High ionic conductivity polymer electrolyte, lithium metal battery and preparation method

Abstract

This invention discloses a high-ionic-conductivity polymer electrolyte, a lithium metal battery, and its preparation method. Belonging to the field of high-energy-density lithium metal battery technology, it is prepared by in-situ polymerization of a polymer precursor solution comprising 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonyl)imide, a crosslinking agent, an initiator, and a plasticizer in the battery. This invention introduces the ultra-long fluorine chain monomer 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate into the polymer electrolyte precursor solution. This monomer exhibits good compatibility with methyl acrylate, does not undergo phase separation, and the resulting ultra-long fluorine chain polymer effectively ensures the structural stability of the electrolyte framework, reduces impedance, improves the ionic conductivity of the electrolyte, and thus increases the electrochemical window. Furthermore, the ultra-long fluorine chain polymer electrolyte of this invention exhibits lithium metal stability and high-voltage stability. In-situ polymerization improves the contact stability at the positive and negative electrode interfaces, further promoting the cycle stability of the lithium metal battery.

Description

Technical Field

[0001] This invention belongs to the field of high energy density lithium metal battery technology, and specifically relates to a polymer electrolyte with high ionic conductivity, a lithium metal battery, and a preparation method thereof. Background Technology

[0002] Solid-state lithium metal batteries have attracted significant attention due to their high safety and high theoretical specific capacity. Among various solid electrolytes, polymer electrolytes have garnered widespread interest for their low interfacial impedance and flexibility, with in-situ polymerized electrolytes showing particular advantages in cost and large-scale production. However, most current polymer electrolytes exhibit low ionic conductivity and weak interfacial stability with lithium metal, leaving considerable room for improvement in their electrochemical performance and limiting the development of polymer electrolyte-based lithium metal batteries. Among polymers, methyl acrylate (MEA) possesses a wide electrochemical window and good compatibility with high-voltage transition metal oxides. However, its low ionic conductivity at room temperature restricts its further development.

[0003] Currently, methods to improve ionic conductivity include adding inorganic fillers such as SiO2, Al2O3, and TiO2. This composite structure not only improves the mechanical strength of the polymer electrolyte but also enhances its ion transport performance. The improvement in performance is related to the type and size of the added filler. However, the addition of inorganic fillers increases the interfacial impedance between the polymer and the inorganic filler, which can negatively impact the polymer's flexibility and processability. Furthermore, high concentrations of filler particles may aggregate, hindering chain segment movement and leading to blockage and disruption of the ion transport network.

[0004] In addition to adding fillers, existing technologies have also proposed introducing small-molecule plasticizers. Compared to inorganic fillers, organic plasticizers are more compatible with the polymer matrix and are easier to disperse uniformly in the polymer. Plasticizers improve the ionic conductivity of polymer electrolytes by weakening the intermolecular forces and disrupting the crystalline regions of crystalline materials. However, with the increase of amorphous regions, the overall mechanical properties of the polymer electrolyte decrease. When the amount of plasticizer added is too small, the molecular chains are more likely to move, causing the non-oriented regions of the polymer to crystallize in an orthogonal manner, which may have a reverse plasticizing effect; when the amount of plasticizer is too large, the matrix has a limited capacity to accommodate the plasticizer, and these small molecules detach from the polymer matrix. At this time, the conductivity mechanism is similar to that of a liquid electrolyte, and the mechanical strength of the electrolyte itself is weakened. Furthermore, the addition of organic plasticizers weakens the high-pressure stability of the polymer matrix. Summary of the Invention

[0005] To address the technical problems mentioned in the background, the main objective of this invention is to provide a polymer electrolyte with high ionic conductivity, a lithium metal battery, and a preparation method thereof. This invention solves the problem of low ionic conductivity of polymer electrolytes without affecting electrolyte impedance, ensuring the electrochemical stability of polymer electrolytes while also exhibiting good compatibility with the lithium metal interface, thereby promoting the cycle stability of lithium metal batteries.

[0006] To achieve the above objectives, the present invention provides a high ionic conductivity polymer electrolyte, which is prepared by in-situ polymerization in a battery of a polymer precursor solution comprising 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonylimide), a crosslinking agent, an initiator, and a plasticizer.

[0007] Further, the volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate to methyl acrylate is x:10-x, wherein 3 <x<7。

[0008] Further, in the polymer precursor solution, the mass fraction of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate is 15-30%.

[0009] Furthermore, in the polymer precursor solution, the molar concentration of lithium bis(trifluoromethanesulfonylimide) is 0.5~3M.

[0010] Furthermore, in the polymer precursor solution, the mass fraction of the crosslinking agent is 0.3~0.5%.

[0011] Furthermore, in the polymer precursor solution, the initiator has a mass fraction of 0.1-0.2%.

[0012] Furthermore, in the polymer precursor solution, the mass fraction of the plasticizer is 20-25%.

[0013] Furthermore, the crosslinking agent is selected from one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, or pentaerythritol tetraacrylate.

[0014] Furthermore, the plasticizer is selected from fluorinated solvents and / or ether solvents.

[0015] In another aspect, the present invention provides a lithium metal battery comprising the aforementioned high ionic conductivity polymer electrolyte.

[0016] In another aspect, the present invention provides a method for preparing the aforementioned lithium metal battery, comprising the following steps:

[0017] S1, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonylimide), crosslinking agent, initiator and plasticizer are mixed to obtain a polymer precursor solution;

[0018] S2, assemble the battery positive electrode, lithium metal negative electrode, separator and the polymer precursor solution to obtain a coin cell;

[0019] S3, the coin cell is first placed under vacuum, and then heated to solidify, so that the polymer precursor solution is polymerized in situ into a solid electrolyte, thus obtaining the lithium metal battery.

[0020] Further, in step S1, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonyl)imide, crosslinking agent, initiator, and plasticizer are mixed to obtain a polymer precursor solution, comprising: stirring and mixing the crosslinking agent, initiator, and plasticizer to obtain a first mixture; mixing 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate and methyl acrylate to obtain a second mixture; mixing the first mixture and the second mixture, and then adding lithium bis(trifluoromethanesulfonyl)imide and stirring to obtain a polymer precursor solution.

[0021] Furthermore, the amount of the polymer precursor solution added is 20~50 μL.

[0022] Furthermore, the vacuum settling time is 0.5 to 3 hours.

[0023] Furthermore, the heating and curing temperature is 60~80℃, and the time is 12~48h.

[0024] Furthermore, the positive electrode of the battery is prepared by the following method: polyvinylidene fluoride, nickel cobalt manganese ternary positive electrode material, lithium bis(trifluoromethanesulfonylimide), acetylene black and solvent are stirred and mixed to obtain a slurry; the slurry is coated on the surface of the current collector aluminum foil and then dried to obtain the positive electrode of the battery.

[0025] Compared with existing technologies, this invention has the following beneficial effects: This invention introduces an ultra-long fluorine chain (>12) monomer, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, into the precursor solution of the polymer electrolyte. This monomer possesses high electronegativity and polarity, significantly improving the oxidative stability of the electrolyte. Furthermore, it exhibits good compatibility with methyl acrylate, without phase separation. The resulting ultra-long fluorine chain polymer effectively ensures the structural stability of the electrolyte framework, reduces impedance, and improves the ionic conductivity of the electrolyte, thereby increasing the electrochemical window. In this invention, a crosslinking agent, initiator, and plasticizer are added to the polymer precursor solution for compounding, promoting the formation of a more uniform and dense polymer network structure. Simultaneously, the ultra-long fluorine chain polymer electrolyte polymerized in situ in this invention exhibits lithium metal stability and high-voltage stability. In-situ polymerization improves the contact stability with the positive and negative electrode interfaces, further promoting the cycle stability of lithium metal batteries. Attached Figure Description

[0026] Figure 1 A scanning electron microscope (SEM) characterization image of the high ionic conductivity polymer electrolyte of Example 1 of the present invention is shown;

[0027] Figure 2 The following diagram shows a before-and-after comparison of the polymer precursor solution of Example 1 of the present invention after curing. Figure 2 2a in the image is a photograph of the polymer precursor solution before it solidifies. Figure 2 2b in the image is a photograph of the polymer precursor solution after curing;

[0028] Figure 3 A comparison graph showing the cycle stability performance of lithium metal batteries of Example 1 and Comparative Examples 1-2 of the present invention is provided.

[0029] Figure 4 A comparative diagram of the electrochemical windows of the lithium metal batteries of Example 1 and Comparative Examples 1-2 of the present invention is shown. Detailed Implementation

[0030] 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.

[0031] To achieve the above objectives, a first aspect of the present invention provides a high ionic conductivity polymer electrolyte, which is prepared by in-situ polymerization in a battery of a polymer precursor solution comprising 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonylimide), a crosslinking agent, an initiator, and a plasticizer.

[0032] This invention introduces an ultra-long fluorine chain (>12) monomer, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, into the precursor solution of a polymer electrolyte. Compared to low-fluorine chains, it exhibits high electronegativity and polarity, significantly improving the oxidative stability and electrochemical window of the electrolyte, thus enabling it to be matched with the high-voltage cathode NCM. Furthermore, the strong fluorine-absorbing groups are beneficial for LII... + The adsorption degree is deepened, and in synergy with methyl acrylate, the two have good compatibility and do not undergo phase separation. The resulting ultra-long fluorinated chain polymer effectively ensures the structural stability of the electrolyte framework, reduces impedance, and improves the ionic conductivity and electrochemical window of the electrolyte. Furthermore, this invention uses fluorinated octyl acrylate, which, compared to other fluorinated low-alkyl acrylates, has excellent compatibility with methyl acrylate and crosslinking agents, and exhibits a more stable interface with the negative electrode lithium metal, further enhancing the ionic conductivity of the polymer electrolyte.

[0033] Furthermore, the large anion volume of lithium bis(trifluoromethanesulfonyl)imide in this invention allows only lithium ions to move within the electrolyte, improving the electrolyte's lithium ion conductivity. At the same time, lithium bis(trifluoromethanesulfonyl)imide exhibits good hydrolytic stability, reducing the risk of battery performance degradation due to moisture absorption, thus improving battery safety and lifespan. Moreover, the chemical environment provided facilitates the copolymerization reaction of octyl tridecafluoroacrylate and methyl acrylate, which is more conducive to lithium ion transport.

[0034] Meanwhile, the polymer precursor solution of this invention is compounded with crosslinking agents, initiators, and plasticizers to promote the formation of a more uniform and dense polymer network structure. Furthermore, the ultra-long fluorine chain polymer electrolyte produced by in-situ polymerization of this invention exhibits lithium metal stability and high-voltage stability. In-situ polymerization improves the contact stability at the positive and negative electrode interfaces, further promoting the cycle stability of lithium metal batteries.

[0035] In a preferred embodiment of the present invention, the volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate to methyl acrylate is x:10 - x, where 3 < x < 7. The inventors have found through research that if the content of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate is too high, it is easy to cause an increase in impedance, and if the content of methyl acrylate is too high, it will cause a decrease in the electrochemical window and a decrease in ionic conductivity. Through a large number of experimental studies, it has been found that the volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate to methyl acrylate within the above range can endow the polymer electrolyte obtained by polymerization with excellent ionic conductivity, high electrochemical window and low impedance performance.

[0036] In a preferred embodiment of the present invention, in order to further provide an excellent lithium ion transmission environment and improve the lithium ion conductivity of the polymer electrolyte, in the polymer precursor solution, the mass fraction of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate is 15% - 30%. More preferably, it is 20% - 25%.

[0037] In a preferred embodiment of the present invention, in order to further improve the ionic conductivity of the polymer electrolyte, in the polymer precursor solution, the molar concentration of lithium bis(trifluoromethanesulfonyl)imide is 0.5 - 3 M. If the concentration of lithium bis(trifluoromethanesulfonyl)imide is too low, the Li + transmission is insufficient, resulting in a decrease in ionic conductivity and a low discharge specific capacity. If the concentration of lithium bis(trifluoromethanesulfonyl)imide is too high, the Li + transmission in the copolymer is congested, also resulting in a decrease in ionic conductivity.

[0038] In some preferred embodiments of the present invention, in the polymer precursor solution, the mass fraction of the crosslinking agent is 0.3% - 0.5%, the mass fraction of the initiator is 0.1% - 0.2%, and the mass fraction of the plasticizer is 20% - 25%.

[0039] In some alternative embodiments of the present invention, the crosslinking agent may be selected from one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate or pentaerythritol tetraacrylate; the initiator may be selected from azobisisobutyronitrile; the plasticizer may be selected from fluorinated solvents and / or ether solvents. For example, the fluorinated solvent is selected from fluoroethylene carbonate (FEC), 2,2,2-trifluoroethyl carbonate (FEMC), ethyl trifluoroethyl carbonate (ETFEC), bis(2,2,2-trifluoroethyl) carbonate (DTFEC). The ether solvent may be selected from ethylene glycol dimethyl ether (DME).

[0040] A second aspect of the present invention provides a lithium metal battery comprising the aforementioned high ionic conductivity polymer electrolyte.

[0041] The high ionic conductivity polymer electrolyte of this invention contains long-chain fluorine, which greatly improves the high-voltage stability of the electrolyte and increases its compatibility with cathode materials such as high-nickel ternary materials. When applied to lithium metal batteries, it can effectively improve the electrochemical window of lithium metal batteries, increase the discharge specific capacity, and thus promote the development of high-energy-density lithium metal batteries.

[0042] A third aspect of the present invention also provides a lithium metal battery as described above, comprising the following steps:

[0043] S1, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonylimide), crosslinking agent, initiator and plasticizer are mixed to obtain a polymer precursor solution;

[0044] S2, assemble the battery positive electrode, lithium metal negative electrode, separator and the polymer precursor solution to obtain a coin cell;

[0045] S3, the coin cell is first placed under vacuum, and then heated to solidify, so that the polymer precursor solution is polymerized in situ into a solid electrolyte, thus obtaining the lithium metal battery.

[0046] In a preferred embodiment of the present invention, the step of mixing 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonyl)imide, a crosslinking agent, an initiator, and a plasticizer to obtain a polymer precursor solution comprises: stirring and mixing the crosslinking agent, initiator, and plasticizer to obtain a first mixture; mixing 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate and methyl acrylate to obtain a second mixture; mixing the first mixture and the second mixture, and then adding lithium bis(trifluoromethanesulfonyl)imide and stirring to obtain a polymer precursor solution.

[0047] This invention prepares a polymer precursor solution by adding ingredients in a specific order. First, a crosslinking agent, initiator, and plasticizer are mixed to prepare a first mixture, which avoids the polymerization of monomers with the crosslinking agent and initiator alone, thus preventing inhomogeneity of the polymer precursor solution. The first monomer and the second monomer are mixed and then mixed with the first mixture, which ensures that the monomers are fully and uniformly mixed in the polymer precursor solution, resulting in a more uniform and dense polymer network structure of the polymer electrolyte.

[0048] In some preferred embodiments of the present invention, the amount of polymer precursor solution added is 20-50 μL. By reasonably controlling the amount of polymer precursor solution added, it can be made to fully wet the separator and cathode while preventing liquid overflow and avoiding affecting the interface performance of the battery. The vacuum settling time is 0.5-3 hours. Vacuum settling for a period of time promotes the polymer precursor solution to wet the electrodes, thereby improving the interface stability with the positive and negative electrodes. The heating curing temperature is 60-80°C, and the time is 12-48 hours. The present invention controls the heating curing temperature and time to ensure that the polymer precursor solution fully completes the polymerization reaction.

[0049] In a preferred embodiment of the present invention, the battery positive electrode is prepared by the following method: polyvinylidene fluoride, nickel-cobalt-manganese ternary positive electrode material, lithium bis(trifluoromethanesulfonyl)imide, acetylene black, and a solvent are stirred and mixed to obtain a slurry; the slurry is coated onto the surface of a current collector aluminum foil, and then dried to obtain the battery positive electrode. The battery positive electrode prepared by the present invention facilitates lithium-ion conduction and improves the electrochemical performance of the battery.

[0050] Furthermore, the mass ratio of polyvinylidene fluoride, nickel-cobalt-manganese ternary cathode material, lithium bis(trifluoromethanesulfonylimide), and acetylene black is 1:6 to 8:1:1.

[0051] In some preferred embodiments of the present invention, in order to improve the in-situ polymerization effect of the polymer precursor solution in the battery and the energy density of the battery, the separator is a 5-25 μm polypropylene membrane. If the separator is too thick, it increases the Li... + The increased internal impedance of the battery leads to a certain decrease in battery mass density; ultrathin films with a thickness of 5μm or more reduce ion transport paths and improve battery energy density to a certain extent.

[0052] 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.

[0053] Example 1

[0054] A method for preparing a lithium metal battery includes the following steps:

[0055] Step 1: Mix azobisisobutyronitrile, polyethylene glycol diacrylate and fluoroethylene carbonate, stir for 20 minutes at 500 rpm to obtain the first mixture.

[0056] Step 2: Mix 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate and methyl acrylate monomer at a volume ratio of 1:1, stir for 10 minutes at a speed of 30 rpm to obtain the second mixture.

[0057] Step 3: Mix the first and second mixtures, add 2M lithium bis(trifluoromethanesulfonyl)imide, and stir for 30 minutes at 500 rpm to obtain the polymer precursor solution. In the polymer precursor solution, the mass fractions of azobisisobutyronitrile (AIB) is 0.118%, polyethylene glycol diacrylate (PEG) is 0.445%, fluoroethylene carbonate (EFC) is 23%, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate (MFA) is 24.68%, and methyl acrylate (Methyl acrylate) is 15.186%.

[0058] Step 4: Mix polyvinylidene fluoride, NCM811 (nickel-cobalt-manganese ternary cathode material), lithium bis(trifluoromethanesulfonylimide), and acetylene black in a mass ratio of 1:7:1:1, then add NMP (N-methylpyrrolidone), and stir for 12 hours to obtain a slurry.

[0059] Step 5: Coat the slurry obtained in Step 4 onto the surface of the current collector aluminum foil, and dry it in a 60°C oven to obtain the battery positive electrode sheet;

[0060] Step 6: Assemble the battery positive electrode, lithium metal negative electrode (Li metal sheet), separator (25μm polypropylene film) obtained in Step 5, and polymer precursor solution obtained in Step 3 (addition amount 20μL) to obtain a coin cell.

[0061] Step 7: Vacuum-set the button cell for 12 hours, then heat-cur it and store it at 60°C for 12 hours to allow the polymer precursor solution to polymerize in situ into a polymer electrolyte with high ionic conductivity, thus obtaining a lithium metal battery.

[0062] Example 2

[0063] A method for preparing a lithium metal battery differs from Example 1 only in that the volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate to methyl acrylate is 3:7.

[0064] Example 3

[0065] A method for preparing a lithium metal battery differs from Example 1 only in that the volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate to methyl acrylate is 7:3.

[0066] Example 4

[0067] A method for preparing a lithium metal battery differs from Example 1 only in that the molar ratio of lithium bis(trifluoromethanesulfonylimide) is 0.5M.

[0068] Example 5

[0069] A method for preparing a lithium metal battery differs from Example 1 only in that the molar ratio of lithium bis(trifluoromethanesulfonylimide) is 3M.

[0070] Example 6

[0071] A method for preparing a lithium metal battery differs from Example 1 only in that the thickness of the separator is 5 μm.

[0072] Example

[0073] A method for preparing a lithium metal battery differs from Example 1 only in that the mass fraction of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate is 30%.

[0074] Example 8

[0075] A method for preparing a lithium metal battery differs from Example 1 only in that the mass fraction of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate is 20%.

[0076] Comparative Example 1

[0077] A method for preparing a lithium metal battery differs from Example 1 only in that the polymer precursor solution does not contain methyl acrylate, and the amount of methyl acrylate added is replaced by an equal amount of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate.

[0078] Comparative Example 2

[0079] A method for preparing a lithium metal battery differs from Example 1 only in that the polymer precursor solution does not contain 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, and the amount of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate added is replaced with methyl acrylate in equal amounts.

[0080] Comparative Example 3

[0081] A method for preparing a lithium metal battery differs from Example 1 only in that the volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate to methyl acrylate is 2:8.

[0082] Performance testing:

[0083] Morphological characterization: The high ionic conductivity polymer electrolyte prepared in Example 1 was characterized by scanning electron microscopy (SEM), and the characterization image is shown below. Figure 1 As shown in the figure, the prepared high ionic conductivity polymer electrolyte is uniform and dense.

[0084] Curing test: The polymer precursor solution of Example 1 was cured (60℃, 12h), and the changes before and after curing were observed. The photograph of the polymer precursor solution before curing is shown below. Figure 2 Photograph of the polymer precursor solution after curing, as shown in section 2a. Figure 2 2b in the middle. From Figure 2 As can be seen in 2a, the polymer precursor solution is uniformly distributed, indicating that 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate and methyl acrylate do not undergo phase separation, thus ensuring the stability of ion transport and mechanical stability. Figure 2 As can be seen from 2b, the polymer precursor solution has a good curing effect, indicating that it has the potential for in-situ preparation.

[0085] Cyclic stability testing method: The cycle stability of the electrolyte-based lithium metal battery was tested using the charge-discharge curves of the full cell. The charge-discharge voltage window was 2.8V-4.3V, and the charge-discharge current was 1 / 3C. The test results are shown in Table 1.

[0086] Electrochemical window testing method: The electrochemical window of the electrolyte was tested using linear voltammetry at a scan rate of 0.5 mV / s. The test results are shown in Table 1.

[0087] Table 1

[0088]

[0089] The cycle stability performance of the lithium metal batteries in Example 1 and Comparative Examples 1-2 is compared to that of... Figure 3 As shown, Example 1 exhibits significantly improved cycle stability compared to Comparative Examples 1 and 2. In Example 1, the addition of an ultra-long-chain fluorinated electrolyte (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate) and methyl acrylate copolymerizes to form an ultra-long-chain fluorinated polymer, enhancing lithium-ion transport capacity and thus increasing the discharge specific capacity of the ternary lithium metal battery. The in-situ polymerized fluorinated polymer also demonstrates good lithium metal stability, further improving the overall cycle stability of the battery. In contrast, Comparative Examples 1 and 2 lack the ultra-long-chain fluorinated polymer formed by the copolymerization of fluorinated electrolyte and acrylate, resulting in poorer ionic conductivity and structural stability, leading to lower discharge specific capacity and poorer cycle stability in their ternary lithium metal batteries.

[0090] The electrochemical windows of the lithium metal batteries in Example 1 and Comparative Examples 1 and 2 are compared to those in Example 2. Figure 4As shown, Comparative Example 1, containing tridecafluorooctyl acrylate, exhibits the highest oxidative stability, thanks to its strong electron-withdrawing groups. The electrochemical window of the copolymerized electrolyte in Example 1 is significantly larger than that in Comparative Example 1. This is because the copolymerization of tridecafluorooctyl acrylate and methyl acrylate forms an ultra-long fluorinated polymer network structure with high antioxidant properties, effectively ensuring the structural stability of the electrolyte framework, reducing impedance, and improving the ionic conductivity of the electrolyte, thereby increasing the electrochemical window.

[0091] 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 polymer electrolyte with high ionic conductivity, characterized in that, The high ionic conductivity polymer electrolyte is prepared by in-situ polymerization in a battery of a polymer precursor solution comprising 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonyl)imide, a crosslinking agent, an initiator, and a plasticizer; wherein the 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate is copolymerized with the methyl acrylate to form a fluoropolymer. The volume ratio of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate to methyl acrylate is x:10-x, wherein 3 <x<7; In the polymer precursor solution, the mass fraction of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate is 15-30%; The molar concentration of the lithium bis(trifluoromethanesulfonylimide) is 0.5~3M.

2. The high ionic conductivity polymer electrolyte according to claim 1, characterized in that, In the polymer precursor solution, the mass fraction of the crosslinking agent is 0.3~0.5%; And / or, in the polymer precursor solution, the initiator has a mass fraction of 0.1-0.2%; And / or, in the polymer precursor solution, the mass fraction of the plasticizer is 20-25%.

3. The high ionic conductivity polymer electrolyte according to claim 1, characterized in that, The crosslinking agent is selected from one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, or pentaerythritol tetraacrylate. And / or, the plasticizer is selected from fluorinated solvents and / or ether solvents.

4. A lithium metal battery, characterized in that, Including polymer electrolytes with high ionic conductivity as described in any one of claims 1 to 3.

5. A method for preparing a lithium metal battery as described in claim 4, characterized in that, Includes the following steps: S1, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonylimide), crosslinking agent, initiator and plasticizer are mixed to obtain a polymer precursor solution; S2, assemble the battery positive electrode, lithium metal negative electrode, separator and the polymer precursor solution to obtain a coin cell; S3, the coin cell is first placed under vacuum, and then heated to solidify, so that the polymer precursor solution is polymerized in situ into a solid electrolyte, thus obtaining the lithium metal battery.

6. The method for preparing a lithium metal battery according to claim 5, characterized in that, In step S1, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, methyl acrylate, lithium bis(trifluoromethanesulfonyl)imide, crosslinking agent, initiator, and plasticizer are mixed to obtain a polymer precursor solution, comprising: The crosslinking agent, initiator, and plasticizer are stirred and mixed to obtain the first mixture; 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate and methyl acrylate were mixed to obtain a second mixture; The first mixture and the second mixture are mixed, and then lithium bis(trifluoromethanesulfonylimide) is added and stirred to obtain a polymer precursor solution.

7. The method for preparing a lithium metal battery according to claim 5, characterized in that, The amount of polymer precursor solution added is 20~50μL; And / or, the heating and curing temperature is 60~80℃, and the time is 12~48h.

8. The method for preparing a lithium metal battery according to claim 5, characterized in that, The positive electrode of the battery is prepared by the following method: polyvinylidene fluoride, nickel cobalt manganese ternary positive electrode material, lithium bis(trifluoromethanesulfonylimide), acetylene black and solvent are stirred and mixed to obtain a slurry; the slurry is coated on the surface of current collector aluminum foil and then dried to obtain the positive electrode of the battery.

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