Preparation method of self-assembled high-performance spherical lithium cobalt oxide positive electrode material of lithium ion battery

Abstract

The invention discloses a preparation method of a self-assembled high-performance spherical lithium cobalt oxide positive electrode material of a lithium ion battery. The preparation method comprises the following steps: (1) complexing and mixing: mixing a cobalt source and complexing agent raw material powder; the cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate or cobalt chloride; the complexing agent is one or more of ammonia water, ammonium carbonate, urea, ethylenediamine tetraacetic acid, citric acid monohydrate or anhydrous oxalic acid; (2) a precipitation reaction and aging step: adding a precipitator into the mixture obtained in the step (1); the precipitant is sodium carbonate, sodium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydroxide or a combination thereof; and (3) a post-treatment step: washing the initial precursor with deionized water, filtering, drying to obtain cobalt precursor powder, mixing the obtained cobalt precursor with a lithium source, and roasting to obtain the lithium cobalt oxide positive electrode material. According to the invention, the raw material cost is reduced, the operation steps are simplified, the product yield is improved, and the low-cost and high-performance lithium cobalt oxide positive electrode material with the spherical structure can be prepared.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation technology, specifically to a method for preparing a self-assembled high-performance spherical lithium cobalt oxide cathode material for lithium-ion batteries. Background Technology

[0002] Lithium cobalt oxide (LiCoO2), as the earliest commercially available cathode material for lithium-ion batteries, laid the foundation for the entire industry through its research and development. Its unique layered α-NaFeO2 crystal structure provides an ideal two-dimensional channel for the reversible insertion and extraction of lithium ions, thus ensuring excellent intrinsic electronic conductivity and rate performance. Despite challenges such as cost, cobalt resource toxicity, and capacity exploitation, the application of advanced modification technologies such as grain boundary regulation, surface coating, and high-voltage stabilization has continuously revitalized the lithium cobalt oxide material system, maintaining its irreplaceable core position in high-end compact electronic devices. Currently, the mainstream methods for synthesizing lithium cobalt oxide include the sol-gel method, the high-temperature solid-state method, and the liquid precipitation method. The sol-gel method involves uniformly mixing raw materials and organic matter in a liquid phase, followed by aging, drying, and calcination to obtain the product. For example, patent CN201510864374.2 describes synthesizing lithium cobalt oxide compounds by sol-gel reaction of lithium ions and cobalt ions at a certain temperature, followed by low-temperature dehydration and high-temperature reconstruction to obtain the final lithium cobalt oxide compound. The sol-gel method can form products with uniform particles, but the operation is complex and requires the use of organic materials, leading to a series of environmental problems in subsequent processing. The high-temperature solid-state method for preparing lithium cobalt oxide involves uniformly mixing lithium source, cobalt source, and additives, followed by sintering in an oxygen atmosphere to form a regular crystal structure and uniform particle morphology. For example, patents CN202210721830.8 and CN201711127640.9 mix qualified cobalt tetroxide (such as a specific median particle size D50) with lithium salt, followed by high-temperature calcination to obtain single-crystal lithium cobalt oxide cathode materials. This route has the advantages of simple process, high material utilization, and potential for large-scale scaling. However, the effectiveness of this technology is highly dependent on the intrinsic purity and initial morphology of the cobalt source raw material, which directly leads to increased production costs. Furthermore, the process usually requires the introduction of additives and the continuous introduction of specific gases, increasing the complexity of the process. The liquid precipitation method involves uniformly mixing a lithium source, a cobalt source, and a precipitant in a solution, followed by filtration, washing, drying, and calcination to obtain lithium cobalt oxide. For example, patent CN202111095797.4 describes a method where cobalt sulfate and a doped salt are mixed into a solution, which is then added dropwise to a reaction vessel along with ammonia and sodium hydroxide using a peristaltic pump. After precipitation under nitrogen, the material is washed, dried, and calcined to obtain the lithium cobalt oxide cathode material. This method can achieve high product yields, but the wastewater generated may increase production costs. Furthermore, the precipitation process requires precise control of conditions (such as pH, precipitant dripping rate, and stirring speed) to ensure product quality, and the low raw material utilization rate leads to resource waste. Meanwhile, patent CN202510350777.9 has also demonstrated that spherical lithium cobalt oxide cathode materials have higher specific capacity and higher cycle stability; however, the spherical formation process typically requires cumbersome procedures such as spraying and segmented calcination, resulting in higher costs.In summary, it is necessary to optimize the traditional preparation method of spherical lithium cobalt oxide, reduce the cost of raw materials, simplify the operation steps, and improve the product yield in order to prepare low-cost, high-performance spherical lithium cobalt oxide cathode materials. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing self-assembled high-performance spherical lithium cobalt oxide cathode material for lithium-ion batteries, which reduces raw material costs, simplifies operation steps, and improves product yield, and can prepare low-cost, high-performance spherical lithium cobalt oxide cathode material.

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a self-assembled high-performance spherical lithium-ion battery lithium cobalt oxide cathode material, comprising the following steps: (1) Solid-state complexing mixing step: Mix the cobalt source with the complexing agent raw material powder; The cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, or cobalt chloride; the complexing agent is one or more of ammonia, ammonium carbonate, urea, ethylenediaminetetraacetic acid, citric acid monohydrate, or anhydrous oxalic acid. (2) Solid precipitation reaction and aging steps: Add a precipitant to the mixture in step (1); The precipitant is sodium carbonate, sodium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydroxide, or a combination thereof; (3) Post-processing steps: The initial precursor is washed, filtered and dried with deionized water to obtain cobalt precursor powder. The obtained cobalt precursor is mixed with lithium source and calcined to obtain lithium cobalt oxide cathode material.

[0005] Furthermore, the complexing agent in step (1) is preferably one or more of ethylenediaminetetraacetic acid, citric acid monohydrate, or anhydrous oxalic acid.

[0006] Furthermore, the precipitant in step (2) is preferably one or more of sodium carbonate, sodium hydroxide, or sodium bicarbonate.

[0007] Further, the mixing parameters in step (1) are: temperature range 0℃-200℃, rotation speed 100rpm-400rpm, and time 10min-1h; The molar ratio of cobalt to complexing agent is 1:1 to 1:10.

[0008] Furthermore, the reaction parameters in step (2) are: temperature range 0℃-950℃, reaction time 30min-100h; The molar ratio of the precipitant to cobalt is 1:1 to 1:10.

[0009] Furthermore, after drying in step (3), the precursor crystal form needs to be calcined at 750℃-1200℃ for 1h-50h to further optimize the precursor crystal form.

[0010] Furthermore, the mixing equipment in step (1) is a stirring tank, a VC mixer, or a pulverizer.

[0011] The beneficial effects of this invention are: 1. Excellent technical performance: By flexibly selecting different cobalt sources (cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, cobalt chloride) and multi-component complexing agents (EDTA, citric acid monohydrate, anhydrous oxalic acid and their composite systems), a series of cobalt precursors (COS-1 to COS-8) were successfully prepared in different temperatures, acid and alkaline environments, and reaction equipment ranging from 0℃ to 950℃; according to SEM experimental results ( Figure 1 , Figure 2 By controlling the type and ratio of complexing agents, the primary particle stacking mode and secondary spherical morphology of the precursors were effectively controlled, resulting in a concentrated particle size distribution and significantly improved tap density. When this series of precursors was used in the synthesis of lithium cobalt oxide cathode materials, the electrochemical performance was significantly improved. Figure 3 It exhibits excellent performance in terms of specific capacity and 1C cycle stability.

[0012] 2. Significant economic benefits: This technical solution is highly adaptable to a variety of cobalt sources, allowing for flexible selection of raw materials based on market prices, thus reducing raw material costs. Compared with the traditional liquid phase method, it reduces reaction steps, lowers energy consumption, and improves production efficiency, further controlling process costs.

[0013] 3. Good environmental and social benefits: By using environmentally friendly complexing agents (such as EDTA, citric acid monohydrate, and anhydrous oxalic acid) and optimized process conditions, the generation of ammonia nitrogen-containing wastewater is reduced, the wastewater treatment cost is lowered, and environmental protection requirements are met. At the same time, the simplified process flow facilitates large-scale production and provides strong technical support for the industrialization of high-performance lithium-ion battery materials. Attached Figure Description

[0014] Figure 1 This is a SEM image of the spherical cobalt precursor COS-1 of the present invention.

[0015] Figure 2 This is a SEM image of CO-1, the single-crystal cobalt precursor of the present invention.

[0016] Figure 3 These are the electrochemical performance test results of the lithium cobalt oxide cathode material of this invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0018] Reference Figures 1 to 3As shown, the present invention provides a method for preparing a self-assembled high-performance spherical lithium cobalt oxide cathode material for lithium-ion batteries, comprising the following steps: (1) Solid-state complexing mixing step: Mix the cobalt source with the complexing agent raw material powder; The cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, or cobalt chloride; the complexing agent is one or more of ammonia, ammonium carbonate, urea, ethylenediaminetetraacetic acid, citric acid monohydrate, or anhydrous oxalic acid. (2) Solid precipitation reaction and aging steps: Add a precipitant to the mixture in step (1); The precipitant is sodium carbonate, sodium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydroxide, or a combination thereof; (3) Post-processing steps: The initial precursor is washed, filtered and dried with deionized water to obtain cobalt precursor powder. The obtained cobalt precursor is mixed with lithium source and calcined to obtain lithium cobalt oxide cathode material.

[0019] Among them, the complexing agent in step (1) is preferably one or more of ethylenediaminetetraacetic acid, citric acid monohydrate or anhydrous oxalic acid, and the mixing equipment is a stirring tank, VC mixer or pulverizer. The mixing parameters are: temperature range 0℃-200℃, rotation speed 100rpm-400rpm, and time 10min-1h; The molar ratio of cobalt to complexing agent is 1:1 to 1:10.

[0020] In step (2), the precipitant is preferably one or more of sodium carbonate, sodium hydroxide, or sodium bicarbonate; The reaction parameters are: temperature range 0℃-950℃, reaction time 30min-100h; The molar ratio of the precipitant to cobalt is 1:1 to 1:10.

[0021] In step (3), after drying, the precursor crystal form needs to be calcined at 750℃-1200℃ for 1h-50h to further optimize the precursor crystal form.

[0022] The following are various embodiments and reference scales, as well as subsequent preparation and assembly testing: Example 1: (1) Weigh 1 mol of cobalt sulfate heptahydrate and add it to a stirred tank. Then add 0.5 mol of ethylenediaminetetraacetic acid and mix at 200 rpm for 1 h at 0 °C. (2) Then add 0.5 mol of sodium carbonate and 0.5 mol of sodium hydroxide. Stir for 1 h and continue stirring at 50 °C for 10 h to obtain the initial precursor. (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake. Place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-1.

[0023] Example 2: (1) Weigh 1 mol of cobalt sulfate heptahydrate and add it to a VC mixer, then add 1 mol of citric acid monohydrate and mix at 200 rpm for 1 h at 50 °C; (2) Then add 1 mol of sodium hydroxide, stir for 1 h and continue stirring at 100 °C for 4 h to obtain the initial precursor; (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake, place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-2.

[0024] Example 3: (1) Weigh 1 mol of cobalt nitrate hexahydrate and add it to a stirred tank. Then add 1 mol of ethylenediaminetetraacetic acid and mix at 100 rpm for 1 h at 25 °C. (2) Then add 1.5 mol of sodium carbonate and 1.5 mol of sodium hydroxide and stir for 2 h. Continue stirring at 200 °C for 6 h to obtain the initial precursor. (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake. Place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-3.

[0025] Example 4: (1) Weigh 1 mol of cobalt nitrate hexahydrate and add it to a pulverizer, then add 2 mol of citric acid monohydrate and mix at 400 rpm for 10 min at 25 °C; (2) Then add 2 mol of sodium carbonate, pulverize for 10 min and continue stirring at 350 °C for 10 h to obtain the initial precursor; (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake, place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-4.

[0026] Example 5: (1) Weigh 1 mol of cobalt sulfate heptahydrate and add it to a stirred tank. Then add 3 mol of anhydrous oxalic acid and mix at 100 rpm for 1 h at 100 °C. (2) Then add 2 mol of sodium carbonate and 2 mol of sodium hydroxide and stir for 1 h. Continue stirring at 550 °C for 5 h to obtain the initial precursor. (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake. Place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-5.

[0027] Example 6: (1) Weigh cobalt chloride (1 mol) and add it to a VC mixer, then add anhydrous oxalic acid (2 mol), and mix at 60°C and 200 rpm for 1 h; (2) Then add sodium carbonate (1.5 mol) and sodium hydroxide (0.5 mol), stir for 1 h, and continue stirring at 750°C for 2 h to obtain the initial precursor; (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake, place the filter cake in an oven at 120°C for 10 h to obtain the cobalt precursor COS-6.

[0028] Example 7: (1) Weigh cobalt chloride (1 mol) and add it to a stirred tank. Then add ethylenediaminetetraacetic acid (0.5 mol) and anhydrous oxalic acid (0.5 mol) and mix at 200 rpm for 1 h at 25 °C. (2) Then add sodium carbonate (1 mol) and sodium hydroxide (1 mol), stir for 1 h and continue stirring at 950 °C for 10 h to obtain the initial precursor. (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake. Place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-7.

[0029] Example 8: (1) Weigh 1 mol of cobalt sulfate heptahydrate and add it to a VC mixer. Then add 0.5 mol of ethylenediaminetetraacetic acid, 1 mol of citric acid monohydrate and 1 mol of anhydrous oxalic acid. Mix at 200 rpm for 1 h at 75 °C. (2) Then add 2 mol of sodium carbonate and stir for 2 h. Continue stirring at 350 °C for 10 h to obtain the initial precursor. (3) Take the initial precursor, wash and filter it with deionized water to obtain a filter cake. Place the filter cake in an oven at 120 °C for 10 h to obtain the cobalt precursor COS-8.

[0030] Reference Example 1: The preparation method is basically the same as in Example 1, except that ethylenediaminetetraacetic acid is not added, and the cobalt precursor CO-1 is obtained.

[0031] Reference Example 2: The preparation method is basically the same as in Example 2, except that citric acid monohydrate is not added, and cobalt precursor CO-2 is obtained.

[0032] Reference Example 3: The preparation method is basically the same as in Example 3, except that ethylenediaminetetraacetic acid is not added, and the cobalt precursor CO-3 is obtained.

[0033] Reference Example 4: The preparation method is basically the same as in Example 4, except that citric acid monohydrate is not added, and the cobalt precursor CO-4 is obtained.

[0034] Reference Example 5: The preparation method is basically the same as in Example 5, except that anhydrous oxalic acid is not added, and the cobalt precursor CO-5 is obtained.

[0035] Reference Example 6: The preparation method is basically the same as in Example 6, except that anhydrous oxalic acid is not added, and the cobalt precursor CO-6 is obtained.

[0036] Reference Example 7: The preparation method is basically the same as in Example 7, except that ethylenediaminetetraacetic acid and anhydrous oxalic acid are not added, and the cobalt precursor CO-7 is obtained.

[0037] Reference Example 8: The preparation method is basically the same as in Example 8, except that ethylenediaminetetraacetic acid, citric acid monohydrate and anhydrous oxalic acid are not added, and the cobalt precursor CO-8 is obtained.

[0038] Preparation of lithium cobalt oxide cathode material for lithium-ion batteries Cobalt precursors COS-1 to COS-8 and CO-1 to CO-8 from Examples 1-8 and Comparative Examples 1-8 were respectively mixed with lithium carbonate, wherein the Li:Co molar ratio was 1.03. The mixture was then pulverized and mixed to obtain a mixture. The mixture was calcined at 500°C for 5 hours and then at 950°C for 15 hours in an air atmosphere. After pulverization, lithium manganese oxide cathode materials for lithium batteries were obtained, and the material numbers were LCOS-1 to LCOS-8 and LCO-1 to LCO-8, respectively.

[0039] Battery assembly and testing Lithium cobalt oxide, conductive carbon black, and binder were mixed in a 94:3:3 ratio to form a slurry. After stirring for 5 hours, the slurry was uniformly coated onto aluminum foil, then vacuum dried and die-cut into Φ12mm electrode sheets. In an argon-filled glove box, using these electrode sheets as the positive electrode and lithium foil as the negative electrode, along with an electrolyte of 1M LiPF6 (dissolved in a solvent with a DMC:EC:EMC volume ratio of 1:1:1) and a polymer separator (PP / PE), a CR2032 type button cell was assembled. After static curing, the cells were tested within a voltage range of 3.0-4.6V: first, the discharge specific capacity at different rates was measured, and then the capacity retention rate after 100 cycles was evaluated at a 1C rate.

[0040] Based on the various precursor preparation schemes provided in this patent embodiment, and through systematic testing and comparative analysis, this technical solution has achieved significant technical progress and comprehensive benefits, specifically reflected in the following aspects: I. Superior Technical Results and Significantly Improved Material Performance. This patent successfully prepared a series of spherical cobalt precursors (LCOS-1 to LCOS-8) in different temperatures (0℃-950℃), acidic / alkaline environments, and reaction equipment by flexibly selecting different cobalt sources (cobalt sulfate, cobalt nitrate, cobalt chloride) and multi-component complexing agents (EDTA, citric acid, oxalic acid, and their composite systems) under various conditions. According to... Figure 1 and Figure 2 SEM experimental results showed that by adjusting the type and ratio of complexing agents, the primary particle stacking mode and secondary spherical morphology of the precursor were effectively controlled, resulting in a concentrated particle size distribution of the obtained product and effectively improving the tap density. Figure 3 It can be seen that the use of this series of precursors in the synthesis of lithium cobalt oxide cathode materials significantly improves electrochemical performance, showing excellent performance in terms of specific capacity and 1C cycle stability.

[0041] II. Significant economic benefits and effective reduction in production costs. This patented technology is highly adaptable to various cobalt sources, allowing for flexible selection of raw materials based on market prices. Compared to the traditional liquid-phase method, this technology reduces the number of reaction steps. In some embodiments (such as Example 4), a pulverizer replaces the traditional stirring equipment, which can reduce energy consumption and improve production efficiency.

[0042] III. Significant Social and Environmental Benefits. By using environmentally friendly complexing agents (such as citric acid) and optimized process conditions, the generation of ammonia-nitrogen-containing wastewater is reduced, and wastewater treatment costs are lowered. In summary, the various precursor preparation schemes provided by this invention, through innovative process combinations, achieve a balance between excellent material performance, reduced production costs, and environmental friendliness, providing strong technical support for the industrialization of high-performance lithium-ion battery materials.

[0043] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing self-assembled high-performance spherical lithium cobalt oxide cathode material for lithium ion batteries, characterized in that, The method comprises the following steps: (1) solid complex mixing step: mixing cobalt source with complexing agent raw material powder; The cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate or cobalt chloride; the complexing agent is one or more of ammonia, ammonium carbonate, urea, ethylenediaminetetraacetic acid, monohydrate citric acid or anhydrous oxalic acid; (2) solid precipitation reaction and aging step: adding a precipitant to the mixture of step (1); The precipitant is sodium carbonate, sodium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydroxide or a combination thereof; (3) post-processing step: washing, filtering and drying the initial precursor with deionized water to obtain cobalt precursor powder, mixing the obtained cobalt precursor with a lithium source, and calcining to obtain a lithium cobalt oxide positive electrode material.

2. The method for preparing a self-assembled high-performance spherical lithium-ion battery lithium cobalt oxide cathode material as described in claim 1, characterized in that, The complexing agent in step (1) is preferably one or more of ethylenediaminetetraacetic acid, monohydrate citric acid or anhydrous oxalic acid.

3. The method for preparing a self-assembled high-performance spherical lithium-ion battery lithium cobalt oxide cathode material as described in claim 1, characterized in that, The precipitant in step (2) is preferably one or more of sodium carbonate, sodium hydroxide or sodium bicarbonate.

4. The method for preparing a self-assembled high-performance spherical lithium cobalt oxide cathode material for lithium-ion batteries as described in claim 1, characterized in that, The mixing parameters in step (1) are: temperature range 0-200℃, rotation speed 100-400rpm, time 10min-1h; The molar ratio of cobalt to complexing agent is 1:1-1:

10.

5. The method for preparing a self-assembled high-performance spherical lithium-ion battery lithium cobalt oxide cathode material as described in claim 1, characterized in that, The reaction parameters in step (2) are: temperature range 0-950℃, reaction time 30min-100h; The molar ratio of precipitant to cobalt is 1:1-1:

10.

6. The method for preparing a self-assembled high-performance spherical lithium-ion battery lithium cobalt oxide cathode material as described in claim 1, characterized in that, In step (3), after drying, it needs to be calcined at 750-1200℃ for 1-50h to further optimize the precursor crystal form.

7. The method for preparing a self-assembled high-performance spherical lithium cobalt oxide cathode material for lithium-ion batteries as described in claim 1, characterized in that, The mixing equipment in step (1) is a stirred tank, a VC mixing machine or a pulverizer.

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