Lithium sulfide composition as well as preparation method and application thereof

Abstract

The invention relates to a lithium sulfide composition as well as a preparation method and application thereof. The lithium sulfide composition at least comprises the following components: lithium sulfide and a compound as shown in a formula (1), in the formula, R is selected from H, alkyl of C1-C6 and alkyl amino of C1-C6; n ranges from 1 to 6; based on the total mass of the lithium sulfide composition, the content of the compound shown in the formula (1) is 10-100 ppm. The preparation method of the lithium sulfide composition provided by the invention has the advantages of good reproducibility, few byproducts in the reaction process, no greenhouse gas emission, environmental friendliness, no need of complex and expensive instruments and equipment, and easiness in large-scale industrial production; the lithium sulfide composition prepared by the method has uniform and small particle size, large specific surface area and high purity, and the sulfide solid electrolyte prepared from the lithium sulfide prepared by the method has high ionic conductivity.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials, and more particularly to a lithium sulfide composition, its preparation method, and its application. Background Technology

[0002] In recent years, all-solid-state lithium-ion batteries have demonstrated high safety and excellent electrochemical performance due to their use of non-flammable solid electrolytes. Sulfide solid electrolytes have attracted widespread attention among various solid electrolyte types due to their high ionic conductivity. Lithium sulfide (Li₂S) is a key raw material for the preparation of sulfide electrolytes in solid-state batteries. A 1 GWh solid-state battery based on Li₆PS₅Cl (LPSC) electrolyte requires 400-450 kg of Li₂S. Currently, the bulk purchase price at the kilogram level is 6000-7000 RMB / kg, accounting for 99% of the raw material cost of LPSC electrolytes. This high price limits its widespread application in the market and hinders the rapid development of sulfide solid-state batteries. Therefore, exploring low-cost, large-scale methods for synthesizing battery-grade lithium sulfide has become one of the key factors for the industrialization of sulfide solid electrolytes.

[0003] Due to the high added value of lithium sulfide, it has attracted many companies and universities to conduct research. Currently, the main preparation methods that have shown signs of industrialization include carbothermal reduction, hydrazine hydrate method, and solid-phase method.

[0004] The carbothermal reduction method involves uniformly mixing a sulfur-containing lithium salt with a carbon source and then subjecting the mixture to a redox reaction at high temperature to generate lithium sulfide. Patent CN 114275742 B discloses a method for preparing lithium sulfide that enables continuous production. This patent uses an organic carbon source to bind and mix carbon materials with a lithium source, employs a three-stage heating and holding process to generate lithium sulfide through a redox reaction, and then uses an alcohol solvent for leaching and purification. After drying, lithium sulfide is obtained. This method produces lithium sulfide with high purity, but the high-temperature holding time during the preparation process is too long, resulting in high energy consumption and high cost. Furthermore, when using an alcohol solvent for leaching and purification, it is impossible to ensure that the heavy components produced by calcination can be effectively removed.

[0005] The hydrazine hydrate method uses hydrazine hydrate as a reducing agent to prepare lithium sulfide. Patent CN 117550562 A discloses a method for preparing high-purity lithium sulfide, which includes the following steps: a) mixing and grinding a sulfur source and a lithium source, then mixing the ground mixture with hydrazine hydrate to obtain a reactant; b) reacting the mixture to obtain a lithium sulfide slurry; c) heating the lithium sulfide slurry to 100℃~120℃, drying for 1~2 hours, then adding sulfur powder and anhydrous hydrazine, heating to 400℃~410℃, and drying for 1~2 hours to obtain high-purity lithium sulfide powder. While this method can achieve the preparation of high-purity lithium sulfide, hydrazine hydrate is a strong reducing agent and is flammable; its vapor can form an explosive mixture with air. Improper operation poses a risk of fire and explosion. Furthermore, hydrazine hydrate usually needs to be added slowly dropwise to the lithium source solution to avoid violent reactions or excessively high local concentrations that could lead to danger or increased side reactions, making the operation relatively complex.

[0006] The solid-state method involves directly reacting lithium metal with sulfur to obtain lithium sulfide. Patent CN 116040587 B discloses a method for preparing high-purity lithium sulfide using battery-grade lithium metal. This patent describes a process where lithium metal and a corresponding amount of sulfur powder are reacted in a sealed container under inert conditions to obtain crude lithium sulfide. This crude product is then pulverized and mixed again with sulfur powder, and kept at a temperature of 2-4 hours to obtain lithium sulfide with a purity of 99.9%. This method for preparing high-purity lithium sulfide using battery-grade lithium metal is simple and practical, producing high-purity lithium sulfide with small primary particles and high purity. However, the use of lithium metal as a raw material results in higher production costs. Summary of the Invention

[0007] To address the shortcomings of existing technologies, one objective of this invention is to provide a lithium sulfide composition. The lithium sulfide composition comprises a small amount of the compound shown in formula (1), which contains a carbonyl oxygen structure.

[0008] The second objective of this invention is to provide a method for preparing the above-mentioned lithium sulfide composition, which has the advantages of mild reaction conditions and low cost, and is suitable for industrial-scale production.

[0009] The third objective of this invention is to provide the application of the above-mentioned lithium sulfide composition in the field of lithium-ion batteries.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect of the invention, a lithium sulfide composition is provided, the lithium sulfide composition comprising at least lithium sulfide and a compound of formula (1);

[0012]

[0013] In the formula, R is selected from H, C1-C6 alkyl groups, and C1-C6 alkylamino groups; n takes values ​​from 1 to 6;

[0014] Based on the total mass of the lithium sulfide composition, the content of the compound shown in formula (1) is 10-100 ppm, such as 10 ppm, 12 ppm, 15 ppm, 20 ppm, 40 ppm, 50 ppm, 60 ppm, 100 ppm, etc., preferably 10-50 ppm.

[0015] In their experiments, the researchers of this invention discovered that when the lithium sulfide composition contains 10-100 ppm of the compound shown in formula (1), the sulfide solid electrolyte prepared from the lithium sulfide composition has a high ionic conductivity. When the content is greater than 100 ppm, the ionic conductivity will decrease, while when it is less than 10 ppm, the effect of improving the ionic conductivity is not obvious.

[0016] In one embodiment, the C1-C6 alkyl group has the structure shown in (2) below:

[0017] In the formula, a takes values ​​from 0 to 6, such as 0, 2, 4, 6, etc., and b takes values ​​from 0 to 6, such as 0, 2, 4, 6, etc.

[0018] Preferably, the alkyl group of C1-C6 is selected from methyl (-CH3), ethyl, propyl, isopropyl, butyl, or isobutyl, etc.

[0019] In one embodiment, the C1-C6 alkylamino group has the structure shown in (3) below:

[0020] In the formula, a takes values ​​from 0 to 6, such as 0, 2, 4, 6, etc., and b takes values ​​from 0 to 6, such as 0, 2, 4, 6, etc.

[0021] Preferably, the alkylamino group of C1-C6 is selected from methylamino (-NH2), isobutylamino, methylamino, ethylamino, propylamino, isopropylamino, or butylamino, etc.

[0022] In one embodiment, the compound represented by formula (1) is selected from at least one of lithium 6-aminohexanoate, lithium 4-(isobutylamino)butanoate, lithium 4-(ethylamino)butanoate, lithium hexanoate, lithium 4-(methylamino)butanoate, lithium valerate, etc., and has the structure shown in the following formula:

[0023]

[0024] The lithium sulfide composition of the present invention is mainly composed of lithium sulfide (Li2S), and is a generally single compound containing more than 99.9 wt.% lithium sulfide. However, since it contains a small amount of the compound shown in formula (1) as a secondary component, it is defined as a lithium sulfide composition.

[0025] Specifically, in the lithium sulfide composition of the present invention, the main component lithium sulfide has a content of 99.9 wt% or more, and the other components are compounds of formula (1) with a content of 10-100 ppm, as well as small amounts of LiHS and Li2S introduced from raw materials or side reactions during the preparation process. X (x≥2) and other trace impurities; in addition, in some cases, trace amounts of raw material residues and other difficult-to-determine impurities may also exist in the system.

[0026] Optionally, the lithium sulfide composition further comprises LiHS and Li2S. X (x≥2), total content ≤10ppm.

[0027] Preferably, the lithium sulfide composition comprises 10-100 ppm of the compound of formula (1), with the remainder being lithium sulfide.

[0028] In one embodiment, the lithium sulfide composition has lithium sulfide particle size ranging from 0.1 to 100 μm, preferably 1 to 5 μm.

[0029] In one embodiment, the lithium sulfide composition has a specific surface area ≥1m². 2 / g, preferably 1-5m 2 / g.

[0030] In a second aspect of the invention, a method for preparing the lithium sulfide composition is provided.

[0031] The method of preparing the lithium sulfide composition is not limited in this invention. The lithium sulfide and the compound shown in formula (1) contained in the composition are both existing products that have been disclosed. The compound shown in formula (1) may be generated as a byproduct in the reaction process of preparing lithium sulfide, or it may be added artificially to obtain the required amount.

[0032] The proportion of the compound represented by formula (1) in this invention can be determined by liquid chromatography.

[0033] As an example, a method for preparing the lithium sulfide composition includes the following steps:

[0034] (1) Salt formation process: Under the protection of an inert atmosphere, lithium hydroxide and organic solvent are mixed evenly, heated to above 130°C, and hydrogen sulfide gas is introduced into it to carry out an acid-base neutralization reaction to obtain a LiHS-containing solution.

[0035] (2) Pyrolysis process: The LiHS-containing solution is filtered, and then heated to above 160°C to carry out the pyrolysis reaction to obtain Li2S dispersion;

[0036] (3) Purification process: The Li2S dispersion is filtered, washed, and dried to obtain the lithium sulfide composition.

[0037] In one implementation, the inert atmosphere described in step (1) is a nitrogen atmosphere or an argon atmosphere.

[0038] In one embodiment, the lithium hydroxide in step (1) is lithium hydroxide hydrate or anhydrous lithium hydroxide.

[0039] In one embodiment, the organic solvent in step (1) is selected from organic aprotic solvents containing a carbonyl oxygen structure, preferably at least one of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-dipropylacetamide, N,N-dimethylbenzamide, lactam compounds, etc.

[0040] Optionally, the lactam compound includes, for example, N-alkylcaprolactams (including caprolactam, N-methylcaprolactam, N-ethylcaprolactam, N-isopropylcaprolactam, N-isobutylcaprolactam, N-n-propylcaprolactam, N-n-butylcaprolactam, N-cyclohexylcaprolactam, etc.), and N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-isobutyl-2-pyrrolidone, N-n-propyl-2-pyrrolidone, etc. At least one of the following: ketone, N-n-butyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-methyl-3-methyl-2-pyrrolidone, N-ethyl-3-methyl-2-pyrrolidone, N-methyl-3,4,5-trimethyl-2-pyrrolidone, N-methyl-2-piperidinone, N-ethyl-2-piperidinone, N-isopropyl-2-piperidinone, N-methyl-6-methyl-2-piperidinone, N-methyl-3-ethyl-2-piperidinone, acetone, pentanone, cyclohexanone, cyclopentanone, etc.

[0041] In one embodiment, the mass ratio of lithium hydroxide to organic solvent in step (1) is 1:2-6, for example, 1:2, 1:3, 1:4, 1:5, 1:6, etc.

[0042] In one embodiment, the molar ratio of lithium hydroxide to hydrogen sulfide in step (1) is 1:1-1.5, for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc.;

[0043] Optionally, the hydrogen sulfide feed flow rate is 0.2-0.6 L / min, for example 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, etc.;

[0044] Optionally, the hydrogen sulfide can be added at any time from the start to the end of the reaction, preferably 2-5 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0045] In one embodiment, the temperature of the acid-base neutralization reaction in step (1) is above 130°C, preferably 130-160°C, such as 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 180°C, 200°C, etc.

[0046] Optionally, the acid-base neutralization reaction time is 1-6 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0047] In one embodiment, the temperature of the pyrolysis reaction in step (2) is above 160°C, preferably 160-190°C, such as 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 200°C, etc.

[0048] Optionally, the pyrolysis reaction takes 3-5 hours, for example, 3 hours, 4 hours, 5 hours, etc.

[0049] The filtration, washing, and drying steps in the purification process of step (3) of this invention are conventional operating procedures in the field and are not particularly limited.

[0050] Optionally, the washing process uses an organic solvent for hot washing at a temperature ≥100℃, preferably 100-120℃, such as 100℃, 105℃, 110℃, 115℃, 120℃, etc.

[0051] Optionally, the number of hot washes is ≥4 times, preferably ≥5 times;

[0052] Preferably, each hot wash lasts for 1-1.5 hours, such as 1 hour, 1.3 hours, or 1.5 hours.

[0053] Optionally, the organic solvent in step (3) is an organic aprotic solvent, and its selection refers to the range defined by the organic solvent in step (1). The two can be the same or different.

[0054] In a third aspect of the invention, the application of the lithium sulfide composition in the field of lithium-ion batteries is provided.

[0055] In this invention, the lithium sulfide composition can be used to prepare a solid electrolyte. Preferably, the prepared solid electrolyte is a lithium phosphorus sulfide chlorine (LPSC) all-solid electrolyte with an ionic conductivity of 7 mS / cm or higher.

[0056] The method for preparing the solid electrolyte as a lithium phosphorus sulfur chlorine (LPSC) all-solid electrolyte is an existing process disclosed in the field, such as described in patents CN117577929A, CN119674199ACN120199877A, etc., and will not be repeated here.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] The present invention provides a lithium sulfide composition containing 10-100 ppm of the compound shown in formula (1), thereby the sulfide solid electrolyte prepared by the lithium sulfide composition has high ionic conductivity.

[0059] The method provided by this invention involves reacting lithium hydroxide with hydrogen sulfide in an organic aprotic solvent via an acid-base neutralization reaction to obtain lithium sulfide. The resulting lithium sulfide has high purity, fine particle size, large specific surface area, good reproducibility, few by-products during the reaction, no greenhouse gas emissions, is environmentally friendly, requires no complex and expensive instruments and equipment, and is easy to mass-produce industrially. Attached Figure Description

[0060] Figure 1 The image shows the XRD pattern of lithium sulfide prepared in Example 1 of this invention.

[0061] Figure 2 This is a particle size distribution diagram of lithium sulfide prepared in Example 2 of the present invention. Detailed Implementation

[0062] Preferred embodiments of the invention have been provided to facilitate understanding of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0063] It should be noted that the endpoints and any values ​​of the ranges disclosed in this specification are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0065] In this invention, the technical features described in an open-ended manner, such as "comprising" or "including", include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0066] In this invention, the term "and / or" as used includes any and all combinations of one or more of the associated listed items.

[0067] In this invention, temperature parameters are involved. Unless otherwise specified, both isothermal processing and processing within a certain temperature range are permitted. The isothermal processing allows temperature fluctuations within the precision range controlled by the instrument.

[0068] In this invention, unless specific experimental steps or conditions are specified in the embodiments, all are performed according to conventional experimental procedures or conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagents or instruments.

[0069] The sources of the main raw materials used in the various embodiments and comparative examples of this invention are as follows:

[0070] Anhydrous lithium hydroxide: Beijing Innocare Technology Co., Ltd., 99.99%, metals basis;

[0071] Lithium hydroxide monohydrate: Thermo Fisher Scientific (China) Co., Ltd., 98+%;

[0072] N-Methylpyrrolidone: Beijing Inokai Technology Co., Ltd. 99.5%, Extra dry;

[0073] N-Isobutyl-2-pyrrolidone: Shanghai Haohong Biomedical Technology Co., Ltd., 98%;

[0074] Caprolactam: Thermo Fisher Scientific (China) Co., Ltd., 99%;

[0075] Toluene: Beijing Innocare Technology Co., Ltd., AR;

[0076] p-Xylene: Beijing Innocare Technology Co., Ltd., 99%, Extra dry;

[0077] Cyclohexanone: Beijing Inokai Technology Co., Ltd., 99%;

[0078] Cyclopentanone: Beijing Inokai Technology Co., Ltd., 99%;

[0079] N-Methyl-2-pyrrolidone: Shanghai Yuanye Biotechnology Co., Ltd., 98%;

[0080] o-Dichlorobenzene: Beijing Innocare Technology Co., Ltd., 99%;

[0081] Hydrogen sulfide: Linde Group 99.5%, water content <20ppm;

[0082] 37% formaldehyde aqueous solution: Shanghai Aladdin Biochemical Technology Co., Ltd., 37wt.%in H2O, containing 10-15% methanol stabilizer;

[0083] Lithium metal: Beijing Innocare Technology Co., Ltd., 15.6×0.45mm;

[0084] N-Ethyl-2-pyrrolidone: Thermo Fisher Scientific (China) Co., Ltd., 99%.

[0085] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:

[0086] Particle size and specific surface area were determined using a laser particle size analyzer: the laser particle size analyzer was a BT-2600 model manufactured by Dandong Better Instruments Co., Ltd. The sample was dispersed in dichloromethane for testing at room temperature and pressure.

[0087] The purity of lithium sulfide and the amount of lithium hydroxide were determined by potentiometric titration. The specific titration method was acid-base titration, referring to the acid-base titration method for the determination of lithium hydroxide content in GB / T 11064.2-2023. The instrument used was a 905Titrando potentiometric titrator manufactured by Metrohm, Switzerland.

[0088] The content of compound (1) was determined by ion chromatography, wherein the ion chromatography instrument was a 940 low-pressure ternary gradient intelligent ion chromatograph manufactured by Metrohm, Switzerland. Before the test, the sample needed to be diluted 50 times in a 37% formaldehyde aqueous solution.

[0089] Ionic conductivity: The lithium sulfide composition was prepared into a lithium phosphorus sulfide chlorine (LPSC) all-solid electrolyte according to the method disclosed in patent CN119674199A, and then measured by electrochemical impedance spectroscopy (EIS). The lithium phosphorus sulfide chlorine (LPSC) all-solid electrolyte was assembled into a Li-Li symmetric battery in a glove box, and constant current charge-discharge test was performed using an electrochemical workstation. The electrochemical workstation was a CHI660F electrochemical workstation manufactured by Shanghai Chenhua Instrument Co., Ltd., and the glove box was a universal (2440 / 1000 / 900) type glove box manufactured by Shanghai Chenhua Instrument Co., Ltd.

[0090] Example 1

[0091] A method for preparing a lithium sulfide composition includes the following steps:

[0092] S1. Under the protection of nitrogen atmosphere, weigh 48g of lithium hydroxide and mix it with 120g of caprolactam.

[0093] S2. After mixing thoroughly, raise the solution temperature to 130-145℃;

[0094] S3. Maintain the temperature at 130-145℃, and introduce hydrogen sulfide into the solution at a flow rate of 0.485L / min for 2h (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.299). Continue the neutralization reaction for 2h to obtain a LiHS-containing solution.

[0095] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution.

[0096] S5. Raise the temperature of the LiHS solution to 175-185℃ and carry out the pyrolysis reaction for 3 hours to obtain a Li2S dispersion.

[0097] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0098] S7. The crude Li2S obtained in S6 was hot-washed five times with caprolactam at 105-110℃, with each hot wash lasting 1.2 h. After drying, 39.1 g of Li2S composition was obtained.

[0099] The obtained lithium sulfide composition was tested to have a purity of 99.97%, a lithium 6-aminohexanoate content of approximately 15 ppm, and a yield of 85%.

[0100] The resulting lithium sulfide composition had a particle size of approximately 2 μm and a specific surface area of ​​4.6 m². 2 / g, Figure 1 The image shows the XRD pattern of the lithium sulfide composition prepared in this embodiment.

[0101] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 10 mS / cm.

[0102] Example 2

[0103] A method for preparing a lithium sulfide composition includes the following steps:

[0104] S1. Under the protection of nitrogen atmosphere, weigh 48g of lithium hydroxide and mix it with 120g of N-isobutyl-2-pyrrolidone.

[0105] S2. After mixing thoroughly, raise the solution temperature to 140-150℃;

[0106] S3. Maintain the temperature at 140-150℃ and introduce hydrogen sulfide into the solution at a flow rate of 0.35L / min for 3 hours (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.406). Continue the neutralization reaction for 2.5 hours to obtain a LiHS-containing solution.

[0107] S4. Filter the LiHS solution obtained in S3 to remove unreacted lithium hydroxide and obtain the LiHS solution.

[0108] S5. Raise the temperature of LiHS to 175-190℃ and carry out the pyrolysis reaction for 4 hours. LiHS will pyrolyze to obtain Li2S dispersion.

[0109] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0110] S7. The crude Li2S obtained in S6 was hot-washed 6 times with toluene at 110-115℃, with each hot wash lasting 1.5h. After drying, 42g of Li2S composition was obtained.

[0111] The obtained lithium sulfide composition was tested to have a purity of 99.95%, a lithium 4-(isobutylamino)butyrate content of approximately 25 ppm, and a yield of 91.3%.

[0112] The resulting lithium sulfide composition has a particle size of approximately 4.5 μm. Figure 2 This is the particle size distribution diagram of the lithium sulfide prepared in this embodiment, with a specific surface area of ​​4m³. 2 / g.

[0113] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 8.5 mS / cm.

[0114] Example 3

[0115] A method for preparing a lithium sulfide composition includes the following steps:

[0116] S1. Under the protection of nitrogen atmosphere, weigh 48g of lithium hydroxide and mix it with 145g of N-ethyl-2-pyrrolidone.

[0117] S2. After mixing thoroughly, raise the solution temperature to 145-155℃;

[0118] S3. Maintain the temperature at 145-155℃ and introduce hydrogen sulfide into the solution at a flow rate of 0.475L / min for 2 hours (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.272). Continue the neutralization reaction for 4.5 hours to obtain a LiHS-containing solution.

[0119] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution; S5. Raise the temperature of LiHS to 180-190℃ and carry out the pyrolysis reaction for 4 hours to obtain a Li2S dispersion.

[0120] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0121] S7. The crude Li2S obtained in S6 was hot-washed 6 times with p-xylene at 110-115℃, with each hot wash lasting 1 hour. After drying, 40g of Li2S composition was obtained.

[0122] The obtained lithium sulfide composition was tested to have a purity of 99.97%, a lithium 4-(ethylamino)butyrate content of approximately 90 ppm, and a yield of 86.9%.

[0123] The obtained lithium sulfide composition had a particle size of approximately 52.1 μm and a specific surface area of ​​1.8 m². 2 / g.

[0124] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 7 mS / cm.

[0125] Example 4

[0126] A method for preparing a lithium sulfide composition includes the following steps:

[0127] S1. Under the protection of nitrogen atmosphere, weigh 48g of lithium hydroxide and mix it with 288g of cyclohexanone.

[0128] S2. After mixing thoroughly, raise the solution temperature to 130-145℃;

[0129] S3. Maintain the temperature at 130-145℃, and introduce hydrogen sulfide into the solution at a flow rate of 0.275 L / min for 4 hours (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.473). Continue the neutralization reaction for 2 hours to obtain a LiHS-containing solution.

[0130] S4 filters the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide, thus obtaining a LiHS solution.

[0131] S5. Raise the temperature of LiHS to 180-190℃ and carry out the pyrolysis reaction for 3 hours to obtain Li2S dispersion;

[0132] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0133] S7. The crude Li2S obtained in S6 was hot-washed 6 times with p-xylene at 110-115℃, with each hot wash lasting 1.3h. After drying, 38g of Li2S composition was obtained.

[0134] The obtained lithium sulfide composition was tested to have a purity of 99.96%, a lithium hexanoate content of approximately 85 ppm, and a yield of 82.6%. The particle size of the obtained lithium sulfide composition was approximately 10.2 μm, and the specific surface area was 3.2 m². 2 / g.

[0135] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 7.6 mS / cm.

[0136] Example 5

[0137] A method for preparing a lithium sulfide composition includes the following steps:

[0138] S1. Under the protection of nitrogen atmosphere, weigh 96g of lithium hydroxide and mix it with 500g of N-methylpyrrolidone.

[0139] S2. After mixing thoroughly, raise the solution temperature to 135-155℃;

[0140] S3. Maintain the temperature at 135-155℃ and introduce hydrogen sulfide into the solution at a flow rate of 0.47L / min for 4 hours (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.259). Continue the neutralization reaction for 5.5 hours to obtain a LiHS-containing solution.

[0141] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution.

[0142] S5. Raise the temperature of LiHS to 165-175℃ and carry out the pyrolysis reaction for 4 hours to obtain Li2S dispersion.

[0143] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0144] S7. The crude Li2S obtained in S6 was hot-washed 6 times with p-xylene at 115-120℃, and then dried to obtain 75g of Li2S composition.

[0145] The obtained lithium sulfide composition was tested to have a purity of 99.97%, a lithium 4-(methylamino)butyrate content of approximately 15 ppm, and a yield of 81.5%.

[0146] The resulting lithium sulfide composition has a particle size of approximately 4 μm and a specific surface area of ​​4 m². 2 / g.

[0147] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 9.6 mS / cm.

[0148] Example 6

[0149] A method for preparing a lithium sulfide composition includes the following steps:

[0150] S1. Under the protection of nitrogen atmosphere, weigh 96g of lithium hydroxide and mix it with 300g of cyclopentanone.

[0151] S2. After mixing thoroughly, raise the solution temperature to 130-145℃;

[0152] S3. Maintain the temperature at 130-145℃, and introduce hydrogen sulfide into the solution at a flow rate of 0.47L / min for 4h (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.259). Continue the neutralization reaction for 6h to obtain a LiHS-containing solution.

[0153] S4. Filter the LiHS solution obtained in S3 to remove unreacted lithium hydroxide and obtain the LiHS solution.

[0154] S5. Raise the temperature of LiHS to 175-190℃ and carry out the pyrolysis reaction for 4 hours. LiHS will pyrolyze to obtain Li2S dispersion.

[0155] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0156] S7. The crude Li2S obtained in S6 was hot-washed 6 times with N-methyl-2-pyrrolidone at 110-120℃, and then dried to obtain 78g of Li2S composition.

[0157] The obtained lithium sulfide composition was tested to have a purity of 99.98%, a lithium valerate content of approximately 65 ppm, and a yield of 84.7%.

[0158] The obtained lithium sulfide composition has a particle size of approximately 13.6 μm and a specific surface area of ​​2.9 m². 2 / g.

[0159] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 7.8 mS / cm.

[0160] Example 7

[0161] A method for preparing a lithium sulfide composition includes the following steps:

[0162] S1. Under the protection of nitrogen atmosphere, weigh 96g of lithium hydroxide and mix it with 300g of cyclopentanone.

[0163] S2. After mixing thoroughly, raise the solution temperature to 130-145℃;

[0164] S3. Maintain the temperature at 130-145℃, and introduce hydrogen sulfide into the solution at a flow rate of 0.47L / min for 4h (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.259). Continue the neutralization reaction for 5h to obtain a LiHS-containing solution.

[0165] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution.

[0166] S5. Raise the temperature of LiHS to 175-190℃ and carry out the pyrolysis reaction for 4 hours. LiHS will pyrolyze to obtain Li2S dispersion.

[0167] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0168] S7. The crude Li2S obtained in S6 was hot-washed 6 times with N-methylpyrrolidone at 110-120℃, and then dried to obtain 78g of Li2S composition.

[0169] The obtained lithium sulfide composition was tested to have a purity of 99.96%, a lithium valerate content of approximately 12 ppm, and a yield of 84.7%.

[0170] The resulting lithium sulfide composition had a particle size of approximately 2 μm and a specific surface area of ​​4.6 m². 2 / g.

[0171] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 10.2 mS / cm.

[0172] Example 8

[0173] A method for preparing a lithium sulfide composition includes the following steps:

[0174] S1. Under the protection of nitrogen atmosphere, weigh 96g of lithium hydroxide and mix it with 300g of caprolactam.

[0175] S2. After mixing thoroughly, raise the solution temperature to 130-145℃;

[0176] S3. Maintain the temperature at 130-145℃, and introduce hydrogen sulfide into the solution at a flow rate of 0.4L / min for 4h (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.071). Continue the neutralization reaction for 3h to obtain a LiHS-containing solution.

[0177] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution; S5. Raise the temperature of LiHS to 175-190℃ and carry out the pyrolysis reaction for 4 hours to obtain a Li2S dispersion.

[0178] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0179] S7. The crude Li2S obtained in S6 was hot-washed 6 times with p-xylene at 110-120℃, and then dried to obtain 78g of Li2S composition.

[0180] The obtained lithium sulfide composition was tested to have a purity of 99.96%, a lithium hexanoate content of approximately 20 ppm, and a yield of 84.7%.

[0181] The resulting lithium sulfide composition has a particle size of approximately 11 μm and a specific surface area of ​​31 m². 2 / g.

[0182] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 8.5 mS / cm.

[0183] Example 9

[0184] A method for preparing a lithium sulfide composition includes the following steps:

[0185] S1. Under the protection of nitrogen atmosphere, weigh 168g of lithium hydroxide monohydrate and mix it with 400g of N-methylpyrrolidone.

[0186] S2. After mixing thoroughly, raise the solution temperature to 130-145℃;

[0187] S3. Maintain the temperature at 130-145℃, and introduce hydrogen sulfide into the solution at a flow rate of 0.4L / min for 4h (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.071). Continue the neutralization reaction for 3h to obtain a LiHS-containing solution.

[0188] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution; S5. Raise the temperature of LiHS to 175-190℃ and decompose for 4 hours to obtain a Li2S dispersion.

[0189] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0190] S7. The crude Li2S obtained in S6 was hot-washed 6 times with p-xylene at 110-120℃, and then dried to obtain 75g of Li2S composition.

[0191] The obtained lithium sulfide composition was tested to have a purity of 99.97%, a lithium 4-(methylamino)butyrate content of approximately 10 ppm, and a yield of 81.4%.

[0192] The resulting lithium sulfide composition had a particle size of approximately 23 μm and a specific surface area of ​​2.6 m². 2 / g.

[0193] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 8.1 mS / cm.

[0194] Example 10

[0195] A method for preparing a lithium sulfide composition includes the following steps:

[0196] S1. Under the protection of nitrogen atmosphere, weigh 168g of lithium hydroxide monohydrate and mix it with 400g of N-methylpyrrolidone.

[0197] S2. After mixing thoroughly, raise the solution temperature to 135-155℃;

[0198] S3. Maintain the temperature at 135-155℃ and introduce hydrogen sulfide into the solution at a flow rate of 0.47L / min for 4 hours (the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1.259). Continue the neutralization reaction for 2.5 hours to obtain a LiHS-containing solution.

[0199] S4. Filter the LiHS-containing solution obtained in S3 to remove unreacted lithium hydroxide and obtain a LiHS solution.

[0200] S5. Raise the temperature of LiHS to 165-175℃ and carry out the pyrolysis reaction for 4 hours to obtain Li2S dispersion.

[0201] S6. Filter the Li2S dispersion obtained in S5 to obtain crude Li2S.

[0202] S7. The crude Li2S obtained in S6 was hot-washed 6 times with p-xylene at 115-120℃, and then dried to obtain 75g of Li2S composition.

[0203] The obtained lithium sulfide composition was tested to have a purity of 99.98%, a lithium 4-(methylamino)butyrate content of approximately 30 ppm, a yield of 81.5%, a particle size of approximately 26 μm, and a specific surface area of ​​2.5 m². 2 / g.

[0204] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this embodiment has an ionic conductivity of approximately 8 mS / cm.

[0205] Comparative Example 1

[0206] The lithium sulfide composition was prepared according to the method of Example 1, except that in step S2, after the lithium hydroxide and caprolactam were mixed evenly, the temperature was raised to 180°C and then kept constant at 180°C to carry out an acid-base neutralization reaction. Other operations and conditions remained unchanged.

[0207] A lithium sulfide composition with a purity of 95% and a lithium 6-aminohexanoate content of approximately 200 ppm was prepared, with a yield of 70%.

[0208] The resulting lithium sulfide composition had a particle size of approximately 82 μm and a specific surface area of ​​1.1 m². 2 / g.

[0209] The LPSC solid electrolyte prepared using lithium sulfide prepared in this comparative example has an ionic conductivity of approximately 3 mS / cm.

[0210] Comparative Example 2

[0211] The lithium sulfide composition was prepared according to the method of Example 1, except that in step S2, after the lithium hydroxide and caprolactam were mixed evenly, the temperature was raised to 100°C and then kept constant at 100°C to carry out an acid-base neutralization reaction, while other operations and conditions remained unchanged.

[0212] A lithium sulfide composition was prepared with a purity of 96.5% and a lithium 6-aminohexanoate content of approximately 2.2 ppm, yielding a yield of 66%.

[0213] The resulting lithium sulfide composition had a particle size of approximately 50 μm and a specific surface area of ​​0.6 m². 2 / g.

[0214] The LPSC solid electrolyte prepared using the lithium sulfide prepared in this comparative example has an ionic conductivity of approximately 2.2 mS / cm.

[0215] Comparative Example 3

[0216] The lithium sulfide product without the structure of formula (1) has a purity of 99.97%, a particle size of approximately 2 μm, and a specific surface area of ​​4.6 m². 2 / g, add 6-aminohexanoic acid at a concentration of 15ppm.

[0217] The LPSC solid electrolyte prepared using lithium sulfide prepared in this comparative example has an ionic conductivity of approximately 1.2 mS / cm.

[0218] Comparative Example 4

[0219] The lithium sulfide product without the structure of formula (1) has a purity of 99.97%, a particle size of approximately 2 μm, and a specific surface area of ​​4.6 m². 2 / g, add n-hexylamine at a concentration of 15ppm.

[0220] The LPSC solid electrolyte prepared using lithium sulfide prepared in this comparative example has an ionic conductivity of approximately 1.1 mS / cm.

Claims

1. A lithium sulfide composition, characterized in that, Its components include at least lithium sulfide and the compound shown in formula (1); In the formula, R is selected from H, C1-C6 alkyl groups, and C1-C6 alkylamino groups; n takes values ​​from 1 to 6; Based on the total mass of the lithium sulfide composition, the content of the compound shown in formula (1) is 10-100 ppm, preferably 10-50 ppm.

2. The lithium sulfide composition according to claim 1, characterized in that, The C1-C6 alkyl group has the structure shown in (2) below: In the formula, a takes values ​​from 0 to 6, and b takes values ​​from 0 to 6; Preferably, the C1-C6 alkyl group is selected from methyl (-CH3), ethyl, propyl, isopropyl, butyl, or isobutyl; and / or, The C1-C6 alkylamino group has the structure shown in (3) below: In the formula, a takes values ​​from 0 to 6, and b takes values ​​from 0 to 6; Preferably, the alkylamino group of C1-C6 is selected from methylamino (-NH2), isobutylamino, methylamino, ethylamino, propylamino, isopropylamino or butylamino.

3. The lithium sulfide composition according to claim 1 or 2, characterized in that, The compound shown in formula (1) is selected from at least one of lithium 6-aminohexanoate, lithium 4-(isobutylamino)butanoate, lithium 4-(ethylamino)butanoate, lithium hexanoate, lithium 4-(methylamino)butanoate, and lithium valerate.

4. The lithium sulfide composition according to any one of claims 1-3, characterized in that, The lithium sulfide composition has a lithium sulfide particle size range of 0.1-100 μm, preferably 1-5 μm; and / or, The lithium sulfide composition has a specific surface area ≥1m². 2 / g, preferably 1-5m 2 / g.

5. A method for preparing the lithium sulfide composition according to any one of claims 1-4, characterized in that the step... include: (1) Salt formation process: Under the protection of an inert atmosphere, lithium hydroxide and organic solvent are mixed evenly, heated to above 130°C, and hydrogen sulfide gas is introduced into it to carry out an acid-base neutralization reaction to obtain a LiHS-containing solution. (2) Pyrolysis process: The LiHS-containing solution is filtered, and then heated to above 160°C to carry out the pyrolysis reaction to obtain Li2S dispersion; (3) Purification process: The Li2S dispersion is filtered, washed, and dried to obtain the lithium sulfide composition.

6. The preparation method according to claim 5, characterized in that, The inert atmosphere described in step (1) is a nitrogen atmosphere or an argon atmosphere; and / or, The lithium hydroxide mentioned in step (1) is lithium hydroxide hydrate or anhydrous lithium hydroxide; and / or, The organic solvent in step (1) is selected from organic aprotic solvents containing a carbonyl oxygen structure, preferably at least one of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-dipropylacetamide, N,N-dimethylbenzamide, and lactam compounds; Optionally, the lactam compound includes, for example, N-alkylcaprolactams (including caprolactam, N-methylcaprolactam, N-ethylcaprolactam, N-isopropylcaprolactam, N-isobutylcaprolactam, N-n-propylcaprolactam, N-n-butylcaprolactam, and N-cyclohexylcaprolactam), as well as N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-isobutyl-2-pyrrolidone, and N-n-propyl-2-pyrrolidone. At least one of the following: ketone, N-n-butyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-methyl-3-methyl-2-pyrrolidone, N-ethyl-3-methyl-2-pyrrolidone, N-methyl-3,4,5-trimethyl-2-pyrrolidone, N-methyl-2-piperidinone, N-ethyl-2-piperidinone, N-isopropyl-2-piperidinone, N-methyl-6-methyl-2-piperidinone, N-methyl-3-ethyl-2-piperidinone, acetone, pentanone, cyclohexanone, cyclopentanone, etc.

7. The preparation method according to claim 5 or 6, characterized in that, In step (1), the mass ratio of lithium hydroxide to organic solvent is 1:2-6; and / or, In step (1), the molar ratio of lithium hydroxide to hydrogen sulfide is 1:1-1.5; optionally, the hydrogen sulfide feed flow rate is 0.2-0.6 L / min; optionally, the hydrogen sulfide feeding time is 2-5 h; and / or, The acid-base neutralization reaction in step (1) is carried out at a temperature of 130-160℃ for 1-6 hours.

8. The preparation method according to any one of claims 5-7, characterized in that, The pyrolysis reaction in step (2) is carried out at a temperature of 160-190℃ for 3-5 hours.

9. The preparation method according to any one of claims 5-8, characterized in that, The washing in step (3) is carried out by hot washing with organic solvent, and the hot washing temperature is ≥100℃; optionally, the number of hot washing cycles is ≥4, preferably ≥5. Preferably, the hot washing time for each cycle is 1-1.5 hours.

10. The use of the lithium sulfide composition according to any one of claims 1-4 or the lithium sulfide composition prepared by the method according to any one of claims 5-7 in the field of lithium-ion batteries.

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