A method for the preparation of an in-situ polymerized electrolyte

Abstract

The application discloses a preparation method of an in-situ polymerized electrolyte, and relates to the field of solid electrolytes. A crosslinking agent and a nitrile additive are added into an elastomer polymer monomer respectively, so that the elastomer polymer monomer is completely dissolved, and a first solution is obtained; a first lithium salt is added into the first solution, a second lithium salt is added after uniform stirring, a free radical polymerization initiator is added after uniform stirring, and an elastomer polymer electrolyte precursor solution is obtained; a cationic polymerization monomer is added into the elastomer polymer electrolyte precursor solution, and then an initiator with flame retardance is added, so that a double-polymer electrolyte precursor solution is obtained; the double-polymer electrolyte precursor solution is added into a battery, and a cationic polymerization reaction is carried out at room temperature; after standing, free radical polymerization is initiated through heating, and an in-situ polymerized double-polymer electrolyte is obtained. The application improves the interface performance, safety performance and electrochemical performance while maintaining the mechanical strength of the electrolyte.

Description

Technical Field

[0001] This application relates to the field of solid electrolyte technology, and in particular to a method for preparing an electrolyte by in-situ polymerization. Background Technology

[0002] With the rapid development of technology and the urgent market demand for energy storage devices with high energy density and high safety performance, traditional lithium-ion batteries are gradually showing their limitations. The liquid electrolyte in lithium-ion batteries poses risks of flammability and leakage, which not only limits their application in fields with high safety requirements but also increases safety hazards during use. Furthermore, the theoretical specific capacity of graphite anodes is limited, further hindering the improvement of lithium-ion battery energy density.

[0003] Given this, lithium metal, with its extremely high theoretical energy density and low reduction potential, is considered an ideal choice for anode materials. To simultaneously improve the safety and energy density of lithium-ion batteries, researchers have proposed using solid-state electrolytes instead of traditional liquid electrolytes. This strategy is expected to significantly meet the dual demands of high energy density and high safety for future energy storage devices.

[0004] However, lithium metal solid-state batteries still face many challenges in practical applications. Among them, the solid-solid contact problem at the interface between the inorganic solid electrolyte and the electrode is particularly prominent. The rigidity and brittleness of inorganic solid electrolytes result in poor interfacial contact performance and high interfacial impedance, which in turn affects battery performance and cycle stability. To address this issue, polymer electrolytes have attracted widespread attention due to their good flexibility and interfacial properties. In-situ generated solid electrolyte precursors are liquid, which can fully wet the electrode-electrolyte interface, and then undergo in-situ polymerization under thermal initiation or ultraviolet light.

[0005] Currently, in-situ generated polymer electrolytes are typically prepared using free radical polymerization. Free radical polymerization introduces an additional initiator and utilizes the opening of double bonds in the monomers during polymerization to generate the polymer electrolyte. Elastomer solid-state electrolytes prepared using this method have shown potential in lithium metal solid-state batteries, particularly in addressing the issues arising from volume changes during charge and discharge. However, polymer electrolytes prepared by free radical polymerization also face some challenges. For example, while the polybutyl acrylate system, which has been extensively studied for in-situ polymerization, exhibits excellent cycle performance in assembled lithium metal symmetric batteries, its poor contact performance with cathode micro / nano particles hinders improvements in rate performance. Furthermore, this system still suffers from flammability, limiting its application in fields with high safety requirements.

[0006] To improve the safety performance of polymer electrolytes, researchers have attempted to add liquid phosphate ester monomers to the system. However, while the introduction of liquid electrolytes improves safety to some extent, it also reduces the mechanical properties of the polymer, weakens its ability to suppress lithium dendrites, and consequently reduces the cycle performance of lithium metal batteries. Summary of the Invention

[0007] This application provides an in-situ polymerized electrolyte preparation method, which solves the problems mentioned in the background art.

[0008] This application provides a method for preparing an electrolyte through in-situ polymerization, comprising:

[0009] Under an argon-protected atmosphere, crosslinking agents and nitrile additives are added to the elastomer polymer monomers respectively, allowing them to dissolve completely to obtain the first solution;

[0010] A first lithium salt, which is lithium bis(trifluoromethanesulfonylimide), lithium hexafluorophosphate, or lithium perchlorate, is added to the first solution. After stirring evenly, a second lithium salt, which is lithium difluorooxalateborate, lithium fluoride, or lithium nitrate, is added. After stirring evenly again, a free radical polymerization initiator is added to obtain an elastomer polymer electrolyte precursor solution.

[0011] The cationic polymer monomer is added to the elastomeric polymer electrolyte precursor solution and stirred until homogeneous. Then, a flame-retardant initiator is added and stirred until homogeneous again to obtain a dual polymer electrolyte precursor solution.

[0012] The bipolymer electrolyte precursor solution was added to the battery and cationic polymerization was carried out at room temperature. After standing for 10-24 hours, free radical polymerization was initiated by heating to obtain the in-situ polymerized bipolymer electrolyte.

[0013] In one possible implementation, adding the dual polymer electrolyte precursor solution to the battery further includes:

[0014] It is applied to the positive electrode surface of the battery by dripping, coating, or a combination of dripping and coating.

[0015] In one possible implementation, the elastomeric polymer monomer includes at least one of methacrylic acid, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hexyl acrylate.

[0016] In one possible implementation, the crosslinking agent comprises a bifunctional monomer.

[0017] In one possible implementation, the bifunctional monomer includes at least one of polyethylene glycol diacrylate and tripropylene glycol diacrylate.

[0018] In one possible implementation, the mass percentage of the bifunctional monomer to the elastomeric polymer monomer is 1%-10%.

[0019] In one possible implementation, the concentration of the first lithium salt is 0.5-3 mol / L; the concentration of the second lithium salt is 0.05-0.3 mol / L; and the mass percentage of the free radical polymerization initiator to the elastomeric polymer monomer ranges from 0.05 wt% to 2 wt%.

[0020] In one possible implementation, the nitrile additive is succinic anionyl nitrile or glutaronitrile; the free radical polymerization initiator is azobisisobutyronitrile.

[0021] In one possible implementation, the cationic polymeric monomer is a cyclic monomer, comprising at least one of dioxane, trioxane, 1,3-dioxane, tetrahydrofuran, and butoxycyclohexane, and the volume percentage of the cationic polymeric monomer to the elastomeric polymeric monomer is 5 vol% to 50 vol%.

[0022] In one possible implementation, the flame-retardant initiator comprises at least one of tris(pentafluorophenyl)boron or tris(hexafluoroisopropyl)borate; the initiator is in the range of 1 wt% to 5 wt% by mass percentage of the cationic polymeric monomer.

[0023] One or more technical solutions provided in the embodiments of this application have at least the following technical effects:

[0024] This application provides a method for preparing electrolytes via in-situ polymerization. Firstly, since this method does not require the introduction of additional liquid components, it optimizes electrolyte performance without significantly reducing the electrolyte's mechanical strength. During the preparation process, a cationic polymerization product is first generated at room temperature, increasing the viscosity of the precursor system. Subsequently, the elastomer polymer monomers undergo thermally initiated free radical polymerization, accompanied by an increase in viscosity. This ensures the uniformity of the free radical polymerization and suppresses volume shrinkage. This characteristic not only maintains the electrolyte's mechanical strength but also effectively improves the interfacial performance between the electrolyte and the cathode micro / nano particles. The improved interfacial performance directly enhances the battery's rate performance, enabling the battery to maintain higher efficiency and stability during rapid charge and discharge.

[0025] Secondly, by introducing a flame-retardant initiator and incorporating flame-retardant units into the polymer chain via cationic polymerization, this method significantly improves the safety performance of the electrolyte and avoids the side reactions associated with liquid flame retardants. When the battery encounters abnormal conditions such as short circuits or overheating, the electrolyte exhibits excellent flame-retardant properties, making it less prone to combustion or explosion, thus effectively protecting the battery and surrounding equipment. This enhanced safety performance is undoubtedly of paramount importance for key applications such as electric vehicles and energy storage systems.

[0026] Finally, this method successfully constructed a stable dual-polymer electrolyte network structure through in-situ polymerization. This unique network structure not only improves the ionic conductivity and electrochemical stability of the electrolyte but also significantly enhances its mechanical strength. Simultaneously, the interweaving of the dual-polymer networks further improves the interfacial compatibility between the electrolyte and the electrode, effectively reducing interfacial impedance. These performance optimizations collectively reduce battery performance degradation during charge and discharge processes, extend battery cycle life, and increase the energy density of lithium metal batteries. Particularly in the field of lithium metal batteries, the in-situ polymerized electrolyte exhibits a significant inhibitory effect, effectively preventing the growth of lithium dendrites. Lithium dendrites are one of the main causes of internal short circuits and capacity loss in lithium metal batteries. The electrolyte prepared by this method can significantly reduce the probability of lithium dendrite formation, thereby improving the safety and cycle stability of lithium metal batteries.

[0027] In summary, the in-situ polymerization electrolyte preparation method provided in this application significantly improves the interfacial properties, safety performance, and electrochemical performance of the electrolyte while maintaining its mechanical strength. These technical effects work together to improve the rate performance, cycle life, and energy density of the battery, injecting new vitality into the development of novel energy storage devices such as lithium metal batteries. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart of the in-situ polymerization electrolyte preparation method provided in the embodiments of this application;

[0030] Figure 2a A schematic diagram showing the addition of the dual polymer electrolyte precursor solution provided in this application embodiment into the battery;

[0031] Figure 2bThis is a schematic diagram of the interior of the battery after the cationic polymerization reaction, as provided in the embodiments of this application.

[0032] Figure 2c This is a schematic diagram of the internal structure of a dual polymer electrolyte battery provided in an embodiment of this application;

[0033] Figure 3a and Figure 3b The images show the flame retardant performance of Example 1 and Comparative Example 1, respectively, provided in this application.

[0034] Figure 4 Magnification diagrams of Embodiment 1 and Comparative Example 1 provided for embodiments of this application;

[0035] Figure 5 Impedance spectra of Embodiment 1 and Comparative Example 1 provided for embodiments of this application.

[0036] Icons: 1-Positive current collector; 2-Positive active material; 3-Conductive additive; 4-Dual polymer electrolyte precursor solution; 5-Supporting film; 6-Lithium metal negative electrode; 7-Flame-retardant cationic linear polymer; 8-Free radical polymerized elastomeric electrolyte precursor; 9-Dual polymer electrolyte; 10-Positive electrode-dual polymer electrolyte interface. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0039] This application provides a method for preparing an electrolyte through in-situ polymerization, such as... Figures 1 to 5 As shown. The preparation method includes the following steps S1-S4:

[0040] S1: Under an argon-protected atmosphere, the crosslinking agent and nitrile additives are added to the elastomer polymer monomers respectively, and they are completely dissolved to obtain the first solution.

[0041] It should be noted that under argon protection, the crosslinking agent can be more uniformly dispersed within the elastomer polymer monomers, creating favorable conditions for the subsequent crosslinking reaction, allowing it to proceed more fully and uniformly. Simultaneously, the addition of nitrile additives aims to improve the ionic conductivity and voltage range of the polymer electrolyte.

[0042] Argon, as an inert gas, effectively isolates impurities such as oxygen and moisture from the air, preventing them from undergoing unintended chemical reactions with elastomer polymer monomers, crosslinking agents, and nitrile additives, thereby significantly improving the chemical stability of the final product. Therefore, adding crosslinking agents and nitrile additives to elastomer polymer monomers and ensuring their complete dissolution under an argon protective atmosphere not only enhances the material's stability and crosslinking effect but also strengthens its weather resistance.

[0043] S2: Add a first lithium salt to the first solution. The first lithium salt is lithium bis(trifluoromethanesulfonylimide), lithium hexafluorophosphate, or lithium perchlorate. Stir until homogeneous, then add a second lithium salt. The second lithium salt is lithium difluorooxalateborate, lithium fluoride, or lithium nitrate. Continue stirring until homogeneous, then add a free radical polymerization initiator to obtain an elastomer polymer electrolyte precursor solution.

[0044] Specifically, the introduction of high-conductivity lithium salts such as lithium bis(trifluoromethanesulfonyl)imide and lithium hexafluorophosphate aims to improve the overall conductivity of the electrolyte, which is crucial for ensuring efficient ion transport within the battery. The addition of modified lithium salts such as lithium difluorooxalateborate further enhances the thermal and chemical stability of the electrolyte, thereby improving battery safety. After the free radical polymerization initiator is uniformly dispersed in solution, it effectively triggers the polymerization reaction of the elastomer polymer monomers in subsequent polymerization steps, thus constructing an elastomer polymer electrolyte network with a specific structure.

[0045] S3: Add the cationic polymer monomer to the elastomer polymer electrolyte precursor solution and stir until homogeneous. Then add the flame-retardant initiator and stir until homogeneous again to obtain the dual polymer electrolyte precursor solution 4.

[0046] It should be noted that the addition of a flame-retardant initiator can introduce flame-retardant elements during the polymerization process, thereby significantly improving the flame-retardant performance of the dual polymer electrolyte 9. This is crucial for improving the safety performance of the battery, especially under extreme conditions such as high temperature or short circuit, which can effectively prevent the risk of thermal runaway and fire.

[0047] S4: Add the dual polymer electrolyte precursor solution 4 to the battery and carry out cationic polymerization at room temperature. After standing for 10-24 hours, initiate free radical polymerization by heating to obtain the in-situ polymerized dual polymer electrolyte 9.

[0048] Furthermore, such as Figure 2a As shown, the dual polymer electrolyte precursor solution 4 is injected into the battery. This solution can fully wet the positive electrode active material 2, conductive additive 3 and lithium metal anode 6 on the surface of the positive electrode current collector 1. At the same time, the presence of the support film 5 effectively prevents direct contact between the positive electrode active material 2 and the lithium metal anode 6, thereby avoiding the risk of short circuit.

[0049] In the first step, this application successfully formed a flame-retardant cationic linear polymer 7 through a cationic polymerization reaction at room temperature, such as... Figure 2b As shown, this polymer not only forms a close contact with the positive electrode active material 2, constructing a good interface, but also significantly increases the viscosity of the free radical polymerized elastomer electrolyte precursor 8. This increase in viscosity plays a key role in effectively suppressing the volume changes that may occur during the free radical polymerization process.

[0050] Next, in the second step, a flame-retardant dipolymer electrolyte 9 was generated through a thermally initiated free radical polymerization reaction, such as... Figure 2c As shown, the dual polymer electrolyte 9 forms an excellent interfacial contact with the positive electrode active material 2, namely the positive electrode-dual polymer electrolyte interface 10, which provides a solid guarantee for the high-rate performance of the battery.

[0051] Specifically, the dual polymer electrolyte precursor solution 4 of this application integrates two polymerization mechanisms: free radical polymerization and cationic polymerization. Because the initiation conditions for these two polymerization mechanisms differ, stepwise polymerization can be achieved. First, a reactive flame retardant such as tris(pentafluorophenyl)boron is used as an initiator to initiate the cationic polymerization reaction at room temperature. By precisely controlling the settling time, the polymerization reaction can be ensured to proceed stepwise, thus generating a long-chain flame-retardant polymer through the first in-situ polymerization. Subsequently, the temperature is increased to trigger the second step of thermally initiated in-situ polymerization. In this stage, the monomers of the elastomeric polymer undergo thermally initiated free radical polymerization. Since the viscosity of the solution has increased at this point, this helps to ensure the uniformity of the free radical polymerization. Without significantly reducing mechanical strength, this stepwise polymerization method can improve the interfacial properties between the elastomeric electrolyte and the cathode micro / nano particles, while simultaneously enhancing its safety.

[0052] It should be noted that the embodiments of this application provide an in-situ polymerization method for preparing electrolytes. Firstly, since this method does not require the introduction of additional liquid components, it optimizes electrolyte performance without significantly reducing the mechanical strength of the electrolyte. During the preparation process, a cationic polymerization product is first generated at room temperature, increasing the viscosity of the precursor system. Subsequently, the elastomer polymer monomers undergo thermally initiated free radical polymerization, accompanied by an increase in viscosity. This ensures the uniformity of the free radical polymerization and suppresses volume shrinkage. This characteristic not only maintains the mechanical strength of the electrolyte but also effectively improves the interfacial performance between the electrolyte and the cathode micro / nano particles. The improved interfacial performance directly enhances the rate performance of the battery, enabling it to maintain higher efficiency and stability during rapid charge and discharge.

[0053] Secondly, by introducing a flame-retardant initiator, flame-retardant units are incorporated into the polymer chain via cationic polymerization. This method significantly improves the safety performance of the electrolyte and avoids the side reactions associated with liquid flame retardants. When the battery encounters abnormal conditions such as short circuits or overheating, the electrolyte exhibits excellent flame-retardant properties, making it less prone to combustion or explosion, thus effectively protecting the battery and surrounding equipment. This improvement in safety performance is undoubtedly of paramount importance for key applications such as electric vehicles and energy storage systems.

[0054] Finally, this method successfully constructed a stable dual-polymer electrolyte network structure via in-situ polymerization. This unique network structure not only improves the ionic conductivity and electrochemical stability of the electrolyte but also significantly enhances its mechanical strength. Simultaneously, the interweaving of the dual-polymer networks further improves the interfacial compatibility between the electrolyte and the electrodes, effectively reducing interfacial impedance. These performance optimizations collectively reduce battery performance degradation during charge and discharge processes, extend battery cycle life, and increase the energy density of lithium metal batteries. Particularly in the field of lithium metal batteries, the in-situ polymerized electrolyte exhibits a significant inhibitory effect, effectively preventing the growth of lithium dendrites. Lithium dendrites are one of the main causes of internal short circuits and capacity loss in lithium metal batteries. The electrolyte prepared by this method can significantly reduce the probability of lithium dendrite formation, thereby improving the safety and cycle stability of lithium metal batteries.

[0055] In summary, the in-situ polymerization electrolyte preparation method provided in this application significantly improves the interfacial properties, safety performance, and electrochemical performance of the electrolyte while maintaining its mechanical strength. These technical effects work together to improve the rate performance, cycle life, and energy density of the battery, injecting new vitality into the development of novel energy storage devices such as lithium metal batteries.

[0056] In this embodiment of the application, adding the dual polymer electrolyte precursor solution 4 to the battery further includes applying it to the positive electrode surface of the battery by dripping, coating, or a combination of dripping and coating.

[0057] It should be noted that, through drop-addition or coating methods, the dual polymer electrolyte precursor solution 4 can uniformly cover the surface and interior of the positive electrode, forming a tight contact. This tight contact helps reduce interfacial resistance and improve ion conduction efficiency, thereby significantly enhancing the electrochemical performance of the battery.

[0058] Meanwhile, in this embodiment, the dual polymer electrolyte precursor solution 4 is first added dropwise to the inside of the battery to ensure deep wetting, and then a layer of dual polymer electrolyte precursor solution 4 is coated on the surface of the battery. This can ensure that the inside of the battery is fully wetted, while ensuring the electrolyte content on the surface.

[0059] In the embodiments of this application, the elastomer polymer monomer includes at least one of methacrylic acid, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hexyl acrylate.

[0060] It should be noted that by selecting appropriate elastomeric polymer monomers, the microstructure and porosity of the electrolyte can be controlled, thereby optimizing the ion conduction pathway and efficiency. This helps improve the battery's ion conduction performance, reduce internal resistance, and increase the battery's charge / discharge rate and energy density. These elastomeric polymer monomers have good compatibility with the cathode material, which helps stabilize the internal electrochemical environment of the battery and extend its cycle life.

[0061] In the embodiments of this application, the crosslinking agent includes a bifunctional monomer.

[0062] In the embodiments of this application, the bifunctional monomer includes at least one of polyethylene glycol diacrylate and tripropylene glycol diacrylate.

[0063] It should be noted that this application uses bifunctional monomers such as polyethylene glycol diacrylate and tripropylene glycol diacrylate as crosslinking agents, which can significantly improve the crosslinking density of the electrolyte, optimize the microstructure, enhance interfacial compatibility and adhesion, improve safety performance, and provide flexible formulation design.

[0064] In the embodiments of this application, the mass percentage of the bifunctional monomer and the elastomeric polymer monomer is 1%-10%.

[0065] When the mass percentages of bifunctional monomers and elastomeric polymer monomers fall within the range of 1%-10%, they can jointly construct an electrolyte network structure with a moderate crosslinking density. This carefully designed network structure not only provides the necessary mechanical support for the electrolyte, effectively preventing electrolyte rupture that may occur during battery charge-discharge cycles, but also ensures good ion conduction performance, thereby guaranteeing the efficient and stable operation of the battery.

[0066] Furthermore, rationally controlling the addition ratio of bifunctional monomers to elastomeric polymer monomers can not only ensure the excellent performance of the electrolyte but also help reduce production costs. Specifically, adding too much elastomeric polymer monomer will lead to an unnecessary increase in production costs, while adding too little elastomeric polymer monomer may weaken the overall performance of the electrolyte.

[0067] In this embodiment, the concentration of the first lithium salt is 0.5-3 mol / L, and the concentration of the second lithium salt is 0.05-0.3 mol / L. Setting the concentration ranges of the first and second lithium salts helps to form an appropriate lithium ion concentration gradient, thereby optimizing the ion conduction pathway and improving the ion conduction efficiency of the electrolyte.

[0068] The mass percentage of the free radical polymerization initiator to the elastomeric polymer monomer ranges from 0.05 wt% to 2 wt%.

[0069] In the embodiments of this application, the nitrile additive is succinic anionyl nitrile or glutaronitrile. The free radical polymerization initiator is azobisisobutyronitrile.

[0070] In the embodiments of this application, the cationic polymer monomer is a cyclic monomer, which includes at least one of dioxane, trioxane, 1,3-dioxane, tetrahydrofuran, and butoxycyclohexane, and the volume percentage of the cationic polymer monomer to the elastomer polymer monomer is 5 vol% to 50 vol%.

[0071] It should be noted that cyclic monomers, such as dioxane, have specific chemical structures that can generate linear polymers, thereby enhancing the thermal stability and flame retardancy of the polymers.

[0072] Controlling the volume percentage of cationic polymer monomers and elastomeric polymer monomers within the range of 5 vol% to 50 vol% ensures the smooth progress of the polymerization reaction and improves production efficiency.

[0073] In this embodiment, the flame-retardant initiator includes at least one of tris(pentafluorophenyl)boron or tris(hexafluoroisopropyl)borate. The mass percentage of the initiator to the cationic polymerizable monomer ranges from 1 wt% to 5 wt%.

[0074] It should be noted that controlling the mass percentage of the initiator to the cationic monomer within the range of 1 wt% to 5 wt% helps to obtain polymer materials with excellent flame-retardant properties. Tris(pentafluorophenyl)boron initiators have a relatively small environmental impact during use and meet environmental protection requirements.

[0075] Example 1:

[0076] A method for preparing an electrolyte through in-situ polymerization includes the following steps:

[0077] Under an argon-protected atmosphere, polyethylene glycol diacrylate (PEGDA) and succinic anhydride modifier were added to butyl acrylate and dissolved completely to obtain the first solution.

[0078] Lithium bis(trifluoromethanesulfonylimide) (LiTFSI) was added to the first solution and stirred until homogeneous. Then lithium difluorooxalate borate (LiDFOB) was added and stirred until homogeneous. Finally, azobisisobutyronitrile was added as an initiator to obtain an elastomer polymer electrolyte precursor solution.

[0079] 1,3-dioxolane was added to the elastomer polymer electrolyte precursor solution and stirred until homogeneous. Then, tris(pentafluorophenyl)boron (TFB) was added as a cationic initiator and stirred until homogeneous again to obtain the dual polymer electrolyte precursor solution 4.

[0080] Injecting the dual polymer electrolyte precursor solution 4 into the battery triggers an in-situ polymerization reaction. This reaction consists of two main steps: the first step involves standing at room temperature for 12 hours, during which 1,3-dioxolane undergoes cationic polymerization; the second step involves heating at 60°C for 12 hours to promote the free radical polymerization of butyl acrylate (as an elastomer monomer). These two steps ultimately yield the in-situ polymerized dual polymer electrolyte 9, which transforms the battery into a solid-state battery.

[0081] The battery uses lithium iron phosphate cathode and lithium metal sheet anode.

[0082] Comparative Example 1:

[0083] A method for preparing an elastomeric electrolyte includes the following steps:

[0084] Under an argon-protected atmosphere, polyethylene glycol diacrylate (PEGDA) and succinic anhydride modifier were added to butyl acrylate and dissolved completely to obtain the first solution.

[0085] Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was added to the first solution and stirred until homogeneous. Then, lithium difluorooxalate borate (LiDFOB) was added and stirred until homogeneous again. Azobisisobutyronitrile (AIB) was then added as an initiator to obtain an elastomer polymer electrolyte precursor solution. This solution was injected into a battery and heated at 60°C for 12 hours to promote the free radical polymerization of butyl acrylate, ultimately yielding the elastomer electrolyte and converting the battery into a solid-state battery. This battery uses a lithium iron phosphate cathode and a lithium metal anode.

[0086] Compared with the preparation method of Example 1, Comparative Example 1-1 did not add cationic polymeric monomers and flame-retardant initiators, such as... Figure 3a and Figure 3b It is known that elastomeric electrolytes without a flame-retardant cationic polymerization system are flammable and have poor safety. Furthermore, due to the lack of a flame-retardant cationic polymerization system, the contact performance between the elastomeric electrolyte and the positive electrode particles is poor, resulting in significantly lower rate performance compared to the dual polymer electrolyte 9. For example... Figure 4 As shown, at low rates (0.1C, 0.2C, 0.5C), the difference in discharge specific capacity between the two is small; however, at high rates (1C, 2C, 5C), the discharge specific capacity of Comparative Example 1-1 (without the addition of the flame-retardant cationic polymerization system) is 87 mAhg. - 1. 42.4mAhg - 1 and 15mAhg - 1. Significantly lower than the 126.7 mAh g of the dual polymer electrolyte 9 (with added flame-retardant cationic polymerization system). - 1. 111.9mAhg - 1 and 85.4mAhg- 1. In addition, such as Figure 5 As shown, the elastomer electrolyte impedance (141.85Ω) of Comparative Example 1-1 (without flame-retardant cationic polymerization system) is significantly higher than that of the dipolymer electrolyte 9 (104.5Ω).

[0087] Comparative Example 2:

[0088] Based on Example 1, tris(pentafluorophenyl)boron (TFB) was replaced with a common cationic initiator, such as aluminum trifluoride, while other components and steps remained unchanged, to prepare a dual-polymer elastomer electrolyte.

[0089] Based on Comparative Example 1, no flame retardant components were added, the electrolyte was easily ignited, resulting in poor safety, but the rate performance was significantly improved.

[0090] Comparative Example 3:

[0091] Compared with Example 1, a liquid flame retardant, such as trimethyl phosphate (TMP), was added to the elastomer electrolyte precursor solution, but no cationic polymer monomer or flame retardant initiator was added. Other components and steps remained unchanged to prepare a liquid additive flame retardant elastomer electrolyte.

[0092] In Comparative Example 3, the addition of liquid flame retardant reduced the mechanical strength of the liquid additive flame-retardant elastomer electrolyte, weakened its ability to suppress lithium dendrites, and reduced the cycle life of the solid-state battery using this electrolyte.

[0093] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0094] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for preparing an electrolyte through in-situ polymerization, characterized in that, include: Under an argon-protected atmosphere, crosslinking agents and nitrile additives are added to the elastomer polymer monomers respectively, allowing them to dissolve completely to obtain the first solution; The elastomer polymer monomer includes at least one of methacrylic acid, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hexyl acrylate; A first lithium salt, which is lithium bis(trifluoromethanesulfonylimide), lithium hexafluorophosphate, or lithium perchlorate, is added to the first solution. After stirring evenly, a second lithium salt, which is lithium difluorooxalateborate, lithium fluoride, or lithium nitrate, is added. After stirring evenly again, a free radical polymerization initiator is added to obtain an elastomer polymer electrolyte precursor solution. A cationic polymer monomer is added to the elastomeric polymer electrolyte precursor solution and stirred until homogeneous. Then, a flame-retardant initiator is added and stirred again until homogeneous, yielding a dual polymer electrolyte precursor solution. The flame-retardant initiator includes at least one of tris(pentafluorophenyl)boron or tris(hexafluoroisopropyl)borate. The cationic polymer monomer is a cyclic monomer, including at least one of dioxane, trioxane, 1,3-dioxane, tetrahydrofuran, and butyrocyclohexane. The bipolymer electrolyte precursor solution was added to the battery and cationic polymerization was carried out at room temperature. After standing for 12 hours, it was heated at 60°C for 12 hours to initiate free radical polymerization, thus obtaining the in-situ polymerized bipolymer electrolyte.

2. The method for preparing electrolytes by in-situ polymerization according to claim 1, characterized in that, Adding the dual polymer electrolyte precursor solution to the battery further includes: It is applied to the positive electrode surface of the battery by dripping, coating, or a combination of dripping and coating.

3. The method for preparing electrolytes by in-situ polymerization according to claim 1, characterized in that, The crosslinking agent includes a bifunctional monomer.

4. The method for preparing electrolytes by in-situ polymerization according to claim 3, characterized in that, The bifunctional monomer includes at least one of polyethylene glycol diacrylate and tripropylene glycol diacrylate.

5. The method for preparing electrolytes by in-situ polymerization according to claim 1, characterized in that, The concentration of the first lithium salt is 0.5-3 mol / L; the concentration of the second lithium salt is 0.05-0.3 mol / L.

6. The method for preparing electrolytes by in-situ polymerization according to claim 1, characterized in that, The nitrile additive is succinic anionyl nitrile or glutaronitrile; the free radical polymerization initiator is azobisisobutyronitrile.

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