A composite electrolyte, its preparation method and application

Abstract

This invention provides a composite electrolyte, its preparation method, and its applications. The composite electrolyte has a sandwich structure, with the inner layer being a composite membrane comprising a polymer electrolyte, a lithium salt, and an alloy material. The outer layers of the composite electrolyte each independently comprise a polymer matrix. The composite electrolyte provided by this invention improves the electrochemical properties of polymer electrolytes in lithium metal anode batteries, enhancing the electrochemical stability and mechanical elasticity of the prepared polymer electrolyte material. The electrolyte can be applied in high-energy-density lithium metal solid-state batteries while maintaining high lithium-ion conductivity.

Description

Technical Field

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

[0002] Lithium-ion batteries (LIBs) have experienced rapid development over the past decade. However, current LIBs achieve high energy density by using organic liquid electrolytes and special additives to increase battery voltage, which may lead to serious safety issues. With the development of new energy power battery technology, traditional liquid batteries are increasingly unable to meet consumer demands, and lithium battery technology is trending towards higher safety and higher energy density. The availability of high-energy-density all-solid-state lithium-ion batteries has accelerated the development of electric vehicles and large-scale energy storage systems such as power grids. Therefore, developing high-energy-density and high-safety all-solid-state lithium-ion batteries (ASSLBs) has become a future trend in the industry.

[0003] Polymer electrolytes have been widely used in solid-state lithium-ion batteries due to their high film-forming properties and lithium-ion conductivity, but they still face problems such as narrow electrochemical stability windows and poor thermal stability. This patent proposes a solid-state electrolyte material composed of a low-temperature detection alloy and a polymer, and its solid-state battery, enabling all-solid-state batteries to achieve high safety, long cycle life, and high charge-discharge performance.

[0004] Polymers, due to their low cost, relatively flexible membranes, and certain cycle stability for anode materials, have been widely developed. Taking PEO as an example, its tendency to crystallize at low temperatures affects its performance on Li... + Due to factors such as insufficient migration sensitivity and inadequate rigidity, most existing PEO-based polymers cannot achieve long-term high-temperature cycling. During cycling, they are prone to uneven lithium deposition and the formation of lithium dendrites. Furthermore, interfacial reactions occur during frequent electroplating and stripping, leading to increased interfacial resistance. Additionally, the potential window of PEO-based polymers is not wide enough; when the voltage exceeds 4V, the polymer electrolyte microstructures are easily oxidized, resulting in reduced activity.

[0005] CN110994014A discloses an all-solid-state polymer electrolyte, its preparation method, and a lithium-ion battery. The all-solid-state polymer electrolyte comprises a polycaprolactone-based block copolymer and a lithium salt, and also includes polymer material particles and / or inorganic material particles; however, the prepared all-solid-state polymer electrolyte still exhibits poor flexibility.

[0006] CN115441125A discloses a composite porous polymer electrolyte membrane and its preparation method. The membrane comprises 30-35% polymer, 35-69% ionic liquid, and 1-30% inorganic nanoparticles. By doping the polymer with inorganic nanoparticles, the crystallinity of the polymer is reduced, thereby improving the ionic conductivity.

[0007] However, the polymers synthesized by adding organic and inorganic fillers to prepare composite membranes also suffer from poor mechanical strength and poor thermal / electrochemical stability, which cannot improve their application status in all-solid-state batteries with lithium metal anodes.

[0008] Therefore, there is an urgent need to develop a novel inorganic alloy and polymer composite solid electrolyte for use in lithium-ion batteries. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a composite electrolyte, its preparation method, and its application, thereby improving the electrochemical characteristics of polymer electrolytes in lithium metal anode batteries. This enhances the electrochemical stability and mechanical elasticity of the prepared polymer electrolyte material, enabling the electrolyte to be used in high-energy-density lithium metal solid-state batteries while maintaining high lithium-ion conductivity.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] One objective of this invention is to provide a composite electrolyte having a sandwich structure, wherein the inner layer of the composite electrolyte is a composite membrane comprising a polymer electrolyte, a lithium salt, and an alloy material, and the outer layers of the composite electrolyte each independently comprise a polymer matrix.

[0012] This invention provides a composite electrolyte with a sandwich structure. In this structure, the polymer matrix and the inner polymer composite film act as a rigid supporting framework. Simultaneously, the polymer matrix protects and improves the interfacial contact between the inner composite film and the positive and negative electrodes, allowing lithium ions to rapidly transport through the matrix within the sandwich layer. This suppresses the growth and puncture of lithium dendrites during lithium metal plating and stripping processes. The inner polymer electrolyte is doped with alloy materials, which play a crucial role in improving the conductivity of the composite film. These alloy materials also act as inorganic fillers, enhancing the rigidity of the composite film and improving the electrochemical characteristics of the inner composite film in lithium metal anode batteries. This results in improved electrochemical stability and mechanical elasticity of the prepared polymer electrolyte material. The electrolyte can be applied in high-energy-density lithium metal solid-state batteries while maintaining high lithium-ion conductivity.

[0013] As a preferred technical solution of the present invention, the thickness of the composite electrolyte is 15-80 mm, wherein the thickness can be 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm or 80 mm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] Preferably, the thickness of the polymer matrix is ​​2 to 40 μm, wherein the thickness can be 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] Preferably, the porosity of the polymer matrix is ​​20-80%, wherein the porosity can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0016] As a preferred embodiment of the present invention, the polymer electrolyte comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polycarbonate, polyacrylonitrile, polyvinylpyrrolidone, polyethylene glycol, polyethylene glycol diacrylate, polyethylene oxide, or polymethyl methacrylate. Typical but non-limiting examples of such combinations include: combinations of polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene, combinations of polyvinylidene fluoride-hexafluoropropylene and polyvinyl alcohol, combinations of polyvinyl alcohol and polycarbonate, combinations of polyacrylonitrile and polyvinylpyrrolidone, combinations of polyethylene glycol and polyethylene glycol diacrylate, combinations of polyethylene glycol diacrylate and polyethylene oxide, or combinations of polyethylene oxide and polymethyl methacrylate, etc., preferably polyvinyl oxide.

[0017] The present invention preferably uses polyethylene oxide (PEO). Compared with other polymer reagents, PEO has good elasticity, low manufacturing and process costs, certain electrical conductivity under high temperature conditions, and is relatively stable to sulfide electrolytes.

[0018] As a preferred technical solution of the present invention, the alloy material includes A a A a A b A a A b A cAny one or at least two of the following, wherein A is selected from any one or at least two of Al, Ga, In, Fe, Y, Sc, Sn, Cu, Zn, Cd, Mg, Ca, Sr, Ba, or La. Typical but non-limiting examples of the combination include: combinations of Al and Ga, combinations of In and Fe, combinations of Y and Sc, combinations of Sn and Cu, combinations of Zn and Cd, combinations of Mg and Ca, combinations of Sr and Ba, or combinations of Ba and La, etc. 0.1%≤a≤100%, 0.1%≤a+b≤100%, 0.1%≤a+b+c≤100%, where the value of a can be 0.1%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc.; the value of a+b can be 0.1%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc.; and the value of a+b+c can be 0.1%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc., but is not limited to the listed values. Other unlisted values ​​within the above ranges also apply.

[0019] As a preferred embodiment of the present invention, the lithium salt includes any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonylimide, lithium bis(oxalateborate), lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium chloride, lithium hexafluorophosphate, lithium difluorooxalateborate, or lithium perchlorate. Typical but non-limiting examples of such combinations include: combinations of lithium bis(trifluoromethanesulfonyl)imide and lithium trifluoromethanesulfonylimide, combinations of lithium trifluoromethanesulfonylimide and lithium bis(oxalateborate), combinations of lithium hexafluoroarsenate and lithium tetrafluoroborate, combinations of lithium chloride and lithium hexafluorophosphate, or combinations of lithium difluorooxalateborate and lithium perchlorate.

[0020] As a preferred embodiment of the present invention, the mass ratio of the polymer electrolyte to the lithium salt is (1-40):(1-10), wherein the mass ratio can be 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 5:1, 5:2, 5:4, 5:6, 5:8, 5:10, 10:1, 10:2, 10:4, 10:6, 10:8, 15:1, 15:2, 15:4, 15:6, 15:8, etc. 15:10, 20:1, 20:2, 20:8, 20:10, 25:1, 25:4, 25:8, 25:10, 30:1, 30:4, 30:8, 30:10, 40:1, 40:4, 40:8, or 40:10, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable. Preferably, it is (1-30):(1-5), more preferably (2.5-4.5):1.

[0021] Preferably, the alloy material accounts for 0.1% to 80% of the polymer electrolyte by mass fraction. The mass fraction can be 0.1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, the mass fraction is 10% to 60%, more preferably 20% to 40%.

[0022] As a preferred technical solution of the present invention, a coating is provided on the surface of the polymer electrolyte matrix, the coating including a single-sided coating and / or a double-sided coating.

[0023] Preferably, the polymer matrix material includes any one or a combination of at least two of the following: nonwoven fabric, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyoxymethylene, polyamide, polycarbonate, polylactic acid, polymethyl methacrylate, acrylonitrile-styrene copolymer, polybutylene terephthalate, polyethylene terephthalate, phenolic resin, polyterephthalate carbonate, polyetherimide, polyimide film, polyacrylonitrile, polytetrafluoroethylene, or amino resin. Typical but non-limiting examples of such combinations include: a combination of nonwoven fabric and polyethylene; a combination of polypropylene, polystyrene, and polyethylene terephthalate; a combination of polyvinyl chloride and polyoxymethylene; a combination of polyamide and polycarbonate; a combination of polylactic acid and polymethyl methacrylate; a combination of acrylonitrile-styrene copolymer and polybutylene terephthalate; a combination of phenolic resin and polyterephthalate carbonate; a combination of polyetherimide and polyimide film; a combination of polyacrylonitrile and polytetrafluoroethylene; or a combination of amino resin and polyethylene.

[0024] Preferably, the coating comprises any one or a combination of at least two of oxide coatings, non-oxidizing coatings, silicate coatings, or composite ceramic coatings, wherein typical but non-limiting examples of the combination include: a combination of oxide coatings and non-oxidizing coatings, a combination of non-oxidizing coatings and silicate coatings, a combination of silicate coatings and composite ceramic coatings, or a combination of oxide coatings and silicate coatings, etc.

[0025] A second objective of this invention is to provide a method for preparing the composite electrolyte as described in one objective, the method comprising the following steps:

[0026] After mixing polymer electrolyte and lithium salt, liquid alloy is added to obtain composite electrolyte slurry. The composite electrolyte slurry is subjected to vacuum thermosetting treatment to obtain composite electrolyte block. The composite electrolyte block is laminated with polymer matrix and then subjected to hot pressing, drying and pressurization in sequence to obtain composite electrolyte.

[0027] This invention employs a solvent-free method to prepare PEO-based composite polymer electrolyte membranes, reducing the impact of solvents on the lithium metal anode, and the preparation process is simple. This invention utilizes a solvent-free method to prepare the membrane, minimizing the influence of solvents on the sulfide electrolyte and lithium metal anode of all-solid-state batteries, while also offering a short process cycle and cost savings.

[0028] As a preferred technical solution of the present invention, the temperature of the vacuum thermosetting treatment is 50-150℃, wherein the temperature can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] Preferably, the RH value of the vacuum thermosetting treatment is 0.01 to 0.5%, wherein the pH value can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] Preferably, the vacuum thermosetting treatment time is 2 to 96 hours, wherein the time can be 2 hours, 5 hours, 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours or 96 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the hot pressing includes hot roller pressing.

[0032] Preferably, the pressure of the hot roller is 120–300 kg / cm². 2 The pressure mentioned therein can be 120 kg / cm². 2 150kg / cm 2 200kg / cm 2 250kg / cm 2 Or 350kg / cm 2 This applies to, but not limited to, the listed values; other unlisted values ​​within this range also apply.

[0033] Preferably, the hot rolling time is 0.5 to 1 min, wherein the time can be 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min or 1 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the hot pressing temperature is 60-130°C, wherein the temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, or 130°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0035] Preferably, the drying time is 2 to 72 hours, wherein the time can be 2 hours, 5 hours, 10 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours or 72 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 4 to 24 hours.

[0036] Preferably, the drying temperature is 20-30°C, wherein the temperature can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] Preferably, the pressure applied is 1 to 10 MPa, wherein the pressure can be 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa or 10 MPa, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] Preferably, the pressurized temperature is 30 to 150°C, wherein the temperature can be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0039] A third objective of this invention is to provide an application of the composite electrolyte as described in one objective, wherein the composite electrolyte is applied in the field of lithium-ion batteries.

[0040] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The composite electrolyte prepared by this invention can achieve a first-cycle discharge capacity of over 192 mAh / g at 0.3C, a retention rate of over 97% after 100 cycles, and a conductivity of over 0.84 mS / cm when applied to lithium-ion batteries. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0044] Example 1

[0045] This embodiment provides a composite electrolyte with a sandwich structure. The inner layer of the composite electrolyte includes a polymer electrolyte PEO, a lithium salt LiTFSI, and an alloy material Ga. 60 In 30 Sn 10 The composite electrolyte comprises a polymer matrix, polyethylene terephthalate, on both sides.

[0046] This embodiment provides a method for preparing a composite electrolyte, the method comprising:

[0047] Under an argon atmosphere, lithium bis(trifluoromethanesulfonyl)imide and polyethylene oxide were weighed out at a mass ratio of 5:1. The mixture was initially ground to obtain a mortar-like slurry, and then Ga was added. 60 In 30 Sn 10 The liquid alloy accounts for 30% of the total PEO. The resulting mixed slurry is vacuum thermo-cured at 100°C and 0.1% RH for 48 hours to obtain a uniform slurry block. This block is then sandwiched between two PET polymer matrix sheets to form a sandwich structure and hot-rolled, achieving a hot-rolling strength of 210 kg / cm². 2 The roller-passing time was 0.5 min, resulting in a 20 mm thick composite membrane. This composite polymer electrolyte membrane was then left to dry at room temperature for 24 h, followed by isostatic pressing at 5 MPa and 80 °C to obtain the final composite polymer electrolyte membrane with a thickness of 16 mm. The composite polymer electrolyte is PEO / LiTFSI / Ga. 60 In 30 Sn 10 / PET.

[0048] Examples 2-4

[0049] Based on Example 1, by adjusting the liquid alloy Ga a In b Sn c The content ratio of a, b, and c in the formula was used to prepare the PEO-based composite polymer electrolyte membrane. The specific parameter adjustments are shown in Table 1.

[0050] Examples 5-8

[0051] Based on Example 1, the PEO-based composite polymer electrolyte membrane was prepared by adjusting the metal element composition of the liquid alloy. The specific parameter adjustments are shown in Table 1.

[0052] Examples 9-10

[0053] Based on Example 1, the PEO-based composite polymer electrolyte membrane was prepared by adjusting the composition of the lithium salt. The specific parameter adjustments are shown in Table 1.

[0054] Examples 11-13

[0055] Based on Example 1, the PEO-based composite polymer electrolyte membrane was prepared by adjusting the alloy content. The specific parameter adjustments are shown in Table 1.

[0056] Examples 14-15

[0057] Based on Example 1, the PEO-based composite polymer electrolyte membrane was prepared by adjusting the type of polymer matrix. The specific parameter adjustments are shown in Table 1.

[0058] Comparative Example 1

[0059] No liquid alloy was added during the preparation of this comparative example, resulting in a PEO / LiTFSI / PET composite electrolyte. All other conditions were the same as in Example 1.

[0060] Comparative Example 2

[0061] This comparative example, except for not preparing an electrolyte matrix, yielded PEO / LiTFSI / Ga 60 In 30 Sn 10 All other conditions are the same as in Example 1.

[0062] Comparative Example 3

[0063] This comparative example includes the prepared PEO / LiTFSI / Ga 60 In 30 Sn 10 Except for mechanical pressure at a certain temperature, the conditions for PET are the same as in Example 1.

[0064] Impedance analysis was performed on the composite electrolytes prepared in Examples 1-15 and Comparative Examples 1-3 to obtain the ionic conductivity values ​​of the electrolytes. The specific operation process is as follows: A sample of a certain size was prepared from the PEO-based composite polymer electrolyte membrane and placed into a special mold sleeve at 60°C. Pressure was manually applied, and AC impedance spectroscopy was performed using an impedance analyzer. The ionic conductivity of the electrolyte material was calculated based on the impedance value. The composite polymer electrolyte membrane was used as the buffer layer of the electrolyte layer in the sulfide all-solid-state lithium metal anode mold battery. The assembly sequence of the mold battery materials was ternary cathode, sulfide electrolyte, polymer electrolyte, and lithium metal anode. Charge-discharge tests were conducted at 0.3C under 25°C conditions. The test results are shown in Table 1.

[0065] Table 1

[0066]

[0067]

[0068] The table above shows that when the mass ratio of polyethylene oxide to lithium salt is 5:1 and the alloy accounts for 30% of the total lithium salt, the PEO-based composite polymer electrolyte membrane prepared by using a PET separator and undergoing certain mechanical pressing composite processes has the highest conductivity, the highest specific capacity under 0.3C charge-discharge cycles at 25℃ for 100 cycles, and a retention rate of 97%.

[0069] A comparison of Examples 5-8 and Example 1 shows that the composite electrolyte exhibits the best performance when all three elements are combined.

[0070] A comparison between Examples 9-10 and Example 1 shows that the performance of the composite electrolyte decreases when the lithium salt content is too high or too low.

[0071] A comparison of Examples 11-13 and Example 1 shows that adjusting the alloy content, whether too much or too little, reduces the conductivity and discharge capacity of the composite polymer electrolyte membrane.

[0072] A comparison of Examples 14-15 and Example 1 shows that adjusting the type of polymer matrix in the preparation of PEO-based composite polymer electrolyte membranes can improve the performance of the composite electrolyte to varying degrees.

[0073] A comparison of Comparative Examples 1-3 and Example 1 shows that the combination of alloy, PET diaphragm and mechanical pressure can effectively improve the electrochemical properties of composite polymer solid electrolyte membranes.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite electrolyte, characterized in that, The composite electrolyte has a sandwich structure. The inner layer of the composite electrolyte is a composite membrane, which includes a polymer electrolyte, a lithium salt, and an alloy material. The outer layer of the composite electrolyte independently includes a polymer matrix, and the alloy material is Ga. a In b Sn c .

2. The composite electrolyte according to claim 1, characterized in that, The thickness of the composite electrolyte is 15~80mm.

3. The composite electrolyte according to claim 1, characterized in that, The thickness of the polymer matrix is ​​2~40µm.

4. The composite electrolyte according to claim 1, characterized in that, The porosity of the polymer matrix is ​​20-80%.

5. The composite electrolyte according to claim 1, characterized in that, The polymer electrolyte includes any one or a combination of at least two of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polycarbonate, polyacrylonitrile, polyvinylpyrrolidone, polyethylene glycol, polyethylene glycol diacrylate, polyethylene oxide, or polymethyl methacrylate.

6. The composite electrolyte according to claim 5, characterized in that, The polymer electrolyte is polyethylene oxide.

7. The composite electrolyte according to claim 1, characterized in that, The lithium salt includes any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonylimide, lithium bis(oxalato)borate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium chloride, lithium hexafluorophosphate, lithium difluorooxalatoborate, or lithium perchlorate.

8. The composite electrolyte according to claim 1, characterized in that, The mass ratio of the polymer electrolyte to the lithium salt is (1~40):(1~10).

9. The composite electrolyte according to claim 8, characterized in that, The mass ratio of the polymer electrolyte to the lithium salt is (1~30):(1~5).

10. The composite electrolyte according to claim 9, characterized in that, The mass ratio of the polymer electrolyzer to the lithium salt is (2.5~4.5):

1.

11. The composite electrolyte according to claim 1, characterized in that, The alloy material accounts for 0.1% to 80% of the polymer electrolyte by mass.

12. The composite electrolyte according to claim 11, characterized in that, The alloy material accounts for 10-60% of the polymer electrolyte by mass.

13. The composite electrolyte according to claim 12, characterized in that, The alloy material accounts for 20-40% of the polymer electrolyte by mass.

14. The composite electrolyte according to claim 1, characterized in that, The polymer electrolyte matrix has a coating on its surface, the coating including a single-sided coating and / or a double-sided coating.

15. The composite electrolyte according to claim 1, characterized in that, The polymer matrix material includes any one or a combination of at least two of the following: nonwoven fabric, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyoxymethylene, polyamide, polycarbonate, polylactic acid, polymethyl methacrylate, acrylonitrile-styrene copolymer, polybutylene terephthalate, polyethylene terephthalate, phenolic resin, polyterephthalate carbonate, polyetherimide, polyimide film, polyacrylonitrile, polytetrafluoroethylene, or amino resin.

16. The composite electrolyte according to claim 14, characterized in that, The coating includes any one or a combination of at least two of the following: oxide coating, non-oxidizing coating, silicate coating, or composite ceramic coating.

17. A method for preparing a composite electrolyte as described in any one of claims 1-16, characterized in that, The preparation method includes: After mixing polymer electrolyte and lithium salt, liquid alloy is added to obtain composite electrolyte slurry. The composite electrolyte slurry is subjected to vacuum thermosetting treatment to obtain composite electrolyte block. The composite electrolyte block is laminated with polymer matrix and then subjected to hot pressing, drying and pressurization in sequence to obtain composite electrolyte.

18. The preparation method according to claim 17, characterized in that, The temperature of the vacuum thermosetting process is 50~150℃.

19. The preparation method according to claim 17, characterized in that, The RH value of the vacuum thermosetting treatment is 0.01~0.5%.

20. The preparation method according to claim 17, characterized in that, The vacuum thermosetting treatment takes 2 to 96 hours.

21. The preparation method according to claim 17, characterized in that, The hot pressing includes hot roller pressing.

22. The preparation method according to claim 21, characterized in that, The pressure of the hot roller is 120~300 kg / cm². 2 .

23. The preparation method according to claim 21, characterized in that, The hot roller pressing time is 0.5~1min.

24. The preparation method according to claim 17, characterized in that, The hot pressing temperature is 60~130℃.

25. The preparation method according to claim 17, characterized in that, The drying time is 2 to 72 hours.

26. The preparation method according to claim 25, characterized in that, The drying time is 4 to 24 hours.

27. The preparation method according to claim 17, characterized in that, The drying temperature is 20~30℃.

28. The preparation method according to claim 17, characterized in that, The pressurization pressure is 1~10 MPa.

29. The preparation method according to claim 17, characterized in that, The pressurization temperature is 30~150℃.

30. An application of the composite electrolyte as described in any one of claims 1-16, characterized in that, The composite electrolyte is used in the field of lithium-ion batteries.

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