A modified nickel-cobalt-manganese ternary positive electrode material and its preparation method and application

Abstract

The present invention provides a modified nickel-cobalt-manganese ternary positive electrode material and a preparation method and application thereof, the preparation method comprising: (1) adding a manganese salt and a lithium salt to a solvent and mixing them to obtain a mixed solution; (2) adding the nickel-cobalt-manganese ternary material to the mixed solution and mixing them, and then sequentially performing heating treatment, heat treatment and cooling treatment to obtain the modified nickel-cobalt-manganese ternary positive electrode material. The modified nickel-cobalt-manganese ternary positive electrode material prepared by the present invention has good stability at the grain boundaries between primary particles and the manganese-containing modification layer formed on the surface of secondary particles, can effectively inhibit the generation of cracks in the nickel-cobalt-manganese ternary positive electrode material during charging and discharging, can effectively inhibit the side reaction between the nickel-cobalt-manganese ternary positive electrode material and the electrolyte, thereby effectively improving the interface stability, slowing down the capacity decay, and having excellent cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery materials, and in particular to a modified nickel-cobalt-manganese ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, light weight and low pollution, and are widely used in electronic equipment and electric vehicles. As a key material in lithium-ion batteries, the performance of positive electrode materials plays a decisive role in the energy density, power density and cycle life of batteries. Nickel-cobalt-manganese ternary positive electrode materials have become the preferred positive electrode materials for power lithium-ion batteries due to their advantages such as high specific capacity and low cost. However, in practical applications, there are still problems such as microcracks due to volume effect during the cycle, capacity reduction with increasing cycle times, and oxygen generation by side reactions with electrolytes that need to be urgently solved. In response to the above problems of nickel-cobalt-manganese ternary positive electrode materials, the positive electrode materials are often modified by modifying the grain boundaries between primary particles and the surface of secondary particles to effectively inhibit the generation of intergranular cracks and reduce the side reactions between materials and electrolytes, thereby improving the cycle performance of the battery.

[0003] However, although the existing modification technology can inhibit the generation of intergranular cracks to a certain extent, the process is complicated, the conditions are harsh, and the process cost is high, which is not conducive to large-scale commercial use. Therefore, it is urgent to provide a modified nickel-cobalt-manganese ternary positive electrode material with simple process, low cost, and effective inhibition of intergranular cracks. Summary of the invention

[0004] The embodiment of the present invention provides a modified nickel-cobalt-manganese ternary positive electrode material and a preparation method and application thereof, which can provide a positive electrode material with simple process, low cost and effective inhibition of intergranular cracking, and can effectively inhibit the side reaction between the nickel-cobalt-manganese ternary positive electrode material and the electrolyte. The modified nickel-cobalt-manganese ternary positive electrode material can be applied to lithium-ion batteries to effectively slow down capacity attenuation and has excellent cycle performance.

[0005] In a first aspect, the present invention provides a method for preparing a modified nickel-cobalt-manganese ternary positive electrode material, the preparation method comprising the following steps:

[0006] (1) adding a manganese salt and a lithium salt into a solvent and mixing them to obtain a mixed solution;

[0007] (2) Adding the nickel-cobalt-manganese ternary material to the mixed solution and mixing well, and then sequentially performing heating treatment, heat treatment and cooling treatment to obtain the modified nickel-cobalt-manganese ternary positive electrode material.

[0008] Preferably, in step (1),

[0009] The lithium salt is lithium acetate, lithium nitrate or lithium chloride;

[0010] The manganese salt is manganese acetate, manganese nitrate or manganese chloride;

[0011] The solvent is anhydrous ethanol, methanol or isopropanol; preferably anhydrous ethanol.

[0012] Preferably, in step (1), the molar ratio of the lithium salt to the manganese salt in the mixed solution is Li:Mn=(1-1.05):2

[0013] Preferably, in step (2), the mass ratio of the content of manganese element in the manganese salt in the mixed solution to the mass of the nickel-cobalt-manganese ternary material is (0.1-1.2):100;

[0014] The solid-to-liquid ratio of the added nickel-cobalt-manganese ternary material to the solvent in the mixed solution is 5g:(40-100mL); preferably 5g:50mL.

[0015] Preferably, in step (2), the chemical formula of the nickel-cobalt-manganese ternary material is LiNi x Co y Mn 1-x-y O2; wherein x is 0.33-0.9, y is 0.05-0.33, and 0<1-xy<1.

[0016] Preferably, in step (2), the temperature of the heating treatment is 40 to 80° C.; wherein the solvent is evaporated by the heating treatment.

[0017] Preferably, in step (2), the heat treatment adopts an oxygen or air atmosphere; wherein the flow rate of the air or oxygen is 40 to 80 mL / min;

[0018] The heat treatment temperature is 600-800° C., the heat preservation time is 4-8 hours, and the heating rate is 5-10° C. / min.

[0019] Preferably, in step (2), the cooling rate of the cooling treatment is 3 to 5°C / min.

[0020] In a second aspect, the present invention provides a modified nickel-cobalt-manganese ternary positive electrode material prepared according to any preparation method described in the first aspect above.

[0021] In a third aspect, the modified nickel-cobalt-manganese ternary positive electrode material provided by the present invention is used in lithium batteries.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] 1. The manganese-containing coating layer formed on the surface of the secondary particles of the modified nickel-cobalt-manganese ternary positive electrode material prepared by the present invention has good stability, can effectively inhibit the irreversible phase change on the surface, and does not destroy the matrix structure, inhibits the side reaction between the nickel-cobalt-manganese ternary positive electrode material and the electrolyte, thereby effectively improving the interface stability, slowing down the capacity decay, and obtaining excellent cycle performance. At a current density of 1C in the voltage range of 3-4.3V, the capacity retention rate is above 98% after 150 cycles; at a current density of 1C in the voltage range of 3-4.5V, the capacity retention rate is above 95% after 100 cycles.

[0024] 2. The raw materials selected for the preparation method of the modified nickel-cobalt-manganese ternary positive electrode material of the present invention are cheap. Compared with other grain boundary modification methods, the process of the present invention is simple, easy to operate and apply in large-scale production. By dissolving manganese salt and lithium salt in an organic solvent, manganese and lithium elements can effectively penetrate between primary particles to complete the surface coating of primary particles. By heat treatment, the infiltrated manganese and lithium elements are stably present at the grain boundaries between primary particles and firmly combined with the matrix, effectively inhibiting the generation of intergranular cracks, avoiding particle breakage and side reactions with the electrolyte, and significantly improving cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is an electron microscope image of the particle morphology of the modified nickel-cobalt-manganese ternary positive electrode material prepared in Example 3 provided by the present invention.

[0027] Figure 2 It is an electron microscope image of the particle cross section of the unmodified nickel-cobalt-manganese ternary positive electrode material in the comparative example provided by the present invention after cycling 100 times at a current density of 0.5C in the voltage range of 3-4.3V.

[0028] Figure 3 This is an electron microscope image of the particle cross-section of the modified nickel-cobalt-manganese ternary positive electrode material prepared in Example 3 provided by the present invention after cycling 100 times at a current density of 0.5C in the voltage range of 3-4.3V.

[0029] Figure 4 It is a cycle performance curve diagram corresponding to the button-type batteries assembled in Examples 2-3 of the present invention and the comparative example at a current density of 1C in the voltage range of 3-4.3V.

[0030] Figure 5It is a cycle performance curve diagram corresponding to the button-type batteries assembled in Examples 1-4 of the present invention and the comparative example at a current density of 1C in the voltage range of 3-4.5V. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] The present invention provides a method for preparing a modified nickel-cobalt-manganese ternary positive electrode material, the preparation method comprising the following steps:

[0033] (1) adding a manganese salt and a lithium salt into a solvent and mixing them to obtain a mixed solution;

[0034] (2) Adding the nickel-cobalt-manganese ternary material to the mixed solution and mixing well, and then sequentially performing heating treatment, heat treatment and cooling treatment to obtain the modified nickel-cobalt-manganese ternary positive electrode material.

[0035] The modified nickel-cobalt-manganese ternary positive electrode material prepared by the present invention has good stability, and the manganese-containing modification layer formed on the grain boundaries between the primary particles and the surface of the secondary particles can effectively inhibit the generation of cracks in the nickel-cobalt-manganese ternary positive electrode material during the charge and discharge process, inhibit the irreversible phase change on the surface, and does not destroy the matrix structure. It can effectively inhibit the side reaction between the nickel-cobalt-manganese ternary positive electrode material and the electrolyte, thereby effectively improving the interface stability, slowing down the capacity decay, and having excellent cycle performance.

[0036] According to some preferred embodiments, in step (1), the lithium salt is lithium acetate, lithium nitrate or lithium chloride;

[0037] The manganese salt is manganese acetate, manganese nitrate or manganese chloride;

[0038] The solvent is anhydrous ethanol, methanol or isopropanol; preferably anhydrous ethanol.

[0039] According to some preferred embodiments, in step (1), the molar ratio of the lithium salt to the manganese salt in the mixed solution is Li:Mn=(1-1.05):2 (for example, 1:2, 1.01:2, 1.02:2, 1.03:2, 1.04:2 or 1.05:2)

[0040] It should be noted that the above-mentioned manganese salt and lithium salt selected in the present invention are both soluble in alcohol solvents to form solutions, so that during the heating treatment process, the manganese salt and lithium salt can effectively penetrate into the grain boundaries between the primary particles of the nickel-cobalt-manganese ternary positive electrode material and adhere to the surface of the secondary particles of the nickel-cobalt-manganese ternary positive electrode material.

[0041] According to some preferred embodiments, in step (2), the mass ratio of the content of manganese element in the manganese salt in the mixed solution to the nickel-cobalt-manganese ternary material is (0.1-1.2):100 (for example, it can be 0.1:100, 0.2:100, 0.4:100, 0.6:100, 0.8:100, 1:100 or 1.2:100);

[0042] The solid-to-liquid ratio of the added nickel-cobalt-manganese ternary material to the solvent in the mixed solution is 5g:(40-100mL) (for example, it can be 5g:40mL, 5g:50mL, 5g:60mL, 5g:70mL, 5g:80mL, 5g:90mL or 5g:100mL).

[0043] According to some more preferred embodiments, in step (2), the solid-to-liquid ratio of the added nickel-cobalt-manganese ternary material to the solvent in the mixed solution is 5 g:50 mL.

[0044] In the present invention, the ratio of the content of manganese in the manganese salt and the mass of the nickel-cobalt-manganese ternary material must be controlled within the above range. The inventors found that when the mass ratio of the two is less than 0.1%, the content of manganese salt and lithium salt is too little, and the manganese salt and lithium salt cannot completely cover the surface of the secondary particles and fully penetrate into the grain boundaries of the primary particles after heat treatment. The substances generated after heat treatment cannot form a stable structure on the surface of the secondary particles and the grain boundaries of the primary particles, and the modification effect is poor. The stability and performance of the modified nickel-cobalt-manganese ternary positive electrode material are less improved; when the mass ratio of the two is higher than 1.2%, the battery capacity is significantly reduced. Based on this, the content of manganese in the manganese salt of the present invention and the mass ratio of the nickel-cobalt-manganese ternary material are preferably within the above range, which can ensure that the thickness of the surface coating layer after heat treatment is moderate and uniform, and can effectively inhibit the side reaction of the modified nickel-cobalt-manganese ternary positive electrode material with the electrolyte, thereby effectively improving the interface stability, slowing down the capacity decay, and obtaining excellent cycle performance.

[0045] It should be noted that the nickel-cobalt-manganese ternary material is a secondary particle formed by the aggregation of primary particles, and there are grain boundaries between the primary particles.

[0046] According to some preferred embodiments, in step (2), the chemical formula of the nickel-cobalt-manganese ternary material is LiNi x Co y Mn 1-x-yO2; wherein x is 0.33-0.9 (for example, 0.33, 0.5, 0.6, 0.65, 0.75, 0.8, 0.83, or 0.9), y is 0.05-0.33 (for example, 0.05, 0.1, 0.12, 0.13, 0.15, 0.2, 0.25 or 0.33), and 0<1-xy<1.

[0047] According to some preferred embodiments, the temperature of the heating treatment is 40-80°C (for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C); wherein the solvent is evaporated by the heating treatment.

[0048] Specifically, the heating treatment is to dissolve the weighed manganese salt and lithium salt in an organic solvent to obtain a mixed solution, then add the nickel-cobalt-manganese ternary material to the mixed solution, heat and stir at 40-80°C until the organic solvent is completely volatilized, and the heating treatment is completed to obtain a solid powder.

[0049] It should be noted that the heating treatment time is the time used to evaporate the solvent; after the heating treatment, the solid powder is dried in a drying oven at 80° C. for 6 to 8 hours to obtain a dry solid powder.

[0050] In the present invention, the heat treatment can achieve the effective attachment of manganese salt and lithium salt on the surface of secondary particles and infiltration in the grain boundaries of primary particles in the nickel-cobalt-manganese ternary material, so that the heat treatment process forms a stable structure at the grain boundaries of the particles and a stable coating layer on the surface.

[0051] According to some preferred embodiments, in step (2), the heat treatment adopts an oxygen or air atmosphere; wherein the flow rate of the air or oxygen is 40 to 80 mL / min (for example, 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min, 60 mL / min, 65 mL / min, 70 mL / min, 75 mL / min or 80 mL / min);

[0052] The heat treatment temperature is 600-800°C (for example, it can be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C or 800°C), the holding time is 4-8h (for example, it can be 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h), and the heating rate is 5-10°C / min (for example, it can be 5°C / min, 5.5°C / min, 6°C / min, 6.5°C / min, 7°C / min, 7.5°C / min, 8°C / min, 8.5°C / min, 9°C / min, 9.5°C / min or 10°C / min).

[0053] According to some preferred embodiments, in step (2), the cooling rate of the cooling treatment is 3 to 5°C / min (for example, it may be 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min).

[0054] More specifically, the heat treatment includes placing the solid powder obtained after the heat treatment into a tubular furnace, heating it to 600-800°C at a heating rate of 5-10°C / min in an oxygen or air atmosphere with a flow rate of 40-80 mL / min, keeping it warm for 4-8 hours, and then cooling it to room temperature (for example, 25°C) at a cooling rate of 3-5°C / min.

[0055] In the present invention, the inventors found that when the heat treatment temperature is lower than 600°C, the substance generated after the reaction of manganese salt and lithium salt cannot form a stable structure on the particle surface and grain boundary, and the formed coating layer has a weak bonding force with the nickel-cobalt-manganese ternary material; and when the heat treatment temperature is higher than 800°C, the manganese element will penetrate into the nickel-cobalt-manganese ternary material, merge with the nickel-cobalt-manganese ternary material, change the components of the nickel-cobalt-manganese ternary material itself, and cannot form a stable coating layer on the surface of the nickel-cobalt-manganese ternary material, thereby affecting the stability and performance of the nickel-cobalt-manganese ternary material. Based on this, in order to ensure the stability and performance of the nickel-cobalt-manganese ternary material while ensuring that the surface coating layer of the modified nickel-cobalt-manganese ternary material can be firmly bonded to the nickel-cobalt-manganese ternary material, the heat treatment temperature of the present invention is preferably within the above range.

[0056] In the present invention, the substance generated after the reaction of manganese salt and lithium salt after heat treatment can form a stable structure at the grain boundary between particles and firmly bond with the matrix material, which can effectively inhibit the generation of cracks; at the same time, a stable surface coating layer can be formed on the surface of the particles, effectively inhibiting the reaction with the electrolyte, thereby obtaining excellent cycle performance.

[0057] In a second aspect, the present invention provides a modified nickel-cobalt-manganese ternary positive electrode material prepared according to any preparation method described in the first aspect above.

[0058] In a third aspect, the modified nickel-cobalt-manganese ternary positive electrode material provided by the present invention is used in lithium batteries.

[0059] The modified nickel-cobalt-manganese ternary positive electrode material prepared by the present invention has good stability, and the manganese-containing modification layer formed on the grain boundaries between the primary particles and the surface of the secondary particles can effectively inhibit the generation of cracks in the nickel-cobalt-manganese ternary positive electrode material during charging and discharging, inhibit the irreversible phase change on the surface, and does not destroy the matrix structure. When used as the positive electrode of a lithium-ion battery, it can effectively inhibit the side reaction between the nickel-cobalt-manganese ternary positive electrode material and the electrolyte, thereby effectively improving the interface stability, slowing down the capacity decay, and having excellent cycle performance. At a current density of 1C in the voltage range of 3-4.3V, the capacity retention rate is above 98% after 150 cycles; at a current density of 1C in the voltage range of 3-4.5V, the capacity retention rate is above 95% after 100 cycles.

[0060] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with embodiments.

[0061] Example 1

[0062] (1) Weighing: Weigh 5g LiNi 0.6 Co 0.2 Mn 0.2 O2, according to the mass of manganese element in manganese salt: LiNi 0.6 Co 0.2 Mn 0.2 O2 mass = 0.1%, Li:Mn = 1.05:2 molar ratio in lithium acetate and manganese acetate, weigh manganese acetate and lithium acetate;

[0063] (2) Dissolving: Dissolve the weighed manganese acetate and lithium acetate in 50 mL of anhydrous ethanol and stir until completely dissolved to obtain a mixed solution;

[0064] (3) Heating treatment: Add weighed LiNi 0.6 Co 0.2 Mn 0.2 O2, heated and stirred at 60°C until the anhydrous ethanol was completely volatilized to obtain a solid powder; then the solid powder was placed in a drying oven and dried at 80°C for 8 hours to obtain a dry solid powder;

[0065] (4) Heat treatment: The dried solid powder in step (3) was placed in a tube furnace, heated to 600°C at a heating rate of 5°C / min in an air atmosphere with an air flow rate of 60 mL / min, kept at this temperature for 4 hours, and then cooled to room temperature at a cooling rate of 3°C / min to obtain a modified LiNi 0.6 Co 0.2 Mn 0.2 O2 ternary positive electrode material.

[0066] (5) Performance test: The modified LiNi 0.6 Co 0.2 Mn 0.2 O2 ternary cathode material and metallic lithium were assembled into button cells, and their electrochemical performance was tested in the voltage range of 3-4.5V. Figure 5 As shown in the cycle performance curve of Example 1, the battery composed of this material has excellent cycle performance. After activation, the first discharge capacity at 1C current density is 181.47 mAh g -1 After 100 cycles, the capacity retention rate is 96.1%, indicating that the cycle performance of the modified material has been significantly improved.

[0067] Example 2

[0068] (1) Weighing: Weigh 5g LiNi 0.6 Co 0.2 Mn 0.2 O2, according to the mass of manganese element in manganese salt: LiNi 0.6 Co 0.2 Mn 0.2 O2 mass = 0.4%, Li:Mn = 1:2 molar ratio in lithium acetate and manganese acetate, weigh manganese acetate and lithium acetate;

[0069] (2) Dissolving: Dissolve the weighed manganese acetate and lithium acetate in 40 mL of anhydrous ethanol and stir until completely dissolved to obtain a mixed solution;

[0070] (3) Heating treatment: Add weighed LiNi 0.6 Co 0.2 Mn 0.2 O2, heated and stirred at 50°C until the anhydrous ethanol was completely volatilized to obtain a solid powder; then the solid powder was placed in a drying oven and dried at 80°C for 7 hours to obtain a dry solid powder;

[0071] (4) Heat treatment: The dried solid powder in step (3) was placed in a tube furnace, heated to 700°C at a heating rate of 5°C / min in an oxygen atmosphere with an oxygen flow rate of 50 mL / min, kept at this temperature for 5 hours, and then cooled to room temperature at a cooling rate of 4°C / min to obtain a modified LiNi 0.6 Co 0.2 Mn 0.2 O2 ternary positive electrode material.

[0072] (5) Performance test: The modified LiNi 0.6 Co 0.2 Mn 0.2The O2 ternary cathode material and metallic lithium were assembled into a button cell, and its electrochemical performance was tested in the voltage range of 3-4.3V. Figure 4 As shown in the cycle performance curve of Example 2, the battery composed of this material has excellent cycle performance. After activation, the first discharge capacity at 1C current density is 163.76 mAh g -1 , the capacity retention rate after 150 cycles is 97.9%; similarly, the electrochemical performance is tested in the 3-4.5V voltage range, such as Figure 5 As shown in the cycle performance curve of Example 2, the battery composed of this material has excellent cycle performance. After activation, the first discharge capacity at 1C current density is 184.57 mAh·g -1 After 100 cycles, the capacity retention rate is 95.3%, indicating that the cycle performance of the modified material has been significantly improved.

[0073] Example 3

[0074] (1) Weighing: Weigh 5g LiNi 0.6 Co 0.2 Mn 0.2 O2, according to the mass of manganese element in manganese salt: LiNi 0.6 Co 0.2 Mn 0.2 O2 mass = 0.8%, Li:Mn = 1.05:2 molar ratio in lithium acetate and manganese acetate, weigh manganese acetate and lithium acetate;

[0075] (2) Dissolving: Dissolve the weighed manganese acetate and lithium acetate in 80 mL of anhydrous ethanol and stir until completely dissolved to obtain a mixed solution;

[0076] (3) Heating treatment: Add weighed LiNi 0.6 Co 0.2 Mn 0.2 O2, heated and stirred at 60°C until the anhydrous ethanol was completely volatilized to obtain a solid powder; then the solid powder was placed in a drying oven and dried at 80°C for 8 hours to obtain a dry solid powder;

[0077] (4) Heat treatment: The dried solid powder in step (3) was placed in a tube furnace and heated to 760°C at a heating rate of 5°C / min in an air atmosphere with an air flow rate of 60 mL / min. After keeping the temperature for 4 hours, the powder was cooled to room temperature at a cooling rate of 3°C / min to obtain a modified LiNi 0.6 Co 0.2 Mn 0.2 O2 ternary cathode material;

[0078] (5) Performance test: The modified LiNi 0.6 Co0.2 Mn 0.2 The O2 ternary cathode material and metallic lithium were assembled into a button cell, and its electrochemical performance was tested in the voltage range of 3-4.3V. Figure 4 As shown in the cycle performance curve of Example 3, the battery composed of this material has excellent cycle performance. After activation, the first discharge capacity at 1C current density is 163.72 mAh·g -1 , the capacity retention rate after 150 cycles is 98.1%; similarly, the electrochemical performance is tested in the voltage range of 3-4.5V, such as Figure 5 As shown in the cycle performance curve of Example 3, the battery composed of this material has excellent cycle performance. After activation, the first discharge capacity at 1C current density is 187.61 mAh·g -1 After 100 cycles, the capacity retention rate is 95.8%, indicating that the cycle performance of the modified material has been significantly improved. Figure 3 As shown, the modified nickel-cobalt-manganese ternary positive electrode material has no cracks inside after 100 cycles at a voltage range of 3-4.3V and a current density of 0.5C, as shown in the electron microscope image of the particle cross-section.

[0079] Example 4

[0080] (1) Weighing: Weigh 5g LiNi 0.6 Co 0.2 Mn 0.2 O2, according to the mass of manganese element in manganese salt: LiNi 0.6 Co 0.2 Mn 0.2 O2 mass = 0.8%, Li:Mn = 1:2 molar ratio in lithium acetate and manganese acetate, weigh manganese acetate and lithium acetate;

[0081] (2) Dissolution: Dissolve the weighed manganese acetate and lithium acetate in 100 mL of anhydrous ethanol and stir until completely dissolved;

[0082] (3) Heating treatment: Add weighed LiNi 0.6 Co 0.2 Mn 0.2 O2, heated and stirred at 80°C until the anhydrous ethanol was completely volatilized to obtain a solid powder; then the solid powder was placed in a drying oven and dried at 80°C for 8 hours to obtain a dry solid powder;

[0083] (4) Heat treatment: The dried solid powder in step (3) was placed in a tube furnace, heated to 800°C at a heating rate of 10°C / min in an air atmosphere with an air flow rate of 80 mL / min, kept at this temperature for 8 hours, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a modified LiNi 0.6 Co0.2 Mn 0.2 O2 ternary positive electrode material.

[0084] (5) Performance test: The modified LiNi 0.6 Co 0.2 Mn 0.2 O2 ternary cathode material and metallic lithium were assembled into button cells, and their electrochemical performance was tested in the voltage range of 3-4.5V. Figure 5 As shown in the cycle performance curve of Example 4, the battery composed of this material has excellent cycle performance. After activation, the first discharge capacity at 1C current density is 184.33 mAh·g -1 After 100 cycles, the capacity retention rate is 96.8%, indicating that the cycle performance of the modified material has been significantly improved.

[0085] Example 5

[0086] (1) Weighing: Weigh 5g LiNi 0.5 Co 0.2 Mn 0.3 O2, according to the mass of manganese element in manganese salt: LiNi 0.5 Co 0.2 Mn 0.3 O2 mass = 0.1%, Li:Mn = 1.05:2 molar ratio in lithium acetate and manganese acetate, weigh manganese acetate and lithium acetate;

[0087] (2) Dissolving: Dissolve the weighed manganese acetate and lithium acetate in 50 mL of anhydrous ethanol and stir until completely dissolved to obtain a mixed solution;

[0088] (3) Heating treatment: Add weighed LiNi 0.5 Co 0.2 Mn 0.3 O2, heated and stirred at 60°C until the anhydrous ethanol was completely volatilized to obtain a solid powder; then the solid powder was placed in a drying oven and dried at 80°C for 8 hours to obtain a dry solid powder;

[0089] (4) Heat treatment: The dried solid powder in step (3) was placed in a tube furnace, heated to 600°C at a heating rate of 5°C / min in an oxygen atmosphere with an oxygen flow rate of 60 mL / min, kept at this temperature for 4 hours, and then cooled to room temperature at a cooling rate of 3°C / min to obtain a modified LiNi 0.5 Co 0.2 Mn 0.3 O2 ternary positive electrode material.

[0090] Example 6

[0091] (1) Weighing: Weigh 5g LiNi0.8 Co 0.1 Mn 0.1 O2, according to the mass of manganese element in manganese salt: LiNi 0.8 Co 0.1 Mn 0.1 O2 mass = 1.2%, Li:Mn = 1.05:2 molar ratio in lithium acetate and manganese acetate, weigh manganese acetate and lithium acetate;

[0092] (2) Dissolving: Dissolve the weighed manganese acetate and lithium acetate in 50 mL of anhydrous ethanol and stir until completely dissolved to obtain a mixed solution;

[0093] (3) Heating treatment: Add weighed LiNi 0.8 Co 0.1 Mn 0.1 O2, heated and stirred at 60°C until the anhydrous ethanol was completely volatilized to obtain a solid powder; then the solid powder was placed in a drying oven and dried at 80°C for 8 hours to obtain a dry solid powder;

[0094] (4) Heat treatment: The dried solid powder in step (3) was placed in a tube furnace, heated to 600°C at a heating rate of 5°C / min in an oxygen atmosphere with an oxygen flow rate of 60 mL / min, kept at this temperature for 4 hours, and then cooled to room temperature at a cooling rate of 3°C / min to obtain a modified LiNi 0.8 Co 0.1 Mn 0.1 O2 ternary positive electrode material.

[0095] Comparative Example

[0096] The unmodified positive electrode material (LiNi 0.6 Co 0.2 Mn 0.2 O2) and metallic lithium were assembled into button cells, and their electrochemical performance was tested in the voltage range of 3-4.3V. Figure 4 As shown in the figure, as the number of cycles increases, the capacity of the corresponding proportional cycle performance curve decays. After activation, the first discharge capacity at 1C current density is 162.27 mAh g -1 , the capacity retention rate after 150 cycles is 93.4%; its electrochemical performance is tested in the voltage range of 3-4.5V, such as Figure 5 As shown in the figure, as the number of cycles increases, the capacity of the corresponding proportional cycle performance curve decays, and the decay is obvious after 50 cycles. After activation, the first discharge capacity at 1C current density is 183.74 mAh g -1 , the capacity retention rate after 100 cycles is 90.5%. Figure 2As shown, the unmodified nickel-cobalt-manganese ternary positive electrode material has obvious cracks inside after 100 cycles at a voltage range of 3-4.3V and a current density of 0.5C, as shown in the electron micrograph of the particle cross-section.

[0097] It should be noted that Figure 4 The curves after 40 cycles are, from top to bottom, the cycle performance curves of Example 3, Example 2, and the comparative example; Figure 5 The curves after 40 cycles are, from top to bottom, the cycle performance curves of Example 3, Example 4, Example 2, Example 1 and the comparative example.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a modified nickel-cobalt-manganese ternary positive electrode material, characterized in that: The preparation method comprises the following steps: (1) adding a manganese salt and a lithium salt into a solvent and mixing them to obtain a mixed solution; the manganese salt is manganese acetate, manganese nitrate or manganese chloride; the lithium salt is lithium acetate, lithium nitrate or lithium chloride; and the solvent is anhydrous ethanol, methanol or isopropanol; (2) adding the nickel-cobalt-manganese ternary material to the mixed solution and mixing, and then sequentially performing heating treatment, heat treatment and cooling treatment to obtain the modified nickel-cobalt-manganese ternary positive electrode material; In step (1), the molar ratio of the lithium salt to the manganese salt in the mixed solution is Li:Mn=(1-1.05):2; In step (2), the mass ratio of the content of manganese element in the manganese salt in the mixed solution to the mass ratio of the nickel-cobalt-manganese ternary material is (0.1-1.2):100; The chemical formula of the nickel-cobalt-manganese ternary material is LiNi x Co y Mn 1-x-y O2; wherein x is 0.33~0.9, y is 0.05~0.33, and 0<1-xy<1; The heat treatment temperature is 600-800°C, the heat preservation time is 4-8h, and the heating rate is 5-10°C / min.

2. The preparation method according to claim 1, characterized in that: In step (2): the solid-liquid ratio of the added nickel-cobalt-manganese ternary material to the solvent in the mixed solution is 5g: 40~100mL.

3. The preparation method according to claim 2, characterized in that: The solid-to-liquid ratio of the added nickel-cobalt-manganese ternary material to the solvent in the mixed solution is 5g:50mL.

4. The preparation method according to claim 1, characterized in that: In step (2): The temperature of the heating treatment is 40-80° C.; wherein the solvent is evaporated by the heating treatment.

5. The preparation method according to claim 1, characterized in that: In step (2): The heat treatment adopts oxygen or air atmosphere; wherein the flow rate of the air or oxygen is 40-80 mL / min.

6. The preparation method according to claim 1, characterized in that: In step (2): The cooling rate of the cooling treatment is 3-5°C / min.

7. A modified nickel-cobalt-manganese ternary positive electrode material, characterized in that: Prepared according to any one of claims 1 to 6.

8. Use of the modified nickel-cobalt-manganese ternary positive electrode material according to claim 7 in lithium batteries.

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