Patent Application
20120058399
This application claims priority of Taiwanese application No. 099130034, filed on Sep. 6, 2010.
1. Field of the Invention
This invention relates to a branched polymer, a method for making the branched polymer, and a polymer electrolyte and a polymer electrolyte film that contain the branched polymer.
2. Description of the Related Art
In recent years, in order to accord with the demand for miniaturization of a battery device, solid polymer electrolytes (SPE) have been developed for use in a small scale battery device because of its adjustable volume. The solid polymer electrolyte is mainly made by mixing and reacting a polymer with a metal salt (such as a lithium salt). At present, polyethylene oxide (PEO), formed from open-ring polymerization by epoxy, is mostly used as the polymer for a solid polymer electrolyte. PEO is a linear polymer that has a helical structure, a low glass transition temperature, and high crystallization. When at a low temperature, the linear structure and the precipitation of PEO crystal may adversely influence the ion conduction of the solid polymer electrolyte made therefrom, thereby resulting in a relatively low conductivity of the final electrolyte product.
Therefore, it is desirable in the art to provide a polymer that has a branched structure and that may overcome the aforesaid drawbacks associated with the prior art.
The object of the present invention is to provide a branched polymer, a method for making the same, and a polymer electrolyte and a polymer electrolyte film made therefrom.
According to one aspect of this invention, a branched polymer is represented by the following formula (I):
wherein at least one of L1, L2, L3, and L4 is a univalent organic group represented by the following formula (II):
wherein D1, D2, and D3 are independently a single bond or a divalent group, at least one of D1, D2, and D3 containing
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000,
n1 being an integer ranging from 1 to 1000,
L5 being hydrogen or a univalent organic group represented by the following formula (III):
wherein R is a univalent end group that optionally contains
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000,
L6 and L7 being independently hydrogen, a univalent organic group of formula (III), or a univalent organic group represented by the following formula (IV):
wherein D2′ and D3′ respectively have the same definitions as D2 and D3,
L8, L9, and L10 respectively having the same definitions as L5,
n2 being an integer ranging from 1 to 1000; and
the remainder of L1, L2, L3, and L4 being independently hydrogen or a univalent organic group represented by formula (III),
with the proviso that, when one of the remainder is hydrogen, the others of the remainder cannot be hydrogen.
According to a second aspect of this invention, a method for making the aforesaid branched polymer comprises: reacting a polyamino compound represented by H2N-D4-NH—Y1 with an epoxy component that includes a diepoxy compound represented by
wherein D4 is a single bond or a divalent group and D5 is a divalent group, at least one of D4 and D5 containing
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000,
Y1 being hydrogen or a univalent end group optionally containing
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000.
According to a third aspect of this invention, a polymer electrolyte comprises the aforesaid branched polymer and a salt.
According to a fourth aspect of this invention, a polymer electrolyte film comprises the aforesaid polymer electrolyte.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which:
The preferred embodiment of a branched polymer according to this invention is represented by the following formula (I):
wherein at least one of L1, L2, L3, and L4 is a univalent organic group represented by the following formula (II):
and
the remainder of L1, L2, L3, and L4 being independently hydrogen or a univalent organic group represented by the following formula (III):
wherein R is a univalent end group that optionally contains
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000,
with the proviso that, when one of the remainder is hydrogen, the others of the remainder cannot be hydrogen.
Preferably, at least three of L1, L2, L3, and L4 are univalent organic groups represented by formula (II).
In formula (II), D1, D2, and D3 are independently a single bond or a divalent group. At least one of D1, D2, and D3 contains
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000.
Preferably, D1, D2, and D3 are independently —X1-G-X2—,
wherein G is a single bond or
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000, and
X1 and X2 being independently selected from the group consisting of a single bond, a C1 to C40 alkylene group, a C2 to C40 alkenylene group, a C3 to C20 cycloalkylene group, a C6 to C10 arylene group, a divalent heterocyclic group, a silanylene group, a siloxanylene group,
and combinations thereof,
wherein the C1 to C40 alkylene group, C2 to C40 alkenylene group, C3 to C20 cycloalkylene group, C6 to C10 arylene group, divalent heterocyclic group, silanylene group, and siloxanylene group are optionally substituted with fluorine or a cyano group.
More preferably, D1 and D3 are the same and are selected from the group consisting of
wherein m1+m2=5 and m4=1−300; and D2 is
In the examples of this invention, D1 and D3 are the same and are
In formula (II), n1 is an integer ranging from 1 to 1000; L5 is hydrogen or a univalent organic group of formula (III); L6 and L7 are independently hydrogen, a univalent organic group of formula (III), or a univalent organic group represented by the following formula (IV):
wherein D2′ and D3′ respectively have the same definitions as D2 and D3 of formula (II),
L8, L9, and L10 respectively having the same definitions as L5 of formula (II), and
n2 being an integer ranging from 1 to 1000.
Preferably, in formula (III), R is selected from the group consisting of a C1 to C40 alkyl group, a C2 to C40 alkenyl group, a C1 to C40 alkoxy group, a C3 to C20 cycloalkyl group, a C6 to C10 aryl group, a heterocyclic group, an amino group, an imine group, a silanyl group, a siloxanyl group, an amido group, an imido group, an ester group, a ketone group, a urea group, an aminoformate group, an anhydride group, a sulfonyl group, a sulfoxide group, an ether group, a formyl group, and combinations thereof, wherein the C1 to C40 alkyl group, C2 to C40 alkenyl group, C3 to C20 cycloalkyl group, C6 to C10 aryl group, heterocyclic group, silanyl group, and siloxanyl group are optionally substituted with fluorine or a cyano group.
In the examples of this invention, R is
wherein p is 4 or an integer ranging from 12 to 14.
Preferably, the branched polymer of this invention has a weight average molecule weight ranging from 1000 to 100000, more preferably, from 4000 to 9000.
Preferably, the branched polymer of this invention has a polydispersity index (PDI) ranging from 1 to 2.
The preferred embodiment of a method for making the aforesaid branched polymer comprises: reacting a polyamino compound represented by H2N-D4-NH—Y1 with an epoxy component that includes a diepoxy compound represented by
wherein D4 and D5 are independently a single bond or a divalent group, at least one of D4 and D5 containing
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000,
Y1 being hydrogen or a univalent end group optionally containing
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000.
Preferably, Y1 has the same definition as R of formula (III), and D4 and D5 respectively have the same definitions as D1 and D2 of formula (I) and formula (II).
More preferably, the polyamino compound is selected from, but is not limited to, the group consisting of polyoxyethylene/oxypropylene diamine (PEDA, e.g.,
wherein m1+m2=5), polyoxyethylene diamine (e.g.,
wherein m4=1−300), and polyoxypropylene diamine (e.g.,
). In the examples of this invention, the polyamino compound is PEDA or polyoxypropylene diamine.
More preferably, the diepoxy compound is selected from, but is not limited to, the group consisting of
(poly(ethylene glycol) diglycidyl ether, PEGDE),
(bisphenol A propoxylate diglycidyl ether),
(ethylene glycol diglycidyl ether),
(1,4-cyclohexanedimethanol diglycidyl ether),
(resorcinol diglycidyl ether), and
(2,3-diepoxypropyl phthalate). In the examples of this invention, the diepoxy compound is PEGDE.
Preferably, the epoxy component used in the method for making the aforesaid branched polymer further includes a monoepoxy compound represented by
wherein Y2 is hydrogen or a univalent end group that optionally contains
in which R1 is hydrogen or a methyl group and n is an integer ranging from 1 to 1000.
Preferably, Y2 has the same definition as R of formula (III). More preferably, the monoepoxy compound is selected from, but is not limited to, the group consisting of
(named butyl glycidyl ether (BGE) when p=4, and dodecyl/tetradecyl glycidyl ether (AGE) when p=12-14,
(phenyl glycidyl ether, PGE), 2-ethylhexyl glycidyl ether, and tert-butyl phenyl glycidyl ether.
It should be noted that the epoxy component may optionally include the monoepoxy compound, and the mole ratio of the polyamino compound, the diepoxy compound, and the monoepoxy compound is adjustable based on actual requirements. Preferably, themole ratioofthepolyamino compound, the diepoxy compound, and the monoepoxy compound ranges from 1:0.1:0.1 to 1:2:4. In the examples of this invention, the mole ratio is 1:0.75:2.5.
A preferred embodiment of a polymer electrolyte of the present invention comprises the aforesaid branched polymer and a salt. The polymer electrolyte may be produced by mixing and reacting the branched polymer with the salt. Alternatively, the polymer electrolyte may be produced by reacting the polyamino compound, the epoxy component, and the salt at the same time.
Preferably, the salt is a salt of lithium or a salt of iodine, such as, but not limited to, LiClO4, LiCF3SO3, LiN(CF3SO2)2, LiI, LiBF4, LiPF6, KI, NaI, N[(CH2)3CH3]4I, etc. In the examples of this invention, the salt is LiClO4, and the mole ratio of the oxygen in the branched polymer to the lithium in the salt of lithium is 15:1.
The aforesaid polymer electrolyte may be used for preparing a battery or an anti-freezing agent.
Because the branched polymer of this invention includes high electronegative atoms that have unpaired electrons (e.g., O and N), a cation dissociated from the salt easily attach to and form a temporary coordination bond with the branched polymer through the electronegative atoms. Accordingly the branched polymer and the salt may coordinate to form a stable electrolyte system. Moreover, since the branched polymer of this invention has a low glass transition temperature and amorphicity that are advantageous to the cations moving in the branched polymers, the polymer electrolyte of this invention has superior conductivity.
The present invention also discloses a polymer electrolyte film including the aforesaid polymer electrolyte. The polymer electrolyte film may be produced by mixing the polymer electrolyte with a solvent to obtain an electrolyte solution, followed by contacting a polymer film with the electrolyte solution, e.g., coating the electrolyte solution on the polymer film, or immersing the polymer film in the electrolyte solution. Preferably, the solvent is alcohol and the polymer film is an epoxy resin film.
Alternatively, the polymer electrolyte film may be produced by mixing the polymer electrolyte with a solvent to obtain an electrolyte solution, followed by mixing the electrolyte solution with an epoxy resin and a curing agent, and thermal curing the mixture. Preferably, the curing agent is present in an amount of 10 parts by weight based on 100 parts by weight of the epoxy resin. Preferably, in the mixture, the weight ratio of the polymer electrolyte to the epoxy resin and the curing agent ranges from 80:20 to 45:55. Preferably, the thermal curing is conducted under a temperature ranging from 40° C. to 70° C. .
1. Poly(ethylene glycol)diglycidyl ether (PEGDE): commercially available from Aldrich, with a molecular weight of 526 g/mol.
2. Phenyl glycidyl ether (PGE): commercially available from Acros, with a molecular weight of 150.18 g/mol.
3. Butyl glycidyl ether (BGE): commercially available from Aldrich, with a molecular weight of 130 g/mol.
4. Dodecyl and tetradecyl glycidyl ether (AGE): commercially available from Aldrich, with a molecular weight of 300 g/mol.
5. Fluorene glycidyl ether (FGE): commercially available from JSI, with a molecular weight of 288 g/mole.
6. Polyoxypropylene diamine: commercially available from Huntsman under a trade name of D-230, with a molecular weight of 230 g/mol.
7. Polyoxyethylene/oxypropylene diamine (PEDA): commercially available from Aldrich, with a molecular weight of 2000 g/mol.
8. LiClO4: commercially available from Aldrich.
9. Tetrahydrofuran (THF): commercially available from Aldrich.
10. Bisphenol A type epoxy: commercially available from Dow Chemical Company under a trade name of D.E.R. 231.
11. Tri(dimethylaminomethyl)phenol: commercially available from Aldrich under a trade name of DMP30.
1. Gel permeation chromatography (GPC): commercially available from Waters under a trade name of 510 HPLC Pump; equipped with a detector under a trade name of RI 2000 and chromatography columns under trade names of PL gel 3 μm 100 Å 300×7.5 mm, PL gel 5 μm MIXED-C 300×7.5 mm, and PL gel 5 μm 50×7.5 mm. Polystyrene was used as a standard.
2. Fourier transformation infrared (FT-IR) spectrometer: commercially available from Perkin Elmer under a trade name of Spectrum 2000.
3. NMR spectrometer: commercially available from Bruker under a trade name of Avance-400 MHz FT NMR. 4.
4. Differential scanning calorimeter (DSC): commercially available from TA Instrument under a trade name of DSC2920.
5. Thermogravimetric analyzer (TGA): commercially available from TA Instrument under a trade name of Q50.
6. Electrochemical analyzer: commercially available from CH Instruments under a trade name of CHI614B.
Predetermined amounts of a polyamino compound, a diepoxy compound (i.e., PEGDE), and a monoepoxy compound were uniformly mixed in a mole ratio of 1:0.75:2.5, followed by heating the mixture to conduct the polymerization reaction. Branched polymers of Examples 1 to 7 were obtained. In the examples of this invention, there were two stages for the polymerization reaction, in which the reaction times for the first and second stages were respectively 2 hours and 10 hours.
The species of the polyamino compound, the monoepoxy compound, and the reaction temperature for the polymerization reactions for each of Examples 1 to 7 are shown in Table 1.
1 gram of the branched polymer prepared from each of Examples 1 to 7 was dissolved in 100 grams of THF. The weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity index (PDI) of the branched polymers were measured using GPC. The conversion rate for each of the polymerization reaction for Examples 1 to 7 was measured and calculated by titration. The measurement results are shown in Table 2.
1 gram of the branched polymer prepared from each of Examples 1 to 6 was dissolved in 100 grams of THF so as to obtain a branched polymer solution, followed by spreading the branched polymer solution on a KBr salt plate. The structures of the branched polymers were identified using FT-IR and 13C-NMR spectra.
Referring to
As shown in
Predetermined amount of each of the branched polymers prepared from Examples 1 to 7 was mixed with predetermined amount of LiClO4, followed by adding dehydrated THF to form a reaction solution. The reaction solution was uniformly mixed in an ultrasonic oscillator for 30minutes, followed by disposing the reaction solution in a vacuum oven at 65° C. for 24 hours to remove THF and to obtain the polymer electrolytes of Examples 8 to 17.
The branched polymer used for preparation of the aforesaid polymer electrolyte and the mole ratio of oxygen to lithium (O/Li ratio) for each of Examples 8 to 17 are shown in Table 3.
Examples 8 to 17 were dried in a vacuum oven at 90° C. for 24 hours before the following analyses in order to prevent moisture from interfering with the test results.
The structure of the polymer electrolytes of Examples 8 to 16 were identified using FT-IR spectra.
Referring to
The temperatures at the 5% weight loss (T5 wt % loss) and at the maximum decomposition rate (Td) for each of Examples 1 to 17 were measured by heating 10 to 15 micrograms of Examples 1 to 17 from room temperature to 600° C. at a heating rate of 20° C. /min using a thermogravimetric analyzer (TGA), in which the flow rate for nitrogen was 90 L/min. The results for T5 wt % loss and Td are shown in Table 4.
The maximum degraded temperatures for Examples 1-6 and 8-16 are all higher than 250° C., which indicate great heat stabilities thereof.
5 to 10 micrograms of each of Examples 1 to 17 were pressed to form a tablet. The glass transit ion temperature (Tg) for each of the tablets was determined using a differential scanning calorimetry (DSC). A heating chamber of the DSC device was quenched with liquid nitrogen to −100° C. and subsequently heated to a temperature of 100° C. at a heating rate of 10° C./min. The measurement results are shown in Table 4.
The ion conductivity of each of Examples 1 to 17 was measured by an AC impedance method (applied voltage: 20 mV; frequency: 1 Hz to 100 kHz using an electrochemical analyzer. The measurement was conducted and recorded at temperatures of 20° C., 30° C., 40° C., 50° C., 60° C., and 70° C., and the results are shown in Table 5. Higher ion conductivity is preferred.
The ion conductivities of Examples 8 to 17 are higher than those of Examples 1 to 7, which indicate that the addition of LiClO4 improves the ion conductivities of the branched polymers of this invention. In the group of Examples 1 to 7 and the group of Examples 8 to 17, Example 7 and Example 17, which contain fluorine glycidyl ether (FGE), respectively have superior ion conductivity than other examples.
In addition, comparing the measurement results of ion conductivity with those of glass transition temperature in Table 3, it is shown that, in the group of Examples 1 to 7 and the group of Examples 8 to 17, the ion conductivity increases as the glass transition temperature decreases. The tendency indicates that the ion conductivity is influenced by the polymer structure and the polydispersity index (PDI) of the branched polymer.
0.685 gram of the polymer electrolyte prepared from Example 12 was dissolved in an alcohol solution (concentration: 99.9 vol %) and mixed in an ultrasonic oscillator for 30 minutes for complete dissolution of the polymer electrolyte in the alcohol solution so as to obtain a polymer electrolyte solution. A porous polymer film, MT-40, was immersed in the polymer electrolyte solution and oscillated in an ultrasonic oscillator for 2 hours such that the porous polymer film absorbed the polymer electrolyte solution to form a polymer electrolyte film. The polymer electrolyte film was dried in a vacuum oven at 100° C. for removing alcohol and was subsequently weighed. A first absorbance of the polymer electrolyte film was measured using the following equation:
Absorbance (wt %)=weight after absorption (g)−weight before absorption (g)/weight before absorption (g)×100%.
After repeating the above steps of immersing the polymer film in the polymer electrolyte solution and drying the same, a second absorbance of the polymer electrolyte film was measured. The first and second absorbances for the polymer electrolyte film of Example 18 were respectively 76 wt % and 78 wt %. The difference between the first and second absorbances is small that indicates the absorptibn of the polymer electrolyte film was substantially saturated at the first time of absorption. The final polymer electrolyte film of Example 18 was obtained after drying in a vacuum oven at 100° C. for 24 hours.
0.8566 gram of the polymer electrolyte prepared from Example 12 was dissolved in an alcohol solution (concentration: 99.9 vol %) and mixed in an ultrasonic oscillator for 30 minutes for complete dissolution of the polymer electrolyte in the alcohol solution so as to obtain a polymer electrolyte solution. Bisphenol A type epoxy and tri(dimethylaminomethyl)phenol (serving as a curing agent) were mixed at a weight ratio of 10:1 to form a reactant mixture.
Each of the polymer electrolyte solutions was mixed with the reactant mixture to form a precursor mixture.
The precursor mixture was poured into a mold and was cured in a hot-air oven at 40° C. for 48 hours, followed by disposing in a vacuum atmosphere at 70° C. for 24 hours to remove alcohol. Subsequently, the precursor mixture was dried in a vacuum oven at 100° C. to obtain the polymer electrolyte film for each of Examples 19 to 24. In the precursor mixture, the respective amounts of the polymer electrolyte and the reactant mixture for each of Examples 19 to 24 are shown in Table 6.
The glass transition temperature (Tg) and ion conductivity for each of Examples 18 to 24 were measured using the same method as described above. The measurement results are shown in Table 7.
The two glass transition temperatures of the polymer electrolyte film prepared from Example 18 indicates that the polymer electrolyte film includes a polymer electrolyte and a polymer film. The measurement results of Tg for Examples 19 to 24 show that Tg is increased with a decrease in the amount of the polymer electrolyte.
The ion conductivity of Example 18 is higher than those of Examples 19 to 24, which indicates that a polymer electrolyte film made from Example 18 has superior properties.
The morphology of the porous polymer film, i.e., MT-40, used in Example 18 and the morphology of the final polymer eletrolyte film of Example 18 were observed using a scanning electron microscope. The morphology observations are shown in
In conclusion, the branched polymers of the present invention have the properties of great thermal stability, low glass transition temperature, and amorphicity, and thus can be used as a conductive material. Moreover, the method for making the branched polymer of this invention is simple and convenient. The polymer electrolyte made from the branched polymer exhibits superior heat stability, and the polymer electrolyte film made from the aforesaid polymer electrolyte has good conductivity.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 099130034 | Sep 2010 | TW | national |
