阅读说明：本技术 一种铁锰基正极材料及其制备方法和应用 (Iron-manganese-based cathode material and preparation method and application thereof ) 是由 陈思贤 江卫军 许鑫培 郑晓醒 于 2021-07-30 设计创作，主要内容包括：本发明提供了一种铁锰基正极材料及其制备方法和应用,所述制备方法包括以下步骤：(1)将铁源、锰源和锂源混合,将得到的混合物料与有机溶剂混合后进行球磨得到混合悬浊液；(2)将步骤(1)得到的混合悬浊液烘干得到烘干材料,对所述烘干材料进行煅烧处理得到所述铁锰基正极材料,本发明省略了前驱体制备过程,利用金属盐通过一步煅烧直接获得了正极材料,极大地简化了材料合成步骤,节约了制备成本,由于未经过前驱体合成过程,削弱了前驱体理化性能波动对材料性能波动的影响,能够有效提升正极材料的稳定性。(The invention provides a ferro-manganese based cathode material and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) mixing an iron source, a manganese source and a lithium source, mixing the obtained mixed material with an organic solvent, and then carrying out ball milling to obtain a mixed suspension; (2) the method has the advantages that a precursor preparation process is omitted, the anode material is directly obtained by one-step calcination of metal salt, the material synthesis steps are greatly simplified, the preparation cost is saved, the influence of precursor physical and chemical property fluctuation on material property fluctuation is weakened due to the fact that the precursor synthesis process is not carried out, and the stability of the anode material can be effectively improved.)

1. The preparation method of the ferro-manganese based cathode material is characterized by comprising the following steps of:

(1) mixing an iron source, a manganese source and a lithium source, mixing the obtained mixed material with an organic solvent, and then carrying out ball milling to obtain a mixed suspension;

(2) and (2) drying the mixed suspension obtained in the step (1) to obtain a dried material, and calcining the dried material to obtain the iron-manganese-based positive electrode material.

2. The method according to claim 1, wherein the iron source of step (1) comprises any one of iron oxide, iron acetate or iron carbonate or a combination of at least two thereof;

preferably, the manganese source comprises any one of manganese carbonate, manganese dioxide or manganese acetate or a combination of at least two of the same;

preferably, the lithium source comprises lithium hydroxide and/or lithium carbonate.

3. The method according to claim 1 or 2, wherein the molar ratio of iron to manganese of the iron source in the step (1) is (0.5-3): (7-9.5);

preferably, the total molar ratio of lithium in the lithium source to iron in the iron source to manganese in the manganese source is (0.2-0.5): 1.

4. The method according to any one of claims 1 to 3, wherein the organic solvent in step (1) comprises any one or a combination of at least two of ethanol, acetone, isopropanol, or N-methylpyrrolidone.

5. The method according to any one of claims 1 to 4, wherein the rotation speed of the ball mill in the step (1) is 100 to 400 rpm;

preferably, the ball milling time is 2-4 h.

6. The production method according to any one of claims 1 to 5, wherein the calcination treatment in step (2) is carried out in an oxygen atmosphere;

preferably, the flow rate of the oxygen is 8-12L/min;

preferably, the temperature of the calcination treatment is 500-800 ℃;

preferably, the time of the calcination treatment is 7-12 h.

7. A ferro-manganese based positive electrode material, characterized in that it is obtained by the method according to any one of claims 1 to 6.

8. The ferromanganese-based positive electrode material as claimed in claim 7, wherein the chemical formula of the ferromanganese-based positive electrode material is Li_aFe_xMn_yO₂Wherein a is more than or equal to 0.1 and less than or equal to 0.5, x is more than or equal to 0.05 and less than or equal to 0.3, y is more than or equal to 0.7 and less than or equal to 0.95, and x + y is 1.

9. A positive electrode sheet, characterized by comprising the iron-manganese-based positive electrode material according to claim 7 or 8.

10. A lithium battery comprising the positive electrode sheet according to claim 9.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and relates to a ferro-manganese based cathode material, and a preparation method and application thereof.

Background

The reversible secondary battery is one of green energy sources in the 21 st century, and a representative product of the reversible secondary battery is developed from a lead storage battery to a current lithium ion battery through decades of developments, so that the reversible secondary battery is greatly improved in energy density, cycle life, volume weight and environmental protection, and is developed to a power lithium ion battery which can be applied to a hybrid electric vehicle or even a pure electric vehicle, thereby bringing great convenience to the life of people.

At present, the domestic cobalt-free material mainly comprises a nickel-manganese binary material and lithium iron phosphate, and the nickel-manganese binary material and the lithium iron phosphate have advantages and disadvantages respectively. However, the synthesis method is that the precursor is subjected to lithium mixing and then is subjected to solid-phase sintering reaction, so that the cathode material is obtained. The positive electrode material obtained by the synthesis method is greatly influenced by the fluctuation of the physical and chemical properties of the precursor. Meanwhile, in the preparation process of the precursor, the transition metal elements are subjected to coprecipitation reaction to obtain a final product, but the pH difference of partial metal element precipitation reaction is large, so that the transition metal proportion is not easy to accurately control.

Besides, the current preparation method of the iron-manganese-based cathode material is generally a three-step method: coprecipitation-solvothermal-solid phase sintering reaction. The preparation process is complex, the preparation period is long, and the finally obtained anode material has large metal proportion difference and poor crystallinity easily due to coprecipitation and solvothermal reaction.

CN111952579A discloses a high energy density sodium ion battery iron manganese based positive electrode material and a preparation method thereof, wherein the method specifically comprises the following steps: (1) dissolving sodium salt, ferric salt, manganese salt and M1 salt in N-methylpyrrolidone (NMP) or ethanol to obtain a mixture A; (2) transferring the mixture A into an agate ball milling tank, and sealing; (3) placing an agate ball milling tank on a planetary ball mill for ball milling; (4) drying and ball-milling to obtain a mixture, namely obtaining a precursor; (5) grinding the precursor obtained by the ball milling method uniformly, weighing a proper amount of powder, and pressing the powder into a sheet shape; (6) and (3) placing the flaky precursor into a tubular furnace to be calcined step by step to obtain the iron-manganese-based layered oxide anode material of the sodium-ion battery. The method needs to synthesize a precursor firstly, the metal proportion control process is complex, the problem of oxidation of transition metal is easy to occur, and the coprecipitation is difficult to form due to the large difference of the precipitation coefficients of iron ions and manganese ions, so that the precursor with ideal metal proportion is difficult to form.

CN113078299A discloses a sodium-lithium-iron-manganese-based layered oxide material, a preparation method and a use thereof, wherein the preparation method comprises: respectively dissolving nitrate or sulfate or carbonate or hydroxide respectively containing iron and manganese in a required stoichiometric ratio into deionized water with a certain volume to respectively form solutions; respectively adding the solution into ammonia water solution with certain concentration and pH value in a dropwise manner by using a peristaltic pump to generate precipitate; cleaning the obtained precipitate with deionized water, drying, and uniformly mixing with sodium carbonate and lithium hydroxide according to a stoichiometric ratio to obtain a precursor; placing the precursor in a crucible, and carrying out heat treatment for 2-24 h at 600-1000 ℃ in an air atmosphere to obtain precursor powder; and grinding the precursor powder after the heat treatment to obtain the layered oxide material. The method also needs to prepare a precursor first and then carry out heat treatment to obtain the material.

The technical scheme has the problems that the materials can be obtained only by carrying out heat treatment on the precursor which is prepared firstly, in the preparation process of the precursor, the metal proportion control process is complex, the problem of oxidation of transition metal is easy to occur, and because the precipitation coefficients of iron ions and manganese ions are greatly different, coprecipitation is difficult to form, the precursor with ideal metal proportion is difficult to form, so that the development of the method for obtaining the iron-manganese-based cathode material without preparing the precursor is necessary.

Disclosure of Invention

The invention aims to provide a ferro-manganese-based cathode material and a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a preparation method of a ferro-manganese based cathode material, which comprises the following steps:

(1) mixing an iron source, a manganese source and a lithium source, mixing the obtained mixed material with an organic solvent, and then carrying out ball milling to obtain a mixed suspension;

(2) and (2) drying the mixed suspension obtained in the step (1) to obtain a dried material, and calcining the dried material to obtain the iron-manganese-based positive electrode material.

According to the invention, lithium salt, ferric salt and manganese salt are directly subjected to wet ball milling and mixing, and the positive electrode materials with different iron-manganese ratios can be obtained by adjusting the ratio of ferric salt to manganese salt, so that the synthesis process of the positive electrode material is greatly simplified, the synthesis cost of the material is reduced, the Fe element and the Mn element can be uniformly mixed at a nano level, wherein the particle size of primary particles of the material is nano level, and then the particles are agglomerated to form secondary particles at a micron level. The existence form of the small polycrystal can provide a good channel for lithium ion migration, and is favorable for improving the specific capacity of the cathode material. Because the preparation method does not use a precursor, the performance of the material is helped to get rid of the material performance fluctuation caused by precursor difference, and the stability of the material is improved.

The invention adopts a wet grinding process to prevent manganese salt and ferric salt with crystal water from being seriously bonded in the material mixing process to influence the material mixing uniformity, and simultaneously adopts an organic solvent as a solvent to ensure suspension in the material process so as to facilitate subsequent drying.

The oxidation of transition metals and the inaccurate control of the proportion often exist in the preparation process of the precursor. In the invention, the selection and the addition proportion of the transition metal salt can be controlled directly in the raw material synthesis process, and finally the anode materials with different metal proportions can be accurately obtained.

Preferably, the iron source of step (1) comprises any one of iron oxide, iron acetate or iron carbonate or a combination of at least two thereof.

Preferably, the manganese source comprises any one of manganese carbonate, manganese dioxide or manganese acetate or a combination of at least two of the same.

Preferably, the lithium source comprises lithium hydroxide and/or lithium carbonate.

Preferably, the molar ratio of the iron in the iron source and the manganese in the manganese source in the step (1) is (0.5-3) to (7-9.5), such as: 0.5:9.5, 1:9, 1.5:8.5, 2:8, 2.5:7.5, 3:7, etc.

Preferably, the total molar ratio of lithium in the lithium source to iron in the iron source to manganese in the manganese source is (0.2-0.5): 1, for example: 0.2:1, 0.3:1, 0.4:1 or 0.5:1, etc.

Preferably, the organic solvent in step (1) comprises any one of ethanol, acetone, isopropanol or NMP or a combination of at least two thereof.

Preferably, the rotation speed of the ball mill in the step (1) is 100-400 rpm, for example: 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 400rpm, or the like.

Preferably, the time of ball milling is 2-4 h, for example: 2h, 2.5h, 3h, 3.5h or 4h and the like.

Preferably, the calcination treatment of step (2) is performed under an oxygen atmosphere.

Preferably, the flow rate of the oxygen is 8-12L/min, for example: 8L/min, 9L/min, 10L/min, 11L/min or 12L/min and the like.

Preferably, the temperature of the calcination treatment is 500 to 800 ℃, for example: 500 deg.C, 550 deg.C, 600 deg.C, 700 deg.C or 800 deg.C, etc.

Preferably, the time of the calcination treatment is 7-12 h, such as: 7h, 8h, 9h, 10h, 11h or 12h and the like.

The invention adopts a solid-phase sintering method, and can obtain the anode materials with different iron-manganese ratios and lithium salt ratios by controlling the addition ratios of iron salt, manganese salt and lithium salt in the material mixing stage. The calcining atmosphere uses oxygen to ensure that the material can be fully oxidized.

In a second aspect, the present invention provides a ferro-manganese based positive electrode material produced by the method according to the first aspect.

Preferably, the chemical formula of the iron-manganese-based cathode material is Li_aFe_xMn_yO₂Wherein a is more than or equal to 0.1 and less than or equal to 0.5For example: 0.1, 0.2, 0.3, 0.4, or 0.5, etc., 0.05 ≦ x ≦ 0.3, such as: 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3, etc., 0.7. ltoreq. y.ltoreq.0.95, for example: 0.7, 0.75, 0.8, 0.85, 0.9, etc., and x + y is 1.

In a third aspect, the invention provides a positive electrode plate, which comprises the iron-manganese-based positive electrode material according to the second aspect.

In a fourth aspect, the invention provides a lithium battery comprising the positive electrode plate according to the third aspect.

Compared with the prior art, the invention has the following beneficial effects:

(1) the positive electrode material can be obtained by one-time sintering after mixing the lithium salt, the ferric salt and the manganese salt, the preparation process is simple, the loss of raw materials in the traditional dry mixing process is reduced, the uniform mixing of the materials is facilitated, and the preparation cost is greatly reduced.

(2) The method weakens the influence of the precursor on the performance fluctuation of the anode material, accurately controls the proportion of each transition metal in the anode material, and gets rid of the limitation of difficult control of the proportion of the precursor metal.

(3) The lithium ion battery prepared from the cathode material has a specific charge capacity of over 104mAh/g and a specific discharge capacity of over 181.6mAh/g, and can have a specific charge capacity of 117.8mAh/g and a specific discharge capacity of 198.1mAh/g by adjusting the molar ratio of iron acetate to manganese acetate and the ratio of lithium to iron to manganese.

Drawings

Fig. 1 is an SEM image of an iron-manganese-based positive electrode material obtained in example 1 of the present invention.

FIG. 2 is a graph comparing charge and discharge curves of the FeMn-based positive electrode materials obtained in examples 1 to 4 of the present invention.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a ferro-manganese-based cathode material, and a preparation method of the ferro-manganese-based cathode material comprises the following steps:

(1) weighing ferric acetate and manganese acetate according to a molar ratio of 1:9 in a drying environment, weighing lithium hydroxide according to a molar ratio (Fe + Mn) and Li being 1:0.4, putting the lithium hydroxide into a ball milling tank, adding ethanol into the ball milling tank, and ball milling the mixed material for 3 hours at 250rpm to obtain mixed suspension;

(2) and (2) drying the mixed suspension obtained in the step (1) to obtain a drying material, calcining the drying material at the oxygen flow rate of 10L/min and the temperature of 600 ℃ for 9h, and cooling to obtain the iron-manganese-based positive electrode material.

The SEM image of the iron-manganese-based cathode material is shown in figure 1.

Example 2

The embodiment provides a ferro-manganese-based cathode material, and a preparation method of the ferro-manganese-based cathode material comprises the following steps:

(1) weighing iron carbonate and manganese carbonate and lithium hydroxide according to a molar ratio of 3:7 in a drying environment, putting the lithium hydroxide into a ball milling tank according to the molar ratio (Fe + Mn) and Li being 1:0.4, adding ethanol into the ball milling tank, and ball milling the mixed material for 3 hours at 270rpm to obtain mixed suspension;

(2) and (2) drying the mixed suspension obtained in the step (1) to obtain a drying material, calcining the drying material at the oxygen flow rate of 11L/min and the temperature of 650 ℃ for 8.5h, and cooling to obtain the iron-manganese-based cathode material.

Example 3

This example differs from example 1 only in that the molar ratio of iron acetate to manganese acetate in step (1) is 5:5, and the other conditions and parameters are exactly the same as in example 1.

Example 4

This example differs from example 1 only in that the molar ratio of iron acetate to manganese acetate in step (1) is 0.1:9.9, and the other conditions and parameters are exactly the same as in example 1.

Example 5

This example differs from example 1 only in that (Fe + Mn) in step (1) is 1:0.1, and the other conditions and parameters are exactly the same as in example 1.

Example 6

This example differs from example 1 only in that (Fe + Mn) in step (1) is 1:0.6 Li, and the other conditions and parameters are exactly the same as in example 1.

Comparative example 1

In the comparative example, the iron-manganese-based positive electrode material is prepared by adopting a traditional precursor lithium mixing and sintering method according to the element proportion of the embodiment 1.

Comparative example 2

This comparative example differs from example 1 only in that step (1) uses water as the solvent, and the other conditions and parameters are exactly the same as in example 1.

And (3) performance testing:

the positive electrode materials prepared in the above examples 1-6 and comparative examples 1-2 were mixed uniformly with the positive electrode material, carbon black conductive agent and binder PVDF glue solution at a mass ratio of 90:5:5 to prepare the battery positive electrode slurry. Coating the slurry on an aluminum foil with the thickness of 20-40 mu M, carrying out vacuum drying, rolling and cutting to prepare a positive electrode plate, taking a lithium metal plate as a negative electrode, and mixing the electrolyte with LiPF of 1.15M₆DMC (1:1 vol%), and assembling the button cell.

The electrical property test of the material is carried out by adopting a blue battery test system at 25 ℃, the test voltage range is 2.0-4.8V, and the test result is shown in table 1:

TABLE 1

	Specific charging capacity (mAh/g)	Specific discharge capacity (mAh/g)
			Example 1	117.8	198.1
Example 2	108.4	184.1
			Example 3	110.0	181.6
Example 4	104.0	194.8
			Example 5	106.5	190.2
Example 6	108.3	187.5
			Comparative example 1	106.2	185.3
Comparative example 2	101.7	175.4

As can be seen from table 1, in examples 1 to 6, the lithium ion battery prepared from the positive electrode material of the present invention has a specific charge capacity of 104mAh/g or more and a specific discharge capacity of 181.6mAh/g or more, and by adjusting the molar ratio of iron acetate to manganese acetate and the ratio of lithium to iron to manganese, the specific charge capacity of 117.8mAh/g and the specific discharge capacity of 198.1 mAh/g.

By comparison of examples 1 to 4, the molar ratio of the iron element to the manganese element affects the performance of the obtained iron-manganese-based cathode material, the molar ratio of the iron element to the manganese element is controlled to be (0.5-3) to (7-9.5), the iron-manganese-based cathode material with excellent performance can be obtained, and if the molar ratio of the iron element is too high, the specific discharge capacity of the material can be affected due to poor electrochemical activity of the iron element; if the molar ratio of the manganese element is too high, the manganese element in the material tends to keep a low valence state more according to the charge conservation principle, so that the cycle performance of the material is influenced.

Compared with the examples 1 and 5-6, the molar ratio of the lithium element affects the performance of the prepared iron-manganese-based cathode material, the molar ratio of the lithium element to (Fe + Mn) is controlled to be 0.1-0.5: 1, the base cathode material with better performance can be prepared, if the lithium content is too high, the lithium metal ratio of the material is affected, meanwhile, the particle size of the material is increased due to too high lithium content, so that the specific discharge capacity of the material is affected, and if the lithium content is too low, part of lithium ions in the SEI film can be consumed by the material when the SEI film is formed, so that the content of electrochemically active lithium ions in the subsequent material is lower, and the electrochemical performance of the material is affected.

Compared with the comparative example 1, the method disclosed by the invention has the advantages that the precursor is not used, the material performance is helped to get rid of the material performance fluctuation caused by precursor difference, the stability of the material is improved, and the electrochemical performance of the material is further improved.

Compared with the embodiment 1 and the comparative example 2, the invention adopts the organic solvent as the solvent, can ensure suspension liquid in the material process, and is convenient for uniform mixing and subsequent drying.

Comparative charge and discharge curves of the ferromanganese-based positive electrode materials obtained in examples 1 to 4 are shown in fig. 2.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.