Three-dimensional graphene nanowire composite doped precursor, positive electrode material and preparation method

Abstract

The invention relates to the technical field of batteries, and relates to a three-dimensional graphene nanowire composite doped precursor, a positive electrode material and a preparation method, the preparation method comprises the following steps: mixing a three-dimensional graphene-nanowire composite material and a ternary precursor solution to obtain a mixed solution; and performing spray pyrolysis on the mixed solution in a protective atmosphere to obtain the three-dimensional graphene nanowire composite doped precursor. By using the three-dimensional graphene-nanowire composite material, the conductivity and ion conductivity of the positive electrode material can be greatly improved, so that the charge-discharge efficiency of the lithium ion battery is improved, and the power performance of the lithium ion battery is enhanced; in addition, the introduction of the composite material is helpful for improving the stability of the positive electrode material, reducing the structure change and capacity fading possibly occurring in multiple charging and discharging processes, and prolonging the service life of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a lithium-ion battery material, in particular to a three-dimensional graphene nanowire composite doping precursor, a positive electrode material and a preparation method. Background Art

[0002] Lithium-ion batteries, essential energy storage devices in modern society, are widely used in daily life and transportation. With increasing demands for the battery life of portable electronic devices and the urgent need to address range concerns in electric vehicles, people are placing higher demands on lithium-ion battery performance indicators such as energy density, reliability, and safety. From traditional lithium iron phosphate batteries to ternary lithium-ion batteries and the promising solid-state lithium-ion batteries, technological innovation has always revolved around these demands.

[0003] Although lithium-ion battery technology has been continuously upgraded and some performance has been improved, there are still many problems that need to be solved in practical applications: First, the energy density of the battery positive electrode material is difficult to break through, and can only reach 85% of the theoretical value; second, the positive electrode material has low electrical conductivity, which seriously restricts the high-rate charge and discharge performance, causing the fast charging process to damage the battery structure and shorten the cycle life. The problem is particularly prominent in low-temperature environments; third, existing batteries are difficult to adapt to the 800V high-voltage charging platform; fourth, insufficient thermal conductivity makes the battery safety worrying, and high-specific capacity positive electrode materials (such as ternary lithium positive electrode materials) have the risk of combustion and explosion in actual use; fifth, the dual limitations of electrical conductivity and thermal conductivity are not conducive to the efficient operation of the battery management system; sixth, the measures taken to ensure safety have greatly increased the application cost of batteries in electric vehicles, aerospace and military equipment.

[0004] While improved technologies such as carbon coating and element doping have been applied, achieving a balance between building a conductive network and maintaining structural stability remains challenging. Graphene, while widely studied in batteries due to its excellent conductivity and mechanical strength, cannot meet the performance requirements of high-performance batteries when used alone. Nanowire materials have attracted considerable attention due to their high surface area and electrochemical activity, but their practical application requires further exploration. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a three-dimensional graphene nanowire composite doped precursor, a positive electrode material and a preparation method. The present invention uses a three-dimensional graphene-nanowire composite material to greatly improve the conductivity and ion conductivity of the positive electrode material, thereby improving the charge and discharge efficiency of the lithium-ion battery and enhancing the power performance of the lithium-ion battery; in addition, the introduction of the composite material helps to improve the stability of the positive electrode material, reduce the structural changes and capacity attenuation that may occur during multiple charge and discharge processes, and extend the service life of the battery.

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

[0007] In a first aspect, the present invention provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, the preparation method comprising the following steps:

[0008] The three-dimensional graphene-nanowire composite material and the ternary precursor solution are mixed to obtain a mixed solution; the mixed solution is spray-pyrolyzed in a protective atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor.

[0009] The present invention uses a three-dimensional graphene-nanowire composite material to greatly improve the electrical conductivity and ion conductivity of the positive electrode material, thereby improving the charge and discharge efficiency of the lithium-ion battery and enhancing the power performance of the lithium-ion battery; in addition, the introduction of the composite material helps to improve the stability of the positive electrode material, reduce structural changes and capacity attenuation that may occur during multiple charge and discharge processes, and extend the service life of the battery; in addition, spray pyrolysis is conducive to achieving continuous production, increasing production capacity and reducing production costs, which is conducive to industrialized green production.

[0010] Preferably, the mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 2 wt % to 6 wt %.

[0011] Preferably, the metal salts in the ternary precursor solution include nickel salt, manganese salt and cobalt salt.

[0012] Preferably, the concentration of the metal salt in the ternary precursor solution is 300 g / L to 500 g / L.

[0013] Preferably, the three-dimensional graphene-nanowire composite material is obtained by combining three-dimensional graphene and nanowires; the material of the nanowires includes metal oxide.

[0014] Preferably, the material of the nanowires includes any one of TiO2, SnO2, Al2O3, ZnO or Co3O4, or a combination of at least two thereof.

[0015] Preferably, the average pore size of the three-dimensional graphene is 20 μm to 50 μm.

[0016] Preferably, the average diameter of the nanowires is 20 nm to 100 nm, and the average length is 5 μm to 10 μm.

[0017] Preferably, the mass ratio of the three-dimensional graphene to the nanowires is 1:0.8 to 1:1.2.

[0018] Preferably, the method for preparing the three-dimensional graphene-nanowire composite material comprises: in-situ growing nanowires on the surface of three-dimensional graphene using a hydrothermal method.

[0019] The nanowires and three-dimensional graphene in the present invention are not simply mixed, but the nanowires are in situ grown on the surface of the three-dimensional graphene by a hydrothermal method. The three-dimensional graphene has high conductivity and a porous structure. The nanowires are evenly embedded in the pores of the three-dimensional graphene to form a fast ion channel and provide a directional ion transmission path. Therefore, the combination of three-dimensional graphene and nanowires improves the rate performance and cycle life of the electrode.

[0020] Preferably, the carrier gas flow rate of the spray pyrolysis is 1 L / min to 5 L / min.

[0021] Preferably, the spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially.

[0022] Preferably, the temperature of the first pyrolysis is 200°C to 300°C.

[0023] Preferably, the temperature of the second pyrolysis is 500°C to 800°C.

[0024] In a second aspect, the present invention provides a three-dimensional graphene nanowire composite doping precursor, which is prepared by the preparation method described in the first aspect.

[0025] In a third aspect, the present invention provides a positive electrode material, which is prepared from the three-dimensional graphene nanowire composite doped precursor described in the second aspect.

[0026] In a fourth aspect, the present invention provides a method for preparing the positive electrode material according to the third aspect, the method comprising the following steps:

[0027] The lithium source and the three-dimensional graphene nanowire composite doping precursor are mixed and sintered under an oxygen-containing atmosphere to obtain the positive electrode material.

[0028] Preferably, the lithium source includes any one of lithium hydroxide, lithium carbonate or lithium acetate, or a combination of at least two of them.

[0029] Preferably, the molar ratio of the three-dimensional graphene nanowire composite doping precursor to the lithium in the lithium source is 1:1.03 to 1:1.06.

[0030] Preferably, the sintering temperature is 700° C. to 900° C., and the sintering time is 12 hours to 24 hours.

[0031] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention uses a three-dimensional graphene-nanowire composite material to greatly improve the electrical conductivity and ion conductivity of the positive electrode material, thereby improving the charge and discharge efficiency of the lithium-ion battery and enhancing the power performance of the lithium-ion battery; in addition, the introduction of the composite material helps to improve the stability of the positive electrode material, reduce structural changes and capacity attenuation that may occur during multiple charge and discharge processes, and extend the service life of the battery; in addition, spray pyrolysis is conducive to achieving continuous production, increasing production capacity and reducing production costs, which is conducive to industrialized green production. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0035] An embodiment of the present invention provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, the preparation method comprising the following steps:

[0036] The three-dimensional graphene-nanowire composite material and the ternary precursor solution are mixed to obtain a mixed solution; the mixed solution is spray-pyrolyzed in a protective atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor.

[0037] The present invention uses a three-dimensional graphene-nanowire composite material to greatly improve the electrical conductivity and ion conductivity of the positive electrode material, thereby improving the charge and discharge efficiency of the lithium-ion battery and enhancing the power performance of the lithium-ion battery; in addition, the introduction of the composite material helps to improve the stability of the positive electrode material, reduce structural changes and capacity attenuation that may occur during multiple charge and discharge processes, and extend the service life of the battery; in addition, spray pyrolysis is conducive to achieving continuous production, increasing production capacity and reducing production costs, which is conducive to industrialized green production.

[0038] In some embodiments, the mass percentage of the three-dimensional graphene-nanowire composite material in the mixed liquid is 2 wt% to 6 wt%, for example, it can be 2 wt%, 3 wt%, 4 wt%, 5 wt% or 6 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] In some embodiments, the metal salt in the ternary precursor solution includes a nickel salt, a manganese salt, and a cobalt salt.

[0040] Optionally, the nickel salt includes any one or a combination of at least two of nickel sulfate, nickel nitrate or nickel chloride. Typical but non-limiting combinations include a combination of nickel sulfate and nickel nitrate, a combination of nickel sulfate and nickel chloride, a combination of nickel nitrate and nickel chloride, or a combination of nickel sulfate, nickel nitrate and nickel chloride.

[0041] Optionally, the manganese salt includes any one or a combination of at least two of manganese sulfate, manganese nitrate or manganese chloride. Typical but non-limiting combinations include a combination of manganese sulfate and manganese nitrate, a combination of manganese sulfate and manganese chloride, a combination of manganese nitrate and manganese chloride, or a combination of manganese sulfate, manganese nitrate and manganese chloride.

[0042] Optionally, the cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt nitrate or cobalt chloride. Typical but non-limiting combinations include a combination of cobalt sulfate and cobalt nitrate, a combination of cobalt sulfate and cobalt chloride, a combination of cobalt nitrate and cobalt chloride, or a combination of cobalt sulfate, cobalt nitrate and cobalt chloride.

[0043] In some embodiments, the molar ratio of nickel, cobalt and manganese in the ternary precursor solution is (6-8):(1-2):(1-2), for example, it can be 6:2:2 or 8:1:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some embodiments, the concentration of the metal salt in the ternary precursor solution is 300 g / L to 500 g / L, for example, it can be 300 g / L, 350 g / L, 400 g / L, 450 g / L or 500 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In certain embodiments, the three-dimensional graphene-nanowire composite material is obtained by combining three-dimensional graphene and nanowires; and the material of the nanowires includes metal oxide.

[0046] In some embodiments, the material of the nanowires includes any one or a combination of at least two of TiO2, SnO2, Al2O3, ZnO or Co3O4. Typical but non-limiting combinations include a combination of TiO2 and SnO2, a combination of Al2O3 and ZnO, a combination of Al2O3 and Co3O4, a combination of TiO2, SnO2 and Al2O3, a combination of SnO2, Al2O3, ZnO and Co3O4, or a combination of TiO2, SnO2, Al2O3, ZnO and Co3O4.

[0047] In some embodiments, the average pore size of the three-dimensional graphene is 20 μm to 50 μm, for example, it can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] Optionally, the three-dimensional graphene of the present invention is prepared by freeze-drying; compared with other methods, the pore size of the graphene obtained by freeze-drying is more uniform, which is beneficial to improving the electrochemical properties of the precursor material.

[0049] Optionally, the freeze-drying method is to add a reducing agent (at least one of L-ascorbic acid, hydrogen iodide or hydroquinone) to the graphene oxide solution to convert it into a gel state. The gelation causes the graphene sheets to be uniformly and orderly cross-linked in the solution to form a continuous network with a certain rigidity. The formed graphene hydrogel is then frozen. At this time, the water solvent in the gel network freezes to form ice crystals, and the ice crystals grow in the gel pores. The solution is then vacuum-dried. Under vacuum and low-temperature conditions, the ice crystals sublime directly, and the remaining cavities (pores) accurately replicate the shape and size of the ice crystals, and the gel network skeleton constitutes the pore wall. Finally, in order to further improve the conductivity and remove residual oxygen-containing groups, chemical reduction or thermal reduction is performed to obtain the corresponding three-dimensional graphene.

[0050] In certain embodiments, the nanowires have an average diameter of 20 nm to 100 nm and an average length of 5 μm to 10 μm.

[0051] The average diameter of the nanowires is 20 nm to 100 nm, for example, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm or 100 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] The average length of the nanowires is 5 μm to 10 μm, for example, 5 μm, 6 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] In some embodiments, the mass ratio of the three-dimensional graphene to the nanowires is 1:0.8 to 1:1.2, for example, 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In certain embodiments, the method for preparing the three-dimensional graphene-nanowire composite material includes: in-situ growing nanowires on the surface of three-dimensional graphene using a hydrothermal method.

[0055] The nanowires and three-dimensional graphene in the present invention are not simply mixed, but the nanowires are in situ grown on the surface of the three-dimensional graphene by a hydrothermal method. The three-dimensional graphene has high conductivity and a porous structure. The nanowires are evenly embedded in the pores of the three-dimensional graphene to form a fast ion channel and provide a directional ion transmission path. Therefore, the combination of three-dimensional graphene and nanowires improves the rate performance and cycle life of the electrode.

[0056] Optionally, the hydrothermal method includes: uniformly mixing three-dimensional graphene and nanowires according to a mass ratio, and obtaining an aerogel by freeze-drying; performing a carbon thermal reduction reaction on the aerogel, and in situ growing nanowires on the surface of the three-dimensional graphene, so that the nanowires are firmly bonded to the three-dimensional graphene.

[0057] The present invention does not impose any specific restrictions on the specific parameters of the hydrothermal method, as long as the average diameter of the nanowires is 20 nm to 100 nm and the average length is 5 μm to 10 μm.

[0058] Optionally, the protective atmosphere comprises nitrogen and / or an inert gas;

[0059] The inert gas includes any one of helium, neon or argon, or a combination of at least two of them.

[0060] In certain embodiments, the carrier gas flow rate of the spray pyrolysis is 1 L / min to 5 L / min, for example, 1 L / min, 2 L / min, 3 L / min, 4 L / min or 5 L / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] In certain embodiments, the spray pyrolysis comprises a first pyrolysis and a second pyrolysis performed sequentially, wherein the first pyrolysis is used to evaporate the solvent to form precursor microspheres, and the second pyrolysis is used to decompose the metal salt into oxides, thereby simultaneously combining the graphene-nanowire composite material with the oxide grains.

[0062] In certain embodiments, the temperature of the first pyrolysis is 200°C to 300°C, for example, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] In certain embodiments, the temperature of the second pyrolysis is 500°C to 800°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] A certain embodiment of the present invention provides a three-dimensional graphene nanowire composite doping precursor, and the three-dimensional graphene nanowire composite doping precursor is prepared by the preparation method described in any embodiment.

[0065] A certain embodiment of the present invention provides a positive electrode material, which is prepared from the three-dimensional graphene nanowire composite doped precursor described in any embodiment.

[0066] A certain embodiment of the present invention provides a method for preparing the positive electrode material according to any embodiment, the preparation method comprising the following steps:

[0067] The lithium source and the three-dimensional graphene nanowire composite doping precursor are mixed and sintered under an oxygen-containing atmosphere to obtain the positive electrode material.

[0068] In certain embodiments, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, or lithium acetate. Typical but non-limiting combinations include a combination of lithium hydroxide and lithium carbonate, a combination of lithium hydroxide and lithium acetate, a combination of lithium carbonate and lithium acetate, or a combination of lithium hydroxide, lithium acetate, and lithium carbonate.

[0069] In some embodiments, the molar ratio of the three-dimensional graphene nanowire composite doping precursor to the lithium in the lithium source is 1:1.03 to 1:1.06, for example, it can be 1:1.03, 1:1.04, 1:1.05 or 1:1.06, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0070] In some embodiments, the sintering temperature is 700° C. to 900° C., and the sintering time is 12 hours to 24 hours.

[0071] The sintering temperature is 700° C. to 900° C., for example, 700° C., 750° C., 800° C., 850° C. or 900° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0072] The sintering time is 12 hours to 24 hours, for example, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, 21 hours or 24 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0073] Example 1

[0074] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, the preparation method comprising the following steps:

[0075] (1) In situ growth of nanowires on the surface of three-dimensional graphene using a hydrothermal method;

[0076] The average pore size of the three-dimensional graphene is 40 μm;

[0077] The nanowires are made of TiO2, have an average diameter of 60 nm and an average length of 8 μm;

[0078] The mass ratio of the three-dimensional graphene to the nanowires is 1:1;

[0079] (2) mixing the three-dimensional graphene-nanowire composite material with the ternary precursor solution, and ultrasonically dispersing the mixture to obtain a mixed solution; spray pyrolysis of the mixed solution in a nitrogen atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor;

[0080] The metal salt in the ternary precursor solution includes nickel chloride, manganese chloride and cobalt chloride, and the molar ratio of nickel, cobalt and manganese is 8:1:1; the concentration of the metal salt in the ternary precursor solution is 400 g / L;

[0081] The mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 4 wt %;

[0082] The spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially, with a carrier gas flow rate of 3 L / min, a temperature of the first pyrolysis at 250° C., and a temperature of the second pyrolysis at 750° C.

[0083] Example 2

[0084] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, the preparation method comprising the following steps:

[0085] (1) In situ growth of nanowires on the surface of three-dimensional graphene using a hydrothermal method;

[0086] The average pore size of the three-dimensional graphene is 20 μm;

[0087] The nanowires are made of TiO2, have an average diameter of 20 nm, and an average length of 5 μm;

[0088] The mass ratio of the three-dimensional graphene to the nanowires is 1:0.8;

[0089] (2) mixing the three-dimensional graphene-nanowire composite material with the ternary precursor solution, and ultrasonically dispersing the mixture to obtain a mixed solution; spray pyrolysis of the mixed solution in a nitrogen atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor;

[0090] The metal salt in the ternary precursor solution includes nickel chloride, manganese chloride and cobalt chloride, and the molar ratio of nickel, cobalt and manganese is 8:1:1; the concentration of the metal salt in the ternary precursor solution is 300 g / L;

[0091] The mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 2 wt %;

[0092] The spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially, with a carrier gas flow rate of 1 L / min, a temperature of the first pyrolysis at 200° C., and a temperature of the second pyrolysis at 500° C.

[0093] Example 3

[0094] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, the preparation method comprising the following steps:

[0095] (1) In situ growth of nanowires on the surface of three-dimensional graphene using a hydrothermal method;

[0096] The average pore size of the three-dimensional graphene is 50 μm;

[0097] The nanowires are made of TiO2, have an average diameter of 100 nm, and an average length of 10 μm;

[0098] The mass ratio of the three-dimensional graphene to the nanowires is 1:1.2;

[0099] (2) mixing the three-dimensional graphene-nanowire composite material with the ternary precursor solution, and ultrasonically dispersing the mixture to obtain a mixed solution; spray pyrolysis of the mixed solution in a nitrogen atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor;

[0100] The metal salt in the ternary precursor solution includes nickel chloride, manganese chloride and cobalt chloride, and the molar ratio of nickel, cobalt and manganese is 8:1:1; the concentration of the metal salt in the ternary precursor solution is 500g / L;

[0101] The mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 6 wt %;

[0102] The spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially, with a carrier gas flow rate of 5 L / min, a temperature of the first pyrolysis at 300° C., and a temperature of the second pyrolysis at 800° C.

[0103] Example 4

[0104] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, which is the same as that of Example 1 except that the material of the nanowire is SnO2.

[0105] Example 5

[0106] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, which is the same as that of Example 1 except that the material of the nanowire is Al2O3.

[0107] Example 6

[0108] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, which is the same as that of Example 1 except that the material of the nanowire is ZnO.

[0109] Example 7

[0110] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, which is the same as that of Example 1 except that the material of the nanowire is Co3O4.

[0111] Example 8

[0112] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doped precursor, which is the same as that of Example 1 except that the mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 1 wt %.

[0113] Example 9

[0114] This embodiment provides a method for preparing a three-dimensional graphene nanowire composite doped precursor, which is the same as that of Example 1 except that the mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 8 wt %.

[0115] Comparative Example 1

[0116] This comparative example provides a method for preparing a three-dimensional graphene nanowire composite doping precursor, the preparation method comprising the following steps:

[0117] (1) stirring and mixing the three-dimensional graphene and the nanowires to obtain a mixture;

[0118] The average pore size of the three-dimensional graphene is 40 μm;

[0119] The nanowires are made of TiO2, have an average diameter of 60 nm and an average length of 8 μm;

[0120] The mass ratio of the three-dimensional graphene to the nanowires is 1:1;

[0121] (2) mixing the mixed material with the ternary precursor solution, and ultrasonically dispersing the mixed solution to obtain a mixed solution; spray pyrolysis of the mixed solution in a nitrogen atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor;

[0122] The metal salt in the ternary precursor solution includes nickel chloride, manganese chloride and cobalt chloride, and the molar ratio of nickel, cobalt and manganese is 8:1:1; the concentration of the metal salt in the ternary precursor solution is 400 g / L;

[0123] The mass percentage of the mixed material in the mixed liquid is 4wt%;

[0124] The spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially, with a carrier gas flow rate of 3 L / min, a temperature of the first pyrolysis at 250° C., and a temperature of the second pyrolysis at 750° C.

[0125] Comparative Example 2

[0126] This comparative example provides a method for preparing a precursor, which comprises the following steps:

[0127] The mixed material is mixed with a ternary precursor solution, and ultrasonically dispersed to obtain a mixed solution; the ternary precursor is spray-pyrolyzed in a nitrogen atmosphere to obtain the precursor;

[0128] The metal salt in the ternary precursor solution includes nickel chloride, manganese chloride and cobalt chloride, and the molar ratio of nickel, cobalt and manganese is 8:1:1; the concentration of the metal salt in the ternary precursor solution is 400 g / L;

[0129] The spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially, with a carrier gas flow rate of 3 L / min, a temperature of the first pyrolysis at 250° C., and a temperature of the second pyrolysis at 750° C.

[0130] Performance Characterization

[0131] The precursors obtained in the above examples and comparative examples were mixed with lithium carbonate at a molar ratio of lithium to precursor of 1.05:1, and then calcined at 800° C. for 20 h in an oxygen atmosphere to obtain a positive electrode material.

[0132] The obtained positive electrode material, conductive carbon black SP (TIMCAL) and polyvinylidene fluoride PVDF (HSV900) were mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone was used as the solvent. The mixture was stirred into a slurry, and the obtained slurry was evenly coated on an aluminum foil with a doctor blade with a coating gap of 100 μm; after coating, it was first blown dried, then rolled and cut into circular electrode sheets, and then vacuum dried at 120°C and weighed to obtain the button half-cell positive electrode sheet; the negative electrode was a metal lithium sheet, the separator was a PP microporous membrane, and the electrolyte was a lithium battery basic electrolyte. The positive electrode sheet, metal lithium sheet, separator and electrolyte were assembled to obtain a button battery; the electrochemical performance was tested in the voltage range of 2.8V-4.3V and at a rate of 0.1C. The results are shown in Table 1.

[0133] Table 1

[0134]

[0135]

[0136] In summary, the present invention, through the use of three-dimensional graphene-nanowire composite materials, can greatly improve the electrical conductivity and ion conductivity of the positive electrode material, thereby improving the charge and discharge efficiency of the lithium-ion battery and enhancing the power performance of the lithium-ion battery; in addition, the introduction of the composite material helps to improve the stability of the positive electrode material, reduce the structural changes and capacity attenuation that may occur during multiple charge and discharge processes, and extend the service life of the battery; in addition, spray pyrolysis is conducive to achieving continuous production, increasing production capacity and reducing production costs, which is conducive to industrialized green production.

[0137] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a three-dimensional graphene nanowire composite doping precursor, characterized in that: The preparation method comprises the following steps: The three-dimensional graphene-nanowire composite material and the ternary precursor solution are mixed to obtain a mixed solution; the mixed solution is spray-pyrolyzed in a protective atmosphere to obtain the three-dimensional graphene nanowire composite doping precursor.

2. The preparation method according to claim 1, characterized in that The mass percentage of the three-dimensional graphene-nanowire composite material in the mixed solution is 2wt% to 6wt%; And / or, the metal salt in the ternary precursor solution includes nickel salt, manganese salt and cobalt salt; And / or, the concentration of the metal salt in the ternary precursor solution is 300 g / L to 500 g / L.

3. The preparation method according to claim 1, characterized in that The three-dimensional graphene-nanowire composite material is obtained by compounding three-dimensional graphene and nanowires; The material of the nanowires includes metal oxide; And / or, the material of the nanowires includes any one of TiO2, SnO2, Al2O3, ZnO or Co3O4, or a combination of at least two thereof.

4. The preparation method according to claim 3, characterized in that The average pore size of the three-dimensional graphene is 20 μm to 50 μm; and / or, the nanowires have an average diameter of 20 nm to 100 nm and an average length of 5 μm to 10 μm; And / or, the mass ratio of the three-dimensional graphene to the nanowires is 1:0.8 to 1:1.

2.

5. The preparation method according to claim 3 or 4, characterized in that The preparation method of the three-dimensional graphene-nanowire composite material comprises: in-situ growing nanowires on the surface of the three-dimensional graphene by a hydrothermal method.

6. The preparation method according to claim 1, characterized in that The carrier gas flow rate of the spray pyrolysis is 1 L / min to 5 L / min; And / or, the spray pyrolysis includes a first pyrolysis and a second pyrolysis performed sequentially; and / or, the temperature of the first pyrolysis is 200° C. to 300° C.; And / or, the temperature of the second pyrolysis is 500°C to 800°C.

7. A three-dimensional graphene nanowire composite doping precursor, characterized in that: The three-dimensional graphene nanowire composite doping precursor is prepared by the preparation method according to any one of claims 1 to 6.

8. A positive electrode material, characterized in that The positive electrode material is prepared from the three-dimensional graphene nanowire composite doped precursor according to claim 7.

9. A method for preparing the positive electrode material according to claim 8, characterized in that: The preparation method comprises the following steps: The lithium source and the three-dimensional graphene nanowire composite doping precursor are mixed and sintered under an oxygen-containing atmosphere to obtain the positive electrode material.

10. The preparation method according to claim 9, characterized in that The lithium source includes any one of lithium hydroxide, lithium carbonate or lithium acetate, or a combination of at least two thereof; and / or, the molar ratio of the three-dimensional graphene nanowire composite doping precursor to the lithium in the lithium source is 1:1.03 to 1:1.06; And / or, the sintering temperature is 700° C. to 900° C., and the sintering time is 12 hours to 24 hours.

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