Solid electrolyte film, preparation method and solid-state battery

Abstract

The present invention relates to the field of solid electrolyte technology, and in particular to a solid electrolyte film, a preparation method and a solid-state battery. The solid electrolyte film provided by the present invention is prepared by using an inorganic solid electrolyte modified by an organic polymer polyacrylonitrile and a polydopamine-modified polytetrafluoroethylene composite binder. On the one hand, by introducing the organic flexible polymer polyacrylonitrile, the flexibility and processability of the inorganic solid electrolyte are improved, and the problem of poor compatibility at the inorganic electrolyte / inorganic electrode interface is improved. On the other hand, by introducing polydopamine containing amino and hydroxyl polar groups, the adhesion of the polytetrafluoroethylene binder with a low friction coefficient is improved, making the solid electrolyte denser and the ion channel more continuous. The solid electrolyte film provided by the present invention is applied to solid-state batteries, which can effectively improve the ion transport performance, redox reversibility and cycle performance of solid-state batteries.

Description

Technical Field

[0001] The present invention relates to the field of solid electrolyte technology, and in particular to a solid electrolyte film, a preparation method and a solid-state battery. Background Art

[0002] In recent years, people have an increasing demand for 3C electronic devices (computers, communications, consumer electronics), electric vehicles, aircraft, etc., and the performance requirements for new energy power supply devices represented by lithium batteries are also getting higher and higher, which must provide higher safety and energy density.

[0003] Solid-state batteries can provide higher energy and higher safety. Inorganic solid electrolytes have low cost, high lithium ion conductivity, high electrochemical stability and good compatibility with metallic lithium. Inorganic solid electrolytes have high hardness, and filling solid electrolyte particles into a lithium ion conductive polymer matrix to prepare a composite electrolyte can improve its ductility and flexibility. However, the mechanism of ion conduction in the current composite electrolyte is still unclear. If the particles do not form a continuous conductive network in the polymer, the contribution of lithium ion transfer between solid electrolyte particles to the total conductivity may be limited. In addition, due to the high mechanical strength of inorganic solid electrolytes, their high ionic conductivity cannot be measured by simple cold pressing. High ionic conductivity can be achieved by high-temperature sintering process, but the flexibility of the membrane will be lost, which faces huge challenges in large-scale production. Summary of the Invention

[0004] Based on this, the present invention provides a solid electrolyte film, a preparation method thereof, and an application in solid-state batteries. The solid electrolyte film provided by the present invention is prepared using an inorganic solid electrolyte modified with an organic polymer polyacrylonitrile and a polydopamine-modified polytetrafluoroethylene composite binder. On the one hand, by introducing the organic flexible polymer polyacrylonitrile, the flexibility and processability of the inorganic solid electrolyte are improved, and the problem of poor compatibility at the inorganic electrolyte / inorganic electrode interface is improved. On the other hand, by introducing polydopamine containing polar groups such as amino groups and hydroxyl groups, the adhesion of the polytetrafluoroethylene binder with a low friction coefficient is improved, making the solid electrolyte more dense and the ion channel more continuous.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a solid electrolyte film, characterized in that it comprises the following steps:

[0007] A. Preparation of polyacrylonitrile-modified solid electrolyte particles:

[0008] A1. Dissolve polyacrylonitrile in dimethyl sulfoxide and perform high-energy ball milling.

[0009] A2. placing an inorganic solid electrolyte and a lithium salt into the ball-milled material and performing a high-energy ball milling process again;

[0010] A3, adding a precipitant 1-propanol to the material obtained in step A2, performing a final ball milling, and then centrifuging and drying the ball-milled product to obtain polyacrylonitrile-modified solid electrolyte particles;

[0011] B. Preparation of polydopamine-modified polytetrafluoroethylene composite binder:

[0012] B1. Pre-treating polytetrafluoroethylene with a potassium permanganate / nitric acid mixed solution to form hydrophilic manganese oxide or manganese hydroxide-coated polytetrafluoroethylene particles;

[0013] B2, adding dopamine monomer and potassium permanganate in proportion to an alkaline solution with a pH of 8.5, and then slowly adding the polytetrafluoroethylene pretreated in step B1 above to carry out a polymerization reaction. After the reaction is completed, ultrasonic washing with deionized water and vacuum drying are performed to obtain a polydopamine-coated polytetrafluoroethylene binder;

[0014] C. Prepared into solid electrolyte film:

[0015] C1. Using a rotary defoamer, the polyacrylonitrile-modified solid electrolyte and the polydopamine-modified polytetrafluoroethylene composite binder are uniformly mixed according to a mass ratio in a protective gas atmosphere, wherein the protective gas is one of argon, nitrogen, and helium;

[0016] C2. Grinding the obtained mixture powder in a dedicated ball mill under a protective gas atmosphere for 3 minutes to obtain a microfibrillated mixture, wherein the protective gas is one of argon, nitrogen, and helium;

[0017] C3. The microfibrillated mixture powder is rolled using a double-roller press under set parameters to fully fiberize the binder to obtain a solid electrolyte film.

[0018] Furthermore, in step A2, the inorganic solid electrolyte is one of a sulfide solid electrolyte, an oxide solid electrolyte and a halide solid electrolyte; the lithium salt is one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6) and lithium hexafluorophosphate (LiPF6).

[0019] Furthermore, in the step A, the mass ratio of polyacrylonitrile to solid electrolyte is (1-3):100.

[0020] Furthermore, in the step C1, based on the total mass of the solid electrolyte film, the mass of the polyacrylonitrile-modified solid electrolyte accounts for 97-99%, and the mass of the polydopamine-modified polytetrafluoroethylene accounts for 1-3%.

[0021] Furthermore, in step C3, the set parameters involve temperature, rolling times, rolling direction and film thickness, the temperature is 25°C to 80°C, the rolling times is 5 to 20 times, the rolling direction is unidirectional or bidirectional, and the film thickness is 50 to 150 μm.

[0022] In a second aspect, the present invention provides a solid electrolyte film, which is prepared by the method described in the above technical solution.

[0023] In a third aspect, the present invention provides a solid-state battery comprising an electrode sheet and the above-mentioned solid electrolyte film; the electrode sheet comprises a current collector and an active layer on the current collector, the active layer comprising an electrode active material, conductive carbon and a polydopamine-modified polytetrafluoroethylene composite binder.

[0024] Furthermore, in the active layer on the current collector, the polydopamine-modified polytetrafluoroethylene composite binder accounts for 1 to 10% of the mass of the active layer.

[0025] Furthermore, the electrode active material includes a positive electrode active material or a negative electrode active material. Positive electrode active materials include but are not limited to lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel cobalt manganese oxide (LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2) at least one; negative electrode active materials include but are not limited to lithium metal, carbon-based, silicon-based negative electrode active materials at least one.

[0026] Furthermore, the silicon-based negative electrode active material includes a silicon-oxygen negative electrode material with a molecular formula of SiOx, where x is any value from 0 to 2. Non-limiting examples include silicon monoxide and silicon dioxide.

[0027] Furthermore, the carbon-based negative electrode active material can adopt carbon negative electrode materials commonly used in the art, including but not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fiber, hard carbon, and soft carbon.

[0028] Furthermore, the active layer further includes conductive carbon, and the conductive carbon includes but is not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene.

[0029] Furthermore, the thickness of the active layer is 50 μm to 200 μm, for example, 50 μm, 100 μm, 150 μm or 200 μm.

[0030] Furthermore, the current collector adopts a current collector commonly used in the art, such as copper foil, aluminum foil, etc.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention uses polyacrylonitrile with high ionic conductivity and high elastic modulus to modify the solid electrolyte, giving it excellent flexibility and processability. The solid electrolyte membrane can effectively achieve Li-ion bonding between particles without sintering or applying external pressure. + transmission;

[0033] 2. In the present invention, the potassium permanganate / nitric acid mixed solution is used to pretreat the polytetrafluoroethylene to increase the subsequent coating area of ​​polydopamine. Polydopamine contains polar groups such as amino groups and hydroxyl groups, which improve the adhesion of the low-friction polytetrafluoroethylene, making the solid electrolyte denser and the ion channel more continuous.

[0034] 3. The solid-state battery provided by the present invention has significantly improved ion transport performance, redox reversibility, and cycling performance. Furthermore, the technical solution of the present invention involves a dry process, i.e., preparing the electrolyte and electrode sheets without the use of solvents. This greatly simplifies the preparation process, reduces preparation costs, and facilitates large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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 description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0036] Figure 1 Schematic diagram of the preparation process of polyacrylonitrile-modified lithium lanthanum zirconium oxide particles in Example 1 of the present invention;

[0037] Figure 2 1 is a SEM image of polyacrylonitrile-modified lithium lanthanum zirconium oxide particles of different sizes in Example 1 of the present invention;

[0038] Figure 3 FT-IR images of polyacrylonitrile, lithium lanthanum zirconium oxide, and polyacrylonitrile-modified lithium lanthanum zirconium oxide in Example 1 of the present invention;

[0039] Figure 4 Schematic diagram of the solid electrolyte film preparation process in Example 1 of the present invention;

[0040] Figure 5 This is a physical diagram of the solid electrolyte film in Example 1 of the present invention;

[0041] Figure 6 Schematic diagram of the microscopic morphology (SEM) of the solid electrolyte film in Example 1 of the present invention;

[0042] Figure 7 1 is a comparison diagram of the impedance of the batteries of Example 6 of the present invention and Comparative Example 1;

[0043] Figure 8 This is a comparison chart of the coulombic efficiency of the batteries of Example 6 of the present invention and Comparative Example 2 during the first three cycles. DETAILED DESCRIPTION

[0044] To facilitate understanding of the present invention, the present invention will be described more fully below. Preferred embodiments of the present invention are provided in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the appended claims outline the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art will recognize that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing a solid electrolyte film, comprising the following steps:

[0047] Step 1: Preparation of polyacrylonitrile (PAN) modified lithium lanthanum zirconium oxide (LLZTO) particles. The specific reaction route is as follows: Figure 1 As shown. The specific operation is: First, weigh 0.15g PAN and dissolve it in 20mL dimethyl sulfoxide and perform high-energy ball milling until the liquid turns light yellow. Secondly, weigh the lithium salt bistrifluoromethanesulfonyl imide, and the mass ratio of PAN to lithium salt is 1:1. At the same time, weigh 5.0g LLZTO nanoparticles, and the mass ratio of LLZTO to PAN is 100:3. The high-energy ball milling process is performed again until the turbid liquid turns brown. Finally, add 2.0mL of precipitant 1-propanol and mix it with ball milling for the last time. After that, centrifuge the supernatant, transfer the mixture precipitate to a vacuum oven, keep it in a vacuum drying oven at 60°C overnight to remove the solvent, and store it in a glove box filled with argon.

[0048] Step 2: Polymerize dopamine on the surface of polytetrafluoroethylene (PTFE). The specific operation is: add buffer salt tris(hydroxymethyl)aminomethane to the dopamine salt solution and adjust the pH to 8.5 to accelerate the polymerization of dopamine. KMnO4 is used as an oxidant, and 0.04 mol of KMnO4 solid and 0.018 mol of dopamine monomer are added to the above alkaline solvent. Then 30.00 g of PTFE pretreated in step 1 is slowly added. At 0°C, high-speed stirring is carried out for polymerization for 24 hours. After the reaction is completed, the obtained solid is washed with water several times until the filtrate is clear and transparent, and then dried under vacuum conditions at 100°C for 12 hours to obtain a polydopamine (PDA)-modified PTFE composite adhesive.

[0049] Step 3: Preparation of solid electrolyte film, the preparation process is as follows Figure 4 The specific operation is as follows: PAN-modified LLZTO electrolyte and PDA-modified PTFE composite binder are uniformly mixed in a mass ratio of 97:3 using a rotary defoamer. Subsequently, the resulting mixture powder is ground in a dedicated ball mill for 3 minutes to obtain a microfibrillated mixture powder. Finally, the obtained microfibrillated mixture powder is placed in a roller press at 80°C with a double roller distance of 50μm, and rolled 15 times in a bidirectional roller press to a thickness of 50μm to obtain a solid electrolyte film.

[0050] Example 2

[0051] This embodiment provides a method for preparing a solid electrolyte film, comprising the following steps:

[0052] Step 1: Preparation of PAN-modified Li 6.4 La3Zr 1.4 Nb 0.6 O 12 (LLZNO) particles. The specific operation is as follows: First, weigh 0.15g PAN and dissolve it in 20mL dimethyl sulfoxide and perform high-energy ball milling until the liquid turns light yellow. Secondly, weigh the lithium salt bistrifluoromethanesulfonyl imide, and the mass ratio of PAN to lithium salt is 1:1. At the same time, weigh 5.0g LLZNO nanoparticles, and the mass ratio of LLZNO to PAN is 100:3. The high-energy ball milling process is performed again until the turbid liquid turns brown. Finally, add 2.0mL of precipitant 1-propanol and mix it with ball milling for the last time. After that, centrifuge the supernatant, transfer the mixture precipitate to a vacuum oven, keep it in a vacuum drying oven at 60°C overnight to remove the solvent, and store it in a glove box filled with argon.

[0053] Step 2: Polymerize dopamine on the PTFE surface. The specific operation is: add buffer salt tris(hydroxymethyl)aminomethane to the dopamine salt solution and adjust the pH to 8.5 to accelerate the polymerization of dopamine. KMnO4 is used as an oxidant, and 0.04 mol of KMnO4 solid and 0.018 mol of dopamine monomer are added to the above alkaline solvent. Then 30.00 g of PTFE pretreated in step 1 is slowly added. At 0°C, high-speed stirring is carried out for polymerization for 24 hours. After the reaction is completed, the obtained solid is washed with water several times until the filtrate is clear and transparent, and then dried under vacuum conditions at 100°C for 12 hours to obtain a PDA-modified PTFE composite adhesive.

[0054] Step 3: Preparation of solid electrolyte film. The specific operation is as follows: PAN-modified LLZNO electrolyte and PDA-modified PTFE composite binder are uniformly mixed in a mass ratio of 97:3 using a rotary defoamer. Subsequently, the obtained mixture powder is ground in a dedicated ball mill for 3 minutes to obtain a microfibrillated mixture powder. Finally, the obtained microfibrillated mixture powder is set at 80°C with a double roller distance of 50μm on a roller press, and rolled 10 times in a bidirectional roller press to 50μm to obtain a solid electrolyte film.

[0055] Example 3

[0056] This embodiment provides a method for preparing a solid electrolyte film, comprising the following steps:

[0057] Step 1: Preparation of PAN-modified LLZTO particles. The specific reaction route is as follows: Figure 1 As shown. The specific operation is: First, weigh 0.15g PAN and dissolve it in 20mL dimethyl sulfoxide and perform high-energy ball milling until the liquid turns light yellow. Secondly, weigh the lithium salt bistrifluoromethanesulfonyl imide, and the mass ratio of PAN to lithium salt is 1:1. At the same time, weigh 15.0g LLZTO nanoparticles, and the mass ratio of LLZTO to PAN is 100:1, and perform high-energy ball milling again until the turbid liquid turns brown. Finally, add 2.0mL of precipitant 1-propanol and mix with ball milling for the last time. After that, centrifuge the supernatant, transfer the mixture precipitate to a vacuum oven, keep it in a vacuum drying oven at 60°C overnight to remove the solvent, and store it in a glove box filled with argon.

[0058] Step 2: Polymerize dopamine on the PTFE surface. The specific operation is: add buffer salt tris(hydroxymethyl)aminomethane to the dopamine salt solution and adjust the pH to 8.5 to accelerate the polymerization of dopamine. KMnO4 is used as an oxidant, and 0.04 mol of KMnO4 solid and 0.018 mol of dopamine monomer are added to the above alkaline solvent. Then 30.00 g of PTFE pretreated in step 1 is slowly added. At 0°C, high-speed stirring is carried out for polymerization for 24 hours. After the reaction is completed, the obtained solid is washed with water several times until the filtrate is clear and transparent, and then dried under vacuum conditions at 100°C for 12 hours to obtain a PDA-modified PTFE composite adhesive.

[0059] Step 3: Preparation of solid electrolyte film. The specific operation is: PAN-modified LLZTO electrolyte and PDA-modified PTFE composite binder are evenly mixed in a mass ratio of 99:1 using a rotary defoamer. Subsequently, the obtained mixture powder is ground in a dedicated ball mill for 3 minutes to obtain a microfibrillated mixture powder. Finally, the obtained microfibrillated mixture powder is set at 80°C with a double roller distance of 50μm on a roller press, and rolled 20 times in a unidirectional roller press to 50μm to obtain a solid electrolyte film.

[0060] Example 4

[0061] This embodiment provides a method for preparing a solid electrolyte film, comprising the following steps:

[0062] Step 1: Preparation of polyacrylonitrile (PAN) modified lithium lanthanum zirconium oxide (LLZTO) particles. The specific reaction route is as follows: Figure 1 As shown. The specific operation is: First, weigh 0.15g PAN and dissolve it in 20mL dimethyl sulfoxide and perform high-energy ball milling until the liquid turns light yellow. Secondly, weigh the lithium salt bistrifluoromethanesulfonyl imide, and the mass ratio of PAN to lithium salt is 1:1. At the same time, weigh 5.0g LLZTO nanoparticles, and the mass ratio of LLZTO to PAN is 100:3, and perform high-energy ball milling again until the turbid liquid turns brown. Finally, add 2.0mL of precipitant 1-propanol and mix by ball milling for the last time. After that, centrifuge the supernatant, transfer the mixture precipitate to a vacuum oven, keep it in a vacuum drying oven at 60°C overnight to remove the solvent, and store it in a glove box filled with argon. The SEM of the electrolyte powder is as shown Figure 2 The FT-IR of PAN, LLZTO and PAN modified LLZTO is shown in 3.

[0063] Step 2: Polymerize dopamine on the PTFE surface. The specific operation is: add buffer salt tris(hydroxymethyl)aminomethane to the dopamine salt solution and adjust the pH to 8.5 to accelerate the polymerization of dopamine. KMnO4 is used as an oxidant, and 0.04 mol of KMnO4 solid and 0.018 mol of dopamine monomer are added to the above alkaline solvent. Then 30.00 g of PTFE pretreated in step 1 is slowly added. At 0°C, high-speed stirring is carried out for polymerization for 24 hours. After the reaction is completed, the obtained solid is washed with water several times until the filtrate is clear and transparent, and then dried under vacuum conditions at 100°C for 12 hours to obtain a PDA-modified PTFE composite adhesive.

[0064] Step 3: Preparation of solid electrolyte film. The specific operation is as follows: PAN-modified LLZTO electrolyte and PDA-modified PTFE composite binder are uniformly mixed in a mass ratio of 97:3 using a rotary defoamer. Subsequently, the obtained mixture powder is ground in a dedicated ball mill for 1 minute to obtain a microfibrillated mixture powder. Finally, the obtained microfibrillated mixture powder is set at 80°C with a double roller distance of 100μm on a roller press, and is rolled 15 times in a bidirectional manner to 100μm to obtain a solid electrolyte film.

[0065] Example 5

[0066] This embodiment provides a method for preparing a solid electrolyte film, comprising the following steps:

[0067] Step 1: Preparation of polyacrylonitrile (PAN) modified lithium lanthanum zirconium oxide (LLZTO) particles. The specific reaction route is as follows: Figure 1 As shown. The specific operation is: First, weigh 0.15g PAN and dissolve it in 20mL dimethyl sulfoxide and perform high-energy ball milling until the liquid turns light yellow. Secondly, weigh the lithium salt bistrifluoromethanesulfonyl imide, and the mass ratio of PAN to lithium salt is 1:1. At the same time, weigh 5.0g LLZTO nanoparticles, and the mass ratio of LLZTO to PAN is 100:3, and perform high-energy ball milling again until the turbid liquid turns brown. Finally, add 2.0mL of precipitant 1-propanol and mix by ball milling for the last time. After that, centrifuge the supernatant, transfer the mixture precipitate to a vacuum oven, keep it in a vacuum drying oven at 60°C overnight to remove the solvent, and store it in a glove box filled with argon. The SEM of the electrolyte powder is as shown Figure 2 The FT-IR of PAN, LLZTO and PAN modified LLZTO is shown in 3.

[0068] Step 2: Polymerize dopamine on the PTFE surface. The specific operation is: add buffer salt tris(hydroxymethyl)aminomethane to the dopamine salt solution and adjust the pH to 8.5 to accelerate the polymerization of dopamine. KMnO4 is used as an oxidant, and 0.04 mol of KMnO4 solid and 0.018 mol of dopamine monomer are added to the above alkaline solvent. Then 30.00 g of PTFE pretreated in step 1 is slowly added. At 0°C, high-speed stirring is carried out for polymerization for 24 hours. After the reaction is completed, the obtained solid is washed with water several times until the filtrate is clear and transparent, and then dried under vacuum conditions at 100°C for 12 hours to obtain a PDA-modified PTFE composite adhesive.

[0069] Step 3: Preparation of solid electrolyte film. The specific operation is as follows: PAN-modified LLZTO electrolyte and PDA-modified PTFE composite binder are uniformly mixed in a mass ratio of 97:3 using a rotary defoamer. Subsequently, the obtained mixture powder is ground in a dedicated ball mill for 1 minute to obtain a microfibrillated mixture powder. Finally, the obtained microfibrillated mixture powder is set at 25°C with a double roller distance of 50μm on a roller press, and is rolled 15 times in a bidirectional manner to 50μm to obtain a solid electrolyte film.

[0070] Example 6

[0071] This embodiment provides a method for preparing a solid electrolyte battery

[0072] Step 1: Preparation of the positive electrode cell. Specifically, lithium iron phosphate (LiFePO4), conductive carbon (Super P), and PDA-modified PTFE composite binder were mixed at a ratio of 87:10:3 at 25°C for 2 hours to form an active mixture. This mixture was then mixed at 25°C for 20 minutes to form a powdered mixture. The powdered mixture was then hot-rolled at 120°C into an 80μm thick active layer, which was then placed on a current collector to form the positive electrode cell.

[0073] Step 2: Assemble the solid-state battery. Specifically, use the solid electrolyte film prepared from the PAN-modified LLZTO electrolyte and PDA-modified PTFE in Example 1 as the battery's solid electrolyte, the electrode sheet prepared in Step 1 as the battery's positive electrode, and the metal Li sheet as the battery's negative electrode. Using a CR2032 coin cell battery case, assemble the solid-state battery in the following order: positive electrode, solid electrolyte, and negative electrode.

[0074] Example 7

[0075] This embodiment provides a method for preparing a solid electrolyte battery:

[0076] Step 1: Preparation of the positive electrode cell. Specifically, lithium iron phosphate (LiFePO4), conductive carbon (Super P), and PDA-modified PTFE composite binder were mixed at a ratio of 80:10:10 at 25°C for 2 hours to form an active mixture. This mixture was then mixed at 25°C for 20 minutes to form a powdered mixture. The powdered mixture was then hot-rolled at 120°C into an 80μm thick active layer, which was then placed on a current collector to form the positive electrode cell.

[0077] Step 2: Assemble the solid-state battery. Specifically, use the solid electrolyte film prepared from the PAN-modified LLZTO electrolyte and PDA-modified PTFE in Example 1 as the battery's solid electrolyte, the electrode sheet prepared in Step 1 as the battery's positive electrode, and the metal Li sheet as the battery's negative electrode. Using a CR2032 coin cell battery case, assemble the solid-state battery in the following order: positive electrode, solid electrolyte, and negative electrode.

[0078] Comparative Example 1

[0079] Comparative Example 1 is basically the same as Example 6, except that in step 2 of Comparative Example 1, the PAN-modified LLZTO in step 2 of Example 6 is replaced by untreated LLZTO. The coulombic efficiency of the batteries of Comparative Example 1 and Example 6 in the first three cycles is as follows: Figure 7 Please see Table 1 for specific test conditions.

[0080] Comparative Example 2

[0081] Comparative Example 2 is basically the same as Example 6, except that the PDA-modified PTFE composite binder in Example 6 is replaced with untreated PTFE. Figure 8 Please see Table 1 for specific test conditions.

[0082] The preparation conditions and proportions of representative examples and comparative examples are shown in Table 1.

[0083] Table 1

[0084]

[0085] like Figure 2 As shown in the SEM image of the electrolyte powder, the PAN@LLZTO particles are irregular, with no agglomeration and uniform distribution.

[0086] like Figure 3 As shown, compared with PAN, PAN@LLZTO has a -1 C-H bond and 2242 cm -1 The -CN stretching vibration peak intensity at the positions of PAN@LLZTO decreased, indicating the successful preparation of PAN@LLZTO.

[0087] Figure 5 This is a physical picture of the solid electrolyte film. The film is smooth and brown in color. Compared with the illustration, it can be seen that the film is very flexible, indicating that it can be mass-produced without sintering or applying external pressure.

[0088] Figure 6 A microscopic diagram of a solid electrolyte film.

[0089] Depend on Figure 7 It can be seen that the impedance value of the solid-state battery prepared by PDA@PTFE is 4.9*10 3 Ω, the impedance value of solid-state battery made of PTFE is 9*10 3 Ω, indicating that PDA@PTFE has stronger ionic conductivity than PTFE, which helps to improve the performance of solid-state batteries.

[0090] Depend on Figure 8 It can be seen that the coulombic efficiency of the solid-state battery prepared by PDA@LLZTO in the first three cycles is 98%, 99% and 99%, respectively, which is significantly higher than that of the solid-state battery prepared by LLZTO (85%, 97%, 98%), indicating that the solid-state battery prepared by PDA@LLZTO has better cycle reversibility.

[0091] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a solid electrolyte film, characterized in that: The steps include: A. Preparation of polyacrylonitrile-modified solid electrolyte particles: A1. Dissolve polyacrylonitrile in dimethyl sulfoxide and perform high-energy ball milling. A2. placing an inorganic solid electrolyte and a lithium salt into the ball-milled material and performing a high-energy ball milling process again; A3, adding a precipitant 1-propanol to the material obtained in step A2, performing a final ball milling, and then centrifuging and drying the ball-milled product to obtain polyacrylonitrile-modified solid electrolyte particles; Preparation of polydopamine-modified polytetrafluoroethylene composite binder: B1. Pre-treating polytetrafluoroethylene with a potassium permanganate / nitric acid mixed solution to form hydrophilic manganese oxide or manganese hydroxide-coated polytetrafluoroethylene particles; B2, adding dopamine monomer and potassium permanganate in proportion to an alkaline solution with a pH of 8.5, and then slowly adding the polytetrafluoroethylene pretreated in step B1 above to carry out a polymerization reaction. After the reaction is completed, ultrasonic washing with deionized water and vacuum drying are performed to obtain a polydopamine-coated polytetrafluoroethylene binder; Prepared into solid electrolyte film: C1. Using a rotary defoamer, the polyacrylonitrile-modified solid electrolyte and the polydopamine-modified polytetrafluoroethylene composite binder are uniformly mixed according to a mass ratio under a protective gas atmosphere; C2. Grinding the obtained mixture powder in a dedicated ball mill under a protective gas atmosphere for 3 minutes to obtain a microfibrillated mixture; C3. Rolling the microfibrillated mixture powder using a double-roller press under set parameters to fully fiberize the binder to obtain a solid electrolyte film; The protective gas in steps C1 and C2 is one of argon, nitrogen and helium.

2. The method for preparing a solid electrolyte film according to claim 1, wherein: In step A2, the inorganic solid electrolyte is one of a sulfide solid electrolyte, an oxide solid electrolyte and a halide solid electrolyte; and the lithium salt is one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate and lithium hexafluorophosphate.

3. The method for preparing a solid electrolyte film according to claim 1, wherein: In step A, the mass ratio of polyacrylonitrile to solid electrolyte is (1-3):

100.

4. The method for preparing a solid electrolyte film according to claim 1, wherein: In the step C1, based on the total mass of the solid electrolyte film, the mass of the polyacrylonitrile-modified solid electrolyte accounts for 97-99%, and the mass of the polydopamine-modified polytetrafluoroethylene accounts for 1-3%.

5. The method for preparing a solid electrolyte film according to claim 1, wherein: In step C3, the set parameters involve temperature, rolling times, rolling direction and film thickness. The temperature is 25-80°C, the rolling times are 5-20 times, the rolling direction is unidirectional or bidirectional, and the film thickness is 50-150 μm.

6. A solid electrolyte film, characterized in that The solid electrolyte film is obtained by the preparation method according to any one of claims 1 to 5.

7. A solid-state battery, characterized in that: The solid-state battery comprises an electrode sheet and the solid electrolyte film according to claim 6.

8. A solid-state battery according to claim 7, characterized in that: The electrode sheet comprises a current collector and an active layer on the current collector, wherein the active layer comprises an electrode active material, conductive carbon and a polytetrafluoroethylene composite binder modified with polydopamine.

9. A solid-state battery according to claim 8, characterized in that: In the active layer on the current collector, the polydopamine-modified polytetrafluoroethylene composite binder accounts for 1-10% of the mass of the active layer.

Images