WO2018032569A1 - Limn1-xfexpo4 cathode material having core-shell structure, preparation method therefor, and lithium-ion battery - Google Patents

Limn1-xfexpo4 cathode material having core-shell structure, preparation method therefor, and lithium-ion battery Download PDF

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WO2018032569A1
WO2018032569A1 PCT/CN2016/099109 CN2016099109W WO2018032569A1 WO 2018032569 A1 WO2018032569 A1 WO 2018032569A1 CN 2016099109 W CN2016099109 W CN 2016099109W WO 2018032569 A1 WO2018032569 A1 WO 2018032569A1
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limn
lithium
core
source compound
shell structure
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Chinese (zh)
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高文超
潘芳芳
肖亚洲
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中航锂电（洛阳）有限公司
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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
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • 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
    • H01M4/624—Electric conductive fillers
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 invention belongs to the technical field of lithium ion batteries, and in particular relates to a core-shell structure LiMn 1-x Fe x PO 4 cathode material, a preparation method thereof and a lithium ion battery.
  • LiMO 2 Mo, Ni, Mn
  • spinel LiMn 2 O 4 spinel LiMn 2 O 4
  • LiFePO 4 has the function of deintercalating lithium.
  • the charge and discharge platform is very stable, and the structure is stable during charge and discharge.
  • the material is non-toxic, environmentally friendly, rich in raw materials, high in specific capacity, good in cycle performance, and can be used at high temperatures.
  • LiFePO 4 has many advantages, there are still some problems in the actual application process, especially the low discharge platform, which is close to 3.4V, which is difficult to meet the demand for battery energy energy density in the future electric vehicle market.
  • LiMnPO 4 with the olivine LiFePO 4 has the same structure, having the LiFePO 4 close to the theoretical specific capacity (171mAh / g) comparable safety, platform 4.1V operating voltage, the theoretical energy density of LiFePO 4 is 1.2 times the material .
  • the electronic conductivity and ion diffusion rate of LiMnPO 4 are low, resulting in poor discharge performance, particularly high current discharge performance.
  • methods for improving the electronic conductivity are mainly carbon coating, metal ion doping, etc.
  • the methods for increasing the ion transport rate are mainly material nanocrystallization and control crystal. Growth direction and materials with good surface ion transport properties.
  • Amorphous phosphate/pyrophosphate is a good Li + transport carrier. Studies have shown that coating it on the surface of LiFePO 4 can effectively improve its electrochemical performance, especially high current discharge performance.
  • the Chinese patent publication CN102842713A provides a lithium iron phosphate material coated with an amorphous pyrophosphate and a preparation method thereof. The material has good rate performance, and the 2C discharge capacity is above 136 mAh/g. However, the single coated amorphous pyrophosphate has limited improvement in material rate performance.
  • the Chinese patent publication CN103050694B coats the metal oxide/metal salt with carbon on the surface of lithium iron phosphate to obtain lithium iron phosphate material with excellent capacity ratio performance.
  • the patent uses ball milling + spray drying method to make metal difficult.
  • the oxide/metal salt and carbon are uniformly coated on the surface of the lithium iron phosphate material, and the agglomeration phenomenon is easily generated in the coating process, which is disadvantageous to the electrochemical performance of the material and the batch stability.
  • Carbon coating is the most common and effective means to improve the surface conductivity of materials and improve the electrochemical performance of materials.
  • the carbon coating layer can alleviate the contact between the active material and the electrolyte, and improve the cycle stability of the material.
  • a series of patents in the prior art use a carbon coating method to effectively improve the conductivity of the lithium iron phosphate material, thereby improving its electrochemical performance.
  • studies have shown that the effect of coating carbon on the surface of LiMn 1-x Fe x PO 4 is not ideal compared to lithium iron phosphate. It is difficult to form a uniform coating on the surface of LiMn 1-x Fe x PO 4 with a single carbon coating.
  • the usual method is to increase the content of coated carbon to ensure the coating effect, however, the weight ratio energy of such materials will be greatly affected.
  • the technical problem to be solved by the present invention is to provide a core-shell structure LiMn 1-x Fe x PO 4 cathode material having high rate performance and a preparation method thereof, and a lithium ion battery.
  • the invention provides a core-shell structure LiMn 1-x Fe x PO 4 cathode material, which is composed of a core and a shell, the core is LiMn 1-x Fe x PO 4 nanoparticles; the shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 ⁇ x ⁇ 0.5.
  • the LiMn 1-x Fe x PO 4 nanoparticles have a particle diameter of 10 to 200 nm.
  • the lithium-containing metal salt is one or more of LiFeP 2 O 7 , LiAlP 2 O 7 and Li 3 V 2 (PO 4 ) 3 .
  • the mass of the carbon is from 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles.
  • the lithium-containing metal salt has a mass of 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles.
  • the invention also provides a preparation method of a core-shell structure LiMn 1-x Fe x PO 4 cathode material, comprising the following steps:
  • LiMn 1-x Fe x PO 4 nanoparticles are prepared as follows:
  • the calcination in the step A) is specifically: raising the temperature to 350 ° C to 450 ° C at a temperature increase rate of 2 to 10 ° C / min, after 4 to 10 h of heat retention, and then increasing the temperature at a temperature increase rate of 2 to 10 ° C / min. To 650 ° C ⁇ 800 ° C, heat 8 ⁇ 20h.
  • the calcination in the step S2) is specifically: raising the temperature to 550 ° C to 700 ° C at a temperature increase rate of 2 to 10 ° C / min, and maintaining the temperature for 2 to 5 hours.
  • the present invention also provides a lithium ion battery comprising a core-shell structure LiMn 1-x Fe x PO 4 cathode material.
  • the invention provides a core-shell structure LiMn 1-x Fe x PO 4 cathode material, which is composed of a core and a shell, the core is LiMn 1-x Fe x PO 4 nanoparticles; the shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 ⁇ x ⁇ 0.5.
  • the present invention uses LiMn 1-x Fe x PO 4 nanoparticles as a core, and material nanocrystallization can shorten the lithium ion diffusion path, reduce the diffusion time of lithium ions between particles, and improve the ion transport performance of materials;
  • the effect of carbon coating is effectively improved, thereby reducing the carbon coating content, thereby significantly improving the rate performance and cycle performance of the core-shell structure cathode material, and having a higher compaction density.
  • Example 1 is a scanning electron micrograph of a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C co-modified nano-LiMn 0.8 Fe 0.2 PO 4 ;
  • Example 2 is a scanning electron micrograph of a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C, which is commonly decorated with nano-LiMn 0.8 Fe 0.2 PO 4 ;
  • Example 3 is a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C co-coated with nano-LiMn 0.8 Fe 0.2 PO 4 and carbon-coated LiMn 0.8 Fe 0.2 PO 4 obtained in Comparative Example 1. 2C charging curve;
  • Example 4 is a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C co-coated with nano-LiMn 0.8 Fe 0.2 PO 4 and carbon-coated LiMn 0.8 Fe 0.2 PO 4 obtained in Comparative Example 1. 3C discharge capacity retention rate graph.
  • the invention provides a core-shell structure LiMn 1-x Fe x PO 4 cathode material, which is composed of a core and a shell, the core is LiMn 1-x Fe x PO 4 nanoparticles; the shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 ⁇ x ⁇ 0.5.
  • the present invention has LiMn 1-x Fe x PO 4 nanoparticles as a core, wherein 0 ⁇ x ⁇ 0.5, preferably 0.2 ⁇ x ⁇ 0.4; in some embodiments provided by the present invention, the x is preferably 0.2; In other embodiments provided by the present invention, the x is preferably 0.4.
  • the particle diameter of the LiMn 1-x Fe x PO 4 nanoparticles is preferably from 10 to 200 nm, more preferably from 20 to 100 nm, still more preferably from 20 to 60 nm.
  • the LiMn 1-x Fe x PO 4 core is externally coated with a shell which is a mixture of carbon and a lithium-containing metal salt, the lithium-containing metal salt being a lithium-containing metal phosphate and/or lithium-containing
  • the metal pyrophosphate is preferably one or more of LiFeP 2 O 7 , LiAlP 2 O 7 and Li 3 V 2 (PO 4 ) 3 ; in the outer shell, the mass of carbon is preferably LiMn 1-x Fe x nano PO 4 0.1% to 10% of the particle mass, and more preferably from 0.5 to 5%; the lithium-containing metal salt is preferably a mass LiMn 1-x Fe x PO 4 0.1% to 10% by nano-particles of the mass, More preferably, it is 0.5% - 5%.
  • the invention uses LiMn 1-x Fe x PO 4 nanoparticles as the core, and material nanocrystallization can shorten the lithium ion diffusion path, reduce the diffusion time of lithium ions between the particles, and improve the ion transport performance of the material; the carbon and the lithium-containing metal
  • the addition of a mixture of phosphate and/or lithium-containing metal pyrophosphate as a coating layer, lithium-containing metal phosphate and/or pyrophosphate, on the one hand can increase the conductivity of the material ions, on the other hand, effectively improve
  • the effect of carbon coating reduces the carbon coating content, so that the rate performance and cycle performance of the core-shell structure cathode material are significantly improved, and at the same time, the compaction density is high.
  • the present invention also provides a method for preparing the above-described core-shell structure LiMn 1-x Fe x PO 4 cathode material, comprising the steps of: S1) first lithium source compound, metal source compound, first phosphorus source compound, LiMn 1 -x Fe x PO 4 nanoparticles, a first complexing agent, a soluble carbon source mixed with water, heated to evaporation of water to obtain an intermediate; 0 ⁇ x ⁇ 0.5; S2) calcining the intermediate to obtain a core Shell structure cathode material.
  • the present invention has no particular limitation on the source of all raw materials, and may be commercially available or homemade.
  • the LiMn 1-x Fe x PO 4 nanoparticles are preferably prepared by the following method: A) combining a second lithium source compound, a manganese source compound, an iron source compound, and a second phosphorus source compound with a second complex The agent is mixed in water, heated to evaporate to dryness, and calcined to obtain LiMn 1-x Fe x PO 4 nanoparticles; lithium ions in the second lithium source compound, manganese ions in the manganese source compound, and iron source compounds The molar ratio of the iron ion to the phosphorus atom in the second phosphorus source compound is 1: (1-x): x:1.
  • the first lithium source compound and the second lithium source compound are lithium source compounds well known to those skilled in the art, and are not particularly limited.
  • each of them is preferably lithium carbonate, lithium hydroxide and acetic acid.
  • One or more of lithium is preferably lithium carbonate, lithium hydroxide and acetic acid.
  • the manganese source compound is not particularly limited as long as it is a manganese source compound well known to those skilled in the art, and one or more of manganese nitrate, manganese chloride, manganese sulfate and manganese acetate are preferred in the present invention.
  • the iron source compound may be an iron source compound well known to those skilled in the art, and is not particularly limited.
  • ferrous oxalate, ferrous acetate, ferrous chloride, ferrous nitrate and ferrous sulfate are preferred. One or more.
  • the first phosphorus source compound and the second phosphoric acid compound are not particularly limited as long as the phosphorus source compound is well known to those skilled in the art, and each of the present invention is preferably ammonium dihydrogen phosphate, diammonium phosphate and phosphoric acid. One or more of ammonium.
  • the metal source compound is not particularly limited as long as it is a metal source compound well known to those skilled in the art, and one or more of iron oxalate, aluminum nitrate and vanadium nitrate are preferred in the present invention.
  • the first complexing agent and the second complexing agent may be any complexing agents well known to those skilled in the art, and are not particularly limited.
  • each of them is preferably citric acid, oxalic acid, adipic acid, ascorbic acid.
  • the soluble carbon source may be a soluble carbon source well known to those skilled in the art, and is not particularly limited.
  • glucose sugar, sucrose, citric acid, tartaric acid, oxalic acid, adipic acid, polyethylene glycol are preferred.
  • One or more of salicylic acid, polyvinyl alcohol, cinnamic acid, fructose, ascorbic acid and malic acid are preferred.
  • the second lithium source compound, the manganese source compound, the iron source compound, the second phosphorus source compound and the second complexing agent are mixed in water, wherein the lithium ion in the second lithium source compound and the manganese in the manganese source compound
  • the molar ratio of the iron ion in the ion and the iron source compound to the phosphorus atom in the second phosphorus source compound is 1: (1-x): x: 1, the x is the same as described above, and is not described herein;
  • the mass of the second complexing agent is preferably from 1% to 10% by mass of the product LiMn 1-x Fe x PO 4 , more preferably from 4% to 8%, still more preferably from 5% to 8%, most preferably 5%.
  • the mixture is heated to evaporate to dryness, and the heating temperature is preferably 60 to 100 ° C, more preferably 70 to 90 ° C, still more preferably 80 ° C; and the heating time is preferably 8 to 12 h.
  • the vacuum drying temperature is preferably 80 ° C ⁇ 100 ° C, more preferably 80 ° C ⁇ 90 ° C, still more preferably 80 ° C ⁇ 85 ° C, most preferably 80 ° C;
  • the pressure for vacuum drying is preferably -0.98 MPa.
  • the calcination is preferably carried out in two stages; the temperature of the first calcination is preferably from 350 ° C to 450 ° C, more preferably from 400 ° C to 450 ° C; the time of the first calcination Preferably, it is 4 to 10 hours, more preferably 4 to 8 hours, still more preferably 6 to 8 hours; and the temperature of the second calcination is preferably 650 to 800 ° C, more preferably 700 to 800 ° C, still more preferably 750 ° C ⁇ 800 ° C; the time of the second calcination is preferably 8 to 20 h, more preferably 8 to 15 h, still more preferably 10 to 15 h.
  • the calcination is preferably carried out according to the following procedure: raising the temperature to a temperature of from 2 to 10 ° C / min to 350 ° C to 450 ° C, after 4 to 10 h of incubation, and then increasing the temperature of 2 to 10 ° C / min 650 ° C ⁇ 800 ° C, heat 8 ⁇ 20h; more preferably according to the following process: 2 ⁇ 8 ° C / min temperature increase rate to 350 ° C ⁇ 450 ° C, after 4 ⁇ 10h, then 2 ⁇ 8 ° C /
  • the heating rate of min is raised to 650 ° C ⁇ 800 ° C, and the temperature is maintained for 8 ⁇ 20 h; further preferably according to the following process: at a temperature increase rate of 4 ⁇ 6 ° C / min to 350 ° C ⁇ 450 ° C, after 4 ⁇ 10 h, then The temperature increase rate of 4 to 6 ° C / min is raised to 650 ° C ⁇ 800 ⁇ 800
  • LiMn 1-x Fe x PO 4 nanoparticles were obtained.
  • the molar ratio of the lithium ion in the lithium ion and the metal source compound to the phosphorus atom in the first phosphorus source compound is preferably (1 to 2): 1: (1.5 to 1), more preferably (1 to 1.5): 1: (1 to 1.5); the total mass of the first lithium salt compound, the metal source compound and the first phosphorus source compound is preferably 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles, more preferably It is 0.5% to 5%; the mass of the first complexing agent is preferably from 1% to 10%, more preferably from 5% to 10%, still more preferably 5% by mass of the LiMn 1-x Fe x PO 4 nanoparticles.
  • the mass of the soluble carbon source is preferably from 0.1% to 10%, more preferably from 0.5% to 10%, still more preferably 1% by mass of the LiMn 1-x Fe x PO 4 nanoparticles. % to 10%, most preferably 5% to 10%.
  • the mixture is heated to evaporate to dryness; the heating temperature is preferably 60 to 100 ° C, more preferably 70 to 90 ° C, still more preferably 80 ° C; and the heating time is preferably 8 to 12 h.
  • the vacuum drying temperature is preferably from 80 ° C to 100 ° C, more preferably from 80 ° C to 90 ° C, still more preferably from 80 ° C to 85 ° C, most preferably It is 80 ° C; the pressure of the vacuum drying is preferably -0.98 MPa.
  • the intermediate is calcined; the calcination temperature is preferably 550 ° C to 700 ° C, more preferably 600 ° C to 700 ° C, still more preferably 600 ° C to 650 ° C; the calcination temperature is preferably 2 to 10 ° C / min, more preferably 2 to 8 ° C / min, still more preferably 4 to 6 ° C / min; the calcination time is preferably 2 to 5 h, more preferably 3 to 4 h; in the present invention, the calcination is preferred Specifically, the temperature is raised to 550 ° C to 700 ° C at a temperature increase rate of 2 to 10 ° C / min, and the temperature is maintained for 2 to 5 hours; more preferably, the temperature is raised to 600 ° C to 700 ° C at a temperature increase rate of 2 to 8 ° C / min, and the heat is maintained. 2 ⁇ 5h; more preferably, the temperature is raised to 650 ° C ⁇ 700 ° C at a heating
  • the invention adopts a sol-gel method to uniformly coat a surface of a nanometer LiMn 1-x Fe x PO 4 with a layer of amorphous phosphate/pyrophosphate and carbon, and the addition of phosphate and pyrophosphate increases on the one hand.
  • the ion conductivity of the material on the other hand, effectively improves the carbon coating effect, and the prepared material has a significantly improved rate performance and cycle performance, and has a higher compaction density.
  • the present invention also provides a lithium ion battery comprising the above-described core-shell structure cathode material.
  • LiMn 0.8 Fe 0.2 PO 4 Li 2 CO 3 , Mn(Ac) 2 , FeC 2 O 4 , NH 4 H 2 PO 4 are dissolved in deionized water according to the stoichiometric ratio of LiMn 0.8 Fe 0.2 PO 4 , and added The mass is obtained by obtaining the theoretical product LiMn 0.8 Fe 0.2 PO 4 5% by weight of citric acid as a complexing agent, and heating and stirring in a water bath at 80 ° C for 8 to 12 hours until the water is evaporated to dryness, and the obtained product is vacuum dried at 80 ° C, -0.98 MPa for 24 hours. .
  • the product After drying, the product is placed in a tube furnace, and is raised to 450 ° C at a heating rate of 5 ° C / min. After 8 h of heat preservation, the temperature is raised to 750 at a heating rate of 5 ° C / min, and the temperature is maintained for 12 h. After cooling, LiMn 0.8 Fe 0.2 PO is obtained. 4 .
  • the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, LiFeP 2 O 7 /C was used to jointly modify the nano-LiMn 0.8 Fe 0.2 PO 4 .
  • the core-shell structure cathode material prepared in Example 1 that is, LiFeP 2 O 7 /C, was coated with nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were measured. The results obtained are shown in Table 1; the 2C charging curve is obtained as shown in FIG. 3; and the 3C discharge capacity retention rate curve is obtained as shown in FIG. 4 .
  • Example 1 The LiFeP 2 O 7 /C composite modified nano-LiMn 0.8 Fe 0.2 PO 4 obtained in Example 1 was analyzed by an electron scanning microscope to obtain a scanning electron micrograph thereof as shown in FIG. 1 and FIG. 2 .
  • the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, LiFeP 2 O 7 /C was used to jointly modify the nano-LiMn 0.8 Fe 0.2 PO 4 .
  • the core-shell structure cathode material prepared in Example 2 that is, LiFeP 2 O 7 /C, was coated with nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
  • the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 h. After cooling, LiFeP 2 O 7 /C was used to jointly modify the nano-LiMn 0.6 Fe 0.4 PO 4 .
  • Li 3 V 2 (PO 4 ) 3 /C co-modified nano-LiMn 0.8 Fe 0.2 PO 4 synthesis 1 mol of Li 2 CO 3 , 2 mol of V(NO3) 3 , 1 mol of NH 4 H 2 PO 4 was dissolved in deionized water, 25 mol of LiMn 0.8 Fe 0.2 PO 4 , a citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 and a mass of 5%, and 5% glucose were added, and the mixture was heated and stirred for 8 to 12 hours in a water bath at 80° C. until the water was evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa.
  • the product After drying, the product is placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, Li 3 V 2 (PO 4 ) 3 /C is used to jointly modify the nano-LiMn 0.8 Fe 0.2 PO. 4 .
  • the core-shell structure cathode material prepared in Example 4 that is, Li 3 V 2 (PO 4 ) 3 /C, was used to modify the nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
  • LiAlP 2 O 7 /C co-modified nano-LiMn 0.8 Fe 0.2 PO 4 synthesis 1 mol of Li 2 CO 3 , 2 mol of Al(NO 3 ) 3 , 1 mol of NH 4 H 2 PO 4 was dissolved in deionized water, and 25 mol of LiMn 0.8 was added.
  • Fe 0.2 PO 4 a citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 and a mass of 5%, and 5% glucose, and heating and stirring in a water bath at 80 ° C for 8 to 12 hours until the water is evaporated to dryness.
  • the obtained product was dried under vacuum at 80 ° C, -0.98 MPa.
  • LiAlP 2 O 7 /C was co-modified with nano-LiMn 0.8 Fe 0.2 PO 4 .
  • Comparative Example 1 The material prepared in Comparative Example 1 was coated with carbon-coated LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were measured. The results obtained are shown in Table 1; the 2C charging curve is obtained as shown in FIG. 3; and the 3C discharge capacity retention rate curve is obtained as shown in FIG. 4 .
  • LiFeP 2 O 7 coated LiMn 0.8 Fe 0.2 PO 4 1 mol of Li 2 CO 3 , 2 mol of FeC 2 O 4 , 2 mol of NH 4 H 2 PO 4 were dissolved in deionized water, and 25 mol of LiMn 0.8 Fe 0.2 PO 4 was added .
  • the citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 mass 5% was heated and stirred in a water bath at 80 ° C for 8 to 12 hours until the water was evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa.
  • LiFeP 2 O 7 was coated with LiMn 0.8 Fe 0.2 PO 4 .
  • LiFeP 2 O 7 prepared in Comparative Example 2 was coated with LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.

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Abstract

The present invention provides a cathode material having a core-shell structure, consisting of a core and a shell. The core is LiMn1-xFexPO4 nanoparticles; the shell is a mixture of carbon and a lithium-containing metal salt; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate, wherein 0<x<0.5. According to the present invention, LiMn1-xFexPO4 nanoparticles are adopted as the core, and the nanosized material can shorten the diffusion path of lithium ions, reduce the diffusion time of lithium ions among particles, and improve the ionic transport property of the material. A mixture of carbon and a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate is adopted as a coating layer, and the addition of the lithium-containing metal phosphate and/or pyrophosphate can increase the ionic conductivity of the material on one hand, and effectively improve the carbon coating effect on the other hand. Thus, the rate performance and the cycling performance of the cathode material having a core-shell structure are significantly improved, and the cathode material having a core-shell structure can also have a higher compact density.

Description

核壳结构LiMn1-xFexPO4正极材料及其制备方法、锂离子电池Core-shell structure LiMn1-xFexPO4 cathode material and preparation method thereof, lithium ion battery
本申请要求于2016年8月19日提交中国专利局、申请号为201610692225.7、发明名称为“核壳结构LiMn1-xFexPO4正极材料及其制备方法、锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。This application claims to be submitted to the Chinese Patent Office on August 19, 2016, the application number is 201610692225.7, and the invention name is “core-shell structure LiMn 1-x Fe x PO 4 cathode material and its preparation method, lithium ion battery” Chinese patent application Priority is hereby incorporated by reference in its entirety.
技术领域Technical field
本发明属于锂离子电池技术领域，尤其涉及一种核壳结构LiMn1-xFexPO4正极材料及其制备方法、锂离子电池。The invention belongs to the technical field of lithium ion batteries, and in particular relates to a core-shell structure LiMn 1-x Fe x PO 4 cathode material, a preparation method thereof and a lithium ion battery.
背景技术Background technique
近年来，绿色环保锂离子二次电池已在各种便携式电子产品和通讯工具中得到广泛应用，并逐步被开发为电动汽车的动力能源。其中，新型电极材料特别是正极材料的研制至关重要。In recent years, green lithium-ion secondary batteries have been widely used in various portable electronic products and communication tools, and have been gradually developed as power sources for electric vehicles. Among them, the development of new electrode materials, especially cathode materials, is crucial.
目前，应用于锂离子电池的正极材料主要是嵌锂的过渡金属氧化物，包括层状LiMO2(M＝Co、Ni、Mn)和尖晶石LiMn2O4，但由于这些材料的价格、安全性、电化学性能等原因使它们在高容量电池的应用方面受到制约。1997年A.K.Padhi首次报道LiFePO4具有脱嵌锂功能，考虑到其具有良好的电化学性能，充放电平台十分平稳，充放电过程中结构稳定。同时，该材料具有无毒、对环境友好、原材料来源丰富、比容量高、循环性能好、可在高温下使用等优点，被认为是动力型锂离子电池最具潜力的正极材料之一。尽管LiFePO4具有诸多优点，但是在实际的应用过程中仍然存在一些问题，特别是其放电平台低，近在3.4V左右，难以满足未来电动汽车市场对电池能量能量密度的需求。At present, the positive electrode materials used in lithium ion batteries are mainly lithium intercalated transition metal oxides, including layered LiMO 2 (M=Co, Ni, Mn) and spinel LiMn 2 O 4 , but due to the price of these materials, Safety, electrochemical performance and other reasons make them restricted in the application of high-capacity batteries. In 1997, AkPadhi reported for the first time that LiFePO 4 has the function of deintercalating lithium. Considering its good electrochemical performance, the charge and discharge platform is very stable, and the structure is stable during charge and discharge. At the same time, the material is non-toxic, environmentally friendly, rich in raw materials, high in specific capacity, good in cycle performance, and can be used at high temperatures. It is considered to be one of the most promising cathode materials for power lithium-ion batteries. Although LiFePO 4 has many advantages, there are still some problems in the actual application process, especially the low discharge platform, which is close to 3.4V, which is difficult to meet the demand for battery energy energy density in the future electric vehicle market.
LiMnPO4与LiFePO4具有相同的橄榄石结构，具有与LiFePO4相近的理论比容量(171mAh/g)与相当的安全性能，其工作电压平台在4.1V，理论能量密度为LiFePO4材料的1.2倍。然而，LiMnPO4的电子电导率和离子扩散速率率及低，导致其放电性能特别是大电流放电性能差。对此国内外的研究者们做了大量工作，其中提高其电子电导率的方法主要有碳包覆、金属离子掺杂等的方法，提高其离子传输速率的方法主要有材料纳米化、控制晶生长方向以及表面包覆离子传输性能良好的材料等。LiMnPO 4 with the olivine LiFePO 4 has the same structure, having the LiFePO 4 close to the theoretical specific capacity (171mAh / g) comparable safety, platform 4.1V operating voltage, the theoretical energy density of LiFePO 4 is 1.2 times the material . However, the electronic conductivity and ion diffusion rate of LiMnPO 4 are low, resulting in poor discharge performance, particularly high current discharge performance. A lot of work has been done by researchers at home and abroad. Among them, methods for improving the electronic conductivity are mainly carbon coating, metal ion doping, etc. The methods for increasing the ion transport rate are mainly material nanocrystallization and control crystal. Growth direction and materials with good surface ion transport properties.
无定型态的磷酸盐/焦磷酸盐是一种良好的Li+传输载体，研究表明，将其 包覆在LiFePO4表面可以有效提高其电化学性能，特别是大电流放电性能。公开号为CN102842713A的中国专利提供了一种表面包覆非晶态焦磷酸盐的磷酸铁锂材料及制备方法，该材料具有良好的倍率性能，2C放电容量在136mAh/g以上。然而单一包覆非晶态焦磷酸盐对材料倍率性能提升有限。公开号为CN103050694B的中国专利将金属氧化物/金属盐与碳共同包覆于磷酸铁锂表面，得到容量倍率性能优异的磷酸铁锂材料，然而，该专利采用球磨+喷雾干燥法很难将金属氧化物/金属盐与碳均匀的包覆在磷酸铁锂材料表面，包覆过程容易产生团聚现象，不利于材料电化学性能的发挥与批次稳定性。Amorphous phosphate/pyrophosphate is a good Li + transport carrier. Studies have shown that coating it on the surface of LiFePO 4 can effectively improve its electrochemical performance, especially high current discharge performance. The Chinese patent publication CN102842713A provides a lithium iron phosphate material coated with an amorphous pyrophosphate and a preparation method thereof. The material has good rate performance, and the 2C discharge capacity is above 136 mAh/g. However, the single coated amorphous pyrophosphate has limited improvement in material rate performance. The Chinese patent publication CN103050694B coats the metal oxide/metal salt with carbon on the surface of lithium iron phosphate to obtain lithium iron phosphate material with excellent capacity ratio performance. However, the patent uses ball milling + spray drying method to make metal difficult. The oxide/metal salt and carbon are uniformly coated on the surface of the lithium iron phosphate material, and the agglomeration phenomenon is easily generated in the coating process, which is disadvantageous to the electrochemical performance of the material and the batch stability.
碳包覆是提高材料表面电导率，改善材料电化学性能的最常见且有效的手段。同时碳包覆层可以缓解活性物质与电解液的接触，提高材料的循环稳定性。现有技术中一系列专利均采用碳包覆的方法有效改善了磷酸铁锂材料的导电率，进而提升了其电化学性能。然而，研究表明，与磷酸铁锂相比，在LiMn1-xFexPO4表面包覆碳效果并不理想，单一碳包覆很难在LiMn1-xFexPO4表面形成均匀包覆层，通常采用的方法是加大包覆碳的含量来保证包覆效果，然而这样材料的重量比能量将会受到较大影响。Carbon coating is the most common and effective means to improve the surface conductivity of materials and improve the electrochemical performance of materials. At the same time, the carbon coating layer can alleviate the contact between the active material and the electrolyte, and improve the cycle stability of the material. A series of patents in the prior art use a carbon coating method to effectively improve the conductivity of the lithium iron phosphate material, thereby improving its electrochemical performance. However, studies have shown that the effect of coating carbon on the surface of LiMn 1-x Fe x PO 4 is not ideal compared to lithium iron phosphate. It is difficult to form a uniform coating on the surface of LiMn 1-x Fe x PO 4 with a single carbon coating. Layer, the usual method is to increase the content of coated carbon to ensure the coating effect, however, the weight ratio energy of such materials will be greatly affected.
发明内容Summary of the invention
有鉴于此，本发明要解决的技术问题在于提供一种倍率性能较高的核壳结构LiMn1-xFexPO4正极材料及其制备方法、锂离子电池。In view of the above, the technical problem to be solved by the present invention is to provide a core-shell structure LiMn 1-x Fe x PO 4 cathode material having high rate performance and a preparation method thereof, and a lithium ion battery.
本发明提供了一种核壳结构LiMn1-xFexPO4正极材料，由内核和外壳组成，所述内核为LiMn1-xFexPO4纳米颗粒；所述外壳为碳与含锂的金属盐的混合物；所述含锂的金属盐为含锂的金属磷酸盐和/或含锂的金属焦磷酸盐；0＜x＜0.5。The invention provides a core-shell structure LiMn 1-x Fe x PO 4 cathode material, which is composed of a core and a shell, the core is LiMn 1-x Fe x PO 4 nanoparticles; the shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 < x < 0.5.
优选的，所述LiMn1-xFexPO4纳米颗粒的粒径为10～200nm。Preferably, the LiMn 1-x Fe x PO 4 nanoparticles have a particle diameter of 10 to 200 nm.
优选的，所述含锂的金属盐为LiFeP2O7，LiAlP2O7与Li3V2(PO4)3中的一种或多种。Preferably, the lithium-containing metal salt is one or more of LiFeP 2 O 7 , LiAlP 2 O 7 and Li 3 V 2 (PO 4 ) 3 .
优选的，所述碳的质量为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％。Preferably, the mass of the carbon is from 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles.
优选的，所述含锂的金属盐的质量为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％。Preferably, the lithium-containing metal salt has a mass of 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles.
本发明还提供了一种核壳结构LiMn1-xFexPO4正极材料的制备方法，包括以下步骤： The invention also provides a preparation method of a core-shell structure LiMn 1-x Fe x PO 4 cathode material, comprising the following steps:
S1)将第一锂源化合物、金属源化合物、第一磷源化合物、LiMn1-xFexPO4纳米颗粒、第一络合剂、可溶性碳源与水混合，加热至水分蒸发干，得到中间体；0＜x＜0.5；S1) mixing the first lithium source compound, the metal source compound, the first phosphorus source compound, the LiMn 1-x Fe x PO 4 nanoparticles, the first complexing agent, the soluble carbon source and water, and heating to evaporate to obtain Intermediate; 0<x<0.5;
S2)将所述中间体进行煅烧，得到核壳结构正极材料。S2) The intermediate is calcined to obtain a core-shell structured positive electrode material.
优选的，所述LiMn1-xFexPO4纳米颗粒按照以下方法制备：Preferably, the LiMn 1-x Fe x PO 4 nanoparticles are prepared as follows:
A)将第二锂源化合物、锰源化合物、铁源化合物、第二磷源化合物与第二络合剂在水中混合，加热至水分蒸发干，煅烧后，得到LiMn1-xFexPO4纳米颗粒；所述第二锂源化合物中的锂离子、锰源化合物中的锰离子、铁源化合物中的铁离子与第二磷源化合物中的磷原子的摩尔比为1：(1-x)：x：1。A) mixing the second lithium source compound, the manganese source compound, the iron source compound, the second phosphorus source compound and the second complexing agent in water, heating to moisture evaporation, and calcining to obtain LiMn 1-x Fe x PO 4 a nanoparticle; a lithium ion in the second lithium source compound; a manganese ion in the manganese source compound; a molar ratio of the iron ion in the iron source compound to the phosphorus atom in the second phosphorus source compound: 1: 1-x ): x:1.
优选的，所述步骤A)中的煅烧具体为：以2～10℃/min的升温速率升至350℃～450℃，保温4～10h后，再以2～10℃/min的升温速率升温至650℃～800℃，保温8～20h。Preferably, the calcination in the step A) is specifically: raising the temperature to 350 ° C to 450 ° C at a temperature increase rate of 2 to 10 ° C / min, after 4 to 10 h of heat retention, and then increasing the temperature at a temperature increase rate of 2 to 10 ° C / min. To 650 ° C ~ 800 ° C, heat 8 ~ 20h.
优选的，所述步骤S2)中的煅烧具体为：以2～10℃/min的升温速率升温至550℃～700℃，保温2～5h。Preferably, the calcination in the step S2) is specifically: raising the temperature to 550 ° C to 700 ° C at a temperature increase rate of 2 to 10 ° C / min, and maintaining the temperature for 2 to 5 hours.
本发明还提供了一种锂离子电池，包括核壳结构LiMn1-xFexPO4正极材料。The present invention also provides a lithium ion battery comprising a core-shell structure LiMn 1-x Fe x PO 4 cathode material.
本发明提供了一种核壳结构LiMn1-xFexPO4正极材料，由内核和外壳组成，所述内核为LiMn1-xFexPO4纳米颗粒；所述外壳为碳与含锂的金属盐的混合物；所述含锂的金属盐为含锂的金属磷酸盐和/或含锂的金属焦磷酸盐；0＜x＜0.5。与现有技术相比，本发明以LiMn1-xFexPO4纳米颗粒为内核，材料纳米化能够缩短锂离子扩散路径，减少锂离子在颗粒之间的扩散时间，提升材料离子传输性能；以碳与含锂的金属磷酸盐和/或含锂的金属焦磷酸盐的混合物作为包覆层，含锂的金属磷酸盐和/或焦磷酸盐的加入，一方面可增加材料离子的传导性能，另一方面，有效改善了碳包覆的效果，从而减小了碳包覆含量，从而使核壳结构正极材料的倍率性能与循环性能得到明显改善，具有较高的压实密度。The invention provides a core-shell structure LiMn 1-x Fe x PO 4 cathode material, which is composed of a core and a shell, the core is LiMn 1-x Fe x PO 4 nanoparticles; the shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 < x < 0.5. Compared with the prior art, the present invention uses LiMn 1-x Fe x PO 4 nanoparticles as a core, and material nanocrystallization can shorten the lithium ion diffusion path, reduce the diffusion time of lithium ions between particles, and improve the ion transport performance of materials; The addition of a mixture of carbon and a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate as a coating layer, the addition of lithium-containing metal phosphate and/or pyrophosphate, on the one hand, increases the conductivity of the material ions. On the other hand, the effect of carbon coating is effectively improved, thereby reducing the carbon coating content, thereby significantly improving the rate performance and cycle performance of the core-shell structure cathode material, and having a higher compaction density.
附图说明DRAWINGS
图1为本发明实施例1中得到的核壳结构正极材料即LiFeP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4的扫描电镜照片；1 is a scanning electron micrograph of a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C co-modified nano-LiMn 0.8 Fe 0.2 PO 4 ;
图2为本发明实施例1中得到的核壳结构正极材料即LiFeP2O7/C共同修 饰纳米LiMn0.8Fe0.2PO4的扫描电镜照片；2 is a scanning electron micrograph of a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C, which is commonly decorated with nano-LiMn 0.8 Fe 0.2 PO 4 ;
图3为本发明实施例1中得到的核壳结构正极材料即LiFeP2O7/C共同包覆纳米LiMn0.8Fe0.2PO4与对比例1中得到的碳包覆LiMn0.8Fe0.2PO4的2C充电曲线图；3 is a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C co-coated with nano-LiMn 0.8 Fe 0.2 PO 4 and carbon-coated LiMn 0.8 Fe 0.2 PO 4 obtained in Comparative Example 1. 2C charging curve;
图4为本发明实施例1中得到的核壳结构正极材料即LiFeP2O7/C共同包覆纳米LiMn0.8Fe0.2PO4与对比例1中得到的碳包覆LiMn0.8Fe0.2PO4的3C放电容量保持率曲线图。4 is a core-shell structure positive electrode material obtained in Example 1 of the present invention, that is, LiFeP 2 O 7 /C co-coated with nano-LiMn 0.8 Fe 0.2 PO 4 and carbon-coated LiMn 0.8 Fe 0.2 PO 4 obtained in Comparative Example 1. 3C discharge capacity retention rate graph.
具体实施方式detailed description
下面将结合本发明实施例，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，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，都属于本发明保护的范围。The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.
本发明提供了一种核壳结构LiMn1-xFexPO4正极材料，由内核和外壳组成，所述内核为LiMn1-xFexPO4纳米颗粒；所述外壳为碳与含锂的金属盐的混合物；所述含锂的金属盐为含锂的金属磷酸盐和/或含锂的金属焦磷酸盐；0＜x＜0.5。The invention provides a core-shell structure LiMn 1-x Fe x PO 4 cathode material, which is composed of a core and a shell, the core is LiMn 1-x Fe x PO 4 nanoparticles; the shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 < x < 0.5.
本发明以LiMn1-xFexPO4纳米颗粒为内核，其中，0＜x＜0.5，优选为0.2≤x≤0.4；在本发明提供的一些实施例中，所述x优选为0.2；在本发明提供的另一些实施例中，所述x优选为0.4。所述LiMn1-xFexPO4纳米颗粒的粒径优选为10～200nm，更优选为20～100nm，再优选为20～60nm。The present invention has LiMn 1-x Fe x PO 4 nanoparticles as a core, wherein 0 < x < 0.5, preferably 0.2 ≤ x ≤ 0.4; in some embodiments provided by the present invention, the x is preferably 0.2; In other embodiments provided by the present invention, the x is preferably 0.4. The particle diameter of the LiMn 1-x Fe x PO 4 nanoparticles is preferably from 10 to 200 nm, more preferably from 20 to 100 nm, still more preferably from 20 to 60 nm.
所述LiMn1-xFexPO4内核外包裹有外壳，所述外壳为碳与含锂的金属盐的混合物，所述含锂的金属盐为含锂的金属磷酸盐和/或含锂的金属焦磷酸盐，优选为LiFeP2O7，LiAlP2O7与Li3V2(PO4)3中的一种或多种；所述外壳中，碳的质量优选为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％，更优选为0.5％～5％；所述含锂的金属盐的质量优选为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％，更优选为0.5％～5％。本发明以LiMn1-xFexPO4纳米颗粒为内核，材料纳米化能够缩短锂离子扩散路径，减少锂离子在颗粒之间的扩散时间，提升材料离子传输性能；以碳与含锂的金属磷酸盐和/或含锂的金属焦磷酸盐的混合物作为包覆层，含锂的金属磷酸盐和/或焦磷酸盐的加入，一方面可增加材料离子的传导性能，另一方面，有效改善了碳包覆的效果，减少了碳包覆含量，从而使核 壳结构正极材料的倍率性能与循环性能得到明显改善，同时具有较高的压实密度。The LiMn 1-x Fe x PO 4 core is externally coated with a shell which is a mixture of carbon and a lithium-containing metal salt, the lithium-containing metal salt being a lithium-containing metal phosphate and/or lithium-containing The metal pyrophosphate is preferably one or more of LiFeP 2 O 7 , LiAlP 2 O 7 and Li 3 V 2 (PO 4 ) 3 ; in the outer shell, the mass of carbon is preferably LiMn 1-x Fe x nano PO 4 0.1% to 10% of the particle mass, and more preferably from 0.5 to 5%; the lithium-containing metal salt is preferably a mass LiMn 1-x Fe x PO 4 0.1% to 10% by nano-particles of the mass, More preferably, it is 0.5% - 5%. The invention uses LiMn 1-x Fe x PO 4 nanoparticles as the core, and material nanocrystallization can shorten the lithium ion diffusion path, reduce the diffusion time of lithium ions between the particles, and improve the ion transport performance of the material; the carbon and the lithium-containing metal The addition of a mixture of phosphate and/or lithium-containing metal pyrophosphate as a coating layer, lithium-containing metal phosphate and/or pyrophosphate, on the one hand, can increase the conductivity of the material ions, on the other hand, effectively improve The effect of carbon coating reduces the carbon coating content, so that the rate performance and cycle performance of the core-shell structure cathode material are significantly improved, and at the same time, the compaction density is high.
本发明还提供了一种上述核壳结构LiMn1-xFexPO4正极材料的制备方法，包括以下步骤：S1)将第一锂源化合物、金属源化合物、第一磷源化合物、LiMn1-xFexPO4纳米颗粒、第一络合剂、可溶性碳源与水混合，加热至水分蒸发干，得到中间体；0＜x＜0.5；S2)将所述中间体进行煅烧，得到核壳结构正极材料。The present invention also provides a method for preparing the above-described core-shell structure LiMn 1-x Fe x PO 4 cathode material, comprising the steps of: S1) first lithium source compound, metal source compound, first phosphorus source compound, LiMn 1 -x Fe x PO 4 nanoparticles, a first complexing agent, a soluble carbon source mixed with water, heated to evaporation of water to obtain an intermediate; 0 < x <0.5; S2) calcining the intermediate to obtain a core Shell structure cathode material.
其中，本发明对所有原料的来源并没有特殊的限制，可为市售也可为自制。Among them, the present invention has no particular limitation on the source of all raw materials, and may be commercially available or homemade.
在本发明中，所述LiMn1-xFexPO4纳米颗粒优选按照以下方法制备：A)将第二锂源化合物、锰源化合物、铁源化合物、第二磷源化合物与第二络合剂在水中混合，加热至水分蒸发干，煅烧后，得到LiMn1-xFexPO4纳米颗粒；所述第二锂源化合物中的锂离子、锰源化合物中的锰离子、铁源化合物中的铁离子与第二磷源化合物中的磷原子的摩尔比为1：(1-x)：x：1。In the present invention, the LiMn 1-x Fe x PO 4 nanoparticles are preferably prepared by the following method: A) combining a second lithium source compound, a manganese source compound, an iron source compound, and a second phosphorus source compound with a second complex The agent is mixed in water, heated to evaporate to dryness, and calcined to obtain LiMn 1-x Fe x PO 4 nanoparticles; lithium ions in the second lithium source compound, manganese ions in the manganese source compound, and iron source compounds The molar ratio of the iron ion to the phosphorus atom in the second phosphorus source compound is 1: (1-x): x:1.
其中，所述第一锂源化合物与第二锂源化合物为本领域技术人员熟知的锂源化合物即可，并无特殊的限制，本发明中各自独立地优选为碳酸锂、氢氧化锂与乙酸锂中的一种或多种。Wherein, the first lithium source compound and the second lithium source compound are lithium source compounds well known to those skilled in the art, and are not particularly limited. In the present invention, each of them is preferably lithium carbonate, lithium hydroxide and acetic acid. One or more of lithium.
所述锰源化合物为本领域技术人员熟知的锰源化合物即可，并无特殊的限制，本发明中优选为硝酸锰、氯化锰、硫酸锰与醋酸锰中的一种或多种。The manganese source compound is not particularly limited as long as it is a manganese source compound well known to those skilled in the art, and one or more of manganese nitrate, manganese chloride, manganese sulfate and manganese acetate are preferred in the present invention.
所述铁源化合物为本领域技术人员熟知的铁源化合物即可，并无特殊的限制，本发明中优选为草酸亚铁、醋酸亚铁、氯化亚铁、硝酸亚铁与硫酸亚铁中的一种或多种。The iron source compound may be an iron source compound well known to those skilled in the art, and is not particularly limited. In the present invention, ferrous oxalate, ferrous acetate, ferrous chloride, ferrous nitrate and ferrous sulfate are preferred. One or more.
所述第一磷源化合物与第二磷酸化合物为本领域技术人员熟知的磷源化合物即可，并无特殊的限制，本发明中各自独立地优选为磷酸二氢铵、磷酸氢二铵与磷酸铵中的一种或多种。The first phosphorus source compound and the second phosphoric acid compound are not particularly limited as long as the phosphorus source compound is well known to those skilled in the art, and each of the present invention is preferably ammonium dihydrogen phosphate, diammonium phosphate and phosphoric acid. One or more of ammonium.
所述金属源化合物为本领域技术人员熟知的金属源化合物即可，并无特殊的限制，本发明中优选为草酸铁、硝酸铝与硝酸钒中的一种或多种。The metal source compound is not particularly limited as long as it is a metal source compound well known to those skilled in the art, and one or more of iron oxalate, aluminum nitrate and vanadium nitrate are preferred in the present invention.
所述第一络合剂与第二络合剂为本领域技术人员熟知的络合剂即可，并无特殊的限制，本发明中各自独立地优选为柠檬酸、草酸、己二酸、抗坏血酸与聚乙二醇的一种或多种。 The first complexing agent and the second complexing agent may be any complexing agents well known to those skilled in the art, and are not particularly limited. In the present invention, each of them is preferably citric acid, oxalic acid, adipic acid, ascorbic acid. One or more with polyethylene glycol.
所述可溶性碳源为本领域技术人员熟知的可溶性碳源即可，并无特殊的限制，本发明中优选为葡糖糖、蔗糖、柠檬酸、酒石酸、草酸、己二酸、聚乙二醇、水杨酸、聚乙烯醇、肉桂酸、果糖、抗坏血酸与苹果酸中的一种或多种。The soluble carbon source may be a soluble carbon source well known to those skilled in the art, and is not particularly limited. In the present invention, glucose sugar, sucrose, citric acid, tartaric acid, oxalic acid, adipic acid, polyethylene glycol are preferred. One or more of salicylic acid, polyvinyl alcohol, cinnamic acid, fructose, ascorbic acid and malic acid.
将第二锂源化合物、锰源化合物、铁源化合物、第二磷源化合物与第二络合剂在水中混合，其中，所述第二锂源化合物中的锂离子、锰源化合物中的锰离子、铁源化合物中的铁离子与第二磷源化合物中的磷原子的摩尔比为1：(1-x)：x：1，所述x同上所述，在此不再赘述；所述第二络合剂的质量优选为产物LiMn1-xFexPO4质量的1％～10％，更优选为4％～8％，再优选为5％～8％，最优选为5％。The second lithium source compound, the manganese source compound, the iron source compound, the second phosphorus source compound and the second complexing agent are mixed in water, wherein the lithium ion in the second lithium source compound and the manganese in the manganese source compound The molar ratio of the iron ion in the ion and the iron source compound to the phosphorus atom in the second phosphorus source compound is 1: (1-x): x: 1, the x is the same as described above, and is not described herein; The mass of the second complexing agent is preferably from 1% to 10% by mass of the product LiMn 1-x Fe x PO 4 , more preferably from 4% to 8%, still more preferably from 5% to 8%, most preferably 5%.
混合后加热至水分蒸发干，所述加热的温度优选为60℃～100℃，更优选为70℃～90℃，再优选为80℃；所述加热的时间优选为8～12h。After mixing, the mixture is heated to evaporate to dryness, and the heating temperature is preferably 60 to 100 ° C, more preferably 70 to 90 ° C, still more preferably 80 ° C; and the heating time is preferably 8 to 12 h.
加热至水分蒸发干后，优选进行真空干燥；所述真空干燥的温度优选为80℃～100℃，更优选为80℃～90℃，再优选为80℃～85℃，最优选为80℃；所述真空干燥的压力优选为-0.98MPa。After heating to moisture evaporation, preferably vacuum drying; the vacuum drying temperature is preferably 80 ° C ~ 100 ° C, more preferably 80 ° C ~ 90 ° C, still more preferably 80 ° C ~ 85 ° C, most preferably 80 ° C; The pressure for vacuum drying is preferably -0.98 MPa.
真空干燥后，进行煅烧；所述煅烧优选为分为两段进行煅烧；第一次煅烧的温度优选为350℃～450℃，更优选为400℃～450℃；所述第一次煅烧的时间优选为4～10h，更优选为4～8h，再优选为6～8h；所述第二次煅烧的温度优选为650℃～800℃，更优选为700℃～800℃，再优选为750℃～800℃；所述第二次煅烧的时间优选为8～20h，更优选为8～15h，再优选为10～15h。在本发明中，该煅烧优选具体按照以下过程进行：以2～10℃/min的升温速率升至350℃～450℃，保温4～10h后，再以2～10℃/min的升温速率升温至650℃～800℃，保温8～20h；更优选按照以下过程进行：以2～8℃/min的升温速率升至350℃～450℃，保温4～10h后，再以2～8℃/min的升温速率升温至650℃～800℃，保温8～20h；再优选按照以下过程进行：以4～6℃/min的升温速率升至350℃～450℃，保温4～10h后，再以4～6℃/min的升温速率升温至650℃～800℃，保温8～20h。After vacuum drying, calcination is carried out; the calcination is preferably carried out in two stages; the temperature of the first calcination is preferably from 350 ° C to 450 ° C, more preferably from 400 ° C to 450 ° C; the time of the first calcination Preferably, it is 4 to 10 hours, more preferably 4 to 8 hours, still more preferably 6 to 8 hours; and the temperature of the second calcination is preferably 650 to 800 ° C, more preferably 700 to 800 ° C, still more preferably 750 ° C ～800 ° C; the time of the second calcination is preferably 8 to 20 h, more preferably 8 to 15 h, still more preferably 10 to 15 h. In the present invention, the calcination is preferably carried out according to the following procedure: raising the temperature to a temperature of from 2 to 10 ° C / min to 350 ° C to 450 ° C, after 4 to 10 h of incubation, and then increasing the temperature of 2 to 10 ° C / min 650 ° C ~ 800 ° C, heat 8 ~ 20h; more preferably according to the following process: 2 ~ 8 ° C / min temperature increase rate to 350 ° C ~ 450 ° C, after 4 ~ 10h, then 2 ~ 8 ° C / The heating rate of min is raised to 650 ° C ~ 800 ° C, and the temperature is maintained for 8 ~ 20 h; further preferably according to the following process: at a temperature increase rate of 4 ~ 6 ° C / min to 350 ° C ~ 450 ° C, after 4 ~ 10 h, then The temperature increase rate of 4 to 6 ° C / min is raised to 650 ° C ~ 800 ° C, and the temperature is maintained for 8 ~ 20h.
冷却后，得到LiMn1-xFexPO4纳米颗粒。After cooling, LiMn 1-x Fe x PO 4 nanoparticles were obtained.
将第一锂源化合物、金属源化合物、第一磷源化合物、LiMn1-xFexPO4纳米颗粒、第一络合剂、可溶性碳源与水混合；其中，所述第一锂源化合物中的 锂离子、金属源化合物中的金属离子与第一磷源化合物中的磷原子的摩尔比优选为(1～2)：1：(1.5～1)，更优选为(1～1.5)：1：(1～1.5)；所述第一锂盐化合物、金属源化合物与第一磷源化合物的总质量优选为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％，更优选为0.5％～5％；所述第一络合剂的质量优选为LiMn1-xFexPO4纳米颗粒质量的1％～10％，更优选为5％～10％，再优选为5％～8％，最优选为5％；所述可溶性碳源的质量优选为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％，更优选为0.5％～10％，再优选为1％～10％，最优选为5％～10％。Mixing a first lithium source compound, a metal source compound, a first phosphorus source compound, LiMn 1-x Fe x PO 4 nanoparticles, a first complexing agent, a soluble carbon source, and water; wherein the first lithium source compound The molar ratio of the lithium ion in the lithium ion and the metal source compound to the phosphorus atom in the first phosphorus source compound is preferably (1 to 2): 1: (1.5 to 1), more preferably (1 to 1.5): 1: (1 to 1.5); the total mass of the first lithium salt compound, the metal source compound and the first phosphorus source compound is preferably 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles, more preferably It is 0.5% to 5%; the mass of the first complexing agent is preferably from 1% to 10%, more preferably from 5% to 10%, still more preferably 5% by mass of the LiMn 1-x Fe x PO 4 nanoparticles. ～8%, most preferably 5%; the mass of the soluble carbon source is preferably from 0.1% to 10%, more preferably from 0.5% to 10%, still more preferably 1% by mass of the LiMn 1-x Fe x PO 4 nanoparticles. % to 10%, most preferably 5% to 10%.
混合后，加热至水分蒸发干；所述加热的温度优选为60℃～100℃，更优选为70℃～90℃，再优选为80℃；所述加热的时间优选为8～12h。After mixing, the mixture is heated to evaporate to dryness; the heating temperature is preferably 60 to 100 ° C, more preferably 70 to 90 ° C, still more preferably 80 ° C; and the heating time is preferably 8 to 12 h.
加热至水分蒸发干后，优选进行真空干燥，得到中间体；所述真空干燥的温度优选为80℃～100℃，更优选为80℃～90℃，再优选为80℃～85℃，最优选为80℃；所述真空干燥的压力优选为-0.98MPa。After heating to evaporate and dry, it is preferably vacuum dried to obtain an intermediate; the vacuum drying temperature is preferably from 80 ° C to 100 ° C, more preferably from 80 ° C to 90 ° C, still more preferably from 80 ° C to 85 ° C, most preferably It is 80 ° C; the pressure of the vacuum drying is preferably -0.98 MPa.
将所述中间体进行煅烧；所述煅烧的温度优选为550℃～700℃，更优选为600℃～700℃，再优选为600℃～650℃；所述煅烧的升温速率优选为2～10℃/min，更优选为2～8℃/min，再优选为4～6℃/min；所述煅烧的时间优选为2～5h，更优选为3～4h；在本发明中，该煅烧优选具体为：以2～10℃/min的升温速率升温至550℃～700℃，保温2～5h；更优选具体为：以2～8℃/min的升温速率升温至600℃～700℃，保温2～5h；再优选具体为：以4～6℃/min的升温速率升温至650℃～700℃，保温2～5h。The intermediate is calcined; the calcination temperature is preferably 550 ° C to 700 ° C, more preferably 600 ° C to 700 ° C, still more preferably 600 ° C to 650 ° C; the calcination temperature is preferably 2 to 10 ° C / min, more preferably 2 to 8 ° C / min, still more preferably 4 to 6 ° C / min; the calcination time is preferably 2 to 5 h, more preferably 3 to 4 h; in the present invention, the calcination is preferred Specifically, the temperature is raised to 550 ° C to 700 ° C at a temperature increase rate of 2 to 10 ° C / min, and the temperature is maintained for 2 to 5 hours; more preferably, the temperature is raised to 600 ° C to 700 ° C at a temperature increase rate of 2 to 8 ° C / min, and the heat is maintained. 2~5h; more preferably, the temperature is raised to 650 ° C ~ 700 ° C at a heating rate of 4 ~ 6 ° C / min, and the temperature is maintained for 2 ~ 5h.
煅烧后冷却，得到核壳结构正极材料。After calcination, it is cooled to obtain a core-shell structure cathode material.
本发明采用溶胶凝胶法在纳米LiMn1-xFexPO4表面均匀包覆一层非晶态磷酸盐/焦磷酸盐与碳的共混材料，磷酸盐与焦磷酸盐的加入一方面增加了材料离子传导性能，另一方面，有效改善了碳包覆效果，制备出的材料倍率性能与循环性能得到明显改善，且具有较高的压实密度。The invention adopts a sol-gel method to uniformly coat a surface of a nanometer LiMn 1-x Fe x PO 4 with a layer of amorphous phosphate/pyrophosphate and carbon, and the addition of phosphate and pyrophosphate increases on the one hand. The ion conductivity of the material, on the other hand, effectively improves the carbon coating effect, and the prepared material has a significantly improved rate performance and cycle performance, and has a higher compaction density.
本发明还提供了一种包括上述核壳结构正极材料的锂离子电池。The present invention also provides a lithium ion battery comprising the above-described core-shell structure cathode material.
为了进一步说明本发明，以下结合实施例对本发明提供的一种核壳结构正极材料及其制备方法进行详细描述。In order to further illustrate the present invention, a core-shell structure positive electrode material and a preparation method thereof provided by the present invention will be described in detail below with reference to the embodiments.
以下实施例中所用的试剂均为市售。 The reagents used in the following examples are all commercially available.
实施例1Example 1
LiMn0.8Fe0.2PO4的合成：将Li2CO3、Mn(Ac)2、FeC2O4、NH4H2PO4按照LiMn0.8Fe0.2PO4中化学计量比溶于去离子水中，加入质量为得到理论产物LiMn0.8Fe0.2PO4质量5％的柠檬酸为络合剂，80℃水浴加热搅拌8～12h，直至水分蒸干，所得产物于80℃、-0.98MPa条件下真空干燥24h。干燥后产物至于管式炉中，以5℃/min的升温速率升至450℃，保温8h后，再以5℃/min的升温速率升温至750，保温12h，冷却后得LiMn0.8Fe0.2PO4。Synthesis of LiMn 0.8 Fe 0.2 PO 4 : Li 2 CO 3 , Mn(Ac) 2 , FeC 2 O 4 , NH 4 H 2 PO 4 are dissolved in deionized water according to the stoichiometric ratio of LiMn 0.8 Fe 0.2 PO 4 , and added The mass is obtained by obtaining the theoretical product LiMn 0.8 Fe 0.2 PO 4 5% by weight of citric acid as a complexing agent, and heating and stirring in a water bath at 80 ° C for 8 to 12 hours until the water is evaporated to dryness, and the obtained product is vacuum dried at 80 ° C, -0.98 MPa for 24 hours. . After drying, the product is placed in a tube furnace, and is raised to 450 ° C at a heating rate of 5 ° C / min. After 8 h of heat preservation, the temperature is raised to 750 at a heating rate of 5 ° C / min, and the temperature is maintained for 12 h. After cooling, LiMn 0.8 Fe 0.2 PO is obtained. 4 .
LiFeP2O7/C共同包覆纳米LiMn0.8Fe0.2PO4的合成：将1mol Li2CO3、2mol FeC2O4、2mol NH4H2PO4溶于去离子水中，加入25mol LiMn0.8Fe0.2PO4、质量分别为LiMn0.8Fe0.2PO4质量5％的柠檬酸络合剂以及5％的葡萄糖，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得LiFeP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4。Synthesis of LiFeP 2 O 7 /C Co-coated with Nano-LiMn 0.8 Fe 0.2 PO 4 : Dissolve 1 mol of Li 2 CO 3 , 2 mol of FeC 2 O 4 , 2 mol of NH 4 H 2 PO 4 in deionized water, and add 25 mol of LiMn 0.8 Fe 0.2 PO 4 and a citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 and a mass of 5%, and 5% glucose, and heating and stirring in a water bath at 80 ° C for 8 to 12 hours until the water is evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, LiFeP 2 O 7 /C was used to jointly modify the nano-LiMn 0.8 Fe 0.2 PO 4 .
以实施例1所制备核壳结构正极材料即LiFeP2O7/C共同包覆纳米LiMn0.8Fe0.2PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1；得到其2C充电曲线图如图3所示；得到其3C放电容量保持率曲线图如图4所示。The core-shell structure cathode material prepared in Example 1 , that is, LiFeP 2 O 7 /C, was coated with nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were measured. The results obtained are shown in Table 1; the 2C charging curve is obtained as shown in FIG. 3; and the 3C discharge capacity retention rate curve is obtained as shown in FIG. 4 .
利用电子扫描显微镜对实施例1中得到的LiFeP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4进行分析，得到其扫描电镜照片，如图1与图2所示。The LiFeP 2 O 7 /C composite modified nano-LiMn 0.8 Fe 0.2 PO 4 obtained in Example 1 was analyzed by an electron scanning microscope to obtain a scanning electron micrograph thereof as shown in FIG. 1 and FIG. 2 .
实施例2Example 2
LiMn0.8Fe0.2PO4的合成：按照实施例1中LiMn0.8Fe0.2PO4的合成方法进行合成。Synthesis of LiMn 0.8 Fe 0.2 PO 4: was synthesized according to Synthesis Example 1 LiMn 0.8 Fe 0.2 PO 4.
LiFeP2O7/C共同包覆纳米LiMn0.8Fe0.2PO4的合成：将2mol Li2CO3、4mol FeC2O4、4mol NH4H2PO4溶于去离子水中，加入25mol LiMn0.8Fe0.2PO4、质量分别为LiMn0.8Fe0.2PO4质量5％的柠檬酸络合剂以及10％的葡萄糖，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得LiFeP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4。Synthesis of LiFeP 2 O 7 /C Co-coated with Nano-LiMn 0.8 Fe 0.2 PO 4 : 2 mol of Li 2 CO 3 , 4 mol of FeC 2 O 4 , 4 mol of NH 4 H 2 PO 4 were dissolved in deionized water, and 25 mol of LiMn 0.8 Fe was added. 0.2 PO 4 , LiMn 0.8 Fe 0.2 PO 4 5% by mass of citric acid complexing agent and 10% glucose, heated and stirred in a water bath at 80 ° C for 8 to 12 h until the water was evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, LiFeP 2 O 7 /C was used to jointly modify the nano-LiMn 0.8 Fe 0.2 PO 4 .
以实施例2所制备核壳结构正极材料即LiFeP2O7/C共同包覆纳米 LiMn0.8Fe0.2PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1。The core-shell structure cathode material prepared in Example 2, that is, LiFeP 2 O 7 /C, was coated with nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
实施例3Example 3
LiMn0.6Fe0.4PO4的合成：按照实施例1中LiMn0.8Fe0.2PO4的合成方法进行合成。Synthesis of LiMn 0.6 Fe 0.4 PO 4 : The synthesis was carried out in accordance with the synthesis method of LiMn 0.8 Fe 0.2 PO 4 in Example 1.
LiFeP2O7/C共同包覆纳米LiMn0.6Fe0.4PO4的合成：将1mol Li2CO3、2mol FeC2O4、1mol NH4H2PO4溶于去离子水中，加入25mol LiMn0.8Fe0.2PO4、质量分别为LiMn0.6Fe0.4PO4质量5％的柠檬酸络合剂以及5％的葡萄糖，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得LiFeP2O7/C共同修饰纳米LiMn0.6Fe0.4PO4。Synthesis of LiFeP 2 O 7 /C Co-coated with Nano-LiMn 0.6 Fe 0.4 PO 4 : Dissolve 1 mol of Li 2 CO 3 , 2 mol of FeC 2 O 4 , 1 mol of NH 4 H 2 PO 4 in deionized water, and add 25 mol of LiMn 0.8 Fe 0.2 PO 4 and a citric acid complexing agent having a mass of LiMn 0.6 Fe 0.4 PO 4 and a mass of 5%, respectively, and 5% glucose, and heating and stirring for 8 to 12 hours in a water bath at 80 ° C until the water is evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 h. After cooling, LiFeP 2 O 7 /C was used to jointly modify the nano-LiMn 0.6 Fe 0.4 PO 4 .
以实施例3所制备核壳结构正极材料即LiFeP2O7/C共同包覆纳米LiMn0.6Fe0.4PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1。The core-shell structure cathode material prepared in Example 3, that is, LiFeP 2 O 7 /C, was coated with nano-LiMn 0.6 Fe 0.4 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
实施例4Example 4
LiMn0.8Fe0.2PO4的合成：按照实施例1中LiMn0.8Fe0.2PO4的合成方法进行合成。Synthesis of LiMn 0.8 Fe 0.2 PO 4: was synthesized according to Synthesis Example 1 LiMn 0.8 Fe 0.2 PO 4.
Li3V2(PO4)3/C共同修饰纳米LiMn0.8Fe0.2PO4的合成：将1mol Li2CO3、2mol V(NO3)3、1mol NH4H2PO4溶于去离子水中，加入25mol LiMn0.8Fe0.2PO4、质量分别为LiMn0.8Fe0.2PO4质量5％的柠檬酸络合剂以及5％的葡萄糖，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得Li3V2(PO4)3/C共同修饰纳米LiMn0.8Fe0.2PO4。Li 3 V 2 (PO 4 ) 3 /C co-modified nano-LiMn 0.8 Fe 0.2 PO 4 synthesis: 1 mol of Li 2 CO 3 , 2 mol of V(NO3) 3 , 1 mol of NH 4 H 2 PO 4 was dissolved in deionized water, 25 mol of LiMn 0.8 Fe 0.2 PO 4 , a citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 and a mass of 5%, and 5% glucose were added, and the mixture was heated and stirred for 8 to 12 hours in a water bath at 80° C. until the water was evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product is placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, Li 3 V 2 (PO 4 ) 3 /C is used to jointly modify the nano-LiMn 0.8 Fe 0.2 PO. 4 .
以实施例4所制备核壳结构正极材料即Li3V2(PO4)3/C共同修饰纳米LiMn0.8Fe0.2PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1。The core-shell structure cathode material prepared in Example 4, that is, Li 3 V 2 (PO 4 ) 3 /C, was used to modify the nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
实施例5Example 5
LiMn0.8Fe0.2PO4的合成：按照实施例1中LiMn0.8Fe0.2PO4的合成方法进行合成。 Synthesis of LiMn 0.8 Fe 0.2 PO 4: was synthesized according to Synthesis Example 1 LiMn 0.8 Fe 0.2 PO 4.
LiAlP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4的合成：将1mol Li2CO3、2mol Al(NO3)3、1mol NH4H2PO4溶于去离子水中，加入25mol LiMn0.8Fe0.2PO4、质量分别为LiMn0.8Fe0.2PO4质量5％的柠檬酸络合剂以及5％的葡萄糖，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得LiAlP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4。LiAlP 2 O 7 /C co-modified nano-LiMn 0.8 Fe 0.2 PO 4 synthesis: 1 mol of Li 2 CO 3 , 2 mol of Al(NO 3 ) 3 , 1 mol of NH 4 H 2 PO 4 was dissolved in deionized water, and 25 mol of LiMn 0.8 was added. Fe 0.2 PO 4 , a citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 and a mass of 5%, and 5% glucose, and heating and stirring in a water bath at 80 ° C for 8 to 12 hours until the water is evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 h. After cooling, LiAlP 2 O 7 /C was co-modified with nano-LiMn 0.8 Fe 0.2 PO 4 .
以实施例5所制备核壳结构正极材料即LiAlP2O7/C共同修饰纳米LiMn0.8Fe0.2PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1。The core-shell structure cathode material prepared in Example 5, namely LiAlP 2 O 7 /C, was used to modify nano-LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
对比例1Comparative example 1
LiMn0.8Fe0.2PO4的合成：按照实施例1中LiMn0.8Fe0.2PO4的合成方法进行合成。Synthesis of LiMn 0.8 Fe 0.2 PO 4: was synthesized according to Synthesis Example 1 LiMn 0.8 Fe 0.2 PO 4.
碳包覆LiMn0.8Fe0.2PO4的合成：将LiMn0.8Fe0.2PO4以及质量分别为LiMn0.8Fe0.2PO4质量5％的柠檬酸络合剂以及、5％的葡萄糖，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得碳包覆LiMn0.8Fe0.2PO4。Synthesis of carbon-coated LiMn 0.8 Fe 0.2 PO 4 : LiMn 0.8 Fe 0.2 PO 4 and a citric acid complexing agent with a mass of LiMn 0.8 Fe 0.2 PO 4 and a mass of 5%, and 5% glucose, heated and stirred in a water bath at 80 ° C 8 ~ 12h, until the water is evaporated. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, carbon coated LiMn 0.8 Fe 0.2 PO 4 was obtained .
以对比例1所制备材料碳包覆LiMn0.8Fe0.2PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1；得到其2C充电曲线图如图3所示；得到其3C放电容量保持率曲线图如图4所示。The material prepared in Comparative Example 1 was coated with carbon-coated LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were measured. The results obtained are shown in Table 1; the 2C charging curve is obtained as shown in FIG. 3; and the 3C discharge capacity retention rate curve is obtained as shown in FIG. 4 .
对比例2Comparative example 2
LiMn0.8Fe0.2PO4的合成：按照实施例1中LiMn0.8Fe0.2PO4的合成方法进行合成。Synthesis of LiMn 0.8 Fe 0.2 PO 4: was synthesized according to Synthesis Example 1 LiMn 0.8 Fe 0.2 PO 4.
LiFeP2O7包覆LiMn0.8Fe0.2PO4的合成：将1mol Li2CO3、2mol FeC2O4、2mol NH4H2PO4溶于去离子水中，加入25mol LiMn0.8Fe0.2PO4、质量为LiMn0.8Fe0.2PO4质量5％的柠檬酸络合剂，80℃水浴加热搅拌8～12h，直至水分蒸干。所得产物于80℃、-0.98MPa条件下真空干燥。干燥后产物置于管式炉中，以5℃/min的升温速率升温至600℃，保温2～5h，冷却后得LiFeP2O7 包覆LiMn0.8Fe0.2PO4。Synthesis of LiFeP 2 O 7 coated LiMn 0.8 Fe 0.2 PO 4 : 1 mol of Li 2 CO 3 , 2 mol of FeC 2 O 4 , 2 mol of NH 4 H 2 PO 4 were dissolved in deionized water, and 25 mol of LiMn 0.8 Fe 0.2 PO 4 was added . The citric acid complexing agent having a mass of LiMn 0.8 Fe 0.2 PO 4 mass 5% was heated and stirred in a water bath at 80 ° C for 8 to 12 hours until the water was evaporated to dryness. The obtained product was dried under vacuum at 80 ° C, -0.98 MPa. After drying, the product was placed in a tube furnace, heated to 600 ° C at a heating rate of 5 ° C / min, and kept for 2 to 5 hours. After cooling, LiFeP 2 O 7 was coated with LiMn 0.8 Fe 0.2 PO 4 .
以对比例2所制备材料LiFeP2O7包覆LiMn0.8Fe0.2PO4为正极，按照常规的方法制备成锂离子电池。然后，检测电池倍率性能以及循环性能，所得结果见表1。LiFeP 2 O 7 prepared in Comparative Example 2 was coated with LiMn 0.8 Fe 0.2 PO 4 as a positive electrode, and a lithium ion battery was prepared according to a conventional method. Then, the battery rate performance and the cycle performance were examined, and the results are shown in Table 1.
表1实施例及比较例正极材料倍率性能测试结果Table 1 Example and Comparative Example Cathode Material Rate Performance Test Results
Figure PCTCN2016099109-appb-000001
Figure PCTCN2016099109-appb-000001

Claims (10)

  1. 一种核壳结构LiMn1-xFexPO4正极材料，由内核和外壳组成，其特征在于，所述内核为LiMn1-xFexPO4纳米颗粒；所述外壳为碳与含锂的金属盐的混合物；所述含锂的金属盐为含锂的金属磷酸盐和/或含锂的金属焦磷酸盐；0＜x＜0.5。A core-shell structure LiMn 1-x Fe x PO 4 cathode material consisting of a core and an outer shell, characterized in that the inner core is LiMn 1-x Fe x PO 4 nanoparticles; the outer shell is carbon and lithium-containing a mixture of metal salts; the lithium-containing metal salt is a lithium-containing metal phosphate and/or a lithium-containing metal pyrophosphate; 0 < x < 0.5.
  2. 根据权利要求1所述的核壳结构LiMn1-xFexPO4正极材料，其特征在于，所述LiMn1-xFexPO4纳米颗粒的粒径为10～200nm。The core-shell structure LiMn 1-x Fe x PO 4 cathode material according to claim 1, wherein the LiMn 1-x Fe x PO 4 nanoparticles have a particle diameter of 10 to 200 nm.
  3. 根据权利要求1所述的核壳结构LiMn1-xFexPO4正极材料，其特征在于，所述含锂的金属盐为LiFeP2O7，LiAlP2O7与Li3V2(PO4)3中的一种或多种。The core-shell structure LiMn 1-x Fe x PO 4 cathode material according to claim 1, wherein the lithium-containing metal salt is LiFeP 2 O 7 , LiAlP 2 O 7 and Li 3 V 2 (PO 4 One or more of 3 .
  4. 根据权利要求1所述的核壳结构LiMn1-xFexPO4正极材料，其特征在于，所述碳的质量为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％。The core-shell structure LiMn 1-x Fe x PO 4 cathode material according to claim 1, wherein the carbon has a mass of 0.1% to 10% by mass of the LiMn 1-x Fe x PO 4 nanoparticles.
  5. 根据权利要求1所述的核壳结构LiMn1-xFexPO4正极材料，其特征在于，所述含锂的金属盐的质量为LiMn1-xFexPO4纳米颗粒质量的0.1％～10％。The core-shell structure LiMn 1-x Fe x PO 4 cathode material according to claim 1, wherein the lithium-containing metal salt has a mass of 0.1% by mass of the LiMn 1-x Fe x PO 4 nanoparticles. 10%.
  6. 一种核壳结构LiMn1-xFexPO4正极材料的制备方法，其特征在于，包括以下步骤：A method for preparing a core-shell structure LiMn 1-x Fe x PO 4 cathode material, comprising the steps of:
    S1)将第一锂源化合物、金属源化合物、第一磷源化合物、LiMn1-xFexPO4纳米颗粒、第一络合剂、可溶性碳源与水混合，加热至水分蒸发干，得到中间体；0＜x＜0.5；S1) mixing the first lithium source compound, the metal source compound, the first phosphorus source compound, the LiMn 1-x Fe x PO 4 nanoparticles, the first complexing agent, the soluble carbon source and water, and heating to evaporate to obtain Intermediate; 0<x<0.5;
    S2)将所述中间体进行煅烧，得到核壳结构LiMn1-xFexPO4正极材料。S2) The intermediate is calcined to obtain a core-shell structure LiMn 1-x Fe x PO 4 cathode material.
  7. 根据权利要求6所述的制备方法，其特征在于，所述LiMn1-xFexPO4纳米颗粒按照以下方法制备：The preparation method according to claim 6, wherein the LiMn 1-x Fe x PO 4 nanoparticles are prepared in the following manner:
    A)将第二锂源化合物、锰源化合物、铁源化合物、第二磷源化合物与第二络合剂在水中混合，加热至水分蒸发干，煅烧后，得到LiMn1-xFexPO4纳米颗粒；所述第二锂源化合物中的锂离子、锰源化合物中的锰离子、铁源化合物中的铁离子与第二磷源化合物中的磷原子的摩尔比为1：(1-x)：x：1。A) mixing the second lithium source compound, the manganese source compound, the iron source compound, the second phosphorus source compound and the second complexing agent in water, heating to moisture evaporation, and calcining to obtain LiMn 1-x Fe x PO 4 a nanoparticle; a lithium ion in the second lithium source compound; a manganese ion in the manganese source compound; a molar ratio of the iron ion in the iron source compound to the phosphorus atom in the second phosphorus source compound: 1: 1-x ): x:1.
  8. 根据权利要求7所述的制备方法，其特征在于，所述步骤A)中的煅烧具体为：以2～10℃/min的升温速率升至350℃～450℃，保温4～10h后，再以2～10℃/min的升温速率升温至650℃～800℃，保温8～20h。 The preparation method according to claim 7, wherein the calcination in the step A) is specifically: raising the temperature to 350 ° C to 450 ° C at a temperature increase rate of 2 to 10 ° C / min, after 4 to 10 hours of heat preservation, and then The temperature is raised to 650 ° C to 800 ° C at a temperature increase rate of 2 to 10 ° C / min, and the temperature is maintained for 8 to 20 hours.
  9. 根据权利要求6所述的制备方法，其特征在于，所述步骤S2)中的煅烧具体为：以2～10℃/min的升温速率升温至550℃～700℃，保温2～5h。The preparation method according to claim 6, wherein the calcination in the step S2) is specifically: raising the temperature to 550 ° C to 700 ° C at a temperature increase rate of 2 to 10 ° C / min, and maintaining the temperature for 2 to 5 hours.
  10. 一种锂离子电池，其特征在于，包括权利要求1～5任意一项所述的核壳结构LiMn1-xFexPO4正极材料或权利要求6～9任意一项所制备的核壳结构LiMn1-xFexPO4正极材料。 A lithium ion battery comprising the core-shell structure LiMn 1-x Fe x PO 4 cathode material according to any one of claims 1 to 5, or the core-shell structure prepared according to any one of claims 6 to 9. LiMn 1-x Fe x PO 4 cathode material.
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