WO2023184656A1 - 一种四氧化三锰预嵌锂中间体及其制备方法和应用 - Google Patents

一种四氧化三锰预嵌锂中间体及其制备方法和应用 Download PDF

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WO2023184656A1
WO2023184656A1 PCT/CN2022/092208 CN2022092208W WO2023184656A1 WO 2023184656 A1 WO2023184656 A1 WO 2023184656A1 CN 2022092208 W CN2022092208 W CN 2022092208W WO 2023184656 A1 WO2023184656 A1 WO 2023184656A1
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lithium
embedded
manganese
tetroxide
kettle
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PCT/CN2022/092208
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English (en)
French (fr)
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刘务华
管晓东
李达飞
易鑫
谌红玉
黄亚君
高智
罗家辉
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贵州大龙汇成新材料有限公司
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/12—Manganates manganites or permanganates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention belongs to the technical field of lithium ion battery cathode materials, and specifically relates to lithium manganate cathode material precursors, preparation methods and applications.
  • Lithium manganate a lithium-ion battery cathode material synthesized using trimanganese tetroxide as a precursor, has the characteristics of high capacity, good cycle and high-temperature performance, low magnetic foreign matter, and good safety performance. It is an ideal choice for making low-cost power and energy storage lithium-ion batteries. Ideal raw material.
  • the process route for synthesizing lithium manganate using manganese tetroxide as a precursor is the same as that of ternary cathode materials. They all use a high-temperature solid phase method, that is, the manganese tetroxide and lithium carbonate or lithium hydroxide are first fully mechanically mixed. , then put the mixture into a sagger, place it in a continuous kiln at 700°C to 850°C in the air for the first roasting for 10 to 15 hours, cool and crush it, and then roast for the second time for about 10 hours. , and then cooled to obtain the product through processes such as crushing, iron removal, and sieving.
  • the advantages of the high-temperature solid-state method for synthesizing cathode materials are: the physical and chemical indicators of the product inherit the advantages of the precursor such as low impurity content, regular and controllable morphology, and the electrical performance indicators take into account the balance between high gram capacity and good cycle performance, and the pressure High solid density is beneficial to improving the energy density of the battery.
  • the shortcomings of the high-temperature solid-phase method of synthesizing lithium manganate using trimanganese tetroxide are also prominent: First, it requires high homogeneous mixing effects. The manganese tetroxide powder is mechanically mixed with lithium carbonate or lithium hydroxide powder. Due to the differences in the input amount, particle size, specific surface area, bulk and tap density of the powder materials, a microscopic homogeneous mixing effect is achieved. It is difficult and prone to local lithium-rich/lithium-poor problems. Second, the process flow is long. After the first roasting is completed, the second roasting is performed, during which operations such as cooling, crushing, screening, refilling the bowl, and feeding are required. The third is high energy consumption.
  • the thermal insulation roasting temperature is higher than the melting temperature of lithium carbonate or lithium hydroxide
  • the process requires a slow temperature rise program to avoid microscopic sagging of the lithium source, which may cause agglomeration and uneven lithium insertion.
  • the holding temperature After reaching the holding temperature, sufficient time is needed for lithium ions and oxygen in the ambient atmosphere to migrate into the interior of the micropowder particles to form a uniform and stable crystal structure.
  • the quality stability is poor. Due to macroscopic and microscopic differences in factors such as homogenization effect, temperature control, heat preservation temperature and time, there are often obvious performance differences between the upper and lower layers of the sagger, and between the edge and the middle of the same sagger. difference.
  • the main method is to mix soluble manganese salts with soluble lithium sources and soluble oxidants and then place them in a pressure reactor. After a high-temperature and pressure reaction of more than 100°C, nanoscale or sub-scale materials are obtained. Micron-sized precipitates are then separated and dried to obtain products. Although the resulting products are distinctive in some performance indicators such as capacity and cycle, the particle size, morphology, specific surface area and other indicators are uncontrollable, and most of the products are mixed with anionic or cationic impurities brought by the reactive raw materials, which affects product quality and electricity. Performance, no practical application.
  • the technical problem to be solved by the present invention is to overcome the shortcomings and defects mentioned in the above background technology (such as long process flow, high energy consumption, difficulty in controlling product uniformity, etc.), and provide a kind of manganese tetroxide pre-embedded lithium intermediate.
  • the body and its preparation method complete the partial oxidation of manganese element and the pre-intercalation of lithium ions in the precursor through a wet process. It also provides the application of the manganese tetroxide pre-intercalation lithium intermediate, and the intermediate is placed in a high-temperature oxidizing atmosphere.
  • the crystal structure transformation is completed in a short to medium time, thereby producing a lithium manganate cathode material with uniform lithium insertion and excellent performance.
  • the technical solution proposed by the present invention is a pre-embedded lithium intermediate of manganese tetroxide.
  • the pre-embedded lithium intermediate includes a trimanganese tetroxide phase and a pre-embedded lithium element.
  • the lithium element is The lithium manganese oxide phase is coated or embedded in the trimanganese tetroxide phase.
  • the molar ratio of the pre-embedded lithium element in the pre-embedded lithium intermediate to the manganese element is consistent with the target based on the preparation of the pre-embedded lithium intermediate.
  • the stoichiometric ratio of lithium and manganese in lithium manganate materials remains consistent.
  • the pre-embedded lithium intermediate proposed by the present invention can achieve structural transformation after one roasting, and obtain a spinel-type lithium manganate cathode material with a stable structure.
  • the lithium manganese oxide may be one or more types.
  • the lithium manganese oxide mainly contains Li 2 MnO 3 .
  • the XRD diffraction pattern of the pre-embedded lithium intermediate can be regarded as meeting the preferred requirements of the present invention if it meets the following conditions: 2 ⁇ has a diffraction peak with an intensity greater than 600cps at 18.5° ⁇ 0.5°; 2 ⁇ is at 44.5° ⁇ 0.5° There is a diffraction peak with an intensity greater than 200 cps (preferably greater than 400 cps), and 2 ⁇ has at least three (preferably 3-4) diffraction peaks with an intensity in the range of 80-260 cps in the range of 58° to 66°.
  • the above-mentioned lithium pre-embedded manganese tetraoxide intermediate is prepared by hydrothermal reaction between trimanganese tetroxide and a lithium source under aerobic conditions.
  • the preferred solution is to first perform a hydrothermal reaction between manganese tetraoxide and a lithium source (such as lithium hydroxide) under the condition of oxygen to obtain a pre-lithium-embedded intermediate, and then roast the pre-lithium-embedded intermediate to achieve the structure. Transformed to obtain a spinel-type lithium manganate cathode material with a stable structure.
  • the present invention also provides a preparation method of manganese tetraoxide pre-embedded lithium intermediate, which includes the following steps:
  • the input amount of the lithium source is determined based on the stoichiometric ratio of lithium element and manganese element in the target lithium manganate material prepared by the pre-embedded lithium intermediate.
  • the above-mentioned preparation method of the present invention performs a hydrothermal reaction on trimanganese tetroxide to insert lithium, and uses oxygen (for example, continuous oxygen flow) as a necessary condition, so that the manganese element in trimanganese tetroxide is oxidized to a higher valence state to achieve Embedded lithium.
  • oxygen for example, continuous oxygen flow
  • the lithium source is lithium hydroxide.
  • Lithium hydroxide was chosen because it is highly alkaline, which helps promote the oxidation of trimanganese tetraoxide without introducing other new impurities or generating new gas products, thus avoiding changes in the reaction atmosphere or uncontrollable reaction pressure.
  • the lithium hydroxide is selected from particles with a particle size less than 10 mm (more preferably less than 5 mm).
  • the input amount of lithium hydroxide raw material is basically determined based on the stoichiometric ratio of the target lithium manganate material.
  • the hydrogen content can basically be determined.
  • the input amount of lithium oxide Since the present invention adopts wet hydrothermal reaction, the lithium hydroxide used does not need to use very fine powder.
  • the pre-lithium embedding effect can be achieved by using granular materials with a particle size of less than 10 mm. At the same time, the operation steps such as ball milling and crushing are reduced and the cost is reduced. reduced energy consumption.
  • the mass ratio of trimanganese tetroxide and water is controlled at 1:0.3-10.
  • concentration of the reaction system in the preparation method of the present invention is controlled by the mass ratio of manganese tetroxide and water. If it is too thick, it will be unfavorable for stirring. If it is too thin, a higher reaction temperature and a longer reaction time will be required. , our repeated experiments show that the aforementioned preferred mass ratio range achieves better results.
  • the temperature in the kettle is controlled at 110°C to 250°C, and the reaction time is controlled at 4 to 12 hours. It is preferable to select a certain temperature value within the aforementioned temperature range for constant temperature reaction. Generally, the higher the temperature is selected, the shorter the time required for the reaction; but our experiments show that if the temperature is too high, it will cause excessive reaction. Soon, floc will appear on the surface of the particles, which will affect the final pre-lithium embedding effect. Although constant temperature control is preferred in production, temperature fluctuations within a certain range are also allowed. The size of the fluctuation range mainly depends on the control accuracy of the temperature control equipment.
  • the gauge pressure inside the pressure kettle is controlled at 0.2-5.0 MPa, and the pressure inside the kettle after oxygen is introduced exceeds the saturated vapor pressure of water vapor at the corresponding temperature inside the kettle.
  • the reaction temperature in the pre-embedded lithium kettle controlled by the present invention exceeds 100°C. Considering the vapor pressure of water, there is pressure in the pressure reaction kettle. Therefore, it is preferred that the pressure in the kettle exceeds the water vapor at the corresponding temperature in the kettle after oxygen is introduced. saturated vapor pressure, otherwise, the oxygenation effect will be difficult to guarantee.
  • the supply of oxygen into the pressure reaction kettle is carried out continuously, and the oxygen supply is carried out when the temperature of the reaction material starts to rise.
  • the pressure reaction kettle is degassed. Our tests show that after completing the feeding and before raising the temperature to the target reaction temperature, it is best to exhaust the air first. Otherwise, the air in the upper part of the pressure reactor will generate greater pressure as the temperature in the reactor rises, affecting Regulation of oxygenation pressure.
  • the operation of exhausting air can be carried out by first vacuuming and then passing oxygen, preferably by continuously passing oxygen. Continuous oxygen supply can be achieved by adjusting the oxygen pressure stabilizing valve. When operating, the pressure in the pressure reactor is higher than the saturated vapor pressure of water vapor at the reaction temperature until the end of the reaction time.
  • the lithium manganese oxide pre-embedded with lithium preferably mainly exists in the form of oxide with the molecular formula Li 2 MnO 3. This is consistent with the detection data of our later XRD pattern.
  • the intermediate particles are likely to be Li 2 MnO 3 packages. Coated Mn 3 O 4 .
  • Our XRD pattern of the pre-embedded lithium intermediate shows (see specific embodiments) that it is mainly composed of Mn 3 O 4 phase and Li 2 MnO 3 phase.
  • the surface layer of the pre-intercalated lithium intermediate is composed of fine crystalline particles, and the XRD pattern of the pre-intercalated lithium intermediate has the characteristics of a lithium-rich manganese phase.
  • the pre-intercalated lithium intermediate is likely to be Mn 3 O 4 and A composition rich in lithium manganese (especially preferably Li 2 MnO 3 ), and preferably a coating structure in which Li 2 MnO 3 coats trimanganese tetroxide.
  • the present invention also provides an application of the above-mentioned manganese tetroxide pre-lithium intercalation intermediate of the present invention.
  • the dry material or wet material of the pre-lithium intercalation intermediate is placed in an aerobic atmosphere (the Roasting is performed under an oxygen atmosphere (which can be air, oxygen or a mixture of the two). After the roasting is complete and the crystal structure transformation is completed, a spinel-type lithium manganate cathode material is obtained.
  • the pre-lithium intermediate slurry is first reacted in a pressure reactor, and then the slurry is solid-liquid separated (the solid-liquid separation method can be suction filtration, pressure filtration or centrifugal separation).
  • the pre-embedded lithium intermediate can be obtained.
  • Our experiments show that the pre-intercalated lithium intermediate can be dried first and then roasted, or the wet material of the pre-intercalated lithium intermediate can be directly roasted, both of which can produce spinel-type lithium manganate with intact crystal structure. product.
  • reaction formula is:
  • the above-mentioned roasting process of the present invention requires supplementing oxygen from the ambient atmosphere in order to undergo phase change to obtain spinel-type lithium manganate with a stable structure. Since the partial oxidation of the manganese element has been completed in the pre-embedded lithium intermediate, the oxygen that needs to be absorbed from the ambient atmosphere is much less than the solid-phase synthesis method, so the conditions of the roasting process can be further simplified.
  • the moisture content of the wet material is below 30%.
  • the moisture content of the wet material is related to the material characteristics (including particle size, specific surface area, particle density, etc.) and the separation method.
  • the wet material can be It is suitable for mud, easy to loosen and easy to flatten. Use simple suction filtration, pressure filtration or centrifugal separation operations to control the moisture content below 30% to achieve roasting. Wet materials with 30% moisture content are difficult to achieve in the existing process route. Direct roasting will seriously affect the quality of the lithium manganate product.
  • the water will be evaporated during the heating stage of the roasting synthesis, and based on the characteristics of the pre-embedded lithium intermediate, the wet material Direct roasting will not have a negative impact on lithium manganate products.
  • direct roasting of wet materials may simplify the operation and save energy consumption.
  • the roasting temperature is 700°C to 850°C, and the roasting time is 3 to 10 hours. Since lithium ions have been pre-embedded into the intermediate, the present invention can shorten the roasting time by more than half compared with the conventional solid-phase synthesis method.
  • the process route of the present invention can omit the slow heating process, and a faster heating rate is acceptable. of.
  • the heating rate generally controlled by solid-phase roasting is 3°C to 5°C/minute, but the heating rate of the method of the present invention is not subject to this restriction. If the production equipment allows, the heating rate can preferably be greater than 10°C/minute. minute.
  • the lithium manganate cathode material prepared by using the manganese tetroxide pre-lithium intercalation intermediate of the present invention can be seen from the XRD pattern that the diffraction peaks are very sharp and the signal-to-noise ratio is high, indicating good crystallinity and no impurity phases. , a pure phase spinel crystal structure.
  • the microscopic particles of the lithium manganate cathode material prepared by the lithium pre-embedded manganese tetroxide intermediate of the present invention maintain the morphology of the precursor, and the particle size distribution also maintains the distribution characteristics of the precursor, realizing the realization of material particles.
  • the uniform lithium insertion avoids the local lithium-rich/poor lithium and agglomeration problems that exist in conventional solid-phase synthesis methods, ensures the consistency of product quality, and improves the gram capacity and cycle performance of the product.
  • the present invention Since the present invention has realized the embedding of lithium ions in the pre-embedded lithium intermediate, there is no agglomeration caused by the sagging of the lithium source material. After the roasting is completed, the material is uniform in color, fluffy and brittle, and does not need to be processed. Crushed, suitable for direct screening.
  • the cathode material product produced by the method of the present invention retains the morphology and particle size characteristics of the precursor, achieves uniform lithium insertion into the material particles, and avoids the local lithium-rich/poor lithium and agglomeration that occur during solid-phase synthesis. problem, ensuring quality consistency and improving the gram capacity and cycle performance of the product.
  • this method simplifies the mixing and secondary roasting processes, shortens the high-temperature roasting time, reduces energy consumption, and increases the productivity of the roasting equipment.
  • Figure 1 is an XRD comparison chart of the manganese tetroxide raw material, the pre-embedded lithium intermediate and the lithium manganate product in Example 1 of the present invention.
  • Figure 2 is an SEM image of the micromorphology of the raw material of manganese tetroxide in Example 1 of the present invention.
  • Figure 3 is an SEM image of the micromorphology of the pre-lithium-intercalated intermediate in Example 1 of the present invention.
  • Figure 4 is an SEM image of the micromorphology of the lithium manganate product in Example 1 of the present invention.
  • Figure 5 is a TG-DSC chart of the pre-lithium-intercalated intermediate in nitrogen in Example 2 of the present invention.
  • Figure 6 is a TG-DSC chart of the pre-lithium-intercalated intermediate in oxygen according to Example 2 of the present invention.
  • Figure 7 is a particle size distribution diagram of the raw material of manganese tetroxide in Example 3 of the present invention.
  • Figure 8 is a particle size distribution diagram of the pre-lithium-intercalated intermediate in Example 3 of the present invention.
  • Figure 9 is a particle size distribution diagram of the lithium manganate product in Example 3 of the present invention.
  • Figure 10 is an XRD pattern of the pre-lithium-intercalated intermediate in Example 1 of the present invention.
  • Figure 11 is an XRD pattern of the pre-lithium-intercalated intermediate in Example 2 of the present invention.
  • Figure 12 is an XRD pattern of the pre-lithium-doped intermediate in Example 3 of the present invention.
  • Figure 13 is an XRD pattern of the pre-lithium-doped intermediate in Example 4 of the present invention.
  • Figure 14 is a cross-sectional SEM image of the precursor trimanganese tetroxide material particles in Example 2 of the present invention.
  • Figure 15 is an SEM image of the micromorphology of the pre-lithium-intercalated intermediate in Example 2 of the present invention.
  • Figure 16 is a cross-sectional SEM image of the pre-lithium intermediate material particles in Example 2 of the present invention.
  • Figure 17 is a cross-sectional SEM image of the lithium manganate product particles in Example 2 of the present invention.
  • Figure 18 is a cross-sectional SEM image of lithium manganate product particles prepared by the existing solid-phase method.
  • Figure 19 is an XRD comparison chart of pre-lithium-intercalated intermediates according to various embodiments of the present invention.
  • the lithium element content is detected using the ICP-AES method
  • the manganese element content is detected using the ferrous ammonium sulfate titration method (see Appendix A of GB/T21836-2008).
  • Conduct electrical performance tests in a 25°C temperature environment and a charge and discharge range of 3.0V to 4.3V. First, test 0.2C for the first time, and then perform a 1C (set lithium manganate material 1C 120mA/g) cycle.
  • a method for preparing trimanganese tetroxide pre-lithium intercalation intermediate of the present invention including the following steps:
  • the moisture content of the wet material of the pre-embedded lithium intermediate is 21%, and its particle size D50 is 11.6 ⁇ m.
  • the filter cake is dried at 120°C for 24 hours.
  • the lithium content of the dried dry material is 4.46% and the manganese content is 61.5%.
  • the XRD patterns are shown in Figures 1 and 10.
  • the XRD of the lithium manganate product in Figure 1 shows that the product is pure lithium manganate without impurity phases.
  • the XRD of Figure 10 shows that the pre-embedded lithium intermediate product is composed of Mn 3 O 4 phase and Li 2 MnO 3 phase. .
  • the raw material of manganese tetroxide, the prepared pre-lithium intercalated intermediate product and the finally prepared lithium manganate product were the same as those of the pre-intercalated lithium intermediate product (its particle size D50 is 11.6 ⁇ m) and the prepared lithium manganate product.
  • the particle size distribution of the manganese oxide raw material (its particle size D50 is 11.4 ⁇ m) is basically the same, and the finally prepared lithium manganate cathode material basically follows the particle size distribution of the pre-embedded lithium intermediate product and the manganese tetroxide raw material. D50 is 12.1 ⁇ m.
  • the above embodiment has prepared a manganese tetroxide pre-embedded lithium intermediate, which includes a trimanganese tetroxide phase and a pre-embedded lithium element.
  • the lithium element is lithium manganese oxide ( The Li 2 MnO 3 ) phase is coated or embedded in the manganese tetroxide phase, and the molar ratio of the pre-embedded lithium element in the pre-embedded lithium intermediate to the manganese element therein is consistent with the target manganese acid prepared based on the pre-embedded lithium intermediate.
  • the stoichiometric ratio of lithium and manganese in lithium materials remains consistent (0.57:1, see Table 1 below for details).
  • the chemical formula of the lithium manganate product finally prepared in this embodiment is Li 1.14 Mn 2 O 4 .
  • the lithium manganate prepared above is subjected to power-off detection:
  • the 0.2C gram capacity is 113mAh/g
  • the 1C capacity is 112mAh/g
  • the capacity retention rate is 95% after 50 cycles at 25°C
  • the capacity retention rate is 92% after 100 cycles.
  • a method for preparing trimanganese tetroxide pre-lithium intercalation intermediate of the present invention including the following steps:
  • the moisture content of the wet material of the pre-embedded lithium intermediate is 20.5%, and its particle size D50 is 9.4 ⁇ m. After drying, the lithium content of the dry material is 4.49% and the manganese content is 60.9%.
  • Figure 11 is an XRD pattern of the pre-lithium-doped intermediate product in this embodiment, which shows that the pre-lithium-doped intermediate product is composed of Mn 3 O 4 phase and Li 2 MnO 3 phase.
  • the pre-intercalated lithium intermediate product the particle size D50 of which is 9.4 ⁇ m
  • the pre-intercalated lithium tetroxide product The particle size distribution of the trimanganese raw material (its particle size D50 is 8.1 ⁇ m) is basically the same, and the finally prepared lithium manganate cathode material basically follows the particle size distribution of the pre-embedded lithium intermediate product and the trimanganese tetroxide raw material, with a particle size of D50 is 9.5 ⁇ m.
  • the morphology of the lithium manganate products is regular spherical particles, with good microscopic morphology, and good product uniformity and consistency.
  • a manganese tetroxide pre-embedded lithium intermediate which includes manganese tetroxide phase and pre-embedded lithium element.
  • the lithium element is wrapped with lithium manganese oxide (Li 2 MnO 3 ) phase. Covered or embedded in the trimanganese tetroxide phase, the molar ratio of the pre-embedded lithium element in the pre-intercalated lithium intermediate to the manganese element is the same as the molar ratio of the lithium element in the target lithium manganate material prepared based on the pre-intercalated lithium intermediate.
  • the stoichiometric ratio of manganese remains consistent (0.58:1, see Table 2 below for details).
  • the chemical formula of the lithium manganate product finally prepared in this embodiment is Li 1.16 Mn 2 O 4 .
  • the degree of oxidation of manganese element can also be roughly judged.
  • the appearance, particle size distribution also maintains the distribution characteristics of the precursor, achieving uniform lithium insertion into the material particles, and avoiding the local lithium-rich/poor lithium and agglomeration problems that exist in conventional solid-phase synthesis methods.
  • the material is uniform in color, fluffy and brittle, does not need to be broken, and is suitable for direct screening. It also has rich active pores, which is more conducive to improving electrochemical performance.
  • the lithium manganate prepared above is subjected to power-off detection:
  • the 0.2C gram capacity is 110mAh/g
  • the 1C capacity is 109mAh/g
  • the capacity retention rate is 98% after 50 cycles at 25°C
  • the capacity retention rate is 97% after 100 cycles.
  • a method for preparing trimanganese tetroxide pre-lithium intercalation intermediate of the present invention including the following steps:
  • the particle size D50 of the pre-embedded lithium intermediate is 10.2 ⁇ m. After drying, the lithium content of the dry material is 4.32% and the manganese content is 61.8%.
  • Figure 12 is an XRD pattern of the pre-lithium-doped intermediate product of this embodiment, which shows that the pre-lithium-doped intermediate product is composed of Mn 3 O 4 phase and Li 2 MnO 3 phase.
  • the pre-lithium intermediate product (its particle size D50 is 10.2 ⁇ m) and the particle size distribution of manganese tetraoxide raw material (its particle size D50 is 9.7 ⁇ m) are basically the same, and the finally prepared lithium manganate cathode material basically follows the pre-embedded lithium intermediate products and tetramanganese tetroxide.
  • the particle size distribution of the raw material of manganese oxide has a particle size D50 of 11.1 ⁇ m.
  • the morphology of the lithium manganate products is regular spherical particles, with good microscopic morphology, and good product uniformity and consistency.
  • a manganese tetroxide pre-embedded lithium intermediate which includes a trimanganese tetroxide phase and a pre-embedded lithium element.
  • the lithium element is lithium manganese oxide ( The Li 2 MnO 3 ) phase is coated or embedded in the manganese tetroxide phase, and the molar ratio of the pre-embedded lithium element in the pre-embedded lithium intermediate to the manganese element therein is consistent with the target manganese acid prepared based on the pre-embedded lithium intermediate.
  • the stoichiometric ratio of lithium and manganese in lithium materials remains consistent (0.55:1, see Table 3 below for details).
  • the chemical formula of the lithium manganate product finally prepared in this embodiment is Li 1.1 Mn 2 O 4 .
  • the lithium manganate prepared above is subjected to power-off detection:
  • the 0.2C gram capacity is 115mAh/g
  • the 1C capacity is 114mAh/g
  • the capacity retention rate is 95% after 50 cycles at 25°C
  • the capacity retention rate is 91% after 100 cycles.
  • a method for preparing trimanganese tetroxide pre-lithium intercalation intermediate of the present invention including the following steps:
  • the particle size D50 of the pre-embedded lithium intermediate was 9.9 ⁇ m, the lithium content was 4.27%, and the manganese content was 62.0%.
  • Figure 13 is an XRD pattern of the pre-lithium-doped intermediate product in this embodiment, which shows that the pre-lithium-doped intermediate product is composed of Mn 3 O 4 phase and Li 2 MnO 3 phase.
  • the pre-intercalated lithium intermediate product (its particle size D50 is 9.9 ⁇ m) and the pre-intercalated lithium tetroxide
  • the particle size distribution of the trimanganese raw material (its particle size D50 is 10.4 ⁇ m) is basically the same, and the finally prepared lithium manganate cathode material basically follows the particle size distribution of the pre-embedded lithium intermediate product and the trimanganese tetroxide raw material, with a particle size D50 is 10.9 ⁇ m.
  • the morphology of the lithium manganate products is regular spherical particles, with good microscopic morphology, and good product uniformity and consistency.
  • the above embodiment has prepared a manganese tetroxide pre-embedded lithium intermediate, which includes a trimanganese tetroxide phase and a pre-embedded lithium element.
  • the lithium element is lithium manganese oxide ( The Li 2 MnO 3 ) phase is coated or embedded in the manganese tetroxide phase, and the molar ratio of the pre-embedded lithium element in the pre-embedded lithium intermediate to the manganese element therein is consistent with the target manganese acid prepared based on the pre-embedded lithium intermediate.
  • the stoichiometric ratio of lithium element and manganese element in lithium materials remains consistent (0.54:1, see Table 4 below for details).
  • the precursor trimanganese tetroxide, the pre-lithium intermediate and the synthesized lithium manganate material it can also be roughly judged that the manganese element is oxidized, indicating that the oxygen introduced during the synthesis of the pre-lithium intermediate has partially oxidized the manganese element. .
  • the chemical formula of the lithium manganate product finally prepared in this embodiment is Li 1.08 Mn 2 O 4 .
  • the lithium manganate prepared above is subjected to power-off detection:
  • the 0.2C gram capacity is 121mAh/g
  • the 1C capacity is 120mAh/g
  • the capacity retention rate is 94% after 50 cycles at 25°C
  • the capacity retention rate is 91% after 100 cycles.
  • 2 ⁇ both contain Mn 3 O 4 phase and Li 2 MnO 3 phase, and in the XRD diffraction pattern of the main pre-lithium intermediate, 2 ⁇ has a diffraction peak with an intensity greater than 600cps at 18.5° ⁇ 0.5°; 2 ⁇ is at 44.5° ⁇ 0.5 There is a diffraction peak with intensity greater than 400cps or at least greater than 200cps at °, and 2 ⁇ has at least 3-4 diffraction peaks with intensity in the range of 80-260cps in the range of 58° to 66°.

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Abstract

本发明公开了一种四氧化三锰预嵌锂中间体，包括四氧化三锰相和预嵌的锂元素，锂元素是以锂锰氧化物相包覆或嵌入到四氧化三锰相中，预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致。制备时将四氧化三锰、锂源、水投入压力反应釜中，在通氧条件下，控制釜内温度在100℃以上，釜内表压在0.1MPa以上，搅拌条件下反应充分完全可得到预嵌锂中间体。将预嵌锂中间体的干料或湿料在有氧气氛下进行焙烧，焙烧完全并完成晶体结构转化后可得到尖晶石型锰酸锂正极材料。本发明具有工艺流程短、能耗低、产品均匀性好等优点。

Description

一种四氧化三锰预嵌锂中间体及其制备方法和应用 技术领域
本发明属于锂离子电池正极材料技术领域，具体涉及锰酸锂正极材料前驱体及制备方法和应用。
背景技术
用四氧化三锰作前驱体合成的锂离子电池正极材料锰酸锂具有容量高、循环与高温性能好、磁性异物低、安全性能好等特点，是制作低成本动力与储能锂离子电池的理想原料。
目前，用四氧化三锰作前驱体合成锰酸锂的工艺路线与三元正极材料一样，均是采用高温固相法，即将四氧化三锰与碳酸锂或氢氧化锂先进行充分的机械混合，然后将混合料装入匣钵中，在空气中置于700℃～850℃的连续炉窑中先进行第一次焙烧10～15小时，冷却与破碎后再进行第二次焙烧10小时左右，再冷却后经粉碎、除铁、过筛等工序制得产品。
高温固相法合成正极材料的优点是：产品理化指标上继承了前驱体的杂质含量低、形貌规整可控等优势，电性能指标上兼顾了克容量高与循环性能好的平衡，而且压实密度高有利于提高电池的能量密度。
用四氧化三锰合成锰酸锂的高温固相法其缺点也比较突出：一是对均混效果的要求高。将四氧化三锰粉末与碳酸锂或氢氧化锂粉末进行机械混合，由于粉体物料在投入量、颗粒大小、比表面积、松装与振实密度等方面的差异，达到微观上的均混效果很难，易于出现局部富锂/贫锂问题。二是工艺流程长。在第一次焙烧完成后再进行第二次焙烧，期间需要进行冷却、粉碎、过筛、重新装钵与投料等操作。三是能耗高。一方面由于保温焙烧温度高于碳酸锂或氢氧化锂的熔融温度，工艺上需要有缓慢的升温程序，避免微观上出现锂源的流挂现象而导致结块与嵌锂不均匀问题，另一方面在达到保温温度后需要足够的时间让锂离子与环境气氛中的氧气迁移到微粉颗粒的内部从而形成均匀稳定的晶体结构。四是质量稳定性差。由于均混效果、升温控制、保温温度与时间等因素的宏观与微观差异，往往同一匣钵的产品，在匣钵的上层与下层之间、匣钵的边缘与中间之间，性能存在明显的差异。
目前，也有很多水热合成锰酸锂的文献报导，主要是将可溶性锰盐与可溶性锂源及可溶性氧化剂混合后置于压力反应器中，经100℃以上的高温带压反应得到纳米级或亚微米级的沉淀物，再经分离与干燥等后处理得到产品。所得产品尽管在容量、循环等部分性能指标上有特色，但颗粒尺寸、形貌、比表面积等指标不可控，且产品大多夹杂有反应原料所带来的阴离子或阳离子杂质，影响产品品质与电性能，没有形成实际应用。
发明内容
本发明所要解决的技术问题是，克服以上背景技术中提到的不足和缺陷(例如工艺流程长、能耗高、产品均匀性控制难度大等)，提供一种四氧化三锰预嵌锂中间体及其制备方法，通过湿法过程完成锰元素的部分氧化与锂离子在前驱体中的预嵌，还提供该四氧化三锰预嵌锂中间体的应用，将中间体在高温氧化性气氛中短时间内完成晶体结构转化，从而制得嵌锂均匀、性能优异的锰酸锂正极材料。
为解决上述技术问题，本发明提出的技术方案为一种四氧化三锰预嵌锂中间体，所述预嵌锂中间体包括四氧化三锰相和预嵌的锂元素，所述锂元素是以锂锰氧化物相包覆或嵌入到四氧化三锰相中，所述预嵌锂中间体中预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致。本发明提出的预嵌锂中间体经过一次焙烧即可实现结构转化，得到结构稳定的尖晶石型锰酸锂正极材料。
上述的四氧化三锰预嵌锂中间体，所述锂锰氧化物可能为一种或多种，我们将该预嵌锂中间体样品在氮气环境下进行差热扫描后发现，在420℃以前失重不到2％，说明结构水含量低；而将其在氧气环境中进行差热扫描，在250℃～613℃之间，质量增加约2％，说明中间体有吸氧的过程，这也表明在预嵌锂中间体合成过程中通入了氧气，使锂锰氧化物相中锰的价态高于四氧化三锰中的锰的平均价态。更优选的，所述锂锰氧化物主要包含Li 2MnO 3。
上述的四氧化三锰预嵌锂中间体，虽然我们可以基本测定其中的物相，但考虑不同工艺条件下锂锰氧化物生成的复杂性以及不同XRD图峰位的可能差异性，我们认为优选的，所述预嵌锂中间体的XRD衍射图谱满足以下条件可视为符合本发明的优选要求：2θ在18.5°±0.5°处有一强度大于600cps的衍射峰；2θ在44.5°±0.5°处有一强度大于200cps(优选大于400cps)的衍射峰，2θ在58°～66°范围内至少有三个(优选3-4个)强度在80-260cps范围内的衍射峰。
上述的四氧化三锰预嵌锂中间体，优选的，所述预嵌锂中间体是四氧化三锰与锂源在通氧条件下经过水热反应后制备得到。该优选的方案是先在通氧的情况下进行四氧化三锰与锂源(例如氢氧化锂)的水热反应得到预嵌锂的中间体，然后对预嵌锂中间体进行焙烧从而实现结构转化，得到结构稳定的尖晶石型锰酸锂正极材料。
作为一个总的技术构思，本发明还提供一种四氧化三锰预嵌锂中间体的制备方法，包括以下步骤：
将四氧化三锰、锂源、水投入压力反应釜中，在通氧条件下(不限于纯氧气)，控制釜内温度在100℃以上，釜内表压在0.1MPa以上，搅拌条件下反应充分完全，得到预嵌锂中间体；
所述锂源的投入量是根据该预嵌锂中间体制备的目标锰酸锂材料中锂元素与锰元素化学 计量比来确定。
本发明的上述制备方法对四氧化三锰进行水热反应嵌锂，且以通氧(例如持续通入氧气)作为必要条件，使四氧化三锰中的锰元素被氧化为更高价态进而实现嵌锂。经过本发明的水热反应，几乎所有的四氧化三锰微观颗粒都能实现锂离子的预嵌，且彻底解决了固相法合成时易出现的嵌锂不均匀现象。
上述的制备方法，优选的，所述锂源为氢氧化锂。选择氢氧化锂是因为其碱性较强，有利于增进四氧化三锰的氧化，且不会引入其它新的杂质或生成新的气体产物，避免反应气氛的变化或反应压力的不可控。更优选的，所述氢氧化锂选用粒径小于10mm(更优选小于5mm)的颗粒料。氢氧化锂原料投入量基本上是根据目标锰酸锂材料的化学计量比来确定，特别是根据投入压力反应釜的四氧化三锰质量与目标锰酸锂中的锂锰比，基本可以确定氢氧化锂的投入量。由于本发明采用湿法水热反应，所用氢氧化锂不必使用粒度很细的微粉，用粒径小于10mm的颗粒料即可达到预嵌锂效果，同时减小了球磨、粉碎等操作步骤及降低了能耗。
上述的制备方法，优选的，所述四氧化三锰与水的质量比控制在1∶0.3～10。本发明制备方法的反应体系浓度，以四氧化三锰与水的质量比例来进行控制，如果太浓稠，则不利进行搅拌，如果太稀薄，则需要更高的反应温度和更长的反应时间，我们反复的实验表明，前述优选的质量比范围达到的效果较佳。
上述的制备方法，优选的，所述釜内温度控制在110℃～250℃，反应时间控制在4～12小时。优选是选定前述温度范围内的某个温度值进行恒温反应，一般地，温度选取的越高，反应所需的时间越短；但我们的试验表明，如果温度过高，则会因反应过快而出现颗粒表层产生絮状物现象，会影响最终的预嵌锂效果。生产上尽管优选控制为恒温，但温度值在一定范围内波动也是允许的，波动范围大小主要取决于温控设备的调控精度。
上述的制备方法，优选的，所述压力釜内表压控制在0.2～5.0MPa，且通入氧气后釜内压力超过相应釜内温度下水蒸汽的饱和蒸气压。本发明控制的预嵌锂釜内反应温度超过了100℃，而考虑水的蒸气压原因，压力反应釜内本是有压力存在，因此优选通入氧气后釜内压力超过相应釜内温度下水蒸汽的饱和蒸气压，否则，通氧效果难以得到保障。至于通氧后釜内压力高出反应温度下水蒸汽的饱和蒸气压多少程度，我们不作特别要求，以能确保氧气能顺利进入釜内即可，但也无需保持过高压力氛围以避免安全风险。
上述的制备方法，优选的，向所述压力反应釜内通氧气是连续进行，且从反应物料开始升温时就进行通氧，通氧前对压力反应釜内进行排空气操作。我们的试验表明，在完成投料后、升温至目标反应温度前，最好先进行排空气操作，否则，压力反应釜内上部的空气会随反应釜内温度的上升而产生较大的压力，影响对通氧压力的调控。而排空气的操作可以采用 先抽真空再通氧气的方式，优选通过连续通氧气来排空气。连续通氧可通过调节氧气的稳压阀实现，操作时，使压力反应釜内的压力高于反应温度下的水蒸汽的饱和蒸气压，直至反应时间结束。
为了得到较好的循环性能，通常添加过量的锂使部分锰离子位置被锂离子替代，形成非化学计量比的锰酸锂，其化学通式可以表述为Li 1+xMn 2O 4。在控制目标锰酸锂产品的锂锰比条件下，在单个中间体颗粒上发生的反应可能包含：
Figure PCTCN2022092208-appb-000001
其中，预嵌锂的锂锰氧化物优选主要以分子式Li 2MnO 3的氧化物形态存在，这与我们后期的XRD图的检测数据是相吻合的，中间体颗粒很可能为Li 2MnO 3包覆的Mn 3O 4。我们对预嵌锂中间体的XRD图表明(参见具体实施方式)，其主要由Mn 3O 4相与Li 2MnO 3相构成。另外，基于后续的电镜图可见，预嵌锂中间体表层为细小结晶颗粒，且预嵌锂中间体XRD图有富锂锰相特征，我们认为预嵌锂中间体很可能为Mn 3O 4与富锂锰(特别优选Li 2MnO 3)的组合物，且优选为Li 2MnO 3包覆四氧化三锰的包覆型结构。
作为一个总的技术构思，本发明还提供一种上述本发明的四氧化三锰预嵌锂中间体的应用，将所述预嵌锂中间体的干料或湿料在有氧气氛(所述的有氧气氛可以是空气、氧气或二者的混合)下进行焙烧，焙烧完全并完成晶体结构转化后，得到尖晶石型锰酸锂正极材料。
在以上的整个技术路线中，先在压力反应釜内反应生成预嵌锂中间体浆料，再对浆料进行固液分离(固液分离的方式可以为抽滤、压滤或离心分离)，即可得到预嵌锂中间体。我们的试验表明，可以将预嵌锂中间体先进行干燥然后再进行焙烧，也可以将预嵌锂中间体的湿料直接进行焙烧，都可制得晶体结构完好的尖晶石型锰酸锂产品。
无论是使用预嵌锂中间体的干料或湿料，其反应式为：
Figure PCTCN2022092208-appb-000002
上述本发明的焙烧过程需要从环境气氛中补充氧气，才能进行相变得到结构稳定的尖晶石型锰酸锂。由于在预嵌锂中间体中，已经完成了锰元素的部分氧化，需要从环境气氛中吸收的氧气较固相法合成会少很多，因此焙烧工艺的条件可以进一步简化。
上述的应用，优选的，选择所述预嵌锂中间体的湿料进行焙烧，所述湿料的含水率在30％以下。一般而言，湿料的含水率跟物料特性(包括粒度、比表面积、颗粒密实性等)及分离方式等有关，但考虑到本发明工艺路线的特点，通过适当控制含水率，以湿料不成泥、易松散、易扒平为宜，采用简单的抽滤、压滤或离心分离操作控制含水率在30％以下即可实现焙烧，30％的含水率湿料在现有工艺路线中是难以进行直接焙烧的，因为会严重影响锰酸锂产品的品质，但在本发明特定的工艺路线下，焙烧合成的升温阶段水分会被蒸发，且基于预嵌 锂中间体的特性，该湿料的直接焙烧也不会对锰酸锂产品有负面影响，相比先干燥后焙烧的两步操作，直接焙烧湿料可能更简化操作和节省能耗。
上述的应用，优选的，所述焙烧的焙烧温度为700℃～850℃，焙烧的时间为3～10小时。由于锂离子已经预嵌到中间体中，本发明较常规固相法合成，焙烧时间可以缩短一半以上。
上述的应用，优选的，通过以大于5℃/分钟的升温速率快速升温至所述的焙烧温度范围。由于锂离子已经预嵌到微观颗粒内部，不存在固相法合成时易产生锂源的流挂问题，所以本发明的工艺路线可以省去缓慢升温的过程，以较快的升温速率是可以接受的。工业生产时，一般固相法焙烧控制的升温速率为3℃～5℃/分钟，而本发明方法的升温速率可不受此限制，在生产设备允许的情况下，升温速率可优选大于10℃/分钟。
与现有技术相比，本发明的有益效果为：
1)采用本发明的四氧化三锰预嵌锂中间体制得的锰酸锂正极材料，从XRD图上可以看出，衍射峰均很尖锐、信噪比高，表明结晶度好、无杂相，为纯相尖晶石型晶体结构。
2)经本发明的四氧化三锰预嵌锂中间体制得的锰酸锂正极材料，其微观颗粒保持了前驱体的形貌，粒度分布上也保持了前驱体的分布特性，实现了物料颗粒的均匀嵌锂，避免了已有常规固相法合成时存在的局部富锂/贫锂与结块问题，保证了产品质量的一致性，提高了产品的克容量与循环性能。
3)由于本发明已经在预嵌锂中间体中实现了锂离子的嵌入，不存在锂源物质的流挂而导致的结块现象，焙烧完成后，物料颜色均匀、蓬松易碎，不需要进行破碎，适合直接进行过筛处理。
综上，本发明方法制得的正极材料产品保留了前驱体的形貌与粒度特征，实现了物料颗粒的均匀嵌锂，避免了固相法合成时存在的局部富锂/贫锂与结块问题，保证了质量一致性，提高了产品的克容量与循环性能。同时，与固相法合成工艺比较，本方法简化了混合与二次焙烧工艺，缩短了高温焙烧时间，降低了能源消耗，提高了焙烧设备的产能。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本发明实施例1中四氧化三锰原材料、预嵌锂中间体与锰酸锂产品的XRD比较图。
图2为本发明实施例1中四氧化三锰原材料的微观形貌SEM图。
图3为本发明实施例1中预嵌锂中间体的微观形貌SEM图。
图4为本发明实施例1中锰酸锂产品的微观形貌SEM图。
图5为本发明实施例2的预嵌锂中间体在氮气中的TG-DSC图。
图6为本发明实施例2的预嵌锂中间体在氧气中的TG-DSC图。
图7为本发明实施例3中四氧化三锰原材料的粒度分布图。
图8为本发明实施例3中预嵌锂中间体的粒度分布图。
图9为本发明实施例3中锰酸锂产品的粒度分布图。
图10为本发明实施例1中预嵌锂中间体的XRD图。
图11为本发明实施例2中预嵌锂中间体的XRD图。
图12为本发明实施例3中预嵌锂中间体的XRD图。
图13为本发明实施例4中预嵌锂中间体的XRD图。
图14为本发明实施例2中前驱体四氧化三锰材料颗粒剖切SEM图。
图15为本发明实施例2中预嵌锂中间体的微观形貌SEM图。
图16为本发明实施例2中预嵌锂中间体材料颗粒剖切SEM图。
图17为本发明实施例2中锰酸锂产品颗粒剖切SEM图。
图18为现有固相法制备的锰酸锂产品颗粒剖切SEM图。
图19为本发明各实施例的预嵌锂中间体的XRD对比图。
具体实施方式
为了便于理解本发明，下文将结合说明书附图和较佳的实施例对本发明做更全面、细致地描述，但本发明的保护范围并不限于以下具体实施例。
除非另有定义，下文中所使用的所有专业术语与本领域技术人员通常理解含义相同。本文中所使用的专业术语只是为了描述具体实施例的目的，并不是旨在限制本发明的保护范围。
除非另有特别说明，本发明中用到的各种原材料、试剂、仪器和设备等均可通过市场购买得到或者可通过现有方法制备得到。
以下实施例中：锂元素含量的检测采用ICP-AES方法，锰元素含量的检测采用硫酸亚铁铵滴定法(见GB/T21836-2008附录A)。
以下实施例中，扣电性能的检测方法可以为：按锰酸锂：PVDF：石墨：乙炔黑＝9:0.6:0.2:0.2配比，以金属锂片作为负极制作成CR2016扣式电池，在25℃温度环境、3.0V～4.3V充放电区间进行电性能测试，先检测0.2C首次、再进行1C(设定锰酸锂材料1C＝120mA/g)循环。
实施例1：
一种本发明的四氧化三锰预嵌锂中间体的制备方法，包括以下步骤：
按四氧化三锰∶水的固液质量比1:5的比例，将1000g锰含量为69.2％、粒度D50为11.4μm的球形四氧化三锰与310g粒径小于1mm、含量为56.5％的氢氧化锂(单水氢氧化锂)及5L纯水，加入到10L容积的衬镍压力反应釜中，接入高压氧气，向压力反应釜内通氧气是连续进行，且从反应物料开始升温时就进行通氧，通氧前对压力反应釜内进行排空气操作；在釜内温度210℃、釜内表压为2.5MPa压力下搅拌反应5小时，然后冷却降温至80℃以下后，移出反应产物，进行抽滤得到预嵌锂中间体。
经检测，预嵌锂中间体湿料的含水率为21％，其粒度D50为11.6μm，将滤饼于120℃下干燥24小时，干燥后的干料的锂含量为4.46％、锰含量为61.5％。
将300g上述制备的预嵌锂中间体干料(或湿料)平铺于刚玉匣钵内，置于空气气氛炉中，以大于5℃/min的升温速度升温至750℃后保温5小时，然后断电冷却至100℃以下后出炉，将物料过120目筛得到304g(选用湿料则为240g)锰酸锂正极材料。经检测，锰酸锂正极材料的粒度D50为12.1μm，锂含量为4.35％，锰含量为60.1％，锂锰摩尔比为0.57:1。
通过XRD图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品，其XRD图如图1、图10所示。该图1的锰酸锂产品的XRD表明，产物为纯锰酸锂，无杂相，该图10的XRD表明，预嵌锂中间体产品是由Mn 3O 4相与Li 2MnO 3相构成。
通过粒度分布图比较，本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品发现，预嵌锂中间体产品(其粒度D50为11.6μm)和四氧化三锰原材料(其粒度D50为11.4μm)的粒度分布基本一致，而最终制备得到的锰酸锂正极材料也基本沿袭了预嵌锂中间体产品和四氧化三锰原材料的粒度分布，其粒度D50为12.1μm。
通过微观形貌的SEM图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品，如图2～图4所示，四氧化三锰原材料、预嵌锂中间体产品和最终制备的锰酸锂产品的形貌均为规则的球形颗粒，微观形貌良好，产品均匀性和一致性好。
基于以上的检测及分析，我们认为上述实施例制备得到了一种四氧化三锰预嵌锂中间体，其包括四氧化三锰相和预嵌的锂元素，锂元素是以锂锰氧化物(Li 2MnO 3)相包覆或嵌入到四氧化三锰相中，预嵌锂中间体中预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致(为0.57:1，具体参见下表1)。通过比较前驱体四氧化三锰、预嵌锂中间体与所合成的锰酸锂材料，可以说明预嵌锂中间体合成时通入的氧使锰元素得到了氧化。
表1：本实施例中前驱体、中间体及锰酸锂的产品组分配比变化
Figure PCTCN2022092208-appb-000003
Figure PCTCN2022092208-appb-000004
本实施例最终制备得到的锰酸锂产品的化学式为Li 1.14Mn 2O 4。
将上述制备得到的锰酸锂进行扣电检测：
检测结果如下：
0.2C克容量113mAh/g，1C容量112mAh/g，25℃循环50次，容量保持率95％，循环100次，容量保持率92％。
实施例2：
一种本发明的四氧化三锰预嵌锂中间体的制备方法，包括以下步骤：
按四氧化三锰∶水的固液质量比1:2的比例，将3000g锰含量约为69.8％、粒度D50为8.1μm的球形四氧化三锰与899g粒径小于1mm、含量为56.5％的氢氧化锂及6L纯水，加入到10L容积的衬镍压力反应釜中，接入高压氧气，向压力反应釜内通氧气是连续进行，且从反应物料开始升温时就进行通氧，通氧前对压力反应釜内进行排空气操作；在釜内温度160℃、釜内表压为0.6MPa压力下搅拌反应10小时，然后冷却降温至80℃以下后，移出反应产物，进行抽滤得到预嵌锂中间体湿料。
经检测，预嵌锂中间体湿料的含水率为20.5％，其粒度D50为9.4μm，将其干燥后的干料的锂含量为4.49％、锰含量为60.9％。
将300g上述制备的预嵌锂中间体干料(或湿料)平铺于刚玉匣钵内，置于空气气氛炉中，以大于5℃/min的升温速度升温至790℃后保温5小时，然后断电冷却至100℃以下后出炉，将物料过120目筛得到307g(选择湿料时为244g)锰酸锂正极材料。经检测，锰酸锂正极材料的粒度D50为9.5μm，锂含量为4.40％，锰含量为59.6％，锂锰摩尔比为0.58:1。
图11是本实施例预嵌锂中间体的XRD图，其表明预嵌锂中间体产品是由Mn 3O 4相与Li 2MnO 3相构成。
通过粒度分布图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品发现，预嵌锂中间体产品(其粒度D50为9.4μm)和四氧化三锰原材料(其粒度D50为8.1μm)的粒度分布基本一致，而最终制备得到的锰酸锂正极材料也基本沿袭了预嵌锂中间体产品和四氧化三锰原材料的粒度分布，其粒度D50为9.5μm。
通过微观形貌的SEM图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品，四氧化三锰原材料、预嵌锂中间体产品和最终制备的锰酸锂产品的形貌均为规则的球形颗粒，微观形貌良好，产品均匀性和一致性好。
基于以上的检测及分析，我们将本实施例的预嵌锂中间体样品在氮气环境下进行差热扫描后发现，在420℃以前失重不到2％，说明结构水含量低(参见图5)；而将其在氧气环境中进行差热扫描，在250℃～613℃之间，质量增加约2％(参见图6)，说明中间体吸氧的结果，这表明尽管在预嵌锂中间体合成过程中通入了氧气，但氧元素并没有足量到位，需要在后续的晶体结构转化过程中进行补充。
我们认为上述实施例制备得到了一种四氧化三锰预嵌锂中间体，其包括四氧化三锰相和预嵌的锂元素，锂元素是以锂锰氧化物(Li 2MnO 3)相包覆或嵌入到四氧化三锰相中，预嵌锂中间体中预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致(为0.58:1，具体参见下表2)。
另外，通过对比本实施例制备得到的四氧化三锰预嵌锂中间体和四氧化三锰的剖切电镜图(参见图14-图16)，我们发现预嵌锂中间体的外层明显生成了不同于内核层的晶体状物质(即锂锰氧化物相)，而内核层则与四氧化三锰相基本一致，这进一步证实了本实施例预嵌锂中间体包覆型结构的形成。
本实施例最终制备得到的锰酸锂产品的化学式为Li 1.16Mn 2O 4。通过比较前驱体四氧化三锰、预嵌锂中间体与所合成的锰酸锂材料也可以粗略判断锰元素被氧化的程度。另外，通过图17、图18所示的锰酸锂材料剖切SEM图的比较可以发现，四氧化三锰预嵌锂中间体制得的锰酸锂正极材料，其微观颗粒保持了前驱体的形貌，粒度分布上也保持了前驱体的分布特性，实现了物料颗粒的均匀嵌锂，避免了已有常规固相法合成时存在的局部富锂/贫锂与结块问题，焙烧完成后，物料颜色均匀、蓬松易碎，不需要进行破碎，适合直接进行过筛处理，且活性孔丰富，更有利于提升电化学性能。
表2：本实施例中前驱体、中间体及锰酸锂的产品组分配比变化
Figure PCTCN2022092208-appb-000005
将上述制备得到的锰酸锂进行扣电检测：
检测结果如下：
0.2C克容量110mAh/g，1C容量109mAh/g，25℃循环50次，容量保持率98％，100次容量保持率97％。
实施例3：
一种本发明的四氧化三锰预嵌锂中间体的制备方法，包括以下步骤：
按四氧化三锰∶水的固液质量比1:3的比例，将1000g锰含量为70.1％、粒度D50为9.7μm的球形四氧化三锰与310g粒径小于1mm、含量为56.5％的氢氧化锂及3L纯水，加入到5L容积的衬镍压力反应釜中，接入高压氧气，向压力反应釜内通氧气是连续进行，且从反应物料开始升温时就进行通氧，通氧前对压力反应釜内进行排空气操作；在釜内温度180℃、釜内表压为2.0MPa压力下搅拌反应7小时，然后冷却降温至80℃以下后，移出反应产物，进行抽滤得到预嵌锂中间体湿料，并将滤饼于120℃干燥24小时得到预嵌锂中间体干料。
经检测，预嵌锂中间体的粒度D50为10.2μm，将其干燥后的干料的锂含量为4.32％、锰含量为61.8％。
将500g上述制备的预嵌锂中间体干料平铺于莫来石匣钵内，置于空气气氛炉中，以大于5℃/min的升温速度升温至750℃后保温5小时，然后断电冷却至100℃以下后出炉，将物料过120目筛得到503g锰酸锂正极材料。经检测，锰酸锂正极材料的粒度D50为11.1μm，锂含量为4.21％，锰含量为59.9％，锂锰摩尔比为0.55:1。
图12是本实施例的预嵌锂中间体的XRD图，其表明预嵌锂中间体产品是由Mn 3O 4相与Li 2MnO 3相构成。
通过粒度分布图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品发现(参见图7、图8和图9)，预嵌锂中间体产品(其粒度D50为10.2μm)和四氧化三锰原材料(其粒度D50为9.7μm)的粒度分布基本一致，而最终制备得到的锰酸锂正极材料也基本沿袭了预嵌锂中间体产品和四氧化三锰原材料的粒度分布，其粒度D50为11.1μm。
通过微观形貌的SEM图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品，四氧化三锰原材料、预嵌锂中间体产品和最终制备的锰酸锂产品的形貌均为规则的球形颗粒，微观形貌良好，产品均匀性和一致性好。
基于以上的检测及分析，我们认为上述实施例制备得到了一种四氧化三锰预嵌锂中间体，其包括四氧化三锰相和预嵌的锂元素，锂元素是以锂锰氧化物(Li 2MnO 3)相包覆或嵌入到四氧化三锰相中，预嵌锂中间体中预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致(为0.55:1，具体参见下表3)。通过比较前驱体四氧化三锰、预嵌锂中间体与所合成的锰酸锂材料可以粗略判断锰元素被氧化。
表3：本实施例中前驱体、中间体及锰酸锂的产品组分配比变化
Figure PCTCN2022092208-appb-000006
本实施例最终制备得到的锰酸锂产品的化学式为Li 1.1Mn 2O 4。
将上述制备得到的锰酸锂进行扣电检测：
检测结果如下：
0.2C克容量115mAh/g，1C容量114mAh/g，25℃循环50次，容量保持率95％，100次容量保持率91％。
实施例4：
一种本发明的四氧化三锰预嵌锂中间体的制备方法，包括以下步骤：
按四氧化三锰∶水的固液质量比1:2.5的比例，将2000g锰含量为70.1％、粒度D50为10.4μm的球形四氧化三锰与606g粒径小于1mm、含量为56.5％的氢氧化锂及5L纯水，加入到10L容积的衬镍压力反应釜中，接入高压氧气，向压力反应釜内通氧气是连续进行，且从反应物料开始升温时就进行通氧，通氧前对压力反应釜内进行排空气操作；在釜内温度180℃、釜内表压为2.0MPa压力下搅拌反应6小时，然后冷却降温至80℃以下后，移出反应产物，进行抽滤得到预嵌锂中间体湿料，并将滤饼于120℃干燥24小时得到预嵌锂中间体干料。
经检测，预嵌锂中间体的粒度D50为9.9μm，锂含量为4.27％、锰含量为62.0％。
将500g上述制备的预嵌锂中间体干料平铺于莫来石匣钵内，置于空气气氛炉中，以大于5℃/min的升温速度升温至790℃后保温5小时，然后断电冷却至100℃以下后出炉，将物料过120目筛得到515g锰酸锂正极材料。经检测，锰酸锂正极材料的粒度D50为10.9μm，锂含量为4.16％，锰含量为60.2％，锂锰摩尔比为0.54:1。
图13是本实施例的预嵌锂中间体的XRD图，其表明预嵌锂中间体产品是由Mn 3O 4相与Li 2MnO 3相构成。
通过粒度分布图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品发现，预嵌锂中间体产品(其粒度D50为9.9μm)和四氧化三锰原材料(其粒度D50为10.4μm)的粒度分布基本一致，而最终制备得到的锰酸锂正极材料也基本沿袭了预嵌锂中间体产品和四氧化三锰原材料的粒度分布，其粒度D50为10.9μm。
通过微观形貌的SEM图比较本实施例中四氧化三锰原材料、制备的预嵌锂中间体产品和最终制备的锰酸锂产品，四氧化三锰原材料、预嵌锂中间体产品和最终制备的锰酸锂产品的形貌均为规则的球形颗粒，微观形貌良好，产品均匀性和一致性好。
基于以上的检测及分析，我们认为上述实施例制备得到了一种四氧化三锰预嵌锂中间体，其包括四氧化三锰相和预嵌的锂元素，锂元素是以锂锰氧化物(Li 2MnO 3)相包覆或嵌入到四氧化三锰相中，预嵌锂中间体中预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致(为0.54:1，具体参见下表4)。通过比较前驱体四氧化三锰、预嵌锂中间体与所合成的锰酸锂材料也可以粗略判断锰元素被氧化，说明预嵌锂中间体合成时通入的氧使锰元素得到了部分氧化。
表4：本实施例中前驱体、中间体及锰酸锂的产品组分配比变化
Figure PCTCN2022092208-appb-000007
本实施例最终制备得到的锰酸锂产品的化学式为Li 1.08Mn 2O 4。
将上述制备得到的锰酸锂进行扣电检测：
检测结果如下：
0.2C克容量121mAh/g，1C容量120mAh/g，25℃循环50次，容量保持率94％，100次容量保持率91％。
如图19所示，为以上各实施例的预嵌锂中间体的XRD对比图，由图19可见，尽管预嵌锂的量有所不同，但各中间体的XRD图均具有共同的特征峰，均含有Mn 3O 4相与Li 2MnO 3相，且主要的预嵌锂中间体的XRD衍射图谱中2θ在18.5°±0.5°处有一强度大于600cps的衍射峰；2θ在44.5°±0.5°处有一强度大于400cps或至少大于200cps的衍射峰，2θ在58°～66°范围内至少有3-4个强度在80-260cps范围内的衍射峰。

Claims (16)

  1. 一种四氧化三锰预嵌锂中间体，其特征在于，所述预嵌锂中间体包括四氧化三锰相和预嵌的锂元素，所述锂元素是以锂锰氧化物相包覆或嵌入到四氧化三锰相中，所述预嵌锂中间体中预嵌的锂元素与其中的锰元素的摩尔比与基于该预嵌锂中间体制备的目标锰酸锂材料中的锂元素与锰元素化学计量比保持一致。
  2. 根据权利要求1所述的四氧化三锰预嵌锂中间体，其特征在于，所述锂锰氧化物相中锰的价态高于四氧化三锰中的锰的平均价态。
  3. 根据权利要求2所述的四氧化三锰预嵌锂中间体，其特征在于，所述锂锰氧化物包含Li 2MnO 3。
  4. 根据权利要求1所述的四氧化三锰预嵌锂中间体，其特征在于，所述预嵌锂中间体的XRD衍射图谱中2θ在18.5°±0.5°处有一强度大于600cps的衍射峰；2θ在44.5°±0.5°处有一强度大于200cps的衍射峰，2θ在58°～66°范围内至少有三个强度在80-260cps范围内的衍射峰。
  5. 根据权利要求1～4中任一项所述的四氧化三锰预嵌锂中间体，其特征在于，所述预嵌锂中间体是四氧化三锰与锂源在通氧条件下经过水热反应后制备得到。
  6. 一种四氧化三锰预嵌锂中间体的制备方法，包括以下步骤：
    将四氧化三锰、锂源、水投入压力反应釜中，在通氧条件下，控制釜内温度在100℃以上，釜内表压在0.1MPa以上，搅拌条件下反应充分完全，得到预嵌锂中间体；
    所述锂源的投入量是根据该预嵌锂中间体制备的目标锰酸锂材料中锂元素与锰元素化学计量比来确定。
  7. 根据权利要求6所述的制备方法，其特征在于，所述锂源为氢氧化锂。
  8. 根据权利要求7所述的制备方法，其特征在于，所述氢氧化锂选用粒径小于10mm的颗粒料。
  9. 根据权利要求6～8中任一项所述的制备方法，其特征在于，所述四氧化三锰与水的质量比控制在1∶0.3～10。
  10. 根据权利要求6～8中任一项所述的制备方法，其特征在于，所述釜内温度控制在110℃～250℃，反应时间控制在4～12小时。
  11. 根据权利要求6～8中任一项所述的制备方法，其特征在于，所述压力釜内表压控制在0.2～5.0MPa，且通入氧气后釜内压力超过相应釜内温度下水蒸汽的饱和蒸气压。
  12. 根据权利要求6～8中任一项所述的制备方法，其特征在于，向所述压力反应釜内通氧气是连续进行，且从反应物料开始升温时就进行通氧，通氧前对压力反应釜内进行排空气操作。
  13. 一种权利要求1～5中任一项所述的四氧化三锰预嵌锂中间体的应用，将所述预嵌锂 中间体的干料或湿料在有氧气氛下进行焙烧，焙烧完全并完成晶体结构转化后，得到尖晶石型锰酸锂正极材料。
  14. 根据权利要求13所述的应用，其特征在于，选择所述预嵌锂中间体的湿料进行焙烧，且所述湿料的含水率在30％以下。
  15. 根据权利要求13～14中任一项所述的应用，其特征在于，所述焙烧的焙烧温度为700℃～850℃，焙烧的时间为3～10小时。
  16. 根据权利要求13～14中任一项所述的应用，其特征在于，通过以大于5℃/分钟的升温速率快速升温至所述的焙烧温度范围。
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