Ruthenium dioxide coated electrostatic spinning precursor, preparation method and positive electrode material

Abstract

The invention relates to a ruthenium dioxide coated electrostatic spinning precursor, a preparation method and a positive electrode material. The preparation method comprises the following steps: preparing a nickel-cobalt-manganese precursor fiber through electrostatic spinning; and dipping the nickel-cobalt-manganese precursor fiber in ruthenium precursor sol, pulling to form a film, drying and calcining to obtain the ruthenium dioxide coated electrostatic spinning precursor. The nickel-cobalt-manganese precursor fiber prepared by electrostatic spinning has a high specific surface area and a uniform structure, and is beneficial to electron ion transmission; a nano-scale uniform coating layer is formed by high-conductivity ruthenium dioxide through a sol-gel method, so that an electronic high-speed channel can be constructed to reduce impedance so as to relieve polarization and improve the rate capability and the capacity retention ratio, the electrolyte is physically isolated to inhibit side reaction, and the CEI layer thickening is reduced so as to improve the cycling stability; the combination of the two avoids the problem of non-uniform traditional coating, and the electrochemical performance is improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a ruthenium dioxide-coated electrospinning precursor, its preparation method, and a cathode material. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long cycle life, and excellent charge-discharge performance, have been widely and significantly applied in many fields, including portable electronic devices, electric vehicles, and large-scale energy storage systems. As a core component of lithium-ion batteries, the performance of the cathode material directly determines key indicators such as energy density, rate performance, and cycle stability. Therefore, the development of high-performance cathode materials has always been a research hotspot and core direction in the field of lithium-ion batteries.

[0003] Nickel-cobalt-manganese (NCM) ternary cathode materials have become one of the most competitive cathode materials in current commercial applications due to their high specific capacity, good electrochemical performance tuning, and relatively balanced cost advantages. With the increasing demands for battery energy density and fast-charging performance in fields such as electric vehicles, high nickel content has become the main development trend for NCM materials. However, in the process of high nickel content and in practical applications, NCM cathode materials still face many technical bottlenecks that urgently need to be addressed, severely restricting their further performance improvement and wider application.

[0004] First, NCM cathode materials inherently suffer from low intrinsic electronic conductivity. This defect is particularly pronounced during high-rate charge-discharge processes, as the electron transport rate within the material and at the interface struggles to match the rapid ion insertion / extraction rates, leading to severe electrode polarization. This intensified polarization not only significantly reduces the battery's charge-discharge efficiency but also causes rapid damage to the active material structure, resulting in rapid capacity decay and failing to meet the demands of electric vehicles and other applications requiring fast charging and long cycle life.

[0005] Secondly, under high-voltage conditions, the surface of NCM materials is prone to a series of side reactions with the electrolyte. These side reactions lead to a continuous thickening of the solid electrolyte interphase (CEI) layer at the electrode / electrolyte interface. The thickened CEI layer further increases the interfacial impedance, hindering lithium-ion transport, and also consumes the active components in the electrolyte, resulting in a continuous deterioration in the battery's cycle stability and rate performance. This problem is particularly pronounced for high-nickel NCM materials, where the proportion of high-valence nickel on the surface is higher, resulting in stronger chemical activity and more intense side reactions with the electrolyte.

[0006] To address the aforementioned issues, existing technologies have proposed surface coating modification strategies. By coating the surface of NCM materials with a layer of functional material, the electronic conductivity of the material can be improved, and direct contact between the material and the electrolyte can be physically isolated, thereby suppressing side reactions. However, traditional coating modification methods, such as ball milling or liquid-phase mixing, inherently suffer from poor coating uniformity. Ball milling easily leads to agglomeration of the coating material, making it difficult to achieve complete coating of NCM particles; in liquid-phase mixing, the coating material is unevenly distributed in the solution, easily resulting in localized over-coating or incomplete coating, ultimately leading to significant local differences in material properties and failing to fully realize the effects of coating modification.

[0007] Therefore, it is necessary to provide a ruthenium dioxide-coated electrospinning precursor, its preparation method, and a cathode material. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a ruthenium dioxide-coated electrospun precursor, its preparation method, and a cathode material. This invention utilizes the high specific surface area and uniform structure of the nickel-cobalt-manganese precursor fibers prepared by electrospinning, which is beneficial for electron-ion transport. Highly conductive ruthenium dioxide is coated into a nanoscale uniform coating layer via a sol-gel method. This coating layer not only constructs a "high-speed electron channel" to reduce impedance and alleviate polarization, thereby improving rate performance and capacity retention, but also physically isolates the electrolyte to suppress side reactions and reduces CEI layer thickening to enhance cycle stability. The combination of these two methods avoids the problem of uneven coating in traditional methods, thus improving electrochemical performance.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, the method comprising the following steps:

[0011] Electrospinning to prepare nickel-cobalt-manganese precursor fibers;

[0012] The nickel-cobalt-manganese precursor fiber is impregnated in ruthenium precursor sol, pulled into a film, dried and calcined to obtain the ruthenium dioxide-coated electrospinning precursor.

[0013] This invention utilizes nickel-cobalt-manganese precursor fibers prepared by electrospinning, which have a high specific surface area and uniform structure, facilitating electron and ion transport. Highly conductive ruthenium dioxide is used to form a nanoscale uniform coating layer via a sol-gel method. This layer can both construct a "high-speed electron channel" to reduce impedance, alleviate polarization, and improve rate performance and capacity retention, and physically isolate the electrolyte to suppress side reactions and reduce CEI layer thickening to improve cycle stability. The combination of these two methods avoids the problem of uneven coating in traditional methods and improves electrochemical performance.

[0014] In some embodiments, the electrospinning preparation of nickel-cobalt-manganese precursor fibers includes: mixing a nickel source, a cobalt source, a manganese source, and a polymer solution to obtain a spinning solution; and using the spinning solution to perform electrospinning to obtain the nickel-cobalt-manganese precursor fibers.

[0015] In some embodiments, the polymer solution comprises a polymer and a solvent;

[0016] The polymer includes polyacrylonitrile (PAN);

[0017] The solvent includes dimethylacetamide (DMAc).

[0018] In some embodiments, the ratio of the total molar amount of metal elements in the nickel source, cobalt source, and manganese source to the mass of the polymer is 1 mol: 50 g to 1 mol: 80 g.

[0019] In some embodiments, the solid content of the spinning solution is 15wt% to 25wt%.

[0020] In some embodiments, the electrospinning satisfies at least one of the following conditions:

[0021] (a) The syringe injection rate is 0.5 mL / h to 1.5 mL / h;

[0022] (b) Voltage is 15kV~25kV;

[0023] (c) The temperature is 20℃~30℃;

[0024] (d) Relative humidity is 30%~50%.

[0025] In some embodiments, the method for preparing the ruthenium precursor sol includes the following steps: mixing a ruthenium source, a complexing agent, and anhydrous ethanol to obtain the ruthenium precursor sol.

[0026] In some embodiments, the ruthenium source includes ruthenium trichloride.

[0027] In some embodiments, the complexing agent includes citric acid;

[0028] In some embodiments, the molar ratio of the ruthenium source to the complexing agent is 1:1.2 to 1:1.5.

[0029] In some embodiments, the concentration of the ruthenium source in the ruthenium precursor sol is 0.05 mol / L to 0.2 mol / L.

[0030] In some embodiments, the immersion time is 10s to 30s.

[0031] In some embodiments, the lifting film formation speed is 5 mm / s to 10 mm / s.

[0032] In some embodiments, the drying temperature is 60°C to 80°C.

[0033] In some embodiments, the drying time is 4 to 6 hours.

[0034] In some embodiments, the calcination is carried out in an air atmosphere.

[0035] In some embodiments, the calcination temperature is 300°C to 320°C.

[0036] In some embodiments, the calcination time is 2h to 3h.

[0037] In a second aspect, the present invention provides a ruthenium dioxide-coated electrospinning precursor, wherein the ruthenium dioxide-coated electrospinning precursor is prepared by the preparation method described in the first aspect.

[0038] Thirdly, the present invention provides a cathode material, which is prepared from the ruthenium dioxide-coated electrospinning precursor described in the second aspect.

[0039] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention uses electrospinning technology to prepare nickel cobalt manganese precursor fibers. The prepared fibers have high specific surface area and uniform microstructure, which provides a good substrate for the uniform deposition of the subsequent coating layer. At the same time, the one-dimensional fiber structure is conducive to the rapid transport of electrons and ions, which improves the conductivity of the material from the morphology.

[0042] (2) Highly conductive ruthenium dioxide is selected as the coating material. A uniform nanoscale coating layer is formed on the surface of the precursor fiber by sol-gel method. This coating layer can form an “electron high-speed channel”, which significantly reduces the interfacial charge transfer impedance of the material, effectively alleviates the polarization phenomenon during high-rate charging and discharging, and improves the rate performance and capacity retention of the battery.

[0043] (3) The ruthenium dioxide coating can physically isolate the nickel-cobalt-manganese material from direct contact with the electrolyte, effectively suppress the side reactions between the two under high voltage conditions, reduce the formation and thickening of the CEI layer, thereby improving the cycle stability and high voltage tolerance of the material;

[0044] (4) Combining the advantages of high specific surface area of ​​electrospinning with the uniform coating characteristics of sol-gel method, ruthenium dioxide was uniformly coated on the surface of nickel-cobalt-manganese precursor at the nanoscale, avoiding the problem of uneven local coating in traditional coating methods and ensuring the consistency of the overall performance of the material. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0046] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0047] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0049] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0050] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0051] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0052] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0053] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0054] Electrospinning, a technique for preparing one-dimensional nanofibers, produces fibers with advantages such as high specific surface area, large aspect ratio, and uniform microstructure. Applying it to the preparation of NCM precursors can effectively optimize the microstructure of the material, providing a good substrate for subsequent coating modification. Ruthenium dioxide (RuO2), as a highly conductive metal oxide, has significantly higher electronic conductivity than NCM materials and also possesses good chemical stability, making it an ideal coating modification material. The sol-gel method is characterized by its simple preparation process and controllable uniform coating layer, making it suitable for achieving precise nanoscale coating. Based on this, this invention combines electrospinning technology, sol-gel coating technology, and the high conductivity of RuO2 to propose a ruthenium dioxide-coated electrospinned precursor, its preparation method, and the corresponding cathode material, aiming to solve the technical problems of poor conductivity and uneven coating in existing NCM cathode materials.

[0055] An embodiment of the present invention provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, the method comprising the following steps:

[0056] Electrospinning to prepare nickel-cobalt-manganese precursor fibers;

[0057] The nickel-cobalt-manganese precursor fiber is impregnated in ruthenium precursor sol, pulled into a film, dried and calcined to obtain the ruthenium dioxide-coated electrospinning precursor.

[0058] This invention utilizes nickel-cobalt-manganese precursor fibers prepared by electrospinning, which have a high specific surface area and uniform structure, facilitating electron and ion transport. Highly conductive ruthenium dioxide is used to form a nanoscale uniform coating layer via a sol-gel method. This layer can both construct a "high-speed electron channel" to reduce impedance, alleviate polarization, and improve rate performance and capacity retention, and physically isolate the electrolyte to suppress side reactions and reduce CEI layer thickening to improve cycle stability. The combination of these two methods avoids the problem of uneven coating in traditional methods and improves electrochemical performance.

[0059] In some embodiments, the electrospinning preparation of nickel-cobalt-manganese precursor fibers includes: mixing a nickel source, a cobalt source, a manganese source, and a polymer solution to obtain a spinning solution; and using the spinning solution to perform electrospinning to obtain the nickel-cobalt-manganese precursor fibers.

[0060] The nickel source can be nickel nitrate and / or nickel acetate.

[0061] The cobalt source can be cobalt nitrate and / or cobalt acetate.

[0062] The manganese source can be manganese nitrate and / or manganese acetate.

[0063] In nickel, cobalt, and manganese sources, the molar ratio of nickel, cobalt, and manganese can be 1:1:1, 5:2:3, 6:2:2, or 8:1:1.

[0064] In some embodiments, the polymer solution comprises a polymer and a solvent;

[0065] The polymer includes polyacrylonitrile (PAN);

[0066] The solvent includes dimethylacetamide (DMAc).

[0067] In some embodiments, the polymer solution can be prepared by adding PAN to DMAc and stirring at a speed of 300 r / min to 500 r / min for 2 h to 4 h in a constant temperature water bath at 40 °C to 60 °C to obtain a homogeneous polymer solution.

[0068] In some embodiments, the ratio of the total molar amount of metal elements in the nickel source, cobalt source, and manganese source to the mass of the polymer is 1 mol:50 g to 1 mol:80 g, for example, it can be 1 mol:50 g, 1 mol:55 g, 1 mol:60 g, 1 mol:65 g, 1 mol:70 g, 1 mol:75 g, or 1 mol:80 g, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the solid content of the spinning solution is 15wt% to 25wt%, for example, it can be 15wt%, 16wt%, 18wt%, 20wt%, 21wt%, 24wt% or 25wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the electrospinning satisfies at least one of the following conditions:

[0071] (a) The syringe injection rate is 0.5 mL / h to 1.5 mL / h, for example, 0.5 mL / h, 0.6 mL / h, 0.8 mL / h, 1 mL / h, 1.2 mL / h or 1.5 mL / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] (b) The voltage is 15kV to 25kV, for example, it can be 15kV, 16kV, 18kV, 20kV, 21kV, 24kV or 25kV, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] (c) The temperature is 20°C to 30°C, for example, 20°C, 21°C, 24°C, 25°C, 27°C, 28°C or 30°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] (d) The relative humidity is 30% to 50%, for example, it can be 30%, 35%, 40%, 45% or 50%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0075] In some embodiments, the electrospinning provided by the present invention further includes vacuum drying at 60°C to 80°C for 8 to 12 hours to remove residual solvent from the fibers obtained by electrospinning, thereby obtaining the nickel-cobalt-manganese precursor fibers.

[0076] In some embodiments, the method for preparing the ruthenium precursor sol includes the following steps: mixing a ruthenium source, a complexing agent, and anhydrous ethanol to obtain the ruthenium precursor sol.

[0077] In some embodiments, the ruthenium source includes ruthenium trichloride.

[0078] In some embodiments, the complexing agent includes citric acid.

[0079] In some embodiments, the molar ratio of the ruthenium source to the complexing agent is 1:1.2 to 1:1.5, for example, it can be 1:1.2, 1:1.3, 1:1.4 or 1:1.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, the concentration of the ruthenium source in the ruthenium precursor sol is 0.05 mol / L to 0.2 mol / L, for example, it can be 0.05 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L or 0.2 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] In some embodiments, the immersion time is 10s to 30s, for example, it can be 10s, 15s, 20s, 25s or 30s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, the lifting film formation speed is 5 mm / s to 10 mm / s, for example, it can be 5 mm / s, 6 mm / s, 8 mm / s, 9 mm / s or 10 mm / s, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the drying temperature is 60°C to 80°C, for example, it can be 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0084] In some embodiments, the drying time is 4h to 6h, for example, it can be 4h, 4.5h, 5h, 5.5h or 6h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0085] This invention removes excess solvent by drying.

[0086] In some embodiments, the calcination is carried out in an air atmosphere.

[0087] In some embodiments, the calcination temperature is 300°C to 320°C, for example, 300°C, 305°C, 310°C, 315°C or 320°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0088] In some embodiments, the calcination time is 2h to 3h, for example, it can be 2h, 2.1h, 2.4h, 2.5h, 2.8h or 3h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0089] This invention utilizes calcination to fully decompose the ruthenium precursor (a complex of the ruthenium source and the complexing agent) into ruthenium dioxide (RuO2).

[0090] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes the following steps:

[0091] (1) Mix nickel source, cobalt source, manganese source and polymer solution to obtain spinning solution with solid content of 15wt%~25wt%; use the spinning solution to perform electrospinning to obtain nickel cobalt manganese precursor fiber;

[0092] The polymer solution comprises polyacrylonitrile and dimethylacetamide;

[0093] The ratio of the total molar amount of metal elements in the nickel, cobalt, and manganese sources to the mass of the polymer is 1 mol: 50 g to 1 mol: 80 g.

[0094] The syringe propulsion rate for electrospinning is 0.5 mL / h to 1.5 mL / h, the voltage is 15 kV to 25 kV, the temperature is 20℃ to 30℃, and the relative humidity is 30% to 50%.

[0095] (2) The nickel-cobalt-manganese precursor fiber is immersed in ruthenium precursor sol for 10s~30s, pulled into a film at a speed of 5mm / s~10mm / s, dried and calcined to obtain the ruthenium dioxide-coated electrospinning precursor;

[0096] The preparation method of the ruthenium precursor sol includes the following steps: mixing ruthenium trichloride, citric acid and anhydrous ethanol to obtain the ruthenium precursor sol; wherein, the molar ratio of the ruthenium source to the complexing agent is 1:1.2~1:1.5; and the concentration of the ruthenium source in the ruthenium precursor sol is 0.05mol / L~0.2mol / L;

[0097] The drying temperature is 60℃~80℃, and the time is 4h~6h;

[0098] The calcination is carried out in an air atmosphere at a temperature of 300℃~320℃ for 2h~3h.

[0099] One embodiment of the present invention provides a ruthenium dioxide-coated electrospinning precursor, which is prepared by the preparation method described in any embodiment.

[0100] One embodiment of the present invention provides a cathode material, which is prepared from the ruthenium dioxide-coated electrospinning precursor described in any embodiment.

[0101] Optionally, the method for preparing the cathode material includes: mixing a lithium source with the ruthenium dioxide-coated electrospinning precursor, and then performing segmented sintering of the resulting mixture in an oxygen atmosphere to obtain the cathode material.

[0102] In some embodiments, the segmented sintering includes heating to 500°C to 600°C at a heating rate of 5°C / min to 10°C / min, holding at that temperature for 4 to 6 hours; then heating to 850°C to 600°C at a heating rate of 3°C / min to 5°C / min, holding at that temperature for 4 to 6 hours, and then cooling to room temperature (20°C to 30°C) at a heating rate of 5°C / min to 10°C / min.

[0103] Example 1

[0104] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, comprising the following steps:

[0105] (1) A nickel source (nickel nitrate), a cobalt source (cobalt nitrate), a manganese source (manganese nitrate) and a polymer solution are mixed to obtain a spinning solution with a solid content of 20 wt%; the spinning solution is used for electrospinning to obtain nickel-cobalt-manganese precursor fibers;

[0106] The polymer solution comprises polyacrylonitrile (PAN-800) and dimethylacetamide;

[0107] The ratio of the total molar amount of metal elements in the nickel, cobalt, and manganese sources to the mass of the polymer is 1 mol: 60 g; the molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese sources is 8:1:1.

[0108] The syringe for electrospinning has a feed rate of 1 mL / h, a voltage of 20 kV, a temperature of 25°C, and a relative humidity of 40%.

[0109] (2) The nickel-cobalt-manganese precursor fiber is immersed in ruthenium precursor sol for 20s, pulled into a film at a speed of 8mm / s, dried and calcined to obtain the ruthenium dioxide-coated electrospinning precursor;

[0110] The preparation method of the ruthenium precursor sol includes the following steps: mixing ruthenium trichloride, citric acid and anhydrous ethanol to obtain the ruthenium precursor sol; wherein, the molar ratio of ruthenium source to complexing agent is 1:1.4; and the concentration of ruthenium source in the ruthenium precursor sol is 0.1 mol / L.

[0111] The drying temperature is 70℃ and the time is 5 hours;

[0112] The calcination is carried out in an air atmosphere at a temperature of 310°C for 2.5 hours.

[0113] Example 2

[0114] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, comprising the following steps:

[0115] (1) A nickel source (nickel nitrate), a cobalt source (cobalt nitrate), a manganese source (manganese nitrate) and a polymer solution are mixed to obtain a spinning solution with a solid content of 15 wt%; the spinning solution is used for electrospinning to obtain nickel-cobalt-manganese precursor fibers;

[0116] The polymer solution comprises polyacrylonitrile (PAN-800) and dimethylacetamide;

[0117] The ratio of the total molar amount of metal elements in the nickel, cobalt, and manganese sources to the mass of the polymer is 1 mol: 50 g; the molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese sources is 8:1:1.

[0118] The syringe for electrospinning has a feed rate of 0.5 mL / h, a voltage of 15 kV, a temperature of 20°C, and a relative humidity of 30%.

[0119] (2) The nickel-cobalt-manganese precursor fiber is immersed in ruthenium precursor sol for 10s, pulled into a film at a speed of 5mm / s, dried and calcined to obtain the ruthenium dioxide-coated electrospinning precursor;

[0120] The preparation method of the ruthenium precursor sol includes the following steps: mixing ruthenium trichloride, citric acid and anhydrous ethanol to obtain the ruthenium precursor sol; wherein, the molar ratio of ruthenium source to complexing agent is 1:1.2; and the concentration of ruthenium source in the ruthenium precursor sol is 0.05 mol / L.

[0121] The drying temperature is 60℃ and the time is 5 hours;

[0122] The calcination is carried out in an air atmosphere at a temperature of 300°C for 3 hours.

[0123] Example 3

[0124] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, comprising the following steps:

[0125] (1) A nickel source (nickel nitrate), a cobalt source (cobalt nitrate), a manganese source (manganese nitrate) and a polymer solution are mixed to obtain a spinning solution with a solid content of 25 wt%; the spinning solution is used for electrospinning to obtain nickel-cobalt-manganese precursor fibers;

[0126] The polymer solution comprises polyacrylonitrile (PAN-800) and dimethylacetamide;

[0127] The ratio of the total molar amount of metal elements in the nickel, cobalt, and manganese sources to the mass of the polymer is 1 mol: 80 g; the molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese sources is 8:1:1.

[0128] The syringe for electrospinning has a feed rate of 1.5 mL / h, a voltage of 25 kV, a temperature of 30°C, and a relative humidity of 50%.

[0129] (2) The nickel-cobalt-manganese precursor fiber is immersed in ruthenium precursor sol for 30s, pulled into a film at a speed of 10mm / s, dried and calcined to obtain the ruthenium dioxide-coated electrospinning precursor;

[0130] The preparation method of the ruthenium precursor sol includes the following steps: mixing ruthenium trichloride, citric acid and anhydrous ethanol to obtain the ruthenium precursor sol; wherein, the molar ratio of ruthenium source to complexing agent is 1:1.5; and the concentration of ruthenium source in the ruthenium precursor sol is 0.2 mol / L.

[0131] The drying temperature is 80℃ and the time is 6 hours;

[0132] The calcination is carried out in an air atmosphere at a temperature of 320°C for 2 hours.

[0133] Example 4

[0134] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor. Except for the ratio of the total molar amount of metal elements in the nickel, cobalt, and manganese sources to the mass of the polymer, which is 1 mol: 40 g, all other methods are the same as in Example 1.

[0135] Example 5

[0136] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor. Except for the ratio of the total molar amount of metal elements in the nickel, cobalt, and manganese sources to the mass of the polymer, which is 1 mol: 90 g, the rest are the same as in Example 1.

[0137] Example 6

[0138] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor. Except for the film-forming speed of 3 mm / s, the method is the same as in Example 1.

[0139] Example 7

[0140] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, which is the same as in Example 1 except that the film-forming speed is 12 mm / s.

[0141] Example 8

[0142] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor. Except for the concentration of the ruthenium source in the ruthenium precursor sol being 0.03 mol / L, the rest is the same as in Example 1.

[0143] Example 9

[0144] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor. Except for the concentration of the ruthenium source in the ruthenium precursor sol being 0.24 mol / L, the rest is the same as in Example 1.

[0145] Example 10

[0146] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, which is the same as in Example 1 except that the calcination temperature is 280°C.

[0147] Example 11

[0148] This embodiment provides a method for preparing a ruthenium dioxide-coated electrospinning precursor, which is the same as in Example 1 except that the calcination temperature is 350°C.

[0149] Performance Characterization

[0150] In the above embodiment, ruthenium dioxide-coated electrospinning precursor and lithium in lithium carbonate were uniformly mixed at a molar ratio of 1:1.05. The mixture was heated to 550°C at a heating rate of 8°C / min in an oxygen atmosphere and held at that temperature for 5 hours. Then, the temperature was increased to 880°C at a heating rate of 4°C / min and held for 5 hours. Finally, the temperature was decreased to 25°C at a cooling rate of 8°C / min to obtain the cathode material. The cathode material was weighed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) at a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone and mixed thoroughly to obtain a slurry. The slurry was then coated onto aluminum foil and dried in a vacuum drying oven at 80°C for 8 hours. The aluminum foil was then pressed into 1.13 cm diameter pieces. 2 The positive electrode is obtained by taking a circular piece of material; a lithium metal sheet is used as the counter electrode, and a polyethylene film (Celgard 2400) is used as the separator. The two are then assembled into a CR2032 button cell in an argon glove box.

[0151] Electrochemical performance was measured using the Blue Electric CT2001A battery testing system in the voltage range of 2.8V to 4.3V. The results are shown in Table 1.

[0152] Table 1

[0153]

[0154] As can be seen from Examples 1 to 3, when the amount of polymer, the film-forming rate, the ruthenium source concentration, and the calcination temperature are within the range required by the process, the prepared ruthenium dioxide-coated electrospinning precursor has excellent first-cycle discharge specific capacity and cycle capacity retention rate, and the effect is the best.

[0155] A comparison of Examples 4 and 5 with Examples 1 to 3 shows that performance decreases when the amount of polymer deviates from the range of 1 mol:(50~80) g. This is because insufficient polymer content results in insufficient viscosity of the spinning solution, poor fiber formation, and uneven morphology; excessive polymer content leads to excessively high solution viscosity, unstable spinning jet, and easy fiber agglomeration, both of which result in uneven coating and reduced capacity and retention.

[0156] A comparison of Examples 6 and 7 with Examples 1 to 3 shows that performance degrades when the film-forming rate exceeds the range of 5 mm / s to 10 mm / s. This is because a slow film-forming rate results in an excessively thick coating layer, increasing impedance; while a fast film-forming rate results in a thin and discontinuous coating layer, which cannot effectively conduct electricity and isolate the electrolyte, exacerbating cyclic side reactions.

[0157] A comparison of Examples 8 and 9 with Examples 1 to 3 shows that performance is poor when the ruthenium source concentration deviates from 0.05 mol / L to 0.2 mol / L. This is because too low a concentration prevents the formation of a complete coating layer; too high a concentration leads to Ru precursor aggregation, uneven coating, increased impedance, and failure of conductivity and isolation effects.

[0158] A comparison of Examples 10 and 11 with Examples 1 to 3 shows that a calcination temperature deviation of 300℃ to 320℃ leads to a decrease in performance. This is because when the temperature is too low, the RuCl3 conversion is incomplete, resulting in poor conductivity; when the temperature is too high, the precursor fiber structure is damaged, the utilization rate of active materials decreases, and the capacity and retention rate decline.

[0159] In summary, this invention utilizes electrospinning technology to prepare nickel-cobalt-manganese precursor fibers. The prepared fibers possess high specific surface area and a uniform microstructure, providing a good substrate for the uniform deposition of the subsequent coating layer. Simultaneously, the one-dimensional fiber structure facilitates rapid electron and ion transport, improving the material's conductivity morphologically. Using highly conductive ruthenium dioxide as the coating material, a uniform nanoscale coating layer is formed on the precursor fiber surface via a sol-gel method. This coating layer can form a "high-speed electron channel," significantly reducing the interfacial charge transfer impedance of the material and effectively mitigating the impact of high-rate charging. The polarization phenomenon during discharge improves the rate performance and capacity retention of the battery; the ruthenium dioxide coating can physically isolate the nickel-cobalt-manganese material from direct contact with the electrolyte, effectively suppressing the side reactions between the two under high voltage conditions, reducing the formation and thickening of the CEI layer, thereby improving the cycle stability and high voltage tolerance of the material; combining the high specific surface area advantage of electrospinning with the uniform coating characteristics of the sol-gel method, nanoscale uniform coating of ruthenium dioxide on the surface of the nickel-cobalt-manganese precursor is achieved, avoiding the problem of uneven local coating in traditional coating methods and ensuring the consistency of the overall performance of the material.

[0160] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a ruthenium dioxide-coated electrospun precursor, characterized by, The preparation method comprises the following steps: The nickel-cobalt-manganese precursor fiber is prepared by electrospinning; The nickel-cobalt-manganese precursor fiber is immersed in a ruthenium precursor sol, and is drawn into a film, dried and calcined to obtain the ruthenium dioxide coated electrospinning precursor.

2. The production method according to claim 1, characterized by, The nickel-cobalt-manganese precursor fiber is prepared by electrospinning, and the preparation method comprises the following steps: mixing a nickel source, a cobalt source, a manganese source and a polymer solution to obtain a spinning glue solution; and electrospinning the spinning glue solution to obtain the nickel-cobalt-manganese precursor fiber.

3. The production method according to claim 2, characterized by, The polymer solution comprises a high molecular polymer and a solvent; The high molecular polymer comprises polyacrylonitrile; The solvent comprises dimethylacetamide; And / or, the ratio of the total metal element molar quantity in the nickel source, the cobalt source and the manganese source to the mass of the high molecular polymer is 1 mol:50 g to 1 mol:80 g; And / or, the solid content of the spinning glue solution is 15 wt% to 25 wt%.

4. The production method according to claim 3, characterized by, The electrospinning satisfies at least one of the following conditions: (a) the injection rate of the syringe is 0.5 mL / h to 1.5 mL / h; (b) the voltage is 15 kV to 25 kV; (c) the temperature is 20℃ to 30℃; (d) the relative humidity is 30% to 50%.

5. The preparation method according to claim 1, characterized in that, The preparation method of the ruthenium precursor sol comprises the following steps: mixing a ruthenium source, a complexing agent and anhydrous ethanol to obtain the ruthenium precursor sol.

6. The production method according to claim 5, wherein The ruthenium source comprises ruthenium trichloride; And / or, the complexing agent comprises citric acid; And / or, the molar ratio of the ruthenium source to the complexing agent is 1:1.2 to 1:1.5; And / or, the concentration of the ruthenium source in the ruthenium precursor sol is 0.05 mol / L to 0.2 mol / L.

7. The preparation method according to claim 1, characterized in that, The immersion time is 10 s to 30 s; And / or, the drawing speed is 5 mm / s to 10 mm / s.

8. The method of any one of claims 1 to 7, wherein the method further comprises the step of: The drying temperature is 60℃ to 80℃; And / or, the drying time is 4 h to 6 h; And / or, the calcination is carried out in an air atmosphere; And / or, the calcination temperature is 300℃ to 320℃; And / or, the calcination time is 2 h to 3 h.

9. A ruthenium dioxide-coated electrospun precursor, characterized in that, The ruthenium dioxide coated electrospinning precursor is prepared by the preparation method of any one of claims 1 to 8.

10. A positive electrode material, characterized in that, The positive electrode material is prepared from the ruthenium dioxide coated electrospinning precursor of claim 9.

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