Self-healing diaphragm, ionic solution, solid electrolyte, preparation method and application

Abstract

The embodiment of the invention relates to a self-healing diaphragm, an ionic solution, a solid electrolyte, a preparation method and application. The preparation method of the diaphragm comprises the following steps: adding a first polymer, a hydroxyl-containing polymer matrix and a fluorine-containing lithium salt into an organic solvent to form a first solution; mixing the nano solid electrolyte with a second polymer to obtain a third solution; the first solution and the third solution are subjected to electrostatic spinning to form a membrane, and the membrane with the self-healing capacity is obtained through drying and piece cutting; the diaphragm contains a self-healing polymer, and hydrogen bond bridging is formed through hydroxyl in a polymer matrix and fluorine ions in fluorine-containing lithium salt, so that self-repairing is realized; the ionic solution is obtained by mixing a polymer monomer, the polymer matrix, a fluorine-containing lithium salt, an auxiliary agent, a film-forming additive and a lithium salt; the diaphragm and the ionic solution are used as a battery diaphragm and an electrolyte to assemble a battery and initiate in-situ polymerization to obtain a gel solid electrolyte with self-healing capability, so that the safety and the stability of the battery can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of new energy battery technology, and in particular to a self-healing separator, ionic solution, solid electrolyte, preparation method and application. Background Technology

[0002] Polymer electrolytes are a class of solid electrolyte materials based on polymers, commonly used in energy storage devices such as lithium-ion batteries and lithium metal batteries. Their main function is to provide a transport channel for lithium ions between electrodes, while preventing electrolyte leakage and improving overall battery safety. Compared to traditional liquid electrolytes, polymer electrolytes possess certain mechanical strength and good flexibility, mitigating contact problems caused by surface irregularities when in contact with the lithium metal anode. However, due to the generally low mechanical properties and ionic conductivity of polymer electrolytes, dendrite growth from the lithium metal anode during charge-discharge cycles can gradually pierce the polymer electrolyte layer, forming micro-short circuits and affecting battery safety and cycle life.

[0003] To improve the mechanical properties of polymer electrolytes and suppress lithium dendrite growth, current techniques typically involve adding nano-inorganic particles, such as zirconium oxide, alumina, or silicates, to the polymer matrix. These added nano-inorganic particles can form multiple cross-linked structures within the polymer matrix, thereby enhancing the mechanical strength of the electrolyte and resisting the risk of lithium dendrite penetration. Furthermore, some inorganic particles can improve the ionic conductivity of the polymer electrolyte. However, this approach faces several technical challenges. First, nano-inorganic particles exhibit poor dispersibility in polymer solutions, easily agglomerating to form inhomogeneous structures, leading to impaired ion transport in the electrolyte. Second, the amount of nanoparticles added is difficult to control precisely; too much or too little will negatively impact the electrolyte's performance. Moreover, because nanoparticles typically possess high surface energy, they readily interact with the polymer interface, making stable dispersion difficult to achieve during industrial production, which increases the preparation difficulty and production cost.

[0004] Another common improvement method is to coat the lithium metal anode surface with a stable additive layer to reduce lithium dendrite growth and side reactions. These additives typically inhibit dendrite growth and prevent interfacial reactions, but they often require the use of a liquid electrolyte. Liquid electrolytes are prone to leakage and may generate uncontrollable side reactions at high temperatures and during prolonged use, posing safety hazards. Furthermore, compatibility issues between these additives and liquid electrolytes increase uncertainties in battery design and practical applications, reducing battery stability and safety.

[0005] In summary, existing polymer electrolytes suffer from the problem of balancing mechanical properties and ionic conductivity. Furthermore, their application in lithium metal anodes presents safety hazards such as lithium dendrite puncture and liquid electrolyte leakage, thus hindering their development and application in solid-state lithium batteries. Summary of the Invention

[0006] The purpose of this invention is to address the deficiencies of existing technologies by providing a self-healing membrane, ionic solution, solid electrolyte, preparation method, and application. The solid electrolyte material is generated through an in-situ reaction of molecular chains by forming hydrogen bonds between hydroxyl groups in a polymer matrix and fluoride ions in a fluorine-containing lithium salt. This material can self-heal during charge-discharge cycles, thereby effectively resisting lithium dendrite penetration and improving the cycle performance and safety of the battery.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing an electrospun diaphragm with self-healing capability, comprising:

[0008] The first polymer, the hydroxyl-containing polymer matrix for forming the self-healing polymer, and the fluorine-containing lithium salt are added to the first organic solvent in a mass ratio of 9:0.5:0.5 to 7:1.5:1.5, and stirred until homogeneous to obtain the first solution;

[0009] Nanoscale solid electrolyte powder material is added to a second organic solvent and ultrasonically treated to obtain a second solution. Then, a second polymer is added to the second solution and stirred until homogeneous to obtain a third solution.

[0010] The first and third solutions are transferred to an electrospinning apparatus for electrospinning to obtain an electrospinned membrane.

[0011] The electrospun membrane is dried and cut into pieces to obtain an electrospun membrane with self-healing ability.

[0012] The electrospun diaphragm with self-healing capability contains a self-healing polymer; the self-healing polymer comprises molecular chains formed by bridging two or more polymer matrices through hydrogen bonds formed by hydrogen bonds between the hydroxyl groups of the polymer matrix and fluoride ions in a fluorine-containing lithium salt.

[0013] Preferably, the polymer matrix comprises: polyvinyl alcohol (PVA) and / or polyurethane acrylate (PUA);

[0014] The fluorine-containing lithium salts include: lithium fluoride LiF and / or lithium tetrafluoroborate LiBF4;

[0015] The first polymer includes one or more of the following: polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), and polyacrylonitrile (PAN);

[0016] The first organic solvent includes: N,N-dimethylformamide (DMF) and / or acetone;

[0017] The solid mass concentration in the first solution is 5%-20%;

[0018] The solid electrolyte powder material includes lithium titanium aluminum phosphate (LATP) and / or lithium lanthanum titanium oxide (LLTO).

[0019] The second organic solvent includes: DMF and / or acetone;

[0020] The solid mass concentration in the second solution is 5%-20%;

[0021] The second polymer includes one or more of PVDF, PEO, and PAN;

[0022] The second polymer has a mass concentration of 5%-10% in the third solution;

[0023] The ultrasonic treatment time is 30-60 minutes;

[0024] The stirring process specifically involves stirring at room temperature for 3-12 hours.

[0025] The drying process specifically involves drying in an oven at 50℃-80℃ for 6-12 hours.

[0026] Secondly, embodiments of the present invention provide a method for preparing an ionic solution for self-healing solid electrolytes, the preparation method comprising:

[0027] The polymer monomer, the hydroxyl-containing polymer matrix for forming the self-healing polymer, and the fluorinated lithium salt are mixed in a mass ratio of [4-6]:[2-3]:[2-3]:[2-3]. The mixture is heated and stirred at 30-50°C for 30-60 minutes. After stirring until homogeneous, 0.2wt%-1wt% of initiator is added and stirring is continued for 30-60 minutes to obtain the first mixture.

[0028] The cosolvent, film-forming additive and lithium salt are mixed in a mass ratio of [5-8]:[0.5-1]:[2-3], and heated and stirred at 30-50℃ for 30-60 minutes to obtain a second mixture;

[0029] The first mixture and the second mixture are mixed at a mass ratio of 1:2 to 2:1 and heated and stirred at 30-50°C for 30-60 minutes to obtain the ionic solution.

[0030] The ionic solution contains a self-healing polymer; the self-healing polymer comprises molecular chains formed by bridging two or more polymer matrices through hydrogen bonds formed by hydroxyl groups of the polymer matrix and fluoride ions in a fluorine-containing lithium salt.

[0031] Preferably, the polymer matrix comprises: polyvinyl alcohol (PVA) and / or polyurethane acrylate (PUA);

[0032] The fluorine-containing lithium salts include: lithium fluoride LiF and / or lithium tetrafluoroborate LiBF4;

[0033] The polymer monomers include: cross-linking monomers and flexible monomers;

[0034] The cross-linking monomers include one or more of polyethylene glycol diacrylate (PEGDA), ethylene glycol dimethacrylate (EGDMA), hydroxyethyl methacrylate (HEMA), or pentaerythritol acrylate (PETA).

[0035] The flexible monomer includes one or more of butyl acrylate (BA), methyl methacrylate (MMA), and butyl methacrylate (MA).

[0036] The initiator includes: azobisisobutyronitrile (AIBN);

[0037] The co-solvent includes one or more of the following: succinate (SN), acetonitrile, propylene carbonate (PC), and tetrahydrofuran (THF).

[0038] The film-forming additives include one or more of the following: fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC).

[0039] The lithium salt includes one or more of the following: lithium bis(trifluoromethanesulfonyl)imide LiTFSI, lithium hexafluorophosphate LiPF6, lithium difluorooxalate borate LiDFOB, lithium bis(fluoromethanesulfonyl)imide LiFSSI, lithium dioxalate borate LiBOB, lithium fluoride LiF, or lithium tetrafluoroborate LiBF4.

[0040] Thirdly, embodiments of the present invention provide an electrospun diaphragm with self-healing capability prepared by the preparation method described in the first aspect above.

[0041] Fourthly, embodiments of the present invention provide an ionic solution for self-healing solid electrolytes prepared by the preparation method described in the second aspect above.

[0042] Fifthly, embodiments of the present invention provide a method for preparing a gel solid electrolyte with self-healing capabilities, comprising:

[0043] Using the electrospun separator described in the second aspect above as the battery separator and the ionic solution described in the third aspect above as the electrolyte, the battery is assembled so that the ionic solution completely wets the electrospun separator, and the polymer monomers in the ionic solution are initiated to polymerize in situ under heating conditions to form an electrospun membrane-based gel solid electrolyte with self-healing ability.

[0044] Preferably, the heating conditions are: heating at 50-80℃ for 3-12 hours.

[0045] In a sixth aspect, embodiments of the present invention provide a gel solid electrolyte with self-healing ability prepared by the preparation method described in the fifth aspect above.

[0046] The method for preparing a self-healing electrospun separator provided in this invention involves forming hydrogen bonds between hydroxyl groups in the polymer matrix and fluoride ions in the fluorine-containing lithium salt, bridging two or more polymer matrices and achieving molecular chain self-healing. The solid electrolyte generated in situ on the separator also exhibits the same properties, thus enabling self-healing during charge-discharge cycles. This effectively resists lithium dendrite penetration, while also possessing good ionic conductivity to ensure rapid lithium ion transport. Furthermore, it effectively improves the stability of the battery interface, significantly enhancing the battery's cycle performance and safety. Attached Figure Description

[0047] Figure 1 A flowchart illustrating the preparation method of an electrospun diaphragm with self-healing capability provided in an embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of a coaxial electrospinning device provided in an embodiment of the present invention;

[0049] Figure 3 This is a flowchart illustrating the preparation method of an ionic solution for self-healing solid electrolytes provided in an embodiment of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] This invention provides a self-healing membrane, an ionic solution, a solid electrolyte, a preparation method, and applications. It not only possesses the self-healing function of the membrane but also enables the generation of a self-healing solid electrolyte on the membrane surface through in-situ polymerization. The following describes the preparation method and performance of the self-healing electrospun membrane, the ionic solution for self-healing solid electrolyte, and the in-situ synthesized gel solid electrolyte with self-healing capabilities proposed in this invention.

[0052] Figure 1The flowchart below shows the preparation method of the electrospun diaphragm with self-healing ability provided in the embodiments of the present invention. Figure 1 The preparation method of the electrospun diaphragm with self-healing ability proposed in this invention will be described.

[0053] like Figure 1 As shown, the method for preparing an electrospun diaphragm with self-healing ability mainly includes the following steps:

[0054] Step 110: The first polymer, the hydroxyl-containing polymer matrix for forming the self-healing polymer, and the fluorine-containing lithium salt are added to the first organic solvent in a mass ratio of 9:0.5:0.5 to 7:1.5:1.5, and stirred until homogeneous to obtain the first solution.

[0055] The first polymer includes one or more of the following: polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), and polyacrylonitrile (PAN).

[0056] The polymer matrix includes: polyvinyl alcohol (PVA) and / or polyurethane acrylate (PUA);

[0057] Fluorine-containing lithium salts include: lithium fluoride (LiF) and / or lithium tetrafluoroborate (LiBF4);

[0058] The first organic solvent includes: N,N-dimethylformamide (DMF) and / or acetone;

[0059] After mixing the above substances in the specified proportions, stir at room temperature for 3-12 hours to form a uniform first solution.

[0060] Step 120: Add nano-sized solid electrolyte powder material to the second organic solvent and sonicate to obtain a second solution. Then add the second polymer to the second solution and stir until homogeneous to obtain a third solution.

[0061] Among them, solid electrolyte powder materials include lithium titanium aluminum phosphate (LATP) and / or lithium lanthanum titanium oxide (LLTO).

[0062] The second organic solvent includes: DMF and / or acetone;

[0063] The solid mass concentration in the second solution is 5%-20%;

[0064] The second polymer includes one or more of PVDF, PEO, and PAN;

[0065] The second polymer has a mass concentration of 5%-10% in the third solution.

[0066] The ultrasonic treatment time is 30-60 minutes.

[0067] Step 130: Transfer the first solution and the third solution to an electrospinning apparatus for electrospinning to obtain an electrospinned membrane;

[0068] The structure of the equipment used for electrospinning is as follows: Figure 2 As shown, the prepared first and third solutions are placed into two syringes 11 and 12, respectively. The two syringes 11 and 12 simultaneously inject the solutions through a coaxial needle 13. The flow rate is controlled by the two syringes to maintain the volume ratio of the first and third solutions entering the coaxial needle 13 at 1:2 to 2:1. A high-voltage power supply 14 applies a high voltage. The electrostatic force generated by the high voltage stretches the solution, forming a jet stream, which is then stretched into nanoscale fibers. The charged fibers are ejected from the coaxial needle 13 under the action of electrostatic force and attracted to a grounded collector 15 under the action of an electric field. The collector 15 can specifically be a rotating cylinder used to uniformly collect the fibers. A fiber membrane, i.e., an electrospun membrane, is deposited on the fiber ejected from the coaxial needle 13 and collected in the collector 15.

[0069] The coaxial needle diameter is 0.3-1 mm, the spinning speed is 0.5-1.5 ml / h, the distance from the coaxial needle to the collector is 8-20 cm, the humidity is 20-30 RT%, the temperature is 25-30℃, and the voltage applied by the high-voltage power supply is 10-20 kV. In a preferred example, the electrospinning parameters include: a coaxial needle diameter of 0.5 mm, a spinning speed of 1 ml / h, a distance from the coaxial needle to the collector of 15 cm, a humidity of 25 RT%, a temperature of 25℃, and a voltage of 10 kV.

[0070] Step 140: Dry and cut the electrospun membrane to obtain an electrospun membrane with self-healing ability.

[0071] Specifically, the drying process involves drying in an oven at 50℃-80℃ for 6-12 hours.

[0072] The electrospun diaphragm with self-healing ability prepared above contains a self-healing polymer; the self-healing polymer includes molecular chains formed by bridging two or more polymer matrices through hydrogen bonds formed by hydrogen bonds between the hydroxyl groups of the polymer matrix and the fluoride ions in the fluorine-containing lithium salt.

[0073] The method for preparing an electrospun diaphragm with self-healing capability provided in this invention involves forming hydrogen bonds between hydroxyl groups in the polymer matrix and fluoride ions in fluorine-containing lithium salts to bridge two or more polymer matrices, thereby achieving molecular chain self-healing. In other words, the self-healing capability mainly depends on the dynamic balance between the formation and breakage of hydrogen bonds.

[0074] To better understand the technical principles of this invention, PVA and lithium fluoride will be used as examples for further explanation below.

[0075] PVA is a polymer with a large number of hydroxyl groups (–OH). These hydroxyl groups are ubiquitous in the PVA molecular chain and can interact with other molecules through hydrogen bonds. Due to the polarity of the hydroxyl groups, PVA has good water solubility and chemical activity.

[0076] When PVA is exposed to fluorinated lithium salts (such as lithium fluoride, LiF), the hydroxyl groups in PVA can form hydrogen bonds with fluoride ions in lithium fluoride. In this process, fluoride ions act as bridging molecules, connecting two or more PVA molecular chains, while lithium ions exist in solution in ionic form.

[0077] When PVA-lithium fluoride composites are subjected to mechanical damage (such as cracks or fractures), the hydrogen bonds that were originally formed between the PVA chains, which are linked by hydrogen bonds, break. This breakage leads to localized movement and rearrangement of the PVA molecular chains. Under appropriate temperature and humidity conditions, the broken hydrogen bonds can reform, thus achieving self-healing. In other words, the broken PVA molecular chains can reform hydrogen bonds with new or existing fluoride ions through hydroxyl groups, thereby helping to repair the structural integrity of the material. This self-healing ability is not limited to microscopic structural reconstruction but can also restore certain physical properties of the material, such as strength and elasticity, on a macroscopic level.

[0078] This invention also provides a method for preparing an ionic solution for self-healing solid electrolytes, the main steps of which are as follows: Figure 2 As shown, it includes:

[0079] Step 210: The polymer monomer, the hydroxyl-containing polymer matrix for forming the self-healing polymer, and the fluorine-containing lithium salt are mixed in a mass ratio of [4-6]:[2-3]:[2-3]:[2-3]. The mixture is heated and stirred at 30-50°C for 30-60 minutes. After stirring until homogeneous, 0.2wt%-1wt% of initiator is added and stirring is continued for 30-60 minutes to obtain the first mixture.

[0080] The polymer matrix includes: polyvinyl alcohol (PVA) and / or polyurethane acrylate (PUA);

[0081] Fluorine-containing lithium salts include: lithium fluoride (LiF) and / or lithium tetrafluoroborate (LiBF4);

[0082] The polymer monomers include: cross-linking monomers and flexible monomers; the cross-linking monomers include one or more of polyethylene glycol diacrylate (PEGDA), ethylene glycol dimethacrylate (EGDMA), hydroxyethyl methacrylate (HEMA), or pentaerythritol acrylate (PETA); the flexible monomers include one or more of butyl acrylate (BA), methyl methacrylate (MMA), and butyl methacrylate (MA).

[0083] Initiators include: azobisisobutyronitrile (AIBN).

[0084] Step 220: Mix the cosolvent, film-forming additive and lithium salt in a mass ratio of [5-8]:[0.5-1]:[2-3], and heat and stir at 30-50℃ for 30-60 minutes to obtain the second mixture.

[0085] The co-solvents include one or more of the following: succinate (SN), acetonitrile, propylene carbonate (PC), and tetrahydrofuran (THF).

[0086] Film-forming additives include one or more of the following: fluoroethylene carbonate (FEC), ethylene carbonate (EC), and methyl ethyl carbonate (EMC).

[0087] Lithium salts include one or more of the following: lithium bis(trifluoromethanesulfonyl)imide (LiTFI), lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiTFI), lithium dioxalate borate (LiBOB), lithium fluoride (LiF), or lithium tetrafluoroborate (LiBF4).

[0088] Step 230: Mix the first mixture and the second mixture at a mass ratio of 1:2 to 2:1, and heat and stir at 30-50°C for 30-60 minutes to obtain an ionic solution.

[0089] The ionic solution prepared above for solid electrolyte self-healing contains a self-healing polymer; the self-healing polymer includes molecular chains formed by bridging two or more polymer matrices through hydrogen bonds formed by the hydroxyl groups of the polymer matrix and the fluoride ions in the fluorine-containing lithium salt.

[0090] The ionic solution prepared in this embodiment can be used as an electrolyte to initiate the in-situ polymerization of solid electrolytes and form solid electrolytes with self-healing capabilities.

[0091] Using the electrospun separator prepared in the above embodiments as the battery separator and the ionic solution prepared in the above embodiments as the electrolyte, the battery is assembled so that the ionic solution completely wets the electrospun separator, and the polymer monomers in the ionic solution are initiated to polymerize in situ under the condition of heating at 50-80°C for 3-12 hours to form an electrospun membrane-based gel solid electrolyte with self-healing ability.

[0092] This invention achieves a self-healing, in-situ generated solid electrolyte material through hydrogen bonding between hydroxyl groups in a polymer matrix and fluoride ions in a fluorinated lithium salt. This not only improves the mechanical properties of the electrolyte and optimizes the contact between the electrolyte and electrodes, increasing the ionic conductivity and electrochemical window of the gel solid electrolyte, but also enables the material to self-heal during charge-discharge cycles, effectively resisting lithium dendrite penetration. It can self-repair microcracks that appear during the use of the solid electrolyte, improving the electrochemical stability and safety of the battery. Testing shows that the gel solid electrolyte prepared by this invention has an ionic conductivity >10. -4 S cm -1 It has an electrochemical window > 4.5V, an elastic modulus > 5MPa, and can complete self-healing in as little as 30 minutes at 60℃.

[0093] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0094] Example 1

[0095] The first step is to mix 0.8g of PVDF, 0.1g of PVA and 0.1g of lithium salt LiF in a certain proportion, and add them to 10ml of organic solvent DMF. Stir at room temperature for 6 hours to form a homogeneous solution, and put it into syringe 1 for electrospinning.

[0096] In the second step, 1g of LATP, a solid electrolyte powder with a nanometer size of 200nm, was added to 10ml of DMF, an organic solvent, and sonicated for 30 minutes. Then, 0.1g of PVDF polymer was added, and the mixture was stirred at room temperature for 6 hours to form a homogeneous solution, which was then placed into syringe 2 for electrospinning.

[0097] The third step is to transfer the prepared syringes 1 and 2 into the electrospinning machine for electrospinning. The main parameters are: needle diameter 0.5 mm, spinning speed 1 ml / h, liquid supply rate of syringes 1 and 2 1:1, distance from needle to collector 15 cm, humidity 25 RT%, temperature 25℃, and voltage 10 kV.

[0098] The fourth step is to place the electrospun film after spinning into an 80°C oven and dry it for 12 hours. Then, cut it into round pieces and put them into a glove box for later use.

[0099] The following operations are all performed inside the glove box:

[0100] Step 5: Heat and stir 500mg of PEGDA, 200mg of BA, 200mg of PVA and 200mg of LiF at 50℃ for 60 minutes. After stirring evenly, add 3mg of initiator AlBN and stir for another 60 minutes. This mixture is named Mixture 1.

[0101] Step 6: Heat and stir 500 mg of SN, 50 mg of FEC and 200 mg of Li BOB at 30°C for 60 minutes, and name it Mixture II.

[0102] Step 7: Mix mixture 1 and mixture 2 at a mass ratio of 1:1, heat and stir at 30°C for 60 minutes until homogeneous to obtain an ionic solution.

[0103] The eighth step involves assembling a button cell using the prepared electrospun membrane as a separator and the prepared ionic solution as an electrolyte.

[0104] The assembly process involves completely impregnating the electrospun membrane with an ionic solution. Furthermore, batteries are assembled separately for ionic conductivity testing, electrochemical window testing, and self-healing function evaluation testing.

[0105] The conductivity test was performed using two stainless steel (SS) inert electrodes assembled into a battery.

[0106] The electrochemical window test used lithium metal sheets as the reference electrode and counter electrode, and stainless steel sheets (SS) as the working electrode to assemble a lithium / stainless steel (Li|SS) battery.

[0107] The self-healing function evaluation test used a button cell assembled with lithium iron phosphate (LFP) as the positive electrode and lithium metal as the negative electrode.

[0108] The ninth step involves heating each group of button batteries at 60°C on a heating platform for 3 hours to perform in-situ polymerization, thereby forming an in-situ polymerized gel solid electrolyte.

[0109] The obtained button batteries were subjected to ionic conductivity and electrochemical window tests, and the mechanical strength of the disassembled in-situ polymerized gel solid electrolyte was tested.

[0110] The test methods are as follows:

[0111] Ionic conductivity testing: Electrochemical impedance spectroscopy (EIS) was performed on an electrochemical workstation. To ensure accuracy, the test battery was placed in a temperature-controlled chamber. In the EIS test, the frequency range was set from 0.01 Hz to 1 MHz, and the amplitude voltage was set to 10 mV to accurately measure the electrolyte resistance. Then, the ionic conductivity of the electrolyte was calculated using a formula based on the Nyquist impedance spectrum analysis. The formula used is as follows: In the determination of ionic conductivity, d in the formula represents the thickness of the electrolyte, R is the volume resistance of the electrolyte read from the Nyquist impedance diagram of EIS, and S represents the effective contact area between the electrolyte and the stainless steel inert electrode. To ensure the accuracy of the measurement, when testing the ionic conductivity at different temperatures, the constant temperature chamber needs to be set to the target temperature and maintained for half an hour to allow the test battery to reach thermal equilibrium. This step ensures the stability of the test environment, thereby allowing for accurate measurement of the ionic conductivity of the electrolyte at various temperatures.

[0112] Electrochemical window testing: The assembled test cell was subjected to linear sweep voltammetry (LSV) in a constant temperature chamber at room temperature. During the test, the scan rate was set to 1 millivolt per second (mV / s), scanning from the open-circuit voltage to 5V.

[0113] Mechanical strength testing: The test was conducted using a universal tensile testing machine. The in-situ polymerized gel solid electrolyte based on the electrospun membrane was cut into rectangular electrolyte sheets of 5cm × 1cm. The thickness of the electrolyte membrane was then measured using vernier calipers. The cut electrolyte sheets were clamped on the tensile testing machine, and the stress strength and elastic modulus were tested by tensile testing.

[0114] Tensile property test: The electrospun membrane obtained in step four was directly impregnated with the ionic solution obtained in step seven, and in-situ thermal polymerization was carried out at 60°C for 3 hours to obtain a gel solid electrolyte. To test the self-healing function of the solid electrolyte, the prepared solid electrolyte was cut in half, and the cut seams were aligned and brought into contact. The healing process was observed after 30 minutes at 60°C. The degree of healing was calculated by dividing the healed length by the total length.

[0115] Self-healing function assessment test: 200 cycles were performed at 3C current density, and the capacity retention rate was recorded.

[0116] The test results are recorded in Table 1.

[0117] Example 2

[0118] The difference between this embodiment and Embodiment 1 is that the lithium salt used in the first, fifth and sixth steps is LiBF4, while the remaining steps and tests are the same.

[0119] Example 3

[0120] The difference between this embodiment and Embodiment 1 is that the polymer matrix used in the first and fifth steps is PUA, while the remaining steps and tests are the same.

[0121] Example 4

[0122] The difference between this embodiment and Embodiment 1 is that the polymer matrix used in step 5 is PUA, while the remaining steps and tests are the same.

[0123] Example 5

[0124] The difference between this embodiment and Embodiment 1 is that the lithium salt used in the first step is LiF, and the lithium salt used in the fifth and sixth steps is LiBF4. The remaining steps and tests are the same.

[0125] Example 6

[0126] The difference between this embodiment and Embodiment 1 is that the solid electrolyte powder material used in the second step is LLTO, while the other steps and tests are the same.

[0127] Comparative Example 1

[0128] The difference from Example 1 is that the lithium salt used in the first, fifth and sixth steps is LiClO4, while the other steps and tests are the same.

[0129] Comparative Example 2

[0130] The difference from Example 1 is that PVA and fluorine-containing lithium salts are not added in the first and fifth steps, while the remaining steps and tests are the same.

[0131] Comparative Example 3

[0132] The difference from Example 1 is that PVA and fluorine-containing lithium salt are not added in the first step, the fifth step is not performed, and the second mixture is used directly as the ionic solution in the seventh step. The remaining steps and tests are the same.

[0133] The test results of the above embodiments and comparative examples are recorded in Table 1.

[0134]

[0135] Table 1

[0136] As can be seen from the data in Table 1, the ionic conductivity of Examples 1-6 is slightly higher than that of Comparative Examples 1-3, the electrochemical window of Examples 1-3 is significantly higher than that of Comparative Examples 1-6, the stress intensity of Examples 1-6 is significantly higher than that of Comparative Examples 1-3, and the degree of healing of Examples 1-6 is also significantly higher than that of Comparative Examples 1-3.

[0137] Comparative Example 1, an electrolyte without fluorinated lithium salts, showed improved electrochemical performance but very low healing ability. Comparative Example 2, an electrolyte without polymer matrix or fluorinated lithium salts, exhibited significantly reduced electrochemical performance and lacked self-healing capabilities. Comparative Example 3, an electrolyte without polymer matrix or fluorinated lithium salts and without in-situ polymerization, resulted in a significantly reduced mechanical strength and electrochemical performance of the prepared electrolyte membrane, and also lacked self-healing capabilities.

[0138] As can be seen from the above data, the present invention achieves the self-healing function of the material by bridging the molecular chains formed by two or more polymer matrices through hydrogen bonds formed by the hydroxyl groups of the polymer matrix and the fluoride ions in the fluorine-containing lithium salt. The electrochemical performance and mechanical strength of the electrospun membrane-based gel solid electrolyte with self-healing function prepared by combining coaxial electrospinning technology and in-situ polymerization technology are greatly improved.

[0139] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an electrospun diaphragm with self-healing ability, characterized in that, The preparation method includes: The first polymer, the hydroxyl-containing polymer matrix for forming the self-healing polymer, and the fluorine-containing lithium salt are added to the first organic solvent in a mass ratio of 9:0.5:0.5 to 7:1.5:1.5, and stirred until homogeneous to obtain the first solution; Nanoscale solid electrolyte powder material is added to a second organic solvent and ultrasonically treated to obtain a second solution. Then, a second polymer is added to the second solution and stirred until homogeneous to obtain a third solution. The first and third solutions are transferred to an electrospinning apparatus for electrospinning to obtain an electrospinned membrane. The electrospun membrane is dried and cut into pieces to obtain an electrospun membrane with self-healing ability. The electrospun diaphragm with self-healing capability contains a self-healing polymer; the self-healing polymer comprises molecular chains formed by bridging two or more polymer matrices through hydrogen bonds formed by hydrogen bonds between the hydroxyl groups of the polymer matrix and fluoride ions in a fluorine-containing lithium salt.

2. The preparation method according to claim 1, characterized in that, The polymer matrix includes: polyvinyl alcohol (PVA) and / or polyurethane acrylate (PUA); The fluorine-containing lithium salts include: lithium fluoride LiF and / or lithium tetrafluoroborate LiBF4; The first polymer includes one or more of the following: polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), and polyacrylonitrile (PAN); The first organic solvent includes: N,N-dimethylformamide (DMF) and / or acetone; The solid mass concentration in the first solution is 5%-20%; The solid electrolyte powder material includes lithium titanium aluminum phosphate (LATP) and / or lithium lanthanum titanium oxide (LLTO). The second organic solvent includes: DMF and / or acetone; The solid mass concentration in the second solution is 5%-20%; The second polymer includes one or more of PVDF, PEO, and PAN; The second polymer has a mass concentration of 5%-10% in the third solution; The ultrasonic treatment time is 30-60 minutes; The stirring process specifically involves stirring at room temperature for 3-12 hours. The drying process specifically involves drying in an oven at 50℃-80℃ for 6-12 hours.

3. A method for preparing an ionic solution for self-healing solid electrolytes, characterized in that, The preparation method includes: The polymer monomer, the hydroxyl-containing polymer matrix for forming the self-healing polymer, and the fluorinated lithium salt are mixed in a mass ratio of [4-6]:[2-3]:[2-3]:[2-3]. The mixture is heated and stirred at 30-50°C for 30-60 minutes. After stirring until homogeneous, 0.2wt%-1wt% of initiator is added and stirring is continued for 30-60 minutes to obtain the first mixture. The cosolvent, film-forming additive and lithium salt are mixed in a mass ratio of [5-8]:[0.5-1]:[2-3], and heated and stirred at 30-50℃ for 30-60 minutes to obtain a second mixture; The first mixture and the second mixture are mixed at a mass ratio of 1:2 to 2:1 and heated and stirred at 30-50°C for 30-60 minutes to obtain the ionic solution. The ionic solution contains a self-healing polymer; the self-healing polymer comprises molecular chains formed by bridging two or more polymer matrices through hydrogen bonds formed by hydroxyl groups of the polymer matrix and fluoride ions in a fluorine-containing lithium salt.

4. The preparation method according to claim 3, characterized in that, The polymer matrix includes: polyvinyl alcohol (PVA) and / or polyurethane acrylate (PUA); The fluorine-containing lithium salts include: lithium fluoride LiF and / or lithium tetrafluoroborate LiBF4; The polymer monomers include: cross-linking monomers and flexible monomers; The cross-linking monomers include one or more of polyethylene glycol diacrylate (PEGDA), ethylene glycol dimethacrylate (EGDMA), hydroxyethyl methacrylate (HEMA), or pentaerythritol acrylate (PETA). The flexible monomer includes one or more of butyl acrylate (BA), methyl methacrylate (MMA), and butyl methacrylate (MA). The initiator includes: azobisisobutyronitrile (AIBN); The co-solvent includes one or more of the following: succinate (SN), acetonitrile, propylene carbonate (PC), and tetrahydrofuran (THF). The film-forming additives include one or more of the following: fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC). The lithium salt includes one or more of the following: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium dioxalate borate (LiBOB), lithium fluoride (LiF), or lithium tetrafluoroborate (LiBF4).

5. An electrospun diaphragm with self-healing capability prepared by the preparation method according to claim 1 or 2.

6. An ionic solution for self-healing solid electrolytes prepared by the preparation method according to claim 3 or 4.

7. A method for preparing a gel solid electrolyte with self-healing ability, characterized in that, The preparation method includes: Using the electrospun separator of claim 5 as the battery separator and the ionic solution of claim 6 as the electrolyte, the battery is assembled so that the ionic solution completely wets the electrospun separator, and the polymer monomers in the ionic solution are initiated to polymerize in situ under heating conditions to form an electrospun membrane-based gel solid electrolyte with self-healing ability.

8. The preparation method according to claim 7, characterized in that, The specific heating conditions are: heating at 50-80℃ for 3-12 hours.

9. A gel solid electrolyte with self-healing ability prepared by the preparation method according to claim 7 or 8.

10. A secondary battery, characterized in that, The secondary battery includes at least one of the electrospun separator of claim 5, the ionic solution of claim 6, or the gel solid electrolyte with self-healing ability of claim 9.

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