All-solid-state sodium-ion battery and preparation method thereof

Abstract

This invention relates to an all-solid-state sodium-ion battery and its preparation method. The battery includes a sodium metal anode, a solid electrolyte, and a cathode. The sodium metal anode is deposited onto a metal foil via physical vapor deposition, and a sodium layer with a thickness of 0.5 μm to 10 μm is formed on the metal foil surface by controlling at least one of the deposition time, deposition temperature, or voltage. The solid electrolyte is prepared by mixing a polymer, sodium salt, binder, and water, casting the resulting mixture onto a substrate, and then vacuum drying it. The cathode is an active material containing sodium ions. The all-solid-state sodium-ion battery preparation method provided by this invention is easy to industrialize. The prepared all-solid-state sodium-ion battery exhibits excellent cycle performance, energy density, and power density, and its safety is improved, showing promising market application prospects.

Description

Technical Field

[0001] This invention relates to the fields of surface coating technology and new energy materials technology, and in particular to an all-solid-state sodium-ion battery and its preparation method. Background Technology

[0002] The ever-increasing consumption of fossil fuels has led to the pressing crises of energy insecurity and climate change. Cost-effective and reliable energy storage technologies are key enablers for achieving seamless integration of fluctuating and intermittent renewable energy sources to offset fossil fuel consumption. Sodium-ion batteries, as a viable alternative to the ubiquitous lithium-ion batteries, benefit from the abundance and low cost of sodium resources, the wide variety of sodium-based solid phases, and their ultra-high theoretical capacity (1165 mA hg). -1 With its low electrode potential (-2.714V vs. SHE), it is considered an ideal choice for large-scale, low-cost energy storage systems.

[0003] Sodium-ion batteries using sodium metal anodes can achieve energy densities comparable to those of state-of-the-art lithium-ion batteries. However, the practical application of sodium metal anodes is hampered by two major challenges related to cycle life and safety, primarily due to their high chemical reactivity and significant volume expansion, which ultimately leads to uncontrolled branching growth of sodium. Simultaneously, the preparation of sodium metal foil is also crucial. Unlike lithium metal, sodium metal foil is not commercially available. Pure sodium metal is highly reactive and must be stored in mineral oil or under an inert gas atmosphere. It reacts rapidly with O2 and H2O in the air to form a passivation layer; the high resistivity of this passivation layer on the sodium metal surface is detrimental to the electrochemical performance of the sodium metal anode.

[0004] Currently, the preparation of Na metal anodes mostly involves scraping and polishing Na cubes. The Na cubes are then rolled into foil using polyethylene rollers or blocks, and the Na metal anode is obtained by stamping the Na foil.

[0005] PVD coating technology has been effectively applied in many surface treatments and thin film material preparations, such as protective coatings for parts, coatings for mold surfaces, conductive and transparent coatings, and hard coatings for mold surfaces. PVD-prepared coatings have uniform surface thickness, controllable thickness, are safe and efficient, and are suitable for large-scale production.

[0006] However, due to the extremely high reactivity of sodium metal, its safety is difficult to guarantee, therefore, sodium layers are not currently deposited directly on metal substrates. Existing technologies also employ PVD (Physical Vapor Deposition) to deposit sodium layers, but this requires the prior formation of a mixed transition layer of negative electrode active material and conductive agent on the substrate layer (e.g., aluminum foil) before sodium layer deposition. This sodium layer only serves as a compensating agent for the positive electrode material. For example, Chinese patent application CN 108336301A proposes depositing a layer of metallic sodium on the surface of the negative electrode active material using physical vapor deposition. This process requires first mixing the negative electrode active material (such as hard carbon, soft carbon, amorphous carbon, etc.) and a conductive agent, then coating it onto the negative electrode current collector aluminum foil, and finally depositing a layer of metallic sodium on the surface using PVD technology. The purpose of depositing the sodium layer is to reduce the loss of active sodium ions in the positive electrode material through the release of sodium ions from the layer, thereby improving the initial coulombic efficiency of the sodium-ion battery. The above methods are cumbersome and costly, and the negative electrode active material is not sodium metal. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems in the preparation of existing sodium anode materials and provide an all-solid-state sodium-ion battery. This all-solid-state sodium-ion battery uses physical vapor deposition to attach a sodium layer on the surface of a metal foil substrate. At the same time, it combines the advantages of flexible solid electrolyte, including excellent film-forming characteristics and thermal stability. The solid electrolyte film replaces both the electrolyte and the separator in conventional sodium-ion batteries, reducing the volume and weight of the finished battery and significantly improving energy and power density.

[0008] On the other hand, the present invention provides a sodium-ion solid-state battery system composed of a polymer electrolyte and a sodium metal anode, which can effectively buffer the volume expansion of the sodium anode during cycling and ensure the safety of the battery system.

[0009] The specific plan is as follows:

[0010] A method for preparing an all-solid-state sodium-ion battery, the all-solid-state sodium-ion battery comprising a sodium metal anode, a solid electrolyte, and a cathode, wherein:

[0011] The sodium metal anode is deposited onto a metal foil via physical vapor deposition, and a sodium layer with a thickness of 0.5 μm to 10 μm is formed on the surface of the metal foil by controlling at least one of the deposition time, deposition temperature or voltage.

[0012] The solid electrolyte is prepared by mixing a polymer, sodium salt, binder and water, casting the resulting mixture onto a plate, and then vacuum drying it to obtain a film-like solid electrolyte.

[0013] The positive electrode is an active material containing sodium ions.

[0014] Furthermore, the physical vapor deposition method is vacuum evaporation coating, vacuum magnetron sputtering coating, or vacuum ion coating, preferably vacuum ion coating;

[0015] Optionally, the metal foil is surface-cleaned before physical vapor deposition by ultrasonic washing in distilled water at 10-40 kHz for 10-60 min, followed by ultrasonic washing in anhydrous ethanol at 10-40 kHz for 10-60 min, and then drying.

[0016] Furthermore, the vacuum degree of the vacuum evaporation coating is 1×10⁻⁶. -3 Pa to 9×10 -3 Pa, evaporation temperature is 100℃-1000℃.

[0017] Furthermore, the vacuum degree of the vacuum magnetron sputtering coating is 1×10⁻⁶. -2 Pa to 9×10 -1 Pa, heated to 50-100℃, under plasma conditions, the positive ions formed by the ionization of inert gas bombard the target surface, and magnetron sputtering is used to deposit a film on the metal foil surface. The sputtering voltage is selected between 100V and 800V, and sodium forms a thin film on the metal foil surface.

[0018] Furthermore, the vacuum degree of the vacuum ion plating is 1×10⁻⁶. -3 Pa to 9×10 -3 Pa, activate the metal target and inject inert gas to achieve a vacuum of 1×10⁻⁶. -2 Pa to 9×10 -1 Within the Pa range; a bias voltage is applied, and a film is deposited on the surface of the metal foil, wherein the deposition time is 10-1000 min, the bias voltage is 10V to 200V, and the duty cycle is 20% to 80%; preferably, the deposition time is 10-1000 min, the bias voltage is 10-200V, and the duty cycle is 40-60%.

[0019] Optionally, glow discharge cleaning is performed before coating, under the following conditions: hydrogen flow rate of 100-1000 sccm, applied bias voltage of 300-500V, duty cycle of 40-60%, and time of 100-1000s.

[0020] Furthermore, the preparation method of the positive electrode includes: mixing Na3V2(PO4)3, conductive agent and binder in a mass ratio of 7-10:1-2:1-2, then adding solvent to obtain a positive electrode slurry, which is then coated on a positive electrode current collector and vacuum dried to obtain the positive electrode;

[0021] Preferably, the conductive agent is at least one of acetylene black, Ketjen black, carbon nanotubes, carbon nanofibers, and graphene; the adhesive is at least one of sodium carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, alginate, sodium alginate, and styrene-butadiene rubber; and the solvent is at least one of N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

[0022] Furthermore, in the method for preparing the solid electrolyte, the polymer is at least one of polyethylene oxide, polyvinylidene fluoride, poly(vinylidene fluoride hexafluoropropylene), and polyethylene glycol.

[0023] Optionally, the sodium salt is at least one of NaClO4, sodium hexafluorophosphate, or sodium bis(fluorosulfonyl)imide;

[0024] Optionally, the adhesive is sodium carboxymethyl cellulose.

[0025] Furthermore, the mass ratio of the polymer, sodium salt, and adhesive is 80-90:1-20:1-20, preferably 82:9:9;

[0026] Optionally, the vacuum drying temperature is 40℃~100℃ and the time is 12h~48h, thereby obtaining the solid electrolyte with a thickness of 10-120 micrometers.

[0027] The present invention also protects the all-solid-state sodium-ion battery prepared by the method described above.

[0028] Furthermore, the all-solid-state sodium-ion battery has an energy density of 370–390 Wh / kg, and retains 85–97% of its capacity after 100 charge-discharge cycles at 1C. Preferably, the all-solid-state sodium-ion battery retains 96.6% of its capacity after 100 charge-discharge cycles at 1C, 91.36% after 300 charge-discharge cycles at 1C, and 85.1% after 500 charge-discharge cycles at 1C.

[0029] Beneficial effects:

[0030] In this invention, the sodium metal anode is deposited onto a metal foil via physical vapor deposition. By controlling at least one of the deposition time, deposition temperature, or voltage to form a sodium layer with a thickness of 0.5 μm to 10 μm on the surface of the metal foil, the formed film layer can be ensured to be stable and not easily detached.

[0031] Furthermore, the full cell constructed by combining the sodium metal anode, the NASICON-structured Na3V2(PO4)3 cathode, and the low-cost all-solid-state polymer electrolyte in this invention provides excellent electrochemical performance. The sodium metal anode, with a thickness of only 0.5-10 μm, effectively reduces the mass of the anode side, thereby improving the energy density and power density of the solid-state sodium-ion battery.

[0032] Furthermore, the sodium-ion solid-state battery system composed of polymer electrolyte and sodium metal anode can effectively buffer the volume expansion of sodium anode during cycling, improve cycle performance, and effectively suppress the growth of sodium anode branching.

[0033] In summary, the method for preparing an all-solid-state sodium-ion battery provided by this invention is easy to industrialize. The prepared all-solid-state sodium-ion battery has excellent cycle performance, energy density, and power density, and its safety is improved, showing good market application prospects. Attached Figure Description

[0034] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0035] Figure 1 This is a charge-discharge cycle diagram of a battery at 1C provided in one embodiment 1 of the present invention. Detailed Implementation

[0036] The following are definitions of some terms used in this invention; other terms not mentioned have definitions and meanings known in the art:

[0037] The all-solid-state sodium-ion battery of this invention includes a sodium metal negative electrode, a solid electrolyte, and a positive electrode, wherein:

[0038] The sodium metal anode is deposited onto a metal foil via physical vapor deposition, and a sodium layer with a thickness of 0.5 μm to 10 μm is formed on the surface of the metal foil by controlling at least one of the deposition time, deposition temperature or voltage.

[0039] The solid electrolyte is prepared by mixing a polymer, sodium salt, binder and water, casting the resulting mixture onto a plate, and then vacuum drying it to obtain a film-like solid electrolyte.

[0040] The positive electrode is an active material containing sodium ions.

[0041] The metal foil can be aluminum foil or copper foil, with a thickness of 1-100 μm, preferably 50 μm. The following explanation uses aluminum foil as an example.

[0042] The present invention does not have any particular requirements for the physical vapor deposition method, and can be vacuum evaporation coating, vacuum sputtering coating or vacuum ion coating, preferably vacuum ion coating.

[0043] If vacuum evaporation coating is used, a vacuum evaporation system is employed, in which both the aluminum foil substrate and the sodium metal block to be coated are placed. The aluminum foil is coated at a vacuum degree of 1×10⁻⁶. -3 Pa to 9×10 -3 Pa, and place the sodium metal block to be plated in an evaporation boat. Start adjusting the evaporation voltage to heat the evaporation boat to reach the evaporation temperature of the metal to be plated, such as 100℃-1000℃. A sodium metal film is deposited on the aluminum foil surface, followed by annealing under an inert gas, such as argon.

[0044] If vacuum sputtering deposition is used, the vacuum level of the aluminum foil should be controlled at 1×10⁻⁶. -2 Pa to 9×10 -1 Within the Pa range, the temperature is heated to 50-100℃. Under plasma conditions, positive ions formed by the ionization of argon gas bombard the target surface, and a film is deposited on the aluminum foil surface by magnetron sputtering. The sputtering voltage is selected between 100V and 800V, and metallic sodium forms a thin film on the aluminum foil surface.

[0045] If vacuum ion plating is used, both the aluminum foil substrate and the sodium metal block to be plated are placed in a vacuum evaporation system. The aluminum foil is then plated at a vacuum level of 1×10⁻⁶. -3 Pa to 9×10 -3 Pa. Start the metal target and inject gas to achieve a vacuum of 1 × 10⁻⁶ Pa. -2 Pa to 9×10 -1 Within the Pa range. A bias voltage is applied, and a film is deposited on the surface of the aluminum foil. The deposition time is 10-1000 min. The applied bias voltage is 10V to 200V, and the duty cycle is 20% to 80%. In this invention, "duty cycle" refers to the ratio of the time occupied by the pulse to the total time during a continuous working period of the device.

[0046] The sodium metal anode of this invention is an ultrathin anode, comprising: an aluminum foil substrate and a sodium metal physical vapor deposition layer uniformly attached to the surface of the aluminum foil substrate, wherein the thickness of the sodium metal film is 0.5 μm-10 μm. The thickness of the aluminum foil is 10-30 μm.

[0047] This invention provides an all-solid-state sodium-ion battery, comprising the aforementioned ultrathin negative electrode material, a solid electrolyte, and a Na3V2(PO4)3 positive electrode. The solid electrolyte is prepared by mixing polymers such as polyethylene oxide (PEO), sodium salts such as NaClO4, and binders such as sodium carboxymethyl cellulose (Na-CMC) in a specific ratio in warm water. Na-CMC serves as both an electrode binder and an electrolyte additive, which helps optimize the electrode / electrolyte interface contact. The mixture is stirred at 80-90°C until a clear, homogeneous liquid solution is obtained. The thin film is formed by casting a hot homogenized solution onto a polytetrafluoroethylene (PTFE) plate, placing it in a vacuum drying oven, and then adjusting the temperature in the vacuum drying oven to a preset temperature and maintaining it for a preset time to obtain the solid electrolyte membrane; the preset time ranges from 12h to 48h; the preset temperature ranges from 40°C to 100°C; and the thickness is 10-120 μm.

[0048] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0049] Example 1:

[0050] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0051] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 30 min, sodium film was deposited on the aluminum foil surface, sodium film negative electrode thickness 0.5 μm.

[0052] Polyethylene oxide (PEO), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0053] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0054] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0055] The sodium-ion battery prepared in Example 1 was tested. Figure 1 The cycle performance of the all-solid-state sodium-ion battery at 1C is as follows: after 100 charge-discharge cycles at 1C, the capacity retention rate is 96.6%; after 300 charge-discharge cycles at 1C, the capacity retention rate is 91.36%; and after 500 charge-discharge cycles at 1C, the capacity retention rate is 85.1%.

[0056] Example 2:

[0057] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0058] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 300 min, sodium film was deposited on the aluminum foil surface, with a sodium film negative electrode thickness of 5 μm.

[0059] Polyethylene oxide (PEO), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0060] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0061] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0062] Example 3:

[0063] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0064] The coating was deposited using vacuum evaporation, with the vacuum level adjusted to 5×10. -3 Pa, inject argon gas at a flow rate of 70 sccm. Perform glow discharge cleaning for 180 s; then inject oxygen at a flow rate of 60 sccm to achieve a vacuum of 4 × 10⁻⁶. -1 Pa, start sodium target for 90s, evaporate for 30min under evaporation current of 800A to form a sodium thin film negative electrode with a thickness of 5μm, the sodium film is on the surface of aluminum foil.

[0065] Polyethylene oxide (PEO), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0066] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0067] Finally, the positive electrode, solid electrolyte membrane, and negative electrode prepared in the above steps are stacked in sequence. The flexible solid electrolyte membrane acts as an isolation between the positive and negative electrode, and at the same time, it can reinforce the sodium film layer deposited on the aluminum foil on the negative electrode side, effectively preventing it from falling off.

[0068] Example 4:

[0069] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0070] Vacuum sputtering deposition was employed, with both the aluminum foil substrate and the sodium metal to be deposited placed within a vacuum evaporation system. Glow photolysis was performed first, under conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The vacuum level within the deposition chamber was controlled at 5 × 10⁻⁶. -1 The solution is heated to 80°C, protected with argon gas, and the magnetic field is adjusted to 500 Gs. The target current is also adjusted. The power is turned on, and the product surface is bombarded for minutes. After this, nitrogen gas is introduced into the coating chamber. The power is then turned on, a bias voltage is applied to the workpiece to be coated, and the bias voltage is controlled at 200V. The target source is turned on, and the target material is sodium metal. Coating begins. The coating time is 50 minutes, and the resulting sodium film thickness is 2 μm.

[0071] Polyethylene oxide (PEO), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0072] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0073] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0074] Example 5:

[0075] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0076] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 300 min, sodium film was deposited on the aluminum foil surface, with a sodium film negative electrode thickness of 5 μm.

[0077] Polyethylene glycol (PEG), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0078] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0079] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0080] Example 6:

[0081] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0082] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 300 min, sodium film was deposited on the aluminum foil surface, with a sodium film negative electrode thickness of 5 μm.

[0083] Polyvinylidene fluoride (PVDF), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time (24 hours) to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0084] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0085] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0086] Example 7:

[0087] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0088] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 300 min, sodium film was deposited on the aluminum foil surface, with a sodium film negative electrode thickness of 5 μm.

[0089] Poly(vinylidene fluoride hexafluoropropylene) (PVDF HFP), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time (24 hours) to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0090] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0091] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0092] Example 8:

[0093] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0094] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 30 min, sodium film was deposited on the aluminum foil surface, sodium film negative electrode thickness 0.5 μm.

[0095] Polyethylene oxide (PEO), NaPF6, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0096] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0097] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0098] Example 9:

[0099] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0100] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 30 min, sodium film was deposited on the aluminum foil surface, sodium film negative electrode thickness 0.5 μm.

[0101] Polyethylene oxide (PEO), NaFSI, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0102] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0103] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0104] Comparative Example 1:

[0105] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0106] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 Pa, gas flow rate 130 sccm, applied bias voltage 100 V, duty cycle 50%, deposition time 30 min, sodium film was deposited on the aluminum foil surface, sodium film negative electrode thickness 0.5 μm.

[0107] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0108] The above-mentioned positive electrode, glass fiber filter membrane, and negative electrode are assembled into a battery in a stacked manner. The electrolyte is 1 mol / L ethylene carbonate / diethyl carbonate (volume ratio 1:1). After encapsulation, a sodium-ion battery is obtained.

[0109] Comparative Example 2:

[0110] A 15μm thick aluminum foil was ultrasonically washed with distilled water at 25kHz for 30 minutes, followed by ultrasonic washing with anhydrous alcohol at 25kHz with distilled water for 30 minutes. The surface of the aluminum foil substrate was then wiped clean. After cleaning, the foil was dried at 100℃.

[0111] Vacuum ion plating was used for coating, with both the aluminum foil substrate and the sodium metal to be plated placed in a vacuum evaporation system. Glow chromatography was performed first under the conditions of a hydrogen flow rate of 300 sccm, a bias voltage of 400 V, a duty cycle of 50%, and a time of 500 s. The aluminum foil was then subjected to a vacuum of 5 × 10⁻⁶. -3 Heating was performed under conditions of Pa, with the furnace temperature adjusted to 80℃. The sodium metal block to be plated was placed in an evaporation boat, the target current was adjusted to 20A, and protective argon gas was injected to achieve a vacuum of 5×10⁻⁶. -1 At 130 sccm, with a gas flow rate of 130 Pa, a bias voltage of 100 V, a duty cycle of 50%, and a deposition time of 15 min, a sodium film was deposited on the surface of an aluminum foil. The thickness of the sodium film negative electrode was only 0.2 μm.

[0112] Polyethylene oxide (PEO), NaClO4, and sodium carboxymethyl cellulose (Na-CMC) were thoroughly mixed in warm water at a mass ratio of 82:9:9. The mixture was then stirred at 80°C until a clear, homogeneous liquid solution was obtained. The heated homogenized solution was cast onto a polytetrafluoroethylene (PTFE) plate and placed in a vacuum drying oven. The temperature in the vacuum drying oven was then adjusted to 25°C and maintained for a preset time, ranging from 24 hours, to obtain a solid electrolyte membrane. The resulting solid electrolyte membrane had a thickness of 95 μm.

[0113] Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. A small amount of N-methylpyrrolidone was then dissolved in the mixture and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 15 μm thick aluminum foil for the positive electrode current collector and dried in a vacuum drying oven at 80 °C to obtain the positive electrode sheet.

[0114] Battery assembly: In a glove box, the prepared negative electrode, solid electrolyte film and positive electrode sheet are cut into appropriate sizes and solid sodium-ion battery cells are prepared by stacking. After packaging, sodium-ion batteries are obtained.

[0115] Test example:

[0116] The negative electrodes prepared in the examples and comparative examples were assembled into batteries for testing. Using a LAND CT2001A battery testing system from Wuhan Landian Electronics Co., Ltd., constant current charge-discharge tests were conducted on the sodium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 under 0.1C and 1C current densities of 2.5–4.0V conditions, and the batteries were cycled more than 100 times. The test results are shown in Table 1. The test results show that the energy density of the all-solid-state sodium-ion batteries prepared using this invention is above 370 Wh / kg, and the capacity retention rate after 100 cycles is better than that of the comparative examples. Therefore, this invention can be effectively applied in the preparation of high-energy-density all-solid-state sodium-ion batteries.

[0117] Table 1. Performance data of all-solid-state sodium-ion batteries

[0118]

[0119] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0120] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0121] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing an all-solid-state sodium-ion battery, characterized in that: The all-solid-state sodium-ion battery comprises a sodium metal anode, a solid electrolyte, and a cathode, wherein: The sodium metal anode is deposited onto a metal foil via physical vapor deposition. A sodium layer with a thickness of 0.5 μm is formed on the metal foil surface by controlling at least one of the deposition time, deposition temperature, or voltage. The physical vapor deposition method is vacuum ion plating, and the vacuum degree of the vacuum ion plating is 1 × 10⁻⁶. -3 Pa to 9×10 -3 Pa, activate the metal target and inject inert gas to achieve a vacuum of 1×10⁻⁶. -2 Pa to 9×10 -1 Within the Pa range; a bias voltage is applied, and a film is deposited on the surface of the metal foil, wherein the deposition time is 10-1000 min, the applied bias voltage is 10V to 200V, and the duty cycle is 20% to 80%; the solid electrolyte is prepared by mixing polymer, sodium salt, binder and water, casting the resulting mixture onto a plate, and then vacuum drying to obtain the film-like solid electrolyte; the polymer is polyethylene oxide; the sodium salt is NaClO4; the binder is sodium carboxymethyl cellulose; the mass ratio of the polymer, sodium salt and binder is 80-90:1-20:1-20; The positive electrode is an active material containing sodium ions. The preparation method of the positive electrode includes: mixing Na3V2(PO4)3, conductive agent and binder in a mass ratio of 7-10:1-2:1-2, then adding solvent to obtain a positive electrode slurry, which is then coated on a positive electrode current collector and vacuum dried to obtain the positive electrode. The all-solid-state sodium-ion battery has an energy density of 370~390Wh / kg and a capacity retention rate of 90.5~97% after 100 charge-discharge cycles at 1C.

2. The method for preparing the all-solid-state sodium-ion battery according to claim 1, characterized in that: Before physical vapor deposition, the metal foil is surface cleaned by ultrasonic washing in distilled water at 10-40 kHz for 10-60 min, followed by ultrasonic washing in anhydrous ethanol at 10-40 kHz for 10-60 min, and then drying.

3. The method for preparing an all-solid-state sodium-ion battery according to claim 1, characterized in that: The coating time is 10-1000 min, the applied bias voltage is 10-200V, and the duty cycle is 40-60%.

4. The method for preparing an all-solid-state sodium-ion battery according to claim 1, characterized in that: Before coating, glow discharge cleaning is performed under the following conditions: hydrogen flow rate of 100-1000 sccm, applied bias voltage of 300-500V, duty cycle of 40-60%, and time of 100-1000s.

5. The method for preparing an all-solid-state sodium-ion battery according to claim 1, characterized in that: The conductive agent is at least one of acetylene black, Ketjen black, carbon nanotubes, carbon nanofibers, and graphene; the adhesive is at least one of sodium carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, alginate, sodium alginate, and styrene-butadiene rubber; and the solvent is at least one of N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

6. The method for preparing an all-solid-state sodium-ion battery according to claim 5, characterized in that: The mass ratio of the polymer, sodium salt, and adhesive is 82:9:

9.

7. The method for preparing an all-solid-state sodium-ion battery according to claim 6, characterized in that: The vacuum drying temperature is 40℃~100℃ and the time is 12h~48h, thereby obtaining the solid electrolyte with a thickness of 10-120 micrometers.

8. The all-solid-state sodium-ion battery prepared by the method of any one of claims 1-7.

9. The all-solid-state sodium-ion battery according to claim 8, characterized in that: The all-solid-state sodium-ion battery has an energy density of 370~390Wh / kg and a capacity retention rate of 90.5~97% after 100 charge-discharge cycles at 1C.

10. The all-solid-state sodium-ion battery according to claim 9, characterized in that: The all-solid-state sodium-ion battery retains 96.6% of its capacity after 100 charge-discharge cycles at 1C; 91.36% after 300 charge-discharge cycles at 1C; and 85.1% after 500 charge-discharge cycles at 1C.

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