3≤d≤0.3, 0≤e≤0.1, 0≤f≤0.

1.

3. The high-voltage lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The chemical formula of the tungstate of the shell (3) is N x W y O z , wherein N is selected from one or more elements of Ca, Mg, and Bi.

4. The high-voltage lithium nickel manganese oxide positive electrode material according to claim 3, characterized in that: The tungstate of the shell (3) is CaWO4, MgWO4 and Bi2 W3O 12 At least one of .

5. The high-voltage lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The chemical formula of the transition layer (2) is LiNi m Mn n M l W g N h O i , wherein M is selected from one or more elements of Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F and Si, 0.3≤m≤0.55, 1.3≤n≤1.55, 0<l≤0.1, 0<g≤0.1, 0<h≤0.1, 3.7≤i≤4.

1.

6. A method for preparing a high-voltage lithium nickel manganese oxide positive electrode material, for preparing a high-voltage lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 5, characterized in that: Please follow the steps below to implement it: Step 1: uniformly mixing a precursor, a lithium-containing compound, and an additive to obtain a primary mixture powder; wherein the additive is doped with one or more elements selected from the group consisting of Na, Sr, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, S, P, B, F, and Si; Step 2: Sintering the mixture powder at high temperature in an air atmosphere, followed by crushing and sieving to obtain a primary sintered material; Step 3: Evenly mix the primary sintered material with tungstate to obtain a secondary mixture powder; wherein the tungstate is doped with one or more elements of Ca, Mg, and Bi; Step 4: Sinter the secondary mixture powder in an air atmosphere, and then crush and sieve it to obtain a secondary sintered material, which is a high-voltage lithium nickel manganese oxide positive electrode material.

7. The method for preparing a high-voltage lithium nickel manganese oxide positive electrode material according to claim 6, characterized in that: In the step 2, the sintering temperature is 700° C. to 1000° C., the sintering time is 6 h to 10 h, and the D50 of the primary sintered material is 3 μm to 12 μm.

8. The method for preparing a high-voltage lithium nickel manganese oxide positive electrode material according to claim 6, characterized in that: In the step 4, the heating and cooling rate of the sintering is 1° C. / min to 5° C. / min, the mixing and sintering are carried out at 300° C. to 800° C. for 4 to 8 hours, and the D50 of the secondary sintered material is 3 μm to 12 μm.

9. A positive electrode for a lithium-ion secondary battery, characterized in that: The invention comprises a current collector, on which is loaded any one of the high-voltage lithium nickel manganese oxide positive electrode materials according to claims 1 to 5.

10. A lithium ion secondary battery, characterized in that: The invention comprises a separator, an electrolyte, a negative electrode and a positive electrode of a lithium ion secondary battery as claimed in claim 9.

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