A method for preparing a ternary cathode material precursor for sodium-ion batteries

Abstract

This invention discloses a method for preparing a ternary cathode material precursor for sodium-ion batteries, relating to the field of sodium battery materials technology. By controlling the pre-oxidation process of the obtained precursor material, this invention effectively solves the problem of numerous small particles in the precursor material while simultaneously improving the tap density of the precursor material and the cycle stability of the cathode material.

Description

Technical Field

[0001] This invention relates to the field of sodium battery materials technology, specifically to a method for preparing a ternary cathode material precursor for sodium-ion batteries. Background Technology

[0002] Ternary precursor materials are the core raw materials for synthesizing ternary cathode materials. Ternary cathode materials inherit the morphology of ternary precursor materials to a certain extent. The particle size of the precursor materials directly affects the particle size distribution of the ternary cathode materials. The appropriate particle size distribution range of the ternary precursor plays a decisive role in the particle size range of the ternary cathode materials and affects the performance of the subsequent cathode materials in the battery cell.

[0003] For example, patent application CN110844947A, by crushing a high-nickel secondary spherical precursor and then coating and fusing it with a solid oxidant, can obtain a high-nickel precursor with smaller and more uniform particle distribution. This crushed high-nickel precursor can be more thoroughly pre-oxidized and react more uniformly and thoroughly with lithium in the subsequent lithium-mixing sintering process, thus obtaining a high-nickel single crystal material with uniform particle size distribution and better sintering uniformity, thereby exhibiting better electrochemical performance. However, the pre-oxidation method of this patent is direct high-temperature calcination, which does not conform to the concept of environmental protection.

[0004] Chinese patent CN 112142125A discloses a method for preparing high-nickel ternary cathode materials using a two-stage growth method. First, a ternary precursor is prepared via co-precipitation to complete the first growth, followed by high-temperature pre-oxidation of the precursor. Then, the precursor, deionized water, sodium hydroxide, and ammonia are added to a reactor to complete the second growth. The resulting precipitate is washed, filtered, and then pre-oxidized at high temperature. The precursor obtained from the second growth is mixed with a lithium source and placed in a sintering furnace, where oxygen is introduced and the process involves periodic pressure holding and depressurization sintering. The precursor prepared by the two-stage growth method continues to grow based on the first growth, achieving a second growth and increasing the particle size of the material. The high-temperature pre-oxidation of the precursor from the first growth solves the problem of insufficient internal oxygen contact during sintering. The breathing sintering method used provides sufficient oxygen during sintering, ultimately yielding a high-nickel ternary material with large particle size and good structural order.

[0005] The main method for synthesizing ternary precursors is coprecipitation. Coprecipitation is a continuous crystal growth process. However, if the reaction becomes uncontrolled, small particles smaller than 1 micrometer can easily erupt, leading to an increase in particle size. This phenomenon significantly affects the particle size distribution and tap density of subsequent materials. Furthermore, the large specific surface area of ​​these small particles, when sintered into cathode materials, can easily lead to increased side reactions in battery cell applications, affecting the cell's cycle performance. Summary of the Invention

[0006] Addressing the shortcomings of existing technologies, this invention pre-oxidizes the products obtained from the co-precipitation reaction. By controlling temperature, humidity, and time through multiple adjustments, Ostwald ripening is induced, effectively eliminating particles smaller than 1 micrometer. This results in adjustable particle size in the precursor material, higher tap density, and sintered cathode material exhibiting excellent cycle performance. Controlling the pre-oxidation of the precursor material effectively controls the particle size distribution, significantly improving the material properties and electrochemical performance.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a ternary cathode material precursor for sodium-ion batteries includes the following steps:

[0009] The ternary cathode material precursor with a water content of 15%-65% obtained by co-precipitation and filtration is pre-oxidized in a pre-oxidation chamber:

[0010] S1. Induction period: Pre-oxidize in a pre-oxidation chamber at a temperature of 25-40℃ and a humidity of 60%-100% for 24-72 hours;

[0011] S2, Curing period: Raise the temperature in the pre-oxidation chamber of step S1 to 80-100℃, reduce the humidity to 20%-40%, and maintain the temperature for 24-60 hours.

[0012] S3. Drying period: Increase the temperature in the pre-oxidation chamber of step S2 to 120-135℃, reduce the humidity to ≤10%, and maintain for 15-24 hours.

[0013] After the reaction, the precursor material is filtered to remove most of the water, and then washed with a large amount of deionized water to control the water content of the reaction product within the range of 15%-65%.

[0014] Preferably, the mass ratio of the large amount of deionized water to the reaction product is ≥20; this can effectively control the sulfate level below 500 ppm.

[0015] Preferably, the water content of the ternary cathode material precursor is 30%-45%, and in step S1, the humidity in the pre-oxidation chamber is 75%-85%, and the pre-oxidation time is 30-45 hours. This prevents the induction period from being too short and directly entering the ripening period.

[0016] Preferably, in step S2, the rate of temperature increase is 0.5-5℃ / h, and the rate of humidity decrease is 1% / h-3% / h. This avoids directly entering the drying stage after a short curing period.

[0017] Preferably, in step S2, the rate of temperature increase is 1.5-2.5℃ / h, and the holding time is 25-35h; the rate of humidity decrease is 0.5% / h-2% / h.

[0018] Preferably, in step S3, the temperature rise rate is 1-3℃ / min, and the humidity decrease rate is 1% / h-5% / h. This can prevent material caking caused by excessive water loss.

[0019] Preferably, the ternary cathode material precursor is pre-oxidized after being stacked, and the thickness of the stack is 5-15 cm. Preferably, the thickness of the stack is 5-10 cm.

[0020] This invention also provides a method for preparing a ternary cathode material for sodium-ion batteries, comprising the following steps:

[0021] (1) A ternary cathode material precursor for sodium-ion batteries is prepared by the method described above for preparing a ternary cathode material precursor for sodium-ion batteries.

[0022] (2) The sodium-ion battery ternary cathode material precursor obtained in step (1) is mixed and ground with sodium salt, and then calcined to obtain the sodium-ion battery ternary cathode material.

[0023] In step (2), the calcination conditions are as follows: first, heat the temperature to 500℃ at 5℃ / min and hold for 5 hours, then continue to heat the temperature to 870℃ at 5℃ / min and hold for 18 hours.

[0024] This invention overcomes the shortcomings of traditional sieving methods, such as the tendency to cause excessive dust, material loss, and the introduction of magnetic foreign objects when controlling material particles.

[0025] The beneficial effects of this invention are:

[0026] This invention effectively solves the problem of numerous small particles in the precursor material by regulating the pre-oxidation process, while also effectively improving the tap density of the precursor material and the cycle stability of the cathode material. Attached Figure Description

[0027] Figure 1 This is a particle size distribution diagram of the precursor material before pre-oxidation in Example 1.

[0028] Figure 2 This is a particle size distribution diagram of the precursor material after pre-oxidation in Example 1.

[0029] Figure 3 The particle size distribution of the precursor material before pre-oxidation in Comparative Example 1 is shown.

[0030] Figure 4 The particle size distribution diagram is shown for the precursor material after drying treatment in Comparative Example 1.

[0031] Figure 5 This is an electron microscope image of the precursor material before pre-oxidation in Example 1.

[0032] Figure 6 This is an electron microscope image of the precursor material after pre-oxidation in Example 1.

[0033] Figure 7 The image shows an electron microscope (EM) image of the precursor material before pre-oxidation in Comparative Example 1.

[0034] Figure 8 The image shows an electron microscope (EM) image of the precursor material after drying treatment in Comparative Example 1.

[0035] Figure 9 The graph shows a comparison of the electrochemical performance of batteries assembled from the pre-oxidized precursor materials in Example 1 and Comparative Example 1. Detailed Implementation

[0036] Example 1

[0037] A mixture of 2.5 mol of equimolar amounts of a mixed sulfate solution (manganese sulfate monohydrate, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate), 5 mol of sodium hydroxide solution, and 15 mol of ammonia solution was added dropwise to a 500 L reactor at rates of 200 ml / min, 200 ml / min, and 10 ml / min, respectively. The reactor was stirred at 500 rpm, and the reaction was continued for 10 hours, yielding approximately 26.2 kg of precursor material. The precursor material was filtered and washed with 600 kg of pure water. After washing, the material was dried using compressed air, and the moisture content was found to be 33%. The precursor material was transferred to an enamel tray, piled to a height of 6 cm, and placed in a drying room.

[0038] In the first stage, the drying chamber was set with an ambient humidity of 70% and a temperature of 28℃ for 36 hours. In the second stage, the ambient humidity in the drying chamber decreased at a rate of 1.5% / h, and the heating rate was set at 2℃ / h. The target ambient humidity was set at 30%, and the temperature at 85℃ for 30 hours. In the third stage, the heating rate was set at 1.5℃ / min, the target ambient temperature was set at 125℃, and the humidity at 8% for 20 hours. The pre-oxidized precursor material was obtained.

[0039] Example 2

[0040] A mixture of 2.5 mol of equimolar amounts of a mixed sulfate solution (manganese sulfate monohydrate, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate), 5 mol of sodium hydroxide solution, and 15 mol of ammonia solution was added dropwise to a 500 L reactor at rates of 200 ml / min, 200 ml / min, and 10 ml / min, respectively. The reactor was stirred at 500 rpm for 8 hours, yielding approximately 22 kg of precursor material. The precursor material was filtered and washed with 520 kg of pure water. After washing, the material was dried using compressed air, and the moisture content was found to be 64.5%. The precursor material was then transferred to an enamel tray, piled to a height of 10 cm, and placed in a drying room.

[0041] The first stage sets the drying chamber environment to 100% humidity and 40℃ for 72 hours. The second stage sets the drying chamber environment humidity to decrease at a rate of 2% / h and the heating rate to increase at 2℃ / h, with target humidity of 40% and temperature of 100℃, maintained for 60 hours. The third stage sets the heating rate to increase at 1.5℃ / min, the drying chamber environment humidity to decrease at a rate of 1% / h, and target temperature of 135℃ and humidity of 8%, maintained for 24 hours. The pre-oxidized precursor material is then obtained.

[0042] Real-time Example 3

[0043] A mixture of 2.5 mol of equimolar amounts of a mixed sulfate solution (manganese sulfate monohydrate, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate), 5 mol of sodium hydroxide solution, and 10 mol of ammonia solution was added dropwise to a 500 L reactor at rates of 100 ml / min, 100 ml / min, and 5 ml / min, respectively. The reactor was stirred at 400 rpm for 12 hours, yielding approximately 14 kg of precursor material. The precursor material was filtered and washed with 440 kg of pure water. After washing, the material was dried using compressed air, and the moisture content was found to be 15.2%. The precursor material was then transferred to an enamel tray, piled to a height of 5 cm, and placed in a drying chamber.

[0044] The first stage sets the drying chamber environment to 60% humidity and 25℃ for 24 hours. The second stage sets the drying chamber environment humidity to decrease at a rate of 0.5% / h, the heating rate to increase at 2℃ / h, the target humidity to be 20%, and the temperature to be 80℃ for 24 hours. The third stage sets the heating rate to increase at 1.5℃ / min, the drying chamber environment humidity to decrease at a rate of 5% / h, the target temperature to be 120℃, and the humidity to be 10% for 15 hours. The pre-oxidized precursor material is then obtained.

[0045] Comparative Example 1

[0046] A mixture of 2.5 mol of equimolar amounts of a mixed sulfate solution (manganese sulfate monohydrate, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate), 5 mol of sodium hydroxide solution, and 15 mol of ammonia solution was added dropwise to a 500 L reactor at rates of 200 ml / min, 200 ml / min, and 10 ml / min, respectively. The reactor was stirred at 500 rpm, and the reaction was continued for 10 hours, yielding approximately 26.2 kg of precursor material. The precursor material was filtered and washed with 600 kg of pure water. After washing, the material was dried using compressed air, and the moisture content was found to be 33%. The precursor material was transferred to an enamel tray, piled to a height of 6 cm, and placed in a drying room.

[0047] The heating rate for the third-stage drying period was set to 1.5℃ / min, the target ambient temperature was set to 125℃, and the humidity was set to 8%, and maintained for 20 hours. The dried precursor material was obtained.

[0048] Test Example 1

[0049] 1. Particle size test

[0050] The material sample to be tested is dispersed in deionized water, and ultrasonicated and stirred until there is no obvious agglomeration. The laser particle size analyzer is preheated and the ultrasonic, stirring and degassing functions of the circulation system are turned on. After the test background is stable, the sample is slowly added to the laser particle size analyzer circulation injection system with a dropper so that the shading rate is between 10-15%. After testing, the particle size distribution map is obtained.

[0051] The particle size distribution of the precursor materials in Example 1 and Comparative Example 1 before and after pre-oxidation was tested, respectively. The test results are as follows: Figures 1-4 As can be seen from the figure, the comparison Figure 1 , Figure 2 The particle size distribution of the material after pre-oxidation shows that particles smaller than 1 μm have essentially disappeared. (Comparison) Figure 3 , Figure 4 The particle size distribution of the unoxidized material shows that particles smaller than 1 μm still exist.

[0052] Electron micrographs of the precursor materials before and after pre-oxidation in Example 1 and Comparative Example 1 are shown below. Figures 5-8 As shown.

[0053] 2. Specific surface area and tapped density

[0054] 1) The specific surface area test

[0055] The dried product was ground in a mortar for 20 minutes and sieved through a 200-mesh screen. The product weight m2 was accurately weighed and placed in a glass tube for degassing at 200°C for 2 hours. The material weight m1 was retested and entered into the test interface. The sample was then placed in a liquid nitrogen tank filled with liquid nitrogen to start the isothermal adsorption method to test the specific surface area and obtain the surface area S.

[0056] 2) The tapped density test

[0057] The dried product was ground in a mortar for 20 minutes and sieved through a 200-mesh screen. The product weight m2 was then accurately measured. The product was allowed to fall freely from the funnel into a graduated cylinder with a capacity of 100 ml. The height of the funnel was 5 cm higher than the graduated cylinder. After the product was completely filled into the graduated cylinder, it was placed on a tapped density meter and vibrated 3000 times. The volume T2 was read, and the tapped density m2 / T2 was obtained.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, the specific surface area of ​​the precursor material after pre-oxidation decreased significantly and the tap density increased significantly, while the specific surface area and tap density did not change significantly before and after the simple drying treatment.

[0061] 3. Electrochemical performance

[0062] The pre-oxidized precursor materials from Example 1 and Comparative Example 1, along with sodium carbonate, were added to a mixer at a mass ratio of 1:0.6. Zirconium balls were added and mixed, with a ball-to-material ratio of 2:1. After mixing for 4 hours, the sample was removed and placed in a muffle furnace. The temperature was increased to 500°C at 5°C / min and held for 5 hours. Then, the temperature was increased to 870°C at 5°C / min and held for 18 hours to obtain cathode materials S2 (containing the pre-oxidized precursor material from Example 1) and S1 (containing the pre-oxidized precursor material from Comparative Example 1).

[0063] The above-mentioned positive electrode material, conductive agent, and binder were mixed and stirred in a mass ratio of 9:0.5:0.5. After being prepared and dried, a positive electrode sheet was made. Using metallic sodium as the negative electrode, the capacity S2-1 and S1-1 were obtained by coin cell testing.

[0064] from Figure 9 It can be seen that the coin cell circuit composed of the precursor material after pre-oxidation treatment and sintering into a positive electrode material has significantly better cycle performance than the coin cell circuit composed of the precursor material after sintering without pre-oxidation treatment.

Claims

1. A method for preparing a ternary cathode material precursor for sodium-ion batteries, characterized in that, Includes the following steps: The ternary cathode material precursor with a water content of 15%-65% obtained by co-precipitation and filtration is pre-oxidized in a pre-oxidation chamber: S1. Induction period: Pre-oxidize in a pre-oxidation chamber at a temperature of 25-40℃ and a humidity of 60%-100% for 24-72 hours; S2, Curing period: The temperature in the pre-oxidation chamber of step S1 is increased to 80-100℃ at a rate of 0.5-5℃ / h, and the humidity is decreased to 20%-40% at a rate of 1% / h-3% / h, and the holding time is 24-60h. S3. Drying period: Increase the temperature in the pre-oxidation chamber of step S2 to 120-135℃ at a rate of 1-3℃ / min, and decrease the humidity to ≤10% at a rate of 1% / h-5% / h, and maintain for 15-24h. The ternary cathode material precursor is pre-oxidized after being stacked, and the thickness of the stack is 5-15 cm.

2. The preparation method according to claim 1, characterized in that, The water content of the ternary cathode material precursor is 30%-45%.

3. The preparation method according to claim 1, characterized in that, In step S1, the humidity in the pre-oxidation chamber is 75%-85%, and the pre-oxidation time is 30-45 hours.

4. The preparation method according to claim 1, characterized in that, In step S2, the temperature rise rate is 1.5-2.5℃ / h, and the holding time is 25-35h; The humidity decrease rate is 0.5% / h-2% / h.

5. The preparation method according to claim 1, characterized in that, The thickness of the accumulation is 5-10 cm.

6. A method for preparing a ternary cathode material for sodium-ion batteries, characterized in that, Includes the following steps: (1) A ternary cathode material precursor for sodium-ion batteries is prepared by any of the preparation methods of sodium-ion battery ternary cathode material precursors according to any one of claims 1 to 5; (2) The sodium-ion battery ternary cathode material precursor obtained in step (1) is mixed and ground with sodium salt, and then calcined to obtain the sodium-ion battery ternary cathode material.

7. The method for preparing the ternary cathode material for sodium-ion batteries as described in claim 6, characterized in that, In step (2), the calcination conditions are as follows: first, heat the temperature to 500℃ at 5℃ / min and hold for 5 hours, then continue to heat the temperature to 870℃ at 5℃ / min and hold for 18 hours.

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