Amorphous small-particle-size cobaltosic oxide as well as preparation method and application thereof

Abstract

The invention provides amorphous small-particle-size cobaltosic oxide as well as a preparation method and application thereof. The preparation method comprises the following steps: enabling a cobalt salt solution and a precipitator solution to flow into a base solution in parallel, carrying out precipitation reaction, and carrying out post-treatment after the reaction is finished, so as to obtain a cobaltosic oxide precursor; calcining the cobaltosic oxide precursor through a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone and a fifth temperature zone in sequence to obtain the amorphous small-particle-size cobaltosic oxide, wherein the temperature of the first temperature zone is 420-480 DEG C, the temperature of the second temperature zone is 460-540 DEG C, the temperature of the third temperature zone is 620-660 DEG C, the temperature of the fourth temperature zone is 620-660 DEG C, and the temperature of the fifth temperature zone is 460-540 DEG C. According to the preparation process, the grain tap density and the particle uniformity of the cobaltosic oxide are regulated and controlled, so that the rate capability and the cycling stability of the battery are remarkably improved on the premise of keeping high capacity.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to an amorphous small-particle-size cobalt tetroxide, its preparation method, and its application. Background Technology

[0002] In recent years, the lithium-ion battery industry in the 3C digital field has developed rapidly. Cathode materials, represented by lithium cobalt oxide, have basically met the market application requirements in terms of discharge capacity, voltage stability, and cycle life, becoming one of the mainstream cathode materials for current lithium-ion rechargeable batteries. With people's increasing demand for lightweight and high-capacity digital products, further improving battery energy density has become an urgent need for the industry, and cobalt tetroxide, as a key precursor of lithium cobalt oxide, has once again become a research focus.

[0003] To improve the electrochemical performance of lithium cobalt oxide, current research focuses on introducing doping elements such as aluminum and magnesium during liquid-phase synthesis to enhance the stability of the lattice structure during charge and discharge, thereby improving cycle performance. With increasing demands for high voltage and long cycle life, doping content is also trending upwards. However, while high doping strategies improve structural stability, they often lead to a decrease in reversible capacity, making it difficult to balance high capacity and high stability. This is especially true for niche applications like drones, which require lightweight design and high capacity, emphasizing long-range operation, thus placing higher demands on the capacity of lithium cobalt oxide. Against this backdrop, lithium cobalt oxide cathode materials sintered from amorphous small-particle cobalt tetroxide have attracted significant attention due to their potential for achieving both lightweight and high capacity batteries. This is because high-capacity battery materials require amorphous morphology to further improve tap density, thereby enhancing the battery's energy density performance. Furthermore, amorphous morphology facilitates a more complete and uniform integration with the lithium source during secondary sintering, resulting in superior first-cycle efficiency compared to doped spherical small-particle cobalt tetroxide.

[0004] However, lithium cobalt oxide prepared from amorphous small-particle cobalt tetroxide still faces a series of process and performance bottlenecks in practical applications: (1) There is still a large room for improvement in the tap density of existing amorphous precursor materials, which restricts the further improvement of electrode compaction density and battery energy density; (2) During the sintering process, it is difficult to control the particle uniformity and reactivity of amorphous cobalt tetroxide, which affects the structural consistency and electrochemical performance stability of the final product.

[0005] Therefore, how to effectively control the tap density and particle uniformity of amorphous small-particle cobalt tetroxide while maintaining its high capacity potential is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an amorphous, small-particle-size cobalt tetroxide, its preparation method, and its applications. This invention employs a synergistic calcination strategy across multiple specific temperature zones to precisely control the grain tap density and particle uniformity of cobalt tetroxide, effectively suppressing excessive crystal growth and ordering, resulting in an amorphous product with fine particle size, low crystallinity, and uniform distribution. This cobalt tetroxide extract, as a precursor for lithium cobalt oxide, exhibits significantly improved reactivity and sintering compatibility. During subsequent lithium cobalt oxide preparation, it forms a dense and uniform microstructure, effectively enhancing not only the tap density and specific capacity of the electrode but also improving electrolyte wettability and lithium-ion transport efficiency. This, in turn, improves the rate performance and cycle stability of the battery while maintaining high capacity, providing material support for meeting the demands of high-end applications for high-energy-density, lightweight lithium-ion batteries.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing amorphous small-particle-size cobalt tetroxide, the method comprising the following steps:

[0009] The cobalt salt solution and the precipitant solution were flowed concurrently into the base liquid to carry out the precipitation reaction. After the reaction was completed, post-processing was performed to obtain the cobalt tetroxide precursor.

[0010] The cobalt tetroxide precursor was calcined sequentially through a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone, and a fifth temperature zone to obtain the amorphous small-particle-size cobalt tetroxide.

[0011] The temperature of the first temperature zone is 420-480℃, the temperature of the second temperature zone is 460-540℃, the temperature of the third temperature zone is 620-660℃, the temperature of the fourth temperature zone is 620-660℃, and the temperature of the fifth temperature zone is 460-540℃.

[0012] This invention precisely controls the grain tap density and particle uniformity of cobalt tetroxide through a specific process and a synergistic calcination strategy at multiple specific temperature zones, effectively suppressing excessive crystal growth and ordering, and obtaining amorphous products with fine particle size, low crystallinity, and uniform distribution. This cobalt tetroxide extract, as a precursor for lithium cobalt oxide, exhibits significantly improved reactivity and sintering compatibility. In the subsequent preparation of lithium cobalt oxide, it can form a dense and uniform microstructure, effectively improving not only the tap density and specific capacity of the cathode material but also electrolyte wettability and lithium-ion transport efficiency. Thus, while maintaining high capacity, it enhances the rate performance and cycle stability of the battery, providing material support for meeting the demands of high-end applications for high-energy-density, lightweight lithium-ion batteries.

[0013] In this invention, the temperature of the first temperature zone is 420-480℃, for example, it can be 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, or 480℃, etc.; the temperature of the second temperature zone is 460-540℃, for example, it can be 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, or 540℃, etc.; and the temperature of the third temperature zone is 620-660℃. For example, it could be 620℃, 630℃, 640℃, 650℃ or 660℃, etc. The temperature of the fourth temperature zone is 620-660℃, for example, it could be 620℃, 630℃, 640℃, 650℃ or 660℃, etc. The temperature of the fifth temperature zone is 460-540℃, for example, it could be 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃ or 540℃, etc.

[0014] This invention sets the temperature of the first temperature zone at 420-480℃. This temperature zone serves as the initial heating stage, primarily aimed at drying moisture and simultaneously allowing the precursor to slowly decompose, forming initial nuclei of cobalt tetroxide. This temperature range helps suppress excessive particle growth and crystallization, promotes the formation of amorphous structures, and also facilitates the removal of volatile components from the precursor. The second temperature zone is set at 460-540℃. In this zone, the precursor further decomposes, accelerating the nucleation process and preventing rapid sintering and crystallization of the particles, thus maintaining miniaturized particle size. It also helps to adjust the pore structure of the material and enhance the specific surface area; setting the temperature of the third temperature zone to 620-660℃ helps to complete the conversion of the precursor to cobalt tetroxide, and also helps to eliminate internal stress in the material and improve structural stability; setting the temperature of the fourth temperature zone to 620-660℃, this stage can ensure the homogenization and defect repair of cobalt tetroxide, further stabilize the amorphous structure, and prevent particle agglomeration; setting the temperature of the fifth temperature zone to 460-540℃, this cooling section can further homogenize the calcination and lock in the amorphous structure.

[0015] Preferably, the base liquid comprises water and ammonium bicarbonate.

[0016] Preferably, the concentration of ammonium bicarbonate in the base solution is 220-280 g / L, for example, it can be 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L or 280 g / L, etc.

[0017] Preferably, the preset temperature of the base liquid is 40-50℃, for example, it can be 40℃, 45℃ or 50℃.

[0018] Preferably, the cobalt salt solution includes any one or a combination of at least two of cobalt chloride solution, cobalt sulfate solution, or cobalt nitrate solution.

[0019] Preferably, the concentration of the cobalt salt solution is 100-150 g / L, for example, it can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0020] Preferably, the precipitant solution comprises an ammonium bicarbonate solution or a sodium hydroxide solution.

[0021] Preferably, the concentration of the precipitant solution is 220-280 g / L, for example, it can be 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L or 280 g / L, etc.

[0022] Preferably, the flow rate of the cobalt salt solution is 200-400 L / h, for example, it can be 200 L / h, 250 L / h, 300 L / h, 350 L / h or 400 L / h.

[0023] Preferably, the flow rate of the precipitant solution is 900-1500 L / h, for example, it can be 900 L / h, 1000 L / h, 1100 L / h, 1200 L / h, 1300 L / h, 1400 L / h or 1500 L / h.

[0024] Preferably, during the precipitation reaction, the pH of the reaction system is 7-7.3, for example, it can be 7, 7.1, 7.2 or 7.3.

[0025] Preferably, during the precipitation reaction, the temperature of the reaction system is 40-50℃, for example, 40℃, 45℃ or 50℃.

[0026] Preferably, the precipitation reaction time is 10-25 hours, for example, 10 hours, 15 hours, 20 hours or 25 hours.

[0027] Preferably, the post-processing step includes washing and dehydrating the slurry obtained after the reaction.

[0028] Preferably, the total residence time of the cobalt tetroxide precursor as it sequentially passes through the first, second, third, fourth, and fifth temperature zones is 1.5-3 hours, for example, it can be 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0029] This invention sets the transfer speed of the cobalt tetroxide precursor through the first, second, third, fourth, and fifth temperature zones in sequence. This speed, in conjunction with the set temperature gradient, enables precise control of the material calcination process. The appropriate transfer speed ensures that the precursor has the optimal time for decomposition, nucleation, phase transformation, and structural stabilization in each temperature zone. This effectively promotes the formation of amorphous structures while strictly inhibiting excessive crystallization, sintering growth, and agglomeration of particles. Ultimately, this successfully produces amorphous cobalt tetroxide with small particle size, good dispersibility, uniform structure, and stable performance.

[0030] Preferably, the residence time in the first temperature zone is 20-40 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0031] Preferably, the residence time in the second temperature zone is 20-40 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0032] Preferably, the residence time in the third temperature zone is 20-40 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0033] Preferably, the residence time in the fourth temperature zone is 20-40 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0034] Preferably, the residence time in the fifth temperature zone is 20-40 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0035] Preferably, the temperature of the third temperature zone is less than or equal to the temperature of the fourth temperature zone.

[0036] In this invention, limiting the temperature of the third temperature zone to be less than or equal to the temperature of the fourth temperature zone can effectively prevent local overheating and abnormal grain growth caused by excessively high temperature in the third temperature zone. This ensures that the material can complete the structural adjustment and solidification in a controlled and uniform high-temperature environment, which is more conducive to obtaining amorphous cobalt tetroxide with consistent crystal structure and concentrated grain size distribution.

[0037] Preferably, the preparation method includes the following steps:

[0038] (1) Preparation of the base solution:

[0039] At a temperature of 40-50℃, water and ammonium bicarbonate are stirred and mixed at a speed of 100-150 rpm (e.g., 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm or 150 rpm, etc.) to obtain the base liquid; the concentration of ammonium bicarbonate in the base liquid is 220-280 g / L.

[0040] (2) The cobalt salt solution and the precipitant solution are fed into the bottom liquid in parallel. The pH of the reaction system is controlled at 7-7.3 and the temperature is 40-50℃. The precipitation reaction is carried out for 10-25 hours to obtain the cobalt tetroxide precursor slurry.

[0041] (3) The cobalt tetroxide precursor slurry is centrifuged and washed at a temperature of 50-80℃ (e.g., 50℃, 60℃, 70℃ or 80℃, etc.) and then dehydrated to obtain the cobalt tetroxide precursor.

[0042] (4) The cobalt tetroxide precursor is fed into a rotary kiln and passes through a first temperature zone of 420-480℃, a second temperature zone of 460-540℃, a third temperature zone of 620-660℃, a fourth temperature zone of 620-660℃, and a fifth temperature zone of 460-540℃ in sequence. After discharge, it is subjected to vibration sieving and iron removal treatment to obtain amorphous small-particle cobalt tetroxide. The residence time of the cobalt tetroxide precursor in the first temperature zone is 20 min; the residence time in the second temperature zone is 20 min; the residence time in the third temperature zone is 30 min; the residence time in the fourth temperature zone is 40 min; and the residence time in the fifth temperature zone is 30 min.

[0043] In a second aspect, the present invention provides an amorphous small-particle-size cobalt tetroxide, wherein the amorphous small-particle-size cobalt tetroxide is prepared by the preparation method described in the first aspect.

[0044] The particle size D50 of the amorphous small-diameter cobalt tetroxide is 5-9 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm or 9 μm, etc.

[0045] The tap density of the amorphous small-particle cobalt tetroxide is 2.2-2.5 g / cm³. 3 For example, it could be 2.2 g / cm³ 3 2.3g / cm 3 2.4g / cm 3 Or 2.5g / cm 3 wait.

[0046] The amorphous small-particle cobalt tetroxide prepared by the preparation method provided by this invention has a tap density that meets the requirements for preparing lithium cobalt oxide. It not only effectively improves the tap density and specific capacity of the electrode, but also improves the electrolyte wettability and lithium-ion transport efficiency, thereby improving the rate performance and cycle stability of the battery while maintaining high capacity.

[0047] Thirdly, the present invention provides an application of amorphous small-particle-size cobalt tetroxide as described in the second aspect in lithium-ion batteries.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] This invention precisely controls the grain tap density and particle uniformity of cobalt tetroxide through a specific process and a synergistic calcination strategy at multiple specific temperature zones, effectively suppressing excessive crystal growth and ordering, and obtaining amorphous products with fine particle size, low crystallinity, and uniform distribution. This cobalt tetroxide extract, as a precursor for lithium cobalt oxide, exhibits significantly improved reactivity and sintering compatibility. In the subsequent preparation of lithium cobalt oxide, it can form a dense and uniform microstructure, effectively improving not only the tap density and specific capacity of the cathode material but also electrolyte wettability and lithium-ion transport efficiency. Thus, while maintaining high capacity, it enhances the rate performance and cycle stability of the battery, providing material support for meeting the demands of high-end applications for high-energy-density, lightweight lithium-ion batteries. Detailed Implementation

[0051] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0052] Example 1

[0053] This embodiment provides a method for preparing amorphous small-particle-size cobalt tetroxide, the preparation method comprising the following steps:

[0054] (1) Preparation of the base solution:

[0055] At a temperature of 45℃, water and ammonium bicarbonate were placed in an 8m bath. 3 The mixture was stirred at 120 rpm in a reaction vessel to obtain the base liquid; the concentration of ammonium bicarbonate in the base liquid was 250 g / L.

[0056] (2) A cobalt chloride solution with a concentration of 125 g / L and an ammonium bicarbonate solution with a concentration of 250 g / L are fed into the bottom liquid in parallel. The pH of the reaction system is controlled at 7.2 and the temperature is 45°C. The precipitation reaction is carried out for 18 h to obtain a cobalt tetroxide precursor slurry. The flow rate of the cobalt chloride solution is 300 L / h and the flow rate of the ammonium bicarbonate solution is 1200 L / h.

[0057] (3) The cobalt tetroxide precursor slurry was centrifuged and washed 5 times at 65°C for 5 minutes each time, using a total of 3 ml of water. 3 Then, it undergoes dehydration treatment to obtain the cobalt tetroxide precursor.

[0058] (4) The cobalt tetroxide precursor is added to the hopper of the rotary kiln and fed through a screw feeder. It passes through a first temperature zone of 450°C, a second temperature zone of 500°C, a third temperature zone of 640°C, a fourth temperature zone of 640°C, and a fifth temperature zone of 500°C in sequence. After discharge, it is subjected to 400-mesh vibrating sieve and iron removal treatment to obtain amorphous small-particle cobalt tetroxide. The residence time of the cobalt tetroxide precursor in the first temperature zone is 20 min; the residence time in the second temperature zone is 30 min; the residence time in the third temperature zone is 30 min; the residence time in the fourth temperature zone is 30 min; the residence time in the fifth temperature zone is 20 min; and the total residence time of the cobalt tetroxide precursor passing through the first, second, third, fourth, and fifth temperature zones in sequence is 130 min.

[0059] Example 2

[0060] This embodiment provides a method for preparing amorphous small-particle-size cobalt tetroxide, the preparation method comprising the following steps:

[0061] (1) Preparation of the base solution:

[0062] At a temperature of 40℃, water and ammonium bicarbonate were placed in an 8m bath. 3 The mixture was stirred at 100 rpm in a reaction vessel to obtain the bottom liquid; the concentration of ammonium bicarbonate in the bottom liquid was 220 g / L.

[0063] (2) A cobalt chloride solution with a concentration of 100 g / L and an ammonium bicarbonate solution with a concentration of 220 g / L are fed into the bottom liquid in parallel. The pH of the reaction system is controlled at 7 and the temperature is 40°C. A precipitation reaction is carried out for 25 h to obtain a cobalt tetroxide precursor slurry. The flow rate of the cobalt chloride solution is 200 L / h and the flow rate of the ammonium bicarbonate solution is 900 L / h.

[0064] (3) The cobalt tetroxide precursor slurry was centrifuged and washed 5 times at 50°C for 5 minutes each time, using a total of 2 ml of water. 3 Then, it undergoes dehydration treatment to obtain the cobalt tetroxide precursor.

[0065] (4) The cobalt tetroxide precursor is added to the hopper of the rotary kiln and fed through a screw feeder. It passes through a first temperature zone of 420°C, a second temperature zone of 460°C, a third temperature zone of 620°C, a fourth temperature zone of 620°C, and a fifth temperature zone of 460°C in sequence. After discharge, it is subjected to 400-mesh vibrating sieve and iron removal treatment to obtain amorphous small-particle cobalt tetroxide. The residence time of the cobalt tetroxide precursor in the first temperature zone is 20 min; the residence time in the second temperature zone is 20 min; the residence time in the third temperature zone is 20 min; the residence time in the fourth temperature zone is 30 min; the residence time in the fifth temperature zone is 20 min; and the transfer speed of the cobalt tetroxide precursor as it passes through the first, second, third, fourth, and fifth temperature zones is 110 min.

[0066] Example 3

[0067] This embodiment provides a method for preparing amorphous small-particle-size cobalt tetroxide, the preparation method comprising the following steps:

[0068] (1) Preparation of the base solution:

[0069] At a temperature of 50°C, water and ammonium bicarbonate were placed in an 8m bath. 3 The mixture was stirred at 150 rpm in a reaction vessel to obtain the base liquid; the concentration of ammonium bicarbonate in the base liquid was 280 g / L.

[0070] (2) A cobalt chloride solution with a concentration of 150 g / L and an ammonium bicarbonate solution with a concentration of 280 g / L are fed into the bottom liquid in parallel. The pH of the reaction system is controlled at 7.3 and the temperature is 50°C. The precipitation reaction is carried out for 10 h to obtain a cobalt tetroxide precursor slurry. The flow rate of the cobalt chloride solution is 400 L / h and the flow rate of the ammonium bicarbonate solution is 1500 L / h.

[0071] (3) The cobalt tetroxide precursor slurry was centrifuged and washed 5 times at 80°C for 5 minutes each time, using a total of 4 m³ of water. 3 Then, it undergoes dehydration treatment to obtain the cobalt tetroxide precursor.

[0072] (4) The cobalt tetroxide precursor is added to the hopper of the rotary kiln and fed through a screw feeder. It passes through a first temperature zone of 480°C, a second temperature zone of 540°C, a third temperature zone of 660°C, a fourth temperature zone of 660°C, and a fifth temperature zone of 540°C in sequence. After discharge, it is subjected to 400-mesh vibrating sieve and iron removal treatment to obtain amorphous small-particle cobalt tetroxide. The residence time of the cobalt tetroxide precursor in the first temperature zone is 20 min; the residence time in the second temperature zone is 20 min; the residence time in the third temperature zone is 30 min; the residence time in the fourth temperature zone is 40 min; the residence time in the fifth temperature zone is 30 min; and the transfer speed of the cobalt tetroxide precursor as it passes through the first, second, third, fourth, and fifth temperature zones is 140 min.

[0073] Example 4

[0074] The difference between this embodiment and Embodiment 1 is that the temperature of the fourth temperature zone is adjusted to 660°C.

[0075] The remaining preparation methods and parameters are consistent with those in Example 1.

[0076] Example 5

[0077] The difference between this embodiment and Embodiment 1 is that the temperature of the fourth temperature zone is adjusted to 620℃.

[0078] The remaining preparation methods and parameters are consistent with those in Example 1.

[0079] Example 6

[0080] The difference between this embodiment and Embodiment 1 is that the total residence time of the cobalt tetroxide precursor as it sequentially passes through the first temperature zone, the second temperature zone, the third temperature zone, the fourth temperature zone, and the fifth temperature zone is 200 min.

[0081] The remaining preparation methods and parameters are consistent with those in Example 1.

[0082] Example 7

[0083] The difference between this embodiment and Embodiment 1 is that the total residence time of the cobalt tetroxide precursor as it sequentially passes through the first temperature zone, the second temperature zone, the third temperature zone, the fourth temperature zone, and the fifth temperature zone is 80 minutes.

[0084] The remaining preparation methods and parameters are consistent with those in Example 1.

[0085] Example 8

[0086] The difference between this embodiment and Embodiment 1 is that the residence time in the fifth temperature zone is 10 minutes.

[0087] The remaining preparation methods and parameters are consistent with those in Example 1.

[0088] Example 9

[0089] The difference between this embodiment and Embodiment 1 is that the residence time in the fifth temperature zone is 50 minutes.

[0090] The remaining preparation methods and parameters are consistent with those in Example 1.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that the temperature of the first temperature zone is 400°C.

[0093] The remaining preparation methods and parameters are consistent with those in Example 1.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that the temperature of the first temperature zone is 500°C.

[0096] The remaining preparation methods and parameters are consistent with those in Example 1.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 1 is that the fourth temperature zone is not provided.

[0099] The remaining preparation methods and parameters are consistent with those in Example 1.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that the fifth temperature zone is not provided.

[0102] The remaining preparation methods and parameters are consistent with those in Example 1.

[0103] Performance testing

[0104] 1. The tap density and particle size D50 of the amorphous small-diameter cobalt tetroxide provided in the above examples and comparative examples were tested using a tap density tester and a Mastersizer 3000 laser particle size analyzer, respectively.

[0105] II. Based on the above embodiments and comparative examples, amorphous small-particle cobalt tetroxide and lithium carbonate were mixed at a molar ratio of 1:1.06, and then sintered at 900°C for 10 hours to obtain lithium cobalt oxide cathode material. The lithium cobalt oxide cathode material, polyvinylidene fluoride, and acetylene black were mixed at a mass ratio of 8:1:1 to form a slurry, which was then coated onto aluminum foil to obtain a positive electrode sheet. A lithium sheet was used as the negative electrode sheet; lithium hexafluorophosphate was used as the solute in the electrolyte, and the solvent was a combination of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1; a polypropylene separator was used; and a CR2032 coin cell was assembled.

[0106] The CR2032 coin cell was subjected to its first charge-discharge performance test: under constant current conditions, the first charge-discharge cycle was performed at a rate of 0.1C, and the first discharge specific capacity was measured.

[0107] Cyclic performance testing was performed on the CR2032 button cell: Under constant current conditions, charge and discharge cycles were performed at a rate of 1C within a voltage range of 2.8V to 4.3V for 100 cycles, and the discharge capacity of the 100th cycle was recorded.

[0108] The CR2032 button cell was subjected to rate performance testing: the cell was discharged at constant current rates of 0.2C, 0.5C, 1C, 2C and 3C to 3.0V at 25±5℃. The ratio of the discharge capacity at 3C rate to the initial capacity was calculated to obtain the rate capacity retention rate.

[0109] The test results are shown in Table 1.

[0110] Table 1

[0111]

[0112] analyze:

[0113] As shown in Table 1, this invention precisely controls the grain tap density and particle uniformity of cobalt tetroxide through a synergistic calcination strategy across multiple specific temperature zones, effectively suppressing excessive crystal growth and ordering, and obtaining amorphous products with fine particle size, low crystallinity, and uniform distribution. This cobalt tetroxide extract, as a precursor for lithium cobalt oxide, exhibits significantly improved reactivity and sintering compatibility. In the subsequent preparation of lithium cobalt oxide, it can form a dense and uniform microstructure, effectively improving not only the tap density and specific capacity of the electrode but also the electrolyte wettability and lithium-ion transport efficiency. Thus, while maintaining high capacity, it enhances the rate performance and cycle stability of the battery, providing material support for meeting the demands of high-end applications for high-energy-density, lightweight lithium-ion batteries.

[0114] As can be seen from the comparison between Example 1 and Example 5, if the temperature of the third temperature zone is greater than that of the fourth temperature zone, the material will suddenly heat up, resulting in uneven gas release during the decomposition of cobalt carbonate and uneven primary grain growth. The resulting cobalt tetroxide has uneven crystallinity and poor structural stability. When used as a precursor, it will reduce the structural integrity and cycle life of the final lithium cobalt oxide product.

[0115] A comparison of Examples 1 and 6-7 shows that if the transfer speed of the cobalt tetroxide precursor through the first, second, third, fourth, and fifth temperature zones is too low, the residence time will be too long, leading to excessive sintering and growth of particles, a significant decrease in specific surface area, and the amorphous structure may transform into a stable crystalline state. If the transfer speed of the cobalt tetroxide precursor through the first, second, third, fourth, and fifth temperature zones is too high, the residence time will be too short, resulting in insufficient decomposition reaction and incomplete phase transformation of the precursor.

[0116] As can be seen from the comparison between Example 1 and Examples 8-9, if the residence time in the fifth temperature zone is too short, the thermal stress cannot be fully released, the product has internal cracks and high surface energy, and poor chemical stability; if the residence time in the fifth temperature zone is too long, it will cause the amorphous structure to undergo an ordered transformation and the grains to grow slowly, resulting in a decrease in specific surface area and a partial loss of its high reactivity advantage.

[0117] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, if the temperature of the first temperature zone is too low, the precursor decomposition is insufficient and a sufficient amount of cobalt tetroxide crystal nuclei cannot be effectively formed; if the temperature of the first temperature zone is too high, the initial nucleation rate is too fast, and the initial crystal nuclei formed will quickly sinter and grow, losing the basis as a "small particle size" product.

[0118] As can be seen from the comparison between Example 1 and Comparative Example 3, if the fourth temperature zone is not set, the material will directly enter the cooling process after coming out of the third temperature zone, which will lead to incomplete phase transformation of some materials.

[0119] As can be seen from the comparison between Example 1 and Comparative Example 4, if the fifth temperature zone is not set, the material is directly moved from the fourth temperature zone to the room temperature environment. This rapid cooling will generate huge thermal stress inside the particles, which can easily cause microcracks or even breakage of the particles, destroying the integrity of the particles, resulting in a decrease in the tap density of the final product, and a large number of lattice defects inside the product, resulting in excessively high chemical activity and instability.

[0120] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing amorphous small-particle-size cobalt tetroxide, characterized in that, The preparation method includes the following steps: The cobalt salt solution and the precipitant solution were flowed concurrently into the base liquid to carry out the precipitation reaction. After the reaction was completed, post-processing was performed to obtain the cobalt tetroxide precursor. The cobalt tetroxide precursor was calcined sequentially through a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone, and a fifth temperature zone to obtain the amorphous small-particle cobalt tetroxide. The temperature of the first temperature zone is 420-480℃, the temperature of the second temperature zone is 460-540℃, the temperature of the third temperature zone is 620-660℃, the temperature of the fourth temperature zone is 620-660℃, and the temperature of the fifth temperature zone is 460-540℃.

2. The preparation method according to claim 1, characterized in that, The base liquid includes water and ammonium bicarbonate; Preferably, the concentration of ammonium bicarbonate in the bottom solution is 220-280 g / L; Preferably, the preset temperature of the base liquid is 40-50℃.

3. The preparation method according to claim 1 or 2, characterized in that, The cobalt salt solution includes any one or a combination of at least two of cobalt chloride solution, cobalt sulfate solution, or cobalt nitrate solution. Preferably, the concentration of the cobalt salt solution is 100-150 g / L; Preferably, the precipitant solution comprises an ammonium bicarbonate solution or a sodium hydroxide solution; Preferably, the concentration of the precipitant solution is 220-280 g / L.

4. The preparation method according to any one of claims 1-3, characterized in that, The flow rate of the cobalt salt solution is 200-400 L / h; Preferably, the flow rate of the precipitant solution is 900-1500 L / h.

5. The preparation method according to any one of claims 1-4, characterized in that, During the precipitation reaction, the pH of the reaction system is 7-7.3; Preferably, during the precipitation reaction, the temperature of the reaction system is 40-50℃; Preferably, the precipitation reaction takes 10-25 hours.

6. The preparation method according to any one of claims 1-5, characterized in that, The post-processing steps include washing and dehydrating the slurry obtained after the reaction.

7. The preparation method according to any one of claims 1-6, characterized in that, The total residence time of the cobalt tetroxide precursor as it sequentially passes through the first, second, third, fourth, and fifth temperature zones is 1.5-3 hours. Preferably, the residence time in the first temperature zone is 20-40 minutes; Preferably, the residence time in the second temperature zone is 20-40 minutes; Preferably, the residence time in the third temperature zone is 20-40 minutes; Preferably, the residence time in the fourth temperature zone is 20-40 minutes; Preferably, the residence time in the fifth temperature zone is 20-40 minutes; Preferably, the temperature of the third temperature zone is less than or equal to the temperature of the fourth temperature zone.

8. The preparation method according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) Preparation of the base solution: Water and ammonium bicarbonate are mixed at 40-50℃ and stirred at 100-150 rpm to obtain the base solution; the concentration of ammonium bicarbonate in the base solution is 220-280 g / L. (2) The cobalt salt solution and the precipitant solution are fed into the bottom liquid in parallel, and the pH of the reaction system is controlled at 7-7.3 and the temperature at 40-50℃. The precipitation reaction is carried out for 10-25 hours to obtain the cobalt tetroxide precursor slurry. (3) The cobalt tetroxide precursor slurry is centrifuged and washed at a temperature of 50-80℃, and then dehydrated to obtain the cobalt tetroxide precursor; (4) The cobalt tetroxide precursor is fed into a rotary kiln and passes through a first temperature zone of 420-480℃, a second temperature zone of 460-540℃, a third temperature zone of 620-660℃, a fourth temperature zone of 620-660℃, and a fifth temperature zone of 460-540℃ in sequence. After discharge, it is subjected to vibration sieving and iron removal treatment to obtain amorphous small-particle cobalt tetroxide. The residence time of the cobalt tetroxide precursor in the first temperature zone is 20-40 min; the residence time in the second temperature zone is 20-40 min; the residence time in the third temperature zone is 20-40 min; the residence time in the fourth temperature zone is 20-40 min; and the residence time in the fifth temperature zone is 20-40 min.

9. An amorphous, small-particle-size cobalt tetroxide, characterized in that, The amorphous small-particle-size cobalt tetroxide is prepared by the preparation method described in any one of claims 1-8; The particle size D50 of the amorphous small-diameter cobalt tetroxide is 5-9 μm; The tap density of the amorphous small-particle cobalt tetroxide is 2.2-2.5 g / cm³. 3 .

10. An application of the amorphous small-particle-size cobalt tetroxide as described in claim 9 in lithium-ion batteries.

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