Process for preparing lithium-sulfur electrolyte raw material based on waste salt

Abstract

The application relates to the technical field of battery material and resource recycling, and provides a process for preparing lithium-sulfur electrolyte raw materials based on waste salt, which comprises the following steps: taking industrial waste salt as a sulfur source, taking lithium-rich waste residue as a lithium source, taking waste carbon as a reducing agent, uniformly mixing the three with a binder, granulating, further calcining to obtain a mixture, mixing the obtained mixture with a solvent A, ball milling, solid-liquid separation, obtaining a liquid phase containing sulfides, subjecting the obtained solid phase to acid immersion treatment and condensation to obtain silicon tetrachloride, mixing and dissolving the liquid phase containing sulfides and lithium chloride, carrying out solid-liquid separation to obtain a solution containing lithium chloride and lithium sulfide, reducing and concentrating the solution containing lithium chloride and lithium sulfide to obtain a mixed product of lithium chloride and lithium sulfide, and further adjusting the proportion to obtain lithium-sulfur electrolyte raw materials. The application realizes the resource utilization of industrial waste salt and lithium-rich waste residue, reduces the preparation cost of lithium-sulfur electrolyte raw materials, simultaneously produces high-value silicon tetrachloride as a byproduct, and reduces waste emission.

Description

Technical Field

[0001] This invention relates to the field of battery materials and resource recycling technology, and provides a process for preparing lithium-sulfur electrolyte raw materials based on waste salt. Background Technology

[0002] With the rapid development of the new energy industry, solid-state lithium-sulfur batteries have become a research hotspot due to their advantages such as high energy density and good safety. Lithium sulfide and lithium chloride are key raw materials for solid-state lithium-sulfur electrolytes. Currently, the preparation of lithium sulfide and lithium chloride mainly uses pure chemical reagents as raw materials, resulting in high production costs and generating certain waste pollutants during the production process.

[0003] On the other hand, industries such as non-ferrous metal smelting, chemical industry, and new energy generate a large amount of industrial waste salt (mainly sodium sulfate). If this waste salt is discharged directly, it will cause soil and water pollution and is difficult to treat. At the same time, the lithium-rich waste residue generated by the lithium extraction industry contains a certain amount of lithium compounds, but due to the high impurity content, it is difficult to recycle and reuse, and most of it is stockpiled, resulting in resource waste and environmental pressure.

[0004] In the existing technology, there is little research on the recycling of industrial waste to prepare electrolyte raw materials. There is no process that can simultaneously and efficiently utilize industrial waste salt and lithium-rich waste residue, directly prepare lithium chloride-lithium sulfide mixed raw materials that meet the requirements of solid lithium-sulfur electrolytes, and produce high-value by-products.

[0005] Therefore, developing a process for preparing lithium-sulfur electrolyte raw materials based on waste salt that is resource-efficient, low-cost, and environmentally friendly is of great practical significance. Summary of the Invention

[0006] To address the problems mentioned in the background art, the main objective of this invention is to provide a process for preparing lithium-sulfur electrolyte raw materials based on waste salt, comprising six steps: raw material pretreatment, high-temperature calcination, ball milling separation, impurity recovery, sodium removal treatment, and product preparation. This process enables the resource utilization of industrial waste salt and lithium-rich waste residue, reduces the preparation cost of lithium-sulfur electrolyte raw materials, and simultaneously produces high-value silicon tetrachloride as a byproduct, thereby reducing waste emissions.

[0007] In a first aspect, the present invention provides a process for preparing lithium-sulfur electrolyte raw materials based on waste salt, including...

[0008] Step 1: Raw material pretreatment: Using industrial waste salt as sulfur source, lithium-rich waste residue as lithium source, and waste carbon as reducing agent, mix them evenly with binder, granulate, and obtain mixed particles;

[0009] Step 2: High-temperature calcination: The mixed particles are calcined to obtain a mixture;

[0010] Step 3: Ball milling separation: The obtained mixture is mixed with solvent A and then ball milled to separate the solid and liquid phases, resulting in a liquid phase containing sulfides and a solid phase containing other substances;

[0011] Step 4: Impurity recovery: The obtained solid phase containing other substances is subjected to acid leaching and condensation to obtain silicon tetrachloride;

[0012] Step 5: Sodium removal treatment: The liquid phase containing sulfides is mixed and dissolved with lithium chloride, and the solution containing lithium chloride and lithium sulfide is obtained by solid-liquid separation;

[0013] Step 6: Product preparation: The solution containing lithium chloride and lithium sulfide is concentrated under reduced pressure to obtain a mixed product of lithium chloride and lithium sulfide, and the ratio is further adjusted to obtain lithium-sulfur electrolyte raw material.

[0014] In some embodiments, the main component of the industrial waste salt is sodium sulfate, which originates from the non-ferrous smelting, chemical, and new energy industries.

[0015] In some embodiments, the lithium-rich waste residue contains lithium sulfate, lithium chloride, lithium carbonate, lithium oxide, lithium hydroxide, silicon dioxide, or aluminum oxide, etc.

[0016] In some embodiments, the waste charcoal is selected from at least one of industrial activated carbon waste, raw charcoal powder waste, coal gasification activated carbon waste, coke waste, and biochar.

[0017] In some embodiments, the binder is an aqueous solution binder prepared from one or more of starch, polyacrylamide, and polyaluminum sulfate, used to increase viscosity and facilitate material granulation.

[0018] In some embodiments, the sulfur source, lithium source, waste carbon, and binder are adjusted according to the sodium sulfate content in industrial waste salt, the lithium compound content in lithium-rich waste residue, and the purity of the target product to ensure that sulfate can be fully reduced and lithium can be fully converted into lithium sulfide in the subsequent calcination reaction.

[0019] In some embodiments, the particle size of the mixed particles is 1-15 cm, preferably 5-10 cm.

[0020] In some embodiments, the calcination is carried out in calcination equipment such as a muffle furnace or a rotary kiln.

[0021] In some embodiments, the calcination temperature is 900-1500℃, preferably 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, or any two of the above values ​​forming a range.

[0022] In some embodiments, the calcination atmosphere may be an inert gas protective atmosphere or a closed atmosphere (the closed atmosphere may be a vacuum atmosphere or a closed atmosphere containing air).

[0023] In some embodiments, the calcination time is 1-6 hours (preferably 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours).

[0024] Under high temperature conditions, waste charcoal (such as biochar) is used as a reducing agent to reduce sodium sulfate in industrial waste salt to sodium sulfide, and at the same time, lithium compounds such as lithium carbonate, lithium oxide, and lithium hydroxide in lithium-rich waste residue are reduced to lithium sulfide. After calcination, a mixture mainly composed of sodium sulfide, lithium sulfide, silicon dioxide, and aluminum oxide is obtained.

[0025] In some embodiments, the solid-liquid ratio of the mixture to solvent A is 1:(5-10) (g / mL), preferably 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any two of the above values ​​forming a range.

[0026] In some embodiments, solvent A is C 1-6 At least one of the following: alcohol solvents (e.g., methanol, ethanol, isopropanol, tert-butyl alcohol), tetrahydrofuran, hexamethylphosphoramide, or ethylene glycol.

[0027] In some embodiments, the ball milling speed is 100-500 r / min, and the ball milling time is 1-6 hours. Preferably, the ball milling speed is any one of 100 r / min, 200 r / min, 300 r / min, 400 r / min, 500 r / min, or any two of the above values. Preferably, the ball milling time is 1-6 hours, more preferably 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0028] Through ball milling, sodium sulfide and lithium sulfide in the mixture are fully dissolved in solvent A, while insoluble impurities such as silica and alumina remain in solid state. After solid-liquid separation (such as filtration and centrifugation), a solvent phase containing sodium sulfide and lithium sulfide and a solid phase containing silica and alumina are obtained.

[0029] In some embodiments, the acid is one or more mixtures of hydrochloric acid, perchloric acid, nitric acid, and sulfuric acid.

[0030] In some embodiments, the acid concentration is 1-12 mol / L, preferably 1 mol / L, 3 mol / L, 6 mol / L, 9 mol / L, 12 mol / L, or any two of the above values ​​forming a range.

[0031] In some embodiments, the acid leaching treatment is carried out at a temperature of 80-180°C for 1-6 hours. Preferably, the temperature is any one of the ranges of 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or any two of the above values. Preferably, the time is any one of the ranges of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any two of the above values.

[0032] During the acid leaching process, the silicon dioxide in the solid phase reacts with hydrochloric acid. The reaction equation is: SiO2 + 4HCl = SiCl4↑ + 2H2O. The generated silicon tetrachloride gas is collected by condensation and used as a raw material in the silicon industry, realizing the resource recovery of impurities.

[0033] In some embodiments, the amount of lithium chloride used is 0.3-0.6 times the mass of the sulfide-containing liquid phase.

[0034] In some embodiments, the mixing and dissolution process is as follows: under low temperature conditions of 0-10°C, the reaction is stirred at a speed of 100-200 r / min for 0.5-2 hours. Utilizing the common ion effect, sodium ions in solvent A combine with chloride ions in lithium chloride to form sodium chloride crystals. Since sodium chloride has extremely low solubility in polar organic phases such as ethanol and ethylene glycol, it will precipitate rapidly. Sodium chloride is removed by solid-liquid separation (such as filtration and centrifugation) to obtain a solution containing lithium chloride and lithium sulfide.

[0035] In some embodiments, the reduced pressure concentration conditions are rotary evaporation at 40-80°C and 0.05-0.09 MPa.

[0036] In some embodiments, the ratio of lithium chloride to lithium sulfide in the mixed product can be controlled by adjusting the raw material ratio and process parameters, which can meet the formulation requirements of lithium sulfide, lithium chloride, and phosphorus pentasulfide molar ratio of 4:3:1 or 5:2:1 in solid lithium-sulfur electrolyte.

[0037] Beneficial effects:

[0038] This invention uses industrial waste salt (mainly sodium sulfate) and lithium-rich waste residue (containing lithium carbonate, lithium oxide, lithium hydroxide, etc.) as raw materials, waste charcoal (such as biochar) as a reducing agent, and starch or sugars as a binder. Through steps such as mixing and granulation, high-temperature calcination, ball milling separation, sodium removal using the common ion effect, and rotary evaporation, a mixed material of lithium chloride and lithium sulfide is finally obtained, along with silicon tetrachloride, a byproduct with utilization value. This invention achieves efficient resource utilization of industrial waste salt and lithium-rich waste residue. The prepared mixed material can be directly used for subsequent formulation of solid lithium-sulfur electrolytes, and the byproduct silicon tetrachloride has market application value. The process is simple, low-cost, and environmentally friendly, solving the problems of high cost and waste pollution associated with traditional electrolyte raw material preparation.

[0039] (1) This invention uses industrial waste salt and lithium-rich waste residue as the main raw materials, realizing the efficient utilization of the two industrial wastes and reducing the environmental pollution caused by waste stockpiling.

[0040] (2) The process of the present invention directly prepares a mixed product of lithium chloride and lithium sulfide, which can be directly used for subsequent formulation of solid lithium-sulfur electrolyte (without the need to prepare the two raw materials separately and then mix them), which simplifies the electrolyte production process and reduces production costs.

[0041] (3) The by-product silicon tetrachloride is an important raw material in the silicon industry and has high market value, which further improves the economic benefits of the process.

[0042] (4) The raw materials used in the process of this invention are widely available and inexpensive. The binder, solvent A, etc. can be recycled and reused. The entire process is simple and easy to operate, and is suitable for large-scale industrial production.

[0043] (5) The sodium removal process of this invention utilizes the common ion effect, eliminating the need for complex separation equipment, achieving good sodium removal effect, ensuring product purity, and preparing chlorine-containing lithium sulfide raw materials in one step for use in solid lithium sulfur electrolytes, thus simplifying subsequent processing. Attached Figure Description

[0044] Figure 1 This is a flowchart of the preparation process of the present invention.

[0045] Figure 2 Comparative images of the mixed particles prepared in Example 1 of this invention and the resulting product. (a) Particles before calcination (2-5 cm), (b) Product obtained after calcination and filtration separation.

[0046] Figure 3 Comparative diagram of the mixed particles prepared in Example 2 of this invention and the resulting product. (a) Particles before calcination (10-15 cm), (b) Product obtained after calcination and filtration separation.

[0047] Figure 4The FTIR spectrum of the product prepared in Example 1.

[0048] Figure 5 The FTIR spectrum of the product prepared in Example 2.

[0049] Figure 6 The XRD spectrum of the product prepared in Example 1.

[0050] Figure 7 The XRD spectrum of the product prepared in Example 2.

[0051] Figure 8 XPS spectrum of the product prepared in Example 1.

[0052] Figure 9 XPS spectrum of the product prepared in Example 2.

[0053] Terminology Explanation

[0054] Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0055] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0056] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] In the following content, all numbers disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a number with a value of N is disclosed, any numbers with values ​​of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0060] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0061] Example 1

[0062] Raw material pretreatment: Select 50g of industrial waste salt (sodium sulfate content 90%), 30g of lithium-rich waste residue (lithium content calculated as lithium oxide 10%), 15g of biochar, and 5g of starch, put them into a mixer and stir for 30 minutes until they are evenly mixed. Then granulate them through a granulator to obtain mixed particles with a particle size of 2-5cm.

[0063] High-temperature calcination: The mixed particles are placed in a muffle furnace and calcined at 1100°C in air for 4 hours to obtain the calcined product;

[0064] Ball milling separation: The calcined product was transferred to a ball mill, 200 mL of isopropanol was added, the ball milling speed was controlled at 300 r / min, the ball milling time was 2 hours, and the mixture was filtered after ball milling to obtain an ethanol solution containing sodium sulfide and lithium sulfide and a solid phase containing silicon dioxide and aluminum oxide.

[0065] Impurity recovery: The solid phase was transferred to an acid leaching reactor, 100 mL of 9 mol / L hydrochloric acid was added, and the reaction was carried out at 200℃ for 1.5 hours. The generated silicon tetrachloride gas was collected and condensed to obtain silicon tetrachloride by-product.

[0066] Sodium removal treatment: Transfer the ethanol solution containing sodium sulfide and lithium sulfide to the reaction vessel, detect the sodium ion content in the solution to be 0.5 mol, add 0.75 mol of lithium chloride (50% excess), stir at 150 r / min for 1 hour at 5℃, and filter to remove the precipitated sodium chloride crystals;

[0067] Product preparation: The sodium-free solution was placed in a rotary evaporator and rotary evaporated at 60℃ and 0.07MPa for 1 hour to remove ethanol, yielding 28.6g of a mixed product of lithium chloride and lithium sulfide.

[0068] The results of the low-temperature digestion and ICP-MS analysis of the obtained products are shown in Table 1.

[0069] Table 1 Test Results

[0070] Measured elements Instrument readings unit Conversion content unit Quality Score % Eu 0 mg / L <20.0 mg / kg <0.0020% Ga 0 mg / L <20.0 mg / kg <0.0020% Nd 0 mg / L <20.0 mg / kg <0.0020% Sc 0 mg / L <20.0 mg / kg <0.0020% Be 0.0001 mg / L <20.0 mg / kg <0.0020% Er 0.0001 mg / L <20.0 mg / kg <0.0020% Hf 0.0001 mg / L <20.0 mg / kg <0.0020% Pr 0.0002 mg / L <20.0 mg / kg <0.0020% V 0.0002 mg / L <20.0 mg / kg <0.0020% Pd 0.0003 mg / L <20.0 mg / kg <0.0020% Mn 0.0004 mg / L <20.0 mg / kg <0.0020% Ho 0.0005 mg / L <20.0 mg / kg <0.0020% Tm 0.0005 mg / L <20.0 mg / kg <0.0020% Zr 0.0007 mg / L <20.0 mg / kg <0.0020% Rh 0.0008 mg / L <20.0 mg / kg <0.0020% La 0.0009 mg / L <20.0 mg / kg <0.0020% Gd 0.001 mg / L <20.0 mg / kg <0.0020% As 0.00114 mg / L <20.0 mg / kg <0.0020% Tb 0.0013 mg / L <20.0 mg / kg <0.0020% Sm 0.0014 mg / L <20.0 mg / kg <0.0020% Zn 0.00146 mg / L <20.0 mg / kg <0.0020% Dy 0.0015 mg / L <20.0 mg / kg <0.0020% Bi 0.00164 mg / L <20.0 mg / kg <0.0020% Ru 0.0019 mg / L <20.0 mg / kg <0.0020% Cd 0.002 mg / L <20.0 mg / kg <0.0020% Sr 0.002 mg / L <20.0 mg / kg <0.0020% Sb 0.00223 mg / L <20.0 mg / kg <0.0020% Cr 0.0028 mg / L <20.0 mg / kg <0.0020% Ba 0.00284 mg / L <20.0 mg / kg <0.0020% W 0.00296 mg / L <20.0 mg / kg <0.0020% Ce 0.0031 mg / L <20.0 mg / kg <0.0020% In 0.0031 mg / L <20.0 mg / kg <0.0020% Ti 0.0036 mg / L <20.0 mg / kg <0.0020% Al 0.00411 mg / L <20.0 mg / kg <0.0020% Tl 0.0042 mg / L <20.0 mg / kg <0.0020% Fe 0.00425 mg / L <20.0 mg / kg <0.0020% Ge 0.00444 mg / L <20.0 mg / kg <0.0020% Lu 0.0053 mg / L <20.0 mg / kg <0.0020% Ta 0.0054 mg / L <20.0 mg / kg <0.0020%

[0071] Continued from Table 1

[0072] Measured elements Instrument readings unit Conversion content unit Quality Score % Ir 0.0065 mg / L <20.0 mg / kg <0.0020% Pt 0.0065 mg / L <20.0 mg / kg <0.0020% Te 0.00665 mg / L <20.0 mg / kg <0.0020% Se 0.0073 mg / L <20.0 mg / kg <0.0020% Ni 0.0078 mg / L <20.0 mg / kg <0.0020% Yb 0.0079 mg / L <20.0 mg / kg <0.0020% Cu 0.0083 mg / L <20.0 mg / kg <0.0020% Y 0.0084 mg / L <20.0 mg / kg <0.0020% Mo 0.0085 mg / L <20.0 mg / kg <0.0020% Co 0.0088 mg / L <20.0 mg / kg <0.0020% Ag 0.0096 mg / L <20.0 mg / kg <0.0020% Au 0.0099 mg / L <20.0 mg / kg <0.0020% Re 0.0099 mg / L <20.0 mg / kg <0.0020% Mg 0.0114 mg / L <20.0 mg / kg <0.0020% Nb 0.0115 mg / L <20.0 mg / kg <0.0020% B 0.01461 mg / L <20.0 mg / kg <0.0020% Hg 0.0223 mg / L <20.0 mg / kg <0.0020% K 0.0255 mg / L <20.0 mg / kg <0.0020% Pb 0.0709 mg / L 32.9461 mg / kg 3.29E-05 Ca 0.1524 mg / L 70.81784 mg / kg 7.08E-05 Sn 0.1872 mg / L 86.98885 mg / kg 8.7E-05 P 0.5162 mg / L 239.8699 mg / kg 0.00024 Si 1.213 mg / L 563.6617 mg / kg 0.000564 Na 1.322 mg / L 614.3123 mg / kg 0.000614 S 8.413 mg / L 391212.8 mg / kg 0.391213 Li 6.465 mg / L 300418.2 mg / kg 0.300418

[0073] As can be seen from the data in Table 1 and the XRD, FTIR, and XPS characterization, when the lithium compounds in the sample are only lithium sulfide and lithium chloride, the molar ratio of lithium chloride to lithium sulfide in the product is 3:4, and the purity reaches more than 98%, which meets the requirements for use of solid lithium sulfur electrolyte.

[0074] like Figure 2 As shown, after calcination using mixed particles of 2-5 cm, the calcined product, after filtration and separation, is a light yellow powder with good uniformity.

[0075] like Figure 4 The following table shows the FTIR spectrum of lithium chloride to lithium sulfide in a molar ratio of 3:4. The positions of the relevant peaks are illustrated in Table 2:

[0076] Table 2. Peak Position Description

[0077]

[0078] Table 3. Data Explanation of XRD Plots

[0079]

[0080] As shown in Table 3 and Figure 6 As shown, both lithium chloride and lithium sulfide in the mixture exist in a crystalline state and each retains its characteristic diffraction peaks; the simultaneous appearance of mixed phase peaks indicates that there is an interfacial interaction between the two substances.

[0081] X-ray photoelectron spectroscopy (XPS) and the corresponding peak table clearly characterize the elemental composition, chemical state, and relative abundance of the sample surface. This invention uses X-ray photoelectron spectroscopy to detect and analyze samples of different components, and studies the XPS spectra of the product prepared in Example 1, such as... Figure 8 As shown in the spectrum, the peak contains Cl 2p d, and the characteristic peak is at 215.4 cm⁻¹. -1 At this location, the characteristic peak of Li 1s is at 62.4 cm⁻¹. -1 At this location, the characteristic peak of S 2p is at 175.4 cm⁻¹. -1 At these locations, the corresponding peak areas are Cl 2p 138461.05 CPS.eV, Li 1s 2870.55 CPS.eV, and S 2p 1733.11 CPS.eV, respectively. The characteristic spectra clearly demonstrate the presence of lithium, sulfur, and chlorine in the sample. Furthermore, the characteristic peaks at S 2p and Cl 2p correspond to S... 2- With Cl - The lithium form is Li. + Therefore, the results of this X-ray photoelectron spectroscopy test prove that the main components of the product are lithium chloride and lithium sulfide.

[0082] Example 2

[0083] Raw material pretreatment: Select 60g of industrial waste salt (sodium sulfate content 85%), 25g of lithium-rich waste residue (lithium content 12% calculated as lithium oxide), 18g of biochar, and 6g of glucose, put them into a mixer and stir for 40 minutes until they are evenly mixed. Then granulate them through a granulator to obtain mixed particles with a particle size of 10-15cm.

[0084] High-temperature calcination: The mixed particles are placed in a rotary kiln and calcined at 950°C for 4 hours under a nitrogen protective atmosphere to obtain the calcined product;

[0085] Ball milling separation: The calcined product was transferred to a ball mill, 250 mL of ethylene glycol was added, the ball milling speed was controlled at 400 r / min, and the ball milling time was 1.5 hours. After the ball milling was completed, centrifugation was performed to obtain an ethylene glycol solution containing sodium sulfide and lithium sulfide and a solid phase containing silicon dioxide and aluminum oxide.

[0086] Impurity recovery: The solid phase was transferred to an acid leaching reactor, 80 mL of 9 mol / L hydrochloric acid was added, and the reaction was carried out at 220℃ for 1 hour. The generated silicon tetrachloride gas was collected and condensed to obtain silicon tetrachloride by-product.

[0087] Sodium removal treatment: The ethylene glycol solution containing sodium sulfide and lithium sulfide was transferred to the reaction vessel. The sodium ion content in the solution was measured to be 0.6 mol. 0.9 mol of lithium chloride (50% excess) was added. The mixture was stirred at 180 r / min at 8°C for 0.8 hours. The precipitated sodium chloride crystals were removed by filtration.

[0088] Product preparation: The sodium-free solution was placed in a rotary evaporator and evaporated at 70°C and 0.08 MPa for 1.2 hours to remove ethylene glycol, yielding a mixed product of lithium chloride and lithium sulfide, weighing 32.3 g.

[0089] Characterized by XRD, FTIR, and XPS, the product has a molar ratio of lithium chloride to lithium sulfide of 2:5 and a purity of over 98.5%, which meets the requirements for use of solid lithium-sulfur electrolytes.

[0090] like Figure 3 As shown, after calcination using mixed particles of 10-15cm, the calcined product, after filtration and separation, is a white powder with good uniformity.

[0091] like Figure 5 The following table shows the FTIR spectra of lithium chloride to lithium sulfide in a molar ratio of 2:5. The positions of the relevant peaks are illustrated in Table 4 below:

[0092] Table 4. Peak Position Description

[0093] <![CDATA[Wavelength (cm -1 )]]> Absorbance / Transmittance Main attribution Remark 438.24 1.19 <![CDATA[Li-S bond bending vibration of lithium sulfide (Li2S)]]> <![CDATA[Characteristic vibration of Li2S (380 - 470 cm -1 range)]]> 530.81 0.79 Li-Cl bond vibration in lithium chloride (LiCl) Low wavenumber lattice vibration peaks of LiCl 648.45 0.97 <![CDATA[Stretching vibration of Li-S bond in lithium sulfide (Li2S)]]> <![CDATA[Characteristic vibration of Li2S (600 - 700 cm -1 interval)]]> 822.49 0.92 Lattice vibrations of lithium chloride (LiCl) <![CDATA[Typical lattice vibration peaks of LiCl (800 - 900 cm -1 ).]]> 1037.03 0.51 lithium-sulfur / chlorine bond interaction peaks of the mixture Characteristic distorted vibrations after mixing two lithium salts 1641.61 0.54 The bending vibration of OH groups in water Water is adsorbed on the surface of the sample during the sampling process. 1971.38 0.73 Combination / Odd-frequency peaks of the mixture Weak combined vibration peaks of lithium salt systems 2636.22 0.65 Combination / Odd-frequency peaks of the mixture Weak combined vibrational peaks of lithium salt systems 3353.12 1.24 The stretching vibration of OH groups in water Water is adsorbed on the surface of the sample during the sampling process. 3585.99 0.85 The stretching vibration of OH groups in water Water is adsorbed on the surface of the sample during the sampling process.

[0094] As shown in Table 4 and Figure 7 As shown, both lithium chloride and lithium sulfide in the mixture exist in a crystalline state and each retains its characteristic diffraction peaks; the simultaneous appearance of mixed phase peaks indicates that there is an interfacial interaction between the two substances.

[0095] The XPS spectra of the product prepared in Example 2 were studied, such as... Figure 9 As shown, the sample surface mainly contains three elements: Li, Cl, and S. Among them, lithium (62.4 cm⁻¹) is the most abundant element. -1 The main cations in the sample were sulfur (175.4 cm⁻¹) and chlorine (215.4 cm⁻¹). -1 The presence of this directly confirms the coexistence of lithium sulfide (Li2S) and lithium chloride (LiCl).

[0096] like Figure 9As shown, peak analysis and chemical state verification were performed on Li, Cl, and S respectively, based on the standard cards: Cl 2p spectrum: A characteristic peak appears at a binding energy of approximately 197.71 eV, which perfectly matches the Cl 2p electron binding energy of Cl⁻ in lithium chloride, confirming the presence of lithium chloride. Li 1s spectrum: A broad peak appears at a binding energy of approximately 53.9 eV, which is a characteristic signal of lithium. Since the chemical environments of Li⁺ in Li₂S and LiCl are similar, this peak position cannot directly distinguish between the two lithium salts. However, combined with the signals of S2p and Cl 2p, it can be confirmed that this is a result jointly contributed by both lithium salts. S 2p spectrum: A characteristic peak appears at a binding energy of approximately 159.31 eV. This peak position is consistent with the S 2p electron binding energy of S²⁻ in lithium sulfide, confirming the presence of lithium sulfide.

[0097] Figure 4 and Figure 5 All are Fourier transform infrared (FTIR) spectra of the samples. Figure 4-5 As shown, at 3500 cm -1 The broad peak nearby corresponds to the OH stretching vibration of adsorbed water on the sample surface; 3333 cm⁻¹ -1 The absorption peak at 1037 cm⁻¹ is related to the stretching vibration of the SH bond in lithium sulfide; -1 922 cm -1 The absorption peaks in the low and medium wavenumber regions correspond to S, respectively. 2- lattice vibrations and Li + Coordination vibrations; the sample at 600 cm -1 The following strong absorption peaks originate from Cl. - The characteristic lattice vibrations of the sample clearly distinguish it from the low-to-mid wavenumber peaks of lithium sulfide, and the infrared absorption peak shapes of the two samples differ significantly: lithium sulfide exhibits peaks in the 3000-3500 cm⁻¹ range. -1 ¹ The SH-related peaks are more pronounced in the region, while those for lithium chloride are more pronounced in the 500–700 cm⁻¹ region. -1 The Cl⁻ characteristic peak in the region is stronger. No absorption peaks of other impurity functional groups were observed in the spectrum, confirming that the sample contains lithium sulfide (Li₂S) and lithium chloride (LiCl) with high purity.

[0098] X-ray diffraction (XRD) detects the coherent scattering signal of X-rays by a crystal, obtaining information on the position, intensity, and shape of diffraction peaks, enabling phase characterization, crystallinity analysis, and crystal structure characterization. This invention uses XRD to test lithium sulfide and lithium chloride samples, combined with background subtraction techniques to improve signal identification. Figures 6 and 7 show the XRD patterns of lithium sulfide (Li₂S) and lithium chloride (LiCl) samples, including the original spectra (red), the spectra after background subtraction (blue), and the diffraction peak positions from the standard PDF card (black vertical lines).

[0099] As can be seen from the XRD pattern, the positions of the characteristic diffraction peaks in the pattern are highly consistent with the corresponding standard cards (black markings at the bottom of Figures 6 and 7). Figure 6 The diffraction peaks at 2θ≈27°, 30°, 45°, and 55° are consistent with the diffraction signals of the standard crystal plane of lithium sulfide. Figure 7 The diffraction peaks at 2θ≈27°, 31°, 36°, and 45° correspond one-to-one with the diffraction signals of the standard crystal plane of lithium chloride. The blue spectral lines after background subtraction further eliminate baseline drift interference and highlight peak shape characteristics. All characteristic peaks are free of obvious impurities or broadened diffuse peaks, indicating that both samples are high-purity crystalline phases without significant impurities or amorphous phases. Regarding crystallinity and crystal integrity, the sharp and high-intensity diffraction peaks of the original red spectral lines indicate good crystallinity and regular atomic arrangement within the crystal. After background subtraction (blue spectral lines), the peak symmetry is excellent, with no obvious broadening or splitting, reflecting few crystal defects, uniform grain size, and no additional lattice distortion introduced during preparation or testing.

[0100] Example 3

[0101] The difference from Example 1 is that biochar is replaced with industrial activated carbon waste. Otherwise, it is the same as Example 1.

[0102] Example 4

[0103] The difference from Example 1 is that starch is replaced with an aqueous solution of polyacrylamide, wherein the amount of polyacrylamide used is 5g and the concentration of the aqueous solution is 1wt%. The rest is the same as in Example 1.

[0104] Example 5

[0105] The difference from Example 1 is that isopropanol is replaced with a mixed solvent of ethanol and tetrahydrofuran in a volume ratio of 1:1. Everything else is the same as in Example 1.

[0106] Example 6

[0107] The difference from Example 1 is that isopropanol is replaced with ethanol. Otherwise, it is the same as Example 1.

[0108] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A process for preparing lithium-sulfur electrolyte raw materials based on waste salt, characterized in that, include Step 1: Raw material pretreatment: Using industrial waste salt as sulfur source, lithium-rich waste residue as lithium source, and waste carbon as reducing agent, mix them evenly with binder, granulate, and obtain mixed particles; the lithium-rich waste residue contains lithium sulfate, lithium chloride, lithium carbonate, lithium oxide, lithium hydroxide, silicon dioxide or aluminum oxide; Step 2: High-temperature calcination: The mixed particles are calcined to obtain a mixture; Step 3: Ball milling separation: The obtained mixture is mixed with solvent A and then ball milled to separate the solid and liquid phases, resulting in a liquid phase containing sulfides and a solid phase containing other substances. The ball milling speed is 100-500 r / min and the ball milling time is 1-6 hours. Step 4: Impurity recovery: The obtained solid phase containing other substances is subjected to acid leaching and condensation to obtain silicon tetrachloride. The acid leaching treatment is carried out at a temperature of 80-180℃ for 1-6 hours. Step 5: Sodium removal treatment: The liquid phase containing sulfides is mixed and dissolved with lithium chloride, and the solution containing lithium chloride and lithium sulfide is obtained by solid-liquid separation; Step 6: Product preparation: The solution containing lithium chloride and lithium sulfide is concentrated under reduced pressure to obtain a mixed product of lithium chloride and lithium sulfide. The ratio is further adjusted to obtain lithium-sulfur electrolyte raw material.

2. The process according to claim 1, characterized in that, The main component of the industrial waste salt is sodium sulfate, which comes from the non-ferrous smelting, chemical and new energy industries. The waste charcoal is selected from at least one of the following: industrial activated carbon waste, raw charcoal powder waste, coal gasification activated carbon waste, coke waste, and biochar. The binder is an aqueous solution of one or more of starch, polyacrylamide, and polyaluminum sulfate. The sulfur source, lithium source, waste char, and binder are adjusted according to the sodium sulfate content in industrial waste salt, the lithium compound content in lithium-rich waste residue, and the purity of the target product to ensure that sulfate can be fully reduced and lithium can be fully converted into lithium sulfide in the subsequent calcination reaction.

3. The process according to claim 1, characterized in that, The particle size of the mixed particles is 1-15 cm; The calcination is carried out in a muffle furnace or rotary kiln calcination equipment; The calcination temperature is 900-1500℃; The calcination atmosphere can be an inert gas protective atmosphere or a closed atmosphere; The calcination time is 1 to 6 hours.

4. The process according to claim 1, characterized in that, The solid-liquid ratio of the mixture to solvent A is 1:(5-10) (g / mL).

5. The process according to claim 1, characterized in that, The solvent A is C. 1-6 At least one of the following: alcohol solvent A, tetrahydrofuran, hexamethylphosphoramide, or ethylene glycol.

6. The process according to claim 1, characterized in that, The acid is one or more of hydrochloric acid, perchloric acid, nitric acid or sulfuric acid; The acid concentration is 1-12 mol / L.

7. The process according to claim 1, characterized in that, The amount of lithium chloride used is 0.3-0.6 times the mass of the sulfide-containing liquid phase; The mixing and dissolving process is as follows: under low temperature conditions of 0-10℃, the mixture is stirred at a speed of 100-200r / min for 0.5-2 hours. The vacuum concentration conditions are rotary evaporation at 40-80℃ and 0.05-0.09MPa.

8. The process according to claim 1, characterized in that, The mixed product is used to adapt to the formulation requirements of solid lithium-sulfur electrolytes with a molar ratio of lithium sulfide, lithium chloride, and phosphorus pentasulfide of 4:3:1 or 5:2:1.

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