Composite coated modified lithium ion battery positive electrode material and preparation method and application thereof

Abstract

The present invention discloses a composite coated modified lithium ion battery positive electrode material and a preparation method and application thereof, comprising a base material, the base material being a lithium ion battery positive electrode material; and a composite coating layer formed on the surface of the base material, the composite coating layer comprising a first component and a second component, wherein the first component is a composite of boron oxide-loaded carbon nanotubes and graphene, and the second component is lithium fluoride. The composite coated modified lithium ion battery positive electrode material utilizes a composite powder (B‑CNTs / GR powder) of boron oxide-loaded carbon nanotubes and graphene to synergize with lithium fluoride coating to modify the lithium ion battery positive electrode material, and constructs a three-dimensional coating layer by composite boron oxide and lithium fluoride, thereby improving the rate performance and high temperature performance of the lithium ion battery positive electrode material under high voltage.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery positive electrode materials, and particularly relates to a composite coated modified lithium ion battery positive electrode material and a preparation method thereof, and also relates to the application of the composite coated modified lithium ion battery positive electrode material in the preparation of lithium ion batteries. Background Art

[0002] Lithium-ion battery (LIBs) is a rechargeable battery that relies on the movement of lithium ions between the positive and negative electrodes. As an efficient green recycling energy source, it has many advantages such as high operating voltage, high specific energy, small size, light weight, and long life.

[0003] The positive electrode material is one of the most critical components in LIBs, and its performance directly restricts the performance of LIBs. At present, the main common positive electrode materials used for lithium-ion batteries are: lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4) and ternary materials. Studies have shown that improving the performance of lithium-ion battery positive electrode materials by coating is one of the most effective methods at present. The commonly used coating materials are mainly carbon materials (such as carbon nanotubes, graphene, etc.), metal oxides, fast ion conductors, etc. Studies have shown that the use of carbon nanotubes and graphene to synergistically coat lithium cobalt oxide positive electrode materials, through the alternating dispersion of carbon nanotubes and graphene on the surface of lithium cobalt oxide particles, to form a three-dimensional nano conductive network, can improve the electrochemical properties of the composite material, especially the specific capacity, cycle stability and rate performance at high rates; but the lithium cobalt oxide material prepared by this scheme has poor first efficiency and high temperature stability at high voltage. Summary of the invention

[0004] In view of this, it is necessary for the present invention to provide a composite coated modified lithium-ion battery positive electrode material, which uses a composite powder of boron oxide loaded carbon nanotubes and graphene (B-CNTs / GR powder) to synergistically coat the lithium ion battery positive electrode material, and constructs a three-dimensional coating layer by composite boron oxide and lithium fluoride to improve the rate performance and high temperature performance of the lithium ion battery positive electrode material under high voltage.

[0005] Improve the electrochemical performance of lithium-ion battery cathode materials.

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

[0007] The present invention provides a composite coated modified lithium ion battery positive electrode material, comprising:

[0008] A base material, wherein the base material is a positive electrode material for a lithium-ion battery;

[0009] And a composite coating layer formed on the surface of the base material, the composite coating layer contains a first component and a second component, wherein the first component is a composite of boron oxide-loaded carbon nanotubes and graphene, and the second component is lithium fluoride.

[0010] In a further embodiment, the positive electrode material of the lithium-ion battery is selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials;

[0011] Preferably, the lithium-ion battery positive electrode material is selected from lithium cobalt oxide.

[0012] In a further embodiment, the thickness of the composite coating layer is between 10 nm and 200 nm.

[0013] The present invention further provides a method for preparing a composite coated modified lithium ion battery positive electrode material, comprising the following steps:

[0014] Providing B-CNTs / GR powder: After the carbon nanotubes are acidified, they are fully dispersed with graphene and boron oxide, and then treated at high temperature under anaerobic conditions to obtain a composite powder of boron oxide-loaded carbon nanotubes and graphene, namely B-CNTs / GR powder;

[0015] The B-CNTs / GR powder, lithium fluoride and lithium ion battery positive electrode material are fully mixed and sintered to obtain a composite coated modified lithium ion battery positive electrode material.

[0016] In a further embodiment, the carbon nanotubes are multi-walled carbon nanotubes with an average diameter of 15-25 nm.

[0017] In a further embodiment, the high temperature treatment is carried out at a temperature of 400-500° C. and a holding time of 2-3 hours.

[0018] In a further embodiment, based on the mass of the positive electrode material of the lithium-ion battery, the added amount of the B-CNTs / GR powder is 0.3%-0.6%, and the added amount of the lithium fluoride is 0.15%-0.5%; in the B-CNTs / GR powder, the mass ratio of boron oxide, carbon nanotubes and graphene is 20-40:1-5:3-8.

[0019] In a further embodiment, the sintering temperature is 700-950° C. and the sintering time is 10-12 hours.

[0020] The present invention also provides a lithium ion battery positive electrode sheet, characterized in that it contains the composite coated modified lithium ion battery positive electrode material as described above or the composite coated modified lithium ion battery positive electrode material prepared by the preparation method as described above.

[0021] The present invention also provides a lithium ion battery, characterized in that the positive electrode sheet thereof adopts the lithium ion battery positive electrode sheet as described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention overcomes the defects of poor lithium ion conductivity and excessive thickness of the coating layer in the traditional inert coating layer. Boron oxide is coated on the surface of the positive electrode material through graphene and carbon nanotubes. Fine carbon nanotubes and thin-film graphene are alternately dispersed on the surface of the positive electrode material particles to form a three-dimensional nanoscale conductive network. In addition, part of the boron oxide is filled in the carbon nanotubes, and part is evenly distributed in the coating layer. Due to the unique electron deficiency of the boron element and the characteristics of boron ions releasing electrons, the electronic conductivity of the electrode material can be greatly improved and the resistivity of the positive electrode material can be reduced. During the embedding and de-embedding process, carbon nanotubes and graphene can provide a high conductivity channel for electron transfer, increase the electron transmission rate, and improve the rate performance and cycle stability of the positive electrode material. However, under high voltage systems,

[0024] The present invention uses lithium fluoride for collaborative coating, fills lithium fluoride on the surface of the material and between the three-dimensional conductive layers, forms a passivation layer, effectively protects the three-dimensional conductive layer and the positive electrode material from being eroded by the electrolyte, and inhibits the irreversible phase change of the material. At the same time, part of the lithium ions provided by lithium fluoride form a SEI film, which can improve the initial charge and discharge efficiency of the positive electrode material and improve the comprehensive performance of the positive electrode material under high voltage. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0027] The first aspect of the present invention discloses a composite coated modified lithium ion battery positive electrode material, which comprises a base material and a composite coating layer formed on the surface of the base material. The base material is not particularly limited and is a conventional lithium ion battery positive electrode material in the art, such as lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and at least one of ternary materials. Preferably, the lithium ion battery positive electrode material is lithium cobalt oxide.

[0028] Furthermore, the composite coating layer is a composite of multiple components, specifically, the composite coating layer contains a first component and a second component, wherein the first component is a composite of boron oxide loaded carbon nanotubes and graphene, i.e., B-CNTs / GR powder, and the second component is lithium fluoride. The B-CNTs / GR powder and lithium fluoride are used to synergistically perform composite coating modification on the positive electrode material of the lithium-ion battery to improve the performance of the coating layer, and the boron oxide and lithium fluoride are composited to construct a three-dimensional coating layer, thereby improving the electrochemical properties of the positive electrode material of the lithium-ion battery, such as rate performance at high voltage and high temperature cycle stability.

[0029] Furthermore, the thickness of the composite coating layer can be adjusted according to actual conditions. In order to achieve optimal and balanced performance in all aspects of the modified lithium-ion battery positive electrode material, preferably, the thickness of the composite coating layer is between 10-200 nm.

[0030] The second aspect of the present invention provides a method for preparing a composite coated modified lithium ion battery positive electrode material, the main steps of which are:

[0031] Preparation of B-CNTs / GR powder

[0032] After the carbon nanotubes are acidified, they are fully dispersed with graphene and boron oxide, and then treated at high temperature under anaerobic conditions to obtain a composite powder of boron oxide-loaded carbon nanotubes and graphene, i.e., B-CNTs / GR powder. Wherein, the carbon nanotubes herein are not particularly limited. According to an embodiment of the present invention, the carbon nanotubes used are multi-walled carbon nanotubes with an average diameter of 15-25nm. Further, the carbon nanotube acidification treatment can be carried out in a conventional manner in the art, the purpose of which is to purify the carbon nanotubes and open their tops, so as to facilitate the subsequent loading of boron oxide in the carbon nanotubes. According to an embodiment of the present invention, the carbon nanotubes are refluxed with nitric acid at 100-150°C for 10-15h to complete the acidification of the carbon nanotubes. Subsequently, the acidified carbon nanotubes and graphene are placed in a beaker, anhydrous ethanol is added as a dispersant, and after being fully dispersed, the ground boron oxide is added and fully dispersed. Wherein, the dispersion method and time are not particularly limited. According to an embodiment of the present invention, ultrasonic dispersion and / or mechanical stirring are adopted, and the specific time can be adjusted according to actual conditions. Finally, the composite powder of boron oxide filled carbon nanotubes and graphene is obtained by high temperature treatment under anaerobic conditions, drying, grinding and sieving. The anaerobic conditions mentioned here are achieved by a protective atmosphere, and the protective atmosphere refers to one of the Group 0 rare gases or nitrogen. According to an embodiment of the present invention, the temperature of the high temperature treatment is 400-500°C, and the insulation time is 2-3h.

[0033] Preparation of composite coated modified lithium ion battery cathode materials

[0034] The B-CNTs / GR powder, lithium fluoride and lithium-ion battery positive electrode material are fully mixed and sintered to obtain a composite coated modified lithium-ion battery positive electrode material. According to an embodiment of the present invention, the thickness of the composite coating layer can be adjusted by controlling the mixing ratio of each raw material, thereby achieving the adjustment of the performance of the lithium-ion battery positive electrode material. Preferably, based on the mass of the lithium-ion battery positive electrode material, the amount of the B-CNTs / GR powder added is 0.3%-0.6%, and the amount of the lithium fluoride added is 0.15%-0.5%. In the B-CNTs / GR powder, the mass ratio of boron oxide, carbon nanotubes and graphene is 20-40:1-5:3-8, preferably 30:3:5. In addition, there is no special limitation on the mixing method, as long as the purpose of uniform mixing can be achieved. Furthermore, the sintering temperature and time can be adjusted according to the type of matrix material, etc. According to an embodiment of the present invention, the sintering temperature is 700-910°C, the time is 10-12h, and preferably, the heating rate and the cooling rate are both 5°C / min. It can be understood that after sintering, a crushing and screening step is also included, which can be adjusted according to actual conditions. According to an embodiment of the present invention, the product is crushed and screened with a three-layer vibrating screen, the vibration frequency is 1000Hz, the mesh number of the first layer of the three-layer vibrating screen is 100 mesh, the mesh number of the second layer of the screen is 200 mesh, and the mesh number of the third layer of the screen is 325 mesh, to obtain a composite coated modified nickel cobalt manganese oxide lithium.

[0035] The third aspect of the present invention provides a lithium ion battery positive electrode sheet, which contains the composite coated modified lithium ion battery positive electrode material as described in the first aspect of the present invention or the composite coated modified lithium ion battery positive electrode material prepared by the preparation method as described in the second aspect of the present invention. It is understood that the composition and preparation of the lithium ion battery positive electrode sheet are not particularly limited, and can be prepared in a conventional manner in the art. In addition to the positive electrode material, its composition may also include functional additives such as conductive agents and binders, which will not be specifically described here.

[0036] The fourth aspect of the present invention discloses a lithium ion battery, characterized in that the positive electrode sheet is the positive electrode sheet of the lithium ion battery described in the third aspect of the present invention. It is understood that the composition of the lithium ion battery also includes a negative electrode sheet, a separator and an electrolyte, etc., and its specific composition is not particularly limited and can be selected conventionally in the art according to actual conditions.

[0037] The lithium-ion battery positive electrode sheet and lithium-ion battery in this article have the same advantages as the lithium-ion battery positive electrode material, and have excellent rate performance under high voltage and high temperature cycle stability.

[0038] The present invention is described below by means of specific examples. It should be noted that the following specific examples are only for illustrative purposes and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0039] Example 1

[0040] Preparation of B-CNTs / GR powder

[0041] 30g of multi-walled carbon nanotubes with an average diameter of 15nm are selected and refluxed with 64%wt nitric acid at 120°C for 10h, then placed in a beaker together with 50g of graphene, and 2L of anhydrous ethanol is added as a dispersant, ultrasonically dispersed for 1h, and stirred for 30min; then 300g of ground boron oxide is added, ultrasonically dispersed and stirred for 0.5h, and then heated to 450°C in an Ar gas flow atmosphere and kept warm for 2h; finally, after drying, grinding and sieving, a composite powder of carbon nanotubes filled with boron oxide and graphene, i.e., B-CNTs / GR powder, is obtained, and the mass ratio of carbon nanotubes, graphene and boron oxide in the powder is 3:5:30.

[0042] Preparation of composite coated modified lithium ion battery cathode materials

[0043] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% of B-CNTs / GR powder and 0.5% of battery-grade lithium fluoride are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0044] Sintering: after the mixed material is put into the sagger, it is shaken and marked, and the temperature is raised to 910°C at a heating rate of 5°C / min and sintered for 12 hours. The sintered material is crushed by a jet mill with a classification frequency of 5Hz and a feeding frequency of 20Hz to obtain a crushed powder;

[0045] Screening: The crushed powder is screened with a three-layer vibrating screen with a vibration frequency of 1000 Hz, the mesh number of the first layer of the three-layer vibrating screen is 100 mesh, the mesh number of the second layer of the screen is 200 mesh, and the mesh number of the third layer of the screen is 325 mesh, to obtain composite coated modified lithium cobalt oxide.

[0046] Example 2

[0047] Preparation of B-CNTs / GR powder

[0048] 30g of multi-walled carbon nanotubes with an average diameter of 15nm are selected and refluxed with 64%wt nitric acid at 120°C for 10h, then placed in a beaker together with 50g of graphene, and 2L of anhydrous ethanol is added as a dispersant, ultrasonically dispersed for 1h, and stirred for 30min; then 300g of ground boron oxide is added, ultrasonically dispersed and stirred for 0.5h, and then heated to 450°C in an Ar gas flow atmosphere and kept warm for 2h; finally, after drying, grinding and sieving, a composite powder of carbon nanotubes filled with boron oxide and graphene, i.e., B-CNTs / GR powder, is obtained, and the mass ratio of carbon nanotubes, graphene and boron oxide in the powder is 3:5:30.

[0049] Preparation of composite coated modified lithium ion battery cathode materials

[0050] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% of B-CNTs / GR powder and 0.35% of battery-grade lithium fluoride are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0051] Sintering: after the mixed material is put into the sagger, it is shaken and marked, and the temperature is raised to 910°C at a heating rate of 5°C / min and sintered for 12 hours. The sintered material is crushed by a jet mill with a classification frequency of 5Hz and a feeding frequency of 20Hz to obtain a crushed powder;

[0052] Screening: The crushed powder is screened with a three-layer vibrating screen with a vibration frequency of 1000 Hz, the mesh number of the first layer of the three-layer vibrating screen is 100 mesh, the mesh number of the second layer of the screen is 200 mesh, and the mesh number of the third layer of the screen is 325 mesh, to obtain composite coated modified lithium cobalt oxide.

[0053] Example 3

[0054] Preparation of B-CNTs / GR powder

[0055] 30g of multi-walled carbon nanotubes with an average diameter of 15nm are selected and refluxed with 64%wt nitric acid at 120°C for 10h, then placed in a beaker together with 50g of graphene, and 2L of anhydrous ethanol is added as a dispersant, ultrasonically dispersed for 1h, and stirred for 30min; then 300g of ground boron oxide is added, ultrasonically dispersed and stirred for 0.5h, and then heated to 450°C in an Ar gas flow atmosphere and kept warm for 2h; finally, after drying, grinding and sieving, a composite powder of carbon nanotubes filled with boron oxide and graphene, i.e., B-CNTs / GR powder, is obtained, and the mass ratio of carbon nanotubes, graphene and boron oxide in the powder is 3:5:30.

[0056] Preparation of composite coated modified lithium ion battery cathode materials

[0057] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm was placed in a high-speed mixer, and 0.2% of B-CNTs / GR powder and 0.5% of battery-grade lithium fluoride were added based on the mass of the lithium cobalt oxide powder. The mixture was mixed at 5000 rpm for 40 minutes to obtain a mixed material.

[0058] Sintering: after putting the mixed material into the sagger, shake it evenly and make grids and lines, sinter it at 910° C. for 12 hours, and grind the sintered material by a jet mill with a classification frequency of 5 Hz and a feeding frequency of 20 Hz to obtain a grinded powder.

[0059] Screening: The crushed powder was screened with a three-layer vibrating screen with a vibration frequency of 1000 Hz, the mesh number of the first layer of the three-layer vibrating screen was 100 mesh, the mesh number of the second layer of the screen was 200 mesh, and the mesh number of the third layer of the screen was 325 mesh, to obtain B-CNTs / GR powder-coated modified lithium cobalt oxide.

[0060] Example 4

[0061] Preparation of B-CNTs / GR powder

[0062] 30g of multi-walled carbon nanotubes with an average diameter of 15nm are selected and refluxed with 64%wt nitric acid at 120°C for 10h, then placed in a beaker together with 50g of graphene, and 2L of anhydrous ethanol is added as a dispersant, ultrasonically dispersed for 1h, and stirred for 30min; then 300g of ground boron oxide is added, ultrasonically dispersed and stirred for 0.5h, and then heated to 450°C in an Ar gas flow atmosphere and kept warm for 2h; finally, after drying, grinding and sieving, a composite powder of carbon nanotubes filled with boron oxide and graphene, i.e., B-CNTs / GR powder, is obtained, and the mass ratio of carbon nanotubes, graphene and boron oxide in the powder is 3:5:30.

[0063] Preparation of composite coated modified lithium ion battery cathode materials

[0064] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% of B-CNTs / GR powder and 0.5% of battery-grade lithium fluoride are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0065] Sintering: after the mixed material is put into the sagger, it is shaken and marked, and the temperature is raised to 750°C at a heating rate of 5°C / min and sintered for 12 hours. The sintered material is crushed by a jet mill with a classification frequency of 5Hz and a feeding frequency of 20Hz to obtain a crushed powder;

[0066] Screening: The crushed powder is screened with a three-layer vibrating screen with a vibration frequency of 1000 Hz, the mesh number of the first layer of the three-layer vibrating screen is 100 mesh, the mesh number of the second layer of the screen is 200 mesh, and the mesh number of the third layer of the screen is 325 mesh, to obtain composite coated modified lithium cobalt oxide.

[0067] Comparative Example 1

[0068] Preparation of CNTs / GR powder

[0069] 30g of multi-walled carbon nanotubes with an average diameter of 15nm were selected and refluxed in 64wt% nitric acid at 120℃ for 10h, and then placed in a beaker with 50g of graphene, and 2L of anhydrous ethanol was added as a dispersant, ultrasonically dispersed for 1h, stirred for 30min; then heated to 450℃ in an Ar gas flow atmosphere and kept warm for 2h; finally dried, ground and sieved to obtain a composite powder of carbon nanotubes and graphene, namely CNTs / GR powder. The mass ratio of carbon nanotubes to graphene in the powder is 3:5.

[0070] Preparation of composite coated modified lithium ion battery cathode materials

[0071] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% of CNTs / GR powder and 0.5% of battery-grade lithium fluoride are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0072] Sintering: same as Example 1;

[0073] Sieving: Same as Example 1.

[0074] Comparative Example 2

[0075] Preparation of lithium fluoride / boron oxide composite coated modified lithium ion battery positive electrode material

[0076] Mixing: lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% battery-grade lithium fluoride and 0.4% boron oxide are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0077] Sintering: same as Example 1;

[0078] Sieving: Same as Example 1.

[0079] Comparative Example 3

[0080] Preparation of B-CNTs / GR powder

[0081] Same as Example 1.

[0082] Preparation of composite coated modified lithium ion battery cathode materials

[0083] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% of B-CNTs / GR powder is added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0084] Sintering: same as Example 1;

[0085] Sieving: Same as Example 1.

[0086] Comparative Example 4

[0087] Preparation of CNTs / GR powder

[0088] Same as Comparative Example 1.

[0089] Preparation of composite coated modified lithium ion battery cathode materials

[0090] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.5% of B-CNTs / GR powder, 0.4% of boron oxide powder and 0.5% of lithium fluoride powder are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0091] Sintering: same as comparative example 1;

[0092] Sieving: Same as Comparative Example 1.

[0093] Test Case

[0094] The lithium cobalt oxide prepared in the embodiment and the comparative example was used as the positive electrode active material, and graphite was used as the negative electrode to assemble a soft pack battery. The battery performance tester was used to test the battery performance. The charge and discharge cut-off voltage was 3-4.45V. The results are shown in Table 1

[0095] Table 1 Test results of electrical properties of lithium cobalt oxide positive electrode materials

[0096]

[0097] The test results are shown in Table 1. After the composite powder of carbon nanotubes and graphene is filled with boron oxide and lithium cobalt oxide is coated with lithium fluoride, the comprehensive electrical properties of the material are optimal.

[0098] Other usual implementation plans

[0099] Example 5

[0100] Preparation of B-CNTs / GR powder

[0101] 10g of multi-walled carbon nanotubes with an average diameter of 20nm were selected and refluxed in 64%wt nitric acid at 100°C for 15h, then placed in a beaker together with 30g of graphene, and 2L of anhydrous ethanol was added as a dispersant, ultrasonically dispersed for 1h, and stirred for 30min; then 200g of ground boron oxide was added, ultrasonically dispersed and stirred for 0.5h, and then heated to 400°C in an Ar gas flow atmosphere and kept warm for 2.5h; finally, after drying, grinding and sieving, a composite powder of boron oxide-filled carbon nanotubes and graphene, namely B-CNTs / GR powder, was obtained.

[0102] Preparation of composite coated modified lithium ion battery cathode materials

[0103] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.3% of B-CNTs / GR powder and 0.2% of battery-grade lithium fluoride are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0104] Sintering: after the mixed material is put into the sagger, it is shaken and marked, and the temperature is raised to 700°C at a heating rate of 5°C / min and sintered for 11 hours. The sintered material is crushed by a jet mill with a classification frequency of 5Hz and a feeding frequency of 20Hz to obtain a crushed powder;

[0105] Screening: The crushed powder is screened with a three-layer vibrating screen with a vibration frequency of 1000 Hz, the mesh number of the first layer of the three-layer vibrating screen is 100 mesh, the mesh number of the second layer of the screen is 200 mesh, and the mesh number of the third layer of the screen is 325 mesh, to obtain composite coated modified lithium cobalt oxide.

[0106] Example 6

[0107] Preparation of B-CNTs / GR powder

[0108] 50g of multi-walled carbon nanotubes with an average diameter of 25nm were selected and refluxed in 64%wt nitric acid at 150°C for 12h, then placed in a beaker together with 80g of graphene, and 2L of anhydrous ethanol was added as a dispersant, ultrasonically dispersed for 1h, and stirred for 30min; then 400g of ground boron oxide was added, ultrasonically dispersed and stirred for 0.5h, and then heated to 500°C in an Ar gas flow atmosphere and kept warm for 3h; finally, after drying, grinding and sieving, a composite powder of boron oxide-filled carbon nanotubes and graphene, namely B-CNTs / GR powder, was obtained.

[0109] Preparation of composite coated modified lithium ion battery cathode materials

[0110] Mixing: Lithium cobalt oxide powder with a particle size of 8 μm is placed in a high-speed mixer, and 0.6% of B-CNTs / GR powder and 0.15% of battery-grade lithium fluoride are added based on the mass of the lithium cobalt oxide powder, and mixed at 5000 rpm for 40 minutes to obtain a mixed material;

[0111] Sintering: after the mixed material is put into the sagger, it is shaken and marked, and the temperature is raised to 950°C at a heating rate of 5°C / min and sintered for 10 hours. The sintered material is crushed by a jet mill with a classification frequency of 5Hz and a feeding frequency of 20Hz to obtain a crushed powder;

[0112] Screening: The crushed powder is screened with a three-layer vibrating screen with a vibration frequency of 1000 Hz, the mesh number of the first layer of the three-layer vibrating screen is 100 mesh, the mesh number of the second layer of the screen is 200 mesh, and the mesh number of the third layer of the screen is 325 mesh, to obtain composite coated modified lithium cobalt oxide.

[0113] Example 7

[0114] The lithium-ion battery positive electrode material in Example 1 is replaced with lithium manganese oxide, lithium iron phosphate, and ternary material nickel cobalt lithium manganese oxide for the same composite coating, which can also improve the electrical properties of the material. Due to limited space, it will not be elaborated here.

[0115] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A composite coated modified lithium ion battery positive electrode material, characterized in that: include: A base material, wherein the base material is a positive electrode material for a lithium-ion battery; and a composite coating layer with a thickness of 10nm-200nm formed on the surface of the base material, wherein the composite coating layer contains a first component and a second component, wherein the first component is a composite of boron oxide loaded carbon nanotubes and graphene, and the second component is lithium fluoride; in the composite coating layer, a part of the boron oxide is filled in the carbon nanotubes, and a part is evenly distributed in the coating layer, and at the same time, the boron oxide and lithium fluoride are composited to construct a three-dimensional coating layer; Based on the mass of the lithium-ion battery positive electrode material, the addition amount of the first component is 0.3%-0.6%, and the addition amount of the lithium fluoride is 0.15%-0.5%; in the first component, the mass ratio of boron oxide, carbon nanotubes and graphene is 20-40:1-5:3-8.

2. The composite coated modified lithium ion battery positive electrode material according to claim 1, characterized in that: The positive electrode material of the lithium-ion battery is selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate and ternary materials.

3. The composite coated modified lithium ion battery positive electrode material according to claim 2, characterized in that: The lithium-ion battery positive electrode material is selected from lithium cobalt oxide.

4. A method for preparing a composite coated modified lithium ion battery positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Providing B-CNTs / GR powder: After the carbon nanotubes are acidified, they are fully dispersed with graphene and boron oxide, and then treated at high temperature under anaerobic conditions to obtain a composite powder of boron oxide-loaded carbon nanotubes and graphene, namely B-CNTs / GR powder; The B-CNTs / GR powder, lithium fluoride and lithium ion battery positive electrode material are fully mixed and sintered to obtain a composite coated modified lithium ion battery positive electrode material.

5. The preparation method according to claim 4, characterized in that: The carbon nanotubes are multi-walled carbon nanotubes with an average diameter of 15-25 nm.

6. The preparation method according to claim 4, characterized in that: The temperature of the high temperature treatment is 400-500° C., and the insulation time is 2-3 hours.

7. The preparation method according to claim 4, characterized in that: Based on the mass of the lithium-ion battery positive electrode material, the added amount of the B-CNTs / GR powder is 0.3%-0.6%, and the added amount of the lithium fluoride is 0.15%-0.5%; in the B-CNTs / GR powder, the mass ratio of boron oxide, carbon nanotubes and graphene is 20-40:1-5:3-8.

8. The preparation method according to claim 4, characterized in that: The sintering temperature is 700-950° C. and the sintering time is 10-12 hours.

9. A positive electrode sheet for a lithium-ion battery, characterized in that: It contains the composite coated modified lithium ion battery positive electrode material as described in any one of claims 1 to 3 or the composite coated modified lithium ion battery positive electrode material prepared by the preparation method as described in any one of claims 4 to 8.

10. A lithium ion battery, characterized in that: The positive electrode sheet is the lithium-ion battery positive electrode sheet as claimed in claim 9.

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