Sulfide bipolar all-solid lithium battery and method for manufacturing the same

Abstract

This invention relates to the field of lithium battery technology, and more particularly to a sulfide bipolar all-solid-state lithium battery and its preparation method. A sulfide bipolar all-solid-state lithium battery includes two or more battery cells, separated by a high-electrode dense glassy protective layer and a bipolar current collector, with the high-electrode dense glassy protective layer disposed between the battery cells and the bipolar current collector; the two or more battery cells, the protective layer, and the bipolar current collector form a battery stacked structure; the outer surface of the battery stacked structure is coated with a thermoplastic elastic material; a positive electrode layer, a sulfide solid electrolyte layer, and a negative electrode layer are sequentially stacked to form a battery cell; lithium polyacrylate is contained on both sides of the sulfide solid electrolyte layer and the bipolar current collector; by adding a protective layer between the sulfide solid electrolyte and the current collector, corrosion of the current collector by hydrogen sulfide gas is avoided, improving the battery cycle life and safety; it also helps to maximize the electrochemical performance of the solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a sulfide bipolar all-solid-state lithium battery and its preparation method. Background Technology

[0002] With the increasing automation and intelligence of the global power grid, advanced energy storage technologies with high energy density, high power density, and high reliability are becoming increasingly important for mobile electronic devices. Solid electrolytes eliminate the possibility of electrolyte leakage, allowing for the design of bipolar battery structures without short-circuit issues. Furthermore, bipolar solid-state batteries reduce the amount of inactive materials required per cell (e.g., wiring) and resistance losses (shorter electron paths, higher contact area), significantly improving specific energy and reducing costs. Common solid electrolytes mainly include inorganic (oxide, sulfide) and organic (polymer) solid electrolytes. Among them, sulfide solid electrolytes have the highest lithium-ion conductivity, even approaching that of liquid lithium-ion electrolytes at room temperature, and possess sufficient oxidation resistance. In recent years, sulfide bipolar solid-state batteries have become one of the hottest research topics in the industry.

[0003] Patent application CN201510378220 discloses a "bipolar electrode, a bipolar all-solid-state battery manufactured using the electrode, and a method for manufacturing the same." By minimizing the thickness of the cathode, anode, and electrolyte in the all-solid-state battery, output and energy density are improved through battery integration. Furthermore, when manufacturing a bipolar all-solid-state battery using the high voltage stability characteristics of a solid electrolyte, differences in elongation or compression ratio between components can be reduced, ensuring or improving process stability and minimizing battery defect rates.

[0004] Patent application number CN201810970840.9 discloses a "current collector configuration structure for a bipolar solid battery", which has a battery cell stack composed of multiple solid battery cells stacked together. It mainly includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer and in contact with the positive electrode active material layer and the negative electrode active material layer respectively. The side of the stack has a positive electrode current collector and a negative electrode current collector.

[0005] Patent application number 201180070981.1 discloses a "bipolar all-solid-state battery", which provides a bipolar all-solid-state battery that can prevent damage to the current collector of the bipolar electrode and can effectively prevent short circuits, as well as a method for manufacturing the above-mentioned bipolar all-solid-state battery. The bipolar electrode has a current collector and an electrode active material layer. The electrode active material layer is composed of a positive electrode active material layer formed on one surface of the current collector and containing a positive electrode active material and a negative electrode active material layer formed on the other surface of the current collector and containing a negative electrode active material. A reinforcing layer is disposed between the end of the electrode active material layer and the surface of the current collector.

[0006] Existing technologies improve battery output energy and application flexibility by optimizing the bipolar structure design, and prevent damage to the bipolar electrode current collector and battery short circuits. However, the current collectors of these bipolar solid-state batteries are susceptible to corrosion, especially since sulfide solid electrolytes easily generate highly corrosive hydrogen sulfide gas. Corrosion of the current collector leads to performance degradation and metal dendrite formation, posing serious safety hazards. Therefore, these technologies are unsuitable for sulfide solid electrolyte systems and have certain technical limitations. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a sulfide bipolar all-solid-state lithium battery and its preparation method. A high-electrode dense glassy protective layer is added between the sulfide solid electrolyte and the current collector. On the one hand, this prevents the current collector from being corroded by hydrogen sulfide gas, thereby improving the battery's cycle life and safety. On the other hand, this protective layer has high lithium-ion transport performance, which is beneficial for maximizing the electrochemical performance of the solid-state battery.

[0008] In a first aspect, this application provides a sulfide bipolar all-solid-state lithium battery, including two or more battery cells, with a high-electric-density glassy protective layer and a bipolar current collector separating the battery cells, and the high-electric-density glassy protective layer is disposed between the battery cells and the bipolar current collector.

[0009] Two or more battery cells, a protective layer, and a bipolar current collector form a battery stacked structure;

[0010] The outer surface of the battery stacked structure is wrapped with a thermoplastic elastic material;

[0011] A battery cell consists of a positive electrode layer, a sulfide solid electrolyte layer, and a negative electrode layer stacked sequentially.

[0012] Both the sulfide solid electrolyte layer and the bipolar current collector contain lithium polyacrylate.

[0013] The bipolar current collector is made of aluminum or aluminum alloy, or copper or copper alloy.

[0014] Furthermore, the protective layer is LLZN containing molten Li3BO3; The molar ratio of lithium in the powder to that in the LLZN material is 1-4:11-23, and the protective layer thickness is 2-6 μm.

[0015] Furthermore, the thickness of the sulfide solid electrolyte is 50-150 μm.

[0016] Furthermore, the two sides of the sulfide electrolyte are coated with lithium polyacrylate with a thickness of 2.0-4.5 μm and high lithium-ion conductivity.

[0017] Furthermore, the two sides of the bipolar current collector are coated with lithium polyacrylate with high lithium-ion conductivity and a thickness of 0.5-1.5 μm.

[0018] Furthermore, the thickness of the thermoplastic elastomer is 2-4 mm.

[0019] Secondly, this application provides a method for preparing a sulfide bipolar all-solid-state lithium battery, comprising the following preparation steps:

[0020] Preparation of LLZN thin films:

[0021] Lithium nitrate and B2O3 were ball-milled and sintered at 500-650℃ under an inert atmosphere for 11-15 hours to obtain Li3BO3 powder.

[0022] Lithium hydroxide, lanthanum oxide, zirconium oxide and niobium oxide powder raw materials were ball-milled; then Li3BO3 powder was added as a co-solvent, wherein the molar ratio of Li3BO3 powder to lithium hydroxide was 2-4:11-16, and then ball milling was performed.

[0023] Then, the temperature is raised to 800-950℃ and heated for 20-35 hours. After cooling, LLZN powder is obtained.

[0024] Next, the LLZN powder is compacted and sintered at 950-1100℃ for 20-40 minutes, then cooled to room temperature to produce LLZN sheets.

[0025] LLZN sheets were placed as protective layers on both sides of a bipolar current collector coated with lithium polyacrylate; lithium polyacrylate was coated on both sides of a sulfide solid electrolyte layer.

[0026] Preparation of sulfide bipolar solid-state batteries:

[0027] A battery stacked structure is formed by sequentially stacking a battery cell, a high-electrode dense glassy state protective layer, a bipolar current collector, another high-electrode dense glassy state protective layer, and the battery cell; wherein, a positive electrode layer, a sulfide solid electrolyte layer, and a negative electrode layer are sequentially stacked to form a battery cell.

[0028] A sulfide bipolar solid-state battery comprises two or more battery cells, which are separated by a high-current dense glassy protective layer and a bipolar current collector, with the high-current dense glassy protective layer disposed between the battery cells and the bipolar current collector.

[0029] Then, at 100-300 standard atmospheres, thermoplastic elastic material is injection molded onto the surface of the battery stack structure to form a sulfide bipolar solid battery.

[0030] Furthermore, the sulfide solid electrolyte in the sulfide solid electrolyte layer is Li6PS5Cl.

[0031] Preferred preparation of Li6PS5Cl sulfide solid electrolyte: Li2S, P2S5 and LiCl are mixed in a molar ratio of 5:1:2 and then ball-milled for 10-16 hours for mechanical alloying treatment. During ball milling, the oxygen partial pressure is ≤0.15ppm and the ball milling speed is 600-800 rpm, and finally Li6PS5Cl sulfide solid electrolyte powder is obtained.

[0032] Preferably, Li6PS5Cl powder is pressed into sheets with a thickness of 50-150 μm under 300-500 standard atmospheres to obtain a Li6PS5Cl sulfide solid electrolyte film.

[0033] Furthermore, during the preparation of LLZN sheets, the temperature is increased to 800-950℃ at a rate of 30-60℃ / min, and then cooled to room temperature at a rate of 10-20℃ / min.

[0034] The LLZN powder was compacted at 10-20 atmospheres for 1-2 hours, and then sintered at 950-1100℃.

[0035] Then it is pressed into a thin sheet under 300-500 standard atmospheres.

[0036] Furthermore, after sintering, the LLZN powder undergoes corona discharge treatment. Specifically, NF3 and H2 gases are introduced into an N2-based plasma, and an AC power supply with a frequency of 15-25 kHz is applied, with the input power maintained at 1.5-2.5 kW. Then, it is pressed into thin sheets with a thickness of 2-6 μm under a standard atmospheric pressure of 300-500 atmospheres.

[0037] In corona discharge treatment, high-energy electrons collide with particles to produce dissociated molecules and atoms, including NF2, NF, F and H, which quickly remove impurities from the surface of objects.

[0038] Preferably, LLZN sheets are placed as protective layers on both sides of a lithium polyacrylate bipolar current collector with high lithium-ion conductivity coated on its surface, wherein the thickness of the lithium polyacrylate is 0.5-1.5 μm.

[0039] Preferably, the thickness of the lithium polyacrylate (PAALi) coated on both sides of the Li6PS5Cl sulfide solid electrolyte layer is 2.0-4.5 μm.

[0040] The solid electrolyte layer is slightly larger than the positive and negative electrode layers, with a redundancy of 2-4 mm at the four edges to prevent short circuits caused by misalignment during assembly. The battery cells are separated by bipolar current collectors. The diagram shows two battery cells, but n different battery cells can be assembled according to the actual discharge voltage requirements.

[0041] The bipolar current collector is made of aluminum or aluminum alloy, copper or copper alloy, etc. The surface of the current collector can be coated with carbon, and the thickness of the current collector can be freely adjusted according to actual needs.

[0042] Preferably, the thickness of the bipolar current collector is 10-50 μm.

[0043] The preparation method of the positive electrode layer is as follows: active material, binder, conductive agent and oxide solid electrolyte particles are added into a high-energy vibration ball mill in a mass ratio of 84-90:3-7:4-8:3-7, and ball milled at room temperature for 15-30 minutes to mix thoroughly. Then, the mixture is pressed into sheets with a thickness of 80-250 μm under 100-200 standard atmospheres.

[0044] The positive electrode active material is one of lithium iron phosphate, lithium manganese oxide, layered ternary material or lithium cobalt oxide, the conductive agent is a carbon-based conductive agent, including one of carbon black, conductive graphite, carbon nanotubes, graphene or Ketjen black, the binder is polytetrafluoroethylene PVDF, and the oxide solid electrolyte particles are one of lithium lanthanum zirconate LLZO or lithium aluminum titanate LATP.

[0045] The negative electrode uses lithium metal (purity > 99.9%), and the solid-state battery assembly process is carried out under conditions where the water and oxygen content are both below 10 ppm.

[0046] Beneficial effects: 1. This application provides a sulfide bipolar all-solid-state lithium battery, including two or more battery cells, with a high-electrode dense glassy protective layer and a bipolar current collector separating the battery cells, and the high-electrode dense glassy protective layer is disposed between the battery cells and the bipolar current collector; the two or more battery cells, the protective layer and the bipolar current collector form a battery stacked structure; the outer surface of the battery stacked structure is wrapped with a thermoplastic elastic material;

[0047] A battery cell consists of a positive electrode layer, a sulfide solid electrolyte layer, and a negative electrode layer stacked sequentially; both the sulfide solid electrolyte layer and the bipolar current collector contain lithium polyacrylate.

[0048] By adding a highly electrically dense glassy protective layer between the sulfide solid electrolyte and the current collector, the current collector is prevented from being corroded by hydrogen sulfide gas, the contact between internal components is strengthened, and the battery cycle life and safety are improved. On the other hand, the protective layer has high lithium-ion transport performance, which is beneficial to the electrochemical performance of the solid battery. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the sulfide bipolar solid-state battery structure of Embodiment 1 of the present invention.

[0050] Figure label:

[0051] 1. Positive electrode layer; 2. Sulfide solid electrolyte; 3. Negative electrode layer; 4. Protective layer; 5. Bipolar current collector; 6. Thermoplastic elastomer; 7. Output terminal. Detailed Implementation

[0052] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Example 1

[0054] A design method for a sulfide bipolar all-solid-state lithium battery involves adding a high-electrode dense glassy protective layer between the sulfide solid electrolyte and the current collector. The solid-state battery has a square stacked structure, with a positive electrode layer, a solid electrolyte layer, and a negative electrode layer forming a battery cell. The solid electrolyte layer has a redundancy of 2-4 mm at its four edges, and the battery cells are separated by bipolar current collectors.

[0055] The actual discharge voltage requirement allows for the assembly of n different battery cells. After battery assembly, thermoplastic elastic material TPE / TPR is injected at 100-300 standard atmospheres, solidified, and then encapsulated to obtain a sulfide bipolar all-solid-state battery. The bipolar current collector is made of aluminum or aluminum alloy, copper or copper alloy, etc. The surface of the current collector can be coated with carbon, and the thickness of the current collector can be freely adjusted according to actual needs, ranging from 10-50 μm.

[0056] The preparation method of the positive electrode layer is as follows: active material, binder, conductive agent and oxide solid electrolyte particles are added into a high-energy vibration ball mill in a mass ratio of 84-90:3-7:4-8:3-7, and ball milled at room temperature for 15-30 minutes to mix thoroughly. Then, the mixture is pressed into sheets with a thickness of 80-250μm under 100-200 standard atmospheres.

[0057] The positive electrode active material is one of lithium iron phosphate, lithium manganese oxide, layered ternary materials, or lithium cobalt oxide. The conductive agent is a carbon-based conductive agent, including one of carbon black, conductive graphite, carbon nanotubes, graphene, or Ketjen black. The binder is polytetrafluoroethylene (PVDF). The oxide solid electrolyte particles are one of lithium lanthanum zirconate (LLZO) or lithium aluminum titanate (LATP). The negative electrode uses a lithium metal sheet (purity > 99.9%). The solid-state battery assembly process is carried out under conditions where the water and oxygen content are both below 10 ppm.

[0058] Its specific preparation is as follows:

[0059] 1. Preparation of sulfide solid electrolytes:

[0060] Lithium nitrate (purity > 99.0%) and B2O3 (purity > 99.0%) were added to a high-energy vibrating ball mill in a stoichiometric ratio (molar ratio of 6:1). After ball milling at room temperature for 15-30 minutes, the mixture was sintered at 500-650℃ under an inert atmosphere for 11-15 hours to obtain Li3BO3 powder.

[0061] Lithium hydroxide, lanthanum oxide, zirconium oxide, and niobium oxide powder (all with a purity greater than 99.0%) were added to a high-energy vibrating ball mill in a lithium:lanthanum:zirconium:niobium molar ratio of 28:12:6:1. Then, an appropriate amount of Li3BO3 powder was added as a co-solvent to lower the synthesis temperature and stabilize the cubic structure of the product. The molar ratio of Li3BO3 powder to lithium hydroxide was 2-4:11-16.

[0062] Then, after ball milling at room temperature for 3-6 hours to ensure thorough and uniform mixing of all raw materials, the mixture is heated in air at 800-950℃ for 20-35 hours at a heating rate of 30-60℃ / min, and then cooled to room temperature at a cooling rate of 10-20℃ / min to obtain LLZN powder. The LLZN powder is then fed into a high-energy vibratory ball mill and ball milled at room temperature for 30-60 minutes to refine the particle size. The ball-milled powder is then compacted at 10-20 atmospheres for 1-2 hours, followed by sintering at 950-1100℃ for 20-40 minutes, and then cooled to room temperature. The purpose of this step is to melt the Li3BO3 particles, which act as a binder, making the LLZN material's crystal structure more compact and increasing its density. This reduces the internal resistance of lithium-ion transport and provides a "waterproof" intermediate layer. The obtained material is subjected to corona discharge treatment. Specifically, NF3 and H2 gases are introduced into an N2-based plasma, and an AC power supply with a frequency of 15-25 kHz is applied, with the input power maintained at 1.5-2.5 kW. High-energy electrons collide with particles to generate dissociated molecules and atoms, including NF2, NF, F, and H, rapidly removing impurities from the object's surface. Then, it is pressed into a thin sheet with a thickness of 2-6 μm under 300-500 standard atmospheres. The LLZN sheet is placed as a protective layer on both sides of the bipolar current collector. To increase the adhesion between the LLZN protective layer and the bipolar current collector, a high-lithium-ion-conductivity lithium polyacrylate (PAALi) with a thickness of 0.5-1.5 μm is coated onto the surface of the bipolar current collector.

[0063] b. Li₂S (purity > 99.9%), P₂S₅ (purity > 99%), and LiCl (purity > 99%) are added to a high-energy vibratory ball mill in a molar ratio of 5:1:2 and ball-milled at room temperature for 10-16 hours for mechanical alloying. During ball milling, the oxygen partial pressure is ≤ 0.15 ppm, and the milling speed is 600-800 rpm, ultimately yielding Li₆PS₅Cl sulfide solid electrolyte powder. The obtained Li₆PS₅Cl powder is pressed into sheets with a thickness of 50-150 μm under 300-500 standard atmospheres to obtain a Li₆PS₅Cl sulfide solid electrolyte film. To suppress side reactions between the sulfide solid electrolyte layer and the positive and negative electrodes, lithium polyacrylate (PAALi) is coated on both sides of the Li₆PS₅Cl sulfide solid electrolyte layer using a scraping method. The PAALi thickness is 2.0-4.5 μm.

[0064] 2. Preparation of sulfide bipolar solid-state batteries:

[0065] The sulfide solid electrolyte layer prepared in step b is used to assemble a bipolar all-solid-state battery, specifically as follows: Figure 1As shown, the solid-state battery has a square stacked structure. Each battery cell consists of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The solid electrolyte layer is slightly larger than the positive and negative electrode layers, with a redundancy of 2-4 mm at the four edges to prevent short circuits caused by misalignment during assembly. The battery cells are separated by bipolar current collectors. The illustration shows two battery cells; n different battery cells can be assembled according to actual discharge voltage requirements. To improve the mechanical stability of the all-solid-state battery, after assembly, thermoplastic elastic material TPE / TPR is injected at 100-300 standard atmospheres. After solidification, it is encapsulated to obtain a sulfide bipolar all-solid-state battery. The bipolar current collector is made of aluminum or aluminum alloy, copper or copper alloy, etc. The surface of the current collector can be coated with carbon. The thickness of the current collector can be freely adjusted according to actual needs; preferably, the thickness is 10-50 μm.

[0066] The positive electrode layer is prepared by adding active materials, binders, conductive agents, and oxide solid electrolyte particles in a mass ratio of 84-90:3-7:4-8:3-7 into a high-energy vibratory ball mill and ball milling for 15-30 minutes at room temperature for thorough mixing. The mixture is then pressed into sheets with a thickness of 80-250 μm under 100-200 standard atmospheres. The positive electrode active material is one of lithium iron phosphate, lithium manganese oxide, layered ternary materials, or lithium cobalt oxide. The conductive agent is a carbon-based conductive agent, including one of carbon black, conductive graphite, carbon nanotubes, graphene, or Ketjen black. The binder is polytetrafluoroethylene (PVDF), and the oxide solid electrolyte particles are one of lithium lanthanum zirconate (LLZO) or lithium aluminum titanate (LATP). The negative electrode sheet uses lithium metal sheets (purity > 99.9%). The solid-state battery assembly process is carried out under conditions where the water and oxygen content are both below 10 ppm.

[0067] 3. Performance Evaluation:

[0068] At 30°C, within an appropriate voltage range (depending on the cathode material), charge-discharge cycle tests were conducted at a 0.2C rate. The discharge capacity of the first cycle was considered the actual capacity. Cycling was continued until a significant short circuit occurred in the battery (voltage drop rate exceeding 5mV / s), at which point the battery was considered to have reached the end of its lifespan, and the test was stopped. At 30°C, the battery's internal resistance was tested using electrochemical impedance spectroscopy (EIS). The battery's state of charge (SOC, the ratio of stored capacity to total capacity in a solid-state battery, usually expressed as a percentage) was adjusted to 50% at a 0.1C rate. The test frequency was 0.1-1000000Hz, and the applied voltage amplitude was 5mV.

[0069] Example 1: A method for preparing a sulfide bipolar all-solid-state lithium battery, comprising the following preparation steps:

[0070] 1. Preparation of sulfide bipolar solid-state batteries:

[0071] a. Lithium nitrate (purity > 99.0%) and B2O3 (purity > 99.0%) were added to a high-energy vibrating ball mill in a stoichiometric ratio (molar ratio of 6:1). After ball milling at room temperature for 22 minutes, the mixture was sintered at 580℃ under an inert atmosphere for 13 hours to obtain Li3BO3 powder.

[0072] Lithium hydroxide, lanthanum oxide, zirconium oxide, and niobium oxide powder (all with a purity greater than 99.0%) were added to a high-energy vibrating ball mill in a lithium:lanthanum:zirconium:niobium molar ratio of 28:12:6:1. Then, an appropriate amount of Li3BO3 powder was added as a co-solvent to lower the synthesis temperature and stabilize the cubic structure of the product. The molar ratio of Li3BO3 powder to lithium hydroxide was 3:13.

[0073] Then, after ball milling at room temperature for 5 hours to ensure thorough and uniform mixing of all raw materials, the mixture was heated at 870°C for 26 hours in air at a heating rate of 40°C / min, and then cooled to room temperature at a cooling rate of 12°C / min to obtain LLZN powder. The LLZN powder was then fed into a high-energy vibratory ball mill and ball milled at room temperature for 45 minutes to refine the powder particle size.

[0074] The ball-milled powder was then compacted at 14 atmospheres for 1.3 hours, and the compacted material was then sintered at 980°C for 30 minutes and cooled to room temperature.

[0075] The obtained material was subjected to corona discharge treatment. Specifically, NF3 and H2 gases were introduced into an N2-based plasma, and an AC power supply with a frequency of 18 kHz and an input power of 2.0 kW was applied. High-energy electrons collided with particles, generating dissociated molecules and atoms, including NF2, NF, F, and H, which rapidly removed impurities from the object's surface. The material was then pressed into a 4 μm thick sheet under 450 standard atmospheres. This sheet effectively removed particulate matter and gaseous pollutants through corona discharge, combining the functions of physical electrostatic capture and chemical plasma oxidation.

[0076] LLZN sheets were placed on both sides of the bipolar current collector as protective layers. To enhance the adhesion between the LLZN protective layer and the bipolar current collector, a high lithium-ion conductivity lithium polyacrylate (PAALi) with a thickness of 0.7 μm was coated on the surface of the bipolar current collector.

[0077] b. Li₂S (purity > 99.9%), P₂S₅ (purity > 99%), and LiCl (purity > 99%) were added to a high-energy vibratory ball mill in a molar ratio of 5:1:2 and ball-milled at room temperature for 14 hours for mechanical alloying. During ball milling, the oxygen partial pressure was ≤ 0.15 ppm, and the milling speed was 700 rpm, ultimately yielding Li₆PS₅Cl sulfide solid electrolyte powder. The obtained Li₆PS₅Cl powder was pressed into sheets with a thickness of 85 μm under 400 standard atmospheres to obtain the Li₆PS₅Cl sulfide solid electrolyte film. To suppress side reactions between the sulfide solid electrolyte layer and the positive and negative electrodes, lithium polyacrylate (PAALi) was coated on both sides of the Li₆PS₅Cl sulfide solid electrolyte layer using a scraping method. The PAALi thickness was 3 μm.

[0078] 2. Preparation of sulfide bipolar solid-state batteries:

[0079] The sulfide solid electrolyte layer prepared in step b is used to assemble a bipolar all-solid-state battery, specifically as follows: Figure 1 As shown, the solid-state battery has a square stacked structure. Each battery cell consists of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The solid electrolyte layer is slightly larger than the positive and negative electrode layers. The four edge redundancy is 3mm to prevent short circuits caused by misalignment during assembly. The battery cells are separated by bipolar current collectors. Figure 1 The battery has two basic cells, and n different basic cells can be assembled according to the actual discharge voltage requirements. To improve the mechanical stability of the all-solid-state battery, after battery assembly, a thermoplastic elastomer (TPE / TPR) (specifically SBS, with a thickness of 12.5 ± 2.5 μm, where the thermoplastic elastomer provides an external binding force to the internal structure) is injected at 150 standard atmospheres. After solidification, it is encapsulated to obtain a sulfide bipolar all-solid-state battery. The bipolar current collector is an aluminum sheet with a thickness of 35 μm.

[0080] The positive electrode layer is prepared by adding active materials, binders, conductive agents and oxide solid electrolyte particles into a high-energy vibratory ball mill at a mass ratio of 88:5:5:2, ball milling at room temperature for 25 minutes to mix thoroughly, and then pressing it into a sheet with a thickness of 180 μm under 10 standard atmospheres.

[0081] The positive electrode active material is lithium iron phosphate, the conductive agent is Ketjen black, the binder is polytetrafluoroethylene (PVDF), and the oxide solid electrolyte particles are lithium lanthanum zirconate (LLZO).

[0082] The negative electrode uses lithium metal (purity > 99.9%), and the solid-state battery assembly process is carried out under conditions where the water and oxygen content are both below 10 ppm.

[0083] Example 2: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, the preparation process in Example 2 is as follows:

[0084] a. Lithium nitrate (purity > 99.0%) and B2O3 (purity > 99.0%) were added to a high-energy vibrating ball mill in a stoichiometric ratio (molar ratio of 6:1). After ball milling at room temperature for 30 minutes, the mixture was sintered at 650℃ under an inert atmosphere for 15 hours to obtain Li3BO3 powder.

[0085] Lithium hydroxide, lanthanum oxide, zirconium oxide, and niobium oxide powder (all with a purity greater than 99.0%) were added to a high-energy vibrating ball mill in a lithium:lanthanum:zirconium:niobium molar ratio of 28:12:6:1. Then, an appropriate amount of Li3BO3 powder was added as a co-solvent to lower the synthesis temperature and stabilize the cubic structure of the product. The molar ratio of Li3BO3 powder to lithium hydroxide was 2:16.

[0086] Then, after ball milling at room temperature for 6 hours to ensure thorough and uniform mixing of all raw materials, the mixture was heated at 950°C for 35 hours in air at a heating rate of 60°C / min, and then cooled to room temperature at a cooling rate of 10°C / min to obtain LLZN powder. The LLZN powder was then fed into a high-energy vibratory ball mill and ball milled at room temperature for 30 minutes to refine the powder particle size.

[0087] The ball-milled powder was then compacted at 10 atmospheres for 1 hour, and then sintered at 950°C for 40 minutes and cooled to room temperature.

[0088] The obtained material was subjected to corona discharge treatment. Specifically, NF3 and H2 gases were introduced into an N2-based plasma, and an AC power supply with a frequency of 15 kHz and an input power of 2.5 kW was applied. High-energy electrons collided with particles, generating dissociated molecules and atoms, including NF2, NF, F, and H, which rapidly removed impurities from the object's surface. The material was then pressed into a thin sheet with a thickness of 6 μm under 500 standard atmospheres.

[0089] LLZN sheets were placed on both sides of the bipolar current collector as protective layers. To enhance the adhesion between the LLZN protective layer and the bipolar current collector, a high lithium-ion conductivity lithium polyacrylate (PAALi) with a thickness of 0.5 μm was coated on the surface of the bipolar current collector.

[0090] The remaining conditions are the same as in Example 1.

[0091] Example 3, a method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, the preparation process of step b in Example 3 is as follows:

[0092] Li₂S (purity > 99.9%), P₂S₅ (purity > 99%), and LiCl (purity > 99%) were added to a high-energy vibratory ball mill in a molar ratio of 5:1:2 and ball-milled at room temperature for 10 hours for mechanical alloying. During ball milling, the oxygen partial pressure was ≤ 0.15 ppm, and the milling speed was 600 rpm, ultimately yielding Li₆PS₅Cl sulfide solid electrolyte powder. The obtained Li₆PS₅Cl powder was pressed into sheets with a thickness of 50 μm under 500 standard atmospheres to obtain a Li₆PS₅Cl sulfide solid electrolyte film. To suppress side reactions between the sulfide solid electrolyte layer and the positive and negative electrodes, lithium polyacrylate (PAALi) was coated on both sides of the Li₆PS₅Cl sulfide solid electrolyte layer using a scraping method. The PAALi thickness was 4.5 μm.

[0093] The remaining conditions are the same as in Example 1.

[0094] Example 4: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, the preparation process in Example 4 is as follows:

[0095] The sulfide solid electrolyte layer prepared in step b is used to assemble a bipolar all-solid-state battery, specifically as follows: Figure 1 As shown, the solid-state battery has a square stacked structure. Each battery cell consists of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The solid electrolyte layer is slightly larger than the positive and negative electrode layers. The four edge redundancy is 4 mm to prevent short circuits caused by misalignment during assembly. The battery cells are separated by bipolar current collectors. Figure 1 The battery has two battery cells. To improve the mechanical stability of the all-solid-state battery, after the battery assembly is completed, thermoplastic elastic material TPE / TPR is injected at 300 standard atmospheres. After solidification, it is encapsulated to obtain a sulfide bipolar all-solid-state lithium battery.

[0096] The positive electrode layer is prepared by adding active material, binder, conductive agent, and oxide solid electrolyte particles in a mass ratio of 90:3:4:3 into a high-energy vibratory ball mill, ball milling at room temperature for 30 minutes to ensure thorough mixing, and then pressing it into a sheet with a thickness of 80 μm under 200 standard atmospheres. The positive electrode active material is lithium manganese oxide, the conductive agent is carbon black, the binder is polytetrafluoroethylene (PVDF), and the oxide solid electrolyte particles are lithium aluminum titanate (LATP).

[0097] The negative electrode uses lithium metal (purity > 99.9%), and the solid-state battery assembly process is carried out under conditions where the water and oxygen content are both below 10 ppm.

[0098] Comparative Example 1: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, the LLZN sheet in Comparative Example 1 does not contain Li3BO3, and the other conditions are the same as in Example 1.

[0099] Comparative Example 2: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, in step a of Comparative Example 2, the mixed powder of LLZN and Li3BO3 was compacted at 20 atmospheres for 2 hours and then did not undergo sintering at 980 °C. The other conditions were the same as in Example 1.

[0100] Comparative Example 3 is a method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, Comparative Example 3 does not contain LLZN+Li3BO3 sheets, and the other conditions are the same as those in Example 1.

[0101] Comparative Example 4: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, Comparative Example 4 does not contain lithium polyacrylate on both sides of the bipolar current collector, and the other conditions are the same as in Example 1.

[0102] Comparative Example 5: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, the sulfide solid electrolyte in Comparative Example 5 does not contain lithium polyacrylate on both sides, and the other conditions are the same as in Example 1.

[0103] Comparative Example 6: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, Comparative Example 6 does not contain lithium polyacrylate on either side of the sulfide solid electrolyte and the bipolar current collector, and the other conditions are the same as in Example 1.

[0104] Comparative Example 7: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, in Comparative Example 7, the sulfide solid electrolyte layer is coated with lithium polyacrylate (PAALi) on both sides with a thickness of 9.0 μm, and the thickness of the lithium polyacrylate (PAALi) on the surface of the bipolar current collector is 5 μm; the other conditions are the same as in Example 1.

[0105] Comparative Example 8: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, the LLZN+Li3BO3 mixed material in Comparative Example 8 was not subjected to corona discharge impurity removal treatment, and the other conditions were the same as in Example 1.

[0106] Comparative Example 9: A method for preparing a sulfide bipolar all-solid-state lithium battery. Compared with Example 1, Comparative Example 9 does not contain thermoplastic elastic material TPE / TPR, and the other conditions are the same as those in Example 1.

[0107] Performance evaluation:

[0108] At 30℃, charge-discharge cycle tests were conducted at a rate of 0.2C within the range of 2.8-3.7V until a significant short circuit appeared in the battery (voltage drop rate exceeding 5mV / s), at which point the battery was considered to have reached the end of its lifespan, and the test was stopped. At 30℃, the battery's internal resistance was measured using electrochemical impedance spectroscopy (EIS). The battery's state of charge (SOC, the ratio of stored capacity to total capacity in a solid-state battery, usually expressed as a percentage) was adjusted to 50% at a rate of 0.1C. The test frequency was 0.1-1000000Hz, and the applied voltage amplitude was 5mV. The test results are shown in Table 1.

[0109] Table 1. Performance Comparison of Sulfide Bipolar Solid-State Batteries Prepared Under Different Conditions

[0110]

[0111] The specific results are shown in Table 1. Combined with Examples 1-4, it can be seen that within the technical scope required by the present invention, the prepared sulfide bipolar solid battery has high actual discharge capacity, low internal resistance and good cycle life, among which Example 1 has the best effect.

[0112] Combining Example 1 and Comparative Examples 1-3, the actual discharge capacity and initial internal resistance of the solid-state batteries are quite similar. However, the cycle life of Comparative Examples 1-3 is lower than that of Example 1. The main reason is that the LLZN protective layer containing molten Li3BO3 can effectively block the generation of hydrogen sulfide byproducts by the sulfide electrolyte, avoid corrosion of the bipolar current collector, and extend the cycle life.

[0113] In conjunction with Examples 1 and Comparative Examples 4-7, coating both sides of the sulfide and both sides of the bipolar current collector with lithium acrylate is beneficial to increase the interfacial bonding strength, reduce the internal resistance of lithium-ion transport, overcome the interfacial contact failure caused by the volume change of the active material during charging and discharging, and extend the cycle life of the solid battery.

[0114] Combining Example 1 and Comparative Example 8, the internal resistance and cycle life of the solid battery were significantly improved after the LLZN+Li3BO3 protective layer was removed by corona discharge. The main reason is that residual impurities on the particle surface reduce conductivity and cause additional polarization loss during cycling, thus reducing the cycle life of the battery.

[0115] In conjunction with Example 1 and Comparative Example 9, injecting thermoplastic elastomer into the battery during assembly can increase the internal pressure of the solid battery, ensuring that the battery materials remain in close contact during cycling, reducing the interfacial contact resistance of the solid battery, and extending the cycle life.

[0116] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A sulfide bipolar all-solid lithium battery characterized by, It includes two or more battery cells, with a high-current dense glassy protective layer and a bipolar current collector separating the battery cells, and the high-current dense glassy protective layer is disposed between the battery cells and the bipolar current collector; Two or more battery cells, a protective layer, and a bipolar current collector form a battery stacked structure; The outer surface of the battery stacked structure is wrapped with a thermoplastic elastic material; A battery cell consists of a positive electrode layer, a sulfide solid electrolyte layer, and a negative electrode layer stacked sequentially. Both the sulfide solid electrolyte layer and the bipolar current collector contain lithium polyacrylate. The bipolar current collector is made of aluminum or aluminum alloy, or copper or copper alloy.

2. The sulfide bipolar all-solid-state lithium battery according to claim 1, characterized in that, The protective layer is LLZN containing molten Li3BO3; The protective layer has a thickness of 2-6 μm and a molar ratio of the powder to lithium in the LLZN material of 1-4:11-23.

3. The sulfide bipolar all-solid lithium battery according to claim 1 or 2, characterized by, The thickness of the sulfide solid electrolyte is 50-150 μm.

4. The sulfide bipolar all-solid lithium battery according to claim 3, characterized by The two sides of the sulfide electrolyte are coated with lithium polyacrylate with a thickness of 2.0-4.5 μm and high lithium-ion conductivity.

5. The sulfide bipolar all-solid lithium battery according to any one of claims 1 to 2, 4, characterized by, The two sides of the bipolar current collector are coated with lithium polyacrylate with high lithium-ion conductivity and a thickness of 0.5-1.5 μm.

6. A sulfide bipolar all-solid-state lithium battery according to claim 5, characterized in that, The thickness of thermoplastic elastomers is 2-4 mm.

7. A method for preparing a sulfide bipolar all-solid-state lithium battery according to any one of claims 1-6, characterized in that, The preparation steps include the following: Preparation of LLZN thin films: Lithium nitrate and B2O3 were ball-milled and sintered at 500-650℃ under an inert atmosphere for 11-15 hours to obtain Li3BO3 powder. Lithium hydroxide, lanthanum oxide, zirconium oxide and niobium oxide powder raw materials were ball-milled; then Li3BO3 powder was added as a co-solvent, wherein the molar ratio of Li3BO3 powder to lithium hydroxide was 2-4:11-16, and then ball milling was performed. Then, the temperature is raised to 800-950℃ and heated for 20-35 hours. After cooling, LLZN powder is obtained. Next, the LLZN powder is compacted and sintered at 950-1100℃ for 20-40 minutes, then cooled to room temperature to produce LLZN sheets. LLZN sheets were placed as protective layers on both sides of a bipolar current collector coated with lithium polyacrylate; lithium polyacrylate was coated on both sides of a sulfide solid electrolyte layer. Preparation of sulfide bipolar solid-state batteries: A battery stacked structure is formed by sequentially stacking a battery cell, a high-electrode dense glassy state protective layer, a bipolar current collector, another high-electrode dense glassy state protective layer, and the battery cell; wherein, a positive electrode layer, a sulfide solid electrolyte layer, and a negative electrode layer are sequentially stacked to form a battery cell. A sulfide bipolar solid-state battery comprises two or more battery cells, which are separated by a high-current dense glassy protective layer and a bipolar current collector, with the high-current dense glassy protective layer disposed between the battery cells and the bipolar current collector. Then, at 100-300 standard atmospheres, thermoplastic elastic material is injection molded onto the surface of the battery stack structure to form a sulfide bipolar solid battery.

8. The method for preparing a sulfide bipolar all-solid-state lithium battery according to claim 7, characterized in that, The sulfide solid electrolyte in the sulfide solid electrolyte layer is Li6PS5Cl.

9. A method for preparing a sulfide bipolar all-solid-state lithium battery according to claim 7 or 8, characterized in that, During the preparation of LLZN sheets, the temperature is increased to 800-950℃ at a rate of 30-60℃ / min, and then cooled to room temperature at a rate of 10-20℃ / min. The LLZN powder was compacted at 10-20 atmospheres for 1-2 hours, and then sintered at 950-1100℃. Then it is pressed into a thin sheet under 300-500 standard atmospheres.

10. The method for preparing a sulfide bipolar all-solid-state lithium battery according to claim 9, characterized in that, After sintering, LLZN powder undergoes corona discharge treatment. Specifically, NF3 and H2 gases are introduced into N2-based plasma, and an AC power supply with a frequency of 15-25 kHz is applied, with the input power maintained at 1.5-2.5 kW. Then, it is pressed into thin sheets with a thickness of 2-6 μm under a standard atmospheric pressure of 300-500 atmospheres.

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