Sodium ion battery multi-element composite negative electrode material and preparation method thereof

Abstract

The application discloses a kind of sodium ion battery multielement composite negative electrode material and preparation method thereof, and relates to the technical field of sodium ion battery.The preparation method of negative electrode material includes hard carbon pretreatment, in-situ deposition Sn-Sb nanoparticles, preparation hard carbon@Sn-Sb-carbon nanotube composite, and electrode negative electrode material step is prepared.The raw materials used include hard carbon, SnCl2·2H2O, SbCl3, NaBH4 solution, single-walled carbon nanotube, polyvinylidene fluoride-hexafluoropropylene copolymer, emulsifier, defoaming agent, nano-alumina, copper foil current collector.The battery negative electrode material prepared by the application has excellent mechanical properties, and can effectively improve the cycle stability and wide temperature range adaptability of sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a sodium-ion battery multi-component composite anode material and its preparation method. Background Technology

[0002] Sodium-ion batteries have broad application prospects in large-scale energy storage and energy storage in extreme environments such as deserts and Gobi due to the abundance of sodium resources, low cost, and excellent safety. As the core component of sodium-ion batteries, the performance of the anode material directly determines the battery's capacity, cycle stability, and wide temperature range adaptability.

[0003] Currently, publicly available sodium-ion battery anode materials mainly include carbon-based materials, alloy materials, metal compounds, and composite systems. Among them, carbon-based materials have the characteristics of structural stability and excellent cycle performance, but their specific capacity is relatively low, making it difficult to meet the application requirements of high-energy-density batteries. Although alloy materials and metal compounds have ultra-high theoretical specific capacity, they will produce huge volume expansion during sodium ion insertion / extraction, leading to electrode structure collapse, active material shedding, and thus a sharp decline in cycle stability. To address the inherent defects of single-component anode materials, multi-component composite strategies have been widely studied. By combining different functional components, synergistic effects can be achieved among the components, balancing high capacity, high conductivity, and structural stability. However, existing multi-component composite anode materials still suffer from problems such as poor interfacial compatibility, uneven component dispersion, complex composite processes, high production costs, and difficulty in large-scale preparation. Prior art disclosed in CN121020557A includes a hard carbon anode material and its preparation method for sodium-ion batteries, as well as the anode and the sodium-ion battery itself. The sodium polyphosphate in this prior art can only optimize ion diffusion but cannot buffer volume expansion, thus offering limited improvement to charge-discharge cycle stability. Prior art disclosed in CN121054704A discloses a method for preparing a sodium-ion battery anode material and a sodium-ion battery. In this prior art, the epoxy resin coating offers limited improvement to the mechanical properties of the electrode material and lacks design for wide temperature range adaptability.

[0004] In summary, although the existing technical solutions have improved some properties of sodium-ion battery anode materials to a certain extent, the following technical problems still exist: the mechanical properties of the battery anode materials are poor, and the cycle stability and wide temperature range adaptability of sodium-ion batteries cannot be effectively improved. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a sodium-ion battery multi-component composite anode material and its preparation method, achieving the following objective: to prepare a battery anode material with excellent mechanical properties that can effectively improve the cycle stability and wide temperature range adaptability of sodium-ion batteries.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A method for preparing a multi-component composite anode material for sodium-ion batteries includes the following steps: hard carbon pretreatment, in-situ deposition of Sn-Sb nanoparticles, preparation of hard carbon@Sn-Sb-carbon nanotube composite, and preparation of the electrode anode material.

[0008] The hard carbon pretreatment involves ball milling the hard carbon, adding hydrochloric acid solution, heating in a water bath, and stirring; then washing and vacuum drying to obtain pretreated hard carbon.

[0009] Furthermore, the mass ratio of the hard carbon to the hydrochloric acid solution is 1:(4-5).

[0010] Furthermore, the ball milling process involves adding hard carbon to a planetary ball mill, using anhydrous ethanol as the dispersion medium, a ball-to-material ratio of (5-6):1, a milling speed of 400-500 rpm, and a milling time of 2-3 hours. The vacuum drying process involves a temperature of 105-110℃, a vacuum degree of 0.09-0.095 MPa, and a drying time of 12-14 hours. The concentration of the hydrochloric acid solution is 1 mol / L.

[0011] Further, the hard carbon is ball-milled, then hydrochloric acid solution is added, and the mixture is heated in a water bath to 60-65°C and stirred for 30-40 minutes at a speed of 200-300 rpm. Then it is washed with deionized water until neutral and dried under vacuum to obtain pretreated hard carbon.

[0012] The in-situ deposited Sn-Sb nanoparticles were prepared by dissolving SnCl2·2H2O and SbCl3 in deionized water, adding anhydrous ethanol, and stirring; then adding pretreated hard carbon, heating, adding NaBH4 solution dropwise, and stirring; filtering and vacuum drying to obtain hard carbon@Sn-Sb alloy particles.

[0013] Furthermore, the mass ratio of SnCl2·2H2O, SbCl3, deionized water, anhydrous ethanol, pretreated hard carbon, and NaBH4 solution is 1:(0.9-1.1):(80-110):(3-5):(7-10):(200-250). The vacuum drying process is carried out at a temperature of 80-85℃, a vacuum degree of 0.09-0.095 MPa, and a drying time of 6-8 hours. The concentration of the NaBH4 solution is 0.1 mol / L.

[0014] Further, SnCl2·2H2O and SbCl3 were dissolved in deionized water, anhydrous ethanol was added, and the mixture was stirred for 30-40 min at a speed of 200-300 rpm. Then, pretreated hard carbon was added, the temperature was raised to 70-75℃, and NaBH4 solution was added dropwise at a rate of 1-1.5 mL / min. The mixture was stirred for 2-2.5 h. The solid was collected by filtration and dried under vacuum to obtain hard carbon@Sn-Sb alloy particles.

[0015] The preparation of the hard carbon@Sn-Sb-carbon nanotube composite involves dispersing hard carbon@Sn-Sb alloy particles and single-walled carbon nanotubes in anhydrous ethanol, subjecting them to ultrasonic treatment, filtration, and vacuum drying to obtain the hard carbon@Sn-Sb-carbon nanotube composite.

[0016] Furthermore, the mass ratio of the hard carbon@Sn-Sb alloy particles, single-walled carbon nanotubes, and anhydrous ethanol is 100:(15-20):(400-500). The ultrasonic treatment involves an ultrasonic power of 300-400W and an ultrasonic time of 60-70 minutes. The vacuum drying process involves a temperature of 80-85℃, a vacuum degree of 0.09-0.095MPa, and a drying time of 6-8 hours.

[0017] The anode material was prepared by: mixing polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone, heating and stirring; cooling to room temperature, adding emulsifier and defoamer, and stirring until dissolved; adding deionized water dropwise, stirring, and distilling under reduced pressure to obtain a polyvinylidene fluoride-hexafluoropropylene copolymer emulsion; mixing the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion with nano-alumina and ultrasonically dispersing; then adding hard carbon@Sn-Sb-carbon nanotube composite and stirring to obtain a mixed slurry; coating the mixed slurry onto a copper foil current collector, and then vacuum drying and annealing to obtain the anode material.

[0018] Furthermore, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, N-methylpyrrolidone, emulsifier, defoamer, and deionized water is 100:(90-110):(0.8-1.2):(0.08-0.12):(85-95). The vacuum distillation is performed at a temperature of 40-45℃, a vacuum degree of 0.07-0.075 MPa, and a distillation time of 60-70 min.

[0019] Furthermore, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion, nano-alumina, and hard carbon@Sn-Sb-carbon nanotube composite is (9-10):(1-1.5):(100-105). The ultrasonic dispersion is performed at a power of 300-350W for 30-40 minutes. The vacuum drying is carried out at a temperature of 120-125℃, a vacuum of 0.09-0.095MPa, and a drying time of 2-2.5 hours. The annealing treatment is performed in a tubular annealing furnace under high-purity argon protection at a flow rate of 50-60 mL / min, heating to 290-300℃ at a rate of 5-7℃ / min, holding at this temperature for 3-3.5 hours, and then cooling to room temperature in the furnace.

[0020] Further, the polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone are mixed, heated to 60-65℃, and stirred for 2-3 hours at a speed of 300-400 rpm. After cooling to room temperature, emulsifier and defoamer are added and stirred until dissolved. The stirring speed is adjusted to 1500-2000 rpm, and deionized water is added dropwise at a rate of 1-2 mL / min. After the addition is complete, the mixture is stirred for 30-40 minutes, and then the solvent is removed by vacuum distillation to obtain the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion.

[0021] Polyvinylidene fluoride-hexafluoropropylene copolymer emulsion was mixed with nano-alumina and ultrasonically dispersed. Then, hard carbon@Sn-Sb-carbon nanotube composite was added, and the mixture was stirred for 2-2.5 hours at a speed of 400-500 rpm to obtain a mixed slurry. The mixed slurry was coated onto a copper foil current collector, with the wet film thickness controlled at 30-40 μm. After vacuum drying and annealing, the negative electrode material was obtained.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) In this invention, the hard carbon in the hard carbon@Sn-Sb-carbon nanotube composite serves as a stable substrate, which can effectively accommodate and bind the Sn-Sb alloy particles deposited on its surface; the Sn-Sb alloy nanoparticles provide ultra-high sodium storage capacity, forming a synergy of basic capacity and high capacity with the hard carbon; the single-walled carbon nanotubes overlap with each other between the hard carbon@Sn-Sb particles to form a three-dimensional continuous conductive network that encapsulates and penetrates the entire active material aggregate, which greatly improves the electron transport rate and significantly reduces the overall internal resistance and polarization of the electrode; it also disperses the local volume expansion stress to the entire electrode layer through its own flexibility and high strength, which greatly enhances the structural stability of the electrode.

[0024] Polyvinylidene fluoride (PVDF)-hexafluoropropylene copolymer (PPF-HFA) firmly binds its components together through the physical entanglement and strong adsorption of its long polymer chains, as well as the hydrogen bonds or dipole interactions formed between the polar groups at the polymer chain ends and the active functional groups on the surface of hard carbon and nano-alumina, thereby improving the mechanical properties of the electrode material. The fluorocarbon chains of PPF-HFA exhibit good compatibility with the electrolyte, reducing the viscosity of the electrolyte at low temperatures and promoting the transport of sodium ions at the electrode / electrolyte interface. Simultaneously, it possesses excellent thermal stability, maintaining the integrity of the coating structure at high temperatures, preventing interfacial peeling caused by thermal aging, inhibiting electrolyte decomposition at high temperatures, and improving high-temperature cycling stability.

[0025] (2) The sodium-ion battery multi-component composite anode material of the present invention can effectively improve the cycle stability of sodium-ion batteries. After the prepared battery anode material is used to prepare a sodium-ion battery, the capacity retention rate is 87.7-90.5% after 1500 charge-discharge cycles.

[0026] (3) The sodium-ion battery multi-component composite anode material of the present invention can effectively improve the wide temperature range adaptability of sodium-ion batteries. After the prepared battery anode material is used to prepare a sodium-ion battery, the capacity retention rate is 89.5-92.7% at -30℃ and 95.2-96.8% at 60℃.

[0027] (4) The sodium-ion battery multi-component composite anode material of the present invention has excellent mechanical properties. The peel strength of the prepared battery anode material reaches 18.5-21.2 N / m. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0029] Example 1: A sodium-ion battery multi-component composite anode material and its preparation method

[0030] A method for preparing a sodium-ion battery multi-component composite anode material, comprising the following steps:

[0031] Step 1: Hard Carbon Pretreatment

[0032] Hard carbon was ball-milled, then hydrochloric acid solution was added, and the mixture was heated to 60°C in a water bath and stirred for 40 minutes at a speed of 200 rpm. It was then washed with deionized water until neutral and dried under vacuum to obtain pretreated hard carbon.

[0033] The mass ratio of the hard carbon to the hydrochloric acid solution is 1:4.

[0034] The ball milling process involves adding hard carbon to a planetary ball mill, using anhydrous ethanol as the dispersion medium, a ball-to-material ratio of 5:1, a ball milling speed of 400 rpm, and a ball milling time of 3 hours.

[0035] The vacuum drying process involves a temperature of 105℃, a vacuum degree of 0.09MPa, and a drying time of 14 hours.

[0036] The concentration of the hydrochloric acid solution is 1 mol / L.

[0037] Step 2: In-situ deposition of Sn-Sb nanoparticles

[0038] SnCl2·2H2O and SbCl3 were dissolved in deionized water, anhydrous ethanol was added, and the mixture was stirred for 30 min at 300 rpm. Then, pretreated hard carbon was added, the temperature was raised to 70 °C, and NaBH4 solution was added dropwise at a rate of 1 mL / min. The mixture was stirred for 2.5 h. The solid was collected by filtration and dried under vacuum to obtain hard carbon@Sn-Sb alloy particles.

[0039] The mass ratio of SnCl2·2H2O, SbCl3, deionized water, anhydrous ethanol, pretreated hard carbon, and NaBH4 solution is 1:0.9:80:3:7:200.

[0040] The vacuum drying process involves a temperature of 80°C, a vacuum level of 0.09 MPa, and a drying time of 8 hours.

[0041] The concentration of the NaBH4 solution is 0.1 mol / L.

[0042] Step 3: Preparation of hard carbon@Sn-Sb-carbon nanotube composite

[0043] Hard carbon@Sn-Sb alloy particles and single-walled carbon nanotubes were dispersed in anhydrous ethanol, subjected to ultrasonic treatment, and then the solid was collected by filtration and vacuum drying to obtain hard carbon@Sn-Sb-carbon nanotube composite.

[0044] The mass ratio of the hard carbon@Sn-Sb alloy particles, single-walled carbon nanotubes, and anhydrous ethanol is 100:15:400.

[0045] The ultrasonic treatment involved an ultrasonic power of 300W and an ultrasonic time of 70 minutes.

[0046] The vacuum drying process involves a temperature of 80°C, a vacuum level of 0.09 MPa, and a drying time of 8 hours.

[0047] Step 4: Obtaining the negative electrode material

[0048] Polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone were mixed, heated to 60°C, and stirred for 3 hours at 300 rpm. After cooling to room temperature, emulsifier and defoamer were added and stirred until dissolved. The stirring speed was adjusted to 1500 rpm, and deionized water was added dropwise at a rate of 1 mL / min. After the addition was complete, the mixture was stirred for 40 min, and then the solvent was removed by vacuum distillation to obtain polyvinylidene fluoride-hexafluoropropylene copolymer emulsion.

[0049] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, N-methylpyrrolidone, emulsifier, defoamer, and deionized water is 100:90:0.8:0.08:85.

[0050] The vacuum distillation was carried out at a temperature of 40°C, a vacuum of 0.07 MPa, and a distillation time of 70 min.

[0051] Polyvinylidene fluoride-hexafluoropropylene copolymer emulsion was mixed with nano-alumina and ultrasonically dispersed. Then, hard carbon@Sn-Sb-carbon nanotube composite was added, and the mixture was stirred for 2 hours at 500 rpm to obtain a mixed slurry. The mixed slurry was coated onto a copper foil current collector, with the wet film thickness controlled at 30-40 μm. After vacuum drying and annealing, the negative electrode material was obtained.

[0052] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion, nano-alumina, and hard carbon@Sn-Sb-carbon nanotube composite is 9:1:100.

[0053] The ultrasonic dispersion was performed with an ultrasonic power of 300W and an ultrasonic time of 40min.

[0054] The vacuum drying process involves a temperature of 120°C, a vacuum degree of 0.09 MPa, and a drying time of 2.5 h.

[0055] The annealing process was carried out in a tubular annealing furnace with high-purity argon gas for protection at a flow rate of 50 mL / min. The temperature was raised to 290°C at a rate of 5°C / min and held for 3.5 hours. The furnace was then cooled to room temperature.

[0056] Example 2: A sodium-ion battery multi-component composite anode material and its preparation method

[0057] A method for preparing a sodium-ion battery multi-component composite anode material, comprising the following steps:

[0058] Step 1: Hard Carbon Pretreatment

[0059] Hard carbon was ball-milled, then hydrochloric acid solution was added, and the mixture was heated to 60°C in a water bath and stirred for 40 minutes at a speed of 300 rpm. It was then washed with deionized water until neutral and dried under vacuum to obtain pretreated hard carbon.

[0060] The mass ratio of the hard carbon to the hydrochloric acid solution is 1:4.5.

[0061] The ball milling process involves adding hard carbon to a planetary ball mill, using anhydrous ethanol as the dispersion medium, a ball-to-material ratio of 5:1, a ball milling speed of 400 rpm, and a ball milling time of 2.5 h.

[0062] The vacuum drying process involves a temperature of 110℃, a vacuum degree of 0.095MPa, and a drying time of 13 hours.

[0063] The concentration of the hydrochloric acid solution is 1 mol / L.

[0064] Step 2: In-situ deposition of Sn-Sb nanoparticles

[0065] SnCl2·2H2O and SbCl3 were dissolved in deionized water, anhydrous ethanol was added, and the mixture was stirred for 35 min at 300 rpm. Then, pretreated hard carbon was added, the temperature was raised to 75 °C, and NaBH4 solution was added dropwise at a rate of 1.5 mL / min. The mixture was stirred for 2.5 h. The solid was collected by filtration and dried under vacuum to obtain hard carbon@Sn-Sb alloy particles.

[0066] The mass ratio of SnCl2·2H2O, SbCl3, deionized water, anhydrous ethanol, pretreated hard carbon, and NaBH4 solution is 1:1:100:4:8:225.

[0067] The vacuum drying process involves a temperature of 80°C, a vacuum level of 0.095 MPa, and a drying time of 7 hours.

[0068] The concentration of the NaBH4 solution is 0.1 mol / L.

[0069] Step 3: Preparation of hard carbon@Sn-Sb-carbon nanotube composite

[0070] Hard carbon@Sn-Sb alloy particles and single-walled carbon nanotubes were dispersed in anhydrous ethanol, subjected to ultrasonic treatment, and then the solid was collected by filtration and vacuum drying to obtain hard carbon@Sn-Sb-carbon nanotube composite.

[0071] The ultrasonic treatment involved an ultrasonic power of 300W and an ultrasonic time of 65 minutes.

[0072] The mass ratio of the hard carbon@Sn-Sb alloy particles, single-walled carbon nanotubes, and anhydrous ethanol is 100:18:450.

[0073] The vacuum drying process involves a temperature of 80°C, a vacuum level of 0.095 MPa, and a drying time of 7 hours.

[0074] Step 4: Obtaining the negative electrode material

[0075] Polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone were mixed, heated to 60°C, and stirred for 3 hours at 300 rpm. After cooling to room temperature, emulsifier and defoamer were added and stirred until dissolved. The stirring speed was adjusted to 1800 rpm, and deionized water was added dropwise at a rate of 2 mL / min. After the addition was complete, the mixture was stirred for 40 min, and then the solvent was removed by vacuum distillation to obtain polyvinylidene fluoride-hexafluoropropylene copolymer emulsion.

[0076] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, N-methylpyrrolidone, emulsifier, defoamer, and deionized water is 100:100:1:0.1:90.

[0077] The vacuum distillation was carried out at a temperature of 40°C, a vacuum of 0.075 MPa, and a distillation time of 70 min.

[0078] Polyvinylidene fluoride-hexafluoropropylene copolymer emulsion was mixed with nano-alumina and ultrasonically dispersed. Then, hard carbon@Sn-Sb-carbon nanotube composite was added, and the mixture was stirred for 2.5 hours at 500 rpm to obtain a mixed slurry. The mixed slurry was coated onto a copper foil current collector, with the wet film thickness controlled at 30-40 μm. After vacuum drying and annealing, the negative electrode material was obtained.

[0079] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion, nano-alumina, and hard carbon@Sn-Sb-carbon nanotube composite is 9:1:100.

[0080] The ultrasonic dispersion was performed with an ultrasonic power of 300W and an ultrasonic time of 40min.

[0081] The vacuum drying process involves a temperature of 120°C, a vacuum degree of 0.095 MPa, and a drying time of 2.5 hours.

[0082] The annealing process was carried out in a tubular annealing furnace with high-purity argon gas for protection at a flow rate of 50 mL / min. The temperature was raised to 290°C at a rate of 6°C / min and held for 3.5 hours. The furnace was then cooled to room temperature.

[0083] Example 3: A sodium-ion battery multi-component composite anode material and its preparation method

[0084] A method for preparing a sodium-ion battery multi-component composite anode material, comprising the following steps:

[0085] Step 1: Hard Carbon Pretreatment

[0086] Hard carbon was ball-milled, then hydrochloric acid solution was added, and the mixture was heated to 65°C in a water bath and stirred for 30 minutes at a speed of 300 rpm. It was then washed with deionized water until neutral and dried under vacuum to obtain pretreated hard carbon.

[0087] The mass ratio of the hard carbon to the hydrochloric acid solution is 1:5.

[0088] The ball milling process involves adding hard carbon to a planetary ball mill, using anhydrous ethanol as the dispersion medium, a ball-to-material ratio of 6:1, a ball milling speed of 500 rpm, and a ball milling time of 2 hours.

[0089] The vacuum drying process involves a temperature of 110℃, a vacuum degree of 0.095MPa, and a drying time of 12 hours.

[0090] The concentration of the hydrochloric acid solution is 1 mol / L.

[0091] Step 2: In-situ deposition of Sn-Sb nanoparticles

[0092] SnCl2·2H2O and SbCl3 were dissolved in deionized water, anhydrous ethanol was added, and the mixture was stirred for 40 min at 200 rpm. Then, pretreated hard carbon was added, the temperature was raised to 75 °C, and NaBH4 solution was added dropwise at a rate of 1.5 mL / min. The mixture was stirred for 2 h. The solid was collected by filtration and dried under vacuum to obtain hard carbon@Sn-Sb alloy particles.

[0093] The mass ratio of SnCl2·2H2O, SbCl3, deionized water, anhydrous ethanol, pretreated hard carbon, and NaBH4 solution is 1:1.1:110:5:10:250.

[0094] The vacuum drying process involves a temperature of 85°C, a vacuum level of 0.095 MPa, and a drying time of 6 hours.

[0095] The concentration of the NaBH4 solution is 0.1 mol / L.

[0096] Step 3: Preparation of hard carbon@Sn-Sb-carbon nanotube composite

[0097] Hard carbon@Sn-Sb alloy particles and single-walled carbon nanotubes were dispersed in anhydrous ethanol, subjected to ultrasonic treatment, and then the solid was collected by filtration and vacuum drying to obtain hard carbon@Sn-Sb-carbon nanotube composite.

[0098] The mass ratio of the hard carbon@Sn-Sb alloy particles, single-walled carbon nanotubes, and anhydrous ethanol is 100:20:500.

[0099] The ultrasonic treatment involved an ultrasonic power of 400W and an ultrasonic time of 60 minutes.

[0100] The vacuum drying process involves a temperature of 85°C, a vacuum level of 0.095 MPa, and a drying time of 6 hours.

[0101] Step 4: Obtaining the negative electrode material

[0102] Polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone were mixed, heated to 65°C, and stirred for 2 hours at 400 rpm. After cooling to room temperature, emulsifier and defoamer were added and stirred until dissolved. The stirring speed was adjusted to 2000 rpm, and deionized water was added dropwise at a rate of 2 mL / min. After the addition was complete, the mixture was stirred for 30 min, and then the solvent was removed by vacuum distillation to obtain polyvinylidene fluoride-hexafluoropropylene copolymer emulsion.

[0103] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, N-methylpyrrolidone, emulsifier, defoamer, and deionized water is 100:110:1.2:0.12:95.

[0104] The vacuum distillation was carried out at a temperature of 45°C, a vacuum of 0.075 MPa, and a distillation time of 60 min.

[0105] Polyvinylidene fluoride-hexafluoropropylene copolymer emulsion was mixed with nano-alumina and ultrasonically dispersed. Then, hard carbon@Sn-Sb-carbon nanotube composite was added, and the mixture was stirred for 2.5 h at 400 rpm to obtain a mixed slurry. The mixed slurry was coated onto a copper foil current collector, with the wet film thickness controlled at 30-40 μm. After vacuum drying and annealing, the negative electrode material was obtained.

[0106] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion, nano-alumina, and hard carbon@Sn-Sb-carbon nanotube composite is 10:1.5:105.

[0107] The ultrasonic dispersion was performed with an ultrasonic power of 350W and an ultrasonic time of 40min.

[0108] The vacuum drying process involves a temperature of 125°C, a vacuum level of 0.095 MPa, and a drying time of 2 hours.

[0109] The annealing process was carried out in a tubular annealing furnace with high-purity argon gas for protection at a flow rate of 60 mL / min. The temperature was raised to 300°C at a rate of 7°C / min and held for 3 hours. The furnace was then cooled to room temperature.

[0110] Comparative Example 1

[0111] A method for preparing a sodium-ion battery multi-component composite anode material, comprising the following steps:

[0112] Step 1: Hard Carbon Pretreatment

[0113] This step is the same as the "hard carbon pretreatment" step in Example 2.

[0114] Step 2: In-situ deposition of Sn-Sb nanoparticles

[0115] This step is the same as the "in-situ deposition of Sn-Sb nanoparticles" step in Example 2.

[0116] Step 3: Preparation of hard carbon@Sn-Sb-carbon nanotube composite

[0117] This step is the same as the step in "Preparation of hard carbon@Sn-Sb-carbon nanotube composite" in Example 2.

[0118] Step 4: Obtaining the negative electrode material

[0119] Nano-alumina was dissolved in anhydrous ethanol and ultrasonically dispersed. Then, hard carbon@Sn-Sb-carbon nanotube composite was added, and the mixture was stirred for 2.5 h at 500 rpm to obtain a mixed slurry. The mixed slurry was coated onto a copper foil current collector, with the wet film thickness controlled at 30-40 μm. After vacuum drying and annealing, the negative electrode material was obtained.

[0120] The mass ratio of the anhydrous ethanol, nano-alumina, and hard carbon@Sn-Sb-carbon nanotube composite is 40:1:100.

[0121] The ultrasonic dispersion was performed with an ultrasonic power of 300W and an ultrasonic time of 40min.

[0122] The vacuum drying process involves a temperature of 120°C, a vacuum degree of 0.095 MPa, and a drying time of 2.5 hours.

[0123] The annealing process was carried out in a tubular annealing furnace with high-purity argon gas for protection at a flow rate of 50 mL / min. The temperature was raised to 290°C at a rate of 6°C / min and held for 3.5 hours. The furnace was then cooled to room temperature.

[0124] Comparative Example 2

[0125] A method for preparing a sodium-ion battery multi-component composite anode material, comprising the following steps:

[0126] Step 1: Hard Carbon Pretreatment

[0127] This step is the same as the "hard carbon pretreatment" step in Example 2.

[0128] Step 2: In-situ deposition of Sn-Sb nanoparticles

[0129] This step is the same as the "in-situ deposition of Sn-Sb nanoparticles" step in Example 2.

[0130] Step 3: Prepare the negative electrode material

[0131] Polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone were mixed, heated to 60°C, and stirred for 3 hours at 300 rpm. After cooling to room temperature, emulsifier and defoamer were added and stirred until dissolved. The stirring speed was adjusted to 1800 rpm, and deionized water was added dropwise at a rate of 2 mL / min. After the addition was complete, the mixture was stirred for 40 min, and then the solvent was removed by vacuum distillation to obtain polyvinylidene fluoride-hexafluoropropylene copolymer emulsion.

[0132] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, N-methylpyrrolidone, emulsifier, defoamer, and deionized water is 100:100:1:0.1:90.

[0133] The vacuum distillation was carried out at a temperature of 40°C, a vacuum of 0.075 MPa, and a distillation time of 70 min.

[0134] Polyvinylidene fluoride-hexafluoropropylene copolymer emulsion was mixed with nano-alumina and ultrasonically dispersed. Then, hard carbon@Sn-Sb alloy particles were added, and the mixture was stirred for 2.5 hours at 500 rpm to obtain a mixed slurry. The mixed slurry was coated onto a copper foil current collector, with the wet film thickness controlled at 30-40 μm. After vacuum drying and annealing, the negative electrode material was obtained.

[0135] The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion, nano-alumina, and hard carbon@Sn-Sb alloy particles is 9:1:100.

[0136] The ultrasonic dispersion was performed with an ultrasonic power of 300W and an ultrasonic time of 40min.

[0137] The vacuum drying process involves a temperature of 120°C, a vacuum degree of 0.095 MPa, and a drying time of 2.5 hours.

[0138] The annealing process was carried out in a tubular annealing furnace with high-purity argon gas for protection at a flow rate of 50 mL / min. The temperature was raised to 290°C at a rate of 6°C / min and held for 3.5 hours. The furnace was then cooled to room temperature.

[0139] Example 4 Performance Test

[0140] (a) The negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 were used to prepare sodium-ion batteries. Cycle performance tests were conducted on the sodium-ion batteries. The assembled sodium-ion batteries were charged and discharged at 25°C with a current density of 0.1 A / g in the range of 0.01-2.0 V. The discharge capacity of the first and 1500th cycles was recorded, and the capacity retention rate after 1500 cycles was calculated. The specific test results are shown in Table 1.

[0141] Table 1

[0142]

[0143] As shown in Table 1, the battery anode materials prepared in Examples 1-3, after being used to fabricate sodium-ion batteries, retained a capacity of 87.7-90.5% after 1500 charge-discharge cycles. This demonstrates that the battery anode materials prepared in this invention can effectively improve the cycle stability of sodium-ion batteries.

[0144] (II) The negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 were used to prepare sodium-ion batteries, and the wide temperature range adaptability of the sodium-ion batteries was tested. The batteries were charged and discharged at -30℃, 25℃, and 60℃ with a current density of 0.1 A / g, and the discharge capacity at each temperature was tested. The capacity retention rate at -30℃ and 60℃ relative to 25℃ was calculated. Specific test results are shown in Table 2.

[0145] Table 2

[0146]

[0147] As shown in Table 2, the battery anode materials prepared in Examples 1-3, after being used to prepare sodium-ion batteries, have a capacity retention rate of 89.5-92.7% at -30℃ and 95.2-96.8% at 60℃, which proves that the battery anode materials prepared in this invention can effectively improve the wide temperature range adaptability of sodium-ion batteries.

[0148] (III) The peel strength of the battery anode materials prepared in Examples 1-3 and Comparative Examples 1-2 was tested according to the test methods specified in GB / T2792-2014. The specific test results are shown in Table 3.

[0149] Table 3

[0150]

[0151] As shown in Table 3, the peel strength of the battery anode materials prepared in Examples 1-3 reached 18.5-21.2 N / m, which proves that the battery anode materials prepared by the present invention have excellent mechanical properties.

[0152] The specific parameters of the raw materials used in this invention are as follows:

[0153] The specific surface area of ​​the hard carbon is 600-800 m². 2 / g, pore volume 0.4-0.7cm 3 / g.

[0154] The copper foil current collector has a thickness of 10-15 μm and a purity of 99.8%-99.99%.

[0155] The particle size of the nano-alumina is 50-100 nm.

[0156] The single-walled carbon nanotubes have a diameter of 8-12 nm and a purity of ≥98%.

[0157] The emulsifier used is Span-80.

[0158] The defoamer used is BYK-024.

[0159] Obviously, there are many other possible implementation methods under the concept of this invention. It should be stated here that any changes made under the inventive concept of this invention will fall within the protection scope of this invention.

Claims

1. A method for preparing a sodium-ion battery multi-element composite anode material, characterized in that: The process includes hard carbon pretreatment, in-situ deposition of Sn-Sb nanoparticles, preparation of hard carbon@Sn-Sb-carbon nanotube composites, and preparation of electrode anode materials. The hard carbon pretreatment involves ball milling the hard carbon, then adding hydrochloric acid solution, heating in a water bath, and stirring; followed by washing and vacuum drying to obtain pretreated hard carbon. The in-situ deposited Sn-Sb nanoparticles were prepared by dissolving SnCl2·2H2O and SbCl3 in deionized water, adding anhydrous ethanol, and stirring; then adding pretreated hard carbon, heating, adding NaBH4 solution dropwise, and stirring; filtering and vacuum drying to obtain hard carbon@Sn-Sb alloy particles. The preparation of the hard carbon @Sn-Sb-carbon nanotube composite involves dispersing hard carbon @Sn-Sb alloy particles and single-walled carbon nanotubes in anhydrous ethanol, subjecting them to ultrasonic treatment, filtration, and vacuum drying to obtain the hard carbon @Sn-Sb-carbon nanotube composite. The anode material was prepared by: mixing polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylpyrrolidone, heating and stirring; cooling to room temperature, adding emulsifier and defoamer, and stirring until dissolved; adding deionized water dropwise, stirring, and removing the solvent by vacuum distillation to obtain a polyvinylidene fluoride-hexafluoropropylene copolymer emulsion; mixing the polyvinylidene fluoride-hexafluoropropylene copolymer emulsion with nano-alumina and ultrasonically dispersing; then adding hard carbon@Sn-Sb-carbon nanotube composite and stirring to obtain a mixed slurry; coating the mixed slurry onto a copper foil current collector, and then vacuum drying and annealing to obtain the anode material.

2. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: The mass ratio of the hard carbon to the hydrochloric acid solution is 1:(4-5).

3. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: The ball milling process involves adding hard carbon to a planetary ball mill, using anhydrous ethanol as the dispersion medium, a ball-to-material ratio of (5-6):1, a ball milling speed of 400-500 rpm, and a ball milling time of 2-3 hours.

4. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: In the in-situ deposition of Sn-Sb nanoparticles, the mass ratio of SnCl2·2H2O, SbCl3, deionized water, anhydrous ethanol, pretreated hard carbon, and NaBH4 solution is 1:(0.9-1.1):(80-110):(3-5):(7-10):(200-250).

5. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: In the step of preparing hard carbon@Sn-Sb-carbon nanotube composite, the mass ratio of hard carbon@Sn-Sb alloy particles, single-walled carbon nanotubes, and anhydrous ethanol is 100:(15-20):(400-500).

6. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: In the step of preparing the electrode negative electrode material, the mass ratio of polyvinylidene fluoride-hexafluoropropylene copolymer, N-methylpyrrolidone, emulsifier, defoamer, and deionized water is 100:(90-110):(0.8-1.2):(0.08-0.12):(85-95).

7. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: In the step of preparing the electrode negative electrode material, the mass ratio of polyvinylidene fluoride-hexafluoropropylene copolymer emulsion, nano-alumina, and hard carbon@Sn-Sb-carbon nanotube composite is (9-10):(1-1.5):(100-105).

8. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: The vacuum distillation is carried out at a temperature of 40-45℃, a vacuum degree of 0.07-0.075MPa, and a distillation time of 60-70min.

9. The method for preparing a sodium-ion battery multi-element composite negative electrode material according to claim 1, characterized in that: In the step of preparing the electrode negative electrode material, vacuum drying is performed at a temperature of 120-125℃, a vacuum degree of 0.09-0.095MPa, and a drying time of 2-2.5h.

10. The method for preparing a sodium-ion battery multi-element composite anode material according to claim 1, characterized in that: The annealing process is carried out in a tubular annealing furnace with high-purity argon gas for protection. The argon gas flow rate is 50-60 mL / min. The temperature is raised to 290-300℃ at a rate of 5-7℃ / min and held for 3-3.5 hours. Then, the furnace is cooled to room temperature.

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