WO2015165347A1 - 磷酸锰锂及磷酸锰锂/碳复合材料的制备方法 - Google Patents

磷酸锰锂及磷酸锰锂/碳复合材料的制备方法 Download PDF

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WO2015165347A1
WO2015165347A1 PCT/CN2015/077107 CN2015077107W WO2015165347A1 WO 2015165347 A1 WO2015165347 A1 WO 2015165347A1 CN 2015077107 W CN2015077107 W CN 2015077107W WO 2015165347 A1 WO2015165347 A1 WO 2015165347A1
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lithium
source
phosphate
manganese
lithium manganese
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PCT/CN2015/077107
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French (fr)
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王莉
何向明
刘少军
张建利
罗晶
尚玉明
李建军
高剑
任玉梅
张宏生
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江苏华东锂电技术研究院有限公司
清华大学
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Publication of WO2015165347A1 publication Critical patent/WO2015165347A1/zh
Priority to US15/333,907 priority Critical patent/US20170040596A1/en

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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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 relates to a preparation method of a cathode material for a lithium ion battery, in particular to a preparation method of lithium manganese phosphate and a preparation method of a lithium manganese phosphate/carbon composite material.
  • the electrode potential of /Fe 2+ relative to Li + /Li is only 3.4 V, which limits the development of LiFePO 4 to some extent.
  • the electrode potential of Mn 3+ /Mn 2+ relative to Li + /Li is 4.1 V, which is located in the stable electrochemical window of the existing commercial electrolyte (LiPF 6 /EC+DMC), so LiMnPO 4 has a higher specific gravity than LiFePO 4 Higher energy density has gradually attracted people's attention.
  • the current modification methods for the LiMnPO 4 cathode material mainly include nanocrystallization, carbon coating and metal ion doping.
  • the existing method for nanocrystallization of LiMnPO 4 cathode material is mainly to prepare lithium iron phosphate nanoparticles by hydrothermal reaction or solvothermal reaction.
  • the hydrothermal reaction or the solvothermal reaction is carried out in a closed autoclave using water or an organic solvent as a reaction medium. By heating the reactor, a high-temperature, high-pressure reaction environment is created to dissolve and re-dissolve the normally insoluble or insoluble matter. crystallization.
  • a hydrothermal reaction or a solvothermal reaction enables a highly crystalline product to be obtained at a relatively low temperature, and has a short reaction time and low energy consumption. Further, the above reaction may be carried out by mixing water with an organic solvent as a reaction medium.
  • a method for preparing lithium manganese phosphate comprising the steps of: mixing and dissolving a source of divalent manganese, a source of lithium and a source of phosphate in a solvothermal reaction medium to form a mixed solution comprising an organic solvent and a cosolvent And the solvothermal reaction of the mixed solution to obtain a reaction product lithium manganese phosphate.
  • a method for preparing a lithium manganese phosphate/carbon composite material comprising the steps of: dispersing a carbon material in a solvothermal reaction medium to form a dispersion, the solvothermal reaction medium comprising an organic solvent and a cosolvent, the carbon material being graphene, At least one of carbon nanotubes, carbon nanofibers, and nanocarbon spheres; mixing and dissolving a source of divalent manganese, a source of lithium, and a source of phosphate in the dispersion to form a mixed solution; and performing a solvothermal reaction on the mixed solution
  • the reaction product lithium manganese phosphate/carbon composite material is obtained.
  • the invention adopts solution thermal synthesis, and can grow lithium manganese phosphate crystal with less defects, good orientation and perfect crystal form under low temperature and equal pressure conditions.
  • a cosolvent By adding a cosolvent to an organic solvent, a solvothermal reaction can be carried out in a pure solvent system to avoid the influence of the addition of a reducing agent on the crystal morphology of the product.
  • the addition of the co-solvent increases the solubility of the inorganic raw material in the organic solvent, and solves the problem of incompatibility between the inorganic raw material and the organic solvent.
  • the obtained lithium manganese phosphate and lithium manganese phosphate/carbon material composites are nano materials, and the crystal grain size is about 100 nm to 300 nm, and has the advantages of larger specific surface, smaller depth of insertion and ejection of Li + , shorter stroke, and the like, so that the electrode can be at a large current. It is charged and discharged under the condition, and has good reversibility and good electrochemical performance.
  • Fig. 1 is an XRD diffraction pattern of lithium manganese phosphate obtained in Example 1 of the present invention.
  • FIG. 2 is a graph showing constant current discharge curves of lithium manganese phosphate/carbon composite materials obtained in Examples 1-5 and Comparative Examples 1-2 of the present invention.
  • Example 3 is a graph showing a constant current charge and discharge cycle at a 1 C rate of the lithium manganese phosphate/carbon composite obtained in Example 2 of the present invention.
  • Embodiments of the present invention provide a method for preparing lithium manganese phosphate, comprising the following steps:
  • the mixed solution is subjected to a solvothermal reaction to obtain a reaction product lithium manganese phosphate.
  • the divalent manganese source may be one or more of manganese chloride, manganese nitrate, manganese sulfate, and manganese acetate.
  • the lithium source may be one or more of lithium hydroxide, lithium acetate, lithium carbonate, and lithium oxalate.
  • the phosphate source may be one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium phosphate, diammonium phosphate, and ammonium dihydrogen phosphate.
  • a metal doping source may be further added to the mixed solution for dissolution, and the final product obtained is a metal-doped lithium manganese phosphate
  • the metal element in the metal doping source may be an alkaline earth metal element, One or more of a group 13 element, a group 14 element, and a transition group element, preferably one or more of Fe, Mg, Ni, Co, Zn, Cu, V, Al, and Mo, more preferably For Fe.
  • the doping metal is Fe
  • the metal-doped lithium manganese phosphate has a chemical formula of LiMn (1-x) Fe x PO 4 , where 0 ⁇ x ⁇ 1.
  • the divalent manganese source, the metal dopant source, the lithium source and the phosphate source are all soluble in the organic solvent, that is, Mn 2+ , Li + , PO 4 3+ and doped metal ions are formed in the organic solvent. (M 2+ ).
  • the organic solvent is an organic solvent that can dissolve the source of divalent manganese, the source of metal doping, the source of lithium, and the source of phosphate.
  • the solvent may be a glycol and/or a polyol, preferably ethylene glycol, glycerol, diethylene glycol, triethylene glycol, tetraethylene glycol, butyl triol, n-butanol and isobutanol.
  • the kind of the organic solvent can be selected depending on the type of the divalent manganese source, the metal dopant source, the lithium source, and the phosphate source used.
  • the co-solvent can increase the divalent manganese source, the metal dopant source, and the lithium source. And solubility of at least one of the phosphate sources in the organic solvent.
  • the co-solvent is one or more of an alkylphenol ethoxylate (APEO), a fatty alcohol polyoxyethylene ether (AE), polyethylene glycol (PEG), and a polyol ester.
  • the content of the co-solvent may also be a certain amount of solubilization. More preferably, the volume ratio of the organic solvent to the co-solvent may be from 9:1 to 3:2.
  • the introduction of water has a great influence on the morphology and electrochemical performance of the product.
  • the reaction medium preferably has no water or less water, for example, only contains the source of divalent manganese, the source of metal dopant, the source of lithium and the source of phosphate.
  • the crystal water introduced by dissolution. Specifically, the water content percentage in the reaction medium is preferably 1% or less.
  • step S1 further includes:
  • the liquid A is gradually added to the lithium source solution to be mixed and reacted to form the mixed solution.
  • the divalent manganese source solution contains Mn 2+
  • the lithium source solution contains Li +
  • the phosphate source solution contains PO 4 3+
  • the solvent in the divalent manganese source solution, the lithium source solution, and the phosphate source solution are all organic solvents, and at least one of them contains the cosolvent.
  • the co-solvent is contained in the divalent manganese source solution.
  • Manganese phosphate is formed in the liquid A in the step S12. However, the manganese phosphate is present in the ionic state in the liquid A, that is, the precipitate is not formed in the solution A, and is still a clear liquid. Specifically, the phosphate source solution is gradually added to the divalent manganese source solution, and the phosphate source solution may be dropwise added to the divalent manganese source solution. The solution can be stirred during the addition to homogenize the mixture and promote the reaction. Specifically, the stirring time may be 0.5 to 24 hours. The molar ratio of the phosphate source to the divalent manganese source is (0.5 to 1.5):1.
  • step S13 a chemical reaction between the liquid A and the lithium source solution is carried out to form an insoluble intermediate product, that is, the mixed solution contains a solid precipitate.
  • the step A is gradually added to the lithium source solution, and the droplet A may be added dropwise to the lithium source solution.
  • the solution can be stirred during the addition to homogenize the mixture and promote the reaction.
  • the stirring time may be 0.5 to 24 hours.
  • the molar ratio of the lithium source to the divalent manganese source is (2.5 to 3.5):1.
  • the solvothermal reaction is carried out in an autoclave at a temperature of from 120 ° C to 240 ° C.
  • the solvothermal reaction vessel may be a sealed autoclave, and the internal pressure of the reactor is raised under the high temperature and high pressure condition by pressurizing the sealed autoclave or using the autogenous pressure of the steam inside the reactor to raise the internal pressure of the reactor. Carry out the reaction.
  • the internal pressure of the reactor can be 0.2 MPa to 30 MPa, and the reaction time is 2 hours to 24 hours, and the nanometer particles having a reaction product of LiMn (1-x) M x PO 4 can be obtained, and the particle size is about 100 nm to 300 nm.
  • the reaction vessel can be naturally cooled to room temperature.
  • the reaction product can be taken out from the reaction vessel, washed and dried.
  • the step of washing may be washing, filtering or centrifuging the reaction product with deionized water.
  • the drying can be vacuum filtration or heat drying.
  • the step S3 is further included, and the obtained lithium manganese phosphate is subjected to a heat treatment in a protective gas at 200 ° C to 800 ° C.
  • the lithium manganese phosphate and the carbon source may be mixed and ground at a certain ratio, and heat-treated under a protective atmosphere, and the temperature is raised to 200 to 800 ° C, calcined for 2 to 20 hours, and naturally cooled to room temperature. That is, an olivine-type lithium manganese phosphate/carbon material composite is obtained.
  • the carbon source may be one or more of glucose, sucrose, fructose, lactose, starch, Super P, PVC, PVA, PVB, PAN, and phenolic resin.
  • the protective atmosphere may be one or more of argon gas, nitrogen gas, hydrogen-nitrogen mixed gas, and hydrogen-argon mixed gas.
  • Embodiments of the present invention also provide a method for preparing a lithium manganese phosphate/carbon composite material, comprising the following steps:
  • A1 dispersing a carbon material in a solvothermal reaction medium to form a dispersion, the solvothermal reaction medium comprising an organic solvent and a cosolvent, the carbon material being at least one of graphene, carbon nanotubes, carbon nanofibers, and nanocarbon spheres Species
  • A2 mixing a divalent manganese (Mn 2+ ) source, a lithium (Li + ) source, and a phosphate (PO 4 3+ ) source in the dispersion to form a mixed solution;
  • the mixed solution is subjected to a solvothermal reaction to obtain a reaction product lithium manganese phosphate/carbon composite material.
  • the steps A2 and A3 are substantially the same as the above steps S1 and S2, except that the carbon material is also dispersed in the solvothermal reaction medium.
  • the carbon material preferably includes graphene oxide which can be produced by a conventional method such as a Brodie method, a Hummers method, or a Staudenmaier method.
  • the method for preparing graphene oxide comprises: mixing graphite, concentrated sulfuric acid, and sodium nitrate to form a mixed solution; adding potassium permanganate while stirring the mixture at 0 ° C to 4 ° C, and maintaining The reaction temperature is below 20 ° C; the mixture is continuously stirred at 35 ° C; water is added to the mixture under stirring, and the temperature of the mixture is brought to 98 ° C - 100 ° C; and an aqueous hydrogen peroxide solution is added to the mixture. After washing and filtering, graphene oxide is obtained.
  • the graphite oxide may be prepared first, and then the graphite oxide is subjected to ultrasonic vibration treatment in a solvent such as water to form graphite oxide.
  • the graphene oxide is dispersed in the solvothermal reaction medium
  • the dispersion was obtained. Specifically, when the graphene oxide solution contains water, the bottom solid remains after centrifugation, and the supernatant is removed, and then the solvothermal reaction medium is added, and the mixture is centrifuged again, thereby removing water by multiple centrifugation.
  • the graphene oxide is dispersed in the solvothermal reaction medium.
  • the graphene oxide can be reduced by a subsequent high temperature reaction process (such as step A4).
  • step A2 further includes:
  • A11 respectively providing a lithium source solution and a phosphate source solution, and dissolving a source of divalent manganese in the dispersion to form a divalent manganese source solution;
  • A12 gradually adding a phosphate source solution to the divalent manganese source solution to form a liquid mixture and reacting;
  • the liquid A is gradually added to the lithium source solution to be mixed and reacted to form the mixed solution.
  • the steps A11 to A13 are basically the same as the above steps S11 to S13, and the carbon material is dispersed only in the divalent manganese source solution.
  • the method for preparing the lithium manganese phosphate/carbon composite material may further include the step of heat-treating the obtained lithium manganese phosphate in a protective gas at 200 ° C to 800 ° C in the step A4.
  • the lithium manganese phosphate and the carbon source may be mixed and ground at a certain ratio, and heat-treated under a protective atmosphere, and the temperature is raised to 200 to 800 ° C, calcined for 2 to 20 hours, and naturally cooled to room temperature. That is, an olivine-type lithium manganese phosphate/carbon material composite is obtained.
  • the lithium manganese phosphate nanoparticles are uniformly distributed in the interlaced pores of the carbon material, and the lithium manganese phosphate particles have a particle diameter of about 100 nm to 300 nm.
  • the carbon material has good electrical conductivity, superior mechanical properties, high specific surface area and pore network structure suitable for ion transport of electrolyte, so that lithium manganese phosphate can have good electrochemical performance as a positive active material for lithium ion batteries.
  • the invention adopts solution thermal synthesis, and can grow lithium manganese phosphate crystal with less defects, good orientation and perfect crystal form under low temperature and equal pressure conditions.
  • Lithium manganese phosphate and lithium manganese phosphate/carbon material composites are nano-materials with a crystal grain size of about 100-300 nm, which has the advantages of larger specific surface, smaller depth of Li + insertion, and shorter stroke, so that the electrode can be under high current conditions. It is charged and discharged, and has good reversibility and good electrochemical performance.
  • the solvothermal reaction using pure organic solvent as the reaction medium can avoid the adverse effects of the reducing agent on the crystal of the product, but the inorganic reactants (such as the inorganic salts of lithium and manganese and the phosphoric acid) in the pure solvent system have poor solubility in the organic solvent.
  • the solubility of the inorganic raw material in the organic solvent can be increased, and the incompatibility problem between the inorganic raw material and the organic solvent can be solved.
  • the co-solvent firstly complexes with metal ions to form an intermediate complex, which improves the dispersion and dissolution of metal ions in an organic solvent; in the mixing reaction stage of the two solutions, since the co-solvent is uniformly wrapped on the surface of the product, The surface energy of the crystal particles is greatly reduced, and the particle size and morphology of the crystal can be effectively controlled, so that the crystal is developed in a direction favorable for improving electrochemical performance; in addition, a film or a double film is formed due to the presence of a co-solvent on the surface of the product particles.
  • the electric layer can make the particles have a charge, which can prevent the particles of the product from coagulating with each other, and the formed precursor emulsion is relatively stable, thereby ensuring high purity and consistency of the product.
  • the inventors further found through research that when the divalent manganese source, the lithium source, and the phosphate source are mixed, the difference in the order of mixing results in a large difference in the final solvothermal product.
  • the order of addition commonly employed in the prior art is to add a manganese source to a mixture of a lithium source and a phosphorus source or to add a lithium source to a mixture of a manganese source and a phosphorus source, and the inventors have found that the order of addition is present in the presence of a cosolvent.
  • the solution A is gradually added to the lithium source solution, that is, a large excess of lithium ions during the mixing of the solution A and the lithium source solution enables the reaction product to have higher electrochemical performance.
  • the solution A was dropwise added to the lithium hydroxide solution, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed, and dried to be a lithium manganese phosphate material.
  • the lithium manganese phosphate material was mixed and ground with 15 wt% of sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to perform a charge and discharge performance test of the battery.
  • the curve a in FIG. 2 is a constant current charge and discharge curve of the lithium manganese phosphate material obtained in the present embodiment, and the discharge specific capacity at a 0.1 C rate is 120.3 mAh/g.
  • lithium hydroxide monohydrate was weighed, added to 100 mL of ethylene glycol, and mechanically stirred for 60 minutes to form a uniform lithium hydroxide solution.
  • the solution A was dropwise added to the lithium hydroxide solution, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed and dried to be a lithium manganese iron phosphate material.
  • the lithium manganese iron phosphate material was mixed and ground with 12 wt% sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to carry out a charge and discharge performance test of the battery, and the battery except the positive electrode active material was the same as in Example 1.
  • Curve b in Fig. 2 is a constant current charge-discharge curve of the ferromanganese phosphate material obtained by adding different ratios of alkylphenol ethoxylates in the present embodiment, and the discharge specific capacity at a rate of 0.1 C is 160.5 mAh/g. 3 is a 500-cycle cycle of constant current charge and discharge at a 1 C rate, and the capacity retention rate is 94.6%. It can be seen that the discharge specific capacity of the positive electrode active material can be improved by performing doping of Fe in LiMnPO 4 .
  • lithium hydroxide monohydrate was weighed, added to 100 mL of ethylene glycol, and mechanically stirred for 60 minutes to form a uniform lithium hydroxide solution.
  • the solution A was dropwise added to the lithium hydroxide solution, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed and dried to be a lithium manganese iron phosphate material.
  • the lithium manganese iron phosphate material was mixed and ground with 12 wt% sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to carry out a charge and discharge performance test of the battery, and the battery was the same as that of Example 1 except for the positive electrode active material.
  • Curve c in Fig. 2 is a constant current charge and discharge curve of the lithium manganese iron phosphate material obtained in the present embodiment, and the specific discharge capacity at a 0.1 C rate is 153.3 mAh/g. It can be seen that when the content of the alkylphenol ethoxylate in the solvent is lowered, the discharge specific capacity of the positive electrode active material is affected.
  • lithium hydroxide monohydrate was weighed, added to 100 mL of ethylene glycol, and mechanically stirred for 60 minutes to form a uniform lithium hydroxide solution.
  • the solution A was dropwise added to the lithium hydroxide solution, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed and dried to be a lithium manganese iron phosphate material.
  • the lithium manganese iron phosphate material was mixed and ground with 12 wt% sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to carry out a charge and discharge performance test of the battery, and the battery was the same as that of Example 1 except for the positive electrode active material.
  • 0.2 g of graphene and 0.3 g of carbon nanotubes were weighed, added to 80 mL of ethylene glycol and 20 mL of alkylphenol ethoxylate, ground for 1 hour, ultrasonically dispersed for 2 hours, and then added 5.533 g of manganese chloride tetrahydrate and 3.3362
  • the ferrous sulfate heptahydrate was mechanically stirred for 60 minutes to form a uniform manganese chloride/ferrous sulfate/carbon material solution.
  • 3 mL of phosphoric acid was weighed and added dropwise to the manganese chloride/ferrous sulfate/carbon material solution, and the mixture was mechanically stirred for 2 hours to form a homogeneous mixed solution A.
  • lithium hydroxide monohydrate was weighed, added to 100 mL of ethylene glycol, and mechanically stirred for 60 minutes to form a uniform lithium hydroxide solution.
  • the solution A was dropwise added to the lithium hydroxide solution, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed and dried to be a lithium manganese iron phosphate/carbon composite material.
  • the lithium iron manganese phosphate/carbon composite material was mixed and ground with 6 wt% sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to perform a charge and discharge performance test of the battery.
  • the curve e in FIG. 2 is a constant current charge and discharge curve of the lithium manganese iron phosphate/carbon material composite obtained in the present embodiment, and the specific discharge capacity at a 0.1 C rate is 140.7 mAh/g.
  • the addition of the carbon material reduces the specific capacity of the material, the electrical conductivity of the material is improved, which is beneficial to the large-rate charge and discharge and cycle performance of the material.
  • the solution A was dropwise added to the lithium hydroxide solution, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed and dried to be a lithium manganese iron phosphate material.
  • the lithium manganese iron phosphate material was mixed and ground with 12 wt% sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to perform a charge and discharge performance test of the battery.
  • the curve f in FIG. 2 is a constant current charge and discharge curve of the lithium manganese iron phosphate material obtained by adding the solvent-free alkylphenol ethoxylate in the present embodiment, and the discharge specific capacity at a 0.1 C rate is 134 mAh/g.
  • lithium hydroxide monohydrate was weighed, added to 100 mL of ethylene glycol, and mechanically stirred for 60 minutes to form a uniform lithium hydroxide solution.
  • the lithium hydroxide solution was dropwise added to the solution A, stirred for 60 minutes, sealed in a high-temperature reaction vessel having a polytetrafluoroethylene liner, and kept at a constant temperature of 180 ° C for 5 hours.
  • the obtained product is centrifuged, washed and dried to be a lithium manganese iron phosphate material.
  • the lithium manganese iron phosphate material was mixed and ground with 12 wt% sucrose for 30 minutes, calcined at a high temperature for 6 hours under a nitrogen atmosphere, calcined at 650 ° C, and then cooled to room temperature to obtain a positive electrode active material.
  • the positive electrode active material was assembled into a lithium ion battery to perform a charge and discharge performance test of the battery.
  • the curve g in Fig. 2 is a constant current charge and discharge curve of the lithium manganese iron phosphate material obtained by changing the order of addition in the present embodiment, and the specific discharge capacity at a 0.1 C rate is 139.6 mAh/g.

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Abstract

本发明涉及一种磷酸锰锂的制备方法，包括以下步骤：将二价锰源、锂源及磷酸根源在一溶剂热反应介质中混合并溶解形成一混合溶液，该溶剂热反应介质包括有机溶剂及助溶剂；以及将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂。本发明还涉及一种磷酸锰锂/碳复合材料的制备方法。

Description

磷酸锰锂及磷酸锰锂/碳复合材料的制备方法 技术领域
本发明涉及一种锂离子电池正极材料的制备方法，尤其涉及一种磷酸锰锂的制备方法及一种磷酸锰锂/碳复合材料的制备方法。
背景技术
橄榄石型LiMPO4(M=Fe, Mn)材料以其无毒、电压平台高、比容量高、循环性能及安全性能好等优点成为锂离子电池正极材料的研究热点之一，但是Fe3+/Fe2+相对于Li+/Li 的电极电势仅为3.4 V，这在一定程度上限制了LiFePO4的发展。而Mn3+/Mn2+相对于Li+/Li 的电极电势为4.1 V，正好位于现有商品化电解液(LiPF6/EC+DMC)的稳定电化学窗口，因此LiMnPO4具有比LiFePO4更高的能量密度，从而逐渐引起了人们的关注。然而，由于LiMnPO4材料近似于被认为是绝缘体限制了其发展应用，目前对LiMnPO4正极材料的改性方法主要有纳米化、碳包覆和金属离子掺杂。
现有的对LiMnPO4正极材料纳米化的方法主要是采用水热反应或溶剂热反应制备出磷酸铁锂纳米颗粒。水热反应或溶剂热反应是在密闭的高压釜中，采用水或有机溶剂作为反应介质，通过对反应器加热，创造一个高温、高压的反应环境，使通常难溶或不溶的物质溶解并重新结晶。水热反应或溶剂热反应能够在较低的温度下得到高度结晶的产品，并且反应时间短、能耗少。另外，也有将水与有机溶剂进行混合作为反应介质进行上述反应。然而，只要反应介质中有水就会存在Mn2+的氧化问题。即使少量的Mn3+也会大大降低LiMnPO4的充放电容量，为了尽量避免或者减少Mn2+的氧化，需要向反应体系中加入还原剂（抗坏血酸、柠檬酸、葡萄糖等）。而还原剂的加入会影响到产物晶体的形貌和尺寸，对材料的电化学性能产生很大的影响。
发明内容
有鉴于此，确有必要提供一种具有较好电化学性能的磷酸锰锂及磷酸锰锂/碳复合材料的制备方法。
一种磷酸锰锂的制备方法，包括以下步骤：将二价锰源、锂源及磷酸根源在一溶剂热反应介质中混合并溶解形成一混合溶液，该溶剂热反应介质包括有机溶剂及助溶剂；以及将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂。
一种磷酸锰锂/碳复合材料的制备方法，包括以下步骤：将碳材料分散在一溶剂热反应介质形成分散液，该溶剂热反应介质包括有机溶剂及助溶剂，该碳材料为石墨烯、碳纳米管、碳纳米纤维及纳米碳球中的至少一种；将二价锰源、锂源及磷酸根源在该分散液中混合并溶解形成一混合溶液；以及将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂/碳复合材料。
本发明采用溶液热法合成，在低温、等压条件下，能够生长出缺陷少、取向好、晶型完美的磷酸锰锂晶体。通过在有机溶剂中加入助溶剂，能够在纯溶剂体系中进行溶剂热反应，避免还原剂的加入对产物晶体形貌的影响。而助溶剂的加入增大无机原料在有机溶剂中的溶解度，解决了无机原料与有机溶剂之间存在的不相容性问题。得到的磷酸锰锂及磷酸锰锂/碳材料复合物为纳米材料，晶体粒径约为100nm~300nm，具有比表面大、Li+嵌入脱出深度小、行程短等优点，使电极能够在大电流条件下充放电，且可逆性好，具有较好的电化学性能。
 附图说明
图1为本发明实施例1得到的磷酸锰锂的XRD衍射图谱。
图2为本发明实施例1-5及对比例1-2得到的磷酸锰锂/碳复合材料的恒流放电曲线。
图3为本发明实施例2得到的磷酸锰锂/碳复合材料的1C倍率下恒流充放电循环曲线。
如下具体实施方式将结合上述附图进一步说明本发明。
具体实施方式
下面将结合附图及具体实施例对本发明提供的磷酸锰锂及磷酸锰锂/碳复合材料的制备方法作进一步的详细说明。
本发明实施方式提供一种磷酸锰锂的制备方法，包括以下步骤：
S1，将二价锰(Mn2+)源、锂（Li+）源及磷酸根（PO4 3+）源在一溶剂热反应介质中混合并溶解形成一混合溶液，该溶剂热反应介质包括有机溶剂及助溶剂；
S2，将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂。
该二价锰源可以为氯化锰、硝酸锰、硫酸锰及醋酸锰中的一种或多种。
该锂源可以为氢氧化锂、乙酸锂、碳酸锂及草酸锂中的一种或多种。
该磷酸根源可以为磷酸、磷酸二氢锂、磷酸铵、磷酸氢二铵及磷酸二氢铵中的一种或多种。
在该步骤S1中，可进一步将金属掺杂源加入该混合溶液中进行溶解，得到的最终产物为金属掺杂的磷酸锰锂，该金属掺杂源中的金属元素可以为碱土金属元素、第13族元素、第14族元素及过渡族元素中的一种或者几种，优选为Fe、Mg、Ni、Co、Zn、Cu、V、Al及Mo中的一种或几种，更为优选为Fe。当该掺杂金属为Fe时，该金属掺杂的磷酸锰锂的化学式为LiMn（1-x）FexPO4，其中0<x<1。
该二价锰源、金属掺杂源、锂源和磷酸根源均可溶于所述有机溶剂，也就是在所述有机溶剂中形成Mn2+、Li+、PO4 3+及掺杂金属离子(M2+)。
该二价锰源、金属掺杂源、锂源和磷酸根源的加入量可根据磷酸锰锂的化学式LiMn（1-x）MxPO4进行计算，其中0≤x<1。也就是理论摩尔比为Li:(M+Mn):P=1:1:1，然而，可以适当使锂过量或放宽磷的比例，具体地，所述二价锰源、金属掺杂源、锂源和磷酸根源可以按照Li:(M+Mn):P的摩尔比为(2.5~3.5):1:(0.5~1.5)的比例进行混合。
所述有机溶剂为可溶解该二价锰源、金属掺杂源、锂源和磷酸根源的有机溶剂。所述有剂溶剂可为二元醇和/或多元醇，优选为乙二醇、丙三醇、二甘醇、三甘醇、四甘醇、丁三醇、正丁醇及异丁醇中的一种或多种。所述有机溶剂的种类可根据使用的二价锰源、金属掺杂源、锂源和磷酸根源的种类而进行选择。虽然能够溶解，但该二价锰源、金属掺杂源、锂源和磷酸根源在有机溶剂中的溶解度均不高，该助溶剂可以增大该二价锰源、金属掺杂源、锂源和磷酸根源中至少一种在该有机溶剂中的溶解度。该助溶剂为烷基酚聚氧乙烯醚（APEO）、脂肪醇聚氧乙烯醚（AE）、聚乙二醇（PEG）和多元醇脂中的一种或多种。由于此类助溶剂在溶液中不是以离子态纯在，所以它的稳定性高，不易受强电解质存在的影响，也不易受酸、碱的影响。该助溶剂的含量较少也可起到一定的助溶作用，较为优选地，该有机溶剂与该助溶剂的体积比可以为9:1~3:2。水的引入会对产物的形貌及电化学性能有较大影响，该反应介质中优选为不含水或少含水，例如仅含有由该二价锰源、金属掺杂源、锂源和磷酸根源的溶解而引入的结晶水。具体地，该反应介质中水质量百分含量优选在1%以下。
在优选的实施例中，该步骤S1进一步包括：
S11，分别提供二价锰源溶液、锂源溶液和磷酸根源溶液；
S12，将磷酸根源溶液逐步加入该二价锰源溶液中混合并进行反应，形成A液；以及
S13，将该A液逐步加入该锂源溶液中混合并进行反应，形成所述混合溶液。
在该步骤S11中，该二价锰源溶液中含Mn2+，该锂源溶液含有Li+，该磷酸根源溶液含有PO4 3+。该二价锰源溶液、锂源溶液和磷酸根源溶液中的溶剂均为有机溶剂，且至少一种中含有所述助溶剂。优选地，该二价锰源溶液中含有所述助溶剂。
在该步骤S12中该A液中生成有磷酸亚锰，然而该磷酸亚锰在A液中以离子态存在，也就是该A溶液中未形成沉淀，仍为澄清液体。具体地，将磷酸根源溶液逐步加入该二价锰源溶液中具体可以为逐滴的将该磷酸根源溶液滴加至该二价锰源溶液中。在加入过程中可对溶液进行搅拌使混合均匀，并促进反应进行。具体地，该搅拌时间可以为0.5~24小时。该磷酸根源与二价锰源的摩尔比为(0.5~1.5):1。
在该步骤S13中，通过A液与锂源溶液进行化学反应，形成不溶的中间产物，也就是该混合溶液中含有固体沉淀。具体地，将该A液逐步加入该锂源溶液中具体可以为逐滴的将该A液滴加至该锂源溶液中。在加入的过程中可对溶液进行搅拌使混合均匀，并促进反应进行。具体地，该搅拌时间可以为0.5~24小时。该锂源与二价锰源的摩尔比为(2.5~3.5):1。
在该步骤S2中，该溶剂热反应在一高压釜中进行，温度为120℃~240℃。所述溶剂热反应釜可为一密封高压釜，通过对该密封高压釜加压或利用反应釜内部蒸汽的自生压力使反应釜内部压力上升，从而使反应釜内部的反应原料在高温高压条件下进行反应。该反应釜内部压力可以为0.2MPa~30MPa，反应时间为2小时至24小时，即可得到反应产物为LiMn（1-x）MxPO4的纳米颗粒，颗粒尺寸约为100nm~300nm。在反应完毕后，所述反应釜可自然冷却至室温。
进一步地，在通过步骤S2得到反应产物后，可从反应釜中将该反应产物取出，并进行洗涤及干燥。该洗涤的步骤可以是采用去离子水对该反应产物进行洗涤、过滤或离心分离。该干燥可以是真空抽滤或加热干燥。
在步骤S2后，进一步包括步骤S3，将得到的磷酸锰锂在保护性气体中200℃~800℃进行热处理的步骤。在该热处理的步骤中，可先将磷酸锰锂与碳源按一定比例进行混合、研磨，在保护性气氛下进行热处理，升温至200~800℃，煅烧2~20小时，自然冷却至室温，即得到橄榄石型磷酸锰锂/碳材料复合物。该碳源可以为葡萄糖、蔗糖、果糖、乳糖、淀粉、Super P、PVC、PVA、PVB、PAN、酚醛树脂中的一种或多种。该保护气氛可以为氩气、氮气、氢-氮混合气及氢-氩混合气中的一种或多种。
本发明实施方式还提供一种磷酸锰锂/碳复合材料的制备方法，包括以下步骤：
A1，将碳材料分散在一溶剂热反应介质形成分散液，该溶剂热反应介质包括有机溶剂及助溶剂，该碳材料为石墨烯、碳纳米管、碳纳米纤维及纳米碳球中的至少一种；
A2，将二价锰(Mn2+)源、锂（Li+）源及磷酸根（PO4 3+）源在该分散液中混合并溶解形成一混合溶液；
A3，将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂/碳复合材料。
该步骤A2与A3与上述步骤S1及S2基本相同，区别仅在该溶剂热反应介质中还分散有该碳材料。
在该步骤A1中，该碳材料优选包括氧化石墨烯，该氧化石墨烯可以通过现有方法，如Brodie法，Hummers法，或Staudenmaier法等方法制备。在一实施例中，该氧化石墨烯的制备方法包括：将石墨、浓硫酸及硝酸钠混合形成一混合液；在0℃-4℃下搅拌该混合液的同时加入高锰酸钾，并保持反应温度在20℃以下；在35℃下持续搅拌该混合液；在搅拌条件下向该混合液加入水，并使混合液温度达到98℃-100℃；以及向混合液加入过氧化氢水溶液，洗涤过滤后得到氧化石墨烯。另外，也可以先制备氧化石墨，再将氧化石墨在溶剂，如水中，通过超声振荡处理，将氧化石墨形成氧化石墨烯。
在将该氧化石墨烯分散在该溶剂热反应介质时优选为使用通过Hummers法直接制备得到的氧化石墨烯溶液为原料，将该氧化石墨烯溶液加入该溶剂热反应介质中离心分离并超声分散，得到该分散液。具体地，当该氧化石墨烯溶液含有水时，离心后保留底部固体，而将上清液去除，然后再加入该溶剂热反应介质，再次离心，从而通过多次离心的方式在除水的同时使氧化石墨烯分散在该溶剂热反应介质中。
由于溶剂体系中二元醇或多元醇具有还原性，氧化石墨烯可通过后续的高温反应过程(如步骤A4)被还原。
在优选的实施例中，该步骤A2进一步包括：
A11，分别提供锂源溶液和磷酸根源溶液，并将二价锰源溶解在该分散液中形成二价锰源溶液；
A12，将磷酸根源溶液逐步加入该二价锰源溶液中形成A液混合并进行反应；以及
A13，将该A液逐步加入该锂源溶液中混合并进行反应，形成所述混合溶液。
该步骤A11~A13与上述步骤S11~S13基本相同，区别仅在该二价锰源溶液中还分散有该碳材料。
另外，与该步骤S3相似地，该磷酸锰锂/碳复合材料的制备方法也可进一步包括步骤A4，将得到的磷酸锰锂在保护性气体中200℃~800℃进行热处理的步骤。在该热处理的步骤中，可先将磷酸锰锂与碳源按一定比例进行混合、研磨，在保护性气氛下进行热处理，升温至200~800℃，煅烧2~20小时，自然冷却至室温，即得到橄榄石型磷酸锰锂/碳材料复合物。
在该磷酸锰锂/碳材料复合物中，磷酸锰锂纳米颗粒均匀的分布在该碳材料交织而成的孔隙之中，磷酸锰锂颗粒的粒径约为100nm~300nm。该碳材料具有良好的导电性、优越的机械性能、高比表面积和适于电解液离子传输的孔隙网络结构，从而可以使磷酸锰锂作为锂离子电池正极活性材料具有较好的电化学性能。
本发明采用溶液热法合成，在低温、等压条件下，能够生长出缺陷少、取向好、晶型完美的磷酸锰锂晶体。磷酸锰锂及磷酸锰锂/碳材料复合物为纳米材料，晶体粒径约为100~300nm，具有比表面大、Li+嵌入脱出深度小、行程短等优点，使电极能够在大电流条件下充放电，且可逆性好，具有较好的电化学性能。将纯有机溶剂作为反应介质的溶剂热反应可以避免还原剂对产物晶体产生的不利影响，但纯溶剂体系中无机反应物(如锂和锰的无机盐及磷酸)在有机溶剂中溶解度较差，通过在有机溶剂中加入助溶剂，能够增大无机原料在有机溶剂中的溶解度，解决了无机原料与有机溶剂之间存在的不相容性问题。该助溶剂首先与金属离子络合形成一种中间体络合物，提高了金属离子在有机溶剂中的分散和溶解；在两种溶液混合反应阶段，由于助溶剂均匀包裹在生成物的表面，大大降低了晶体颗粒的表面能，能够有效控制晶体的粒径大小和形貌，使得晶体朝着有利于提高电化学性能方向发展；此外，由于生成物颗粒表面助溶剂的存在，形成薄膜或双电层，可使颗粒带有电荷，这样就能阻止生成物颗粒互相凝结，使形成的前驱体乳浊液比较稳定，保证了产物的高纯度和一致性。
另外，发明人通过研究进一步发现将该二价锰源、锂源和磷酸根源进行混合时，混合顺序不同会导致最终溶剂热产物存在较大差别。现有技术中普遍采用的加料顺序为将锰源向锂源与磷源的混合物中加入或将锂源向锰源与磷源的混合物中加入，而发明人发现在助溶剂存在时将加料顺序变为所述溶液A逐步加入锂源溶液中，也就是在溶液A与锂源溶液混合过程中使锂离子大量过量能够使反应产物具有更高的电化学性能。
实施例1
量取70mL乙二醇和30mL烷基酚聚氧乙烯醚混合均匀，然后加入7.916g四水合氯化亚锰，机械搅拌60分钟，形成均匀的氯化亚锰溶液。量取3mL磷酸，逐滴滴加到氯化亚锰溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取5.035g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将溶液A逐滴滴加到氢氧化锂溶液中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰锂材料。将磷酸锰锂材料与15wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试。
图1为本实施例得到的正极活性材料的XRD谱图，图中衍射峰都很好的对应了LiMnPO4的衍射峰，没有杂质峰，说明所得产物为纯相LiMnPO4。图2中曲线a为本实施例得到的磷酸锰锂材料的恒流充放电曲线，0.1C倍率下放电比容量为120.3mAh/g。
实施例2
量取70mL乙二醇和30mL烷基酚聚氧乙烯醚混合均匀，然后加入5.533g四水合氯化亚锰和3.3362七水合硫酸亚铁，机械搅拌60分钟，形成均匀的氯化亚锰和硫酸亚铁混合溶液。量取3mL磷酸，逐滴滴加到氯化亚锰和硫酸亚铁混合溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取5.035g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将溶液A逐滴滴加到氢氧化锂溶液中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰铁锂材料。将磷酸锰铁锂材料与12wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试，电池除该正极活性材料外的其它部分均与实施例1相同。
图2中曲线b为本实施例添加不同比例烷基酚聚氧乙烯醚得到的磷酸锰铁锂材料的恒流充放电曲线，0.1C倍率下放电比容量为160.5mAh/g。图3为本实施例得到的磷酸锰铁锂材料在1C倍率下恒流充放电500次循环曲线，容量保持率为94.6%。可以看出通过在LiMnPO4中进行Fe的掺杂可以提高正极活性材料的放电比容量。
实施例3
量取90mL乙二醇和10mL烷基酚聚氧乙烯醚混合均匀，然后加入5.533g四水合氯化亚锰和3.3362七水合硫酸亚铁，机械搅拌60分钟，形成均匀的氯化亚锰和硫酸亚铁混合溶液。量取3mL磷酸，逐滴滴加到氯化亚锰和硫酸亚铁混合溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取5.035g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将溶液A逐滴滴加到氢氧化锂溶液中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰铁锂材料。将磷酸锰铁锂材料与12wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试，电池除该正极活性材料外的其它部分与实施例1相同。图2中曲线c为本实施例得到的磷酸锰铁锂材料的恒流充放电曲线，0.1C倍率下放电比容量为153.3mAh/g。可以看出，当该烷基酚聚氧乙烯醚在该溶剂中含量降低会对该正极活性材料的放电比容量造成影响。
实施例4
量取60mL乙二醇和40mL烷基酚聚氧乙烯醚混合均匀，然后加入5.533g四水合氯化亚锰和3.3362七水合硫酸亚铁，机械搅拌60分钟，形成均匀的氯化亚锰和硫酸亚铁混合溶液。量取3mL磷酸，逐滴滴加到氯化亚锰和硫酸亚铁混合溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取5.035g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将溶液A逐滴滴加到氢氧化锂溶液中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰铁锂材料。将磷酸锰铁锂材料与12wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试，电池除该正极活性材料外的其它部分与实施例1相同。图2中曲线d为本实施例添加不同比例烷基酚聚氧乙烯醚得到的磷酸锰铁锂材料的恒流充放电曲线，0.1C倍率下放电比容量为143.3mAh/g，结果表明助溶剂的添加量并不是越多越好。
实施例5
称取0.2g石墨烯和0.3g碳纳米管，加入到80mL乙二醇和20mL烷基酚聚氧乙烯醚中，研磨1小时，超声分散2小时，然后加入5.533g四水合氯化亚锰和3.3362七水合硫酸亚铁，机械搅拌60分钟，形成均匀的氯化亚锰/硫酸亚铁/碳材料溶液。量取3mL磷酸，逐滴滴加到氯化亚锰/硫酸亚铁/碳材料溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取3.316g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将溶液A逐滴滴加到氢氧化锂溶液中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰铁锂/碳复合材料。将磷酸锰铁锂/碳复合材料与6wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试。
图2中曲线e为本实施例得到的磷酸锰铁锂/碳材料复合物的恒流充放电曲线，0.1C倍率下放电比容量为140.7mAh/g。碳材料的加入虽然降低了材料的比容量，但是材料的导电性能得到了提高，对材料的大倍率充放电和循环性能有益。
对比例1
量取100mL乙二醇，然后加入5.533g四水合氯化亚锰和3.3362七水合硫酸亚铁，机械搅拌60分钟，形成均匀的氯化亚锰和硫酸亚铁混合溶液。量取3mL磷酸，逐滴滴加到氯化亚锰和硫酸亚铁混合溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取5.035g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将溶液A逐滴滴加到氢氧化锂溶液中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰铁锂材料。将磷酸锰铁锂材料与12wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试。图2中曲线f为本实施例不添加助溶剂烷基酚聚氧乙烯醚得到的磷酸锰铁锂材料的恒流充放电曲线，0.1C倍率下放电比容量为134mAh/g。
对比例2
量取70mL乙二醇和30mL烷基酚聚氧乙烯醚混合均匀，然后加入5.533g四水合氯化亚锰和3.3362七水合硫酸亚铁，机械搅拌60分钟，形成均匀的氯化亚锰和硫酸亚铁混合溶液。量取3mL磷酸，逐滴滴加到氯化亚锰和硫酸亚铁混合溶液中，机械搅拌反应2小时，形成均匀的混合溶液A。再称取5.035g一水合氢氧化锂，加入到100mL乙二醇中，机械搅拌60分钟，形成均匀的氢氧化锂溶液。将氢氧化锂溶液逐滴滴加到溶液A中搅拌反应60分钟，密封至具有聚四氟乙烯内衬的高温反应釜中，恒温180℃，反应5小时。所得产物经离心、洗涤、干燥即为磷酸锰铁锂材料。将磷酸锰铁锂材料与12wt%蔗糖混合研磨30分钟，在氮气气氛保护下高温煅烧6小时，煅烧温度为650℃，然后冷却至室温得到正极活性材料。将该正极活性材料组装锂离子电池进行电池的充放电性能测试。图2中曲线g为本实施例改变加料顺序得到的磷酸锰铁锂材料的恒流充放电曲线，0.1C倍率下放电比容量为139.6mAh/g。
另外，本领域技术人员还可在本发明精神内做其他变化，当然，这些依据本发明精神所做的变化，都应包含在本发明所要求保护的范围之内。

Claims (11)

  1. 一种磷酸锰锂的制备方法，包括以下步骤：
    将二价锰源、锂源及磷酸根源在一溶剂热反应介质中混合并溶解形成一混合溶液，该溶剂热反应介质包括有机溶剂及助溶剂；以及
    将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂。
  2. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，进一步包括将金属掺杂源加入该混合溶液中进行溶解的步骤，得到的反应产物为金属掺杂的磷酸锰锂。
  3. 如权利要求2所述的磷酸锰锂的制备方法，其特征在于，该金属掺杂源中的金属元素为Fe，该金属掺杂的磷酸锰锂的化学式为LiMn（1-x）FexPO4，0<x<1。
  4. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，该二价锰源为氯化锰、硝酸锰、硫酸锰及醋酸锰中的一种或多种，该锂源为氢氧化锂、乙酸锂、碳酸锂及草酸锂中的一种或多种，该磷酸根源为磷酸、磷酸二氢锂、磷酸铵、磷酸氢二铵及磷酸二氢铵中的一种或多种。
  5. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，该有剂溶剂为二元醇及多元醇中的至少一种。
  6. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，该有剂溶剂为乙二醇、丙三醇、二甘醇、三甘醇、四甘醇、丁三醇、正丁醇及异丁醇中的一种或多种。
  7. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，该助溶剂为烷基酚聚氧乙烯醚、脂肪醇聚氧乙烯醚、聚乙二醇和多元醇脂中的一种或多种。
  8. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，该有机溶剂与该助溶剂的体积比为9:1~3:2。
  9. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，该形成混合溶液的步骤进一步包括：
    分别提供二价锰源溶液、锂源溶液和磷酸根源溶液；
    将磷酸根源溶液逐步加入该二价锰源溶液中混合并进行反应，形成A液；以及
    将该A液逐步加入该锂源溶液中混合并进行反应，形成所述混合溶液。
  10. 如权利要求1所述的磷酸锰锂的制备方法，其特征在于，进一步包括将得到的磷酸锰锂在保护性气体中200℃~800℃进行热处理的步骤。
  11. 一种磷酸锰锂/碳复合材料的制备方法，包括以下步骤：
    将碳材料分散在一溶剂热反应介质形成分散液，该溶剂热反应介质包括有机溶剂及助溶剂，该碳材料为石墨烯、碳纳米管、碳纳米纤维及纳米碳球中的至少一种；
    将二价锰源、锂源及磷酸根源在该分散液中混合并溶解形成一混合溶液；以及
    将该混合溶液进行溶剂热反应，得到反应产物磷酸锰锂/碳复合材料。
PCT/CN2015/077107 2014-04-29 2015-04-21 磷酸锰锂及磷酸锰锂/碳复合材料的制备方法 WO2015165347A1 (zh)

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CN114314551B (zh) * 2021-12-31 2023-03-10 江苏贝特瑞纳米科技有限公司 一种爆炸法制备高压实磷酸锰铁锂的方法
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