A method and device for improving the surface residual alkali degree of a high-nickel ternary cathode material of a lithium ion battery

Abstract

The application provides a method for improving residual alkali degree of a high-nickel ternary positive electrode material of a lithium ion battery, which comprises: reacting residual alkali on the surface of the high-nickel ternary positive electrode material with gaseous water; and drying the obtained reaction product under vacuum. The treatment method provided by the application can make H2O molecules only react with the residual alkali on the surface of the high-nickel ternary positive electrode material, without entering the crystal lattice, so that the crystal structure of the material is maximally protected, the high-nickel ternary positive electrode material after treatment has the minimum surface side reaction, good electrical performance, and the cycle stability is greatly improved, and the cycle DCR growth is obviously inhibited.

Description

Technical Field

[0001] This invention belongs to the field of ternary cathode material technology, and particularly relates to a method and apparatus for improving the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries. Background Technology

[0002] Among ternary materials with different compositions, those with higher nickel content have higher capacity, but the lithium carbonate and lithium hydroxide impurities on their surface are more difficult to control, easily leading to excessive impurities. Regarding methods to reduce the surface activity and lithium carbonate and lithium hydroxide impurities in nickel-rich materials, currently available methods suggest that water washing is the most effective way to remove lithium impurities from the surface of nickel-rich materials. Generally, deionized water and high-nickel cathode material are mixed evenly in a certain proportion. Since the solubility of residual alkali is higher at low temperatures than at room temperature, stirring is performed at a low temperature of 5–10°C to dissolve as much of the residual alkali floating on the surface of the high-nickel cathode material as possible into the water. The mixture is then filtered and dried to remove moisture from the high-nickel cathode material, thus reducing the residual alkali content.

[0003] The existing method for washing high-nickel ternary materials typically involves placing the powdered high-nickel ternary cathode material in pure water and stirring for 5–20 minutes. The washed material is then dried at 120°C and subjected to a secondary calcination at 700°C. The pH value of the washed sample is significantly lower than that of the unwashed sample, indicating that washing plays a role in lowering the pH value. While washing can reduce residual lithium on the surface of the high-nickel ternary cathode material to some extent, the surface is unstable after washing. The lithium on the surface easily absorbs moisture and carbon sources from the surrounding environment, forming new residual lithium on the surface. This places very stringent requirements on the storage environment of the high-nickel material, resulting in a short shelf life. Furthermore, the specific surface area of ​​the washed and dried ternary material is significantly higher than that of the unwashed material, indicating that washing damages the surface structure of the high-nickel ternary material to some extent, leading to poorer cycle stability and a significant increase in cycle DCR. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method and apparatus for improving the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries. The method provided by the present invention can effectively reduce the residual alkalinity on the surface of high-nickel ternary cathode materials. In subsequent electrical performance tests, the surface side reactions are minimized, the electrical performance is better, the cycle stability is greatly improved, and the growth of cycle DCR is also significantly suppressed.

[0005] This invention provides a method for improving the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries, comprising:

[0006] The residual alkali and gaseous water on the surface of the high-nickel ternary cathode material react together.

[0007] The reaction products were dried under vacuum conditions.

[0008] Preferably, the gaseous water is obtained by placing liquid water in a vacuum environment.

[0009] Preferably, the vacuum degree of the vacuum condition is ≤5×10⁻⁶. -3 Pa.

[0010] Preferably, the vacuum level of the vacuum environment is ≤5×10⁻⁶. -3 Pa.

[0011] Preferably, the mass ratio of the high-nickel ternary cathode material to gaseous water is 100:(0.5-5).

[0012] Preferably, the reaction temperature is 5–10°C.

[0013] Preferably, the reaction time is 0.1 to 4 hours.

[0014] Preferably, the flow rate of the gaseous water is 5 to 200 sccm.

[0015] Preferably, the drying temperature is 100–400°C.

[0016] This invention provides a device for improving the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries, comprising:

[0017] The components include a magnetron sputtering vacuum chamber, a sample tray, heating elements, an inlet pipe, an inlet pipe flow valve, an exhaust pipe, and a vacuum pump.

[0018] The processing method provided by this invention ensures that H2O molecules react only with residual alkali on the surface of the high-nickel ternary cathode material, without entering the crystal lattice. This maximizes the protection of the material's crystal structure. The treated high-nickel ternary cathode material exhibits minimal surface side reactions, superior electrical performance, and significantly improved cycle stability in subsequent electrical performance tests, with a marked suppression of cycle DCR growth. The method provided by this invention effectively improves the residual alkali on the cathode material surface and further reduces the material's pH value, while achieving significantly higher cycle retention and cycle DCR compared to existing processes. Attached Figure Description

[0019] Figure 1 The results of cycle retention rate testing of high-nickel ternary cathode materials after processing in the embodiments and comparative examples of this invention;

[0020] Figure 2 The results of DCR testing of high-nickel ternary cathode materials after processing in the examples and comparative examples are shown.

[0021] Figure 3This is a schematic diagram of the magnetron sputtering device in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a method for improving the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries, comprising:

[0024] The residual alkali and gaseous water on the surface of the high-nickel ternary cathode material react together.

[0025] The reaction products were dried under vacuum conditions.

[0026] In embodiments of the present invention, the high-nickel ternary cathode material can be a high-nickel ternary cathode material in powder form; the composition of the high-nickel ternary cathode material can be:

[0027] LiNi x Co y Mn z O2,

[0028] Where 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.2, and x+y+z=1.

[0029] In embodiments of the present invention, x can be 0.9, y can be 0.1, and z can be 0.1.

[0030] In the embodiments of the present invention, the high-nickel ternary cathode material can also be doped and / or coated using methods well known in the art, such as adding doping and / or coating elements to the above composition formula; there are no special restrictions on the doping and coating elements, and doping and coating elements well known in the art can be used, such as doping elements can be Al or Mg; coating elements can be V or Zr; the cathode material can be prepared according to the doping and coating methods well known in the art.

[0031] In embodiments of the present invention, the gaseous water is water in its gaseous form. Gaseous water can be obtained by placing liquid water in a vacuum environment based on the saturated vapor pressure of water. The vacuum degree of the vacuum environment can be ≤5×10⁻⁶. -3 Pa. In embodiments of the present invention, the reaction can be carried out in a vacuum environment, thereby causing liquid water to transform into a gaseous state to participate in the reaction.

[0032] In embodiments of the present invention, the reaction can be carried out under magnetron sputtering conditions; the flow rate of gaseous water during the reaction can be 5-200 sccm, 10-150 sccm, 30-120 sccm, 50-100 sccm, or 60-80 sccm.

[0033] In embodiments of the present invention, the mass ratio of high-nickel ternary cathode material to gaseous water can be 100:(0.5-5), 100:(1-4), or 100:(2-3).

[0034] In embodiments of the present invention, the reaction temperature can be 5 to 10°C, such as 6°C, 7°C, 8°C, or 9°C; the reaction time can be 0.1 to 4 hours, 0.5 to 3 hours, 1 to 2 hours, or 1.5 hours.

[0035] In embodiments of the present invention, the drying process is carried out under vacuum conditions, wherein the vacuum degree can be ≤5×10⁻⁶. -3 Pa; the drying temperature can be 100~400℃, 150~350℃, 200~300℃, or 250℃.

[0036] This invention provides a device for improving the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries, comprising:

[0037] The components include a magnetron sputtering vacuum chamber, a sample tray, heating elements, an inlet pipe, an inlet pipe flow valve, an exhaust pipe, and a vacuum pump.

[0038] In an embodiment of the present invention, a schematic diagram of the device for improving the residual alkalinity on the surface of high-nickel ternary cathode material of lithium-ion batteries can be shown as follows: Figure 3 As shown (heating device not shown in the figure), it includes: a magnetron sputtering vacuum chamber 101, a sample tray 102, an air inlet pipe 103, an air inlet pipe flow valve 104, an exhaust pipe 105, and a vacuum pump 106; the heating device can be a heating wire, which is coiled under the sample tray to dry the substance in the sample tray.

[0039] In embodiments of the present invention, the residual alkalinity on the surface of high-nickel ternary cathode materials for lithium-ion batteries can be improved using a device for improving the residual alkalinity of such materials. Specific methods include:

[0040] High-nickel ternary cathode material powder is placed on sample tray 102 inside magnetron sputtering vacuum chamber 101, and the vacuum level of the magnetron sputtering chamber is set to ~5×10⁻⁶. -3Pa, water is slowly introduced through the air inlet pipe 103, and the water flow rate is adjusted by adjusting the flow valve 104 of the air inlet pipe, so that the H2O molecules in the chamber can fully contact the high-nickel ternary cathode material. The residual alkali on the surface of the high-nickel ternary cathode material reacts with H2O, and the reaction products and excess water can be removed by the vacuum pump group 106 through the exhaust pipe 105 connected to the vacuum chamber to obtain reaction product I.

[0041] The reaction product I was placed on the sample tray in the vacuum chamber of the magnetron sputtering, and the heating temperature of the sample tray was set to 100-400℃. The high-nickel ternary cathode material was dried in the vacuum chamber to completely remove the residual moisture on the surface of the high-nickel ternary cathode material.

[0042] The method provided by this invention can effectively improve the residual alkali on the surface of the cathode material and further reduce the pH value of the material. Moreover, the cycle retention rate and cycle DCR are significantly higher than those of existing processes.

[0043] The high-nickel ternary cathode material used in the following embodiments and comparative examples of this invention has a composition of LiNi. 83 Co 11 Mn6O2.

[0044] Example 1

[0045] High-nickel ternary cathode material powder is placed in a magnetron sputtering vacuum chamber (e.g.) Figure 3 On the sample tray shown, the positive electrode material powder is evenly spread on the sample tray, and the vacuum degree of the magnetron sputtering chamber is set to ~5×10⁻⁶. -3 Pa, water is slowly introduced through the air inlet pipe, and the flow valve of the air inlet pipe is adjusted to 100 sccm to allow the H2O molecules in the chamber to fully contact the high-nickel ternary cathode material. The residual alkali on the surface of the high-nickel ternary cathode material reacts with H2O. The reaction temperature is 5℃ and the reaction time is 15min. The reaction products and excess water can be pumped away by the pump group through the exhaust pipe connected to the vacuum chamber to obtain reaction product I.

[0046] The reaction product I was placed on the sample tray in the vacuum chamber of the magnetron sputtering, and the heating temperature of the sample tray was set to 400°C. The high-nickel ternary cathode material was dried in the vacuum chamber to completely remove the residual moisture on the surface of the high-nickel ternary cathode material.

[0047] Example 2

[0048] High-nickel ternary cathode material powder is placed in a magnetron sputtering vacuum chamber (e.g.) Figure 3 On the sample tray shown, the positive electrode material powder is evenly spread on the sample tray, and the vacuum degree of the magnetron sputtering chamber is set to ~5×10⁻⁶. -3Pa, water is slowly introduced through the air inlet pipe, and the flow valve of the air inlet pipe is adjusted to 50 sccm to allow the H2O molecules in the chamber to fully contact the high-nickel ternary cathode material. The residual alkali on the surface of the high-nickel ternary cathode material reacts with H2O. The reaction temperature is 5℃ and the reaction time is 5h. The reaction products and excess water can be pumped away by the pump group through the exhaust pipe connected to the vacuum chamber to obtain reaction product I.

[0049] The reaction product I was placed on the sample tray in the vacuum chamber of the magnetron sputtering, and the heating temperature of the sample tray was set to 400°C. The high-nickel ternary cathode material was dried in the vacuum chamber to completely remove the residual moisture on the surface of the high-nickel ternary cathode material.

[0050] Example 3

[0051] High-nickel ternary cathode material powder is placed in a magnetron sputtering vacuum chamber (e.g.) Figure 3 On the sample tray shown, the positive electrode material powder is evenly spread on the sample tray, and the vacuum degree of the magnetron sputtering chamber is set to ~5×10⁻⁶. -3 Pa, water is slowly introduced through the air inlet pipe, and the flow valve of the air inlet pipe is adjusted to 300 sccm to allow the H2O molecules in the chamber to fully contact the high-nickel ternary cathode material. The residual alkali on the surface of the high-nickel ternary cathode material reacts with H2O. The reaction temperature is 5℃ and the reaction time is 1h. The reaction products and excess water can be pumped away by the pump group through the exhaust pipe connected to the vacuum chamber to obtain reaction product I.

[0052] The reaction product I was placed on the sample tray in the vacuum chamber of the magnetron sputtering, and the heating temperature of the sample tray was set to 400°C. The high-nickel ternary cathode material was dried in the vacuum chamber to completely remove the residual moisture on the surface of the high-nickel ternary cathode material.

[0053] Comparative Example 1

[0054] The high-nickel ternary material is washed using existing water washing technology. The specific method is as follows:

[0055] The high-nickel ternary cathode material powder was placed in pure water and stirred for 10 minutes. Then, the washed high-nickel ternary material was dried in a vacuum oven at 120°C and subjected to a second calcination treatment at 700°C.

[0056] Performance testing

[0057] The high-nickel ternary cathode material processed according to the embodiments and comparative examples of the present invention was used to prepare CR2032 coin cells. The cathode, anode, separator, and electrolyte were assembled in a glove box. The cathode was prepared by adding high-nickel ternary cathode material, conductive carbon black, NMP, and PVDF in a mass ratio of 9:0.5:0.5:0.5 to a ball mill and ball milling for 0.5 hours to obtain a black slurry. This slurry was then coated onto aluminum foil at a coating amount of 12 mg / cm³. 2 The coated aluminum foil was vacuum dried at 120℃ for 10 hours. The coated aluminum foil was then processed several times on an electric roller mill and cut into electrode sheets with a diameter of 13 mm. The negative electrode sheet was a lithium foil. The electrolyte was LiPF6 electrolyte; the separator was a Celgard 2500 separator.

[0058] The battery obtained above was subjected to cycle retention rate and DC internal resistance (DCR) testing during the cycle process. The testing methods for cycle retention rate and DC internal resistance (DCR) are as follows: ① The lithium-ion battery was discharged at a constant current of 0.5C to the specified termination voltage (2.5V) at an ambient temperature of 45℃, and then charged at a constant current of 0.5C to the termination voltage (4.3V), and then switched to constant voltage charging (the charging termination current is generally 0.05C); ② The lithium-ion battery was discharged at a constant current of 0.5C to the specified discharge termination voltage at an ambient temperature of 45℃; ③ The lithium-ion battery was cycled at an ambient temperature of 45℃, and the battery was rested for 20 minutes between charging and discharging or between discharging and charging; ④ The lithium-ion battery was discharged and charged in accordance with steps ① and ② until 50 cycles were completed.

[0059] Test results as follows Figure 1 and Figure 2 As shown; by Figure 1 and Figure 2 It can be seen that the ternary cathode material in the embodiments of the present invention has better cycle characteristics after the residual alkalinity on the surface is treated by magnetron sputtering.

[0060] The conventional water washing process involves placing high-nickel ternary cathode material powder in pure water and stirring for 5–20 minutes, followed by drying the washed high-nickel ternary material in a vacuum oven at 120°C and then subjecting it to a secondary calcination treatment at 700°C. Stirring the high-nickel ternary cathode material powder in pure water damages the surface structure, causing it to collapse and further deteriorating the material's cycle stability, resulting in a significant increase in cycle DCR. This invention improves upon the conventional water washing process by employing a treatment method that allows H2O molecules to react only with residual alkali on the surface of the high-nickel ternary cathode material, without penetrating the crystal lattice. This maximizes the protection of the material's crystal structure. The treated high-nickel ternary cathode material exhibits minimal surface side reactions, better electrical performance, significantly improved cycle stability, and a marked suppression of cycle DCR growth in subsequent electrical performance tests.

[0061] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A method for improving the residual alkalinity on the surface of high-nickel ternary cathode material for lithium-ion batteries, comprising: The residual alkali on the surface of the high-nickel ternary cathode material is reacted with gaseous water; the reaction temperature is 5~10℃, the reaction time is 0.1~4h, and the flow rate of the gaseous water is 5~200sccm. The reaction products were dried under vacuum conditions. The vacuum condition is a vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, the drying temperature is 100~400℃.

2. The method according to claim 1, characterized in that, The gaseous water is obtained by placing liquid water in a vacuum environment.

3. The method according to claim 2, characterized in that, The vacuum level of the vacuum environment is ≤5×10⁻⁶. -3 Pa.

4. The method according to claim 1, characterized in that, The mass ratio of the high-nickel ternary cathode material to gaseous water is 100:(0.5~5).

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