A kind of lithium ion battery separator and preparation method thereof of nano-cellulose improvement
Technical field
Present invention design prepares a kind of lithium ion battery separator and preparation method thereof, and in particular to a kind of novel nano fiber
The lithium ion battery separator and preparation method thereof of element improvement.
Background technology
Cellulose is a kind of renewable resource of rich reserves in nature, is had using the material that cellulose is produced as raw material
Many good characteristics, if dielectric constant is high, puncture is strong, chemical stability is good, thermostabilization is good, degradable etc., in papermaking, electricity
The fields such as sub- product, industrial processes, medicine are widely used.In recent years, many membrane material researchers were devoted to research and develop
Inexpensive, reproducible cellulosic material prepares High-performance diaphragm, especially based on cellulose, modification and the cellulose of enhancing
The lithium ion battery separator of body raw material, and with polyalkene diaphragm in heat resistance, puncture, intensity, resistance sizes, high voltage withstanding
Property etc. is compared research.In cellulosic molecule, intermolecular hydrogen bonding and under the action of Van der Waals force, cellulose divides greatly
Subchain flocks together the cellulose primitive fibril formd with cellulose Ⅰ crystalline structure.But the cellulose in nature
Aggregation is not a kind of perfect crystal structure, and there is also a large amount of amorphous domains.It can be by way of physics, chemistry
Cellulose primitive fibril effectively, is completely stripped out from native cellulose state of aggregation.Currently, native cellulose nanometer material
Material preparation method mainly has Mechanical Method, acid-hydrolysis method and TEMPO catalytic oxidations.The fibre that TEMPO methods are prepared in comparison
The plain nanofiber of dimension largely maintains the structure feature of natural wood pulp primitive fibril, therefore cellulose nano-fibrous tool
There are many outstanding properties of native cellulose primitive fibril, such as:Extremely small diameter (about 3~4nm), draw ratio are more than 250
(length can reach micron order), higher elasticity modulus (140~150GPa), smaller density (1.6g.cm-3), higher knot
Brilliant degree (70%~95%), the optical refractive index that can be compared favourably with glass and smaller coefficient of thermal expansion etc..In addition, passing through
The mode of metal ion exchanged can also improve cellulose nano-fibrous thermal stability.
Lithium ion battery has that energy density is high, specific power is big, cycle performance as a kind of high-energy green secondary cell
Good, memory-less effect, it is pollution-free the features such as, be widely used to Intelligent mobile equipment, hybrid vehicle, electric vehicle, the sun
The new energy fields such as energy electricity generation system, quickly grow.These fields do not require nothing more than battery with high-energy, power density, to electricity
The security requirement in pond is also higher and higher.And diaphragm is influence and determine lithium ion battery chemical property and safety important
Factor.Currently, the diaphragm material of commercial lithium-ion batteries mainly still uses polyethylene, microporous polypropylene membrane.But poly- second
Alkene, polypropylene diaphragm are poor to electrolyte compatibility, there are imbibition rate and protect the low deficiency of liquid rate, electrolyte is easy to happen side
Leakage, there are hidden danger for the safety of battery.
Invention content
The object of the present invention is to provide one kind having higher hydrophily, imbibition rate, protects liquid rate, mechanical performance and environment friend
The lithium ion battery separator and preparation method thereof of the novel nano cellulose improvement of good property.
The present invention is achieved by the following technical solution:
A kind of lithium ion battery separator of novel nano cellulose improvement includes following components in weight percent:
Cellulose nano-fibrous-lithium (CNFs-Li) 0%~20%,
Polymeric matrix 80%~100%,
The polymeric matrix is polyethylene, polypropylene, polyvinyl chloride, cellulose acetate, Kynoar, poly- methyl-prop
One in e pioic acid methyl ester, cyanethyl cellulose, polyimides, polyurethane, polysulfones, polyether sulfone, polyvinyl alcohol, polyethylene glycol oxide
Kind.
Further, the cellulose nano-fibrous-lithium is prepared via a method which:
A. synthetic cellulose nanofiber-sodium (CNFs-Na):Reagent cellulose, TEMPO, sodium bromide, sodium hypochlorite quality
Than 15:0.25:0.5:100, pH controls are stirred to react 6~12h, then ultrasound obtains cellulose Nanowire at room temperature 9~11
Dimension-sodium;
B. plain nanofiber-sodium acidification is tieed up:The hydrochloric acid of 0.5mol/L, control is added dropwise to cellulose nano-fibrous sodium at room temperature
PH is 2 ± 0.2, reaction 12~for 24 hours, and obtained material is dialysed 3~7 days in distilled water, until pH is neutrality, ultrasound obtains fibre
Plain nanofiber-the hydrogen of dimension;
C. cellulose nano-fibrous-hydrogen (CNFs-H) alkalizes:At room temperature to cellulose nano-fibrous sodium be added dropwise 5~
The lithium hydroxide of 10wt.%, control pH are 10 ± 0.2, reaction 12~for 24 hours, and obtained material is dialysed 3~7 days in distilled water,
Until pH is neutrality, ultrasound obtains cellulose nano-fibrous-lithium.
The preparation method of above-mentioned lithium ion battery separator includes step:
A. it prepares and scrapes film liquid:The polymeric matrix is dissolved with solvent, cellulose nano-fibrous-lithium is mixed with water, is surpassed
Evenly dispersed sound is suspension, and addition polymeric matrix, which is made, scrapes film liquid, scrapes a concentration of 8~20wt.% of film liquid, wherein cellulose
Nanofiber-lithium concentration is 0.1~2wt.%, wt.%, that is, mass percent;
The selection of solvent is specially:Polymeric matrix is oiliness matrix polyethylene, polypropylene, polyvinyl chloride, acetate fiber
One in element, Kynoar, polymethyl methacrylate, cyanethyl cellulose, polyimides, polyurethane, polysulfones, polyether sulfone
When kind, it is dissolved with one or more of mixed solvents of oil-dissolving solvent dimethylformamide, dimethylacetylamide;
When polymeric matrix is aqueous matrix polyvinyl alcohol or polyethylene glycol oxide, with water-soluble solvent water, alcohols it is one or more of
Mixed solvent dissolves it;
Cellulose nano-fibrous-lithium aqueous solution and polymeric matrix mixing specific method are:Polymeric matrix is aqueous base
When body, the two directly mixes;When polymeric matrix is oiliness matrix, by required oil-dissolving solvent and cellulose nano-fibrous-lithium
1.2~1vt.% of aqueous solution, 55~80 DEG C hang steaming after volume reduction half, ultrasonic disperse, continue to dose required oily molten
Property solvent, continue outstanding steaming, ultrasonic disperse, until aqueous solution all steams, the oil for obtaining required cellulose nano-fibrous-lithium is molten
Property suspension, then obtained suspension is mixed with polymer matrix liquid solution, vt.% is percentage by volume;
B. film liquid heating deaeration is scraped, is cooled to room temperature;
C. glass plate used in mould is scraped to pre-process:Glass plate is placed in the mixed solution of absolute ethyl alcohol/water, it is even that silane is added
The dosage for joining agent KH570, the silane coupling agent KH570 is 5~20vt.% of the mixed solution of absolute ethyl alcohol/water, is then used
Oxalic acid regulation system pH to 4 ± 0.2 is ultrasonically treated 3~6h in 70~80 DEG C, and rear clean is dried, the absolute ethyl alcohol and water
Volume ratio is 3:1;
D. knifing:Glass plate takes evenly laid out in glass plate edge, removal wherein bubble of scraping film liquid in fixed on platform,
100~500 μm of face knifing of scraper are taken, a moment is stood, is placed in solvent and carries out coagulating bath.
Solvent selected by coagulating bath dissolves each other with the solvent of dissolving matrix, but matrix does not dissolve wherein, can be it is a kind of or
A variety of mixed solvents.
Further, solvent used in coagulating bath selects as follows in the step D:Scrape film liquid is using solvent
When polyvinyl alcohol, coagulating bath solvent selects ethyl alcohol, and it is cellulose acetate, cyanethyl cellulose, polyarylether to scrape film liquid using solvent
Ketone, polyethylene, polypropylene, polyvinyl chloride, polymethyl methacrylate, polyimides, polyurethane, polysulfones, gathers Kynoar
When a kind of in ether sulfone, coagulating bath solvent selects deionized water.
Further, described to scrape film liquid, the parameter with microwave heating method mixed configuration, microwave heating is:Temperature is polymerization
The solution temperature of object in a solvent, if polyvinyl alcohol water solution temperature is 90 DEG C, the dimethyl formamide solution of cellulose acetate
It is 40 DEG C.Microwave heating dissolving greatly accelerates dissolved efficiency, and the time is about 30~60min, and power is 100~300W.
The present invention has the advantages that:
1. the lithium ion battery separator of cellulose nano-fibrous-lithium improvement prepared by the present invention, cellulose nano-fibrous-
Lithium, maintains I crystalline structure of native cellulose well, assigns composite membrane and puies forward preferable mechanical performance, big draw ratio,
And its surface institute is electrically charged, ensures that its is evenly dispersed, and improve the hydrophily of composite membrane, the introducing of metal-lithium ion improves
The thermal stability of diaphragm.
When the lithium ion battery separator for cellulose nano-fibrous-lithium improvement that 2, prepared by the present invention, using microwave heating method
Film liquid is scraped in configuration, can effectively improve configuration solution efficiency, and it is few to scrape film liquid bubble obtained by this kind of method, greatly reduces de-
Steep the time.
3, the present invention prepare it is cellulose nano-fibrous-lithium improvement lithium ion battery separator when, to knifing glass plate into
It has gone a degree of hydrophobic or hydrophilic treated, has conveniently taken off film, ensure that the complete structure of diaphragm.
4, the lithium ion battery separator for cellulose nano-fibrous-lithium improvement that prepared by the present invention has superior imbibition rate,
Full liquid rate and preparation method is environmental-friendly, has very high industrialization production ability, application prospect very wide.
Description of the drawings
Fig. 1 is the surface scan electron microscope of film prepared by embodiment 4;
Fig. 2 is the profile scanning electron microscope of film prepared by embodiment 4;
Fig. 3 is the surface scan electron microscope of film prepared by embodiment 9;
Fig. 4 is the profile scanning electron microscope of film prepared by embodiment 9.
Specific implementation mode
With reference to specific embodiment, the present invention will be further described.The embodiment is only the preferred implementation of the present invention
Example, is not intended to restrict the invention, for those skilled in the art, the present invention can have various changes and change
Change.All within the spirits and principles of the present invention, any modification, equivalent replacement, improvement and so on should be included in the present invention
Protection domain within.
(1) it is 77000 polyvinyl alcohol that polymeric matrix, which is molecular weight,.Cellulose nano-fibrous-lithium accounts for polymeric matrix
0.1~20wt.%.
(2) porous structure of diaphragm is obtained by phase disengagement method, and will scrape film liquid with scraper scrapes film forming on a glass, with
Room temperature is underlying afterwards carries out coagulating bath for 24 hours in ethyl alcohol, then is dried at room temperature for, and takes to obtain required diaphragm off.
(3) when film liquid is scraped in preparation, with microwave heating method mixing pva and solvent, uniform solution is obtained, temperature is
80~100 DEG C, heating time is 20~50min, and heating power is controlled in 100~200W.
(4) scraping film liquid when knifing, in (3) needs deaeration, need to be cooled to room temperature, and uses the faces scraper 150nm knifing.
(5) glass plate used in (3), takes off film for convenience, needs to carry out a degree of hydrophobic treatment, agents useful for same is silicon
Alkane coupling agent, oxalic acid, ethyl alcohol etc..Before use, glass plate need to be kept clean.
Above-mentioned diaphragm be it is porous, porosity be 50%~80%, aperture be 20nm~1 μm, thickness be 15~30 μ
m。
Thickness, porosity, imbibition rate, pattern, ionic conductivity, interface stability are carried out to gained diaphragm and carry out test table
Sign.
Porosity is measured using imbibition priting.Will be dry that diaphragm is completely immersed in n-butanol, the n-butanol absorbed by film
Amount calculate the volume in hole.The calculation formula of porosity is:
P=(M/ ρ)/(M/ ρ+Mm/ρp) × 100%
In formula:M is the quality (g) for the n-butanol that diaphragm absorbs, and M_m is the quality (g) after diaphragm drying, and ρ is n-butanol
Density (g/cm3).
Imbibition rate is tested, and load weighted diaphragm is impregnated in the electrolytic solution, is taken out after fully absorbing electrolyte.It is inhaled with filter paper
The electrolyte for removing excess surface, weighs.Whole process carries out in glove box.Imbibition rate asks calculation with following formula:
ξ=(M-M0)/M0× 100%
In formula:M0It is respectively the quality (g) of wet film after dry film and dipping electrolyte with M.
On electrochemical workstation, the ionic conductivity that electrolyte infiltrates diaphragm is measured using AC impedence method.Specifically
Operating method:Between electrolyte infiltration diaphragm is added in the stainless steel electrode of two known areas as sandwich, it is used in combination mating
Battery case seals.It must ensure that inside battery does not have bubble and electrode surface height smooth, diaphragm is made to be come into full contact with electrode.It will
One electrode of battery is connected with the working electrode of test system, another electrode is connected with reference electrode and auxiliary electrode, hands over
Stream perturbation amplitude is 5mV, and test frequency is 1~105Hz, 20~90 DEG C of temperature.The ac impedance spectroscopy measured is to have centainly tiltedly
The intersection value of the straight line of rate, straight line and real axis is the bulk resistance wind of diaphragm.Ionic conductivity is calculated according to the following formula:
σ=d (Rb·S)
In formula:The conductivity (S/cm) of σ-diaphragm;The thickness (cm) of d- diaphragms;RbThe bulk resistance (Ω) of diaphragm;S- is not
Area (the cm of rust steel electrode2)。
Table 1 be different content it is cellulose nano-fibrous-thickness of polyvinyl alcohol membranes of lithium improvement, porosity, imbibition rate,
Ionic conductivity, Fig. 1 and Fig. 2 are respectively surface and the profile scanning electron microscope of film prepared by embodiment 4.As can be seen from the table
Diaphragm has good hydrophily, and with the increase of cellulose nano-fibrous-lithium content, imbibition rate obviously increases, to electrolyte
Good wellability and retentivity so that ionic conductivity is also promoted therewith.Gained diaphragm porosity is 60%~80%.
The thickness of the PVA diaphragms of 1 different content CNFs-Li improvement of table, porosity, imbibition rate, ionic conductivity
|
Embodiment 1 |
Embodiment 2 |
Embodiment 3 |
Embodiment 4 |
Embodiment 5 |
Embodiment 6 |
CNFs-Li mass fractions |
0 |
0.2% |
0.5% |
1% |
2% |
5% |
Thickness (μm) |
23 |
25 |
20 |
23 |
25 |
24 |
Porosity (%) |
60.72 |
61.40 |
61.65 |
68.83 |
72.88 |
75.84 |
Imbibition rate |
1.45 |
1.68 |
1.91 |
2.22 |
2.34 |
3.34 |
Ionic conductivity (mScm-1) |
0.254 |
0.255 |
0.255 |
0.267 |
0.303 |
0.644 |
(1) polymeric matrix cellulose acetate (CAS:9004-35-7), outstanding steam of cellulose nano-fibrous-lithium solution is set
It changes in dimethyl formamide solution, it is ultrasonic to obtain evenly dispersed suspension, a concentration of 0.1~2wt.%.Cellulose Nanowire
Dimension-lithium accounts for 0.1~20wt.% of polymeric matrix, and configuration polyvinyl alcohol scrapes film liquid for 10wt.%'s.
(2) porous structure of diaphragm is obtained by phase disengagement method, and will scrape film liquid with scraper scrapes film forming on a glass, with
Room temperature is underlying afterwards carries out coagulating bath for 24 hours in deionized water, then is dried at room temperature for, and takes to obtain required diaphragm off.
(3) it prepares when scraping film liquid, cellulose acetate and dimethylformamide is mixed with microwave heating method, obtain uniform molten
Liquid, temperature are 40~50 DEG C, and heating time is 20~50min, and heating power is controlled in 100~200W.
(4) scraping film liquid when knifing, in (3) needs deaeration, need to be cooled to room temperature, and uses 150 μm of face knifing of scraper.
Above-mentioned diaphragm be it is porous, porosity be 50%~80%, aperture be 20nm~1 μm, thickness be 15~30 μ
m。
Thickness, porosity, imbibition rate, pattern, ionic conductivity, interface stability are carried out to gained diaphragm and carry out test table
Sign.Porosity is measured using imbibition priting.Will be dry that diaphragm is completely immersed in n-butanol, by film absorb n-butanol amount come
Calculate the volume in hole.The calculation formula of porosity is:
P=(M/ ρ)/(M/ ρ+Mm/ρp) × 100%
In formula:M is the quality (g) for the n-butanol that diaphragm absorbs, and M_m is the quality (g) after diaphragm drying, and ρ is n-butanol
Density (g/cm3).
Imbibition rate is tested, and load weighted diaphragm is impregnated in the electrolytic solution, is taken out after fully absorbing electrolyte.It is inhaled with filter paper
The electrolyte for removing excess surface, weighs.Whole process carries out in glove box.Imbibition rate asks calculation with following formula:
ξ=(M-M0)/M0× 100%
In formula:M0It is respectively the quality (g) of wet film after dry film and dipping electrolyte with M.
On electrochemical workstation, the ionic conductivity that electrolyte infiltrates diaphragm is measured using AC impedence method.Specifically
Operating method:Between electrolyte infiltration diaphragm is added in the stainless steel electrode of two known areas as sandwich, it is used in combination mating
Battery case seals.It must ensure that inside battery does not have bubble and electrode surface height smooth, diaphragm is made to be come into full contact with electrode.It will
One electrode of battery is connected with the working electrode of test system, another electrode is connected with reference electrode and auxiliary electrode, hands over
Stream perturbation amplitude is 5mV, and test frequency is 1~105Hz, 20~90 DEG C of temperature.The ac impedance spectroscopy measured is to have centainly tiltedly
The intersection value of the straight line of rate, straight line and real axis is the bulk resistance of diaphragm.Ionic conductivity is calculated according to the following formula:
σ=d/ (Rb·S)
In formula:The conductivity (S/cm) of σ-diaphragm;The thickness (cm) of d- diaphragms;RbThe bulk resistance (Ω) of diaphragm;S- is not
Area (the cm of rust steel electrode2)。
Table 2 be different content it is cellulose nano-fibrous-thickness of cellulose acetate of lithium improvement, porosity, imbibition rate, from
Electron conductivity, Fig. 3 and Fig. 4 are respectively surface and the profile scanning electron microscope of film prepared by embodiment 9.As can be seen from the table every
Film has good hydrophily, and with the increase of cellulose nano-fibrous-lithium content, imbibition rate obviously increases, good to electrolyte
Wellability and retentivity so that ionic conductivity is also promoted therewith.Gained diaphragm porosity is 60%~80%.
The thickness of the CA diaphragms of 2 different content CNFs-Li improvement of table, porosity, imbibition rate, ionic conductivity
|
Embodiment 7 |
Embodiment 8 |
Embodiment 9 |
Embodiment 10 |
Embodiment 11 |
Embodiment 12 |
CNFs-Li mass fractions |
0 |
0.2% |
0.5% |
1% |
2% |
5% |
Thickness (μm) |
23 |
25 |
20 |
23 |
25 |
24 |
Porosity (%) |
45.11 |
49.67 |
54.68 |
60.49 |
63.72 |
67.12 |
Imbibition rate |
1.18 |
1.28 |
1.51 |
1.83 |
2.01 |
2.54 |
Ionic conductivity (mScm-1) |
0.601 |
0.685 |
0.733 |
0.926 |
1.003 |
1.272 |
In addition, by experiment it has also been found that, either which kind of polymeric matrix, with cellulose nano-fibrous-lithium content
Increasing, interface impedance value is gradually reduced, i.e., has good interface stability between electrolyte infiltration diaphragm and metal lithium electrode,
Inventor has also been made its principle and centainly probes into:On the one hand it is because of the porosity and imbibition rate that diaphragm has had, high porosity
Can be effectively facilitated electrolyte and interelectrode compatibility with the larger specific surface area of fiber in film, ion can it is smooth unimpededly
It is quickly conducted in two interpolars;On the other hand may be to be increased because introducing lithium ion in cellulose nano-fibrous-lithium
The quantity of lithium ion, while CNFs-Li, as Ionomer, itself also has the ability for combining and ionizing out lithium ion.
Diaphragm not only ensure that the formation of the passivating film of lithium electrode surface stabilization with lower impedance, can also be during circulating battery
Slow down concentration polarization and ohmic polarization, to significantly increase the cycle performance of battery, extends the service life of battery.