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WO2024192604A1 - 一种磷酸锰铁锂正极材料及其制备方法与应用 - Google Patents

一种磷酸锰铁锂正极材料及其制备方法与应用 Download PDF

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WO2024192604A1
WO2024192604A1 PCT/CN2023/082364 CN2023082364W WO2024192604A1 WO 2024192604 A1 WO2024192604 A1 WO 2024192604A1 CN 2023082364 W CN2023082364 W CN 2023082364W WO 2024192604 A1 WO2024192604 A1 WO 2024192604A1
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positive electrode
lithium
source
ball milling
electrode material
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PCT/CN2023/082364
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English (en)
French (fr)
Inventor
余海军
谢英豪
李爱霞
李长东
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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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Priority to CN202380008749.8A priority Critical patent/CN116723998A/zh
Priority to PCT/CN2023/082364 priority patent/WO2024192604A1/zh
Publication of WO2024192604A1 publication Critical patent/WO2024192604A1/zh

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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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • H01M4/58—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
    • H01M4/62—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 invention relates to the technical field of lithium ion battery positive electrode materials, and in particular to a lithium manganese iron phosphate positive electrode material and a preparation method and application thereof.
  • Phosphate-based cathode materials have an olivine structure and have high safety performance and cost advantages.
  • lithium iron phosphate has been applied on a large scale in some power battery fields, but its voltage platform is low and its theoretical energy density is low, making it difficult to meet higher demands.
  • lithium iron manganese phosphate can improve its voltage platform and theoretical energy density by utilizing the synergistic effect of manganese and iron.
  • lithium iron manganese phosphate has low electronic conductivity, low lithium ion diffusion rate, and low compaction density, which affects the electrochemical performance and energy density of the battery.
  • the technical solution adopted by the present invention is: a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the added amounts of the lithium source, iron source, manganese source and phosphorus source are calculated according to the stoichiometric ratio of LiFe x Mn 1-x PO 4 , wherein 0.1 ⁇ x ⁇ 0.5; the mass of the carbon source is 1-5% of the total mass of the lithium source, iron source, manganese source, phosphorus source and carbon source.
  • the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium dihydrogen phosphate;
  • the iron source is at least one of ferrous nitrate, ferrous sulfate, ferrous chloride, ferrous oxalate, and ferric phosphate;
  • the manganese source is at least one of manganese carbonate, manganese oxalate, manganese phosphate, manganese sulfate, manganese dioxide, and manganese tetraoxide;
  • the phosphorus source is at least one of iron phosphate, manganese phosphate, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate;
  • the carbon source is at least one of sucrose, fructose, glucose, starch, maltose and citric acid;
  • the emulsifier is one of polyethylene glycol, glycerol fatty acid ester, sucrose fatty acid ester and polyoxyethylene ether.
  • the rotation speed of dry ball milling and wet ball milling is 300-600 r/min, for example, 300 r/min, 350 r/min, 400 r/min, 450 r/min, 500 r/min, 550 r/min or 600 r/min; the total time of dry ball milling and wet ball milling is 3-8 h, for example, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h.
  • step S1 the specific steps of calcining are: placing the ground product in an inert gas atmosphere furnace for sintering, the sintering heating rate is 5-10°C/min, the sintering temperature is 400-500°C, and the sintering time is 3-5h.
  • the inert gas is one of nitrogen, argon and helium.
  • drying temperature is 80-100° C. and the drying time is 3-5 h.
  • step S2 control the ball milling speed and ball milling time in step S2 to obtain a large-particle precursor with a D50 of 0.8-1.5 ⁇ m and a small-particle precursor with a D50 of 0.1-0.4 ⁇ m; for example, the ball milling speed of the large-particle precursor is 300-600 r/min, and the time is 2-5 h; the ball milling speed of the small-particle precursor is 300-600 r/min, and the time is 10-13 h.
  • the method for preparing the starch suspension comprises: adding starch into deionized water and stirring uniformly to obtain a starch suspension;
  • the mass of the cross-linking agent is 0.1-1% of the mass of the starch; the cross-linking agent is sodium trimetaphosphate;
  • the heating temperature is 40-65°C
  • the temperature rising rate is 1-10°C/min
  • the stirring reaction time is 1-3h.
  • Heating at a slow heating rate allows the cross-linking agent to react with starch to form a colloid, which can better disperse the small particle size precursor evenly.
  • the ball milling speed is 300-600 r/min, and the ball milling time is 3-8 h.
  • the mass ratio of the large particle size precursor to the material C is 1-3:1.
  • the mass ratio of the large-particle precursor to the material C within the above-mentioned preferred ratio range can greatly improve the compaction density and electrochemical performance of the lithium manganese iron phosphate positive electrode material.
  • the calcination temperature is 650-800° C.
  • the calcination time is 8-12 h.
  • step S4 the mixture needs to be pre-sintered before calcination, the pre-sintering temperature is 250-350° C., and the pre-sintering time is 3-4 hours.
  • lithium manganese iron phosphate precursors By combining pre-sintering and calcination, bonding, densification, organizational structure changes and rearrangement between lithium manganese iron phosphate precursors can be achieved within different temperature ranges, thereby improving the compaction density and electrochemical properties of lithium manganese iron phosphate positive electrode materials.
  • step S4 both the pre-sintering and the calcining are performed under the protection of an inert gas, and the inert gas is one of nitrogen, argon and helium.
  • the calcined product may be post-processed to further improve the morphology of the lithium manganese iron phosphate positive electrode material.
  • the post-processing steps include crushing, screening, etc.
  • the present invention provides a lithium iron manganese phosphate positive electrode material, and the lithium iron manganese phosphate positive electrode material is prepared by the preparation method of the lithium iron manganese phosphate positive electrode material.
  • the present invention provides a positive electrode sheet, which includes the lithium iron manganese phosphate positive electrode material.
  • the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode sheet.
  • the present invention has the following beneficial effects:
  • the present invention disperses the small-particle precursor with a starch suspension and then dries it to prevent the small-particle precursor from agglomerating. At the same time, the surface of the dried small-particle precursor is coated with starch. During the mixing process with the large-particle precursor, the barrier effect of the starch prevents the small-particle precursor and the large-particle precursor from agglomerating. After uniform mixing, sintering is performed to obtain a lithium iron manganese phosphate positive electrode material with uniform particle size distribution, thereby improving the cycle performance of the lithium iron manganese phosphate positive electrode material.
  • the carbon source forms a carbon coating layer on the surface of the large-particle precursor and the small-particle precursor.
  • the starch coated on the surface of the small-particle precursor will be converted into carbon during the subsequent calcination process, and further forms a carbon coating layer on the surface of the large-particle precursor and the small-particle precursor.
  • the carbon coating layer can not only prevent the lithium manganese iron phosphate positive electrode material from
  • the rich carbon coating on the surface of the lithium manganese iron phosphate positive electrode material provides more pathways for electron transmission, thereby improving the electrochemical performance of the lithium manganese iron phosphate positive electrode material.
  • This embodiment provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 400°C
  • the heating rate was 5°C/min
  • the sintering time was 3h to obtain material B.
  • step S2 placing the material B obtained in step S1 in a ball mill, and obtaining precursors of different particle sizes by controlling the ball milling time at a ball milling speed of 400 r/min; wherein the D 50 of the small particle size precursor is 0.2 ⁇ m, and the ball milling time is 12 h; the D 50 of the large particle size precursor is 0.8 ⁇ m, and the ball milling time is 5 h;
  • the obtained mixed material 2 was placed in a blast furnace for drying, and the obtained dry product was placed in a ball mill jar, and ball milled at a ball mill speed of 400 r/min for 1 h to obtain material C;
  • step S4 The large-particle precursor obtained in step S2 and the material C obtained in step S3 are mixed evenly, and the obtained mixture is sintered under the protection of a nitrogen atmosphere.
  • the sintering is divided into two stages, first calcined at 300°C for 3 hours, and then heated to 650°C for calcination for 12 hours; the sintered material is crushed and sieved to obtain a lithium manganese iron phosphate positive electrode material; wherein the mass ratio of the large-particle precursor to the material C is 2:1.
  • This embodiment also provides a method for preparing a lithium ion battery, comprising the following steps:
  • the lithium iron manganese phosphate positive electrode material obtained in this embodiment, the conductive agent SP, PVDF, are added to N-methylpyrrolidone in a mass ratio of 80:10:10, and the obtained mixture is ball-milled to obtain a positive electrode slurry; the positive electrode slurry is coated on aluminum foil, and vacuum dried to obtain a positive electrode sheet, and 1 mol/L LiPF 6 is used as an electrolyte, Celgard polypropylene film is used as a diaphragm, and a metal lithium sheet is used as a negative electrode to assemble a lithium-ion battery.
  • the electrochemical performance of the battery is tested at a voltage range of 2.5V-4.5V and a rate of 0.1C. The test results are shown in Table 1.
  • This embodiment provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 400°C
  • the heating rate was 5°C/min
  • the sintering time was 3h to obtain material B.
  • step S3 Add 100 mL of deionized water and 3.2 g of starch to a reactor equipped with an ultrasonic device, and stir evenly by ultrasonic stirring to obtain a starch suspension; add the small-particle precursor obtained in step S1 to the starch suspension, and disperse by ultrasonic stirring during the addition process.
  • step S3 After uniform mixing, add 0.05 g of sodium trimetaphosphate, and heat the obtained mixed material 1 to 60° C. at a heating rate of 3° C./min under stirring to completely convert the mixed material 1 into a colloidal mixture, and continue stirring for 0.8 h to disperse the small-particle precursor evenly in the starch colloid: to obtain a mixed material 2;
  • the obtained mixed material 2 is placed in a blast furnace for drying, and the obtained dried product is placed in a ball mill.
  • the material C was obtained by ball milling for 1 h at a ball milling speed of 400 r/min.
  • step S4 The large-particle precursor obtained in step S2 and the material C obtained in step S3 are mixed evenly, and the obtained mixture is sintered under the protection of a nitrogen atmosphere.
  • the sintering is divided into two stages, first calcined at 300°C for 3 hours, and then heated to 650°C for calcination for 12 hours; the sintered material is crushed and sieved to obtain a lithium manganese iron phosphate positive electrode material; wherein the mass ratio of the large-particle precursor to the material C is 3:1.
  • This embodiment provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 400°C
  • the heating rate was 5°C/min
  • the sintering time was 3h to obtain material B.
  • step S2 placing the material B obtained in step S1 in a ball mill, and obtaining precursors of different particle sizes by controlling the ball milling time at a ball milling speed of 400 r/min; wherein the D 50 of the small particle size precursor is 0.1 ⁇ m, and the ball milling time is 13 h; the D 50 of the large particle size precursor is 1.2 ⁇ m, and the ball milling time is 3 h;
  • step S3 Add 100 mL of deionized water and 3.2 g of starch to a reactor equipped with an ultrasonic device, and stir evenly by ultrasonic stirring to obtain a starch suspension; add the small-particle precursor obtained in step S1 to the starch suspension, and disperse by ultrasonic stirring during the addition process. After uniform mixing, add 0.05 g of sodium trimetaphosphate, and heat the obtained mixed material 1 to 45° C. at a heating rate of 3° C./min under stirring to completely convert the mixed material 1 into a colloidal mixture, and continue stirring for 1 h to disperse the small-particle precursor evenly in the starch colloid to obtain a mixed material 2;
  • the obtained mixed material 2 was placed in a blast furnace for drying, and the obtained dry product was placed in a ball mill jar, and ball milled at a ball mill speed of 400 r/min for 1 h to obtain material C;
  • step S4 The large-particle precursor obtained in step S2 and the material C obtained in step S3 are mixed evenly.
  • the compound was sintered under nitrogen atmosphere protection, and the sintering was divided into two stages, first calcined at 300°C for 3 hours, and then heated to 650°C for 12 hours; the sintered material was crushed and sieved to obtain lithium manganese iron phosphate positive electrode material; the mass ratio of the large-particle precursor and material C was 1:1.
  • the preparation method of the battery in this embodiment is different from that in Embodiment 1 only in that the lithium iron manganese phosphate positive electrode material is the lithium iron manganese phosphate positive electrode material obtained in this embodiment.
  • the battery testing method in this embodiment is consistent with that in Embodiment 1.
  • This embodiment provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 450°C
  • the heating rate was 8°C/min
  • the sintering time was 4h to obtain material B.
  • step S2 placing the material B obtained in step S1 in a ball mill, and obtaining precursors of different particle sizes by controlling the ball milling time at a ball milling speed of 400 r/min; wherein the D 50 of the small particle size precursor is 0.2 ⁇ m, and the ball milling time is 12 h; the D 50 of the large particle size precursor is 0.8 ⁇ m, and the ball milling time is 5 h;
  • step S3 Add 100 mL of deionized water and 3.2 g of starch to a reactor equipped with an ultrasonic device, and stir evenly by ultrasonic stirring to obtain a starch suspension; add the small-particle precursor obtained in step S1 to the starch suspension, and disperse by ultrasonic stirring during the addition process.
  • step S3 After uniform mixing, add 0.05 g of sodium trimetaphosphate, and heat the obtained mixed material 1 to 50° C. at a heating rate of 3° C./min under stirring to completely convert the mixed material 1 into a colloidal mixture, and continue stirring for 1 h to disperse the small-particle precursor evenly in the starch colloid to obtain a mixed material 2;
  • the obtained mixed material 2 was placed in a blast furnace for drying, and the obtained dry product was placed in a ball mill jar, and ball milled at a ball mill speed of 400 r/min for 1 h to obtain material C;
  • step S4 The large-particle precursor obtained in step S2 and the material C obtained in step S3 are mixed evenly, and the obtained mixture is sintered under the protection of a nitrogen atmosphere.
  • the sintering is divided into two stages, first calcined at 300°C for 3h, and then heated to 700°C for 10h; the sintered material is crushed and sieved to obtain a lithium manganese iron phosphate positive electrode.
  • the preparation method of the battery in this embodiment is different from that in Embodiment 1 only in that the lithium iron manganese phosphate positive electrode material is the lithium iron manganese phosphate positive electrode material obtained in this embodiment.
  • the battery testing method in this embodiment is consistent with that in Embodiment 1.
  • This embodiment provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 500°C
  • the heating rate was 10°C/min
  • the sintering time was 5h to obtain material B.
  • step S2 placing the material B obtained in step S1 in a ball mill, and obtaining precursors of different particle sizes by controlling the ball milling time at a ball milling speed of 400 r/min; wherein the D 50 of the small particle size precursor is 0.2 ⁇ m, and the ball milling time is 12 h; the D 50 of the large particle size precursor is 0.8 ⁇ m, and the ball milling time is 5 h;
  • step S3 Add 100 mL of deionized water and 3.2 g of starch to a reactor equipped with an ultrasonic device, and stir evenly by ultrasonic stirring to obtain a starch suspension; add the small-particle precursor obtained in step S1 to the starch suspension, and disperse by ultrasonic stirring during the addition process.
  • step S3 After uniform mixing, add 0.05 g of sodium trimetaphosphate, and heat the obtained mixed material 1 to 50° C. at a heating rate of 3° C./min under stirring to completely convert the mixed material 1 into a colloidal mixture, and continue stirring for 1 h to disperse the small-particle precursor evenly in the starch colloid to obtain a mixed material 2;
  • the obtained mixed material 2 was placed in a blast furnace for drying, and the obtained dry product was placed in a ball mill jar, and ball milled at a ball mill speed of 400 r/min for 1 h to obtain material C;
  • step S4 The large-particle precursor obtained in step S2 and the material C obtained in step S3 are mixed evenly, and the obtained mixture is sintered under the protection of a nitrogen atmosphere.
  • the sintering is divided into two stages, first calcined at 300°C for 3 hours, and then heated to 800°C for calcination for 8 hours; the sintered material is crushed and sieved to obtain a lithium manganese iron phosphate positive electrode material; wherein the mass ratio of the large-particle precursor to the material C is 5:1.
  • the preparation method of the battery in this embodiment is different from that in embodiment 1 only in that: the positive electrode material of lithium manganese iron phosphate is The material is the lithium manganese iron phosphate positive electrode material obtained in this example.
  • the battery testing method in this example is consistent with that in Example 1.
  • This comparative example provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 400°C
  • the heating rate was 5°C/min
  • the sintering time was 3h to obtain material B.
  • step S2 placing the material B obtained in step S1 in a ball mill, and obtaining precursors of different particle sizes by controlling the ball milling time at a ball milling speed of 400 r/min; wherein the D 50 of the small particle size precursor is 0.2 ⁇ m, and the ball milling time is 12 h; the D 50 of the large particle size precursor is 0.8 ⁇ m, and the ball milling time is 5 h;
  • step S3 Add 100 mL of deionized water and 3.2 g of starch to a reactor equipped with an ultrasonic device, and stir evenly by ultrasonic stirring to obtain a starch suspension; add the small-particle precursor obtained in step S1 to the starch suspension, and disperse by ultrasonic stirring during the addition process. After uniform mixing, add the large-particle precursor to the mixed material 1, disperse by ultrasonic stirring until uniform mixing, and then add 0.05 g of sodium trimetaphosphate. The obtained mixed material 2 is heated to 50° C. at a heating rate of 3° C./min under stirring to completely convert the mixed material 2 into a colloidal mixture, and continue stirring for 1 h to disperse the small-particle precursor evenly in the starch colloid: to obtain a mixed material 3;
  • the obtained mixed material 3 was placed in a blast furnace for drying, and the obtained dry product was placed in a ball mill jar and ball milled at a ball mill speed of 400 r/min for 1 h to obtain material C;
  • step S4 The material C obtained in step S3 is sintered under the protection of a nitrogen atmosphere. The sintering is divided into two stages. First, it is calcined at 300°C for 3 hours, and then the temperature is raised to 650°C for calcination for 12 hours. The sintered material is crushed and sieved to obtain a lithium manganese iron phosphate positive electrode material. The mass ratio of the large-particle precursor to the material C is 2:1.
  • the preparation method of the battery in this comparative example is different from that in Example 1 only in that the lithium iron manganese phosphate positive electrode material is the lithium iron manganese phosphate positive electrode material obtained in this comparative example.
  • the battery testing method in this comparative example is consistent with that in Example 1.
  • This comparative example provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:
  • the slurry A was placed in a blast furnace for drying, and then crushed and ground.
  • the obtained powder was placed in an inert gas atmosphere furnace and sintered under the protection of inert gas.
  • the sintering temperature was 400°C
  • the heating rate was 5°C/min
  • the sintering time was 3h to obtain material B.
  • step S2 placing the material B obtained in step S1 in a ball mill, and obtaining precursors of different particle sizes by controlling the ball milling time at a ball milling speed of 400 r/min; wherein the D 50 of the small particle size precursor is 0.2 ⁇ m, and the ball milling time is 12 h; the D 50 of the large particle size precursor is 0.8 ⁇ m, and the ball milling time is 5 h;
  • step S3 The large-particle precursor and the small-particle precursor of step S2 are mixed evenly, and the resulting mixture is sintered under the protection of a nitrogen atmosphere.
  • the sintering is divided into two stages, first calcined at 300°C for 3 hours, and then heated to 650°C for 12 hours; the sintered material is crushed and sieved to obtain a lithium manganese iron phosphate positive electrode material; wherein the mass ratio of the large-particle precursor to material C is 2:1.
  • the preparation method of the battery in this comparative example is different from that in Example 1 only in that the lithium iron manganese phosphate positive electrode material is the lithium iron manganese phosphate positive electrode material obtained in this comparative example.
  • the battery testing method in this comparative example is consistent with that in Example 1.
  • Table 1 shows the electrochemical performance of the batteries obtained in various embodiments and comparative examples.
  • the capacity of the battery prepared by the lithium iron manganese phosphate positive electrode material of the present invention is 145-147mAh/g, and the capacity after 100 cycles is 138-143mAh/g; it shows that the lithium iron manganese phosphate positive electrode material of the present invention has excellent electrochemical performance.
  • the capacity of the battery prepared by the lithium iron manganese phosphate positive electrode material obtained in Comparative Example 2 is 132mAh/g, and the capacity after 100 cycles is 128mAh/g; compared with Example 1, it is shown that directly mixing precursors of large and small particle sizes will reduce the capacity and cycle performance of the battery.
  • the capacity of the battery prepared with the lithium iron manganese phosphate positive electrode material obtained in Comparative Example 1 is 135 mAh/g, and the capacity after 100 cycles is 130 mAh/g; compared with Example 1, it is shown that adding precursors of large and small particle sizes to the starch suspension together will cause the particles of the lithium iron manganese phosphate positive electrode material to aggregate, resulting in a decrease in the capacity and cycle performance of the battery.

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Abstract

本发明公开了一种磷酸锰铁锂正极材料及其制备方法与应用，属于锂离子电池正极材料技术领域。该制备方法包括以下步骤：将锂源、铁源、锰源、磷源、碳源、乳化剂进行球磨，所得浆料A经干燥、研磨、煅烧、球磨后，得到D50为0.8-1.5μm的大粒径前驱体和D50为0.1-0.4μm的小粒径前驱体；然后将小粒径前驱体加入淀粉悬浊液中，超声分散后，加入交联剂，加热搅拌反应，所得胶体混合物经干燥、球磨，得到材料C；最后将大粒径前驱体和材料C混合，所得混合物在保护气体下进行煅烧，得到磷酸锰铁锂正极材料。该制备方法减少了磷酸锰铁锂正极材料的团聚，并增加磷酸锰铁锂正极材料的分散性和导电性，从而提升电池综合性能。

Description

一种磷酸锰铁锂正极材料及其制备方法与应用 技术领域
本发明涉及锂离子电池正极材料技术领域，具体涉及一种磷酸锰铁锂正极材料及其制备方法与应用。
背景技术
磷酸盐基正极材料为橄榄石型结构，具有较高的安全性能和成本优势。目前，磷酸铁锂在部分动力电池领域得到了规模化的应用，但其电压平台较低，理论能量密度低，难以满足更高的需求。而磷酸锰铁锂在继承磷酸铁锂优势的基础上，利用锰和铁的协同效应，能够提升其电压平台和理论能量密度。但磷酸锰铁锂的电子电导率低、锂离子扩散速率低，压实密度较小，影响电池的电化学性能和能量密度。为了提高磷酸锰铁锂正极材料的电化学性能，常采取以下方法：降低晶体尺寸至纳米级、控制粒子形貌、包覆导电碳以及掺杂阳离子等。但当颗粒粒径减少时，相应的比表面积和表面能会增加，颗粒间的聚合倾向也会增加导致分散困难，影响分散均匀性；同时，颗粒越小副反应越多，循环性能越差。
发明内容
本发明的目的在于克服现有技术的不足，提供一种磷酸锰铁锂正极材料及其制备方法与应用，该制备方法可以减少磷酸锰铁锂正极材料制备过程中的团聚，并增加磷酸锰铁锂正极材料的分散性和导电性，从而提升电池综合性能。
为实现上述目的，本发明采取的技术方案为：一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：将锂源、铁源、锰源、磷源、碳源混合进行干法球磨，然后加入乳化剂进行湿法球磨，所得浆料A经干燥、研磨、煅烧，得到材料B；
S2：将材料B进行球磨，得到D50为0.8-1.5μm的大粒径前驱体和D50为0.1-0.4μm的小粒径前驱体；
S3：将小粒径前驱体加入淀粉悬浊液中，超声分散后，加入交联剂，加热搅拌反应，所得胶体混合物经干燥、球磨，得到材料C；
S4：将大粒径前驱体和材料C混合，所得混合物在保护气体下进行煅烧，得到磷酸锰铁锂正极材料；大粒径前驱体和材料C的质量比为0.5-5:1。
本发明所提供的方法，将小粒径前驱体加入淀粉悬浊液中，通过超声分散，使团聚的小粒径前驱体暂时分开，加热搅拌使交联剂和淀粉交联反应形成胶体，把暂时维持分散状态的小粒径前驱体逐渐固定在淀粉胶体形成的三维网络中，避免撤去超声分散后，小粒径前驱体再次团聚在一起。
本发明所提供的方法，将大粒径前驱体和材料C混合均匀，大粒径前驱体紧密排列形成的空隙，由小粒径的材料C填充，大大提高磷酸锰铁锂正极材料的压实密度和形貌；材料C被淀粉包覆，大粒径前驱体和材料C混合时，淀粉的阻隔作用使小粒径前驱体和大粒径前驱体不会团聚，混合均匀后进行烧结，能够得到粒径分布均匀的磷酸锰铁锂正极材料，从而提高磷酸锰铁锂正极材料的循环性能；此外，碳源在大粒径前驱体和小粒径前驱体表面形成碳包覆层，淀粉在步骤S4中的烧结过程中会转变为碳，进一步在大粒径前驱体和小粒径前驱体表面形成碳包覆层，碳包覆层不仅能够防止磷酸锰铁锂正极材料发生团聚，而且磷酸锰铁锂正极材料表面丰富的碳包覆层为电子传输提供了更多的路径，进而提升了磷酸锰铁锂正极材料的电化学性能。
在步骤S1中，为了进一步提高材料B的压实密度和形貌，在煅烧前，将干燥后的产品进行粉碎和研磨，获得粒径较为均匀的粉末。
优选地，所述步骤S1中，锂源、铁源、锰源、磷源的加入量按照LiFexMn1-xPO4的化学计量比计算得到，其中0.1≤x≤0.5；所述碳源的质量为锂源、铁源、锰源、磷源和碳源总质量的1-5％。
优选地，所述锂源为碳酸锂、氢氧化锂、乙酸锂、磷酸二氢锂中的至少一种；
优选地，所述铁源为硝酸亚铁、硫酸亚铁、氯化亚铁、草酸亚铁、磷酸铁中的至少一种；
优选地，所述锰源为碳酸锰、草酸锰、磷酸锰、硫酸锰、二氧化锰、四氧化三锰中的至少一种；
优选地，所述磷源为磷酸铁、磷酸锰、磷酸二氢锂、磷酸二氢铵、磷酸氢二铵中的至少一种；
优选地，所述碳源为蔗糖、果糖、葡萄糖、淀粉、麦芽糖、柠檬酸中的至少一种；
优选地，所述乳化剂为聚乙二醇、甘油脂肪酸酯、蔗糖脂肪酸酯、聚氧乙烯醚中的一种。
优选地，所述步骤S1中，干法球磨和湿法球磨的转速均为300-600r/min，例如300r/min、350r/min、400r/min、450r/min、500r/min、550r/min或600r/min；干法球磨和湿法球磨的总时间的时间为3-8h，例如3h、4h、5h、6h、7h或8h。
本发明通过干法球磨和湿法球磨将锂源、铁源、锰源、磷源、碳源均匀分散在浆料A中，提高了磷酸锰铁锂正极材料中各组分的分散性，从而提高磷酸锰铁锂正极材料的电化学性能。
优选地，所述步骤S1中，煅烧的具体步骤为：将研磨所得产物置于惰性气体气氛炉中进行烧结，烧结的升温速率为5-10℃/min，烧结的温度为400-500℃，烧结的时间为3-5h。
优选地，所述惰性气体为氮气、氩气和氦气中的一种。
本领域技术人员可以根据实际情况选择合适的干燥温度和干燥时间对浆料A进行干燥，例如干燥温度为80-100℃，干燥时间为3-5h。
本领域技术人员可以根据实际需要，通过控制步骤S2中的球磨转速和球磨时间以获得D50为0.8-1.5μm的大粒径前驱体和D50为0.1-0.4μm的小粒径前驱体；例如，大粒径前驱体的球磨转速为300-600r/min，时间为2-5h；小粒径前驱体的球磨转速为300-600r/min，时间为10-13h。
优选地，所述步骤S3中，淀粉悬浊液的制备方法为包括：将淀粉加入去离子水中，搅拌均匀，得到淀粉悬浊液；
优选地，所述交联剂的质量为淀粉质量的0.1-1％；交联剂为三偏磷酸钠；
优选地，所述步骤S3中，加热的温度为40-65℃，温度的升温速率为1-10℃/min，搅拌反应的时间为1-3h。
以缓慢的升温速率加热是交联剂与淀粉交联反应形成胶体，能够更好的将小粒径前驱体分散均匀。
优选的，所述步骤S3中，球磨的转速为300-600r/min，球磨的时间为3-8h。
优选地，所述步骤S4中，大粒径前驱体和材料C的质量比为1-3:1。
本发明中，大粒径前驱体和材料C的质量比在上述优选比例范围内能够较大程度的提高磷酸锰铁锂正极材料压实密度和电化学性能。
优选地，所述步骤S4中，煅烧的温度为650-800℃，煅烧的时间为8-12h。
优选地，所述步骤S4中，所述混合物在煅烧前还需要进行预烧结，预烧结的温度为250-350℃，预烧结的时间为3-4h。
利用预烧结和煅烧结合的方法，可以在不同温度区间内实现磷酸锰铁锂前驱体间的粘结、致密化、组织结构变化及重排，提高磷酸锰铁锂正极材料的压实密度和电化学性能。
优选地，所述步骤S4中，预烧结和煅烧都是在惰性气体保护下进行，惰性气体为氮气、氩气和氦气中的一种。
优选地，所述步骤S4中，煅烧所得产物可以进行后处理，以进一步提高磷酸锰铁锂正极材料的形貌。后处理的步骤有粉碎、过筛等。
第二方面，本发明提供了一种磷酸锰铁锂正极材料，所述磷酸锰铁锂正极材料由所述磷酸锰铁锂正极材料的制备方法制得。
第三方面，本发明提供了一种正极片，所述正极片包括所述磷酸锰铁锂正极材料。
第四方面，本发明提供了一种锂离子电池，所述锂离子电池包括所述正极片。
与现有技术相比，本发明的有益效果为：
1、本发明将小粒径前驱体用淀粉悬浊液进行分散后，进行干燥，避免小粒径前驱体发生团聚；同时干燥后的小粒径前驱体表面包覆有淀粉，在和大粒径前驱体的混合过程中，淀粉的阻隔作用使小粒径前驱体和大粒径前驱体不会团聚，混合均匀后进行烧结，能够得到粒径分布均匀的磷酸锰铁锂正极材料，从而提高磷酸锰铁锂正极材料的循环性能。
2、本发明中，碳源在大粒径前驱体和小粒径前驱体表面形成碳包覆层，小粒径表面包覆的淀粉后续煅烧过程中会转变为碳，进一步在大粒径前驱体和小粒径前驱体表面形成碳包覆层，碳包覆层不仅能够防止磷酸锰铁锂正极材料发 生团聚，而且磷酸锰铁锂正极材料表面丰富的碳包覆层为电子传输提供了更多的路径，进而提升了磷酸锰铁锂正极材料的电化学性能。
具体实施方式
为了更好地说明本发明的目的、技术方案和优点，下面将结合具体实施例及对比例对本发明作进一步说明，其目的在于详细地理解本发明的内容，而不是对本发明的限制。本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明的保护范围。本发明实施所涉及的实验试剂及仪器，除非特别说明，均为常用的普通试剂及仪器。
实施例1
本实施例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨1h，干法球磨的转速为400r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨3h，湿法球磨的转速为600r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为400℃，升温速率为5℃/min，烧结时间为3h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.2μm，球磨时间为12h；大粒径前驱体的D50为0.8μm，球磨时间为5h；
S3：在带超声装置的反应釜中加入100mL的去离子水中和3.2g的淀粉，超声搅拌均匀得到淀粉悬浊液；将步骤S1所得小粒径前驱体加入淀粉悬浊液中，加入过程中同时超声分散，混合均匀后，加入三偏磷酸钠0.05g，所得混合物料1在搅拌下以3℃/min的升温速率加热至50℃，使混合物料1完全变成胶体混合物，继续搅拌1h使小粒径前驱体在淀粉胶体中分散均匀:，得到混合物料2；
将所得混合物料2置于鼓风炉中干燥，所得干燥产物放入球磨罐中，在400r/min的球磨转速下，球磨1h，得到材料C；
S4：将步骤S2所得大粒径前驱体和步骤S3所得材料C混合均匀，所得混合物在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至650℃煅烧12h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极材料；其中大粒径前驱体和材料C的质量比为2:1。
本实施例还提供了一种锂离子电池的制备方法，包括以下步骤：
将本实施例所得磷酸锰铁锂正极材料，与导电剂SP、PVDF，按照80:10:10的质量比加入N-甲基吡咯烷酮中，所得混合物进行球磨均匀，得到正极浆料；将正极浆料涂覆在铝箔上，真空烘干制得正极极片，以1mol/L的LiPF6为电解液，Celgard聚丙烯膜为隔膜，金属锂片为负极，组装成锂离子电池。在2.5V-4.5V的电压范围，0.1C倍率下测试电池的电化学性能。测试结果如表1所示。
实施例2
本实施例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨1h，干法球磨的转速为400r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨3h，湿法球磨的转速为600r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为400℃，升温速率为5℃/min，烧结时间为3h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.3μm，球磨时间为11h；大粒径前驱体的D50为1.0μm，球磨时间为4h；
S3：在带超声装置的反应釜中加入100mL的去离子水中和3.2g的淀粉，超声搅拌均匀得到淀粉悬浊液；将步骤S1所得小粒径前驱体加入淀粉悬浊液中，加入过程中同时超声分散，混合均匀后，加入三偏磷酸钠0.05g，所得混合物料1在搅拌下以3℃/min的升温速率加热至60℃，使混合物料1完全变成胶体混合物，继续搅拌0.8h使小粒径前驱体在淀粉胶体中分散均匀:，得到混合物料2；
将所得混合物料2置于鼓风炉中干燥，所得干燥产物放入球磨罐中，在 400r/min的球磨转速下，球磨1h，得到材料C；
S4：将步骤S2所得大粒径前驱体和步骤S3所得材料C混合均匀，所得混合物在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至650℃煅烧12h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极材料；其中大粒径前驱体和材料C的质量比为3:1。
本实施例中电池的制备方法与实施例1的区别仅在于：磷酸锰铁锂正极材料为本实施例所得磷酸锰铁锂正极材料。本实施例中电池测试方法同实施例1保持一致。
实施例3
本实施例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨1h，干法球磨的转速为400r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨3h，湿法球磨的转速为600r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为400℃，升温速率为5℃/min，烧结时间为3h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.1μm，球磨时间为13h；大粒径前驱体的D50为1.2μm，球磨时间为3h；
S3：在带超声装置的反应釜中加入100mL的去离子水中和3.2g的淀粉，超声搅拌均匀得到淀粉悬浊液；将步骤S1所得小粒径前驱体加入淀粉悬浊液中，加入过程中同时超声分散，混合均匀后，加入三偏磷酸钠0.05g，所得混合物料1在搅拌下以3℃/min的升温速率加热至45℃，使混合物料1完全变成胶体混合物，继续搅拌1h使小粒径前驱体在淀粉胶体中分散均匀:，得到混合物料2；
将所得混合物料2置于鼓风炉中干燥，所得干燥产物放入球磨罐中，在400r/min的球磨转速下，球磨1h，得到材料C；
S4：将步骤S2所得大粒径前驱体和步骤S3所得材料C混合均匀，所得混 合物在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至650℃煅烧12h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极材料；其中大粒径前驱体和材料C的质量比为1:1。
本实施例中电池的制备方法与实施例1的区别仅在于：磷酸锰铁锂正极材料为本实施例所得磷酸锰铁锂正极材料。本实施例中电池测试方法同实施例1保持一致。
实施例4
本实施例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨2h，干法球磨的转速为300r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨6h，湿法球磨的转速为400r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为450℃，升温速率为8℃/min，烧结时间为4h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.2μm，球磨时间为12h；大粒径前驱体的D50为0.8μm，球磨时间为5h；
S3：在带超声装置的反应釜中加入100mL的去离子水中和3.2g的淀粉，超声搅拌均匀得到淀粉悬浊液；将步骤S1所得小粒径前驱体加入淀粉悬浊液中，加入过程中同时超声分散，混合均匀后，加入三偏磷酸钠0.05g，所得混合物料1在搅拌下以3℃/min的升温速率加热至50℃，使混合物料1完全变成胶体混合物，继续搅拌1h使小粒径前驱体在淀粉胶体中分散均匀:，得到混合物料2；
将所得混合物料2置于鼓风炉中干燥，所得干燥产物放入球磨罐中，在400r/min的球磨转速下，球磨1h，得到材料C；
S4：将步骤S2所得大粒径前驱体和步骤S3所得材料C混合均匀，所得混合物在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至700℃煅烧10h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极 材料；其中大粒径前驱体和材料C的质量比为0.5:1。
本实施例中电池的制备方法与实施例1的区别仅在于：磷酸锰铁锂正极材料为本实施例所得磷酸锰铁锂正极材料。本实施例中电池测试方法同实施例1保持一致。
实施例5
本实施例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨1h，干法球磨的转速为600r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨5h，湿法球磨的转速为300r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为500℃，升温速率为10℃/min，烧结时间为5h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.2μm，球磨时间为12h；大粒径前驱体的D50为0.8μm，球磨时间为5h；
S3：在带超声装置的反应釜中加入100mL的去离子水中和3.2g的淀粉，超声搅拌均匀得到淀粉悬浊液；将步骤S1所得小粒径前驱体加入淀粉悬浊液中，加入过程中同时超声分散，混合均匀后，加入三偏磷酸钠0.05g，所得混合物料1在搅拌下以3℃/min的升温速率加热至50℃，使混合物料1完全变成胶体混合物，继续搅拌1h使小粒径前驱体在淀粉胶体中分散均匀:，得到混合物料2；
将所得混合物料2置于鼓风炉中干燥，所得干燥产物放入球磨罐中，在400r/min的球磨转速下，球磨1h，得到材料C；
S4：将步骤S2所得大粒径前驱体和步骤S3所得材料C混合均匀，所得混合物在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至800℃煅烧8h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极材料；其中大粒径前驱体和材料C的质量比为5:1。
本实施例中电池的制备方法与实施例1的区别仅在于：磷酸锰铁锂正极材 料为本实施例所得磷酸锰铁锂正极材料。本实施例中电池测试方法同实施例1保持一致。
对比例1
本对比例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨1h，干法球磨的转速为400r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨3h，湿法球磨的转速为600r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为400℃，升温速率为5℃/min，烧结时间为3h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.2μm，球磨时间为12h；大粒径前驱体的D50为0.8μm，球磨时间为5h；
S3：在带超声装置的反应釜中加入100mL的去离子水中和3.2g的淀粉，超声搅拌均匀得到淀粉悬浊液；将步骤S1所得小粒径前驱体加入淀粉悬浊液中，加入过程中同时超声分散，混合均匀后，向混合物料1中加入大粒径前驱体，超声分散至混合均匀，然后加入三偏磷酸钠0.05g，所得混合物料2在搅拌下以3℃/min的升温速率加热至50℃，使混合物料2完全变成胶体混合物，继续搅拌1h使小粒径前驱体在淀粉胶体中分散均匀:，得到混合物料3；
将所得混合物料3置于鼓风炉中干燥，所得干燥产物放入球磨罐中，在400r/min的球磨转速下，球磨1h，得到材料C；
S4：将步骤S3所得材料C在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至650℃煅烧12h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极材料；其中大粒径前驱体和材料C的质量比为2:1。
本对比例中电池的制备方法与实施例1的区别仅在于：磷酸锰铁锂正极材料为本对比例所得磷酸锰铁锂正极材料。本对比例中电池测试方法同实施例1保持一致。
对比例2
本对比例提供了一种磷酸锰铁锂正极材料的制备方法，包括以下步骤：
S1：称取9.05g磷酸铁、3.48g二氧化锰、3.75g碳酸锂、4.60g磷酸二氢铵、1.55g蔗糖加入球磨罐中进行干法球磨1h，干法球磨的转速为400r/min；然后加入120g水和0.2g聚乙二醇进行湿法球磨3h，湿法球磨的转速为600r/min，得到浆料A；
将浆料A置于鼓风炉中进行干燥，然后进行粉碎研磨后，所得粉末置于惰性气体气氛炉中在惰性气体保护下进行烧结，烧结的温度为400℃，升温速率为5℃/min，烧结时间为3h，得到材料B；
S2：将步骤S1所得材料B置于球磨罐中，在400r/min的球磨转速下，通过控制球磨时间得到不同粒径的前驱体；其中小粒径前驱体的D50为0.2μm，球磨时间为12h；大粒径前驱体的D50为0.8μm，球磨时间为5h；
S3：将步骤S2大粒径前驱体和小粒径前驱体混合均匀，所得混合物在氮气气氛保护下进行烧结，烧结分为两段，先在300℃下煅烧3h，然后升温至650℃煅烧12h；烧结所得材料进行粉碎、过筛后，得到磷酸锰铁锂正极材料；其中大粒径前驱体和材料C的质量比为2:1。
本对比例中电池的制备方法与实施例1的区别仅在于：磷酸锰铁锂正极材料为本对比例所得磷酸锰铁锂正极材料。本对比例中电池测试方法同实施例1保持一致。
表1为各实施例和对比例所得电池的电化学性能。
表1

从表1的试验结果可知，本发明的磷酸锰铁锂正极材料制备的电池的容量为145-147mAh/g，100次循环后的容量为138-143mAh/g；说明本发明的磷酸锰铁锂正极材料具有优异的电化学性能。对比例2所得磷酸锰铁锂正极材料制备的电池的容量为132mAh/g，100次循环后的容量为128mAh/g；与实施例1相比，说明直接将大小粒径的前驱体直接混合，会降低电池的容量和循环性能。
对比例1所得磷酸锰铁锂正极材料制备的电池的容量为135mAh/g，100次循环后的容量为130mAh/g；与实施例1相比，说明将大小粒径的前驱体共同加入淀粉悬浊液中，会导致磷酸锰铁锂正极材料的颗粒聚集，导致电池的容量和循环性能下降。
最后所应当说明的是，以上实施例用以说明本发明的技术方案而非对本发明保护范围的限制，尽管参照较佳实施例对本发明作了详细说明，本领域的普通技术人员应当理解，可以对本发明的技术方案进行修改或者同等替换，而不脱离本发明技术方案的实质和范围。

Claims (10)

  1. 一种磷酸锰铁锂正极材料的制备方法，其特征在于，包括以下步骤：
    S1：将锂源、铁源、锰源、磷源、碳源混合进行干法球磨，然后加入乳化剂进行湿法球磨，所得浆料A经干燥、研磨、煅烧，得到材料B；
    S2：将材料B进行球磨，得到D50为0.8-1.5μm的大粒径前驱体和D50为0.1-0.4μm的小粒径前驱体；
    S3：将小粒径前驱体加入淀粉悬浊液中，超声分散后，加入交联剂，加热搅拌反应，所得胶体混合物经干燥、球磨，得到材料C；
    S4：将大粒径前驱体和材料C混合，所得混合物在保护气体下进行煅烧，得到磷酸锰铁锂正极材料；大粒径前驱体和材料C的质量比为0.5-5:1。
  2. 如权利要求1所述的制备方法，其特征在于，所述步骤S1中，锂源、铁源、锰源、磷源的加入量按照LiFexMn1-xPO4的化学计量比计算得到，其中0.1≤x≤0.5；所述碳源的质量为锂源、铁源、锰源、磷源和碳源总质量的1-5％。
  3. 如权利要求1所述的制备方法，其特征在于，所述步骤S1中，干法球磨和湿法球磨的转速均为300-600r/min，干法球磨和湿法球磨的总时间为3-8h。
  4. 如权利要求1所述的制备方法，其特征在于，所述步骤S1中，煅烧的具体步骤为：将研磨所得产物置于惰性气体气氛炉中进行烧结，烧结的升温速率为5-10℃/min，烧结的温度为400-500℃，烧结的时间为3-5h。
  5. 如权利要求1所述的制备方法，其特征在于，所述步骤S3中，交联剂的质量为淀粉质量的0.1-1％；交联剂为三偏磷酸钠；加热的温度为40-65℃，温度的升温速率为1-10℃/min，搅拌反应的时间为1-3h。
  6. 如权利要求1所述的制备方法，其特征在于，所述步骤S4中，大粒径前驱体和材料C的质量比为1-3:1。
  7. 如权利要求1所述的制备方法，其特征在于，所述步骤S4中，煅烧的温度为650-800℃，煅烧的时间为8-12h；
    优选地，所述步骤S4中，所述混合物在煅烧前还需要进行预烧结，预烧结 的温度为250-350℃，预烧结的时间为3-4h。
  8. 一种磷酸锰铁锂正极材料，其特征在于，由权利要求1-7任一项所述的制备方法制得。
  9. 一种正极片，其特征在于，所述正极片包含如权利要求8所述的磷酸锰铁锂正极材料。
  10. 一种锂离子电池，其特征在于，所述锂离子电池包含如权利要求9所述的正极片。
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