Lithium cobalt oxide positive electrode material and preparation method and application thereof

Abstract

The invention provides a lithium cobalt oxide positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a cobalt precursor and a lithium source, and carrying out primary sintering to obtain a primary sintered product; and carrying out secondary sintering on the primary sintered product to obtain the lithium cobalt oxide positive electrode material, the kiln pressure of the primary sintering is 0 Pa or below, and / or the kiln pressure of the secondary sintering is 0 Pa or below; according to the preparation method, by controlling the kiln pressure in the sintering process, sintering black spots of the lithium cobalt oxide positive electrode material are avoided, the particle morphology is improved, the growth uniformity is improved, lithium salt and CO2 in the sintering process can be removed in time, the content of residual alkali on the particle surface of the lithium cobalt oxide positive electrode material is reduced, and the cycle performance of the positive electrode material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to a lithium cobalt oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] With the rapid development of 3C electronic products, lithium cobalt oxide positive electrode materials have been widely studied due to their advantages such as high operating voltage, stable discharge and good cycle performance. In order to cope with the requirements of the continuously upgraded consumer electronic products for higher energy density and cycle performance of lithium batteries, the preparation process of lithium cobalt oxide positive electrode materials has also begun to diversify. The most widely used method is to prepare lithium cobalt oxide materials by a multi-stage sintering method. For example, CN 115642235A discloses a lithium cobalt oxide positive electrode material and its preparation method and application. The preparation method comprises the following steps: a) mixing a cobalt source A, a lithium source C and a doping element D, performing a first sintering, and mechanically crushing to obtain a matrix lithium cobalt oxide; b) mixing a cobalt source B, a lithium source C and a doping element E, performing a second sintering, and obtaining a primary lithium cobalt oxide after air flow crushing; c) mixing the matrix lithium cobalt oxide obtained in step a), the primary lithium cobalt oxide obtained in step b) and an additive, performing a third sintering, and mechanically crushing to obtain a single-sintered product having a core-shell structure; d) mixing the single-sintered product having a core-shell structure obtained in step c) with a coating agent, performing a fourth sintering, and depolymerizing to obtain a lithium cobalt oxide positive electrode material.

[0003] However, in the sintering process of the current existing technology, the volatilized lithium salt and CO2 cannot be removed in time, resulting in the appearance of "black spots" in the material after sintering. The material at this location has a large particle size and a high residual alkali, resulting in abnormal particle size of the overall sample and high residual alkali on the surface. In addition, during the sintering process, as the temperature rises, the gas expands, causing excessive reaction and a large number of particles to agglomerate.

[0004] Based on the above research, it is necessary to provide a method for preparing a lithium cobalt oxide positive electrode material, which can avoid the sintering "black spots" of the lithium cobalt oxide positive electrode material, improve the particle morphology, reduce the amount of residual alkali on the surface of the lithium cobalt oxide positive electrode material particles, and improve the cycle performance of the positive electrode material. Summary of the invention

[0005] The object of the present invention is to provide a lithium cobalt oxide positive electrode material and a preparation method and application thereof. The preparation method avoids the sintering "black spots" of the lithium cobalt oxide positive electrode material by controlling the kiln pressure during the sintering process, improves the particle morphology, enhances the growth uniformity, and can timely remove lithium salts and CO2 during the sintering process, thereby reducing the residual alkali content on the surface of the lithium cobalt oxide positive electrode material particles and improving the cycle performance of the positive electrode material.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a lithium cobalt oxide positive electrode material, the preparation method comprising the following steps:

[0008] (1) mixing a cobalt precursor and a lithium source and sintering them once to obtain a sintered product;

[0009] (2) performing secondary sintering on the first sintered product of step (1) to obtain the lithium cobalt oxide positive electrode material;

[0010] Wherein, the kiln pressure of the primary sintering in step (1) is below 0 Pa, and / or the kiln pressure of the secondary sintering in step (2) is below 0 Pa.

[0011] The present invention mainly adjusts the kiln pressure during the sintering process. Since the kiln pressure reflects the exhaust balance, when the kiln pressure is below 0Pa, the volatilized lithium salt and the generated carbon dioxide gas can be discharged in time to ensure the continuous reaction, reduce the residual alkali on the surface of the lithium cobalt oxide particles, and improve the material processing performance and electrical properties. Therefore, the present invention controls the exhaust balance by real-time regulation of the kiln pressure, solves the influence of gas on the particle morphology and structure during the sintering process of high-voltage lithium cobalt oxide materials, and avoids the sintering "black spots" of lithium cobalt oxide positive materials.

[0012] The kiln pressure of the primary sintering in step (1) of the present invention is below 0Pa, and / or the kiln pressure of the secondary sintering in step (2) is below 0Pa, including the following situations: ① the kiln pressure of the primary sintering is below 0Pa, and the kiln pressure of the secondary sintering is below 0Pa or greater than 0Pa, ② the kiln pressure of the primary sintering is greater than 0Pa, and the kiln pressure of the secondary sintering is below 0Pa.

[0013] Preferably, the kiln pressure of the secondary sintering in step (2) is -5 to 5 Pa, for example, -5 Pa, 0 Pa or 5 Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0014] Preferably, the kiln pressure of the primary sintering in step (1) is below 0 Pa, for example, it can be 0 Pa, -10 Pa, -20 Pa, -30 Pa, -40 Pa, -50 Pa or -60 Pa, and the kiln pressure of the secondary sintering in step (2) is greater than 0 Pa, for example, it can be 10 Pa, 50 Pa, 100 Pa, 200 Pa or 500 Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] In the preparation method of the present invention, it is only necessary to control the kiln pressure of the primary sintering. Since the primary sintering process is the reaction of lithium salt and cobalt salt and the growth process of lithium cobalt oxide crystals, the crystallinity, primary particle morphology and surface residual alkali of the lithium cobalt oxide formed in this stage directly affect the gram capacity and cycle performance of the product. Therefore, the present invention only needs to control the kiln pressure of the primary sintering process to improve the crystallinity, particle morphology and surface residual alkali of the lithium cobalt oxide positive electrode material, thereby improving the product performance.

[0016] Preferably, the kiln pressure for the primary sintering in step (1) is -50Pa to 0Pa, for example, it can be -50Pa, -40Pa, -30Pa, -20Pa, -10Pa or 0Pa, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably -30Pa to -10Pa.

[0017] The kiln pressure for primary sintering of the present invention is preferably in the range of -30Pa to -10Pa. When the kiln pressure is too low, excessive exhaust will occur, thereby taking away the Li necessary for the sintering process, resulting in incomplete reaction and serious agglomeration. When the kiln pressure is too high, the volatilized lithium salts and the produced CO2 during the sintering process cannot be discharged in time, resulting in excessive particle reaction and larger particle growth size. In order to obtain the designed particle size, the particles are broken up during the pulverization process, resulting in an increase in slag on the particle surface and an increase in residual alkali. During the battery cycle, the contact with the electrolyte will increase, resulting in poor cycle performance.

[0018] Preferably, the exhaust flow rate of the primary sintering in step (1) is greater than or equal to the intake air flow rate.

[0019] The present invention controls the kiln pressure during the sintering process by controlling the flow rates of intake and exhaust during the sintering process. When the exhaust flow rate of the present invention is greater than the intake flow rate, the kiln pressure can be made less than 0Pa.

[0020] Preferably, the ratio of the exhaust flow rate to the intake flow rate of the primary sintering in step (1) is (1-1.8):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1 or 1.8:1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably (1.16-1.48):1.

[0021] During the sintering process of the present invention, air is always inlet and outlet, and by controlling the ratio of exhaust flow rate to air inlet flow rate, the kiln pressure of the reaction is controlled in real time within a specific range, and the particle uniformity and surface residual alkali content are controlled.

[0022] Preferably, the exhaust frequency of the sintering furnace used in the primary sintering in step (1) is 5-50 Hz, for example, 5 Hz, 15 Hz, 25 Hz, 35 Hz, 45 Hz or 50 Hz, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] The present invention can control the exhaust flow rate of sintering by controlling the exhaust frequency of the sintering furnace, thereby controlling the kiln pressure of the sintering process. That is, the kiln pressure, the ratio of the exhaust flow rate to the intake flow rate, and the exhaust frequency of the present invention are matched with each other to achieve the purpose of real-time control of the sintering process; and, by changing the exhaust frequency, the present invention eliminates the need for process steps such as adjusting the exhaust gate valve and the air supply port under different processes, thereby avoiding misoperation or missed operation when switching the lithium cobalt oxide sintering under different voltages. The present invention only needs to regulate the kiln pressure to improve the reaction process and growth process of the material during sintering.

[0024] Preferably, the sintering furnace used for the primary sintering in step (1) is a box-type sintering furnace.

[0025] Preferably, the primary sintering temperature in step (1) is 600-700°C, for example, 600°C, 650°C or 700°C, and the sintering time is 15-30h, for example, 15h, 20h, 25h or 30h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the atmosphere for the primary sintering in step (1) is an air atmosphere.

[0027] Preferably, when the cobalt precursor and the lithium source are mixed in step (1), a dopant is also added.

[0028] Preferably, the amount of the dopant added is 0.1-1.0wt% of the cobalt precursor in step (1), for example, it can be 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 0.9wt% or 1.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the dopant includes any one or a combination of at least two of a lithium-containing compound, a magnesium-containing compound, an aluminum-containing compound, a zirconium-containing compound, a titanium-containing compound, a cobalt-containing compound, a fluorine-containing compound, a yttrium-containing compound or a lanthanum-containing compound.

[0030] Preferably, the cobalt precursor in step (1) is doped cobalt tetroxide, preferably aluminum-doped cobalt tetroxide.

[0031] Preferably, the lithium source in step (1) comprises lithium carbonate and / or lithium hydroxide.

[0032] Preferably, the kiln pressure of the secondary sintering in step (2) is 0-5 Pa, but excluding 0 Pa.

[0033] Preferably, the temperature of the secondary sintering in step (2) is 600-1000°C, for example, 600°C, 700°C, 800°C, 900°C or 1000°C, and the time is 5-16h, for example, 5h, 10h, 15h or 16h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the atmosphere for the secondary sintering in step (2) is an air atmosphere.

[0035] Preferably, the first sintered product in step (1) is mixed with a coating agent before the second sintering.

[0036] Preferably, the coating agent is added in an amount of 0.1-1.0 wt % of the sintered product, for example, 0.1 wt %, 0.5 wt % or 1.0 wt %, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the coating agent comprises any one or a combination of at least two of a lithium-containing compound, a magnesium-containing compound, an aluminum-containing compound, a zirconium-containing compound, a titanium-containing compound, a cobalt-containing compound, a fluorine-containing compound, a yttrium-containing compound or a lanthanum-containing compound.

[0038] Preferably, the secondary sintering in step (2) is followed by screening.

[0039] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0040] (1) mixing a cobalt precursor, a lithium source and a dopant, and then sintering them at a kiln pressure of -30Pa to -10Pa and a temperature of 600-700°C for 15-30h to obtain a sintered product;

[0041] The exhaust flow rate of the primary sintering is greater than the intake flow rate, and the ratio of the exhaust flow rate to the intake flow rate of the primary sintering is (1.16-1.48):1, and the exhaust frequency of the sintering furnace used in the primary sintering is 5-50Hz;

[0042] The amount of the dopant added is 0.1-1.0 wt% of the cobalt precursor in step (1);

[0043] (2) mixing the first sintered product of step (1) with a coating agent, and then secondary sintering at a kiln pressure greater than 0 Pa and a temperature of 600-1000° C. for 5-16 h, and then sieving to obtain the lithium cobalt oxide positive electrode material;

[0044] The coating agent is added in an amount of 0.1-1.0 wt % of the sintered product.

[0045] In a second aspect, the present invention provides a lithium cobalt oxide positive electrode material, wherein the lithium cobalt oxide positive electrode material is prepared by the preparation method described in the first aspect.

[0046] In a third aspect, the present invention provides a battery, comprising the lithium cobalt oxide positive electrode material as described in the second aspect.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention eliminates the need to adjust exhaust valves, air inlets and other process steps under different processes, thereby avoiding misoperation or missed operation when switching lithium cobalt oxide sintering under different voltages. The present invention only needs to adjust the kiln pressure to improve the reaction process and growth process of the material during sintering;

[0049] (2) The present invention improves the state of the sintered material block by regulating the kiln pressure, making the particle distribution uniform, reducing the agglomeration phenomenon, and increasing the crystallinity, thereby reducing the residual alkali on the surface of the positive electrode material and improving the cycle performance of the battery;

[0050] (3) The present invention improves and reduces the sintering variables of lithium cobalt oxide positive electrode materials, making the lithium cobalt oxide sintering process more stable under different voltages. When conducting DOE experiments, variable verification is reduced, thereby improving experimental efficiency and sample preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is an optical photograph of the mixture obtained after mixing in step (1) of Example 1 of the present invention;

[0052] Figure 2 This is an optical photograph of a fired product described in Example 1 of the present invention;

[0053] Figure 3 This is a SEM image of a sintered product described in Example 1 of the present invention at a scale of 50 μm;

[0054] Figure 4 This is a curve diagram showing the change of oxygen concentration with temperature during the primary sintering process described in Example 1, Example 4, Example 5 and Example 6 of the present invention;

[0055] Figure 5 The XRD diagram of the sintered product described in Example 1, Example 4, Example 5 and Example 6 of the present invention;

[0056] Figure 6 This is an optical photograph of the mixture obtained after mixing in step (1) of Example 4 of the present invention;

[0057] Figure 7This is an optical photograph of a fired product described in Example 4 of the present invention;

[0058] Figure 8 This is a SEM image of a sintered product described in Example 4 of the present invention at a scale of 50 μm;

[0059] Fig. 9 This is an optical photograph of the mixture obtained after mixing in step (1) of Example 5 of the present invention;

[0060] Fig.10 This is an optical photograph of a fired product described in Example 5 of the present invention;

[0061] Fig.11 This is a SEM image of a sintered product described in Example 5 of the present invention at a scale of 50 μm;

[0062] Fig.12 This is a SEM image of a sintered product described in Example 5 of the present invention at a scale of 10 μm;

[0063] Fig.13 This is an optical photograph of the mixture obtained after mixing in step (1) of Example 6 of the present invention;

[0064] Fig.14 This is an optical photograph of a fired product described in Example 6 of the present invention;

[0065] Fig.15 This is a SEM image of a sintered product described in Example 6 of the present invention at a scale of 50 μm;

[0066] Fig.16 This is a SEM image of a sintered product described in Example 6 of the present invention at a scale of 5 μm. DETAILED DESCRIPTION

[0067] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0068] Example 1

[0069] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, the preparation method comprising the following steps:

[0070] (1) mixing a cobalt precursor, a lithium source and a dopant, and then sintering the mixture in an air atmosphere at a kiln pressure of -30 Pa and a temperature of 700° C. for 25 h to obtain a sintered product;

[0071] The exhaust flow rate of the primary sintering is greater than the intake flow rate, the ratio of the exhaust flow rate to the intake flow rate of the primary sintering is 1.48:1, and the exhaust frequency of the sintering furnace used in the primary sintering is 30 Hz;

[0072] The amount of the dopant added is 0.6wt% of the cobalt precursor in step (1); the lithium source is lithium carbonate, the cobalt precursor is cobalt tetraoxide containing 0.08 mol% Al, and the dopant is zirconium oxide;

[0073] (2) mixing the first sintered product of step (1) with a coating agent, and then sintering for a second time in an air atmosphere at a kiln pressure of 5 Pa and a temperature of 800° C. for 8 h, and then sieving to obtain the lithium cobalt oxide positive electrode material;

[0074] The coating agent is added in an amount of 0.5wt% of the first sintered product; the coating agent is yttrium oxide; the sintering furnaces used for the first sintering and the second sintering are both box-type sintering furnaces;

[0075] The D0 of a sintered product obtained in this embodiment is 7.61 μm, D10 is 12.31 μm, D50 is 18.53 μm, D90 is 28.39 μm, D100 is 42.17 μm, and in the XRD test results, 2θ(003) is 18.885, 2θ(104) is 45.192, the unit cell parameters ab are 2.81668, and c is 14.06545;

[0076] The optical photograph of the mixture obtained after mixing in step (1) of this embodiment is as follows: Figure 1 As shown, the optical photograph of the fired product is as shown in Figure 2 As shown, the SEM image at 50 μm scale is Figure 3 As shown in the figure, during the first sintering process, the oxygen concentration changes with temperature. Figure 4 As shown, the XRD pattern of a fired product is as follows Figure 5 shown.

[0077] Example 2

[0078] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, the preparation method comprising the following steps:

[0079] (1) mixing a cobalt precursor, a lithium source and a dopant, and then sintering the mixture in an air atmosphere at a kiln pressure of -30 Pa and a temperature of 650° C. for 15 h to obtain a sintered product;

[0080] The exhaust flow rate of the primary sintering is greater than the intake flow rate, the ratio of the exhaust flow rate to the intake flow rate of the primary sintering is 1.48:1, and the exhaust frequency of the sintering furnace used in the primary sintering is 30 Hz;

[0081] The amount of the dopant added is 1.0 wt% of the cobalt precursor in step (1); the lithium source is lithium carbonate, the cobalt precursor is cobalt tetraoxide containing 0.08 mol% Al, and the dopant is zirconium oxide;

[0082] (2) mixing the first sintered product of step (1) with a coating agent, and then sintering for a second time in an air atmosphere at a kiln pressure of 3 Pa and a temperature of 1000° C. for 5 h, and then sieving to obtain the lithium cobalt oxide positive electrode material;

[0083] The added amount of the coating agent is 0.1wt% of the first sintered product; the coating agent is magnesium oxide; the sintering furnaces used for the first sintering and the second sintering are both box-type sintering furnaces.

[0084] Example 3

[0085] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, the preparation method comprising the following steps:

[0086] (1) mixing a cobalt precursor, a lithium source and a dopant, and then sintering the mixture in an air atmosphere at a kiln pressure of -30 Pa and a temperature of 600° C. for 30 h to obtain a sintered product;

[0087] The exhaust flow rate of the primary sintering is greater than the intake flow rate, the ratio of the exhaust flow rate to the intake flow rate of the primary sintering is 1.48:1, and the exhaust frequency of the sintering furnace used in the primary sintering is 30 Hz;

[0088] The amount of the dopant added is 0.1wt% of the cobalt precursor in step (1); the lithium source is lithium carbonate, the cobalt precursor is cobalt tetraoxide containing 0.08 mol% Al, and the dopant is zirconium oxide;

[0089] (2) mixing the first sintered product of step (1) with a coating agent, and then sintering for a second time in an air atmosphere at a kiln pressure of 1 Pa and a temperature of 600° C. for 16 h, and then sieving to obtain the lithium cobalt oxide positive electrode material;

[0090] The added amount of the coating agent is 1.0wt% of the first sintered product; the coating agent is lanthanum oxide; the sintering furnaces used for the first sintering and the second sintering are both box-type sintering furnaces.

[0091] Example 4

[0092] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Embodiment 1 except that the exhaust frequency of the sintering furnace used in the first sintering in step (1) is 15 Hz, the ratio of the exhaust flow rate to the intake flow rate of the first sintering is 1.16:1, and the kiln pressure is -10 Pa.

[0093] The D0 of a sintered product obtained in this embodiment is 7.52 μm, D10 is 11.47 μm, D50 is 18.64 μm, D90 is 28.48 μm, D100 is 42.25 μm, and in the XRD test results, 2θ(003) is 18.879, 2θ(104) is 45.192, the unit cell parameters ab are 2.81718, and c is 14.06226;

[0094] The optical photograph of the mixture obtained after mixing in step (1) of this embodiment is as follows: Figure 6 As shown, the optical photograph of the fired product is as shown in Figure 7 As shown in the SEM images Figure 8 As shown in the figure, during the first sintering process, the oxygen concentration changes with temperature. Figure 4 As shown, the XRD pattern of a fired product is as follows Figure 5 shown.

[0095] Example 5

[0096] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Embodiment 1 except that the exhaust frequency of the sintering furnace used in the first sintering in step (1) is 50 Hz, the ratio of the exhaust flow rate to the intake flow rate of the first sintering is 1.8:1, and the kiln pressure is -50 Pa.

[0097] The D0 of a sintered product obtained in this embodiment is 7.42 μm, D10 is 11.09 μm, D50 is 18.44 μm, D90 is 28.37 μm, D100 is 41.09 μm, and in the XRD test results, 2θ(003) is 18.877, 2θ(104) is 45.181, the unit cell parameters ab are 2.81722, and c is 14.06198;

[0098] The optical photograph of the mixture obtained after mixing in step (1) of this embodiment is as follows: Fig. 9 As shown, the optical photograph of the fired product is as shown in Fig.10 As shown, the SEM image at 50 μm scale is Fig.11 As shown, the SEM image at 10 μm scale is Fig.12 As shown in the figure, during the first sintering process, the oxygen concentration changes with temperature. Figure 4 As shown, the XRD pattern of a fired product is as follows Figure 5 shown.

[0099] Example 6

[0100] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Embodiment 1 except that the exhaust frequency of the sintering furnace used in the first sintering in step (1) is 5 Hz, the ratio of the exhaust flow rate to the intake flow rate of the first sintering is 1:1, and the kiln pressure is 0 Pa.

[0101] The D0 of a sintered product obtained in this embodiment is 1.42 μm, D10 is 10.28 μm, D50 is 18.78 μm, D90 is 28.17 μm, D100 is 41.79 μm, and in the XRD test results, 2θ(003) is 18.871, 2θ(104) is 45.163, the unit cell parameters ab are 2.81749, and c is 14.06219;

[0102] The optical photograph of the mixture obtained after mixing in step (1) of this embodiment is as follows: Fig.13 As shown, the optical photograph of the fired product is as shown in Fig.14 As shown, the SEM image at 50 μm scale is Fig.15 As shown, the SEM image at 5 μm scale is Fig.16 As shown in the figure, during the first sintering process, the oxygen concentration changes with temperature. Figure 4 As shown, the XRD pattern of a fired product is as follows Figure 5 shown.

[0103] Example 7

[0104] The present embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Embodiment 1, except that the ratio of the exhaust flow rate to the intake flow rate of the primary sintering in step (1) is 2:1, so that the exhaust frequency and the kiln pressure change accordingly.

[0105] Example 8

[0106] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Embodiment 1, except that the exhaust frequency in step (1) is 60 Hz, so that the kiln pressure and the ratio of the exhaust flow rate to the intake flow rate are changed accordingly.

[0107] Example 9

[0108] The present embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Example 1 except that the conditions for the secondary sintering in step (2) are the same as those for the primary sintering, the exhaust frequency of the sintering furnace used is 30 Hz, the ratio of the exhaust flow rate to the intake flow rate of the secondary sintering is 1.48:1, and the kiln pressure is -30 Pa.

[0109] Example 10

[0110] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as that of Embodiment 1 except that the kiln pressure of the primary sintering and the secondary sintering in step (2) is replaced.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as Example 1 except that the kiln pressure of the first sintering in step (1) is the same as the kiln pressure of the second sintering.

[0113] Comparative Example 2

[0114] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material. The preparation method is the same as Example 1 except that the exhaust frequency of the sintering furnace used in the first sintering in step (1) is 2 Hz, the ratio of the exhaust flow rate to the intake flow rate of the first sintering is 0.9:1, and the kiln pressure is 20 Pa.

[0115] The particle size SPAN (characterizing the uniformity of particles, the smaller the value, the more uniform the particles), the residual alkali content, and the values ​​of I003 / I104 and unit cell parameter c / a in the XRD test results (where I003 / I104 and c / a can reflect the crystallinity, cation order and optimal lithium ion channel of the product), and the capacity retention rate of the obtained lithium cobalt oxide positive electrode material at 25°C and 4.0V for 200 cycles are shown in Table 1 below

[0116] Table 1

[0117]

[0118]

[0119] From Table 1, we can see the following points:

[0120] (1) The present invention can effectively control the particle uniformity, crystallinity, residual alkali content and cycle performance of a fired product by controlling the kiln pressure of a single sintering, wherein SPAN is in the range of 0.86-0.96, the residual alkali content is in the range of 400-2000ppm, I003 / I104 is in the range of 1.33-1.49, c / a is in the range of 4.94-5.00, and the capacity retention rate of 200 cycles is in the range of 81-90%; by combining Example 1 with Examples 4-6, Figure 1-Figure 14It can be seen that when the kiln pressure is 0Pa, a large number of "black spots" appear in the sintered material. The hardness of the "black spot" block material is much higher than that of other block materials, the sintering state is uneven, and when the kiln pressure is 0Pa, the particle distribution is uneven, and there are a large number of "debris" on the surface of the particles. This is mainly because the volatilized lithium salts and the produced CO2 during the sintering process are not discharged in time, resulting in excessive particle reaction and larger particle growth size. In order to obtain the required particle size, the particles are broken during the crushing process, resulting in more debris on the particle surface and more residual alkali. During the battery cycle, it will increase the contact with the electrolyte, resulting in poor cycle performance. When the kiln pressure is too small, at -50Pa, the particles are more aggregated and the exhaust volume is excessive, causing too much volatilized lithium salt to be carried away, resulting in incomplete reaction and an increase in agglomerated particles, which has a negative effect on battery manufacturing and material cycle performance.

[0121] (2) It can be seen from Example 1 and Examples 7-8 that the ratio of the exhaust flow rate to the intake flow rate and the exhaust frequency of the present invention will affect the kiln pressure of sintering; it can be seen from Example 1 and Examples 9-10 that since the primary sintering controls the product morphology, the present invention preferably controls the kiln pressure during the primary sintering to improve the material recycling performance, etc.; and when the kiln pressure is regulated in both the primary sintering and the secondary sintering, the kiln pressure regulation during the secondary sintering process will cause part of the coated additive to oxidize, causing the additive coating to fail, which will in turn reduce the performance; it can be seen from Example 1 and Comparative Examples 1-2 that the present invention can improve the particle uniformity and crystallinity, reduce the residual alkali content, and improve the recycling performance by controlling the kiln pressure of the primary sintering.

[0122] In summary, the present invention provides a lithium cobalt oxide positive electrode material and a preparation method and application thereof. The preparation method avoids the sintering "black spots" of the lithium cobalt oxide positive electrode material by controlling the kiln pressure during the sintering process, improves the particle morphology, enhances the growth uniformity, and can promptly remove lithium salts and CO2 during the sintering process, thereby reducing the residual alkali content on the surface of the lithium cobalt oxide positive electrode material particles and improving the cycle performance of the positive electrode material.

[0123] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a lithium cobalt oxide positive electrode material, characterized in that: The preparation method comprises the following steps: (1) mixing a cobalt precursor and a lithium source and sintering them once to obtain a sintered product; (2) performing secondary sintering on the first sintered product of step (1) to obtain the lithium cobalt oxide positive electrode material; Wherein, the kiln pressure of the primary sintering in step (1) is below 0 Pa, and / or the kiln pressure of the secondary sintering in step (2) is below 0 Pa.

2. The preparation method according to claim 1, characterized in that: The kiln pressure of the first sintering in step (1) is below 0 Pa, and the kiln pressure of the second sintering in step (2) is greater than 0 Pa; Preferably, the kiln pressure of the primary sintering in step (1) is -50Pa to 0Pa, preferably -30Pa to -10Pa.

3. The preparation method according to claim 1 or 2, characterized in that: The exhaust flow rate of the primary sintering in step (1) is greater than or equal to the intake flow rate; Preferably, the ratio of the exhaust gas flow rate to the intake air flow rate of the primary sintering in step (1) is (1-1.8):1, preferably (1.16-1.48):

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that The exhaust frequency of the sintering furnace used in the primary sintering in step (1) is 5-50 Hz; Preferably, the sintering furnace used for the primary sintering in step (1) is a box-type sintering furnace.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The primary sintering temperature in step (1) is 600-700° C. and the sintering time is 15-30 hours; Preferably, the atmosphere of the primary sintering in step (1) is an air atmosphere; Preferably, when the cobalt precursor and the lithium source are mixed in step (1), a dopant is also added; Preferably, the amount of the dopant added is 0.1-1.0 wt % of the cobalt precursor in step (1); Preferably, the dopant includes any one or a combination of at least two of a lithium-containing compound, a magnesium-containing compound, an aluminum-containing compound, a zirconium-containing compound, a titanium-containing compound, a cobalt-containing compound, a fluorine-containing compound, a yttrium-containing compound or a lanthanum-containing compound.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The kiln pressure of the secondary sintering in step (2) is 0-5 Pa, but excluding 0 Pa; Preferably, the secondary sintering in step (2) is carried out at a temperature of 600-1000° C. and for a time of 5-16 hours; Preferably, the atmosphere for the secondary sintering in step (2) is an air atmosphere.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The first sintered product in step (1) is mixed with a coating agent before the second sintering; Preferably, the coating agent is added in an amount of 0.1-1.0wt% of the sintered product; Preferably, the coating agent comprises any one or a combination of at least two of a lithium-containing compound, a magnesium-containing compound, an aluminum-containing compound, a zirconium-containing compound, a titanium-containing compound, a cobalt-containing compound, a fluorine-containing compound, a yttrium-containing compound or a lanthanum-containing compound; Preferably, the secondary sintering in step (2) is followed by screening.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) mixing a cobalt precursor, a lithium source and a dopant, and then sintering them at a kiln pressure of -30Pa to -10Pa and a temperature of 600-700°C for 15-30h to obtain a sintered product; The exhaust flow rate of the primary sintering is greater than the intake flow rate, and the ratio of the exhaust flow rate to the intake flow rate of the primary sintering is (1.16-1.48):1, and the exhaust frequency of the sintering furnace used in the primary sintering is 5-50Hz; The amount of the dopant added is 0.1-1.0 wt% of the cobalt precursor in step (1); (2) mixing the first sintered product of step (1) with a coating agent, and then secondary sintering at a kiln pressure greater than 0 Pa and a temperature of 600-1000° C. for 5-16 h, and then sieving to obtain the lithium cobalt oxide positive electrode material; The coating agent is added in an amount of 0.1-1.0 wt % of the sintered product.

9. A lithium cobalt oxide positive electrode material, characterized in that: The lithium cobalt oxide positive electrode material is prepared by the preparation method according to any one of claims 1 to 8.

10. A battery, characterized in that: The battery comprises the lithium cobalt oxide positive electrode material as claimed in claim 9.

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