Synthesis method for preparing single crystal-single crystal-like spherical lithium-rich manganese-based positive electrode material precursor by using solid precipitation method

Abstract

The invention discloses a synthesis method for preparing a single crystal-single crystal-like spherical lithium-rich manganese-based positive electrode material precursor by using a solid precipitation method, which comprises the following steps: (1) complexing and mixing: premixing a nickel source, a cobalt source, a manganese source and a complexing agent in a powder form at the mixing temperature of 0-750 DEG C for 10 minutes to 2 hours at the rotating speed of 100-400 rpm; (2) precipitation reaction and aging / heat treatment: adding a precipitator into the mixture obtained in the step (1), and reacting for 10 minutes to 100 hours in a wide temperature range from room temperature to 950 DEG C; and (3) post-treatment: washing the initial precursor with deionized water, filtering, and drying a filter cake at 120 DEG C for 10 hours to obtain the lithium-rich manganese-based precursor. According to the invention, the technical bottlenecks of uneven element distribution, serious cation mixing, disordered growth of primary particles, low tap density and the like when the material is prepared by a traditional coprecipitation method are solved, and excellent structural stability and cycle life of a single crystal material are realized while the excellent manufacturability of the spherical particles is kept.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a method for synthesizing single-crystal to near-single-crystal spherical lithium-rich manganese-based cathode material precursors using a solid-state precipitation method. Background Technology

[0002] Lithium-ion batteries, as a new generation of energy storage devices, have broad application prospects in electric vehicles and large-scale energy storage. However, the discharge specific capacity of existing commercial cathode materials (such as lithium iron phosphate and ternary materials) is generally lower than 200 mAh / g, which is insufficient to meet the growing market demand for high-energy-density batteries. Lithium-rich manganese-based oxide (LRMO) cathode materials are considered one of the most promising cathode materials for next-generation high-energy-density lithium-ion batteries due to their ultra-high discharge specific capacity (>250 mAh / g) and high operating voltage. From the perspective of material structure design, there are currently two main technical routes: First, polycrystalline spherical secondary particle structure. This structure is usually prepared by co-precipitation and has the advantages of high tap density and good electrode processing performance, which is the main form currently used in commercial applications. For example, patent CN118954633A obtains lithium-rich manganese-based cathode materials with high tap density, high capacity, and high cycle performance through a co-precipitation-milling-spraying process. However, spherical particles require complex processes such as spraying, resulting in high costs. Furthermore, these spherical particles are typically formed by the aggregation of countless primary nanoparticles. Under repeated cyclic stress, microcracks easily form within the secondary particles. These microcracks expose new active surfaces, exacerbating electrolyte side reactions and providing channels for the dissolution of transition metal ions, thereby accelerating structural damage and performance degradation of the material. The second approach is to construct single-crystal particle structures. This structure effectively suppresses microcrack formation by eliminating grain boundaries, exhibiting excellent cycling stability and voltage retention. For example, patents CN120774477A and CN120841588A use a liquid precipitation method to prepare transition metal salts into hydroxides, which are then mixed with a lithium source and calcined to obtain lithium-rich manganese-based cathode materials. However, the preparation of single-crystal materials usually requires high-temperature sintering or complex molten salt methods, resulting in high process costs and difficulty in control. More importantly, single-crystal materials typically have low tap density, which is detrimental to improving electrode energy density; simultaneously, their dense bulk structure also restricts the bulk diffusion kinetics of lithium ions, leading to often unsatisfactory rate performance. In summary, while existing polycrystalline spherical structures are beneficial for industrialization, they suffer from insufficient structural stability. Single-crystal structures, on the other hand, offer excellent stability but face bottlenecks such as difficult fabrication, poor rate performance, and poor processing capabilities. Therefore, there is an urgent need for an innovative material structure design that can simultaneously achieve the superior structural stability and cycle life of single-crystal materials while retaining the excellent processability of spherical particles. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a synthesis method for preparing single-crystal-quasi-single-spherical lithium-rich manganese-based cathode material precursors using solid-state precipitation. This method overcomes the technical bottlenecks in the traditional co-precipitation method for preparing such materials, such as uneven element distribution, severe cation mixing, disordered growth of primary particles, and low tap density. While retaining the excellent processability of spherical particles, this method achieves the same excellent structural stability and cycle life as single-crystal materials.

[0004] To address the aforementioned technical problems, this invention provides a method for synthesizing single-crystal-quasi-single-crystal spherical lithium-rich manganese-based cathode material precursors using a solid-state precipitation method, comprising the following steps: (1) Complexation mixing step: The nickel source, cobalt source, manganese source and complexing agent are premixed in powder form. The mixing temperature is 0℃-750℃, the mixing time is 10min-2h, and the rotation speed is 100rpm-400rpm. (2) Precipitation reaction and aging / heat treatment steps: Add precipitant to the mixture in step (1) and react for 10 min to 100 h in a wide temperature range from room temperature to 950 °C; (3) Post-processing steps: The initial precursor was washed and filtered with deionized water, and the filter cake was dried at 120°C for 10 h to obtain lithium-rich manganese-based precursor.

[0005] Further, the mixing equipment in step (1) is a stirring tank, a VC mixer or a pulverizer.

[0006] Furthermore, the nickel source in step (1) is nickel sulfate hexahydrate, nickel nitrate hexahydrate, or nickel chloride; The cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, or cobalt chloride. The manganese source is manganese sulfate monohydrate, manganese nitrate tetrahydrate, or manganese chloride. The complexing agent is one or more of gluconic acid, citric acid monohydrate, tartaric acid, anhydrous oxalic acid, ethylenediaminetetraacetic acid, urea, and ammonium carbonate. The precipitant is one or more of sodium carbonate, sodium hydroxide, and sodium bicarbonate.

[0007] Furthermore, the complexing agent is preferably an organic acid that does not contain nitrogen, such as gluconic acid, citric acid monohydrate, tartaric acid, or combinations thereof.

[0008] The beneficial effects of this invention are: optimized structural performance: a lithium-rich manganese precursor with a single crystal / quasi-single crystal spherical morphology was successfully prepared. SEM testing showed that the precursor was a regular spherical secondary particle composed of well-grown single crystal / quasi-single crystal primary particles, which effectively improved the tap density and structural stability of the material. Improved electrochemical performance: The specific capacity of the example samples (LRMS-1 to LRMS-8) at 0.1C first discharge was stable in the range of 290-293 mAh / g, with an average of 291.7 mAh / g, which is an absolute increase of about 40 mAh / g compared with the reference sample (average 250.8 mAh / g), and a relative increase of 16.3%. The specific capacity at 0.5C rate was better than that of the reference sample, and the lithium-ion diffusion kinetics were better. After 100 cycles at 1C rate, the average capacity retention rate reached 90.06%, which is more than 7 percentage points higher than that of the reference sample (82.84%). Reduced production costs: The use of inexpensive transition metal salts such as manganese sulfate and nickel sulfate avoids the dependence on precision reaction vessels and complex pH control systems required by traditional liquid phase coprecipitation, thereby reducing equipment investment, lowering energy consumption, and improving production efficiency. Enhanced environmental friendliness: The use of nitrogen-free organic acids as complexing agents avoids the generation of ammonia nitrogen wastewater at the source, thus meeting environmental protection requirements. Attached Figure Description

[0009] Figure 1 This is a SEM image of MS-1, the single-crystal / quasi-single-crystal spherical lithium-rich manganese precursor of the present invention.

[0010] Figure 2 This is a SEM image of the polycrystalline lithium-rich manganese precursor M-1 of the present invention.

[0011] Figure 3 This is a table showing the electrochemical performance test results of the experimental materials of this invention. Detailed Implementation

[0012] 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.

[0013] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0014] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0015] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0017] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0018] Reference Figures 1 to 3 As shown, an embodiment of the synthesis method of a single-crystal-quasi-single-crystal spherical lithium-rich manganese-based cathode material precursor prepared by solid-state precipitation according to the present invention includes the following steps: (1) Complexation mixing step: The nickel source, cobalt source, manganese source and complexing agent are premixed in powder form. The mixing temperature is 0℃-750℃, the mixing time is 10min-2h, and the rotation speed is 100rpm-400rpm. (2) Precipitation reaction and aging / heat treatment steps: Add precipitant to the mixture in step (1) and react for 10 min to 100 h in a wide temperature range from room temperature to 950 °C; (3) Post-processing steps: The initial precursor was washed and filtered with deionized water, and the filter cake was dried at 120°C for 10 h to obtain lithium-rich manganese-based precursor.

[0019] The mixing equipment in step (1) is a stirred tank, a VC mixer, or a pulverizer; the nickel source is nickel sulfate hexahydrate, nickel nitrate hexahydrate, or nickel chloride; the cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, or cobalt chloride; the manganese source is manganese sulfate monohydrate, manganese nitrate tetrahydrate, or manganese chloride; the complexing agent is one or more of gluconic acid, citric acid monohydrate, tartaric acid, anhydrous oxalic acid, ethylenediaminetetraacetic acid, urea, and ammonium carbonate, preferably an organic acid that does not contain nitrogen, namely gluconic acid, citric acid monohydrate, tartaric acid, or combinations thereof; the precipitant is one or more of sodium carbonate, sodium hydroxide, and sodium bicarbonate. The core function of transition metal salts is to provide the nickel, cobalt, and manganese elements necessary for lithium-rich manganese-based cathode materials. The core function of complexing agents is to form stable complexes with metal ions, control the release and co-precipitation rate of metal ions, and inhibit the oxidation and segregation of manganese ions. The core function of precipitants is to provide hydroxide ions and carbonate anions, which react with complexed metal ions to generate co-precipitation products and regulate the precursor crystal form and tap density.

[0020] The following are specific examples: Example 1: (1) Weigh nickel sulfate hexahydrate (0.13 mol), cobalt sulfate heptahydrate (0.13 mol), and manganese sulfate monohydrate (0.54 mol) and add them to a grinder, then add gluconic acid (0.8 mol) and grind and mix at room temperature for 10 min; (2) Then add sodium carbonate (1.6 mol) and continue to grind at room temperature for 10 min to obtain the initial precursor; (3) Take the initial precursor, then wash and filter it with deionized water to obtain a filter cake. Place the filter cake in an oven at 120℃ for 10 h to obtain the lithium-rich manganese-based precursor MS-1.

[0021] Example 2: (1) Weigh nickel sulfate hexahydrate (0.13 mol), cobalt sulfate heptahydrate (0.13 mol), and manganese sulfate monohydrate (0.54 mol) and add them to a stirred tank. Then add citric acid monohydrate (1.6 mol) and mix at 200 rpm for 1 h at 50 °C. (2) Then add sodium hydroxide (0.8 mol) and sodium carbonate (0.8 mol), stir for 2 h, and continue stirring at 50 °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 cobalt hydroxide precursor MS-2.

[0022] Example 3: (1) Weigh nickel nitrate hexahydrate (0.13 mol), cobalt sulfate heptahydrate (0.13 mol), and manganese chloride (0.54 mol) and add them to a VC mixer. Then add tartaric acid (1.6 mol) and mix at 100 rpm for 1 h at 25 °C. (2) Then add sodium carbonate (1.2 mol) and sodium hydroxide (1.2 mol), stir for 1 h, and 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 cobalt hydroxide precursor MS-3.

[0023] Example 4: (1) Weigh nickel sulfate hexahydrate (0.13 mol), cobalt sulfate heptahydrate (0.13 mol), and manganese nitrate tetrahydrate (0.54 mol) and add them to a stirred tank. Then add gluconic acid (0.8 mol) and tartaric acid (0.8 mol) and mix at 150°C and 200 rpm for 30 min. (2) Then add sodium bicarbonate (0.8 mol) and sodium carbonate (2.4 mol), stir for 1 h and continue stirring at 50°C for 20 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 cobalt hydroxide precursor MS-4.

[0024] Example 5: (1) Weigh nickel chloride (0.13 mol), cobalt chloride (0.13 mol), and manganese sulfate monohydrate (0.54 mol) and add them to a VC mixer. Then add anhydrous oxalic acid (1.6 mol) and mix at 100°C and 100 rpm for 1 h. (2) Then add sodium carbonate (1.2 mol) and sodium hydroxide (1.2 mol), stir for 1 h, and continue stirring at 350°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 hydroxide precursor MS-5.

[0025] Example 6: (1) Weigh nickel sulfate hexahydrate (0.13 mol), cobalt chloride (0.13 mol), and manganese sulfate monohydrate (0.54 mol) and add them to a stirred tank. Then add tartaric acid (1.2 mol) and mix at 200 rpm for 2 h at 50 °C. (2) Then add sodium carbonate (1.2 mol) and sodium hydroxide (0.8 mol), stir for 1 h, and continue stirring at 550 °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 cobalt hydroxide precursor MS-6.

[0026] Example 7: (1) Weigh nickel sulfate hexahydrate (0.13 mol), cobalt chloride (0.13 mol), and manganese nitrate tetrahydrate (0.54 mol) and add them to a stirred tank. Then add ethylenediaminetetraacetic acid (1.6 mol) and mix at 0°C and 200 rpm for 1 h. (2) Then add sodium carbonate (1 mol) and sodium hydroxide (1 mol), stir for 1 h, and continue stirring at 750°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 cobalt hydroxide precursor MS-7.

[0027] Example 8: (1) Weigh nickel sulfate hexahydrate (0.13 mol), cobalt nitrate hexahydrate (0.13 mol), and manganese nitrate tetrahydrate (0.54 mol) and add them to a stirred tank. Then add citric acid monohydrate (2.4 mol) and tartaric acid (0.8 mol) and mix at 0°C and 200 rpm for 1 h. (2) Then add sodium bicarbonate (0.8 mol) and sodium hydroxide (1.6 mol), stir for 1 h and continue stirring at 950°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 cobalt hydroxide precursor MS-8.

[0028] Reference Example 1: The preparation method is basically the same as in Example 1, except that gluconic acid is not added, and layered oxide M-1 is obtained.

[0029] Reference Example 2: The preparation method is basically the same as in Example 2, except that citric acid monohydrate is not added, and layered oxide M-2 is obtained.

[0030] Reference Example 3: The preparation method is basically the same as in Example 3, except that tartaric acid is not added, and layered oxide M-3 is obtained.

[0031] Reference Example 4: The preparation method is basically the same as in Example 4, except that gluconic acid and tartaric acid are not added, and layered oxide M-4 is obtained.

[0032] Reference Example 5: The preparation method is basically the same as in Example 5, except that anhydrous oxalic acid is not added, and layered oxide M-5 is obtained.

[0033] Reference Example 6: The preparation method is basically the same as in Example 6, except that tartaric acid is not added, and layered oxide M-6 is obtained.

[0034] Reference Example 7: The preparation method is basically the same as in Example 7, except that ethylenediaminetetraacetic acid is not added, and layered oxide M-7 is obtained.

[0035] Reference Example 8: The preparation method is basically the same as in Example 8, except that citric acid monohydrate and tartaric acid are not added, and layered oxide M-8 is obtained.

[0036] Preparation of lithium-rich manganese-based cathode materials for lithium-ion batteries Precursors MS-1 to MS-8 and M-1 to M-8 from Examples 1-8 and Comparative Examples 1-8 were respectively mixed with lithium carbonate, wherein the Li:M (total transition metal) molar ratio was 1.2:0.8. The mixture was then pulverized and mixed to obtain a mixture. The mixture was calcined at 500°C for 5 hours and then at 900°C for 15 hours in an air atmosphere. After pulverization, lithium-rich manganese-based cathode materials for lithium batteries were obtained, with material numbers LRMS-1 to LRMS-8 and LRM-1 to LRM-8 respectively.

[0037] Battery assembly and testing A slurry was prepared by mixing lithium-rich manganese material, conductive carbon, and binder in a 94:3:3 ratio. After mixing in a ball mill 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 a lithium metal sheet 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 2.0-4.8V: 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.

[0038] Based on the above embodiments and the drawings, it can be seen that: Example 1 precursor MS-1 exhibits regular spherical secondary particles composed of well-grown single-crystal / quasi-single-crystal primary particles. This unique structure effectively improves the tap density and structural stability of the material. In contrast, the reference example 1 precursor M-1 (without a complexing agent) Figure 2The material is an irregular polycrystalline aggregate with a loose structure. Furthermore, electrochemical performance tests fully demonstrate that the initial discharge specific capacity at 0.1C for the example samples (LRMS-1 to LRMS-8) remained stable in the range of 290-293 mAh / g, averaging 291.7 mAh / g, representing an absolute increase of approximately 40 mAh / g and a relative increase of 16.3% compared to the reference sample (average 250.8 mAh / g). At 0.5C, the specific capacity of the example samples was also significantly better than that of the reference sample, indicating superior lithium-ion diffusion kinetics. After 100 cycles at 1C, the average capacity retention of the example samples reached 90.06%, an increase of over 7 percentage points compared to the reference sample (82.84%), proving that the single-crystal / quasi-single-crystal structure effectively suppressed particle breakage and interfacial side reactions during cycling.

[0039] 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 synthesizing single-crystal to near-single-crystal spherical lithium-rich manganese-based cathode material precursors using solid-state precipitation, characterized in that, Includes the following steps: (1) Complexation mixing step: The nickel source, cobalt source, manganese source and complexing agent are premixed in powder form. The mixing temperature is 0℃-750℃, the mixing time is 10min-2h, and the rotation speed is 100rpm-400rpm. (2) Precipitation reaction and aging / heat treatment steps: Add precipitant to the mixture in step (1) and react for 10 min to 100 h in a wide temperature range from room temperature to 950 °C; (3) Post-processing steps: The initial precursor was washed and filtered with deionized water, and the filter cake was dried at 120°C for 10 h to obtain lithium-rich manganese-based precursor.

2. The synthesis method for preparing single-crystal-quasi-single-crystal spherical lithium-rich manganese-based cathode material precursors using solid-state precipitation as described in claim 1, characterized in that, The mixing equipment in step (1) is a stirring tank, a VC mixer or a pulverizer.

3. The method for synthesizing single-crystal-quasi-single-crystal spherical lithium-rich manganese-based cathode material precursors using solid-state precipitation as described in claim 1, characterized in that... The nickel source in step (1) is nickel sulfate hexahydrate, nickel nitrate hexahydrate, or nickel chloride; The cobalt source is cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, or cobalt chloride. The manganese source is manganese sulfate monohydrate, manganese nitrate tetrahydrate, or manganese chloride. The complexing agent is one or more of gluconic acid, citric acid monohydrate, tartaric acid, anhydrous oxalic acid, ethylenediaminetetraacetic acid, urea, and ammonium carbonate. The precipitant is one or more of sodium carbonate, sodium hydroxide, and sodium bicarbonate.

4. The method for synthesizing single-crystal-quasi-single-crystal spherical lithium-rich manganese-based cathode material precursors using solid-state precipitation as described in claim 3, characterized in that... The complexing agent is preferably an organic acid that does not contain nitrogen, such as gluconic acid, citric acid monohydrate, tartaric acid, or combinations thereof.

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