Spherical lithium cobalt oxide positive electrode material with O2 phase structure as well as preparation method and application of spherical lithium cobalt oxide positive electrode material

Abstract

The invention relates to a spherical lithium cobalt oxide positive electrode material with an O2 phase structure and a preparation method and application thereof, the chemical general formula of the spherical lithium cobalt oxide positive electrode material is LiaXbMpAlqCo (1-p-q) O2, 0.5 < a < = 1, 0 < = b < 0.2, 0 < = p < = 0.5, 0 < = q < = 0.5, an X element is selected from at least one of Na and K, and an M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F or Ti; xRD (X-Ray Diffraction) characteristic peaks exist at the same time when 2 theta A1 is equal to 18.3 to 18.9 degrees, 2 theta A2 is equal to 37.9 to 38.4 degrees and 2 theta A3 is equal to 46.7 to 47.3 degrees, and the full width at half maximum of the (002) characteristic peak is 0.355 to 0.495; the spherical lithium cobalt oxide positive electrode material has higher specific capacity and higher cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for batteries, and particularly to a spherical lithium cobalt oxide cathode material with an O2-phase structure, a preparation method thereof, and an application thereof. Background Art

[0002] In the new energy industry, as a high-energy density, lightweight, and environmentally friendly energy storage technology, lithium-ion batteries have become the main energy storage devices and are widely used in fields such as electric vehicles, energy storage systems, and portable electronic products. Lithium cobalt oxide cathode materials have advantages such as high capacity, high voltage, and relatively high cycle life, and play an important role in lithium-ion batteries.

[0003] Commercially applied lithium cobalt oxide materials belong to the hexagonal crystal system, and the crystal structure is a layered structure, belonging to the space group R-3m. Each lithium cobalt oxide unit cell contains a cobalt ion (Co 3+ ) layer and two lithium ion (Li + ) layers. The cobalt ion layer is composed of octahedrons, and each cobalt ion is surrounded by six oxygen ions (O 2- ). The lithium ion layer is composed of octahedrons and tetrahedrons, and each lithium ion is surrounded by six oxygen ions. This layered structure enables lithium cobalt oxide materials to have good ion diffusion performance and conductivity, which is beneficial to the high-speed charge and discharge of batteries. Lithium cobalt oxide has a relatively high electrode potential and specific capacity, that is, it can provide a relatively high voltage output, enabling more lithium ions to be stored per unit mass or volume. At the same time, lithium cobalt oxide materials have good cycle stability and life, and can maintain relatively high battery performance during multiple charge and discharge cycles.

[0004] Traditional O3-type lithium cobalt oxide has a relatively fast capacity decay rate during charge and discharge cycles. This is mainly because the oxidation state change range of cobalt ions in the traditional lithium cobalt oxide structure is relatively large, resulting in large volume expansion and contraction of cobalt ions during charge and discharge, thereby causing damage to the crystal structure and capacity loss. The structural change may lead to the accumulation of internal stress in the material, increasing the risk of thermal runaway during the cyclic charge and discharge of the battery, and there are certain safety hazards. Therefore, lithium cobalt oxide is prone to thermal runaway reactions at high temperatures, leading to safety problems such as battery combustion or explosion.

[0005] In summary, traditional O3-type lithium cobalt oxide has problems such as limited cycle stability and capacity utilization of lithium cobalt oxide, and it has been difficult to meet the usage requirements of the industry for high-energy density and high-safety batteries. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and provide a spherical lithium cobalt oxide cathode material with an O2-phase structure, a preparation method thereof, and an application thereof.

[0007] The spherical lithium cobalt oxide cathode material with O2-phase structure provided by the present invention is in a spherical agglomerated state and has a P63mc-phase structure. Among them, the oxygen atoms in this structure adopt a distorted cubic close-packed manner, showing higher discharge capacity and better rate performance. In addition, due to the more stable crystal structure of the spherical lithium cobalt oxide cathode material with O2-phase structure at high voltages, the cathode material exhibits better cycle stability and can greatly improve the energy density of the battery.

[0008] To achieve the above object, in the first aspect, an embodiment of the present invention provides a spherical lithium cobalt oxide cathode material with O2-phase structure. The chemical general formula of the spherical lithium cobalt oxide cathode material is: Li a X b M p Al q Co (1-p-q) O2, where 0.5 < a ≤ 1, 0 ≤ b < 0.2, 0 ≤ p ≤ 0.5, 0 ≤ q ≤ 0.5. The X element is selected from at least one of Na and K, and the M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F, or Ti;

[0009] Among them, the spherical lithium cobalt oxide cathode material has XRD diffraction characteristic peaks at the same time when 2θ A1 = 18.3° - 18.9°, 2θ A2 = 37.9° - 38.4°, 2θ A3 = 46.7° - 47.3°; the full width at half maximum value k of the (002) characteristic peak of the spherical lithium cobalt oxide cathode material satisfies 0.355 ≤ k ≤ 0.495.

[0010] Preferably, the spherical lithium cobalt oxide cathode material is composed of secondary spherical particles formed by clusters of primary flaky particles, and the secondary spherical particles do not agglomerate;

[0011] The thickness j of the primary flaky particles ranges from 0 < j ≤ 800 nm;

[0012] The median particle size of the primary flaky particles is measured by a laser particle size analyzer to be D 50 less than or equal to 1000 nm, and the median particle size of the secondary spherical particles is D 50 greater than or equal to 3 μm and less than or equal to 15 μm.

[0013] Preferably, the specific surface area of the spherical lithium cobalt oxide cathode material is 0.35 m 2 / g - 0.55 m 2 / g;

[0014] and / or, the tap density of the lithium cobalt oxide cathode material is 3.6 g / cm3 ~4.2 g / cm 3 。

[0015] In a second aspect, an embodiment of the present invention provides a method for preparing the spherical lithium cobalt oxide cathode material with an O2 phase structure described in the first aspect above. The preparation method includes:

[0016] Step S1: Uniformly mix a cobalt precursor, a compound containing element X, and / or a compound containing element M in proportion to obtain a mixed material;

[0017] Step S2: Subject the mixed material to high-temperature calcination treatment to obtain a primary sintered product;

[0018] Step S3: Weigh a certain amount of a lithium compound and dissolve it in pure water to obtain an aqueous solution of the lithium compound;

[0019] Step S4: Weigh the primary sintered product according to a certain molar ratio of lithium element to element X and add it to the aqueous solution of the lithium compound, grind it to an appropriate particle size, and simultaneously perform ion exchange to obtain primary flaky particles;

[0020] Step S5: Wash and filter the primary flaky particles in sequence to remove reaction by-products, add deionized water to the obtained filter cake, and prepare a slurry with a certain solid content;

[0021] Step S6: Perform spray granulation and drying on the slurry to obtain a spherical dried product;

[0022] Step S7: Subject the spherical dried product to secondary calcination to obtain the spherical lithium cobalt oxide cathode material with an O2 phase structure.

[0023] Preferably, in step S1, the molar ratio of Co element in the cobalt precursor to element X satisfies: n(X) / n(Co) > 0.5, preferably n(X) / n(Co) ≥ 0.6; wherein, element X is selected from at least one of Na and K;

[0024] The molar ratio of Co element in the cobalt precursor to element M satisfies: n(M) / n(Co) = 0 - 0.1; wherein, element M is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F, or Ti; the element M is derived from the compound containing element M and / or the cobalt precursor.

[0025] Preferably, the cobalt precursor includes one or more of cobalt oxide, cobalt hydroxide, cobalt carbonate, cobalt sulfate, cobalt chloride, cobalt oxalate, and cobalt oxyhydroxide; the cobalt precursor is formed by agglomeration and accumulation of primary particles of a Co-containing compound, wherein the particle size of the primary particles of the Co-containing compound is between 100 nm and 500 nm.

[0026] Preferably, in step S2, the temperature of the high-temperature calcination is 700 °C to 1000 °C, preferably 750 °C to 950 °C; the time of the high-temperature calcination is 6 hours to 15 hours, preferably 8 hours to 12 hours;

[0027] The high-temperature calcination is carried out in an oxygen atmosphere, and the oxygen concentration ≥ 90%;

[0028] The primary particles of the primary sintered product are flaky, and the thickness of the primary particles ≤ 2 μm.

[0029] Preferably, in step S3, the concentration of the lithium compound in the aqueous solution of the lithium compound ≥ 1 mol / L, preferably ≥ 2 mol / L; the lithium compound includes one or more of lithium nitrate, lithium hydroxide, lithium carbonate, lithium chloride, lithium iodide, lithium fluoride, lithium bromide, and lithium phosphate.

[0030] Preferably, in step S4, the molar ratio of lithium element to X element is n(Li) / n(X) ≥ 2.5, preferably n(Li) / n(X) ≥ 5; the appropriate particle size D50 ≤ 800 nm; the time of ion exchange ≥ 5 hours;

[0031] In step S5, the solid content of the slurry is 10 wt% to 50 wt%;

[0032] In step S6, the median particle size D50 of the spherical dried product is 5 μm to 15 μm;

[0033] In step S7, the temperature of the secondary calcination is 200 °C to 300 °C, preferably 220 °C to 280 °C; the time of the secondary calcination is 2 hours to 8 hours, preferably 3 hours to 7 hours; the secondary calcination is carried out in an oxygen atmosphere or an air atmosphere.

[0034] In a third aspect, an embodiment of the present invention provides a lithium battery or a battery cell or a battery pack, which includes the spherical lithium cobaltate cathode material with an O2 phase structure described in the first aspect above, or the spherical lithium cobaltate cathode material with an O2 phase structure prepared by the preparation method described in the third aspect above.

[0035] An embodiment of the present invention provides a spherical lithium cobaltate cathode material with an O2 phase structure, its preparation method and application, having the following technical effects:

[0036] (1) A preparation method of a spherical lithium cobaltate cathode material with an O2-phase structure provided by an embodiment of the present invention. By weighing cobalt precursors, compounds containing element X, and / or compounds containing doping element M according to a specific molar ratio, mixing them, and then performing high-temperature calcination treatment, the obtained primary sintered product is added to an aqueous solution of a lithium compound, ground to an appropriate particle size, and ion exchange is carried out simultaneously to obtain primary flaky particles. After washing and filtering, it is formulated into a slurry, and then spray granulation and drying are carried out, and finally secondary calcination is carried out to finally obtain a spherical lithium cobaltate cathode material with an O2-phase structure. This preparation method is simple to operate and applicable to batch production.

[0037] (2) The spherical lithium cobaltate cathode material with an O2-phase structure provided by an embodiment of the present invention has XRD diffraction characteristic peaks simultaneously at positions where 2θ A1 = 18.3° - 18.9°, 2θ A2 = 37.9° - 38.4°, and 2θ A3 = 46.7° - 47.3°. This indicates that the spherical lithium cobaltate cathode material with an O2-phase structure is a lithium cobaltate material with a P63mc structure. In addition, the FWHM value k of the (002) characteristic peak of this spherical lithium cobaltate cathode material satisfies 0.355 ≤ k ≤ 0.495, indicating that the spherical lithium cobaltate cathode material of the present invention has a pure O2-phase structure and does not contain miscellaneous phases such as P2 phase. This spherical lithium cobaltate cathode material with an O2-phase structure exhibits better electrochemical performance.

[0038] Compared with the traditional lithium cobaltate material with an O3-phase structure, the oxygen atoms in the spherical lithium cobaltate cathode material with an O2-phase structure of the present invention adopt a distorted cubic close-packed mode. This distorted packing mode enables the cobalt layer and the lithium layer to be alternately distributed on both sides of the oxygen layer and occupy the octahedral voids. The layered CoO2 framework structure provides a two-dimensional tunnel for the migration of lithium ions, and this structural feature is more favorable for the insertion and extraction of lithium ions during the charge and discharge process of the battery. This structure makes the movement of lithium ions between the layers have a certain directionality and regularity, which helps to improve the characteristics of the material in terms of specific capacity, cycle stability, rate performance, energy density, and thermal stability at high voltages (≥4.6V).

[0039] (3) The spherical lithium cobalt oxide cathode material with an O2-phase structure provided by the embodiments of the present invention can be used as a cathode active material to prepare a cathode electrode sheet, and the cathode electrode sheet can be applied to an energy storage device, which includes a lithium battery, or a battery cell or battery pack composed of lithium batteries; the lithium-ion button half-cell prepared by using the spherical lithium cobalt oxide cathode material with an O2-phase structure provided by the embodiments of the present invention has an initial discharge specific capacity of greater than or equal to 228.0 mAh / g at 0.1C, a discharge specific capacity of greater than or equal to 218 mAh / g at 0.33C, and a capacity of greater than or equal to 208 mAh / g at 1.0C; the capacity retention rate after 100 cycles at 0.5C is greater than or equal to 73%; the spherical lithium cobalt oxide cathode material with an O2-phase structure provided by the embodiments of the present invention has a capacity about 20 mAh / g higher than that of traditional lithium cobalt oxide, and the cycle retention rate is increased by about 10% - 30%, indicating that the spherical lithium cobalt oxide cathode material with an O2-phase structure provided by the embodiments of the present invention can improve the specific capacity and cycle stability of lithium-ion batteries, thereby improving the safety performance of the batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flowchart of the preparation method of the spherical lithium cobalt oxide cathode material with an O2-phase structure provided by the embodiments of the present invention.

[0041] Figure 2 It is a scanning electron microscope (SEM) image of the cobalt precursor Co3O4 used in Example 1 of the present invention.

[0042] Figure 3 It is an SEM image of the spherical lithium cobalt oxide cathode material with an O2-phase structure prepared in Example 1 of the present invention.

[0043] Figure 4 It is an X-ray diffraction (XRD) pattern of the spherical lithium cobalt oxide cathode material with an O2-phase structure in Example 1 of the present invention and the traditional lithium cobalt oxide material in Comparative Example 1.

[0044] Figure 5 It is the initial charge-discharge curve of the button batteries assembled in Example 1 and Comparative Example 1 at 0.1C.

[0045] Figure 6 It is the charge-discharge curve of the button batteries assembled in Example 1 and Comparative Example 1 in the second week at 0.1C.

[0046] Figure 7 It is the capacity of the button batteries assembled in Example 1 and Comparative Example 1 during 100 cycles at 0.5C.

[0047] Figure 8 It is the capacity retention rate of the button batteries assembled in Example 1 and Comparative Example 1 during 100 cycles at 0.5C.

[0048] Figure 9Rate performance graph of the coin cells assembled in Example 1 and Comparative Example 1. Detailed Description of the Invention

[0049] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0050] For those experimental steps or conditions not specified in the examples, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments not specified by the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0051] For a better understanding of the present invention, some technical terms will be described below first.

[0052] The technical term "primary particle" refers to an individual flaky particle that is directly crystallized and not agglomerated.

[0053] The technical term "secondary spherical particle" refers to a spherical agglomerated particle formed by the agglomeration of primary flaky particles.

[0054] The technical term "median particle size D50" refers to the particle size corresponding to a cumulative volume distribution value of 50% in a sample of secondary particles.

[0055] The technical terms "initial charge specific capacity" and "initial discharge specific capacity" respectively refer to the charge specific capacity and discharge specific capacity of the first cycle.

[0056] The technical term "activation" refers to cycling once at 0.1C for the first time.

[0057] The technical term "initial discharge specific capacity" refers to the next discharge specific capacity after "activation", that is, the discharge specific capacity in the second week at 0.1C.

[0058] Based on the understanding of the above technical terms, the technical solutions of the present invention will be further described in detail below through the accompanying drawings and examples.

[0059] The inventors of the present invention found that by improving the process, lithium cobaltate with a spherical O2 phase structure can be obtained, which helps to obtain a lithium cobaltate cathode material with excellent cycle stability, safety and high energy density. Therefore, it is of great significance to continue to deeply study the crystal structure of lithium cobaltate materials for further improving the electrochemical performance of lithium-ion batteries, solving safety problems and promoting the development of the new energy industry.

[0060] An embodiment of the present invention provides a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the spherical lithium cobalt oxide cathode material is: Li a X b M p Al q Co (1-p-q) O2, where 0.5 < a ≤ 1, 0 ≤ b < 0.2, 0 ≤ p ≤ 0.5, 0 ≤ q ≤ 0.5. The X element is selected from at least one of Na and K, and the M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F, or Ti.

[0061] Among them, the spherical lithium cobalt oxide cathode material has XRD diffraction characteristic peaks at 2θ A1 = 18.3° - 18.9°, 2θ A2 = 37.9° - 38.4°, and 2θ A3 = 46.7° - 47.3° simultaneously.

[0062] The full width at half maximum (FWHM) k of the (002) characteristic peak of the spherical lithium cobalt oxide cathode material satisfies 0.355 ≤ k ≤ 0.495. When the FWHM value is within this range, the lithium cobalt oxide cathode material has a purer O2 phase structure and better electrochemical performance, such as higher capacity performance.

[0063] The space group of the lithium cobalt oxide cathode material provided by the embodiment of the present invention is P63mc. The oxygen atoms in the spherical lithium cobalt oxide cathode material adopt a distorted cubic close-packed manner. This distorted packing method enables the cobalt layer and the lithium layer to be alternately distributed on both sides of the oxygen layer and occupy the octahedral voids. The spherical lithium cobalt oxide cathode material with a P63mc structure has a special spatial structure distribution, that is, half of the tetrahedral sites in the crystal structure do not have a coplanar CoO6 layer. This feature reduces the repulsion suffered by lithium ions during migration and accelerates diffusion. Furthermore, it can effectively improve the charge transport path and ion diffusion performance in the lithium cobalt oxide cathode material and has better electrochemical performance than traditional lithium cobalt oxide materials.

[0064] The spherical lithium cobalt oxide cathode material with an O2-phase structure provided by the embodiments of the present invention is composed of secondary spherical particles formed by clusters of primary flaky particles, and the secondary spherical particles do not agglomerate, that is, they are distributed dispersedly among the secondary particles. The spherical lithium cobalt oxide cathode material with this structure has better fluidity and dispersibility, and exhibits better processing performance. The thickness of the primary flaky particles is measured by SEM. Among them, the range of the thickness j of the primary flaky particles is 0 < j ≤ 800 nm, and it can be any value within the above range, such as 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 800 nm, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0065] The median particle size of the above primary flaky particles is measured by a laser particle size analyzer to be D 50 less than or equal to 1000 nm, and it can be any value within the above range, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 800 nm, 600 nm, 800 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0066] The median particle size D of the secondary spherical particles is tested using a laser particle size analyzer 50 is 3 μm to 15 μm, and it can be any value within the above range, such as 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0067] The spherical lithium cobalt oxide cathode material has at least one of the following characteristics (1) and (2):

[0068] Characteristic (1): The specific surface area of the spherical lithium cobalt oxide cathode material is 0.35 m 2 / g to 0.55 m 2 / g; it can be any value within the above range, such as 0.35 m 2 / g, 0.4 m 2 / g, 0.45 m 2 / g, 0.5 m 2 / g, 0.55 m 2 / g, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. Among them, the specific surface area is obtained by testing with a specific surface area analyzer;

[0069] Feature (2): The tap density of the lithium cobalt oxide cathode material is 3.6 g / cm 3 ~4.2 g / cm 3 , which can be any value within the above range, such as 3.6 g / cm 3 , 3.7 g / cm 3 , 3.8 g / cm 3 , 3.9 g / cm 3 , 4.0 g / cm 3 , 4.1 g / cm 3 , 4.2 g / cm 3 etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0070] The spherical lithium cobalt oxide cathode material with an O2 phase structure prepared by the present invention may have a small amount of residual Li and residual element X; among them, the content (mass percentage) of residual free Li in the spherical lithium cobalt oxide cathode material is 0.5% - 5%, which can be any value within the above range, such as 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; the content of residual free element X is 0.5% - 3.5%, which can be any value within the above range, such as 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.5%, 1.6%, 1.8%, 2.0%, 2.5%, 3.0%, 3.5%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0071] The embodiment of the present invention provides a preparation method of the above-mentioned spherical lithium cobalt oxide cathode material with an O2 phase structure, as Figure 1 shown, including the following steps:

[0072] Step S1, uniformly mix the cobalt precursor, the compound containing element X, and / or the compound containing element M in proportion to obtain a mixed material;

[0073] Among them, the molar ratio of Co element to X element in the cobalt precursor satisfies: n(X) / n(Co) > 0.5, which can be any value within the above range, such as 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The molar ratio of Co element to X element in the cobalt precursor is preferably n(X) / n(Co) ≥ 0.6; Limiting the molar ratio of n(X) / n(Co) can ensure that the crystal structure of the lithium cobaltate cathode material is the P2 phase structure;

[0074] The molar ratio of Co element to M element in the cobalt precursor satisfies: n(M) / n(Co) = 0 to 0.1, which can be any value within the above range, such as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0075] The X element is selected from at least one of Na and K, and the compounds containing the X element include: at least one of sodium oxide, sodium hydroxide, sodium carbonate, sodium acetate, sodium bicarbonate, sodium oxalate, sodium hydrogen oxalate, sodium sulfate, sodium hydrogen sulfate, potassium oxide, potassium hydroxide, potassium carbonate, potassium acetate, potassium bicarbonate, potassium oxalate, potassium hydrogen oxalate, potassium sulfate, potassium hydrogen sulfate;

[0076] The M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F or Ti; The M element can be derived from a compound containing the M element or from the cobalt precursor;

[0077] The cobalt precursor includes: one or more of cobalt oxide, cobalt hydroxide, cobalt carbonate, cobalt sulfate, cobalt chloride, cobalt oxalate, cobalt oxyhydroxide; The cobalt precursor is formed by the agglomeration and accumulation of primary particles of Co-containing compounds, and the particle size of the primary particles of Co-containing compounds is between 100 nm and 500 nm;

[0078] Since the cobalt precursor used in the present invention is formed by the agglomeration of primary particles of Co-containing compounds, it has the advantages of fewer grain boundaries, higher capacity, and better dispersibility compared to directly using primary particles of Co-containing compounds (single crystal compounds).

[0079] Step S2, subject the mixture to high-temperature calcination treatment to obtain a primary sintered product;

[0080] Among them, the temperature of the high-temperature calcination is 700 °C to 1000 °C, preferably 750 °C to 950 °C; The time of the high-temperature calcination is 6 hours to 15 hours, preferably 8 hours to 12 hours;

[0081] The high-temperature calcination is carried out in an oxygen atmosphere with an oxygen concentration ≥ 90%;

[0082] The primary particles of the primary sintered product are flaky, and the thickness of the primary particles ≤ 2 μm;

[0083] The primary sintered product obtained by calcination in this step S2 is a P2-phase lithium cobaltate precursor. Subsequently, the P2-phase lithium cobaltate precursor can undergo ion exchange with lithium ions to obtain flaky lithium cobaltate.

[0084] Step S3: Weigh a certain amount of lithium compound and dissolve it in pure water to obtain an aqueous solution of lithium compound;

[0085] Among them, the concentration of the lithium compound in the aqueous solution of lithium compound ≥ 1 mol / L, which can be any value within the above range, such as 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable; the concentration of the lithium compound in the aqueous solution of lithium compound is preferably ≥ 2 mol / L; the concentration of the aqueous solution of lithium compound directly affects the rate and process of subsequent ion exchange. The concentration of the aqueous solution of lithium compound is positively correlated with the rate and process of ion exchange. If the concentration is too small, it is not conducive to the subsequent ion exchange of the aqueous solution of lithium compound. If the concentration is too large, an aqueous solution of lithium compound cannot be formed;

[0086] The lithium compound specifically includes one or more of lithium nitrate, lithium hydroxide, lithium carbonate, lithium chloride, lithium iodide, lithium fluoride, lithium bromide, and lithium phosphate.

[0087] Step S4: Weigh the primary sintered product according to a certain molar ratio of lithium element to X element and add it to the aqueous solution of lithium compound, grind it to an appropriate particle size, and simultaneously carry out ion exchange to obtain primary flaky particles;

[0088] Among them, the molar ratio of lithium element to X element is n(Li) / n(X) ≥ 2.5, which can be any value within the above range, such as 2.5, 3.0, 3.5, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, etc. The molar ratio of lithium element to X element is preferably n(Li) / n(X) ≥ 5; by limiting n(Li) / n(X) within the above range, it can ensure sufficient ion exchange, and the X atoms in the P2-phase sodium cobaltate precursor are replaced by lithium atoms, thereby obtaining lithium cobaltate with O2-phase primary flaky particles;

[0089] The appropriate particle size D ground in this step 50≤800 nm; the ion exchange time ≥ 5 hours.

[0090] Step S5: The primary flaky particles are successively washed and filtered to remove reaction by-products. Deionized water is added to the obtained filter cake to prepare a slurry with a certain solid content.

[0091] Among them, both washing and filtering are conventional methods. Washing is carried out with deionized water, and the number of washing times is at least 5 times; the solid content of the slurry is 10 wt% - 50 wt%.

[0092] Step S6: The slurry is spray granulated and dried to obtain a spherical dried product.

[0093] Among them, both spray granulation and drying are conventional methods; spray granulation adopts spray drying method. The inlet air temperature of the spray dryer used in the spray drying method is 120°C - 250°C, the outlet air temperature is 90°C - 110°C, and the steam pressure is 0.4 Mpa - 0.8 Mpa; drying can be carried out in a vacuum drying oven, the drying temperature is 80°C - 120°C, and the drying time is 1 hour - 24 hours.

[0094] The median particle size D of the spherical dried product 50 is 5 μm - 15 μm.

[0095] Step S7: The spherical dried product is calcined twice to obtain a spherical lithium cobalt oxide cathode material with an O2-phase structure.

[0096] Among them, the temperature of the second calcination is between 200°C and 300°C, and can be any value within the above range, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable. The temperature of the second calcination is preferably 220°C - 280°C; the time of the second calcination is 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable. The time of the second calcination is preferably 3 hours - 7 hours; the second calcination is carried out in an oxygen atmosphere or an air atmosphere; after the ion exchange, spray drying, and second calcination in the above grinding process, the lithium cobalt oxide cathode material with a P2-phase crystal structure is transformed into a spherical lithium cobalt oxide cathode material with an O2-phase structure.

[0097] The prepared spherical lithium cobalt oxide cathode material with an O2-phase structure has a chemical general formula of: Li a X b M p Al q Co (1-p-q)O2, where 0.5 < a ≤ 1, 0 ≤ b < 0.2, 0 ≤ p ≤ 0.5, 0 ≤ q ≤ 0.5, the X element is selected from at least one of Na, and the M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F or Ti; the spherical lithium cobaltate cathode material at 2θ A1 = 18.3° to 18.9°, 2θ A2 = 37.9° to 38.4°, 2θ A3 = 46.7° to 47.3° simultaneously have XRD diffraction characteristic peaks; the full width at half maximum (FWHM) k of the characteristic peak at the (002) position of the spherical lithium cobaltate cathode material satisfies 0.355 ≤ k ≤ 0.495. The FWHM value of the characteristic peak of the spherical lithium cobaltate cathode material at the (002) position is related to the calcination temperature. The temperature of the first calcination is in the range of 700 °C to 1000 °C. The higher the temperature, the lower the FWHM value, and it is between 0.355 and 0.495. Within this range of FWHM values, the crystal structure of the spherical lithium cobaltate cathode material has a pure O2 phase structure, and the unit cell size of the lithium cobaltate cathode material can be controlled, thereby improving the capacity.

[0098] The spherical lithium cobaltate cathode material with an O2 phase structure prepared by the above preparation method can be used as the positive electrode active material in an energy storage device to prepare a positive electrode plate, where the energy storage device includes a lithium battery, or a battery cell or battery pack composed of lithium batteries.

[0099] The lithium ion coin-type half cell assembled with the positive electrode plate prepared from the spherical lithium cobaltate cathode material with an O2 phase structure provided in the embodiment of the present invention has a first-week discharge specific capacity of greater than or equal to 228.0 mAh / g at 0.1C, a discharge specific capacity of greater than or equal to 218 mAh / g at 0.33C, and a capacity of greater than or equal to 208 mAh / g at 1.0C; the capacity retention rate after 100 cycles at 0.5C is greater than or equal to 73%; the spherical lithium cobaltate cathode material with an O2 phase structure provided in the embodiment of the present invention has a capacity approximately 20 mAh / g higher than that of traditional lithium cobaltate, and the cycle retention rate is increased by approximately 10% to 30%.

[0100] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the preparation process and characteristics of the spherical lithium cobaltate cathode material with an O2 phase structure of the present invention.

[0101] Example 1

[0102] This example provides a preparation process of a spherical lithium cobaltate cathode material with an O2 phase structure. The chemical formula of the spherical lithium cobaltate cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971O2 (abbreviation: SS-1), the preparation process is as follows:

[0103] (1) Take a total of 500 g of Co3O4, Na2CO3, and Al2O3 according to the molar ratio n(Co):n(Na):n(Al) = 0.971:0.8:0.029 and mix them evenly to obtain a mixed material.

[0104] (2) Subject the mixed material to high-temperature calcination treatment, control the heating rate at 5 °C / min, and under an oxygen atmosphere, heat it to 780 °C and calcine for 10 hours to obtain a primary sintered product.

[0105] (3) Weigh a certain amount of lithium nitrate and dissolve it in pure water to prepare an aqueous solution of lithium compound with a concentration of 2.5 mol / L.

[0106] (4) Weigh the primary sintered product according to the molar ratio of n(Li) / n(Na) = 5 and add it to the aqueous solution of lithium compound and grind it. Control the median particle size D 50 to be 450 nm, and at the same time control the grinding time to be 5 hours. Ion exchange is carried out during grinding to obtain primary flaky particles with a median particle size D 50 of 450 nm.

[0107] (5) After the ion exchange is completed, wash and filter 4 times to remove reaction by-products. Add deionized water to the obtained filter cake to prepare a uniform slurry with a solid content of 30 wt%.

[0108] (6) Spray granulate and dry the slurry. Control the median particle size D50 of the spherical dried product to be 10 μm and the moisture content ≤ 10% to obtain a spherical dried product; among them, the inlet air temperature of the spray dryer for spray granulation is 160 °C, the outlet air temperature is 90 °C, and the steam pressure is 0.5 Mpa; drying can be carried out in a vacuum drying oven, the drying temperature is 10 °C, and the drying time is 3 hours.

[0109] (7) The spherical dried product is subjected to secondary calcination in an air atmosphere. Control the temperature at 250 °C and the secondary calcination time at 3 hours. After secondary calcination, a spherical lithium cobalt oxide cathode material with an O2 phase structure is obtained, and the chemical formula is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2.

[0110] The SEM image of the cobalt precursor Co3O4 used in this example is as shown in Figure 2 It can be seen that the cobalt precursor Co3O4 is composed of primary flaky Co3O4 particles stacked together.

[0111] The scanning electron microscope (SEM) image of the spherical lithium cobalt oxide cathode material prepared in this example is as shown inFigure 3 As shown, it can be seen that the spherical lithium cobalt oxide cathode material is spherical particles formed by the agglomeration of primary flaky particles.

[0112] The thickness of the primary flaky particles was measured to be 708 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material in this example was measured using a laser particle size analyzer 50 to be 6.2 μm.

[0113] The XRD pattern of the spherical lithium cobalt oxide cathode material prepared in this example is as Figure 4 shown. The abscissa is 2θ (unit: °), and the ordinate is the diffraction peak intensity (unit: a.u.). The XRD test pattern shows that the spherical lithium cobalt oxide cathode material SS-1 has XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.370.

[0114] Example 2

[0115] This example provides a preparation process of a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the spherical lithium cobalt oxide cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as SS-2), and the preparation method is as follows:

[0116] Step (1): The cobalt precursor is Al-doped Co3O4, and the molar ratio of Al to Co is n(Al) / n(Co) = 0.0299. Na2CO3 is weighed according to the molar ratio of n(Co):n(Na) = 0.971:0.8, and a total of 500 g is uniformly mixed to obtain a mixture.

[0117] The preparation processes of steps (2) to (7) are the same as those in Example 1.

[0118] The thickness of the primary flaky particles was measured to be 687 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material in this example was measured using a laser particle size analyzer 50 to be 5.96 μm.

[0119] For the spherical lithium cobalt oxide cathode material with an O2 phase structure prepared in this example, XRD testing shows that the spherical lithium cobalt oxide cathode material SS-2 has XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3There is an XRD diffraction characteristic peak at 2θ = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.377.

[0120] Example 3

[0121] This example provides a preparation process of a spherical lithium cobaltate cathode material with an O2 phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.79 Na 0.01 Al 0.014 Co 0.986 O2 (abbreviation: SS-3), and the preparation method is as follows:

[0122] Step (1): Uniformly mix Co3O4, Na2CO3, and Al2O3 according to the molar ratio n(Co):n(Na):n(Al) = 0.986:0.8:0.014 to obtain 500 g of a mixed material.

[0123] Steps (2) to (7) are the same as those in Example 1.

[0124] Using a scanning electron microscope to test, the thickness of the primary flaky particles is 787 nm. Using a laser particle size analyzer to test the particle size D of the spherical lithium cobaltate cathode material in this example 50 is 6.36 μm.

[0125] For the spherical lithium cobaltate cathode material with an O2 phase structure prepared in this example, XRD testing shows that the spherical lithium cobaltate cathode material SS-3 has XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.366.

[0126] Example 4

[0127] This example provides a preparation process of a spherical lithium cobaltate cathode material with an O2 phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.79 Na 0.01 Al 0.022 Co 0.978 O2 (abbreviation: SS-4), and the preparation method is as follows:

[0128] Step (1): Uniformly mix Co3O4, Na2CO3, and Al2O3 according to the molar ratio n(Co):n(Na):n(Al) = 0.978:0.8:0.022 to obtain 500 g of a mixed material.

[0129] Steps (2) to (7) are the same as those in Example 1.

[0130] The thickness of the primary flaky particles was measured to be 750 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material of this example was measured using a laser particle size analyzer 50 to be 6.22 μm.

[0131] For the spherical lithium cobalt oxide cathode material with an O2 phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-4 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.368.

[0132] Example 5

[0133] This example provides a preparation process for a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.79 Na 0.01 Al 0.036 Co 0.964 O2 (abbreviated as SS-5), and the preparation method is as follows:

[0134] Step (1): Uniformly mix Co3O4, Na2CO3, and Al2O3 in a molar ratio of n(Co):n(Na):n(Al) = 0.964:0.8:0.036 to obtain 500 g of a mixed material.

[0135] Steps (2) to (7) are the same as in Example 1.

[0136] The thickness of the primary flaky particles was measured to be 631 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material of this example was measured using a laser particle size analyzer 50 to be 5.33 μm.

[0137] For the spherical lithium cobalt oxide cathode material with an O2 phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-5 had XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.372.

[0138] Example 6

[0139] This example provides a preparation process for a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.79 Na 0.01 Mg0.029 Co 0.971 O2 (abbreviated as SS-6), the preparation method is as follows:

[0140] Step (1): Co3O4, Na2CO3, and MgO are uniformly mixed according to the molar ratio of n(Co):n(Na):n(Mg) = 0.971:0.8:0.029 to obtain 500 g of a mixed material.

[0141] Steps (2) to (7) are the same as those in Example 1.

[0142] Using a scanning electron microscope, the thickness of the primary flaky particles is measured to be 690 nm, and using a laser particle size analyzer, the particle size D of the spherical lithium cobalt oxide cathode material in this example 50 is 6.03 μm.

[0143] For the spherical lithium cobalt oxide cathode material with an O2 phase structure prepared in this example, XRD testing shows that the spherical lithium cobalt oxide cathode material SS-6 has XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.380.

[0144] Example 7

[0145] This example provides a preparation process for a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.79 Na 0.01 Ti 0.029 Co 0.971 O2 (abbreviated as SS-7), the preparation method is as follows:

[0146] Step (1): Co3O4, Na2CO3, and TiO2 are uniformly mixed according to the molar ratio of n(Co):n(Na):n(Ti) = 0.971:0.8:0.029 to obtain 500 g of a mixed material.

[0147] Steps (2) to (7) are the same as those in Example 1.

[0148] Using a scanning electron microscope, the thickness of the primary flaky particles is measured to be 710 nm, and using a laser particle size analyzer, the particle size D of the spherical lithium cobalt oxide cathode material in this example 50 is 6.18 μm.

[0149] The spherical lithium cobaltate cathode material with O2-phase structure prepared in this example. XRD test shows that the spherical lithium cobaltate cathode material SS-7 has XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.383.

[0150] Example 8

[0151] This example provides a preparation process of a spherical lithium cobaltate cathode material with O2-phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.69 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as SS-8), and the preparation method is as follows:

[0152] Step (1): Uniformly mix Co3O4, Na2CO3, and Al2O3 according to the molar ratio n(Co):n(Na):n(Al) = 0.971:0.7:0.029 to obtain 500 g of a mixed material.

[0153] Steps (2) to (7) are the same as those in Example 1.

[0154] The thickness of the primary flaky particles is measured to be 695 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobaltate cathode material in this example is measured using a laser particle size analyzer 50 is 6.02 μm.

[0155] The spherical lithium cobaltate cathode material with O2-phase structure prepared in this example. XRD test shows that the spherical lithium cobaltate cathode material SS-8 has XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.365.

[0156] Example 9

[0157] This example provides a preparation process of a spherical lithium cobaltate cathode material with O2-phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.89 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as SS-9), and the preparation method is as follows:

[0158] Step (1): Uniformly mix Co3O4, Na2CO3, and Al2O3 according to the molar ratio n(Co):n(Na):n(Al) = 0.971:0.9:0.029 to obtain 500 g of a mixed material.

[0159] Steps (2) to (7) are the same as those in Example 1.

[0160] The thickness of the primary flaky particles was tested to be 703 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material in this example was tested using a laser particle size analyzer 50 to be 6.15 μm.

[0161] For the spherical lithium cobalt oxide cathode material with an O2 phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-9 had XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.375.

[0162] Example 10

[0163] This example provides a preparation process for a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as SS-10), and the preparation method is as follows:

[0164] Step (1) is the same as that in Example 1.

[0165] Step (2): Sinter the mixture, control the heating rate at 5 °C / min, and calcine at 720 °C for 10 h in an oxygen atmosphere to obtain a primary sintered product.

[0166] Steps (3) to (7) are the same as those in Example 1.

[0167] The thickness of the primary flaky particles was tested to be 453 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material in this example was tested using a laser particle size analyzer 50 to be 3.30 μm.

[0168] For the spherical lithium cobalt oxide cathode material with an O2 phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-10 had XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.455.

[0169] Example 11

[0170] This example provides a preparation process for a spherical lithium cobalt oxide cathode material with an O2 phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li0.79 Na 0.01 Al 0.029 Co 0.971 O₂ (abbreviation: SS-11), the preparation method is as follows.

[0171] Step (1) is the same as that in Example 1.

[0172] Step (2): Sinter the mixture, control the heating rate at 5 °C / min, and calcine it at 850 °C for 10 h in an oxygen atmosphere to obtain a primary sintered product.

[0173] Steps (3) to (7) are the same as those in Example 1.

[0174] Using a scanning electron microscope to test the thickness of the primary flaky particles is 790 nm, and using a laser particle size analyzer to test the particle size D of the spherical lithium cobalt oxide cathode material in this example 50 is 6.88 μm.

[0175] For the spherical lithium cobalt oxide cathode material with O₂ phase structure prepared in this example, XRD test shows that the spherical lithium cobalt oxide cathode material SS-11 has XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.355.

[0176] Example 12

[0177] This example provides a preparation process of a spherical lithium cobalt oxide cathode material with O₂ phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.70 Na 0.10 Al 0.029 Co 0.971 O₂ (abbreviation: SS-12), the preparation method is as follows:

[0178] Steps (1) and (2) are the same as those in Example 1.

[0179] Step (3): Weigh a certain amount of lithium nitrate and dissolve it in pure water to prepare an aqueous solution of lithium compound with a concentration of 1.0 mol / L.

[0180] Steps (4) - (7) are the same as those in Example 1.

[0181] Using a scanning electron microscope to test the thickness of the primary flaky particles is 679 nm, and using a laser particle size analyzer to test the particle size D of the spherical lithium cobalt oxide cathode material in this example 50 is 5.83 μm.

[0182] The spherical lithium cobaltate cathode material with O2-phase structure prepared in this example, XRD test shows that the spherical lithium cobaltate cathode material SS-12 has XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.475.

[0183] Example 13

[0184] This example provides a preparation process of a spherical lithium cobaltate cathode material with O2-phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviation: SS-13), and the preparation method is as follows:

[0185] Steps (1) and (2) are the same as those in Example 1.

[0186] Step (3): Weigh a certain amount of lithium nitrate and dissolve it in pure water to prepare a 5.0 mol / L aqueous solution of lithium compound.

[0187] Steps (4) - (7) are the same as those in Example 1.

[0188] Using a scanning electron microscope to test, the thickness of the primary flaky particles is 682 nm. Using a laser particle size analyzer to test, the particle size D of the spherical lithium cobaltate cathode material in this example 50 is 5.93 μm.

[0189] The spherical lithium cobaltate cathode material with O2-phase structure prepared in this example, XRD test shows that the spherical lithium cobaltate cathode material SS-13 has XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.367.

[0190] Example 14

[0191] This example provides a preparation process of a spherical lithium cobaltate cathode material with O2-phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.71 Na 0.09 Al 0.029 Co 0.971 O2 (abbreviation: SS-14), and the preparation method is as follows:

[0192] Steps (1) and (2) are the same as those in Example 1.

[0193] Step (3): Weigh a certain amount of lithium chloride and dissolve it in pure water to prepare an aqueous solution of lithium compound with a concentration of 2.5 mol / L.

[0194] Steps (4) to (7) are the same as those in Example 1.

[0195] The thickness of the primary flaky particles was measured to be 692 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material in this example was measured using a laser particle size analyzer. 50 was 6.05 μm.

[0196] For the spherical lithium cobalt oxide cathode material with an O2-phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-14 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.379.

[0197] Example 15

[0198] This example provides a preparation process of a spherical lithium cobalt oxide cathode material with an O2-phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.65 Na 0.15 Al 0.029 Co 0.971 O2 (abbreviated as SS-15), and the preparation method is as follows:

[0199] Steps (1) to (3) are the same as those in Example 1.

[0200] Step (4): Weigh the primary sintered product according to n(Li) / n(Na) = 2.5 and add it to the aqueous solution of lithium compound for grinding. Control the D50 of the grinding end point to be 450 nm, and at the same time control the grinding time to be 5 h. Ion exchange is carried out during grinding.

[0201] Steps (5) to (7) are the same as those in Example 1.

[0202] The thickness of the primary flaky particles was measured to be 695 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material in this example was measured using a laser particle size analyzer. 50 was 5.98 μm.

[0203] For the spherical lithium cobalt oxide cathode material with an O2-phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-15 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3There is an XRD diffraction characteristic peak at 2θ = 46.7~47.3°, and the FWHM value k of the (002) characteristic peak is 0.488.

[0204] Example 16

[0205] This example provides a preparation process of a spherical lithium cobaltate cathode material with an O2 phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as SS-16), and the preparation method is as follows:

[0206] Steps (1)-(3) are the same as those in Example 1.

[0207] Step (4): Weigh the primary sintered product according to n(Li) / n(Na) = 10 and add it to the aqueous solution of lithium compound for grinding. Control the final grinding particle size D50 to be 450 nm, and at the same time control the grinding time to be 5 h. Ion exchange is carried out during grinding;

[0208] Steps (5)-(7) are the same as those in Example 1.

[0209] Using a scanning electron microscope to test the thickness of the primary flaky particles is 688 nm, and using a laser particle size analyzer to test the particle size D of the spherical lithium cobaltate cathode material of this example 50 is 5.97 μm.

[0210] For the spherical lithium cobaltate cathode material with an O2 phase structure prepared in this example, XRD test shows that the spherical lithium cobaltate cathode material SS-16 has XRD diffraction characteristic peaks at 2θA1 = 18.3~18.9°, 2θA2 = 37.9~38.4°, 2θA3 = 46.7~47.3°, and the FWHM value k of the (002) characteristic peak is 0.368.

[0211] Example 17

[0212] This example provides a preparation process of a spherical lithium cobaltate cathode material with an O2 phase structure. The chemical formula of the lithium cobaltate cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as SS-17), and the preparation method is as follows:

[0213] Steps (1)-(6) are the same as those in Example 1.

[0214] Step (7): The spherical dried product is subjected to secondary calcination in an air atmosphere, control the temperature to be 220 °C, and the calcination time to be 3 hours. After secondary calcination, a new type of spherical lithium cobaltate cathode material is obtained.

[0215] The thickness of the primary flaky particles was tested to be 672 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material of this example was tested using a laser particle size analyzer 50 was 5.88 μm.

[0216] For the spherical lithium cobalt oxide cathode material with an O2-phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-17 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.494.

[0217] Example 18

[0218] This example provides a preparation process for a spherical lithium cobalt oxide cathode material with an O2-phase structure. The chemical formula of the lithium cobalt oxide cathode material is: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviation: SS-18), and the preparation method is as follows:

[0219] Steps (1) to (6) are the same as those in Example 1.

[0220] Step (7): The spherical dried product is subjected to secondary calcination in an air atmosphere, controlling the temperature at 280 °C and the calcination time at 3 hours to obtain a novel spherical lithium cobalt oxide cathode material.

[0221] The thickness of the primary flaky particles was tested to be 690 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material of this example was tested using a laser particle size analyzer 50 was 5.96 μm.

[0222] For the spherical lithium cobalt oxide cathode material with an O2-phase structure prepared in this example, XRD testing showed that the spherical lithium cobalt oxide cathode material SS-17 had XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.366.

[0223] Comparative Example 1

[0224] This comparative example uses traditional O3-type spherical lithium cobalt oxide with the chemical formula: LiCoO2 (abbreviation: DB-1);

[0225] The XRD pattern of the traditional O3-type spherical lithium cobalt oxide in this comparative example is as Figure 2As shown, XRD tests indicate that the novel spherical lithium cobalt oxide cathode material DB-1 does not have XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°.

[0226] Comparative Example 2

[0227] This comparative example provides a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.39 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as DB-2), and the preparation method is as follows.

[0228] Step (1): Uniformly mix Co3O4, Na2CO3, and Al2O3 in a molar ratio of n(Co):n(Na):n(Al) = 0.971:0.4:0.029 to obtain 500 g of a mixed material;

[0229] Steps (2) - (7) are the same as those in Example 1.

[0230] Using a scanning electron microscope to test, the thickness of the primary flaky particles is 1250 nm. Using a laser particle size analyzer to test, the particle size D of the spherical lithium cobalt oxide cathode material in this comparative example 50 is 10.25 μm.

[0231] XRD tests of a spherical lithium cobalt oxide cathode material prepared in this comparative example indicate that the spherical lithium cobalt oxide cathode material DB-2 does not have XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°.

[0232] Comparative Example 3

[0233] This comparative example provides a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as DB-3), and the preparation method is as follows:

[0234] Step (1) is the same as that in Example 1.

[0235] Step (2): Sinter the mixed material, control the heating rate at 5 °C / min, and calcine it at 650 °C for 10 h in an oxygen atmosphere to obtain a primary sintered product;

[0236] Steps (3) - (7) are the same as those in Example 1.

[0237] The thickness of the primary flaky particles was measured to be 285 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material of this comparative example was measured using a laser particle size analyzer. 50 was 2.26 μm.

[0238] XRD testing of a spherical lithium cobalt oxide cathode material prepared in this comparative example showed that the spherical lithium cobalt oxide cathode material DB-3 had XRD diffraction characteristic peaks at 2θA1 = 18.3 - 18.9°, 2θA2 = 37.9 - 38.4°, and 2θA3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.565. This indicates that due to the too low primary calcination temperature, a pure-phase P2 structure was not formed, resulting in the lithium cobalt oxide cathode material after ion exchange containing a heterophase of the cobalt precursor.

[0239] Comparative Example 4

[0240] This comparative example provides a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as DB-4), and the preparation method is as follows:

[0241] Step (1) is the same as that in Example 1.

[0242] Step (2): Sinter the mixture, control the heating rate at 5 °C / min, and calcine at 1100 °C for 10 h in an oxygen atmosphere to obtain a primary sintered product;

[0243] Steps (3) to (7) are the same as those in Example 1.

[0244] The thickness of the primary flaky particles was measured to be 1007 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material of this comparative example was measured using a laser particle size analyzer. 50 was 9.95 μm.

[0245] XRD testing of a spherical lithium cobalt oxide cathode material prepared in this comparative example showed that the spherical lithium cobalt oxide cathode material DB-4 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.345. This indicates that with the increase of the primary calcination temperature, the crystallinity of the material is further improved, but it leads to an increase in the primary particles of the cathode material, a decrease in the specific surface area, affects the degree of ion exchange, and at the same time increases the diffusion path of lithium ions in the battery, reducing the diffusion rate of lithium ions and the electron transport efficiency.

[0246] Comparative Example 5

[0247] This comparative example provides a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.35 Na 0.45 Al 0.029 Co 0.971 O2 (abbreviated as DB-5), and the preparation method is as follows:

[0248] Steps (1) and (2) are the same as those in Example 1.

[0249] Step (3): Weigh a certain amount of lithium nitrate and dissolve it in pure water to prepare an aqueous solution of lithium compound with a concentration of 0.5 mol / L;

[0250] Steps (4) to (7) are the same as those in Example 1.

[0251] The thickness of the primary flaky particles is measured to be 670 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material is measured using a laser particle size analyzer 50 to be 5.63 μm.

[0252] XRD testing of a spherical lithium cobalt oxide cathode material prepared in this comparative example shows that the spherical lithium cobalt oxide cathode material DB-5 has XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak is 0.575. The K value in Comparative Example 5 is significantly larger, indicating that a pure O2 phase structure cannot be formed in an aqueous solution of lithium compound at a low concentration, and the concentration of the aqueous solution of lithium compound will affect the degree of ion exchange.

[0253] Comparative Example 6

[0254] This comparative example provides a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.45 Na 0.35 Al 0.029 Co 0.971 O2 (abbreviated as DB-6), and the preparation method is as follows:

[0255] Steps (1) - (3) are the same as those in Example 1.

[0256] Step (4): Weigh the primary sintered product according to n(Li) / n(Na) = 1 and add it to the aqueous solution of lithium compound for grinding. Control the D50 of the grinding end point to be 450 nm, and at the same time control the grinding time to be 5 h. Ion exchange is carried out during grinding.

[0257] Steps (5) - (7) are the same as those in Example 1.

[0258] The thickness of the primary flaky particles was tested by a scanning electron microscope to be 682 nm, and the particle size D of the spherical lithium cobalt oxide cathode material was tested by a laser particle size analyzer. 50 was 5.91 μm.

[0259] XRD testing of a spherical lithium cobalt oxide cathode material prepared in this comparative example showed that the spherical lithium cobalt oxide cathode material DB-6 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.598. Due to the too low ratio of n(Li) / n(Na), the concentration difference required for ion exchange could not be provided, resulting in incomplete ion exchange and the failure to form a pure-phase O2 structure.

[0260] Comparative Example 7

[0261] This comparative example provided a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (DB-7), and the preparation method was as follows:

[0262] Steps (1) to (6) were the same as those in Example 1.

[0263] Step (7): The spherical dried product was subjected to secondary calcination in an air atmosphere, controlling the temperature at 180 °C and the calcination time at 3 h. After secondary calcination, a novel spherical lithium cobalt oxide cathode material was obtained.

[0264] The thickness of the primary flaky particles was tested by a scanning electron microscope to be 671 nm, and the particle size D of the spherical lithium cobalt oxide cathode material was tested by a laser particle size analyzer. 50 was 5.73 μm.

[0265] XRD testing of a spherical lithium cobalt oxide cathode material prepared in this comparative example showed that the spherical lithium cobalt oxide cathode material DB-7 had XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9°, 2θ A2 = 37.9 - 38.4°, 2θ A3 = 46.7 - 47.3°, and the FWHM value k of the (002) characteristic peak was 0.624. Due to the too low secondary calcination temperature, it was impossible to completely convert to O2-phase lithium cobalt oxide, and a small amount of P2 phase was mixed in the O2 phase.

[0266] Comparative Example 8

[0267] This comparative example provides a spherical lithium cobalt oxide cathode material with the chemical formula: Li 0.79 Na 0.01 Al 0.029 Co 0.971 O2 (abbreviated as DB-8), and the preparation method is as follows:

[0268] Steps (1) to (6) are the same as those in Example 1.

[0269] Step (7): The spherical dried product is subjected to secondary calcination in an air atmosphere, the temperature is controlled at 320 °C, and the calcination time is 3 h. After secondary calcination, a novel spherical lithium cobalt oxide cathode material is obtained;

[0270] The thickness of the primary flaky particles is measured to be 677 nm using a scanning electron microscope, and the particle size D of the spherical lithium cobalt oxide cathode material is measured using a laser particle size analyzer 50 is 5.95 μm.

[0271] XRD test of a spherical lithium cobalt oxide cathode material prepared in this comparative example shows that the spherical lithium cobalt oxide cathode material DB-8 has no XRD diffraction characteristic peaks at 2θ A1 = 18.3 - 18.9 °, 2θ A2 = 37.9 - 38.4 °, 2θ A3 = 46.7 - 47.3 °. Due to the too high calcination temperature, an O2 and O3 composite structure phase is formed.

[0272] The physical and chemical index analysis tests are carried out on the materials of the above-mentioned examples and comparative examples, and the test items and methods are as follows:

[0273] The materials of Examples 1-18 and Comparative Examples 1-8 are tested for element content, median particle size, specific surface area, tap density, residual alkali, free sodium, and XRD.

[0274] Test of element content: Measured using an Agilent 5800 ICP-OES spectrometer in the United States. The argon partial pressure gauge is controlled at 80 psi - 100 psi, the liquid argon booster valve compresses and controls the pressure above 200 psi, nitrogen is 60 psi - 100 psi, and compressed air is 80 psi - 100 psi; when making a standard curve, three-point calibration needs to be done according to the concentration of the sample, and the coefficient of the standard curve is above 0.9999.

[0275] Test of median particle size: Measured using a Malvern laser particle size analyzer Mastersizer 3000. A certain amount of sodium pyrophosphate dispersant is added, and the sample is added to the range of light obscuration of 10% - 20%. After ultrasonic treatment for 3 min, the test is started, and the average value of three tests is taken as the measured value of the median particle size.

[0276] Tap density test: Tested by the BT-310 tap density meter from Dandong BETTER, vibrating 250 ± 15 times per minute for 12 minutes. Measure the volume of the powder in the measuring cylinder, and the ratio of the powder mass to the volume is the tap density of the powder.

[0277] Specific surface area test: Tested by the Tristar II 3020 specific surface area tester from Micromeritics, USA. Set the degassing temperature: 300 °C, degassing time: 120 min.

[0278] Residual alkali and free sodium test: Determined by potentiometric titration. All reagents used are of analytical reagent grade and primary water conforming to the regulations in GB / T 6682. Stir and mix at 800 r / min for 5 min, and titrate with 0.1 mol / L hydrochloric acid standard titration solution. Before titration, calibrate the pH electrode of the potentiometric titrator, and perform three-point calibration using pH standard buffer solution with the slope in the range of 0.95 - 1.05.

[0279] XRD test: Tested by the XRD-6000 X-ray powder diffractometer from Shimadzu, Japan. Set the voltage at 40 kV, current at 40 mA, step size at 0.005 °, height limit slit at 10 mm, divergence slit at 1 / 2 °, anti-scattering slit at 8 mm, receiving slit open. Set the test scanning 2θ angle from 10 ° to 80 °, continuously scan in 1D mode, and the scanning speed is 1.2 ° / min.

[0280] Table 1 summarizes the test results of the physical and chemical indexes of the materials in Examples 1 - 18 and Comparative Examples 1 - 8.

[0281]

[0282]

[0283] Table 1

[0284] From the test data in Table 1, it can be seen that the FWHM value of the (002) characteristic peak (the characteristic peak at about 2θ = 18.6 °) of the spherical lithium cobalt oxide cathode materials in Examples 1 - 18 of the present invention is in the range of 0.355 - 0.495. The FWHM value of the (002) characteristic peak of the lithium cobalt oxide materials in Comparative Examples 1 - 8 is not in the range of 0.355 - 0.495 or the (002) characteristic peak does not exist. There are significant differences in the median particle size, specific surface area, residual Li, and free sodium content between the traditional O3-type spherical lithium cobalt oxide in Comparative Example 1 and the examples and comparative examples of the present invention, while there are no obvious differences in the median particle size, specific surface area, tap density, residual Li, and free sodium content of the other comparative examples.

[0285] The coin-type half-cells were prepared using the materials of the above-mentioned examples and comparative examples, and the electrochemical performance was tested. The battery assembly and testing procedures are as follows:

[0286] The preparation steps of the coin-type half-cell were as follows: The cathode materials of Examples 1-18 and Comparative Examples 1-8 were respectively mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 98:1:1, and the mixture was added to the solvent N-methylpyrrolidone to form a uniform slurry. Then the slurry was coated on an aluminum foil with a thickness of 10 μm, and the areal loading was 14 mg / cm 2 , and after drying, it was cut into circular cathode plates with a diameter of 12 mm. Using the obtained circular plates as the cathode, lithium metal as the anode, and a PE separator double-sided coated with alumina, an electrolyte of 1 mol / L LiPF6 dissolved in EC:DMC = 1:1 solvent was selected, and a CR2032 coin-type half-cell was assembled with an injection volume of 70 μL.

[0287] The assembled CR2032 coin-type half-cell was tested using a charge-discharge tester. The steps were as follows:

[0288] (1) Capacity test at 30 °C: The coin-type half-cell was placed in a constant-temperature oven at 30 °C. The current density was set to 27.4 mA / g (0.1C), the charge cut-off voltage was 4.6 V (vs Li + / Li), and the discharge cut-off voltage was 3 V (vs Li + / Li), and it was cycled for two weeks.

[0289] (2) Cycle performance test at 30 °C: The coin-type half-cell was placed in a constant-temperature oven at 30 °C. After cycling for two weeks in step (1), the current was reset to 137 mA / g (0.5C), the charge cut-off voltage was 4.6 V (vs Li + / Li), and the discharge cut-off voltage was 3 V (vs Li + / Li), and it was cycled for 100 weeks.

[0290] (3) Rate charge-discharge performance test at 30 °C: The coin-type half-cell was placed in a constant-temperature oven at 30 °C. The charge cut-off voltage was 4.6 V (vs Li + / Li), and the discharge cut-off voltage was 3 V (vs Li + / Li). Constant current charge-discharge was carried out at 27.4 mA / g (0.1C), 137 mA / g (0.5C), and 274 mA / g (1.0C) respectively, and it was cycled for 5 weeks at each current density, and the first-cycle capacity was taken for comparison.

[0291] The initial charge-discharge curves of the coin-type half-cells assembled with Example 1 and Comparative Example 1 at 0.1C are as shown in Figure 5As shown, it can be seen that the discharge specific capacity of the button-type half-cell assembled in Example 1 is significantly higher than that of the cell in Comparative Example 1.

[0292] The charge-discharge curves of the button-type half-cells assembled in Example 1 and Comparative Example 1 at 0.1C in the second week are as Figure 6 shown. It can be seen that the discharge specific capacity of the button-type half-cell assembled in Example 1 in the second week is significantly higher than that of the button-type half-cell in Comparative Example 1.

[0293] The capacity and capacity retention rate of the button-type half-cells assembled in Example 1 and Comparative Example 1 after 100 cycles at 0.5C are respectively as Figure 7 、 Figure 8 shown. It can be seen that the discharge specific capacity and cycle capacity retention rate of the button-type half-cell containing the spherical lithium cobalt oxide cathode material with the O2 phase structure in Example 1 after 100 cycles at 0.5C are much higher than those of the button-type half-cell containing the traditional O3-type spherical lithium cobalt oxide in Comparative Example 1.

[0294] The comparison chart of the rate performance of the button-type half-cells assembled in Example 1 and Comparative Example 1 is as Figure 9 shown. It can be seen that the rate performance of the button-type half-cell in Example 1 is better than that of the button-type half-cell in Comparative Example 1.

[0295] The first-week discharge specific capacity, first-week Coulomb efficiency, initial discharge specific capacity (the discharge specific capacity in the second week), rate performance, the discharge specific capacity and capacity retention rate in the 100th week at 0.5C measured for the cells of Examples 1-18 and Comparative Examples 1-8 are summarized in Table 2.

[0296]

[0297] Table 2

[0298] From the test data in Table 2, it can be seen that in the spherical lithium cobalt oxide cathode materials of Examples 1-5, for every 1 mol of lithium cobalt oxide, the doping amounts of Al are 0.029 mol, 0.029 mol, 0.014 mol, 0.022 mol, and 0.036 mol respectively. The first-week discharge specific capacities of the CR2032 coin-type half-cells prepared therefrom are 232.0 mAh / g, 231.6 mAh / g, 233.2 mAh / g, 232.8 mAh / g, and 230.8 mAh / g respectively at 0.1C. Therefore, the above-mentioned Al-doped lithium cobalt oxide cathode materials all have excellent first-week specific capacities, all higher than 230.0 mAh / g. The first-week Coulombic efficiencies are 122.5%, 120.8%, 121.5%, 122.4%, and 122.4% respectively, and the Coulombic efficiencies of each example exceed 120%; the first-week discharge specific capacities at 0.5C are 222.3 mAh / g, 221.8 mAh / g, 222.6 mAh / g, 222.3 mAh / g, and 221.2 mAh / g respectively, and the first-week discharge specific capacities at 0.5C are all higher than 221 mAh / g. The first-week discharge specific capacities at 1C are 211.7 mAh / g, 212.4 mAh / g, 212.8 mAh / g, 212.2 mAh / g, and 211.2 mAh / g respectively, and the first-week discharge specific capacities at 1C are all higher than 211 mAh / g. The 100-week discharge specific capacities at 0.5C are 178.1 mAh / g, 178.2 mAh / g, 179.2 mAh / g, 179.4 mAh / g, and 176.8 mAh / g respectively, and the discharge specific capacities after 100 cycles at 0.5C are all higher than 176 mAh / g. The retention rates of the 100-week discharge specific capacities at 0.5C are 80.12%, 80.34%, 80.50%, 80.70%, and 79.93% respectively, and each example has good cycle stability. It can be seen that for the spherical lithium cobalt oxide cathode materials with O2-phase structure prepared in Examples 1-5 of the present invention, the percentage of Al doping is within a suitable range, and both the first-week discharge specific capacity and the capacity retention rate after 100 cycles are relatively excellent. Generally speaking, it can be seen that the lithium cobalt oxide cathode materials with O2-phase structure provided in Examples 1-5 of the present invention all have excellent discharge specific capacities and can meet the requirements of the battery for high energy density.

[0299] In Example 6 and Example 7, the doped elements of the spherical lithium cobalt oxide cathode material are Mg and Ti respectively. For every 1 mol of lithium cobalt oxide, the doping amount is 0.029 mol. The discharge specific capacities of the coin-type half-cells assembled in Example 6 and Example 7 at 0.1C are 230.1 mAh / g and 230.3 mAh / g respectively, the first-cycle Coulombic efficiencies are 121.5% and 121.7% respectively, the first-cycle discharge specific capacities at 0.5C are 220.1 mAh / g and 220.6 mAh / g respectively, the 100-cycle discharge specific capacities at 0.5C are 175.6 mAh / g and 176.6 mAh / g respectively, and the capacity retention rates are 79.78% and 80.05% respectively. It can be seen that, compared with Example 1, after the doped element is changed from Al to Mg and Ti, the discharge specific capacity and the 100-cycle capacity retention rate are still relatively high. It can be seen that the spherical lithium cobalt oxide cathode materials prepared in Example 6 and Example 7 of the present invention doped with different elements all exhibit excellent discharge specific capacity and good cycle stability.

[0300] In the raw material ratio of step (1) for preparing the spherical lithium cobalt oxide cathode material in Example 8, n(Na) / n(Co) is about 0.7, in Example 9, n(Na) / n(Co) is about 0.9, and in Example 1, n(Na) / n(Co) is about 0.8. The discharge specific capacities of the coin-type half-cells assembled in Example 8 and Example 9 at 0.1C are 231.1 mAh / g and 232.4 mAh / g respectively, the first-cycle Coulombic efficiencies are 119.8% and 122.4% respectively, the first-cycle discharge specific capacities at 0.5C are 221.5 mAh / g and 222.8 mAh / g respectively, the 100-cycle discharge specific capacities at 0.5C are 175.1 mAh / g and 175.2 mAh / g respectively, and the capacity retention rates are 79.05% and 78.64% respectively. It can be seen that as the ratio of n(Na) / n(Co) increases, the first-cycle discharge specific capacities at 0.1C and 0.5C increase, but the discharge specific capacity and the capacity retention rate after 100 cycles show a trend of first increasing and then decreasing.

[0301] In the raw material ratio of step (1) for preparing the spherical lithium cobaltate cathode material in Comparative Example 2, n(Na) / n(Co) was approximately 0.4, while in Example 1, n(Na) / n(Co) was approximately 0.8. The discharge specific capacities of the coin-type half-cells assembled in Comparative Example 2 at 0.1C were 176.0 mAh / g respectively, and the first-cycle Coulombic efficiencies were 97.7% respectively. The first-cycle discharge specific capacities at 0.5C were 167.5 mAh / g respectively. The batteries in Comparative Example 2 could not be cycled and the 100-cycle discharge specific capacities were not measured. In contrast, the discharge specific capacity of Example 1 at 0.1C was 56 mAh / g higher than that of Comparative Example 2. Generally speaking, when within the range of the n(Na) / n(Co) ratio of the present invention, the spherical lithium cobaltate cathode material with an O2-phase structure all has excellent discharge specific capacity and good cycle stability, and can meet the requirements of the battery for high energy density. When the n(Na) / n(Co) ratio is too low, the discharge specific capacity, cycle performance, etc. are poor, and it is difficult to meet the usage requirements of the battery.

[0302] The primary sintering temperatures of the spherical lithium cobaltate cathode materials in Examples 10 and 11 were 720°C and 850°C respectively, and the sintering temperature in Example 1 was 780°C. The discharge specific capacities of the coin-type half-cells assembled in Examples 10 and 11 at 0.1C were 232.8 mAh / g and 229.3 mAh / g respectively, and the first-cycle Coulombic efficiencies were 121.8% and 121.7% respectively. The first-cycle discharge specific capacities at 0.5C were 223.1 mAh / g and 219.5 mAh / g respectively, and the 100-cycle discharge specific capacities at 0.5C were 178.8 mAh / g and 174.2 mAh / g respectively, and the capacity retention rates were 80.14% and 79.36% respectively. It can be seen that as the sintering temperature increases, its discharge specific capacity gradually decreases. The primary sintering temperatures of the lithium cobaltate cathode materials in Comparative Examples 3 and 4 were 650°C and 1100°C respectively. The first-cycle discharge specific capacities of the coin-type half-cells assembled were 155.3 mAh / g and 210.9 mAh / g respectively at 0.1C, and the first-cycle Coulombic efficiencies were 97.2% and 123.1% respectively. The lithium cobaltate cathode material in Comparative Example 3 could not be cycled to 100 weeks at 0.5C, while the 100-cycle discharge specific capacity of Comparative Example 4 at 0.5C was 146.5 mAh / g, and the capacity retention rate was 73.8%. The discharge specific capacity of Example 1 at 0.1C was 76.7 mAh / g and 21.1 mAh / g higher than that of Comparative Examples 3 and 4 respectively. The discharge specific capacity of Example 1 cycled for 100 weeks at 0.5C was 31.6 mAh / g higher than that of Comparative Example 4. Generally speaking, by controlling the temperature within a suitable ratio range in the present invention, it all has excellent discharge specific capacity and high capacity retention rate, and can meet the requirements of the battery for high energy density.

[0303] In Examples 12 and 13, the concentrations of the lithium nitrate solution are 1 mol / L and 5 mol / L respectively, and the concentration of the lithium nitrate solution in Example 1 is 2.5 mol / L. The first-week discharge specific capacities of the coin-type half-cells assembled in Examples 12 and 13 at 0.1C are 228.0 mAh / g and 233.8 mAh / g respectively, the first-week Coulombic efficiencies are 120.2% and 122.2% respectively, the first-week discharge specific capacities at 0.5C are 218.1 mAh / g and 221.8 mAh / g respectively, the 100-week discharge specific capacities at 0.5C are 173.2 mAh / g and 175.4 mAh / g respectively, and the capacity retention rates are 79.41% and 79.08% respectively. It can be seen that when the concentration of the lithium nitrate solution is different, the positive electrode materials exhibit different electrochemical performances. When the concentration of the lithium nitrate solution increases, its first-week discharge specific capacity at 0.1C increases, and the first-week discharge specific capacity at 0.5C and the capacity retention rate after 100 cycles show a trend of increasing first and then decreasing. In Comparative Example 5, the concentration of the lithium nitrate solution is 0.5 mol / L. The first-week discharge specific capacity of the coin-type half-cell assembled therein at 0.1C is 208.7 mAh / g, the first-week Coulombic efficiency is 118.5%, the first-week discharge specific capacity at 0.5C is 195.3 mAh / g, the 100-week discharge specific capacity at 0.5C is 155.9 mAh / g, and the capacity retention rate is 79.83%. The first-week discharge specific capacity of Example 1 at 0.1C is 23.3 mAh / g higher than that of Comparative Example 5, and the 100-week discharge specific capacity at 0.5C is 22.2 mAh / g higher than that of Comparative Example 5. Generally speaking, when the concentration of the lithium nitrate solution is controlled within a suitable proportion range in the present invention, it has excellent discharge specific capacity and high capacity retention rate, and can meet the requirements of the battery for high energy density.

[0304] The lithium salt used for ion exchange in Example 1 is lithium nitrate, which is replaced by lithium chloride in Example 14. The first-week discharge specific capacity of the coin-type half-cell assembled in Example 14 at 0.1C is 229.1 mAh / g, the first-week Coulombic efficiency is 120.5%, the 100-week discharge specific capacity at 0.5C is 173.4 mAh / g, and the capacity retention rate is 79.43%. Different types of lithium salts used for ion exchange with the precursor have a certain impact on the discharge specific capacity of the lithium cobaltate positive electrode material, and lithium nitrate shows a higher discharge specific capacity. Generally speaking, when the present invention adopts a suitable lithium salt for ion exchange, it has excellent discharge specific capacity and high capacity retention rate, and can meet the requirements of the battery for high energy density.

[0305] In Examples 15 and 16, the n(Li) / n(Na) during the ion exchange process is 2.5 and 10 respectively, and it is 5 in Example 1. The initial discharge specific capacities of the coin-type half-cells assembled in Examples 15 and 16 at 0.1C are 228.5 mAh / g and 233.5 mAh / g respectively, and the initial Coulombic efficiencies are 120.8% and 122.4% respectively. The 100-cycle discharge specific capacities at 0.5C are 173.8 mAh / g and 178.5 mAh / g respectively, and the capacity retention rates are 79.69% and 79.83% respectively. It can be seen that when the n(Li) / n(Na) is different during the ion exchange process, there are also differences in the discharge specific capacity and the capacity retention rate. When the ratio of n(Li) / n(Na) increases, the discharge specific capacity at each rate also increases, while the capacity retention rate after 100 cycles first increases and then decreases. In Comparative Example 6, the n(Li) / n(Na) is 1.0. The initial discharge specific capacity of the coin-type half-cell assembled is 215.6 mAh / g at 0.1C, the initial Coulombic efficiency is 117.4%, the 100-cycle discharge specific capacity at 0.5C is 148.5 mAh / g, and the capacity retention rate is 74.55%. The discharge specific capacity of Example 1 at 0.1C is 16.4 mAh / g higher than that of Comparative Example 6, and the 100-cycle discharge specific capacity at 0.5C is 29.6 mAh / g higher than that of Comparative Example 6. Generally speaking, when the n(Li) / n(Na) is controlled within a suitable ratio range in the present invention, it has excellent discharge specific capacity and high capacity retention rate, and can meet the requirements of the battery for high energy density.

[0306] In Examples 17 and 18, the temperatures of the secondary calcination are 220 °C and 280 °C respectively. In Example 1, it is 250 °C. The initial discharge specific capacities of the assembled coin-type half-cells in Examples 17 and 18 at 0.1C are 229.5 mAh / g and 230.2 mAh / g respectively, and the initial Coulombic efficiencies are 121.2% and 120.9% respectively. The 100-week discharge specific capacities at 0.5C are 174.8 mAh / g and 175.8 mAh / g respectively, and the capacity retention rates are 79.53% and 79.80% respectively. It can be seen that as the temperature of the secondary calcination increases, the discharge specific capacity first increases and then decreases, while the capacity retention rates after 100 cycles are not very different. In Comparative Examples 7 and 8, the temperatures of the secondary calcination of the lithium cobaltate cathode material are 180 °C and 320 °C respectively. The initial discharge specific capacities of the assembled coin-type half-cells at 0.1C are 207.1 mAh / g and 220.8 mAh / g respectively, and the initial Coulombic efficiencies are 115.8% and 112.2% respectively. The 100-week discharge specific capacities of Comparative Example 7 and Comparative Example 8 at 0.5C are 145.1 mAh / g and 162.5 mAh / g respectively, and the capacity retention rates are 73.10% and 76.76% respectively. The initial discharge specific capacity of Example 1 at 0.1C is 24.9 mAh / g and 11.2 mAh / g higher than that of Comparative Example 7 and Comparative Example 8 respectively. The discharge specific capacity of Example 1 after 100 cycles at 0.5C is 33 mAh / g and 15.6 mAh / g higher than that of Comparative Example 7 and Comparative Example 8 respectively. Generally speaking, when the temperature of the secondary calcination is controlled within a suitable temperature range in the present invention, it has excellent discharge specific capacity and high capacity retention rate, and can meet the requirements of the battery for high energy density.

[0307] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A spherical lithium cobalt oxide positive electrode material with an O2 phase structure, characterized in that: The chemical formula of the spherical lithium cobalt oxide positive electrode material is: Li a X b M p Al q Co (1-p-q) O2, wherein 0.5<a≤1, 0≤b<0.2, 0≤p≤0.5, 0≤q≤0.5, X element is selected from at least one of Na and K, and M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F or Ti; Wherein, the spherical lithium cobalt oxide positive electrode material has a 2θ A1 =18.3°~18.9°, 2θ A2 =37.9°~38.4°, 2θ A3 =46.7°~47.3° and there are XRD diffraction characteristic peaks at the same time; the half-maximum full width value k of the (002) characteristic peak of the spherical lithium cobalt oxide positive electrode material satisfies 0.355≤k≤0.

495.

2. The spherical lithium cobalt oxide positive electrode material with an O2 phase structure according to claim 1, characterized in that: The spherical lithium cobalt oxide positive electrode material is a secondary spherical particle formed by a cluster of primary flaky particles, and the secondary spherical particles are not agglomerated; The thickness j of the primary flake particles is in the range of 0<j≤800nm; The median particle size of the primary flake particles is D 50 Less than or equal to 1000nm; the median particle size of the secondary spherical particles is D 50 Greater than or equal to 3μm and less than or equal to 15μm.

3. The spherical lithium cobalt oxide positive electrode material with an O2 phase structure according to claim 1, characterized in that: The specific surface area of ​​the spherical lithium cobalt oxide positive electrode material is 0.35 m 2 / g~0.55m 2 / g; And / or, the tap density of the lithium cobalt oxide positive electrode material is 3.6 g / cm 3 ~4.2g / cm 3 .

4. A method for preparing a spherical lithium cobalt oxide positive electrode material having an O2 phase structure as claimed in any one of claims 1 to 3, characterized in that: The preparation method comprises: Step S1, uniformly mixing a cobalt precursor, a compound containing an element X, and / or a compound containing an element M in proportion to obtain a mixture; Step S2, subjecting the mixed material to high temperature calcination to obtain a primary sintered product; Step S3, weighing a certain amount of lithium compound and dissolving it in pure water to obtain a lithium compound aqueous solution; Step S4, weighing the primary sintered product according to a certain molar ratio of lithium element to X element, adding it to the lithium compound aqueous solution, grinding it to an appropriate particle size, and simultaneously performing ion exchange to obtain primary flaky particles; Step S5, washing and filtering the primary flaky particles in sequence to remove reaction byproducts, adding deionized water to the filter cake obtained by filtration to prepare a slurry with a certain solid content; Step S6, spray granulating and drying the slurry to obtain a spherical dry product; Step S7, subjecting the spherical dried product to secondary calcination to obtain a spherical lithium cobalt oxide positive electrode material with an O2 phase structure.

5. The preparation method according to claim 4, characterized in that: In the step S1, the molar ratio of the Co element in the cobalt precursor to the X element satisfies: n(X) / n(Co)>0.5, preferably n(X) / n(Co≥0.6; wherein the X element is selected from at least one of Na and K; The molar ratio of the Co element to the M element in the cobalt precursor satisfies: n(M) / n(Co)=0-0.1; wherein the M element is selected from at least one of Ni, Mn, Mg, Cu, Ca, Zn, Zr, B, Nb, Fe, Cr, Y, La, Ce, Cd, Mo, F or Ti; and the M element is derived from the compound containing the M element and / or the cobalt precursor.

6. The preparation method according to claim 4 or 5, characterized in that: The cobalt precursor includes: one or more of cobalt oxide, cobalt hydroxide, cobalt carbonate, cobalt sulfate, cobalt chloride, cobalt oxalate, and cobalt oxyhydroxy; the cobalt precursor is formed by agglomeration and accumulation of primary particles containing Co compounds, wherein the particle size of the primary particles containing Co compounds is between 100nm and 500nm.

7. The preparation method according to claim 4, characterized in that: In the step S2, the high temperature calcination temperature is 700°C to 1000°C, preferably 750°C to 950°C; the high temperature calcination time is 6 hours to 15 hours, preferably 8 hours to 12 hours; The high temperature calcination is carried out in an oxygen atmosphere, and the oxygen concentration is ≥90%; The primary particles of the primary sintered product are in the form of flakes, and the thickness of the primary particles is ≤2 μm.

8. The preparation method according to claim 4, characterized in that: In step S3, the concentration of the lithium compound in the lithium compound aqueous solution is ≥1 mol / L, preferably ≥2 mol / L; the lithium compound includes: one or more of lithium nitrate, lithium hydroxide, lithium carbonate, lithium chloride, lithium iodide, lithium fluoride, lithium bromide, and lithium phosphate.

9. The preparation method according to claim 4, characterized in that: In the step S4, the molar ratio of lithium element to X element is n(Li) / n(X)≥2.5, preferably n(Li) / n(X)≥5; the appropriate particle size D50≤800nm; the ion exchange time is ≥5 hours; In the step S5, the solid content of the slurry is 10wt% to 50wt%; In step S6, the median particle size D50 of the spherical dried product is 5 μm to 15 μm; In the step S7, the temperature of the secondary calcination is 200°C to 300°C, preferably 220°C to 280°C; the time of the secondary calcination is 2 hours to 8 hours, preferably 3 hours to 7 hours; the secondary calcination is carried out in an oxygen atmosphere or an air atmosphere.

10. A lithium battery or battery cell or battery pack, characterized in that: The lithium battery or battery cell or battery pack comprises the spherical lithium cobalt oxide positive electrode material with an O2 phase structure as described in any one of claims 1 to 4, or the spherical lithium cobalt oxide positive electrode material with an O2 phase structure prepared by the preparation method as described in any one of claims 5 to 9.

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