CN106816600B - Lithium iron manganese phosphate material, preparation method thereof, battery slurry, positive electrode and lithium battery - Google Patents

Lithium iron manganese phosphate material, preparation method thereof, battery slurry, positive electrode and lithium battery Download PDF

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CN106816600B
CN106816600B CN201510863430.0A CN201510863430A CN106816600B CN 106816600 B CN106816600 B CN 106816600B CN 201510863430 A CN201510863430 A CN 201510863430A CN 106816600 B CN106816600 B CN 106816600B
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lithium
active component
preparation
manganese phosphate
lithium iron
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CN106816600A (en
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徐茶清
陈靖华
游军飞
肖峰
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BYD Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention discloses a lithium iron manganese phosphate material, a preparation method thereof, battery slurry, a positive electrode and a lithium battery. The lithium iron manganese phosphate material comprises LiMnxFe1‑x‑yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and a coating layer coated on the surface of the active component, wherein the coating layer contains an amorphous metal compound. The lithium iron manganese phosphate material is prepared by adding LiMnxFe1‑x‑yMyPO4The active component surface of the/C structure is coated with a coating layer containing an amorphous metal compound with low water absorption, so that the electrochemical performance of the lithium manganese iron phosphate material is maintained, the water absorption of the lithium manganese iron phosphate material is reduced, and the storage capacity retention rate of the lithium battery at high temperature is improved correspondingly.

Description

Lithium iron manganese phosphate material, preparation method thereof, battery slurry, positive electrode and lithium battery
Technical Field
The invention relates to the field of lithium battery preparation, in particular to a lithium manganese iron phosphate material and a preparation method thereof, and also relates to battery slurry comprising the lithium manganese iron phosphate material.
Background
The lithium ion secondary battery is a novel green high-energy rechargeable battery, has the advantages of high voltage, large energy density, good cycle performance, small self-discharge, no memory effect, wide working range and the like, is widely applied to mobile phones, notebook computers, portable electric tools, electronic instruments, weaponry and the like, also has good application prospect in electric automobiles, and has become the key point of competitive research and development of all countries in the world at present. The positive electrode material is an important component of the lithium ion battery, and not only lithium required for reciprocating insertion/extraction in positive and negative lithium insertion compounds but also lithium required for forming an SEI film on the surface of the negative electrode material are required to be provided in the charge and discharge processes of the lithium ion battery, so that research and development of the high-performance positive electrode material are key points in the development of the lithium ion battery.
In the lithium ion battery anode material, the lithium iron manganese phosphate material has the best comprehensive performance, and is considered as an ideal lithium ion secondary power battery anode material. However, the particle size of the existing lithium iron manganese phosphate material is generally controlled to be nano-scale, the specific surface area is large, once the material is contacted with humid air, moisture is easy to contact with Li with hydrophilicity on the surface of the material, and after the lithium iron manganese phosphate is contacted with the humid air within a period of time (several weeks), surface lithium also can have lithiation reaction with water, so that the moisture content of the lithium iron manganese phosphate material is increased. When the lithium iron manganese phosphate material with relatively high water content is used as a battery anode material, water in the material is difficult to remove in the subsequent battery batching and slurry drawing process and is always reserved in the battery, so that the storage capacity retention rate of the battery is mostly poor. In order to improve the storage capacity retention rate of the battery, researchers have studied various schemes, such as reducing the water absorption rate of lithium manganese iron phosphate materials.
In the chinese patent application No.200910053346, a method for improving the conductivity of a lithium iron phosphate positive electrode material is disclosed, which uses raw materials of an iron source, a lithium source and a phosphate source, the synthesis method is a solid phase method, and does not need any doping activation, and on the basis of synthesizing the lithium iron phosphate material according to a conventional method, residual moisture in the lithium iron phosphate material is removed by introducing a gas capable of dehydrating during high-temperature calcination, pumping water by a vacuum pump, absorbing water by phosphorus pentoxide and the like, thereby greatly improving the conductivity of the material. However, the processing process of the method is complex, a plurality of auxiliary raw materials are required to be introduced to remove moisture in the material, and the lithium iron phosphate anode material prepared by the method cannot ensure the water absorption of the material in subsequent air contact.
In Chinese patent application No.200910044154, a surface modified lithium ion battery anode material lithium cobaltate material and a modification method thereof are disclosed, wherein lithium salt and cobalt salt are respectively weighed according to the molar mass ratio of Li to Co of 1.038; firstly adding lithium salt, then adding a coating substance calcium carbonate, then adding cobalt salt and finally adding industrial alcohol into a ball mill for ball milling; after the ball-milled materials are dried in vacuum, the materials are sintered for the first time; crushing and crushing the fired material, washing with deionized water, and firing for the second time; and (4) performing dispersion treatment to obtain the positive electrode material with a layer of calcium carbonate coated on the surface of the lithium cobaltate. According to the modification method, the surface of the lithium cobaltate is coated with a layer of calcium carbonate with hydrophobicity, so that the contact between the active material and water can be blocked, the water absorption performance of the lithium cobaltate is improved to a certain extent, and excessive impurities are introduced to cause the reduction of the active component, so that the electrochemical performance of the final material is influenced.
As is apparent from the above, although some proposals have been made in the prior art to reduce the water absorption of lithium iron manganese phosphate-based materials, the effects are not satisfactory, and the high-temperature storage capacity retention rate of batteries using electrodes made of such materials is often not good.
Disclosure of Invention
The invention aims to provide a lithium iron manganese phosphate material, a preparation method thereof, a battery slurry, a positive electrode and a lithium battery, so as to provide the lithium iron manganese phosphate material with low water absorption rate, and further improve the capacity retention rate of the battery under high-temperature storage.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a lithium iron manganese phosphate-based material including a material having LiMnxFe1-x-yMyPO4Of the structure/CThe active component, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and a coating layer wrapped on the surface of the active component, wherein the coating layer contains an amorphous metal compound.
According to a second aspect of the present invention, there is provided a method for preparing a lithium manganese iron phosphate-based material, comprising the steps of: s1, providing LiMnxFe1-x-yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and S2, taking the active component as a base material, and forming a coating layer containing an amorphous metal compound on the surface of the active component.
According to a third aspect of the present invention, a lithium iron manganese phosphate-based material is provided, which is prepared by the above preparation method.
According to a fourth aspect of the present invention, a battery slurry is provided, which includes a lithium manganese iron phosphate material and a solvent, wherein the lithium manganese iron phosphate material is the above-mentioned lithium manganese iron phosphate material of the present invention.
According to a fifth aspect of the present invention, there is provided a positive electrode comprising a current collector and a positive active material layer disposed on the current collector, the positive active material layer comprising the lithium iron manganese phosphate-based material of the present invention.
According to a sixth aspect of the present invention, there is provided a lithium battery, wherein the lithium battery is internally provided with a positive electrode, and the positive electrode is the positive electrode material of the present invention.
The invention provides a lithium manganese iron phosphate material, a preparation method thereof, battery slurry, a positive electrode and a lithium battery, wherein the lithium manganese iron phosphate material is prepared by adding LiMnxFe1-x-yMyPO4The active component surface of the/C structure is coated with a coating layer containing an amorphous metal compound with low water absorption, so that the electrochemical performance of the lithium manganese iron phosphate material is maintained, the water absorption of the lithium manganese iron phosphate material is reduced, the water content of the anode prepared from the material is reduced, and the improvement of the anode prepared from the material is facilitatedThe lithium battery prepared by the electrode material has the storage capacity retention rate at high temperature.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 shows a 5 μm Scanning Electron Microscope (SEM) spectrum of lithium iron manganese phosphate-based material P1 prepared according to preparation example 1 of the present invention;
fig. 2 shows a 5 μm Scanning Electron Microscope (SEM) spectrum of the lithium iron manganese phosphate-based material DP1 prepared according to comparative example 1 of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The technical problem pointed out in the background of the invention section of "in the prior art there is a storage capacity retention rate of the battery that mostly performs poorly" is solved. The inventors of the present invention have made a lot of work and studies on removing moisture and the like of a material. And according to a first aspect of the present invention, there is provided a lithium iron manganese phosphate-based material comprising a material having LiMnxFe1-x-yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and a coating layer coated on the surface of the active component, wherein the coating layer contains an amorphous metal compound.
In the present invention, "having LiMnxFe1-x-yMyPO4The active component of the structure of/C refers to a carbon-coated lithium manganese iron phosphate material (LiMn)xFe1-x-yMyPO4) An active component of structure.
The invention providesThe lithium iron manganese phosphate material is prepared by adding LiMnxFe1-x-yMyPO4The surface of the active component of the/C structure is coated with the coating layer containing the amorphous metal compound with low water absorption rate, so that the electrochemical performance of the lithium manganese iron phosphate material is maintained, the water absorption rate of the lithium manganese iron phosphate material is reduced, the water content of the anode material prepared from the material is further reduced, and the storage capacity retention rate of the lithium battery prepared from the anode material at high temperature is favorably improved.
In the lithium iron manganese phosphate material of the present invention, there is no special requirement for the particle size of the material, and the conventional selection in the field, such as the particle size D, can be referred to50May be 0.5 to 2.0 μm. The particle size of the lithium iron manganese phosphate material to be prepared can reasonably arrange the particle size of the active component in the lithium iron manganese phosphate material and the thickness of the coating layer, and the coating layer containing the amorphous metal compound is coated on the surface of the active component. In the invention, the particle size D of the active component in the lithium iron manganese phosphate material is preferably selected50Is 0.5-1.0 μm, preferably 0.5-0.8 μm, and the amorphous metal compound coating layer has a thickness of 1-5 nm. In the present invention, among them, the particle diameter D50The volume average particle size is obtained by dispersing powder to be tested in water, then carrying out ultrasonic oscillation for 30 minutes, and carrying out particle size test by using a laser particle size analyzer.
In the lithium iron manganese phosphate material of the present invention, there is no particular requirement for the amorphous metal compound in the coating layer as long as the water absorption rate thereof is lower than that of the active component. In the invention, the amorphous metal compound is preferably selected from one or a mixture of more of amorphous aluminum oxide, amorphous lithium phosphate, amorphous lithium pyrophosphate, amorphous ferric pyrophosphate, amorphous lithium ferrous pyrophosphate, amorphous lithium manganese pyrophosphate and amorphous silver oxide. The inventors of the present invention have found that the cladding layers formed of these amorphous metal compounds have a lower absorption rate than the cladding layers formed of conventional crystalline metal compounds. The inventor speculates that the amorphous metal compound is generally regularly and disorderly grown, nonpolar bonds are formed on the surface of the amorphous metal compound, and the nonpolar bonds are not easy to combine with polar water, so that the amorphous metal compound can play a role in blocking moisture permeation, active components can be better prevented from contacting with moisture, and the water absorption performance of the lithium iron manganese phosphate material is further improved.
In a preferred embodiment of the present invention, the lithium iron manganese phosphate material further includes a conductive carbon layer coated on the surface of the coating layer, and the conductive carbon layer is further disposed on the surface of the coating layer containing the amorphous metal compound, which is favorable for further optimizing the conductivity of the material. More preferably the thickness of the conductive carbon layer is 2-10 nm.
In the lithium iron manganese phosphate-based material of the present invention, the material having LiMnxFe1-x-yMyPO4The element ratio in the active component of the structure/C is not particularly limited, and it may be determined by referring to the conventional element ratio in the art as long as the aforementioned structure can be formed. Preferably, the molar ratio of Li to the sum of Mn, Fe and M is from 0.98 to 1.02: 1. meanwhile, the content of the C element in the active component is preferably 0.5-3.5 wt% of the total weight of the active component.
In the invention, the magnetic induction intensity of the lithium iron manganese phosphate material is not particularly required, and the lithium iron manganese phosphate material can be selected according to the conventional selection in the field. However, in order to optimize the electrochemical performance of the prepared lithium iron manganese phosphate material, the magnetic induction intensity of the lithium iron manganese phosphate material is preferably 750-1100 ppm. The magnetic induction intensity of the lithium iron manganese phosphate material is tested by adopting a magnetic analyzer MA1040 of a microphone instrument. The testing method comprises the steps of filling lithium iron manganese phosphate material powder into a sample cup (the height of a sample is 12cm), and measuring the magnetic strength of 5 different directions to obtain an average value.
According to the second aspect of the invention, the invention also provides a preparation method of the lithium ferric manganese phosphate material. The lithium ferric manganese phosphate material can be prepared by the conventional method in the fieldIt can also be prepared by the preferred preparation method provided by the invention. The preparation method provided by the invention comprises the following steps: s1 preparation of LiMn-containing alloyxFe1-x-yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and S2, taking the active component as a base material, and forming a coating layer containing an amorphous metal compound on the surface of the active component.
According to the preparation method of the lithium manganese iron phosphate material, the active component and the coating layer coated on the surface of the active component are formed in different steps, so that the electrochemical performance of the lithium manganese iron phosphate material is guaranteed, the coating layer is uniformly and completely coated on the surface of the active component, the contact between the active component and water is blocked, and the water absorption performance of lithium manganese iron phosphate is improved.
In the above preparation method, S1 provides the catalyst with LiMnxFe1-x-yMyPO4In the step of the active component of the structure/C, has LiMnxFe1-x-yMyPO4The active component of the structure/C may be a commercially available product or may be prepared by a method conventional in the art. In the present invention, it is preferred to prepare the compound by using a high temperature solid phase method, which comprises the following steps: s11, mixing a lithium source, an optional iron source, an optional manganese source, an optional M source, a phosphorus source and a first carbon source in proportion, and drying to obtain a first dry mixture; s12, sintering the first dry mixture at 600-800 ℃ for 5-30h at constant temperature to form the active component.
In S11 of the above preparation method, the raw materials may be mixed in proportion by grinding, which may be performed by means including, but not limited to, ball milling, sand milling, or agitator milling. The process conditions for milling can be referred to those conventionally employed in the art, for example, milling at a speed of 1000-. The step of grinding and mixing also comprises the step of adding grinding fluid, wherein the grinding fluid comprises but is not limited to deionized water and C1-C5One or more of alcohols. C1-C5Alcohol is preferably C1-C5Monohydric alcohols, which include, but are not limited to, one or more of methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, n-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, and 2, 2-dimethyl-1-propanol, preferably ethanol.
In S11 of the above preparation method, the drying treatment includes, but is not limited to, vacuum drying, inert gas protected heating drying, spray drying, freeze drying or flash drying, and the like, wherein spray drying is preferred, and the conditions for spray drying can refer to the process conditions conventionally selected in the art, such as an inlet air temperature of 200-300 ℃ and an outlet air temperature of 80-200 ℃.
In S12 of the above preparation method, the step of sintering the first dried mixture can be performed according to the conventional operation manner in the art, as long as the first dried mixture is sintered at 600-800 ℃ for 5-30 h. In the invention, the first dry mixture is preferably heated to 600-800 ℃ at the speed of 0.1-2 ℃/min and is treated for 5-30h at constant temperature. The well-developed crystalline lithium manganese iron phosphate body material is formed by adjusting the temperature rise speed of the first dry mixture, so that the material is ensured to have relatively high electrochemical activity.
In S11 of the above preparation method, a catalyst having LiMn was preparedxFe1-x-yMyPO4The amount of each raw material used in the step of the active component having the structure/C is not particularly limited, and it is preferable to form LiMn in accordance with the intended formationxFe1-x-yMyPO4The structure of/C, the dosage of the corresponding raw materials is reasonably selected. In the present invention, it is preferred that the molar ratio of the lithium source, calculated as Li, to the optional iron source, the optional manganese source, the optional M source, calculated as Fe + Mn + M, is from 0.98 to 1.02: 1. the molar ratio of the lithium source calculated as Li to the phosphorus source calculated as phosphorus is 0.98-1.02: 1. in the invention, the selection of each raw material is not particularly required, and the conventional materials adopted in the preparation of the lithium iron manganese phosphate material in the field can be referred. Wherein:
lithium sources that may be used include, but are not limited to, one or more of lithium hydroxide, lithium peroxide, lithium oxide, lithium carbonate, and lithium phosphate.
The phosphorus source that may be used includes, but is not limited to, one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, lithium phosphate, and lithium pyrophosphate.
The Fe source that can be used includes, but is not limited to, one or more of ferrous oxide, ferroferric oxide, ferric nitrate, ferrous acetate, and ferrous formate.
Mn sources that may be used include, but are not limited to, one or more of manganese dioxide, manganous oxide, manganous tetraoxide, manganese carbonate, manganese nitrate, manganous acetate, manganous formate
The optional M source is a compound containing one or more of Co, Ni, Mg, Zn, V and Ti. Among them, Co-containing compounds that may be used include, but are not limited to, one or more of cobaltosic oxide, cobalt nitrate, cobaltous oxide, cobalt hydroxide, cobalt acetate, and cobalt phosphate; ni-containing compounds that may be used include, but are not limited to, one or more of nickel protoxide, nickel oxide, nickel nitrate, nickel hydroxide, nickel acetate, and nickel phosphate; mg-containing compounds that may be used include, but are not limited to, one or more of magnesium oxide, magnesium nitrate, magnesium hydroxide, and magnesium acetate; zn-containing compounds that may be used include, but are not limited to, one or more of zinc oxide, zinc nitrate, zinc hydroxide, and zinc acetate; compounds containing V that may be used include, but are not limited to, one or more of vanadia oxide, vanadium pentoxide, vanadium trioxide, vanadium nitrate, vanadium hydroxide, and vanadium acetate; ti-containing compounds that may be used include, but are not limited to, one or more of titanium dioxide, titanium hydroxide, titanium acetate, and tetrabutyl titanate.
Carbon sources that may be used include, but are not limited to, glucose, sucrose, lactose, phenolic resins, graphene, carbon nanotubes, graphite, and the like, organic or inorganic carbon sources that have been carbonized or may be carbonized at high temperatures. Preparation of LiMn in the inventionxFe1-x-yMyPO4The carbon source is added in the step of adding the active component of the structure/C in order to improve the electronic conductivity of the material, andthe same as the conventional method in the field, the carbon source added in the invention can be enriched on the surface of the lithium iron manganese phosphate material in the sintering process, so LiMn is formedxFe1-x-yMyPO4A lithium iron manganese phosphate material with a/C structure, namely a carbon-coated structure. The amount of the carbon source added in the present invention can be referred to the amount conventionally used in the art, for example, the amount of the C source is such that the content of C element in the active component is 0.5-3.5 wt% based on the total weight of the active component.
In S2 of the above production method, in the step of producing the amorphous metal compound coating layer, there is no particular limitation on the method of forming the coating layer containing the amorphous metal compound, as long as the substance in the formed coating layer exists in an amorphous form. Preferably, the S2 includes the steps of: s21, mixing the active component with a source of material (in a solvent, such as water) for forming the metal compound, and drying to obtain a second dry mixture; s22, heating the second dry mixture to 300-500 ℃ and directly cooling without heat preservation to form the amorphous metal compound coating layer on the surface of the active component.
In S21 of the above preparation method, there is no particular requirement for the manner of mixing the active component with the material source for forming the metal compound, as long as both are relatively uniformly dispersed in the solvent, and for example, the mixing of both can be relatively uniform by means of stirring for 15 to 50 min.
In S21 of the above preparation method, the drying treatment may include, but is not limited to, vacuum drying, inert gas protected heating drying, spray drying, freeze drying or flash drying, and the like, wherein spray drying is preferred, and for the conditions of spray drying, reference may be made to process conditions conventionally selected in the art, and details thereof are not repeated herein.
In S22 of the above preparation method, there is no particular requirement for the manner of the heat treatment, as long as the second dry mixture is heated to 300-500 ℃ and the temperature is directly lowered without heat preservation, so as to form the amorphous metal compound-containing coating layer on the surface of the active component. In the present invention, it is preferred that the second dry mixture is heated to 300-500 ℃ at a rate of 30-80 ℃/min. The second dry mixture is heated to 300-500 ℃ at a speed of 30-80 ℃/min, which is favorable for forming a coating layer containing amorphous metal compounds on the surface of the material.
In S2 of the above preparation method, a coating layer containing an amorphous metal compound is mainly formed on the surface of the active component to reduce the water absorption rate and the water content of the lithium manganese iron phosphate material. In order to further reduce the water absorption rate and the water content of the prepared lithium iron manganese phosphate material, the amorphous metal compound contained in the coating layer is preferably selected from one or a mixture of more of amorphous aluminum oxide, amorphous lithium phosphate, amorphous lithium pyrophosphate, amorphous ferric pyrophosphate, amorphous lithium ferrous pyrophosphate, amorphous lithium manganese pyrophosphate and amorphous silver oxide.
Preferably, the source of material from which the alumina can be formed includes, but is not limited to, alumina, aluminum acetate, aluminum nitrate, or aluminum hydroxide. Sources of materials from which lithium phosphate can be formed include lithium sources including, but not limited to, lithium hydroxide or lithium carbonate, and phosphorus sources including, but not limited to, phosphoric acid or lithium phosphate sources including, but not limited to, lithium dihydrogen phosphate or lithium phosphate. Sources of materials from which lithium pyrophosphate can be formed include lithium sources including, but not limited to, lithium hydroxide or lithium carbonate and phosphorus sources including, but not limited to, phosphoric acid or lithium pyrophosphate. Sources of materials from which ferric pyrophosphate may be formed include iron sources and phosphorous sources, or ferrophosphorus sources. Wherein the iron source includes, but is not limited to, iron trioxide or iron acetate, the phosphorous source includes, but is not limited to, phosphoric acid, and the phosphorous iron source includes, but is not limited to, iron phosphate. Sources of materials from which lithium iron pyrophosphate can be formed include lithium sources including, but not limited to, lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium phosphate; iron sources include, but are not limited to, iron sesquioxide, iron acetate, or iron phosphate, and phosphorous sources include, but are not limited to, phosphoric acid, lithium dihydrogen phosphate, lithium phosphate. Sources of materials that can form lithium manganese pyrophosphate include lithium sources, manganese sources, and phosphorus sources. Wherein the lithium source includes, but is not limited to, lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, or lithium phosphate; manganese sources include, but are not limited to, manganese dioxide, manganese carbonate, manganese acetate, or trimanganese tetroxide; the phosphorus source includes, but is not limited to, lithium dihydrogen phosphate or lithium phosphate. Sources of materials from which silver oxide can be formed include, but are not limited to, silver oxide, silver acetate, silver nitrate, or silver hydroxide.
In a preferred embodiment of the present invention, the above preparation method further comprises the steps of: s3 is a process in which the intermediate product obtained in S2 is used as a substrate, and a conductive carbon layer is formed on the surface of the intermediate product. The step of forming the conductive carbon layer may be performed according to conventional methods and conventional process parameters in the art. In the present invention, it is preferable that the S3 includes the steps of: mixing the intermediate obtained in S2 with a second carbon source (in a solvent, e.g., water), and drying to obtain a third dry mixture; and heating the third dry mixture to 600-750 ℃, and then preserving the heat for 3-10h to form the conductive carbon layer on the surface of the active component.
In S3 of the above preparation method, the mixing method of the intermediate product and the second carbon source is not particularly limited, as long as both are relatively uniformly dispersed in the solvent, and for example, the mixing method can be used to relatively uniformly mix both, and the stirring time is 15 to 50 min.
In S3 of the above preparation method, the drying treatment may include, but is not limited to, vacuum drying, inert gas protected heating drying, spray drying, freeze drying or flash drying, and the like, wherein spray drying is preferred, and for the conditions of spray drying, reference may be made to process conditions conventionally selected in the art, and details thereof are not repeated herein.
In S3 of the above preparation method, there is no special requirement for the heating method, as long as the third dry mixture is heated to 600-750 ℃ and is kept warm for 3-10 h. In the present invention, it is preferable to raise the temperature of the third dry mixture to 300-500 ℃ at a rate of 2-10 ℃/min. The second dry mixture is heated to 300-500 ℃ at a speed of 2-10 ℃/min, which is favorable for forming an amorphous coating layer on the surface.
In the above production process of the present invention, it is preferable that both S1 and S2 be carried out entirely in the presence of an inert gas. The S1 (preparation of active components) and S2 (preparation of an inner coating layer with an amorphous metal compound structure) are carried out in the presence of inert gas, so that introduction of impurities is avoided, and the electrochemical performance of the prepared lithium iron manganese phosphate material is optimized. Inert gases that may be employed include, but are not limited to, nitrogen, argon, helium, and mixtures of one or more thereof.
Meanwhile, according to a third aspect of the invention, a lithium iron manganese phosphate material is also provided, and the lithium iron manganese phosphate material is prepared by the preparation method. The lithium iron manganese phosphate material comprises LiMnxFe1-x-yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and a coating layer which is coated on the surface of the active component and contains amorphous metal compounds. Preferably, the particle size D of the active component50Is 0.5-1.0 μm, and the inorganic amorphous material coating layer has a thickness of 1-5 nm.
Preferably, the amorphous metal compound in the coating layer is selected from one or a mixture of more of amorphous aluminum oxide, amorphous lithium phosphate, amorphous lithium pyrophosphate, amorphous ferric pyrophosphate, amorphous lithium ferrous pyrophosphate, amorphous lithium manganese pyrophosphate and amorphous silver oxide
Preferably, the lithium iron manganese phosphate material further comprises a conductive carbon layer coated on the surface of the coating layer; preferably, the thickness of the conductive carbon layer is 2-10 nm.
Preferably, the compound has LiMnxFe1-x-yMyPO4In the active component of the structure/C, the molar ratio of Li to the sum of Mn, Fe and M is 0.98-1.02: 1; preferably, the content of the C element in the active component is 0.5-3.5 wt% of the total weight of the active component.
In addition, according to a fourth aspect of the present invention, a battery slurry is also provided, where the battery slurry includes a lithium iron manganese phosphate material and a solvent, and the lithium iron manganese phosphate material is the lithium iron manganese phosphate material of the present invention. The solvent that may be used in the above battery paste includes, but is not limited to, one of water and N-methylpyrrolidone.
In the process of preparing the battery slurry, no special requirement is made on the solid content of the battery slurry, and the solid content can be properly selected according to the use requirement of the battery slurry. Generally, the above battery slurry has a solid content of 30 to 60 wt%, preferably 40 to 50 wt%, more preferably 45 to 50 wt%.
The battery slurry also comprises a solvent, a binder and a conductive agent. The raw materials and the use amounts of the binder, the conductive agent and the solvent can be selected according to the routine selection in the field, for example, the binder can be polyvinylidene fluoride, the conductive agent can be acetylene black, and the weight ratio of the lithium manganese iron phosphate material (positive electrode active material) to the conductive agent and the binder is 80:10: 10. Solvents that may be used in the above-described battery slurry include, but are not limited to, one or more of water, ethanol, and methanol.
According to the fifth aspect of the present invention, there is still further provided a positive electrode comprising a current collector and a positive active material layer disposed on the current collector, the positive active material layer comprising the lithium iron manganese phosphate-based material of the present invention. The positive electrode provided by the invention is prepared by adopting the battery slurry containing the lithium manganese iron phosphate material, and the water absorption rate of the positive electrode is lower due to the fact that the lithium manganese iron phosphate material is lower. Preferably, the current collector may refer to a conductive metal material conventionally used in the art, for example, including, but not limited to, platinum (Pt) foil, palladium (Pd) foil, aluminum (Al) foil, and the like.
The invention further provides a lithium battery, wherein the lithium battery is internally provided with a positive electrode, and the positive electrode is the positive electrode. According to the lithium battery provided by the invention, the cathode material with lower water content provided by the invention is adopted, so that the residual water content in the battery pole piece is lower, particularly, under high-temperature storage, the possibility of generating HF (hydrogen fluoride) component by irreversible side reaction between water and electrolyte is reduced, the deterioration result of dissolving the electrode material is avoided, and the storage capacity retention rate of the battery in a high-temperature state is improved.
The lithium iron manganese phosphate material, the preparation method thereof, the positive electrode and the lithium battery, and the beneficial effects thereof will be further described below by combining specific examples and comparative examples.
The test items and test methods referred to in the following preparation examples, preparation comparative examples, examples and comparative examples are as follows:
in the following preparation examples and comparative preparation examples, the composition of the lithium iron manganese phosphate material of the present invention was measured by inductively coupled plasma emission spectrometry (ICP); the shape and the particle size of the lithium iron manganese phosphate material are observed by a Transmission Electron Microscope (TEM) atlas.
In the following preparation examples and comparative preparation examples, the average particle size (volume average particle size) of the lithium iron manganese phosphate-based material of the present invention was measured using a laser particle size tester commercially available from all new powder test equipment ltd. The thickness of the middle cladding layer of the lithium iron manganese phosphate material is presumed and observed by a front-back particle size comparison method and a Transmission Electron Microscope (TEM) atlas.
In the following preparation examples and comparative preparation examples, the spray drying step adopts the same process conditions, including the air inlet temperature of 200-300 ℃ and the air outlet temperature of 80-200 ℃.
First, preparation example and comparative preparation example
Preparation example 1
For explaining the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound in the coating layer is amorphous aluminum oxide)
(1) Weighing 3.69 g of lithium carbonate, 11.50 g of ammonium dihydrogen phosphate, 7.98 g of ferric oxide and 1.42 g of sucrose, adding the materials into a sand mill, grinding for 3h at the rotating speed of 2000rpm, spray-drying, slowly heating up to 680 ℃ at the heating rate of 0.1 ℃/min under the protection of nitrogen, keeping the temperature for 5h, and naturally cooling to obtain the LiFePO4An active component of the structure/C, the particle diameter D of the active component500.58 μm;
(2) 0.58 g of aluminum nitrate nonahydrate are weighed out, 1L of water and 15.75 g of the above-mentioned LiFePO are added4Stirring active component with structure for 30min, spray drying, slowly heating at 30 deg.C/min under nitrogen protection to 500 deg.C, directly cooling without heat preservation, forming amorphous aluminum oxide coating layer on the surface of active component to obtain final productObtaining an intermediate product, wherein the thickness of the coating layer is 3.9 nm;
(3) weighing 1.16 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray-drying, slowly heating to 700 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, keeping the temperature for 3h, cooling, and coating a conductive carbon layer on the surface of the intermediate product to obtain a final product P1, wherein the thickness of the conductive carbon layer is 8.2 nm.
(4) The above-mentioned final product P1 was examined using a transmission electron microscope tester of Japanese Electron JEM-2010(HR) type. And (3) testing conditions are as follows: under the conditions of accelerating voltage of 200KV and vacuum degree less than 2X 10-5Pa. The test method comprises the following steps: dispersing the final product P1 in an ethanol solution, performing ultrasonic dispersion for 30min, dropwise adding onto a copper net, and performing vacuum drying for 2 h.
And (3) testing results: a TEM spectrum of the particle morphology of P1 prepared in preparation example 1 is shown in fig. 1, and it is obvious that in fig. 1, two coating layers are provided on the surface of the active component, the inner layer is an amorphous metal compound coating layer (with low water absorption) and the outer layer is a conductive carbon layer (with good conductivity), and the presence of the two coating layers is beneficial to promoting that the prepared lithium iron manganese phosphate material has low water absorption and good conductivity.
Preparation example 2
For illustrating the lithium iron manganese phosphate material of the present invention and the method for preparing the same (wherein the amorphous metal compound is amorphous lithium phosphate)
(1) Weighing 3.69 g of lithium carbonate, 11.50 g of ammonium dihydrogen phosphate, 7.98 g of ferric oxide and 1.42 g of sucrose, adding the materials into a sand mill, grinding for 3h at the rotating speed of 2000rpm, spray-drying, slowly heating at the temperature of 800 ℃ at the heating rate of 2 ℃/min under the protection of nitrogen, keeping the temperature for 20h, and naturally cooling to obtain the LiFePO4An active component of the structure/C, the particle diameter D of the active component500.61 μm;
(2) weighing 0.16 g of phosphoric acid (with the content of 85 wt%) and 0.17 g of lithium hydroxide monohydrate, adding 1L of water and 15.78 g of the active component, stirring for 30min, spray-drying, slowly heating to 300 ℃ at the heating rate of 80 ℃/min under the protection of nitrogen, directly cooling without heat preservation, forming an amorphous lithium phosphate coating layer on the surface of the active component, and obtaining an intermediate product, wherein the thickness of the coating layer in the obtained intermediate product is 3.5 nm;
(3) weighing 1.16 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray drying, slowly heating to 600 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, preserving heat for 10h, and cooling to obtain a final product P2, wherein the thickness of the conductive carbon layer is 8.2 nm.
Preparation example 3
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous lithium pyrophosphate)
(1) Weighing 3.69 g of lithium carbonate, 18.68 g of ferric phosphate dihydrate and 1.42 g of cane sugar, adding the materials into a sand mill, grinding for 3h at the rotating speed of 1000rpm, spray-drying, slowly heating up to 800 ℃ at the heating rate of 0.1 ℃/min under the protection of nitrogen, keeping the temperature for 5h, and naturally cooling to obtain the LiFePO4An active component of the structure/C, the particle diameter D of the active component500.75 μm;
(2) weighing 0.31 g of phosphoric acid (with the content of 85 wt%) and 0.34 g of lithium hydroxide, adding 1L of water and 15.75 g of the active component, stirring for 30min, carrying out spray drying, slowly heating to 500 ℃ at the heating rate of 30 ℃/min under the protection of nitrogen, and directly cooling without heat preservation to form an amorphous lithium pyrophosphate coating layer on the surface of the active component to obtain an intermediate product, wherein the thickness of the amorphous lithium pyrophosphate coating layer is 2.4 nm;
(3) weighing 1.0 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray-drying, slowly heating to 750 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, keeping the temperature for 6h, cooling, and coating a conductive carbon layer on the surface of the intermediate product to obtain a final product P3, wherein the thickness of the conductive carbon layer is 7.1 nm.
Preparation example 4
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous ferric pyrophosphate)
(1) Similar to step (1) of preparation example 3, a catalyst having LiFePO was obtained4An active component of the structure/C, the particle diameter D of the active component500.74 μm;
(2) weighing 0.24 g of ferric phosphate dihydrate, adding 1L of water and 15.75 g of the active component, stirring for 30min, spray-drying, slowly heating to 700 ℃ at a heating rate of 30 ℃/min under the protection of nitrogen, and directly cooling without heat preservation to form an amorphous ferric pyrophosphate coating on the surface of the active component to obtain an intermediate product, wherein the thickness of the coating is 2.1 nm;
(3) weighing 1.16 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray-drying, slowly heating to 700 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, keeping the temperature for 10h, cooling, and coating a conductive carbon layer on the surface of the intermediate product to obtain a final product P4, wherein the thickness of the conductive carbon layer is 7.0 nm.
Preparation example 5
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous ferrous lithium pyrophosphate)
(1) Similar to step (1) of preparation example 3, a catalyst having LiFePO was obtained4An active component of the structure/C, the particle diameter D of the active component500.74 μm;
(2) weighing 0.10 g of ferric phosphate dihydrate, 0.08 g of phosphoric acid (content: 85 wt%) and 0.02 g of lithium carbonate, adding 1L of water and 15.75 g of the active component, stirring for 30min, carrying out spray drying, slowly heating to 500 ℃ at a heating rate of 30 ℃/min under the protection of nitrogen, directly cooling without heat preservation to form an amorphous lithium iron pyrophosphate coating layer on the surface of the active component, and obtaining an intermediate product, wherein the thickness of the coating layer is 1.4 nm;
(3) weighing 0.50 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray-drying, slowly heating to 700 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, keeping the temperature for 10h, cooling, and coating a conductive carbon layer on the surface of the intermediate product to obtain a final product P5, wherein the thickness of the conductive carbon layer is 3.5 nm.
Preparation example 6
For illustrating the lithium manganese iron phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous lithium manganese pyrophosphate)
(1) Obtained in the same manner as in step (1) of production example 3Having LiFePO4An active component of the structure/C, the particle diameter D of the active component500.75 μm;
(2) weighing 0.12 g of manganese carbonate, 0.12 g of phosphoric acid (with the content of 85 wt%) and 0.07 g of lithium carbonate, adding 1L of water and 15.75 g of the active components, stirring for 30min, carrying out spray drying, slowly heating at the heating rate of 30 ℃/min under the protection of nitrogen, and directly cooling without heat preservation to form an amorphous lithium manganese pyrophosphate coating layer on the surface of the active components to obtain an intermediate product, wherein the thickness of the coating layer is 1.4 nm;
(3) weighing 1.00 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray-drying, slowly heating to 700 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, keeping the temperature for 10h, cooling, and coating a conductive carbon layer on the surface of the intermediate product to obtain a final product P6, wherein the thickness of the conductive carbon layer is 7.1 nm.
Preparation example 7
For illustrating the lithium iron manganese phosphate material of the present invention and the preparation method thereof (wherein the amorphous metal compound is amorphous silver oxide)
(1) Similar to step (1) of preparation example 3, a catalyst having LiFePO was obtained4An active component of the structure/C, the particle diameter D of the active component500.75 μm;
(2) weighing 0.08 g of silver oxide, adding 1L of water and 15.78 g of the active component, stirring for 30min, spray-drying, slowly heating to 500 ℃ at the heating rate of 30 ℃/min under the protection of nitrogen, and directly cooling to form an amorphous silver oxide coating layer on the surface of the active component without heat preservation to obtain an intermediate product, wherein the thickness of the coating layer is 1.2 nm;
(3) weighing 1.0 g of sucrose, adding 100mL of water and 15.75 g of the intermediate product, stirring for 30min, spray-drying, slowly heating to 700 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, keeping the temperature for 10h, cooling, and coating a conductive carbon layer on the surface of the intermediate product to obtain a final product P7, wherein the thickness of the conductive carbon layer is 6.0 nm.
Preparation example 8
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous ferric pyrophosphate)
The preparation method of the lithium manganese iron phosphate material comprises the following steps: with reference to preparation 3, the difference is:
(1) weighing 3.69 g of lithium carbonate, 4.60 g of manganese carbonate, 9.34 g of iron phosphate, 1.19 g of cobalt carbonate and 1.42 g of cane sugar, adding the materials into a sand mill, grinding for 3h at the rotating speed of 1000rpm, spray-drying, slowly heating up to 750 ℃ at the heating rate of 0.1 ℃/min under the protection of nitrogen, keeping the temperature for 5h, and naturally cooling to obtain the LiMn-containing material0.4Fe0.5Co0.1PO4Active ingredient of structure, particle diameter D of the active ingredient500.76 μm; the final product obtained from this process was designated P8.
Preparation example 9
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous ferric pyrophosphate)
The preparation method of the lithium manganese iron phosphate material comprises the following steps: with reference to preparation 3, the difference is:
in the step (1), the temperature is slowly raised to 800 ℃ at the heating rate of 3 ℃/min, the temperature is kept for 5h, and the LiFePO is obtained after natural cooling4An active component of the structure/C, the particle diameter D of the active component50It was 0.77 μm. The final product obtained from this process was designated P9.
Preparation examples 10 to 11
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous ferric pyrophosphate)
The preparation method of the lithium manganese iron phosphate material comprises the following steps: with reference to preparation 3, the difference is:
in the step (2), the temperature is slowly raised to 500 ℃ at the heating rates of 20 ℃/min and 100 ℃/min respectively, and the temperature is directly lowered without heat preservation to form an amorphous lithium pyrophosphate coating layer on the surface of the active component, so as to obtain an intermediate product, wherein the thicknesses of the amorphous lithium pyrophosphate coating layer are 2.2nm and 2.9nm respectively. The final products obtained from this process are designated P10 and P11.
Preparation example 12
For illustrating the lithium iron manganese phosphate material and the preparation method thereof (wherein the amorphous metal compound is amorphous ferric pyrophosphate)
The preparation method of the lithium manganese iron phosphate material comprises the following steps: with reference to preparation 3, the difference is:
in the step (3), the temperature is slowly increased to 750 ℃ at the temperature increase rate of 15 ℃/min, the temperature is kept for 6h, the temperature is reduced, and a conductive carbon layer is coated on the surface of the intermediate product to obtain a final product P12, wherein the thickness of the conductive carbon layer is 6.8 nm. The final product obtained from this process was designated P12.
Comparative preparation example 1
For comparison, the lithium iron manganese phosphate material and the preparation method thereof
(1) The same procedure as in step (1) of example 1 gave a catalyst having a composition of LiFePO4An active component of structure;
(2) weighing 1.16 g of sucrose, adding 100mL of water and 15.75 g of the active components, stirring for 30min, spray drying, slowly heating to 700 ℃ at the heating rate of 5 ℃/min under the protection of nitrogen, keeping the temperature for 3h, and cooling to obtain a final product DP 1.
(3) The above-mentioned final product P1 was examined using a transmission electron microscope tester of Japanese Electron JEM-2010(HR) type. And (3) testing conditions are as follows: under the conditions of accelerating voltage of 200KV and vacuum degree less than 2X 10-5Pa. The test method comprises the following steps: dispersing the final product DP1 in ethanol solution, ultrasonically dispersing for 30min, dripping on a copper net, and vacuum drying for 2 h.
And (3) testing results: the TEM pattern of the particle morphology of DP1 prepared in comparative preparation example 1 is shown in fig. 2, and it is apparent in fig. 2 that there is a conductive carbon coating layer on the surface of the active component, in which there is no amorphous metal compound coating layer. The lithium iron manganese phosphate material with such a structure has no amorphous metal compound coating layer although the thickness of the conductive carbon layer is increased, and when the material is in contact with water, water can still easily permeate through the carbon layer to be combined with Li in the material.
Comparative preparation example 2
The lithium iron manganese phosphate material prepared by the method in the embodiment 1 of the chinese patent application with the application number of 200910053346 is referred to as DP 2.
Comparative preparation example 3
Refer to the lithium iron manganese phosphate material prepared by the method in example 1 of chinese patent application No.200910044154, and is designated as DP 3.
Second, examples 1 to 12 and comparative examples 1 to 3
The positive electrode of the invention and the method for producing the same are explained.
The preparation method comprises the following steps: lithium iron manganese phosphate material, acetylene black and polyvinylidene fluoride (obtained from Qingfeng plastic raw material Co., Ltd., Dongguan, with the trademark of FR900) are dissolved in N-methyl pyrrolidone according to the weight ratio of 80:10:10 to form battery slurry with the solid content of 50 wt%, the slurry obtained after uniform stirring is coated on an aluminum foil with the thickness of 25 mu m, and the aluminum foil is baked at the temperature of 110 +/-5 ℃ to form a material layer with the thickness of 20 mu m, so that the anode material is obtained. The prepared positive electrode and the lithium iron manganese phosphate material contained therein are in a comparison relationship as shown in table 1.
Table 1.
Positive electrode material Lithium manganese iron phosphate material Positive electrode material Lithium manganese iron phosphate material
S1 P1 S2 P2
S3 P3 S4 P4
S5 P5 S6 P6
S7 P7 S8 P8
S9 P9 S10 P10
S11 P11 S12 P12
DS1 DP1 DS2 DP2
DS3 DP3
And (3) testing:
lithium iron manganese phosphate-based materials P1-P12 and DP1-DP3 prepared in preparation examples 1 to 12 of the present invention and comparative preparation examples 1 to 3, respectively, and positive electrodes S1-S12 and DS1-DS12 prepared in preparation examples 1 to 12 of the present invention and comparative examples 1 to 3 were subjected to performance tests.
(1) The water content of the lithium manganese iron phosphate material is as follows: lithium iron manganese phosphate-based materials were prepared according to the methods in preparation examples 1 to 12 and comparative preparation examples 1 to 3, and the water content of the lithium iron manganese phosphate-based materials was directly tested after sintering and tapping.
The test method comprises the following steps: firstly testing the moisture content M0 of a blank bottle, then weighing 0.2g of a sample, heating to 200 ℃ at a heating rate of 15 ℃/min under the condition that the air flow rate is 40ml/min, and obtaining the total moisture content M1, wherein the moisture content M2 of the lithium iron manganese phosphate material is equal to M1-M0.
And (3) testing results: as shown in table 2:
TABLE 2
Examples Water content (ppm) Examples Water content (ppm)
P1 980.4 P2 863.7
P3 250.3 P4 525.2
P5 343.3 P6 344.6
P7 350.0 P8 258.3
P9 325.6 P10 550.0
P11 725.0 P12 601.2
DP1 3860 DP2 2068.3
DP3 2845.2
(2) Water content of the positive electrode (corresponding to water absorption of the lithium manganese iron phosphate material): the lithium iron manganese phosphate-based materials prepared in preparation examples 1 to 12 and comparative preparation examples 1 to 3 were prepared into positive electrodes within the same time period, and then the water contents of the positive electrodes S1-S12 and DS1-DS3 were measured.
The test method comprises the following steps: the water content N0 of a blank bottle is tested, then 0.2g of a sample is weighed, the temperature is raised to 200 ℃ at the temperature rise rate of 15 ℃/min under the condition that the air flow velocity is 40ml/min, the total water content N1 is obtained, the water absorption rate N2 of the lithium iron manganese phosphate material is equal to N1-N0-M2, and M2 is the water content of the lithium iron manganese phosphate material.
And (3) testing results: as shown in table 3:
table 3.
Examples Water content (%) Examples Water content (%)
S1 876.5 S2 1106.4
S3 412.7 S4 875.4
S5 572.1 S6 574.3
S7 583.3 S8 418.7
S9 1041.7 S10 916.7
S11 1208.3 S12 1002.3
DS1 2880.2 DS2 2106.4
DS3 3670.4
As can be seen from the data in tables 2 and 3: the lithium iron manganese phosphate materials prepared in examples 1 to 12 according to the preparation method of the present invention have low water content and low water absorption, which are significantly superior to those of the lithium iron manganese phosphate materials prepared in comparative examples 1 to 3.
Third, practical application examples 1-12 and comparative application examples 1-3
For illustrating the lithium battery and the method of manufacturing the same according to the present invention.
The preparation method comprises the following steps: examples application of positive electrodes S1-S12 and DS1-DS3 prepared in examples 1 to 12 and comparative examples 1 to 3 were used to fabricate lithium ion monolithic batteries T1-T12 and DT1-DT3, in which the negative electrode material was graphite, the separator material was PVDF (polyvinylidene fluoride, a product commercially available from Achima (orthodox) fluorine chemical Co., Ltd., No. PVDF HSV 900), and the electrolyte was 1 mol/iPF6(EC + DMC) (where LiPF6 is lithium hexafluorophosphate, EC is ethylene carbonate, DMC is dimethyl carbonate, and the volume ratio of EC to DMC is 1: 1).
The prepared lithium battery and the positive electrode material contained therein were compared as shown in table 4.
Table 4.
Positive electrode material Lithium manganese iron phosphate material Positive electrode material Lithium manganese iron phosphate material
T1 S1 T2 S2
T3 S3 T4 S4
T5 S5 T6 S6
T7 S7 T8 S8
T9 S9 T10 S10
T11 S11 T12 S12
DT1 DS1 DT2 DS2
DT3 DS3
And (3) testing:
the lithium batteries T1-T12 and DT1-DT3 prepared in practical application examples 1-12 and comparative application examples 1-3 were subjected to performance tests, respectively.
(1) Test items and methods:
firstly, the specific capacity of mass: the prepared lithium ion batteries are respectively placed on a test cabinet, constant-current and constant-voltage charging is firstly carried out at 0.1C, the charging range is 2.5-4.35V, the first discharging capacity of the batteries is recorded, the discharging capacity of the batteries is recorded again, and the mass specific capacity of the batteries is calculated according to the following formula.
The specific mass capacity is equal to the first discharge capacity (milliamp hour)/weight (gram) of the positive electrode material.
② capacity retention ratio of lithium battery stored at high temperature (60 ℃) for 25 days: firstly, charging and discharging the battery for one week under the current of 0.1C, and recording the discharge capacity C0; and fully charging the battery at 0.1 ℃, storing the battery in a 65 ℃ oven at a high temperature for 7 days, taking out the battery, cooling the battery, discharging the battery until the voltage is cut off to 2.5V, and recording the residual capacity C1, wherein the high-temperature capacity retention rate is (C0/C1) × 100%.
(3) And (3) testing results: as shown in table 5:
table 5.
Figure BDA0000863163990000251
As can be seen from the data in table 5, the initial capacity of the batteries T1-T3 prepared by applying examples 1 to 12 according to the embodiment of the present invention has an adverse effect (see the mass specific capacity data), and has an excellent high-temperature capacity retention rate; the initial capacity of the batteries DT1-DT3 prepared according to comparative application examples 1 to 3 was significantly affected, and the high-temperature capacity retention rate was relatively poor.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (13)

1. The lithium iron manganese phosphate material is characterized by comprising LiMnxFe1-x- yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti; and a coating layer coated on the surface of the active component, wherein the coating layer contains an amorphous metal compound,
the particle size D50 of the active component is 0.5-1.0 μm, and the thickness of the coating layer is 1-5 nm;
the lithium iron manganese phosphate material also comprises a conductive carbon layer coated on the surface of the coating layer;
the amorphous metal compound is selected from one or a mixture of more of amorphous ferric pyrophosphate, amorphous ferrous lithium pyrophosphate, amorphous manganese lithium pyrophosphate and amorphous silver oxide;
the thickness of the conductive carbon layer is 2-10 nm;
the compound has LiMnxFe1-x-yMyPO4In the active component of the structure/C, the molar ratio of Li to the sum of Mn, Fe and M is 0.98-1.02: 1;
the content of the C element in the active component is 0.5-3.5 wt% of the total weight of the active component.
2. The preparation method of the lithium iron manganese phosphate-based material according to claim 1, comprising the steps of:
s1, providing LiMnxFe1-x-yMyPO4The active component of the structure/C, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and M is one or more of Co, Ni, Mg, Zn, V and Ti;
and S2, taking the active component as a base material, and forming a coating layer containing an amorphous metal compound on the surface of the active component.
3. The preparation method according to claim 2, wherein the preparation method of the active ingredient in S1 comprises the following steps:
s11, mixing a lithium source, an optional iron source, an optional manganese source, an optional M source, a phosphorus source and a first carbon source in proportion, and drying to obtain a first dry mixture;
s12, sintering the first dry mixture at 600-800 ℃ for 5-30h at constant temperature to form the active component.
4. The preparation method as claimed in claim 3, wherein the first dry mixture is heated to 600-800 ℃ at a rate of 0.1-2 ℃/min in the S12.
5. The preparation method according to claim 3, wherein in the S11, the molar ratio of the lithium source calculated as Li to the optional iron source, the optional manganese source and the optional M source calculated as Fe + Mn + M is 0.98-1.02: 1.
6. the preparation method according to claim 2, wherein the S2 includes the steps of:
s21, mixing the active component with a material source for forming the amorphous metal compound, and drying to obtain a second dry mixture;
s22, heating the second dry mixture to 300-500 ℃ and directly cooling without heat preservation to form the coating layer containing the amorphous metal compound on the surface of the active component.
7. The preparation method as claimed in claim 6, wherein the temperature of the second dry mixture in the step S22 is raised to 300-500 ℃ at a rate of 30-80 ℃/min.
8. The method of manufacturing of claim 2, wherein the method of manufacturing further comprises the steps of:
s3, mixing the intermediate product obtained in the S2 with a second carbon source, drying to obtain a third dry mixture, heating the third dry mixture to 600-750 ℃, and then preserving heat for 3-10h to form a conductive carbon layer on the surface of the intermediate product.
9. The preparation method as claimed in claim 8, wherein the third dry mixture is heated to 600-750 ℃ at a rate of 2-10 ℃/min in the S3.
10. A lithium iron manganese phosphate-based material, characterized in that the lithium iron manganese phosphate-based material is prepared by the preparation method of any one of claims 2 to 9.
11. A battery paste comprising a lithium iron manganese phosphate-based material and a solvent, characterized in that the lithium iron manganese phosphate-based material is the lithium iron manganese phosphate-based material of claim 1 or 10.
12. A positive electrode comprising a current collector and a positive active material layer disposed on the current collector, characterized in that the positive active material layer comprises the lithium iron manganese phosphate-based material of claim 1 or 10.
13. A lithium battery having a positive electrode mounted therein, wherein the positive electrode material comprises the positive electrode according to claim 12.
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Families Citing this family (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107128892A (en) * 2017-06-12 2017-09-05 百川化工(如皋)有限公司 A kind of preparation method of lithium iron manganese phosphate anode material
CN107623117B (en) * 2017-10-10 2020-12-11 合肥国轩高科动力能源有限公司 Preparation method of high-capacity and high-tap-density lithium iron phosphate material
CN110400917A (en) * 2019-05-31 2019-11-01 宜春天赐高新材料有限公司 A kind of high capacity type lithium ferric manganese phosphate positive electrode and preparation method thereof
CN111180702B (en) * 2020-01-06 2021-08-20 天能帅福得能源股份有限公司 Preparation method of coated lithium manganate positive electrode material and positive electrode material thereof
CN114256448A (en) * 2020-09-25 2022-03-29 比亚迪股份有限公司 Lithium iron manganese phosphate composite material, preparation method thereof and lithium ion battery
CN112117452B (en) * 2020-10-09 2023-07-28 中伟新材料股份有限公司 Positive electrode material coating agent and preparation method thereof, lithium ion battery positive electrode material, lithium ion battery and electric equipment
CN112456560B (en) * 2020-12-09 2023-03-21 安徽科技学院 Preparation method of two-dimensional manganese oxide material formed by self-assembly of nanoparticles
WO2023066394A1 (en) * 2021-10-22 2023-04-27 宁德时代新能源科技股份有限公司 Positive electrode active material, positive electrode sheet, secondary battery, battery module, battery pack, and electric device
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EP4358187A1 (en) * 2022-03-31 2024-04-24 Contemporary Amperex Technology Co., Limited Positive electrode plate, secondary battery, battery module, battery pack, and electric apparatus
CN117678092A (en) * 2022-03-31 2024-03-08 宁德时代新能源科技股份有限公司 Positive electrode sheet, secondary battery and electricity utilization device
CN117223130A (en) * 2022-04-01 2023-12-12 宁德时代新能源科技股份有限公司 Positive electrode active material composition, positive electrode sheet, secondary battery, battery module, battery pack, and electric device
WO2023184495A1 (en) * 2022-04-01 2023-10-05 宁德时代新能源科技股份有限公司 Positive electrode active material, method for preparing same and positive electrode sheet comprising same, secondary battery, and electrical device
EP4280311A1 (en) * 2022-04-01 2023-11-22 Contemporary Amperex Technology Co., Limited Positive-electrode active material composition, positive electrode plate, secondary battery, battery module, battery pack and electric apparatus
WO2023184504A1 (en) * 2022-04-01 2023-10-05 宁德时代新能源科技股份有限公司 Positive electrode active material and preparation method therefor, positive electrode plate comprising same, secondary battery and electric device
CN117321800A (en) * 2022-04-01 2023-12-29 宁德时代新能源科技股份有限公司 Secondary battery, battery module, battery pack, and power consumption device
WO2023206379A1 (en) * 2022-04-29 2023-11-02 宁德时代新能源科技股份有限公司 Secondary battery, battery module, battery pack, and electrical device
CN114899371B (en) * 2022-04-29 2024-03-19 深圳市德方纳米科技股份有限公司 Low-water-content positive electrode material, preparation method thereof and lithium ion battery
CN117461167A (en) * 2022-05-24 2024-01-26 宁德时代新能源科技股份有限公司 Positive electrode active material, positive electrode sheet, secondary battery, battery module, battery pack, and electricity device
EP4318655A1 (en) * 2022-06-17 2024-02-07 Contemporary Amperex Technology Co., Limited Positive electrode active material and preparation method therefor, positive electrode sheet, secondary battery, battery module, battery pack and electrical device
WO2023245682A1 (en) * 2022-06-24 2023-12-28 宁德时代新能源科技股份有限公司 Positive electrode material composition and preparation method therefor, positive electrode sheet comprising positive electrode material composition, secondary battery, and electrical device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102769131A (en) * 2012-05-10 2012-11-07 浙江瓦力新能源科技有限公司 Method for preparing manganese phosphate lithium / carbon composite material
CN104011913A (en) * 2012-01-26 2014-08-27 Jx日矿日石金属株式会社 Cathode active material for lithium ion battery, cathode for lithium ion battery, and lithium ion battery
CN104852035A (en) * 2015-04-28 2015-08-19 湖南瑞翔新材料股份有限公司 Preparation method of alumina coated lithium titanate

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2111659A2 (en) * 2007-01-25 2009-10-28 Massachusetts Institute of Technology Oxide coatings on lithium oxide particles
CN103441269B (en) * 2013-08-05 2016-08-17 北大先行科技产业有限公司 A kind of pyrophosphoric acid lithium/carbon-coated lithium iron phosphate composite and preparation method thereof
CN103730657B (en) * 2014-01-09 2016-05-18 北大先行科技产业有限公司 A kind of preparation method of lithium phosphate/carbon-coated lithium iron phosphate composite

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104011913A (en) * 2012-01-26 2014-08-27 Jx日矿日石金属株式会社 Cathode active material for lithium ion battery, cathode for lithium ion battery, and lithium ion battery
CN102769131A (en) * 2012-05-10 2012-11-07 浙江瓦力新能源科技有限公司 Method for preparing manganese phosphate lithium / carbon composite material
CN104852035A (en) * 2015-04-28 2015-08-19 湖南瑞翔新材料股份有限公司 Preparation method of alumina coated lithium titanate

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"纳米Al2O3包覆改性LiFePO4/C正极材料的电化学性能";赵世玺等;《第十六届全国固态离子学学术会议暨下一代能源材料与技术国际研讨会-会议论文摘要集》;20120706;第A25页 *
赵世玺等."纳米Al2O3包覆改性LiFePO4/C正极材料的电化学性能".《第十六届全国固态离子学学术会议暨下一代能源材料与技术国际研讨会-会议论文摘要集》.2012, *

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