CN114142159B - Polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm and preparation method and application thereof - Google Patents

Polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm and preparation method and application thereof Download PDF

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CN114142159B
CN114142159B CN202111368879.1A CN202111368879A CN114142159B CN 114142159 B CN114142159 B CN 114142159B CN 202111368879 A CN202111368879 A CN 202111368879A CN 114142159 B CN114142159 B CN 114142159B
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polyacrylonitrile
cellulose
hydroxyapatite
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composite membrane
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CN114142159A (en
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王翔
陈伟平
王钧
段华军
杨小利
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Wuhan University of Technology WUT
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
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    • D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
    • D06M11/68—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with phosphorus or compounds thereof, e.g. with chlorophosphonic acid or salts thereof
    • D06M11/70—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with phosphorus or compounds thereof, e.g. with chlorophosphonic acid or salts thereof with oxides of phosphorus; with hypophosphorous, phosphorous or phosphoric acids or their salts
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    • D06M15/01—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with natural macromolecular compounds or derivatives thereof
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    • D06M15/05—Cellulose or derivatives thereof
    • D06M15/07—Cellulose esters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
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    • D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
    • D06M2101/16—Synthetic fibres, other than mineral fibres
    • D06M2101/18—Synthetic fibres consisting of macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D06M2101/26—Polymers or copolymers of unsaturated carboxylic acids or derivatives thereof
    • D06M2101/28—Acrylonitrile; Methacrylonitrile
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The invention discloses a polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm and a preparation method and application thereof. The preparation method of the polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm comprises the following steps: (1) Preparing a polyacrylonitrile nanofiber membrane by adopting electrostatic spinning and hot pressing; (2) Adding hydroxyapatite and a dispersant into an organic solvent, stirring and ultrasonically mixing uniformly to obtain a hydroxyapatite dispersion liquid; adding cellulose into the hydroxyapatite dispersion liquid, and uniformly mixing to prepare a hydroxyapatite cellulose solution; (3) And (3) soaking the polyacrylonitrile nano-fiber membrane in the step (1) into the cellulose solution of the hydroxyapatite in the step (2), and then taking out and drying in vacuum. The preparation method provided by the invention is simple, convenient and efficient, overcomes the defects of poor thermal stability, poor electrolyte compatibility and the like of the polyolefin diaphragm, meets the requirement of large-scale production, and has important market value.

Description

Polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm and preparation method and application thereof
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm and a preparation method and application thereof.
Background
The development of sustainable energy storage technology is one of the powerful measures to alleviate the contradiction between economic development and environmental protection. Lithium batteries, as rechargeable batteries, are an important development direction for electrical energy storage technology. The lithium battery consists of a positive electrode, a negative electrode, electrolyte, a diaphragm and an external packaging material; the diaphragm not only isolates the positive electrode and the negative electrode, but also avoids safety accidents such as battery ignition and explosion caused by short circuit caused by direct contact; the battery is also provided with pores, so that lithium ions can smoothly migrate back and forth on two sides in the charging and discharging processes of the battery. The separator plays an important role in the safety and stability of the lithium battery.
The polyolefin diaphragm of polyethylene, polypropylene and the like has the advantages of low cost, regular chemical structure, high mechanical strength and the like, and is widely applied to the manufacture of commercial lithium batteries. However, due to the low melting point, the size of the diaphragm shrinks under a high-temperature environment, so that the anode and the cathode are in direct contact, short circuit is caused, and safety accidents such as fire, explosion and the like are caused. On the other hand, the molecular structure of the polyolefin diaphragm has no polar group, the hydrophilicity is poor, the polyolefin diaphragm cannot be fully infiltrated by electrolyte, the electrolyte retention rate is low, the migration of lithium ions is difficult, and the comprehensive performance of the lithium battery is influenced.
In order to improve the thermal stability and electrochemical performance of lithium batteries, polymer electrolyte membranes may be used instead of conventional polyolefin separators. The polymer electrolyte membrane can solve the safety problems of electrolyte leakage and the like caused by thermal shrinkage to a great extent. Polyacrylonitrile (PAN) is a commonly used polymer electrolyte membrane substrate, having excellent thermal properties; the cyano group in the molecular structure can interact with the lithium ion in the electrolyte, is compatible with the electrolyte and improves the electrochemical performance. But the electrostatic spinning polyacrylonitrile fiber membrane has low mechanical strength and certain application limitation. Therefore, the method has important market value for improving the mechanical strength of the polyacrylonitrile membrane and further improving the electrochemical performance by a simple and efficient method.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm and a preparation method and application thereof, and solves the problems of poor thermal stability and poor electrolyte compatibility of the existing polyolefin diaphragm.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm comprises the following steps:
(1) Preparing a polyacrylonitrile nanofiber membrane by adopting electrostatic spinning and hot pressing;
(2) Adding hydroxyapatite and a dispersant into an organic solvent, stirring and ultrasonically mixing uniformly to obtain a hydroxyapatite dispersion liquid; adding cellulose into the hydroxyapatite dispersion liquid, and uniformly mixing to prepare a hydroxyapatite cellulose solution;
(3) And (3) soaking the polyacrylonitrile nano-fiber membrane in the step (1) into the cellulose solution of the hydroxyapatite in the step (2), and then taking out and drying in vacuum.
Preferably, the electrostatic spinning and hot pressing treatment in step (1) is carried out in the following manner: adding polyacrylonitrile powder into the organic solution, stirring at 40-80 ℃ to obtain spinning solution, spinning to obtain a polyacrylonitrile fiber membrane, and hot-pressing the polyacrylonitrile fiber membrane at 90-125 ℃ for 15-40 min.
Preferably, the concentration of the polyacrylonitrile powder in the organic solvent is 0.095-0.18 g/mL.
Preferably, the polyacrylonitrile has a relative molecular mass of 80000 to 250000.
Preferably, the organic solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran and dichloromethane.
Preferably, the organic solvent in step (2) is at least one of formic acid, acetone, methanol, dioxane and chloroform.
Preferably, the ratio of the organic solvent, the hydroxyapatite, the cellulose and the dispersant in the step (2) is 100: 0.5-1.5.
Preferably, the average particle size of the hydroxyapatite in the step (A) is 20 to 60nm.
Preferably, the cellulose is at least one of methyl cellulose, cellulose acetate, hydroxymethyl cellulose and cellulose triacetate.
Preferably, the dispersant is at least one of polyethylene glycol 400, polyethylene glycol 2000, polyethylene glycol 4000 and polyvinylpyrrolidone (K30).
Preferably, the dipping time in the step (3) is 15-30 min, the vacuum drying temperature is 50-80 ℃, and the vacuum drying time is 12-18 h.
The polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm prepared by the preparation method of the polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm.
The polyacrylonitrile/cellulose/hydroxyapatite composite diaphragm is applied to the preparation of lithium ion battery diaphragms.
Compared with the prior art, the invention has the beneficial effects that:
(1) The nano-hydroxyapatite adopted by the invention has small and uniform particle size, large specific surface area and high surface activity, is adsorbed on polyacrylonitrile nano-fiber filaments, can reduce the crystallinity of polyacrylonitrile, increase the surface activity and ion channels of the membrane and increase the migration efficiency of lithium ions.
(2) The cellulose adopted by the invention is used as a thermoplastic polymer and can play a role of a binder, so that polyacrylonitrile nano-fiber yarns are mutually interacted to generate adhesion, and the mechanical strength of the membrane is increased.
(3) According to the invention, the polyacrylonitrile nano-fiber membrane is modified by combining nano-hydroxyapatite and cellulose, so that the prepared polyacrylonitrile composite membrane not only makes up for the defect of insufficient mechanical strength, but also has excellent thermal stability at high temperature; the pore distribution is reasonable, the absorption rate of the electrolyte is high, and the electrolyte has stable multiplying power and cycle performance.
(4) The preparation method provided by the invention is simple, convenient and efficient, overcomes the defects of poor thermal stability, poor electrolyte compatibility and the like of the polyolefin diaphragm, meets the requirement of large-scale production, and has important market value.
Drawings
Fig. 1 is an SEM plan view of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1.
Fig. 2 is an SEM plan view of the polyacrylonitrile lithium battery separator prepared in comparative example 1.
Fig. 3 is a thermogravimetric plot of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1.
Fig. 4 is a discharge specific capacity-cycle diagram of a button lithium battery assembled by the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1, which is cycled for 50 cycles under a voltage range of 2.5-4.2V and a multiplying power of 0.5C.
Fig. 5 is a discharge specific capacity-rate diagram of a button lithium battery assembled by the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1, which is cycled for 5 cycles under the multiplying power of 0.2C, 0.5C, 1C, 2C and 0.2C in the voltage range of 2.5-4.2V.
Fig. 6 is a voltage-charge/discharge specific capacity diagram of a button lithium battery assembled by the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1 after the first charge and discharge cycle at 0.2C, 0.5C, 1C and 2C multiplying power in a voltage range of 2.5-4.2V.
Fig. 7 is a process flow diagram of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
Adding 10.49g of vacuum-dried polyacrylonitrile powder into 100.00ml of N, N-dimethylformamide solvent, and magnetically stirring for 8 hours at 60 ℃ to prepare polyacrylonitrile spinning solution; 5ml of the spinning solution is extracted by a 10ml disposable medical injector, and is placed in a pushing device of an electrostatic spinning instrument, and electrostatic spinning is carried out for 4 hours by a No. 20 spinning needle head according to spinning parameters of positive voltage of 16.00KV, negative voltage of 2.00KV, receiving distance of 15cm and pushing speed of 0.09mm/min, so as to prepare the polyacrylonitrile fiber membrane with the average diameter of 310 nm. Cutting the membrane into 10cm in length and width, placing the membrane between stainless steel plates, clamping the membrane by a G-shaped clamp, and placing the membrane in a blast drying oven at 120 ℃ for hot pressing for 35min to obtain the polyacrylonitrile nanofiber membrane with the thickness maintained within the range of 30-55 mu m.
Adding 1.50g of nano hydroxyapatite and 0.09g of polyethylene glycol 2000 dispersant into 190.36ml of acetone solution, and performing ultrasonic treatment for 2 hours to obtain nano hydroxyapatite dispersion. Adding 7.5g of cellulose acetate into the dispersion, and magnetically stirring for 12 hours at room temperature to obtain a cellulose acetate solution with uniformly dispersed nano-hydroxyapatite. And (3) soaking the polyacrylonitrile nanofiber membrane subjected to hot pressing in the solution for 30min, then placing the polyacrylonitrile nanofiber membrane in a vacuum drying oven, vacuumizing, and drying at 80 ℃ for 18h to obtain the polyacrylonitrile/cellulose/hydroxyapatite composite membrane.
Example 2
10.49g of polyacrylonitrile powder which is dried in vacuum is added into 100.00ml of N, N-dimethylformamide solvent, and magnetic stirring is carried out for 8 hours at the temperature of 60 ℃ to prepare the polyacrylonitrile spinning solution. 5ml of the spinning solution is extracted by a 10ml disposable medical injector, and is placed in a pushing device of an electrostatic spinning instrument, and electrostatic spinning is carried out for 4 hours by a No. 20 spinning needle head according to spinning parameters of positive voltage of 16.00KV, negative voltage of 2.00KV, receiving distance of 15cm and pushing speed of 0.09mm/min, so as to prepare the polyacrylonitrile fiber membrane with the average diameter of 310 nm. Cutting the membrane into 10cm long and wide, placing between stainless steel plates, clamping with G-shaped clamp, and hot pressing in 120 deg.C blast drying oven for 35min to obtain polyacrylonitrile fiber membrane with thickness of 30-55 μm.
0.75g of nano-hydroxyapatite and 0.03g of polyethylene glycol 2000 dispersant are added into 190.36ml of acetone solution, and the nano-hydroxyapatite dispersion liquid is obtained after 2 hours of ultrasonic treatment. Adding 7.5g of cellulose acetate into the dispersion, and magnetically stirring for 12 hours at room temperature to obtain a cellulose acetate solution with uniformly dispersed nano-hydroxyapatite. And (3) soaking the polyacrylonitrile nanofiber membrane subjected to hot pressing in the solution for 30min, then placing the polyacrylonitrile nanofiber membrane in a vacuum drying oven, vacuumizing, and drying at 80 ℃ for 18h to obtain the polyacrylonitrile/cellulose/hydroxyapatite composite membrane.
Example 3
10.49g of polyacrylonitrile powder which is dried in vacuum is added into 100.00ml of N, N-dimethylformamide solvent, and magnetic stirring is carried out for 8 hours at the temperature of 60 ℃ to prepare the polyacrylonitrile spinning solution. 5ml of the spinning solution is extracted by a 10ml disposable medical injector, and is placed in a pushing device of an electrostatic spinning instrument, and electrostatic spinning is carried out for 4 hours by a No. 20 spinning needle head according to spinning parameters of positive voltage of 16.00KV, negative voltage of 2.00KV, receiving distance of 15cm and pushing speed of 0.09mm/min, so as to prepare the polyacrylonitrile fiber membrane with the average diameter of 310 nm. Cutting the membrane into 10cm long and wide, placing between stainless steel plates, clamping with G-shaped clamp, and hot pressing in 120 deg.C blast drying oven for 35min to obtain polyacrylonitrile fiber membrane with thickness of 30-55 μm.
2.25g of nano hydroxyapatite and 1.5g of polyethylene glycol 2000 dispersant are added into 190.36ml of acetone solution, and ultrasonic treatment is carried out for 2 hours to obtain nano hydroxyapatite dispersion. Adding 7.5g of cellulose acetate into the dispersion, and magnetically stirring for 12 hours at room temperature to obtain a cellulose acetate solution with uniformly dispersed nano-hydroxyapatite. And (3) soaking the polyacrylonitrile nanofiber membrane subjected to hot pressing in the solution for 30min, then placing the polyacrylonitrile nanofiber membrane in a vacuum drying box, vacuumizing, and drying at 80 ℃ for 18h to obtain the polyacrylonitrile/cellulose/hydroxyapatite composite membrane.
Comparative example 1
10.49g of polyacrylonitrile powder which is dried in vacuum is added into 100.00ml of N, N-dimethylformamide solvent, and magnetic stirring is carried out for 8 hours at the temperature of 60 ℃ to prepare the polyacrylonitrile spinning solution. 5ml of the spinning solution is extracted by a 10ml disposable medical syringe, the spinning solution is placed in a pushing device of an electrostatic spinning instrument, and electrostatic spinning is carried out for 4 hours by a No. 20 spinning needle according to the spinning parameters of positive voltage of 16.00KV, negative voltage of 2.00KV, receiving distance of 15cm and pushing speed of 0.09mm/min, so as to prepare the polyacrylonitrile fiber membrane with the average diameter of 310 nm. Cutting the membrane into 10cm in length and width, placing between stainless steel plates, clamping with G-shaped clamp, and hot pressing in 120 deg.C blast drying oven for 35min to obtain polyacrylonitrile fiber membrane with thickness of 30-55 μm.
Comparative example 2
A Celgard 2500 commercial lithium battery separator (20 μm thick) was used as a blank control.
Comparative example 3
10.49g of polyacrylonitrile powder which is dried in vacuum is added into 100.00ml of N, N-dimethylformamide solvent, and magnetic stirring is carried out for 8 hours at the temperature of 60 ℃ to prepare the polyacrylonitrile spinning solution. 5ml of the spinning solution is extracted by a 10ml disposable medical injector, and is placed in a pushing device of an electrostatic spinning instrument, and electrostatic spinning is carried out for 4 hours by a No. 20 spinning needle head according to spinning parameters of positive voltage of 16.00KV, negative voltage of 2.00KV, receiving distance of 15cm and pushing speed of 0.09mm/min, so as to prepare the polyacrylonitrile fiber membrane with the average diameter of 310 nm. Cutting the membrane into 10cm in length and width, placing between stainless steel plates, clamping with G-shaped clamp, and hot pressing in 120 deg.C blast drying oven for 35min to obtain polyacrylonitrile fiber membrane with thickness of 30-55 μm.
7.5g cellulose acetate is added into 190.36ml acetone solution, and stirred magnetically for 12 hours at room temperature to obtain cellulose acetate solution. And (3) soaking the polyacrylonitrile nanofiber membrane subjected to hot pressing in the solution for 30min, then placing the polyacrylonitrile nanofiber membrane in a vacuum drying oven, vacuumizing, and drying at 80 ℃ for 18h to obtain the polyacrylonitrile/cellulose/hydroxyapatite composite membrane.
The performance results of the separators prepared in examples 1 to 3 and comparative examples 1 to 3 are shown in table 1.
Table 1 summary of various performance tests
Figure BDA0003361590610000061
From table 1, it can be known that the defects of low ionic conductivity and the like of the polyolefin diaphragm caused by poor electrolyte compatibility are overcome by adopting the combined modification of the nano-hydroxyapatite and the cellulose acetate; the mechanical strength of the polyacrylonitrile fiber membrane is improved, the pore distribution is reasonable, the electrolyte absorption rate is high, and the ionic conductivity is higher, so that the electrochemical performance of the lithium battery is improved.
Fig. 1 is an SEM plan view of a polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1; fig. 2 is an SEM plan view of the polyacrylonitrile lithium battery separator prepared in comparative example 1. As can be seen by comparing FIGS. 1-2: the polyacrylonitrile nanometer fiber has uniform thickness, uniform dispersion and no bead granules. Meanwhile, cellulose acetate and nano-hydroxyapatite are successfully introduced into the polyacrylonitrile fiber membrane. This somewhat reduced the porosity of the example 1 separator, but the cellulose acetate resin effectively improved the adhesion between the polyacrylonitrile filaments, increasing the mechanical strength of the separator.
Fig. 3 is a thermogravimetric graph of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1, and it can be seen from fig. 3 that: the composite diaphragm begins to have large-scale mass loss at 312 ℃, the weight loss rate reaches the maximum at 362 ℃, and the carbon residue rate reaches 68.94%. The composite diaphragm has more stable high-temperature thermal performance, and the safety reliability of the lithium ion battery in a high-temperature environment can be improved.
Fig. 4 is a discharge specific capacity-cycle diagram of a button lithium battery assembled by the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1, which is cycled for 50 cycles under a voltage range of 2.5-4.2V and a multiplying power of 0.5C. The preparation method of the button lithium battery comprises the following steps: the lithium iron phosphate pole piece is used as a positive pole, the metal lithium piece is used as a negative pole, and a glove box for assembling the lithium ion battery needs to be filled with high-purity argon. The assembly sequence is as follows: placing a negative electrode shell, a gasket (stainless steel) and a lithium metal electrode plate, then dropwise adding 3 drops of 1mol/L LiPF6-EC/DMC/EMC electrolyte, then placing a diaphragm at the center of the diaphragm, supplementing 1-2 drops of electrolyte on the diaphragm, then placing a lithium iron phosphate positive plate at the center of the diaphragm, covering the positive plate with a positive shell, and finally sealing by a button cell hydraulic sealing machine. From fig. 4 it can be derived that: the button cell assembled by the composite diaphragm shows excellent and stable cyclic discharge performance in the process of circulating for 50 circles at 0.5C multiplying power, and the discharge specific capacity is as high as 156.6mAh/g.
Fig. 5 is a discharge specific capacity-rate diagram of a button lithium battery assembled by the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1, which is cycled for 5 cycles under the rate of 0.2C, 0.5C, 1C, 2C and 0.2C in the voltage range of 2.5-4.2V, and can be seen from fig. 5: the button cell assembled by the composite diaphragm has the discharge specific capacity which is reduced along with the increase of the multiplying power, because the multiplying power is increased and the current density is increased in the charging and discharging process, so that the polarization result of the electrode is caused. Under the multiplying power of 0.2C, the discharge specific capacity of the battery reaches 160.42mAh/g, and the discharge performance is quite excellent; although the discharge specific capacity is reduced to 130.88mAh/g under the 2C multiplying power, the capacity retention rate is up to 81.56% (based on the 0.2C multiplying power), and the battery does not have serious capacity attenuation and has practical application value.
Fig. 6 is a voltage-charge/discharge specific capacity diagram of a button lithium battery assembled by the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1 after the first charge and discharge cycle at 0.2C, 0.5C, 1C and 2C multiplying power in a voltage range of 2.5-4.2V; as can be seen from fig. 6: the button cell assembled by the composite diaphragm has a flat and wide charging and discharging platform, and stable voltage is maintained. Along with the increase of the multiplying power, the charging and discharging specific capacity is reduced, and the rule of the multiplying power performance is met.
Fig. 7 is a process flow diagram of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared in example 1.
The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.

Claims (8)

1. A preparation method of a polyacrylonitrile/cellulose/hydroxyapatite composite membrane is characterized by comprising the following steps:
(1) Preparing a polyacrylonitrile nanofiber membrane by adopting electrostatic spinning and hot pressing;
(2) Adding hydroxyapatite and a dispersant into an organic solvent, stirring and ultrasonically mixing uniformly to obtain a hydroxyapatite dispersion liquid; adding cellulose into the hydroxyapatite dispersion liquid, and uniformly mixing to prepare a hydroxyapatite cellulose solution;
(3) Soaking the polyacrylonitrile nano-fiber membrane in the step (1) into the cellulose solution of the hydroxyapatite in the step (2), and then taking out and drying in vacuum;
the electrostatic spinning and hot-pressing treatment mode in the step (1) is as follows: adding polyacrylonitrile powder into an organic solution, stirring at 40 to 80 ℃ to obtain a spinning solution, spinning to obtain a polyacrylonitrile fiber filament film, and hot pressing the polyacrylonitrile fiber filament film at 90 to 125 ℃ for 15 to 40min;
the average particle size of the hydroxyapatite is 20 to 60nm.
2. The preparation method of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane as claimed in claim 1, wherein the concentration of the polyacrylonitrile powder in the organic solvent is 0.095 to 0.18g/mL.
3. The preparation method of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane according to claim 2, wherein the relative molecular mass of the polyacrylonitrile is 80000 to 250000;
the organic solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran and dichloromethane.
4. The preparation method of polyacrylonitrile/cellulose/hydroxyapatite composite membrane according to claim 1, characterized in that the mass ratio of the organic solvent, hydroxyapatite, cellulose and dispersant in the step (2) is 100:0.5 to 1.5, 3 to 7.
5. The preparation method of polyacrylonitrile/cellulose/hydroxyapatite composite membrane according to claim 1 or 4, characterized in that, the organic solvent in the step (2) is at least one of formic acid, acetone, methanol, dioxane and chloroform;
the cellulose in the step (2) is at least one of methyl cellulose, cellulose acetate, hydroxymethyl cellulose and cellulose triacetate;
the dispersant in the step (2) is at least one of polyethylene glycol 400, polyethylene glycol 2000, polyethylene glycol 4000 and polyvinylpyrrolidone.
6. The preparation method of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane according to claim 1 or 4, characterized in that the soaking time in the step (3) is 15 to 30min, the vacuum drying temperature is 50 to 80 ℃, and the vacuum drying time is 12 to 18 hours.
7. The polyacrylonitrile/cellulose/hydroxyapatite composite membrane prepared by the preparation method of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane of any one of claims 1~6.
8. The use of the polyacrylonitrile/cellulose/hydroxyapatite composite membrane of claim 7 in the preparation of a lithium ion battery membrane.
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