A titanium dioxide nanofiber-based in-situ polymerized solid-state electrolyte, a preparation method and applications thereof

Abstract

This invention discloses an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, its preparation method, and its applications, relating to the field of solid polymer electrolyte materials for lithium metal batteries. The raw materials of the in-situ polymerized solid electrolyte, by mass percentage, include the following components: 42-52 wt.% cyclic ether polymer monomers, 10-18 wt.% lithium salt, 5-10 wt.% functional ionic liquid, and 30-40 wt.% titanium dioxide nanofibers. The in-situ polymerized solid electrolyte is obtained by mixing the above raw materials and then performing an in-situ polymerization reaction. This in-situ polymerized solid electrolyte constructs a synergistic system of "nanofiber framework confinement + ionic liquid interface lithium conduction," which can homogenize the interfacial electric field, suppress the growth of lithium dendrites at the lithium metal anode interface, and weaken the space charge layer at the high-nickel cathode interface, resulting in excellent cycle performance of the solid lithium metal battery.

Description

Technical Field

[0001] This invention relates to the field of solid polymer electrolyte materials for lithium metal batteries, and in particular to an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, its preparation method, and its application. Background Technology

[0002] Solid-state lithium metal batteries theoretically possess higher energy density and superior safety performance, making them a highly promising core development direction in the field of power batteries. Solid-state polymer-based electrolytes, with their excellent flexibility and superior lithium salt dissolution capabilities, provide key technological support for the industrial application of solid-state lithium metal batteries. Among them, solid-state electrolytes constructed from cyclic ether polymer monomers through in-situ polymerization have become a key research focus in this field due to their combination of high ionic conductivity and excellent electrode-electrolyte interface integration.

[0003] However, this type of in-situ polymerized solid electrolyte still faces two major technical bottlenecks: First, uneven ion flux leads to electric field concentration at the lithium metal anode interface, which in turn induces lithium dendrite growth, severely restricting the safety and cycle stability of the battery; Second, under rapid charge and discharge conditions, the space charge layer at the cathode interface cannot be effectively suppressed, which greatly affects the rate performance of batteries paired with high-nickel cathodes (LiNi0.8Mn0.1Co0.1O2, NCM811). Summary of the Invention

[0004] To address the problems of poor interfacial stability between the electrolyte and electrode, and poor cycle performance of lithium metal batteries, existing in-situ polymerized solid electrolytes present in this invention, this invention proposes an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, its preparation method, and its applications. This invention prepares titanium dioxide nanofibers with high dielectric constant and a continuous three-dimensional structure using electrospinning technology. These nanofibers are then composited (mixed) with cyclic ether polymer monomers and lithium salts, and functional ionic liquids are added to further improve ion transport. In-situ polymerization is then used to prepare a solid polymer electrolyte with a continuous dielectric network (i.e., in-situ polymerized solid electrolyte). This in-situ polymerized solid electrolyte constructs a synergistic system of "nanofiber framework confinement + ionic liquid interface lithium conduction," which can regulate ion flux and interfacial electric field to achieve a stable electrolyte / electrode interface. Lithium metal batteries assembled based on this in-situ polymerized solid electrolyte simultaneously achieve excellent cycle stability and rate performance.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, wherein the raw materials include the following components by mass percentage: 42-52 wt.% cyclic ether polymer monomers, 10-18 wt.% lithium salt (as an in-situ polymerization initiator), 5-10 wt.% functional ionic liquid and 30-40 wt.% titanium dioxide nanofibers.

[0006] The titanium dioxide nanofibers used in this invention possess high dielectric constant and a continuous three-dimensional structure, enabling the regulation of ion flux at the electrolyte / electrode interface and achieving a redistribution of the interfacial electric field. The addition of functional ionic liquids synergistically works with the titanium dioxide nanofibers to construct a synergistic system of "nanofiber framework confinement + ionic liquid interfacial lithium conduction," further improving ion transport and enhancing the stability of the electrolyte / electrode interface. The uniform interfacial electric field effectively suppresses lithium dendrite growth, achieving stable cycling of the solid-state lithium metal battery. Simultaneously, the synergistic system of "nanofiber framework confinement + ionic liquid interfacial lithium conduction" optimizes the space charge layer, significantly improving the rate performance of the solid-state lithium metal battery when paired with a high-nickel cathode.

[0007] Furthermore, the cyclic ether polymer monomer includes at least one selected from 1,3-dioxolane, 2-ethyl-1,3-dioxolane, 1,3,5-trioxane, 1,4-dioxane, 1,3-dioxane, 1,2-epoxycyclopentene, and 1,2-epoxycyclopentene derivatives.

[0008] Furthermore, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0009] Furthermore, the functional ionic liquid includes at least one of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, 1-butyl-1-methylpyrrolidine bis(fluorosulfonyl)imide salt, and 1-propyl-3-methylimidazolium bis(fluorosulfonyl)imide salt.

[0010] Furthermore, the titanium dioxide nanofibers are prepared by electrospinning.

[0011] Furthermore, the preparation steps of the titanium dioxide nanofibers include: A mixed solution was obtained by mixing polyvinylidene fluoride-hexafluoropropylene copolymer with acetone in N,N-dimethylformamide; Titanium dioxide is dispersed in the mixed solution to obtain a precursor solution; The precursor solution was electrospun to obtain the titanium dioxide nanofibers.

[0012] Furthermore, the titanium dioxide is rutile titanium dioxide.

[0013] Furthermore, the average particle size of the rutile titanium dioxide is 20-30 nm.

[0014] Furthermore, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, acetone, and N,N-dimethylformamide is 1:1.5:10.

[0015] Furthermore, the titanium dioxide accounts for 2 wt.% of the mass of the precursor solution.

[0016] Furthermore, the conditions for electrospinning include: a feed rate of 1.0 mL / h, a voltage of 15 kV, a distance of 18 cm between the syringe and the roller, a roller speed of 65 rpm, a spinning environment humidity of 30 ± 5%, and a temperature of 26 ± 2 °C.

[0017] The second technical solution of the present invention: a method for preparing the above-mentioned in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, comprising the following steps: Cyclic ether polymer monomers, lithium salts, functional ionic liquids, and titanium dioxide nanofibers are mixed and subjected to in-situ polymerization to obtain the in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

[0018] Furthermore, the process of mixing cyclic ether polymer monomers, lithium salts, functional ionic liquids, and titanium dioxide nanofibers, as well as the in-situ polymerization reaction, are all carried out under an inert gas atmosphere.

[0019] Furthermore, the in-situ polymerization reaction is carried out at room temperature (25±2℃) for 20-28 hours.

[0020] The third technical solution of the present invention: the application of the above-mentioned in-situ polymerized solid electrolyte based on titanium dioxide nanofibers in the preparation of lithium metal batteries.

[0021] The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers provided by this invention exhibits excellent electrolyte / electrode interface stability, further improving the electrochemical performance and safety of the battery.

[0022] The fourth technical solution of the present invention: a lithium metal battery, the raw materials of which include the above-mentioned in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

[0023] Furthermore, the preparation steps of the lithium metal battery include: Cyclic ether polymer monomers, lithium salts, functional ionic liquids, and titanium dioxide nanofibers are mixed and placed in a battery casing for in-situ polymerization to obtain a lithium metal battery with an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

[0024] The present invention discloses the following technical effects: The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers provided by this invention constructs a synergistic system of "nanofiber framework confinement + ionic liquid interface lithium conduction", which has excellent ability to suppress lithium dendrite growth and space charge layer, and significantly improves the rate performance and cycle stability of solid lithium metal batteries.

[0025] The titanium dioxide nanofibers in the in-situ polymerized solid electrolyte based on titanium dioxide nanofibers provided by this invention are made from polyvinylidene fluoride-hexafluoropropylene copolymer, which has strong polarization ability and high dielectric constant, and can provide the ability to homogenize the interfacial electric field for the in-situ polymerized solid electrolyte.

[0026] The preparation method provided by this invention is environmentally friendly, low-cost, and scalable, and further optimizes battery performance. It has promising application prospects in the field of solid-state lithium metal batteries. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. 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 effort.

[0028] Figure 1 This is a scanning electron microscope image of the titanium dioxide nanofibers prepared in Example 1.

[0029] Figure 2 Arrhenius spectra of the in-situ polymerized solid electrolytes in Examples 1, 2, 1, 2, and 3.

[0030] Figure 3 Linear sweep voltammetry curves of the in-situ polymerized solid electrolytes in Examples 1, 2, 1, 2, and 3.

[0031] Figure 4 Tafel curves for lithium metal symmetric batteries prepared in Application Example 1, Application Example 2, Comparative Application Example 1, Comparative Application Example 2, and Comparative Application Example 3.

[0032] Figure 5 Time-voltage curves of lithium metal symmetric cells prepared in Application Example 1 and Comparative Application Example 1 are shown.

[0033] Figure 6 Scanning electron microscope image of the lithium metal anode after cycling of the PVTE-b symmetric battery prepared in Example 2 for comparison.

[0034] Figure 7The image shows a scanning electron microscope image of the lithium metal anode of the PVTE symmetric battery prepared in Example 1 after cycling.

[0035] Figure 8 The rate performance graphs are for the Li||NCM811 full cells prepared in Application Example 3, Application Example 4 and Comparative Application Example 4.

[0036] Figure 9 The graph shows the long-cycle performance of the Li||NCM811 cells prepared in Application Example 3, Comparative Application Example 4, and Comparative Application Example 5 at 1C. Detailed Implementation

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to 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. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0040] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0041] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0042] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0043] As a first aspect of the present invention, the present invention provides an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, wherein the raw materials comprise the following components by mass percentage: 42-52 wt.% cyclic ether polymer monomers, 10-18 wt.% lithium salt, 5-10 wt.% functional ionic liquid and 30-40 wt.% titanium dioxide nanofibers.

[0044] As a preferred embodiment of the present invention, the in-situ polymerized solid electrolyte raw material based on titanium dioxide nanofibers comprises the following components by mass percentage: 45 wt.% cyclic ether polymer monomer, 10 wt.% lithium salt, 5 wt.% functional ionic liquid and 40 wt.% titanium dioxide nanofibers.

[0045] As an optional embodiment of the present invention, the cyclic ether polymer monomer includes at least one selected from 1,3-dioxolane, 2-ethyl-1,3-dioxolane, 1,3,5-trioxane, 1,4-dioxane, 1,3-dioxane, 1,2-epoxycyclopentene, and 1,2-epoxycyclopentene derivatives, preferably 1,3-dioxolane.

[0046] As an optional embodiment of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide, preferably lithium bis(fluorosulfonyl)imide.

[0047] As an optional embodiment of the present invention, the functional ionic liquid includes at least one of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, 1-butyl-1-methylpyrrolidine bis(fluorosulfonyl)imide salt and 1-propyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, preferably 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt.

[0048] As an optional embodiment of the present invention, the titanium dioxide nanofibers are prepared by electrospinning.

[0049] As an optional embodiment of the present invention, the preparation steps of the titanium dioxide nanofibers include: A mixed solution was obtained by mixing polyvinylidene fluoride-hexafluoropropylene copolymer with acetone in N,N-dimethylformamide; Titanium dioxide is dispersed in the mixed solution to obtain a precursor solution; The precursor solution was electrospun to obtain the titanium dioxide nanofibers.

[0050] In a preferred embodiment of the present invention, the titanium dioxide is rutile titanium dioxide.

[0051] In a preferred embodiment of the present invention, the average particle size of the rutile titanium dioxide is 20-30 nm.

[0052] In a preferred embodiment of the present invention, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, acetone and N,N-dimethylformamide is 1:1.5:10.

[0053] In a preferred embodiment of the present invention, the titanium dioxide in the precursor solution accounts for 2 wt.% by mass.

[0054] As a preferred embodiment of the present invention, the conditions for electrospinning include: a feed rate of 1.0 mL / h, a voltage of 15 kV, a distance of 18 cm between the syringe and the roller, a roller speed of 65 rpm, a spinning environment humidity of 30 ± 5%, and a temperature of 26 ± 2 °C.

[0055] As a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, comprising the following steps: Cyclic ether polymer monomers, lithium salts, functional ionic liquids, and titanium dioxide nanofibers are mixed and subjected to in-situ polymerization to obtain the in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

[0056] In a preferred embodiment of the present invention, the process of mixing the cyclic ether polymer monomer, lithium salt, functional ionic liquid and titanium dioxide nanofibers and the in-situ polymerization reaction are both carried out under an inert gas atmosphere.

[0057] As an optional embodiment of the present invention, the in-situ polymerization reaction is carried out at room temperature (25±2℃) for 20-28 hours, preferably 24 hours.

[0058] As a third aspect of the present invention, the present invention provides an application of the above-mentioned in-situ polymerized solid electrolyte based on titanium dioxide nanofibers in the preparation of lithium metal batteries, wherein the in-situ polymerized solid electrolyte based on titanium dioxide nanofibers is used as an electrolyte material for lithium metal batteries.

[0059] The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers provided by this invention exhibits excellent electrolyte / electrode interface stability, further improving the electrochemical performance and safety of the battery.

[0060] As a fourth aspect of the present invention, the present invention provides a lithium metal battery, the raw materials of which include the above-mentioned in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

[0061] As an optional embodiment of the present invention, the preparation steps of the lithium metal battery include: Cyclic ether polymer monomers, lithium salts, functional ionic liquids, and titanium dioxide nanofibers are mixed and placed in a battery casing for in-situ polymerization to obtain a lithium metal battery with an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

[0062] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0063] In the specific embodiments of the present invention, the room temperature referred to is specifically 25±2℃ unless otherwise specified.

[0064] All raw materials used in the following embodiments, application examples and test examples of this invention are common commercial products. Among them, the average particle size of rutile titanium dioxide is 25 nm, and the molecular weight of polyvinylidene fluoride-hexafluoropropylene copolymer is ≈400,000.

[0065] Example 1 A method for preparing an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, comprising the following steps: Preparation of S1, titanium dioxide nanofibers: (1) Polyvinylidene fluoride-hexafluoropropylene copolymer and acetone were mixed in N,N-dimethylformamide in a mass ratio of 1:1.5:10 to obtain a mixed solution; (2) Disperse rutile titanium dioxide in the mixed solution at a mass ratio of 2 wt.% (i.e., the mass ratio of rutile titanium dioxide in the precursor solution is 2 wt.%) to obtain the precursor solution; (3) Titanium dioxide nanofibers were obtained by electrospinning the precursor solution. The conditions for electrospinning were: feed rate of 1.0 mL / h, voltage of 15 kV, distance between syringe and roller of 18 cm, roller speed of 65 rpm, humidity of spinning environment of 30 ± 5%, and temperature of 26 ± 2℃.

[0066] The scanning electron microscope image of the obtained titanium dioxide nanofibers (denoted as PVTF) is shown below. Figure 1 As shown, the average diameter of the titanium dioxide nanofibers is approximately 200 nm.

[0067] S2. Preparation of in-situ polymerized solid electrolytes based on titanium dioxide nanofibers: 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, and titanium dioxide nanofibers were mixed in an argon atmosphere at a mass ratio of 9:2:1:8 (i.e., mass percentages of 45 wt.%, 10 wt.%, 5 wt.%, and 40 wt.%, respectively). After in-situ polymerization at room temperature for 24 h, an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers was obtained, denoted as PVTE.

[0068] Example 2 Same as Example 1, except that the mass percentage of 1,3-dioxolane is 50 wt.%, the mass percentage of lithium bis(fluorosulfonyl)imide is 15 wt.%, the mass percentage of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt is 5 wt.%, and the mass percentage of titanium dioxide nanofibers is 30 wt.% (the mass ratio of each component is 10:3:1:6).

[0069] The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers obtained in this embodiment is denoted as PVTE-a.

[0070] Comparative Example 1 1,3-dioxolane and lithium difluorosulfonylimide were mixed in an argon atmosphere at a mass ratio of 9:2 and then subjected to in-situ polymerization at room temperature for 24 hours to obtain an in-situ polymerized solid electrolyte, denoted as PE.

[0071] Comparative Example 2 A method for preparing an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, comprising the following steps: Preparation of S1, titanium dioxide nanofibers: (1) Polyvinylpyrrolidone (PVP K30) and acetone were mixed in N,N-dimethylformamide in a mass ratio of 1:1.5:10 to obtain a mixed solution; (2) Disperse rutile titanium dioxide in the mixed solution at a mass ratio of 2 wt.% (i.e., the mass ratio of rutile titanium dioxide in the precursor solution is 2 wt.%) to obtain the precursor solution; (3) Titanium dioxide nanofibers were obtained by electrospinning the precursor solution. The conditions for electrospinning were: feed rate of 1.0 mL / h, voltage of 15 kV, distance between syringe and roller of 18 cm, roller speed of 65 rpm, humidity of spinning environment of 30 ± 5%, and temperature of 26 ± 2℃.

[0072] S2. Preparation of in-situ polymerized solid electrolytes based on titanium dioxide nanofibers: 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, and titanium dioxide nanofibers were mixed in an argon atmosphere at a mass ratio of 9:2:1:8 (i.e., mass percentages of 45 wt.%, 10 wt.%, 5 wt.%, and 40 wt.%, respectively). After in-situ polymerization at room temperature for 24 h, an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers was obtained, denoted as PVTE-b.

[0073] Comparative Example 3 Same as Example 1, except that the non-functional ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt is added, the mass percentage of 1,3-dioxolane is 50 wt.%, the mass percentage of lithium bis(fluorosulfonyl)imide is 10 wt.%, and the mass percentage of titanium dioxide nanofibers is 40 wt.% (the mass ratio of each component is 5:1:4).

[0074] The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers obtained in this comparative example is denoted as PVTE-c.

[0075] Test Example 1 Performance testing of the in-situ polymerized solid electrolytes in each embodiment and comparative example: The mixtures obtained by mixing the components under an argon atmosphere in each embodiment and comparative example were placed in a CR-2032 stainless steel gasket (SS) ||SS battery casing and subjected to in-situ polymerization at room temperature under an argon atmosphere for 24 hours to obtain test batteries. Variable-temperature AC impedance testing was performed on each test battery, with the frequency range set to 1 MHz to 1 Hz, to obtain Arrhenius spectra, as shown below. Figure 2 As shown. From Figure 2 As can be seen from the data, the ionic conductivity of PVTE, PVTE-a, PVTE-b, and PVTE-c in-situ polymerized solid electrolytes is higher than that of PE in-situ polymerized solid electrolyte in a certain temperature range. This indicates that the addition of titanium dioxide nanofibers can improve the ion transport performance of in-situ polymerized solid electrolytes, with PVTE in-situ polymerized solid electrolyte showing the best performance.

[0076] The mixtures obtained by mixing the components under an argon atmosphere in each embodiment and comparative example were placed in a CR-2032 type Li|| stainless steel gasket (SS) battery casing and subjected to in-situ polymerization at room temperature under an argon atmosphere for 24 hours to obtain test batteries. The assembled test batteries were then subjected to a 0.1 mV ss... -1 Linear scan voltammetry was performed at a scan rate to obtain the linear scan voltammetry curve, as shown below. Figure 3 As shown. From Figure 3As can be seen, the decomposition voltages of PVTE, PVTE-a, PVTE-b, and PVTE-c in-situ polymerized solid electrolytes are all higher than those of PE in-situ polymerized solid electrolytes. This indicates that the introduction of titanium dioxide nanofibers can broaden the electrochemical window of the electrolyte by homogenizing the interfacial electric field, while the introduction of functional ionic liquids can further improve ion transport. Among them, the PVTE in-situ polymerized solid electrolyte exhibits the best performance. Furthermore, the decomposition voltage of the PVTE in-situ polymerized solid electrolyte is as high as 5.39V, significantly higher than the 4.21V of the PVTE-b in-situ polymerized solid electrolyte. This demonstrates that the addition of titanium dioxide nanofibers prepared using polyvinylidene fluoride-hexafluoropropylene copolymer can broaden the electrochemical window of the electrolyte and improve the stability of the electrolyte / electrode interface, exhibiting superior performance compared to titanium dioxide nanofibers prepared using other polymer systems. This is because the polyvinylidene fluoride-hexafluoropropylene copolymer can further increase the dielectric constant of the nanofibers, thereby making the electric field at the electrode / electrolyte interface more uniform. This avoids electrolyte breakdown and side reactions caused by localized electric field concentration, thus improving the high-voltage stability of the electrolyte.

[0077] Application Example 1 The preparation steps of a lithium metal symmetric battery are as follows: Under an argon atmosphere, 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt and titanium dioxide nanofibers in the mass ratio of 9:2:1:8 from Example 1 were mixed and placed in a Li||Li symmetric battery shell for in-situ polymerization at room temperature for 24 h to obtain a CR-2032 type Li||Li symmetric battery, denoted as PVTE symmetric battery.

[0078] Application Example 2 The preparation steps of a lithium metal symmetric battery are as follows: Under an argon atmosphere, 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt and titanium dioxide nanofibers in the mass ratio of 10:3:1:6 from Example 2 were mixed and placed in a Li||Li symmetric battery shell for in-situ polymerization at room temperature for 24 h to obtain a CR-2032 type Li||Li symmetric battery, denoted as PVTE-a symmetric battery.

[0079] Comparative Application Example 1 Under an argon atmosphere, 1,3-dioxolane and lithium difluorosulfonylimide in a mass ratio of 9:2 from Comparative Example 1 were mixed and placed in a Li||Li symmetric cell shell for in-situ polymerization at room temperature for 24 h to obtain a CR-2032 type Li||Li symmetric cell, denoted as PE symmetric cell.

[0080] Comparative Application Example 2 Under an argon atmosphere, 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt and titanium dioxide nanofibers in the mass ratio of 9:2:1:8 of Comparative Example 2 were mixed and placed in a Li||Li symmetric cell shell for in-situ polymerization at room temperature for 24 h to obtain a CR-2032 type Li||Li symmetric cell, denoted as PVTE-b symmetric cell.

[0081] Comparative Application Example 3 Under an argon atmosphere, 1,3-dioxolane, lithium bisfluorosulfonylimide and titanium dioxide nanofibers in a mass ratio of 5:1:4 from Comparative Example 3 were mixed and placed in a Li||Li symmetric battery shell for in-situ polymerization at room temperature for 24 h to obtain a CR-2032 type Li||Li symmetric battery, denoted as PVTE-c symmetric battery.

[0082] Test Example 2 Performance testing of lithium metal symmetric batteries: Figure 4 Tafel curves (test voltage range -0.2~0.2V) are shown for the lithium metal symmetric batteries prepared in Application Example 1, Application Example 2, Comparative Application Example 1, Comparative Application Example 2, and Comparative Application Example 3. From... Figure 4 As can be seen, the exchange currents of PVTE, PVTE-a, PVTE-b, and PVTE-c in-situ polymerized solid electrolytes are all higher than those of PE in-situ polymerized solid electrolyte, indicating that the introduction of titanium dioxide nanofibers can improve electrode reaction kinetics. Among them, PVTE in-situ polymerized solid electrolyte exhibits the best performance. Furthermore, the exchange current of PVTE in-situ polymerized solid electrolyte is significantly higher than that of PVTE-c in-situ polymerized solid electrolyte, indicating that the introduction of ionic liquid can stabilize the electrolyte / electrode interface and further enhance the performance of the in-situ polymerized solid electrolyte.

[0083] Figure 5 To obtain the time-voltage curves of the lithium metal symmetric cells prepared in Application Example 1 and Comparative Application Example 1, from... Figure 5 As can be seen from this, the PVTE symmetric cell at 0.5 mA cm⁻¹ −2 / 0.5mAh cm −2 The battery can cycle stably for more than 2000 hours, indicating that the addition of titanium dioxide nanofibers and functional ionic liquids can improve the cycle stability of in-situ polymerized solid lithium metal batteries.

[0084] Figure 6 To compare the PVTE-b symmetric cell prepared in Example 2 after cycling (at 0.5 mA cm⁻¹) −2 / 0.5mAh cm −2 Scanning electron microscope image of lithium metal anode after 2000 hours of cycling; Figure 7After cycling (at 0.5 mA cm⁻¹) the PVTE symmetric cell prepared in Example 1, −2 / 0.5mAh cm −2 Scanning electron microscope image of the lithium metal anode after 2000 hours of cycling. Figures 6-7 As can be seen from the data, the lithium metal anode has a smoother surface morphology after cycling in the PVTE symmetric battery, indicating that the addition of titanium dioxide nanofibers prepared from polyvinylidene fluoride-hexafluoropropylene copolymer has a higher dielectric constant, which can regulate the interfacial electric field and improve the electrolyte's ability to suppress lithium dendrites.

[0085] Application Example 3 The preparation of an NCM811 full cell involves the following steps: (1) Electrode preparation: high-nickel cathode material LiNi 0.8 Mn 0.1 Co 0.1 O2 (NCM811), conductive carbon black, and polyvinylidene fluoride were mixed and ground in a mass ratio of 8:1:1. Then, an appropriate amount of N-methylpyrrolidone was added to form a slurry, which was then evenly coated onto an aluminum foil current collector using a scraper (active material loading was 2.5 mg / cm²). -2 After drying, the material is cut into pieces to serve as the positive electrode of the NCM811 full cell (circular electrode, electrode size 0.95 cm). 2 Lithium foil was used as the negative electrode. (2) The positive and negative electrodes were placed in the CR-2032 full cell casing. Under an argon atmosphere, 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt and titanium dioxide nanofibers in the mass ratio of 9:2:1:8 in Example 1 were mixed and placed in the above battery casing for in-situ polymerization at room temperature for 24 h to obtain the CR-2032 Li||NCM811 full cell, which is denoted as PVTE full cell.

[0086] Application Example 4 The preparation of an NCM811 full cell involves the following steps: (1) Electrode preparation: Same as in application example 3; (2) The positive and negative electrodes were placed in the CR-2032 full cell casing. Under an argon atmosphere, 1,3-dioxolane, lithium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt and titanium dioxide nanofibers in the mass ratio of 10:3:1:6 in Example 2 were mixed and placed in the above battery casing for in-situ polymerization at room temperature for 24 h to obtain the CR-2032 Li||NCM811 full cell, which was denoted as PVTE-a full cell.

[0087] Comparative Application Example 4 The preparation of an NCM811 full cell involves the following steps: (1) Electrode preparation: Same as in application example 3; (2) The positive and negative electrodes were placed in the CR-2032 full cell casing. Under an argon atmosphere, 1,3-dioxolane and lithium difluorosulfonylimide in a mass ratio of 9:2 in Comparative Example 1 were mixed and placed in the above battery casing for in-situ polymerization at room temperature for 24 h to obtain the CR-2032 Li||NCM811 full cell, denoted as PE full cell.

[0088] Comparative Application Example 5 The preparation of an NCM811 full cell involves the following steps: (1) Electrode preparation: Same as in application example 3; (2) The positive and negative electrodes were placed in the CR-2032 type full cell casing; under an argon atmosphere, 1,3-dioxolane, lithium bis(fluorosulfonyl)imide and titanium dioxide nanofibers in the mass ratio of 5:1:4 of Comparative Example 3 were mixed and placed in the above battery casing for in-situ polymerization reaction at room temperature for 24 h to obtain the CR-2032 type Li||NCM811 full cell, denoted as PVTE-c full cell.

[0089] Test Example 3 Performance testing of NCM811 full battery: Figure 8 The rate performance graphs of the Li||NCM811 full cells prepared in Application Example 3, Application Example 4, and Comparative Application Example 4 are shown below. Figure 8 As can be seen, both PVTE and PVTE-a full cells exhibit higher discharge specific capacities than PE full cells in the 0.5-10C rate range (at 10C, the discharge specific capacities of PVTE, PVTE-a, and PE full cells are 113.4 mAh g⁻¹, respectively). −1 46.3 mAh g −1 and 6.8 mAh g −1 This indicates that the addition of titanium dioxide nanofibers and functional ionic liquids can significantly improve the rate performance of in-situ polymerized solid electrolyte Li||NCM811 full cells under rapid charge and discharge conditions. Among them, the PVTE full cell exhibits the best performance.

[0090] Figure 9 The graphs show the long-term cycling performance of the Li||NCM811 full cells prepared in Application Example 3, Comparative Application Example 4, and Comparative Application Example 5 at 1C. Figure 9As can be seen, PVTE full cells and PVTE-c full cells exhibit better capacity retention and cycle stability at 1C than PE full cells. The initial discharge specific capacity of PVTE full cells, PVTE-c full cells, and PE full cells is 185.2 mAh g⁻¹. −1 170.7 mAh g −1 and 154.5 mAh g −1 After 300 cycles, the capacity retention rate was 90.6% (167.8 mAh g). −1 ), 81.5% (139.1 mAh g) −1 ) and 40.1% (61.9 mAh g) −1 This indicates that the addition of titanium dioxide nanofibers and functional ionic liquids can significantly improve the long-term cycling stability of the in-situ polymerized solid electrolyte Li||NCM811 full cell. Meanwhile, the cycling performance of the PVTE full cell is superior to that of the PVTE-c full cell, suggesting that the introduction of functional ionic liquids can further improve the electrode / electrolyte interface and enhance the battery's stability during cycling.

[0091] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An in-situ polymerized solid electrolyte based on titanium dioxide nanofibers, characterized in that, By mass percentage, the raw materials include the following components: 42-52 wt.% cyclic ether polymer monomers, 10-18 wt.% lithium salt, 5-10 wt.% functional ionic liquid and 30-40 wt.% titanium dioxide nanofibers.

2. The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in claim 1, characterized in that, The cyclic ether polymer monomers include at least one selected from 1,3-dioxolane, 2-ethyl-1,3-dioxolane, 1,3,5-trioxane, 1,4-dioxane, 1,3-dioxane, 1,2-epoxycyclopentene, and 1,2-epoxycyclopentene derivatives.

3. The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in claim 1, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

4. The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in claim 1, characterized in that, The functional ionic liquid includes at least one of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-butyl-1-methylpyrrolidine bis(fluorosulfonyl)imide, and 1-propyl-3-methylimidazolium bis(fluorosulfonyl)imide.

5. The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in claim 1, characterized in that, The titanium dioxide nanofibers were prepared by electrospinning.

6. The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in claim 5, characterized in that, The preparation steps of the titanium dioxide nanofibers include: A mixed solution was obtained by mixing polyvinylidene fluoride-hexafluoropropylene copolymer with acetone in N,N-dimethylformamide; Titanium dioxide is dispersed in the mixed solution to obtain a precursor solution; The precursor solution was electrospun to obtain the titanium dioxide nanofibers.

7. The in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in claim 6, characterized in that, The titanium dioxide is rutile titanium dioxide; And / or, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, acetone and N,N-dimethylformamide is 1:1.5:10; And / or, the titanium dioxide accounts for 2 wt.% of the mass of the precursor solution. And / or, the conditions for electrospinning include: a feed rate of 1.0 mL / h, a voltage of 15 kV, a distance of 18 cm between the syringe and the roller, a roller speed of 65 rpm, a spinning environment humidity of 30 ± 5%, and a temperature of 26 ± 2 °C.

8. A method for preparing an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in any one of claims 1-7, characterized in that, Includes the following steps: Cyclic ether polymer monomers, lithium salts, functional ionic liquids, and titanium dioxide nanofibers are mixed and subjected to in-situ polymerization to obtain the in-situ polymerized solid electrolyte based on titanium dioxide nanofibers.

9. The application of an in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in any one of claims 1-7 in the preparation of lithium metal batteries.

10. A lithium metal battery, characterized in that, The raw materials include the in-situ polymerized solid electrolyte based on titanium dioxide nanofibers as described in any one of claims 1-7.

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