Lithium-rich manganese-based positive electrode material, preparation method thereof and lithium ion battery

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to a lithium-rich manganese-based positive electrode material, a preparation method thereof and a lithium ion battery. Mixing the precursor material of the lithium-rich manganese-based positive electrode material with a lithium source, and sintering; after sintering is finished, a sintered product is immediately put into deionized water at the temperature of 0-10 DEG C and stirred, after stirring is conducted for 3-10 min, solid-liquid separation is conducted, a solid phase is dried, and the lithium-rich manganese-based positive electrode material is obtained. And the sintering product is quenched, the amorphous interface morphology is formed on the secondary particle surface of the sintering product due to the huge temperature difference, and internal pores of the sintering product are greatly reduced or even completely eliminated. The amorphous interface morphology can improve the interface stability of the lithium-rich manganese-based positive electrode material, and the pore-less or pore-free internal structure can effectively improve the ion diffusion kinetics of the lithium-rich manganese-based positive electrode material. The material having an amorphous structure has an excellent capacity retention rate after undergoing an electrochemical cycle.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a lithium-rich manganese-based cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of lithium-ion batteries, high capacity has become one of the research and development directions of lithium-ion batteries. The energy density of lithium iron phosphate in the cathode material is 580 Wh / kg, the energy density of lithium nickel cobalt manganese oxide is 750 Wh / kg, while the energy density of the lithium-rich manganese-based cathode material is as high as 900 Wh / kg, making it a lithium-ion battery cathode material with great development potential. At the same time, the content of cobalt and nickel in the lithium-rich manganese-based cathode material is only about 30% of that of the ternary material, and it can also be cobalt-free, with a lower cost.

[0003] However, the lithium-rich manganese-based cathode material also has the following disadvantages: the first discharge efficiency is very low; oxygen evolution occurs during the cycling process, posing a safety hazard; the cycle life is very poor; and the rate performance is relatively low. To solve these problems, a large number of studies have been carried out by researchers. The main ideas are: obtaining a specific precursor material by regulating the preparation process of the precursor material of the lithium-rich manganese-based material, or regulating the sintering process of the precursor material. CN110323430A discloses a preparation method of a lithium-rich manganese-based material. A mixed metal salt solution of Mn 2+ and M 2+ , a complexing agent, a precipitating agent, and a reducing agent are mixed to prepare a lithium-rich manganese precursor; the washed and dried lithium-rich manganese precursor is mixed with a lithium source and sintered; wherein, M 2+ includes at least one of Ni 2+ and Co 2+ ; the reducing agent includes at least one of hydrazine hydrate, sulfite, and bisulfite; the complexing agent is at least one of an acid solution, a salt solution, ethylenediamine, and 2-methyl-8-hydroxyquinoline; this preparation method is easier to control the concentration of the reducing agent, so as to facilitate the preparation of a lithium-rich manganese-based material with better electrochemical performance. CN118206162A discloses a preparation method of a lithium-rich manganese-based cathode material. First, a nickel-manganese hydroxide precursor is subjected to a first sintering at 300 °C - 650 °C to obtain nickel-manganese oxide; then the nickel-manganese oxide is mixed evenly with a lithium salt and subjected to a second sintering to obtain the lithium-rich manganese-based cathode material; wherein, the second sintering includes the following process: heating from room temperature to a first plateau temperature at a first heating rate, then heating from the first plateau temperature to a second plateau temperature at a second heating rate; continuing to cool from the second plateau temperature to a third plateau temperature at a first cooling rate; finally cooling from the third plateau temperature to room temperature. This preparation method reduces the formation of the spinel phase, and the obtained lithium-rich manganese-based cathode material has better consistency and stability, higher mechanical strength, can achieve a higher tap density, and improves the battery capacity.

[0004] Other preparation or modification ideas for lithium-rich manganese-based cathode materials are also the directions constantly explored by researchers. Summary of the Invention

[0005] The first object of the present invention is to provide a preparation method for a lithium-rich manganese-based cathode material.

[0006] The second object of the present invention is to provide a lithium-rich manganese-based cathode material.

[0007] The third object of the present invention is to provide a lithium-ion battery.

[0008] The present invention provides the following specific technical solutions.

[0009] First of all, the present invention provides a preparation method for a lithium-rich manganese-based cathode material, including: Mixing a precursor material of the lithium-rich manganese-based cathode material with a lithium source and sintering; After the sintering is completed, immediately put the sintered product into deionized water at a temperature of 0-10 °C and stir. After stirring for 3-10 minutes, perform solid-liquid separation and dry the solid phase to obtain the lithium-rich manganese-based cathode material.

[0010] In a further preferred embodiment, the chemical formula of the precursor material of the lithium-rich manganese-based cathode material is Mn x N y (OH)2, N is one or more of Ni, Co, Fe, Al, Zn, the value range of x is 0.5 ≤ x < 1, the value range of y is 0 < y ≤ 0.5, and x + y = 1.

[0011] In a further preferred embodiment, the lithium source is at least one of lithium oxide, lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.

[0012] In a further preferred embodiment, the molar ratio of lithium in the precursor material of the lithium-rich manganese-based cathode material to lithium in the lithium source is 1:1.12-1.48.

[0013] In a further preferred embodiment, the sintering temperature is 900-1100 °C and the sintering time is 10-30 h.

[0014] In a further preferred embodiment, the mass ratio of the sintered product to deionized water is 1:50-100.

[0015] Secondly, the present invention provides a lithium-rich manganese-based cathode material prepared by the above preparation method.

[0016] The present invention also provides a lithium-ion battery, including the aforementioned lithium-rich manganese-based cathode material.

[0017] One or more of the foregoing technical solutions of the present invention have at least one of the following beneficial effects: The residual lithium content of the prepared lithium-rich manganese-based cathode material is low; The preparation method is simple; After the prepared lithium-rich manganese-based cathode material is assembled into a battery, the capacity retention rate of the battery is significantly improved. Brief Description of the Drawings

[0018] Figure 1 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Example 1.

[0019] Figure 2 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 1.

[0020] Figure 3 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 2.

[0021] Figure 4 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 3.

[0022] Figure 5 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 4.

[0023] Figure 6 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 5.

[0024] Figure 7 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 6.

[0025] Figure 8 It is the HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 7. Detailed Description of the Embodiments

[0026] In a first aspect, some embodiments of the present invention provide a method for preparing a lithium-rich manganese-based cathode material, including: Mixing a precursor material of the lithium-rich manganese-based cathode material with a lithium source and sintering; After the sintering is completed, immediately put the sintered product into deionized water at a temperature of 0-10°C and stir. After stirring for 3-10 minutes, perform solid-liquid separation and dry the solid phase to obtain the lithium-rich manganese-based cathode material.

[0027] After the precursor material and the lithium source are mixed and sintered, the temperature of the obtained sintered product is relatively high. Immediately put the sintered product with a relatively high temperature into deionized water at a temperature of 0-10°C: First, the sintered product is quenched rapidly. The huge temperature difference causes an amorphous interfacial morphology to form on the surface of the secondary particles of the sintered product, and the internal pores of the sintered product are greatly reduced or even completely eliminated. The amorphous interfacial morphology can improve the interfacial stability of the lithium-rich manganese-based cathode material, and the less porous or pore-free internal structure can effectively improve the ion diffusion kinetics of the lithium-rich manganese-based cathode material.

[0028] Secondly, the sintered product is added to deionized water, and the temperature of the deionized water will also rise. The deionized water at a higher temperature is more likely to wash away the residual lithium in the sintered product.

[0029] The temperature of the deionized water cannot be lower than 0 °C, otherwise, the water will turn into ice and cannot contact the material well; the temperature of the deionized water cannot be higher than 10 °C either, otherwise, the temperature is too high to meet the cooling rate, so that an amorphous layer cannot be formed on the surface.

[0030] In addition, the stirring time after the sintered product and deionized water are mixed cannot be too long, and 3 - 10 min is better; if the time is too long, it will cause the lithium ions in the inner layer of the material to precipitate, affecting the crystal structure of the material.

[0031] It should be noted that: "immediately" mentioned in the present invention means that after sintering, the sintered product is added to deionized water in an extremely short time. The shorter this extremely short time is, the better. In the actual operation process, the temperature reduction amplitude before the sintered product is added to deionized water can also be controlled not to exceed 100 - 150 °C.

[0032] In some specific embodiments, the chemical formula of the precursor material of the lithium-rich manganese-based cathode material is Mn x N y (OH)₂, N is one or more of Ni, Co, Fe, Al, Zn, the value range of x is 0.5 ≤ x < 1, the value range of y is 0 < y ≤ 0.5, and x + y = 1.

[0033] In some specific embodiments, the lithium source is at least one of lithium oxide, lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate. Those skilled in the art can also select other conventional lithium sources in the art.

[0034] In some specific embodiments, the molar ratio of lithium in the precursor material of the lithium-rich manganese-based cathode material to the lithium in the lithium source is 1:1.12 - 1.48.

[0035] In some specific embodiments, the sintering temperature is 900 - 1100 °C, and the sintering time is 10 - 30 h. If the sintering temperature is too high, it is easy to cause irreversible changes in the crystal structure; if the sintering temperature is too low, a homogeneous lithium-rich manganese-based cathode material cannot be formed. The sintering time can be adjusted adaptively according to the sintering temperature.

[0036] In some specific embodiments, the mass ratio of the sintered product to deionized water is 1:50 - 100. If the amount of the sintered product is too large, some areas of the product will not be fully immersed in water; if the amount of deionized water is too large, it will cause waste of water resources and reduce the efficiency of removing residual lithium.

[0037] In a second aspect, some embodiments of the present invention provide a lithium-rich manganese-based cathode material prepared by the above preparation method.

[0038] In a third aspect, the present invention also provides a lithium-ion battery, including the aforementioned lithium-rich manganese-based cathode material.

[0039] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0040] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0041] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0042] Example 1 Mix 0.1 mol of Mn 0.67 Co 0.33 (OH)₂ with 0.123 mol of lithium hydroxide mechanically, then place the mixture in a muffle furnace and sinter it at a high temperature of 980 °C for 20 h. After the sintering is completed, immediately take out the sintered product from the muffle furnace and put it into 600 ml of deionized water at about 3 °C (this process is completed within 5 seconds), stir for 5 min, filter, and dry the solid phase obtained by filtration to obtain the lithium-rich manganese-based cathode material.

[0043] Figure 1 Figure HTEM of the lithium-rich manganese-based cathode material obtained in Example 1. It can be seen from the figure that there is an amorphous phase on the surface of the material.

[0044] Comparative Example 1 Mix 0.1 mol of Mn 0.67 Co 0.33 (OH)₂ with 0.123 mol of lithium hydroxide mechanically, then place the mixture in a muffle furnace and sinter it at a high temperature of 980 °C for 20 h. After the sintering is completed, cool it naturally to room temperature to obtain the lithium-rich manganese-based cathode material.

[0045] Figure 2HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 1. It can be seen from the figure that no amorphous layer is formed on the material surface.

[0046] Comparative Example 2 Mix 0.1 mol of Mn 0.67 Co 0.33 (OH)2 with 0.123 mol of lithium hydroxide mechanically, and then place the mixture in a muffle furnace and sinter at 980 °C for 20 h. After sintering, cool it naturally to room temperature, and then put it into 600 ml of deionized water at about 3 °C, stir for 5 min, filter, and dry the solid phase obtained by filtration to obtain the lithium-rich manganese-based cathode material.

[0047] Figure 3 HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 2. It can be seen from the figure that no amorphous layer is formed on the material surface.

[0048] Comparative Example 3 Mix 0.1 mol of Mn 0.67 Co 0.33 (OH)2 with 0.123 mol of lithium hydroxide mechanically, and then place the mixture in a muffle furnace and sinter at 980 °C for 20 h. After sintering, take out the sintered product from the muffle furnace and purge it with an inert gas to cool it rapidly. After cooling to room temperature, the lithium-rich manganese-based cathode material is obtained.

[0049] Figure 4 HTERM diagram of the lithium-rich manganese-based cathode material obtained in Comparative Example 3. It can be seen from the figure that no amorphous layer is formed on the material surface.

[0050] Comparative Example 4 Mix 0.1 mol of Mn 0.67 Co 0.33 (OH)2 with 0.123 mol of lithium hydroxide mechanically, and then place the mixture in a muffle furnace and sinter at 980 °C for 20 h. After sintering, take out the sintered product from the muffle furnace and purge it with an inert gas to cool it rapidly. After cooling to room temperature, put the sintered product into 600 ml of deionized water at about 3 °C, stir for 5 min, filter, and dry the solid phase obtained by filtration to obtain the lithium-rich manganese-based cathode material.

[0051] Comparative Example 5 The difference between this comparative example and Example 1 is only that: the temperature of the deionized water is 30 °C.

[0052] Comparative Example 6 The difference between this comparative example and Example 1 is only that: the temperature of the deionized water is 100 °C.

[0053] Comparative Example 7 The difference between this comparative example and Example 1 is only that: the stirring time of the sintered product in deionized water is 30 min.

[0054] Figure 5 、 Figure 6 、 Figure 7 are the HTERM diagrams of the Li-rich manganese-based cathode materials obtained from Comparative Example 5, Comparative Example 6, and Comparative Example 7, respectively. It can be seen that no amorphous layer is formed on the material surface.

[0055] Figure 8 is the HTERM diagram of the Li-rich manganese-based cathode material obtained from Comparative Example 7. It can be seen from the figure that although there is also an amorphous phase on the surface, due to the excessive extraction of Li inside, the overall crystallinity of the crystal decreases and the lattice fringes weaken.

[0056] Example 2 Mix 0.1 mol of Mn 0.75 Co 0.25 (OH)2 with 0.154 mol of lithium nitrate mechanically, and then place the mixture in a muffle furnace and sinter it at a high temperature of 900 °C for 30 h. After the sintering is completed, immediately take out the sintered product from the muffle furnace and put it into 528 ml of deionized water at about 10 °C (this process is completed within 5 seconds), stir for 8 min, filter, and dry the solid phase obtained by filtration to obtain the Li-rich manganese-based cathode material.

[0057] Example 3 Mix 0.1 mol of Mn 0.83 Co 0.17 (OH)2 with 0.12 mol of lithium oxide mechanically, and then place the mixture in a muffle furnace and sinter it at a high temperature of 1100 °C for 10 h. After the sintering is completed, immediately take out the sintered product from the muffle furnace and put it into 1257 ml of deionized water at about 8 °C (this process is completed within 5 seconds), stir for 3 min, filter, and dry the solid phase obtained by filtration to obtain the Li-rich manganese-based cathode material.

[0058] Example 4 Mix 0.1 mol of Mn 0.5 Co 0.5 (OH)2 with 0.188 mol of lithium acetate mechanically, and then place the mixture in a muffle furnace and sinter it at a high temperature of 1000 °C for 16 h. After the sintering is completed, immediately take out the sintered product from the muffle furnace and put it into 1000 ml of deionized water at about 5 °C (this process is completed within 5 seconds), stir for 4 min, filter, and dry the solid phase obtained by filtration to obtain the Li-rich manganese-based cathode material.

[0059] The residual lithium in the lithium-rich manganese-based cathode materials obtained in Examples 1-4 and Comparative Examples 1-7 was detected by the following method: GB / T 41704-2022. The results are shown in Table 1.

[0060] Table 1 Residual lithium content in the lithium-rich manganese-based cathode materials The lithium-rich manganese-based cathode materials obtained in Examples 1-4 and Comparative Examples 1-7 were assembled into batteries in the following manner: Weigh and grind according to the mass ratio of cathode material: conductive graphite: PVDF of 8:1:1, then add an appropriate amount of N-methylpyrrolidone (NMP) and continue to grind and stir to form a uniform slurry. Use a mold to uniformly coat the slurry on the aluminum foil with a coating thickness of 200 μm, and place it in a drying oven at 90 °C for 10 h, and then cut it into circular pieces with a diameter of 12 mm. Using the circular pieces as the positive electrode and lithium pieces as the negative electrode, the electrolyte includes a solvent and LiPF6, where the concentration of LiPF6 is 1 mol / L, and the solvent of the electrolyte is a mixed solvent of EC, DEC, and DMC with a volume ratio of 1:1:1. Assemble the battery in the order of button battery assembly in a glove box.

[0061] The assembled batteries were subjected to the following tests: Perform performance tests on the above-assembled batteries. Place the assembled batteries that have been left standing overnight in a LAND2001CT battery test chamber for charge-discharge tests, and conduct tests under the conditions of 25 °C, 1C, and a cycling voltage of 2-4V for 100 cycles. The test results can be seen in Table 2.

[0062] It can be seen from Table 2 that after process optimization, the material with an amorphous structure has the highest capacity retention rate after electrochemical cycling, proving that the material has the strongest structural stability and the best phase change reversibility.

[0063] Table 2 The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a lithium-rich manganese-based cathode material, characterized in that, Comprising: Mixing a precursor material of a lithium-rich manganese-based cathode material with a lithium source and sintering; After the sintering is completed, immediately put the sintered product into deionized water at a temperature of 0-10°C and stir. After stirring for 3-10 minutes, perform solid-liquid separation and dry the solid phase to obtain the lithium-rich manganese-based cathode material.

2. The preparation method of the lithium-rich manganese-based cathode material according to claim 1, characterized in that, The chemical formula of the precursor material of the lithium-rich manganese-based cathode material is Mn x N y (OH)2, where N is one or more of Ni, Co, Fe, Al, Zn, the value range of x is 0.5 ≤ x < 1, the value range of y is 0 < y ≤ 0.5, and x + y = 1.

3. The preparation method of the lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, The lithium source is at least one of lithium oxide, lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.

4. The preparation method of the lithium-rich manganese-based cathode material according to claim 3, wherein The molar ratio of lithium in the precursor material of the lithium-rich manganese-based cathode material to lithium in the lithium source is 1:1.12-1.

48.

5. The preparation method of the lithium-rich manganese-based cathode material according to claim 1, characterized in that, The sintering temperature is 900-1100°C, and the sintering time is 10-30 hours.

6. The preparation method of the lithium-rich manganese-based cathode material according to claim 1, characterized in that, The mass ratio of the sintered product to deionized water is 1:50-100.

7. A lithium-rich manganese-based cathode material, characterized in that, Prepared by the preparation method according to any one of claims 1-6.

8. A lithium-ion battery, characterized in that, Comprising the lithium-rich manganese-based cathode material according to claim 7.

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