Solid-state electrolyte and preparation method and application thereof

Abstract

The application discloses a kind of solid electrolyte and its preparation method and application, the polymer solid electrolyte includes filler, polymer, crystallization inhibitor and lithium salt, the mass ratio of polymer and lithium salt is 1:(1-1.2);The mass ratio of filler and polymer is (1-10):100;The mass ratio of crystallization inhibitor and polymer is (2-8):100.Polymer solid electrolyte in the application has higher ionic conductivity, higher ion transference number, wider electrochemical window, better cycle rate performance and better stress strain capacity, can inhibit lithium dendrite phenomenon of lithium battery using the polymer solid electrolyte, so that lithium battery has greater capacity, longer working time and higher safety.

Description

Technical Field

[0001] This invention belongs to the field of batteries, specifically relating to a solid electrolyte, its preparation method, and its application. Background Technology

[0002] Solid-state electrolytes possess advantages such as effectively suppressing lithium dendrite growth, low leakage risk, and low flammability, exhibiting characteristics of high safety, high energy density, and high stability. Currently, all-solid-state electrolytes are mainly classified into inorganic solid-state electrolytes and polymer electrolytes. Among inorganic solid-state electrolytes, oxides and sulfides exhibit high ionic conductivity (10⁻⁶). -4 ~10 -2 S·cm -1 However, inorganic solid electrolytes are brittle, difficult to process, and the interface problem between them and electrodes remains unresolved. For example, oxide-based inorganic solid electrolytes exhibit poor mechanical compliance, leading to high interfacial impedance; while sulfide-based inorganic solid electrolytes are sensitive to humid air and easily generate harmful gases. Polymer electrolytes, such as polyethylene oxide (PEO) and polyacrylonitrile (PAN), while possessing advantages like high stability and ease of processing, typically exhibit low ionic conductivity (<10) at room temperature. -4 S·cm -1 This makes it difficult to meet diverse commercial needs.

[0003] Currently, high-salt polymer solid electrolyte systems with added LiTFSI can better dissociate lithium ions at room temperature, giving the electrolyte superior electrochemical performance. By introducing different types of fillers, its performance can be further enhanced. Existing technologies use the introduction of sulfides into polymer solid electrolytes, which improves the electrolyte's flexibility and mechanical strength to some extent. However, due to the high interfacial contact resistance between the electrode and the sulfide electrolyte, its widespread applicability in commercial applications is still limited by interfacial compatibility and stability. Existing technologies also include the introduction of MOF fillers to improve conductivity and mechanical properties. However, MOF fillers are structurally unstable and prone to disintegration under high temperature and high pressure, limiting their applicability. Furthermore, existing polymer solid electrolyte systems generally suffer from the following problems: (1) Ionic conductivity does not meet commercial requirements, leading to battery overheating during charging and discharging, posing a safety hazard. (2) Insufficient cycle and rate performance results in short battery life and slow charging and discharging. (3) Lithium dendrite growth is not effectively suppressed, easily causing short circuits and explosions. (4) The electrochemical window is not wide enough, the interfacial stability between the electrolyte and the positive and negative electrodes is poor, and the applicable range is not wide enough. (5) The energy density needs to be improved, which is insufficient to meet the power supply needs of new energy vehicles, mobile devices, etc. (6) The production cost and process difficulty are too high, which is not conducive to large-scale industrial production and commercial promotion. Summary of the Invention

[0004] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide a solid electrolyte.

[0005] The second objective of this invention is to provide a method for preparing a solid electrolyte.

[0006] The third objective of this invention is to provide a lithium-ion battery.

[0007] The fourth objective of this invention is to provide an application of solid electrolyte in the field of batteries.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a solid electrolyte comprising a filler, a polymer, a crystallization inhibitor, and a lithium salt, wherein the mass ratio of the polymer to the lithium salt is 1:(1-1.2); the mass ratio of the filler to the polymer is (1-10):100; the mass ratio of the crystallization inhibitor to the polymer is (2-8):100; and the filler is selected from at least one of β-cyclodextrin, hexagonal boron nitride, lithium lanthanum titanate, and lithium lanthanum zirconium oxide.

[0010] Preferably, the crystallization inhibitor is selected from at least one of polyethylene glycol, succinic anhydride, ethylene carbonate, and polycarbonate.

[0011] Preferably, the polymer is selected from at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinylidene fluoride.

[0012] Preferably, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, and lithium tetrafluoroborate.

[0013] Preferably, the solid electrolyte is a thin film material with a thickness of 90–150 μm.

[0014] The second aspect of the present invention provides a method for preparing the solid electrolyte provided in the first aspect of the present invention, comprising the following steps:

[0015] After dissolving and mixing the raw materials, a polymer electrolyte precursor solution is obtained; then, the polymer electrolyte precursor solution is used to form a film on a substrate; the film is separated from the substrate and dried to obtain the solid electrolyte.

[0016] Preferably, the preparation method of the polymer electrolyte precursor solution is as follows: dissolving and mixing the polymer and lithium salt to obtain a high-salt electrolyte precursor solution; and mixing the high-salt electrolyte precursor solution with filler and crystallization inhibitor at 50-70°C.

[0017] Preferably, the step of forming a film of the polymer electrolyte precursor solution on the substrate is as follows: the polymer electrolyte precursor solution is coated onto the substrate, and then placed at a temperature of 20-30°C and a humidity of 70-90% for 2-4 hours to form a film. Specific temperature and humidity conditions are more conducive to electrolyte formation. At this time, the electrolyte still contains some solvent, which needs to be dried to obtain a solid electrolyte.

[0018] Preferably, the drying temperature is 55–65°C, and the drying time is 20–30 h. The solvent evaporation causes the electrolyte to solidify, and the resulting fine pores help increase the ionic conductivity of the electrolyte membrane.

[0019] A third aspect of the present invention provides a lithium-ion battery comprising the solid electrolyte provided in the first aspect of the present invention.

[0020] Preferably, the ion transference number of the lithium-ion battery is 0.45 to 0.65.

[0021] Preferably, the lithium-ion battery has an ionic conductivity of 1.19 × 10⁻⁶. -4 ~2.23×10 -4 S / cm.

[0022] Preferably, the electrochemical window of the lithium-ion battery is 4.8–5.1 V.

[0023] The fourth aspect of the present invention provides the application of the solid electrolyte provided in the first aspect of the present invention in the field of batteries.

[0024] The beneficial effects of this invention are: the solid electrolyte in this invention has high ionic conductivity, high ion transport number, wide electrochemical window, good cycle rate performance, and good stress-strain capability. It can effectively suppress lithium dendrite formation in lithium batteries using this solid electrolyte, enabling lithium batteries to have greater capacity, longer operating time, and higher safety. A detailed analysis follows:

[0025] (1) This invention significantly improves electrochemical performance by introducing fillers and crystallinity inhibitors, resulting in a high-performance high-salt solid electrolyte. When assembled into a lithium battery, this significantly enhances the battery's cycle performance, rate performance, and other properties. Specifically, the introduction of crystallinity inhibitors rapidly reduces the crystallinity of the electrolyte system, improving polymer chain mobility and lithium salt dissociation, thus significantly increasing the electrochemical performance of the polymer electrolyte membrane. The hydroxyl groups (-OH) on the filler surface attract lithium ions via electrostatic attraction, promoting lithium salt dissociation and increasing the lithium ion content in the electrolyte. Furthermore, they form hydrogen bonds with fluorine atoms (F) in the lithium salt to bind TFSI. -The presence of anions ensures the rapid transport of lithium ions within the system, resulting in superior electrochemical performance of the electrolyte.

[0026] (2) Effectively inhibits the growth of lithium dendrites. Because the added filler has high mechanical strength, and the crystallinity inhibitor can also reduce the crystallinity of the polymer, the strength of the electrolyte is improved when both are added at the same time, thereby inhibiting the growth of lithium dendrites and preventing lithium dendrites from piercing the electrolyte membrane and causing battery short circuits, which can effectively reduce safety hazards.

[0027] (3) High ionic conductivity. The solid electrolyte in this invention is a high-salt system, which forms a small number of ion clusters and transient polymer segments composed of ion clusters and the polymer matrix, constituting a unique lithium-ion transport channel to accelerate lithium-ion transport. Simultaneously, the ionic conductivity of the electrolyte is significantly improved by adding fillers and crystallinity inhibitors to the solid polymer electrolyte, reaching 2.23 × 10⁻⁶. -4 S / cm. The addition of crystallization inhibitors can effectively reduce the crystallinity of PVDF-HFP, promote the movement of polymer chain segments and the dissociation of lithium salt, thereby ensuring the high ionic conductivity of this composite solid electrolyte.

[0028] (4) Wide electrochemical window. The solid electrolyte in this invention has an electrochemical window of 4.8 to 5.1 V, which makes it less prone to oxidation and decomposition under high voltage, thus extending its service life. At the same time, the wide electrochemical window can also be adapted to a variety of commercial cathodes.

[0029] (5) High lithium-ion transference number. The lithium-ion transference number of the solid electrolyte in this invention reaches 0.45 to 0.65. Lithium ions are the only cations involved in the transfer of lithium batteries. A high cation transference number means a low anion transference number. A high ion transference number is beneficial to reducing concentration polarization during charging and discharging, and is also beneficial to fast charging.

[0030] (6) Good stress-strain performance. The molecular interactions within the solid electrolyte system of this invention enhance the stress-strain capacity of the electrolyte, resulting in good bending and stretching recovery performance. This is beneficial for the battery to operate in harsh environments and continue to function even after partial deformation. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the preparation process of the polymer solid electrolyte in this invention.

[0032] Figure 2 This is a scanning electron microscope image of the PVHLi electrolyte membrane in Comparative Example 1.

[0033] Figure 3 This is a scanning electron microscope image of the PVSC2 electrolyte membrane in Example 2.

[0034] Figure 4 The figure shows the AC impedance test results of the PVHLi electrolyte membrane in Comparative Example 1.

[0035] Figure 5 The diagram shows the AC impedance test results of the electrolyte membrane in Comparative Example 2.

[0036] Figure 6 The diagram shows the AC impedance test results of the PVSC1 electrolyte membrane in Example 1.

[0037] Figure 7 The diagram shows the AC impedance test results of the PVSC2 electrolyte membrane in Example 2.

[0038] Figure 8 The image shows the AC impedance test results of the PVSC3 electrolyte membrane in Example 3.

[0039] Figure 9 The graph shows the linear voltammetry results of the PVHLi electrolyte membrane in Comparative Example 1.

[0040] Figure 10 The graph shows the linear voltammetry test results of the electrolyte membrane in Comparative Example 2.

[0041] Figure 11 The image shows a linear voltammetry test result of the PVSC1 electrolyte membrane in Example 1.

[0042] Figure 12 The image shows a linear voltammetry test result of the PVSC2 electrolyte membrane in Example 2.

[0043] Figure 13 The image shows a linear voltammetry test result of the PVSC3 electrolyte membrane in Example 3.

[0044] Figure 14 The graphs show the lithium-ion transference number of the electrolyte membranes in Examples 1-3.

[0045] Figure 15 The graph shows the charge-discharge cycle test results of the PVHLi electrolyte membrane in Comparative Example 1 at 0.2C.

[0046] Figure 16 The graph shows the electrolyte membrane in Comparative Example 2 under charge-discharge cycle test at 0.2C.

[0047] Figure 17 This is a charge-discharge cycle test diagram of the PVSC2 electrolyte membrane in Example 2 at 0.2C.

[0048] Figure 18 The graphs show the rate testing results of the PVSC2 electrolyte membrane in Example 2 at 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C.

[0049] Figure 19 The stress-strain test results for the PVHLi electrolyte membrane in Comparative Example 1 are shown.

[0050] Figure 20 The stress-strain test diagram of the electrolyte membrane in Comparative Example 2 is shown.

[0051] Figure 21 This is a stress-strain test diagram of the PVSC2 electrolyte membrane in Example 2. Detailed Implementation

[0052] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0053] The information on the instruments and materials used in the embodiments and comparative examples of this invention is as follows:

[0054] Instruments used: glove box, constant temperature water bath mixing vessel, constant temperature and humidity chamber, vacuum drying oven, slicer, press, ball mill;

[0055] Materials used: β-cyclodextrin (CD) as filler, succinate (SN) as crystallinity inhibitor, PVDF-HFP, LiTFSI, N,N-dimethylformamide (DMF), and lithium lanthanum zirconium tantalum oxide powder.

[0056] Example 1

[0057] Reference Figure 1 The preparation process flow diagram is shown in the figure. This example provides a method for preparing a polymer solid electrolyte, and the preparation steps are as follows:

[0058] 1. Weigh 0.300g of PVDF-HFP polymer, 0.330g of LiTFSI, and 1.25g of DMF into a small vial, and gently shake until LiTFSI dissolves. DMF is used as the solvent, and the mass ratio of PVDF-HFP polymer to LiTFSI is controlled at 1:1.1 to form a high-salt system.

[0059] 2. Then add 0.009g CD (3% by mass of CD, based on 100% PVDF-HFP) and 0.015g SN (5% by mass of SN, based on 100% PVDF-HFP), and stir in a 60℃ water bath overnight.

[0060] 3. After the above mixed solution is stirred, pour the solution onto a clean glass plate and use a stainless steel scraper with a height of 400μm to spread it into a film. Immediately afterwards, place the glass plate in a constant temperature and humidity chamber at 25℃ and 80% humidity for 3 hours to initially form an electrolyte film. Specific temperature and humidity are more conducive to electrolyte formation. At this stage, the electrolyte still contains some solvent and needs to be dried to obtain a solid electrolyte.

[0061] 4. Immediately after peeling the electrolyte membrane off the glass plate, place it in a vacuum drying oven at 60℃ for 24 hours to remove residual solvent, obtaining a solid electrolyte membrane with a thickness of approximately 100 μm. The evaporation of the solvent causes the electrolyte to solidify, and the fine pores left after evaporation help increase the ionic conductivity of the electrolyte membrane.

[0062] 5. After drying, immediately remove the electrolyte membrane and cut it into 16mm diameter round slices using a slicer. Then quickly place them in a plastic bag and seal them for storage to obtain the polymer solid electrolyte in this example, denoted as PVSC1. The polymer solid electrolyte membrane is extremely hygroscopic, so all steps from removing it from the vacuum drying oven to sealing and storing it must be done quickly.

[0063] Example 2

[0064] Reference Figure 1 The preparation process flow diagram is shown in the figure. This example provides a method for preparing a polymer solid electrolyte, and the preparation steps are as follows:

[0065] 1. Weigh 0.300g of PVDF-HFP polymer, 0.330g of LiTFSI salt, and 1.25g of DMF into a small bottle, and shake gently until LiTFSI dissolves. DMF is used as the solvent, and the mass ratio of PVDF-HFP polymer to LiTFSI is controlled at 1:1.1 to form a high-salt system.

[0066] 2. Then add 0.015g CD (based on a total mass percentage of PVDF-HFP of 100%, CD accounts for 5% of the mass) and 0.015g SN (based on a total mass percentage of PVDF-HFP of 100%, SN accounts for 5% of the mass) to the bottle, and then place it in a 60℃ water bath and stir overnight.

[0067] 3. After the above mixed solution is stirred, pour the solution onto a clean glass plate and use a stainless steel scraper with a height of 400μm to spread it into a film. Immediately afterwards, place the glass plate in a constant temperature and humidity chamber at 25℃ and 80% humidity for 3 hours to initially form an electrolyte film. Specific temperature and humidity are more conducive to electrolyte formation. At this stage, the electrolyte still contains some solvent and needs to be dried to obtain a solid electrolyte.

[0068] 4. Immediately after peeling the electrolyte membrane off the glass plate, place it in a vacuum drying oven at 60℃ for 24 hours to remove residual solvent, obtaining a solid electrolyte membrane with a thickness of approximately 100 μm. The evaporation of the solvent causes the electrolyte to solidify, and the fine pores left after evaporation help increase the ionic conductivity of the electrolyte membrane.

[0069] 5. After drying, immediately remove the electrolyte membrane and cut it into 16mm diameter round slices using a slicer. Then quickly place them in a plastic bag and seal them for storage to obtain the polymer solid electrolyte in this example, denoted as PVSC2. Solid electrolyte membranes are extremely hygroscopic, so all steps from removing them from the vacuum drying oven to sealing and storing them must be done quickly.

[0070] Example 3

[0071] Reference Figure 1 The preparation process flow diagram is shown in the figure. This example provides a method for preparing a polymer solid electrolyte, and the preparation steps are as follows:

[0072] 1. Weigh 0.300g of PVDF-HFP polymer, 0.330g of LiTFSI salt, and 1.25g of DMF into a small bottle, and shake gently until LiTFSI dissolves. DMF is used as the solvent, and the mass ratio of PVDF-HFP polymer to LiTFSI is controlled at 1:1.1 to form a high-salt system.

[0073] 2. Then add 0.021g CD (7% by mass of CD, 100% by mass of PVDF-HFP) and 0.015g SN (5% by mass of SN, 100% by mass of PVDF-HFP) to the bottle, and stir overnight in a 60°C water bath.

[0074] 3. After the above mixed solution is stirred, pour the solution onto a clean glass plate and use a stainless steel scraper with a height of 400μm to spread it into a film. Immediately afterwards, place the glass plate in a constant temperature and humidity chamber at 25℃ and 80% humidity for 3 hours to initially form an electrolyte film. Specific temperature and humidity are more conducive to electrolyte formation. At this stage, the electrolyte still contains some solvent and needs to be dried to obtain a solid electrolyte.

[0075] 4. Immediately after peeling the electrolyte membrane off the glass plate, place it in a vacuum drying oven at 60℃ for 24 hours to remove residual solvent, obtaining a solid electrolyte membrane with a thickness of approximately 100 μm. The evaporation of the solvent causes the electrolyte to solidify, and the fine pores left after evaporation help increase the ionic conductivity of the electrolyte membrane.

[0076] 5. After drying, immediately remove the electrolyte membrane and cut it into 16mm diameter round slices using a slicer. Then quickly place them in a plastic bag and seal them for storage to obtain the polymer solid electrolyte in this example, denoted as PVSC3. Solid electrolyte membranes are extremely hygroscopic, so all steps from removing them from the vacuum drying oven to sealing and storing them must be done quickly.

[0077] Comparative Example 1

[0078] This example provides a method for preparing a polymer solid electrolyte, the preparation steps of which are as follows:

[0079] 1. Weigh 0.300g of PVDF-HFP polymer, 0.330g of LiTFSI salt, and 1.25g of DMF into a small bottle, and shake gently until LiTFSI dissolves. DMF is used as the solvent, and the mass ratio of PVDF-HFP polymer to LiTFSI is controlled at 1:1.1 to form a high-salt system.

[0080] 2. Place the prepared solution in a 60℃ water bath and stir overnight to initially form a high-salt polymer system.

[0081] 3. After the above mixed solution is stirred, pour the solution onto a clean glass plate and use a stainless steel scraper with a height of 400μm to spread it into a film. Immediately afterwards, place the glass plate in a constant temperature and humidity chamber at 25℃ and 80% humidity for 3 hours to initially form an electrolyte film. Specific temperature and humidity are more conducive to electrolyte formation. At this stage, the electrolyte still contains some solvent and needs to be dried to obtain a solid electrolyte.

[0082] 4. Immediately after peeling the electrolyte membrane off the glass plate, place it in a vacuum drying oven at 60℃ for 24 hours to remove residual solvent, obtaining a solid electrolyte membrane with a thickness of approximately 100 μm. The evaporation of the solvent causes the electrolyte to solidify, and the fine pores left after evaporation help increase the ionic conductivity of the electrolyte membrane.

[0083] 5. After drying, immediately remove the electrolyte membrane and cut it into 16mm diameter round slices using a slicer. Then quickly place them in a plastic bag and seal them for storage to obtain the polymer solid electrolyte in this example, denoted as PVHLi. Solid electrolyte membranes are extremely hygroscopic, so all steps from removing them from the vacuum drying oven to sealing and storing them must be done quickly.

[0084] Comparative Example 2

[0085] This example provides a method for preparing a solid electrolyte, the preparation steps of which are as follows:

[0086] 1. Add 70% lithium lanthanum zirconium tantalum oxide powder and 10% PVDF-HFP to a ball mill and mix thoroughly;

[0087] 2. Add 15% LiTFSI to step 1 and mix well;

[0088] 3. Add 5% β-CD to step 2 and mix well;

[0089] 4. The mixture prepared in step 3 is pressed into a film at 60°C and a pressure of 800 MPa to obtain the solid electrolyte membrane in this example.

[0090] Performance testing:

[0091] (1) Surface morphology test

[0092] The surface morphology of the PVHLi electrolyte membrane in Comparative Example 1 and the PVSC2 electrolyte membrane in Example 2 was tested using scanning electron microscopy. The specific test results are as follows: Figure 2 , Figure 3 As shown. By Figure 2 , Figure 3 It can be seen that the surface of the PVSC2 electrolyte membrane is smoother than that of PVHLi.

[0093] (2) AC impedance, linear volt-ampere test, charge-discharge cycle test and rate test

[0094] Electrolyte membranes from PVSC1, PVSC2, PVSC3, PVHLi, and Comparative Example 2 were assembled into batteries according to their respective testing requirements for performance testing. The cathode material was an NCM811 electrode, and the anode material was a lithium metal sheet. Lithium metal batteries were assembled using the following methods: cathode shell, spring, gasket, solid electrolyte membrane, gasket, and anode shell for ion exchange impedance spectroscopy (IEIS); lithium metal batteries were assembled using the same method for measuring the electrochemical window; and lithium metal batteries were assembled using the same method for measuring cycle life and rate capability. All batteries were pressurized to 50 N using a pressure machine. IISIS and IISIS tests were performed using a CHI660E electrochemical workstation. The voltage range for IISIS was 2V-5.5V, and the scan rate was 0.1 mV / s. The frequency for IISIS was 106 Hz, and the amplitude was 5 mV. The battery's cycle performance and rate performance were tested using a Blue Battery testing system. Cycle performance was tested at a voltage of 2.5V-3.5V and a current of 0.2C; rate performance was tested at a voltage range of 2.5V-3.5V and currents of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C. All tests were conducted at 25℃. Ionic conductivity was calculated from the measured impedance value using the following formula:

[0095]

[0096] Where R is the AC impedance of the electrolyte membrane obtained from the impedance diagram, L is the thickness of the electrolyte membrane, and S is the effective contact area between the electrolyte and the electrode. Considering that the membrane will thin under pressure during battery assembly, the actual L of the membrane needs to be measured after the test battery is disassembled.

[0097] The ion transport number is calculated from the measured impedance value using the following formula:

[0098]

[0099] In the formula, I0, I S These are the current values ​​in the initial and steady states, respectively, R0 and R... s The impedances are the initial and steady-state impedances, respectively, obtained by EIS fitting, and ΔU is the voltage applied to the battery during the test.

[0100] All the above experimental steps were performed in a glove box under an argon atmosphere to avoid the influence of water and oxygen on the experimental results. Following the above testing methods, the performance of the PVHLi, Comparative Example 2, PVSC1, PVSC2, and PVSC3 electrolyte membranes was tested using electrochemical impedance spectroscopy (ELS) and linear voltammetry (LSV). Specific test results are as follows: Figures 4 to 18 As shown in Table 1, the test data for ion transport number, ion conductivity, and electrochemical window are as follows.

[0101] Table 1. Electrochemical performance test results of electrolyte membranes in Examples 1-3 and Comparative Examples 1-2

[0102]

[0103]

[0104] As shown in Table 1, compared with Comparative Examples 1-2, the electrolyte membranes in Examples 1-3 of the present invention have all shown a certain degree of improvement in ion transport number, electronic conductivity, and electrochemical window. Among them, the PVSC2 electrolyte has an ion transport number of 0.59 and an ion conductivity of 2.23 × 10⁻⁶. -4 The electrochemical performance was significantly better than that of comparative examples 1-2, with an S / cm and an electrochemical window of 5.03V.

[0105] Depend on Figures 17-18 It can be seen that the PVSC2 electrolyte membrane, due to the addition of the crystallinity inhibitor SN and the filler CD, exhibits synergistic effects between SN, CD, and the high-salt polymer system, resulting in better long-term performance, less heat generation, and higher coulombic efficiency compared to batteries using comparative examples 1-2 electrolyte membranes. Simultaneously, due to... Figures 4-14 It can be seen that, compared with PVSC1 and PVSC3, PVSC2 has significantly improved ion transport number, ionic conductivity and electrochemical window.

[0106] (3) Mechanical property testing

[0107] Stress-strain tests were conducted on the electrolyte membranes of PVHLi, Comparative Example 2, and PVSC2 using an electronic tensile testing machine. The specific test results are as follows: Figure 19 , Figure 20 , Figure 21 As shown, the tensile and stretch test data are recorded in Table 2.

[0108] Table 2 shows the stress-strain test results of the electrolyte membrane in Example 2 and Comparative Example 1.

[0109]

[0110] As shown in Table 2, compared with Comparative Examples 1 and 2, the PVSC2 electrolyte membrane in Example 2 has excellent mechanical properties and can effectively suppress lithium dendrite growth.

[0111] In summary, compared with Comparative Examples 1 and 2, the polymer solid electrolyte of the present invention has the following properties, specifically:

[0112] (1) Excellent electrochemical performance. First, due to the addition of the crystallinity inhibitor SN, the crystallinity of the electrolyte system decreases rapidly, improving the mobility of polymer chain segments and the dissociation degree of lithium salt, thus significantly increasing the electrochemical performance of the polymer electrolyte membrane. Second, due to the addition of CD, the hydroxyl groups (-OH) on the CD surface attract Li through electrostatic attraction. + Promotes the dissociation of lithium salts and increases the Li content in the electrolyte. + On the one hand, it contains fluorine; on the other hand, it forms hydrogen bonds with fluorine atoms (F) in lithium salts to bind TFSI. - Anions, thus ensuring Li + Rapid transport within the system enhances the electrochemical performance of the electrolyte.

[0113] (2) Effectively inhibits the growth of lithium dendrites. Because the added organic filler CD has high mechanical strength, and the crystallinity inhibitor SN can also reduce the crystallinity of the polymer, the addition of the filler improves the strength of the electrolyte, thereby inhibiting the growth of lithium dendrites and preventing lithium dendrites from piercing the electrolyte membrane and causing battery short circuits, thus effectively reducing safety hazards.

[0114] (3) High ionic conductivity. Generally, when the lithium salt content in a solid polymer electrolyte exceeds 50%, a high-salt polymer system is formed. In this case, a small number of ion clusters and transient polymer segments composed of ion clusters and the polymer matrix are formed, constituting unique lithium-ion transport channels to accelerate lithium-ion transport. Simultaneously, the addition of CD and the crystallinity inhibitor SN to the solid polymer electrolyte significantly improves the electrolyte's ionic conductivity, reaching 2.23 × 10⁻⁶. - 4 The addition of S / cm can effectively reduce the crystallinity of PVDF-HFP, promote the movement of polymer chain segments and the dissociation of lithium salt, thereby ensuring the high ionic conductivity of this composite solid electrolyte.

[0115] (4) Wide electrochemical window. The electrochemical window of PVSC2 electrolyte reaches 5.03V, so the electrolyte is not easily oxidized and decomposed under high voltage, which makes its service life longer. At the same time, the wide electrochemical window can also be adapted to a variety of commercial cathodes.

[0116] (5) High lithium-ion transference number. The lithium-ion transference number of PVSC2 electrolyte reaches 0.59. Lithium ions are the only cations involved in the transfer of lithium batteries. A high cation transference number means a low anion transference number. A high ion transference number is beneficial to reducing concentration polarization during charging and discharging, and is also beneficial to fast charging.

[0117] (6) Good stress-strain performance. The molecular interactions within the electrolyte system enhance the electrolyte's stress-strain capacity. The polymer solid electrolyte membrane in this invention exhibits excellent bending and stretching recovery properties, which is beneficial for the battery to operate in harsh environments and continue to function even after partial deformation.

[0118] (7) The production process is simple and easy to produce. The production process is relatively simple, the equipment is easy to operate, and the parameters of the production process are also very clear, making it easy to promote and realize industrialization, large-scale production, and commercialization.

[0119] (8) Good economic benefits. The raw materials used in this invention, such as polymers, lithium salts, and fillers, are readily available, inexpensive, and highly competitive in the market. Furthermore, there is no waste or excess product in the entire process, resulting in a high utilization rate of raw materials.

[0120] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A solid electrolyte, characterized in that: It is composed of filler, polymer, crystallization inhibitor and lithium salt, wherein the mass ratio of polymer to lithium salt is 1:1.1; the mass ratio of filler to polymer is 5:100; the mass ratio of crystallization inhibitor to polymer is 5:100; and the filler is β-cyclodextrin. The polymer is a polyvinylidene fluoride-hexafluoropropylene copolymer; The crystallization inhibitor is succinic acid; The solid electrolyte is a thin film material with a thickness of 90~150μm.

2. The solid electrolyte according to claim 1, characterized in that: The lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, and lithium tetrafluoroborate.

3. The method for preparing the solid electrolyte according to any one of claims 1 to 2, characterized in that: Includes the following steps: After dissolving and mixing the raw materials, a polymer electrolyte precursor solution is obtained; then the polymer electrolyte precursor solution is used to form a film on a substrate. The membrane was separated from the substrate and dried to obtain the solid electrolyte.

4. The method for preparing a solid electrolyte according to claim 3, characterized in that: The preparation method of the polymer electrolyte precursor solution is as follows: dissolve and mix the polymer and lithium salt to obtain a high-salt electrolyte precursor solution; mix the high-salt electrolyte precursor solution with filler and crystallization inhibitor at 50~70℃.

5. The method for preparing a solid electrolyte according to claim 3, characterized in that: The step of forming a film of the polymer electrolyte precursor solution on the substrate is as follows: the polymer electrolyte precursor solution is coated on the substrate, and then placed at a temperature of 20~30℃ and a humidity of 70~90% for 2~4 hours to form a film.

6. The method for preparing a solid electrolyte according to claim 3, characterized in that: The drying temperature is 55~65℃, and the drying time is 20~30h.

7. A lithium-ion battery, characterized in that: Includes the solid electrolyte as described in any one of claims 1 to 2.

8. The lithium-ion battery according to claim 7, characterized in that: The lithium-ion battery has at least one of the following characteristics: (a) Ion transport number is 0.45–0.65; (b) Ionic conductivity is 1.19 × 10⁻⁶ -4 ~2.23×10 -4 S / cm; (c) The electrochemical window is 4.8~5.1V.

9. The application of the solid electrolyte according to any one of claims 1 to 2 in the field of batteries.

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