CN111403804A - A kind of polymer matrix composite solid electrolyte film and preparation method thereof - Google Patents

Abstract

The invention relates to a polymer-based composite solid electrolyte film using magnetic composite fiber as filler and a preparation method thereof, and the polymer-based composite solid electrolyte film comprises the following components: a magnetic composite fiber; and a polymer matrix in which lithium salt is dissolved, wherein the volume ratio of the magnetic composite fibers is 0.5-2%, the volume ratio of the polymer is 99.5-98%, and the magnetic composite fibers are vertically oriented in the polymer matrix. The method comprises the following steps: 1) preparing the precursor sol into the magnetic composite fiber by an electrostatic spinning method and a calcining process; 2) the polymer matrix dissolved with lithium salt and the magnetic composite fiber are compounded again to form a film, and a magnetic field is introduced for orientation regulation. The process can control the distribution and orientation of the filler in the composite film, thereby improving the mechanical and electrical properties of the composite film by regulating and controlling the distribution structure of the filler and finally improving the room-temperature ionic conductivity of the solid electrolyte film.

Description

A kind of polymer matrix composite solid electrolyte film and preparation method thereof

technical field

The invention belongs to the technical field of preparation of solid electrolyte materials, in particular to a polymer-based composite solid electrolyte film using magnetic composite fibers as fillers and a preparation method thereof.

Background technique

As an important electrochemical energy storage device, lithium batteries are widely used in portable electronic devices such as mobile phones and notebook computers due to their high energy density, low self-discharge effect, and fast charge-discharge characteristics. Vehicles occupy a large share, and many famous car brands are scrambling to research lithium battery-based power vehicles with higher energy density and higher safety performance. In the field of energy storage device materials, with the rapid development of electronic devices in recent years, widely used energy storage devices are developing in the direction of high energy storage, miniaturization and environmental protection. The electrolyte material of traditional lithium-ion batteries is composed of organic solvents dissolved in lithium salts. There is a danger of electrolyte leakage, combustion, and even explosion, and the battery packaging requirements are very high, and lithium dendrites are easily generated during use. , The electrolyte is unstable and easy to decompose. On the contrary, since the solid electrolyte does not contain liquid components, it can effectively avoid the danger of electrolyte burning and explosion, and because it does not contain liquid components, the volume of the entire battery can be compressed to a small size, which improves the energy density of the battery; but solid electrolytes The contact with the electrodes is poor, resulting in a large interfacial contact resistance, resulting in a low room temperature ionic conductivity. Polymer materials are widely used in solid electrolyte materials due to their advantages of easy processing, good flexibility, light weight, good compatibility with electrodes, and the ability to form large-area membranes. The selection requirements for polymer materials are: light weight, easy processing, low cost and good mechanical properties, low glass transition temperature, etc. This polymer solid electrolyte has low contact resistance between the electrode and the electrode, and its thermodynamic performance is good, but their room temperature ionic conductivity is low, and the mechanical properties need to be improved to suppress the lithium dendrite problem and prevent the battery from The electrolyte membrane is ruptured due to collision during use, and the positive and negative electrodes are short-circuited. The study found that adding a certain amount of small-sized inorganic ceramic fillers can reduce the crystallinity of the polymer and promote the movement of polymer segments, and some groups of the inorganic ceramic fillers may interact with the polymer matrix and lithium salts. This interaction is beneficial to the dissociation of lithium salts and inhibits the kinetics of polymer recrystallization, thereby increasing the concentration of lithium ion carriers, the mobility of amorphous polymer segments, and improving the ionic conductivity at room temperature.

At present, there has been a lot of progress in the research of polymer-based composite solid-state electrolyte materials. Most of these works are based on the consideration of polymer matrix, inorganic ceramic filler and their interaction. A polymer matrix with a low degree of density is used, a fast ion conductor filler that can transport lithium ions by itself is selected, and surface modification is carried out by means of atomic deposition (ALD) to design favorable interactions and accelerate lithium ion conduction. Zhang et al., studied the synergistic coupling between tantalum-doped lithium lanthanum zirconium oxide (Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ ) and polyvinylidene fluoride (PVDF) and the electrolyte ionic conductivity, mechanical strength, thermodynamic stability relationship between sex. The study found that the La atom in LLZTO can cooperate with solvent molecules, such as the N atom and C=O functional group in nitrogen nitrogen dimethylformamide (DMF), resulting in the N atom being in an electron-rich state, showing the characteristics of Lewis base. , induces the dehydrofluorination behavior of PVDF chains, and the partially modified PVDF segments can activate the interaction between PVDF, lithium salts, and LLZTO segments, resulting in improved ionic conductivity, mechanical properties, and thermal stability of the composite electrolyte. Yi et al. studied the effect of the shape (nanofibers, nanotubes, nanosheets) of barium titanate (BaTiO3 ₎ nanofillers on the properties of polyethylene oxide (PEO)-based electrolytes, and found that: BaTiO3 nanofillers have organic surface The functional group has a good affinity with the PEO matrix, so that it can be distributed evenly in the electrolyte film _; when BaTiO3 nanosheets are added, the XRD main diffraction peak intensity of the polymer matrix PEO is the lowest, and the DSC melting temperature Tm is the lowest. The effect of reducing the crystallinity of the polymer matrix of BaTiO ₃ nanosheets has the greatest impact; the study of the shift of the COC peak in the infrared spectrum (FTIR) shows that the -OH and -OR groups on the surface of BaTiO ₃ nanofillers can interact with the polymer matrix PEO O atoms in the segment, Li ⁺ in lithium salts interact, thereby weakening the complexation between Li ⁺ and O atoms and promoting Li ⁺ transport along the PEO segment _; BaTiO3 nanofillers spontaneous polarization and surface charge induction The interface is formed, and the formed interface has a high dielectric constant, there are various defects, which is conducive to the migration of Li ⁺ , _of which BaTiO3 nanosheets have the largest specific surface area, which is most conducive to the formation of this interface, and thus the ionic conductivity The improvement is the most significant, and the room temperature ionic conductivity of BaTiO3 nanosheet-PEO- _LiTFSI electrolyte reaches 1.8 × 10 ^-5 S/cm.

The researchers found that fast lithium ion transport can be achieved by designing the size and shape of the interface between the polymer matrix and the inorganic ceramic filler, thereby improving the room temperature ionic conductivity of the electrolyte. Liu et al., investigated the effect of ceramic nanofibers without alignment on the ionic conductivity of composite polymer electrolytes. The study found that when the ceramic nanofiber filler in the polymer matrix has an included angle of 0° with the normal direction of the electrode surface, that is, when the fast conduction path of Li ⁺ along the fiber-polymer interface is the shortest, compared with the pure polymer electrolyte without filler ( 4.31×10 ^-7 S/cm), the composite polymer electrolyte (7.82 × 10 ^-6 S/cm) with any arrangement of fiber fillers, the composite polymer electrolyte with good arrangement and the shortest fast conduction path has better ionic conductivity. The ionic conductivity at room temperature reaches 5.02×10 ^-5 S/cm, and the corresponding mechanical properties and cycle stability are also improved. Zhang et al. investigated the effect of continuous vertically aligned nanoscale ceramic-polymer interfaces on the ionic conductivity of composite solid polymer electrolytes, first designing alumina (Al ₂ O ₃ ) ceramic disks with different nanotube sizes , and then the polyethylene oxide-lithium bistrifluoromethanesulfonimide (PEO-LiTFSI) solid polymer electrolyte film was laminated on the Al ₂ O ₃ ceramic disk at 65 °C, and finally the laminated film was placed on the ceramic disk. The composite solid-state polymer electrolyte with vertical, continuous nano-scale interface was deposited in a vacuum furnace at 215 °C, and the electrolyte was fully melted and penetrated into the Al ₂ O ₃ nanotubes. Atomic deposition technology (ALD) was used to deposit a nanotube. A strong Lewis acid-AlF ₃ , further studies found that: for pure polymer electrolyte (PEO ^- LiTFSI) Li transport can only be achieved by ether oxygen-assisted hopping or polymer segment motion; composite solid polymer electrolyte (PEO-LiTFSI) PEO-LiTFSI ^- Al ₂ O ₃ ) has two Li conduction pathways, the first is Li transport induced by ether oxygen or polymer segment motion, ^and the second is transport along the ceramic-polymer interface. Finally, by selecting a reasonable and smaller size of Al ₂ O ₃ ceramic sheets for nanotubes, surface modification of the nanotubes by ALD, and selecting PEG with a smaller molecular weight as the polymer matrix, a room temperature ionic conductivity of 5.82× was obtained. 10 ^-4 S/cm composite solid polymer electrolyte.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a polymer-based composite solid electrolyte film and a preparation method thereof in view of the above-mentioned prior art, which can shorten the lithium ion transmission path, realize the rapid transmission of lithium ions, and improve the room temperature ionic conductivity of the solid electrolyte.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a polymer-based composite solid electrolyte film, which comprises: magnetic composite fibers; and a polymer matrix dissolved with lithium salt, wherein the volume ratio of the magnetic composite fibers is 0.5 % to 2%, the volume ratio of the polymer is 99.5% to 98%, and the magnetic composite fibers are arranged in a vertical orientation in the polymer matrix.

According to the above scheme, the magnetic composite fiber is composed of a 1-dimensional fiber matrix and 0-dimensional magnetic oxide particles filled in the fiber, the material of the fiber matrix is lithium lanthanum titanate, and the 0-dimensional magnetic oxide particles The particles are ferric oxide nanoparticles, and the lithium salt is lithium bistrifluoromethanesulfonimide.

According to the above scheme, the diameter of the magnetic composite fiber is 200 nm-1 μm, the length is 1 μm-20 μm, and the filled 0-dimensional magnetic oxide particles have a diameter of 20 nm.

According to the above scheme, the polymer matrix is composed of one or more materials selected from polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), and polyacrylonitrile (PAN).

According to the above scheme, the thickness of the composite solid electrolyte membrane is 20 μm˜60 μm.

According to the above scheme, in the magnetic composite fiber, the volume ratio of the filled 0-dimensional magnetic oxide particles to the 1-dimensional fiber matrix is 1:2.

The preparation method of the polymer-based composite solid electrolyte film comprises the following steps:

1) preparing the precursor sol by an electrospinning method and a calcination process to obtain a magnetic composite fiber;

2) The polymer matrix dissolved in lithium salt and the magnetic composite fiber are composited into a film again, and a magnetic field is introduced to adjust the orientation.

According to the above scheme, wherein the polymer matrix and the magnetic composite fiber are composited into a film again by a solution casting method and a method of introducing an external magnetic field perpendicular to the upper and lower sides of the electrolyte film during the solvent drying process.

According to the above scheme, the precursor sol is prepared by the following method: using lithium nitrate and lanthanum nitrate hexahydrate as the source of Li and La, weighed according to the molar ratio of Li excess 10%, dissolved in DMF and acetic acid, and dissolved completely Then, tetrabutyl titanate was added as the Ti source, and the LLTO stock solution was obtained after the stirring was completed, and then an appropriate amount of ferric tetroxide nanoparticles was added, and after stirring uniformly, polyvinylpyrrolidone was finally added, and the spinning precursor was obtained after the stirring was completed. sol.

In the composite solid polymer electrolyte, the transport paths of lithium ions mainly include: ① through the polymer phase; ② through the ceramic phase; ③ through the polymer/ceramic interface. And due to the excellent electrochemical properties of the ceramic phase, lithium ions are more inclined to pass through the ceramic phase and the polymer/ceramic interface. Therefore, by designing the vertical orientation of the ceramic filler in the polymer matrix, the fast transport path of lithium ions can be shortened to achieve Further improvement of the ionic conductivity of composite solid polymer electrolytes. Therefore, based on the idea of designing the interface between the polymer matrix and the inorganic ceramic filler perpendicular to the surface of the solid electrolyte film, the present invention designs a novel composite solid electrolyte film preparation process, which can not only prepare high-efficiency composite solid electrolyte films. High-quality organic-inorganic composite solid electrolyte film, and at the same time, the distribution and orientation of inorganic fillers in the polymer composite material can be regulated, and a composite solid electrolyte film with a specific composite structure is prepared.

The invention firstly prepares the magnetic composite fibers, and then composites the treated magnetic composite fibers with the polymer matrix. Through the auxiliary action of an external magnetic field, the magnetic nano-composite fibers are arranged in a vertical orientation in the polymer matrix, and the lithium ions are shortened. It can realize the rapid transmission of lithium ions, thereby improving the room temperature ionic conductivity of the polymer-based composite solid electrolyte. At the same time, because the ceramic fillers are arranged along the out-of-plane direction of the electrolyte film, the mechanical properties of the electrolyte film in the out-of-plane direction are further improved. It is beneficial to inhibit the growth of lithium dendrites during the cycle of the battery.

The effective effects of the present invention are: (1) the preparation process is simpler, and the thickness of the film can be effectively controlled; (2) the general composite solid electrolyte film preparation process can only prepare a composite film with randomly dispersed fillers, and the process of the present invention can be controlled The distribution and orientation of the filler inside the composite film, so that the mechanical and electrical properties of the composite film can be improved by adjusting the distribution structure of the filler, and finally the room temperature ionic conductivity of the solid electrolyte film can be improved. Compared with the random distribution of fibers in the polymer matrix, the room temperature ionic conductivity of the composite solid electrolyte film is greatly improved, and it is expected to be widely used in solid electrolyte materials.

Description of drawings

Fig. 1 is the scanning electron microscope picture before calcination of the composite nanofiber prepared by the electrospinning method in Example 1;

Fig. 2 is the scanning electron microscope picture and EDS picture after calcination of the composite nanofiber prepared by the electrospinning method in embodiment 1;

3 is a scanning electron microscope picture of the cross-section of the solid electrolyte film with random distribution and vertical orientation distribution of fibers prepared by casting after mixing PVDF and composite fibers with different contents in Example 2, Example 3, Example 4, and Example 5;

4 is the AC impedance spectrum of the composite solid electrolyte with fiber volume fractions of 0vol%, 0.5vol%, 1vol%, and 2vol% in Example 2, Example 3, Example 4, and Example 5, respectively;

Figure 5 shows the room temperature ions of the solid electrolytes with random distribution and vertical orientation distribution of fibers with fiber volume fractions of 0vol%, 0.5vol%, 1vol%, and 2vol% in Example 2, Example 3, Example 4, and Example 5, respectively. Plot of conductivity as a function of fiber content.

Fig. 6 shows the random distribution and vertical orientation distribution of solid electrolytes with fiber volume fractions of 0vol%, 0.5vol%, 1vol%, and 2vol% in Example 2, Example 3, Example 4, and Example 5 at room temperature. relative battery performance.

Detailed ways

Taking the γ-Fe ₂ O ₃ nanoparticle/LLTO nanocomposite fiber and PVDF as the polymer matrix and LiTFSI as the lithium salt as an example, the preparation process of the composite fiber and its polymer-based solid electrolyte film is as follows:

(1) Preparation of precursor sol for composite fiber spinning, taking the preparation of γ-Fe ₂ O ₃ nanoparticles/Li _0.33 La _0.557 TiO ₃ magnetic nanocomposite fibers as an example: first measure a certain amount of lithium nitrate and lanthanum nitrate hexahydrate , the mass of lithium is more than 10wt%, which is used to compensate for the loss of lithium in the subsequent high-temperature sintering process. The molar ratio of the remaining Li and La is 0.33:0.557, which is dissolved in a certain amount of DMF and acetic acid. Add a certain amount of tetrabutyl titanate, wherein the molar ratio of La to Ti is 0.557:1, and then add a certain amount of acetylacetone until the solution is stirred evenly to obtain the LLTO stock solution, then take a certain amount of the above stock solution, add an equal amount DMF, weighed an appropriate amount of Fe ₃ O ₄ nanoparticles, crushed the cells, added the mixed solution of the previous step, stirred evenly, and finally added polyvinylpyrrolidone (PVP, M=1300000) and stirred to a uniform and stable state to form a spinning Silk precursor sol.

(2) Transfer the above-mentioned spinning precursor sol into a syringe, electrospin at a voltage of 1 kV/cm, and adopt a roller receiving method to obtain a composite fiber precursor.

(3) The composite fiber precursor was sintered at 850° C. for 2 hours at a heating rate of 5° C./min to obtain a composite fiber.

(4) After the above-mentioned magnetic composite fibers are treated by ultrasonic, drying and other means, they are added to the fully dissolved PVDF and LiTFSI solutions, and after stirring evenly, a film of a certain thickness is obtained by the solution casting method, and vacuum-dried at 80°C At the same time, an external magnetic field with suitable magnetic field strength perpendicular to the upper and lower sides of the electrolyte film is introduced, and finally a solid electrolyte film in which the magnetic composite fiber filler is vertically aligned in the polymer matrix is obtained.

The following examples will further illustrate the present invention:

Example 1:

Weigh and measure 1.045g lithium nitrate, 5.47g lanthanum nitrate hexahydrate, dissolve in 5ml DMF, 2ml acetic acid, and stir to a uniform and stable state, then add 10.419g of tetrabutyl titanate and continue stirring to a uniform and stable state to obtain LLTO stock solution, then Take out 3ml of the above prepared stock solution, add 0.5g Fe ₃ O ₄ nanoparticles and pulverize 300W power cells in 3ml DMF for 8 hours, add 3ml LLTO stock solution taken out in the previous step, stir evenly for 30 minutes, add 0.5g PVP and stir for 3 hours to form a stable sol, transfer the sol to Electrospinning was carried out in a syringe. Electrospinning was carried out under an electric field of 1kV/cm, and the sol was changed every 30 min. The morphology of the electrospun fibers was obtained by roller collection. The diameter of the fiber was about 1 μm, and the Fe ₃ O ₄ nanoparticles were relatively uniformly attached to the surface of the fiber; then the fiber was calcined at 800 °C at a heating rate of 5 °C/min for 2 h to obtain the final magnetic composite fiber. The morphology of the obtained magnetic composite fiber is shown in SEM Figure 2. It can be seen that the diameter of the fiber after calcination is reduced to about 200 nm, and the magnetic particles are uniformly distributed on the surface of the fiber from the EDS energy spectrum.

Comparative Example 2:

Weigh 1g PVDF powder and 0.33g LiTFSI in the glove box, dissolve them in 10ml DMF solvent, fully stir for 24h, carry out solution-casting, and dry at 80°C for 24h to obtain PVDF/LiTFSI solid polymer electrolyte film. As can be seen from a ₀ and a ₁ in Figure 3, the cross-section of the pure PVDF/LiTFSI solid polymer electrolyte film is relatively dense, and no obvious pores are generated, which is beneficial to the transport of lithium ions.

Example 3:

Take 0.05g of the magnetic composite fiber in Example 1 into 50ml of ethanol, ultrasonicate for 2min under 40W power, and then centrifuge and dry to obtain short magnetic composite fibers with a size of 1μm-20μm. Measure 3ml of DMF solvent, add 0.014g , the composite fiber, 40W ultrasonic for 2min, and then added to the sol with PVDF and LiTFSI that was stirred evenly in advance, stirred for 5h to a uniform and stable state, and then the mixed solution was cast, and dried at 80 °C for 24h. A part of the composite solid electrolyte film with a volume fraction of 0.5vol% fibers randomly oriented and vertically oriented can be obtained by introducing a parallel magnetic field with suitable magnetic field strength along the upper and lower sides of the electrolyte film while drying. As can be seen from b ₀ and b ₁ in Figure 3, the fiber fillers in the composite electrolyte film oriented by the magnetic field obviously show a vertical orientation arrangement trend (as shown in Figure b ₀ ), while in the composite electrolyte film without magnetic field adjustment, the fibers The fillers are obviously randomly distributed and tend to be parallel distributed along the plane. (shown in Figure b1 ₎

Example 4:

Take 0.05g of the composite fiber in Example 1 into 50ml of ethanol, ultrasonicate for 2min under 40W power, then centrifuge and dry to obtain short magnetic composite fibers with a size of 1μm-20μm, measure 3ml of DMF solvent, add 0.028g of The composite fiber was ultrasonicated at 40W for 2 minutes, then added to the sol with PVDF and LiTFSI that had been stirred evenly in advance, stirred for 5 hours to a uniform and stable state, and then the mixture was cast and dried at 80 °C for 24 hours. While drying, a parallel magnetic field with suitable magnetic field strength is introduced along the upper and lower sides of the electrolyte membrane to obtain a composite solid electrolyte membrane in which the fibers are randomly distributed and oriented with a volume fraction of 1 vol% and the fibers are arranged in a vertical orientation. As can be seen from c ₀ and c ₁ in Figure 3, the fiber fillers in the composite electrolyte film oriented by the magnetic field obviously show a vertical orientation trend (as shown in Figure c ₀ ), while in the composite electrolyte film without magnetic field adjustment, the fibers The fillers are obviously randomly distributed and tend to be parallel distributed along the plane. (Fig. c ₁ ) At the same time, due to the increase of fibrous filler content, the filler begins to agglomerate in the polymer matrix, which will be unfavorable for the transport of lithium ions.

Example 5:

Take 0.05g of the composite fiber in Example 1 into 50ml of ethanol, ultrasonicate for 2min under 40W power, and then centrifuge and dry to obtain short magnetic composite fibers with a size of 1μm-20μm, measure 3ml DMF solvent, add 0.056g of The composite fibers were ultrasonicated at 40W for 2 minutes, then added to the sol with PVDF and LiTFSI that had been stirred evenly in advance, stirred for 5 hours to a uniform and stable state, and then the mixture was cast and dried at 80 °C for 24 hours. While drying, a parallel magnetic field with suitable magnetic field strength is introduced along the upper and lower sides of the electrolyte film to obtain a composite solid electrolyte film with a volume fraction of 2 vol% fibers randomly distributed and oriented and the fibers are arranged in a vertical orientation. As shown in d ₀ and d ₁ in Figure 3, it can be seen that the fiber fillers in the composite electrolyte film oriented by the magnetic field obviously show a vertical orientation arrangement trend (as shown in Figure d ₀ ), while in the composite electrolyte film without magnetic field adjustment, The fibrous fillers are obviously randomly distributed and tend to be parallel in the plane. (Fig. d ₁ ) At the same time, due to the further increase of the fibrous filler content, the agglomeration of the filler in the polymer matrix is serious, and the cross-section of the electrolyte membrane begins to show obvious holes.

Example 6:

Take the pure PVDF/LiTFSI solid polymer electrolyte film in Example 2 and the composite solid electrolyte film in which the fibers with a filler content of 1 vol% are randomly distributed and oriented and the fibers are vertically oriented in Example ₄ , and LiCoO2 is assembled in a glove box. |Solid electrolyte membrane|Li battery, cycled for 30 cycles at a rate of 0.1C to compare the cycling performance of the three batteries. As shown in Figure 6, it can be seen that the pure PVDF/LiTFSI solid polymer electrolyte battery has poor cycle performance due to low room temperature ionic conductivity, and the capacity decays from 119.8mAh g ^-1 in the first cycle to 38.0mAh g after 30 cycles. ^-1 (as shown in Figure 6a); the composite solid-state electrolyte battery with 1vol% fibers randomly distributed and oriented, due to the improvement of ionic conductivity at room temperature, the battery cycle performance is significantly improved, and the capacity after 30 cycles decays from 113.9mAh g ^-1 in the first cycle to 111.4mAh g ^-1 , but due to the redox reaction between LLTO and Li metal in the composite fiber, the battery cycle is not stable (as shown in Figure 6b); the composite solid electrolyte battery with 1 vol% fiber out-of-plane distribution orientation is due to the room temperature ionic conductivity After 30 cycles, the capacity of the battery changed from 117.0mAh g ^-1 in the first cycle to 119.5mAh g ^-1 , and due to the vertical orientation of the fibers along the electrolyte membrane, the contact between the composite fibers and Li metal The smaller area avoids a large number of reactions between the fiber filler and Li metal, so the battery has more stable and excellent cycle performance. (Figure 6c)

Figure 4 is the AC impedance spectrum of the electrolyte films prepared in Examples 2, 3, 4, and 5. According to the AC impedance spectrum, the bulk impedance of the electrolyte membrane can be obtained, and then the peaks of each electrolyte film can be calculated according to the ionic conductivity calculation formula The ionic conductivity is shown in Figure 5. It can be found that after adding ceramic fillers, the ionic conductivity of the composite solid dielectric film is higher than that of the pure polymer electrolyte film, and in all components, the fibers after the magnetic field control show The ionic conductivity of the vertically oriented composite solid electrolyte film is further improved, which is higher than that of the composite solid electrolyte film with random distribution of fibers of the same composition.

Claims (9)

1. A polymer-based composite solid electrolyte membrane having a composition comprising: a magnetic composite fiber; and a polymer matrix in which lithium salt is dissolved, wherein the volume ratio of the magnetic composite fibers is 0.5-2%, the volume ratio of the polymer is 99.5-98%, and the magnetic composite fibers are vertically oriented in the polymer matrix.

2. The polymer-based composite solid electrolyte membrane according to claim 1, wherein the magnetic composite fiber is composed of a 1-dimensional fiber matrix and 0-dimensional magnetic oxide particles filled in the fiber, the fiber matrix is made of lanthanum lithium titanate, the 0-dimensional magnetic oxide particles are ferroferric oxide nanoparticles, and the lithium salt is lithium bistrifluoromethanesulfonylimide.

3. The polymer-based composite solid electrolyte membrane according to claim 2, characterized in that the magnetic composite fiber has a diameter of 200nm to 1 μm and a length of 1 μm to 20 μm, and the filled 0-dimensional magnetic oxide particle has a diameter of 20 nm.

4. The polymer-based composite solid electrolyte membrane according to claim 1, wherein the polymer matrix is made of one or more materials selected from polyvinylidene fluoride, polyethylene oxide, and polyacrylonitrile.

5. The polymer-matrix composite solid electrolyte membrane according to claim 1, characterized in that the thickness of said composite solid electrolyte membrane is 20 μm to 60 μm.

6. The polymer-based composite solid electrolyte membrane according to claim 2, characterized in that the magnetic composite fiber has a volume ratio of filled 0-dimensional magnetic oxide particles to 1-dimensional fiber matrix of 1: 2.

7. The method for producing a polymer-based composite solid electrolyte membrane according to claim 1, comprising the steps of:

1) preparing the precursor sol into the magnetic composite fiber by an electrostatic spinning method and a calcining process;

2) the polymer matrix dissolved with lithium salt and the magnetic composite fiber are compounded again to form a film, and a magnetic field is introduced for orientation regulation.

8. The method for producing a polymer-based composite solid electrolyte membrane according to claim 7, wherein the polymer matrix and the magnetic composite fiber are again compounded to form a membrane by a solution casting method and an external magnetic field is introduced perpendicularly to the upper and lower surfaces of the electrolyte membrane during solvent drying.

9. The preparation method of the polymer-based composite solid electrolyte film according TO claim 7 or 8, characterized in that the precursor sol is prepared by taking lithium nitrate and lanthanum nitrate hexahydrate as L i and L a sources, weighing according TO the molar ratio of L i excessive by 10%, dissolving in DMF and acetic acid, adding tetrabutyl titanate as a Ti source after complete dissolution, stirring completely TO obtain LL TO stock solution, then adding a proper amount of ferroferric oxide nanoparticles, stirring uniformly, finally adding polyvinylpyrrolidone, and stirring completely TO obtain spinning precursor sol.

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