Preparation method of sulfide solid electrolyte

Abstract

The invention discloses a preparation method of sulfide solid electrolyte, and belongs to the technical field of solid-state batteries. The preparation method comprises the following steps: performing premixing treatment on sulfur powder and lithium powder under an inert condition to obtain a Li2S precursor, and performing reaction on the Li2S precursor and molten P2S5 in a stirring state at 400-700 DEG C to obtain an electrolyte precursor solution; performing quenching treatment on the electrolyte precursor solution to obtain a block, and performing crushing treatment to obtain first precursor powder; introducing the first precursor powder into a second sealed container, stirring and heating to a molten state, carrying out quenching treatment to obtain a block, and crushing the block to obtain second precursor powder; and sequentially carrying out dry ball milling and sintering treatment on the second precursor powder to obtain the sulfide solid electrolyte. The method has the advantages of simplicity and convenience in operation, simple and efficient production process, low cost, excellent material mixing uniformity and the like, and is convenient for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a method for preparing a sulfide solid electrolyte. Background Art

[0002] All-solid-state batteries offer advantages such as high energy density, rapid charge and discharge, excellent low-temperature performance, high safety, and long life, and have great application potential in electric vehicles and related fields. Solid-state electrolytes, including polymer solid electrolytes, oxide solid electrolytes, and sulfide solid electrolytes, have a significant impact on the performance of all-solid-state batteries. Sulfide solid electrolytes are widely used due to their high ionic conductivity, wide electrochemical window, low grain boundary resistance, and easy film formation. However, sulfide solid electrolytes have the disadvantage of high cost, as their main raw materials are expensive Li2S, P2S5, LiCl, etc.

[0003] The related technology uses cheap Li and S as raw materials to replace expensive Li2S, and realizes the effective synthesis of sulfide solid electrolytes through high-energy ball milling.

[0004] However, the method provided by the related art requires long-term high-energy ball milling, with the ball milling time being as long as 50 hours, making its production process cumbersome and inefficient, and the material mixing uniformity is difficult to control, all of which are not conducive to large-scale industrial production. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a sulfide solid electrolyte, which can solve the technical problems existing in the related art.

[0006] Specifically, the following technical solutions are included:

[0007] A method for preparing a sulfide solid electrolyte, the preparation method comprising:

[0008] Under inert atmosphere protection conditions, sulfur powder and lithium powder are premixed to obtain a Li2S precursor;

[0009] Under inert atmosphere protection, the Li2S precursor and molten P2S5 are introduced into a first sealed container in a molar ratio, and the internal temperature of the first sealed container is raised to 400° C. to 700° C. under stirring to react to obtain an electrolyte precursor solution;

[0010] The electrolyte precursor liquid is quenched to obtain a block, which is then crushed to obtain a first precursor powder of the electrolyte;

[0011] The first precursor powder is introduced into a second sealed container, stirred and heated until it is molten, quenched to obtain a block, and crushed to obtain a second precursor powder of the electrolyte;

[0012] The second precursor powder is subjected to dry ball milling and sintering treatments in sequence to obtain the sulfide solid electrolyte.

[0013] In some possible implementations, the premix processing is performed in a premixing tank, which is configured to have a cooling and temperature control function and adopt a mixing method that combines forward and reverse rotation of the blade.

[0014] In some possible implementations, the molten P2S5 is prepared by the following method:

[0015] Liquid sulfur and liquid phosphorus are placed in a reactor, and reacted, distilled, and cooled in sequence to obtain molten P2S5, wherein the liquid sulfur is obtained by melting sulfur powder, and the liquid phosphorus is obtained by melting phosphorus powder.

[0016] In some possible implementations, the liquid sulfur and the liquid phosphorus are reacted in the reactor at 300° C.-400° C. according to a mass ratio of sulfur:phosphorus=2.57-2.6:1.

[0017] In some possible implementations, the internal temperature of the first sealed container is increased to 400° C.-700° C. at a rate of 1° C. / min-10° C. / min.

[0018] In some possible implementations, the crushing process includes dry coarse crushing and dry fine crushing performed sequentially;

[0019] For the dry coarse crushing, the particle size of the crushed powder is 0.1mm-10mm;

[0020] For the dry fine crushing, the particle size of the crushed powder is 1 μm-100 μm.

[0021] In some possible implementations, the first precursor powder is introduced into a second sealed container and heated with stirring at 400° C.-700° C. until it is in a molten state.

[0022] In some possible implementations, the second precursor powder and ball milling beads are placed in a ball milling jar at a mass ratio of 1:8-15 for dry ball milling, and the dry ball milling time is 10 min-180 min.

[0023] In some possible implementations, for the sintering process, the sintering temperature is 150° C.-500° C., and the holding time is 1 hour-10 hours.

[0024] In some possible implementations, the sulfide solid electrolyte is mLi2S-(1-mbn)(Q y S z )-nP2S5-bLiX, where 0<m≤1, 0<n≤1, 0≤b≤1;

[0025] Q is at least one of Sn, In, P, Si, Ge, As, Al, Zr, Se, and Te;

[0026] X is at least one of F, Cl, Br, I, (BH4)-, (TFSI)-, (FSI)-, (BF4)-, (PF6)-, and (ClO4)-.

[0027] The beneficial effects of the technical solution provided by the embodiment of the present invention include at least:

[0028] The preparation method of the sulfide solid electrolyte provided by the embodiment of the present invention adopts sulfur powder and lithium powder to prepare Li2S precursor, and then the Li2S precursor is mixed with molten state P2S5 and reacted to obtain an electrolyte precursor solution, which effectively avoids the use of expensive Li2S raw materials and is conducive to reducing costs. Subsequently, based on the electrolyte precursor solution, by quenching, block crushing, melting, quenching again, and block crushing process again, not only the mixing uniformity between the components in the sulfide solid electrolyte is increased, but also the amorphization efficiency of the precursor powder material is improved, and deep reaction is achieved. On the basis of reaching a shortened process time, it is conducive to improving product purity. Finally, by dry spheroidal graphite and sintering treatment, a sulfide solid electrolyte with higher purity is prepared. In summary, the preparation method of the sulfide solid electrolyte provided by the embodiment of the present invention has the advantages of easy operation, simple and efficient production process, low cost, excellent material mixing uniformity, the purity of the prepared sulfide solid electrolyte is higher and thus its performance is more excellent, and it is convenient to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A flow chart for preparing an exemplary sulfide solid electrolyte provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] An embodiment of the present invention provides a method for preparing a sulfide solid electrolyte, the preparation method comprising:

[0033] Step S1: Under inert atmosphere protection conditions, sulfur powder and lithium powder are premixed to obtain a Li2S precursor.

[0034] Step S2: Under inert atmosphere protection, introduce the Li2S precursor and the molten P2S5 into a first sealed container in a molar ratio, and heat the internal temperature of the first sealed container to 400°C-700°C under stirring to react and obtain an electrolyte precursor solution.

[0035] Step S3: quenching the electrolyte precursor liquid to obtain a block and crushing it to obtain a first precursor powder of the electrolyte.

[0036] Step S4: introducing the first precursor powder into a second sealed container, stirring and heating it to a molten state, performing a quenching treatment, obtaining a block and crushing it to obtain a second precursor powder of the electrolyte.

[0037] Step S5: dry-milling and sintering the second precursor powder in sequence to obtain a sulfide solid electrolyte.

[0038] The preparation method of the sulfide solid electrolyte provided by the embodiment of the present invention adopts sulfur powder and lithium powder to prepare Li2S precursor, and then the Li2S precursor is mixed with molten state P2S5 and reacted to obtain an electrolyte precursor solution, which effectively avoids the use of expensive Li2S raw materials and is conducive to reducing costs. Subsequently, based on the electrolyte precursor solution, by quenching, block crushing, melting, quenching again, and block crushing process again, not only the mixing uniformity between the components in the sulfide solid electrolyte is increased, but also the amorphization efficiency of the precursor powder material is improved, and deep reaction is achieved. On the basis of reaching a shortened process time, it is conducive to improving product purity. Finally, by dry spheroidal graphite and sintering treatment, a sulfide solid electrolyte with higher purity is prepared. In summary, the preparation method of the sulfide solid electrolyte provided by the embodiment of the present invention has the advantages of easy operation, simple and efficient production process, low cost, excellent material mixing uniformity, the purity of the prepared sulfide solid electrolyte is higher and thus its performance is more excellent, and it is convenient to large-scale industrial production.

[0039] It should be noted that, for step S2, other optional raw materials may be added to the reaction system, and the corresponding raw materials may be selected according to the specific composition of the sulfide solid electrolyte. For example, the chemical formula of the sulfide solid electrolyte is: Li 7-a+b P 1-b M b S 6-a-c N c X a , wherein M is Si, Ge or Sn, N is Se or Te, and X is Cl, Br or I. Accordingly, the other raw materials can be one or more of Si source, Ge source, Sn source, Se source, Te source, Cl source, Br source, and I source. These raw materials can be added in the form of simple substances or compounds. Taking Cl source, Br source or I source as an example, they can be used in the form of corresponding lithium compounds.

[0040] Molten P2S5 can be prepared using currently known P2S5 raw materials, or using liquid sulfur and liquid phosphorus. When molten P2S5 is prepared using liquid sulfur and liquid phosphorus, this operation can be performed sequentially or simultaneously with the preparation of the Li2S precursor.

[0041] In some examples, molten P2S5 is prepared by placing liquid sulfur and liquid phosphorus in a reactor, reacting, distilling, and cooling in sequence to obtain molten P2S5, wherein liquid sulfur is obtained by melting sulfur powder, and liquid phosphorus is obtained by melting phosphorus powder.

[0042] Accordingly, the preparation method of the sulfide solid electrolyte may include the following steps:

[0043] Step S1: Under inert atmosphere protection conditions, sulfur powder and lithium powder are premixed to obtain a Li2S precursor.

[0044] Step S2: placing liquid sulfur and liquid phosphorus in a reactor, reacting, distilling, and cooling in sequence to obtain molten P2S5; introducing a Li2S precursor and molten P2S5 in a molar ratio into a first sealed container under inert atmosphere protection conditions; raising the internal temperature of the first sealed container to 400°C-700°C under stirring to react and obtain an electrolyte precursor solution.

[0045] Step S3: quenching the electrolyte precursor liquid to obtain a block and crushing it to obtain a first precursor powder of the electrolyte.

[0046] Step S4: introducing the first precursor powder into a second sealed container, stirring and heating it to a molten state, performing a quenching treatment, obtaining a block and crushing it to obtain a second precursor powder of the electrolyte.

[0047] Step S5: dry-milling and sintering the second precursor powder in sequence to obtain a sulfide solid electrolyte.

[0048] The following further describes the specific operations and functions of each step involved in the method for preparing the sulfide solid electrolyte provided in the embodiment of the present invention:

[0049] In step S1, sulfur powder and lithium powder are premixed under an inert atmosphere to produce a Li2S precursor. Subsequently, a Li2S precursor is obtained based on the premix. In step S1, low-cost lithium and sulfur powders are used to replace expensive Li2S, significantly reducing raw material costs.

[0050] In some examples, the premix processing is performed in a premix tank, which is configured to have a cooling and temperature control function and adopts a mixing method that combines forward and reverse rotation of the blade.

[0051] On the one hand, blade mixing can achieve efficient dispersion and homogenization of materials, increase the contact area between materials, and achieve uniform mixing of lithium powder and sulfur powder. This is beneficial for improving production efficiency and shortening process time. For example, the corresponding rotation speed of blade mixing can be greater than or equal to 500rpm.

[0052] Furthermore, the mixing method, that is, the stirring method, adopts a method of combining forward and reverse rotation of the blade. This can be performed alternately, or forward and reverse rotation can be performed simultaneously. By adopting a stirring method combining forward and reverse rotation to perform premixing, it is beneficial to further improve the mixing uniformity between materials and shorten the premixing time.

[0053] Illustratively, the forward and reverse rotation speeds are each independently 100 rpm-1000 rpm, and can further be 300 rpm-600 rpm, including but not limited to 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, etc.

[0054] In some examples, the premixing time is 1 min to 180 min, and further can be 1 min to 30 min.

[0055] On the other hand, by giving the premixing tank a cooling and temperature control function, the heat generated by the blade mixing method can be dispersed in a timely manner, the reaction degree of the pre-reaction can be accurately controlled, thermal runaway can be prevented, and ultimately a high-purity and highly uniform Li2S precursor can be obtained.

[0056] In some examples, an inert gas atmosphere can be created in the premixing tank by continuously injecting inert gas into the premixing tank. Moreover, the flow of the inert gas in the premixing tank can drive the movement of sulfur powder and lithium powder, thereby further increasing the mixing uniformity between the materials based on gas convection and shortening the premixing time.

[0057] Adapting to the above scheme, the inert gas can be input from the bottom of the premixing tank, and a pressure relief valve is provided on the top of the premixing tank, thereby allowing the inert gas to be continuously input and moved from bottom to top in the premixing tank, and the pressure can be released in time through the pressure relief valve.

[0058] In some examples, the D50 particle size of the sulfur powder and the lithium powder is independently 0.1 μm-100 μm, further 0.1 μm-10 μm, including but not limited to: 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., which is beneficial for improving the dispersion uniformity and contact area of ​​the sulfur powder and the lithium powder.

[0059] For step S2, liquid sulfur and liquid phosphorus are placed in a reactor, reacted, distilled, and cooled in sequence to obtain molten P2S5. Under inert atmosphere protection conditions, a Li2S precursor and molten P2S5 are introduced into a first sealed container in a molar ratio. The internal temperature of the first sealed container is raised to 400°C-700°C under stirring to react and obtain an electrolyte precursor solution.

[0060] Liquid sulfur is obtained by melting sulfur powder, and liquid phosphorus is obtained by melting phosphorus powder. For example, sulfur powder is melted in a sulfur melting kettle and then transferred to a liquid sulfur storage tank. Yellow phosphorus powder is melted in a phosphorus melting tank and then pumped into a liquid phosphorus storage tank. The liquid sulfur in the liquid sulfur storage tank and the yellow phosphorus in the liquid phosphorus storage tank are then pumped into the reactor.

[0061] P2S5 is a commonly used industrial raw material, and its solid-phase synthesis process is relatively mature. The embodiment of the present invention adopts the solid-phase method to synthesize P2S5, which is beneficial to improving the preparation efficiency and ensuring the high quality of P2S5.

[0062] In some examples, liquid sulfur and liquid phosphorus are reacted in a reactor at 300°C to 400°C at a mass ratio of sulfur to phosphorus of 2.57-2.6:1. For example, liquid sulfur and liquid phosphorus can be continuously added to the reactor for reaction while maintaining the internal temperature of the reactor at 300°C to 400°C. These operations ensure that P2S5 is synthesized with high purity.

[0063] In some examples, in order to ensure that molten P2S5 is obtained, liquid sulfur and liquid phosphorus are continuously added to the reactor for reaction. After distillation, the reaction materials are cooled to 300°C-350°C to obtain molten P2S5. The molten P2S5 can be sent to a storage tank for storage.

[0064] The reaction temperature of the Li2S precursor and the molten P2S5 is 400°C-700°C, including but not limited to 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, etc., to obtain an electrolyte precursor solution. At this temperature, the Li2S precursor and the molten P2S5 fully react based on high-temperature melting, while the oxygen is isolated based on an inert atmosphere such as Ar, N1, etc., to ensure the formation of a pure sulfide system.

[0065] In some examples, the internal temperature of the first sealed container is increased to 400° C. to 700° C. at a rate of 1° C. / min to 10° C. / min. Further, the heating rate can be 1° C. / min to 5° C. / min, the holding temperature is 400° C. to 500° C., and the constant temperature stirring time is 10 min to 120 min, further 10 min to 60 min.

[0066] The above-mentioned temperature increase operation ensures that the Li2S precursor and the molten P2S5 react in stages and proceed gradually, allowing the reaction to proceed precisely and controllably. At the same time, it is also beneficial to the regulation of crystal structure and phase purity, as well as the regulation of thermal stress and material stability.

[0067] Both step S3 and step S4 involve crushing processes. In some examples, the crushing processes include dry coarse crushing and dry fine crushing performed in sequence.

[0068] Accordingly, step S3 involves quenching the electrolyte precursor liquid to obtain a block, which is then subjected to dry coarse crushing and dry fine crushing to obtain a first electrolyte precursor powder. Step S4 involves introducing the first precursor powder into a second sealed container, stirring and heating it until it is molten, quenching it to obtain a block, and then subjecting it to dry coarse crushing and dry fine crushing to obtain a second electrolyte precursor powder.

[0069] Quenching can be achieved by rapidly immersing the material in a cooling medium (e.g., water, oil, polymer solution, etc.) to achieve rapid cooling. This quenching treatment can inhibit excessive crystal growth, form a uniform microstructure, maintain chemical composition uniformity, avoid component segregation, improve material stability, and reduce side reactions.

[0070] By sequentially carrying out dry coarse crushing and dry fine crushing, the crushing efficiency can be improved, energy consumption can be reduced, the powder particle size distribution can be controlled, agglomeration can be reduced, the powder specific surface area can be increased, and the subsequent processing performance can be optimized.

[0071] It can be seen that step S3, through "quenching treatment + dry graded crushing", can control the micromorphology and crystal state of the electrolyte at the structural level, improve the efficiency of material amorphization, ensure material purity and ion conductivity at the performance level, and adapt to the moisture-sensitive characteristics of sulfide electrolytes at the process level, laying the foundation for the subsequent preparation of high-performance all-solid-state batteries.

[0072] For example, for dry coarse crushing, the powder particle size after crushing is 0.1mm-10mm, and can further be 0.1mm-1mm. For dry fine crushing, the powder particle size after crushing, for example, the D50 particle size is 1μm-100μm, and can further be 1μm-20μm, to achieve the purpose of optimizing the above effects.

[0073] Step S4 has at least the following advantages through secondary melting quenching + secondary dry crushing operation: further improving the dispersion and reaction effect, eliminating the local stress in the primary quenching, and further eliminating the component segregation by fully mixing again in the secondary melting, ensuring the consistency of the chemical composition of each particle, realizing crystal structure regulation and conductivity optimization, achieving particle size distribution and surface performance improvement, impurity control and purity improvement, which is of great significance for the preparation of sulfide solid electrolytes with high conductivity, high stability and high consistency.

[0074] For example, for dry coarse crushing, the powder particle size after crushing is 0.1mm-10mm, and can further be 0.1mm-1mm. For dry fine crushing, the powder particle size after crushing, for example, the D50 particle size is 1μm-100μm, and can further be 1μm-20μm, to achieve the purpose of optimizing the above effects.

[0075] In some examples, the first precursor powder is introduced into the second sealed container and heated with stirring at 400° C. to 700° C. until it is molten. At a temperature of 400° C. to 700° C., the first precursor powder can be fully melted.

[0076] In step S5, the second precursor powder is dry-milled and sintered to obtain a sulfide solid electrolyte. For example, the second precursor powder is placed in a ball mill with milling beads, dry-milled for a period of time, then transferred to a sintering tank and heated to a set temperature and kept at this temperature for a set time.

[0077] Through step S5, the sulfide powder is converted into a solid electrolyte material having superionic conductivity, electronic insulation, and mechanical stability.

[0078] In some examples, dry milling involves placing the second precursor powder and milling beads (e.g., zirconium beads) in a milling jar at a mass ratio of 1:8-15 for dry milling for 10-180 minutes. This dry milling process can further refine grains and enhance grain boundary conduction.

[0079] Among them, parameters such as dry ball milling time, number of times, rotation speed and ball-to-material ratio can be adjusted to achieve the purpose of optimizing the dry ball milling effect.

[0080] In some examples, the sintering temperature is 150° C. to 500° C., and the holding time is 1 hour to 10 hours. The sintering operation can achieve phase transformation and stabilization of the sulfide solid electrolyte, while also achieving interface strengthening and improved mechanical properties.

[0081] Based on the above-mentioned solutions, combined with Figure 1 As shown, the preparation process of a sulfide solid electrolyte can be as follows:

[0082] Step 1: Weigh appropriate sulfur powder and lithium powder according to a molar ratio, and premix the sulfur powder and lithium powder in a premixing tank under inert atmosphere to obtain a Li2S precursor.

[0083] Step 2: Melt sulfur powder in a sulfur melting kettle and transfer it to a liquid sulfur storage tank. Melt yellow phosphorus powder in a phosphorus melting tank and transfer it to a liquid phosphorus storage tank via a pump. The liquid sulfur in the liquid sulfur storage tank and the yellow phosphorus in the liquid phosphorus storage tank are then pumped into the reactor. The reaction, distillation, and cooling to 300°C-350°C are sequentially performed to obtain molten P2S5. The molten P2S5 can be transferred to a storage tank for storage.

[0084] Step 3: Under inert atmosphere, introduce a Li2S precursor and molten P2S5 in a molar ratio into a first sealed container, raise the internal temperature of the first sealed container to 400°C-700°C while stirring, and react for a set time to obtain an electrolyte precursor solution. The internal temperature of the first sealed container is raised to 400°C-700°C at a rate of 1°C / min-10°C / min.

[0085] Step 4: The electrolyte precursor solution is injected into a quenching tank for quenching. The block is removed and subjected to dry coarse crushing and dry fine crushing in sequence to obtain the first electrolyte precursor powder. For dry coarse crushing, the powder particle size after crushing is 0.1mm-10mm, and for dry fine crushing, the powder particle size after crushing is 1μm-100μm.

[0086] Step 5: The first precursor powder is introduced into a second sealed container, stirred and heated until molten, quenched, and the bulk is removed. Dry coarse crushing and dry fine crushing are then performed in sequence to obtain the second precursor powder of the electrolyte. For dry coarse crushing, the crushed powder particle size is 0.1 mm to 10 mm, and for dry fine crushing, the crushed powder particle size is 1 μm to 100 μm.

[0087] Step 6: The second precursor powder is placed in a ball mill with ball milling beads, dry-milled for a set time, and then transferred to a sintering tank and heated to a set temperature and kept warm for a set time to prepare a sulfide solid electrolyte.

[0088] The preparation method of the sulfide solid electrolyte provided by the embodiment of the present invention uses low-cost lithium powder and sulfur powder to premix and achieve preliminary mixing, and then combines the two with the mature melting treatment process in the P2S5 solid-phase method process to achieve the combination of raw material dispersion and reaction, thereby avoiding the use of expensive Li2S raw materials, effectively and fully improving the dispersion uniformity of the material, greatly improving the efficiency of material amorphization through melting, quenching, etc., avoiding the negative impact of the use of solvents on the electrolyte material, and at the same time increasing the degree of reaction, which is beneficial to improving the performance of the prepared sulfide solid electrolyte.

[0089] In summary, the method for preparing the sulfide solid electrolyte provided by the embodiment of the present invention has at least the following advantages:

[0090] 1. Use low-cost lithium powder and sulfur powder to replace expensive Li2S, greatly reducing the cost of raw materials.

[0091] 2. The production process is closely connected, which can achieve continuous and efficient production.

[0092] 3. As a commonly used industrial raw material, P2S5 has a relatively mature solid-phase synthesis process and has good adaptability when combined with the sulfide electrolyte production process.

[0093] 4. The efficient amorphization process of sulfide electrolyte is completed by two melting and crushing processes, avoiding the long and tedious dry ball milling, shoveling and crushing processes, significantly shortening the process time and improving the preparation efficiency.

[0094] It should be noted that, for any of the above-mentioned methods for preparing the sulfide solid electrolyte provided in the embodiments of the present invention, Li powder and S powder can replace 100% of the Li2S raw material required for preparing the electrolyte, or Li powder and S powder can replace part of the Li2S raw material, and at the same time, part of the ready-made Li2S raw material can be used in the above-mentioned step 3. That is to say, the replacement rate of Li powder and S powder for the Li2S raw material required for preparing the electrolyte can be 50%-100%, and further 80%-100%.

[0095] Accordingly, P powder and S powder can replace 100% of the P2S5 raw material required for preparing the electrolyte, or P powder and S powder can replace part of the P2S5 raw material, and at the same time, some ready-made P2S5 raw materials are used to participate in the above step 3. That is to say, the replacement rate of P powder and S powder for the P2S5 raw material required for preparing the electrolyte can be 0-100%, and further can be 50%-100%.

[0096] With respect to any of the above-mentioned methods for preparing sulfide solid electrolytes, all currently known sulfide solid electrolytes can be prepared, and the ratio of the raw materials therein can be adaptively determined according to the chemical formula of the sulfide solid electrolyte.

[0097] In some examples, the chemical formula of the sulfide solid electrolyte that can be prepared by the embodiments of the present disclosure can be mLi2S-(1-mbn)(Q y S z )-nP2S5-bLiX, where 0<m≤1, 0<n≤1, 0≤b≤1, and the values ​​of y and z are determined according to Q y S z The specific type of compound can be adaptively designed, for example, 1≤y≤5, 1≤z≤5. Wherein, Q is at least one of Sn, In, P, Si, Ge, As, Al, Zr, Se, and Te; and X is at least one of F, Cl, Br, I, (BH4)-, (TFSI)-, (FSI)-, (BF4)-, (PF6)-, and (ClO4)-. Wherein, (TFSI)- is the anion of bis(trifluoromethylsulfonyl)imide, and TFSI is the abbreviation for Bis(trifluoromethylsulfonyl)imide. (FSI)- is the anion of fluorosulfonylimide, and FSI is the abbreviation for Fluorosulfonylimide.

[0098] It should be noted that the chemical formula of the above-mentioned sulfide solid electrolyte uses the following raw material compounds Li2S, Q y S z , P2S5, and LiX, the numbers of the various elements involved in these raw materials can be added up according to actual parameters, so that the chemical formula can intuitively present the number of each element.

[0099] For example, the chemical formula of a sulfide solid electrolyte is Li3PS4, referred to as LPS314, which corresponds to the chemical formula mLi2S-(1-mn)(P y S z)-nP2S5, where the values ​​of each number are as follows: m=3 / 4, n=1 / 4, y=1, z=3, b=0.

[0100] For example, a sulfide solid electrolyte has the general chemical formula Li7P3S 11 , referred to as LPS7311, corresponding to the chemical formula mLi2S-(1-mn)(P y S z )-nP2S5, where the values ​​of each number are as follows: m=7 / 10, n=3 / 10, y=1, z=3, b=0.

[0101] For example, the chemical formula of a sulfide solid electrolyte is L7P2S8I, which corresponds to the chemical formula mLi2S-(1-mbn)(Q y S z )-nP2S5-bLiI, wherein the values ​​of each number are as follows: m=1 / 5, n=3 / 5, y=1, z=2, b=1.

[0102] Below will be described in more detail exemplary embodiments of the present invention. Although the following describes exemplary embodiments of the present invention, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. In the examples, if specific techniques or conditions are not indicated, they are carried out according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments used that do not indicate the manufacturer are conventional products that can be obtained commercially.

[0103] Example 1

[0104] This embodiment provides a sulfide electrolyte, which is prepared by the following preparation method:

[0105] Step 1, preparation of Li2S precursor: lithium powder and sulfur powder were weighed separately in a molar ratio of 2:1.02, and slowly added to the premixing tank under the protection of high-purity argon. During this process, the coolant temperature of the premixing tank was controlled at 10°C. The premixing tank was first mixed at a low speed of 100 rpm for 10 minutes, then the speed was increased to 400 rpm, forward for 10 minutes, stopped for 5 minutes, and reversed for 10 minutes, with argon backflushing during the process.

[0106] Step 2, synthesis of high-purity P2S5: P powder and S powder are added continuously in a molten state into a reactor with a stirrer at a molar ratio of 2:5 at 60°C and 130°C, respectively (P2S5 mother liquor is reserved in the reactor), the reaction temperature is 350°C, and the reaction pressure is 0.15MPa. During the reaction, the P:S ratio is adjusted to maintain it at 2:5. After the reaction is complete, it is distilled and cooled, and then pumped into a high-temperature storage tank under the protection of inert gas to obtain molten P2S5.

[0107] Step 3: Under the protection of an inert atmosphere, introduce the Li2S precursor and molten P2S5 in a molar ratio of 3:1 into the first high-temperature sealed tank, slowly stir for 30 minutes, then gradually heat to 420°C, and stir at a constant temperature for 30 minutes to obtain an electrolyte precursor solution.

[0108] Step 4: inject the electrolyte precursor liquid into a quenching tank for quenching treatment, take out the block, crush it with a disc crusher to D90 <1mm, and then dry-crush it with an ultracentrifugal crusher to D90 <30um to obtain the first precursor powder.

[0109] Step 5: introduce the first precursor powder into a second high-temperature sealed tank, stir and heat to a molten state at 420°C, keep stirring for 30 minutes, perform secondary quenching, and perform dry coarse crushing and dry fine crushing in sequence to obtain a second precursor powder.

[0110] Step 6: The second electrolyte precursor is loaded into a ball mill with zirconium balls at a mass ratio of 1:10, dry-milled for 30 minutes, taken out and transferred to a sealed sintering tank, heated to 200°C and kept warm for 2 hours to obtain the sulfide solid electrolyte Li3PS4, referred to as LPS314.

[0111] Example 2

[0112] This embodiment provides a sulfide electrolyte, which is prepared by the following preparation method:

[0113] Step 1, preparation of Li2S precursor: lithium powder and sulfur powder were weighed separately in a molar ratio of 2:1.02 and slowly added to the premixing tank under the protection of high-purity argon. During this process, the coolant temperature of the premixing tank was controlled at 10°C. The premixing tank was first mixed at a low speed of 100 rpm for 10 minutes, then the speed was increased to 400 rpm, forward for 10 minutes, stopped for 5 minutes, and reversed for 10 minutes, with argon backflushing during the process.

[0114] Step 2, synthesis of high-purity P2S5: P powder and S powder are added continuously in a molten state into a reactor with a stirrer at 60°C and 130°C, respectively (P2S5 mother liquor is reserved in the reactor), the reaction temperature is 350°C, and the reaction pressure is 0.15MPa. During the reaction, the P:S ratio is adjusted to maintain it at 2:5. After the reaction is complete, it is distilled and cooled in sequence, and then pumped into a high-temperature storage tank under the protection of inert gas to obtain molten P2S5.

[0115] Step 3: Under the protection of an inert atmosphere, introduce the obtained Li2S precursor and molten P2S5 into a first high-temperature sealed tank in a molar ratio of 3:1, slowly stir for 30 minutes, then gradually raise the temperature to 500°C, and stir at a constant temperature for 30 minutes to obtain an electrolyte precursor solution.

[0116] Step 4: inject the above electrolyte precursor solution into a quenching tank for quenching treatment, take out the block, crush it with a disc crusher to D90 <1mm, and then dry-crush it with an ultracentrifugal crusher to D90 <30um to obtain the first precursor powder.

[0117] Step 5: introduce the first precursor powder into a second high-temperature sealed tank, stir and heat to a molten state at 450°C, keep stirring for 30 minutes, perform secondary quenching, and perform dry coarse crushing and dry fine crushing in sequence to obtain a second precursor powder.

[0118] Step 6: The second electrolyte precursor was placed in a ball mill with zirconium balls at a mass ratio of 1:10, and dry milled for 30 minutes. After removal, the mixture was transferred to a sealed sintering tank and heated to 250°C for 1.5 hours to obtain the sulfide solid electrolyte Li7P3S. 11 , referred to as LPS7311.

[0119] Example 3

[0120] This embodiment provides a sulfide electrolyte, which is prepared by the following preparation method:

[0121] Step 1, preparation of Li2S precursor: lithium powder and sulfur powder were weighed separately in a molar ratio of 2:1.02 and slowly added to the premixing tank under the protection of high-purity argon. During this process, the coolant temperature of the premixing tank was controlled at 10°C. The premixing tank was first mixed at a low speed of 100 rpm for 10 minutes, then the speed was increased to 400 rpm, forward for 15 minutes, stopped for 5 minutes, and reversed for 15 minutes, with argon backflushing during the process.

[0122] Step 2, synthesis of high-purity P2S5: P powder and S powder are added continuously in a molten state into a reactor with a stirrer at a molar ratio of 2:5 at 60°C and 130°C, respectively (P2S5 mother liquor is reserved in the reactor), the reaction temperature is 350°C, and the reaction pressure is 0.15MPa. During the reaction, the P:S ratio is adjusted to maintain it at 2:5. After distillation and cooling, the mixture is pumped into a high-temperature storage tank under the protection of inert gas to obtain molten P2S5.

[0123] Step 3: Under the protection of an inert atmosphere, introduce the obtained Li2S precursor, LiI and molten P2S5 in a molar ratio of 3:1:1 into a first high-temperature sealed tank, slowly stir for 30 minutes, then gradually heat to 530°C, and stir at a constant temperature for 30 minutes to obtain an electrolyte precursor solution.

[0124] Step 4: inject the above electrolyte precursor solution into a quenching tank for quenching treatment, take out the block, crush it with a disc crusher to D90 <1mm, and then dry-crush it with an ultracentrifugal crusher to D90 <30um to obtain the first precursor powder.

[0125] Step 5: introduce the first precursor powder into a second high-temperature sealed tank, stir and heat to a molten state at 510°C, keep stirring for 30 minutes, then quench twice and perform dry coarse crushing and dry fine crushing in sequence to obtain a second precursor powder.

[0126] Step 6: The second electrolyte precursor is loaded into a ball mill with zirconium balls at a mass ratio of 1:10, dry-milled for 30 minutes, taken out and transferred to a sealed sintering tank, heated to 200°C and kept warm for 2 hours to obtain the sulfide solid electrolyte L7P2S8I.

[0127] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte, characterized in that: The preparation method comprises: Under inert atmosphere protection conditions, sulfur powder and lithium powder are premixed to obtain a Li2S precursor; Under inert atmosphere protection, the Li2S precursor and molten P2S5 are introduced into a first sealed container in a molar ratio, and the internal temperature of the first sealed container is raised to 400° C. to 700° C. under stirring to react to obtain an electrolyte precursor solution; The electrolyte precursor liquid is quenched to obtain a block, which is then crushed to obtain a first precursor powder of the electrolyte; The first precursor powder is introduced into a second sealed container, stirred and heated until it is molten, quenched to obtain a block, and crushed to obtain a second precursor powder of the electrolyte; The second precursor powder is subjected to dry ball milling and sintering treatments in sequence to obtain the sulfide solid electrolyte.

2. The method for preparing a sulfide solid electrolyte according to claim 1, wherein: The premix processing is carried out in a premixing tank, which is configured to have a cooling and temperature control function and adopt a mixing method that combines forward and reverse rotation of the blade.

3. The method for preparing a sulfide solid electrolyte according to claim 1, wherein: The molten P2S5 is prepared by the following method: Liquid sulfur and liquid phosphorus are placed in a reactor, and reacted, distilled, and cooled in sequence to obtain molten P2S5, wherein the liquid sulfur is obtained by melting sulfur powder, and the liquid phosphorus is obtained by melting phosphorus powder.

4. The method for preparing a sulfide solid electrolyte according to claim 3, wherein: The liquid sulfur and the liquid phosphorus are reacted in the reactor at 300° C.-400° C. according to a mass ratio of sulfur:phosphorus=2.57-2.6:

1.

5. The method for preparing a sulfide solid electrolyte according to claim 1, wherein: The internal temperature of the first sealed container is increased to 400° C.-700° C. at a rate of 1° C. / min-10° C. / min.

6. The method for preparing a sulfide solid electrolyte according to any one of claims 1 to 5, characterized in that: The crushing process includes dry coarse crushing and dry fine crushing performed in sequence; For the dry coarse crushing, the particle size of the crushed powder is 0.1mm-10mm; For the dry fine crushing, the particle size of the crushed powder is 1 μm-100 μm.

7. The method for preparing a sulfide solid electrolyte according to any one of claims 1 to 6, characterized in that: The first precursor powder is introduced into a second sealed container and heated with stirring at 400° C. to 700° C. until it is in a molten state.

8. The method for preparing a sulfide solid electrolyte according to any one of claims 1 to 7, characterized in that: The second precursor powder and ball milling beads are placed in a ball milling jar at a mass ratio of 1:8-15 for dry ball milling, and the dry ball milling time is 10 min-180 min.

9. The method for preparing a sulfide solid electrolyte according to any one of claims 1 to 8, characterized in that: For the sintering treatment, the sintering temperature is 150° C.-500° C., and the holding time is 1 hour-10 hours.

10. The method for preparing a sulfide solid electrolyte according to any one of claims 1 to 9, characterized in that: The sulfide solid electrolyte is mLi2S-(1-mbn)(Q y S z )-nP2S5-bLiX, where 0<m≤1, 0<n≤1, 0≤b≤1; Q is at least one of Sn, In, P, Si, Ge, As, Al, Zr, Se, and Te; X is at least one of F, Cl, Br, I, (BH4)-, (TFSI)-, (FSI)-, (BF4)-, (PF6)-, and (ClO4)-.

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