Ultrathin self-supporting composite solid-state electrolyte membrane, preparation method thereof and solid-state battery

Abstract

The invention provides an ultrathin self-supporting composite solid electrolyte membrane, a preparation method thereof and a solid-state battery, and relates to the field of solid-state batteries. The method comprises the following steps: under an alkaline condition, mixing sulfate lignin, formaldehyde and water, and carrying out hydroxymethyl reaction to obtain a product after hydroxymethyl reaction; mixing the hydroxymethyl reaction product with a sulfonating agent, and carrying out sulfonation reaction to obtain sulfonated lignin; the preparation method comprises the following steps: mixing sulfonated lignin, a conductive ionic polymer, a lithium salt, a fast ionic conductor and a first solvent to obtain a spinning precursor liquid, and carrying out electrostatic spinning on the spinning precursor liquid to obtain a high-ionic-conductivity cellulose-based support membrane; and mixing the sulfide solid electrolyte, the glue solution and a second solvent to obtain sulfide slurry, mixing the sulfide slurry and the high-ion-conductivity cellulose-based supporting membrane, and carrying out vacuum impregnation-drying and rolling to obtain the ultrathin self-supporting sulfide electrolyte membrane. The method is simple to operate and easily available in raw materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid-state batteries, and in particular to an ultrathin self-supporting composite solid-state electrolyte film, a preparation method thereof and a solid-state battery. BACKGROUND

[0002] Solid-state lithium batteries are expected to significantly improve the safety and energy density of batteries by using solid-state electrolytes, and are considered as one of the most promising directions in the next generation of battery technology. Among the many types of solid-state electrolytes, sulfide solid-state electrolytes have the most practical prospects due to their ultra-high ionic conductivity.

[0003] Due to the rigidity and brittleness of inorganic solid electrolyte powder, to ensure the forming of the electrolyte sheet and inhibit the penetration of lithium dendrites, the thickness of the solid electrolyte layer is usually several hundred microns to about 1 mm. However, too high a thickness greatly reduces the energy density of the solid-state battery, and also increases the internal resistance and energy loss. Therefore, reducing the thickness of the solid electrolyte layer and improving the flexibility of the solid electrolyte are crucial for improving the energy density of the solid-state battery and avoiding brittle short circuit problems.

[0004] To solve the above technical problems, one of the solutions in the prior art is to use a flexible support carrier to realize the flexibility and thinning of the solid-state electrolyte film. Patent CN114759253A proposes a preparation method of an ultrathin, lightweight, high-mechanical-strength PEO-based solid-state electrolyte using a cellulose membrane as a support layer. By introducing a cellulose separator as a support layer, an ultrathin, lightweight, high-mechanical-strength PEO-based solid-state electrolyte film is prepared by simple coating and hot pressing technology. Patent CN115602914A casts a Li6PS5Cl suspension on a cellulose membrane, dries it, and then cold-presses it to obtain a sulfide solid-state electrolyte thin film. Patent CN117154208A mixes cellulose aerogel with solid-state electrolyte precursors, uses cellulose aerogel as a support body, and adds inorganic solid-state electrolytes to overcome the difficulty of poor flexibility and difficulty in self-supporting film formation of inorganic solid-state electrolytes.

[0005] However, the cellulose used as a support in the prior art is directly compounded with the solid-state electrolyte to prepare a solid-state electrolyte film, but the ion transport capacity of the cellulose matrix itself is limited, so the supporting intermediate layer will inevitably hinder ion transport, affecting the overall ion transport performance of the solid-state electrolyte film.

[0006] Therefore, there is an urgent need to provide a solid-state electrolyte film to solve the above problems. SUMMARY

[0007] The purpose of the present application is to provide an ultrathin self-supporting composite solid-state electrolyte film, a preparation method thereof and a solid-state battery to solve the above problems.

[0008] To achieve the above object, the first aspect of the present application provides a preparation method of an ultrathin self-supporting composite solid-state electrolyte film, comprising: Under alkaline conditions, sulfite lignin, formaldehyde and water are mixed and subjected to a hydroxymethylation reaction to obtain a post-hydroxymethylation reaction product; The post-hydroxymethylation reaction product and a sulfonating agent are mixed and subjected to a sulfonation reaction to obtain sulfonated lignin; The sulfonated lignin, an ion-conducting polymer, a lithium salt, a fast ion conductor and a first solvent are mixed to obtain a spinning precursor solution, and the spinning precursor solution is subjected to electrospinning to obtain a high-ionic-conducting cellulose-based support film; A sulfide solid-state electrolyte, a glue solution and a second solvent are mixed to obtain a sulfide slurry, and the sulfide slurry and the high-ionic-conducting cellulose-based support film are mixed, vacuum-impregnated and dried, and rolled to obtain an ultrathin self-supporting sulfide electrolyte film.

[0009] Optionally, the preparation method of the ultrathin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) The base in the alkaline conditions comprises sodium hydroxide; (2) The pH value of the hydroxymethylation reaction is greater than or equal to 10; (3) The molar ratio of the sulfite lignin, the formaldehyde and the sulfonating agent is 1:1.2-1.8:1.1-1.5; (4) The sulfonating agent comprises sodium sulfite.

[0010] Optionally, the preparation method of the ultrathin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) The ion-conducting polymer comprises one or more of polyethylene oxide, polyacrylonitrile-based, polyvinylidene fluoride-based, polymethyl methacrylate and polyvinyl alcohol; (2) The lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisdifluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium bis-oxalate borate and difluoro-oxalate borate lithium; (3) The fast ion conductor comprises an oxide-based solid-state electrolyte; (4) The first solvent comprises one or more of dimethylformamide, dimethylacetamide, acetic acid, water, N-methylpyrrolidone, acetone, tetrahydrofuran, dimethyl sulfoxide and imidazole-based ionic liquid; (5) The mass ratio of the sulfonated lignin, the ion-conducting polymer, the lithium salt and the fast ion conductor is 90:5-10:5-10:1-5; (6) The solid content of the spinning precursor solution is 5%-20%.

[0011] Optionally, the oxide-based solid-state electrolyte comprises one or more of garnet-type lithium lanthanum zirconium oxide, perovskite-type lithium lanthanum titanium oxide, NASICON-type lithium aluminum titanium phosphate.

[0012] Optionally, the method for preparing the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) during the preparation of the spinning precursor solution, the stirring speed of the mixing is 200-800 rpm, the stirring time is 12-24 h, and the stirring temperature is 25-80℃; (2) the voltage of the electrospinning is 5-25 kV, the distance between the spinning needle and the collector is 5-25 cm, and the liquid supply rate of the spinning injector is 0.1-1 mL / h.

[0013] Optionally, the method for preparing the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) the sulfide solid-state electrolyte comprises a sulfide glass phase electrolyte and / or a sulfide crystal phase electrolyte; (2) the glue solution is prepared by mixing glue particles and a second solvent, and the glue particles comprise one or more of styrene-butadiene rubber, nitrile-butadiene rubber, hydrogenated styrene-butadiene rubber, and carboxylated styrene-butadiene rubber; (3) the second solvent comprises a non-polar solvent and / or a low-polar solvent; (4) the mass fraction of the glue particles in the glue solution is 3%-10%; (5) the mass ratio of the sulfide solid-state electrolyte to the glue particles is 95-99:1-5; (6) the solid content of the sulfide slurry is 30%-70%; (7) during the preparation of the sulfide slurry, the stirring speed of the mixing is 800-1500 rpm, and the stirring time is 1-5 h; (8) the vacuum degree of the vacuum impregnation-drying is 0.1 kPa-50 kPa, the drying temperature is 40-80℃, and the drying time is 1-5 h; (9) the roll gap of the rolling is 0.01-0.2 mm, the rolling pressure is 0.5T-5T, and the roll speed is 1-5 cm / min.

[0014] Optionally, the method for preparing the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) the sulfide glass phase electrolyte comprises one or more of Li2S, P2S5, SiS2, B2S3, and GeS3; (2) the sulfide crystal phase electrolyte comprises one or more of LiGeP2S 12 , lithium sulfide argyrodite, and the like. (3) The second solvent includes one or more of benzene solvents, ester solvents, and alkane solvents.

[0015] The second aspect of the present application provides a super-thin self-supporting composite solid electrolyte film, which is prepared by the preparation method of the super-thin self-supporting composite solid electrolyte film. The thickness of the super-thin self-supporting composite solid electrolyte film is 30-40 μm.

[0016] The third aspect of the present application provides a solid-state battery, which comprises the super-thin self-supporting composite solid electrolyte film.

[0017] Optionally, the solid-state battery further comprises a positive electrode and a negative electrode. The positive electrode material in the positive electrode comprises a high-nickel positive electrode material, and the negative electrode material in the negative electrode comprises a lithium-indium alloy.

[0018] Compared with the prior art, the beneficial effects of the present application include: The preparation method of the super-thin self-supporting composite solid electrolyte film provided by the present application sulfonates conventional lignin, so that it has the characteristics of fast ion conduction, and reduces the ion transmission resistance. At the same time, the cellulose-based supporting film is prepared by using an electrostatic spinning process. The supporting film contains ion-conducting sulfonated lignin, polymers, and solid electrolytes, which can construct a three-dimensional ion transmission channel, greatly improve the ion conductivity of the fiber substrate. At the same time, the ion-conducting polymer and the sulfonated lignin can interact through multiple hydrogen bonds, thereby improving the mechanical strength and flexibility of the supporting substrate. In addition, by using the immersion-rolling method, the sulfide slurry is uniformly filled into the ion-conducting fiber substrate, thereby improving the compactness of the sulfide electrolyte film, reducing the ion transmission tortuosity, and greatly improving the ion transmission performance of the electrolyte film.

[0019] The super-thin self-supporting composite solid electrolyte film provided by the present application has the characteristics of ultra-thin and self-supporting, which shortens the ion transmission distance and mechanical integrity, which is the key to improving the volume and weight energy density of the full solid-state battery. The lignin fiber substrate film (high ion-conducting cellulose-based supporting film) has good ion transmission characteristics, avoiding the hindering effect of conventional non-ion-conducting fiber membranes on ion transmission. The ion is transmitted directly along the ion-conducting fiber. This structure ensures that lithium ions can migrate in multiple paths and without dead angles in the film, significantly reducing the tortuosity of ion transmission, thereby achieving high ion conductivity while promoting uniform distribution of interface ion flow during the battery charging and discharging process, effectively inhibiting the side reactions and lithium dendrite initiation caused by excessive local current density. In addition, the ion-conducting polymer and the sulfonated lignin can interact through multiple hydrogen bonds, thereby improving the mechanical strength, flexibility, and resistance to dendrite penetration of the supporting substrate. The sulfide slurry improves the filling amount of the fast ion conductor sulfide in the fiber film, and reduces the interface contact impedance.

[0020] The solid-state battery provided by the application has improved rate performance, power density and cycle life, and helps to inhibit lithium dendrites, improve fast charging capacity and safety. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as limiting the scope of the application.

[0022] Figure 1 A physical diagram of the ultra-thin self-supporting composite solid-state electrolyte film provided for the embodiment 1. DETAILED DESCRIPTION

[0023] First, the scheme provided by the application is explained in more detail, as follows: The first aspect of the application provides a preparation method of an ultra-thin self-supporting composite solid-state electrolyte film, comprising: Mixing, hydroxymethyl reaction of sulfite lignin, formaldehyde and water under alkaline conditions to obtain a hydroxymethyl reaction product; Mixing and sulfonation reaction of the hydroxymethyl reaction product and a sulfonating agent to obtain sulfonated lignin; Mixing of the sulfonated lignin, an ion-conducting polymer, a lithium salt, a fast ion conductor and a first solvent to obtain a spinning precursor liquid, and electrospinning of the spinning precursor liquid to obtain a high-ionic-conducting cellulose-based supporting film; Mixing of a sulfide solid-state electrolyte, a glue solution and a second solvent to obtain a sulfide slurry, and mixing, vacuum impregnation-drying and rolling of the sulfide slurry and the high-ionic-conducting cellulose-based supporting film to obtain an ultra-thin self-supporting sulfide electrolyte film.

[0024] In some embodiments, the preparation method of the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) The base in the alkaline condition comprises sodium hydroxide; It should be noted that the amount of sodium hydroxide added is 1%-4% of the total mass of the reaction system; (2) The pH value of the hydroxymethyl reaction is greater than or equal to 10; Optionally, the pH value of the hydroxymethyl reaction can be 10, 10.5, 11, 11.5 or any value greater than or equal to 10; (3) The molar ratio of the sulfite lignin, the formaldehyde and the sulfonating agent is 1:1.2-1.8:1.1-1.5; Optionally, the molar ratio of the sulfated lignin, the formaldehyde and the sulfonating agent can be any value between 1:1.2:1.1, 1:1.4:1.1, 1:1.6:1.1, 1:1.8:1.1, 1:1.2:1.3, 1:1.2:1.5 or 1:1.2-1.8:1.1-1.5; (4) the sulfonating agent comprises sodium sulfite.

[0025] In some embodiments, the method for preparing the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) the ion-conducting polymer comprises one or more of polyethylene oxide, polyacrylonitrile-based, polyvinylidene fluoride-based, polymethyl methacrylate, polyvinyl alcohol; (2) the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisdifluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium bis-oxalate borate and lithium difluoro-oxalate borate; (3) the fast ion conductor comprises an oxide-based solid-state electrolyte; (4) the first solvent comprises one or more of dimethylformamide, dimethylacetamide, acetic acid, water, N-methyl pyrrolidone, acetone, tetrahydrofuran, dimethyl sulfoxide and imidazolium ionic liquid; (5) the mass ratio of the sulfonated lignin, the ion-conducting polymer, the lithium salt and the fast ion conductor is 90:5-10:5-10:1-5; Optionally, the mass ratio of the sulfonated lignin, the ion-conducting polymer, the lithium salt and the fast ion conductor can be any value between 90:5:5:1, 90:10:5:1, 90:5:10:1, 90:5:5:5, 90:10:10:5 or 90:5-10:5-10:1-5; (6) the solid content of the spinning precursor solution is 5%-20%.

[0026] Optionally, the solid content of the spinning precursor solution can be 5%, 10%, 15%, 20% or any value between 5% and 20%.

[0027] In some embodiments, the oxide-based solid-state electrolyte comprises one or more of garnet-type lithium lanthanum zirconium oxide, perovskite-type lithium lanthanum titanium oxide, NASICON-type lithium aluminum titanium phosphate.

[0028] In some embodiments, the method for preparing the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) during the preparation of the spinning precursor solution, the stirring speed of the mixing is 200-800 rpm, the stirring time is 12-24 h and the stirring temperature is 25-80°C; Optionally, in the process of preparing the spinning precursor liquid, the stirring speed of the mixing can be 200 rpm, 400 rpm, 600 rpm, 800 rpm, or any value between 200-800 rpm, the stirring time can be 12 h, 15 h, 18 h, 21 h, 24 h, or any value between 12-24 h, and the stirring temperature can be 25℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, or any value between 25-80℃; (2) The voltage of the electrospinning is 5-25 kV, the distance between the spinning needle and the collector is 5-25 cm, and the liquid supply rate of the spinning injector is 0.1-1 mL / h.

[0029] Optionally, the voltage of the electrospinning can be 5 kV, 10 kV, 15 kV, 20 kV, 25 kV, or any value between 5-25 kV, the distance between the spinning needle and the collector can be 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, or any value between 5-25 cm, and the liquid supply rate of the spinning injector can be 0.1 mL / h, 0.5 mL / h, 1 mL / h, or any value between 0.1-1 mL / h.

[0030] In some embodiments, the method for preparing the ultra-thin self-supporting composite solid-state electrolyte film satisfies at least one of the following conditions: (1) The sulfide solid-state electrolyte comprises a sulfide glass phase electrolyte and / or a sulfide crystal phase electrolyte; (2) The glue solution is prepared by mixing glue particles and a second solvent, and the glue particles comprise one or more of styrene-butadiene rubber, nitrile-butadiene rubber, hydrogenated styrene-butadiene rubber, and carboxylated styrene-butadiene rubber; (3) The second solvent comprises a non-polar solvent and / or a low-polar solvent; (4) The mass fraction of the glue particles in the glue solution is 3%-10%; Optionally, the mass fraction of the glue particles in the glue solution can be 3%, 5%, 7%, 9%, 10%, or any value between 3-10%; (5) The mass ratio of the sulfide solid-state electrolyte to the glue particles is 95-99:1-5; Optionally, the mass ratio of the sulfide solid-state electrolyte to the glue particles can be 95:5, 96:4, 97:3, 98:2, 99:1, or any value between 95-99:1-5; (6) The solid content of the sulfide slurry is 30%-70%; Optionally, the solid content of the sulfide slurry can be 30%, 40%, 50%, 60%, 70%, or any value between 30-70%. (7) In the process of preparing the sulfide slurry, the stirring speed of the mixing is 800-1500 rpm, and the stirring time is 1-5 h; Optionally, in the process of preparing the sulfide slurry, the stirring speed of the mixing can be 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, or any value between 800-1500 rpm, and the stirring time can be 1 h, 2 h, 3 h, 4 h, 5 h, or any value between 1-5 h; (8) The vacuum degree of the vacuum impregnation-drying is 0.1 kPa-50 kPa, the drying temperature is 40-80℃, and the drying time is 1-5 h; Optionally, the vacuum degree of the vacuum impregnation-drying can be 0.1 kPa, 1 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, or any value between 0.1-50 kPa, the drying temperature can be 40℃, 50℃, 60℃, 70℃, 80℃, or any value between 40-80℃, and the drying time can be 1 h, 2 h, 3 h, 4 h, 5 h, or any value between 1-5 h; (9) The roll gap of the rolling is 0.01-0.2 mm, the rolling pressure is 0.5T-5T, and the rolling speed is 1-5 cm / min.

[0031] Optionally, the roll gap of the rolling can be 0.01 mm, 0.1 mm, 0.2 mm, or any value between 0.01-0.2 mm, the rolling pressure can be 0.5T, 1T, 3T, 5T, or any value between 0.5-5T, and the rolling speed can be 1 cm / min, 2 cm / min, 3 cm / min, 4 cm / min, 5 cm / min, or any value between 1-5 cm / min.

[0032] It should be noted that the rolling can further reduce the gap between the filler fibers, improve the densification of the sulfide electrolyte membrane, and greatly improve the ionic conductivity of the electrolyte membrane.

[0033] In some embodiments, the preparation method of the ultra-thin self-supporting composite solid-state electrolyte membrane satisfies at least one of the following conditions: (1) The sulfide glass phase electrolyte includes one or more of Li2S, P2S5, SiS2, B2S3, and GeS3; (2) The sulfide crystal phase electrolyte includes one or more of LiGeP2S 12 , lithium argyrodite, and the like; (3) the second solvent comprises one or more of benzene solvents, ester solvents, and alkane solvents.

[0034] The second aspect of the present application provides an ultrathin self-supporting composite solid electrolyte film prepared by the preparation method of the ultrathin self-supporting composite solid electrolyte film. The thickness of the ultrathin self-supporting composite solid electrolyte film is 30-40 μm.

[0035] Optionally, the thickness of the ultrathin self-supporting composite solid electrolyte film can be 30 μm, 35 μm, 40 μm, or any value between 30 μm and 40 μm.

[0036] The third aspect of the present application provides a solid-state battery comprising the ultrathin self-supporting composite solid electrolyte film.

[0037] In some embodiments, the solid-state battery further comprises a positive electrode and a negative electrode. The positive electrode material in the positive electrode comprises a high-nickel positive electrode material, and the negative electrode material in the negative electrode comprises a lithium-indium alloy.

[0038] It should be noted that the ultrathin self-supporting electrolyte film has good electrochemical stability and a wide electrochemical window, and can match a high-nickel positive electrode and a lithium-indium negative electrode to improve the energy density of the battery.

[0039] The embodiments of the present application will be described in detail below with reference to specific examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0040] Example 1 The present embodiment provides an ultrathin self-supporting composite solid electrolyte film and a preparation method thereof. The specific preparation steps are as follows: S1, preparation of sulfonated lignin: 5 g of sulfate lignin and 0.8 g of sodium hydroxide are dispersed in 50 mL of deionized water, the reaction temperature is maintained at 65℃, and the stirring is continued for 30 min, then 4.05 g of mass fraction 37% formaldehyde solution is added to the reaction system, and the reaction is carried out at 80℃ for 1.5 h to complete the hydroxymethylation reaction, 1.8 g of anhydrous sodium sulfite is added, and the reaction is carried out at 100℃ for 1.5 h; finally, high-purity sulfonated lignin is obtained after neutralization, purification and drying; S2, Preparation of high ion-conductive cellulose-based support membrane: 5 g of sulfonated lignin, 0.5 g of PVA, and 0.5 g of lithium salt LiTFSI were dispersed in 40 g of water, and dissolved by stirring at 50°C; then 0.5 g of fast ion conductor LLZO was added to the above completely dissolved solution, to form a high ion-conductive spinning precursor solution; then a high ion-conductive cellulose-based support membrane was prepared by electrospinning, with a spinning voltage of 20 Kv and a collector distance from the spinning needle of 20 cm; S3, Preparation of self-supporting sulfide electrolyte membrane: first, 0.5 g of NBR rubber particles was added to 9.5 g of dimethylbenzene solvent, and dissolved by mechanical stirring for 12 h to form a NBR rubber solution with a mass fraction of 5%; then, 20 g of sulfide electrolyte LPSC was added to a certain amount of SBR rubber solution and dimethylbenzene mixed solution, and dispersed by mechanical stirring at 1200 rpm for 5 h to form a LPSC sulfide slurry, wherein the mass ratio of sulfide electrolyte LPSC to NBR was 99:1, and the solid content of the LPSC sulfide slurry was 60%; the prepared LPSC sulfide slurry was vacuum impregnated into the high ion-conductive cellulose-based support membrane, and dried at 45°C for 1 h to volatilize the solvent, and the above operation was repeated 3 times to allow the sulfide electrolyte to be fully filled into the fiber membrane skeleton; finally, a mechanical roller was used to obtain an ultra-thin self-supporting composite solid electrolyte membrane.

[0041] The ultra-thin self-supporting composite solid electrolyte membrane provided in Example 1 is shown in Figure 1 .

[0042] Example 2 Compared with Example 1, the mass ratio of sulfonated cellulose to PVA polymer in this embodiment is only adjusted to 9:1.

[0043] Example 3 Compared with Example 1, the solid content of the LPSC sulfide slurry in this embodiment is only adjusted to 45%.

[0044] Example 4 Compared with Example 1, in the S2 step, the polymer PVA is replaced by PAN, and the solvent is replaced by DMF in this embodiment.

[0045] Example 5 Compared with Example 1, the mass ratio of fast ion conductor LLZO in the high ion-conductive spinning precursor solution in this embodiment is only adjusted to 20%.

[0046] Example 6 Compared with Example 1, the mass ratio of sulfide electrolyte LPSC to SBR in the sulfide slurry in the S3 step in this embodiment is only adjusted to 95:5.

[0047] Comparative Example 1 Compared to Example 1, the lignin in this comparative example was not sulfonated, i.e., step S1 was not performed.

[0048] Comparative Example 2 Compared to Example 1, this comparative example uses a dry rolling method to prepare a self-supporting electrolyte membrane. The specific preparation process is as follows: 0.08g of PTFE binder and 3.92g of sulfide electrolyte LPSC are sheared and mixed, and then mechanically rolled to obtain a self-supporting electrolyte membrane.

[0049] Comparative Example 3 Compared to Example 1, this comparative example does not use vacuum impregnation to penetrate the sulfurized material slurry into the high ion conductivity cellulose-based support membrane. Instead, the sulfurized material slurry is first coated on aluminum foil and dried to form a film. Then, according to the structure of sulfurized electrolyte membrane-high ion conductivity cellulose-based support membrane-sulfide electrolyte membrane, a self-supporting electrolyte membrane is obtained by mechanical pressing.

[0050] Comparative Example 4 Compared to Example 1, this comparative example uses an ion-conducting inert glass fiber skeleton membrane instead of a high ion-conducting cellulose-based support membrane.

[0051] Comparative Example 5 Compared to Example 1, this comparative example did not undergo a rolling process.

[0052] Solid-state batteries were prepared using the solid electrolyte membranes provided in Examples 1 and Comparative Examples 1-3 according to the stainless steel (SS), self-supporting sulfide electrolyte membrane and stainless steel (SS) structure. Electrochemical impedance spectroscopy was performed at an ambient temperature of 30°C to obtain the ionic conductivity of the self-supporting electrolyte membrane. The test results are shown in Table 1.

[0053] Table 1 Ionic Conductivity

[0054] Galvanostatic charge-discharge (GCD) testing involves charging and discharging an all-solid-state battery with a constant current to study its charge-discharge performance, including charge-discharge voltage plateau, specific capacity, charge-discharge efficiency, and cycle stability. The all-solid-state battery fabrication method is as follows: Ultra-thin supporting electrolyte membrane discs with a diameter of 10 mm are cut using a cutting machine and placed in a glove box for later use. The mold battery is assembled in an argon-atmosphere glove box according to a high-nickel cathode-ultra-thin self-supporting electrolyte membrane-lithium-indium alloy structure. The charge-discharge cutoff voltage range is 1.9-3.7 V (vs Li). +The test temperature was 30°C, the constant current charge-discharge rate was 1C (1C = 220 mA / g), the capacity retention rate after 200 cycles was recorded, and the above data are shown in Table 2.

[0055] Table 2: First efficiency, initial discharge capacity and cycle capacity retention rate of the all-solid-state battery

[0056] Analysis: From the above results, it can be seen that the ultrathin self-supporting composite solid electrolyte film in the embodiments of the present application exhibits higher initial discharge capacity, good rate performance and excellent cycle stability. Specifically, the lignin in Comparative Example 1 is not subjected to sulfonation treatment, lacks coordination functional groups with lithium ions, and is ionically inert, resulting in blocked ion transmission in the middle layer, poor battery rate performance. In Comparative Example 2, a dry electrolyte membrane is prepared using a PTFE binder. Due to the ionically inert PTFE, the ion transmission path is blocked, the ionic conductivity of the electrolyte membrane is reduced, and the tensile strength of the electrolyte membrane is low, making it difficult to withstand the expansion of the positive and negative electrode interfaces during long-term cycling. In Comparative Example 3, the dry electrolyte membrane is roll-composed with a high-ionic-conductivity matrix membrane. The sulfide particles are difficult to uniformly penetrate, resulting in a decrease in the internal ion transmission path and an increase in the interface impedance. In Comparative Example 4, a glass fiber membrane is used as a mechanical support skeleton. On the one hand, the glass fiber is ionically inert, affecting the ion transmission within the electrolyte membrane. On the other hand, compared with an organic fiber skeleton, the glass fiber has poor flexibility and poor electrolyte interface affinity, resulting in increased interface impedance. In Comparative Example 5, the electrolyte membrane is not subjected to roll-composition, and the high porosity of the sulfide electrolyte membrane results in a decrease in the ionic conductivity of the electrolyte membrane.

[0057] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0058] In addition, those skilled in the art will appreciate that although some embodiments herein include certain features rather than others included in other embodiments, the combination of features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, any one of the claimed embodiments can be used in any combination. The information disclosed in the BACKGROUND section is only intended to deepen the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing an ultrathin self-supporting composite solid electrolyte membrane, characterized in that, include: Under alkaline conditions, sulfate lignin, formaldehyde and water are mixed and reacted with hydroxymethyl to obtain the product after the hydroxymethyl reaction. The product of the hydroxymethyl reaction and the sulfonating agent are mixed and sulfonated to obtain sulfonated lignin; The sulfonated lignin, ion-conducting polymer, lithium salt, fast ion conductor and first solvent are mixed to obtain a spinning precursor solution. The spinning precursor solution is then electrospun to obtain a high ion-conducting cellulose-based support membrane. A sulfide solid electrolyte, a colloid, and a second solvent are mixed to obtain a sulfide slurry. The sulfide slurry is then mixed with the high ion-conducting cellulose-based support membrane, vacuum impregnated and dried, and rolled to obtain an ultrathin self-supporting sulfide electrolyte membrane.

2. The method for preparing an ultrathin self-supporting composite solid electrolyte membrane according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The alkali in the alkaline conditions includes sodium hydroxide; (2) The pH value of the hydroxymethylation reaction is greater than or equal to 10; (3) The molar ratio of the sulfate lignin, the formaldehyde, and the sulfonating agent is 1:1.2-1.8:1.1-1.5; (4) The sulfonating agent includes sodium sulfite.

3. The method for preparing an ultrathin self-supporting composite solid electrolyte membrane according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The ion-conducting polymer includes one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and polyvinyl alcohol; (2) The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalateborate) and lithium difluorooxalateborate. (3) The fast ion conductor includes an oxide-based solid electrolyte; (4) The first solvent includes one or more of dimethylformamide, dimethylacetamide, acetic acid, water, N-methylpyrrolidone, acetone, tetrahydrofuran, dimethyl sulfoxide and imidazole ionic liquids; (5) The mass ratio of the sulfonated lignin, the ion-conducting polymer, the lithium salt and the fast ion conductor is 90:5-10:5-10:1-5; (6) The solid content of the spinning precursor liquid is 5%-20%.

4. The method for preparing the ultrathin self-supporting composite solid electrolyte membrane according to claim 3, characterized in that, The oxide-based solid electrolyte includes one or more of the following: garnet-type lithium lanthanum zirconium oxide, perovskite-type lithium lanthanum titanium oxide, and NASICON-type lithium aluminum titanium phosphate.

5. The method for preparing an ultrathin self-supporting composite solid electrolyte membrane according to claim 1, characterized in that, At least one of the following conditions must be met: (1) In the process of preparing the spinning precursor liquid, the stirring speed of the mixture is 200-800 rpm, the stirring time is 12-24 h, and the stirring temperature is 25-80℃. (2) The voltage of the electrospinning is 5-25kV, the distance between the spinning needle and the collector is 5-25cm, and the liquid supply rate of the spinning syringe is 0.1-1mL / h.

6. The method for preparing an ultrathin self-supporting composite solid electrolyte membrane according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The sulfide solid electrolyte includes a sulfide glass phase electrolyte and / or a sulfide crystalline phase electrolyte; (2) The adhesive solution is prepared by mixing adhesive particles and a second solvent, wherein the adhesive particles include one or more of styrene-butadiene rubber, nitrile rubber, hydrogenated styrene-butadiene rubber and carboxylated styrene-butadiene rubber; (3) The second solvent includes nonpolar solvents and / or low-polar solvents; (4) The mass fraction of the adhesive particles in the adhesive solution is 3%-10%; (5) The mass ratio of the sulfide solid electrolyte to the colloidal particles is 95-99:1-5; (6) The solid content of the sulfurized material slurry is 30%-70%; (7) In the process of preparing the sulfided material slurry, the mixing speed is 800-1500 rpm and the mixing time is 1-5 h; (8) The vacuum degree of the vacuum impregnation-drying is 0.1kPa-50kPa, the drying temperature is 40-80℃, and the drying time is 1-5h; (9) The roll gap of the roller press is 0.01-0.2mm, the roll pressure is 0.5T-5T, and the roll speed is 1-5cm / min.

7. The method for preparing an ultrathin self-supporting composite solid electrolyte membrane according to claim 6, characterized in that, At least one of the following conditions must be met: (1) The sulfide glass phase electrolyte includes one or more of Li2S, P2S5, SiS2, B2S3, and GeS3; (2) The sulfide crystalline electrolyte includes LiGeP2S 12 One or more of lithium-sulfur silver-germanium ore and similar substances; (3) The second solvent includes one or more of benzene solvents, ester solvents, and alkane solvents.

8. An ultrathin self-supporting composite solid electrolyte membrane, characterized in that, It is prepared by the method for preparing the ultrathin self-supporting composite solid electrolyte membrane according to any one of claims 1-7; The thickness of the ultrathin self-supporting composite solid electrolyte membrane is 30-40 μm.

9. A solid-state battery, characterized in that, Includes the ultrathin self-supporting composite solid electrolyte membrane as described in claim 8.

10. The solid-state battery according to claim 9, characterized in that, It also includes positive and negative electrodes; The positive electrode material in the positive electrode includes a high-nickel positive electrode material, and the negative electrode material in the negative electrode includes a lithium-indium alloy.

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