Positive electrode material and preparation method thereof, positive electrode sheet, battery, and electrical equipment

Abstract

The present invention provides a positive electrode material, a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. The positive electrode material comprises a core and micro-nanostructures distributed on the core surface. The core and micro-nanostructures are the same positive electrode material; the micro-nanostructures comprise a plurality of pillars. The surface of the positive electrode material provided herein includes micro-nanostructures, which increase the material's contact angle, making it superhydrophobic, effectively reducing the formation of residual alkali, thereby increasing the battery's initial discharge capacity and cycle capacity retention, and improving the battery's electrochemical performance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] Lithium ion residues are likely to remain on the surface of the positive electrode material, which will cause interfacial side reactions between the electrode material surface and the electrolyte to produce residual alkali, exacerbating the deterioration of the electrode surface structure and battery performance.

[0003] In order to reduce the residual alkali on the surface of the positive electrode material, it can be achieved by washing the surface of the material. However, although washing can reduce the residual lithium ions on the surface, it will cause Li + / H + Ion exchange occurs between + The loss of cations will aggravate the cation mixing phenomenon, resulting in a decrease in battery performance.

[0004] Therefore, how to reduce the formation of residual alkali on the surface of the positive electrode material while ensuring stable battery performance is an urgent problem to be solved. Summary of the Invention

[0005] The present invention provides a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. The micro-nano structure included in the positive electrode material can effectively reduce the adhesion between water droplets and the material, reduce the residence time and contact area of ​​water molecules on the surface, and thus reduce the residual alkali on the surface. Formation of residual base (reaction to form residual base: ), thereby improving battery performance.

[0006] In a first aspect of the present invention, a positive electrode material is provided, comprising a core and micro-nano structures distributed on the surface of the core, wherein the core and the micro-nano structures are the same positive electrode material;

[0007] The micro-nano structure includes a plurality of columns.

[0008] According to an embodiment of the present invention, the plurality of columns are arranged at equal intervals.

[0009] According to one embodiment of the present invention, the diameter R of the pillar is 8 nm to 15 nm;

[0010] And / or, the height H of the pillars is 15 nm to 45 nm;

[0011] And / or, the distance L between the columns is 3 nm to 8 nm.

[0012] According to one embodiment of the present invention, the L / R of the micro-nanostructure is 0.3-0.6;

[0013] And / or, the H / L of the micro-nano structure is 5-10.

[0014] According to one embodiment of the present invention, the positive electrode material includes a nickel-containing material. The nickel-containing material includes and / or , where 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, and x+y+z=1.

[0015] According to an embodiment of the present invention, the positive electrode material further includes: a coating layer, the coating layer coating at least a portion of the surface of the positive electrode material; the coating layer includes a hydrophobic chemical group or a fluorinated substance.

[0016] According to one embodiment of the present invention, the hydrophobic chemical group includes 、 At least one of; the fluorinated substance includes At least one of .

[0017] A second aspect of the present invention provides a method for preparing the positive electrode material according to the first aspect, the method comprising the following steps:

[0018] The positive electrode material is obtained by etching the initial positive electrode material particles.

[0019] According to one embodiment of the present invention, the etching of initial positive electrode material particles to obtain the positive electrode material comprises:

[0020] The positive electrode material is obtained by etching the initial positive electrode material particles with a laser.

[0021] According to one embodiment of the present invention, the power of the laser is 5W~50W;

[0022] And / or, the scanning speed of the laser is ;

[0023] And / or, the laser etching time is 10 min to 120 min.

[0024] According to one embodiment of the present invention, the preparation method further includes:

[0025] The positive electrode material is mixed with a solution of a substance providing hydrophobic chemical groups to obtain a positive electrode material having a coating layer with hydrophobic chemical groups.

[0026] According to one embodiment of the present invention, the preparation method further includes:

[0027] The positive electrode material and the fluorinated substance are mixed and ground to obtain a positive electrode material having a coating layer with the fluorinated substance.

[0028] A third aspect of the present invention provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector;

[0029] The positive electrode active material layer includes the positive electrode material described in the first aspect or the positive electrode material prepared by the preparation method of the positive electrode material described in the second aspect.

[0030] A fourth aspect of the present invention provides a battery, comprising the positive electrode sheet described in the third aspect.

[0031] According to a fifth aspect of the present invention, there is provided an electrical device, wherein the electrical device comprises the battery according to the fourth aspect.

[0032] The present invention provides a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. The surface of the positive electrode material has a micro-nano structure, which includes a plurality of columns. The columns arranged on the surface of the positive electrode material core can increase the contact angle of the material surface, reduce the spreading of water droplets, and make the positive electrode material super-hydrophobic. The high roughness of the hydrophobic surface causes water vapor to condense into droplets and roll off through the "lotus effect", reducing the residence time and contact area of ​​water molecules on the surface of the positive electrode material, thereby reducing surface residual alkali Formation of residual base (reaction to form residual base: ), and the micro-nano structure increases the active contact area, which is beneficial to the transmission of ions, thereby increasing the initial discharge capacity and cycle capacity retention rate of the battery and improving the electrochemical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the positive electrode material provided in this application. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0035] A first aspect of the present invention provides a positive electrode material, which includes a core and a micro-nano structure distributed on the surface of the core, wherein the core and the micro-nano structure are the same positive electrode material; the micro-nano structure includes a plurality of columns.

[0036] Among them, the core and the micro-nano structure are the same positive electrode material, that is, the core and the micro-nano structure are an integrated structure, and the core and the columns distributed on the surface of the core are collectively called positive electrode materials.

[0037] The production process and inherent properties of positive electrode materials result in the presence of residual lithium ions on their surfaces. Exposure to environments containing H2O and CO2 can result in the formation of residual alkali on the surface. Excessive residual alkali on the surface can affect battery performance. This invention aims to reduce the contact area between the material surface and water droplets by forming a micro-nanostructure on the material surface. The multiple pillars included in the micro-nanostructure allow water droplets to form a "bridge"-like structure on the material surface, reducing direct contact between the material surface and water droplets, thereby reducing the formation of residual alkali and improving battery performance.

[0038] Therefore, the surface of the positive electrode material provided by the present invention has a micro-nano structure, which includes a plurality of columns. The columns arranged on the surface of the positive electrode material core can increase the contact angle of the material surface, reduce the spreading of water droplets, and make the positive electrode material super hydrophobic. The high roughness of the hydrophobic surface condenses water vapor into droplets and rolls off through the "lotus effect", reducing the residence time and contact area of ​​water molecules on the surface of the positive electrode material, thereby reducing the residual alkali on the surface. Formation of residual base (reaction to form residual base: ), and the micro-nano structure increases the active contact area, which is beneficial to the transmission of ions, thereby increasing the initial discharge capacity and cycle capacity retention rate of the battery and improving the electrochemical performance of the battery.

[0039] For example, the schematic diagram of the positive electrode material provided in this application is as follows Figure 1 As shown, R is the diameter of the micro-nano structure column, H is the height of the micro-nano structure column, and L is the distance between the micro-nano structure columns.

[0040] In a preferred embodiment, multiple pillars are arranged at equal intervals. Arranging the micro-nanostructured pillars at equal intervals on the core surface results in a uniform distribution of micro-nanostructures within the positive electrode material, thereby ensuring that all locations within the positive electrode material possess superhydrophobicity, reducing direct contact between the material surface and water droplets and lowering the formation of residual alkali on the surface. Consequently, batteries fabricated using this positive electrode material exhibit superior performance.

[0041] In a specific embodiment, the diameter R of the pillars is 8 nm to 15 nm; and / or the height H of the pillars is 15 nm to 45 nm; and / or the spacing L between the pillars is 3 nm to 8 nm. Exemplarily, the diameter R of the pillars is 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, or a range consisting of any two of the above values. Exemplarily, the height H of the pillars is 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or a range consisting of any two of the above values. Exemplarily, the spacing L between the pillars is 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, or a range consisting of any two of the above values. By controlling the diameter and height of the pillars within the above ranges, structural strength and reactivity can be balanced, thereby maintaining good mechanical strength and specific surface area. The spacing between the columns is controlled within the range of 3nm to 8nm, so that the micro-nanostructures in the positive electrode material are evenly distributed, thereby ensuring that all positions of the positive electrode material have superhydrophobicity, reducing direct contact between the material surface and water droplets, and reducing the formation of residual alkali on the surface. Therefore, the battery performance prepared using this positive electrode material is more stable.

[0042] In a specific embodiment, the L / R of the micro-nanostructure is 0.3-0.6; and / or the H / L of the micro-nanostructure is 5-10. Exemplarily, the L / R of the micro-nanostructure is 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6 or a range consisting of any two of the above values. Exemplarily, the H / L of the micro-nanostructure is 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or a range consisting of any two of the above values. L / R reflects the spatial openness and mechanical stability of the structure. Within this range, the micro-nanostructure is dense and has moderate strength. H / L determines the aspect ratio and stress distribution of the columnar array. Within this range, the stability of the micro-nanostructure can be ensured while facilitating vertical ion transport.

[0043] In a preferred embodiment, the positive electrode material includes a nickel-containing material. The nickel-containing material includes and / or , where 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, and x+y+z=1. The positive electrode material with 0.6≤x≤1 is a high-nickel positive electrode material. Due to its high nickel content, more lithium ions remain on the surface of the material. Therefore, the high-nickel positive electrode material containing micro-nano structure has a more significant effect in reducing the formation of residual alkali.

[0044] In a preferred embodiment, the positive electrode material further comprises a coating layer, which coats at least a portion of the surface of the positive electrode material; the coating layer comprises a hydrophobic chemical group or a fluorinated substance. In addition to the micro-nanostructure, a hydrophobic coating layer can be applied to the surface of the material to further enhance the hydrophobicity of the positive electrode material, thereby reducing the formation of residual alkali on the material surface and improving battery performance.

[0045] Among them, the hydrophobic chemical group can be one or more of a hydrocarbon group, an ester group, a nitro group, a halogen atom, etc.; the fluorinated substance can be one or more of polytetrafluoroethylene, fluorinated graphene, polyvinyl fluoride, lithium fluoride, etc., which is not limited in this embodiment.

[0046] In a preferred embodiment, the hydrophobic chemical group comprises At least one of; Fluorinated substances include The positive electrode material prepared by using the coating layer selected from the above materials has better hydrophobicity.

[0047] A second aspect of the present invention provides a method for preparing the positive electrode material according to the first aspect, the method comprising the following steps: etching initial positive electrode material particles using an etching method to obtain the positive electrode material.

[0048] The initial positive electrode material particles are positive electrode material particles that have not been etched, that is, the initial positive electrode material particles do not include micro-nano structures.

[0049] The etching method may include chemical etching, plasma etching, laser etching, etc., which is not limited in this embodiment.

[0050] Specifically, after cleaning the initial positive electrode material particles, a photoresist is coated on their surface, a mask pattern is designed, and they are immersed in an etching solution to obtain the positive electrode material by chemical reaction; or a high-density plasma is generated by an excitation source such as radio frequency, such as using The mixed gas generates volatile fluorides based on the reaction of F radicals with metals, and ion bombardment enhances anisotropy to form a vertical columnar structure, thereby obtaining a positive electrode material with a micro-nano structure.

[0051] In a specific embodiment, etching the initial positive electrode material particles to obtain the positive electrode material comprises: etching the initial positive electrode material particles to obtain the positive electrode material using a laser.

[0052] Specifically, the surface of the initial cathode material particles is cleaned with an organic solvent, fixed to aluminum foil, and then etched using a nanosecond laser under the protection of an inert gas. The etching process can be monitored in real time using a microscope to ensure that the structure formed meets the design requirements. After processing is completed, the sample is allowed to cool naturally to obtain the cathode material. Before etching begins, parameters such as laser wavelength, laser power, scanning speed, and repetition rate can be set in the nanosecond laser to obtain the material that meets the requirements.

[0053] The organic solvent may be one or more of acetone, ethanol, etc.; the inert gas may be one or more of nitrogen, argon, etc., which is not limited in this embodiment.

[0054] In a specific embodiment, the power of the laser is 5W~50W; and / or the scanning speed of the laser is ; and / or, the laser etching time is 10 min to 120 min. Exemplarily, the laser power is 5 W, 10 W, 15 W, 20 W, 25 W, 30 W, 35 W, 40 W, 45 W, 50 W, or a range consisting of any two of the above values. Exemplarily, the laser scanning speed is 0.001 μm / s, 0.002 μm / s, 0.003 μm / s, 0.004 μm / s, 0.005 μm / s, 0.006 μm / s, 0.007 μm / s, 0.008 μm / s, 0.009 μm / s, 0.01 μm / s, or a range consisting of any two of the above values. For example, the laser etching time is 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes, or a range consisting of any two of the above values. By controlling the scanning speed, etching time, and power during laser etching, the shape, size, and spacing of the pillars can be controlled within a suitable range, thereby reducing the formation of residual alkali on the material surface and improving battery performance.

[0055] In a specific embodiment, the wavelength of the laser is 200nm~400nm, preferably 355nm; the pulse width of the laser is 10 nanoseconds~50 nanoseconds; the repetition frequency of the laser is Exemplarily, the laser pulse width is 10 nanoseconds, 20 nanoseconds, 30 nanoseconds, 40 nanoseconds, 50 nanoseconds or a range consisting of any two of the above values. Exemplarily, the laser repetition frequency is 、 、 Or a range consisting of any two of the above values.

[0056] In a preferred embodiment, the preparation method further comprises: mixing the positive electrode material with a solution of a substance providing hydrophobic chemical groups to obtain a positive electrode material having a coating layer with hydrophobic chemical groups. For example, the positive electrode material is vacuum dried at 80°C for 12 hours to remove surface adsorbed water; a silane coupling agent (3-aminopropyltriethoxysilane) solution is prepared and dissolved in an ethanol / water mixed solvent (9:1 volume ratio) at a mass ratio of 0.5% to 5% by weight, stirred for 30 minutes to hydrolyze and generate silanols; the positive electrode material is dispersed in the solution, ultrasonically treated for 1 hour to ensure sufficient surface contact, and magnetically stirred for 3 to 6 hours to promote chemical bonding (Si-OM, where M is the metal on the material surface); finally, the cathode material is centrifuged, washed with ethanol three times to remove unreacted coupling agent, and vacuum dried at 60°C for 12 hours to obtain the positive electrode material having a surface coating layer. Coating the surface of the positive electrode material with a coating layer having hydrophobic chemical groups can be combined with the micro-nano structure to further enhance the hydrophobicity of the positive electrode material, thereby reducing the formation of residual alkali on the surface of the material and improving battery performance.

[0057] In a preferred embodiment, the preparation method further comprises: mixing and grinding the positive electrode material with a fluorinated substance to obtain a positive electrode material having a coating layer comprising the fluorinated substance. For example, the positive electrode material and LiF powder are mixed at a mass ratio of 0.5% to 5%, ball milled (at 300 rpm) for 2 hours to achieve uniform mixing, and sintered in an oxygen atmosphere at 400°C to 600°C for 4 to 6 hours to obtain a positive electrode material having a surface coating layer. Coating the positive electrode material with a fluorinated substance coating layer can be combined with micro-nanostructures to further enhance the hydrophobicity of the positive electrode material, thereby reducing the formation of residual alkali on the material surface and improving battery performance.

[0058] The third aspect of the present invention provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector; the positive electrode active material layer comprises the positive electrode material of the first aspect or the positive electrode material prepared by the preparation method of the positive electrode material of the second aspect.

[0059] The positive electrode current collector of the present invention can be selected from positive electrode current collectors commonly used in the art, such as aluminum foil.

[0060] The positive electrode active material layer of the present invention also includes components such as a conductive agent and a binder. The conductive agent includes, but is not limited to, one or more of conductive carbon black, graphene, acetylene black, Ketjen black, and carbon nanofibers. The binder includes, but is not limited to, one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, and styrene-butadiene rubber.

[0061] In a specific embodiment, the positive electrode sheet can be prepared by the following method: the positive electrode material, the conductive agent and the binder are dispersed in a solvent in proportion to obtain a slurry, and the slurry is then coated on at least one surface of the positive electrode collector. The positive electrode sheet can be obtained after drying, slitting and rolling.

[0062] The fourth aspect of the present invention provides a battery comprising the positive electrode sheet of the third aspect. In addition to the positive electrode sheet, the battery of the present invention further comprises a negative electrode sheet and an electrolyte.

[0063] Among them, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. Among them, the negative electrode current collector can be selected from the negative electrode current collectors conventionally used in the art, such as copper foil. The negative electrode active material layer can also refer to the conventional composition in the art, for example, the negative electrode active material layer includes a negative electrode active substance, a conductive agent and a binder. The negative electrode active substance can be selected from the negative electrode active substances conventionally used in the art, including but not limited to one or more of natural graphite, artificial graphite, silicon-carbon material, silicon-oxygen material, and hard carbon. The composition of the conductive agent and the binder can refer to the types of conductive agent and binder in the positive electrode sheet, which will not be repeated here.

[0064] The electrolyte is a medium between the positive and negative electrodes that conducts lithium ions. It can be a gel, solid, or liquid electrolyte. This application does not specifically limit the type of electrolyte; it can be selected from gel, solid, or liquid electrolytes commonly used in the art.

[0065] In a specific embodiment, the battery of the present invention can be prepared by the following method: a positive electrode sheet, a separator, and a negative electrode sheet are wound or stacked to form a bare cell, and the bare cell is encapsulated in a pre-stamped aluminum-plastic film bag. The encapsulated battery is dried at 85°C, and then an electrolyte is injected into the dried battery. The battery is then allowed to stand, formed, and resealed to obtain the battery of the present invention.

[0066] The batteries of the present application may include battery cells, battery modules, and battery packs. In some embodiments, battery cells may be assembled into a battery module, which may contain one or more battery cells, with the specific number selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, which may contain one or more battery modules, with the specific number selected by those skilled in the art based on the application and capacity of the battery pack.

[0067] There is no particular restriction on the specific type of battery in this application. For example, from the perspective of shape, the battery includes but is not limited to square shell batteries, soft pack batteries and cylindrical batteries, etc., and this application does not impose any particular restrictions. From the perspective of the core structure, the core of the battery can be a wound core (i.e., the positive electrode sheet, the negative electrode sheet and the separator are stacked and then wound to form the core), or it can be a laminated core (i.e., multiple positive electrode sheets, negative electrode sheets and separators are stacked to form the core). The outer shell can be a hard shell (such as a steel shell, a hard plastic shell, etc.), or a soft shell (such as an aluminum plastic film, a bag-type soft shell, etc.). This application does not impose any particular restrictions.

[0068] A fifth aspect of the present invention provides an electrical device comprising the battery described above. The present invention does not particularly limit the type of electrical device; the device may be any electrical device comprising the battery, including but not limited to mobile phones, portable devices, laptop computers, electric bicycles, electric vehicles, electric toys, and energy storage devices.

[0069] The following will introduce the positive electrode material and its preparation method, positive electrode sheet, battery, and electrical equipment provided by the present invention in detail through specific examples.

[0070] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are conventional reagents, conventional materials, and conventional instruments in the art and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0071] Example 1

[0072] Preparation of positive electrode materials

[0073] 1) Take the initial positive electrode material particles Disperse in ethanol, stir at room temperature for 2 hours to obtain a mixed solution, then heat it to 80°C while stirring until the solvent evaporates, and then dry the remaining material in a vacuum oven at 100°C for 12 hours to obtain cleaned initial positive electrode material particles;

[0074] 2) Use CAD software to design an evenly spaced circular array on the surface of the initial positive electrode material particles, with a diameter R of 8nm and a spacing L of 3nm, export it as a vector file, import the vector file into the laser instrument, and make the laser scan along the path. Fix the cleaned initial positive electrode material particles on aluminum foil. Under the protection of argon gas, use a nanosecond laser with a laser wavelength of 355nm, a laser power of 15W, and a scanning speed of , start the etching process, and after etching for 30 minutes, allow it to cool naturally to obtain the positive electrode material.

[0075] Example 2

[0076] The difference between this embodiment and embodiment 1 is that, in step 2), CAD software is used to design randomly arranged circular patterns on the surface of the initial positive electrode material particles, with a diameter R of 8 nm and varying spacings. The other conditions are the same as those in embodiment 1.

[0077] Example 3

[0078] The difference between this embodiment and embodiment 1 is that in step 2), the diameter R of the circular array of the CAD software is 10 nm, the spacing L is 5 nm, the laser power is 25 W, and the scanning speed is , the etching time is 60 min, and the other conditions are the same as those in Example 1.

[0079] Example 4

[0080] The difference between this embodiment and embodiment 1 is that in step 2), the diameter R of the circular array of the CAD software is 15 nm, the spacing L is 8 nm, the laser power is 40 W, and the scanning speed is , etching time is 90 min, and other conditions are the same as those in Example 1.

[0081] Example 5

[0082] The difference between this embodiment and embodiment 1 is that in step 2), the diameter R of the circular array in the CAD software is 5 nm, the spacing L is 1 nm, the laser power is 5 W, the scanning speed is 0.001 μm / s, and the etching time is 20 min. The other conditions are the same as those in embodiment 1.

[0083] Example 6

[0084] The difference between this embodiment and embodiment 1 is that in step 2), the diameter R of the circular array of the CAD software is 20 nm, the spacing L is 10 nm, the laser power is 50 W, and the scanning speed is , etching time is 100 min, and other conditions are the same as those in Example 1.

[0085] Example 7

[0086] The difference between this embodiment and embodiment 1 is that in step 2), the spacing L is 1 nm, the laser power is 5 W, and the scanning speed is , etching time is 20 min, and other conditions are the same as those in Example 1.

[0087] Example 8

[0088] The difference between this embodiment and embodiment 1 is that in step 2), the diameter R of the circular array in the CAD software is 5 nm, the spacing L is 1 nm, the laser power is 5 W, and the scanning speed is 0.001 μm / s. The other conditions are the same as those in embodiment 1.

[0089] Example 9

[0090] The difference between this embodiment and embodiment 1 is that in step 2), the diameter R of the circular array of the CAD software is 5 nm, the spacing L is 5 nm, the laser power is 25 W, and the scanning speed is , etching time is 20 min, and other conditions are the same as those in Example 1.

[0091] Example 10

[0092] The difference between this embodiment and embodiment 1 is that in step 2), the spacing L is 1 nm, the laser power is 5 W, and the scanning speed is , the remaining conditions are the same as in Example 1.

[0093] Example 11

[0094] The difference between this embodiment and embodiment 1 is that the etching time in step 2) is 20 minutes, and the other conditions are the same as those in embodiment 1.

[0095] Example 12

[0096] The difference between this embodiment and embodiment 1 is that the diameter R of the circular array in the CAD software in step 2) is 5 nm, and the other conditions are the same as those in embodiment 1.

[0097] Example 13

[0098] The difference between this embodiment and embodiment 1 is that the initial positive electrode material particles in step 1) are , the remaining conditions are the same as in Example 1.

[0099] Example 14

[0100] The difference between this embodiment and embodiment 1 is that the initial positive electrode material particles in step 1) are , the remaining conditions are the same as in Example 1.

[0101] Example 15

[0102] The difference between this embodiment and embodiment 1 is that the initial positive electrode material particles in step 1) are , the remaining conditions are the same as in Example 1.

[0103] Example 16

[0104] The difference between this embodiment and embodiment 1 is that step 3 is added) the positive electrode material is vacuum dried at 80° C. for 12 hours to remove surface adsorbed water; a (3-mercaptopropyl)trimethoxysilane solution is prepared, dissolved in an ethanol / water mixed solvent (volume ratio of 9:1) at a 1% mass ratio, and stirred for 30 minutes; the positive electrode material is dispersed in the above solution, ultrasonically treated for 1 hour, and magnetically stirred for 5 hours; finally, centrifuged, washed with ethanol three times, and vacuum dried at 60° C. for 12 hours to obtain a positive electrode material with a surface coating layer. The remaining conditions are the same as those in embodiment 1.

[0105] Example 17

[0106] The difference between this embodiment and embodiment 1 is that step 3) the positive electrode material is added The powders were mixed at a mass ratio of 1%, ball milled (rotation speed 300 rpm) for 2 h, and sintered at 500° C. for 5 h in an oxygen atmosphere to obtain a positive electrode material with a coating layer on the surface. The other conditions were the same as in Example 1.

[0107] Example 18

[0108] The difference between this embodiment and embodiment 16 is that (3-mercaptopropyl)trimethoxysilane in step 3) is replaced with trimethylmethoxysilane, and the other conditions are the same as those in embodiment 16.

[0109] Example 19

[0110] The difference between this embodiment and embodiment 17 is that in step 3) Replaced with LiF, the other conditions are the same as in Example 17.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Example 1 is that step 1) is not included, that is, the material is not etched, and the other conditions are the same as those in Example 1.

[0113] Test Case

[0114] 1. The following tests were performed on the positive electrode materials of the above embodiments and comparative examples:

[0115] 1. Residual alkali content test

[0116] Testing Method: The positive electrode materials from the above examples and comparative examples were stored in a cabinet at 25°C and 80% humidity for 14 days. The residual alkali content of the materials was measured before and after 14 days. Titration with a 0.01M HCl standard solution was performed to generate a titration curve, which was used to determine the LiOH content in the positive electrode materials. The results are shown in Table 2.

[0117] 2. Contact angle test

[0118] Test method: The cathode material powders of the above-mentioned embodiments and comparative examples were placed in a mold and a pressure of 30 MPa was applied using a tablet press to form flat and dense discs (about 1 cm in diameter). The sample surface was treated with a plasma cleaner for 3 minutes to remove organic contamination. 4 μL of ultrapure water was drawn up with a microsyringe and a droplet was gently deposited on the sample surface. An image was captured within 10 seconds after the droplet contacted the surface. The droplet profile was fitted using software in combination with the Young-Laplace equation to calculate the contact angle. At least five different positions of each sample were measured and the average value was taken. The results are shown in Table 2.

[0119] 3. Column R, H, L test

[0120] Test method: The cathode material is placed on the sample stage of the SEM, and the columnar structure on the sample surface is observed by setting the acceleration voltage (usually between 10kV and 50kV) and the appropriate magnification (10,000-50,000 times). The image acquisition system is used to photograph different areas of the material to obtain information on the columnar structure at different positions. Finally, the captured SEM image is opened using the ImageJ image software, and the diameter R, height H and spacing L of the columnar structure on the surface of the cathode material are measured using the ruler tool. The measurement tool is selected in the software, and multiple measurements are averaged. At least 50 different positions are measured to improve the reliability of the data. The average value is taken and recorded. The results are shown in Table 1.

[0121] 2. The positive electrode materials of the above embodiment and comparative example were prepared into positive electrode sheets before and after being placed for 14 days, and then assembled with the negative electrode sheet, electrolyte and separator according to the following method to obtain button-type half-cells. The method is as follows:

[0122] 1) Mix the positive electrode material, PVDF, and conductive agent SuperP in a ratio of 90:5:5 and stir evenly to obtain a slurry containing the positive electrode material. Apply the slurry onto an aluminum foil current collector, dry it, and roll-press it into a sheet to obtain a positive electrode sheet.

[0123] 2) Mix the above-mentioned positive electrode sheet with the separator, negative electrode (metal lithium) and electrolyte (ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate) in a volume ratio of 1:1:1 in a glove box, and then add 1M ) are assembled to obtain a button half-cell.

[0124] The button half-cell assembled above was tested for the following performance:

[0125] 1. Initial discharge specific capacity

[0126] Test method: On a charge and discharge cabinet, the 0.1C capacity measurement was performed in the voltage range of 2.8~4.3V. The initial 1C setting was 200mA / g. The battery was cycled for 3 cycles at 0.1C in this voltage range at 25℃. The capacity of the last cycle was taken as the initial discharge specific capacity. The results are shown in Table 2.

[0127] 2. Cycle capacity retention rate

[0128] Test method: On a charge and discharge cabinet, cycle 100 times at a current of 1C (the discharge capacity measured above) in the voltage range of 2.8-4.3V. The discharge capacity of the last cycle divided by the discharge capacity of the first cycle is the cycle capacity retention rate. The results are shown in Table 2.

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135] As shown in Table 1 and Table 2, it can be seen from the comparison of Example 1 and Comparative Example 1 that when the positive electrode material includes a micro-nano structure, the contact angle of the material surface is significantly increased, indicating that the positive electrode material has super-hydrophobicity. The residual alkali content of the positive electrode material after 0 days and 14 days is compared. The residual alkali content on the surface of the positive electrode material including the micro-nano structure is significantly reduced. The battery prepared using the positive electrode material containing the micro-nano structure has a smaller difference in initial discharge specific capacity and cycle capacity retention rate between 0 and 14 days, and the electrochemical performance of the battery is more stable. As can be seen from the comparison of Example 2 and Example 1, when the columns are arranged at equal intervals on the surface of the positive electrode material, the residual alkali content on the surface of the material can be more effectively reduced, and the corresponding battery electrochemical performance is also more stable. Example 1 and Examples 3 to 12 illustrate that when the diameter R of the column is 8 nm~15nm; height H is 15nm~45nm; when the spacing L between the columns is in the range of 3nm~8nm, the residual alkali content on the surface of the positive electrode material is low, and the initial discharge specific capacity and cycle capacity retention rate of the corresponding battery are more stable; from the comparison of Examples 13~15 with Example 1, it can be seen that the high-nickel material including the micro-nano structure improves the formation of residual alkali more significantly, and the electrochemical performance of the battery is also more stable; from the comparison of Example 1 with Examples 16~19, it can be seen that when a layer with hydrophobic properties is coated on the surface of the material, especially the positive electrode material including -Si(CH3)3 and LiF in the coating layer, the residual alkali content on the surface of the material is further reduced, and the electrochemical performance of the obtained battery is more stable.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode material, characterized in that The positive electrode material includes a core and micro-nano structures distributed on the surface of the core, and the core and the micro-nano structures are the same positive electrode material; The micro-nano structure includes a plurality of columns; the diameter R of the columns is 8nm-15nm; the height H of the columns is 15nm-45nm; and the distance L between the columns is 3nm-8nm.

2. The positive electrode material according to claim 1, characterized in that The plurality of columns are arranged at equal intervals.

3. The positive electrode material according to claim 1, characterized in that The L / R of the micro-nano structure is 0.3 to 0.6; And / or, the H / L of the micro-nano structure is 5-10.

4. The positive electrode material according to claim 1, characterized in that The positive electrode material includes a nickel-containing material, and the nickel-containing material includes and / or , where 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, and x+y+z=1.

5. The positive electrode material according to claim 1, characterized in that The positive electrode material further includes: a coating layer, which coats at least a portion of the surface of the positive electrode material; the coating layer includes a hydrophobic chemical group or a fluorinated substance.

6. The positive electrode material according to claim 5, characterized in that The hydrophobic chemical groups include At least one of; the fluorinated material includes LiF, At least one of .

7. A method for preparing the positive electrode material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: The positive electrode material is obtained by etching the initial positive electrode material particles.

8. The preparation method according to claim 7, characterized in that The method of etching the initial positive electrode material particles to obtain the positive electrode material comprises: The positive electrode material is obtained by etching the initial positive electrode material particles with a laser.

9. The preparation method according to claim 8, characterized in that The power of the laser is 5W~50W; And / or, the scanning speed of the laser is ; And / or, the laser etching time is 10 min to 120 min.

10. The preparation method according to claim 7, characterized in that The preparation method further comprises: The positive electrode material is mixed with a solution of a substance providing a hydrophobic group to obtain a positive electrode material having a coating layer with a hydrophobic group.

11. The method according to claim 7, characterized in that The preparation method further comprises: The positive electrode material and the fluorinated substance are mixed and ground to obtain a positive electrode material having a coating layer with the fluorinated substance.

12. A positive electrode sheet, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector; The positive electrode active material layer includes the positive electrode material according to any one of claims 1 to 6 or a positive electrode material prepared by the method for preparing a positive electrode material according to any one of claims 7 to 11.

13. A battery, characterized in that: The battery comprises the positive electrode sheet according to claim 12.

14. An electrical device, characterized in that: The electric device comprises the battery as claimed in claim 13.

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