Amphoteric network polymer solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses an amphiphilic network polymer solid electrolyte as well as a preparation method and application thereof, and belongs to the technical field of polymer solid lithium metal batteries. The method comprises the following steps: providing a porous polyimide rigid diaphragm; a flexible polymer monomer precursor solution is prepared, the flexible polymer monomer precursor solution comprises a polymeric monomer, an initiator, a lithium salt, a plasticizer and a cross-linking agent, and the polymeric monomer comprises 2, 2, 3, 4, 4, 4-hexafluorobutyl acrylate; assembling the porous polyimide rigid diaphragm and the flexible polymer monomer precursor solution with the positive electrode and the negative electrode of the battery to obtain an assembled battery; and heating the assembled battery, and initiating in-situ polymerization of the flexible polymer monomer precursor solution to obtain the amphiphilic network polymer solid electrolyte. According to the invention, the ion transmission capability is accelerated through the rigid-flexible amphiphilic polymer chain segment, the ion deposition is homogenized, the growth of lithium dendrites is inhibited, and the cycling stability and safety of the high-energy-density solid-state lithium metal battery are realized.

Description

Technical Field

[0001] This invention belongs to the field of polymer solid-state lithium metal battery technology, and specifically relates to a bipolar network polymer solid electrolyte, its preparation method, and its application. Background Technology

[0002] Compared to traditional graphite anodes (~372 mAh / g), lithium metal anodes have a higher theoretical specific capacity (3860 mAh / g). -1 The lithium metal exhibits high reactivity, leading to thermodynamic instability at the lithium metal-organic electrolyte interface, susceptibility to exothermic reactions, and low plating / stripping coulombic efficiency (CE), thus limiting its practical applications.

[0003] Traditional lithium metal batteries mostly use liquid organic electrolytes as the electrolyte, but liquid electrolytes are flammable, volatile, and prone to leakage, leading to poor safety issues. Replacing the liquid electrolyte with a membrane-based electrolyte using a solid-state electrolyte made from polymers can significantly improve battery safety and energy density. Currently, commonly used polymer solid-state electrolytes are mostly semi-crystalline polymer solid-state electrolytes such as polyvinylidene fluoride (PVDF) and polyethylene oxide (PEO). However, these traditional polymer solid-state electrolytes have low mechanical strength and a low glass transition temperature (T0). g High and severe interfacial dehydrogenation and fluorination cause the electrode / electrolyte interface to deteriorate significantly during electrochemical cycling, accompanied by uneven lithium deposition and dendrite growth, which in turn makes it easy to puncture low-strength electrolytes and greatly reduces the cycle life of polymer solid-state batteries.

[0004] Traditional PVDF and PEO-based polymer segments possess semi-crystalline properties, significantly restricting their chain mobility at room temperature. This results in weak ion conductivity, leading to rapid capacity decay of the battery as temperature decreases. Traditional modification methods involve introducing inorganic particles into the polymer matrix or using plasticizers (such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate organic solvents) to reduce the To of the polymer electrolyte. g Plasticizers can improve the mobility of polymer chain segments, thereby increasing the ionic conductivity of electrolytes. However, inorganic particles are prone to random agglomeration in the polymer matrix, and plasticizers can further reduce the mechanical stability of polymer electrolytes, making it difficult to achieve the expected modification effect. Summary of the Invention

[0005] The main objective of this invention is to provide a bipolar network polymer solid electrolyte, its preparation method, and its application, in order to solve the problems that existing traditional polymer solid electrolytes cannot simultaneously achieve high mechanical stability and excellent ionic conductivity, and cannot suppress the formation of lithium dendrites, resulting in short battery cycle life.

[0006] To achieve the above objectives, the present invention provides a method for preparing a bipolar network polymer solid electrolyte, comprising the following steps: Provides porous polyimide rigid diaphragms; A flexible polymer monomer precursor solution is prepared, wherein the flexible polymer monomer precursor solution comprises a polymerizing monomer, an initiator, a lithium salt, a plasticizer, and a crosslinking agent, wherein the polymerizing monomer comprises 2,2,3,4,4,4-hexafluorobutyl acrylate. The porous polyimide rigid separator, the flexible polymer monomer precursor liquid, and the positive and negative electrodes of the battery are assembled to obtain an assembled battery. The assembled battery is heated to initiate in-situ polymerization of the flexible polymer monomer precursor liquid, resulting in the amphoteric network polymer solid electrolyte.

[0007] Furthermore, the 2,2,3,4,4,4-hexafluorobutyl acrylate accounts for 10-20% of the mass fraction of the flexible polymer monomer precursor liquid.

[0008] Furthermore, the initiator accounts for 0.1-1% of the mass fraction of the flexible polymer monomer precursor liquid.

[0009] Furthermore, the crosslinking agent accounts for 0.5-2% of the mass fraction of the flexible polymer monomer precursor liquid.

[0010] Furthermore, the plasticizer accounts for 5-15% of the mass fraction of the flexible polymer monomer precursor liquid.

[0011] Furthermore, in the flexible polymer monomer precursor solution, the molar concentration of the lithium salt is 0.5-3M.

[0012] Furthermore, the plasticizer is selected from one or more of fluoroethylene carbonate (FEC), succinate, or tetraethylene glycol.

[0013] Furthermore, the crosslinking agent is selected from one or more of polyethylene glycol diacrylate, ethylene glycol dimethacrylate, or ethoxyethyl acrylate.

[0014] Furthermore, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, or lithium bis(difluorosulfonyl)imide.

[0015] Furthermore, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

[0016] Furthermore, the heating temperature is 60~80℃, and the heating time is 18~24h.

[0017] Furthermore, the porous polyimide rigid diaphragm is prepared by the following method: The polyimide polymer is dissolved in a solvent to form a polyimide solution; The polyimide solution is applied to a substrate, and then the substrate containing the polyimide solution is immersed in an aqueous ethanol solution to form a porous polyimide membrane. The porous polyimide membrane is dried, and after the solvent evaporates, a porous polyimide rigid membrane is obtained.

[0018] Furthermore, the mass fraction of the solute in the polyimide solution is 10-20%.

[0019] Furthermore, the volume fraction of ethanol in the ethanol-water solution is 10-20%.

[0020] Furthermore, the soaking time is 15 seconds to 3 minutes.

[0021] Furthermore, the polyimide solution coating thickness is 600~1000μm.

[0022] Furthermore, the drying temperature is 60~80℃, and the time is 12~24h.

[0023] In another aspect, the present invention provides a bipolar network polymer solid electrolyte, which is prepared by the aforementioned method for preparing bipolar network polymer solid electrolytes.

[0024] In another aspect, the present invention provides the application of the aforementioned bipolar network polymer solid electrolyte in solid lithium metal batteries.

[0025] Compared with existing technologies, this invention has the following advantages: By introducing flexible (fluorinated) 2,2,3,4,4,4-hexafluorobutyl acrylate segments capable of in-situ polymerization into the rigid-chain polyimide polymer segment structure, this invention ensures that the electrolyte possesses the high strength characteristics of the rigid segments. Simultaneously, an integrated electrode / electrolyte interface is constructed at the lithium metal anode interface through an in-situ polymerization strategy. The combination of rigidity and flexibility in the amphoteric polymer segments accelerates ion transport, homogenizes ion deposition, and suppresses lithium dendrite growth, thereby achieving high-energy-density solid-state lithium metal batteries with excellent cycle stability and safety. Attached Figure Description

[0026] Figure 1A cross-sectional morphology diagram of the porous polyimide rigid separator prepared in Example 1 of the present invention is shown; Figure 2 The surface morphology of the amphoteric network polymer solid electrolyte prepared in Example 1 of the present invention is shown. Figure 3 A comparison graph showing the cycle performance of the NCM lithium metal batteries of Example 1 and Comparative Example 1 of the present invention at room temperature 0.3C is provided. Figure 4 The graph shows a comparison of the cycling performance of the lithium symmetric batteries of Example 1 and Comparative Example 1 at room temperature, 0.2 mA / 0.2 mAh, and a cycling time of 2 h. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range. The invention will now be described in detail with reference to embodiments.

[0028] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a bipolar network polymer solid electrolyte, comprising the following steps: Provides porous polyimide rigid diaphragms; A flexible polymer monomer precursor solution is prepared, wherein the flexible polymer monomer precursor solution comprises a polymerizing monomer, an initiator, a lithium salt, a plasticizer, and a crosslinking agent, wherein the polymerizing monomer comprises 2,2,3,4,4,4-hexafluorobutyl acrylate. The porous polyimide rigid separator, the flexible polymer monomer precursor liquid, and the positive and negative electrodes of the battery are assembled to obtain an assembled battery. The assembled battery is heated to initiate in-situ polymerization of the flexible polymer monomer precursor liquid, resulting in the amphoteric network polymer solid electrolyte.

[0029] This invention introduces flexible fluorinated segments of 2,2,3,4,4,4-hexafluorobutyl acrylate, capable of in-situ polymerization, into the rigid segment structure of a polyimide polymer, forming a bipolar polymer network structure that combines rigidity and flexibility. The porous polyimide rigid separator, serving as the polymer substrate for the rigid segments, enhances the mechanical strength and thermal stability of the polymer electrolyte, resists and inhibits dendrite growth at the lithium metal interface, and the imide rings (-CO-NR-CO-) on the rigid main chain are difficult to rotate, thus effectively improving the strength of the flexible polymer chain under the influence of substances such as plasticizers, maintaining the stability of battery cycling. Simultaneously, compared to traditional rigid polymer electrolytes, the porous polyimide rigid separator of this invention has a higher porosity, which facilitates the effective penetration of the flexible polymer monomer precursor liquid into the polymer substrate, thereby enabling the construction of a bipolar network structure polymer solid electrolyte.

[0030] Its flexible polymer monomer precursor liquid is polymerized in situ to form flexible fluorinated segments, which have low T g (Glass transition temperature) The F element in the chain segment effectively weakens the coordination of the O element, which can effectively improve the ionic conductivity of the electrolyte and accelerate the ion transport rate. There is a van der Waals adsorption between the fluorinated ester functional group in its flexible fluorinated chain and the rigid chain imide ring in the polymer matrix, which helps to build a stable structure between the amphoteric network polymer chains.

[0031] Furthermore, based on porous polyimide polymer electrolytes, this invention utilizes an in-situ polymerization strategy to construct a bipolar network polymer solid electrolyte at the positive and negative electrode interfaces, achieving excellent electrode / electrolyte interface contact and stability, constructing fast ion transport channels, and realizing uniform ion deposition during electrochemical processes.

[0032] In a preferred embodiment of the present invention, the 2,2,3,4,4,4-hexafluorobutyl acrylate accounts for 10-20% of the mass fraction of the flexible polymer monomer precursor liquid. For example, it can be 10%, 12%, 14%, 15%, 16%, 18%, or 20%. Extensive experimental research has shown that within the above-mentioned mass fraction range, the 2,2,3,4,4,4-hexafluorobutyl acrylate can achieve both high ionic conductivity and excellent mechanical strength, thereby improving the cycle stability of solid-state lithium metal batteries. If the proportion of 2,2,3,4,4,4-hexafluorobutyl acrylate monomer exceeds 20%, it leads to a significant decrease in ionic conductivity and simultaneously causes exacerbated volume shrinkage during polymerization, resulting in deteriorated interfacial contact. If the proportion of 2,2,3,4,4,4-hexafluorobutyl acrylate monomer is less than 10%, it results in a loose polymer network and reduced thermal stability.

[0033] In some preferred embodiments of the present invention, the initiator accounts for 0.1-1% of the mass fraction of the flexible polymer monomer precursor liquid. For example, it can be 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or 1%. The crosslinking agent accounts for 0.5-2% of the mass fraction of the flexible polymer monomer precursor liquid, for example, it can be 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, or 2.0%. The present invention controls the segmental freedom and T of the fluorinated flexible segments by controlling the ratio of crosslinking agent to initiator in the flexible polymer monomer precursor liquid. g This increases the initiator ratio in the flexible polymer monomer precursor solution to accelerate the film formation of fluorinated ester segments in the pores, thereby accelerating ion transport. The high-porosity rigid substrate of this invention requires increasing the initiator ratio to accelerate the film formation of fluorinated ester segments in the pores, forming a dense amphoteric polymer electrolyte. Simultaneously, a high initiator ratio enhances the polymer crosslinking degree, further constructing an integrated, high-strength amphoteric network polymer electrolyte. More preferably, the crosslinking agent is selected from one or more of polyethylene glycol diacrylate, succinate (SN), or tetraethylene glycol (TEG); the initiator is selected from one or more of azobisisobutyronitrile, ethylene glycol dimethacrylate, or ethoxyethyl acrylate.

[0034] To further improve the ionic conductivity and mechanical strength of the amphoteric network polymer solid electrolyte, in a preferred embodiment of the present invention, the plasticizer accounts for 5-15% of the mass fraction of the flexible polymer monomer precursor liquid, for example, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, or 15%. If the plasticizer ratio is too high (above 15%), it will weaken the intermolecular forces, leading to a loose cross-linked network, and the free plasticizer may react with lithium metal. If the plasticizer ratio is too low (below 5%), it will result in a higher crystallinity of the polymer network, thus affecting the ionic conductivity. Further, the plasticizer may be selected from one or more of fluoroethylene carbonate (FEC), succinic anionyl nitrile, or tetraethylene glycol.

[0035] In a preferred embodiment of the present invention, the molar concentration of the lithium salt in the flexible polymer monomer precursor solution is 0.5-3M, for example, 0.5M, 0.75M, 1.0M, 1.25M, 1.5M, 2M, 2.5M, or 3M. At this ratio, the lithium salt can fully dissociate, ensuring high ionic conductivity while forming a stable SEI in situ.

[0036] In a preferred embodiment of the present invention, the heating temperature is 60-80°C, and the heating time is 18-24 hours. This heating condition ensures high reaction efficiency and conversion rate, while also guaranteeing the uniformity and low defects of the polymer network, and effectively improving interface stability.

[0037] In a preferred embodiment of the present invention, the porous polyimide rigid membrane is prepared by the following method: The polyimide polymer is dissolved in a solvent to form a polyimide solution; The polyimide solution is applied to a substrate, and then the substrate containing the polyimide solution is immersed in an aqueous ethanol solution to form a porous polyimide membrane. The porous polyimide membrane is dried, and after the solvent evaporates, a porous polyimide rigid membrane is obtained.

[0038] In some preferred embodiments of the present invention, the solute mass fraction of the polyimide solution is 10-20%. For example, it can be 10%, 12%, 14%, 15%, 16%, 18%, or 20%. Solutions with this solute mass fraction have easily viscous flows, exhibit small deviations in film thickness uniformity, and demonstrate excellent film quality, including tensile strength, elongation at break, and elastic modulus. Further, the solvent for the polyimide solution can be selected from N-methylpyrrolidone (NMP).

[0039] In some preferred embodiments of the present invention, the volume fraction of ethanol in the aqueous ethanol solution is 10-20%, for example, 10%, 12%, 14%, 15%, 16%, 18%, or 20%. The soaking time is 15 seconds to 3 minutes.

[0040] This invention utilizes a phase reversal method to prepare porous polyimide rigid membranes. Reducing the ethanol concentration in water accelerates the exchange rate between the solvent and non-solvent water in the PI (polyimide) solution, resulting in increased porosity of the prepared rigid PI membrane. Since high-concentration electrolytes have increased viscosity, a high-porosity substrate facilitates the flow of the high-concentration electrolyte precursor solution within the substrate. Simultaneously, the large pores facilitate the storage of the precursor solution, which is beneficial for subsequent heating and curing to form flexible segments. Therefore, this invention precisely controls the ethanol concentration and soaking time in the ethanol-water solution to regulate the pore structure and porosity of the rigid linear polyimide membrane, thereby obtaining a high-porosity porous polyimide rigid membrane.

[0041] To further improve the overall performance of the bipolar network polymer solid electrolyte, in some preferred embodiments of the present invention, the polyimide solution coating thickness is 600~1000μm, the porous polyimide membrane is dried at a temperature of 60~80℃, and the drying time is 12~24h.

[0042] A second aspect of the present invention also provides a bipolar network polymer solid electrolyte, which is prepared by the aforementioned method for preparing bipolar network polymer solid electrolytes.

[0043] Based on the reasons mentioned above, the bipolar network polymer solid electrolyte prepared by this invention has both high mechanical stability and excellent ionic conductivity, which is beneficial for homogenizing ion deposition, suppressing lithium dendrite growth, and achieving high energy density solid lithium metal battery cycle stability and safety.

[0044] A third aspect of the present invention also provides the application of a bipolar network polymer solid electrolyte in a solid lithium metal battery.

[0045] Based on the reasons mentioned above, solid-state lithium metal batteries can achieve high energy density and high cycle stability.

[0046] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0047] Example 1 A bipolar network polymer solid electrolyte, the preparation method of which includes the following steps: (1) Preparation of porous polyimide rigid membrane: PI (polyimide) powder was uniformly dispersed in NMP solvent, with the solute mass fraction maintained at 10%, and a uniform polyimide solution was obtained by heating and stirring at 60°C. The polyimide solution was applied to a glass plate, and the thickness was controlled to 900 μm by the doctor blade to ensure uniform application on an automatic coating machine. The glass plate containing the polyimide solution was immersed in an ethanol-water solution (10% by volume) for 30 seconds, thereby displacing the NMP solvent in the PI solution into the water to form a porous polyimide membrane, providing conditions for the in-situ polymer penetration. The porous polyimide membrane was placed at 60°C. o The porous polyimide rigid membrane was obtained by vacuum drying in an oven at temperature C for 24 hours, allowing the solvent to evaporate. The cross-section of the prepared porous polyimide rigid membrane is shown below. Figure 1 As shown in the figure, the obtained porous polyimide film exhibits a uniform sponge-like porous structure.

[0048] (2) Preparation of flexible polymer monomer precursor solution: A flexible polymer monomer precursor solution is formed by mixing 2,2,3,4,4,4-hexafluorobutyl acrylate, azobisisobutyronitrile (AIBN) as an initiator, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a lithium salt, fluoroethylene carbonate (FEC) as a plasticizer, and polyethylene glycol diacrylate (PEGDA) as a crosslinking agent. The lithium salt concentration is 2M, AIBN accounts for 0.1% of the mass fraction of the flexible polymer monomer precursor solution, the crosslinking agent accounts for 1% of the mass fraction of the flexible polymer monomer precursor solution, 2,2,3,4,4,4-hexafluorobutyl acrylate accounts for 20% of the mass fraction of the flexible polymer monomer precursor solution, and the plasticizer accounts for 12% of the mass fraction of the flexible polymer monomer precursor solution.

[0049] (3) In-situ polymerization: Preparation of the battery positive electrode: The positive electrode material is NCM811, the binder used in the preparation is polyvinylidene fluoride, the conductive additive is C45, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide. The positive electrode material, conductive agent, binder and lithium salt are mixed evenly in N-methylpyrrolidone (NMP) solvent at a mass ratio of 7:1:1:1 to obtain a slurry. The evenly stirred slurry is coated on aluminum foil with a coating thickness of 800 μm. Then the aluminum foil coated with slurry is placed in an oven at 80°C and vacuum dried for 24 h to obtain the battery positive electrode. The above-mentioned porous polyimide rigid separator, the above-mentioned flexible polymer monomer precursor liquid, the above-mentioned battery positive electrode, and lithium metal negative electrode are assembled to obtain an assembled battery. The assembled battery was placed in a 60°C oven for 24 hours to allow the flexible polymer monomer precursor solution to polymerize in situ, forming a bipolar network polymer solid electrolyte. The surface morphology of the bipolar network polymer solid electrolyte obtained in this embodiment is as follows: Figure 2 As shown, it exhibits a dense surface.

[0050] Example 2 A bipolar network polymer solid electrolyte, which differs from the preparation method of Example 1 only in that the mass fraction of the polyimide solution is 20%.

[0051] Example 3 A bipolar network polymer solid electrolyte differs from the preparation method of Example 1 only in that the glass plate containing the polyimide solution is immersed in an ethanol aqueous solution for 1 minute.

[0052] Example 4 A bipolar network polymer solid electrolyte differs from the preparation method of Example 1 only in that the concentration of lithium salt in the flexible polymer monomer precursor solution is 1M.

[0053] Example 5 A bipolar network polymer solid electrolyte differs from the preparation method of Example 2 only in that 2,2,3,4,4,4-hexafluorobutyl acrylate accounts for 15% of the mass fraction of the flexible polymer monomer precursor solution.

[0054] Example 6 A bipolar network polymer solid electrolyte differs from the preparation method of Example 2 only in that 2,2,3,4,4,4-hexafluorobutyl acrylate accounts for 10% of the mass fraction of the flexible polymer monomer precursor solution.

[0055] Example 7 A bipolar network polymer solid electrolyte differs from the preparation method of Example 2 only in that the plasticizer accounts for 5% of the mass fraction of the flexible polymer monomer precursor liquid.

[0056] Comparative Example 1 A polymer solid electrolyte, the preparation method of which is as follows: (1) Preparation of PVDF / LiTFSI polymer film: Polyvinylidene fluoride (PVDF) powder was uniformly dispersed in NMP solvent, with the solute mass fraction maintained at 10%. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), with the same mass fraction as PVDF, was then added as a lithium salt. Both components were heated and stirred at 60°C to obtain a homogeneous slurry with uniform composition.

[0057] The above slurry was applied to a glass plate, and the thickness was controlled to 900 μm using a doctor blade to ensure even application on an automatic coating machine. The coated glass plate was then placed at 60°C. o The film was dried in an oven at temperature C for 24 hours under vacuum until the solvent evaporated, resulting in a dense PVDF / LiTFSI polymer film.

[0058] (2) Preparation of flexible polymer monomer precursor solution: The same flexible polymer monomer precursor solution as in Example 1 is used.

[0059] (3) In-situ polymerization: The positive electrode of the battery is prepared by the same method as in Example 1, and the above PVDF / LiTFSI polymer film, the above flexible polymer monomer precursor liquid, the above positive electrode of the battery and the lithium metal negative electrode are assembled to obtain the assembled battery; the above assembled battery is placed in an oven at 60°C for 24 hours to allow the flexible polymer monomer precursor liquid to polymerize in situ to form a polymer solid electrolyte.

[0060] Comparative Example 2 A bipolar network polymer solid electrolyte, which differs from the preparation method of Example 1 only in that 2,2,3,4,4,4-hexafluorobutyl acrylate is replaced with methyl acrylate.

[0061] Performance testing: The cycle performance of the NCM lithium metal batteries prepared in the above examples and comparative examples was tested at room temperature and 0.3C. The test results are shown in Table 1. The cycle performance comparison between Example 1 and Comparative Example 1 is as follows: Figure 3 As shown, with similar capacity retention, Example 1 has a specific capacity that is 15-25 mAh / g higher than that of Comparative Example 1.

[0062] Table 1

[0063] The polymer solid electrolytes prepared in Example 1 and Comparative Example 1 were assembled into lithium symmetric batteries and their cycle performance was tested at room temperature and 0.2 mA / 0.2 mAh. Each cycle lasted 2 hours. The performance comparison graph is shown below. Figure 4 As shown, it can be seen that the overpotential of Example 1 is much lower than that of Comparative Example 1, and it is more stable.

[0064] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. The present invention can also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of the present invention should be defined by the appended claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A method for preparing a bipolar network polymer solid electrolyte, characterized in that, Includes the following steps: Provides porous polyimide rigid diaphragms; A flexible polymer monomer precursor solution is prepared, wherein the flexible polymer monomer precursor solution comprises a polymerizing monomer, an initiator, a lithium salt, a plasticizer, and a crosslinking agent, wherein the polymerizing monomer comprises 2,2,3,4,4,4-hexafluorobutyl acrylate. The porous polyimide rigid separator, the flexible polymer monomer precursor liquid, and the positive and negative electrodes of the battery are assembled to obtain an assembled battery. The assembled battery is heated to initiate in-situ polymerization of the flexible polymer monomer precursor liquid, resulting in the amphoteric network polymer solid electrolyte.

2. The method for preparing the amphoteric network polymer solid electrolyte according to claim 1, characterized in that, The 2,2,3,4,4,4-hexafluorobutyl acrylate accounts for 10-20% of the mass fraction of the flexible polymer monomer precursor solution; And / or, the initiator accounts for 0.1% to 1% of the mass fraction of the flexible polymer monomer precursor solution; And / or, the crosslinking agent accounts for 0.5-2% of the mass fraction of the flexible polymer monomer precursor solution; And / or, the plasticizer accounts for 5-15% of the mass fraction of the flexible polymer monomer precursor liquid; And / or, in the flexible polymer monomer precursor solution, the molar concentration of the lithium salt is 0.5-3M.

3. The method for preparing the amphoteric network polymer solid electrolyte according to claim 1, characterized in that, The plasticizer is selected from one or more of fluoroethylene carbonate (FEC), succinate, or tetraethylene glycol; And / or, the crosslinking agent is selected from one or more of polyethylene glycol diacrylate, ethylene glycol dimethacrylate, or ethoxyethyl acrylate; And / or, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, or lithium bis(difluorosulfonyl)imide; And / or, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

4. The method for preparing the amphoteric network polymer solid electrolyte according to claim 1, characterized in that, The heating temperature is 60~80℃, and the time is 18~24h.

5. The method for preparing the amphoteric network polymer solid electrolyte according to claim 1, characterized in that, The porous polyimide rigid diaphragm is prepared by the following method: The polyimide polymer is dissolved in a solvent to form a polyimide solution; The polyimide solution is applied to a substrate, and then the substrate containing the polyimide solution is immersed in an aqueous ethanol solution to form a porous polyimide membrane. The porous polyimide membrane is dried, and after the solvent evaporates, a porous polyimide rigid membrane is obtained.

6. The method for preparing the amphoteric network polymer solid electrolyte according to claim 5, characterized in that, The solute mass fraction of the polyimide solution is 10~20%.

7. The method for preparing the amphoteric network polymer solid electrolyte according to claim 5, characterized in that, The volume fraction of ethanol in the ethanol-water solution is 10-20%. And / or, the soaking time is 15s to 3min.

8. The method for preparing the amphoteric network polymer solid electrolyte according to claim 5, characterized in that, The polyimide solution coating thickness is 600~1000μm.

9. A bipolar network polymer solid electrolyte, characterized in that, The solid electrolyte is prepared by any one of the methods described in claims 1 to 9.

10. The application of the bipolar network polymer solid electrolyte as described in claim 9 in a solid lithium metal battery.

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