Positive electrode material and preparation method thereof, positive plate, battery and electric equipment

Abstract

The embodiment of the invention provides a positive electrode material and a preparation method thereof, a positive plate, a battery and electric equipment. The positive electrode material comprises an inner core and a micro-nano structure distributed on the surface of the inner core, wherein the inner core and the micro-nano structure are the same positive electrode material; the micro-nano structure comprises a plurality of columns. The surface of the positive electrode material provided by the invention comprises the micro-nano structure, so that the contact angle of the material is increased, the positive electrode material has super-hydrophobicity, the formation of residual alkali can be effectively reduced, the initial discharge specific capacity and the cycle capacity retention ratio of the battery are further improved, and the electrochemical performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a cathode material, a preparation method thereof, a cathode sheet, a battery, and an electrical device. Background Art

[0002] Lithium ions are likely to remain on the surface of the cathode material, which will cause side reactions between the surface of the electrode material and the electrolyte to generate residual alkali, exacerbating the deterioration of the electrode surface structure and battery performance.

[0003] To reduce the surface residual alkali of the cathode material, it can be achieved by washing the surface of the material with water. However, although washing with water can reduce the lithium ions remaining on the surface, it will cause ion exchange between Li + / H + , and the loss of Li + will exacerbate the cation mixing phenomenon, resulting in a decline in battery performance.

[0004] Therefore, how to ensure the stability of battery performance while reducing the formation of surface residual alkali of the cathode material is an urgent problem to be solved. Summary of the Invention

[0005] The present invention provides a cathode material, a preparation method thereof, a cathode sheet, a battery, and an electrical device. The micro-nano structure included in the cathode material can effectively reduce the adhesion force between water droplets and the material, reduce the residence time and contact area of water molecules on the surface, thereby reducing the formation of surface residual alkali (reaction for forming residual alkali: ), and further improve battery performance.

[0006] In the first aspect of the present invention, a cathode material is provided. The cathode material includes a core and a micro-nano structure distributed on the surface of the core, and the core and the micro-nano structure are the same cathode material;

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

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

[0009] According to an embodiment of the present invention, the diameter R of the columnar object is 8 nm to 15 nm;

[0010] and / or, the height H of the columnar object is 15 nm to 45 nm;

[0011] and / or, the spacing L between the columnar objects is 3 nm to 8 nm.

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

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

[0014] According to an embodiment of the present invention, 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.

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

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

[0017] In a second aspect of the present invention, there is provided a method for preparing a positive electrode material as in the first aspect, and the method includes the following steps:

[0018] Etching the initial positive electrode material particles by an etching method to obtain the positive electrode material.

[0019] According to an embodiment of the present invention, the step of etching the initial positive electrode material particles by an etching method to obtain the positive electrode material includes:

[0020] Etching the initial positive electrode material particles with a laser to obtain the positive electrode material.

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

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

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

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

[0025] Mixing the positive electrode material with a solution providing a hydrophobic chemical group substance to obtain a positive electrode material with a coating layer having a hydrophobic chemical group.

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

[0027] Mixing and grinding the positive electrode material with the fluorinated substance to obtain a positive electrode material with a coating layer having a fluorinated substance.

[0028] In a third aspect of the present invention, a positive electrode sheet is provided, which 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;

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

[0030] In a fourth aspect of the present invention, a battery is provided, which includes the positive electrode sheet as described in the third aspect.

[0031] In a fifth aspect of the present invention, an electrical device is provided, which includes the battery as described in the fourth aspect.

[0032] The present invention provides a positive electrode material, 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. The micro-nano structure includes a plurality of columnar objects. The columnar objects arranged on the surface of the positive electrode material core can increase the contact angle on the material surface, reduce the spreading of water droplets, and endow the positive electrode material with superhydrophobicity. 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 the formation of surface residual alkali The reaction for forming residual alkali: ), and the micro-nano structure increases the active contact area, which is beneficial to ion transport, thereby improving the initial discharge specific capacity and cycle capacity retention rate of the battery and improving the electrochemical performance of the battery. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the positive electrode material provided by this application. Detailed Embodiments

[0034] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below. The specific embodiments listed below only describe the principles and features of the present invention, and the examples given are only used to explain the present invention and do not 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 creative efforts fall within the scope of protection of the present invention.

[0035] In a first aspect of the present invention, a positive electrode material is provided. The positive electrode material includes a core and a micro-nano structure distributed on the surface of the core. The core and the micro-nano structure are the same positive electrode material; the micro-nano structure includes a plurality of columnar objects.

[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 integral structure. The core and the columnar objects distributed on the surface of the core are collectively referred to as the positive electrode material.

[0037] The production process of the cathode material and its own characteristics result in the easy presence of residual lithium ions on its surface. When exposed to an environment containing H 2 O and CO 2 , surface residual alkali will be formed. Excessive surface residual alkali will affect the battery performance. Starting from the perspective of reducing the contact area between the material surface and water droplets, a micro-nano structure is formed on the material surface. The multiple columnar structures included in the micro-nano structure can enable water droplets to form a structure similar to a "bridge" on the material surface, reducing the direct contact between the material surface and water droplets, thereby reducing the formation of residual alkali and improving the battery performance.

[0038] Therefore, the surface of the cathode material provided by the present invention has a micro-nano structure, which includes multiple columnar structures. The columnar structures arranged on the surface of the cathode material core can increase the contact angle of the material surface, reduce the spreading of water droplets, and make the cathode material have superhydrophobicity. 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 cathode material, thereby reducing the formation of surface residual alkali (reaction for forming residual alkali: ). Moreover, the micro-nano structure increases the active contact area, which is beneficial to the transport of ions, thereby improving the initial discharge specific capacity and cycle capacity retention rate of the battery and improving the electrochemical performance of the battery.

[0039] Exemplarily, the schematic diagram of the cathode material provided by the present application is as shown in Figure 1 . Among them, R is the diameter of the columnar structure of the micro-nano structure, H is the height of the columnar structure of the micro-nano structure, and L is the spacing of the columnar structures of the micro-nano structure.

[0040] In a preferred embodiment, the multiple columnar structures are arranged at equal intervals. The columnar structures of the micro-nano structure are arranged at equal intervals on the surface of the core, so that the micro-nano structure in the cathode material is uniformly distributed, ensuring that all positions of the cathode material have superhydrophobicity, reducing the direct contact between the material surface and water droplets, and reducing the formation of surface residual alkali. Therefore, the battery prepared with this cathode material has more excellent performance.

[0041] In a specific embodiment, the diameter R of the columnar structure is 8 nm to 15 nm; and / or, the height H of the columnar structure is 15 nm to 45 nm; and / or, the spacing L between the columnar structures is 3 nm to 8 nm. Exemplarily, the diameter R of the columnar structure is 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm or a range composed of any two of the above values. Exemplarily, the height H of the columnar structure is 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or a range composed of any two of the above values. Exemplarily, the spacing L between the columnar structures is 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm or a range composed of any two of the above values. By controlling the diameter and height of the columnar structure within the above ranges, the structural strength and reactivity can be balanced, enabling it to maintain good mechanical strength and specific surface area. Controlling the spacing between the columnar structures within the range of 3 nm to 8 nm makes the micro-nano structure distribution in the cathode material uniform, thereby ensuring that all positions of the cathode material have superhydrophobicity, reducing the direct contact between the material surface and water droplets, and reducing the formation of surface residual alkali. Therefore, the battery performance prepared with this cathode material is more stable.

[0042] In a specific embodiment, 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 to 10. Exemplarily, the L / R of the micro-nano structure 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 composed of any two of the above values. Exemplarily, the H / L of the micro-nano structure is 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or a range composed of any two of the above values. L / R reflects the spatial openness and mechanical stability of the structure. Within this range, the micro-nano structure is dense and has moderate strength; H / L determines the aspect ratio and stress distribution of the columnar array. Within this range, both the stability of the micro-nano structure can be ensured and the ion transport in the vertical direction is facilitated.

[0043] In a preferred embodiment, the cathode 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. The cathode material with 0.6 ≤ x ≤ 1 is a high-nickel cathode material. Due to its higher nickel content, more lithium ions remain on the material surface. Therefore, the effect of reducing the formation of residual alkali of the high-nickel cathode material containing micro-nano structures is more significant.

[0044] In a preferred embodiment, the positive electrode material further comprises: a coating layer, which coats at least a part of the surface of the positive electrode material; the coating layer comprises a hydrophobic chemical group or a fluorinated substance. On the basis of having a micro-nano structure, a hydrophobic coating layer is further coated on the material surface, which can combine with the micro-nano structure to further enhance the hydrophobicity of the positive electrode material, thereby reducing the formation of residual alkali on the material surface and further improving the 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., and this embodiment does not make any limitation thereto.

[0046] In a preferred embodiment, the hydrophobic chemical group includes at least one of; the fluorinated substance includes at least one of. The hydrophobicity of the positive electrode material prepared by selecting the coating layer from the above substances is more excellent.

[0047] The second aspect of the present invention provides a preparation method of the positive electrode material as in the first aspect, and the method comprises the following steps: etching the initial positive electrode material particles by an etching method to obtain the positive electrode material.

[0048] Among them, 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 a micro-nano structure.

[0049] Among them, the etching method can include a chemical etching method, a plasma etching method, a laser etching method, etc., and this embodiment does not make any limitation thereto.

[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, and the positive electrode material is obtained by a chemical reaction; or a high-density plasma is generated by a radio frequency and other excitation sources, such as using a mixed gas, based on the reaction of F radicals with metals to generate volatile fluorides, 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 by an etching method to obtain the positive electrode material includes: etching the initial positive electrode material particles by a laser to obtain the positive electrode material.

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

[0053] Among them, the organic solvent can be one or more of acetone, ethanol, etc.; the inert gas can be one or more of nitrogen, argon, etc., and this embodiment does not limit this.

[0054] In a specific embodiment, the power of the laser is 5W to 50W; and / or, the scanning speed of the laser is ; and / or, the etching time of the laser is 10 min to 120 min. Exemplarily, the power of the laser is 5W, 10W, 15W, 20W, 25W, 30W, 35W, 40W, 45W, 50W or a range composed of any two of the above values. Exemplarily, the scanning speed of the laser 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 composed of any two of the above values. Exemplarily, the etching time of the laser is 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min or a range composed 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 columns can be controlled within a suitable range, thereby reducing the formation of residual alkali on the material surface and improving the performance of the battery.

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

[0056] In a preferred embodiment, the above preparation method further includes: mixing the cathode material with a solution providing a hydrophobic chemical group substance to obtain a cathode material with a hydrophobic chemical group on the coating layer. Exemplarily, the cathode material is vacuum dried at 80 °C for 12 h to remove surface adsorbed water; a silane coupling agent (3-aminopropyltriethoxysilane) solution is prepared, dissolved in an ethanol / water mixed solvent (volume ratio 9:1) according to a mass ratio of 0.5% to 5%, stirred for 30 minutes to hydrolyze to form silanol; the cathode material is dispersed in the above solution, ultrasonically treated for 1 hour to fully contact the surface, and magnetically stirred for 3 to 6 hours to promote chemical bonding (Si-O-M, M is the metal on the material surface); finally, centrifuged and washed with ethanol 3 times to remove the unreacted coupling agent, and vacuum dried at 60 °C for 12 hours to obtain a cathode material with a coating layer on the surface. Coating a layer with a hydrophobic chemical group on the surface of the cathode material can combine with the micro-nano structure to further enhance the hydrophobicity of the cathode material, thereby reducing the formation of residual alkali on the material surface and further improving the battery performance.

[0057] In a preferred embodiment, the above preparation method further includes: mixing and grinding the cathode material with a fluorinated substance to obtain a cathode material with a fluorinated substance on the coating layer. Exemplarily, the cathode material is mixed with LiF powder according to a mass ratio of 0.5% to 5%, ball milled (rotation speed 300 rpm) for 2 h to achieve uniform mixing, and sintered in an oxygen atmosphere at 400 °C to 600 °C for 4 h to 6 h to obtain a cathode material with a coating layer on the surface. Coating a layer with a fluorinated substance on the surface of the cathode material can combine with the micro-nano structure to further enhance the hydrophobicity of the cathode material, thereby reducing the formation of residual alkali on the material surface and further improving the battery performance.

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

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

[0060] The positive electrode active material layer of the present invention further includes components such as a conductive agent and a binder. Among them, 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, polyvinylpyrrolidone, polytetrafluoroethylene, and styrene-butadiene rubber.

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

[0062] The fourth aspect of the present invention provides a battery, including the positive electrode plate of the third aspect. In addition to the above positive electrode plate, the battery of the present invention further includes a negative electrode plate and an electrolyte.

[0063] Among them, the negative electrode plate 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 commonly used in the art, such as copper foil. The composition of 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 commonly used in the art, including but not limited to one or more of natural graphite, artificial graphite, silicon-carbon materials, silicon-oxygen materials, and hard carbon. The composition of the conductive agent and the binder can refer to the types of the conductive agent and the binder in the positive electrode plate, which will not be elaborated here.

[0064] The electrolyte is a medium for conducting lithium ions between the positive electrode plate and the negative electrode plate. It can be a gel electrolyte, a solid electrolyte or a liquid electrolyte. The present application does not specifically limit the type of the electrolyte, and it can be selected from the gel electrolytes, solid electrolytes 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: the positive electrode plate, the separator and the negative electrode plate are wound or laminated to obtain a bare battery cell, and the bare battery cell is encapsulated into a pre-stamped aluminum-plastic film bag. After the encapsulated battery is dried at 85°C to remove moisture, the electrolyte is injected into the dried battery, and after the battery is left standing, formed and secondarily sealed, the battery of the present invention can be obtained.

[0066] The battery of the present application can include the form of a battery cell, a battery module and a battery pack. In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0067] There is no particular limitation on the specific type of the battery of the present application. For example, from the perspective of shape, the battery includes but is not limited to square shell batteries, soft pack batteries, cylindrical batteries, etc., and no special limitation is made in the present application. From the perspective of the electrode core structure, the electrode core of the battery can be a wound electrode core (that is, a positive electrode sheet, a negative electrode sheet, and a separator are stacked and then made into an electrode core through a winding process), or a laminated electrode core (that is, multiple positive electrode sheets, negative electrode sheets, and separators are stacked to form an electrode 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.). No special limitation is made in the present application.

[0068] The fifth aspect of the present invention provides an electrical device including the battery as above. The present invention does not make a particular limitation on the type of the electrical device, and it can be any electrical device including the battery, including but not limited to mobile phones, portable devices, laptop computers, electric bicycles, electric vehicles, electric toys, energy storage devices, etc.

[0069] The positive electrode material, its preparation method, the positive electrode sheet, the battery, and the electrical device provided by the present invention will be specifically introduced below through specific examples.

[0070] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are all conventional reagents, conventional materials, and conventional instruments in the art, and can all be obtained through commercial purchase. The reagents involved can also be obtained through conventional methods in the art.

[0071] Example 1

[0072] Preparation of the positive electrode material

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

[0074] 2) Use CAD software to design a circular array arranged at equal intervals on the surface of the initial positive electrode material particles, with a diameter R of 8 nm and a spacing L of 3 nm, export it as a vector file, import the vector file into a laser instrument, make the laser scan according to this path, fix the cleaned initial positive electrode material particles on an aluminum foil, and under the protection of argon gas, use a nanosecond laser, set the laser wavelength to 355 nm, the laser power to 15 W, and the scanning speed to and start the etching process. After etching for 30 min, let it 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), circular patterns arranged arbitrarily are designed on the surface of the initial cathode material particles using CAD software, with a diameter R of 8 nm and unequal spacings, and the other conditions are the same as those in Embodiment 1.

[0077] Embodiment 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 , and the etching time is 60 min, and the other conditions are the same as those in Embodiment 1.

[0079] Embodiment 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 , and the etching time is 90 min, and the other conditions are the same as those in Embodiment 1.

[0081] Embodiment 5

[0082] 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 1 nm, the laser power is 5 W, the scanning speed is 0.001 µm / s, the etching time is 20 min, and the other conditions are the same as those in Embodiment 1.

[0083] Embodiment 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 , and the etching time is 100 min, and the other conditions are the same as those in Embodiment 1.

[0085] Embodiment 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 , and the etching time is 20 min, and the other conditions are the same as those in Embodiment 1.

[0087] Embodiment 8

[0088] 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 1 nm, the laser power is 5 W, the scanning speed is 0.001 µm / s, and the other conditions are the same as those in Embodiment 1.

[0089] Embodiment 9

[0090] 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 pitch L is 5 nm, the laser power is 25 W, and the scanning speed is , the etching time is 20 min, and the remaining conditions are the same as those in Embodiment 1.

[0091] Embodiment 10

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

[0093] Embodiment 11

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

[0095] Embodiment 12

[0096] 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, and the remaining conditions are the same as those in Embodiment 1.

[0097] Embodiment 13

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

[0099] Embodiment 14

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

[0101] Embodiment 15

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

[0103] Embodiment 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 h to remove the surface adsorbed water; a (3-mercaptopropyl)trimethoxysilane solution is prepared, dissolved in an ethanol / water mixed solvent (volume ratio 9:1) according to a mass ratio of 1%, and stirred for 30 minutes; the positive electrode material is dispersed in the above solution, ultrasonically treated for 1 h, and magnetically stirred for 5 h; finally, centrifuged and washed with ethanol 3 times, and vacuum-dried at 60 °C for 12 h to obtain a positive electrode material with a coating layer on the surface, and the other conditions are the same as those in Embodiment 1.

[0105] Embodiment 17

[0106] The difference between this embodiment and Embodiment 1 is that Step 3) is added: the positive electrode material is mixed with powder in 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, and the other conditions are the same as those in Embodiment 1.

[0107] Embodiment 18

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

[0109] Embodiment 19

[0110] The difference between this embodiment and Embodiment 17 is that in Step 3), is replaced with LiF, and the other conditions are the same as those in Embodiment 17.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Embodiment 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 Embodiment 1.

[0113] Test Example

[0114] I. The positive electrode materials of the above embodiments and comparative examples are tested as follows:

[0115] 1. Residual alkali content test

[0116] Test method: The positive electrode materials in the above embodiments and comparative examples are placed in a cabinet at 25 °C and 80% humidity for 14 days, and the residual alkali content of the materials before and after being placed for 14 days is measured respectively. A 0.01 M HCl standard solution is used for titration to obtain a titration curve, and the LiOH content in the positive electrode material is tested. The results are shown in Table 2.

[0117] 2. Contact angle test

[0118] Test method: Put the cathode material powders in the above examples and comparative examples into a mold, apply a pressure of 30 MPa with a tablet press to make a flat and dense disc (with a diameter of about 1 cm), use a plasma cleaner to treat the sample surface for 3 minutes to remove organic contamination, suck 4 μL of ultrapure water with a micro syringe, gently deposit the liquid drop on the sample surface, take an image within 10 seconds after the liquid drop contacts the surface, use software to fit the liquid drop profile in combination with the Young-Laplace equation, calculate the contact angle, measure at least 5 different positions for each sample, take the average value, and the results are shown in Table 2.

[0119] 3. Tests on the columns R, H, and L

[0120] Test method: Place the cathode material on the sample stage of the SEM, observe the columnar structure on the sample surface by setting the acceleration voltage (usually between 10 kV and 50 kV) and an appropriate magnification (10,000 - 50,000 times), use an image acquisition system to take pictures of different areas of the material to obtain columnar structure information at different positions, finally open the SEM image obtained by shooting with ImageJ image software, use the scale tool to measure the diameter R, height H, and spacing L of the columnar structure on the cathode material surface, select the measurement tool in the software, measure multiple times and take the average, measure at least 50 different positions to improve the reliability of the data, take the average value and record it, and the results are shown in Table 1.

[0121] II. Prepare the cathode sheets from the cathode materials in the above examples and comparative examples 14 days before and 14 days after placement respectively, and assemble them with the anode sheet, electrolyte, and separator to obtain a coin-type half-cell according to the following method:

[0122] 1) Mix the cathode material, PVDF, and conductive agent SuperP in a ratio of 90:5:5 and stir evenly to obtain a slurry containing the cathode material. Coat the slurry on an aluminum foil current collector, dry it, roll it into a sheet to obtain the cathode sheet;

[0123] 2) In the glove box, assemble the above-mentioned cathode sheet with the separator, anode (lithium metal), and electrolyte (ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate mixed in a volume ratio of 1:1:1, and then add 1 M of ) to obtain a coin-type half-cell.

[0124] Perform the following performance tests on the coin-type half-cells assembled above:

[0125] 1. Initial discharge specific capacity

[0126] Test method: On the charge and discharge cabinet, the 0.1C capacity was measured in the voltage range of 2.8 - 4.3V. The initial 1C was set at 200 mA / g. In this voltage range at 0.1C, it was cycled 3 times at 25°C. The capacity of the last cycle was taken as the initial discharge specific capacity. The results are shown in Table 2.

[0127] 2. Cycling capacity retention rate

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

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135] As shown in Table 1 and Table 2, by comparing Example 1 and Comparative Example 1, it can be seen that when the positive electrode material includes micro - nano structures, the contact angle on the material surface increases significantly, indicating that the positive electrode material has super - hydrophobicity. By comparing the residual alkali content of the positive electrode material placed for 0 days and 14 days, the residual alkali content on the surface of the positive electrode material including micro - nano structures is significantly reduced. For the battery made of the positive electrode material containing micro - nano structures, the difference in the initial discharge specific capacity and the cycling capacity retention rate between 0 day and 14 days is smaller, and the electrochemical performance of the battery is more stable. From the comparison between Example 2 and Example 1, it can be seen that when the columnar objects are arranged at equal intervals on the surface of the positive electrode material, it can more effectively reduce the residual alkali content on the material surface, and the corresponding battery electrochemical performance is also more stable. Examples 1 and 3 - 12 show that when the diameter R of the columnar objects is 8 nm - 15 nm; the height H is 15 nm - 45 nm; and the spacing L between each columnar object is 3 nm - 8 nm, the residual alkali content on the surface of the positive electrode material is lower, and the initial discharge specific capacity and the cycling capacity retention rate of the corresponding battery are more stable. From the comparison between Examples 13 - 15 and Example 1, it can be seen that for the high - nickel material including micro - nano structures, the improvement of the formation of residual alkali is more significant, and the electrochemical performance of its battery is also more stable. From the comparison between Example 1 and Examples 16 - 19, it can be seen that when a hydrophobic coating layer is coated on the material surface, especially when the coating layer includes - Si(CH 3 ) 3The cathode material with LiF further reduces the residual alkali content on the material surface, and the prepared battery has more stable electrochemical performance.

[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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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 comprises a core and a micro-nano structure distributed on the surface of the core, and the core and the micro-nano structure are the same positive electrode material; The micro-nano structure includes a plurality of columns.

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 or 2, characterized in that The diameter R of the column is 8nm~15nm; And / or, the height H of the columnar object is 15nm~45nm; And / or, the distance L between each of the columns is 3nm~8nm.

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

5. 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.

6. 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.

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

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

9. The preparation method according to claim 8, 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.

10. The preparation method according to claim 9, 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.

11. The preparation method according to claim 8, characterized in that: The preparation method further comprises: 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.

12. The preparation method according to claim 8, characterized in that: The preparation method further comprises: The positive electrode material is mixed with the fluorinated substance and ground to obtain a positive electrode material having a coating layer with the fluorinated substance.

13. A positive electrode sheet, characterized in that: The positive electrode sheet comprises 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 claims 1 to 7 or the positive electrode material prepared by the method for preparing the positive electrode material according to claims 8 to 12.

14. A battery, characterized in that: The battery comprises the positive electrode sheet as claimed in claim 13.

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

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