Sulfide solid electrolyte, method of preparation and all-solid-state lithium-ion battery

Abstract

The application provides a preparation method of a sulfide solid-state electrolyte, according to a chemical formula of the sulfide solid-state electrolyte, the proportion of other corresponding substances except sulfur is obtained; the corresponding substances are stacked and compressed to obtain a solid-state alloy; the solid-state alloy is subjected to sulfidation treatment to obtain the sulfide solid-state electrolyte sample; and the sulfide solid-state electrolyte sample is subjected to annealing treatment to obtain the sulfide solid-state electrolyte. The Li4SnS4 prepared by the above embodiment of the application has better ionic conductivity than traditional solid-state electrolytes, the ionic conductivity reaches 3.5*10(‑4) S cm(‑1), and compared with other sulfide solid-state electrolytes, the sulfide solid-state electrolyte has very excellent air stability, and doping of the solid-state electrolyte with M metal can significantly improve the ionic conductivity. The above preparation method is easy to scale up, the metal sulfidation reaction has high activity, the corresponding sulfide is easy to produce, the cost of preparation of the sulfide solid-state electrolyte is greatly reduced, the production cycle is shortened, and large-scale industrialization of the Li4SnS4 becomes possible.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of all-solid-state lithium ion batteries, in particular to a sulfide solid electrolyte, a preparation method and an all-solid-state lithium ion battery. BACKGROUND

[0002] Traditional lithium ion batteries cannot meet the current demand from the perspective of energy density or safety, so it is urgent to explore a battery system with better performance. All-solid-state batteries greatly improve the safety of the battery because the electrolyte is solid. The commonly used solid electrolytes at present mainly include LiPON, Li2SiO3, Li7La3Zr2O 12 However, the room temperature ionic conductivity of the currently used solid electrolyte is low, and the preparation rate is generally slow. It is difficult to replace the liquid electrolyte battery on the market. Before the room temperature ionic conductivity is improved to the ideal effect, it is difficult to obtain large-scale commercial use. Sulfide solid electrolytes have high ionic conductivity and low grain boundary resistance. However, most of them have poor air stability. According to the hard-soft acid-base theory, Li4SnS4 has very good air stability and does not react with air to release toxic hydrogen sulfide gas. In addition, a solid solution Li4-x S b x Sn1-xS4 can be formed in the Li4SnS4-Li3SbS4 system. In this system, the ionic conductivity of Li 3.8 Sb 0.2 Sn 0.8 S4 is the highest, reaching 3.5*10(-4) S cm(-1), which is 5 times that of Li4SnS4. High-temperature powder sintering is one of the main methods for preparing Li4SnS4 solid electrolyte at present. However, this method uses unstable, expensive lithium sulfide and tin sulfide, and sulfur powder as synthesis raw materials. Lithium sulfide is easily deliquesced in air to release hydrogen sulfide gas, and the preparation process includes long-time mechanical ball milling and long-time high-temperature sintering. SUMMARY

[0003] In view of this, it is necessary to provide a high-conductivity, stable, high-energy-density hydrosulfide solid electrolyte, a preparation method and an all-solid-state lithium ion battery in view of the defects in the prior art.

[0004] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0005] One of the purposes of the present application is to provide a preparation method of a sulfide solid electrolyte, comprising the following steps:

[0006] According to the chemical formula of the sulfide solid electrolyte, the proportion of other corresponding substances except sulfur is obtained;

[0007] The corresponding substances are stacked and compressed to obtain a solid alloy;

[0008] The solid alloy is subjected to vulcanization treatment to obtain the sulfide solid electrolyte sample;

[0009] The sulfide solid electrolyte sample is subjected to annealing treatment to obtain the sulfide solid electrolyte.

[0010] In some embodiments, in the step of obtaining the proportion of the corresponding substances according to the chemical formula of the sulfide solid electrolyte, the chemical formula of the sulfide solid electrolyte is Li4SnS4, and the atomic ratio of Li and Sn is 4:1.

[0011] In some embodiments, the Sn atoms are derived from a tin foil or a tin-based alloy foil, and the alloy includes a tin-antimony alloy, a tin-lanthanum alloy, and the Li atoms are derived from a lithium strip.

[0012] In some embodiments, the thickness of the lithium strip is 20 μm, and the thickness of the tin foil is 30 μm.

[0013] In some embodiments, the step of stacking the corresponding substances and compressing to obtain a solid alloy specifically includes the following steps:

[0014] The corresponding substances are stacked and compressed to obtain a solid alloy;

[0015] In some embodiments, the rolling machine is a cold-rolling rolling machine with gap adjustment and anti-sticking coating rollers.

[0016] In some embodiments, the step of subjecting the solid alloy to vulcanization treatment to obtain the sulfide solid electrolyte sample specifically includes the following steps:

[0017] After the solid alloy is subjected to inert gas protection and sealing treatment, it is transferred to a vacuum annealing furnace, and is subjected to pre-sulfurization treatment at 200-380°C for 30-60 minutes in an argon and hydrogen sulfide gas atmosphere or a pure hydrogen sulfide gas atmosphere, and is then heated to 400-550°C for complete vulcanization treatment, with a vulcanization time of 1-2 hours, to obtain the sulfide solid electrolyte.

[0018] In some embodiments, the step of subjecting the sulfide solid electrolyte sample to annealing treatment to obtain the sulfide solid electrolyte specifically includes the following steps:

[0019] The sulfide solid electrolyte sample is ground, tabletted, placed in a vacuum annealing furnace, filled with 25Kpa of argon and 5Kpa of hydrogen sulfide mixed gas, and subjected to crystallization annealing, with an annealing temperature of 470-540 DEG C and an annealing time of 1-2 hours.

[0020] The second object of the present application provides a sulfide solid electrolyte prepared by the preparation method of the sulfide solid electrolyte.

[0021] The third object of the present application provides a full solid-state lithium ion battery comprising the sulfide solid electrolyte.

[0022] The technical scheme of the present application has the following beneficial effects:

[0023] The method for preparing the sulfide solid electrolyte provided by the present application obtains the proportion of other corresponding substances except sulfur according to the chemical formula of the sulfide solid electrolyte, stacks and compresses the corresponding substances to obtain a solid alloy, sulfidizes the solid alloy to obtain the sulfide solid electrolyte sample, and anneals the sulfide solid electrolyte sample to obtain the sulfide solid electrolyte. The Li4SnS4 prepared by the above-mentioned embodiments of the present application has better ionic conductivity than traditional solid electrolytes, with an ionic conductivity of 3.5*10(-4) S cm(-1). Compared with other sulfide solid electrolytes, the sulfide solid electrolyte has very good air stability, and doping the solid electrolyte with M metal can significantly improve the ionic conductivity. The above-mentioned preparation method is easy to scale up, and the metal sulfidation reaction has high activity and is easy to produce corresponding sulfides, which greatly reduces the cost of preparing the sulfide solid electrolyte, shortens the production cycle, and makes large-scale industrialization of Li4SnS4 possible. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application or the prior art description. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0025] Figure 1 The step flow chart of the method for preparing the sulfide solid electrolyte provided in Embodiment 1 of the present application.

[0026] Figure 2 The lithium-tin alloy foil is the pressed and bonded lithium-tin alloy foil in Embodiment 1 of the present application.

[0027] Figure 3 The scanning electron microscope cross-sectional view of the lithium-tin alloy foil in Embodiment 1 of the present application.

[0028] Figure 4 is the solid-state electrolyte after sulfidation annealing in embodiment 1 of the present application.

[0029] Figure 5 is the cross-sectional view of the solid-state electrolyte wafer after crystallization annealing in embodiment 1 of the present application.

[0030] Figure 6 is the EIS impedance spectrum in embodiment 1 of the present application.

[0031] Figure 7 is the Raman test graph in embodiment 1 of the present application. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below with reference to the accompanying drawings. The embodiments shown in the drawings are examples for explaining the present application and should not be construed as limiting the present application.

[0033] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present application.

[0034] In addition, the terms "first", "second" are only for the purpose of description, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features referred to. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0035] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Please refer to Figure 1 The embodiment of the present application provides a step flow chart of a sulfide solid-state electrolyte method, which comprises the following steps S110 to S130, and the implementation manner of each step is described in detail below.

[0037] Step S110: According to the chemical formula of the sulfide solid-state electrolyte, the proportion of other corresponding substances except sulfur is obtained.

[0038] In some embodiments, in the step of obtaining the proportion of corresponding substances according to the chemical formula of the sulfide solid electrolyte, the chemical formula of the sulfide solid electrolyte is the chemical formula of Li4SnS4, and the proportion of Li and Sn atoms is 4:1.

[0039] In some embodiments, the Sn atoms used are derived from a tin foil or a tin-based alloy foil, and the alloy includes a tin-antimony alloy, a tin-lanthanum alloy, and the Li atoms are derived from a lithium ribbon.

[0040] In some embodiments, the thickness of the lithium ribbon is 20 μm, and the thickness of the tin foil is 30 μm.

[0041] Step S120: stacking and compressing the corresponding substances to obtain a solid alloy.

[0042] In some embodiments, in the step of stacking and compressing the corresponding substances to obtain a solid alloy, the step specifically includes the following steps: stacking the corresponding substances, and using a roller press to compress the thickness to half of the original thickness, folding and roller pressing, repeating the above operation more than 6 times, until the thickness of the solid alloy after the last roller pressing is between 0.14 mm and 0.04 mm.

[0043] In some embodiments, the roller press is a cold-pressing roller press with gap adjustment and anti-sticking coating rollers.

[0044] Step S130: sulfidizing the solid alloy to obtain the sulfide solid electrolyte sample.

[0045] In some embodiments, in the step of sulfidizing the solid alloy to obtain the sulfide solid electrolyte sample, the step specifically includes the following steps:

[0046] After the solid alloy is subjected to inert gas protection and sealing treatment, it is transferred to a vacuum annealing furnace, and is subjected to a pre-sulfurization treatment at 200-380°C for 30-60 minutes in an argon and hydrogen sulfide gas atmosphere or a pure hydrogen sulfide gas atmosphere, and is then subjected to a complete sulfidization treatment at 400-550°C for 1-2 hours, to obtain a sulfide solid electrolyte.

[0047] Step S140: annealing the sulfide solid electrolyte sample to obtain the sulfide solid electrolyte.

[0048] In some embodiments, in the step of annealing the sulfide solid electrolyte sample to obtain the sulfide solid electrolyte, the step specifically includes the following steps:

[0049] The sulfide solid electrolyte sample is ground, tabletted, placed in a vacuum annealing furnace, filled with 25 Kpa of argon and 5 Kpa of hydrogen sulfide mixed gas, and crystallized annealed at an annealing temperature of 470-540 DEG C for 1-2 hours.

[0050] The Li4SnS4 prepared in the above embodiments of the present application has better ionic conductivity than traditional solid electrolytes, and the ionic conductivity reaches 3.5*10(-4) S cm(-1). Compared with other sulfide solid electrolytes, the Li4SnS4 has very good air stability, and doping the solid electrolyte with M metal can significantly improve the ionic conductivity. The above preparation method is easy to scale up, and the metal sulfidation reaction has high activity, so it is easy to produce the corresponding sulfide, greatly reducing the cost of preparing the sulfide solid electrolyte, shortening the production cycle, and making large-scale industrialization of the Li4SnS4 possible.

[0051] The above technical solutions of the present application are described in detail below in combination with specific embodiments.

[0052] In the embodiments of the present application, the materials and equipment used are purchased through commercial channels unless otherwise specified. The tin material used in the alloying process in the present application is 99.99% tin particles produced by Zhongnuo New Materials, which is fully melted in a crucible and then rolled to a thickness of 30 μm by a roller press, or purchased through general commercial channels. The lithium ribbon is produced by Zhongneng Lithium Industry Co., Ltd., and has a standard thickness of 20 μm. The roller press is a general foil-making small roller press, and the rolling mill is a special rolling mill with an anti-sticking coating on the surface.

[0053] Example 1

[0054] According to the target product chemical formula Li: Sn = 4: 1, for example, 5 pieces of 20 μm thick lithium ribbon and 1 piece of 30 μm thick tin foil are needed for an area of 3 cm*5 cm. Then the lithium ribbon and tin foil are cut to the appropriate size in a glove box with scissors, and then the lithium ribbon is stacked in the order of two layers on top and three layers on the bottom, with the tin foil sandwiched in the middle, to form a sandwiched layered structure. The metal stack is pre-pressed with a release film to prevent wrinkles during rolling. Formal rolling: first adjust the distance between the two rollers to one third of the thickness of the metal stack, roll back and forth three times, and then reduce the roller gap by 0.05 mm after the alloy foil is pressed, and repeat the above operation until the roller gap distance is half of the thickness of the alloy foil; fold the alloy foil in half, and align the two ends. Repeat the above rolling operation steps. After repeating 5 times, the thickness of the last pressing is 0.06 mm.

[0055] The lithium-tin alloy sample is placed in a corundum crucible, sealed with an argon bag, and transferred to a vacuum annealing furnace. Vacuum is drawn, and argon is purged three times. Hydrogen sulfide at 10 KPa and argon at 40 KPa are introduced. The temperature program is set as follows: 25 degrees Celsius is raised to 380 degrees Celsius in 40 minutes, and then held for 1 hour. Then, 380 degrees Celsius is raised to 500 degrees Celsius in 45 minutes, and then held for 2 hours. After sulfuration, the electrolyte is obtained. The sample is placed in a mortar and ground thoroughly. The electrolyte is pressed into a round sheet under a pressure of 30 MPa. Then, the sample is placed in a rotary annealing furnace, and a mixed gas of hydrogen sulfide at 3 KPa and argon at 27 KPa is introduced. Crystallization annealing is performed at 530 degrees Celsius for 2 hours to obtain an annealed and crystallized sheet.

[0056] Figure 2 is a lithium-tin alloy foil after compaction in an embodiment of the present application; Figure 3 is a scanning electron microscope cross-sectional view of a lithium-tin alloy foil in an embodiment of the present application; Figure 4 is a solid-state electrolyte after sulfuration annealing in an embodiment of the present application; Figure 5 is a cross-sectional view of a solid-state electrolyte round sheet after crystallization annealing in an embodiment of the present application; Figure 6 is an EIS test graph of Example 1. Figure 7 is a Raman test graph of Example 1.

[0057] Example 2

[0058] According to the target product chemical formula Li: Sn = 4: 1, for an area of 3 cm * 5 cm, 5 pieces of lithium tape with a thickness of 20 μm and 1 piece of tin foil with a thickness of 30 μm are required. Then, in the glove box, the lithium tape and tin foil are cut to the appropriate size with scissors. Then, according to the upper two layers and the lower three layers of lithium tape, the tin foil is sandwiched in the middle to form a sandwiched structure. The metal stack is pre-pressed with a release film to prevent wrinkles during rolling. Formal rolling: first adjust the distance between the two rollers to one third of the thickness of the metal stack, roll back and forth three times. After compaction, the roller gap is adjusted by 0.05 mm, and the above operation is repeated until the roller gap distance is half of the thickness of the alloy foil. Fold the alloy foil in half, and align the two ends. Repeat the above rolling steps. After 5 times, the thickness of the last compaction is 0.06 mm.

[0059] The lithium-tin alloy sample is placed in a corundum crucible, sealed with an argon bag, and transferred to a vacuum annealing furnace. Vacuum is drawn, and argon is purged three times. 50 KPa of pure hydrogen sulfide gas is introduced. The temperature program is set as follows: 25 degrees Celsius is raised to 380 degrees Celsius in 40 minutes, and then held for 1 hour. Then, 380 degrees Celsius is raised to 500 degrees Celsius in 45 minutes, and then held for 2 hours. After sulfuration, the electrolyte is obtained. The sample is placed in a mortar and ground thoroughly. The electrolyte is pressed into a round sheet under a pressure of 30 MPa. Then, the sample is placed in a rotary annealing furnace, and a mixture of 3 KPa of hydrogen sulfide and 27 KPa of argon is introduced. Crystallization annealing is performed at 530 degrees Celsius for 2 hours to obtain an annealed crystalline sheet.

[0060] Example 3

[0061] According to the formula Li: Sn = 4: 1 in the target product, for example, an area of 3 cm * 5 cm requires 5 pieces of lithium tape with a thickness of 20 μm and 1 piece of tin foil with a thickness of 30 μm. Then, in the glove box, the lithium tape and tin foil are cut to the appropriate size with scissors. Then, according to the upper two layers and the lower three layers of lithium tape, the tin foil is sandwiched in the middle to form a sandwiched layered structure. The metal layer is pre-pressed with a release film to prevent wrinkles during rolling. Formal rolling: first adjust the distance between the two rollers to one third of the thickness of the metal layer, roll back and forth three times. After the rolling is completed, the gap between the rollers is reduced by 0.05 mm, and the above operation is repeated until the gap between the rollers is half the thickness of the alloy foil. Fold the alloy foil in half, and align the two ends. Repeat the above rolling steps. After 5 times, the thickness of the last rolling is 0.06 mm.

[0062] The lithium-tin alloy sample is placed in a corundum crucible, sealed with an argon bag, and transferred to a vacuum annealing furnace. Vacuum is drawn, and argon is purged three times. 10 KPa of hydrogen sulfide and 40 KPa of argon are introduced. The temperature program is set as follows: 25 degrees Celsius is raised to 380 degrees Celsius in 40 minutes, and then held for 1 hour. Then, 380 degrees Celsius is raised to 470 degrees Celsius in 45 minutes, and then held for 2 hours. After sulfuration, the electrolyte is obtained. The sample is placed in a mortar and ground thoroughly. The electrolyte is pressed into a round sheet under a pressure of 30 MPa. Then, the sample is placed in a rotary annealing furnace, and a mixture of 3 KPa of hydrogen sulfide and 27 KPa of argon is introduced. Crystallization annealing is performed at 530 degrees Celsius for 2 hours to obtain an annealed crystalline sheet.

[0063] Example 4

[0064] According to the formula of the target product Li: Sn = 4: 1, for example, an area of 3 cm * 5 cm requires 5 pieces of 20 μm thick lithium ribbon and 1 piece of 30 μm thick tin foil. Then cut the lithium ribbon and tin foil to the appropriate size in the glove box with scissors, and then according to the upper two layers and the lower three layers of lithium ribbon, sandwich the tin foil in the middle to form a sandwich structure. Use the release film to pre-press the metal stack to prevent wrinkles during rolling. Formal rolling: first adjust the distance between the two rollers to one third of the thickness of the metal stack, roll back and forth three times, and after the rolling is completed, lower the roller gap by 0.05 mm, repeat the above operation until the roller gap distance is half of the alloy foil; fold the alloy foil in half and align the two ends. Repeat the above rolling operation steps. After repeating 5 times, the thickness of the last rolling is 0.06 mm.

[0065] The lithium-tin alloy sample described above is placed in a corundum crucible, sealed with an argon bag and transferred to a vacuum annealing furnace. Vacuum is drawn, argon is purged, and the process is repeated three times. 10 KPa of hydrogen sulfide and 40 KPa of argon are introduced. Set the temperature program: 25 degrees Celsius to 380 degrees Celsius for 40 minutes, hold for 1 hour, then from 380 degrees Celsius to 500 degrees Celsius for 45 minutes, hold for 1 hour. After sulfidation, the electrolyte is obtained, and the sample is placed in a mortar for thorough grinding, and is pressed into an electrolyte disc under a pressure of 30 MPa. Then the sample is placed in a rotary annealing furnace, and a mixture of 3 KPa of hydrogen sulfide and 27 KPa of argon gas is introduced, and crystallization annealing is carried out at 530 degrees Celsius for 2 hours to obtain an annealed crystalline sheet.

[0066] It can be understood that any combination of the technical features of the above-described embodiments can be made. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0067] The above is only a preferred embodiment of the present application, and only the technical principles of the present application are specifically described, and these descriptions are only for the purpose of explaining the principles of the present application, and cannot be interpreted in any way as a limitation on the scope of protection of the present application. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principles of the present application, and other specific embodiments of the present application that can be easily conceived by those skilled in the art without requiring creative labor, should be included within the scope of protection of the present application.

Claims

1. A method for producing a sulfide solid-state electrolyte, characterized by, It comprises the following steps: Step S1: according to the formula Li4SnS4 of the target product, the lithium strip and the tin foil are cut into corresponding sizes with scissors, and the area is 3cm*5cm, 5 pieces of 20μm thick lithium strip and 1 piece of 30μm thick tin foil are selected, and then the tin foil is sandwiched in the middle according to the upper two layers and the lower three layers of lithium strip, and a sandwich structure is made, that is, a metal stack is obtained; Step S2: the metal stack is pre-pressed flat with a release film; Step S3: adjust the distance between the two rollers to one third of the thickness of the metal stack, roll back and forth three times, after the rolling is completed, reduce the roller gap by 0.05mm, repeat the above operation until the roller gap distance is half of the alloy foil, and the thickness of the alloy foil is half of the thickness of the metal stack; Step S4: fold the alloy foil in half from the middle, and align the two ends; Step S5: repeat the above steps S3 and S4, after repeating 5 times, the thickness of the last rolling is 0.06mm, and a lithium-tin alloy sample is obtained; Step S6: place the lithium-tin alloy sample above in a corundum crucible, seal with an argon bag, transfer to a vacuum annealing furnace, vacuumize, and purify with argon three times; Step S7: introduce 10KPa of hydrogen sulfide and 40KPa of argon, set the temperature program: 25 degrees Celsius for 40 minutes to 380 degrees Celsius for 1 hour, then from 380 degrees Celsius to 500 degrees Celsius for 2 hours, and get the sulfided sample; Step S8: the sulfided sample is placed in a mortar and ground thoroughly, and is pressed into an electrolyte disc under a pressure of 30MPa; Step S9: then the electrolyte disc is placed in a rotary annealing furnace, and a mixed gas of 3KPa of hydrogen sulfide and 27KPa of argon is introduced, and crystallization annealing is carried out at 530 degrees Celsius for 2 hours, and a sulfide solid-state electrolyte is obtained.

2. A sulfide solid-state electrolyte, characterized by, The sulfide solid-state electrolyte is prepared by the preparation method of claim 1.

3. An all-solid-state lithium-ion battery, characterized by, The sulfide solid-state electrolyte of claim 2 is included. The sulfide solid-state electrolyte of claim 2 is included.

Images