Negative electrode material, sodium ion battery and electronic equipment

Abstract

The embodiment of the invention provides a negative electrode material, a sodium ion battery and electronic equipment, and relates to the technical field of batteries. The negative electrode material comprises carbonaceous particles, the carbonaceous particles comprise one-dimensional crystalline carbon and amorphous carbon, the one-dimensional crystalline carbon is mutually overlapped to form a skeleton structure, and the skeleton structure is filled with the amorphous carbon. The negative electrode material comprises the one-dimensional crystalline carbon, and the one-dimensional crystalline carbon has relatively high conductivity, so that the conductivity of the negative electrode material can be improved. Therefore, the conductivity of the negative pole piece in the sodium ion battery can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a negative electrode material, a sodium ion battery, and an electronic device. Background Art

[0002] With the development of large-scale energy storage technologies, electrochemical energy storage technologies have good application prospects in large-scale energy storage demonstration projects, base stations, etc. Sodium ion batteries have the advantages of rich reserves, low cost, high safety, etc., and can be widely used in large-scale energy storage scenarios.

[0003] As an important part of a sodium ion battery, the performance of the negative electrode material largely determines the energy density and cycle life of the battery. Usually, hard carbon materials are used as the negative electrode material of the battery. However, the carbon microstructure of hard carbon materials presents a relatively disordered structure, which will affect the internal electron transport channels of the material and reduce the conductivity of the material. How to improve the conductivity of the negative electrode material is an urgent problem to be solved in this field. Summary of the Invention

[0004] Embodiments of the present application provide a negative electrode material, a sodium ion battery, and an electronic device. By introducing one-dimensional crystalline carbon into the negative electrode material, the negative electrode material has a high conductivity and is conducive to improving the conductivity of the sodium ion battery.

[0005] To achieve the above object, the embodiments of the present application adopt the following technical solutions:

[0006] In a first aspect, an embodiment of the present application provides a negative electrode material, which includes carbonaceous particles. The carbonaceous particles include one-dimensional crystalline carbon and amorphous carbon. The one-dimensional crystalline carbons are mutually overlapped to form a framework structure, and the amorphous carbon is filled in the framework structure.

[0007] On the one hand, the negative electrode material includes one-dimensional crystalline carbon, which has a high conductivity and can improve the conductivity of the negative electrode material. Thus, the conductivity of the negative electrode sheet in the sodium ion battery can be improved, and to a certain extent, the rapid diffusion of sodium ions is promoted. Furthermore, the current performance of the sodium ion battery is improved.

[0008] On the other hand, the one-dimensional crystalline carbons can be mutually overlapped to form a framework structure, and the amorphous carbon can be filled in the framework structure. This framework structure is a conductive network structure formed with one-dimensional crystalline carbon as the framework, which is not only conducive to improving the conductivity of the negative electrode material, but also can improve the conductivity of the amorphous carbon. At the same time, it can also catalyze the conversion of sodium ions to sodium clusters and improve the conversion efficiency.

[0009] In a realizable manner, the diameter of the one-dimensional crystalline carbon is 5 nm - 200 nm, and the length of the one-dimensional crystalline carbon is 500 nm - 50 μm.

[0010] One-dimensional crystalline carbon has a small diameter and a long length, which gives it a high electrical conductivity and can improve the electrical conductivity of the negative electrode material. Furthermore, it can improve the electrical conductivity of the negative electrode sheet in a sodium-ion battery.

[0011] In one achievable manner, the length of the one-dimensional crystalline carbon is 500 nm - 5 μm.

[0012] The length of the one-dimensional crystalline carbon can preferably be 500 nm - 5 μm. Controlling the length of the one-dimensional crystalline carbon within the above range can improve the electrical conductivity of the negative electrode material to a greater extent.

[0013] In one achievable manner, the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles is 0.05% - 5%.

[0014] By regulating the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles to keep the content of the one-dimensional crystalline carbon within a more suitable range, the electrical conductivity of the negative electrode material can be improved, and the rapid diffusion of sodium ions can be promoted to a certain extent. Furthermore, the current performance of the sodium-ion battery can be improved.

[0015] In one achievable manner, the electrical conductivity of the one-dimensional crystalline carbon is greater than or equal to 500 S / cm. Specifically, the electrical conductivity of the one-dimensional crystalline carbon is greater than or equal to 500 S / cm and less than or equal to 600 S / cm. The one-dimensional crystalline carbon has a high electrical conductivity, which improves the rate performance of the negative electrode material.

[0016] In one achievable manner, the interlayer spacing of the one-dimensional crystalline carbon is 0.335 nm - 0.36 nm. The distance between the lamellar structures in the one-dimensional crystalline carbon is small, which can improve the electrical conductivity of the one-dimensional crystalline carbon. Thus, the electrical conductivity of the negative electrode material is improved, and the electrochemical performance of the sodium-ion battery is ensured.

[0017] In one achievable manner, the one-dimensional crystalline carbon includes carbon fibers and carbon nanotubes.

[0018] In one achievable manner, the amorphous carbon includes a closed pore structure, and the closed pore volume of the closed pore structure is 0.05 ml / g - 0.5 ml / g.

[0019] The amorphous carbon includes a closed pore structure, which can store sodium ions, and the closed pore volume range of the closed pore structure within the above range can also improve the sodium storage capacity to a certain extent. In this way, the capacity utilization of the negative electrode material can be improved. Thus, the energy density of the sodium-ion battery is improved.

[0020] In one feasible implementation, the interlayer spacing of the amorphous carbon is 0.375 nm - 0.395 nm. In the embodiments of the present application, the interlayer spacing corresponding to the amorphous carbon is within the above range, which enables the negative electrode material to have a more stable structure and improves the sodium storage capacity of the negative electrode material.

[0021] In one feasible implementation, the mass percentage of the amorphous carbon in the carbonaceous particles is 95% - 99.5%.

[0022] By regulating the mass percentage of the amorphous carbon in the carbonaceous particles, the content of the amorphous carbon is maintained within a more suitable range. In this way, the amorphous carbon can be filled in the framework structure from all directions and overlap with the one-dimensional crystalline carbon. The compactness of the amorphous carbon in the framework structure can be improved. Thus, the structural stability of the negative electrode material is enhanced.

[0023] In one feasible implementation, the carbonaceous particles include first particles and second particles. The average particle size of the first particles is 1 μm - 4 μm, and the average particle size of the second particles is 6 μm - 20 μm.

[0024] In the embodiments of the present application, two kinds of particles with different particle sizes are provided. The average particle sizes of the two kinds of particles differ by 3 to 5 times. Through the particle size grading, the porosity of the particle packing is effectively reduced, achieving a dense packing effect. Thus, the tap density of the powder corresponding to the carbonaceous particles is increased, and the volumetric energy density of the sodium-ion battery is improved.

[0025] In one feasible implementation, the volume ratio of the first particles to the second particles is 10 - 40:100.

[0026] In the embodiments of the present application, the volume ratio of the two kinds of particles with different particle sizes is further provided. By controlling the volume ratio of the two kinds of particles within this range, the packing effect between the two kinds of particles can be made more compact, and the porosity of the particle packing is effectively reduced. Thus, the tap density of the powder corresponding to the carbonaceous particles is increased, and the volumetric energy density of the sodium-ion battery is improved.

[0027] In one feasible implementation, the tap density of the negative electrode material is greater than 1 g / cm 3 , the packing porosity of the negative electrode material is 2% - 10%, and the oxygen content of the negative electrode material is less than 3%.

[0028] This negative electrode material has a high tap density and a low packing porosity, which can improve the volumetric energy density of the sodium-ion battery. In addition, the oxygen content of the negative electrode material is less than 3%, which can not only promote the formation of a stable carbon layer structure in the amorphous carbon, but also promote the overlap between the one-dimensional crystalline carbon and the amorphous carbon. At the same time, the conductivity of the negative electrode material is effectively improved.

[0029] In one feasible implementation, the conductivity of the negative electrode material is greater than 250 S / cm. This negative electrode material has a high conductivity, which can significantly improve the electron transport characteristics inside the negative electrode material and reduce the polarization of the negative electrode material. Furthermore, the electrochemical performance of the sodium-ion battery is improved.

[0030] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode material. The method includes: sequentially adding a crystalline carbon precursor and a pore-forming agent to an amorphous carbon precursor dissolved in a solvent to obtain a carbon precursor dispersion. Then, drying the carbon precursor dispersion to obtain carbonaceous particles; the carbonaceous particles include one-dimensional crystalline carbon and amorphous carbon, and the one-dimensional crystalline carbon and the amorphous carbon are mutually overlapped to form a porous framework structure. Then, pyrolyzing the carbonaceous particles to obtain the negative electrode material.

[0031] Through the above preparation method, the embodiment of the present application can prepare a negative electrode material including one-dimensional crystalline carbon and amorphous carbon. The one-dimensional crystalline carbons can be mutually overlapped to form a framework structure, and the amorphous carbon can be filled in the framework structure. This framework structure is a conductive network structure formed based on the one-dimensional crystalline carbon as the framework, so that the negative electrode material has a high conductive ability.

[0032] In one feasible implementation, pyrolyzing the carbonaceous particles to obtain the negative electrode material includes: heating the carbonaceous particles to 400°C - 700°C and thermally decomposing at a constant temperature for 1 h - 5 h to obtain pyrolytic carbon microspheres. Then, heating the pyrolytic carbon microspheres to 1000°C - 1400°C under the protection of an inert gas and thermally decomposing at a constant temperature for 2 h - 6 h, and cooling to room temperature to obtain the negative electrode material.

[0033] The embodiment of the present application can obtain the negative electrode material by pre-carbonizing and high-temperature carbonizing and forming the carbonaceous particles. The negative electrode material forms a framework structure including one-dimensional crystalline carbon and amorphous carbon, so that the negative electrode material has a high conductive ability.

[0034] In one feasible implementation, drying the carbon precursor dispersion to obtain carbonaceous particles includes: spray-drying the carbon precursor dispersion and adjusting the process to spray granulate to obtain first particles and second particles; the average particle size of the first particles is 1 μm - 4 μm, and the average particle size of the second particles is 6 μm - 20 μm;

[0035] Among them, the inlet temperature is 80°C - 120°C, the feeding speed is 200 ml / h - 1000 ml / h, and the fan frequency is 30 Hz - 60 Hz.

[0036] Thus, the embodiments of the present application can obtain the first particles and the second particles with different average particle sizes by using spray drying. By the obtained first particles and second particles with different average particle sizes, the porosity of particle packing can be effectively reduced, so that the negative electrode material has a close packing effect. Thereby, the volume energy density of the sodium-ion battery is improved.

[0037] In one realizable manner, the mass ratio of the amorphous carbon precursor, the crystalline carbon precursor, and the pore-forming agent is 100:(0.05 - 5):(1 - 20).

[0038] By controlling the mass ratio of the amorphous carbon precursor, the crystalline carbon precursor, and the pore-forming agent, not only can the high electrical conductivity of the one-dimensional crystalline carbon be ensured, but also a certain closed pore structure can be formed in the negative electrode material. Thus, the sodium storage capacity of the negative electrode material is improved. Furthermore, the conductivity and the battery energy density of the sodium-ion battery are improved.

[0039] In a third aspect, the embodiments of the present application provide a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. The negative electrode material layer includes the negative electrode material as described in the first aspect or the negative electrode material prepared by the preparation method as described in the second aspect.

[0040] In a fourth aspect, the embodiments of the present application provide a sodium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator located between the positive electrode sheet and the negative electrode sheet, and an electrolyte. The electrolyte is filled between the positive electrode sheet and the negative electrode sheet. The negative electrode sheet includes the negative electrode material as described in the first aspect or the negative electrode material prepared by the preparation method as described in the second aspect.

[0041] In a fifth aspect, the embodiments of the present application provide an electronic device, which includes a housing, electronic components and a battery received in the housing. The battery powers the electronic components, and the battery includes the sodium-ion battery as described in the third aspect above. Description of the Drawings

[0042] Figure 1 It is a schematic structural diagram of a sodium-ion battery provided by an embodiment of the present application;

[0043] Figure 2 It is a schematic structural diagram of a negative electrode material provided by an embodiment of the present application;

[0044] Figure 3 It is a schematic flow diagram of a method for preparing a negative electrode material provided by an embodiment of the present application;

[0045] Figure 4 It is a schematic microstructural diagram of a method for preparing carbonaceous particles provided by an embodiment of the present application. Detailed Embodiments

[0046] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application. Among them, in the description of the present application, unless otherwise specified, " / " means that the objects associated before and after are in an "or" relationship. For example, A / B may represent A or B; "and / or" in the present application is only a description of the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. These three situations, where A and B may be singular or plural. Also, in the description of the present application, unless otherwise specified, "a plurality" means two or more than two. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, at least one (item) of a, b, or c may represent: a, b, c, a - b, a - c, b - c, or a - b - c, where a, b, c may be single or multiple. In addition, in order to facilitate a clear description of the technical solutions in the embodiments of the present application, in the embodiments of the present application, terms such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and roles.

[0047] Those skilled in the art can understand that terms such as "first" and "second" do not limit the quantity and execution order, and terms such as "first" and "second" do not necessarily limit being different. At the same time, in some embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly speaking, using words such as "exemplary" or "for example" aims to present relevant concepts in a specific way for easy understanding.

[0048] For ease of understanding, some explanations of concepts related to the embodiments of the present application are given as examples for reference. As follows:

[0049] Cathode: In a primary battery, the electrode with a higher electrode potential from which the current flows out is the cathode, which gains electrons and undergoes a reduction reaction. In an electrolytic cell, the positive electrode is the electrode connected to the positive pole of the power supply, which loses electrons and undergoes an oxidation reaction.

[0050] Anode: In a primary battery, the electrode with a lower electrode potential into which the current flows in is the anode, which loses electrons and undergoes an oxidation reaction. In an electrolytic cell, the negative electrode is the electrode connected to the negative pole of the power supply, which gains electrons and undergoes a reduction reaction.

[0051] Electrolyte: Provides a medium for ion exchange between the positive and negative electrodes of the battery.

[0052] Separator: The main function of the separator is to separate the positive and negative electrodes of the battery to prevent short - circuiting due to contact between the two poles. In addition, it also has the function of allowing electrolyte ions to pass through.

[0053] Film - forming additive: It is a type of substance that decomposes preferentially on the material surface in an organic solvent to form an interfacial film, which can significantly improve the battery performance.

[0054] D50: The particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%.

[0055] D002 interlayer spacing: It refers to the distance between the layered structures in the material.

[0056] In the related art, a negative electrode material is provided. This negative electrode material uses pitch as the raw material for hard carbon. Through a heating and oxidation process, a conductive agent is introduced and pitch cross - linking is achieved, so that the conductive agent is dispersed inside the material. However, during the heating process, the conductive agent is strongly oxidized by active oxygen molecules, resulting in an increase in surface defects of the negative electrode material, a significant decrease in conductivity, and the conductive agent cannot play its role.

[0057] In the related art, a negative electrode material is also provided. This negative electrode material is prepared using phenolic resin as the raw material. Specifically, phenolic resin microspheres are obtained by the polymerization reaction of phenolic monomers and aldehyde monomers, and then through processes such as pre - oxidation and high - temperature carbonization, the negative electrode material is obtained. However, the carbon microstructure of the obtained negative electrode material shows a more disordered structure, which will affect the electron transport channels inside the material, reducing the rate performance and conductivity of the material. At the same time, the tap density of the phenolic resin microsphere structure is relatively low, which is not conducive to improving the energy density of sodium - ion batteries.

[0058] To solve the above problems, embodiments of the present application provide a negative electrode material, a sodium - ion battery, and an electronic device. Among them, the negative electrode material can be used to prepare the negative electrode plate of a sodium - ion battery. The negative electrode material proposed in the present application includes carbonaceous particles. The carbonaceous particles include one - dimensional crystalline carbon and amorphous carbon. The one - dimensional crystalline carbons are mutually overlapped to form a framework structure, and the amorphous carbon is filled in the framework structure.

[0059] On the one hand, the negative electrode material includes one - dimensional crystalline carbon. The one - dimensional crystalline carbon has a high electrical conductivity, which can improve the electrical conductivity of the negative electrode material. Thus, it can improve the electrical conductivity of the negative electrode plate in the sodium - ion battery and, to a certain extent, promote the rapid diffusion of sodium ions. Furthermore, it improves the current performance of the sodium - ion battery.

[0060] On the other hand, one-dimensional crystalline carbon can be mutually overlapped to form a framework structure, and amorphous carbon can be filled in the framework structure. The framework structure is a conductive network structure formed based on one-dimensional crystalline carbon as the framework, which not only helps to improve the conductivity of the negative electrode material, but also can improve the conductivity of amorphous carbon. At the same time, it can also catalyze the conversion of sodium ions to sodium clusters and improve the conversion efficiency.

[0061] An embodiment of the present application also provides a sodium-ion battery. Figure 1 It is a schematic structural diagram of the sodium-ion battery provided by the embodiment of the present application. As Figure 1 shown, the sodium-ion battery includes a positive electrode sheet 10, a negative electrode sheet 20, a separator 30, and an electrolyte 40. Among them, the separator 30 is disposed between the positive electrode sheet 10 and the negative electrode sheet 20, and the electrolyte 40 is filled between the positive electrode sheet 10 and the negative electrode sheet 20 and infiltrates the separator 30. During charging, sodium ions are released from the positive electrode material 102 of the positive electrode sheet 10 and embedded in the negative electrode material 202 of the negative electrode sheet 20 after passing through the electrolyte 40; during discharging, sodium ions are released from the negative electrode material 202 and inserted into the positive electrode material 102 after passing through the electrolyte 40.

[0062] Continue to refer to Figure 1 , in the sodium-ion battery provided by the embodiment of the present application, the separator 30 blocks the passage of electrons and allows ions to pass through. The separator 30 includes, but is not limited to, single-layer polypropylene (PP), single-layer polyethylene (PE), double-layer PP / PE, double-layer PP / PP, triple-layer PP / PE / PP, and ceramic-coated PE, etc. In the sodium-ion battery, the electrolyte 40 is a transmission medium when sodium ions are transmitted between the positive electrode sheet 10 and the negative electrode sheet 20.

[0063] As Figure 1 shown, the positive electrode sheet 10 includes a positive electrode current collector 101 and a positive electrode material layer coated on the surface of the positive electrode current collector 101. In addition to the positive electrode material 102, the positive electrode material layer may also include a certain amount of binder, conductive agent, and other components.

[0064] Among them, the positive electrode current collector 101 can be a metal foil, such as aluminum foil, gold foil, platinum foil, etc. The positive electrode material 102 can reversibly insert / extract sodium ions. The positive electrode material 102 includes, but is not limited to, at least one of layered sodium transition metal oxides, Prussian white compounds, Prussian blue compounds, and sodium polyanion-type compounds.

[0065] Sodium transition metal oxides such as sodium nickel iron manganese (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 , NFM111), Prussian white compounds such as (Na 2Mn[Fe(CN) 6 ,PBA), Prussian blue compounds such as (NaMn[Fe(CN) 6 ,PBA), sodium polyanion compounds such as sodium iron phosphate (NaFePO 4 ,NFP), sodium iron sulfate (Na 2 Fe 2 (SO 4 ) 3 ,NFS). The binder can be, for example, polyvinylidene fluoride (poly1,1-difluoroethylene, PVDF), and the conductive agent can be, for example, conductive carbon black (super P), graphite, amorphous carbon, carbon nanotubes, carbon fibers, graphene, etc. The positive current collector 101, positive electrode material 102, binder, and conductive agent used to prepare the positive electrode sheet 10 are only for illustrative purposes, and the embodiments of the present application are not limited thereto. Taking the positive electrode material 102 as an example, theoretically, it can be a compound that can reversibly intercalate / deintercalate sodium ions.

[0066] Continuing to refer to Figure 1 ,in the sodium-ion battery provided by the embodiments of the present application, the negative electrode sheet 20 includes a negative current collector 201 and a negative electrode material layer coated on the surface of the negative current collector. In addition to the negative electrode material 202, the negative electrode material layer can also include a certain amount of binder, conductive agent and other components. Among them, the negative current collector 201 can be a metal foil, such as copper foil, aluminum foil, gold foil, platinum foil, etc. The conductive agent can be, for example, acetylene black, graphite, amorphous carbon, etc. It should be noted that the negative current collector 201, binder, and conductive agent used to prepare the negative electrode sheet 20 are only for illustrative purposes, and the embodiments of the present application are not limited thereto.

[0067] In one embodiment of the present application, referring to Figure 2 ,the negative electrode material 202 can include carbonaceous particles, and the morphology of the carbonaceous particles can be a spherical morphology. For example, the carbonaceous particles can be hard carbon microspheres. Of course, the morphology of the carbonaceous particles can also include rod-like morphology, plate-like morphology, and angular morphology, etc., and the embodiments of the present application do not specifically limit it.

[0068] The carbonaceous particles can include one-dimensional crystalline carbon and amorphous carbon. The one-dimensional crystalline carbons are mutually overlapped to form a framework structure, and the amorphous carbon is filled in the framework structure. Among them, the average particle size (D50) of the carbonaceous particles can be 1μm - 20μm.

[0069] In this way, the one-dimensional crystalline carbon provided by the embodiments of the present application can overlap with the amorphous carbon to form a framework structure. The one-dimensional crystalline carbons can randomly intersect with each other in the amorphous carbon to form a framework structure, and at the same time form carbonaceous particles with the amorphous carbon.

[0070] In this skeletal structure, amorphous carbon can be connected by one-dimensional crystalline carbon to form a porous skeletal structure. The amorphous carbon can also be located at different positions on the one-dimensional crystalline carbon, such as the ends of the one-dimensional crystalline carbon. Thus, a network structure formed with one-dimensional crystalline carbon as the skeleton and amorphous carbon filling in the skeleton has a high electrical conductivity, which can improve the electrical conductivity of the negative electrode material. Therefore, it can improve the electrical conductivity of the negative electrode sheet in the sodium-ion battery and, to a certain extent, promote the rapid diffusion of sodium ions. Furthermore, it can improve the high-current performance of the sodium-ion battery.

[0071] In some embodiments of the present application, the diameter of the one-dimensional crystalline carbon can be 5 nm - 200 nm, and the length of the one-dimensional crystalline carbon is 500 nm - 50 μm.

[0072] As an exemplary illustration, the diameter of the above-mentioned one-dimensional crystalline carbon can specifically be 5 nm, 200 nm, and any value between 5 nm - 200 nm, such as 5 nm, 6 nm, 100 nm, 195 nm, 200 nm, etc. They are not listed one by one here.

[0073] The length of the one-dimensional crystalline carbon can specifically be 500 nm, 50 μm, and any value between 500 nm - 50 μm, such as 500 nm, 600 nm, 800 nm, 5 μm, 30 μm, etc. They are not listed one by one here.

[0074] The one-dimensional crystalline carbon in the embodiments of the present application has a small diameter and a long length, making it have a high electrical conductivity and being able to improve the electrical conductivity of the negative electrode material. Therefore, it can improve the electrical conductivity of the negative electrode sheet in the sodium-ion battery.

[0075] In some embodiments of the present application, the length of the one-dimensional crystalline carbon can be 500 nm - 5 μm. Thus, the length of the one-dimensional crystalline carbon can preferably be 500 nm - 5 μm. Controlling the length of the one-dimensional crystalline carbon within the above range can improve the electrical conductivity of the negative electrode material to a greater extent.

[0076] In some embodiments of the present application, the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles is 0.05% - 5%.

[0077] It should be understood that for the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles, in practical applications, there may be certain measurement test system errors. The values within the system error range are all within the scope defined by the embodiments of the present application.

[0078] In addition, as an exemplary illustration, the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles may specifically be 0.05%, 5%, or any value between 0.05% and 5%, such as 0.06%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, etc. They are not listed one by one here.

[0079] In this way, by regulating the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles so that the content of the one-dimensional crystalline carbon is maintained within a relatively suitable range, the conductivity of the anode material can be improved, and to a certain extent, the rapid diffusion of sodium ions is promoted. Furthermore, the current performance of the sodium-ion battery is improved.

[0080] In some embodiments of the present application, the conductivity of the one-dimensional crystalline carbon may be greater than or equal to 500 S / cm.

[0081] Specifically, the conductivity of the one-dimensional crystalline carbon is greater than or equal to 500 S / cm and less than or equal to 600 S / cm. In this way, the one-dimensional crystalline carbon provided in the embodiments of the present application has a relatively high conductivity, improving the rate performance of the anode material.

[0082] In some embodiments of the present application, the interlayer spacing of the one-dimensional crystalline carbon is 0.335 nm - 0.36 nm.

[0083] As an exemplary illustration, the interlayer spacing of the one-dimensional crystalline carbon may specifically be 0.335 nm, 0.36 nm, or any value between 0.335 nm and 0.36 nm, such as 0.339 nm, 0.341 nm, 0.346 nm, 0.348 nm, 0.35 nm, etc. They are not listed one by one here.

[0084] In this way, the D002 interlayer spacing of the one-dimensional crystalline carbon provided in the embodiments of the present application is within the above range, and the distance between the layered structures in the one-dimensional crystalline carbon is relatively small, which can improve the conductivity of the one-dimensional crystalline carbon. Thus, the conductivity of the anode material is improved, ensuring the electrochemical performance of the sodium-ion battery.

[0085] In some embodiments of the present application, the one-dimensional crystalline carbon includes carbon fibers and carbon nanotubes.

[0086] In some embodiments of the present application, the amorphous carbon includes a closed pore structure, and the closed pore volume of the closed pore structure is 0.05 ml / g - 0.5 ml / g.

[0087] Continue to refer to Figure 2, the amorphous carbon provided in the embodiments of the present application includes a closed pore structure, and the closed pore volume range of the closed pore structure can be 0.05 ml / g - 0.5 ml / g. In this way, the closed pore structure formed in the amorphous carbon can store sodium ions, and the closed pore volume range of the closed pore structure within the above range can also improve the sodium storage capacity to a certain extent. In this way, the capacity of the negative electrode material can be improved. Therefore, the energy density of the sodium ion battery is improved.

[0088] In one implementable manner, the above-mentioned closed pore structure cannot be wetted by butanol and can be filled with helium. The test method for the closed pore volume of the closed pore structure may include: taking a certain mass of the sample, using butanol as the wetting liquid, and testing the volume V1 of the sample per unit mass based on the Archimedes principle by the impregnation method (specific gravity bottle method). Then, the volume V2 of the sample per unit mass is tested by the helium pressure displacement method, and V2 - V1 is the closed pore volume of the closed pores of the sample per unit mass. The embodiments of the present application do not specifically limit the test method for the closed pore volume of the closed pore structure.

[0089] In some embodiments of the present application, the interlayer spacing of the amorphous carbon is 0.375 nm - 0.395 nm.

[0090] As an exemplary illustration, the interlayer spacing of the amorphous carbon can specifically be 0.375 nm, 0.395 nm, and any value between 0.375 nm - 0.395 nm, such as 0.375 nm, 0.385 nm, 0.386 nm, 0.388 nm, 0.395 nm, etc. They are not listed one by one here.

[0091] In this way, the D002 interlayer spacing of the amorphous carbon provided in the embodiments of the present application is within the above range, making the negative electrode material have a more stable structure and improving the sodium storage capacity of the negative electrode material.

[0092] In some embodiments of the present application, the mass percentage of the amorphous carbon in the carbonaceous particles is 95% - 99.5%.

[0093] It should be understood that for the mass percentage of the amorphous carbon in the carbonaceous particles, in practical applications, there may be a certain measurement test system error, and the values within the system error range are all within the range defined in the embodiments of the present application.

[0094] In addition, as an exemplary illustration, the mass percentage of the above-mentioned amorphous carbon in the carbonaceous particles can specifically be 95%, 99.5%, and any value between 95% - 99.5%, such as 96%, 98%, 99.1%, 99.2%, 99.5%, etc. They are not listed one by one here.

[0095] Thus, the mass percentage of amorphous carbon in the carbonaceous particles provided in the embodiment of the present application is in the range of 95%-99.5%. Thus, by regulating the mass percentage of amorphous carbon in the carbonaceous particles, the content of amorphous carbon is maintained within a more suitable range. In this way, amorphous carbon can be filled in the skeleton structure from all directions and overlapped with one-dimensional crystalline carbon. The compactness of amorphous carbon in the skeleton structure can be improved. Thus, the structural stability of the negative electrode material is improved.

[0096] In some embodiments of the present application, the carbonaceous particles include first particles and second particles, the average particle size (D50) of the first particles is 1 μm-4 μm, and the average particle size (D50) of the second particles is 6 μm-20 μm. The first particles and the second particles both include one-dimensional crystalline carbon and amorphous carbon, the one-dimensional crystalline carbon overlaps each other to form a skeleton structure, and the amorphous carbon is filled in the skeleton structure.

[0097] As an exemplary illustration, the average particle size of the first particles may be 1 μm, 4 μm, or any value between 1 μm and 4 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, etc. These values ​​are not listed here one by one.

[0098] The average particle size of the second particles may specifically be 6 μm, 20 μm, or any value between 6 μm and 20 μm, such as 7 μm, 8 μm, 9 μm, 15 μm, etc. These values ​​are not listed here one by one.

[0099] In some embodiments, the carbonaceous particles are tested by a laser particle size analyzer, and the obtained particle size distribution curve can be clearly observed to have a bimodal morphology, with two peaks located between 1 μm-4 μm and 6 μm-20 μm, corresponding to the first particles and the second particles mentioned above.

[0100] Thus, two particles of different particle sizes are provided in the embodiment of the present application, and the average particle sizes of the two particles differ by 3 to 5 times. Through the particle size grading, the void ratio of the particle stacking is effectively reduced to achieve a dense stacking effect. Thus, the compaction density of the carbonaceous particles corresponding to the powder is increased, and the volume energy density of the sodium ion battery is improved.

[0101] In some embodiments of the present application, the volume ratio of the first particles to the second particles is 10-40:100.

[0102] As an exemplary illustration, the volume ratio of the first particles to the second particles may be 10:100, 40:100, or any value between 10-40:100, such as 12:100, 20:100, 22:100, 30:100, etc. These are not listed here one by one.

[0103] Thus, the volume ratio of particles of two different particle sizes is further provided in the embodiment of the present application. By controlling the volume ratio of the two particles within this range, the stacking effect between the two particles can be made tighter, and the void ratio of the particle stacking can be effectively reduced. Thus, the compaction density of the powder corresponding to the carbonaceous particles is increased, and the volume energy density of the sodium ion battery is improved.

[0104] In some embodiments of the present application, the compaction density of the negative electrode material is greater than 1 g / cm 3 , the stacking porosity of the negative electrode material is 2%-10%, and the oxygen content of the negative electrode material is less than 3%.

[0105] Thus, the negative electrode material provided in the embodiment of the present application has a higher compaction density and a lower stacking porosity, which can improve the volume energy density of the sodium ion battery. In addition, the oxygen content of the negative electrode material is less than 3%, which can not only promote the formation of a stable carbon layer structure in the amorphous carbon, but also promote the overlap between the one-dimensional crystalline carbon and the amorphous carbon. At the same time, the conductivity of the negative electrode material is effectively improved.

[0106] In some embodiments of the present application, the conductivity of the negative electrode material is greater than 250 S / cm. In this way, the negative electrode material provided in the embodiments of the present application has a high conductivity, which can significantly improve the electron transport characteristics inside the negative electrode material and reduce the polarization of the negative electrode material. In turn, the electrochemical performance of the sodium ion battery is improved.

[0107] The present application also provides a method for preparing a negative electrode material, see Figure 3 , including the following steps:

[0108] S301, adding a crystalline carbon precursor and a pore-forming agent to an amorphous carbon precursor dissolved in a solvent in sequence to obtain a carbon precursor dispersion.

[0109] In some embodiments of the present application, a carbon precursor dispersion may be prepared first. Specifically, an amorphous carbon precursor is dissolved in a solvent and poured into a reactor of a high-speed stirring device at a speed of 1000 r / min-3000 r / min, and stirring is started. Next, a crystalline carbon precursor and a pore-forming agent are sequentially added to the amorphous carbon precursor, stirred evenly, and diluted to 1%-5% with a solvent to obtain a carbon precursor dispersion.

[0110] In some embodiments of the present application, the amorphous carbon precursor includes one or more of phenolic resin, epoxy resin and furfuryl alcohol resin.

[0111] In some embodiments of the present application, the solvent includes one or more of water, methanol, ethanol and ethylene glycol.

[0112] In some embodiments of the present application, the pore former includes one or more of polyvinyl alcohol, polyvinyl butyral, polymethyl acrylate, polystyrene, and polyacrylamide. The residual carbon value of the pore former is 0.1%-10%, and the average molecular weight of the pore former is between 5000 and 50000.

[0113] S302. Dry the carbon precursor dispersion to obtain carbonaceous particles. The carbonaceous particles include one-dimensional crystalline carbon and amorphous carbon, and the one-dimensional crystalline carbon and the amorphous carbon overlap with each other to form a porous skeleton structure.

[0114] In some embodiments of the present application, particulate precursors of different particle sizes are prepared. In the process of drying the above carbon precursor dispersion to obtain carbonaceous particles, the carbon precursor dispersion can be spray-dried, and the process spray granulation is adjusted to obtain a first particle and a second particle. The average particle size of the first particle is 1μm - 4μm, and the average particle size of the second particle is 6μm - 20μm.

[0115] Exemplarily, the carbon precursor dispersion can be transferred to a spray dryer at 80°C - 120°C, with a feed rate of 200 ml / h - 1000 ml / h and a fan frequency of 20 Hz - 60 Hz. The process spray granulation is adjusted to obtain a first microsphere such as the above first particle and a second microsphere such as the above second particle. Then, the two obtained microspheres are mixed evenly by a V-type mixer according to a volume ratio of 10 - 40:100 to obtain carbonaceous particles.

[0116] S303. Pyrolyze the carbonaceous particles to obtain the negative electrode material.

[0117] In some embodiments of the present application, the carbonaceous particles can be pre-carbonized and high-temperature carbonized into a shape. Specifically, the carbonaceous particles are heated to 400°C - 700°C and thermally decomposed at a constant temperature for 1 h - 5 h to obtain pyrolytic carbon microspheres. Then, the pyrolytic carbon microspheres are heated to 1000°C - 1400°C under the protection of an inert gas and thermally decomposed at a constant temperature for 2 h - 6 h, and the negative electrode material is obtained after cooling to room temperature.

[0118] Exemplarily, the evenly mixed carbonaceous particles obtained are placed in a tubular furnace and heated to 400°C - 700°C, and thermally decomposed at a constant temperature for 1 h - 5 h to obtain pyrolytic carbon microspheres. Then, the obtained pyrolytic carbon microspheres are placed in a box-type carbonization furnace, heated to 1000°C - 1400°C under the protection of an inert gas, pyrolyzed for 2 - 6 h, and cooled to room temperature to obtain the negative electrode material.

[0119] In some embodiments of the present application, the mass ratio of the amorphous carbon precursor, the crystalline carbon precursor, and the pore former is 100:(0.05 - 5):(1 - 20).

[0120] Thus, by controlling the mass ratio of the amorphous carbon precursor, the crystalline carbon precursor, and the pore former, not only can the high electrical conductivity of the one-dimensional crystalline carbon be ensured, but also a certain closed pore structure can be formed in the anode material, thereby improving the sodium storage capacity of the anode material. Furthermore, the conductivity and energy density of the sodium-ion battery are enhanced.

[0121] It can be understood that for the calculated values of the above numerical ratios, during actual test operations, a certain measurement test system error is allowed, and the values within the system error range can be understood as the range defined by the embodiments of the present application.

[0122] The above anode material is introduced below through specific embodiments.

[0123] Example 1

[0124] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle with a high-speed stirring device, with a rotation speed of 2000 r / min, start stirring, and sequentially add carbon fiber (Vapor-grown carbon fiber, VGCF) and polyvinyl alcohol (PVA) to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of the phenolic resin carbon precursor: VGCF: PVA is 100:3:10, and then dilute it with ethanol to 5%, obtaining a carbon precursor dispersion.

[0125] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 200 ml / h, and a fan frequency of 50 HZ, and adjust the process for spray granulation to obtain the first particles, with an average particle size of 1.5 μm. Subsequently, adjust the feeding speed to 500 ml / h and the fan frequency to 50 Hz, and perform spray granulation to obtain the second particles, with an average particle size of 9 μm. Mix the obtained two kinds of particles according to a volume ratio of 30:100 through a V-type mixer to obtain carbonaceous particles.

[0126] Place the obtained uniformly mixed carbonaceous particles in a tube furnace, heat to 500 °C, and thermally decompose at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0127] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, under the protection of an inert gas, heat to 1300 °C, pyrolyze for 5 h, and cool to room temperature to obtain the anode material.

[0128] Example 2

[0129] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle equipped with a high-speed stirring device, set the rotation speed to 2000 r / min, start stirring, and sequentially add VGCF and PVA to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PVA is 100:1.5:10. Subsequently, dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0130] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 200 ml / h, and a fan frequency of 50 HZ. Adjust the process to spray granulate to obtain the first particles, and the average particle size of the first particles is 1.5 μm. Subsequently, adjust the feeding speed to 500 ml / h and the fan frequency to 50 Hz, and spray granulate to obtain the second particles, and the average particle size of the second particles is 9 μm. Mix the obtained two kinds of particles according to a volume ratio of 25:100 through a V-type mixer to obtain carbonaceous particles.

[0131] Place the obtained uniformly mixed carbonaceous particles in a tubular furnace, heat to 500 °C, and thermally decompose at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0132] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, under the protection of an inert gas, heat to 1300 °C, pyrolyze for 5 h, and cool to room temperature to obtain the negative electrode material.

[0133] Example 3

[0134] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle equipped with a high-speed stirring device, set the rotation speed to 2000 r / min, start stirring, and sequentially add VGCF and PVA to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PVA is 100:2.5:10. Subsequently, dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0135] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 200 ml / h, and a fan frequency of 50 HZ. Adjust the process to spray granulate to obtain the first particles, and the average particle size of the first particles is 1.5 μm. Subsequently, adjust the feeding speed to 500 ml / h and the fan frequency to 50 Hz, and spray granulate to obtain the second particles, and the average particle size of the second particles is 9 μm. Mix the obtained two kinds of particles according to a volume ratio of 20:100 through a V-type mixer to obtain carbonaceous particles.

[0136] Place the obtained uniformly mixed carbonaceous particles in a tubular furnace, heat to 500 °C, and thermally decompose at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0137] The obtained pyrolytic carbon microspheres were placed in a box-type carbonization furnace, heated to 1300 °C under the protection of inert gas, pyrolyzed for 5 h, and cooled to room temperature to obtain the anode material.

[0138] Example 4

[0139] The phenolic resin carbon precursor was dissolved in ethanol and poured into a reaction kettle equipped with a high-speed stirring device. The rotation speed was 2000 r / min. Stirring was started, and VGCF and PVA were successively added to the amorphous carbon precursor solution and stirred evenly. Among them, the mass ratio of the phenolic resin carbon precursor: VGCF: PVA was 100:2.5:10. Subsequently, it was diluted with ethanol to 5% to obtain a carbon precursor dispersion.

[0140] The obtained carbon precursor dispersion was transferred to a spray dryer. The inlet temperature was 100 °C, the feeding speed was 200 ml / h, and the fan frequency was 50 HZ. The process was adjusted for spray granulation to obtain the first particles, and the average particle size of the first particles was 1.5 μm. Subsequently, the feeding speed was adjusted to 500 ml / h and the fan frequency was 50 Hz for spray granulation to obtain the second particles, and the average particle size of the second particles was 9 μm. The obtained two kinds of particles were mixed evenly according to a volume ratio of 40:100 through a V-type mixer to obtain carbonaceous particles.

[0141] The obtained uniformly mixed carbonaceous particles were placed in a tubular furnace, heated to 500 °C, and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0142] The obtained pyrolytic carbon microspheres were placed in a box-type carbonization furnace, heated to 1300 °C under the protection of inert gas, pyrolyzed for 5 h, and cooled to room temperature to obtain the anode material.

[0143] Example 5

[0144] The phenolic resin carbon precursor was dissolved in water and poured into a reaction kettle equipped with a high-speed stirring device. The rotation speed was 2500 r / min. Stirring was started, and VGCF and polystyrene (PS) were successively added to the amorphous carbon precursor solution and stirred evenly. Among them, the mass ratio of the phenolic resin carbon precursor: VGCF: PS was 100:3:15. Subsequently, it was diluted with ethanol to 3% to obtain a carbon precursor dispersion.

[0145] The obtained carbon precursor dispersion was transferred to a spray dryer. The inlet temperature was 120 °C, the feeding speed was 200 ml / h, and the fan frequency was 60 HZ. The process was adjusted for spray granulation to obtain the first particles, and the average particle size of the first particles was 1.8 μm. Subsequently, the feeding speed was adjusted to 800 ml / h and the fan frequency was 60 Hz for spray granulation to obtain the second particles, and the average particle size of the second particles was 8.8 μm. The obtained two kinds of particles were mixed evenly according to a volume ratio of 30:100 through a V-type mixer to obtain carbonaceous particles.

[0146] The obtained uniformly mixed carbonaceous particles are placed in a tubular furnace, heated to 600 °C, and pyrolyzed at a constant temperature for 4 h to obtain pyrolytic carbon microspheres.

[0147] The obtained pyrolytic carbon microspheres are placed in a box-type carbonization furnace, heated to 1400 °C under the protection of an inert gas, pyrolyzed for 4 h, and cooled to room temperature to obtain the anode material.

[0148] Example 6

[0149] Dissolve the phenolic resin carbon precursor in water, pour it into a reaction kettle with a high-speed stirring device, rotate at 2500 r / min, start stirring, and sequentially add VGCF and polyacrylamide (PAM) to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PAM is 100:2.8:10, and then dilute it to 3% with ethanol to obtain a carbon precursor dispersion.

[0150] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 120 °C, a feeding speed of 200 ml / h, and a fan frequency of 60 HZ. Adjust the process for spray granulation to obtain the first particles, and the average particle size of the first particles is 1.8 μm. Subsequently, adjust the feeding speed to 800 ml / h and the fan frequency to 60 Hz, and spray granulate to obtain the second particles, and the average particle size of the second particles is 8.8 μm. Mix the obtained two kinds of particles evenly according to a volume ratio of 35:100 through a V-type mixer to obtain carbonaceous particles.

[0151] The obtained uniformly mixed carbonaceous particles are placed in a tubular furnace, heated to 600 °C, and pyrolyzed at a constant temperature for 4 h to obtain pyrolytic carbon microspheres.

[0152] The obtained pyrolytic carbon microspheres are placed in a box-type carbonization furnace, heated to 1400 °C under the protection of an inert gas, pyrolyzed for 4 h, and cooled to room temperature to obtain the anode material.

[0153] Example 7

[0154] Dissolve the epoxy resin carbon precursor in ethanol, pour it into a reaction kettle with a high-speed stirring device, rotate at 2000 r / min, start stirring, and sequentially add carbon nano tubes (CNT) and polyvinyl alcohol (PVA) to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of epoxy resin carbon precursor: CNT: PVA is 100:4:10, and then dilute it to 5% with ethanol to obtain a carbon precursor dispersion.

[0155] Transfer the obtained carbon precursor dispersion to a spray dryer. The inlet temperature is 100 °C, the feeding rate is 200 ml / h, and the fan frequency is 50 HZ. Adjust the process for spray granulation to obtain the first particles, and the average particle size of the first particles is 1.5 μm. Subsequently, adjust the feeding rate to 500 ml / h and the fan frequency to 50 Hz, and perform spray granulation to obtain the second particles, and the average particle size of the second particles is 9 μm. Mix the obtained two kinds of particles in a volume ratio of 30:100 and mix them evenly through a V-type mixer to obtain carbonaceous particles.

[0156] Mix the evenly mixed carbonaceous particles obtained above in a tubular furnace, heat to 500 °C, and carry out isothermal pyrolysis for 3 h to obtain pyrolytic carbon microspheres.

[0157] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, heat to 1300 °C under the protection of inert gas, pyrolyze for 5 h, and cool to room temperature to obtain the anode material.

[0158] Example 8

[0159] Dissolve the furfuryl alcohol resin carbon precursor in ethanol, pour it into a reaction kettle with a high-speed stirring device, the rotation speed is 2000 r / min, start stirring, and sequentially add CNT and polyvinyl alcohol (PVA) to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of furfuryl alcohol resin carbon precursor:CNT:PVA is 100:1:10, and then dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0160] Transfer the obtained carbon precursor dispersion to a spray dryer. The inlet temperature is 100 °C, the feeding rate is 200 ml / h, and the fan frequency is 40 HZ. Adjust the process for spray granulation to obtain the first particles, and the average particle size of the first particles is 1.5 μm. Subsequently, adjust the feeding rate to 800 ml / h and the fan frequency to 50 Hz, and perform spray granulation to obtain the second particles, and the average particle size of the second particles is 8.8 μm. Mix the obtained two kinds of particles in a volume ratio of 30:100 and mix them evenly through a V-type mixer to obtain carbonaceous particles.

[0161] Mix the evenly mixed carbonaceous particles obtained above in a tubular furnace, heat to 500 °C, and carry out isothermal pyrolysis for 3 h to obtain pyrolytic carbon microspheres.

[0162] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, heat to 1300 °C under the protection of inert gas, pyrolyze for 5 h, and cool to room temperature to obtain the anode material.

[0163] Comparative Example 1

[0164] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle equipped with a high-speed stirring device, set the rotation speed to 2000 r / min, start stirring, add PVA to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of the phenolic resin carbon precursor to PVA is 100:10. Subsequently, dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0165] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 200 ml / h, and a fan frequency of 50 HZ. Adjust the process for spray granulation to obtain the first particles, with an average particle size of 2 μm for the first particles. Subsequently, adjust the feeding speed to 500 ml / h and the fan frequency to 50 Hz, and perform spray granulation to obtain the second particles, with an average particle size of 6 μm for the second particles. Mix the two obtained types of particles evenly according to a volume ratio of 30:100 through a V-type mixer to obtain carbonaceous particles.

[0166] Mix the obtained evenly mixed carbonaceous particles in a tubular furnace, heat to 500 °C, and perform isothermal pyrolysis for 3 h to obtain pyrolytic carbon microspheres.

[0167] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, under the protection of an inert gas, heat to 1300 °C, pyrolyze for 5 h, and cool to room temperature to obtain the negative electrode material.

[0168] Comparative Example 2

[0169] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle equipped with a high-speed stirring device, set the rotation speed to 2000 r / min, start stirring, add PVA to the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of the phenolic resin carbon precursor to PVA is 100:10. Subsequently, dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0170] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 200 ml / h, and a fan frequency of 50 HZ. Adjust the process for spray granulation to obtain the first particles, with an average particle size of 2 μm for the first particles. Subsequently, adjust the feeding speed to 800 ml / h and the fan frequency to 50 Hz, and perform spray granulation to obtain the second particles, with an average particle size of 8 μm for the second particles. Mix the two obtained types of particles evenly according to a volume ratio of 30:100 through a V-type mixer to obtain carbonaceous particles.

[0171] Mix the obtained evenly mixed carbonaceous particles in a tubular furnace, heat to 500 °C, and perform isothermal pyrolysis for 3 h to obtain pyrolytic carbon microspheres.

[0172] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, under the protection of an inert gas, heat to 1300 °C, pyrolyze for 5 h, and cool to room temperature to obtain the negative electrode material.

[0173] Comparative Example 3

[0174] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle equipped with a high-speed stirring device, with a rotation speed of 2000 r / min, start stirring, and sequentially add carbon fiber (Vapor-grown carbon fiber, VGCF) and polyvinyl alcohol (PVA) into the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PVA is 100:3:10, and then dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0175] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 800 ml / h, a fan frequency of 50 HZ, and spray granulation to obtain carbonaceous particles, and the average particle size of the carbonaceous particles is 8 μm.

[0176] Mix the obtained carbonaceous particles in a tube furnace, heat to 500 °C, and thermally decompose at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0177] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, under the protection of an inert gas, heat to 1300 °C, pyrolyze for 5 h, and cool to room temperature to obtain the anode material.

[0178] Comparative Example 4

[0179] Dissolve the phenolic resin carbon precursor in ethanol, pour it into a reaction kettle equipped with a high-speed stirring device, with a rotation speed of 2000 r / min, start stirring, and add VGCF into the amorphous carbon precursor solution, and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF is 100:10, and then dilute it with ethanol to 5% to obtain a carbon precursor dispersion.

[0180] Transfer the obtained carbon precursor dispersion to a spray dryer, with an inlet temperature of 100 °C, a feeding speed of 200 ml / h, a fan frequency of 50 HZ, adjust the process for spray granulation to obtain the first particles, and the average particle size of the first particles is 1.5 μm. Subsequently, adjust the feeding speed to 500 ml / h and the fan frequency to 50 Hz, and spray granulation to obtain the second particles, and the average particle size of the second particles is 9 μm. Mix the obtained two kinds of particles evenly according to a volume ratio of 30:100 through a V-type mixer to obtain carbonaceous particles.

[0181] Mix the obtained uniformly mixed carbonaceous particles in a tube furnace, heat to 500 °C, and thermally decompose at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0182] Place the obtained pyrolytic carbon microspheres in a box-type carbonization furnace, under the protection of an inert gas, heat to 1300 °C, pyrolyze for 5 h, and cool to room temperature to obtain the anode material.

[0183] The performance tests were conducted on the anode materials prepared in the above Examples 1-8 and Comparative Examples 1-4, respectively, as well as on the corresponding sodium-ion batteries. The test results are shown below:

[0184] In some embodiments of the present application, the morphology and structure of Example 1 were analyzed by scanning electron microscopy. See Figure 4 , the sample prepared in Example 1 presented a round spherical structure, and there were two spherical structures with different average particle sizes.

[0185] In some embodiments of the present application, in order to systematically characterize the influence of the particle size distribution of materials on the overall powder structure performance of the anode material, technical characterizations such as particle size distribution, tapped density, and powder compaction density were carried out on the above samples, as shown in Table 1 below. The carbonaceous particles in Comparative Example 3 did not include two types of particles with different average particle sizes and different volume ratios, and its tapped density and powder compaction density were the lowest. Thus, it can be shown that for other samples except Comparative Example 3, by setting two types of particles with different average particle sizes and different volume ratios, the tapped density and compaction density of the anode material can be improved. Therefore, the energy density of the sodium-ion battery can be increased. At the same time, by comparing Comparative Example 1 and Comparative Example 2 with Comparative Example 3, it can be found that the greater the particle size dispersion degree of the particles, the more obvious the increase in the overall compaction density and tapped density of the anode material.

[0186] Table 1

[0187] Sample Number D10 (μm) D50 (μm) D90 (μm) <![CDATA[Tap density (g / cm 3 )]]> <![CDATA[5T electronic compaction (g / cm 3 )]]> Example 1 2.1 8.1 9.2 0.94 1.06 Example 2 1.9 8.8 9.3 0.95 1.08 Example 3 1.8 8.7 9.4 0.94 1.05 Example 4 2.4 8.2 9 0.93 1.05 Example 5 2 8.5 9.3 0.94 1.07 Example 6 2.2 8.7 9.6 0.94 1.06 Example 7 2.1 8.6 9.5 0.91 1.03 Example 8 1.9 8.5 9.2 0.93 1.05 Comparative Example 1 2.8 5.6 9.5 0.78 0.96 Comparative Example 2 2.8 7.9 12.3 0.79 0.95 Comparative Example 3 7.5 8.1 9.3 0.73 0.89 Comparative Example 4 2 7.9 9 0.92 1.04

[0188] In some embodiments of the present application, in order to characterize the influence of the introduction of one-dimensional crystalline carbon material on the internal electron transport of the anode material and analyze the influence of the pore-forming agent on the electrochemical performance of the anode material, the powder conductivity, closed pore volume, discharge capacity of the sodium-ion battery in the coin cell test, and the first Coulombic efficiency of the anode material were respectively tested, as shown in Table 2 below.

[0189] First, no pore-forming agent was added in Comparative Example 4, and its closed pore volume was relatively low, and the reversible capacity of the sodium battery was also relatively low. Thus, it can be shown that for other samples except Comparative Example 4, by adding a pore-forming agent, the closed pore volume of the anode material can be improved. Therefore, the sodium storage capacity of the anode material can be increased.

[0190] Second, no one-dimensional crystalline carbon was added in Comparative Example 1 and Comparative Example 2, and their conductivity decreased significantly, and the first Coulombic efficiency was also relatively low. Thus, it can be shown that for other samples except Comparative Example 1 and Comparative Example 2, by introducing one-dimensional crystalline carbon, the conductivity of the anode material can be significantly improved, the internal electron transport characteristics of the anode material can be improved, the polarization of the anode material can be reduced, and the electrochemical performance of the sodium-ion battery can be improved.

[0191] Table 2

[0192] Sample Number <![CDATA[Closed pore volume (cm 3 / g)]]> Powder Conductivity at 25 MPa (S / cm) Sodium Electrochemical Reversible Capacity Initial Coulombic Efficiency Example 1 0.12 412.4 347.3 88.8 Example 2 0.13 358.5 348.2 88.5 Example 3 0.12 426.5 346.7 88.7 Example 4 0.15 296.8 352.1 88.2 Example 5 0.11 440.7 341.7 87.8 Example 6 0.13 388.5 345.4 89.1 Example 7 0.12 390.2 342.1 88.4 Example 8 0.13 320.5 339.2 88.3 Comparative Example 1 0.14 25.4 340.2 87.4 Comparative Example 2 0.12 25.6 336.5 87.8 Comparative Example 3 0.12 352.4 345.8 88.1 Comparative Example 4 0.03 392.1 290.2 87.6

[0193] In summary, on the one hand, the one-dimensional crystalline carbons in the embodiments of the present application can intersect with each other to form a framework structure, which can catalyze the conversion of sodium ions to sodium clusters and improve the low-voltage sodium storage kinetics of carbon materials. At the same time, the conductivity of the one-dimensional crystalline carbon is one to two orders of magnitude higher than that of amorphous carbon. The framework formed by the intersection of one-dimensional crystalline carbons serves as a conductive network, which can greatly improve the conductivity of amorphous carbon and enhance the high-current performance of sodium-ion batteries. On the other hand, by mixing different particles with a diameter ratio of 3 to 5 times according to a certain volume ratio in the embodiments of the present application, the porosity of particle packing can be effectively reduced, achieving a close packing effect, thereby increasing the corresponding tap density of carbonaceous particles and improving the volumetric energy density of sodium-ion batteries.

[0194] The embodiments of the present application also provide a negative electrode plate, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. The negative electrode material layer includes the above-mentioned negative electrode material or the negative electrode material prepared by the above-mentioned preparation method.

[0195] The embodiments of the present application also provide a sodium-ion battery, which includes a positive electrode plate, a negative electrode plate, a separator located between the positive electrode plate and the negative electrode plate, and an electrolyte. The electrolyte is filled between the positive electrode plate and the negative electrode plate. The negative electrode plate includes the above-mentioned negative electrode material or the negative electrode material prepared by the above-mentioned preparation method.

[0196] The embodiments of the present application also provide an electronic device, which includes a housing, electronic components and a battery housed in the housing. The battery powers the electronic components, and the battery includes the above-mentioned sodium-ion battery.

[0197] The electronic device can be, for example, a mobile phone, a smart screen, a tablet computer, a personal computer (PC), a personal digital assistant (PDA), a smart watch, a mobile power supply, a netbook, a wearable device, an augmented reality (AR) device, a virtual reality (VR) device, a vehicle-mounted device, an energy storage device, a base station, an automobile, etc. The embodiments of the present application do not impose any special restrictions on the specific form of the electronic device.

[0198] In some solutions, multiple embodiments of the present application can be combined and the combined solution can be implemented. Optionally, some operations in the processes of the method embodiments are optionally combined, and / or the order of some operations is optionally changed. Moreover, the execution order between the steps of each process is only exemplary and does not constitute a limitation on the execution order between the steps. There can also be other execution orders between the steps. It is not intended to indicate that the execution order is the only order in which these operations can be performed.

[0199] Those of ordinary skill in the art will think of various ways to reorder the operations described in the embodiments of the present application. Additionally, it should be noted that the process details involved in a certain embodiment of the present application are similarly applicable to other embodiments in a similar manner, or different embodiments can be used in combination.

[0200] Furthermore, some steps in the method embodiments can be equivalently replaced with other possible steps. Or, some steps in the method embodiments can be optional and can be deleted in certain usage scenarios. Or, other possible steps can be added to the method embodiments. And, the method embodiments can be implemented separately or in combination. The above content is only the specific implementation manners of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A negative electrode material, characterized in that, the negative electrode material comprises carbonaceous particles, the carbonaceous particles comprise one-dimensional crystalline carbon and amorphous carbon, the one-dimensional crystalline carbons are mutually lapped to form a framework structure, and the amorphous carbon is filled in the framework structure.

2. The negative electrode material according to claim 1, characterized in that, the diameter of the one-dimensional crystalline carbon is 5 nm - 200 nm, and the length of the one-dimensional crystalline carbon is 500 nm - 50 μm.

3. The negative electrode material according to claim 1 or 2, characterized in that, the length of the one-dimensional crystalline carbon is 500 nm - 5 μm.

4. The negative electrode material according to any one of claims 1 - 3, characterized in that, the mass percentage content of the one-dimensional crystalline carbon in the carbonaceous particles is 0.05% - 5%.

5. The negative electrode material according to any one of claims 1 - 4, characterized in that, the conductivity of the one-dimensional crystalline carbon is greater than or equal to 500 S / cm.

6. The negative electrode material according to claim 5, characterized in that, the conductivity of the one-dimensional crystalline carbon is greater than or equal to 500 S / cm and less than or equal to 600 S / cm.

7. The negative electrode material according to any one of claims 1 - 6, characterized in that, the interlayer spacing of the one-dimensional crystalline carbon is 0.335 nm - 0.36 nm.

8. The negative electrode material according to any one of claims 1 - 7, characterized in that, the one-dimensional crystalline carbon comprises carbon fibers and carbon nanotubes.

9. The negative electrode material according to any one of claims 1 - 8, characterized in that, the amorphous carbon comprises a closed pore structure, and the closed pore volume of the closed pore structure is 0.05 ml / g - 0.5 ml / g.

10. The negative electrode material according to any one of claims 1 - 9, characterized in that, the interlayer spacing of the amorphous carbon is 0.375 nm - 0.395 nm.

11. The negative electrode material according to any one of claims 1 - 10, characterized in that, the mass percentage content of the amorphous carbon in the carbonaceous particles is 95% - 99.5%.

12. The negative electrode material according to any one of claims 1 - 11, characterized in that, the carbonaceous particles comprise first particles and second particles, the average particle size of the first particles is 1 μm - 4 μm, and the average particle size of the second particles is 6 μm - 20 μm.

13. The negative electrode material according to claim 12, characterized in that, the volume ratio of the first particles to the second particles is 10 - 40:

100.

14. The negative electrode material according to any one of claims 1 - 13, characterized in that, The tap density of the negative electrode material is greater than 1 g / cm 3 , the packing porosity of the negative electrode material is 2%-10%, and the oxygen content of the negative electrode material is less than 3%.

15. The negative electrode material according to any one of claims 1 - 14, characterized in that, the conductivity of the negative electrode material is greater than 250 S / cm.

16. A method for preparing a negative electrode material, characterized in that, the method comprises: sequentially adding a crystalline carbon precursor and a pore-forming agent to an amorphous carbon precursor dissolved in a solvent to obtain a carbon precursor dispersion; The carbon precursor dispersion is dried to obtain carbonaceous particles; the carbonaceous particles include one-dimensional crystalline carbon and amorphous carbon, and the one-dimensional crystalline carbon and the amorphous carbon are mutually overlapped to form a porous framework structure; The carbonaceous particles are pyrolyzed to obtain a negative electrode material.

17. According to the method described in claim 16, it is characterized in that, the step of pyrolyzing the carbonaceous particles to obtain a negative electrode material includes: heating the carbonaceous particles to 400°C - 700°C and thermally decomposing them at a constant temperature for 1h - 5h to obtain pyrolytic carbon microspheres; heating the pyrolytic carbon microspheres to 1000°C - 1400°C under the protection of an inert gas and thermally decomposing them at a constant temperature for 2h - 6h, and then cooling to room temperature to obtain the negative electrode material.

18. According to the method described in claim 16 or 17, it is characterized in that, the step of drying the carbon precursor dispersion to obtain carbonaceous particles includes: spray-drying the carbon precursor dispersion and adjusting the process to spray granulate to obtain first particles and second particles; the average particle size of the first particles is 1μm - 4μm, and the average particle size of the second particles is 6μm - 20μm; wherein, the inlet temperature is 80°C - 120°C, the feeding rate is 200ml / h - 1000ml / h, and the fan frequency is 30Hz - 60Hz.

19. According to the method described in any one of claims 16 - 18, it is characterized in that, the mass ratio of the amorphous carbon precursor, the crystalline carbon precursor, and the pore-forming agent is 100:(0.05 - 5):(1 - 20).

20. A negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one side of the negative electrode current collector, it is characterized in that, the negative electrode material layer includes the negative electrode material described in any one of claims 1 - 15 or the negative electrode material prepared by the preparation method described in any one of claims 16 - 19.

21. A sodium-ion battery, it is characterized in that, it includes a positive electrode sheet, a negative electrode sheet, a separator located between the positive electrode sheet and the negative electrode sheet, and an electrolyte. The electrolyte is filled between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet includes the negative electrode material described in any one of claims 1 - 15 or the negative electrode material prepared by the preparation method described in any one of claims 16 - 19.

22. An electronic device, it is characterized in that, the electronic device includes a housing, and electronic components and a battery accommodated in the housing. The battery supplies power to the electronic components, and the battery includes the sodium-ion battery described in claim 21.

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