A solid electrolyte, its preparation method and application

Abstract

This invention discloses a solid electrolyte, its preparation method, and its application. The solid electrolyte comprises a composite of a fibrous membrane and an electrolyte. The fibrous membrane is composed of hollow fibers, each comprising a circumferential fiber wall and a central hollow portion. The fiber wall has a porous structure, and the electrolyte fills the hollow portion of the core and the porous structure of the fiber wall. The porous and hollow structure of the fibrous membrane used in this invention is particularly advantageous for absorbing and storing the electrolyte, while the base membrane also meets the requirement of preventing electrolyte leakage when bent or folded.

Description

Technical Field

[0001] This invention belongs to the field of electrolytes, and particularly relates to solid electrolytes. Specifically, it relates to a solid electrolyte, its preparation method, and its application. Background Technology

[0002] With the dwindling supply of fossil fuels and their unavoidable environmental pollution, the demand for new environmentally friendly energy sources is becoming increasingly urgent. Flexible energy devices, in particular, have received widespread attention due to their ability to withstand bending and deformation. Recent research has focused on flexible zinc-air batteries, aiming to improve their flexibility through improvements and optimizations of various components. Traditionally, the electrolyte in zinc-air batteries is liquid, which poses a risk of leakage when the battery is bent.

[0003] Therefore, alkaline gel electrolytes, as a type of semi-solid electrolyte, have attracted researchers' attention. The most common is the KOH-PVA gel electrolyte, which is low-cost, easy to prepare, and has been widely studied in zinc-air batteries (e.g., Energy Storage Materials 15(2018)124–130; Adv. Funct. Mater. 2020, 2003407; Adv. Sci. 2018, 5, 1800760). However, this KOH-PVA gel electrolyte still has many drawbacks, such as poor mechanical properties, low ionic conductivity, and easy dehydration leading to poor environmental stability during use. These significantly affect the discharge performance and lifespan of flexible zinc-air batteries. To address this, some researchers have prepared porous PVA-SiO2 by adding SiO2 particles and polyethylene glycol (PEG) to PVA, and then prepared PVA-SiO2 gel solid electrolyte by adsorbing electrolyte. This method improves the electrolyte adsorption capacity compared to pure PVA gel. The highest adsorption capacity reached 225% (Nano Energy 56, (2019) 454-462).

[0004] Some researchers have also used bacterial cellulose as a substrate to form bacterial cellulose-based semi-solid gel electrolytes by impregnating them with electrolytes, but the electrolyte storage capacity of such materials is still not high. (Journal of power sources 482(2021)228963)

[0005] Therefore, there is a need to develop a simple solid electrolyte that can adsorb and store electrolyte at high levels and has excellent water retention to improve the discharge performance and lifespan of flexible zinc-air batteries. Summary of the Invention

[0006] To overcome the problems existing in the prior art, the present invention provides a solid electrolyte, its preparation method and application. The solid electrolyte has the advantages of novel structure, high electrolyte storage capacity, good water retention, and green and environmentally friendly preparation process.

[0007] One objective of this invention is to provide a solid electrolyte comprising a composite of a fiber membrane and an electrolyte, wherein the fiber membrane is composed of hollow fibers, the hollow fibers comprising a circumferential fiber wall and a hollow portion of a core, the fiber wall having a porous structure, and the electrolyte filling the hollow portion of the core and the porous structure of the fiber wall.

[0008] In a preferred embodiment, the average diameter of the hollow fiber is 50-2000 nm, preferably 500-1500 nm.

[0009] For example, the diameter of the hollow fiber is 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm or 1000nm.

[0010] In a preferred embodiment, the inner diameter of the hole ranges from 5 to 200 nm, preferably from 40 to 180 nm.

[0011] In a preferred embodiment, the average hollowness of the hollow fiber is 10-80%, preferably 20-70%, wherein the hollowness is defined as the ratio of the cross-sectional area of ​​the hollow portion to the total cross-sectional area of ​​the fiber.

[0012] For example, the average hollowness of the fiber is 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%.

[0013] In this method, the hollow fiber membrane with a porous structure can fully absorb the electrolyte, thereby filling the interior of the fiber with the electrolyte.

[0014] In a preferred embodiment, the hollow fiber is made from a polymer containing nitrile groups.

[0015] In a further preferred embodiment, the hollow fiber is one or a combination of two of acrylonitrile homopolymer polyacrylonitrile and acrylonitrile-containing copolymers.

[0016] In a further preferred embodiment, the hollow fiber is prepared from one or two of the copolymers of polyacrylonitrile, butadiene, and acrylonitrile.

[0017] In a further preferred embodiment, the hollow fiber is selected from polyacrylonitrile fiber and is prepared from polyacrylonitrile.

[0018] Among them, the metal ions of the nitrile group in polyacrylonitrile (such as zinc ions) have excellent conductivity.

[0019] In a preferred embodiment, the electrolyte is a mixed aqueous solution containing an alkali and a zinc salt.

[0020] In a further preferred embodiment, the alkali is selected from at least one of potassium hydroxide and sodium hydroxide;

[0021] In a further preferred embodiment, the molar concentration of the alkali in the electrolyte is 1 to 10 mol / L, preferably 2 to 8 mol / L; and / or the molar concentration of the zinc salt is 0.01 to 1 mol / L, preferably 0.05 to 0.5 mol / L.

[0022] In a preferred embodiment, the weight of the electrolyte in the solid electrolyte is 2 to 50 times the weight of the hollow fiber, preferably 10 to 35 times.

[0023] In the solid electrolyte, the weight of the electrolyte is 5, 10, 15, 20, 25, 30, or 35 times the weight of the hollow fiber.

[0024] In this invention, the hollow structure and porous structure of the hollow fiber enable high electrolyte retention and good water retention. This solid electrolyte exhibits excellent charge-discharge cycle performance at 3 mA cm⁻¹. -2 At a current density of 1200 min, it can be cycled 60 times.

[0025] A second objective of this invention is to provide a method for preparing a solid electrolyte, preferably used to prepare the solid electrolyte described in one objective of this invention. The preparation method includes: first obtaining the fiber membrane, and then immersing the fiber membrane in the electrolyte to obtain the solid electrolyte.

[0026] In this process, the fiber membrane is allowed to adsorb the electrolyte until it reaches saturation.

[0027] In a preferred embodiment, the fiber membrane is placed in the electrolyte for 5 to 60 hours, preferably 20 to 40 hours, and more preferably 30 to 38 hours.

[0028] For example, the fiber membrane is placed in the electrolyte for 5h, 10h, 20h, 30h, 32h, 34h, 36h, 38h, 40h, 50h or 60h.

[0029] The term "placement" refers to the electrolyte solution covering all fiber membranes, meaning that all fiber membranes are fully immersed in the electrolyte.

[0030] In a preferred embodiment, the fiber membrane is obtained by the following method:

[0031] (1) Prepare the skin spinning solution and the core spinning solution: Mix the non-water-soluble polymer, the pore-forming agent and the solvent to form the skin spinning solution, and mix the pore-forming agent and the solvent to form the core spinning solution;

[0032] (2) Using the sheath spinning solution as the sheath and the core spinning solution as the core, solid fiber membranes are fabricated by coaxial electrospinning.

[0033] (3) The solid fiber membrane is immersed in water to remove the pore-forming agent, and then dried to obtain the fiber membrane.

[0034] In a preferred embodiment, the water-insoluble polymer is selected from nitrile-containing polymers, preferably from one or a combination of two of acrylonitrile homopolymer polyacrylonitrile and polyacrylonitrile-containing copolymers.

[0035] In a further preferred embodiment, the non-water-soluble polymer is selected from one or two of the copolymers of polyacrylonitrile, butadiene, and acrylonitrile.

[0036] In a further preferred embodiment, the water-insoluble polymer is selected from polyacrylonitrile.

[0037] In this process, a non-water-soluble polymer is used as the skin layer, so that the skin layer will not dissolve in step (3).

[0038] In a further preferred embodiment, the number average molecular weight of the water-insoluble polymer (PAN) is 50,000 to 150,000, preferably 80,000 to 120,000.

[0039] In a preferred embodiment, the pore-forming agent is a water-soluble polymer.

[0040] In this way, the polymer can not only be spun, but also dissolves in water during the soaking in step (3). The core layer originally formed by the material becomes a hollow part, and the material in the fiber wall (skin layer) also dissolves in water to form a porous structure.

[0041] In a further preferred embodiment, the pore-forming agent is selected from at least one of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG).

[0042] In a further preferred embodiment, the number average molecular weight of the pore-forming agent polyvinylpyrrolidone is 40,000 to 80,000, preferably 50,000 to 65,000; and the number average molecular weight of the pore-forming agent polyethylene glycol is 10,000 to 40,000, preferably 20,000 to 30,000.

[0043] For example, PVP is one or more of type K30 or K25; the molecular weight of the PEG used is 20,000.

[0044] This invention involves blending a water-soluble pore-forming agent with a non-water-soluble polymer, followed by coaxial electrospinning to form a nanofiber membrane. The pore-forming agent is then removed by washing with water to obtain the fibrous membrane. This method is simple and easy to implement; removing the pore-forming agent requires only water and no other organic solvents, making it environmentally friendly.

[0045] In a preferred embodiment, the solvent is selected from organic solvents.

[0046] In a further preferred embodiment, the solvent is selected from at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and dimethyl sulfoxide (DMSO).

[0047] In a preferred embodiment, the weight concentration of the non-water-soluble polymer in the skin spinning solution is 5 to 40 wt%; and / or the weight concentration of the pore-forming agent is 2 to 15 wt%.

[0048] In a further preferred embodiment, the weight concentration of the non-water-soluble polymer in the skin spinning solution is 7-20 wt%; and / or the weight concentration of the pore-forming agent is 5-15 wt%.

[0049] For example, in the skin spinning solution, the weight concentration of the non-water-soluble polymer is 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%; and / or, the weight concentration of the pore-forming agent is 2 wt%, 5 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%.

[0050] In a preferred embodiment, the pore-forming agent has a weight concentration of 20–70 wt%, preferably 30–70 wt%, in the core spinning solution.

[0051] For example, in the core spinning solution, the weight concentration of the pore-forming agent is 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or 70 wt%.

[0052] In a preferred embodiment, a disposable syringe is used to extract the above-mentioned sheath spinning solution and core spinning solution respectively, and coaxial electrospinning is performed.

[0053] In a preferred embodiment, in step (2), the parameters of the coaxial electrospinning are: temperature of 10-40℃, voltage of 5-50KV, jet flow rate of 0.1-1mL / h, and distance between the needle and the receiving plate of 5-50cm.

[0054] In a further preferred embodiment, in step (2), the parameters of the coaxial electrospinning are: temperature of 20-30℃, voltage of 15-25KV, jet flow rate of 0.3-0.7ml / h, and distance between the needle and the receiving plate of 12-28cm.

[0055] For example, the temperature is 10℃, 20℃, 30℃, or 40℃; the voltage is 5KV, 10KV, 15KV, 20KV, 25KV, 30KV, 40KV, or 50KV; the ejection flow rate is 0.1mL / h, 0.2mL / h, 0.3mL / h, 0.4mL / h, 0.5mL / h, 0.6mL / h, 0.7mL / h, 0.8mL / h, 0.9mL / h, or 1mL / h; and the distance between the needle and the receiving plate is 5cm, 10cm, 15cm, 20cm, 25cm, 30cm, 40cm, or 50cm.

[0056] In a preferred embodiment, in step (3), the soaking time is 10-70 h; and / or the soaking temperature (i.e., water temperature) is 10-80 °C.

[0057] In a further preferred embodiment, in step (3), the soaking time is 20-50 hours, preferably 24-36 hours; and / or, the soaking temperature (i.e., water temperature) is room temperature to 50°C.

[0058] In a preferred embodiment, in step (3), the drying temperature is 40–90°C; and / or the drying time is 2–40 h.

[0059] In a further preferred embodiment, in step (3), the drying temperature is 50-70°C, preferably 50-60°C; and / or, the drying time is 10-20 hours, preferably 12-15 hours.

[0060] In this invention, coaxial electrospinning enables the aggregation of different components into a single fiber. After solvent evaporation during the spinning process, a fiber membrane composed of nanofibers, resembling nonwoven fabric, is obtained. When a water-soluble pore-forming agent is used as the fiber core layer for coaxial electrospinning, combined with the subsequent removal of the fiber core by water dissolution, nanofibers with a hollow structure can be easily prepared. Similarly, pores are also created on the fiber wall, which not only improves the absorption and retention of electrolyte but also reduces ion transport paths and increases ion conductivity.

[0061] The third objective of this invention is to provide a solid electrolyte obtained by the preparation method described in the second objective of this invention.

[0062] The fourth objective of this invention is to provide the application of the solid electrolyte described in the first objective of this invention or the solid electrolyte obtained by the preparation method described in the second objective of this invention in air batteries, especially in zinc-air batteries.

[0063] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) The present invention obtains a solid fiber membrane by coaxial electrospinning, and then after two soakings, the fiber membrane for use in solid electrolyte is finally obtained;

[0066] (2) The water washing process overcomes the shortcomings of existing porous fiber membrane preparation technology, such as complicated processing steps, time and labor. This invention provides a one-step water washing and soaking method to realize hollow structure and porous structure, which has the advantages of simple operation, high yield and low cost.

[0067] (3) The fiber membrane with porous and hollow structure used in this invention is particularly advantageous for absorbing and storing electrolyte, and the base membrane can meet the requirement that the electrolyte does not leak when bent and folded.

[0068] (4) The solid electrolyte, when applied to air batteries (e.g., solid zinc-air batteries), exhibits excellent charge-discharge cycle performance. After 60 cycles (1200 min), the charge-discharge voltage gap of the solid zinc-air battery did not increase significantly. Attached Figure Description

[0069] Figure 1 This is a cross-sectional morphology diagram of the fiber membrane prepared in Example 1 of the present invention;

[0070] Figure 2 This is a surface morphology diagram of the fiber membrane prepared in Example 1 of the present invention;

[0071] Figure 3 This is a morphology diagram of a single fiber in the fiber membrane prepared in Example 1 of the present invention;

[0072] Figure 4 The results show the charge-discharge cycle performance of a zinc-air battery assembled using the solid electrolyte prepared in Example 1 of this invention. Detailed Implementation

[0073] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0074] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0075] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0076] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0077]

Example 1

[0078] The method for preparing hierarchical porous polyacrylonitrile-based thin films for solid electrolytes in zinc-air batteries includes the following steps:

[0079] (1) Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) are dissolved together in DMF solvent to obtain a mixed solution, wherein PAN is 12.5% ​​relative to the solvent, PAN has a number average molecular weight of 130,000, PVP is 12.5% ​​relative to the solvent, and PVP is of type K30. This mixed solution is used as the skin spinning solution.

[0080] (2) Dissolve PVP in DMF solvent to obtain a mixed solution, which is used as the core spinning solution; wherein the PVP type is K30 and the PVP relative solvent is 68%.

[0081] (3) Use a disposable syringe to extract the spinning solution of the shell layer and the core layer respectively, and perform coaxial electrospinning to obtain a polyacrylonitrile-based film; the specific process parameters of coaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between needle and receiving plate 18cm.

[0082] (4) The polyacrylonitrile-based film obtained in step (3) above is immersed in a water bath at room temperature for 36 hours and dried under vacuum at 60°C for 18 hours to obtain a multi-level porous polyacrylonitrile-based film.

[0083] The fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a hollow core portion, the fiber wall having a porous structure; wherein, the average diameter of the hollow fiber is 1100 nm, the inner diameter of the pores ranges from 60 to 180 nm, and the average hollowness of the hollow fiber is 65%.

[0084] (5) The hierarchical porous polyacrylonitrile-based film obtained in step (4) above is immersed in a zinc-air battery electrolyte (6M KOH + 0.2M Zn(CH3COO)2) for 36 hours to obtain a solid electrolyte for zinc-air batteries, wherein the weight of the electrolyte is 35 times the weight of the hollow fiber. The zinc-air battery assembled with this solid electrolyte membrane performs well at 3 mA / cm². -2 Undergo 60 charge-discharge cycles (20 hours).

[0085]

Example 2

[0086] The multi-level porous polyacrylonitrile-based nanofiber membrane for solid electrolyte in zinc-air batteries and its preparation method include the following steps:

[0087] (1) Dissolve PAN and PVP together in DMF solvent to obtain a mixed solution, which is used as the skin spinning solution; wherein PAN is 15% relative to the solvent, the number average molecular weight of PAN is 120,000, the relative solvent of PVP is 12%, and the PVP type is K30.

[0088] (2) PVP is dissolved in DMF solvent, and the resulting solution is used as the core spinning solution; wherein the relative concentration of PVP in the solvent is 61%.

[0089] (3) Use a disposable syringe to extract the spinning solution of the shell layer and the core layer respectively, and perform coaxial electrospinning to obtain a polyacrylonitrile-based film; the specific process parameters of coaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between needle and receiving plate 19cm.

[0090] (4) The polyacrylonitrile-based nanofiber membrane obtained in step (3) above is soaked in a water bath at 40°C for 30 hours and dried under vacuum at 60°C for 18 hours to obtain a hierarchical porous PAN nanofiber membrane.

[0091] The fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a central hollow portion, the fiber wall having a porous structure; wherein, the average diameter of the hollow fiber is 1020 nm, the inner diameter of the pore ranges from 50 to 160 nm, and the average hollowness of the hollow fiber is 55%.

[0092] (5) The hierarchical porous PAN nanofiber membrane obtained in step (4) was immersed in an electrolyte (6MKOH + 0.2M Zn(CH3COO)2) for 36 hours to obtain a solid electrolyte for zinc-air batteries, wherein the weight of the electrolyte was 32 times the weight of the hollow fibers. The zinc-air battery assembled with this solid electrolyte membrane performed at 3 mA / cm². -2 The charge-discharge cycle was 52 times (17.3 hours).

[0093]

Example 3

[0094] The multi-level porous polyacrylonitrile-based nanofiber membrane for solid electrolyte in zinc-air batteries and its preparation method include the following steps:

[0095] (1) Dissolve PAN and PVP together in DMF solvent to obtain a mixed solution, which is used as the skin spinning solution; wherein the relative solvent of PAN is 14.5%, the number average molecular weight of PAN is 130,000, the relative solvent of PVP is 10.5%, and the PVP type is K30.

[0096] (2) PVP is dissolved in DMF solvent to obtain a mixed solution, which is used as the core spinning solution; wherein PVP accounts for 50.7% of the solvent.

[0097] (3) Use a disposable syringe to extract the spinning solution of the shell layer and the core layer respectively, and perform coaxial electrospinning to obtain a polyacrylonitrile-based film; the specific process parameters of coaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between needle and receiving plate 22cm.

[0098] (4) The polyacrylonitrile nanofiber membrane obtained in step (3) above is soaked in a water bath at room temperature for 50 h and dried under vacuum at 60 °C for 18 h to obtain a hierarchical porous PAN nanofiber membrane.

[0099] The fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a central hollow portion, the fiber wall having a porous structure; wherein, the average diameter of the hollow fiber is 980 nm, the inner diameter of the pore ranges from 50 to 150 nm, and the average hollowness of the hollow fiber is 53%.

[0100] (5) The hierarchical porous PAN-based nanofiber membrane obtained in step (4) above was immersed in a zinc-air battery electrolyte (6MKOH + 0.2M Zn(CH3COO)2) for 35 hours to obtain a solid electrolyte for zinc-air batteries, wherein the weight of the electrolyte was 28 times the weight of the hollow fibers. The zinc-air battery assembled with this solid electrolyte membrane performed at 3 mA / cm². -2 The charge-discharge cycle was 49 times (16.5 hours).

[0101]

Example 4

[0102] The multi-level porous polyacrylonitrile-based nanofiber membrane for solid electrolyte in zinc-air batteries and its preparation method include the following steps:

[0103] (1) Dissolve PAN and PEG together in DMAc solvent to obtain a mixed solution, which is used as the skin spinning solution; wherein PAN is 13% relative to the solvent and the number average molecular weight of PAN is 120,000, PEG is 10% relative to the solvent and the number average molecular weight of PEG is 20,000.

[0104] (2) Dissolve PEG in DMAc solvent and use the resulting solution as the core spinning solution; wherein the relative concentration of PEG in the solvent is 55%.

[0105] (3) Use a disposable syringe to extract the spinning solution of the shell layer and the core layer respectively, and perform coaxial electrospinning to obtain a polyacrylonitrile-based film; the specific process parameters of coaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between needle and receiving plate 20cm.

[0106] (4) The polyacrylonitrile-based nanofiber membrane obtained in step (3) above was soaked in a water bath at 50°C for 36 hours and dried under vacuum at 60°C for 18 hours to obtain a hierarchical porous PAN nanofiber membrane.

[0107] The fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a central hollow portion, the fiber wall having a porous structure; wherein, the average diameter of the hollow fiber is 1080 nm, the inner diameter of the pore ranges from 55 to 155 nm, and the average hollowness of the hollow fiber is 53%.

[0108] (5) The hierarchical porous PAN nanofiber membrane obtained in step (4) was immersed in an electrolyte (6M KOH + 0.2M Zn(CH3COO)2) for 36 hours to obtain a solid electrolyte for zinc-air batteries, wherein the weight of the electrolyte was 29 times the weight of the hollow fibers. The zinc-air battery assembled with this solid electrolyte membrane performed at 3 mA / cm². -2 50 charge-discharge cycles (16.5 hours) were performed.

[0109]

Example 5

[0110] The method for preparing hierarchical porous polyacrylonitrile-based thin films for solid electrolytes in zinc-air batteries includes the following steps:

[0111] (1) Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) are dissolved together in DMF solvent to obtain a mixed solution, which is used as the shell spinning solution; PAN has a relative solvent content of 12.5%, PAN has a number average molecular weight of 80,000, PVP is type K30, and PVP has a relative solvent content of 12.5%.

[0112] (2) Dissolve PVP in DMF solvent to obtain a mixed solution, which is used as the core spinning solution; wherein the PVP type is K30 and the PVP relative solvent content is 45.7%.

[0113] (3) Use a disposable syringe to extract the spinning solution of the shell layer and the core layer respectively, and perform coaxial electrospinning to obtain a polyacrylonitrile-based film; the specific process parameters of coaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between needle and receiving plate 20cm.

[0114] (4) The polyacrylonitrile-based film obtained in step (3) above was soaked in a water bath at room temperature for 36 hours and dried under vacuum at 60°C for 18 hours to obtain a hierarchical porous PAN nanofiber membrane.

[0115] The fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a central hollow portion, the fiber wall having a porous structure; wherein, the average diameter of the hollow fiber is 950 nm, the inner diameter of the pore ranges from 40 to 140 nm, and the average hollowness of the hollow fiber is 45%.

[0116] (5) The hierarchical porous polyacrylonitrile-based film obtained in step (4) above is immersed in a zinc-air battery electrolyte (6M KOH + 0.2M Zn(CH3COO)2) for 36 hours to obtain a solid electrolyte for zinc-air batteries, wherein the weight of the electrolyte is 25 times the weight of the hollow fiber. The zinc-air battery assembled with this solid electrolyte membrane performs well at 3 mA / cm². -2 The charge-discharge cycle is 45 times (15 hours).

[0117]

Example 6

[0118] The method for preparing hierarchical porous polyacrylonitrile-based thin films for solid electrolytes in zinc-air batteries includes the following steps:

[0119] (1) Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) are dissolved together in DMF solvent to obtain a mixed solution, which is used as the shell spinning solution; PAN has a relative solvent content of 15%, the number average molecular weight of PAN is 120,000, the PVP type is K30, and the relative solvent content of PVP is 12%.

[0120] (2) Dissolve PVP in DMF solvent to obtain a mixed solution, which is used as the core spinning solution; wherein the PVP type is K30 and the PVP relative solvent is 30.7%.

[0121] (3) Use a disposable syringe to extract the spinning solution of the shell layer and the core layer respectively, and perform coaxial electrospinning to obtain a polyacrylonitrile-based film; the specific process parameters of coaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between needle and receiving plate 20cm.

[0122] (4) The nanofiber membrane obtained in step (3) above was soaked in a water bath at room temperature for 36 hours and dried under vacuum at 60°C for 18 hours to obtain a hierarchical porous PAN nanofiber membrane.

[0123] The fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a central hollow portion, the fiber wall having a porous structure; wherein, the average diameter of the hollow fiber is 890 nm, the average inner diameter of the pore is 80 nm, and the average hollowness of the hollow fiber is 35%.

[0124] (5) The hierarchical porous polyacrylonitrile-based film obtained in step (4) above is immersed in a zinc-air battery electrolyte (6M KOH + 0.2M Zn(CH3COO)2) for 36 hours to obtain a solid electrolyte for zinc-air batteries, wherein the weight of the electrolyte is 21 times the weight of the hollow fiber. The zinc-air battery assembled with this solid electrolyte membrane performs well at 3 mA / cm². -2 Perform 35 charge-discharge cycles (12 hours).

[0125]

Comparative Example 1

[0126] (1) Dissolve PAN and PVP together in DMF solvent to obtain a mixed solution, which is used as the spinning solution. The relative solvent content of PAN is 12.5%, and the PVP type is K30 with a relative solvent content of 12.5%.

[0127] (2) Using a disposable syringe, perform uniaxial electrospinning of the above spinning solution to obtain a PAN / PVP nanofiber membrane; the specific process parameters for uniaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between the needle and the receiving plate 20cm.

[0128] (3) The PAN / PVP nanofiber membrane obtained in step (2) above is soaked in a water bath to remove the PVP component, and then vacuum dried to obtain a PAN nanofiber membrane with a porous structure.

[0129] (4) The porous PAN nanofiber membrane obtained in step (3) above is immersed in zinc-air battery electrolyte (6MKOH + 0.2M Zn(CH3COO)2) to obtain a solid electrolyte membrane for zinc-air batteries. The zinc-air battery assembled with this solid electrolyte membrane performs well at 3 mA / cm². -2 The charge-discharge cycle is repeated 24 times (8 hours).

[0130] [Comparative Example 2]

[0131] (1) Dissolve PAN in DMF solvent to obtain a mixed solution, which is used as the spinning solution. The relative solvent content of PAN is 12.5%.

[0132] (2) Using a disposable syringe, perform uniaxial electrospinning of the above spinning solution to obtain a PAN nanofiber membrane; the specific process parameters for uniaxial electrospinning are: temperature 25℃, voltage 20KV, spray flow rate 0.5ml / h, and distance between the needle and the receiving plate 20cm.

[0133] (3) The PAN nanofiber membrane obtained in step (2) above is immersed in zinc-air battery electrolyte (6M KOH + 0.2M Zn(CH3COO)2) to obtain a solid electrolyte membrane for zinc-air batteries. The zinc-air battery assembled with this solid electrolyte membrane performs well at 3 mA / cm². -2 Perform 10 charge-discharge cycles (3 hours).

[0134] As can be seen from the comparison of Comparative Examples 1, 2, and 1-6, the PAN-based nanofiber membrane prepared using the solid electrolyte structure designed in this invention and the method provided in this invention is an excellent matrix for zinc-air solid electrolytes, possessing advantages such as high electrolyte adsorption capacity and good stability. Furthermore, the preparation process is simple, achieving good technical results.

[0135] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A solid electrolyte, comprising: A composite of a fiber membrane and an electrolyte, wherein the fiber membrane is composed of hollow fibers, each hollow fiber comprising a circumferential fiber wall and a hollow core portion, the fiber wall having a porous structure, and the electrolyte filling the hollow core portion and the porous structure of the fiber wall, the electrolyte being a mixed aqueous solution of an alkali and a zinc salt; the inner diameter of the pores ranges from 40 to 200 nm, and the average porosity of the hollow fibers is 40 to 80%; in the solid electrolyte, the weight of the electrolyte is 20 to 50 times the weight of the hollow fibers.

2. The solid electrolyte according to claim 1, characterized in that, The hollow fibers have an average diameter of 50-2000 nm; and / or, The inner diameter of the hole ranges from 40 to 180 nm.

3. The solid electrolyte according to claim 1, characterized in that, The hollow fiber has an average diameter of 500–1500 nm.

4. The solid electrolyte according to claim 1, characterized in that, The hollow fiber has an average hollowness of 40-70%, where hollowness is defined as the ratio of the cross-sectional area of ​​the hollow portion to the total cross-sectional area of ​​the fiber.

5. The solid electrolyte according to claim 1, characterized in that, The hollow fiber is made from a polymer containing nitrile groups.

6. The solid electrolyte according to claim 1, characterized in that, The hollow fiber is made of one or a combination of two of the following: acrylonitrile homopolymer polyacrylonitrile and a copolymer containing polyacrylonitrile.

7. The solid electrolyte according to claim 1, characterized in that, The alkali is selected from at least one of potassium hydroxide and sodium hydroxide; the zinc salt is selected from either zinc acetate or zinc chloride.

8. The solid electrolyte according to claim 1, characterized in that, In the electrolyte, the molar concentration of the alkali is 1 to 10 mol / L; and / or, the molar concentration of the zinc salt is 0.01 to 1 mol / L.

9. The solid electrolyte according to claim 1, characterized in that, In the electrolyte, the molar concentration of the alkali is 2–8 mol / L; and / or, the molar concentration of the zinc salt is 0.05–0.5 mol / L.

10. The solid electrolyte according to any one of claims 1 to 9, characterized in that, In the solid electrolyte, the weight of the electrolyte is 20 to 35 times the weight of the hollow fiber.

11. A method for preparing a solid electrolyte, used to prepare the solid electrolyte according to any one of claims 1 to 10, the preparation method comprising: First, the fiber membrane is obtained, and then the fiber membrane is immersed in the electrolyte to obtain the solid electrolyte. The fiber membrane is obtained by the following method: (1) Prepare the skin spinning solution and the core spinning solution: mix the non-water-soluble polymer, the pore-forming agent and the solvent to form the skin spinning solution, and mix the pore-forming agent and the solvent to form the core spinning solution; (2) Use the skin spinning solution as the skin layer and the core spinning solution as the core layer to spin a solid fiber membrane by coaxial electrospinning; (3) Immerse the solid fiber membrane in water to remove the pore-forming agent, and then dry it to obtain the fiber membrane; the pore-forming agent is a water-soluble polymer; in the skin spinning solution, the weight concentration of the pore-forming agent is 7-15 wt%; in the core spinning solution, the weight concentration of the pore-forming agent is 40-70 wt%.

12. The preparation method according to claim 11, characterized in that, The fiber membrane is placed in the electrolyte for 5 to 60 hours.

13. The preparation method according to claim 11, characterized in that, The fiber membrane is placed in the electrolyte for 20 to 40 hours.

14. The preparation method according to claim 11, characterized in that, The above-mentioned sheath spinning solution and core spinning solution were extracted separately using disposable syringes and then coaxial electrospinning was performed.

15. The preparation method according to claim 14, characterized in that, The pore-forming agent is selected from at least one of polyvinylpyrrolidone and polyethylene glycol; and / or In the skin spinning solution, the weight concentration of the non-water-soluble polymer is 5-40 wt%.

16. The preparation method according to claim 15, characterized in that, In the core spinning solution, the weight concentration of the pore-forming agent is 40-50 wt%.

17. The preparation method according to claim 14, characterized in that, In step (2), the parameters of the coaxial electrospinning are: temperature 10-40℃, voltage 5-50KV, jet flow rate 0.1-1mL / h, and distance between the needle and the receiving plate 5-50cm; and / or, In step (3), the soaking time is 10-70 hours; and / or, the soaking temperature is 10-80°C; and / or, In step (3), the drying temperature is 40–90°C; and / or the drying time is 2–40 h.

18. A solid electrolyte obtained by the preparation method according to any one of claims 11 to 17.

19. The application of the solid electrolyte according to any one of claims 1 to 10 or the solid electrolyte obtained by the preparation method according to any one of claims 11 to 17 in an air battery.

20. The application according to claim 19, in a zinc-air battery.

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