WO2015003568A1 - Method for preparing positive electrode active material of lithium ion battery - Google Patents

Method for preparing positive electrode active material of lithium ion battery Download PDF

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WO2015003568A1
WO2015003568A1 PCT/CN2014/081509 CN2014081509W WO2015003568A1 WO 2015003568 A1 WO2015003568 A1 WO 2015003568A1 CN 2014081509 W CN2014081509 W CN 2014081509W WO 2015003568 A1 WO2015003568 A1 WO 2015003568A1
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solution
source
lithium
source compound
manganese
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PCT/CN2014/081509
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French (fr)
Chinese (zh)
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王莉
叶飞鹏
何向明
戴仲葭
黄贤坤
李建军
王继贤
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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 WO2015003568A1 publication Critical patent/WO2015003568A1/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
    • H01M4/36—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
    • 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
    • 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
    • H01M4/364—Composites as mixtures
    • 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
    • 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
    • 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 lithium ion positive electrode active material, in particular to a preparation method of a positive electrode active material lithium manganese iron phosphate.
  • Lithium iron phosphate (LiFePO 4 ) has been receiving great attention as a positive active material for lithium ion batteries with good safety, low cost and environmental friendliness.
  • the voltage platform of lithium iron phosphate 3.4V severely limits the increase in energy density of lithium ion batteries.
  • lithium manganese phosphate (LiMnPO 4 ) can greatly increase the energy density of lithium ion batteries.
  • the electronic conductivity and the lithium ion diffusion rate of lithium manganese phosphate are low, so that the unmodified lithium manganese phosphate positive active material cannot meet the actual needs.
  • lithium manganese phosphate is usually doped with a metal element to modify the lithium manganese phosphate positive active material.
  • a method for preparing a metal element doped lithium manganese phosphate positive active material which has been reported so far is a solid phase synthesis method.
  • the solid phase synthesis method specifically comprises: mixing a phosphorus source, a lithium source, a manganese source, a metal element source and a solvent in a certain ratio and ball milling; and then calcining at a high temperature in an inert atmosphere to obtain a metal element doped lithium manganese phosphate cathode active material.
  • the solid phase synthesis method is simple, however, the metal element doped lithium manganese phosphate cathode active material prepared by the method has the disadvantages of large particles, uneven particle size and impurities, so that the metal element doped lithium manganese phosphate The performance stability of the positive active material is low, thereby affecting the electrochemical performance of the metal element doped lithium manganese phosphate positive active material.
  • the hydrothermal method is also a method of commonly used lithium manganese phosphate or lithium iron phosphate.
  • the hydrothermal method is synthesized by a liquid phase method, and ions can be uniformly mixed, thereby preparing a positive crystal active material having a better crystal form, but
  • the particle size of the lithium iron phosphate or lithium manganese phosphate positive electrode active material prepared by hydrothermal method is still large, and also contains impurities, and the reaction time required for preparation is long.
  • a method for preparing a positive electrode active material for a lithium ion battery comprising the steps of: respectively providing a lithium source solution, a divalent manganese source solution, a divalent iron source solution, and a phosphate source solution, the lithium source solution, the divalent manganese source solution,
  • the divalent iron source solution and the phosphate source solution are respectively obtained by dissolving a lithium source compound, a divalent manganese source compound, a divalent iron source compound, and a phosphate source compound in an organic solvent, and the divalent manganese source compound and the divalent iron are obtained.
  • the source compound is a strong acid salt; mixing the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution to form a first solution, wherein the divalent manganese source solution and the divalent iron source solution are manganese: iron. Mixing a molar ratio of 0.9:0.1; adding the lithium source solution to the first solution to form a second solution; wherein the divalent manganese source compound, the divalent iron source compound, the phosphate source compound, and The total concentration of the lithium source compound in the second solution is 3 mol/L or less; and the second solution is heated in a solvothermal reactor to carry out a reaction to obtain a reaction product LiMn 0.9 Fe 0.1 PO 4 .
  • the embodiment of the present invention uses a solvothermal method to prepare a positive active material LiMn 0.9 Fe 0.1 PO 4 , and controls the type of the divalent iron source compound and the divalent manganese source compound in the preparation method, and the bivalent value.
  • the preparation time required for the method is short and LiMn 0.9 Fe 0.1 PO 4 nanoparticles having a uniform size can be obtained, and the LiMn 0.9 Fe 0.1 PO 4 nanoparticles have better electrochemical performance as a positive electrode active material.
  • FIG. 1 is a flow chart of a method for preparing a positive active material for a lithium ion battery according to an embodiment of the present invention.
  • Example 2 is an XRD chart of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
  • Example 3 is a scanning electron micrograph of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
  • Example 4 is a scanning electron micrograph of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 2 of the present invention.
  • Fig. 5 is an XRD chart of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in a comparative example of the present invention.
  • Fig. 6 is a graph showing the first charge and discharge curves of the LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
  • Fig. 7 is a graph showing the cycle performance test of the LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
  • an embodiment of the present invention provides a method for preparing a positive active material for a lithium ion battery, which includes the following steps:
  • S1 respectively providing a lithium source solution, a divalent manganese source solution, a divalent iron source solution, and a phosphate source solution, wherein the lithium source solution, the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution are respectively lithium source compounds,
  • the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound are obtained by dissolving in an organic solvent, and the divalent manganese source compound and the divalent iron source compound are strong acid salts;
  • the second solution is heated in a solvothermal reactor to carry out a reaction to obtain a reaction product of LiMn 0.9 Fe 0.1 PO 4 .
  • the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound may be dissolved in the organic solvent. That is, lithium ions, divalent manganese ions, divalent iron ions, and phosphate ions can be formed in the organic solvent.
  • the lithium source compound may be selected from one or more of lithium hydroxide, lithium chloride, lithium sulfate, lithium nitrate, lithium dihydrogen phosphate, and lithium acetate.
  • the divalent manganese source compound and the divalent iron source compound are strong acid salts.
  • the divalent manganese source compound may be one or more of manganese chloride, manganese sulfate, and manganese nitrate.
  • the divalent manganese source compound is manganese chloride.
  • the divalent iron source compound may be selected from one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride.
  • the phosphate-derived compound has a phosphate, and may be one or more selected from the group consisting of phosphoric acid, lithium dihydrogen phosphate, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.
  • the organic solvent is an organic solvent capable of dissolving the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphorus source compound, such as a glycol, a polyol or a polymer alcohol, preferably ethylene glycol.
  • a glycol preferably ethylene glycol.
  • the kind of the organic solvent can be selected depending on the kind of the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound to be used.
  • the lithium source solution, the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution may respectively adopt different organic solvents, but the selected organic solvent may simultaneously dissolve the divalent manganese source compound and the divalent iron source compound. , a phosphate source compound, and a lithium source compound.
  • the organic solvent in the examples of the present invention is ethylene glycol.
  • the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution may have a molar ratio of manganese:iron:phosphorus of 0.9:0.1:(0.8 to 1.5). That is, when the molar amount of manganese is 0.9 parts, the molar amount of iron is 0.1 part, and the molar amount of phosphorus is 0.8 to 1.5 parts.
  • the step S2 may further comprise a step of stirring to uniformly mix the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution.
  • the manner of stirring may be that the stirring may be mechanical stirring or ultrasonic vibration or the like.
  • the molar ratio between lithium: (manganese + iron): phosphorus may be (2 ⁇ 3): 1: (0.8 ⁇ 1.5). That is, when the total molar ratio of manganese to iron is 1 part, the molar amount of lithium is 2 to 3 parts, and the molar amount of phosphorus is 0.8 to 1.5 parts.
  • the concentration in the second solution is too high, it is easy to form LiFePO 4 or LiMnPO 4 phase separation in the reaction of the step S4, so that the pure phase olivine-type LiMn 0.9 Fe 0.1 PO 4 cannot be obtained.
  • the total concentration of the divalent manganese source compound, the divalent iron source compound, the lithium source compound, and the phosphate source compound in the second solution should be less than or equal to 3 mol/L. Further, when the divalent manganese source compound and the divalent iron source compound are weak acid salts, it is also easy to cause a hetero phase such as Li 3 PO 4 in the reaction product.
  • the divalent manganese source compound and the divalent iron source compound should be strong acid salts, and in the second solution formed by the mixing, the divalent manganese source compound
  • the total concentration of the divalent iron source compound, the phosphate source compound, and the lithium source compound in the second solution should be 3 mol/L or less.
  • the total molar concentration of the divalent manganese source compound and the divalent iron source compound in the second solution may be from 0.1 mol/L to 0.3 mol/L.
  • the total concentration of the divalent manganese source compound and the divalent iron source compound in the second solution is 0.2 mol/L.
  • the lithium source solution may be injected into the first solution for mixing at a small flow rate.
  • the lithium source solution may be added to the first solution by dropping.
  • the rate at which the lithium source solution is added may be greater than or equal to 3 mL/min.
  • the rate of addition is from 3 mL/min to 40 mL/min.
  • LiMn 0.9 Fe 0.1 PO 4 obtained by the above mixing method has a good crystallinity.
  • continuous stirring may be performed at a certain stirring rate during the process of adding the lithium source solution to the first solution.
  • the agitation rate can range from 60 revolutions per minute to 600 revolutions per minute.
  • the solvothermal reaction vessel may be a sealed autoclave, and the internal pressure of the reactor is raised by pressurizing the sealed autoclave or using the autogenous pressure of the steam inside the reactor to increase the internal pressure of the reactor.
  • the reaction raw materials are reacted under high temperature and high pressure conditions.
  • the internal pressure of the reactor may be 5 MPa to 30 MPa, the heating temperature is 100 ° C to 180 ° C, and the reaction time is 1 hour to 24 hours, thereby obtaining a nanoparticle having a reaction product of LiMn 0.9 Fe 0.1 PO 4 .
  • the reaction vessel can be naturally cooled to room temperature.
  • the reaction product can be separated and purified from the second solution.
  • the reaction product may be separated from the liquid phase by filtration or centrifugation, then washed with deionized water and dried.
  • the reaction product LiMn 0.9 Fe 0.1 PO 4 may be subjected to carbonization treatment.
  • the method of encapsulating carbon may be: providing a solution of a carbon source compound; adding the LiMn 0.9 Fe 0.1 PO 4 to the carbon source compound solution to form a mixture; and subjecting the mixture to heat treatment.
  • the carbon source compound is preferably a reducing organic compound which can be cracked into a simple substance of carbon such as amorphous carbon under heating, and no other solid phase substance is formed.
  • the carbon source compound may be sucrose, glucose, sban 80, phenolic resin, epoxy resin, furan resin, polyacrylic acid, polyacrylonitrile, polyethylene glycol or polyvinyl alcohol.
  • the concentration of the carbon source compound solution is from about 0.005 g/ml to 0.05 g/ml.
  • further stirring may be performed to sufficiently coat the LiMn 0.9 Fe 0.1 PO 4 nanoparticles with the carbon source compound solution.
  • the mixture of LiMn 0.9 Fe 0.1 PO 4 and the carbon source compound solution may be evacuated by a vacuuming step to sufficiently evacuate air between the LiMn 0.9 Fe 0.1 PO 4 nanoparticles.
  • LiMn 0.9 Fe 0.1 PO 4 having a solution of a carbon source compound on the surface may be taken out from the solution of the carbon source compound and dried.
  • the temperature of the heat treatment is preferably from 300 ° C to 800 ° C.
  • the heat treatment time is preferably from 0.3 hours to 8 hours.
  • the temperature of the heat treatment in the examples of the present invention was 650 °C.
  • the divalent manganese source compound and the divalent iron source compound are coprecipitated by the solvothermal method to form a pure phase of LiMn 0.9 Fe 0.1 PO 4 .
  • the LiMn 0.9 Fe 0.1 PO 4 has good crystallinity and has a uniform nanometer scale. Further, the LiMn 0.9 Fe 0.1 PO 4 nanoparticles formed by the above method have good dispersibility.
  • the LiMn 0.9 Fe 0.1 PO 4 is a rod-shaped or sheet-like nanoparticle.
  • the morphology of the LiMn 0.9 Fe 0.1 PO 4 nanoparticles is related to the type of the divalent manganese source compound, the divalent iron source compound, the lithium source compound or the phosphate source compound added above, and the LiMn 0.9 Fe formed by the same reaction conditions.
  • 0.1 PO 4 nanoparticles have consistent morphology.
  • the lithium source compound is lithium hydroxide
  • the divalent manganese source compound is manganese chloride
  • the divalent iron source compound is ferrous sulfate
  • the phosphate source compound is phosphoric acid.
  • the organic solvent is ethylene glycol.
  • the second solution is placed in a solvothermal reaction vessel, and after solvothermal reaction at a temperature of 180 ° C for 4 hours, the solution is taken out, naturally cooled to room temperature, and then the reaction product is centrifuged and dried at 80 ° C. And the reaction product was subjected to XRD test. Referring to FIG.
  • the diffraction peak of the XRD pattern of the reaction product is consistent with the diffraction peak of the standard spectrum of the lithium manganese phosphate material, and the reaction product prepared by the above method is pure phase and the crystallinity of the olivine-type LiMn 0.9 Fe 0.1 PO is good. 4 .
  • FIG. 3 Please refer to FIG. 3 for further observation of the reaction product by scanning electron microscopy. It can be found that the reaction product is uniform in morphology of LiMn 0.9 Fe 0.1 PO 4 , which is a rod-like structure with a length of less than 300 nm and a width of less than 80 nm. Less than 40 nanometers. Further, the specific surface area of the reaction product was 29.691 g/m 2 on average.
  • This embodiment is basically the same as the above-described Embodiment 1, except that the divalent iron source compound is ferrous chloride, and the solvothermal reaction time is 12 hours.
  • the XRD test showed that the reaction product was pure phase olivine-type LiMn 0.9 Fe 0.1 PO 4 with pure phase and good crystallinity.
  • the reaction product LiMn 0.9 Fe 0.1 PO 4 is a nanosheet-like structure having uniform morphology.
  • the nanosheet-like structure had an average specific surface area of 49.892 g/m 2 .
  • This comparative example is basically the same as the above-described Example 2, except that the divalent manganese source compound is manganese acetate Mn(CH 3 COO) 2 .
  • the reaction product was obtained as an olivine-type LiMn 0.9 Fe 0.1 PO 4 particle containing a lithium phosphate impurity phase.
  • the LiMn 0.9 Fe 0.1 PO 4 obtained in the above Example 1 was added to a sucrose solution to obtain a mixture, and then the mixture was calcined at 650 ° C for 5 hours in a N 2 atmosphere to obtain a composite material of LiMn 0.9 Fe 0.1 PO 4 and carbon. . Thereafter, a positive electrode composed of a composite material of LiMn 0.9 Fe 0.1 PO 4 and carbon having a mass percentage of 80%, 5% acetylene black, 5% conductive graphite, and 10% polyvinylidene fluoride was formed.
  • Celgard 2400 microporous polypropylene film as the separator with 1mol/L LiPF 6 /EC+DMC+EMC (1:1:1 volume ratio) as the electrolyte, CR2032 is formed in the argon atmosphere glove box.
  • the button cell battery was tested for battery performance after standing at room temperature for a period of time.
  • the first charging specific capacity and the first discharging specific capacity of the battery of the above embodiment 3 are 161 mAh/g and 150 mAh/g, respectively.
  • the first coulombic efficiency of the battery is over 90%, and the voltage difference between the charge and discharge curves is very small. It is indicated that LiMn 0.9 Fe 0.1 PO 4 has a high purity and a good carbon coating effect in the composite material of LiMn 0.9 Fe 0.1 PO 4 and carbon.
  • the battery prepared in Example 3 has a better initial discharge specific capacity at a rate of 0.1 C, and the capacity retention rate after the charge and discharge cycle of 40 times is 95%.
  • the battery also has better cycle stability and capacity retention at a magnification of 0.2 C to 2 C. It is indicated that the LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared by the above solvothermal method has stable electrochemical performance and can greatly improve the capacity retention rate of the lithium ion battery.

Abstract

A method for preparing a positive electrode active material of a lithium ion battery. The method comprises the following steps: respectively providing a lithium source solution, a divalent manganese source solution, a ferrous source solution and a phosphate radical source solution; mixing the divalent manganese source solution, the ferrous source solution and the phosphate radical source solution to form a first solution, wherein the divalent manganese source solution and the ferrous source solution are mixed in the molar ratio of manganese to iron of 0.9:0.1; adding the lithium source solution into the first solution to form a second solution, wherein the total concentration of a divalent manganese source compound, a ferrous source compound, a phosphate radical source compound and a lithium source compound in the second solution is less than or equal to 3 mol/L; and heating the second solution in a solvent thermal reactor to react so as to obtain a reaction product LiMn0.9Fe0.1PO4.

Description

锂离子电池正极活性材料的制备方法Method for preparing lithium ion battery positive active material 技术领域Technical field
本发明涉及一种锂离子正极活性材料的制备方法，尤其涉及一种正极活性材料磷酸锰铁锂的制备方法。The invention relates to a preparation method of a lithium ion positive electrode active material, in particular to a preparation method of a positive electrode active material lithium manganese iron phosphate.
背景技术Background technique
磷酸铁锂（LiFePO4）作为一种具有较好安全性，价格低廉且对环境友好的锂离子电池正极活性材料一直受到人们极大的关注。然而磷酸铁锂3.4V的电压平台严重限制了锂离子电池能量密度的提高。与磷酸铁锂相比，磷酸锰锂（LiMnPO4）能极大地提高锂离子电池的能量密度。然而，磷酸锰锂的电子电导率和锂离子扩散速率较低，使得未经改性的磷酸锰锂正极活性材料无法满足实际需要。Lithium iron phosphate (LiFePO 4 ) has been receiving great attention as a positive active material for lithium ion batteries with good safety, low cost and environmental friendliness. However, the voltage platform of lithium iron phosphate 3.4V severely limits the increase in energy density of lithium ion batteries. Compared with lithium iron phosphate, lithium manganese phosphate (LiMnPO 4 ) can greatly increase the energy density of lithium ion batteries. However, the electronic conductivity and the lithium ion diffusion rate of lithium manganese phosphate are low, so that the unmodified lithium manganese phosphate positive active material cannot meet the actual needs.
为提高磷酸锰锂正极活性材料的电子电导率和锂离子扩散速率，人们通常用金属元素掺杂磷酸锰锂以对磷酸锰锂正极活性材料改性。目前已报道的制备金属元素掺杂磷酸锰锂正极活性材料的方法有固相合成法。固相合成法具体为：按一定比例将磷源、锂源、锰源、金属元素源及溶剂混合并球磨；之后在惰性氛围下高温煅烧获得金属元素掺杂的磷酸锰锂正极活性材料。该固相合成法工艺简单，然而，通过该方法制备的金属元素掺杂的磷酸锰锂正极活性材料具有颗粒大、粒径不均一以及含有杂项等缺点，使得该金属元素掺杂的磷酸锰锂正极活性材料的性能稳定性较低，从而影响了该金属元素掺杂的磷酸锰锂正极活性材料的电化学性能。此外，水热法也是一种常用磷酸锰锂或磷酸铁锂的方法，水热法由于使用液相法合成，离子间可以均匀混合，从而可以制备出较好晶型的正极活性材料，但通过水热法制备的磷酸铁锂或磷酸锰锂正极活性材料颗粒的粒径仍然偏大，还含有杂质，而且制备需要的反应时间较长。In order to increase the electronic conductivity and the lithium ion diffusion rate of the lithium manganese phosphate positive active material, lithium manganese phosphate is usually doped with a metal element to modify the lithium manganese phosphate positive active material. A method for preparing a metal element doped lithium manganese phosphate positive active material which has been reported so far is a solid phase synthesis method. The solid phase synthesis method specifically comprises: mixing a phosphorus source, a lithium source, a manganese source, a metal element source and a solvent in a certain ratio and ball milling; and then calcining at a high temperature in an inert atmosphere to obtain a metal element doped lithium manganese phosphate cathode active material. The solid phase synthesis method is simple, however, the metal element doped lithium manganese phosphate cathode active material prepared by the method has the disadvantages of large particles, uneven particle size and impurities, so that the metal element doped lithium manganese phosphate The performance stability of the positive active material is low, thereby affecting the electrochemical performance of the metal element doped lithium manganese phosphate positive active material. In addition, the hydrothermal method is also a method of commonly used lithium manganese phosphate or lithium iron phosphate. The hydrothermal method is synthesized by a liquid phase method, and ions can be uniformly mixed, thereby preparing a positive crystal active material having a better crystal form, but The particle size of the lithium iron phosphate or lithium manganese phosphate positive electrode active material prepared by hydrothermal method is still large, and also contains impurities, and the reaction time required for preparation is long.
发明内容Summary of the invention
有鉴于此，确有必要提供一种制备时间较短且具有较小尺寸的锂离子电池正极活性材料的制备方法，通过该方法获得的锂离子正极活性材料具有较好的电化学性能。In view of this, it is indeed necessary to provide a preparation method of a lithium ion battery positive active material having a short preparation time and a small size, and the lithium ion positive electrode active material obtained by the method has good electrochemical performance.
一种锂离子电池正极活性材料的制备方法，其包括以下步骤：分别提供锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液，该锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液分别为锂源化合物、二价锰源化合物、二价铁源化合物以及磷酸根源化合物在有机溶剂中溶解得到，所述二价锰源化合物与所述二价铁源化合物为强酸盐；混合所述二价锰源溶液、二价铁源溶液以及磷酸根源溶液形成一第一溶液，其中所述二价锰源溶液与二价铁源溶液以锰:铁的摩尔比为0.9:0.1进行混合；将所述锂源溶液加入到所述第一溶液中形成一第二溶液；其中，所述二价锰源化合物、二价铁源化合物、磷酸根源化合物、以及锂源化合物在该第二溶液中的总浓度小于等于3mol/L；以及将该第二溶液在溶剂热反应釜中加热进行反应，得到反应产物LiMn0.9Fe0.1PO4。A method for preparing a positive electrode active material for a lithium ion battery, comprising the steps of: respectively providing a lithium source solution, a divalent manganese source solution, a divalent iron source solution, and a phosphate source solution, the lithium source solution, the divalent manganese source solution, The divalent iron source solution and the phosphate source solution are respectively obtained by dissolving a lithium source compound, a divalent manganese source compound, a divalent iron source compound, and a phosphate source compound in an organic solvent, and the divalent manganese source compound and the divalent iron are obtained. The source compound is a strong acid salt; mixing the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution to form a first solution, wherein the divalent manganese source solution and the divalent iron source solution are manganese: iron. Mixing a molar ratio of 0.9:0.1; adding the lithium source solution to the first solution to form a second solution; wherein the divalent manganese source compound, the divalent iron source compound, the phosphate source compound, and The total concentration of the lithium source compound in the second solution is 3 mol/L or less; and the second solution is heated in a solvothermal reactor to carry out a reaction to obtain a reaction product LiMn 0.9 Fe 0.1 PO 4 .
相对于现有技术，本发明实施例利用溶剂热的方式来制备正极活性材料LiMn0.9Fe0.1PO4，通过在制备方法中控制二价铁源化合物以及二价锰源化合物的种类，以及二价锰源化合物、二价铁源化合物、磷酸根源化合物、以及锂源化合物在整个第二溶液中的摩尔浓度以及混合顺序，从而可获得纯相且结晶度较好的橄榄石型LiMn0.9Fe0.1PO4。该方法所需的制备时间较短且可以获得具有均一尺寸的LiMn0.9Fe0.1PO4纳米颗粒，而且该LiMn0.9Fe0.1PO4纳米颗粒作为正极活性材料具有较好的电化学性能。Compared with the prior art, the embodiment of the present invention uses a solvothermal method to prepare a positive active material LiMn 0.9 Fe 0.1 PO 4 , and controls the type of the divalent iron source compound and the divalent manganese source compound in the preparation method, and the bivalent value. The molar concentration of the manganese source compound, the divalent iron source compound, the phosphate source compound, and the lithium source compound in the entire second solution, and the mixing order, thereby obtaining an olivine-type LiMn 0.9 Fe 0.1 PO having a pure phase and a good crystallinity. 4 . The preparation time required for the method is short and LiMn 0.9 Fe 0.1 PO 4 nanoparticles having a uniform size can be obtained, and the LiMn 0.9 Fe 0.1 PO 4 nanoparticles have better electrochemical performance as a positive electrode active material.
附图说明DRAWINGS
图1是本发明实施例的锂离子电池正极活性材料制备方法流程图。1 is a flow chart of a method for preparing a positive active material for a lithium ion battery according to an embodiment of the present invention.
图2是本发明实施例1制备得到的LiMn0.9Fe0.1PO4正极活性材料的XRD谱图。2 is an XRD chart of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
图3是本发明实施例1制备得到的LiMn0.9Fe0.1PO4正极活性材料的扫描电镜照片。3 is a scanning electron micrograph of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
图4是本发明实施例2制备得到的LiMn0.9Fe0.1PO4正极活性材料的扫描电镜照片。4 is a scanning electron micrograph of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 2 of the present invention.
图5是本发明对比例制备得到的LiMn0.9Fe0.1PO4正极活性材料的XRD谱图。Fig. 5 is an XRD chart of a LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in a comparative example of the present invention.
图6是本发明实施例1制备得到的LiMn0.9Fe0.1PO4正极活性材料的首次充放电曲线。Fig. 6 is a graph showing the first charge and discharge curves of the LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
图7是本发明实施例1制备得到的LiMn0.9Fe0.1PO4正极活性材料的循环性能测试曲线。Fig. 7 is a graph showing the cycle performance test of the LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared in Example 1 of the present invention.
具体实施方式detailed description
以下将结合附图详细说明本发明实施例锂离子电池正极活性材料的制备方法。Hereinafter, a method for preparing a positive electrode active material for a lithium ion battery according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
请参阅图1，本发明实施例提供一种锂离子电池正极活性材料的制备方法，其包括以下步骤：Referring to FIG. 1 , an embodiment of the present invention provides a method for preparing a positive active material for a lithium ion battery, which includes the following steps:
S1，分别提供锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液，该锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液分别为锂源化合物、二价锰源化合物、二价铁源化合物以及磷酸根源化合物在有机溶剂中溶解得到，所述二价锰源化合物与所述二价铁源化合物为强酸盐；S1, respectively providing a lithium source solution, a divalent manganese source solution, a divalent iron source solution, and a phosphate source solution, wherein the lithium source solution, the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution are respectively lithium source compounds, The divalent manganese source compound, the divalent iron source compound, and the phosphate source compound are obtained by dissolving in an organic solvent, and the divalent manganese source compound and the divalent iron source compound are strong acid salts;
S2，混合所述二价锰源溶液、二价铁源溶液以及磷酸根源溶液形成一第一溶液，其中所述二价锰源溶液与二价铁源溶液以锰:铁的摩尔比为0.9:0.1进行混合；S2, mixing the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution to form a first solution, wherein the molar ratio of the divalent manganese source solution to the divalent iron source solution in manganese:iron is 0.9: 0.1 for mixing;
S3，将所述锂源溶液加入到所述第一溶液中形成一第二溶液；其中，所述二价锰源化合物、二价铁源化合物、磷酸根源化合物、以及锂源化合物在该第二溶液中的总浓度小于等于3mol/L；以及S3, adding the lithium source solution to the first solution to form a second solution; wherein the divalent manganese source compound, the divalent iron source compound, the phosphate source compound, and the lithium source compound are in the second The total concentration in the solution is less than or equal to 3 mol/L;
S4，将该第二溶液在溶剂热反应釜中加热进行反应，得到反应产物LiMn0.9Fe0.1PO4。S4, the second solution is heated in a solvothermal reactor to carry out a reaction to obtain a reaction product of LiMn 0.9 Fe 0.1 PO 4 .
上述步骤S1中，所述锂源化合物、二价锰源化合物、二价铁源化合物及磷酸根源化合物均可溶于所述有机溶剂。即可以在所述有机溶剂形成锂离子、二价锰离子、二价铁离子及磷酸根离子。该锂源化合物可选择为氢氧化锂、氯化锂、硫酸锂、硝酸锂、磷酸二氢锂、醋酸锂中的一种或多种。该二价锰源化合物以及二价铁源化合物为强酸盐。优选地，该二价锰源化合物可为氯化亚锰、硫酸锰以及硝酸锰一种或几种。更为优选地，所述二价锰源化合物为氯化亚锰。所述二价铁源化合物可选择为硫酸亚铁、硝酸亚铁以及氯化亚铁中的一种或多种。所述磷酸根源化合物具有磷酸根，可选择为磷酸、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。In the above step S1, the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound may be dissolved in the organic solvent. That is, lithium ions, divalent manganese ions, divalent iron ions, and phosphate ions can be formed in the organic solvent. The lithium source compound may be selected from one or more of lithium hydroxide, lithium chloride, lithium sulfate, lithium nitrate, lithium dihydrogen phosphate, and lithium acetate. The divalent manganese source compound and the divalent iron source compound are strong acid salts. Preferably, the divalent manganese source compound may be one or more of manganese chloride, manganese sulfate, and manganese nitrate. More preferably, the divalent manganese source compound is manganese chloride. The divalent iron source compound may be selected from one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride. The phosphate-derived compound has a phosphate, and may be one or more selected from the group consisting of phosphoric acid, lithium dihydrogen phosphate, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.
所述有机溶剂为可溶解该锂源化合物、二价锰源化合物、二价铁源化合物及磷源化合物的有机溶剂，如二元醇、多元醇或聚合物醇，优选可以为乙二醇、丙三醇、二甘醇、三甘醇、四甘醇、丁三醇及聚乙二醇中的一种或多种。所述有机溶剂的种类可根据使用的锂源化合物、二价锰源化合物、二价铁源化合物及磷酸根源化合物的种类而进行选择。该锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液可以分别采用不同的有机溶剂，但所选择的有机溶剂可同时溶解所述二价锰源化合物、二价铁源化合物、磷酸根源化合物以及锂源化合物。本发明实施例中所述有机溶剂为乙二醇。The organic solvent is an organic solvent capable of dissolving the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphorus source compound, such as a glycol, a polyol or a polymer alcohol, preferably ethylene glycol. One or more of glycerol, diethylene glycol, triethylene glycol, tetraethylene glycol, butyl triol, and polyethylene glycol. The kind of the organic solvent can be selected depending on the kind of the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound to be used. The lithium source solution, the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution may respectively adopt different organic solvents, but the selected organic solvent may simultaneously dissolve the divalent manganese source compound and the divalent iron source compound. , a phosphate source compound, and a lithium source compound. The organic solvent in the examples of the present invention is ethylene glycol.
在所述步骤S2中，所述二价锰源溶液、二价铁源溶液以及磷酸根源溶液可以锰：铁：磷的摩尔比为0.9：0.1：（0.8~1.5）。即，锰的摩尔量为0.9份时，铁的摩尔量0.1份，磷的摩尔量为0.8~1.5份。In the step S2, the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution may have a molar ratio of manganese:iron:phosphorus of 0.9:0.1:(0.8 to 1.5). That is, when the molar amount of manganese is 0.9 parts, the molar amount of iron is 0.1 part, and the molar amount of phosphorus is 0.8 to 1.5 parts.
所述步骤S2可进一步包括一搅拌的步骤使所述二价锰源溶液、二价铁源溶液以及磷酸根源溶液均匀混合。所述搅拌的方式可以为所述搅拌的方式可为机械搅拌或超声振荡等。The step S2 may further comprise a step of stirring to uniformly mix the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution. The manner of stirring may be that the stirring may be mechanical stirring or ultrasonic vibration or the like.
在所述步骤S3形成的第二溶液中，锂：（锰+铁）：磷之间的摩尔比可为(2~3):1:(0.8~1.5)。即，锰与铁的总的摩尔比为1份时，锂的摩尔量为2~3份，磷的摩尔量为0.8~1.5份。In the second solution formed in the step S3, the molar ratio between lithium: (manganese + iron): phosphorus may be (2~3): 1: (0.8~1.5). That is, when the total molar ratio of manganese to iron is 1 part, the molar amount of lithium is 2 to 3 parts, and the molar amount of phosphorus is 0.8 to 1.5 parts.
当所述第二溶液的中的浓度太高时，容易在步骤S4的反应过程中形成LiFePO4或LiMnPO4分相，从而无法获得纯相的橄榄石型LiMn0.9Fe0.1PO4。为避免形成LiFePO4或LiMnPO4分相，所述第二溶液中，所述二价锰源化合物、二价铁源化合物、锂源化合物以及磷酸根源化合物的总浓度应小于或等于3mol/L。另外，当该二价锰源化合物以及二价铁源化合物为弱酸盐时，也容易使所述反应产物中产生杂相，如Li3PO4。因此，为了获得纯相的LiMn0.9Fe0.1PO4，该二价锰源化合物以及二价铁源化合物应为强酸盐，且所述混合形成的第二溶液中，所述二价锰源化合物、二价铁源化合物、磷酸根源化合物、以及锂源化合物在该第二溶液中的总浓度应小于等于3mol/L。When the concentration in the second solution is too high, it is easy to form LiFePO 4 or LiMnPO 4 phase separation in the reaction of the step S4, so that the pure phase olivine-type LiMn 0.9 Fe 0.1 PO 4 cannot be obtained. In order to avoid the formation of LiFePO 4 or LiMnPO 4 phase separation, the total concentration of the divalent manganese source compound, the divalent iron source compound, the lithium source compound, and the phosphate source compound in the second solution should be less than or equal to 3 mol/L. Further, when the divalent manganese source compound and the divalent iron source compound are weak acid salts, it is also easy to cause a hetero phase such as Li 3 PO 4 in the reaction product. Therefore, in order to obtain pure phase LiMn 0.9 Fe 0.1 PO 4 , the divalent manganese source compound and the divalent iron source compound should be strong acid salts, and in the second solution formed by the mixing, the divalent manganese source compound The total concentration of the divalent iron source compound, the phosphate source compound, and the lithium source compound in the second solution should be 3 mol/L or less.
此外，所述二价锰源化合物与二价铁源化合物在该第二溶液中的总摩尔浓度可为0.1mol/L至0.3mol/L。优选地，所述述二价锰源化合物与二价铁源化合物在该第二溶液中的总浓度为0.2mol/L。所述锂源化合物、二价锰源化合物、二价铁源化合物以及磷酸根源化合物在该第二溶液中的摩尔浓度比可为锂：（锰+铁）：磷=2.7:1:1。Further, the total molar concentration of the divalent manganese source compound and the divalent iron source compound in the second solution may be from 0.1 mol/L to 0.3 mol/L. Preferably, the total concentration of the divalent manganese source compound and the divalent iron source compound in the second solution is 0.2 mol/L. The molar ratio of the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound in the second solution may be lithium: (manganese + iron): phosphorus = 2.7:1:1.
在所述步骤S3中，所述锂源溶液可以一较小的流速注入到所述第一溶液中进行混合。优选地，所述锂源溶液可以通过滴加的方式加入到所述第一溶液中。所述锂源溶液加入的速率可以大于等于3mL/min。优选地，加入的速率为3mL/min至40mL/min。通过上述混合方式获得的LiMn0.9Fe0.1PO4具有较好的结晶度。此外，在将所述锂源溶液加入到所述第一溶液的过程中可按照一定的搅拌速率进行持续搅拌。该搅拌速率可以为60转/分钟至600转/分钟。In the step S3, the lithium source solution may be injected into the first solution for mixing at a small flow rate. Preferably, the lithium source solution may be added to the first solution by dropping. The rate at which the lithium source solution is added may be greater than or equal to 3 mL/min. Preferably, the rate of addition is from 3 mL/min to 40 mL/min. LiMn 0.9 Fe 0.1 PO 4 obtained by the above mixing method has a good crystallinity. Further, continuous stirring may be performed at a certain stirring rate during the process of adding the lithium source solution to the first solution. The agitation rate can range from 60 revolutions per minute to 600 revolutions per minute.
在所述步骤S4中，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5MPa~30MPa，该加热温度为100℃至180℃，反应时间为1小时至24小时，即可得到反应产物为LiMn0.9Fe0.1PO4的纳米颗粒。在反应完毕后，所述反应釜可自然冷却至室温。In the step S4, the solvothermal reaction vessel may be a sealed autoclave, and the internal pressure of the reactor is raised by pressurizing the sealed autoclave or using the autogenous pressure of the steam inside the reactor to increase the internal pressure of the reactor. The reaction raw materials are reacted under high temperature and high pressure conditions. The internal pressure of the reactor may be 5 MPa to 30 MPa, the heating temperature is 100 ° C to 180 ° C, and the reaction time is 1 hour to 24 hours, thereby obtaining a nanoparticle having a reaction product of LiMn 0.9 Fe 0.1 PO 4 . After the reaction is completed, the reaction vessel can be naturally cooled to room temperature.
进一步地，在通过所述步骤S4得到所述反应产物后，可从所述第二溶液中将该反应产物分离提纯。具体地，可采用过滤或离心的方式将所述反应产物从液相中分离，然后用去离子水洗涤并干燥。Further, after the reaction product is obtained by the step S4, the reaction product can be separated and purified from the second solution. Specifically, the reaction product may be separated from the liquid phase by filtration or centrifugation, then washed with deionized water and dried.
进一步地，在通过步骤S4得到反应产物后，可将该反应产物LiMn0.9Fe0.1PO4进行包碳处理。该包碳的方法可以是：提供一碳源化合物的溶液；将所述LiMn0.9Fe0.1PO4加入该碳源化合物溶液中形成混合体；以及将该混合体进行热处理。所述碳源化合物优选为还原性有机化合物，该类有机化合物在加热条件下可裂解成碳单质，如无定形碳，且无其它固相物质生成。所述碳源化合物可为蔗糖、葡萄糖、司班80、酚醛树脂、环氧树脂、呋喃树脂、聚丙烯酸、聚丙烯腈、聚乙二醇或聚乙烯醇等。该碳源化合物溶液的浓度约为0.005g/ml至0.05g/ml。在将所述LiMn0.9Fe0.1PO4加入该碳源化合物溶液后，可进一步搅拌，使该碳源化合物溶液充分包覆该LiMn0.9Fe0.1PO4纳米颗粒。另外，可采用一抽真空的步骤对该LiMn0.9Fe0.1PO4和碳源化合物溶液的混合体抽真空，使LiMn0.9Fe0.1PO4纳米颗粒之间的空气充分排出。进一步地，在加热该混合体前，可先将表面具有碳源化合物溶液的LiMn0.9Fe0.1PO4从碳源化合物溶液中捞出并烘干。该热处理的温度优选为300℃至800℃。该热处理的时间优选为0.3小时至8小时。本发明实施例中所述热处理的温度为650℃。Further, after the reaction product is obtained by the step S4, the reaction product LiMn 0.9 Fe 0.1 PO 4 may be subjected to carbonization treatment. The method of encapsulating carbon may be: providing a solution of a carbon source compound; adding the LiMn 0.9 Fe 0.1 PO 4 to the carbon source compound solution to form a mixture; and subjecting the mixture to heat treatment. The carbon source compound is preferably a reducing organic compound which can be cracked into a simple substance of carbon such as amorphous carbon under heating, and no other solid phase substance is formed. The carbon source compound may be sucrose, glucose, sban 80, phenolic resin, epoxy resin, furan resin, polyacrylic acid, polyacrylonitrile, polyethylene glycol or polyvinyl alcohol. The concentration of the carbon source compound solution is from about 0.005 g/ml to 0.05 g/ml. After the LiMn 0.9 Fe 0.1 PO 4 is added to the carbon source compound solution, further stirring may be performed to sufficiently coat the LiMn 0.9 Fe 0.1 PO 4 nanoparticles with the carbon source compound solution. Alternatively, the mixture of LiMn 0.9 Fe 0.1 PO 4 and the carbon source compound solution may be evacuated by a vacuuming step to sufficiently evacuate air between the LiMn 0.9 Fe 0.1 PO 4 nanoparticles. Further, before heating the mixture, LiMn 0.9 Fe 0.1 PO 4 having a solution of a carbon source compound on the surface may be taken out from the solution of the carbon source compound and dried. The temperature of the heat treatment is preferably from 300 ° C to 800 ° C. The heat treatment time is preferably from 0.3 hours to 8 hours. The temperature of the heat treatment in the examples of the present invention was 650 °C.
通过上述溶剂热法可使所述二价锰源化合物、二价铁源化合物共沉淀形成纯相的LiMn0.9Fe0.1PO4。该LiMn0.9Fe0.1PO4具有良好的结晶度，且具有均一的纳米尺度。此外，通过上述方法形成的LiMn0.9Fe0.1PO4纳米颗粒具有良好的分散性。该LiMn0.9Fe0.1PO4为棒状或片状纳米颗粒。该LiMn0.9Fe0.1PO4纳米颗粒的形貌与上述加入的二价锰源化合物、二价铁源化合物、锂源化合物或磷酸根源化合物的种类有关，且相同的反应条件所形成的LiMn0.9Fe0.1PO4纳米颗粒形貌一致。The divalent manganese source compound and the divalent iron source compound are coprecipitated by the solvothermal method to form a pure phase of LiMn 0.9 Fe 0.1 PO 4 . The LiMn 0.9 Fe 0.1 PO 4 has good crystallinity and has a uniform nanometer scale. Further, the LiMn 0.9 Fe 0.1 PO 4 nanoparticles formed by the above method have good dispersibility. The LiMn 0.9 Fe 0.1 PO 4 is a rod-shaped or sheet-like nanoparticle. The morphology of the LiMn 0.9 Fe 0.1 PO 4 nanoparticles is related to the type of the divalent manganese source compound, the divalent iron source compound, the lithium source compound or the phosphate source compound added above, and the LiMn 0.9 Fe formed by the same reaction conditions. 0.1 PO 4 nanoparticles have consistent morphology.
实施例1Example 1
本实施例中，所述锂源化合物为氢氧化锂，所述二价锰源化合物为氯化亚锰，所述二价铁源化合物为硫酸亚铁，所述磷酸根源化合物为磷酸，所述有机溶剂为乙二醇。首先，将氯化亚锰、硫酸亚铁以及磷酸荣誉乙二醇中形成第一溶液。其次，将氢氧化锂的乙二醇溶液逐滴加入到所述第一溶液中混合并搅拌10分钟形成第二溶液。在该第二溶液中，所述氯化亚锰和硫酸亚铁在该第二溶液中的总浓度为0.2mol/L，所述氢氧化锂、氯化亚锰、硫酸亚铁以及磷酸在该第二溶液中的摩尔浓度比为锂：（锰+铁）：磷=2.7：1：1。最后，将该第二溶液放入溶剂热反应釜中，在180℃的温度下溶剂热反应4小时后，取出溶液，自然冷却至室温，然后将反应产物离心分离，并在80℃下烘干，并对该反应产物进行XRD测试。请参阅图2，该反应产物的XRD图谱的衍射峰与磷酸锰锂材料的标准图谱的衍射峰一致，证明上述方法制备的反应产物为纯相且结晶度良好的橄榄石型LiMn0.9Fe0.1PO4。请进一步参阅图3，将该反应产物通过扫描电镜进行观察，可以发现该反应产物为LiMn0.9Fe0.1PO4的形貌均一，均为棒状结构，其长度小于300纳米，宽度小于80纳米，厚度小于40纳米。此外，该反应产物的比表面积平均为29.691 g/m2。In this embodiment, the lithium source compound is lithium hydroxide, the divalent manganese source compound is manganese chloride, the divalent iron source compound is ferrous sulfate, and the phosphate source compound is phosphoric acid. The organic solvent is ethylene glycol. First, a first solution is formed in manganese chloride, ferrous sulfate, and ammonium glycol phosphate. Next, a solution of lithium hydroxide in ethylene glycol was added dropwise to the first solution and stirred for 10 minutes to form a second solution. In the second solution, the total concentration of the manganese chloride and the ferrous sulfate in the second solution is 0.2 mol/L, and the lithium hydroxide, manganese chloride, ferrous sulfate, and phosphoric acid are in the The molar concentration ratio in the second solution was lithium: (manganese + iron): phosphorus = 2.7: 1:1. Finally, the second solution is placed in a solvothermal reaction vessel, and after solvothermal reaction at a temperature of 180 ° C for 4 hours, the solution is taken out, naturally cooled to room temperature, and then the reaction product is centrifuged and dried at 80 ° C. And the reaction product was subjected to XRD test. Referring to FIG. 2, the diffraction peak of the XRD pattern of the reaction product is consistent with the diffraction peak of the standard spectrum of the lithium manganese phosphate material, and the reaction product prepared by the above method is pure phase and the crystallinity of the olivine-type LiMn 0.9 Fe 0.1 PO is good. 4 . Please refer to FIG. 3 for further observation of the reaction product by scanning electron microscopy. It can be found that the reaction product is uniform in morphology of LiMn 0.9 Fe 0.1 PO 4 , which is a rod-like structure with a length of less than 300 nm and a width of less than 80 nm. Less than 40 nanometers. Further, the specific surface area of the reaction product was 29.691 g/m 2 on average.
实施例2Example 2
本实施例与上述实施例1基本相同，其区别仅在于，所述二价铁源化合物为氯化亚铁，且溶剂热反应的时间为12小时。经XRD测试，反应产物为纯相且结晶度良好的纯相橄榄石型LiMn0.9Fe0.1PO4。此外，请参阅图4，从图中可以看出，反应产物LiMn0.9Fe0.1PO4为形貌均一的纳米片状结构。该纳米片状结构的比表面积平均为49.892 g/m2。This embodiment is basically the same as the above-described Embodiment 1, except that the divalent iron source compound is ferrous chloride, and the solvothermal reaction time is 12 hours. The XRD test showed that the reaction product was pure phase olivine-type LiMn 0.9 Fe 0.1 PO 4 with pure phase and good crystallinity. In addition, referring to FIG. 4, it can be seen from the figure that the reaction product LiMn 0.9 Fe 0.1 PO 4 is a nanosheet-like structure having uniform morphology. The nanosheet-like structure had an average specific surface area of 49.892 g/m 2 .
对比例Comparative example
本对比例与上述实施例2基本相同，其区别在于，所述二价锰源化合物为醋酸锰Mn(CH3COO)2。请参阅图5，经XRD测试发现，获得反应产物为含有磷酸锂杂质相的橄榄石型LiMn0.9Fe0.1PO4颗粒。This comparative example is basically the same as the above-described Example 2, except that the divalent manganese source compound is manganese acetate Mn(CH 3 COO) 2 . Referring to FIG. 5, it was found by XRD analysis that the reaction product was obtained as an olivine-type LiMn 0.9 Fe 0.1 PO 4 particle containing a lithium phosphate impurity phase.
实施例3Example 3
将上述实施例1得到的LiMn0.9Fe0.1PO4加入到蔗糖溶液中搅拌得到一混合物，然后将该混合物在N2气氛中以650摄氏度煅烧5小时获得LiMn0.9Fe0.1PO4与碳的复合材料。之后，形成一由质量百分比为80%的LiMn0.9Fe0.1PO4与碳的复合材料、5%的乙炔黑、5%的导电石墨及10%的聚偏氟乙烯混合组成的正极。以金属锂为负极，Celgard 2400微孔聚丙烯膜为隔膜，以1mol/L LiPF6/EC+DMC+EMC（1:1:1体积比）为电解液，在氩气气氛手套箱中组成CR2032型纽扣电池，在室温下静置一段时间后进行电池性能测试。The LiMn 0.9 Fe 0.1 PO 4 obtained in the above Example 1 was added to a sucrose solution to obtain a mixture, and then the mixture was calcined at 650 ° C for 5 hours in a N 2 atmosphere to obtain a composite material of LiMn 0.9 Fe 0.1 PO 4 and carbon. . Thereafter, a positive electrode composed of a composite material of LiMn 0.9 Fe 0.1 PO 4 and carbon having a mass percentage of 80%, 5% acetylene black, 5% conductive graphite, and 10% polyvinylidene fluoride was formed. Using lithium metal as the negative electrode, Celgard 2400 microporous polypropylene film as the separator, with 1mol/L LiPF 6 /EC+DMC+EMC (1:1:1 volume ratio) as the electrolyte, CR2032 is formed in the argon atmosphere glove box. The button cell battery was tested for battery performance after standing at room temperature for a period of time.
请参阅图6，从图中可以看出，上述实施例3的电池的首次充电比容量以及首次放电比容量较高，分别为161mAh/g和150mAh/g。该电池的首次库伦效率达到90%以上，并且充放电曲线间的电压差非常小。表明该LiMn0.9Fe0.1PO4与碳的复合材料中LiMn0.9Fe0.1PO4的纯度高且碳包覆效果好。Referring to FIG. 6, it can be seen from the figure that the first charging specific capacity and the first discharging specific capacity of the battery of the above embodiment 3 are 161 mAh/g and 150 mAh/g, respectively. The first coulombic efficiency of the battery is over 90%, and the voltage difference between the charge and discharge curves is very small. It is indicated that LiMn 0.9 Fe 0.1 PO 4 has a high purity and a good carbon coating effect in the composite material of LiMn 0.9 Fe 0.1 PO 4 and carbon.
请参阅图7，从图中可以看出，实施例3制备的电池在0.1C倍率下具有较好的首次放电比容量，且40次充放电循环后的容量保持率达95%。此外，从图中可以看出，在0.2C至2C的倍率下，该电池也具有较好的循环稳定性以及容量保持率。表明上述溶剂热法制备的LiMn0.9Fe0.1PO4正极活性材料具有稳定的电化学性能，可大大提高锂离子电池的容量保持率。Referring to FIG. 7, it can be seen from the figure that the battery prepared in Example 3 has a better initial discharge specific capacity at a rate of 0.1 C, and the capacity retention rate after the charge and discharge cycle of 40 times is 95%. In addition, as can be seen from the figure, the battery also has better cycle stability and capacity retention at a magnification of 0.2 C to 2 C. It is indicated that the LiMn 0.9 Fe 0.1 PO 4 positive electrode active material prepared by the above solvothermal method has stable electrochemical performance and can greatly improve the capacity retention rate of the lithium ion battery.
另外，本领域技术人员还可在本发明精神内作其它变化，当然这些依据本发明精神所作的变化，都应包含在本发明所要求保护的范围内。In addition, those skilled in the art can make other changes within the spirit of the invention, and it is to be understood that these changes are intended to be included within the scope of the invention.

Claims (10)

  1. 一种锂离子电池正极活性材料的制备方法，其包括：A method for preparing a positive active material for a lithium ion battery, comprising:
    分别提供锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液，该锂源溶液、二价锰源溶液、二价铁源溶液以及磷酸根源溶液分别为锂源化合物、二价锰源化合物、二价铁源化合物以及磷酸根源化合物在有机溶剂中溶解得到，所述二价锰源化合物与所述二价铁源化合物为强酸盐；Providing a lithium source solution, a divalent manganese source solution, a divalent iron source solution, and a phosphate source solution, respectively, the lithium source solution, the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution are respectively lithium source compounds, and bivalent The manganese source compound, the divalent iron source compound, and the phosphate source compound are obtained by dissolving in an organic solvent, and the divalent manganese source compound and the divalent iron source compound are strong acid salts;
    混合所述二价锰源溶液、二价铁源溶液以及磷酸根源溶液形成一第一溶液，其中所述二价锰源溶液与二价铁源溶液以锰:铁的摩尔比为0.9:0.1进行混合；Mixing the divalent manganese source solution, the divalent iron source solution, and the phosphate source solution to form a first solution, wherein the divalent manganese source solution and the divalent iron source solution are at a molar ratio of manganese:iron of 0.9:0.1. mixing;
    将所述锂源溶液加入到所述第一溶液中形成一第二溶液；其中，所述二价锰源化合物、二价铁源化合物、磷酸根源化合物、以及锂源化合物在该第二溶液中的总浓度小于等于3mol/L；以及Adding the lithium source solution to the first solution to form a second solution; wherein the divalent manganese source compound, the divalent iron source compound, the phosphate source compound, and the lithium source compound are in the second solution The total concentration is less than or equal to 3 mol / L;
    将该第二溶液在溶剂热反应釜中加热进行反应，得到反应产物LiMn0.9Fe0.1PO4。The second solution was heated in a solvothermal reactor to carry out a reaction to obtain a reaction product of LiMn 0.9 Fe 0.1 PO 4 .
  2. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述二价锰源化合物为氯化亚锰、硫酸锰以及硝酸锰中的一种或几种。 The method for preparing a positive electrode active material for a lithium ion battery according to claim 1, wherein the divalent manganese source compound is one or more of manganese chloride, manganese sulfate, and manganese nitrate.
  3. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述二价铁源化合物为硫酸亚铁、硝酸亚铁以及氯化亚铁中的一种或几种。 The method for producing a positive electrode active material for a lithium ion battery according to claim 1, wherein the divalent iron source compound is one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride.
  4. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述有机溶剂为乙二醇、丙三醇、二甘醇、三甘醇、四甘醇、丁三醇及聚乙二醇中的一种或多种。 The method for preparing a positive electrode active material for a lithium ion battery according to claim 1, wherein the organic solvent is ethylene glycol, glycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, butyl alcohol, and One or more of polyethylene glycols.
  5. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述二价锰源化合物为氯化亚锰、所述二价铁源化合物为硫酸亚铁，所述锂源化合物为氢氧化锂，所述磷酸根源化合物为磷酸，所述有机溶剂为乙二醇。 The method for preparing a positive electrode active material for a lithium ion battery according to claim 1, wherein the divalent manganese source compound is manganese chloride, the divalent iron source compound is ferrous sulfate, and the lithium source The compound is lithium hydroxide, the phosphate source compound is phosphoric acid, and the organic solvent is ethylene glycol.
  6. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述锂源溶液以3毫升/分钟至40毫升/分钟的速度滴加到第一溶液中混合。 The method for preparing a positive electrode active material for a lithium ion battery according to claim 1, wherein the lithium source solution is added dropwise to the first solution at a rate of from 3 ml/min to 40 ml/min.
  7. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述二价锰源化合物以及二价铁源化合物在所述第二溶液中的总摩尔浓度为0.1mol/L至0.3mol/L。 The method for preparing a positive electrode active material for a lithium ion battery according to claim 1, wherein the total molar concentration of the divalent manganese source compound and the divalent iron source compound in the second solution is 0.1 mol/L. To 0.3 mol/L.
  8. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述锂源化合物、二价锰源化合物、二价铁源化合物以及磷酸根源化合物在该第二溶液中的摩尔浓度比为锂：（锰+铁）：磷=2.7:1:1。 The method for preparing a positive electrode active material for a lithium ion battery according to claim 1, wherein the lithium source compound, the divalent manganese source compound, the divalent iron source compound, and the phosphate source compound are in the second solution. The concentration ratio is lithium: (manganese + iron): phosphorus = 2.7: 1:1.
  9. 如权利要求1所述的锂离子电池正极活性材料的制备方法，其特征在于，所述加热的温度为100摄氏度至180摄氏度，反应时间为1小时至24小时。 The method for producing a positive electrode active material for a lithium ion battery according to claim 1, wherein the heating temperature is from 100 ° C to 180 ° C, and the reaction time is from 1 hour to 24 hours.
  10. 如权利要求9所述的锂离子电池正极活性材料的制备方法，其特征在于，所述反应时间为4小时。 The method of producing a positive electrode active material for a lithium ion battery according to claim 9, wherein the reaction time is 4 hours.
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