Method for preparing a positive electrode material and positive electrode material

Abstract

The present disclosure relates to a method for preparing a positive electrode material and the positive electrode material, the method comprising: mixing a manganese-containing precursor with a lithium source and then calcining in an oxygen-containing atmosphere to obtain a layered lithium-rich manganese-based positive electrode material matrix; performing a washing treatment on the layered lithium-rich manganese-based positive electrode material matrix to obtain a washed layered lithium-rich manganese-based positive electrode material matrix; mixing the washed layered lithium-rich manganese-based positive electrode material matrix with an aluminum source and then performing secondary calcination in an oxygen-containing atmosphere to obtain the positive electrode material. By using a step-by-step calcination process, a large amount of aluminum elements can be uniformly introduced into the internal crystal structure of the layered lithium-rich manganese-based positive electrode material, which can significantly improve the structural stability of the positive electrode material, thereby effectively improving the problem of rapid decay of the discharge median voltage of the positive electrode material during the cycle process. Therefore, the positive electrode material prepared by the method has a slower decay of the discharge median voltage, and has good cycle performance and rate performance.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, specifically to a method for preparing a cathode material and the cathode material itself. Background Technology

[0002] With the rapid development of new energy vehicles, the demand for high-energy-density lithium-ion batteries is increasing daily. Cathode materials are a key factor determining the energy density of lithium-ion batteries. Currently, commercially available lithium-ion battery cathode materials mainly include lithium manganese oxide, lithium iron phosphate, and ternary materials, but these materials all suffer from low specific capacity.

[0003] Layered lithium-rich manganese-based cathode materials, such as xLi₂MnO₃·(1-x)LiMO₂ (M = at least one of Mn, Ni, and Co), possess numerous advantages, including high discharge specific capacity (>250 mAh / g), high energy density, low raw material cost, environmental friendliness, and high safety. They are considered important candidate cathode materials for developing high-energy-density (300 Wh / kg), low-cost, and high-safety lithium-ion batteries. However, layered lithium-rich manganese-based cathode materials also suffer from poor cycle performance, poor rate capability, and rapid decay of the median discharge voltage. In particular, the significant decay of the median discharge voltage during cycling severely restricts their commercial application.

[0004] Introducing Al into layered lithium-rich manganese-based cathode materials can improve the internal crystal structure of these materials, thereby alleviating the problem of severe discharge median voltage decay. However, in related technologies, the amount of Al introduced into layered lithium-rich manganese-based cathode materials is still relatively small, and the effect of resisting discharge median voltage decay is not significant enough. Summary of the Invention

[0005] The purpose of this disclosure is to address the problem in the prior art that the amount of Al element introduced into the layered lithium-rich manganese-based cathode material is too small, resulting in insufficient anti-discharge median voltage decay effect, and to provide a method for preparing cathode material and cathode material.

[0006] To achieve the above objectives, this disclosure provides a method for preparing a cathode material, the method comprising:

[0007] The manganese-containing precursor was mixed with a lithium source and then calcined in an oxygen-containing atmosphere to obtain a layered lithium-rich manganese-based cathode material matrix.

[0008] The layered lithium-rich manganese-based cathode material matrix is ​​washed to obtain a washed layered lithium-rich manganese-based cathode material matrix.

[0009] The washed layered lithium-rich manganese-based cathode material matrix is ​​mixed with an aluminum source and then calcined a second time in an oxygen-containing atmosphere to obtain the cathode material.

[0010] Optionally, when obtaining the layered lithium-rich manganese-based cathode material matrix by calcination, the calcination includes low-temperature pre-calcination and high-temperature sintering; wherein,

[0011] The conditions for low-temperature pre-firing include: a heating rate of 1-5℃ / min, a pre-firing temperature of 400-550℃, and a pre-firing time of 3-5h;

[0012] The conditions for high-temperature sintering include: a heating rate of 1–3 °C / min, a sintering temperature of 800–900 °C, and a sintering time of 10–15 h.

[0013] Optionally, the washing process includes:

[0014] The layered lithium-rich manganese-based cathode material matrix was mixed with a washing solution and washed under stirring conditions. After washing, it was filtered and dried to obtain the washed layered lithium-rich manganese-based cathode material matrix.

[0015] The amount of the washing liquid used is 10 to 20 parts by weight relative to 1 part by weight of the layered lithium-rich manganese-based cathode material matrix; the washing conditions include: stirring speed of 100 to 1000 rpm, washing temperature of 20 to 100°C, and washing time of 30 to 180 min; the drying conditions include: drying temperature of 100 to 150°C, and drying time of 2 to 8 h.

[0016] Optionally, when the cathode material is obtained by secondary calcination, the conditions for secondary calcination include: a heating rate of 3 to 10 °C / min, a calcination temperature of 600 to 900 °C, and a calcination time of 6 to 15 h.

[0017] Preferably, the heating rate is 4–8 °C / min, the calcination temperature is 700–800 °C, and the calcination time is 8–14 h.

[0018] Optionally, the manganese-containing precursor includes a nickel-cobalt-manganese ternary precursor, wherein the nickel-cobalt-manganese ternary precursor includes Mn a Co b Ni c (OH)2 and / or Mn a Co b Ni c CO3, where 0.5≤a≤1, 0<b≤0.25, 0<c≤0.25, and a+b+c=1.

[0019] Optionally, the lithium source includes lithium carbonate and / or lithium hydroxide; based on elemental molar amounts, the amounts of the nickel-cobalt-manganese ternary precursor and the lithium source satisfy the following relationship: Li / (Ni+Co+Mn)=(1.0~1.5):1, preferably (1.1~1.4):1.

[0020] Optionally, the aluminum source includes at least one of alumina, aluminum hydroxide, aluminum nitrate, or boehmite; based on the molar amount of the elements, the amount of the washed layered lithium-rich manganese-based cathode material matrix and the amount of the aluminum source satisfy the following relationship: Al / (Ni+Co+Mn+Al)=(0.01~0.1):1, preferably (0.03~0.05):1.

[0021] This disclosure also provides a cathode material comprising a layered lithium-rich manganese-based cathode material matrix and aluminum uniformly distributed in the layered lithium-rich manganese-based cathode material matrix, wherein the aluminum loading is not less than 2% by weight based on the total weight of the cathode material, preferably not less than 3% by weight.

[0022] Optionally, the general chemical formula of the cathode material is Li. 1.2+x [(Mn a Co b Ni c ) 1-d Al d ] 0.8-x O2, where -0.2 < x ≤ 0.3, 0.5 ≤ a ≤ 1, 0 < b ≤ 0.25, 0 < c ≤ 0.25, 0.01 ≤ d ≤ 0.1, and a + b + c = 1;

[0023] Preferably, 0.005≤x≤0.015, 0.5≤a≤0.8, 0.1<b≤0.2, 0.1<c≤0.2, and 0.03≤d≤0.05.

[0024] Optionally, the positive electrode material is spherical particles with a particle size of 5–20 μm and a particle size D50 of 8–12 μm.

[0025] This disclosure also provides a positive electrode sheet for a lithium-ion battery, wherein the positive electrode sheet contains a positive electrode material prepared by the method described in any one of the above-mentioned methods or a positive electrode material described in any one of the above-mentioned methods.

[0026] This disclosure also provides a lithium-ion battery having the above-described positive electrode.

[0027] Through the above technical solution, the method disclosed herein, by employing a stepwise calcination process, can uniformly introduce a large amount of aluminum into the internal crystal structure of the layered lithium-rich manganese-based cathode material. This significantly improves the structural stability of the cathode material, thereby effectively addressing the problem of rapid decay of the median discharge voltage during cycling. Therefore, the cathode material prepared by the method disclosed herein exhibits slower decay of the median discharge voltage and better cycle performance and rate capability.

[0028] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0029] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0030] Figure 1 This is an electron microscope scan of the nickel-cobalt-manganese ternary precursor material in Embodiment 1 of this disclosure;

[0031] Figure 2 These are XRD analysis results of the cathode material S1 prepared in Example 1 of this disclosure and the cathode material D1 prepared in Comparative Example 1;

[0032] Figure 3 These are electron microscope scanning images of the positive electrode material S1 prepared in Example 1 of this disclosure and the positive electrode material D1 prepared in Comparative Example 1;

[0033] Figure 4 This is a graph showing the EPAM analysis results of the cathode material S1 prepared in Example 1 of this disclosure;

[0034] Figure 5 This is a comparison chart of the cycle performance of the cathode material S1 prepared in Example 1 of this disclosure and the cathode material D1 prepared in Comparative Example 1 at a rate of 0.2C.

[0035] Figure 6 This is a comparison curve of the rate performance of the cathode material S1 prepared in Example 1 of this disclosure and the cathode material D1 prepared in Comparative Example 1 at a rate of 0.1 to 3C.

[0036] Figure 7 This is a comparison chart of the median discharge voltage decay of the positive electrode material S1 prepared in Example 1 of this disclosure and the positive electrode material D1 prepared in Comparative Example 1 at a discharge rate of 0.2C. Detailed Implementation

[0037] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0038] The first aspect of this disclosure provides a method for preparing a cathode material, the method comprising: mixing a manganese-containing precursor with a lithium source and calcining the mixture in an oxygen-containing atmosphere to obtain a layered lithium-rich manganese-based cathode material matrix; washing the layered lithium-rich manganese-based cathode material matrix to obtain a washed layered lithium-rich manganese-based cathode material matrix; and mixing the washed layered lithium-rich manganese-based cathode material matrix with an aluminum source and calcining the mixture a second time in an oxygen-containing atmosphere to obtain the cathode material.

[0039] Introducing aluminum into layered lithium-rich manganese-based cathode materials has two main advantages. First, the higher Al-O bond energy significantly improves the structural stability of the cathode material, thereby enhancing its electrochemical and thermal stability. Second, Al... 3+ It can reduce the cathode material in Li + The volume change during the insertion / extraction process effectively suppresses the occurrence and propagation of microcracks in secondary particles.

[0040] In related technologies, when introducing aluminum into layered lithium-rich manganese-based cathode materials, the manganese-containing precursor, lithium source and aluminum source are usually mixed and then sintered at high temperature. The inventors of this disclosure have discovered that since Al and Li are prone to react under high temperature and oxygen-containing conditions to generate LiAlO2, the amount of aluminum introduced into the layered lithium-rich manganese-based cathode material is relatively small.

[0041] In this disclosure, a stepwise calcination process is employed. First, a layered lithium-rich manganese-based cathode material matrix is ​​obtained through calcination. Excess Li is then washed away. Next, the washed layered lithium-rich manganese-based cathode material matrix is ​​subjected to a second calcination with an aluminum source to obtain the cathode material. This method avoids the reaction between Li and Al in an oxygen-containing atmosphere, preventing the formation of LiAlO2, and also preserves the microstructure of the layered lithium-rich manganese-based cathode material matrix. This ensures a uniform distribution of aluminum within the layered lithium-rich manganese-based cathode material, significantly improving the structural stability of the cathode material and effectively mitigating the problem of rapid discharge median voltage decay during cycling. Therefore, the cathode material prepared by the method of this disclosure exhibits slow discharge median voltage decay, high discharge specific capacity, and good cycle performance and rate capability.

[0042] Furthermore, the methods and processes disclosed herein are simple and easy to implement, convenient to operate, low in cost, and controllable, making them suitable for large-scale industrial production.

[0043] According to this disclosure, when calcining to obtain the layered lithium-rich manganese-based cathode material matrix, the calcination conditions can vary within a certain range. For example, the calcination can include low-temperature pre-calcination and high-temperature sintering. The conditions for low-temperature pre-calcination can include: a heating rate of 1–5 °C / min, a pre-calcination temperature of 400–550 °C, and a pre-calcination time of 3–5 h. The conditions for high-temperature sintering can include: a heating rate of 1–3 °C / min, a sintering temperature of 800–900 °C, and a sintering time of 10–15 h.

[0044] In this disclosure, specifically, ball milling can be used to uniformly mix the manganese-containing precursor and the lithium source. The ball milling conditions can vary within a certain range; for example, the ball milling speed can be 150–250 rpm, and the ball milling time can be 0.5–3 h. When calcining the mixture of the manganese-containing precursor and the lithium source, the gas in the oxygen-containing atmosphere can be air and / or oxygen.

[0045] According to this disclosure, the washing process may include: mixing the layered lithium-rich manganese-based cathode material matrix with a washing solution and washing the layered lithium-rich manganese-based cathode material matrix under stirring conditions; after washing, filtering and drying are performed to obtain the washed layered lithium-rich manganese-based cathode material matrix; wherein, relative to 1 part by weight of the layered lithium-rich manganese-based cathode material matrix, the amount of the washing solution may be 10 to 20 parts by weight; the washing conditions may include: stirring speed of 100 to 1000 rpm, washing temperature of 20 to 100°C, and washing time of 30 to 180 min; the drying conditions may include: drying temperature of 100 to 150°C, and drying time of 2 to 8 h.

[0046] In this disclosure, specifically, the washing liquid can be selected from a certain range; for example, the washing liquid can be deionized water.

[0047] According to this disclosure, when the cathode material is obtained by secondary calcination, the conditions of the secondary calcination can vary within a certain range. For example, the conditions of the secondary calcination may include: a heating rate of 3 to 10 °C / min, a calcination temperature of 600 to 900 °C, and a calcination time of 6 to 15 h; preferably, the heating rate is 4 to 8 °C / min, the calcination temperature is 700 to 800 °C, and the calcination time is 8 to 14 h.

[0048] In this disclosure, specifically, ball milling can be used to uniformly mix the washed layered lithium-rich manganese-based cathode material matrix with the aluminum source. The ball milling conditions can vary within a certain range; for example, the ball milling speed can be 150–250 rpm, and the ball milling time can be 0.5–3 h. During the secondary calcination of the mixture of the washed layered lithium-rich manganese-based cathode material matrix and the aluminum source, the gas in the oxygen-containing atmosphere can be air and / or oxygen.

[0049] According to this disclosure, the manganese-containing precursor can be selected from a certain range. For example, the manganese-containing precursor may include a nickel-cobalt-manganese ternary precursor, which may include Mn. a Co b Ni c (OH)2 and / or Mn a Co b Ni c CO3, where 0.5≤a≤1, 0<b≤0.25, 0<c≤0.25, and a+b+c=1.

[0050] According to this disclosure, the lithium source can be selected within a certain range. For example, the lithium source may include lithium carbonate and / or lithium hydroxide. Based on the molar amount of elements, the amount of the nickel-cobalt-manganese ternary precursor and the amount of the lithium source satisfy the following relationship: Li / (Ni+Co+Mn)=(1.0~1.5):1, preferably (1.1~1.4):1.

[0051] According to this disclosure, the aluminum source can be selected within a certain range. For example, the aluminum source may include at least one of alumina, aluminum hydroxide, aluminum nitrate, or boehmite. Based on the molar amount of the elements, the amount of the washed layered lithium-rich manganese-based cathode material matrix and the amount of the aluminum source satisfy the following relationship: Al / (Ni+Co+Mn+Al)=(0.01~0.1):1, preferably (0.03~0.05):1.

[0052] A second aspect of this disclosure provides a cathode material comprising a layered lithium-rich manganese-based cathode material matrix and aluminum uniformly distributed in the layered lithium-rich manganese-based cathode material matrix, wherein the aluminum loading is not less than 2% by weight based on the total weight of the cathode material; preferably, the aluminum loading is not less than 3% by weight.

[0053] In the cathode material disclosed herein, aluminum elements are deeply penetrated into the internal crystal structure of the layered lithium-rich manganese-based cathode material matrix, and the aluminum elements are evenly distributed. Therefore, the internal structure of the cathode material is relatively stable, the median discharge voltage decays slowly, and it has high discharge specific capacity, good cycle performance, and rate performance.

[0054] According to this disclosure, the general chemical formula of the cathode material can be Li 1.2+x [(Mn a Co b Ni c ) 1-d Al d ] 0.8-xO2, where -0.2 < x ≤ 0.3, 0.5 ≤ a ≤ 1, 0 < b ≤ 0.25, 0 < c ≤ 0.25, 0.01 ≤ d ≤ 0.1, and a + b + c = 1; preferably, 0.005 ≤ x ≤ 0.015, 0.5 ≤ a ≤ 0.8, 0.1 < b ≤ 0.2, 0.1 < c ≤ 0.2, 0.03 ≤ d ≤ 0.05.

[0055] According to this disclosure, the positive electrode material can be spherical particles with a particle size of 5 to 20 μm and a particle size D50 of 8 to 12 μm.

[0056] A third aspect of this disclosure provides a positive electrode sheet for a lithium-ion battery, wherein the positive electrode sheet contains a positive electrode material prepared by the method described in any one of the preceding claims or a positive electrode material described in any one of the preceding claims.

[0057] A fourth aspect of this disclosure provides a lithium-ion battery having the aforementioned positive electrode.

[0058] The present disclosure is further illustrated below by means of examples, but the present disclosure is not limited thereto. Unless otherwise specified, the raw materials, reagents, instruments and equipment involved in the embodiments of the present disclosure can all be obtained by purchase.

[0059] The analysis methods involved in this embodiment are as follows:

[0060] XRD Analysis: The crystal structure of the powder sample was analyzed using a Thermo Fisher Thermo ESCALAB 250 X-ray powder diffractometer (USA). Sample Preparation: A certain amount of powder sample was placed in the groove of a frosted glass slide and flattened with a plate. Test Parameters: Cu target Kα light source, wavelength λ = 0.154 nm, scan rate 5° / min, step size 0.04°, equipment test power 200 kW.

[0061] SEM analysis: The morphology of the samples was observed using a FEI Quanta 200FEG scanning electron microscope.

[0062] EPMA analysis: The internal elemental distribution of the sample was analyzed using a JXA-8230 electron probe microanalyzer from Japan.

[0063] Example 1

[0064] The cathode material S1 was prepared according to the following method:

[0065] (1) The nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8Lithium carbonate and lithium carbonate were placed in a ball mill jar at a molar ratio of Li:M = 1.3 (Li excess 5%, M = Ni + Mn + Co) and ball milled until fully mixed. The mixture was then transferred to an air-filled box furnace and pre-fired at 500°C for 5 hours at a heating rate of 2°C / min. The temperature was then increased to 850°C at a heating rate of 1°C / min and held for 15 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain a layered lithium-rich manganese-based cathode material matrix.

[0066] (2) The layered lithium-rich manganese-based cathode material matrix obtained in step (1) is mixed with deionized water at a ratio of 1:10, and stirred vigorously at 80°C and 500 rpm for 1 hour. Then it is filtered and dried to obtain the washed layered lithium-rich manganese-based cathode material matrix.

[0067] (3) The layered lithium-rich manganese-based cathode material matrix washed in step (2) and nano Al2O3 were ball-milled in a planetary ball mill at a speed of 200 rpm for 1 h at a ratio of Al / (Ni+Co+Mn+Al)=0.03. Then, it was transferred to a box furnace and heated to 850℃ at a heating rate of 5℃ / min. The temperature was held for 8 h, cooled with the furnace, crushed, and sieved to obtain cathode material S1.

[0068] Example 2

[0069] The cathode material S2 was prepared according to the following method:

[0070] (1) The nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8 Lithium carbonate and lithium carbonate were placed in a ball mill jar at a molar ratio of Li:M = 1.3 (Li excess 5%, M = Ni + Mn + Co) and ball milled until fully mixed. The mixture was then transferred to an air-filled box furnace and pre-fired at 500°C for 5 hours at a heating rate of 2°C / min. The temperature was then increased to 820°C at a heating rate of 1°C / min and held for 12 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain a layered lithium-rich manganese-based cathode material matrix.

[0071] (2) The layered lithium-rich manganese-based cathode material matrix obtained in step (1) is mixed with deionized water at a ratio of 1:10, and stirred vigorously at 50°C and 800 rpm for 1 hour. Then it is filtered and dried to obtain the washed layered lithium-rich manganese-based cathode material matrix.

[0072] (3) The layered lithium-rich manganese-based cathode material matrix washed in step (2) is mixed with nano-Al2O3 in a planetary ball mill at a speed of 200 rpm for 1 h at a ratio of Al / (Ni+Co+Mn+Al)=0.05. Then it is transferred to a box furnace and heated to 850℃ at a heating rate of 10℃ / min. The temperature is held for 10 h, cooled with the furnace, crushed and sieved to obtain cathode material S2.

[0073] Example 3

[0074] The cathode material S3 was prepared according to the following method:

[0075] (1) The nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8 Lithium carbonate and lithium carbonate were placed in a ball mill jar at a molar ratio of Li:M = 1.3 (Li excess 5%, M = Ni + Mn + Co) and ball milled until fully mixed. The mixture was then transferred to an air-filled box furnace and pre-fired at 500°C for 5 hours at a heating rate of 2°C / min. The temperature was then increased to 850°C at a heating rate of 1°C / min and held for 10 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain a layered lithium-rich manganese-based cathode material matrix.

[0076] (2) The layered lithium-rich manganese-based cathode material matrix obtained in step (1) is mixed with deionized water at a ratio of 1:20, and stirred vigorously at 60°C and 600 rpm for 1 hour. Then it is filtered and dried to obtain the washed layered lithium-rich manganese-based cathode material matrix.

[0077] (3) The layered lithium-rich manganese-based cathode material matrix washed in step (2) is mixed with nano Al(OH)3 in a planetary ball mill at a speed of 250 rpm for 1 h at a ratio of Al / (Ni+Co+Mn+Al)=0.03. Then it is transferred to a box furnace and heated to 850℃ at a heating rate of 5℃ / min. The temperature is held for 8 h, cooled with the furnace, crushed and sieved to obtain cathode material S3.

[0078] Example 4

[0079] The cathode material S4 was prepared according to the following method:

[0080] (1) The nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8Lithium carbonate and lithium carbonate were placed in a ball mill jar at a molar ratio of Li:M = 1.3 (Li excess 5%, M = Ni + Mn + Co) and ball milled until fully mixed. The mixture was then transferred to an air-filled box furnace and pre-fired at 500°C for 5 hours at a heating rate of 2°C / min. The temperature was then increased to 850°C at a heating rate of 1°C / min and held for 12 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain a layered lithium-rich manganese-based cathode material matrix.

[0081] (2) The layered lithium-rich manganese-based cathode material matrix obtained in step (1) is mixed with deionized water at a ratio of 1:20, and stirred vigorously at 80°C and 500 rpm for 1 hour. Then it is filtered and dried to obtain the washed layered lithium-rich manganese-based cathode material matrix.

[0082] (3) The layered lithium-rich manganese-based cathode material matrix washed in step (2) is mixed with boehmite in a planetary ball mill at a speed of 200 rpm for 1 h at a ratio of Al / (Ni+Co+Mn+Al)=0.03. Then it is transferred to a box furnace and heated to 850℃ at a heating rate of 10℃ / min. The temperature is held for 10 h, cooled with the furnace, crushed and sieved to obtain cathode material S4.

[0083] Comparative Example 1

[0084] The cathode material D1 was prepared according to the following method:

[0085] Nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8 Lithium carbonate and nano-Al2O3 were placed in a ball mill jar and ball-milled (molar ratio Li:M = 1.3, M = Ni + Mn + Co, molar ratio Al / (Ni + Co + Mn + Al) = 0.03). After being thoroughly mixed, the mixture was transferred to an air-filled box furnace. The furnace was first heated to 500℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 850℃ at a heating rate of 1℃ / min for 12 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain the cathode material D1.

[0086] Comparative Example 2

[0087] The cathode material D2 was prepared according to the following method:

[0088] Nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8Lithium carbonate and nano-Al2O3 were placed in a ball mill jar and ball-milled (molar ratio Li:M=1.3, M=Ni+Mn+Co, molar ratio Al / (Ni+Co+Mn+Al)=0.05). After being thoroughly mixed, the mixture was transferred to an air-filled box furnace. It was first heated to 500℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 850℃ at a heating rate of 1℃ / min for 15 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain the cathode material D2.

[0089] Comparative Example 3

[0090] The cathode material D3 was prepared according to the following method:

[0091] Nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8 Lithium carbonate and nano-Al(OH)3 were placed in a ball mill jar and ball-milled (molar ratio Li:M = 1.3, M = Ni + Mn + Co, molar ratio Al / (Ni + Co + Mn + Al) = 0.03). After being thoroughly mixed, the mixture was transferred to an air-filled box furnace. The furnace was first heated to 500℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 850℃ at a heating rate of 1℃ / min for 10 hours. The mixture was then cooled in the furnace, crushed, and sieved to obtain the cathode material D3.

[0092] Comparative Example 4

[0093] The cathode material D4 was prepared according to the following method:

[0094] Nickel-cobalt-manganese ternary precursor material (Mn 0.54 Co 0.13 Ni 0.13 (CO3) 0.8 The mixture was placed in a ball mill jar with lithium carbonate and ball milled (molar ratio Li:M = 1.3, M = Ni + Mn + Co). After being thoroughly mixed, it was transferred to a box furnace filled with air. It was first heated to 500℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 850℃ at a heating rate of 1℃ / min for 15 hours. After cooling in the furnace, it was crushed and sieved to obtain the cathode material D4.

[0095] Test Example 1

[0096] (1) Electron microscopy was performed on the nickel-cobalt-manganese ternary precursor material involved in Example 1. The scanning results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the nickel-cobalt-manganese ternary precursor material exhibits a good spherical morphology, with a median particle size D50 of about 10 μm and uniform particle size.

[0097] (2) XRD analysis was performed on the cathode material S1 prepared in Example 1 and the cathode material D1 prepared in Comparative Example 1, respectively. The analysis results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the cathode materials S1 and D1 have the same structure, both belonging to the hexagonal crystal system of α-NaFeO2, and have narrow half-widths, high peak intensities, and good crystallinity.

[0098] (3) Electron microscopy was performed on the positive electrode material S1 prepared in Example 1 and the positive electrode material D1 prepared in Comparative Example 1, respectively. The scanning results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the cathode materials S1 and D1 basically maintain the spherical morphology of the nickel-cobalt-manganese ternary precursor materials and have uniform particle size; however, compared with cathode material D1, there is no obvious agglomeration phenomenon on the surface of cathode material S1, which indicates that aluminum element has entered the internal crystal structure of the layered lithium-rich manganese-based cathode material matrix and has not reacted with lithium to form LiAlO2.

[0099] (4) The cathode material S1 prepared in Example 1 was subjected to EPAM analysis, and the analysis results are as follows: Figure 4 As shown, by Figure 4 It can be seen that in the cathode material S1, aluminum has penetrated deeply into the internal crystal structure of the layered lithium-rich manganese-based cathode material matrix, and the aluminum is evenly distributed.

[0100] Test Example 2

[0101] Lithium-ion batteries s1-s4 and d1-d4 were prepared using cathode materials S1-S4 and D1-D4, respectively, using the following methods:

[0102] Preparation of electrode sheets: The positive electrode material, acetylene black and polyvinylidene fluoride (PVDF) are added to N-methylpyrrolidone (NMP) in a mass ratio of 8:1:1. After being mixed evenly, the mixture is coated on aluminum foil and dried at 110°C for 1 hour. The dried electrode sheets are then rolled and cut into positive electrode sheets with a diameter of 12 mm using a punching machine. The positive electrode sheets are then vacuum dried at 110°C for 12 hours in a vacuum oven to obtain the positive electrode sheets.

[0103] Battery assembly: Using a metallic Li sheet as the negative electrode, a 1 mol / L LiPF6 EC-DEC-EMC solution (volume ratio 1:1:1) as the electrolyte, and a single-layer polyethylene membrane (Celgard 2300) as the separator, a CR2032 coin cell was assembled in an argon-filled glove box.

[0104] Electrochemical tests were performed on lithium-ion batteries s1–s4 and d1–d4 respectively, using the following methods:

[0105] Electrochemical performance was tested using Wuhan Landian Systems. The 1C charge / discharge current density was 250 mA / g, and the test temperature was 25℃. The assembled coin cells were charged and discharged at 2.0–4.6V and 0.1C to evaluate the initial discharge specific capacity and initial coulombic efficiency of each cathode material. The assembled coin cells were cycled 50 times at 2.0–4.6V and 0.2C to evaluate the cycle performance and voltage decay of the cathode materials. The assembled coin cells were charged and discharged at 2.0–4.6V, 0.1C, 0.2C, 0.5C, 1C, 2C, and 3C to evaluate the rate performance of the cathode materials. The test results are as follows: Figures 5-7 As shown in Table 1.

[0106] in, Figure 5 This is a comparison chart of the cycle performance of the cathode material S1 prepared in Example 1 and the cathode material D1 prepared in Comparative Example 1 at a rate of 0.2C. Figure 1 It can be seen that the capacity retention rate of cathode material S1 after 50 cycles at 0.2C rate is much higher than that of cathode material D1; Figure 6 This is a comparison curve of the rate performance of the cathode material S1 prepared in Example 1 and the cathode material D1 prepared in Comparative Example 1 at rates of 0.1–3C. Figure 6 It can be seen that the rate performance of cathode material S1 is significantly higher than that of cathode material D1; Figure 7 This is a comparison chart of the median discharge voltage decay of the positive electrode material S1 prepared in Example 1 and the positive electrode material D1 prepared in Comparative Example 1 at a discharge rate of 0.2C. Figure 7 It can be seen that the discharge median voltage decay of cathode material S1 is significantly lower than that of cathode material D1.

[0107] Table 1

[0108]

[0109] As can be seen from Table 1, the cathode material disclosed in this invention exhibits a slow discharge median voltage decay, high discharge specific capacity, good cycle performance, and rate performance.

[0110] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0112] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for producing a positive electrode material, characterized by, The method includes: The manganese-containing precursor was mixed with a lithium source and then calcined in an oxygen-containing atmosphere to obtain a layered lithium-rich manganese-based cathode material matrix. The layered lithium-rich manganese-based cathode material matrix is ​​washed to obtain a washed layered lithium-rich manganese-based cathode material matrix. The washed layered lithium-rich manganese-based cathode material matrix is ​​mixed with an aluminum source and then calcined twice in an oxygen-containing atmosphere to obtain the cathode material; the calcination temperature of the second calcination is 850-900℃. The washing process includes: The layered lithium-rich manganese-based cathode material matrix was mixed with a washing solution and washed under stirring conditions. After washing, it was filtered and dried to obtain the washed layered lithium-rich manganese-based cathode material matrix. The amount of the washing solution used is 10 to 20 parts by weight relative to 1 part by weight of the layered lithium-rich manganese-based cathode material matrix; the washing conditions include: stirring speed of 100 to 1000 rpm, washing temperature of 20 to 100°C, and washing time of 30 to 180 min; the drying conditions include: drying temperature of 100 to 150°C, and drying time of 2 to 8 h. The aluminum source includes at least one of alumina, aluminum hydroxide, aluminum nitrate, or boehmite. The manganese-containing precursor includes a nickel-cobalt-manganese ternary precursor, and the lithium source includes lithium carbonate and / or lithium hydroxide; based on the molar amount of elements, the amounts of the nickel-cobalt-manganese ternary precursor and the lithium source satisfy the following relationship: Li / (Ni+Co+Mn) = (1.0~1.5):1; Based on the molar amount of elements, the amount of the layered lithium-rich manganese-based cathode material matrix and the amount of the aluminum source after washing satisfy the following relationship: Al / (Ni+Co+Mn+Al)=(0.01~0.1):

1.

2. The method of claim 1, wherein, When obtaining the layered lithium-rich manganese-based cathode material matrix by calcination, the calcination includes low-temperature pre-calcination and high-temperature sintering; wherein, The conditions for low-temperature pre-firing include: a heating rate of 1-5℃ / min, a pre-firing temperature of 400-550℃, and a pre-firing time of 3-5h; The conditions for high-temperature sintering include: a heating rate of 1–3 °C / min, a sintering temperature of 800–900 °C, and a sintering time of 10–15 h.

3. The method of claim 1, wherein, When the cathode material is obtained by secondary calcination, the conditions for secondary calcination include: a heating rate of 3 to 10 °C / min and a calcination time of 6 to 15 h.

4. The method of claim 3, wherein, The conditions for the secondary calcination include: a heating rate of 4–8 °C / min and a calcination time of 8–14 h.

5. The method according to any one of claims 1 to 4, characterized in that, The nickel-cobalt-manganese ternary precursor comprises Mn a Co b Ni c (OH)2 and / or Mn a Co b Ni c CO3, wherein 0.5≤a≤1, 0 6. The method of claim 1, wherein, Based on the molar amount of elements, the amounts of the nickel-cobalt-manganese ternary precursor and the lithium source satisfy the following relationship: Li / (Ni+Co+Mn) = (1.1~1.4):

1.

7. The method according to claim 1, characterized in that, Based on the molar amount of elements, the amount of the layered lithium-rich manganese-based cathode material matrix and the amount of the aluminum source after washing satisfy the following relationship: Al / (Ni+Co+Mn+Al)=(0.03~0.05):

1.

8. A cathode material prepared by the method of claim 1, characterized in that, The cathode material includes a layered lithium-rich manganese-based cathode material matrix and aluminum uniformly distributed in the layered lithium-rich manganese-based cathode material matrix. Based on the total weight of the cathode material, the loading of aluminum is not less than 2% by weight.

9. The positive electrode material according to claim 8, characterized in that, Based on the total weight of the positive electrode material, the aluminum loading is not less than 3% by weight.

10. The cathode material according to claim 8, characterized in that, The chemical general formula of the positive electrode material is Li 1.2+x [(Mn a Co b Ni c ) 1-d Al d ] 0.8-x O2, wherein -0.2 < x ≤ 0.3, 0.5 ≤ a ≤ 1, 0 < b ≤ 0.25, 0 < c ≤ 0.25, 0.01 ≤ d ≤ 0.1, and a + b + c = 1.

11. The cathode material according to claim 10, characterized in that, 0.005≤x≤0.015, 0.5≤a≤0.8, 0.1<b≤0.2, 0.1<c≤0.2, 0.03≤d≤0.

05.

12. The cathode material according to claim 8, characterized in that, The positive electrode material is spherical particles with a particle size of 5–20 μm and a particle size D50 of 8–12 μm.

13. A positive electrode sheet for a lithium-ion battery, characterized in that, The positive electrode sheet contains the positive electrode material prepared by the method according to any one of claims 1 to 7 or the positive electrode material according to any one of claims 8 to 12.

14. A lithium-ion battery, characterized in that, The lithium-ion battery has the positive electrode as described in claim 13.

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