CN115863905A - Lithium battery diaphragm and preparation method thereof - Google Patents
Lithium battery diaphragm and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a lithium battery diaphragm and a preparation method thereof, and belongs to the technical field of battery films. The lithium battery diaphragm is prepared by compounding modified cellulose, keratin and modified polyacrylonitrile. Compared with the prior art, the lithium battery diaphragm prepared by the invention has the advantages of compact structure, good thermal stability, high porosity and high ionic conductivity.
Description
Technical Field
The invention relates to the technical field of battery films, in particular to a lithium battery diaphragm.
Background
The lithium ion battery mainly comprises a diaphragm, a positive electrode material, a negative electrode material and electrolyte, wherein the diaphragm is an insulating layer with holes. In a lithium battery, a separator absorbs an electrolyte and then separates a positive electrode and a negative electrode while allowing lithium ions to permeate therethrough. When overcharging or temperature rises, the diaphragm can be subjected to high-temperature self-closing to block current conduction, so that the battery is prevented from exploding. Meanwhile, the lithium battery diaphragm also has the characteristics of high strength, fire resistance, electrolyte resistance, acid and alkali corrosion resistance, no toxicity, biocompatibility and the like. According to the components and the structure of the lithium battery diaphragm, the lithium battery diaphragm can be divided into a microporous polymer diaphragm, a non-woven fabric diaphragm and an inorganic particle composite diaphragm, wherein the microporous polymer diaphragm comprises diaphragms such as PP (polyethylene), PE (polypropylene), HDPE (high density polyethylene), UHMWPE (ultra-high molecular weight polyethylene), PP-PE multilayer composite and the like, and the diaphragms have uniform pore structures and have excellent mechanical properties, thermal closed pore properties and electrochemical stability. But due to thisThe inherent lyophobic property and the low surface energy of the materials cause the membrane to have poor wettability, and when the temperature is too high, the membrane also generates great thermal contraction; the nonwoven fabric separator is a membrane made by randomly or directionally arranging fibers (generally having a diameter of less than 5 μm) and then reinforcing the arranged fiber network structure by a certain method (physical or chemical method, etc.), and the nonwoven fabric separator is made of a material comprising: natural material cellulose and its derivatives, synthetic material PA (polyamide), PVDF (polyvinylidene fluoride), PVC (polyvinyl chloride), PTFE (polytetrafluoroethylene), PSA (polysulfonamide) and the like, and the diaphragm has good thermal stability, is superior to the polyolefin diaphragm in the aspect of pore size distribution, but has certain defects in the aspects of pore size, diaphragm thickness and the like; inorganic particle composite separator, also called ceramic separator, is made by mixing some inorganic particles (e.g., al) with a binder or the like 2 O 3 ，TiO 2 ) The composite membrane is filled in a base membrane to form the composite membrane, the membrane couples the better mechanical property of the traditional polyolefin membrane, the composite membrane not only has good mechanical strength and thermal shutdown function and excellent thermal stability, but also has good affinity to electrolyte, is beneficial to improving wettability and has good safety, but the inorganic particles of the membrane are easy to fall off, and can influence the mechanical property, the electrochemical property and the like of a lithium battery after falling off.
At present, the preparation process of the lithium battery diaphragm comprises a dry method (including dry single-drawing and dry double-drawing) and a wet method: the dry diaphragm process is the most commonly used method in the diaphragm preparation process, and the process comprises the steps of mixing high molecular polymer and additive raw materials to form uniform melt, forming a lamellar structure under tensile stress during extrusion, then carrying out heat treatment on the lamellar structure to obtain a hard elastic polymer film, stretching at a certain temperature to form slit-shaped micropores, and carrying out heat setting to obtain the microporous film. The method mainly comprises two processes of dry unidirectional stretching and bidirectional stretching at present, wherein the dry stretching process is simple in procedure, environment-friendly and pollution-free, and high in productivity, but the thickness, the pore diameter and the porosity distribution of the produced microporous membrane are difficult to control, the uniformity of the membrane is poor, the internal micro short circuit of the battery is easy to cause, and the capacity retention and the safety reliability are not high; the wet process is to mix plasticizer (high boiling point liquid hydrocarbon or some low molecular weight substance) with polyolefin resin by using the principle of thermal phase separation, heat and melt to form a uniform mixture, then cool to generate solid-liquid phase or liquid-liquid phase separation, press to form a membrane, heat the membrane to a temperature close to the melting point, stretch in two directions to make the molecular chain orientation consistent, keep the temperature for a certain time, extract the plasticizer from the film by volatile substances (such as dichloromethane and trichloroethylene), thereby preparing the microporous membrane material with communicated submicron size, and finally the porous film passes through a solvent extractor to remove the solvent. The manufacturing process of the wet process is easy to regulate and control, the manufactured diaphragm has high biaxial tensile strength and high puncture strength, perforation cannot be caused in the normal process flow, the size of micropores is small and the distribution is uniform, the diaphragm can be very thin, the mechanical property and the product uniformity are better, the diaphragm is suitable for being used as a high-capacity battery, the diaphragm has high porosity and air permeability, but a large amount of solvent is needed in the wet process, and the environmental pollution is easily caused; compared with the dry process, the method has the advantages of complex equipment, large investment, long period, high cost and large energy consumption; because only a thin single-layer PE film can be produced, the melting point is only 130 ℃, and the thermal stability is poor.
The invention patent with publication number CN112928383A discloses a lithium battery diaphragm and a preparation method thereof, wherein the lithium battery diaphragm consists of a base film and a functional coating positioned on the surface of the base film; the base film is selected from any one of polyethylene base film, polypropylene base film, non-woven fabric base film or polyimide base film, the thickness of the functional coating is 2-4 microns, and the functional coating is formed by curing diaphragm slurry; the diaphragm slurry comprises deionized water, a dispersing agent, a flocculating agent, a binder, a wetting agent and ceramic powder; the flocculating agent is high molecular weight polyethylene oxide; the wetting agent is selected from any one of anionic surfactant or nonionic surfactant. The preparation method comprises preheating the base film; coating the diaphragm slurry on the surface of the base film; and finally, drying the diaphragm slurry to form a functional coating, thereby obtaining the lithium battery diaphragm. The obtained lithium battery diaphragm has high safety and good ionic conductivity, and improves the adhesive property and the thermal stability. However, the inorganic particles on the surface of the prepared separator are easy to fall off, and the porosity is low.
The invention patent with publication number CN110289382A discloses a preparation method of a lithium battery diaphragm and the lithium battery diaphragm, wherein the lithium battery diaphragm is composed of polymer base material and silicate powder, and the mass ratio of the polymer base material to the silicate powder is 40-99.9 wt%. The silicate powder is added to form a chain in the lithium battery diaphragm, so that the strength of the lithium battery diaphragm is effectively improved, and the capability of the diaphragm in inhibiting lithium dendrites and the thermal stability are improved; the silicate powder is wrapped by the polymer chain, so that the silicate powder is effectively prevented from falling off from the lithium battery diaphragm; the lithium battery diaphragm is prepared by adopting an electrophoretic deposition method, so that the uniformity of the thickness of the diaphragm is effectively ensured. But the resulting separator has poor ionic conductivity.
The invention patent with publication number CN109742300B discloses a lithium battery diaphragm and a preparation method thereof, wherein the lithium battery diaphragm comprises polyethylene doped with polybutylene terephthalate and compatilizer; the polyethylene doped with polybutylene terephthalate and compatilizer comprises the following raw materials in percentage by mass: 93.4 to 97.25 percent of polyethylene, 2.5 to 6 percent of polybutylene terephthalate and 0.25 to 0.6 percent of compatilizer, and the obtained lithium battery diaphragm is a single-layer composite system; by doping polybutylene terephthalate in polyethylene and utilizing the incompatibility characteristic of the polybutylene terephthalate and the polyethylene to form a microporous structure in the biaxial stretching process, when the temperature of the structure rises, the polyethylene is melted to form closed pores of the diaphragm, and the polybutylene terephthalate provides a supporting point, so that the integrity of the diaphragm is ensured, and the occurrence of short-circuit accidents caused by the contact of the positive electrode and the negative electrode in the battery is effectively prevented; the lithium battery diaphragm formed after biaxial stretching has better strength in the longitudinal direction and the transverse direction. However, the pore diameter and the porosity of the separator prepared by the method are not easy to control, and the use of the battery is easily influenced.
Disclosure of Invention
In view of the problems of easy falling of inorganic particles, poor ionic conductivity, low porosity and the like of the lithium battery diaphragm in the prior art, the invention aims to solve the technical problem of obtaining the lithium battery diaphragm which has compact structure, good thermal stability and mechanical property, higher porosity, good affinity to electrolyte and higher ionic conductivity.
In order to achieve the aim, the invention provides a preparation method of a lithium battery diaphragm, which comprises the following steps: adding hydrochloric acid into modified cellulose, adjusting the pH value of the modified cellulose to 2-3, adding 1, 5-glutaraldehyde, keratin and modified polyacrylonitrile, stirring at 45-65 ℃ for 1-5 hours, cooling to 20-25 ℃, filtering by a dialysis bag, collecting substances in the dialysis bag, homogenizing for 20-45 minutes, performing suction filtration to obtain a colloid membrane, performing hot pressing at 60-80 ℃ for 1-4 hours, and drying at 60-100 ℃ for 45-110 minutes to obtain the lithium battery diaphragm.
Preferably, the preparation method of the lithium battery separator comprises the following steps in parts by weight: adding 10-25 wt% hydrochloric acid into 98-104.5 parts of modified cellulose, adjusting the pH value of the modified cellulose to 2-3, adding 16.5-17.5 parts of 1, 5-glutaraldehyde, 15-25 parts of keratin and 5-24 parts of modified polyacrylonitrile, stirring at 45-65 ℃ for 1-5 hours at 300-500 r/min, cooling to 20-25 ℃, filtering by a dialysis bag with the specification of 3500-10000 Da, collecting substances in the dialysis bag, homogenizing at 8000-12000 r/min for 20-45 minutes, performing suction filtration to obtain a colloid membrane, performing hot pressing at 60-80 ℃ for 1-4 hours, and drying at 60-100 ℃ for 45-110 minutes to obtain the lithium battery diaphragm.
Preferably, the modified cellulose is prepared by the following method in parts by weight: uniformly mixing 11-19 parts of lithium hydroxide, 10-30 parts of urea and 120-210 parts of water to obtain a solvent, and precooling to-5 to-15 ℃ for later use; adding 1-3.5 parts of nano-cellulose into 96.5-99 parts of solvent under the precooling condition of-5 to-15 ℃, and stirring for 22-28 hours at 400-600 revolutions per minute to obtain a cellulose solution; then 0.5-2 parts of bismuth trioxide/aluminum magnesium layered double hydroxide composite material is added into the cellulose solution under the pre-cooling condition of-5 to-15 ℃, the temperature is kept at-5 to-15 ℃, the mixture is stirred for 100 to 140 minutes at 1100 to 1500 revolutions per minute, a dialysis bag with the specification of 3500 to 10000Da is filtered, and substances in the dialysis bag are collected to obtain the modified cellulose.
Preferably, the preparation method of the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material comprises the following steps in parts by weight: boiling 500-1000 parts of water, and cooling to 25-35 ℃ for later use; dissolving 8-15 parts of aluminum nitrate nonahydrate and 12-22 parts of magnesium nitrate hexahydrate in 150-350 parts of water, then adding 3-12 parts of urea for dissolving, then adding 1-3 parts of bismuth trioxide, carrying out ultrasonic treatment for 3-8 minutes, reacting for 50-90 minutes at the temperature of 100-110 ℃, cooling to 93-98 ℃, continuing to react for 22-28 hours, centrifuging at 8000-12000 r/min, collecting solids, washing with water until supernatant is clear, drying the cleaned solids for 20-26 hours at the temperature of 55-65 ℃, and grinding to obtain the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material.
Preferably, the preparation method of the modified polyacrylonitrile comprises the following steps in parts by weight:
s1, dissolving 5-15 parts of polyacrylonitrile in 35-120 parts of dimethylformamide, adding 0.08-0.2 part of sodium dodecyl sulfate and 2-13 parts of potassium persulfate, and stirring at the temperature of 85-100 ℃ and under the nitrogen atmosphere for 20-45 minutes at 300-500 revolutions per minute to obtain hydroxylated polyacrylonitrile;
s2, cooling 42.08-148.2 parts of hydroxylated polyacrylonitrile prepared in the step S1 to 70-80 ℃, keeping the nitrogen atmosphere, adding 35-85 parts of butyl acrylate, 10-30 parts of potassium persulfate and 5-16 parts of sodium thiosulfate, and stirring at 300-500 r/min for 3-5 hours to obtain the modified polyacrylonitrile.
According to the invention, the bismuth oxide/magnesium aluminum layered double hydroxide composite material and the nano-cellulose are compounded to obtain the modified cellulose, and then the modified cellulose, the keratin and the modified polyacrylonitrile are connected through the pentanediol to obtain the composite diaphragm, wherein the diaphragm has good electrolyte affinity and ion conductivity. The bismuth trioxide and the magnesium-aluminum layered double hydroxide are compounded, so that the thermal stability and the ionic conductivity of the composite diaphragm are improved, the thermal shrinkage rate of the composite diaphragm is reduced, and the charge and discharge performance and the capacity of the battery are improved. In the modified cellulose, the bismuth trioxide/magnesium aluminum layered double hydroxide composite material is combined with the nano cellulose, the molecular chain of the nano cellulose enters the layers of the bismuth trioxide/magnesium aluminum layered double hydroxide composite material to interact with atoms and molecules on the sheet layer, the mechanical property of the composite diaphragm is enhanced, solid particles are combined with the composite diaphragm more tightly, the dispersion of the bismuth trioxide/magnesium aluminum layered double hydroxide composite material in the composite diaphragm is better, and the porosity of the composite diaphragm is increased. The 1, 5-glutaraldehyde is respectively subjected to a cross-linking reaction with keratin and an acetal reaction with the modified cellulose to form an interpenetrating network structure polymer, so that the compactness, the ionic conductivity and the stable distribution of pores of the composite diaphragm can be improved, and the heat shrinkage of the composite diaphragm is reduced. And the modified polyacrylonitrile is compounded and interacted with, so that the electrolyte affinity of the composite diaphragm and the mechanical property of the composite diaphragm are improved.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages: 1) The bismuth trioxide is compounded with the layered double hydroxides, so that the thermal stability of the composite diaphragm is improved, the thermal shrinkage rate of the composite diaphragm is reduced, and the ionic conductivity of the composite diaphragm is enhanced; 2) The modified cellulose and the keratin form a polymer with an interpenetrating network structure, so that the pore distribution of the composite membrane is more uniform, the tightness and the ionic conductivity of the composite membrane are improved, and the heat shrinkage of the composite membrane is reduced; 3) The modified polyacrylonitrile is compounded with the formed interpenetrating network structure polymer and interacts with the formed interpenetrating network structure polymer, so that the electrolyte affinity of the composite diaphragm and the mechanical property of the composite diaphragm are improved.
Detailed Description
The examples and comparative examples use part of the raw material sources: bismuth oxide: light yellow powder with the density of 2-3.5 g/cm 3 The particle size: d505-15 μm; nano-cellulose: the solid content is 50 percent, the average diameter is 30nm, and the length is 500-1000 nm; keratin: the molecular weight is 20-30 kd; polyacrylonitrile, average molecular weight Mw 150000.
Example 1
A preparation method of a lithium battery diaphragm comprises the following steps:
step 1, boiling 800g of water, and cooling to 30 ℃ for later use; dissolving 12g of aluminum nitrate nonahydrate and 18g of magnesium nitrate hexahydrate in 200g of water, adding 7.5g of urea for dissolving, adding 2g of bismuth trioxide, performing ultrasonic treatment for 6 minutes, reacting at 105 ℃ for 65 minutes, cooling to 95 ℃, continuing to react for 24 hours, centrifuging at 10000 revolutions per minute, collecting solids, washing with water until the supernatant is clear, drying the washed solid matter at 60 ℃ for 24 hours, and grinding to obtain the bismuth trioxide/aluminum magnesium layered double hydroxide composite material;
step 2, uniformly mixing 15g of lithium hydroxide, 24g of urea and 160g of water to obtain a solvent, and precooling to-10 ℃ for later use; adding 1.5g of nano-cellulose into 98.5g of solvent at the temperature of minus 10 ℃, and stirring for 24 hours at 500 revolutions per minute to obtain a cellulose solution; then adding 1.2g of the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material prepared in the step 1 into a cellulose solution under the condition of precooling at the temperature of minus 10 ℃, keeping the temperature at minus 10 ℃, stirring for 120 minutes at 1300 revolutions per minute, filtering by a dialysis bag with the specification of 7000Da, and collecting substances in the dialysis bag to obtain modified cellulose; adding hydrochloric acid with the concentration of 20wt%, adjusting the pH value of modified cellulose to be within the range of 2-3, adding 17g 1, 5-glutaraldehyde, 20g keratin and 15g modified polyacrylonitrile, stirring for 4 hours at the temperature of 50 ℃ at 400 rpm, cooling to 22 ℃, filtering by a dialysis bag with 7000Da, collecting substances in the dialysis bag, homogenizing for 30 minutes at 10000 rpm, performing suction filtration by a vacuum pump to obtain a colloid membrane, performing hot pressing for 2 hours at the temperature of 65 ℃ by a hot press, and drying for 100 minutes at 80 ℃ to obtain the lithium battery diaphragm.
The preparation method of the modified polyacrylonitrile comprises the following steps:
s1, dissolving 10g of polyacrylonitrile in 80g of dimethylformamide, adding 0.18g of sodium dodecyl sulfate and 7.5g of potassium persulfate, and stirring at the temperature of 90 ℃ for 35 minutes at 400 revolutions per minute in a nitrogen atmosphere to obtain hydroxylated polyacrylonitrile;
s2, cooling 97.5g of hydroxylated polyacrylonitrile prepared in the step S1 to 75 ℃, keeping the nitrogen atmosphere, adding 60g of butyl acrylate, 15g of potassium persulfate and 10g of sodium thiosulfate, and stirring at 400 revolutions per minute for 4 hours to obtain the modified polyacrylonitrile.
Comparative example 1
A preparation method of a lithium battery diaphragm comprises the following steps:
step 1, boiling 800g of water, and cooling to 30 ℃ for later use; dissolving 12g of aluminum nitrate nonahydrate and 18g of magnesium nitrate hexahydrate in 200g of water, adding 7.5g of urea for dissolving, carrying out ultrasonic treatment for 6 minutes, reacting at 105 ℃ for 65 minutes, cooling to 95 ℃, continuing to react for 24 hours, centrifuging at 10000 revolutions per minute, collecting solids, washing with water until the supernatant is clear, drying the washed solid matter at 60 ℃ for 24 hours, and grinding to obtain the aluminum-magnesium layered double hydroxide composite material;
step 2, uniformly mixing 15g of lithium hydroxide, 24g of urea and 160g of water to obtain a solvent, and precooling to-10 ℃ for later use; adding 1.5g of nano-cellulose into 98.5g of solvent at the temperature of minus 10 ℃, and stirring for 24 hours at 500 revolutions per minute to obtain a cellulose solution; adding 1.2g of the aluminum-magnesium layered double hydroxide composite material prepared in the step 1 into a cellulose solution under the condition of precooling at the temperature of minus 10 ℃, keeping the temperature at minus 10 ℃, stirring for 120 minutes at 1300 revolutions per minute, filtering by a dialysis bag with the specification of 7000Da, and collecting substances in the dialysis bag to obtain modified cellulose; adding hydrochloric acid with the concentration of 20wt%, adjusting the pH value of modified cellulose to be within the range of 2-3, adding 17g 1, 5-glutaraldehyde, 20g keratin and 15g modified polyacrylonitrile, stirring for 4 hours at the temperature of 50 ℃ at 400 rpm, cooling to 22 ℃, filtering by a dialysis bag with 7000Da, collecting substances in the dialysis bag, homogenizing for 30 minutes at 10000 rpm, performing suction filtration by a vacuum pump to obtain a colloid membrane, performing hot pressing for 2 hours at the temperature of 65 ℃ by a hot press, and drying for 100 minutes at 80 ℃ to obtain the lithium battery diaphragm.
The preparation method of the modified polyacrylonitrile is the same as that of the example 1.
Comparative example 2
A preparation method of a lithium battery diaphragm comprises the following steps:
step 1, boiling 800g of water, and cooling to 30 ℃ for later use; dissolving 12g of aluminum nitrate nonahydrate and 18g of magnesium nitrate hexahydrate in 200g of water, adding 7.5g of urea for dissolving, adding 2g of bismuth trioxide, performing ultrasonic treatment for 6 minutes, reacting at 105 ℃ for 65 minutes, cooling to 95 ℃, continuing to react for 24 hours, centrifuging at 10000 revolutions per minute, collecting solids, washing with water until the supernatant is clear, drying the washed solid matter at 60 ℃ for 24 hours, and grinding to obtain the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material;
step 2, uniformly mixing 15g of lithium hydroxide, 24g of urea and 160g of water to obtain a solvent, and precooling to-10 ℃ for later use; adding 1.5g of nano-cellulose into 98.5g of solvent at the temperature of minus 10 ℃, and stirring for 24 hours at 500 revolutions per minute to obtain a cellulose solution; then adding 1.2g of the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material prepared in the step 1 into a cellulose solution under the condition of precooling at the temperature of minus 10 ℃, keeping the temperature at minus 10 ℃, stirring for 120 minutes at 1300 revolutions per minute, filtering by a dialysis bag with the specification of 7000Da, and collecting substances in the dialysis bag to obtain modified cellulose; adding hydrochloric acid with the concentration of 20wt%, adjusting the pH value of modified cellulose to be within the range of 2-3, adding 17g 1, 5-glutaraldehyde and 15g modified polyacrylonitrile, stirring for 4 hours at the temperature of 50 ℃ at 400 r/min, cooling to 22 ℃, filtering by a dialysis bag with the temperature of 7000Da, collecting substances in the dialysis bag, homogenizing for 30 minutes at 10000 r/min, obtaining a colloid membrane by suction filtration through a vacuum pump, carrying out hot pressing for 2 hours at the temperature of 65 ℃ by a hot press, and drying for 100 minutes at 80 ℃ to obtain the lithium battery diaphragm.
The preparation method of the modified polyacrylonitrile is the same as that of the example 1.
Comparative example 3
The preparation method of the lithium battery diaphragm comprises the following steps:
step 1, boiling 800g of water, and cooling to 30 ℃ for later use; dissolving 12g of aluminum nitrate nonahydrate and 18g of magnesium nitrate hexahydrate in 200g of water, adding 7.5g of urea for dissolving, adding 2g of bismuth trioxide, performing ultrasonic treatment for 6 minutes, reacting at 105 ℃ for 65 minutes, cooling to 95 ℃, continuing to react for 24 hours, centrifuging at 10000 revolutions per minute, collecting solids, washing with water until the supernatant is clear, drying the washed solid matter at 60 ℃ for 24 hours, and grinding to obtain the bismuth trioxide/aluminum magnesium layered double hydroxide composite material;
step 2, uniformly mixing 15g of lithium hydroxide, 24g of urea and 160g of water to obtain a solvent, and precooling to-10 ℃ for later use; adding 1.5g of nano-cellulose into 98.5g of solvent at the temperature of minus 10 ℃, and stirring for 24 hours at 500 revolutions per minute to obtain a cellulose solution; then adding 1.2g of the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material prepared in the step 1 into a cellulose solution under the condition of precooling at the temperature of minus 10 ℃, keeping the temperature at minus 10 ℃, stirring for 120 minutes at 1300 revolutions per minute, filtering by a dialysis bag with the specification of 7000Da, and collecting substances in the dialysis bag to obtain modified cellulose; adding hydrochloric acid with the concentration of 20wt%, adjusting the pH value of the modified cellulose to be within the range of 2-3, adding 17g 1, 5-glutaraldehyde and 20g keratin, stirring for 4 hours at the temperature of 50 ℃ at 400 r/min, cooling to 22 ℃, filtering by a dialysis bag with the temperature of 7000Da, collecting substances in the dialysis bag, homogenizing for 30 minutes at 10000 r/min, obtaining a colloid membrane by suction filtration through a vacuum pump, carrying out hot pressing for 2 hours at the temperature of 65 ℃ by a hot press, and drying for 100 minutes at 80 ℃ to obtain the lithium battery diaphragm.
Comparative example 4
The preparation method of the lithium battery diaphragm comprises the following steps:
step 1, boiling 800g of water, and cooling to 30 ℃ for later use; dissolving 12g of aluminum nitrate nonahydrate and 18g of magnesium nitrate hexahydrate in 200g of water, adding 7.5g of urea for dissolving, adding 2g of bismuth trioxide, performing ultrasonic treatment for 6 minutes, reacting at 105 ℃ for 65 minutes, cooling to 95 ℃, continuing to react for 24 hours, centrifuging at 10000 revolutions per minute, collecting solids, washing with water until the supernatant is clear, drying the washed solid matter at 60 ℃ for 24 hours, and grinding to obtain the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material;
step 2, uniformly mixing 15g of lithium hydroxide, 24g of urea and 160g of water to obtain a solvent, and precooling to-10 ℃ for later use; adding 1.5g of nano-cellulose into 98.5g of solvent at the temperature of minus 10 ℃, and stirring for 24 hours at 500 revolutions per minute to obtain a cellulose solution; then adding 1.2g of the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material prepared in the step 1 into a cellulose solution under the condition of precooling at the temperature of minus 10 ℃, keeping the temperature at minus 10 ℃, stirring for 120 minutes at 1300 revolutions per minute, filtering by a dialysis bag with the specification of 7000Da, and collecting substances in the dialysis bag to obtain modified cellulose; adding hydrochloric acid with the concentration of 20wt%, adjusting the pH value of modified cellulose to be within the range of 2-3, adding 17g 1, 5-glutaraldehyde, 20g keratin and 15g polyacrylonitrile, stirring for 4 hours at the temperature of 50 ℃ at 400 revolutions per minute, cooling to 22 ℃, filtering by a dialysis bag with the temperature of 7000Da, collecting substances in the dialysis bag, homogenizing for 30 minutes at 10000 revolutions per minute, performing suction filtration by a vacuum pump to obtain a colloid membrane, performing hot pressing for 2 hours at the temperature of 65 ℃ by a hot press, and drying for 100 minutes at the temperature of 80 ℃ to obtain the lithium battery diaphragm.
The polyacrylonitrile is obtained by dissolving 10g of polyacrylonitrile in 80g of dimethylformamide.
Test example 1
Testing the heat shrinkage performance:
the heat shrinkage performance test of the lithium battery diaphragm sample is carried out according to the following steps: firstly, a lithium battery diaphragm sample is cut into a sample of 15mm multiplied by 130mm, wherein 130mm is an initial length L 0 Placing the sample in a 200 ℃ oven for constant-temperature baking for 1 hour, taking out the sample, naturally cooling to room temperature, and measuring the length L of the sample 1 The sample thermal shrinkage γ was calculated by equation 1:
5 replicates of each sample were taken and averaged, and the results are shown in Table 1. Test example 2
And (3) testing mechanical properties:
the mechanical performance test of a diaphragm sample is carried out by referring to the performance test of a 2.2.4 diaphragm of a Master thesis (improved preparation and performance regulation of a cellulose/nylon 6 lithium battery diaphragm, author: wang Aiai, university of Fukung Mero, 2020), and the test method is as follows: the separator was cut into 20mm × 150mm samples, and the composition was changed to lithium hexafluorophosphate: ethylene carbonate: soaking for 2h in electrolyte with dimethyl carbonate = 1: 1 (mol/g/g), taking out with tweezers, suspending for 1min, sucking off redundant electrolyte on the surface of the diaphragm by using filter paper, and testing the tensile strength and the elongation at break of the diaphragm by using an intelligent electronic tensile testing machine under the test conditions that: the test temperature is 25 +/-2 ℃, the relative humidity is 50 +/-5%, the stretching speed is 25mm/min, 5 samples are paralleled, and the average value is obtained, and the result is shown in table 1.
Test example 3
And (3) porosity testing:
porosity of a diaphragm sample is tested by referring to a Master thesis (improved preparation and performance regulation of a cellulose/nylon 6 lithium battery diaphragm, author: wang Aiai, university of Fumons Master, 2020) 2.2.4 performance test of a diaphragm, and the test method is as follows: cutting the diaphragm into 20mm × 20mm sample, dried at 60 ℃ for 3h, cooled and weighed on an electronic balance and recorded as m 0 The separator was then immersed in a solution having the composition lithium hexafluorophosphate: ethylene carbonate: soaking in electrolyte with dimethyl carbonate = 1: 1 (mol/g/g) for 2h, taking out with tweezers, suspending for 1min, sucking off excessive electrolyte on the surface of the diaphragm with filter paper, weighing, and recording as m 1 Porosity is calculated according to equation 1:
5 replicates of each sample were taken and averaged, and the results are shown in Table 1.
Test example 4
And (3) ion conductivity test:
ion conductivity tests were carried out on the membrane samples with reference to characterization analysis of 2.2.5 membranes of Master thesis (improved preparation and performance control of cellulose/nylon 6 lithium battery membranes, author: wang Aiai, university of Venus Fumons, 2020), the test method is as follows: the bulk resistance was tested on an electrochemical workstation using an ac impedance method. The battery test system is 'SS/diaphragm/SS', the SS is a stainless steel gasket, and the scanning frequency is 1-10 5 Hz, sinusoidal amplitude of 5mV, ion conductivity calculated according to equation 2
Wherein, σ -ionic conductivity (S/cm); d-membrane thickness (cm); r-bulk resistance (Ω); s-effective area (cm) 2 )。
5 replicates of each sample were taken and averaged, and the results are shown in Table 1.
Table 1 composite separator performance test results
Comparing example 1 with comparative examples 1-4, it is found that the performance of the composite diaphragm of example 1 is superior to that of the comparative examples, because the bismuth trioxide, the keratin and the modified polyacrylonitrile are added in example 1, and the bismuth trioxide is compounded with the layered double hydroxide, so that the thermal stability of the composite diaphragm is increased, the thermal shrinkage rate of the composite diaphragm is reduced, and the ionic conductivity of the composite diaphragm is enhanced; the modified cellulose and the keratin form a polymer with an interpenetrating network structure, so that the pore distribution of the composite membrane is more uniform, the ionic conductivity of the composite membrane is improved, and the heat shrinkage of the composite membrane is reduced; the modified polyacrylonitrile and the formed interpenetrating network structure polymer are compounded and interacted, so that the mechanical property of the composite diaphragm is improved.
Claims (9)
1. A preparation method of a lithium battery diaphragm is characterized by comprising the following steps: adding hydrochloric acid into modified cellulose, adjusting the pH value of the modified cellulose to 2-3, adding 1, 5-glutaraldehyde, keratin and modified polyacrylonitrile, stirring for 1-5 hours at the temperature of 45-65 ℃, cooling to 20-25 ℃, filtering by a dialysis bag, collecting substances in the dialysis bag, homogenizing for 20-45 minutes, performing suction filtration to obtain a colloid membrane, performing hot pressing for 1-4 hours at the temperature of 60-80 ℃, and drying for 45-110 minutes at the temperature of 60-100 ℃ to obtain the lithium battery diaphragm.
2. The method of preparing a lithium battery separator according to claim 1, wherein the modified cellulose is prepared by the following steps: uniformly mixing lithium hydroxide, urea and water to obtain a solvent, and precooling to-5-15 ℃ for later use; adding nano-cellulose into a solvent under the precooling condition of-5 to-15 ℃, and stirring for 22 to 28 hours to obtain a cellulose solution; then adding the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material into the cellulose solution under the precooling condition of-5 to-15 ℃, keeping the temperature at-5 to-15 ℃, stirring for 100 to 140 minutes, filtering the dialysis bag, and collecting substances in the dialysis bag to obtain the modified cellulose.
3. The method for preparing a lithium battery separator as claimed in claim 2, wherein the bismuth oxide/aluminum magnesium layered double hydroxide composite material is prepared by the following steps: boiling water, and cooling to 25-35 ℃ for later use; dissolving aluminum nitrate nonahydrate and magnesium nitrate hexahydrate in water, then adding urea for dissolving, then adding bismuth trioxide, performing ultrasonic treatment for 3-8 minutes, reacting at the temperature of 100-110 ℃ for 50-90 minutes, cooling to 93-98 ℃, continuing to react for 22-28 hours, centrifuging, collecting solids, washing with water until supernatant is clear, drying at the temperature of 55-65 ℃ for 20-26 hours, and grinding to obtain the bismuth trioxide/aluminum-magnesium layered double hydroxide composite material.
4. The method for preparing a lithium battery separator as claimed in claim 1, wherein: the concentration of the hydrochloric acid is 10-25 wt%.
5. The method of preparing a lithium battery separator as claimed in claim 2, wherein: the rotating speed of stirring for 100-140 minutes is 1100-1500 revolutions per minute.
6. The method for preparing a lithium battery separator as claimed in claim 1 or 2, wherein: the specification of the dialysis bag is 3500-10000 Da.
7. The method for preparing a lithium battery separator as claimed in claim 1, wherein the modified polyacrylonitrile is prepared as follows:
s1, dissolving polyacrylonitrile in dimethylformamide, adding sodium dodecyl sulfate and potassium persulfate, and stirring for 20-45 minutes at 85-100 ℃ in a nitrogen atmosphere to obtain hydroxylated polyacrylonitrile;
and S2, cooling the hydroxylated polyacrylonitrile prepared in the step S1 to 70-80 ℃, keeping the nitrogen atmosphere, adding butyl acrylate, potassium persulfate and sodium thiosulfate, and stirring for 3-5 hours to obtain the modified polyacrylonitrile.
8. The method of preparing a lithium battery separator as claimed in claim 1, wherein: the homogenizing rotating speed is 8000-12000 r/min.
9. A lithium battery separator characterized by: prepared by the method of any one of claims 1 to 8.
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| CN202211617343.3A CN115863905A (en) | 2022-12-14 | 2022-12-14 | Lithium battery diaphragm and preparation method thereof |
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| CN202211617343.3A CN115863905A (en) | 2022-12-14 | 2022-12-14 | Lithium battery diaphragm and preparation method thereof |
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