Composite sulfide solid electrolyte membrane, preparation method thereof and lithium ion battery

Abstract

The invention provides a composite sulfide solid electrolyte membrane, a preparation method thereof and a lithium ion battery. The composite sulfide solid electrolyte membrane comprises a halide layer and a sulfide layer which are sequentially arranged from top to bottom; the halide layer comprises a halide solid electrolyte material; the sulfide layer contains a sulfide solid electrolyte material with particle size grading, and sulfide particles with different particle sizes are uniformly mixed; a connecting surface is arranged between the sulfide layer and the halide layer, and the halide solid electrolyte material in the connecting surface is filled into a gap of the sulfide solid electrolyte material. The composite sulfide solid-state electrolyte membrane comprises the halide layer and the sulfide layer which are sequentially arranged from top to bottom, the compactness of the sulfide solid-state electrolyte membrane can be improved by grading sulfide solid-state electrolyte materials with different particle sizes, and a composite channel structure with high stability and high ionic conductivity is formed; the ion transmission efficiency and the interface long-term stability are both considered.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a composite sulfide solid electrolyte membrane, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] With the rapid development of new energy vehicles and energy storage systems, people have higher requirements for the energy density and safety performance of lithium-ion batteries. The liquid electrolytes in traditional lithium-ion batteries have safety risks such as flammability and leakage. Solid-state lithium-ion batteries have become a research hotspot due to their high energy density and high safety.

[0003] Solid electrolyte is the core component of all-solid-state batteries, and its performance directly determines the energy density, safety, cycle life and applicable environment of the battery. Sulfide solid electrolyte materials have high ionic conductivity (10 -3 ~10 -2 S cm -1 ) and good machinability, and is considered one of the most industrially viable solid electrolytes. However, sulfide solid electrolyte materials still face the following problems in practical applications:

[0004] (1) Poor interface contact: At present, the main method for assembling sulfide all-solid-state lithium-ion batteries is to press the composite positive electrode powder, sulfide solid electrolyte powder and composite negative electrode powder layer by layer into one body. However, it is difficult to ensure the uniformity of the electrolyte layer when using electrolyte powder, which often leads to poor contact of the solid-solid interface.

[0005] (2) Poor high voltage stability: PS4 in sulfide solid electrolyte 3- It is easily oxidized under high voltage, resulting in the breakage of PS bonds and the generation of by-products such as polysulfides, LiCl, and Li3PO4, forming a poor interface layer and thus hindering lithium ion transmission.

[0006] (3) Easy growth of lithium dendrites: Due to the different sizes of sulfide electrolyte particles, the gaps between the particles are large, which provides an environment for lithium dendrites to grow along the grain boundaries in the gaps between the particles, affecting the cycle stability and safety of the battery.

[0007] In the prior art, there are many methods that attempt to solve the above problems. The preparation method disclosed in the Chinese invention patent application with authorization number CN113394445B can be used to continuously produce halide solid electrolyte membranes with good performance, but the ionic conductivity of the halide solid electrolyte is low and it will cause serious side reactions with low-voltage negative electrode materials, resulting in battery failure. The composite solid electrolyte membrane disclosed in the Chinese invention patent application with publication number CN116505063A is prepared by mechanically pressing halide electrolyte powder and sulfide electrolyte powder to directly compound. Although this method improves the high-voltage stability of the composite solid electrolyte membrane, the powder blending system is prone to component segregation during the pressing process, resulting in difficulty in controlling the uniformity of the composite solid electrolyte phase distribution, and the preparation efficiency of the multiple pressing process is low. The composite solid electrolyte membrane disclosed in Chinese invention patent application publication number CN117558993A is produced by roll-pressing a fiberized halide electrolyte layer and a fiberized sulfide electrolyte layer. While this method addresses poor interfacial contact while improving high-voltage stability, the interfacial contact of the electrolyte layers, both prepared using a dry process, is still insufficient. The composite solid electrolyte membrane disclosed in Chinese invention patent application publication number CN111509293A reduces grain boundary resistance and improves interfacial contact by forming a halide electrolyte membrane on the surface of oxide electrolyte particles or electrode particles, but its ionic conductivity is relatively low.

[0008] Therefore, there is an urgent need to develop a sulfide solid electrolyte membrane with high voltage stability, good interface contact and excellent ion transport capability to meet the practical application requirements of all-solid-state lithium-ion batteries. Summary of the Invention

[0009] The technical problems to be solved by the present invention are the poor interfacial contact, poor high-voltage stability, and susceptibility to lithium dendrite growth of existing composite solid-state electrolyte membranes. To this end, the present invention provides a composite sulfide solid-state electrolyte membrane, a preparation method, and a lithium-ion battery. The membrane significantly improves high-voltage stability, interfacial contact, and ion transport capabilities through a unique material combination and preparation process.

[0010] To achieve the above-mentioned object, the present invention provides a composite sulfide solid electrolyte membrane, comprising a halide layer and a sulfide layer sequentially arranged from top to bottom; the halide layer comprises a halide solid electrolyte material having a particle size of 0.5 to 0.8 μm; the sulfide layer comprises a sulfide solid electrolyte material having a graded particle size, wherein the sulfide solid electrolyte material comprises three particle sizes of 1 to 3 μm, 5 to 8 μm, and 10 to 12 μm, respectively, and the mass ratio of each particle size is 4 to 6:2 to 4:1 to 3, respectively, and the sulfide particles of different particle sizes are uniformly mixed;

[0011] There is a contact surface between the sulfide layer and the halide layer with a thickness of 2 to 8 μm. The halide solid electrolyte material in the contact surface is filled into the gaps of the sulfide solid electrolyte material. The mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material is 80 to 90:10 to 20.

[0012] In the composite solid electrolyte membrane designed by the present invention, the halide layer plays the following roles in the structure:

[0013] (1) Improve oxidation stability and protect high-voltage positive electrode materials: Compared with sulfide electrolytes, halide solid electrolytes have a higher oxidation decomposition voltage. Therefore, halide acts as a protective layer to block the corrosion of the internal sulfide layer by the high-voltage oxidation environment, thereby improving the cycle life and high-voltage stability of the battery.

[0014] (2) Improve the interfacial contact between the positive electrode and the electrolyte layer: The halide dense layer formed by slurry coating has good interfacial wettability and film-forming properties, which can fill the gaps between the positive electrode particles and improve the contact between the electrode and the electrolyte interface; in addition, the elastic modulus of the halide solid electrolyte is low, which has a certain buffering effect, further improving the interfacial mechanical matching performance.

[0015] (3) Construction of a stable and continuous ion channel: By combining a small-particle halide layer with a large-particle sulfide layer, the interlayer particles are in closer contact, forming a composite channel structure with high stability and high ionic conductivity, taking into account both ion transmission efficiency and long-term interface stability;

[0016] In the composite solid electrolyte membrane designed by the present invention, the sulfide layer plays the following roles in the structure:

[0017] (1) Improve ionic conductivity and achieve efficient lithium ion transport: The sulfide layer with high ionic conductivity constitutes the main lithium ion transport channel of the entire electrolyte membrane, which helps to achieve high rate performance and reduce interfacial polarization.

[0018] (2) It forms a core support layer with a stable interface, giving the membrane flexibility and integrity: The dry-process sulfide solid electrolyte membrane not only achieves high ionic conductivity, but also has strong mechanical toughness and processability. The sulfide layer serves as a structural skeleton layer to support the halide membrane, avoiding structural peeling or powdering, and improving the stability of the membrane layer.

[0019] (3) Inhibiting the growth of lithium dendrites: By grading sulfide solid electrolyte materials with different particle sizes, the density of the sulfide solid electrolyte membrane can be improved, the gap between particles can be reduced, and the growth of lithium dendrites in the grain boundary gaps can be inhibited.

[0020] In the composite solid electrolyte membrane designed by the present invention, there is a contact surface between the sulfide layer and the halide layer:

[0021] The sulfide solid electrolyte membranes prepared from graded particles of large (10-12 μm), medium (5-8 μm), and small (1-3 μm) have small pores (1-2 μm) on their surfaces. This allows nanoscale halide solid electrolyte material particles (0.5-0.8 μm) to be packed into the pores while maintaining a smooth surface. This synergistically constructs a dense composite solid electrolyte membrane interface, improves ionic conductivity, and inhibits the growth of lithium dendrites in grain boundary crevices. The selection of small halide particles and the gradation of sulfide materials with different particle sizes are both aimed at achieving dense filling of this interface. This structure helps to reduce the energy barrier for ion transport between particles, shorten the ion migration path, reduce interfacial impedance, improve ionic conductivity, and enhance the efficiency of ion transport in the bulk and at the interface.

[0022] Preferably, the composite sulfide solid electrolyte membrane has a thickness of 20 to 60 μm, of which the halide layer has a thickness of 5 to 15 μm, the sulfide layer has a thickness of 15 to 45 μm, and the thickness ratio of the sulfide layer to the halide layer is 1 to 9:1. If the halide layer is too thick (e.g., greater than 15 μm), the ionic conductivity of the entire composite electrolyte membrane will be reduced; if the halide layer is too thin (e.g., less than 5 μm), it will not be conducive to filling the pores on the surface of the sulfide layer, affecting the interfacial contact.

[0023] Preferably, the material of the sulfide layer includes one or more of argyrodite, Thio-LISICON, Li3PS4 and its derivatives or amorphous / glass ceramic type sulfides, more preferably Li 5.5 PS 4.5 Cl 1.5 ;Li 5.5 PS 4.5 Cl 1.5 The material of the halide layer includes one or more of Li3InCl6, Li2ZrCl6, Li3TaCl6, Li3NbCl6, Li3AlCl6, Li3GaCl6, Li3YBr6 or Li3InBr6, more preferably Li3InCl6. Li3InCl6 has stable electrochemical properties.

[0024] Preferably, the sulfide layer further comprises a sulfide binder, and the sulfide binder includes one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) or a fluorinated diene copolymer, more preferably PTFE; the ratio of the sulfide solid electrolyte material to the binder is 110-99:1-5, more preferably 99:1.

[0025] The dry sulfide layer prepared by fiberizing a binder such as PTFE can provide good mechanical flexibility and alleviate volume expansion, and is particularly suitable for negative electrodes with large volume changes such as silicon-based ones.

[0026] The halide layer also contains a halide binder, which includes one or more of ethyl cellulose (EC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), epoxy resin, polyurethane rubber or polyisobutylene (PIB), more preferably EC; the ratio of the halide solid electrolyte membrane to the binder is 95-99:1-5, more preferably 98:2.

[0027] Under the same technical concept, the present invention also provides a method for preparing a composite sulfide solid electrolyte membrane, comprising the following steps:

[0028] (1) crushing and screening the sulfide solid electrolyte material and the halide solid electrolyte material, wherein the sulfide solid electrolyte material is screened into three particle sizes of 1-3 μm, 5-8 μm and 10-12 μm;

[0029] (2) grading sulfide solid electrolyte materials of three particle sizes, uniformly mixing them with a sulfide binder, and pressing them to obtain a sulfide solid electrolyte membrane;

[0030] (3) uniformly mixing a halide solid electrolyte material and a halide binder, adding a dispersant, and stirring thoroughly to obtain a slurry, coating the slurry on the surface of a sulfide solid electrolyte membrane, and vacuum drying to obtain a halide-coated sulfide solid electrolyte membrane;

[0031] (4) Cold pressing the halide-coated sulfide solid electrolyte membrane at low temperature to obtain a composite sulfide solid electrolyte membrane.

[0032] Preferably, the crushing in step (1) adopts acoustic resonance technology, and the parameters controlled by the acoustic resonance technology include frequency, acceleration and time; during the crushing process, the acceleration is adjusted to 50-100g at a frequency of 30-70Hz, and the time is 5-30min;

[0033] Acoustic resonance technology uses low-frequency mechanical resonance in the vertical direction of the entire field, combined with multiple micro-scale operating zones within the field, to achieve acoustic flow of the processed material within the reactor. This forces intense mass transfer and heat exchange within the reactor, generating friction and collision forces between the materials and between the materials and the reactor walls. This is an enhanced technology that accelerates the physical or chemical treatment effects of the materials. The acoustic resonance technology used in this invention utilizes acoustic resonance equipment to achieve particle crushing and refinement of the material.

[0034] The pressing in step (2) uses a roller machine and an oil press; the roller speed of the roller machine is 1 to 15 min -1 The temperature of the upper and lower rollers of the roller machine is 50 to 120°C; the pressure of the hydraulic press is 20 to 80 MPa; the pressing time of the hydraulic press is 1 to 3 minutes.

[0035] Preferably, the dispersant in step (3) includes one or more of anisole, toluene, xylene, cyclohexane, n-hexane, isobutyl isobutyrate or butyl acetate, more preferably anisole, and the liquid-solid mass ratio of the dispersant to the halide solid electrolyte is 1 to 5:1, more preferably 3:1.

[0036] Preferably, the stirring speed in step (3) is 300 rpm and the time is 15 min; the drying temperature is 40° C. and the time is 8 h;

[0037] The temperature of the low-temperature cold pressing in step (4) is -60 to 0°C, more preferably -40°C; the pressure is 50 to 150 MPa, more preferably 100 MPa.

[0038] Under the same technical concept, the present invention also provides an all-solid-state lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, and the composite sulfide solid electrolyte membrane located between the positive electrode sheet and the negative electrode sheet.

[0039] Preferably, the raw materials of the positive electrode sheet include positive electrode material, sulfide solid electrolyte powder and binder, and the positive electrode material includes one or more of NCM811 electrode sheet, lithium iron phosphate electrode sheet, lithium cobalt oxide electrode sheet or lithium nickel oxide electrode sheet; more preferably, NCM811 electrode sheet.

[0040] The positive electrode sheet is obtained by uniformly mixing positive electrode material, sulfide solid electrolyte powder and binder in a certain proportion and then rolling the mixture using a double-roller machine.

[0041] The raw materials of the negative electrode sheet include negative electrode material, sulfide solid electrolyte powder and binder. The negative electrode material includes one or more of silicon carbon, graphite, hard carbon or metallic lithium, and is more preferably a silicon carbon electrode sheet.

[0042] The negative electrode sheet is obtained by uniformly mixing the negative electrode material, sulfide solid electrolyte powder and a binder in a certain proportion and then rolling the mixture using a double-roller machine.

[0043] The above solution of the present invention has the following beneficial effects:

[0044] (1) The composite sulfide solid electrolyte membrane of the present invention includes a halide layer and a sulfide layer arranged in sequence from top to bottom. By grading sulfide solid electrolyte materials with different particle sizes, the density of the sulfide solid electrolyte membrane can be improved, the gap between particles can be reduced, and the growth of lithium dendrites in the grain boundary gaps can be inhibited. In addition, the small-particle halide layer is combined with the large-particle sulfide layer to make the interlayer particles contact more closely, forming a composite channel structure with high stability and high ionic conductivity, taking into account both ion transmission efficiency and long-term interface stability;

[0045] (2) The preparation method of the composite sulfide solid electrolyte membrane of the present invention can significantly improve the interface contact and reduce the interface impedance: the dry sulfide layer + wet coating halide layer has better interlayer adhesion and interface uniformity, and the low-temperature cold pressing technology can further densify the interface structure, effectively avoiding the failure of the electrolyte membrane such as delamination and falling off during use;

[0046] (3) The preparation method of the composite sulfide solid electrolyte membrane of the present invention can improve the ion transport performance and inhibit the growth of lithium dendrites: the surface of the sulfide solid electrolyte membrane prepared by the conventional method has relatively large pores (>3μm), which makes the surface flatness of the thin halide solid electrolyte membrane coated thereon poor, and lithium dendrites are easily grown on the surface contacting the negative electrode side, causing battery failure; the present invention uses acoustic resonance technology to crush and screen the sulfide solid electrolyte material particles, and the surface of the sulfide solid electrolyte membrane prepared by the three graded particle sizes of large (10-12μm), medium (5-8μm), and small (1-3μm) has relatively small pores (1-2μm), which can fill the pores of the halide solid electrolyte membrane with nano-scale halide solid electrolyte material particles (0.5-0.8μm) while ensuring the flatness of the halide solid electrolyte membrane surface, synergistically constructing a dense composite solid electrolyte membrane interface, improving ionic conductivity, and inhibiting the growth of lithium dendrites in the grain boundary gaps;

[0047] (4) Good process compatibility and suitability for large-scale production: The present invention adopts a process route of dry preparation + wet coating + cold pressing, which is easy to integrate with the existing lithium-ion battery preparation process and is compatible with industrial equipment such as roller pressing and coating. Compared with methods such as those requiring high-temperature sintering, the method adopted by the present invention has lower energy consumption and equipment requirements, can effectively reduce costs, and is more conducive to large-scale production applications;

[0048] (5) In the all-solid-state lithium-ion battery of the present invention, the sulfide layer and the halide layer are compounded, and the sulfide layer with high ionic conductivity and the halide layer with high oxidative stability are placed on the negative electrode side and the positive electrode side, respectively, so as to give full play to the performance advantages of the two types of solid electrolytes and significantly improve the voltage adaptability range and safety of the whole battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 This is a schematic structural diagram of a composite sulfide solid electrolyte membrane provided in Example 1 of the present invention.

[0051] Figure 2 This is a flow chart of a method for preparing a composite sulfide solid electrolyte membrane provided by the present invention.

[0052] Figure 3 This is a SEM image of the interface of the sulfide solid electrolyte membrane prepared after particle crushing, screening and grading using acoustic resonance technology in Example 1 of the present invention.

[0053] Figure 4 This is an SEM image of the sulfide solid electrolyte membrane of the present invention prepared without particle crushing, screening and grading in Comparative Example 7 of the present invention. DETAILED DESCRIPTION

[0054] To make the technical problems, technical solutions, and advantages to be solved by the present invention more clear, the following is a detailed description with reference to the accompanying drawings and specific embodiments. It is obvious that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to a locking connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0057] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] Example 1

[0059] This embodiment provides a composite sulfide solid electrolyte membrane, the structural diagram of which is shown in FIG. Figure 1 As shown, it includes a halide layer and a sulfide layer arranged in sequence from top to bottom; the halide layer contains a halide solid electrolyte material Li3InCl6 with a particle size of 0.5 to 0.8 μm; the sulfide layer contains a sulfide solid electrolyte material Li 5.5 PS 4.5 Cl 1.5 , specifically 5.5g of 10-12μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials, 3.3g of 5-8μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials and 2.2g of 1-3μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials, sulfide particles of different sizes are evenly mixed;

[0060] There is a junction surface between the sulfide layer and the halide layer with a thickness of 5 μm. The halide solid electrolyte material in the junction surface is filled into the gaps of the sulfide solid electrolyte material. The mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material is 90:10. The SEM image of the junction surface of the sulfide solid electrolyte membrane prepared by particle crushing, screening and grading using acoustic resonance technology in Example 1 is shown in FIG. Figure 3 shown.

[0061] The thickness of the sulfide layer was 30 μm, and the thickness of the halide layer was 10 μm.

[0062] The sulfide layer further contained 0.10 g of PTFE as a sulfide binder, and the halide layer further contained 0.20 g of EC as a halide binder.

[0063] This embodiment provides a method for preparing the composite sulfide solid electrolyte membrane, the flow chart of which is as follows: Figure 2 As shown, the preparation method comprises the following steps:

[0064] S1: Under an inert protective atmosphere (Ar), add 10g of ZrO2 beads with a diameter of 8mm into a 15mL acoustic resonance device and 5.5 PS 4.5 Cl 1.5 Fill the container to 80% of its volume, fix it in the acoustic resonance device, adjust the acceleration to 50g at 60Hz for 6min, and sieve to obtain Li particles with particle sizes of 1-3μm, 5-8μm and 10-12μm. 5.5 PS 4.5 Cl 1.5 Materials. 10 g of 8 mm diameter ZrO beads were added to a 15 mL acoustic resonance chamber. Li₃InCl₆ was filled to 80% of the volume of the chamber. The chamber was secured in the acoustic resonance chamber and subjected to 60 Hz frequency and 100 g acceleration for 30 minutes. Sieving yielded Li₃InCl₆ particles of 0.5 to 0.8 μm.

[0065] S2: Under an inert protective atmosphere (Ar), 5.5 g of 10-12 μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials, 3.3g of 5-8μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials and 2.2g of 1-3μm particle size Li 5.5 PS 4.5 Cl 1.5 After the materials are fully mixed, 0.10g of PTFE is added and the mixture is fully fiberized using a roller mill with a roller speed of 5m / min. -1 The upper and lower rollers were both at 80°C, and then a hydraulic press was used to press for 2 minutes at a pressure of 50 MPa to obtain a flat 30 μm thick sulfide solid electrolyte membrane. For specific SEM images, see Figure 3 ;

[0066] S3: Under an inert protective atmosphere (Ar), 9.8 g of 0.5-0.8 μm particle size Li3InCl6 material and 0.20 g of EC were uniformly mixed, and 30 g of anisole was added. The mixture was stirred at 300 rpm for 15 min using a homogenizer to obtain a uniform slurry; the slurry was applied to the surface of the pre-prepared sulfide solid electrolyte membrane, and dried at 20-60 ° C for 6-10 h under a vacuum environment to obtain a 10 μm thick halide solid electrolyte membrane;

[0067] S4: Under an inert protective atmosphere (Ar), the dried membrane was placed in a low-temperature cold press and subjected to an interface densification treatment at -40°C and a pressure of 100 MPa to obtain a composite sulfide solid electrolyte membrane.

[0068] Comparative Example 1:

[0069] The difference between this comparative example and Example 1 is that in step S2, 5.0 g of 10-12 μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials and 5.0g of 1-3μm particle size Li 5.5 PS 4.5 Cl 1.5 After the materials are fully mixed, 0.10g of PTFE is added and the mixture is fully fiberized using a roller mill with a roller speed of 5m / min. -1 The temperature of the upper and lower rollers was 80°C, and then a hydraulic press was used to press at a pressure of 50 MPa for 2 minutes to obtain a flat 30 μm thick sulfide solid electrolyte membrane.

[0070] Comparative Example 2:

[0071] The difference between this comparative example and Example 1 is that in step S2, 5.0 g of 10-12 μm particle size Li 5.5 PS 4.5 Cl 1.5 Materials and 5.0g of 5-8μm particle size Li 5.5 PS 4.5 Cl 1.5 After the materials are fully mixed, 0.10g of PTFE is added and the mixture is fully fiberized using a roller mill with a roller speed of 5m / min. -1 The temperature of the upper and lower rollers was 80°C, and then a hydraulic press was used to press at a pressure of 50 MPa for 2 minutes to obtain a flat 30 μm thick sulfide solid electrolyte membrane.

[0072] Comparative Example 3:

[0073] This embodiment is based on Example 1, and differs from Example 1 in that there is no halide solid electrolyte membrane and the interface between the sulfide solid electrolyte and the halide solid electrolyte is not included. Other conditions are the same.

[0074] Comparative Example 4:

[0075] This embodiment is based on Example 1, except that the thickness of the halide layer is 5 μm, the thickness of the interface between the sulfide solid electrolyte and the halide solid electrolyte is 1 μm, the mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material in the interface is 99:1, and the other conditions are the same.

[0076] Comparative Example 5:

[0077] This embodiment is based on Example 1, except that the thickness of the halide layer is 15 μm, the thickness of the interface between the sulfide solid electrolyte and the halide solid electrolyte is 10 μm, the mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material in the interface is 70:30, and the other conditions are the same.

[0078] Comparative Example 6:

[0079] This comparative example is based on Example 1, and differs from Example 1 in that, in step S1, acoustic resonance technology is not used to crush and screen the Li3InCl6 material, the particle size of the Li3InCl6 material used to prepare the halide solid electrolyte membrane is 1 to 20 μm, the interface thickness between the sulfide solid electrolyte and the halide solid electrolyte is less than 1 μm, the mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material in the interface is greater than 99:1, and the other conditions are the same.

[0080] Comparative Example 7:

[0081] This comparative example is based on Example 1. The difference from Example 1 is that in step S1, the acoustic resonance technology is not used to 5.5 PS 4.5 Cl 1.5 The material is crushed, and in step S2, no grading is performed. The Li 5.5 PS 4.5 Cl 1.5 The particle size of the material is 10-12 μm, the interface thickness between the sulfide solid electrolyte and the halide solid electrolyte is 9 μm, the mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material in the interface is 75:25, and the other conditions are the same. The specific SEM image of the interface of the sulfide solid electrolyte membrane prepared by particle crushing, screening and grading using acoustic resonance technology in Comparative Example 5 is shown in FIG. Figure 4 .

[0082] Comparative Example 8:

[0083] This comparative example is based on Example 1, and differs from Example 1 in that, during the low-temperature cold pressing process in step S4, the pressing temperature is 25° C., and the other conditions are the same.

[0084] Comparative Example 9:

[0085] This comparative example is based on Example 1, and differs from Example 1 in that, during the low-temperature cold pressing process in step S4, the pressing temperature is 80° C., and the other conditions are the same.

[0086] Performance Testing

[0087] The composite sulfide solid electrolyte membranes provided in the above examples and comparative examples were subjected to ion conductivity and interface impedance tests. The test temperatures for ion conductivity and interface impedance were both 25° C., wherein the interface impedance was measured in a Li symmetric battery system.

[0088] In addition, the assembly of an all-solid-state lithium-ion battery based on the composite sulfide solid electrolyte membrane provided in the above embodiments and comparative examples includes the following specific steps:

[0089] (1) Preparation of positive electrode composite sheet and negative electrode composite sheet: NCM811 and silicon carbon material are respectively 5.5 PS 4.5 Cl 1.5 The powder and PTFE were mixed and fiberized in a ratio of 75:24:1 and rolled on a roller machine (roller speed was 5 mm / min). -1 , the upper and lower roller temperatures are both 80°C) to obtain NCM811 positive electrode composite pole pieces and silicon-carbon negative electrode composite pole pieces.

[0090] (2) Assembly of an all-solid-state lithium-ion battery: The silicon-carbon negative electrode composite electrode sheet, the solid electrolyte membrane prepared in the above embodiments and comparative examples, and the NCM811 positive electrode composite electrode sheet are stacked in sequence on an aluminum-plastic film. After welding the electrode tabs, the aluminum-plastic film is sealed at a pressure of -96 kPa to obtain an all-solid-state lithium-ion battery.

[0091] The electrochemical performance of the all-solid-state lithium-ion battery was tested, wherein the charge and discharge window was 2.8-4.3V, the current was 0.2C (1C = 190mAg -1 ).

[0092] The above test results are shown in Table 1.

[0093] Table 1 Electrochemical performance test results of all-solid-state lithium-ion batteries

[0094]

[0095] From the data analysis in Table 1, we can get:

[0096] (1) The composite sulfide solid electrolyte membrane prepared in Example 1 has a high ionic conductivity, which can be attributed to the fact that Li 5.5 PS 4.5 Cl 1.5The high ionic conductivity and low-temperature cold pressing technology at -40°C improve the density of the membrane structure, effectively compact the particle contact interface, and reduce the gaps; in addition, the nano-scale halide solid electrolyte material is filled into the particle gaps on the surface of the membrane made of micron-scale sulfide solid electrolyte material by coating method, so that the sulfide solid electrolyte membrane and the halide solid electrolyte membrane can synergistically improve the ion transport performance and improve the ion conductivity; by grading sulfide solid electrolyte materials with different particle sizes, the density of the sulfide solid electrolyte membrane can be improved, the gaps between particles can be reduced, and the growth of lithium dendrites in the grain boundary gaps can be inhibited.

[0097] (2) The ionic conductivity and capacity retention of Comparative Examples 1 and 2 are low, the interface impedance is high, and there is slight dendrite in Example 3. This is because the sulfide solid electrolyte layer in Examples 2 and 3 does not adopt the grading of small, medium, and large particle sizes.

[0098] (3) In Comparative Example 3, since the halide solid electrolyte membrane was eliminated, although the ionic conductivity was improved compared with Example 1, the indicators such as interface impedance, initial decomposition voltage and 100-time capacity retention rate were all low. This shows that the presence of the halide solid electrolyte membrane can effectively improve the interface contact problem and enhance the high-voltage stability of the composite solid electrolyte membrane.

[0099] (4) In Comparative Example 4, since the thickness of the halide layer and the thickness of the interface between the sulfide solid electrolyte and the halide solid electrolyte were reduced, the interface of the interface was not obvious, the sulfide solid electrolyte material and the halide solid electrolyte material were unevenly distributed in the interface, and the less halide solid electrolyte material could not fully fill the interface, resulting in a larger porosity in the interface, resulting in poor interface contact, increased interface impedance, and a low 100-cycle capacity retention rate.

[0100] (5) In Comparative Example 5, the thickness of the halide layer and the interface thickness between the sulfide solid electrolyte and the halide solid electrolyte were increased, and although the interface contact problem was improved, the content of the halide solid electrolyte material with low ion transport efficiency was too high (the mass ratio of the sulfide solid electrolyte to the halide solid electrolyte in the interface was 70:30), which directly led to a decrease in ionic conductivity.

[0101] (6) The halide solid electrolyte material in Comparative Example 6 has a large particle size and is difficult to penetrate into the sulfide solid electrolyte layer to construct an interface. Moreover, the thickness of the interface is small, and the halide solid electrolyte material and the sulfide solid electrolyte material in the interface are unevenly distributed. This makes the porosity in the structure larger and the interface contact poor, resulting in a significant decrease in ionic conductivity.

[0102] (7) The sulfide solid electrolyte material in Comparative Example 7 was not crushed by acoustic resonance technology, and the material particle size was large, and the contact between the composite sulfide solid electrolyte membrane and the negative electrode was poor, which resulted in poor indicators such as ionic conductivity, interface impedance and 100-time capacity retention rate, and severe lithium dendrite growth occurred after 100 cycles; in addition, the sulfide solid electrolyte membrane constructed of larger-particle-size sulfide solid electrolyte material had larger pores, which easily allowed small-particle-size halide particles to penetrate and form a thicker interface, resulting in uneven distribution of halide solid electrolyte material on the surface of the halide layer and reduced overall ionic conductivity.

[0103] (8) The all-solid-state batteries in Examples 8 and 9 did not use low-temperature cold pressing technology. Although they maintained a voltage stability window of 4.4V, their interface density was poor.

[0104] In summary, the present invention provides a composite sulfide solid electrolyte membrane and a method for preparing the same. This method is simple to operate and suitable for large-scale production and application. Through a unique material combination and preparation process, the present invention successfully fabricates a composite sulfide solid electrolyte membrane that exhibits high voltage stability, good interfacial contact, and excellent ion transport capabilities, providing a new solution for the industrialization of all-solid-state lithium-ion batteries.

[0105] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite sulfide solid electrolyte membrane, characterized in that: The invention comprises a halide layer and a sulfide layer arranged in sequence from top to bottom; the halide layer comprises a halide solid electrolyte material having a particle size of 0.5 to 0.8 μm; the sulfide layer comprises a sulfide solid electrolyte material with a particle size distribution, the sulfide solid electrolyte material comprises three particle sizes of 1 to 3 μm, 5 to 8 μm and 10 to 12 μm, respectively, and the mass ratio of each particle size is 4 to 6:2 to 4:1 to 3, respectively, and the sulfide particles of different particle sizes are uniformly mixed; There is a contact surface between the sulfide layer and the halide layer with a thickness of 2 to 8 μm. The halide solid electrolyte material in the contact surface is filled into the gaps of the sulfide solid electrolyte material. The mass ratio of the sulfide solid electrolyte material to the halide solid electrolyte material is 80 to 90:10 to 20.

2. The composite sulfide solid electrolyte membrane according to claim 1, wherein The thickness of the composite sulfide solid electrolyte membrane is 20-60 μm, wherein the thickness of the halide layer is 5-15 μm, the thickness of the sulfide layer is 15-45 μm, and the thickness ratio of the sulfide layer to the halide layer is 1-9:

1.

3. The composite sulfide solid electrolyte membrane according to claim 1, wherein The material of the sulfide layer includes one or more of argyrodite, Thio-LISICON, Li3PS4 and its derivatives or amorphous / glass-ceramic sulfides; the material of the halide layer includes one or more of Li3InCl6, Li2ZrCl6, Li3TaCl6, Li3NbCl6, Li3AlCl6, Li3GaCl6, Li3YBr6 or Li3InBr6.

4. The composite sulfide solid electrolyte membrane according to claim 1, wherein The sulfide layer further comprises a sulfide binder, wherein the sulfide binder comprises one or more of polytetrafluoroethylene, polyvinylidene fluoride or fluorinated diene copolymer, and the mass ratio of the sulfide solid electrolyte material to the binder is 110-99:1-5; The halide layer also contains a halide binder, which includes one or more of ethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, polyurethane rubber and polyisobutylene. The mass ratio of the halide solid electrolyte material to the binder is 95-99:1-5.

5. A method for preparing a composite sulfide solid electrolyte membrane, characterized in that: The following steps are involved: (1) crushing and screening the sulfide solid electrolyte material and the halide solid electrolyte material, wherein the sulfide solid electrolyte material is screened into three particle sizes of 1-3 μm, 5-8 μm and 10-12 μm; (2) grading sulfide solid electrolyte materials of three particle sizes, uniformly mixing them with a sulfide binder, and pressing them to obtain a sulfide solid electrolyte membrane; (3) uniformly mixing a halide solid electrolyte material and a halide binder, adding a dispersant, and stirring thoroughly to obtain a slurry, coating the slurry on the surface of a sulfide solid electrolyte membrane, and vacuum drying to obtain a halide-coated sulfide solid electrolyte membrane; (4) Cold pressing the halide-coated sulfide solid electrolyte membrane at low temperature to obtain a composite sulfide solid electrolyte membrane.

6. The method according to claim 5, wherein The crushing in step (1) adopts acoustic resonance technology, and the parameters controlled by the acoustic resonance technology include frequency, acceleration and time; during the crushing process, the acceleration is adjusted to 50-100g at a frequency of 30-70Hz, and the time is 5-30min; The pressing in step (2) uses a roller machine and an oil press; the roller speed of the roller machine is 1 to 15 min -1 The temperature of the upper and lower rollers of the roller machine is 50 to 120°C; the pressure of the hydraulic press is 20 to 80 MPa; the pressing time of the hydraulic press is 1 to 3 minutes.

7. The method according to claim 5, wherein The dispersant in step (3) includes one or more of anisole, toluene, xylene, cyclohexane, n-hexane, isobutyl isobutyrate or butyl acetate, and the liquid-solid mass ratio of the dispersant to the halide electrolyte is 1 to 5:

1.

8. The method according to claim 5, wherein The stirring speed in step (3) is 100-500 rpm and the time is 10-20 min; the drying temperature is 20-60° C. and the time is 6-10 h; The temperature of the low-temperature cold pressing in step (4) is -60 to 0°C; the pressure is 50 to 150 MPa.

9. An all-solid-state lithium-ion battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet and a composite sulfide solid electrolyte membrane according to any one of claims 1 to 4 located between the positive electrode sheet and the negative electrode sheet.

10. The all-solid-state lithium-ion battery according to claim 9, wherein: The raw materials of the positive electrode sheet include positive electrode material, sulfide solid electrolyte powder and binder, and the positive electrode material includes one or more of NCM811 electrode sheet, lithium iron phosphate electrode sheet, lithium cobalt oxide electrode sheet or lithium nickel oxide electrode sheet; The raw materials of the negative electrode sheet include negative electrode material, sulfide solid electrolyte powder and a binder. The negative electrode material includes one or more of silicon carbon, graphite, hard carbon or metallic lithium.

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