阅读说明：本技术 一种硫化锂材料的制备方法 (Preparation method of lithium sulfide material ) 是由 董甜甜 董国超 崔浩然 于 2021-07-28 设计创作，主要内容包括：本发明属于电池技术领域,具体涉及到一种制备高纯度硫化锂材料的新型工艺方法,该方法所得硫化锂材料可用于制备锂硫电池正极材料和硫化物电解质材料。以氢氧化锂、硫脲和硫粉作为原料,原料混合后通过球磨机混合,而后在惰性气体保护下烧结制备硫化锂。本发明制备工艺简单,重现性好,易于操作,使用的原材料无毒害,便于大规模工业化生产。另外,制备的硫化锂具有较高的纯度,可用于制备正极、硫化物电解质材料。(The invention belongs to the technical field of batteries, and particularly relates to a novel process method for preparing a high-purity lithium sulfide material. Lithium hydroxide, thiourea and sulfur powder are used as raw materials, the raw materials are mixed through a ball mill, and then the mixture is sintered under the protection of inert gas to prepare the lithium sulfide. The preparation method has the advantages of simple preparation process, good reproducibility, easy operation, no toxicity of the used raw materials and convenience for large-scale industrial production. In addition, the prepared lithium sulfide has high purity and can be used for preparing anode and sulfide electrolyte materials.)

1. A preparation method of a lithium sulfide material is characterized by comprising the following steps: lithium hydroxide, thiourea and sulfur powder are used as raw materials, the raw materials are mixed through a ball mill, and then the mixture is sintered under the protection of inert gas to prepare the lithium sulfide.

2. The method for preparing lithium sulfide according to claim 1, wherein the raw materials of lithium hydroxide, thiourea and sulfur powder are respectively dried in vacuum and then transferred into a ball mill for mixing; wherein the vacuum heating drying condition is 60-100 ℃, and the drying time is 5-12 h.

3. The method for preparing lithium sulfide according to claim 1 or 2, wherein the lithium hydroxide, thiourea and sulfur powder are mixed in a mass ratio of 1: 0.5-3.

4. The preparation method of lithium sulfide as claimed in claim 1, wherein the raw materials are mixed in proportion after being dried and then transferred into a ball mill, and are ball milled and mixed at room temperature for 1-6 h, and the rotation speed of the ball mill is 300-600 r/min.

5. The method for preparing lithium sulfide as claimed in claim 1, wherein the inert gas is introduced at a flow rate of 5 mL/min to 100 mL/min during the sintering under the protection of inert gas, and the sintering time is 1 to 5 hours at a sintering temperature of 300-.

6. The method of preparing lithium sulfide as claimed in claim 1, wherein the inert gas is one or more of nitrogen, argon and helium.

7. The method for preparing lithium sulfide according to claim 1, wherein the thiourea (CH) is₄N₂S) is obtained by reacting ammonium thiocyanate derivatives or inorganic sulfides with urea or amine compounds; wherein, the inorganic sulfide is one or more of sodium sulfide, potassium sulfide and barium sulfide; the amine compound is one or more of organic amines.

8. Use of a lithium sulfide material obtained by the method of claim 1, wherein: the lithium sulfide material is used as a positive electrode material of a lithium-sulfur battery or a raw material for synthesizing sulfide solid electrolyte.

Technical Field

The invention belongs to the technical field of batteries, and particularly relates to a novel process method for preparing a high-purity lithium sulfide material.

Background

With the continuous development of electric vehicles and portable electronic devices, the disadvantages of limited energy density and poor safety of the conventional lithium batteries are gradually revealed. The traditional lithium battery adopts volatile and flammable organic electrolyte, so that the traditional lithium battery inevitably faces safety risks such as battery combustion, explosion and the like. Under such a background, the replacement of an organic electrolyte with a solid electrolyte is expected to greatly improve the energy density and safety of a lithium battery. The solid electrolyte is an important component of a solid-state battery, and its physical chemistryThe properties largely determine the electrochemical performance of a solid-state lithium battery. The sulfide solid electrolyte exhibits high ion conductivity (more than 10) at room temperature compared to the polymer solid electrolyte^-3S/cm), which is comparable to the ionic conductivity of the liquid electrolyte; in addition, the sulfide solid electrolyte can form better interface contact with the electrode than the garnet-type, lisicon-type inorganic solid electrolyte, thereby reducing interface impedance. Therefore, sulfide becomes one of the most potentially useful solid electrolytes.

The high-purity lithium sulfide is one of necessary raw materials for preparing the high-performance sulfide solid electrolyte, is also a commonly used anode material in a lithium-sulfur battery, and has wide market prospect. Because lithium sulfide is extremely sensitive to water, great cost is generally required to be invested in the production, purification, storage and transportation processes of lithium sulfide to reduce the water content in a generated environment, the preparation and storage processes are limited, and finally the production cost of lithium sulfide is extremely high and the market price is high. Therefore, the search for a simple and inexpensive method for preparing high-purity lithium sulfide is one of the problems to be solved. The earliest method for producing lithium sulfide is to directly use the combination of the two elements to prepare lithium sulfide, for example, the liquid ammonia solution of lithium reacts with elemental sulfur to obtain lithium sulfide; other preparation processes were subsequently developed, such as: reacting lithium with hydrogen sulfide in tetrahydrofuran, and decomposing an ethanol adduct of lithium hydrosulfide by using lithium ethoxide; lithium carbonate reacts with hydrogen sulfide, etc. However, the existing preparation methods of the high-purity lithium sulfide have the defects of high reaction temperature, long period, flammable and explosive organic solvents, irritation, toxicity and the like.

Lithium sulfide can be obtained by a sealing reaction of sulfur powder and lithium salt (lithium carbonate, lithium nitrate or lithium oxalate) at a high temperature. The invention patent CN 102177090A discloses a method for preparing lithium sulfide by directly mixing one or more lithium salt compounds with sulfur and heating the mixture in a sealed container to 650 ℃ for reaction, and adding lithium fluoride or borax mineralizer into the reaction system can reduce the reaction temperature to a certain extent, but the purity of the lithium sulfide prepared by the method is lower. To increase the purity of the synthesized lithium sulfide, Zhao et al used lithium triethylborohydride as a lithium source toThe elemental sulfur is used as a sulfur source to react in tetrahydrofuran solution at 90 ℃ for 10min to prepare the lithium sulfide. The method not only can improve the purity of the lithium sulfide, but also can make the particle size of the lithium sulfide more uniform [ ZHao Y, Smith W, Wolden C A. Scalable synthesis of Li₂S nanocrystals for solid-state electrolyte applications. Journal of The Electrochemical Society, 2020, 167(7): 070520；Nan C, Lin Z, Liao H, et al. Durable carbon-coated Li₂S core-shell spheres for high performance lithium/sulfur cells. Journal of the American Chemical Society, 2014, 136(12): 4659-4663]However, the lithium triethylborohydride has high storage requirement due to the strong reducibility, and has potential safety hazards such as ignition and explosion. In order to obtain lithium sulfide materials with smaller sizes, lithium sulfide nano materials with small sizes can be synthesized by a graphite confinement strategy through a reaction of sulfur and lithium triethylborohydride [ Zhang K, Wang L, Hu Z, et al₂S nanoparticles anchored in graphene nanosheets for high-energy lithium-ion batteries. Scientific reports, 2014, 4(1): 1-7]. Although the application range of the ultra-small-size lithium sulfide nano material is expanded, according to some reports of synthesizing the small-size lithium sulfide material at present, the reaction conditions are harsh, the cost is relatively high, and the large-scale commercial application is not facilitated. In order to increase the production scale of lithium sulfide, a scheme of first preparing a composite material of lithium sulfide and carbon and then further purifying is widely adopted. According to the reaction temperature conditions, the synthesis of lithium metal and sulfur or carbon disulfide in organic liquid (Tan G, Xu R, Xing Z, et al, Burning lithium in CS) at low temperature can be divided into₂ for high-performing compact Li₂S-graphene nanocapsules for Li-S batteries, Nature Energy, 2017, 2(7): 1-10.) and a scheme of reaction preparation of lithium salt and carbon at high temperature in an atmosphere of hydrogen sulfide (lithium sulfide and hard carbon react at high temperature in an atmosphere of hydrogen sulfide to generate lithium sulfide, Chinese patent publication No. CN 108400327A; shi J, Zhang J, Zhao Y, et al Synthesis of Li₂S-Carbon Cathode Materials via Carbothermic Reduction of Li₂SO₄Frontiers in Energy Research, 2019, 7: 53). However, the above method is complicated in operation, time-consuming and energy-consumingHigh raw material cost and limited purity; there is therefore a need to obtain a process for preparing lithium sulphide that is efficient, inexpensive and of high purity.

Disclosure of Invention

The invention aims to provide a method for preparing high-purity lithium sulfide at low cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a lithium sulfide material comprises the steps of taking lithium hydroxide, thiourea and sulfur powder as raw materials, mixing the raw materials through a ball mill, and sintering under the protection of inert gas to prepare lithium sulfide.

Further, the raw materials of lithium hydroxide, thiourea and sulfur powder are respectively dried in vacuum and then transferred into a ball mill for mixing; wherein the vacuum heating drying condition is 60-100 ℃, and the drying time is 5-12 h.

The lithium hydroxide, the thiourea and the sulfur powder are mixed according to the mass ratio of 1: 0.5-3, and the preferable mixing ratio is 1: 0.5-2.

The raw materials are mixed according to a certain proportion after being dried and then are transferred into a ball mill, and are subjected to ball milling and mixing at room temperature, the ball milling time is 1-6 h, and the rotating speed of the ball mill is 300-600 r/min; the particle size of the reaction mixture after ball milling is below 50 microns.

The inert gas is introduced at the flow rate of 5 mL/min-100 mL/min during the sintering under the protection of the inert gas, the sintering temperature is 800 ℃ and the sintering time is 1-5 h.

The inert gas is one or more of nitrogen, argon and helium.

The thiourea (CH)₄N₂S) is obtained by reacting ammonium thiocyanate derivatives or inorganic sulfides with urea or amine compounds; wherein, the inorganic sulfide is one or more of sodium sulfide, potassium sulfide and barium sulfide; the amine compound is one or more of organic amines.

The application of the lithium sulfide material obtained by the method, wherein the lithium sulfide material is used as a positive electrode material of a lithium-sulfur battery or a raw material for synthesizing sulfide solid electrolyte.

The heating area range of the quartz heating tube can be adjusted according to the amount of reactants, and if kilogram-level preparation is needed, a quartz sintering tube with an effective heating area of 300mm can be selected.

Compared with the prior art, the invention has the following advantages:

1. the novel preparation method of the lithium sulfide utilizes the thiourea, the sulfur powder and the lithium salt which are easily obtained and have lower price as raw materials, thereby having lower production cost, and simultaneously having the characteristics of low energy consumption, less impurities and the like in the reaction process.

2. The novel preparation method disclosed by the invention is simple in process, short in preparation period, free of purification, simple in preparation equipment, easy to operate and convenient for large-scale industrial production.

3. According to the novel preparation method of the lithium sulfide, the purity of the product lithium sulfide is high, the content of the lithium sulfide is more than 98%, and the particle size is uniform.

Drawings

Fig. 1 is an SEM image of a lithium sulfide material prepared according to example 1 of the present invention.

Fig. 2 is an SEM image of a lithium sulfide material prepared according to example 2 of the present invention.

Fig. 3 is an XRD pattern of the lithium sulfide material prepared according to example 1 of the present invention.

Fig. 4 is an XRD pattern of the lithium sulfide material prepared according to example 2 of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples, which are illustrative only and not intended to be limiting, and the scope of the present invention is not limited thereby.

Example 1

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at 60 ℃ for 12h for later use. Drying raw materials, mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 1: 2: 2, then grinding for 3 hours in a planetary ball mill with a model of BYXQM-0.4L at normal temperature, setting the rotation speed of the ball mill to be 300 r/min, and reducing the particle size of reactant particles to be less than 50 micrometers (generally about 40 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the tube completely by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the tube, and then adjusting the flow rate of inert gas to 10 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the temperature for 5 h. After cooling to room temperature, a lithium sulfide material with a bulk structure purity of 98% was obtained (see fig. 1 and 3).

As can be seen from FIGS. 1 and 3, the prepared lithium sulfide material has uniform particle size and satisfactory purity despite agglomeration.

Example 2

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at the temperature of 80 ℃ for 12 hours for later use. Mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 1: 2: 1, then grinding for 3 hours at normal temperature in a planetary ball mill with a model of BYXQM-0.4L, setting the rotation speed of the ball mill to be 400 r/min, and reducing the particle size of reactant particles to be less than 50 micrometers (generally about 30 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the adaptive few-connection pipe by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the pipe, and then adjusting the flow rate of inert gas to 10 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the temperature for 5 h. After cooling to room temperature, lithium sulfide material with uniform particle size and purity of 99% is obtained (see fig. 2 and 4);

as can be seen from FIG. 2, the prepared lithium sulfide material has uniform particle size and good dispersibility. In addition, as can be seen from fig. 4, the obtained XRD diffraction peak of lithium sulfide matches with the standard card, and there is no obvious impurity peak, indicating that the synthesized material has good crystallinity and high purity.

Example 3

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at 60 ℃ for 10 hours for later use. Mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 1: 1: 2, then grinding for 3 hours at normal temperature in a planetary ball mill with a model of BYXQM-0.4L, setting the rotation speed of the ball mill to be 300 r/min, and reducing the particle size of reactant particles to be less than 50 micrometers (generally about 40 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the adaptive few-connection pipe by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the pipe, and then adjusting the flow rate of inert gas to 10 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the temperature for 5 h. Cooling to room temperature to obtain a lithium sulfide material with the purity of 98%;

example 4

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at 90 ℃ for 10 hours for later use. Mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 1: 1: 1, then grinding for 5 hours at normal temperature in a planetary ball mill with a model of BYXQM-0.4L, setting the rotation speed of the ball mill to be 300 r/min, and reducing the particle size of reactant particles to below 50 micrometers (generally about 35 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the adaptive few-connection pipe by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the pipe, and then adjusting the flow rate of inert gas to 10 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the temperature for 5 h. Cooling to room temperature to obtain a lithium sulfide material with the purity of 98%;

example 5

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at 70 ℃ for 10 hours for later use. Mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 2: 1: 1, then grinding for 5 hours in a planetary ball mill with a model of BYXQM-0.4L at normal temperature, setting the rotation speed of the ball mill to be 400 r/min, and reducing the particle size of reactant particles to be less than 50 micrometers (generally about 30 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the adaptive few-connection pipe by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the pipe, and then adjusting the flow rate of inert gas to 20 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the temperature for 5 h. Cooling to room temperature to obtain a lithium sulfide material with the purity of 98%;

example 6

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at the temperature of 80 ℃ for 10 hours for later use. Mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 2: 1: 2, then grinding for 5 hours in a planetary ball mill with a model of BYXQM-0.4L at normal temperature, setting the rotation speed of the ball mill to be 300 r/min, and reducing the particle size of reactant particles to be less than 50 micrometers (generally about 40 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the adaptive few-connection pipe by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the pipe, and then adjusting the flow rate of inert gas to 10 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the temperature for 5 h. Cooling to room temperature to obtain a lithium sulfide material with the purity of 98%;

example 7

The reaction raw materials, namely: and respectively drying the lithium hydroxide, the thiourea and the sulfur powder in a forced air drying oven at the temperature of 80 ℃ for 10 hours for later use. Mixing lithium hydroxide, thiourea and sulfur powder according to a mass ratio of 2: 1: 3, then grinding for 5 hours in a planetary ball mill with a model of BYXQM-0.4L at normal temperature, setting the rotation speed of the ball mill to be 300 r/min, and reducing the particle size of reactant particles to be less than 50 micrometers (generally about 40 micrometers) after the ball milling is finished; the reactants were then sealed in a reaction vessel and transferred into the quartz sintering tube of a tube furnace. Pumping the gas in the adaptive few-connection pipe by using a vacuum pump, then filling high-purity nitrogen, repeating for three times, completely replacing the air in the pipe, and then adjusting the flow rate of inert gas to 10 mL/min; starting a tubular furnace heating device, raising the temperature to 700 ℃ at the temperature rise speed of 5 ℃/min, and preserving the heat for 3 h. Cooling to room temperature to obtain a material with the purity of lithium sulfide of 98%;

the purity of the lithium sulfide material obtained by the embodiments can reach more than 98 percent, so that the lithium sulfide material can be directly used as a sulfide electrolyte raw material, and the material obtained by the method is uniform in particle; the material obtained by the method is further applied to a solid lithium ion battery as a solid electrolyte, and the high purity and uniform particle size of the material enable the material to be used in the synthesis of electrolytes. Meanwhile, the lithium ion battery can be used as a positive electrode material of a lithium battery and can be applied to a lithium-sulfur battery system.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

All documents referred to herein are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes and modifications of the present invention can be made by those skilled in the art after reading the above teachings of the present invention, and these equivalents also fall within the scope of the present invention as defined by the appended claims.