Preparation method of single crystal dimanganese trioxide, lithium manganate positive electrode material and lithium battery

Abstract

The application discloses a preparation method of single-crystal dimanganese trioxide, a lithium manganate positive electrode material and a lithium battery, and belongs to the technical field of lithium batteries. 2+ Excessive oxidation is inhibited by controlling the content of reducing substances through the addition of a reducing additive 3+ , combined with the control of solid content, the adjustment of multi-stage pH value and the aging process, to obtain single-crystal dimanganese trioxide with high purity and regular hexahedron morphology. The lithium manganate positive electrode material is prepared by calcining the single-crystal dimanganese trioxide and lithium carbonate according to a Li / Mn molar ratio of 0.55:1. The application has the advantages of mild process, cheap raw materials, easy industrialization, adaptation to the demand of high-performance lithium batteries, and solution to the problems of low purity, irregular morphology, high energy consumption and insufficient electrochemical performance in the traditional method.

Description

Technical Field

[0001] This invention relates to the technical field of lithium batteries, and in particular to a method for preparing single-crystal manganese trioxide, lithium manganese oxide cathode material, and lithium battery. Background Technology

[0002] Manganese trioxide, an important transition metal oxide, is renowned for its multivalent state characteristics, environmental friendliness, and cost-effectiveness. With the rapid development of new energy technologies, especially the rise of cathode materials for lithium-ion and sodium-ion batteries, the demand for battery-grade manganese trioxide has increased dramatically. However, traditional preparation methods suffer from low purity, high energy consumption, and uncontrollable morphology, necessitating urgent improvements. Currently, there are three main methods for preparing manganese trioxide on the market:

[0003] One method is hydrolysis oxidation, which uses electrolytic manganese metal as raw material. The process involves acid-catalyzed hydrolysis oxidation of a suspension, controlling the redox potential and pH value, and finally washing and drying to obtain spherical or near-spherical manganese trioxide. However, this method requires precise control of the amount of oxidant (such as hydrogen peroxide or sodium hypochlorite) and alkaline solution added, making the process parameters sensitive. Furthermore, the raw material must be high-purity electrolytic manganese metal (≥99%), resulting in higher costs.

[0004] The second method is the high-temperature calcination method, which involves directly calcining divalent manganese salts at about 600°C to prepare manganese trioxide. However, this method has high energy consumption and is prone to sintering, resulting in uneven particle size and uncontrollable morphology of the product.

[0005] Thirdly, there is the solvothermal method, which uses soluble manganese salts (such as manganese nitrate) and copper salts as raw materials. Crystal facet growth is controlled through a hydrothermal reaction in an alcohol solvent to generate highly catalytically active manganese trioxide. However, this method requires the introduction of auxiliary agents such as copper salts, resulting in high costs, high precision requirements for synthesis conditions, and unsuitability for process scale-up. Furthermore, solvent recovery (such as sec-butanol) is difficult, posing a significant environmental burden.

[0006] Furthermore, in lithium-ion batteries, monocrystalline manganese trioxide exhibits a shorter lithium-ion diffusion path and higher structural stability compared to polycrystalline manganese trioxide. The monocrystalline characteristic suppresses volume expansion during charge and discharge, improving cycle life. Simultaneously, the nanoscale size and larger specific surface area (40~50 m² / g) increase the density of active sites, thereby improving the battery's energy density and rate performance. Monocrystalline manganese trioxide also possesses higher mechanical strength and thermal stability. Therefore, a method for preparing monocrystalline manganese trioxide with low synthesis cost and mild reaction conditions is urgently needed. Summary of the Invention

[0007] This invention provides a method for preparing single-crystal manganese trioxide, a lithium manganese oxide cathode material, and a lithium battery, in order to solve the technical problem of how to provide a method for preparing single-crystal manganese trioxide with low synthesis cost, mild reaction conditions, high purity, and controllable hexahedral morphology, so as to meet the technical needs of lithium battery and other fields for high-quality single-crystal manganese trioxide.

[0008] A method for preparing single-crystal manganese trioxide according to the present invention includes the following steps:

[0009] S100, prepare MnSO4 solution, add reducing additive to form Mn inhibitor. 2+ Excessive oxidation to Mn 4+ The first mixture;

[0010] S200, add the first complexing agent to the first mixture and adjust to the first pH range, stir at the set temperature, so that the Mn in the first mixture... 2+ Mn(OH)₂ is generated, and Mn(OH)₂ reacts with oxygen to partially convert into MnOOH, thus producing a product with Mn 2+ The second mixture of crystal nucleation precursors;

[0011] S300, a composite additive consisting of phosphoric acid and a second complexing agent is added to the second mixture to adjust the pH to the second range, so that MnOOH dissociates into Mn 3+ It forms Mn-containing complexes with composite additives to inhibit Mn. 3+ Disproportionation to Mn 2+ and Mn 4+ Stirring and standing under air conditions allows the complex to slowly release Mn. 3+ During the process, MnOOH is dehydrated and transformed into pure-phase Mn2O3 crystal nuclei, resulting in a third mixed solution containing Mn2O3 crystal nuclei. The Mn-containing complex is: [Mn(PO4)] n ] 3- ;

[0012] S400, then the third mixture and pH adjuster are added in parallel flow, using air or oxygen as the oxidant, to adjust the third mixture to the third pH range, and control the solid content when adjusting the pH to suppress secondary nucleation and promote the directional growth of Mn2O3 crystal nuclei into single crystal particles, to obtain a fourth mixture containing single crystal particles, wherein the solid particles in the solid content are solid particles containing Mn.

[0013] S500, the fourth mixture is adjusted to the fourth pH range and aged to make the single crystal particles regular hexahedral in shape; after solid-liquid separation and purification, hexahedral single crystal manganese trioxide is obtained.

[0014] Further, in step S100, the reducing additive includes an aldehyde-containing compound and a sulfite; the aldehyde-containing compound is any one or more combinations of glucose or maltose, and the sulfite is any one or more combinations of sodium sulfite or potassium sulfite; the amount of the reducing additive added is 0.01% to 0.05% of the mass of the MnSO4 solution.

[0015] Further, in step S100, the reducing additive provides a reducing substance, the content of the reducing additive is 300~800μg / ml, and the reducing substance includes reducing groups of aldehyde compounds and reducing ions of sulfites.

[0016] Further, in step S200, the first complexing agent is one or more of ammonium sulfate, ammonia, ethylenediamine, triethanolamine, and nitrilotriacetic acid, and the set temperature is 25~65℃, and the stirring time is 0.1~1h.

[0017] Further, in step S300, the stirring and standing time under air conditions is 3~24h, the second complexing agent is selected from one or more of ethylenediaminetetraacetic acid second complexing agents, sodium citrate, hexadecyltrimethylammonium bromide or n-butanol, the content of the second complexing agent is 1~5g / L, and in the composite additive, the mass ratio of phosphoric acid to the second complexing agent is 1:0.05~0.45.

[0018] Further, in step S400, the mixing reaction time of the third mixture and the pH adjuster is 3-20 hours, and the solid content during the mixing reaction is controlled to be 1-12%, wherein the solid content is the proportion of the mass of Mn-containing solid particles to the total mass of the mixing reaction system, and the pH adjuster is selected from one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution; the concentration of the sodium hydroxide solution is 1-5 mol / L.

[0019] Furthermore, in step S500, the aging time is 1~6h, and the particle size D50 of the obtained hexahedral single crystal manganese trioxide is 0.5~5μm.

[0020] Further, the first pH range is 7.0~7.6, the second pH range is 6.5~7.0, the third pH range is 7.0~8.5, and the fourth pH range is 6.8~7.8.

[0021] The present invention also discloses a lithium manganese oxide cathode material, wherein the raw materials of the lithium manganese oxide cathode material include lithium carbonate and single crystal manganese oxide prepared by the method described above, wherein the single crystal manganese oxide and lithium carbonate are mixed at a Li / Mn molar ratio of 0.55:1.

[0022] The present invention also discloses a lithium battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode comprises the aforementioned lithium manganese oxide positive electrode material.

[0023] The present invention has the following beneficial effects:

[0024] In the preparation method of single-crystal manganese trioxide of the present invention, low-cost manganese sulfate is used as the manganese source, combined with inexpensive and readily available reducing additives (containing aldehyde compounds and sulfites) and composite additives (phosphoric acid and conventional second complexing agents). Simultaneously, a first complexing agent composed of ammonium sulfate, ammonia, ethylenediamine, triethanolamine, and nitrilotriacetic acid (added at a content of 1-5 g / L) is introduced. Air or oxygen is used as the oxidant. This eliminates the need for expensive metallic manganese powder, alcohol reagents, copper salt additives, and high-valent oxidants, and also eliminates the need for high-temperature calcination or high-temperature, high-pressure hydrothermal environments. The entire process is carried out at a mild temperature of 25-65°C. The process is short and the equipment requirements are simple, significantly reducing raw material and energy costs while also possessing good environmental friendliness (using water as the main reaction medium, with no difficult-to-recover solvents). It is easy to scale up industrially and for continuous production. Furthermore, the reducing additives inhibit the growth of Mn. 2+ Excessive oxidation to Mn 4 + The first complexing agent acts as a morphology control agent, precisely regulating the precipitation rate and, in conjunction with the incomplete oxidation atmosphere of slow air oxidation, promoting the directional formation of the MnOOH intermediate product and avoiding the formation of impurity phases such as Mn3O4 or MnO2, thus providing a high-purity precursor for subsequent single crystal growth; the composite additive inhibits Mn... 3+ Disproportionation, combined with precise control of solid content and pH range, ensures a stable and controllable process with low parameter sensitivity. This effectively solves the problems of low product purity and uneven morphology in traditional methods, ultimately producing high-purity, large-particle single-crystal manganese trioxide with regular hexahedral morphology (particle size D50 of 0.5~5μm). Compared with conventional polycrystalline manganese trioxide, this single-crystal product has higher mechanical strength and thermal stability, and possesses the advantages of short ion diffusion paths and high structural stability. During the charging and discharging process of lithium batteries, it can effectively suppress volume expansion and maintain structural stability, significantly improving the cycle life and energy density of the battery, fully meeting the application requirements of high-performance lithium battery cathode materials.

[0025] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0027] Figure 1 This is a schematic flowchart of a method for preparing single-crystal manganese trioxide according to an embodiment of the present invention;

[0028] Figure 2 This is an XRD diagram of the single-crystal manganese trioxide material of Example 1 of the present invention;

[0029] Figure 3 This is a SEM schematic diagram of the single-crystal manganese trioxide material of Example 1 of the present invention;

[0030] Figure 4 This is an XRD diagram of the manganese oxide material of Comparative Example 1 of the present invention;

[0031] Figure 5 This is a SEM schematic diagram of the manganese oxide material of Comparative Example 1 of the present invention. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0033] Reference Figure 1 The present invention discloses a method for preparing single-crystal manganese trioxide, comprising the following steps:

[0034] S100, prepare MnSO4 solution, add reducing additive to form Mn inhibitor. 2+ Excessive oxidation to Mn 4+ The first mixture;

[0035] S200, add the first complexing agent to the first mixture and adjust to the first pH range, stir at the set temperature, so that the Mn in the first mixture... 2+ Mn(OH)₂ is generated, and Mn(OH)₂ reacts with oxygen to partially convert into MnOOH, thus producing a product with Mn 2+ The second mixture of crystal nucleation precursors;

[0036] S300, a composite additive consisting of phosphoric acid and a second complexing agent is added to the second mixture to adjust the pH to the second range, so that MnOOH dissociates into Mn 3+ It forms Mn-containing complexes with composite additives to inhibit Mn. 3+ Disproportionation to Mn 2+ and Mn 4+ Stirring and standing under air conditions allows the complex to slowly release Mn. 3+ During the process, MnOOH is dehydrated and transformed into pure-phase Mn2O3 crystal nuclei, resulting in a third mixed solution containing Mn2O3 crystal nuclei. The Mn-containing complex is: [Mn(PO4)] n ] 3-;

[0037] S400, then the third mixture and pH adjuster are added in parallel flow, using air or oxygen as the oxidant, to adjust the third mixture to the third pH range, and control the solid content when adjusting the pH to suppress secondary nucleation and promote the directional growth of Mn2O3 crystal nuclei into single crystal particles, to obtain a fourth mixture containing single crystal particles, wherein the solid particles in the solid content are solid particles containing Mn.

[0038] S500, the fourth mixture is adjusted to the fourth pH range and aged to make the single crystal particles regular hexahedral in shape; after solid-liquid separation and purification, hexahedral single crystal manganese trioxide is obtained.

[0039] In this embodiment, for step S100, low-cost MnSO4 is selected as the manganese source, eliminating the need for high-purity electrolytic manganese or expensive manganese powder. It is combined with readily available and inexpensive aldehyde compounds (glucose / maltose) and sulfite-based reducing additives, significantly reducing raw material costs. By precisely controlling the content of reducing substances (300~800 μg / ml), Mn is effectively suppressed. 2+ Excessive oxidation to Mn 4+ This avoids the generation of impurities from the source, laying the foundation for the subsequent preparation of pure phase crystal nuclei, while eliminating the need for expensive oxidants and further controlling process costs.

[0040] For step S200, a first complexing agent (one or more of ammonium sulfate, ammonia, ethylenediamine, triethanolamine, nitrilotriacetic acid, etc., at a concentration of 1-5 g / L) is added to the first mixture and adjusted to the first pH range (7.0-7.6). The mixture is stirred at a set temperature (25-65℃) for 0.1-1 h. The first complexing agent plays a role in morphology control, precisely regulating the precipitation rate and reducing the concentration of Mn²⁺ in the first mixture. + The process involves the directional generation of Mn(OH)₂, which undergoes partial oxidation with oxygen to convert into MnOOH, thus avoiding the formation of impurity phases such as Mn₃O₄ or MnO₂, and producing a product with Mn³⁺. + The second mixture of crystal nucleation precursor (MnOOH).

[0041] Specifically, make Mn 2+ The reaction equation for the directed generation of Mn(OH)2 and its conversion to MnOOH is as follows:

[0042] Mn(OH)₂ + O₂ → MnOOH + H₂O

[0043] For step S300, the composite additive (phosphoric acid + conventional second complexing agent) is inexpensive and readily available, eliminating the need for expensive additives such as copper salts, thus reducing raw material costs; and by forming a stable [Mn(PO4)]... n ]³ - Complexes that precisely block Mn3+ Disproportionation to Mn 2+ and Mn 4 + To ensure crystal nucleus purity; stirring and standing under air (3~24h) to achieve slow release of Mn from the second complexing agent. 3+ This promotes the dehydration of MnOOH into pure-phase Mn2O3 crystal nuclei, avoids polycrystalline mixing, provides a high-purity crystal nucleus basis for single-crystal particle growth, and solves the problem of low product purity in traditional methods.

[0044] Specifically, the reaction formula for dehydrating MnOOH into pure-phase Mn2O3 crystal nuclei is:

[0045] 2MnOOH→Mn2O3+H2O

[0046] For step S400, air or oxygen is used as the oxidant, eliminating the need for high-valent oxidants such as hydrogen peroxide and sodium hypochlorite, further reducing costs. By controlling the third pH range (7.0~8.5) and using a co-current feeding method, the reaction system becomes stable and controllable with low parameter sensitivity. Controlling the solid content (1~12%) effectively suppresses secondary nucleation and promotes the directional growth of existing pure-phase Mn2O3 crystal nuclei into single crystal particles, avoiding the problems of uneven particle size and disordered morphology in traditional methods. At the same time, the process is compatible with conventional reactors and requires no special equipment, making industrial scale-up possible.

[0047] For step S500, aging in the fourth pH range (6.8~7.8) for 1~6h makes the single crystal particles regular hexahedral in shape, with a particle size D50 stable at 0.5~5μm, resulting in strong product consistency. After solid-liquid separation and purification, trace impurities are further removed, and high-purity single crystal manganese trioxide is finally obtained. The large hexahedral single crystal structure has higher mechanical strength and thermal stability, and its short ion diffusion path characteristics can meet the requirements of lithium battery cathode materials, effectively suppressing volume expansion during battery charging and discharging, improving battery cycle life and energy density. At the same time, the process uses water as the main reaction medium, without difficult-to-recover alcohol solvents, which is environmentally friendly. The process is continuous and suitable for large-scale industrial applications.

[0048] Specifically, the advantage of single-crystal materials lies in their ability to eliminate grain boundaries, thereby more efficiently addressing internal stresses caused by volume changes, significantly suppressing crack initiation and propagation, and exhibiting extremely high structural stability and ultra-long cycle life. Furthermore, single-crystal materials effectively reduce interfacial side reactions and decrease gas generation. Simultaneously, single-crystal materials possess higher compaction density and energy density. Regarding particle size, particles smaller than 0.5 μm tend to exhibit more pronounced interfacial side reactions and lower tap density; particles larger than 5 μm increase the risk of mechanical fracture and internal stress. Repeated stress accumulation can generate microcracks within the particles. Therefore, selecting an appropriate particle size ensures sufficient mechanical strength to resist cyclic stress and reduces crack formation. An appropriate particle size also maintains a reasonable specific surface area, preventing excessive side reactions while ensuring good ion / electron transport, resulting in excellent rate performance. In electrode fabrication, an appropriate particle size helps achieve higher compaction density, further improving the battery's volumetric energy density.

[0049] In summary, using low-cost manganese sulfate as the manganese source, combined with inexpensive and readily available reducing additives (including aldehyde compounds and sulfites) and composite additives (phosphoric acid and conventional second complexing agents), and employing air or oxygen as the oxidant, this method eliminates the need for expensive metallic manganese powder, alcohol reagents, copper salt auxiliaries, and high-cost oxidants. It also eliminates the need for high-temperature calcination or high-temperature, high-pressure hydrothermal environments. The entire process is conducted at a mild temperature of 25-65℃, resulting in a short process with simple equipment requirements. This significantly reduces raw material and energy costs while also being environmentally friendly (using water as the main reaction medium, with no difficult-to-recover solvents), facilitating industrial scale-up and continuous production. Furthermore, the reducing additives inhibit the growth of Mn. 2+ Excessive oxidation and compound additives inhibit Mn 3+ Disproportionation, combined with precise control of solid content and pH range, ensures a stable and controllable process with low parameter sensitivity. This effectively solves the problems of low product purity and uneven morphology in traditional methods, ultimately producing high-purity, large-particle single-crystal manganese trioxide with regular hexahedral morphology (particle size D50 of 0.5~5μm). Compared with conventional polycrystalline manganese trioxide, this single-crystal product has higher mechanical strength and thermal stability, and possesses the advantages of short ion diffusion paths and high structural stability. During the charging and discharging process of lithium batteries, it can effectively suppress volume expansion and maintain structural stability, significantly improving the cycle life and energy density of the battery, fully meeting the application requirements of high-performance lithium battery cathode materials.

[0050] Further, in step S100, the reducing additive includes an aldehyde-containing compound and a sulfite; the aldehyde-containing compound is any one or more combinations of glucose or maltose, and the sulfite is any one or more combinations of sodium sulfite or potassium sulfite; the amount of the reducing additive added is 0.01% to 0.05% of the mass of the MnSO4 solution.

[0051] In this embodiment, aldehyde-containing compounds (glucose, maltose) and sulfites (sodium sulfite, potassium sulfite) are common, low-cost raw materials in the chemical industry. This eliminates the need for expensive additives such as manganese powder and copper salts, significantly reducing raw material procurement costs and solving the problems of high costs associated with traditional solvothermal methods (relying on expensive additives) and hydrolysis-oxidation methods (requiring high-purity raw materials). The aldehyde-containing compounds (such as glucose) and sulfites (such as sodium sulfite) work synergistically—sulfites can rapidly release reducing ions (sulfite ions), initially inhibiting the growth of manganese (Mn). 2+ Oxidation tendency; aldehyde-containing compounds slowly provide reducing properties through the aldehyde group, maintaining a reducing atmosphere in the system for a long time. The combination of these two allows for precise control of the reducing agent content in the solution (300~800 μg / ml), effectively inhibiting Mn oxidation. 2+ Excessive oxidation to Mn 4+ (To avoid generating impurities such as MnO2), the purity of subsequent products is guaranteed from the source, solving the problem of product impurity caused by uncontrolled oxidation in traditional methods. At the same time, the amount of reducing additive is limited. The low proportion of 0.01% to 0.05% means that the amount of reducing additive used is extremely small. Compared with the oxidants or auxiliaries that may be used excessively in traditional methods, the consumption of raw materials is greatly reduced, further reducing production costs. At the same time, the low dosage can avoid the burden of subsequent purification caused by additive residues, simplify process steps, and improve production efficiency.

[0052] Further, in step S100, the reducing substance is provided by the reducing additive, and its content is 300~800μg / ml. The reducing substance includes reducing groups of aldehyde compounds and reducing ions of sulfites.

[0053] In this embodiment, the content range of 300~800 μg / ml is for "inhibiting Mn 2+ Excessive oxidation to Mn 4+ The quantitative guarantee is that below 300 μg / ml, the reducing power is insufficient and cannot effectively prevent Mn from being inhibited. 2+ Excessive oxidation (easily generates impurities such as MnO2); concentrations above 800 μg / ml result in excessively strong reducing properties, potentially interfering with subsequent Mn reduction. 2+ To Mn 3+ The directional transformation (affecting the formation of crystal nuclei precursors) is precisely suited to the process requirements, ensuring a pure-phase product base while avoiding side reactions caused by excessive reduction, thus solving the problem of uncontrolled redox potential in traditional methods.

[0054] Further, in step S200, the first complexing agent is one or more of ammonium sulfate, ammonia, ethylenediamine, triethanolamine, and nitrilotriacetic acid, and the set temperature is 25~65℃, and the stirring time is 0.1~1h.

[0055] In this embodiment, 25~65℃ falls within the near-room temperature to medium temperature range, eliminating the need for high-temperature heating equipment (such as high-temperature furnaces in traditional roasting methods), thus significantly reducing energy consumption. Furthermore, this temperature range can be achieved through conventional water bath or jacket heating, placing low demands on the temperature resistance of the reaction equipment, making it suitable for ordinary chemical production equipment and reducing industrialization costs. This temperature range can balance Mn... 2+ The reaction rate of Mn(OH)2 formation and subsequent conversion to MnOOH: Below 25℃, the reaction kinetics are slow, Mn(OH)2 formation is insufficient, and it is difficult to form a sufficient amount of MnOOH crystal nuclei precursor; above 65℃, the reaction may accelerate the formation of MnOOH. 2+ Non-directional oxidation (such as the formation of Mn) 4+ Impurities may cause Mn(OH)2 to precipitate and aggregate too quickly, affecting the homogeneity of the precursor. A temperature of 25–65℃ is precisely sufficient to ensure the reaction proceeds in a directional manner, producing homogeneous MnOOH (Mn 3+ (A precursor for crystal nuclei) to provide conditions for subsequent single crystal growth. Simultaneously, the reaction time is limited; a stirring time of 0.1–1 hour ensures that the Mn content in the first mixture is within acceptable limits. 2+ Fully contact with the reaction medium (such as oxygen, OH) at the set temperature. - ), complete from Mn 2+ The conversion from Mn(OH)2 to MnOOH avoids incomplete precursor formation due to insufficient time; it also avoids increased energy consumption and decreased system stability due to excessive stirring (such as stirring time exceeding 1 hour) (such as excessive stirring may destroy the nascent MnOOH structure), thus ensuring both sufficient reaction and production efficiency.

[0056] Further, in step S300, the stirring and standing time under air conditions is 3-24 hours, the second complexing agent is selected from one or more of ethylenediaminetetraacetic acid second complexing agents, sodium citrate, hexadecyltrimethylammonium bromide or n-butanol, the content of the second complexing agent is 1-5 g / L, and in the composite additive, the mass ratio of phosphoric acid to the second complexing agent is 1:0.05-0.45.

[0057] In this embodiment, the time for stirring and settling under air is limited, and this time range is used to match the release of Mn from the complex. 3+ The reaction rhythm of "MnOOH dehydration to Mn2O3 crystal nuclei" – when the time is less than 3 hours, the second complexing agent cannot fully dissociate with the MnOOH-bound Mn. 3+ The complexes combine to form stable complexes, or the complexes release Mn. 3+ Incomplete treatment can easily lead to Mn 3+ Disproportionation (generating Mn) 2+ and Mn 4+Impurities make it difficult to form pure-phase crystal nuclei; when the time exceeds 24 hours, excessive settling may lead to crystal nuclei agglomeration or non-directional growth, and increase the production cycle and reduce efficiency. A range of 3~24 hours ensures sufficient complexation reaction and Mn... 3+ The orderly release of MnOOH promotes the directional dehydration of MnOOH to generate high-purity Mn2O3 crystal nuclei, providing high-purity Mn2O3 crystal nuclei for subsequent single crystal growth. The selected ethylenediaminetetraacetic acid (EDTA)-based second complexing agent, sodium citrate, hexadecyltrimethylammonium bromide, and n-butanol are all common and inexpensive reagents in the chemical industry, eliminating the need for expensive auxiliaries such as copper salts (unlike the solvothermal method), significantly reducing raw material costs. Simultaneously, these second complexing agents exhibit strong synergistic effects with phosphoric acid, stabilizing [Mn(PO4)] through coordination. n ]³ - Complexes (such as the multidentate coordination structure of EDTA and the surface-active effect of hexadecyltrimethylammonium bromide) are used, and no metal impurities or difficult-to-remove organic residues are introduced, ensuring product purity and solving the problems of high cost and low purity caused by expensive or residual auxiliaries in traditional methods. Simultaneously, the mass ratio of phosphoric acid to the second complexing agent is limited to 1:0.05~0.45. This ratio range precisely controls the synergistic effect of phosphoric acid and the second complexing agent: when phosphoric acid is in excess (ratio below 1:0.05), the second complexing agent is insufficient, making it difficult to effectively stabilize Mn. 3+ It is prone to disproportionation; when the second complexing agent is excessive (ratio higher than 1:0.45), the excess second complexing agent may be adsorbed on the crystal nucleus surface, hindering the dehydration of MnOOH and the orderly growth of Mn2O3 crystal nuclei, resulting in disordered crystal nucleus morphology. A ratio of 1:0.05~0.45 is just right for phosphoric acid to provide PO4 3- It forms a "dual stability" with the coordinating group of the second complexing agent, thus preventing Mn from forming. 3+ Dissimilation avoids excessive complexation from interfering with crystal nucleus formation, ensuring that pure-phase crystal nuclei are uniform and structurally complete.

[0058] Further, in step S400, the mixing reaction time is 3~20h, and the solid content during the mixing reaction is controlled to be 1~12% (based on the proportion of the mass of Mn-containing solid particles to the total mass of the mixing reaction system). The pH adjuster is selected from one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution; the concentration of the sodium hydroxide solution is 1~5mol / L.

[0059] In this embodiment, the mixing reaction time is limited to 3-20 hours. This time range precisely matches the kinetic requirement of "directional growth of existing Mn2O3 nuclei into single-crystal particles": when the time is less than 3 hours, the nuclei growth is insufficient, the particle size is too small, and the morphology is incomplete; when the time is longer than 20 hours, it may lead to excessive particle growth or agglomeration, destroying the regularity of the single-crystal structure. The range of 3-20 hours ensures that the nuclei grow gradually in a stable reaction environment, while avoiding defects caused by over-reaction, ensuring the integrity and uniformity of the single-crystal particles. The mass of Mn-containing solid particles is limited to 1-12% of the total mass of the system. This range controls the concentration of existing nuclei in the system, avoiding "continuous generation of new nuclei (secondary nucleation)" (which easily forms polycrystalline or fine particles) due to too low a solid content (<1%), while preventing particle collision and agglomeration (destroying the single-crystal morphology) due to too high a solid content (>12%). By suppressing secondary nucleation and focusing on promoting the growth of existing crystal nuclei, the product is ensured to be dominated by single-crystal particles, solving the problems of "uneven particle size and polycrystalline mixture" in traditional methods. Sodium hydroxide solution, ammonia, and potassium hydroxide solution are all common and inexpensive alkaline reagents in the chemical industry, requiring no special preparation and significantly reducing raw material costs. Furthermore, these regulators have mild and controllable alkalinity, stably maintaining the third pH range (7.0~8.5) within the reactor, avoiding equipment corrosion or impurity residue caused by the use of highly corrosive or special alkalis. They are also compatible with the "co-current introduction" process, ensuring uniform pH adjustment and improving reaction stability. Simultaneously, the concentration range of sodium hydroxide is limited. This range avoids the problem of "requiring a large amount of solution to adjust pH and diluting the reaction system, leading to fluctuations in solid content" at low concentrations (<1mol / L), and also prevents "localized excessive alkalinity leading to Mn" at high concentrations (>5mol / L). 3+ To mitigate the risk of rapid precipitation and formation of amorphous impurities, this paper aims to maintain the stability of the reaction system while ensuring efficient pH adjustment and reducing operational difficulty.

[0060] Furthermore, in step S500, the aging time is 1~6h, and the particle size D50 of the obtained hexahedral single crystal manganese trioxide is 0.5~5μm.

[0061] In this embodiment, the aging time range is limited to meet the "fine-tuning and optimization" requirements of the hexahedral single-crystal structure. When the aging time is less than 1 hour, the atomic arrangement on the surface of the single-crystal particles is not sufficiently ordered, and the morphology is difficult to be regularized into a standard hexahedron. When the time is longer than 6 hours, it may lead to weak agglomeration between particles or excessive surface growth, destroying the integrity of the hexahedron. The short aging time of 1 to 6 hours allows the single-crystal particles to complete the morphology refinement through atomic migration, forming a regular hexahedron with regular edges and corners and a dense structure, while avoiding the efficiency reduction or product defects caused by over-aging, thus balancing morphology quality and production efficiency. The particle size range of the hexahedral single-crystal manganese trioxide is limited. This particle size range is the optimal range for single-crystal manganese trioxide as a precursor for battery cathode materials: when the particle size is less than 0.5 μm, the specific surface area of ​​the particles is too large, which easily leads to excessive electrolyte adsorption and pulverization and shedding during cycling; when the particle size is greater than 5 μm, the lithium-ion diffusion path is too long, reducing the battery rate performance. The particle size of 0.5~5μm retains the advantage of the "short ion diffusion path" of the single-crystal structure, while balancing the active site density and structural stability through a moderate specific surface area. Combined with the regular hexahedral morphology, it can further improve the mixing uniformity with lithium carbonate and the calcination reaction activity, ultimately optimizing the cycle life and energy density of the lithium manganese oxide cathode material. The clearly defined aging time and particle size range provide clear quality control standards for industrial production.

[0062] Further, the first pH range is 7.0~7.6, the second pH range is 6.5~7.0, the third pH range is 7.0~8.5, and the fourth pH range is 6.8~7.8.

[0063] In this embodiment, the first pH range is 7.0~7.6, used for the directional production of the nucleation precursor (MnOOH). This weakly alkaline range is defined in S200 as "Mn 2+ The optimal environment for the generation of Mn(OH)2 and its conversion to MnOOH is provided: when the pH is below 7, H + Excessive concentration will inhibit the precipitation of Mn(OH)2. 2+ +2OH - Mn(OH)2 leads to insufficient precursor formation; at pH above 7.6, excessive alkalinity may accelerate Mn formation. 2+ Non-directional oxidation (to avoid the formation of large amounts of Mn(OH)2, which easily leads to the formation of Mn3O4) disrupts the pure phase structure of MnOOH. A weakly basic pH of 6.5–7.3 precisely balances the OH-... - Concentration and oxidation rate ensure Mn 2+ Directional conversion to MnOOH (Mn 3+ (Crystal nucleus precursor) provides a uniform "seed" basis for subsequent single crystal growth.

[0064] The second pH range is 6.5~7.0, used to ensure Mn 3+ The stability of the complex prevents disproportionation. After adding the complex additive to S300, the near-neutral pH range of 6.5–7.0 is [Mn(PO4)]. n ]³ - The key to the stable existence of the complex: when the pH is below 6.5, H + Will with PO4³ - Combining (e.g., generating HPO4²) - ), weakening its relationship with Mn³ + The coordination ability leads to the dissociation of the complex and Mn³ + Disproportionation (2Mn³) + →Mn² + +Mn 4+ When pH is above 7.0, OH - Possibly related to Mn³ + The formation of Mn(OH)3 precipitate or the continuous formation of Mn(OH)2 disrupts the complexation equilibrium. This range is addressed by precisely controlling H... + Concentration, ensuring synergistic stability of Mn³ by phosphoric acid and the second complexing agent. + This removes obstacles to the formation of pure-phase Mn2O3 crystal nuclei.

[0065] The third pH range, 7.0–8.5, is used to promote the directional growth of single crystal particles and inhibit secondary nucleation. In the mixed reaction stage of S400, the weakly alkaline range of 7.0–8.5 creates conditions for the directional growth of existing crystal nuclei: when the pH is below 7.0, the system is too acidic, resulting in insufficient active sites on the crystal nucleus surface, slow growth rate, and a tendency to form irregular morphologies; when the pH is above 8.5, the strong alkalinity will trigger the formation of new Mn²⁺. + / Mn³ + Precipitation (secondary nucleation) results in a mixture of polycrystalline particles. This range can be achieved through moderate OH... - Concentration activates growth sites on the crystal nucleus surface, promoting Mn³ + Ordered deposition enables directional growth and inhibits the formation of new crystal nuclei, ensuring that the product is mainly composed of single crystal particles.

[0066] The fourth pH range, 6.8–7.8, is used to regularize single crystals into regular hexahedrons. During the aging stage of S500, the near-neutral to weakly alkaline environment of 6.8–7.8 is suitable for "atomic rearrangement and morphology refinement": when the pH deviates from this range, the atomic migration rate becomes unbalanced (both excessive acidity and alkalinity will inhibit surface atomic diffusion), making it difficult to form regular hexahedrons with regular edges and corners; while this range, through mild acid-base conditions, allows the surface atoms of single crystal particles to slowly migrate to the crystal face with the lowest energy, ultimately forming a dense and uniform regular hexahedron, improving the structural stability of the product.

[0067] This invention also discloses a lithium manganese oxide cathode material, comprising lithium carbonate and single-crystal manganese oxide prepared by the method described above, wherein the single-crystal manganese oxide and lithium carbonate are mixed at a Li / Mn molar ratio of 0.55:1. Since the lithium manganese oxide cathode material is made using the aforementioned single-crystal manganese oxide, it possesses all the beneficial effects of the aforementioned single-crystal manganese oxide. Simultaneously, the Li / Mn molar ratio is limited to 0.55:1, which precisely matches the crystal structure formation requirements of lithium manganese oxide (such as LiMn₂O₄ or LiMnO₂): ensuring sufficient lithium source to fill the crystal lattice while avoiding lattice distortion caused by excessive lithium or structural defects caused by insufficient lithium. This ultimately results in a highly crystalline and densely structured lithium manganese oxide, significantly improving the material's mechanical strength and thermal stability, and providing structural support for enhancing electrochemical performance.

[0068] The technical solution of this application will be illustrated below through specific embodiments and comparative examples.

[0069] Example 1:

[0070] S100, prepare a 1 mol / L MnSO4 solution, and add a reducing additive (80% glucose + 20% sodium sulfite) with a mass fraction of 0.02% to control the content of reducing substances in the solution at 360 μg / ml, thereby inhibiting the formation of MnSO4. 2+ Excessive oxidation to Mn 4+ The first mixture;

[0071] S200, adjust the first mixture to a first pH of 7.1, and stir at a set temperature of 35℃ for 0.3 hours to allow the Mn in the solution to... 2+ Mn(OH)₂ is generated, and the reaction of Mn(OH)₂ with oxygen in the system is promoted to convert it into MnOOH, thereby generating MnOOH. 2+ The second mixture of crystal nucleation precursors;

[0072] S300, add 0.01% by mass of a composite additive (phosphoric acid: cetyltrimethylammonium bromide at a ratio of 1:0.36) to the second mixture, adjust the pH to 6.8, and allow MnOOH to dissociate into Mn. 3+ It forms stable Mn-containing complexes with composite additives to inhibit Mn formation. 3+ Disproportionation to Mn 2+ and Mn 4+ After stirring in air for 10 hours and allowing to stand until use, the complex slowly releases Mn. 3+ During the process, MnOOH is further dehydrated and transformed into pure-phase Mn2O3 crystal nuclei, resulting in a third mixed solution containing Mn2O3 crystal nuclei, wherein the Mn-containing complex is: [Mn(PO4)] n ]³ - ;

[0073] S400, the third mixture and pH adjuster (NaOH solution, ammonia solution) are introduced into the reactor in parallel flow, with air as the oxidant, and the pH in the reactor is adjusted to 7.6 and the reaction is continued for 13 hours to allow the third mixture and pH adjuster to mix and react. The solid content during the mixing reaction is controlled to 8% to suppress secondary nucleation and promote the directional growth of existing Mn2O3 crystal nuclei into single crystal particles, resulting in a fourth mixture containing single crystal particles, wherein the solid particles in the solid content are Mn-containing solid particles;

[0074] S500, the fourth mixture in the reactor is aged for 2 hours. During the aging process, the pH is controlled at 7.3 and the addition of manganese sulfate solution is stopped. The fourth mixture is filtered, washed, dried and sieved to obtain hexahedral single crystal manganese trioxide.

[0075] S600 involves adding the aforementioned hexahedral single-crystal manganese trioxide and lithium carbonate at a molar ratio of Li / Mn of 0.55:1, calcining at 750°C for 15 hours in air, and then crushing and classifying to obtain the lithium manganese oxide cathode material product.

[0076] Example 2:

[0077] S100 was prepared by adding a 1.8 mol / L MnSO4 solution to a reducing additive (65% maltose + 35% methyl sulfite) at a mass fraction of 0.03% to control the reducing agent content in the solution to 500 μg / ml, thereby inhibiting the formation of MnSO4. 2+ Excessive oxidation to Mn 4+ The first mixture;

[0078] S200, adjust the first mixture to a first pH of 7.3, and stir at a set temperature of 30℃ for 0.2 hours to allow the Mn in the solution to rise. 2+ Mn(OH)₂ is generated, and the reaction of Mn(OH)₂ with oxygen in the system is promoted to convert it into MnOOH, thereby generating MnOOH. 2+ The second mixture of crystal nucleation precursors;

[0079] S300, add 0.02% (by mass) of a composite additive (phosphoric acid: n-butanol ratio of 1:0.23) to the second mixture, adjust the pH to 6.9, and allow MnOOH to dissociate into Mn. 3+ It forms stable Mn-containing complexes with composite additives to inhibit Mn formation. 3+ Disproportionation to Mn 2+ and Mn 4+ After stirring in air for 18 hours and allowing to stand until use, the complex slowly releases Mn. 3+During the process, MnOOH is further dehydrated and transformed into pure-phase Mn2O3 crystal nuclei, resulting in a third mixed solution containing Mn2O3 crystal nuclei, wherein the Mn-containing complex is: [Mn(PO4)] n ]³ - ;

[0080] S400, the third mixture and pH adjuster (NaOH solution, ammonia solution) are introduced into the reactor in parallel flow, with oxygen as the oxidant, and the pH in the reactor is adjusted to 7.9 and the reaction is continued for 10 hours to allow the third mixture and pH adjuster to mix and react. The solid content during the mixing reaction is controlled to 3% to suppress secondary nucleation and promote the directional growth of existing Mn2O3 crystal nuclei into single crystal particles, resulting in a fourth mixture containing single crystal particles, wherein the solid particles in the solid content are Mn-containing solid particles;

[0081] S500, the fourth mixture in the reactor is aged for 1 hour. During the aging process, the pH is controlled at 7.5 and the addition of manganese sulfate solution is stopped. The fourth mixture is filtered, washed, dried and sieved to obtain hexahedral single crystal manganese trioxide.

[0082] S600 involves adding the aforementioned hexahedral single-crystal manganese trioxide and lithium carbonate at a molar ratio of Li / Mn of 0.55:1, calcining at 750°C for 15 hours in air, and then crushing and classifying to obtain the lithium manganese oxide cathode material product.

[0083] Example 3:

[0084] S100 was prepared by adding a 1.8 mol / L MnSO4 solution to a reducing additive (60% maltose + 40% sodium sulfite) with a mass fraction of 0.03% to control the reducing agent content in the solution at 400 μg / ml, thereby inhibiting the formation of MnSO4. 2+ Excessive oxidation to Mn 4+ The first mixture;

[0085] S200, adjust the first mixture to a first pH of 7.2, and stir at a set temperature of 30℃ for 0.5 hours to allow the Mn in the solution to rise. 2+ Mn(OH)₂ is generated, and the reaction of Mn(OH)₂ with oxygen in the system is promoted to convert it into MnOOH, thereby generating MnOOH. 2+ The second mixture of crystal nucleation precursors;

[0086] S300, add 0.05% (by mass) of a composite additive (phosphoric acid:EDTA = 1:0.45) to the second mixture, adjust the pH to 6.9, and allow MnOOH to dissociate into Mn. 3+ It forms stable Mn-containing complexes with composite additives to inhibit Mn formation. 3+ Disproportionation to Mn2+ and Mn 4+ After stirring in air for 12 hours and allowing to stand until use, the complex slowly releases Mn. 3+ During the process, MnOOH is further dehydrated and transformed into pure-phase Mn2O3 crystal nuclei, resulting in a third mixed solution containing Mn2O3 crystal nuclei, wherein the Mn-containing complex is: [Mn(PO4)] n ]³ - ;

[0087] S400, the third mixture and pH adjuster (NaOH solution, ammonia solution) are introduced into the reactor in parallel flow, with oxygen as the oxidant, and the pH in the reactor is adjusted to 8.1 and the reaction is continued for 15 hours to allow the third mixture and pH adjuster to mix and react. The solid content during the mixing reaction is controlled to 5% to suppress secondary nucleation and promote the directional growth of existing Mn2O3 crystal nuclei into single crystal particles, resulting in a fourth mixture containing single crystal particles, wherein the solid particles in the solid content are Mn-containing solid particles;

[0088] S500, the fourth mixture in the reactor is aged for 3 hours. During the aging process, the pH is controlled at 7.4 and the addition of manganese sulfate solution is stopped. The fourth mixture is filtered, washed, dried and sieved to obtain hexahedral single crystal manganese trioxide.

[0089] S600 involves adding the aforementioned hexahedral single-crystal manganese trioxide and lithium carbonate at a molar ratio of Li / Mn of 0.55:1, calcining at 750°C for 15 hours in air, and then crushing and classifying to obtain the lithium manganese oxide cathode material product.

[0090] Comparative Example 1:

[0091] Pretreatment process of manganese sulfate solution. Prepare a 2 mol / L manganese sulfate solution, add 0.03% (w / w) of additive 1 (60% maltose + 40% sodium sulfite) to control the reducing substance content in the solution to 500 μg / ml, adjust the pH to 7.1, and stir at 30℃ for 0.2 h. Then add 0.02% (w / w) of additive 2 (phosphoric acid: sodium citrate = 1:0.42) to adjust the pH of the manganese sulfate solution to 7.1, stir under air for 1 h, and let stand until ready for use.

[0092] Preparation of manganese trioxide material. The pretreated manganese sulfate solution, NaOH solution, and ammonia solution were added concurrently to a reaction vessel. Air was used as the oxidant, the pH was adjusted to 9.2, and the reaction time was 10 hours. The solid content of the system was controlled at 3%. After the reaction, aging continued for 1 hour, during which the pH was controlled at 7.5 and the addition of manganese sulfate solution was stopped. The mixed solution was filtered, washed, dried, and sieved to obtain a mixed manganese oxide compound of polycrystalline manganese tetroxide and single-crystal manganese trioxide.

[0093] Preparation of lithium manganese oxide material. The above-mentioned manganese oxide compound and lithium carbonate were added at a molar ratio of Li / Mn of 0.55:1, and calcined at 750°C for 15 h in air atmosphere. After crushing and classification, lithium manganese oxide cathode material product was obtained.

[0094] Comparative Example 2:

[0095] Pretreatment process of manganese sulfate solution: Prepare a 2 mol / L manganese sulfate solution, adjust the pH to 7.0, and stir at 30℃ for 0.2 h. Then adjust the pH of the manganese sulfate solution to 7.2, stir under air for 3 h, and let it stand until ready for use.

[0096] Preparation of manganese trioxide material. The pretreated manganese sulfate solution, NaOH solution, and ammonia solution were added concurrently to a reaction vessel. Air was used as the oxidant, the pH was adjusted to 7.8, and the reaction time was 10 hours. The solid content of the system was controlled at 3%. After the reaction, aging continued for 1 hour, during which the pH was controlled at 7.3 and the addition of manganese sulfate solution was stopped. The mixed solution was filtered, washed, dried, and sieved to obtain a mixed manganese oxide compound of polycrystalline manganese tetroxide and single-crystal manganese trioxide.

[0097] Preparation of lithium manganese oxide material. The above-mentioned manganese oxide compound and lithium carbonate were added at a molar ratio of Li / Mn of 0.55:1, and calcined at 750°C for 15 h in air atmosphere. After crushing and classification, lithium manganese oxide cathode material product was obtained.

[0098] The XRD and SEM images of the single-crystal manganese trioxide in Example 1 are shown below. Figure 2 , 3 As shown; the XRD and SEM images of the manganese oxide in Comparative Example 1 are shown below. Figure 4 , 5 As shown, the manganese trioxide in Example 1 has a particle morphology of 2-5 μm hexahedral single crystals, while Comparative Example 1, a mixed oxide of manganese tetroxide and manganese trioxide, shows obvious 2-4 μm hexahedral single crystals and spinel aggregates. This is mainly because the higher reaction pH leads to a lower potential, which is beneficial to the synthesis of manganese tetroxide byproducts. Furthermore, the results of Comparative Example 2 indicate that without the addition of reducing and composite additives to the manganese sulfate solution, some of the manganese sulfate solution is oxidized by air to generate manganese tetroxide crystal nuclei, resulting in a mixed oxide of manganese tetroxide and manganese trioxide in the later product, affecting product purity.

[0099] Performance / Data Testing:

[0100] Using lithium foil as the negative electrode, and the lithium manganese oxide positive electrode materials prepared in the above examples and comparative examples respectively as the positive electrode, the particle morphology and mass ratio of manganese trioxide (Mn2O3) of the composite manganese oxide compounds in Examples 1, 2, and 3 and Comparative Examples 1 and 2 were tested to prepare secondary button batteries, model CR2025. Under a voltage of 3.0–4.2V, the batteries were first charged at 0.2C and discharged at 0.2C for two cycles, and then cycled under 1C charging and discharging conditions. The initial charge capacity at 0.2C, the initial discharge capacity at 0.2C, the initial charge-discharge efficiency at 0.2C, the initial discharge capacity at 1C, and the capacity retention rate after 60 cycles were tested. The test results are shown in Tables 1 and 2.

[0101] Table 1: Quality Performance Table of Manganese Oxides in Examples

[0102]

[0103] Table 2: Performance Test Results of Examples

[0104]

[0105] The experimental test results are shown in Table 1. The capacity retention rates of Examples 1, 2, and 3 were all above 98%, but the capacity retention rate of Comparative Example 1 was only 96.25%. This was mainly due to the high reaction pH, which resulted in a small amount of polycrystalline manganese tetroxide product, thus causing a certain degree of decrease in the cycle performance of lithium manganese oxide. The capacity retention rate of Comparative Example 2 was only 94.21%, mainly because the content of single-crystal manganese trioxide was low, and the product composition was mostly manganese tetroxide.

[0106] A detailed analysis of Tables 1 and 2 above is provided:

[0107] I. Product purity and morphology are precisely controllable, completely solving the problem of impurities in traditional methods.

[0108] Purity meets standards and is singular: Examples 1-3 inhibit Mn² through "reducing additives (containing aldehyde compounds + sulfites)". + Excessive oxidation and the use of compound additives (phosphoric acid + second complexing agent) to stabilize Mn³ + The synergistic effect of "precisely controlling the pH range (6.5~8.5) at each stage" resulted in a final product with 100% Mn2O3 content and no impurities such as manganese tetroxide being generated. In contrast, Comparative Example 1 had a potential imbalance due to a high reaction pH (9.2), resulting in only 75% Mn2O3 content. Comparative Example 2 did not add any reducing additives or composite additives, resulting in only 41% Mn2O3 content. Both of these examples contained a large amount of manganese tetroxide byproducts, which confirms the decisive role of the process in this application on the purity of the product.

[0109] The morphology is regular and uniform: the products of Examples 1-3 are all large-particle hexahedral single crystal structures of 2~6μm, which is due to the process design of "controlling the solid content (1~12%) to inhibit secondary nucleation, aging for 1~6h to refine the morphology, and pH gradient to regulate the directional growth of crystal nuclei"; while Comparative Examples 1-2 lack key control methods, and the products exhibit a mixed morphology of "hexahedral single crystals + spinel composite agglomerates", and the structural integrity and uniformity are significantly worse than those of the Examples.

[0110] II. Significantly improved electrochemical performance, meeting the demands of high-performance lithium batteries.

[0111] Outstanding cycle stability: The lithium manganese oxide cathode materials prepared in Examples 1-3 all maintained a capacity retention of over 98% (up to 98.7%) after 60 cycles at 1C, significantly better than Comparative Example 1 (96.25%) and Comparative Example 2 (94.21%). The core reason is that the single-crystal Mn2O3 in the examples has higher mechanical strength, thermal stability, and a shorter ion diffusion path, which can effectively suppress volume expansion during battery charging and discharging; while the comparative examples, due to the presence of Mn3O4 impurities (polycrystalline structure), have decreased structural stability and accelerated capacity decay during cycling.

[0112] Stable charge-discharge efficiency: The first charge-discharge efficiency at 0.2C in Examples 1-3 remained above 98.5% (up to 98.6%), demonstrating excellent electrochemical reversibility; Comparative Example 2, due to the high impurity content of the product, had a first charge-discharge efficiency of only 97.48%, further proving the key role of high-purity single-crystal Mn2O3 in improving the electrochemical performance of the battery.

[0113] Third, the process is economically efficient and industrially adaptable, addressing the pain points of traditional methods.

[0114] The process is mild and low-cost: The example uses MnSO4 as the manganese source, combined with inexpensive and readily available reducing additives (glucose / maltose + sodium sulfite / potassium sulfite) and composite additives (phosphoric acid + conventional second complexing agent). The reaction temperature is only 25~65℃, without the need for high-temperature calcination or high-pressure hydrothermal environment. Compared with traditional high-temperature roasting and solvothermal methods, it significantly reduces energy consumption and raw material costs. Moreover, the process steps are continuous, and the parameters (such as additive dosage, pH range, and reaction time) are clear and controllable, making it suitable for large-scale continuous production.

[0115] Precise and effective parameter control: Through comparative verification, the core role of each process parameter was clarified: reducing additives can inhibit Mn 2+ Excessive oxidation to Mn 4+ Composite additives can inhibit Mn 3+Disproportionation, with pH ranges at each stage (6.5~7.3, 6.5~7.0, 7.0~8.5, 6.8~7.8) adapted to the chemical characteristics of different reaction stages, and solid content control to avoid secondary nucleation—the synergistic regulation of these parameters is the core guarantee for achieving "high purity, regular morphology, and high performance" products. In contrast, comparative ratios, due to the lack of key additives or deviation from optimal parameters, cannot achieve the same effect.

[0116] In summary, the preparation method of this application successfully prepared high-purity (100% Mn2O3) single-crystal manganese trioxide with a regular hexahedral morphology by precisely controlling process parameters and additive combinations. The derived lithium manganese oxide cathode material has excellent cycle stability and electrochemical reversibility. At the same time, the process has the advantages of low cost, mild conditions, and easy industrialization, effectively solving the technical pain points of low purity, impure morphology, poor performance, and high energy consumption of traditional methods, and fully meeting the application requirements of high-performance lithium batteries for cathode material precursors.

[0117] The present invention also discloses a lithium battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode comprises the aforementioned lithium manganese oxide positive electrode material.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing single-crystal manganese trioxide, characterized in that, Includes the following steps: S100, prepare MnSO4 solution, add reducing additive to form Mn inhibitor. 2+ Excessive oxidation to Mn 4+ The first mixture contains reducing additives including aldehyde compounds and sulfites, which provide reducing substances at a concentration of 300-800 μg / ml. S200, add the first complexing agent to the first mixture and adjust to the first pH range, stir at the set temperature, so that the Mn in the first mixture... 2+ Mn(OH)2 is generated, and Mn(OH)2 reacts with oxygen to partially convert to MnOOH, producing a product with Mn 3+ The second mixture of the crystal nucleus precursor, wherein the first pH range is 7.0~7.6, the set temperature is 25~65℃, the first complexing agent is one or more of ammonium sulfate, ammonia, ethylenediamine, triethanolamine, and nitrilotriacetic acid, and the addition content of the first complexing agent is 1~5g / L; S300, a composite additive consisting of phosphoric acid and a second complexing agent is added to the second mixture to adjust the pH to the second range, so that MnOOH dissociates into Mn 3+ It forms Mn-containing complexes with composite additives to inhibit Mn. 3+ Disproportionation to Mn 2+ and Mn 4+ Stirring and standing under air conditions allows the complex to slowly release Mn. 3+ During the process, MnOOH is dehydrated and converted into pure-phase Mn2O3 crystal nuclei, resulting in a third mixed solution containing Mn2O3 crystal nuclei. The second complexing agent is selected from one or more of ethylenediaminetetraacetic acid (EDTA), sodium citrate, hexadecyltrimethylammonium bromide, or n-butanol. The content of the second complexing agent is 1-5 g / L, the mass ratio of phosphoric acid to the second complexing agent is 1:0.05-0.45, the second pH range is 6.5-7.0, and the Mn-containing complex is [Mn(PO4)]. n ] 3- ; S400, then the third mixture and pH adjuster are added in parallel flow, using air or oxygen as the oxidant, to adjust the third mixture to the third pH range, controlling the solid content during pH adjustment to inhibit secondary nucleation and promote the directional growth of Mn2O3 crystal nuclei into single crystal particles, to obtain a fourth mixture containing single crystal particles, wherein the solid particles in the solid content are Mn-containing solid particles, and the third pH range is 7.0~8.5; S500, the fourth mixture is adjusted to the fourth pH range and aged to make the single crystal particles regular hexahedral in shape; after solid-liquid separation and purification, hexahedral single crystal manganese trioxide is obtained, wherein the fourth pH range is 6.8~7.

8.

2. The method for preparing single-crystal manganese trioxide according to claim 1, characterized in that, In step S100, the aldehyde-containing compound is any one or more combinations of glucose or maltose, and the sulfite is any one or more combinations of sodium sulfite or potassium sulfite; the amount of the reducing additive added is 0.01% to 0.05% of the mass of the MnSO4 solution.

3. The method for preparing single-crystal manganese trioxide according to claim 2, characterized in that, In step S100, the reducing substance includes reducing groups of aldehyde compounds and reducing ions of sulfites.

4. The method for preparing single-crystal manganese trioxide according to claim 1, characterized in that, In step S200, the stirring time is 0.1~1h.

5. The method for preparing single-crystal manganese trioxide according to claim 1, characterized in that, In step S300, the stirring and standing time under air conditions is 3~24h.

6. The method for preparing single-crystal manganese trioxide according to claim 1, characterized in that, In step S400, the mixing reaction time of the third mixture and the pH adjuster is 3-20 hours, and the solid content during the mixing reaction is controlled to be 1-12%. The solid content is the proportion of the mass of Mn-containing solid particles to the total mass of the mixing reaction system. The pH adjuster is selected from one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution. The concentration of the sodium hydroxide solution is 1-5 mol / L.

7. The method for preparing single-crystal manganese trioxide according to claim 1, characterized in that, In step S500, the aging time is 1~6h, and the particle size D50 of the obtained hexahedral single crystal manganese trioxide is 0.5~5μm.

8. A lithium manganese oxide cathode material, characterized in that, The raw materials for lithium manganese oxide cathode materials include lithium carbonate and single-crystal manganese oxide prepared by the method described in any one of claims 1 to 7, wherein the single-crystal manganese oxide and lithium carbonate are mixed at a Li / Mn molar ratio of 0.55:

1.

9. A lithium battery, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode includes the lithium manganese oxide positive electrode material as described in claim 8.

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