WO2022242715A1 - 铁锰基正极材料及其制备方法和应用 - Google Patents

铁锰基正极材料及其制备方法和应用 Download PDF

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WO2022242715A1
WO2022242715A1 PCT/CN2022/093829 CN2022093829W WO2022242715A1 WO 2022242715 A1 WO2022242715 A1 WO 2022242715A1 CN 2022093829 W CN2022093829 W CN 2022093829W WO 2022242715 A1 WO2022242715 A1 WO 2022242715A1
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manganese
iron
positive electrode
electrode material
based positive
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PCT/CN2022/093829
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English (en)
French (fr)
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陈思贤
江卫军
许鑫培
郑晓醒
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蜂巢能源科技股份有限公司
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Priority to EP22804035.8A priority Critical patent/EP4310953A1/en
Publication of WO2022242715A1 publication Critical patent/WO2022242715A1/zh

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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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium-ion batteries, in particular to an iron-manganese-based positive electrode material and its preparation method and application.
  • lithium-ion batteries occupy a core position
  • cathode materials are the most important.
  • the positive electrode material accounts for as much as 32% of the cost, while the electrolyte, separator and negative electrode account for only about 25%.
  • the electrochemical performance of the cathode material is also closely related to the overall performance of the battery. Therefore, the cathode material of lithium ion battery is the top priority of the whole battery.
  • Cobalt is a scarce resource, mainly concentrated in Africa, and its price is about four times that of nickel. Therefore, it is in line with the development trend to develop cobalt-free resource-rich nickel-manganese materials.
  • the explosive growth of lithium-ion batteries in the future will inevitably cause the demand for cobalt resources to exceed the supply, and the price will also fluctuate unstablely. Therefore, considering the long-term development of electric vehicles, getting rid of the dependence on rare metals and reducing costs is the only way for the healthy development of the new energy vehicle industry.
  • the cathode materials are still mainly ternary, which will inevitably be affected by the price of precious metals, especially precious metal elements such as nickel and cobalt, which are important factors affecting the cost of cathode materials.
  • the current preparation methods are usually complicated, usually using a three-step method of coprecipitation-solvothermal-solid-state sintering reaction, the preparation process is complex, the preparation cycle is long, and the preparation cost is high, which is not suitable for large-scale production. Production.
  • the crystallinity and morphology of the material are usually poor.
  • the high content of Li in the existing iron-manganese-based cathode materials (a: (x+y) ⁇ 1 in the Li a Fe x Mn y O 2 material), the material will contain Li 2 MnO 3 impurity phases.
  • the Li 2 MnO 3 phase is unstable, and it is easy to decompose during the charge and discharge process, which will release oxygen and increase the concentration of cations, resulting in high charge capacity and low discharge capacity, resulting in low first effect, and poor cycle stability. .
  • the main purpose of the present application is to provide an iron-manganese-based cathode material and its preparation method and application, so as to solve the problem of poor first effect of iron-manganese-based cathode materials in the prior art.
  • the present application provides an iron-manganese-based positive electrode material on the one hand
  • the particle size of the iron-manganese-based positive electrode material is 140-1000 nm, preferably 140-500 nm.
  • the content of residual alkali in the above-mentioned iron-manganese-based positive electrode material is 1400-1900 ppm.
  • the characteristic peak intensity between 31° and 33° and/or the characteristic peak intensity between 43° and 45° of the Li 2 MnO 3 crystal phase in the XRD spectrum of the above-mentioned iron-manganese-based cathode material is smaller than that of the iron-manganese-based cathode material 1/3 of the strongest characteristic peak intensity.
  • the above oxidation sintering is carried out in an oxygen-containing gas, preferably the oxygen content in the oxygen-containing gas is 20-100%, and the flow rate of the oxygen-containing gas is preferably 2-5 L/min.
  • the above preparation method includes: performing the first-stage oxidation and sintering of the lithium inorganic compound and the Fe x Mny (OH) 2 precursor to obtain the precursor of the iron-manganese-based positive electrode material; Two-stage oxidation sintering to obtain iron-manganese-based positive electrode materials.
  • the temperature of the first-stage oxidation sintering is 600-800°C, and the holding time is 6-12h.
  • the temperature of the second-stage oxidation sintering is 300-500°C, and the holding time is 2 hours. ⁇ 6h.
  • the heating rate before the above-mentioned oxidation sintering is 2-5°C/min
  • the cooling rate between the first-stage oxidation sintering and the second-stage oxidation sintering is 2-4°C/min
  • the temperature after the second-stage oxidation sintering is completed The cooling rate is 2-4°C/min.
  • the alkaline reagent is selected from one or more of sodium hydroxide and sodium carbonate; the preferred coprecipitation reaction temperature is 40-60°C, preferably under nitrogen Or the co-precipitation reaction is carried out in a second inert gas atmosphere, the second inert gas is selected from one of argon, helium and hydrogen, preferably stirring during the co-precipitation reaction, preferably at a stirring speed of 200-400rpm.
  • the above-mentioned first raw material system also includes a complexing agent and a solvent
  • the preparation process of the F x Mny (OH ) precursor includes: Step S1, the ferrous salt, the divalent manganese salt, the complexing agent and the solvent Mix to obtain the first raw material system, preferably the complexing agent is selected from one or more of ammonia water, ammonium sulfate and ethylenediaminetetraacetic acid, preferably in the first raw material system, the content of the complexing agent is 28-53g/L ; Step S2, in nitrogen or the second inert gas atmosphere and under stirring conditions, after heating the first raw material system to the co-precipitation reaction temperature, the first raw material system is mixed with the alkaline reagent, and the co-precipitation reaction occurs, after aging A Fe x Mny (OH) 2 precursor is obtained.
  • Another aspect of the present application provides a lithium ion battery, including electrolyte, positive electrode material and negative electrode material
  • the positive electrode material includes iron-manganese-based positive electrode material
  • the iron-manganese-based positive electrode material is any one of the above-mentioned iron-manganese-based positive electrode materials or An iron-manganese-based positive electrode material prepared by any one of the above-mentioned preparation methods.
  • Fig. 1 shows the XRD spectrum of the iron-manganese-based cathode material prepared in Example 1 of the present application
  • Figure 2 shows the XRD spectrum of the Fe-Mn-based positive electrode material prepared in Example 2 of the present application
  • Fig. 3 shows the XRD spectrum of the Fe-Mn-based cathode material prepared in Comparative Example 1 of the present application
  • Fig. 4 shows the XPS diagram of the iron-manganese-based positive electrode material prepared in Example 1 of the present application
  • Figure 5 shows the XPS diagram of the Fe-Mn-based positive electrode material prepared in Example 2 of the present application
  • Figure 6 shows the scanning electron microscope image of the iron-manganese-based positive electrode material prepared in Example 1 of the present application.
  • FIG. 7 shows the charge-discharge curves of the iron-manganese-based positive electrode materials prepared in Examples 1 and 2 and Comparative Example 1 of the present application.
  • the material will contain The Li 2 MnO 3 impurity phase makes the lithium-rich iron-manganese-based cathode material have low first effect and poor cycle stability.
  • the application provides an iron-manganese-based cathode material and its preparation method and application.
  • the content of lithium in the iron-manganese-based positive electrode material of the present application is low, but also the valence state and crystal form of manganese are well controlled.
  • part of the manganese in the material is positive tetravalent manganese.
  • the particle size of the iron-manganese-based positive electrode material of the present application is smaller than that of the iron-manganese-based positive electrode material in the prior art, and is 140-1000 nm, preferably 140-500 nm. This makes the specific surface area of the material larger, and it can be better dispersed when making a battery for homogenate coating, so that the material can better contact with the electrolyte during the charge and discharge process, and the electrochemical performance of the material is improved.
  • the content of residual alkali (including lithium hydroxide and lithium carbonate) in the iron-manganese-based positive electrode material of the present application is relatively low, ranging from 1400 to 1900 ppm.
  • the low residual alkali content prevents the material from cross-linking with the electrode binder polyvinylidene fluoride (PVDF), making it easier to homogeneously coat.
  • PVDF electrode binder polyvinylidene fluoride
  • Li2MnO3 crystalline phase is not expected to exist in the iron - manganese - based positive electrode material of the present application, and the characteristic peak intensity and/or The characteristic peak intensity between 43° and 45° is less than 1/3 of the strongest characteristic peak intensity of the iron-manganese-based positive electrode material.
  • the iron-manganese-based cathode material finally prepared forms a lithium-poor structure by using an inorganic compound with less lithium and a Fe x Mny (OH) 2 precursor for oxidation sintering.
  • the lithium-poor structure not only ensures that the lithium content in the material is low, but also controls the valence state and crystal form of manganese well.
  • part of the manganese in the material is positive tetravalent manganese.
  • the characteristic peaks corresponding to the Li 2 MnO 3 crystal phase that is, the characteristic peaks between 20 ⁇ 25°, 31 ⁇ 33°, 43 ⁇ 45° and 53 ⁇ 55° Peak
  • maximum intensity is less than 1/3 of the strongest characteristic peak intensity of iron-manganese-based positive electrode material or does not appear Li 2 MnO 3
  • the characteristic peak of crystalline phase so there is only little or no above-mentioned Li 2 MnO in the positive electrode material of the present application 3 phases, so there will be no problems of oxygen release and cation concentration increase due to the Li 2 MnO 3 phase is easy to decompose during the charge and discharge process.
  • the electrical properties of the iron-manganese-based cathode material are effectively improved, and the first effect and cycle performance are well improved.
  • the above oxidation sintering is carried out in an oxygen-containing gas, preferably the oxygen content in the oxygen-containing gas is 20-100%, and the flow rate of the oxygen-containing gas is preferably 2-5 L/min.
  • the content of oxygen in the oxygen-containing gas and the flow rate of the oxygen-containing gas it can be further ensured that the content of positive tetravalent Mn in the above-mentioned iron-manganese-based positive electrode material can effectively improve the electrical performance of the positive electrode material of the present application.
  • the above-mentioned preparation method includes: performing the first-stage oxidation sintering of the lithium inorganic compound and the Fe x Mny (OH) 2 precursor to obtain the iron-manganese-based positive electrode material
  • Precursor The iron-manganese-based positive electrode material precursor is oxidized and sintered in the second stage to obtain the iron-manganese-based positive electrode material.
  • the sintering temperature is 300-500° C., and the holding time is 2-6 hours.
  • the first-stage oxidation sintering can realize the oxidation of iron and manganese, and by controlling the temperature of the second-stage oxidation sintering And time, to avoid the peroxidation of iron and manganese lead to too much high-valent manganese (pentavalent and hexavalent), so that the cycle performance and first effect of the material are further improved.
  • the second stage of oxidation sintering is also conducive to the further reaction of incompletely reacted materials, and is conducive to purifying the material structure, removing impurities, obtaining positive electrode materials with better crystallinity, and further improving the electrical properties of positive electrode materials.
  • a faster heating rate before sintering and a faster cooling rate after sintering will cause more defects in the positive electrode material, and will also lead to uneven distribution of elements in the material, insufficient reaction between the precursor and lithium salt, resulting in electrical properties of the material. It is preferred that the temperature rise rate before the oxidation sintering is 2-5°C/min, and the temperature drop rate between the first-stage oxidation sintering and the second-stage oxidation sintering is 2-4°C/min. After the second-stage oxidation sintering is completed, The cooling rate is 2-4°C/min.
  • the distribution of elements in the positive electrode material is more uniform, the crystallization is better, and the grains are refined, which can eliminate the stress inside the material, and to a certain extent offset the contact area with the electrolyte due to the small particles.
  • the side reactions caused by larger particles are intensified, resulting in particle breakage, and thus better electrical properties.
  • the above-mentioned preparation method also includes the preparation process of the FexMny ( OH) 2 precursor
  • the preparation process of the FexMny ( OH) 2 precursor includes: under alkaline conditions, making the Co-precipitation reaction occurs in the first raw material system of iron salt and divalent manganese salt to obtain Fe x Mny (OH) 2 precursor;
  • preferred ferrous salt is selected from one of ferrous chloride, ferrous nitrate and ferrous oxalate
  • the ratio of iron and manganese in the precursor and the physical properties of the precursor can be better controlled, which not only makes the oxidation and sintering of the precursor of the application and lithium inorganic substances easier, Moreover, the particle size and iron-manganese content of the iron-manganese-based cathode material can be better controlled, and a cathode material that is more in line with actual use requirements can be obtained.
  • the preparation process of the F x Mny (OH ) precursor includes : Step S1, mixing ferrous salt, divalent manganese salt, complexing agent and solvent to obtain the first raw material system, preferably the complexing agent is selected from one or more of ammonia, ammonium sulfate and ethylenediaminetetraacetic acid , preferably in the first raw material system, the content of complexing agent is 28 ⁇ 53g/L; step S2, in nitrogen or the second inert gas atmosphere and under stirring conditions, after heating the first raw material system to the co-precipitation reaction temperature, the The first raw material system is mixed with an alkaline reagent, a co-precipitation reaction occurs, and a Fe x Mn y (OH) 2 precursor is obtained after aging.
  • Step S1 mixing ferrous salt, divalent manganese salt, complexing agent and solvent to obtain the first raw material system, preferably the complexing agent is selected from one or more of ammonia, ammonium sulfate and ethylened
  • a lithium-ion battery including an electrolyte, a positive electrode material and a negative electrode material
  • the positive electrode material includes an iron-manganese-based positive electrode material
  • the iron-manganese-based positive electrode material is any one of the above-mentioned iron-manganese-based positive electrodes material or an iron-manganese-based positive electrode material prepared by any one of the above-mentioned preparation methods.
  • the lithium-ion battery using the iron-manganese-based positive electrode material of the present application avoids the formation of Li 2 MnO 3 crystal phase, and has tetravalent manganese ions and low lithium content, so the cycle stability and first effect are greatly improved compared with the prior art.
  • step 3 the flow rate of air is 2L/min.
  • step 3 the air flow rate is 1 L/min.
  • step 3 the flow rate of the air is 7L/min.
  • step 3 air is replaced with pure oxygen, and the flow rate is 4L/min.
  • Example 2 The difference from Example 2 is that the oxidation sintering temperature in step 3) is 600°C.
  • Example 2 The difference from Example 2 is that the oxidation and sintering temperature in step 3) is 800°C.
  • Example 2 The difference from Example 2 is that the oxidation sintering temperature in step 3) is 900°C.
  • Example 2 The difference from Example 2 is that the oxidation sintering time in step 3) is 6h.
  • Example 2 The difference from Example 2 is that the oxidation and sintering time in step 3) is 12h.
  • Example 2 The difference from Example 2 is that the oxidation and sintering time in step 3) is 4h.
  • Example 2 The difference from Example 2 is that the oxidation and sintering time in step 3) is 14h.
  • Example 2 The difference from Example 2 is that the oxidation sintering temperature in step 4) is 300°C.
  • Example 2 The difference from Example 2 is that the oxidation sintering temperature in step 4) is 500°C.
  • Example 2 The difference from Example 2 is that the oxidation sintering temperature in step 4) is 200°C.
  • Example 2 The difference from Example 2 is that the oxidation and sintering temperature in step 4) is 600°C.
  • Example 2 The difference from Example 2 is that the oxidation and sintering time in step 4) is 2h.
  • Example 2 The difference from Example 2 is that the oxidation sintering time in step 4) is 6h.
  • Example 2 The difference from Example 2 is that the oxidation and sintering time in step 4) is 1 h.
  • Example 2 The difference from Example 2 is that the oxidation and sintering time in step 4) is 8h.
  • step 4 under the above-mentioned condition of ventilating the air, after cooling to 400° C. at a cooling rate of 2° C./min, after keeping the temperature for 4 hours, stop heating, and drop to 400° C. at a cooling rate of 3° C./min.
  • a Li 0.4 Fe 0.5 Mn 0.5 O 2 iron-manganese-based cathode material is obtained.
  • step 4 under the above-mentioned condition of ventilating the air, after cooling to 400° C. at a cooling rate of 4° C./min, after keeping the temperature for 4 hours, stop heating, and drop to 400° C. at a cooling rate of 3° C./min.
  • a Li 0.4 Fe 0.5 Mn 0.5 O 2 iron-manganese-based cathode material is obtained.
  • step 4 under the above-mentioned condition of ventilating the air, after cooling to 400° C. at a cooling rate of 5° C./min, after keeping the temperature for 4 hours, stop heating, and drop to 400° C. at a cooling rate of 3° C./min.
  • a Li 0.4 Fe 0.5 Mn 0.5 O 2 iron-manganese-based cathode material is obtained.
  • step 4 under the above-mentioned condition of ventilating air, after cooling to 400° C. at a cooling rate of 3° C./min, after keeping the temperature for 4 hours, stop heating, and drop to 400° C. at a cooling rate of 2° C./min.
  • a Li 0.4 Fe 0.5 Mn 0.5 O 2 iron-manganese-based cathode material is obtained.
  • step 4 under the above-mentioned condition of ventilating air, after cooling to 400° C. at a cooling rate of 3° C./min, after keeping the temperature for 4 hours, stop heating, and drop to 400° C. at a cooling rate of 4° C./min.
  • a Li 0.4 Fe 0.5 Mn 0.5 O 2 iron-manganese-based cathode material is obtained.
  • step 4 under the above-mentioned condition of ventilating the air, after cooling to 400° C. at a cooling rate of 3° C./min, after keeping the temperature for 4 hours, stop heating, and drop to 400° C. at a cooling rate of 5° C./min.
  • a Li 0.4 Fe 0.5 Mn 0.5 O 2 iron-manganese-based cathode material is obtained.
  • Example 1 The difference with Example 1 is that 1) 500g ferrous chloride and 500g manganese acetate and 2000mL water are mixed in the reactor, add 1.4g ammonia complexing agent in the reactor, with the speed of 3L/min to the reactor Introduce nitrogen into the reactor, heat the dispersion in the reaction kettle to 40°C, add sodium hydroxide solution to the reaction kettle to adjust the pH of the dispersion to 12, and stir the dispersion at 200rpm to carry out coprecipitation reaction, and settle the product obtained by the reaction After 20 h, filter through a funnel, wash with water, and dry in an oven at 100° C. to obtain a Fe 0.5 Mn 0.5 (OH) 2 precursor.
  • FIG. 4 An XPS test was performed on the iron-manganese-based cathode material prepared in Example 1, and the results are shown in FIG. 4 .
  • Figure 4 comparing the Database spectrum and the spectrum of the iron-manganese-based cathode material prepared in Example 1 before and after etching, it is speculated that the form of Mn before etching is MnO 2 , and it is MnO after etching.
  • the iron-manganese-based positive electrode material prepared in Example 1 contains tetravalent manganese ions.
  • positive electrode material iron-manganese-based positive electrode material prepared in Example or Comparative Example 1
  • binder polyvinylidene fluoride
  • conductive agent conductive carbon black
  • Button electrical assembly according to the positive electrode shell (304 stainless steel) - shrapnel (304 stainless steel) - gasket (304 stainless steel) - positive electrode (aluminum foil coated with positive electrode material) - diaphragm (PE) - electrolyte (1mol/L LiPF 6.
  • the solvent is EC (ethylene carbonate): DEC (diethyl carbonate) with a volume ratio of 3:7) - negative electrode (lithium sheet) - negative electrode shell (304 stainless steel) for electrical assembly in sequence.
  • the assembled battery was left to stand for 12 hours to allow the electrolyte to fully infiltrate the electrode material. It is then tested on the LAND CT-2001A test system.
  • Example 1 The test results of Example 1, Example 2 and Comparative Example 1 are shown in Figure 1, and the test results of all Examples and Comparative Example 1 are shown in Table 1.
  • Example 1 500 2100 154.3 92.1
  • Example 2 300 1640 161.7 90.2
  • Example 3 250 1850 143.5 87.5
  • Example 4 180 2330 117.2 81.2
  • Example 5 730 1720 161.6 82.3
  • Example 6 700 1640 142.5 91.2
  • Example 7 270 2580 145.3 88.2
  • Example 8 330 1570 155.2 87.9
  • Example 9 250 3200 115.2 81.7
  • Example 10 450 1530 118.8 82.6
  • Example 11 230 3180 160.2 86.9
  • Example 12 420 1620 131.2 88.5
  • Example 13 210 2320 113.2 75.9
  • Example 14 460 1590 108.9 82.1
  • Example 16 320 1600 155.2 87.3
  • Example 17 270 1800 117.6 78.2
  • Example 18 320 1620 153.5 81.2
  • Example 19 290 1680 142.6 88.3
  • Example 20 780 1650 138.5 91.5
  • Example 21 500 1680 12
  • oxidation sintering is carried out by using less lithium inorganic compounds and FexMny ( OH) 2 precursors, so that the finally prepared iron-manganese-based positive electrode material forms a lithium-poor structure.
  • the lithium-poor structure not only ensures that the lithium content in the material is low, but also controls the valence state and crystal form of manganese well.
  • part of the manganese in the material is positive tetravalent manganese.
  • the characteristic peaks corresponding to the Li 2 MnO 3 crystal phase that is, the characteristic peaks between 20 ⁇ 25°, 31 ⁇ 33°, 43 ⁇ 45° and 53 ⁇ 55° Peak
  • maximum intensity is less than 1/3 of the strongest characteristic peak intensity of iron-manganese-based positive electrode material or does not appear Li 2 MnO 3
  • the characteristic peak of crystalline phase so there is only little or no above-mentioned Li 2 MnO in the positive electrode material of the present application 3 phases, so there will be no problems of oxygen release and cation concentration increase due to the Li 2 MnO 3 phase is easy to decompose during the charge and discharge process.
  • the electrical properties of the iron-manganese-based cathode material are effectively improved, and the first effect and cycle performance are well improved.

Abstract

本申请提供了一种铁锰基正极材料及其制备方法和应用。该铁锰基正极材料为Li aFe xMnyO2，其中a＝0.1～0.5，0＜x＜1.0，0＜y＜1.0，x+y＝1，铁锰基正极材料中的至少部分锰元素的价态为正四价，且铁锰基正极材料的XRD谱图中Li2MnO 3晶相的特征峰最大强度小于铁锰基正极材料的最强特征峰强度的1/3或者不出现Li2MnO 3晶相的特征峰。本申请通过对铁锰基正极材料的成分、晶体结构进行控制，进而使得首效和循环性能得到了很好地提升。

Description

铁锰基正极材料及其制备方法和应用
本申请是以CN申请号为202110548471.6，申请日为2021年5月19日的中国申请为基础，并主张其优先权，该CN申请的公开内容再次作为整体引入本申请中。
技术领域
本申请涉及锂离子电池技术领域，具体而言，涉及一种铁锰基正极材料及其制备方法和应用。
背景技术
随着能源危机、环境污染等问题的日益突出，新能源的开发与利用势在必行。在未来的几年中，锂离子电池在新能源汽车行业的应用需求将不断增加。
在新能源汽车中，锂离子电池占据核心地位，而在锂离子电池中，正极材料又是重中之重。以NCM523动力电池为例，正极材料占据成本高达32％，而电解液、隔膜以及负极总占比也仅为约25％。除却成本因素外，正极材料的电化学性能方面也与电池的整体性能息息相关。因此，锂离子电池正极材料是整个电池的重中之重。
钴是一种稀缺资源，主要集中在非洲，价格是镍的大约4倍。因此开发无钴的资源丰富镍锰材料是符合发展趋势的。根据咨询机构的预测，未来锂离子电池爆发增长必将引起钴资源的需求大于供给，价格还会出现不稳定的波动。因此，从电动汽车的长远发展考虑，摆脱稀有金属的依赖性，降低成本是新能源汽车行业健康发展的必经之路。目前正极材料仍然以三元为主，不可避免会受到贵金属价格的影响，尤其是镍、钴等贵金属元素，是正极材料成本的重要影响因素。
目前很多公司在提倡低钴甚至去钴化，但是仍在采用价格较高的镍等过渡金属元素，对于正极材料的成本控制是治标不治本。从电动汽车的长远发展考虑，摆脱稀有金属的依赖性，降低成本是新能源汽车行业健康发展的必经之路。
对于铁锰基正极材料，目前制备方法通常比较复杂，通常采用共沉淀—溶剂热—固相烧结反应的三步法制备，制备工艺复杂，制备周期长，制备成本较高，不适宜于大规模生产。而且由于溶剂热过程的存在，通常导致材料结晶性以及形貌较差。并且，现有铁锰基正极材料中由于Li的含量较高(Li aFe xMn yO 2材料中a:(x+y)≥1)，材料中会包含有Li 2MnO 3杂相。Li 2MnO 3相不稳定，在充放电过程中很容易分解，会释氧并且使阳离子的浓度升高，使得充电容量高而放电容量低导致首效低的问题，并且循环稳定性也较差。
发明内容
本申请的主要目的在于提供一种铁锰基正极材料及其制备方法和应用，以解决现有技术中铁锰基正极材料首效差的问题。
为了实现上述目的，本申请一方面提供了一种铁锰基正极材料，该铁锰基正极材料为Li aFe xMn yO 2，其中a＝0.1～0.5，0＜x＜1.0，0＜y＜1.0，x+y＝1，铁锰基正极材料中的至少部分锰元素的价态为正四价，且铁锰基正极材料的XRD谱图中Li 2MnO 3晶相的特征峰最大强度小于铁锰基正极材料的最强特征峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，Li 2MnO 3晶相在20～25°之间、31～33°之间、43～45°之间以及53～55°之间存在特征峰。
进一步地，上述铁锰基正极材料的粒径为140～1000nm，优选为140～500nm。
进一步地，上述铁锰基正极材料中残碱的含量为1400～1900ppm。
进一步地，上述铁锰基正极材料的XRD谱图中Li 2MnO 3晶相的31～33°之间的特征峰强度和/或43～45°之间的特征峰强度小于铁锰基正极材料的最强特征峰强度的1/3。
本申请的另一个方面还提供了一种铁锰基正极材料的制备方法，制备方法包括：将锂的无机化合物和Fe xMn y(OH) 2前驱体进行氧化烧结，得到铁锰基正极材料，其中，0＜x＜1.0，0＜y＜1.0，x+y＝1，锂的无机化合物中的Li的摩尔量和Fe xMn y(OH) 2前驱体中的Fe和Mn的总摩尔量的比值为0.1:1～0.5:1。
进一步地，上述氧化烧结在含氧气体中进行，优选含氧气体中氧气的含量为20～100％，优选含氧气体的流量为2～5L/min。
进一步地，上述制备方法包括：将锂的无机化合物和Fe xMn y(OH) 2前驱体进行第一阶段氧化烧结，得到铁锰基正极材料前体；将铁锰基正极材料前体进行第二阶段氧化烧结，得到铁锰基正极材料，优选第一阶段氧化烧结的温度为600～800℃，保温时间为6～12h，第二阶段氧化烧结的温度为300～500℃，保温时间为2～6h。
进一步地，上述氧化烧结前的升温速率为2～5℃/min，第一阶段氧化烧结和第二阶段氧化烧结之间的降温速率为2～4℃/min，第二阶段氧化烧结完成之后的降温速率为2～4℃/min。
进一步地，上述制备方法还包括Fe xMn y(OH) 2前驱体的制备过程，制备过程包括：在碱性条件下，使包括亚铁盐和二价锰盐的第一原料体系发生共沉淀反应，得到Fe xMn y(OH) 2前驱体；优选亚铁盐选自氯化亚铁、硝酸亚铁和草酸亚铁中的一种或多种，优选二价锰盐选自氯化锰、硝酸锰和乙酸锰的一种或多种，优选第一原料体系中，Mn 2+和Fe 2+的摩尔比为10:1～1:1；优选第一原料体系的pH值＝12～13，优选使用碱性试剂调节第一原料体系的pH值，碱性试剂选自氢氧化钠、碳酸钠中的一种或多种；优选共沉淀反应的温度为40～60℃，优选在氮气或第二惰性气体氛围中进行共沉淀反应，第二惰性气体选自氩气、氦气和氢气中的一种，优选在共沉淀反应过程中进行搅拌，优选搅拌的速度为200～400rpm。
进一步地，上述第一原料体系中还包括络合剂和溶剂，Fe xMn y(OH) 2前驱体的制备过程包括：步骤S1，将亚铁盐、二价锰盐、络合剂和溶剂混合，得到第一原料体系，优选络合剂选自氨水、硫酸铵和乙二胺四乙酸中的一种或多种，优选第一原料体系中，络合剂的含量为28～53g/L；步骤S2，在氮气或第二惰性气体氛围中和搅拌条件下，加热第一原料体系至共沉淀反 应温度后，将第一原料体系和碱性试剂混合，发生共沉淀反应，经过陈化后得到Fe xMn y(OH) 2前驱体。
本申请的又一个方面提供了一种锂离子电池，包括电解液、正极材料和负极材料，正极材料包括铁锰基正极材料，该铁锰基正极材料为上述任一种铁锰基正极材料或上述任一种制备方法制备得到的铁锰基正极材料。
应用本申请的技术方案，不仅铁锰基正极材料中的锂含量较低，而且对锰的价态和晶形进行了很好地控制，一方面，材料中的部分锰为正四价的锰，另一方面，本申请实施例制备得到的铁锰基正极材料XRD谱图中，Li 2MnO 3晶相所对应的特征峰(即20～25°、31～33°、43～45°以及53～55°之间的特征峰)最大强度小于铁锰基正极材料的最强特征峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，因此本申请正极材料中仅存在极少或不存在上述Li 2MnO 3相，因此也不会存在由于Li 2MnO 3相易在充放电过程中分解造成的释氧和阳离子浓度增高的问题。在上述结构、成分特征的协同作用下，有效改善了铁锰基正极材料的电学性能，使得首效和循环性能得到了很好地提升。
附图说明
构成本申请的一部分的说明书附图用来提供对本申请的进一步理解，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1示出了本申请实施例1制备得到的铁锰基正极材料的XRD谱图；
图2示出了本申请实施例2制备得到的铁锰基正极材料的XRD谱图；
图3示出了本申请对比例1制备得到的铁锰基正极材料的XRD谱图；
图4示出了本申请实施例1制备得到的铁锰基正极材料的XPS图；
图5示出了本申请实施例2制备得到的铁锰基正极材料的XPS图；
图6示出了本申请实施例1制备得到的铁锰基正极材料的扫描电镜图；以及
图7示出了本申请实施例1和2以及对比例1制备得到的铁锰基正极材料的充放电曲线图。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本申请。
如本申请背景技术中所描述的，现有铁锰基正极材料中由于Li的含量较高(Li aFe xMn yO 2材料中a:(x+y)≥1)，材料中会包含有Li 2MnO 3杂相，使得富锂铁锰基正极材料的首效较低，循环稳定性差，为了解决上述问题，本申请提供了一种铁锰基正极材料及其制备方法和应用。
根据本申请一种典型的实施方式，提供了一种铁锰基正极材料，该铁锰基正极材料为Li aFe xMn yO 2，其中a＝0.1～0.5，0＜x＜1.0，0＜y＜1.0，x+y＝1，铁锰基正极材料中的至少部分锰元素的价态为正四价，且铁锰基正极材料的XRD谱图中Li 2MnO 3晶相的特征峰最大强度小于铁锰基正极材料的最强特征峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，Li 2MnO 3晶相在20～25°、31～33°、43～45°以及53～55°之间存在特征峰。
本申请的铁锰基正极材料中的不仅锂含量较低，而且对锰的价态和晶形进行了很好地控制，一方面，材料中的部分锰为正四价的锰，另一方面，本申请实施例制备得到的铁锰基正极材料XRD谱图中，Li 2MnO 3晶相所对应的特征峰(即20～25°、31～33°、43～45°以及53～55°之间的特征峰)最大强度小于铁锰基正极材料的最强特征峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，因此本申请正极材料中仅存在极少或不存在上述Li 2MnO 3相，因此也不会存在由于Li 2MnO 3相易在充放电过程中分解造成的释氧和阳离子浓度增高的问题。在上述结构、成分特征的协同作用下，有效改善了铁锰基正极材料的电学性能，使得首效和循环性能得到了很好地提升。
本申请铁锰基正极材料的粒径较现有技术中的铁锰基正极材料较小，为140～1000nm，优选为140～500nm。这使得材料的比表面积较大，并且在制作电池进行匀浆涂布时可以更好地分散，使得材料在充放电过程中可以更好地与电解液接触，提升了材料的电化学性能。
本申请铁锰基正极材料中残碱(包括氢氧化锂和碳酸锂)的含量较低，为1400～1900ppm。较低的残碱含量使得材料不会与电极粘接剂聚偏氟乙烯(PVDF)发生交联反应，更易于进行匀浆涂布，同时在充放电过程中的副反应可以有效降低，降低电池涨气的可能性。
本申请的铁锰基正极材料中不希望存在Li 2MnO 3晶相，优选铁锰基正极材料的XRD谱图中Li 2MnO 3晶相的31～33°之间的特征峰强度和/或43～45°之间的特征峰强度小于铁锰基正极材料的最强特征峰强度的1/3。
根据本申请另一种典型的实施方式，一种铁锰基正极材料的制备方法，该制备方法包括：将锂的无机化合物和Fe xMn y(OH) 2前驱体进行氧化烧结，得到铁锰基正极材料，其中，0＜x＜1.0，0＜y＜1.0，x+y＝1，锂的无机化合物中的Li的摩尔量和Fe xMn y(OH) 2前驱体中的Fe和Mn的总摩尔量的比值为0.1:1～0.5:1。
本申请通过使用较少锂的无机化合物和Fe xMn y(OH) 2前驱体进行氧化烧结，使得最终制备得到的铁锰基正极材料形成贫锂结构。该贫锂结构不仅保证了材料中锂含量较低，而且对锰的价态和晶形进行了很好地控制，一方面，材料中的部分锰为正四价的锰，另一方面，本申请实施例制备得到的铁锰基正极材料XRD谱图中，Li 2MnO 3晶相所对应的特征峰(即20～25°、31～33°、43～45°以及53～55°之间的特征峰)最大强度小于铁锰基正极材料的最强特征峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，因此本申请正极材料中仅存在极少或不存在上述Li 2MnO 3相，因此也不会存在由于Li 2MnO 3相易在充放电过程中分解造成的释氧和阳离子浓度增高的问题。在上述结构、成分特征的协同作用下，有效改善了铁锰基正极材料的电学性能，使得首效和循环性能得到了很好地提升。
在一些实施例中，上述氧化烧结在含氧气体中进行，优选含氧气体中氧气的含量为20～100％，优选含氧气体的流量为2～5L/min。通过控制含氧气体中氧气的含量和含氧气体的流量，可以进一步保证上述铁锰基正极材料中正四价的Mn的含量有效地提升本申请正极材料的电学性能。
为了进一步对正极材料电学性能进行改善，在一些实施例中，上述制备方法包括：将锂的无机化合物和Fe xMn y(OH) 2前驱体进行第一阶段氧化烧结，得到铁锰基正极材料前体；将铁锰基正极材料前体进行第二阶段氧化烧结，得到铁锰基正极材料，优选第一阶段氧化烧结的温度为600～800℃，保温时间为6～12h，第二阶段氧化烧结的温度为300～500℃，保温时间为2～6h。通过将氧化烧结分为温度较高的第一阶段氧化烧结和温度较低的第二阶段氧化烧结，第一阶段氧化烧结可以实现对铁和锰的氧化，并且通过控制第二阶段氧化烧结的温度和时间，避免了铁锰的过氧化导致高价锰(五价和六价)过多，从而使材料的循环性能和首效得到进一步的提升。除此之外，第二段氧化烧结还有利于未完全反应的材料进一步反应，并且有利于纯化材料结构，去除杂相，获得结晶性更好的正极材料，进而进一步提升正极材料的电学性能。
在烧结前较快的升温速度和烧结后较快的降温速度会使正极材料中出现更多的缺陷，也会导致材料中元素分布不均，前驱体与锂盐反应不充分，导致材料电学性能的下降，优选上述氧化烧结前的升温速率为2～5℃/min，第一阶段氧化烧结和第二阶段氧化烧结之间的降温速率为2～4℃/min，第二阶段氧化烧结完成之后的降温速率为2～4℃/min。通过进一步限定上述升温和降温速度，使得正极材料中各元素分布更均匀，结晶情况更佳，细化晶粒，能够消除材料内部的应力，一定程度上抵消由于颗粒过小，与电解液接触面积较大引起的副反应加剧，从而造成的颗粒破碎情况，进而获得更优良的电学性能。
在一些实施例中，上述制备方法还包括Fe xMn y(OH) 2前驱体的制备过程，该Fe xMn y(OH) 2前驱体的制备过程包括：在碱性条件下，使包括亚铁盐和二价锰盐的第一原料体系发生共沉淀反应，得到Fe xMn y(OH) 2前驱体；优选亚铁盐选自氯化亚铁、硝酸亚铁和草酸亚铁中的一种或多种，优选二价锰盐选自氯化锰、硝酸锰和乙酸锰的一种或多种，优选第一原料体系中，Mn 2+和Fe 2+的摩尔比为10:1～1:1；优选第一原料体系的pH值＝12～13，优选使用碱性试剂调节第一原料体系的pH值，碱性试剂选自氢氧化钠、碳酸钠中的一种或多种；优选共沉淀反应的温度为40～60℃，优选在氮气或第二惰性气体氛围中进行共沉淀反应，第二惰性气体选自氩气、氦气和氢气中的一种，优选在共沉淀反应过程中进行搅拌，优选搅拌的速度为200～400rpm。通过自制Fe xMn y(OH) 2前驱体，可以更好地控制前驱体中铁和锰的比例和前驱体的物理性能，进而不仅使本申请前驱体和锂的无机物的氧化烧结更易进行，而且可以更好地控制铁锰基正极材料的粒径和铁锰含量，获得更符合实际使用需求的正极材料。
为了进一步提升Fe xMn y(OH) 2前驱体的制备效率和结构稳定性，优选上述第一原料体系中还包括络合剂和溶剂，Fe xMn y(OH) 2前驱体的制备过程包括：步骤S1，将亚铁盐、二价锰盐、络合剂和溶剂混合，得到第一原料体系，优选络合剂选自氨水、硫酸铵和乙二胺四乙酸中的一种或多种，优选第一原料体系中，络合剂的含量为28～53g/L；步骤S2，在氮气或第二惰性 气体氛围中和搅拌条件下，加热第一原料体系至共沉淀反应温度后，将第一原料体系和碱性试剂混合，发生共沉淀反应，经过陈化后得到Fe xMn y(OH) 2前驱体。
根据本申请的又一个方面，提供了一种锂离子电池，包括电解液、正极材料和负极材料，正极材料包括铁锰基正极材料，该铁锰基正极材料为上述任一种铁锰基正极材料或上述任一种制备方法制备得到的铁锰基正极材料。
使用本申请铁锰基正极材料的锂离子电池由于避免形成Li 2MnO 3晶相，并且均有四价锰离子和低锂含量，因此循环稳定性和首效较现有技术有较大地提升。
以下结合具体实施例对本申请作进一步详细描述，这些实施例不能理解为限制本申请所要求保护的范围。
实施例1
1)将500g氯化亚铁和500g乙酸锰和2000mL水在反应釜中混合，向反应釜中加入300g氨水络合剂，以3L/min的速度向反应釜中通入氮气，加热反应釜中分散液至45℃，向反应釜加入氢氧化钠溶液调节分散液的pH＝12，并以300rpm搅拌分散液，进行共沉淀反应，对反应得到的产物进行沉降20h后，经过漏斗过滤后，用水洗涤，并在烘箱中以100℃干燥，得到Fe 0.5Mn 0.5(OH) 2前驱体。
2)在干燥环境下，将100gFe 0.5Mn 0.5(OH) 2前驱体与18.8g氢氧化锂(n Li:(n Fe+n Mn)＝0.4)进行球磨至均匀。
3)将混合均匀后的材料置于纳博热箱式炉中，以4L/min的流速向箱式炉通入空气，并以2℃/min的升温速度升温至700℃后，保温9h，以3℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例2
1)将500g氯化亚铁和500g乙酸锰和2000mL水在反应釜中混合，向反应釜中加入300g氨水络合剂，以3L/min的速度向反应釜中通入氮气，加热反应釜中分散液至45℃，向反应釜加入氢氧化钠溶液调节分散液的pH＝12，并以300rpm搅拌分散液，进行共沉淀反应，对反应得到的产物进行沉降20h后，经过漏斗过滤后，用水洗涤，并在烘箱中以100℃干燥，得到Fe 0.5Mn 0.5(OH) 2前驱体。
2)在干燥环境下，将100gFe 0.5Mn 0.5(OH) 2前驱体与18.8g氢氧化锂(n Li:(n Fe+n Mn)＝0.4)进行球磨至均匀。
3)将混合均匀后的材料置于纳博热箱式炉中，以4L/min的流速向箱式炉通入空气，并以2℃/min的升温速度升温至700℃后，保温9h，得到中间产物。
4)在上述通空气的条件下，以2℃/min的降温速度降温至400℃后，保温4h后，停止加热，以3℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例3
与实施例2的区别在于，步骤3)中，空气的流量为2L/min。
实施例4
与实施例2的区别在于，步骤3)中，空气的流量为1L/min。
实施例5
与实施例2的区别在于，步骤3)中，空气的流量为7L/min。
实施例6
与实施例2的区别在于，步骤3)中，用纯氧替代空气，流量为4L/min。
实施例7
与实施例2的区别在于，步骤3)中氧化烧结的温度为600℃。
实施例8
与实施例2的区别在于，步骤3)中氧化烧结的温度为800℃。
实施例9
与实施例2的区别在于，步骤3)中氧化烧结的温度为500℃。
实施例10
与实施例2的区别在于，步骤3)中氧化烧结的温度为900℃。
实施例11
与实施例2的区别在于，步骤3)中氧化烧结的时间为6h。
实施例12
与实施例2的区别在于，步骤3)中氧化烧结的时间为12h。
实施例13
与实施例2的区别在于，步骤3)中氧化烧结的时间为4h。
实施例14
与实施例2的区别在于，步骤3)中氧化烧结的时间为14h。
实施例15
与实施例2的区别在于，步骤4)中氧化烧结的温度为300℃。
实施例16
与实施例2的区别在于，步骤4)中氧化烧结的温度为500℃。
实施例17
与实施例2的区别在于，步骤4)中氧化烧结的温度为200℃。
实施例18
与实施例2的区别在于，步骤4)中氧化烧结的温度为600℃。
实施例19
与实施例2的区别在于，步骤4)中氧化烧结的时间为2h。
实施例20
与实施例2的区别在于，步骤4)中氧化烧结的时间为6h。
实施例21
与实施例2的区别在于，步骤4)中氧化烧结的时间为1h。
实施例22
与实施例2的区别在于，步骤4)中氧化烧结的时间为8h。
实施例23
与实施例2的区别在于，步骤4)中在上述通空气的条件下，以2℃/min的降温速度降温至400℃后，保温4h后，停止加热，以3℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例24
与实施例2的区别在于，步骤4)中在上述通空气的条件下，以4℃/min的降温速度降温至400℃后，保温4h后，停止加热，以3℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例25
与实施例2的区别在于，步骤4)中在上述通空气的条件下，以5℃/min的降温速度降温至400℃后，保温4h后，停止加热，以3℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例26
与实施例2的区别在于，步骤4)中在上述通空气的条件下，以3℃/min的降温速度降温至400℃后，保温4h后，停止加热，以2℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例27
与实施例2的区别在于，步骤4)中在上述通空气的条件下，以3℃/min的降温速度降温至400℃后，保温4h后，停止加热，以4℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例28
与实施例2的区别在于，步骤4)中在上述通空气的条件下，以3℃/min的降温速度降温至400℃后，保温4h后，停止加热，以5℃/min的降温速度降到100℃，得到Li 0.4Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例29
与实施例1的区别在于，将100gFe 0.5Mn 0.5(OH) 2前驱体与4.7g氢氧化锂(n Li:(n Fe+n Mn)＝0.1)进行球磨至均匀，经过步骤3)后，得到Li 0.1Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例30
与实施例1的区别在于，将100gFe 0.5Mn 0.5(OH) 2前驱体与23.5g氢氧化锂(n Li:(n Fe+n Mn)＝0.5)进行球磨至均匀，经过步骤3)后，得到Li 0.5Fe 0.5Mn 0.5O 2铁锰基正极材料。
实施例31
1)将500g氯化亚铁和5000g乙酸锰和2000mL水在反应釜中混合，向反应釜中加入2.65g氨水络合剂，以3L/min的速度向反应釜中通入氮气，加热反应釜中分散液至60℃，向反应釜加入氢氧化钠溶液调节分散液的pH＝13，并以400rpm搅拌分散液，进行共沉淀反应，对反应得到的产物进行沉降20h后，经过漏斗过滤后，用水洗涤，并在烘箱中以100℃干燥，得到Fe 0.1Mn 0.9(OH) 2前驱体。
2)在干燥环境下，将100gFe 0.1Mn 0.9(OH) 2前驱体与18.8g氢氧化锂(n Li:(n Fe+n Mn)＝0.4)进行球磨至均匀。
3)将混合均匀后的材料置于纳博热箱式炉中，以4L/min的流速向箱式炉通入空气，并以5℃/min的升温速度升温至700℃后，保温9h，以3℃/min的降温速度降到100℃，得到Li 0.4Fe 0.1Mn 0.9O 2铁锰基正极材料。
实施例32
与实施例1的区别在于，1)将500g氯化亚铁和500g乙酸锰和2000mL水在反应釜中混合，向反应釜中加入1.4g氨水络合剂，以3L/min的速度向反应釜中通入氮气，加热反应釜中分散液至40℃，向反应釜加入氢氧化钠溶液调节分散液的pH＝12，并以200rpm搅拌分散液， 进行共沉淀反应，对反应得到的产物进行沉降20h后，经过漏斗过滤后，用水洗涤，并在烘箱中以100℃干燥，得到Fe 0.5Mn 0.5(OH) 2前驱体。
对比例1
与实施例1的区别在于，步骤2)中氢氧化锂的加入量为51.7g(n Li:(n Fe+n Mn)＝1.1)。
对实施例1和2以及对比例1制备得到的铁锰基正极材料进行XRD测试，测试结果如图1、2和3所示。从图1至2中可以看出实施例1和2制备得到的铁锰基正极材料的XRD谱图中不出现Li 2MnO 3晶相的特征峰，说明其中不包含Li 2MnO 3晶相。
从图3中可以看出XRD谱图中20～25°、31～33°、43～45°以及53～55°分别存在杂峰，20～25°对应于(020)晶面，其峰强值为800～1000；31～33°对应于(-113)晶面，其峰强为3000～4000；43～45°对应于材料(-133)晶面，其峰强在2000～2500；53～55°处对应于材料的(115)晶面，其峰强为800～1000。
对实施例1制备得到的铁锰基正极材料进行XPS测试，结果如图4所示。从图四中可以看出，对比Database谱图以及实施例1制备的铁锰基正极材料刻蚀前后的谱图，推测刻蚀前Mn的存在形式为MnO 2，刻蚀后为MnO，说明实施例1制备的铁锰基正极材料中含有四价锰离子。
利用电位滴定法(GB/T 9725-2007)方法测试各实施例和对比例1制备得到的铁锰基正极材料的残碱量，结果如表1所示。
锂离子电池的制作
1.匀浆涂布：正极材料(实施例或对比例1中制备得到的铁锰基正极材料)：粘结剂(聚偏氟乙烯)：导电剂(导电炭黑)＝92：4：4，置于脱泡机中混合均匀，然后进行扣电组装。
2.扣电组装：按照正极壳(304不锈钢)—弹片(304不锈钢)—垫片(304不锈钢)—正极(涂覆正极材料的铝箔)—隔膜(PE)—电解液(1mol/L的LiPF 6，溶剂为EC(碳酸乙烯酯)：DEC(碳酸二乙酯)体积比为3:7)—负极(锂片)—负极壳(304不锈钢)顺序进行扣电组装。
性能测试
扣电测试：
在恒温25℃条件下，将组装好的电池静置12小时，使电解液充分浸润电极材料。然后将其在LAND CT-2001A测试系统上进行测试。
实施例1、实施例2以及对比例1的测试结果见图1，所有实施例和对比例1的测试结果见表1。
表1
  平均粒径/nm 残碱含量/ppm 首效(％) 循环稳定性(％)
实施例1 500 2100 154.3 92.1
实施例2 300 1640 161.7 90.2
实施例3 250 1850 143.5 87.5
实施例4 180 2330 117.2 81.2
实施例5 730 1720 161.6 82.3
实施例6 700 1640 142.5 91.2
实施例7 270 2580 145.3 88.2
实施例8 330 1570 155.2 87.9
实施例9 250 3200 115.2 81.7
实施例10 450 1530 118.8 82.6
实施例11 230 3180 160.2 86.9
实施例12 420 1620 131.2 88.5
实施例13 210 2320 113.2 75.9
实施例14 460 1590 108.9 82.1
实施例15 270 1670 153.5 88.1
实施例16 320 1600 155.2 87.3
实施例17 270 1800 117.6 78.2
实施例18 320 1620 153.5 81.2
实施例19 290 1680 142.6 88.3
实施例20 780 1650 138.5 91.5
实施例21 500 1680 123.6 82.3
实施例22 870 1660 121.7 80.2
实施例23 340 1680 144.6 87.9
实施例24 280 1650 147.8 87.6
实施例25 280 1630 117.8 81.5
实施例26 300 1700 143.1 89.5
实施例27 300 1610 143.7 89.1
实施例28 310 1660 112.4 82.7
实施例29 470 1730 105.6 72.1
实施例30 520 1760 152.2 91.1
实施例31 500 2200 153.3 90
实施例32 510 2120 151.3 89.5
对比例1 850 4200 32.1 75.2
从以上的描述中，可以看出，本申请上述的实施例实现了如下技术效果：
本申请通过使用较少的锂的无机化合物和Fe xMn y(OH) 2前驱体进行氧化烧结，使得最终制备得到的铁锰基正极材料形成贫锂结构。该贫锂结构不仅保证了材料中锂含量较低，而且对锰的价态和晶形进行了很好地控制，一方面，材料中的部分锰为正四价的锰，另一方面，本申请实施例制备得到的铁锰基正极材料XRD谱图中，Li 2MnO 3晶相所对应的特征峰(即20～25°、31～33°、43～45°以及53～55°之间的特征峰)最大强度小于铁锰基正极材料的最强特征 峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，因此本申请正极材料中仅存在极少或不存在上述Li 2MnO 3相，因此也不会存在由于Li 2MnO 3相易在充放电过程中分解造成的释氧和阳离子浓度增高的问题。在上述结构、成分特征的协同作用下，有效改善了铁锰基正极材料的电学性能，使得首效和循环性能得到了很好地提升。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种铁锰基正极材料，其特征在于，所述铁锰基正极材料为Li aFe xMn yO 2，其中a＝0.1～0.5，0＜x＜1.0，0＜y＜1.0，x+y＝1，所述铁锰基正极材料中的至少部分锰元素的价态为正四价，且所述铁锰基正极材料的XRD谱图中Li 2MnO 3晶相的特征峰最大强度小于所述铁锰基正极材料的最强特征峰强度的1/3或者不出现Li 2MnO 3晶相的特征峰，所述Li 2MnO 3晶相在20～25°之间、31～33°之间、43～45°之间以及53～55°之间存在特征峰。
  2. 根据权利要求1所述的铁锰基正极材料，其特征在于，所述铁锰基正极材料的粒径为140～1000nm，优选为140～500nm，优选所述铁锰基正极材料中残碱的含量为1400～1900ppm。
  3. 根据权利要求1所述的铁锰基正极材料，其特征在于，所述铁锰基正极材料的XRD谱图中Li 2MnO 3晶相的31～33°之间的特征峰强度和/或43～45°之间的特征峰强度小于所述铁锰基正极材料的最强特征峰强度的1/3。
  4. 一种铁锰基正极材料的制备方法，其特征在于，所述铁锰基正极材料的的制备方法包括：
    将锂的无机化合物和Fe xMn y(OH) 2前驱体进行氧化烧结，得到所述铁锰基正极材料，其中，0＜x＜1.0，0＜y＜1.0，x+y＝1，所述锂的无机化合物中的Li的摩尔量和所述Fe xMn y(OH) 2前驱体中的Fe和Mn的总摩尔量的比值为0.1:1～0.5:1。
  5. 根据权利要求4所述的铁锰基正极材料的制备方法，其特征在于，所述氧化烧结在含氧气体中进行，优选所述含氧气体中氧气的含量为20～100％，优选所述含氧气体的流量为2～5L/min。
  6. 根据权利要求5所述的铁锰基正极材料的制备方法，其特征在于，所述铁锰基正极材料的制备方法包括：
    将锂的无机化合物和Fe xMn y(OH) 2前驱体进行第一阶段氧化烧结，得到所述铁锰基正极材料前体；
    将所述铁锰基正极材料前体进行第二阶段氧化烧结，得到所述铁锰基正极材料；
    优选所述第一阶段氧化烧结的温度为600～800℃，保温时间为6～12h，所述第二阶段氧化烧结的温度为300～500℃，保温时间为2～6h。
  7. 根据权利要求6所述的铁锰基正极材料的制备方法，其特征在于，所述氧化烧结前的升温速率为2～5℃/min，所述第一阶段氧化烧结和所述第二阶段氧化烧结之间的降温速率为2～4℃/min，所述第二阶段氧化烧结完成之后的降温速率为2～4℃/min。
  8. 根据权利要求4所述的铁锰基正极材料的制备方法，其特征在于，所述铁锰基正极材料的制备方法还包括Fe xMn y(OH) 2前驱体的制备过程，所述Fe xMn y(OH) 2前驱体的制备过程包括：
    在碱性条件下，使包括亚铁盐和二价锰盐的第一原料体系发生共沉淀反应，得到Fe xMn y(OH) 2前驱体；
    优选所述亚铁盐选自氯化亚铁、硝酸亚铁和草酸亚铁中的一种或多种，优选所述二价锰盐选自氯化锰、硝酸锰和乙酸锰的一种或多种，优选所述第一原料体系中，Mn 2+和Fe 2+的摩尔比为10:1～1:1；
    优选所述第一原料体系的pH值＝12～13，优选使用碱性试剂调节所述第一原料体系的pH值，所述碱性试剂选自氢氧化钠、碳酸钠中的一种或多种；
    优选所述共沉淀反应的温度为40～60℃，优选在氮气或第二惰性气体氛围中进行所述共沉淀反应，所述第二惰性气体选自氩气、氦气和氢气中的一种，优选在所述共沉淀反应过程中进行搅拌，优选所述搅拌的速度为200～400rpm。
  9. 根据权利要求8所述的铁锰基正极材料的制备方法，其特征在于，所述第一原料体系中还包括络合剂和溶剂，所述Fe xMn y(OH) 2前驱体的制备过程包括：
    步骤S1，将所述亚铁盐、所述二价锰盐、所述络合剂和所述溶剂混合，得到所述第一原料体系，优选所述络合剂选自氨水、硫酸铵和乙二胺四乙酸中的一种或多种，优选所述第一原料体系中，所述络合剂的含量为28～53g/L；
    步骤S2，在所述氮气或所述第二惰性气体氛围中和所述搅拌条件下，加热所述第一原料体系至所述共沉淀反应温度后，将所述第一原料体系和所述碱性试剂混合，发生所述共沉淀反应，经过陈化后得到所述Fe xMn y(OH) 2前驱体。
  10. 一种锂离子电池，包括电解液、正极材料和负极材料，所述正极材料包括铁锰基正极材料，其特征在于，所述铁锰基正极材料为权利要求1至3中任一项所述的铁锰基正极材料或权利要求4至9中任一项的制备方法制备得到的铁锰基正极材料。
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