阅读说明：本技术 具有自关闭功能的高离子电导率锂电池隔膜及其制备方法 (High-ionic-conductivity lithium battery diaphragm with self-closing function and preparation method thereof ) 是由 魏真真 顾嘉怡 李家仪 赵燕 于 2021-06-18 设计创作，主要内容包括：本发明涉及一种具有自关闭功能的高离子电导率锂电池隔膜及其制备方法,方法：(1)将含有粘性物质的导电无机物溶液在微纳米纤维膜的一侧进行真空抽滤,然后真空干燥；(2)将含有粘性物质的陶瓷纳米颗粒溶液在步骤(1)得到的膜的两侧先后进行真空抽滤,每次抽滤后均进行真空干燥,得到复合膜；制得的锂电池隔膜,沿厚度方向,是由依次为陶瓷纳米颗粒层、导电无机物层、微纳米纤维膜和陶瓷纳米颗粒层组成的复合膜；复合膜中的陶瓷纳米颗粒、导电无机物和微纳米纤维膜(材质为纯聚丁二酸丁二醇酯)之间的相对位置由粘性物质固定；复合膜的孔隙率为50～56％；本发明具有较高的热敏感度和热尺寸稳定性,使锂电池安全和使用性能更高,极具应用前景。(The invention relates to a high ionic conductivity lithium battery diaphragm with a self-closing function and a preparation method thereof, wherein the method comprises the following steps: (1) carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substance on one side of the micro-nano fiber membrane, and then carrying out vacuum drying; (2) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (1) in sequence, and carrying out vacuum drying after each filtration to obtain a composite membrane; the prepared lithium battery diaphragm is a composite film which is composed of a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber film and a ceramic nanoparticle layer in sequence in the thickness direction; the relative positions of the ceramic nanoparticles, the conductive inorganic substance and the micro-nano fiber membrane (made of pure poly butylene succinate) in the composite membrane are fixed by sticky substances; the porosity of the composite membrane is 50-56%; the invention has higher thermal sensitivity and thermal dimension stability, ensures that the lithium battery has higher safety and service performance, and has great application prospect.)

1. A high ionic conductivity lithium battery diaphragm with a self-closing function is characterized in that: the composite membrane is a four-layer composite membrane formed by ceramic nano particles, conductive inorganic substances and micro-nano fiber membranes;

the four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber film and a ceramic nanoparticle layer in sequence along the thickness direction of the composite film;

the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by sticky substances;

the micro-nano fiber membrane is made of pure poly (butylene succinate);

the porosity of the composite membrane is 50-56%.

2. The lithium battery separator with self-shutdown function and high ionic conductivity as claimed in claim 1, wherein the adhesive is styrene-butadiene latex binder, and the ceramic nanoparticles are hydrophilic nano-SiO₂The particles and the conductive inorganic matter are MXene with a lamellar structure; nano SiO₂The average particle size of the particles is 7-40 nm; the average diameter of the nano fibers in the micro-nano fiber membrane is 100-200 nm, and the average diameter of the micro fibers is 1.5-3 mu m.

3. The lithium battery separator with self-shutdown function and high ionic conductivity as claimed in claim 2, wherein the density of MXene on the composite membrane is 0.080-0.318 mg/cm²Nano SiO₂The density of the particles is 0.159-0.557 mg/cm²。

4. The lithium battery diaphragm with self-closing function and high ionic conductivity as claimed in claim 3, characterized in that the liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 410-650%; the ionic conductivity of the composite membrane is 3.31 multiplied by 10^-3～4.13×10^-3S/cm；

The composite membrane has closed pores at the temperature corresponding to the melting point of the pure poly (butylene succinate) and has no deformation at the temperature of 300 ℃.

5. The method for preparing a lithium battery separator with a self-shutdown function and high ionic conductivity as claimed in any one of claims 1 to 4, comprising the steps of:

(1) carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substance on one side of the micro-nano fiber membrane, and then carrying out vacuum drying;

(2) and (2) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substance on two sides of the membrane obtained in the step (1) in sequence, and carrying out vacuum drying after each filtration to obtain the composite membrane.

6. The method for preparing the lithium battery diaphragm with the self-closing function and the high ionic conductivity as claimed in claim 5, wherein the volume of the conductive inorganic substance solution containing the viscous substance is 5-12 mL during the suction filtration in the step (1);

and (3) during suction filtration in the step (2), the volume of the ceramic nanoparticle solution containing the viscous substances is 5-10 mL.

7. The method for preparing a lithium battery separator with a self-shutdown function and a high ionic conductivity as claimed in claim 5, wherein the temperature of vacuum drying is 40-60 ℃ and the time is 55-65 min.

8. The method for preparing a lithium battery separator with a self-shutdown function and a high ionic conductivity as claimed in claim 5, wherein the concentration of the viscous substance in the conductive inorganic substance solution containing the viscous substance is 0.001 wt%, and the mass-to-volume ratio of the conductive inorganic substance to the solvent is 0.3 to 0.8 mg/mL; the preparation process of the conductive inorganic substance solution containing the viscous substances comprises the following steps: dispersing conductive inorganic matter in water solution, and mixing with water solution containing viscous substance;

in the ceramic nanoparticle solution containing the viscous substance, the concentration of the viscous substance is 0.001 wt%, and the mass-volume ratio of the ceramic nanoparticles to the solvent is 0.3-0.8 mg/mL; the preparation process of the ceramic nanoparticle solution containing the viscous substance comprises the following steps: the ceramic nano-particles are dispersed in an aqueous solution and then mixed with an aqueous solution containing a viscous substance to obtain the ceramic nano-particles.

9. The preparation method of the self-shutdown high-ionic-conductivity lithium battery diaphragm is characterized in that the micro-nano fiber film is obtained by performing vacuum drying on a fiber film prepared by an electrostatic spinning process at 40-60 ℃ for 12-24 hours and then performing rolling at a pressure of 4-6 MPa.

10. The method for preparing a lithium battery separator with a self-shutdown function and a high ionic conductivity as claimed in claim 9, wherein the parameters of the electrospinning process are as follows: the mass fraction of solute in the spinning solution is 18-22 wt%, and the applied voltage of spinning is 8-15 kV; the solution propelling speed is 1.5-2 mL/h.

Technical Field

The invention belongs to the technical field of lithium batteries, and relates to a high-ionic-conductivity lithium battery diaphragm with a self-closing function and a preparation method thereof.

Background

Lithium batteries have a potential ideal energy storage system due to their high energy density, high-rate charge and discharge capability, low self-discharge rate, long cycle life, and environmental friendliness. The diaphragm is used as an important component of the battery, and does not directly participate in electrochemical reaction, but plays the roles of isolating the positive electrode and the negative electrode in the battery, providing an ion transmission channel and preventing the internal short circuit of the battery, and the structure and the performance of the diaphragm have important influence on the use and the safety performance of the battery.

At present, polyolefin diaphragms such as PP, PE and the like are mainly used as diaphragms widely applied to lithium batteries, but the thermal stability of the diaphragms is poor due to the lower melting points of the PP and the PE. To improve the thermal stability of the separator, a number of efforts have been developed. In patent application CN111769236A, the shell-like structure composite diaphragm prepared from lithium magnesium silicate nanoparticles and nanocellulose fibers is used to improve the thermal stability of the diaphragm, but the diaphragm does not have a self-closing function and cannot cut off the current in time to avoid internal short circuit.

The self-closing function of the diaphragm is that in the temperature rising process, when a certain temperature is reached, the diaphragm can be closed through the hole in time to block ion transportation, a current loop is cut off, and meanwhile, the size stability can be kept to avoid the internal short circuit of the battery. In patent CN102544416A, a method for preparing a battery separator with a PE/PP bilayer structure and a PE/PP/PE trilayer structure is disclosed, in which the battery separator can exhibit its self-shutdown performance at 135 ℃, but the separator thermally shrinks after exceeding 165 ℃, and the thermal dimensional stability of the separator is poor. And the temperature difference between the melting points of PP and PE is only 30 ℃ lower than that of large-scale thermal runaway, and the safety accidents such as fire explosion and the like are still easy to cause. Therefore, lowering the self-shutdown temperature of the separator and increasing the thermal dimensional stability temperature of the separator are of great significance for the safe use of the separator in a battery.

Meanwhile, the diaphragm has high ionic conductivity, which is one of the basic conditions for a lithium battery to have good electrochemical performance. Patent application CN105390645A discloses a method for preparing a membrane by stretching a mixture membrane of polytetrafluoroethylene and an amino-modified sulfonic acid polymer at a higher temperature, wherein the membrane has good thermal stability and high ionic conductivity, and has good electrochemical properties and good thermal safety. But it does not prevent the battery from causing a greater risk in the event of an internal short circuit of the battery because it does not have a self-shutdown function. The patent CN101562243A application discloses a diaphragm prepared by mixing and spinning a high-performance polyarylether resin solution and a general engineering resin solution (or solution), which has improved thermal stability and ionic conductivity, and also has self-closing performance, but has poor thermal sensitivity.

Therefore, the development of a preparation method of the battery diaphragm which has self-closing performance, higher thermal sensitivity and thermal dimensional stability and can keep higher ionic conductivity has practical significance.

Disclosure of Invention

The invention aims to solve the problems of low ionic conductivity, no self-closing function or high self-closing temperature, namely low thermal sensitivity and poor thermal stability of a lithium battery diaphragm in the prior art, and provides a lithium battery diaphragm which has high thermal sensitivity (namely, the diaphragm can be self-closed at a lower temperature), high ionic conductivity and high thermal dimensional stability and a preparation method thereof. The method takes an organic low-melting-point polymer (poly butylene succinate (PBS)) as a raw material, utilizes an electrostatic spinning technology to prepare a micro-nano fiber film, and takes the micro-nano fiber film as a diaphragm substrate after rolling; secondly, respectively dispersing inorganic particles MXene and silicon dioxide particles in an aqueous solution, and mixing the inorganic particles MXene and silicon dioxide particles with a viscous substance styrene-butadiene latex aqueous solution to obtain an MXene solution containing the viscous substance and a silicon dioxide solution containing the viscous substance; and finally, carrying out suction filtration on the MXene solution containing the viscous substances on one side of the diaphragm substrate, drying, carrying out suction filtration on the silica solution containing the viscous substances on the two sides of the fiber membrane, and carrying out vacuum drying to obtain the composite fiber membrane. The lithium battery diaphragm prepared by the invention can endow the diaphragm with self-closing performance, and can obviously improve the thermal dimensional stability and the ionic conductivity of the diaphragm.

The invention aims to provide a high-ionic-conductivity lithium battery diaphragm with a self-closing function, which is a diaphragm which is compounded by an organic low-melting-point polymer and an inorganic material and has a self-closing function and excellent thermal dimensional stability, and is a diaphragm which is formed by conductive particles and electrophilic electrolyte ceramic particles and improves ionic conductivity.

The invention also aims to provide a preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity, which comprises the steps of coating an inorganic particle aqueous solution on the surface of an electrostatic spinning micro-nano fiber membrane through vacuum filtration, and adhering inorganic particles on the fiber membrane through an adhesive material.

In order to achieve the purpose, the invention adopts the following scheme:

a high ionic conductivity lithium battery diaphragm with self-closing function is a four-layer composite membrane composed of ceramic nano particles, conductive inorganic substances and a micro-nano fiber membrane;

the four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber film and a ceramic nanoparticle layer in sequence along the thickness direction of the composite film;

the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by sticky substances;

the micro-nano fiber membrane is made of pure poly (butylene succinate) (the poly (butylene succinate) is a biodegradable environment-friendly material, is easy to obtain and low in cost, ensures that each membrane melts at a low melting point to play a self-closing function, and is simple to prepare and low in cost due to a single component);

the porosity of the composite membrane is 50-56%. Too high porosity, too low fiber film density, and too low ionic conductivity.

The self-closing function is formed by combining two substances with different melting points, when the temperature reaches the melting point of the low-melting-point substance, the low-melting-point substance melts and blocks pores, and the high-melting-point substance keeps shape stability. In the self-closing function, the safety window temperature represents the melting point difference of the substance. In addition, the low melting point substance has a low melting point, so that the heat sensitivity of the membrane can be ensured to be higher, the larger the safety window is, and the better safety performance of the membrane is. The prior art generally only increases the melting point of the separator. When the battery short circuit and other conditions occur, the temperature of the battery rises sharply, and the high-melting-point diaphragm also shrinks and deforms or melts when reaching the melting point, so that more serious accidents are caused. The diaphragm with the self-closing function can play the self-closing function (namely has thermal sensitivity) and simultaneously keep stable size when the conditions are not serious and the temperature of the battery is not too high, and thoroughly separates the positive electrode and the negative electrode, thereby preventing the continuous occurrence of short circuit and achieving the effect of protecting the safety of the battery.

The ceramic nanoparticles and the conductive inorganic particles on the surface of the composite fiber membrane are fixed by the viscous substance. When the battery is in short circuit and the temperature reaches the melting point (about 115 ℃) of the micro-nano fiber film, the micro-nano fiber film melts and blocks the pores, and the ceramic nano particles and the conductive inorganic particles fixed on the surface of the fiber film keep dimensional stability, so that the positive electrode and the negative electrode are thoroughly separated, the short circuit cannot continue to occur, and the diaphragm realizes the self-closing function.

The micro-nanofiber membrane is a micro-nanofiber crossed membrane, and the structure is more favorable for improving the ionic conductivity because: compared with a nanofiber membrane, the micro-nanofiber cross membrane with the same density has better mechanical tensile property, and is beneficial to the assembly production of lithium batteries; compared with a micron fiber membrane, the membrane with the crossed micro-nanofibers has larger specific surface area, and can ensure the porosity of the fiber membrane while ensuring the density of the fiber membrane, thereby being beneficial to improving the ionic conductivity.

The conductive particles and the non-conductive particles are used in a matched manner, so that the ionic conductivity can be improved while the thermal stability of the diaphragm is improved because: first, both the conductive particles and the non-conductive particles are high-melting-point inorganic particles, and are not melted or deformed at high temperature, thereby ensuring the thermal stability of the separator. Secondly, the non-conductive particles of the invention have good electrolyte wettability, thereby further improving the ionic conductivity of the conductive material on the basis of improving the ionic conductivity of the film.

When the condition of hole closure is considered, in order to ensure that the hole is fused and closed in time, a polymer with a lower melting point needs to be selected. The selected polymer can meet the condition of electrostatic spinning film forming, fibers in the film forming are micro-nano fibers, the yield and the demand of the diaphragm are very large, the PBS material is a biodegradable material, and compared with PP \ PE, the PBS material has the advantages of low melting point, electrostatic spinning performance and environmental friendliness.

As a preferred technical scheme:

the lithium battery diaphragm with the self-closing function and the high ionic conductivity has the advantages that the viscous substance is the styrene-butadiene latex adhesive, and the ceramic nano particles are hydrophilic nano SiO₂Particles (spherical), wherein the conductive inorganic matter is MXene with a lamellar structure; nano SiO₂The average particle size of the particles is 7-40 nm; the average diameter of the nano fibers in the micro-nano fiber membrane is 100-200 nm, and the average diameter of the micro fibers is 1.5-3 mu m.

The lithium battery diaphragm with the self-closing function and the high ionic conductivity has the advantages that the density (namely the mass per unit area) of MXene on the composite film is 0.080-0.318 mg/cm²Nano SiO₂The density (i.e., mass per unit area) of the particles is 0.159 to 0.557mg/cm². Excessive MXene tends to form conductive paths in the separator, resulting in electricityThe cell is short-circuited, and the MXene content is too small to play a role in improving the ion conductivity of the diaphragm; SiO 2₂Too large amount of the composite diaphragm, too small porosity of the composite diaphragm and too low ionic conductivity of the diaphragm; coating SiO₂In an excessively small amount, nano SiO₂The electrophilic electrolyte property of the particles cannot function, and the electrolyte wettability of the separator cannot be improved.

The lithium battery diaphragm with the self-closing function and the high ionic conductivity has the advantages that the liquid absorption rate of the composite membrane to LiTFSI (lithium bis (trifluoromethyl) sulfenamide) electrolyte is 410-650%; the ionic conductivity was 3.31X 10^-3～4.13×10^-3S/cm；

The composite membrane has closed pores when the melting point of the pure poly (butylene succinate) (about 115 ℃) is reached, and has no deformation (no deformation for a long time) at the temperature of 300 ℃; after self-closing, the diaphragm has no gap and the ions have no shuttle channel.

The cell separator Celgard 2325 which is commercially available in the prior art has a closed cell temperature of 135 ℃, deforms when heated at 130 ℃ for 30s, generates a thermal shrinkage of about 10% after 30min, and has an ionic conductivity of 0.78X 10^-3About S/cm.

The invention also provides a preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity, which comprises the following steps:

(1) carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substance on one side of the micro-nano fiber membrane, and then carrying out vacuum drying; conducting inorganic substance solution is filtered on both sides, so that the conducting inorganic substance solution is easily communicated through pores, and the short circuit of the battery is caused;

(2) and (2) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substance on two sides of the membrane obtained in the step (1) in sequence, and carrying out vacuum drying after each filtration to obtain the composite membrane.

The conductive inorganic substance solution is filtered and filtered firstly, and then the ceramic nano-particle solution is filtered and filtered, so that the ceramic nano-particle solution can be ensured to be on the surface of the diaphragm, and the wettability of the diaphragm to the electrolyte can be exerted.

As a preferred technical scheme:

according to the preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity, during suction filtration in the step (1), the volume of a conductive inorganic substance solution containing viscous substances is 5-12 mL;

and (3) during suction filtration in the step (2), the volume of the ceramic nanoparticle solution containing the viscous substances is 5-10 mL.

According to the preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity, the vacuum drying temperature is 40-60 ℃ and the vacuum drying time is 55-65 min (the diaphragm cannot be dried after the drying time is too short, and the drying time of the used SBR can reduce the performance of the diaphragm, so the time is not too long).

The preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity comprises the following steps of (1) in a conductive inorganic substance solution containing a viscous substance, wherein the concentration of the viscous substance is 0.001 wt%, and the mass-volume ratio of the conductive inorganic substance to a solvent (generally deionized water) is 0.3-0.8 mg/mL; the preparation process of the conductive inorganic substance solution containing the viscous substances comprises the following steps: dispersing conductive inorganic matter in water solution, and mixing with water solution containing viscous substance;

in the ceramic nanoparticle solution containing the viscous substance, the concentration of the viscous substance is 0.001 wt%, and the mass-volume ratio of the ceramic nanoparticles to the solvent (generally deionized water) is 0.3-0.8 mg/mL; the preparation process of the ceramic nanoparticle solution containing the viscous substance comprises the following steps: the ceramic nano-particles are dispersed in an aqueous solution and then mixed with an aqueous solution containing a viscous substance to obtain the ceramic nano-particles.

The parameters listed here are parameters that have important influence on the porosity and ionic conductivity of the composite fiber membrane, and the ratio of the conductive inorganic substance and the ceramic nanoparticles to the solvent is too large, so that the conductive inorganic substance and the ceramic nanoparticles are not uniform enough; the ratio of the conductive inorganic substance to the ceramic nano particles to the solvent is too small, the volume of the suction filtration solution is too small, the composite conductive inorganic substance and the ceramic nano particles are not enough, the thermal stability is too low, and the electrochemical performance cannot achieve the ideal effect;

too high concentration of the viscous substance easily causes too small porosity of the composite diaphragm and too low ionic conductivity of the diaphragm; the concentration of the viscous substance is too low, the binding force between the ceramic nano particles and the micro-nano fiber membrane is too low, and the battery is easy to peel off in the circulating process.

According to the preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity, the micro-nano fiber film is obtained by firstly performing vacuum drying on a fiber film prepared by an electrostatic spinning process at the temperature of 40-60 ℃ for 12-24 hours and then performing rolling at the pressure of 4-6 MPa (the rolling time is 1-3 min); the micro-nano fiber membrane prepared by electrostatic spinning can ensure that the diaphragm has higher porosity, and is beneficial to the circulation of lithium ions in the battery. Drying is to remove the solvent that is not volatilized in the fiber membrane; the roll pressing is to adjust the average pore diameter of the fiber membrane and to smooth the surface of the fiber membrane. Too big meeting of roll-in pressure is mashed with the fibre membrane pressure, and the undersize can make the compactness between the fibre insufficient, and the fibre membrane is inhomogeneous and can not prevent the hole UNICOM, and inorganic matter coating is inhomogeneous when leading to the suction filtration, and conductive material forms electrically conductive channel in the hole UNICOM even.

According to the preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity, the parameters of the electrostatic spinning process are as follows: the mass fraction of solute in the spinning solution is 18-22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform in a mass ratio of 1: 4), and the spinning applied voltage is 8-15 kV; the solution propelling speed is 1.5-2 mL/h. The listed parameters are parameters which have important influence on the diameter and the porosity of the micro-nanofiber membrane, and the fibers can form beads when the spinning solution concentration is too high, the spinning solution propelling speed is too high, and the spinning applied voltage is too low; the discontinuous fiber can be caused by overlarge spinning applied voltage and too slow advancing speed of the spinning solution; the concentration of the spinning solution is too low, so that the solution is difficult to form fibers after being sprayed; other parameters are: the environment temperature is 20-25 ℃, the environment humidity is 40-50%, and the distance between the injection needle and the receiving plate is 10-20 cm.

The principle of the invention is as follows:

the invention compounds the organic low-melting polymer micro-nano fiber and the inorganic nano particles, and adds the viscous substance into the inorganic particle aqueous solution used in the suction filtration,the inorganic particles are dispersed on the surface of the organic fiber, and after drying, the inorganic particles and the organic fiber can be bonded together through an adhesive substance. Moreover, the invention designs a four-layer structure, wherein the uppermost layer and the lowermost layer in the four-layer structure are all ceramic SiO₂Particles, which are protected on both sides with non-conductive ceramic particles in order to prevent the conductive particles from forming pore connections which could cause internal short circuits. The inner layer is a PBS nanofiber layer, the function of the PBS nanofiber layer is firstly to provide a basic plane layer for coated inorganic particles, the low melting point of the PBS nanofiber layer plays a main role in self-closing performance, and the flexibility of the PBS nanofiber layer provides a good basis for production, transportation and application of the diaphragm. Ceramic SiO of the nanofiber layer and the uppermost layer₂The conductive particle MXene layer is arranged in the middle of the particle layer, and the main function of the conductive particle MXene layer is to increase the ionic conductivity of the diaphragm. In addition, ceramic SiO₂The particles and the conductive particle MXene layer both provide good thermal shape stability for the diaphragm at high temperature, and the organic low-melting-point polymer can be melted at low temperature to block pores, so that the self-closing performance and the thermal dimensional stability of the diaphragm can be endowed. Since the melting point of PBS is lower than that of PP and PE, PBS can melt at a lower temperature to exhibit self-shutdown properties, i.e., the self-shutdown temperature can be lowered and the thermal sensitivity can be improved.

Particularly, the polymer PBS micro-nano fiber membrane with low melting point, conductive particles and inorganic SiO for improving the ionic conductivity₂The synergistic effect of the three granules. Compared with polyolefin PP and PE films, the PBS micro-nano fiber film has higher porosity and liquid absorption rate, so that the ion transport capacity can be improved, and meanwhile, in the preparation process, the used inorganic particles are conductive particles MXene and nano-silica particles. The MXene material has good electronic conductivity (reaching 5000S/cm), mechanical property and the like, and the ionic conductivity and the service life of the diaphragm can be greatly improved by coating the MXene material; the electrophilic electrolyte property of the nano silicon dioxide particles can make up the defect of MXene sparse electrolyte, so that the wettability of the diaphragm to the electrolyte can be improved, the ionic conductivity of the diaphragm is further improved, and the electrochemical performance of the lithium battery is greatly improved.

In addition, the suction filtration mode adopted by the invention is to coat the solid in the solution on the fiber membrane by using the pressure difference between vacuum and atmospheric pressure. Therefore, the suction filtration can make the coating more uniform compared with a simple soaking method and the like, and compared with a method of only spraying the solid onto the surface of the fiber membrane, such as rotary spraying, electrostatic spraying and the like, the suction filtration coated solid has larger bonding force with the fiber membrane, and the coated solid can be more firmly fixed on the fiber membrane.

Advantageous effects

(1) The high-ionic-conductivity lithium battery diaphragm with the self-closing function has high thermal sensitivity, high thermal dimensional stability and high ionic conductivity, so that the lithium battery is high in safety and usability, and has a wide application prospect;

(2) the preparation method of the lithium battery diaphragm with the self-closing function and the high ionic conductivity has the advantages of simple process and wide application range.

Drawings

Fig. 1 is a micro-topography of the surface of the separator manufactured in example 1 after heat treatment at 110 c and 120 c, respectively.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The method for testing the liquid absorption rate comprises the following steps: soaking the prepared diaphragm (composite membrane) in electrolyte for 2h, weighing the diaphragm before and after soaking, and respectively recording as M₀And M, liquid uptake rate ═ M-M₀)/M₀×100％。

Ion conductivity test method: the diaphragm (composite membrane) is clamped between two stainless steel electrodes, an electrochemical workstation is used for electrochemical impedance measurement, the measurement frequency range is 0.1 Hz-0.1 MHz, the amplitude is 10mV, the ionic conductivity sigma is calculated according to the formula sigma ═ d/(Rb × S), wherein d is the thickness of the diaphragm, S is the sectional area, and Rb is the resistance of a Nyquist diagram at the high-frequency intercept on a real axis.

Thermal dimensional stability test method: placing the diaphragm (composite membrane) in corresponding temperature environment for 30min, and recording the areas of the diaphragm before and after heat treatment as V₀And V, heat shrinkage ═ V₀-V)/V₀×100％。

The preparation method of MXene with a lamellar structure comprises the following steps: ti is added according to the mass-to-volume ratio of 0.067g/ml₃AlC₂Adding the powder into a hydrogen fluoride solution with the mass concentration of 49 wt%, and magnetically stirring the solution at room temperature for 6 hours after ultrasonic dispersion. And (2) centrifuging the solution with water (4000r/min) after hydrofluoric acid treatment, cleaning for multiple times to remove residual hydrofluoric acid solution, stopping centrifuging until the pH value of supernatant is 7, pouring out the supernatant, dissolving the cleaned sample in 10ml of tetramethylammonium hydroxide (TMAH, 50 wt%), stirring the solution at room temperature for 10 hours under the protection of nitrogen, centrifuging for multiple times (3000-4000 r/min) with water until the supernatant is transparent, and finally adding the supernatant after multiple times of centrifugation into a conical flask, and sealing and storing with nitrogen for later use.

Example 1

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.5mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.5mg/mL₂Particles with an average particle diameter of 7nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtainTo a ceramic nanoparticle solution containing a viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 60 ℃ for 12 hours, and then carrying out rolling under the pressure of 6MPa for 2 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 1.5 mL/h; the environment temperature is 20 ℃, the environment humidity is 44%, and the distance from the injection needle to the receiving plate is 15 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 152nm, and the average diameter of the micro-fibers is 2.1 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 60 ℃, and the drying time is 55 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 6 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 60 ℃ and time is 55min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 5 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substances and the micro-nano fiber membrane in the composite membrane are determined byFixing with adhesive (styrene-butadiene latex adhesive); the porosity of the composite membrane was 52.4%. On the composite film, the density of the conductive inorganic substance is 0.08mg/cm²The density of the ceramic nanoparticles was 0.159mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 439 percent; the ionic conductivity was 3.31X 10^-3S/cm, the composite membrane has closed pores at the melting point (115 ℃) of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃, and as shown in figure 1, the composite membrane is a surface micro-topography diagram of the membrane (composite membrane) after heat treatment at 110 ℃ and 120 ℃.

Comparative example 1

A method for preparing a lithium battery diaphragm with high ionic conductivity and self-closing function, which is basically the same as the embodiment 1, and is only different from the embodiment 1 in that the applied voltage is 20kV in the electrostatic spinning process.

The prepared nano fiber is discontinuous because the voltage is too high, the fiber injection speed is too high during spinning so that the fiber is discontinuous, and the pore diameter of the nano fiber membrane is large, so that the membrane is easy to cause pore communication, thereby causing the short circuit of the battery.

Comparative example 2

A method for preparing a lithium battery separator with a self-shutdown function and high ionic conductivity, which is substantially the same as in example 1, except that in the preparation of a ceramic nanoparticle solution containing a viscous substance and a conductive inorganic substance solution containing a viscous substance, a conductive inorganic substance (MXene in a lamellar structure), and ceramic nanoparticles (hydrophilic nano SiO) are included₂Particles) to aqueous solution were all 1.5 mg/mL.

The prepared lithium battery diaphragm with the self-closing function and the high ionic conductivity has uneven distribution of the conductive inorganic substance and the ceramic nano particles.

When the lithium battery separators of example 1 and comparative example 5 are used in a battery, and under the same use conditions, when the battery corresponding to the lithium battery separator of comparative example 2 is short-circuited, the battery corresponding to example 1 is not short-circuited, because the mass-to-volume ratio of the conductive inorganic substance, the ceramic nanoparticles and the aqueous solution of comparative example 2 is too high, so that the conductive inorganic substance and the ceramic nanoparticles are not uniformly distributed in the solution, and the pore size distribution of the fiber membrane is not uniform, so that the battery separator is easy to short-circuit or has too small ionic conductivity, and the battery performance is not good.

Comparative example 3

A method for preparing a lithium battery separator having a self-shutdown function and a high ionic conductivity, which is substantially the same as in example 1, except that the concentration of the viscous substance (styrene-butadiene latex binder) in the conductive inorganic substance solution containing the viscous substance and the ceramic nanoparticle solution containing the viscous substance, both prepared in step (1), is 0.01%.

The prepared lithium battery diaphragm with the self-closing function and the high ionic conductivity is wrinkled and has low porosity, because the lithium battery diaphragm obtained in the comparative example 3 has the defects that the content of a viscous substance (styrene-butadiene latex binder) is too high, the bonding force among fibers is too high, an uneven diaphragm cannot be applied to a lithium battery, and the ionic conductivity of the diaphragm with the low porosity is too low.

Comparative example 4

A method for preparing a lithium battery separator having a self-shutdown function and a high ionic conductivity, which is substantially the same as in example 1, except that a binder (styrene-butadiene latex binder) is not added in the preparation of a ceramic nanoparticle solution containing the binder and a conductive inorganic solution containing the binder.

After the prepared high-ionic-conductivity lithium battery diaphragm with the self-closing function is kneaded, the conductive inorganic substance (MXene with a lamellar structure) and the ceramic nanoparticles (hydrophilic nano SiO) on the surface of the diaphragm₂Particles) are liable to be exfoliated and thus cause unstable battery performance as a battery separator.

Example 2

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.5mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.5mg/mL₂Particles with an average particle diameter of 10nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 60 ℃ for 12 hours, and then carrying out rolling under the pressure of 6MPa for 2 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 1.5 mL/h; the environment temperature is 20 ℃, the environment humidity is 41%, and the distance from the injection needle to the receiving plate is 15 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 135nm, and the average diameter of the micro-fibers is 1.8 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 60 ℃, and the drying time is 56 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 8 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 60 ℃ and time is 56min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 5 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 55.5%. On the composite film, the density of the conductive inorganic substance is 0.159mg/cm²The density of the ceramic nanoparticles was 0.159mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 567%; the ionic conductivity was 3.59X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.

Example 3

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.5mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.5mg/mL₂Particles with an average particle diameter of 20nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the obtained pottery containing viscous substanceThe concentration of the viscous substance in the porcelain nanoparticle solution was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 60 ℃ for 12 hours, and then carrying out rolling under the pressure of 6MPa for 2 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 1.5 mL/h; the environment temperature is 20 ℃, the environment humidity is 43%, and the distance from the injection needle to the receiving plate is 15 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 146nm, and the average diameter of the micro-fibers is 1.9 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 60 ℃, and the drying time is 57 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 8 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 60 ℃ and time is 57min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 8 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 54.3%. CompoundingThe density of the conductive inorganic substance on the film was 0.159mg/cm²The density of the ceramic nanoparticles was 0.318mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 650 percent; the ionic conductivity was 3.86X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.

Example 4

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.5mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.5mg/mL₂Particles with an average particle diameter of 40nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 60 ℃ for 12 hours, and then carrying out rolling under the pressure of 6MPa for 2 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 1.5 mL/h; the environment temperature is 20 ℃, the environment humidity is 44%, and the distance from the injection needle to the receiving plate is 15 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 155nm, and the average diameter of the micro-fibers is 2.2 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 60 ℃, and the drying time is 58 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 8 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 60 ℃ and time is 58min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 10 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 52.1%. On the composite film, the density of the conductive inorganic substance is 0.159mg/cm²The density of the ceramic nano-particles is 0.557mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 410%; the ionic conductivity was 3.46X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.

Example 5

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.5mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.5mg/mL₂Particles with an average particle diameter of 30nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 60 ℃ for 12 hours, and then carrying out rolling under the pressure of 6MPa for 2 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 1.5 mL/h; the environment temperature is 20 ℃, the environment humidity is 48%, and the distance from the injection needle to the receiving plate is 15 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 177nm, and the average diameter of the micro-fibers is 2.3 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 60 ℃, and the drying time is 59 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 10 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 60 ℃ and time is 59min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 5 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 51.7%. On the composite film, the density of the conductive inorganic substance is 0.239mg/cm²The density of the ceramic nanoparticles was 0.318mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 525%; the ionic conductivity was 3.99X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.

Example 6

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.5mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.5mg/mL₂The particles are selected from the group consisting of,average particle size of 25nm) in an aqueous solution, and mixing the aqueous solution with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 60 ℃ for 12 hours, and then carrying out rolling under the pressure of 6MPa for 2 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 22 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 1.5 mL/h; the environment temperature is 20 ℃, the environment humidity is 48%, and the distance from the injection needle to the receiving plate is 15 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 162nm, and the average diameter of the micro-fibers is 2.5 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 60 ℃, and the drying time is 62 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 12 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 60 ℃ and time is 62min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 5 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite film, four layers are sequentially a ceramic nanoparticle layer, a conductive inorganic layer and a micro-nano fiberA membrane and a ceramic nanoparticle layer; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 50.7%. On the composite film, the density of the conductive inorganic substance is 0.318mg/cm²The density of the ceramic nanoparticles was 0.318mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 444%; the ionic conductivity was 4.13X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.

Example 7

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.8mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.8mg/mL₂Particles with an average particle diameter of 27nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at 40 ℃ for 24 hours, and then carrying out rolling under the pressure of 4MPa for 3 minutes to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 18 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 15 kV; the solution propelling speed is 2 mL/h; the environment temperature is 25 ℃, the environment humidity is 50%, and the distance from the injection needle to the receiving plate is 20 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 198nm, and the average diameter of the micro-fibers is 3 microns.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 40 ℃, and the drying time is 64 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 5 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 40 ℃ and time is 64min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 6 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 50%. On the composite film, the density of the conductive inorganic substance is 0.159mg/cm²The density of the ceramic nanoparticles was 0.318mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 598%; the ionic conductivity was 3.78X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.

Example 8

A preparation method of a high-ionic conductivity lithium battery diaphragm with a self-closing function comprises the following specific steps:

(1) preparing raw materials;

preparation of a solution of conductive inorganic substances containing viscous substances:

dispersing a conductive inorganic substance (MXene with a lamellar structure) in an aqueous solution according to a mass-to-volume ratio of 0.3mg/mL, and mixing the conductive inorganic substance with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a conductive inorganic substance solution containing the viscous substance; the concentration of the viscous substance in the obtained conductive inorganic substance solution containing the viscous substance was 0.001 wt%.

Preparation of ceramic nanoparticle solution containing viscous substance:

ceramic nanoparticles (hydrophilic nano SiO) with a mass-to-volume ratio of 0.3mg/mL₂Particles with an average particle diameter of 22nm) are dispersed in an aqueous solution, and then the particles are mixed with an aqueous solution containing a viscous substance (styrene-butadiene latex binder) to obtain a ceramic nanoparticle solution containing the viscous substance; the concentration of the viscous substance in the prepared ceramic nanoparticle solution containing the viscous substance was 0.001 wt%.

Preparing a micro-nano fiber membrane:

carrying out vacuum drying on the fiber membrane prepared by the electrostatic spinning process at the temperature of 45 ℃ for 20 hours, and then carrying out rolling under the pressure of 5MPa for 1min to obtain a micro-nano fiber membrane;

the parameters of the electrostatic spinning process are as follows: the mass fraction of a solute (poly butylene succinate) in the spinning solution is 20 wt% (the solvent is a mixed solution of hexafluoroisopropanol and chloroform with the mass ratio of 1: 4), and the spinning applied voltage is 8 kV; the solution propelling speed is 1.8 mL/h; the environment temperature is 22 ℃, the environment humidity is 40%, and the distance from the injection needle to the receiving plate is 10 cm;

the average diameter of the nano-fibers in the prepared micro-nano fiber membrane is 101nm, and the average diameter of the micro-fibers is 1.5 mu m.

(2) Carrying out vacuum filtration on the conductive inorganic substance solution containing the viscous substances on one side of the micro-nano fiber membrane, and then carrying out vacuum drying (the drying temperature is 50 ℃, and the drying time is 65 min); during suction filtration, the volume of the conductive inorganic substance solution containing the viscous substances is 12 mL;

(3) carrying out vacuum filtration on the ceramic nanoparticle solution containing the viscous substances on two sides of the membrane obtained in the step (2) in sequence, and carrying out vacuum drying (drying temperature is 50 ℃ and time is 65min) after each filtration to obtain a composite membrane; during each suction filtration, the volume of the ceramic nanoparticle solution containing the viscous substances is 8 mL;

the prepared high-ionic conductivity lithium battery diaphragm with the self-closing function is made of ceramic nano particles (hydrophilic nano SiO)₂Particles), a conductive inorganic substance (MXene with a lamellar structure) and a micro-nano fiber membrane (made of pure poly butylene succinate); along the thickness direction of the composite membrane, four layers are a ceramic nanoparticle layer, a conductive inorganic layer, a micro-nano fiber membrane and a ceramic nanoparticle layer in sequence; the relative positions among the ceramic nano particles, the conductive inorganic substance and the micro-nano fiber membrane in the composite membrane are fixed by a sticky substance (styrene-butadiene latex binder); the porosity of the composite membrane was 56%. On the composite film, the density of the conductive inorganic substance is 0.159mg/cm²The density of the ceramic nanoparticles was 0.159mg/cm²(ii) a The liquid absorption rate of the composite membrane to the LiTFSI electrolyte is 576 percent; the ionic conductivity was 3.64X 10^-3S/cm; the composite membrane has closed pores at the melting point of Poly Butylene Succinate (PBS) and has no deformation at the temperature of 300 ℃.