Pre-sodium-modified graphene negative electrode, preparation method and application thereof, and sodium ion capacitor

Abstract

The invention provides a pre-sodium-modified graphene negative electrode, a preparation method and application thereof, and a sodium ion capacitor, and belongs to the technical field of sodium ion capacitors. The preparation method comprises the following steps: preparing a graphene oxide dispersion liquid by adjusting the mass ratio of graphene oxide to water to aliphatic hydrocarbon; preparing the graphene oxide dispersion liquid into a wet film, wherein the wet film has a first surface and a second surface which are opposite to each other; a magnetic field vertically pointing to the second surface from the first surface is applied to the wet film, and a graphene oxide film is prepared; carrying out reduction treatment on the graphene oxide film to prepare a graphene film; compounding the graphene film on a negative electrode current collector to prepare a graphene negative electrode; the graphene negative electrode is subjected to pre-sodium treatment, the sodium embedding distribution uniformity, efficiency and depth of the pre-sodium graphene negative electrode are improved, and after the pre-sodium graphene negative electrode is assembled into the sodium ion capacitor, the initial coulombic efficiency, capacity, rate capability and cycle performance of the sodium ion capacitor can be improved.

Description

Technical Field

[0001] This application relates to the field of sodium-ion capacitor technology, and in particular to a pre-sodium graphene anode, its preparation method and application, and sodium-ion capacitors. Background Technology

[0002] Sodium-ion supercapacitors are secondary supercapacitors that use sodium ions as charge carriers. They are mainly composed of positive and negative electrodes, electrolyte, and separator. Energy storage and release are achieved through the insertion and extraction of sodium ions between the positive and negative electrodes.

[0003] In traditional technologies, carbon materials are typically used as the main material for the negative electrode of sodium-ion capacitors, with the sodium storage mechanism being "adsorption-intercalation-pore filling." Pre-sodiumization is an effective method to improve the initial coulombic efficiency (ICE) of sodium-ion capacitors. Without pre-sodiumization, the formation of the SEI film (solid electrolyte interface) during the first charge and discharge of the negative electrode material consumes sodium ions, leading to a decrease in the initial coulombic efficiency (ICE). A lower ICE means that oxygen-containing functional groups and defects in the negative electrode material of the capacitor system will consume a large amount of sodium ions extracted from the positive electrode material. + Therefore, not only will sodium-ion capacitors produce gas, but their capacity will also decay rapidly, thereby reducing their energy density.

[0004] However, the reported pre-sodiumification methods have limited effect on improving the initial coulombic efficiency, cycle performance, rate performance, and other properties of sodium-ion capacitors. Summary of the Invention

[0005] Based on this, the main objective of this application is to provide a pre-sodium graphene anode, its preparation method and application, and a sodium-ion capacitor, so as to improve the initial coulombic efficiency, capacity, rate performance and cycle performance of sodium-ion capacitors.

[0006] The first aspect of this application provides a method for preparing a pre-sodium graphene anode, comprising the following steps:

[0007] A graphene oxide dispersion was prepared by mixing graphene oxide, water, and aliphatic hydrocarbons in a mass ratio of 1:(1-10):(0.5-10).

[0008] The graphene oxide dispersion is prepared into a wet film, the wet film having a first surface and a second surface opposite to each other;

[0009] A magnetic field perpendicular to the second surface is applied to the wet film to prepare a graphene oxide film;

[0010] The graphene oxide film was reduced to prepare a graphene film.

[0011] The graphene film is composited onto the negative electrode current collector to prepare a graphene negative electrode;

[0012] The graphene anode is pre-sodiumized to prepare the pre-sodiumized graphene anode.

[0013] In some embodiments, the strength of the magnetic field is 6000 Gs-15000 Gs.

[0014] In some embodiments, the aliphatic hydrocarbon includes one or more of C6-18 straight-chain aliphatic hydrocarbons, C6-18 branched aliphatic hydrocarbons, and C6-18 alicyclic hydrocarbons.

[0015] In some embodiments, the aliphatic hydrocarbon includes C6-18 straight-chain aliphatic hydrocarbons; the C6-18 straight-chain aliphatic hydrocarbons include one or more of n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecanane, n-hexadecane, n-heptadecane, and n-octadecane.

[0016] In some embodiments, the mass ratio of the graphene oxide, water, and aliphatic hydrocarbon is 1:(2-3):(3-5).

[0017] In some embodiments, the graphene oxide dispersion is prepared into a wet film by the following steps: extruding the graphene oxide dispersion at an extrusion temperature of 20°C-40°C to prepare a wet film.

[0018] In some embodiments, the reduction treatment conditions include: using hydrazine hydrate, NaHSO3, Na2S‧9H2O, Na2S2O3, SOCl2, or SO2 for reduction treatment.

[0019] In some embodiments, after reduction treatment, the process further includes carbonization and rolling; the carbonization conditions include: an inert gas atmosphere; a temperature of 400°C-1000°C; the rolling conditions include: a pressure of 10 tons-30 tons.

[0020] In some embodiments, after applying a magnetic field perpendicular from the first surface to the second surface to the wet film, a drying step is further included; the drying conditions include a temperature of 65°C-115°C.

[0021] In some embodiments, the thickness of the graphene film is 30 μm-80 μm.

[0022] In some embodiments, the graphene anode undergoes a pre-sodiuming treatment, comprising the following steps: vacuum evaporation of sodium metal onto the graphene anode; the vacuum evaporation conditions include: a temperature of 150℃-250℃; a time of 20s-60s; and a vacuum degree of 2×10⁻⁶. -4 Pa-1×10-2 Pa.

[0023] In a second aspect of this application, a presodium graphene anode prepared by the method described in the first aspect is provided.

[0024] The third aspect of this application provides the application of the pre-sodium graphene anode prepared by the method described in the first aspect or the pre-sodium graphene anode described in the second aspect in sodium-ion capacitors.

[0025] In a fourth aspect of this application, a sodium-ion capacitor is provided, comprising a pre-sodium graphene anode prepared by the method described in the first aspect or the pre-sodium graphene anode described in the second aspect.

[0026] Compared with traditional technologies, this application has at least the following beneficial effects:

[0027] This application prepares a graphene oxide dispersion by adjusting the mass ratio of graphene oxide, water, and aliphatic hydrocarbons to improve the dispersibility of the graphene oxide dispersion. The graphene oxide dispersion is then prepared into a wet film, which has opposing first and second surfaces. A magnetic field perpendicular to the second surface is applied to the wet film to prepare a graphene oxide film. The graphene oxide film is then reduced to prepare a graphene film. This graphene film is then composited onto a negative electrode current collector to prepare a graphene negative electrode. Finally, the graphene negative electrode is pre-sodiumized to prepare a pre-sodiumized graphene negative electrode. This process improves the uniformity, efficiency, and depth of sodium intercalation in the pre-sodiumized graphene negative electrode. Furthermore, when the pre-sodiumized graphene negative electrode is assembled into a sodium-ion capacitor, it not only improves the initial coulombic efficiency and capacity of the sodium-ion capacitor but also reduces its internal resistance, thereby enhancing its rate performance and cycle performance. Attached Figure Description

[0028] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0029] Figure 1 This is a schematic diagram of the process for preparing a wet film and a graphene oxide film in one embodiment; wherein, 1 represents an extrusion die, 2 represents a wet film, 3 represents a metal device, 4 represents an induction coil, 5 represents a wire, 6 represents an induction heating power supply, 7 represents a forced-air drying oven, and 8 represents a graphene oxide film.

[0030] Figure 2 A schematic diagram showing the orientation of graphene oxide in the wet film before a magnetic field is applied;

[0031] Figure 3 This is a schematic diagram of the orientation arrangement of graphene oxide in the wet film after a magnetic field is applied. Detailed Implementation

[0032] The present application will be further described in detail below with reference to the embodiments and examples. These embodiments and examples are only for illustrating the present application and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. In addition, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] the term

[0035] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0036] The term "aliphatic hydrocarbon" refers to hydrocarbons that possess the basic properties of aliphatic compounds. These can be saturated or unsaturated straight-chain aliphatic hydrocarbons, branched aliphatic hydrocarbons, and alicyclic hydrocarbons. For example, C6-18 aliphatic hydrocarbons refer to aliphatic hydrocarbons containing 6-18 carbon atoms. Each occurrence can be independently classified as C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, or C18 aliphatic hydrocarbons. Suitable examples include, but are not limited to, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecanane, n-hexadecane, n-heptadecane, n-octadecane, and cyclohexane.

[0037] The term "C6-18 straight-chain aliphatic hydrocarbon" refers to a saturated or unsaturated straight-chain aliphatic hydrocarbon containing 6-18 carbon atoms. Each time it appears, it can be independently referred to as a C6 straight-chain aliphatic hydrocarbon, C7 straight-chain aliphatic hydrocarbon, C8 straight-chain aliphatic hydrocarbon, C9 straight-chain aliphatic hydrocarbon, C10 straight-chain aliphatic hydrocarbon, C11 straight-chain aliphatic hydrocarbon, C12 straight-chain aliphatic hydrocarbon, C13 straight-chain aliphatic hydrocarbon, C14 straight-chain aliphatic hydrocarbon, C15 straight-chain aliphatic hydrocarbon, C16 straight-chain aliphatic hydrocarbon, C17 straight-chain aliphatic hydrocarbon, or C18 straight-chain aliphatic hydrocarbon. Suitable examples include, but are not limited to, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecanane, n-hexadecane, n-heptadecane, and n-octadecane.

[0038] The term "C6-18 branched aliphatic hydrocarbons" refers to saturated or unsaturated branched aliphatic hydrocarbons containing 6-18 carbon atoms. Each occurrence can be independently referred to as C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, or C18 branched aliphatic hydrocarbons. Hydrocarbons, suitable examples including but not limited to: 2-methylpentane, 3-methylpentane, 2,2-dimethylpentane, 2,3-dimethylpentane, 3-ethylpentane, 2,2,5-trimethylhexane, 3,3-diethylpentane, 2,2,3,5-tetramethylheptane, 3,3,5-trimethylheptane, 3-ethyl-2,2-dimethylnonane, 3,6,9-trimethyldodecane, 3,7,11,15-tetramethylhexadecane, and 2,6,10,14-tetramethylhexadecane.

[0039] The term "C6-18 alicyclic hydrocarbon" refers to saturated or unsaturated alicyclic hydrocarbons containing 6-18 carbon atoms. Each time it appears, it can be independently referred to as a C6 alicyclic hydrocarbon, C7 alicyclic hydrocarbon, C8 alicyclic hydrocarbon, C9 alicyclic hydrocarbon, C10 alicyclic hydrocarbon, C11 alicyclic hydrocarbon, C12 alicyclic hydrocarbon, C13 alicyclic hydrocarbon, C14 alicyclic hydrocarbon, C15 alicyclic hydrocarbon, C16 alicyclic hydrocarbon, C17 alicyclic hydrocarbon, or C18 alicyclic hydrocarbon. Suitable examples include, but are not limited to, cyclohexane, methylcyclopentane, methylcyclohexane, 1,1-dimethylcyclopentane, 1,2-dimethylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, heptylcyclohexane, octylcyclohexane, nonylcyclohexane, decylcyclohexane, and undecylcyclohexane.

[0040] Traditional pre-sodiumation methods suffer from low electrical performance in sodium-ion capacitors, including low initial coulombic efficiency, cycling performance, and rate capability. This is primarily due to the difficulty of sodium atom insertion and extraction, low sodium insertion efficiency, and insufficient sodium insertion depth. This application addresses this issue by adjusting the mass ratio of graphene oxide, water, and aliphatic hydrocarbons to prepare a graphene oxide dispersion, thereby improving its dispersibility. The graphene oxide dispersion is then used to prepare a wet film with opposing first and second surfaces. A magnetic field perpendicular to the second surface is applied to the wet film to prepare a graphene oxide film. The graphene oxide film is then reduced to prepare a graphene film. This graphene film is then composited onto a negative electrode current collector to prepare a graphene negative electrode. Finally, the graphene negative electrode undergoes pre-sodiumation treatment to prepare a pre-sodiumized graphene negative electrode. This process improves the uniformity, efficiency, and depth of sodium insertion in the pre-sodiumized graphene negative electrode. Furthermore, when pre-sodium graphene anodes are assembled into sodium-ion capacitors, not only can the initial coulombic efficiency and capacity of sodium-ion capacitors be improved, but the internal resistance of sodium-ion capacitors can also be reduced, thereby improving the rate performance and cycle performance of sodium-ion capacitors.

[0041] The first aspect of this application provides a method for preparing a pre-sodium graphene anode, comprising the following steps:

[0042] A graphene oxide dispersion was prepared by mixing graphene oxide, water, and aliphatic hydrocarbons in a mass ratio of 1:(1-10):(0.5-10).

[0043] The graphene oxide dispersion is prepared into a wet film, the wet film having a first surface and a second surface opposite to each other;

[0044] A magnetic field perpendicular to the second surface is applied to the wet film to prepare a graphene oxide film;

[0045] The graphene oxide film was reduced to prepare a graphene film.

[0046] The graphene film is composited onto the negative electrode current collector to prepare a graphene negative electrode;

[0047] The graphene anode is pre-sodiumized to prepare the pre-sodiumized graphene anode.

[0048] The method for preparing the pre-sodium graphene anode described in this application is beneficial for improving the uniformity of sodium intercalation distribution, sodium intercalation efficiency, and sodium intercalation depth of the pre-sodium graphene anode.

[0049] In some embodiments, before preparing the graphene oxide dispersion, a step of preparing graphene oxide is included, which comprises the following steps:

[0050] Graphite was oxidized using the Hummers method;

[0051] The graphite includes natural flake graphite; the Hummers process includes: using graphite as raw material, in a mixed system of concentrated sulfuric acid and sodium nitrate, the graphite is oxidized and exfoliated by the strong oxidizing effect of potassium permanganate to prepare graphene oxide.

[0052] In some embodiments, the Hummers method for oxidizing graphite specifically includes the following steps: under ice bath conditions, graphite is mixed with concentrated sulfuric acid and sodium nitrate, and then potassium permanganate is added and stirred to achieve surface oxidation of graphite; then, the mixture is transferred to a medium temperature of 30℃-60℃ and stirred continuously for 24 hours to achieve intercalation treatment between graphite layers by intercalating agents (sulfate ions and nitrate ions); finally, under a high temperature of 80℃-98℃, water is added to initiate the hydrolysis of the intercalating agents to prepare a graphene oxide dispersion; the graphene dispersion is then post-treated, specifically including: reducing potassium permanganate in the graphene dispersion with hydrogen peroxide, centrifuging, washing, and drying to prepare graphene oxide.

[0053] In some embodiments, the Hummers method for oxidizing graphite specifically includes the following steps: mixing graphite, sodium nitrate, and concentrated sulfuric acid, adding potassium permanganate powder, and stirring at 20°C for 2-3 hours to prepare a mixed solution; heating the mixed solution to 35°C-45°C and reacting at a constant temperature for 24 hours, then adding deionized water and reacting at 90°C-98°C for 1 hour; after the reaction is completed, adding deionized water and hydrogen peroxide solution to terminate the reaction, acid washing with hydrochloric acid solution, dialysis using a dialysis bag to remove impurities, and freeze-drying to prepare graphene oxide.

[0054] In some embodiments, a modified Hummers method is used to oxidize graphite, specifically including the following steps: oxidizing natural flake graphite (from BTR, model HRG-3) to prepare graphene oxide. The specific steps of the modified Hummers method are as follows: ① Add 1 kg of potassium persulfate and 1 kg of phosphorus pentoxide sequentially to a beaker, seal the beaker, add 3 L of concentrated sulfuric acid to the beaker, stir at 300 rpm until homogeneous, then heat in an 80°C constant temperature water bath, seal the beaker, and stir at 300 rpm for 30 min; ② Add 2 kg of natural flake graphite to the mixed solution, stir at 1200 rpm until homogeneous, then place in an 80°C constant temperature drying oven for 6 h, remove and cool to room temperature; ③ Then wash with deionized water and filter until the washing liquid is neutral. The obtained solid was dried at room temperature (25℃) to constant weight to prepare pre-oxidized graphite; ④ The obtained pre-oxidized graphite and 1 kg sodium nitrate were added to 46 L concentrated sulfuric acid and stirred at 1200 rpm for 30 min to mix evenly; ⑤ 6 kg potassium permanganate powder was gradually added and stirred at 20℃ for 2 h to obtain a mixed solution; ⑥ The mixed solution was heated to 35℃ and reacted at a constant temperature for 2 h; ⑦ 60 L deionized water was added to the mixed solution and reacted at 95℃ for 15 min; ⑧ The reaction was terminated by adding 60 L deionized water and 5 L hydrogen peroxide (concentration of 30 wt%) solution, and then washed 9 times with 10 wt% hydrochloric acid; ⑨ Then, the solution was dialyzed for one week using a dialysis bag (Soleport YA1075 type) to remove impurities such as metal ions and acid radical ions; ⑩ Graphene oxide was prepared by freeze drying.

[0055] In some embodiments, the step of preparing the graphene oxide dispersion includes:

[0056] The graphene oxide dispersion was prepared by kneading graphene oxide, water and aliphatic hydrocarbons in a mass ratio of 1:(1-10):(0.5-10) using a kneader.

[0057] In some embodiments, the mass ratio of graphene oxide, water, and aliphatic hydrocarbons is 1:(1-10):(0.5-10), which can be 1:1:0.5, 1:1:10, 1:2:0.5, 1:2:10, 1:2.4:0.5, 1:2.4:3, 1:2.4:3.6, 1:2.4:4, 1:2.4:5, 1:2.4:10, 1:5:0.5, 1:5:10, 1:10:0.5, or 1:10:10. This application improves the dispersibility and stability of the graphene oxide dispersion by adjusting the mass ratio of graphene oxide, water, and aliphatic hydrocarbons. Specifically, by using aliphatic hydrocarbons to adjust the viscosity and surface tension of the graphene oxide dispersion, and given that the aliphatic hydrocarbons have an emulsifying effect, the dispersibility of the graphene oxide dispersion can be further improved.

[0058] In some embodiments, the aliphatic hydrocarbon includes one or more of C6-18 straight-chain aliphatic hydrocarbons, C6-18 branched aliphatic hydrocarbons, and C6-18 alicyclic hydrocarbons.

[0059] In some embodiments, the aliphatic hydrocarbon includes C6-18 straight-chain aliphatic hydrocarbons; the C6-18 straight-chain aliphatic hydrocarbons include one or more of n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecanane, n-hexadecane, n-heptadecane, and n-octadecane.

[0060] In some embodiments, the mass ratio of graphene oxide, water and aliphatic hydrocarbon is 1:(2-3):(3-5), which can be 1:2:3, 1:2.4:3.6, 1:2.4:4, 1:2.4:5, 1:3:3 or 1:3:5.

[0061] In some embodiments, the graphene oxide dispersion is prepared into a wet film by the following steps: extruding the graphene oxide dispersion at an extrusion temperature of 20°C-40°C, which can be 20°C, 25°C, 30°C, 35°C or 40°C, to prepare a wet film.

[0062] In some implementations, the extrusion apparatus includes a single-screw extruder, a twin-screw extruder, a multi-screw extruder, or a plunger extruder.

[0063] In some embodiments, the thickness of the wet film is 50μm-500μm, and can be 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 360μm or 400μm.

[0064] In some embodiments, the strength of the magnetic field is 6000 Gs-15000 Gs, and can be 6000 Gs, 7000 Gs, 8000 Gs, 9000 Gs, 10000 Gs, 11000 Gs, 12000 Gs, 12500 Gs, 13000 Gs, 14000 Gs, or 15000 Gs. This application prepares a graphene oxide film by applying a magnetic field perpendicular to the second surface from the first surface to the wet film, thereby adjusting the orientation of the graphene sheets. The first and second surfaces are the surfaces with the largest area of ​​the wet film. In the graphene oxide film, the graphene oxide sheets are oriented and arranged in an orderly manner under the magnetic field, which is beneficial to improving the uniformity of sodium intercalation distribution, sodium intercalation efficiency, and sodium intercalation depth of the subsequent graphene anode. Using the prepared pre-sodium graphene anode in a sodium-ion capacitor can improve the capacitance, cycle performance, and rate performance of the sodium-ion capacitor.

[0065] In some implementations, the magnetic field can be provided by a permanent magnet or an electromagnet.

[0066] In some embodiments, after applying a magnetic field perpendicular from the first surface to the second surface to the wet film, a drying step is further included; the drying conditions include a temperature of 65°C-115°C, which can be 65°C, 70°C, 80°C, 90°C, 100°C, 110°C or 115°C.

[0067] Figure 1 This is a schematic diagram of the process for preparing a wet film and a graphene oxide film in one embodiment; wherein, 1 represents an extrusion die, 2 represents a wet film, 3 represents a metal device, 4 represents an induction coil, 5 represents a wire, 6 represents an induction heating power supply, 7 represents a forced-air drying oven, and 8 represents a graphene oxide film. Figure 1 In the process, the graphene oxide dispersion is extruded through the extrusion die 1 to prepare a wet film 2. Then, the wet film is treated with a magnetic field perpendicular to the first and second surfaces of the wet film provided by the metal device 3, the induction coil 4, the wire 5 and the induction heating power supply 6. The first and second surfaces are the largest area surfaces of the wet film. Finally, the wet film treated with the external magnetic field is dried using a forced-air drying oven 7 to obtain a graphene oxide film 8.

[0068] In some embodiments, the reduction conditions include reduction using hydrazine hydrate, NaHSO3, Na2S‧9H2O, Na2S2O3, SOCl2, or SO2.

[0069] In some embodiments, the reduction conditions include reducing the graphene oxide film with a hydrazine hydrate solution, wherein the concentration of the hydrazine hydrate solution is 20 mg / L-60 mg / L, and can be 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L or 60 mg / L.

[0070] In some embodiments, after reduction treatment, the process further includes carbonization and rolling steps; the carbonization conditions include: an inert gas atmosphere, wherein the inert gas can be nitrogen, argon or helium; and a temperature of 400℃-1000℃, which can be 400℃, 500℃, 600℃, 700℃, 800℃, 900℃ or 1000℃; the rolling conditions include: a pressure of 10 tons-30 tons, which can be 20 tons.

[0071] In some implementations, the rolling process is performed using a hydraulic double roller press.

[0072] In some embodiments, the thickness of the graphene film is 30μm-80μm, and can be 30μm, 40μm, 50μm, 60μm, 70μm or 80μm.

[0073] In some embodiments, the negative current collector comprises carbon-coated aluminum foil.

[0074] In some embodiments, the step of compositing the graphene film onto the negative electrode current collector includes:

[0075] The graphene film is thermally laminated on both sides onto the negative electrode current collector.

[0076] In some embodiments, the graphene anode undergoes a pre-sodiuming treatment, comprising the following steps: vacuum evaporation of sodium metal onto the graphene anode; the vacuum evaporation conditions include: a temperature of 150℃-250℃, which can be 150℃, 180℃, 200℃, 220℃, or 250℃; a time of 20s-60s, which can be 20s, 30s, 40s, 50s, or 60s; and a vacuum degree of 2×10⁻⁶. - 4 Pa-1×10 -2 Pa. This application improves the sodium insertion depth of graphene anodes by controlling the temperature and time of vacuum evaporation. Using the prepared pre-sodium graphene anodes in sodium-ion capacitors can improve the capacitance, cycle performance, and rate performance of sodium-ion capacitors.

[0077] In a second aspect of this application, a presodium graphene anode prepared by the method described in the first aspect is provided.

[0078] The third aspect of this application provides the application of the pre-sodium graphene anode prepared by the method described in the first aspect or the pre-sodium graphene anode described in the second aspect in sodium-ion capacitors.

[0079] In a fourth aspect of this application, a sodium-ion capacitor is provided, comprising a pre-sodium graphene anode prepared by the method described in the first aspect or the pre-sodium graphene anode described in the second aspect.

[0080] In this embodiment, the sodium-ion capacitor is a soft-pack multilayer sodium-ion capacitor.

[0081] The pre-sodium graphene anode and cathode described in this application, when assembled into a sodium-ion capacitor, can not only improve the initial efficiency of the sodium-ion capacitor, but also reduce the internal resistance of the sodium-ion capacitor and improve the rate performance and cycle performance of the sodium-ion hybrid capacitor.

[0082] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0083] Example 1

[0084] The preparation method of pre-sodium graphene anode is as follows:

[0085] 1) Graphene oxide was prepared by oxidizing natural flake graphite (from BTR, model HRG-3) using a modified Hummers method. The specific steps of the modified Hummers method were as follows: ① 1 kg of potassium persulfate and 1 kg of phosphorus pentoxide were added sequentially to a beaker, sealed, and 3 L of concentrated sulfuric acid was added to the beaker. After stirring at 300 rpm until homogeneous, the beaker was placed in an 80°C constant temperature water bath and heated, then sealed and stirred at 300 rpm for 30 min; ② 2 kg of natural flake graphite was added to the mixed solution, and after stirring at 1200 rpm until homogeneous, the solution was placed in an 80°C constant temperature drying oven and kept at that temperature for 6 h. After removal, the solution was cooled to room temperature; ③ The solution was then washed with deionized water and filtered until the washing liquid was neutral. The obtained solid was then cooled to room temperature (2 ④ Dry the pre-oxidized graphite to constant weight at 5℃ to prepare pre-oxidized graphite; ⑤ Add the obtained pre-oxidized graphite and 1 kg sodium nitrate to 46 L concentrated sulfuric acid, and stir at 1200 rpm for 30 min to mix evenly; ⑥ Gradually add 6 kg potassium permanganate powder, and stir at 20℃ for 2 h to obtain a mixed solution; ⑦ Heat the mixed solution to 35℃ and react at a constant temperature for 2 h; ⑧ Add 60 L deionized water to the mixed solution and react at 95℃ for 15 min; ⑨ Continue to add 60 L deionized water and 5 L hydrogen peroxide (concentration of 30 wt%) solution to terminate the reaction, and wash with 10 wt% hydrochloric acid 9 times; ⑨ Then dialyze once using a dialysis bag (Soleport YA1075 type) to remove impurities such as metal ions and acid radical ions; ⑩ Freeze-dry to prepare graphene oxide;

[0086] 2) Add 500g of graphene oxide obtained in step 1) to a 5L kneader, then add 1200g of deionized water and 2500g of n-octadecane in sequence, and knead under vacuum at 25°C for 30min to prepare a graphene oxide dispersion.

[0087] 3) According to Figure 1 At 25°C, a twin-screw extruder was used to extrude the graphene oxide dispersion obtained in step 2) through an extrusion die to prepare a wet film with a thickness of 400 μm (the orientation of the graphene oxide in the wet film is as follows). Figure 2 As shown), an 8000 Gs magnetic field (provided by a metal device, induction coil, wires, and induction heating power supply) is applied to the wet film. The direction of the magnetic field is perpendicular to the first and second surfaces of the wet film (the first and second surfaces are the largest surface areas of the wet film). After applying the magnetic field, the orientation arrangement of graphene oxide in the wet film is as follows. Figure 3 As shown, the graphene oxide film was then dried in a forced-air drying oven at 90°C.

[0088] 4) The graphene oxide film obtained in step 3) was immersed in a hydrazine hydrate solution with a concentration of 40 mg / L for a reduction reaction for 15 min. The reduced graphene oxide film was transferred to a high-temperature furnace and carbonized at 700 °C for 6 h under argon protection. Then it was transferred to a hydraulic roller press and rolled under a pressure of 20 tons to prepare a graphene film with a thickness of 40 μm.

[0089] 5) The graphene film obtained in step 4) is thermally laminated on both sides onto a 24μm thick carbon-coated aluminum foil (provided by Guangzhou Nano New Material Technology Co., Ltd.), and then rolled over with 10 tons to prepare a 100μm thick graphene anode.

[0090] 6) Use a vacuum coating machine at 200℃ and 5×10 -4 Under vacuum conditions, sodium metal was used to vacuum-deposit the graphene anode obtained in step 5) for 30 seconds to prepare a pre-sodium graphene anode.

[0091] The preparation method of sodium-ion capacitors is as follows:

[0092] Sodium nickel manganese ferrite, activated carbon, conductive carbon black and polyvinylidene fluoride were mixed in a mass ratio of 84:5:6:5 to form a slurry, which was then coated onto a 22μm etched aluminum foil. After being dried at 100℃ and rolled at 80 tons, a sodium ion capacitor positive electrode with a thickness of 95μm was obtained.

[0093] The prepared pre-sodium graphene negative electrode and sodium-ion hybrid capacitor positive electrode were die-cut using a die-cutting machine. Then, 19 positive electrodes, 20 negative electrodes, and a cellulose separator were stacked together using an automatic stacking machine to obtain a 06×53×83mm multilayer sodium-ion hybrid capacitor core package. After the core package was assembled into a 06×53×83mm soft-pack multilayer sodium-ion hybrid capacitor crude product, the soft-pack multilayer sodium-ion hybrid capacitor crude product was subjected to formation and aging treatments in a voltage range of 2V-4V to obtain a 06×53×83mm soft-pack multilayer sodium-ion capacitor.

[0094] Example 2

[0095] The preparation method of pre-sodium graphene anode is as follows:

[0096] 1) Natural flake graphite (produced by BTR, model HRG-3) was oxidized using the improved Hummers method to prepare graphene oxide. The specific steps of the improved Hummers method are the same as in Example 1.

[0097] 2) Add 500g of graphene oxide obtained in step 1) to a 5L kneader, then add 1200g of deionized water and 2000g of n-tetradecane in sequence, and knead under vacuum for 30min to prepare a graphene oxide dispersion.

[0098] 3) According to Figure 1At 25°C, a twin-screw extruder was used to extrude the graphene oxide dispersion obtained in step 2) through an extrusion die to prepare a wet film with a thickness of 360 μm. An external magnetic field of 11000 Gs (provided by metal devices, induction coils, wires and induction heating power supply) was applied to the wet film. The direction of the external magnetic field was perpendicular to the first and second surfaces of the wet film (the first and second surfaces are the largest area surfaces of the wet film). Then, the film was dried in a forced-air drying oven at 90°C to prepare the graphene oxide film.

[0099] 4) The graphene oxide film obtained in step 3) was immersed in a hydrazine hydrate solution with a concentration of 40 mg / L for a reduction reaction for 15 min. The reduced graphene oxide film was transferred to a high-temperature furnace and carbonized at 700 °C for 6 h under argon protection. Then it was transferred to a hydraulic roller press and rolled under a pressure of 20 tons to prepare a graphene film with a thickness of 40 μm.

[0100] 5) The graphene film obtained in step 4) is thermally laminated on both sides onto a 24μm thick carbon-coated aluminum foil (provided by Guangzhou Nano New Material Technology Co., Ltd.), and then rolled over with 10 tons to prepare a 100μm thick graphene anode.

[0101] 6) Use a vacuum coating machine at 200℃ and 5×10 -4 Under vacuum conditions, sodium metal was used to vacuum-deposit the graphene anode obtained in step 5) for 30 seconds to prepare a pre-sodium graphene anode.

[0102] Sodium-ion capacitors were prepared according to the method in Example 1.

[0103] Example 3

[0104] The preparation method of pre-sodium graphene anode is as follows:

[0105] 1) Graphene oxide was prepared by oxidizing natural flake graphite (produced by BTR, model HRG-3) using the improved Hummers method. The specific steps of the improved Hummers method are the same as in Example 1.

[0106] 2) Add 500g of graphene oxide obtained in step 1) to a 5L kneader, then add 1200g of deionized water and 1800g of n-decane in sequence, and knead under vacuum for 30min to prepare a graphene oxide dispersion.

[0107] 3) According to Figure 1At 25°C, a twin-screw extruder was used to extrude the graphene oxide dispersion obtained in step 2) through an extrusion die to prepare a wet film with a thickness of 300 μm. An external magnetic field of 12500 Gs (provided by metal devices, induction coils, wires and induction heating power supply) was applied to the wet film. The direction of the external magnetic field was perpendicular to the first and second surfaces of the wet film (the first and second surfaces are the largest area surfaces of the wet film). Then, the film was dried in a forced-air drying oven at 90°C to prepare the graphene oxide film.

[0108] 4) The graphene oxide film obtained in step 3) was immersed in a hydrazine hydrate solution with a concentration of 40 mg / L for a reduction reaction for 15 min. The reduced graphene oxide film was transferred to a high-temperature furnace and carbonized at 700 °C for 6 h under argon protection. Then it was transferred to a hydraulic roller press and rolled under a pressure of 20 tons to prepare a graphene film with a thickness of 40 μm.

[0109] 5) The graphene film obtained in step 4) is thermally laminated on both sides onto a 24μm thick carbon-coated aluminum foil (provided by Guangzhou Nano New Material Technology Co., Ltd.), and then rolled over with 10 tons to prepare a 100μm thick graphene anode.

[0110] 6) Use a vacuum coating machine at 200℃ and 5×10 -4 Under vacuum conditions, sodium metal was used to vacuum-deposit the graphene anode obtained in step 5) for 30 seconds to prepare a pre-sodium graphene anode.

[0111] Sodium-ion capacitors were prepared according to the method in Example 1.

[0112] Comparative Example 1

[0113] The preparation method of pre-sodium graphene anode is as follows:

[0114] 1) Graphene oxide was prepared by oxidizing natural flake graphite (produced by BTR, model HRG-3) using the improved Hummers method. The specific steps of the improved Hummers method are the same as in Example 1.

[0115] 2) Add 500g of graphene oxide obtained in step 1) to a 5L kneader, add 4000g of deionized water in sequence, stir with a mixer to form a uniform graphene oxide dispersion, coat the obtained graphene oxide dispersion on a PET substrate, and dry at 80℃ to obtain a graphene oxide film with a thickness of 60μm.

[0116] 3) Separate the PET substrate and immerse the graphene oxide film obtained in step 2) in a hydrazine hydrate solution with a concentration of 40 mg / L for a reduction reaction for 15 min. Transfer the reduced graphene oxide film to a high-temperature furnace and carbonize it at 700 °C for 6 h under argon protection. Then transfer it to a hydraulic roller mill and roll it under a pressure of 20 tons to prepare a graphene film with a thickness of 40 μm.

[0117] 4) The graphene film obtained in step 3) is thermally laminated on both sides onto a 24μm thick carbon-coated aluminum foil (provided by Guangzhou Nano New Material Technology Co., Ltd.), and then rolled over with 10 tons to prepare a 100μm thick graphene anode.

[0118] 6) Use a vacuum coating machine at 200℃ and 5×10 -4 Under vacuum conditions, sodium metal was used to vacuum-deposit the graphene anode obtained in step 4) for 30 seconds to prepare a pre-sodium graphene anode.

[0119] Sodium-ion capacitors were prepared according to the method in Example 1.

[0120] Comparative Example 2

[0121] The preparation methods of the pre-sodium graphene anodes in Comparative Example 2 and Example 3 are basically the same, except that no external magnetic field is applied to the wet film.

[0122] Pre-sodium graphene anode and sodium-ion capacitor were prepared according to the method in Example 3.

[0123] Comparative Example 3

[0124] The preparation method of pre-sodium graphene anode is as follows:

[0125] 1) Graphene oxide was prepared by oxidizing natural flake graphite (produced by BTR, model HRG-3) using the improved Hummers method. The specific steps of the improved Hummers method are the same as in Example 1.

[0126] 2) Add 500g of graphene oxide obtained in step 1) to a 5L kneader, then add 200g of deionized water and 2000g of n-decane in sequence, and knead under vacuum for 30min to prepare a graphene oxide dispersion.

[0127] 3) According to Figure 1 At 25°C, a twin-screw extruder was used to extrude the graphene oxide dispersion obtained in step 2) through an extrusion die to prepare a wet film with a thickness of 300 μm. An external magnetic field of 12500 Gs (provided by metal devices, induction coils, wires and induction heating power supply) was applied to the wet film. The direction of the external magnetic field was perpendicular to the first and second surfaces of the wet film (the first and second surfaces are the largest area surfaces of the wet film). Then, the film was dried in a forced-air drying oven at 90°C to prepare the graphene oxide film.

[0128] Steps 4) to 6) are the same as in Example 1, preparing a pre-sodium graphene anode.

[0129] Sodium-ion capacitors were prepared according to the method in Example 1.

[0130] Comparative Example 4

[0131] The preparation method of the pre-sodium graphene anode of Comparative Example 4 is basically the same as that of Example 1, except that: in step 2), 1200 grams of deionized water was not added and an external magnetic field of 12500 Gs was applied to the wet film.

[0132] Pre-sodium graphene anode and sodium-ion capacitor were prepared according to the method in Example 1.

[0133] Comparative Example 5

[0134] The preparation method of the pre-sodium graphene anode of Comparative Example 5 is basically the same as that of Example 1, except that the amount of deionized water added in step 2 is increased to 6000g, and an external magnetic field of 12500Gs is applied to the wet film.

[0135] Pre-sodium graphene anode and sodium-ion capacitor were prepared according to the method in Example 1.

[0136] Experimental Example 1

[0137] (1) The initial capacitance and internal resistance of the soft-pack multilayer sodium-ion capacitors of Examples 1-3 and Comparative Examples 1-5 were tested under the condition of “5C charging / 5C discharging”. Then, the capacitance and internal resistance were tested after 3000 cycles under the condition of “5C charging / 5C discharging”. The test results are shown in Table 1.

[0138] Table 1 Initial electrical performance and cycle performance of soft-pack multilayer sodium-ion capacitors

[0139]

[0140] The results in Table 1 show that, compared with Comparative Examples 1-5, the initial capacity and cycle performance of the soft-pack multilayer sodium-ion capacitors in Examples 1-3 are significantly improved, and the initial internal resistance is significantly reduced.

[0141] Compared with Comparative Example 1, the initial capacitance of the soft-pack multilayer sodium-ion capacitors in Examples 1-3 increased by 23%-26%, the initial internal resistance decreased by 21%, and the initial coulombic efficiency increased by 13%. After 3000 cycles, the capacitance increased by 31%-33%, and the internal resistance decreased by 21%. It can be seen that this application can significantly improve the initial capacitance and cycling performance of the soft-pack multilayer sodium-ion capacitor by preparing a graphene oxide dispersion and simultaneously applying a magnetic field to the wet film.

[0142] Compared to Comparative Example 2, where no magnetic field was applied to the wet film, the initial capacitance of the soft-pack multilayer sodium-ion capacitors in Examples 1-3 increased by 21%-23%, and the initial internal resistance decreased by 19%; after 3000 cycles, the capacitance increased by 28%-30%, and the internal resistance decreased by 19%. It is evident that by applying a magnetic field to the wet film, this application can significantly improve the initial capacitance and cycle performance of the soft-pack multilayer sodium-ion capacitor.

[0143] Compared to Comparative Example 3, which used a mass ratio of 1:0.4:5 to prepare a graphene oxide dispersion, Example 1 used a mass ratio of 1:2.4:5 to prepare a graphene oxide dispersion. This resulted in a 23% increase in the initial capacitance, a 21% decrease in the initial internal resistance, and a 14% increase in the initial coulombic efficiency of the soft-pack multilayer sodium-ion capacitor. After 3000 cycles, the capacitance increased by 31% and the internal resistance decreased by 23%. It can be seen that the mass ratio of graphene oxide, water, and n-decane used in Comparative Example 3 was not within the range of 1:(1-10):(0.5-10). Even with an increased external magnetic field, the uniformity of sodium intercalation distribution, intercalation efficiency, and intercalation depth of the pre-sodium graphene anode were significantly reduced, leading to a significant decrease in the initial capacitance and cycling performance of the soft-pack multilayer sodium-ion capacitor.

[0144] Compared to Example 1, which used a 1:2.4:5 mixture of graphene oxide, water, and n-decane to prepare a graphene oxide dispersion, Comparative Example 4, which did not add deionized water and used a 1:5 mass ratio of graphene oxide and n-decane to prepare a graphene oxide dispersion, still showed a 21% decrease in initial capacitance, a 26% increase in initial internal resistance, and a 12% decrease in initial coulombic efficiency of its pouch-type multilayer sodium-ion capacitor, even with an increased external magnetic field. After 3000 cycles, the capacitance decreased by 26% and the internal resistance increased by 26%. This indicates that Comparative Example 4, which only used graphene oxide and n-decane to prepare the graphene oxide dispersion, significantly reduced the uniformity of sodium intercalation distribution, intercalation efficiency, and intercalation depth of its pre-sodium graphene anode, even with an increased external magnetic field, resulting in a significant decrease in the initial capacitance and cycling performance of the pouch-type multilayer sodium-ion capacitor.

[0145] Compared to Example 1, which used a 1:2.4:5 mixture of graphene oxide, water, and n-decane to prepare a graphene oxide dispersion, Comparative Example 5, which used a 1:12:5 mass ratio of graphene oxide, water, and n-decane, still showed a 21% decrease in initial capacitance, a 26% increase in initial internal resistance, and an 11% decrease in initial coulombic efficiency of its pouch-type multilayer sodium-ion capacitor, even with an increased external magnetic field strength. After 3000 cycles, the capacitance decreased by 25% and the internal resistance increased by 27%. It can be seen that the mass ratio of graphene oxide, water, and n-decane used in Comparative Example 5 was not within the range of 1:(1-10):(0.5-10). Even with an increased external magnetic field strength, the uniformity of sodium intercalation distribution, sodium intercalation efficiency, and sodium intercalation depth of the pre-sodium graphene anode were significantly reduced, resulting in a significant decrease in the initial capacitance and cycling performance of the pouch-type multilayer sodium-ion capacitor.

[0146] Comparing Example 1 and Comparative Examples 3-5, it can be seen that preparing a graphene oxide dispersion by mixing graphene oxide, water and aliphatic hydrocarbons in a mass ratio of 1:(1-10):(0.5-10) can significantly improve the uniformity of sodium intercalation distribution, sodium intercalation efficiency and sodium intercalation depth of the pre-sodium graphene anode, thereby improving the initial capacity and cycle performance of the soft-pack multilayer sodium-ion capacitor.

[0147] (2) The rate performance of the soft-pack multilayer sodium-ion capacitors of Examples 1-3 and Comparative Examples 1-5 was tested according to the charging / discharging values ​​of “5C / 10C”, “5C / 20C”, “5C / 30C”, “5C / 40C” and “5C / 50C” respectively. The test results are shown in Table 2.

[0148] Table 2 Rate performance of soft-pack multilayer sodium-ion capacitors

[0149]

[0150] The results in Table 2 show that, compared with Comparative Examples 1-5, the rate performance of the soft-pack multilayer sodium-ion capacitors in Examples 1-3 is significantly improved, and the initial internal resistance is significantly reduced.

[0151] Compared with Comparative Example 1, the soft-pack multilayer sodium-ion capacitors of Examples 1-3 showed a 26%-49% increase in capacitance and a 22%-28% decrease in internal resistance at 5C charging / 10C-50C discharging rates. It is evident that this application can significantly improve the rate performance of soft-pack multilayer sodium-ion capacitors by preparing a graphene oxide dispersion and simultaneously applying a magnetic field to the wet film.

[0152] Compared to Comparative Example 2, where no magnetic field was applied to the wet film, the soft-pack multilayer sodium-ion capacitors of Examples 1-3 showed a 23%-46% increase in capacitance and a 21%-27% decrease in internal resistance at 5C charging / 10C-50C discharging rates. This demonstrates that the present application can significantly improve the rate performance of soft-pack multilayer sodium-ion capacitors by applying a magnetic field to the wet film.

[0153] Compared to Comparative Example 3, which used a 1:0.4:5 mass ratio of graphene oxide, water, and n-decane to prepare a graphene oxide dispersion, Example 1 used a 1:2.4:5 mass ratio of graphene oxide, water, and n-decane to prepare a graphene oxide dispersion. The resulting soft-pack multilayer sodium-ion capacitor exhibited a 28%-45% increase in capacitance and a 23%-29% decrease in internal resistance at a 5C charging / 10C-50C discharging rate. It is evident that the mass ratio of graphene oxide, water, and n-decane used in Comparative Example 3 was not within the range of 1:(1-10):(0.5-10). Even with an increased external magnetic field, the uniformity of sodium intercalation distribution, intercalation efficiency, and intercalation depth of the pre-sodium graphene anode were significantly reduced, resulting in a significant decrease in the rate performance of the soft-pack multilayer sodium-ion capacitor.

[0154] Compared to Example 1, which used a 1:2.4:5 mixture of graphene oxide, water, and n-decane to prepare a graphene oxide dispersion, Comparative Example 4, which did not add deionized water and used a 1:5 mass ratio of graphene oxide and n-decane to prepare a graphene oxide dispersion, even with an increased external magnetic field strength, showed a 23%-32% increase in capacitance and a 30%-41% decrease in internal resistance in its soft-pack multilayer sodium-ion capacitor at a 5C charging / 10C-50C discharging rate. This indicates that Comparative Example 4, which only used graphene oxide and n-decane to prepare the graphene oxide dispersion, even with an increased external magnetic field strength, still significantly reduced the uniformity of sodium intercalation distribution, sodium intercalation efficiency, and sodium intercalation depth in its pre-sodium graphene anode, resulting in a significant decrease in the rate performance of the soft-pack multilayer sodium-ion capacitor.

[0155] Compared to Example 1, which used a 1:2.4:5 mixture of graphene oxide, water, and n-decane to prepare a graphene oxide dispersion, Comparative Example 5, which used a 1:12:5 mass ratio of graphene oxide, water, and n-decane, showed that even with an increased external magnetic field, its soft-pack multilayer sodium-ion capacitor exhibited a 22%-32% increase in capacitance and a 29%-40% decrease in internal resistance at a 5C charging / 10C-50C discharging rate. This indicates that because the mass ratio of graphene oxide, water, and n-decane used in Comparative Example 5 was not within the range of 1:(1-10):(0.5-10), even with an increased external magnetic field, the uniformity of sodium intercalation distribution, intercalation efficiency, and intercalation depth of the pre-sodium graphene anode were significantly reduced, resulting in a significant decrease in the rate performance of the soft-pack multilayer sodium-ion capacitor.

[0156] Comparing Example 1 and Comparative Examples 3-5, it can be seen that preparing a graphene oxide dispersion by mixing graphene oxide, water and aliphatic hydrocarbons in a mass ratio of 1:(1-10):(0.5-10) can significantly improve the uniformity of sodium intercalation distribution, sodium intercalation efficiency and sodium intercalation depth of the pre-sodium graphene anode, thereby improving the rate performance of the soft-pack multilayer sodium-ion capacitor.

[0157] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a pre-sodium graphene anode, characterized in that, Includes the following steps: A graphene oxide dispersion was prepared by mixing graphene oxide, water, and aliphatic hydrocarbons in a mass ratio of 1:(1-10):(0.5-10). The graphene oxide dispersion is prepared into a wet film, the wet film having a first surface and a second surface opposite to each other; A magnetic field perpendicular to the second surface is applied to the wet film to prepare a graphene oxide film; The graphene oxide film was reduced to prepare a graphene film. The graphene film is composited onto the negative electrode current collector to prepare a graphene negative electrode; The graphene anode is pre-sodiumized to prepare the pre-sodiumized graphene anode.

2. The method for preparing the pre-sodium graphene anode according to claim 1, characterized in that, The strength of the magnetic field is 6000Gs-15000Gs.

3. The method for preparing the pre-sodium graphene anode according to claim 1, characterized in that, The aliphatic hydrocarbons include one or more of C6-18 straight-chain aliphatic hydrocarbons, C6-18 branched aliphatic hydrocarbons, and C6-18 alicyclic hydrocarbons.

4. The method for preparing the pre-sodium graphene anode according to claim 3, characterized in that, The aliphatic hydrocarbons include C6-18 straight-chain aliphatic hydrocarbons; the C6-18 straight-chain aliphatic hydrocarbons include one or more of the following: n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecanane, n-hexadecane, n-heptadecane, and n-octadecane.

5. The method for preparing the pre-sodium graphene anode according to claim 3 or 4, characterized in that, The mass ratio of the graphene oxide, water and aliphatic hydrocarbon is 1:(2-3):(3-5).

6. The method for preparing the pre-sodium graphene anode according to claim 1, characterized in that, One or more of the following conditions must be met: (1) The graphene oxide dispersion is prepared into a wet film by the following steps: extruding the graphene oxide dispersion at an extrusion temperature of 20℃-40℃ to prepare a wet film; (2) The conditions for reduction treatment include: using hydrazine hydrate, NaHSO3, Na2S‧9H2O, Na2S2O3, SOCl2 or SO2 for reduction treatment; (3) After reduction treatment, the process also includes carbonization and rolling. The conditions for carbonization include: inert gas atmosphere; temperature of 400℃-1000℃; the conditions for rolling include: pressure of 10 tons-30 tons. (4) After applying a magnetic field perpendicular from the first surface to the second surface to the wet film, the process further includes a drying step; the drying conditions include a temperature of 65℃-115℃. (5) The thickness of the graphene film is 30μm-80μm.

7. The method for preparing the pre-sodium graphene anode according to claim 1, characterized in that, The pre-sodiuming treatment of the graphene anode includes the following steps: vacuum evaporation of sodium metal onto the graphene anode; the vacuum evaporation conditions include: temperature of 150℃-250℃; time of 20s-60s; and vacuum degree of 2×10⁻⁶. -4 Pa-1×10 -2 Pa.

8. The presodium graphene anode prepared by the method for preparing the presodium graphene anode according to any one of claims 1-7.

9. The application of the pre-sodium graphene anode prepared by the method of any one of claims 1-7 or the pre-sodium graphene anode of claim 8 in a sodium-ion capacitor.

10. A sodium-ion capacitor, characterized in that, The presodium graphene anode prepared by the method described in any one of claims 1-7 or the presodium graphene anode described in claim 8.

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