Nano hard alloy composite solid electrolyte membrane as well as preparation method and application thereof

Abstract

The invention discloses a nano hard alloy composite solid electrolyte membrane as well as a preparation method and application thereof, and belongs to the technical field of solid lithium batteries. The nano hard alloy composite solid electrolyte membrane comprises the following raw materials: nano hard alloy modified inorganic solid electrolyte, a spinning polymer, an organic dispersing agent and lithium salt, the nano hard alloy modified inorganic solid electrolyte comprises the following raw materials: nano hard alloy, a fluxing agent, a metal binder and an inorganic solid electrolyte. The invention also discloses a preparation method and application of the nano hard alloy composite solid electrolyte membrane. The problems of poor mechanical property, poor thermal stability, low ionic conductivity and poor electrochemical stability of the polymer solid electrolyte can be solved, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium batteries, and particularly relates to a nano-cemented carbide composite solid electrolyte membrane, a preparation method thereof, and an application thereof. Background Art

[0002] As an important candidate technology for the next-generation high-safety and high-energy-density energy storage system, the research on the core component, solid electrolyte, of solid-state lithium metal batteries has received extensive attention. Among many solid electrolyte materials, polymer-based solid electrolytes stand out due to their unique processing characteristics and interfacial adaptability. Such materials are usually composed of a polymer matrix, a lithium salt, and a functional additive. Their ion conduction mechanism mainly depends on the thermal motion of polymer segments, that is, lithium ions migrate through the formation of local free volume and the cooperative motion of segments. This unique conduction mechanism makes the regulation of the material's microstructure a key breakthrough for performance optimization.

[0003] Currently, the development of polymer solid electrolytes faces multiple technical bottlenecks. The primary contradiction lies in the inherent antagonistic relationship between mechanical strength and ionic conductivity; to achieve a high ionic conductivity, it is necessary to reduce the crystallinity of the material to enhance the segment motion ability. However, during this process, the elastic modulus of the polymer decreases significantly, and it is prone to plastic deformation at room temperature, severely affecting its mechanical strength. Secondly, the interfacial side reaction rate between lithium metal and the polymer will increase significantly under high-temperature environments, and an unstable solid electrolyte interface may be formed. This dynamically changing interfacial layer severely restricts the cycle life of the battery. At the same time, there is a long-term chemical stability problem between polymer segments and highly active lithium metal. In some polymer solid electrolyte systems, the interfacial passivation layer will thicken abnormally after long-term storage.

[0004] How to solve the problems of poor mechanical properties, poor thermal stability, low ionic conductivity, and poor electrochemical stability of polymer solid electrolytes and achieve the leap from laboratory to industrialization of polymer solid electrolytes is one of the current research hotspots in this field. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a nano-cemented carbide composite solid electrolyte membrane, a preparation method thereof, and an application thereof to solve the problems of poor mechanical properties, poor thermal stability, low ionic conductivity, and poor electrochemical stability of polymer solid electrolytes.

[0006] To solve the technical problems, the technical solution adopted is to provide a nano-cemented carbide composite solid electrolyte membrane, which comprises the following raw materials in parts by mass: 2 - 20 parts of an inorganic solid electrolyte modified with nano-cemented carbide, 20 - 80 parts of a spinning polymer, 0.1 - 10 parts of an organic dispersant, and 5 - 40 parts of a lithium salt; The inorganic solid electrolyte modified by nano-cemented carbide comprises raw materials in the following parts by mass: 2-30 parts of nano-cemented carbide, 0.5-10 parts of flux, 3-25 parts of metal binder, and 70-90 parts of inorganic solid electrolyte; The nano-cemented carbide is at least one of silicon carbide, tungsten carbide, boron carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide, boron carbide, hafnium carbide, tantalum carbide, molybdenum carbide, niobium carbide, aluminum nitride, silicon nitride, boron nitride, titanium nitride, aluminum nitride, vanadium nitride, chromium nitride, titanium oxynitride, zirconium nitride, zirconium diboride, lanthanum hexaboride, titanium diboride, hafnium diboride, tantalum silicide, hafnium silicide, molybdenum silicide, and zirconium silicide; the flux is at least one of metal oxides, borates, alkali metal halides, fluorides, and phosphates; the metal binder is at least one of cobalt, nickel, iron, copper, chromium, molybdenum, tungsten, silver, and zinc; the inorganic solid electrolyte is an oxide solid electrolyte or a sulfide solid electrolyte.

[0007] The beneficial effects of the present invention adopting the above technical solutions are as follows: The uniform heterojunction network formed by the nano-cemented carbide and the inorganic solid electrolyte at high temperature can effectively improve the ionic conductivity of the inorganic solid electrolyte, and the nano-cemented carbide can crosslink the spinning polymer by chemical bonding and improve the nano-pore size distribution during the electrospinning process, further enhancing the ionic conductivity of the composite solid electrolyte. In addition, the nano-cemented carbide is introduced into the composite solid electrolyte by chemical bonding and a composite separator is prepared by electrospinning technology. This composite method effectively combines the high thermal stability and high mechanical properties of the nano-cemented carbide, forming a solid electrolyte membrane with unique composite properties; when it is used in a solid-state lithium battery, at the interface between the nano-cemented carbide composite solid electrolyte membrane and the lithium or lithium composite negative electrode, continuous electrochemical reactions will induce the formation of flat and uniform inorganic non-metal nanowires, such as silicon nanowires, on the surface of the lithium or lithium composite negative electrode, which can effectively inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery, providing a new way to solve the problem of lithium dendrites; at the same time, the addition of the nano-cemented carbide significantly improves the thermal stability of the composite solid electrolyte membrane, making the composite solid electrolyte membrane have good thermal stability and low thermal shrinkage rate at high temperature, and still maintaining a complete structure at high temperature; in addition, the nano-cemented carbide also reduces the diameter of the polymer fiber, improves the tensile strength and longitudinal mechanical properties of the polymer solid electrolyte membrane, and enhances its puncture resistance; the nano-cemented carbide also improves the surface roughness of the separator and the interaction with the electrolyte, enhances the wettability of the separator to the electrolyte, and increases the electrolyte absorption rate, which is beneficial to improving the ionic conductivity of the battery. It solves the problems of poor mechanical properties, poor thermal stability, low ionic conductivity, and poor electrochemical stability of the polymer solid electrolyte.

[0008] Preferably, the nano-cermet composite solid electrolyte membrane comprises the following raw materials in parts by mass: 10 parts of an inorganic solid electrolyte modified with nano-cermet, 60 parts of a spinning polymer, 2 parts of an organic dispersant, and 28 parts of a lithium salt; The inorganic solid electrolyte modified with nano-cermet comprises the following raw materials in parts by mass: 10 parts of nano-cermet, 2 parts of a flux, 3 parts of a metal binder, and 85 parts of an inorganic solid electrolyte.

[0009] Preferably, the flux is TiO 2 , ZrO 2 , B 2 O 3 , Li 2 B 4 O 7 , LiF, NaF, KCl, AlF 3 , CaF 2 , and Li 3 PO 4 and at least one of the following.

[0010] Preferably, the inorganic solid electrolyte is at least one of a fluorite-type solid electrolyte, a perovskite-type solid electrolyte, a garnet-type solid electrolyte, a NASICON-type solid electrolyte, a Thio-LISICON-type solid electrolyte, a Li-argyrodite-type solid electrolyte, an LGPS-type solid electrolyte, and a thiogermanate-type solid electrolyte.

[0011] Preferably, the particle size of the nano-cermet is 10-800 nm.

[0012] More preferably, the particle size of the nano-cermet is 20 nm.

[0013] More preferably, the nano-cermet is silicon nitride or titanium nitride; the flux is TiO 2 ; the metal binder is cobalt; the inorganic solid electrolyte is Li 7 La 3 Zr 2 O 12 .

[0014] More preferably, the inorganic solid electrolyte modified with nano-cermet is prepared by the following steps: mixing the nano-cermet, the flux, the metal binder, and the inorganic solid electrolyte, and reacting at 400-1300 °C for 10-40 h to obtain the inorganic solid electrolyte modified with nano-cermet.

[0015] More preferably, the inorganic solid electrolyte modified with nano cemented carbide is prepared through the following steps: uniformly stirring nano cemented carbide, a flux, a metal binder and an inorganic solid electrolyte, and reacting at 1000 °C for 18 h to obtain the inorganic solid electrolyte modified with nano cemented carbide.

[0016] More preferably, the spinning polymer is at least one of polyethylene oxide, polysiloxane, polyvinylidene fluoride, polyacrylonitrile, sulfonated polyether ether ketone, sulfonated polyphenylene ether, polyethylene glycol succinate, polymethyl ether acrylate, polydioxolane, polyphosphazene, polycarbonate, polycyanoacrylate, polypropylene diamide, polyoxalate, polyethylene imine and polyvinylidene fluoride - hexafluoropropylene; the organic dispersant is at least one of sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and polyvinylpyrrolidone; and the lithium salt is at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide and lithium difluorophosphate.

[0017] More preferably, the spinning polymer is at least one of polyvinylidene fluoride, sulfonated polyether ether ketone and polyvinylidene fluoride - hexafluoropropylene; the organic dispersant is polyvinylpyrrolidone; and the lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate and lithium difluoro(oxalato)borate.

[0018] The present invention also provides a method for preparing the above - mentioned nano cemented carbide composite solid electrolyte membrane, comprising the following steps: (1) Dispersing the inorganic solid electrolyte modified with nano cemented carbide, the spinning polymer, the organic dispersant and the lithium salt in an organic solvent, and stirring evenly to obtain a spinning solution; (2) Preparing the spinning solution into a composite polymer membrane by electrospinning; (3) Sequentially subjecting the composite polymer membrane to vacuum drying, hot pressing treatment and heat preservation treatment to obtain the nano cemented carbide composite solid electrolyte membrane.

[0019] Preferably, in step (1), the organic solvent is at least one of N,N - dimethylformamide, dimethyl sulfoxide, hexafluoroisopropanol, chloroform, acetone, tetrahydrofuran and toluene; and the mass fraction of the solid in the spinning solution is 8 - 25 wt.%.

[0020] More preferably, in step (1), the organic solvent is N,N - dimethylformamide; and the mass fraction of the solid in the spinning solution is 20 wt.%.

[0021] Preferably, in step (2), the syringe plunger propulsion speed of electrospinning is 0.1 - 0.8 mL / h, the syringe needle tip voltage is 15 - 30 kV, the distance between the collection substrate and the emission port is 10 - 28 cm, the rotation speed of the collection substrate is 180 - 320 rpm; and the thickness of the composite polymer membrane is 20 - 100 μm.

[0022] More preferably, in step (2), the plunger pushing speed of the electrospinning syringe is 0.5 mL / h, the voltage at the syringe tip is 20 kV, the distance between the collection substrate and the emission port is 13 cm, and the rotation speed of the collection substrate is 200 rpm; the thickness of the composite polymer film is 25 μm.

[0023] Preferably, in step (3), the temperature for vacuum drying is 80-100 °C, the time is 10-24 h; the temperature for hot pressing treatment is 40-120 °C, the pressure is 5-25 MPa, and the time is 5-30 min; the temperature for heat preservation treatment is 130-190 °C, and the time is 30-120 min.

[0024] More preferably, in step (3), the temperature for vacuum drying is 80 °C, the time is 12 h; the temperature for hot pressing treatment is 100 °C, the pressure is 20 MPa, and the time is 20 min; the temperature for heat preservation treatment is 160 °C, and the time is 120 min.

[0025] The present invention also provides the application of the above-mentioned nano-cemented carbide composite solid electrolyte membrane in the preparation of solid-state lithium batteries.

[0026] The present invention also provides a solid-state lithium battery, comprising a lithium negative electrode, a positive electrode, and the above-mentioned nano-cemented carbide composite solid electrolyte membrane.

[0027] Preferably, the lithium negative electrode is a lithium metal negative electrode or a lithium composite negative electrode.

[0028] The present invention has the following beneficial effects: (1) In the present invention, the nano-cemented carbide in the nano-cemented carbide modified inorganic solid electrolyte forms an interpenetrating network structure with the inorganic solid electrolyte through a metal binder. The nano-cemented carbide, as a rigid skeleton, can improve the mechanical properties of the composite material and inhibit the piercing of lithium dendrites; at the same time, after the surface of the nano-cemented carbide particles is activated by a flux, a co-firing interface can be formed with the inorganic solid electrolyte particles, reducing the grain boundary impedance and expanding the lithium ion transmission path; in addition, the metal binder can also absorb the volume change stress during charge and discharge through plastic deformation, avoiding the problem of electrolyte layer cracking.

[0029] (2) In the present invention, the nano-cemented carbide is introduced into the composite solid electrolyte through chemical bonding and a composite solid electrolyte membrane is prepared by electrospinning technology. This composite method effectively combines the high thermal stability and high mechanical properties of the nano-cemented carbide, forming a solid electrolyte membrane with unique composite properties; when the prepared nano-cemented carbide composite solid electrolyte membrane is used in a lithium solid battery, it can still maintain a high discharge capacity, rate performance, and cycle stability, demonstrating its high electrochemical stability.

[0030] (3) The preparation method of the present invention is simple, and the raw materials are easily available, which can meet the diverse performance requirements, with strong practicability and functionality, providing an economically feasible new way for the progress of energy technology. Brief Description of the Drawings

[0031] Figure 1 It is the SEM diagram of the composite solid electrolyte membrane; among them, (a) is the SEM diagram of the composite solid electrolyte membrane of Example 1; (b) is the SEM diagram of the composite solid electrolyte membrane of Example 2; (c) is the SEM diagram of the composite solid electrolyte membrane of Comparative Example 1; (d) is the SEM diagram of the composite solid electrolyte membrane of Comparative Example 2. Detailed Embodiments

[0032] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0033] Therefore, the following detailed description of the provided embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0035] Example 1 A nano-cemented carbide composite solid electrolyte membrane, comprising the following raw materials in parts by mass: 10 parts of an inorganic solid electrolyte modified with nano-cemented carbide, 60 parts of sulfonated polyether ether ketone, 2 parts of polyvinylpyrrolidone, and 28 parts of lithium hexafluorophosphate; Among them, the inorganic solid electrolyte modified with nano-cemented carbide comprises the following raw materials in parts by mass: 10 parts of silicon nitride with a particle size of 20 nm, TiO 2 2 parts, 3 parts of cobalt, and Li 7 La 3 Zr 2 O 12 85 parts; the inorganic solid electrolyte modified with nano-cemented carbide is prepared through the following steps: uniformly mixing silicon nitride with a particle size of 20 nm, TiO 2 , cobalt, and Li 7 La 3 Zr 2 O 12 by mechanical stirring, and reacting at 1000 °C for 18 h to obtain the inorganic solid electrolyte modified with nano-cemented carbide.

[0036] This embodiment also provides a method for preparing the above-mentioned nano-cermet composite solid electrolyte membrane, including the following steps: (1) Disperse the inorganic solid electrolyte modified by nano-cermet, sulfonated polyether ether ketone, polyvinylpyrrolidone, and lithium hexafluorophosphate in N,N-dimethylformamide, and stir evenly to obtain a spinning solution; the mass fraction of solids in the spinning solution is 20 wt.%. (2) Inject the spinning solution into an electrospinning device, set the advancing speed of the syringe plunger for electrospinning to 0.5 mL / h, the voltage of the syringe tip to 20 kV, the distance between the collection substrate and the emission port to 13 cm, and the rotation speed of the collection substrate to 200 rpm to obtain a composite polymer membrane with a thickness of 25 μm; (3) Vacuum-dry the composite polymer membrane at 80°C for 12 h, then perform hot pressing treatment at 100°C and 20 MPa for 20 min, and finally place it in an oven at 160°C for heat preservation treatment for 120 min to obtain the nano-cermet composite solid electrolyte membrane.

[0037] Example 2 A nano-cermet composite solid electrolyte membrane, comprising the following raw materials in parts by mass: 10 parts of an inorganic solid electrolyte modified by nano-cermet, 30 parts of polyvinylidene fluoride, 30 parts of polyvinylidene fluoride-hexafluoropropylene, 2 parts of polyvinylpyrrolidone, 16.8 parts of lithium hexafluorophosphate, 8.4 parts of lithium tetrafluoroborate, and 2.8 parts of lithium difluorooxalate borate; Among them, the inorganic solid electrolyte modified by nano-cermet comprises the following raw materials in parts by mass: 10 parts of titanium nitride with a particle size of 20 nm, TiO 2 2 parts, 3 parts of cobalt, and Li 7 La 3 Zr 2 O 12 85 parts; the inorganic solid electrolyte modified by nano-cermet is prepared through the following steps: Mechanically stir and mix evenly titanium nitride with a particle size of 20 nm, TiO 2 , cobalt, and Li 7 La 3 Zr 2 O 12 React at 1000°C for 18 h to obtain the inorganic solid electrolyte modified by nano-cermet.

[0038] This embodiment also provides a method for preparing the above-mentioned nano-cermet composite solid electrolyte membrane, including the following steps: (1)Disperse the inorganic solid electrolyte modified with nano-cemented carbide, sulfonated polyether ether ketone, polyvinylpyrrolidone and lithium hexafluorophosphate in N,N-dimethylformamide and stir evenly to obtain a spinning solution; the mass fraction of solids in the spinning solution is 20 wt.%. (2)Inject the spinning solution into an electrospinning device, set the pushing speed of the syringe plunger for electrospinning to 0.5 mL / h, the voltage of the syringe tip to 20 kV, the distance between the collection substrate and the emission port to 13 cm, and the rotation speed of the collection substrate to 200 rpm to obtain a composite polymer membrane with a thickness of 25 μm. (3)Vacuum dry the composite polymer membrane at 80 °C for 12 h, then perform hot pressing treatment at 100 °C and 20 MPa for 20 min, and finally place it in an oven at 160 °C for heat preservation treatment for 120 min to obtain the nano-cemented carbide composite solid electrolyte membrane.

[0039] Example 3 A nano-cemented carbide composite solid electrolyte membrane, comprising the following raw materials in parts by mass: 2 parts of inorganic solid electrolyte modified with nano-cemented carbide, 80 parts of polyethylene oxide, 0.1 part of sodium dodecyl sulfate, and 17.9 parts of lithium perchlorate; Among them, the inorganic solid electrolyte modified with nano-cemented carbide comprises the following raw materials in parts by mass: 6.5 parts of tungsten carbide with a particle size of 200 nm, Li 2 B 4 O 7 0.5 part, 3 parts of nickel, and Li 7 La 3 Zr 2 O 12 90 parts; the inorganic solid electrolyte modified with nano-cemented carbide is prepared through the following steps: Mix tungsten carbide with a particle size of 200 nm, Li 2 B 4 O 7 , nickel and Li 7 La 3 Zr 2 O 12 Mix them evenly by mechanical stirring and react at 400 °C for 40 h to obtain the inorganic solid electrolyte modified with nano-cemented carbide.

[0040] The preparation method of the composite solid electrolyte membrane in this example is the same as that in Example 1.

[0041] Example 4 A nano-cemented carbide composite solid electrolyte membrane, comprising the following raw materials in parts by mass: 20 parts of inorganic solid electrolyte modified with nano-cemented carbide, 30 parts of polymethylethacrylate, 10 parts of polyacrylic acid, and 40 parts of lithium bis(trifluoromethanesulfonyl)imide; Among them, the inorganic solid electrolyte modified by nano-cemented carbide includes the following raw materials in parts by mass: 15 parts of lanthanum hexaboride with a particle size of 600 nm, 5 parts of NaF, 10 parts of copper, and Li 7 La 3 Zr 2 O 12 70 parts; the inorganic solid electrolyte modified by nano-cemented carbide is prepared through the following steps: Mix lanthanum hexaboride with a particle size of 600 nm, NaF, copper, and Li 7 La 3 Zr 2 O 12 uniformly by mechanical stirring, and react at 1300 °C for 10 h to obtain the inorganic solid electrolyte modified by nano-cemented carbide.

[0042] In this embodiment, the preparation method of the composite solid electrolyte membrane is the same as that in Example 1.

[0043] Example 5 A nano-cemented carbide composite solid electrolyte membrane, which has the same raw materials and parts by mass as in Example 1.

[0044] This embodiment also provides a preparation method of the above nano-cemented carbide composite solid electrolyte membrane, including the following steps: (1) Disperse the inorganic solid electrolyte modified by nano-cemented carbide, sulfonated polyether ether ketone, polyvinylpyrrolidone, and lithium hexafluorophosphate in dimethyl sulfoxide, and stir evenly to obtain a spinning solution; the mass fraction of solids in the spinning solution is 8 wt.%. (2) Inject the spinning solution into an electrospinning device, set the advancing speed of the syringe plunger for electrospinning to 0.1 mL / h, the voltage of the syringe needle tip to 15 kV, the distance between the collection substrate and the emission port to 10 cm, and the rotation speed of the collection substrate to 180 rpm to obtain a composite polymer membrane with a thickness of 20 μm; (3) Vacuum-dry the composite polymer membrane at 80 °C for 24 h, then perform hot pressing treatment at 50 °C and 25 MPa for 30 min, and finally place it in an oven at 130 °C for heat preservation treatment for 50 min to obtain the nano-cemented carbide composite solid electrolyte membrane.

[0045] Example 6 A nano-cemented carbide composite solid electrolyte membrane, which has the same raw materials and parts by mass as in Example 1.

[0046] This embodiment also provides a preparation method of the above nano-cemented carbide composite solid electrolyte membrane, including the following steps: (1)Disperse the inorganic solid electrolyte modified with nano-cemented carbide, sulfonated polyether ether ketone, polyvinylpyrrolidone and lithium hexafluorophosphate in dimethyl sulfoxide and stir evenly to obtain a spinning solution; the mass fraction of solids in the spinning solution is 25 wt.%. (2)Inject the spinning solution into an electrospinning device, set the advancing speed of the syringe plunger for electrospinning to 0.8 mL / h, the voltage of the syringe tip to 30 kV, the distance between the collection substrate and the emission port to 28 cm, and the rotation speed of the collection substrate to 320 rpm to obtain a composite polymer membrane with a thickness of 100 μm; (3)Vacuum dry the composite polymer membrane at 100 °C for 10 h, then perform hot pressing treatment at 120 °C and 5 MPa for 5 min, and finally place it in an oven at 190 °C for heat preservation treatment for 100 min to obtain the nano-cemented carbide composite solid electrolyte membrane.

[0047] Comparative Example 1 A composite solid electrolyte membrane, comprising the following raw materials in parts by mass: 10 parts of inorganic solid electrolyte, 60 parts of sulfonated polyether ether ketone, 2 parts of polyvinylpyrrolidone and 28 parts of lithium hexafluorophosphate; wherein, the inorganic solid electrolyte is Li 7 La 3 Zr 2 O 12 .

[0048] The preparation method of the composite solid electrolyte membrane in this comparative example is the same as that in Example 1.

[0049] Comparative Example 2 A composite solid electrolyte membrane, comprising the following raw materials in parts by mass: 10 parts of inorganic solid electrolyte, 30 parts of polyvinylidene fluoride, 30 parts of polyvinylidene fluoride-hexafluoropropylene, 2 parts of polyvinylpyrrolidone, 16.8 parts of lithium hexafluorophosphate, 8.4 parts of lithium tetrafluoroborate and 2.8 parts of lithium difluorooxalate borate; wherein, the inorganic solid electrolyte is Li 7 La 3 Zr 2 O 12 .

[0050] The preparation method of the composite solid electrolyte membrane in this comparative example is the same as that in Example 2.

[0051] Experimental Example 1. Structure Characterization Perform scanning electron microscopy (SEM) analysis on the nano-cemented carbide composite solid electrolyte membranes prepared in Examples 1-2 and the composite solid electrolyte membranes prepared in Comparative Examples 1-2. The results are as Figure 1 shown.

[0052] From Figure 1 it can be seen that in Examples 1-2 (Figure 1 In the case of the nano-cemented carbide composite solid electrolyte membranes in Figs. (a) and (b) in the middle, the introduction of nano-cemented carbide particles changes the electrostatic repulsion and viscosity of the spinning solution, thereby promoting fiber refinement. The fiber diameter is reduced to 150 nm, the surface roughness is significantly increased, and the nano-cemented carbide particles are evenly dispersed in the fibers to form a multi-scale pore structure, which can significantly improve the electrolyte wettability and mechanical properties of the separator. In contrast, for Comparative Examples 1-2 ( Figure 1 In the case of the composite solid electrolyte membranes corresponding to Figs. (c) and (d) in the middle, the average diameter of the nanofibers is 220 nm, forming a continuous but narrow-pored porous network.

[0053] 2. Mechanical property test The nano-cemented carbide composite solid electrolyte membranes prepared in Examples 1-2 and the composite solid electrolyte membranes prepared in Comparative Examples 1-2 were tested for mechanical properties.

[0054] 2.1 A single-axis tensile test was carried out using a MTS microcomputer-controlled plastic tensile testing machine (CMT6104) to measure its tensile strength The solid electrolyte membrane was cut into dumbbell-shaped specimens (gage section size: 25 mm × 5 mm, thickness 25 μm); both ends of the specimen were clamped in the upper and lower fixtures of the tensile machine, and the clamping distance was set to 20 mm; a uniaxial tensile force was applied at a constant tensile rate (5 mm / min) until the specimen broke; the stress-strain curve was recorded in real time, and the tensile strength was calculated; 2.2 The maximum load and modulus were measured using an American iNano nano-indentation instrument (KLA) The separator sample was fixed on a flat substrate to avoid local deformation; the maximum indentation depth was set to 2000 nm, and the loading rate was 0.5 mN / s; after the indenter contacted the surface of the sample, it was gradually loaded to the target depth, held for 5 s and then unloaded; according to the load-displacement curve, the maximum load and modulus were calculated.

[0055] The test results are shown in Table 1.

[0056] Table 1 Mechanical property test table of each solid electrolyte membrane

[0057] As can be seen from Table 1, by combining Examples 1-2 and Comparative Examples 1-2, it can be found that the nano-hard alloy composite solid electrolyte membrane prepared by the present invention has relatively high tensile strength, maximum load and modulus, and the technical effect of Example 1 is the best. From the results of Example 1 and Comparative Example 1, it can be seen that the inorganic solid electrolyte modified by nano-silicon nitride can effectively improve the mechanical properties of the polymer and inorganic composite solid electrolyte membrane. By combining the results of Examples 1-2 and Comparative Examples 1-2, it can be found that the inorganic solid electrolyte modified by nano-hard alloys such as silicon nitride and titanium nitride can indeed effectively improve the mechanical properties of the composite solid electrolyte membrane.

[0058] 3. Thermal stability test The nano-hard alloy composite solid electrolyte membranes prepared in Examples 1-2 and the composite solid electrolyte membranes prepared in Comparative Examples 1-2 were tested for their thermal stability through the following steps: The solid electrolyte membrane was cut into circular samples with a diameter of 5 cm, and the initial area (S i ) was marked; then, isogradient tests were carried out at annealing temperatures of 100 °C, 150 °C, and 190 °C, and the temperature was kept constant for 1 h; after annealing, it was cooled to room temperature, and the final area (S f ) was measured, and the thermal shrinkage rate of the solid electrolyte membrane after high-temperature annealing was calculated through the following formula (1) to evaluate its thermal stability; Thermal shrinkage rate (%) = (S i - S f / S i ) × 100 (1).

[0059] Table 2 Thermal stability test table of each solid electrolyte membrane

[0060] As can be seen from Table 2, by combining Examples 1-2 and Comparative Examples 1-2, it can be found that the nano-hard alloy composite solid electrolyte membrane prepared by the present invention has a relatively low thermal shrinkage rate at high temperatures, and the technical effect of Example 1 is the best. From the results of Example 1 and Comparative Example 1, it can be seen that the inorganic solid electrolyte modified by nano-silicon nitride can effectively improve the thermal stability of the polymer and inorganic composite solid electrolyte. By combining the results of Examples 1-2 and Comparative Examples 1-2, it can be found that the inorganic solid electrolyte modified by nano-hard alloys such as silicon nitride and titanium nitride can indeed effectively improve the thermal stability of the composite solid electrolyte membrane.

[0061] 4. Ion conductivity test The ion conductivities of the nano-hard alloy composite solid electrolyte membranes prepared in Examples 1-2 and the composite solid electrolyte membranes prepared in Comparative Examples 1-2 were tested.

[0062] The electrochemical impedance spectrum was tested using the Donghua DH7000 electrochemical workstation at a constant temperature of 30 °C in the frequency range of 100 kHz - 0.01 Hz. The ohmic resistance (R 0 ) was obtained by equivalent circuit fitting, and the ionic conductivity (σ) was calculated using the following formula (2); σ = I / (R 0 × A)(2) where I is the diaphragm thickness, 25 μm; A is the effective area.

[0063] Table 3 Ionic conductivity test table of each solid electrolyte membrane

[0064] As can be seen from Table 3, by combining Examples 1 - 2 and Comparative Examples 1 - 2, it can be found that the nano - cemented carbide composite solid electrolyte membrane prepared by the present invention has a relatively high ionic conductivity, and the technical effect of Example 1 is the best. From the results of Example 1 and Comparative Example 1, it can be seen that the inorganic solid electrolyte modified by nano - silicon nitride can effectively improve the ionic conductivity of the polymer and inorganic composite solid electrolyte. By combining the results of Examples 1 - 2 and Comparative Examples 1 - 2, it can be found that the inorganic solid electrolytes modified by nano - cemented carbides such as silicon nitride and titanium nitride can indeed effectively improve the ionic conductivity of the composite solid electrolyte.

[0065] 5. Cycle performance test of solid - state lithium batteries The nano - cemented carbide composite solid electrolyte membranes prepared in Examples 1 - 2 and the composite solid electrolyte membranes prepared in Comparative Examples 1 - 2 were used in the preparation of solid - state lithium batteries. The specific steps are as follows: (1) Lithium iron phosphate was selected as the positive electrode material, polyvinylidene fluoride as the binder, and lithium metal as the negative electrode material; lithium iron phosphate and polyvinylidene fluoride were mixed evenly and coated on the positive electrode current collector to make the positive electrode; lithium metal and polyvinylidene fluoride were mixed evenly and coated on the negative electrode current collector to make the negative electrode; (2) The negative electrode, the nano - cemented carbide composite solid electrolyte membranes prepared in Examples 1 - 2 or the composite solid electrolyte membranes prepared in Comparative Examples 1 - 2, and the positive electrode were assembled in sequence, and sealed in an inert gas glove box (H 2 O and O 2 contents are both <0.1 ppm) to assemble a solid - state lithium battery.

[0066] The prepared solid - state lithium batteries were respectively subjected to constant - current charge - discharge tests using a Neware CT - 4008 T battery tester. Each assembled solid - state lithium battery was subjected to a 1 C charge - discharge cycle test at 25 °C, and the test results are shown in Table 4.

[0067] Table 4 Charge - discharge cycle test table of each solid - state lithium battery

[0068] As can be seen from Table 4, by combining Examples 1-2 and Comparative Examples 1-2, it can be found that the nano-cermet composite solid electrolyte membrane prepared by the present invention has good cycle life, and the technical effect of Example 1 is the best. From the results of Example 1 and Comparative Example 1, it can be seen that the inorganic solid electrolyte modified by nano-silicon nitride can effectively improve the electrochemical stability of the polymer and inorganic composite solid electrolyte, and significantly improve the cycle stability of the solid-state lithium battery. By combining the results of Examples 1-2 and Comparative Examples 1-2, it can be found that the inorganic solid electrolyte modified by nano-cermet such as silicon nitride and titanium nitride can indeed effectively improve the comprehensive electrochemical performance of the composite solid electrolyte. Taking silicon nitride as an example: Silicon nitride can induce roughening of the surface of sulfonated polyether ether ketone to reduce the fiber diameter, and increase the local disorder of the fiber network through physical hindrance, thereby forming through holes with multi-scale distribution between the fibers, which can significantly improve the electrolyte wettability and lithium ion transport kinetics of the solid electrolyte membrane; Secondly, silicon nitride and sulfonated polyether ether ketone form stable Si-O-S and Si-N-S covalent bonds through acid-base reactions and condensation reactions of surface functional groups, and strengthen the interfacial bonding by combining with the hydrogen bond network. This chemical bonding can significantly improve the mechanical strength and thermal stability of the separator, and endow the solid electrolyte membrane with excellent safety and electrochemical performance; At the same time, the elemental silicon generated by the electrochemical reduction reaction (Si 3 N 4 +Li + →Si+Li 3 N) between silicon nitride and the lithium metal interface forms a nanowire structure through one-dimensional directional aggregation. The high specific surface area of the nanowires can provide uniform nucleation sites, guide the lateral deposition of lithium ions along the surface of the nanowires, and inhibit the vertical growth of dendrites, thereby significantly improving the safety and long cycle stability of the battery.

[0069] The above research shows that the nano-cermet of the present invention has application feasibility in the composite solid electrolyte, and can further provide a solid-state lithium battery with long cycle life and high safety.

[0070] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of the present invention.

Claims

1. A nano-hard alloy composite solid electrolyte membrane, characterized in that: The method comprises the following raw materials in parts by weight: 2 to 20 parts of inorganic solid electrolyte modified by nano-hard alloy, 20 to 80 parts of spinning polymer, 0.1 to 10 parts of organic dispersant and 5 to 40 parts of lithium salt; The inorganic solid electrolyte modified by nano-hard alloy comprises the following raw materials in parts by weight: 2-30 parts of nano-hard alloy, 0.5-10 parts of flux, 3-25 parts of metal binder and 70-90 parts of inorganic solid electrolyte; The nano cemented carbide is at least one of silicon carbide, tungsten carbide, boron carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide, boron carbide, hafnium carbide, tantalum carbide, molybdenum carbide, niobium carbide, aluminum nitride, silicon nitride, boron nitride, titanium nitride, aluminum nitride, vanadium nitride, chromium nitride, titanium oxynitride, zirconium nitride, zirconium diboride, lanthanum hexaboride, titanium diboride, hafnium diboride, tantalum silicide, hafnium silicide, molybdenum silicide and zirconium silicide; the flux is at least one of metal oxides, borates, alkali metal halides, fluorides and phosphates; the metal binder is at least one of cobalt, nickel, iron, copper, chromium, molybdenum, tungsten, silver and zinc; the inorganic solid electrolyte is an oxide solid electrolyte or a sulfide solid electrolyte.

2. The nano-hard alloy composite solid electrolyte membrane according to claim 1, characterized in that: The method comprises the following raw materials in parts by weight: 10 parts of inorganic solid electrolyte modified by nano-hard alloy, 60 parts of spinning polymer, 2 parts of organic dispersant and 28 parts of lithium salt; The inorganic solid electrolyte modified by nano-hard alloy comprises the following raw materials in parts by mass: 10 parts of nano-hard alloy, 2 parts of flux, 3 parts of metal binder and 85 parts of inorganic solid electrolyte.

3. The nano-hard alloy composite solid electrolyte membrane according to claim 1 or 2, characterized in that: The inorganic solid electrolyte modified by nano-hard alloy is prepared by the following steps: mixing nano-hard alloy, flux, metal binder and inorganic solid electrolyte, and reacting at 400-1300° C. for 10-40 h to obtain the inorganic solid electrolyte modified by nano-hard alloy.

4. The nano-hard alloy composite solid electrolyte membrane according to claim 1 or 2, characterized in that: The spinning polymer is at least one of polyethylene oxide, polysiloxane, polyvinylidene fluoride, polyacrylonitrile, sulfonated polyetheretherketone, sulfonated polyphenylene ether, polyethylene glycol succinate, polymethyl ether acrylate, polydioxolane, polyphosphazene, polycarbonate, polynitrile acrylate, polymalonamide, polyoxalate, polyethyleneimine and polyvinylidene fluoride-hexafluoropropylene; the organic dispersant is at least one of sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and polyvinyl pyrrolidone; the lithium salt is at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate, lithium difluorooxalate borate, lithium bistrifluoromethanesulfonyl imide and lithium difluorophosphate.

5. The method for preparing the nano-hard alloy composite solid electrolyte membrane according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) dispersing an inorganic solid electrolyte modified by nano-hard alloy, a spinning polymer, an organic dispersant and a lithium salt in an organic solvent, and stirring them uniformly to obtain a spinning solution; (2) preparing a composite polymer membrane by electrospinning the spinning solution; (3) The composite polymer membrane is subjected to vacuum drying, hot pressing treatment and heat preservation treatment in sequence to obtain a nano-hard alloy composite solid electrolyte membrane.

6. The method for preparing a nano-hard alloy composite solid electrolyte membrane according to claim 5, characterized in that: In the step (1), the organic solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, hexafluoroisopropanol, chloroform, acetone, tetrahydrofuran and toluene; and the mass fraction of the solid in the spinning solution is 8-25 wt.%.

7. The method for preparing a nano-hard alloy composite solid electrolyte membrane according to claim 5, characterized in that: In the step (2), the syringe plunger advancement speed of the electrospinning is 0.1-0.8 mL / h, the syringe needle tip voltage is 15-30 kV, the distance between the collecting substrate and the emission port is 10-28 cm, and the rotation speed of the collecting substrate is 180-320 rpm; the thickness of the composite polymer film is 20-100 μm.

8. The method for preparing a nano-hard alloy composite solid electrolyte membrane according to claim 5, characterized in that: In the step (3), the vacuum drying temperature is 80-100°C and the time is 10-24 h; the hot pressing temperature is 40-120°C, the pressure is 5-25 MPa, and the time is 5-30 min; the insulation treatment temperature is 130-190°C and the time is 30-120 min.

9. Use of the nano-hard alloy composite solid electrolyte membrane according to any one of claims 1 to 4 in the preparation of solid-state lithium batteries.

10. A solid-state lithium battery, characterized in that: It comprises a lithium negative electrode, a positive electrode and the nano-hard alloy composite solid electrolyte membrane according to any one of claims 1 to 4.

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