WO2024130851A1 - Matériau d'électrode positive à double revêtement, son procédé de préparation et son utilisation - Google Patents

Matériau d'électrode positive à double revêtement, son procédé de préparation et son utilisation Download PDF

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WO2024130851A1
WO2024130851A1 PCT/CN2023/079171 CN2023079171W WO2024130851A1 WO 2024130851 A1 WO2024130851 A1 WO 2024130851A1 CN 2023079171 W CN2023079171 W CN 2023079171W WO 2024130851 A1 WO2024130851 A1 WO 2024130851A1
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positive electrode
electrode material
manganese
coating layer
double
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PCT/CN2023/079171
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Chinese (zh)
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余海军
李长东
谢英豪
李爱霞
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广东邦普循环科技有限公司
湖南邦普循环科技有限公司
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Publication of WO2024130851A1 publication Critical patent/WO2024130851A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • H01M4/36—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
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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

Definitions

  • the present application belongs to the field of electrode materials, and specifically relates to a double-coated positive electrode material and a preparation method and application thereof.
  • lithium iron manganese phosphate As an advanced version of lithium iron phosphate, has received more and more attention. Compared with lithium iron phosphate, lithium iron manganese phosphate has an additional "manganese" element. Manganese has the characteristic of high voltage. Introducing manganese into the positive electrode material can increase the voltage. The higher the voltage, the higher the energy density. The voltage platform of lithium iron manganese phosphate is as high as 4.1V, which is much higher than the 3.4V of lithium iron phosphate. Therefore, its theoretical energy density under the same conditions can be more than 15% higher than that of lithium iron phosphate, and it has a good development prospect. However, manganese is a metal element with very poor conductivity, so the conductivity of lithium iron manganese phosphate is further reduced compared with lithium iron phosphate, and the electronic conductivity is only 10-13 S/cm.
  • CN102738465B discloses a method for preparing a lithium iron manganese phosphate positive electrode composite material, wherein a lithium source, a trivalent iron source, manganese dioxide and a carbon source are placed in a ball mill, and an appropriate amount of a dispersant and a complexing agent are added. Then, the ball mill is placed on a ball mill and ball milled at 200-500r/min for 4-6h; the mixed material obtained after ball milling is dried and ground again to obtain a LiMn x Fe 1-x PO 4 precursor; and the carbon-coated lithium iron manganese phosphate positive electrode material is obtained after calcination.
  • CN111900344B discloses a method for preparing a carbon-coated lithium manganese iron phosphate positive electrode material.
  • a transition metal salt solution A, a phosphorus solution B and an ammonia solution C are prepared according to the molar ratio of Mn to Fe and are simultaneously added dropwise.
  • into a reactor to prepare a precursor of lithium iron manganese phosphate positive electrode material; then the precursor is matched with a lithium source according to a molar ratio, and a coating carbon source and a doped metal compound are added, and calcined under inert atmosphere protection to obtain a carbon-coated lithium iron manganese phosphate positive electrode material.
  • the above method uses a simple solid phase coating, which makes it difficult to form a uniform coating layer on the surface, and the coating layer is easy to fall off during the cycle.
  • CN109888205A discloses a nano-micro spherical carbon-coated lithium manganese iron phosphate composite material and preparation method, lithium battery positive electrode material, and lithium battery.
  • the composite material includes lithium manganese iron phosphate and an outer carbon layer coated on the outside of the lithium manganese iron phosphate.
  • the chemical composition of the lithium manganese iron phosphate is LiMn 1-x Fe x PO 4 , wherein 0.1 ⁇ x ⁇ 1, the particle size D50 of the composite material is 1 to 10 ⁇ m, and the mass content of carbon in the lithium manganese iron phosphate is 1% to 10%.
  • the patent uses nano-spherical lithium manganese iron phosphate, which is difficult to form a uniform coating on the surface, but will aggravate the shedding of the coating during the cycle.
  • the purpose of the present application is to provide a double-coated positive electrode material and a preparation method and application thereof.
  • the present application uses a manganese-containing positive electrode material as the core, a boron coating layer coated on the surface of the core as the first shell layer, and a carbon coating layer coated on the surface of the first shell layer as the second shell layer, thereby forming a double-coated positive electrode material.
  • the boron coating layer as the first shell layer can not only improve the conductivity and structural stability of the positive electrode material, but also, under the action of the boron coating layer, the interaction between the carbon coating layer and the core of the manganese-containing positive electrode material is enhanced, so that the carbon coating layer is uniformly coated, which effectively improves the conductivity of the double-coated positive electrode material.
  • the double-coated positive electrode material can maintain a high capacity at a high rate, and has excellent High rate capacity retention.
  • the present application provides a double-coated positive electrode material, the double-coated positive electrode material comprising a manganese-containing positive electrode material core, and a first shell layer and a second shell layer sequentially coated on the surface of the core;
  • the first shell layer is a boron coating layer
  • the second shell layer is a carbon coating layer
  • the present application uses a manganese-containing positive electrode material as the core, a boron coating layer coated on the surface of the core as the first shell layer, and a carbon coating layer coated on the surface of the first shell layer as the second shell layer, thereby forming a double-coated positive electrode material.
  • the boron coating layer is used as the first shell layer, and the boron therein can form an Mn-B bond with the manganese in the core, thereby improving the electrical conductivity of the material, and at the same time, it can also prevent Mn from leaving the surface of the positive electrode material during the charge and discharge process, and stabilize the structure of the material; in addition, the boron coating layer, as an intermediate layer between the core and the carbon coating layer, plays an important bridging role.
  • the interaction between the carbon coating layer and the core of the manganese-containing positive electrode material is enhanced, so that the carbon coating layer can be uniformly coated, effectively improving the electrical conductivity of the double-coated positive electrode material, and at the same time, the double-coated positive electrode material can maintain a high capacity at a high rate, and has an excellent high-rate capacity retention rate.
  • the core of the manganese-containing positive electrode material has poor affinity with the carbon coating layer. If a boron coating layer is not added, it is difficult to obtain a uniform carbon coating layer, and the carbon coating layer is easily detached from the manganese-containing positive electrode material during the cycle.
  • the mass fraction of the boron coating layer is 1-3%, for example, it can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%, etc.
  • the mass fraction of the boron coating layer is too low, it will affect the uniformity of the subsequent carbon coating layer, resulting in the inability to improve the conductivity and rate performance of the material; if the mass fraction of the boron coating layer is too high, it will affect the gram capacity.
  • the mass ratio of the boron coating layer to the carbon coating layer is 1:(0.5-2), for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.
  • the mass ratio of the boron coating layer to the carbon coating layer is too small, that is, the proportion of the boron coating layer is too low, it is difficult to form a uniform carbon coating layer, resulting in reduced conductivity; if the mass ratio of the boron coating layer to the carbon coating layer is too large, that is, the proportion of the boron coating layer is too high, then because the conductivity of boron is lower than that of carbon, the conductivity of the material will be reduced.
  • the mass content of the manganese-containing positive electrode material core is 91-98.5%, for example, it can be 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 98.5%, etc.
  • the manganese-containing positive electrode material includes any one of lithium iron manganese phosphate, lithium manganate or lithium-rich manganese-based materials, preferably lithium iron manganese phosphate.
  • the present application provides a method for preparing the double-coated positive electrode material as described in the first aspect, the preparation method comprising the following steps:
  • step (1) The intermediate product of step (1) is mixed with a carbon source, and then subjected to secondary calcination to obtain the double-coated positive electrode material.
  • the surface coating of the manganese-containing positive electrode material with boron can enhance the interaction between the carbon source and the manganese-containing positive electrode material, so that the carbon source can be evenly coated on the surface of the intermediate product to form a uniform carbon coating layer, thereby significantly improving the conductivity of the double-coated positive electrode material and improving the electrochemical properties of the material.
  • the boron source is a boron-based Lewis acid.
  • boryl Lewis acids can attract groups with lone pairs of electrons.
  • the boron-based Lewis acid comprises any one of boric acid, borate or boron oxide or at least A combination of at least two, illustratively, the borate may be, for example, lithium borate, manganese borate, sodium tetraborate or iron borate.
  • the mass content of the boron source is 1-5%, for example, 1%, 2%, 3%, 4% or 5%.
  • the carbon source is an organic carbon source.
  • the boron-based Lewis acid can attract organic carbon sources with groups having lone pair electrons, thereby enhancing the interaction between the organic carbon source and lithium manganese iron phosphate, so that the organic carbon source can be evenly coated on the surface of the boron coating layer, effectively improving the conductivity of the double-coated positive electrode material.
  • the functional group of the organic carbon source includes any one of a hydroxyl group, an imino group or an amino group, or a combination of at least two of them.
  • the organic carbon source may be glucose or 2-mercaptoimidazole.
  • the mass content of the carbon source is 1-6%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%, etc.
  • the mass content of the carbon source is too high, the formed carbon coating layer will be too thick, which will reduce the gram capacity of the positive electrode material; if the mass content of the carbon source is too low, the rate performance of the positive electrode material will be reduced.
  • the raw materials of the manganese-containing positive electrode material include a manganese source, a lithium source, a phosphorus source and an iron source.
  • the manganese source includes any one of manganous carbonate, manganese dioxide, manganese acetate or manganese nitrate, or a combination of at least two thereof.
  • the lithium source includes any one of lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate, or a combination of at least two of them.
  • the phosphorus source includes any one of phosphoric acid, ammonium dihydrogen phosphate or phosphorus pentoxide, or a combination of at least two of them.
  • the iron source includes any one of iron phosphate, iron oxide, iron oxalate or iron sulfate, or a combination of at least two thereof, such as iron phosphate, ferroferric oxide, iron oxalate or iron sulfate.
  • the mixing method in step (1) is ball milling
  • the ball milling speed is 300-600 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm, etc.
  • the ball milling time is 2-8 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h, etc.
  • the mixing method in step (2) is ball milling
  • the ball milling rate is 200-500rpm, for example, it can be 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm or 500rpm, etc.
  • the ball milling time is 2-8h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h or 8h, etc.
  • the primary calcination temperature is 500-600°C, for example, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C.
  • the primary calcination time is 4-10 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h.
  • the temperature of the secondary calcination is 600-800°C, for example, it can be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C or 800°C.
  • the secondary calcination time is 4-10 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h.
  • the atmosphere of the primary calcination and the secondary calcination is an inert atmosphere
  • the gas in the inert atmosphere includes any one of nitrogen, helium or argon, or a combination of at least two of them.
  • the preparation method comprises the following steps:
  • step (2) The intermediate product of step (1) and an organic carbon source having a mass content of 1-6% are mixed at 200-500 rpm. The mixture is ball-milled and mixed for 2-8 hours, and secondary calcined in an inert atmosphere at 600-800° C. for 4-10 hours to obtain the double-coated positive electrode material.
  • the present application provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery includes the double-coated positive electrode material described in the first aspect.
  • the present application provides a double-coated positive electrode material, wherein the double-coated positive electrode material has a manganese-containing positive electrode material as a core, a boron coating layer coated on the surface of the core as a first shell layer, and a carbon coating layer coated on the surface of the first shell layer as a second shell layer.
  • the boron coating layer as the first shell layer can not only improve the conductivity and structural stability of the positive electrode material, but also, under the action of the boron coating layer, the interaction between the carbon coating layer and the core of the manganese-containing positive electrode material is enhanced, so that the carbon coating layer can be uniformly coated, effectively improving the conductivity of the double-coated positive electrode material;
  • the double-coated positive electrode material provided in the present application can maintain a relatively high capacity at a high rate and has an excellent high-rate capacity retention rate.
  • FIG. 1 is a SEM image of the double-coated positive electrode material provided in Example 1 of the present application.
  • FIG2 is a charge and discharge curve diagram of the double-coated positive electrode material provided in Example 1 of the present application.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 96.9%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 2%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:2.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of boron oxide is 1.1%;
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) into a ball mill, adding glucose, and ball milling at 500 rpm for 2 h, and then placing it in a furnace with a nitrogen atmosphere at 800° C. for a second calcination for 10 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of glucose is 5%.
  • FIG1 shows a SEM image of the double-coated positive electrode material provided in this embodiment. It can be seen from the image that the lithium manganese iron phosphate positive electrode material particles prepared in this embodiment are complete and have a uniform particle size distribution.
  • FIG2 shows a charge and discharge curve of the double-coated positive electrode material provided in this embodiment.
  • the gram capacity of the lithium manganese iron phosphate positive electrode material prepared in this embodiment can reach 156.3 mAh/g.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 98.3%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 0.6%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:0.6.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of boron oxide is 1.1%;
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) into a ball mill, adding glucose, and ball milling at 600 rpm for 2 h, and then placing it in a furnace with a nitrogen atmosphere at 800° C. for a second calcination for 10 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of glucose is 1.5%.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 97.1%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 1.8%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:1.8.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of boron oxide is 1.1%;
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) to a ball mill, adding 2-mercaptoimidazole, and ball milling at 600 rpm for 2 h, and then placing it in a furnace with a nitrogen atmosphere at 800° C. for a second calcination for 10 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of 2-mercaptoimidazole is 5%.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 96.9%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 2%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:2.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of boron oxide is 1.1%;
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) into a ball mill, adding glucose, and ball milling at 600 rpm for 2 h, and then placing it in a furnace with a nitrogen atmosphere at 700° C. for a second calcination for 10 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of glucose is 5%.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 96.9%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 2%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:2.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of boron oxide is 1.1%;
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) into a ball mill, adding glucose, and ball milling at 600 rpm for 2 h, and then placing it in a furnace with a nitrogen atmosphere at 800° C. for a second calcination for 10 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of glucose is 5%.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 97.82%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 1.08%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:1.08.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of boric acid is 3.9%
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) to a ball mill, adding 2-mercaptoimidazole, and ball milling at 350 rpm for 5 h, and then placing it in a helium atmosphere furnace at 800° C. for a second calcination for 4 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of 2-mercaptoimidazole is 3%.
  • the present embodiment provides a double-coated positive electrode material, which includes a lithium manganese iron phosphate core, and a boron coating layer and a carbon coating layer sequentially coated on the surface of the core.
  • the mass content of the lithium manganese iron phosphate core is 98.5%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass fraction of the carbon coating layer is 1.5%
  • the mass ratio of the boron coating layer to the carbon coating layer is 1.1:1.5.
  • This embodiment also provides a method for preparing a double-coated positive electrode material, the preparation method comprising the following steps:
  • the mass content of sodium tetraborate is 1.6%;
  • step (2) transferring the boron-coated lithium manganese iron phosphate in step (1) into a ball mill, adding glucose, and ball milling at 200 rpm for 8 h, and then placing it in an argon atmosphere furnace at 600° C. for a second calcination for 7 h, and cooling it to obtain the double-coated positive electrode material;
  • the mass content of glucose is 5%.
  • the mass fraction of the boron coating layer is 0.8%
  • the mass fraction of the carbon coating layer is 1.45%
  • the mass content of the lithium manganese iron phosphate core is 97.75%
  • the mass ratio of the boron coating layer to the carbon coating layer remains unchanged.
  • the mass fraction of the boron coating layer is 3.5%
  • the mass fraction of the carbon coating layer is 5.82%
  • the mass content of the lithium manganese iron phosphate core is 90.68%
  • the mass ratio of the boron coating layer to the carbon coating layer remains unchanged.
  • the mass ratio of the boron coating layer to the carbon coating layer is 1:0.3
  • the mass fraction of the carbon coating layer is 0.33%
  • the mass fraction of the boron coating layer is 1.1%
  • the mass content of the lithium manganese iron phosphate core is 98.57%.
  • the mass ratio of the boron coating layer to the carbon coating layer is 1:3, the mass fraction of the carbon coating layer is 3.3%, the mass fraction of the boron coating layer is 1.1%, and the mass content of the lithium manganese iron phosphate core is 95.6%.
  • Example 5 The difference between this comparative example and Example 5 is that the double-coated positive electrode material does not have a boron coating layer, that is, no boron oxide is added to the raw material in step (1), and the mass content of the lithium manganese iron phosphate core is 98%.
  • Example 5 The difference between this comparative example and Example 5 is that the double-coated positive electrode material does not have a carbon coating layer, that is, only step (1) is performed without step (2), and the mass content of the lithium manganese iron phosphate core is 98.9%.
  • the double-coated positive electrode material is lithium manganese iron phosphate, which is not coated, that is, there is no step (2), and boron oxide is not added in step (1).
  • Example 5 The difference between this comparative example and Example 5 is that the surface of the lithium manganese iron phosphate core is firstly coated with carbon and then with boron.
  • the double-coated positive electrode materials provided by Examples 1-11 and Comparative Examples 1-4 the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1, and a certain amount of organic solvent N-methylpyrrolidone (NMP) is added, and the mixture is stirred and coated on an aluminum foil to form a positive electrode sheet; a metal lithium sheet is used as the negative electrode; the separator is a Celgard2400 polypropylene porous membrane; the solvent in the electrolyte is a solution composed of EC, DMC and EMC in a mass ratio of 1:1:1, the solute is LiPF6 , and the concentration of LiPF6 is 1.0 mol/L; and a 2023 button battery is assembled in a glove box.
  • NMP organic solvent N-methylpyrrolidone
  • the battery was subjected to a charge and discharge cycle performance test, and the discharge specific capacity at 0.2C and 1C was tested within a cut-off voltage range of 2.2-4.3V.
  • the positive electrode material prepared by the method provided in this application has better gram capacity and rate performance. This is because the present solution pre-coates the Lewis acid. Thereby, a uniformly coated carbon coating layer is obtained, and thus, good rate performance can be obtained when a lower mass fraction of the carbon coating layer is used.
  • Example 1 By comparing the data results of Example 1 with those of Examples 8-9, it can be seen that when the mass fraction of the boron coating is too low, the conductivity and rate performance of the material are reduced, but the gram capacity of the material is improved due to the reduction in the total content of inactive substances; and when the mass fraction of the boron coating is too high, because the conductivity of boron is lower than that of carbon, excessive boron will also reduce the conductivity of the coating, affecting the gram capacity and rate performance of the material.
  • Example 1 From the comparison of the data results of Example 1 and Examples 10-11, it can be seen that when the mass ratio of the boron coating layer to the carbon coating layer is too large, since the carbon coating layer content is too low, a uniform carbon coating layer cannot be formed, and the conductivity is reduced. However, since the surface of the positive electrode material has a boron coating layer, it still has good conductivity. When the mass ratio of the boron coating layer to the carbon coating layer is too small, the carbon coating layer is too thick, which will reduce the gram capacity of the material.
  • Example 5 From the comparison of the data results of Example 5 and Comparative Example 1, it can be seen that if the boron coating layer is not added, it is difficult to obtain a uniform carbon coating layer, and the carbon coating layer is easy to fall off from the manganese-containing positive electrode material during the cycle.
  • the present application illustrates the process method of the present application through the above-mentioned embodiments, but the present application is not limited to the above-mentioned process steps, that is, it does not mean that the present application must rely on the above-mentioned process steps to be implemented.
  • Those skilled in the art should understand that any improvement to the present application, equivalent replacement of the raw materials used in the present application, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present application.

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Abstract

La présente demande concerne un matériau d'électrode à double revêtement, ainsi que son procédé de préparation et un son utilisation. Le matériau d'électrode positive à double revêtement comprend un noyau de matériau d'électrode positive contenant du manganèse, et une première couche d'enveloppe et une seconde couche d'enveloppe qui sont séquentiellement revêtues sur la surface du noyau, la première couche d'enveloppe étant une couche de revêtement de bore, et la seconde couche d'enveloppe étant une couche de revêtement de carbone. Dans la présente invention, le matériau d'électrode positive contenant du manganèse est pris en tant que noyau, la couche de revêtement de bore revêtant la surface du noyau est prise en tant que première couche d'enveloppe, et la couche de revêtement de carbone revêtant la surface de la première couche d'enveloppe est prise en tant que seconde couche d'enveloppe, formant ainsi le matériau d'électrode positive à double revêtement. La prise de la couche de revêtement de bore en tant que première couche d'enveloppe peut non seulement améliorer la conductivité et la stabilité structurale du matériau d'électrode positive, mais améliore également l'interaction entre la couche de revêtement de carbone et le noyau de matériau d'électrode positive contenant du manganèse sous l'action de la couche de revêtement de bore, de telle sorte que la couche de revêtement de carbone réalise un revêtement uniforme, et la conductivité du matériau d'électrode positive à double revêtement est efficacement améliorée ; de plus, le matériau d'électrode positive à double revêtement peut maintenir une capacité relativement élevée à une vitesse élevée, et a un bon taux de rétention de capacité à fort grossissement.
PCT/CN2023/079171 2022-12-19 2023-03-02 Matériau d'électrode positive à double revêtement, son procédé de préparation et son utilisation WO2024130851A1 (fr)

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