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

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a lithium cobalt oxide positive electrode material and a preparation method and application thereof. When the D50 particle size of the lithium cobalt oxide positive electrode material is 10-20 microns, the specific surface area of the lithium cobalt oxide positive electrode material is 0.4-0.8 m < 2 > / g; the real density of the lithium cobalt oxide positive electrode material is 4.85-5.03 g / cm < 3 >, and the tap density is 2.35-2.50 g / cm < 3 >; the lithium cobalt oxide positive electrode material has an R3-m space group structure, and the peak intensity ratio I (003) / I (104) of a 003 peak to a 104 peak in an XRD spectrogram of the lithium cobalt oxide positive electrode material is greater than or equal to 2.5. The method is characterized in that inert gas is introduced into a Li-Na hydrothermal replacement system to form aerosol, and Li-Na exchange is carried out under the protection of the aerosol, so that the D50 particle size, the specific surface area, the true density, the tap density and the I (003) / I (104) of XRD of the lithium cobalt oxide positive electrode material are in specific parameter ranges; the obtained lithium cobalt oxide positive electrode material has excellent lithium de-intercalation dynamic performance, so that a lithium ion battery is endowed with excellent capacity performance and rate capability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a lithium cobaltate positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the development and progress of lithium ion battery technology, higher and higher requirements are put forward for the capacity thereof. In the composition of the lithium ion battery, the capacity of the positive electrode material is a crucial factor affecting the capacity of the lithium ion battery. In order to improve the capacity of the lithium ion battery, an important way is to increase the charge-discharge voltage, but with the increase of the charge voltage, the positive electrode material will face a series of problems such as unstable crystal structure, rapid capacity decay and greatly reduced cycle performance.

[0003] Lithium cobaltate (LiCoO2, LCO) as a common lithium battery positive electrode material is often used in consumer 3C battery fields such as mobile phones and tablets due to its high tap density and high energy density. At present, the existing technology often adopts sodiumization solid phase sintering of the positive electrode material first and then Li-Na ion exchange to obtain lithium cobaltate material with O2 phase stacking structure. Compared with O3 phase lithium cobaltate material, the lithium cobaltate material has a more stable structure and exhibits multiple charge-discharge phase change platforms in the electrochemical process, which can better play the electrochemical performance. However, the O2 phase lithium cobaltate material prepared by the above method still has a capacity decay problem in the high charge voltage interval, which limits the improvement of the capacity performance and cycle performance of the positive electrode material and the lithium battery.

[0004] Therefore, it is a very key task to improve the interface stability of the positive electrode material at high voltage and to develop a lithium ion battery positive electrode material with high specific capacity, rate performance and cycle performance. SUMMARY

[0005] One of the purposes of the present application is to provide a lithium cobaltate positive electrode material which has excellent capacity performance and rate performance and can be well applied in the production and manufacturing of high energy density lithium ion batteries.

[0006] The second purpose of the present application is to provide a preparation method of the lithium cobaltate positive electrode material.

[0007] The third purpose of the present application is to provide the lithium cobaltate positive electrode material prepared by the above method.

[0008] The fourth purpose of the present application is to also provide the application of the above lithium cobaltate positive electrode material in lithium ion batteries.

[0009] Specifically, when the D50 particle size of the lithium cobaltate positive electrode material provided by the present application is 10-20 μm, the specific surface area thereof is 0.4-0.8 m 2 / g; the true density of the lithium cobalt oxide positive electrode material is 4.85-5.03g / cm 3 , tap density is 2.35~2.50g / cm 3 ; In the XRD spectrum of the lithium cobalt oxide positive electrode material, the lithium cobalt oxide positive electrode material has an R3-m space group structure, and the peak intensity ratio of the 003 peak to the 104 peak in the XRD spectrum of the lithium cobalt oxide positive electrode material is I(003) / I(104)≧2.5.

[0010] In a preferred embodiment, in the XRD spectrum of the lithium cobalt oxide positive electrode material, the 2θ value of the 003 peak is 18.7-19.2°, and the 2θ value of the 104 peak is 45.0-45.5°.

[0011] In a preferred embodiment, the chemical formula of the lithium cobalt oxide positive electrode material is Li y Na z Co 1-a- b A a M b O2, wherein 0.93≤y≤1.02, 0≤z≤0.02, 0≤a≤0.1, 0≤b≤0.05, A is selected from Ni and / or Mn, and M is selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, and Y.

[0012] In a preferred embodiment, the M is selected from at least one of Al, Mg, Ti, and Y.

[0013] In a preferred embodiment, the Na content in the lithium cobalt oxide positive electrode material is within 500 ppm.

[0014] The preparation method of the lithium cobalt oxide positive electrode material provided by the present invention comprises the following steps:

[0015] S1. The lithium cobalt oxide cathode material precursor is mixed with a sodium source, and the resulting mixture is sintered to obtain a sodium-containing semi-finished material;

[0016] S2. The sodium-containing semi-finished material is mixed with a lithium source and an inert gas is introduced to form an aerosol. The reaction system is then subjected to a hydrothermal reaction. After the reaction is completed, the solid-liquid separation, water washing, and drying are performed to obtain a solid product, which is a lithium cobalt oxide positive electrode material.

[0017] In a preferred embodiment, in step S1, the lithium cobalt oxide positive electrode material precursor has (Co 1-a- b A a M b )3O4 and / or Co 1-a-b A a Mb The structure shown in (OH)2, wherein 0≤a≤0.1, 0≤b≤0.05, A is selected from Ni and / or Mn, and M is selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, and Y.

[0018] In a preferred embodiment, in step S1, the M is selected from at least one of Al, Mg, Ti, and Y.

[0019] In a preferred embodiment, in step S1, the sodium source is selected from at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium nitrate, sodium sulfate, sodium acetate and sodium oxalate.

[0020] In a preferred embodiment, in step S1, the molar ratio of Co in the lithium cobalt oxide positive electrode material to Na in the sodium source is 1:(0.75-1.20).

[0021] In a preferred embodiment, in step S1, the sintering treatment temperature is 700-1000° C., and the time is 16-48 hours.

[0022] In a preferred embodiment, in step S2, the lithium source is selected from at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium chloride, lithium bromide and lithium iodide.

[0023] In a preferred embodiment, in step S2, the molar ratio of Na in the sodium-containing semi-finished material to Li in the lithium source is 1:(1-4).

[0024] In a preferred embodiment, in step S2, the process of mixing the sodium-containing semi-finished material with a lithium source and then introducing an inert gas to form an aerosol includes: mixing a lithium source and water to obtain a lithium source solution, first heating the reaction system containing the lithium source solution to 80-100° C., then adding the sodium-containing semi-finished material and introducing an inert gas into the reaction system to form an aerosol.

[0025] In a preferred embodiment, in step S2, the conditions of the hydrothermal reaction include a temperature of 160-200° C. and a time of 2-6 hours.

[0026] In a preferred embodiment, in step S2, the solid content of the reaction system during the hydrothermal reaction is 40-60 wt%.

[0027] In a preferred embodiment, in step S2, the inert gas is selected from at least one of nitrogen, neon, argon, xenon and radon.

[0028] In a preferred embodiment, in step S2, the amount of the inert gas introduced is based on ensuring that the pressure of the reaction system is 0.3-2.0 MPa.

[0029] In a preferred embodiment, in step S2, the inert gas is introduced at a flow rate of 2 to 5 L / min and for a time of 1 to 5 min.

[0030] After extensive and in-depth research, the inventors of the present invention discovered that in the process of preparing lithium cobalt oxide materials using a combination of sodium solid-phase sintering and Li-Na ion exchange in the existing technology, due to the shrinkage of the unit cell volume during the replacement process, obvious internal defects will be generated, resulting in a significant increase in the specific surface area of ​​the positive electrode material. Excessive specific surface area not only reduces the crystal structure stability of the positive electrode material, but also causes problems such as gas production and increased side reactions when used in lithium-ion batteries, which is not conducive to improving the capacity performance and rate performance of lithium-ion batteries and has poor cycle performance. It was also found that regulating the formation of specific crystal plane structures of positive electrode materials is beneficial to improving the kinetic performance of lithium ion insertion and extraction.

[0031] Beneficial effect: The key to the present invention is to introduce an inert gas into the Li-Na hydrothermal exchange system to form an aerosol, and to carry out Li-Na exchange under the protection of the aerosol, so that the D50 particle size of the lithium cobalt oxide positive electrode material is within 10-20 μm and its specific surface area is 0.4-0.8 m 2 / g, the true density is 4.85~5.03g / cm 3 , tap density is 2.35~2.50g / cm 3 , and the lithium cobalt oxide positive electrode material has an R3-m space group structure, and the peak intensity ratio of the 003 peak to the 104 peak in the XRD spectrum of the lithium cobalt oxide positive electrode material is I(003) / I(104)≧2.5. At this time, the lithium cobalt oxide positive electrode material has excellent lithium ion deintercalation kinetics, thereby showing excellent capacity performance and rate performance compared with traditional lithium cobalt oxide materials. The possible reason is that: due to its special 003 crystal plane and 104 crystal plane growth structure, wherein the 003 crystal plane is the lithium ion deintercalation crystal plane, I(003) / I(104)≧2.5 indicates that the 003 crystal plane is fully exposed, and combined with the morphological structure characteristics of the pore size and particle size of the lithium cobalt oxide positive electrode material, the positive electrode material can have more lithium ion deintercalation channels and better lithium ion deintercalation performance, making the lithium cobalt oxide positive electrode material more advantageous in charge and discharge kinetics and having good structural stability, thereby improving its capacity performance and rate performance.

[0032] In a preferred embodiment, when the lithium cobalt oxide positive electrode material further contains at least one of A and / or M metal elements, the cycle performance of the positive electrode material can be further improved while ensuring high capacity performance. DETAILED DESCRIPTION

[0033] When the D50 particle size of the lithium cobalt oxide positive electrode material provided by the present invention is 10 to 20 μm, such as 10 μm, 12 μm, 15 μm, 18 μm, 20 μm or any value therebetween; its specific surface area is 0.4 to 0.8 m 2 / g, such as 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g or any value therebetween, which is beneficial for providing more channels for the lithium cobalt oxide positive electrode material during the electrochemical deintercalation and deintercalation of lithium, improving the kinetics of deintercalation and deintercalation of lithium, while also ensuring that the material maintains the stability of the crystal structure during the deintercalation and deintercalation of lithium, thereby enabling the lithium-ion battery to have excellent capacity performance and rate performance. The true density of the lithium cobalt oxide positive electrode material is 4.85 to 5.03 g / cm 3 , such as 4.85g / cm 3 , 4.88g / cm 3 , 4.90g / cm 3 , 4.92g / cm 3 , 4.95g / cm 3 , 4.98g / cm 3 , 5.00g / cm 3 , 5.03g / cm 3 Or any value between them, the tap density is 2.35~2.50g / cm 3 , such as 2.35g / cm 3 , 2.38g / cm 3 , 2.40g / cm 3 , 2.42g / cm 3 , 2.45g / cm 3 , 2.48g / cm 3 , 2.50g / cm 3or any value between them, at this time the lithium cobaltate positive electrode material has good capacity performance and rate performance advantages, the reason is that compared with the traditional lithium cobaltate material, the lower true density can increase the cell volume of the material, the larger crystallographic c-axis of the material under the same chemical formula is beneficial to the lithium ion insertion and extraction of the positive electrode material in the charge and discharge process, thereby reducing the material impedance, improving the gram capacity and rate performance of the positive electrode material. In the XRD spectrum of the lithium cobaltate positive electrode material, the lithium cobaltate positive electrode material has an R3-m space group structure, and the peak intensity ratio I(003) / I(104) of the 003 peak and the 104 peak in the XRD spectrum of the lithium cobaltate positive electrode material is greater than or equal to 2.5, at this time the lithium cobaltate positive electrode material has good capacity performance and rate performance advantages, the reason is that the 003 crystal face is a lithium ion deintercalation crystal face, and the sufficient exposure of the 003 crystal face can make the positive electrode material have better lithium ion deintercalation channel and better lithium ion deintercalation performance, thereby making the positive electrode material have more advantages in charge and discharge dynamics, thereby good capacity performance and improved rate performance. The ratio of I(003) / I(104) is preferably 2.5-3.8, such as 2.5, 2.6, 2.8, 3.0, 3.2, 3.5, 3.6, 3.8 or any value between them.

[0034] In addition, the term "D50 particle size" means the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample.

[0035] In the present application, in the XRD spectrum of the lithium cobaltate positive electrode material, the 2θ value of the 003 peak is preferably 18.7-19.2°, and the 2θ value of the 104 peak is preferably 45.0-45.5°.

[0036] In the present application, the chemical formula of the lithium cobaltate positive electrode material is preferably Li y Na z Co 1-a-b A a M bPreferably, 0.93≤y≤1.02, y may be 0.93, 0.95, 0.98, 1.00, 1.01, 1.02, or any value therebetween. Preferably, 0≤z≤0.02, z may be 0, 0.005, 0.01, 0.015, 0.01, or any value therebetween. Preferably, 0≤a≤0.1, a may be 0, 0.02, 0.05, 0.08, 0.1, or any value therebetween. Preferably, 0≤b≤0.05, b may be 0, 0.01, 0.02, 0.03, 0.04, 0.05, or any value therebetween. The A is preferably Ni and / or Mn. In this case, the lithium cobalt oxide positive electrode material has a better electrochemical cycle performance advantage because the Ni and / or Mn elements can provide Co layer structural stability, thereby delaying the structural collapse of the lithium cobalt oxide positive electrode material during the electrochemical lithium deintercalation process, thereby improving the cycle performance of the lithium cobalt oxide positive electrode material. The M is preferably selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, and Y. In this case, the lithium cobalt oxide positive electrode material has better rate performance and cycle performance because the M element doping can significantly reduce the metal-O bond length in the positive electrode material structure and reduce polarization. The M is more preferably selected from at least one of Al, Mg, Ti, and Y, which is more conducive to improving the cycle performance of the positive electrode material.

[0037] In the present invention, the Na content in the lithium cobalt oxide positive electrode material is preferably within 500 ppm, which has the advantage of improving the cycle performance. The reason is that an appropriate amount of Na doping can help support the structure of the positive electrode material, reduce the volume change rate of the positive electrode material after lithium is removed, and further optimize the cycle performance.

[0038] The preparation method of the lithium cobalt oxide positive electrode material provided by the present invention comprises the following steps:

[0039] S1. The lithium cobalt oxide cathode material precursor is mixed with a sodium source, and the resulting mixture is sintered to obtain a sodium-containing semi-finished material;

[0040] S2. The sodium-containing semi-finished material is subjected to a hydrothermal reaction with a lithium source. The hydrothermal reaction is carried out under the protection of an aerosol formed by an inert gas. After the reaction is completed, the solid-liquid separation, water washing, and drying are performed to obtain a solid product, which is a lithium cobalt oxide positive electrode material.

[0041] In the present invention, in step S1, the lithium cobalt oxide positive electrode material precursor preferably has (Co 1-a-b A a M b )3O4 or Co 1-a-b A a M b(OH)2, that is, the lithium cobalt oxide positive electrode material precursor can be at least one of cobalt tetroxide, cobalt hydroxide, cobalt tetroxide containing A, cobalt hydroxide containing A, cobalt tetroxide containing M, cobalt hydroxide containing M, cobalt tetroxide containing A and M, and cobalt hydroxide containing A and M. 1-a-b A a M b )3O4 or Co 1-a-b A a M b The compound of the structure shown in (OH)2 can be purchased or prepared according to existing methods. 1-a-b A a M b (OH)2 can be prepared by coprecipitation: coprecipitation reaction of cobalt salt and optional A salt and M salt with alkaline precipitant, washing and drying the solid product is Co 1-a-b A a M b (OH)2. Specifically, (Co 1-a-b A a M b )3O4 can be obtained by heat-treating a cobalt salt and optionally an A salt and an M salt, or by first subjecting the cobalt salt and optionally an A salt and an M salt to a coprecipitation reaction with an alkaline precipitant, and then heat-treating the solid product after washing and drying. Wherein, 0≤a≤0.1, a can be 0, 0.02, 0.05, 0.08, 0.1, or any value therebetween; 0≤b≤0.05, b can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, or any value therebetween; A is preferably selected from Ni and / or Mn; and M is preferably selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, and Y, and more preferably selected from at least one of Al, Mg, Ti, and Y.

[0042] In the present invention, in step S1, the sodium source can be a class of various existing Na-containing compounds used to prepare positive electrode materials, and specific examples thereof include but are not limited to at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium nitrate, sodium sulfate, sodium acetate and sodium oxalate.

[0043] In the present invention, in step S1, the molar ratio of Co in the lithium cobalt oxide positive electrode material to Na in the sodium source is preferably 1:(0.75-1.20), such as 1:0.75, 1:0.80, 1:0.85, 1:0.90, 1:0.95, 1:1.00, 1:1.05, 1:1.10, 1:1.15, 1:1.20 or any value therebetween.

[0044] In the present invention, in step S1, the temperature of the sintering treatment is preferably 700-1000°C, such as 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C or any value therebetween; the time is preferably 16-48h, such as 16h, 20h, 24h, 28h, 30h, 36h, 40h, 44h, 48h or any value therebetween.

[0045] In the present invention, in step S2, the lithium source can be a class of various existing Li-containing compounds used to prepare positive electrode materials, examples of which include but are not limited to at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium chloride, lithium bromide and lithium iodide.

[0046] In the present invention, in step S2, the molar ratio of Na in the sodium-containing semi-finished material to Li in the lithium source is preferably 1:(1-4), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4 or any value therebetween.

[0047] In the present invention, in step S2, the process of introducing an inert gas to form an aerosol after mixing the sodium-containing semi-finished material with a lithium source preferably includes: mixing a lithium source and water to obtain a lithium source solution, first heating the reaction system containing the lithium source solution to 80-100°C, then adding the sodium-containing semi-finished material and introducing an inert gas into the reaction system to form an aerosol. The temperature of the sodium-containing semi-finished material when added to the reaction system is preferably controlled at 80-100°C, such as 80°C, 85°C, 90°C, 95°C, 100°C or any value therebetween, and the feed temperature at this time is more conducive to increasing the Li-Na replacement rate while reducing the H-Na replacement rate, so that Li-Na fully replaces the positive electrode material to provide more lithium ions that can be intercalated and deintercalated and improve the material structure stability, thereby improving the cycle performance of the positive electrode material.

[0048] In the present invention, the solid content of the reaction system during the hydrothermal reaction is preferably 40 to 60 wt%, such as 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or any value therebetween. This is more conducive to the Li-Na replacement reaction, and is more conducive to controlling the Na content of the lithium cobalt oxide positive electrode material to within 500 ppm, thereby increasing the Li concentration of the lithium cobalt oxide positive electrode material, thereby improving the capacity performance and rate performance of the positive electrode material.

[0049] In the present invention, specific examples of the inert gas include, but are not limited to, at least one of nitrogen, neon, argon, xenon and radon.

[0050] In the present invention, the amount of the inert gas introduced is preferably to ensure that the pressure of the reaction system is 0.3 to 2.0 MPa. Specifically, the inert gas introduction flow rate is preferably 2 to 5 L / min, such as 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, 4 L / min, 4.5 L / min, 5 L / min or any value therebetween, and the introduction time is preferably 1 to 5 min, such as 1 min, 2 min, 3 min, 4 min, 5 min or any value therebetween. At this time, the obtained lithium cobalt oxide positive electrode material has better capacity performance and rate performance advantages, because an appropriate amount of inert gas helps to form a layer of aerosol on the surface of the material, controls the degree of defect formation of the material during the replacement process, thereby increasing the specific surface area of ​​the material, and providing more lithium ion deintercalation channels for the positive electrode material, which is beneficial to the improvement of the gram capacity and rate performance of the positive electrode material.

[0051] The present invention also provides an application of the above-mentioned lithium cobalt oxide positive electrode material in a lithium ion battery. Specifically, the present invention provides a lithium ion battery containing the above-mentioned lithium cobalt oxide positive electrode material.

[0052] The present invention will be described in detail below through specific examples. The examples of the embodiments are intended to explain the present invention and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0053] Preparation Example 1

[0054] This example is used to illustrate the precursor (Co 0.95 Ni 0.03 Al 0.02 )3O4 preparation, the specific process is as follows:

[0055] S1. Dissolve 58.2 g of cobalt sulfate (CoSO4·7H2O), 1.72 g of nickel sulfate (NiSO4·6H2O), and 0.75 g of aluminum sulfate (Al2(SO4)3) in 1 L of deionized water and stir until the solution is clear and free of precipitate.

[0056] S2. Prepare 500 mL of 1.0 M sodium carbonate (Na2CO3) solution as a precipitant;

[0057] S3. At room temperature (25°C), the sodium carbonate solution was added dropwise to the nickel cobalt aluminum sulfate solution at a rate of 20 mL / min, with continuous stirring at 200 rpm;

[0058] S4. After the addition is completed, continue stirring for 1 hour to generate pink nickel cobalt aluminum carbonate (Co 0.95 Ni0.03 Al 0.02 CO3) precipitation;

[0059] S5. The precipitate was washed three times with deionized water by centrifugation and once with anhydrous ethanol to remove impurity ions. The precipitate was then dried in an oven at 80°C for 12 h to obtain a carbonate precursor.

[0060] S6. The dried precursor was placed in a muffle furnace, heated to 700°C at 5°C / min in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to obtain nickel cobalt aluminum oxide (Co 0.95 Ni 0.03 Al 0.02 )3O4 powder.

[0061] Preparation Example 2

[0062] This example is used to illustrate the precursor (Co 0.95 Mn 0.03 Mg 0.02 )3O4 preparation, the specific process is as follows:

[0063] S1. Dissolve 58.2 g of cobalt sulfate (CoSO4·7H2O), 1.11 g of manganese sulfate (MnSO4·H2O), and 0.53 g of magnesium sulfate (MgSO4) in 1 L of deionized water and stir until the solution is clear and free of precipitate.

[0064] S2. Prepare 500 mL of 1.0 M sodium carbonate (Na2CO3) solution as a precipitant;

[0065] S3. At room temperature (25°C), the sodium carbonate solution was added dropwise to the nickel cobalt aluminum sulfate solution at a rate of 20 mL / min, with continuous stirring at 200 rpm;

[0066] S4. After the addition is completed, continue stirring for 1 hour to generate pink nickel cobalt aluminum carbonate (Co 0.95 Mn 0.03 Mg 0.02 CO3) precipitation;

[0067] S5. The precipitate was washed three times with deionized water by centrifugation and once with anhydrous ethanol to remove impurity ions. The precipitate was then dried in an oven at 80°C for 12 h to obtain a carbonate precursor.

[0068] S6. The dried precursor was placed in a muffle furnace, heated to 700°C at 5°C / min in an air atmosphere, kept at this temperature for 3 hours, and then naturally cooled to obtain nickel cobalt aluminum oxide (Co 0.95 Mn 0.03 Mg 0.02 )3O4 powder.

[0069] Preparation Example 3

[0070] This example is used to illustrate the precursor (Co 0.95 Ni 0.03 Ti 0.02 )3O4 preparation, the specific process is as follows:

[0071] According to the method of Preparation Example 1, the precursor (Co 0.95 Ni 0.03 Ti 0.02 )3O4, except that 0.70g of titanium oxysulfate (TiOSO4) was used instead of 0.75g of aluminum sulfate (Al2(SO4)3) in step S1, and the other conditions were the same as those in Preparation Example 1, thereby preparing the precursor (Co 0.95 Ni 0.03 Ti 0.02 )3O4.

[0072] Preparation Example 4

[0073] This example is used to illustrate the precursor (Co 0.95 Mn 0.03 Y 0.02 )3O4 preparation, the specific process is as follows:

[0074] According to the method of Preparation Example 2, the precursor (Co 0.95 Mn 0.03 Y 0.02 )3O4, except that 0.56g of yttrium nitrate (Y(NO3)3·6H2O) was used instead of 0.53g of magnesium sulfate (MgSO4) in step S1, and the other conditions were the same as those in Preparation Example 2, thereby preparing the precursor (Co 0.95 Mn 0.03 Y 0.02 )3O4.

[0075] Preparation Example 5

[0076] This example is used to illustrate the precursor (Co 0.95 Ni 0.03 Ca 0.02 )3O4 preparation, the specific process is as follows:

[0077] According to the method of Preparation Example 1, the precursor (Co 0.95 Ni 0.03 Ca 0.02 )3O4, except that 0.59g calcium sulfate (CaSO4) was used instead of 0.75g aluminum sulfate (Al2(SO4)3) in step S1, and the other conditions were the same as those in Preparation Example 1, thereby preparing the precursor (Co 0.95 Ni 0.03 Ca 0.02 )3O4.

[0078] Preparation Example 6

[0079] This example is used to illustrate the precursor (Co 0.95 Ni 0.05 )3O4 preparation, the specific process is as follows:

[0080] According to the method of Preparation Example 1, the precursor (Co 0.95 Ni 0.05 )3O4, except that in step S1, 58.2g of cobalt sulfate (CoSO4·7H2O) and 2.86g of nickel sulfate (NiSO4·6H2O) were dissolved in 1L of deionized water, and the other conditions were the same as those in Preparation Example 1, thereby preparing the precursor (Co 0.95 Ni 0.05 )3O4.

[0081] Preparation Example 7

[0082] This example is used to illustrate the precursor (Co 0.95 Al 0.05 )3O4 preparation, the specific process is as follows:

[0083] According to the method of Preparation Example 1, the precursor (Co 0.95 Al 0.05 )3O4, except that in step S1, 58.2g of cobalt sulfate (CoSO4·7H2O) and 1.86g of aluminum sulfate (Al2(SO4)3) were dissolved in 1L of deionized water. The other conditions were the same as those in Preparation Example 1, thereby preparing the precursor (Co 0.95 Al 0.05 )3O4.

[0084] Example 1

[0085] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0086] S1. Prepare the precursor (Co 0.95 Ni 0.03 Al 0.02 )3O4 and sodium hydroxide are mixed in a molar ratio of Co:Na of 1:0.75. The mixed mixture is placed in a muffle furnace for sintering at a sintering temperature of 900°C and a sintering time of 48h. After sintering, the material is crushed and sieved with a jaw crusher to obtain a sodium-containing semi-finished material Na 0.75 Co 0.95 Ni 0.03 Al 0.02 O2;

[0087] S2. Li-Na hydrothermal replacement reaction of sodium-containing semi-finished materials, the replacement solid content is 40wt%, in the replacement system, the sodium-containing semi-finished material Na 0.75 Co 0.95 Ni 0.03 Al 0.02 O2 and Li in solution + The molar ratio is 1:3. The replacement process is as follows: lithium hydroxide is dissolved in water according to the stoichiometric ratio to prepare a lithium source solution, which is pumped into a hydrothermal kettle with a peristaltic pump, and the hydrothermal kettle is heated from room temperature to 180°C for 2 hours. When the hydrothermal kettle is heated from room temperature to 90°C, sodium-containing semi-finished materials are added and nitrogen is introduced into the solution (the flow rate is 3L / min, and the introduction time is 3min). The hydrothermal kettle is then heated to 180°C and a hydrothermal reaction is carried out at this temperature for 4 hours. After the reaction is completed, the temperature is lowered to room temperature, the mixed solution is discharged and filtered, and deionized water is added to wash the solid after filtration. The washing is stopped when the conductivity of the filtered mother liquor is <200μS / cm. The washed solid material is vacuum dried at 200°C for 24 hours and sieved through 325 mesh to obtain a lithium cobalt oxide positive electrode material with the general chemical formula of Li 0.995 Na 0.005 Co 0.95 Ni 0.03 Al 0.02 O2.

[0088] Example 2

[0089] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0090] S1. Prepare the precursor (Co 0.95 Mn 0.03 Mg 0.02 )3O4 and sodium nitrate are mixed in a molar ratio of Co:Na of 1:0.75. The mixed mixture is placed in a muffle furnace for sintering at a sintering temperature of 800°C and a sintering time of 36h. After sintering, the material is crushed and sieved with a jaw crusher to obtain a sodium-containing semi-finished material Na 0.75 Co 0.95 Mn 0.03 Al 0.02 O2;

[0091] S2. Li-Na hydrothermal replacement reaction of sodium-containing semi-finished material, the replacement solid content is 50wt%, in the replacement system, the sodium-containing semi-finished material Na 0.75 Co 0.95 Mn 0.03 Mg 0.02 O2 and Li in solution +The molar ratio is 1:3. The replacement process is as follows: lithium nitrate is dissolved in water according to the stoichiometric ratio to prepare a lithium source solution, which is pumped into a hydrothermal kettle with a peristaltic pump, and the hydrothermal kettle is heated from room temperature to 160°C for 2 hours. When the hydrothermal kettle is heated from room temperature to 80°C, sodium-containing semi-finished materials are added and nitrogen is introduced into the solution (the flow rate is 3L / min, and the introduction time is 3min). The hydrothermal kettle is then heated to 160°C and a hydrothermal reaction is carried out at this temperature for 6 hours. After the reaction is completed, the temperature is lowered to room temperature, the mixed solution is discharged and filtered, and deionized water is added to wash the solid after filtration. The washing is stopped when the conductivity of the filtered mother liquor is <200μS / cm. The washed solid material is vacuum dried at 200°C for 24 hours and sieved through 325 mesh to obtain a lithium cobalt oxide positive electrode material with the general chemical formula of Li 0.99 5Na 0.005 Co 0.95 Mn 0.03 Mg 0.02 O2.

[0092] Example 3

[0093] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0094] S1. Prepare the precursor (Co 0.95 Ni 0.03 Ti 0.02 )3O4 and sodium nitrate are mixed in a molar ratio of Co:Na of 1:1. The mixed mixture is placed in a muffle furnace for sintering at a sintering temperature of 1000℃ and a sintering time of 24h. After sintering, the material is crushed and sieved by a jaw crusher to obtain a sodium-containing semi-finished material NaCo 0.95 Ni 0.03 Ti 0.02 O2;

[0095] S2. Li-Na hydrothermal replacement reaction of sodium-containing semi-finished material, the replacement solid content is 60wt%, in the replacement system, the sodium-containing semi-finished material NaCo 0.95 Ni 0.03 Ti 0.02 O2 and Li in solution +The molar ratio is 1:3. The replacement process is as follows: lithium nitrate is dissolved in water according to the stoichiometric ratio to prepare a lithium source solution, which is pumped into a hydrothermal kettle with a peristaltic pump, and the hydrothermal kettle is heated from room temperature to 200°C for 2 hours. When the hydrothermal kettle is heated from room temperature to 100°C, sodium-containing semi-finished materials are added and nitrogen is introduced into the solution (the flow rate is 4L / min, and the introduction time is 3min). The hydrothermal kettle is then heated to 200°C and a hydrothermal reaction is carried out at this temperature for 2 hours. After the reaction is completed, the temperature is lowered to room temperature, the mixed solution is discharged and filtered, and deionized water is added to wash the solid after filtration. The washing is stopped when the conductivity of the filtered mother liquor is <200μS / cm. The washed solid material is vacuum dried at 200°C for 24 hours and sieved through 325 mesh to obtain a lithium cobalt oxide positive electrode material with the general chemical formula of Li 0.995 Na 0.005 Co 0.95 Ni 0.03 Ti 0.02 O2.

[0096] Example 4

[0097] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0098] The lithium cobalt oxide positive electrode material was prepared according to the method of Example 2, except that the precursor (Co 0.95 Mn 0.03 Y 0.02 )3O4 and sodium hydroxide were mixed in a molar ratio of Co:Na of 1:0.75, and the other conditions were the same as in Example 2, thereby preparing a lithium cobalt oxide positive electrode material, the chemical formula of which is Li 0.995 Na 0.005 Co 0.95 Mn 0.03 Y 0.02 O2.

[0099] Example 5

[0100] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0101] The lithium cobalt oxide positive electrode material was prepared according to the method of Example 1, except that the precursor (Co 0.95 Ni 0.03 Ca 0.02 )3O4 and sodium hydroxide were mixed in a molar ratio of Co:Na of 1:0.75, and the other conditions were the same as in Example 1, thereby preparing a lithium cobalt oxide positive electrode material, the chemical formula of which is Li 0.995 Na 0.005 Co 0.95Ni 0.03 Ca 0.02 O2.

[0102] Example 6

[0103] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0104] The lithium cobalt oxide positive electrode material was prepared according to the method of Example 1, except that in step S1, the precursor Co3O4 and sodium hydroxide were mixed in a molar ratio of Co:Na of 1:0.75. The other conditions were the same as those of Example 1, thereby preparing a lithium cobalt oxide positive electrode material, whose chemical formula is Li 0.995 Na 0.005 CoO2.

[0105] Example 7

[0106] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0107] The lithium cobalt oxide positive electrode material was prepared according to the method of Example 1, except that in step S2, the lithium source solution was first mixed with the sodium-containing semi-finished material, pumped into a hydrothermal kettle with a peristaltic pump and nitrogen was introduced, and then the hydrothermal kettle was heated from room temperature to 180°C. The other conditions were the same as those in Example 1, thereby preparing a lithium cobalt oxide positive electrode material, whose chemical formula is Li 0.99 Na 0.01 Co 0.95 Ni 0.03 Al 0.02 O2.

[0108] Example 8

[0109] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0110] The lithium cobalt oxide positive electrode material was prepared according to the method of Example 1, except that the precursor (Co 0.95 Ni 0.05 )3O4 and sodium hydroxide were mixed in a molar ratio of Co:Na of 1:0.75, and the other conditions were the same as in Example 1, thereby preparing a lithium cobalt oxide positive electrode material, the chemical formula of which is Li 0.995 Na 0.005 Co 0.95 Ni 0.05 O2.

[0111] Example 9

[0112] This example is used to illustrate the preparation of a lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0113] The lithium cobalt oxide positive electrode material was prepared according to the method of Example 1, except that the precursor (Co 0.95 Al 0.05 )3O4 and sodium hydroxide were mixed in a molar ratio of Co:Na of 1:0.75, and the other conditions were the same as in Example 1, thereby preparing a lithium cobalt oxide positive electrode material, the chemical formula of which is Li 0.995 Na 0.005 Co 0.95 Al 0.05 O2.

[0114] Comparative Example 1

[0115] This comparative example is used to illustrate the preparation of a reference lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0116] A reference lithium cobalt oxide positive electrode material was prepared according to the method of Example 1, except that in step S2, nitrogen was not introduced when the sodium-containing semi-finished material was added to the hydrothermal kettle. The other conditions were the same as those in Example 1, thereby preparing a reference lithium cobalt oxide positive electrode material.

[0117] Comparative Example 2

[0118] This comparative example is used to illustrate the preparation of a reference lithium cobalt oxide positive electrode material, and the specific process is as follows:

[0119] The precursor (Co 0.95 Ni 0.03 Al 0.02 )3O4 and lithium hydroxide are mixed in a Co:Li molar ratio of 1:1.05. The evenly mixed mixture is placed in a muffle furnace for sintering at a sintering temperature of 900°C and a sintering time of 48h. After sintering, the material is crushed and sieved with a jaw roller to obtain a reference lithium cobalt oxide positive electrode material.

[0120] Test Case

[0121] This test example is used to illustrate the relevant properties of the lithium cobalt oxide positive electrode materials prepared by the above examples and comparative examples. The results are shown in Tables 1 and 2.

[0122] 1. Microstructure testing

[0123] (1) D50 particle size test: A laser particle size analyzer (Malvern Mastersizer 3000) was used, the dispersion medium was deionized water, and the dispersant was 0.5% sodium hexametaphosphate (NaPO3)6 (to prevent particle agglomeration).

[0124] The test steps are as follows:

[0125] a. Take about 50 mg of sample and add it to 50 mL of dispersion medium. Ultrasonic dispersion is carried out for 5 to 10 minutes (power 200 W, frequency 40 kHz).

[0126] b. Inject the dispersed suspension into the instrument sample cell and perform background calibration before testing.

[0127] c. Set the refractive index (1.52) and absorbance (0.1) and start the dynamic light scattering (DLS) mode.

[0128] d. Repeat the test 3 times and take the average value as the final result.

[0129] (2) Specific surface area test: The test was performed using a surface area analyzer (Micromeritics ASAP 2460). The test steps are as follows: a. Take 100-200 mg of sample and degas at 120°C for 4 h to remove surface adsorbents; b. At liquid nitrogen temperature (77K), measure the N2 adsorption-desorption isotherm and calculate the BET specific surface area (relative pressure P / P0 range: 0.05-0.3).

[0130] (3) True density test: A helium pycnometer (AccuPyc II 1340) was used for the test. The test method is as follows: a. Weigh 5-10g of dry sample and place it in the sample cell. Pass high-purity helium (99.999%) to remove pore gas. b. Measure the volume using the gas displacement method and calculate the true density (repeat three times and take the average value).

[0131] (4) Tap density test: A tap density tester (Hosokawa PT-E) was used. The test method is as follows: a. Place 20 g of sample in a 50 mL graduated cylinder, with the initial volume recorded as V0. b. Vibrate the cylinder 500 times at a frequency of 250 beats / min, and record the final volume after tapping (V1). c. Tap density = mass (20 g) / V1.

[0132] (5) XRD test: X-ray diffractometer (Bruker D8 Advance) was used for the test. Parameter conditions: target material is Cu Kα The voltage was 40 kV, the current was 40 mA, the scanning range was 10-80° (2θ), the step size was 0.02°, and the scanning speed was 5° / min. The peak intensity ratio of the 003 peak to the 104 peak, I(003) / I(104), was calculated based on the obtained XRD spectrum data.

[0133] 2. Electrochemical performance test

[0134] (1) Preparation of button-type full battery: lithium cobalt oxide positive electrode material, acetylene black, and polytetrafluoroethylene (PVDF) were weighed and mixed in a mass ratio of 90:5:5, and the slurry was adjusted in a degassing machine to control the viscosity of the slurry to 8000 mPa·s. Then, an automatic coating machine was used to evenly coat the slurry on aluminum foil to form an original electrode sheet, which was placed in a vacuum oven at 130°C for 4 hours and then placed in a blast oven at 80°C for 12 hours to obtain a test piece; a punching die with a diameter of 14 mm was used to cut out several small electrode sheets at different positions of the above test piece, and the electrode sheets with regular morphology, smooth surface and edges were selected. The small electrode sheet was weighed with a 1 / 10,000 balance, and the weighed small electrode sheet was placed in a vacuum drying oven and evacuated to 0.1 MPa to obtain the positive electrode sheet, which was stored for future use; in an inert gas glove box with a water and oxygen mass content of less than or equal to 0.0005%, a button battery was assembled according to the battery specifications of CR2023, wherein the negative electrode was a lithium sheet, the separator was a polypropylene film, the high-voltage electrolyte solvent was a mixed solution of ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, and the conductive salt was 1M lithium hexafluorophosphate. After the assembly was completed, it was packaged at 800 Pa for 5s to obtain a button full battery.

[0135] (2) Charge and discharge performance test: The button-type full battery assembled according to the method in (1) was charged at a constant current of 0.1C to a voltage of 4.6V under normal temperature battery laboratory conditions, and then charged at a constant voltage of 4.6V to a current of 0.05C. The battery was left to stand for 5 minutes, and the charge capacity was recorded. The button-type full battery was then discharged at a constant current of 0.1C to a voltage of 3.0V, and the discharge capacity was recorded. The first charge specific capacity and first coulombic efficiency at 0.1C were calculated (first efficiency = discharge capacity / charge capacity*100%).

[0136] (3) Rate performance test: The button-type full battery assembled according to the method in (1) was charged at a constant current of 0.5C to a voltage of 4.6V under normal temperature battery laboratory conditions, and then charged at a constant voltage of 4.6V to a current of 0.05C. The battery was left to stand for 5 minutes, and the charge capacity was recorded. The button-type full battery was then discharged at a constant current of 0.5C to a voltage of 3.0V, and the discharge capacity was recorded. The discharge capacity in grams at 0.5C was calculated, and the ratio of the discharge capacity in grams at 0.5C to the first discharge capacity in grams at 0.1C was calculated.

[0137] (4) The button-type full battery assembled according to the method in (1) was charged and discharged 50 times at a constant current of 1C in the voltage range of 3.0 to 4.6V under normal temperature battery laboratory conditions, and the capacity retention rate of the battery before and after the cycle was calculated.

[0138] Table 1

[0139]

[0140]

[0141] Table 2

[0142]

[0143] As can be seen from the results in Table 1, compared with Comparative Examples 1 and 2, when the D50 particle size of the lithium cobalt oxide positive electrode material is similar, the lithium cobalt oxide positive electrode materials obtained in Examples 1 to 9 of the present invention have more moderate specific surface area, true density, tap density and higher I(003) / I(104) ratio. As can be seen from the results in Table 2, compared with Comparative Examples 1 and 2, the lithium cobalt oxide positive electrode materials obtained in Examples 1 to 9 of the present invention have higher charge specific capacity performance, 0.5C / 0.1C reversible specific capacity retention rate and cycle retention rate.

[0144] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A lithium cobalt oxide positive electrode material, characterized in that: When the D50 particle size of the lithium cobalt oxide positive electrode material is 10-20 μm, its specific surface area is 0.4-0.8 m 2 / g; the true density of the lithium cobalt oxide positive electrode material is 4.85 to 5.03 g / cm 3 , tap density is 2.35~2.50g / cm 3 ; The lithium cobalt oxide positive electrode material has an R3-m space group structure, and the peak intensity ratio of the 003 peak to the 104 peak in the XRD spectrum of the lithium cobalt oxide positive electrode material is I(003) / I(104)≧2.

5.

2. The lithium cobalt oxide positive electrode material according to claim 1, characterized in that In the XRD spectrum of the lithium cobalt oxide positive electrode material, the 2θ value of the 003 peak is 18.7-19.2°, and the 2θ value of the 104 peak is 45.0-45.5°.

3. The lithium cobalt oxide positive electrode material according to claim 1, characterized in that The general chemical formula of the lithium cobalt oxide positive electrode material is Li y Na z Co 1-a-b A a M b O2, wherein 0.93≤y≤1.02, 0≤z≤0.02, 0≤a≤0.1, 0≤b≤0.05, A is selected from Ni and / or Mn, and M is selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, and Y.

4. The lithium cobalt oxide positive electrode material according to claim 3, characterized in that The M is selected from at least one of Al, Ti, Y, and Mg.

5. The lithium cobalt oxide positive electrode material according to claim 3, characterized in that The Na content in the lithium cobalt oxide positive electrode material is within 500 ppm.

6. A method for preparing a lithium cobalt oxide positive electrode material, characterized in that: The method comprises the following steps: S1. The lithium cobalt oxide cathode material precursor is mixed with a sodium source, and the resulting mixture is sintered to obtain a sodium-containing semi-finished material; S2. The sodium-containing semi-finished material is mixed with a lithium source and an inert gas is introduced to form an aerosol. The reaction system is then subjected to a hydrothermal reaction. After the reaction is completed, the solid-liquid separation, water washing, and drying are performed to obtain a solid product, which is a lithium cobalt oxide positive electrode material.

7. The method for preparing a lithium cobalt oxide positive electrode material according to claim 6, wherein: In step S1, the lithium cobalt oxide positive electrode material precursor has (Co 1-a-b A a M b )3O4 and / or Co 1-a-b A a M b (OH)2, wherein 0≤a≤0.1, 0≤b≤0.05, A is selected from Ni and / or Mn, and M is selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, and Y; Preferably, the M is selected from at least one of Al, Mg, Ti, and Y; Preferably, the sodium source is selected from at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium nitrate, sodium sulfate, sodium acetate and sodium oxalate; Preferably, the molar ratio of Co in the lithium cobalt oxide positive electrode material to Na in the sodium source is 1:(0.75-1.20); Preferably, the sintering treatment is performed at a temperature of 700 to 1000° C. and for a time of 16 to 48 hours.

8. The method for preparing a lithium cobalt oxide positive electrode material according to claim 6, wherein: Step S2, the lithium source is selected from at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium chloride, lithium bromide and lithium iodide; Preferably, the molar ratio of Na in the sodium-containing semi-finished material to Li in the lithium source is 1:(1-4).

9. The method for preparing a lithium cobalt oxide positive electrode material according to claim 6, wherein: In step S2, the process of mixing the sodium-containing semi-finished material with a lithium source and then introducing an inert gas to form an aerosol includes: mixing the lithium source and water to obtain a lithium source solution, first heating the reaction system containing the lithium source solution to 80-100° C., then adding the sodium-containing semi-finished material and introducing an inert gas into the reaction system to form an aerosol; Preferably, the conditions of the hydrothermal reaction include a temperature of 160 to 200° C. and a time of 2 to 6 h; Preferably, the solid content of the reaction system during the hydrothermal reaction is 40 to 60 wt%; Preferably, the inert gas is selected from at least one of nitrogen, neon, argon, xenon and radon; Preferably, the amount of the inert gas introduced is such as to ensure that the pressure of the reaction system is 0.3 to 2.0 MPa; Preferably, the inert gas is introduced at a flow rate of 2 to 5 L / min and for a time of 1 to 5 min.

10. A lithium cobalt oxide positive electrode material prepared by the method according to any one of claims 6 to 9.

11. Use of the lithium cobalt oxide positive electrode material according to any one of claims 1 to 5 and 10 in a lithium ion battery.

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