Alloy negative electrode composite sodium solid electrolyte material and preparation method and application thereof

Abstract

The invention discloses an alloy negative electrode composite sodium solid electrolyte material and a preparation method and application thereof, and belongs to the technical field of battery materials. The chemical formula of the material of the alloy negative electrode composite sodium solid electrolyte is alphaNa < 3 + a > MbZr2-cSi2-dP1-eO12-delta. (1-alpha) NaxNy, wherein Na < 3 + a > MbZr2-cSi2-dP1-eO12-delta is a sodium solid electrolyte, NaxNy is a sodium alloy negative electrode, 0.1 < = alpha < = 0.5,-0.4 < = a < = 0.4, 0 < = b < = 1.5, 0 < = c < = 0.5, 0 < = d < = 0.5, 0 < = e < = 0.5, b = c + d + e + delta, 0 < = delta < = 0.10, 0 < = x < = 15, and 0 < y < = 5; the solid-state electrolyte can be applied to preparation of a solid-state sodium ion battery, and solves the problems of low conductivity, large contact resistance between solid-state electrolyte particles and a sodium alloy negative electrode interface, short cycle life and poor safety in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a material, preparation method and application of an alloy negative electrode composite sodium solid electrolyte. Background Technology

[0002] Sodium-ion batteries offer significant advantages in cost, safety, low-temperature performance, and rate capability. This battery system stores energy based on the reversible migration of sodium ions between the positive and negative electrodes. Its electrochemical principle is similar to that of lithium-ion batteries, but sodium's abundance in the Earth's crust (2.74%) is significantly higher than lithium's (0.0065%), giving it a natural cost advantage. Technically, sodium-ion batteries exhibit excellent high and low temperature characteristics (-40℃ to 80℃), intrinsic safety, and deep discharge storage capabilities. They also outperform lithium-ion batteries in high-rate (above 50C) charge-discharge performance. This makes sodium-ion batteries highly competitive in large-scale energy storage power stations, new energy vehicles, start-stop power supplies, and low-speed vehicles. Particularly noteworthy is that with the optimization of material systems and the emergence of economies of scale in the industrial chain, the cost per kilowatt-hour of sodium-ion batteries is expected to further decrease. Replacing traditional lead-acid batteries in areas such as two-wheeled vehicles will become a clear industrial trend, thus building a diversified battery technology ecosystem that complements lithium-ion batteries.

[0003] Currently, traditional liquid sodium-ion batteries suffer from low energy density, short cycle life, and safety hazards caused by liquid electrolytes. Solid-state batteries, on the other hand, offer high energy density, safety, and long cycle life, making them a hot research topic. The core of a solid-state battery is the solid electrolyte, which possesses advantages such as high thermal stability, a wide electrochemical voltage window, good safety, and high mechanical strength. Furthermore, replacing organic electrolytes with solid electrolytes can improve the voltage platform and energy density of sodium batteries, as well as enhance coulombic efficiency. On the other hand, solid electrolytes can replace organic electrolytes and separators, reducing the number of battery components and preventing battery bulging. Therefore, research on solid-state sodium battery electrolytes is particularly important. NZSP (NaZrSiPO4) oxide solid electrolytes exhibit high conductivity (>1.0×10⁻⁶). -4 S·cm -1 However, the sintering temperature of NZSP electrolytes is generally above 1100℃, which leads to the volatilization of Na and P elements, resulting in a decrease in conductivity. In addition, the poor interface between the oxide electrolyte and the Na alloy anode results in high impedance. Isostatic pressing is usually used to increase the interface contact and reduce the interface impedance, but this results in high equipment requirements and difficulties in industrialization.

[0004] Therefore, improving the conductivity of the solid electrolyte in sodium-ion batteries and reducing the high contact resistance at the interface between solid electrolyte particles and sodium alloy anode is a key technical challenge. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides a material, preparation method and application of an alloy negative electrode composite sodium solid electrolyte, so as to solve the technical problems of low conductivity of sodium-ion battery solid electrolyte and high contact impedance at the interface between solid electrolyte particles and sodium alloy negative electrode in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: to provide an alloy negative electrode composite sodium solid electrolyte material, the chemical formula of which is αNa. 3+a M b Zr 2-c Si 2-d P 1-e O 12-δ ·(1-α)Na x N y Na 3+a M b Zr 2-c Si 2-d P 1- e O 12-δ It is a sodium solid electrolyte, Na x N y The anode is a sodium alloy with the following properties: 0.1≤α≤0.5, -0.4≤a≤0.4, 0≤b≤1.5, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.5, b=c+d+e+δ, 0≤δ≤0.10, 0<x≤15, 0<y≤5; M is a dopant element, which is at least one of Ca, Cu, Mg, Fe, F, Zn, Sr, B, Al, La, Ce, Ga, Gd, Yb, Y, Ti, Sn, Nb, V, Nd, Ta, Sc, and Ge; N is at least one of Sn, Sb, P, Bi, Pb, Si, and Ge.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the thickness of the sodium solid electrolyte is 5–20 μm; the conductivity of the sodium solid electrolyte is 0.001–0.01 S / cm. -1 The thickness of the sodium alloy negative electrode is 5~25μm.

[0009] The beneficial effects of the above-mentioned further technical solutions of this invention are: controlling the thickness of the solid electrolyte can maintain better conductivity and strength. A larger thickness can improve the strength of the solid electrolyte, thereby inhibiting the growth of sodium dendrites and resisting short circuits in the battery, reducing the risk of fire or explosion, thus improving the safety characteristics of sodium-ion batteries. However, excessive electrolyte thickness reduces conductivity and battery energy density, and also deteriorates the battery's low-temperature and rate characteristics. Controlling the thickness of the sodium alloy can reduce the expansion of sodium metal and the generation of sodium dendrites during charge-discharge cycles, optimize the migration speed of sodium ions, and simultaneously improve the volumetric and gravimetric energy density of the sodium battery.

[0010] Furthermore, the preparation method of the alloy negative electrode composite sodium solid electrolyte material includes the following steps: S1: Sodium source, zirconium source, silicon source, phosphorus source, and dopant containing dopant element M are added to deionized water, followed by nitric acid and polymer. After dissolution, the pH of the solution is adjusted by the amount of nitric acid added, and the mixture is stirred to form a gel solution. The gel solution is transferred to an electrospinning machine, a voltage is applied, and a polymer nanofiber precursor containing Na, M, Zr, Si, and P elements is obtained on a receiving plate. M is at least one of Ca, Cu, Mg, Fe, F, Zn, Sr, B, Al, La, Ce, Ga, Gd, Yb, Y, Ti, Sn, Nb, V, Nd, Ta, Sc, and Ge. S2: The polymer nanofiber precursor is dried and then microwave sintered to obtain sodium solid electrolyte; S3: Place a sodium metal sheet in a sodium solid electrolyte and heat it (the sodium metal sheet) in an inert protective atmosphere to form a liquid state. Then add elemental N nanoparticles, where N is at least one of Sn, Sb, P, Bi, Pb, Si, and Ge. Disperse the nanoparticles with ultrasound and then cool them rapidly to obtain the final product.

[0011] The beneficial effects of the above-mentioned further technical solutions of this invention are as follows: Electrospinning for the preparation of sodium solid electrolyte involves forming a jet of the precursor solution of the solid electrolyte into nanofibers under a high-voltage electric field, followed by solid-state sintering to obtain the nanofiber solid electrolyte. Its advantages include high electrical conductivity and high needle-punch resistance of the formed nanofibers, while their interface easily wets the sodium alloy interface, thus reducing the interfacial impedance between the solid electrolyte and the sodium alloy. The preparation method in this invention employs a simple synthesis process and a low sintering temperature, resulting in NZSP materials with high electrical conductivity and low interfacial impedance with the sodium alloy anode.

[0012] Furthermore, the sodium source is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide; the zirconium source and silicon source are at least one of zirconium and silicon phosphate, oxide, hydroxide, and metallic element, respectively; the phosphorus source is a phosphate or an oxide of phosphorus; and the dopant containing the dopant element M is elemental M or a compound of M.

[0013] Preferably, the dopant containing dopant element M is at least one of calcium oxide, calcium hydroxide, metallic copper, copper oxide, copper hydroxide, magnesium oxide, magnesium hydroxide, metallic iron, iron oxide, iron hydroxide, sodium fluoride, zinc oxide, zinc hydroxide, strontium oxide, strontium hydroxide, boric acid, boron oxide, cesium oxide, aluminum oxide, aluminum hydroxide, lanthanum oxide, cerium oxide, gadolinium oxide, gallium oxide, ytterbium oxide, yttrium oxide, titanium oxide, tin oxide, niobium oxide, vanadium oxide, neodymium oxide, tantalum oxide, scandium oxide, and germanium oxide.

[0014] The beneficial effects of the above-mentioned further technical solutions of the present invention are: to improve the conductivity of sodium solid electrolyte, while NZSP solid electrolyte is not stable in air and will react with H in H2O. + / Na + An exchange occurs, forming a layer of sodium ion insulating byproducts that increase impedance. Therefore, a dopant is introduced into the NZSP, which is elemental M or a compound of M. The purpose of adding the polymer in step S1 is to increase the viscosity of the solution and to coordinate with the elements of the solid electrolyte, which is beneficial to the stability and uniformity of the elements. At the same time, the concentration of the polymer can control the diameter of the nanofiber solid electrolyte.

[0015] Furthermore, the polymers are PI (polyimide), PAN (polyacrylonitrile), PVdF (polyvinylidene fluoride), PLA (polylactic acid), PMMA (polymethyl methacrylate), PS (polystyrene), PVP (polyvinylpyrrolidone), PAA (polyacrylic acid), PVA (polyvinyl alcohol), PAM (polyacrylamide), PEO (polyethylene oxide), PEG (polyethylene glycol), NTA (nitrilotriacetic acid), and EGTA (ethylene glycol bis(2-aminoethyl ether)tetraacetic acid). At least one of the following: Acid, EUG (Eucommia Ulmoides Gum), EA (Ethyl Acrylate), PEG-EA (Polyethylene Glycol-Ethyl Acrylate), ADH (Adipic Dihydrazide), and DAAM (Diacetone Acrylamide).

[0016] Furthermore, in step S1, the sodium source, zirconium source, silicon source, phosphorus source, and dopant containing dopant element M are mixed with deionized water at a solid-liquid ratio of 0.4~0.7g:1mL, the mass ratio of deionized water, nitric acid, and polymer is 100:0.5~5:10~30, and the pH of the solution is 4~6.

[0017] The beneficial effects of the above-mentioned further technical solutions of this invention are as follows: Too low a solid content can easily lead to nanofiber breakage and reduced production capacity; too high a content can easily lead to uneven nanofiber diameter and imbalanced elemental ratios. Adjusting the pH ensures that Na, Zr, Si, P, and doping elements can dissolve completely. Too low a pH can cause equipment corrosion, while too high a pH can easily lead to uneven elemental distribution or precipitation.

[0018] Furthermore, the voltage applied in step S1 is 30~100kV, and the diameter of the obtained polymer nanofiber precursor is 150~250nm.

[0019] Preferably, the diameter of the polymer nanofiber precursor is 150, 200, 220 or 250 nm.

[0020] The beneficial effects of the above-mentioned further technical solutions of the present invention are: controlling the magnitude of the voltage to control the thickness of the nanofiber diameter, and applying a high voltage in step S1 so that the liquid can overcome the surface tension and spray out filamentous nanofibers.

[0021] Furthermore, in step S2, the microwave sintering temperature is 800~900℃ and the time is 1~3h.

[0022] The beneficial effects of the above-mentioned further technical solutions of the present invention are: if the temperature is too low, a NASICON-type oxide solid electrolyte with a three-dimensional ion transport framework and high thermal stability cannot be formed; if the temperature is too high, it will easily lead to the volatilization of Na and P elements, causing a decrease in the conductivity of the solid electrolyte.

[0023] Furthermore, in step S3, the heating temperature is 100~150℃, and the size of the elemental N nanoparticles is 50~100nm.

[0024] Preferably, in step S3, the ultrasonic frequency is 10~20kHz and the ultrasonic time is 10~20min.

[0025] The beneficial effects of the above-mentioned further technical solutions of this invention are as follows: Since the melting point of metallic sodium is 97.72℃, it is easy to melt into a metal solution when heated to 100℃. However, excessively high temperatures can cause sodium to easily volatilize and create safety hazards. Adding a stabilizer (i.e., elemental N nanoparticles) can stabilize sodium and form a sodium alloy, while reducing the interfacial contact angle between the sodium metal solution and the solid electrolyte, thereby increasing interfacial wettability. In addition, the ultrasonic waves applied in step S3 can, on the one hand, uniformly disperse the nano-stabilizer, and on the other hand, ultrasonic vibration can promote the rapid diffusion of atoms at the interface to form a tight bonding interface. Moreover, ultrasonic friction can destroy the oxide film on the metal surface and the gas film on the solid electrolyte surface, promoting effective wetting of the metal and electrolyte, enabling the sodium alloy anode to be firmly coated on the NZSP material surface and reducing the porosity of the sodium alloy. Therefore, the sodium-ion battery alloy anode composite sodium oxide solid electrolyte prepared by the method of this invention reduces the expansion and cracking of the sodium alloy anode during long-term cycling, and also reduces the interfacial impedance between the solid electrolyte and the sodium alloy anode.

[0026] Furthermore, the application of alloy anode composite sodium solid electrolyte materials in the preparation of solid sodium-ion batteries.

[0027] The beneficial effects of this invention are: 1. Traditional oxide solid electrolytes (NZSPs) are synthesized through wet milling, spray drying, and sintering. Although the particle size of the solid electrolyte after wet milling is around 500 nm, it easily agglomerates into micron-sized particles after sintering, thus reducing the conductivity of the solid electrolyte. This invention uses electrospinning technology to synthesize fibrous NZSP solid electrolytes with a diameter of 150-250 nm. A nanofiber membrane with an interconnected 3D network is formed by efficient microwave heating. This method can effectively transport Na+. + This avoids the aggregation of solid electrolyte particles, thus achieving higher ionic conductivity than existing technologies.

[0028] 2. Traditional solid electrolyte film formation requires isostatic pressing equipment capable of applying pressures of 200-400 MPa to reduce porosity and interfacial impedance, thereby improving ionic conductivity. The core components of this equipment need to be imported and are expensive, making industrialization difficult in the short term. This invention, however, does not require applying significant pressure. By heating a sodium sheet, adding a stabilizer, and using ultrasonic dispersion, interfacial impedance can be reduced. Therefore, the process is simple, feasible, low-cost, and easily scalable for mass production. Attached Figure Description

[0029] Figure 1 SEM image of the sodium solid electrolyte nanofiber precursor prepared in Example 1; Figure 2 The image shows a SEM image of the sodium solid electrolyte nanofiber product prepared in Example 1. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0031] Example 1 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.5Na3Cu 0.1 Fe 0.1 Ca 0.1 Mg 0.1 Zr 1.8 Si 1.9 P 0.9 O 12 0.5Na 15 Sn4 is prepared by the following steps: S1: Na₂CO₃, ZrO₂, SiO₂, NH₄H₂PO₄, and dopants were added to deionized water according to the molar ratio of the elements in the molecular formula, with a solid-liquid ratio of 0.4:1. The dopants were elemental metals Cu and Fe, as well as CaO and MgO. Nitric acid and polymers were then added, with a mass ratio of deionized water, nitric acid, and polymers of 100:1:10. The polymers were PI, PAN, PVdF, and PLA, with a mass ratio of 1:1:1:1. The pH of the solution was adjusted to 4 by adjusting the amount of nitric acid added. After stirring, a gel solution was formed. The gel solution was transferred to the pump of an electrospinning machine, and a high voltage of 30 kV was applied. On the receiving plate, a polymer nanofiber precursor containing Na, Cu, Fe, Ca, Mg, Zr, Si, and P elements was obtained by electrospinning.

[0032] S2: The above nanofiber precursor is dried and then microwave sintered at a temperature of 800℃ for 3 hours to obtain NZSP fiber solid electrolyte with a diameter of 150nm.

[0033] S3: Place the sodium metal sheet into the solid electrolyte obtained in step S2, and heat it to 150°C in an inert protective atmosphere, holding it at that temperature for 1 hour to form liquid sodium metal; then add Sn nanoparticles with a particle size of 50 nm. The amounts of each component are calculated according to the chemical formula of the material. Simultaneously, apply ultrasonic waves to disperse the nanoparticles at a frequency of 20 kHz for 10 minutes, followed by rapid cooling, finally obtaining 0.5Na3Cu. 0.1 Fe 0.1 Ca 0.1 Mg 0.1 Zr 1.8 Si 1.9 P 0.9 O 12 0.5Na 15 The Sn4 material has a solid electrolyte thickness of 5 μm and an alloy anode thickness of 25 μm.

[0034] Example 2 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.1Na 2.6 F 0.1 Zn 0.2 Sr 0.1 B 0.1 Al 0.1 Zr 1.9 Si 1.8 P 0.8 O 11.9 0.9Na3Sb 0.5 P 0.5 Its preparation method includes the following steps: S1: NaHCO3, Zr(OH)4, Si, P2O5, and dopants were added to deionized water according to the molar ratio of the elements in the molecular formula, with a solid-liquid ratio of 0.7:1. The dopants were NaF, ZnO, SrO, B2O3, and Al2O3. Nitric acid and polymers were then added, with a mass ratio of deionized water, nitric acid, and polymers of 100:0.5:30. The polymers were PMMA, PS, PVP, PAA, and PVA, with a mass ratio of 1:1:1:1:1. The pH of the solution was adjusted to 6 by adjusting the amount of nitric acid added. After stirring, a gel solution was formed. The gel solution was transferred to the pump of an electrospinning machine, and a high voltage of 50 kV was applied. On the receiving plate, a polymer nanofiber precursor containing Na, F, Zn, Sr, B, Al, Zr, Si, and P elements was obtained by electrospinning.

[0035] S2: The above nanofiber precursor is dried and then microwave sintered at a temperature of 900℃ for 1 hour to obtain NZSP fiber solid electrolyte with a diameter of 250nm.

[0036] S3: Place the sodium metal sheet into the solid electrolyte obtained in step S2, and heat it to 100°C in an inert protective atmosphere to form liquid sodium metal; then add Sb and P nanoparticles with a particle size of 100 nm. The amount of each component is calculated according to the chemical formula of the material. At the same time, apply ultrasonic waves to disperse the nanoparticles at a frequency of 15 kHz for 15 min, and then rapidly cool to obtain 0.1 Na. 2.6 F 0.1 Zn 0.2 Sr 0.1 B 0.1 Al 0.1 Zr 1.9 Si 1.8 P 0.8 O 11.9 0.9Na3Sb 0.5 P 0.5 The material has a solid electrolyte thickness of 20 μm and an alloy anode thickness of 25 μm.

[0037] Example 3 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.3Na 3.4 La 0.1 Ce 0.1 Ga 0.1 Gd 0.1 Yb 0.1 Zr 1.9 Si 1.8 P 0.8 O 12 0.7Na5Bi 3.4 Pb 0.6Its preparation method includes the following steps: S1: NaOH, Zr(OH)4, SiO2, P2O5, and dopants were added to deionized water according to the molar ratio of the elements in the molecular formula, with a solid-liquid ratio of 0.65:1. The dopants were La2O3, CeO2, Ga2O3, Gd2O3, and Yb2O3. Nitric acid and polymers were then added, with a mass ratio of deionized water, nitric acid, and polymers of 100:5:25. The polymers were PAM, PEO, PEG, NTA, and EGTA, with a mass ratio of 1:1:1:1:1. The pH of the solution was adjusted to 5.5 by adjusting the amount of nitric acid added. After stirring, a gel solution was formed. The gel solution was transferred to the pump of an electrospinning machine, and a high voltage of 80 kV was applied. On the receiving plate, a polymer nanofiber precursor containing Na, La, Ce, Ga, Gd, Yb, Zr, Si, and P elements was obtained by electrospinning.

[0038] S2: The above nanofiber precursor is dried and then microwave sintered at a temperature of 830℃ for 2.5h to obtain NZSP fiber solid electrolyte with a diameter of 200nm.

[0039] S3: Place the sodium metal sheet into the solid electrolyte obtained in step S2, and heat it to 120°C in an inert protective atmosphere to form liquid sodium metal; then add Bi and Pb nanoparticles with a particle size of 70 nm. The amount of each component is calculated according to the chemical formula of the material. At the same time, apply ultrasonic waves to disperse the nanoparticles at a frequency of 20 kHz for 10 min, and then rapidly cool to obtain 0.3Na. 3.4 La 0.1 Ce 0.1 Ga 0.1 Gd 0.1 Yb 0.1 Zr 1.9 Si 1.8 P 0.8 O 12 0.7Na5Bi 3.4 Pb 0.6 The material has a solid electrolyte thickness of 10 μm and an alloy negative electrode thickness of 5 μm.

[0040] Example 4 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.8Na 3.2 Y 0.1 Ti 0.5 Sn 0.5 Nb 0. 1V 0.3 Zr 1.5 Si 1.5 P 0.5 O 120.2Na 0.76 Si 3.4 Ge 0.6 Its preparation method includes the following steps: S1: Na₂CO₃, ZrO₂, SiO₂, NH₄H₂PO₄, and dopants were added to deionized water according to the molar ratio of the elements in the molecular formula, with a solid-liquid ratio of 0.5:1. The dopants were Y₂O₃, TiO₂, SnO₂, NbO, and V₂O₃. Nitric acid and polymers were then added, with a mass ratio of deionized water, nitric acid, and polymers of 100:2:13. The polymers were PEO, PEG, NTA, EGTA, and EUG, with a mass ratio of 1:1:1:1:1. The pH of the solution was adjusted to 4.5 by adjusting the amount of nitric acid added. After stirring, the solution became a gel solution. The gel solution was transferred to the pump of an electrospinning machine, and a high voltage of 100 kV was applied. On the receiving plate, a polymer nanofiber precursor containing Na, Y, Ti, Sn, Nb, V, Zr, Si, and P elements was obtained by electrospinning.

[0041] S2: The above nanofiber precursor is dried and then microwave sintered at a temperature of 870℃ for 1 hour to obtain NZSP fiber solid electrolyte with a diameter of 180nm.

[0042] S3: Place the sodium metal sheet into the solid electrolyte obtained in step S2, and heat it to 135°C in an inert protective atmosphere to form liquid sodium metal; then add Si and Ge nanoparticles with a particle size of 60 nm. The amount of each component is calculated according to the chemical formula of the material. At the same time, apply ultrasonic waves to disperse the nanoparticles at a frequency of 10 kHz for 18 min, and then rapidly cool to obtain 0.8Na. 3.2 Y 0.1 Ti 0.5 Sn 0.5 Nb 0.1 V 0.3 Zr 1.5 Si 1.5 P 0.5 O 12 0.2Na 0.76 Si 3.4 Ge 0.6 The material has a solid electrolyte thickness of 15 μm and an alloy negative electrode thickness of 20 μm.

[0043] Example 5 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.9Na 3.4 La 0.1 Ce 0.1 Zn 0.5 Zr 1.6 Si 1.9 P0.8 O 12 0.1Na 15 Pb4 is prepared by the following steps: S1: Na₂CO₃, ZrO₂, SiO₂, P₂O₅, and dopants were added to deionized water according to the molar ratio of the elements in the molecular formula, with a solid-liquid ratio of 0.65:1. The dopants were La₂O₃, CeO₂, and Zn(OH)₂. Nitric acid and polymer were then added, with a mass ratio of deionized water, nitric acid, and polymer PAN of 100:3.1:28. The pH of the solution was adjusted to 4.0 by adjusting the amount of nitric acid added. After stirring, a gel solution was formed. The gel solution was transferred to the pump of an electrospinning machine, and a high voltage of 30 kV was applied. On the receiving plate, a polymer nanofiber precursor containing Na, La, Ce, Zn, Zr, Si, and P elements was obtained by electrospinning.

[0044] S2: The above nanofiber precursor is dried and then microwave sintered at a temperature of 850℃ for 2 hours to obtain NZSP fiber solid electrolyte with a diameter of 220nm. S3: Place the sodium metal sheet into the solid electrolyte obtained in step S2, and heat it to 140°C in an inert protective atmosphere to form liquid sodium metal; then add Pb nanoparticles with a particle size of 100 nm. The amounts of each component are calculated according to the chemical formula of the material. At the same time, apply ultrasonic waves to disperse the nanoparticles at a frequency of 15 kHz for 10 min, and then rapidly cool to obtain 0.9Na. 3.4 La 0.1 Ce 0.1 Zn 0.5 Zr 1.6 Si 1.9 P 0.8 O 12 0.1Na 15 The Pb4 material has a solid electrolyte thickness of 7 μm and an alloy anode thickness of 12 μm.

[0045] Example 6 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.2Na 3.4 La 0.1 Ce 0.1 Ga 0.1 Gd 0.1 Yb 0.1 Zr 1.9 Si 1.8 P 0.8 O 12 0.8Na9Sn4, the preparation method of which includes the following steps: S1: NaOH, Zr(OH)4, SiO2, P2O5, and dopants were added to deionized water according to the molar ratio of the elements in the molecular formula, with a solid-liquid ratio of 0.55:1. The dopants were La2O3, CeO2, Ga2O3, Gd2O3, and Yb2O3. Nitric acid and polymers were then added, with a mass ratio of deionized water, nitric acid, and polymers of 100:5:25. The polymers were PVP, PAA, PVA, and PAM, with a mass ratio of 1:1:1:1. The pH of the solution was adjusted to 5.5 by adjusting the amount of nitric acid added. After stirring, a gel solution was formed. The gel solution was transferred to the pump of an electrospinning machine, and a high voltage of 30 kV was applied. On the receiving plate, a polymer nanofiber precursor containing Na, La, Ce, Ga, Gd, Yb, Zr, Si, and P elements was obtained by electrospinning.

[0046] S2: The above nanofiber precursor is dried and then microwave sintered at a temperature of 830℃ for 2.5h to obtain NZSP fiber solid electrolyte with a diameter of 200nm. S3: Place the sodium metal sheet into the solid electrolyte obtained in step S2, and heat it to 120°C in an inert protective atmosphere to form liquid sodium metal; then add Sn nanoparticles with a particle size of 70 nm. The amounts of each component are calculated according to the chemical formula of the material. Simultaneously, apply ultrasonic waves to disperse the nanoparticles at a frequency of 20 kHz for 20 min, followed by rapid cooling, to finally obtain 0.2Na 3.4 La 0.1 Ce 0.1 Ga 0.1 Gd 0.1 Yb 0.1 Zr 1.9 Si 1.8 P 0.8 O 12 The material is 0.8Na9Sn4, with a solid electrolyte thickness of 10μm and an alloy anode thickness of 5μm.

[0047] Comparative Example 1 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.5Na3Zr2Si2P2O 12 0.5Na 15 Sn4 differs from Example 1 in that the sodium solid electrolyte was not doped, while the rest of the preparation steps are the same as in Example 1.

[0048] Comparative Example 2 A composite sodium solid electrolyte alloy anode material with the chemical formula 0.5Na3Zr2Si2P2O 12 0.5Na 15Sn4 differs from Example 1 in that the sodium solid electrolyte was not doped, and the thickness of the obtained sodium solid electrolyte was 2 μm. The remaining preparation steps were the same as in Example 1.

[0049] Performance testing: 1. Conductivity test Electrochemical impedance spectroscopy was performed on the electrolyte material using the Shanghai Chenhua electrochemical workstation. The test conditions were: frequency of 1Hz to 1MHz, micro voltage of 5mV, and the conductivity σ of the electrolyte was measured using the AC impedance method.

[0050] 2. Battery cycle test The cathode material (NaFe) 0.5 Mn 0.5 O2), conductive carbon black, and PVDF binder were mixed in a mass ratio of 95:3:2, and NMP was added to form a uniform slurry. This slurry was then coated onto aluminum foil, dried, and rolled to prepare the positive electrode sheet. The alloy negative electrode composite sodium solid electrolyte material (prepared in Examples 1-6 and Comparative Examples 1-2) of this invention was used to assemble a 15150140 soft-pack sodium-ion battery with the positive electrode sheet. The sodium-ion battery testing conditions were: temperature 24-26℃, charge / discharge cycle voltage range 1.5-4.2V, and cycle tests were conducted at 1C charge / 1C discharge (1C=140mAh / g). The results are shown in Table 1.

[0051] 3. Needle prick safety test A high-temperature resistant steel needle (such as tungsten steel) with a diameter of 5-8 mm and a cone angle of 45° was used. The needle was inserted into the geometric center of the battery from a direction perpendicular to the battery plates at a speed of 20-30 mm / s. The needle remained in the battery for 1 hour, and the results are shown in Table 1.

[0052] Table 1. Electrical performance and needle penetration safety of sodium-ion batteries

[0053] As shown in Table 1, the sodium-ion cathode materials prepared in Examples 1-6 exhibit excellent 1C discharge capacity and 500-cycle performance, with a 500-cycle retention rate exceeding 98%, while maintaining a conductivity of 7.0 × 10⁻⁶. -3 S / cm -1 All of the above have passed the needle penetration safety test. However, Comparative Example 1, due to the lack of doping of the solid electrolyte, has a lower conductivity of only 0.5 × 10⁻⁶. -3 S / cm -1 This is an order of magnitude lower than the example. In NSZP ionic crystals, Na... +For ions to move from one location to another, they need to overcome a certain energy barrier to achieve ion conduction in a solid electrolyte. The size of the energy barrier and the ability of transported ions to overcome it affect the conductivity of the solid electrolyte. Appropriate doping can typically achieve a lower point defect concentration and energy barrier, thus improving the ionic conductivity of NSZP. In Comparative Example 2, the electrolyte thickness was only 2 μm, which was too thin, resulting in insufficient resistance to needle penetration. This could cause the battery to catch fire or explode, thus failing the needle penetration safety test.

[0054] according to Figure 1 It can be seen that the sodium-ion battery oxide solid electrolyte precursor prepared by electrospinning in Example 1 is in the form of nanofibers, and the thickness is uniform with a diameter of 150 nm. Figure 2 The finished oxide solid electrolyte product is obtained by microwave sintering of the solid electrolyte precursor in Example 1. Cross-linked nanofibers are clearly visible, which increases the strength of the electrolyte.

[0055] Although specific embodiments of the present invention have been described in detail with reference to examples, they should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A material for an alloy negative electrode composite sodium solid electrolyte, characterized in that: The chemical formula of the alloy negative electrode composite sodium solid electrolyte is αNa. 3+a M b Zr 2-c Si 2-d P 1-e O 12-δ ·(1-α)Na x N y Na 3+a M b Zr 2-c Si 2-d P 1- e O 12-δ It is a sodium solid electrolyte, Na x N y The anode is a sodium alloy with the following properties: 0.1≤α≤0.5, -0.4≤a≤0.4, 0≤b≤1.5, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.5, b=c+d+e+δ, 0≤δ≤0.10, 0<x≤15, 0<y≤5; M is a dopant element, which is at least one of Ca, Cu, Mg, Fe, F, Zn, Sr, B, Al, La, Ce, Ga, Gd, Yb, Y, Ti, Sn, Nb, V, Nd, Ta, Sc, and Ge; N is at least one of Sn, Sb, P, Bi, Pb, Si, and Ge.

2. The alloy negative electrode composite sodium solid electrolyte material according to claim 1, characterized in that: The thickness of the sodium solid electrolyte is 5~20 μm; the conductivity of the sodium solid electrolyte is 0.001~0.01 S / cm. -1 The thickness of the sodium alloy negative electrode is 5~25μm.

3. The method for preparing the alloy negative electrode composite sodium solid electrolyte material according to claim 1 or 2, characterized in that, Includes the following steps: S1: Add sodium source, zirconium source, silicon source, phosphorus source and dopant containing dopant element M to deionized water, then add nitric acid and polymer, dissolve, adjust the pH of the solution by the amount of nitric acid added, and stir to form a gel solution. The gel solution was transferred to an electrospinning machine, a voltage was applied, and a polymer nanofiber precursor containing Na, M, Zr, Si and P elements was obtained on the receiving plate. M is at least one of Ca, Cu, Mg, Fe, F, Zn, Sr, B, Al, La, Ce, Ga, Gd, Yb, Y, Ti, Sn, Nb, V, Nd, Ta, Sc, and Ge; S2: The polymer nanofiber precursor is dried and then microwave sintered to obtain sodium solid electrolyte; S3: Place a sodium metal sheet into the sodium solid electrolyte and heat it in an inert protective atmosphere to form a liquid state. Then add elemental nanoparticles of element N, where N is at least one of Sn, Sb, P, Bi, Pb, Si, and Ge. Disperse the nanoparticles with ultrasound and then cool them rapidly to obtain the final product.

4. The method for preparing the alloy negative electrode composite sodium solid electrolyte material according to claim 3, characterized in that: The sodium source is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide; the zirconium source and silicon source are at least one of zirconium and silicon phosphate, oxide, hydroxide, and elemental metal, respectively; the phosphorus source is a phosphate or an oxide of phosphorus; the dopant containing the dopant element M is elemental M or a compound of M.

5. The method for preparing the alloy negative electrode composite sodium solid electrolyte material according to claim 3, characterized in that: The polymer is at least one of PI, PAN, PVdF, PLA, PMMA, PS, PVP, PAA, PVA, PAM, PEO, PEG, NTA, EGTA, EUG, EA, PEG-EA, ADH, and DAAM.

6. The method for preparing the alloy negative electrode composite sodium solid electrolyte material according to claim 3, characterized in that: In step S1, the sodium source, zirconium source, silicon source, phosphorus source, and dopant containing dopant element M are mixed with deionized water at a solid-liquid ratio of 0.4~0.7g:1mL. The mass ratio of deionized water, nitric acid, and polymer is 100:0.5~5:10~30, and the pH of the solution is 4~6.

7. The method for preparing the alloy negative electrode composite sodium solid electrolyte material according to claim 3, characterized in that: The voltage applied in step S1 is 30~100kV, and the diameter of the obtained polymer nanofiber precursor is 150~250nm.

8. The method for preparing the alloy negative electrode composite sodium solid electrolyte according to claim 3, characterized in that: In step S2, the microwave sintering temperature is 800~900℃ and the time is 1~3h.

9. The material method for the alloy negative electrode composite sodium solid electrolyte according to claim 3, characterized in that: In step S3, the heating temperature is 100~150℃, and the size of the element N nanoparticles is 50~100nm.

10. The application of the alloy negative electrode composite sodium solid electrolyte as described in claim 1 or 2, characterized in that: It is used in the preparation of solid-state sodium-ion batteries.

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