Lithium ion battery cathode material lithium manganate and preparation method of doped lithium manganate

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of lithium ion battery positive electrode material lithium manganate and doped lithium manganate, which comprises the following steps: S1, dissolving a lithium source and a manganese source in a solvent according to a stoichiometric ratio, and uniformly mixing the solvent through a stirring device to obtain a finished product mixed solvent; s2, adding a complexing agent into the mixed solvent obtained in the step S1 to form sol; s3, putting the sol obtained in the step S1 into a drying oven for heating and evaporating, so that the sol is dried, and finally, gel is obtained; s4, putting the gel obtained in the step S3 into a muffle furnace, calcining, and pre-sintering at low temperature, so as to decompose organic matters in the gel; s5, putting the gel which is cooled after low-temperature calcination in the step S4 into the muffle furnace for high-temperature calcination again to crystallize the gel, so as to obtain a lithium manganate granular material; and step S6, putting the lithium manganate particle material in the step S5 into a grinding machine for grinding to obtain the modified lithium manganate positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for preparing lithium manganese oxide, a positive electrode material for lithium ion batteries, and doped lithium manganese oxide. Background Art

[0002] Lithium-ion batteries have the advantages of high voltage, high energy density, long cycle life, low self-discharge, and no memory effect, and have been rapidly developed and widely used. The cathode materials currently in practical use are mainly lithium cobalt oxide (LiCoO2), ternary materials (LiNi1 / 3Co1 / 3Mn1 / 3O2), lithium iron phosphate (LiFePO4), and lithium manganese oxide (LiMn2O4).

[0003] Lithium cobalt oxide is expensive due to the shortage of cobalt resources. Its cost is much higher than that of the negative electrode, accounting for more than one-third of the total battery cost, which limits the large-scale application of lithium-ion batteries, especially in the field of electric vehicles. In addition, lithium cobalt oxide also has poor thermal stability and safety issues; the price of ternary materials is also high, and they have poor thermal stability and a low voltage platform; lithium iron phosphate has poor conductivity and too low density; spinel lithium manganese oxide has the advantages of low cost and environmental friendliness, but poor cycle performance. Therefore, we propose a preparation method of lithium manganese oxide, a positive electrode material for lithium-ion batteries, and doped lithium manganese oxide. Summary of the Invention

[0004] The object of the present invention is to provide a lithium-ion battery positive electrode material lithium manganate and a preparation method of doped lithium manganate to solve the problems raised in the above background technology.

[0005] In view of this, the present invention provides a method for preparing lithium manganese oxide, a positive electrode material for lithium ion batteries, and doped lithium manganese oxide, comprising the following steps:

[0006] Step S1: dissolving a lithium source and a manganese source in a solvent according to a stoichiometric ratio, and uniformly mixing the solvent by a stirring device to obtain a finished mixed solvent;

[0007] Step S2, adding a complexing agent to the mixed solvent obtained in step S1 to form a sol;

[0008] Step S3, placing the sol obtained in step S1 into an oven for heating and evaporation to dry the sol and finally obtain a gel;

[0009] Step S4: placing the gel obtained in step S3 into a muffle furnace for low-temperature pre-calcination. The raw materials begin to undergo a preliminary chemical reaction, forming a preliminary structure of lithium manganate. The atmosphere in the high-temperature furnace can be selected from air, oxygen, or inert gas as needed. Air or oxygen atmospheres are conducive to the oxidation reaction of manganese elements and promote the formation of lithium manganate. In an inert gas atmosphere, the introduction of impurities can be reduced, the purity of the product can be improved, and organic matter in the gel can be decomposed.

[0010] Step S5: placing the gel cooled after low-temperature calcination in step S4 into a muffle furnace and calcining it again at high temperature. The secondary sintering can allow the doping elements to more fully incorporate into the lattice structure of the lithium manganese oxide, further optimizing the performance of the material. During the secondary sintering process, the distribution and content of the doping elements in the lattice can be controlled by adjusting the sintering temperature and time, thereby achieving precise control of the material properties and causing it to crystallize to obtain a lithium manganese oxide granular material.

[0011] Step S6: After the heating reaction is completed, the material is cooled to 600-650° C. in a muffle furnace and annealed for 2-8 hours. Annealing can eliminate stress inside the material, making the structure of the material more stable, thereby improving the performance of the material;

[0012] Step S7, subjecting the lithium manganese oxide granular material in step S5 to coarse and fine crushing processes to reduce its particle size to an appropriate range. The coarse crushing can be performed using equipment such as a jaw crusher and a hammer crusher to crush the material to a particle size of less than 10 mm; the fine crushing can be performed using equipment such as a ball mill and a jet mill to further crush the material to a particle size between 1 and 10 microns. The crushed material is screened through a vibrating screen to remove oversized or undersized particles to ensure uniformity of the product particle size, thereby obtaining a modified lithium manganese oxide positive electrode material;

[0013] Step S8: In order to further improve the performance of the material, the crushed and screened material can be surface treated. The surface treatment methods include coating, doping, surface modification, etc. For example, coating the material surface with a layer of metal oxide or carbon material by chemical deposition can effectively improve the surface stability of the material and reduce side reactions with the electrolyte. By doping the surface with a small amount of other elements, the electronic structure of the material surface can be adjusted, and the electronic conductivity and ion diffusion rate of the material can be improved. During the surface treatment process, the treatment conditions must be strictly controlled to ensure the uniformity and stability of the surface treatment layer.

[0014] Step S9, finished product packaging: The post-processed material is the final lithium manganate or doped lithium manganate product, which is vacuum-packed or filled with inert gas to prevent the product from moisture and oxidation during storage and transportation, thereby ensuring the long-term stability of product quality.

[0015] In the above technical solution, further, in step S1, the molar ratio of the lithium source to the manganese source is 1:2.

[0016] In the above technical solution, further, the complexing agent in step S2 is one or a mixture of more of citric acid, oxalic acid, acetic acid, and tartaric acid.

[0017] Citric acid: most commonly used, with Li + 、Mn2+ It forms a stable complex and leaves no residue after high temperature decomposition.

[0018] Oxalic acid: Oxalic acid is a strong organic acid used primarily as a complexing agent, precipitant, or carbon source in the preparation of lithium-ion battery cathode materials. Its strong coordination and reducing properties give it unique advantages in controlling the valence state of manganese ions and particle morphology.

[0019] Acetic acid: A weak organic acid, acetic acid is primarily used as a complexing agent, pH adjuster, or reaction medium in the preparation of lithium-ion battery cathode materials. While its complexing ability is weaker than that of stronger complexing agents like citric acid and EDTA, acetic acid can still be used to control the uniform distribution of metal ions and is useful in sol-gel or coprecipitation methods.

[0020] Tartaric acid: Tartaric acid is a natural organic acid containing two carboxyl groups and two hydroxyl groups. In the preparation of lithium-ion battery positive electrode materials, it can be used as an efficient complexing agent in the sol-gel method or co-precipitation method to improve the uniformity and electrochemical properties of the material.

[0021] In the above technical solution, further, in step S3, the oven heating temperature is 80-120° C., and the drying time is 14-20 hours, which can effectively remove the moisture inside the sol and dry the sol.

[0022] In the above technical solution, further, in step S4, the low-temperature pre-firing temperature is 300-500°C, and the low-temperature pre-firing time is 2-4 hours. Low-temperature pre-firing may cause residual organic solvents, bound water or ammonium salts in the gel. Low-temperature pre-firing can gradually decompose these impurities, avoiding the sudden release of gas in the high-temperature stage and causing damage to the material structure.

[0023] In the above technical solution, further, in step S5, the high-temperature calcination temperature is 600-800°C, and the low-temperature pre-calcination time is 4-6 hours. At high temperature, the atomic mobility is enhanced, the internal defects of the crystal are repaired through the annealing effect, and the grain growth is more complete.

[0024] In the above technical solution, further, in step S1, the manganese source material is selected from one or a mixture of manganese dioxide, trimanganese tetraoxide, manganese hydroxide or trimanganese dioxide.

[0025] In the above technical solution, further, the lithium source material involved in step S1 is selected from a mixture of one or more of lithium hydroxide, lithium carbonate, and lithium oxalate.

[0026] The beneficial effects of the present invention are:

[0027] 1. The preparation method of lithium manganese oxide and doped lithium manganese oxide, which are positive electrode materials for lithium ion batteries, comprises the following steps: obtaining a mixed solvent by mixing a lithium source and a manganese source, forming a sol by mixing the mixed solvent with a complexing agent, drying the sol in an oven to obtain a gel, and forming the lithium manganese oxide granular material through two calcination steps of low-temperature pre-calcination and high-temperature calcination after the gel is formed, and finally processing the material through a grinder to obtain a modified lithium manganese oxide positive electrode material. These steps are more complete than those of existing modified lithium manganese oxide positive electrode material production, and the obtained modified lithium manganese oxide positive electrode material is of higher quality and better quality.

[0028] 2. The preparation method of lithium manganese oxide, a positive electrode material for lithium-ion batteries, and doped lithium manganese oxide, rationally selects dopants and precisely controls their doping amount and doping method, allowing the doping elements to effectively incorporate into the lattice structure of lithium manganese oxide, improving the order and disorder within the material and avoiding severe bulk phase distortion during cycling. At the same time, the introduction of doping elements also optimizes the electronic structure and ion diffusion path of the material, improving the electronic conductivity and ion diffusion rate of the material, thereby improving the charge and discharge performance and rate performance of the battery. For example, the discharge specific capacity of the lithium manganese oxide positive electrode material doped with niobium under high-rate charge and discharge conditions is increased by more than 20% compared to the undoped lithium manganese oxide positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0031] In the description of this application, it should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0032] It should be noted that, in the present application, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0033] Example 1:

[0034] See also Figure 1 -As shown in the figure, this embodiment provides a preparation method of lithium manganese oxide, a positive electrode material for lithium ion batteries, and doped lithium manganese oxide.

[0035] The following steps are involved:

[0036] Step S1: dissolving a lithium source and a manganese source in a solvent according to a stoichiometric ratio, and uniformly mixing the solvent by a stirring device to obtain a finished mixed solvent;

[0037] Step S2, adding a complexing agent to the mixed solvent obtained in step S1 to form a sol;

[0038] Step S3, placing the sol obtained in step S1 into an oven for heating and evaporation to dry the sol and finally obtain a gel;

[0039] Step S4: placing the gel obtained in step S3 into a muffle furnace for low-temperature pre-calcination. The raw materials begin to undergo a preliminary chemical reaction, forming a preliminary structure of lithium manganate. The atmosphere in the high-temperature furnace can be selected from air, oxygen, or inert gas as needed. Air or oxygen atmospheres are conducive to the oxidation reaction of manganese elements and promote the formation of lithium manganate. In an inert gas atmosphere, the introduction of impurities can be reduced, the purity of the product can be improved, and organic matter in the gel can be decomposed.

[0040] Step S5: placing the gel cooled after low-temperature calcination in step S4 into a muffle furnace and calcining it again at high temperature. The secondary sintering can allow the doping elements to more fully incorporate into the lattice structure of the lithium manganese oxide, further optimizing the performance of the material. During the secondary sintering process, the distribution and content of the doping elements in the lattice can be controlled by adjusting the sintering temperature and time, thereby achieving precise control of the material properties and causing it to crystallize to obtain a lithium manganese oxide granular material.

[0041] Step S6: After the heating reaction is completed, the material is cooled to 600-650° C. in a muffle furnace and annealed for 2-8 hours. Annealing can eliminate stress inside the material, making the structure of the material more stable, thereby improving the performance of the material;

[0042] Step S7, subjecting the lithium manganese oxide granular material in step S5 to coarse and fine crushing processes to reduce its particle size to an appropriate range. The coarse crushing can be performed using equipment such as a jaw crusher and a hammer crusher to crush the material to a particle size of less than 10 mm; the fine crushing can be performed using equipment such as a ball mill and a jet mill to further crush the material to a particle size between 1 and 10 microns. The crushed material is screened through a vibrating screen to remove oversized or undersized particles to ensure uniformity of the product particle size, thereby obtaining a modified lithium manganese oxide positive electrode material;

[0043] Step S8: In order to further improve the performance of the material, the crushed and screened material can be surface treated. The surface treatment methods include coating, doping, surface modification, etc. For example, coating the material surface with a layer of metal oxide or carbon material by chemical deposition can effectively improve the surface stability of the material and reduce side reactions with the electrolyte. By doping the surface with a small amount of other elements, the electronic structure of the material surface can be adjusted, and the electronic conductivity and ion diffusion rate of the material can be improved. During the surface treatment process, the treatment conditions must be strictly controlled to ensure the uniformity and stability of the surface treatment layer.

[0044] Step S9, finished product packaging: The post-processed material is the final lithium manganese oxide or doped lithium manganese oxide product. The product is vacuum packaged or filled with inert gas to prevent the product from getting damp, oxidized, etc. during storage and transportation, to ensure the long-term stability of product quality, and to rationally select dopants and accurately control their doping amount and doping method so that the doping elements can effectively enter the lattice structure of lithium manganese oxide, thereby improving the order and disorder inside the material and avoiding serious bulk phase distortion during the cycle. At the same time, the introduction of doping elements also optimizes the electronic structure and ion diffusion path of the material, improves the electronic conductivity and ion diffusion rate of the material, thereby improving the charge and discharge performance and rate performance of the battery. For example, the discharge specific capacity of the lithium manganese oxide positive electrode material doped with niobium under high-rate charge and discharge conditions is increased by more than 20% compared with the undoped lithium manganese oxide positive electrode material.

[0045] Example 2:

[0046] This embodiment provides a method for preparing lithium manganese oxide, a positive electrode material for a lithium-ion battery, and doped lithium manganese oxide. In addition to the technical solutions of the above embodiments, it also has the following technical features.

[0047] Wherein, in step S1, the molar ratio of the lithium source to the manganese source is 1:2.

[0048] Wherein, the complexing agent in step S2 is one or a mixture of multiple kinds of citric acid, oxalic acid, acetic acid and tartaric acid.

[0049] Citric acid: most commonly used, with Li + 、Mn 2+ It forms a stable complex and leaves no residue after high-temperature decomposition. Oxalic acid: Oxalic acid is a strong organic acid that is primarily used as a complexing agent, precipitant, or carbon source in the preparation of lithium-ion battery cathode materials. Its strong coordination ability and reducing properties give it unique advantages in controlling the valence state of manganese ions and particle morphology.

[0050] Acetic acid: A weak organic acid, acetic acid is primarily used as a complexing agent, pH adjuster, or reaction medium in the preparation of lithium-ion battery cathode materials. While its complexing ability is weaker than that of stronger complexing agents like citric acid and EDTA, acetic acid can still be used to control the uniform distribution of metal ions and is useful in sol-gel or coprecipitation methods.

[0051] Tartaric acid: Tartaric acid is a natural organic acid containing two carboxyl groups and two hydroxyl groups. In the preparation of lithium-ion battery positive electrode materials, it can be used as an efficient complexing agent in the sol-gel method or co-precipitation method to improve the uniformity and electrochemical properties of the material.

[0052] In step S3, the oven heating temperature is 80-120° C. and the drying time is 14-20 hours, which can effectively remove the moisture inside the sol and dry the sol.

[0053] Example 3:

[0054] This embodiment provides a method for preparing lithium manganese oxide, a positive electrode material for a lithium-ion battery, and doped lithium manganese oxide. In addition to the technical solutions of the above embodiments, it also has the following technical features.

[0055] Among them, the low-temperature pre-firing temperature in step S4 is 300-500°C, and the low-temperature pre-firing time is 2-4 hours. Low-temperature pre-firing may cause residual organic solvents, bound water or ammonium salts in the gel. Low-temperature pre-firing can gradually decompose these impurities and avoid the sudden release of gas in the high-temperature stage, which may cause damage to the material structure.

[0056] Among them, the high-temperature calcination temperature in step S5 is 600-800°C, and the low-temperature pre-calcination time is 4-6 hours. At high temperature, the atomic mobility is enhanced, the internal defects of the crystal are repaired through the annealing effect, and the grain growth is more complete.

[0057] Wherein, in step S1, the manganese source material is selected from one or a mixture of manganese dioxide, trimanganese tetraoxide, manganese hydroxide or trimanganese dioxide.

[0058] The lithium source material involved in step S1 is selected from a mixture of one or more of lithium hydroxide, lithium carbonate, and lithium oxalate.

[0059] During use: a mixed solvent is obtained by mixing a lithium source and a manganese source, a sol is formed by mixing the mixed solvent and a chelating agent, and the sol is dried in an oven to obtain a gel. After the gel is formed, the lithium manganese oxide particle material is formed through two calcination steps of low-temperature pre-sintering and high-temperature calcination, and finally the modified lithium manganese oxide positive electrode material is obtained by processing in a grinder. These steps are more complete than the existing modified lithium manganese oxide positive electrode material production, and the obtained modified lithium manganese oxide positive electrode material is of higher quality and better quality.

[0060] The embodiments of the present application are described above in conjunction with the accompanying drawings. Unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A method for preparing lithium manganate as a positive electrode material for lithium ion batteries and doped lithium manganate, characterized in that: The following steps are involved: Step S1: dissolving a lithium source and a manganese source in a solvent according to a stoichiometric ratio, and uniformly mixing the solvent by a stirring device to obtain a finished mixed solvent; Step S2, adding a complexing agent to the mixed solvent obtained in step S1 to form a sol; Step S3, placing the sol obtained in step S1 into an oven for heating and evaporation to dry the sol and finally obtain a gel; Step S4: placing the gel obtained in step S3 into a muffle furnace for low-temperature pre-calcination. The raw materials begin to undergo a preliminary chemical reaction, forming a preliminary structure of lithium manganate. The atmosphere in the high-temperature furnace can be selected from air, oxygen, or inert gas as needed. Air or oxygen atmospheres are conducive to the oxidation reaction of manganese elements and promote the formation of lithium manganate. In an inert gas atmosphere, the introduction of impurities can be reduced, the purity of the product can be improved, and organic matter in the gel can be decomposed. Step S5: placing the gel cooled after low-temperature calcination in step S4 into a muffle furnace and calcining it again at high temperature. The secondary sintering can allow the doping elements to more fully incorporate into the lattice structure of the lithium manganese oxide, further optimizing the performance of the material. During the secondary sintering process, the distribution and content of the doping elements in the lattice can be controlled by adjusting the sintering temperature and time, thereby achieving precise control of the material properties and causing it to crystallize to obtain a lithium manganese oxide granular material. Step S6: After the heating reaction is completed, the material is cooled to 600-650° C. in a muffle furnace and annealed for 2-8 hours. Annealing can eliminate stress inside the material, making the structure of the material more stable, thereby improving the performance of the material; Step S7, subjecting the lithium manganese oxide granular material in step S5 to coarse and fine crushing processes to reduce its particle size to an appropriate range. The coarse crushing can be performed using equipment such as a jaw crusher and a hammer crusher to crush the material to a particle size of less than 10 mm; the fine crushing can be performed using equipment such as a ball mill and a jet mill to further crush the material to a particle size between 1 and 10 microns. The crushed material is screened through a vibrating screen to remove oversized or undersized particles to ensure uniformity of the product particle size, thereby obtaining a modified lithium manganese oxide positive electrode material; Step S8: In order to further improve the performance of the material, the crushed and screened material can be surface treated. The surface treatment methods include coating, doping, surface modification, etc. For example, coating the material surface with a layer of metal oxide or carbon material by chemical deposition can effectively improve the surface stability of the material and reduce side reactions with the electrolyte. By doping the surface with a small amount of other elements, the electronic structure of the material surface can be adjusted, and the electronic conductivity and ion diffusion rate of the material can be improved. During the surface treatment process, the treatment conditions must be strictly controlled to ensure the uniformity and stability of the surface treatment layer. Step S9, finished product packaging: The post-processed material is the final lithium manganate or doped lithium manganate product, which is vacuum-packed or filled with inert gas to prevent the product from moisture and oxidation during storage and transportation, thereby ensuring the long-term stability of product quality.

2. The method for preparing lithium manganate and doped lithium manganate as a positive electrode material for lithium ion batteries according to claim 1, characterized in that: In step S1, the molar ratio of the lithium source to the manganese source is 1:

2.

3. The method for preparing lithium manganese oxide and doped lithium manganese oxide as a positive electrode material for lithium ion batteries according to claim 1, characterized in that: In step S2, the complexing agent is one or a mixture of multiple kinds of citric acid, oxalic acid, acetic acid, and tartaric acid.

4. The method for preparing lithium manganate and doped lithium manganate as a positive electrode material for lithium ion batteries according to claim 1, characterized in that: In step S3, the oven heating temperature is 80-120° C., and the drying time is 14-20 hours.

5. The method for preparing lithium manganate as a positive electrode material for lithium ion batteries and doped lithium manganate according to claim 1, characterized in that: In step S4, the low-temperature pre-firing temperature is 300-500° C., and the low-temperature pre-firing time is 2-4 hours.

6. The method for preparing lithium manganate as a positive electrode material for lithium ion batteries and doped lithium manganate according to claim 1, characterized in that: In step S5, the high-temperature calcination temperature is 600-800° C., and the low-temperature pre-calcination time is 4-6 hours.

7. The method for preparing lithium manganate and doped lithium manganate as a positive electrode material for lithium ion batteries according to claim 1, characterized in that: In the step S1, the manganese source material is selected from one or a mixture of manganese dioxide, trimanganese tetraoxide, manganese hydroxide or trimanganese dioxide.

8. The method for preparing lithium manganese oxide and doped lithium manganese oxide as a positive electrode material for lithium ion batteries according to claim 1, characterized in that: The lithium source material involved in step S1 is selected from a mixture of one or more of lithium hydroxide, lithium carbonate, and lithium oxalate.

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