CN113683122A - Iron-manganese-based positive electrode material, and preparation method and application thereof - Google Patents
Iron-manganese-based positive electrode material, and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a ferro-manganese based anode material, a preparation method and application thereof, wherein the preparation method comprises the following steps: and mixing the first lithium salt and the ferromanganese precursor for primary sintering to obtain a base material, and mixing the base material with the second lithium salt for secondary sintering to obtain the ferromanganese-based positive electrode material. Through twice sintering, the material is supplemented with lithium, a coating layer is formed on the surface of the anode material, and meanwhile, lithium ions can be dispersed on the surface of the anode material in a gradient manner, so that the cycling stability of the anode material is effectively improved, and the lithium ion battery anode material has the characteristics of simple preparation process, low cost, good electrical property and the like.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a ferro-manganese based positive electrode material, and a preparation method and application thereof.
Background
The lithium ion battery is greatly improved in energy density, cycle life, volume weight and environmental protection, and can be applied to power lithium ion batteries of hybrid electric vehicles and even pure electric vehicles, so that great convenience is brought to life of people.
Currently, the commonly used anode materials are ternary materials, lithium iron phosphate and the like. The ternary material has high price because of the existence of metals such as cobalt, nickel and the like; the lithium iron phosphate material has excellent cycle performance but low capacity. The ferromanganese-based positive electrode material has high capacity but poor cycling stability, which is caused by Jahn-Teller effect under low voltage condition.
In addition, the capacity of the lithium manganate anode material is low, the theoretical specific capacity is 148mAh/g, and the main limiting factor is Jahn-Teller effect caused by Mn element existing in the lithium manganate with valence +3 under low voltage, so that the structure of the material is changed from cubic symmetry to tetragonal symmetry, and the performance of the material is rapidly deteriorated. So that the capacity of the lithium manganate can not be exerted under low voltage. The lithium ferromanganese anode material has a relatively high capacity, but generally has a problem of poor cycle stability.
CN112310391A discloses a positive electrode material precursor, a positive electrode material, a preparation method of the positive electrode material, a lithium ion battery positive electrode, a lithium ion battery and electric equipment. A precursor of the positive electrode material, wherein the molecular formula of the precursor of the positive electrode material is NixMnyFez(OH)2. The preparation method of the precursor of the anode material comprises the following steps: mixing raw materials including a nickel source, a manganese source, ammonium iron oxalate and a precipitator to prepare a mixed solution, and reacting to obtain the precursor of the positive electrode material. A positive electrode material having a molecular formula of Li1+nNixMnyFezO2. The preparation method of the cathode material comprises the following steps: mixing a precursor of the positive electrode material with a lithium source, and sintering in an oxygen-containing atmosphere to obtain the positive electrode material. The positive electrode of the lithium ion battery uses a positive electrode materialAnd (5) preparing the material. The lithium ion battery comprises the lithium ion battery anode. The electric equipment comprises the lithium ion battery. The lithium battery prepared from the cathode material provided by the scheme has excellent chemical stability and electrical property.
CN104577119A discloses a preparation method of lithium iron manganese phosphate as a lithium ion battery anode material. The method comprises the steps of taking a manganese source compound and an iron source compound as raw materials, respectively preparing a manganese-rich solution and a manganese-poor solution, synthesizing a ferromanganese phosphate precursor with a gradient structure by a coprecipitation method by controlling the sample adding speed, and then carrying out lithium doping and high-temperature calcination to prepare the lithium ferromanganese phosphate with the gradient structure, wherein the lithium ferromanganese phosphate gradually reduces the manganese content and gradually increases the iron content from inside to outside along the particle radius of the lithium ferromanganese phosphate. The lithium iron manganese phosphate anode material with the gradient structure has the characteristics of high energy density, good cycle performance, excellent rate performance and the like, and is suitable for the application field of lithium ion power batteries.
The existing anode materials all have the problems of high cost, poor electrical property, complex preparation process and the like, so that the problems that how to improve the electrical property of the iron-manganese based anode material, the cost is low, the preparation method is simple and the like are needed to be solved urgently at present.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a ferro-manganese-based positive electrode material, a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a preparation method of a ferromanganese-based positive electrode material, including: and mixing the first lithium salt and the ferromanganese precursor for primary sintering to obtain a base material, and mixing the base material with the second lithium salt for secondary sintering to obtain the ferromanganese-based positive electrode material.
According to the invention, lithium loss of the positive electrode material in the charge-discharge cycle process is supplemented in a lithium salt coating manner by secondary sintering, and a new phase is formed by coating lithium on the surface of the positive electrode material, so that the structure of the positive electrode material is stabilized, and the cycle stability of the material is improved. In the process, after a lithium-deficient material is obtained through primary sintering, lithium elements are continuously added through secondary sintering, and the anode material is controlled to obtain a proper lithium salt ratio. In addition, the invention can avoid excessive lithium adding amount for the first time through twice sintering and step-by-step lithium adding mode, and meanwhile, when the lithium salt ratio is more than 1, the matrix material is easy to form a lithium-rich structure, thereby influencing the electrical property of the matrix material; on the other hand, the lithium salt added in the secondary sintering can carry out gradient doping in the material, which is beneficial to the material to form a new phase on the surface layer and improve the electrochemical performance of the material.
It should be noted that the mixing manner of the present invention is not specifically required and limited, and the mixing manner includes, but is not limited to, conventional grinding, ball milling or wet mixing, and it is sufficient to ensure uniform mixing.
In a preferred embodiment of the present invention, the molar ratio of the lithium element to the sum of the iron and manganese elements in the matrix material is (0.3 to 0.7):1, for example, 0.30:1, 0.35:1, 0.40:1, 0.45:1, 0.50:1, 0.55:1, 0.60:1, 0.65:1, or 0.70: 1.
According to the invention, by controlling the molar ratio of the lithium element to the sum of the iron and manganese elements in the matrix material to be (0.3-0.7): 1, the ratio of the lithium metal in the primary sintering process is controlled to be low, so that the positive electrode material is ensured to have good electrical properties and a stable structure, and the situation that the positive electrode material forms a lithium-rich structure due to the addition of excessive lithium salt in the primary sintering process is effectively avoided, thereby affecting the performance of the battery; if the molar ratio is less than 0.3:1, the lithium content of the material after formation is low, so that the problem of reduction of the first lithium removal amount occurs, meanwhile, because too many lithium coordination sites are not provided, the lithium ion intercalation can be influenced, the material capacity can be influenced, meanwhile, in the SEI film formation process, a part of lithium ions can be consumed, and if the initial lithium ions are too few, the SEI film formation is not facilitated. If the molar ratio is higher than 0.7:1, excessive lithium ions will cause the material to form Li2MnO3Phase, Li2MnO3The phase is easy to decompose in the charging and discharging process, which causes the problems of oxygen release and increased cation concentration, leads to the fact of oxygen atoms of the material and influences the structural stability of the material.
Preferably, the molar ratio of the lithium element to the sum of the iron and manganese elements in the ferromanganese-based positive electrode material is (0.8-1.5): 1, for example, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5: 1.
In a preferred embodiment of the present invention, the temperature of the primary sintering is 700 to 900 ℃, for example 700 ℃, 720 ℃, 740 ℃, 760 ℃, 780 ℃, 800 ℃, 820 ℃, 840 ℃, 860 ℃, 880 ℃ or 900 ℃.
Preferably, the temperature rise rate of the primary sintering is 2-5 ℃/min, such as 2.0 ℃/min, 2.2 ℃/min, 2.4 ℃/min, 2.6 ℃/min, 2.8 ℃/min, 3.0 ℃/min, 3.2 ℃/min, 3.4 ℃/min, 3.6 ℃/min, 3.8 ℃/min, 4.0 ℃/min, 4.2 ℃/min, 4.4 ℃/min, 4.6 ℃/min, 4.8 ℃/min, or 5.0 ℃/min.
According to the invention, the temperature rise rate of primary sintering is controlled to be 2-5 ℃/min, so that the base material has a proper particle size, and the performance and stability of the material are ensured. If the temperature rise rate is lower than 2 ℃/min, the particle size of the base material is small, the side reaction of the material and the electrolyte is aggravated, and the stability of the material is influenced; if the temperature rise rate is higher than 5 ℃/min, the particle size of the material particles is increased, so that the internal resistance of the material is increased, and the capacity is influenced.
Preferably, the heat preservation time of the primary sintering is 9-15 h, such as 9h, 10h, 11h, 12h, 13h, 14h or 15 h.
In a preferred embodiment of the present invention, the temperature of the secondary sintering is 500 to 700 ℃, for example, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃ or 700 ℃.
According to the invention, the temperature of secondary sintering is controlled to be 500-700 ℃, lithium salt is completely reacted, the particle size is proper, the material performance is good, if the sintering temperature is lower than 500 ℃, the lithium salt is incompletely reacted in the secondary sintering, so that the residual lithium on the surface of the material is increased, and the subsequent homogenization and coating processes of the material are not facilitated; if the sintering temperature is higher than 700 ℃, the material particles are easily enlarged under the action of high temperature, and the material performance is further influenced.
Preferably, the heat preservation time of the secondary sintering is 5-8 h, such as 5.0h, 5.2h, 5.4h, 5.6h, 5.8h, 6.0h, 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, 7.8h or 8.0 h.
As a preferred embodiment of the present invention, the first lithium salt includes one or a combination of at least two of lithium carbonate, lithium hydroxide, or lithium chloride.
Preferably, the second lithium salt includes a low melting point lithium salt, and further preferably lithium hydroxide and/or lithium acetate.
Preferably, the ferromanganese precursor is prepared by coprecipitation of manganese salt and iron salt.
Illustratively, a preparation method of a ferromanganese precursor is provided, comprising: weighing ferric salt and manganese salt with a molar ratio of 1:1, and adopting a coprecipitation method, wherein in the coprecipitation method, the pH value is controlled to be 11-13, the temperature is 40-60 ℃, the protective atmosphere is inert atmosphere, the precipitator is sodium hydroxide and/or ammonia water, and the stirring speed is 200-400 rpm. Wherein the ferric salt comprises one or the combination of at least two of ferric acetate, ferric sulfate or ferric nitrate, the manganese salt comprises manganese acetate and/or manganese sulfate, and the inert atmosphere gas comprises argon.
As a preferred technical scheme of the invention, the preparation method specifically comprises the following steps:
mixing a first lithium salt and a ferromanganese precursor, and performing primary sintering for 9-15 hours at a speed of 2-5 ℃/min to 700-900 ℃ to prepare a base material, wherein the molar ratio of lithium to the sum of iron and manganese in the base material is (0.3-0.7): 1;
and (II) mixing the base material prepared in the step (I) with a second lithium salt, and performing secondary sintering at 500-700 ℃ for 5-8 hours to prepare the ferro-manganese-based positive electrode material, wherein the molar ratio of lithium to the sum of ferro-manganese elements in the ferro-manganese-based positive electrode material is (0.8-1.5): 1.
In a second aspect, the invention provides a ferro-manganese based cathode material, which is prepared by the preparation method of the ferro-manganese based cathode material in the first aspect.
As a preferable technical scheme of the invention, the chemical formula of the iron-manganese-based cathode material is LixMnyFezO2Wherein y + z is 1 and x/(y + z) is 0.5 to 1.2, e.g. x/(y + z) is 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2, 0.8. ltoreq. x.ltoreq.1.5, e.g. x is 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5, 0.2. ltoreq. y.ltoreq.0.8, e.g. y is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8, 0.2. ltoreq. z.ltoreq.0.8, e.g. z is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8.
As a preferred embodiment of the present invention, the iron-manganese-based positive electrode material includes a first lithium salt layer.
Preferably, the second lithium salt is gradient doped in the iron-manganese-based positive electrode material.
In a third aspect, the invention provides a battery comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode comprises the iron-manganese-based positive electrode material of the second aspect.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, the mode of adding lithium salt in multiple times is utilized, the ratio of lithium metal in the material is controlled to be low in the primary sintering process, and the phenomenon that the material forms a lithium-rich structure due to the addition of excessive lithium salt in the primary sintering process can be avoided.
(2) The lithium salt is continuously added in the secondary sintering process, so that the material can keep a proper lithium salt ratio, and enough lithium ions can be obtained to ensure the consumption of the lithium ions in the subsequent SEI (solid electrolyte phase interface film) formation process and the consumption of the lithium ions in the subsequent material circulation process.
(3) The lithium ions added in the secondary sintering can also disperse the lithium ions on the surface of the anode material in a gradient manner, and the method has the advantages that the lithium ions can form a new phase on the surface of the anode so as to protect the body of the anode material and be beneficial to improving the cycle stability of the anode material.
Drawings
Fig. 1 is a scanning electron microscope image of a ferromanganese-based positive electrode material provided in example 1 of the present invention;
fig. 2 is a charge and discharge graph of examples 1, 4, 5 and comparative example 1 of the present invention.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.
The ferromanganese precursor is prepared from manganese acetate and manganese sulfate in a molar ratio of 1:1 by using a coprecipitation method under the conditions that the pH value is 12, the temperature is 50 ℃, the stirring speed is 300rpm, and the protective gas is argon, and sodium hydroxide is used as a precipitator.
Example 1
This example provides a method for preparing a ferrimanganic cathode material with a chemical formula of Li0.5Mn0.5Fe0.5O2The preparation method specifically comprises the following steps:
mixing lithium carbonate and ferromanganese precursors, and heating to 800 ℃ at the speed of 3.5 ℃/min for 12 hours for primary sintering to prepare a base material, wherein the molar ratio of lithium element to iron-manganese element in the base material is 0.5: 1;
and (II) mixing the base material prepared in the step (I) with lithium hydroxide, and performing secondary sintering at 600 ℃ for 6.5 hours to prepare the ferro-manganese-based positive electrode material, wherein the molar ratio of lithium to the sum of ferro-manganese elements in the ferro-manganese-based positive electrode material is 1.2: 1.
Example 2
This example provides a method for preparing a ferrimanganic cathode material with a chemical formula of Li0.3Mn0.5Fe0.5O2The preparation method specifically comprises the following steps:
mixing lithium hydroxide and ferromanganese precursors, and heating to 700 ℃ at the speed of 2 ℃/min for once sintering for 15h to prepare a base material, wherein the molar ratio of lithium element to iron-manganese element in the base material is 0.3: 1;
and (II) mixing the base material prepared in the step (I) with lithium acetate, and performing secondary sintering at 500 ℃ for 5 hours to prepare the ferro-manganese-based positive electrode material, wherein the molar ratio of lithium to ferro-manganese in the ferro-manganese-based positive electrode material is 0.8: 1.
Example 3
This example provides a method for preparing a ferrimanganic cathode material with a chemical formula of Li0.7Mn0.5Fe0.5O2The preparation method specifically comprises the following steps:
mixing lithium chloride and ferromanganese precursors, and heating to 900 ℃ at the speed of 5 ℃/min for 9 hours for primary sintering to prepare a base material, wherein the molar ratio of lithium element to iron-manganese element in the base material is 0.7: 1;
and (II) mixing the base material prepared in the step (I) with lithium acetate, and performing secondary sintering at 700 ℃ for 8 hours to prepare the ferro-manganese-based positive electrode material, wherein the molar ratio of lithium to ferro-manganese in the ferro-manganese-based positive electrode material is 1.5: 1.
Example 4
This example provides a method for preparing a ferromanganese-based positive electrode material, which is different from example 1 in that, in step (ii), the molar ratio of lithium element to sum of iron and manganese elements in the ferromanganese-based positive electrode material is 0.8:1, and the rest of operations and parameters are completely the same as those in example 1.
Example 5
This example provides a method for preparing a ferromanganese-based positive electrode material, which is different from example 1 in that, in step (ii), the molar ratio of lithium element to sum of iron and manganese elements in the ferromanganese-based positive electrode material is 1.5:1, and the rest of operations and parameters are completely the same as those in example 1.
Example 6
This example provides a method for preparing a ferrimanganic based cathode material, which is different from example 1 in that in step (i), the molar ratio of lithium element to the sum of ferrimanganic element in the matrix material is 0.2:1, and the rest of the operations and parameters are exactly the same as those in example 1.
Example 7
This example provides a method for preparing a ferrimanganic positive electrode material, which is different from example 1 in that in step (i), the molar ratio of lithium element to the sum of ferrimanganic element in the matrix material is 0.8:1, and the rest of the operations and parameters are the same as those in example 1.
Example 8
This example provides a method for preparing a fe-mn-based positive electrode material, which is different from example 1 in that the temperature of the secondary sintering in step (ii) is 400 ℃, and the rest of the operations and parameters are exactly the same as those in example 1.
Example 9
This example provides a method for preparing a fe-mn-based positive electrode material, which is different from example 1 in that the temperature of the secondary sintering in step (ii) is 800 ℃, and the rest of the operations and parameters are exactly the same as those in example 1.
Example 10
This example provides a method for preparing a ferrimanganic positive electrode material, which is different from example 1 in that, in the step (i), the temperature rise rate of one-time sintering is 1 ℃/min, and the rest of the operation and parameters are completely the same as those in example 1.
Example 11
This example provides a method for preparing a fe-mn-based positive electrode material, which is different from example 1 in that the temperature increase rate of the primary sintering in step (i) is 6 ℃/min, and the rest of the operations and parameters are exactly the same as those in example 1.
Comparative example 1
This comparative example provides a method for preparing a ferromanganese-based positive electrode material, which is different from example 1 in that step (ii) is not performed.
The ferro-manganese based anode material provided by the invention comprises a first lithium salt layer and a second lithium salt which is doped in the ferro-manganese based anode material in a gradient manner.
The invention also provides a battery which comprises a positive electrode, a negative electrode and a diaphragm, wherein the positive electrode comprises the iron-manganese-based positive electrode material.
The ferromanganese-based positive electrode material obtained in example 1 was subjected to electron microscope scanning, as shown in fig. 1. The ferro-manganese based positive electrode materials prepared in the above examples and comparative examples were subjected to a power-on assembly and an electrical property test, wherein:
the assembling method comprises the following steps: and (3) homogenate coating: a positive electrode material: binder (polyvinylidene fluoride): the mass ratio of (conductive carbon black) is 80: 10: and 10, placing the mixture in a defoaming machine, uniformly mixing, and then performing electric fastening assembly.
And (4) buckling and assembling: and (4) carrying out electricity buckling assembly according to the sequence of the positive electrode shell, the elastic sheet, the gasket, the positive electrode, the diaphragm, the electrolyte, the negative electrode and the negative electrode shell.
The test method comprises the following steps: constant current charging and constant voltage charging, wherein the voltage test interval is 1.5-4.8V.
The test results are shown in table 1, and the charge and discharge curves of example 1, example 4, example 5, and comparative example 1 are shown in fig. 2.
TABLE 1
From the above table, it can be seen that:
(1) compared with the embodiments 6 and 7, the parameters of the embodiment 1 are superior to those of the embodiments 6 and 7, and therefore, the invention can be seen that by controlling the molar ratio of the lithium element to the sum of the iron and manganese elements in the matrix material to be (0.3-0.7): 1, the ratio of the lithium metal in the primary sintering process is controlled to be low, and the lithium-rich structure formed by the positive electrode material in the primary sintering process is effectively avoided while the positive electrode material is ensured to have good electrical properties and a stable structure, so that the battery performance is influenced; if the molar ratio is less than 0.3:1, the material after formation has a low lithium contentMeanwhile, because of no excessive lithium coordination sites, the lithium ion intercalation can be influenced, the material capacity is further influenced, meanwhile, in the SEI film formation process, a part of lithium ions can be consumed, and if the initial lithium ions are too few, the SEI film formation is not facilitated. If the molar ratio is higher than 0.7:1, excessive lithium ions will cause the material to form Li2MnO3Phase, Li2MnO3The phase is easy to decompose in the charging and discharging process, which causes the problems of oxygen release and increased cation concentration, leads to the fact of oxygen atoms of the material and influences the structural stability of the material.
(2) Compared with the embodiments 8 and 9, the parameters of the embodiment 1 are superior to those of the embodiments 8 and 9, so that the invention can be seen that the temperature of the secondary sintering is controlled to be 500-700 ℃, the lithium salt is completely reacted, the particle size is proper, the material performance is good, if the sintering temperature is lower than 500 ℃, the lithium salt is incompletely reacted in the secondary sintering, the residual lithium on the surface of the material is increased, and the subsequent homogenization and coating processes of the material are not facilitated; if the sintering temperature is higher than 700 ℃, the material particles are easily enlarged under the action of high temperature, and the material performance is further influenced.
(3) Compared with the embodiments 10 and 11, the parameters of the embodiment 1 are superior to those of the embodiments 10 and 11, and therefore, the method can be seen that the substrate material has a proper particle size by controlling the temperature rise rate of primary sintering to be 2-5 ℃/min, and the material performance and stability are ensured. If the temperature rise rate is lower than 2 ℃/min, the particle size of the base material is small, the side reaction of the material and the electrolyte is aggravated, and the stability of the material is influenced; if the temperature rise rate is higher than 5 ℃/min, the particle size of the material particles is increased, so that the internal resistance of the material is increased, and the capacity is influenced.
(4) Compared with the comparative example 1, the parameters of the example 1 are better than those of the comparative example 1, and in combination with fig. 2, it can be seen that after lithium coating, the material has a more obvious discharge plateau around 2.0V, but when the lithium salt ratio is higher, the material forms a lithium-rich phase, which is shown in that when the voltage of a charging curve is more than 4.5V, the material has a obviously large charging plateau. Therefore, after the lithium-deficient material is obtained through the first sintering, the lithium element is continuously added through the second sintering, and the positive electrode material is controlled to obtain the proper lithium salt ratio. In addition, the invention can avoid excessive lithium adding amount for the first time through twice sintering and step-by-step lithium adding mode, and meanwhile, when the lithium salt ratio is more than 1, the matrix material is easy to form a lithium-rich structure, thereby influencing the electrical property of the matrix material; on the other hand, the lithium salt added in the secondary sintering can carry out gradient doping in the material, which is beneficial to the material to form a new phase on the surface layer and improve the electrochemical performance of the material.
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.
Claims (10)
1. A preparation method of a ferro-manganese based cathode material is characterized by comprising the following steps: and mixing the first lithium salt and the ferromanganese precursor for primary sintering to obtain a base material, and mixing the base material with the second lithium salt for secondary sintering to obtain the ferromanganese-based positive electrode material.
2. The preparation method according to claim 1, wherein the molar ratio of the lithium element to the sum of the iron and manganese elements in the matrix material is (0.3-0.7): 1;
preferably, the molar ratio of the lithium element to the sum of the iron and manganese elements in the ferro-manganese-based positive electrode material is (0.8-1.5): 1.
3. The preparation method according to claim 1 or 2, wherein the temperature of the primary sintering is 700-900 ℃;
preferably, the temperature rise rate of the primary sintering is 2-5 ℃/min;
preferably, the heat preservation time of the primary sintering is 9-15 h.
4. The method according to any one of claims 1 to 3, wherein the temperature of the secondary sintering is 500 to 700 ℃;
preferably, the heat preservation time of the secondary sintering is 5-8 h.
5. The production method according to any one of claims 1 to 4, wherein the first lithium salt includes one or a combination of at least two of lithium carbonate, lithium hydroxide, or lithium chloride;
preferably, the second lithium salt comprises a low melting point lithium salt, further preferably lithium hydroxide and/or lithium acetate;
preferably, the ferromanganese precursor is prepared by coprecipitation of manganese salt and iron salt.
6. The preparation method according to any one of claims 1 to 5, comprising in particular the steps of:
mixing a first lithium salt and a ferromanganese precursor, and performing primary sintering for 9-15 hours at a speed of 2-5 ℃/min to 700-900 ℃ to prepare a base material, wherein the molar ratio of lithium to the sum of iron and manganese in the base material is (0.3-0.7): 1;
and (II) mixing the base material prepared in the step (I) with a second lithium salt, and performing secondary sintering at 500-700 ℃ for 5-8 hours to prepare the ferro-manganese-based positive electrode material, wherein the molar ratio of lithium to the sum of ferro-manganese elements in the ferro-manganese-based positive electrode material is (0.8-1.5): 1.
7. A ferro-manganese-based cathode material, characterized in that the ferro-manganese-based cathode material is prepared by the method for preparing a ferro-manganese-based cathode material according to any one of claims 1 to 6.
8. The iron-manganese-based positive electrode material according to claim 7, characterized in that the chemical formula of the iron-manganese-based positive electrode material is LixMnyFezO2Wherein y + z is 1, x/(y + z) is 0.5-1.2, x is more than or equal to 0.8 and less than or equal to 1.5, y is more than or equal to 0.2 and less than or equal to 0.8, and z is more than or equal to 0.2 and less than or equal to 0.8.
9. The ferromanganese-based positive electrode material according to claim 7 or 8, characterized in that the ferromanganese-based positive electrode material comprises a first lithium salt layer;
preferably, the second lithium salt is gradient doped in the iron-manganese-based positive electrode material.
10. A battery comprising a positive electrode, a negative electrode and a separator, wherein the material in the positive electrode comprises the iron-manganese-based positive electrode material according to any one of claims 7 to 9.
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