Lithium manganate positive electrode material, preparation method thereof and lithium battery

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a lithium manganate positive electrode material, a preparation method thereof and a lithium battery, and the method comprises the following steps: adding a manganese sulfate solution, a precipitator and a complexing agent into a reaction kettle in a parallel flow manner, reacting under a first preset reaction condition, and introducing a first oxidant while reacting to obtain a mixed solution; concentrating the mixed solution to preset solid content, and adding a curing agent for curing reaction to obtain manganous-manganic oxide slurry; adding a manganese sulfate solution, a precipitant and a complexing agent into the reaction kettle in a parallel flow manner again, reacting with the manganous-manganic oxide slurry under a second preset reaction condition, introducing a second oxidizing agent while reacting to obtain a composite manganese oxide mixed solution, and filtering, washing and drying to obtain a composite manganese oxide; the composite manganese oxide and lithium carbonate are mixed, calcined, crushed and graded to obtain the lithium manganate positive electrode material, so that the electrochemical performance of the lithium manganate positive electrode material is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium batteries, and in particular, relates to a lithium manganate positive electrode material and a preparation method thereof, and a lithium battery. Background Art

[0002] Spinel lithium manganese oxide (LiMn2O4) is one of the positive electrode materials for lithium batteries, and the theoretical specific capacity of spinel lithium manganese oxide is 148mAh / g. At present, lithium manganese oxide is mainly prepared by using manganese tetraoxide as a precursor or by high-temperature calcination of manganese tetraoxide and manganese dioxide. However, the manganese atoms in spinel lithium manganese oxide are densely arranged on the (111) crystal plane, which cannot further improve the diffusion rate of lithium ions, thereby limiting the electrochemical performance of lithium manganese oxide positive electrode materials.

[0003] The existing technology has the problem that the electrochemical performance of spinel lithium manganese oxide is limited and cannot meet the scene requirements. Summary of the invention

[0004] The present application provides a lithium manganese oxide positive electrode material and a preparation method thereof, and a lithium battery, which aims to solve the problem that the electrochemical performance of spinel lithium manganese oxide is limited and cannot meet the scene requirements to a certain extent.

[0005] In a first aspect, the present application provides a method for preparing a lithium manganese oxide positive electrode material, comprising:

[0006] Adding a manganese sulfate solution, a precipitant and a complexing agent into a reactor in parallel, reacting under a first preset reaction condition, and introducing a first oxidant into the reactor during the reaction to obtain a manganese tetraoxide mixed solution, wherein the manganese sulfate solution is fed at a first feeding rate;

[0007] Concentrating the manganese tetraoxide mixed solution to a preset solid content, and adding a aging agent to perform a aging reaction to obtain manganese tetraoxide slurry;

[0008] The manganese sulfate solution, the precipitant and the complexing agent are added to the reactor in parallel again, reacting with the manganese tetraoxide slurry under a second preset reaction condition, and a second oxidant is introduced into the reactor during the reaction to obtain a composite manganese oxide mixed solution, wherein the manganese sulfate solution is fed at a second feeding rate;

[0009] The composite manganese oxide compound mixed solution is filtered, washed and dried to obtain a composite manganese oxide compound, wherein the composite manganese oxide compound is manganese trioxide embedded in a spinel manganese tetraoxide substrate in the form of a regular hexahedral single crystal;

[0010] The composite manganese oxide compound is mixed with lithium carbonate, calcined in an air atmosphere, and crushed and classified to obtain a lithium manganate positive electrode material.

[0011] In a second aspect, the present application provides a lithium manganese oxide positive electrode material, which is prepared according to the preparation method of the lithium manganese oxide positive electrode material described in any one of the contents of the first aspect.

[0012] In a third aspect, the present application provides a lithium battery, comprising a positive electrode, wherein the positive electrode comprises a lithium manganese oxide positive electrode material prepared by the method for preparing the lithium manganese oxide positive electrode material described in the second aspect.

[0013] It can be understood that the beneficial effects of the second to third aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] Compared with the prior art, the preparation method of the lithium manganate positive electrode material of the present application first prepares a manganese trioxide base material, and then oxidizes the valence of part of manganese from +2 to +3 in a strong oxidizing atmosphere to obtain a composite manganese oxide compound including dimanganese trioxide. Since the dimanganese trioxide is embedded in the spinel manganese trioxide base in the form of a regular hexahedral single crystal by a liquid phase coprecipitation method to form a composite manganese oxide compound, the number of (100) crystal planes in the lithium manganate is increased, and then the lithium manganate positive electrode material is obtained. While the discharge capacity of the lithium manganate positive electrode material is improved, the capacity retention rate of the lithium manganate positive electrode material is also improved, thereby improving the electrochemical performance of the lithium manganate positive electrode material, and the liquid phase coprecipitation method is used to reduce the manufacturing cost of the lithium manganate positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a schematic flow chart of a method for preparing a lithium manganese oxide positive electrode material provided in one embodiment of the present application;

[0018] Figure 2 is an XRD schematic diagram of the composite manganese oxide compound provided in Example 1 of the present application;

[0019] Figure 3 is a SEM schematic diagram of the composite manganese oxide compound provided in Example 1 of the present application;

[0020] Figure 4 This is a schematic diagram of the XRD of the composite manganese oxide compound provided in Comparative Example 1 of the present application;

[0021] Figure 5 This is a SEM schematic diagram of the composite manganese oxide compound provided in Comparative Example 1 of the present application;

[0022] Figure 6 This is a SEM schematic diagram of the composite manganese oxide compound provided in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0025] In the present application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all mean: a, b, c, a~b (i.e. a and b), a~c, b~c, or a~b~c, where a, b, c can be single or multiple, respectively.

[0026] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the implementation regulations of this application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0027] The terms used in the embodiments of the present application are only for the purpose of describing specific implementation rules, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the implementation rules of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0028] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0029] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0030] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0032] Spinel lithium manganese oxide (LiMn2O4) is one of the positive electrode materials for lithium batteries, and the theoretical specific capacity of spinel lithium manganese oxide is 148mAh / g. At present, lithium manganese oxide is mainly prepared by using manganese tetraoxide as a precursor or by high-temperature calcination of manganese tetraoxide and manganese dioxide. Due to the unique three-dimensional tunnel structure of spinel lithium manganese oxide, lithium ions can be reversibly deintercalated from the spinel lattice, but the manganese atoms in spinel lithium manganese oxide are densely arranged on the (111) crystal plane, which cannot further improve the diffusion rate of lithium ions, thereby limiting the electrochemical performance of lithium manganese oxide positive electrode materials.

[0033] In order to solve the above problems to a certain extent, the first aspect of the present application provides a method for preparing a lithium manganese oxide positive electrode material, comprising:

[0034] S100, adding a manganese sulfate solution, a precipitant, and a complexing agent into a reactor in parallel, reacting under a first preset reaction condition, and introducing a first oxidant into the reactor during the reaction to obtain a manganese tetraoxide mixed solution, wherein the manganese sulfate solution is fed at a first feeding rate;

[0035] S200, concentrating the manganese tetraoxide mixed solution to a preset solid content, and adding a aging agent to perform a aging reaction to obtain a manganese tetraoxide slurry;

[0036] S300, adding the manganese sulfate solution, the precipitant and the complexing agent into the reactor again in parallel, reacting with the manganese tetraoxide slurry under the second preset reaction condition, and introducing the second oxidant into the reactor during the reaction to obtain a composite manganese oxide mixed solution, wherein the liquid inlet speed of the manganese sulfate solution is the second liquid inlet speed;

[0037] S400, filtering, washing and drying the composite manganese oxide compound mixed solution to obtain a composite manganese oxide compound, wherein the composite manganese oxide compound is manganese trioxide embedded in a spinel manganese tetraoxide substrate in the form of a regular hexahedral single crystal;

[0038] S500, mixing the composite manganese oxide compound with lithium carbonate, calcining in an air atmosphere, and crushing and grading to obtain a lithium manganate positive electrode material.

[0039] Compared with the prior art, the present application prepares a manganese tetraoxide base material first, and then oxidizes the valence of part of manganese from +2 to +3 in a strong oxidizing atmosphere to obtain a composite manganese oxide compound including dimanganese trioxide. Since the dimanganese trioxide is embedded in the spinel manganese tetraoxide base in the form of a regular hexahedral single crystal by a liquid phase co-precipitation method to form a composite manganese oxide compound, the number of (100) crystal planes in lithium manganate is increased, and then a lithium manganate positive electrode material is obtained. While the discharge capacity of the lithium manganate positive electrode material is increased, the capacity retention rate of the lithium manganate positive electrode material is also increased, thereby improving the electrochemical performance of the lithium manganate positive electrode material, and the liquid phase co-precipitation method is used to reduce the manufacturing cost of the lithium manganate positive electrode material. Among them, in step S200, the manganese tetraoxide mixed solution is concentrated to a preset solid content, and a curing agent is added to perform a curing reaction. Since the solid content of the manganese tetraoxide mixed solution is increased, the probability of collision between particles is increased. After the curing agent is added, the oxidation activity of the manganese tetraoxide surface is increased while the manganese tetraoxide mixed solution is homogenized, and the curing agent also acts as a template to guide the manganese tetraoxide to form a base material.

[0040] It should be noted that the lithium manganate (LiMn2O4) crystal synthesized using manganese tetraoxide has a small degree of distortion, uniform shape and size, and a good morphology is conducive to the deintercalation of lithium ions, reducing the crystal structure changes caused by deintercalation, and has excellent rate performance and stability, good safety performance, and improves the cycle performance of LiMn2O4. Since the preparation methods of manganese trioxide in the prior art are mainly potassium permanganate hydrothermal method and manganese salt high-temperature calcination method, it has high requirements on reaction equipment and reaction temperature, and cubic manganese trioxide is prepared by high-temperature sintering of manganese carbonate, which increases the manufacturing cost; for example, potassium manganate or manganese salt is used as a raw material to prepare manganese carbonate, and then manganese carbonate is sintered at a high temperature of 400-600°C to obtain manganese trioxide. The chemical reaction formula is as follows:

[0041]

[0042] MnCO3+O2→2Mn2O3+4CO2↑

[0043] Among them, MnO3 is a precipitate, and CO2 and NH3 are gases.

[0044] This embodiment adopts a liquid phase co-precipitation method to prepare a manganese oxide compound of manganese tetraoxide and manganese trioxide in situ composite, so that the manganese oxide compound not only takes into account the cycle performance of lithium manganate, but also improves the discharge capacity of lithium manganate, and the reaction conditions are relatively mild, reducing the manufacturing cost. Due to the addition of the aging reaction and the secondary strong oxidation reaction, hexahedral single crystal manganese trioxide is precipitated and grown on the substrate of spinel manganese tetraoxide, and then embedded to form a composite manganese oxide compound. Manganese tetraoxide and manganese trioxide are tightly combined and not easy to fall off, and the composite manganese oxide compound has good processing performance; the chemical reaction is as follows:

[0045]

[0046] In some embodiments, the first preset reaction condition includes: maintaining the pH value of the mixed solution in the reactor at 8.5 to 9.0, the reaction temperature at 50°C to 70°C, and the reaction time at 12h to 18h; the second preset reaction condition includes: maintaining the pH value of the mixed solution in the reactor at 9.2 to 9.8, the reaction temperature at 70°C to 90°C, and the reaction time at 15h to 25h. In this embodiment, since the pH value of the second preset reaction condition is greater than the pH value of the first preset reaction condition, and the reaction temperature of the second preset reaction condition is also greater than the reaction temperature of the first preset reaction condition, the redox potential of the mixed solution in the reactor is increased, which is conducive to the oxidation reaction, promotes the oxidation of the manganese ion from +2 to +3, and increases the speed of generating manganese trioxide.

[0047] In some embodiments, the molar ratio of manganese sulfate solution, precipitant and complexing agent added to the reactor in parallel for the first time is 10:(18-26):(8-13); the molar ratio of manganese sulfate solution, precipitant and complexing agent added to the reactor in parallel again is 10:(24-30):(1-16). The ratio range of this embodiment can improve the reaction efficiency of liquid phase co-precipitation method to embed manganese trioxide in the form of regular hexahedral single crystals on the substrate of spinel manganese tetraoxide to form a composite manganese oxide compound.

[0048] In some embodiments, the radius of manganese trioxide is 0.5 μm to 5 μm, and the mass percentage of manganese trioxide in the composite manganese oxide compound is less than or equal to 30%, that is, the mass ratio of manganese trioxide to manganese tetraoxide in the composite manganese oxide compound is (1 to 3):7; in this embodiment, controlling the radius of manganese trioxide can make manganese trioxide more conducive to embedding on the spinel manganese tetraoxide substrate in the form of a regular hexahedral single crystal, and when the mass percentage of manganese trioxide in the composite manganese oxide compound is controlled to be less than or equal to 30%, increasing the mass percentage of manganese trioxide can Increasing the number of (100) crystal planes in lithium manganese oxide increases the diffusion rate of lithium ions in the lithium manganese oxide positive electrode material, thereby increasing the discharge capacity of lithium manganese oxide. When the mass percentage of manganese trioxide in the composite manganese oxide compound is greater than 30%, the poor reversibility, low cycle stability and low Coulomb efficiency of manganese trioxide will reduce the cycle stability of lithium manganese oxide and reduce the capacity retention rate of lithium batteries.

[0049] In some embodiments, the first liquid inlet rate is 3% / h to 8% / h of the reactor volume; the second liquid inlet rate is 1% / h to 5% / h of the reactor volume; the liquid inlet rate of this embodiment is beneficial to controlling the reaction rate and forming a composite manganese oxide compound with better morphology.

[0050] In some embodiments, the concentration of the manganese sulfate solution is 50 g / L to 300 g / L, the mass percentage of the precipitant is 20% to 35%, and the mass percentage of the complexing agent is 5% to 25%; controlling the concentration of the manganese sulfate solution, the mass percentages of the precipitant and the complexing agent is conducive to forming a better multidimensional structure, allowing manganese trioxide to be embedded in the spinel manganese trioxide substrate in the form of a regular hexahedral single crystal, thereby improving the structural stability.

[0051] In some embodiments, the preset solid content ranges from 20% to 30%, and the mass percentage of the curing agent is 0.5% to 2%; the curing agent includes F127 non-ionic surfactant, sodium hypochlorite, and ammonium bicarbonate, and the mass ratio of F127 non-ionic surfactant, sodium hypochlorite and ammonium bicarbonate is 40:(10-30):(15-25); the solid content of the manganese tetraoxide mixed solution is increased, and the collision probability between particles is increased. After adding the curing agent of the mass ratio of this embodiment, the F127 non-ionic surfactant emulsifies the manganese tetraoxide mixed solution, and the sodium hypochlorite constructs an active oxygen atmosphere. While homogenizing the manganese tetraoxide mixed solution, the oxidation activity of the manganese tetraoxide surface is increased. The ammonium bicarbonate also acts as a template agent, guiding the manganese tetraoxide to form a base material, so as to form a regular hexahedral single crystal of dimanganese trioxide and precipitate on the base formed by the manganese tetraoxide.

[0052] In some embodiments, the reaction temperature of the aging reaction is 70° C. to 90° C., and the aging time is 6 h to 10 h, which provides a better reaction environment for forming the complex manganese oxide compound.

[0053] In some embodiments, the first oxidant is air or oxygen. When the manganese trioxide mixed solution is formed, the oxidizing property of the first oxidant is relatively low because there is no need to oxidize the +2-valent manganese ions; the second oxidant is a combination of any one or more of oxygen, hydrogen peroxide, sodium persulfate, ozone, sodium hypochlorite or potassium dichromate. Since it is necessary to oxidize the +2-valent manganese ions into +3-valent manganese ions, the oxidizing property of the second oxidant is greater than that of the first oxidant; the precipitant is a combination of any one or more of sodium hydroxide, potassium hydroxide, sodium methoxide or sodium ethoxide; the complexing agent is a combination of any one or more of ammonia water, ammonium sulfate, disodium ethylenediaminetetraacetate, polyethylene glycol, triethanolamine or sodium dodecylsulfonate; the use of the precipitant and complexing agent of this embodiment is conducive to the formation of regular hexahedral single crystals of manganese trioxide and precipitation on the substrate formed by the manganese trioxide.

[0054] In some embodiments, the molar ratio of lithium in lithium carbonate to manganese in the composite manganese oxide compound is (0.5-0.55):1, the calcination temperature is 700°C-800°C, and the calcination time is 10h-14h; the lithium-manganese ratio of this embodiment is adopted to improve the electrochemical properties of lithium manganate; the calcination reaction conditions can better allow lithium ions to combine with the composite manganese oxide, thereby improving the electrochemical properties of lithium manganate.

[0055] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0056] Example 1

[0057] A method for preparing a lithium manganate positive electrode material, comprising:

[0058] 1) adding a manganese sulfate solution with a volume concentration of 180 g / L, 28% by mass of sodium hydroxide and 20% by mass of disodium ethylenediaminetetraacetate into a reactor in parallel, the liquid feeding rate of the manganese sulfate solution is 6% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 8.6, the reaction temperature is 60° C., the reaction time is 14 h, and oxygen is introduced into the reactor during the reaction to obtain a manganese tetraoxide mixed solution;

[0059] 2) starting a concentrator to concentrate the manganese tetraoxide mixed solution to 25%, and adding 0.6% by mass of a aging agent for aging reaction to obtain a manganese tetraoxide slurry, wherein the aging agent includes F127 non-ionic surfactant, sodium hypochlorite, and ammonium bicarbonate, the mass ratio of F127 non-ionic surfactant, sodium hypochlorite and ammonium bicarbonate is 40:25:18, the reaction temperature of the aging reaction is 80° C., and the aging time is 6 hours;

[0060] 3) adding a manganese sulfate solution having a volume concentration of 180 g / L, 28% by mass of sodium hydroxide and 20% by mass of disodium ethylenediaminetetraacetate into a reactor in parallel, the manganese sulfate solution is fed at a rate of 4% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 9.3, the reaction temperature is 70° C., the reaction time is 16 h, and the mixture is reacted with the manganese tetraoxide slurry, while ozone is introduced into the reactor to obtain a composite manganese oxide mixed solution;

[0061] 4) filtering, washing and drying the composite manganese oxide compound mixed solution to obtain a composite manganese oxide compound;

[0062] 5) Mixing the composite manganese oxide compound with lithium carbonate, wherein the molar ratio of lithium in the lithium carbonate to manganese in the composite manganese oxide compound is 0.53:1, calcining in an air atmosphere at a calcination temperature of 780° C. for 12 h, and crushing and grading to obtain a lithium manganate positive electrode material.

[0063] The XRD diagram of the composite manganese oxide compound formed in Example 1 is as follows: Figure 2 As shown, the SEM schematic diagram of the composite manganese oxide compound provided in Example 1 is as follows Figure 3 shown.

[0064] Example 2: The difference from Example 1 is that the concentration of the manganese sulfate solution in the first liquid inlet, the mass percentage of the precipitant sodium hydroxide and the complexing agent ammonia water, the first liquid inlet speed, the first preset reaction condition, the preset solid content, the second preset reaction condition, and the second oxidant are different, and the rest of the contents are the same.

[0065] 1) adding a manganese sulfate solution with a volume concentration of 200 g / L, 25% by mass of sodium hydroxide and 18% by mass of ammonia water into a reactor in parallel, the liquid feeding rate of the manganese sulfate solution is 5% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 8.7, the reaction temperature is 65° C., the reaction time is 14 hours, and oxygen is introduced into the reactor during the reaction to obtain a manganese tetraoxide mixed solution;

[0066] 2) starting a concentrator to concentrate the manganese tetraoxide mixed solution to 20%, and adding 0.7% by mass of a aging agent for aging reaction to obtain a manganese tetraoxide slurry, wherein the aging agent includes F127 non-ionic surfactant, sodium hypochlorite, and ammonium bicarbonate, the mass ratio of F127 non-ionic surfactant, sodium hypochlorite and ammonium bicarbonate is 40:16:15, the reaction temperature of the aging reaction is 80° C., and the aging time is 6 hours;

[0067] 3) adding a manganese sulfate solution with a volume concentration of 180 g / L, 28% by mass of sodium hydroxide and 20% by mass of disodium ethylenediaminetetraacetate into the reactor in parallel, the manganese sulfate solution is fed at a rate of 6% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 9.2, the reaction temperature is 75° C., the reaction time is 12 h, and the mixture is reacted with the manganese tetraoxide slurry, and sodium persulfate is introduced into the reactor during the reaction to obtain a composite manganese oxide mixed solution.

[0068] Example 3: The difference from Example 1 is that the concentration of the manganese sulfate solution, the complexing agent is ammonium sulfate, the first liquid inlet speed, the first preset reaction condition, the preset solid content, the mass percentage of the aging agent, the aging time, the second preset reaction condition, and the second oxidant are different, and the rest of the contents are the same.

[0069] 1) adding a manganese sulfate solution with a volume concentration of 120 g / L, 28% by mass of sodium hydroxide and 20% by mass of ammonium sulfate into a reactor in parallel, the feeding rate of the manganese sulfate solution is 5% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 8.9, the reaction temperature is 65° C., the reaction time is 14 h, and oxygen is introduced into the reactor during the reaction to obtain a manganese tetraoxide mixed solution;

[0070] 2) Turn on the concentrator to concentrate the manganese tetraoxide mixed solution to 30%, and add 0.9% by mass of a aging agent for aging reaction to obtain a manganese tetraoxide slurry, wherein the aging agent includes F127 non-ionic surfactant, sodium hypochlorite, and ammonium bicarbonate, the mass ratio of F127 non-ionic surfactant, sodium hypochlorite and ammonium bicarbonate is 40:28:20, the reaction temperature of the aging reaction is 80° C., and the aging time is 12 hours;

[0071] 3) A manganese sulfate solution with a volume concentration of 120 g / L, 28% by mass of sodium hydroxide and 20% by mass of ammonium sulfate are added to the reactor in parallel, the manganese sulfate solution is fed at a rate of 3% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 9.6, the reaction temperature is 80° C., the reaction time is 18 h, and the mixture is reacted with the manganese tetraoxide slurry, and hydrogen peroxide is introduced into the reactor during the reaction to obtain a composite manganese oxide mixed solution.

[0072] Comparative Example 1: The difference from Example 1 is that the concentration of the manganese sulfate solution, the mass percentages of the precipitant sodium hydroxide and the complexing agent ammonia water, and the pH value of the first preset reaction condition are different, and the aging reaction and the secondary reaction of step 3) are not performed.

[0073] 1) adding a manganese sulfate solution with a volume concentration of 200 g / L, 25% by mass of sodium hydroxide and 18% by mass of ammonium sulfate into a reactor in parallel, the liquid feeding rate of the manganese sulfate solution is 5% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 8.7, the reaction temperature is 65° C., the reaction time is 14 h, and oxygen is introduced into the reactor during the reaction to obtain a manganese tetraoxide mixed solution;

[0074] 2) Turn on the concentrator to concentrate the manganese tetraoxide mixed solution to 30% to obtain manganese tetraoxide slurry;

[0075] 3) filtering, washing and drying the composite manganese oxide compound mixed solution to obtain a composite manganese oxide compound;

[0076] 4) Mixing the composite manganese oxide compound with lithium carbonate, wherein the molar ratio of lithium in the lithium carbonate to manganese in the composite manganese oxide compound is 0.53:1, calcining in an air atmosphere at a calcination temperature of 780° C. for 12 h, and crushing and grading to obtain a lithium manganate positive electrode material.

[0077] Among them, the XRD schematic diagram of the composite manganese oxide compound formed in Comparative Example 1 is as follows Figure 4 As shown, the SEM schematic diagram of the composite manganese oxide compound provided in Comparative Example 1 is as follows Figure 5 shown.

[0078] Comparative Example 2: Mixing manganese tetraoxide and manganese trioxide by solid phase method

[0079] 1) uniformly mixing manganese tetraoxide and manganese trioxide in a mass ratio of 3.2:1;

[0080] 2) Mixing the composite manganese oxide compound with lithium carbonate, wherein the molar ratio of lithium in the lithium carbonate to manganese in the composite manganese oxide compound is 0.53:1, calcining in an air atmosphere at a calcination temperature of 780° C. for 12 h, and crushing and grading to obtain a lithium manganate positive electrode material.

[0081] Comparative Example 3 differs from Example 1 in that the mass percentages of the precipitant sodium hydroxide and the complexing agent, the first liquid inlet rate, and the first preset reaction conditions are different, and the aging reaction and the secondary reaction of step 3) are not performed, and the rest of the contents are the same.

[0082] 1) adding a manganese sulfate solution with a volume concentration of 180 g / L, 26% by mass of sodium hydroxide and 10% by mass of disodium ethylenediaminetetraacetate into a reactor in parallel, the liquid feeding rate of the manganese sulfate solution is 4% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 8.6, the reaction temperature is 65° C., the reaction time is 15 h, and oxygen is introduced into the reactor during the reaction to obtain a manganese tetraoxide mixed solution;

[0083] 2) Turn on the concentrator to concentrate the manganese tetraoxide mixed solution to 25% to obtain manganese tetraoxide slurry;

[0084] 3) adding a manganese sulfate solution having a volume concentration of 180 g / L, 28% by mass of sodium hydroxide and 10% by mass of disodium ethylenediaminetetraacetate into the reactor in parallel, the manganese sulfate solution is fed at a rate of 4% / h of the volume of the reactor, the pH value of the mixed solution in the reactor is maintained at 9.3, the reaction temperature is 70° C., the reaction time is 16 h, and the mixture is reacted with the manganese tetraoxide slurry, while ozone is introduced into the reactor to obtain a composite manganese oxide mixed solution;

[0085] The XRD diagram of the composite manganese oxide compound formed in Example 1 is as follows: Figure 2 As shown, the SEM schematic diagram of the composite manganese oxide compound provided in Example 1 is as follows Figure 3 shown.

[0086] Performance / data testing:

[0087] The lithium sheet was used as the negative electrode, and the lithium manganate positive electrode materials prepared in the above embodiments and comparative examples were used as the positive electrode. The composite manganese oxide compounds of embodiments 1, 2, 3 and comparative examples 1, 2, 3 were respectively tested for particle morphology and mass ratio of manganese trioxide (Mn2O3) to prepare secondary button batteries of model CR2025. At a voltage of 3.0 to 4.2 V, 0.2C charge / 0.2C discharge was first performed for two cycles, and then a cyclic discharge test was performed under 1C charge / 1C discharge conditions to test the 0.2C first charge capacity, 0.2C first discharge capacity, 0.2C first charge and discharge efficiency, 1C first discharge capacity and 60-week cycle performance capacity retention rate. The test results are shown in Tables 1 and 2:

[0088] Table 1

[0089]

[0090]

[0091] Table 2

[0092]

[0093] Comparative Example 2 is a ball milling solid phase dry mixing of manganese trioxide. Since Comparative Example 3 does not undergo a aging reaction and a secondary strong oxidation reaction, neither of Comparative Examples 2 and 3 forms a composite manganese oxide compound in which single crystal regular hexahedral manganese trioxide is embedded in a spinel manganese tetraoxide substrate.

[0094] Since Comparative Example 1 does not mix manganese trioxide, while Comparative Example 2 mixes manganese trioxide by ball milling solid phase dry method, Comparative Example 2 improves the 1C first discharge capacity, but compared with Comparative Example 1, the cycle performance of Comparative Example 2 is significantly reduced.

[0095] Since Comparative Example 3 uses a liquid phase method to mix manganese tetraoxide and manganese trioxide at the nanoscale, while Comparative Example 2 uses a ball milling solid phase dry method to mix manganese trioxide, Comparative Example 3 improves the 1C first discharge capacity more significantly.

[0096] The results of Example 1 and Example 3 show that the composite manganese oxide compound in which the single crystal hexahedral manganese trioxide prepared by the liquid phase method is embedded in the spinel manganese tetraoxide substrate has improved discharge capacity and significantly improved cycle stability compared with Comparative Examples 2 and 3.

[0097] The test results of Example 1, Example 2, and Example 3 show that as the content of single-crystalline manganese trioxide increases, the 1C discharge capacity of the lithium manganate positive electrode material continues to increase, but when the content of single-crystalline manganese trioxide exceeds 30%, the cycle stability of lithium manganate decreases, resulting in a decrease in capacity retention rate.

[0098] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0099] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0100] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing a lithium manganese oxide positive electrode material, characterized in that: include: Adding a manganese sulfate solution, a precipitant and a complexing agent into a reactor in parallel, reacting under a first preset reaction condition, and introducing a first oxidant into the reactor during the reaction to obtain a manganese tetraoxide mixed solution, wherein the manganese sulfate solution is fed at a first feeding rate; Concentrating the manganese tetraoxide mixed solution to a preset solid content, and adding a aging agent to perform a aging reaction to obtain manganese tetraoxide slurry; The manganese sulfate solution, the precipitant and the complexing agent are added to the reactor in parallel again, reacting with the manganese tetraoxide slurry under a second preset reaction condition, and a second oxidant is introduced into the reactor during the reaction to obtain a composite manganese oxide mixed solution, wherein the manganese sulfate solution is fed at a second feeding rate; The composite manganese oxide compound mixed solution is filtered, washed and dried to obtain a composite manganese oxide compound, wherein the composite manganese oxide compound is manganese trioxide embedded in a spinel manganese tetraoxide substrate in the form of a regular hexahedral single crystal; The composite manganese oxide compound is mixed with lithium carbonate, calcined in an air atmosphere, and crushed and classified to obtain a lithium manganate positive electrode material.

2. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The first preset reaction condition includes: The pH value of the mixed solution in the reactor is maintained at 8.5 to 9.0, the reaction temperature is 50° C. to 70° C., and the reaction time is 12 h to 18 h; The second preset reaction condition includes: The pH value of the mixed solution in the reactor is maintained at 9.2-9.8, the reaction temperature is maintained at 70° C.-90° C., and the reaction time is maintained at 15 h-25 h.

3. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The first liquid inlet rate is 3% / h to 8% / h of the volume of the reactor; the second liquid inlet rate is 1% / h to 5% / h of the volume of the reactor.

4. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The concentration of the manganese sulfate solution is 50 g / L to 300 g / L, the mass percentage of the precipitant is 20% to 35%, and the mass percentage of the complexing agent is 5% to 25%.

5. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The preset solid content ranges from 20% to 30%, and the mass percentage of the curing agent is from 0.5% to 2%; The curing agent includes F127 non-ionic surfactant, sodium hypochlorite and ammonium bicarbonate, and the mass ratio of the F127 non-ionic surfactant, the sodium hypochlorite and the ammonium bicarbonate is 40:(10-30):(15-25).

6. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The reaction temperature of the aging reaction is 70° C. to 90° C., and the aging time is 6 h to 10 h.

7. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The first oxidant is air or oxygen; The second oxidant is any one or more of oxygen, hydrogen peroxide, sodium persulfate, ozone, sodium hypochlorite or potassium dichromate; The precipitant is a combination of any one or more of sodium hydroxide, potassium hydroxide, sodium methoxide or sodium ethoxide; The complexing agent is any one or more of ammonia water, ammonium sulfate, disodium ethylenediaminetetraacetate, polyethylene glycol, triethanolamine or sodium dodecyl sulfate.

8. The method for preparing the lithium manganate positive electrode material according to claim 1, characterized in that: The molar ratio of lithium in the lithium carbonate to manganese in the composite manganese oxide is (0.5-0.55):1, the calcination temperature is 700° C.-800° C., and the calcination time is 10 h-14 h.

9. A lithium manganate positive electrode material, characterized in that: The method for preparing the lithium manganese oxide positive electrode material according to any one of claims 1 to 8 is used.

10. A lithium battery, characterized in that: It comprises a positive electrode, wherein the positive electrode comprises a lithium manganese oxide positive electrode material prepared by the method for preparing a lithium manganese oxide positive electrode material as claimed in claim 9.

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