Lithium sulfide precursor, preparation method thereof and lithium sulfide material
By preparing a spherical porous lithium-sulfur compound matrix with high specific surface area and filling it with carbon, the problems of uneven mixing of lithium-sulfur compounds and carbon sources and close carbonization decomposition temperatures were solved, thus achieving high purity and efficient carbothermic reduction reaction of lithium sulfide.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-10
AI Technical Summary
In existing technologies, uneven mixing of lithium-sulfur compounds and carbon sources, along with the close proximity of carbonization decomposition temperatures, leads to numerous side reactions, affecting the purity of lithium sulfide and the efficiency of carbothermic reduction reactions.
By employing the principles of gas-phase molecular adsorption and gas-phase chemical deposition, a spherical porous lithium-sulfur compound matrix with high specific surface area is prepared, and carbon is filled into its porous structure to form a lithium sulfide precursor, ensuring the completeness and efficiency of the carbothermic reduction reaction.
This improved the purity and reaction efficiency of lithium sulfide products, reduced the occurrence of side reactions, and enhanced the cycle stability and electrochemical performance of the material.
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Figure CN121823482A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of lithium ion battery solid electrolyte, in particular to a lithium sulfide precursor, a preparation method thereof and a lithium sulfide material. BACKGROUND
[0002] In the field of lithium ion battery solid electrolyte, sulfide solid electrolyte is considered as one of the most likely commercialized solid electrolyte systems in the short term due to its high ionic conductivity and good interface performance. The current preparation of sulfide solid electrolyte requires the precursor lithium sulfide to have extremely high purity in order to reduce the adverse effects such as the generation of side reactions in the subsequent battery cycle process, the reduction of resistivity and the like caused by impurities. This also requires the purity of the lithium sulfide precursor to be high enough and the reaction process of generating lithium sulfide to be complete without residual raw materials.
[0003] One of the current mainstream processes for preparing lithium sulfide is carbon thermal reduction reaction, which mainly utilizes the reducing property of carbon to obtain lithium sulfide (Li2S) product through high-temperature chemical reaction of lithium sulfide compound such as lithium sulfate and carbon source after compounding.
[0004] In the currently disclosed technical literature for preparing lithium sulfide by carbothermal reduction, there are generally two methods for compounding lithium sulfide compounds and carbon sources. The first method is a solid-phase physical mixing method of lithium sulfide compounds and carbon source materials. For example, anhydrous lithium sulfate and a carbon source polyvinyl alcohol are mixed in a high-speed mixer in a certain proportion and then ball milled, and then the material is calcined after ball milling to obtain a lithium sulfide material. However, such a solid-phase mixing method can easily lead to uneven mixing of lithium sulfide compounds and carbon sources at the microscale, resulting in incomplete carbothermal reduction reaction of the subsequent carbon source, leaving excess carbon impurities or unreacted lithium sulfide compounds in the prepared lithium sulfide. The second method is to dissolve the solid-phase lithium sulfide compounds and the soluble carbon source in a liquid solvent to form a homogeneous solution, and then remove the solvent through different drying processes to obtain a solid mixture precursor for preparing lithium sulfide by carbothermal reaction. However, the soluble carbon source in the precursor needs to be carbonized and decomposed at a high temperature to obtain elemental carbon, and the carbonization temperature is often very close to the reaction temperature for preparing lithium sulfide. It is found that such a multi-reaction system has many side reactions during the temperature rising process, resulting in the formation of many products including lithium sulfide, which reduces the purity of the target product lithium sulfide. At the same time, during the temperature rising process, the carbonization and decomposition of the carbon source needs to emit a large amount of decomposition gas products, causing the structure of the mixture precursor particles to collapse, and the remaining elemental carbon cannot be in close contact with the lithium sulfide molecules in the original precursor particles, affecting the effective progress of the carbothermal reduction reaction.
[0005] In view of this, the present application is proposed. SUMMARY
[0006] The present application aims to provide a lithium sulfide precursor, a preparation method thereof, and a lithium sulfide material. The present application first prepares a spherical porous lithium sulfide compound matrix with a high specific surface area, and then obtains a lithium sulfide precursor with carbon filled in the porous structure of the spherical porous lithium sulfide compound matrix through gas-phase molecular adsorption and gas-phase chemical deposition principles, which is used for the carbothermal reduction reaction for preparing lithium sulfide. The lithium sulfide precursor obtained by the present technology can make the carbothermal reduction reaction of lithium sulfide more complete and efficient, and can improve the purity of the lithium sulfide product.
[0007] The present application is implemented as follows: In a first aspect, the present application provides a lithium sulfide precursor, which comprises a spherical porous lithium sulfide compound matrix and carbon filled in the porous structure of the spherical porous lithium sulfide compound matrix; the sphericity of the spherical porous lithium sulfide compound matrix is 0.7-1.0, and the spherical porous lithium sulfide compound matrix has large pores, mesopores, and micropores, wherein the large pore rate is ≥18%, the mesopore rate is ≥70%, the micropore rate is ≥5%, the total pore volume is ≥0.15 cc / g, and the specific surface area is ≥70 m 2 / g.
[0008] In an alternative embodiment, the macropore rate is 18-23%, the mesopore rate is 70-77%, the micropore rate is 5-10%, the total pore volume is 0.15-0.25 cc / g, and the specific surface area is 70-140 m 2 / g.
[0009] In an alternative embodiment, the particle size of the lithium sulfide precursor ranges from 0.1 to 50 μm; and / or, the elemental molar ratio of lithium, sulfur and carbon in the lithium sulfide precursor is 1:0.5-1.0:0.5-1.0; and / or, the water content of the lithium sulfide precursor is 0-0.1 wt.%; and / or, the Na impurity content in the lithium sulfide precursor is 0.1-20 ppm, the K impurity content is 0.1-20 ppm, the Ca impurity content is 0.1-20 ppm, the Fe impurity content is 0.1-20 ppm, the Cu impurity content is 0.1-20 ppm, and the Mg impurity content is 0.1-20 ppm.
[0010] In a second aspect, the present application provides a method for preparing a lithium sulfide precursor, comprising: mixing a lithium source, a dilute sulfuric acid solution and an organic pore-forming agent to obtain a mixture; subjecting the mixture to atomization drying and pore-forming drying to obtain a spherical porous lithium sulfide compound matrix;
[0011] In an alternative embodiment, the molar ratio of lithium in the lithium source to sulfur in the dilute sulfuric acid solution is 2-2.5:1; and / or, the amount of the organic pore-forming agent added is 10-70 wt.% of the total amount of the lithium source and the organic pore-forming agent.
[0012] In an alternative embodiment, the inlet temperature of the atomization drying is 150-300°C, and the outlet temperature is 90-120°C; and / or, the temperature of the pore-forming drying is 300°C-900°C, and the holding time is 1-72 h.
[0013] In an alternative embodiment, the mixture further comprises adjusting the pH of the mixture to 5-7 before the atomization drying.
[0014] In an alternative embodiment, the amount of the carbon source gas introduced is 0.5-3 L / min; and / or, the amount of the carrier gas introduced is 0.5-4 L / min; And / or, the heating conditions are a heating temperature of 500-700℃ and a holding time of 1-72h.
[0015] In an optional embodiment, the lithium source includes one or more of LiOH, Li2CO3, LiHCO3, pure elemental Li, and Li2O; And / or, the concentration of the dilute sulfuric acid solution is 1-5 mol / L; And / or, the organic pore-forming agent includes one or more of P123, F127, PVA, amylose and amylopectin; And / or, the carbon source gas includes one or a mixture of more than one of methane, acetylene, ethylene and propane; And / or, the carrier gas includes one or more of nitrogen and argon.
[0016] Thirdly, the present invention provides a lithium sulfide material prepared from a lithium sulfide precursor as described in any of the foregoing embodiments, or prepared from a lithium sulfide precursor prepared by a method for preparing a lithium sulfide precursor according to any of the foregoing embodiments.
[0017] The present invention has the following beneficial effects: The method for preparing lithium sulfide precursors provided by this invention involves first creating pores with an organic pore-forming agent to prepare a spherical porous lithium-sulfur compound matrix with a high specific surface area. Then, through gas-phase molecular adsorption and gas-phase chemical deposition, a lithium sulfide precursor with carbon-filled porous structure within the spherical porous lithium-sulfur compound matrix is obtained for the carbothermic reduction reaction of lithium sulfide. This spherical porous lithium-sulfur compound matrix has abundant mesopores (2-50 nm), with a mesopore rate exceeding 70%. When using a carbon source gas for filling, the carbon reducing agent can be adsorbed into the particle interior, allowing for sufficient contact between the reducing agent and the spherical porous lithium-sulfur compound matrix, improving reaction integrity and resulting in higher purity of the finished product. The abundant pore structure provides more active sites, lowering the reaction energy and enabling a more complete reaction at the same temperature. The spherical particles have a high tap density, allowing for more material to be packed in the same volume, improving production efficiency. The porous structure provides a channel for water vapor to disperse during drying, preventing incomplete drying of bound water within the particles and reducing high water content, thus minimizing side reactions. The lithium sulfide precursor obtained by this technology enables the carbothermic reduction reaction of lithium sulfide to proceed more completely and efficiently, and can improve the purity of lithium sulfide products. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a SEM image of the spherical porous lithium-sulfur compound matrix provided in Example 1 of the present invention at a scale bar of 50 μm; Figure 2 This is a SEM image of the spherical porous lithium-sulfur compound matrix provided in Example 1 of the present invention, with a scale bar of 10 μm. Figure 3 The image shows a spherical porous lithium-sulfur compound matrix provided in Example 1 of this invention, with a scale bar of 5 μm. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0021] This invention provides a lithium sulfide precursor, comprising a spherical porous lithium-sulfur compound matrix and carbon filling the porous structure within the spherical porous lithium-sulfur compound matrix; the sphericity of the spherical porous lithium-sulfur compound matrix is 0.7-1.0, and the spherical porous lithium-sulfur compound matrix has macropores, mesopores, and micropores, wherein the macroporosity is ≥18%, the mesoporosity is ≥70%, the microporosity is ≥5%, the total pore volume is ≥0.15 cc / g, and the specific surface area is ≥70 m². 2 / g.
[0022] In this invention, by constructing a spherical porous lithium-sulfur compound matrix, the spherical structure makes the matrix more uniform during subsequent carbon deposition in the vapor phase, resulting in a more even distribution of the porous structure. This improves reaction efficiency and ensures complete conversion of the precursor reactants, leading to higher purity lithium sulfide. Even after carbon filling, the lithium sulfide precursor retains its spherical structure. As a precursor in the preparation of lithium sulfide materials, this allows for a more complete and efficient carbothermic reduction reaction. Furthermore, due to the high packing density of the spherical particles, more precursor material can be filled into the carbothermic reactor for the reaction.
[0023] The limitation of "sphericity of 0.7-1.0" results in low interparticle friction in the spherical porous lithium-sulfur compound matrix, leading to denser packing and improved reaction efficiency. Furthermore, the spherical structure ensures uniform stress distribution, reducing particle breakage due to stress concentration during use and enhancing the material's cycle stability. The regular spherical morphology also allows for more uniform contact between the matrix and the electrolyte and active materials (such as sulfur), preventing localized reaction imbalances.
[0024] The limitations on macroporosity, mesoporosity, microporosity, total pore volume, and specific surface area in this application all reflect the porous structure of the spherical porous lithium-sulfur compound matrix in this application.
[0025] Among them, macropores (>50nm) have large pore spaces, allowing large molecules, particles, or fluids to pass through rapidly, and can accommodate a large amount of carbonaceous material. Preferably, the macroporosity in this invention is 18-23%.
[0026] The mesopores (2-50 nm) have a moderate pore size, which can well accommodate carbon materials to form a conductive network. The mesopores provide a buffer space after carbon filling, and at the same time, they can cope with volume fluctuations during subsequent lithium sulfide formation or charge-discharge processes, maintaining structural integrity. Preferably, the mesopore rate of the present invention is 70-77%.
[0027] The high adsorption energy of micropores (<2nm) can firmly fix carbon particles, preventing carbon from falling off during use, while improving the adsorption of reaction intermediates (such as polysulfides) and suppressing the shuttle effect. Micropores can refine the carbon filling morphology, increase the contact area between carbon and the matrix, and between carbon particles, further optimizing the continuity of the conductive network. Preferably, the microporosity in this invention is 5-10%.
[0028] In this invention, the total pore volume is limited to ≥0.15 cc / g to ensure sufficient carbon content, improve the conductivity of the precursor, and avoid electron transport obstruction due to insufficient carbon content. The total pore volume provides ample space for subsequent chemical reactions, ensuring complete reaction and improving precursor utilization. Preferably, the total pore volume in this invention is 0.15-0.25 cc / g.
[0029] In this invention, the specific surface area is limited to ≥70m². 2 The larger specific surface area (70-140 m² / g) increases the contact interface between the matrix and carbon, improving the efficiency of the conductive network. It also increases the reaction interface between the precursor and the electrolyte, accelerating reaction kinetics. The larger specific surface area provides more surface sites, enhancing the loading stability of carbon and improving the adsorption capacity for reactants, thus optimizing the electrochemical performance of the precursor. Preferably, in this invention, the specific surface area is 70-140 m² / g. 2 / g.
[0030] The lithium sulfide precursor provided by this invention has a particle size range of 0.1-50 μm; And / or, the elemental molar ratio of lithium, sulfur and carbon in the lithium sulfide precursor is 1:0.5-1.0:0.5-1.0; And / or, the water content of the lithium sulfide precursor is 0-0.1 wt.%; the porous structure provides a channel for water vapor to disperse during the drying process, avoiding the incomplete drying of bound water inside the particles, which would result in high water content in the particles, and a more thorough dehydration process reduces the generation of side reactions.
[0031] And / or, the lithium sulfide precursor contains 0.1-20 ppm of Na impurities, 0.1-20 ppm of K impurities, 0.1-20 ppm of Ca impurities, 0.1-20 ppm of Fe impurities, 0.1-20 ppm of Cu impurities, and 0.1-20 ppm of Mg impurities.
[0032] Furthermore, the present invention provides a method for preparing a lithium sulfide precursor, which includes the following steps: S1. A mixture of lithium source, dilute sulfuric acid solution and organic pore-forming agent is atomized and dried to obtain a spherical porous lithium-sulfur compound matrix.
[0033] (1) Mix the lithium source, dilute sulfuric acid solution and organic pore-forming agent, cool to room temperature, and adjust the pH of the mixture to 5-7 to obtain a lithium-sulfur mixed solution with pore-forming agent embedded.
[0034] The molar ratio of lithium in the lithium source to sulfur in the dilute sulfuric acid solution is 2-2.5:1; the concentration of the dilute sulfuric acid solution is 1-5 mol / L; and the amount of organic pore-forming agent added is 10-70 wt.% of the total amount of lithium source and organic pore-forming agent.
[0035] The lithium source includes, but is not limited to, one or more of LiOH, Li2CO3, LiHCO3, pure elemental Li, and Li2O; the organic pore-forming agent includes, but is not limited to, one or more of P123, F127, PVA, amylose, and amylopectin.
[0036] In this invention, one or more of the following known and commercially available organic pore-forming agents are selected: P123 (polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer), F127 (also known as poloxamer 407), PVA (polyvinyl alcohol), amyl starch, and amylopectin. Combined with subsequent specific pore-forming processes, the organic pore-forming agent in this invention can be used to design the porous structure of the matrix, resulting in high pore size consistency and adjustable pore volume. A more precise ratio of lithium-sulfur compounds to carbon can be obtained by calculating the adsorption amount. Furthermore, the organic pore-forming agent can be directly burned off during sintering, leaving a porous structure, unlike inorganic pore-forming agents which require washing removal, thus avoiding the destruction of the precursor's special structure during washing.
[0037] (2) Atomization drying The lithium-sulfur mixed solution containing the pore-forming agent was fed into an atomizing drying device using a peristaltic pump for atomizing and drying, resulting in spherical non-porous lithium-sulfur salt microspheres.
[0038] Among them, atomization drying can rapidly transform the lithium-sulfur mixed solution containing the pore-forming agent into granular, near-spherical or semi-spherical solids with uniform particle size, good flowability, and the ability to retain the original activity of the material.
[0039] In this invention, the atomizing drying equipment includes, but is not limited to, one of the following: centrifugal spray dryer, pressure spray dryer, fluidized bed dryer, rotary drum dryer, boiling dryer, and two-fluid spray dryer. The inlet air temperature for atomizing drying is 150-300℃, and the outlet temperature is 90-120℃.
[0040] (3) Hole-making and drying A spherical porous lithium sulfide compound matrix was obtained by pore-forming and drying of spherical non-porous lithium sulfide microspheres.
[0041] The pore-forming drying is carried out in a drying device, which includes, but is not limited to, one of the following: vacuum drying oven, rotary flash dryer, rotary vacuum dryer, tunnel hot air oven, forced air oven, box sintering furnace, tube sintering furnace, roller kiln and rotary furnace; the temperature of pore-forming drying is 300℃-900℃, and the holding time is 1-72h.
[0042] In this invention, the organic pore-forming agent is burned off at a higher temperature, thereby forming a spherical porous lithium-sulfur compound matrix. P123 or F127 has a relatively low thermal decomposition temperature, completely burning off at 300-450℃. The decomposition process is staged: first, side chains are lost at 200-300℃, and the main chain breaks above 350℃, leaving pores without requiring excessively high temperatures. PVA (polyvinyl alcohol): has a slightly higher thermal decomposition temperature, completely decomposing at 400-600℃. Degradation begins around 400℃, and above 500℃, it is completely converted into gas (CO2, H2O, etc.), avoiding residual carbon. Amylose or amylopectin (natural polysaccharides): can be burned off at 350-550℃. Below 300℃, it undergoes dehydration and carbonization first; above 350℃, the carbonization products further oxidize and decompose, requiring sufficient oxygen to avoid residual carbon.
[0043] The present invention specifies a pore-forming drying temperature of 300℃-900℃, which can ensure that the organic pore-forming agent is fully burned off to form a porous structure.
[0044] S2. A carbon source gas and a carrier gas are introduced into a spherical porous lithium-sulfur compound matrix under heating conditions to obtain a lithium sulfide precursor in which carbon is filled in the porous structure of the spherical porous lithium-sulfur compound matrix.
[0045] In this invention, a carbon source gas is used as the carbon source. The gas can pass through the porous structure of the spherical porous lithium-sulfur compound matrix, thereby being adsorbed into the porous structure of the matrix. The gas is uniformly distributed throughout the matrix, ensuring sufficient contact between the carbothermic reducing agent and the lithium-sulfur compound. Furthermore, the precise ratio of the reactants can be designed based on the pore structure, improving the reaction integrity of the composite precursor and resulting in higher purity of the lithium sulfide product. In this invention, the spherical porous lithium-sulfur compound matrix, with its abundant micropores and mesopores, provides more active sites for carbothermic reduction, reducing the reaction energy and making the reaction more complete and efficient.
[0046] The carbon source gas flow rate is 0.5-3 L / min; the carrier gas flow rate is 0.5-4 L / min; the heating temperature is 500-700℃; and the holding time is 1-72 h.
[0047] The carbon source gas includes, but is not limited to, one or a mixture of more than one of methane, acetylene, ethylene and propane; the carrier gas includes, but is not limited to, one or a mixture of more than one of nitrogen and argon.
[0048] In addition, the present invention provides a lithium sulfide material prepared from the above-mentioned lithium sulfide precursor, or prepared from a lithium sulfide precursor obtained by the above-mentioned method for preparing lithium sulfide precursor.
[0049] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0050] Example 1 This embodiment provides a lithium sulfide precursor, the preparation method of which includes: S1. Prepare 1L of 2mol / L dilute sulfuric acid solution, add 4mol of LiOH powder, stir to room temperature, and adjust the pH to 6 by adding a small amount of the same concentration of dilute sulfuric acid solution dropwise; add pore-forming agent P123, the amount of pore-forming agent P123 being 40% of the volume of the dilute sulfuric acid solution, and after P123 is completely dissolved, pass it into a two-fluid spray drying instrument, setting the inlet air temperature to 200℃ and the outlet air temperature to 100℃. After spray drying, obtain non-porous lithium sulfide microspheres embedded with pore-forming agent P123; place the non-porous lithium sulfide microspheres in a box sintering furnace, and heat to 700℃ at 5℃ / min under air atmosphere and hold for 1h to obtain a spherical porous lithium sulfide compound matrix rich in mesopores. From Figure 1 , Figure 2 and Figure 3 As can be seen from a macroscopic perspective, the materials are all spherical particles with a certain degree of sphericity and have a rich porous structure.
[0051] S2. The obtained spherical porous lithium-sulfur compound matrix is placed in a rotary furnace, nitrogen gas is introduced at 3L / min, the temperature is raised to 600℃ and held, acetylene gas is introduced at 2L / min during the holding time, and the holding time is 1h to obtain the lithium sulfide precursor.
[0052] Example 2 S1. Prepare 1L of 2mol / L dilute sulfuric acid solution, add 4mol of LiOH powder to it, stir to room temperature, and add a small amount of the same concentration of dilute sulfuric acid solution to adjust the pH to 6; add pore-forming agent F127, the amount of pore-forming agent F127 is 40% of the volume of dilute sulfuric acid solution, and after F127 is completely dissolved, pass it into a two-fluid spray drying instrument, set the inlet air temperature to 200℃ and the outlet air temperature to 100℃, and after spray drying, obtain non-porous lithium sulfide microsphere material embedded with pore-forming agent F127; place the non-porous lithium sulfide microsphere material in a box sintering furnace, and heat it to 700℃ at 5℃ / min in air atmosphere and hold it for 1h to obtain a spherical porous lithium sulfide compound matrix rich in mesopores.
[0053] S1. The obtained spherical porous lithium-sulfur compound matrix is placed in a fluidized bed, nitrogen gas is introduced at 3L / min, the temperature is raised to 600℃ and held at that temperature, acetylene gas is introduced at 2L / min during the holding time, and the holding time is 1h to obtain the lithium sulfide precursor.
[0054] Example 3 S1. Prepare 1L of 2mol / L dilute sulfuric acid solution, add 4mol of LiOH powder to it, stir to room temperature, and add a small amount of the same concentration of dilute sulfuric acid solution to adjust the pH to 6; add pore-forming agent PVA, the amount of pore-forming agent PVA added is 40% of the volume of dilute sulfuric acid solution, after PVA is completely dissolved, pass it into a two-fluid spray dryer, set the inlet air temperature to 200℃ and the outlet air temperature to 100℃, and after spray drying, obtain non-porous lithium sulfide microsphere material with pore-forming agent PVA embedded; place the non-porous lithium sulfide microsphere material in a box sintering furnace, and heat it to 700℃ at 5℃ / min in air atmosphere and hold it for 1h to obtain a spherical porous lithium sulfide compound matrix rich in mesopores.
[0055] S2. The obtained spherical porous lithium-sulfur compound matrix is placed in a rotary furnace, nitrogen gas is introduced at 3L / min, the temperature is raised to 650℃ and held, acetylene gas is introduced at 2L / min during the holding time, and the holding time is 1h to obtain the lithium sulfide precursor.
[0056] Example 4 S1. Prepare 1L of 2mol / L dilute sulfuric acid solution, add 4.4mol of Li2CO3 powder to it, stir to room temperature, and add a small amount of the same concentration of dilute sulfuric acid solution to adjust the pH to 5; add pore-forming agent amylose, the amount of pore-forming agent amylose is 10% of the volume of dilute sulfuric acid solution, after the amylose is completely dissolved, pass it into a two-fluid spray dryer, set the inlet air temperature to 150℃ and the outlet air temperature to 90℃, and after spray drying, obtain non-porous lithium sulfide microsphere material embedded with pore-forming agent amylose; place the non-porous lithium sulfide microsphere material in a box sintering furnace, and heat it to 350℃ at 5℃ / min in air atmosphere and hold it for 72h to obtain a spherical porous lithium sulfide compound matrix rich in mesopores.
[0057] S2. The obtained spherical porous lithium-sulfur compound matrix is placed in a rotary furnace, nitrogen gas is introduced at 0.5 L / min, the temperature is raised to 500℃ and held, methane gas is introduced at 0.5 L / min during the holding time, and the holding time is 72 h to obtain the lithium sulfide precursor.
[0058] Example 5 S1. Prepare 1L of 2mol / L dilute sulfuric acid solution, add 5mol of Li2O powder to it, stir to room temperature, and add a small amount of the same concentration of dilute sulfuric acid solution to adjust the pH to 7; add pore-forming agent amylopectin, the amount of pore-forming agent amylopectin added is 70% of the volume of dilute sulfuric acid solution, after the amylopectin is completely dissolved, pass it into a two-fluid spray dryer, set the inlet air temperature to 300℃ and the outlet air temperature to 120℃, and after spray drying, obtain non-porous lithium sulfide microsphere material embedded with pore-forming agent amylopectin; place the non-porous lithium sulfide microsphere material in a box sintering furnace, and heat it to 500℃ at 5℃ / min under air atmosphere and hold for 24h to obtain a spherical porous lithium sulfide compound matrix rich in mesopores.
[0059] S2. The obtained spherical porous lithium-sulfur compound matrix is placed in a rotary furnace, argon gas is introduced at a rate of 4 L / min, the temperature is raised to 700℃ and held at that temperature, ethylene gas is introduced at a rate of 3 L / min during the holding period, and the holding time is 24 h to obtain the lithium sulfide precursor.
[0060] Comparative Example 1 This comparative example provides a lithium sulfide precursor, the preparation method of which includes: Prepare 1L of 2mol / L dilute sulfuric acid solution, add 4mol of LiOH powder to it, stir to room temperature, add a small amount of the same concentration of dilute sulfuric acid solution to adjust the pH to 6, and then add glucose to dissolve it so that the elemental ratio S:C = 1:1; without adding any additional pore-forming agent, pass it into a two-fluid spray dryer, set the inlet air temperature to 200℃ and the outlet air temperature to 100℃, and obtain the control particles after spray drying.
[0061] Comparative Example 2 This comparative example is basically the same as Example 1, except that the pore-forming agent used in this comparative example is NaCl.
[0062] Comparative Example 3 This comparative example is basically the same as Example 1, except that the pore-forming agent used in this comparative example is nano-calcium carbonate.
[0063] Comparative Example 4 This comparative example is basically the same as Example 1, except that the pore-forming agent used in this comparative example is the organic polymer material SBS (styrene-butadiene-styrene block copolymer).
[0064] Comparative Example 5 This comparative example is basically the same as Example 1, except that in this comparative example, instead of using carbon source gas, glucose is used as the carbon source. Furthermore, S2 is adjusted as follows: the obtained spherical porous lithium-sulfur compound matrix and glucose are mixed and ground, placed in a rotary kiln, nitrogen gas is introduced at 3L / min, the temperature is raised to 600℃ and held for 1 hour to obtain the lithium sulfide precursor.
[0065] Experimental Example 1 The spherical porous lithium-sulfur compound matrices prepared in the above examples and comparative examples were subjected to performance testing. The test items included: multi-point BET specific surface area, total pore volume, micropore volume, microporosity, mesopore volume, and mesoporosity.
[0066] The detection methods include: (1) Multi-point specific surface area: The specific surface area is calculated by using a microporous analyzer to test the amount of nitrogen adsorbed by the sample under different partial pressures, calculating the amount of nitrogen adsorbed by a single layer using BET theory; (2) Total pore volume: The sum of the volumes of macropores, mesopores and micropores in the material, measured using a micropore analyzer; (3) Micropore volume: The micropore volume was measured using a micropore analyzer and calculated based on the NLDFT model; (4) Microporosity: The proportion of micropore volume to total pore volume; (5) Mesopore volume: The mesopore volume was measured using a micropore analyzer and calculated based on the BJH model; (6) Mesopority: The proportion of mesopore volume to total pore volume.
[0067] Please refer to Table 1 for the test results: Table 1. Statistical table of performance test results of spherical porous lithium-sulfur compound matrices of different examples
[0068] As can be seen from the table above, the spherical porous lithium-sulfur compound matrix prepared in the embodiments of the present invention has a significantly larger specific surface area and total pore volume than the comparative examples, and the proportion of mesopores reaches more than 70%, which can meet the requirements of chemical vapor deposition adsorption. In contrast, in Comparative Example 1, no pore-forming process was performed; glucose, dilute sulfuric acid, and LiOH powder were directly mixed, resulting in a significant decrease in both specific surface area and total pore volume. Comparative Example 2 used NaCl as a pore-forming agent, but even using the operating method of the present invention, it was impossible to obtain the spherical porous lithium-sulfur compound matrix with high specific surface area and high mesopore ratio of the present application. The data from Comparative Example 3 shows that sintering with nano-sodium carbonate cannot produce a suitable pore structure, mainly because the calcium oxide material produced by sintering calcium carbonate blocks the pores, resulting in a pore structure dominated by macropores. The data from Comparative Example 4 shows that due to the lack of oxygen-containing groups, a suitable pore structure cannot be obtained through sintering. The data from Comparative Example 5 shows that changing the carbon source has little effect on the porosity distribution.
[0069] Experimental Example 2 This experimental example uses the precursor materials obtained in the above-described embodiments and comparative examples to prepare lithium sulfide materials. The specific preparation method includes thermal sintering. Subsequently, the purity of the different prepared lithium sulfide materials was tested using ICP-OES and carbon-sulfur analysis. The test data are shown in Table 2. Table 2. Statistical table of purity test results of lithium sulfide materials prepared from different precursor materials.
[0070] As can be seen from the table above, the impurity content of the lithium sulfide material prepared in the embodiments of the present invention is significantly lower than that of the comparative examples. In Comparative Example 1, no pore-forming process was performed; glucose, dilute sulfuric acid, and LiOH powder were directly mixed, resulting in excessive levels of carbon (C) impurities. Comparative Example 2 showed excessive levels of both C and Na impurities, requiring the use of an organic pore-forming agent. Data from Comparative Example 3 shows that Ca could not be removed, and C, Na, and K levels were also excessive. Data from Comparative Example 4 shows that due to the lack of a porous structure, the contact area between the C material and the matrix material was small, resulting in incomplete reaction and significant residue. Data from Comparative Example 5 shows that due to the use of a grinding method for carbon doping, the porous structure was not effectively utilized, resulting in a higher residual C content compared to the embodiments and poor product purity.
[0071] In summary, the method for preparing lithium sulfide precursors provided by this invention involves first creating pores using an organic pore-forming agent to prepare a spherical porous lithium-sulfur compound matrix with a high specific surface area. Then, through gas-phase molecular adsorption and gas-phase chemical deposition, a lithium sulfide precursor with carbon-filled porous structure within the spherical porous lithium-sulfur compound matrix is obtained for the carbothermic reduction reaction of lithium sulfide. This spherical porous lithium-sulfur compound matrix has abundant mesopores (2-50 nm), with a mesopore rate exceeding 70%. When using a carbon source gas for filling, the carbon reducing agent can be adsorbed into the particle interior, allowing for sufficient contact between the reducing agent and the spherical porous lithium-sulfur compound matrix, improving reaction integrity and resulting in higher purity of the finished product. The abundant pore structure provides more active sites, lowering the reaction energy and enabling a more complete reaction at the same temperature. The spherical particles have a high tap density, allowing for more material to be packed in the same volume, improving production efficiency. The porous structure provides a channel for water vapor to disperse during drying, preventing incomplete drying of bound water within the particles and reducing high water content, thus minimizing side reactions. The lithium sulfide precursor obtained by this technology enables the carbothermic reduction reaction of lithium sulfide to proceed more completely and efficiently, and can improve the purity of lithium sulfide products.
[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A lithium sulfide precursor, characterized in that, It comprises a spherical porous lithium-sulfur compound matrix and carbon filling the porous structure within the spherical porous lithium-sulfur compound matrix; the sphericity of the spherical porous lithium-sulfur compound matrix is 0.7-1.0, and the spherical porous lithium-sulfur compound matrix has macropores, mesopores, and micropores, wherein the macroporosity is ≥18%, the mesoporosity is ≥70%, the microporosity is ≥5%, the total pore volume is ≥0.15cc / g, and the specific surface area is ≥70m². 2 / g.
2. The lithium sulfide precursor according to claim 1, characterized in that, The macroporosity is 18-23%, the mesoporosity is 70-77%, the microporosity is 5-10%, the total pore volume is 0.15-0.25 cc / g, and the specific surface area is 70-140 m². 2 / g.
3. The lithium sulfide precursor according to claim 1, characterized in that, The particle size range of the lithium sulfide precursor is 0.1-50 μm; And / or, the elemental molar ratio of lithium, sulfur and carbon in the lithium sulfide precursor is 1:0.5-1.0:0.5-1.0; And / or, the water content of the lithium sulfide precursor is 0-0.1 wt.%; And / or, the lithium sulfide precursor contains 0.1-20 ppm of Na impurities, 0.1-20 ppm of K impurities, 0.1-20 ppm of Ca impurities, 0.1-20 ppm of Fe impurities, 0.1-20 ppm of Cu impurities, and 0.1-20 ppm of Mg impurities.
4. A method for preparing a lithium sulfide precursor, characterized in that, It includes: A mixture of lithium source, dilute sulfuric acid solution and organic pore-forming agent is atomized and dried to obtain a spherical porous lithium-sulfur compound matrix. The spherical porous lithium-sulfur compound matrix is heated and then passed through a carbon source gas and a carrier gas to obtain a lithium sulfide precursor in which carbon is filled in the porous structure of the spherical porous lithium-sulfur compound matrix.
5. The method for preparing the lithium sulfide precursor according to claim 4, characterized in that, The molar ratio of lithium in the lithium source to sulfur in the dilute sulfuric acid solution is 2-2.5:1; And / or, the amount of the organic pore-forming agent added is 10-70 wt.% of the volume of the dilute sulfuric acid solution.
6. The method for preparing the lithium sulfide precursor according to claim 4, characterized in that, The inlet air temperature of the atomizing dryer is 150-300℃, and the outlet temperature is 90-120℃; And / or, the temperature for pore drying is 300℃-900℃, and the holding time is 1-72h.
7. The method for preparing the lithium sulfide precursor according to claim 4, characterized in that, Prior to the atomization drying, the mixture is further adjusted to a pH of 5-7.
8. The method for preparing the lithium sulfide precursor according to claim 4, characterized in that, The rate of introduction of the carbon source gas is 0.5-3 L / min; And / or, the carrier gas flow rate is 0.5-4 L / min; And / or, the heating conditions are a heating temperature of 500-700℃ and a holding time of 1-72h.
9. The method for preparing the lithium sulfide precursor according to any one of claims 4-8, characterized in that, The lithium source includes one or more of LiOH, Li2CO3, LiHCO3, pure elemental Li, and Li2O; And / or, the concentration of the dilute sulfuric acid solution is 1-5 mol / L; And / or, the organic pore-forming agent includes one or more of P123, F127, PVA, amylose and amylopectin; And / or, the carbon source gas includes one or a mixture of more than one of methane, acetylene, ethylene and propane; And / or, the carrier gas includes one or more of nitrogen and argon.
10. A lithium sulfide material, characterized in that, It is prepared from the lithium sulfide precursor as described in any one of claims 1-3, or from the lithium sulfide precursor prepared by the method for preparing the lithium sulfide precursor as described in any one of claims 4-9.