Double-layer sulfide electrolyte gradient interface all-solid-state nanobattery and preparation method thereof

Abstract

The application provides a double-layer sulfide electrolyte gradient interface all-solid-state nanobattery and a preparation method thereof, and belongs to the all-solid-state battery field. The battery comprises a positive electrode, a lithium metal negative electrode and a sulfide solid electrolyte nanometer assembly arranged between the positive electrode and the lithium metal negative electrode. The sulfide solid electrolyte nanometer assembly is sequentially stacked with a first electrolyte layer and a second electrolyte layer along an ion transmission direction. A first gradient interface is formed between the positive electrode and the first electrolyte layer, a second gradient interface is formed between the first electrolyte layer and the second electrolyte layer, and the first gradient interface and the second gradient interface are both nanometer interfaces with continuous and gradual changes in chemical composition and / or microstructure and without composition mutation. A composite buffer layer is arranged between the second electrolyte layer and the lithium metal negative electrode. The application solves the technical problems that a single electrolyte cannot simultaneously consider the stability of the positive electrode and high ion conductivity, interface mutation leads to excessively high impedance, sulfide electrolyte and lithium metal negative electrode have poor compatibility and easily cause side reactions and lithium dendrites.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, and in particular to an all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte and its preparation method. Background Technology

[0002] Solid-state lithium-ion batteries have become a key research and development direction in the field of electrochemical energy storage and power supply due to their core advantages of high safety and high energy density. Among them, sulfide solid electrolytes have excellent room temperature ionic conductivity, and the solid-state battery system formed by combining them with lithium metal anodes is a key technology route to break through the performance limit of traditional liquid lithium batteries. It has extremely high industrialization value in the fields of new energy vehicles and portable energy storage devices.

[0003] Currently, sulfide-based all-solid-state batteries still have significant technical shortcomings in practical research and application: a single sulfide electrolyte cannot simultaneously achieve both chemical stability and high ionic conductivity with a high-voltage cathode; the interfaces between electrodes and electrolytes, and between different electrolyte layers, are mostly heterogeneous interfaces with abrupt changes in composition and microstructure, which easily lead to lattice mismatch and lithium-ion transport barriers, resulting in persistently high battery interface impedance; at the same time, the chemical and electrochemical compatibility between sulfide electrolytes and lithium metal anodes is poor, and side reactions easily occur at the interface, inducing lithium dendrite growth, which directly affects the cycle stability and safety of the battery.

[0004] Furthermore, existing technologies often employ methods such as doping and modifying a single sulfide electrolyte, applying single-interface coating modification to the electrode surface, or performing simple physical stacking of two electrolytes, or setting a single-component buffer layer on the negative electrode side to improve battery performance. Among these methods, single-electrolyte doping modification can only slightly optimize a single performance aspect and still cannot simultaneously achieve cathode compatibility and high ion transport efficiency; single-interface coating modification can only optimize a single interface contact, and the interfaces between electrolyte layers remain abrupt, with a significant lithium-ion transport barrier; simple electrolyte physical stacking does not achieve a continuous transition of interface composition and structure, and the lattice mismatch problem cannot be alleviated; and single-component buffer layers cannot simultaneously achieve ion conduction and interface passivation, and cannot effectively suppress side reactions and lithium dendrite formation in the long term.

[0005] Furthermore, the aforementioned existing technical solutions cannot achieve synergistic optimization of interface impedance, ion transport, and negative electrode stability at the structural level, which restricts the improvement of the overall performance of sulfide-based all-solid-state batteries. In particular, the defects in nanoscale structural adaptability and micro-nano interface stability make it difficult to meet the performance and application requirements of all-solid-state nanobatteries. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, the present invention aims to provide a bilayer sulfide electrolyte gradient interface all-solid-state nanobattery and its preparation method. By constructing a bilayer functionalized sulfide electrolyte nanocomponent and a nanoscale continuous gradient interface, and setting a nano-dense composite buffer layer on the negative electrode side, the technical problems of a single electrolyte being unable to simultaneously achieve positive electrode stability and high ionic conductivity, high impedance caused by interface abrupt changes, and poor compatibility between sulfide electrolyte and lithium metal negative electrode easily leading to side reactions and lithium dendrites are solved. The invention achieves low interface impedance, high ion transport efficiency, and long-cycle stable operation of the all-solid-state nanobattery.

[0007] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a double-layer sulfide electrolyte gradient interface all-solid-state nanobattery, including a positive electrode, a lithium metal negative electrode, and a sulfide solid electrolyte nanoassembly disposed between the positive electrode and the lithium metal negative electrode; the sulfide solid electrolyte nanoassembly has a first electrolyte layer and a second electrolyte layer stacked sequentially along the ion transport direction; a first gradient interface is formed between the positive electrode and the first electrolyte layer, and a second gradient interface is formed between the first electrolyte layer and the second electrolyte layer, wherein the first gradient interface and the second gradient interface are both nanoscale interfaces with continuous and gradual changes in chemical composition and / or microstructure without abrupt changes in composition; a composite buffer layer is disposed between the second electrolyte layer and the lithium metal negative electrode.

[0008] Preferably, the positive electrode is LiNi x Co y Mn z O2 ternary cathode material, wherein x≥0.9, y and z are positive numbers greater than 0 and satisfy x+y+z=1; the nanometer widths of the first gradient interface and the second gradient interface are both 200~400nm, and they remain thermodynamically stable within the operating temperature range of -20~60℃, with no harmful phase precipitation.

[0009] Preferably, the first electrolyte layer is a silver-germanium ore-type nanocrystalline sulfide electrolyte of the general formula Li6PS5X, where X is selected from one or more of Cl, Br, and I, and the room temperature ionic conductivity is 5~8 mS / cm; the second electrolyte layer is Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The nanocrystalline sulfide electrolyte has an ionic conductivity of 12~15 mS / cm at room temperature.

[0010] Preferably, the second gradient interface has a nanoscale continuous gradient structure with linearly decreasing X element content and linearly increasing Si element content along the ion transport direction, and the P and S element contents transition smoothly, with the ionic conductivity continuously increasing from 5~8 mS / cm to 12~15 mS / cm.

[0011] Preferably, the composite buffer layer is a Li3PS4-LiF nano-dense composite buffer layer with a thickness of 10 μm and a Li3PS4 to LiF mass ratio of 4:1; the composite buffer layer forms a kinetically stable nano-interface with the lithium metal anode, and has an electronic conductivity ≤10. -8 S / cm, ionic conductivity ≥10 -3 S / cm.

[0012] On the other hand, the present invention also provides a method for preparing the above-mentioned bilayer sulfide electrolyte gradient interface all-solid-state nanobatteries, comprising the following steps: S1. Mix the positive electrode material, conductive agent and binder to form a slurry, coat it with the current collector, and then dry, roll and punch to obtain the positive electrode sheet; S2. Place the positive electrode sheet in a glove box and use an air nozzle coating machine to perform in-situ continuous coating to sequentially form a first gradient interface, a first electrolyte layer, a second gradient interface and a second electrolyte layer. S3. A composite buffer layer is formed by coating the surface of the second electrolyte layer with an air nozzle coating machine inside the glove box to obtain a positive electrode sheet with electrolyte and buffer layer. S4. Align and stack the positive electrode and the lithium metal negative electrode in the glove box. Transfer the stacked unit to the voltage regulator for asymmetric hot pressing with complete protection against water and oxygen. Then return the hot-pressed stacked unit to the glove box for vacuum sealing and activation to obtain the double-layer sulfide electrolyte gradient interface all-solid-state nano battery.

[0013] Preferably, in S1, the mass ratio of the positive electrode material, conductive agent and binder is 96:2:2, N-methylpyrrolidone is used as the slurry solvent, and after coating, it is vacuum dried at 85~95℃ for 4.5~5.5h, and the rolling pressure is 60~70MPa. After stamping, a positive electrode sheet with uniform size and nanoscale flat surface is obtained.

[0014] Preferably, in step S2, the entire process is carried out in a sealed, anhydrous, and oxygen-free glove box. A gas nozzle coating machine is used to linearly adjust the slurry supply at a rate of 8-12 mL / min to form a second gradient interface. The adjustment time is 25-35 min to achieve continuous coating and forming of each layer. After coating, the glove box is subjected to heat treatment at 160-170℃ in an argon atmosphere for 6-8 h to achieve low-temperature ordered interdiffusion and crystallization of the nanoscale interface.

[0015] Preferably, in S3, the entire process of air spraying is carried out in the glove box using an air sprayer to control the coating thickness to 10 μm, so that the LiF component is uniformly dispersed in the Li3PS4 matrix to form a dense, pinhole-free nanoscale composite buffer layer.

[0016] Preferably, in step S4, the entire stacking process is completed in a sealed glove box, and the transfer process of the stacking unit adopts anhydrous and oxygen-free protection measures; asymmetric hot pressing is carried out in a voltage regulator, and the hot pressing parameters are: positive electrode side temperature 140~160℃, pressure 180~200MPa, holding pressure for 4~6min; negative electrode side temperature 40~50℃, pressure 50MPa, holding pressure for 4~6min; vacuum sealing is completed in a glove box, and the sealing vacuum degree is ≤10. -3 Pa, activation is performed by charging and discharging three times with a small current of 0.06~0.08C, with a charging and discharging voltage range of 2.5~4.3V.

[0017] Compared with the prior art, the present invention discloses at least the following technical effects: This invention eliminates abrupt interface and lattice mismatch problems between the electrode and electrolyte, and between the electrolyte layer, by constructing a continuously gradient bilayer sulfide electrolyte interface with a nanoscale of 200~400nm. This achieves a smooth transition of ionic conductivity and improves the utilization rate of active materials. At the same time, a kinetically stable negative electrode interface is constructed through a nano-dense composite buffer layer, which effectively blocks electron tunneling and interface side reactions, and suppresses lithium dendrite growth from the root.

[0018] In the preparation process, the present invention uses an air nozzle coating machine inside a glove box to complete continuous coating, combined with the process of waterless oxygen protection transfer of the stacking unit and asymmetric hot pressing by an external voltage regulator. The entire process is carried out in a waterless and oxygen-free closed operation and low temperature heat treatment to avoid material decomposition and element migration, thus ensuring the construction of nanoscale interfaces.

[0019] Furthermore, based on the preparation method of this invention, the battery can achieve excellent performance with a capacity output of 835mAh and a rated voltage of 3.84V, with a charge-discharge cycle of no less than 2600 times and a capacity decay rate of ≤15% after 2600 cycles. It can stably output in a wide temperature range of -20~60℃, solving the technical problems of high interface impedance, low ion transport efficiency, cycle interface degradation and rapid capacity decay of traditional sulfide all-solid-state batteries. At the same time, it avoids the safety risks caused by lithium dendrites, ensuring the performance and safety of the battery, and laying a technical foundation for the commercial application of sulfide-based all-solid-state batteries. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the overall layered structure of the all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte provided by the present invention; Figure 2 A flowchart illustrating the preparation method of the all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte provided by the present invention; Figure 3 This is a graph showing the cycle performance of the all-solid-state nanobattery of this invention.

[0022] Explanation of reference numerals in the attached figures: 1. Positive electrode; 2. First gradient interface; 3. First electrolyte layer; 4. Second gradient interface; 5. Second electrolyte layer; 6. Composite buffer layer; 7. Lithium metal negative electrode. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, this invention provides a double-layer sulfide electrolyte gradient interface all-solid-state battery, including a positive electrode 1, a lithium metal negative electrode 7, and a sulfide solid electrolyte nano-assembly disposed between the positive electrode 1 and the lithium metal negative electrode 7. The sulfide solid electrolyte nano-assembly has a first electrolyte layer 3 and a second electrolyte layer 5 sequentially stacked along the ion transport direction; a first gradient interface 2 is formed between the positive electrode 1 and the first electrolyte layer 3, and a second gradient interface 4 is formed between the first electrolyte layer 3 and the second electrolyte layer 5. Both the first gradient interface 2 and the second gradient interface 4 are nanoscale interfaces with continuous and gradual changes in chemical composition and / or microstructure without abrupt changes in composition; a composite buffer layer 6 is disposed between the second electrolyte layer 5 and the lithium metal negative electrode 7.

[0026] Specifically, cathode 1 uses LiNi x Coy Mn z The O2 ternary cathode material, wherein x ≥ 0.9, y and z are positive numbers greater than 0 and satisfy x + y + z = 1, ensures that the battery has a high energy density output, meeting the high-performance requirements of all-solid-state nano-batteries. The nanoscale widths of the first gradient interface 2 and the second gradient interface 4 are both controlled to 200~400 nm, specifically exhibiting a continuous gradient nanocrystalline structure. Both gradient interfaces maintain thermodynamic stability within an operating temperature range of -20~60℃, with no harmful phase precipitation, avoiding lithium-ion transport obstruction caused by interfacial element segregation and structural degradation during long-term cycling.

[0027] The first electrolyte layer 3 is a silver-germanium ore-type nanocrystalline sulfide electrolyte with the general formula Li6PS5X, where X is selected from one or more of Cl, Br, and I. Its room temperature ionic conductivity is stable at 5-8 mS / cm, ensuring chemical compatibility with the high-voltage positive electrode and suppressing side reactions at the positive electrode. The second electrolyte layer 5 is Li... 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The nanocrystalline sulfide electrolyte exhibits a room-temperature ionic conductivity of 12-15 mS / cm, achieving highly efficient lithium-ion conduction and overcoming the shortcomings of single electrolytes in ion transport efficiency. The first gradient interface 4 is a nanoscale continuous gradient interface formed between the cathode 1 and the first electrolyte layer 3. Along the ion transport direction, it achieves a smooth transition in chemical composition and microstructure between the cathode material and the sulfide electrolyte, without abrupt changes in composition or crystal form. This effectively eliminates the lattice mismatch problem between the cathode and electrolyte, reduces the cathode / electrolyte interface impedance, and simultaneously suppresses the dissolution of active elements on the cathode side and the occurrence of interfacial side reactions, improving the thermodynamic stability of the interface. The second gradient interface 4 is a nanoscale continuous gradient structure along the ion transport direction, with linearly decreasing X and linearly increasing Si content. The P and S content transitions smoothly, continuously increasing the ionic conductivity from 5-8 mS / cm to 12-15 mS / cm without nanoscale lattice mismatch defects, completely eliminating lattice mismatch and transport barriers between electrolyte layers.

[0028] Furthermore, the composite buffer layer 6 is a Li3PS4-LiF composite buffer layer with a thickness of 10 μm and a Li3PS4 to LiF mass ratio of 4:1. The composite buffer layer 6 forms a kinetically stable nano-interface with the lithium metal anode 7, with an electronic conductivity ≤10. -8 S / cm, ionic conductivity ≥10 -3 S / cm can achieve efficient lithium-ion conduction while blocking electron tunneling, thus suppressing lithium dendrite growth and interfacial side reactions at the source.

[0029] like Figure 2As shown, the present invention also provides a method for preparing the above-mentioned all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte, specifically including the following steps: S1. The positive electrode material, conductive agent and binder are mixed to form a slurry, which is then coated onto the current collector and dried, rolled and stamped to obtain the positive electrode sheet.

[0030] Specifically, the mass ratio of the positive electrode material, conductive agent, and binder is 96:2:2. N-methylpyrrolidone is used as the slurry solvent to ensure that the positive electrode material, conductive agent, and binder are fully mixed and dispersed to form a uniform and stable positive electrode slurry. After coating, vacuum drying is carried out at 85~95℃ for 4.5~5.5h to quickly remove the solvent and ensure that there is no residual moisture inside the positive electrode sheet while avoiding thermal decomposition of the slurry. The rolling pressure is 60~70MPa, which can make the density of the positive electrode sheet meet the standard without damaging the material structure. After stamping, a positive electrode sheet with uniform size and nanoscale flat surface is obtained.

[0031] S2. Place the positive electrode sheet in a glove box and use an air nozzle coating machine to perform in-situ continuous coating to sequentially form a first gradient interface, a first electrolyte layer, a second gradient interface, and a second electrolyte layer.

[0032] Specifically, the entire process is carried out in a sealed, anhydrous, and oxygen-free environment within a glove box. A gas nozzle coating machine is used to linearly adjust the slurry supply at a rate of 8-12 mL / min to form a second gradient interface. The adjustment time is 25-35 minutes, controlling the rate of change of interface composition and the gradient width to ensure the formation of a continuous gradient interface without abrupt changes, thus achieving continuous coating and forming of each layer. After coating, the interface is heat-treated at 160-170℃ in an argon atmosphere within the glove box for 6-8 hours. This process achieves interface crystallization through low-temperature ordered interdiffusion, avoiding element migration and material decomposition problems caused by high temperatures. It also improves the interfacial bonding strength and structural stability. Furthermore, the anhydrous and oxygen-free environment effectively prevents the sulfide electrolyte from decomposing and failing upon contact with water and oxygen.

[0033] S3. A composite buffer layer is formed by coating the surface of the second electrolyte layer with an air nozzle coating machine inside the glove box to obtain a positive electrode sheet with electrolyte and buffer layer.

[0034] Specifically, the entire process is carried out in a glove box using an air-jet coating machine to precisely control the coating thickness to 10μm, so that the LiF component is uniformly dispersed in the Li3PS4 matrix, forming a dense, pinhole-free nanoscale composite buffer layer. This ensures that the buffer layer has a uniform thickness and a dense structure, and achieves a synergistic effect of electronic insulation and ion conduction, providing long-term protection for the lithium metal anode. At the same time, the water- and oxygen-free coating environment avoids interfacial side reactions in the buffer layer material.

[0035] S4. Align and stack the positive electrode and the lithium metal negative electrode in the glove box. Transfer the stacked unit to the voltage regulator for asymmetric hot pressing with complete protection against water and oxygen. Then return the hot-pressed stacked unit to the glove box for vacuum sealing and activation to obtain the double-layer sulfide electrolyte gradient interface all-solid-state nano battery.

[0036] Specifically, the parameters for the asymmetric hot pressing are: positive electrode side temperature 140~160℃, pressure 180~200MPa, holding pressure for 4~6min; negative electrode side temperature 40~50℃, pressure 50MPa, holding pressure for 4~6min. Asymmetric hot pressing can adapt to differences in the thermal stability and pressure resistance of different layers, avoiding side reactions caused by high temperature and high pressure on the negative electrode side, while ensuring a tight bond between each layer without gaps. The entire stacking process is completed in a sealed glove box, and the transfer process employs water- and oxygen-free protection measures to prevent material failure caused by contact between the stacking unit and water / oxygen. Vacuum sealing is completed in a glove box, with a sealing vacuum degree ≤10. -3 Pa completely isolates the battery from air and moisture. Activation is achieved by charging and discharging three times with a small current of 0.06~0.08C, with a charging and discharging voltage range of 2.5~4.3V. This gently activates the battery interface, forming a stable battery nano-interface structure and ensuring stable output of the battery's subsequent electrochemical performance.

[0037] The above content will be further described below through specific implementation methods. The provided embodiments are only some embodiments of the present invention.

[0038] Example 1 In this embodiment, the preparation process of a bilayer sulfide electrolyte gradient interface all-solid-state nanobattery is provided, specifically including: First, prepare the positive electrode: use LiNi 0.9 Co 0.05 Mn 0.05 O2 cathode material, conductive agent and binder are mixed in a mass ratio of 96:2:2, N-methylpyrrolidone solvent is added to form a slurry, which is then coated on the surface of aluminum current collector and vacuum dried at 90°C for 5 hours. After being pressed by a 65MPa pressure roller, a cathode sheet with uniform size and nanoscale flat surface is obtained.

[0039] Secondly, the electrolyte and gradient interface are coated: the positive electrode is placed in a glove box, and in-situ continuous coating is carried out in a closed environment without water or oxygen using a gas nozzle coating machine. The slurry supply is linearly adjusted at a rate of 10 mL / min, and the adjustment time is 30 min to form the second gradient interface. The first gradient interface, the first electrolyte layer, the second gradient interface, and the second electrolyte layer are coated sequentially. Then, the electrode is heat-treated at 165℃ for 7.5 h in an argon atmosphere in the glove box to achieve low-temperature ordered interdiffusion and crystallization of the nanoscale interface.

[0040] Next, the composite buffer layer is coated: a Li3PS4-LiF composite buffer layer is coated on the surface of the second electrolyte layer using an air spray coating machine inside the glove box. The coating thickness is controlled to be 10μm, so that LiF is uniformly dispersed in the Li3PS4 matrix at a mass ratio of 8:2, forming a dense nanoscale composite buffer layer without pinholes, and a positive electrode sheet with electrolyte and buffer layer is obtained.

[0041] Finally, the lamination hot pressing and encapsulation activation are performed: The positive electrode and lithium metal negative electrode are aligned and stacked inside the glove box. The stacked unit is then transferred to a voltage regulator for asymmetric hot pressing using anhydrous and oxygen-free protection measures. The positive electrode side temperature is 150℃, the pressure is 190MPa, and the holding pressure is 5 minutes; the negative electrode side temperature is 45℃, the pressure is 50MPa, and the holding pressure is 5 minutes. After hot pressing, the stacked unit is returned to the glove box and encapsulated under a vacuum of ≤10... -3 Vacuum encapsulation was completed under Pa conditions, and activation was achieved by charging and discharging three times with a small current of 0.075C in the voltage range of 2.5~4.3V to form a stable battery nano-interface structure, resulting in a bilayer sulfide electrolyte gradient interface all-solid-state nano-battery.

[0042] The dimensions of the all-solid-state nanobattery prepared in this embodiment were measured, revealing that it is completely consistent with existing samples of the same specifications, with a dimensional error of 0.3 mm. Based on this, after completing the preparation of the bilayer sulfide electrolyte gradient interface all-solid-state nanobattery described in Example 1, to further evaluate its electrochemical performance stability at different charge-discharge rates, a rate performance comparison test was conducted between the all-solid-state nanobattery of Example 1 and conventional sulfide all-solid-state nanobatteries in the prior art. The test conditions were as follows: charge-discharge tests were conducted at 25°C with charge-discharge rates of 0.1C (baseline), 0.2C, 0.5C, 1C, 2C, and 5C, respectively, and the capacity retention rate at each rate was recorded. The test results are shown in Table 1.

[0043] Table 1 Comparison of rate performance data between Example 1 and existing technologies.

[0044] As shown in Table 1, at a base rate of 0.1C, both the present invention and the prior art batteries maintain a capacity retention rate of 100.0%. As the charge / discharge rate increases, the capacity retention rate of the prior art batteries decreases rapidly, reaching only 45.3% at a high rate of 5C. In contrast, the capacity retention rate of the all-solid-state nano-battery of the present invention is significantly higher than that of the prior art at all rates, maintaining an 88.7% capacity retention rate even at a high rate of 5C. This fully demonstrates that the present invention significantly improves lithium-ion transport efficiency through the design of a nanoscale gradient interface and a nanoscale dense composite buffer layer, enabling the all-solid-state nano-battery to maintain excellent capacity output and structural stability even in high-rate charge / discharge scenarios. This makes it suitable for applications with high rate performance requirements, such as new energy vehicles and portable energy storage.

[0045] In addition, such as Figure 3 As shown, this figure is a cycle performance curve of the all-solid-state nanobattery prepared in this embodiment. Figure 3 As can be seen, the all-solid-state nano battery in this embodiment can be charged and discharged up to 2600 times, with a capacity decay rate of ≤15% after 2600 cycles, and the capacity output is stable at 835mAh with a rated voltage of 3.84V, demonstrating excellent long-cycle stability and high capacity retention.

[0046] Example 2 The difference between this embodiment and Embodiment 1 lies in the preparation process parameters; all other aspects are the same. This embodiment specifically includes: Preparation of positive electrode: LiNi 0.92 Co 0.06 Mn 0.02 O2 cathode material, conductive agent and binder are mixed in a mass ratio of 96:2:2, N-methylpyrrolidone solvent is added to form a slurry, which is then coated on the surface of aluminum current collector and vacuum dried at 85°C for 4.5 hours. After being pressed by a 60MPa pressure roller, a cathode sheet with uniform size and nanoscale flat surface is obtained.

[0047] Electrolyte and gradient interface coating: The positive electrode is placed in a glove box and coated in situ continuously using an air nozzle coating machine in an anhydrous and oxygen-free sealed environment. The slurry supply is linearly adjusted at a rate of 8 mL / min and the adjustment time is 25 min to form the second gradient interface. The first gradient interface, the first electrolyte layer, the second gradient interface, and the second electrolyte layer are coated sequentially. After coating, the electrode is heat-treated at 160℃ for 6 h in an argon atmosphere in the glove box to achieve low-temperature ordered interdiffusion and crystallization of the nanoscale interface.

[0048] Coating composite buffer layer: In the glove box, a Li3PS4-LiF composite buffer layer is coated on the surface of the second electrolyte layer using an air spray coating machine. The coating thickness is controlled to be 10μm, so that LiF is uniformly dispersed in the Li3PS4 matrix at a mass ratio of 4:1, forming a dense nanoscale composite buffer layer without pinholes, and obtaining a positive electrode with electrolyte and buffer layer.

[0049] Lamination Hot Pressing and Encapsulation Activation: The positive electrode and lithium metal negative electrode are aligned and stacked within a glove box. The stacked unit is then transferred to a voltage regulator for asymmetric hot pressing under anhydrous and oxygen-free protection. The positive electrode side temperature is 140℃, pressure is 180MPa, and the pressure is held for 4 minutes; the negative electrode side temperature is 40℃, pressure is 50MPa, and the pressure is held for 4 minutes. After hot pressing, the stacked unit is returned to the glove box and encapsulated under a vacuum of ≤10... -3 Vacuum encapsulation was completed under Pa conditions, and activation was achieved by charging and discharging three times with a small current of 0.06C in the voltage range of 2.5~4.3V to form a stable battery nano-interface structure, thus obtaining an all-solid-state nano-battery.

[0050] Example 3 The difference between this embodiment and Embodiment 1 lies in the preparation process parameters; all other aspects are the same. This embodiment specifically includes: Preparation of positive electrode: LiNi 0.95 Co 0.03 Mn 0.02 O2 cathode material, conductive agent and binder are mixed in a mass ratio of 96:2:2, N-methylpyrrolidone solvent is added to form a slurry, which is then coated on the surface of aluminum current collector and vacuum dried at 95°C for 5.5 hours. After being pressed by a roller at 70MPa pressure, a cathode sheet with uniform size and nanoscale flatness is obtained.

[0051] Electrolyte and gradient interface coating: The positive electrode is placed in a glove box and coated in situ continuously using an air nozzle coating machine in an anhydrous and oxygen-free sealed environment. The slurry supply is linearly adjusted at a rate of 12 mL / min and the adjustment time is 35 min to form the second gradient interface. The first gradient interface, the first electrolyte layer, the second gradient interface, and the second electrolyte layer are coated sequentially. After coating, the electrode is heat-treated at 170℃ for 8 h in an argon atmosphere in the glove box to achieve low-temperature ordered interdiffusion and crystallization of the nanoscale interface.

[0052] Coating composite buffer layer: In the glove box, a Li3PS4-LiF composite buffer layer is coated on the surface of the second electrolyte layer using an air spray coating machine. The coating thickness is controlled to be 10μm, so that LiF is uniformly dispersed in the Li3PS4 matrix at a mass ratio of 4:1, forming a dense nanoscale composite buffer layer without pinholes, and obtaining a positive electrode with electrolyte and buffer layer.

[0053] Lamination Hot Pressing and Encapsulation Activation: The positive electrode and lithium metal negative electrode are aligned and stacked within a glove box. The stacked unit is then transferred to a voltage regulator for asymmetric hot pressing under anhydrous and oxygen-free protection. The positive electrode side temperature is 160℃, pressure is 200MPa, and the pressure is held for 6 minutes; the negative electrode side temperature is 50℃, pressure is 50MPa, and the pressure is held for 6 minutes. After hot pressing, the stacked unit is returned to the glove box and encapsulated under a vacuum of ≤10... -3 Vacuum encapsulation was completed under Pa conditions, and activation was achieved by charging and discharging three times with a small current of 0.08C in the voltage range of 2.5~4.3V to form a stable battery nano-interface structure, thus obtaining an all-solid-state nano-battery.

[0054] Therefore, by adopting the above-mentioned bilayer sulfide electrolyte gradient interface all-solid-state nanobattery and its preparation method, by constructing a bilayer functionalized sulfide electrolyte nanocomponent and a nanoscale continuous gradient interface, and setting a nano-dense composite buffer layer on the negative electrode side, the technical problems of a single electrolyte being unable to simultaneously achieve positive electrode stability and high ionic conductivity, excessive impedance caused by interface abrupt changes, and poor compatibility between sulfide electrolyte and lithium metal negative electrode easily leading to side reactions and lithium dendrites are solved, thus realizing the low interface impedance, high ion transport efficiency and long-cycle stable operation of the all-solid-state nanobattery.

[0055] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0056] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A bilayer sulfide electrolyte gradient interface all-solid-state nanobattery, characterized in that, The device includes a positive electrode, a lithium metal negative electrode, and a sulfide solid electrolyte nanoassembly disposed between the positive electrode and the lithium metal negative electrode. The sulfide solid electrolyte nanoassembly has a first electrolyte layer and a second electrolyte layer stacked sequentially along the ion transport direction. A first gradient interface is formed between the positive electrode and the first electrolyte layer, and a second gradient interface is formed between the first electrolyte layer and the second electrolyte layer. Both the first gradient interface and the second gradient interface are nanoscale interfaces with continuous and gradual changes in chemical composition and / or microstructure without abrupt changes in composition. A composite buffer layer is disposed between the second electrolyte layer and the lithium metal negative electrode.

2. The all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte according to claim 1, characterized in that, The positive electrode is LiNi x Co y Mn z O2 ternary cathode material, wherein x≥0.9, y and z are positive numbers greater than 0 and satisfy x+y+z=1; the nanometer widths of the first gradient interface and the second gradient interface are both 200~400nm, and they remain thermodynamically stable within the operating temperature range of -20~60℃, with no harmful phase precipitation.

3. The all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte according to claim 1, characterized in that, The first electrolyte layer is a silver-germanium ore-type nanocrystalline sulfide electrolyte with the general formula Li6PS5X, where X is selected from one or more of Cl, Br, and I, and has an ionic conductivity of 5~8 mS / cm at room temperature; the second electrolyte layer is Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The nanocrystalline sulfide electrolyte has an ionic conductivity of 12~15 mS / cm at room temperature.

4. The all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte according to claim 1, characterized in that, The second gradient interface has a nanoscale continuous gradient structure with linearly decreasing X content and linearly increasing Si content along the ion transport direction, and a gradual transition in P and S content. The ionic conductivity increases continuously from 5~8 mS / cm to 12~15 mS / cm.

5. The all-solid-state nanobattery with a gradient interface of bilayer sulfide electrolyte according to claim 1, characterized in that, The composite buffer layer is a Li3PS4-LiF nano-dense composite buffer layer with a thickness of 10 μm and a Li3PS4 to LiF mass ratio of 4:

1. The composite buffer layer forms a kinetically stable nano-interface with the lithium metal anode, and has an electronic conductivity ≤10. -8 S / cm, ionic conductivity ≥10 -3 S / cm.

6. A method for preparing a bilayer sulfide electrolyte gradient interface all-solid-state nanobattery as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Mix the positive electrode material, conductive agent and binder to form a slurry, coat it with the current collector, and then dry, roll and punch to obtain the positive electrode sheet; S2. Place the positive electrode sheet in a glove box and use an air nozzle coating machine to perform in-situ continuous coating to sequentially form a first gradient interface, a first electrolyte layer, a second gradient interface and a second electrolyte layer. S3. A composite buffer layer is formed by coating the surface of the second electrolyte layer with an air nozzle coating machine inside the glove box to obtain a positive electrode sheet with electrolyte and buffer layer. S4. Align and stack the positive electrode and the lithium metal negative electrode in the glove box. Transfer the stacked unit to the voltage regulator for asymmetric hot pressing with complete protection against water and oxygen. Then return the hot-pressed stacked unit to the glove box for vacuum sealing and activation to obtain the double-layer sulfide electrolyte gradient interface all-solid-state nano battery.

7. The method according to claim 6, characterized in that, In S1, the mass ratio of the positive electrode material, conductive agent and binder is 96:2:

2. N-methylpyrrolidone is used as the slurry solvent. After coating, the material is vacuum dried at 85~95℃ for 4.5~5.5h. The rolling pressure is 60~70MPa. After stamping, a positive electrode sheet with uniform size and nanoscale flat surface is obtained.

8. The method according to claim 6, characterized in that, In S2, the entire process is carried out in a sealed, anhydrous, and oxygen-free glove box. An air-spray coating machine is used to linearly adjust the slurry supply at a rate of 8~12mL / min to form a second gradient interface. The adjustment time is 25~35min to achieve continuous coating and forming of each layer. After coating, the coating is heat-treated at 160~170℃ in an argon atmosphere in a glove box for 6~8 hours to achieve low-temperature ordered interdiffusion and crystallization of the nanoscale interface.

9. The method according to claim 6, characterized in that, In S3, the entire process is carried out in the glove box using an air spray coating machine to control the coating thickness to 10μm, so that the LiF component is uniformly dispersed in the Li3PS4 matrix to form a dense, pinhole-free nanoscale composite buffer layer.

10. The method according to claim 6, characterized in that, In S4, the entire wafer stacking process is completed in a sealed glove box, and the transfer process of the wafer stacking unit adopts anhydrous and oxygen-free protection measures; asymmetric hot pressing is carried out in a voltage regulator, with the following hot pressing parameters: positive electrode side temperature 140~160℃, pressure 180~200MPa, holding pressure for 4~6min; negative electrode side temperature 40~50℃, pressure 50MPa, holding pressure for 4~6min; vacuum sealing is completed in a glove box, with a sealing vacuum degree ≤10. -3 Pa, activation is performed by charging and discharging three times with a small current of 0.06~0.08C, with a charging and discharging voltage range of 2.5~4.3V.

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