Preparation method of negative-electrode-free PEO-based solid-state lithium-sulfur battery

Abstract

The invention belongs to the technical field of lithium-sulfur all-solid-state electrolyte, and discloses a preparation method of a negative-electrode-free PEO-based solid-state lithium-sulfur battery. The preparation method comprises the following steps: coating LLZTO with lithium iodide in situ, and dissolving LLZTO, Li2S6 and PEO in anhydrous acetonitrile to prepare a solid electrolyte; and the Ketjen black molten sulfur is mixed with a lithium carboxymethyl cellulose / butadiene styrene rubber binder to obtain the sulfur positive pole piece. The prepared electrolyte and the positive pole piece can be arranged in the negative-electrode-free all-solid-state lithium-sulfur battery, so that the safety is improved, the cost is reduced, the energy density of the battery is increased, the dissolution of long-chain lithium polysulfide in the PEO-based all-solid-state lithium-sulfur battery is inhibited, the utilization rate of active substances in the battery is increased, the cycle life of the battery is prolonged, and the stability of the battery is improved; and high-content sulfur loading of the PEO-based all-solid-state lithium-sulfur battery is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolytes, and particularly relates to a preparation method of a lithium-free PEO-based solid-state lithium-sulfur battery. Background Art

[0002] Lithium-sulfur batteries are considered to be one of the most promising energy storage systems due to their high energy density, high theoretical specific capacity, low cost, non-toxicity, etc. At present, solid-state lithium-sulfur batteries with polymer solid electrolytes have great development potential due to their high flexibility and reliable safety; they can inhibit uncontrollable Li dendrites and the flammability of liquid electrolytes; and they have good interfacial compatibility compared with inorganic solid electrolytes. Among them, poly(ethylene oxide) (PEO)-based solid polymer electrolytes have the advantages of low cost, good mechanical stability, good compatibility with electrodes, and good film-forming ability. However, in previous reports, at working temperatures, PEO cannot effectively block the shuttle of long-chain polysulfides, and long-chain polysulfides will dissolve into the PEO-based electrolyte, resulting in the loss of active substances in the battery. In addition, the inherent volume expansion and low ion / electron conductivity of lithium-sulfur batteries result in a low sulfur loading in PEO-based solid-state lithium-sulfur batteries at present.

[0003] In the present invention, long-chain polysulfides and lithium iodide-coated LLZTO are dissolved in PEO. The presence of LLZTO provides a transport path for lithium ions in the high-concentration electrolyte, and lithium iodide is in-situ generated on LLZTO to form a tight and uniform coating layer. Lithium iodide can further increase the ionic conductivity of the electrolyte by promoting the stripping and recovery of lithium ions, and can also make lithium ions transport more uniformly and stably in the electrolyte. The saturation of polysulfides in the PEO electrolyte effectively prevents the further dissolution of polysulfides on the electrode. In addition, the high-concentration solid polymer electrolyte can also reduce the crystallinity of PEO. Lithium carboxymethyl cellulose / styrene-butadiene rubber is used as a water-soluble binder in the sulfur cathode, which can relieve the volume expansion during charge and discharge, inhibit the aggregation of discharge products (insulating short-chain polysulfides), and promote the conversion of short-chain polysulfides. This electrolyte matching this cathode system can cycle charge and discharge under lithium-free conditions, and can avoid the reaction between polysulfides in the electrolyte and lithium metal, improve safety, reduce cost, increase the energy density of the battery, and achieve a high sulfur loading in the solid-state lithium-sulfur battery. Summary of the Invention

[0004] The present invention provides a preparation method of a lithium-free PEO-based solid-state lithium-sulfur battery. In the present invention, lithium iodide is in-situ coated on LLZTO, and it is combined with Li 2 S 6PEO and [substance] are dissolved in anhydrous acetonitrile to form a solid electrolyte; Ketjen black and molten sulfur are used as the electroconductive active material, and the binder is a mixture of lithium carboxymethyl cellulose and styrene-butadiene rubber; the electroconductive active material and the binder are dissolved in water to make a slurry and form a film, obtaining a three-dimensional electroconductive network electrode; finally, the electrode matching the PEO solid electrolyte is assembled into a lithium-sulfur battery without a negative electrode for testing.

[0005] The object of the present invention is specifically achieved through the following technical solutions:

[0006] A preparation method of a lithium-sulfur battery based on a PEO solid electrolyte without a negative electrode, comprising the following steps:

[0007] S1: Inorganic garnet-type ceramic powder and iodine are ball-milled and mixed, and then heated in a high-pressure sealed reactor to uniformly deposit iodine on the ceramic powder to obtain solid A; solid A, an inorganic compound of lithium, and hydrazine hydrate react fully in a solvent, and after centrifugation, washing, and drying, solid B is collected. The first high-temperature dehydration is carried out under a protective atmosphere, and the second high-temperature dehydration is carried out in a vacuum oven to obtain ceramic powder coated with lithium iodide;

[0008] S2: In a glove box filled with argon, the ceramic powder coated with lithium iodide prepared in S1, long-chain polysulfide lithium, and PEO are added to a solvent and mixed and stirred, and then coated on a glass plate and dried to obtain a PEO-based solid electrolyte.

[0009] S3: The electroconductive carbon material and sulfur are mixed and ground, and calcined under a protective atmosphere to obtain a sulfur-carbon composite cathode material; the sulfur-carbon composite material and the binder are dissolved in a solvent and mixed to make a slurry, and the uniformly mixed slurry is coated on electroconductive aluminum foil and dried to obtain a cathode electrode. The cathode electrode prepared above is cut into a circular sheet with a diameter of 12 mm as the cathode of the battery, the PEO-based solid electrolyte prepared above is cut into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and the copper foil is cut into a 16-mm circle as the negative electrode of the battery. In a glove box with a water content and an oxygen content both lower than 0.01 ppm and filled with an argon atmosphere, it is sealed and assembled into a CR2032-type button battery in the order of the positive electrode case, the positive electrode, the solid electrolyte, the negative electrode, the steel sheet, the gasket, and the negative electrode case.

[0010] Preferably, in step S1, the inorganic ceramic powder is at least one of lithium lanthanum zirconium gallium oxide (LLZGO), lithium lanthanum zirconium aluminum oxide (LLZAO), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium niobium oxide (LLZNO), lithium lanthanum zirconium scandium oxide (LLZSO), lithium lanthanum tin niobium oxide (LLSNO), lithium lanthanum tin tantalum oxide (LLSTO), and lithium lanthanum zirconium tantalum oxide (LLZTO); the mass ratio of iodine to the inorganic ceramic powder is 1:2 - 0.5.

[0011] Preferably, in step S1, the rotation speed of the ball mill is 400 - 600 r / min, the ball milling time is 0.5 - 3 h, the heating temperature of the oven is 70 - 150 °C; the heating time is 4 - 16 h.

[0012] Preferably, the inorganic compound of lithium in step S1 is at least one of lithium hydroxide, lithium sulfate, lithium carbonate, lithium amide and lithium imide.

[0013] Preferably, in step S1, the mass ratio of solid A to the inorganic compound of lithium to hydrazine hydrate is 1:0.05-0.25:0.1-0.5.

[0014] Preferably, the solvent in step S1 is at least one of methanol, water, dimethyl sulfoxide, N,N-dimethylformamide, ethanol, ether, chloroform, acetone and toluene; and the mass ratio of the solid A to the solvent is 1:25-50.

[0015] Preferably, in step S1, the protective gas is at least one of helium, argon, nitrogen and neon; the dehydration temperature is 90-120° C.; and the dehydration time is 8 to 16 hours.

[0016] Preferably, the temperature of the second dehydration oven in step S1 is 180-220° C.; and the dehydration time is 12 to 20 hours.

[0017] Preferably, the lithium polysulfide in step S2 is Li 2 S 4 , Li 2 S 5 , Li 2 S 6 , Li 2 S 7 and Li 2 S 8 At least one of the following: the mass ratio of PEO to lithium iodide coated ceramic powder to lithium polysulfide is 5:1-5:0.1-1.

[0018] Preferably, the organic solvent in step S2 is at least one of anhydrous acetonitrile, anhydrous ethanol, anhydrous methanol, N,N-dimethylformamide, anhydrous acetone, and anhydrous propionitrile, and the mass ratio of PEO to the organic solvent is 1:8-16.

[0019] Preferably, in step S2, the stirring temperature is 40-80° C., and the stirring time is 10-15 hours.

[0020] Preferably, the thickness of the solid electrolyte membrane in step S2 is 40-60 μm.

[0021] Preferably, the conductive carbon material in step S3 is at least one of conductive carbon black, Ketjen black, acetylene black, conductive graphite and carbon nanotubes.

[0022] Preferably, in step S3, the mass ratio of the conductive material to elemental sulfur is 1:1-5.

[0023] Preferably, in step S3, the protective atmosphere is at least one of nitrogen, argon, neon, helium, hydrogen-argon, and oxygen; the calcination temperature is 130-170 °C; the calcination time is 8-16 h.

[0024] Preferably, in step S3, the binder is at least one of sodium carboxymethyl cellulose, polyvinylidene fluoride, polyethylene oxide, lithium carboxymethyl cellulose / styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polymethyl methacrylate, polytetrafluoroethylene, polyacrylic acid, polyacrylonitrile, and polyacrylate. The mass ratio of the binder to the sulfur-carbon composite is 1:7-11.

[0025] Preferably, in step S3, the solvent is at least one of N-methylpyrrolidone, water, dimethyl sulfoxide, N,N-dimethylformamide, ethanol, and acetone. The mass ratio of the binder to the solvent is 1:100-300.

[0026] In the present invention, lithium iodide is in-situ coated on LLZTO, and lithium iodide is tightly combined with LLZTO. The presence of LLZTO provides a transport path for lithium ions in the high-concentration electrolyte. The lithium iodide coating layer can further increase the ionic conductivity of the electrolyte by promoting the stripping and recovery of lithium ions, and can also make lithium ions transport more uniformly and stably in the electrolyte. Lithium iodide coats LLZTO, Li 2 S 6 , PEO is dissolved in anhydrous acetonitrile, and after drying, a solid electrolyte is made; the saturation of polysulfide lithium in the PEO electrolyte effectively prevents the further dissolution of polysulfide lithium on the electrode; in addition, the high-concentration solid polymer electrolyte can also reduce the crystallinity of PEO. Lithium carboxymethyl cellulose / styrene-butadiene rubber, as a water-soluble binder, is applied to the sulfur cathode, which can relieve the volume expansion during charge and discharge, inhibit the aggregation of discharge products (insulating short-chain polysulfide lithium), and promote the conversion of short-chain polysulfide lithium. This electrolyte matching this cathode system can cycle charge and discharge under the condition of no anode, and at the same time can avoid the reaction between polysulfide lithium in the electrolyte and lithium flakes, solve the problems of polysulfide lithium dissolution, low sulfur utilization rate, low sulfur loading, poor conductivity, and volume expansion in lithium-sulfur batteries, improve safety, reduce costs, increase the battery energy density, and realize high sulfur loading in solid-state lithium-sulfur batteries. The present invention designs a modification method with simple operation and capable of realizing large-scale synthesis, which provides a reference value for the application of solid-state lithium-sulfur batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the cycle performance diagram of Examples 1-3, Comparative Examples 1 and 2; Figure 2 It is the electrochemical impedance spectroscopy diagram of Examples 1-3, Comparative Examples 1 and 2; Figure 3 It is the cycle performance diagram of Example 1 with high-quality sulfur loading; DETAILED DESCRIPTION OF THE INVENTION

[0028] Example 1

[0029] S1: 3g LLZTO powder and 2g elemental iodine were ball-milled at 500r / min for 1.5 hours, and then heated at 120℃ for 10h in a high-pressure sealed reactor to uniformly deposit iodine on the ceramic powder to obtain solid A; 2g solid A was fully reacted with 0.3g lithium hydroxide and 0.6g hydrazine hydrate in 70g water, and solid B was collected by centrifugation, washing, drying and collection. Solid B was first dehydrated at 105℃ for 12h under argon protection, and then secondly dehydrated at 200℃ in a vacuum oven for 16h to obtain LiI-coated LLZTO powder;

[0030] S2: 0.45 g LiI coated LLZTO powder, 0.75 g PEO and 0.075 g Li 2 S 6 Dissolve in 9g of anhydrous acetonitrile, stir at 60℃ for 12h, and let stand to defoam. Pour the defoamed solution onto a polytetrafluoroethylene glass plate, apply evenly with a scraper, and dry to obtain a 50μm solid electrolyte membrane. Punch into discs for later use.

[0031] S3: Mix and grind 250 mg of Ketjen black and 750 mg of elemental sulfur, calcine at 155 ° C for 12 hours to obtain a sulfur-carbon composite positive electrode material; dissolve 180 mg of sulfur-carbon composite material and 20 mg of carboxymethyl cellulose lithium / styrene-butadiene rubber composite binder in 4 g of water to mix and slurry, apply the slurry on a conductive aluminum foil, and dry to obtain a positive electrode sheet. The prepared positive electrode sheet is cut into a circular sheet with a diameter of 12 mm as the positive electrode of the battery, the prepared PEO-based solid electrolyte is cut into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and the copper foil is cut into a 16 mm circular sheet as the negative electrode of the battery. In a glove box filled with argon atmosphere with a water content and an oxygen content of less than 0.01 ppm, the positive electrode shell, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, and negative electrode shell are sealed and assembled into a CR2032 button battery.

[0032] After the battery was assembled, it was placed at 60°C for 10 hours and then subjected to charge and discharge tests. The discharge capacity after 100 cycles at a voltage of 1.7-2.8V and a current density of 0.5C was 1113.2mAh g -1 At the same time, the electrochemical impedance test showed that the battery resistance R was about 92Ω. With a content of 5mg high-quality sulfur on the positive electrode, the discharge specific capacity after 100 cycles at a current density of 0.5C was as high as 661.0mAh g -1 .

[0033] Example 2

[0034] S1: 4g LLZO powder and 2g elemental iodine were ball-milled at 400r / min for 3 hours, and then heated at 110℃ for 16h in a high-pressure sealed reactor to uniformly deposit iodine on the ceramic powder to obtain solid A; 2g solid A was fully reacted with 0.1g lithium carbonate and 0.2g hydrazine hydrate in 50g acetone, and solid B was collected by centrifugation, washing, drying and collection. Solid B was first dehydrated at 120℃ for 8h under nitrogen protection, and then secondly dehydrated at 200℃ for 16h in a vacuum oven to obtain LiI-coated LLZO powder;

[0035] S2: 0.15 g LiI coated LLZO powder, 0.75 g PEO and 0.075 g Li 2 S 4 Dissolve in anhydrous acetonitrile, stir at 60℃ for 12h, and let stand to defoam. Pour the defoamed solution onto a polytetrafluoroethylene glass plate, apply evenly with a scraper, and dry to obtain a 60μm solid electrolyte membrane. Punch into discs for later use.

[0036] S3: Mix and grind 250 mg of Ketjen black and 750 mg of elemental sulfur, calcine at 155 ° C for 12 hours to obtain a sulfur-carbon composite positive electrode material; dissolve 180 mg of sulfur-carbon composite material and 20 mg of carboxymethyl cellulose lithium / styrene-butadiene rubber composite binder in 4 g of water to mix and slurry, apply the slurry on a conductive aluminum foil, and dry to obtain a positive electrode sheet. The prepared positive electrode sheet is cut into a circular sheet with a diameter of 12 mm as the positive electrode of the battery, the prepared PEO-based solid electrolyte is cut into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and the copper foil is cut into a 16 mm circular sheet as the negative electrode of the battery. In a glove box filled with argon atmosphere with a water content and an oxygen content of less than 0.01 ppm, the positive electrode shell, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, and negative electrode shell are sealed and assembled into a CR2032 button battery.

[0037] After the battery was assembled, it was placed at 60°C for 10 hours and then subjected to charge and discharge tests. The discharge capacity after 100 cycles at a voltage of 1.7-2.8V and a current density of 0.5C was 1019.5mAh g -1 At the same time, the electrochemical impedance test showed that the battery resistance R was about 158Ω. With a content of 5mg high-quality sulfur on the positive electrode, the discharge specific capacity after 100 cycles at a current density of 0.5C was as high as 673.7mAh g -1 .

[0038] Example 3

[0039] S1: 2g LLZAO powder and 2g elemental iodine were ball-milled at 600r / min for 0.5 hours, and then heated at 130℃ for 16h in a high-pressure sealed reactor to uniformly deposit iodine on the ceramic powder to obtain solid A; 2g solid A was fully reacted with 0.5g lithium amide and 1g hydrazine hydrate in 50mL ethanol, and solid B was collected by centrifugation, washing, drying and collection. Solid B was first dehydrated at 90℃ for 8h under neon protection, and then secondly dehydrated at 200℃ for 16h in a vacuum oven to obtain LiI-coated LLZAO powder;

[0040] S2: 0.45 g LiI coated LLZAO powder, 0.75 g PEO and 0.075 g Li 2 S 8 Dissolve in 9g of anhydrous acetonitrile, stir at 60℃ for 12h, and let stand to defoam. Pour the defoamed solution onto a polytetrafluoroethylene glass plate, apply evenly with a scraper, and dry to obtain a 50μm solid electrolyte membrane. Punch into discs for later use.

[0041] S3: Mix and grind 250 mg of Ketjen black and 750 mg of elemental sulfur, calcine at 155 ° C for 12 hours to obtain a sulfur-carbon composite positive electrode material; dissolve 180 mg of sulfur-carbon composite material and 20 mg of carboxymethyl cellulose lithium / styrene-butadiene rubber composite binder in 4 g of water to mix and slurry, apply the slurry on a conductive aluminum foil, and dry to obtain a positive electrode sheet. The prepared positive electrode sheet is cut into a circular sheet with a diameter of 12 mm as the positive electrode of the battery, the prepared PEO-based solid electrolyte is cut into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and the copper foil is cut into a 16 mm circular sheet as the negative electrode of the battery. In a glove box filled with argon atmosphere with a water content and an oxygen content of less than 0.01 ppm, the positive electrode shell, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, and negative electrode shell are sealed and assembled into a CR2032 button battery.

[0042] After the battery was assembled, it was placed at 60°C for 10 hours and then subjected to charge and discharge tests. The discharge capacity after 100 cycles at a voltage of 1.7-2.8V and a current density of 0.5C was 1010.8mAh g -1 At the same time, the electrochemical impedance test showed that the battery resistance R was about 125Ω. With a content of 5mg high-quality sulfur on the positive electrode, the discharge capacity after 100 cycles at a current density of 0.5C was as high as 612.4mAh g -1 .

[0043] Example 4

[0044] S1: 1g LLSNO powder was mixed with 2g elemental iodine by ball milling at 450r / min for 2.5 hours, and then heated at 70℃ for 14h in a high-pressure sealed reactor to uniformly deposit iodine on the ceramic powder to obtain solid A; 2g solid A was fully reacted with 0.2g lithium sulfate and 0.4g hydrazine hydrate in 30mL chloroform, and solid B was collected by centrifugation, washing, drying and collection. Solid B was first dehydrated at 110℃ for 15h under helium protection, and then secondly dehydrated at 200℃ in a vacuum oven for 16h to obtain LiI-coated LLSNO powder;

[0045] S2: 0.75 g LiI coated LLSNO powder, 0.75 g PEO and 0.075 g Li 2 S 5 Dissolve in 9g of anhydrous acetonitrile, stir at 60℃ for 12h, and let stand to defoam. Pour the defoamed solution onto a polytetrafluoroethylene glass plate, apply evenly with a scraper, and dry to obtain a 55μm solid electrolyte membrane. Punch into discs for later use.

[0046] S3: Mix and grind 250 mg of Ketjen black and 750 mg of elemental sulfur, calcine at 155 ° C for 12 hours to obtain a sulfur-carbon composite positive electrode material; dissolve 180 mg of sulfur-carbon composite material and 20 mg of PEO binder in 4 g of water to mix and slurry, apply the slurry on a conductive aluminum foil, and dry to obtain a positive electrode sheet. The prepared positive electrode sheet is cut into a circular sheet with a diameter of 12 mm as the positive electrode of the battery, the prepared PEO-based solid electrolyte is cut into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and the copper foil is cut into a 16 mm circular sheet as the negative electrode of the battery. In a glove box filled with argon atmosphere with a water content and an oxygen content of less than 0.01 ppm, the positive electrode shell, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, and negative electrode shell are sealed and assembled into a CR2032 button battery.

[0047] After the battery was assembled, it was left at 60°C for 10 hours before the charge and discharge test. The discharge capacity after 100 cycles at 1.7-2.8V and 0.5C current density was 945.6mAh g -1 At the same time, the electrochemical impedance test showed that the battery resistance R was about 179Ω. With a content of 5mg high-quality sulfur on the positive electrode, the discharge capacity after 100 cycles at a current density of 0.5C was as high as 528.5mAh g -1 .

[0048] Comparative Example 1

[0049] S1: Dissolve 0.15g LLZTO powder, 0.3g LiTFSI, and 0.75g PEO in 9g anhydrous acetonitrile, stir at 60℃ for 12h, and let stand to defoam. Pour the defoamed solution onto a polytetrafluoroethylene glass plate, apply it evenly with a scraper, and dry to obtain a 50μm solid electrolyte membrane. Punch it into discs for later use.

[0050] S2: Mix and grind 250 mg of Ketjen black and 750 mg of elemental sulfur, calcine at 155 °C for 12 h to obtain a sulfur-carbon composite cathode material; dissolve 180 mg of the sulfur-carbon composite material and 20 mg of polyvinylidene fluoride binder in 4 g of water and mix to make a slurry. Coat the slurry on a conductive aluminum foil and dry to obtain a positive electrode sheet. Cut the above-prepared positive electrode sheet into a circular sheet with a diameter of 12 mm as the positive electrode of the battery, cut the above-prepared PEO-based solid electrolyte into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and cut a copper foil into a 16-mm circular sheet as the negative electrode of the battery. In a glove box with a water content and an oxygen content both lower than 0.01 ppm and filled with an argon atmosphere, assemble and seal into a CR2032 coin cell in the order of positive electrode case, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, negative electrode case.

[0051] After the battery assembly is completed, let it stand at 60 °C for 10 h and then perform charge-discharge tests. At a voltage of 1.7 - 2.8 V and a current density of 0.5 C, the discharge specific capacity after 100 cycles is 161.5 mAh g -1 。Meanwhile, through electrochemical impedance testing, the battery resistance R is approximately 545 Ω. At a content of 5 mg of high-quality sulfur on the positive electrode, the discharge specific capacity after 80 cycles at a current density of 0.5 C is as high as 128.1 mAh g -1 。

[0052] Comparative Example 2

[0053] S1: Dissolve 0.3 g of LiFSI, 0.75 g of PEO, and 0.075 g of Li 2 S 6 in 9 g of anhydrous acetonitrile, stir at 60 °C for 12 h, and then let it stand to defoam. Pour the defoamed solution onto a polytetrafluoroethylene glass plate, scrape it evenly with a spatula, and dry to obtain a 50-μm solid electrolyte membrane. Punch it into circular sheets for standby.

[0054] S3: Mix and grind 250 mg of Ketjen black and 750 mg of elemental sulfur, calcine at 155 °C for 12 h to obtain a sulfur-carbon composite cathode material; dissolve 180 mg of the sulfur-carbon composite material and 20 mg of polymethyl methacrylate binder in 4 g of water and mix to make a slurry. Coat the slurry on a conductive aluminum foil and dry to obtain a positive electrode sheet. Cut the above-prepared positive electrode sheet into a circular sheet with a diameter of 12 mm as the positive electrode of the battery, cut the above-prepared PEO-based solid electrolyte into a circular sheet with a diameter of 16 mm as the separator and electrolyte of the battery, and cut a copper foil into a 16-mm circular sheet as the negative electrode of the battery. In a glove box with a water content and an oxygen content both lower than 0.01 ppm and filled with an argon atmosphere, assemble and seal into a CR2032 coin cell in the order of positive electrode case, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, negative electrode case.

[0055] After the battery assembly is completed, it is left standing at 60 °C for 10 h and then charge-discharge tests are carried out. At a voltage of 1.7 - 2.8 V and a current density of 0.5 C, the discharge specific capacity after 50 cycles is 229.8 mAh g -1 . At the same time, through electrochemical impedance tests, the battery resistance R is obtained to be approximately 716 Ω. At a content of 5 mg of high-quality sulfur on the positive electrode, the discharge specific capacity after 100 cycles at a current density of 0.5 C is as high as 70.0 mAh g -1 .

[0056] Comparative Example 3

[0057] S1: Dissolve 0.3 g of LiI, 0.4 g of LLZTO, 0.75 g of PEO, and 0.075 g of Li 2 S 6 in 9 g of anhydrous acetonitrile, stir at 60 °C for 12 h, and then leave it standing to defoam. After defoaming, pour the solution onto a polytetrafluoroethylene glass plate, scrape it evenly with a spatula, and dry it to obtain a 50-μm solid electrolyte membrane. Punch it into circular pieces for standby.

[0058] S3: Mix and grind 250 mg of Ketjenblack and 750 mg of elemental sulfur, calcine at 155 °C for 12 h to obtain a sulfur-carbon composite positive electrode material; dissolve 180 mg of the sulfur-carbon composite material and 20 mg of polymethyl methacrylate binder in 4 g of water and mix to make a slurry. Coat the slurry on a conductive aluminum foil and dry it to obtain a positive electrode plate. Cut the above-prepared positive electrode plate into circular pieces with a diameter of 12 mm as the positive electrode of the battery, cut the above-prepared PEO-based solid electrolyte into circular pieces with a diameter of 16 mm as the separator and electrolyte of the battery, and cut a copper foil into a circular piece with a diameter of 16 mm as the negative electrode of the battery. In a glove box with a water content and an oxygen content both lower than 0.01 ppm and filled with an argon atmosphere, assemble and seal it into a CR2032-type button battery in the order of the positive electrode case, positive electrode, solid electrolyte, negative electrode, steel sheet, gasket, and negative electrode case.

[0059] After the battery assembly is completed, it is left standing at 60 °C for 10 h and then charge-discharge tests are carried out. At a voltage of 1.7 - 2.8 V and a current density of 0.5 C, the discharge specific capacity after 100 cycles is 232.8 mAh g -1 . At the same time, through electrochemical impedance tests, the battery resistance R is obtained to be approximately 716 Ω. At a content of 4 mg of high-quality sulfur on the positive electrode, the discharge specific capacity after 35 cycles at a current density of 0.5 C is as high as 41.1 mAh g -1 .

Claims

1. A method for preparing a negative electrode-free PEO-based solid-state lithium-sulfur battery, characterized in that The preparation of the PEO-based solid electrolyte membrane comprises the following steps: S1: Inorganic garnet ceramic powder and elemental iodine are ball-milled and mixed, and then heated in a high-pressure sealed reactor to allow the iodine to sublime and evenly deposit on the ceramic powder to obtain solid A; S2: The solid A obtained in S1 is fully reacted with an inorganic compound of lithium and hydrazine hydrate in a solvent, and the solid B is collected by centrifugation, washing, and drying. The solid B is first dehydrated at high temperature under a protective atmosphere, and then dehydrated at high temperature for the second time in a vacuum oven to obtain a lithium iodide-coated ceramic powder; S3: In an argon-filled glove box, add the lithium iodide-coated ceramic powder, long-chain lithium polysulfide and PEO prepared in S2 into the solvent, mix and stir, coat on a glass plate and dry to obtain a PEO-based solid electrolyte.

2. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: In step S1, the inorganic ceramic powder is at least one of lithium lanthanum zirconium gallium oxide (LLZGO), lithium lanthanum zirconium aluminum oxide (LLZAO), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium niobium oxide (LLZNO), lithium lanthanum zirconium scandium oxide (LLZSO), lithium lanthanum tin niobium oxide (LLSNO), lithium lanthanum tin tantalum oxide (LLSTO), and lithium lanthanum zirconium tantalum oxide (LLZTO); the mass ratio of elemental iodine to the inorganic ceramic powder is 1:2-0.

5.

3. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: In step S1, the ball mill speed is 400-600 r / min, the ball milling time is 0.5-3 h, the oven heating temperature is 70-150° C., and the heating time is 4-16 h.

4. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: The inorganic compound of lithium in step S2 is at least one of lithium hydroxide, lithium sulfate, lithium carbonate, lithium amide and lithium imide.

5. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: In step S2, the mass ratio of solid A to the inorganic compound of lithium to hydrazine hydrate is 1:0.05-0.25:0.1-0.

5.

6. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: The solvent in step S2 is at least one of methanol, water, dimethyl sulfoxide, N,N-dimethylformamide, ethanol, ether, chloroform, acetone and toluene; the mass ratio of solid A to the solvent is 1:25-50.

7. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: In step S2, the protective gas is at least one of helium, argon, nitrogen and neon; the dehydration temperature is 100-180° C.; and the dehydration time is 8-16 hours.

8. The method for preparing a PEO-based solid electrolyte membrane according to claim 1, characterized in that: In step S3, the lithium polysulfide is at least one of Li2S4, Li2S5, Li2S6, Li2S7 and Li2S8; The mass ratio of PEO and lithium iodide coated ceramic powder to lithium polysulfide is 5:1-5:0.1-1.

9. The preparation of the PEO-based solid electrolyte membrane according to claim 1, characterized in that: The thickness of the solid electrolyte membrane in step S3 is 40-60 μm.

Images