Method for mechanically preparing a sulfide / oxide solid-state electrolyte with a melon structure

Abstract

The application belongs to the technical field of solid electrolyte, and particularly relates to a method for preparing melon pulp structure sulfide / oxide solid electrolyte by a mechanical method, which comprises the following steps: under the condition of a protective atmosphere, pre-mixing sulfide solid electrolyte powder and oxide solid electrolyte powder, then speed-changing ball milling the obtained pre-mixed material to obtain a mixed powder; the speed-changing ball milling is sequentially low-speed ball milling and high-speed ball milling under the condition of low-temperature nitrogen; heat pressing the mixed powder under the condition of a protective atmosphere to obtain a sulfide / oxide composite solid electrolyte; the rotating speed of the low-speed ball milling is 100-150 rpm; the rotating speed of the high-speed ball milling is 350-390 rpm; during the high-speed ball milling, the low-temperature nitrogen is continuously introduced into a ball milling chamber so that the temperature in the ball milling chamber is 0-10 DEG C. The application realizes high interface bonding strength and high lithium ion conductivity by the combination of speed-changing ball milling, low temperature and heat pressing processes.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, specifically relating to a method for mechanically preparing a sucrose / oxide solid electrolyte with a pulp-like structure. Background Technology

[0002] With the rapid development and market application of electric vehicles, safety hazards caused by battery thermal runaway or short circuits are becoming increasingly frequent. Solid electrolytes, compared to existing commercial liquid electrolytes, have attracted much attention due to their non-flammability and high safety. Oxide solid electrolytes have the advantages of high air stability and low cost, but they suffer from high grain boundary resistance and low ionic conductivity. Sulfide solid electrolytes, on the other hand, have high ionic conductivity, but are expensive and have poor air stability. Therefore, mixing oxide and sulfide solid electrolytes in a certain proportion to prepare composite electrolytes can simultaneously achieve high ionic conductivity and low cost, and has become a hot topic in the research of novel solid electrolytes, with significant application value.

[0003] However, the grinding or low-speed ball milling methods used in existing sulfide / oxide composite solid electrolytes cannot achieve uniform dispersion of the two phases and effective contact at the composite interface, resulting in low lithium-ion conductivity. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a mechanical method for preparing a sulfide / oxide solid electrolyte with a pulp structure. The sulfide / oxide solid electrolyte composite solid electrolyte prepared by the preparation method provided by the present invention has good dispersibility and high conductivity.

[0005] To achieve the above objectives, this invention provides a method for mechanically preparing a jujube-like structured sulfide / oxide solid electrolyte, comprising the following steps:

[0006] Under a protective atmosphere, sulfide solid electrolyte powder and oxide solid electrolyte powder are premixed, and the resulting premix is ​​ball-milled at variable speed to obtain a mixed powder; the variable speed ball milling is performed by sequentially performing low-speed ball milling and high-speed ball milling under low-temperature nitrogen conditions.

[0007] The mixed powder was hot-pressed under a protective atmosphere to obtain a sulfide / oxide composite solid electrolyte.

[0008] The low-speed ball mill operates at a speed of 100-150 rpm; the high-speed ball mill operates at a speed of 350-390 rpm; during the high-speed ball milling, low-temperature nitrogen gas is continuously introduced into the ball milling chamber to maintain a temperature of 0-10°C within the chamber.

[0009] Preferably, the low-speed ball milling time is 2-5 hours; during the low-speed ball milling process, there is a 10-20 minute stop after every 30-45 minutes of low-speed ball milling; the high-speed ball milling time is 18-22 hours; during the high-speed ball milling process, there is a 10-20 minute stop after every 30-45 minutes of high-speed ball milling; the time interval between the high-speed ball milling and the low-speed ball milling is 0.8-1.2 hours.

[0010] Preferably, the temperature of the cryogenic nitrogen gas is -50 to -40°C; the flow rate of the cryogenic nitrogen gas is 1-2 L / min.

[0011] Preferably, the low-speed ball milling and the high-speed ball milling are independently bidirectional ball milling with dual grinding beads.

[0012] Preferably, the dual grinding beads include a large-diameter grinding bead and a small-diameter grinding bead; the large-diameter grinding bead has a diameter of 15 mm; and the small-diameter grinding bead has a diameter of 10 mm.

[0013] Preferably, the ratio of the number of large-diameter grinding beads to the number of small-diameter grinding beads is 3:2, and the ratio of the mass of the premix to the number of the two grinding beads is 1-2g:25.

[0014] Preferably, the hot pressing conditions include: a pressure of 500-600 MPa; a hot pressing temperature of 280-300°C; and a hot pressing time of 6-8 hours.

[0015] Preferably, the oxide solid electrolyte powder is Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1+x Al x Ge 2-x (PO4)3 and Li 3x La 2 / 3-x One or more of TiO3; the sulfide solid electrolyte powder is xLi2S·(1-x)P2S5, where 80≤x≤85.

[0016] Preferably, the particle sizes of the sulfide solid electrolyte powder and the oxide solid electrolyte powder are independently 0.1-1 μm and 0.1-0.5 μm.

[0017] Preferably, the mass ratio of the sulfide solid electrolyte to the oxide solid electrolyte powder is (9-4):1.

[0018] The mechanical method for preparing a pulp-structured sulfide / oxide solid electrolyte described in this invention has the advantage over existing technologies in that it combines variable-speed ball milling with low-temperature and hot-pressing processes to embed oxide grains into a sulfide matrix, forming a pulp-structured composite electrolyte material. This results in an amorphous sulfide solid electrolyte after ball milling, which undergoes a phase transition during hot pressing to form Thio-lisicon II crystals. This provides higher lithium-ion conductivity based on high interfacial bonding strength, thereby achieving high performance of the sulfide / oxide composite solid electrolyte.

[0019] Specifically, this invention achieves uniform mixing of oxides and sulfides in the early stages through low-speed ball milling with variable-speed ball milling, followed by high-speed ball milling to refine oxide grains and coat oxides with sulfides. The uniformity ensures a sufficient number of migrateable lithium ions and maintains the continuity of ion migration channels; the refinement of oxide grains increases the sulfide / oxide interface content in the material, and the presence of lithium ion vacancies at this interface significantly improves the ionic conductivity of the material; while the sulfide coating of the oxides facilitates the interdiffusion of sulfur and oxygen atoms at the interface during hot pressing, enhancing the interfacial bonding strength.

[0020] The uniformity achieved through low-speed ball milling in the early stages provides the high efficiency of ion conduction for high-speed ball milling. This prevents the electrolyte powder from agglomerating when high-speed ball milling is used alone, which would otherwise prevent the uniform distribution of oxides within the sulfide and lead to oxide particle aggregation. This aggregation would prevent lithium ions from migrating to those locations, while other areas, free of oxides, would allow lithium ions to migrate within the sulfide electrolyte. The ionic conductivity of this transport method is lower than that of the oxide / sulfide interface conduction method. Conversely, low-speed ball milling alone cannot achieve the refinement of oxide grains and the coating of oxides by sulfides. These large grains prevent lithium ions from migrating along the interface and force them to cross the interface and migrate within the oxide, severely hindering the improvement of ion migration capability.

[0021] This invention also creates a low-temperature ball milling environment through high-speed ball milling under low-temperature nitrogen conditions, which makes the sulfide solid electrolyte after ball milling an amorphous phase. During hot pressing, a phase transition occurs to form Thio-lisicon II crystals, which exhibit higher lithium-ion conductivity. Compared with the lithium-ion activation energy of ball milling at room temperature, the lithium-ion activation energy of the electrolyte obtained by low-temperature ball milling is lower. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the low-temperature nitrogen gas introduced into the ball mill device in an embodiment of the present invention;

[0023] Figure 2This is a comparison chart of the ionic conductivity of the composite electrolyte under low-temperature ball milling and room-temperature ball milling conditions in the embodiments of the present invention.

[0024] Figure 3 The XRD patterns of the ball-milled products obtained by ball milling Li2S and P2S5 under high-speed ball milling conditions of 374 rpm in the embodiments of the present invention are shown.

[0025] Figure 4 The image shows a scanning electron microscope (SEM) image and an energy dispersive spectral distribution of each element in the sulfide / oxide composite solid electrolyte prepared in Example 1.

[0026] Figure 5 Here is a high-magnification SEM image of the sulfide / oxide composite solid electrolyte prepared in Example 1;

[0027] Figure 6 Scanning electron microscope (SEM) image and energy dispersive spectral distribution of each element of the sulfide / oxide composite solid electrolyte prepared for Comparative Example 1.

[0028] Figure 7 High-magnification SEM image of the sulfide / oxide composite solid electrolyte prepared in Comparative Example 1;

[0029] Figure 8 The AC impedance curves of the composite solid electrolytes prepared in Example 1 and Comparative Example 1 are shown.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1-Air pump; 2-Air pipe; 3-Liquid nitrogen; 4-Liquid nitrogen tank; 5-Grinding chamber; 6-Grinding jar. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] This invention provides a method for mechanically preparing a sucrose / oxide solid electrolyte with a pulp-like structure, comprising the following steps:

[0034] Under a protective atmosphere, sulfide solid electrolyte powder and oxide solid electrolyte powder were premixed, and the resulting premix was ball-milled at variable speed to obtain a mixed powder; the variable speed ball milling consisted of low-speed ball milling followed by high-speed ball milling under low-temperature nitrogen conditions.

[0035] The mixed powder was hot-pressed under a protective atmosphere to obtain a sulfide / oxide composite solid electrolyte.

[0036] The rotation speed of the low-speed ball mill is 100-150 rpm; the rotation speed of the high-speed ball mill is 350-450 rpm; during high-speed ball milling, low-temperature nitrogen gas is continuously introduced into the ball milling chamber to keep the temperature inside the ball milling chamber at 0-10℃.

[0037] This invention combines variable-speed ball milling with low-temperature and hot-pressing processes to achieve oxide grains embedded in a sulfide matrix, forming a composite electrolyte material with a pulp-like structure. This results in an amorphous sulfide solid electrolyte after ball milling, which undergoes a phase transition during hot pressing to form Thio-lisicon II crystals. This material exhibits higher lithium-ion conductivity based on high interfacial bonding strength, thereby achieving high performance of the sulfide / oxide composite solid electrolyte.

[0038] Specifically, in this embodiment of the invention, low-speed ball milling with variable speed ball milling achieves uniform mixing of oxides and sulfides in the early stages, followed by high-speed ball milling to refine oxide grains and coat oxides with sulfides. The uniformity achieved provides a sufficient number of migrateable lithium ions and ensures the continuity of ion migration channels; the refinement of oxide grains increases the sulfide / oxide interface content in the material, and the presence of lithium ion vacancies at this interface significantly improves the ionic conductivity of the material; while the coating of oxides with sulfides facilitates the interdiffusion of sulfur and oxygen atoms at the interface during hot pressing, improving the interfacial bonding strength.

[0039] The uniformity achieved through low-speed ball milling in the early stages provides the high efficiency of ion conduction for high-speed ball milling. This prevents the electrolyte powder from agglomerating when high-speed ball milling is used alone, which would otherwise prevent the uniform distribution of oxides within the sulfide and lead to oxide particle aggregation. This aggregation would prevent lithium ions from migrating to those locations, while other areas, free of oxides, would allow lithium ions to migrate within the sulfide electrolyte. The ionic conductivity of this transport method is lower than that of the oxide / sulfide interface conduction method. Conversely, low-speed ball milling alone cannot achieve the refinement of oxide grains and the coating of oxides by sulfides. These large grains prevent lithium ions from migrating along the interface and force them to cross the interface and migrate within the oxide, severely hindering the improvement of ion migration capability.

[0040] The embodiments of the present invention also utilize the low-temperature ball milling environment created by high-speed ball milling under low-temperature nitrogen conditions to make the sulfide solid electrolyte after ball milling an amorphous phase. During hot pressing, a phase transition occurs to form Thio-lisicon II crystals, which exhibit higher lithium-ion conductivity. Compared with the lithium-ion activation energy of ball milling at room temperature, the lithium-ion activation energy of the electrolyte obtained by low-temperature ball milling is lower.

[0041] In this embodiment of the invention, the protective atmosphere is preferably high-purity argon, and the purity of the high-purity argon is preferably 99.999%.

[0042] In this embodiment of the invention, a variable-speed ball milling process is adopted. The initial low-speed ball milling is to reduce the ball milling energy, so as to achieve uniform mixing of sulfide and oxide solid electrolytes and prevent the two electrolytes from adhering to the surface of the grinding balls or the inner wall of the grinding jar, thereby reducing material loss and achieving uniform mixing of the two electrolytes. The high-speed ball milling stage is to apply high collision energy to the sulfide solid electrolyte, so that the sulfide solid electrolyte is transformed into an amorphous glass molten state, which promotes the coating of sulfide solid electrolyte on the surface of oxide solid electrolyte and reduces the porosity after coating, thereby improving the interface between oxide and sulfide. In this way, a composite solid electrolyte with good dispersion of sulfide and oxide solid electrolytes, low porosity defect density, and high lithium-ion conductivity is prepared.

[0043] Specifically, after high-speed ball milling, lithium ions are conducted inside the sulfide solid electrolyte. After low-speed ball milling, lithium ion conduction is a combination of conduction inside the sulfide and interfacial conduction. However, large oxide grains can hinder ion conduction. In variable-speed ball milling, interfacial conduction is the main mode of lithium ion migration, which greatly improves the conductivity of lithium ions.

[0044] In this embodiment of the invention, a grinding aid is also added. A tetrahydrofuran / ethanol composite grinding aid is added during the ball milling process, wherein the ratio of tetrahydrofuran:ethanol:raw material is 1:0.5:8-1:0.5:9. The addition of the liquid phase is beneficial to improving the dispersibility of oxides in the composite electrolyte. In addition, the dissolving effect of tetrahydrofuran on sulfides can inhibit their crystallization and agglomeration during the ball milling process, while the addition of ethanol is beneficial to realizing the replacement of some sulfur atoms by oxygen atoms in the sulfide solid electrolyte.

[0045] In an embodiment of the present invention, the premixing method is grinding.

[0046] In an embodiment of the present invention, the ball milling is preferably dry milling.

[0047] In some specific embodiments, the low-speed ball milling time is 2-5 hours; during the low-speed ball milling process, there is a 10-20 minute stop after every 30-45 minutes of low-speed ball milling; the high-speed ball milling time is 18-22 hours; during the high-speed ball milling process, there is a 10-20 minute stop after every 30-45 minutes of high-speed ball milling; the time interval between the high-speed ball milling and the low-speed ball milling is 0.8-1.2 hours.

[0048] In this embodiment of the invention, preferably, the time interval between the high-speed ball milling and the low-speed ball milling is 1 hour; preferably, the rotation speed of the high-speed ball milling is 370-400 rpm and the time is 18-22 hours, preferably 20 hours; during the high-speed ball milling process, every 30 minutes of high-speed ball milling is followed by a 10-minute stop.

[0049] Therefore, intermittent low-speed ball milling is more conducive to the uniform mixing of oxides and sulfides in the early stage, while intermittent high-speed ball milling is more conducive to the input of nitrogen, improving the accuracy of temperature control in the ball milling chamber. In addition, while improving the coating rate of sulfides on oxides, the ball-milled sulfide solid electrolyte is an amorphous phase, which is conducive to the subsequent phase transformation to form Thio-lisicon II crystals during hot pressing, further improving the lithium-ion conductivity.

[0050] In some specific embodiments, the temperature of the cryogenic nitrogen gas is -50 to -40°C; the flow rate of the cryogenic nitrogen gas is 1-2 L / min.

[0051] According to such Figure 1 The cryogenic apparatus shown introduces cryogenic nitrogen gas into the ball milling chamber at a flow rate of 1-2 L / min during the high-speed ball milling stage. Preferably, the nitrogen gas temperature is -50 to -40°C. This process reduces the temperature inside the ball milling chamber from over 100°C after cryogenic ball milling to 0-10°C. During high-speed ball milling at room temperature, the sulfide solid electrolyte crystallizes under high temperature and pressure, producing Li4P2S6 crystals. This crystalline phase has extremely low ionic conductivity and good thermal stability, making it difficult for phase transformation to occur during subsequent hot pressing, thus failing to improve ionic conductivity. However, the cryogenic high-speed ball milling environment created in this embodiment is beneficial for the grain refinement of the oxide solid electrolyte during the process, while preventing the crystallization of the sulfide solid electrolyte. This results in the ball-milled sulfide solid electrolyte being an amorphous phase, which undergoes a phase transformation during hot pressing to form Thio-lisicon II crystals, exhibiting higher lithium-ion conductivity. Furthermore, compared to the lithium-ion activation energy of 18.5 kJ / mol obtained by ball milling at room temperature, the lithium-ion activation energy of the electrolyte obtained by ball milling at low temperature is even lower, at only 12.1 kJ / mol. Figure 2 As shown, the ion activation energy decreased by more than 30%.

[0052] Combination Figure 3As shown in the figure, the XRD pattern of the ball-milled product obtained by ball milling Li₂S and P₂S₅ at a molar ratio of 4:1 at 374 rpm is as follows. It can be observed that when low-temperature nitrogen gas is introduced into the ball milling chamber at a flow rate of 1-2 L / min, the product is in an amorphous glassy state, containing no crystalline phase. This amorphous glassy phase can undergo a phase transition during hot pressing, transforming into a new phase, Thio-lisicon II, with high ionic conductivity. However, in the high-energy ball milling process without the introduction of low-temperature gas, the ball milling temperature is higher, and the product partially crystallizes, forming the low-ionic conductive phase Li₄P₂S₆. This phase does not undergo a phase transition during hot pressing and is thus retained in the final product. Furthermore, compared to Thio-lisicon II, the low-ionic conductive phase Li₄P₂S₆ has lower ionic conductivity and the interface formed with the sulfide electrolyte cannot generate lithium vacancies, thus not reducing the interfacial resistance for lithium-ion transport and consequently lowering the lithium-ion conductivity of the final product.

[0053] In some specific embodiments, the low-speed ball milling and high-speed ball milling are independently bidirectional ball milling with dual grinding beads. This results in more uniform dispersion and better ball milling effect.

[0054] In some specific embodiments, the dual grinding balls include large-diameter grinding balls and small-diameter grinding balls; the large-diameter grinding balls have a diameter of 15 mm; and the small-diameter grinding balls have a diameter of 10 mm. Thus, using two types of grinding balls in the ball milling process allows the large balls to generate more energy during grinding, enabling rapid sample pulverization, while the small balls improve the precision and consistency of sample grinding.

[0055] In some specific embodiments, the material of the dual grinding beads is aluminum oxide.

[0056] In some specific embodiments, the ratio of large-diameter grinding beads to small-diameter grinding beads is 3:2, and the ratio of the mass of the premix to the number of grinding beads is 1-2 g: 25 beads. This improves the grinding effect of the variable-speed ball mill, which is beneficial for increasing ionic conductivity.

[0057] In some specific embodiments, the hot pressing conditions include: a pressure of 500-600 MPa; a hot pressing temperature of 280-300°C; and a hot pressing time of 6-8 hours.

[0058] In this embodiment of the invention, the hot pressing process at 500-600 MPa and 280-300 °C achieves the transformation of xLi₂S·(1-x)P₂S₅ (80≤x≤85) into the high-ionic-conducting phase Thiolisicon II and the softening of the sulfide. Simultaneously, under pressure, the "hard" oxide embeds itself into the "soft" sulfide, achieving good bonding at the two-phase interface. Furthermore, under the combined effects of high temperature and pressure, oxygen and sulfur atoms at the interface diffuse into each other. Due to the different attraction of these two types of atoms to lithium ions, lithium vacancies can appear at the interface, significantly reducing the activation energy for lithium ion migration and achieving higher ionic conductivity. Separating the heating and pressurizing processes, such as calcination followed by cold pressing or cold pressing followed by calcination, results in only mechanical contact at the two-phase interface. This leads to bulk defects such as pores at the contact interface, hindering lithium ion migration and reducing its ionic conductivity. Preferably, the hot pressing effect is optimal at a pressure of 550 MPa, a temperature of 290 °C, and a time of 7 hours.

[0059] Therefore, during the hot pressing process, the amorphous sulfide solid electrolyte undergoes a phase transition to form Thio-lisicon II crystals. This phase exhibits higher lithium-ion conductivity, and the lithium-ion activation energy of the Thio-lisicon II crystals is lower than that of the lithium-ion activation energy of the ball milling at room temperature.

[0060] In some specific embodiments, a hot pressing device is preferably used, wherein the heating resistance wire of the hot pressing device is located around the mold and above the lower pressure head, which is more uniform than the flat plate heating method; the sample is constrained in the horizontal direction, so that greater pressure can be used during the hot pressing process without causing the electrolyte sheet to break; the rotating design of the bearing above the upper pressure head can improve the flatness of the electrolyte sheet surface and the density of the electrolyte sheet.

[0061] Compared to flat plate pressing, this method provides stronger horizontal constraint on the electrolyte, achieving higher heating pressure. Furthermore, the rotation of the upper pressure head during heating improves the surface flatness of the electrolyte sheet. The rotation of the upper pressure head also promotes particle flow and densification, increasing the density of the electrolyte sheet. Conventional flat plate hot pressing achieves a relative density of approximately 95%, while the improved rotary hot pressing device can achieve a density exceeding 99%.

[0062] In some specific embodiments, after hot pressing, the process preferably includes sequential cooling and demolding. The cooling is preferably performed with the furnace to room temperature. In this embodiment of the invention, the demolding operation is not specifically limited; any operation well-known in the art can be used.

[0063] In some specific embodiments, the oxide solid electrolyte powder is Li 1.3 Al 0.3 Ti1.7 (PO4)3, Li 1+ x Al x Ge 2-x (PO4)3 and Li 3x La 2 / 3-x One or more of TiO3; the sulfide solid electrolyte powder is xLi2S·(1-x)P2S5, where 80≤x≤85. In some embodiments, the sulfide solid electrolyte is preferably 80Li2S-20P2S5, and the molar content of lithium in the sulfide in the embodiments of the present invention reaches 42.1%-47.2%, which is higher than the 40% lithium content in conventional sulfides; the oxide solid electrolyte is preferably Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0064] Specifically, this embodiment employs two electrolytes: a soft sulfide and a hard oxide. After variable-speed ball milling followed by hot pressing, the final product achieves a pulp-like structure, where the "hard" oxide is embedded within a "soft" xLi₂S·(1-x)P₂S₅ matrix. This unique structure creates a well-bonded interface, facilitating the formation of lithium vacancies and significantly reducing the activation energy for lithium ion migration. Simultaneously, the hard oxide electrolyte particles inhibit the growth of lithium dendrites. In contrast, variable-speed ball milling of single sulfide, halide, or oxide electrolytes lacks a two-phase interface that promotes lithium ion migration, limiting lithium ion migration to within the milled product. This improves the ionic conductivity of the mechanically prepared pulp-like sulfide / oxide solid electrolyte.

[0065] In some specific embodiments, the particle sizes of the sulfide solid electrolyte powder and the oxide solid electrolyte powder are independently 0.1-1 μm and 0.1-0.5 μm, respectively. In some embodiments, the particle size of the sulfide solid electrolyte powder is preferably 0.1-0.5 μm, more preferably 0.2 μm; the particle size of the oxide solid electrolyte powder is preferably 0.1-0.5 μm, more preferably 0.3 μm. This is more beneficial for the uniformity of dispersion during low-speed ball milling and the coating properties after high-speed ball milling.

[0066] In some specific embodiments, the mass ratio of the sulfide solid electrolyte to the oxide solid electrolyte powder is (9-4):1. More preferably, it is 6:1. This is more beneficial for the uniformity of dispersion during low-speed ball milling and the coating properties after high-speed ball milling.

[0067] To further illustrate the present invention, the following detailed description of the embodiments is provided in conjunction with the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0068] Example 1

[0069] Under a protective atmosphere of 99.999% pure argon, sulfide solid electrolyte (80Li2S-20P2S5) powder (particle size 0.2μm) and oxide solid electrolyte (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) powder (particle size 0.3μm) was premixed in a mortar at a mass ratio of 9:1. 1g of sample was placed in a 100mL alumina ball mill jar and 5 alumina grinding beads with a diameter of 10mm and 15 alumina grinding beads with a diameter of 5mm were added.

[0070] Ball milling was performed bidirectionally for 2.5 hours at a low speed of 120 r / min. During the ball milling process, the milling was stopped for 10 minutes after every 30 minutes of milling.

[0071] After a 1-hour pause in low-speed ball milling, the mixture was ball-milled bidirectionally at a high speed of 370 r / min for 20 hours, with a 10-minute pause after every 30 minutes of ball milling. The resulting mixed powder was transferred to a hot-pressing mold and hot-pressed for 6 hours under 99.999% high-purity argon gas, a pressure of 500 MPa, and a temperature of 280°C. After cooling to room temperature in the furnace, the composite solid electrolyte was obtained by demolding. Figure 4 The scanning electron microscope (SEM) image and energy dispersive spectroscopy (EDS) distribution of each element of the sulfide / oxide composite solid electrolyte prepared in Example 1 are shown. It can be found that the P, S, Al, Ti and O elements are evenly distributed, indicating that the sulfide and oxide are evenly dispersed. Figure 5 This is a high-magnification SEM image of the sulfide / oxide composite solid electrolyte prepared in Example 1. Figure 5 It can be seen that the solid electrolyte has a low internal porosity and the oxide grains are embedded in the sulfide matrix, thus realizing the preparation of a high-density, low-defect-content, pulp-structured oxide / sulfide composite solid electrolyte.

[0072] Comparative Example 1

[0073] Under a 99.999% argon protective atmosphere, sulfide solid electrolyte (80Li2S-20P2S5) powder (particle size 0.2μm) and oxide solid electrolyte (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) powder (particle size 0.3μm) was premixed in a mortar at a mass ratio of 4:1. 1g of sample was placed in a 100mL alumina ball mill jar and 5 alumina grinding beads with a diameter of 10mm and 15 alumina grinding beads with a diameter of 5mm were added.

[0074] Ball milling was performed bidirectionally for 20 hours at a low speed of 120 r / min, with a 10-minute stop after every 30 minutes of ball milling.

[0075] Under a protective atmosphere of 99.999% high-purity argon, the obtained composite solid electrolyte powder is transferred to a hot pressing mold and hot-pressed for 6 hours at a pressure of 500 MPa and a temperature of 280°C. After cooling to room temperature in the furnace, the composite solid electrolyte prepared by low-speed ball milling is obtained by demolding.

[0076] Figure 6 The scanning electron microscope (SEM) images and energy dispersive spectral distributions of the sulfide / oxide composite solid electrolyte prepared in Comparative Example 1 reveal an uneven elemental distribution. 1.3 Al 0.3 Ti 1.7 (PO4)3)) showed significant aggregation.

[0077] Figure 7 Here is a high-magnification SEM image of the sulfide / oxide composite solid electrolyte prepared in Comparative Example 1, from... Figure 7 It can be seen that the composite solid electrolyte has a high porosity, large size, and high defect density between grains, which is not conducive to the migration of lithium ions inside the solid electrolyte.

[0078] Figure 8 The AC impedance curves of the composite solid electrolytes prepared in Example 1 and Comparative Example 1 are shown in the figure. The ionic conductivity σ is used to obtain the impedance curves. Li Calculations using d / (RS) show that the ionic conductivity (σ) of the composite solid electrolyte sheets prepared in Example 1 and Comparative Example 1 is... Li The values ​​were 1.60 mS / cm and 0.62 mS / cm, respectively.

[0079] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for mechanically preparing a sucrose / oxide solid electrolyte with a pulp-like structure, characterized in that, Includes the following steps: Under a protective atmosphere, sulfide solid electrolyte powder and oxide solid electrolyte powder are premixed, and the resulting premix is ​​ball-milled at variable speed to obtain a mixed powder; the variable speed ball milling is performed by sequentially performing low-speed ball milling and high-speed ball milling under low-temperature nitrogen conditions. The mixed powder was hot-pressed under a protective atmosphere to obtain a sulfide / oxide composite solid electrolyte; the pressure was 500-600 MPa; the hot-pressing temperature was 280-300℃; and the hot-pressing time was 6-8 h. The low-speed ball mill operates at a rotation speed of 100-150 rpm; the high-speed ball mill operates at a rotation speed of 350-390 rpm; during the high-speed ball milling, low-temperature nitrogen gas is continuously introduced into the ball milling chamber to maintain a temperature of 0-10°C within the chamber.

2. The method for preparing a pulp-structured sulfide / oxide solid electrolyte according to claim 1, characterized in that, The low-speed ball milling time is 2-5 hours; during the low-speed ball milling process, there is a 10-20 minute stop after every 30-45 minutes of low-speed ball milling; the high-speed ball milling time is 18-22 hours; during the high-speed ball milling process, there is a 10-20 minute stop after every 30-45 minutes of high-speed ball milling; the time interval between the high-speed ball milling and the low-speed ball milling is 0.8-1.2 hours.

3. The method for preparing a melon pulp structure sulfide / oxide solid electrolyte by mechanical means according to claim 1, characterized in that, The temperature of the cryogenic nitrogen gas is -50 to -40°C; the flow rate of the cryogenic nitrogen gas is 1-2 L / min.

4. The method for preparing a melon pulp structure sulfide / oxide solid electrolyte by mechanical means according to claim 1, characterized in that, The low-speed ball mill and the high-speed ball mill are independently bidirectional ball mills with dual grinding beads.

5. The method for preparing a pulp-structured sulfide / oxide solid electrolyte according to claim 4, characterized in that, The dual grinding beads include a large-diameter grinding bead and a small-diameter grinding bead; the large-diameter grinding bead has a diameter of 15mm; and the small-diameter grinding bead has a diameter of 10mm.

6. The method for preparing a pulp-structured sulfide / oxide solid electrolyte according to claim 5, characterized in that, The ratio of the number of large-diameter grinding beads to the number of small-diameter grinding beads is 3:2, and the ratio of the mass of the premix to the number of the two grinding beads is 1-2g:

25.

7. The method for preparing a melon pulp structure sulfide / oxide solid electrolyte by mechanical means according to claim 1, characterized in that, The hot pressing conditions include: a pressure of 500-600 MPa; a hot pressing temperature of 280-300 ℃; and a hot pressing time of 6-8 h.

8. The method for preparing a pulp-structured sulfide / oxide solid electrolyte according to claim 1, characterized in that, The oxide solid electrolyte powder is Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1+x Al x Ge 2-x (PO4)3 and Li 3x La 2 / 3-x One or more of TiO3, including Li 1+x Al x Ge 2-x In (PO4)3, the range of x is 0 ≤ x ≤ 0.65, Li 3x La 2 / 3- x The range of x in TiO3 is 0.06≤x≤0.14; the sulfide solid electrolyte powder is xLi2S·(100-x)P2S5, where 80≤x≤85.

9. The method for preparing a pulp-structured sulfide / oxide solid electrolyte according to claim 1 or 8, characterized in that, The particle sizes of the sulfide solid electrolyte powder and the oxide solid electrolyte powder are independently 0.1-1 μm and 0.1-0.5 μm, respectively.

10. The method for preparing a pulp-structured sulfide / oxide solid electrolyte according to claim 1 or 8, characterized in that, The mass ratio of the sulfide solid electrolyte to the oxide solid electrolyte powder is (9-4):1.

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