Composite solid electrolyte membrane and preparation method and application thereof

Abstract

This invention provides a composite solid electrolyte membrane, its preparation method, and its application. The composite solid electrolyte membrane comprises a polymer fiber base membrane containing alkali lignin and a mixed slurry of an oxide-inorganic solid electrolyte and a lithium-containing polymer solid electrolyte coated on both sides of the polymer fiber base membrane. The polymer fiber membrane mixed with alkali lignin is initially prepared using electrospinning technology. Finally, the composite solid electrolyte membrane is obtained by casting the slurry containing the oxide-inorganic solid electrolyte and the lithium-containing polymer solid electrolyte. This invention provides an ultra-thin composite solid electrolyte membrane with good tensile strength, realizing the "waste" reuse of alkali lignin. Simultaneously, the prepared composite solid electrolyte membrane achieves high room temperature ionic conductivity, good ability to suppress lithium dendrites, and excellent electrochemical performance such as long cycle life of all-solid-state lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a composite solid electrolyte membrane, its preparation method and application. Background Technology

[0002] Commercial lithium-ion batteries are now used in all aspects of life, but safety issues such as leakage and spontaneous combustion still need to be addressed. Replacing the liquid electrolyte inside commercial lithium-ion batteries with a solid electrolyte, thus constructing an all-solid-state lithium-ion battery, can fundamentally solve these safety problems.

[0003] The commercialization of all-solid-state lithium-ion batteries requires solid electrolytes to possess sufficient mechanical strength and toughness to suppress lithium dendrite growth, while simultaneously demanding that the solid electrolyte be as thin and lightweight as possible without sacrificing these strengths to achieve high energy density all-solid-state lithium-ion batteries. Polymer solid electrolytes, as an important branch of solid electrolytes, possess characteristics such as thinness, flexibility, ease of fabrication, and ease of scalability; however, their low mechanical strength and ionic conductivity hinder their development in all-solid-state lithium-ion batteries. By adding inorganic solid electrolytes with high mechanical strength and high ionic conductivity to polymer solid electrolytes, composite solid electrolytes can be prepared, which can overcome the aforementioned shortcomings of polymer solid electrolytes.

[0004] Lignin is the second most abundant organic compound in nature after cellulose and is one of the most important renewable resources. Lignin is derived from the papermaking process; it must be removed before wood pulp can be converted into high-quality paper, resulting in a large amount of lignin waste on Earth. However, lignin has good biocompatibility and biodegradability, and contains a large number of benzene rings and phenolic hydroxyl groups, which can participate in chemical reactions, giving it extremely high recycling value.

[0005] Electrospinning is one of the main methods for preparing nanofiber membranes. Through electrospinning, solid electrolytes can be designed into nanofiber membranes with a certain thickness and mechanical strength. CN110190335A discloses a solid electrolyte interface modification strategy, which involves coating a 20-1000 nm layer of metal oxide onto the surface of an oxide-inorganic solid electrolyte using electrospinning technology, and then combining the coated solid electrolyte with LiNi... 0.8 Co 0.1 Mn 0.1 The O2 cathode and the lithium metal anode form an all-solid-state lithium-ion battery, which improves its cycle stability but has poor flexibility.

[0006] Therefore, in order to further promote the commercialization of all-solid-state lithium-ion batteries, it is necessary to design the composition of composite solid electrolyte membranes and improve the preparation process. While ensuring good mechanical strength and electrochemical performance, the thickness of composite solid electrolyte membranes should be further reduced to achieve the goal of thinning and lightening. Summary of the Invention

[0007] The purpose of this invention is to provide a composite solid electrolyte membrane, its preparation method, and its application. This invention prepares a polymer fiber base membrane containing alkali lignin by electrospinning technology, and then coats both sides of the membrane with a mixed slurry of oxide inorganic solid electrolyte and polymer solid electrolyte containing lithium salt to obtain a composite solid electrolyte membrane, thereby improving the electrochemical performance such as cycle stability of lithium-ion batteries.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a composite solid electrolyte membrane, the composite solid electrolyte membrane comprising a polymer fiber base membrane containing alkali lignin and a mixed slurry of an oxide inorganic solid electrolyte and a polymer solid electrolyte containing lithium salt coated on both sides of the polymer fiber base membrane.

[0010] The composite solid electrolyte membrane described in this invention uses a polymer fiber membrane containing alkali lignin as a supporting substrate, with its thickness controlled at around 20 μm. This lays an important foundation for the realization of a green, ultra-thin, tough composite solid electrolyte membrane. Subsequently, a mixed slurry of oxide inorganic solid electrolyte and polymer solid electrolyte containing lithium salt is coated to fill the voids in the polymer fiber base membrane, so as to achieve full contact between the substrate and the polymer solid electrolyte, and also to provide space for lithium ion transport.

[0011] Preferably, the polymer fiber-based membrane containing alkali lignin is made from a mixture of polymer and alkali lignin.

[0012] Preferably, the polymer comprises any one or a combination of at least two of polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA), for example, it can be polyacrylonitrile and polyvinylpyrrolidone, polyvinylidene fluoride, or polyvinyl alcohol.

[0013] Preferably, the oxide inorganic solid electrolyte includes any one or a combination of at least two of the following: NASICON-type inorganic solid electrolyte, garnet-type inorganic solid electrolyte, or perovskite-type inorganic solid electrolyte, with garnet-type inorganic solid electrolyte being the most preferred.

[0014] Preferably, the NASICON-type inorganic solid electrolyte is Li 1+x Al x Ti2-x (PO4)3, where the range of x is 0 < x < 2, and for example, it can be 0, 0.3, 0.5, 1, 1.2, 2.

[0015] Preferably, the garnet-type inorganic solid electrolyte is Li7La3Zr2O 12 、Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 6.24 La3Zr2Al 0.24 O 11.98 、Li 6.25 La3Zr2Ga 0.25 O 12 or Li 6.375 La3Zr 1.375 Nb 0.625 O 12 Among any one or a combination of at least two of them, for example, it can be Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 6.24 La3Zr2Al 0.24 O 11.98 、Li 6.25 La3Zr2Ga 0.25 O 12 or Li 6.375 La3Zr 1.375 Nb 0.625 O 12 .

[0016] Preferably, the perovskite-type inorganic solid electrolyte is where represents a vacancy, 0 < x < 0.16, and for example, it can be 0, 0.05, 0.1, 0.12, 0.16.

[0017] Preferably, the polymer solid electrolyte in the polymer solid electrolyte containing a lithium salt includes any one or a combination of at least two of polyethylene oxide, polymethacrylate or polyethylene glycol dimethacrylate.

[0018] Preferably, the viscosity-average molecular weight of polyethylene oxide in the polymer solid electrolyte is 60W to 500W, for example, 60W, 100W, or 500W; the weight-average molecular weight of polymethacrylate is 15,000 to 350,000, for example, 15,000, 100,000, 120,000, or 350,000; and the number-average molecular weight of polyethylene glycol dimethyl acrylate is 550 to 20,000, for example, 550, 750, 1,000, 10,000, or 20,000.

[0019] Preferably, the lithium salt in the polymer solid electrolyte containing lithium salt includes any one or a combination of at least two of LiClO4, LiBF4, LiPF6, LiFSI, LiTFSI, LiBETI, LiCTFSI, LiBOB, LiTDI, LiPDI, LiDCTA, or LiB(CN)4, for example, it can be LiClO4 and LiBF4, LiPF6, LiFSI, LiTFSI, or LiBETI.

[0020] In a second aspect, the present invention provides a method for preparing the composite solid electrolyte membrane described in the first aspect, the method comprising the following steps:

[0021] (1) The polymer, alkali lignin and solvent are mixed to form a spinning solution, and then electrospinning is used to obtain a polymer fiber base film containing alkali lignin. The polymer fiber base film is then vacuum dried and rolled.

[0022] (2) The oxide inorganic solid electrolyte, lithium salt and polymer solid electrolyte are mixed with organic solvent to obtain a composite solid electrolyte slurry;

[0023] (3) The composite solid electrolyte slurry obtained in step (2) is coated on one side of the polymer fiber base membrane. After drying, the composite solid electrolyte slurry obtained in step (2) is coated on the other side of the polymer fiber base membrane to obtain the composite solid electrolyte membrane.

[0024] In this invention, the composite solid electrolyte membrane uses a polymer fiber membrane containing alkali lignin as a supporting substrate. After electrospinning, the substrate is dried and rolled to control its thickness to about 20 μm. This lays an important foundation for the realization of green, ultrathin, and tough composite solid electrolytes. Subsequently, a mixed slurry of polymer solid electrolyte containing oxide inorganic solid electrolyte is coated to fill the voids in the polymer fiber membrane, so as to achieve full contact between the substrate and the solid polymer electrolyte and also provide space for lithium ion transport.

[0025] Preferably, the solvent in step (1) includes any one or a combination of at least two of deionized water, N,N-dimethylformamide or acetone.

[0026] Preferably, the mass concentration of the polymer in the spinning solution in step (1) is 5wt%-30wt%, more preferably 10wt%-20wt%, for example, it can be 5wt%, 7wt%, 9wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, or 30wt%.

[0027] In this invention, the mass concentration of the polymer in the spinning solution in step (1) is adjusted to be within the range of 5wt%-30wt%. If the mass concentration is too low, a stable jet cannot be formed, resulting in the generation of beads in the polymer fiber membrane. Conversely, if the mass concentration is too high, the difficulty of jet splitting will increase, resulting in an increase in fiber diameter.

[0028] Preferably, the mass ratio of the polymer to alkali lignin in step (1) is (9:1) to (1:9), more preferably (8:2) to (4:6), for example, it can be 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, or 1:9.

[0029] In this invention, by adjusting the mass ratio of the polymer and alkali lignin in step (1) to a range of (9:1) to (1:9), a mass ratio that is too low will increase the difficulty of spinning and reduce the ionic conductivity of the composite solid electrolyte membrane. Conversely, a mass ratio that is too high will reduce the porosity of the polymer fiber membrane, inhibit the penetration of the composite solid electrolyte slurry, and reduce the migration of lithium ions inside the composite solid electrolyte.

[0030] Preferably, the spinning parameters in step (1) include the distance between the needle and the roller receiver, the voltage, the needle advance speed, and the rotational speed of the roller receiver.

[0031] Preferably, the distance between the needle tip and the roller receiver is 10-20cm, more preferably 10-15cm, for example, it can be 10cm, 11cm, 12cm, 13cm, 14cm, 15cm, 16cm, 17cm, 18cm, 19cm, or 20cm.

[0032] Preferably, the voltage is 10-20kV, more preferably 10-15kV, for example, it can be 10kV, 11kV, 12kV, 13kV, 14kV, 15kV, 16kV, 17kV, 18kV, 19kV, or 20kV.

[0033] Preferably, the needle advance speed is 0.05-0.2 mm / min, more preferably 0.08-0.1 mm / min, for example, it can be 0.05 mm / min, 0.07 mm / min, 0.08 mm / min, 0.09 mm / min, 0.1 mm / min, 0.12 mm / min, 0.14 mm / min, 0.16 mm / min, 0.18 mm / min, or 0.2 mm / min.

[0034] Preferably, the rotational speed of the roller receiver is 50-200 rpm, more preferably 50-100 rpm, for example, it can be 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, or 200 rpm.

[0035] Preferably, the vacuum drying temperature in step (1) is 40-80℃, more preferably 50-60℃, for example, 40℃, 45℃, 50℃, 52℃, 55℃, 58℃, 60℃, 65℃, 70℃, 75℃, or 80℃.

[0036] Preferably, the vacuum drying time in step (1) is 10-24h, more preferably 18-24h, for example, 10h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h.

[0037] Preferably, the distance of the roller pressing in step (1) is 5-30μm, more preferably 15-25μm, for example, it can be 5μm, 15μm, 18μm, 20μm, 22μm, 25μm, or 30μm.

[0038] Preferably, the mass fraction of the oxide inorganic solid electrolyte in the composite solid electrolyte slurry in step (2) is 1-10 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%.

[0039] In this invention, the mass fraction of the oxide inorganic solid electrolyte in the composite solid electrolyte slurry in step (2) is adjusted to be in the range of 1-10 wt%. If the mass fraction is too low, it will reduce the number of lithium ions in the composite solid electrolyte slurry, thereby reducing the ionic conductivity. Conversely, it will cause the oxide inorganic solid electrolyte to agglomerate, hindering the migration of lithium ions.

[0040] Preferably, the lithium salt in step (2) is LiTFSI.

[0041] Preferably, the polymer solid electrolyte in step (2) is polyethylene oxide.

[0042] Preferably, the organic solvent in step (2) includes anhydrous acetonitrile, tetrahydrofuran or N,N-dimethylformamide, and more preferably anhydrous acetonitrile.

[0043] Preferably, the molar ratio of the polymer solid electrolyte and the lithium salt in step (2) is (10-20):1, more preferably 16:1-19:1, for example, 10:1, 16:1, 17:1, 18:1, 19:1, 20:1.

[0044] In this invention, the molar ratio of polymer solid electrolyte to lithium salt refers to the molar ratio of the basic structural unit of polymer solid electrolyte to the lithium ions in lithium salt.

[0045] In this invention, the molar ratio of the polymer solid electrolyte and lithium salt in step (2) is adjusted to be within the range of (10-20):1. If the molar ratio is too low, the composite solid electrolyte slurry will have high viscosity and will not be easy to form a film. Conversely, if the molar ratio is too high, the number of lithium ions inside the composite solid electrolyte will be reduced, and high ionic conductivity cannot be achieved.

[0046] Preferably, the polymer solid electrolyte in step (2) accounts for 4-10 wt% of the organic solvent mass, more preferably 5-8 wt%, for example, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 10 wt%.

[0047] In this invention, the mass of the polymer solid electrolyte in step (2) is adjusted to be within the range of 4-10 wt%. If the mass fraction is too low, the viscosity of the composite solid electrolyte slurry will be too low, making it difficult for the organic solvent to evaporate and reducing the film formation efficiency. Conversely, if the mass fraction is too high, the viscosity of the composite solid electrolyte slurry will be too high, reducing its permeation rate in the polymer fiber membrane and making it easy to generate bubbles on the surface of the composite solid electrolyte membrane, thus failing to obtain a homogeneous membrane.

[0048] Preferably, the mixing in step (2) is carried out under stirring.

[0049] Preferably, the stirring time is 12-24 hours, more preferably 12-18 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0050] Preferably, the stirring speed is 800-1600 rpm, more preferably 1000-1200 rpm, for example, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, or 1600 rpm.

[0051] Preferably, the drying in step (3) includes two natural drying processes and one vacuum drying process.

[0052] In this invention, natural drying refers to placing the composite solid electrolyte membrane in an air environment to air dry naturally.

[0053] Preferably, the two natural drying times are both 4-8 hours, more preferably 4-6 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.

[0054] Preferably, the vacuum drying temperature is 50-65℃, more preferably 55-60℃, for example, 50℃, 52℃, 55℃, 58℃, 60℃, or 65℃.

[0055] Preferably, the vacuum drying time is 12-24 hours, more preferably 18-24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0056] Thirdly, the present invention provides an all-solid-state lithium-ion battery, the all-solid-state lithium-ion battery comprising a positive electrode, a negative electrode and a solid electrolyte, wherein the solid electrolyte is a composite solid electrolyte membrane according to the first aspect.

[0057] Compared with the prior art, the present invention has the following innovations and beneficial effects:

[0058] (1) This invention provides a composite solid electrolyte membrane, which uses a polymer fiber membrane containing alkali lignin as the matrix and a mixed slurry containing oxide inorganic solid electrolyte and polymer solid electrolyte as the auxiliary. The innovation is that after the polymer fiber base membrane is prepared by electrospinning technology, it is not directly composited with the mixed slurry containing oxide inorganic solid electrolyte and polymer solid electrolyte. Instead, the thickness of the fiber membrane is first controlled by rolling technology to make the fiber membrane dense. This has a good effect on controlling the thickness of the final composite solid electrolyte membrane and achieving close contact between the composite solid electrolyte membrane and lithium metal, which further promotes the commercial development of all-solid-state lithium-ion batteries.

[0059] (2) The present invention also designed the composition of the composite solid electrolyte membrane: the polymer components in the selected polymer fiber base membrane have good compatibility with the polymer solid electrolyte and can all have a unique effect with lithium salt to accelerate the transport of lithium ions; alkali lignin can further improve the compatibility between the polymer fiber base membrane and the polymer solid electrolyte, and at the same time provide a lignin reuse channel, so that the composite solid electrolyte membrane has the advantages of high ionic conductivity and high mechanical strength. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the preparation process of the composite solid electrolyte membrane provided in Example 1. Detailed Implementation

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are only helpful in understanding the present invention and should not be considered as specific limitations of the present invention.

[0062] Example 1

[0063] This embodiment provides a composite solid electrolyte membrane, which includes a polyacrylonitrile (PAN) fiber base membrane containing alkali lignin, an LLZTO oxide inorganic solid electrolyte and a polyethylene oxide (PEO) solid electrolyte containing lithium salt coated on both sides of the polyacrylonitrile fiber base membrane.

[0064] The composite solid electrolyte membrane is prepared by the following method: Figure 1 As shown:

[0065] (1) Dissolve 0.95g PAN (weight average molecular weight 15W, P823208, Maclean's reagent) and 0.4g alkali lignin (471003, Sigma reagent) in 10mL of N,N-dimethylformamide (AR, 99.5%, D111999, Aladdin reagent) to prepare a spinning solution with a concentration of 10wt%. Heat and magnetically stir at 75℃ for 24h to form a transparent and homogeneous spinning solution. Inject the spinning solution into a 10mL syringe using a No. 22 needle. Set the positive voltage at the needle to 15kV, the negative voltage at the roller receiver to 2kV, the distance between the needle and the roller receiver to 15cm, the roller receiver rotation speed to 100rpm, the spinning solution propulsion speed to 0.1mm / min, the spinning temperature to 20-25℃, and the humidity to 18-23%. After spinning, the PAN fiber base film is placed in a vacuum drying oven and dried at 60°C for 24 hours. After drying, the PAN fiber base film is placed between two rollers 20 μm apart for rolling. After rolling, it is stored in a glove box.

[0066] (2) Dissolve 0.5g PEO (viscosity-average molecular weight of 60W, P101341, Aladdin reagent), 0.18g LiTFSI (99%, B102576, Aladdin reagent) and 0.036g LLZTO (300nm, Shenzhen Huaqingxin Materials Technology Co., Ltd.) (5wt%) in 10mL of anhydrous acetonitrile (anhydrous grade, 99.8%, H2O≤0.003%, A119012, Aladdin reagent) at room temperature with magnetic stirring at 1000rpm for 24h to obtain a transparent and uniform composite solid electrolyte slurry;

[0067] (3) Fix the PAN fiber base membrane on the polytetrafluoroethylene template, use a 10mL pipette to draw a certain amount of slurry, and evenly drop it onto the surface of the fiber base membrane. After natural drying for 6 hours, turn the fiber base membrane over and drop the slurry evenly again. After natural drying for 6 hours, place the composite solid electrolyte fiber membrane in a vacuum drying oven and dry it at 60℃ for 24 hours. After drying, demold and slice to obtain the composite solid electrolyte membrane.

[0068] Example 2

[0069] This embodiment provides a composite solid electrolyte membrane, which includes a polyvinylidene fluoride (PVDF) fiber base membrane containing alkali lignin, an LLZTO oxide inorganic solid electrolyte and a lithium-containing polyethylene oxide (PEO) solid electrolyte coated on both sides of the PVDF fiber base membrane.

[0070] The composite solid electrolyte membrane is prepared by the following method:

[0071] (1) Dissolve 1.5g PVDF (weight average molecular weight 40W, P169015, Aladdin reagent) and 0.64g alkali lignin (source same as in Example 1) in 10mL of a mixed solution of N,N-dimethylformamide (source same as in Example 1) and acetone (AR, ≥99.5%, 10000418, Sinopharm reagent) (DMF to acetone volume ratio 3:2) to prepare a spinning solution with a concentration of 17wt%. Heat and magnetically stir at 60℃ for 24h to form a transparent and homogeneous spinning solution. Inject the spinning solution into a 10mL syringe using a No. 22 needle. Set the positive voltage at the needle to 10kV, the negative voltage at the roller receiver to 1.5kV, the distance between the needle and the roller receiver to 15cm, the roller receiver rotation speed to 60rpm, the spinning solution propulsion speed to 0.08mm / min, the spinning temperature to 20-25℃, and the humidity to 18-23%. After spinning, the PVDF fiber membrane is placed in a vacuum drying oven at 60°C for 24 hours. After drying, the PVDF fiber membrane is placed between two rollers 20 μm apart for rolling. After rolling, it is stored in a glove box.

[0072] (2) Dissolve 0.5g PEO (viscosity-average molecular weight of 60W, source same as in Example 1), 0.18g LiTFSI (source same as in Example 1), and 0.036g LLZTO (source same as in Example 1) (5wt%) in 10mL of anhydrous acetonitrile and stir magnetically at 1000rpm for 24h at room temperature to obtain a transparent and uniform composite solid electrolyte slurry.

[0073] (3) Fix the PVDF fiber base membrane on the polytetrafluoroethylene template, use a 10mL pipette to draw a certain amount of slurry, and evenly drop it onto the surface of the fiber membrane. After natural drying for 4 hours, turn the fiber membrane over and drop the slurry evenly again. After natural drying for 6 hours, place the composite solid electrolyte fiber membrane in a vacuum drying oven and dry it at 55℃ for 18 hours. After drying, demold and slice to obtain the composite solid electrolyte membrane.

[0074] Example 3

[0075] This embodiment provides a composite solid electrolyte membrane, which includes a polyvinylpyrrolidone (PVP) fiber base membrane containing alkali lignin, an LLZTO oxide inorganic solid electrolyte and a polyethylene oxide (PEO) solid electrolyte containing lithium salt coated on both sides of the PVP fiber base membrane.

[0076] The composite solid electrolyte membrane is prepared by the following method:

[0077] (1) Dissolve 1.5g PVP (weight-average molecular weight 130W, P110610, Aladdin reagent) and 0.64g alkali lignin (source same as in Example 1) in 10mL of deionized water to prepare a spinning solution with a concentration of 15wt%. Stir magnetically at room temperature for 24h to form a transparent and homogeneous spinning solution. Inject the spinning solution into a 10mL syringe using a No. 22 needle. Set the positive voltage at the needle tip to 10kV, the negative voltage at the roller receiver to 2kV, the distance between the needle tip and the roller receiver to 12cm, the roller receiver rotation speed to 100rpm, the spinning solution feed speed to 0.1mm / min, the spinning temperature to 20-25℃, and the humidity to 18-23%. After spinning, place the PVP fiber membrane in a vacuum drying oven at 55℃ for 24h. After drying, place the PVDF fiber membrane between two rollers 20μm apart for rolling. After rolling, store it in a glove box.

[0078] (2) Dissolve 0.5g PEO (viscosity-average molecular weight of 60W, source same as in Example 1), 0.18g LiTFSI (source same as in Example 1), and 0.036g LLZTO (source same as in Example 1) (5wt%) in 10mL of anhydrous acetonitrile and stir magnetically at 1000rpm for 24h at room temperature to obtain a transparent and uniform composite solid electrolyte slurry.

[0079] (3) Fix the PVP fiber base membrane on the polytetrafluoroethylene template, use a 10mL pipette to draw a certain amount of slurry, and evenly drop it onto the surface of the fiber membrane. After natural drying for 5 hours, turn the fiber base membrane over and drop the slurry evenly again. After natural drying for 5 hours, place the composite solid electrolyte fiber base membrane in a vacuum drying oven and dry it at 60℃ for 18 hours. After drying, demold and slice to obtain the composite solid electrolyte membrane.

[0080] Example 4

[0081] This embodiment provides a composite solid electrolyte membrane, which includes a polyvinyl alcohol (PVA) fiber base membrane containing alkali lignin, an LLZTO oxide inorganic solid electrolyte coated on both sides of the PVA fiber base membrane, and a polyethylene oxide (PEO) solid electrolyte containing lithium salt.

[0082] The composite solid electrolyte membrane is prepared by the following method:

[0083] (1) Dissolve 1g PVA (type 1788, P105124, Aladdin reagent) and 0.43g alkali lignin (source same as in Example 1) in 10mL of deionized water to prepare a spinning solution with a concentration of 10wt%. Heat and magnetically stir at 90℃ for 2h to form a transparent and homogeneous spinning solution. Inject the spinning solution into a 10mL syringe using a No. 22 needle. Set the positive voltage at the needle tip to 12kV, the negative voltage at the roller receiver to 2kV, the distance between the needle tip and the roller receiver to 15cm, the roller receiver rotation speed to 50rpm, the spinning solution feed speed to 0.1mm / min, the spinning temperature to 20-25℃, and the humidity to 18-23%. After spinning, place the PVA fiber membrane in a vacuum drying oven at 60℃ for 24h. After drying, place the PVDF fiber membrane between two rollers 20μm apart for rolling. After rolling, store it in a glove box.

[0084] (2) Dissolve 0.5g PEO (viscosity-average molecular weight of 60W, source same as in Example 1), 0.18g LiTFSI (source same as in Example 1), and 0.036g LLZTO (source same as in Example 1) (5wt%) in 10mL of anhydrous acetonitrile and stir magnetically at 1000rpm for 24h at room temperature to obtain a transparent and uniform composite solid electrolyte slurry.

[0085] (3) Fix the PVA fiber base membrane on the polytetrafluoroethylene template, use a 10mL pipette to draw a certain amount of slurry, and evenly drop it onto the surface of the fiber base membrane. After natural drying for 6 hours, turn the fiber base membrane over and drop the slurry evenly again. After natural drying for 6 hours, place the composite solid electrolyte fiber base membrane in a vacuum drying oven and dry it at 60℃ for 24 hours. After drying, demold and slice to obtain the composite solid electrolyte membrane.

[0086] Example 5

[0087] The only difference between this embodiment and Embodiment 1 is that the mass fraction of LLZTO is adjusted to 1%, i.e., 0.0069g. All other conditions and parameters are exactly the same as in Embodiment 1.

[0088] Example 6

[0089] The only difference between this embodiment and Embodiment 1 is that the mass fraction of LLZTO is adjusted to 10%, i.e., 0.076g. All other conditions and parameters are exactly the same as in Embodiment 1.

[0090] Example 7

[0091] The only difference between this embodiment and Embodiment 2 is that the mass fraction of LLZTO is adjusted to 1%, i.e., 0.0069g. All other conditions and parameters are exactly the same as in Embodiment 2.

[0092] Example 8

[0093] The only difference between this embodiment and Embodiment 2 is that the mass fraction of LLZTO is adjusted to 10%, i.e., 0.076g. All other conditions and parameters are exactly the same as in Embodiment 2.

[0094] Example 9

[0095] The only difference between this embodiment and Embodiment 3 is that the mass fraction of LLZTO is adjusted to 1%, i.e., 0.0069g. All other conditions and parameters are exactly the same as in Embodiment 3.

[0096] Example 10

[0097] The only difference between this embodiment and embodiment 3 is that the mass fraction of LLZTO is adjusted to 10%, i.e., 0.076g. All other conditions and parameters are exactly the same as in embodiment 3.

[0098] Example 11

[0099] The only difference between this embodiment and embodiment 4 is that the mass fraction of LLZTO is adjusted to 1%, i.e., 0.0069g. All other conditions and parameters are exactly the same as in embodiment 4.

[0100] Example 12

[0101] The only difference between this embodiment and embodiment 4 is that the mass fraction of LLZTO is adjusted to 10%, i.e., 0.076g. All other conditions and parameters are exactly the same as in embodiment 4.

[0102] Example 13

[0103] The only difference between this embodiment and Example 1 is that the spinning solution is prepared with a concentration of 20 wt%, while the other conditions and parameters are exactly the same as in Example 1.

[0104] Example 14

[0105] The only difference between this embodiment and Example 1 is that in step (1), 0.95g PAN and 1.43g alkali lignin are dissolved in 10mL N,N-dimethylformamide and the rolling distance is 15μm. All other conditions and parameters are exactly the same as in Example 1.

[0106] Example 15

[0107] The only difference between this embodiment and Example 1 is that in step (1), 0.95g PAN and 0.24g alkali lignin are dissolved in 10mL N,N-dimethylformamide, and the rolling distance is 25μm. All other conditions and parameters are exactly the same as in Example 1.

[0108] Example 16

[0109] The only difference between this embodiment and Example 1 is that in step (2), 0.5g PEO, 0.2g LiTFSI and 0.036g LLZTO (5wt%) are dissolved in 12mL of anhydrous acetonitrile. All other conditions and parameters are exactly the same as in Example 1.

[0110] Example 17

[0111] The only difference between this embodiment and Example 1 is that in step (2), 0.5g PEO, 0.17g LiTFSI and 0.036g LLZTO (5wt%) are dissolved in 8mL of anhydrous acetonitrile. All other conditions and parameters are exactly the same as in Example 1.

[0112] Example 18

[0113] This embodiment provides a composite solid electrolyte membrane, which includes a polyacrylonitrile (PAN) fiber base membrane containing alkali lignin and Li7La3Zr2O coated on both sides of the PAN fiber base membrane. 12 Oxide inorganic solid electrolytes and polymethyl methacrylate solid electrolytes containing lithium salts.

[0114] The composite solid electrolyte membrane is prepared by the following method:

[0115] (1) Dissolve 0.47g PAN (source same as in Example 1) and 4.23g alkali lignin (source same as in Example 1) in 10mL of N,N-dimethylformamide (source same as in Example 1) to prepare a spinning solution with a concentration of 5wt%. Heat and magnetically stir at 75℃ for 24h to form a transparent and homogeneous spinning solution. Inject the spinning solution into a 10mL syringe using a No. 22 needle. Set the positive voltage at the needle tip to 15kV, the negative voltage at the roller receiver to 2kV, the distance between the needle tip and the roller receiver to 15cm, the roller receiver rotation speed to 100rpm, the spinning solution feed speed to 0.1mm / min, the spinning temperature to 20-25℃, and the humidity to 18-23%. After spinning, place the PAN fiber base film in a vacuum drying oven at 60℃ for 24h. After drying, place the PAN fiber base film between two rollers 5μm apart for rolling. After rolling, store it in a glove box.

[0116] (2) Add 0.23g PEO (from the same source as in Example 1), 0.08g LiPF6 (97%, L157770, Aladdin reagent), and 0.003g Li7La3Zr2O 12 (1wt%) (Shenzhen Huaxin Fresh Materials Technology Co., Ltd.) was dissolved in 10mL of anhydrous acetonitrile (source same as in Example 1), and magnetically stirred at 1000rpm for 24h at room temperature to obtain a transparent and uniform composite solid electrolyte slurry.

[0117] (3) Fix the PAN fiber base membrane on the polytetrafluoroethylene template, use a 10mL pipette to draw a certain amount of slurry, and evenly drop it onto the surface of the fiber base membrane. After natural drying for 6 hours, turn the fiber base membrane over and drop the slurry evenly again. After natural drying for 6 hours, place the composite solid electrolyte fiber membrane in a vacuum drying oven and dry it at 60℃ for 24 hours. After drying, demold and slice to obtain the composite solid electrolyte membrane.

[0118] Example 19

[0119] This embodiment provides a composite solid electrolyte membrane, which includes a polyacrylonitrile (PAN) fiber base membrane containing alkali lignin and Li7La3Zr2O coated on both sides of the PAN fiber base membrane. 12 Oxide inorganic solid electrolytes and polymethyl methacrylate solid electrolytes containing lithium salts.

[0120] The composite solid electrolyte membrane is prepared by the following method:

[0121] (1) Dissolve 2.84g of PAN (source same as in Example 1) and 0.32g of alkali lignin (source same as in Example 1) in 10mL of N,N-dimethylformamide (source same as in Example 1) to prepare a spinning solution with a concentration of 30wt%. Heat and magnetically stir at 75°C for 24h to form a transparent and homogeneous spinning solution. Inject the spinning solution into a 10mL syringe using a No. 22 needle. Set the positive voltage at the needle tip to 15kV, the negative voltage at the roller receiver to 2kV, the distance between the needle tip and the roller receiver to 15cm, the roller receiver rotation speed to 100rpm, the spinning solution feed speed to 0.1mm / min, the spinning temperature to 20-25°C, and the humidity to 18-23%. After spinning, place the PAN fiber base film in a vacuum drying oven at 60°C for 24h. After drying, place the PAN fiber base film between two rollers 5μm apart for rolling. After rolling, store it in a glove box.

[0122] (2) 0.66g PEO (source same as in Example 1), 0.11g LiPF6 (source same as in Example 18), and 0.008g Li7La3Zr2O were added. 12 (Source same as Example 18) (10wt%) was dissolved in 10mL of anhydrous acetonitrile (source same as Example 1), and magnetically stirred at 1000rpm for 24h at room temperature to obtain a transparent and uniform composite solid electrolyte slurry.

[0123] (3) Fix the PAN fiber base membrane on the polytetrafluoroethylene template, use a 10mL pipette to draw a certain amount of slurry, and evenly drop it onto the surface of the fiber base membrane. After natural drying for 6 hours, turn the fiber base membrane over and drop the slurry evenly again. After natural drying for 6 hours, place the composite solid electrolyte fiber membrane in a vacuum drying oven and dry it at 60℃ for 24 hours. After drying, demold and slice to obtain the composite solid electrolyte membrane.

[0124] Example 20

[0125] The only difference between this embodiment and embodiment 1 is that the PAN fiber base film containing alkali lignin is not rolled. After the fiber base film is dried, the composite solid electrolyte slurry obtained in step (2) is directly added. Other conditions and parameters are exactly the same as in embodiment 1.

[0126] Example 21

[0127] The only difference between this embodiment and Embodiment 1 is that the spinning solution is prepared with a concentration of 1 wt%, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0128] Example 22

[0129] The only difference between this embodiment and Example 1 is that the spinning solution is prepared with a concentration of 35 wt%, while the other conditions and parameters are exactly the same as in Example 1.

[0130] Example 23

[0131] The only difference between this embodiment and Embodiment 1 is that the molar ratio of polyethylene oxide solid electrolyte and LiTFSI in step (2) is 5:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0132] Example 24

[0133] The only difference between this embodiment and Embodiment 1 is that the molar ratio of polyethylene oxide solid electrolyte and LiTFSI in step (2) is 25:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0134] Example 25

[0135] The only difference between this embodiment and embodiment 1 is that the polyethylene oxide solid electrolyte in step (2) accounts for 1 wt% of the organic solvent mass, while the other conditions and parameters are exactly the same as in embodiment 1.

[0136] Example 26

[0137] The only difference between this embodiment and Embodiment 1 is that the polyethylene oxide solid electrolyte in step (2) accounts for 15 wt% of the organic solvent mass, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0138] Comparative Example 1

[0139] The difference between this comparative example and Example 1 is that a polymer fiber membrane is not prepared; instead, a PEO / LiTFSI / LLZTO composite solid electrolyte is prepared directly using a solution casting method. All other conditions and parameters are exactly the same as in Example 1.

[0140] The specific process of the solution casting method is as follows: 0.5g PEO (viscosity average molecular weight of 60W), 0.18g LiTFSI and 0.036g LLZTO (5wt%) are dissolved in 10mL of anhydrous acetonitrile. The mixture is magnetically stirred at 1000rpm for 24h at room temperature to obtain a transparent and uniform composite solid electrolyte slurry. The slurry is then poured into a polytetrafluoroethylene mold and allowed to dry naturally at room temperature for 12h to form a film. After that, it is dried in a vacuum drying oven at 60℃ for 12h to completely evaporate the organic solvent anhydrous acetonitrile.

[0141] Comparative Example 2

[0142] The difference between this comparative example and Example 1 is that LLZTO is not added, while the other conditions and parameters are exactly the same as in Example 1.

[0143] Comparative Example 3

[0144] The difference between this comparative example and Example 1 is that no alkali lignin was added, but the other conditions and parameters are exactly the same as in Example 1.

[0145] Application Example 1-26 and Comparative Application Example 1-3

[0146] The composite solid electrolyte membranes, lithium iron phosphate (LiFePO4) positive electrode sheets, and lithium metal negative electrode sheets provided in Examples 1-26 and Comparative Examples 1-3 were assembled into an all-solid-state lithium-ion battery. The assembly method is as follows:

[0147] Assembly of all-solid-state lithium-ion batteries: Assembly is carried out in an argon-filled glove box, and from bottom to top, the positive electrode shell, LiFePO4, composite solid electrolyte membrane, lithium metal, gasket, spring, and negative electrode shell are assembled in sequence, and then packaged on a button cell packaging machine.

[0148] Test conditions:

[0149] The conductivity of the composite solid electrolyte membranes provided in Examples 1-26 and Comparative Examples 1-3 was tested using the following methods:

[0150] (1) Ionic conductivity test:

[0151] The pre-cut composite solid electrolyte membrane was sandwiched between two stainless steel sheets, and the room temperature (25℃) ionic conductivity was tested using the AC impedance tester of the Shanghai Chenhua Electrochemical Workstation with a frequency range of 0.1-1MHz and an amplitude of 10mV.

[0152] (2) Mechanical property testing:

[0153] The mechanical properties of the composite solid electrolyte membrane were characterized by stress tensile testing. Before the test, the environment in which the instrument was located was dehumidified and the ambient temperature was controlled at 25℃. The composite solid electrolyte membrane to be tested was cut to a length of 60mm and a width of 20mm, and the tensile speed was set to 50cm / min.

[0154] The lithium-ion batteries provided in Application Example 1-26 and Comparative Application Example 1-3 were subjected to performance tests, and the test methods are as follows:

[0155] The lithium-ion battery was subjected to constant current charge and discharge at 60°C and 0.5C within a voltage window of 2.8-4.0V. The initial discharge specific capacity was tested, and the discharge specific capacity and capacity retention rate were tested after 500 cycles.

[0156] The performance test results of the composite solid electrolyte membrane and the corresponding all-solid-state lithium-ion battery are shown in Table 1:

[0157] Table 1. Performance comparison of composite solid electrolyte membranes and corresponding all-solid-state batteries provided in each embodiment and comparative example.

[0158]

[0159]

[0160] Note: -- indicates that it cannot be prepared.

[0161] As shown in Table 1, and based on Examples 1-12, the composite solid electrolyte used in this invention achieves a maximum ionic conductivity and a maximum tensile strength of 4.3 × 10⁻⁶. -4 With an initial discharge specific capacity of up to 152.32 mAh / g and a capacity retention rate of up to 97% after 500 cycles, the all-solid-state battery of this invention, with a pressure of S / cm and 55 MPa, can achieve a maximum capacity of 152.32 mAh / g.

[0162] A comparison between Examples 1-4, or Examples 5, 7, 9, 11, or Examples 6, 8, 10, 12 reveals that the effects of polymer fiber membranes with different compositions on PEO polymer solid electrolytes vary. This depends on the interaction between the unique functional groups in the polymer, the ether oxygen functional groups in PEO, and the anions of LiTFSI.

[0163] Comparisons between Examples 1, 5, and 6, or Examples 2, 7, and 8, or Examples 3, 9, and 10, or Examples 4, 11, and 12 show that the composite solid-state electrolyte and all-solid-state lithium-ion battery exhibit the best electrochemical and mechanical properties when the LLZTO addition amount is 5 wt%. This is because when the LLZTO addition amount is insufficient, the number of freely moving lithium ions in the composite solid-state electrolyte is small, and the mechanical strength is insufficient, making it difficult to obtain satisfactory electrochemical and mechanical properties. When the LLZTO addition amount is excessive, the aggregated LLZTO will hinder the migration rate of lithium ions in the polymer matrix, and the large differences in mechanical strength at different locations in the polymer matrix will also make it difficult to obtain satisfactory electrochemical and mechanical properties.

[0164] A comparison of Examples 1 and 20 shows that the rolling operation can significantly improve the ionic conductivity, cycle stability, and maximum tensile strength of the composite solid electrolyte. This is because the rolling operation makes the composite solid electrolyte membrane thinner and denser. On the one hand, this can shorten the diffusion distance of lithium ions, improve the interfacial contact between the solid electrolyte and metallic lithium, thereby suppressing the formation of lithium dendrites and promoting long-term cycling of all-solid-state lithium-ion batteries. On the other hand, it can enable the polymer membrane to obtain a higher volume density and improve the mechanical strength of the composite solid electrolyte.

[0165] A comparison of Example 1 with Examples 21-26 reveals that experimental groups outside the reference ranges for spinning solution concentration, polymer solid electrolyte to lithium salt molar ratio, and polymer solid electrolyte to organic solvent ratio are not feasible. This is because: too low a spinning solution concentration will prevent the spinning of fiber morphology; too high a concentration will clog the spinning needle, preventing the formation of fiber membranes; too low a molar ratio of polymer solid electrolyte to lithium salt will severely affect the number of freely moving lithium ions in the composite solid electrolyte, leading to poor electrochemical performance; too high a ratio will make the composite solid electrolyte slurry too viscous, failing to bond well with the fiber membrane; too low a ratio of polymer solid electrolyte to organic solvent will greatly increase the amount of organic solvent used, which is detrimental to energy conservation and environmental protection; too high a ratio will also make the composite solid electrolyte slurry too viscous, with poor fluidity, failing to bond well with the fiber membrane.

[0166] As can be seen from the comparison between Example 1 and Comparative Example 1, the composite solid electrolyte with polymer fiber membrane has better mechanical and electrochemical properties, especially mechanical properties. This fully demonstrates that the compacted and thinned polymer fiber membrane, as the matrix of the composite solid electrolyte, can improve the overall mechanical strength and help suppress lithium dendrites. At the same time, through the interaction with PEO and LiTFSI, it can reduce the crystallinity of PEO and promote the rapid migration of lithium ions.

[0167] A comparison of Example 1 and Comparative Example 2 shows that the addition of LLZTO has a significant impact on the ionic conductivity of the composite solid electrolyte and the cycle stability of the full cell, while having a relatively small impact on the mechanical properties of the composite solid electrolyte. This confirms the excellent electrochemical performance of LLZTO itself and its positive role in the rapid movement of lithium ions in the polymer matrix.

[0168] A comparison of Example 1 and Comparative Example 3 shows that the addition of alkali lignin has a significant impact on the electrochemical properties, such as ionic conductivity, and mechanical properties of the composite solid electrolyte. This confirms the important role of alkali lignin in reducing the crystallinity of PEO and improving the porosity of polymer fiber membranes.

[0169] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A composite solid electrolyte membrane, characterized in that, The composite solid electrolyte membrane includes a polymer fiber base membrane containing alkali lignin and a mixed slurry of an oxide inorganic solid electrolyte and a polymer solid electrolyte containing lithium salt coated on both sides of the polymer fiber base membrane. The polymer in the polymer fiber base film includes any one or a combination of at least two of polyacrylonitrile, polyvinylidene fluoride, polyvinylpyrrolidone, or polyvinyl alcohol. The method for preparing the composite solid electrolyte membrane includes the following steps: (1) The polymer, alkali lignin and solvent are mixed to form a spinning solution, and then electrospinning is performed to obtain a polymer fiber base film containing alkali lignin. The polymer fiber base film is then vacuum dried and rolled. (2) The oxide inorganic solid electrolyte, lithium salt and polymer solid electrolyte are mixed with organic solvent to obtain a composite solid electrolyte slurry; (3) The composite solid electrolyte slurry obtained in step (2) is coated on one side of the polymer fiber base membrane. After drying, the composite solid electrolyte slurry obtained in step (2) is coated on the other side of the polymer fiber base membrane to obtain the composite solid electrolyte membrane. The polymer concentration in the spinning solution in step (1) is 5wt%-30wt%; The distance of the roller pressing in step (1) is 5-30 μm; The polymer solid electrolyte mentioned in step (2) accounts for 4-10 wt% of the organic solvent mass; The mass fraction of the oxide inorganic solid electrolyte in the composite solid electrolyte slurry mentioned in step (2) is 1-5 wt%. The polymer solid electrolyte mentioned in step (2) is polyethylene oxide; In step (2), the molar ratio of polymer solid electrolyte to lithium salt is (10~20):

1.

2. The composite solid electrolyte membrane according to claim 1, characterized in that, The oxide inorganic solid electrolyte includes any one or a combination of at least two of the following: NASICON-type inorganic solid electrolyte, garnet-type inorganic solid electrolyte, or perovskite-type inorganic solid electrolyte.

3. The composite solid electrolyte membrane according to claim 1, characterized in that, The oxide inorganic solid electrolyte is a garnet-type inorganic solid electrolyte.

4. The composite solid electrolyte membrane according to claim 2, characterized in that, The NASICON-type inorganic solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, where the range of x is 0. <x<2。 5. The composite solid electrolyte membrane according to claim 2, characterized in that, The garnet-type inorganic solid electrolyte is Li7La3Zr2O 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li 6.24 La3Zr2Al 0.24 O 11.98 Li 6.25 La3Zr2Ga 0.25 O 12 Or Li 6.375 La3Zr 1.375 Nb 0.625 O 12 Any one or at least two of them.

6. The composite solid electrolyte membrane according to claim 2, characterized in that, The perovskite-type inorganic solid electrolyte is Li 3x La 2 / 3-x □ 1 / 3-2x TiO3, where □ represents a vacancy, and 0 < x < 0.

16.

7. The composite solid electrolyte membrane according to claim 1, characterized in that, The viscosity-average molecular weight of the polyethylene oxide in the polymer solid electrolyte is 60W~500W.

8. The composite solid electrolyte membrane according to claim 1, characterized in that, The lithium salt in the polymer solid electrolyte containing lithium salt includes any one or a combination of at least two of LiClO4, LiBF4, LiPF6, LiFSI, LiTFSI, LiBETI, LiCTFSI, LiBOB, LiTDI, LiPDI, LiDCTA, or LiB(CN)4.

9. A method for preparing a composite solid electrolyte membrane according to any one of claims 1-8, characterized in that, The method includes the following steps: (1) The polymer, alkali lignin and solvent are mixed to form a spinning solution, and then electrospinning is performed to obtain a polymer fiber base film containing alkali lignin. The polymer fiber base film is then vacuum dried and rolled. (2) The oxide inorganic solid electrolyte, lithium salt and polymer solid electrolyte are mixed with organic solvent to obtain a composite solid electrolyte slurry; (3) The composite solid electrolyte slurry obtained in step (2) is coated on one side of the polymer fiber base membrane. After drying, the composite solid electrolyte slurry obtained in step (2) is coated on the other side of the polymer fiber base membrane to obtain the composite solid electrolyte membrane.

10. The method according to claim 9, characterized in that, The solvent mentioned in step (1) includes any one or a combination of at least two of deionized water, N,N-dimethylformamide or acetone.

11. The method according to claim 9, characterized in that, The mass concentration of the polymer in the spinning solution in step (1) is 10wt%-20wt%.

12. The method according to claim 9, characterized in that, The mass ratio of the polymer and alkali lignin in step (1) is (9:1)-(1:9).

13. The method according to claim 9, characterized in that, The mass ratio of the polymer and alkali lignin in step (1) is (8:2) to (4:6).

14. The method according to claim 9, characterized in that, The electrospinning parameters mentioned in step (1) include the distance between the needle and the roller receiver, voltage, needle advance speed, and the rotational speed of the roller receiver.

15. The method according to claim 14, characterized in that, The distance between the needle and the roller receiver is 10-20cm.

16. The method according to claim 14, characterized in that, The distance between the needle and the roller receiver is 10-15cm.

17. The method according to claim 14, characterized in that, The voltage is 10-20kV.

18. The method according to claim 14, characterized in that, The voltage is 10-15kV.

19. The method according to claim 14, characterized in that, The needle advance speed is 0.05-0.2 mm / min.

20. The method according to claim 14, characterized in that, The needle advance speed is 0.08-0.1 mm / min.

21. The method according to claim 14, characterized in that, The rotational speed of the roller receiver is 50-200 rpm.

22. The method according to claim 14, characterized in that, The rotational speed of the roller receiver is 50-100 rpm.

23. The method according to claim 9, characterized in that, The vacuum drying temperature in step (1) is 40-80℃.

24. The method according to claim 9, characterized in that, The vacuum drying temperature in step (1) is 50-60℃.

25. The method according to claim 9, characterized in that, The vacuum drying time in step (1) is 10-24 hours.

26. The method according to claim 9, characterized in that, The vacuum drying time in step (1) is 18-24 hours.

27. The method according to claim 9, characterized in that, The distance of the roller pressing in step (1) is 15-25μm.

28. The method according to claim 9, characterized in that, The lithium salt mentioned in step (2) is LiTFSI.

29. The method according to claim 9, characterized in that, The organic solvent mentioned in step (2) includes anhydrous acetonitrile, tetrahydrofuran, or N,N-dimethylformamide.

30. The method according to claim 9, characterized in that, The organic solvent mentioned in step (2) is anhydrous acetonitrile.

31. The method according to claim 9, characterized in that, In step (2), the molar ratio of polymer solid electrolyte to lithium salt is (16:1) to (19:1).

32. The method according to claim 9, characterized in that, The polymer solid electrolyte in step (2) accounts for 5 to 8 wt% of the organic solvent.

33. The method according to claim 9, characterized in that, The mixing described in step (2) is carried out under stirring.

34. The method according to claim 33, characterized in that, The stirring time is 12-24 hours.

35. The method according to claim 33, characterized in that, The stirring time is 12-18 hours.

36. The method according to claim 33, characterized in that, The stirring speed is 800-1600 rpm.

37. The method according to claim 33, characterized in that, The stirring speed is 1000-1200 rpm.

38. The method according to claim 9, characterized in that, The drying process described in step (3) includes two natural drying processes and one vacuum drying process.

39. The method according to claim 38, characterized in that, The natural drying time for both processes was 4-8 hours.

40. The method according to claim 38, characterized in that, The natural drying time for both processes was 4-6 hours.

41. The method according to claim 38, characterized in that, The vacuum drying temperature is 50-65℃.

42. The method according to claim 38, characterized in that, The vacuum drying temperature is 55-60℃.

43. The method according to claim 38, characterized in that, The vacuum drying time is 12-24 hours.

44. The method according to claim 38, characterized in that, The vacuum drying time is 18-24 hours.

45. An all-solid-state lithium-ion battery, characterized in that, The all-solid-state lithium-ion battery includes a positive electrode, a negative electrode, and a solid electrolyte, wherein the solid electrolyte is a composite solid electrolyte membrane according to any one of claims 1-8.

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