A magnesium-copper co-doped NCM-type high-nickel ternary material, its preparation method and application

Abstract

This invention relates to a magnesium-copper co-doped NCM-type high-nickel ternary material, its preparation method, and its applications. The chemical composition of the magnesium-copper co-doped NCM high-nickel ternary material is LiNi. 1‑x‑y‑z‑ a Co x Mn y Mg z Cu a O2; where 0.05≤x≤0.15, 0.05≤y≤0.15, 0<z≤0.03, 0<a≤0.03.

Description

Technical Field

[0001] This invention relates to a magnesium-copper co-doped NCM-type high-nickel ternary material, its preparation method, and its application, belonging to the field of battery material technology. Background Technology

[0002] Lithium-ion batteries (LIBs) play a crucial role in electric vehicles and energy storage power stations due to their high energy density, low cost, and long cycle life. However, the energy density of current LIB technologies is still primarily limited by the cathode material, making it difficult to meet the long-range requirements of electric vehicles. Therefore, there is an urgent need to develop cathode materials with high specific capacity. Among these, layered ternary materials like LiNi are particularly important. b Co c Mn d O2, especially high-nickel layered materials with b≥0.6, reduces the amount of cobalt used while increasing the nickel content, thereby reducing costs and increasing the energy density of the material. It has been successfully commercialized and applied to electric vehicles.

[0003] However, NCM materials still face some challenges in practical applications. Increased Ni content leads to severe lithium-nickel mixing, affecting the structural stability of the cathode material and causing performance degradation. Furthermore, surface structural reorganization and phase transitions during long-cycle cycles; oxygen evolution reactions at high potentials and interfacial side reactions between electrolytes; and the generation and propagation of microcracks induced by anisotropic strain, allowing electrolyte to penetrate the particle interior, also contribute to capacity decay and can trigger safety issues. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a Mg / Cu co-doped NCM high-nickel ternary material, its preparation method, and its applications. This invention optimizes the structural stability of the material by reducing lithium-nickel mixing, promoting its sintering performance, and improving its high-temperature cycling performance and thermal stability.

[0005] In a first aspect, the present invention provides a magnesium-copper co-doped NCM high-nickel ternary material, wherein the chemical composition of the magnesium-copper co-doped NCM high-nickel ternary material is LiNi. 1-x-y-z-a Co x Mn y Mg z Cu a O2; where 0.05≤x≤0.15, 0.05≤y≤0.15, 0<z≤0.03, 0<a≤0.03.

[0006] Preferably, 0.01≤z≤0.02, 0.01≤a≤0.02; more preferably, x=0.1, y=0.07, z=0.015, a=0.015.

[0007] Secondly, the present invention provides a method for preparing a magnesium-copper co-doped NCM high-nickel ternary material, comprising:

[0008] (1) Mix MgO, CuO and nickel cobalt manganese precursor, then add lithium source and continue mixing to obtain a mixture;

[0009] (2) The resulting mixture is sintered to obtain the magnesium-copper co-doped NCM high-nickel ternary material.

[0010] Preferably, the nickel-cobalt-manganese precursor is Ni 0.8 Co 0.1 Mn 0.1 (OH)2, wherein the mixing method is ball milling, the ball milling speed is 300-500 rpm, and the total time is 6-12 hours.

[0011] Preferably, the molar ratio of MgO, CuO and nickel-cobalt-manganese precursor is (0-0.03):(0-0.03):1; more preferably, the Mg:Cu:Ni:Co:Mn ratio in the mixture is 0.015:0.015:0.8:0.1:0.1.

[0012] Preferably, the lithium source is at least one of lithium hydroxide, lithium carbonate, and lithium acetate; the molar ratio of the lithium source to the nickel-cobalt-manganese precursor is 1.06:1.

[0013] Preferably, the sintering atmosphere is oxygen; the sintering temperature is 780–850°C, and the time is 12–20 hours; more preferably, the sintering heating rate is 2–5°C / min.

[0014] Preferably, the sintering process includes: first heating to 450°C and holding for 4–6 hours, then heating to 850°C and holding for 12–20 hours.

[0015] Thirdly, the present invention provides an electrode comprising: a current collector and an electrode layer coated on the surface of the current collector; the electrode layer comprises the above-mentioned magnesium-copper co-doped NCM high-nickel ternary material;

[0016] Preferably, the electrode layer comprises a magnesium-copper co-doped NCM high-nickel ternary material, a conductive agent, and a binder;

[0017] Preferably, the current collector is an Al foil or a carbon-coated Al foil;

[0018] Fourthly, this invention provides an application of magnesium-copper co-doped NCM high-nickel ternary material in lithium-ion batteries.

[0019] The present invention has the following beneficial effects:

[0020] 1. The Mg and Cu co-doped NCM811 type high-nickel ternary material of the present invention incorporates Mg and Cu during the sintering process. Mg doping replaces lithium sites, while Cu doping replaces transition metal sites. The role of Mg doping is to replace lithium sites, reducing lithium-nickel mixing and improving the material's structural stability. The role of Cu doping is to replace transition metal sites, increasing the interlayer spacing of the material's layered structure due to the difference in ionic radius between Cu and transition metals, thereby widening the Li-Ni alloy. + The purpose of improving diffusion channels is to enhance the stability of battery materials while ensuring high capacity through the co-doping of Mg and Cu elements.

[0021] 2. When the Mg and Cu co-doped NCM811 high-nickel ternary material is used as the cathode material for lithium-ion batteries, it exhibits excellent cycle stability. At a current density of 0.1C, the initial discharge specific capacity is 187.05 mAh / g and 225 mAh / g within the voltage window of 2.7–4.3V and 2.7–4.5V, respectively. After 100 charge-discharge cycles at a current density of 0.5C within the 2.7–4.3V range, its specific capacity stabilizes at approximately 171.9 mAh / g, with a coulombic efficiency of 99.8%. Attached Figure Description

[0022] Figure 1 Crystal structure diagram of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1;

[0023] Figure 2 The X-ray powder diffraction pattern of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 is shown below.

[0024] Figure 3 Transmission electron microscope image of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1;

[0025] Figure 4 The results show the cycling performance of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1.

[0026] Figure 5 The constant current charge-discharge diagram of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 in the voltage range of 2.7 to 4.3 V is shown.

[0027] Figure 6 The constant current charge-discharge diagram of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 in the voltage range of 2.7 to 4.5 V is shown.

[0028] Figure 7The cycling performance results are for the Mg-doped NCM811 high-nickel ternary material prepared in Comparative Example 1.

[0029] Figure 8 The cycling performance results are for the Cu-doped NCM811 high-nickel ternary material prepared in Comparative Example 2. Detailed Implementation

[0030] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0031] In this disclosure, the chemical formula of the Mg and Cu co-doped NCM-type high-nickel ternary material is LiNi. 1-x-y-z- a Co x Mn y Mg z Cu a O2; where 0.05≤x≤0.15, 0.05≤y≤0.15, 0<z≤0.03, 0<a≤0.03. This material uses Ni... 0.8 Co 0.1 Mn 0.1 (OH)₂ is used as the precursor, doped with Mg and Cu elements; the molar ratio of Mg:Cu:Ni:Co:Mn is 0.015:0.015:0.8:0.1:0.1. Comparing NCM811 high-nickel ternary materials doped with Mg or Cu alone, the capacity decreases significantly with Mg doping alone, while the long-cycle stability is not significantly improved with Cu doping alone. Therefore, the molar ratio of each element needs to be strictly controlled to Mg:Cu:Ni:Co:Mn = 0.015:0.015:0.8:0.1:0.1.

[0032] The following exemplarily illustrates a method for preparing Mg and Cu co-doped NCM811 type high-nickel ternary materials, including:

[0033] First, MgO, CuO, and the precursor Ni are added. 0.8 Co 0.1 Mn 0.1 (OH)₂ is placed in a ball mill jar and ball-milled. After the above materials are mixed evenly, a lithium source is added and ball milling continues. The ball milling speed can be 300-500 rpm, and the time is 6-12 hours. The ratio of the lithium source to the precursor is 1.06:1. The lithium salt is at least one of lithium hydroxide, lithium carbonate, and lithium acetate. If the amount of lithium source used is too small, the prepared cathode material will have severe nickel-lithium mixing, low capacity, and poor cycle performance; if the amount of lithium source used is too large, there will be too much free lithium, severe nickel-lithium mixing, and poor cycle performance.

[0034] The thoroughly ground sample is sintered to obtain a Mg and Cu co-doped NCM811 type high-nickel ternary material. The sintering is a gradient sintering process performed in an oxygen atmosphere furnace; for example, first sintering at a low temperature, then sintering at a high temperature. Preferably, the sintering process includes: introducing oxygen, holding at 450°C for 4–6 hours, then raising the temperature to 850°C and holding at that temperature for 12–20 hours, with a heating rate of 2–5°C / min.

[0035] In this invention, the electrode comprises: a current collector and an electrode layer coated on the surface of the current collector. The electrode layer comprises the aforementioned active electrode material, Super P, and a binder. The current collector is an Al foil or a carbon-coated Al foil.

[0036] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0037] Example 1

[0038] (1) MgO, CuO and precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ was added to a ball mill jar at a ratio of 0.015:0.015:0.8 and ball milled. After the sample was thoroughly mixed, a lithium source was added and ball milled again for 6–12 hours until the mixture was homogeneous. During the ball milling process, the sample was removed and scraped off the inner wall of the ball mill jar.

[0039] (2) A high-temperature solid-state method was used. The uniformly mixed sample was placed in a tube furnace along with a corundum ceramic boat for sintering. Oxygen was introduced to ensure complete oxidation of the material during the sintering process. Initially, low-temperature sintering was performed at 450℃ for 4–6 hours, followed by heating to 850℃ and holding for 12–20 hours. The heating rate was 2℃ / min to ensure the integrity of the material's crystal structure, resulting in a high-nickel ternary material. The chemical formula of the obtained high-nickel ternary material is LiNi. 0.8 Co 0.1 Mn 0.07 Mg 0.015 Cu 0.015 O2.

[0040] Structural analysis:

[0041] Figure 1The image shows the crystal structure of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1. Its structure is an α-NaFeO2 type compound, R-3m space group. Oxygen ions are arranged in a face-centered cubic close-packed configuration, occupying position 6c. Li and transition metal ions are alternately arranged on the rock salt phase (111) plane, occupying positions 3a and 3b of the oxygen octahedral voids, respectively. The oxygen octahedra are stacked in an O3 sequence (AB-CA-BC) to form the transition metal layer and the Li layer. + It allows for flexible insertion and extraction on a two-dimensional plane between transition metal layers.

[0042] Composition analysis:

[0043] Table 1 shows the ICP composition analysis results of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1, where the molar ratio of each component Mg:Cu:Ni:Co:Mn = 0.015:0.015:0.8:0.1:0.07.

[0044] Table 1:

[0045]

[0046] Morphological characteristics:

[0047] Figure 2 The X-ray powder diffraction pattern of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 is shown. Compared with the standard card, all the major diffraction peaks of the sample match the structure of the hexagonal layered α-NaFeO2 type compound (R-3m space group). Furthermore, the two pairs of adjacent diffraction peaks (006) / (012) and (018) / (110) show significant splitting, indicating that the prepared samples all possess a well-ordered layered structure. In addition, the relative intensity of I(003) / I(104) is relatively high, and this ratio is related to the degree of cation mixing in the layered cathode material. Therefore, the intensity of the diffraction peaks further confirms that the material has a good layered structure.

[0048] Figure 3 The image shows a transmission electron microscope image of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1, indicating that the material has a layered structure.

[0049] Example 2

[0050] Using the positive electrode material obtained in Example 1 as the active material, the preparation process of the electrode material is illustrated as follows: the active material is weighed according to a mass ratio of 8:1:1, the conductive agent (Super P) and the binder (polyvinylidene fluoride: PVDF) are ground and mixed evenly, and the mixture is prepared into a slurry with a solvent (N-methylpyrrolidone). The slurry is coated on aluminum foil to make an electrode sheet. The electrode sheet is dried in a forced-air drying oven at 70-100°C for a period of time, and then dried in a vacuum drying oven at 100-120°C for 10-12 hours. An MSK-T10 manual slicing machine with a mold diameter of 8-14 mm is selected to cut the dried electrode sheet to obtain a circular electrode sheet, which is then weighed for later use.

[0051] Battery assembly: In an argon-filled glove box, the obtained circular electrode sheet is used as the positive electrode of the battery, and the lithium disc is used as the negative electrode. The battery casing is a CR2032 button cell, the separator is Whatman glass fiber, and the electrolyte is a 1 mol / L LiPF6 (EC+DMC+EMC) mixed solution, where EC is ethylene carbonate, DMC is dimethyl carbonate, and EMC is ethyl hydroxymethyl propylene oxide. The volume ratio of EC, DEC and EMC is 1:1:1.

[0052] Electrochemical performance testing: The battery was tested in a constant temperature chamber at 25℃ using a LAND testing system. Charge-discharge curves were tested under a constant current of 0.1C (1C = 200mAh / g) for voltage windows of 2.7–4.3V and 2.7–4.5V. Within the voltage window of 2.7–4.3V, constant current charge-discharge was performed at current densities of 0.1C, 0.5C, 0.8C, 1C, 2C, 3C, and 0.1C, with 5 cycles at each rate. The number of charge-discharge cycles at a current density of 0.5C was 100.

[0053] Analysis of electrochemical performance test results:

[0054] Figure 4 The cycling performance results of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 (NCM-1: NCM811 high-nickel ternary material co-doped with anions and cations; NCM: undoped NCM811 high-nickel ternary material) show that, in a long cycling period of 2.7–4.3 V and 0.5 C, the capacity retention after 100 cycles increased from 63.23% to 94.91% compared to the undoped NCM811 high-nickel ternary material.

[0055] Figure 5 The galvanostatic charge-discharge curves for the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 are shown in the voltage range of 2.7–4.3 V. NCM and NCM-1 show current-depletion rates of 180.21 and 187.05 mAh g, respectively. -1 The capacity.

[0056] Figure 6 The image shows the galvanostatic charge-discharge curves of the Mg and Cu co-doped NCM811 high-nickel ternary material prepared in Example 1 within the voltage range of 2.7–4.5 V. NCM and NCM-1 show current-to-discharge ratios of 215 and 225 mAh g, respectively. -1 The capacity.

[0057] Comparative Example 1

[0058] The preparation process of the magnesium-copper co-doped NCM811 high-nickel ternary material in Comparative Example 1 is the same as in Example 1, except that x, y, z are fixed and a = 0. Figure 7 The cycling performance results of the Mg-doped NCM811 high-nickel ternary materials prepared in Comparative Example 1 (NCM: undoped NCM811 high-nickel ternary material; NCM-2: Mg-doped NCM811 high-nickel ternary material) show that, during long cycling at 2.7–4.3 V and 0.5 C, the capacity retention of NCM-2 increased from 63.23% to 83.40% compared to NCM. However, NCM and NCM-2 exhibited capacity retention of 175 and 157 mAh g⁻¹, respectively. -1 The initial capacity. Doping with Mg alone improves capacity retention, but has some impact on the capacity of NCM.

[0059] Comparative Example 2

[0060] The preparation process of the magnesium-copper co-doped NCM811 high-nickel ternary material in Comparative Example 2 is the same as in Example 1, except that x, y, and a are fixed and z = 0. Figure 8 The cycling performance results of the Cu-doped NCM811 high-nickel ternary materials prepared for Comparative Example 2 (NCM: undoped NCM811 high-nickel ternary material; NCM-3: Cu-doped NCM811 high-nickel ternary material) show that, during long cycling at 2.7–4.3 V and 0.5 C, the capacity retention of NCM-3 decreased from 63.23% to 41.19% after 100 cycles compared to NCM-1. However, NCM and NCM-3 showed capacities of 175 and 174.3 mAh g, respectively. -1 The initial capacity. Single Cu doping reduces capacity retention but does not reduce the capacity of NCM.

Claims

1. A method for preparing a magnesium-copper co-doped NCM high-nickel ternary material, characterized in that, The chemical composition of the magnesium-copper co-doped NCM high-nickel ternary material is LiNi. 1-x-y-z-a Co x Mn y Mg z Cu a O2; wherein 0.05≤x≤0.15, 0.05≤y≤0.15, 0<z≤0.03, 0<a≤0.03, and the preparation method includes: (1) After mixing MgO, CuO and nickel-cobalt-manganese precursors, a lithium source is added and the mixture is continued to be mixed to obtain a mixture; (2) The resulting mixture is sintered to obtain the magnesium-copper co-doped NCM high-nickel ternary material.

2. The preparation method according to claim 1, characterized in that, The nickel-cobalt-manganese precursor is Ni 0.8 Co 0.1 Mn 0.1 (OH)2, wherein the mixing method is ball milling, the ball milling speed is 300-500 rpm, and the total time is 6-12 hours.

3. The preparation method according to claim 1, characterized in that, The molar ratio of MgO, CuO and nickel-cobalt-manganese precursor is (0-0.03):(0-0.03):

1.

4. The preparation method according to claim 3, characterized in that, The mixture contains Mg:Cu:Ni:Co:Mn = 0.015:0.015:8:1:

1.

5. The preparation method according to claim 1, characterized in that, The lithium source is at least one of lithium hydroxide, lithium carbonate, and lithium acetate; the molar ratio of the lithium source to the nickel-cobalt-manganese precursor is 1.06:

1.

6. The preparation method according to any one of claims 1-5, characterized in that, The sintering atmosphere is oxygen; the sintering temperature is 780–850°C, and the sintering time is 12–20 hours; the sintering heating rate is 2–5°C / min.

7. The preparation method according to claim 6, characterized in that, The sintering process includes: first heating to 450℃ and holding for 4-6 hours, then heating to 850℃ and holding for 12-20 hours.

8. A magnesium-copper co-doped NCM high-nickel ternary material prepared by the preparation method according to any one of claims 1-7, wherein the chemical composition of the magnesium-copper co-doped NCM high-nickel ternary material is LiNi. 1-x-y-z-a Co x Mn y Mg z Cu a O2; where 0.05≤x≤0.15, 0.05≤y≤0.15, 0<z≤0.03, 0<a≤0.

03.

9. The magnesium-copper co-doped NCM high-nickel ternary material according to claim 8, characterized in that, 0.01≤z≤0.02, 0.01≤a≤0.

02.

10. The magnesium-copper co-doped NCM high-nickel ternary material according to claim 9, characterized in that, x=0.1, y=0.07, z=0.015, a=0.

015.

11. An electrode, characterized in that, include: A current collector and an electrode layer coated on the surface of the current collector; the electrode layer comprises a magnesium-copper co-doped NCM high-nickel ternary material as described in any one of claims 8-10; The electrode layer comprises a magnesium-copper co-doped NCM high-nickel ternary material, a conductive agent, and a binder; The current collector is an Al foil or a carbon-coated Al foil.

12. The application of a magnesium-copper co-doped NCM high-nickel ternary material as described in any one of claims 8-10 in lithium-ion batteries.

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