A lithium-rich manganese-based positive electrode material, a preparation method, a battery positive electrode and a battery

Abstract

This invention provides a lithium-rich manganese-based cathode material, a preparation method, a battery cathode, and a battery, comprising: mixing citric acid, a lithium source, a nickel source, a cobalt source, a manganese source, and a dopant source to form a first mixed solution, wherein the dopant source is composed of a sodium source and / or a potassium source; drying the first mixed solution after the reaction to obtain a first precursor; sintering the first precursor to obtain a first powder; mixing the first powder with citric acid and then sintering to obtain the lithium-rich manganese-based cathode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-rich manganese-based cathode materials, and in particular to a lithium-rich manganese-based cathode material, its preparation method, a battery cathode, and a battery. Background Technology

[0002] Lithium-ion batteries, as an important energy supply device, are widely used in various portable devices and large-scale energy storage devices due to their advantages such as low self-discharge, high energy density, and good safety performance. Among them, lithium-rich manganese-based materials are considered one of the most valuable and promising cathode materials for lithium-ion batteries due to their high reversible cycle capacity, high operating voltage, low production cost, and environmental friendliness.

[0003] However, lithium-rich manganese-based materials are prone to irreversible oxygen loss, transition metal migration, lithium-nickel mixing, and electrolyte decomposition under high voltage during charge and discharge, resulting in voltage hysteresis and rapid capacity decay, exhibiting poor cycle stability and rate performance.

[0004] Doping modification is recognized as a simple yet important method to improve the structural stability of cathode materials. Successful doping can effectively suppress Li / Ni mixing and stabilize the crystal structure of the material, thereby improving overall performance. However, elemental doping only targets internal material modification and has limited protective effect on the material surface. Therefore, doping has a relatively limited effect on improving the performance of lithium-rich manganese-based materials. Summary of the Invention

[0005] Therefore, it is necessary to address the issue that the performance improvement of lithium-rich manganese-based cathode materials through doping is limited, and to provide a lithium-rich manganese-based cathode material, its preparation method, battery cathode, and battery.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing a lithium-rich manganese-based cathode material includes:

[0008] Citric acid, lithium source, nickel source, cobalt source, manganese source and dopant source are mixed to form a first mixture, wherein the dopant source is composed of sodium source and / or potassium source;

[0009] The first mixture after the reaction is completed is dried to obtain the first precursor;

[0010] The first precursor is sintered to obtain the first powder.

[0011] The first powder is mixed with citric acid and then sintered to obtain a lithium-rich manganese-based cathode material.

[0012] The temperature at which the first mixture is dried in this invention is 230-270℃.

[0013] The sintering temperature of the first powder and citric acid in this invention is 250-350℃.

[0014] The mass ratio of the first powder to citric acid in this invention is 80:20-90:10.

[0015] The first powder of this invention is sintered with citric acid in an inert gas atmosphere.

[0016] A lithium-rich manganese-based cathode material was obtained through a preparation method.

[0017] The chemical formula of this invention is Li 1.194 Na x K y Ni 0.13 Co 0.13 Mn 0.54 x + y = 0.006.

[0018] A battery cathode, comprising a lithium-rich manganese-based cathode material.

[0019] A battery, including a positive electrode.

[0020] The beneficial effects of the present invention include at least one of the following:

[0021] 1. Lithium-rich manganese-based cathode materials, through doping with potassium and / or sodium, enable lithium batteries to have better electrical performance;

[0022] 2. Citric acid in the first mixture acts as a complexing agent, and citric acid acts as a coating agent when the first powder and citric acid are sintered, thereby enhancing the protection of the particle surface of the lithium-rich manganese-based cathode material, inhibiting the occurrence of side reactions, stabilizing the crystal structure, and improving the electrochemical performance and thermal stability of the cathode material particle surface. Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0024] Example 1:

[0025] This embodiment provides a lithium-rich manganese-based cathode material with the chemical formula:

[0026] Li 1.194 Na x K y Ni 0.13 Co 0.13Mn 0.54 , where x≥0, y≥0, x+y=0.006.

[0027] More specifically, in this embodiment, x = 0.06 and y = 0.

[0028] Correspondingly, the preparation method of the lithium-rich manganese-based cathode material in this embodiment includes the following steps:

[0029] Step S1: Prepare a 0.5 mol / L citric acid aqueous solution, and under stirring conditions, use Li 1194 Na 0006 Ni 013 Co 013 Mn 054 Lithium hydroxide (lithium source), nickel acetate tetrahydrate (nickel source), cobalt acetate tetrahydrate (cobalt source), manganese acetate tetrahydrate (manganese source), and sodium citrate (sodium source) are added in a molar ratio to form a first mixture, wherein the total concentration of metal ions in the first mixture is 1 mol / L.

[0030] Step S2: After the first mixture has reacted completely, it is transported to a centrifugal spray dryer for spray drying. The solvent is completely evaporated to form the first precursor. The inlet air temperature of the centrifugal spray dryer is T1, and the outlet air temperature is 105℃.

[0031] In this embodiment, T1 = 200℃.

[0032] Step S3: Transfer the first precursor to a kiln and sinter it in an air atmosphere to convert the first precursor into the first powder. The sintering process is as follows: first, heat the material to 350°C at a heating rate of 3°C / min, then hold it at that temperature for 3 hours, then heat the material to 950°C at a heating rate of 5°C / min, and then hold it at that temperature for 9 hours.

[0033] Step S4: The first powder is placed in a mixer, and then citric acid powder is added and stirred until uniform. The mass ratio of the first powder to citric acid is a. The mixture of the first powder and citric acid is then sintered at a temperature T2 and under a nitrogen atmosphere for 3 hours. In this embodiment, T2 = 300℃ and a = 90:10.

[0034] Step S5: The sintered product is placed in an air jet mill to disperse it, and then sieved to obtain Li. 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0035] Example 2:

[0036] The difference between this embodiment and Embodiment 1 is that T1 = 230℃.

[0037] Example 3:

[0038] The difference between this embodiment and Embodiment 1 is that T1 = 250℃.

[0039] Example 4:

[0040] The difference between this embodiment and Embodiment 1 is that T1 = 270℃.

[0041] Comparative Example 1:

[0042] The difference between this comparative embodiment and Embodiment 1 is that: the first mixture does not contain citric acid, and step S4 is omitted; the first powder is directly placed into an air jet mill for dispersion, and then sieved to obtain Li. 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0043] The Li prepared in Comparative Example 1 and Examples 1-4 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 Conductive agent (SP) and binder (PVDF) were mixed in a mass ratio of 8:1:1, and NMP was added to prepare a slurry. The slurry was coated onto aluminum foil and dried at 100°C. Then, the foil was sliced, rolled, and stamped to form the positive electrode of the battery. A lithium metal sheet was used as the negative electrode, with DMC / EC / DEC = 1 / 1 / 1 (1 mol / L LiPF6), and the cells were assembled to form a button cell. The charge / discharge voltage range of the button cell is 2-4.8V. The test performance of the button cell is shown in Table 1.

[0044] Table 1

[0045]

[0046] By comparing Example 1 and Example 2, it can be seen that adding citric acid to the first mixture and coating the first powder with citric acid has a comprehensive effect on improving battery performance. Furthermore, the performance of the batteries in Examples 2-4 is superior to that of the battery in Example 1 in all aspects. Further comparison of the battery performance in Examples 1-4 shows that the rate performance and initial coulombic efficiency of the batteries in Examples 2 and 3 are superior to those in Examples 1 and 4. Example 3 exhibits the best rate performance at 0.1C, while Example 2 exhibits the best rate performance at 5C. However, conversely, Example 2 has the best initial coulombic efficiency, while Example 3 has the best capacity retention rate after 200 cycles at 1C. The difference in battery performance in Examples 1-4 is most likely due to the different T1 values, which cause changes in the size of the first precursor and subsequent first powder, resulting in variations in the coating thickness of the first powder in step S4 under the same mass of citric acid coating. Therefore, it can be understood that by doping lithium-rich manganese-based cathode materials with Na and adjusting T1, the battery can achieve maximum improvement in at least one of the following parameters: rate performance, initial coulombic efficiency, and capacity retention after 200 cycles at 1C.

[0047] Example 5:

[0048] The difference between this embodiment and Embodiment 3 is that T2 = 350℃.

[0049] Example 6:

[0050] The difference between this embodiment and Embodiment 3 is that T2 = 400℃.

[0051] Comparative Example 2:

[0052] The difference between this comparative embodiment and Embodiment 3 is that step S4 is omitted; instead, the first powder is directly placed into an air jet mill for dispersion, and then sieved to obtain Li. 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0053] Comparative Example 3:

[0054] The difference between this comparative example and Example 3 is that the first mixture does not contain citric acid.

[0055] The Li prepared in Examples 5 and 6 and Comparative Examples 2 and 3 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 Button batteries were prepared using the same method as in Examples 1-4, and the test performance of the button batteries is shown in Table 2.

[0056] Table 2

[0057]

[0058] First, by comparing Examples 1, 2, and 3, it can be seen that whether only citric acid is included in the first mixture or only citric acid is used to coat the first powder, both methods have a comprehensive improvement effect on battery performance, but the improvement effect is very limited. However, by comparing Examples 2, 3, and 3, it can be seen that by simultaneously using citric acid in the first mixture and citric acid coating the first powder, the battery performance is further improved, and the improvement effect is significant, indicating that the inclusion of citric acid in the first mixture and the citric acid coating of the first powder have a strong synergistic effect on improving battery performance. Furthermore, by comparing Examples 3 and 5, it can be seen that when T2 is increased from 300℃ to 350℃, most of the battery performance is slightly improved again, with only a slight decrease in the initial coulombic efficiency, indicating that citric acid coating has a good inhibitory effect on the surface side reactions of the lithium-rich manganese-based cathode material. However, in Example 6, as T2 was heated to 400°C, most of the battery’s performance began to decline. This may be because the excessively high temperature caused the carbonization film of citric acid to gradually break down, and the coating effect on the surface of the lithium-rich manganese-based cathode material began to decrease.

[0059] Example 7:

[0060] The difference between this embodiment and embodiment 5 is that a = 95:5.

[0061] Example 8:

[0062] The difference between this embodiment and Embodiment 5 is that a = 97:3.

[0063] The Li prepared in Examples 7 and 8 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 Button batteries were prepared using the same method as in Examples 1-4, and the test performance of the button batteries is shown in Table 3.

[0064] Table 3

[0065]

[0066] Comparing Examples 5, 7, and 8, the thickness of the coating film formed by citric acid gradually decreased, and its shielding effect on the first powder gradually decreased, resulting in a slight improvement in rate performance and initial coulombic efficiency. However, its protective effect on the first powder, specifically in inhibiting the surface alkali content and the occurrence of side reactions, decreased, thus reducing its capacity retention.

[0067] Example 9:

[0068] The difference between this embodiment and Embodiment 5 is that x = 0 and y = 0.06. In the first mixture, sodium citrate is replaced with potassium citrate (potassium source), corresponding to the obtained Li... 1.194 K 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0069] Comparative Example 4:

[0070] The difference between Comparative Example 4 and Example 9 is that the first mixture does not contain citric acid, and step S4 is omitted. The first powder is directly placed into an air jet mill for dispersion, and then sieved to obtain Li. 1.194 K 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0071] The Li prepared in Example 9 and Comparative Example 4 1.194 K 0.006 Ni 0.13 Co 0.13 Mn 0.54 Button batteries were prepared using the same method as in Examples 1-4, and the test performance of the button batteries is shown in Table 4.

[0072] Table 4

[0073]

[0074] Based on the comparison of battery performance in Example 9 and Comparative Example 4, it can be seen that using a first mixture containing citric acid and citric acid-coated first powder can improve the performance of Li. 1.194 K 0.006 Ni 0.13 Co 0.13 Mn 0.54 The prepared battery also achieved a significant improvement in electrical performance, with the improvement being comparable to that of Li. 1.194 Na 0.006 Ni 0.13 Co 0.13 Mn 0.54 The situation is similar.

[0075] Comparative Example 5:

[0076] The difference between this embodiment and Embodiment 9 is that potassium citrate in the first mixture is replaced with cesium acetate, resulting in the corresponding Li 1.194 Cs 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0077] Comparative Example 6:

[0078] The difference between this comparative example and Comparative Example 5 is that the first mixture does not contain citric acid, and step S4 is omitted. The first powder is directly placed into an air jet mill for dispersion, and then sieved to obtain Li. 1.194 Cs 0.006 Ni 0.13 Co 0.13 Mn 0.54 .

[0079] The Li prepared in Comparative Examples 5 and 6 1.194 Cs 0.006 Ni 0.13 Co 0.13 Mn 0.54 Button batteries were prepared using the same method as in Examples 1-4, and the test performance of the button batteries is shown in Table 5.

[0080] Table 5

[0081]

[0082] Comparing Examples 5 and 6, it can be seen that the coating effect of citric acid on Li 1.194 Cs 0.006 Ni 0.13 Co 0.13 Mn 0.54 For the prepared batteries, the improvement in electrical performance is very limited, especially in terms of capacity retention after 200 cycles at 1C. This indicates that citric acid has a very limited effect on the Li-C mixture in the first mixture. 1.194 Cs 0.006 Ni 0.13 Co 0.13 Mn 0.54 Modification and Li 1.194 Cs 0.006 Ni 0.13 Co 0.13 Mn 0.54 The two functions of coating have almost no significant impact on battery performance, or there may be some conflict between the two functions.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a lithium-rich manganese-based cathode material, characterized in that, include: Citric acid, lithium source, nickel source, cobalt source, manganese source and dopant source are mixed to form a first mixture, wherein the dopant source is composed of sodium source and / or potassium source; The first mixture after the reaction is completed is dried to obtain the first precursor; The first precursor is sintered to obtain the first powder. The first powder is mixed with citric acid and then sintered to obtain a lithium-rich manganese-based cathode material. The temperature for drying the first mixture is 230-270℃; The sintering temperature for the first powder and citric acid is 250-350℃; The mass ratio of the first powder to citric acid is 80:20-90:

10.

2. The method for preparing lithium-rich manganese-based cathode material according to claim 1, characterized in that, The first powder and citric acid are sintered in an inert gas atmosphere.

3. A lithium-rich manganese-based cathode material, characterized in that, Obtained by the preparation method described in any one of claims 1-2.

4. The lithium-rich manganese-based cathode material according to claim 3, characterized in that, The chemical formula is Li 1.194 Na x K y Ni 0.13 Co 0.13 Mn 0.54 x + y = 0.

006.

5. A battery positive electrode, characterized in that, Including the lithium-rich manganese-based cathode material as described in claim 3.

6. A battery, characterized in that, Includes the battery positive electrode as described in claim 5.

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