A gel polymer electrolyte precursor solution, and a preparation method and application thereof

Abstract

The present application relates to a kind of gel polymer electrolyte precursor solution and its preparation method and application, the gel polymer electrolyte precursor solution includes the following components: monomer, electrolyte and initiator;The monomer includes fluorine-containing acrylate monomer and double acrylamide monomer.The gel polymer electrolyte precursor solution provided by the present application is made into fluorine-containing polyamide-based gel polymer electrolyte, which has good thermal stability and higher ionic conductivity, can effectively improve the electrochemical stability of lithium battery under high-voltage charge and discharge conditions, and has good cycle stability and rate performance.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a gel polymer electrolyte precursor solution, its preparation method, and its application. Background Technology

[0002] Electric vehicles and portable devices have placed higher demands on high-performance power and energy storage batteries, requiring greater energy density, cycle stability, and safety. Lithium metal batteries, using lithium metal as the negative electrode, have become a hot topic due to their extremely high energy density. However, when lithium metal negative electrodes are used in conjunction with carbonate-based liquid electrolytes, although the liquid electrolyte system has the advantage of high ionic conductivity, its inherent low flash point characteristics pose safety hazards.

[0003] To address this issue, existing technologies have proposed gel polymer electrolytes, which use polymers to swell and adsorb liquid solvents to form electrolytes. This can reduce leakage and swelling problems and improve safety to some extent. However, the presence of polymers still affects the lithium-ion migration rate. Furthermore, due to the properties of the electrolyte and the polymer itself, gel electrolyte batteries will still generate a large amount of heat and gas during overcharging, puncture, and compression, and may even burn and explode, posing a safety hazard.

[0004] CN112713302A discloses a flame-retardant polymer gel electrolyte composition, a gel electrolyte, its preparation method, and its applications. The flame-retardant polymer gel electrolyte composition comprises a polymeric monomer, a low vapor pressure flame retardant, a high vapor pressure flame retardant, a solvent, a polymerization initiator, and a lithium salt. The gel electrolyte prepared from this flame-retardant polymer gel electrolyte composition exhibits good flame-retardant properties. However, the direct incorporation of the flame retardant into the polymer electrolyte leads to reduced ionic conductivity and electrochemical stability, resulting in a decrease in battery performance.

[0005] Therefore, there is a need to develop a gel polymer electrolyte with high safety and high electrochemical performance. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a gel polymer electrolyte precursor solution, its preparation method, and its application. The fluorinated polyamide-based gel polymer electrolyte prepared from the gel polymer electrolyte precursor solution exhibits good thermal stability and high ionic conductivity, effectively improving the electrochemical stability of lithium batteries under high-voltage charge-discharge conditions, and possessing good cycle stability and rate performance.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a gel polymer electrolyte precursor solution, the gel polymer electrolyte precursor solution comprising the following components: monomer, electrolyte and initiator; the monomer includes fluorinated acrylate monomers and bisacrylamide monomers.

[0008] In this invention, fluorinated acrylate monomers and bisacrylamide monomers are used as monomers to form a gel polymer electrolyte precursor solution with electrolyte and initiator. After the reaction, a certain amount of fluorinated groups with high voltage stability and flame retardancy can be introduced into the polyamide polymer backbone to construct a fluorinated polyamide gel polymer electrolyte. The strongly electronegative fluorinated groups can endow the fluorinated polyamide gel polymer electrolyte with high antioxidant capacity, and the amide groups (-CO-NH-) help to construct a stable nitrogen-rich interface film. The resulting fluorinated polyamide gel polymer electrolyte has both good thermal stability and high ionic conductivity, which can effectively improve the electrochemical stability of lithium batteries under high voltage charge and discharge conditions, and has good cycle stability and rate performance.

[0009] In this invention, the high voltage refers to a voltage of 3~4.4 V.

[0010] Preferably, the molar amount of the fluorinated acrylate monomer is 10% to 90% (e.g., 20%, 30%, 40%, 50%, 60%, 70%, or 80%), and more preferably 20% to 30%, based on the total molar amount of the monomers as 100%.

[0011] Preferably, the fluorinated acrylate monomer includes 1H,1H,2H,2H-perfluorodecyl acrylate (PFDA).

[0012] Preferably, the bisacrylamide monomer includes N,N'-methylenebisacrylamide (MBAM).

[0013] In this invention, the amide group in the N,N'-methylenebisacrylamide helps to construct a stable nitrogen-rich interface film, thereby improving the cycle stability of the battery. The 1H,1H,2H,2H-perfluorodecyl acrylate has a -CF2- group, and the strongly electronegative fluorinated group enables the formed polymer to effectively attract electrons and lower the highest occupied molecular orbital energy level, thus endowing the electrolyte with high antioxidant capacity. The reaction of N,N'-methylenebisacrylamide and 1H,1H,2H,2H-perfluorodecyl acrylate forms the backbone of the fluorinated polyamide-based gel polymer electrolyte. Through the synergistic flame-retardant effect of the fluorinated and nitrogen-containing functional groups, the thermal stability of the fluorinated polyamide-based gel polymer electrolyte and the safety of the battery are significantly improved. In addition, the amide group and fluorinated segments provide abundant binding sites for the rapid migration of lithium ions, thereby promoting the uniform deposition or stripping of lithium and endowing the battery with excellent electrochemical performance. By rationally combining monomers with different functional groups, complementary advantages between monomers can be achieved in fluorinated polyamide-based gel polymer electrolytes, resulting in gel polymer electrolytes with high safety and high electrochemical performance, thereby improving battery safety and cycle stability.

[0014] Preferably, the mass of the monomer is 1% to 20% based on the total mass of the monomer and electrolyte as 100%, for example, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17% or 19%, etc.

[0015] Preferably, the electrolyte comprises a solvent and a lithium salt.

[0016] Preferably, the solvent includes cyclic carbonates and linear carbonates.

[0017] Preferably, the volume ratio of the cyclic carbonate to the linear carbonate is (1~4.5):3, for example, 1.2:3, 1.5:3, 1.8:3, 2.1:3, 2.4:3, 2.7:3, 3.0:3, 3.3:3, 3.6:3, 3.9:3 or 4.2:3, etc.

[0018] Preferably, the cyclic carbonate comprises ethylene carbonate (EC) and / or propylene carbonate.

[0019] Preferably, the linear carbonate includes any one or a combination of at least two of dimethyl carbonate, ethyl methyl carbonate (EMC), or diethyl carbonate.

[0020] Preferably, the concentration of lithium salt in the electrolyte is 0.2 mol / L to 1.2 mol / L, such as 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, or 1.1 mol / L.

[0021] Preferably, the lithium salt comprises any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium di(oxalato)borate (LiBOB), lithium di(fluorooxalato)borate, lithium perchlorate, or lithium hexafluorophosphate.

[0022] Preferably, the mass of the initiator is 0.01% to 5% of the total mass of the monomer and electrolyte, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%.

[0023] Preferably, the initiator includes a photoinitiator and / or a thermal initiator.

[0024] Preferably, the photoinitiator comprises 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and / or 2-hydroxy-2-methyl-1-phenylpropanone (1173).

[0025] Preferably, the thermal initiator includes any one or a combination of at least two of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile, or benzoyl peroxide (BPO).

[0026] Secondly, the present invention provides a method for preparing a gel polymer electrolyte precursor solution, the preparation method comprising the following steps: mixing a monomer, an electrolyte and an initiator to obtain the gel polymer electrolyte precursor solution.

[0027] Thirdly, the present invention provides a fluorinated polyamide-based gel polymer electrolyte, which is prepared from a gel polymer electrolyte precursor solution as described in the first aspect.

[0028] Fourthly, the present invention provides a method for preparing a fluorinated polyamide-based gel polymer electrolyte as described in the third aspect, the method comprising the following steps: performing a polymerization reaction on a gel polymer electrolyte precursor solution as described in the first aspect to obtain the fluorinated polyamide-based gel polymer electrolyte.

[0029] Preferably, the polymerization reaction includes an in-situ polymerization reaction carried out on the electrode surface.

[0030] In ultra-high voltage environments, there is still room for improvement in the interfacial compatibility between polyamide-based gel polymer electrolytes and electrodes. In this invention, a fluorinated polyamide-based gel polymer electrolyte is prepared by photo-initiated or thermally-initiated in-situ polymerization of a precursor solution formed by mixing monomers, electrolytes and initiators on the electrode surface. This not only significantly reduces interfacial impedance and extends battery life, but also ensures compatibility with existing liquid battery production lines, resulting in significant industrialization cost advantages.

[0031] Preferably, the polymerization reaction includes a thermally initiated free radical polymerization reaction, wherein the reaction temperature is 50~100℃ (e.g., 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃, etc.), and the reaction time is 1~48 h (e.g., 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h or 45 h, etc.).

[0032] Preferably, the polymerization reaction includes a photoinitiated free radical polymerization reaction, wherein the wavelength of the ultraviolet light used in the photoinitiated free radical polymerization reaction is 254~365 nm (e.g., 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm or 360 nm, etc.), and the irradiation time of the ultraviolet light is 5~60 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min, etc.).

[0033] Fifthly, the present invention provides a lithium battery comprising a positive electrode, a negative electrode, and a fluorinated polyamide-based gel polymer electrolyte as described in the third aspect or a fluorinated polyamide-based gel polymer electrolyte prepared by the preparation method described in the fourth aspect.

[0034] In this invention, the positive and negative electrodes of the lithium battery are components conventionally used in lithium batteries. This invention does not impose excessive limitations; the examples provided are merely illustrative and are not intended to limit the invention further. In this invention, the positive electrode comprises a positive electrode active material, optionally a conductive agent, and optionally a binder, and the negative electrode comprises a negative electrode active material, optionally a conductive agent, and optionally a binder. Exemplary examples are provided below: For example, the positive electrode active material includes lithium oxide.

[0035] For example, the lithium oxide includes Li 1-x NiO2, Li 1-x MnO2, Li 1-x CoO2, Li 1- x Ni 0.6 Co 0.2 Mn 0.2 O2, Li 1-x FePO4, Li 1-x NiO2 derivatives, Li 1-x MnO2 derivatives, Li 1-x CoO2 derivatives, Li1-x Ni 0.6 Co 0.2 Mn 0.2 O2 derivatives or Li 1-x Any one or at least two of the derivatives of FePO4, where x is a number from 0 to 1.

[0036] For example, the lithium oxide includes LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622).

[0037] For example, the negative electrode comprises a lithium-intercalable / deintercalable material.

[0038] For example, the lithium intercalation / deintercalation material includes any one or a combination of at least two of lithium metal, graphite, silicon, silicon-carbon, or hard carbon.

[0039] For example, the conductive agents in the positive and negative electrodes each independently include any one or a combination of at least two of acetylene black, carbon nanotubes, or graphene.

[0040] For example, the adhesive includes any one or a combination of at least two of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), or carboxymethyl cellulose (CMC).

[0041] For example, the positive or negative electrode can be prepared by mixing a positive or negative active material, a conductive agent, a binder, and a solvent to form a slurry, which is then coated on one or both sides of the current collector and dried to obtain the positive or negative electrode.

[0042] For example, the solvent may include an organic solvent or deionized water.

[0043] For example, the organic solvent includes any one or a combination of at least two of N-methylpyrrolidone (NMP), N,N-dimethylformamide, acetone, tetrahydrofuran, or dimethyl sulfoxide.

[0044] In this invention, the shape of the lithium battery is not limited in much; any shape that can be made into a lithium battery can be used, such as coin-shaped, cylindrical, square, etc.

[0045] In a sixth aspect, the present invention provides an electrical device comprising a lithium battery as described in the fifth aspect.

[0046] For example, the electrical equipment includes any one of the following: a device having a lithium battery as described in the fifth aspect, a device powered by a lithium battery as described in the fifth aspect, or a device storing energy by a lithium battery as described in the fifth aspect.

[0047] For example, the electrical equipment includes any one or a combination of at least two of the following: electric vehicles, electric bicycles, power banks, mobile phones, tablets, electronic watches, power tools, energy storage battery packs, or energy storage power stations, but is not limited thereto.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects: The fluorinated polyamide-based gel polymer electrolyte formed from the gel polymer electrolyte precursor solution of the present invention has fluorinated groups with high voltage stability and flame retardancy, and amide groups that help to build a stable nitrogen-rich interface film. This gives the fluorinated polyamide-based gel polymer electrolyte good thermal stability and high ionic conductivity, which can effectively improve the electrochemical stability of lithium batteries under high voltage charge and discharge conditions, and has good cycle stability and rate performance. The stainless steel symmetric battery prepared from the gel polymer electrolyte precursor solution has an ionic conductivity ≥0.1 mS / cm; when the thermogravimetric analysis (TGA) is performed at 100°C, the mass loss of the fluorinated polyamide-based gel polymer electrolyte prepared from the gel polymer electrolyte precursor solution is <3.5 wt.%, exhibiting excellent thermal stability; the Li||NCM622 battery prepared from the gel polymer electrolyte precursor solution has a capacity retention rate ≥75% after 200 cycles. Preferably, the stainless steel symmetric battery prepared from the gel polymer electrolyte precursor solution has an ionic conductivity ≥0.2 mS / cm; when the thermogravimetric analysis (TGA) is performed at 100°C, the mass loss of the fluorinated polyamide-based gel polymer electrolyte prepared from the gel polymer electrolyte precursor solution is ≤2.5 wt.%, exhibiting excellent thermal stability; the Li||NCM622 battery prepared from the gel polymer electrolyte precursor solution has a capacity retention rate ≥85% after 200 cycles. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the Li||NCM622 battery structure fabricated using the gel polymer electrolyte precursor solution provided in Example 1, and also shows the possible polymerization reaction pathways and Li||NCM622 in the gel polymer electrolyte precursor solution. + A schematic diagram of the transmission process; Among them, 1-positive electrode, 2-composite system of polyethylene membrane and electrolyte, 3-polyethylene membrane, 4-negative electrode; Figure 2Infrared spectrum of fluorinated polyamide-based gel polymer electrolyte formed by solution polymerization of 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide and the gel polymer electrolyte precursor provided in Example 1. Figure 3 The electrochemical impedance spectroscopy diagram of a stainless steel symmetrical cell, measured during the battery impedance test. Figure 4 The ionic conductivity and linear fitting graphs of stainless steel symmetric cells prepared using the gel polymer electrolyte precursor solution provided in Example 1 and stainless steel symmetric cells prepared using the electrolyte provided in Comparative Example 1 are shown at different temperatures. Figure 5 The cyclic voltammetry curves of the Li||SS battery prepared using the electrolyte provided in Comparative Example 1 are shown. Figure 6 The cyclic voltammetry curves of the Li||SS battery prepared using the gel polymer electrolyte precursor solution provided in Example 1 are shown. Figure 7 Thermogravimetric curves of the electrolyte provided in Comparative Example 1 and the fluorinated polyamide-based gel polymer electrolyte prepared using the gel polymer electrolyte precursor solution provided in Example 1. Figure 8 The graph shows the results of lithium-ion transport number testing for a lithium-symmetric battery made using the electrolyte provided in Comparative Example 1. Figure 9 The graph shows the lithium-ion transport number test results of a lithium-symmetric battery prepared using the gel polymer electrolyte precursor solution provided in Example 1. Figure 10 Cyclic performance graphs of Li||NCM622 batteries made with the electrolyte provided in Comparative Example 1, Li||NCM622 batteries made with the gel polymer electrolyte precursor solution provided in Example 1, and Li||NCM622 batteries made with the gel polymer electrolyte precursor solution provided in Example 8. Figure 11 The rate performance graphs show the Li||NCM622 battery made using the electrolyte provided in Comparative Example 1 and the Li||NCM622 battery made using the gel polymer electrolyte precursor solution provided in Example 1. Detailed Implementation

[0050] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0051] Unless otherwise specified, the materials and equipment involved in the following detailed embodiments are all conventional materials and equipment in the art and will not affect the technical effects of the present invention.

[0052] Example 1 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The gel polymer electrolyte precursor solution is prepared by the following method: A solvent was prepared by mixing cyclic carbonate (ethylene carbonate) and linear carbonate (ethyl methyl carbonate) in a volume ratio of 2:3. Lithium salts (lithium bis(trifluoromethanesulfonyl)imide and lithium dioxolaneborate) were dissolved in the solvent at room temperature (25°C) and stirred until homogeneous to obtain an electrolyte. The concentration of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte was 0.8 mol / L and the concentration of lithium dioxolaneborate was 0.4 mol / L.

[0053] The monomers (1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide in a molar ratio of 30:70) were added to the above electrolyte and mixed evenly. Then, a thermal initiator (azobisisobutyronitrile) was added. Based on the total mass of monomers and electrolytes being 100%, the mass of the monomers was 5%, and the mass of the initiator was 0.1% of the total mass of monomers and electrolytes. The mixture was stirred and mixed evenly to obtain the gel polymer electrolyte precursor solution.

[0054] Example 2 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The gel polymer electrolyte precursor solution is prepared by the following method: A solvent was prepared by mixing cyclic carbonate (ethylene carbonate) and linear carbonate (methyl ethyl carbonate) in a volume ratio of 1:3. Lithium salts (lithium trifluoromethanesulfonate and lithium hexafluorophosphate) were dissolved in the solvent at room temperature (25°C) and stirred until homogeneous to obtain an electrolyte. The concentration of lithium trifluoromethanesulfonate in the electrolyte was 0.5 mol / L, and the concentration of lithium hexafluorophosphate was 0.5 mol / L.

[0055] The monomers (1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide in a molar ratio of 30:70) were added to the above electrolyte and mixed evenly. Then, a thermal initiator (azobisisobutyronitrile) was added. Based on the total mass of monomers and electrolytes being 100%, the mass of the monomers was 10%, and the mass of the initiator was 0.2% of the total mass of monomers and electrolytes. The mixture was stirred and mixed evenly to obtain the gel polymer electrolyte precursor solution.

[0056] Example 3 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The gel polymer electrolyte precursor solution is prepared by the following method: A solvent was prepared by mixing cyclic carbonate (propylene carbonate) and linear carbonate (dimethyl carbonate) in a volume ratio of 4.5:3. Lithium salts (lithium bis(fluorosulfonyl)imide and lithium difluorooxalate borate) were dissolved in the solvent at room temperature (25°C) and stirred until homogeneous to obtain an electrolyte. The concentration of lithium bis(fluorosulfonyl)imide and lithium difluorooxalate borate in the electrolyte was 0.6 mol / L.

[0057] The monomers (1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide in a molar ratio of 30:70) were added to the above electrolyte and mixed evenly. Then, a thermal initiator (azobisisobutyronitrile) was added. Based on the total mass of monomers and electrolytes being 100%, the mass of the monomers was 20%, and the mass of the initiator was 0.4% of the total mass of monomers and electrolytes. The mixture was stirred and mixed evenly to obtain the gel polymer electrolyte precursor solution.

[0058] Example 4 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The difference between this embodiment and Example 1 is that the molar ratio of monomers 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide is adjusted to 10:90, while other conditions are the same as in Example 1.

[0059] Example 5 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The difference between this embodiment and Example 1 is that the molar ratio of monomers 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide is adjusted to 20:80, while other conditions are the same as in Example 1.

[0060] Example 6 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The difference between this embodiment and Example 1 is that the molar ratio of monomers 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide is adjusted to 50:50, while other conditions are the same as in Example 1.

[0061] Example 7 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The difference between this embodiment and Example 1 is that the molar ratio of monomers 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide is adjusted to 70:30, while other conditions are the same as in Example 1.

[0062] Example 8 This embodiment provides a gel polymer electrolyte precursor solution and its preparation method. The difference between this embodiment and Example 1 is that 1H,1H,2H,2H-perfluorodecyl acrylate is replaced with the same molar amount of trifluoroethyl methacrylate (TFMA), while other conditions are the same as in Example 1.

[0063] Comparative Example 1 This comparative example provides an electrolyte prepared by the following method: a solvent is obtained by mixing cyclic carbonate (ethylene carbonate) and linear carbonate (ethyl methyl carbonate) in a volume ratio of 2:3; lithium salts (lithium bis(trifluoromethanesulfonyl)imide and lithium dioxolaneborate) are dissolved in the solvent at room temperature (25°C) and stirred until homogeneous to obtain the electrolyte. The concentration of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte is 0.8 mol / L, and the concentration of lithium dioxolaneborate is 0.4 mol / L.

[0064] Comparative Example 2 This comparative example provides a gel polymer electrolyte precursor solution and its preparation method. The difference between this and Example 1 is that the monomer is N,N'-methylenebisacrylamide, and 1H,1H,2H,2H-perfluorodecyl acrylate is not added. Other conditions are the same as in Example 1.

[0065] The following performance tests were performed on the gel polymer electrolyte precursor solutions provided in Examples 1-8 and Comparative Example 2, as well as the electrolyte provided in Comparative Example 1.

[0066] (1) Impedance test of the battery: Stainless steel symmetric battery (SS||SS symmetric battery) was prepared. The electrolyte in the stainless steel symmetric battery was prepared by polymerizing the gel polymer electrolyte precursor solution provided in Examples 1-8 and Comparative Example 2, respectively. The electrolyte provided in Comparative Example 1 was used as the electrolyte in the stainless steel symmetric battery.

[0067] Specifically, the gel polymer electrolyte precursor solutions provided in Examples 1-8 and Comparative Example 2 were dropped onto both sides of a polyethylene membrane, with a total amount of 60 µL. Stainless steel sheets were used as the positive and negative electrodes to assemble a 2025 coin cell. The cells were then placed in a forced-air oven at 60°C and heated at a constant temperature for 12 h to allow the gel polymer electrolyte precursor solution to polymerize in situ, resulting in a stainless steel symmetrical cell. The electrolyte provided in Comparative Example 1 was dropped onto both sides of a polyethylene membrane, with a total amount of 60 µL. Stainless steel sheets were used as the positive and negative electrodes to assemble a 2025 coin cell, resulting in a stainless steel symmetrical cell.

[0068] The electrochemical impedance spectroscopy (EIS) of the above-mentioned stainless steel symmetrical cell was tested using an electrochemical workstation (PGSTAT-302N, Switzerland). The test frequency of the AC signal was 100 kHz to 1 Hz, and the voltage amplitude was 10 mV.

[0069] Calculate the ionic conductivity using the following formula; ; Where σ is the ionic conductivity. The thickness of the polyethylene membrane is used. Since the electrolyte and the polyethylene membrane are integrated and inseparable, and the ion transport path is constrained by the membrane skeleton, the thickness of the polyethylene membrane is used as the effective thickness for ion conduction. R is the bulk impedance of the electrolyte, which is obtained by the intersection of the extension line fitted to the Nyquist point of the EIS spectrum and the X-axis. S is the contact area of ​​the composite system of stainless steel sheet, polyethylene membrane and electrolyte.

[0070] The ionic conductivity at different temperatures was tested and linearly fitted. When it conforms to the Arrhenius equation, the activation energy (Ea) can be calculated according to the following formula. ; Where T is the thermodynamic temperature, A is the pre-exponential factor, and k is the Boltzmann constant (k = 1.38 × 10⁻⁶). -23 J / K).

[0071] (2) Cyclic voltammetry (CV) test of the battery: a lithium battery, specifically a Li||SS battery, was prepared by polymerizing the gel polymer electrolyte precursor solution provided in Example 1 to prepare the electrolyte in the Li||SS battery, and the electrolyte provided in Comparative Example 1 was used as the electrolyte in the Li||SS battery.

[0072] Specifically, the gel polymer electrolyte precursor solution provided in Example 1 was dropped onto both sides of a polyethylene membrane, with a total amount of 60 µL. A stainless steel sheet was used as the positive electrode and lithium metal as the negative electrode to assemble a 2025 coin cell. The coin cell was then placed in a 60°C oven and heated at a constant temperature for 12 h to allow the gel polymer electrolyte precursor solution to polymerize in situ, thus obtaining a Li||SS battery. The electrolyte provided in Comparative Example 1 was dropped onto both sides of a polyethylene membrane, with a total amount of 60 µL. A stainless steel sheet was used as the positive electrode and lithium metal as the negative electrode to assemble a 2025 coin cell, thus obtaining a Li||SS battery.

[0073] The CV curves of the above Li||SS cells were tested using a multichannel electrochemical workstation (VMP3, Bio-Logic, France). The scan started from the open-circuit voltage and proceeded negatively to -0.5 V, then positively to 5 V, and finally negatively back to the open-circuit voltage at a scan rate of 1 mVs. -1 .

[0074] (3) Thermogravimetric analysis: The gel polymer electrolyte precursor solutions provided in Examples 1-8 were placed in a 60°C oven and heated at a constant temperature for 12 h to polymerize the gel polymer electrolyte precursor solutions to form fluorinated polyamide-based gel polymer electrolytes; the thermogravimetric analysis was performed using a TFA5500 instrument with a test temperature range of 50~600°C and a heating rate of 10°C / min.

[0075] The electrolyte provided in Comparative Example 1 was tested using a thermogravimetric analyzer (TFA5500) at a temperature range of 50~600℃ and a heating rate of 10℃ / min.

[0076] The gel polymer electrolyte precursor solution provided in Comparative Example 2 was placed in a 60°C oven and heated at a constant temperature for 12 h to polymerize the gel polymer electrolyte precursor solution to form a polyamide-based gel polymer electrolyte.

[0077] (4) Lithium-ion transport number test: Lithium symmetric battery (Li||Li symmetric battery) was prepared by polymerizing the gel polymer electrolyte precursor solution provided in Example 1 to prepare the electrolyte in the lithium symmetric battery, and the electrolyte provided in Comparative Example 1 was used as the electrolyte in the lithium symmetric battery.

[0078] Specifically, the gel polymer electrolyte precursor solution provided in Example 1 was dropped onto both sides of a polyethylene membrane, with a total amount of 60 µL. Lithium metal was used as the positive and negative electrodes to assemble a 2025 coin cell. The coin cell was then placed in a 60°C oven and heated at a constant temperature for 12 h to allow the gel polymer electrolyte precursor solution to polymerize in situ, thus obtaining a lithium symmetric battery. The electrolyte provided in Comparative Example 1 was dropped onto both sides of a polyethylene membrane, with a total amount of 60 µL. Lithium metal was used as the positive and negative electrodes to assemble a 2025 coin cell, thus obtaining a lithium symmetric battery.

[0079] The Bruce-Vincent method can be used to measure the lithium-ion transference number. The aforementioned lithium-symmetric battery was tested using a multi-channel electrochemical workstation (VMP3, Bio-Logic, France). The test consisted of two EIS tests before and after polarization, and one chronoamperometry (CA) test. The EIS test frequency ranged from 100 kHz to 1 Hz with an amplitude of 10 mV, and the polarization voltage for the CA test was 10 mV. The test data were processed using the Bruce-Vincent formula to calculate the lithium-ion transference number (t). Li+ ). Among them, R O and R SS The interfacial impedances of the cell before and after polarization are I0 and I0, respectively. O and I SS These are the initial and steady-state currents, respectively. This is the polarization voltage.

[0080] (5) Cyclic performance test and rate performance test of the battery: Lithium battery, specifically Li||NCM622 battery, was prepared by polymerizing the gel polymer electrolyte precursor solution provided in Examples 1-8 and Comparative Example 2 to prepare the electrolyte in the Li||NCM622 battery, or by using the electrolyte provided in Comparative Example 1 as the electrolyte in the Li||NCM622 battery.

[0081] Specifically, NCM622 positive electrode active powder, conductive agent (acetylene black), and binder (PVDF) were mixed evenly at a mass ratio of 8:1:1. Then, solvent (N-methylpyrrolidone) was added and stirred until homogeneous, resulting in a slurry with a solid content of 27 wt.%. This slurry was then evenly coated onto an aluminum foil current collector and transferred to a vacuum oven, where it was dried at 120°C for 12 h, yielding a loading of 2.3 mg / cm³. -2 The electrode sheet was cut into small circular pieces with a diameter of 12 mm to obtain the NCM622 positive electrode sheet. The gel polymer electrolyte precursor solutions provided in Examples 1-8 and Comparative Example 2 were dropped onto both sides of a polyethylene separator, with a total volume of 60 µL. Using the above-mentioned NCM622 positive electrode sheet as the positive electrode and lithium metal as the negative electrode, a 2025 coin cell was assembled. Then, it was placed in a 60°C oven and heated at a constant temperature for 12 h to allow the gel polymer electrolyte precursor solution to polymerize in situ, obtaining the Li||NCM622 battery. Figure 1 As shown, the electrolyte provided in Comparative Example 1 was dropwise added to both sides of the polyethylene separator, with a total amount of 60 µL. Using NCM622 as the positive electrode and lithium metal as the negative electrode, a 2025 coin cell was assembled to obtain the Li||NCM622 battery.

[0082] The Li||NCM622 battery was tested using a Land CT2001A system (Wuhan Land Electronics Co., Ltd.) under constant current charge and discharge conditions. The test temperature was 25℃, the voltage range was 3~4.4 V, the rate was 0.5C, and the capacity retention rate was tested after 200 and 300 cycles.

[0083] Constant current charge-discharge tests were conducted using a Land CT2001A system (Wuhan Land Electronics Co., Ltd.). The test temperature was 25°C, and the voltage range was 3~4.4 V. The tests were conducted on the discharge capacity and capacity recovery capability of the Li||NCM622 battery prepared with the gel polymer electrolyte precursor solution provided in Example 1 and the Li||NCM622 battery prepared with the electrolyte provided in Comparative Example 1 at rates of 0.1C, 0.2C, 0.3C, 0.5C, 1C, and 2C.

[0084] The test results are shown in Table 1 and Figures 1-11 As shown.

[0085] Table 1 In Table 1, " / " indicates that the test was not performed.

[0086] According to Table 1 and Figures 1-11 The test results show that the fluorinated polyamide-based gel polymer electrolytes prepared from the gel polymer electrolyte precursor solutions provided in Examples 1-8 have good thermal stability and high ionic conductivity. The lithium batteries made from these electrolytes have good cycle stability and excellent electrochemical performance.

[0087] The fluorinated polyamide-based gel polymer electrolyte formed by the solution polymerization of 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide, as well as the gel polymer electrolyte precursor solution provided in Example 1, was characterized using an infrared spectrometer (BRUKER TENSOR 27, Germany) at a wavenumber of 4000 cm⁻¹. -1 ~400 cm -1 The obtained infrared spectrum is as follows Figure 2 As shown, 1H,1H,2H,2H-perfluorodecyl acrylate at 1145 cm⁻¹ -1 The characteristic peak of -CF3 appears at 3300 cm⁻¹; N,N'-methylenebisacrylamide shows a peak at 3300 cm⁻¹. -1 The peak of -NH- stretching vibration is shown at 1670 cm⁻¹. -1 and 1545 cm -1 The peaks at 1630 cm⁻¹ correspond to the C=O stretching vibration and -NH₃ bending vibration, respectively, and are characteristic peaks of amide groups. These characteristic functional groups are retained in the fluorinated polyamide gel polymer electrolyte, confirming the presence of characteristic functional groups of 1H,1H,2H,2H-perfluorodecyl acrylate and N,N'-methylenebisacrylamide in the polymer obtained after polymerization. Furthermore, 1630 cm⁻¹... -1 (C=C vibration) and 3065 cm -1 The absorption peak at (=CH-H vibration) disappears in the fluorinated polyamide-based gel polymer electrolyte, indicating that the polymerization reaction proceeds through the breaking of unsaturated double bonds in the monomer.

[0088] The impedance spectrum of a portion of the stainless steel symmetrical cell tested at room temperature (25°C) is as follows: Figure 3As shown, the stainless steel symmetric battery prepared with the gel polymer electrolyte precursor solution provided in Example 1 exhibits an ionic conductivity as high as 0.69 mS / cm, which is the best among the examples and close to the level of the electrolyte (Comparative Example 1) (0.75 mS / cm). The impedance spectra of the stainless steel symmetric battery prepared with the gel polymer electrolyte precursor solution provided in Example 1 and the stainless steel symmetric battery prepared with the electrolyte provided in Comparative Example 1 were tested at different temperatures, and the ionic conductivity was calculated. A plot of the logarithm of the ionic conductivity versus the reciprocal of the temperature conforms to the Arrhenius equation, as shown below. Figure 4 As shown, the activation energy of the stainless steel symmetric battery prepared with the gel polymer electrolyte precursor solution provided in Example 1 was calculated to be 12.19 kJ / mol, while the activation energy of the stainless steel symmetric battery prepared with the electrolyte provided in Comparative Example 1 was 21.54 kJ / mol. The lower the activation energy, the less energy is required for ion migration, resulting in a lower ion migration barrier and promoting Li... + Rapid migration is beneficial to improving the cycle performance and rate performance of the battery.

[0089] Depend on Figure 5 and Figure 6 It can be seen that the Li||SS battery prepared using the electrolyte provided in Comparative Example 1 exhibits a large oxidation current response in the voltage range of 4.5~5.0 V, indicating that it undergoes an oxidation decomposition reaction above 4.5 V. In contrast, the Li||SS battery prepared using the gel polymer electrolyte precursor solution provided in Example 1 remains stable in this voltage range, proving that the fluorinated polyamide-based gel polymer electrolyte prepared using the gel polymer electrolyte precursor solution provided in Example 1 is suitable for 5 V cathode materials.

[0090] Depend on Figure 7 It can be seen that when the temperature rises to 100°C, the electrolyte provided in Comparative Example 1 loses 19.8% of its mass, while the fluorinated polyamide-based gel polymer electrolyte prepared using the gel polymer electrolyte precursor solution provided in Example 1 loses only 1.6%, demonstrating excellent thermal stability.

[0091] Depend on Figure 8 and Figure 9 It is known that the lithium symmetric battery made from the gel polymer electrolyte precursor solution provided in Example 1 has a higher lithium-ion transference number, reaching 0.71. The high lithium-ion transference number helps to reduce system polarization, thereby improving the electrochemical performance of the battery.

[0092] Depend on Figure 10 It can be seen that the initial discharge specific capacity of the Li||NCM622 battery made using the electrolyte provided in Comparative Example 1 is 167 mAh g. -1After 200 cycles, the capacity retention rate was only 79%, and after 300 cycles, the capacity retention rate was only 71%. In contrast, the Li||NCM622 battery prepared using the gel polymer electrolyte precursor solution polymerized in Example 1 had an initial discharge specific capacity of 165 mAh g⁻¹. -1 After 200 and 300 cycles, both showed higher capacity retention. Compared with Example 1, the Li||NCM622 battery prepared by polymerizing the gel polymer electrolyte precursor solution provided in Example 8 had a higher initial discharge specific capacity of 178 mAh g. -1 However, the capacity retention rate decreased significantly after 200 cycles, but it was still higher than that of the Li||NCM622 battery made using the electrolyte provided in Comparative Example 1. Therefore, it can be seen that the fluorinated polyamide-based gel polymer electrolyte prepared by solution polymerization of the gel polymer electrolyte precursor provided by this invention can improve the cycle stability of the battery, and the performance is even better when using fluorinated acrylate monomers, preferably 1H,1H,2H,2H-perfluorodecyl acrylate.

[0093] Depend on Figure 11 It can be seen that, at discharge rates of 0.1C, 0.2C, 0.3C, 0.5C, 1C, and 2C, the Li||NCM622 battery prepared by polymerizing the gel polymer electrolyte precursor solution provided in Example 1 has a discharge capacity of 185.1 mAh g⁻¹. -1 181.7mAh g -1 179.2 mAh g -1 172.7 mAh g -1 164.9 mAh g -1 and 154.6 mAh g -1 When the current density recovers to 0.1C, its specific capacity rebounds to 178.6 mAh g⁻¹. -1 This indicates that the material possesses excellent rate performance and capacity recovery capability. In contrast, the Li||NCM622 battery prepared with the electrolyte provided in Comparative Example 1 exhibits a discharge capacity of 188.7 mAh g⁻¹ at the same rate. -1 183.1 mAh g -1 179.9 mAh g -1 173.0 mAh g -1 163.4 mAh g -1 and 148.1mAh g -1It is worth noting that at a high 2C rate, its discharge capacity is significantly lower than that of the Li||NCM622 battery prepared by solution polymerization of the gel polymer electrolyte precursor provided in Example 1. Therefore, it can be seen that the fluorinated polyamide-based gel polymer electrolyte prepared by solution polymerization of the gel polymer electrolyte precursor provided by the present invention can improve the rate performance and capacity recovery capability of the battery.

[0094] Compared with Example 1, the molar percentage of the fluorinated acrylate monomers is smaller when the total molar amount of the monomers is 100% (Example 4). As a result, the ionic conductivity and thermal stability of the stainless steel symmetric battery made from the prepared gel polymer electrolyte precursor solution decrease.

[0095] Compared with Example 1, if the total molar amount of the monomers is 100%, the molar amount of the fluorinated acrylate monomers is larger (Example 6) or (Example 7). Therefore, the stainless steel symmetric battery made from the prepared gel polymer electrolyte precursor solution has better thermal stability, but its ionic conductivity is significantly reduced.

[0096] Compared to Example 1, replacing 1H,1H,2H,2H-perfluorodecyl acrylate with the same molar amount of trifluoroethyl methacrylate (Example 8) resulted in shorter fluorinated segments in the fluorinated acrylate monomers and poorer thermal stability.

[0097] Compared with Example 1, the stainless steel symmetric battery prepared from the gel polymer electrolyte precursor solution has low ionic conductivity if no fluorinated acrylate monomers are added (Comparative Example 2).

[0098] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A gel polymer electrolyte precursor solution, characterized in that, The gel polymer electrolyte precursor solution comprises the following components: monomer, electrolyte and initiator; The monomers include fluorinated acrylate monomers and bisacrylamide monomers.

2. The gel polymer electrolyte precursor solution according to claim 1, characterized in that, Based on the total molar amount of monomers being 100%, the molar amount of the fluorinated acrylate monomers is 10% to 90%; Preferably, the fluorinated acrylate monomer includes 1H,1H,2H,2H-perfluorodecyl acrylate; Preferably, the bisacrylamide monomer includes N,N'-methylenebisacrylamide.

3. The gel polymer electrolyte precursor solution according to claim 1 or 2, characterized in that, The monomer comprises 1% to 20% of the total mass of monomer and electrolyte, with the total mass of monomer and electrolyte being 100%. Preferably, the electrolyte comprises a solvent and a lithium salt; Preferably, the solvent includes cyclic carbonates and linear carbonates; Preferably, the volume ratio of the cyclic carbonate to the linear carbonate is (1~4.5):3; Preferably, the cyclic carbonate comprises ethylene carbonate and / or propylene carbonate; Preferably, the linear carbonate includes any one or a combination of at least two of dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate; Preferably, the concentration of lithium salt in the electrolyte is 0.2 mol / L to 1.2 mol / L; Preferably, the lithium salt comprises any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium di(oxalate)borate, lithium difluorooxalateborate, lithium perchlorate, or lithium hexafluorophosphate.

4. The gel polymer electrolyte precursor solution according to any one of claims 1 to 3, characterized in that, The mass of the initiator is 0.01% to 5% of the total mass of the monomer and electrolyte; Preferably, the initiator includes a photoinitiator and / or a thermal initiator; Preferably, the photoinitiator comprises 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and / or 2-hydroxy-2-methyl-1-phenylpropanone; Preferably, the thermal initiator includes any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

5. A method for preparing a gel polymer electrolyte precursor solution, characterized in that, The preparation method includes the following steps: mixing monomer, electrolyte and initiator to obtain the gel polymer electrolyte precursor solution.

6. A fluorinated polyamide-based gel polymer electrolyte, characterized in that, The fluorinated polyamide-based gel polymer electrolyte is prepared from the gel polymer electrolyte precursor solution as described in any one of claims 1 to 4.

7. A method for preparing a fluorinated polyamide-based gel polymer electrolyte as described in claim 6, characterized in that, The preparation method includes the following steps: performing a polymerization reaction on the gel polymer electrolyte precursor solution as described in any one of claims 1 to 4 to obtain the fluorinated polyamide-based gel polymer electrolyte.

8. The preparation method according to claim 7, characterized in that, The polymerization reaction includes an in-situ polymerization reaction carried out on the electrode surface; Preferably, the polymerization reaction includes a thermally initiated free radical polymerization reaction, wherein the reaction temperature is 50~100℃ and the reaction time is 1~48 h; Preferably, the polymerization reaction includes a photoinitiated free radical polymerization reaction, wherein the wavelength of the ultraviolet light used in the photoinitiated free radical polymerization reaction is 254~365 nm, and the irradiation time of the ultraviolet light is 5~60 min.

9. A lithium battery, characterized in that, The lithium battery includes a positive electrode, a negative electrode, and a fluorinated polyamide-based gel polymer electrolyte as described in claim 6 or a fluorinated polyamide-based gel polymer electrolyte prepared by the preparation method described in claim 7 or 8.

10. An electrical-related device, characterized in that, The electrical equipment includes the lithium battery as described in claim 9.

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