Preparation method and application of lithium sulfide

Abstract

The invention relates to the technical field of battery materials, in particular to a preparation method and application of lithium sulfide. Lithium sulfide is generated on a cathode of an electrolytic tank device based on the electrolytic tank device; a lithium aqueous solution is contained in an anode tank of the electrolytic tank device; an organic solution is contained in a cathode tank of the electrolytic tank device; sequentially carrying out drying, dissolving, suction filtration and evaporation treatment on the cathode with the lithium sulfide to obtain lithium sulfide powder; and sintering the lithium sulfide powder to obtain the target lithium sulfide. The preparation method of the lithium sulfide provided by the invention has the characteristics of simple preparation process and high purity of the prepared lithium sulfide.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a preparation method of lithium sulfide and application thereof. Background Art

[0002] With the rapid development of portable electronic devices, electric vehicles and large-scale energy storage systems, the market has higher and higher requirements for battery performance. Although traditional lithium-ion batteries have been widely used, they use liquid electrolytes, which poses potential safety hazards such as leakage, combustion and explosion risks. In addition, due to the relatively narrow electrochemical window of liquid electrolytes, it is difficult to be compatible with higher voltage cathode materials, so the use of liquid electrolytes also limits the further improvement of battery energy density. Solid electrolytes are considered to be key technologies for improving battery safety and energy density due to their non-flammability, non-corrosiveness, non-volatility, and wider electrochemical window. Therefore, all-solid-state battery technology has become the focus of scientific and technological competition among countries around the world, and it is also an important area of ​​international cooperation. Research institutions and companies in different countries and regions have carried out extensive cooperation and competition in the field of solid-state batteries, striving to gain a leading position in this field. Among them, high ionic conductivity sulfide solid electrolytes, as key materials for all-solid-state batteries, can effectively inhibit the formation of lithium dendrites, match high energy density cathode materials and metal lithium anodes, thereby significantly improving battery safety and energy density.

[0003] In the preparation process of sulfide solid electrolyte, lithium sulfide is usually used as one of its precursors. At present, lithium sulfide is usually synthesized by the following schemes, namely direct reaction method, liquid phase method and carbon reduction method, etc. The direct reaction method refers to the direct mixing of metallic lithium and elemental sulfur. At a certain temperature and pressure, metallic lithium and elemental sulfur directly react to prepare lithium sulfide. Although there is no solvent involved, it has high requirements for equipment; the liquid phase method is the mixed reaction of lithium / lithium compounds and sulfur / sulfur compounds in a solvent medium to prepare lithium sulfide. The process is simple, easy to operate, and has low energy consumption, but the cost is high; the carbon reduction method refers to the preparation of lithium sulfide by adding strongly reducing carbon to the lithium sulfide material. The reaction is milder, but the prepared product has poor stability and is prone to produce impurities such as lithium carbonate. It can be seen that the existing lithium sulfide preparation scheme has the problems of harsh synthesis conditions, high process requirements, and uncontrollable reaction rate. Summary of the invention

[0004] In order to solve the above technical problems, the present application discloses, on one hand, a method for preparing lithium sulfide, which comprises:

[0005] Based on the electrolytic cell device, lithium sulfide is generated on the cathode of the electrolytic cell device; the anode tank of the electrolytic cell device contains a lithium aqueous solution; the cathode tank of the electrolytic cell device contains an organic solution;

[0006] The cathode having the lithium sulfide is sequentially dried, dissolved, filtered and evaporated to obtain lithium sulfide powder;

[0007] The lithium sulfide powder is sintered to obtain target lithium sulfide.

[0008] In an exemplary embodiment, a solid electrolyte is provided between the cathode tank and the anode tank to isolate the lithium aqueous solution and the organic solution; an anode is inserted in the lithium aqueous solution, and a cathode is inserted in the organic solution; and the anode is connected to the positive electrode of a power supply, and the cathode is connected to the negative electrode of the power supply.

[0009] In an exemplary embodiment, the concentration of the lithium aqueous solution is 0.2 to 1 mol / L.

[0010] In an exemplary embodiment, the lithium aqueous solution includes one or more of a lithium chloride solution, a lithium bromide solution, a lithium iodide solution, or a lithium hydroxide solution;

[0011] The organic solvent includes an ester solvent or an ether solvent.

[0012] In an exemplary embodiment, the material of the solid electrolyte is a garnet-type electrolyte, a lithium superion conductor-type LTP electrolyte, or a derivative doped electrolyte thereof.

[0013] In an exemplary embodiment, the cathode material is a sulfur-containing mixture;

[0014] The molar ratio of the molar content of lithium ions in the lithium aqueous solution to the molar content of sulfur in the cathode is 1:1 to 4:1.

[0015] In an exemplary embodiment, the drying temperature is 100 to 180° C., and the drying time is 6 to 12 hours.

[0016] In an exemplary embodiment, the sintering conditions are:

[0017] Sinter at 500 to 600°C for 1 to 4 hours under an inert atmosphere.

[0018] On the other hand, the present application also discloses a method for preparing a sulfide solid electrolyte, which is prepared based on lithium sulfide prepared by the above-mentioned preparation method.

[0019] On the other hand, the present application also discloses a solid-state battery, which includes the sulfide solid electrolyte prepared by the above-mentioned preparation method.

[0020] The embodiment of the present application generates lithium sulfide on the cathode of the electrolytic cell device based on an electrolytic cell device; the anode tank of the electrolytic cell device contains a lithium aqueous solution; the cathode tank of the electrolytic cell device contains an organic solution; the cathode with the lithium sulfide is dried, dissolved, filtered and evaporated in sequence to obtain lithium sulfide powder; the lithium sulfide powder is sintered to obtain the target lithium sulfide. In this way, the electrochemical method is used to prepare lithium sulfide, which has low requirements on process equipment and controllable reactions. Through drying, filtration, evaporation and sintering, the entire process steps are simple and the purity of lithium sulfide can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 It is a schematic structural diagram of an exemplary electrolytic cell device of the present application;

[0023] Figure 2 is an XRD pattern of lithium sulfide prepared in Example 1 of the present application;

[0024] Figure 3 is an XRD pattern of lithium sulfide prepared in Example 2 of the present application;

[0025] Figure 4 is an XRD pattern of lithium sulfide prepared in Example 3 of the present application;

[0026] Figure 5 is an XRD pattern of lithium sulfide prepared in Example 4 of the present application;

[0027] Figure 6 This is an XRD spectrum of lithium sulfide prepared in Example 5 of the present application.

[0028] The following is a supplementary description of the attached drawings:

[0029] 1- anode tank; 2- cathode tank; 3- solid electrolyte; 4- lithium aqueous solution; 5- organic solution; 6- anode; 7- cathode; 8- power supply. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present application. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may include one or more of the features explicitly or implicitly. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

[0032] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0033] When a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be deemed to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0034] The present application discloses a method for preparing lithium sulfide, which may specifically include the following steps:

[0035] Firstly, lithium sulfide is generated on the cathode of the electrolytic cell device based on the electrolytic cell device; a lithium aqueous solution is contained in the anode tank of the electrolytic cell device; and an organic solution is contained in the cathode tank of the electrolytic cell device.

[0036] See also Figure 1 The electrolytic cell device may specifically include a cathode tank 2, an anode tank 1, a cathode 7, an anode 6 and a power supply 8; a lithium aqueous solution 4 is contained in the anode tank 1 of the electrolytic cell device; an organic solution 5 is contained in the cathode tank 2 of the electrolytic cell device; a channel is provided between the cathode tank 2 and the anode tank 1, and a solid electrolyte 3 is provided in the channel to isolate the lithium aqueous solution 4 and the organic solution 5 to avoid direct contact between the two and a side reaction, and at the same time, the electrolyte solution can be allowed to pass, so that an oxidation reaction can occur at the anode 6 and a reduction reaction can occur at the cathode 7, thereby improving the efficiency of the electrolysis process and the purity of the product; an anode 6 is inserted in the lithium aqueous solution 4, and a cathode 7 is inserted in the organic solution 5; and the anode 6 is connected to the positive electrode of the power supply 8, and the cathode 7 is connected to the negative electrode of the power supply 8. Therefore, when the power supply 8 is powered on, the anode 6 generates gas, such as oxygen, and the solid electrolyte 3 can be provided to avoid direct contact between the gas and the substance generated by the cathode 7, thereby causing unnecessary chemical reactions and affecting the electrolysis efficiency and product purity. And the ions (such as lithium ions) in the anode tank 1 can pass through the solid electrolyte 3 to enter the cathode tank 2, and a reduction reaction occurs on the cathode 7 to generate lithium sulfide. The raw material is a lithium aqueous solution 4, which has the advantages of simple preparation and low cost, and is suitable for mass production. The preparation equipment used, that is, the electrolytic cell device, also has a simple structure and relatively tolerant reaction conditions. The reaction rate can be regulated by regulating the ratio of the lithium aqueous solution 4 to the sulfur in the cathode 7.

[0037] Optionally, when the lithium aqueous solution is a lithium chloride solution, the principle of the electrochemical reaction of the present application can be expressed as follows:

[0038] LiCl+H2O+S=Li2S+O2↑+HCl

[0039] Due to the oxidation reaction at the anode, ionization produces O2 and H + , there is at least Li in the lithium aqueous solution + , Cl - , O2 and H + , Li + Under the action of the electric field, the ions migrate to the cathode through the solid electrolyte (which only allows ions to pass through and prevents electrons from passing through), and a reduction reaction occurs on the cathode. + The reaction generates the product Li2S.

[0040] In an exemplary embodiment, the concentration of the lithium aqueous solution is 0.2 to 1 mol / L. Specifically, the concentration of the lithium aqueous solution refers to the concentration of the solute (lithiation), which can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L. To ensure that the lithium compound can be completely dissolved in water, thereby improving the utilization rate of raw materials.

[0041] In an exemplary embodiment, the lithium aqueous solution includes one or more of a lithium chloride solution, a lithium bromide solution, a lithium iodide solution, or a lithium hydroxide solution. Generally, the process of preparing a lithium aqueous solution may include: weighing a certain amount of a lithium compound, placing the lithium compound in deionized water, and configuring the lithium aqueous solution to a desired concentration according to a desired ratio. Optionally, the lithium compound may include, but is not limited to, one or more of lithium chloride, lithium bromide, lithium iodide, and lithium hydroxide.

[0042] Exemplarily, the organic solvent includes one or more combinations of ester solvents or ether solvents. Specifically, ester solvents may include ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), etc.; ether solvents may include dimethyl ether (DME), 1,3-dioxolane (DOL), etc. Organic solvents are used to transfer lithium ions, so ether or ester solvents that can be used to transfer lithium ions are all acceptable, not limited to the organic substances exemplified above.

[0043] In an exemplary embodiment, the material of the solid electrolyte is a garnet-type electrolyte (LLZO), a lithium superion conductor (Li SI CON) type LTP electrolyte, or a derivative doped electrolyte of the two. Optionally, the derivative doped electrolyte of LLZO and Li SI CON may be a tantalum-doped garnet-type electrolyte (Ta-LLZO), a niobium-doped garnet-type electrolyte (Nb-LLZO), a gallium-doped garnet-type electrolyte (Ga-LLZO), an aluminum-doped garnet-type electrolyte (A l-LLZO), LATP, LAGP, etc. Optionally, the solid electrolyte may be a ceramic product, and the ceramic may be cut and polished to obtain a solid electrolyte that meets the required size requirements.

[0044] Exemplarily, the thickness of the solid electrode material is 4 to 10 mm, which is determined based on the error in the preparation process, sealing and uniformity of tableting. If it is too thick, the ion transmission resistance will increase, and if it is too thin, it will easily break.

[0045] In an exemplary embodiment, the cathode material is a sulfur-containing mixture, and specifically, the cathode can be in the form of a sheet or a rod. The anode is an inert material, such as platinum, gold, graphite, etc. In the embodiment of the present application, platinum can be selected as the anode material. The cathode and the anode need to be placed relatively parallel in the electrolytic cell, and their specific sizes are not limited here, and the two can be roughly the same.

[0046] Exemplarily, the preparation process of the cathode may include: mixing sulfur powder and a conductive agent uniformly, adding a binder and an organic solvent to form a cathode slurry, applying it to one side of a metal foil, performing a first drying process, and then applying the cathode slurry to the other side of the metal foil, performing a second drying process, and forming a cathode. Optionally, the metal foil may be a metal foil such as aluminum foil, nickel foil, titanium foil, gold foil, silver foil, etc., as long as the metal material can be stable at a high potential, and there is no limitation here. In the embodiment of the present application, the metal foil may be aluminum foil, which has a lower cost.

[0047] For example, the mass ratio of sulfur powder, conductive agent and binder may be (70-90): (20-5): (15-5).

[0048] For example, in the cathode preparation process, the temperature of the first drying process may be 100 to 180° C., and the time may be 6 to 12 hours. The temperature of the second drying process may be 60 to 180° C., and the time may be 6 to 12 hours.

[0049] Exemplarily, the conductive agent is mainly various carbon materials, such as graphite, artificial graphite, carbon nanotubes, carbon black (Super P), graphene, nano carbon fiber (VGCF), etc., the binder can be polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), etc., and the organic solvent is mainly N-methyl pyrrolidone (NMP), and ethers (such as DOL, DME), esters (such as EC, DEC, DMC, etc.) can also be used. In the embodiment of the present application, the conductive agent can be carbon black, the binder can be PVDF, and the organic solvent can be NMP.

[0050] Exemplarily, the molar ratio of the molar content of lithium ions in the lithium aqueous solution to the sulfur content in the cathode is 1:1 to 4:1. Specifically, the molar ratio of the molar content of lithium ions in the lithium aqueous solution to the sulfur content in the cathode can be 1:1, 2:1, 3:1 or 4:1. This can effectively ensure the lithium ion concentration and improve the yield of the product.

[0051] Exemplarily, the power supply for providing voltage may be an adjustable power supply with a voltage range of 5V. During the electrochemical reaction, the voltage will change with the change of current, but will not exceed 5V and will be reduced to a certain extent, such as around 3V.

[0052] In the embodiments of the present application, lithium sulfide can be prepared in a dew point environment of -60 to -40°C.

[0053] Next, the cathode containing the lithium sulfide is sequentially dried, dissolved, filtered and evaporated to obtain lithium sulfide powder.

[0054] For example, the synthesized lithium sulfide can be first dried under vacuum to remove the organic solvent, and then the obtained lithium sulfide can be immersed in a solvent (such as ethanol) to obtain a mixed solution, so that the lithium sulfide can be dissolved in the solvent, and the mixed solution can be vacuum filtered to obtain a filtrate and a filter residue, and the material insoluble in the solvent can be filtered out by suction filtration, and then the obtained filtrate is subjected to rotary evaporation using a rotary evaporator to evaporate and remove the solvent in the filtrate to obtain lithium sulfide powder. Optionally, the immersion time can be 6 to 12 hours.

[0055] In an exemplary embodiment, the temperature for drying the cathode may be 100 to 180° C., and the time may be 6 to 12 hours. Specifically, the drying temperature may be 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C. or 180° C. The drying time may be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0056] Finally, the lithium sulfide powder is sintered to obtain the target lithium sulfide.

[0057] In an exemplary embodiment, the sintering process is performed under an inert atmosphere (such as nitrogen) at 500 to 600° C. for 1 to 4 hours. Specifically, the sintering temperature may be 500° C., 520° C., 540° C., 560° C., 580° C. or 600° C. The sintering time may be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0058] On the other hand, the present application also discloses a method for preparing a sulfide solid electrolyte, which is prepared based on lithium sulfide prepared by the above-mentioned preparation method.

[0059] On the other hand, the present application also discloses a solid-state battery, which includes the sulfide solid electrolyte prepared by the above-mentioned preparation method.

[0060] In order to better illustrate the technical effects and solutions of the present application, the following is a description of specific embodiments:

[0061] Example 1

[0062] In a dry environment with a dew point temperature of -60°C, 0.2 mol LiCl was added to 1L of deionized water to obtain a lithium aqueous solution with a concentration of 0.2 mol / L. Sulfur powder, conductive carbon black, and binder were prepared into a cathode slurry (containing 0.2 mol sulfur active substance) in a mass ratio of 70:20:10 and evenly coated on aluminum foil. Ta-doped LLZO powder with a cubic phase structure was used to obtain Ta-doped LLZO ceramics after pressing and sintering, and then the ceramic sheet was polished to a thickness of 4 mm. Organic solvents EC and DMC were mixed in a volume ratio of 1:1 to obtain a mixed organic solvent.

[0063] Then, a lithium aqueous solution is added to the anode tank of the electrolytic cell, an inert platinum electrode is inserted, a mixed organic solvent is added to the cathode tank of the electrolytic cell, and the prepared cathode is inserted into the cathode tank of the electrolytic cell. Finally, a Ta-doped LLZO ceramic sheet is placed in the middle through hole of the electrolytic cell to transmit lithium ions and isolate the organic solvent and lithium aqueous solution.

[0064] The positive pole of the power supply is connected to the anode tank, and the negative pole is connected to the cathode tank. The output voltage is controlled to 5V. At this time, gas will be produced on the anode side and collected using a collection device. Lithium sulfide will be generated on the cathode side. When the current of the power supply is less than 10μA, turn off the power supply.

[0065] Finally, the cathode is taken out and placed in a vacuum oven at 100°C for 12 hours to dry the organic solvent. The dried cathode is placed in ethanol and soaked for 6 hours. The filtrate and filter residue are obtained by vacuum filtration. The filtrate is evaporated with a rotary evaporator to obtain lithium sulfide powder. The lithium sulfide powder is sintered in a muffle furnace at 500°C for 1 hour under a nitrogen atmosphere to obtain high-purity lithium sulfide.

[0066] Example 2

[0067] In a dry environment with a dew point temperature of -50°C, 0.4 mol Li Br was added to 1L of deionized water to obtain a lithium aqueous solution with a concentration of 0.4 mol / L. Sulfur powder, conductive carbon black, and binder were prepared into a cathode slurry (containing 0.2 mol sulfur active substance) in a mass ratio of 70:15:15, and evenly coated on aluminum foil to obtain a cathode. Nb-doped LLZO powder with a cubic phase structure was used to obtain Nb-doped LLZO ceramics after pressing and sintering, and then the ceramic sheet was polished to a thickness of 6 mm. Organic solvents EC and EMC were mixed in a volume ratio of 1:1 to obtain a mixed organic solvent.

[0068] Then add the lithium aqueous solution into the anode tank of the electrolytic cell we designed, insert an inert platinum electrode, add the mixed organic solvent into the cathode tank of the electrolytic cell, and insert the prepared cathode into the cathode tank of the electrolytic cell. Finally, place the Nb-doped LLZO ceramic sheet in the middle slot of the electrolytic cell to transmit lithium ions and isolate the organic solvent and lithium aqueous solution.

[0069] Then connect the power supply, connect the positive pole to the anode tank, and the negative pole to the cathode tank, and control the output voltage to 5V. At this time, gas will be produced on the anode side, which will be collected using a collection device. Lithium sulfide will be generated on the cathode side. When the current of the power supply is less than 10μA, turn off the power supply.

[0070] Finally, the cathode is taken out and dried in a vacuum oven at 120°C for 10 hours to remove the organic solvent. The dried cathode is soaked in ethanol for 8 hours and filtered under reduced pressure to obtain a filtrate and a filter residue. The filtrate is evaporated using a rotary evaporator to obtain lithium sulfide powder, and the lithium sulfide powder is sintered in a muffle furnace at 500°C for 2 hours under a nitrogen atmosphere to obtain high-purity lithium sulfide.

[0071] Example 3

[0072] The steps of its preparation method are as follows:

[0073] In a dry environment with a dew point temperature of -40°C, 0.8 mol Li I was added to 1L of deionized water to obtain a lithium aqueous solution with a concentration of 0.8 mol / L. Sulfur powder, conductive carbon black, and binder were prepared into a cathode slurry (containing 0.2 mol sulfur active substance) in a mass ratio of 80:15:5, and evenly coated on aluminum foil to obtain a cathode. Using LISI CON powder, Ga ceramics were obtained by pressing and sintering, and then the ceramic sheet was polished to a thickness of 8 mm. Organic solvents EC, EMC, and DEC were mixed in a volume ratio of 1:1:1 to obtain a mixed organic solvent.

[0074] Then add the lithium aqueous solution into the anode tank of the electrolytic cell, insert an inert platinum electrode, add the mixed organic solvent into the cathode tank of the electrolytic cell, and insert the prepared cathode into the cathode tank of the electrolytic cell. Finally, place the LATP ceramic sheet in the through hole of the electrolytic cell to transmit lithium ions and isolate the organic solvent and lithium aqueous solution.

[0075] The positive pole of the power supply is connected to the anode tank, and the negative pole is connected to the cathode tank. The output voltage is controlled to 5V. At this time, gas will be produced on the anode side and collected using a collection device. Lithium sulfide will be generated on the cathode side. When the current of the power supply is less than 10μA, turn off the power supply.

[0076] Finally, the cathode is taken out and placed in a vacuum oven at 140°C for 8 hours to dry the organic solvent. The dried cathode is placed in ethanol and soaked for 10 hours. The filtrate and filter residue are obtained by vacuum filtration. The filtrate is evaporated with a rotary evaporator to obtain lithium sulfide powder. The lithium sulfide powder is sintered in a muffle furnace at 500°C for 4 hours under a nitrogen atmosphere to obtain high-purity lithium sulfide.

[0077] Example 4

[0078] The steps of its preparation method are as follows:

[0079] In a dry environment with a dew point temperature of -50°C, 1 mol NaOH is added to 1L of deionized water to obtain a lithium aqueous solution with a concentration of 0.1 mol / L. Sulfur powder, conductive carbon black, and binder are prepared into a cathode slurry (containing 0.5 mol sulfur active substance) in a mass ratio of 80:10:10, and evenly coated on aluminum foil to obtain a cathode. LATP powder is used to obtain LATP ceramics through pressing and sintering, and then the ceramic sheet is polished to a thickness of 10 mm. The organic solvents DOL and DME are mixed in a volume ratio of 1:1:1 to obtain a mixed organic solvent.

[0080] Then add the lithium aqueous solution into the anode tank of the electrolytic cell, insert an inert platinum electrode, add the mixed organic solvent into the cathode tank of the electrolytic cell, and insert the prepared cathode into the cathode tank of the electrolytic cell. Finally, place the LATP ceramic sheet in the through hole of the electrolytic cell to transmit lithium ions and isolate the organic solvent and lithium aqueous solution.

[0081] Then connect the power supply, connect the positive pole to the anode tank, and the negative pole to the cathode tank, and control the output voltage to 5V. At this time, gas will be produced on the anode side, which will be collected using a collection device. Lithium sulfide will be generated on the cathode side. When the current of the power supply is less than 10μA, turn off the power supply.

[0082] Finally, the cathode is taken out and placed in a vacuum oven at 160°C for 6 hours to dry the organic solvent. The dried cathode is placed in ethanol and soaked for 12 hours. The filtrate and filter residue are obtained by vacuum filtration. The filtrate is evaporated with a rotary evaporator to obtain lithium sulfide powder. The lithium sulfide powder is sintered in a muffle furnace at 600°C for 2 hours under a nitrogen atmosphere to obtain high-purity lithium sulfide.

[0083] Example 5

[0084] The steps of its preparation method are as follows:

[0085] In a dry environment with a dew point temperature of -40°C, 1 mol LiOH was added to 1L of deionized water to obtain a lithium aqueous solution with a concentration of 1 mol / L. Sulfur powder, conductive carbon black, and binder were prepared into a cathode slurry (containing 0.4 mol sulfur active substance) in a mass ratio of 90:5:5, and evenly coated on aluminum foil to obtain a cathode. LAGP powder was used to obtain LATP ceramics after pressing and sintering, and then the ceramic sheet was polished to a thickness of 8 mm.

[0086] Then add the lithium aqueous solution into the anode tank of the electrolytic cell we designed, insert the inert platinum electrode, add the DME organic solvent into the cathode tank of the electrolytic cell, and insert the prepared cathode into the cathode tank of the electrolytic cell. Finally, place the LAGP ceramic sheet in the through hole of the electrolytic cell to transmit lithium ions and isolate the organic solvent and lithium aqueous solution.

[0087] Then connect the power supply, connect the positive pole to the anode tank, and the negative pole to the cathode tank, and control the output voltage to 5V. At this time, gas will be produced on the anode side, which will be collected using a collection device. Lithium sulfide will be generated on the cathode side. When the current of the power supply is less than 10μA, turn off the power supply.

[0088] Finally, the cathode is taken out and placed in a vacuum oven at 120°C for 12 hours to dry the organic solvent. The dried cathode is placed in ethanol and soaked for 12 hours. The filtrate and filter residue are obtained by vacuum filtration. The filtrate is evaporated with a rotary evaporator to obtain lithium sulfide powder. The lithium sulfide powder is sintered in a muffle furnace at 600°C for 4 hours under a nitrogen atmosphere to obtain high-purity lithium sulfide.

[0089] Specifically, the products (lithium sulfide) prepared in the above examples 1-5 and the yields are shown in the following table:

[0090]

[0091]

[0092] Among them, the discharge rate = actual mass of the product / theoretical mass of the product. The theoretical mass of the product is the mass of lithium sulfide completely converted from the lithium salt and the sulfur positive electrode active material, and the actual mass of the product is the mass of lithium sulfide actually prepared based on the preparation scheme of this scheme, that is, the mass of the product in the above table.

[0093] It can be seen from the above table data that the yield of lithium sulfide using the solution of the present application is relatively high. By properly adjusting the concentration of the lithium aqueous solution, the yield of lithium sulfide can be further greatly increased, and can reach more than 70%. For further information, please refer to Figures 2 to 6, which are the XRD spectra of the lithium sulfide prepared in Examples 1-5, respectively. It can be seen that the product lithium sulfide material prepared by the scheme of the present application is the main phase. It can also be seen from the sharpness of the peak that the crystallinity of the prepared lithium sulfide is good (the sharper the XRD peak, the better the crystallinity of the lithium sulfide material).

[0094] The above description is only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing lithium sulfide, characterized in that: include: generating lithium sulfide on a cathode of the electrolytic cell device based on the electrolytic cell device; The anode tank of the electrolytic cell device contains a lithium aqueous solution; the cathode tank of the electrolytic cell device contains an organic solution; The cathode having the lithium sulfide is sequentially dried, dissolved, filtered and evaporated to obtain lithium sulfide powder; The lithium sulfide powder is sintered to obtain target lithium sulfide.

2. The preparation method according to claim 1, characterized in that: A solid electrolyte is provided between the cathode tank and the anode tank to isolate the lithium aqueous solution and the organic solution; an anode is inserted in the lithium aqueous solution, and a cathode is inserted in the organic solution; and the anode is connected to the positive electrode of a power supply, and the cathode is connected to the negative electrode of the power supply.

3. The preparation method according to claim 1, characterized in that: The concentration of the lithium aqueous solution is 0.2 to 1 mol / L.

4. The preparation method according to claim 1, characterized in that: The lithium aqueous solution includes one or more of lithium chloride solution, lithium bromide solution, lithium iodide solution or lithium hydroxide solution; The organic solvent includes an ester solvent or an ether solvent.

5. The preparation method according to claim 2, characterized in that: The material of the solid electrolyte is a garnet-type electrolyte, a lithium superion conductor-type LTP electrolyte, or a derivative doped electrolyte thereof.

6. The preparation method according to claim 2, characterized in that: The material of the cathode is a sulfur-containing mixture; The molar ratio of the molar content of lithium ions in the lithium aqueous solution to the molar content of sulfur in the cathode is 1:1 to 4:

1.

7. The preparation method according to claim 1, characterized in that: The drying temperature is 100 to 180° C., and the drying time is 6 to 12 hours.

8. The preparation method according to claim 1, characterized in that: The conditions of the sintering treatment are: Sinter at 500 to 600°C for 1 to 4 hours under an inert atmosphere.

9. A method for preparing a sulfide solid electrolyte, characterized in that: It is prepared based on lithium sulfide prepared by the preparation method according to any one of claims 1 to 8.

10. A solid-state battery, characterized in that: It comprises a sulfide solid electrolyte prepared by the preparation method as claimed in claim 9.

Images