A lithium cobalt oxide material and its preparation method and application

Abstract

The present invention discloses a lithium cobalt oxide material, its preparation method, and its application. The lithium cobalt oxide material is hollow, spherical, and contains a doping element A. The lithium cobalt oxide material of the present invention is structurally stable and can be used as a positive electrode material in a secondary battery, thereby enhancing the structural stability of the positive electrode material during battery operation and improving the battery's cycling stability.

Description

Technical Field

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

[0002] Lithium cobalt oxide is one of the most commonly used cathode materials in current consumer electronic portable devices. Its advantages include a high theoretical specific capacity (274 mAh / g), good rate performance, and high tap density. However, the gram capacity of commercial batteries using lithium cobalt oxide is currently between 170 and 185 mAh / g. This is mainly due to the fact that during the continuous insertion and removal of lithium ions, the crystal structure of lithium cobalt oxide gradually undergoes a phase transition due to repeated expansion and contraction, from a layered structure suitable for reversible lithium ion insertion and removal to a spinel phase that causes structural failure. As a result, conventional lithium cobalt oxide materials currently have poor stability. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a lithium cobalt oxide material which is hollow spherical and has good stability.

[0004] The present invention also provides a method for preparing the lithium cobalt oxide material.

[0005] The present invention also provides a positive electrode material.

[0006] The present invention also provides a secondary battery.

[0007] The present invention also proposes the application of the lithium cobalt oxide material.

[0008] In a first aspect of the present invention, a lithium cobalt oxide material is provided. The lithium cobalt oxide material is in a hollow spherical shape and contains a doping element A.

[0009] The lithium cobalt oxide material according to the embodiment of the present invention has at least the following beneficial effects:

[0010] The lithium cobalt oxide material of the present invention is hollow and spherical, with a stable structure. Using the lithium cobalt oxide material as a positive electrode material in a secondary battery improves the structural stability of the positive electrode material during battery operation, enhancing battery performance such as cycle stability. Specifically, the hollow structure provides a certain buffer space for the expansion and contraction of the lithium cobalt oxide material during operation, improving structural stability and facilitating battery cycle stability. The hollow structure also increases the specific surface area of ​​the lithium cobalt oxide material, increases the contact area between the electrolyte and the lithium cobalt oxide, improves lithium ion reaction kinetics, and has a certain improvement in the low-temperature performance of the battery.

[0011] Furthermore, the lithium cobalt oxide material of the present invention is suitable for high-voltage applications. With the most commonly used voltages on the market currently being 4.40V and 4.45V, and even above 4.5V (e.g., 4.50-4.53V), the lithium cobalt oxide material of the present invention resists lithium ion deintercalation and structural collapse during cycling, resulting in strong stability in high-voltage applications.

[0012] It should be noted that A herein refers to a doping element, which means that element A can be located anywhere in the lithium cobalt oxide material. For example, element A can be doped inside or on the outer surface of the lithium cobalt oxide material. Alternatively, element A (such as W) can be used as a component of a coating material to coat the outer surface of the lithium cobalt oxide matrix. The lithium cobalt oxide matrix refers to the material components of the hollow spherical lithium cobalt oxide material, excluding the outer surface.

[0013] In some embodiments of the present invention, the general formula of the lithium cobalt oxide material is Li a Co b A c O2; among them, 0.4≤a≤1.8, 0.6≤b≤1.5, 0≤c≤0.08.

[0014] In some preferred embodiments of the present invention, 0.45≤a≤1.75, 0.65≤b≤1.45, and 0.01≤c≤0.08.

[0015] In some embodiments of the present invention, the mass fraction of Li element in the lithium cobalt oxide material is 5-9%.

[0016] In some embodiments of the present invention, the mass fraction of Co element in the lithium cobalt oxide material is 56-64%.

[0017] In some embodiments of the present invention, the element A includes at least one of Re, Al, Zr, W, Ga, Hf, Mg, Sn, Zn, Ni, Mn, V, Mo, Nb, Cu, Fe, In or Cr.

[0018] Through the above embodiment, the doping of doping element A (such as Zr, Al) can be used to stabilize the crystalline structure of lithium cobalt oxide, preventing the dissolution of cobalt caused by the high detachment state of lithium cobalt oxide at high voltage, resulting in structural collapse, battery attenuation, and diving. In addition, doping element A (such as W, Re) can also be used as a component element of the coating material, and the coating material is used to coat the outer surface of the lithium cobalt oxide matrix to reduce the side reaction between lithium cobalt oxide and the electrolyte and protect the positive electrode material. The lithium cobalt oxide matrix refers to the matrix composed of substances other than the surface of the hollow spherical lithium cobalt oxide material.

[0019] For the element Re, due to the large atomic radius of the Re element, it is not easy to enter the crystal lattice, resulting in a weak doping depth. Therefore, conventional lithium cobalt oxide usually cannot obtain a higher Re doping amount. In the present invention, the lithium cobalt oxide material has a hollow structure and a large specific surface area, which is more suitable for Re doping. Re is more likely to be concentrated on the inner and outer surfaces of the hollow lithium cobalt oxide matrix, resulting in a higher doping amount. The doping of the Re element is beneficial to improving the high-voltage cycle performance of the battery. Moreover, when Re and W are both used as doping elements, Re and W elements form a solid solution after coating, which improves the overall ionic conductivity of the material, improves the battery polarization, and reduces the internal resistance.

[0020] In some preferred embodiments of the present invention, the element A includes Re and at least one of Al, Zr, W, Ga, Hf, Mg, Sn, Zn, Ni, Mn, V, Mo, Nb, Cu, Fe, In or Cr.

[0021] In some preferred embodiments of the present invention, the element A includes at least one of Re, Al, W or Zr.

[0022] In some preferred embodiments of the present invention, the element A includes Re and W, and further includes at least one of Al and Zr.

[0023] Through the above embodiment, when Al and Zr are doped into lithium cobalt oxide as doping elements, Al and / or Zr elements can replace Co to stabilize the crystalline structure. Al is preferably doped because it is easy to prepare and inexpensive. The Re element has a larger atomic radius and is more likely to concentrate on the surface of the hollow lithium cobalt oxide matrix. For example, if it is located on the outer surface of the lithium cobalt oxide matrix, it can form a solid solution after being coated with the W element, thereby improving the overall ionic conductivity of the material, improving battery polarization, and reducing internal resistance.

[0024] In some preferred embodiments of the present invention, the mass fraction of Re element in the lithium cobalt oxide material is 1000 ppm to 4000 ppm.

[0025] In some more preferred embodiments of the present invention, the mass fraction of Re element in the lithium cobalt oxide material is 2000ppm to 3000ppm.

[0026] In some preferred embodiments of the present invention, the mass fraction of Al element in the lithium cobalt oxide material is 5500-11000 ppm.

[0027] In some more preferred embodiments of the present invention, the mass fraction of Al element in the lithium cobalt oxide material is 6500-8500 ppm.

[0028] In some preferred embodiments of the present invention, the mass fraction of the Zr element in the lithium cobalt oxide material is 50-450 ppm.

[0029] In some more preferred embodiments of the present invention, the mass fraction of the Zr element in the lithium cobalt oxide material is 150-350 ppm.

[0030] In some preferred embodiments of the present invention, the mass fraction of W element in the lithium cobalt oxide material is 1000-3000 ppm.

[0031] In some more preferred embodiments of the present invention, the mass fraction of W element in the lithium cobalt oxide material is 1500-2500 ppm.

[0032] In the present invention, the content of element doping or element coating is relatively small, preferably at the ppm level. Trace element doping can make the material structurally stable while not easily losing the specific capacity, rate performance and other characteristics of the lithium cobalt oxide material itself.

[0033] In some preferred embodiments of the present invention, the lithium cobalt oxide material includes lithium cobalt oxide matrix particles and a coating material coated on the outer surface of the lithium cobalt oxide matrix particles, and the coating material includes the element A.

[0034] In some more preferred embodiments of the present invention, the coating material includes at least one of the elements Al, Zr or W.

[0035] In some more preferred embodiments of the present invention, the coating material includes at least one of the elements W or Zr.

[0036] Through the above embodiment, the coating material includes the element W, which can reduce the residual alkali on the surface of the lithium cobalt oxide material and improve the processability of the lithium cobalt oxide material. At the same time, the formed lithium tungstate has good conductivity and corrosion resistance.

[0037] In some more preferred embodiments of the present invention, the coating material includes at least one of tungsten oxide or zirconium oxide.

[0038] In some more preferred embodiments of the present invention, the coating method is island coating.

[0039] In some preferred embodiments of the present invention, the element A includes element A1 and element A2, the lithium cobaltate material includes lithium cobaltate matrix particles and a coating material coated on the outer surface of the lithium cobaltate matrix particles, the lithium cobaltate matrix particles include element A1, and the coating material includes the element A2.

[0040] In some more preferred embodiments of the present invention, the element A1 includes at least one of Al, Zr, W, Ga, Hf, Mg, Sn, Zn, Ni, Mn, V, Mo, Nb, Cu, Fe, In or Cr; and the element A2 includes at least one of Re, Al, Zr, W, Ga, Hf, Mg, Sn, Zn, Ni, Mn, V, Mo, Nb, Cu, Fe, In or Cr.

[0041] In some more preferred embodiments of the present invention, the element A1 includes at least one of Al or Zr, and the element A2 includes at least one of Re, Al, W or Zr.

[0042] In some more preferred embodiments of the present invention, the element A1 includes at least one of Al or Zr, and the element A2 includes Re and further includes at least one of Al, W or Zr.

[0043] In some embodiments of the present invention, the lithium cobalt oxide material is a hollow spherical nano-lithium cobalt oxide material.

[0044] Through the above implementation, the nano-lithium cobalt oxide material is a single-crystal hollow nano-microsphere with strong structural stability and good application prospects.

[0045] In some embodiments of the present invention, the particle size of the lithium cobalt oxide material is 100-1500 nm.

[0046] In some preferred embodiments of the present invention, the particle size of the lithium cobalt oxide material is 500-800 nm.

[0047] In some embodiments of the present invention, the wall thickness of the lithium cobalt oxide material is 10-300 nm.

[0048] In some preferred embodiments of the present invention, the wall thickness of the lithium cobalt oxide material is 50-100 nm.

[0049] In the present invention, the control of the wall thickness may be related to the preparation process, and appropriate preparation process parameters may be regulated and selected according to actual needs to obtain the desired wall thickness.

[0050] In some embodiments of the present invention, the tap density of the lithium cobalt oxide material is 1.5-3.0 g / cm 3 .

[0051] In some preferred embodiments of the present invention, the tap density of the lithium cobalt oxide material is 2.1-2.6 g / cm 3 .

[0052] In some embodiments of the present invention, the compacted density of the lithium cobalt oxide material is 3.5-4.7 g / cm3 .

[0053] In some preferred embodiments of the present invention, the compacted density of the lithium cobalt oxide material is 4.0-4.2 g / cm 3 .

[0054] In some embodiments of the present invention, the chemical formula of the lithium cobalt oxide material is LiCoO2Re n Zr x W y Al z , where 0≤x≤0.05, 0≤y≤0.4, 0≤z≤0.9, 0≤n≤0.4.

[0055] In a second aspect of the present invention, a method for preparing a lithium cobalt oxide material is provided, the method comprising the following steps:

[0056] S1, taking an aqueous solution containing template carbon spheres and cobalt salt, adding a precipitant, and calcining to obtain a hollow spherical cobalt trioxide precursor;

[0057] S2, taking a mixture containing a lithium salt and the precursor, and calcining it to obtain a hollow spherical lithium cobalt oxide material;

[0058] In step S1, the aqueous solution further includes raw material I containing A; or / and, in step S2, the mixture further includes raw material II containing A.

[0059] The method for preparing a hollow spherical lithium cobalt oxide material according to an embodiment of the present invention has at least the following beneficial effects: the present invention uses a template method to synthesize a hollow lithium cobalt oxide material, which is beneficial for buffering the volume deformation of the material during cycling. The resulting material structure is stable, thereby improving the cycling stability of the battery used. In step S1, the precursor is a cobalt oxide precursor or a cobalt oxide precursor doped with element A.

[0060] In some embodiments of the present invention, in step S1, the cobalt salt includes at least one of cobalt sulfate, cobalt nitrate or cobalt chloride.

[0061] In some embodiments of the present invention, in step S1, the precipitant includes at least one of a carbonate or an alkali.

[0062] In some preferred embodiments of the present invention, in step S1, the precipitant includes at least one of sodium hydroxide or sodium carbonate.

[0063] In some embodiments of the present invention, in step S1, the calcination temperature is 300-800°C.

[0064] In some embodiments of the present invention, in step S1, the calcination time is more than 2 hours.

[0065] In some preferred embodiments of the present invention, in step S1, the calcination time is 3-5 hours.

[0066] In some embodiments of the present invention, in step S1, the aqueous solution further includes raw material I containing A1; or / and, in step S2, the mixture further includes raw material II containing A2.

[0067] In some preferred embodiments of the present invention, the raw material I includes at least one of ammonium perrhenate, aluminum salt or zirconium salt; the raw material II includes at least one of ammonium perrhenate, zirconium oxide, tungsten oxide, aluminum oxide or lithium tungstate.

[0068] In some preferred embodiments of the present invention, the raw material I comprises at least one of an aluminum salt or a zirconium salt; the raw material II comprises ammonium perrhenate and at least one of zirconium oxide, tungsten oxide, aluminum oxide, or lithium tungstate. Preferably, the aluminum salt and the zirconium salt are both soluble salts.

[0069] In step S1, the aqueous solution includes aluminum salt and / or zirconium salt. Al and / or Zr are doped into the lithium cobalt oxide as doping elements. Al and / or Zr elements can replace Co positions to stabilize the crystalline structure. Doping with Al is preferred because it is easy to prepare and inexpensive. Due to the large atomic radius of the Re element, it is easier to concentrate on the surface of the hollow lithium cobalt oxide matrix. After being coated with the W element, a solid solution is formed, which improves the overall ionic conductivity of the material, improves battery polarization, and reduces internal resistance.

[0070] In some preferred embodiments of the present invention, the aluminum salt includes at least one of aluminum sulfate, aluminum nitrate, aluminum carbonate or aluminum chloride.

[0071] In some preferred embodiments of the present invention, the zirconium salt includes at least one of zirconium sulfate, zirconium nitrate or zirconium chloride.

[0072] In some embodiments of the present invention, in step S2, the precursor is mixed with a lithium salt and a raw material II containing A to obtain the mixture, and the mixture is calcined to obtain the hollow spherical lithium cobalt oxide material. Preferably, the raw material II containing A includes ammonium perrhenate and at least one of zirconium oxide, tungsten oxide, aluminum oxide, or lithium tungstate.

[0073] In some embodiments of the present invention, in step S1, the aqueous solution further includes a surfactant.

[0074] In some preferred embodiments of the present invention, the surfactant comprises ethanol.

[0075] Through the above embodiment, the addition of ethanol to the aqueous solution can reduce the polarity of the solution, facilitate the diffusion of ions, and increase the permeability of metal ions on the carbon spheres. Ethanol, also known as alcohol.

[0076] In some more preferred embodiments of the present invention, the volume ratio of the ethanol to the water in the aqueous solution is 1:2 to 3:2, preferably (1.5-2):1.

[0077] According to the above embodiment, compared with the volume ratio of ethanol to water exceeding 3:2, the volume ratio of ethanol to water of 1:2 to 3:2 is less likely to reduce the solubility of the solute in the solvent and is more conducive to the concentration and diffusion of metal ions.

[0078] In some embodiments of the present invention, in step S1, an aqueous solution containing template carbon spheres and cobalt salt is taken, a precipitant is added, and the solution is allowed to stand and then filtered to obtain a precipitate, which is then calcined to obtain a hollow spherical precursor.

[0079] In some embodiments of the present invention, in step S2, the lithium salt includes lithium carbonate.

[0080] In some embodiments of the present invention, in step S2, the calcination conditions include first keeping the temperature at 600-900°C for 2-4 hours, and then keeping the temperature at 900-1200°C for 4-6 hours.

[0081] In some preferred embodiments of the present invention, in step S2, the calcination conditions include first keeping the temperature at 750°C for 3 hours and then keeping the temperature at 1100°C for 5 hours.

[0082] In some preferred embodiments of the present invention, in step S2, the calcination conditions are: raising the temperature to 600-900°C at 2-6°C / min and keeping the temperature for 2-4 hours, and then raising the temperature to 900-1200°C at 2-6°C / min and keeping the temperature for 4-6 hours.

[0083] In some embodiments of the present invention, the preparation method further comprises the preparation of template carbon spheres, and the preparation of the template carbon spheres comprises the following operations: taking monosaccharides and subjecting them to a hydrothermal reaction to obtain the template carbon spheres.

[0084] In some preferred embodiments of the present invention, the reaction temperature of the hydrothermal reaction is 160-200°C.

[0085] In some preferred embodiments of the present invention, the reaction time of the hydrothermal reaction is 4-8 hours.

[0086] In some preferred embodiments of the present invention, the preparation of the template carbon spheres comprises the following operations: taking an aqueous solution containing monosaccharides, heating, and filtering to obtain the template carbon spheres.

[0087] In some more preferred embodiments of the present invention, the monosaccharide comprises glucose.

[0088] In some more preferred embodiments of the present invention, the heating temperature is 170-190°C.

[0089] In some more preferred embodiments of the present invention, the heating time is 5-7 hours.

[0090] In some more preferred embodiments of the present invention, the template carbon spheres are obtained by heating, filtering, washing, and drying. Preferably, water is used for washing.

[0091] In a third aspect of the present invention, a positive electrode material is provided, wherein the positive electrode material includes the above-mentioned lithium cobalt oxide material.

[0092] According to a fourth aspect of the present invention, a secondary battery is provided. The secondary battery includes a positive electrode, and the raw materials for preparing the positive electrode include the above-mentioned positive electrode material.

[0093] In some embodiments of the present invention, the secondary battery includes at least one of a lithium ion battery or a sodium ion battery.

[0094] The fifth aspect of the present invention proposes the use of the above-mentioned lithium cobalt oxide material in the preparation of electrical devices.

[0095] The beneficial effects of the present invention include:

[0096] The present invention improves the stability of the lithium cobalt oxide material by controlling the stability of the material in terms of structural morphology, and uses the hollow spherical lithium cobalt oxide material as a positive electrode material in a secondary battery, thereby improving the cycle stability of the battery. The lithium cobalt oxide material in the present invention is suitable for high-voltage application environments. The doping of doping element A (such as Zr, Al) can be used to stabilize the crystalline structure of lithium cobalt oxide, preventing the dissolution of cobalt caused by the high detachment state of lithium cobalt oxide under high voltage, resulting in structural collapse, battery attenuation, and diving. In addition, doping element A (such as W) can also be used as a constituent element of a coating material, and the coating material is used to coat the outer surface of the lithium cobalt oxide matrix to reduce the side reaction between lithium cobalt oxide and the electrolyte and protect the positive electrode material. When the doping element A contains Re, a solid solution can be formed after the W element is coated, thereby improving the overall ionic conductivity of the material, improving battery polarization, and reducing internal resistance.

[0097] The present invention adopts a template method to synthesize a hollow lithium cobalt oxide material, which is beneficial to buffering the volume deformation of the material during the cycle. The obtained material has a stable structure, thereby improving the cycle stability of the battery used. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0099] Figure 1 This is a diagram showing the microstructure test results of the hollow spherical lithium cobalt oxide material in Example 1 of the present invention;

[0100] Figure 2 This is a comparison chart of 45°C high-temperature cycle charge-discharge data of the hollow spherical lithium cobalt oxide materials of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0101] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0102] The experimental methods in the following examples, for which specific conditions are not specified, are generally performed in accordance with conventional conditions in the art or conditions recommended by the manufacturers; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets.

[0103] Example 1

[0104] This embodiment discloses a hollow spherical lithium cobalt oxide material, the preparation process of which includes:

[0105] (I) Synthesizing a sacrificial template for nanocarbon spheres, comprising:

[0106] A certain amount of glucose was dissolved in water and stirred evenly to obtain an aqueous solution with a glucose concentration of 0.12 g / mL. A hydrothermal reaction was carried out at a heating temperature of 180°C and a reaction time of 6 hours. After the reaction, the product (nanocarbon sphere template) was repeatedly washed and filtered with deionized water and dried for later use.

[0107] (II) preparing a hollow spherical nano-lithium cobalt oxide material, comprising:

[0108] The nanocarbon sphere template prepared in step (I) is dispersed in deionized water (the ratio of carbon spheres to deionized water is 1g:100mL), and cobalt sulfate and aluminum sulfate (aluminum carbonate can also be used) are added. Sodium hydroxide (sodium carbonate can also be used) is added as a precipitant, and ethanol is added as a surfactant to increase the permeability of metal ions on the carbon spheres (the volume ratio of ethanol to the deionized water is 1.5:2, wherein the volume ratio is (1.5-2:1). After standing, the precipitate is filtered and calcined at 500°C (calcination time 3-5h) to remove the carbon sphere template, thereby obtaining an aluminum-doped spherical hollow cobalt tetroxide precursor. The ratio of carbon spheres, cobalt sulfate, and aluminum sulfate is 1g:3mol:0.75mol, and the ratio of the sum of the molar amounts of cobalt sulfate and aluminum sulfate to the molar amount of sodium hydroxide is approximately 1:3.

[0109] The cobalt oxide precursor is mixed with lithium carbonate (wherein the molar ratio of lithium carbonate to cobalt oxide contained in the cobalt oxide precursor is 3:2), ammonium perrhenate, zirconium oxide, and tungsten oxide are added, and high-temperature calcination is performed (the calcination conditions are specifically 4°C / min to 750°C and kept for 3 hours, then changed to 4°C / min to 1100°C and kept for 5 hours) to synthesize a hollow spherical morphology of a nano-lithium cobalt oxide material. Wherein, the molar ratio of ammonium perrhenate, zirconium oxide, tungsten oxide to cobalt oxide contained in the cobalt oxide precursor is 0.2:0.025:0.2:2. The obtained hollow spherical morphology of the nano-lithium cobalt oxide material includes aluminum-doped lithium cobalt oxide base particles and a coating material (including tungsten oxide) coated on the outer surface of the lithium cobalt oxide base particles, and the coating form of the coating material includes island coating.

[0110] The prepared nano-lithium cobalt oxide material was measured:

[0111] Particle size 500-800nm; wall thickness 50-100nm;

[0112] Element content (mass fraction): Li: 7% ± 2%, Co: 60% ± 4%, Al: 7500ppm ± 1000ppm, Zr: 250ppm ± 100ppm, W: 2000ppm ± 500ppm, Re: 2000ppm ~ 3000ppm;

[0113] The total content of Al, Zr and W is 8000-10000ppm;

[0114] Tap density: 2.1-2.6g / cm 3 , compacted density: 4.0-4.2g / cm 3 ;

[0115] This embodiment also provides a positive electrode material, including the hollow spherical lithium cobalt oxide material prepared in this embodiment.

[0116] This embodiment further provides a lithium-ion battery, including a positive electrode, wherein the raw material for preparing the positive electrode includes the positive electrode material of this embodiment.

[0117] Example 2

[0118] This embodiment discloses a hollow spherical lithium cobalt oxide material. The only difference between this embodiment and the first embodiment is that the preparation step (II) is different. Step (II) of this embodiment - preparing the hollow spherical nano-lithium cobalt oxide material - includes the following operations:

[0119] The nanocarbon sphere template prepared in step (I) is dispersed in deionized water, and cobalt sulfate, a soluble aluminum salt, and a zirconium salt are added. Sodium hydroxide is added as a precipitant, and ethanol is added as a surfactant to increase the permeability of metal ions on the carbon spheres (wherein the volume ratio of ethanol to the deionized water is 1:2). After standing, the precipitate is filtered and calcined at 500°C (calcination time 3-5h) to remove the carbon sphere template to obtain an aluminum-doped spherical hollow cobalt tetroxide precursor. The ratio of carbon spheres to cobalt sulfate can be 1g:(0.5-3.5)mol.

[0120] The cobalt trioxide precursor was mixed with lithium carbonate (wherein the molar ratio of lithium carbonate to cobalt trioxide contained in the cobalt trioxide precursor was 3:2), ammonium perrhenate and tungsten oxide were added, and high-temperature calcination was performed (the calcination conditions were specifically increased to 750°C at 4°C / min and kept for 3 hours, then changed to 1100°C at 4°C / min and kept for 5 hours) to obtain a hollow spherical morphology of a nano-lithium cobalt oxide material.

[0121] In this embodiment, the aluminum salt can be selected from one or more of aluminum sulfate, aluminum nitrate, aluminum carbonate or aluminum chloride, and the zirconium salt can be selected from one or more of zirconium sulfate, zirconium nitrate or zirconium chloride; the specific addition amounts of ammonium perrhenate, aluminum salt, zirconium salt and tungsten oxide can be selected according to actual production requirements.

[0122] This embodiment also provides a positive electrode material, including the hollow spherical lithium cobalt oxide material prepared in this embodiment.

[0123] This embodiment further provides a lithium-ion battery, including a positive electrode, wherein the raw material for preparing the positive electrode includes the positive electrode material of this embodiment.

[0124] Example 3

[0125] This embodiment discloses a hollow spherical lithium cobalt oxide material. The only difference between this embodiment and the first embodiment is that the preparation step (II) is different. Step (II) of this embodiment - preparing the hollow spherical nano-lithium cobalt oxide material - includes the following operations:

[0126] The nanocarbon sphere template prepared in step (I) is dispersed in deionized water (the ratio of carbon spheres to deionized water is 1g:100mL), cobalt sulfate, a soluble zirconium salt, and sodium hydroxide as a precipitant. Ethanol can be added as a surfactant to increase the permeability of metal ions on the carbon spheres (wherein the volume ratio of ethanol to the deionized water is 1:2). After standing, the precipitate is filtered and calcined at 500°C (calcination time 3-5h) to remove the carbon sphere template to obtain an aluminum-doped spherical hollow cobalt tetraoxide precursor. Wherein, the ratio of carbon spheres to cobalt sulfate can be 1g:(0.5-3.5)mol.

[0127] The cobalt trioxide precursor was mixed with lithium carbonate (wherein the molar ratio of lithium carbonate to cobalt trioxide contained in the cobalt trioxide precursor was 3:2), and ammonium perrhenate, aluminum oxide, and tungsten oxide were added and calcined at high temperature (the calcination conditions were specifically: heating to 750°C at 4°C / min and holding for 3 hours, then changing to heating to 1100°C at 4°C / min and holding for 5 hours) to obtain a hollow spherical morphology of a nano-lithium cobalt oxide material.

[0128] In this embodiment, the zirconium salt can be selected from one or more of zirconium sulfate, zirconium nitrate or zirconium chloride; the specific addition amounts of ammonium perrhenate, zirconium salt, aluminum oxide and tungsten oxide can be selected according to actual production requirements.

[0129] This embodiment also provides a positive electrode material, including the hollow spherical lithium cobalt oxide material prepared in this embodiment.

[0130] This embodiment further provides a lithium-ion battery, including a positive electrode, wherein the raw material for preparing the positive electrode includes the positive electrode material of this embodiment.

[0131] Example 4

[0132] This embodiment discloses a hollow spherical lithium cobalt oxide material. The only difference between this embodiment and the first embodiment is that the preparation step (II) is different. Step (II) of this embodiment - preparing the hollow spherical nano-lithium cobalt oxide material - includes the following operations:

[0133] The nanocarbon sphere template prepared in step (I) is dispersed in deionized water (the ratio of carbon spheres to deionized water is 1g:100mL), cobalt sulfate is added, sodium hydroxide is added as a precipitant, and alcohol is added as a surfactant to increase the permeability of metal ions on the carbon spheres (wherein the volume ratio of ethanol to the deionized water is 1:2). After standing, the precipitate is filtered and calcined at 500°C (calcination time 3-5h) to remove the carbon sphere template to obtain an aluminum-doped spherical hollow cobalt tetroxide precursor. Wherein, the ratio of carbon spheres to cobalt sulfate can be 1g:(0.5-3.5)mol.

[0134] The cobalt trioxide precursor was mixed with lithium carbonate (wherein the molar ratio of lithium carbonate to cobalt trioxide contained in the cobalt trioxide precursor was 3:2), and ammonium perrhenate, zirconium oxide, aluminum oxide, and tungsten oxide were added and calcined at high temperature (the calcination conditions were specifically: 4°C / min to 750°C and kept for 3 hours, then changed to 4°C / min to 1100°C and kept for 5 hours) to obtain a hollow spherical morphology of a nano-lithium cobalt oxide material.

[0135] The specific addition amounts of ammonium perrhenate, zirconium oxide, aluminum oxide, and tungsten oxide in this embodiment can be selected according to actual production requirements.

[0136] This embodiment also provides a positive electrode material, including the hollow spherical lithium cobalt oxide material prepared in this embodiment.

[0137] This embodiment further provides a lithium-ion battery, including a positive electrode, wherein the raw material for preparing the positive electrode includes the positive electrode material of this embodiment.

[0138] Example 5

[0139] This embodiment discloses a hollow spherical lithium cobalt oxide material, which differs from Example 1 only in that lithium tungstate is used in preparation step (II) of this embodiment instead of tungsten oxide in Example 1.

[0140] Comparative Example 1

[0141] This comparative example discloses a hollow spherical lithium cobalt oxide material having a chemical formula of LiCoO2. The only difference between this comparative example and Example 1 is that the hollow spherical lithium cobalt oxide material in this comparative example is not doped with Al, Zr, and W. The preparation of the hollow spherical lithium cobalt oxide material in this comparative example specifically includes the following steps:

[0142] (I) Synthesis of sacrificial template of nanocarbon spheres: same as in Example 1;

[0143] (II) preparing a hollow spherical nano-lithium cobalt oxide material, comprising:

[0144] The nanocarbon sphere template prepared in step (I) is dispersed in deionized water (the ratio of carbon spheres to deionized water is 1g:100mL), cobalt sulfate is added, sodium hydroxide is added as a precipitant, and ethanol can be added as a surfactant to increase the permeability of metal ions on the carbon spheres (wherein the volume ratio of ethanol to the deionized water is 1:2). After standing, the precipitate is filtered and calcined at 500°C (calcination time 3-5h) to remove the carbon sphere template to obtain a spherical hollow cobalt tetraoxide precursor. Wherein, the ratio of carbon spheres to cobalt sulfate is 1g:3mol.

[0145] The cobalt trioxide precursor was mixed with lithium carbonate (wherein the molar ratio of lithium carbonate to cobalt trioxide contained in the cobalt trioxide precursor was 3:2), and calcined at high temperature (the calcination conditions were specifically: increasing the temperature to 750°C at 4°C / min and holding for 3 hours, then changing to increasing the temperature to 1100°C at 4°C / min and holding for 5 hours) to obtain a hollow spherical nano-lithium cobalt oxide material.

[0146] Test example

[0147] This test example tested the performance of the lithium cobalt oxide materials obtained in the examples and comparative examples, specifically including:

[0148] 1. Test the microstructure of the lithium cobalt oxide material obtained in Example 1. The test results are as follows: Figure 1 shown.

[0149] 2. Testing the electrochemical properties of the lithium cobalt oxide material prepared in Example 1 (a button cell was prepared for performance testing, wherein the positive electrode material of the button cell was the lithium cobalt oxide material prepared in Example 1):

[0150] 1) Gram capacity test: measured gram capacity: 190-194mAh / g; specific test steps include: 0.1C charge to 4.55V cutoff current 0.02C, 0.1C discharge to 3V, charge and discharge benchmark gram capacity is 195mAh / g.

[0151] 2) First efficiency test: the first efficiency is 94% ± 2%. The first efficiency is calculated as: first discharge capacity / first charge capacity;

[0152] 3) Discharge platform: 3.8-3.95V, the specific steps include: the platform uses the discharge energy Wh of the 2nd-3rd cycle curve divided by the capacity Ah.

[0153] 3. Comparison of 45°C high-temperature cycle charge data, specifically including: calculated based on a benchmark capacity of 195mAh / g, charging to 4.55V at 3C, with a cut-off current of 200mA, and discharging to 3V at 3C.

[0154] The 45°C high temperature cycle charge data of the lithium cobalt oxide materials in Example 1 and Comparative Example 1 were measured. Figure 2 As shown, hollow LCO represents the test curve of Example 1, and normal LCO represents the test curve of Comparative Example 1.

[0155] In summary, the present invention designs the structure of the material to synthesize structurally stable single-crystal hollow nanospheres, and at the same time dopes transition metals during the sintering process to stabilize the microscopic crystal structure, thereby improving the structural stability of the lithium cobalt oxide positive electrode material during battery operation.

[0156] The present invention uses a template method to synthesize a hollow lithium cobalt oxide material, which helps buffer the volume deformation of the material during the cycle and provides more reactive sites. Al and Zr elements are doped to replace Co in the synthesis of the cobalt oxide precursor to stabilize its unit cell structure. W and Re elements are then introduced during the subsequent calcination process to reduce the amount of residual lithium on the material surface, improve the material's machinability, and enhance the material's processing and manufacturability. The Re and W elements form a solid solution after coating, which improves the material's overall ionic conductivity, improves battery polarization, and reduces internal resistance.

[0157] At the same time, the wall thickness of the lithium cobalt oxide material in the present invention can be preferably controllably adjusted according to two factors: the contact time between the metal ions and the carbon template during the adsorption stage and / or the compounding ratio of deionized water and ethanol in the solution (the main function of adding ethanol is to reduce the polarity of the solution, so that the ions in the solution can better penetrate into the surface of the carbon balls), so as to obtain a more preferred lithium cobalt oxide material that better meets the actual specific production needs.

[0158] It should be noted that, unless otherwise specified, “room temperature” or “normal temperature” herein refers to approximately 25° C.; and “approximately” for numerical values ​​herein means an error of ±2%.

[0159] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A lithium cobalt oxide material, characterized in that: The lithium cobalt oxide material is hollow spherical, and the lithium cobalt oxide material contains a doping element A, the element A includes an element A1 and an element A2, the lithium cobalt oxide material includes a lithium cobalt oxide matrix particle and a coating material coated on the outer surface of the lithium cobalt oxide matrix particle, the lithium cobalt oxide matrix particle includes the element A1, the coating material includes the element A2, the element A2 includes Re and W, and the element A1 includes at least one of Al, Zr, W, Ga, Hf, Mg, Sn, Zn, Ni, Mn, V, Mo, Nb, Cu, Fe, In or Cr; The mass fraction of Re is 1000ppm~4000ppm.

2. The lithium cobalt oxide material according to claim 1, characterized in that The element A2 also includes at least one of Al, Zr, Ga, Hf, Mg, Sn, Zn, Ni, Mn, V, Mo, Nb, Cu, Fe, In or Cr.

3. The lithium cobalt oxide material according to claim 1, characterized in that In the lithium cobalt oxide material, the mass fraction of Al element is 5500-11000 ppm.

4. The lithium cobalt oxide material according to claim 1, characterized in that In the lithium cobalt oxide material, the mass fraction of the Zr element is 50-450 ppm.

5. The lithium cobalt oxide material according to claim 1, characterized in that In the lithium cobalt oxide material, the mass fraction of W element is 1000-3000 ppm.

6. The lithium cobalt oxide material according to claim 1, characterized in that The particle size of the lithium cobalt oxide material is 100-1500 nm.

7. The lithium cobalt oxide material according to claim 6, characterized in that The wall thickness of the lithium cobalt oxide material is 10-300 nm.

8. The lithium cobalt oxide material according to claim 1, characterized in that The tap density of the lithium cobalt oxide material is 1.5-3.0 g / cm 3 .

9. The lithium cobalt oxide material according to claim 8, characterized in that The compacted density of the lithium cobalt oxide material is 3.5-4.7 g / cm 3 .

10. A method for preparing the lithium cobalt oxide material according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: S1, taking an aqueous solution containing template carbon spheres and cobalt salt, adding a precipitant, and calcining to obtain a hollow spherical precursor; S2, taking a mixture containing a lithium salt and the precursor, and calcining it to obtain a hollow spherical lithium cobalt oxide material; In step S1, the aqueous solution further includes raw material I containing A; or / and, in step S2, the mixture further includes raw material II containing A, the raw material I includes at least one of aluminum salt or zirconium salt; the raw material II includes ammonium perrhenate and tungsten oxide.

11. The method for preparing the lithium cobalt oxide material according to claim 10, characterized in that: The raw material II further comprises at least one of zirconium oxide, aluminum oxide or lithium tungstate.

12. A positive electrode material, characterized in that The positive electrode material includes the lithium cobalt oxide material according to any one of claims 1 to 9 or the lithium cobalt oxide material prepared by the preparation method according to any one of claims 10 to 11.

13. A secondary battery, characterized in that: The secondary battery includes a positive electrode, and a raw material for preparing the positive electrode includes the positive electrode material according to claim 12.

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