A monoclinic phase layered lithium manganate and a method for preparing the same

Abstract

The application provides a monoclinic phase layered lithium manganate and a preparation method thereof, wherein the monoclinic phase layered lithium manganate is subjected to XRD test using CuK alpha rays, a first diffraction peak corresponding to a (001) crystal plane appears at 18.3+ / -1.0 degrees, the peak intensity is I(001), a second diffraction peak corresponding to a (201) crystal plane appears at 33.0+ / -1.0 degrees, the peak intensity is I(201), and 0.10 + Mn dissolution caused by Jahn-Teller distortion phenomenon in the process of embedding / extraction; a high monoclinic layered LiMnO2 structure is formed through sintering, the lithium-manganese mixing degree is reduced, and the capacity is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium manganese oxide technology, and particularly relates to a monoclinic layered lithium manganese oxide and its preparation method. Background Technology

[0002] Whether it's new energy vehicles or various portable electronic devices, they all rely on the development and support of lithium-ion battery technology. Lithium-ion batteries have expanded from their initial applications in the 3C (computer, communication, and consumer electronics) field to include energy storage, power, and other areas, achieving significant progress. Cathode materials are one of the key materials in the manufacture of lithium-ion batteries, accounting for approximately 40% of the total cell cost.

[0003] Currently, manganese-based cathode materials, as one of the lithium-ion cathode materials, have advantages such as being non-toxic and low-cost, and have broad application prospects in the 3C and two-wheeled vehicle markets. The currently used product on the market is spinel-type LiMn2O4, which has a lithium-deficient structure and a theoretical capacity of 148 mAh / g. However, after doping and modification, the actual capacity is difficult to exceed 130 mAh / g.

[0004] Layered LiMnO2, as another manganese-based material, boasts higher energy density and theoretical capacity compared to spinel-type LiMn2O4, and is considered one of the most promising cathode materials. Layered LiMnO2 is a homogeneous polycrystalline compound with both orthorhombic and monoclinic structures. The orthorhombic phase is thermodynamically more stable, while the monoclinic phase exhibits better electrochemical activity, but its synthesis requires stringent conditions. Numerous methods exist for synthesizing layered LiMnO2, including hydrothermal synthesis, sol-gel synthesis, solid-state synthesis, molten salt synthesis, and ion exchange. Among these methods, monoclinic LiMnO2 is typically prepared using ion exchange, but this method is cumbersome, costly, and difficult to industrialize. Hydrothermal and molten salt methods require excessive amounts of lithium source, which is not atom-economical. Solid-state synthesis of LiMnO2, usually in the orthorhombic phase, has not yet been reported for industrialization, and even kilogram-scale samples are not readily available on the market.

[0005] In manganese-based cathode materials, common examples include spinel LiMn₂O₄ and layered LiMnO₂, both containing Mn(III). Due to its high spin properties, Mn(III) exhibits a strong Jahn-Teller effect, leading to distorted crystal structures and significantly reduced material stability. Furthermore, the disproportionation reaction of Mn(III) causes Mn to dissolve in the electrolyte—a manganese leaching problem. Mn(III) is the root cause of manganese leaching. Solutions typically involve using lower-valence metals, such as Ni(II), to increase the valence of some Mn(IV). Mn(IV) is spinless and stable, thus mitigating leaching. However, in layered LiMnO₂, the Jahn-Teller effect of Mn(III) is significant, inevitably causing severe manganese leaching. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a monoclinic layered lithium manganese oxide with higher capacity and reduced manganese dissolution.

[0007] Correspondingly, this invention also provides a method for preparing the above-mentioned monoclinic layered lithium manganese oxide. To solve the above technical problems, the technical solution proposed by this invention is as follows:

[0008] A monoclinic layered lithium manganese oxide, wherein the monoclinic layered lithium manganese oxide is subjected to CuKα XRD testing, and a first diffraction peak corresponding to the (001) crystal plane appears at 18.3 ±1.0° with a peak intensity of I(001), and a second diffraction peak corresponding to the (201) crystal plane appears at 33.0 ±1.0° with a peak intensity of I(201), and 0.10 < I(201) / I(001) < 0.20.

[0009] Preferably, the monoclinic layered lithium manganese oxide exhibits a third diffraction peak corresponding to the (010) crystal plane at 15.3±1.0°, with a peak intensity of I(010) and 0<I(010) / I(001)<0.25.

[0010] Preferably, the monoclinic layered lithium manganese oxide is mainly composed of 80wt-100wt% monoclinic phase and 0-20wt% orthorhombic phase.

[0011] Preferably, the chemical formula of the monoclinic layered lithium manganese oxide is Li. n Mn a M b O 2-c Z c, 0.80≤n≤1.2, 0.8≤a≤1.2, 0≤b≤0.1, 0≤c≤0.05, and 0.80≤n / (a+b)≤1.20, M is the doped metal element, and Z is the doped non-metal element.

[0012] Preferably, M is one or more of Ni, Co, Al, Mg, Ca, Na, Ti, Zr, Sc, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo, and B.

[0013] Preferably, Z is one or more of P, S, Cl, and F.

[0014] Preferably, the monoclinic layered lithium manganese oxide has a D50 particle size of 1 μm-20 μm and a specific surface area of ​​0.1-2.0 m². 2 / g.

[0015] As a general inventive concept, this invention provides a method for preparing monoclinic layered lithium manganese oxide, comprising the following steps:

[0016] (1) Weigh the lithium source, manganese source and dopant according to the designed molar ratio, mix them with deionized water to obtain a slurry with a solid content of 10%-70%, stir and grind, and control the viscosity of the slurry and the particle size of the particles in the slurry.

[0017] (2) The slurry obtained in step (1) is spray-dried at a certain temperature and the powder is collected;

[0018] (3) A protective gas is introduced, and the material is pulverized after high-temperature solid-state sintering to obtain the product.

[0019] Preferably, in step (1), the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium peroxide, and lithium nitrate, and the manganese source is at least one of manganese oxide, manganese carbonate, and manganese oxyhydroxide. The dopant includes at least one of M source and Z source. The M source is a compound or compound containing one or more elements selected from Ni, Co, Al, Mg, Ca, Na, Ti, Zr, Sc, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo, and B. The Z source is a compound or compound containing one or more elements selected from P, S, Cl, and F.

[0020] Preferably, in step (1), the viscosity of the slurry after grinding at room temperature is controlled to be 100 Pa·s-10000 Pa·s, and the D50 particle size of the slurry particles is controlled to be 0.1 μm-3.0 μm.

[0021] Preferably, in step (3), the sintering temperature is 800℃-1100℃ and the time is 5h-30h.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The layered lithium manganese oxide of the present invention suppresses the growth of the (201) crystal plane, thereby reducing I(201) / I(001), and can effectively improve the performance of Li during charging and discharging. + Mn dissolution is caused by Jahn-Teller distortion during the insertion / extraction process; at the same time, as the sintering temperature increases, lithium and manganese atoms gradually diffuse and separate into layers, forming a monoclinic layered LiMnO2 structure, which reduces the lithium-manganese mixing degree and effectively improves the capacity.

[0024] (2) The present invention premixes the raw materials and then performs wet grinding to achieve uniform mixing of the materials. After spray drying and granulation, the lithium source, manganese source and dopant are uniformly dispersed. The granulated particles have a large specific surface area and good particle size uniformity, which greatly improves the reactivity of the material. In addition, the introduction of a specific amount of dopant can also stabilize the formation of metastable monoclinic phase, suppress the I(010) / I(001) value, and is more conducive to the formation of monoclinic phase, thus improving the electrochemical activity of the material.

[0025] (3) The monoclinic layered LiMnO2 material of the present invention has a high solid-state sintering temperature, and the finished product has a single crystal round morphology. The material has a small specific surface area, which reduces the side reaction with the electrolyte and is beneficial to reducing Mn dissolution.

[0026] (4) In the process of preparing monoclinic layered LiMnO2 material in this invention, compared with the traditional ion exchange method and hydrothermal method, the grinding and spray drying equipment is mature, the cost is significantly reduced, and it is easy to realize industrialization. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a scanning electron microscope image of the monoclinic layered LiMnO2 prepared in Example 1;

[0029] Figure 2 This is a scanning electron microscope image of the orthorhombic layered LiMnO2 prepared in Comparative Example 2;

[0030] Figure 3 EPMA image of monoclinic layered LiMnO2 prepared in Example 1;

[0031] Figure 4These are the XRD patterns of the layered LiMnO2 prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0032] Figure 5 This is a graph showing the initial charge capacity of the layered LiMnO2 prepared in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0033] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0034] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0036] Example 1:

[0037] A monoclinic layered lithium manganese oxide with the molecular formula LiMn 0.97 Al 0.03 O2, this monoclinic layered lithium manganese oxide was XRDed using CuKα radiation, X-ray source The first diffraction peak corresponding to the (001) crystal plane appears at 18.3±1.0°, with a peak intensity of I(001). The second diffraction peak corresponding to the (201) crystal plane appears at 33.0±1.0°, with a peak intensity of I(201). I(201) / I(001)=0.1362. The monoclinic layered lithium manganese oxide exhibits a third diffraction peak corresponding to the (010) crystal plane at 15.3±1.0°, with a peak intensity of I(010). (010) / I(001)=0.0597. (Specific details are as follows...) Figure 4 As shown. (Through) Figure 4 The XDR data shown was refined to reveal that the monoclinic layered lithium manganese oxide accounted for 94.7%.

[0038] The preparation method of the above-mentioned monoclinic layered lithium manganese oxide includes the following steps:

[0039] (1) Weigh 4000g of Mn3O4, 2137g of LiOH·H2O and 98.5g of dopant Al2O3 respectively, and put them into a mixing tank containing 16L of deionized water to make the solid content 28%. Premix at 500 rpm for 1h, control the ratio of grinding zirconia beads to material to be 10:1, and introduce the material in the mixing tank into the grinding equipment for stirring and grinding for 4h to prepare a sand grinding slurry with a D50 particle size of 0.30μm and a viscosity of 2200Pa.S. The slurry is loaded into the container and prepared for the next spray drying process.

[0040] (2) Set the air inlet temperature of the spray dryer to 250℃ and the air outlet temperature to 120℃. Spray dry the slurry obtained in step (1). After spray drying, collect the spray-dried powder. The powder D50 is 11.30μm. Prepare for the next sintering process.

[0041] (3) The spray-dried powder obtained in step (2) is packed into a mortar with holes and placed into a box furnace. After purging with a large amount of nitrogen for 1 hour, the nitrogen flow rate is reduced to a small amount. The temperature is increased to 970°C at a rate of 2.5°C / min and held for 20 hours. After cooling, the powder is removed from the furnace and crushed and sieved to obtain brown monoclinic layered lithium manganese oxide, i.e. monoclinic layered LiMnO2.

[0042] like Figure 1 As shown in the image, scanning electron microscopy reveals that the monoclinic layered LiMnO2 material exhibits a smooth, blocky morphology with uniform particle distribution, a D50 particle size of 9.90 μm, and a specific surface area of ​​0.43 m². 2 / g. The elemental distribution of doped elements in monoclinic layered LiMnO2 was analyzed using EPMA technology, such as... Figure 3 As shown, the results indicate that Al is uniformly distributed and not enriched in monoclinic layered LiMnO2 materials.

[0043] Button charge test: At 25℃ and a voltage range of 3.0-4.3V, 0.1C charging was performed, and the charging platform was around 4.0V. The results showed that the charging capacity reached 238.8mAh / g at 0.1C. After storage at 80℃ for 40h, the Mn dissolution was 0.038%.

[0044] Example 2:

[0045] A monoclinic layered lithium manganese oxide with the molecular formula LiMn 0.97 Al 0.03 O 1.99 F 0.01 The monoclinic layered lithium manganese oxide was subjected to XRD testing using CuKα radiation. The first diffraction peak corresponding to the (001) crystal plane appears at 18.3±1.0°, with a peak intensity of I(001). The second diffraction peak corresponding to the (201) crystal plane appears at 33.0±1.0°, with a peak intensity of I(201), and I(201) / I(001) = 0.1612. The monoclinic layered lithium manganese oxide exhibits a third diffraction peak corresponding to the (010) crystal plane at 15.3±1.0°, with a peak intensity of I(010), and I(010) / I(001) = 0.0990. After XDR data refinement, the proportion of monoclinic layered lithium manganese oxide is found to be 81.4%.

[0046] The preparation method of the above-mentioned monoclinic layered lithium manganese oxide includes the following steps:

[0047] (1) Weigh 4000g of Mn3O4, 2161.9g of LiOH·H2O and 126.2g of dopant Al(OH)3 respectively, and put them into a mixing tank containing 14L of deionized water. The solid content is 30.69%. Premix at 500 rpm for 1h. Control the ratio of grinding zirconia beads to material to be 10:1. After the material in the mixing tank is introduced into the grinding equipment and stirred and ground for 4h, a sand-milled slurry is prepared with a D50 particle size of 1.5μm and a viscosity of 1200Pa.S. The slurry is loaded into a container and prepared for the next spray drying process.

[0048] (2) Set the air inlet temperature of the spray dryer to 250℃ and the air outlet temperature to 120℃. Spray dry the slurry obtained after step (1). After spray drying, collect the spray-dried powder. The powder D50 is 18.30μm. Prepare for the next sintering process.

[0049] (3) The spray-dried powder obtained in step (2) is packed into a mortar, punched, and placed into a box furnace. After purging with a large volume of nitrogen for 1 hour, a small volume of nitrogen is then introduced. The temperature is raised to 970°C at a rate of 2.5°C / min and held for 16 hours. After cooling, the powder is removed from the furnace. The material is then crushed and sieved to obtain brown monoclinic layered lithium manganese oxide, i.e., monoclinic layered LiMnO2.

[0050] Scanning electron microscopy revealed that the monoclinic layered LiMnO2 exhibited a smooth, blocky morphology with uniform particle distribution, a D50 particle size of 10.40 μm, and a specific surface area of ​​0.37 m². 2 / g. The elemental distribution of doped elements in monoclinic layered LiMnO2 was analyzed by EPMA technology. The results showed that Al and F elements were uniformly distributed and not enriched in the monoclinic layered LiMnO2 cathode material.

[0051] Button charge test: Under the conditions of 25℃ and voltage range of 3.0-4.3V, 0.1C charging was performed, and the charging platform was around 4.0V. The results showed that the charging capacity reached 235.2mAh / g at 0.1C. After storage at 80℃ for 40h, the Mn dissolution was 0.046%.

[0052] Example 3:

[0053] A monoclinic layered lithium manganese oxide with the molecular formula LiMn 0.97 Al 0.03 O2. This monoclinic layered lithium manganese oxide was subjected to XRD analysis using CuKα radiation. The radiation source... The first diffraction peak corresponding to the (001) crystal plane appears at 18.3±1.0°, with a peak intensity of I(001). The second diffraction peak corresponding to the (201) crystal plane appears at 33.0±1.0°, with a peak intensity of I(201), and I(201) / I(001) = 0.1374. The monoclinic layered lithium manganese oxide exhibits a third diffraction peak corresponding to the (010) crystal plane at 15.3±1.0°, with a peak intensity of I(010), and I(010) / I(001) = 0.0560. After XDR data refinement, the proportion of monoclinic layered lithium manganese oxide is found to be 94.7%.

[0054] The preparation method of the monoclinic layered lithium manganese oxide described above differs from that in Example 1 in that the raw materials used are 4000g of Mn2O3, 2135.3g of LiOH·H2O, and 98.5g of dopant Al2O3. All other steps are the same as in Example 1.

[0055] Scanning electron microscopy (SEM) revealed that the monoclinic layered LiMnO2 morphology consisted of smooth, small, uniformly distributed particles with a D50 particle size of 10.70 μm. EPMA analysis of the elemental distribution of dopants in the monoclinic layered LiMnO2 showed that Al was uniformly distributed without enrichment in the cathode material.

[0056] Button charge test: Under the conditions of 25℃ and voltage range of 3.0-4.3V, 0.1C charging was performed, and the charging platform was around 4.0V. The results showed that the charging capacity reached 220.3mAh / g at 0.1C. After storage at 80℃ for 40h, the Mn dissolution was 0.053%.

[0057] Comparative Example 1:

[0058] Layered LiMnO2 material without wet grinding and spray drying processes was prepared according to Example 1, with the molecular formula LiMn 0.97 Al 0.03 O2, the preparation method of which includes the following steps:

[0059] 4000g of Mn3O4, 2161.9g of LiOH·H2O and 98.5g of dopant Al(OH)3 were weighed and mixed evenly by dry method. The material was placed in a mortar with holes punched in it and then placed in a box furnace. A large volume of nitrogen was introduced to purge the material for 1 hour. Then, a small volume of nitrogen was introduced and the temperature was raised to 970℃ at a rate of 2.5℃ / min and held for 20 hours. After cooling, the material was removed from the furnace, crushed and sieved to obtain brownish-green highly orthorhombic layered LiMnO2.

[0060] Scanning electron microscopy revealed that the sintered orthorhombic layered LiMnO2 exhibited a coexistence of elongated and cylindrical morphologies, with uniform particle distribution, a D50 particle size of 18.3 μm, and a specific surface area of ​​0.44 m². 2 / g. XRD test, radiation source I(010) / I(001)=0.8281, I(201) / I(001)=0.2341, such as Figure 4 As shown.

[0061] pass Figure 4 The XDR data shown was refined to reveal that the monoclinic layered lithium manganese oxide accounted for only 54.7%.

[0062] The elemental distribution of doped elements in layered LiMnO2 was analyzed by EPMA technology. The results showed that Al was uniformly distributed and not enriched in the highly orthorhombic layered LiMnO2 cathode material.

[0063] Button charge test: Under the conditions of 25℃ and voltage range of 3.0-4.3V, 0.1C charging was performed, and the results showed that the charging capacity at 0.1C was only 168mAh / g.

[0064] Comparative Example 2:

[0065] Prepare undoped layered LiMnO2 material with the molecular formula Li 1.01 Mn 0.99 O2, the preparation method of which includes the following steps:

[0066] (1) Weigh 4000g of Mn3O4 and 2137g of LiOH·H2O respectively, put them into a mixing tank containing 16L of deionized water, with a solid content of 27.7%, premix at 500 rpm for 1h, control the ratio of grinding zirconia beads to material to be 8:1, and then introduce the material in the mixing tank into the grinding equipment for grinding for 3h to prepare a sand grinding slurry with a D50 particle size of 2.5μm and a viscosity of 1000Pa.S. The slurry is then loaded into a container and prepared for the next spray drying process.

[0067] (2) Set the inlet temperature of the spray dryer to 240℃ and the outlet temperature to 115℃, and spray dry the slurry obtained in step (1). After spray drying, collect the spray-dried powder with a D50 of 17.30μm, and prepare it for the next sintering process.

[0068] (3) The spray-dried powder obtained in step (2) is packed into a box furnace, punched, and then purged with a large amount of nitrogen for 1 hour. Then, the nitrogen flow rate is reduced to a small amount, and the temperature is raised to 880°C at a rate of 2.5°C / min and held for 20 hours. After cooling, the powder is removed from the furnace, crushed, and sieved to obtain brown orthorhombic layered LiMnO2.

[0069] Scanning electron microscopy (SEM) images of the above-mentioned orthorhombic layered LiMnO2 are shown below. Figure 2 As shown, the morphology is elongated, with uniform particle distribution, a D50 particle size of 13.3 μm, and a specific surface area of ​​0.62 m². 2 / g. XRD test, radiation source I(010) = 1743, with no peaks at (001) and (201), as shown in the figure. Figure 4 As shown.

[0070] pass Figure 4 The XDR data shown was refined to reveal that layered lithium manganese oxide is an orthorhombic phase, while monoclinic layered lithium manganese oxide accounts for only 0%.

[0071] Button charge test: Under the conditions of 25℃ and voltage range of 3.0-4.3V, 0.1C charging was performed, and the charging platform was around 3.6V. The results show that the charging capacity of 0.1C is only 203.1mAh / g.

[0072] The initial charge capacity curves of the layered LiMnO2 prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention are all as shown in the figure. Figure 5 As shown.

Claims

1. A monoclinic layered lithium manganese oxide, characterized in that, The monoclinic layered lithium manganese oxide was XRDed using CuKα rays. The first diffraction peak corresponding to the (001) crystal plane appeared at 18.3±1.0° with a peak intensity of I(001), and the second diffraction peak corresponding to the (201) crystal plane appeared at 33.0±1.0° with a peak intensity of I(201). 0.10<I(201) / I(001)<0.20; The monoclinic layered lithium manganese oxide exhibits a third diffraction peak corresponding to the (010) crystal plane at 15.3±1.0°, with a peak intensity of I(010), 0<I(010) / I(001)<0.25; The chemical formula of the monoclinic layered lithium manganate is Li n Mn a M b O 2-c Z c , 0.80 ≤ n ≤ 1.2, 0.8 ≤ a ≤ 1.2, 0 < b ≤ 0.1, 0 ≤ c ≤ 0.05, and 0.80 ≤ n / (a + b) ≤ 1.20, M is a doped metal element, and Z is a doped non-metal element.

2. The monoclinic layered lithium manganese oxide according to claim 1, characterized in that, The monoclinic layered lithium manganese oxide is mainly composed of 80wt-100wt% monoclinic phase and 0-20wt% orthorhombic phase.

3. The monoclinic layered lithium manganese oxide according to claim 1, characterized in that, M is one or more of Ni, Co, Al, Mg, Ca, Na, Ti, Zr, Sc, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo, and B.

4. The monoclinic layered lithium manganese oxide according to claim 1, characterized in that, Z can be one or more of P, S, Cl, and F.

5. The monoclinic layered lithium manganese oxide according to claim 1, characterized in that, The monoclinic layered lithium manganese oxide has a D50 particle size of 1 μm-20 μm and a specific surface area of ​​0.1-2.0 m². 2 / g.

6. A method for preparing monoclinic layered lithium manganese oxide as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Weigh the lithium source, manganese source and dopant according to the designed molar ratio, mix them with deionized water to obtain a slurry with a solid content of 10%-70%, stir and grind, and control the viscosity of the slurry and the particle size of the particles in the slurry. (2) The slurry obtained after step (1) is spray-dried at a certain temperature and the powder is collected; (3) A protective gas is introduced, and the material is pulverized after high-temperature solid-state sintering to obtain the product.

7. The preparation method according to claim 6, characterized in that, In step (1), the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium peroxide and lithium nitrate, and the manganese source is at least one of manganese oxide, manganese carbonate and manganese oxyhydroxide.

8. The preparation method according to claim 6, characterized in that, In step (1), the viscosity of the slurry after grinding at room temperature is controlled to be 100 Pa·s-10000 Pa·s, and the D50 particle size of the slurry particles is controlled to be 0.1 μm-3.0 μm.

9. The method for preparing monoclinic layered lithium manganese oxide according to claim 6, characterized in that, In step (3), the sintering temperature is 800℃-1100℃ and the time is 5h-30h.

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