O3 phase lithium cobalt oxide cathode material, preparation method and application thereof

Abstract

The application belongs to the technical field of lithium battery cathode materials, and particularly relates to an O3 phase lithium cobaltate cathode material and a preparation method and application thereof. The cathode material comprises an O3 phase lithium cobaltate matrix and yttrium oxide coated on the surface of the O3 phase lithium cobaltate matrix; and the O3 phase lithium cobaltate matrix contains a doped element Ca, and the Ca is embedded in the crystal lattice of the O3 phase lithium cobaltate matrix. The key of the application is to introduce the doped element Ca into the body phase of sodium cobaltate first, then coat yttrium oxide on the surface, and then obtain the lithium cobaltate cathode material through Li-Na replacement sintering. The O3 phase lithium cobaltate cathode material prepared by using the above specific sequence has the structural characteristics of Ca body phase doping and yttrium oxide surface coating, can not only maintain and improve the crystal structure of the lithium cobaltate and the particle crushing condition in the Li-Na replacement sintering, but also help to improve the structural stability of the lithium cobaltate cathode material when lithium is de-embedded at high voltage, so as to improve the capacity performance and cycle performance of the lithium cobaltate cathode material at high voltage.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery cathode material technology, specifically relating to an O3 phase lithium cobalt oxide cathode material, its preparation method, and its application. Background Technology

[0002] As modern life becomes increasingly intelligent, electronic products play an increasingly important role in human life, gradually becoming an indispensable part of modern living. Lithium-ion batteries, as energy storage modules in electronic products, represent a crucial direction for future market development, particularly high-energy-density lithium-ion batteries. Cathode materials, as a key component affecting the capacity and performance of lithium-ion batteries, are essential for the effective development of high-energy-density lithium-ion batteries through research and development of high-performance cathode materials.

[0003] Lithium cobalt oxide (LiCoO2) cathode materials, with their high compaction density and high capacity, have become the preferred cathode material for lithium batteries used in portable consumer electronics. For a long time, increasing the charging voltage has been the necessary path to developing higher energy density lithium cobalt oxide materials. However, the development of high-voltage (>4.55V) LiCoO2 cathode materials faces a series of difficulties, mainly because as the voltage increases, irreversible phase transitions, interfacial side reactions, and surface failures occur in the cathode material's microstructure, leading to a decrease in capacity performance and a corresponding reduction in lifespan. Currently, researchers mostly use any one of the modification methods such as bulk doping, surface modification, and surface coating for improvement, but existing modification methods have limited effectiveness in improving the capacity and cycle performance of LiCoO2 cathode materials at high voltages (>4.55V). Summary of the Invention

[0004] The purpose of this invention is to address the problem that existing modification methods for lithium cobalt oxide cathode materials have limited effectiveness in improving capacity and cycle performance at high voltages (>4.55V). This invention provides an O3-phase lithium cobalt oxide cathode material with a specific structure of bulk Ca doping and surface yttrium oxide coating. This structure exhibits good structural stability at high voltages (>4.55V), which is beneficial for improving the capacity and cycle performance of O3-type lithium cobalt oxide cathode materials.

[0005] In a first aspect, the present invention provides an O3-phase lithium cobalt oxide cathode material. The O3-phase lithium cobalt oxide cathode material comprises an O3-phase lithium cobalt oxide matrix and yttrium oxide coated on the surface of the O3-phase lithium cobalt oxide matrix; the O3-phase lithium cobalt oxide matrix contains a dopant element Ca, and the Ca is embedded in the crystal lattice of the O3-phase lithium cobalt oxide matrix.

[0006] In a preferred embodiment, the general chemical formula of the O3 phase lithium cobalt oxide matrix is ​​Li. x Ca y Coz M a O2, wherein 0.96≦x≦1.02, 0<y≦0.04, 0.96≦z≦1.02, 0≦a≦0.05, and M is at least one selected from the group consisting of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, Y and F.

[0007] In a preferred embodiment, the D50 particle size of the O3-phase lithium cobaltate cathode material is 6.5 to 7.5 μm.

[0008] In a preferred embodiment, the doping amount of Ca in the O3-phase lithium cobaltate cathode material is 3000 to 10000 ppm.

[0009] In a preferred embodiment, the doping amount of M in the O3-phase lithium cobaltate cathode material is 2000 to 8000 ppm.

[0010] In a preferred embodiment, the coating amount of yttrium oxide in the O3-phase lithium cobaltate cathode material is 2000 to 5000 ppm.

[0011] In a preferred embodiment, the thickness of the yttrium oxide coating layer is 5 to 10 nm.

[0012] In a second aspect, the present invention provides a method for preparing an O3-phase lithium cobaltate cathode material. The preparation method comprises the following steps: S1. after mixing a cobalt-based precursor with a sodium source and a calcium source, subjecting the obtained first mixture to a first sintering treatment to obtain Ca-doped sodium cobaltate; S2. after mixing the obtained Ca-doped sodium cobaltate with a yttrium source, subjecting the obtained second mixture to a second sintering treatment to obtain yttrium oxide-coated Ca-doped sodium cobaltate; S3. after mixing the yttrium oxide-coated Ca-doped sodium cobaltate with a lithium source, subjecting the obtained third mixture to a third sintering treatment, and the obtained product is the O3-phase lithium cobaltate cathode material.

[0013] In a preferred embodiment, in step S1, the cobalt-based precursor is selected from (Co 1-b M b )3O4 and / or at least one compound having a general formula structure of (Co 1-b M b )(OH)2, wherein 0≦b≦0.05, and M is at least one selected from the group consisting of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La and Y.

[0014] In a preferred embodiment, in step S1, the molar ratio of metal ions in the cobalt-based precursor to Na in the sodium source is 1:(1.0 to 1.2).

[0015] In a preferred embodiment, in step S1, the sodium source is selected from at least one of sodium hydroxide, sodium nitrate, sodium chloride, and sodium sulfate.

[0016] In a preferred embodiment, in step S1, the amount of calcium source used is such that the Ca content in the O3 phase lithium cobalt oxide cathode material is 3000-10000 ppm.

[0017] In a preferred embodiment, in step S1, the calcium source is selected from at least one of calcium hydroxide, calcium oxide, calcium nitrate, calcium chloride, and calcium sulfate.

[0018] In a preferred embodiment, step S1 includes a first sintering and a second sintering performed sequentially.

[0019] In a preferred embodiment, in step S1, the conditions for the first sintering include: an oxygen-containing atmosphere or an air atmosphere, a temperature of 400–600°C, and a time of 2–5 hours.

[0020] In a preferred embodiment, in step S1, the conditions for the secondary sintering include: an oxygen-containing atmosphere or an air atmosphere, a temperature of 700–900°C, and a time of 8–12 hours.

[0021] In a preferred embodiment, in step S2, the yttrium source is selected from at least one of yttrium oxide, yttrium nitrate, and yttrium chloride.

[0022] In a preferred embodiment, in step S2, the amount of yttrium source is such that the yttrium oxide content in the O3 phase lithium cobalt oxide cathode material is 2000-5000 ppm.

[0023] In a preferred embodiment, in step S2, the conditions for the second sintering treatment include: an oxygen-containing atmosphere or an air atmosphere, a temperature of 500–700°C, and a time of 4–6 hours.

[0024] In a preferred embodiment, in step S2, the 2θ value of the 003 peak in the XRD spectrum of the yttrium oxide-coated, Ca-doped sodium cobaltate is 16.4–16.6°.

[0025] In a preferred embodiment, in step S3, the molar ratio of Na in the yttrium oxide-coated, Ca-doped sodium cobaltate to Li in the lithium source is 1:(1.1~1.3).

[0026] In a preferred embodiment, in step S3, the lithium source is selected from at least one of lithium nitrate, lithium hydroxide, and lithium chloride.

[0027] In a preferred embodiment, in step S3, the conditions for the third sintering treatment include: an oxygen-containing atmosphere or an air atmosphere, a temperature of 200–350°C, and a time of 5–10 hours.

[0028] Thirdly, the present invention provides an O3 phase lithium cobalt oxide cathode material prepared by the above method.

[0029] Fourthly, the present invention provides the application of the above-mentioned O3 phase lithium cobalt oxide cathode material in lithium batteries.

[0030] After extensive and in-depth research, the inventors of this application discovered that in the preparation process of most existing O3-phase lithium cobalt oxide cathode materials, the Li-Na substitution process has a significant adverse effect on the fragmentation of cathode material particles, resulting in poor structural stability of the prepared cathode material. This leads to lattice distortion and side reactions during charge and discharge, resulting in a decrease in capacity and cycle performance. Although many patent documents have reported methods for modifying lithium cobalt oxide materials using doping and surface coating, most modification methods cannot allow dopant elements to enter the lithium cobalt oxide lattice, thus having a limited effect on stabilizing the structure, especially on improving cycle performance. Furthermore, most modification methods involve coating after the lithium cobalt oxide preparation is completed, which fails to improve the stability of the crystal structure during the preparation process, thus having a limited effect on improving the capacity and cycle performance of the cathode material.

[0031] The key to this invention lies in first introducing the doping element Ca into the bulk phase of sodium cobalt oxide, then coating the surface with a yttrium oxide coating layer, and finally obtaining a lithium cobalt oxide cathode material through Li-Na substitution sintering. The O3 phase lithium cobalt oxide cathode material prepared by the above specific sequence has the structural characteristics of Ca bulk doping and yttrium oxide surface coating. It can not only maintain the good crystal structure of lithium cobalt oxide and improve the breakage of lithium cobalt oxide particles during Li-Na substitution sintering, but also help to improve the structural stability of lithium cobalt oxide cathode material during charge and discharge, especially the structural stability during lithium deintercalation at high voltage, and reduce the structural phase transition of lithium cobalt oxide at high voltage, thereby improving the capacity performance and cycle performance of lithium cobalt oxide cathode material at high voltage. The reasons for this are speculated to be as follows: Ca ions and Na ions have similar radii. Introducing the dopant element Ca during the preparation of sodium cobaltate has two advantages. First, it facilitates Ca embedding into the sodium cobaltate lattice, which helps ensure the stability of the crystal structure and improves the breakage of lithium cobaltate particles during subsequent Li-Na replacement sintering. Second, Ca is mainly located in the Li layer of the resulting lithium cobaltate material after replacement, which helps improve the stability of the Li ion channels during discharge, thus improving the capacity and cycle performance of the lithium cobaltate cathode material. Third, the yttrium oxide coating followed by Li-Na replacement sintering has two advantages. First, the yttrium oxide coating structure does not hinder the entry of lithium Li ions into the sodium cobaltate to replace Na ions. Instead, it controls the rate of Li-Na replacement, reducing the damage to the material structure caused by Li-Na replacement. This, along with Ca, improves the structural stability of the prepared lithium cobaltate cathode material. Second, the yttrium oxide coating may also form a certain chemical bond with the internal lithium cobaltate during the Li-Na replacement sintering process, further enhancing the structural stability of the material. Therefore, this is beneficial for improving the capacity and cycle performance of the lithium cobaltate cathode material. Attached Figure Description

[0032] Figure 1 This is a SEM image of the O3 phase lithium cobalt oxide cathode material prepared in Example 1. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Furthermore, unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0034] The O3 phase lithium cobalt oxide cathode material provided by the present invention includes an O3 phase lithium cobalt oxide matrix and yttrium oxide coated on the surface of the O3 phase lithium cobalt oxide matrix; the O3 phase lithium cobalt oxide matrix contains a dopant element Ca and the Ca is embedded in the crystal lattice of the O3 phase lithium cobalt oxide matrix.

[0035] In the present invention, the general chemical formula of the O3-phase lithium cobaltate substrate is preferably Li x Ca y Co z M a O2, wherein 0.96≦x≦1.02, and x can be 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02 or any value between any of the foregoing; 0<y≦0.04, and y can be 0.001, 0.005, 0.01, 0.02, 0.03, 0.04 or any value between any of the foregoing; 0.96≦z≦1.02, and z can be 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02 or any value between any of the foregoing; 0≦a≦0.05, and a can be 0, 0.002, 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05 or any value between any of the foregoing; M is selected from at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La and Y. When the O3-phase lithium cobaltate substrate contains element M, it is beneficial to further improve the cycling performance of the cathode material.

[0036] In the present invention, the D50 particle size of the O3-phase lithium cobaltate cathode material is preferably 6.5 to 7.5 μm, such as 6.5 μm, 6.8 μm, 7.0 μm, 7.2 μm, 7.5 μm or any value between any of the foregoing. The term "D50 particle size" refers to the corresponding particle size when the cumulative particle size distribution percentage of a sample reaches 50%.

[0037] In the present invention, the doping amount of Ca in the O3-phase lithium cobaltate cathode material is preferably 3000 to 10000 ppm, such as 3000 ppm, 5000 ppm, 6000 ppm, 8000 ppm, 9000 ppm, 10000 ppm or any value between any of the foregoing. When the doping amount of Ca is controlled within the above preferred range, it has the advantage of further improving the capacity performance and cycling performance. The reason is that during the sintering process for forming sodium cobaltate, appropriate amount of Ca enters the Na sites of the material by virtue of the similar atomic radius of Ca ions and Na ions, and occupies the Li sites of the lithium cobaltate cathode material after replacement. During charging and discharging of the cathode material, Li ions are continuously detached and embedded, and Ca can well play a role in supporting the structure, improving the capacity and cycling stability of the cathode material. When the Ca doping amount is too high, insoluble substances are easily formed during the Li-Na replacement process, which affects the ion exchange efficiency of the material and reduces the capacity of the material.

[0038] In this invention, the doping amount of M in the O3 phase lithium cobalt oxide cathode material is preferably 2000–8000 ppm, such as 2000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 8000 ppm, or any value between them. Controlling the doping amount of M within the above-mentioned preferred range has the advantage of further improving the cycle performance of the cathode material. This is because appropriate doping of M helps reduce grain boundaries, lowers the probability of grain boundary cracking during charge-discharge cycling, improves structural stability, and reduces the occurrence of side reactions.

[0039] In this invention, the yttrium oxide coating amount in the O3 phase lithium cobalt oxide cathode material is preferably 2000-5000 ppm, such as 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, or any value between them. Controlling the yttrium oxide coating amount within the above-mentioned preferred range has the advantage of further improving the cycle performance of the cathode material. This is because an appropriate amount of yttrium oxide coating does not hinder Li-Na replacement and can reduce the impact of the replacement rate on material damage, resulting in a more stable material structure. However, excessive yttrium oxide coating not only affects the Li-Na replacement efficiency but also the Li deintercalation rate during charging and discharging, leading to a decrease in cycle and capacity performance.

[0040] In this invention, the thickness of the yttrium oxide coating layer is preferably 5–10 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any value between them. This has the advantage of further improving the capacity and cycle performance of the cathode material because the rate of Li-Na replacement can be better controlled, reducing the damage to the material structure caused by Li-Na replacement.

[0041] The method for preparing the O3 phase lithium cobalt oxide cathode material provided by this invention includes the following steps:

[0042] S1. After mixing the cobalt-based precursor with sodium and calcium sources, the resulting first mixture is subjected to a first sintering treatment to obtain Ca-doped sodium cobaltate.

[0043] S2. After mixing the obtained Ca-doped sodium cobaltate with a yttrium source, the resulting second mixture is subjected to a second sintering treatment to obtain yttrium oxide-coated, Ca-doped sodium cobaltate;

[0044] S3. After mixing yttrium oxide-coated, Ca-doped sodium cobalt oxide with a lithium source, the resulting third mixture undergoes a third sintering treatment, and the product obtained is the O3 phase lithium cobalt oxide cathode material.

[0045] In this invention, in step S1, the cobalt-based precursor is preferably derived from a source having (Co... 1-b M b )3O4 and / or (Co 1-b M bAt least one compound with the general formula (OH)₂. Wherein, 0 ≦ b ≦ 0.05, and b can be 0, 0.002, 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, or any value between them; M is preferably at least one of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, Y, and F. That is, the cobalt-based precursor can be at least one of cobalt tetroxide, cobalt tetroxide containing M, cobalt hydroxide, and cobalt hydroxide containing M. Having (Co) 1-b M b )3O4 and / or (Co 1-b M b Compounds with the general formula ()(OH)₂ can be commercially available or prepared using existing methods. Specifically, (Co) 1-b M b (OH)₂ can be prepared by co-precipitation: cobalt salt and optionally M salt are co-precipitated with an alkaline precipitant, and the solid product after washing and drying is (Co)₂. 1-b M b (OH)2. Specifically, (Co 1-b M b Cobalt salt and optional M salt can be obtained by heat treatment, or by first co-precipitating cobalt salt and optional M salt with an alkaline precipitant, and then heat-treating the solid product after washing and drying.

[0046] In this invention, in step S1, the first mixture preferably further includes a source of M. That is, the M element can be obtained through (Co) b M c )3O4 and / or Co b M c The M source can be introduced as a compound with the general formula (OH)2 or as an M source. The M source can be selected from at least one of the oxides, nitrates, chlorides, and sulfates of Al, Mg, Ti, Tc, Mo, Ca, W, Nb, Zr, La, Y, and F.

[0047] In this invention, in step S1, the molar ratio of metal ions in the cobalt-based precursor to Na in the sodium source is preferably 1:(1.0 to 1.2), such as 1:1.0, 1:1.05, 1:1.1, 1:1.15, 1:1.2, or any value between them. The sodium source is any existing compound capable of providing sodium, such as at least one of sodium hydroxide, sodium nitrate, sodium chloride, and sodium sulfate.

[0048] In this invention, in step S1, the amount of calcium source is preferably such that the Ca content in the O3 phase lithium cobalt oxide cathode material is 3000-10000 ppm. The calcium source is any existing compound that can provide Ca, such as at least one of calcium hydroxide, calcium oxide, calcium nitrate, calcium chloride, and calcium sulfate.

[0049] In this invention, step S1 preferably includes a first sintering process and a second sintering process performed sequentially. At the first sintering temperature, the cobalt-based precursor and the sodium source form a molten mixture. Then, at the second sintering temperature, the molten mixture forms sodium cobaltate, and during this process, Ca ions, due to their similar radius to Na ions, enter the sodium cobaltate lattice for doping. Using the above-mentioned preferred sintering method has the advantage of further improving the capacity of the cathode material. This is because the morphology of the semi-finished product is first fixed by the first sintering, and then the second sintering crystallizes the material, allowing Ca to be doped into the bulk phase, resulting in highly compacted particles, thereby increasing the material's capacity. The conditions for the first sintering preferably include: being carried out in an oxygen-containing atmosphere or an air atmosphere; a temperature of 400–600°C, such as 400°C, 450°C, 500°C, 550°C, 600°C, or any value between them; and a time of 2–5 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, or any value between them. The conditions for the secondary sintering include: being carried out in an oxygen-containing atmosphere or an air atmosphere; a temperature of 700–900°C, such as 700°C, 750°C, 800°C, 850°C, 900°C or any value between them; and a time of 8–12 hours, such as 8 hours, 9 hours, 10 hours, 10.5 hours, 11 hours, 12 hours or any value between them.

[0050] In this invention, in step S2, the amount of yttrium source is preferably such that the yttrium oxide content in the O3 phase lithium cobalt oxide cathode material is 2000-5000 ppm. The yttrium source can be any existing compound capable of providing yttrium, such as at least one of yttrium oxide, yttrium nitrate, and yttrium chloride.

[0051] In this invention, in step S2, the conditions for the second sintering treatment preferably include: being carried out in an oxygen-containing atmosphere or an air atmosphere; a temperature of 500–700°C, such as 500°C, 550°C, 600°C, 650°C, 700°C or any value between them; and a time of 4–6 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours or any value between them.

[0052] In this invention, in step S2, the 2θ value of the 003 peak in the XRD pattern of the yttrium oxide-coated, Ca-doped sodium cobaltate is preferably 16.4–16.6°, such as 16.4°, 16.45°, 16.5°, 16.55°, 16.6°, or any value between them. At this time, the main phase of the sodium cobaltate material is P3', which has a higher sodium intercalation capacity compared to traditional P2 phase materials. More Na facilitates the exchange of more Li into the crystal lattice, thereby improving the material's capacity performance.

[0053] In this invention, in step S3, the molar ratio of Na in the yttrium oxide-coated, Ca-doped sodium cobaltate to Li in the lithium source is preferably 1:(1.1 to 1.3), such as 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, or any value between them. The lithium source is any existing compound capable of providing lithium, such as at least one of lithium nitrate, lithium hydroxide, and lithium chloride.

[0054] In this invention, the conditions for the third sintering treatment in step S3 preferably include: being carried out in an oxygen-containing atmosphere or an air atmosphere; a temperature of 200–350°C, such as 200°C, 220°C, 250°C, 280°C, 300°C, 320°C, 350°C or any value between them; and a time of 5–10 h, such as 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or any value between them.

[0055] Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or as a specific limitation on the type or quantity of the indicated technical features.

[0056] The present invention will be described in detail below through specific embodiments. These embodiments are intended to explain the invention and should not be construed as limiting it. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0057] Preparation Example 1

[0058] This preparation example illustrates the preparation of a 2000 ppm aluminum-doped cobalt tetroxide precursor. The specific process is as follows:

[0059] S1. Weigh out cobalt chloride (CoCl2·6H2O) and aluminum sulfate (Al2(SO4)3) according to the molar ratio Co:Al=1:0.006 and dissolve them in 1L of deionized water. Stir until clear and free of precipitate to obtain a mixed metal ion solution; prepare 500mL of 1.0M ammonium bicarbonate ((NH4)HCO3) solution as a precipitant.

[0060] S2. Under 40℃ water bath heating, the mixed metal ion solution was added dropwise to the ammonium bicarbonate solution at a rate of 50 mL / min, and the mixture was continuously stirred (200 rpm) to generate a pink precipitate. The precipitate was washed three times with deionized water by centrifugation, and then washed once with anhydrous ethanol to remove impurity ions. The precipitate was then dried in a 100℃ oven for 8 hours to obtain the aluminum-doped cobalt carbonate precursor.

[0061] S3. The dried aluminum-doped cobalt carbonate precursor was placed in a muffle furnace and heated to 720°C at 5°C / min in an air atmosphere. The temperature was held for 3 hours and then naturally cooled before sieving to obtain cobalt tetroxide doped with 2000 ppm aluminum.

[0062] Preparation Example 2

[0063] This preparation example illustrates the preparation of a cobalt tetroxide precursor doped with 8000 ppm magnesium. The specific process is as follows:

[0064] S1. Weigh out cobalt chloride (CoCl2·6H2O) and magnesium carbonate (MgCO3) according to the molar ratio Co:Mg=1:0.0264 and dissolve them in 1L of deionized water. Stir until clear and free of precipitate to obtain a mixed metal ion solution; prepare 500mL of 1.0M ammonium bicarbonate ((NH4)HCO3) solution as a precipitant.

[0065] S2. Under 40℃ water bath heating, the mixed metal ion solution was added dropwise to the ammonium bicarbonate solution at a rate of 50 mL / min, and the mixture was continuously stirred (200 rpm) to generate a pink precipitate. The precipitate was washed three times with deionized water by centrifugation, and then washed once with anhydrous ethanol to remove impurity ions. The precipitate was then dried in a 100℃ oven for 8 hours to obtain the magnesium-doped cobalt carbonate precursor.

[0066] S3. The dried magnesium-doped cobalt carbonate precursor was placed in a muffle furnace and heated to 720°C at 5°C / min in an air atmosphere. The temperature was maintained for 3 hours, and after natural cooling, it was sieved to obtain cobalt tetroxide doped with 2000ppm magnesium.

[0067] Example 1

[0068] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0069] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to a molar ratio of Co:Na = 1:1.1, and add calcium hydroxide additive (calcium hydroxide dosage = precursor mass * 0.73 * (0.9wt% / 60wt%) / calcium mass percentage in calcium hydroxide) and mix. The resulting mixture is sintered at 500℃ for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 800℃ for 10.5 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain Ca-doped sodium cobaltate.

[0070] S2. The obtained Ca-doped sodium cobaltate was mixed with yttrium oxide (the amount of yttrium oxide = precursor mass * 0.73 * (0.3wt% / 60wt%) / the mass percentage of yttrium in the yttrium oxide) and the resulting mixture was sintered in air at 600°C for 5 hours to obtain yttrium oxide-coated, Ca-doped sodium cobaltate. A 5g sample of the obtained sodium cobaltate was subjected to XRD analysis, and the position of its 003 peak was found to be 16.575°.

[0071] S3. Yttrium oxide-coated, Ca-doped sodium cobaltate and lithium nitrate were mixed at a molar ratio of Na:Li = 1:1.2. The mixture was then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain the O3 phase lithium cobaltate cathode material. The chemical formula of the O3 phase lithium cobaltate matrix is ​​Li. 0.98 Ca 0.02 The Co1O2 has a D50 particle size of 7.1 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 3000 ppm, and a coating layer thickness of 7.3 nm.

[0072] The SEM test results of the obtained O3 phase lithium cobalt oxide cathode material are as follows: Figure 1 As shown, the O3 phase lithium cobalt oxide cathode material particles prepared after Li-Na substitution are complete, have smooth surfaces, and have good morphology.

[0073] Example 2

[0074] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0075] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to the molar ratio Co:Na = 1:1.0, and add calcium hydroxide additive (calcium hydroxide dosage = precursor mass * 0.73 * (0.9wt% / 60wt%) / calcium mass percentage in calcium hydroxide) and mix. The resulting mixture is sintered at 400℃ for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 700℃ for 12 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain Ca-doped sodium cobaltate.

[0076] S2. The obtained Ca-doped sodium cobaltate was mixed with yttrium oxide (the amount of yttrium oxide = precursor mass * 0.73 * (0.2wt% / 60wt%) / the mass percentage of yttrium in the yttrium oxide) and the resulting mixture was sintered in air at 600°C for 5 hours to obtain yttrium oxide-coated, Ca-doped sodium cobaltate. A 5g sample of the obtained sodium cobaltate was subjected to XRD analysis, and the position of its 003 peak was found to be 16.535°.

[0077] S3. Yttrium oxide-coated, Ca-doped sodium cobaltate and lithium nitrate were mixed at a molar ratio of Na:Li = 1:1.1. The mixture was then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain the O3 phase lithium cobaltate cathode material. The chemical formula of the O3 phase lithium cobaltate matrix is ​​Li. 0.98 Ca 0.02 The Co1O2 has a D50 particle size of 7.0 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 2000 ppm, and a coating layer thickness of 5.6 nm.

[0078] Example 3

[0079] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0080] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to the molar ratio Co:Na = 1:1.2, and add calcium nitrate additive (calcium nitrate amount = precursor mass * 0.73 * (0.9wt% / 60wt%) / mass percentage of calcium in calcium nitrate) and mix. The resulting mixture is sintered at 600℃ for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 900℃ for 8 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain Ca-doped sodium cobaltate.

[0081] S2. The obtained Ca-doped sodium cobaltate was mixed with yttrium nitrate (the amount of yttrium nitrate = precursor mass * 0.73 * (0.5wt% / 60wt%) / mass percentage of yttrium in yttrium nitrate). The resulting mixture was sintered in air at 600°C for 5 hours to obtain yttrium oxide-coated, Ca-doped sodium cobaltate. A 5g sample of the obtained sodium cobaltate was subjected to XRD analysis, revealing that its 003 peak position was 16.585°.

[0082] S3. Yttrium oxide-coated, Ca-doped sodium cobaltate and lithium nitrate were mixed at a molar ratio of Na:Li = 1:1.3. The mixture was then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain the O3 phase lithium cobaltate cathode material. The chemical formula of the O3 phase lithium cobaltate matrix is ​​Li. 0.98 Ca 0.02 The Co1O2 has a D50 particle size of 7.2 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 5000 ppm, and a coating layer thickness of 9.6 nm.

[0083] Example 4

[0084] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0085] O3-phase lithium cobalt oxide cathode material was prepared according to the method of Example 1, except that in step S1, the amount of calcium hydroxide was calculated as: precursor mass * 0.73 * (0.6 wt% / 60 wt%) / mass percentage of calcium in calcium hydroxide. All other conditions were the same as in Example 1. Thus, O3-phase lithium cobalt oxide cathode material was prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.985 Ca 0.015 The Co1O2 has a D50 particle size of 6.9 μm, a Ca doping amount of 6000 ppm, a yttrium oxide coating amount of 3000 ppm, and a coating layer thickness of 7.1 nm.

[0086] Example 5

[0087] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0088] O3-phase lithium cobalt oxide cathode material was prepared according to the method of Example 1, except that in step S1, the amount of calcium hydroxide was calculated as: precursor mass * 0.73 * (1 wt% / 60 wt%) / calcium mass percentage in calcium hydroxide. All other conditions were the same as in Example 1. Thus, O3-phase lithium cobalt oxide cathode material was prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.976 Ca 0.024The Co1O2 has a D50 particle size of 7.3 μm, a Ca doping amount of 10000 ppm, a yttrium oxide coating amount of 3000 ppm, and a coating layer thickness of 7.8 nm.

[0089] Example 6

[0090] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0091] The O3-phase lithium cobalt oxide cathode material was prepared according to the method of Example 2, except that in step S1, a cobalt tetroxide precursor (from Preparation Example 1) doped with aluminum (2000 ppm) and sodium hydroxide were weighed in a molar ratio of Co:Na = 1:1.0, and calcium hydroxide additive was added for mixing. All other conditions were the same as in Example 1. Thus, the O3-phase lithium cobalt oxide cathode material was prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.98 Ca 0.02 Co 0.994 Al 0.006 The O2 particles have a D50 size of 6.8 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 2000 ppm, and a coating thickness of 5.4 nm.

[0092] Example 7

[0093] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0094] The O3-phase lithium cobalt oxide cathode material was prepared according to the method of Example 2, except that in step S1, a magnesium-doped cobalt tetroxide precursor (from Preparation Example 2) with a molar ratio of Co:Na = 1:1.0 was weighed and sodium hydroxide was added, along with calcium hydroxide additive for mixing. All other conditions were the same as in Example 1. Thus, the O3-phase lithium cobalt oxide cathode material was prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.98 Ca 0.02 Co 0.975 Mg 0.025 The O2 particles have a D50 size of 6.9 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 2000 ppm, and a coating thickness of 5.8 nm.

[0095] Example 8

[0096] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0097] O3-phase lithium cobalt oxide cathode material was prepared according to the method of Example 1, except that in step S1, the resulting mixture was directly sintered in air at 800°C for 10.5 h. After sintering, the mixture was rolled, crushed, and sieved to obtain Ca-doped sodium cobalt oxide. All other conditions were the same as in Example 1. Thus, O3-phase lithium cobalt oxide cathode material was prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.98 Ca 0.02 The Co1O2 has a D50 particle size of 6.9 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 3000 ppm, and a coating layer thickness of 7.6 nm.

[0098] Example 9

[0099] This embodiment illustrates the preparation of an O3 phase lithium cobalt oxide cathode material, and the specific process is as follows:

[0100] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to a molar ratio of Co:Na = 1:1.1, and add calcium hydroxide additive (calcium hydroxide dosage = precursor mass * 0.73 * (0.9wt% / 60wt%) / calcium mass percentage in calcium hydroxide) and mix. The resulting mixture is sintered at 500℃ for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 800℃ for 10.5 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain Ca-doped sodium cobaltate.

[0101] S2. Ca-doped sodium cobaltate and lithium nitrate were mixed at a molar ratio of Na:Li = 1:1.2, and then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain the lithium cobaltate matrix material Li. 0.98 Ca 0.02 Co1O2.

[0102] S2. The obtained lithium cobalt oxide matrix material Li 0.98 Ca 0.02 Co1O2 and yttrium oxide (the amount of yttrium oxide = precursor mass * 0.73 * (0.3wt% / 60wt%) / mass percentage of yttrium in yttrium oxide) were mixed, and the resulting mixture was sintered in air at 600℃ for 5 hours to obtain a yttrium oxide-coated, Ca-doped O3 phase lithium cobalt oxide cathode material with a D50 particle size of 7.2 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 3000 ppm, and a coating layer thickness of 7.9 nm.

[0103] Example 10

[0104] This embodiment illustrates the preparation of an O3-phase lithium cobalt oxide cathode material. The specific process is as follows: The O3-phase lithium cobalt oxide cathode material is prepared according to the method of Example 1. The difference is that in step S2, the amount of yttrium oxide is calculated as: precursor mass * 0.73 * (0.8 wt% / 60 wt%) / yttrium mass percentage in the yttrium oxide. All other conditions are the same as in Example 1. Thus, an O3-phase lithium cobalt oxide cathode material is prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.98 Ca 0.02 The Co1O2 has a D50 particle size of 6.8 μm, a Ca doping amount of 9000 ppm, a yttrium oxide coating amount of 8000 ppm, and a coating layer thickness of 11.7 nm.

[0105] Example 11

[0106] This embodiment illustrates the preparation of an O3-phase lithium cobalt oxide cathode material. The specific process is as follows: The O3-phase lithium cobalt oxide cathode material is prepared according to the method of Example 1. The difference is that in step S1, the amount of calcium hydroxide is calculated as: precursor mass * 0.73 * (1.5 wt% / 60 wt%) / the mass percentage of calcium in the calcium hydroxide. All other conditions are the same as in Example 1. Thus, the O3-phase lithium cobalt oxide cathode material is prepared. The chemical formula of the O3-phase lithium cobalt oxide matrix is ​​Li. 0.97 Ca 0.03 The Co1O2 has a D50 particle size of 7.2 μm, a Ca doping amount of 15000 ppm, a yttrium oxide coating amount of 3000 ppm, and a coating layer thickness of 7.6 nm.

[0107] Comparative Example 1

[0108] This comparative example illustrates the preparation of a reference lithium cobalt oxide cathode material. The specific process is as follows:

[0109] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to the molar ratio Co:Na = 1:1.1 and mix them. The resulting mixture is sintered at 500°C for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 800°C for 10.5 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain sodium cobaltate.

[0110] S2. Sodium cobalt oxide and lithium nitrate were mixed in a molar ratio of Na:Li = 1:1.2, and then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain a reference lithium cobalt oxide cathode material with the chemical formula LiCoO2 and a D50 particle size of 7.1 μm.

[0111] Comparative Example 2

[0112] This comparative example illustrates the preparation of a reference lithium cobalt oxide cathode material. The specific process is as follows:

[0113] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to a molar ratio of Co:Na = 1:1.1, and add calcium hydroxide additive (calcium hydroxide dosage = precursor mass * 0.73 * (0.9wt% / 60wt%) / calcium mass percentage in calcium hydroxide) and mix. The resulting mixture is sintered at 500℃ for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 800℃ for 10.5 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain Ca-doped sodium cobaltate.

[0114] S2. Ca-doped sodium cobaltate and lithium nitrate were mixed at a molar ratio of Na:Li = 1:1.2, and then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain a reference lithium cobaltate cathode material. The chemical formula of the lithium cobaltate matrix is ​​Li. 0.98 Ca 0.02 The Co1O2 has a D50 particle size of 7.3 μm and a Ca doping concentration of 9000 ppm.

[0115] Comparative Example 3

[0116] This comparative example illustrates the preparation of a reference lithium cobalt oxide cathode material. The specific process is as follows:

[0117] S1. Weigh out cobalt tetroxide precursor and sodium hydroxide according to the molar ratio Co:Na = 1:1.1 and mix them. The resulting mixture is sintered at 500°C for 3 hours in an oxygen atmosphere (oxygen concentration above 90%). After sintering, the mixture is rolled, crushed, and sieved. Then, it is sintered at 800°C for 10.5 hours in an air atmosphere. After sintering, the mixture is rolled, crushed, and sieved to obtain sodium cobaltate.

[0118] S2. The obtained sodium cobaltate was mixed with yttrium oxide (the amount of yttrium oxide = precursor mass * 0.73 * (0.3wt% / 60wt%) / the mass percentage of yttrium in the yttrium oxide) and the resulting mixture was sintered in air at 600°C for 5 hours to obtain yttrium oxide-coated, Ca-doped sodium cobaltate. A 5g sample of the obtained sodium cobaltate was subjected to XRD analysis, and the position of its 003 peak was found to be 16.57°.

[0119] S3. Sodium cobalt oxide coated with yttrium oxide was mixed with lithium nitrate at a molar ratio of Na:Li = 1:1.2. The mixture was then sintered at 270°C for 6 hours in an oxygen atmosphere (oxygen concentration above 90%). The resulting product was centrifuged, washed with water, and then heat-treated in a vacuum oven at 150°C for 24 hours to obtain a reference lithium cobalt oxide cathode material. The chemical formula of the lithium cobalt oxide matrix was LiCoO2, the D50 particle size was 6.9 μm, the yttrium oxide coating amount was 3000 ppm, and the coating layer thickness was 5.8 nm.

[0120] Test case

[0121] The lithium cobalt oxide cathode material, acetylene black, and polyvinylidene fluoride (PVDF) prepared in the above examples and comparative examples were mixed at a mass ratio of 90:5:5. The slurry viscosity was controlled to 8000 mPa·s in a degassing machine. Then, the slurry was uniformly coated onto aluminum foil using an automatic coating machine to form the original electrode sheet. The electrode sheet was dried in a vacuum oven at 130°C for 4 hours, and then placed in a forced-air oven at 80°C for 12 hours to obtain the test sheet. Several small electrode sheets were cut from different positions of the test sheet using a 14 mm diameter die, selecting those with regular morphology and smooth surfaces and edges. The small electrode pieces were weighed using a balance with a weight of 0.0001 g / L. The weighed small electrode pieces were placed in a vacuum drying oven and evacuated to 0.1 MPa to obtain the positive electrode piece, which was then stored for later use. In an inert gas glove box with water and oxygen content of less than or equal to 0.0005%, coin cells were assembled according to the battery specifications of CR2023. The negative electrode was a lithium sheet, the separator was a polypropylene membrane, the high-voltage electrolyte solvent was a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1, and the conductive salt was 1M lithium hexafluorophosphate. After assembly, the cells were encapsulated at 800 Pa for 5 seconds to obtain a coin cell.

[0122] (1) Charge and discharge performance test: The assembled coin cell 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. After standing for 5 minutes, the charging capacity was recorded. Then the coin cell was 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 the first coulombic efficiency at 0.1C were calculated (first efficiency = discharge capacity / charge capacity * 100%).

[0123] (2) Cyclic performance test: The assembled button cell was charged and discharged 300 times under normal temperature battery laboratory conditions with a constant current of 1C in a voltage range of 3.0 to 4.6V, and the capacity retention rate of the battery before and after the cycle was calculated.

[0124] Table 1

[0125] Example 1 236.2 95.6 97.1 Example 2 235.8 95.2 95.3 Example 3 235.9 95.3 96.5 Example 4 235.4 95.1 95.8 Example 5 233.3 95.1 94.9 Example 6 230.3 94.5 95.5 Example 7 230.8 94.3 95.4 Example 8 224.5 93.2 92.1 Example 9 230.6 94.5 90.7 Example 10 229.5 93.8 88.1 Example 11 233.3 94.1 87.5 Comparative Example 1 199.5 92.6 80.6 Comparative Example 2 205.3 94.8 84.1 Comparative Example 3 203.7 94.6 82.3

[0126] As shown in Table 1, compared with Comparative Examples 1-3, the O3 phase lithium cobalt oxide cathode materials provided in Examples 1-11 of the present invention have better charge specific capacity and cycle retention rate.

[0127] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An O3-phase lithium cobalt oxide cathode material, characterized in that, The O3 phase lithium cobalt oxide cathode material includes an O3 phase lithium cobalt oxide matrix and yttrium oxide coated on the surface of the O3 phase lithium cobalt oxide matrix; the O3 phase lithium cobalt oxide matrix contains the dopant element Ca and the Ca is embedded in the crystal lattice of the O3 phase lithium cobalt oxide matrix; the coating amount of yttrium oxide in the O3 phase lithium cobalt oxide cathode material is 2000~5000ppm.

2. The O3 phase lithium cobalt oxide cathode material according to claim 1, characterized in that, The general chemical formula of the O3-phase lithium cobaltate matrix is Li x Ca y Co z M a O2, wherein 0.96≤x≤1.02, 0<y≤0.04, 0.96≤z≤1.02, 0≤a≤0.05, and M is selected from at least one of Al, Mg, Ti, Tc, Mo, W, Nb, Zr, La, Y and F.

3. The O3 phase lithium cobalt oxide cathode material according to claim 1, characterized in that, The D50 particle size of the O3 phase lithium cobalt oxide cathode material is 6.5~7.5μm.

4. The O3 phase lithium cobalt oxide cathode material according to claim 1, characterized in that, The Ca doping amount in the O3 phase lithium cobalt oxide cathode material is 3000~10000ppm.

5. The O3 phase lithium cobalt oxide cathode material according to claim 2, characterized in that, The doping amount of M in the O3 phase lithium cobalt oxide cathode material is 2000~8000ppm.

6. The O3 phase lithium cobalt oxide cathode material according to claim 1, characterized in that, The thickness of the yttrium oxide coating is 5~10 nm.

7. The method for preparing the O3 phase lithium cobalt oxide cathode material according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: S1. After mixing the cobalt-based precursor with sodium and calcium sources, the resulting first mixture is subjected to a first sintering treatment to obtain Ca-doped sodium cobaltate. S2. After mixing the obtained Ca-doped sodium cobaltate with a yttrium source, the resulting second mixture is subjected to a second sintering treatment to obtain yttrium oxide-coated, Ca-doped sodium cobaltate; S3. After mixing yttrium oxide-coated, Ca-doped sodium cobalt oxide with a lithium source, the resulting third mixture undergoes a third sintering treatment, and the product obtained is the O3 phase lithium cobalt oxide cathode material.

8. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S1, the cobalt-based precursor is selected from those having (Co) 1-b M b )3O4 and / or (Co 1-b M b At least one of the compounds with the general formula (OH)2, wherein 0 ≤ b ≤ 0.05, and M is selected from at least one of Al, Mg, Ti, Tc, Mo, W, Nb, Zr, La, and Y.

9. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S1, the molar ratio of metal ions in the cobalt-based precursor to Na in the sodium source is 1:(1.0~1.2).

10. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S1, the sodium source is selected from at least one of sodium hydroxide, sodium nitrate, sodium chloride, and sodium sulfate.

11. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S1, the amount of calcium source used is such that the Ca content in the O3 phase lithium cobalt oxide cathode material is 3000~10000ppm.

12. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S1, the calcium source is selected from at least one of calcium hydroxide, calcium oxide, calcium nitrate, calcium chloride, and calcium sulfate.

13. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S1, the first sintering process includes a first sintering and a second sintering performed sequentially.

14. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 13, characterized in that, In step S1, the conditions for the first sintering include: an oxygen-containing atmosphere, a temperature of 400~600℃, and a time of 2~5h; the conditions for the second sintering include: an oxygen-containing atmosphere, a temperature of 700~900℃, and a time of 8~12h.

15. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S2, the yttrium source is selected from at least one of yttrium oxide, yttrium nitrate, and yttrium chloride.

16. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S2, the amount of yttrium source used is such that the yttrium oxide content in the O3 phase lithium cobalt oxide cathode material is 2000~5000ppm.

17. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S2, the conditions for the second sintering treatment include: an oxygen-containing atmosphere, a temperature of 500~700℃, and a time of 4~6h.

18. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S2, the 2θ value of the 003 peak in the XRD spectrum of the yttrium oxide-coated, Ca-doped sodium cobaltate is 16.4~16.6°.

19. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S3, the molar ratio of Na to Li in the yttrium oxide-coated, Ca-doped sodium cobaltate is 1:(1.1~1.3).

20. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S3, the lithium source is selected from at least one of lithium nitrate, lithium hydroxide, and lithium chloride.

21. The method for preparing the O3 phase lithium cobalt oxide cathode material according to claim 7, characterized in that, In step S3, the conditions for the third sintering treatment include: an oxygen-containing atmosphere, a temperature of 200~350℃, and a time of 5~10h.

22. The application of the O3 phase lithium cobalt oxide cathode material according to any one of claims 1 to 6 in lithium batteries.

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