Preparation method of lithium sulfide

Abstract

The embodiment of the invention discloses a preparation method of lithium sulfide. According to the lithium sulfide preparation method provided by the invention, metal lithium or lithium alloy is taken as a negative electrode, a carbon-sulfur compound is taken as a positive electrode, a solid electrolyte membrane is taken as an electrolyte layer, and electrochemical reaction is carried out through discharge of an electrochemical workstation; metal lithium or lithium alloy reacts at the negative electrode to obtain metal lithium ions, and the carbon-sulfur compound reacts at the positive electrode to obtain sulfur ions; metal lithium ions are transmitted to the positive electrode through the solid electrolyte membrane and react with sulfur ions to obtain a lithium sulfide target product. The lithium sulfide is prepared by adopting an electrochemical method and an all-solid-state battery, the participation of an organic solvent is reduced in the reaction process, the whole process is all-solid-phase chemical change, the safety is high, and the preparation purity of the lithium sulfide is favorably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-sulfur batteries, and in particular to a method for preparing lithium sulfide. Background Art

[0002] Since the beginning of the 21st century, smart phones, drones, new energy vehicles, etc. have become widely popular, and the requirements for battery energy density and safety have become increasingly higher. Traditional liquid lithium-ion batteries have the risk of electrolyte leakage and flammability, and their energy density also needs to be further improved. As one of the routes for all-solid-state batteries, sulfide solid electrolytes have the characteristics of high ionic conductivity, good thermal stability and electrochemical stability, and are favored by related research and development. As one of the important raw materials for sulfide solid electrolytes, lithium sulfide is currently sold at a high price in the market, which has become a huge obstacle to reducing the cost of sulfide solid electrolytes.

[0003] At present, common methods for preparing lithium sulfide are direct reaction method, liquid phase method and carbon reduction method, among which the direct reaction method refers to directly mixing metallic lithium and elemental sulfur, and directly reacting metallic lithium and elemental sulfur at a certain temperature and pressure to prepare lithium sulfide (such as patent CN113788458A), which has the advantage of no solvent involvement, and the disadvantage of high equipment requirements; the liquid phase method is that lithium / lithium compounds and sulfur / sulfur compounds are mixed and reacted in a solvent medium to prepare lithium sulfide (such as patent CN112678781A), which has the advantages of simple process, strong operability, low energy consumption, and high cost; the carbon reduction method refers to adding strongly reducing carbon to lithium sulfate materials to prepare lithium sulfide (such as patent CN117509686A), which has the advantage of milder reaction, and the disadvantage of poor product stability and easy generation of impurities such as lithium carbonate. Summary of the invention

[0004] In view of the above problems of the prior art, the present application provides a method for preparing lithium sulfide. The present application adopts an electrochemical method and an all-solid-state battery to prepare lithium sulfide, reduces the participation of organic solvents in the reaction process, and the overall process is a full solid-phase chemical change, which is highly safe and is conducive to improving the preparation purity of lithium sulfide. The specific preparation method is as follows:

[0005] A method for preparing lithium sulfide, using metallic lithium or lithium alloy as a negative electrode, a carbon-sulfur composite as a positive electrode, a solid electrolyte membrane as an electrolyte layer, and performing an electrochemical reaction by discharging in an electrochemical workstation;

[0006] The metallic lithium or lithium alloy reacts at the negative electrode to obtain metallic lithium ions, and the carbon-sulfur composite reacts at the positive electrode to obtain sulfur ions;

[0007] The metal lithium ions are transported to the positive electrode through the solid electrolyte membrane and react with the sulfur ions to obtain the target product of lithium sulfide.

[0008] In some specific embodiments, the electrochemical reaction is carried out by discharging in an electrochemical workstation using metallic lithium or lithium alloy as the negative electrode, a carbon-sulfur composite as the positive electrode, and a solid electrolyte membrane as the electrolyte layer, and includes:

[0009] S1: Weigh a certain amount of solid electrolyte and press it into the solid electrolyte membrane;

[0010] S2: placing the carbon-sulfur composite at one end of the solid electrolyte membrane and pressing the carbon-sulfur composite;

[0011] S3: placing the metal lithium or lithium alloy at the other end of the solid electrolyte membrane and pressing the metal lithium or lithium alloy;

[0012] S4: connecting the positive electrode of the electrochemical workstation to one end of the carbon-sulfur composite, and connecting the negative electrode of the electrochemical workstation to one end of the metallic lithium or lithium alloy;

[0013] S5: discharging through the electrochemical workstation to activate the metallic lithium or lithium alloy and the carbon-sulfur composite to perform an electrochemical reaction.

[0014] In some specific embodiments, the metal lithium ions are transported to the positive electrode through the solid electrolyte membrane, and react with the sulfur ions to obtain the target product of lithium sulfide, comprising:

[0015] S1: dissolving the lithium sulfide target product in anhydrous ethanol to obtain a solution;

[0016] S2: filtering the solution to obtain a filtrate;

[0017] S3: drying the filtrate by rotary evaporation to obtain lithium sulfide powder;

[0018] S4: sintering the lithium sulfide powder under an inert atmosphere to obtain a final lithium sulfide product.

[0019] In some specific embodiments, the carbon in the carbon-sulfur composite is at least one of conductive carbon tubes, carbon black, graphite, and conductive carbon.

[0020] In some specific embodiments, the metallic lithium is metallic lithium sheet or metallic lithium powder; the lithium alloy is lithium alloy sheet or lithium alloy powder.

[0021] In some specific embodiments, the solid electrolyte membrane is a sulfide Li 10 GeP2S 12 , Li3PS4, Li6PS5X (X = Br, Cl, I), Li7P2S8I.

[0022] In some specific embodiments, the current applied by the electrochemical workstation is a constant current of 1 μA to 5 mA.

[0023] In some specific embodiments, the solid electrolyte membrane has a thickness of 0.5 to 5 mm.

[0024] In some specific embodiments, the sulfur content in the carbon-sulfur composite is 10% to 85%.

[0025] In some specific embodiments, the pressing steps S1, S2 and S3 of the solid electrolyte, the carbon-sulfur composite and the metal lithium or lithium alloy are performed by using a reaction device; wherein the reaction device comprises a sleeve 300, a first plug 201 and a second plug 202, wherein the first plug 201 and the second plug 202 are sleeved at both ends of the sleeve 300; the pressing comprises:

[0026] The solid electrolyte is loaded into the sleeve 300, the first plug 201 and the second plug 202 are inserted, and the sleeve is placed in a press for the first pressurization; wherein the pressure of the first pressurization is 0.5-50 MPa;

[0027] After the first pressurization is completed, the first plug 201 is taken out, the carbon-sulfur composite is loaded into the sleeve 300, the first plug 201 is inserted, and the sleeve is put into the press for the second pressurization; wherein the pressure of the second pressurization is 0.5-30 MPa;

[0028] After the second pressurization is completed, the second plug 202 is taken out, metallic lithium or lithium alloy is placed in the sleeve 300, the second plug 202 is inserted, and the press is placed under the press for the third pressurization; wherein the pressure of the third pressurization is 0.5-5MPa.

[0029] By adopting the above technical solution, the lithium sulfide preparation method provided in the present application has the following beneficial effects:

[0030] The embodiment of the present application discloses a method for preparing lithium sulfide. The present application provides a method for preparing lithium sulfide, which uses metallic lithium or lithium alloy as the negative electrode, a carbon-sulfur composite as the positive electrode, and a solid electrolyte membrane as the electrolyte layer, and discharges through an electrochemical workstation to perform an electrochemical reaction; the metallic lithium or lithium alloy reacts at the negative electrode to obtain metallic lithium ions, and the carbon-sulfur composite reacts at the positive electrode to obtain sulfur ions; the metallic lithium ions are transferred to the positive electrode through the solid electrolyte membrane, and react with the sulfur ions to obtain the target product of lithium sulfide. The present application adopts an electrochemical method and an all-solid-state battery to prepare lithium sulfide, which reduces the participation of organic solvents in the reaction process. The overall process is a full solid-phase chemical change, which is highly safe and is conducive to improving the preparation purity of lithium sulfide. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 A schematic diagram of materials in a reaction device provided in an embodiment of the present application;

[0033] Figure 2 The X-ray diffraction (XRD) pattern of the final lithium sulfide product prepared in the embodiment of the present application;

[0034] Figure 3 The XRD standard card spectrum of lithium sulfide provided in the embodiment of the present application;

[0035] Figure 4 This is a comparison chart of the lithium sulfide discharge rates in Examples 1-5 of the present application;

[0036] Figure 5 This is a schematic diagram of a reaction device provided in an embodiment of the present application.

[0037] The following is a supplementary description of the attached drawings:

[0038] 100-reaction material; 101-metal lithium or lithium alloy; 102-solid electrolyte membrane; 103-lithium sulfide target product; 104-carbon-sulfur composite;

[0039] 201-first plug; 202-second plug;

[0040] 300-sleeve. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions 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 making creative work are within the scope of protection of this application.

[0042] For the following defined terms, these definitions shall apply unless a different definition is given in the claims or elsewhere in this specification. All numerical values, whether or not explicitly indicated, are defined herein as modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art considers to be equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A numerical range indicated by a lower value and a higher value is defined to include all numerical values ​​included in the numerical range and all subranges included in the numerical range.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings 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 interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] A method for preparing lithium sulfide provided in an embodiment of the present application uses metallic lithium or lithium alloy as a negative electrode, a carbon-sulfur composite as a positive electrode, and a solid electrolyte membrane as an electrolyte layer, and discharges through an electrochemical workstation to perform an electrochemical reaction; the metallic lithium or lithium alloy reacts at the negative electrode to obtain metallic lithium ions, and the carbon-sulfur composite reacts at the positive electrode to obtain sulfur ions; the metallic lithium ions are transported to the positive electrode through the solid electrolyte membrane, and react with the sulfur ions to obtain the target product of lithium sulfide. Specifically, an electrochemical reaction system is established and charged to perform an electrochemical reaction. The metallic lithium or lithium alloy at the negative electrode undergoes a reduction reaction to obtain metallic lithium ions, and the carbon-sulfur complex at the positive electrode undergoes an oxidation reaction to obtain sulfur ions; the metallic lithium ions at the negative electrode are transferred to the positive electrode, and are combined with the sulfur ions obtained by the positive electrode reaction to form a target product of lithium sulfide at the positive electrode. After the electrochemical reaction is completed, the material obtained by the positive electrode reaction is collected. The preparation method of the present application uses an all-solid-state battery process as a template, and uses a solid electrolyte membrane as an ion channel to achieve the effect of lithium ion transmission, thereby achieving the preparation of lithium sulfide by an all-solid-state battery, which can reduce the participation of organic solvents in the reaction process, and does not require solvent separation, drying and other processes. In addition, the intermediate layer electrolyte can be repeatedly recycled, which is beneficial to reducing production costs and saving resources. At the same time, the overall reaction process is a full solid-phase chemical change, which is highly safe, and the purity of the lithium sulfide finally prepared is also relatively high.

[0046] Among them, by adopting the above preparation method, with metallic lithium or lithium alloy as the negative electrode, with carbon-sulfur composite as the positive electrode, with solid electrolyte membrane as the electrolyte layer, an electrochemical reaction system is formed under an applied voltage, wherein the electrolytic cell reaction is:

[0047] Anode reaction: Li→Li + +e - ;

[0048] Cathode reaction: S+2e - →S 2- ;

[0049] Overall electrochemical reaction: 2Li + +S 2- →L i2S;

[0050] From the reaction formula, we can know that under the electrochemical workstation, the electrochemical reaction is carried out, and the reactants are forced by the electric field to undergo reduction and oxidation reactions at the cathode and cathode respectively. The electrons and lithium ions obtained from the anode reaction are transmitted to the cathode through the external circuit and the internal solid electrolyte membrane respectively. At the cathode, the sulfur ions obtained from the cathode reaction combine with lithium ions to form lithium sulfide. During the continuous cycle of discharge, lithium sulfide will be continuously deposited, and the target product of lithium sulfide will be obtained.

[0051] In some specific embodiments, metallic lithium or lithium alloy is used as the negative electrode, a carbon-sulfur composite is used as the positive electrode, and a solid electrolyte membrane is used as the electrolyte layer. The electrochemical reaction is carried out by discharging in an electrochemical workstation. The specific preparation method includes:

[0052] S1: Weigh a certain amount of solid electrolyte and press it into a solid electrolyte membrane;

[0053] S2: placing a carbon-sulfur composite at one end of the solid electrolyte membrane and pressing the carbon-sulfur composite;

[0054] S3: placing metallic lithium or lithium alloy at the other end of the solid electrolyte membrane and pressing the metallic lithium or lithium alloy;

[0055] S4: connecting the positive electrode of the electrochemical workstation to one end of the carbon-sulfur composite, and connecting the negative electrode of the electrochemical workstation to one end of the metallic lithium or lithium alloy;

[0056] S5: Discharge through an electrochemical workstation to activate metallic lithium or lithium alloy and carbon-sulfur composite for electrochemical reaction.

[0057] Among them, see Figure 1 , the reaction materials 100 in the reaction device represent metallic lithium or lithium alloy 101, solid electrolyte membrane 102, lithium sulfide target product 103 and carbon-sulfur composite 104 from top to bottom; specifically, in an inert atmosphere such as nitrogen, argon or a low dew point (below -60°C) environment, the weighed solid electrolyte is placed in a mold, shaken and flattened, and placed in a press for pressurization to obtain a solid electrolyte membrane, and the carbon-sulfur composite is placed on the prepared solid electrolyte membrane, shaken and flattened, and placed in a press for pressurization again to obtain a composite layer of the carbon-sulfur composite and the electrolyte membrane; metallic lithium or lithium alloy is placed on the side of the composite layer away from the carbon-sulfur composite, and placed in a press for pressurization again to obtain the carbon-sulfur composite. The invention discloses an all-solid-state battery comprising a carbon-sulfur composite, an electrolyte membrane and metallic lithium or a lithium alloy, and an electrochemical reaction system is formed under an external voltage applied across the carbon-sulfur composite and the metallic lithium or the lithium alloy to carry out an electrochemical reaction, wherein the applied discharge current is a trickle discharge (discharged at about 0.005C to 0.01C to 2V, and then forced to trickle discharge to a current of 5μA). After the discharge is completed (the voltage is reduced to below 1V, and the discharge cut-off current is 5μA), the power supply is removed, and the material obtained by the positive electrode reaction is taken out to obtain a target product of lithium sulfide. The preparation method has a simple process, strong operability, and the required preparation equipment is simple, and the equipment requirements are low. The above preparation can be completed in a normal laboratory.

[0058] In some specific embodiments, after the metal lithium ions are transferred to the positive electrode through the solid electrolyte membrane and react with the sulfur ions to obtain the target product of lithium sulfide, the method comprises:

[0059] S1: dissolving the target lithium sulfide product in anhydrous ethanol to obtain a solution;

[0060] S2: filtering the solution to obtain a filtrate;

[0061] S3: drying the filtrate by rotary evaporation to obtain lithium sulfide powder;

[0062] S4: Sintering the lithium sulfide powder under an inert atmosphere to obtain a final lithium sulfide product.

[0063] Specifically, in an inert atmosphere such as nitrogen, argon or a low dew point environment (below -60°C), the lithium sulfide target product obtained in the positive electrode reaction is first dissolved in anhydrous ethanol to obtain a solution, which is stirred evenly and filtered after being fully dissolved to obtain a filtrate and a filter residue. The filtrate is rotary evaporated and dried to obtain lithium sulfide powder, and the lithium sulfide powder is sintered in an inert atmosphere to obtain a final lithium sulfide product; wherein, preferably, the temperature for sintering the lithium sulfide powder in an inert atmosphere can be 600°C, and the sintering time can be 2h, and the obtained lithium sulfide final product has a higher purity.

[0064] In some specific embodiments, the carbon in the carbon-sulfur composite is at least one of conductive carbon tubes, carbon black, graphite, and conductive carbon.

[0065] In some specific embodiments, the metallic lithium is a metallic lithium sheet or a metallic lithium powder; and the lithium alloy is a lithium alloy sheet or a lithium alloy powder.

[0066] In some specific embodiments, the solid electrolyte membrane is a sulfide Li 10 GeP2S 12 At least one of Li3PS4, Li6PS5X (X = Br, Cl, I), and Li7P2S8I, using a sulfide solid electrolyte membrane as the electrolyte layer, reduces the participation of organic solvents in the reaction process, and is beneficial to improving the purity of lithium sulfide.

[0067] In some specific embodiments, the current applied by the electrochemical workstation is a constant current of 1 μA to 5 mA.

[0068] In some specific implementations, the thickness of the solid electrolyte membrane is 0.5 to 5 mm, so that the solid electrolyte membrane is not easily broken during pressing during the preparation process, the structure is more complete, and the preparation efficiency is higher.

[0069] In some specific embodiments, the sulfur content in the carbon-sulfur composite is 10% to 85%. According to the different sulfur contents in the carbon-sulfur composite, the final lithium sulfide products obtained at different sulfur contents are measured. According to experiments, under the condition of a discharge current of 3 mA, when the sulfur content is 85%, the final lithium sulfide product prepared is the highest.

[0070] In some specific implementations, see Figure 5 The solid electrolyte, carbon-sulfur composite and metal lithium or lithium alloy are pressed in the steps S1, S2 and S3 by using a reaction device; wherein the reaction device comprises a sleeve 300, a first plug 201 and a second plug 202, and the first plug 201 and the second plug 202 are sleeved at both ends of the sleeve 300; the pressing comprises:

[0071] The solid electrolyte is loaded into the sleeve 300, and the first plug 201 and the second plug 202 are inserted into the sleeve, and the sleeve is placed in a press for the first pressurization; wherein the pressure of the first pressurization is 0.5-50 MPa;

[0072] After the first pressurization is completed, the first plug 201 is removed, the carbon-sulfur composite is loaded into the sleeve 300, the first plug 201 is inserted, and the sleeve is placed under the press for the second pressurization; wherein the pressure of the second pressurization is 0.5-30 MPa;

[0073] After the second pressurization is completed, the second plug 202 is removed, the metallic lithium or lithium alloy is placed in the sleeve 300, the second plug 202 is inserted, and the press is placed under the press for the third pressurization; wherein the pressure of the third pressurization is 0.5-5MPa.

[0074] Among them, the sleeve 300 adopts a pressure-resistant insulating material, such as polyetheretherketone (PEEK) material, polytetrafluoroethylene (PTFE) material, etc., and the first plug 201 and the second plug 202 are made of stainless steel, copper, aluminum and metal alloy; the inner cavity of the sleeve 300 is filled with reactants of positive and negative electrodes and electrolytes, and the first plug 201 and the second plug 202 are inserted into the two ends of the sleeve 300 to form a sealed reaction container with the sleeve 300, and the reaction device equipped with positive and negative electrodes and electrolytes is connected to the electrochemical workstation, the positive electrode of the electrochemical workstation is connected to the first plug 201, and the negative electrode of the electrochemical workstation is connected to the second plug 202 to carry out an electrochemical reaction. No organic solvent is involved in the preparation process, the preparation efficiency is controllable, the equipment requirements are low, and the prepared lithium sulfide has a high purity.

[0075] The following is a specific embodiment of the present application, which is described in combination with the above-mentioned method of using metallic lithium or lithium alloy as the negative electrode, a carbon-sulfur composite as the positive electrode, and a solid electrolyte membrane as the electrolyte layer, and performing an electrochemical reaction by discharging in an electrochemical workstation. The following embodiments describe the technical scheme of the present application in more detail, and these embodiments are only used for illustrative purposes, because it is obvious to those skilled in the art to make various modifications and changes within the scope of the disclosure of the present application. The reagents used in the embodiments can be obtained by commercial purchase or synthesized according to conventional methods, and can be used directly without further treatment, and the instruments and devices used in the embodiments can be obtained commercially.

[0076] Example 1

[0077] A carbon-sulfur composite formed by mixing sublimated sulfur powder and carbon nanotubes with a sulfur content of 85% is used as the positive electrode, a lithium sheet is used as the negative electrode, sulfide Li3PS4 is used as the electrolyte membrane material, and a φ11.5mm PEEK sleeve 300 and a matching stainless steel first plug 201 and second plug 202 are used as the reaction device.

[0078] Weigh 0.3g of Li3PS4 electrolyte and put it into the sleeve 300. Insert the first plug 201 and the second plug 202 at both ends of the sleeve 300. Put the assembled reaction device into the hydraulic press and pressurize it at 0.5MPa. The pressure is maintained for about 30s to press the electrolyte into an electrolyte ceramic membrane. Take out the first plug 201, weigh 0.2g of carbon-sulfur composite as the positive electrode material, put it into the sleeve 300, insert the first plug 201, pressurize it again at 0.5MPa, take out the second plug 202 after pressurization, cut the 1mm thick lithium sheet into φ11.5 round pieces, put them into the sleeve 300, insert the second plug 202, and pressurize it again at 0.5MPa. The pressed reaction device is connected to the electrochemical workstation, the positive electrode of the electrochemical workstation is connected to the first plug 201, the negative electrode of the electrochemical workstation is connected to the second plug 202, and discharge is performed with a discharge current of 3mA. When the discharge voltage is lower than 2V, forced trickle discharge is performed until the voltage is lower than 1V and the minimum current is about 1μA.

[0079] After the discharge is completed, the first plug 201 is removed, and the material obtained by the positive electrode reaction is taken out from the sleeve 300, put into ethanol and stirred to dissolve to obtain a solution, the solution is filtered to obtain a filtrate, and the filtrate obtained by filtration is subjected to rotary evaporation purification to precipitate lithium sulfide, and finally the precipitated lithium sulfide is sintered for 2 hours in a nitrogen atmosphere at a sintering temperature of 600°C, and the final product of lithium sulfide is obtained after natural cooling.

[0080] Example 2

[0081] A carbon-sulfur composite formed by mixing sublimated sulfur powder and carbon nanotubes with a sulfur content of 60% is used as the positive electrode, a lithium sheet is used as the negative electrode, a sulfide Li6PS5C l is used as the electrolyte membrane material, and a φ11.5mm PEEK sleeve 300 and a matching stainless steel first plug 201 and a second plug 202 are used as the reaction device.

[0082] 1.0g of Li6PS5C l electrolyte was weighed and loaded into the sleeve 300. The first plug 201 and the second plug 202 were inserted into the two ends of the sleeve 300. The assembled reaction device was placed in a hydraulic press and pressurized at 25MPa for about 30s to press the electrolyte into an electrolyte ceramic membrane. The first plug 201 was taken out, 1.5g of carbon-sulfur composite was weighed as the positive electrode material, loaded into the sleeve 300, inserted into the first plug 201, and pressurized at 25MPa again, then the second plug 202 was taken out, and the 8mm thick lithium sheet was cut into φ11.5 round pieces, placed in the sleeve 300, inserted into the second plug 202, and pressurized at 5MPa again. The pressed reaction device is connected to the electrochemical workstation, the positive electrode of the electrochemical workstation is connected to the first plug 201, the negative electrode of the electrochemical workstation is connected to the second plug 202, and discharge is performed with a discharge current of 20mA. When the discharge voltage is lower than 2V, forced trickle discharge is performed until the voltage is lower than 1V, and the minimum current is about 5μA.

[0083] After the discharge is completed, the first plug 201 is removed, and the material obtained by the positive electrode reaction is taken out from the sleeve 300, put into ethanol and stirred to dissolve to obtain a solution, the solution is filtered to obtain a filtrate, and the filtrate obtained by filtration is subjected to rotary evaporation purification to precipitate lithium sulfide, and finally the precipitated lithium sulfide is sintered for 2 hours in a nitrogen atmosphere at a sintering temperature of 600°C, and the final product of lithium sulfide is obtained after natural cooling.

[0084] Example 3

[0085] A carbon-sulfur composite made of sublimated sulfur powder and carbon nanotubes with a sulfur content of 30% was used as the positive electrode, a lithium sheet was used as the negative electrode, and Li 10 GeP2S 12 As the sulfide electrolyte membrane material, a φ11.5 mm PEEK sleeve 300 and a matching stainless steel first plug 201 and a second plug 202 are used as a reaction device.

[0086] Weigh 1.0g of Li 10 GeP2S 12The electrolyte is loaded into the sleeve 300, and the first plug 201 and the second plug 202 are inserted into the two ends of the sleeve 300. The assembled reaction device is placed in a hydraulic press and pressurized at 30MPa. The pressure is maintained for about 30s to press the electrolyte into an electrolyte ceramic diaphragm. The first plug 201 is taken out, 3g of carbon-sulfur composite is weighed as the positive electrode material, loaded into the sleeve 300, and the first plug 201 is inserted. After pressurizing at 30MPa again, the second plug 202 is taken out, and the 8mm thick lithium sheet is cut into φ11.5 round pieces, placed in the sleeve 300, and the second plug 202 is inserted, and pressurized at 1.5MPa again. The pressed reaction device is connected to the electrochemical workstation, the positive electrode of the electrochemical workstation is connected to the first plug 201, the negative electrode of the electrochemical workstation is connected to the second plug 202, and discharge is performed with a discharge current of 14mA. When the discharge voltage is lower than 2V, forced trickle discharge is performed until the voltage is lower than 1V, and the minimum current is about 5μA.

[0087] After the discharge is completed, the first plug 201 is removed, and the material obtained by the positive electrode reaction is taken out from the sleeve 300, put into ethanol and stirred to dissolve to obtain a solution, the solution is filtered to obtain a filtrate, and the filtrate obtained by filtration is subjected to rotary evaporation purification to precipitate lithium sulfide, and finally the precipitated lithium sulfide is sintered for 2 hours in a nitrogen atmosphere at a sintering temperature of 600°C, and the final product of lithium sulfide is obtained after natural cooling.

[0088] Example 4

[0089] A carbon-sulfur composite formed by mixing sublimated sulfur powder and carbon nanotubes with a sulfur content of 10% is used as the positive electrode, a lithium sheet is used as the negative electrode, Li7P2S8I is used as the sulfide electrolyte membrane material, and a φ11.5mm PEEK sleeve 300 and a matching stainless steel first plug 201 and a second plug 202 are used as the reaction device.

[0090] Weigh 1.5g of Li7P2S8I electrolyte and put it into the sleeve 300. Insert the first plug 201 and the second plug 202 at both ends of the sleeve 300. Put the assembled reaction device into the hydraulic press and pressurize it at 50MPa. The pressure is maintained for about 30s to press the electrolyte into an electrolyte ceramic membrane. Take out the first plug 201, weigh 10g of carbon-sulfur composite as the positive electrode material, put it into the sleeve 300, insert the first plug 201, pressurize it again at 50MPa, take out the second plug 202, cut the 10mm thick lithium sheet into φ11.5 round pieces, put them into the sleeve 300, insert the second plug 202, and pressurize it again at 1.5MPa. The pressed reaction device is connected to the electrochemical workstation, the positive electrode of the electrochemical workstation is connected to the first plug 201, the negative electrode of the electrochemical workstation is connected to the second plug 202, and discharge is performed with a discharge current of 16mA. When the discharge voltage is lower than 2V, forced trickle discharge is performed until the voltage is lower than 1V, and the minimum current is about 5μA.

[0091] After the discharge is completed, the first plug 201 is removed, and the material obtained by the positive electrode reaction is taken out from the sleeve 300, put into ethanol and stirred to dissolve to obtain a solution, the solution is filtered to obtain a filtrate, and the filtrate obtained by filtration is subjected to rotary evaporation purification to precipitate lithium sulfide, and finally the precipitated lithium sulfide is sintered for 2 hours in a nitrogen atmosphere at a sintering temperature of 600°C, and the final product of lithium sulfide is obtained after natural cooling.

[0092] Example 5

[0093] A carbon-sulfur composite formed by mixing sublimated sulfur powder and carbon nanotubes with a sulfur content of 60% is used as the positive electrode, a lithium sheet is used as the negative electrode, Li6PS5Br is used as the sulfide electrolyte membrane material, and a φ11.5mm PEEK sleeve 300 and a matching stainless steel first plug 201 and second plug 202 are used as the reaction device.

[0094] Weigh 1.0g of Li6PS5Br electrolyte and put it into the sleeve 300. Insert the first plug 201 and the second plug 202 at both ends of the sleeve 300. Put the assembled reaction device into the hydraulic press and pressurize it at 35MPa. The pressure is maintained for about 30s to press the electrolyte into an electrolyte ceramic membrane. Take out the first plug 201, weigh 3g of carbon-sulfur composite as the positive electrode material, put it into the sleeve 300, insert the first plug 201, pressurize it again at 35MPa, take out the second plug 202, cut the 15mm thick lithium sheet into φ11.5 round pieces, put them into the sleeve 300, insert the second plug 202, and pressurize it again at 1.0MPa. The pressed reaction device is connected to the electrochemical workstation, the positive electrode of the electrochemical workstation is connected to the first plug 201, the negative electrode of the electrochemical workstation is connected to the second plug 202, and discharge is performed with a discharge current of 90mA. When the discharge voltage is lower than 2V, forced trickle discharge is performed until the voltage is lower than 1V, and the minimum current is about 5μA.

[0095] After the discharge is completed, the first plug 201 is removed, and the material obtained by the positive electrode reaction is taken out from the sleeve 300, put into ethanol and stirred to dissolve to obtain a solution, the solution is filtered to obtain a filtrate, and the filtrate obtained by filtration is subjected to rotary evaporation purification to precipitate lithium sulfide, and finally the precipitated lithium sulfide is sintered for 2 hours in a nitrogen atmosphere at a sintering temperature of 600°C, and the final product of lithium sulfide is obtained after natural cooling.

[0096] Among them, see Figure 2 and Figure 3 , Figure 2 This is the XRD pattern of the final lithium sulfide product prepared in Examples 1-5 of the present application, Figure 3 It is the XRD standard card map of lithium sulfide; According to the XRD standard card map of lithium sulfide, the characteristic peak value of the final product prepared by comparison Example 1-5 can be obtained, and the final product prepared by Example 1-5 of the present application is lithium sulfide.

[0097] Among them, see Figure 4 In Examples 1-5, the yield of lithium sulfide is obtained according to the different sulfur powder contents added. Comparative Examples 1-5 show that the carbon-sulfur composite prepared by mixing sublimated sulfur powder and carbon nanotubes with a sulfur content of 85% is used as the positive electrode, and 0.3g of sulfide Li3PS4 is weighed as the electrolyte membrane material. The yield of lithium sulfide prepared is the highest, and the yield can reach 76.47%.

[0098] The present application adopts an electrochemical method and an all-solid-state battery to prepare lithium sulfide, and uses solid sulfide as the electrolyte layer, which reduces the participation of organic solvents in the reaction process. The overall process is a full solid-phase chemical change, which is highly safe and is conducive to improving the preparation purity of lithium sulfide.

[0099] The above description has fully disclosed the specific embodiments of the present invention. It should be pointed out that any changes made by those skilled in the art to the specific embodiments of the present invention do not deviate from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not limited to the above specific embodiments.

Claims

1. A method for preparing lithium sulfide, characterized in that: With metallic lithium or lithium alloy as negative electrode, carbon-sulfur composite as positive electrode, solid electrolyte membrane as electrolyte layer, the electrochemical reaction is carried out by discharging in an electrochemical workstation; The metallic lithium or lithium alloy reacts at the negative electrode to obtain metallic lithium ions, and the carbon-sulfur composite reacts at the positive electrode to obtain sulfur ions; The metal lithium ions are transported to the positive electrode through the solid electrolyte membrane and react with the sulfur ions to obtain the target product of lithium sulfide.

2. A method for preparing lithium sulfide according to claim 1, characterized in that: The method uses metal lithium or lithium alloy as the negative electrode, carbon-sulfur composite as the positive electrode, and solid electrolyte membrane as the electrolyte layer, and discharges through an electrochemical workstation to perform an electrochemical reaction, including: S1: Weigh a certain amount of solid electrolyte and press it into the solid electrolyte membrane; S2: placing the carbon-sulfur composite at one end of the solid electrolyte membrane and pressing the carbon-sulfur composite; S3: placing the metal lithium or lithium alloy at the other end of the solid electrolyte membrane and pressing the metal lithium or lithium alloy; S4: connecting the positive electrode of the electrochemical workstation to one end of the carbon-sulfur composite, and connecting the negative electrode of the electrochemical workstation to one end of the metallic lithium or lithium alloy; S5: discharging through the electrochemical workstation to activate the metallic lithium or lithium alloy and the carbon-sulfur composite to perform an electrochemical reaction.

3. A method for preparing lithium sulfide according to claim 1, characterized in that: The metal lithium ions are transported to the positive electrode through the solid electrolyte membrane and react with the sulfur ions to obtain the target product of lithium sulfide, comprising: S1: dissolving the lithium sulfide target product in anhydrous ethanol to obtain a solution; S2: filtering the solution to obtain a filtrate; S3: drying the filtrate by rotary evaporation to obtain lithium sulfide powder; S4: sintering the lithium sulfide powder under an inert atmosphere to obtain a final lithium sulfide product.

4. A method for preparing lithium sulfide according to claim 1, characterized in that: The carbon in the carbon-sulfur composite is at least one of conductive carbon tubes, carbon black, graphite and conductive carbon.

5. A method for preparing lithium sulfide according to claim 1, characterized in that: The metallic lithium is metallic lithium sheet or metallic lithium powder; the lithium alloy is lithium alloy sheet or lithium alloy powder.

6. A method for preparing lithium sulfide according to claim 1, characterized in that: The solid electrolyte membrane is sulfide Li 10 GeP2S 12 , Li3PS4, Li6PS5X (X = Br, Cl, I), Li7P2S8I.

7. A method for preparing lithium sulfide according to claim 2, characterized in that: The current applied by the electrochemical workstation is a constant current of 1 μA to 5 mA.

8. A method for preparing lithium sulfide according to claim 1, characterized in that: The thickness of the solid electrolyte membrane is 0.5 to 5 mm.

9. A method for preparing lithium sulfide according to claim 1, characterized in that: The sulfur content in the carbon-sulfur composite is 10% to 85%.

10. A method for preparing lithium sulfide according to claim 2, characterized in that: The steps S1, S2 and S3 are pressed using a reaction device; wherein the reaction device comprises a sleeve (300), a first plug (201) and a second plug (202), wherein the first plug (201) and the second plug (202) are sleeved at both ends of the sleeve (300); the pressing comprises: The solid electrolyte is loaded into the sleeve (300), the first plug (201) and the second plug (202) are inserted, and the sleeve is placed in a press for a first pressurization; wherein the pressure of the first pressurization is 0.5 to 50 MPa; After the first pressurization is completed, the first plug (201) is taken out, the carbon-sulfur composite is loaded into the sleeve (300), the first plug (201) is inserted, and the sleeve is placed under the press for a second pressurization; wherein the pressure of the second pressurization is 0.5-30 MPa; After the second pressurization is completed, the second plug (202) is taken out, metallic lithium or lithium alloy is placed in the sleeve (300), the second plug (202) is inserted, and the press is placed under the press for the third pressurization; wherein the pressure of the third pressurization is 0.5 to 5 MPa.

Images