Hard carbon negative electrode active material, and preparation method and application thereof
By using gelatin and reducing sugars combined with electrospinning and heat treatment techniques, a hard carbon anode active material with controllable pore structure was prepared, solving the structural control problem of biomass hydrocarbon precursors in the preparation process, improving battery performance, simplifying the process, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WANHUA CHEM GRP BATTERY TECH CO LTD
- Filing Date
- 2024-12-02
- Publication Date
- 2026-06-09
AI Technical Summary
The structure of biomass-derived hydrocarbon precursors is difficult to control during the preparation of hard carbon anode active materials, which leads to a decline in battery performance. In addition, the use of conductive agents and binders increases cost and complexity.
Using gelatin and reducing sugars as raw materials, combined with electrospinning and heat treatment techniques, a hard carbon anode active material with controllable pore structure was prepared, avoiding the use of supports and binders. Nanofiber membranes were formed by electrospinning and pre-carbonized and high-temperature carbonized in a nitrogen atmosphere.
The pore structure and microstructure of hard carbon anode active materials were controlled, which improved the energy density and power density of the battery, reduced material costs, and simplified the manufacturing process.
Smart Images
Figure CN122166748A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of sodium-ion battery technology. Specifically, this application relates to a hard carbon negative electrode active material, its preparation method, and its application. Background Technology
[0002] Biomass-based hard carbon materials hold great promise for the commercial application of sodium-ion batteries. However, the complex composition of biomass-derived hydrocarbon precursors often requires significant effort to achieve controlled structures and desired performance. The content of defects and the evolution of pore structures are difficult to control, which is crucial for battery performance and technological advancement. Commonly used biomass materials such as bamboo and coconut shells share the common characteristic of being rich in hydroxyl groups. Their carbonization process mainly involves complex pyrolysis and gasification stages, accompanied by the release of large amounts of gas, leading to poor control of hydrocarbon microstructure, carbon loss, and reduced process efficiency. Furthermore, biomass-based hard carbon anode active materials require the application of conductive agents, dispersants, and binders onto the current collector, resulting in high raw material costs and complex manufacturing processes. Additionally, binder failure can cause active materials to detach from the current collector, increasing battery internal resistance and reducing battery performance. Therefore, further research is necessary to improve the preparation process of biomass-based hard carbon anode active materials and enhance their performance. Summary of the Invention
[0003] This application aims to at least partially address one of the technical problems in the related art. To this end, embodiments of this application propose a hard carbon anode active material, its preparation method, and its application. The hard carbon anode active material has a tunable pore structure and hydrocarbon microstructure, and requires no support or binder, thereby reducing the weight and volume of the electrode and improving the overall energy density and power density of the battery.
[0004] The first aspect of this application provides a method for preparing a hard carbon anode active material, comprising the following steps:
[0005] (1) Dissolve gelatin and reducing sugar in water to obtain an electrospinning solution;
[0006] (2) Electrospinning the electrospinning solution with aluminum foil as the receiving substrate to obtain an electrospinned nanofiber membrane, and then allowing it to stand to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0007] (3) The gelatin-based nanofiber anode precursor is first pre-carbonized in a nitrogen atmosphere, then carbonized at high temperature, and cooled to obtain the hard carbon anode active material.
[0008] In some embodiments, in step (1), the reducing sugar includes at least one of glucose, fructose, galactose, lactose, and maltose.
[0009] In some embodiments, in step (1), the mass ratio of the gelatin to the reducing sugar is (5-9):(1-5).
[0010] In some embodiments, in step (1), the mass concentration of the electrospinning solution is 5% to 15%.
[0011] In some embodiments, in step (2), the electrospinning voltage is 10-20kV, the receiving distance is 8-20cm, the injection speed is 0.05-0.3mm / min, and the receiving roller speed is 50-300r.
[0012] In some embodiments, in step (3), the temperature of the pre-carbonization treatment is 150-350°C, the heating rate is 1-5°C / min, and the holding time is 1-5h.
[0013] In some embodiments, in step (3), the high-temperature carbonization temperature is 500-1500°C, the heating rate is 1-10°C / min, and the holding time is 1-5h.
[0014] The second aspect of this application also provides a hard carbon anode active material, which is prepared by the preparation method described in the first aspect.
[0015] The third aspect of this application provides a negative electrode sheet, comprising a hard carbon negative electrode active material prepared by the preparation method described in the first aspect or a hard carbon negative electrode active material described in the second aspect.
[0016] A fourth aspect of this application provides a sodium-ion battery, including the negative electrode sheet as described in the third aspect.
[0017] The advantages and beneficial effects of the preparation method of the hard carbon negative electrode active material in this application are as follows:
[0018] This application embodiment uses gelatin and reducing sugar as reaction raw materials. Gelatin, as a hard carbon precursor material, is widely available, inexpensive, easily pyrolyzed into carbon, and has good film-forming properties, which is beneficial for controlling the evolution of the hard carbon microstructure, thereby achieving the controllability of the pore structure and hydrocarbon microstructure of the hard carbon anode active material. The reducing sugar can promote intermolecular cross-linking, thereby enhancing the stability of the hydrocarbon structure during pyrolysis and improving process efficiency. Combined with electrospinning and heat treatment technologies, a biomass-based hard carbon anode active material for sodium-ion batteries with controllable pore structure, high conductivity, self-supporting, and no binder required is prepared. Attached Figure Description
[0019] Figure 1This is a SEM image of the hard carbon anode active material prepared in Example 7 of this application. Detailed Implementation
[0020] The embodiments of this application are described in detail below. These embodiments are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0021] 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 pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.
[0022] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.
[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0024] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
[0025] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.
[0026] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).
[0027] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0028] The first aspect of this application provides a method for preparing a hard carbon anode active material, comprising the following steps:
[0029] (1) Dissolve gelatin and reducing sugar in water to obtain an electrospinning solution;
[0030] (2) Electrospinning the electrospinning solution with aluminum foil as the receiving substrate to obtain an electrospinned nanofiber membrane, and then allowing it to stand to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0031] (3) The gelatin-based nanofiber anode precursor is first pre-carbonized in a nitrogen atmosphere, then carbonized at high temperature, and cooled to obtain the hard carbon anode active material.
[0032] In some embodiments, in step (1), the reducing sugar includes at least one of glucose, fructose, galactose, lactose, and maltose.
[0033] It should be noted that the gelatin mentioned in this article is a protein product obtained by partially hydrolyzing collagen from animal skin, bones, and ligaments, specifically including bovine skin gelatin, bovine bone gelatin, pig skin gelatin, pig bone gelatin, fish bone gelatin, fish skin gelatin, chicken skin gelatin, and chicken bone gelatin.
[0034] This application uses gelatin as a precursor for hard carbon materials. Its abundant -COOH and -NH2 groups promote cross-linking, helping to control the evolution of the hard carbon microstructure, including defect levels, average interlayer spacing, and pore structure. Furthermore, this application also selects reducing sugars as reactants, which can undergo a condensation reaction with amino-containing compounds (proteins), known as the Maillard reaction. This promotes intermolecular cross-linking, thereby enhancing the stability of the hydrocarbon structure during pyrolysis and improving process efficiency.
[0035] In some embodiments, in step (1), the mass ratio of gelatin to reducing sugar is (5-9):(1-5), with non-limiting examples such as 5:1, 5:5, 8:2, 8:5, 9:1, 9:3, etc. The inventors have found that when the amount of gelatin added is too high, the intermolecular forces are weaker, thus weakening the Maillard reaction and ultimately resulting in poor carbonization. However, if the amount of gelatin added is too low, the film-forming effect based on electrospinning technology will be poor, making it difficult to form a gelatin-based film material with a good structure. Therefore, in this application embodiment, the mass ratio of gelatin to reducing sugar is controlled within the range of (5-9):(1-5).
[0036] In some embodiments, in step (1), the mass concentration of the electrospinning solution (i.e., the sum of the masses of gelatin and reducing sugar / the sum of the masses of gelatin, reducing sugar and solvent water) is 5% to 15%, and non-limiting examples include: 5%, 8%, 10%, 12%, 15%, etc.
[0037] In some embodiments, in step (2), the electrospinning voltage is 10-20kV (non-limiting examples include: 10kV, 12kV, 15kV, 18kV, 20kV, etc.), the receiving distance (i.e., the distance between the electrospinning nozzle and the receiving roller) is 8-20cm (non-limiting examples include: 8cm, 10cm, 12cm, 15cm, 17cm, 18cm, 20cm, etc.), the injection speed is 0.05-0.3mm / min (non-limiting examples include: 0.05mm / min, 0.08mm / min, 0.1mm / min, 0.2mm / min, 0.25mm / min, 0.3mm / min, etc.), and the receiving roller rotation speed is 50-300r (non-limiting examples include: 50r, 80r, 100r, 150r, 200r, 300r, etc.). The inventors discovered through research that when the spinning voltage is <10kV, the electric field force is insufficient to overcome the surface tension, which can lead to fiber blockage and affect the film formation effect. However, when the spinning voltage is >20kV, the fiber diameter becomes too small, which is not conducive to the control of the pore structure of the membrane material. Therefore, it is advantageous to control the spinning voltage to 10-20kV in the embodiments of this application.
[0038] The preparation method of hard carbon negative electrode active material in this application adopts electrospinning technology, which has the advantages of adjustable fiber diameter, diverse fiber morphology, strong adaptability to fiber materials, high efficiency, environmental protection and economy. The preliminary pore structure can be controlled by adjusting key process parameters such as spinning voltage, receiving distance and injection speed.
[0039] In some embodiments, in step (3), the temperature of the pre-carbonization treatment is 150-350°C (non-limiting examples: 150°C, 180°C, 200°C, 250°C, 300°C, 350°C, etc.), the heating rate is 1-5°C / min (non-limiting examples: 1°C / min, 2°C / min, 4°C / min, 5°C / min, etc.), and the holding time is 1-5h (non-limiting examples: 1h, 2h, 3h, 4h, 5h, etc.);
[0040] In some embodiments, in step (3), the high-temperature carbonization temperature is 500-1500℃ (non-limiting examples: 500℃, 800℃, 1000℃, 1200℃, 1500℃, etc.), the heating rate is 1-10℃ / min (non-limiting examples: 1℃ / min, 2℃ / min, 5℃ / min, 8℃ / min, 10℃ / min, etc.), and the holding time is 1-5h (non-limiting examples: 1h, 2h, 3h, 4h, 5h, etc.). The inventors have found through research that when the carbonization temperature is <500℃, the material will not be completely carbonized, resulting in poor conductivity. When the carbonization temperature is >1500℃, the material surface will be over-carbonized, leading to burn-off and deformation, which will affect the carbonization effect.
[0041] In the preparation method of hard carbon anode active material in this application embodiment, by performing a two-step heating treatment on the gelatin-based nanofiber anode precursor under a nitrogen atmosphere, nitrogen doping can be introduced to a certain extent, which is beneficial to Na… + Migration, thereby improving the electrochemical performance of the material; and the low-temperature pre-carbonization process can change the internal structure of the material, forming a carbon conductive network, promoting polymerization, and thus improving the yield and conductivity of the material; and the further high-temperature carbonization process after pre-carbonization can enrich carbon elements and remove non-carbon elements, promote cross-linking, regulate the pore structure of molecules, and transform the gelatin-based nanofiber anode precursor into gelatin-based carbon nanofibers, thereby obtaining hard carbon anode active materials.
[0042] The second aspect of this application also provides a hard carbon anode active material, which is prepared by the preparation method described in the first aspect.
[0043] The third aspect of this application provides a negative electrode sheet, including the hard carbon negative electrode active material prepared by the preparation method described in the first aspect or the hard carbon negative electrode active material described in the second aspect.
[0044] Furthermore, the negative electrode sheet can be obtained by cutting the hard carbon negative electrode active material prepared by the preparation method described in the first aspect or the hard carbon negative electrode active material described in the second aspect.
[0045] A fourth aspect of this application provides a sodium-ion battery, including the negative electrode sheet as described in the third aspect.
[0046] In some embodiments, the sodium-ion battery described above also includes a positive electrode.
[0047] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.
[0048] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.
[0049] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
[0050] In this application, the positive electrode active material is capable of reversibly inserting and de-inserting Na. + Compounds. For example, positive electrode active materials include transition metal oxides, polyanionic compounds, Prussian blue analogs, etc.
[0051] In some implementations, the positive electrode active material is a transition metal oxide. As an example, Na can be cited. x MO2 or Na y M₂O₄ (where M is a transition metal, 0≤x≤1, 0≤y≤2) represents sodium-containing complex oxides, spinel-like oxides, layered metal chalcogenides, olivine structures, etc. Examples include sodium cobalt oxides such as NaCoO₂, sodium manganese oxides such as NaMn₂O₄, sodium nickel oxides such as NaNiO₂, and Na… 4 / 3 Ti 5 / 3 Sodium titanium oxides such as O4, sodium manganese nickel composite oxides, sodium manganese nickel cobalt composite oxides; materials with olivine-type crystal structures such as NaMPO4 (M=Fe, Mn, Ni), etc.
[0052] In some embodiments, the positive electrode active material may optionally be a layered or spinel-like sodium-containing composite oxide, such as NaCoO2, NaMn2O4, NaNiO2, or NaNi 1 / 2 Mn 1 / 2 Sodium-manganese-nickel composite oxides, represented by O2, etc., with NaNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, NaNi 0.6 Mn 0.2 Co 0.2 Sodium-manganese-nickel-cobalt composite oxides, represented by O2, or NaNi 1-x-y- z Co x Aly Mg z Sodium-containing composite oxides such as O2 (where 0≤x≤1, 0≤y≤0.1, 0≤z≤0.1, 0≤1-xyz≤1). Furthermore, sodium-containing composite oxides in which a portion of the constituent elements of the aforementioned sodium-containing composite oxides are replaced by additive elements such as Ge, Ti, Zr, Mg, Al, Mo, and Sn are also included within the scope of this application.
[0053] In some embodiments, the positive electrode active material is optionally a polyanionic compound. As an example, the polyanionic compound may be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, or Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn, and Ni), and Na3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).
[0054] In some embodiments, the positive electrode active material is optionally a Prussian blue analogue. As an example, Prussian blue compounds may contain sodium ions, transition metal ions, and cyanide ions (CN). -A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.
[0055] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.
[0056] In some embodiments, the binder may optionally account for 0.1-3.5% of the total weight of the positive electrode film, and optionally 0.5-2.5%.
[0057] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
[0058] In some embodiments, the conductive agent may optionally account for 0.05-5% of the total weight of the positive electrode film, and optionally 0.5-3%.
[0059] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.
[0060] In some embodiments, the sodium-ion battery described above also includes a separator.
[0061] As for the aforementioned separator, this application does not have any particular limitations. Any known porous structure separator with electrochemical and mechanical stability can be selected according to actual needs. For example, it can be a single-layer or multi-layer film containing one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
[0062] In some embodiments, the sodium-ion battery described above also includes an electrolyte.
[0063] The electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte may include an electrolyte salt and a solvent.
[0064] As an example, the electrolyte sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.
[0065] As an example, the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), and methyl butyrate. One or more of the following: (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran, 1,3-dioxopentane, 1,3-dioxane, 1,4-dioxane, tetrahydropyran, methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).
[0066] In some embodiments, the electrolyte also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.
[0067] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.
[0068] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0069] Example 1
[0070] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0071] (1) Dissolve bovine gelatin and fructose in water at a mass ratio of 9:1 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0072] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 15cm, the injection speed was 0.15mm / min, and the receiving roller speed was 200r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0073] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0074] Example 2
[0075] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0076] (1) Dissolve bovine bone gelatin and fructose in water at a mass ratio of 5:5 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0077] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 15cm, the injection speed was 0.15mm / min, and the receiving roller speed was 200r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0078] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0079] Example 3
[0080] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0081] (1) Dissolve fish skin gelatin and fructose in water at a mass ratio of 8:2 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0082] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 10kV, the receiving distance was 10cm, the injection speed was 0.1mm / min, and the receiving roller speed was 150r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0083] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0084] Example 4
[0085] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0086] (1) Dissolve fish bone gelatin and fructose in water at a mass ratio of 8:2 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0087] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 20kV, the receiving distance was 20cm, the injection speed was 0.3mm / min, and the receiving roller speed was 300r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0088] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0089] Example 5
[0090] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0091] (1) Dissolve chicken skin gelatin and fructose in water at a mass ratio of 8:2 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0092] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 15cm, the injection speed was 0.15mm / min, and the receiving roller speed was 200r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0093] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 200°C at a heating rate of 2°C / min for pre-carbonization treatment. After holding at the temperature for 2 hours, it is then heated to 500°C at a heating rate of 5°C / min for high-temperature carbonization. After carbonization for 3 hours, the hard carbon anode active material can be obtained after cooling.
[0094] Example 6
[0095] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0096] (1) Dissolve pork bone gelatin and fructose in water at a mass ratio of 8:2 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 15%.
[0097] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 15cm, the injection speed was 0.15mm / min, and the receiving roller speed was 200r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0098] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 300°C at a heating rate of 2°C / min for pre-carbonization treatment, and then heated to 1500°C at a heating rate of 5°C / min for high-temperature carbonization. After carbonization for 5 hours, the hard carbon anode active material can be obtained after cooling.
[0099] Example 7
[0100] This embodiment proposes a method for preparing a hard carbon anode active material, including the following steps:
[0101] (1) Dissolve pigskin gelatin and fructose in water at a mass ratio of 8:2 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 12%.
[0102] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 15cm, the injection speed was 0.15mm / min, and the receiving roller speed was 200r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25°C to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0103] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization. After carbonization for 5 hours, the hard carbon anode active material can be obtained after cooling.
[0104] Figure 1 The image shows a SEM image of the hard carbon anode active material prepared in this embodiment. As can be seen from the image, the anode active material exhibits a three-dimensional dense carbon network structure with abundant pores. The conductive three-dimensional dense nanofiber structure is very suitable for providing more channels and sites for the rapid transport and storage of sodium ions, promoting redox reactions and the utilization of active substances.
[0105] Comparative Example 1
[0106] This comparative example presents a method for preparing a negative electrode active material, comprising the following steps:
[0107] (1) Dissolve pigskin gelatin and fructose in water at a mass ratio of 3:7 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0108] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 10cm, the injection speed was 0.15mm / min, and the receiving roller speed was 100r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25℃ to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0109] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0110] Comparative Example 2
[0111] This comparative example presents a method for preparing a negative electrode active material, comprising the following steps:
[0112] (1) Dissolve pig bone gelatin and cellulose in water at a mass ratio of 8:2 and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0113] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 10cm, the injection speed was 0.15mm / min, and the receiving roller speed was 100r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25℃ to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor.
[0114] (3) In a nitrogen atmosphere, the gelatin-based nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0115] Comparative Example 3
[0116] This comparative example presents a method for preparing a negative electrode active material, comprising the following steps:
[0117] (1) Dissolve fructose in water and stir magnetically at 25°C to form a uniformly dispersed electrospinning solution with a mass concentration of 10%.
[0118] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 10cm, the injection speed was 0.15mm / min, and the receiving roller speed was 100r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25℃ to allow the water to evaporate completely, forming a fructose nanofiber negative electrode precursor.
[0119] (3) In a nitrogen atmosphere, the fructose nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment. After holding at the temperature for 3 hours, it is then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization. After carbonization for 3 hours, the hard carbon anode active material can be obtained after cooling.
[0120] Comparative Example 4
[0121] This comparative example presents a method for preparing a negative electrode active material, comprising the following steps:
[0122] (1) Polyacrylonitrile is dissolved in N,N-dimethylformamide and stirred at 25°C with magnetic force to form a uniformly dispersed electrospinning solution with a mass concentration of 12%.
[0123] (2) The above electrospinning solution was electrospinned using aluminum foil as the receiving substrate. The electrospinning conditions were controlled as follows: the spinning voltage was 15kV, the receiving distance was 10cm, the injection speed was 0.15mm / min, and the receiving roller speed was 200r. Finally, an electrospinned nanofiber membrane was obtained. Then, it was left to stand at 25℃ to allow the solvent to evaporate completely, forming a polyacrylonitrile nanofiber negative electrode precursor.
[0124] (3) In a nitrogen atmosphere, the polyacrylonitrile nanofiber anode precursor is first heated to 260°C at a heating rate of 3°C / min for pre-carbonization treatment, and then heated to 1000°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours. After cooling, the hard carbon anode active material can be obtained.
[0125] The porosity of the negative electrode active materials prepared in the above embodiments and comparative examples can be determined using a mercury porosimeter (AutoPore IV 9510) according to standard GB / T 42697-2023. Specifically: weigh the sample, transfer the sample to a dilatometer, and test in both the low-pressure chamber and the high-pressure chamber to obtain the porosity data, as shown in Table 1.
[0126] The pore size of the negative electrode active materials prepared in the above embodiments and comparative examples can be measured using a BET surface area analyzer (CN61M / SZB-9) in accordance with standard GB / T 19587-2017. Specifically, the samples were first heated and degassed under vacuum, then placed in liquid nitrogen. The amount of nitrogen adsorbed was measured at different pressure points to obtain adsorption isotherms. The data was processed by computer, and the average pore size was calculated from the adsorption isotherms. The results are shown in Table 1.
[0127] The conductivity of the negative electrode active materials prepared in the above embodiments and comparative examples can be measured using a four-probe resistance meter (HAD-ST2258A) in accordance with standard NB / T 10827-2021. Specifically: at 25°C, the negative electrode active material to be tested is pressed with a four-probe needle, and the button is adjusted to the required thickness to obtain the data. The results are shown in Table 1.
[0128] Electrochemical performance testing
[0129] 1. Battery assembly
[0130] The negative electrode active materials prepared in each embodiment and each comparative example were used as negative electrode sheets, and then assembled into CR2025 coin cells for electrochemical performance testing.
[0131] The assembly method of the CR2025 button cell includes the following steps:
[0132] 1) Preparation of negative electrode sheet: The negative electrode active materials prepared in the above examples and comparative examples are cut into small circular pieces with a diameter of 17 mm using a cutting machine to obtain the negative electrode sheet;
[0133] 2) Preparation of positive electrode sheet: The positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 90:5:5. After stirring for 12 hours, the mixture is uniformly coated on carbon-coated aluminum foil. After drying, it is cut into small round pieces with a diameter of 12 mm using a cutting machine to obtain the positive electrode sheet.
[0134] 3) Separator: Celgard's PP separator is used. It is cut into small round pieces with a diameter of 19mm using a cutting machine to obtain the separator.
[0135] 4) Electrolyte: Dissolve NaPF6 in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DMC) (volume ratio EC:DMC = 1:1) to obtain a NaPF6 solution with a concentration of 1 mol / L.
[0136] 5) Assembly of CR2025 button cell: Place the negative electrode shell flat on an insulating platform, then place the negative electrode sheet obtained in step 1) in the center of the negative electrode shell, then place the separator flat on the negative electrode sheet, and drop an appropriate amount of electrolyte (1M NaPF6EC / DEC) on the surface of the separator. Then, use insulating tweezers to place the positive electrode sheet, gasket, spring sheet and positive electrode shell on the separator in sequence. Finally, use insulating tweezers to place the button cell with the negative electrode side facing up on the button cell sealing machine mold for sealing, thus obtaining the CR2025 button cell.
[0137] 2. Electrochemical performance testing
[0138] 1) Cyclic performance
[0139] The button cells involved in each embodiment and comparative example were subjected to 1C / 1C charge-discharge cycle performance tests. Specifically, they were charged to 4V at 1C, then discharged to 2V at 1C after resting, and the cycle was repeated.
[0140] 2) Charge / discharge specific capacity
[0141] The coin cells involved in each embodiment and comparative example were subjected to charge-discharge capacity tests at 0.2C / 0.2C. Specifically, they were first discharged to 2V at 0.2C, then charged to 4V at 0.2C after resting, and finally discharged to 2V at 0.2C to obtain the charge-discharge capacity.
[0142] 3) Ratio performance
[0143] The button cells involved in each embodiment and comparative example were subjected to rate performance tests at charge / discharge rates of 0.2C / 0.2C, 0.33C, 0.5C, 1C, 3C, 5C, and 10C. Specifically, they were charged to 4V at 0.2C, then discharged to 2V at 0.2C after resting. Subsequently, only the discharge current was changed, while other test parameters remained unchanged.
[0144] The results of the above electrochemical performance tests are shown in Table 1.
[0145] Table 1
[0146]
[0147] As can be seen from Table 1, compared with Comparative Examples 1-4, the coin cells made using the hard carbon anode active material in Examples 1-7 of this application have significant advantages in discharge specific capacity, rate performance and cycle performance, indicating that the hard carbon anode active material of this application has significant implications for the development of electrochemical technology in the field of energy storage.
[0148] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. A method for preparing a hard carbon anode active material, characterized in that, Includes the following steps: (1) Dissolve gelatin and reducing sugar in water to obtain an electrospinning solution; (2) Electrospinning the electrospinning solution with aluminum foil as the receiving substrate to obtain an electrospinned nanofiber membrane, and then allowing it to stand to allow the water to evaporate completely, forming a gelatin-based nanofiber negative electrode precursor. (3) The gelatin-based nanofiber anode precursor is first pre-carbonized in a nitrogen atmosphere, then carbonized at high temperature, and cooled to obtain the hard carbon anode active material.
2. The method for preparing the hard carbon anode active material according to claim 1, characterized in that, In step (1), the reducing sugar includes at least one of glucose, fructose, galactose, lactose, and maltose.
3. The method for preparing the hard carbon anode active material according to claim 1, characterized in that, In step (1), the mass ratio of the gelatin to the reducing sugar is (5-9):(1-5).
4. The method for preparing the hard carbon anode active material according to claim 1, characterized in that, In step (1), the mass concentration of the electrospinning solution is 5% to 15%.
5. The method for preparing the hard carbon anode active material according to claim 1, characterized in that, In step (2), the electrospinning voltage is 10-20kV, the receiving distance is 8-20cm, the injection speed is 0.05-0.3mm / min, and the receiving roller speed is 50-300r.
6. The method for preparing the hard carbon anode active material according to claim 1, characterized in that, In step (3), the temperature of the pre-carbonization treatment is 150-350℃, the heating rate is 1-5℃ / min, and the holding time is 1-5h.
7. The method for preparing the hard carbon anode active material according to claim 1, characterized in that, In step (3), the high-temperature carbonization temperature is 500-1500℃, the heating rate is 1-10℃ / min, and the holding time is 1-5h.
8. A hard carbon anode active material, characterized in that, The hard carbon anode active material is prepared by the preparation method according to any one of claims 1-7.
9. A negative electrode sheet, characterized in that, Includes the hard carbon anode active material prepared by the preparation method according to any one of claims 1-7 or the hard carbon anode active material according to claim 8.
10. A sodium-ion battery, characterized in that, Includes the negative electrode sheet as described in claim 9.