1. A preparation method of lithium sulfide is characterized by comprising the following steps: and reacting carbon monoxide with powdery anhydrous lithium sulfate to obtain the lithium sulfide.

2. The method for preparing lithium sulfide as claimed in claim 1, wherein the method for preparing the powdery anhydrous lithium sulfate comprises the steps of:

dehydrating and purifying the lithium sulfate monohydrate to obtain anhydrous lithium sulfate;

and carrying out ball milling and refining treatment on the anhydrous lithium sulfate to obtain the powdery anhydrous lithium sulfate.

3. The method for preparing lithium sulfide according to claim 2, wherein the step of dehydrating and purifying lithium sulfate monohydrate specifically comprises:

adding lithium sulfate monohydrate into ethanol to obtain a mixed solution;

transferring the mixed solution into a closed dehydration device, and heating the closed dehydration device to 180-200 ℃ for dehydration and purification treatment.

4. The method for preparing lithium sulfide according to claim 2, wherein the anhydrous lithium sulfate has a water content of <50 ppm.

5. The method for producing lithium sulfide according to claim 1 or 2, wherein the powdery anhydrous lithium sulfate D50 is maintained at 50 μm or less.

6. The method of preparing lithium sulfide as claimed in claim 1, wherein the reaction comprises: firstly reacting at 600-700 ℃ for 3-5h, and then reacting at 950-1000 ℃ for 1-2 h.

7. The method for preparing lithium sulfide according to claim 1, wherein the step of reacting carbon monoxide with powdery lithium sulfate anhydrous specifically comprises: putting the powdery anhydrous lithium sulfate into a reaction furnace, raising the temperature of the reaction furnace to 600-fold-sand 700 ℃, introducing carbon monoxide until the pressure of the reaction furnace is 0.05-0.1mpa, keeping the temperature for 3-5h, continuing raising the temperature of the reaction furnace to 950-fold-sand 1000 ℃, and keeping the temperature for 1-2 h.

8. The method for preparing lithium sulfide according to claim 1, wherein after the reaction is completed and before the lithium sulfide is obtained, the method further comprises the steps of: ball milling treatment and sieving treatment are carried out in sequence.

9. The method for preparing lithium sulfide as claimed in claim 8, wherein the lithium sulfide D50 is 10-50 μm.

10. The method for producing lithium sulfide according to claim 3, wherein the lithium sulfate monohydrate is mixed in a mass-to-volume ratio of 1: 2 is added into ethanol.

Background

Lithium sulfide is a key raw material for synthesizing sulfide solid electrolyte, a Toyota solid battery is about to come out in 2021 years, the cost is reduced at the moment, and how to prepare lithium sulfide in large quantity and high quality becomes a key factor for solid battery application.

In the current existing lithium sulfide preparation methods, the following methods are mainly used:

(1) the lithium sulfate is prepared by carbon reduction under the high temperature condition, and the preparation method is characterized in that solid reacts with solid, the purity is low, and a large amount of impurities are contained;

(2) lithium hydroxide and hydrogen sulfide react in NMP to prepare the lithium sulfide, the reaction conditions of the preparation method are harsh, and the lithium sulfide is easy to deteriorate and difficult to purify due to water generated in the reaction process;

(3) prepared by reacting metallic lithium with hydrogen sulfide, the preparation method is violent in reaction, easy to explode and easy to generate polysulfide.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide a preparation method of lithium sulfide, aiming at solving the problems of low purity and high cost of the prior art.

The technical scheme of the invention is as follows:

a preparation method of lithium sulfide comprises the following steps: and reacting carbon monoxide with powdery anhydrous lithium sulfate to obtain the lithium sulfide.

Optionally, the method for preparing the powdery anhydrous lithium sulfate comprises the following steps:

dehydrating and purifying the lithium sulfate monohydrate to obtain anhydrous lithium sulfate;

and carrying out ball milling and refining treatment on the anhydrous lithium sulfate to obtain the powdery anhydrous lithium sulfate.

Optionally, the step of performing dehydration purification treatment on the lithium sulfate monohydrate specifically includes:

adding lithium sulfate monohydrate into ethanol to obtain a mixed solution;

transferring the mixed solution into a closed dehydration device, and heating the closed dehydration device to 180-200 ℃ for dehydration and purification treatment.

Optionally, mixing lithium sulfate monohydrate in a mass-to-volume ratio of 1: 2 is added into ethanol.

Optionally, the anhydrous lithium sulfate has a water content <50 ppm.

Optionally, the powdered anhydrous lithium sulfate D50 is maintained below 50 μm.

Optionally, the reaction comprises: firstly reacting at 600-700 ℃ for 3-5h, and then reacting at 950-1000 ℃ for 1-2 h.

Optionally, the step of reacting carbon monoxide with powdered lithium sulfate anhydrous specifically includes: putting the powdery anhydrous lithium sulfate into a reaction furnace, raising the temperature of the reaction furnace to 600-fold-sand 700 ℃, introducing carbon monoxide until the pressure of the reaction furnace is 0.05-0.1mpa, keeping the temperature for 3-5h, continuing raising the temperature of the reaction furnace to 950-fold-sand 1000 ℃, and keeping the temperature for 1-2 h.

Optionally, after the reaction is finished and before the lithium sulfide is obtained, the method further includes the steps of: ball milling treatment and sieving treatment are carried out in sequence.

Optionally, the lithium sulfide D50 is 10-50 μm.

Has the advantages that: in the invention, CO is used as a reaction raw material, other impurities cannot be introduced, the CO and the powdery anhydrous lithium sulfate completely react, the impurity content is low, the purity is high, and the generation of hydrogen sulfide extremely toxic gas is avoided. In addition, the reaction condition of CO and lithium sulfate is relatively slow, so that the yield is large, and tens kg of lithium sulfide can be prepared at one time. In addition, the current price of CO is 1m³The price of lithium sulfate is 5 ten thousand yuan/ton, and the cost of raw materials for preparing the lithium sulfide is only 15 ten thousand/ton, so the method has the advantage of low cost.

Drawings

Fig. 1 is an XRD pattern of the high purity lithium sulfide prepared in example 1.

Detailed Description

The invention provides a preparation method of lithium sulfide, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a preparation method of lithium sulfide, which comprises the following steps: and reacting carbon monoxide with powdery anhydrous lithium sulfate to obtain the lithium sulfide.

In the embodiment, other impurities cannot be introduced when the CO is used as a reaction raw material, the CO and the powdery anhydrous lithium sulfate completely react, the impurity content is low, the purity is high, and the generation of hydrogen sulfide extremely toxic gas is avoided. In addition, the reaction condition of CO and lithium sulfate is relatively slow, so that the yield is large, and tens kg of lithium sulfide can be prepared at one time. In addition, the current price of CO is 1m³1-2 yuan, the price of lithium sulfate is 5 ten thousand yuan/ton, and the cost of raw materials for preparing lithium sulfide is only 15 ten thousand/ton, so the method has the advantage of low cost。

In one embodiment, the method for preparing the powdery anhydrous lithium sulfate comprises the steps of:

s1, dehydrating and purifying the lithium sulfate monohydrate to obtain anhydrous lithium sulfate;

s2, performing ball milling and refining treatment on the anhydrous lithium sulfate to obtain the powdery anhydrous lithium sulfate.

In one embodiment, step S1 specifically includes:

s11, adding lithium sulfate monohydrate into ethanol to obtain a mixed solution;

s12, transferring the mixed solution into a sealed dehydration device, and heating the sealed dehydration device to 180-200 ℃ for dehydration and purification treatment to obtain anhydrous lithium sulfate.

The lithium sulfate is easy to absorb water and turns into lithium sulfate monohydrate, the lithium sulfate monohydrate begins to lose water at 130 ℃, if the lithium sulfate monohydrate is completely dehydrated, high temperature of more than 300 ℃ is needed, and the lithium sulfate is combined with water and ethanol to form an azeotrope within the range of 180-200 ℃, so that the combined water can be well removed, and the anhydrous lithium sulfate is obtained.

In one embodiment, the anhydrous lithium sulfate has a water content of <50 ppm. That is, the anhydrous lithium sulfate has a water content of <50ppm after the dehydration purification treatment. The lower the moisture content of the anhydrous lithium sulfate, the higher the purity of the finally formed lithium sulfide. Since lithium sulfide readily reacts with moisture to form lithium hydroxide, the lower the moisture content of the anhydrous lithium sulfate, the less lithium sulfide will eventually react with moisture to form lithium hydroxide, and the higher the purity of the lithium sulfide.

In step S11, in one embodiment, lithium sulfate monohydrate is mixed in a mass to volume ratio of 1: 2 is added into ethanol. For example, 2 to 5kg of lithium sulfate monohydrate is mixed in a mass to volume ratio of 1: 2, adding the mixture into 4-10L of ethanol, and fully and uniformly mixing to obtain the mixed solution.

In one embodiment, the powdered lithium anhydrous sulfate D50 is maintained below 50 μm. That is, the ball milling was performed until the powder of anhydrous lithium sulfate D50 was kept at 50 μm or less. Because the powdered anhydrous lithium sulfate after ball milling and refining has larger surface area, the required reaction temperature is lower, and the reaction is more complete. In addition, when the reaction is carried out by using the powdery anhydrous lithium sulfate, a catalyst is not required to be added, so that the introduction of impurities is avoided.

In one embodiment, the reaction comprises: firstly reacting at 600-700 ℃ for 3-5h, and then reacting at 950-1000 ℃ for 1-2 h. In the reaction process of this example, the following reactions were involved:

Li₂SO₄---Li₂SO₃+0.5O₂；

Li₂SO₃---Li₂S+1.5O₂；

CO+0.5O₂----CO₂；

4CO+Li₂SO₄--------Li₂S+4CO₂；

lithium sulfate starts to decompose at 600 ℃, and CO consumes O₂The reaction is carried out in the forward direction, and the powdery anhydrous lithium sulfate is easier to react with CO due to the large contact area. The melting point of the lithium sulfide is 938 ℃, the melting point of the lithium sulfate is 859 ℃, the lithium sulfide and the residual lithium sulfate can be changed into liquid when the temperature is increased to 950 ℃ and 1000 ℃, the lithium sulfate liquid continuously reacts with CO, the CO and the lithium sulfate are completely reacted, and finally the lithium sulfide with the purity of more than 99.9 percent is obtained. It should be noted that, if the temperature is directly raised to 950-.

In one embodiment, the step of reacting carbon monoxide with powdered lithium sulfate anhydrous specifically comprises: and putting the powdery anhydrous lithium sulfate into a reaction furnace, raising the temperature of the reaction furnace to 600-fold-sand-type 700 ℃, introducing carbon monoxide until the pressure of the reaction furnace is 0.05-0.1mpa, keeping the temperature for 3-5h, continuing raising the temperature of the reaction furnace to 950-fold-sand-type 1000 ℃, and keeping the temperature for 1-2 h.

Specifically, the powdery anhydrous lithium sulfate is flatly paved in a titanium barrel in a reaction furnace, the vacuum degree of the reaction furnace is maintained at minus 0.1mpa by vacuumizing, the temperature of the reaction furnace is increased to 600-700 ℃,and introducing a reducing gas CO until the reaction furnace is kept at 0.05-0.1mpa with slight positive pressure, stopping introducing the gas, keeping the temperature for 3-5h, then continuously raising the temperature of the reaction furnace to 950-1000 ℃, and keeping the temperature for 1-2 h. In this embodiment, argon may be continuously introduced after the reaction is completed to introduce CO and CO that have not reacted completely₂And introducing a tail gas treatment device.

In one embodiment, after the reaction is completed and before the lithium sulfide is obtained, the method further comprises the steps of: ball milling treatment and sieving treatment are carried out in sequence. Further, after the sieving treatment, the lithium sulfide D50 was obtained in a range of 10 to 50 μm.

The invention is further illustrated by the following specific examples.

Example 1

A. And (3) dehydration and purification: 2kg of lithium sulfate monohydrate (> 99.9%) were mixed in a mass to volume ratio of 1: 2, adding the mixture into 4L of ethanol, fully and uniformly mixing to obtain a mixed solution, transferring the mixed solution into a closed dehydration device, and heating the closed dehydration device to 180 ℃ for negative pressure dehydration and purification to obtain the anhydrous lithium sulfate.

B. Ball milling and refining: putting the anhydrous lithium sulfate into a zirconia ball milling tank, and carrying out ball milling for 8h at the rotating speed of 500r/h to keep the powdery anhydrous lithium sulfate D50 below 50 um.

C. And (3) carbonization and reduction: flatly spreading powdery anhydrous lithium sulfate into a titanium barrel in a reaction furnace, vacuumizing to enable the vacuum degree of the reaction furnace to be-0.1 mpa, raising the temperature of the reaction furnace to 600 ℃, introducing reducing gas CO, keeping the slight positive pressure of the reaction furnace at 0.05mpa, stopping introducing air, keeping the temperature for 3 hours, continuously raising the temperature of the reaction furnace to 950 ℃, keeping the temperature for 1 hour, continuously introducing argon after the reaction is finished, and enabling CO and CO which are not completely reacted to be continuously introduced₂And introducing a tail gas treatment device.

D. Ball-milling and packaging: the reacted lithium sulfide was transferred to a glove box, and then ball-milled and sieved to obtain lithium sulfide having a particle size of 22 μm controlled at D50, and an XRD pattern of the lithium sulfide is shown in fig. 1.

Example 2

A. And (3) dehydration and purification: 3kg of lithium sulfate monohydrate (> 99.9%) were mixed in a mass to volume ratio of 1: 2, adding the mixture into 6L of ethanol, fully and uniformly mixing to obtain a mixed solution, transferring the mixed solution into a closed dehydration device, and heating the closed dehydration device to 190 ℃ for negative pressure dehydration and purification to obtain the anhydrous lithium sulfate.

B. Ball milling and refining: putting the anhydrous lithium sulfate into a zirconia ball milling tank, and carrying out ball milling for 9h at the rotating speed of 550r/h to keep the powdery anhydrous lithium sulfate D50 below 50 um.

C. And (3) carbonization and reduction: flatly spreading powdery anhydrous lithium sulfate into a titanium barrel in a reaction furnace, vacuumizing the reaction furnace to ensure that the vacuum degree is-0.1 mpa, raising the temperature of the reaction furnace to 650 ℃, introducing reducing gas CO, keeping the slight positive pressure of the reaction furnace at 0.08mpa, stopping introducing air, keeping the temperature for 4 hours, continuously raising the temperature of the reaction furnace to 980 ℃, preserving the temperature for 1.5 hours, continuously introducing argon after the reaction is finished, and adding unreacted CO and CO₂And introducing a tail gas treatment device.

D. Ball-milling and packaging: and transferring the reacted lithium sulfide into a glove box, and then, carrying out ball milling, crushing and sieving to obtain the lithium sulfide with the particle size controlled at 45 mu m D50.

Example 3

A. And (3) dehydration and purification: 5kg of lithium sulfate monohydrate (> 99.9%) were mixed in a mass to volume ratio of 1: 2, adding the mixture into 10L of ethanol, fully and uniformly mixing to obtain a mixed solution, transferring the mixed solution into a closed dehydration device, and heating the closed dehydration device to 200 ℃ for negative pressure dehydration and purification to obtain the anhydrous lithium sulfate.

B. Ball milling and refining: putting the anhydrous lithium sulfate into a zirconia ball milling tank, and carrying out ball milling for 9h at the rotating speed of 600r/h to keep the powdery anhydrous lithium sulfate D50 below 50 um.

C. And (3) carbonization and reduction: flatly spreading powdery anhydrous lithium sulfate into a titanium barrel in a reaction furnace, vacuumizing to ensure that the vacuum degree of the reaction furnace is-0.1 mpa, raising the temperature of the reaction furnace to 700 ℃, introducing reducing gas CO, keeping the slight positive pressure of the reaction furnace at 0.01mpa, stopping introducing air, keeping the temperature for 5 hours, continuously raising the temperature of the reaction furnace to 1000 ℃, keeping the temperature for 2 hours, continuously introducing argon after the reaction is finished, and adding CO and CO which are not completely reacted₂And introducing a tail gas treatment device.

D. Ball-milling and packaging: and transferring the reacted lithium sulfide into a glove box, and then, carrying out ball milling, crushing and sieving to obtain the lithium sulfide with the particle size controlled at 30 mu m D50.

The purity of the lithium sulfide prepared in examples 1-3 above is shown in Table 1 below:

TABLE 1

As is clear from Table 1, the lithium sulfides obtained in examples 1 to 3 all had a purity of 99.9% or more, and Li₂SO₄Residual amount and Li₂SO₃The residual quantity is low.

In summary, the invention provides a preparation method of lithium sulfide. In the invention, CO is used as a reaction raw material, other impurities cannot be introduced, the CO and the powdery anhydrous lithium sulfate completely react, the impurity content is low, the purity is high, and the generation of hydrogen sulfide extremely toxic gas is avoided. In addition, excess CO is oxidized to form CO₂，CO₂And no tail gas is generated by absorption of alkali liquor. In addition, the reaction condition of CO and lithium sulfate is relatively slow, so that the yield is large, and tens kg of lithium sulfide can be prepared at one time. And the current price of CO is 1m³The price of lithium sulfate is 5 ten thousand yuan/ton, the cost of raw materials for preparing the lithium sulfide is only 15 ten thousand/ton, and the method has the advantage of low cost.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.