Cobalt tetroxide and its preparation method, lithium cobalt oxide and positive electrode sheet

Abstract

This invention discloses a cobalt tetroxide, its preparation method, lithium cobalt oxide, and a positive electrode sheet, relating to the field of lithium battery positive electrode materials technology. The particle size difference of the cobalt tetroxide at 7500N pressure relative to that at zero pressure is ΔDv5≤0.37μm, ΔDv10≤0.5μm, and ΔDv50≤1.95μm. This invention employs flash drying to dehydrate and pre-oxidize cobalt carbonate at high temperature, followed by sintering in a suspension furnace. The resulting cobalt tetroxide exhibits high specific surface area and tap density, as well as strong processing strength. The subsequent lithium-ionized and sintered lithium cobalt oxide demonstrates excellent discharge specific capacity.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode materials, and more specifically, to a cobalt tetroxide and its preparation method, lithium cobalt oxide, and a cathode sheet. Background Technology

[0002] Cobalt tetroxide particles are layered and have weak interlayer bonding, making them brittle and prone to breakage during processing. Existing technologies employ various methods to improve the processing performance of cobalt tetroxide, such as increasing the crystallinity of its outer layer, but the results are not ideal. Furthermore, to improve the bonding ability of cobalt tetroxide with lithium and the electrochemical performance of the resulting lithium cobalt oxide, it is necessary to further increase the specific surface area and tap density of cobalt tetroxide.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide cobalt tetroxide and its preparation method, lithium cobalt oxide, and positive electrode sheet, aiming to improve the processing strength, specific surface area, and tap density of cobalt tetroxide, thereby improving the electrochemical performance of the lithium cobalt oxide obtained from it.

[0005] This invention is implemented as follows:

[0006] In a first aspect, the present invention provides cobalt tetroxide, having the following characteristics:

[0007] Feature 1: The particle size difference ΔDv5 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤0.37μm;

[0008] Feature 2: The particle size difference ΔDv10 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤0.5μm;

[0009] Feature 3: The particle size difference ΔDv50 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤1.95μm.

[0010] In some embodiments of the present invention, the cobalt tetroxide has at least one of the following characteristics:

[0011] Feature 4: The value of ΔDv5 is 0.26μm≤ΔDv5≤0.37μm; the value of ΔDv10 is 0.4μm≤ΔDv10≤0.5μm; the value of ΔDv50 is 1.85μm≤ΔDv50≤1.95μm;

[0012] Feature 5: The specific surface area of ​​the cobalt tetroxide is greater than or equal to 10 m². 2 / g; preferably, the specific surface area is 10–12.6 m² / g.2 / g;

[0013] Feature 6: The tap density of the cobalt tetroxide is greater than or equal to 2.25 g / cm³. 3 Preferably, the tap density is 2.25–2.4 g / cm³. 3 .

[0014] Secondly, the present invention provides a method for preparing cobalt tetroxide, comprising the following steps:

[0015] Step 1: The cobalt carbonate is fed into a flash dryer for drying to obtain the pre-oxidized material;

[0016] Step 2: The pre-oxidized material is fed into a suspension furnace for sintering, cooled, sieved, and demagnetized to obtain cobalt tetroxide.

[0017] In some embodiments of the present invention, the drying temperature in step one is 250–400°C and the time is 10–30 seconds.

[0018] In some embodiments of the present invention, the pre-oxidized material has a moisture content of ≤1.5% and a cobalt content of 60%-72.2%.

[0019] In some embodiments of the present invention, the sintering temperature in step two is 710–750°C and the time is 2–3 min.

[0020] In some embodiments of the present invention, the feed rate of cobalt carbonate into the flash dryer in step one is 5 to 15 kg / min.

[0021] In some embodiments of the present invention, the feeding rate of the pre-oxidized material in step two into the suspension furnace is 4 to 11 kg / min.

[0022] Thirdly, the present invention provides a lithium cobalt oxide obtained by mixing cobalt tetroxide obtained from the first aspect or any embodiment of the second aspect with a lithium source and sintering it.

[0023] Fourthly, the present invention provides a positive electrode sheet comprising the aforementioned lithium cobalt oxide.

[0024] Fifthly, the present invention also provides a lithium battery comprising the above-mentioned positive electrode sheet.

[0025] The present invention has the following beneficial effects:

[0026] This invention provides cobalt tetroxide and its preparation method. The cobalt tetroxide exhibits good processing strength, high specific surface area, and tap density. First, cobalt carbonate is dehydrated and pre-oxidized at high temperature using flash drying. Then, it is further sintered in a suspension furnace. Both flash drying and suspension furnace sintering processes reduce the material processing time, allowing the material to shrink rapidly at high temperatures, improving the bonding strength within the material particles, and thus increasing the tap density, specific surface area, and processing strength. The lithium cobalt oxide obtained by subsequent lithium addition and sintering exhibits good discharge specific capacity. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 SEM images of cobalt tetroxide prepared in Example 1(a) and Comparative Example 3(b);

[0029] Figure 2 SEM images of cobalt tetroxide prepared in Example 1(a) and Comparative Example 3(b) after ball milling experiments;

[0030] Figure 3 The charge-discharge curves of cobalt tetroxide prepared in Example 1 and Comparative Example 3 are shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0032] This invention provides cobalt tetroxide, which has the following characteristics:

[0033] Feature 1: The particle size difference ΔDv5 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤0.37μm;

[0034] Feature 2: The particle size difference ΔDv10 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤0.5μm;

[0035] Feature 3: The particle size difference ΔDv50 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤1.95μm.

[0036] Dv5, Dv10, and Dv50 refer to the particle size corresponding to the cumulative volume distribution of particle size based on volume reaching 5%, 10%, and 50%, respectively. ΔDv5, ΔDv10, and ΔDv50 refer to the changes in Dv5, Dv10, and Dv50 of cobalt tetroxide under 7500N pressure relative to zero pressure. The smaller ΔDv is, the greater the processing strength of cobalt tetroxide, and the less likely the particles are to break during pressing. This is beneficial for obtaining lithium cobalt oxide with high sphericity and high tap density when mixed and sintered with lithium source, which in turn is beneficial for the electrochemical performance of lithium cobalt oxide.

[0037] In some embodiments of the present invention, the cobalt tetroxide has at least one of the following characteristics:

[0038] Feature 4: The value of ΔDv5 is 0.26μm≤ΔDv5≤0.37μm; the value of ΔDv10 is 0.4μm≤ΔDv10≤0.5μm; the value of ΔDv50 is 1.85μm≤ΔDv50≤1.95μm;

[0039] Feature 5: The specific surface area of ​​the cobalt tetroxide is greater than or equal to 10 m². 2 / g; preferably, the specific surface area is 10–12.6 m² / g. 2 / g;

[0040] Feature 6: The tap density of the cobalt tetroxide is greater than or equal to 2.25 g / cm³. 3 Preferably, the tap density is 2.25–2.4 g / cm³. 3 .

[0041] This invention provides a method for preparing cobalt tetroxide, comprising the following steps:

[0042] Step 1: The cobalt carbonate is fed into a flash dryer for drying to obtain the pre-oxidized material;

[0043] Step 2: The pre-oxidized material is fed into a suspension furnace for sintering, cooled, sieved, and demagnetized to obtain cobalt tetroxide.

[0044] In this invention, cobalt carbonate undergoes partial oxidation during drying and dehydration in a flash dryer to obtain a pre-oxidized material. This effectively prevents the material from sticking to the wall during subsequent sintering in a suspension furnace. Sticking to the wall is not conducive to sufficient contact between particles and oxygen, which can lead to uneven oxidation and other problems.

[0045] This invention employs a suspension furnace for sintering pre-oxidized materials. In the suspension furnace, the material is in a suspended state, resulting in a much higher heat and mass transfer rate compared to materials in fixed or fluidized beds. The gas inside the furnace is in a state of intense turbulence, ensuring uniform heating and a high reaction rate. This sintering method produces small grain sizes and high sintering activity, resulting in cobalt tetroxide with good homogeneity, high tap density, high specific surface area, and high processing strength.

[0046] Both flash drying and suspension furnace sintering processes reduce the material processing time, enabling the material to shrink rapidly at high temperatures, thereby increasing the bonding strength within the material particles and consequently improving the material's tap density, specific surface area, and processing strength.

[0047] In some embodiments of the present invention, the drying temperature in step one is 250–400°C, which can be 250°C, 300°C, 350°C, 400°C, etc.; the drying time is 10–30 seconds, which can be 10 seconds, 20 seconds, 30 seconds, etc.; the temperature and time of flash drying affect the degree of pre-oxidation of cobalt carbonate. The higher the temperature and the longer the time, the higher the degree of oxidation of cobalt carbonate; if the temperature is too low, the degree of pre-oxidation of cobalt carbonate is low, which is not conducive to improving the tap density of the material; if the temperature is too high, the equipment requirements are high, which will lead to design waste and reduce the sintering activity of cobalt tetroxide.

[0048] In some embodiments of the present invention, the moisture content of the pre-oxidized material in step one is ≤1.5%, which can be 1.5%, 1.2%, 0.8%, 0.5%, 0.2%, etc.; the cobalt content is 60%-72.2%, which can be 60%, 62%, 64%, 66%, 68%, 70%, 72.2%, etc.

[0049] In some embodiments of the present invention, the feed rate of cobalt carbonate into the flash dryer in step one is 5 to 15 kg / min.

[0050] In some embodiments of the present invention, the sintering temperature in step two is 710-750°C, which can be 710°C, 720°C, 730°C, 740°C, 750°C, etc.; the time is 2-3 min, which can be 2 min, 2.5 min, 3 min, etc. The sintering temperature and time affect the performance of cobalt tetroxide. Too high a temperature will cause the material to become too sintered and agglomerated; too low a temperature will cause insufficient oxidation and impure product.

[0051] In some embodiments of the present invention, the feeding rate of the pre-oxidized material into the suspension furnace is 4 kg to 11 kg / min, which can be 4 kg / min, 7 kg / min, 9 kg / min, 11 kg / min, etc.

[0052] This invention also provides a lithium cobalt oxide, which is obtained by mixing a lithium source with cobalt tetroxide from any of the above embodiments and then sintering.

[0053] In an optional embodiment, the lithium source includes at least one of lithium carbonate and lithium hydroxide.

[0054] This invention also provides a positive electrode sheet comprising the aforementioned lithium cobalt oxide.

[0055] This invention also provides a lithium battery, including the above-mentioned positive electrode sheet. The lithium battery also includes a negative electrode sheet, an electrolyte, a separator, etc., forming a complete battery structure with good cycle performance.

[0056] Specifically, the types of negative electrode, electrolyte, and separator are not limited. During the charging and discharging process of a secondary battery, active ions are inserted and removed back and forth between the positive and negative electrode, while the electrolyte plays the role of conducting ions between the positive and negative electrode.

[0057] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0058] Example 1

[0059] A method for preparing cobalt tetroxide includes the following steps:

[0060] Step 1: Take cobalt carbonate with a moisture content of 10% and flash dry it in a flash dryer to obtain pre-oxidized material. The flash dryer is set at a temperature of 300℃, a feed rate of 10 kg / min, and a drying time of 20 s. The resulting pre-oxidized material has a moisture content of 1.2% and a cobalt content of 63%.

[0061] Step 2: The pre-oxidized material is directly fed into the suspension furnace for sintering. After cooling, it is sieved and demagnetized to obtain cobalt tetroxide. The sintering temperature is 730℃, the sintering time is 2min, and the feeding rate is 7kg / min.

[0062] Example 2

[0063] A method for preparing cobalt tetroxide includes the following steps:

[0064] Step 1: Take cobalt carbonate with a moisture content of 10% and flash dry it in a flash dryer to obtain pre-oxidized material. The flash dryer is set to a temperature of 250℃, a feed rate of 15 kg / min, and a drying time of 30 s. The resulting pre-oxidized material has a moisture content of 1.4% and a cobalt content of 60%.

[0065] Step 2: The pre-oxidized material is directly fed into a suspension furnace for sintering. After cooling, it is sieved and demagnetized to obtain cobalt tetroxide. The sintering temperature is 710℃, the sintering time is 3min, and the feeding rate is 11kg / min.

[0066] Example 3

[0067] A method for preparing cobalt tetroxide includes the following steps:

[0068] Step 1: Take cobalt carbonate with a moisture content of 10% and flash dry it in a flash dryer to obtain pre-oxidized material. The flash dryer is set at a temperature of 400℃, a feed rate of 5 kg / min, and a drying time of 10 s. The resulting pre-oxidized material has a moisture content of 0.6% and a cobalt content of 69%.

[0069] Step 2: The pre-oxidized material is directly fed into a suspension furnace for sintering. After cooling, it is sieved and demagnetized to obtain cobalt tetroxide. The sintering temperature is 750℃, the sintering time is 2min, and the feeding rate is 4kg / min.

[0070] Example 4

[0071] The difference from Example 1 is that the flash dryer in step one is set to a temperature of 250°C.

[0072] The resulting pre-oxidized material had a moisture content of 1.3% and a cobalt content of 62%.

[0073] Example 5

[0074] The difference from Example 1 is that the flash dryer in step one is set to a temperature of 350°C.

[0075] The resulting pre-oxidized material had a moisture content of 1.1% and a cobalt content of 64%.

[0076] Example 6

[0077] The difference from Example 1 is that the drying time in step one is 30 seconds.

[0078] The resulting pre-oxidized material has a moisture content of 0.8% and a cobalt content of 64%.

[0079] Example 7

[0080] The difference from Example 1 is that the sintering temperature in step two is 710°C.

[0081] Example 8

[0082] The difference from Example 1 is that the sintering temperature in step two is 750°C.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that step one uses an oven for drying. The specific steps are as follows: take cobalt carbonate with a water content of 10%, put it into a forced-air oven for drying, set the temperature to 110°C, and dry for 8 hours.

[0085] The resulting pre-oxidized material has a moisture content of 5% and a cobalt content of 53%.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that step two uses a rotary kiln for sintering. The specific steps are as follows: the pre-oxidized material is put into the rotary kiln for sintering, and after cooling, it is sieved and demagnetized to obtain cobalt tetroxide. The sintering temperature is 730℃, the sintering time is 4h, and the feeding rate is 200kg / h.

[0088] The resulting pre-oxidized material had a moisture content of 1.2% and a cobalt content of 63%.

[0089] Comparative Example 3

[0090] Step 1: Take cobalt carbonate with a water content of 10%, put it in a forced-air drying oven and dry it at a temperature of 110℃ for 8 hours to obtain dried cobalt tetroxide.

[0091] Step 2: Place the dried cobalt tetroxide into a rotary kiln for sintering. After cooling, sieve and demagnetize to obtain cobalt tetroxide. The sintering temperature is 750℃, the sintering time is 4h, and the feeding rate is 200kg / h.

[0092] The resulting pre-oxidized material has a moisture content of 5% and a cobalt content of 53%.

[0093] Comparative Example 4

[0094] The difference from Example 1 is that the flash dryer in step one is set to a temperature of 150°C.

[0095] The resulting pre-oxidized material has a moisture content of 3% and a cobalt content of 48%.

[0096] Comparative Example 5

[0097] The difference from Example 1 is that the flash dryer in step one is set to a temperature of 500°C.

[0098] The resulting pre-oxidized material has a moisture content of 0.9% and a cobalt content of 70%.

[0099] Figure 1 The images show scanning electron microscope (SEM) images of cobalt tetroxide prepared in Example 1(a) and Comparative Example 3(b). The images show that the primary particles in the Example 1 material are small and tightly bound. In contrast, the primary particles in the Comparative Example material are large and have large gaps between them.

[0100] Experimental Example 1

[0101] The processing strength of cobalt tetroxide prepared in the examples and comparative examples was evaluated. The processing strength of the powder was evaluated by the change in particle size after pressing. The specific method is as follows: The initial particle size Dv5, Dv10, and Dv50 of the powder to be tested were measured. Then, the powder sample was placed on a pressure particle size analyzer and the pressure parameter was set to 7500N. After pressing, the particle size Dv5', Dv10', and Dv50' of the powder sample were measured again. Then, the particle size difference ΔDv5, ΔDv10, and ΔDv50 were calculated. Taking ΔDv5 as an example, ΔDv5 = Dv5 - Dv5'. The particle size difference data of the examples and comparative examples are shown in Table 1.

[0102] Experimental Example 2

[0103] Ball milling tests were conducted on the cobalt tetroxide prepared in Example 1 and Comparative Example 3, and the morphological changes of the particles after ball milling were observed by scanning electron microscopy. The ball milling conditions were as follows: rotation speed of 500 rpm and ball milling time of 10 min.

[0104] Figure 2 The images show SEM images of cobalt tetroxide prepared in Example 1(a) and Comparative Example 3(b) after ball milling experiments. It can be seen from the images that the particles of Example 1 have a lower degree of breakage compared to those of Comparative Example 3, indicating that Example 1 has better processing strength.

[0105] Experimental Example 3

[0106] According to GB / T 21354-2008 Method for Determination of Tap Density of Powder Products, the tap density (TD) of cobalt tetroxide was determined by vibrating 500 times. The results are shown in Table 1.

[0107] Test Example 4

[0108] The specific surface area of ​​cobalt tetroxide prepared in the examples and comparative examples was analyzed. The specific method is as follows: the TriStar3020 (Mc) analyzer was used for testing, liquid nitrogen adsorption was performed, the weight before and after adsorption was weighed, and the specific surface area (BET) was calculated. The results are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] As shown in Table 1, the cobalt tetroxide prepared in this embodiment exhibits higher processing strength compared to the comparative example. The change in Dv50 particle size under 7500N pressing is less than 2μm. This is because the combined flash drying and suspension furnace sintering processes reduce the material processing time, allowing for rapid shrinkage at high temperatures, thus improving the internal bonding strength of the material particles and consequently enhancing the processing strength. Specifically, Comparative Example 1 uses a blower box to dry cobalt carbonate. The powder obtained in step one not only has a high moisture content but also low cobalt carbonate dispersion, making the particles prone to sintering and agglomeration, resulting in a smaller specific surface area for the obtained cobalt tetroxide. Comparative Example 2 uses a rotary kiln to oxidize and sinter the pre-oxidized material. At the same sintering temperature, the rotary kiln sintering time is 4 hours, while the suspension furnace sintering time in Example 1 is only 2 minutes. Furthermore, the product obtained in Example 1 has higher tap density and specific surface area, indicating that suspension sintering enables rapid particle shrinkage.

[0113] Comparing Examples 1, 4, and 5, and Comparative Examples 4 and 5, it can be seen that the flash drying temperature affects the processing strength, specific surface area, and tap density of cobalt tetroxide. The material with the best comprehensive performance is obtained when the flash drying temperature is 300℃. This is because excessively high temperature reduces the sintering activity of the pre-oxidized material, while excessively low temperature causes cobalt carbonate to stick to the wall. Neither of these conditions is conducive to improving the performance of cobalt tetroxide.

[0114] Comparing Examples 1 and 6, it can be seen that the flash drying time affects the processing strength, specific surface area, and tap density of cobalt tetroxide. Specifically, the longer the flash drying time, the greater the mechanical collision of particles, which makes it easier for powder to fall off, affecting product quality. Therefore, the cobalt tetroxide obtained in Example 6 is slightly worse than that obtained in Example 1.

[0115] Comparing Examples 1, 7, and 8, it can be seen that the sintering temperature has a significant impact on the specific surface area and tap density of cobalt tetroxide, but a relatively small impact on its processing strength. Specifically, as the sintering temperature increases, the specific surface area of ​​the material becomes smaller and the tap density becomes larger. A suitable temperature can be selected according to the requirements.

[0116] Experimental Example 5

[0117] The cobalt tetroxide prepared in the examples and comparative examples was mixed with a lithium source and sintered to obtain lithium cobalt oxide cathode material. Then, after assembling the battery, charge-discharge tests were performed. The specific method is as follows:

[0118] (1) Cobalt tetroxide and lithium carbonate were mixed in a molar ratio of Li:Co=1.05:1, ground and mixed, and then sintered to obtain lithium cobalt oxide; the sintering temperature was 1100℃ and the time was 24h.

[0119] (2) Lithium cobalt oxide, acetylene black, and PVDF are ground and mixed in a weight ratio of 8:1:1, and then N-methylpyrrolidone (NMP) is added to obtain a positive electrode slurry; graphite, acetylene black, hydroxymethyl cellulose, and styrene-butadiene rubber are ground and mixed in a mass ratio of 94.5:2:1.5:2, and then added to deionized water to obtain a negative electrode slurry; the positive electrode slurry and the negative electrode slurry are uniformly coated on aluminum foil and copper foil respectively, dried and rolled to obtain a positive electrode sheet and a negative electrode sheet.

[0120] (3) Button cell assembly: The positive and negative electrode sheets are further punched into circular electrode sheets with a diameter of 12 mm. Then, a glass fiber membrane is used as the separator and a 1M LiPF6 solution (the solvent is a mixed solution of EMC, DC and DMC with a volume ratio of 1:1:1) is used as the electrolyte to assemble a CR2032 button cell.

[0121] (4) Charge and discharge test: The button battery is charged and discharged at a rate of 0.1C.

[0122] The initial discharge specific capacity of the batteries finally prepared using cobalt tetroxide as a raw material in the examples and comparative examples is shown in Table 2. The charge-discharge curves of the batteries finally prepared using cobalt tetroxide as a raw material in Example 1 and Comparative Example 3 are shown in Table 2. Figure 3 .

[0123] Table 2

[0124]

[0125] The electrochemical performance of cobalt tetroxide is affected by its specific surface area and tap density. Specifically, the tap density has a greater impact on the specific capacity of the material. As can be seen from the analysis of Table 2, when comparing Examples 1, 4, and 5, the higher the tap density of the material, the larger the specific surface area and the larger the specific capacity; when comparing Examples 1 and 6, the higher the tap density of the material, the larger the specific surface area and the larger the specific capacity; when comparing Examples 1, 7, and 8, the higher the tap density of the material, the larger the specific capacity.

[0126] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cobalt tetroxide, characterized in that, It has the following characteristics: Feature 1: The particle size difference of the cobalt tetroxide Dv5 under 7500N pressure compared to Dv5 under zero pressure ΔDv5≤0.37μm; Feature 2: The particle size difference ΔDv10 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤0.5μm; Feature 3: The particle size difference ΔDv50 of the cobalt tetroxide under 7500N pressure relative to that under zero pressure is ≤1.95μm.

2. The cobalt tetroxide according to claim 1, characterized in that, It has at least one of the following characteristics: Feature 4: The value of ΔDv5 is 0.26μm≤ΔDv5≤0.37μm; the value of ΔDv10 is 0.4μm≤ΔDv10≤0.5μm; the value of ΔDv50 is 1.85μm≤ΔDv50≤1.95μm; Feature 5: The specific surface area of ​​the cobalt tetroxide is greater than or equal to 10 m². 2 / g; Feature 6: The tap density of the cobalt tetroxide is greater than or equal to 2.25 g / cm³. 3 .

3. The method for preparing cobalt tetroxide according to any one of claims 1 to 2, characterized in that, Includes the following steps: Step 1: The cobalt carbonate is fed into a flash dryer for drying to obtain the pre-oxidized material; Step 2: The pre-oxidized material is fed into a suspension furnace for sintering, cooled, sieved, and demagnetized to obtain cobalt tetroxide.

4. The method for preparing cobalt tetroxide according to claim 3, characterized in that, The drying temperature in step one is 250–400°C, and the time is 10–30 seconds.

5. The method for preparing cobalt tetroxide according to claim 3 or 4, characterized in that, The pre-oxidized material has a moisture content of ≤1.5% and a cobalt content of 60%-72.2%.

6. The method for preparing cobalt tetroxide according to claim 3, characterized in that, The sintering temperature in step two is 710–750°C, and the time is 2–3 minutes.

7. The method for preparing cobalt tetroxide according to claim 3, characterized in that, The feed rate of cobalt carbonate into the flash dryer in step one is 5-15 kg / min.

8. The method for preparing cobalt tetroxide according to claim 3, characterized in that, The feeding rate of the pre-oxidized material into the suspension furnace in step two is 4 to 11 kg / min.

9. A lithium cobalt oxide, characterized in that, The lithium cobalt oxide is obtained by mixing a lithium source with cobalt tetroxide as described in any one of claims 1 to 2 and then sintering.

10. A positive electrode plate, characterized in that, Includes the lithium cobalt oxide as described in claim 9.

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