Crosslinked polyvinylidene chloride film with lithium ion conduction and preparation method thereof
By doping lithium salts and toughening agents in lithium metal batteries, the problem of polyvinylidene chloride film not having lithium ion conduction and brittleness is solved, and a crosslinked polyvinylidene chloride film that can work normally in lithium metal batteries was prepared.
Patent Information
- Application Number
- CN202411851103.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-16
- Publication Date
- 2025-05-06
AI Technical Summary
Polyvinylidene chloride does not have lithium ion conduction channels in lithium metal batteries, and the film becomes brittle after doping with lithium salts.
Crosslinked polyvinylidene chloride films with lithium ion conduction were prepared by doping different lithium salts and adding toughening agents. The film is prepared by mixing polyvinylidene chloride with lithium salt in a solvent and dried by pouring or coating.
The film preparation of lithium ion conduction is achieved, avoiding the problem of film becoming brittle, and at the same time, normal charging and discharging cycles can be carried out in lithium metal batteries.
Smart Images
Figure CN119944241A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lithium metal battery films, and in particular relates to a cross-linked polyvinylidene chloride film with lithium ion conductivity. Background Art
[0002] Polyvinylidene chloride (PVDC) is a linear polymer chain with a melting point range of 160-200°C, a symmetrical molecular structure and high crystallinity. PVDC has high molecular cohesion, good crystallinity, and the chlorine molecules in the PVDC molecules are highly hydrophobic, so they cannot produce hydrogen bonding effects. It is also difficult for oxygen molecules and water molecules to move freely within the PVDC molecules, so it has excellent oxygen and moisture barriers, and its oxygen barrier is not affected by the humidity of the surrounding environment. PVDC is a plastic packaging material, widely recognized as the material with the best barrier properties at present, which can effectively block water vapor, oxygen, odor and fragrance under various temperature and humidity conditions. Applying its characteristics to lithium metal batteries can better isolate oxygen and water molecules to protect the lithium metal negative electrode.
[0003] However, polyvinylidene chloride only has the function of isolating oxygen and water molecules in lithium metal batteries. It does not provide a channel for lithium ion conduction, and when modified by doping with lithium salts, the film becomes brittle. This phenomenon causes polyvinylidene chloride to be unable to be used normally as a film in lithium metal batteries. Summary of the invention
[0004] The invention provides a cross-linked polyvinylidene chloride film with lithium ion conduction and a preparation method thereof, which solves the problem that the existing polyvinylidene chloride does not provide a lithium ion conduction channel and the film becomes brittle after being doped with lithium salt.
[0005] In order to solve the above technical problems, the technical solution of the present invention is: The invention provides a cross-linked polyvinylidene chloride film with lithium ion conduction, which solves the problem that polyvinylidene chloride does not have lithium ion conduction by doping different lithium salts. The film is prepared by uniformly mixing polyvinylidene chloride and lithium salt in a solvent, and then casting or coating and drying.
[0006] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0007] Wherein, the lithium salt is any one or more of lithium bis(trifluoromethanesulfonyl imide), lithium nitrate, lithium bis(fluorosulfonyl imide), and lithium difluorooxalate borate; different combinations of the four lithium salts include: lithium bis(trifluoromethanesulfonyl imide); lithium bis(trifluoromethanesulfonyl imide and lithium nitrate; lithium bis(trifluoromethanesulfonyl imide and lithium bis(fluorosulfonyl imide); lithium bis(trifluoromethanesulfonyl imide and lithium difluorooxalate borate; lithium bis(trifluoromethanesulfonyl imide, lithium nitrate, lithium bis(fluorosulfonyl imide), and lithium difluorooxalate borate.
[0008] Wherein, the solvent is tetrahydrofuran; the template used for casting is a polytetrafluoroethylene plate, and the template used for coating is a glass plate.
[0009] The mass ratio of the lithium salt to polyvinylidene chloride is (2-4): (5-8), and the mass ratio of the solvent to polyvinylidene chloride is (4-10): (1-2).
[0010] Wherein, a toughening agent is also added when the polyvinylidene chloride is mixed with the lithium salt, and the toughening agent is any one or more of thermoplastic polyurethane elastomer, sodium hexafluoroantimonate, resin toughening agent, triglycidyl isocyanurate, polyethylene glycol diacrylate, and lithium hexafluoroantimonate; the amount of the toughening agent added is 10%, 15%, 20% or 25% of the mass of the polyvinylidene chloride.
[0011] A method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity comprises the following steps: (1) mixing polyvinylidene chloride monomer and solvent and stirring them uniformly to form a polyvinylidene chloride emulsion, and then adding lithium salt and continuing to stir them uniformly to obtain a composite emulsion; (2) subjecting the composite emulsion to ultrasonic treatment at 25°C to 35°C for 30 min to 40 min to remove bubbles in the emulsion; (3) The composite emulsion after ultrasound is poured onto a polytetrafluoroethylene plate for drying or the emulsion is coated onto a glass plate using a glass rod.
[0012] Wherein, in step (1), a toughening agent is also added to the polyvinylidene chloride emulsion.
[0013] Wherein, in step (1), the mixing and stirring speed is 250 r / min to 400 r / min, the mixing and stirring environment is light-proof, and the ambient temperature is 25° C. to 35° C.
[0014] The above-mentioned method is to obtain a cross-linked polyvinylidene chloride film with lithium ion conduction by coating on a glass plate and drying naturally, wherein four layers of transparent tape are fixed on both sides of the glass plate, and a glass rod is used to evenly scratch from top to bottom, and the natural drying time is 7h to 8h.
[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention solves the problem that polyvinylidene chloride does not have lithium ion conduction by doping with different kinds of lithium salts, and solves the problem that polyvinylidene chloride does not have a channel for providing lithium ion conduction by adding a toughening agent, resulting in the defects of the film being not tough, relatively brittle and relatively thick. The prepared polyvinylidene chloride film with lithium ion conduction not only has the function of isolating oxygen and water molecules, but also has a channel for providing lithium ion conduction, and can perform normal charge and discharge cycles in lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 This is a graph showing the test results of the first charge and discharge specific capacity and the first coulombic efficiency of a CR2032 battery assembled using the film of Example 1, the film of Example 2, the film of Example 3, the film of Example 4, and the PP film.
[0017] Figure 2 This is a graph of the discharge specific capacity results of CR2032 batteries assembled using Example 1 film, Example 2 film, Example 3 film, Example 4 film, and PP film at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C.
[0018] Figure 3 It is a cycle performance curve diagram of CR2032 batteries assembled with Example 1 film, Example 2 film, Example 3 film, Example 4 film, and PP film at a 1C rate.
[0019] Figure 4 This is the scanning electron microscope image of the film with toughening agent added and the PP film.
[0020] Figure 5 This is a graph showing the discharge specific capacity results of CR2032 batteries assembled using Example 4 film, Example 5 film, Example 6 film, and PP film at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C.
[0021] Figure 6 It is a tensile force test result graph of the tensile force test using the film of Example 5, the film of Example 6, the PP film, and the film without toughening agent cut into 30mm*3mm rectangles. DETAILED DESCRIPTION
[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1
[0023] This embodiment provides a cross-linked polyvinylidene chloride film with lithium ion conductivity, which is prepared by uniformly mixing polyvinylidene chloride and lithium salt in tetrahydrofuran, and then casting and drying.
[0024] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0025] Wherein, the lithium salt is lithium bis(trifluoromethanesulfonyl imide); the mass ratio of lithium bis(trifluoromethanesulfonyl imide) to polyvinylidene chloride is 2:8, and the mass ratio of the solvent to polyvinylidene chloride is 2:1.
[0026] The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity in this embodiment comprises the following steps: (1) Mixing polyvinylidene chloride monomer and solvent and stirring them evenly to form a polyvinylidene chloride emulsion, then adding lithium bis(trifluoromethanesulfonyl imide) and continuing to stir evenly, the mixing and stirring speed is 250 r / min, the mixing and stirring environment is protected from light, and the ambient temperature is 35° C., to obtain a composite emulsion; (2) subjecting the composite emulsion to ultrasonic treatment at 25°C for 40 min to remove bubbles in the emulsion; (3) The polyvinylidene chloride-lithium salt emulsion prepared by ultrasonication in step (2) is poured onto a polytetrafluoroethylene plate, and after natural drying, a polyvinylidene chloride film having lithium ion conductivity is formed. Example 2
[0027] This embodiment provides a cross-linked polyvinylidene chloride film with lithium ion conductivity, which is prepared by uniformly mixing polyvinylidene chloride and lithium salt in tetrahydrofuran, and then casting and drying.
[0028] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0029] Among them, the lithium salts are lithium bis(trifluoromethanesulfonyl imide) and lithium nitrate; the mass ratio of lithium bis(trifluoromethanesulfonyl imide) to polyvinylidene chloride is 2:5, the mass ratio of lithium nitrate to polyvinylidene chloride is 2:5, and the mass ratio of the solvent to polyvinylidene chloride is 5:1.
[0030] The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity in this embodiment comprises the following steps: (1) Mixing polyvinylidene chloride monomer and solvent to form polyvinylidene chloride emulsion, adding lithium salt and continuing to stir evenly, the mixing and stirring speed is 400 r / min, the mixing and stirring environment is protected from light, and the ambient temperature is 25° C., to obtain a composite emulsion; (2) subjecting the composite emulsion to ultrasonic treatment at 35°C for 30 min to remove bubbles in the emulsion; (3) The polyvinylidene chloride-lithium salt emulsion prepared by ultrasonication in step (2) is poured onto a polytetrafluoroethylene plate, and after natural drying, a polyvinylidene chloride film having lithium ion conductivity is formed. Example 3
[0031] This embodiment provides a cross-linked polyvinylidene chloride film with lithium ion conductivity, which is prepared by uniformly mixing polyvinylidene chloride and lithium salt in tetrahydrofuran, and then casting and drying.
[0032] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0033] Wherein, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalatoborate;.
[0034] The mass ratio of the lithium bis(trifluoromethanesulfonyl)imide to poly(vinylidene chloride) is 2:7, the mass ratio of the lithium difluorooxalatoborate to poly(vinylidene chloride) is 1:7, and the mass ratio of the solvent to poly(vinylidene chloride) is 6:1.
[0035] The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity in this embodiment comprises the following steps: (1) Mixing polyvinylidene chloride monomer and solvent and stirring them evenly to form a polyvinylidene chloride emulsion, then adding lithium salt and continuing to stir evenly, the mixing and stirring speed is 350 r / min, the mixing and stirring environment is protected from light, and the ambient temperature is 30° C., to obtain a composite emulsion; (2) subjecting the composite emulsion to ultrasonic treatment at 35°C for 35 min to remove bubbles in the emulsion; (3) The polyvinylidene chloride-lithium salt emulsion prepared by ultrasonication in step (2) is poured onto a polytetrafluoroethylene plate, and after natural drying, a polyvinylidene chloride film having lithium ion conductivity is formed. Example 4
[0036] This embodiment provides a cross-linked polyvinylidene chloride film with lithium ion conductivity, which is prepared by uniformly mixing polyvinylidene chloride and lithium salt in tetrahydrofuran, and then casting and drying.
[0037] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0038] Among them, the mass ratio of polyvinylidene chloride to tetrahydrofuran is 1:10; The lithium salt is a mixture of lithium bis(trifluoromethanesulfonyl imide), lithium nitrate, lithium bis(fluorosulfonyl imide) and lithium difluorooxalate borate; the mass ratio of polyvinylidene chloride to lithium bis(trifluoromethanesulfonyl imide) is 7:2, and the molar ratio of polyvinylidene chloride to the other three lithium salts is 1:10.
[0039] The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity in this embodiment comprises the following steps: (1) Mixing polyvinylidene chloride monomer and solvent and stirring them uniformly to form polyvinylidene chloride emulsion, then adding lithium salt and stirring them magnetically at 250 r / min, maintaining the ambient temperature at 25° C. to 30° C., controlling the stirring time at 1440 min to 1500 min, and keeping away from light during the stirring process to obtain polyvinylidene chloride-lithium salt emulsion; (2) The polyvinylidene chloride-lithium salt emulsion stirred in step (1) is subjected to ultrasonic treatment for 30 minutes to remove bubbles in the emulsion, and the temperature is maintained at 25° C. to 30° C. during the ultrasonic treatment.
[0040] (3) The polyvinylidene chloride-lithium salt emulsion prepared by ultrasonication in step (2) is poured onto a polytetrafluoroethylene plate, and after natural drying, a polyvinylidene chloride film having lithium ion conductivity is formed.
[0041] The casting area of the polytetrafluoroethylene plate used in Example 1, Example 2, Example 3, and Example 4 is 120 mm*150 mm, the thickness is 0.5 mm, and the casting amount is 10 ml to 15 ml of tetrahydrofuran.
[0042] In order to demonstrate that a polyvinylidene chloride film with lithium ion conductivity can undergo normal charge and discharge cycles in lithium metal batteries, a polyvinylidene chloride film with lithium ion conductivity in Example 1, Example 2, Example 3, and Example 4 was selected to replace the 25μm microporous monolayer membrane (PP) for CR2032 button battery assembly, and the charge and discharge tests were carried out on the Newwell battery testing system with the CR2032 button battery assembled with the 25μm microporous monolayer membrane (PP), and then compared by tabulation and graphing.
[0043] After 5 cycles of testing at 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, and 200 cycles of charging and discharging at 1C, the results include the following: pass Figure 1It can be seen from the test results of the first charge and discharge specific capacity and the first coulomb efficiency that the first coulomb efficiency of Example 1, Example 2, Example 3, and Example 4 using polyvinylidene chloride as the film is higher than that of the PP film. Among them, the first coulomb efficiency of the battery of Example 2 is the highest, while the first charge and discharge specific capacity is the lowest among Examples 1, 2, 3, and 4, while the first charge and discharge specific capacity of the battery of Example 4 is the highest among Examples 1, 2, 3, and 4.
[0044] pass Figure 2 The discharge capacity results at the rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C show that the battery of Example 4 has the highest discharge capacity at the rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C in the table. However, the discharge capacity of Examples 1, 2, and 3 at a rate of 5C are all lower than 1 mgh / g. This indicates that the film of Example 4 using four lithium salts, namely, lithium bistrifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium difluorooxalate borate, and lithium nitrate, can be compatible with the PP film at a rate of 5C.
[0045] pass Figure 3 It can be seen from the cycle performance curves of the batteries of Example 1, Example 2, Example 3, and Example 4 at 1C rate that the battery cycle curve using the film doped with polyvinylidene chloride is smoother than the battery cycle curve of the PP film. Among them, Example 4 containing four lithium salts of bistrifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium difluorooxalatoborate and lithium nitrate has the highest discharge specific capacity.
[0046] Figure 4 The figures are scanning electron microscope images of the film of Example 4 and the PP film, wherein (1) and (3) are scanning electron microscope images of the film of Example 4, and (2) and (4) are scanning electron microscope images of the PP film.
[0047] Through the above first charge and discharge specific capacity and first coulomb efficiency test results, and the discharge specific capacity results at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C rates, and the cycle performance curves of the batteries of Example 1, Example 2, Example 3, and Example 4 at 1C rate, it can be known that adding lithium salt to the film doped with polyvinylidene chloride can make the lithium metal battery have better cycle performance. However, the film prepared by this method is not tough, relatively brittle and thick.
[0048] In order to solve the above problem that polyvinylidene chloride does not have channels to provide lithium ion conduction, resulting in the film having defects of not having toughness, being relatively brittle and being relatively thick, the present invention further makes up for the defects by doping a toughening agent into the polyvinylidene chloride-lithium salt emulsion. Example 5
[0049] This embodiment provides a cross-linked polyvinylidene chloride film with lithium ion conductivity, which is prepared by uniformly mixing polyvinylidene chloride, lithium salt and toughening agent in tetrahydrofuran, and then coating and drying.
[0050] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0051] Among them, the lithium salts are lithium bis(trifluoromethanesulfonyl imide) and lithium nitrate; the mass ratio of lithium bis(trifluoromethanesulfonyl imide) to polyvinylidene chloride is 2:5, the mass ratio of lithium nitrate to polyvinylidene chloride is 2:5, and the mass ratio of the solvent to polyvinylidene chloride is 5:1.
[0052] The toughening agent is a thermoplastic polyurethane elastomer and lithium hexafluoroantimonate in a mass ratio of 2:1; the added amount of the toughening agent is 15% of the mass of the polyvinylidene chloride.
[0053] The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity in this embodiment comprises the following steps: (1) Mixing polyvinylidene chloride monomer and solvent to form polyvinylidene chloride emulsion, adding lithium salt and toughening agent and continuing to stir evenly, the mixing and stirring speed is 400r / min, the mixing and stirring environment is protected from light, and the ambient temperature is 25°C, to obtain a composite emulsion; (2) subjecting the composite emulsion to ultrasonic treatment at 35°C for 30 min to remove bubbles in the emulsion; (3) Pour the polyvinylidene chloride-lithium salt / toughening emulsion prepared by ultrasonication in step (2) onto a glass plate with two side walls of 0.16 mm in height, apply it from top to bottom using a glass rod, and wait for natural drying to form a cross-linked polyvinylidene chloride film with lithium ion conductivity. Example 6
[0054] This embodiment provides a cross-linked polyvinylidene chloride film with lithium ion conductivity, which is prepared by uniformly mixing polyvinylidene chloride, lithium salt and toughening agent in tetrahydrofuran, and then coating and drying.
[0055] Wherein, the polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
[0056] Among them, the mass ratio of polyvinylidene chloride to tetrahydrofuran is 1:10; The lithium salt is a mixture of lithium bis(trifluoromethanesulfonyl imide), lithium nitrate, lithium bis(fluorosulfonyl imide) and lithium difluorooxalate borate; the mass ratio of polyvinylidene chloride to lithium bis(trifluoromethanesulfonyl imide) is 7:2, and the molar ratio of polyvinylidene chloride to the other three lithium salts is 1:10.
[0057] The toughening agent is a thermoplastic polyurethane elastomer and polyethylene glycol diacrylate in a mass ratio of 1:2; the added amount of the toughening agent is 25% of the mass of the polyvinylidene chloride.
[0058] The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity in this embodiment comprises the following steps: (1) Mixing polyvinylidene chloride monomer and solvent and stirring them evenly to form polyvinylidene chloride emulsion, then adding lithium salt and toughening agent and stirring them magnetically at 250 r / min, maintaining the ambient temperature at 25° C. to 30° C., controlling the stirring time at 1440 min to 1500 min, and keeping away from light during the stirring process to obtain polyvinylidene chloride-lithium salt emulsion; (2) The polyvinylidene chloride-lithium salt emulsion stirred in step (1) is subjected to ultrasonic treatment for 30 minutes to remove bubbles in the emulsion, and the temperature is maintained at 25° C. to 30° C. during the ultrasonic treatment.
[0059] (3) Pour the polyvinylidene chloride-lithium salt / toughening emulsion prepared by ultrasonication in step (2) onto a glass plate with two side walls of 0.16 mm in height, apply it from top to bottom using a glass rod, and wait for natural drying to form a cross-linked polyvinylidene chloride film with lithium ion conductivity.
[0060] In order to demonstrate that a cross-linked polyvinylidene chloride film with lithium ion conductivity can complete normal charge and discharge cycles in lithium metal batteries after being doped with a toughening agent, a cross-linked polyvinylidene chloride film with lithium ion conductivity in Example 5 and Example 6 was selected to replace the 25μm microporous monolayer membrane (PP) for CR2032 button battery assembly, and the charge and discharge tests were carried out on the Newwell battery testing system with the CR2032 button battery assembled using the 25μm microporous monolayer membrane (PP), and then compared by tabulation and drawing.
[0061] After 5 cycles of testing at 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, and 200 cycles of charging and discharging at 1C, the results include the following: pass Figure 5 From the discharge specific capacity results at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, it can be seen that the battery of Example 5 has the highest discharge specific capacity at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C in the table.
[0062] pass Figure 6 From the tensile force result graph of the Example 5 film, the Example 6 film, the PP film, and the film without a toughening agent, it can be seen that the Example 5 film and the Example 6 film have better tensile properties than the film without a toughening agent, among which the Example 6 film has the best tensile property.
[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A cross-linked polyvinylidene chloride film having lithium ion conductivity, characterized in that: The invention is prepared by uniformly mixing polyvinylidene chloride and lithium salt in a solvent, and then drying the mixture by pouring or coating.
2. The cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 1, characterized in that: The polyvinylidene chloride is a polyvinylidene chloride monomer with a molecular weight of 10,000 to 20,000.
3. The cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 1, characterized in that: The lithium salt is any one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium nitrate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.
4. The cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 1, characterized in that: The solvent is tetrahydrofuran; the template used for casting is a polytetrafluoroethylene plate, and the template used for coating is a glass plate.
5. The cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 1, characterized in that: The mass ratio of the lithium salt to polyvinylidene chloride is (2-4): (5-8), and the mass ratio of the solvent to polyvinylidene chloride is (4-10): (1-2).
6. The cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 1, characterized in that: When the polyvinylidene chloride is mixed with the lithium salt, a toughening agent is also added, and the toughening agent is any one or more of thermoplastic polyurethane elastomer, sodium hexafluoroantimonate, resin toughening agent, triglycidyl isocyanurate, lithium hexafluoroantimonate, and polyethylene glycol diacrylate; the added amount of the toughening agent is 10%, 15%, 20% or 25% of the mass of the polyvinylidene chloride.
7. A method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity according to any one of claims 1 to 5, characterized in that The steps include: (1) mixing polyvinylidene chloride monomer and solvent and stirring them uniformly to form a polyvinylidene chloride emulsion, and then adding lithium salt and continuing to stir them uniformly to obtain a composite emulsion; (2) subjecting the composite emulsion to ultrasonic treatment at 25°C to 35°C for 30 min to 40 min to remove bubbles in the emulsion; (3) The composite emulsion after ultrasound is poured onto a polytetrafluoroethylene plate for drying or the emulsion is coated onto a glass plate using a glass rod.
8. The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 7, characterized in that: In step (1), a toughening agent is also added to the polyvinylidene chloride emulsion.
9. The method for preparing a cross-linked polyvinylidene chloride film having lithium ion conductivity according to claim 7, characterized in that: In step (1), the mixing and stirring speed is 250 r / min to 400 r / min, the mixing and stirring environment is light-proof, and the ambient temperature is 25° C. to 35° C.