High-voltage polymer electrolyte, preparation method thereof and application of high-voltage polymer electrolyte in all-solid-state battery

Abstract

The invention discloses a high-voltage polymer electrolyte, a preparation method thereof and application of the high-voltage polymer electrolyte in an all-solid-state lithium metal battery, and relates to the technical field of solid-state electrolytes. The high-pressure polymer electrolyte provided by the invention comprises a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, a phosphate ester solvent and a lithium salt, wherein a solvation structure rich in anions is formed between the phosphate ester solvent and the lithium salt. The phosphate ester solvent (TEP / TMP / DMMP) and the lithium salt with high oxidation stability such as lithium bis (fluorosulfonyl) imide (LiTFSI / LiFSI / LiDFOB) have a synergistic effect, phosphate ester and the lithium salt form a solvated structure rich in anions, the solvated structure formed by the lithium salt and the phosphate ester solvent is transferred on a polymer chain segment, and the ionic conductivity is improved to 4.6 * 10 <-4 > S / cm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state electrolyte, and particularly relates to a high-voltage polymer electrolyte, a preparation method thereof and application thereof in all-solid-state batteries. BACKGROUND

[0002] With the increasing demand for driving range of global electric vehicle industry and the growing demand for energy density of energy storage system, the development of high-voltage positive electrode materials (such as layered ternary material LiNi 0.8 Mn 0.1 Co 0.1 O2, spinel LiNi 0.5 Mn 1.5 O4, etc.) with a working voltage of 4.5V or more has become the core development direction of lithium battery technology. Such materials can push the battery energy density to more than 300Wh / kg, significantly exceeding the current commercial system. However, the traditional liquid organic electrolyte faces serious challenges in the high-voltage environment: when the voltage exceeds 4.3V, the solvent molecules (such as ethylene carbonate EC) will undergo irreversible oxidative decomposition, producing CO2 and other gases and causing battery swelling; at the same time, the side reaction of electrolyte and high-activity positive electrode interface will accelerate the dissolution of transition metal ions, leading to a sharp increase in interface impedance and capacity decay. More seriously, the uncontrollable growth of lithium dendrites in high-voltage cycling may penetrate the separator, causing internal short circuit and thermal runaway risk. Solid-state polymer electrolyte (SPE) has inherent safety advantages due to the complete elimination of flammable liquid components, and is considered by the academic and industrial circles as an ideal solution for the next generation of high-energy-density batteries. However, the existing SPE system has fundamental defects: the traditional matrix material represented by polyethylene oxide (PEO) has a generally low electrochemical window, which cannot match the high-voltage positive electrode (such as LNMO with a working voltage of 4.7V); while inorganic solid-state electrolyte (such as LLZO) has a wide electrochemical window, but it is difficult to be applied on a large scale due to poor rigid interface contact, brittleness, high manufacturing cost and other problems. Therefore, the development of a new type of SPE with a wide electrochemical window (≥4.5V vs. Li + / Li), high interface compatibility and excellent ion transport performance has become a key path to break through the technical bottleneck of high-voltage solid-state batteries.

[0003] Among the many polymer matrices, polyvinylidene fluoride (PVDF) and its copolymers show unique potential for high-voltage adaptation. The C-F bond in its molecular chain has a high bond energy of 485kJ / mol, which gives the material excellent thermal stability and electrochemical stability; at the same time, the high dielectric constant (8.4) of PVDF can effectively promote the dissociation of lithium salt and increase the carrier concentration, and the dipole moment formed by the all-trans conformation in the beta crystal phase is more conducive to lithium ion migration. Experiments show that the room temperature ionic conductivity of PVDF-HFP-based electrolyte can reach 10 -4With a tensile strength on the order of S / cm and >10MPa, it can physically suppress lithium dendrite puncture. However, existing solvent systems severely limit the performance upper limit of PVDF-based electrolytes: traditional polar solvents such as N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP) can effectively dissolve PVDF, but their highest occupied molecular orbital (HOMO) energy levels are high, making them prone to oxidative decomposition at voltages >4.3V, resulting in a narrowing of the practical electrochemical window to below 4.5V. Residual solvent molecules can also react with the lithium metal anode to form organolithium salts, consuming active lithium and forming a high-resistivity interface layer. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a high-voltage polymer electrolyte, its preparation method and its application in all-solid-state batteries.

[0005] This invention innovatively utilizes a phosphate ester solvent system (TEP / TMP / DMMP) with intrinsic flame retardancy and high chemical stability, combined with a highly oxidatively stable lithium salt such as lithium bis(fluorosulfonyl)imide (LiTFSI / LiFSI), to achieve an electrochemical window of 4.8 V and a 4.6 × 10⁻⁶ ohmmeter in a PVDF-TrFE-CTFE polymer matrix. -4 With an S / cm-level ionic conductivity, it provides an electrolyte solution for high-voltage solid-state batteries that combines performance, safety, and process feasibility.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a high-voltage polymer electrolyte comprising a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, a phosphate ester solvent, and a lithium salt; wherein the phosphate ester solvent and the lithium salt form an anion-rich solvation structure.

[0008] In a preferred embodiment of the present invention, the high-voltage polymer electrolyte is obtained by using the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer as a matrix, and introducing the phosphate ester solvent and the lithium salt onto the matrix;

[0009] The phosphate ester solvent forms an anion-rich solvation structure with the lithium salt and is transferred along the chain segments of the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, wherein the lithium salt includes lithium bis(fluorosulfonyl)imide.

[0010] In a preferred embodiment of the present invention, the phosphate ester solvent includes at least one of TEP, TMP and DMMP.

[0011] In a preferred embodiment of the present invention, the lithium salt includes at least one of LiTFSI, LiFSI, and LiDFOB.

[0012] In a preferred embodiment of the present invention, the mass ratio of the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, lithium salt, and phosphate ester solvent is 1:0.1-2:5-14.

[0013] Secondly, the present invention provides a method for preparing the high-voltage polymer electrolyte, comprising the following steps:

[0014] S1. Polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, phosphate ester solvent and lithium salt are mixed to obtain a homogeneous electrolyte solution;

[0015] S2. The electrolyte solution is coated onto the carrier to obtain a uniform electrolyte solution film;

[0016] S3. The electrolyte solution film is vacuum dried to obtain a high-pressure polymer electrolyte.

[0017] In a preferred embodiment of the present invention, in step S1, polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, phosphate ester solvent and lithium salt are mixed at a temperature range of 60℃-90℃ for 5h to 7h to obtain a uniform electrolyte solution.

[0018] In a preferred embodiment of the present invention, in step S2, the thickness of the electrolyte solution coated on the carrier is 10 μm to 1000 μm.

[0019] In a preferred embodiment of the present invention, in step S3, the vacuum drying pressure is 0.001 MPa to 0.01 MPa, the temperature is 80°C to 120°C, and the drying time is 10h to 48h.

[0020] Thirdly, the present invention provides an all-solid-state battery, comprising a solid electrolyte, wherein the solid electrolyte is the high-voltage polymer electrolyte described above or the high-voltage polymer electrolyte obtained by the above preparation method.

[0021] This invention has at least one of the following beneficial effects:

[0022] This invention, through "ternary synergistic innovation (polymer structure design - solvent system expansion - lithium salt optimization)," has successfully developed a PVDF-based solid electrolyte that combines high voltage compatibility, intrinsic safety, and industrialization feasibility. Its core advantages are reflected in:

[0023] 1) The phosphate ester solvent (TEP / TMP / DMMP) of the present invention works synergistically with highly oxidatively stable lithium salts such as lithium bis(fluorosulfonyl)imide (LiFSI / LiTFSI / LiDFOB) to form anion-rich solvated structures of Li-3FSI-TEP and Li-2FSI-TEP. Furthermore, the solvated structures formed by the lithium salt and phosphate ester solvent are transferred along the polymer chain segments, increasing the ionic conductivity to 4.6 × 10⁻⁶. -4 S / cm.

[0024] 2) The anion-rich solvation structure formed by this invention not only forms a Li2O passivation film to stabilize the lithium metal anode, but the TEP in the solvation structure can also form a Li3PO4 CEI layer on the cathode surface, effectively preventing cathode structure degradation and increasing the electrochemical window to 4.8V-5.1V (vs. Li + / Li), breaking through the traditional PVDF electrolyte's 4.3V upper limit, can be matched with NMC811 (4.5V) and LiFe. 0.4 Mn 0.6 High energy density cathodes such as PO4 (4.7V).

[0025] 3) The phosphate ester solvent of the present invention can not only impart inherent flame retardant properties to the system, but also completely eliminate the risk of combustion of organic electrolytes.

[0026] 4) The solution casting method (scraping + vacuum drying) used in this invention is compatible with existing lithium battery production lines, requiring no additional equipment, and the film thickness can be controlled to ≤50μm, significantly reducing manufacturing costs. Attached Figure Description

[0027] Figure 1 This is a SEM image of the TEP-based polymer electrolyte prepared by the blade coating method in Example 1 of the present invention.

[0028] Figure 2 This is the TG curve of the TEP-based polymer electrolyte obtained in Example 1 of the present invention.

[0029] Figure 3 This is the impedance spectrum of the TEP-based polymer obtained in Example 1 of the present invention at room temperature.

[0030] Figure 4 This is the LSV curve of the TEP-based polymer electrolyte obtained in Example 1 of the present invention.

[0031] Figure 5 This is the charge-discharge curve of the Li||NCM811 battery with TEP-based polymer film as solid electrolyte obtained in Example 1 of the present invention at an ultra-high voltage of 4.7V.

[0032] Figure 6This is a long-cycle test of the Li||NCM811 battery with TEP-based polymer film as solid electrolyte obtained in Example 1 of the present invention at a voltage of 4.5V.

[0033] Figure 7 This is a long-cycle test of the Li||LFMP battery with TEP-based polymer film as solid electrolyte obtained in Example 1 of the present invention at a voltage of 4.7V.

[0034] Figure 8 This is the TG curve of the TEP-based polymer electrolyte obtained in Example 2 of the present invention.

[0035] Figure 9 This is the impedance spectrum of the TEP-based polymer obtained in Example 2 of the present invention at room temperature.

[0036] Figure 10 This is the LSV curve of the TEP-based polymer electrolyte obtained in Example 2 of the present invention.

[0037] Figure 11 This is the LSV curve of the TEP-based polymer electrolyte obtained in Example 3 of the present invention.

[0038] Figure 12 This is the impedance spectrum of the TEP-based polymer obtained in Example 3 of the present invention at room temperature.

[0039] Figure 13 This is the LSV curve of the TMP-based polymer electrolyte obtained in Example 4 of the present invention.

[0040] Figure 14 This is the LSV curve of the DMF-based polymer electrolyte obtained in Comparative Example 1 of this invention.

[0041] Figure 15 This is the charge-discharge curve of the Li||NCM811 battery with DMF-based polymer as solid electrolyte obtained in Comparative Example 1 of the present invention at a high voltage of 4.5V. Detailed Implementation

[0042] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0043] An embodiment of the present invention provides a high-voltage polymer electrolyte comprising a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, a phosphate ester solvent, and a lithium salt; wherein the phosphate ester solvent and the lithium salt form an anion-rich solvation structure.

[0044] This invention relates to a high-voltage compatible solid polymer electrolyte (SPE) using polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (PVDF-TrFE-CTFE) copolymer as the matrix, phosphate esters as solvents, and highly oxidation-stable lithium salts such as lithium difluorosulfonylimide as the conductive lithium salt. It is suitable for solid-state lithium batteries with high-voltage cathode systems (such as NMC811 and LNMO) of ≥4.5V. This invention differs from traditional DMF or NMP solvents used to dissolve PVDF polymer materials; instead, it employs highly stable, non-flammable phosphate ester-based solvents (such as triethyl phosphate (TEP), trimethyl phosphate (TMP), dimethyl methyl phosphate (DMMP), etc.) to dissolve the polymer and lithium salt to prepare a series of high-voltage polymer solid electrolytes.

[0045] In some embodiments, the high-voltage polymer electrolyte is obtained by introducing the phosphate ester solvent and the lithium salt into the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer as the matrix;

[0046] The phosphate ester solvent forms an anion-rich solvation structure with the lithium salt and is transferred along the chain segments of the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, wherein the lithium salt includes lithium bis(fluorosulfonyl)imide.

[0047] With the above structure, the ionic conductivity of the present invention can be increased to 4.6 × 10⁻⁶. -4 The S / cm ratio is high, and this anion-rich solvation structure not only forms a Li2O passivation film to stabilize the lithium metal anode, but the TEP in the solvation structure can also form a Li3PO4 CEI layer on the cathode surface, effectively preventing cathode structure degradation and increasing the electrochemical window to 4.8V-5.1V (vs. Li + / Li), breaking through the traditional PVDF electrolyte's 4.3V upper limit, can be matched with NMC811 (4.5V) and LiFe. 0.4 Mn 0.6 High energy density cathodes such as PO4 (4.7V).

[0048] In some embodiments, the phosphate ester solvent includes at least one of TEP, TMP, and DMMP. TEP is preferred.

[0049] In some embodiments, the lithium salt includes at least one of LiTFSI, LiFSI, and LiDFOB. LiFSI is preferred.

[0050] In some embodiments, the mass ratio of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) copolymer, the lithium salt, and the phosphate ester solvent is a:b:c, where a = 1; 0 < b ≤ 2; 5 < c ≤ 14. Preferably, the mass ratio of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) copolymer, the lithium salt, and the phosphate ester solvent is 1:0.5 - 1.5:6 - 10. More preferably, the mass ratio of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) copolymer, the lithium salt, and the phosphate ester solvent is 1:0.6 - 0.8:6 - 8.

[0051] Another embodiment of the present invention provides a method for preparing the high-voltage polymer electrolyte, comprising the following steps:

[0052] S1. Mix the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) copolymer, the phosphate ester solvent, and the lithium salt to obtain a homogeneous electrolyte solution;

[0053] S2. Coat the electrolyte solution on a carrier to obtain a uniform electrolyte solution film;

[0054] S3. Vacuum-dry the electrolyte solution film to obtain a high-voltage polymer electrolyte.

[0055] The present invention provides such high-voltage polymer electrolytes, their preparation methods, and applications. Their electrochemical stability window can reach 4.8V, the components have great adjustability, and when applied to all-solid-state lithium metal batteries, they can exhibit good electrochemical performance. The preparation process is relatively simple, which is conducive to expanding production.

[0056] In some embodiments, in step S1, the raw materials are mixed at a temperature range of 60°C - 90°C for 5h - 7h to form a homogeneous electrolyte solution.

[0057] In some embodiments, in step S2, the obtained electrolyte solution is evenly scraped onto a glass plate with a spatula, and the scraping thickness is controlled by the size of the spatula to form a uniform electrolyte solution film.

[0058] In some embodiments, in step S2, the thickness range of the electrolyte solution coated on the carrier (glass plate) is 10um - 1000um. Preferably, the thickness range is 10um - 八百um. More preferably, the thickness range is 10um - 300um. Specifically, it can be 10um, 30um, 50um, 80um, 100um, 200um, 300um, 500um, 600um, 800um, and 1000um, etc.

[0059] It should be noted that there is an error in the original Chinese text where "八百um" is used. It should be "800um" in the English translation.In some embodiments, in step S3, the vacuum drying pressure is 0.001 MPa to 0.01 MPa, the temperature is 80°C to 120°C, and the drying time is 10 h to 48 h. Preferably, the pressure is 0.001 MPa to 0.005 MPa, the temperature is 80°C to 110°C, and the drying time is 24 h to 48 h. More preferably, the pressure is 0.001 MPa to 0.003 MPa, the temperature is 90°C to 100°C, and the drying time is 36 h to 48 h. Specifically, the pressure can be 0.001 MPa, 0.002 MPa, and 0.003 MPa, etc.; the temperature can be 80°C, 90°C, 100°C, 110°C, and 120°C; and the drying time can be 10 h, 15 h, 20 h, 24 h, 30 h, 36 h, and 48 h, etc.

[0060] Another embodiment of the present invention provides an all-solid-state battery, including a solid electrolyte, wherein the solid electrolyte is the high-voltage polymer electrolyte described above or the high-voltage polymer electrolyte obtained by the above preparation method.

[0061] The polymer solid electrolyte of this invention can be used as an electrolyte material for lithium-ion batteries and can maintain stable contact with the cathode material. When applied to all-solid-state lithium metal batteries, the polymer solid electrolyte exhibits excellent electrochemical performance.

[0062] In some embodiments, the all-solid-state battery further includes a positive electrode active material, which includes, but is not limited to, LiCoO2, LiFePO4, NCM ternary materials, and LiFe 0.4 Mn 0.6 At least one of PO4, lithium-rich phase lithium manganese oxide and lithified layered oxide, and lithified layered sulfide.

[0063] In some embodiments, the all-solid-state battery further includes a conductive agent, which includes at least one of graphite, carbon black, acetylene black, Ketjen black, and carbon fiber.

[0064] In some embodiments, the negative electrode is Li metal.

[0065] In some embodiments, the assembly method of the all-solid-state battery includes: using lithium metal as the negative electrode, the polymer film developed in this invention as the solid electrolyte, and lithium iron phosphate (LiFePO4) and LiFe... 0.4 Mn 0.6 PO4, LiCoO2 and NCM811 materials are used as cathodes to assemble an all-solid-state battery.

[0066] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0067] Raw material sources: TEP (Maclean, 98%), LiFSI (Koluode, 99.5%), LiTFSI (Maclean, 99%).

[0068] Example 1

[0069] This embodiment prepares a high-voltage polymer solid electrolyte with high ionic conductivity and high electrochemical stability, and applies it to an all-solid-state lithium metal battery. The specific preparation steps are as follows:

[0070] (1) Preparation of raw materials: Weigh the raw material powders as follows: 1g PVDF-TrFE-CTFE, 0.67g LiFSI and 7g TEP.

[0071] (2) High-temperature stirring: Place the above three raw materials in a glass bottle and stir them on a magnetic stirrer to dissolve them. The heating temperature is 80℃ and the stirring time is 6h to form a transparent and uniform electrolyte slurry.

[0072] (3) Doctor blade coating: Using a 250μm doctor blade, the obtained electrolyte slurry is uniformly coated onto the glass plate.

[0073] (4) Vacuum drying: The coated electrolyte slurry is placed in a vacuum drying oven with a vacuum pressure of 0.001 MPa and the temperature is raised to 95°C and held for 48 hours to obtain a polymer solid electrolyte.

[0074] (5) All-solid-state battery assembly: All steps were performed in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). The dried polymer solid electrolyte membrane was cut into 18 mm diameter discs for later use. Then, the positive electrode was made of NCM811 and LiFe. 0.4 Mn 0.6 The electrodes (12mm in diameter) are coated with PO4 and cut to size. The negative electrode uses 0.5mm thick lithium metal with a diameter of 14mm. The electrodes are stacked and packaged in the following order: positive electrode shell / positive electrode / electrolyte / negative electrode / pad / spring sheet / negative electrode shell. No electrolyte components are used during this process.

[0075] (5) Performance testing: Using the Neware battery testing system at 30°C, the battery was tested at 2.7V-4.5V (vs. Li / Li). + The electrochemical performance was evaluated within the voltage range and at various current densities.

[0076] Test results are as follows Figures 1-7 As shown.

[0077] Figure 1 This is a SEM image of the TEP-based polymer solid electrolyte prepared by the blade coating method in Example 1 of the present invention. As can be seen from the image, the prepared polymer electrolyte membrane is flat and dense.

[0078] Figure 2 This is the TG curve of the TEP-based polymer electrolyte obtained in Example 1 of the present invention. As can be seen from the figure, the prepared polymer electrolyte membrane has almost no weight loss within 150°C and the TEP solvent content is low.

[0079] Figure 3 The impedance spectrum of the TEP-based polymer obtained in Example 1 of this invention at room temperature shows that the ionic conductivity of the polymer electrolyte is 4.6 × 10⁻⁶. -4 S / cm.

[0080] Figure 4 The figure shows the LSV curve of the TEP-based polymer electrolyte obtained in Example 1 of this invention. As can be seen from the figure, the electrochemical window of the TEP-based polymer electrolyte is 4.8V.

[0081] Figure 5 This is the charge-discharge curve of the Li||NCM811 battery with TEP-based polymer film as solid electrolyte obtained in Example 1 of the present invention at an ultra-high voltage of 4.7V. As can be seen from the figure, the solid battery based on TEP-based polymer can be charged and discharged normally at a high voltage of 4.7V, and the first discharge capacity at 0.2C is 250mAh / g.

[0082] Figure 6 The figure shows the long-cycle test of the Li||NCM811 battery with TEP-based polymer film as solid electrolyte obtained in Example 1 of this invention at 4.5V. As can be seen from the figure, the TEP-based polymer all-solid-state battery has excellent cycle stability, with a capacity retention of 87% after 500 cycles.

[0083] Figure 7 The figure shows the long-cycle test of the Li||LFMP battery with TEP-based polymer film as solid electrolyte obtained in Example 1 of this invention at a voltage of 4.7V. As can be seen from the figure, the all-solid-state battery with TEP-based polymer also has excellent cycle stability at an ultra-high voltage of 4.7V.

[0084] Example 2

[0085] The difference from Example 1 is that the vacuum drying temperature was adjusted to 80°C, while everything else remained the same as in Example 1. This example prepared a high-voltage polymer solid electrolyte with high ionic conductivity and high electrochemical stability, and applied it to an all-solid-state lithium metal battery. The specific preparation steps are as follows:

[0086] (1) Preparation of raw materials: Weigh the raw material powders as follows: 1g PVDF-TrFE-CTFE, 0.67g LiFSI and 7g TEP.

[0087] (2) High-temperature stirring: Place the above three raw materials in a glass bottle and stir them on a magnetic stirrer to dissolve them. The heating temperature is 80℃ and the stirring time is 6h to form a transparent and uniform electrolyte slurry.

[0088] (3) Doctor blade coating: Using a 250μm doctor blade, the obtained electrolyte slurry is uniformly coated onto the glass plate.

[0089] (4) Vacuum drying: The coated electrolyte slurry is placed in a vacuum drying oven with a vacuum pressure of 0.001 MPa and the temperature is raised to 80°C and held for 48 hours to obtain a polymer solid electrolyte.

[0090] The test results of Example 2 are as follows Figures 8-10 As shown.

[0091] Figure 8 This is the TG curve of the TEP-based polymer electrolyte obtained in Example 2 of the present invention. According to the graph, there is basically no weight loss within 150°C, and the TEP solvent content is relatively low.

[0092] Figure 9 The impedance spectrum of the TEP-based polymer obtained in Example 2 of this invention is shown at room temperature. From this spectrum, the ionic conductivity of the polymer electrolyte can be calculated to be 5.6 × 10⁻⁶. -4 S / cm.

[0093] Figure 10 The figure shows the LSV curve of the TEP-based polymer electrolyte obtained in Example 2 of this invention. As can be seen from the figure, the electrochemical window of the TEP-based polymer electrolyte is 4.5V.

[0094] Example 3

[0095] The difference from Example 1 is that the amount of LiFSI added is adjusted to 0.3g, while the rest is the same as Example 1.

[0096] The LSV test results of the electrochemical window in Example 3 are as follows: Figure 11 As shown in the figure, the electrochemical window of the polymer electrolyte can be further increased to 4.9V when the lithium salt concentration is reduced, indicating strong antioxidant capacity. However, the test results of ionic conductivity after reducing the lithium salt concentration are as follows: Figure 12 As shown, the ionic conductivity is 6.7 × 10⁻⁶. -5 S / cm.

[0097] Example 4

[0098] The difference from Example 1 is that TEP is replaced with TMP and LiFSI is replaced with LiDFOB. The specific preparation steps are as follows:

[0099] (1) Preparation of raw materials: Weigh the raw material powders as follows: 1g PVDF-TrFE-CTFE, 0.4g LiDFOB and 9g TMP.

[0100] (2) High-temperature stirring: The above three raw materials are placed in a glass bottle and stirred and dissolved on a magnetic stirrer. The heating temperature is 60℃ and the stirring time is 6h to form a transparent and uniform electrolyte slurry.

[0101] (3) Doctor blade coating: Using a 500μm doctor blade, the obtained electrolyte slurry is uniformly coated onto the glass plate.

[0102] (4) Vacuum drying: The coated electrolyte slurry is placed in a vacuum drying oven with a vacuum pressure of 0.002 MPa and the temperature is raised to 85°C and maintained for 24 hours to obtain a polymer solid electrolyte.

[0103] The LSV test results of the electrochemical window in Example 4 are as follows: Figure 13 As shown in the figure, the electrochemical window of the polymer electrolyte can be further increased to 5.0V when the lithium salt concentration is reduced, indicating strong antioxidant capacity.

[0104] Comparative Example 1

[0105] The difference from Example 1 is that TEP is replaced with DMF, the vacuum drying temperature is adjusted to 80°C and maintained for 48 hours, and everything else is the same as Example 1.

[0106] The LSV test results for the electrochemical window of Comparative Example 1 are as follows: Figure 14 As shown in the figure, the electrochemical window of the polymer electrolyte with DMF as solvent is only 4.3V, indicating weak antioxidant capacity and easy decomposition under high voltage.

[0107] Furthermore, the initial charge-discharge curves of the Li / NCM811 battery assembled with DMF as the solvent at 4.5V are as follows: Figure 15 As shown in the figure, the full cell with DMF as the solvent for the polymer electrolyte exhibits continuous overcharging at a high voltage of 4.5V, resulting in the continuous decomposition of the polymer electrolyte at high voltage. This indicates that the polymer electrolyte with DMF as the solvent does not possess high-voltage stability.

[0108] In summary, this invention has successfully developed a PVDF-based solid electrolyte that combines high voltage compatibility, intrinsic safety, and industrial feasibility through polymer structure design, solvent system expansion, and lithium salt optimization.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-voltage polymer electrolyte, characterized in that, The high-voltage polymer electrolyte comprises a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, a phosphate ester solvent, and a lithium salt; wherein the phosphate ester solvent and the lithium salt form an anion-rich solvation structure.

2. The high-voltage polymer electrolyte according to claim 1, characterized in that, The high-voltage polymer electrolyte is obtained by using the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer as the matrix, and introducing the phosphate ester solvent and the lithium salt onto the matrix; The phosphate ester solvent forms an anion-rich solvation structure with the lithium salt and is transferred along the chain segments of the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, wherein the lithium salt includes lithium bis(fluorosulfonyl)imide.

3. The high-voltage polymer electrolyte according to claim 1, characterized in that, The phosphate ester solvents include at least one of TEP, TMP, and DMMP.

4. The high-voltage polymer electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of LiTFSI, LiFSI, and LiDFOB.

5. The high-voltage polymer electrolyte according to claim 1, characterized in that, The mass ratio of the polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, lithium salt, and phosphate ester solvent is 1:0.1-2:5-14.

6. The method for preparing the high-voltage polymer electrolyte according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, phosphate ester solvent and lithium salt are mixed to obtain a homogeneous electrolyte solution; S2. The electrolyte solution is coated onto the carrier to obtain a uniform electrolyte solution film; S3. The electrolyte solution film is vacuum dried to obtain a high-pressure polymer electrolyte.

7. The preparation method according to claim 6, characterized in that, In step S1, polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer, phosphate ester solvent and lithium salt are mixed at a temperature range of 60℃-90℃ for 5h to 7h to obtain a homogeneous electrolyte solution.

8. The preparation method according to claim 6, characterized in that, In step S2, the thickness of the electrolyte solution coated on the carrier is 10 μm to 1000 μm.

9. The preparation method according to claim 6, characterized in that, In step S3, the vacuum drying pressure is 0.001 MPa to 0.01 MPa, the temperature is 80℃ to 120℃, and the time is 10h to 48h.

10. An all-solid-state battery, comprising a solid electrolyte, characterized in that, The solid electrolyte is the high-voltage polymer electrolyte according to any one of claims 1 to 5 or the high-voltage polymer electrolyte obtained by the preparation method according to any one of claims 6 to 9.

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