Manufacturing method and application of high-performance sulfide solid electrolyte
High-performance sulfide solid electrolytes were prepared by high-energy ball milling and slow cooling processes, which solved the problems of low ionic conductivity and poor stability of sulfide solid electrolytes and improved the overall performance and electrochemical stability of the battery.
Patent Information
- Application Number
- CN202610027400.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-09
- Publication Date
- 2026-05-01
AI Technical Summary
Existing sulfide solid electrolytes have low room temperature ionic conductivity, poor stability to lithium metal anodes, and difficulty in controlling crystallinity during the preparation process, resulting in high grain boundary impedance and limiting the performance of all-solid-state batteries.
Amorphous precursor powder was prepared by high-energy ball milling. Combined with slow cooling process and strictly controlled heat treatment, a high-performance sulfide solid electrolyte with high crystallinity and low grain boundary impedance was formed. The crystal structure and electrochemical stability were optimized by introducing germanium disulfide and lithium chloride.
The room temperature ionic conductivity and electrochemical stability of the sulfide solid electrolyte were improved, the grain boundary impedance was reduced, and the all-solid-state battery was able to operate stably over a wide voltage range and achieve long-cycle charge-discharge performance.
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Figure CN121964805A_ABST
Abstract
Description
A method for manufacturing a high-performance sulfide solid electrolyte and its application Technical Field
[0001] This invention relates to the field of all-solid-state lithium battery materials technology, specifically to a method for manufacturing and applying a high-performance sulfide solid electrolyte. Background Technology
[0002] All-solid-state lithium batteries have become an important development direction for the next generation of energy storage technology due to their high energy density and high safety. They can solve the safety hazards such as electrolyte leakage and flammability and explosion faced by traditional liquid lithium-ion batteries. Among the many solid electrolyte materials, sulfide solid electrolytes are considered to be one of the most commercially promising solid electrolyte systems because they have high room temperature ionic conductivity and suitable mechanical ductility, which can form good interfacial contact with electrode active materials.
[0003] However, existing sulfide solid electrolytes still face many problems in practical applications. On the one hand, the conventional crystal structure of sulfide systems greatly restricts the transport channels of lithium ions, resulting in a high lithium ion migration barrier, which makes it difficult to further improve the room temperature ionic conductivity. Moreover, the electrochemical window of sulfide solid electrolytes for lithium metal anodes is narrow, and irreversible redox reactions easily occur at the interface, leading to a decrease in battery cycle stability. On the other hand, in existing preparation processes, high-temperature melting followed by rapid quenching or simple solid-state sintering is used. This rapid cooling or heat treatment process without precise control leads to a large number of amorphous phases, vacancy clusters, and lattice distortions inside the material, resulting in incomplete grain development and poor grain boundary contact. This generates high grain boundary impedance, which hinders the macroscopic transport of lithium ions inside the electrolyte and limits the performance of all-solid-state batteries at high rates.
[0004] Therefore, this invention proposes a method for manufacturing and applying a high-performance sulfide solid electrolyte to address the shortcomings of existing technologies. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a method for manufacturing and applying a high-performance sulfide solid electrolyte, which solves the problems of low room-temperature ionic conductivity, poor stability to lithium metal anodes, and high grain boundary impedance caused by difficulties in controlling crystallinity during the preparation process.
[0006] To achieve the above objectives, the present invention provides the following technical solution: Firstly, the present invention provides a method for manufacturing a high-performance sulfide solid electrolyte, comprising the following steps:
[0007] S1: Under an inert atmosphere, lithium sulfide, phosphorus pentasulfide, germanium disulfide and lithium chloride are ball-milled in the molar proportions described in the first aspect to obtain an amorphous precursor powder.
[0008] S2: The amorphous precursor powder is sealed in a carbon-coated quartz tube, and the carbon-coated quartz tube is vacuumed. Then the carbon-coated quartz tube is placed in a heating device for constant temperature heat treatment.
[0009] S3: After the constant temperature heat treatment is completed, the program cooling mode of the heating device is started, and the heating device is controlled to reduce the temperature to below 200℃ at a cooling rate of 0.5℃ / min to 3.0℃ / min. When the temperature is reduced to below 200℃, the power supply of the heating device is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature along with the heating device. The sintered block is then removed and ground to obtain the high-performance sulfide solid electrolyte.
[0010] By adopting the above technical solution, especially the program-controlled slow cooling process, a high-performance sulfide solid electrolyte with high crystallinity and low grain boundary impedance was obtained. The preparation mechanism of this invention is as follows:
[0011] Mechanical alloying by high-energy ball milling: The ball milling process in step S1 destroys the original crystal structure of lithium sulfide, phosphorus pentasulfide, germanium disulfide and lithium chloride through mechanical force, so that the raw materials are mixed uniformly at the atomic scale, forming an amorphous precursor powder in a high-energy metastable state, which reduces the activation energy of subsequent solid-phase reactions.
[0012] Controlled crystallization kinetics: In step S3, strictly controlling the cooling rate from 0.5℃ / min to 3.0℃ / min is key to forming a highly conductive phase. Unlike traditional natural cooling or quenching processes, the slow cooling process provided by this invention allows lithium ions, phosphorus ions, germanium ions, sulfur ions and chloride ions sufficient time for thermodynamic rearrangement, promoting the ordered growth of high-performance sulfide solid electrolyte crystal structures and reducing the formation of lattice defects and vacancy clusters.
[0013] Optimization of grain boundary properties: The slow cooling rate avoids grain breakage and microcracks caused by thermal shock, resulting in closer grain contact inside the high-performance sulfide solid electrolyte, reducing grain boundary resistance, and thus improving the overall ionic conductivity of the high-performance sulfide solid electrolyte.
[0014] Preferably, based on molar parts, the lithium sulfide is 2.50 to 2.90 parts, the phosphorus pentasulfide is 0.10 to 0.40 parts, the germanium disulfide is 0.20 to 0.80 parts, and the lithium chloride is 0.80 to 1.20 parts.
[0015] By adopting the above technical solution, and through the co-doping of a quaternary system using lithium sulfide, phosphorus pentasulfide, germanium disulfide, and lithium chloride, this invention achieves high ionic conductivity and high stability. The specific mechanism is as follows:
[0016] The lattice expansion mechanism of germanium: By introducing germanium disulfide into the basic framework of lithium sulfide and phosphorus pentasulfide, the larger ionic radius of germanium ions replaces some phosphorus ion sites. This substitution effect expands the lattice volume, broadens the three-dimensional transport channels of lithium ions inside the lattice, and lowers the migration energy barrier of lithium ions.
[0017] The structural regulation mechanism of halide anions: When chloride ions are introduced into the sulfide lattice from lithium chloride, the introduction of chloride ions changes the local electron cloud distribution due to the stronger electronegativity of chloride ions than that of sulfide ions. This weakens the Coulomb interaction between lithium ions and the anion framework, allowing lithium ions to migrate more freely. At the same time, the addition of lithium chloride can form a halogen-rich passivation layer on the surface of the high-performance sulfide solid electrolyte, improving the electrochemical stability of the high-performance sulfide solid electrolyte to the lithium metal anode.
[0018] Preferably, in step S1, the ball milling speed is 400 rpm to 600 rpm, and the ball milling time is 10 h to 20 h.
[0019] By adopting the above technical solution, a rotation speed of 400 rpm to 600 rpm and a time of 10 h to 20 h can ensure that the input mechanical energy is sufficient to break the chemical bonds of lithium sulfide, phosphorus pentasulfide, germanium disulfide and lithium chloride, while avoiding the decomposition of raw materials due to excessive energy or the uneven mixing due to insufficient energy.
[0020] Preferably, in step S1, the ball milling process is carried out under conditions where the ball-to-material mass ratio is 15:1 to 25:1.
[0021] By adopting the above technical solution, a ball-to-material mass ratio of 15:1 to 25:1 ensures the collision frequency between the grinding balls and the material, and improves the uniformity of the amorphous precursor powder.
[0022] Preferably, in step S2, the internal pressure of the carbon-coated quartz tube after vacuum treatment is less than 10 Pa.
[0023] By adopting the above technical solution, the vacuum environment below 10 Pa effectively eliminates the interference of oxygen and moisture, preventing lithium sulfide and phosphorus pentasulfide from undergoing oxidation or hydrolysis at high temperatures to generate oxide impurities, thus ensuring the purity of the high-performance sulfide solid electrolyte.
[0024] Preferably, in step S2, the heating rate of the heating device to the temperature of the constant temperature heat treatment is 2.0℃ / min to 4.0℃ / min.
[0025] By adopting the above technical solution, a heating rate of 2.0℃ / min to 4.0℃ / min can avoid local overheating and agglomeration of amorphous precursor powder caused by excessively rapid heating, while also avoiding reduced production efficiency caused by excessively slow heating.
[0026] Preferably, in step S2, the temperature of the constant temperature heat treatment is 520°C to 580°C, and the holding time of the constant temperature heat treatment is 3h to 5h.
[0027] By adopting the above technical solution, the heat treatment temperature of 520℃ to 580℃ is the thermodynamically stable range for the formation of highly conductive crystalline phases in high-performance sulfide solid electrolytes. Combined with a holding time of 3h to 5h, it can ensure that the solid-phase reaction is carried out thoroughly and eliminate residual unreacted raw materials.
[0028] Preferably, in step S3, the grinding is performed by grinding the sintered block into powder using an agate mortar and pestle, and then sieving the powder using a sieve.
[0029] By adopting the above technical solution, the particle size distribution of the final high-performance sulfide solid electrolyte can be controlled using an agate mortar and sieve, making it suitable for the preparation of all-solid-state batteries.
[0030] Secondly, this invention provides an application of a high-performance sulfide solid electrolyte, employing the following technical solution:
[0031] An application of a high-performance sulfide solid electrolyte in an all-solid-state secondary battery, the all-solid-state secondary battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer or the positive electrode layer contains a high-performance sulfide solid electrolyte prepared by the manufacturing method of the high-performance sulfide solid electrolyte.
[0032] Preferably, the positive electrode layer comprises a positive electrode active material, the high-performance sulfide solid electrolyte, and a conductive agent; the operating voltage range of the all-solid-state secondary battery is 2.5V to 4.2V.
[0033] By adopting the above technical solution, the all-solid-state secondary battery uses a high-performance sulfide solid electrolyte with high ionic conductivity and a wide electrochemical window, enabling the all-solid-state battery to operate stably in a wide voltage range of 2.5V to 4.2V and exhibiting excellent charge-discharge cycle performance.
[0034] This invention provides a method for manufacturing a high-performance sulfide solid electrolyte and its application. It has the following beneficial effects:
[0035] 1. The high-performance sulfide solid electrolyte provided by this invention is modified by introducing germanium disulfide and lithium chloride. The large ionic radius of germanium ions expands the transport channels of the crystal structure, while the electronegativity of chloride ions weakens the binding force between lithium ions and the framework. The synergistic effect of this quaternary system reduces the migration energy barrier of lithium ions, thereby improving the room temperature ionic conductivity of the high-performance sulfide solid electrolyte.
[0036] 2. The manufacturing method provided by this invention adopts a program-controlled slow cooling process, which is different from the traditional rapid cooling technology. This allows the high-temperature solid-phase reaction products sufficient thermodynamic time for lattice rearrangement and grain growth. This controlled crystallization process reduces vacancy defects inside the lattice and promotes close contact between grains, thereby reducing the grain boundary resistance of the material and improving the overall crystallinity.
[0037] 3. The high-performance sulfide solid electrolyte of the present invention has excellent electrochemical stability. The addition of lithium chloride helps to form a stable passivation layer at the interface between the electrolyte and the negative electrode, suppressing the side reaction between the sulfide and metallic lithium. Applying this electrolyte to an all-solid-state battery enables the battery to adapt to a wide operating voltage range and maintain long-term charge-discharge cycle stability. Attached Figure Description
[0038] Figure 1 is a schematic diagram of the X-ray diffraction (XRD) pattern of the present invention;
[0039] Figure 2 is a schematic diagram showing the comparison of the initial ionic conductivity of the present invention;
[0040] Figure 3 is a schematic diagram showing the comparison of conductivity retention rate after the water resistance test of the present invention.
[0041] Figure 4 is a schematic diagram of the charge-discharge cycle characteristics of the present invention. Detailed Implementation
[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, comparative examples, test examples, and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0043] Preparation Examples 1-4:
[0044] Preparation Example 1:
[0045] In an argon-filled glove box, weigh 2.75 mol of lithium sulfide, 0.25 mol of phosphorus pentasulfide, 0.50 mol of germanium disulfide, and 1.00 mol of lithium chloride. Place the weighed lithium sulfide, phosphorus pentasulfide, germanium disulfide, and lithium chloride together in a 500 mL zirconia ball mill jar. Add zirconia grinding balls with a diameter of 10 mm to the zirconia ball mill jar, controlling the ball-to-material mass ratio to be 20:1. After sealing the zirconia ball mill jar, remove it from the glove box and install it on a planetary ball mill. Set the speed of the planetary ball mill to 500 rpm and the continuous ball milling time to 15 h. After the ball milling is completed, put the zirconia ball mill jar back into the argon-filled glove box, open it, take out the powder obtained from the ball milling, and sieve the powder using a 200-mesh sieve to obtain amorphous precursor powder.
[0046] Preparation Example 2:
[0047] In an argon-filled glove box, 2.65 moles of lithium sulfide, 0.35 moles of phosphorus pentasulfide, 0.30 moles of germanium disulfide, and 1.00 moles of lithium chloride were weighed. The weighed lithium sulfide, phosphorus pentasulfide, germanium disulfide, and lithium chloride were placed together in a zirconia ball mill jar, and zirconia grinding balls were added. The size and ball-to-material mass ratio of the zirconia grinding balls were the same as in Preparation Example 1. The zirconia ball mill jar was sealed and installed on a planetary ball mill. The ball milling was carried out at 500 rpm for 15 hours. After the ball milling was completed, the product was sieved in the glove box to obtain amorphous precursor powder.
[0048] Preparation Example 3:
[0049] In an argon-filled glove box, 2.85 moles of lithium sulfide, 0.15 moles of phosphorus pentasulfide, 0.70 moles of germanium disulfide, and 1.00 moles of lithium chloride were weighed. The weighed lithium sulfide, phosphorus pentasulfide, germanium disulfide, and lithium chloride were placed together in a zirconia ball mill jar, and zirconia grinding balls were added. The size and ball-to-material mass ratio of the zirconia grinding balls were the same as in Preparation Example 1. The zirconia ball mill jar was sealed and installed on a planetary ball mill. The ball milling was carried out at 500 rpm for 15 hours. After the ball milling was completed, the product was sieved in the glove box to obtain amorphous precursor powder.
[0050] Preparation Example 4:
[0051] In an argon-filled glove box, 2.50 moles of lithium sulfide, 0.50 moles of phosphorus pentasulfide, and 1.00 moles of lithium chloride were weighed. The weighed lithium sulfide, phosphorus pentasulfide, and lithium chloride were placed in a zirconia ball mill jar. In this preparation example, germanium disulfide was not added. Zirconia grinding balls were added, and the size and ball-to-material mass ratio of the zirconia grinding balls were kept the same as in Preparation Example 1. The zirconia ball mill jar was sealed and installed on a planetary ball mill. The ball milling was carried out at 500 rpm for 15 hours. After the ball milling was completed, the product was sieved in the glove box to obtain amorphous reference precursor powder.
[0052] Examples 1-5:
[0053] Example 1:
[0054] This embodiment provides a high-performance sulfide solid electrolyte, the preparation method of which includes the following steps:
[0055] In a glove box filled with argon, the amorphous precursor powder prepared in Preparation Example 1 was measured and loaded into a carbon-coated quartz tube. The carbon-coated quartz tube containing the amorphous precursor powder was vacuum-sealed to reduce the pressure inside the carbon-coated quartz tube to below 10 Pa.
[0056] The sealed carbon-coated quartz tube was placed in the constant temperature zone of the tubular heating furnace. The heating program of the tubular heating furnace was set, and the heating furnace was heated to 550℃ at a heating rate of 3.0℃ / min. The amorphous precursor powder was kept at a constant temperature of 550℃ for 4 hours.
[0057] After the constant temperature heat treatment is completed, the program cooling mode of the tubular furnace is started, and the tubular furnace is controlled to reduce the temperature to 200℃ at a cooling rate of 1.0℃ / min. When the temperature is reduced to 200℃, the power supply of the tubular furnace is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature with the furnace.
[0058] The carbon-coated quartz tube was opened in an argon-filled glove box, the sintered block was removed, and the sintered block was ground into powder using an agate mortar and sieved to obtain sulfide solid electrolyte powder.
[0059] Example 2:
[0060] This embodiment provides a high-performance sulfide solid electrolyte. The preparation method includes the following steps: in a glove box filled with argon, the amorphous precursor powder prepared in Preparation Example 2 is measured, the amorphous precursor powder is loaded into a carbon-coated quartz tube, and the carbon-coated quartz tube containing the amorphous precursor powder is vacuum-sealed to reduce the pressure inside the carbon-coated quartz tube to below 10 Pa.
[0061] The sealed carbon-coated quartz tube was placed in the constant temperature zone of the tubular heating furnace. The heating program of the tubular heating furnace was set, and the heating furnace was heated to 550℃ at a heating rate of 3.0℃ / min. The amorphous precursor powder was kept at a constant temperature of 550℃ for 4 hours.
[0062] After the constant temperature heat treatment is completed, the program cooling mode of the tubular furnace is started, and the tubular furnace is controlled to reduce the temperature to 200℃ at a cooling rate of 1.0℃ / min. When the temperature is reduced to 200℃, the power supply of the tubular furnace is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature with the furnace.
[0063] The carbon-coated quartz tube was opened in an argon-filled glove box, the sintered block was removed, ground and sieved to obtain sulfide solid electrolyte powder.
[0064] Example 3:
[0065] This embodiment provides a high-performance sulfide solid electrolyte, the preparation method of which includes the following steps:
[0066] In an argon-filled glove box, the amorphous precursor powder prepared in Preparation Example 3 was measured and placed into a carbon-coated quartz tube. The carbon-coated quartz tube containing the amorphous precursor powder was then vacuum-sealed to reduce the pressure inside the tube to below 10 Pa.
[0067] The sealed carbon-coated quartz tube was placed in the constant temperature zone of the tubular heating furnace. The heating program of the tubular heating furnace was set, and the heating furnace was heated to 550℃ at a heating rate of 3.0℃ / min. The amorphous precursor powder was kept at a constant temperature of 550℃ for 4 hours.
[0068] After the constant temperature heat treatment is completed, the program cooling mode of the tubular furnace is started, and the tubular furnace is controlled to reduce the temperature to 200℃ at a cooling rate of 1.0℃ / min. When the temperature is reduced to 200℃, the power supply of the tubular furnace is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature with the furnace.
[0069] The carbon-coated quartz tube was opened in an argon-filled glove box, the sintered block was removed, ground and sieved to obtain sulfide solid electrolyte powder.
[0070] Example 4:
[0071] This embodiment provides a high-performance sulfide solid electrolyte, the preparation method of which includes the following steps:
[0072] In an argon-filled glove box, the amorphous precursor powder prepared in Example 1 was measured, and the amorphous precursor powder was loaded into a carbon-coated quartz tube and vacuum-sealed. The sealing conditions were the same as in Example 1.
[0073] The sealed carbon-coated quartz tube was placed in a tube furnace, and the heating program of the tube furnace was set to heat the tube furnace to 520℃ at a heating rate of 3.0℃ / min. The amorphous precursor powder was kept at a constant temperature of 520℃ for 4 hours.
[0074] After the constant temperature heat treatment is completed, the program cooling mode of the tubular furnace is started, and the tubular furnace is controlled to reduce the temperature to 200℃ at a cooling rate of 3.0℃ / min. When the temperature drops to 200℃, the power supply of the tubular furnace is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature with the furnace.
[0075] The carbon-coated quartz tube was opened in an argon-filled glove box, the sintered block was removed, ground and sieved to obtain the sulfide solid electrolyte powder described in Example 4.
[0076] Example 5:
[0077] This embodiment provides a high-performance sulfide solid electrolyte, the preparation method of which includes the following steps:
[0078] In an argon-filled glove box, the amorphous precursor powder prepared in Example 1 was measured, and the amorphous precursor powder was loaded into a carbon-coated quartz tube and vacuum-sealed. The sealing conditions were the same as in Example 1.
[0079] The sealed carbon-coated quartz tube was placed in a tube furnace, and the heating program of the tube furnace was set to heat the tube furnace to 580℃ at a heating rate of 3.0℃ / min. The amorphous precursor powder was kept at a constant temperature of 580℃ for 4 hours.
[0080] After the constant temperature heat treatment is completed, the program cooling mode of the tubular heating furnace is started, and the temperature of the tubular heating furnace is reduced to 200℃ at a cooling rate of 0.5℃ / min. When the temperature is reduced to 200℃, the power supply of the tubular heating furnace is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature with the furnace.
[0081] The carbon-coated quartz tube was opened in an argon-filled glove box, the sintered block was removed, ground and sieved to obtain sulfide solid electrolyte powder.
[0082] Comparative Examples 1-5:
[0083] Comparative Example 1:
[0084] Compared with Example 1, the difference lies in the cooling step after the heat treatment. In Comparative Example 1, after the amorphous precursor powder was kept at a constant temperature of 550°C for 4 hours, the carbon-coated quartz tube was immediately taken out of the tube furnace and quickly immersed in an ice-water mixture at 0°C for quenching and cooling, so that the temperature of the carbon-coated quartz tube dropped to room temperature within 1 minute. The remaining preparation steps were the same as in Example 1.
[0085] Comparative Example 2:
[0086] Compared with Example 1, the difference lies in the temperature of the isothermal heat treatment. In Comparative Example 2, the tubular furnace was heated to 750°C and the amorphous precursor powder was kept at 750°C for 4 hours. The remaining preparation steps were the same as in Example 1.
[0087] Comparative Example 3:
[0088] Compared with Example 1, the difference lies in the temperature of the isothermal heat treatment. In Comparative Example 3, the tubular furnace was heated to 450°C and the amorphous precursor powder was kept at 450°C for 4 hours. The remaining preparation steps were the same as in Example 1.
[0089] Comparative Example 4:
[0090] Compared with Example 1, the difference lies in the raw materials used. In Comparative Example 4, the amorphous reference precursor powder prepared in Preparation Example 4 was used to replace the amorphous precursor powder prepared in Preparation Example 1, and the remaining preparation steps were consistent with those in Example 1.
[0091] Comparative Example 5:
[0092] Compared with Example 1, the difference lies in the cooling step after the heat treatment. In Comparative Example 5, after the amorphous precursor powder was kept at a constant temperature of 550°C for 4 hours, the programmed cooling mode of the tube furnace was not started. Instead, the power supply of the tube furnace was directly turned off, allowing the carbon-coated quartz tube to cool naturally to room temperature with the tube furnace (the initial cooling rate during the natural cooling process was greater than 5.0°C / min and the rate changed non-linearly). The remaining preparation steps were consistent with those in Example 1.
[0093] Test Example 1-3:
[0094] Test Example 1: Crystal Structure Analysis
[0095] This test example utilizes powder X-ray diffraction to analyze the phase composition and crystallinity of sulfide solid electrolyte powders prepared in Examples 1 to 5 and Comparative Examples 1 to 5. The selected instrument is a D8 Advance X-ray diffractometer manufactured by Bruker GmbH, Germany. The radiation source is copper target Kα rays with a wavelength λ of 1.5406 Å. The tube voltage and tube current during the test are set to 40 kV and 40 mA, respectively.
[0096] Experimental procedure:
[0097] In an argon glove box with a dew point below -60°C, take an appropriate amount of the sulfide solid electrolyte powder to be tested, fill the sulfide solid electrolyte powder into the groove of a special airtight sample holder, and cover the surface with a polyimide film to isolate the sample from moisture and oxygen in the external air, so as to prevent the sample from hydrolyzing or oxidizing during the test.
[0098] Transfer the sample holder loaded with the sample to the test stage of the X-ray diffractometer, set the scanning mode to continuous scanning, the scanning range of the diffraction angle (2-Theta) to 10° to 60°, the scanning step size to 0.02°, and the dwell time for each step to 0.2s.
[0099] After the test, the collected diffraction pattern data were processed using analysis software. The measured pattern was compared with the standard crystal structure card data of silver-germanium sulfide to confirm the main crystal phase. The diffraction signal intensity in the range of 29.0° to 30.0° with a diffraction angle of 2-Theta was analyzed to determine whether there were any impurity phases.
[0100] The main diffraction peak (corresponding to the 311 crystal plane) was selected, and the average grain size was calculated according to the Scherrer formula. The crystallinity of the sulfide solid electrolyte powder prepared in Example 1 was used as 100% as the benchmark to calculate the relative crystallinity of other samples.
[0101] Experimental data:
[0102] Table 1. Crystal structure parameters and impurity phase analysis data of each embodiment and comparative sample.
[0103]
[0104] Analysis of test results: According to the experimental data shown in Table 1 and the X-ray diffraction pattern analysis in Figure 1, the sulfide solid electrolyte powders prepared in Examples 1 to 5 did not show obvious impurity peak signals near 29.5°, and the half-width of the main crystal plane (311) was narrow, and the relative crystallinity was maintained above 93%. This shows that heat treatment in a specific temperature range of 520°C to 580°C, combined with a controlled slow cooling process of 0.5°C / min to 3.0°C / min, can ensure the full diffusion and orderly arrangement of sulfur, phosphorus, germanium and chlorine atoms at the lattice sites, forming a structurally complete sulfosilver germanium mineral crystal phase, and suppressing the precipitation of low conductivity impurity phases.
[0105] In contrast, Comparative Example 1, which employed an ice-water quenching process, resulted in a significant increase in the half-width at half-maximum (WHM) of the sample to 0.289 degrees, and the appearance of an impurity peak with an intensity of 358 counts at 29.5°. This confirms that a sharp temperature drop introduces enormous thermal stress into the crystal, hindering the lattice's ordering process and causing metastable impurity phases to be frozen within the structure. Comparative Example 2, due to its excessively high heat treatment temperature (750°C), caused some sulfur or chlorine elements to volatilize, disrupting the stoichiometric balance and generating a large number of decomposition products, characterized by extremely high impurity peak intensity (1312 counts) and extremely low crystallinity (44.6%). Comparative Example 5, which used a natural furnace cooling method, although the cooling rate was slower than quenching, still could not completely eliminate the defects caused by the thermal history due to the uncontrolled and rapid initial cooling rate, resulting in a crystallinity lower than that of Example 1 and the presence of a small amount of impurity phases.
[0106] The above results verify that a specific slow cooling process plays a decisive role in obtaining high-purity, high-crystallinity germanium-doped sulfide solid electrolytes.
[0107] Test Example 2: Ionic Conductivity Test
[0108] This test mainly uses AC impedance spectroscopy to quantitatively characterize the lithium-ion transport capacity of the sulfide solid electrolyte powders prepared in Examples 1 to 5 and Comparative Examples 1 to 5 at room temperature. The equipment used for the test is a high-performance 1260A impedance analyzer with a 1287A electrochemical interface.
[0109] The experimental procedure is as follows:
[0110] In an argon atmosphere glove box, accurately weigh 120 mg of the sulfide solid electrolyte powder to be tested, load the sulfide solid electrolyte powder into a polyether ether ketone insulating mold with an inner diameter of 10 mm, apply a cold pressing pressure of 360 MPa to the sulfide solid electrolyte powder in the mold using a hydraulic press, maintain the pressure for 3 min, densify the sulfide solid electrolyte powder, and form sulfide solid electrolyte discs.
[0111] Polished stainless steel sheets with a diameter of 10 mm were placed on the upper and lower surfaces of the sulfide solid electrolyte disc as blocking electrodes. The sandwich structure fixture composed of the stainless steel sheet and the sulfide solid electrolyte disc was placed in the test battery casing under a constant stacking pressure of 50 MPa, and the sealing bolts were tightened to ensure good electrical contact and air isolation.
[0112] Connect the assembled test cell to the electrochemical workstation. Allow it to stand at a constant temperature of 25°C for 2 hours to reach thermal equilibrium. Start the AC impedance test program, setting the applied AC voltage amplitude to 10mV and the scan frequency range to 0.1Hz to 1MHz.
[0113] After the test, the Nyquist plot composed of the real and imaginary impedances was obtained. The Nyquist plot was analyzed, and the right intercept of the high-frequency semicircle with the real axis was read as the total resistance value of the sulfide solid electrolyte disc. The thickness of a sulfide solid electrolyte disc was measured using a micrometer screw gauge. The cross-sectional area of the sulfide solid electrolyte disc was calculated based on the mold diameter. According to the formula
[0114] Calculate ionic conductivity .
[0115] Experimental data:
[0116] Table 2. Impedance test data and ionic conductivity calculation results for each embodiment and comparative sample.
[0117]
[0118] Analysis of test results: Based on the test data in Table 2 and Figure 2, the sulfide solid electrolytes prepared in Examples 1 to 5 all exhibited excellent ion conduction performance, with their ion conductivity values concentrated between 1.14 mS / cm and 1.23 mS / cm.
[0119] Comparing Example 1 (1.23 mS / cm) with Comparative Example 4 (1.01 mS / cm), it can be seen that under the same crystal structure matrix, the introduction of germanium to replace part of phosphorus can significantly improve the migration rate of lithium ions. This is because the ionic radius of germanium ions is larger than that of phosphorus ions. The introduction of germanium causes volume expansion in the crystal lattice, which widens the transport channels of lithium ions. At the same time, the high polarizability of germanium helps to reduce the activation energy of lithium ions transitioning in the interlattice.
[0120] Comparing Example 1 with Comparative Example 1 (0.92 mS / cm) and Comparative Example 5 (1.04 mS / cm), it can be seen that the cooling process after heat treatment has a decisive influence on the final conductivity. The quenching process used in Comparative Example 1 resulted in a large number of grain boundary defects and amorphous regions inside the sulfide solid electrolyte. These defects became scattering centers for lithium-ion transport, increasing grain boundary impedance. The controlled slow cooling process used in Example 1 promoted the complete development of grains, reduced the number of grain boundaries, and lowered the grain boundary barrier, thereby constructing a more unobstructed long-range lithium-ion transport network. The extremely low conductivity of Comparative Example 2 (0.38 mS / cm) further confirms that phase decomposition and impurity generation caused by high temperature can severely block ion transport paths.
[0121] The above results demonstrate that the present invention achieves an increase in the ionic conductivity of sulfide solid electrolytes through the synergistic effect of germanium doping and a specific heat treatment process.
[0122] Test Example 3: Water Resistance Stability (Air Stability) Test
[0123] This test case aims to evaluate the chemical stability of the sulfide solid electrolyte powders prepared in Examples 1 to 5 and Comparative Examples 1 to 5 under controlled humid conditions. The resistance to moisture erosion is quantified by monitoring the changes in ionic conductivity of the sulfide solid electrolyte before and after exposure to a specific humidity environment.
[0124] The experimental procedure is as follows:
[0125] A stable testing environment was constructed and maintained using a programmable temperature and humidity chamber. The ambient temperature was set to 25°C and the relative humidity to 50%. In an argon glove box, the sulfide solid electrolyte powders to be tested were spread evenly in several open weighing bottles. The weighing bottles containing the sulfide solid electrolyte powders were quickly transferred to the temperature and humidity chamber and the timing was started. A portion of the sulfide solid electrolyte powders was removed from the temperature and humidity chamber after 1 hour, 3 hours and 6 hours of exposure.
[0126] The extracted sulfide solid electrolyte powder was quickly transferred back to the vacuum drying oven for short-term vacuum drying (25℃, -0.1MPa, 30min) to remove the physically adsorbed moisture on the surface, and then transferred to an argon glove box.
[0127] Following the method described in Test Example 2, the exposed sulfide solid electrolyte powder was cold-pressed into sheets and assembled into a blocking battery. Its ionic conductivity after exposure was determined using AC impedance spectroscopy.
[0128] The initial ionic conductivity of the unexposed sample measured in Test Example 2 was used.
[0129] Based on the formula Calculate conductivity retention rate .
[0130] Table 3. Conductivity retention test data of each embodiment and comparative sample under humid conditions.
[0131]
[0132] Test conclusion analysis: The data in Table 3 and Figure 3 reveal that the germanium-doped sulfide solid electrolyte prepared in this invention has excellent water resistance and stability. After being exposed to an environment with a relative humidity of 50% for 1 hour, the conductivity retention rate of the samples in Examples 1 to 5 was maintained at over 90%, and even after being exposed for 6 hours, it could still maintain about 60% of the initial performance.
[0133] Comparing the data differences between Example 1 and Comparative Example 4 (without germanium doping) (6h retention rate: 61.0% vs 17.8%), it is confirmed that the introduction of germanium significantly enhances the resistance of the crystal framework to water molecules. This is attributed to the fact that the bond energy of germanium-sulfur bonds (Ge-S) is higher than that of phosphorus-sulfur bonds (PS), and that germanium-sulfur tetrahedral structural units are less likely to undergo hydrolysis to generate hydrogen sulfide gas when encountering water molecules compared to phosphorus-sulfur tetrahedrons, thus delaying the collapse of the crystal structure at the microscopic level.
[0134] Meanwhile, comparing Example 1 with Comparative Example 1 (quenched, 6h retention rate: 5.4%) and Comparative Example 5 (natural cooling, 6h retention rate: 30.8%), the results show that high crystallinity is another core factor in improving water resistance. Example 1 obtained high-quality crystal particles with few surface defects and tight grain boundary bonding through a slow cooling process, reducing the diffusion path of water molecules penetrating into the grain interior. In contrast, Comparative Example 1 generated a large number of microcracks and highly active amorphous phases due to rapid cooling. These defect sites became the breakthrough points for water molecules, causing the material to hydrolyze in a short time, and the electrical conductivity decreased exponentially.
[0135] In summary, this invention solves the technical bottleneck of air sensitivity in sulfide solid electrolytes through a dual strategy of component optimization (germanium doping) and structural control (high crystallinity).
[0136] Test Example 4: Cycle Performance Test of All-Solid-State Battery
[0137] This test case aims to evaluate the electrochemical compatibility and long-cycle stability of the sulfide solid electrolyte powders prepared in Examples 1, 3, 1, 2, and 4 in all-solid-state lithium secondary batteries. The specific discharge capacity and capacity retention data were obtained by assembling laboratory-grade mold batteries and performing constant current charge-discharge cycles under controlled conditions.
[0138] The experimental procedure is as follows:
[0139] Preparation of the positive electrode mixture: In an argon glove box, single-crystal lithium nickel cobalt manganese oxide was weighed as the positive electrode active material, the sulfide solid electrolyte powder to be tested was weighed as the positive electrode side electrolyte, and vapor-grown carbon fiber (VGCF) was weighed as the conductive agent. The positive electrode active material, sulfide solid electrolyte powder and conductive agent were mixed at a mass ratio of 70:27:3 and ground and mixed in an agate mortar for 30 minutes to obtain the positive electrode composite powder.
[0140] Assembly of all-solid-state batteries: A polyether ether ketone (PEEK) mold with an inner diameter of 10 mm was selected as the battery casing. First, 80 mg of the sulfide solid electrolyte powder to be tested was weighed and added to the mold. 100 MPa pressure was applied for cold pressing to form a solid electrolyte layer. Then, 15 mg of the prepared positive electrode composite powder was weighed and evenly spread on one side surface of the solid electrolyte layer. 240 MPa pressure was applied for compaction to form a positive electrode layer.
[0141] A lithium-indium alloy sheet with a diameter of 10 mm and a thickness of 0.1 mm was placed on the other side of the solid electrolyte layer. The foil is used as the negative electrode. A pressure of 120MPa is applied to make the interfaces of each layer in close contact. Finally, a stainless steel current collector is placed in and the battery mold bolts are tightened to maintain a constant stacking pressure of 50MPa.
[0142] Battery performance testing: The assembled all-solid-state battery was connected to the Blue Battery testing system. Under a constant temperature environment of 25℃, the charge / discharge voltage range was set from 2.5V to 4.2V. First, an initial charge / discharge activation cycle was performed at a rate of 0.05C. Subsequently, the rate was adjusted to 0.1C for long-cycle testing. The specific capacity of the first discharge cycle and the specific capacity after the 200th cycle were recorded. The specific capacity was then calculated according to the formula... Calculate the capacity retention rate over 200 cycles.
[0143] Table 4. Cyclic performance test data of all-solid-state batteries assembled in each embodiment and comparative example.
[0144]
[0145] Test conclusion analysis: According to the cycle performance data in Table 4 and Figure 4, the all-solid-state battery assembled using the sulfide solid electrolyte prepared in Example 1 of this invention exhibits the best electrochemical stability, with a discharge specific capacity of 172.5 mAh / g in the first cycle and a capacity retention rate of up to 92.1% after 200 cycles.
[0146] Comparing Example 1 with Comparative Example 1 (quenched, retention rate 37.8%), the performance difference is significant. This confirms that the crystal quality of the electrolyte itself is directly related to the cycle life of the battery. The metastable impurity phase and lattice stress present in Comparative Example 1 easily induce local collapse of the crystal structure and the propagation of microcracks during the repeated insertion and extraction of lithium ions during charging and discharging. These microcracks cut off the ion transport channels and aggravate the side reactions at the interface between the electrolyte and the cathode material, resulting in rapid capacity decay. In contrast, the highly crystalline structure of Example 1 not only provides stable ion channels but also enhances the mechanical strength of the material, enabling it to better adapt to volume changes during charging and discharging.
[0147] Comparing Example 1 with Comparative Example 4 (without germanium, retention rate 75.0%), it can be seen that germanium doping has a positive effect on improving the interface stability under high voltage. Although the initial capacity of Comparative Example 4 is acceptable, it decays rapidly during long-term cycling. From a mechanistic perspective, the high conductivity germanium-doped electrolyte in Example 1 reduces the polarization resistance inside the battery, and the introduction of germanium optimizes the electrochemical window stability of the positive electrode electrolyte interface, inhibiting oxidation decomposition under high voltage. In Comparative Example 2 (high temperature), due to the extremely low ionic conductivity and high impurity content of the electrolyte itself, the battery is severely polarized, the utilization rate of active materials is low, and it basically cannot meet the requirements of normal cycling.
[0148] In summary, the technical solution of this invention solves the key problems of increased interface impedance and poor cycle stability in all-solid-state batteries.
Claims
1. A method for manufacturing a high-performance sulfide solid electrolyte, characterized in that, Includes the following steps: S1: Under an inert atmosphere, lithium sulfide, phosphorus pentasulfide, germanium disulfide, and lithium chloride are ball-milled to obtain amorphous precursor powder; S2: The amorphous precursor powder is sealed in a carbon-coated quartz tube, and the carbon-coated quartz tube is evacuated. Then, the carbon-coated quartz tube is placed in a heating device for isothermal heat treatment; S3: After the isothermal heat treatment, the programmed cooling mode of the heating device is activated, and the heating device is controlled to reduce the temperature to below 200°C at a cooling rate of 0.5°C / min to 3.0°C / min. When the temperature drops below 200°C, the power supply of the heating device is turned off, and the carbon-coated quartz tube is allowed to cool naturally to room temperature with the heating device. The sintered block is then removed and ground to obtain the high-performance sulfide solid electrolyte.
2. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, The lithium sulfide comprises 2.50 to 2.90 parts by molar amount, the phosphorus pentasulfide comprises 0.10 to 0.40 parts by molar amount, the germanium disulfide comprises 0.20 to 0.80 parts by molar amount, and the lithium chloride comprises 0.80 to 1.20 parts by molar amount.
3. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, In step S1, the ball milling speed is 400 rpm to 600 rpm, and the ball milling time is 10 h to 20 h.
4. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, In step S1, the ball milling process is carried out under conditions where the ball-to-material mass ratio is 15:1 to 25:
1.
5. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, In step S2, the internal pressure of the carbon-coated quartz tube after vacuum treatment is less than 10 Pa.
6. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, In step S2, the heating rate of the heating device to the temperature of the constant temperature heat treatment is 2.0℃ / min to 4.0℃ / min.
7. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, In step S2, the temperature of the constant temperature heat treatment is 520°C to 580°C, and the holding time of the constant temperature heat treatment is 3 hours to 5 hours.
8. The method for manufacturing a high-performance sulfide solid electrolyte according to claim 1, characterized in that, In step S3, the grinding process involves using an agate mortar to grind the sintered block into powder, and then using a sieve to sieve the powder.
9. An application of a high-performance sulfide solid electrolyte, characterized in that, The invention relates to an all-solid-state secondary battery, the all-solid-state secondary battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer or the positive electrode layer contains a high-performance sulfide solid electrolyte prepared by the manufacturing method of a high-performance sulfide solid electrolyte according to any one of claims 1 to 8.
10. The application of a high-performance sulfide solid electrolyte according to claim 9, characterized in that, The positive electrode layer includes a positive electrode active material, the high-performance sulfide solid electrolyte, and a conductive agent; the operating voltage range of the all-solid-state secondary battery is 2.5V to 4.2V.