A lithium-rich lithium manganate, a preparation method and application thereof

Abstract

The application provides a lithium-rich lithium manganate, a preparation method and application thereof, and belongs to the field of lithium batteries. The application provides a preparation method of the lithium-rich lithium manganate, which comprises the following steps: mixing lithium oxide, manganese monoxide and tetravalent metal oxide, and then sintering to obtain the lithium-rich lithium manganate. The introduced tetravalent metal ions can improve structural stability, improve cycle performance, increase the average valence of transition metal oxides, inhibit cation mixing and irreversible phase transition (such as H2-H3 phase transition of nickel-rich materials and Jahn-Teller distortion of manganese-based materials) in the charging and discharging process, thereby significantly improving the long cycle stability of the material. In addition, the electronic and ionic transport kinetics can be optimized, and the rate performance can be improved. The introduction of tetravalent metal can adjust the electronic structure of the material, reduce the band gap, and improve the electronic conductivity of the material, thereby reducing the charge transfer resistance and improving the large-current charging and discharging performance.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, specifically to a lithium-rich manganese oxide, its preparation method, and its applications. Background Technology

[0002] A common problem with lithium-ion batteries is that during the initial charge, a large amount of lithium ions released from the positive electrode are consumed to form the SEI film on the negative electrode surface; secondly, lithium-ion batteries continue to consume active lithium during normal use. This leads to a decrease in the initial capacity of the cell and a reduction in battery life. To address the phenomenon of reduced initial capacity and lifespan caused by the SEI film consuming active lithium in lithium-ion batteries, current solutions involve replenishing lithium lost during cycling through lithium replenishment technology.

[0003] Currently, there are two main methods for lithium replenishment technology: negative electrode lithium replenishment and positive electrode lithium replenishment. Negative electrode lithium replenishment is mainly achieved through metal-based lithium replenishment at the electrode end or chemical-based lithium replenishment at the material end. Electrode-based negative electrode lithium replenishment involves the use of flammable and explosive metallic lithium, posing a high safety risk. Chemical-based lithium replenishment at the material end is complex, and the materials are highly alkaline, making material processing difficult. Furthermore, material-based lithium replenishment damages the negative electrode structure, affecting cycle life. Overall, negative electrode lithium replenishment presents significant safety risks and complex processing challenges.

[0004] Compared to negative electrode lithium replenishment, positive electrode lithium replenishment is simpler. The lithium source is added during the positive electrode slurry mixing process, completely avoiding the safety and cost risks associated with negative electrode lithium replenishment. The positive electrode lithium replenishment process involves adding a small amount of high-capacity lithium-replenishing additive during the positive electrode slurry mixing process. During charging, excess lithium elements are extracted from these high-capacity positive electrode materials and intercalated into the negative electrode to replenish the irreversible capacity during the initial charge-discharge cycle. Currently, the most common positive electrode lithium-replenishing additives include Li₂NiO₂, Li₅FeO₄, Li₂MnO₃, and Li₆CoO₄, but the initial efficiency, energy density, and cycle performance of batteries prepared using these additives still need improvement. Summary of the Invention

[0005] This invention provides a lithium-rich manganese oxide, its preparation method, and its application. The lithium-rich manganese oxide prepared by this invention can effectively improve the first-stage efficiency, energy density, and cycle performance of the battery as a positive electrode lithium supplement, and the preparation cost is low.

[0006] This invention provides a method for preparing lithium manganese oxide rich in lithium, comprising the following steps: Lithium oxide, manganese monoxide, and tetravalent metal oxide are mixed and sintered to obtain lithium-rich manganese oxide.

[0007] Preferably, the molar ratio of lithium oxide to manganese monoxide is 2.7 to 6.5:1.

[0008] Preferably, the tetravalent metal oxide includes one or more of titanium dioxide, magnesium dioxide, and zirconium dioxide.

[0009] Preferably, the molar ratio of manganese monoxide to tetravalent metal oxide is 1 to 9:1.

[0010] Preferably, the mixing process includes ball milling lithium oxide, manganese monoxide, tetravalent metal oxide and dispersant, followed by drying of the resulting slurry.

[0011] Preferably, the ball milling is performed in a high-energy ball mill; The ball mill operates at a speed of 500-2000 r / min for 5-15 h.

[0012] Preferably, the sintering temperature is 600~900℃ and the time is 10~18h.

[0013] Preferably, the rate of heating to the sintering temperature is 0.5~5℃ / min.

[0014] The present invention also provides lithium manganese oxide rich in lithium prepared by the preparation method described in the above technical solution.

[0015] This invention also provides the application of the lithium-rich manganese oxide described in the above technical solution in the field of lithium batteries.

[0016] The tetravalent metal ions introduced in this invention can enhance structural stability, improve cycling performance, and increase the average valence state of transition metal oxides, suppressing cation mixing and irreversible phase transitions during charge and discharge (such as the H2-H3 phase transition in nickel-rich materials and the Jahn-Teller distortion in manganese-based materials), thereby significantly improving the long-cycle stability of the material (such as improving capacity retention). In addition, it can optimize electron and ion transport kinetics and improve rate performance: the introduction of tetravalent metals can adjust the electronic structure of the material, reduce the band gap, and increase the electronic conductivity of the material, thereby reducing charge transfer resistance and improving high-current charge and discharge performance (rate performance).

[0017] During the first charge, the formation of an SEI film on the negative electrode surface consumes a large amount of active lithium. The lithium-rich manganese oxide prepared in this invention, acting as a lithium replenishing agent for the positive electrode, releases additional lithium ions to compensate for this loss, significantly improving the battery's initial coulombic efficiency. The lithium ions released by the lithium replenishing agent participate in the redox reaction of the positive electrode, directly increasing the battery's first charge capacity and overall energy density, effectively compensating for the initial capacity loss caused by high-capacity negative electrodes (such as silicon-based ones). After releasing a large amount of lithium initially, its residue can still slowly release lithium ions in subsequent cycles, providing continuous compensation for lithium loss during long cycles and slowing down capacity decay. Manganese participates in providing high specific capacity (through the redox couple of manganese and anion redox). At the same time, by reducing the amount of expensive cobalt and nickel, the battery cost is effectively reduced, making it a potential material for future high-energy-density lithium batteries. Detailed Implementation

[0018] This invention provides a method for preparing lithium manganese oxide rich in lithium, comprising the following steps: Lithium oxide, manganese monoxide, and tetravalent metal oxide are mixed and sintered to obtain lithium-rich manganese oxide.

[0019] In this invention, the mixing preferably includes ball milling lithium oxide, manganese monoxide, tetravalent metal oxide and dispersant, and then drying the resulting slurry.

[0020] In this invention, the dispersant preferably comprises water and / or ethanol; the ball milling is preferably carried out in a high-energy ball mill.

[0021] In this invention, the preferred rotational speed of the ball mill is 500~2000 r / min, and the preferred time is 5~15 h. In specific embodiments of this invention, the rotational speed can be 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1700 r / min, 1800 r / min, or 1900 r / min.

[0022] In this invention, the molar ratio of lithium oxide to manganese monoxide is preferably 2.7 to 6.5:1. In specific embodiments of this invention, it can be 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4:1, 4.1:1, 4.2:1, 4.3:1, 4.4:1, 4.5:1, 4.6:1, 4.7:1, 4.8:1, 4.9:1, 5:1, 5.1:1, 5.2:1, 5.3:1, 5.4:1, 5.5:1, 5.6:1, 5.7:1, 5.8:1, 5.9:1, 6:1, 6.1:1, 6.2:1, 6.3:1, or 6.4:1.

[0023] In this invention, the molar ratio of manganese monoxide to tetravalent metal oxide is preferably 1 to 9:1. In specific embodiments of this invention, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1. The tetravalent metal oxide preferably includes one or more of titanium dioxide, magnesium dioxide and zirconium dioxide.

[0024] In this invention, the sintering temperature is preferably 600~900℃, and the sintering time is preferably 10~18h. In specific embodiments of this invention, the sintering temperature can be 650℃, 700℃, 750℃, 800℃ or 850℃, and the sintering time can be 11h, 12h, 13h, 14h, 15h, 16h or 17h.

[0025] In this invention, the rate of heating to the sintering temperature is 0.5~5℃ / min, and in specific embodiments of this invention, it can be 1℃ / min, 2℃ / min, 3℃ / min or 4℃ / min.

[0026] In this invention, after sintering, the invention preferably further includes sieving the resulting product.

[0027] In this invention, the mesh size of the sieve used for sieving is preferably 400 mesh.

[0028] The present invention also provides lithium manganese oxide rich in lithium prepared by the preparation method described in the above technical solution.

[0029] This invention also provides the application of the lithium-rich manganese oxide described in the above technical solution in the field of lithium batteries.

[0030] In this invention, the lithium battery preferably includes a button cell or a pouch cell.

[0031] In a specific embodiment of the present invention, the method for preparing the coin cell is as follows: lithium manganese oxide rich in lithium, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) are weighed in a mass ratio of 8:1:1, mixed and homogenized, and then coated, baked, cold-pressed, cut and assembled into coin cells.

[0032] In this invention, the positive electrode active material of the soft-pack battery is a mixture of lithium-rich manganese oxide and lithium cobalt oxide; the mass ratio of lithium-rich manganese oxide to lithium cobalt oxide is preferably 0.03:1.

[0033] In this invention, the mass ratio of the mixture, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) in the positive electrode material of the pouch battery is 90:5:5.

[0034] In this invention, the negative electrode of the soft-pack battery is preferably graphite, CMC, SP (conductive carbon black), and SBR; the mass ratio of graphite, CMC, SP (conductive carbon black), and SBR is preferably 93.2:1.8:2.5:2.5.

[0035] In this invention, the electrolyte of the soft-pack battery preferably includes LiPF6, EC and DMC; the concentration of LiPF6 in the electrolyte is 1 mol / L, and the volume ratio of EC and DMC is preferably 1:1.

[0036] In this invention, the separator of the soft-pack battery is preferably a polypropylene microporous film.

[0037] The following detailed description, in conjunction with embodiments, illustrates the lithium-rich manganese oxide, its preparation method, and its applications provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1 A method for preparing lithium-rich manganese oxide, a lithium-ion battery cathode lithium supplement additive, comprising the following steps: (1) First, weigh 21.55g lithium oxide, 15g manganese monoxide, 1.89g titanium dioxide (Mn:Ti=9:1) and 50mL water into a high-energy ball mill, and then adjust the speed to 1800r / min and mix for 30min to obtain mixture 1; (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (2) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; Example 2 A method for preparing lithium-rich manganese oxide, a lithium-ion battery cathode lithium supplement additive, comprising the following steps: (1) First, weigh 27.71g lithium oxide, 15g manganese monoxide, 7.31g titanium dioxide (Mn:Ti=7:3) and 50mL anhydrous ethanol and place them in a high-energy ball mill. Then, adjust the speed to 1800r / min and mix for 30min to obtain mixture 1. (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (3) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; Example 3 A method for preparing lithium-rich manganese oxide, a lithium-ion battery cathode lithium supplement additive, comprising the following steps: (1) First, weigh 32.33g lithium oxide, 15g manganese monoxide, 11.37g titanium dioxide (Mn:Ti=6:4) and 50mL water into a high-energy ball mill, and then adjust the speed to 1800r / min and mix for 30min to obtain mixture 1; (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (3) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; Example 4 A method for preparing lithium-rich manganese oxide, a lithium-ion battery cathode lithium supplement additive, comprising the following steps: (1) First, weigh 38.8g lithium oxide, 15g manganese monoxide, 17.06g titanium dioxide (Mn:Ti=5:5) and 50mL water and put them into a high-energy ball mill. Then, adjust the speed to 1800r / min and mix for 30min to obtain mixture 1. (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (3) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; Example 5 A method for preparing lithium-rich manganese oxide, a lithium-ion battery cathode lithium supplement additive, comprising the following steps: (1) First, weigh 32.33g lithium oxide, 15g manganese monoxide, 4.25g magnesium dioxide (Mn:Mg=6:4) and 50mL water and put them into a high-energy ball mill. Then, adjust the speed to 1800r / min and mix for 30min to obtain mixture 1. (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (3) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; Example 6 A method for preparing lithium-rich manganese oxide, a lithium-ion battery cathode lithium supplement additive, comprising the following steps: (1) First, weigh 32.33g lithium oxide, 15g manganese monoxide, 7.26g zirconium dioxide (Mn:Zr=6:4) and 50mL water into a high-energy ball mill, and then adjust the speed to 1800r / min and mix for 30min to obtain mixture 1; (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (3) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; Comparative Example 1 (1) First, weigh 19.4g of lithium oxide, 15g of manganese monoxide and 50mL of water into a high-energy ball mill, and then adjust the speed to 1800r / min and mix for 30min to obtain mixture 1; (2) The mixture 1 was dried in a vacuum oven (110°C) to obtain solid 1; (3) The solid 1 obtained in step (2) is sintered in a tube furnace, and the temperature is raised to 850°C at a heating rate of 2°C / min and held for 15 hours to obtain solid 2. (4) Sieve solid 2 through a 400-mesh sieve to obtain solid 3; The lithium-rich manganese oxide prepared in the above examples and comparative examples was tested, and the testing process is as follows: The electrical performance of CR2032 coin cells was tested. The test procedure was as follows: First, the lithium-rich manganese oxide additive, carbon black, and PVDF were weighed in a mass ratio of 8:1:1, and then homogenized, coated, vacuum dried, cold-pressed, cut, and assembled into coin cells for testing. The coin cells were charged to 4.3V at a constant current and constant voltage of 0.1C. The specific capacity results are shown in Table 1.

[0039] The lithium-rich manganese oxide additive prepared above was mixed with commercially available cathode material lithium cobalt oxide at a weight ratio of 0.03:1. Then, the cathode material was prepared by mixing the mixture of lithium-rich manganese oxide and lithium cobalt oxide by weight: conductive carbon black (SP): polyvinylidene fluoride (PVDF) = 90:5:5. The anode material was prepared by mixing graphite: CMC (sodium carboxymethyl cellulose thickener): SP (conductive carbon black): SBR (styrene-butadiene rubber water-based binder) = 93.2:1.8:2.5:2.5. The anode was prepared by mixing graphite: CMC (sodium carboxymethyl cellulose thickener): SP (conductive carbon black): SBR (styrene-butadiene rubber water-based binder) = 93.2:1.8:2.5:2.5. The electrolyte was 1 mol / L LiPF6 / EC-DMC (1:1), and the separator was a polypropylene microporous film.

[0040] The specific processes for battery manufacturing include: slurry homogenization, coating, rolling, cutting, stacking, tab welding, side and top sealing, baking, electrolyte injection, settling, formation, aging, and testing.

[0041] The assembled pouch cells were tested using the Xinwei Battery Testing System. The voltage window was 3.0-4.5V, and the cells were charged and discharged at 0.1C / 0.1C. The discharge specific capacity was recorded, and the initial charge and discharge efficiency and capacity retention rate after 50 cycles were calculated. The results are shown in Table 2.

[0042] Table 1. Capacity comparison of each embodiment and comparative example (4.3V)

[0043] Table 2 Charge-discharge test data for each embodiment and comparative example.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing lithium manganese oxide rich in lithium, characterized in that, Includes the following steps: Lithium oxide, manganese monoxide, and tetravalent metal oxide are mixed and sintered to obtain lithium-rich manganese oxide.

2. The preparation method according to claim 1, characterized in that, The molar ratio of lithium oxide to manganese monoxide is 2.7 to 6.5:

1.

3. The preparation method according to claim 1, characterized in that, The tetravalent metal oxide includes one or more of titanium dioxide, magnesium dioxide, and zirconium dioxide.

4. The preparation method according to claim 1 or 3, characterized in that, The molar ratio of manganese monoxide to tetravalent metal oxide is 1 to 9:

1.

5. The preparation method according to claim 1, characterized in that, The mixing process involves ball milling lithium oxide, manganese monoxide, tetravalent metal oxide and dispersant, followed by drying the resulting slurry.

6. The preparation method according to claim 5, characterized in that, The ball milling is carried out in a high-energy ball mill. The ball mill operates at a speed of 500-2000 r / min for 5-15 h.

7. The preparation method according to claim 1, characterized in that, The sintering temperature is 600~900℃ and the time is 10~18h.

8. The preparation method according to claim 1 or 7, characterized in that, The rate of heating to the sintering temperature is 0.5~5℃ / min.

9. Lithium manganese oxide rich in lithium prepared by the preparation method according to any one of claims 1 to 8.

10. The application of lithium-rich manganese oxide as described in claim 9 in the field of lithium batteries.

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