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

Abstract

Provided in the present disclosure are a sodium-ion battery, a preparation method for the sodium-ion battery, an electric device and a carbon-based material. The sodium-ion battery comprises a negative electrode sheet, wherein 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, with the negative electrode film layer comprising a carbon-based material. Upon the determination by means of a nitrogen adsorption method, the carbon-based material comprises a porous structure, and the porous structure comprises pores having a pore size of 2-8 nm; and upon the determination by means of the nitrogen adsorption method, the pore volume of the pores having a pore size of 2-8 nm is 0.0004 cm3 / g-0.0040 cm3 / g.

Description

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

[0001] Cross-reference to related applications

[0002] The present disclosure is based on the Chinese Patent Application No. 202410718131.7, filed on June 4, 2024, entitled "Negative electrode sheet, secondary battery, electric device and hard carbon material", and the International Patent Application No. PCT / CN2025 / 077585, filed on February 17, 2025, entitled "Sodium-ion battery, sodium-ion battery preparation method, electric device and hard carbon material", and claims priority to the above-mentioned Chinese Patent Application and International Patent Application, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

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

[0004] In recent years, with the continuous development and expansion of the new energy industry, the demand for lithium-ion batteries has been increasing year by year. Under this background, the consumption of lithium resources leads to a rapid increase in the cost of lithium-ion batteries, which is not conducive to the long-term development of the new energy industry. Sodium-ion batteries can share part of the supply and demand pressure. Due to the advantages of sodium in resources and cost, sodium-ion batteries have become an important development direction of energy storage batteries. Carbon-based materials are one of the mainstream negative active materials in this field due to their excellent overall performance, wide applicability and relatively low price. However, carbon-based materials still have a lot of room for improvement in terms of gravimetric capacity and kinetic performance. SUMMARY

[0005] The present disclosure is made in view of the above-mentioned problems, and aims to provide a sodium-ion battery, a sodium-ion battery preparation method, an electric device and a carbon-based material. The negative electrode sheet provided by the present disclosure has improved kinetic performance while providing better capacity.

[0006] To achieve the above-mentioned purpose, the present disclosure provides a sodium-ion battery. The sodium-ion battery comprises a negative electrode sheet, the negative electrode sheet comprises 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 comprises a carbon-based material. The carbon-based material comprises a porous structure, the porous structure comprises pores with a pore size of 2-8 nm, and the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g-0.0040 cm 3 / g as determined by nitrogen adsorption method.

[0007] The carbon-based material included in the negative electrode film layer of the negative electrode tab of the sodium-ion battery provided by the present disclosure has an optimized pore structure. Specifically, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0004 cm 3 / g-0.0040 cm 3 / g, so as to improve the kinetic performance of the carbon-based material while taking into account the gravimetric capacity.

[0008] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0010 cm 3 / g-0.0040 cm 3 / g, so as to further improve the kinetic performance of the carbon-based material while taking into account the gravimetric capacity.

[0009] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material accounts for 3.5%-30% of the total pore volume of the carbon-based material. In this way, the balance between the kinetic performance and the gravimetric capacity is improved, and the structural stability is maintained.

[0010] In some embodiments, the pore volume of the pores with a pore size of less than or equal to 1 nm of the carbon-based material is denoted as V1, and the pore volume of the pores with a pore size of 1-2 nm of the carbon-based material is denoted as V2, as determined by the carbon dioxide adsorption method and the nitrogen adsorption method, respectively. Then, V1+V2 is in the range of 0.0006 cm 3 / g to 0.0050 cm 3 / g. The pore volume of the pores with a pore size of less than 2 nm of the carbon-based material is in the above range, which is more conducive to the carbon-based material having a suitable gravimetric capacity.

[0011] In some embodiments, V1+V2 is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g, so as to reduce the gas bubbling phenomenon during the preparation of the negative electrode slurry while making the carbon-based material have a suitable gravimetric capacity, thereby obtaining a negative electrode tab with improved capacity and uniform negative electrode film layer, reducing the risk of negative electrode slurry coating leakage, and improving the performance of the sodium-ion battery. Preferably, V1+V2 is in the range of 0.0020 cm 3 / g to 0.0035 cm 3 / g.

[0012] In some embodiments, the proportion of V1+V2 to the total pore volume of the carbon-based material is in the range of 18%-30%. The proportion of the pore volume of the pores with a pore size of less than 2 nm to the total pore volume of the carbon-based material is in the above range, which is more conducive to improving the gravimetric capacity of the carbon-based material.

[0013] In some embodiments, the carbon-based material comprises 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 of pores with a pore size of 1.0 nm-1.5 nm versus a logarithm of the pore size D determined by nitrogen adsorption method is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm)). This is conducive to reducing the gas bubble phenomenon in the slurry process, and can further improve the performance of the negative electrode sheet, reduce the risk of negative electrode slurry coating leakage, and improve the performance of the secondary battery.

[0014] In some embodiments, the carbon-based material comprises 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 of pores with a pore size of 1.0 nm-1.5 nm versus a logarithm of the pore size D determined by nitrogen adsorption method is in the range of 0.001 cm 3 / (g·log(nm))-0.006 cm 3 / (g·log(nm)). This is further conducive to reducing the gas bubble phenomenon in the slurry process.

[0015] In some embodiments, the carbon-based material comprises pores with a pore size in the range of 1.0 nm-1.5 nm, and a pore volume of pores with a pore size of 1.0 nm-1.5 nm accounts for 6% to 14% of the total pore volume of the carbon-based material.

[0016] 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.

[0017] In some embodiments, the negative electrode film layer comprises at least one of a first water-based binder, a water-based dispersant, and a first conductive agent.

[0018] In some embodiments, the water-based binder comprises one or more of styrene-butadiene rubber, acrylate rubber; the water-based dispersant comprises one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum, carrageenan; and the conductive agent comprises one or more of Super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0019] In some embodiments, the mass content of the carbon-based material in the negative electrode film layer is above 80%.

[0020] In some embodiments, the mass content of the carbon-based material in the negative electrode film layer is above 85%, the mass content of the water-based binder is 0% to 5%, the mass content of the water-based dispersant is 0% to 5%, and the mass content of the conductive agent is 0% to 5%.

[0021] 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.

[0022] In some embodiments, the negative electrode film layer further comprises an intercalation-type sodium storage material, the intercalation-type sodium storage material has a crystal face spacing d 002 satisfying: 0.24 nm≤d 002 ≤0.8 nm. Thus, the intercalation-type sodium storage material with the crystal face spacing within the above range can slide between layers in the microstructure, which helps to increase the powder compaction density of the negative electrode sheet when applied in a sodium ion battery, thereby helping to improve the energy density of the sodium ion battery. The mass content of the intercalation-type sodium storage material in the negative electrode film layer is less than or equal to 10%. Alternatively, the mass content of the intercalation-type sodium storage material is between 0.5% and 5%.

[0023] In some embodiments, the intercalation-type sodium storage material comprises at least one of a carbon-based intercalation-type sodium storage material, a sulfur-based intercalation-type sodium storage material, a titanium-based intercalation-type sodium storage material; the carbon-based intercalation-type sodium storage material comprises at least one of a soft carbon intercalation-type sodium storage material, a modified graphite intercalation-type sodium storage material; the soft carbon has I D / I G satisfying: 0.9≤I D / I G ≤1.6, 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 .

[0024] In some embodiments, the negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer arranged in a stack, the first negative electrode film layer is arranged between the negative electrode current collector and the second negative electrode film layer, the first negative electrode film layer comprises a first active material, and the second negative electrode film layer comprises a second active material; the first active material and the second active material each comprise at least one of a carbon-based material and an intercalation-type sodium storage material, and at least one of the first active material and the second active material comprises a carbon-based material. The intercalation-type sodium storage material can affect the sodium storage mechanism of the negative electrode active material, reducing the deposition of sodium ions in the carbon-based material to form metal-like sodium, thereby reducing the risk of thermal runaway of sodium ions.

[0025] In some embodiments, the first active material comprises a carbon-based material, and the second active material comprises a soft carbon intercalation-type sodium storage material. Thus, it is more conducive to improve the kinetic performance.

[0026] In some embodiments, the negative electrode sheet further comprises a primer layer; the thickness of the primer layer is 0.5 μm-3 μm. Thus, it is conducive to reduce the risk of leakage and improve the coating quality of the sheet.

[0027] Since the slurry for preparing the electrode tab of the carbon-based material is water-based slurry, and the surface energy of the metal current collector is quite different, it is easy to cause leakage coating, which has safety risks.

[0028] In some embodiments, the primer layer comprises inorganic oxide and aqueous binder. The primer layer is water-resistant and has strong adhesion to the metal current collector. The inorganic oxide can enhance the anchoring effect between the primer layer and the active layer, meet the water resistance requirement, and have strong affinity to the surface of the metal current collector, which is more conducive to reducing the risk of leakage coating, improving the coating quality of the electrode tab, and improving the adhesion strength of the electrode tab, reducing the elongation rate of the electrode tab during cold pressing, and effectively controlling the resistance of the current collector while taking into account the electrochemical performance of the battery.

[0029] In some embodiments, the primer layer comprises inorganic oxide, dispersant, second aqueous binder, and second conductive agent.

[0030] In some embodiments, in the primer layer, the inorganic oxide comprises one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide; and the mass fraction of the inorganic oxide is 30%-60%. The inorganic oxide in the primer layer within the above mass range can enhance the adhesion to the metal current collector, further reduce the risk of leakage coating, and improve the coating quality of the electrode tab.

[0031] In some embodiments, the primer layer comprises 30%-60% inorganic oxide, 1%-8% dispersant, 10%-40% second aqueous binder, and 10%-40% second conductive agent.

[0032] In some embodiments, the primer layer further comprises thickening agent and / or wetting agent; the wetting agent comprises one or more of polyethoxy ether surfactant, polyether silicone surfactant, non-ionic fluorocarbon polymer surfactant, and alkyne surfactant; and the thickening agent comprises one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum, and carrageenan.

[0033] In some embodiments, the negative current collector comprises at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, nickel foil, nickel-iron foil, nickel-copper foil, and nickel-iron-copper foil.

[0034] In some embodiments, the total content of metal ions in the carbon-based material is ≤800 ppm, and the content of metal ions with valence of two or more is ≤20 ppm. The total content of metal ions and the content of metal ions with valence of two or more in the carbon-based material within the above range is conducive to maintaining appropriate slurry viscosity, thereby facilitating the coating of the slurry to obtain a negative electrode tab with a uniform negative electrode film layer.

[0035] In some embodiments, the total content of metal ions in the carbon-based material is 20 ppm-800 ppm, and the content of metal ions with valence of two or more is 0.1 ppm-20 ppm. The total content of metal ions and the content of metal ions with valence of two or more in the carbon-based material within the above ranges is conducive to increasing the inorganic content of the SEM film, thereby reducing the generation of sodium dendrites or the precipitation of sodium on the surface of the carbon-based material, and thus improving the cycle performance.

[0036] In some embodiments, the metal ions include at least one of Na + , K + , Ca 2+ , Mg 2+ , Mn 2+ , Ba 2+ , and Al 3+ .

[0037] In some embodiments, the metal ions with valence of two or more are Ca 2+ . The content of calcium ions in the carbon-based material has a greater impact on the viscosity of the negative electrode slurry, and the content within the above range is conducive to obtaining a suitable negative electrode slurry viscosity, thereby facilitating the coating of the fast slurry and avoiding the virtual edge and slurry flow, and obtaining a negative electrode tab with a uniform negative electrode film layer.

[0038] In some embodiments, the surface oxygen element content of the carbon-based material is 6%-14%. The surface oxygen element content of the carbon-based material within the above range is conducive to maintaining a suitable interaction force between the dispersant and the carbon-based material, making the slurry uniformly dispersed during the mixing process and having good fluidity, thereby facilitating the coating of the slurry without gelling phenomenon.

[0039] In some embodiments, the surface oxygen element content of the carbon-based material is 8%-12%. The surface oxygen element content of the carbon-based material within the above range is more conducive to the coating process of the slurry.

[0040] In some embodiments, the solvent in the electrolyte includes a carbonate solvent, and the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate. In this way, the high-pressure resistance of the electrolyte is improved.

[0041] In some embodiments, the volume fraction of propylene carbonate relative to the volume of the solvent is 15%-55%. In this way, not only is the oxidation resistance of the electrolyte improved, but the dissociation of sodium salt also improves the electrical conductivity.

[0042] In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes at least one of a sodium-containing layered oxide, a polyanion sodium ion compound, and a Prussian blue sodium ion compound.

[0043] In some embodiments, the sodium-containing layered oxide is at least one of an iron-manganese-based layered oxide, a nickel-iron-manganese-based layered oxide, and a copper-iron-manganese-based layered oxide.

[0044] The present disclosure also provides a method for preparing a sodium-ion battery, comprising preparing a negative electrode sheet, wherein the preparation of the negative electrode sheet comprises: mixing negative electrode components and a solvent to obtain a negative electrode slurry, wherein the negative electrode components comprise a carbon-based material, the carbon-based material comprises a porous structure, the porous structure comprises pores with a pore size of 2-8 nm, the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g-0.0040 cm 3 / g as determined by nitrogen adsorption method; and coating the negative electrode slurry on a negative electrode current collector. The pores with a pore size of 2-8 nm have suitable pore volumes to improve the kinetic performance of the carbon-based material, and the pores with this pore size can also contribute to part of the capacity, so that the negative electrode sheet can have improved kinetic performance and capacity.

[0045] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0010 cm 3 / g-0.0040 cm 3 / g as determined by nitrogen adsorption method. Thus, it is more conducive to improving the kinetic performance of the carbon-based material and balancing the capacity.

[0046] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material accounts for 3.5%-30% of the total pore volume of the carbon-based material as determined by nitrogen adsorption method. Thus, it is further conducive to balancing the kinetic performance and capacity of the carbon-based material, and maintaining suitable structural stability.

[0047] In some embodiments, the pore volume of the pores with a pore size of less than or equal to 1 nm of the carbon-based material is denoted as V1, and the pore volume of the pores with a pore size of 1-2 nm of the carbon-based material is denoted as V2 as determined by nitrogen adsorption method, then V1+V2 is in the range of 0.0006 cm 3 / g to 0.0050 cm 3 / g. By further limiting V1+V2 in the above range, it is more conducive to making the carbon-based material have suitable capacity.

[0048] In some embodiments, V1+V2 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 of less than or equal to 2 nm is in the range of 0.0006 cm 3 / g to 0.0035 cm 3The carbon-based material has a pore volume in the range of 0.0020 cm3 / g to 0.0035 cm3 / g, which is beneficial for reducing the gas bubble phenomenon in the slurry preparation process, improving the processability of the carbon-based material, and improving the uniformity of the negative electrode sheet, reducing the risk of negative electrode slurry coating leakage, and improving the performance of the sodium-ion battery.

[0049] In some embodiments, V1+V2 is in the range of 0.0020 cm3 / g to 0.0035 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0020 cm3 / g to 0.0035 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0020 cm3 / g to 0.0035 cm3 / g.

[0050] In some embodiments, V1+V2 accounts for 18% to 30% of the pore volume of the carbon-based material. The proportion of the pore volume of the pores with a pore size of less than 2 nm in the total pore volume of the carbon-based material is in the above range, which is more beneficial for improving the gram capacity of the carbon-based material.

[0051] In some embodiments, the carbon-based material contains pores with a pore size in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size of 1.0 nm to 1.5 nm with respect to the logarithm of the pore size D determined by the nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm)) to 0.009 cm3 / (g·log(nm)). 3 In some embodiments, the carbon-based material contains pores with a pore size in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size of 1.0 nm to 1.5 nm with respect to the logarithm of the pore size D determined by the nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm)) to 0.009 cm3 / (g·log(nm)). 3 In some embodiments, the carbon-based material contains pores with a pore size in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size of 1.0 nm to 1.5 nm with respect to the logarithm of the pore size D determined by the nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm)) to 0.009 cm3 / (g·log(nm)).

[0052] In some embodiments, the carbon-based material contains pores with a pore size in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size of 1.0 nm to 1.5 nm with respect to the logarithm of the pore size D determined by the nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm)) to 0.009 cm3 / (g·log(nm)). 3 In some embodiments, the carbon-based material contains pores with a pore size in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size of 1.0 nm to 1.5 nm with respect to the logarithm of the pore size D determined by the nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm)) to 0.009 cm3 / (g·log(nm)). 3 In some embodiments, the carbon-based material contains pores with a pore size in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size of 1.0 nm to 1.5 nm with respect to the logarithm of the pore size D determined by the nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm)) to 0.009 cm3 / (g·log(nm)).

[0053] In some embodiments, the pore volume of the pores with a pore size of 1.0 nm to 1.5 nm of the carbon-based material accounts for 6% to 14% of the total pore volume of the carbon-based material.

[0054] In some embodiments, the mass percentage of the negative electrode components is 50% to 60% with respect to the mass of the negative electrode slurry. Thus, the uniformity and stability of the slurry are improved.

[0055] In some embodiments, the mass percentage of the carbon-based material is 80% to 95% with respect to the mass of the negative electrode components. Thus, the energy density of the battery is improved.

[0056] In some embodiments, the negative electrode component further comprises one or more of a conductive agent, a binder, and a dispersant. The conductive agent can effectively accelerate the electron transmission rate, 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 dispersant can improve the dispersibility of the particles of the negative electrode component in the solvent, making the slurry easy to coat.

[0057] In some embodiments, mixing the negative electrode component and the solvent comprises vacuum stirring at 0-30°C for 1-4h.

[0058] When the above-mentioned carbon-based material is used to prepare a negative electrode slurry, the bubbling time can be significantly reduced, which is conducive to the smooth progress of the slurry preparation, and also conducive to the subsequent coating and cold pressing processes, thereby improving the uniformity of the negative electrode film layer and preventing the current collector from being exposed.

[0059] The disclosure also provides a power utilization device comprising the sodium-ion battery of the disclosure or the sodium-ion battery obtained by the sodium-ion battery preparation method of the disclosure.

[0060] The power utilization device of the disclosure comprises the sodium-ion battery provided by the disclosure, and thus at least has the same advantages as the sodium-ion battery.

[0061] The disclosure also provides a carbon-based material. The carbon-based material comprises a porous structure, wherein the porous structure comprises pores with a pore size of 2-8 nm, and the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g-0.0040 cm 3 / g, as determined by nitrogen adsorption method.

[0062] The carbon-based material provided by the disclosure has an optimized pore structure. Specifically, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0004 cm 3 / g-0.0040 cm 3 / g, thereby improving the kinetic performance of the carbon-based material while taking into account the specific capacity.

[0063] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0010 cm 3 / g-0.0040 cm 3 / g, as determined by nitrogen adsorption method. This is more conducive to the kinetic performance of the carbon-based material while taking into account the specific capacity.

[0064] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material accounts for 3.5%-30% of the total pore volume of the carbon-based material, as determined by nitrogen adsorption method. This is conducive to the balance between kinetic performance and specific capacity, and maintains suitable structural stability.

[0065] In some embodiments, the pore volume of pores with a pore size of 1 nm or less of the carbon-based material is denoted as V1, the pore volume of pores with a pore size of 1 nm-2 nm of the carbon-based material is denoted as V2, and V1+V2 is in the range of 0.0006 cm3 / g to 0.0050 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g.

[0066] In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g, so as to reduce the gas bubble phenomenon in the preparation of the negative electrode slurry while ensuring the appropriate gram capacity of the carbon-based material, thereby obtaining a negative electrode sheet with improved capacity and uniform negative electrode film layer, reducing the risk of negative electrode slurry coating leakage, and improving the performance of the sodium-ion battery. Preferably, V1+V2 is in the range of 0.0020 cm3 / g to 0.0035 cm3 / g. 3 In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g. 3

[0067] In some embodiments, the proportion of V1+V2 in the total pore volume of the carbon-based material is in the range of 18% to 30%. The proportion of the pore volume of pores with a pore size of 2 nm or less in the total pore volume of the carbon-based material is in the above range, which is more conducive to improving the gram capacity of the carbon-based material.

[0068] 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 of pores with a pore size of 1.0 nm-1.5 nm with respect to the logarithm of the pore size D determined by nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm))-0.009 cm3 / (g·log(nm)). 3 In some embodiments, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of pores with a pore size of 1.0 nm-1.5 nm with respect to the logarithm of the pore size D determined by nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm))-0.009 cm3 / (g·log(nm)). 3 This is conducive to reducing the gas bubble phenomenon in the slurry preparation process, further improving the performance of the negative electrode sheet, reducing the risk of negative electrode slurry coating leakage, and improving the performance of the secondary battery.

[0069] In some embodiments, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of pores with a pore size of 1.0 nm-1.5 nm with respect to the logarithm of the pore size D determined by nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm))-0.009 cm3 / (g·log(nm)). 3 In some embodiments, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of pores with a pore size of 1.0 nm-1.5 nm with respect to the logarithm of the pore size D determined by nitrogen adsorption method is in the range of 0.001 cm3 / (g·log(nm))-0.009 cm3 / (g·log(nm)). 3 This is further conducive to reducing the gas bubble phenomenon in the slurry preparation process.

[0070] ​In some embodiments, the pore volume of pores with a pore size of 1.0 nm-1.5 nm accounts for 6% to 14% of the total pore volume of the carbon-based material.

[0071] In some embodiments, the total content of metal ions in the carbon-based material is ≤800 ppm, and the content of metal ions with valence of two or more is ≤20 ppm. The total content of metal ions and the content of metal ions with valence of two or more in the carbon-based material within the above ranges is conducive to maintaining a suitable slurry viscosity, thereby facilitating the coating of the slurry to obtain a negative electrode sheet with a uniform negative electrode film layer.

[0072] In some embodiments, the total content of metal ions in the carbon-based material is 20 ppm-800 ppm, and the content of metal ions with valence of two or more is 0.1 ppm-20 ppm. The total content of metal ions and the content of metal ions with valence of two or more in the carbon-based material within the above ranges is conducive to increasing the inorganic content of the SEM film, thereby reducing the generation of sodium dendrites or the precipitation of sodium on the surface of the carbon-based material, and thus improving the cycle performance.

[0073] In some embodiments, the metal ions include at least one of Na + , K + , Ca 2+ , Mg 2+ , Mn 2+ , Ba 2+ , and Al 3+ .

[0074] In some embodiments, the metal ions with valence of two or more are Ca 2+ . The content of calcium ions in the carbon-based material has a greater impact on the viscosity of the negative electrode slurry, and the content within the above range is conducive to obtaining a suitable negative electrode slurry viscosity, thereby facilitating the coating of the fast slurry and avoiding the edge void and slurry flow, and obtaining a negative electrode sheet with a uniform negative electrode film layer.

[0075] In some embodiments, the surface oxygen element content of the carbon-based material is 6%-14%. The surface oxygen element content of the carbon-based material within the above range is conducive to maintaining a suitable interaction force between the dispersant and the carbon-based material, allowing the slurry to be uniformly dispersed during the mixing process and having good fluidity, thereby facilitating the coating of the slurry without gelling phenomenon.

[0076] In some embodiments, the surface oxygen element content of the carbon-based material is 8%-12%. The surface oxygen element content of the carbon-based material within the above range is more conducive to the coating process of the slurry.

[0077] 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

[0078] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present disclosure.

[0079] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to an embodiment of the present disclosure.

[0080] FIG. 3 is a schematic view of a battery module according to an embodiment of the present disclosure.

[0081] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present disclosure.

[0082] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present disclosure.

[0083] 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.

[0084] BRIEF DESCRIPTION OF DRAWINGS 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 top cap assembly DETAILED DESCRIPTION

[0085] Hereinafter, embodiments of a sodium-ion battery, a sodium-ion battery production method, an electric device, and a carbon-based material according to the present disclosure will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are well known, repeated description of substantially identical structures are omitted. This is to avoid the following description becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, 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.

[0086] The ranges disclosed herein are defined by their lower and upper limit, given that a range is defined by selecting a lower limit and an upper limit, the selected lower and upper limits define the boundaries of a particular range. Ranges defined by such limits are inclusive 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 a range of 60-120 and a range of 80-110 are listed for a particular parameter, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then 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" indicates a shorthand way of describing all of the real combinations of "a-b," wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all of the real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand way of describing these numerical combinations. In addition, when a parameter is stated to be an integer > 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0087] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0088] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions.

[0089] Unless otherwise specified, all steps of the present disclosure can be performed in sequence or randomly, and preferably in sequence. For example, a method comprises steps (a) and (b) indicates that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, it is mentioned that the method can further comprise step (c), indicating 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.

[0090] The carbon-based material has a rich pore structure. Generally, increasing the amount of micropores below 2 nm in the porous structure of the carbon-based material is beneficial for sodium storage to improve the gravimetric capacity, but a large amount of micropores is not conducive to the kinetic performance and can cause sodium precipitation risk. On the other hand, micropores in the carbon-based material can store sodium and also allow gas molecules to enter and exit, causing bubbling.

[0091] Specifically, the current theory believes that a large number of micropores will slow down the electrolyte infiltration, the Na intercalation site will be greatly hindered at a high rate, the charge transfer will be further hindered, the kinetic performance will be significantly deteriorated, and part of the sodium ions will be reduced to metallic Na and precipitated at the interface. At the same time, the proportion of this part of the microporous structure will increase the surface area, form more solid electrolyte interface (SEI) films, and consume more active ions, further exacerbating the occurrence of sodium precipitation. In addition, too many microporous structures will enhance the entry and exit of gas molecules, causing continuous bubbling during processing. For carbon-based materials that continue to produce gas and bubble, such as carbon-based materials that still bubble after 2 hours of pulping, processing is difficult to proceed, and the prepared negative electrode sheet has a risk of exposing the underlying negative current collector, resulting in negative electrode sheet defects, reducing the performance of the sodium ion battery, and the defects in the electrode coating may also cause differences in the concentration distribution of electrons and Na ions on the surface of the electrode sheet, increasing the risk of sodium precipitation, and further causing safety hazards in the use of the battery.

[0092] Based on this, the present disclosure provides a sodium ion battery, a sodium ion battery preparation method, an electric device and a carbon-based material. The above-mentioned scheme can improve the kinetic performance, reduce the risk of negative electrode slurry leakage on the surface of the current collector, and improve the performance and safety of the sodium ion battery. The following are described in detail respectively.

[0093] Sodium ion battery

[0094] The first aspect of the present disclosure provides a sodium ion battery, comprising a negative electrode sheet. The negative electrode sheet comprises 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 comprises a carbon-based material, wherein the carbon-based material comprises a porous structure, and the porous structure comprises pores with a pore size of 2-8 nm, and the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g-0.0040 cm 3 / g, as determined by nitrogen adsorption method.

[0095] The carbon-based material in the negative electrode sheet provided by the present disclosure has an optimized pore structure. Specifically, the pore volume of the pores with a pore size of 2-8 nm in the carbon-based material is 0.0004 cm 3 / g-0.0040 cm 3 / g. Through research, it is found that the pores with a pore size of 2-8 nm can improve the kinetic performance of the carbon-based material when the pore volume is appropriate, and the pores with this pore size can also contribute part of the capacity, so that the negative electrode sheet can have improved kinetic performance and capacity.

[0096] Exemplarily, the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g, 0.0008 cm 3 / g, 0.0010 cm 3 / g, 0.0012 cm 3 / g, 0.0014 cm 3 / g, 0.0016 cm 3 / g, 0.0018 cm 3 / g, 0.0020 cm 3 / g, 0.0022 cm 3 / g, 0.0024 cm 3 / g, 0.0026 cm 3 / g, 0.0028 cm 3 / g, 0.0030 cm 3 / g, 0.0032 cm 3 / g, 0.0035 cm 3 / g, 0.0040 cm 3 / g or a value between any two of the numerical values.

[0097] In the present disclosure, the pore volume of the carbon-based material is in the meaning known in the art and can be determined by instruments and methods known in the art. Illustratively, the method known in the art can be a gas adsorption characterization technique, mercury intrusion method, etc. Illustratively, the nitrogen adsorption method can be used to test the adsorption and desorption isotherms according to GB / T 19587-2017, and the DFT model is used to fit the cumulative pore volume distribution curve with respect to the pore size, and the pore volume of the pores with a pore size ranging from 2 nm to 8 nm is obtained. The carbon-based material can be the carbon-based material as a raw material, or can be obtained from the carbon-based material obtained by disassembling and separating the sodium-ion battery.

[0098] In some embodiments, the pore volume of the pores with a pore size of 2 nm to 8 nm of the carbon-based material determined by the nitrogen adsorption method is 0.0010 cm 3 / g to 0.0040 cm 3 / g. Thus, it is more conducive to improve the kinetic performance of the carbon-based material and balance the specific capacity.

[0099] In some embodiments, the pore volume of the pores with a pore size of 2 nm to 8 nm of the carbon-based material determined by the nitrogen adsorption method accounts for 3.5% to 30% of the total pore volume of the carbon-based material. Thus, it is further conducive to balance the kinetic performance and specific capacity of the carbon-based material, and maintain suitable structural stability. Illustratively, the proportion of the pore volume of the pores with a pore size of 2 nm to 8 nm to the total pore volume of the carbon-based material is 3.5%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30% or a value between any two of the numerical values.

[0100] In some embodiments, the pore volume of pores having a pore diameter of less than or equal to 1 nm of the carbon-based material is denoted as VI, the pore volume of pores having a pore diameter of 1 nm to 2 nm of the carbon-based material is denoted as V2, and VI + V2 is in the range of 0.0006 cm3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm 3 / g.

[0101] By further limiting VI + V2 in the above range, it is more advantageous to make the carbon-based material have a suitable gravimetric capacity.

[0102] Illustratively, VI + V2 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, 0.0038 cm 3 / g, 0.0040 cm 3 / g, 0.0043 cm 3 / g, 0.0045 cm 3 / g, 0.0048 cm 3 / g, 0.0050 cm 3 / g or a value between any two of the numerical values.

[0103] VI, the pore volume of pores having a pore diameter of less than or equal to 1 nm of the carbon-based material, can be determined by conventional methods in the art. For example, CO2adsorption-desorption pore volume pore diameter test method. By this method, the pore volume of pores having a pore diameter of 1 nm or less, in particular in the range of 0.4 nm to 1 nm, is usually determined. Illustratively, the CO2adsorption method can be used to test the adsorption and desorption isotherms, and a DFT model is used to fit the cumulative pore volume versus pore diameter distribution curve, and the pore volume of pores having a specific pore diameter range of less than or equal to 1 nm is obtained.

[0104] V2, the pore volume of pores having a pore diameter of 1 nm to 2 nm of the carbon-based material, can be determined by conventional methods in the art. For example, the above-mentioned N2adsorption-desorption pore volume pore diameter test method.

[0105] For the total pore volume of the carbon-based material, conventional methods in the art can be used. For example, the above-mentioned N2adsorption-desorption pore volume pore size test method is combined with the CO2adsorption-desorption pore volume pore size test method to obtain the pore volume of pores with a pore size of 1 nm or more and the pore volume of pores with a pore size of less than 1 nm, respectively, and then the two are added together to obtain the total pore volume.

[0106] In some embodiments, V1+V2 is in the range of 0.0006 cm3 / g to 0.0035 cm3 / g. 3 3 Further research found that pores with a pore size of 2 nm or less would cause a certain degree of gas bubbling during the preparation of the negative electrode slurry. For carbon-based materials that continuously produce gas bubbles, such as carbon-based materials that still bubble after 2 hours of slurry preparation, it is difficult to process, and the prepared negative electrode sheet has the risk of exposing the underlying negative current collector, leading to negative electrode sheet defects, which in turn affects the performance of the sodium-ion battery. The present application found that the pore volume of pores with a pore size of 2 nm or less in the range of 0.0006 cm3 / g to 0.0035 cm3 / g is also beneficial to reducing the gas bubbling phenomenon during the slurry preparation process, improving the processability of the carbon-based material, and improving the uniformity of the negative electrode sheet, reducing the risk of negative electrode slurry leakage, and improving the performance of the sodium-ion battery. 3 3 Further research found that pores with a pore size of 2 nm or less would cause a certain degree of gas bubbling during the preparation of the negative electrode slurry. For carbon-based materials that continuously produce gas bubbles, such as carbon-based materials that still bubble after 2 hours of slurry preparation, it is difficult to process, and the prepared negative electrode sheet has the risk of exposing the underlying negative current collector, leading to negative electrode sheet defects, which in turn affects the performance of the sodium-ion battery. The present application found that the pore volume of pores with a pore size of 2 nm or less in the range of 0.0006 cm3 / g to 0.0035 cm3 / g is also beneficial to reducing the gas bubbling phenomenon during the slurry preparation process, improving the processability of the carbon-based material, and improving the uniformity of the negative electrode sheet, reducing the risk of negative electrode slurry leakage, and improving the performance of the sodium-ion battery.

[0107] In some embodiments, V1+V2 is in the range of 0.0020 cm3 / g to 0.0035 cm3 / g. 3 3 In some embodiments, V1+V2 is in the range of 0.0020 cm3 / g to 0.0035 cm3 / g.

[0108] In some embodiments, the proportion of V1+V2 to the total pore volume of the carbon-based material is in the range of 18% to 30%. The proportion of the pore volume of pores with a pore size of 2 nm or less to the total pore volume of the carbon-based material in the above range is more beneficial to improving the gram capacity of the carbon-based material.

[0109] For example, the proportion of V1+V2 to the total pore volume is 18%, 20%, 23%, 25%, 28%, 30%, or a value between any two of the above values.

[0110] For the total pore volume of the carbon-based material, conventional methods in the art can be used. For example, the above-mentioned N2adsorption-desorption pore volume pore size test method is combined with the CO2adsorption-desorption pore volume pore size test method to obtain the pore volume of pores with a pore size of 1 nm or more and the pore volume of pores with a pore size of less than 1 nm, respectively, and then the two are added together to obtain the total pore volume.

[0111] ​​​The dV / d(logD) referred to in the present disclosure reflects the pore volume contributed by unit pore size, which can be determined by gas adsorption characterization techniques on carbon-based materials. For example, it can be determined by a specific surface apparatus-static capacity method. Specifically, according to embodiments of the present disclosure, it can be measured by a flow method gas adsorption specific surface area measuring device (device model Micromeritics ASAP-2460). Nitrogen adsorption method test adsorption and desorption isotherms are obtained, and a DFT model is used to fit the dV / d(logD) distribution curve with respect to the pore size D. The maximum value is read in the range of 1.0 nm-2.0 nm of the pore size.

[0112] 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 of the pores with a pore size in the range of 1.0 nm-1.5 nm with respect to 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)). This is more conducive to reducing the gas bubble phenomenon in the pulping process.

[0113] Illustratively, the maximum value of dV / d(logD) of the pores with a pore size in the range 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 cm 3 / (g·log(nm)), 0.009 cm 3 / (g·log(nm)), or a value between any two of the above-mentioned values.

[0114] In some embodiments, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores with a pore size in the range of 1.0 nm-1.5 nm with respect to 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))-0.006 cm 3 / (g·log(nm)). This is further conducive to reducing the gas bubble phenomenon in the pulping process.

[0115] In some embodiments, the pore volume of pores with a pore size of 1.0 nm-1.5 nm accounts for 6% to 14% of the total pore volume of the carbon-based material. This further helps to reduce the gas production phenomenon in the pulping process. Illustratively, the pore volume of pores with a pore size of 1.0 nm-1.5 nm accounts for 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% of the total pore volume, or a value between any two of the above values.

[0116] In some embodiments, the negative electrode film layer further comprises an intercalation-type sodium storage material, the intercalation-type sodium storage material has a crystal face spacing d 002 satisfying: 0.24 nm≤d 002 ≤0.8 nm. Thus, the intercalation-type sodium storage material with the crystal face spacing within the above range can interlayer slip in the microstructure, which helps to increase the powder compaction density of the negative electrode sheet when applied in a sodium ion battery, thereby helping to improve the energy density of the sodium ion battery. The mass content of the intercalation-type sodium storage material in the negative electrode film layer is less than or equal to 10%. Alternatively, the mass content of the intercalation-type sodium storage material is between 0.5% and 5%.

[0117] In some embodiments, the intercalation-type sodium storage material comprises at least one of a carbon-based intercalation-type sodium storage material, a sulfur-based intercalation-type sodium storage material, a titanium-based intercalation-type sodium storage material; the carbon-based intercalation-type sodium storage material comprises at least one of a soft carbon intercalation-type sodium storage material, a modified graphite intercalation-type sodium storage material; the soft carbon has an I D / I G satisfying: 0.9≤I D / I G ≤1.6, 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 .

[0118] In some embodiments, the negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer arranged in a stack, the first negative electrode film layer is arranged between the negative electrode current collector and the second negative electrode film layer, the first negative electrode film layer comprises a first active material, and the second negative electrode film layer comprises a second active material; the first active material and the second active material respectively comprise at least one of a carbon-based material and an intercalation-type sodium storage material, and at least one of the first active material and the second active material comprises a carbon-based material. The intercalation-type sodium storage material can affect the sodium storage mechanism of the negative electrode active material, reduce the deposition of sodium ions in the carbon-based material to form metal-like sodium, thereby reducing the risk of thermal runaway of sodium ions.

[0119] In some embodiments, the first active material comprises a carbon-based material, and the second active material comprises a soft carbon intercalation type sodium storage material. In this way, the kinetic performance is more favorably improved.

[0120] In addition to improving the specific capacity and kinetic performance and effectively reducing the problem of gas bubble generation, the carbon-based material of the further embodiment of the present disclosure has further improved processability.

[0121] In some embodiments, the total content of metal ions in the carbon-based material is ≤800 ppm, and the content of metal ions with valence of two or more is ≤20 ppm.

[0122] The present disclosure finds that the total content of metal ions and the content of metal ions with valence of two or more in the above range have little effect on other ingredients in the negative electrode slurry, such as thickening agents, dispersants, etc., and in particular, sodium carboxymethyl cellulose, which is conducive to maintaining a suitable viscosity of the slurry during slurry preparation, thereby facilitating uniform coating of the slurry on the negative electrode current collector.

[0123] The metal ions in the carbon-based material may, for example, be introduced by the metal elements contained in the carbon source or by doping. For hard carbon prepared from a carbon source with high metal element content such as biomass or pitch / coal, when the total amount of metal ions, in particular the total amount of metal ions with valence of two or more, is in the above range, it is particularly advantageous for the slurry preparation and coating process.

[0124] The content of metal ions in the carbon-based material can be measured by conventional methods in the art. For example, inductively coupled plasma atomic emission spectrometry, etc.

[0125] In some embodiments, the total content of metal ions in the carbon-based material is 20 ppm-800 ppm, and the content of metal ions with valence of two or more is 0.1 ppm-20 ppm. By further bringing the total content of metal ions and the content of metal ions with valence of two or more in the above range, the present disclosure can not only improve the processability of the carbon-based material, but also increase the inorganic content of the negative electrode SEI film, which is conducive to reducing the generation of sodium dendrites or sodium precipitation on the surface of the carbon-based material.

[0126] In some embodiments, the metal ions include at least one of Na + , K + , Ca 2+ , Mg 2+ , Mn 2+ , Ba 2+ , Al 3+ , but are not limited thereto.

[0127] In some embodiments, the metal ions with valence of two or more are Ca 2+The research finds that the content of calcium ions in the carbon-based material has a greater impact on the negative electrode slurry. Controlling the content of calcium ions in the above range is conducive to obtaining a negative electrode slurry with a suitable viscosity and conducive to subsequent coating processes, thereby obtaining a negative electrode sheet with improved quality.

[0128] In some embodiments, the surface oxygen element content of the carbon-based material is 6%-14%. The surface of the carbon-based material usually has some oxygen-containing groups, such as -COOR, -COOH, -C=O, -OH, -C-O-C-, etc. The research finds that different surface oxygen element contents affect the viscosity of the slurry, and in turn affect the processing performance. It is speculated that when the amount of these oxygen-containing groups is too large, it interacts with the components in the slurry such as the binder, thickener, etc., affects the uniform dispersion of the system, causes gelation, and the degree of gelation increases with the increase of the standing time. This will affect the subsequent process, block the filter core, or cause the surface of the coated electrode sheet to be uneven.

[0129] For example, the surface oxygen element content of the carbon-based material is 6%, 7%, 8%, 9%, 9.5%, 10%, 10.5%, 11%, 12%, 13%, 14%, or a range formed by any two of the above values.

[0130] In some embodiments, the surface oxygen element content of the carbon-based material is 8%-12%. The surface oxygen element content of the carbon-based material in the above range is more conducive to improving the coating performance of the carbon-based material.

[0131] The carbon-based material of the present disclosure can further satisfy one or more of the following to further improve the performance of at least one aspect of the carbon-based material, such as the reversible capacity, the compaction density, etc.

[0132] (1) The carbon-based material has a surface coating layer. The surface coating layer can reduce surface defects.

[0133] In some embodiments, the surface coating layer is a carbon coating layer.

[0134] (2) The carbon-based material has an I D / I G ≤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 carbon-based material has an I D / I G Within the above range, the appropriate proportion of disordered carbon on the surface of the carbon-based material can be maintained, and a certain amount of layered structure of ordered carbon is conducive to improving the compaction density of the carbon-based material by slipping between carbon layers, and improving the energy storage density of the negative electrode.

[0135] In some embodiments, the carbon-based material has an I D / I G of 0.7-1.32. For example, the carbon-based material has an I D / I G of 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.30, or any value within a range between any two of these values.

[0136] (3) The carbon-based material has a number distribution particle size Dn10 of 0.5-1.0 μm, which is more conducive to the compaction density of the negative electrode sheet, and in addition, fewer low particle size particles indicate that the pore structure of the carbon-based material is appropriate and the material skeleton strength is moderate.

[0137] (4) The particle size of the carbon-based material satisfies: the volume distribution particle size Dv10 of the carbon-based material is ≤3.0 μm; the volume distribution particle size Dv50 of the carbon-based material is ≤7.9 μm; and the volume distribution particle size Dv90 of the carbon-based material is ≤15 μm. The particle size of the carbon-based material satisfies the above collocation, which is further conducive to the compaction density of the negative electrode sheet.

[0138] (5) The compaction density ρ1 of the carbon-based material under 50000 N is ≥0.9 g / cm 3 .

[0139] (6) The specific surface area of the carbon-based material is 2 m 2 / g-12 m 2 / g. The specific surface area of the carbon-based material within the above range is conducive to obtaining an appropriate pore structure and balancing the gram capacity.

[0140] In some embodiments, the specific surface area of the carbon-based material is 3 m 2 / g-8 m 2 / g. The specific surface area of the carbon-based material within the above range is more conducive to balancing the gram capacity.

[0141] (7) The tap density ρ2 of the carbon-based material is 0.75 g / cm 3 -0.9 g / cm 3 .

[0142] 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.

[0143] 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, is (2-5):(5-8).

[0144] In some embodiments, the carbon-based material is a mixture of hard carbon material and graphite, wherein the mass ratio of graphite to hard carbon material is (1-2.5):(7.5-9), optionally (1.5-2.2):(7.8-8.5).

[0145] In some embodiments, when the carbon-based material is a mixture of hard carbon material and soft carbon material, the hard carbon material and the soft carbon material can be distinguished by thermal gravimetric analysis. Specifically, the thermal stability of the hard carbon material and the soft carbon material is different. The soft carbon material is relatively stable at high temperature due to having a certain graphitization structure, and the thermal weight loss curve is relatively flat. The hard carbon material contains more amorphous carbon and heteroatoms, and thermal decomposition and oxidation reactions can occur at a lower temperature, and the thermal weight loss is relatively large, and the thermal weight loss curve has a large slope in 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 hard carbon material and soft carbon material.

[0146] 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 a 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 >1. By analyzing the X-ray diffraction peak and Raman spectrum of the carbon-based material, it can be determined whether the carbon-based material contains hard carbon material and graphite.

[0147] In the present disclosure, the pore volume and specific surface area of the carbon-based material are of the meanings well known in the art and can be determined using instruments and methods known in the art. For example, the specific surface area of the carbon-based material can be determined by testing the adsorption and desorption isotherms using the nitrogen adsorption method according to GB / T 19587-2017, using the BET (Brunauer Emmett Teller) method to calculate the specific surface area, using the DFT model to fit the cumulative pore volume versus pore size distribution curve and the dV / d(logD)-D curve, and obtaining the pore volume of the pores in a specific pore size range of 1 nm or more. The testing instrument can be, for example, an ASAP-2460 specific surface area and pore size analyzer from Micromeritics, USA. The kinetic diameter of a carbon dioxide molecule is smaller than that of a nitrogen molecule, and the saturation vapor pressure at 273 K is higher, so the gas can diffuse faster into a void of 1 nm or less at this temperature, thereby enabling analysis and detection of smaller microporous structures. Therefore, the pore volume of the pores in a specific pore size range of 0-1 nm can be obtained by testing the adsorption and desorption isotherms using the carbon dioxide adsorption method, using the DFT model to fit the cumulative pore volume versus pore size distribution curve.

[0148] In the present disclosure, the metal elements and their contents of the carbon-based material can be determined using instruments and methods known in the art. For example, the metal elements and their contents can be determined by testing according to the inductively coupled plasma atomic emission spectrometry method of US EPA 6010D-2014, using a testing instrument such as, for example, an ICP-OES, Thermo ICAP7400.

[0149] In the present disclosure, the surface oxygen element content of the carbon-based material can be determined using instruments and methods known in the art. For example, the surface oxygen element content can be determined by testing according to the specification requirements for data recording and reporting of surface chemical analysis X-ray photoelectron spectroscopy (XPS) of GB / T 33502-2017, using a testing instrument such as, for example, an Axis Supra+ X-ray photoelectron spectrometer.

[0150] 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 intensity of the D peak of the Raman spectrum of the material at 1350±50 cm -1 , corresponding to the breaking of symmetry, i.e., the presence of disorder and lattice defects in the structure. G represents the intensity of the G peak of the Raman spectrum of the material at 1580±50 cm -1 , corresponding to the G (graphite) band of in-plane C-C vibrations. The testing conditions are: excitation wavelength of 532 nm, testing wave number range of 500-2500 cm -1, the grating is 600 lines, the objective lens is 50 times, the integration time is 10 s, the cumulative number is 3 times, the surface scanning is obtained, and the D peak and G peak intensity of 100 points are calculated D / I G , remove the maximum and minimum 30 I D / I G , the average value of the remaining 40 points is the I D / I G of the material. The testing instrument can be Horiba LabRAM HR800 Raman spectrometer.

[0151] In the present disclosure, the tap density of the carbon-based material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, it can be measured by an electronic pressure testing machine (for example, it can be a UTM7305 type electronic pressure testing machine) according to GB / T 24533-2009. The exemplary test method is as follows: 1g of sample powder is weighed and added to a mold with a bottom area of 1.327cm 2 , pressurized to 50000N, hold for 30s, then release pressure, hold for 10s, then record and calculate the powder tap density of the material under 50000N pressure.

[0152] In the present disclosure, the tap density of the carbon-based material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, it can be measured by an electronic pressure testing machine (for example, it can be a UTM7305 type electronic pressure testing machine) according to GB / T 24533-2009. The exemplary test method is as follows: 1g of sample powder is weighed and added to a mold with a bottom area of 1.327cm 3 .

[0153] In the present disclosure, the number distribution particle size Dn10 and the volume distribution particle size Dv10, Dv50 and Dv90 of the carbon-based material are the meanings known in the art, which can be measured by instruments and methods known in the art. For example, it can be measured by a laser particle size analyzer according to GB / T 19077-2016. The testing instrument can be a Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Ltd., UK, or the particle size of the carbon-based material can be measured and counted by a microscope image.

[0154] As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0155] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as a metal foil, a lithium ion battery can employ a copper foil, and a sodium ion battery can employ an aluminum foil. 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, and 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.

[0156] In some embodiments, the negative current collector includes at least one of a copper foil, an aluminum foil, a stainless steel foil, a titanium foil, a nickel foil, a nickel-iron foil, a nickel-copper foil, and a nickel-iron-copper foil.

[0157] In some embodiments, the negative film layer can further optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), acrylate rubber, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0158] In some embodiments, the first binder can be a first aqueous binder. The first aqueous binder can be selected from one or more of styrene butadiene rubber and acrylate rubber.

[0159] In some embodiments, the negative film layer can further optionally include an aqueous dispersant. The aqueous dispersant can be selected from one or more of sodium carboxymethyl cellulose (CMC-Na), sodium alginate, xanthan gum, and carrageenan. In some embodiments, the negative film layer can further optionally include a first conductive agent. The first 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.

[0160] In some embodiments, the negative film layer can further optionally include other auxiliary agents.

[0161] In some embodiments, the negative film layer includes at least one of a first aqueous binder, an aqueous dispersant, and a first conductive agent.

[0162] In some embodiments, the mass content of the carbon-based material in the negative film layer is 80% or more.

[0163] In some embodiments, the mass content of the carbon-based material in the negative electrode film layer is above 85%. Illustratively, above 88%, above 90%, above 92%, above 94%, above 95%. Illustratively, the mass content of the carbon-based material in the negative electrode film layer is below 99.3%, below 99.0%, below 98.8%, below 98.5%, below 98.3%, below 98.0%.

[0164] In some embodiments, the mass content of the aqueous binder is 0% to 5%, optionally 0% to 3%, further optionally 0.5% to 2%.

[0165] In some embodiments, the mass content of the aqueous dispersant is 0% to 5%, optionally 0% to 2%, further optionally 0.1% to 1%.

[0166] In some embodiments, the mass content of the conductive agent is 0% to 5%, optionally 0% to 2%, further optionally 0.1% to 2%.

[0167] In some embodiments, the negative electrode tab further comprises a primer layer; the thickness of the primer layer is 0.5 μm to 3 μm. In this way, the tab coating quality is improved.

[0168] In some embodiments, the primer layer comprises inorganic oxide and a second aqueous binder. The inorganic oxide has a large density and better affinity with the metal current collector substrate, and is less likely to shrink or displace under the surface tension of the slurry compared to the carbon-based material or the conductive agent in the film layer. The aqueous slurry comprising the aqueous binder has a large surface tension, and when coated on the current collector, there is often a large surface energy difference and poor coating quality. The inclusion of inorganic oxide in the primer layer can particularly solve the problem of poor compatibility of the aqueous slurry with the current collector substrate, and improve the coating quality of the aqueous slurry on the current collector substrate. In this way, the risk of missing coating is reduced, and the tab coating quality is improved.

[0169] In some embodiments, in the primer layer, the inorganic oxide comprises one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide; the mass content of the inorganic oxide in the primer layer is 30% to 60%. The inclusion of inorganic oxide in the primer layer within the above mass range can not only improve the tab coating quality, but also improve the tab adhesion strength, reduce the elongation rate during cold pressing of the tab, and effectively control the resistance of the current collector, while taking into account the electrochemical performance of the battery.

[0170] The second water-based binder can also be selected from one or more of styrene butadiene rubber and acrylate rubber. The second water-based binder can be the same as or different from the first water-based binder. The second water-based binder has both water and oil amphiphilicity, and can exhibit better water resistance than a linear binder that has stronger affinity with a water solvent, so that the base coat layer can remain stable during coating of an upper film layer containing an active material, and further play a role of improving coating quality of the base coat layer.

[0171] In some embodiments, the base coat layer includes an inorganic oxide, a dispersant, a second water-based binder, and a second conductive agent.

[0172] The dispersant includes one or more of polyacrylic polymers. The polyacrylic polymers can effectively disperse the inorganic oxide and assist the inorganic oxide to fully play its role. In some embodiments, the mass content of the dispersant in the base coat layer is 1%-8%, which can be selected as 1%-5%.

[0173] The second conductive agent can be selected from one or more of Super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The second conductive agent can be the same as or different from the first conductive agent. In some embodiments, the mass content of the second conductive agent in the base coat layer is 10%-40%.

[0174] In some embodiments, the base coat layer includes 30%-60% inorganic oxide, 1%-8% dispersant, 10%-40% second water-based binder, and 10%-40% second conductive agent.

[0175] In some embodiments, the base coat layer further includes a thickening agent and / or a wetting agent.

[0176] The wetting agent can be selected from one or more of polyethenoxy ether surfactants, polyether silicone surfactants, non-ionic fluorocarbon polymer surfactants, and alkyne surfactants. The mass content of the thickening agent in the base coat layer is 0.5%-4%.

[0177] The thickening agent can be selected from one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum, and carrageenan. The mass content of the thickening agent in the base coat layer is 0.2%-1%.

[0178] The sodium-ion battery includes a positive electrode sheet, a separator film between the negative electrode sheet and the positive electrode sheet, an electrolyte, and the negative electrode sheet in any of the above embodiments. The sodium-ion battery of the present disclosure is described below with appropriate reference to the accompanying drawings.

[0179] The term "sodium-ion battery" mentioned herein refers to a battery monomer, a battery module, or a battery pack. The following are described respectively.

[0180] Generally, a sodium-ion battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte (liquid), and a separator. During charging and discharging of the battery, active ions, such as sodium ions, are intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet and functions to prevent short circuiting between the positive and negative electrodes while allowing ions to pass through.

[0181] [Positive electrode sheet]

[0182] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0183] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0184] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, 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.).

[0185] In some embodiments, the battery cell is a sodium-ion battery, and the positive electrode active material can be a positive electrode active material known in the art for use in sodium-ion batteries. As an example, the positive electrode active material can include a sodium-containing layered oxide, a polyanion sodium-ion compound, a Prussian blue sodium-ion compound, etc., but the present disclosure is not limited to these materials and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries can also be used. For example, as an alternative technical solution of the present disclosure, in the sodium-containing layered oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, 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.

[0186] In some embodiments, the positive electrode active material includes at least one of a sodium-containing layered oxide, a polyanion sodium-ion compound, and a Prussian blue sodium-ion compound.

[0187] As an example, the sodium-containing layered oxide can be an iron-manganese-based layered oxide. The iron-manganese-based layered oxide includes at least one of a nickel-iron-manganese-based layered oxide and a copper-iron-manganese-based layered oxide.

[0188] As an alternative technical means of the present disclosure, the polyanionic sodium ion compound can be a compound having a sodium ion, a transition metal ion, and a tetrahedral (YO4) n- anion unit. 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 sodium ion compound can also be a compound having a sodium ion, a transition metal ion, a tetrahedral (YO4) n- anion unit, and a halogen anion. 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. The polyanionic sodium ion compound can also be a compound having a sodium ion, a tetrahedral (YO4) n- anion unit, a polyhedral unit (ZO y ) m+ , and an optional halogen anion. 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+ . The halogen can be at least one of F, Cl, and Br. The polyanionic sodium ion compound is, for example, at least one of 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).

[0189] As an alternative technical means of the present disclosure, the polyanionic sodium ion compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q dwherein A represents an alkali metal element doped to substitute Na, M represents a metal element doped to substitute V, D represents a doping element doped to substitute P, Q represents a doping element doped to substitute F, D includes at least one of Si and S, Q 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, 0≤d≤0.2z. Optionally, A includes at least one of K and Li; M includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu and Co.

[0190] As an optional technical manner of the present disclosure, the polyanionic sodium ion compound can be Na x R y (PO4)2P2O7, wherein x=3.5-4.5, y=2.75-3.25, 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.

[0191] As an optional technical manner of the present disclosure, the polyanionic sodium ion compound can be Na 4+x R 3-y P 4-m O 15 / C;

[0192] wherein 0

[0193] 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

[0194] In some embodiments, the battery cell can be a lithium ion battery, and the positive electrode active material can employ a positive electrode active material for a lithium ion battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present disclosure is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2), and a modified compound thereof, etc. Examples of the lithium-containing phosphate of an olivine structure can include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4(also referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon.

[0195] The battery is accompanied by deintercalation and consumption of active ions (Li or Na) during charging and discharging, and the molar content of Li or Na is different when the battery is discharged to different states. In the enumeration of the positive electrode active material in the present disclosure, the molar content of Li or Na is the initial state of the material, i.e., the state before feeding, and the positive electrode active material is applied to the battery system. After charging and discharging cycles, the molar content of Li or Na will change.

[0196] In the enumeration of the positive electrode active material in the present disclosure, the molar content of oxygen is only the theoretical state value, and the oxygen release of the crystal lattice will cause the molar content of oxygen to change, and the actual molar content of oxygen will appear to be floating.

[0197] In some embodiments, the positive electrode film layer further optionally includes 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.

[0198] In some embodiments, the positive electrode film layer further optionally includes 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.

[0199] [Electrolyte]

[0200] The electrolyte plays a role in conducting ions between the positive electrode tab and the negative electrode tab. The present disclosure does not have a specific limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0201] In some embodiments, the electrolyte adopts an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0202] In some embodiments, the battery cell is a sodium-ion battery, and the electrolyte salt can be selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bisfluorosulfonylimide, sodium bis-trifluoromethylsulfonylimide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluoroboric oxalate, sodium bisoxalate borate, sodium difluorodioxalate phosphate, and sodium tetrafluorodioxalate phosphate.

[0203] In some embodiments, the battery cell is a lithium-ion battery, and the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoroboric oxalate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate.

[0204] 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.

[0205] In some embodiments, the solvent in the electrolyte includes a carbonate solvent, and the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate. In this way, the high-pressure resistance of the electrolyte can be improved.

[0206] In some embodiments, the volume ratio of propylene carbonate to the volume of the solvent is 15% to 55%. In this way, the oxidation resistance of the electrolyte can be improved, and the dissociation of sodium salt can also be improved to increase the conductivity.

[0207] In some embodiments, the electrolyte 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 that can improve certain properties of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature or low-temperature performance of the battery, and the like.

[0208] [Separator]

[0209] In some embodiments, the battery cell further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The type of separator is not particularly limited in the present disclosure, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0210] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0211] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte.

[0212] 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, and the like. The outer package of the battery cell can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, and the like can be listed.

[0213] The shape of the battery cell is not particularly limited in the present disclosure, and it can be cylindrical, square, or any other shape. For example, FIG. 1 is a battery cell 5 of a square structure as an example.

[0214] In some embodiments, referring to FIG. 2, the outer package can include a housing 51 and a top cover assembly 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged 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.

[0215] 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.

[0216] 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 used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0217] 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.

[0218] 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.

[0219] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0220] Method for manufacturing sodium-ion battery

[0221] The embodiment of the present disclosure further provides a method for manufacturing a sodium-ion battery, which comprises manufacturing a negative electrode tab, wherein the manufacturing of the negative electrode tab comprises: mixing a negative electrode component and a solvent to obtain a negative electrode slurry, wherein the negative electrode component comprises a carbon-based material, the carbon-based material comprises a porous structure, the porous structure comprises pores with a pore size of 2-8 nm, and the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g-0.0040 cm 3 / g; and coating the negative electrode slurry on the negative electrode current collector. The pores with a pore size of 2 nm-8 nm and a suitable pore volume can improve the kinetic performance of the carbon-based material, and the pores with this pore size can also contribute to part of the capacity, so that the negative electrode sheet can have improved kinetic performance and capacity.

[0222] In some embodiments, the pore volume of the pores with a pore size of 2 nm-8 nm of the carbon-based material is 0.0010 cm 3 / g-0.0040 cm 3 / g. Thus, it is more beneficial to improve the kinetic performance of the carbon-based material and balance the capacity.

[0223] In some embodiments, the pore volume of the pores with a pore size of 2 nm-8 nm of the carbon-based material accounts for 3.5%-30% of the total pore volume of the carbon-based material. Thus, it is further beneficial to balance the kinetic performance and capacity of the carbon-based material, and to maintain suitable structural stability.

[0224] In some embodiments, the pore volume of the pores with a pore size of less than or equal to 1 nm of the carbon-based material is denoted as V1, and the pore volume of the pores with a pore size of 1 nm-2 nm of the carbon-based material is denoted as V2, as measured by the carbon dioxide adsorption method, then V1+V2 is in the range of 0.0006 cm 3 / g to 0.0050 cm 3 / g. By further limiting V1+V2 in the above range, it is more beneficial to make the carbon-based material have suitable capacity.

[0225] In some embodiments, V1+V2 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 of 2 nm or less is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g, it is also beneficial to reduce the gas bubble phenomenon in the slurry production process while making the carbon-based material have suitable capacity, improve the processability of the carbon-based material, and improve the uniformity of the negative electrode sheet, reduce the risk of negative electrode slurry leakage, and improve the performance of the sodium ion battery.

[0226] In some embodiments, V1+V2 is in the range of 0.0020 cm 3 / g to 0.0035 cm 3 / g.

[0227] In some embodiments, V1+V2 is 18% to 30% of the pore volume of the carbon-based material. The proportion of the pore volume of the carbon-based material in the pores having a pore diameter of 2 nm or less to the total pore volume is within the above range, which is more favorable to improving the gravimetric capacity of the carbon-based material.

[0228] In some embodiments, the carbon-based material contains pores having a pore diameter in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores having a pore diameter of 1.0 nm to 1.5 nm with respect to the logarithm of the pore diameter D, as determined by the nitrogen adsorption method, is in the range of 0.001 cm 3 / (g·log(nm)) to 0.009 cm 3 / (g·log(nm)). This is more favorable to reducing the gas evolution bubbling phenomenon in the pulping process.

[0229] In some embodiments, the carbon-based material contains pores having a pore diameter in the range of 1.0 nm to 1.5 nm, and the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores having a pore diameter of 1.0 nm to 1.5 nm with respect to the logarithm of the pore diameter D, as determined by the nitrogen adsorption method, is in the range of 0.001 cm 3 / (g·log(nm)) to 0.006 cm 3 / (g·log(nm)). This is further favorable to reducing the gas evolution bubbling phenomenon in the pulping process.

[0230] In some embodiments, the pore volume of the pores having a pore diameter of 1.0 nm to 1.5 nm of the carbon-based material is 6% to 14% of the total pore volume of the carbon-based material. This is further favorable to reducing the gas evolution phenomenon in the pulping process.

[0231] In some embodiments, the mass percentage of the carbon-based material with respect to the mass of the negative electrode slurry is 80% to 95%. Thus, the energy density of the battery is favorable. Illustratively, the mass percentage of the carbon-based material with respect to the mass of the negative electrode slurry is 80%, 82%, 85%, 87%, 90%, 92%, 95%, or a value between a range consisting of any two of the numerical values.

[0232] In some embodiments, the mass percentage of the carbon-based material with respect to the mass of the negative electrode slurry is 80% to 95%. Thus, the energy density of the battery is favorable. Illustratively, the mass percentage of the carbon-based material with respect to the mass of the negative electrode slurry is 80%, 82%, 85%, 87%, 90%, 92%, 95%, or a value between a range consisting of any two of the numerical values.

[0233] 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.

[0234] In some embodiments, the negative electrode component further comprises one or more of a conductive agent, a binder, and a dispersant. The conductive agent can effectively accelerate the electron transmission rate, thereby improving the charge and discharge efficiency of the battery. The binder is conducive to maintaining the integrity of the electrode structure during the charge and discharge process of the battery. The dispersant can improve the dispersibility of the particles of the negative electrode component in the solvent, making the slurry easy to coat.

[0235] In some embodiments, mixing the negative electrode component and the solvent comprises vacuum stirring at 0-30°C for 1-4 hours. The present disclosure does not have specific limitations on the vacuum stirring, and appropriate process conditions such as vacuum degree, temperature, time, stirring speed, etc. can be selected according to actual production needs. Generally, after vacuum stirring, the slurry can be kept uniform and stable before proceeding to the next process. In some specific embodiments, the negative electrode component comprises a carbon-based material, a dispersant, a conductive agent, and a binder, and the negative electrode slurry is prepared by mixing the carbon-based material, the dispersant, the conductive agent, and the solvent, and vacuum stirring; and further adding the binder and further stirring for 2-4 hours.

[0236] When the above-mentioned carbon-based material is used to prepare the negative electrode slurry, the bubbling time can be significantly reduced, which is conducive to the smooth progress of the slurry preparation, and also conducive to the subsequent coating and cold pressing processes, thereby improving the uniformity of the negative electrode film layer and preventing the current collector from being exposed.

[0237] In some embodiments, the preparation of the negative electrode sheet further comprises coating the negative electrode slurry on at least one surface of the negative electrode current collector and then performing processes such as drying, cold pressing, and die cutting. The present disclosure does not have specific limitations on these processes for the preparation of the negative electrode sheet, and those skilled in the art can use appropriate process methods according to actual needs.

[0238] For example, the negative electrode sheet is prepared by mixing the carbon-based material, the conductive agent (SP), the dispersant (CMC), and an appropriate amount of deionized water in a mass ratio of 93:2:3.5:1.5, and vacuum stirring, wherein the vacuum stirring is performed at room temperature for about 1-4 hours at a speed of, for example, 1000 r / min; then, the binder (SBR) is added and the stirring is continued for about 2-4 hours to form a negative electrode slurry with good fluidity; the negative electrode slurry is coated on the current collector of Cu or Al at a coating speed of 1-3 m / min, and the surface of the sheet is good without bubbles, voids, and scratches; the coated sheet is dried at 80°C, the coating speed is adjusted to 1-3 m / min, and then the sheet is wound, and the surface of the sheet has no obvious exposed foil, pinhole, or coating leakage; the required sheet is subjected to cold pressing treatment, the sheet is cut into tabs by laser, and the negative electrode process is completed, thereby obtaining the negative electrode sheet.

[0239] In some embodiments, the method for preparing the sodium-ion battery further comprises: preparing the positive electrode sheet.

[0240] The preparation of the positive electrode sheet is not particularly limited in the present disclosure, and the materials used for preparing the positive electrode sheet are as described above, and a person skilled in the art can select appropriate materials and processes to prepare the positive electrode sheet according to the needs. For example, the positive electrode sheet is prepared by mixing the positive electrode active material, the conductive agent and the binder in a mass ratio of 8:1:1, mixing the positive electrode active material (polyanion or layer oxygen-based positive electrode), the conductive agent (such as SP) and the binder (PVDF) with an appropriate amount of NMP (N-methyl pyrrolidone), and stirring at room temperature at a speed of 1000 r / min to form a positive electrode slurry with good fluidity; coating the positive electrode slurry on an Al current collector at a belt speed of 1-3 m / min, and the surface of the sheet is good without bubbles, voids and scratches; drying the coated sheet at 80°C, adjusting the belt speed to 1-3 m / min, and then winding, and the surface of the sheet is free of obvious foil exposure, pinholes or coating leakage; and the sheet meeting the requirements is subjected to cold pressing treatment, laser die cutting to form tabs and winding, and the preparation of the positive electrode sheet is completed.

[0241] In some embodiments, the method for preparing the sodium-ion battery further comprises: assembling the positive electrode sheet, the negative electrode sheet and the separator into an electrode assembly that can be prepared by a winding process or a stacking process; placing the electrode assembly in an outer package, filling with electrolyte and then packaging to form a battery cell. In some specific embodiments, the electrode assembly can be prepared by a winding process or a stacking process, and the present disclosure is not particularly limited in this regard. Further, the battery cell can be further assembled into a battery module.

[0242] Similarly, the separator and the electrolyte are not particularly limited in the present disclosure, and the materials used as the separator and the components of the electrolyte are as described above, and a person skilled in the art can select appropriate separator materials and electrolyte components according to the needs.

[0243] Electric device

[0244] 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.

[0245] The electric device mentioned in the embodiments of the present disclosure includes the sodium-ion battery provided by the present disclosure or the sodium-ion battery obtained by the method for preparing the sodium-ion battery of 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.

[0246] As the power consuming device, a battery cell, a battery module, or a battery pack can be selected according to the use requirement thereof.

[0247] FIG. 6 is a power consuming device as an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of sodium ion batteries for the power consuming device, a battery pack or a battery module can be used.

[0248] As another example of the device, a mobile phone, a tablet computer, a notebook computer, etc. can be used. The device usually requires thin and light, and a battery cell can be used as the power source.

[0249] Carbon-based material

[0250] The present disclosure also provides a carbon-based material. The carbon-based material comprises a porous structure, wherein the porous structure comprises pores with a pore size of 2-8 nm, and the pore volume of the pores with a pore size of 2-8 nm is 0.0004 cm 3 / g-0.0040 cm 3 / g, as determined by nitrogen adsorption method.

[0251] The carbon-based material provided by the present disclosure has an optimized pore structure. Specifically, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0004 cm 3 / g-0.0040 cm 3 / g, so that the kinetic performance of the carbon-based material can be improved while the specific capacity is taken into account.

[0252] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material is 0.0010 cm 3 / g-0.0040 cm 3 / g, as determined by nitrogen adsorption method. This is more conducive to the kinetic performance of the carbon-based material while the specific capacity is taken into account.

[0253] In some embodiments, the pore volume of the pores with a pore size of 2-8 nm of the carbon-based material accounts for 3.5%-30% of the total pore volume of the carbon-based material, as determined by nitrogen adsorption method. This is conducive to the balance of kinetic performance and specific capacity, and maintains suitable structural stability.

[0254] In some embodiments, the pore volume of the pores with a pore size of less than or equal to 1 nm of the carbon-based material is represented as V1, and the pore volume of the pores with a pore size of 1-2 nm of the carbon-based material is represented as V2, as determined by carbon dioxide adsorption method and nitrogen adsorption method, respectively. Then, V1+V2 is 0.0006 cm 3 / g-0.0050 cm 3Within the range of / g, the pore volume of carbon-based materials with pore sizes below 2nm within the above range is more conducive to carbon-based materials having suitable specific capacity.

[0255] In some implementations, V1+V2 is at 0.0006cm 3 / g to 0.0035cm 3 Within a range of / g, this approach, while ensuring the carbon-based material possesses a suitable specific capacity, helps reduce gas generation and bubbling during the negative electrode slurry preparation process. This results in a negative electrode sheet with improved capacity and a uniform negative electrode film layer, reducing the risk of negative electrode slurry leakage and improving sodium-ion battery performance. Preferably, within 0.0020 cm⁻¹... 3 / g to 0.0035cm 3 Within the range of / g.

[0256] In some embodiments, the proportion of V1+V2 to the total pore volume of the carbon-based material is in the range of 18% to 30%. Having the proportion of pore volume with a diameter of less than 2 nm to the total pore volume within this range is more beneficial for improving the specific capacity of the carbon-based material.

[0257] In some embodiments, the carbon-based material comprises pores with a diameter in the range of 1.0 nm to 1.5 nm. The maximum value of the derivative of the cumulative pore volume V of the pores with a diameter in the range of 1.0 nm to 1.5 nm, dV / d(logD), determined by nitrogen adsorption, is 0.001 cm⁻¹. 3 / (g·log(nm))-0.009cm 3 / (g·log(nm)). This is more conducive to reducing gas generation and bubbling during the pulping process.

[0258] For example, the maximum dV / d(logD) value for a pore with a diameter of 1.0 nm to 1.5 nm is 0.001 cm. 3 / (g·log(nm)), 0.002cm 3 / (g·log(nm)), 0.003cm 3 / (g·log(nm)), 0.004cm 3 / (g·log(nm)), 0.005cm 3 / (g·log(nm)), 0.006cm 3 / (g·log(nm)), 0.007cm 3 / (g·log(nm)), 0.008cm 3 / (g·log(nm)), 0.009cm 3 / (g·log(nm)) can be any value within a range consisting of any two of these values.

[0259] In some embodiments, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V of pores with a pore diameter of 1.0 nm-1.5 nm versus the logarithm of the pore diameter D, measured by nitrogen adsorption method, is in the range of 0.001 cm3 / (g·log(nm))-0.006 cm3 / (g·log(nm)). 3 / (g·log(nm))-0.006 cm 3 / (g·log(nm)). This is further conducive to reducing the gas bubble phenomenon during the slurry process.

[0260] In some embodiments, the pore volume of pores with a pore diameter of 1.0 nm-1.5 nm of the carbon-based material accounts for 6% to 14% of the total pore volume of the carbon-based material.

[0261] In some embodiments, the total content of metal ions in the carbon-based material is ≤800 ppm, and the content of metal ions with valence of two or more is ≤20 ppm. The total content of metal ions and the content of metal ions with valence of two or more in the carbon-based material in the above range is conducive to maintaining a suitable slurry viscosity, thereby facilitating the coating of the slurry to obtain a negative electrode sheet with a uniform negative electrode film layer.

[0262] In some embodiments, the total content of metal ions in the carbon-based material is 20 ppm-800 ppm, and the content of metal ions with valence of two or more is 0.1 ppm-20 ppm. The total content of metal ions and the content of metal ions with valence of two or more in the carbon-based material in the above range is conducive to increasing the inorganic content of the SEM film, thereby reducing the generation of sodium dendrites or the precipitation of sodium on the surface of the carbon-based material, thereby improving the cycle performance.

[0263] In some embodiments, the metal ions include at least one of Na + , K + , Ca 2+ , Mg 2+ , Mn 2+ , Ba 2+ , and Al 3+ .

[0264] In some embodiments, the metal ions with valence of two or more are Ca 2+ . The content of calcium ions in the carbon-based material has a greater impact on the viscosity of the negative electrode slurry, and the content in the above range is conducive to obtaining a suitable negative electrode slurry viscosity, thereby facilitating the coating of the fast slurry and avoiding the virtual edge and slurry flow, and obtaining a negative electrode sheet with a uniform negative electrode film layer.

[0265] In some embodiments, the carbon-based material has a surface oxygen element content of 6-14%. The surface oxygen element content of the carbon-based material within the above range is conducive to maintaining a suitable interaction force between the dispersant and the carbon-based material, so that the slurry is uniformly dispersed during mixing and has good fluidity, which is conducive to preventing the slurry from gelling during slurry preparation, thereby facilitating the coating of the slurry.

[0266] In some embodiments, the carbon-based material has a surface oxygen element content of 8-12%. The surface oxygen element content of the carbon-based material within the above range is more conducive to the coating process of the slurry.

[0267] 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.

[0268] The carbon-based material has unique physical and chemical properties such as disordered crystal structure, large interlayer spacing, and abundant pores, which enable the carbon-based material to adapt to different ion storage and transmission 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, and potassium ion batteries.

[0269] 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 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 store and release electric charges. In some embodiments, the carbon-based material can be used as a negative active material of a lithium ion battery or a negative active material of a sodium ion battery.

[0270] When the carbon-based material is a hard carbon material, the hard carbon material can be obtained by adjusting the preparation method. The preparation method of the hard carbon material is not particularly limited, and the carbon source that can be used includes pitch / coal, biomass materials, and synthetic polymer materials, etc. 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-mentioned hard carbon material can be prepared by adjusting the process conditions.

[0271] Synthetic polymer materials, such as phenolic resin, epoxy resin, furan resin, etc., have structural designability and low impurity content. By polymerizing the precursors (such as polymerized monomers or prepolymers) of the synthetic polymer materials, or by dispersing, pore-making, or etching the synthetic polymer materials, the microstructure of the carbon source can be well controlled, and thus the pore structure of the hard carbon material can be controlled.

[0272] Exemplarily, but not limited to, the method for preparing the hard carbon material with the synthetic polymer material as the carbon source comprises the following steps: a solidification step, solidifying a solution comprising a polymerization monomer or prepolymer and a solvent to obtain a carbon source; an etchant treatment step, immersing the carbon source in an etchant; a low-temperature pre-carbonization step, pre-carbonizing the immersed carbon source at a low temperature to obtain a pre-carbonized product; a crushing step, crushing the pre-carbonized product; a deashing step, and a high-temperature carbonization step.

[0273] Exemplarily, the polymerization monomer can be a monomer of a phenolic resin, an epoxy resin, a furan resin, or the like.

[0274] Exemplarily, the prepolymer can be, for example, a resol phenolic resin.

[0275] Exemplarily, the solvent is at least one of methanol, ethanol, ethylene glycol, polyethylene glycol, glycerol, isopropyl alcohol, and other polyhydric alcohols. The solvent uniformly disperses the synthetic polymer material, which is conducive to the subsequent formation of a suitable pore structure.

[0276] The present disclosure does not have a particular limitation on the temperature of solidification. Those skilled in the art can select a suitable solidification reaction temperature according to the type of the specific polymerization monomer or prepolymer. Exemplarily, when the prepolymer is a resol phenolic resin, the temperature of solidification is 80-150°C.

[0277] Exemplarily, the etchant comprises at least one of phosphoric acid, hydrogen peroxide, sulfuric acid, nitric acid, and ZnCl2.

[0278] Exemplarily, the concentration of the etchant is 5-20wt%. For example, the concentration of the etchant is 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, 19wt%, 20wt%, and a range between any two of them. Preferably, the concentration of the etchant is 7-13wt%.

[0279] In some embodiments, the temperature of the low-temperature pre-carbonization is 400-600°C. Exemplarily, the temperature of the low-temperature pre-carbonization is 400°C, 450°C, 500°C, 550°C, 600°C, and a range between any two of them. Through the low-temperature pre-carbonization treatment at the temperature, water, part of the dissolved impurities, and surface active groups can be removed, a pre-carbonized product with a suitable degree of compactness is formed, and the etchant is allowed to fully etch the pores, which is conducive to adjusting the pore structure to a suitable pore structure in the subsequent high-temperature carbonization.

[0280] Exemplarily, the crushing can be, for example, crushing by an air jet mill or mechanical grinding, which is not particularly limited by the present disclosure. 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 a suitable pore structure in the subsequent high-temperature carbonization, fully dissolving the impurities, and making the particle size distribution of the final hard carbon suitable.

[0281] For example, the deashing step can be performed by immersing the product in an acid tank with 1-5 M acid to remove metal impurities.

[0282] In some embodiments, the high temperature carbonization is performed at a temperature of 1000-1300 °C. This is advantageous to form a final suitable pore structure, thus improving the gravimetric capacity and kinetic performance. In addition, high temperature carbonization can also reduce the amount of surface defects. For example, the high temperature carbonization is performed at a temperature of 1000 °C, 1100 °C, 1200 °C, 1300 °C, and any range between any two of the foregoing temperatures. Alternatively, the high temperature carbonization is performed at a temperature of 1100-1200 °C.

[0283] In some embodiments, the preparation method further comprises a step of forming a coating layer. This step can be performed, for example, before high temperature carbonization. The present disclosure does not make special limitations on the specific coating process, and for example, it can be a conventional gas phase coating, liquid phase coating or solid phase coating in the art.

[0284] In some embodiments, the surface oxygen content of the hard carbon can be adjusted by oxidation or reduction treatment. For example, a pre-oxidation treatment can be performed before high temperature carbonization, which comprises holding at 80-400 °C in air or oxygen for 0.5-5 h. Alternatively, a reduction treatment can be performed before high temperature carbonization, which comprises holding at 400-800 °C in a mixture of hydrogen and argon for 0.5-10 h. By the above steps, the surface oxygen content of the hard carbon material can be 6-14%.

[0285] In some embodiments, the preparation method further comprises a grading treatment and a magnetic removal treatment before obtaining the final hard carbon product, which can further optimize the problems of slurry bubbling, low slurry viscosity and battery capacity decay.

[0286] In the above method, the porosity and pore structure are adjusted by steps such as etchant treatment of the carbon source, temperature and time of low temperature pre-carbonization, to obtain the above hard carbon material with improved kinetic performance and consideration of gravimetric capacity.

[0287] Biomass materials are widely available, such as coconut shell, rice husk, bamboo, wheat husk, straw, lignin, etc. Using biomass materials as carbon source has both economic and environmental effects.

[0288] Exemplarily, the preparation of hard carbon material from biomass material as carbon source includes the following steps. An etchant treatment step, in which the biomass material is mixed with an etchant for impregnation; a pre-carbonization step, in which the material is heated at 300-500°C, optionally 400-500°C for 2-6h. The etchant treatment combined with the pre-carbonization step can remove the volatile matter in the biomass, and at the same time can achieve a slight pre-pore formation. A crushing step, in which the pre-carbonized product is crushed to a particle size of Dv10≤3μm, Dv50≤3μm and Dv90≤3μm. The crushing step can enable the final hard carbon material to 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 shape with tightly packed particles, reducing the exposed area, preventing sintering and volatile matter from oxidizing and damaging the carbon, and controlling the porosity. A carbonization step, in which the material is heated at 1100-1300°C for 2-6h to remove the remaining volatile matter. Similarly, the preparation method can further include a step of forming a coating layer, for example, which can be performed before the carbonization step.

[0289] Exemplarily, the etchant includes at least one of phosphoric acid, hydrogen peroxide, sulfuric acid, nitric acid, and ZnCl2.

[0290] Exemplarily, the concentration of the etchant is 5-20wt%. For example, the concentration of the etchant is 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, 19wt%, 20wt%, and any range between any two of them. Preferably, the concentration of the etchant is 7-13wt%.

[0291] Exemplarily, the crushing can be, for example, by jet milling or mechanical grinding, which is not specifically limited in the present disclosure. 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 hard carbon suitable.

[0292] Exemplarily, in the de-ashing step, the acid includes at least one of hydrochloric acid, sulfuric acid, nitric acid, etc. De-ashing can reduce the ash content, which is various metals and their oxides.

[0293] In some embodiments, the amount of metal ions volatilized from the inside and remaining on the surface layer can be further adjusted by water washing after carbonization. For example, using coconut shell as 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 content of cations, especially divalent cations (such as calcium ions), in the final hard carbon material can be adjusted, thereby facilitating the preparation process of the electrode plate.

[0294] In the above method, the porosity and pore structure are adjusted by steps such as etchant treatment combined with pre-carbonization, and the temperature and time of carbonization step, to obtain hard carbon material with improved gravimetric capacity and kinetic performance.

[0295] Asphalt and coal are common chemical raw materials, which are widely available and low in price, so it is low in cost to prepare hard carbon material using asphalt or coal as carbon source.

[0296] Exemplarily, but not limited to, the preparation of hard carbon material using asphalt as carbon source includes the following steps. A pre-oxidation step, in which asphalt or modified asphalt is mixed with an oxidizing agent and heated at 200-300°C for 2-5h to form a hard carbon precursor. The oxygen content of the hard carbon precursor can be adjusted by the pre-oxidation step. Exemplarily, the oxidizing agent can be oxygen, nitric acid, or hydrogen peroxide, which is not particularly limited in the present disclosure. A pre-carbonization step, in which the above hard carbon precursor is heated at 400-600°C for 2-4h. A crushing step, in which the pre-carbonized product is crushed to a particle size of Dv10≤3μm, Dv50≤3μm and Dv90≤30μm. A pre-pressing step, in which the crushed product is pressed into a cake shape with close packing of particles, reducing the exposed area, preventing the oxidation damage of carbon by sintering volatiles, and controlling the porosity. A carbonization step, in which it is treated at 1000-1200°C for 2-4h. Similarly, the preparation method can further include a step of forming a coating layer, for example, which can be performed before the carbonization step.

[0297] Exemplarily, the crushing can be by air jet milling or mechanical milling, which is not particularly limited in the present disclosure. 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 a suitable pore structure in the subsequent high-temperature carbonization, fully dissolving impurities, and making the particle size distribution of the final hard carbon suitable.

[0298] In some embodiments, the preparation method further includes a deashing step and a demagnetization step after the carbonization step. A suitable deashing step can control the content of cations, especially divalent cations (such as calcium ions) in the final product, thereby further facilitating the preparation of hard carbon material for electrode plate process.

[0299] In the above method, the porosity and pore structure are adjusted by steps such as crushing of the pre-carbonized product, temperature and pressure of the pre-pressing step, temperature and time of the carbonization step, to obtain carbon-based material with improved gravimetric capacity and kinetic performance.

[0300] In some embodiments, the carbon-based material includes soft carbon material, which can be obtained by crushing, purifying, carbonizing, crushing and grinding a soft carbon precursor.

[0301] 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 the oversized or undersized particles by sieving to ensure the 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 product after carbonization.

[0302] In some embodiments, the soft carbon precursor comprises at least one of petroleum coke, pitch, and biomass.

[0303] Examples

[0304] 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 mentioned are performed in accordance with the techniques or conditions described in the literature in the field or in accordance with the product manual. The reagents or instruments used, for which the manufacturer is not mentioned, are all conventional products that can be obtained commercially.

[0305] Example 1

[0306] Preparation of hard carbon material with biomass material as carbon source:

[0307] 1) Etchant treatment

[0308] The lignin was mixed with ZnCl2 aqueous solution (10% wt) at a mass ratio of 1:3 and immersed for 12 h, and then dried.

[0309] 2) Pre-carbonization

[0310] The product obtained in step 1) above was added to a hot press furnace (TOP INDUSTRIAL TECHNOLOGY, VHP-777) and treated at 400℃ under normal pressure N2 atmosphere for 2 h to obtain a pre-carbonized product.

[0311] 3) Crushing

[0312] The pre-carbonized product obtained in step 2) above was subjected to jet milling in a jet mill (Shengxing Environmental Protection: SX1210) to obtain a product with Dv1 of 2 μm, Dv50 of 5 μm, and Dv90 of 12 μm.

[0313] 4) Deashing

[0314] The crushed product in step 3) above was immersed in a 2M aqueous hydrochloric acid solution at room temperature for 10 h in an acid washing kettle, filtered, washed with water 3 times, and then dried at 100℃ in a continuous kiln.

[0315] 5) Pre-pressing

[0316] The product obtained in step 4) above was sintered at 50T pressure for 1h in a hot press furnace (manufacturer: Dingli Science and Technology, model: VHP-777).

[0317] 6) Carbonization

[0318] The product obtained in step 5) above was sintered at 2℃ / min heating rate to 1400℃ for 2h under normal pressure N2 atmosphere, washed with water for 3 times, and then dried at 100℃ in a continuous kiln to obtain the sample of Example 1.

[0319] Preparation of negative electrode slurry:

[0320] The hard carbon material, conductive agent and dispersant were mixed in a ratio of 8:1:1 in deionized water, vacuum stirring at room temperature for 2.5h (to keep the uniform state of the negative electrode slurry within 4h after vacuum stirring without further bubbles, the vacuum stirring time is adjusted in the following examples and comparative examples according to the situation, but the longest is not more than 4h), and uniformly dispersed to obtain a uniform negative electrode slurry, wherein the dispersant is sodium carboxymethyl cellulose, and the conductive agent is conductive carbon black.

[0321] Preparation of negative electrode sheet:

[0322] The uniformly stirred negative electrode slurry was coated on both sides of the Al foil by a double-sided coating machine, and after the double-sided coating was completed, vacuum drying at 80℃, cold pressing, slitting and sheeting were sequentially performed to prepare the negative electrode sheet.

[0323] Preparation of button-type half cell:

[0324] The prepared negative electrode sheet was assembled in a glove box, a metal sodium sheet was used as the counter electrode, and an electrolyte was an EC: DMC (volume ratio) = 1:1 solvent containing NaPF6, wherein 10v / v% FEC was added.

[0325] The positive electrode sheet, the separator, and the negative electrode sheet were sequentially stacked, the above-mentioned electrolyte was added, and after packaging, standing, formation, and aging processes, a button-type half cell was prepared.

[0326] Example 2

[0327] Preparation of hard carbon material with synthetic polymer material as carbon source:

[0328] 1) Curing

[0329] 25g of anhydrous ethanol was mixed with 50g of resol (phenolic resin model 2150, solid content 80%) and stirred to obtain a uniform solution. The solution was incubated at 80℃ for 10h in an oven to obtain a hard carbon material precursor.

[0330] 2) Etchant treatment

[0331] The hard carbon material precursor obtained in step 1) above and 10wt% phosphoric acid aqueous solution were mixed and impregnated at a mass ratio of 1:3 for 12h.

[0332] 3) Low-temperature pre-carbonization

[0333] The hard carbon material precursor was coarsely broken, and then heated to 600℃ at a temperature rising rate of 2℃ / min under normal pressure in a N2 atmosphere in a tube furnace for 5h to obtain a pre-carbonized product.

[0334] 4) Breaking

[0335] The pre-carbonized product obtained in step 3) above was broken in a ball mill (MSK-SFM-1-1L planetary ball mill) at 300rpm for 2h, with zirconia as the material of the ball mill beads, and the mass ratio of the material to the ball mill beads being 1:3. The particle size distribution of the broken sample was measured by a Mastersizer 3000 laser particle size analyzer, and the Dv50 was 5μm.

[0336] 5) Deashing

[0337] The pre-carbonized product broken in step 4) above was soaked in a 2M hydrochloric acid aqueous solution at room temperature for 10h in an acid pickling kettle, filtered, washed with water for 3 times, and dried at a temperature of 100℃ in a continuous kiln.

[0338] 6) High-temperature carbonization

[0339] The product obtained in step 5) above was heated to 1150℃ at a temperature rising rate of 2℃ / min under normal pressure in a N2 atmosphere in a tube furnace for 2h.

[0340] 7) Classification

[0341] The product obtained in step 6) above was classified in an air flow classification device (manufacturer: Jing Hua Powder, model: AB03), the particle size of the outflow was continuously monitored and tested until the Dv50 reached 5μm, and the classification was completed.

[0342] 8) Demagnetization

[0343] The product obtained in step 7) above was demagnetized in a demagnetization device (manufacturer: Wan Yedai Magnetoelectric, model: GDG-250) until the magnetism of the product disappeared.

[0344] Preparation of negative electrode slurry, negative electrode sheet and button half-cell:

[0345] According to a method similar to that of Example 1, the hard carbon material of the present example was used to prepare a negative electrode slurry, a negative electrode sheet, and a button half-cell.

[0346] Example 3

[0347] Preparation of hard carbon material using pitch / coal as hard carbon material precursor:

[0348] 1) Pre-oxidation

[0349] The modified coal pitch (8994-94-4) was added to an oxidation reactor, and normal pressure air was introduced, and heated at 300°C for 3h.

[0350] 2) Pre-carbonization

[0351] The pre-oxidized pitch obtained in step 1) above was heated at 450°C for 3h in a tube furnace.

[0352] 3) Pre-pressing

[0353] The product obtained in step 2) above was pressed at 30T for 1h in a hot press (manufacturer: Dingli Science and Technology, model: VHP-777).

[0354] 4) Carbonization

[0355] The product obtained in step 3) above was heated at 1100°C for 2h in a tube furnace under normal pressure N2 atmosphere.

[0356] 5) Deashing

[0357] The product obtained in step 4) above was immersed in 2M hydrochloric acid aqueous solution at room temperature for 10h in an acid pickling kettle, filtered, washed with water 3 times, and dried at 100°C in a continuous kiln.

[0358] 6) Demagnetization

[0359] The product obtained in step 5) above was demagnetized in a demagnetization device (manufacturer: Wan Yedam, model: GDG-250) until the product lost its magnetism.

[0360] Preparation of negative electrode slurry, negative electrode sheet, and button half cell:

[0361] The negative electrode slurry, negative electrode sheet, and button half cell were prepared according to the method similar to that of Example 1, using the hard carbon material prepared in this example.

[0362] Example 4

[0363] The hard carbon material was prepared according to the method similar to that of Example 2, except that the hard carbon material precursor was mixed and impregnated with 20% phosphoric acid aqueous solution when preparing the hard carbon material.

[0364] Example 5

[0365] The hard carbon material was prepared according to the method similar to that of Example 2, except that the hard carbon material precursor was mixed and impregnated with 10% phosphoric acid aqueous solution at a mass ratio of 1:5 when preparing the hard carbon material.

[0366] Comparative Example 1

[0367] The hard carbon material was prepared in a similar manner as in Example 1, except that the precursor was not impregnated with ZnCl2 aqueous solution and the high-temperature sintering condition was 1500°C for 10 h.

[0368] Comparative Example 2

[0369] The hard carbon material was prepared in a similar manner as in Example 1, except that the raw material was mixed with 50 wt% ZnCl2 aqueous solution at a mass ratio of 1:1 for impregnation.

[0370] Hard carbon material related tests:

[0371] Gas adsorption test

[0372] For the hard carbon material, nitrogen and carbon dioxide adsorption methods were used to test the adsorption and desorption isotherms, respectively, according to GB / T 19587-2017. Both the nitrogen and carbon dioxide adsorption methods used a specific surface and porosity analyzer (Micromeritics ASAP-2460, USA). The specific surface area of the hard carbon material was calculated using the BET (Brunauer Emmett Teller) method based on the adsorption and desorption isotherms measured by the nitrogen adsorption method. The dV / d(logD) distribution curve versus pore diameter D was fitted using the DFT model, and the maximum value was read in the pore diameter range of 1.0-2.0 nm. The cumulative pore volume distribution curve versus pore diameter was also fitted, and the pore volume V2 of the pores in the pore diameter range of 1 nm-2 nm and the pore volume of the pores with a pore diameter of more than 1.0 nm were obtained. The cumulative pore volume distribution curve versus pore diameter was fitted using the DFT model based on the adsorption and desorption isotherms measured by the carbon dioxide adsorption method, and the pore volume V1 of the pores in the pore diameter range of less than 1 nm was obtained. The test results are shown in Table 1. The total pore volume of the hard carbon material was the sum of the pore volume of the pores in the pore diameter range of more than 1 nm and V1.

[0373] Hard carbon material gram capacity and average Na insertion voltage test

[0374] The coin-type half-cells of the above examples and comparative examples were subjected to sodium insertion at a rate of 0.05C to 0V, and the obtained capacity was the initial charge capacity and charge capacity. Sodium extraction at a rate of 0.1C to a cutoff voltage of 2.5V, and the obtained capacity was the initial discharge capacity. The mass of the hard carbon material in the negative electrode tab was calculated based on the coating weight and area of the slurry in the above tab preparation process, and the gram capacity was further calculated.

[0375] Gram capacity = initial charge capacity / mass of hard carbon material.

[0376] The average Na-embedding voltage V is calculated by the following formula:

[0377] The average Na-embedding voltage = the first charge energy / capacity.

[0378] The greater the average Na-embedding voltage, the faster the cross-sectional charge transfer and the greater the Na-embedding rate under the same conditions.

[0379] The pore characteristics, average Na-embedding voltage, and specific capacity test results of the hard carbon materials prepared in Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0380] Table 1:

[0381] As can be seen from Table 1, the pore volume of the pores with a pore size of 2 nm-8 nm of the hard carbon material is 0.0004 cm 3 / g-0.0040 cm 3 / g, which provides better capacity and improved kinetic performance.

[0382] The present disclosure found that, in the study of the processability of the negative electrode sheet prepared from the hard carbon material, due to the rich pore structure of the hard carbon material, gas bubbles are continuously produced during the preparation of the negative electrode slurry from the hard carbon material, such as the hard carbon material that still bubbles after 2 hours of starting the slurry preparation, which makes the process difficult to proceed, and the prepared negative electrode sheet has the risk of exposing the underlying negative electrode current collector, which can cause defects in the negative electrode sheet and thus affect the performance of the sodium ion battery. The following examples further adjust the pore structure to improve the processability.

[0383] Example 6

[0384] The hard carbon material was prepared in a similar manner to Example 2, except that during the preparation of the hard carbon material, the hard carbon material precursor and the phosphoric acid aqueous solution were mixed and immersed for 6 h, and the temperature of the high-temperature carbonization was 1200°C.

[0385] Example 7

[0386] The hard carbon material was prepared in a similar manner to Example 2, except that during the preparation of the hard carbon material, the hard carbon material precursor was not subjected to phosphoric acid oxidation treatment, and the temperature of the high-temperature carbonization was 1300°C.

[0387] Example 8

[0388] The hard carbon material was prepared in a similar manner to Example 2, except that during the preparation of the hard carbon material, the hard carbon material precursor and the 80 wt% phosphoric acid aqueous solution were mixed and immersed, and the temperature of the high-temperature carbonization was 1300°C.

[0389] Test of bubbling in the preparation of negative electrode slurry

[0390] The hard carbon materials prepared in the above examples and comparative examples were observed for the time when bubbling stopped during preparation of the negative electrode slurry. The cases where bubbling continued for 2 hours after mixing the components of the negative electrode slurry to prepare the slurry were recorded.

[0391] In addition, 50 g of the hard carbon materials prepared in the above examples and comparative examples were respectively added to a 500 mL closed reaction vessel equipped with temperature and pressure sensors, 200 mL of water was added, and then the reaction vessel was quickly closed, and stirring was started until the temperature and pressure became constant. The volume of gas emitted per unit mass of the hard carbon material was calculated based on the pressure change value and the ideal gas equation, as a measure of the amount of bubbling.

[0392] The pore characteristics, bubbling, kinetic performance, and gram capacity test results of the hard carbon materials prepared in Examples 2 and 6-8 above are shown in Table 2.

[0393] Table 2:

[0394] As can be seen from Table 2, the pore volume of the hard carbon material in the pores with a pore diameter of less than 2 nm is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g, which is beneficial to reducing the gas production bubbling phenomenon during the slurry preparation process while improving the gram capacity. The proportion of the pore volume of the hard carbon material in the pores with a pore diameter of less than 2 nm to the total pore volume is in the range of 18% to 30%, which is beneficial to making the hard carbon material have a suitable gram capacity.

[0395] Example 9

[0396] The hard carbon material was prepared in a similar manner to Example 2, except that during preparation of the hard carbon material, the hard carbon material precursor and the aqueous phosphoric acid solution were mixed and impregnated at a mass ratio of 1:1 for 6 h, and the temperature for high-temperature carbonization was 1200°C.

[0397] Example 10

[0398] The hard carbon material was prepared in a similar manner to Example 2, except that during preparation of the hard carbon material, the concentration of the aqueous phosphoric acid solution was 30%, and the temperature for high-temperature carbonization was 1200°C.

[0399] The pore characteristics, bubbling, kinetic performance, and gram capacity test results of the hard carbon materials prepared in Examples 9 and 10 above are shown in Table 3.

[0400] Table 3:

[0401] As can be seen from Table 3, when the maximum value of dV / d(logD) is in the range of 0.001 mL / (g·nm) to 0.009 mL / (g·nm), the gram capacity and kinetic performance are improved, and the continuous bubbling is further reduced.

[0402] Example 11

[0403] The hard carbon material was prepared according to the similar method of Example 1, except that the number of water washing after carbonization was 2 times.

[0404] Example 12

[0405] The hard carbon material was prepared according to the similar method of Example 1, except that the number of water washing after carbonization was 1 time.

[0406] Example 13

[0407] The hard carbon material was prepared according to the similar method of Example 1, except that the concentration of hydrochloric acid used was 1 M.

[0408] Metal ion content test

[0409] The hard carbon materials of Examples 1 and 11-13 were used to prepare negative electrode slurries with a solid content of 20%, and the slurries were stirred for half an hour, and then filtered to obtain clear liquids, which were used to test the ion contents of water-soluble Ca, Mg, Na and K.

[0410] Negative electrode slurry viscosity test after standing for 24 h

[0411] The appropriate rotor was selected, the viscometer was fixed, and the negative electrode slurries of Examples 1 and 11-13 were placed under the viscometer after standing for 24 h, with the slurry just submerging the scale line of the rotor. The instrument model was Shanghai Fangrui NDJ-5S, the rotor was 63# (2000-10000 mPa.s) or 64# (10000-50000 mPa.s), the rotation speed was 12 r / min, the test temperature was 25°C, and the test time was 5 min. The data was read when the reading was stable.

[0412] The test results of the metal ion contents and the negative electrode slurry viscosities of the hard carbon materials prepared in Examples 1 and 11-13 are shown in Table 4.

[0413] Table 4:

[0414] As can be seen from Table 4, when the total content of metal ions is below 800 ppm, and the content of metal ions with a valence of two or more is low, such as about 20 ppm or less, it is beneficial to maintain the viscosity of the slurry during slurry preparation, thereby facilitating uniform coating of the slurry on the negative electrode current collector and facilitating processing. In general, a slurry viscosity of 4000 Pa.s or more is more advantageous. The uneven coating phenomenon, such as wavy edge, can be effectively reduced. In Example 13, although the total amount of metal ions is low, the concentration of Ca 2+ is too large, and the content of Ca 2+Complexation with CMC-Na, resulting in the difficulty of CMC-Na to capture free water, weakening its dispersant effect, leading to too low viscosity of the slurry, which is not conducive to the coating of the slurry.

[0415] Example 14

[0416] The hard carbon material was prepared according to the method similar to Example 2, except that during the preparation of the hard carbon material, the etchant treatment was impregnated with 10% phosphoric acid aqueous solution for 6h.

[0417] Example 15

[0418] The hard carbon material was prepared according to the method similar to Example 2, except that during the preparation of the hard carbon material, the etchant treatment was impregnated with 20% phosphoric acid aqueous solution for 5h.

[0419] Example 16

[0420] The hard carbon material was prepared according to the method similar to Example 2, except that during the preparation of the hard carbon material, no etchant treatment was made, and the pre-carbonization was reduced at 500℃ under Ar / H2(95:5) mixed gas atmosphere for 2h.

[0421] Example 17

[0422] The hard carbon material was prepared according to the method similar to Example 2, except that during the preparation of the hard carbon material, the etchant treatment was impregnated with 30% phosphoric acid aqueous solution for 6h.

[0423] Surface oxygen element content test

[0424] For the hard carbon materials of Examples 2, 14-17, referring to GB / T 33502-2017, three different parts of the same material were selected, and the surface oxygen element content of the hard carbon material was tested by X-ray photoelectron spectroscopy (instrument model Axis Supra / Supra+).

[0425] Gelation degree of negative electrode slurry

[0426] The hard carbon materials prepared in Examples 2 and 14-17 above were observed when preparing negative electrode slurry, for example, by picking up the slurry with a small spoon and observing the dripping condition when pouring, to qualitatively judge the gelation degree.

[0427] The test results of the negative electrode slurry viscosity of the hard carbon materials prepared in Examples 2 and 14-17 and the gelation degree are shown in Table 5.

[0428] Table 5:

[0429] As can be seen from the above Table 5, the surface oxygen element of the hard carbon material is in the range of 5%-15%, which can make the viscosity of the slurry suitable and the flowability good.

[0430] Example 18

[0431] A button-type half cell was prepared in a similar manner to Example 1, except that the preparation of the negative electrode slurry was carried out as follows:

[0432] The carbon-based material (soft carbon material and hard carbon material prepared in Example 1 in a mass ratio of 5:5), conductive agent and dispersant were mixed in a ratio of 8:1:1 in deionized water, and vacuum stirring was carried out at room temperature for 2.5 h (so that the negative electrode slurry remained uniform without further bubbles appearing within 4 h after vacuum stirring, and the vacuum stirring time was adjusted in the following examples and comparative examples according to the situation, but was not more than 4 h), and a uniform negative electrode slurry was prepared by dispersion, wherein the dispersant was sodium carboxymethyl cellulose, and the conductive agent was conductive carbon black.

[0433] The carbon-based material in Example 18 was tested in a similar manner to the hard carbon material in Example 1, and the button-type half cell of Example 18 was tested in a similar manner to Example 1, and the specific test results are shown in Table 6 below.

[0434] Table 6

[0435] As can be seen from Table 6, when the carbon-based material in Example 18 is a mixture of soft carbon and hard carbon in the above ratio, it can also provide a better capacity under the premise of improved kinetic performance.

[0436] It should be noted that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope of the main idea of the present disclosure, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present disclosure.

Claims

1. 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 a porous structure, the porous structure comprising pores with a pore size of 2 nm to 8 nm. The pore volume of the pores having a pore diameter of 2 nm to 8 nm was 0.0004 cm 3 / g to 0.0040 cm 3 / g.

2. The sodium-ion battery of claim 1, wherein, The pore volume of the pores having a pore diameter of 2 nm to 8 nm of the carbon-based material is 0.0010 cm3 / g to 0.0040 cm3 / g as determined by nitrogen adsorption method. 3 / g to 0.0040 cm3 / g. 3 / g.

3. The sodium-ion battery of claim 1 or 2, wherein, The pore volume of the pores with a pore size of 2 nm to 8 nm of the carbon-based material accounts for 3.5% to 30% of the total pore volume of the carbon-based material.

4. The sodium-ion battery of any one of claims 1-3, wherein, The pore volume of pores having a pore diameter of less than or equal to 1 nm of the carbon-based material is denoted as VI, and the pore volume of pores having a pore diameter of 1 nm to 2 nm of the carbon-based material is denoted as V2, as determined by the carbon dioxide adsorption method, and then VI + V2 is in the range of 0.0006 cm3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm3 / g.

5. The sodium-ion battery of claim 4, wherein, V1+V2 is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

6. The sodium-ion battery of claim 5, wherein, V1+V2 is in the range of 0.0020 cm 3 / g to 0.0035 cm 3 / g.

7. The sodium-ion battery of any one of claims 4-6, wherein, V1+V2 accounts for 18% to 30% of the pore volume of the carbon-based material.

8. The sodium-ion battery of any one of claims 1-7, wherein, The carbon-based material comprises pores having a pore diameter in the range of 1.0-1.5 nm, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V with respect to the logarithm of the pore diameter D for pores having a pore diameter of 1.0-1.5 nm, determined by the nitrogen adsorption method, is in the range of 0.001 cm 3 / (g·log(nm))-0.009 cm 3 / (g·log(nm))·0.009 cm / (g·log(nm))·0.009 cm 9. The sodium-ion battery of claim 8, wherein, The maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores having a pore diameter of 1.0 nm to 1.5 nm with respect to the logarithm of the pore diameter D is 0.001 cm 3 / (g·log(nm)) to 0.006 cm 3 / (g·log(nm)) to 0.006 cm 10. The sodium-ion battery of any one of claims 8-9, wherein, The pore volume of the pores with a pore size of 1.0 nm to 1.5 nm of the carbon-based material accounts for 6% to 14% of the total pore volume of the carbon-based material.

11. The sodium-ion battery of any one of claims 1-10, wherein, The negative electrode film layer comprises at least one of a first aqueous binder, an aqueous dispersant and a first conductive agent.

12. The sodium-ion battery of claim 11, wherein, The first aqueous binder comprises one or more of styrene-butadiene rubber and acrylate rubber; the aqueous dispersant comprises one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum and carrageenan; and the first conductive agent comprises one or more of Super-P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

13. The sodium-ion battery of claim 11 or 12, wherein, The mass content of the carbon-based material in the negative electrode film layer is more than 80%.

14. The sodium-ion battery of claim 13, wherein, The mass content of the carbon-based material in the negative electrode film layer is more than 85%, the mass content of the first aqueous binder is 0% to 5%, the mass content of the aqueous dispersant is 0% to 5%, and the mass content of the first conductive agent is 0% to 5%.

15. The sodium-ion battery of any one of claims 1-14, wherein, The negative electrode film layer further comprises an intercalation-type sodium storage material, the intercalation-type sodium storage material has a crystal face spacing d 002 satisfies: 0.24 nm ≤ d 002 ≤ 0.8 nm; the mass content of the intercalation-type sodium storage material in the negative electrode film layer is less than or equal to 10%.

16. The sodium-ion battery of claim 15, wherein, The embedded sodium storage material includes at least one of a carbon-based embedded sodium storage material, a sulfur-based embedded sodium storage material, and a titanium-based embedded sodium storage material; the carbon-based embedded sodium storage material includes at least one of a soft carbon embedded sodium storage material and a modified graphite embedded sodium storage material; the soft carbon embedded sodium storage material has I D / I G satisfies: 0.9≤I D / I G ≤1.6, wherein I D represents the D peak intensity of the Raman spectrum at 1350±50cm -1 , I G represents the G peak intensity of the Raman spectrum at 1580±50cm -1 .

17. The sodium-ion battery of claim 16, wherein, The negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer arranged in a stack, the first negative electrode film layer is arranged between the negative electrode current collector and the second negative electrode film layer, the first negative electrode film layer comprises a first active material, and the second negative electrode film layer comprises a second active material; the first active material and the second active material each comprise at least one of the carbon-based material and the intercalation-type sodium storage material, and at least one of the first active material and the second active material comprises the carbon-based material.

18. The sodium-ion battery of claim 17, wherein, The first active material comprises the carbon-based material, and the second active material comprises the soft carbon intercalation-type sodium storage material.

19. The sodium-ion battery of any one of claims 1-18, wherein, The negative electrode sheet further comprises a primer layer; the thickness of the primer layer is 0.5 μm to 3 μm.

20. The sodium-ion battery of claim 19, wherein, The primer layer comprises an inorganic oxide and a second aqueous binder.

21. The sodium-ion battery of claim 19, wherein, The primer layer comprises an inorganic oxide, a dispersant, a second aqueous binder and a second conductive agent.

22. The sodium-ion battery of claim 20 or 21, wherein, In the primer layer, the inorganic oxide comprises one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide and zirconium oxide; and the mass content of the inorganic oxide is 30% to 60%.

23. The sodium-ion battery of claim 21, wherein, The primer layer comprises 30% to 60% inorganic oxide, 1% to 8% dispersant, 10% to 40% second aqueous binder and 10% to 40% second conductive agent.

24. The sodium-ion battery of any one of claims 20-23, wherein, The base coat further comprises a thickening agent and / or a wetting agent; the wetting agent comprises one or more of polyethoxy ether surfactants, polyether silicone surfactants, non-ionic fluorocarbon polymer surfactants, acetylenic surfactants; the thickening agent comprises one or more of sodium carboxymethylcellulose, sodium alginate, xanthan gum, carrageenan.

25. The sodium-ion battery of any one of claims 1-24, wherein, The negative current collector comprises at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, nickel foil, nickel-iron foil, nickel-copper foil, nickel-iron-copper foil.

26. The sodium-ion battery of any one of claims 1-25, wherein, The total content of metal ions in the carbon-based material is ≤800 ppm, and the content of metal ions with valence of two or more is ≤20 ppm.

27. The sodium-ion battery of claim 26, wherein, The total content of metal ions in the carbon-based material is 20 ppm-800 ppm, and the content of metal ions with valence of two or more is 0.1 ppm-20 ppm.

28. The sodium-ion battery of claim 26 or 27, wherein, The metal ions include at least one of Na + , K + , Ca 2+ , Mg 2+ , Mn 2+ , Ba 2+ , Al 3+ .

29. The sodium-ion battery of any one of claims 26-28, wherein, The divalent or more metal ion is Ca 2+ .

30. The sodium-ion battery of any one of claims 1-29, wherein, The surface oxygen element content of the carbon-based material is 5%-15%.

31. The sodium-ion battery of claim 30, wherein, The surface oxygen element content of the carbon-based material is 8%-12%.

32. The sodium-ion battery of any one of claims 1-31, wherein, 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.

33. The sodium-ion battery of any one of claims 1-32, wherein, The sodium ion battery further comprises a positive electrode sheet, a separator film between the negative electrode sheet and the positive electrode sheet, and an electrolyte, wherein the solvent in the electrolyte comprises a carbonate solvent, and the carbonate solvent comprises at least one of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

34. The sodium-ion battery of claim 33, wherein, The volume percentage of the propylene carbonate in the solvent is 15%-55%.

35. The sodium-ion battery of claim 33 or 34, wherein, The positive electrode sheet comprises a positive current collector and a positive film layer on at least one surface of the positive current collector, and the positive film layer comprises a positive active material, wherein the positive active material comprises at least one of sodium-containing layered oxide, polyanion sodium ion compound, and Prussian blue sodium ion compound.

36. The sodium-ion battery of claim 35, wherein, The sodium-containing layered oxide is an iron-manganese-based layered oxide, and the iron-manganese-based layered oxide comprises at least one of nickel-iron-manganese-based layered oxide and copper-iron-manganese-based layered oxide.

37. A method of preparing a sodium-ion battery, comprising preparing a negative electrode sheet, wherein, Preparation of a negative electrode sheet comprises: The negative electrode component and the solvent are mixed to obtain a negative electrode slurry, wherein the negative electrode component includes a carbon-based material, the carbon-based material includes a porous structure, the porous structure includes pores with a pore diameter of 2 nm to 8 nm, and the pore volume of the pores with a pore diameter of 2 nm to 8 nm is 0.0004 cm 3 / g to 0.0040 cm 3 / g; and The negative electrode slurry is coated on the negative current collector.

38. The method of manufacturing according to claim 37, wherein, The pore volume of the pores having a pore diameter of 2 nm to 8 nm of the carbon-based material is 0.0010 cm3 / g to 0.0040 cm3 / g as determined by nitrogen adsorption method. 3 / g to 0.0040 cm3 / g. 3 / g.

39. The method of manufacturing according to claim 37 or 38, wherein, The pore volume of the pores with a pore size of 2 nm-8 nm in the carbon-based material accounts for 3.5%-30% of the total pore volume of the carbon-based material.

40. The method of manufacturing according to any one of claims 37 to 39, wherein, The pore volume of pores having a pore diameter of less than or equal to 1 nm of the carbon-based material is denoted as VI, and the pore volume of pores having a pore diameter of 1 nm to 2 nm of the carbon-based material is denoted as V2, as determined by the carbon dioxide adsorption method, and then VI + V2 is in the range of 0.0006 cm3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm3 / g.

41. The method of manufacturing according to claim 40, wherein, V1+V2 is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

42. The method of manufacturing according to claim 41, wherein, V1+V2 is in the range of 0.0020 cm 3 / g to 0.0035 cm 3 / g.

43. The method of making according to any one of claims 40 to 42, wherein, V1+V2 accounts for 18%-30% of the pore volume of the carbon-based material.

44. The method of manufacturing according to any one of claims 37 to 43, wherein, The carbon-based material comprises pores having a pore diameter in the range of 1.0 nm to 1.5 nm, the maximum value of the derivative dV / d(logD) of the cumulative pore volume V with respect to the logarithm of the pore diameter D for pores having a pore diameter of 1.0 nm to 1.5 nm determined by the nitrogen adsorption method is in the range of 0.001 cm 3 / (g log(nm)) to 0.009 cm 3 / (g log(nm)).

45. The method of manufacturing according to claim 44, wherein, The maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores having a pore diameter of 1.0 nm to 1.5 nm with respect to the logarithm of the pore diameter D is 0.001 cm 3 / (g·log(nm)) to 0.006 cm 3 / (g·log(nm)) to 0.006 cm / (g·log(nm)) to 0.006 cm 46. The method of making according to any one of claims 37 to 45, wherein, The pore volume of the pores with a pore size of 1.0 nm-1.5 nm in the carbon-based material accounts for 6%-14% of the total pore volume of the carbon-based material.

47. The method of manufacturing according to any one of claims 37 to 46, wherein, The mass percentage of the negative electrode components in the negative electrode slurry is 50%-60%.

48. The method of manufacturing according to any one of claims 37 to 47, wherein, The mass percentage of the carbon-based material in the negative electrode components is 80%-95%.

49. The method of making according to any one of claims 37 to 48, wherein, The negative electrode components further comprise one or more of conductive agents, binders, and dispersants.

50. The method of making according to any one of claims 37 to 49, wherein, The mixing of the negative electrode components and the solvent comprises vacuum stirring at 0°C-30°C for 1 h-4 h.

51. An electric device comprising the sodium ion battery according to any one of claims 1-36 or prepared by the method of any one of claims 37-50.

52. A carbon-based material comprising pores having a pore diameter of 2 nm to 8 nm, the pore volume of the pores having a pore diameter of 2 nm to 8 nm determined by nitrogen adsorption being 0.0004 cm 3 / g to 0.0040 cm 3 / g.

53. The carbon-based material of claim 52, wherein, The pore volume of the pores having a pore diameter of 2 nm to 8 nm of the carbon-based material is 0.0010 cm3 / g to 0.0040 cm3 / g as determined by nitrogen adsorption method. 3 / g to 0.0040 cm3 / g. 3 / g.

54. The carbon-based material of claim 52 or 53, wherein, The pore volume of pores having a pore diameter of 2 nm to 8 nm of the carbon-based material accounts for 3.5% to 30% of the total pore volume of the carbon-based material.

55. The carbon-based material of any one of claims 52-54, wherein, The pore volume of pores having a pore diameter of less than or equal to 1 nm of the carbon-based material is denoted as VI, and the pore volume of pores having a pore diameter of 1 nm to 2 nm of the carbon-based material is denoted as V2, as determined by the carbon dioxide adsorption method, and then VI + V2 is in the range of 0.0006 cm3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm3 / g. 3 / g to 0.0050 cm3 / g.

56. The carbon-based material of claim 55, wherein, V1+V2 is in the range of 0.0006 cm 3 / g to 0.0035 cm 3 / g.

57. The carbon-based material of claim 56, wherein, V1+V2 is in the range of 0.0020 cm 3 / g to 0.0035 cm 3 / g.

58. The carbon-based material of any one of claims 55-57, wherein, V1+V2 accounts for 18% to 30% of the total pore volume of the carbon-based material.

59. The carbon-based material of any one of claims 52-58, wherein, The carbon-based material comprises pores having a pore diameter in the range of 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 for pores having a pore diameter of 1.0-1.5 nm as determined by the nitrogen adsorption method is in the range of 0.001 cm 3 / (g·log(nm)) - 0.009 cm 3 / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g·log(nm)) - 0.009 cm / (g 60. The carbon-based material of claim 59, wherein, The maximum value of the derivative dV / d(logD) of the cumulative pore volume V of the pores having a pore diameter of 1.0 nm to 1.5 nm with respect to the logarithm of the pore diameter D is 0.001 cm 3 / (g·log(nm)) to 0.006 cm 3 / (g·log(nm)) to 0.006 cm 61. The carbon-based material of any one of claims 52-60, wherein, The pore volume of pores having a pore diameter of 1.0 nm to 1.5 nm of the carbon-based material accounts for 6% to 14% of the total pore volume of the carbon-based material.

62. The carbon-based material of any one of claims 52-61, wherein, The total content of metal ions in the carbon-based material is ≤800 ppm, and the content of metal ions with valence of two or more is ≤20 ppm.

63. The carbon-based material of claim 62, wherein, The total content of metal ions in the carbon-based material is 20 ppm to 800 ppm, and the content of metal ions with valence of two or more is 0.1 ppm to 20 ppm.

64. The carbon-based material of claim 62 or 63, wherein, The metal ions include at least one of Na + , K + , Ca 2+ , Mg 2+ , Mn 2+ , Ba 2+ , Al 3+ .

65. The carbon-based material of any one of claims 62-64, wherein, The divalent or more metal ion is Ca 2+ .

66. The carbon-based material of any one of claims 52-65, wherein, The content of surface oxygen elements of the carbon-based material is 5% to 15%.

67. The carbon-based material of claim 66, wherein, The content of surface oxygen elements of the carbon-based material is 8% to 12%.

68. The carbon-based material of any one of claims 52-67, wherein, 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.

69. A secondary battery comprising the carbon-based material of any one of claims 52 to 68.

70. The secondary battery of claim 69, wherein the secondary battery is at least one of a potassium ion battery, a sodium ion battery, a lithium ion battery, and a sodium-potassium ion hybrid battery.

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