Composite double-super-ion solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a composite double-super-ion solid electrolyte and preparation and application thereof, the composite double-super-ion solid electrolyte comprises a polymer matrix, a lithium salt and an inorganic electrolyte filler, the mass ratio of the inorganic electrolyte filler to the polymer matrix is 1: 1-20, and the lithium salt accounts for 1-80 wt% of the total weight of the solid electrolyte. According to the composite double-super-ion solid-state electrolyte, the inorganic electrolyte filler is added and is combined with the polymer matrix, so that the composite double-super-ion solid-state electrolyte integrates the advantages of the polymer solid-state electrolyte and the inorganic solid-state electrolyte, and the inorganic electrolyte filler provides an additional Li < + > transmission path; the conductivity and the lithium ion transference number of the electrolyte are effectively improved, and the solid electrolyte has excellent mechanical properties and is simple to prepare, so that the solid electrolyte has relatively high mechanical strength, electrochemical stability, interfacial compatibility and room-temperature ionic conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer solid electrolyte materials, and particularly to a composite double superionic solid electrolyte and a preparation method and application thereof. Background Art

[0002] As a new type of battery technology, lithium metal anode solid-state batteries have attracted extensive research interest globally in recent years. To achieve the commercial application of lithium metal anode solid-state batteries, the key lies in developing solid electrolytes with high ionic conductivity, excellent mechanical strength, good interfacial compatibility, easy processing, and excellent chemical / electrochemical stability.

[0003] Currently, there are still many problems in the practical application of solid-state batteries. For example, inorganic / ceramic solid electrolytes have poor chemical and electrochemical stability, poor processability, and large solid / solid interfacial impedance, which are prone to side reactions; there are internal contradictions among ionic conductivity, lithium ion transference number, and mechanical strength in polymer electrolytes. The above adverse factors will damage the internal structure of solid-state batteries and lead to battery failure, severely limiting the practical application of high specific energy solid-state batteries. Patent CN118825387A developed a polymer solid electrolyte material with a new transmission mechanism and disclosed a composite double superionic solid electrolyte of chemically grafted polyvinylidene fluoride-based. The introduction of functional groups increased the proportion of the highly polar β crystalline phase of the PVDF-based polymer and the dielectric constant of the copolymer, which was beneficial to the further dissociation of high-concentration lithium salts. Combining the high-density polar functional groups in the functional groups to construct a lithium ion transport channel realized the decoupling of lithium ion conduction and segmental motion, showing the characteristics of a superionic conductor. The solid electrolyte of the PVDF graft copolymer showed high ionic conductivity and a relatively high lithium ion transference number. However, in the above technology, relying solely on the dissociation of lithium salts by chemically grafting polyvinylidene fluoride-based and the decoupling of lithium ion conduction and segmental motion, there is still a relatively low ionic conductivity in practical applications. Its ionic conductivity at 30 °C is at most 4.2×10 -4 S·cm -1 and at least 1.7×10 -4 S·cm -1 . Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a composite double superionic solid electrolyte to solve the above-mentioned traditional technical problems. This solid electrolyte has high mechanical strength, electrochemical stability, interfacial compatibility, and room temperature ionic conductivity.

[0005] Another objective of the present invention is to provide a preparation method of the above composite double superionic solid electrolyte.

[0006] A third object of the present invention is to provide an application of using the above composite double superionic solid electrolyte in the preparation of secondary batteries.

[0007] The first object of the present invention is achieved by the following technical solutions:

[0008] A composite double superionic solid electrolyte, comprising a polymer matrix, a lithium salt, and an inorganic electrolyte filler, wherein the mass ratio of the inorganic electrolyte filler to the polymer matrix is 1:1 to 20, and the lithium salt accounts for 1 wt% to 80 wt% of the total weight of the solid electrolyte.

[0009] In the present invention, by adding an inorganic electrolyte filler and combining it with the polymer matrix, the composite double superionic solid electrolyte combines the advantages of polymer solid electrolytes and inorganic solid electrolytes. The inorganic electrolyte filler provides an additional Li + transport path, effectively improving the electrolyte conductivity and lithium ion transference number, and having excellent mechanical properties and simple preparation, making the solid electrolyte have high mechanical strength, electrochemical stability, interfacial compatibility, and room temperature ionic conductivity.

[0010] In the present invention, the mass ratio of the inorganic electrolyte filler to the polymer matrix can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.

[0011] The proportion of the lithium salt in the total weight of the solid electrolyte can be 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, etc.

[0012] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objects and beneficial effects of the present invention can be better achieved.

[0013] Further, the mass ratio of the inorganic electrolyte filler to the polymer matrix is 1:3 to 13.

[0014] Further, the mass ratio of the lithium salt to the polymer matrix is 1:2 to 30.

[0015] Further, the inorganic electrolyte filler is one or more of an oxide ceramic electrolyte, a halide ceramic electrolyte, or a sulfide ceramic electrolyte. Preferably, the inorganic electrolyte filler is a lithium indium chloride halide solid electrolyte (Li 3InCl 6 ) and lithium lanthanum zirconium tantalum oxide ceramic electrolyte (Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , abbreviated as LLZTO), lithium lanthanum titanate / lithium titanate oxide electrolyte (Li 0.33 La 0.56 TiO 3 , abbreviated as LLTO), lithium lanthanum zirconium oxide / lithium zirconate oxide electrolyte (Li 7 La 3 Zr 2 O 12 , abbreviated as LLZO), lithium aluminum titanium phosphate electrolyte (Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 , abbreviated as LATP), lithium zirconium chloride halide electrolyte (Li 2 ZrCl 6 ), Thio-LISICON type sulfide solid electrolyte (chemical general formula is Li4-xGe1-xPxS4 (A = Ge, Si, etc., B = P, Al, Zn, etc.)), LGPS series sulfide solid electrolytes (such as Li 10 GeP 2 S 12 ), Li-argyrodite type sulfide solid electrolyte (including Li 6 PS 5 X (X = Cl, Br, I, etc.) materials), sulfide glass and glass ceramic solid electrolytes (Li 2 S-P 2 S 5 , Li 2 S-SiS 2 , Li 2 S-B 2 S 3 ), layered structure sulfide solid electrolyte (such as Li 0.6 [Li 0.2 Sn 0.8 S 2 ).

[0016] Among them, the halide is Cl, Br, F, I.

[0017] Furthermore, the polymer matrix is chemically grafted polyvinylidene fluoride, poly(vinylidene fluoride-trifluorochloroethylene) copolymer or poly(vinylidene fluoride-hexafluoropropylene) copolymer, and their structural formulas are shown in Formula 1, Formula 2, and Formula 3 respectively:

[0018]

[0019] Among them, R 1 and R 2 groups are independently selected from one of the following groups;

[0020]

[0021] R 1 ' and R 2 ' are selected from H or CH 3 ;

[0022] m, n, x, and y represent the number of repeating units of the polymerization monomer; m is any integer from 100 to 10,000, n is any integer from 100 to 10,000, x is any integer from 100 to 100,000, and y is any integer from 100 to 10,000.

[0023] The above polymer matrix can be prepared by a conventional free radical polymerization method.

[0024] Furthermore, the lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium fluoride, lithium bromide, and lithium iodide.

[0025] The second object of the present invention is achieved by the following technical solution:

[0026] A preparation method of a composite double superionic solid electrolyte includes the following steps:

[0027] S1: Dissolve the polymer matrix and the lithium salt separately in an organic solvent, stir to form a homogeneous transparent solution, and obtain a mixed solution;

[0028] S2: Add an inorganic electrolyte filler to the mixed solution, ultrasonically mix evenly to obtain an electrolyte mixture;

[0029] S3: Film the above electrolyte mixture, volatilize part of the organic solvent in a dry environment, and transfer it to a vacuum drying oven for further drying to finally obtain a composite double superionic solid electrolyte.

[0030] Furthermore, in step S1, the organic solvent is one or more of DMF, NMP, DMAC, EAC, and DMSO.

[0031] Furthermore, in step S3, the film formation method is to use a doctor blade coating or casting film formation method, or a hot pressing method to prepare a uniform electrolyte film.

[0032] The third object of the present invention is achieved by the following technical solution:

[0033] A secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the above-mentioned composite double superionic solid electrolyte.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. By adding inorganic electrolyte fillers to the composite double superionic solid electrolyte of the present invention, the combination with the polymer matrix enables the composite double superionic solid electrolyte to integrate the advantages of polymer solid electrolytes and inorganic solid electrolytes. The inorganic electrolyte fillers provide additional Li + transport paths, effectively improving the electrolyte conductivity and lithium ion transference number, and having excellent mechanical properties and simple preparation, making the solid electrolyte have high mechanical strength, electrochemical stability, interfacial compatibility, and room temperature ionic conductivity.

[0036] 2. The composite polymer double superionic solid electrolyte of the present invention is a composite double superionic solid electrolyte composed of a polymer matrix, a lithium salt, and inorganic electrolyte fillers. The polymer matrix is a chemically grafted polyvinylidene fluoride-based polymer, and the inorganic electrolyte fillers are oxide, halide, or sulfide ceramic electrolytes. The present invention introduces inorganic electrolyte fillers into the chemically grafted polyvinylidene fluoride-based polymer electrolyte system, providing multiple Li + transport paths, capable of rapidly conducting lithium ions, effectively improving the electrolyte conductivity, and simultaneously having the advantages of polymer solid electrolytes and inorganic solid electrolytes.

[0037] 3. Taking the oxide solid electrolyte (Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , LLZTO) @ chemically grafted polyacrylonitrile polyvinylidene fluoride-based polymer (PVDF-g-PAN) composite solid electrolyte prepared in the examples as an example, it has the following advantages:

[0038] 1) The polymer phase of the composite double superionic solid electrolyte has been proven to conduct by the hopping mechanism, achieving decoupling from the segmental motion. The PAN phase in the microphase separation network contains a large number of polar cyano groups, constructing a complete and high-density lithium ion transport site, which is conducive to the rapid transition of Li + along the C≡N sites and the PVDF / PAN two-phase interface. + 2) The introduction of inorganic electrolyte fillers provides additional Li

[0039] transport paths, including the inorganic electrolyte phase and the two-phase interface of inorganic electrolyte and polymer, changing the Li + transport path, including the inorganic electrolyte phase and the two-phase interface of inorganic electrolyte and polymer, changing the Li +The solvation environment effectively improves the electrolyte conductivity. The ionic conductivity of the LLZTO@PVDF-g-PAN composite solid electrolyte reaches up to 6.74×10 -4 S·cm -1 at 30 °C.

[0040] 1) The composite solid electrolyte prepared by the method of the present invention has a simple processing method and can be prepared on a large scale by doctor blade casting or hot pressing at high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 are the optical photographs of the composite double superionic solid electrolytes obtained in Examples 1-5 and Comparative Example 2 of the present invention;

[0042] Figure 2 are the ionic conductivities of the composite double superionic solid electrolytes obtained in Examples 1-5 and Comparative Examples 1-2 of the present invention at different temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention will be further described in detail below through specific examples. The following examples are only used to illustrate the present invention, but are not used to limit the scope of implementation of the present invention. All technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present invention. The raw materials and equipment used in the present invention are all common raw materials and equipment in the art without special instructions; the methods used in the present invention are all conventional methods in the art without special instructions.

[0044] Example 1

[0045] A composite double superionic solid electrolyte includes the following preparation steps:

[0046] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution at a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0047] S2: Add LLZTO to the mixed solution and ultrasonically mix evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:2;

[0048] S3: Film the above electrolyte mixture, volatilize part of the organic solvent in a dry environment, and transfer it to a vacuum drying oven for further drying to finally obtain a composite double superionic solid electrolyte.

[0049] Example 2

[0050] A composite double superionic solid electrolyte includes the following preparation steps:

[0051] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution according to a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0052] S2: Add LLZTO to the mixed solution and ultrasonically mix it evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:3;

[0053] S3: Prepare a film from the above electrolyte mixture, volatilize part of the organic solvent in a dry environment, and transfer it to a vacuum drying oven for further drying to finally obtain a composite double superionic solid electrolyte.

[0054] Example 3

[0055] A composite double superionic solid electrolyte includes the following preparation steps:

[0056] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution according to a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0057] S2: Add LLZTO to the mixed solution and ultrasonically mix it evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:4;

[0058] S3: Prepare a film from the above electrolyte mixture, volatilize part of the organic solvent in a dry environment, and transfer it to a vacuum drying oven for further drying to finally obtain a composite double superionic solid electrolyte.

[0059] Example 4

[0060] A composite double superionic solid electrolyte includes the following preparation steps:

[0061] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution according to a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0062] S2: Add LLZTO to the mixed solution and ultrasonically mix it evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:6;

[0063] S3: Fabricate a film from the above electrolyte mixture. In a dry environment, volatilize some of the organic solvents, and transfer it to a vacuum drying oven for further drying to finally obtain a composite dual-superionic solid electrolyte.

[0064] Example 5

[0065] A composite dual-superionic solid electrolyte includes the following preparation steps:

[0066] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution at a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0067] S2: Add LLZTO to the mixed solution and ultrasonically mix it evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:13;

[0068] S3: Fabricate a film from the above electrolyte mixture. In a dry environment, volatilize some of the organic solvents, and transfer it to a vacuum drying oven for further drying to finally obtain a composite dual-superionic solid electrolyte.

[0069] After testing, in Examples 1-5 above, from Figure 1 The optical photos show that LLZTO is evenly distributed in the PVDF-g-PAN polymer and agglomerates and precipitates when the LLZTO content increases to a mass ratio of 1:3 with the polymer.

[0070] Example 6

[0071] A composite dual-superionic solid electrolyte includes the following preparation steps:

[0072] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution at a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0073] S2: Add the lithium indium chloride solid electrolyte (Li 3 InCl 6 , LIC) to the mixed solution and ultrasonically mix it evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:4;

[0074] S3: Fabricate a film from the above electrolyte mixture. In a dry environment, volatilize some of the organic solvents, and transfer it to a vacuum drying oven for further drying to finally obtain a composite dual-superionic solid electrolyte.

[0075] Comparative Example 1

[0076] A solid electrolyte includes the following preparation steps:

[0077] S1: Dissolve the polyvinylidene fluoride-based polymer matrix PVDF-g-PAN polymer grafted with chemically modified polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution at a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0078] S2: Film the above mixed solution, volatilize part of the organic solvent in a dry environment, and transfer it to a vacuum drying oven for further drying to finally obtain a solid electrolyte.

[0079] Comparative Example 2

[0080] A solid electrolyte includes the following preparation steps:

[0081] S1: Dissolve the PVDF polymer and lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) in a DMF solution at a mass ratio of 2:1, and stir at 60 °C until a uniform transparent solution is formed to obtain a mixed solution;

[0082] S2: Add LLZTO to the mixed solution and ultrasonically mix evenly to obtain an electrolyte mixture; wherein, the mass ratio of LLZTO to the polymer matrix is 1:9;

[0083] S3: Film the above electrolyte mixture, volatilize part of the organic solvent in a dry environment, and transfer it to a vacuum drying oven for further drying to finally obtain a solid electrolyte.

[0084] After testing, as Figure 1 shown in the optical photograph, the solid electrolyte of Comparative Example 2 shows that LLZTO is unevenly distributed in the PVDF matrix.

[0085] Performance Test

[0086] Application Example 1

[0087] For the solid electrolytes in Examples 1-5, Comparative Example 1 and Comparative Example 2, perform an ion conductivity test: The sample to be tested is assembled into a battery by sandwiching it between two stainless steel sheets (SS, stainless steel). Using a French Bio-Logic VPM3 multi-channel electrochemical workstation, in the frequency range of 1-10 5Under the condition of a sine amplitude voltage of 10 mV at [[Hz]], an AC impedance spectrum test was carried out, and the temperature for the ionic conductivity test was 30 - 80 °C. The ionic conductivity (σ) can be calculated by the following formula: σ = d / R × S, where σ represents the ionic conductivity, d represents the thickness of the test sample, R represents the bulk resistance, and S represents the area of contact between the test sample and the steel sheet.

[0088] From Figure 1 It shows that for the electrolytes of Examples 1 - 5, the ionic conductivity at 30 °C first increases and then decreases with the increase in the content of LLZTO. The ionic conductivities of the composite double superionic solid electrolytes with the mass ratios of LLZTO to the polymer matrix of 1:2, 1:3, 1:4, 1:6, and 1:13 are respectively: 2.33×10 -4 、4.40×10 -4 、6.74×10 -4 、5.42×10 -4 and 5.00×10 - 4 S·cm -1 , among which, when the mass ratio of LLZTO to the polymer matrix is 1:4, the ionic conductivity of the solid electrolyte is the highest, which is 6.74×10 -4 .

[0089] This is because as the content of LLZTO increases to 20 wt%, LLZTO can form a continuous and complete inorganic electrolyte phase and a two-phase interface Li + transport path in the electrolyte, improving the ionic conductivity; but when the content continues to increase, it leads to the agglomeration and precipitation of LLZTO, blocking the Li + transport and reducing the ionic conductivity. In addition, the ionic conductivity of Example 6 at 30 °C is 5.67×10 - 4 S·cm -1 .

[0090] In summary, among the above examples, the ionic conductivities of the electrolytes of Examples 2 - 6 are much higher than those of the comparative examples (Comparative Example 1 is 3.17×10 -4 S·cm -1 , and Comparative Example 2 is 7.17×10 -5 S·cm -1 ).

[0091] The variation relationship between the conductivity of the electrolyte in the example and the temperature conforms to the Arrhenius equation, indicating that Li +The conduction mechanism in the polymer is different from the traditional segmental motion conduction and conforms to the characteristics of superionic solid electrolytes. The Arrhenius equation is used to linearly fit the relationship curves between the ionic conductivity and temperature change of the three electrolytes, and the activation energies for lithium ion transport in the electrolytes of Examples 1-5 can be calculated to be 0.23 eV, 0.23 eV, 0.23 eV, 0.25 eV, and 0.21 eV, respectively.

[0092] Obviously, the activation energy of the composite double superionic solid electrolyte is much lower than that of the comparative example electrolyte (0.28 eV for Comparative Example 1). This is because the polymer phase of the composite double superionic solid electrolyte realizes the conduction by the hopping transition mechanism and decouples from the segmental motion; the introduction of the inorganic electrolyte filler provides additional Li + transport paths, including the inorganic electrolyte phase and the two-phase interface between the inorganic electrolyte and the polymer, which changes the solvation environment of Li + and effectively improves the electrolyte conductivity. +

[0093] In addition, the ionic conductivities of the electrolytes of Examples 2-6 at 30 °C are 4.40×10 -4 , 6.74×10 -4 , 5.42×10 -4 , 5.00×10 -4 S·cm -1 and 5.67×10 -4 S·cm -1 , respectively, all higher than 4.2×10 -4 S·cm -1 of the prior art, that is, the composite double superionic solid electrolyte of the present invention has a high ionic conductivity.

[0094] In the above embodiments, since other oxide ceramic electrolytes, halide ceramic electrolytes, or sulfide ceramic electrolytes are used to replace Li 3 InCl 6 or LLZTO, the same effects can be achieved, which will not be elaborated here.

[0095] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.​

Claims

1. A composite double superionic solid electrolyte, characterized in that: The invention comprises a polymer matrix, a lithium salt and an inorganic electrolyte filler, wherein the mass ratio of the inorganic electrolyte filler to the polymer matrix is ​​1:1-20, and the lithium salt accounts for 1wt%-80wt% of the total weight of the solid electrolyte.

2. The composite double superionic solid electrolyte according to claim 1, characterized in that: The mass ratio of the inorganic electrolyte filler to the polymer matrix is ​​1:3-13.

3. The composite double superionic solid electrolyte according to claim 1, characterized in that The mass ratio of the lithium salt to the polymer matrix is ​​1:2-30.

4. The composite double superionic solid electrolyte according to claim 1, characterized in that: The inorganic electrolyte filler is one or more of an oxide ceramic electrolyte, a halide ceramic electrolyte or a sulfide ceramic electrolyte.

5. The composite double superionic solid electrolyte according to claim 1, characterized in that: The polymer matrix is ​​a chemically grafted polyvinylidene fluoride, a poly(vinylidene fluoride-chlorotrifluoroethylene) copolymer or a poly(vinylidene fluoride-hexafluoropropylene) copolymer, and the structural formulas thereof are shown in Formula 1, Formula 2 and Formula 3, respectively: Wherein, R1 and R2 groups are independently selected from one of the following groups; R1', R2' are selected from H or CH3; m, n, x, and y represent the number of repeating units of the polymerized monomer; m is any integer from 100 to 10,000, n is any integer from 100 to 10,000, x is any integer from 100 to 100,000, and y is any integer from 100 to 10,000.

6. The composite double superionic solid electrolyte according to claim 1, characterized in that: The lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide salt, lithium trifluorosulfonate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium fluoride, lithium bromide and lithium iodide.

7. A method for preparing a composite dual superionic solid electrolyte according to any one of claims 1 to 6, characterized in that: The steps include: S1: dissolving the polymer matrix and the lithium salt respectively into an organic solvent, stirring to form a uniform transparent solution, and obtaining a mixed solution; S2: adding the inorganic electrolyte filler to the mixed solution, and mixing uniformly by ultrasonication to obtain an electrolyte mixed solution; S3: Forming a membrane with the electrolyte mixture, volatilizing part of the organic solvent in a dry environment, and transferring the membrane to a vacuum drying oven for further drying to finally obtain a composite dual superionic solid electrolyte.

8. The method for preparing the composite double superionic solid electrolyte according to claim 7, characterized in that: In step S1, the organic solvent is one or more of DMF, NMP, DMAC, EAC and DMSO.

9. The method for preparing the composite double superionic solid electrolyte according to claim 7, characterized in that: In step S3, the film is prepared by using a blade coating or tape casting method, or a hot pressing method to prepare a uniform electrolyte film.

10. A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte is a composite double superionic solid electrolyte as described in any one of claims 1 to 6.

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