A sulfide solid electrolyte, its preparation method and battery

Abstract

This invention discloses a sulfide solid electrolyte, its preparation method, and a battery, belonging to the field of battery material technology. The preparation of the sulfide solid electrolyte includes: thermally reacting the raw materials for the preparation of the sulfide solid electrolyte; tangentially filtering the material obtained after the thermal reaction; and spray-drying the solid obtained from the tangential flow filtration. The raw materials include a first precursor, a second precursor, and a solvent. The first precursor includes lithium sulfide, and the second precursor includes at least one selected from phosphorus pentasulfide, silicon sulfide, germanium sulfide, tin sulfide, sodium sulfide, potassium sulfide, ammonium sulfide, calcium sulfide, and arsenic sulfide. This method has a relatively simple process flow and operation, low energy consumption and cost, and high production efficiency, making it suitable for industrial production. The sulfide solid electrolyte obtained in this way is relatively soft, making it easier to contact the positive and negative electrodes under extrusion conditions during the further preparation of the battery, improving density, thereby facilitating electron transport and reducing losses.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a sulfide solid electrolyte, its preparation method, and a battery. Background Technology

[0002] Solid-state lithium batteries offer improvements in safety and energy density compared to traditional liquid lithium batteries. The core of a solid-state lithium battery is a solid electrolyte, most of which are non-flammable, fundamentally solving the flammability problem of electrolytes in traditional liquid lithium batteries. Simultaneously, the dense, non-porous solid electrolyte film possesses high mechanical strength, effectively suppressing short circuits caused by lithium dendrite piercing at the negative electrode. Solid electrolytes also exhibit superior thermal and electrochemical stability, significantly enhancing the safety performance of lithium batteries.

[0003] However, the preparation process of solid electrolytes is currently lengthy, complex, and requires stringent conditions, resulting in high energy consumption, high cost, and low efficiency.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a sulfide solid electrolyte, its preparation method, and a battery, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing a sulfide solid electrolyte, comprising the following steps: subjecting the raw materials for preparing the sulfide solid electrolyte to a thermal reaction, subjecting the material obtained after the thermal reaction to tangential flow filtration, and subjecting the solid obtained from the tangential flow filtration to spray drying.

[0008] The raw materials used in the preparation include a first precursor, a second precursor, and a solvent.

[0009] The first precursor includes lithium sulfide, and the second precursor includes at least one of phosphorus pentasulfide, silicon sulfide, germanium sulfide, tin sulfide, sodium sulfide, potassium sulfide, ammonium sulfide, calcium sulfide, and arsenic sulfide.

[0010] In an optional embodiment, the raw material further includes LiX; LiX includes at least one of lithium chloride, lithium bromide, lithium iodide, lithium nitride, lithium carbide, and lithium fluoride.

[0011] In an optional embodiment, the ratio of the total molar amount of the first precursor and LiX to the molar amount of the second precursor is 3:0.9 to 3:1.2.

[0012] In an optional implementation, the mass of LiX does not exceed 30% of the total mass of LiX and the first precursor.

[0013] In an optional embodiment, the solvent includes at least one of ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, and butyl acetate.

[0014] In optional embodiments, the mixing method includes at least one of emulsification, ball milling, and stirring.

[0015] In an optional implementation, the mixing method is selected from at least one of emulsification and ball milling.

[0016] In an optional embodiment, when the mixing method is emulsification, the emulsification speed is 2500 r / min to 3000 r / min, and the total emulsification time is 5 min to 3 h;

[0017] Alternatively, when the mixing method is ball milling, the ball milling speed is 1000 r / min to 1500 r / min, the ball milling time is 1 h to 4 h, and the diameter of the zirconium beads used for ball milling is 1 mm to 3 mm.

[0018] In an optional implementation, the thermal reaction is a hydrothermal reaction;

[0019] The hydrothermal reaction temperature is 80℃~150℃, and the hydrothermal reaction time is 3h~5h.

[0020] In an optional implementation, the pore size of the ceramic tube used for tangential flow filtration does not exceed 500 nm.

[0021] In an optional implementation, tangential flow filtration is performed under room temperature, normal pressure, and closed conditions.

[0022] In an optional embodiment, the spray drying temperature is 80°C to 120°C.

[0023] In an optional embodiment, the solids obtained from tangential flow filtration are washed and then dried.

[0024] In an optional embodiment, the washing agent used for cleaning includes n-hexane.

[0025] Secondly, the present invention provides a sulfide solid electrolyte, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0026] In an optional embodiment, the ionic conductivity of the sulfide solid electrolyte is not less than 1×10⁻⁶. -3 S / Cm;

[0027] In an optional embodiment, the solvent weight loss rate of the sulfide solid electrolyte is <8% before reaching 250°C.

[0028] Thirdly, the present invention provides a battery in which the electrode surface has the sulfide solid electrolyte of the aforementioned embodiments.

[0029] The beneficial effects of this invention include:

[0030] This invention utilizes a thermal reaction to prepare the raw materials for the sulfide solid electrolyte, which helps to reduce the drying temperature of the material in the later stages, thereby reducing energy consumption and costs. By subjecting the material obtained after the thermal reaction to tangential flow filtration, it enables more continuous product processing than ordinary filtration methods (such as centrifugation or pressure filtration), reducing manual operation, minimizing human error, and improving overall cost. Furthermore, by spray drying the solid obtained from tangential flow filtration, it facilitates continuous post-processing of the product compared to other commonly used drying methods (such as baking, airflow drying, vacuum drying, etc.), while simultaneously achieving the effect of heat treatment activation during the product drying process.

[0031] The preparation method of the sulfide solid electrolyte provided by this invention has a relatively simple process flow and operation, low energy consumption and cost, and high production efficiency, making it suitable for industrial production. The sulfide solid electrolyte obtained in this way is relatively soft, making it easier to contact the positive and negative electrodes under extrusion conditions during the further preparation of batteries, thereby improving density, which is beneficial for electron transport and reducing losses. Attached Figure Description

[0032] 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.

[0033] Figure 1 The XRD pattern of the sulfide solid electrolyte prepared in Example 1;

[0034] Figure 2 Thermogravimetric analysis results of the sulfide solid electrolyte prepared in Example 1 are shown.

[0035] Figure 3 The XRD pattern of the sulfide solid electrolyte prepared in Example 2 is shown below.

[0036] Figure 4 The thermogravimetric analysis results are shown in the diagram for the sulfide solid electrolyte prepared in Example 2. Detailed Implementation

[0037] 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.

[0038] The following provides a detailed description of the sulfide solid electrolyte, its preparation method, and the battery provided by this invention.

[0039] This invention proposes a method for preparing a sulfide solid electrolyte, comprising the following steps: subjecting the raw materials for preparing the sulfide solid electrolyte to a thermal reaction, subjecting the material obtained after the thermal reaction to tangential flow filtration, and subjecting the solid obtained from the tangential flow filtration to spray drying.

[0040] The raw materials used in the preparation include a first precursor, a second precursor, and a solvent.

[0041] The first precursor may, but is not limited to, lithium sulfide, and the second precursor may, but is not limited to, at least one of phosphorus pentasulfide, silicon sulfide, germanium sulfide, tin sulfide, sodium sulfide, potassium sulfide, ammonium sulfide, calcium sulfide, and arsenic sulfide.

[0042] It should be noted that in this invention, the solvent does not need to completely dissolve the first and second precursors, nor does it need to uniformly disperse the first and second precursors in the solvent. That is, the raw materials can be in the form of a solution, dispersion, or suspension after mixing.

[0043] In some embodiments, the solvent is a single solvent, that is, only one solvent is used to mix the first precursor and the second precursor. Exemplarily, the solvent may include at least one of ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, and butyl acetate.

[0044] By using a single solvent, the operation is simple and convenient, and it is also conducive to recycling, which has the advantages of reducing costs and increasing efficiency.

[0045] Furthermore, the raw materials used in the preparation may also include LiX, where X can be a halogen, N, or C, etc. For example, LiX may include at least one of lithium chloride, lithium bromide, lithium iodide, lithium nitride, lithium carbide, and lithium fluoride.

[0046] In some embodiments, the ratio of the total molar amount of the first precursor and LiX to the molar amount of the second precursor is 3:0.9 to 3:1.2, such as 3:0.9, 3:0.95, 3:1, 3:1.05, 3:1.1, 3:1.15 or 3:2, or other values ​​within the range of 3:0.9 to 3:1.2.

[0047] The mass of LiX does not exceed 30% of the total mass of LiX and the first precursor. For example, the value of LiX:(LiX+first precursor) can be 30:100, 25:100, 20:100, 15:100, 10:100, 5:100, 2:100, 1:100, 0.5:100, or 0.1:100, etc.

[0048] If the mass of LiX exceeds 30% of the total mass of LiX and the first precursor, it is not conducive to the stability of the crystal structure and is likely to lead to structural collapse.

[0049] In some preferred embodiments, the mass of LiX is 5% to 10% of the total mass of LiX and the first precursor, such as 5%, 6%, 7%, 8%, 9% or 10%.

[0050] In some embodiments, the mixing method may include at least one of emulsification, ball milling, and stirring. For example, it may be any one of emulsification, ball milling, or stirring, or a combination of ball milling and emulsification, a combination of ball milling and stirring, a combination of emulsification and stirring, or a combination of emulsification, ball milling, and stirring.

[0051] In some preferred embodiments, the mixing method is selected from at least one of emulsification and ball milling. By employing emulsification and / or ball milling for mixing, the particle size of the mixture can be reduced, increasing the probability of collision between materials and improving the degree of reaction.

[0052] When the mixing method is emulsification, the emulsification speed can be between 2500 r / min and 3000 r / min, such as 2500 r / min, 2600 r / min, 2700 r / min, 2800 r / min, 2900 r / min, or 3000 r / min, or other values ​​within the range of 2500 r / min to 3000 r / min. The total emulsification time can be between 5 min and 3 h, such as 5 min, 10 min, 30 min, 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, or other values ​​within the range of 5 min to 3 h. When the emulsification time is long, the emulsification process can be a non-continuous process, for example, it can be stopped for 5 min to 10 min after every 5 min of operation.

[0053] When ball milling is used for mixing, the milling speed can be from 1000 r / min to 1500 r / min, such as 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, or 1500 r / min, or other values ​​within the range of 1000 r / min to 1500 r / min. The milling time can be from 1 h to 4 h, such as 1 h, 2 h, 3 h, or 4 h, or any other value within the range of 1 h to 4 h. The diameter of the zirconium beads used for milling can be from 1 mm to 3 mm, such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm.

[0054] In some embodiments, the thermal reaction is a hydrothermal reaction. The temperature of the hydrothermal reaction can be between 80°C and 150°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, or any other value within the range of 80°C to 150°C. The time of the hydrothermal reaction can be between 3 hours and 5 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours, or any other value within the range of 3 hours to 5 hours.

[0055] In other embodiments, the thermal reaction may also be a solvothermal reaction, and the solvent may be an organic solvent, such as at least one of ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, and butyl acetate.

[0056] The above-mentioned thermal reaction helps to reduce the drying temperature of the material in the later stages.

[0057] In this invention, filtration is not performed using conventional methods such as centrifugation or pressure filtration, but rather tangential flow filtration. Tangential flow refers to a filtration method where the liquid flow direction is perpendicular to the filtration direction. Using this method facilitates continuous production and reduces filter cake accumulation during the filtration process.

[0058] In some implementations, the pore size of the ceramic tube used for tangential flow filtration does not exceed 500 nm, such as 500 nm, 400 nm, 300 nm, 200 nm, 100 nm, 80 nm, 60 nm, 50 nm, 20 nm or 10 nm.

[0059] If the pore size of the ceramic tube used in tangential flow filtration is greater than 500nm, particles smaller than 500nm will be filtered out, thereby reducing the yield.

[0060] In this invention, the above-mentioned tangential flow filtration process is carried out under conditions of room temperature, normal pressure, and a closed system.

[0061] In some implementations, the solids obtained from tangential flow filtration are first washed and then dried.

[0062] The washing agent used for cleaning may, by way of example but not by way of limitation, include n-hexane. Using n-hexane as a washing agent is advantageous because it is relatively inexpensive and can be removed by volatilization during the spray drying process.

[0063] The drying process of this invention uses spray drying, which is more conducive to continuous production than other commonly used drying methods (such as oven drying, airflow drying, vacuum drying, etc.).

[0064] In some embodiments, the spray drying temperature can be 80°C to 120°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, or any other value within the range of 80°C to 120°C.

[0065] If the spray drying temperature is below 80℃, it is difficult to remove the detergent; if the spray drying temperature is above 120℃, it will easily lead to excessive energy consumption and reduced product performance.

[0066] In some embodiments, the solvent content of the spray-dried solid is not higher than 5%.

[0067] Using a filtration and drying method helps to save on preparation costs.

[0068] As described above, the preparation method of the sulfide solid electrolyte provided by this invention has a relatively simple process flow and operation, low energy consumption and cost, and high production efficiency, making it suitable for industrial production. The temperature range involved in this preparation process is relatively low, which avoids hardening of the sulfide solid electrolyte crystal structure after high-temperature treatment, thereby helping to reduce the gap between particles and thus facilitating ion transport.

[0069] Accordingly, the present invention also provides a sulfide solid electrolyte, which is prepared by the above-described preparation method.

[0070] In some embodiments, the ionic conductivity of the sulfide solid electrolyte is not less than 1×10⁻⁶. -3 S / Cm. In some preferred embodiments, the ionic conductivity of this sulfide solid electrolyte is 1.30 × 10⁻⁶. -3 S / Cm~2.05×10 - 3 S / Cm.

[0071] In some embodiments, the sulfide solid electrolyte prepared by the method provided by the present invention has low crystallinity and is relatively soft. During the further fabrication of the sulfide solid electrolyte into a battery, its softness makes it easier to contact the positive and negative electrodes under extrusion conditions, increasing density and thus facilitating electron transport and reducing losses. In some embodiments, the sulfide solid electrolyte prepared by the method provided by the present invention exhibits a solvent weight loss rate of <8% and a total product weight loss rate of <12% before reaching 250°C.

[0072] In addition, the present invention also provides a battery having the above-mentioned sulfide solid electrolyte on the electrode surface.

[0073] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0074] Example 1

[0075] This embodiment provides a sulfide solid electrolyte, the preparation method of which includes:

[0076] Take 1.378g of lithium sulfide, 2.445g of phosphorus pentasulfide and 0.400g of lithium iodide, add them to 40ml of butyl acetate, and use an emulsifier to emulsify uniformly at 2500r / min at room temperature and normal pressure for a total of 30min (stop for 10min every 5min of emulsification) to obtain a mixed raw material liquid.

[0077] The mixed raw material liquid was transferred to a hydrothermal tank and subjected to a constant temperature of 100°C for 3 hours for thermal reaction.

[0078] The material obtained from the thermal reaction was subjected to tangential flow filtration and solution concentration in a tangential flow filtration system using ceramic tubes with a pore size of 500 nm. Subsequently, hexane was continuously added to clean the product.

[0079] The cleaned solids were spray-dried at 100°C.

[0080] Example 2

[0081] Take 1.378g of lithium sulfide, 2.445g of phosphorus pentasulfide and 0.127g of lithium chloride, add them to 40ml of ethyl acetate, and use a ball mill to ball mill at 1000r / min for 1h at room temperature and atmospheric pressure (the diameter of the zirconium beads used in the ball milling process is 2mm) to obtain a mixed slurry.

[0082] The mixed slurry was transferred to a hydrothermal tank and subjected to a constant temperature of 120°C for 5 hours for thermal reaction.

[0083] The material obtained from the thermal reaction was subjected to tangential flow filtration and solution concentration in a tangential flow filtration system using ceramic tubes with a pore size of 500 nm. Subsequently, hexane was continuously added to clean the product.

[0084] The cleaned solids were spray-dried at 120°C.

[0085] Example 3

[0086] The difference between this embodiment and Embodiment 1 is that the emulsification speed is 3000 r / min and the total emulsification time is 2 h.

[0087] Example 4

[0088] The difference between this embodiment and Embodiment 1 is that the mixing method is stirring, the stirring speed is 2500 r / min, and the stirring time is 3 h.

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 1 is that the filtration is carried out by centrifugation, and the solvent content of the solid material after centrifugation is basically the same as that in Example 1.

[0091] Comparative Example 2

[0092] The difference between this comparative example and Example 1 is that the mass of lithium chloride is 35% of the total mass of lithium chloride and lithium sulfide.

[0093] Comparative Example 3

[0094] The difference between this comparative example and Example 1 is that the hydrothermal reaction temperature is 160°C.

[0095] Test case

[0096] ① Taking Examples 1 and 2 as examples, the obtained sulfide solid electrolytes were subjected to thermogravimetric analysis and XRD characterization.

[0097] The thermogravimetric analysis test procedure is as follows: The thermogravimetric analyzer is placed in a glove box, 10 mg of sample is placed in the sample chamber, the temperature is controlled by program, and after reaching 105℃ at 10℃ / min, it is kept at that temperature for 5 to 10 min; the temperature is then increased from 105℃ to 500℃ at the same heating rate.

[0098] XRD testing was performed according to conventional methods in the field.

[0099] The results are as follows Figures 1 to 4 As shown.

[0100] Depend on Figure 1 and Figure 3It can be seen that the diffraction peaks of the prepared sulfide solid electrolyte are relatively flat compared to those of the solid-phase synthesis method, without high-intensity diffraction peaks. This indicates that the product prepared by this synthesis method has relatively low crystallinity. Low crystallinity makes the electrolyte more flexible than the product of the solid-phase synthesis method, which is more conducive to the manufacture of battery cells.

[0101] Depend on Figure 2 and Figure 4 It can be seen that: before 250℃, the solvent weight loss rate of the product is <8%, which also indicates the difference between this type of product and solid-phase synthesis; the total weight loss rate of the product is <12%.

[0102] ② The ionic conductivity of the sulfide solid electrolytes prepared in Examples 1-4 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0103] Table 1 Test Results

[0104] Ionic conductivity Example 1 <![CDATA[1.30×10 -3 S / Cm]]> Example 2 <![CDATA[2.05×10 -3 S / Cm]]> Example 3 <![CDATA[1.42×10 -3 S / Cm]]> Example 4 <![CDATA[0.79×10 -3 S / Cm]]> Comparative Example 1 <![CDATA[0.78×10 -3 S / Cm]]> Comparative Example 2 <![CDATA[0.53×10 -3 S / Cm]]> Comparative Example 3 <![CDATA[0.89×10 -4 S / Cm]]>

[0105] As can be seen from Table 1, the sulfide solid electrolyte provided in the embodiments of the present invention has a high ionic conductivity.

[0106] Furthermore, the sulfide solid electrolyte prepared in the embodiments of the present invention is softer than the sulfide solid electrolyte prepared in the comparative example.

[0107] In summary, the preparation method of the sulfide solid electrolyte provided by this invention has a relatively simple process flow and operation, low energy consumption and cost, and high production efficiency, making it suitable for industrial production. The sulfide solid electrolyte obtained in this way is relatively soft, making it easier to contact the positive and negative electrodes under extrusion conditions during the further preparation of batteries, thereby improving density, facilitating electron transport, and reducing losses.

[0108] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 method for preparing a sulfide solid electrolyte, characterized in that, The product is prepared by the following steps: the raw materials for preparing sulfide solid electrolyte are subjected to thermal reaction, the material obtained after thermal reaction is subjected to tangential flow filtration, and the solid obtained from tangential flow filtration is spray dried. The raw materials for preparation include a first precursor, a second precursor, a solvent, and LiX; The first precursor is lithium sulfide, and the second precursor is at least one of phosphorus pentasulfide, silicon sulfide, germanium sulfide, tin sulfide, sodium sulfide, potassium sulfide, ammonium sulfide, calcium sulfide, and arsenic sulfide. The LiX is at least one of lithium chloride, lithium bromide, lithium iodide, lithium nitride, lithium carbide, and lithium fluoride; The ratio of the total molar amount of the first precursor and the LiX to the molar amount of the second precursor is 3:0.9 to 3:1.2; the mass of the LiX does not exceed 30% of the total mass of the LiX and the first precursor. The solvent is selected from at least one of ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, and butyl acetate; The thermal reaction is a hydrothermal reaction; the temperature of the hydrothermal reaction is 80℃~150℃, and the time of the hydrothermal reaction is 3h~5h; The pore size of the ceramic tubes used in tangential flow filtration does not exceed 500 nm; The ionic conductivity of the sulfide solid electrolyte is not less than 1×10⁻⁶. -3 S / Cm; The solvent weight loss rate of the sulfide solid electrolyte is <8% before 250°C; The mixing method is selected from at least one of emulsification and ball milling; when the mixing method is emulsification, the emulsification speed is 2500 r / min to 3000 r / min, and the total emulsification time is 5 min to 3 h; when the mixing method is ball milling, the ball milling speed is 1000 r / min to 1500 r / min, the ball milling time is 1 h to 4 h, and the diameter of the zirconium beads used for ball milling is 1 mm to 3 mm. The spray drying temperature is 80℃~120℃.

2. The preparation method according to claim 1, characterized in that, Tangential flow filtration is carried out under closed conditions at room temperature and normal pressure.

3. The preparation method according to claim 1, characterized in that, The solids obtained from tangential flow filtration are washed and then dried.

4. The preparation method according to claim 3, characterized in that, The cleaning reagents used include n-hexane.

5. A sulfide solid electrolyte, characterized in that, Prepared by the preparation method according to any one of claims 1 to 4; The ionic conductivity of the sulfide solid electrolyte is not less than 1×10⁻⁶. -3 S / Cm; The solvent weight loss rate of the sulfide solid electrolyte is <8% before 250°C.

6. A battery, characterized in that, The electrode surface of the battery has the sulfide solid electrolyte as described in claim 5.

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