A preparation method of lithium sulfide and lithium sulfide

Abstract

The present invention provides a method for preparing lithium sulfide and lithium sulfide, so as to prepare a high-purity lithium sulfide without increasing the purification cost. The method includes: keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture; wherein, the first condition includes a heat preservation temperature of 130-180 °C; reacting the mixture with hydrogen sulfide under a second condition to obtain lithium sulfide; wherein, the second condition includes a temperature condition of 500-760 °C.

Description

Technical Field

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

[0002] Sulfide solid electrolytes have high value for preparing high-performance secondary batteries due to their good lithium ion conductivity. Among them, lithium sulfide is particularly notable. Specifically, it can be used as a raw material for solid electrolytes or as a cathode material for lithium-sulfur batteries.

[0003] Existing lithium sulfide generally has problems of high price and inconsistent purity. One of the existing methods for preparing lithium sulfide is the solid-phase method based on carbothermal reduction of lithium sulfate. However, this method has problems such as low production capacity and inability to guarantee purity. That is to say, there is still a lack of a method for preparing high-purity lithium sulfide. Summary of the Invention

[0004] The present invention provides a method for preparing lithium sulfide and lithium sulfide to prepare a high-purity lithium sulfide without increasing the purification cost.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing lithium sulfide, including:

[0006] Keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture; wherein, the first condition includes a heat preservation temperature of 130-180°C;

[0007] Reacting the mixture with hydrogen sulfide under a second condition to obtain lithium sulfide; wherein, the second condition includes a temperature condition of 500-760°C.

[0008] In a possible implementation manner, the heat preservation temperature in the first condition is 140-160°C; the temperature condition in the second condition is 570-590°C.

[0009] In a possible implementation manner, the first condition includes: continuously introducing an inert gas into a first reaction device where the thiourea and lithium hydroxide are located until the mixture is obtained.

[0010] In a possible implementation manner, the step of keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture includes:

[0011] Adding thiourea to a saturated solution of lithium hydroxide, and mixing the lithium hydroxide and thiourea in the saturated solution under stirring to obtain the mixture.

[0012] In a possible implementation manner, the lithium hydroxide is obtained by reacting lithium carbonate or lithium sulfate dissolved in water with barium ions.

[0013] A possible implementation manner, before keeping thiourea and lithium hydroxide warm under the first condition to obtain a mixture, further includes:

[0014] React lithium carbonate, barium hydroxide and water under a temperature condition not higher than 10°C to generate the lithium hydroxide.

[0015] A possible implementation manner, the lithium carbonate is in excess, and the excess lithium carbonate does not exceed 105% of the theoretical molar amount.

[0016] A possible implementation manner, the reaction of lithium carbonate, barium hydroxide and water under a temperature condition not higher than 10°C to generate the lithium hydroxide includes:

[0017] Introduce a lithium carbonate solution with a temperature not higher than 5°C into a second reaction device at a speed less than 0.5 L / min within a first time range, and react the introduced lithium carbonate solution with the barium hydroxide solution in the second reaction device; wherein, the first time range is less than 1 / 2 of the total duration of introducing the lithium carbonate solution into the second reaction device, and the concentration of the lithium carbonate solution is less than or equal to 0.005 g / L;

[0018] Increase the introduction speed of the lithium carbonate solution to obtain the lithium hydroxide; wherein, the introduction speed is less than or equal to 1 L / min.

[0019] A possible implementation manner, before keeping thiourea and lithium hydroxide warm under the first condition to obtain a mixture, further includes:

[0020] React lithium sulfate, barium hydroxide and water under a temperature condition not higher than 20°C to generate the lithium hydroxide.

[0021] A possible implementation manner, the lithium sulfate is in excess, and the excess lithium sulfate does not exceed 103% of the theoretical molar amount.

[0022] A possible implementation manner, the hydrogen sulfide and barium hydroxide are obtained by reacting barium sulfide with water.

[0023] In a second aspect, an embodiment of the present application provides a lithium sulfide, and the lithium sulfide is prepared by the method according to the first aspect and any one of the possible implementation manners.

[0024] One or more technical solutions provided by the embodiments of the present application have at least the following technical effects:

[0025] First, the raw materials for preparing lithium sulfide are readily available, low in cost, and the preparation method is easy to implement, so mass production can be achieved at low cost. Moreover, NH3, the non-target product generated during the preparation process, is in a gaseous state and has the advantage of being easy to remove, thus ensuring that the purity of lithium sulfide is not less than 97%. On this basis, the problems of low efficiency, high energy consumption, and increased cost caused by further purification of lithium sulfide are avoided.

[0026] Second, the raw materials for preparing lithium sulfide also have the characteristics of being easy to prepare in batches at low cost, and the impurities (mainly barium carbonate or barium sulfate) are easy to remove during the preparation process of each raw material. Therefore, the cost is further reduced in the process of preparing raw materials for lithium sulfide.

[0027] Third, the reactants hydrogen sulfide and barium hydroxide solution (intermediate reactant) involved in the preparation of lithium sulfide can be obtained in one step. Therefore, while achieving efficient preparation, the raw material waste rate is effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic flow chart of a method for preparing lithium sulfide provided by an embodiment of the present application;

[0029] Figure 2 is a schematic diagram of the feeding sequence of Example 1 and Example 2 provided by an embodiment of the present application;

[0030] Figure 3 is a SEM diagram of lithium sulfide in Example 1 provided by an embodiment of the present application;

[0031] Figure 4 is an XRD diagram of lithium sulfide in Example 1 provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following provides a detailed description of a method for preparing lithium sulfide and lithium sulfide provided by an embodiment of the present application. It should be noted that the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] An embodiment of the present application provides a method for preparing lithium sulfide, and the method includes the following implementation steps. Please refer to Figure 1 :

[0034] Step 101: Keep thiourea and lithium hydroxide warm under the first condition to obtain a mixture.

[0035] Among them, the first condition includes a heat preservation temperature of 130 - 180 °C.

[0036] In some embodiments, the heat preservation temperature in the first condition is 140 - 160 °C; the heat preservation time is 1 - 6 h.

[0037] Preferably, the temperature condition in the first condition is 150 °C; the heat preservation time is 2 h.

[0038] This heat preservation stage is a pretreatment stage. In some embodiments, a small amount of gaseous by-products are generated in this stage. Therefore, an inert gas is continuously introduced into the first reaction device where thiourea and lithium hydroxide are located during the heat preservation process, so that thiourea and lithium hydroxide in the heat preservation stage are in an inert atmosphere, and the by-products in the heat preservation stage can leave the reaction system with the inert gas; until the second mixture is obtained, the introduction of the inert gas is stopped.

[0039] The above-mentioned inert gas can be, for example, argon and / or nitrogen.

[0040] To mix evenly, thiourea can be added to the saturated lithium hydroxide solution and then heat-preserved. In this way, this heat preservation stage can also promote the uniform mixing of thiourea and lithium hydroxide in the saturated lithium hydroxide solution under the stirring action, and the water in the saturated solution evaporates into water vapor under the first condition and leaves the reaction system with the inert gas.

[0041] In the embodiments of the present application, lithium hydroxide can be obtained by reacting the barium ions in barium hydroxide with a solution containing soluble lithium salt Li₂TM. "TM" in LiTM represents the salt anion of the soluble lithium salt. Then the corresponding chemical reaction equation is:

[0042] Ba 2+ +OH - +Li + +TM → LiOH + BaTM↓.

[0043] That is to say, in the embodiments of the present application, through the combination reaction of Ba 2+ with TM to form a precipitate that is almost insoluble in water, while preparing lithium hydroxide, the influence of impurities (the remaining products other than lithium hydroxide obtained when preparing lithium hydroxide) on the target product (i.e., LiOH) of this reaction is significantly avoided.

[0044] This precipitate can be removed by filtration. Further, after filtering the precipitate, the water in the lithium hydroxide solution can be evaporated to make it a saturated lithium hydroxide solution, so that after thiourea enters the saturated lithium hydroxide solution, it can contact lithium hydroxide fully and efficiently under the stirring action.

[0045] During the process of evaporating the lithium hydroxide solution to obtain a saturated lithium hydroxide solution, the evaporated water vapor can be collected to realize the recycling of water.

[0046] In some embodiments, TM is That is, the soluble lithium salt is lithium carbonate. Since the solubility of lithium carbonate in water decreases with increasing temperature, lithium carbonate, barium hydroxide and water can be reacted at a temperature not higher than 10 °C to produce lithium hydroxide. To promote the efficient and complete reaction, the lithium carbonate can be in excess, and the excess lithium carbonate does not exceed 105% of the theoretical molar amount.

[0047] The corresponding chemical equation is: BaOH + Li2CO3 + H2O → BaCO3↓ + 2LiOH.

[0048] Specifically, under the conditions of satisfying the aforementioned mass ratio and temperature, solid barium hydroxide can be added to the lithium carbonate solution.

[0049] Alternatively, under the conditions of satisfying the aforementioned mass ratio and temperature, solid lithium carbonate can be added to the barium hydroxide solution.

[0050] It is also possible to first mix the solid barium hydroxide and lithium carbonate under the conditions of satisfying the aforementioned mass ratio and temperature, and then introduce the solvent: water.

[0051] The temperature of the reaction of the above lithium carbonate and barium hydroxide in water is preferably 0 - 5 °C, such as 2 °C.

[0052] For example, the lithium carbonate solution with a temperature not higher than 5 °C can be introduced into the reaction equipment (the second reaction equipment) for preparing lithium hydroxide at a speed of less than 0.5 L / min within the first time range, so as to avoid the problem that the amount of solvent (water) in the second reaction equipment is small at the beginning of the reaction and the precipitation reaction rate of lithium carbonate decreases. The first time range is less than 1 / 2 of the total duration of introducing the lithium carbonate solution; for example, it can be 1 / 3. For example, it is 10 min.

[0053] Then, increase the introduction speed of the lithium carbonate solution until the reaction ends to obtain lithium hydroxide. The introduction speed is less than or equal to 1 L / min.

[0054] Among them, the concentration of the lithium carbonate solution is less than or equal to 0.005 g / L; the mass percentage of the barium hydroxide solution does not exceed 5%, that is, the amount of barium hydroxide contained in every 100 g of the barium hydroxide solution does not exceed 5 g.

[0055] In some embodiments, TM is That is, the soluble lithium salt is lithium sulfate. Although the solubility of lithium sulfate in water is greater than that of lithium carbonate in water, the solubility of lithium sulfate in water still decreases with increasing temperature. Therefore, lithium sulfate, barium hydroxide and water can be reacted at a temperature not higher than 20 °C to produce the lithium hydroxide.

[0056] Similarly, the above lithium sulfate can also be in excess to promote the full progress of the chemical reaction. In some embodiments, the excess lithium sulfate does not exceed 103% of the theoretical molar amount.

[0057] Step 102: React the mixture with hydrogen sulfide under a second condition to obtain lithium sulfide.

[0058] Among them, the second condition includes a temperature condition of 500 - 760 °C.

[0059] The temperature condition in this second condition can be 570 - 590 °C; preferably 580 °C.

[0060] Specifically, the reaction equation is as follows:

[0061] 2LiOH + H2S + CH4N2S → Li2S + H2O + NH3↑.

[0062] In some embodiments, to further save energy and reduce costs, the above-mentioned barium hydroxide solution and hydrogen sulfide can be directly obtained by dissolving barium sulfide in water:

[0063] BaS + H2O → BaOH + H2S↑.

[0064] Obviously, except for the target substance and water, the reaction products involved in Steps 101 - 102 are all discharged in the form of precipitation or gas. Therefore, in addition to the easy availability of raw materials, low cost, and easy implementation of the preparation method, the lithium sulfide provided in the embodiments of the present application does not require a separate lithium sulfide purification step, which further improves the cost and efficiency of lithium sulfide preparation.

[0065] Based on the same inventive concept, the embodiments of the present application provide a lithium sulfide, which is obtained based on the aforementioned Steps 101 - 102, and has the advantage of high purity due to this.

[0066] That is to say, this lithium sulfide only contains trace impurities (mainly lithium carbonate or lithium sulfate), and the above impurity content is less than 2% (mass fraction).

[0067] Unless otherwise specified, the theoretical molar amounts described in the embodiments of the present application are all calculated according to the stoichiometric coefficients in the chemical equation.

[0068] The following combines Figure 2 , and details through specific examples:

[0069] Example 1

[0070] S1. Dissolve 0.3 mol of BaS (AR) in 1 L of deionized water, collect the gas through a gas collection device to obtain a barium hydroxide solution and hydrogen sulfide gas.

[0071] S2. Dissolve Li2CO3 in cold water (2 °C) to obtain a lithium carbonate solution with a concentration of 0.005 g / L.

[0072] S3. While stirring, add the lithium carbonate solution to the barium hydroxide solution at a flow rate of 100 ml / min within 2 min, and then starting from the 2nd min, gradually increase the feeding rate of the lithium carbonate solution until 1 L / min. Filter the solid-liquid mixture obtained from the reaction to remove barium hydroxide, and obtain a lithium hydroxide solution.

[0073] The total amount of the lithium carbonate solution is determined with a 3% excess of lithium carbonate in this process.

[0074] S4. Heat the lithium hydroxide solution to evaporate the water in the lithium hydroxide solution. There will be a small amount of precipitate after heating, and filter again to obtain a saturated solution of lithium hydroxide.

[0075] S5. Add thiourea to the saturated solution of lithium hydroxide, stir well and mix, put it into a reaction kettle, keep it warm at 150 °C for 2 h, and keep the ventilation of argon or nitrogen during this period to obtain a mixture of dry thiourea and lithium hydroxide.

[0076] S6. Pass hydrogen sulfide into the mixture of thiourea and lithium hydroxide, raise the temperature to 580 °C for reaction, and obtain the product Li2S.

[0077] The SEM image of the product Li2S is shown in Figure 3 , and the XRD pattern is shown in Figure 4 .

[0078] By dissolving the product in water at room temperature (20 °C) and using ICP test, the purity of lithium sulfide Li2S is obtained as 97%.

[0079] Example 2

[0080] S1. Dissolve 0.3 BaS (AR) in 1 L of deionized water, collect the gas through a gas collection device to obtain a barium hydroxide solution and hydrogen sulfide gas.

[0081] S2. Dissolve Li2CO3 in cold water at (1 °C) to obtain a lithium carbonate solution with a concentration of 0.004 g / L.

[0082] S3. While stirring, pass the lithium carbonate solution into the barium hydroxide solution at a flow rate of 100 ml / min within 3 min, and then starting from the 3rd min, gradually increase the feeding rate of the lithium carbonate solution until 1 L / min. Filter the solid-liquid mixture obtained from the reaction to remove barium hydroxide, and obtain a lithium hydroxide solution.

[0083] The total amount of the lithium carbonate solution is determined with a 1% excess of lithium carbonate in this process.

[0084] S4. Heat the lithium hydroxide solution to evaporate the water in the lithium hydroxide solution. There will be a small amount of precipitate after heating, and filter again to obtain a saturated solution of lithium hydroxide.

[0085] S5. Add thiourea to the saturated solution of lithium hydroxide, stir well to mix, put it into a reaction kettle, keep it warm at 150 °C for 2 h, and keep the argon or nitrogen gas flowing during this period to obtain a dry mixture of thiourea and lithium hydroxide.

[0086] S6. Pass hydrogen sulfide into the mixture of thiourea and lithium hydroxide, raise the temperature to 600 °C for reaction to obtain the product Li2S.

[0087] By dissolving the product in water at room temperature (20 °C) and using ICP test, the purity of lithium sulfide Li2S is obtained as 98%.

[0088] Comparative Example 1

[0089] S1. Dissolve 0.3 mol of BaS (AR) in 1 L of deionized water, collect the gas through a gas collection device to obtain barium hydroxide solution and hydrogen sulfide gas.

[0090] S2. Dissolve Li2CO3 in cold water at (2 °C) to obtain a lithium carbonate solution with a concentration of 0.005 g / L.

[0091] While stirring, add the lithium carbonate solution to the barium hydroxide solution at a flow rate of 100 ml / min within 2 min, and then start from the 2nd min, gradually increase the flow rate of the lithium carbonate solution until 1 L / min. Filter the solid-liquid mixture obtained from the reaction to remove barium hydroxide to obtain a lithium hydroxide solution.

[0092] In this process, the total amount of the lithium carbonate solution is determined with 3% excess of lithium carbonate.

[0093] Heat the lithium hydroxide solution to evaporate the water in the lithium hydroxide solution. There will be a small amount of precipitate after heating, and after filtering again, a saturated solution of lithium hydroxide is obtained.

[0094] S5. Add thiourea to the saturated solution of lithium hydroxide, stir and then pass hydrogen sulfide, raise the temperature to 580 °C for reaction to obtain the product Li2S.

[0095] By dissolving the product in water at room temperature (20 °C) and using ICP test, the purity of lithium sulfide Li2S is obtained as 95%.

[0096] Obviously, those skilled in the art can make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application also intends to include these changes and modifications.

Claims

1. A method for preparing lithium sulfide, characterized in that, Comprising: Keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture; wherein, the first condition includes a heat preservation temperature of 130 - 180°C; Reacting the mixture with hydrogen sulfide under a second condition to obtain lithium sulfide; wherein, the second condition includes a temperature condition of 500 - 760°C; The step of keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture includes: Adding thiourea to a saturated solution of lithium hydroxide, and mixing the lithium hydroxide and thiourea in the saturated solution under stirring to obtain the mixture.

2. The method according to claim 1, wherein The heat preservation temperature in the first condition is 140 - 160°C; the temperature condition in the second condition is 570 - 590°C.

3. The method according to claim 1, characterized in that, The first condition includes: continuously introducing an inert gas into a first reaction device where the thiourea and lithium hydroxide are located until the mixture is obtained.

4. The method according to any one of claims 1 to 3, characterized in that, The lithium hydroxide is obtained by reacting lithium carbonate or lithium sulfate dissolved in water with barium ions.

5. The method according to any one of claims 1 to 3, characterized in that, Before the step of keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture, it further includes: Reacting lithium carbonate, barium hydroxide and water under a temperature condition not higher than 10°C to generate the lithium hydroxide.

6. The method according to claim 5, characterized in that, The step of reacting lithium carbonate, barium hydroxide and water under a temperature condition not higher than 10°C to generate the lithium hydroxide includes: Introducing a lithium carbonate solution with a temperature not higher than 5°C into a second reaction device at a speed less than 0.5 L / min within a first time range, and reacting the introduced lithium carbonate solution with the barium hydroxide solution in the second reaction device; wherein, the first time range is less than 1 / 2 of the total duration of introducing the lithium carbonate solution into the second reaction device, and the concentration of the lithium carbonate solution is less than or equal to 0.005 g / L; Increasing the introduction speed of the lithium carbonate solution to obtain the lithium hydroxide; wherein, the introduction speed is less than or equal to 1 L / min.

7. The method according to any one of claims 1 to 3, characterized in that, Before the step of keeping thiourea and lithium hydroxide warm under a first condition to obtain a mixture, it further includes: Reacting lithium sulfate, barium hydroxide and water under a temperature condition not higher than 20°C to generate the lithium hydroxide.

8. The method according to any one of claims 1 to 3, characterized in that The hydrogen sulfide and barium hydroxide are obtained by reacting barium sulfide with water.

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