Ternary positive electrode material and preparation method and application thereof

Abstract

The invention discloses a ternary positive electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The preparation method of the ternary positive electrode material comprises the following steps: (1) mixing a cobalt source, citric acid, water and ethylene glycol to obtain a mixed solution; heating the mixed solution for reaction, and sintering the obtained solid to obtain Co3O4 powder; and (2) mixing the Co3O4 powder, a nickel source, a manganese source, a lithium source and a solvent, reacting, and sintering the obtained solid to obtain the ternary positive electrode material. The ternary positive electrode material disclosed by the invention has a hollow multilayer special morphology, so that the stability of the material in a circulation process can be effectively improved, and the cycle performance of a battery is improved; meanwhile, the transmission efficiency of lithium ions is greatly improved, and the power performance of the positive electrode material is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a ternary cathode material, its preparation method and application, and more specifically to a ternary cathode material with a special morphology and its preparation method. Background Technology

[0002] With the rapid development of portable electronic products and the new energy vehicle industry, the requirements for the electrochemical performance of cathode materials are becoming increasingly stringent. High-nickel ternary cathode materials possess higher specific capacity and specific energy, with energy density increased by more than 30% compared to traditional lithium cobalt oxide cathode materials. High-nickel ternary cathode materials achieve a longer cycle life, meaning more charge-discharge cycles while maintaining good capacity retention. Due to their excellent cycle performance, high-nickel ternary cathode materials maintain battery stability during charge-discharge cycles, resulting in a longer lifespan in practical applications. Compared to lithium cobalt oxide cathode materials, their chemical composition is more stable, leading to better safety performance and effectively preventing overheating, explosions, and other safety issues during charge-discharge processes. Ternary materials are considered the preferred material for lithium-ion batteries due to their low cost and stable performance.

[0003] Nickel-rich (Ni) ternary layered transition metal oxides (LiNi) x CoyM 1-x-y O2 (M=Mn or Al) has become a research hotspot due to its superior energy density and low cost. However, Ni-rich ternary layered transition metal oxides still have some drawbacks in application, such as lithium-nickel mixing, irreversible phase transitions in the layered structure, and crystal cracking. Therefore, further improving their performance is an urgent problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a ternary cathode material, its preparation method, and its application. This invention can effectively utilize the performance of ternary layered materials through a reasonable structural design of the ternary cathode material.

[0005] This invention first provides a method for preparing a ternary cathode material, comprising the following steps: (1) Mix cobalt source, citric acid, water and ethylene glycol to obtain a mixed solution; heat the mixed solution to react, and then sinter the resulting solid to obtain Co3O4 powder; (2) The Co3O4 powder, nickel source, manganese source, lithium source and solvent are mixed and reacted, and the resulting solid is sintered to obtain the ternary cathode material.

[0006] After sintering and annealing, micron- or nano-sized cobalt tetroxide (Co3O4) possesses a unique porous and hollow morphology. This invention selects micron- or nano-sized cobalt tetroxide as a template for synthesizing ternary cathode materials. The synthesized ternary cathode material, due to its multi-layered structure, can serve as a lithium-ion transport channel, significantly enhancing lithium-ion diffusion efficiency and thus improving the power performance of the cathode material. Simultaneously, the multi-layered structure effectively prevents internal materials from being corroded by the electrolyte and from undergoing side reactions, thereby improving the stability of the ternary cathode material and the cycle performance of the battery.

[0007] In step (1), during the heating of the mixed solution, citric acid and ethylene glycol undergo an esterification reaction, generating smooth cubic-like particles in the presence of cobalt ions. During subsequent sintering, the outer shell of the cubic particles is oxidized first, forming an outer shell, while the organic matter inside the material decomposes simultaneously, resulting in internal shrinkage forces. When the shrinkage force exceeds the bonding force between the interior and the outer shell, cavities are formed, ultimately resulting in a multi-layered, hollow cubic-like particle morphology.

[0008] In the above-mentioned method for preparing ternary cathode materials, in step (1), the cobalt source is an inorganic salt of cobalt; specifically, it can be cobalt sulfate (CoSO4) and / or cobalt nitrate Co(NO3)2; The molar ratio of the cobalt source to citric acid is 1:1-2; specifically, it can be 1:1. The molar ratio of the cobalt source to the volume of water is 1 mol: 2-3 L; specifically, it can be 1 mol: 2 L. The molar ratio of the cobalt source to the volume of ethylene glycol is 1 mol: 2-3 L; specifically, it can be 1 mol: 2 L.

[0009] In the above-mentioned method for preparing ternary cathode materials, in step (1), the temperature for heating the reaction is 100-150℃, preferably 110-130℃; the time is 10-15h, preferably 10-12h. In step (1), the sintering temperature is 400-500℃, preferably 450℃; the sintering time is 2-4h, preferably 3h. The sintering is carried out in an inert atmosphere, specifically a nitrogen or argon atmosphere.

[0010] The above-mentioned method for preparing ternary cathode materials includes a step (1) after the reaction, where the solid is washed with anhydrous ethanol and then dried; after drying, sintering is performed; specifically, the drying temperature is 50-80℃ and the time is 4-6h.

[0011] In the preparation method of the above ternary cathode material, in step (2), the nickel source is an organic salt of nickel, such as nickel acetate (NiC4H6O4) and / or nickel formate (NiC2H2O4); the manganese source is an organic salt of manganese, such as manganese acetate (MnC4H6O4) and / or manganese formate (MnC2H2O4), etc.; the lithium salt is lithium carbonate (Li2CO3) and / or lithium hydroxide (LiOH); The molar ratio of the Co3O4 powder, nickel source, manganese source and lithium source is 1:20 - 24:7 - 9:9.19 - 9.54; specifically, it can be 1:23.3:8:9.3; The solvent is ethanol and / or water; The mass ratio of the total mass of the Co3O4 powder, nickel source, manganese source and lithium source to the volume of the solvent is 1 - 1.5 g:1 mL.

[0012] In the preparation method of the above ternary cathode material, in step (2), the reaction temperature is 80 - 100 °C, preferably 80 °C; the reaction time is 4 - 8 h, preferably 5 - 6 h.

[0013] In the preparation method of the above ternary cathode material, in step (2), the sintering temperature is 500 - 700 °C, preferably 500 - 600 °C; the sintering time is 10 - 15 h, preferably 12 h; The heating rate of the sintering is 2 - 5 °C / min, preferably 2 °C / min; The sintering is carried out in an oxygen atmosphere.

[0014] The present invention further provides a ternary cathode material prepared by the above preparation method.

[0015] The chemical formula of the ternary cathode material is LiNi x Co y Mn z O2, where 0.3 < x < 1, 0 < y < 0.4, 0 < z < 1, and x + y + z = 1; preferably, 0.3 ≤ x ≤ 0.65, 0.05 ≤ y < 0.4, 0.05 ≤ z < 0.4, and x + y + z = 1. [[ID=二十九]]

[0016] Finally, the present invention provides a positive electrode of a lithium-ion battery, and its active component is the ternary cathode material.

[0017] A lithium-ion battery, whose positive electrode is the positive electrode of the battery.

[0018] The ternary cathode material prepared by this invention possesses a unique hollow multilayer morphology. This hollow multilayer structure effectively mitigates structural collapse caused by volume expansion during cycling, thereby significantly improving the material's stability and enhancing battery cycle performance. Secondly, the unique hollow multilayer morphology forms an interconnected conductive network, providing channels for lithium-ion transport and greatly improving lithium-ion transport efficiency, thus enhancing the cathode material's power performance. Finally, the hollow multilayer structure helps reduce cation mixing and transition metal dissolution, further improving the cathode material's stability during cycling. Attached Figure Description

[0019] Figure 1 The image shows a SEM image of the NCM cathode material with a special morphology prepared in Example 1. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0021] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0022] Unless otherwise specified, the quantitative experiments in the following examples are all repeated three times, and the results are averaged.

[0023] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0024] Example 1 (1) Add 155.0 g (1 mol) of CoSO4 and 192.1 g (1 mol) of anhydrous citric acid to 2 L of deionized water and stir continuously until fully dissolved to obtain a clear and transparent solution. Then add 2 L of ethylene glycol to the above solution and stir continuously for 30 min to obtain a uniformly mixed solution.

[0025] (2) The solution obtained in step (1) was placed in a polytetrafluoroethylene container and kept at 120°C for 10 hours. The resulting solid was washed by suction filtration with anhydrous ethanol and dried at 60°C for 4 hours. The dried powder was placed in a sagger and sintered in a muffle furnace at 450°C for 3 hours in a nitrogen atmosphere to obtain Co3O4 powder with a special morphology.

[0026] (3) Add 24.08 g (0.1 mol) Co3O4 powder, 412.49 g (2.33 mol) NiC4H6O4, 138.38 g (0.8 mol) MnC4H6O4 and 22.32 g (0.93 mol) LiOH obtained in step (2) to 500 mL of deionized water, heat to 80 °C and stir continuously for 6 h. Place the resulting solid in an oven and heat continuously to dry the moisture to obtain a dry solid powder.

[0027] (4) The solid powder obtained in step (3) is placed in a muffle furnace for sintering, oxygen is introduced, and the temperature is raised to 600℃ at a heating rate of 2℃ / min, and held for 12h; it is then passed through a 200-mesh sieve to obtain an NCM cathode material with a special morphology, the SEM image of which is shown in [image missing]. Figure 1 .

[0028] Example 2 (1) Add 155.0g of CoSO4 and 192.1g of anhydrous citric acid to 2L of deionized water and stir continuously until fully dissolved to obtain a clear and transparent solution. Then add 2L of ethylene glycol to the above solution and stir continuously for 30min to obtain a uniformly mixed solution.

[0029] (2) The solution obtained in step (1) was placed in a polytetrafluoroethylene container and kept at 120°C for 10 hours. The resulting solid was washed by suction filtration with anhydrous ethanol and dried at 60°C for 4 hours. The dried powder was placed in a sagger and sintered in a muffle furnace at 400°C for 3 hours in a nitrogen atmosphere to obtain Co3O4 powder with a special morphology.

[0030] Steps (3) and (4) are the same as in Example 1.

[0031] Example 3 (1) Add 155.0g of CoSO4 and 192.1g of anhydrous citric acid to 2L of deionized water and stir continuously until fully dissolved to obtain a clear and transparent solution. Then add 2L of ethylene glycol to the above solution and stir continuously for 30min to obtain a uniformly mixed solution.

[0032] (2) The solution obtained in step (1) was placed in a polytetrafluoroethylene container and kept at 120°C for 10 hours. The resulting solid was washed by suction filtration with anhydrous ethanol and dried at 60°C for 4 hours. The dried powder was placed in a sagger and sintered in a muffle furnace at 500°C for 3 hours in a nitrogen atmosphere to obtain Co3O4 powder with a special morphology.

[0033] Steps (3) and (4) are the same as in Example 1.

[0034] Example 4 Steps (1)-(3) are the same as in Example 1.

[0035] (4) The solid powder obtained in step (3) is placed in a muffle furnace for sintering, oxygen is introduced, and the temperature is raised to 500°C at a heating rate of 2°C / min and held for 12 hours; the powder is then passed through a mesh sieve to obtain NCM cathode material with a special morphology.

[0036] The NCM cathode material prepared in Examples 1-4, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5. A slurry was prepared using NMP as a solvent and then uniformly coated onto aluminum foil to obtain the cathode. A lithium metal sheet was used as the anode, a polypropylene microporous membrane as the separator, and 1 mol / L LiPF6 as the electrolyte (a mixed solvent of EC, DEC, and DMC in a volume ratio of 1:1:1). A CR2032 coin cell was fabricated in an argon-filled glove box. The electrochemical performance of the fabricated coin cells was tested. Tests were conducted at room temperature (25°C). For the first four weeks, the cells were charged and discharged at 0.2C / 0.2C, 0.33C / 0.33C, 1C / 1C, and 0.2C / 0.2C, respectively. Afterward, they were charged and discharged at 1C / 1C for 50 cycles. The performance data of the coin cells are shown in Table 1.

[0037] Table 1. Battery performance of NCM cathode materials prepared in Examples 1-4

[0038] As can be seen from Examples 1-3, the capacity and cycle performance changed with the change of the sintering temperature of the obtained Co3O4 powder. The sample in Example 1 (450℃) had the best performance because too low a temperature is not conducive to the formation of special morphologies, while too high a temperature will lead to the damage of special morphologies. Then, comparing Example 4 and Example 1, it can be seen that the sample with a subsequent sintering temperature of 600℃ has better performance, possibly because the crystal structure of the sample is more fully developed.

Claims

1. A method for preparing a ternary cathode material, characterized in that: The preparation method includes the following steps: (1) Mix cobalt source, citric acid, water and ethylene glycol to obtain a mixed solution; heat the mixed solution to react, and then sinter the resulting solid to obtain Co3O4 powder; (2) The Co3O4 powder, nickel source, manganese source, lithium source and solvent are mixed and reacted, and the resulting solid is sintered to obtain the ternary cathode material.

2. The method for preparing the ternary cathode material according to claim 1, characterized in that: In step (1), the cobalt source is an inorganic salt of cobalt; The molar ratio of the cobalt source to citric acid is 1:1-2; The molar ratio of the cobalt source to the volume of water is 1 mol: 2-3 L; The molar ratio of the cobalt source to the volume ratio of ethylene glycol is 1 mol: 2-3 L.

3. The method for preparing the ternary cathode material according to claim 1, characterized in that: In step (1), the cobalt source is cobalt sulfate and / or cobalt nitrate.

4. The method for preparing the ternary cathode material according to claim 1, characterized in that: In step (1), the temperature at which the reaction is carried out by heating is 100-150℃; the time is 10-15h. In step (1), the sintering temperature is 400-500℃; the sintering time is 2-4h; and the sintering is carried out in an inert atmosphere.

5. The method for preparing the ternary cathode material according to claim 1, characterized in that: In step (2), the nickel source is an organic salt of nickel, specifically nickel acetate and / or nickel formate; The manganese source is an organic salt of manganese, specifically manganese acetate and / or manganese formate; The lithium source is lithium carbonate and / or lithium hydroxide; The molar ratio of the Co3O4 powder, nickel source, manganese source, and lithium source is 1:20-24:7-9:9.19-9.54; The solvent is ethanol and / or water.

6. The method for preparing the ternary cathode material according to claim 1, characterized in that: In step (2), the reaction temperature is 80-100℃; The reaction time is 4-8 hours.

7. The method for preparing the ternary cathode material according to claim 1, characterized in that: In step (2), the sintering temperature is 500-700℃; the sintering time is 10-15h. The heating rate for sintering is 2-5℃ / min; The sintering is carried out in an oxygen atmosphere.

8. The ternary cathode material prepared by the preparation method according to any one of claims 1-7.

9. A lithium-ion battery cathode, wherein the active component is the ternary cathode material as described in claim 8.

10. An ion battery, wherein the positive electrode is the positive electrode of the battery according to claim 9.

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