High-performance aramid nanofiber-reinforced regenerated cellulose separator and preparation method and application thereof

Abstract

The application discloses a kind of high-performance aramid nanofiber reinforced regenerated cellulose diaphragm and its preparation method and application.The preparation method includes: aramid fiber is used as raw material, aramid nanofiber dispersion is prepared by dimethyl sulfoxide and potassium hydroxide system, and aramid nanofiber is obtained by washing and spray drying;Cellulose fiber is dissolved in cellulose solvent system to obtain cellulose solution;Aramid nanofiber, cellulose solution and pore-forming agent are blended in proportion, and high-performance aramid nanofiber reinforced regenerated cellulose diaphragm is prepared by flow casting, pre-stretching treatment, washing and drying.The diaphragm has high strength, high ionic conductivity, controllable pore structure, excellent electrolyte wettability and thermal stability, and is suitable for lithium ion battery, sodium ion battery, super capacitor, flexible energy storage device and other fields.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials and functional membrane preparation technology, specifically relating to a high-performance aramid nanofiber reinforced regenerated cellulose membrane and its preparation method and application. Background Technology

[0002] With the rapid development of electrochemical energy storage technology, the separator, as one of the core components of a battery, directly affects the battery's energy density, cycle life, and safety. Traditional polyolefin separators (such as polyethylene and polypropylene), while possessing certain mechanical strength and chemical stability, suffer from poor thermal dimensional stability, insufficient electrolyte wettability, and difficulty in degradation, making them unsuitable for the demands of high-safety, high-energy-density energy storage devices. Regenerated cellulose, derived from natural plant fibers, possesses excellent hydrophilicity, biodegradability, thermal stability, and renewability, making it an ideal green separator substrate. However, pure regenerated cellulose membranes generally suffer from insufficient mechanical strength, high brittleness, and uncontrollable pore structure, limiting their application in high-performance batteries.

[0003] Aramid nanofibers (ANFs) are considered promising nanomaterials for reinforcement due to their high specific strength, high modulus, excellent thermal stability, and chemical inertness. At the nanoscale, ANFs possess a larger specific surface area and abundant surface amide groups, enabling them to form strong interfacial interactions with polymer matrices such as cellulose, thereby effectively improving the mechanical properties and dimensional stability of composite materials. Traditional ANF preparation often relies on the prolonged dissociation of aramid fibers in a dimethyl sulfoxide / potassium hydroxide (DMSO / KOH) system. ANFs obtained through this method are prone to hydrophobic aggregation and re-agglomeration in aqueous media, making it difficult to achieve uniform dispersion and stable composites in alkaline cellulose solvents (such as alkali / urea aqueous solutions). Although protonation can improve their dispersibility in water, protonated ANFs typically use water or alcohol as the dispersion medium. Introducing protonated ANFs disrupts the solubility equilibrium of the cellulose solution, causing premature phase separation or gelation of the cellulose, leading to decreased uniformity and deterioration of film-forming properties in the blend.

[0004] Solvent-free phase separation is a commonly used film formation method, where the pore size and porosity of the membrane can be controlled by selecting the coagulation bath and process conditions. However, regenerated cellulose membranes obtained solely through phase separation often have limited mechanical strength, and their pore structure is mostly isotropic, making it difficult to simultaneously meet the requirements of high strength and high ion transport efficiency. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a high-performance aramid nanofiber reinforced regenerated cellulose membrane.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned high-performance aramid nanofiber reinforced regenerated cellulose membrane.

[0007] Another object of the present invention is to provide the application of the above-mentioned high-performance aramid nanofiber reinforced regenerated cellulose membrane.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing a high-performance aramid nanofiber-reinforced regenerated cellulose membrane includes the following steps:

[0010] (1) Preparation of aramid nanofibers: Aramid fibers were washed and dried. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide and stirred at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried to obtain dried aramid nanofibers.

[0011] (2) Preparation of cellulose solution: At a certain temperature, the required fiber raw material is added to the prepared solvent and stirred vigorously at a certain stirring rate for a period of time at this temperature to obtain a cellulose mixed solution. Then, under constant temperature conditions, the cellulose mixed solution is centrifuged to remove undissolved residual fibers and finally obtain a transparent cellulose solution.

[0012] (3) Blending and pre-stretching treatment: The aramid nanofibers obtained in step (1), the cellulose solution obtained in step (2) and the pore-forming agent are mixed evenly at room temperature. The mixture is coated on a clean substrate, and then the substrate is immersed in a coagulation bath to regenerate the film. The wet film is pre-stretched and then soaked in water or ethanol to wash away the residual solvent and pore-forming agent. After drying, the high-performance aramid nanofiber-reinforced regenerated cellulose membrane is obtained.

[0013] In the above preparation method, the present invention optimizes the post-processing process and obtains dry ANFs that are easy to store and weigh by means of spray drying technology. Due to their good redispersibility and surface activity, the dried ANFs can be uniformly and stably compounded with cellulose solution by mechanical stirring, thereby effectively avoiding agglomeration and giving full play to their nano-reinforcing effect, laying the foundation for the construction of high-performance composite membranes.

[0014] Furthermore, this invention introduces a controllable pre-stretching process after wet membrane formation. This process allows the cellulose molecular chains and the aramid nanofibers dispersed within them to align along the stretching direction, significantly improving the tensile strength and modulus of the membrane in the orientation direction. It also facilitates the formation of elongated pore structures that are more conducive to longitudinal ion transport after the pore-forming agent is eluted. Therefore, combining non-solvent-induced phase separation with directional pre-stretching in the construction of aramid nanofiber-reinforced regenerated cellulose membranes can synergistically optimize the membrane's mechanical properties and ion conduction characteristics, thus providing an effective approach for developing energy storage device membranes that combine high safety and high electrochemical performance.

[0015] Preferably, the aramid fiber mentioned in step (1) is at least one of fully aromatic polyamide fiber or heterocyclic aromatic polyamide fiber.

[0016] Preferably, the drying temperature in step (1) is 60~105℃ and the time is 2~12h; preferably, the drying temperature is 105℃ and the time is 8h.

[0017] Preferably, the mass ratio of aramid fiber, potassium hydroxide and dimethyl sulfoxide in step (1) is (1~10):(1~10):(50~1000); more preferably it is 2:3:98.

[0018] Preferably, the stirring speed in step (1) is 100~10000 rpm and the time is 1~10 days; preferably, the stirring speed is 1000 rpm and the time is 7 days.

[0019] Preferably, the concentration of the aramid nanofiber dispersion obtained in step (1) is 0.1~5wt%; more preferably 2wt%.

[0020] Preferably, the cleaning in step (1) involves cleaning the aramid fibers sequentially with acetone, ethanol, and deionized water.

[0021] Preferably, the washing in step (1) is performed by alternating washing with anhydrous ethanol and water 1 to 10 times; more preferably, it is performed by alternating washing with anhydrous ethanol and water 3 to 5 times.

[0022] Preferably, the inlet air temperature of the spray drying in step (1) is 100~220℃, the outlet air temperature is 60~100℃, and the drying time is 1~300s; preferably, the inlet air temperature is 180℃, the outlet air temperature is 75℃, and the drying time is 30s.

[0023] Preferably, the solvent in step (2) is at least one of ionic liquid, N-methylmorpholine-N-oxide aqueous solution, alkali / urea aqueous solution or lithium chloride / dimethylacetamide, and eutectic solvent system; preferably, it is an alkali / urea aqueous solution system, wherein the alkali is sodium hydroxide, and the mass ratio of sodium hydroxide, urea and water is 7:12:81.

[0024] Preferably, the fiber raw material in step (2) is at least one of cotton pulp, wood pulp, bamboo pulp, hemp pulp, and dissolving pulp; preferably cotton pulp, with an addition amount of 6 wt%.

[0025] Preferably, the dissolution temperature in step (2) is -18~120℃, the stirring rate is 100~10000rpm, and the stirring time is 1~10h; more preferably, the dissolution temperature is -12℃, the stirring rate is 1000rpm, and the stirring time is 1h.

[0026] Preferably, the centrifugation speed in step (2) is 1000~10000 rpm, the centrifugation temperature is 0~25℃, the centrifugation time is 1~60 min, and the concentration of the obtained cellulose solution is 1~10 wt%; preferably, the centrifugation speed is 10000 rpm, the temperature is 5℃, the time is 20 min, and the concentration of the cellulose solution is 4 wt%.

[0027] Preferably, the mass ratio of aramid nanofibers to cellulose in step (3) is (0~10):(1~10); more preferably (1~4):10.

[0028] Preferably, the pore-forming agent in step (3) is at least one of polyethylene glycol, polyvinylpyrrolidone, and sodium chloride, and the amount of pore-forming agent added is 10% to 100% of the dry weight of cellulose; preferably, polyethylene glycol-200 or polyethylene glycol-600, and the amount added is 30% to 60% of the dry weight of cellulose.

[0029] Preferably, the mixing method in step (3) is mechanical stirring, with a speed of 100~1000 rpm and a time of 1~6 h; preferably, the speed is 300 rpm and the time is 2 h.

[0030] Preferably, the coating rate in step (3) is 1~10cm / s and the thickness is 10~600μm; more preferably, the coating rate is 5cm / s and the thickness is 400μm.

[0031] Preferably, the coagulation bath used in step (3) is at least one of water, ethanol, aqueous ethanol solution, acetone, aqueous acetone solution, aqueous sulfuric acid solution, aqueous sodium sulfate solution, aqueous sulfuric acid / sodium sulfate solution, aqueous sulfuric acid / sodium sulfate / zinc sulfate solution, aqueous ammonium sulfate solution, and aqueous acetic acid solution; preferably, it is an aqueous sulfuric acid / sodium sulfate solution, with the mass fractions of sulfuric acid and sodium sulfate being 5 wt% and 5~15 wt%, respectively.

[0032] Preferably, the regeneration time in the coagulation bath in step (3) is 1 to 30 minutes; preferably 5 minutes.

[0033] Preferably, the stretching ratio of the pre-stretching treatment in step (3) is 1~3, the stretching temperature is 25~120℃, and the stretching time is 1~30min; more preferably, the stretching ratio is 2, the stretching temperature is 25℃, and the stretching time is 10min.

[0034] Preferably, the soaking time in step (3) is 24 to 96 hours, with the water or ethanol changed every 6 hours; more preferably, the soaking time is 48 hours, with the water or ethanol changed every 6 hours.

[0035] Preferably, the drying temperature in step (3) is 25~100℃ and the drying time is 1~96h; preferably, the drying temperature is 25℃ and the drying time is 48h.

[0036] The aforementioned high-performance aramid nanofiber-reinforced regenerated cellulose membrane can be applied in fields such as lithium-ion batteries, sodium-ion batteries, supercapacitors, and flexible energy storage devices.

[0037] The present invention has the following advantages and effects compared with the prior art:

[0038] 1. This invention obtains dry aramid nanofibers with good redispersibility by spray drying an aramid nanofiber dispersion. The nanofibers can be uniformly and stably composited with cellulose solution through mechanical stirring. The abundant amide groups on the surface of the aramid nanofibers can form a dense hydrogen bond network with the hydroxyl groups of cellulose, constructing a stable three-dimensional nano-reinforced skeleton, which significantly improves the tensile strength and elongation at break of the membrane, and inhibits the brittle fracture tendency of cellulose through interfacial synergistic effect, thereby enhancing the overall toughness and dimensional stability of the material.

[0039] 2. This invention utilizes a non-solvent-induced phase separation method to form a film, with polyethylene glycol added as a pore-forming agent. When the cast film is immersed in a coagulation bath, the solvent and non-solvent undergo rapid exchange, initiating phase separation and solidifying the cellulose into a gel network. Simultaneously, the hydrophilic pore-forming agent is selectively washed out in the coagulation bath, leaving regular micro- and nano-pores in situ. By adjusting the molecular weight and addition ratio of the pore-forming agent, the porosity, pore size, and their distribution can be precisely controlled.

[0040] 3. In the wet film stage, the present invention performs a pre-stretching treatment. Under the directional traction of external force, the cellulose molecular chains and the aramid nanofibers dispersed therein will undergo preferential orientation alignment along the stretching direction. This process not only improves the orderliness of the components, but also straightens the molecular chains and straightens the fibers at the microscopic level, and promotes the reconstruction and strengthening of secondary valence bonds such as hydrogen bonds in the orientation direction, which greatly improves the strength and modulus of the membrane in the stretching direction. At the same time, it also helps to form ellipsoidal or slit-like structures that are more conducive to the longitudinal transport of ions after the pore-forming agent is washed out, further reducing the resistance to ion migration.

[0041] 4. The main raw material used in this invention is renewable cellulose, the solvent can be recycled, the pore-forming agent can be eluted, and the process is environmentally friendly and meets the requirements of sustainable development.

[0042] 5. The high-performance aramid nanofiber-reinforced regenerated cellulose membrane prepared in this invention can be widely used in lithium-ion batteries, sodium-ion batteries, supercapacitors, flexible energy storage devices and other fields. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the preparation process of the high-performance aramid nanofiber reinforced regenerated cellulose membrane in Example 1 of the present invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Test methods in the following embodiments that do not specify specific experimental conditions are generally performed according to conventional experimental conditions or the experimental conditions recommended by the manufacturer. Unless otherwise specified, the starting materials in the preparation methods of the present invention can be purchased from the market or prepared according to existing technical methods.

[0045] In the embodiments and comparative examples of this invention, tensile strength and elongation at break were tested according to GB / T36363-2018 standard. Ionic conductivity was obtained by assembling a stainless steel (SS) symmetric cell and performing electrochemical impedance spectroscopy (EIS) on an electrochemical workstation, and calculated from the impedance value in the high-frequency region.

[0046] To evaluate the electrochemical performance of the separators, the separators prepared in the examples and control examples were tested in lithium-ion batteries. The specific steps are as follows:

[0047] (1) Preparation of positive electrode sheet: The active material (lithium iron phosphate LiFePO4), conductive agent (acetylene black) and binder (polyvinylidene fluoride PVDF) are mixed in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) is added to prepare a slurry, which is uniformly coated on aluminum foil. After drying, rolling and punching, the positive electrode sheet is obtained.

[0048] (2) Battery assembly: Assemble the R2032 button battery in an argon-filled glove box. The assembly sequence is as follows: negative electrode shell, lithium sheet, separator, electrolyte, positive electrode sheet, gasket, spring sheet, positive electrode shell. The electrolyte is a 1 mol / L lithium hexafluorophosphate (LiPF6) solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) / diethyl carbonate (DEC) (mass ratio 1:1:1).

[0049] (3) Battery performance test: After the battery assembled in step (2) was left to stand for 12 hours, it was activated (2 charge-discharge cycles) under the conditions of a voltage range of 2.5-4.2 V and a current density of 0.2 C. Subsequently, the cycle stability of the battery was tested at 0.5 C (200 charge-discharge cycles). In the rate performance test, the discharge current densities were 0.2 C, 0.5 C, 1.0 C, 2.0 C, 5.0 C and 0.2 C, and the charging current density was fixed at 0.2 C. The cyclic voltammetry curve was tested at a voltage of 2.3-4.5 V, with the scanning direction being the positive electrode direction and the scanning rate being 0.2 mV / s.

[0050] Example 1

[0051] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0052] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0053] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0054] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 10% of the dry weight of the cellulose. Polyethylene glycol-200 of 30% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 hours at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for 5 min to regenerate. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 16 ± 2 μm.

[0055] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 128.5 MPa, 12.4%, and 1.58 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 90.8%, and the capacity retention after 200 cycles at 0.5C was 89.2%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 162.5 mAh / g, 155.2 mAh / g, 147.8 mAh / g, 135.6 mAh / g, and 110.3 mAh / g, respectively. The discharge specific capacity at 0.2C was 160.1 mAh / g.

[0056] Example 2

[0057] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0058] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0059] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0060] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 25% of the dry weight of the cellulose. Polyethylene glycol-200 of 30% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for regeneration for 5 min. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 17 ± 1 μm.

[0061] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 152.8 MPa, 15.6%, and 1.42 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 91.6%, and the capacity retention after 200 cycles at 0.5C was 93.5%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 160.8 mAh / g, 152.0 mAh / g, 144.8 mAh / g, 132.1 mAh / g, and 105.6 mAh / g, respectively. The discharge specific capacity at 0.2C was 159.2 mAh / g.

[0062] Example 3

[0063] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0064] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0065] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0066] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 40% of the dry weight of the cellulose. Polyethylene glycol-200 of 30% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for 5 min to regenerate. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 24 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 18 ± 2 μm.

[0067] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 146.3 MPa, 14.1%, and 1.32 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 91.9%, and the capacity retention after 200 cycles at 0.5C was 92.8%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 159.2 mAh / g, 150.5 mAh / g, 142.1 mAh / g, 128.4 mAh / g, and 100.2 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 157.4 mAh / g.

[0068] Example 4

[0069] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0070] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0071] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0072] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 25% of the dry weight of the cellulose. Polyethylene glycol-200 of 60% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for 5 min to regenerate. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 19 ± 2 μm.

[0073] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 118.5 MPa, 11.8%, and 1.95 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 89.8%, and the capacity retention after 200 cycles at 0.5C was 87.5%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 163.5 mAh / g, 157.2 mAh / g, 150.8 mAh / g, 140.5 mAh / g, and 118.0 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 159.8 mAh / g.

[0074] Example 5

[0075] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0076] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0077] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0078] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 25% of the dry weight of the cellulose. Polyethylene glycol-600 of 30% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 15 wt% sodium sulfate solution for regeneration for 5 min. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 16 ± 1 μm.

[0079] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 148.2 MPa, 15.0%, and 1.48 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 91.8%, and the capacity retention after 200 cycles at 0.5C was 92.9%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 161.2 mAh / g, 153.1 mAh / g, 145.6 mAh / g, 133.0 mAh / g, and 107.3 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 159.6 mAh / g.

[0080] Example 6

[0081] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0082] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0083] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0084] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 25% of the dry weight of the cellulose. Polyethylene glycol-200 of 30% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 15 wt% sodium sulfate solution for regeneration for 5 min. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 60 °C for 24 h to obtain the high-performance aramid nanofiber reinforced regenerated cellulose membrane with a thickness of 15 ± 1 μm.

[0085] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 158.0 MPa, 14.2%, and 1.38 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 91.3%, and the capacity retention after 200 cycles at 0.5C was 91.5%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 159.5 mAh / g, 151.0 mAh / g, 143.2 mAh / g, 129.8 mAh / g, and 103.5 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 157.9 mAh / g.

[0086] Compare with Example 1

[0087] A high-performance regenerated cellulose membrane is prepared by the following method:

[0088] (1) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1h at this temperature at a stirring rate of 1000rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20min (10000rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0089] (2) Regenerated membrane and pre-stretching treatment: 30% of the dry weight of polyethylene glycol-200 was added to the prepared cellulose solution and stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for 5 min to regenerate. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber reinforced regenerated cellulose membrane with a thickness of 15 ± 1 μm.

[0090] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 85.2 MPa, 5.2%, and 1.70 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 88.8%, and the capacity retention after 200 cycles at 0.5C was 82.5%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 158.5 mAh / g, 148.2 mAh / g, 137.2 mAh / g, 118.3 mAh / g, and 88.5 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 154.5 mAh / g.

[0091] Compare with Example 2

[0092] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0093] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0094] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0095] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 25% of the dry weight of the cellulose. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for 5 min to regenerate. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 16 ± 1 μm.

[0096] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 158.4 MPa, 16.5%, and 1.10 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 89.5%, and the capacity retention after 200 cycles at 0.5C was 93.8%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 151.1 mAh / g, 135.5 mAh / g, 116.8 mAh / g, 90.2 mAh / g, and 55.6 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 148.1 mAh / g.

[0097] Compare with Example 3

[0098] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0099] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0100] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0101] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above are mixed evenly. The mass of the aramid nanofibers is 25% of the dry weight of the cellulose. At the same time, polyethylene glycol-200 of 30% of the dry weight of the cellulose is added. The mixture is stirred at 300 rpm for 2 hours at room temperature to obtain a uniform blend. The blend is uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate is then immersed in a 5 wt% sulfuric acid / 5 wt% sodium sulfate solution for 5 min to regenerate. After the membrane is regenerated, the wet membrane is soaked in deionized water for 48 hours (the water is changed every 6 hours) to wash away residual solvent and pore-forming agent. The wet membrane is dried at 25°C for 48 hours to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 20 ± 2 μm.

[0102] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 122.3 MPa, 13.5%, and 1.36 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 91.2%, and the capacity retention after 200 cycles at 0.5C was 88.1%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 160.1 mAh / g, 149.5 mAh / g, 141.4 mAh / g, 127.2 mAh / g, and 100.1 mAh / g, respectively. The discharge specific capacity at 0.2C was 157.4 mAh / g.

[0103] Compare with Example 4

[0104] A high-performance aramid nanofiber-reinforced regenerated cellulose membrane is prepared by the following method:

[0105] (1) Preparation of aramid nanofibers: Aramid fibers were washed sequentially with acetone, ethanol and deionized water. After washing, the aramid fibers were dried in an oven at 105°C for 8 hours. Then, the dried aramid fibers and potassium hydroxide were added to dimethyl sulfoxide (mass ratio 2:3:98). The mixture was magnetically stirred at 1000 rpm for 7 days at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed 3-5 times with anhydrous ethanol and water under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 75°C and a drying time of 30s to obtain dried aramid nanofibers, which were then stored for later use.

[0106] (2) Preparation of cellulose solution: The mixed solvent containing 7wt% sodium hydroxide / 12wt% urea / 81wt% water was pre-cooled to -12℃ in a refrigerator, and the well dispersed cotton pulp was added. The mixture was stirred vigorously for 1 hour at this temperature at a stirring rate of 1000 rpm to obtain a semi-transparent cellulose mixed solution. Then, the cellulose mixed solution was centrifuged for 20 minutes (10000 rpm) at a constant temperature of 5℃ to remove undissolved residual fibers. Finally, a transparent cellulose solution was obtained, collected and stored in a refrigerator for later use.

[0107] (3) Blending and pre-stretching treatment: The aramid nanofibers and cellulose solution prepared above were mixed evenly. The mass of the aramid nanofibers was 25% of the dry weight of the cellulose. Polyethylene glycol-200 of 30% of the dry weight of the cellulose was added at the same time. The mixture was stirred at 300 rpm for 2 h at room temperature to obtain a uniform blend. The blend was uniformly coated on a clean glass plate at a speed of 5 cm / s and a thickness of 400 μm using a doctor blade coater. The glass plate was then immersed in deionized water for 5 min to regenerate. After the membrane was regenerated, the wet membrane was pre-stretched at room temperature with a stretching ratio of 2 and a stretching time of 10 min. The wet membrane was then soaked in deionized water for 48 h (the water was changed every 6 h) to wash away residual solvent and pore-forming agent. The wet membrane was dried at 25 °C for 48 h to obtain the high-performance aramid nanofiber-reinforced regenerated cellulose membrane with a thickness of 22 ± 2 μm.

[0108] The performance of the high-performance aramid nanofiber-reinforced regenerated cellulose separator was tested, and the tensile strength, elongation at break, and ionic conductivity were 118.8 MPa, 14.1%, and 1.38 mS / cm, respectively. The separator was assembled into a lithium-ion battery for testing. The initial coulombic efficiency was 90.5%, and the capacity retention after 200 cycles at 0.5C was 86.5%. The discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C were 158.1 mAh / g, 148.2 mAh / g, 139.5 mAh / g, 125.7 mAh / g, and 97.1 mAh / g, respectively. The discharge specific capacity after returning to 0.2C was 154.8 mAh / g.

[0109] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance aramid nanofiber-reinforced regenerated cellulose membrane, characterized in that... Includes the following steps: (1) The aramid fiber was washed and dried. Then, the dried aramid fiber and potassium hydroxide were added to dimethyl sulfoxide and stirred at room temperature to obtain an aramid nanofiber dispersion. The dispersion was washed under vacuum filtration until the filtrate was neutral. After washing, the dispersion was spray-dried to obtain dried aramid nanofibers. (2) Add the fiber raw material to the solvent, stir to dissolve and obtain a cellulose mixed solution, then centrifuge the cellulose mixed solution to remove undissolved residual fibers, and finally obtain a transparent cellulose solution; (3) Blending and pre-stretching treatment: The aramid nanofibers obtained in step (1), the cellulose solution obtained in step (2) and the pore-forming agent are mixed evenly at room temperature. The mixture is coated on the substrate, and then the substrate is immersed in a coagulation bath to regenerate the film. The wet film is pre-stretched and then soaked in water or ethanol to wash away the residual solvent and pore-forming agent. After drying, the high-performance aramid nanofiber-reinforced regenerated cellulose membrane is obtained.

2. The preparation method according to claim 1, characterized in that: The aramid fiber mentioned in step (1) is at least one of fully aromatic polyamide fiber or heterocyclic aromatic polyamide fiber; the drying temperature is 60~105℃ and the time is 2~12h.

3. The preparation method according to claim 1, characterized in that: The mass ratio of aramid fiber, potassium hydroxide and dimethyl sulfoxide in step (1) is (1~10):(1~10):(50~500); the stirring speed is 100~10000 rpm and the time is 1~10 days; the concentration of the obtained aramid nanofiber dispersion is 0.1~5wt%; the washing refers to washing with anhydrous ethanol and water alternately 1~10 times; the inlet air temperature of the spray drying is 100~220℃, the outlet air temperature is 60~100℃, and the drying time is 1~300s.

4. The preparation method according to claim 1, characterized in that: The solvent mentioned in step (2) is at least one of ionic liquid, N-methylmorpholine-N-oxide aqueous solution, alkali / urea aqueous solution or lithium chloride / dimethylacetamide, and eutectic solvent system; the fiber raw material is at least one of cotton pulp, wood pulp, bamboo pulp, hemp pulp, and dissolving pulp; the stirring and dissolving temperature is -18~120℃, the stirring rate is 100~10000rpm, and the stirring time is 1~10h.

5. The preparation method according to claim 1, characterized in that: In step (2), the centrifugation speed is 1000~10000 rpm, the centrifugation temperature is 0~25℃, the centrifugation time is 1~60 min, and the concentration of the obtained cellulose solution is 1~10 wt%.

6. The preparation method according to claim 1, characterized in that: The dry weight ratio of aramid nanofibers to cellulose in step (3) is (0~10):(1~10); the pore-forming agent is at least one of polyethylene glycol, polyvinylpyrrolidone, and sodium chloride, and the amount of pore-forming agent added is 10%~100% of the dry weight of cellulose; the mixing method is mechanical stirring, the speed is 100~1000 rpm, and the time is 1~6h.

7. The preparation method according to claim 1, characterized in that: The coating rate in step (3) is 1~10 cm / s and the thickness is 10~600 μm; the coagulation bath used for regenerating the membrane is at least one of water, ethanol, aqueous ethanol solution, acetone, aqueous acetone solution, aqueous sulfuric acid solution, aqueous sodium sulfate solution, aqueous sulfuric acid / sodium sulfate solution, aqueous sulfuric acid / sodium sulfate / zinc sulfate solution, aqueous ammonium sulfate solution, and aqueous acetic acid solution; the regeneration time in the coagulation bath is 1~30 min; the stretching ratio of the pre-stretching treatment is 1~3, the stretching temperature is 25~120℃, and the stretching time is 1~30 min.

8. The preparation method according to claim 1, characterized in that: The soaking time in step (3) is 24~96h, and the water or ethanol is changed every 6h; the drying temperature is 25~100℃, and the drying time is 1~96h.

9. A high-performance aramid nanofiber-reinforced regenerated cellulose membrane, characterized in that: It is prepared by the method described in any one of claims 1 to 8.

10. The application of the high-performance aramid nanofiber reinforced regenerated cellulose separator according to claim 9 in lithium-ion batteries, sodium-ion batteries, supercapacitors or flexible energy storage devices.

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