Negative electrode material, sodium-ion battery, and electronic device

Abstract

A negative electrode material, a sodium-ion battery, and an electronic device, relating 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 overlaps each other to form a skeleton structure, and the amorphous carbon fills the skeleton structure. The negative electrode material comprises one-dimensional crystalline carbon, and the one-dimensional crystalline carbon has relatively high electrical conductivity, improving the conductivity of the negative electrode material. Thus, the conductivity of the negative electrode sheet in the sodium-ion battery can be improved.

Description

A negative electrode material, sodium ion battery and electronic device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 24, 2023, with application number 202311594010.8 and application name “A negative electrode material, sodium ion battery and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a negative electrode material, a sodium ion battery and an electronic device. Background Art

[0003] With the development of large-scale energy storage technology, electrochemical energy storage technology has great application prospects in large-scale energy storage demonstration projects and base stations. Sodium-ion batteries have the advantages of abundant reserves, low cost, and high safety, and can be widely used in large-scale energy storage scenarios.

[0004] Anode materials are a crucial component of sodium-ion batteries, and their performance largely determines the battery's energy density and cycle life. Hard carbon materials are commonly used as anode materials for batteries. However, the relatively disordered carbon microstructure of hard carbon materials can affect the electron transport pathways within the material and reduce its electrical conductivity. Improving the electrical conductivity of anode materials is an urgent challenge in this field.

[0005] Summary of the Invention

[0006] The 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 higher electrical conductivity and is beneficial to improving the conductivity of the sodium ion battery.

[0007] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0008] 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 carbon is overlapped with each other to form a skeleton structure, and the amorphous carbon is filled in the skeleton structure.

[0009] On the one hand, the negative electrode material includes one-dimensional crystalline carbon, which has high electrical conductivity and can improve the conductivity of the negative electrode material. This can improve the conductivity of the negative electrode sheet in the sodium-ion battery and, to a certain extent, promote the rapid diffusion of sodium ions. This, in turn, improves the current performance of the sodium-ion battery.

[0010] On the other hand, one-dimensional crystalline carbon can overlap with each other to form a skeleton structure, and amorphous carbon can be filled in this skeleton structure. This skeleton structure is a conductive network structure formed based on one-dimensional crystalline carbon as a skeleton. It not only helps to improve the conductivity of the negative electrode material, but also improves the conductivity of amorphous carbon. At the same time, it can also catalyze the conversion of sodium ions into sodium clusters, improving conversion efficiency.

[0011] In one embodiment, the diameter of the one-dimensional crystalline carbon is 5 nm to 200 nm, and the length of the one-dimensional crystalline carbon is 500 nm to 50 μm.

[0012] One-dimensional crystalline carbon has a small diameter and a long length, which gives it high electrical conductivity, improving the conductivity of negative electrode materials and, in turn, the conductivity of negative electrode sheets in sodium-ion batteries.

[0013] In one achievable embodiment, the length of the one-dimensional crystalline carbon is 500 nm to 5 μm.

[0014] The length of the one-dimensional crystalline carbon may preferably be 500 nm-5 μm. Controlling the length of the one-dimensional crystalline carbon within the above range can greatly improve the conductivity of the negative electrode material.

[0015] In one achievable manner, the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles is 0.05%-5%.

[0016] By regulating the mass percentage of one-dimensional crystalline carbon in the carbonaceous particles, the content of one-dimensional crystalline carbon is kept within a relatively suitable range, which can improve the conductivity of the negative electrode material and promote the rapid diffusion of sodium ions to a certain extent. In turn, it improves the current performance of the sodium-ion battery.

[0017] In one embodiment, 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.

[0018] In one implementation, the interlayer spacing of the one-dimensional crystalline carbon is 0.335nm-0.36nm. The smaller distance between the layers in the one-dimensional crystalline carbon improves its electrical conductivity, thereby enhancing the conductivity of the negative electrode material and ensuring the electrochemical performance of the sodium-ion battery.

[0019] In one implementation, the one-dimensional crystalline carbon includes carbon fibers and carbon nanotubes.

[0020] In one achievable embodiment, the amorphous carbon includes a closed pore structure, and a closed pore volume of the closed pore structure is 0.05 ml / g to 0.5 ml / g.

[0021] Amorphous carbon contains a closed pore structure that can store sodium ions. The closed pore volume range of the closed pore structure within the above range can also increase the sodium storage capacity to a certain extent. This can improve the capacity of the negative electrode material and thus increase the energy density of the sodium-ion battery.

[0022] In one embodiment, the interlayer spacing of the amorphous carbon is 0.375 nm to 0.395 nm. In the embodiment of the present application, the interlayer spacing of the amorphous carbon is within the above range, which makes the negative electrode material have a more stable structure and improves the sodium storage capacity of the negative electrode material.

[0023] In one achievable manner, the mass percentage of amorphous carbon in the carbonaceous particles is 95%-99.5%.

[0024] By regulating the mass percentage of amorphous carbon in the carbonaceous particles, the amorphous carbon content is maintained within a suitable range. This allows the amorphous carbon to be incorporated into the skeleton structure from all directions and to overlap with the one-dimensional crystalline carbon. This improves the tightness of the amorphous carbon within the skeleton structure, thereby enhancing the structural stability of the negative electrode material.

[0025] In one implementation, the carbonaceous particles include first particles and second particles, the first particles have an average particle size of 1 μm to 4 μm, and the second particles have an average particle size of 6 μm to 20 μm.

[0026] The present invention provides two different particle sizes, with an average particle size difference of 3 to 5 times. By using particle size grading, the porosity of the particles is effectively reduced, achieving a dense packing effect. This increases the compaction density of the carbonaceous particles relative to the powder, improving the volumetric energy density of sodium-ion batteries.

[0027] In one implementation, the volume ratio of the first particles to the second particles is 10-40:100.

[0028] The present application further provides a volume ratio of particles of two different particle sizes. By controlling the volume ratio of the two particles within this range, the two particles can be packed more tightly together, effectively reducing the void ratio of the particle packing. This increases the compaction density of the carbonaceous particles and improves the volumetric energy density of the sodium-ion battery.

[0029] In one embodiment, 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%.

[0030] This negative electrode material has a high compaction density and low bulk porosity, which can improve the volumetric energy density of sodium-ion batteries. Furthermore, the negative electrode material's oxygen content is less than 3%, which not only promotes the formation of a stable carbon layer structure within the amorphous carbon but also facilitates the bridging of one-dimensional crystalline carbon and amorphous carbon, effectively enhancing the negative electrode material's electrical conductivity.

[0031] In one embodiment, the negative electrode material has an electrical conductivity greater than 250 S / cm. This high electrical conductivity significantly improves the electron transport characteristics within the negative electrode material, reduces polarization of the negative electrode material, and thus enhances the electrochemical performance of the sodium-ion battery.

[0032] Secondly, embodiments of the present application provide a method for preparing a negative electrode material, comprising: 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 then dried to obtain carbonaceous particles; the carbonaceous particles include one-dimensional crystalline carbon and amorphous carbon, which overlap to form a porous skeleton structure. The carbonaceous particles are then pyrolyzed to obtain the negative electrode material.

[0033] The present invention uses the above-described preparation method to prepare a negative electrode material comprising one-dimensional crystalline carbon and amorphous carbon. The one-dimensional crystalline carbon can overlap to form a skeleton structure, and the amorphous carbon can be filled within the skeleton structure. This skeleton structure is a conductive network structure formed by the one-dimensional crystalline carbon as a skeleton, which makes the negative electrode material have high conductivity.

[0034] In one implementation, the carbonaceous particles are pyrolyzed to obtain the negative electrode material, including heating the carbonaceous particles to 400°C-700°C and pyrolyzing them at this constant temperature for 1-5 hours to obtain pyrolytic carbon microspheres. The pyrolytic carbon microspheres are then heated to 1000°C-1400°C under an inert gas atmosphere, pyrolyzed at this constant temperature for 2-6 hours, and cooled to room temperature to obtain the negative electrode material.

[0035] In the embodiment of the present application, the negative electrode material can be obtained by pre-carbonizing and high-temperature carbonizing the carbonaceous particles, so that the negative electrode material forms a skeleton structure including one-dimensional crystalline carbon and amorphous carbon, and thus has high electrical conductivity.

[0036] In one achievable embodiment, a carbon precursor dispersion is dried to obtain carbonaceous particles, including: spray drying the carbon precursor dispersion, adjusting the spray granulation process 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;

[0037] Among them, the inlet temperature is 80℃-120℃, the feed rate is 200ml / h-1000ml / h, and the fan frequency is 30Hz-60Hz.

[0038] In this manner, the embodiments of the present application can utilize spray drying to obtain first and second particles of different average particle sizes. The obtained first and second particles of different average particle sizes can effectively reduce the porosity of the particle stacking, resulting in a densely packed negative electrode material. This improves the volumetric energy density of the sodium-ion battery.

[0039] In one embodiment, the mass ratio of the amorphous carbon precursor, the crystalline carbon precursor, and the pore former is 100:(0.05-5):(1-20).

[0040] By controlling the mass ratio of the amorphous carbon precursor, crystalline carbon precursor, and pore-forming agent, not only can the high electrical conductivity of the one-dimensional crystalline carbon be achieved, but a closed pore structure can also be created in the negative electrode material, thereby increasing the sodium storage capacity of the negative electrode material. Furthermore, this improves the conductivity and energy density of the sodium-ion battery.

[0041] In a third aspect, an embodiment of the present application provides a negative electrode plate, which includes a negative electrode current collector and a negative electrode material layer arranged on at least one side of the negative electrode current collector, and the negative electrode material layer includes the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method described in the second aspect.

[0042] In a fourth aspect, an embodiment of the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator located between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the electrolyte is filled between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet comprises the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method described in the second aspect.

[0043] In a fifth aspect, an embodiment of the present application provides an electronic device, which includes a housing, and electronic components and a battery housed in the housing. The battery supplies power to the electronic components, and the battery includes the sodium ion battery described in the third aspect above. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG1 is a schematic structural diagram of a sodium ion battery provided in an embodiment of the present application;

[0045] FIG2 is a schematic structural diagram of a negative electrode material provided in an embodiment of the present application;

[0046] FIG3 is a schematic diagram of a process for preparing a negative electrode material according to an embodiment of the present application;

[0047] FIG4 is a schematic diagram of the microstructure of a method for preparing carbonaceous particles provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Among them, in the description of the present application, unless otherwise specified, " / " indicates that the objects associated before and after are in an "or" relationship. For example, A / B can represent A or B; "and / or" in the present application is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. In addition, in the description of the present application, unless otherwise specified, "multiple" refers to two or more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple. In addition, in order to facilitate a clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish identical or similar items with basically the same functions and effects.

[0049] Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit differences. 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 described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or design. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0050] For ease of understanding, some examples of concepts related to the embodiments of this application are provided for reference as follows:

[0051] Cathode: In a primary cell, the electrode from which current flows has a higher potential and is the positive electrode, gaining electrons to perform a reduction process. In an electrolytic cell, the positive electrode is the electrode connected to the positive terminal of the power supply and loses electrons to perform an oxidation process.

[0052] Anode: In a primary cell, the electrode into which current flows has a lower potential and is the negative electrode, losing electrons and causing oxidation. In an electrolytic cell, the anode is the electrode connected to the negative terminal of the power supply and receives electrons and causes reduction.

[0053] Electrolyte: A medium that provides ion exchange between the positive and negative electrodes of a battery.

[0054] Separator: The main function of the separator is to separate the positive and negative electrodes of the battery to prevent the two electrodes from contacting and short-circuiting. In addition, it also has the function of allowing electrolyte ions to pass through.

[0055] Film-forming additives: A type of substance that decomposes on the surface of materials before organic solvents to form an interfacial film, which can significantly improve battery performance.

[0056] D50: The particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%.

[0057] D002 interlayer spacing: refers to the distance between the layered structures in the material.

[0058] Related art provides a negative electrode material that uses asphalt as a hard carbon raw material. Through a heating and oxidation process, a conductive agent is introduced and the asphalt is cross-linked, dispersing the conductive agent within the material. However, during the heating process, the conductive agent is strongly oxidized by reactive oxygen molecules, resulting in an increase in surface defects in the negative electrode material and a significant decrease in conductivity, rendering it ineffective as a conductive agent.

[0059] Related art also provides a negative electrode material, which is prepared using phenolic resin as a raw material. Specifically, the polymerization reaction of phenol monomers and aldehyde monomers is used to obtain phenolic resin microspheres, which are then subjected to pre-oxidation and high-temperature carbonization to obtain the negative electrode material. However, the carbon microstructure of the resulting negative electrode material exhibits a more disordered structure, which affects the electron transmission channels within the material and reduces the material's rate performance and conductivity. At the same time, the compaction density of the phenolic resin microsphere structure is low, which is not conducive to improving the energy density of sodium-ion batteries.

[0060] To address the above-mentioned issues, embodiments of the present application provide a negative electrode material, a sodium-ion battery, and an electronic device. The negative electrode material can be used to prepare a negative electrode plate for a sodium-ion battery. The negative electrode material proposed in this application includes carbonaceous particles, which include one-dimensional crystalline carbon and amorphous carbon. The one-dimensional crystalline carbon is overlapped to form a skeleton structure, and the amorphous carbon is filled within the skeleton structure.

[0061] On the one hand, the negative electrode material includes one-dimensional crystalline carbon, which has high electrical conductivity and can improve the conductivity of the negative electrode material. This can improve the conductivity of the negative electrode sheet in the sodium-ion battery and, to a certain extent, promote the rapid diffusion of sodium ions. This, in turn, improves the current performance of the sodium-ion battery.

[0062] On the other hand, one-dimensional crystalline carbon can overlap with each other to form a skeleton structure, and amorphous carbon can be filled in this skeleton structure. This skeleton structure is a conductive network structure formed based on one-dimensional crystalline carbon as a skeleton. It not only helps to improve the conductivity of the negative electrode material, but also improves the conductivity of amorphous carbon. At the same time, it can also catalyze the conversion of sodium ions into sodium clusters, improving conversion efficiency.

[0063] The present application also provides a sodium ion battery. FIG1 is a schematic diagram of the structure of the sodium ion battery provided in the present application. As shown in FIG1 , the sodium ion battery includes a positive electrode sheet 10, a negative electrode sheet 20, a separator 30, and an electrolyte 40, wherein the separator 30 is provided 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 after passing through the electrolyte 40, they are embedded in the negative electrode material 202 of the negative electrode sheet 20; during discharging, sodium ions are released from the negative electrode material 202, and after passing through the electrolyte 40, they are inserted into the positive electrode material 102.

[0064] Continuing with Figure 1 , in the sodium-ion battery provided in the embodiments of the present application, the separator 30 blocks the passage of electrons while allowing the passage of ions. 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. In a sodium-ion battery, the electrolyte 40 serves as the transmission medium for sodium ions between the positive electrode 10 and the negative electrode 20.

[0065] As shown in FIG1 , 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 . The positive electrode material layer may include not only the positive electrode material 102 but also a certain amount of binder, conductive agent and other components.

[0066] The positive electrode current collector 101 can be a metal foil, such as aluminum foil, gold foil, or platinum foil. The positive electrode material 102 can reversibly intercalate and deintercalate sodium ions. The positive electrode material 102 includes, but is not limited to, at least one of a layered sodium transition metal oxide, a Prussian white compound, a Prussian blue compound, and a sodium polyanion compound.

[0067] Sodium transition metal oxides such as sodium nickel iron manganese (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2, NFM111), Prussian white compounds such as (Na2Mn[Fe(CN)6], PBA), Prussian blue compounds such as (NaMn[Fe(CN)6], PBA), sodium polyanionic compounds such as sodium iron phosphate (NaFePO4, NFP), sodium iron sulfate (Na2Fe2(SO4)3, NFS). The binder may be, for example, polyvinylidene fluoride (poly 1,1-difluoroethylene, PVDF), and the conductive agent may be, for example, conductive carbon black (super P), graphite, amorphous carbon, carbon nanotubes, carbon fiber, graphene, etc. The above-mentioned positive electrode current collector 101, positive electrode material 102, binder and conductive agent for preparing the positive electrode plate 10 are only exemplary illustrations, and the embodiments of the present application are not limited thereto. Taking the positive electrode material 102 as an example, in theory, it can be a compound that can reversibly embed / de-embed sodium ions.

[0068] Continuing to refer to FIG1 , in the sodium ion battery provided in the embodiment of the present application, the negative electrode plate 20 includes a negative electrode current collector 201 and a negative electrode material layer coated on the surface of the negative electrode current collector. In addition to the negative electrode material 202, the negative electrode material layer may also include a certain amount of binder, conductive agent and other components. Among them, the negative electrode 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 electrode current collector 201, binder and conductive agent used to prepare the negative electrode plate 20 are only exemplary descriptions and are not limited in this embodiment of the present application.

[0069] In one embodiment of the present application, referring to FIG. 2 , the negative electrode material 202 may include carbonaceous particles, which may be spherical in shape. For example, the carbonaceous particles may be hard carbon microspheres. Of course, the carbonaceous particles may also have rod-like, plate-like, and angular shapes, which are not specifically limited in this embodiment of the present application.

[0070] The carbonaceous particles may include one-dimensional crystalline carbon and amorphous carbon, wherein the one-dimensional crystalline carbon is overlapped to form a skeleton structure, and the amorphous carbon is filled in the skeleton structure. The average particle size (D50) of the carbonaceous particles may be 1 μm to 20 μm.

[0071] Thus, the one-dimensional crystalline carbon provided by the embodiment of the present application can overlap with the amorphous carbon to form a skeleton structure. The one-dimensional crystalline carbon can randomly interlace with each other in the amorphous carbon to form a skeleton structure, while forming carbonaceous particles with the amorphous carbon.

[0072] In this skeleton structure, amorphous carbon can be overlapped by one-dimensional crystalline carbon to form a porous skeleton structure. Amorphous carbon can also be located at different positions on the one-dimensional crystalline carbon, such as the end of the one-dimensional crystalline carbon. In this way, based on the one-dimensional crystalline carbon as the skeleton, the network structure formed by amorphous carbon filling in the skeleton has a high electrical 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 the rapid diffusion of sodium ions can be promoted to a certain extent. Furthermore, the high current performance of the sodium ion battery is improved.

[0073] In some embodiments of the present application, the diameter of the one-dimensional crystalline carbon may be 5 nm-200 nm, and the length of the one-dimensional crystalline carbon may be 500 nm-50 μm.

[0074] As an example, the diameter of the one-dimensional crystalline carbon may be 5 nm, 200 nm, or any value between 5 nm and 200 nm, such as 5 nm, 6 nm, 100 nm, 195 nm, 200 nm, etc. These values ​​are not listed here.

[0075] The length of the one-dimensional crystalline carbon can be specifically 500 nm, 50 μm, or any value between 500 nm and 50 μm, such as 500 nm, 600 nm, 800 nm, 5 μm, 30 μm, etc. A full list of these is omitted here.

[0076] The one-dimensional crystalline carbon in the embodiment of the present application has a smaller diameter and a longer length, which gives it a higher electrical conductivity, thereby improving the conductivity of the negative electrode material and, in turn, the conductivity of the negative electrode sheet in the sodium ion battery.

[0077] In some embodiments of the present application, the length of the one-dimensional crystalline carbon may be 500 nm-5 μm. Thus, the length of the one-dimensional crystalline carbon may preferably be 500 nm-5 μm. Controlling the length of the one-dimensional crystalline carbon within the above range can further improve the conductivity of the negative electrode material.

[0078] In some embodiments of the present application, the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles is 0.05%-5%.

[0079] It should be understood that in actual applications, the mass percentage of one-dimensional crystalline carbon in the carbonaceous particles may be subject to certain measurement and testing system errors, and the values ​​within the system error range are all within the range defined in the embodiments of the present application.

[0080] In addition, as an example, the mass percentage of the one-dimensional crystalline carbon in the carbonaceous particles can 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. These values ​​are not listed here.

[0081] By regulating the mass percentage of one-dimensional crystalline carbon in the carbonaceous particles and maintaining it within a suitable range, the conductivity of the negative electrode material can be improved, and to a certain extent, the rapid diffusion of sodium ions can be promoted. This, in turn, improves the current performance of the sodium-ion battery.

[0082] In some embodiments of the present application, the electrical conductivity of the one-dimensional crystalline carbon may be greater than or equal to 500 S / cm.

[0083] 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. Thus, the one-dimensional crystalline carbon provided in the embodiments of the present application has a high electrical conductivity, which improves the rate performance of the negative electrode material.

[0084] In some embodiments of the present application, the interlayer spacing of the one-dimensional crystalline carbon is 0.335 nm-0.36 nm.

[0085] As an example, the interlayer spacing of one-dimensional crystalline carbon can 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. These values ​​are not listed here.

[0086] Thus, the D002 interlayer spacing corresponding to the one-dimensional crystalline carbon provided in the embodiments of the present application is within the above range. The distance between the layered structures in the one-dimensional crystalline carbon is small, which can improve the electrical conductivity of the one-dimensional crystalline carbon. This improves the conductivity of the negative electrode material and ensures the electrochemical performance of the sodium-ion battery.

[0087] In some embodiments of the present application, the one-dimensional crystalline carbon includes carbon fibers and carbon nanotubes.

[0088] 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.

[0089] Continuing to refer to FIG2 , the amorphous carbon provided in the embodiment of the present application includes a closed pore structure, and the closed pore volume of the closed pore structure can range from 0.05 ml / g to 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 increase the sodium storage capacity to a certain extent. In this way, the capacity of the negative electrode material can be improved. Thus, the battery energy density of the sodium ion battery is improved.

[0090] In one achievable manner, the above-mentioned closed pore structure cannot be wetted by butanol, but can be filled with helium. The closed-pore volume test method of a closed-pore structure may include: taking a certain mass of sample, using butanol as the infiltration liquid, and testing the volume V1 of the unit mass sample by the immersion method (pycnometer method) based on the Archimedes principle. Then, the volume V2 of the unit mass sample is tested by the helium pressurized displacement method, and V2-V1 is the closed-pore volume of the closed pores of the unit mass sample. The embodiment of the present application does not specifically limit the closed-pore volume test method of the closed-pore structure.

[0091] In some embodiments of the present application, the interlayer spacing of the amorphous carbon is 0.375 nm-0.395 nm.

[0092] As an example, the interlayer spacing of amorphous carbon can be 0.375 nm, 0.395 nm, or any value between 0.375 nm and 0.395 nm, such as 0.375 nm, 0.385 nm, 0.386 nm, 0.388 nm, 0.395 nm, etc. These values ​​are not listed here.

[0093] Thus, the D002 interlayer spacing corresponding to the amorphous carbon provided in the embodiment of the present application is within the above range, so that the negative electrode material has a more stable structure and improves the sodium storage capacity of the negative electrode material.

[0094] In some embodiments of the present application, the mass percentage of amorphous carbon in the carbonaceous particles is 95%-99.5%.

[0095] It should be understood that in actual applications, the mass percentage of amorphous carbon in carbonaceous particles may be subject to certain measurement and testing system errors, and the values ​​within the system error range are all within the range defined in the embodiments of the present application.

[0096] In addition, as an example, the mass percentage of the amorphous carbon in the carbonaceous particles can be 95%, 99.5%, or any value between 95% and 99.5%, such as 96%, 98%, 99.1%, 99.2%, 99.5%, etc. These values ​​are not listed here.

[0097] Thus, the mass percentage of amorphous carbon in the carbonaceous particles provided in the embodiments of the present application is in the range of 95%-99.5%. In this way, by regulating the mass percentage of amorphous carbon in the carbonaceous particles, the content of amorphous carbon is maintained within a relatively suitable range. In this way, amorphous carbon can be filled into the skeleton structure from all directions and overlapped with the one-dimensional crystalline carbon. This can improve the compactness of amorphous carbon in the skeleton structure. Thus, the structural stability of the negative electrode material is improved.

[0098] In some embodiments of the present application, the carbonaceous particles include first particles and second particles, wherein the first particles have an average particle size (D50) of 1 μm to 4 μm, and the second particles have an average particle size (D50) of 6 μm to 20 μm. The first and second particles each include one-dimensional crystalline carbon and amorphous carbon, wherein the one-dimensional crystalline carbon overlaps to form a skeleton structure, and the amorphous carbon fills the skeleton structure.

[0099] As an example, the average particle size of the first particles can 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.

[0100] The average particle size of the second particles can 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.

[0101] 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 the two peaks being located between 1 μm-4 μm and 6 μm-20 μm, respectively, corresponding to the first particles and the second particles mentioned above.

[0102] Thus, the present embodiment provides particles of two different particle sizes, with an average particle size difference of 3 to 5 times. By using particle size grading, the porosity of the particles is effectively reduced, achieving a dense packing effect. This increases the compaction density of the carbonaceous particles relative to the powder, improving the volumetric energy density of the sodium-ion battery.

[0103] In some embodiments of the present application, the volume ratio of the first particles to the second particles is 10-40:100.

[0104] As an example, the volume ratio of the first particles to the second particles can be 10:100, 40:100, or any value between 10 and 40:100, such as 12:100, 20:100, 22:100, 30:100, etc. A full list is omitted here.

[0105] Thus, the present invention further provides a volume ratio of particles of two different particle sizes within this range. By controlling the volume ratio of the two particles within this range, the two particles can be packed more tightly together, effectively reducing the void ratio of the particle packing. This increases the compaction density of the carbonaceous particles and improves the volumetric energy density of the sodium-ion battery.

[0106] 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%.

[0107] Thus, the negative electrode material provided by the embodiments of the present application has a high compaction density and a low bulk porosity, which can improve the volumetric energy density of sodium-ion batteries. In addition, the oxygen content of the negative electrode material is less than 3%, which not only promotes the formation of a stable carbon layer structure in the amorphous carbon, but also promotes 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.

[0108] In some embodiments of the present application, the negative electrode material has a conductivity greater than 250 S / cm. Thus, the negative electrode material provided by the embodiments of the present application has a high conductivity, which can significantly improve the electron transport properties within the negative electrode material and reduce the polarization of the negative electrode material. This, in turn, enhances the electrochemical performance of the sodium-ion battery.

[0109] The present invention also provides a method for preparing a negative electrode material, as shown in FIG3 , which includes the following steps:

[0110] S301 , 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.

[0111] In some embodiments of the present application, a carbon precursor dispersion can be prepared first. Specifically, an amorphous carbon precursor is dissolved in a solvent and poured into a reactor in a high-speed stirring device at a speed of 1000-3000 r / min, with stirring started. Next, a crystalline carbon precursor and a pore-forming agent are sequentially added to the amorphous carbon precursor, stirred evenly, and diluted with a solvent to 1%-5% to obtain a carbon precursor dispersion.

[0112] In some embodiments of the present application, the amorphous carbon precursor includes one or more of phenolic resin, epoxy resin, and furfuryl alcohol resin.

[0113] In some embodiments of the present application, the solvent includes one or more of water, methanol, ethanol and ethylene glycol.

[0114] In some embodiments of the present application, the pore-forming agent includes one or more of polyvinyl alcohol, polyvinyl butyral, polymethyl acrylate, polystyrene and polyacrylamide, the residual carbon value of the pore-forming agent is 0.1%-10%, and the average molecular weight of the pore-forming agent is 5000-50000.

[0115] S302, 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 overlap each other to form a porous skeleton structure.

[0116] In some embodiments of the present application, particle precursors of different particle sizes are prepared. During the drying process of the carbon precursor dispersion to obtain carbonaceous particles, the carbon precursor dispersion can be spray-dried, and the spray granulation process can be adjusted 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.

[0117] For example, the carbon precursor dispersion can be transferred to a spray dryer at 80°C-120°C, a feed rate of 200ml / h-1000ml / h, and a fan frequency of 20Hz-60Hz. The spray granulation process is adjusted to obtain first microspheres such as the first particles described above and second microspheres such as the second particles described above. The two microspheres are then mixed in a V-type mixer at a volume ratio of 10-40:100 to obtain carbonaceous particles.

[0118] S303, pyrolyzing the carbonaceous particles to obtain negative electrode materials.

[0119] In some embodiments of the present application, the carbonaceous particles can be pre-carbonized and then carbonized at high temperature to form the particles. Specifically, the carbonaceous particles are heated to 400°C-700°C and pyrolyzed at this temperature for 1-5 hours to produce pyrolytic carbon microspheres. The pyrolytic carbon microspheres are then heated to 1000°C-1400°C under an inert gas atmosphere, pyrolyzed at this temperature for 2-6 hours, and cooled to room temperature to produce the negative electrode material.

[0120] For example, the mixed carbonaceous particles are placed in a tube furnace, heated to 400-700°C, and pyrolyzed at constant temperature for 1-5 hours to obtain pyrolytic carbon microspheres. The obtained pyrolytic carbon microspheres are then placed in a box-type carbonization furnace, heated to 1000-1400°C under inert gas protection, pyrolyzed for 2-6 hours, and cooled to room temperature to obtain the negative electrode material.

[0121] 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).

[0122] By controlling the mass ratio of the amorphous carbon precursor, crystalline carbon precursor, and pore-forming agent, not only can the high electrical conductivity of the one-dimensional crystalline carbon be achieved, but a closed pore structure can also be created in the negative electrode material, thereby increasing the negative electrode material's sodium storage capacity. Furthermore, this improves the conductivity and energy density of the sodium-ion battery.

[0123] It can be understood that the calculated values ​​of the above numerical ratios may allow for certain measurement test system errors during actual test operations, and the values ​​within the system error range may be understood as the range defined by the embodiments of the present application.

[0124] The above-mentioned negative electrode materials are introduced below through specific examples.

[0125] Example 1

[0126] A phenolic resin carbon precursor was dissolved in ethanol and poured into a reactor equipped with a high-speed stirring device at a speed of 2000 r / min. Vapor-grown carbon fiber (VGCF) and polyvinyl alcohol (PVA) were added to the amorphous carbon precursor solution in sequence and stirred evenly. The mass ratio of phenolic resin carbon precursor: VGCF: PVA was 100:3:10. Ethanol was then added to dilute the mixture to 5% to obtain a carbon precursor dispersion.

[0127] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 1.5μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency to 50Hz, and second particles were obtained by spray granulation with an average particle size of 9μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0128] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0129] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0130] Example 2

[0131] Dissolve the phenolic resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirring device at a speed of 2000r / min. Start stirring and add VGCF and PVA to the amorphous carbon precursor solution in sequence and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PVA is 100:1.5:10. Then add ethanol to dilute to 5% to obtain a carbon precursor dispersion.

[0132] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 1.5μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency to 50Hz, and second particles were obtained by spray granulation with an average particle size of 9μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 25:100 to obtain carbonaceous particles.

[0133] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0134] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0135] Example 3

[0136] Dissolve the phenolic resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirring device at a speed of 2000r / min. Start stirring and add VGCF and PVA to the amorphous carbon precursor solution in sequence and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PVA is 100:2.5:10. Then add ethanol to dilute to 5% to obtain a carbon precursor dispersion.

[0137] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 1.5μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency to 50Hz, and second particles were obtained by spray granulation with an average particle size of 9μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 20:100 to obtain carbonaceous particles.

[0138] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0139] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0140] Example 4

[0141] Dissolve the phenolic resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirring device at a speed of 2000r / min. Start stirring and add VGCF and PVA to the amorphous carbon precursor solution in sequence and stir evenly. Among them, the mass ratio of phenolic resin carbon precursor: VGCF: PVA is 100:2.5:10. Then add ethanol to dilute to 5% to obtain a carbon precursor dispersion.

[0142] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 1.5μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency to 50Hz, and second particles were obtained by spray granulation with an average particle size of 9μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 40:100 to obtain carbonaceous particles.

[0143] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0144] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0145] Example 5

[0146] The phenolic resin carbon precursor was dissolved in water and poured into a reactor equipped with a high-speed stirring device at a speed of 2500r / min. VGCF and polystyrene (PS) were added to the amorphous carbon precursor solution in sequence and stirred evenly. The mass ratio of phenolic resin carbon precursor: VGCF: PS was 100:3:15. Ethanol was then added to dilute it to 3% to obtain a carbon precursor dispersion.

[0147] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 120°C, a feed rate of 200ml / h, and a fan frequency of 60HZ. The process was adjusted to spray granulate to obtain the first particles, and the average particle size of the first particles was 1.8μm. Subsequently, the feed rate was adjusted to 800ml / h, the fan frequency was 60Hz, and the second particles were spray granulated to obtain the average particle size of the second particles. The two particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0148] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 600°C, and pyrolyzed at a constant temperature for 4 hours to obtain pyrolytic carbon microspheres.

[0149] The obtained pyrolytic carbon microspheres were placed in a box-type carbonization furnace, heated to 1400°C under the protection of inert gas, pyrolyzed for 4 hours, and cooled to room temperature to obtain the negative electrode material.

[0150] Example 6

[0151] A phenolic resin carbon precursor was dissolved in water and poured into a reactor equipped with a high-speed stirrer at 2500 rpm. VGCF and polyacrylamide (PAM) were then added sequentially to the amorphous carbon precursor solution and stirred thoroughly. The mass ratio of phenolic resin carbon precursor: VGCF: PAM was 100:2.8:10. The mixture was then diluted to 3% with ethanol to obtain a carbon precursor dispersion.

[0152] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 120°C, a feed rate of 200ml / h, and a fan frequency of 60HZ. The process was adjusted to spray granulate to obtain the first particles, and the average particle size of the first particles was 1.8μm. Subsequently, the feed rate was adjusted to 800ml / h, the fan frequency was 60Hz, and the second particles were spray granulated to obtain the average particle size of the second particles. The two particles were mixed evenly in a V-type mixer at a volume ratio of 35:100 to obtain carbonaceous particles.

[0153] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 600°C, and pyrolyzed at a constant temperature for 4 hours to obtain pyrolytic carbon microspheres.

[0154] The obtained pyrolytic carbon microspheres were placed in a box-type carbonization furnace, heated to 1400°C under the protection of inert gas, pyrolyzed for 4 hours, and cooled to room temperature to obtain the negative electrode material.

[0155] Example 7

[0156] The epoxy resin carbon precursor was dissolved in ethanol and poured into a reactor equipped with a high-speed stirrer at 2000 rpm. Carbon nanotubes (CNTs) and polyvinyl alcohol (PVA) were then added to the amorphous carbon precursor solution in a sequential order, stirring evenly. The mass ratio of epoxy resin carbon precursor: CNT: PVA was 100:4:10. Ethanol was then added to dilute the mixture to 5% to obtain a carbon precursor dispersion.

[0157] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 1.5μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency to 50Hz, and second particles were obtained by spray granulation with an average particle size of 9μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0158] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0159] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0160] Example 8

[0161] Dissolve the furfuryl alcohol resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirrer at 2000 rpm. Then, sequentially add CNTs and polyvinyl alcohol (PVA) to the amorphous carbon precursor solution and stir until evenly combined. The mass ratio of furfuryl alcohol resin carbon precursor: CNTs: PVA is 100:1:10. Ethanol is then added to dilute the mixture to 5% to obtain a carbon precursor dispersion.

[0162] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 40HZ. The process was adjusted to spray granulate to obtain the first particles, and the average particle size of the first particles was 1.5μm. Subsequently, the feed rate was adjusted to 800ml / h and the fan frequency was 50Hz, and the second particles were spray granulated to obtain the average particle size of the second particles. The two particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0163] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0164] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0165] Comparative Example 1

[0166] Dissolve the phenolic resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirring device at a speed of 2000r / min. Start stirring and add PVA to the amorphous carbon precursor solution and stir evenly. The mass ratio of phenolic resin carbon precursor to PVA is 100:10. Then add ethanol to dilute to 5% to obtain a carbon precursor dispersion.

[0167] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 2μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency was adjusted to 50Hz, and second particles were obtained by spray granulation with an average particle size of 6μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0168] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0169] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0170] Comparative Example 2

[0171] Dissolve the phenolic resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirring device at a speed of 2000r / min. Start stirring and add PVA to the amorphous carbon precursor solution and stir evenly. The mass ratio of phenolic resin carbon precursor to PVA is 100:10. Then add ethanol to dilute to 5% to obtain a carbon precursor dispersion.

[0172] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 2μm. Subsequently, the feed rate was adjusted to 800ml / h and the fan frequency was 50Hz, and second particles were obtained by spray granulation with an average particle size of 8μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0173] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0174] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0175] Comparative Example 3

[0176] A phenolic resin carbon precursor was dissolved in ethanol and poured into a reactor equipped with a high-speed stirring device at a speed of 2000 r / min. Vapor-grown carbon fiber (VGCF) and polyvinyl alcohol (PVA) were added to the amorphous carbon precursor solution in sequence and stirred evenly. The mass ratio of phenolic resin carbon precursor: VGCF: PVA was 100:3:10. Ethanol was then added to dilute the mixture to 5% to obtain a carbon precursor dispersion.

[0177] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100° C., a feed rate of 800 ml / h, and a fan frequency of 50 Hz for spray granulation to obtain carbonaceous particles with an average particle size of 8 μm.

[0178] The obtained carbonaceous particles were mixed and placed in a tube furnace, heated to 500°C, and pyrolyzed at a constant temperature for 3 hours to obtain pyrolytic carbon microspheres.

[0179] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0180] Comparative Example 4

[0181] Dissolve the phenolic resin carbon precursor in ethanol and pour it into a reactor equipped with a high-speed stirring device at a speed of 2000r / min. Start stirring and add VGCF to the amorphous carbon precursor solution and stir evenly. The mass ratio of phenolic resin carbon precursor to VGCF is 100:10. Then add ethanol to dilute to 5% to obtain a carbon precursor dispersion.

[0182] The obtained carbon precursor dispersion was transferred to a spray dryer with an inlet temperature of 100°C, a feed rate of 200ml / h, and a fan frequency of 50HZ. The process was adjusted to spray granulate to obtain first particles with an average particle size of 1.5μm. Subsequently, the feed rate was adjusted to 500ml / h and the fan frequency to 50Hz, and second particles were obtained by spray granulation with an average particle size of 9μm. The two obtained particles were mixed evenly in a V-type mixer at a volume ratio of 30:100 to obtain carbonaceous particles.

[0183] The obtained uniformly mixed carbonaceous particles were placed in a tube furnace, heated to 500° C., and pyrolyzed at a constant temperature for 3 h to obtain pyrolytic carbon microspheres.

[0184] 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 hours, and cooled to room temperature to obtain the negative electrode material.

[0185] The negative electrode materials prepared in Examples 1-8 and Comparative Examples 1-4 and the corresponding sodium ion batteries were tested for performance. The test results are shown below:

[0186] In some embodiments of the present application, the morphology of Example 1 was analyzed by scanning electron microscopy. Referring to FIG4 , the sample prepared in Example 1 exhibited a rounded spherical structure and two spherical structures with different average particle sizes.

[0187] In some embodiments of the present application, in order to systematically characterize the effect of the material particle gradation on the overall powder structure performance of the negative electrode material, the above-mentioned samples were subjected to technical characterization in terms of particle size distribution, tap density, powder compaction density, etc., as shown in Table 1 below. The carbonaceous particles in Comparative Example 3 do not include two particles with different average particle sizes and different volume ratios, and their tap density and powder compaction density are both the lowest. In this way, it can be shown that the other samples except Comparative Example 3 can improve the tap density and compaction density of the negative electrode material by setting two particles with different average particle sizes and different volume ratios. Thus, the battery energy density of sodium ions can be improved. At the same time, by comparing Comparative Example 1 and Comparative Example 2 with Comparative Example 3, it can be found that the larger the particle size dispersion, the more obvious the increase in the compaction density and tap density of the negative electrode material as a whole.

[0188] Table 1

[0189] In some embodiments of the present application, in order to characterize the effect of the introduction of one-dimensional crystalline carbon material on the internal electron transport of the negative electrode material and to analyze the effect of the pore former on the electrochemical properties of the negative electrode material, the powder conductivity, closed pore volume, sodium ion battery charge test capacity and first coulombic efficiency of the negative electrode material were tested respectively, as shown in Table 2 below.

[0190] First, Comparative Example 4, which lacks a pore-forming agent, exhibits a low closed-pore volume and a low sodium electroreversible capacity. This demonstrates that, in samples other than Comparative Example 4, the addition of a pore-forming agent can increase the closed-pore volume of the negative electrode material, thereby improving the negative electrode material's sodium storage capacity.

[0191] Secondly, in Comparative Examples 1 and 2, where no one-dimensional crystalline carbon was added, the electrical conductivity was significantly reduced, and the initial coulombic efficiency was also low. This indicates that the introduction of one-dimensional crystalline carbon in the samples other than Comparative Examples 1 and 2 can significantly improve the electrical conductivity of the negative electrode material, improve the electron transport properties within the negative electrode material, reduce the polarization of the negative electrode material, and enhance the electrochemical performance of the sodium ion battery.

[0192] Table 2

[0193] In summary, on the one hand, the one-dimensional crystalline carbons in the embodiments of the present application can be intertwined to form a skeleton 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 electrical conductivity of one-dimensional crystalline carbon is one to two orders of magnitude higher than that of amorphous carbon. The skeleton formed by the interlacing of one-dimensional crystalline carbons serves as a conductive network, which can greatly improve the conductivity of amorphous carbon and improve the high current performance of sodium ion batteries. On the other hand, the embodiments of the present application can effectively reduce the void ratio of particle accumulation by mixing different particles with diameters that differ by 3 to 5 times according to a certain volume ratio, thereby achieving a dense stacking effect, thereby increasing the compaction density corresponding to the carbonaceous particles and improving the volume energy density of the sodium ion battery.

[0194] An embodiment of the present application also provides a negative electrode plate, which includes a negative electrode current collector and a negative electrode material layer arranged on at least one side of the negative electrode current collector, and 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] An embodiment of the present application also provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator located between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the electrolyte is filled between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet comprises the negative electrode material as described above or the negative electrode material prepared by the preparation method as described above.

[0196] An embodiment of the present application further provides an electronic device, which includes a housing, and electronic components and a battery housed in the housing. The battery supplies power to the electronic components, and the battery includes the sodium ion battery described above.

[0197] Electronic devices may include, for example, mobile phones, smart screens, tablet computers, personal computers (PCs), personal digital assistants (PDAs), smart watches, power banks, netbooks, wearable devices, augmented reality (AR) devices, virtual reality (VR) devices, vehicle-mounted devices, energy storage devices, base stations, and automobiles. The embodiments of the present application do not impose any special restrictions on the specific form of the electronic device.

[0198] In some embodiments, multiple embodiments of the present application may be combined and the combined embodiments may be implemented. Optionally, some operations in the processes of the various method embodiments may be optionally combined, and / or the order of some operations may be optionally changed. Furthermore, the execution order between the steps of each process is merely exemplary and does not constitute a limitation on the execution order between the steps. Other execution orders may also be used between the steps. This is not intended to indicate that the execution order is the only order in which these operations may be performed.

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

[0200] In addition, some steps in the method embodiment may be equivalently replaced with other possible steps. Alternatively, some steps in the method embodiment may be optional and may be deleted in certain usage scenarios. Alternatively, other possible steps may be added to the method embodiment. Moreover, each method embodiment may be implemented separately or in combination. The above content is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed in the present application shall be covered within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be based on the scope of protection of the claims.

Claims

1. A negative electrode material, characterized in that: The negative electrode material includes carbonaceous particles, and the carbonaceous particles include one-dimensional crystalline carbon and amorphous carbon. The one-dimensional crystalline carbons are overlapped with each other to form a skeleton structure, and the amorphous carbon is filled in the skeleton structure.

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

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

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

5. The negative electrode material according to any one of claims 1 to 4, characterized in that: The electrical 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 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.

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

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

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

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

12. The negative electrode material according to any one of claims 1 to 11, characterized in that: The carbonaceous particles include first particles and second particles, the first particles have an average particle size of 1 μm to 4 μm, and the second particles have an average particle size of 6 μm to 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 to 13, characterized in that: The compaction density of the negative electrode material is greater than 1g / 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%.

15. The negative electrode material according to any one of claims 1 to 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: Adding a crystalline carbon precursor and a pore-forming agent sequentially into an amorphous carbon precursor dissolved in a solvent to obtain a carbon precursor dispersion; 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 overlap each other to form a porous skeleton structure; The carbonaceous particles are pyrolyzed to obtain negative electrode materials.

17. The method according to claim 16, characterized in that The step of subjecting the carbonaceous particles to pyrolysis to obtain a negative electrode material comprises: The carbonaceous particles are heated to 400° C.-700° C. and pyrolyzed at a constant temperature for 1 h-5 h to obtain pyrolytic carbon microspheres; The pyrolytic carbon microspheres are heated to 1000° C.-1400° C. under the protection of an inert gas, pyrolyzed at a constant temperature for 2 h-6 h, and cooled to room temperature to obtain the negative electrode material.

18. The method according to claim 16 or 17, characterized in that The step of drying the carbon precursor dispersion to obtain carbonaceous particles comprises: The carbon precursor dispersion is spray-dried, and the process is adjusted 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; Among them, the inlet temperature is 80℃-120℃, the feed rate is 200ml / h-1000ml / h, and the fan frequency is 30Hz-60Hz.

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

20. A negative electrode plate, comprising a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, characterized in that: The negative electrode material layer includes the negative electrode material according to any one of claims 1 to 15 or the negative electrode material prepared by the preparation method according to any one of claims 16 to 19.

21. A sodium ion battery, 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, wherein the electrolyte is filled between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet includes the negative electrode material as described in any one of claims 1 to 15 or the negative electrode material prepared by the preparation method as described in any one of claims 16 to 19.

22. An electronic device, characterized in that: The electronic device comprises a shell, and electronic components and a battery housed in the shell, wherein the battery supplies power to the electronic components, and the battery comprises the sodium ion battery according to claim 21.

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