Sodium ion battery, preparation method for sodium ion battery, electrical apparatus and carbon-based material

Abstract

Provided in the present disclosure are a negative electrode sheet, a secondary battery, an electrical apparatus and a carbon-based material. The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a carbon-based material, the carbon-based material comprises graphene sheet layers, and the space volume H1 between graphene sheet layers with the interlayer spacing greater than 0.4 nm and the total space volume Htotal between all the graphene sheet layers satisfy: 40%≤H1 / Htotal≤60%.

Description

Sodium-ion battery, method for manufacturing sodium-ion battery, electric device, and carbon-based material

[0001] Cross-reference to related applications

[0002] The present disclosure is based on and claims priority to Chinese Patent Application No. 202410649325.6, filed on May 23, 2024, entitled “Negative electrode sheet, secondary battery, electric device, and hard carbon material”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of secondary batteries, and in particular to a sodium-ion battery, a method for manufacturing a sodium-ion battery, an electric device, and a carbon-based material. BACKGROUND

[0004] In recent years, secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, etc. With the application and promotion of secondary batteries, people have increasingly high requirements for the performance of secondary batteries, and the negative active material, as an important component of secondary batteries, plays an important role in the performance of secondary batteries. Currently, carbon-based materials are commonly used as negative active materials for secondary batteries. However, carbon-based materials as negative active materials cannot balance the kinetic performance and the first coulomb efficiency. SUMMARY

[0005] The present disclosure is made in view of the above-mentioned problems, and aims to provide a sodium-ion battery, a method for manufacturing a sodium-ion battery, an electric device, and a carbon-based material, which can have excellent kinetic performance and first coulomb efficiency.

[0006] To achieve the above-mentioned purpose, the present disclosure provides a sodium-ion battery, comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a carbon-based material, the carbon-based material comprising graphene sheets with an interlayer spacing greater than 0.4 nm, the volume of space between the graphene sheets with an interlayer spacing greater than 0.4 nm being H1, and the total volume of space between the layers in the graphene sheets being H 总 satisfying: 40%≤H1 / H 总 ≤60%.

[0007] In the present disclosure, by making the proportion of the volume of space between the graphene sheets with an interlayer spacing greater than 0.4 nm in the carbon-based material within the above-mentioned specific range, the sodium-ion battery can have excellent kinetic performance and first coulomb efficiency.

[0008] In some embodiments, 40%≤H1 / H 总 ≤55%.

[0009] By making the space volume H1 between graphene layers with an interlayer spacing of greater than 0.4 nm and the total space volume H 总 Within the above range, it is more helpful to have excellent kinetic performance and the first coulombic efficiency.

[0010] In some embodiments, the space volume H2 between graphene layers with an interlayer spacing of 0.36 nm to 0.4 nm and the total space volume H 总 Satisfies: 22%≤H2 / H 总 ≤60%.

[0011] In some embodiments, 29%≤H2 / H 总 ≤42%.

[0012] In the present disclosure, by making the space volume H2 between graphene layers with an interlayer spacing of 0.36 nm to 0.4 nm and the total space volume H 总 Within the above range, it is possible to improve the capacity of the sodium ion battery while improving the kinetics of the sodium ion battery.

[0013] In some embodiments, the space volume H3 between graphene layers with an interlayer spacing of less than 0.36 nm and the total space volume H 总 Satisfies: H3 / H 总 ≤18%.

[0014] By making the space volume H3 between graphene layers with an interlayer spacing of less than 0.36 nm and the total space volume H 总 Within the above range, it is possible to reduce the risk of sodium precipitation, improve the capacity of the cathode, and improve the energy density of the sodium ion battery.

[0015] In some embodiments, the carbon-based material further includes micropores with a pore size of less than or equal to 2 nm and mesopores with a pore size of greater than 2 nm and less than 10 nm; the pore volume V1 of the micropores and the pore volume V2 of the mesopores satisfy: 0.5≤V 1 / V2≤9.7.

[0016] By setting the pore volume V1 of the micropores and the pore volume V2 of the mesopores to satisfy the above relationship, it is helpful to make the sodium ion battery have excellent capacity and kinetic performance.

[0017] In some embodiments, the carbon-based material comprises pores having a pore size in the range of 1.0 nm-1.5 nm, and a maximum value of the derivative dV / d(logD) of the cumulative pore volume V versus the logarithm of the pore size D, as determined by nitrogen adsorption method, is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)). The carbon-based material provided by the present disclosure has an optimized pore structure, in particular, the feature dV / d(logD) of the pores having a pore size of 1.0 nm-1.5 nm of the carbon-based material, corresponding to the pore volume value contributed by the unit pore size, has a maximum value in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)), which is more conducive to reducing the gas production bubbling phenomenon in the pulping process.

[0018] In some embodiments, the carbon-based material has a maximum value of dV / d(logD) of the pores having a pore size of 1.0 nm-1.5 nm in the range of 0.001 cm 3 / (g·log(nm))-0.006 cm 3 / (g·log(nm)), which is more conducive to reducing the gas production bubbling phenomenon in the pulping process.

[0019] In some embodiments, the carbon-based material has a pore volume of the pores having a pore size less than 1 nm, as determined by carbon dioxide adsorption method, represented as V a , and a pore volume of the pores having a pore size of 1 nm-2 nm, as determined by nitrogen adsorption method, represented as V b , then V a +V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g. The pore volume of the pores having a pore size of 2 nm or less of the carbon-based material in the above range is more conducive to reducing the gas production bubbling phenomenon in the pulping process while maintaining the gram capacity.

[0020] In some embodiments, the carbon-based material has V a +V b in the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

[0021] In some embodiments, the pore volume V1 of the micropores having a pore size less than or equal to 2 nm and the total pore volume V 总 of the carbon-based material satisfy: 4.5%≤V1 / V 总≤ 30%. The ratio of the pore volume of the micropores in the total pore volume is in the above range, which is conducive to improving the capacity of the sodium ion battery.

[0022] In some embodiments, the pore volume V2 of the mesopores with a pore size greater than 2 nm and less than 10 nm and the total pore volume V of the carbon-based material satisfy: 0.0003 cm3 / g ≤ V2 ≤ 0.0012 cm3 / g. 总 satisfy: 2.5% ≤ V2 / V 总 ≤ 10%. The ratio of the pore volume of the mesopores in the total pore volume is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery.

[0023] In some embodiments, the carbon-based material has a surface oxygen element content of 5% to 15%. 3 / g ≤ V2 ≤ 0.0012 cm 3 / g. The pore volume of the mesopores is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery.

[0024] In some embodiments, the carbon-based material includes heteroatoms, and the heteroatoms account for 0.4 wt% to 5 wt% of the total mass of the carbon-based material. In some embodiments, the heteroatoms include at least one of O, N, S, P, B, and F. The presence of the heteroatoms can expand the interlayer spacing of the graphene layers in the carbon-based material, so that the spacing between the graphene layers in the carbon-based material is greater than 0.4 nm, which is conducive to the kinetics of the sodium ion battery. In addition, the mass ratio of the heteroatoms in the carbon-based material is in the above range, which can make the ratio of the graphene layers with an interlayer spacing greater than 0.4 nm in the total graphene layers in the carbon-based material be in the above range, so as to balance the kinetic performance and the first coulomb efficiency of the sodium ion battery.

[0025] In some embodiments, the I D / I G of the carbon-based material is 1.1 to 1.35; wherein I D represents the D peak intensity of the Raman spectrum at 1350±50 cm -1 -1, and I G represents the G peak intensity of the Raman spectrum at 1580±50 cm -1 -1. By making the I D / I G of the carbon-based material be in the above range, the order degree of the surface carbon of the carbon-based material is high, and the surface defects are few, which is conducive to improving the first coulomb efficiency of the battery and also conducive to improving the compaction density.

[0026] In some embodiments, the surface oxygen element content of the carbon-based material is 5% to 15%.

[0027] The surface oxygen element content of the carbon-based material is in the above range, which can make the viscosity of the slurry containing the carbon-based material be in a suitable range, and is conducive to improving the processing performance of the sodium ion battery.

[0028] In some embodiments, the powder compaction density of the carbon-based material at 2t is 0.9 g / cm³. 3 -1.2g / cm 3 When the compaction density of carbon-based material powder is within the above range, it is beneficial to increase the cold-pressed density of the negative electrode sheet, which in turn is beneficial to increase the volumetric energy density of sodium-ion batteries.

[0029] In some embodiments, the carbon-based material satisfies at least one of the following:

[0030] (1) The specific surface area of ​​the carbon-based material is 2m². 2 / g-8m 2 / g; The specific surface area of ​​carbon-based materials is within the above range, which is beneficial to improving the initial coulombic efficiency of sodium-ion batteries.

[0031] (2) The tap density of the carbon-based material is 0.78 g / cm³. 3 -0.9g / cm 3 When the tap density of carbon-based materials is within the above range, it is beneficial to increase the compaction density of the negative electrode film and improve the energy density of sodium-ion batteries.

[0032] (3) The true density of the carbon-based material is 2.0 g / cm³. 3 -2.3g / cm 3 When the true density of carbon-based materials is within the above range, it is beneficial to improve the capacity of sodium-ion batteries.

[0033] (4) The volume distribution particle size Dv10 of the carbon-based material is 1.8 μm-3 μm;

[0034] (5) The volume distribution particle size Dv50 of the carbon-based material is 4μm-7μm;

[0035] (6) The volume distribution particle size Dv90 of the carbon-based material is 9μm-15μm.

[0036] When the particle size distribution of carbon-based materials falls within the aforementioned range (Dv10, Dv50, Dv90), it is beneficial to reduce the specific surface area of ​​the carbon-based materials, thereby reducing the occurrence of side reactions and improving the initial coulombic efficiency of sodium-ion batteries. Simultaneously, it can also shorten the bulk transport path of active ions, further enhancing the kinetic performance of sodium-ion batteries.

[0037] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from soft carbon materials and graphite.

[0038] In some embodiments, the sodium-ion battery further comprises a positive electrode tab, the positive electrode tab comprising a positive electrode current collector and a positive electrode film layer on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising at least one of a sodium-containing transition metal oxide, a polyanion sodium-ion compound, and a Prussian blue sodium-ion compound.

[0039] The present disclosure also provides a method for preparing a sodium-ion battery, wherein the method comprises a step of preparing a negative electrode tab, the step comprising: step (1), mixing a negative electrode component and a solvent to obtain a negative electrode slurry, the negative electrode component comprising a carbon-based material, the carbon-based material comprising graphene sheets, the volume of space H1 between graphene sheets with an interlayer spacing of greater than 0.4 nm and the total volume of space H 总 satisfying: 40%≤H1 / H 总 ≤60%; and step (2), coating the negative electrode slurry on a negative electrode current collector. By adding the above-mentioned carbon-based material when preparing the negative electrode slurry, the van der Waals force between active material particles can be reduced, so that the active material is more easily dispersed; meanwhile, the hard carbon satisfying the above-mentioned condition forms a more uniform pore structure during compaction, which is beneficial to compaction. The battery prepared by the preparation method of the present disclosure has excellent kinetic performance and first coulomb efficiency.

[0040] In some embodiments, 40%≤H1 / H 总 ≤55%.

[0041] In some embodiments, the volume of space H2 between graphene sheets with an interlayer spacing of 0.36 nm to 0.4 nm and the total volume of space H 总 satisfies: 22%≤H2 / H 总 ≤60%.

[0042] In some embodiments, 29%≤H2 / H 总 ≤42%.

[0043] In some embodiments, the volume of space H3 between graphene sheets with an interlayer spacing of less than 0.36 nm and the total volume of space H 总 satisfies: H3 / H 总 ≤18%.

[0044] In some embodiments, the carbon-based material further comprises micropores with a pore size of less than or equal to 2 nm and mesopores with a pore size of greater than 2 nm and less than 10 nm; the pore volume V1 of the micropores and the pore volume V2 of the mesopores satisfy: 0.5≤V1 / V2≤9.7.

[0045] In some embodiments, the carbon-based material comprises pores having a pore size in the range of 1.0 nm-1.5 nm, and a maximum value of the derivative dV / d(logD) of the cumulative pore volume V versus the logarithm of the pore size D is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)).

[0046] In some embodiments, the carbon-based material comprises pores having a pore size in the range of 1.0 nm-1.5 nm, and a maximum value of the derivative dV / d(logD) of the cumulative pore volume V versus the logarithm of the pore size D is in the range of 0.001 cm 3 / (g·log(nm))-0.006 cm 3 / (g·log(nm)).

[0047] In some embodiments, the carbon-based material comprises pores having a pore size in the range of 1.0 nm-1.5 nm, and a maximum value of the derivative dV / d(logD) of the cumulative pore volume V versus the logarithm of the pore size D is in the range of 0.001 cm a , and a maximum value of the derivative dV / d(logD) of the cumulative pore volume V versus the logarithm of the pore size D is in the range of 0.001 cm b , then V a +V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

[0048] In some embodiments, the carbon-based material comprises pores having a pore size in the range of 1.0 nm-1.5 nm, and a maximum value of the derivative dV / d(logD) of the cumulative pore volume V versus the logarithm of the pore size D is in the range of 0.001 cm a +V b is in the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

[0049] In some embodiments, the mass percentage of the carbon-based material with respect to the mass of the negative electrode slurry is in the range of 85%-98%. Thereby, it is beneficial for the formation of a good conductive network and stable structure of the electrode sheet.

[0050] In some embodiments, the mass percentage of the carbon-based material with respect to the mass of the negative electrode slurry is in the range of 85%-98%. Thereby, it is beneficial for the formation of a good conductive network and stable structure of the electrode sheet.

[0051] In some embodiments, the negative electrode component further comprises one or more of a conductive agent, a binder, and a thickening agent. The conductive agent can effectively accelerate the electron transmission rate, and improve the charge-discharge efficiency of the battery. The binder is conducive to maintaining the integrity of the electrode structure during the charge-discharge process of the battery. The thickening agent can increase the viscosity of the slurry, ensure uniform dispersion of the negative electrode component particles and stable suspension, and prevent sedimentation, thereby facilitating the uniformity and stability of the subsequent coating process.

[0052] In some embodiments, the mass percentage of the conductive agent in the negative electrode component is 0.3%-3% relative to the mass of the negative electrode component. In this way, a continuous conductive network can be formed between the hard carbon particles, thereby reducing the internal resistance of the battery.

[0053] The present disclosure also provides an electric device comprising the above-mentioned sodium-ion battery of the present disclosure, or a sodium-ion battery obtained by the sodium-ion battery preparation method of the present disclosure. The electric device of the present disclosure comprises the sodium-ion battery of the present disclosure, and thus at least has the same advantages as the sodium-ion battery.

[0054] The present disclosure also provides a carbon-based material comprising graphene layers, wherein the volume of the space between graphene layers with an interlayer spacing greater than 0.4 nm H1 and the total volume of the space between layers in the graphene layers H 总 satisfies: 40%≤H1 / H 总 ≤60%.

[0055] In the present disclosure, by making the proportion of the volume of the space between graphene layers with an interlayer spacing greater than 0.4 nm in the carbon-based material within the above-mentioned specific range, the sodium-ion battery can have excellent kinetic performance and first coulomb efficiency.

[0056] In some embodiments, 40%≤H1 / H 总 ≤55%.

[0057] By making the volume of the space between graphene layers with an interlayer spacing greater than 0.4 nm H1 and the total volume of the space between layers in the graphene layers H 总 within the above-mentioned range, it is more conducive to having excellent kinetic performance and first coulomb efficiency.

[0058] In some embodiments, the volume of the space between graphene layers with an interlayer spacing of 0.36 nm-0.4 nm H2 and the total volume of the space between layers in the graphene layers H 总 satisfies: 22%≤H2 / H 总 ≤60%.

[0059] In some embodiments, 29%≤H2 / H 总 ≤42%.

[0060] In the present disclosure, by making the space volume H2 between graphene sheet layers with an interlayer spacing of 0.36-0.4 nm and the total space volume H 总 Within the above range, the capacity of the sodium ion battery can be improved while improving the kinetics of the sodium ion battery.

[0061] In some embodiments, the space volume H3 between graphene sheet layers with an interlayer spacing of less than 0.36 nm and the total space volume H 总 satisfies: H3 / H 总 ≤18%.

[0062] By making the space volume H3 between graphene sheet layers with an interlayer spacing of less than 0.36 nm and the total space volume H 总 Within the above range, the risk of sodium precipitation can be reduced, the cathode capacity can be improved, and the energy density of the sodium ion battery can be improved.

[0063] In some embodiments, the carbon-based material further comprises micropores with a pore size of less than or equal to 2 nm and mesopores with a pore size of greater than 2 nm and less than 10 nm; the pore volume V1 of the micropores and the pore volume V2 of the mesopores satisfy: 0.5≤V 1 / V2≤9.7.

[0064] By setting the pore volume V1 of the micropores and the pore volume V2 of the mesopores to satisfy the above relationship, the sodium ion battery can have excellent capacity and kinetic performance.

[0065] In some embodiments, the carbon-based material comprises pores with a pore size in the range of 1.0-1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V with respect to the logarithm of the pore size D is in the range of 0.001 cm 3 / (g·log(nm))0.009cm 3 / (g·log(nm)) measured by nitrogen adsorption method. The carbon-based material provided by the present disclosure has an optimized pore structure. Specifically, the feature dV / d(logD) of the pores with a pore size of 1.0-1.5 nm of the carbon-based material, which corresponds to the pore volume value contributed by the unit pore size, has a maximum value in the range of 0.001 cm 3 / (g·log(nm))-0.009cm 3 / (g·log(nm)), which is beneficial to reduce the gas bubble phenomenon during the pulping process.

[0066] In some embodiments, the maximum value of dV / d(logD) of the pores with a pore size of 1.0-1.5 nm of the carbon-based material is in the range of 0.001 cm 3(g·log(nm)) - 0.006 cm 3 / g 3 (g·log(nm)) - 0.006 cm 3 / g, which is more conducive to reducing the gas bubble phenomenon in the pulping process.

[0067] In some embodiments, the pore volume of the pores with a pore size less than 1 nm of the carbon-based material is represented as V a , the pore volume of the pores with a pore size of 1 nm-2 nm of the carbon-based material is represented as V b , and V a + V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g. The pore volume of the pores with a pore size less than 2 nm of the carbon-based material is in the above range, which is more conducive to reducing the gas bubble phenomenon in the pulping process while maintaining the gram capacity. 3 3 / g. The pore volume of the pores with a pore size less than 2 nm of the carbon-based material is in the above range, which is more conducive to reducing the gas bubble phenomenon in the pulping process while maintaining the gram capacity.

[0068] In some embodiments, V a + V b is in the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g. 3 3 / g.

[0069] In some embodiments, the pore volume V1 of the micropores with a pore size less than or equal to 2 nm and the total pore volume V 总 of the carbon-based material satisfy: 4.5%≤V1 / V 总 ≤30%. The proportion of the pore volume of the micropores in the total pore volume is in the above range, which is conducive to improving the capacity of the sodium ion battery.

[0070] In some embodiments, the pore volume V2 of the mesopores with a pore size greater than 2 nm and less than 10 nm and the total pore volume V 总 of the carbon-based material satisfy: 2.5%≤V2 / V 总 ≤10%. The proportion of the pore volume of the mesopores in the total pore volume is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery.

[0071] In some embodiments, 0.0003 cm 3 / g≤V2≤0.0012 cm 3 / g. The pore volume of the mesopores is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery. 3 3 / g. The pore volume of the mesopores is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery.

[0072] ​​​In some embodiments, the carbon-based material includes heteroatoms, and the heteroatoms account for 0.4wt%-5wt% of the total mass of the carbon-based material. In some embodiments, the heteroatoms include at least one of O, N, S, P, B, and F. The presence of the heteroatoms can expand the interlayer spacing of the graphene layers in the carbon-based material, so that the spacing between the graphene layers in the carbon-based material is greater than 0.4nm, which is beneficial to the kinetics of the sodium-ion battery. In addition, the mass ratio of the heteroatoms in the carbon-based material is within the above range, which can make the proportion of the graphene layers with an interlayer spacing greater than 0.4nm in the total graphene layers in the carbon-based material within the above range, so as to balance the kinetic performance and the first coulombic efficiency of the sodium-ion battery.

[0073] In some embodiments, the I D / I G of the carbon-based material is 1.1-1.35; wherein I D represents the D-peak intensity of the Raman spectrum at 1350±50cm -1 -1; and I G represents the G-peak intensity of the Raman spectrum at 1580±50cm -1 -1. By making the I D / I G of the carbon-based material within the above range, the order degree of the surface carbon of the carbon-based material is high, and the surface defects are few, which is beneficial to improving the first coulombic efficiency of the battery and is also beneficial to improving the compaction density.

[0074] In some embodiments, the content of the surface oxygen elements of the carbon-based material is 5%-15%.

[0075] When the content of the surface oxygen elements of the carbon-based material is within the above range, the viscosity of the slurry containing the carbon-based material can be within a suitable range, which is beneficial to improving the processing performance of the sodium-ion battery.

[0076] In some embodiments, the powder compaction density of the carbon-based material at 2t is 0.9g / cm 3 -1.2g / cm 3 . When the powder compaction density of the carbon-based material is within the above range, the cold-pressing density of the negative electrode sheet can be improved, and in turn the volume energy density of the sodium-ion battery can be improved.

[0077] In some embodiments, the carbon-based material satisfies at least one of the following conditions:

[0078] (1) the specific surface area of the carbon-based material is 2m 2 / g-8m 2 / g; when the specific surface area of the carbon-based material is within the above range, the first coulombic efficiency of the sodium-ion battery can be improved.

[0079] (2) the tap density of the carbon-based material is 0.78 g / cm3 3 -0.9 g / cm3 3 When the tap density of the carbon-based material is within the above range, it is beneficial to improve the compaction density of the negative electrode film layer and improve the energy density of the sodium ion battery.

[0080] (3) the true density of the carbon-based material is 2.0 g / cm3 3 -2.3 g / cm3 3 When the true density of the carbon-based material is within the above range, it is beneficial to improve the capacity of the sodium ion battery.

[0081] (4) the volume distribution particle size Dv10 of the carbon-based material is 1.8 μm-3 μm;

[0082] (5) the volume distribution particle size Dv50 of the carbon-based material is 4 μm-7 μm;

[0083] (6) the volume distribution particle size Dv90 of the carbon-based material is 9 μm-15 μm.

[0084] When the volume distribution particle sizes Dv10, Dv50 and Dv90 of the particles of the carbon-based material are within the above ranges, it is beneficial to reduce the specific surface area of the carbon-based material, reduce the occurrence of side reactions, and thus improve the initial coulombic efficiency of the sodium ion battery. At the same time, the bulk transport path of active ions can be shortened, and thus the kinetic performance of the sodium ion battery is improved.

[0085] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite. BRIEF DESCRIPTION OF DRAWINGS

[0086] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present disclosure;

[0087] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to an embodiment of the present disclosure;

[0088] FIG. 3 is a schematic view of a battery module according to an embodiment of the present disclosure;

[0089] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present disclosure;

[0090] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present disclosure;

[0091] FIG. 6 is a schematic view of an electric device using a sodium ion battery as a power source according to an embodiment of the present disclosure;

[0092] FIG. 7 is an X-ray diffraction spectrum of a hard carbon material according to Example 1 of the present disclosure;

[0093] FIG. 8 is a graph of the lithium intercalation capacity of the hard carbon material of Example 1 and Comparative Example 1 of the present disclosure as a negative active material for sodium ion batteries;

[0094] FIG. 9 is a partial enlarged view of FIG. 8;

[0095] FIG. 10 is a graph of the pore size distribution of the hard carbon material prepared in Example 11 of the present disclosure, as measured by nitrogen adsorption;

[0096] FIG. 11 is a graph of the pore size distribution of the hard carbon material prepared in Example 12 of the present disclosure, as measured by nitrogen adsorption.

[0097] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0098] Hereinafter, embodiments of the sodium ion battery, the method of manufacturing a sodium ion battery, the power using device, and the carbon-based material of the present disclosure are specifically disclosed with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known in the art, repetitive descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0099] The "ranges" disclosed in the present disclosure are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present disclosure, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing any real combination of numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand manner of describing these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0100] If there is no special indication, all the embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0101] If there is no special indication, all the technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions.

[0102] If there is no special indication, all the steps of the present disclosure can be performed in sequence or randomly, and the preferred is performed in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0103] If there is no special indication, the terms used in the present disclosure have the commonly understood meanings understood by those skilled in the art.

[0104] If there is no special indication, the values of the parameters mentioned in the present disclosure can be measured by various test methods commonly used in the art, for example, can be measured according to the test method given in the present disclosure.

[0105] If there is no special indication, in the present disclosure, the term "active ion" refers to an ion that can be reversibly inserted and extracted between the positive and negative electrodes of a secondary battery, including but not limited to sodium ion.

[0106] In the present disclosure, the term "spatial volume" refers to the size of the space formed between adjacent graphene layers.

[0107] At present, due to the advantages of sodium in resources and cost, sodium ion battery has become an important development direction of energy storage battery. Hard carbon material has large interlayer spacing, rich pore structure and good electronic conductivity, and the structure is relatively stable during the deintercalation process of sodium ion, which is the most promising sodium storage negative electrode material at present. However, the current hard carbon as negative active material cannot balance the kinetic performance and the first coulomb efficiency.

[0108] Therefore, the present disclosure provides a sodium ion battery, a preparation method of a sodium ion battery, an electric device, and a carbon-based material, which can balance the kinetic performance and the first coulomb efficiency at the same time.

[0109] Sodium ion battery

[0110] The present disclosure provides a sodium ion battery, wherein a negative electrode sheet is included, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a carbon-based material, the carbon-based material includes graphene layers with different layer spacings, and the space volume H1 between graphene layers with a layer spacing greater than 0.4 nm is greater than 40% of the total space volume H between layers in the graphene layers 总 and satisfies: 40%≤H1 / H 总 ≤60%.

[0111] The carbon-based material is widely used in sodium ion battery negative electrode active materials due to its advantages of abundant reserves, low cost, diverse structure, fast ion diffusion, good cycle stability and environmental friendliness. When the carbon-based material, especially hard carbon material, is used as a sodium ion battery negative electrode active material, its capacity includes a slope section capacity and a platform section capacity, wherein the voltage of the slope section capacity is >0.1V, and the voltage of the platform section capacity is 0V-0.1V. Research has found that when the platform section capacity ratio is large, the longer the time of sodium storage at low voltage during fast charging, the more likely sodium precipitation occurs. Therefore, by increasing the proportion of the slope section capacity, the risk of sodium precipitation can be reduced, and the kinetic performance of the hard carbon material can be improved. However, too high a slope section capacity will affect the initial coulombic efficiency, because active ions are adsorbed on the surface of large layer spacing microcrystals or amorphous carbon during energy storage in the slope section, but large layer spacing microcrystals also have a large number of defects, dangling bonds and the like, which are easy to form stable chemical bonds with active ions, so that active ions cannot be reversibly removed, thereby affecting the initial coulombic efficiency. Therefore, the proportion of the slope section capacity of the material should be within an appropriate range to balance the kinetic performance and the initial coulombic efficiency of the secondary battery.

[0112] The carbon-based material includes stacked graphene layers, and the graphene layers have different layer spacings. The size of the space between adjacent graphene layers affects the deintercalation of sodium ions. For convenience of description, we define H1 as the size of the space between graphene layers with a layer spacing greater than 0.4 nm between adjacent graphene layers, H2 as the size of the space between graphene layers with a layer spacing of 0.36 nm-0.4 nm between adjacent graphene layers, H3 as the size of the space between graphene layers with a layer spacing less than 0.36 nm between adjacent graphene layers, and H 总 is the total space volume between layers in the graphene layers in the carbon-based material, specifically the sum of the space volumes between graphene layers with different layer spacings, i.e. 总 H = H1+H2+H3.

[0113] The inventors found that the graphene layers with an interlayer spacing greater than 0.4 nm can make it easier for active ions to be embedded due to the large space volume between the layers, and can store sodium through the "adsorption" mechanism, so as to obtain a higher capacity in the slope section above 0.1 V. Therefore, the ratio of H1 / H 总 to some extent reflects the proportion of the capacity in the slope section of the material. However, the space volume between the graphene layers with an interlayer spacing greater than 0.4 nm is too large, which leads to a too high capacity in the slope section, thereby affecting the initial coulombic efficiency of the sodium ion battery.

[0114] In view of this, in the present disclosure, by making the ratio of H1 / H 总 in the above specific range, the proportion of the capacity in the slope section is in an appropriate range, which on the one hand enables the active ions to be adsorbed on the surface of the graphene layers to store energy, and on the other hand can also control the number of defects, thereby balancing the kinetic performance and the initial coulombic efficiency of the sodium ion battery.

[0115] For H1 / H 总 , it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or a value between any two of the above values.

[0116] In some embodiments, 40%≤H1 / H 总 ≤55%.

[0117] The space volume H1 between the graphene layers with an interlayer spacing greater than 0.4 nm and the total space volume H 总 In the above range, the proportion of the part with an interlayer spacing greater than 0.4 nm in the carbon-based material is in a more appropriate range, i.e., the proportion of the capacity in the slope section is in a more appropriate range, which is more helpful to balance the kinetic performance and the initial coulombic efficiency of the sodium ion battery.

[0118] In some embodiments, the space volume H2 between the graphene layers with an interlayer spacing of 0.36 nm to 0.4 nm and the total space volume H 总 satisfies: 22%≤H2 / H 总 ≤60%. For example, H2 / H 总 is 22%, 25%, 27%, 29%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, 55%, 60%, or a value between any two of the above values. In some embodiments, 22%≤H2 / H 总 ≤50%, preferably 25%≤H2 / H 总≤45%, more preferably 29%≤H2 / H 总 ≤42%.

[0119] The graphene sheet layers with an interlayer spacing of 0.36-0.4 nm mainly store sodium through an interlayer embedding mechanism, thereby exhibiting high capacity of the low-voltage platform (i.e., obtaining the platform capacity). However, the proportion of the graphene sheet layers with an interlayer spacing of 0.36-0.4 nm is too large, which easily causes sodium precipitation, affects the reversible capacity of the sodium ion battery, and further affects the initial coulombic efficiency of the sodium ion battery.

[0120] In the present disclosure, the space volume H2 between the graphene sheet layers with an interlayer spacing of 0.36-0.4 nm and the total space volume H1 between the layers in the graphene sheet layers are set to satisfy the following relationship: 总 Within the above range, the proportion of the graphene sheet layers with an interlayer spacing of 0.36-0.4 nm in the carbon-based material is within an appropriate range, which can improve the kinetic performance of the sodium ion battery while improving the capacity of the sodium ion battery.

[0121] In some embodiments, the space volume H3 between the graphene sheet layers with an interlayer spacing less than 0.36 nm and the total space volume H1 between the layers in the graphene sheet layers are set to satisfy the following relationship: 总 H3 / H 总 ≤18%. For example, H3 / H 总 is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or a value between any two of the above values.

[0122] The graphene sheet layers with an interlayer spacing less than 0.36 nm are difficult to store sodium due to the small layer space, but this part of the graphene sheet layers can provide sliding, which is beneficial to improve the compaction density of the negative electrode sheet. In the present disclosure, the space volume H3 between the graphene sheet layers with an interlayer spacing less than 0.36 nm and the total space volume H1 between the layers in the graphene sheet layers are set to satisfy the following relationship: 总 Within the above range, the proportion of the graphene sheet layers with an interlayer spacing less than 0.36 nm in the carbon-based material is within an appropriate range, which can reduce the risk of sodium precipitation, improve the capacity of the cathode, and is beneficial to the energy density of the sodium ion battery.

[0123] In the present disclosure, the above H1 / H 总 , H2 / H 总 , and H3 / H 总 may be obtained by peak fitting of the XRD spectrum of the carbon-based material.

[0124] Specifically, the XRD diffraction spectrum of the carbon-based material is first tested by the following method: the XRD diffraction spectrum of the carbon-based material can be tested by using an X-ray diffractometer according to JIS K 0131-1996. The test conditions are as follows: the carbon-based material and silicon powder are uniformly mixed at a mass ratio of 5:1, a flat plate is used for sample preparation, CuKα ray is used as the radiation source, a copper target is used as the anode target, the wavelength λ of the copper target is , the scanning 2θ angle range is 10°-40°, and the scanning rate is 1° / min. The test instrument can be a Bruker D8 Discover X-ray diffractometer.

[0125] Next, the XRD diffraction spectrum of the carbon-based material is fitted by using XPS peak software. The XRD spectrum of the carbon-based material is fitted into three small peaks, namely a first fitting peak A, a second fitting peak B, and a third fitting peak C, and the fitting standard is as follows: the 2θ angle of the first fitting peak A is less than 22.2°, the 2θ angle of the second fitting peak B is 22.2°-24.7°, and the 2θ angle of the third fitting peak C is greater than 24.7°.

[0126] The interlayer spacing and the 2θ angle satisfy the Bragg formula: 2dsinθ=kλ, where d is the interlayer spacing of the (002) crystal plane of the carbon-based material, θ is the diffraction angle, k is the reflection order, and λ is the wavelength of the copper target. In the present disclosure, k is 1, and λ is According to the Bragg formula, it can be determined that the 2θ angle corresponding to the graphene sheet layer with an interlayer spacing greater than 0.4 nm is less than 22.2°, the 2θ angle corresponding to the graphene sheet layer with an interlayer spacing of 0.36 nm-0.4 nm is 22.2°-24.7°, and the 2θ angle corresponding to the graphene sheet layer with an interlayer spacing less than 0.36 nm is greater than 24.7°.

[0127] Finally, the ratio of the area of the first fitting peak to the total area of the three fitting peaks is equal to the ratio (H1 / H 总 ) of the space volume H1 between the graphene sheet layers with an interlayer spacing greater than 0.4 nm to the total space volume H 总 between the layers in the graphene sheet layers; the ratio of the area of the second fitting peak to the total area of the three fitting peaks is equal to the ratio (H2 / H 总 ) of the space volume H2 between the graphene sheet layers with an interlayer spacing of 0.36 nm-0.4 nm to the total space volume H 总 between the layers in the graphene sheet layers; and the ratio of the area of the third fitting peak to the total area of the three fitting peaks is equal to the ratio (H3 / H 总 ) of the space volume H3 between the graphene sheet layers with an interlayer spacing less than 0.36 nm to the total space volume H 总 between the layers in the graphene sheet layers.

[0128] Exemplarily, H1 / H 总 , H2 / H总 and H3 / H 总 The area of the graphene sheet can be calculated as 15.24 mm 2 H1 / H 总 = 15.24 mm 2 * the sum of interlayer distances greater than 0.4 nm in the carbon-based material / 15.24 mm 2 * the sum of interlayer distances in the carbon-based material = 15.24 mm 2 * the area of the first fitted peak / 15.24 mm 2 *(the first fitted peak area + the second fitted peak area + the third fitted peak area) = the area of the first fitted peak / (the first fitted peak area + the second fitted peak area + the third fitted peak area) = the area of the first fitted peak / the total area of the three fitted peaks. H2 / H 总 = 15.24 mm 2 * the sum of interlayer distances from 0.36 nm to 0.4 nm in the carbon-based material / 15.24 mm 2 * the sum of interlayer distances in the carbon-based material = 15.24 mm 2 * the area of the second fitted peak / 15.24 mm 2 *(the first fitted peak area + the second fitted peak area + the third fitted peak area) = the area of the second fitted peak / (the first fitted peak area + the second fitted peak area + the third fitted peak area) = the area of the second fitted peak / the total area of the three fitted peaks. H3 / H 总 = 15.24 mm 2 * the sum of interlayer distances less than 0.36 nm in the carbon-based material / 15.24 mm 2 * the sum of interlayer distances in the carbon-based material = 15.24 mm 2 * the area of the third fitted peak / 15.24 mm 2 *(the first fitted peak area + the second fitted peak area + the third fitted peak area) = the area of the third fitted peak / (the first fitted peak area + the second fitted peak area + the third fitted peak area) = the area of the third fitted peak / the total area of the three fitted peaks.

[0129] In some embodiments, the carbon-based material further comprises micropores less than or equal to 2 nm and mesopores having a pore size greater than 2 nm and less than 10 nm; the micropore volume V1 and the mesopore volume V2 satisfy: 0.5 ≤ V 1 / V2≤ 9.7.

[0130] The micropores with a pore size less than or equal to 2 nm in the carbon-based material can achieve sodium storage, but sodium ions are not easy to be removed due to the small pore size. The mesopores with a pore size greater than 2 nm and less than 10 nm in the carbon-based material can make active ions be more easily adsorbed and removed due to the large pore size, which is beneficial to the kinetics of the sodium ion battery. In the present disclosure, the pore volume V1 of the micropores and the pore volume V2 of the mesopores satisfy the above relationship, which is beneficial to the capacity and kinetics performance of the sodium ion battery.

[0131] In some embodiments, the micropores comprise pores with a pore size in the range of 1.0 nm-1.5 nm, and a maximum value of a derivative dV / d(logD) of a cumulative pore volume V with respect to a logarithm of a pore size D is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)) by nitrogen adsorption method.

[0132] The present disclosure proposes that the pores with a pore size of 1.0 nm-1.5 nm have a significant impact on the sustained gas bubble generation. By regulating the pores with this specific pore size, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V with respect to the logarithm of the pore size D is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)), the sustained bubble generation can be significantly reduced. Research has found that the pores with a larger pore size (pores with a pore size greater than 1.5 nm) have less impact on processability, presumably because the bubble duration caused by this part of the pores is short; the pores with a smaller pore size (pores with a pore size less than 1.0 nm) may have limited impact on processability due to small gas storage capacity; and by limiting the volume contribution rate of the pores with a pore size of 1.0 nm-1.5 nm, i.e., the maximum value of dV / d(logD) is controlled within the above range, the gas bubble generation phenomenon during pulping can be effectively reduced, while the sodium storage effect of this pore size is taken into account.

[0133] Exemplarily, the maximum value of dV / d(logD) of the pores with a pore size of 1.0 nm-1.5 nm is 0.001 cm 3 / (g·log(nm)), 0.002 cm 3 / (g·log(nm)), 0.003 cm 3 / (g·log(nm)), 0.004 cm 3 / (g·log(nm)), 0.005 cm 3 / (g·log(nm)), 0.006 cm 3 / (g·log(nm)), 0.007 cm 3 / (g·log(nm)), 0.008 cm3 / (g·log(nm)), 0.009cm 3 / (g·log(nm)) can be any value within a range consisting of any two of these values.

[0134] The dV / d(logD) mentioned in this disclosure reflects the pore volume contributed per unit pore size. This value can be obtained by measuring carbon-based materials using conventional methods in the art. For example, it can be determined using a surface area analyzer-static volumetric method. Specifically, according to embodiments of this disclosure, a flow-type gas adsorption surface area measuring device (device model Micromeritics ASAP-2460) can be used to measure the adsorption and desorption isotherms of nitrogen adsorption, and a DFT model can be used to fit the distribution curve of dV / d(logD) relative to the pore size D, reading the maximum value in the pore size range of 1.0-1.5 nm. The carbon-based material can be a carbon-based material used as a raw material, or it can be a carbon-based material obtained from the disassembly and separation of sodium-ion batteries.

[0135] In some embodiments, the carbon-based material has a pore size of 1.0 nm to 1.5 nm, and the maximum value of dV / d(logD) is 0.001 cm⁻¹. 3 / (g·log(nm))-0.006cm 3 / (g·log(nm)), which is more conducive to reducing gas generation and bubbling during the pulping process.

[0136] In some embodiments, the carbon-based material has pores with a diameter of 1.0 nm to 1.5 nm and a pore volume of 0.0003 cm³. 3 / g-0.0017cm 3 / g. This is more conducive to reducing gas generation during pulping while also considering specific volume. For example, the pore volume of pores with a pore size of 1.0nm-1.5nm is 0.0003cm³. 3 / g, 0.0005cm 3 / g, 0.0007cm 3 / g, 0.0009cm 3 / g, 0.0011cm 3 / g, 0.0013cm 3 / g, 0.0015cm 3 / g, 0.0017cm 3 / g or a value within a range of any two of these values. Optionally, the total pore volume of pores with a diameter of 1.0 nm to 1.5 nm is 0.0009 cm³. 3 / g-0.0014cm 3 / g.

[0137] The pore volume of the pores with a pore size of 1.0 nm-1.5 nm of the carbon-based material is also obtained by determining the carbon-based material by a conventional determination method in the art, for example, a N2sorption-desorption pore volume pore size test method. Illustratively, the N2sorption method can be referred to GB / T 19587-2017, the adsorption and desorption isotherms are tested, the DFT model is used to fit the distribution curve of the cumulative pore volume versus the pore size, and the pore volume of the pores with a specific pore size range of 1.0 nm-1.5 nm is obtained.

[0138] In some embodiments, the pore volume of the pores with a pore size of less than 1 nm of the carbon-based material is determined by a carbon dioxide adsorption method and is represented as V a The pore volume of the pores with a pore size of 1 nm-2 nm of the carbon-based material is determined by a nitrogen adsorption method and is represented as V b Then V a +V b (i.e., V1) is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

[0139] Further research found that when preparing the negative electrode slurry, the pores with a pore size of 2 nm or less will cause a certain degree of gas bubbling, among which the pores with a pore size of less than 1 nm will not cause a large amount of bubbling, but too much pore volume will cause the duration of the bubbling to be longer; the pores with a pore size of 1.5-2 nm also cause a certain bubbling problem, but the duration of the bubbling is relatively short. The pores with a pore size of 2 nm or less in the material can contribute to the specific capacity. By further limiting V a +V b In the above range, while further reducing the continuous bubbling, it is more conducive to the balance between the specific capacity and the processability. Illustratively, the pore volume of the pores with a pore size of 2 nm or less is 0.0006 cm 3 / g, 0.0010 cm 3 / g, 0.0013 cm 3 / g, 0.0015 cm 3 / g, 0.0018 cm 3 / g, 0.0020 cm 3 / g, 0.0023 cm 3 / g, 0.0025 cm 3 / g, 0.0028 cm 3 / g, 0.0030 cm 3 / g, 0.0033 cm 3 / g, 0.0035 cm 3 / g, or a value between any two of the above values. Alternatively, V a +V b is in the range of 0.0020 cm3 / g to 0.0030 cm / g 3 / g.

[0140] V1, the pore volume of pores with a pore size of less than 1 nm in the carbon-based material a may be determined by using conventional methods in the art. For example, the CO2adsorption-desorption pore volume pore size test method. By this method, the pore volume of pores with a pore size of less than 1 nm, especially in the range of greater than 0.4 nm and less than 1 nm, is usually determined. Exemplarily, the CO2adsorption method test adsorption and desorption isotherms can be measured according to GB / T 34709-2017, and the cumulative pore volume versus pore size distribution curve is fitted using the DFT model, and the total pore volume V of pores in a specific pore size range of less than 1 nm is obtained a .

[0141] V2, the pore volume of pores with a pore size of 1 nm-2 nm in the carbon-based material b may be determined by using a method similar to the above method, and V is obtained by integrating in a specific pore size range of 1 nm-2 nm b .

[0142] In some embodiments, the pore volume V1 of micropores with a pore size of less than or equal to 2 nm and the total pore volume V of the carbon-based material 总 satisfy: 4.5%≤V1 / V 总 ≤30%. The proportion of the pore volume of micropores in the total pore volume is in the above range, which is beneficial to improve the capacity of the sodium ion battery. Exemplarily, V1 / V 总 is 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or a value between any two of them.

[0143] In some embodiments, the pore volume V2 of mesopores with a pore size of greater than 2 nm and less than 10 nm and the total pore volume V of the carbon-based material 总 satisfy: 2.5%≤V2 / V 总 ≤10%. The proportion of the pore volume of mesopores in the total pore volume is in the above range, which is beneficial to improve the kinetic performance of the sodium ion battery. Exemplarily, V2 / V 总 is 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a value between any two of them.

[0144] In some embodiments, 0.0003 cm 3 / g≤V2≤0.0012 cm 3The mesoporous pore volume is in the above range, which is beneficial to improve the kinetic performance of the sodium ion battery.

[0145] In some embodiments, the carbon-based material comprises heteroatoms.

[0146] The presence of the heteroatoms can expand the interlayer spacing of the graphene layers in the carbon-based material, so that the spacing between the graphene layers in the carbon-based material is greater than 0.4 nm, thereby making it easier for active ions to enter and be adsorbed, and being beneficial to the kinetics of the sodium ion battery.

[0147] In some embodiments, the heteroatoms can include at least one of O, N, S, P, B, F. For example, the heteroatoms can include O and N, or O and S, or O and P, or O and B, or O and F, or O, N and S, or O, N and P, or O, N and B, or O, N and F, or O, N, S and P, or O, N, S and B, or O, N, S and F, or O, N, S, P and B, or O, N, S, P and F, or O, N, S, P, B and F, or N and S, or N and P, or N and B, or N and F, or N, S and P, or N, S and B, or N, S and B, or N, S, P and B, or N, S, P and F, or N, S, P, B and F, or S and P, or S and B, or S and F, or S, P and B, or S, P and F, or S, P, B and F, or P and B, or P and F, or P, B and F, or B and F.

[0148] In some embodiments, the heteroatoms account for 0.4wt%-5wt% of the total mass of the carbon-based material. For example, the heteroatoms account for 0.4wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or any value within the range of any two values of the total mass of the carbon-based material. The total mass of the heteroatoms in the carbon-based material is in the above range, which can make the proportion of the graphene layers with an interlayer spacing greater than 0.4 nm in the total graphene layers in the carbon-based material be in the above range, and be beneficial to the kinetics and the first coulombic efficiency.

[0149] In some embodiments, the I D / I G is 1.1-1.35; wherein, I D represents the D peak intensity of the Raman spectrum at 1350±50cm -1 -1, and I G represents the G peak intensity of the Raman spectrum at 1580±50cm-1 The I D G 1.1, 1.2, 1.3, 1.35, or any value within the range consisting of any two of these values. The I D G Within the above range, the carbon-based material has a high degree of order of surface carbon and few surface defects, which is conducive to improving the initial coulombic efficiency of the battery and improving the compaction density.

[0150] In some embodiments, the content of surface oxygen elements of the carbon-based material is 5% to 15%. Illustratively, the content of surface oxygen elements of the carbon-based material is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value within the range consisting of any two of these values. When the content of surface oxygen elements of the carbon-based material is within the above range, the viscosity of the slurry containing the carbon-based material can be within a suitable range, which is conducive to improving the processing performance of the sodium ion battery.

[0151] In some embodiments, the powder compaction density of the carbon-based material at 2t is 0.9 g / cm 3 -1.2 g / cm 3 When the powder compaction density of the carbon-based material is within the above range, it is conducive to improving the cold-pressing density of the negative electrode sheet, and further improving the volume energy density of the sodium ion battery.

[0152] In some embodiments, the carbon-based material satisfies at least one of the following:

[0153] (1) The specific surface area of the carbon-based material is 2 m 2 / g to 8 m 2 / g; when the specific surface area of the carbon-based material is within the above range, it is conducive to improving the initial coulombic efficiency of the sodium ion battery.

[0154] (2) The tap density of the carbon-based material is 0.78 g / cm 3 -0.9 g / cm 3 ; when the tap density of the carbon-based material is within the above range, it is conducive to improving the compaction density of the negative electrode film layer and improving the energy density of the sodium ion battery.

[0155] (3) The true density of the carbon-based material is 2.0 g / cm 3 -2.3 g / cm 3 ; when the true density of the carbon-based material is within the above range, it is conducive to improving the capacity of the sodium ion battery.

[0156] ​​It should be noted that the true density refers to the mass of a material per unit actual volume (excluding internal voids, i.e., not including open and closed pores and inter-particle voids) in an absolutely dense state.

[0157] (4) the volume distribution particle size Dv10 of the carbon-based material is 1.8 μm-3 μm;

[0158] (5) the volume distribution particle size Dv50 of the carbon-based material is 4 μm-7 μm;

[0159] (6) the volume distribution particle size Dv90 of the carbon-based material is 9 μm-15 μm.

[0160] When the volume distribution particle sizes Dv10, Dv50 and Dv90 of the particles of the carbon-based material are within the above ranges, the specific surface area of the carbon-based material is reduced, the occurrence of side reactions is reduced, and thus the first coulombic efficiency of the sodium ion battery is improved. At the same time, the bulk transport path of active ions is shortened, and thus the kinetic performance of the sodium ion battery is improved.

[0161] In some embodiments, the carbon-based material is a hard carbon material, or is a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite. Alternatively, the carbon-based material is a hard carbon material.

[0162] In some embodiments, the carbon-based material is a mixture of a hard carbon material and a soft carbon material, wherein the mass ratio of the soft carbon material to the hard carbon material is (0.5-6):(4-9.5), or alternatively (2-5):(5-8).

[0163] In some embodiments, the carbon-based material is a mixture of a hard carbon material and graphite, wherein the mass ratio of the graphite to the hard carbon material is (1-2.5):(7.5-9), or alternatively (1.5-2.2):(7.8-8.5).

[0164] In some embodiments, when the carbon-based material is a mixture of a hard carbon material and a soft carbon material, the hard carbon material and the soft carbon material can be distinguished by thermal gravimetric analysis. Specifically, the thermal stabilities of the hard carbon material and the soft carbon material are different. The soft carbon material is relatively stable at high temperatures due to having a certain graphitization structure, and the thermal weight loss curve is relatively flat. The hard carbon material contains a large amount of amorphous carbon and heteroatoms, and thermal decomposition and oxidation reactions can occur at relatively low temperatures, and the thermal weight loss is relatively large, and the thermal weight loss curve has a large slope within a certain temperature range. By analyzing the thermal weight loss curve of the carbon-based material, it can be determined whether the carbon-based material contains a hard carbon material and a soft carbon material.

[0165] In some embodiments, when the carbon-based material is a mixture of hard carbon material and graphite, the hard carbon material and the graphite can be distinguished by Raman test combined with X-ray diffraction test. Specifically, the graphite has very obvious (002) crystal face diffraction peak, and the I D / I G of the graphite is generally close to 0.1, while the I D / I G of the hard carbon material is greater than 1. By analyzing the X-ray diffraction peak and the Raman spectrum of the carbon-based material, it can be determined whether the carbon-based material contains hard carbon material and graphite.

[0166] In the present disclosure, the pore volume V1, V2 and the pore volume V 总 of the micropores and mesopores of the carbon-based material can be determined according to GB / T 19587-2017.

[0167] In the present disclosure, the I D / I G value of the carbon-based material can be tested using a Raman spectrometer, I D represents the D peak intensity of the Raman spectrum of the material at 1350±50 cm -1 , and I G represents the G peak intensity of the Raman spectrum of the material at 1580±50 cm -1 . The test conditions are as follows: excitation wavelength is 532 nm, power is 0.5%, grating is 600 lines, objective lens is 50 times, integration time is 10 s, cumulative number is 3 times, surface scanning, 100 points of D peak and G peak intensity are obtained, 100 points of I D / I G are calculated, 30 I D / I G with the largest and the smallest are removed, and the average value of the remaining 40 points is the I D / I G of the material. The test instrument can be a Horiba LabRAM HR800 Raman spectrometer.

[0168] In the present disclosure, the surface oxygen content of the carbon-based material can be obtained by semi-quantitative analysis of the surface functional groups of the carbon-based material, i.e., by X-ray photoelectron spectroscopy test of the carbon-based material, converting the signal intensity measured by X-ray photoelectron spectroscopy into the content of the element, and converting the peak area into the content of the corresponding element. The device model used is Axis Supra / Supra+, sensitivity 450W Al Kα / Ag Lα monochromatic X-ray source, energy resolution ≤0.45eV. Specifically, the XPS spectrum of the carbon-based material is fitted by XPS peak41, a suitable baseline is set, fitting peaks are added, and then Gaussian fitting is performed until the residual is less than 10.

[0169] In the present disclosure, the tap density of the carbon-based material has the meaning well known in the art and can be determined by using the instruments and methods known in the art. For example, it can be determined by referring to GB / T 24533-2009, by using an electronic pressure testing machine (for example, it can be a UTM7305 type electronic pressure testing machine). The exemplary test method is as follows: 1 g of sample powder is weighed and added to a mold with a bottom area of 1.327 cm 2 , and is pressed to 2 t, kept for 30 s, then released, kept for 10 s, and then recorded and calculated to obtain the tap density of the material at 2 t pressure.

[0170] In the present disclosure, the specific surface area BET of the carbon-based material has the meaning well known in the art and can be determined by using the instruments and methods known in the art. For example, it can be tested by referring to GB / T 19587-2017, by using a nitrogen adsorption specific surface area analysis test method, and calculated by using the BET (Brunauer Emmett Teller) method. The test instrument can be a Tri-Star 3020 type specific surface area and pore size analysis tester of Micromeritics Company, USA.

[0171] In the present disclosure, the tap density of the carbon-based material has the meaning well known in the art and can be determined by using the instruments and methods known in the art. For example, it can be determined by referring to GB / T 5162-2006, by using a powder tap density tester. The test instrument can be a Dandong Bitai BT-301, and the test parameters are as follows: vibration frequency 250 ± 15 times / min, vibration amplitude 3 ± 0.2 mm, vibration times 5000 times, and cylinder volume 25 mL.

[0172] In the present disclosure, the true density of the carbon-based material has the meaning well known in the art and can be tested by using the methods known in the art. As an example, a carbon-based material with a mass of M is weighed, and the carbon-based material is placed in a true density tester (AccuPyc II 1340 analyzer) at room temperature (15-25°C), the test system is closed, and helium is introduced according to the program. By detecting the gas pressure in the sample chamber and the expansion chamber, the gas volumes in the sample chamber and the expansion chamber are calculated respectively according to the ideal gas state equation, and the difference between the two is the gas volume of the carbon-based material at a certain temperature and pressure, which is the true volume V of the carbon-based material. The true density of the carbon-based material is the mass M of the carbon-based material / the true volume V of the carbon-based material, and the unit of the true density is g / cm 3 .

[0173] In the present disclosure, the volume distribution particle sizes Dv10, Dv50, Dv90 of the carbon-based material are of the meanings commonly known in the art, which respectively represent the particle sizes corresponding to the cumulative volume distribution percentages of 10%, 50%, and 90% of the material, and can be determined by using instruments and methods known in the art. For example, GB / T 19077-2016 can be referred to, and a laser particle size analyzer can be used for determination. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0174] In the present disclosure, the contents of the heteroatoms S, B, P, and F in the carbon-based material can be determined by using instruments and methods known in the art. For example, EPA 6010D-2014 inductively coupled plasma atomic emission spectrometry can be referred to for measuring the elements and their contents in the carbon-based material.

[0175] In the present disclosure, the contents of the heteroatoms O and N in the carbon-based material can be determined by using instruments and methods known in the art. For example, a nitrogen-hydrogen-oxygen analyzer can be used for testing.

[0176] In the present disclosure, the microstructure of the carbon-based material can be observed by a scanning electron microscope or a transmission electron microscope.

[0177] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0178] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0179] In some embodiments, the negative electrode active material includes the carbon-based material provided in the above embodiments or prepared according to the preparation method of the above embodiments.

[0180] In some embodiments, the negative electrode film layer can further optionally include a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0181] In some embodiments, the negative electrode film layer further optionally comprises a conductive agent. The conductive agent can be selected from at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0182] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0183] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after drying, cold pressing, and the like, the negative electrode sheet can be obtained.

[0184] The term “sodium-ion battery” referred to herein refers to a battery cell, a battery module, or a battery pack. The following are described separately.

[0185] Generally, a sodium-ion battery cell comprises a positive electrode sheet, the above-mentioned negative electrode sheet, an electrolyte, and a separator film. During the charging and discharging of the battery, active ions are reversibly intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator film is arranged between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuiting between the positive electrode and the negative electrode, while allowing ions to pass through.

[0186] Positive electrode sheet

[0187] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material of the present disclosure.

[0188] By way of example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer is arranged on either one or both of the two opposite surfaces of the positive electrode current collector.

[0189] In some embodiments, the positive electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be adopted. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0190] In some embodiments, the battery cell is a sodium-ion battery, and the positive active material can employ positive active materials known in the art for sodium-ion batteries. As an example, the positive active material can include at least one of sodium transition metal oxides, polyanionic compounds, Prussian blue type compounds, but the present disclosure is not limited to these materials, and other conventionally known materials that can be used as positive active materials for sodium-ion batteries can also be used. For example, as an alternative technical solution of the present disclosure, in the sodium transition metal oxides, the transition metal can be at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb, and Ce. The sodium transition metal oxide is, for example, Na x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x < 1.

[0191] As an alternative technical solution of the present disclosure, the polyanionic compound can be a compound having sodium ions, transition metal ions, and tetrahedral (YO4) n- anion units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; and n represents the valence of (YO4) n- . The polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- anion units, and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents the valence of (YO4) n- ; and the halogen can be at least one of F, Cl, and Br.

[0192] The polyanionic compound can also be a compound having sodium ions, tetrahedral (YO4) n- anion units, polyhedral (ZO y ) m+ m) units, and optional halogen anions. Y can be at least one of P, S, and Si; n represents the valence of (YO4) n- ; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; and m represents the valence of (ZO y ) m+valence; the halogen can be at least one of F, Cl, and Br. The polyanionic compound is, for example, NaFePO4, Na3V2(PO4)3, NaM’PO4F (M’ is one or more of V, Fe, Mn, and Ni), and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1) at least one.

[0193] As an optional technical manner of the present disclosure, the polyanionic compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q d , wherein the A element represents an alkali metal element doped to replace the Na element, the M element represents a metal element doped to replace the V element, the D element represents a doping element doped to replace the P element, and the Q element represents a doping element doped to replace the F element, the D element includes at least one of Si and S, and the Q element includes at least one of Cl and O; 3.5≤x≤4.5, 0≤a≤0.15x, 0.8≤y≤1.1, 0≤b≤0.3y, 0≤c≤0.15, 0.8≤z≤1.1, and 0≤d≤0.2z. Optionally, the A element includes at least one of K and Li; and the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0194] As an optional technical manner of the present disclosure, the polyanionic compound can be Na x R y (PO4)2P2O7, wherein x=3.5-4.5, y=2.75-3.25, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0195] As an optional technical manner of the present disclosure, the polyanionic compound can be Na 4+x R 3-y P 4-m O 15 / C; wherein 0

[0196] The Prussian blue compound can be a compound having sodium ions, transition metal ions, and cyanide ions (CN ). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound is, for example, Na a Me b Me’ c (CN)6, wherein Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a < 2, 0 < b < 1, and 0 < c < 1.

[0197] In some embodiments, the positive active material includes at least one of a sodium-containing transition metal oxide, a polyanionic sodium ion compound, and a Prussian blue sodium ion compound.

[0198] In other embodiments, the battery cell can also be a lithium ion battery, and the positive active material can be a positive active material known in the art for use in lithium ion batteries.

[0199] In the listing of the positive active material in the present disclosure, the molar content of oxygen is only the theoretical state value, and the lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of oxygen will float.

[0200] In some embodiments, the positive electrode film layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0201] In some embodiments, the positive electrode film layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0202] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying and cold pressing, obtaining the positive electrode sheet.

[0203] Electrolyte

[0204] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not specifically limited in the present disclosure and can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0205] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0206] In some embodiments, when the battery cell is a sodium-ion battery, the electrolyte salt can be selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bisfluorosulfonylimide, sodium bis-trifluoromethanesulfonylimide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluorobisoxalate borate, sodium bisoxalate borate, sodium difluorophosphate, sodium difluorobisoxalate phosphate, and sodium tetrafluorobisoxalate phosphate.

[0207] In some embodiments, when the battery cell is a lithium-ion battery, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0208] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0209] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, etc.

[0210] Separator film

[0211] In some embodiments, the battery cell further includes a separator film. The type of separator film is not particularly limited in the present disclosure, and any known porous structure separator film having good chemical stability and mechanical stability can be used.

[0212] In some embodiments, the material of the separator film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0213] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be made into an electrode assembly through a winding process or a stacking process.

[0214] In some embodiments, the battery cell can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte.

[0215] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0216] The present disclosure does not have a particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG. 1 is a battery cell 5 of a square structure as an example.

[0217] In some embodiments, referring to FIG. 2, the outer package can include a shell 51 and a top cover assembly 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator film can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0218] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0219] FIG. 3 is a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be made. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0220] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0221] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0222] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case can be included in the battery pack 1. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is capable of being disposed on the lower case 3 and forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0223] In some embodiments, the first discharge curve of the button cell prepared using the negative electrode tab of the present disclosure has a proportion of discharge capacity corresponding to a voltage greater than 0.1 V to the total discharge capacity of 28% to 55% at a current density of 0.1 C.

[0224] Method for preparing sodium-ion battery

[0225] The present disclosure also provides a method for preparing a sodium-ion battery, which comprises a step of preparing a negative electrode tab, the step comprising: step (1), mixing a negative electrode component and a solvent to obtain a negative electrode slurry, the negative electrode component comprising a carbon-based material, the carbon-based material comprising graphene sheets, the space volume H1 between graphene sheets with an interlayer spacing greater than 0.4 nm and the total space volume H 总 satisfying: 40%≤H1 / H 总 ≤60%; and step (2), coating the negative electrode slurry on a negative electrode current collector. By adding the above-mentioned carbon-based material when preparing the negative electrode slurry, the van der Waals force between active material particles can be reduced, so that the active material is more easily dispersed; and the carbon-based material satisfying the above-mentioned condition forms a more uniform pore structure during compaction, which is beneficial to compaction. The battery prepared by the preparation method of the present disclosure has excellent kinetic performance and first coulomb efficiency.

[0226] The carbon-based material herein is the same as the carbon-based material described in the “Sodium-ion battery” section above.

[0227] In some embodiments, 40%≤H1 / H 总 ≤55%.

[0228] In some embodiments, the space volume H2 between graphene sheets with an interlayer spacing of 0.36 nm to 0.4 nm and the total space volume H 总 satisfies: 22%≤H2 / H 总 ≤60%.

[0229] In some embodiments, 29%≤H2 / H 总 ≤42%.

[0230] In some embodiments, the space volume H3 between graphene sheets with an interlayer spacing less than 0.36 nm and the total space volume H总 satisfies: H3 / H 总 ≤ 18%.

[0231] In some embodiments, the carbon-based material further comprises micropores with a pore size of 2 nm or less and mesopores with a pore size of greater than 2 nm and less than 10 nm; the pore volume of the micropores V1 and the pore volume of the mesopores V2 satisfy: 0.5≤V1 / V2≤9.7.

[0232] In some embodiments, the carbon-based material comprises pores with a pore size in the range of 1.0-1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V with respect to the logarithm of the pore size D is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)) as determined by nitrogen adsorption method.

[0233] In some embodiments, the carbon-based material has a maximum value of dV / d(logD) of pores with a pore size of 1.0-1.5 nm in the range of 0.001 cm 3 / (g·log(nm))-0.006 cm 3 / (g·log(nm)) as determined by nitrogen adsorption method.

[0234] In some embodiments, the pore volume of pores with a pore size of less than 1 nm of the carbon-based material as determined by carbon dioxide adsorption method is represented as V a , the pore volume of pores with a pore size of 1-2 nm of the carbon-based material as determined by nitrogen adsorption method is represented as V b , then V a + V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

[0235] In some embodiments, V a + V b is in the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

[0236] In some embodiments, the mass percentage of the negative electrode components relative to the mass of the negative electrode slurry is in the range of 40%-60%, or optionally, 45%-55%. In this way, the flowability of the slurry is facilitated, so that the slurry is easily and uniformly coated, thereby facilitating the improvement of the performance of the sodium ion battery.

[0237] In some embodiments, the mass percentage of the carbon-based material is 85-98%, optionally 90-95%, relative to the mass of the negative electrode component. In this way, a good conductive network and stable structure of the electrode sheet are facilitated.

[0238] In some embodiments, the negative electrode component further comprises one or more of a conductive agent, a binder, and a thickening agent. The conductive agent can effectively accelerate the electron transmission rate and improve the charge-discharge efficiency of the battery. The binder is conducive to maintaining the integrity of the electrode structure during the charge-discharge process of the battery. The thickening agent can increase the viscosity of the slurry, ensure uniform dispersion of the negative electrode component particles and stable suspension, and prevent sedimentation, thereby facilitating the uniformity and stability of the subsequent coating process.

[0239] In some embodiments, the conductive agent comprises highly conductive carbon black or graphene, and the highly conductive carbon black can be Super P, for example.

[0240] In some embodiments, the mass percentage of the conductive agent is 0.3-3%, relative to the mass of the negative electrode component. In this way, a continuous conductive network is formed between the carbon-based particles, thereby reducing the internal resistance of the battery.

[0241] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite. Optionally, the carbon-based material is a hard carbon material.

[0242] Electric device

[0243] The present disclosure also provides an electric device, and the sodium-ion battery of the present disclosure is described below with appropriate reference to the accompanying drawings.

[0244] The electric device mentioned in the embodiments of the present disclosure comprises the sodium-ion battery provided by the present disclosure. The sodium-ion battery can be used as a power source of the electric device, or as an energy storage unit of the electric device. The electric device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0245] As the electric device, a battery cell, a battery module, or a battery pack can be selected according to the usage requirements thereof.

[0246] FIG. 6 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the sodium-ion battery for the electric device, a battery pack or a battery module can be used.

[0247] As another example, the device can be a mobile phone, a tablet, a notebook computer, or the like. The device generally requires thinness, and a battery cell can be used as a power source.

[0248] Carbon-based material

[0249] The present disclosure also provides a carbon-based material. The carbon-based material includes graphene sheets, and a volume of spaces H1 between the graphene sheets having an interlayer spacing of greater than 0.4 nm is within a certain range with respect to a total volume of spaces H 总 satisfies: 40% ≤ H1 / H 总 ≤ 60%.

[0250] In the present disclosure, by having the volume of spaces between the graphene sheets having an interlayer spacing of greater than 0.4 nm within the above certain range, a sodium ion battery can have both excellent kinetic performance and a first coulomb efficiency.

[0251] In some embodiments, 40% ≤ H1 / H 总 ≤ 55%.

[0252] By having the volume of spaces H1 between the graphene sheets having an interlayer spacing of greater than 0.4 nm and the total volume of spaces H 总 Within the above range, it is more helpful to have both excellent kinetic performance and a first coulomb efficiency.

[0253] In some embodiments, a volume of spaces H2 between the graphene sheets having an interlayer spacing of 0.36 nm to 0.4 nm and the total volume of spaces H 总 satisfies: 22% ≤ H2 / H 总 ≤ 60%.

[0254] In some embodiments, 29% ≤ H2 / H 总 ≤ 42%.

[0255] In the present disclosure, by having the volume of spaces H2 between the graphene sheets having an interlayer spacing of 0.36 nm to 0.4 nm and the total volume of spaces H 总 Within the above range, it is possible to improve the capacity of a sodium ion battery while improving the kinetics of the sodium ion battery.

[0256] In some embodiments, a volume of spaces H3 between the graphene sheets having an interlayer spacing of less than 0.36 nm and the total volume of spaces H 总 satisfies: H3 / H 总 ≤ 18%.

[0257] by setting the volume of the space H3 between the graphene layers with an interlayer spacing of less than 0.36 nm to be smaller than the total volume of the space H between the layers in the graphene layers 总 Within the above range, the risk of sodium precipitation can be reduced, the cathode capacity can be improved, and the energy density of the sodium ion battery can be improved.

[0258] In some embodiments, the carbon-based material further comprises micropores with a pore size of less than or equal to 2 nm and mesopores with a pore size of greater than 2 nm and less than 10 nm; the pore volume V1 of the micropores and the pore volume V2 of the mesopores satisfy: 0.5≤V 1 / V2≤9.7.

[0259] By setting the pore volume V1 of the micropores and the pore volume V2 of the mesopores to satisfy the above relationship, the sodium ion battery can have excellent capacity and kinetic performance.

[0260] In some embodiments, the carbon-based material comprises pores with a pore size in the range of 1.0 nm-1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V with respect to the logarithm of the pore size D is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)) as determined by nitrogen adsorption method. The carbon-based material provided by the present disclosure has an optimized pore structure. Specifically, the feature dV / d(logD) of the pores with a pore size of 1.0 nm-1.5 nm of the carbon-based material corresponds to the pore volume value contributed by the unit pore size, and the maximum value thereof is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)), which is beneficial to reduce the gas bubble phenomenon during the pulping process.

[0261] In some embodiments, the maximum value of dV / d(logD) of the pores with a pore size of 1.0 nm-1.5 nm of the carbon-based material is in the range of 0.001 cm 3 / (g·log(nm))-0.006 cm 3 / (g·log(nm)), which is more beneficial to reduce the gas bubble phenomenon during the pulping process.

[0262] In some embodiments, the pore volume of the pores with a pore size of less than 1 nm of the carbon-based material is represented as V a , and the pore volume of the pores with a pore size of 1 nm-2 nm of the carbon-based material is represented as V b , then V a +V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g. The pore volume of the carbon-based material in pores with a pore size of 2 nm or less is in the above range, which is more conducive to reducing the gas bubble phenomenon in the pulping process while maintaining the gram capacity.

[0263] In some embodiments, the V a +V b is in the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

[0264] In some embodiments, the pore volume V1 of micropores with a pore size of 2 nm or less and the total pore volume V 总 satisfies: 4.5%≤V1 / V 总 ≤30%. The proportion of the pore volume of micropores in the total pore volume is in the above range, which is conducive to improving the capacity of the sodium ion battery.

[0265] In some embodiments, the pore volume V2 of mesopores with a pore size of 2 nm to 10 nm and the total pore volume V 总 satisfies: 2.5%≤V2 / V 总 ≤10%. The proportion of the pore volume of mesopores in the total pore volume is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery.

[0266] In some embodiments, 0.0003 cm 3 / g≤V2≤0.0012 cm 3 / g. The pore volume of mesopores is in the above range, which is conducive to improving the kinetic performance of the sodium ion battery.

[0267] In some embodiments, the carbon-based material includes heteroatoms, and the mass percentage of the heteroatoms in the total mass of the carbon-based material is 0.4wt%-5wt%. In some embodiments, the heteroatoms include at least one of O, N, S, P, B, and F. The presence of the heteroatoms can expand the interlayer spacing of the graphene layers in the carbon-based material, so that the spacing between the graphene layers in the carbon-based material is greater than 0.4 nm, which is conducive to the kinetics of the sodium ion battery. In addition, the mass percentage of the heteroatoms in the carbon-based material is in the above range, which can make the proportion of the graphene layers with an interlayer spacing greater than 0.4 nm in the total graphene layers in the carbon-based material be in the above range, which is conducive to balancing the kinetic performance and the first coulomb efficiency of the sodium ion battery.

[0268] In some embodiments, the I D / I G of the carbon-based material is 1.1-1.35; wherein, I D represents the D peak intensity of the Raman spectrum at 1350±50 cm -1 , and I G represents the G peak intensity of the Raman spectrum at 1580±50 cm-1 The G-peak intensity of the carbon-based material is determined by the I D / I G Within the above range, the order degree of the surface carbon of the carbon-based material is high, and the surface defects are few, which is beneficial to improve the initial coulombic efficiency of the battery and also beneficial to improve the compaction density.

[0269] In some embodiments, the content of surface oxygen elements of the carbon-based material is 5% to 15%.

[0270] The content of surface oxygen elements of the carbon-based material is within the above range, which can make the viscosity of the slurry containing the carbon-based material within a suitable range, and is beneficial to improve the processing performance of the sodium ion battery.

[0271] In some embodiments, the powder compaction density of the carbon-based material at 2t is 0.9 g / cm 3 -1.2 g / cm 3 When the powder compaction density of the carbon-based material is within the above range, it is beneficial to improve the cold compaction density of the negative electrode sheet, and further beneficial to improve the volume energy density of the sodium ion battery.

[0272] In some embodiments, the carbon-based material satisfies at least one of the following:

[0273] (1) The specific surface area of the carbon-based material is 2 m 2 / g-8 m 2 / g; when the specific surface area of the carbon-based material is within the above range, it is beneficial to improve the initial coulombic efficiency of the sodium ion battery.

[0274] (2) The tap density of the carbon-based material is 0.78 g / cm 3 -0.9 g / cm 3 ; when the tap density of the carbon-based material is within the above range, it is beneficial to improve the compaction density of the negative electrode film layer and improve the energy density of the sodium ion battery.

[0275] (3) The true density of the carbon-based material is 2.0 g / cm 3 -2.3 g / cm 3 ; when the true density of the carbon-based material is within the above range, it is beneficial to improve the capacity of the sodium ion battery.

[0276] (4) The volume distribution particle size Dv10 of the carbon-based material is 1.8 μm-3 μm;

[0277] (5) The volume distribution particle size Dv50 of the carbon-based material is 4 μm-7 μm;

[0278] (6) The volume distribution particle size Dv90 of the carbon-based material is 9 μm-15 μm.

[0279] When the volume distribution particle sizes Dv10, Dv50, and Dv90 of the particles of the carbon-based material are within the above range, the specific surface area of the carbon-based material can be reduced, the occurrence of side reactions can be reduced, and thus the first coulombic efficiency of the sodium-ion battery can be improved. At the same time, the bulk transport path of active ions can be shortened, and thus the kinetic performance of the sodium-ion battery can be improved.

[0280] In some embodiments, the carbon-based material is a hard carbon material, or is a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite. Alternatively, the carbon-based material is a hard carbon material.

[0281] The carbon-based material has unique physical and chemical properties such as disordered crystal structure, large interlayer spacing, and rich pores, which enable the carbon-based material to adapt to different ion storage and transport requirements. The carbon-based material can be used as a negative electrode material in energy storage devices such as lithium-ion batteries, sodium-ion batteries, sodium-potassium hybrid batteries, potassium-ion batteries, and supercapacitors.

[0282] A sodium-lithium hybrid battery generally uses a positive electrode material of a sodium-ion battery and a negative active material of a lithium-ion battery, or uses a positive electrode material of a lithium-ion battery and a negative electrode material of a sodium-ion battery. During charging and discharging, sodium ions and lithium ions migrate between the positive and negative electrodes, respectively, to achieve storage and release of electric charge. In some embodiments, the carbon-based material can be used as a negative active material of a lithium-ion battery, or can be used as a negative active material of a sodium-ion battery.

[0283] Method for preparing hard carbon material

[0284] When the carbon-based material is a hard carbon material, the carbon sources that can be used in the preparation of the hard carbon material include biomass materials and synthetic polymer materials. In some embodiments, different carbon sources can also be combined with each other, for example, a synthetic polymer material can be combined with other carbon sources to obtain a hard carbon material with more favorable internal / external structure. The above hard carbon material can be prepared by adjusting the process conditions.

[0285] Biomass materials have a wide range of sources, such as coconut shells, rice husks, bamboo, wheat chaff, straw, lignin, and the like. Using biomass materials as carbon sources has both economic and environmental benefits.

[0286] In some embodiments, the above hard carbon material can be prepared by the following preparation method, which specifically includes a pre-carbonization step, a doping step, and a carbonization step; the pre-carbonization step includes pre-carbonization treatment of a biomass precursor at 300-500°C; and the carbonization step includes carbonization treatment at 1000-1200°C.

[0287] In the present disclosure, the pre-carbonization step, the doping step and the carbonization step are carried out under the above conditions when preparing the hard carbon material, so that the proportion of graphene layers with an interlayer spacing greater than 0.4 nm in the total graphene layers in the prepared hard carbon material is within the above range, which is beneficial to balancing the kinetic performance and the first coulombic efficiency of the sodium ion battery.

[0288] Further, the carbonization temperature is within the above range, which can also make the amount of active sites (i.e. defects) in the hard carbon material within a suitable range, which is beneficial to balancing the first coulombic efficiency and the reversible capacity of the hard carbon material as the negative active material of the sodium ion battery.

[0289] In some embodiments, the biomass precursor comprises cellulose, hemicellulose and lignin, the mass proportion of cellulose in the biomass precursor is 40% to 60%, the mass proportion of hemicellulose in the biomass precursor is <40%, and the mass proportion of lignin in the biomass precursor is 20% to 40%.

[0290] Since the crystallinity of hemicellulose in the biomass precursor is high, long-range ordered carbon layers are easily stacked during high-temperature pyrolysis, while lignin and cellulose are mostly amorphous components and can prevent the graphitization of carbon layers and increase the interlayer spacing of carbon layers during high-temperature pyrolysis. Therefore, in the present disclosure, by setting the proportions of cellulose, lignin and hemicellulose in the biomass carbon precursor within the above range, the proportion of graphene layers with an interlayer spacing greater than 0.4 nm in the total graphene layers in the formed hard carbon material is within the above range, which is beneficial to balancing the kinetic performance and the first coulombic efficiency of the sodium ion battery.

[0291] In some embodiments, the biomass precursor is formed by the following steps: dissolving a carbon source in a solvent and stirring to form a uniform solution, transferring the mixed solution to a reaction kettle for heat reaction, and then cooling and suction filtering to obtain the carbon precursor. The carbon source includes one or more of lignin, cellulose and sugar; and the solvent is one or more of water, methanol, ethanol and acetone. The heat reaction can be performed at 180°C to 250°C in an oven for 4-12h.

[0292] In the present disclosure, the heat reaction in the preparation process of the biomass precursor is carried out at the above temperature, which can make the carbon source reaction more complete, and the prepared carbon precursor will not fuse.

[0293] In some embodiments, after the biomass precursor is prepared, the sample is further purified by acid washing and water washing to remove or reduce the ash in the biomass precursor.

[0294] In some embodiments, in the doping step, heteroatom doping is performed so that the carbon-based material comprises 0.4wt%-5wt% of the heteroatoms. In some embodiments, the heteroatoms comprise at least one of O, N, S, P, B, and F.

[0295] In the present disclosure, the total mass proportion of the heteroatoms in the carbon-based material is within the above range, which can make the proportion of the graphene layers with an interlayer spacing greater than 0.4nm in the total graphene layers within a suitable range, and is conducive to balancing the kinetic performance and the initial coulombic efficiency of the sodium ion battery.

[0296] In some embodiments, in the pre-carbonization step, the carrier gas is introduced to increase the temperature to 200-500℃ at a temperature increasing rate of 1-10℃ / min and is maintained for 0.5-3h; the flow rate of the carrier gas is 10-30mL / min. The pre-carbonization in the above step can form a carbon skeleton with a suitable spacing, which is conducive to the subsequent formation of graphene layers with a suitable interlayer spacing.

[0297] In some embodiments, the carrier gas is a non-reactive gas, which can be nitrogen or an inert gas such as helium, neon, argon, krypton, xenon, etc.

[0298] In some embodiments, the pre-carbonization step and the doping step are performed simultaneously; in the doping step, doping is performed using a doping gas or a doping agent.

[0299] It should be noted that, since the pre-carbonization process is a process of forming a carbon skeleton, the heteroatoms are mixed in this process. Since the radius of the heteroatoms is greater than that of the carbon atoms, the interlayer spacing of the carbon layers can be expanded, so that the active ions can more easily enter and be adsorbed for sodium storage, which is conducive to the kinetics of the sodium ion battery.

[0300] In some embodiments, the doping gas comprises at least one of an oxygen-containing gas, a nitrogen-containing gas, or a fluorine-containing gas; and the volume ratio of the doping gas to the carrier gas is 0.02:1-0.11:1. The volume ratio of the amount of the doping gas to the carrier gas within the above range can make the doping amount of the heteroatoms in the carbon-based material within a suitable range, which is conducive to balancing the kinetic performance and the initial coulombic efficiency of the sodium ion battery.

[0301] In some embodiments, the oxygen-containing gas can be oxygen or ozone; the nitrogen-containing gas can be ammonia or nitric oxide; and the fluorine-containing gas can be fluorine gas or hydrogen fluoride gas.

[0302] In some embodiments, as the dopant, for example, polypyrrole, polyaniline, triphenylphosphine, sulfur, cyanamide, dicyandiamide, boric acid, melamine, thiourea, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, etc. can be mentioned. Preferably, the dopant includes at least one of boric acid, melamine, thiourea, ammonium dihydrogen phosphate, diammonium hydrogen phosphate; the mass ratio of the dopant to the carbon precursor is 0.05:1-2:1. The mass ratio of the dopant to the carbon precursor in the above range makes the doping amount of heteroatoms in the carbon-based material in a suitable range, which is beneficial to balance the kinetic performance and the first coulombic efficiency of the sodium ion battery.

[0303] In some embodiments, after the pre-carbonization step, the pre-carbonized product is subjected to a crushing treatment to break the biomass precursor to a target particle size. In this way, on the one hand, it is beneficial to the subsequent pulping process, and on the other hand, it can improve the electrochemical performance of the carbon-based material as the negative active material of the sodium ion battery.

[0304] In some embodiments, the crushing treatment is carried out by a jet mill or a mechanical mill.

[0305] In some embodiments, the carbonization treatment is carried out under an inert atmosphere for 1h-6h. The carbonization treatment can remove water, volatile matter and surface groups in the pre-carbonized product, and can also adjust the structure of the carbon-based material, which is beneficial to the electrochemical performance of the sodium ion battery.

[0306] In some embodiments, the doping step is carried out after the carbonization step; in the doping step, at least one of nitric acid solution, sulfuric acid solution, potassium permanganate solution, hydrogen peroxide solution is used for doping for 0.5h-5h; the mass ratio of the solute in the doping solution to the carbon-based material obtained in the carbonization step is (3-40):1.

[0307] Since nitric acid solution, sulfuric acid solution, potassium permanganate solution, hydrogen peroxide solution, etc. have strong oxidizing properties, they can realize O atom doping of the carbon-based material obtained in the carbonization step to expand the interlayer spacing of the carbon-based material. In addition, the time of doping treatment using the doping solution, the mass ratio of the solute in the doping solution to the carbon-based material obtained in the carbonization step in the above range can make the doping amount of heteroatoms in the carbon-based material in a suitable range, which is beneficial to balance the kinetic performance and the first coulombic efficiency of the sodium ion battery.

[0308] In some embodiments, the doping solution can use nitric acid solution with a mass concentration of 10%-40%, sulfuric acid solution with a mass concentration of 10%-60%, potassium permanganate acid solution with a mass concentration of 0.5%-10%, and hydrogen peroxide with a mass concentration of 1%-10%.

[0309] In some embodiments, after the carbonization step or the doping step, a grading and magnetic removal treatment is further included.

[0310] In some embodiments, the carbon-based material can also be prepared by the following method, which comprises: a pre-carbonization step, in which the biomass material is heated at 300-500°C, optionally 400-500°C, for 2-6h. The pre-carbonization step can remove the volatile matter in the biomass; a crushing step, in which the pre-carbonized product is crushed to a particle size of Dv10≤3μm, Dv50≤8μm and Dv90≤30μm. The crushing step can make the final carbon-based material have a suitable particle size distribution; a de-ashing step, in which the product is soaked in an acid tank with 1-5M acid to remove metal impurities. The biomass contains a large amount of metal impurities, and the de-ashing step can reduce the content of metal impurities; a pre-pressing step, in which the de-ashed product is pressed into a cake-shaped product with tightly packed particles, reducing the exposed area, preventing sintering and volatile matter from oxidizing and damaging the carbon, and controlling the porosity; and a carbonization step, in which the product is heated at 1300-1600°C for 2-6h to remove the remaining volatile matter.

[0311] Illustratively, the crushing can be by air jet milling or mechanical milling, and the present disclosure does not make special limitations thereon. In some embodiments, the crushing makes the Dv50 of the particles 4-8μm, which is more conducive to adjusting the pore structure of the pre-carbonized product to obtain a suitable pore structure in the subsequent high-temperature carbonization, and also conducive to fully dissolving the impurities and making the particle size distribution of the final carbon-based material suitable.

[0312] Illustratively, the acid includes at least one of hydrochloric acid, sulfuric acid, nitric acid, etc. The de-ashing can reduce the ash, which is various metals and their oxides.

[0313] In some embodiments, the amount of metal ions volatilized from the inside and remaining on the surface can be further adjusted by water washing after carbonization. For example, using coconut shell as the carbon source, the ion content can be further reduced by water washing 3-4 times after carbonization. By combining the previous de-ashing step, the cation content in the final carbon-based material can be adjusted, thereby facilitating the preparation process of the electrode plate.

[0314] In the above method, the porosity and pore structure are adjusted by steps such as crushing of the pre-carbonized product, pre-oxidation, sintering temperature and time, etc., to obtain a carbon-based material with reduced or eliminated bubbling in the pulping process.

[0315] In some embodiments, the carbon-based material includes soft carbon material, which can be obtained by crushing, purifying, carbonizing, crushing and grinding the soft carbon precursor.

[0316] In some embodiments, the preparation of the soft carbon material comprises the following steps: S1, crushing the soft carbon precursor to a certain range (100-200 mesh), and then removing oversized or undersized particles by sieving to ensure uniformity of the raw material particle size; S2, removing inorganic impurities in the raw material by acid washing, alkali washing and the like; S3, heating the carbonization furnace to 600-1000 at a heating rate of 5-20 ℃ / min for carbonization treatment; S4, crushing and grinding the carbonized product to make the particle size meet: Dv10 particle size meets, Dv50 particle size meets, and Dv90 particle size meets.

[0317] In some embodiments, the soft carbon precursor comprises at least one of petroleum coke, pitch, and biomass.

[0318] Examples

[0319] Hereinafter, examples of the present disclosure will be described. The examples described below are exemplary and are for the purpose of explaining the present disclosure only and are not to be construed as limiting the present disclosure. In the examples, specific techniques or conditions not noted are performed in accordance with techniques or conditions described in the literature in the field or in accordance with product manuals. The reagents or instruments used, when not noted by the manufacturer, are all conventional products that can be obtained commercially.

[0320] Example 1

[0321] Preparation of the hard carbon material:

[0322] (1) Pre-carbonization step and doping step, under the conditions of passing in carrier gas nitrogen and doping gas oxygen, the biomass carbon precursor coconut shell was placed in a box furnace and heated to 300℃ at a heating rate of 5℃ / min and kept for 3h for pre-carbonization treatment, wherein the volume ratio of the passed in oxygen and nitrogen was 0.05:1; the flow rate of the mixed gas of nitrogen and oxygen was 10mL / min;

[0323] (2) Carbonization step, heated to 1100℃ under the condition of passing in nitrogen and kept for 2h, cooled to room temperature;

[0324] (3) The sample obtained in the above carbonization step was crushed, fractionated, sieved, and de-magnetized, and finally a hard carbon negative electrode material was obtained.

[0325] Hard carbon material related tests:

[0326] 1) XRD test

[0327] The hard carbon material prepared in Example 1 above and silicon powder were uniformly mixed at a mass ratio of 5:1, and a flat plate sample preparation method was used to prepare the sample. The testing instrument was a Bruker D8 Discover X-ray diffractometer. CuKa ray was used as the radiation source, and a copper target was used as the anode target. The scanning 2θ angle range was 10°-40°, and the scanning rate was 1° / min. The XRD diffraction spectrum of the hard carbon material was obtained, as shown in FIG. 7. In the figure, the peak with noise is the original data, and the peak without noise is the fitting data.

[0328] After fitting, the XRD spectrum of the hard carbon material included three small fitting peaks. The angle corresponding to the strongest peak of the first fitting peak (shown by a dotted line) was located at 2θ of 21.16°. The area of the first fitting peak represented the space volume H1 between the graphene layers with an interlayer spacing greater than 0.4 nm in the hard carbon material. The ratio of the area of the first fitting peak to the total area of the three fitting peaks was equal to the proportion of the space volume H1 between the graphene layers with an interlayer spacing greater than 0.4 nm in the hard carbon material in the total space volume H between the layers in the graphene layers, H1 / H 总 总 was 52.41%. The angle corresponding to the strongest peak of the second fitting peak (shown by a dashed line) was located at 2θ of 23.53°. The area of the second fitting peak represented the space volume H2 between the graphene layers with an interlayer spacing of 0.36 nm-0.4 nm in the hard carbon material. The ratio of the area of the second fitting peak to the total area of the three fitting peaks was equal to the proportion of the space volume H2 between the graphene layers with an interlayer spacing of 0.36 nm-0.4 nm in the hard carbon material in the total space volume H between the layers in the graphene layers, H2 / H 总 总 was 33.77%. The angle corresponding to the strongest peak of the third fitting peak (shown by a solid line) was located at 2θ of 25.46°. The area of the third fitting peak represented the space volume H3 between the graphene layers with an interlayer spacing less than 0.36 nm in the hard carbon material. The ratio of the area of the third fitting peak to the total area of the three fitting peaks was equal to the proportion of the space volume H3 between the graphene layers with an interlayer spacing less than 0.36 nm in the hard carbon material in the total space volume H between the layers in the graphene layers, H3 / H 总 总 was 13.82%.

[0329] 2) Pore size and pore volume test

[0330] ​​​For hard carbon material, nitrogen and carbon dioxide adsorption method were used to test the adsorption and desorption isotherms according to GB / T 19587-2017, in which nitrogen adsorption method used specific surface and porosity analyzer (Micromeritics ASAP-2460, USA), and carbon dioxide adsorption method used specific surface and porosity analyzer (Micromeritics ASAP-2460, USA). For the adsorption and desorption isotherms measured by nitrogen adsorption method, DFT model was used to fit the pore size distribution curve, and the pore volume of the pores in specific pore size range (1.0 nm-1.5 nm, 1 nm-2 nm, 2 nm above) and total specific surface area were obtained. For the adsorption and desorption isotherms measured by carbon dioxide adsorption method, DFT model was used to fit the pore size distribution curve, and the pore volume of the pores in pore size range less than 1 nm was obtained by mathematical method. Thus, the pore size and pore volume parameters V1, V2, V 总 .

[0331] Preparation of battery:

[0332] The hard carbon material prepared in Example 1 was mixed with binder styrene-butadiene rubber (SBR), thickening agent sodium carboxymethyl cellulose (CMC-Na), and conductive agent Super p in a mass ratio of 96:2.5:0.8:0.7 in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry. The mass percentage content of the negative electrode components (hard carbon material, binder, thickening agent, and conductive agent) was 48% relative to the mass of the negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of the negative electrode current collector copper foil, and after drying in an oven at 80°C under vacuum for 12 h, the negative electrode sheet was cut into slices.

[0333] Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1 to obtain an organic solvent, and then NaPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1.4 mol / L.

[0334] Then, a CR2430 button cell was assembled in a glove box using a piece of metallic sodium as the counter electrode and a polyethylene (PE) film as the separator film.

[0335] Battery performance test

[0336] First coulombic efficiency and kinetic performance

[0337] At 25°C, the button cell prepared above was first discharged at a current density of 0.1C to 0.1V, and the capacity above 0.1V of the button cell was recorded. Then, the button cell was continuously discharged at a current density of 0.1C to 0V, and the first cycle discharge capacity (i.e., the first sodium intercalation capacity) of the button cell was recorded. Subsequently, the button cell was charged at a current density of 0.1C to 2.0V, and the first cycle charge capacity (i.e., the first sodium extraction capacity) of the button cell was recorded.

[0338] The first coulombic efficiency of the secondary battery (%) = the first sodium extraction capacity / the first sodium intercalation capacity x 100%;

[0339] The capacity ratio (%) at 0.1 V or above = the capacity at 0.1 V or above / the first sodium intercalation capacity x 100%;

[0340] The capacity ratio at 0.1 V can reflect the kinetic performance of the secondary battery, and the greater the capacity ratio at 0.1 V, the better the kinetic performance of the secondary battery.

[0341] The lithium intercalation capacity graph was plotted according to the raw capacity-voltage data of the first circle discharge specific capacity, as shown by the solid line in FIGS. 8 and 9, which is a partial enlarged view of FIG. 8. The slope segment ratio of the secondary battery in Example 1 at 0.1 V or above was as high as 39.6%, and the capacity at 0.1 V or above was 129.6 mAh / g.

[0342] Examples 2-4

[0343] The hard carbon material was prepared in a manner similar to that of Example 1, and was assembled into a secondary battery, with the only difference being that when the hard carbon material was prepared, the pre-carbonization temperature and the amount of doping of heteroatoms were adjusted to obtain hard carbon materials with different H1 / H 总 , as shown in Table 1 and Table 2.

[0344] Example 5

[0345] Preparation of the hard carbon material:

[0346] (1) The pre-carbonization step: under the condition of flowing carrier gas nitrogen, the biomass carbon precursor coconut shell was placed in a box furnace and heated to 400°C at a heating rate of 5°C / min and kept for 3h for pre-carbonization treatment, and the nitrogen flow rate was 10 mL / min;

[0347] (2) The carbonization step: under the condition of flowing nitrogen, heating to 1200°C for 2h, and cooling to room temperature;

[0348] (3) The doping step: the hard carbon material after carbonization and a 15% mass concentration nitric acid solution were mixed uniformly and kept for 1.5h to obtain the doped hard carbon material;

[0349] (4) The doped hard carbon material sample was crushed, classified, sieved, and demagnetized, and finally the hard carbon material with H1 / H 总 of 60% was obtained.

[0350] Next, the secondary battery was assembled in a manner similar to that of Example 1.

[0351] Examples 6, 8, 10

[0352] The hard carbon materials were prepared in a similar manner as in Example 1 and assembled into secondary batteries, with the only difference being that the pre-carbonization temperature and the amount of doping of heteroatoms were adjusted when preparing the hard carbon materials to obtain hard carbon materials with different V1 / V2, as shown in Tables 1 and 2.

[0353] Examples 7 and 9

[0354] The hard carbon materials were prepared in a similar manner as in Example 5 and assembled into secondary batteries, with the only difference being that the pre-carbonization temperature and the amount of doping of heteroatoms were adjusted when preparing the hard carbon materials to obtain hard carbon materials with different V1 / V2, as shown in Tables 1 and 2.

[0355] Comparative Example 1

[0356] The hard carbon materials were prepared in a similar manner as in Example 1 and assembled into secondary batteries, with the only difference being that the pre-carbonization temperature and the amount of doping of heteroatoms were adjusted when preparing the hard carbon materials to obtain hard carbon materials with different V1 / V2, as shown in Tables 1 and 2. 总 less than 40% of the hard carbon materials, as shown in Tables 1 and 2.

[0357] The secondary battery in Comparative Example 1 was subjected to charge-discharge tests in the same manner as in Example 1, and the lithium intercalation capacity graph was plotted according to the original capacity-voltage data of the first circle discharge specific capacity of the secondary battery in Comparative Example 1, as shown by the dashed line in FIGS. 8 and 9. The slope segment of the secondary battery in Comparative Example 1 above 0.1 V accounted for 24.4%, and the capacity above 0.1 V was 89.4 mAh / g.

[0358] Comparative Example 2

[0359] The hard carbon materials were prepared in a similar manner as in Example 5 and assembled into secondary batteries, with the only difference being that the pre-carbonization temperature and the amount of doping of heteroatoms were adjusted when preparing the hard carbon materials to obtain hard carbon materials with different V1 / V2, as shown in Tables 1 and 2. 总 more than 60% of the hard carbon materials, as shown in Tables 1 and 2.

[0360] The parameters of the hard carbon materials prepared in Examples 1-10 and Comparative Examples 1 and 2 and the performance test results of the secondary batteries are shown in Tables 1-3 below.

[0361] Table 1

[0362] In Table 1, " / " indicates that the item does not exist.

[0363] Table 2

[0364] Table 3

[0365] As can be seen from Tables 2 and 3 above, compared with Comparative Example 1 (hard carbon material with H1 / H 总<40%) and Comparative Example 2 (H1 / H 总 > 60%), in Examples 1-10, by making the H1 / H 总 When the V1 / V2 of the hard carbon material is between 0.5 and 9.7, the capacity ratio of the secondary battery of 0.1 V or more is further improved, and more excellent effects are obtained.

[0366] In addition, compared with Example 9 (V1 / V2 of the hard carbon material < 0.5) and Example 10 (V1 / V2 of the hard carbon material > 9.7), in Examples 1-8, by making the V1 / V2 of the hard carbon material between 0.5 and 9.7, the capacity ratio of the secondary battery of 0.1 V or more is further improved, and more excellent effects are obtained.

[0367] Example 11

[0368] Preparation of hard carbon material with biomass material as carbon source:

[0369] 1) Pre-carbonization; lignin as raw material, 400℃ for 2h under normal pressure N2 atmosphere in a hot press furnace (Top Science Technology, VHP-777), to obtain pre-carbonized product.

[0370] 2) Breaking; the pre-carbonized product obtained in step 1) is subjected to air flow milling in an air flow mill (Shengxing Environmental Protection: SX1210), to obtain a product with Dv10 of 2μm, Dv50 of 5μm, and Dv90 of 12μm.

[0371] 3) Deashing; the product after breaking in step 2) is soaked in 2M hydrochloric acid aqueous solution at room temperature for 10h in an acid pickling kettle, filtered, washed with water for 3 times, and then dried at 100℃ in a continuous kiln.

[0372] 4) Pre-pressing; the product obtained in step 3) is subjected to pre-pressing in a hot press furnace (manufacturer: Top Science Technology, model: VHP-777) at a pressure of 50T for 1h.

[0373] 5) Carbonization; the product obtained in step 4) is sintered at 1400℃ under normal pressure N2 atmosphere at a temperature rising rate of 2℃ / min for 2h, washed with water for 3 times, and then dried at 100℃ in a continuous kiln, to obtain a hard carbon material.

[0374] Preparation of negative electrode slurry:

[0375] The prepared hard carbon material, conductive agent and dispersant are dispersed in deionized water in a ratio of 8:1:1 to prepare a uniform negative electrode slurry, wherein the dispersant is sodium carboxymethyl cellulose, and the conductive agent is conductive carbon black.

[0376] Preparation of the negative electrode sheet:

[0377] The uniformly stirred negative electrode slurry was coated on both sides of the Al foil by a double-sided coating machine. After the double-sided coating was completed, vacuum drying at 80°C, cold pressing, slitting, and sheeting were sequentially performed to prepare the negative electrode sheet.

[0378] Preparation of the secondary battery:

[0379] The prepared negative electrode sheet was used for battery assembly in a glove box. Metallic sodium was used as the counter electrode, and the electrolyte was a solvent of EC: DMC (volume ratio) = 1:1 in which NaPF6 was dissolved, and 10 v / v% FEC was added.

[0380] The positive electrode sheet, the separator, and the negative electrode sheet were sequentially stacked, and the above electrolyte was added. After the processes of packaging, standing, formation, and aging, a coin-type half battery was prepared.

[0381] Example 12

[0382] The hard carbon material was prepared according to the method similar to that of Example 11, except that the temperature for high-temperature carbonization was 1000°C.

[0383] Gas adsorption test

[0384] The time at which bubbling stopped was observed when the hard carbon material prepared in each of the above examples was used to prepare a negative electrode slurry. The case in which bubbling still occurred 2 hours after the components of the negative electrode slurry were mixed was recorded.

[0385] The hard carbon materials of Examples 11 and 12 were tested for adsorption and desorption isotherms using nitrogen and carbon dioxide adsorption method according to GB / T 19587-2017, wherein both the nitrogen and carbon dioxide adsorption methods were analyzed using a specific surface and porosity analyzer (Micromeritics ASAP-2460, USA). For the adsorption and desorption isotherms measured by the nitrogen adsorption method, the specific surface area of the hard carbon material was calculated using the BET (Brunauer Emmett Teller) method, and the dV / d(logD) versus pore diameter D distribution curve was fitted using the DFT model, and the maximum value was read in the pore diameter range of 1.0 nm-1.5 nm, and the cumulative pore volume versus pore diameter distribution curve was fitted to obtain the pore volume of the pores in the specific pore diameter range (1.0 nm-1.5 nm and 1 nm-2 nm). For the adsorption and desorption isotherms measured by the carbon dioxide adsorption method, the cumulative pore volume versus pore diameter distribution curve was fitted using the DFT model, and the pore volume of the pores in the pore diameter range less than 1 nm was obtained. The test results of the hard carbon materials prepared in Examples 11 and 12 are shown in Table 4 below. FIGS. 10 and 11 are the dV / d(logD) versus specific range of pore diameter curves of the hard carbon materials prepared in Example 11 and Example 12, respectively, based on the nitrogen adsorption method. Referring to FIG. 10, the maximum value of dV / d(logD) of the hard carbon material prepared in Example 11 of the present disclosure in the pore diameter range of 1.0 nm-1.5 nm is 0.006 cm 3 / (g·log(nm)). Referring to FIG. 11, the maximum value of dV / d(logD) of the hard carbon material prepared in Example 12 of the present disclosure in the pore diameter range of 1.0 nm-1.5 nm is 0.013 cm 3 / (g·log(nm)). It can be seen that the dV / d(logD) of the pores with a pore diameter of 1.0 nm-1.5 nm of the hard carbons of Examples 11 and 12 are significantly different.

[0386] Test of bubbling in preparation of negative electrode slurry

[0387] 50 g of the hard carbon materials prepared in Examples 11 and 12 were respectively added to a sealed reaction kettle equipped with temperature and pressure sensors, and after adding 200 ml of water, the reaction kettle was quickly closed, and stirring was started until the temperature and pressure were constant. According to the pressure change value and the ideal gas equation, the volume of gas emitted per unit mass of hard carbon was calculated as a measure of the amount of bubbling. The test results of the hard carbon materials prepared in Examples 11 and 12 are shown in Table 5 below.

[0388] Gravimetric capacity test of hard carbon material

[0389] The half-cells prepared in Examples 11 and 12 were cycled at 0.05C rate to 0V vs. Na+ / Na, and the capacity obtained was the first charge capacity; the half-cells were cycled at 0.1C rate to 2.5V vs. Na+ / Na, and the capacity obtained was the first discharge capacity. The mass of hard carbon material in the negative electrode was calculated according to the coating weight and area of the slurry in the electrode preparation process. The total sodium storage capacity Q = first charge capacity / mass of hard carbon material. The test results of the hard carbon materials prepared in Examples 11 and 12 are shown in Table 5 below.

[0390] Table 4 shows the pore characteristics and interlayer spacing characteristics of the hard carbon materials prepared in Examples 11 and 12, and Table 5 shows the bubble amount and capacity test results of the hard carbon materials prepared in Examples 11 and 12.

[0391] Table 4

[0392] Table 5

[0393] As can be seen from Table 4 and Table 5, when the maximum value of dV / d(logD) is 0.006 cm 3 / (g·log(nm)), the continuous bubbling can be effectively reduced.

[0394] Example 13

[0395] A secondary battery was prepared in a similar manner to Example 1, except that the negative electrode was prepared as follows:

[0396] A carbon-based material (mass ratio of soft carbon material to hard carbon material prepared in Example 1 was 2:8), a binder styrene-butadiene rubber (SBR), a thickening agent sodium carboxymethyl cellulose (CMC-Na), and a conductive agent Super p were mixed in a mass ratio of 96:2.5:0.8:0.7 in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry. The mass percentage content of the negative electrode components (hard carbon material, soft carbon material, binder, thickening agent, conductive agent) was 48% relative to the mass of the negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of the negative electrode current collector copper foil, and after drying in an oven at 80°C under vacuum for 12h, the negative electrode was cut into a negative electrode sheet.

[0397] The carbon-based material in Example 13 was tested in a similar manner to the hard carbon material in Example 1, and the secondary battery in Example 13 was tested in a similar manner to Example 1. The specific test results are shown in Tables 6 and 7 below.

[0398] Table 6

[0399] Table 7

[0400] As can be seen from Tables 6 and 7, when the carbon-based material in Example 13 is a mixture of soft carbon and hard carbon, similar effects to those of Example 1 can be obtained, and both the kinetic performance and the initial coulombic efficiency of the secondary battery can be taken into account.

[0401] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present disclosure are included in the technical scope of the present disclosure. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments or by combining part of the constituent elements of the embodiments are also included in the scope of the present disclosure without departing from the spirit of the present disclosure.

Claims

1. A sodium-ion battery, comprising a negative electrode tab, the negative electrode tab comprising a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a carbon-based material, The carbon-based material includes graphene sheets, and a space volume H1 between graphene sheets with an interlayer spacing of greater than 0.4 nm and a total space volume H between each layer in the graphene sheets 总 satisfies: 40% < H1 / H 总 ≤ 60%.

2. The sodium-ion battery of claim 1, wherein, 40% < H1 / H 总 ≤ 55%.

3. The sodium-ion battery of claim 1 or 2, wherein, H2 is the volume of the space between graphene layers having an interlayer distance of 0.36 nm to 0.4 nm, and H is the total volume of the space between the layers in the graphene layers 总 satisfies: 22% < H2 / H < 60%. 总 satisfies: 22% < H2 / H < 60%.

4. The sodium-ion battery of claim 3, wherein, 29% < H2 / H 总 ≤ 42%.

5. The sodium-ion battery of any one of claims 1-4, wherein, a volume of space H3 between graphene sheet layers having an interlayer spacing of less than 0.36 nm 总 satisfies: H3 / H 总 ≤ 18%.

6. The sodium-ion battery of any one of claims 1-5, wherein, the carbon-based material further comprising micropores with a pore size of 2 nm or less and mesopores with a pore size of greater than 2 nm and less than 10 nm; the micropores having a pore volume V1 and the mesopores having a pore volume V2 satisfying 0.5≤V1 / V2≤9.

7.

7. The sodium-ion battery of any one of claims 1-6, wherein, The carbon-based material comprises pores having a pore diameter in the range 1.0-1.5 nm, the maximum value of the derivative dV / d(log D) of the cumulative pore volume V with respect to the logarithm of the pore diameter D being in the range 0.001 cm 3 / (g log(nm)) - 0.009 cm 3 / (g log(nm)).

8. The sodium-ion battery of claim 7, wherein, The maximum value of dV / d(logD) of the pores of the carbon-based material having a pore diameter of 1.0 nm to 1.5 nm is 0.001 cm 3 / (g·log(nm)) to 0.006 cm 3 / (g·log(nm)) to 0.006 cm 9. The sodium-ion battery of any one of claims 1-8, wherein, The pore volume of the pores of the carbon-based material having a pore diameter of less than 1 nm, as determined by carbon dioxide adsorption, is denoted by V a The pore volume of the pores of the carbon-based material having a pore diameter of 1 nm to 2 nm, as determined by nitrogen adsorption, is denoted by V b V a + V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

10. The sodium-ion battery of claim 9, wherein, V of the carbon-based material a +V b In the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

11. The sodium-ion battery of claim 6, wherein, the pore volume V1 of the micropores having a pore diameter of 2 nm or less and the total pore volume V of the carbon-based material 总 satisfies: 4.5%≤V1 / V 总 ≤30%.

12. The sodium-ion battery of claim 6 or 11, wherein, the pore volume V2 of the mesopores having a pore diameter greater than 2 nm and less than 10 nm and the total pore volume V of the carbon-based material 总 satisfies: 2.5% < V2 / V 总 ≤ 10%.

13. The sodium-ion battery of claim 11 or 12, wherein, The mesopore has a pore volume V2 satisfying: 0.0003 cm3 / g ≤ V2 ≤ 0.0012 cm3 / g. 3 / g ≤ V2 ≤ 0.0012 cm3 / g. 3 / g.

14. The sodium-ion battery of any one of claims 1-13, wherein, the carbon-based material comprising heteroatoms, the heteroatoms accounting for 0.4 wt%-5 wt% of the total mass of the carbon-based material.

15. The sodium-ion battery of claim 14, wherein, the heteroatoms comprising at least one of O, N, S, P, B, and F.

16. The sodium-ion battery of any one of claims 1-15, wherein, I D / I G 1.1-1.35; I D D peak intensity of the Raman spectrum at 1350 ± 50 cm -1 G G peak intensity of the Raman spectrum at 1580 ± 50 cm -1 G peak intensity of the Raman spectrum at 1580 ± 50 cm​ 17. The sodium-ion battery of any one of claims 1-16, wherein, the carbon-based material having a content of surface oxygen elements of 5%-15%.

18. The sodium-ion battery of any one of claims 1-17, wherein, The powder compaction density of the carbon-based material at 2t is 0.9 g / cm 3 -1.2 g / cm 3 .

19. The sodium-ion battery of any one of claims 1-18, wherein, the carbon-based material satisfying at least one of the following: (1) the carbon-based material has a specific surface area of 2 m 2 / g-8 m 2 / g; (2) the carbon-based material has a tap density of 0.78 g / cm3 3 -0.9 g / cm3 3 ; (3) the carbon-based material has a true density of 2.0 g / cm3 3 - 2.3 g / cm3 3 ; (4) the carbon-based material having a volume distribution particle size Dv10 of 1.8-3 μm; (5) the carbon-based material having a volume distribution particle size Dv50 of 4-7 μm; (6) the carbon-based material having a volume distribution particle size Dv90 of 9-15 μm.

20. The sodium-ion battery of any one of claims 1-19, wherein, the carbon-based material being a hard carbon material or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

21. The sodium-ion battery of any one of claims 1-20, wherein, the sodium-ion battery further comprising a positive electrode tab, the positive electrode tab comprising a positive electrode current collector and a positive electrode film layer on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising at least one of a sodium-containing transition metal oxide, a polyanion sodium-ion compound, and a Prussian blue sodium-ion compound. 22.A method for preparing a sodium-ion battery, comprising a step of preparing a negative electrode tab, the step comprising: Step (1), mixing a negative electrode component and a solvent to obtain a negative electrode slurry, the negative electrode component including a carbon-based material including graphene sheets, a space volume H1 between graphene sheets having an interlayer spacing greater than 0.4 nm and a total space volume H 总 satisfying: 40% ≤ H1 / H 总 ≤ 60%; and (2) coating the negative electrode slurry on a negative electrode current collector.

23. The method of producing a sodium-ion battery according to claim 22, wherein, 40% < H1 / H 总 ≤ 55%.

24. The method of preparing a sodium-ion battery according to claim 23 or 23, wherein, H2 is the volume of the space between graphene layers having an interlayer distance of 0.36 nm to 0.4 nm, and H is the total volume of the space between the layers in the graphene layers 总 satisfies: 22% < H2 / H 总 ≤ 60%.

25. The method of producing a sodium-ion battery according to any one of claims 22-24, wherein, 29% < H2 / H 总 ≤ 42%.

26. The method of preparing a sodium-ion battery according to any one of claims 22-25, wherein, a volume of space H3 between graphene sheet layers having an interlayer spacing of less than 0.36 nm 总 satisfies: H3 / H 总 ≤ 18%.

27. The method of producing a sodium-ion battery according to any one of claims 22-26, wherein, the carbon-based material further comprising micropores with a pore size of 2 nm or less and mesopores with a pore size of greater than 2 nm and less than 10 nm; the micropores having a pore volume V1 and the mesopores having a pore volume V2 satisfying 0.5≤V1 / V2≤9.

7.

28. The method of producing a sodium-ion battery according to any one of claims 22-27, wherein, The carbon-based material comprises pores having a pore diameter in the range 1.0-1.5 nm, the maximum value of the derivative dV / d(log D) of the cumulative pore volume V with respect to the logarithm of the pore diameter D being in the range 0.001 cm 3 / (g log(nm)) - 0.009 cm 3 / (g log(nm)).

29. The method of producing a sodium-ion battery according to claim 28, wherein, The maximum value of dV / d(logD) of the pores of the carbon-based material having a pore diameter of 1.0 nm to 1.5 nm is 0.001 cm 3 / (g·log(nm)) - 0.006 cm 3 / (g·log(nm)) - 0.006 cm 30. The method of preparing a sodium-ion battery of any one of claims 22-29, wherein, The pore volume of the pores of the carbon-based material having a pore diameter of less than 1 nm, as determined by carbon dioxide adsorption, is denoted by V a The pore volume of the pores of the carbon-based material having a pore diameter of 1 nm to 2 nm, as determined by nitrogen adsorption, is denoted by V b then V a + V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

31. The method of producing a sodium-ion battery according to claim 30, wherein, V of the carbon-based material a +V b In the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

32. The method of preparing a sodium-ion battery of any one of claims 22-31, wherein, the negative electrode components having a mass percentage of 40%-60% relative to the mass of the negative electrode slurry.

33. The method of preparing a sodium-ion battery of any one of claims 22-32, wherein, the carbon-based material having a mass percentage of 85%-98% relative to the mass of the negative electrode components.

34. The method of preparing a sodium-ion battery of any one of claims 22-33, wherein, the negative electrode components further comprising one or more of a conductive agent, a binder, and a thickening agent.

35. The method of producing a sodium-ion battery according to claim 34, wherein, the conductive agent having a mass percentage of 0.3%-3% relative to the mass of the negative electrode components. 36.An electric device comprising the sodium-ion battery of any one of claims 1-21, or the sodium-ion battery prepared by the method of any one of claims 22-35.

37. A carbon-based material comprising graphene sheets, the volume of space H1 between graphene sheets having an interlayer spacing greater than 0.4 nm and the total volume of space H between each of the graphene sheets satisfying: 40% < H1 / H < 60%. 总 总 40% < H1 / H < 60%.​ 38. The carbon-based material of claim 37, wherein, 40% < H1 / H 总 ≤ 55%.

39. The carbon-based material of claim 37 or 38, wherein, H2 is the volume of the space between graphene layers having an interlayer distance of 0.36 nm to 0.4 nm, and H is the total volume of the space between the layers in the graphene layers 总 satisfies: 22% < H2 / H 总 ≤ 60%.

40. The carbon-based material of claim 39, wherein, 29% < H2 / H 总 ≤ 42%.

41. The carbon-based material of any one of claims 37-40, wherein, a volume of space H3 between graphene sheet layers having an interlayer spacing of less than 0.36 nm 总 satisfies: H3 / H 总 ≤ 18%.

42. The carbon-based material of any one of claims 37-41, wherein, the carbon-based material further comprising micropores with a pore size of 2 nm or less and mesopores with a pore size of greater than 2 nm and less than 10 nm; the micropores having a pore volume V1 and the mesopores having a pore volume V2 satisfying 0.5≤V1 / V2≤9.

7.

43. The carbon-based material of any one of claims 37-42, wherein, The carbon-based material comprises pores having a pore diameter in the range 1.0-1.5 nm, the maximum value of the derivative dV / d(log D) of the cumulative pore volume V with respect to the logarithm of the pore diameter D being in the range 0.001 cm 3 / (g log(nm)) - 0.009 cm 3 / (g log(nm)).

44. The carbon-based material of claim 43, wherein, The maximum value of dV / d(logD) of the pores of the carbon-based material having a pore diameter of 1.0 nm to 1.5 nm is 0.001 cm 3 / (g log(nm)) - 0.006 cm 3 / (g log(nm)) - 0.006 cm 45. The carbon-based material of any one of claims 37-44, wherein, The pore volume of the pores of the carbon-based material having a pore diameter of less than 1 nm, as determined by carbon dioxide adsorption, is denoted by V a The pore volume of the pores of the carbon-based material having a pore diameter of 1 nm - 2 nm, as determined by nitrogen adsorption, is denoted by V b V a + V b is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

46. The carbon-based material of claim 45, wherein, V of the carbon-based material a +V b In the range of 0.0020 cm 3 / g to 0.0030 cm 3 / g.

47. The carbon-based material of claim 42, wherein, the pore volume V1 of the micropores having a pore diameter of 2 nm or less and the total pore volume V of the carbon-based material 总 satisfies: 4.5%≤V1 / V 总 ≤30%.

48. The carbon-based material of claim 42 or 47, wherein, the pore volume V2 of the mesopores having a pore diameter greater than 2 nm and less than 10 nm and the total pore volume V of the carbon-based material 总 satisfies: 2.5% < V2 / V 总 ≤ 10%.

49. The carbon-based material of claim 47 or 48, wherein, The mesopore has a pore volume V2 satisfying: 0.0003 cm3 / g ≤ V2 ≤ 0.0012 cm3 / g. 3 / g ≤ V2 ≤ 0.0012 cm3 / g. 3 / g.

50. The carbon-based material of any one of claims 37-49, wherein, the carbon-based material comprising heteroatoms, the heteroatoms accounting for 0.4 wt%-5 wt% of the total mass of the carbon-based material.

51. The carbon-based material of claim 50, wherein, the heteroatoms comprising at least one of O, N, S, P, B, and F.

52. The carbon-based material of any one of claims 37-51, wherein, I D / I G 1.1-1.35; I D D peak intensity of the Raman spectrum at 1350 ± 50 cm -1 -1, denoted I G G peak intensity of the Raman spectrum at 1580 ± 50 cm -1 -1, denoted I 53. The carbon-based material of any one of claims 37-52, wherein, The carbon-based material has a content of surface oxygen elements of 5% to 15%.

54. The carbon-based material of any one of claims 37-53, wherein, The powder compaction density of the carbon-based material at 2t is 0.9 g / cm 3 -1.2 g / cm 3 .

55. The carbon-based material of any one of claims 37-54, wherein, The carbon-based material satisfies at least one of the following: (1) the carbon-based material has a specific surface area of 2 m 2 / g to 8 m 2 / g; (2) the carbon-based material has a tap density of 0.78 g / cm 3 -0.9 g / cm 3 ; (3) the carbon-based material has a true density of 2.0 g / cm3 3 - 2.3 g / cm3 3 ; (4) the carbon-based material has a volume distribution particle size Dv10 of 1.8 μm to 3 μm; (5) the carbon-based material has a volume distribution particle size Dv50 of 4 μm to 7 μm; (6) the carbon-based material has a volume distribution particle size Dv90 of 9 μm to 15 μm.

56. The carbon-based material of any one of claims 37-55, wherein, The carbon-based material is a hard carbon material, or is a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

57. A secondary battery comprising the carbon-based material of any one of claims 37-56.

58. The secondary battery of claim 57, wherein the secondary battery is at least one of a potassium ion battery, a sodium ion battery, a lithium ion battery, a sodium-potassium ion hybrid battery, and a supercapacitor.

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