A method for preparing a high-performance positive electrode material based on a manganese sulfate precursor

Abstract

This invention discloses a high-performance cathode material based on a manganese sulfate precursor, belonging to the field of electrode material technology. The chemical formula is xLi₂MnO₃·(1-x)LiMO₂, where M includes Ni, Co, and Mn, and a dopant element Y, with a molar doping amount of Y of 1% to 5% of Mn. The manganese sulfate precursor mixture is prepared via a sol-gel method combined with a solid-state reaction, wherein the manganese sulfate precursor mixture is formed from nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate under the action of a chelating agent. This invention utilizes yttrium doping to achieve uniform distribution in the crystal lattice, stabilizing the layered structure, suppressing phase transitions and oxygen release during cycling, and significantly reducing voltage decay. It also optimizes the Li₂... + The diffusion pathway improves the initial coulombic efficiency and specific capacity, resulting in high capacity retention after 100 cycles. By introducing chelating agents, yttrium is ensured to be uniformly distributed at the molecular level, avoiding phase separation and lattice distortion, thereby enhancing material consistency and electrochemical stability.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a method for preparing a high-performance cathode material based on a manganese sulfate precursor. Background Technology

[0002] Lithium-ion batteries are widely used in new energy vehicles, portable electronic devices, and energy storage systems due to their high energy density, stable discharge characteristics, and lack of memory effect. Lithium-rich manganese-based cathode materials are considered ideal cathode materials for next-generation high-energy-density lithium-ion batteries due to their high specific capacity, high operating voltage, and low cost. However, existing lithium-rich manganese-based cathode materials have the following drawbacks:

[0003] Voltage decay: During cycling, the irreversible transformation of the material from a layered structure to a spinel structure and the release of oxygen cause the operating voltage to drop continuously, reducing the energy density.

[0004] Poor cycle stability: Structural instability and electrolyte side reactions lead to rapid capacity decay, limiting battery cycle life.

[0005] Low initial coulombic efficiency: The activation of Li2MnO3 components and the release of oxygen during the initial charge cause significant irreversible capacity loss. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing high-performance cathode materials based on manganese sulfate precursors. The specific technical solution is as follows:

[0007] The chemical formula of the high-performance cathode material prepared based on manganese sulfate precursor is xLi2MnO3·(1-x)LiMO2, where M includes Ni, Co and Mn, and Y is a dopant element, with the molar doping amount of Y being 1% to 5% of Mn. The high-performance cathode material is prepared by a sol-gel method combined with solid-state reaction of a manganese sulfate precursor mixture, wherein the manganese sulfate precursor mixture is formed by nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate under the action of a chelating agent.

[0008] Preferably, the molar ratio of Ni:Co:Mn in the manganese sulfate precursor mixture is (1.0~1.5):(1.0~1.5):(5.0~6.0).

[0009] Preferably, the chelating agent is selected from citric acid, ethylenediaminetetraacetic acid, or a combination thereof, wherein the amount of citric acid added is 0.8 to 1.3 times the total amount of metal ions, and the amount of ethylenediaminetetraacetic acid added is 0.3 to 0.5 times the total amount of metal ions.

[0010] The present invention also provides a preparation method for preparing a high-performance cathode material based on manganese sulfate precursor as described in any one of the above claims, the preparation method comprising the following steps:

[0011] a. Preparation of manganese sulfate precursor mixture: Dissolve nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate in a solvent, add a chelating agent, adjust the pH to 7-8 and stir evenly, heat to form a gel, and dry to obtain the product;

[0012] b. Synthesis of cathode material: The mixture of manganese sulfate precursor components is mixed with Li2CO3, ball-milled, and then subjected to solid-state reaction and calcination to obtain the cathode material.

[0013] Preferably, in step a:

[0014] The solvent is deionized water;

[0015] Alternatively, the solvent may be a microemulsion system, which includes an aqueous phase and an oil phase, wherein the aqueous phase includes deionized water and the oil phase includes an organic solvent and a surfactant.

[0016] Preferably:

[0017] The organic solvent is selected from n-hexane, isooctyl alcohol, or a combination thereof;

[0018] The surfactant is selected from hexadecyltrimethylammonium bromide.

[0019] Preferably, in step a:

[0020] The volume ratio of the aqueous phase to the oil phase is 1:(3~5), and the total concentration of metal ions in the aqueous phase is 0.8~1.2 M;

[0021] The concentration of the surfactant is 0.05~0.1 M;

[0022] The microemulsion system was prepared by slowly adding the aqueous phase dropwise to the oil phase while stirring at a speed of 500-1000 rpm.

[0023] Ammonia was selected as the pH adjuster, with a concentration of 1.0~2.0 M and a dropping rate of 0.5~2 mL / min.

[0024] The ball milling speed is 400~600 rpm, the ball milling time is 3~5 hours, and the ball-to-material mass ratio is (10~20):1.

[0025] Preferably, in step b, the solid-state reaction calcination employs a segmented temperature-controlled process, specifically including:

[0026] Keep warm at 350~450℃ for 3~5 hours;

[0027] Keep warm at 700~800℃ for 5~7 hours;

[0028] Keep warm at 850~950℃ for 7~9 hours;

[0029] Cool to room temperature at a cooling rate of 3~7℃ / min.

[0030] Preferably, the solvent is a microemulsion system, and step a specifically includes the following sub-steps:

[0031] a1. Dissolve nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate in deionized water to form aqueous phase A, wherein the amount of yttrium nitrate added is 4%~5% of the amount of manganese sulfate; dissolve nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate in deionized water to form aqueous phase B, wherein the amount of yttrium nitrate added is 1%~2% of the amount of manganese sulfate;

[0032] a2. After mixing the organic solvent and surfactant, stir until homogeneous to form an oil phase;

[0033] a3. Add aqueous phase A and aqueous phase B slowly dropwise into the oil phase at a volume ratio of 1:1, stirring continuously during the dropwise addition process;

[0034] a4. Add the chelating agent to the mixture and stir until homogeneous;

[0035] a5. Add a pH adjuster to adjust the pH to 7-8, heat at 75-85℃ for 3-5 hours to form a gel, and dry at 95-105℃ for 10-14 hours to obtain the final product.

[0036] Preferably, step b is followed by step c, which specifically includes the following sub-steps:

[0037] c1. Disperse the positive electrode material obtained in step b in ethanol to prepare a suspension with a mass concentration of 50~100 g / L;

[0038] c2. Add Al(NO3)3 and stir until homogeneous, wherein the mass of Al(NO3)3 is 1%~2% of the cathode material;

[0039] c3. Calcination at 450~550℃ for 3~5 hours to form an Al2O3 nano-coating layer.

[0040] The high-performance cathode material prepared based on manganese sulfate precursor provided by this invention has the following beneficial effects:

[0041] 1. Yttrium doping stabilizes the layered structure by uniformly distributing it in the crystal lattice, suppresses phase transitions and oxygen release during cycling, and significantly reduces voltage decay.

[0042] 2. Yttrium doping optimizes the Li+ diffusion path, improves the initial coulombic efficiency and specific capacity, and maintains a capacity retention of over 92% after 100 cycles, thus extending battery life.

[0043] 3. By introducing chelating agents in the manganese sulfate precursor stage through the sol-gel method, yttrium is ensured to be uniformly distributed at the molecular level, avoiding phase separation and lattice distortion, and improving material consistency and electrochemical stability. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0045] Figure 1 This is a SEM image of the high-performance cathode material prepared based on manganese sulfate precursor provided in Embodiment 1 of the present invention;

[0046] Figure 2 This is a SEM image of a high-performance cathode material prepared based on a manganese sulfate precursor, provided in Embodiment 2 of the present invention.

[0047] Figure 3 The XRD comparison diagrams are of the high-performance cathode materials prepared based on manganese sulfate precursors provided in Embodiments 1 and 2 of the present invention. Detailed Implementation

[0048] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0049] Please see Figures 1 to 3 This embodiment provides a high-performance cathode material based on a manganese sulfate precursor, with the general chemical formula xLi2MnO3·(1-x)LiMO2, wherein M includes Ni, Co and Mn, and a dopant element Y, the molar doping amount of Y being 1%~5% of the Mn element; the high-performance cathode material is prepared by a sol-gel method combined with a solid-state reaction of a manganese sulfate precursor mixture, wherein the manganese sulfate precursor mixture is formed by nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate under the action of a chelating agent.

[0050] The high-performance cathode material prepared based on manganese sulfate precursor provided in this embodiment has the following beneficial effects:

[0051] 1. Yttrium doping stabilizes the layered structure by uniformly distributing it in the crystal lattice, suppresses phase transitions and oxygen release during cycling, and significantly reduces voltage decay.

[0052] 2. Yttrium doping optimizes Li +The diffusion path improves the initial coulombic efficiency and specific capacity, and the capacity retention rate reaches more than 92% after 100 cycles, thus extending battery life.

[0053] 3. By introducing chelating agents in the manganese sulfate precursor stage through the sol-gel method, yttrium is ensured to be uniformly distributed at the molecular level, avoiding phase separation and lattice distortion, and improving material consistency and electrochemical stability.

[0054] Furthermore, the molar ratio of Ni:Co:Mn in the manganese sulfate precursor mixture is (1.0~1.5):(1.0~1.5):(5.0~6.0); preferably 1.3:1.3:5.4.

[0055] Furthermore, the chelating agent is selected from citric acid, ethylenediaminetetraacetic acid, or a combination thereof, wherein the amount of citric acid added is 0.8 to 1.3 times the total amount of metal ions, and the amount of ethylenediaminetetraacetic acid added is 0.3 to 0.5 times the total amount of metal ions.

[0056] This embodiment also provides a preparation method for preparing a high-performance cathode material based on manganese sulfate precursor as described in any of the above embodiments. The preparation method includes the following steps:

[0057] a. Preparation of manganese sulfate precursor mixture: Dissolve nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate in a solvent, add a chelating agent, adjust the pH to 7-8 and stir evenly, heat to form a gel, and dry to obtain the product.

[0058] b. Synthesis of cathode material: The mixture of manganese sulfate precursor components is mixed with Li2CO3, ball-milled, and then subjected to solid-state reaction and calcination to obtain the cathode material.

[0059] The preparation method provided in this embodiment uses a sol-gel method combined with a chelating agent to prepare a precursor, ensuring a uniform distribution of yttrium doping, overcoming the problem of uneven distribution in traditional direct doping, and improving the stability of material properties.

[0060] Furthermore, in step a:

[0061] The solvent is deionized water.

[0062] Alternatively, the solvent may be a microemulsion system, which includes an aqueous phase and an oil phase. The aqueous phase includes deionized water, and the oil phase includes organic solvents and surfactants.

[0063] This preparation method supports a variety of solvent systems (deionized water or microemulsion system), and the process parameters can be adjusted according to industrial needs. The microemulsion system further improves doping uniformity and particle size control, and enhances electrochemical performance.

[0064] Furthermore:

[0065] The organic solvent is selected from hexane, isooctyl alcohol, or combinations thereof.

[0066] The surfactant is selected from hexadecyltrimethylammonium bromide.

[0067] Furthermore, in step a:

[0068] The volume ratio of the aqueous phase to the oil phase is 1:(3~5), and the total concentration of metal ions in the aqueous phase is 0.8~1.2 M.

[0069] The concentration of the surfactant is 0.05~0.1 M.

[0070] The microemulsion system was prepared by slowly adding the aqueous phase dropwise to the oil phase while stirring at a speed of 500-1000 rpm.

[0071] Ammonia was selected as the pH adjuster, with a concentration of 1.0~2.0 M and a dropping rate of 0.5~2 mL / min.

[0072] The ball mill speed is 400~600 rpm, the ball milling time is 3~5 hours, and the ball-to-material mass ratio is (10~20):1.

[0073] Furthermore, in step b, the solid-state reaction calcination employs a segmented temperature-controlled process, specifically including:

[0074] The temperature is maintained at 350~450℃ for 3~5 hours to promote the decomposition of Li2CO3 and the formation of initial crystal nuclei, and to avoid lattice defects or uneven reactions caused by direct high-temperature calcination.

[0075] Holding at 700~800℃ for 5~7 hours induces further growth, inhibits the generation of oxygen vacancies, and enhances the integrity of the crystal structure.

[0076] By holding the temperature at 850~950℃ for 7~9 hours, the grain size is optimized, the crystal regularity is improved, and structural stress or phase transformation caused by excessive grain growth is avoided.

[0077] Cool to room temperature at a cooling rate of 3~7℃ / min.

[0078] Furthermore, the solvent is a microemulsion system, and step a specifically includes the following sub-steps:

[0079] a1. Dissolve nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate in deionized water to form aqueous phase A, wherein the amount of yttrium nitrate added is 4%~5% of the amount of manganese sulfate; dissolve nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate in deionized water to form aqueous phase B, wherein the amount of yttrium nitrate added is 1%~2% of the amount of manganese sulfate.

[0080] a2. Mix the organic solvent and surfactant thoroughly to form an oil phase.

[0081] a3. Add aqueous phase A and aqueous phase B slowly dropwise into the oil phase at a volume ratio of 1:1, stirring continuously during the dropwise addition process.

[0082] a4. Add the chelating agent to the mixture and stir until homogeneous.

[0083] a5. Add a pH adjuster to adjust the pH to 7-8, heat at 75-85℃ for 3-5 hours to form a gel, and dry at 95-105℃ for 10-14 hours to obtain the final product.

[0084] Two aqueous phases with different yttrium doping concentrations were designed and added dropwise to the oil phase in a 1:1 volume ratio to form a gradient-doped microemulsion system. This stepwise doping strategy resulted in a more uniform distribution of yttrium at the molecular level, avoiding localized oversaturation or agglomeration that could occur with single high-concentration doping. The uniform yttrium distribution further stabilized the layered crystal structure of the cathode material, reduced the risk of lattice distortion and phase separation, and improved the structural consistency and electrochemical stability of the material.

[0085] The microemulsion system itself can effectively control the morphology of precursor particles through the interfacial interaction between the aqueous and oil phases. The introduction of the aqueous two-phase further refines the size distribution of the microemulsion droplets, resulting in finer and more uniform gel particles. Gradient doping and uniformly distributed yttrium optimize the Li... + The diffusion pathway reduces the irreversible capacity loss caused by the activation of the Li2MnO3 component during the first charge, thereby improving the initial coulombic efficiency. The stable crystal structure suppresses phase transitions (transition from layered structure to spinel structure) and oxygen release during cycling, significantly reducing voltage decay.

[0086] The aqueous two-phase process design increases the flexibility of yttrium doping control, allowing adjustment of the doping ratio of aqueous phases A and B according to specific application requirements. This process, in conjunction with the stirring, heating, and drying parameters of the microemulsion system, ensures the reproducibility and industrial applicability of the precursor preparation process.

[0087] Furthermore, step b is followed by step c, which specifically includes the following sub-steps:

[0088] c1. Disperse the positive electrode material obtained in step b in ethanol to prepare a suspension with a mass concentration of 50~100 g / L.

[0089] c2. Add Al(NO3)3 and stir until homogeneous, wherein the mass of Al(NO3)3 is 1%~2% of the cathode material.

[0090] c3. Calcination at 450~550℃ for 3~5 hours to form an Al2O3 nano-coating layer.

[0091] The Al2O3 nano-coating layer acts as a protective layer, effectively isolating the cathode material from direct contact with the electrolyte, reducing electrolyte decomposition and side reactions during cycling, and significantly improving the cycling stability of the material. The chemical inertness of Al2O3 inhibits the formation of oxygen vacancies and the dissolution of transition metal ions on the cathode material surface, maintaining the integrity of the layered structure and extending battery life. The surface coating stabilizes the cathode material structure at high voltages, reducing the irreversible transformation from a layered structure to a spinel structure during cycling and lowering voltage decay.

[0092] Al₂O₃ nanocoatings improve the initial coulombic efficiency by optimizing the surface electrochemical interface and reducing irreversible side reactions (such as oxygen release) during the first charge. The thin coating (Al(NO₃)₃ content is only 1%–2% by mass) avoids the negative impact of excessively thick coatings on Li₂O₃. + The conduction barrier maintains a high specific capacity, while enhancing electrochemical reaction activity and improving the stability of the cathode material in high-temperature environments. It also reduces structural degradation and capacity decay during high-temperature cycling, making it suitable for demanding applications such as new energy vehicles.

[0093] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0094] Example 1

[0095] Weigh out 26.28 g of nickel sulfate, 18.11 g of cobalt sulfate, 66.43 g of manganese sulfate, 1.60 g of yttrium nitrate, and 141.22 g of citric acid using an electronic balance. Weigh out 600 mL of deionized water and 50 mL of ammonia (1.5 M).

[0096] Nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate were dissolved in 600 mL of deionized water to prepare a 1.0 M solution. Citric acid was added under magnetic stirring at 500 rpm, and the pH was adjusted to 7.5 with ammonia solution at a dropping rate of 1 mL / min. The mixture was heated in an 80°C water bath with stirring (500 rpm) for 4 hours to form a homogeneous gel. The gel was transferred to a forced-air drying oven and dried at 100°C for 12 hours to obtain the yttrium-doped Ni-Co-Mn precursor.

[0097] The precursor was mixed with Li₂CO₃ (22.79 g) and ball-milled in ethanol medium (500 rpm, 4 hours, zirconia balls, ball-to-material mass ratio 15:1). The mixture was placed in an alumina crucible and calcined in air in a tube furnace at 900 °C for 12 hours, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain yttrium-doped LRMO.

[0098] XRD confirmed the layered structure and yttrium doping; SEM analyzed the particle morphology and size.

[0099] Coin cell assembly: positive electrode slurry (active material: conductive carbon black: PVDF=80:10:10), counter electrode lithium foil, electrolyte is 1 M LiPF6 (EC:DMC=1:1), separator is Celgard 2400.

[0100] Charge / discharge test: 0.1C, voltage range 2.0~4.8 V, 25℃.

[0101] Cyclic performance test: 0.5C, 100 cycles.

[0102] The test data is shown in the table below:

[0103]

[0104] Example 2

[0105] Weigh out 26.28 g of nickel sulfate, 18.11 g of cobalt sulfate, 66.43 g of manganese sulfate, 1.60 g of yttrium nitrate, and 141.22 g of citric acid using an electronic balance. Weigh out 150 mL of deionized water, 480 mL of n-hexane, 120 mL of isooctyl alcohol, 28.83 g of CTAB, and 50 mL of ammonia (1.5 M).

[0106] Nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate were dissolved in 150 mL of deionized water, and citric acid was added to prepare the aqueous phase. An oil phase (n-hexane + isooctyl alcohol + CTAB) was prepared, and the aqueous phase was added dropwise to the oil phase at 1 mL / min while stirring at 800 rpm to form a microemulsion. The pH was adjusted to 7.5 with ammonia at 1 mL / min. The mixture was heated in an 80°C water bath with stirring (800 rpm) for 4 hours to form a homogeneous gel. The gel was then dried in a 100°C forced-air drying oven for 12 hours to obtain the yttrium-doped Ni-Co-Mn precursor.

[0107] The precursor was mixed with Li₂CO₃ (22.79 g) and ball-milled in ethanol medium (500 rpm, 4 hours, zirconia balls, ball-to-material mass ratio 15:1). The mixture was placed in an alumina crucible and heated at 400 °C for 4 hours at a heating rate of 5 °C / min; at 750 °C for 6 hours at a heating rate of 5 °C / min; at 900 °C for 8 hours at a heating rate of 5 °C / min; and cooled at a cooling rate of 5 °C / min to obtain yttrium-doped LRMO.

[0108] XRD confirmed the layered structure and yttrium doping; SEM analyzed the particle morphology and size.

[0109] Coin cell assembly: positive electrode slurry (active material: conductive carbon black: PVDF=80:10:10), counter electrode lithium foil, electrolyte is 1 M LiPF6 (EC:DMC=1:1), separator is Celgard 2400.

[0110] Charge / discharge test: 0.1C, voltage range 2.0~4.8 V, 25℃.

[0111] Cyclic performance test: 0.5C, 100 cycles.

[0112] The test data is shown in the table below:

[0113]

[0114] Example 3

[0115] Weigh out 26.28 g of nickel sulfate, 18.11 g of cobalt sulfate, 66.43 g of manganese sulfate, 1.60 g of yttrium nitrate, and 141.22 g of citric acid using an electronic balance. Weigh out 300 mL of deionized water, 480 mL of n-hexane, 120 mL of isooctyl alcohol, 28.83 g of CTAB, and 50 mL of ammonia (1.5 M).

[0116] Dissolve 13.14 g of nickel sulfate, 9.06 g of cobalt sulfate, 33.22 g of manganese sulfate, and 1.33 g of yttrium nitrate in 150 mL of deionized water to prepare a 1.0 M aqueous phase A. Dissolve 13.14 g of nickel sulfate, 9.06 g of cobalt sulfate, 33.22 g of manganese sulfate, and 0.27 g of yttrium nitrate in 150 mL of deionized water to prepare a 1.0 M aqueous phase B. Mix 480 mL of n-hexane, 120 mL of isooctanol, and 28.83 g of CTAB and stir until homogeneous under magnetic stirring at 800 rpm to form an oil phase.

[0117] At a stirring speed of 800 rpm, 150 mL each of aqueous phase A and aqueous phase B were slowly added dropwise to the oil phase at a dropping rate of 1 mL / min, and stirring was continued until a uniform microemulsion system was formed.

[0118] Add 141.22 g of citric acid to the microemulsion and stir well to ensure that the chelating agent and metal ions react fully.

[0119] The pH was adjusted to 7.5 using 1.5 M ammonia solution at a dropping rate of 1 mL / min. The mixture was heated in an 80°C water bath at 800 rpm for 4 hours with stirring to form a homogeneous gel. The gel was then transferred to a forced-air drying oven and dried at 100°C for 12 hours to obtain the yttrium-doped Ni-Co-Mn precursor.

[0120] The precursor was mixed with Li₂CO₃ (22.79 g) and ball-milled in ethanol medium (500 rpm, 4 hours, zirconia balls, ball-to-material mass ratio 15:1). The mixture was placed in an alumina crucible and calcined in air in a tube furnace at 900 °C for 12 hours, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain yttrium-doped LRMO. It was then dispersed in ethanol to prepare a suspension with a mass concentration of 75 g / L. Al(NO₃)₃ was added to the suspension and stirred until homogeneous, ensuring uniform distribution of Al(NO₃)₃. After drying, the mixture was placed in an alumina crucible and calcined in air at 500 °C for 4 hours, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to form yttrium-doped LRMO with an Al₂O₃ nanocoating.

[0121] Coin cell assembly: positive electrode slurry (active material: conductive carbon black: PVDF=80:10:10), counter electrode lithium foil, electrolyte is 1 M LiPF6 (EC:DMC=1:1), separator is Celgard 2400.

[0122] Charge / discharge test: 0.1C, voltage range 2.0~4.8 V, 25℃.

[0123] Cyclic performance test: 0.5C, 100 cycles.

[0124] The test data is shown in the table below:

[0125]

[0126] Comparative Example

[0127] Weigh out 26.28 g of nickel sulfate, 18.11 g of cobalt sulfate, and 66.43 g of manganese sulfate using an electronic balance. Weigh out 600 mL of deionized water and 50 mL of ammonia (1.5 M).

[0128] Nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate were dissolved in 600 mL of deionized water to prepare a 1.0 M solution. The pH was adjusted to 7.5 with ammonia solution at a dropping rate of 1 mL / min under magnetic stirring at 500 rpm. The solution was heated in an 80°C water bath with stirring (500 rpm) for 4 hours to form a homogeneous gel. The gel was transferred to a forced-air drying oven and dried at 100°C for 12 hours to obtain the Ni-Co-Mn precursor.

[0129] The precursor was mixed with Li₂CO₃ (22.79 g) and ball-milled in ethanol medium (500 rpm, 4 hours, zirconia balls, ball-to-material mass ratio 15:1). The mixture was placed in an alumina crucible and calcined in air in a tube furnace at 900 °C for 12 hours, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain LRMO.

[0130] Coin cell assembly: positive electrode slurry (active material: conductive carbon black: PVDF=80:10:10), counter electrode lithium foil, electrolyte is 1 M LiPF6 (EC:DMC=1:1), separator is Celgard 2400.

[0131] Charge / discharge test: 0.1C, voltage range 2.0~4.8 V, 25℃.

[0132] Cyclic performance test: 0.5C, 100 cycles.

[0133] The test data is shown in the table below:

[0134]

[0135] The data above show that the high-performance cathode materials prepared in Examples 1, 2 and 3 are significantly better than the comparative examples in terms of specific capacity, initial coulombic efficiency, cycle stability and voltage decay, demonstrating the synergistic optimization effect of yttrium doping, microemulsion system, segmented temperature control process and Al2O3 nano-coating.

[0136] In Example 1, a deionized water solvent and a single high-temperature calcination process (900°C, 12 hours) were used. SEM analysis showed that the particles had uniform morphology and relatively regular surface grains, but the particle size was relatively large. This indicates that although a single solvent system and direct calcination process can form a stable layered structure, there is still room for optimization in particle size control and doping uniformity.

[0137] Example 2 employed a microemulsion system and a segmented temperature control process (400℃ / 4h, 750℃ / 6h, 900℃ / 8h). SEM analysis showed a significant reduction in particle size, with finer surface grains and a more uniform morphology. The microemulsion system effectively controlled the morphology of the precursor particles through the interfacial interaction between the aqueous and oil phases, while the segmented temperature control process further optimized grain growth and reduced lattice defects.

[0138] XRD analysis confirmed that Examples 1 and 2 both have typical lithium-rich manganese-based lattice structures, and that yttrium doping did not introduce impurity phases, indicating that yttrium was successfully incorporated into the crystal lattice.

[0139] Regarding electrochemical performance, Example 1 addressed the issues of voltage decay, poor cycle stability, and low initial coulombic efficiency in existing lithium-rich manganese-based cathode materials through yttrium doping. Example 2 further optimized particle morphology and crystal structure through a microemulsion system and segmented temperature control process, thereby improving electrochemical performance. Example 3 achieved a comprehensive performance improvement through a two-phase aqueous microemulsion system and Al2O3 nano-coating technology, addressing both internal doping and surface protection.

[0140] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance cathode material based on a manganese sulfate precursor, characterized in that, The high-performance cathode material prepared based on manganese sulfate precursor has the general chemical formula xLi2MnO3·(1-x)LiMO2, where M includes Ni, Co, and Mn, and a dopant element Y, with a molar doping amount of Y being 1%~5% of Mn. The high-performance cathode material is prepared by a sol-gel method combined with a solid-state reaction using a manganese sulfate precursor mixture, wherein the manganese sulfate precursor mixture is formed from nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate under the action of a chelating agent. The preparation method includes the following steps: a) Preparation of manganese sulfate precursor mixture: Dissolve nickel sulfate, cobalt sulfate, manganese sulfate and yttrium nitrate in a solvent, add a chelating agent, adjust the pH to 7-8 and stir evenly, heat to form a gel, and dry to obtain the product; b) Synthesis of cathode material: The mixture of manganese sulfate precursor components and Li2CO3 is mixed, ball-milled, and then subjected to solid-state reaction and calcination to obtain the cathode material. The solvent is a microemulsion system, which includes an aqueous phase and an oil phase. The aqueous phase includes deionized water, and the oil phase includes an organic solvent and a surfactant. Step a specifically includes the following sub-steps: a1) Dissolve nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate in deionized water to form aqueous phase A, wherein the amount of yttrium nitrate added is 4%~5% of the amount of manganese sulfate; dissolve nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium nitrate in deionized water to form aqueous phase B, wherein the amount of yttrium nitrate added is 1%~2% of the amount of manganese sulfate; a2) Mix the organic solvent and surfactant thoroughly to form an oil phase; a3) Add aqueous phase A and aqueous phase B slowly dropwise into the oil phase at a volume ratio of 1:1, stirring constantly during the dropwise addition process; a4) Add the chelating agent to the mixture and stir until homogeneous; a5) Add a pH adjuster to adjust the pH to 7-8, heat at 75-85℃ for 3-5 hours to form a gel, and dry at 95-105℃ for 10-14 hours to obtain the final product.

2. The method of claim 1, wherein the high-performance cathode material is prepared based on a manganese sulfate precursor. The molar ratio of Ni:Co:Mn in the manganese sulfate precursor mixture is (1.0~1.5):(1.0~1.5):(5.0~6.0).

3. The method of claim 1, wherein the high-performance cathode material is prepared based on a manganese sulfate precursor. The chelating agent is selected from citric acid, ethylenediaminetetraacetic acid, or a combination thereof, wherein the amount of citric acid added is 0.8 to 1.3 times the total amount of metal ions, and the amount of ethylenediaminetetraacetic acid added is 0.3 to 0.5 times the total amount of metal ions.

4. The method for preparing high-performance cathode materials based on manganese sulfate precursor according to claim 1, characterized in that: The organic solvent is selected from n-hexane, isooctyl alcohol, or a combination thereof; The surfactant is selected from hexadecyltrimethylammonium bromide.

5. The method of claim 1, wherein the high performance cathode material is prepared based on a manganese sulfate precursor. In step a: The volume ratio of the aqueous phase to the oil phase is 1:(3~5), and the total concentration of metal ions in the aqueous phase is 0.8~1.2 M; The concentration of the surfactant is 0.05~0.1 M; The microemulsion system was prepared by slowly adding the aqueous phase dropwise to the oil phase while stirring at a speed of 500-1000 rpm. Ammonia was selected as the pH adjuster, with a concentration of 1.0~2.0 M and a dropping rate of 0.5~2 mL / min. The ball milling speed is 400~600 rpm, the ball milling time is 3~5 hours, and the ball-to-material mass ratio is (10~20):

1.

6. The method of claim 1, wherein the high performance cathode material is prepared based on a manganese sulfate precursor. In step b, the solid-state reaction calcination employs a segmented temperature-controlled process, specifically including: Keep warm at 350~450℃ for 3~5 hours; Keep warm at 700~800℃ for 5~7 hours; Keep warm at 850~950℃ for 7~9 hours; Cool to room temperature at a cooling rate of 3~7℃ / min.

7. The method of claim 1, wherein the high-performance cathode material is prepared based on a manganese sulfate precursor. Step b is followed by step c, which specifically includes the following sub-steps: c1) Disperse the positive electrode material obtained in step b in ethanol to prepare a suspension with a mass concentration of 50~100 g / L; c2) Add Al(NO3)3 and stir until homogeneous, wherein the mass of Al(NO3)3 is 1%~2% of the cathode material; c3) Calcination at 450~550℃ for 3~5 hours forms an Al2O3 nano-coating layer.

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