U.S. patent application number 12/390634 was filed with the patent office on 2009-09-03 for processes for producing monolithic porous carbon disks from aromatic organic precursors.
Invention is credited to Jing Wang.
Application Number | 20090220722 12/390634 |
Document ID | / |
Family ID | 35799241 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090220722 |
Kind Code |
A1 |
Wang; Jing |
September 3, 2009 |
PROCESSES FOR PRODUCING MONOLITHIC POROUS CARBON DISKS FROM
AROMATIC ORGANIC PRECURSORS
Abstract
Disclosed are processes for producing monolithic and metal doped
monolithic porous carbon disks from prepolymer organic precursors
in the powder form composed of either or both polyimide and
polybenzimidazole. The powders are consolidated (compressed) into
disks and then pyrolyzed to form the desired porous carbon disk.
Porous carbon-carbon composite disks are also prepared by adding
carbon to the prepolymer organic precursors.
Inventors: |
Wang; Jing; (Amherst,
MA) |
Correspondence
Address: |
JACKSON WALKER LLP
901 MAIN STREET, SUITE 6000
DALLAS
TX
75202-3797
US
|
Family ID: |
35799241 |
Appl. No.: |
12/390634 |
Filed: |
February 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11202989 |
Aug 11, 2005 |
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12390634 |
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10919450 |
Aug 16, 2004 |
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11202989 |
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Current U.S.
Class: |
428/64.1 ;
264/29.6 |
Current CPC
Class: |
H01M 8/0234 20130101;
Y02E 60/10 20130101; H01G 11/24 20130101; H01M 4/0471 20130101;
C04B 2235/40 20130101; C04B 35/524 20130101; C04B 2235/3256
20130101; H01M 4/583 20130101; H01M 4/9083 20130101; H01M 4/622
20130101; H01G 11/32 20130101; C04B 2235/404 20130101; H01M 4/96
20130101; H01M 4/621 20130101; Y02E 60/50 20130101; Y10T 428/21
20150115; B82Y 30/00 20130101; H01M 4/625 20130101; H01M 4/926
20130101; Y02E 60/13 20130101; C04B 2235/80 20130101; H01M 4/8882
20130101; H01G 9/042 20130101; H01M 4/626 20130101; H01M 4/8875
20130101 |
Class at
Publication: |
428/64.1 ;
264/29.6 |
International
Class: |
B32B 3/02 20060101
B32B003/02; C01B 31/00 20060101 C01B031/00 |
Claims
1-26. (canceled)
27. A monolithic porous carbon-carbon composite made by a process
comprising the steps of: preparing a precursor powder comprising
either or both polymide and polybenzimidazole; consolidating the
precursor powder under pressure; and pyrolyzing the monolith in an
inert atmosphere or carbon dioxide to form a monolithic porous
carbon disk.
28. A monolithic porous carbon-carbon composite made by the method
of claim 27 wherein the process further comprises adding carbon to
the precursor powders to form a monolithic porous carbon-carbon
composite disk.
29. (canceled)
Description
[0001] This is a continuation-in-part of U.S. application Ser. No.
10/919,450, filed Aug. 16, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the preparation of
precursors composed of either or both polyimide and
polybenzimidazole as organic precursors for producing monolithic
porous carbon with density less than or equal to 1.0 g/cc; and the
processes for producing monolithic porous carbon from either or
both polyimide and polybenzimidazole precursors in the powder form.
The present invention further relates to the processes for
producing monolithic porous carbon derived from either or both
polyimide and polybenzimidazole precursors having one or more than
one metals dispersed therein. The present invention even further
relates to the processes for producing carbon-carbon composite
prepared from precursors comprising either or both polyimide and
polybenzimidazole and activated carbon in the form of powders
and/or fibers.
[0004] 2. Description of Related Art
[0005] Monolithic porous carbon, which possess interpenetrating
pore structure, high density, high surface area, suitable pore
size, and well defined pore size distribution, are highly desirable
as electrode materials for lithium batteries, electrochemical
capacitors, fuel cells, as well as other electrochemical devices.
The following description will be directed to disk products
although it will be understood that other such products can be made
from the porous carbon.
[0006] One approach to produce monolithic porous carbon disk is
through sol-gel technologies. The sol-gel technology generally
consists of preparation of gels from solution, drying the gel while
minimizing the gel shrinkage. The pyrolysis of thin gel films
yields porous monolithic carbon disks. RF carbon aerogel currently
in the market as electrode material for supercapacitors is derived
from resorcinol and formaldehyde organic precursors. RF carbon
aerogel provide high surface area and narrow pore size
distribution. Yet, the potential market of RF carbon aerogel as
electrode and material for ultracapacitors and supercapacitors is
severely limited by the low operating voltage of the capacitor
(<=5V) and high manufacturing cost of monolithic RF carbon
aerogel materials.
[0007] Another approach to produce monolithic porous carbon disks
is from powders of porous polymeric precursors by compressing them
into a monolith disk followed by pyrolysis. There are 2 obstacles
in this approach. One is the compressibility of the polymer
precursor and the other is the difficulty in retaining
interpenetrating network of the pores during the compression
process. U.S. Pat. No. 6,544,648 discloses a process for making
monolithic carbon disks by compressing carbon black powder with
high surface area under vacuum at temperatures at or beyond
800.degree. C. and a pressure at or beyond 3000 psi. This approach
produces carbon disks with more undesirable micro-pores with pore
diameter less than 2 nm than the ones by the sol-gel approach. The
compression of carbon powder under vacuum at 800.degree. C.
displays severe technical challenges and high manufacturing
costs.
[0008] Yet, another approach to produce monolithic porous carbon is
from carbon black powder consolidated in a matrix of a carbonized
synthetic resin. U.S. Pat. Nos. 5,776,633; 5,172,307; and 5,973,912
described processes of producing such porous carbon-carbon
composites. The synthetic resin is phenolic resin in the
patents.
[0009] Although this approach has the merit of low cost by using
inexpensive carbon black powder it has the difficulty in retaining
open pores of synthetic resin, thus reducing the efficiency of pore
surface area.
[0010] Bearing in mind the problems and deficiencies of prior art,
it is therefore an object of the present invention to provide
monolithic porous carbon disks with high surface area, high pore
volume, high surface activity, well defined pore structure and
morphology, and good mechanical properties. It would also be
desirable to provide a process for producing such monolithic porous
carbon disks with significantly lower cost as compared to the ones
currently in the market.
[0011] Still other objects and advantages of the invention will in
part be obvious and will in part be apparent from the
specification.
SUMMARY OF THE INVENTION
[0012] The present invention provides processes for producing
monolithic porous carbon, e.g., disks, from a group of aromatic
organic precursors comprising either or both polyimide or
polybenzimidazole. The processes include the steps of: (1)
preparation of the organic precursors in the powder form; (2)
consolidation of the powders into a monolith; (3) pyrolysis
producing a monolithic porous carbon product such as a disk.
[0013] The present invention further provides processes for
producing monolithic porous carbon disks doped with transition
metals from a group of aromatic organic precursors comprising
either or both polyimide or polybenzimidazole and metallic
compounds. The processes include the steps of: (1) preparation of
the precursors in-situ doped with metallic compounds in the powder
forms; (2) consolidation of the powders into a monolith; (3)
pyrolysis producing monolithic porous carbon product such as a
disk.
[0014] The present invention even further provides processes for
producing porous carbon-carbon composite from the precursors of
this invention and carbon in the forms of powders, or fibers, or
nanotubers, or bulky balls (C60, or C70, or others), or fullerenes,
or a mixture thereof. Preferably, the carbon that is used in the
present processes is activated carbon powder and activated carbon
fiber. The processes include the steps of: (1) preparation of the
precursors either in the powder form or a viscous solution; (2)
blending together the carbon and the precursor in which the case of
the solvent is removed after mixing; (3) consolidation of the
mixture into a monolith; (4) pyrolysis producing a porous
carbon-carbon composite.
[0015] The organic precursors of this invention have
nitrogen-containing heterocyclic structures that connect monomer
units into rod-like molecular chain structures with few flexible
links or hinges. The chain architecture of the precursors consists
of either linear chains, or a three-dimensional network, or
hyberbranched chain structure. One group of the precursors
comprises polyimide with imide group in the molecular structure.
Another group of the precursors comprises polybenzimidazole with
benzimidazole group in the molecular structure. Yet, another group
of the precursors comprises both polyimide and polybenzimidazole
with both imide and benzimidazole groups in the molecular
structure.
[0016] The monolithic porous carbon disks produced from this
invention can be further reinforced by fibers or fiber pads or
other additive by incorporating fibers, inorganic or organic
particles, fiber pads, or other additives during the compression
molding process.
[0017] The precursor powders may be further assembled with other
additives in addition to carbon before consolidation into a
monolith. Such additives include transition metal oxide powders,
organic particles, inorganic particles, graphite fibers or flakes,
metal fibers, porous substrates including membranes, metallic
meshes, carbon cloth, carbon felt, foams, and polymeric resins,
such as phenolic resins and commercial polyimide resins.
[0018] The precursors prepared from the aromatic organic monomers
of this invention may comprise other components in the molecular
chain structure, such as polybenzimidazole, polyamide,
polyetherimide, siloxane, or silica, but have the polyimide and
aromatic organic composition preferably greater than or equal to
50% by weight.
[0019] The polyimide and polybenzimidazole may be represented by
the formulas:
##STR00001## [0020] wherein A1 and A4 [0021] represent difunctional
phenyl, difunctional biphenyl, an optionally substituted
difunctional aryl, optionally substituted difunctional alkylene, an
optionally substituted difunctional heteroaryl, or a combination
thereof; [0022] wherein A2 and A5 represents tetra functional
phenyl, biphenyl, an optionally substituted tetra functional aryl
group, or an optionally substituted heteroaryl group; [0023]
wherein A3 [0024] represent multifunctional phenyl with
functionality more than or equal to 2, multifunctional biphenyl
with functionality more than or equal to 2, an optionally
substituted multifunctional aryl with functionality more than or
equal to 2, optionally substituted multifunctional alkylene with
functionality more than or equal to 2, an optionally substituted
multifunctional heteroaryl with functionality more than or equal to
2, or a combination thereof; n1, n2 and n3 are greater or equal to
1; and (y+2) are more than or equal to 2.
[0025] One application of this invention is to provide a novel
carbon electrode for use in electrochemical capacitors, batteries,
and fuel cells.
[0026] Another application of this invention is to provide a novel
composite of carbon and transition metal oxides, such as MnO.sub.2,
as an electrode for use in lithium batteries or
hybrid-battery/electrochemical capacitor systems.
[0027] Another application of this invention is to provide a
catalytic carbon support for use in fuel cells and electrochemical
water purification systems.
[0028] While the present invention has been particularly described,
in conjunction with a specific preferred embodiment, it is evident
that many alternatives, modifications, and variations will be
apparent to those skilled in the art of the foregoing description.
It is therefore contemplated that the appended claims will embrace
any such alternatives, modifications, and variations as falling
within the true scope and spirit of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The features of the invention believed to be novel and the
elements characteristic of the invention are set forth with
particularly in the appended claims. The figures are for
illustration purposes only and are not drawn to scale.
[0030] The invention itself, however, both as to organization and
method of operation, may best be understood by reference to the
detailed description which follows taken in conjunction with the
accompanying drawings in which:
[0031] FIG. 1 is a cyclic voltammetry (CV) graph of Example 1
showing C (F/gram) versus voltage at a scan rate of 5 mV/sec.
[0032] FIG. 2 is a cyclic voltammetry (CV) graph of Example 2
showing C (F/gram) versus Voltage at a scan rate of 5 m V/sec.
[0033] FIG. 3 is a cyclic voltammetry (CV) graph of Example 3
showing C (F/gram) versus Voltage at a scan rate of 5 m V/sec.
[0034] FIG. 4 is impedance data of Samples 9a and 9b at 0.75 V bias
level with the sulfuric acid electrolyte. (--black) from Sample 9a
and (--red) from the capacitor with Sample 9b.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0035] In describing the preferred embodiment of the present
invention, reference will be made herein to FIGS. 1-4 of the
drawings in which like numerals refer to like features of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] In a first aspect, the present invention provides processes
for producing monolithic disks comprising either or both polyimide
and polybenzimidazole as organic precursors for producing
monolithic porous carbon which have surface area at or above 500
m.sup.2/gram and sufficiently high mechanical strength.
[0037] The aromatic monomers for preparing polyimide precursors of
this invention are preferably selected from one of the following
groups: aromatic dianhydride, aromatic diamine, and as an option,
an aromatic polyamine compounds with amine functionality beyond 2;
or aromatic tetracarboxylic acids, aromatic diamine, and as an
option, an aromatic polyamine compounds with amine functionality
beyond 2; or ester(s) of aromatic tetracarboxylic acids, aromatic
diamine, and as an option, an aromatic polyamine compounds with
amine functionality beyond 2; or aromatic dianhydride, aromatic
isocyanates including diisocyanate and polyisocyanate with
functionality beyond 2.
[0038] The aromatic monomers for preparing polybenzimidazole
precursors are preferably selected from one of the following
monomer groups: aromatic dialdehydes and aromatic tetraamines; or
diesters of aromatic dicarboxylic acids and aromatic tetraamines;
or aromatic dicarboxylic acids and aromatic tetraamines.
[0039] The precursors comprising either or both polyimide and
polybenzimidazole can preferably be synthesized from the monomers
either in the presence of a solvent or in the melt state by the
following procedures:
[0040] Procedure 1 [0041] Admixing all the ingredients in the
presence of a solvent. The solvent is removed by distillation,
assisted by vacuum if it is necessary to form a homogeneous mixture
in the powder form. Further chemical reactions to produce
un-fusible and un-meltable high molecular weight polymeric
materials proceed after solvent removal or even after consolidation
compression molding of the powders into a monolith such as a
disk.
[0042] Procedure 2 [0043] Carrying out the condensation reaction of
the aromatic monomers in the solution to produce precursors as a
precipitate in the forms of either precipitate or gel. The
precipitate could be either a precipitated powder or a precipitated
film onto another solid substrate. The solvent in the precursors is
removed by distillation, assisted by vacuum if it is necessary. The
precursors are further ground into fine powder or porous particles,
filtered through a sieve if it is necessary.
[0044] Procedure 3 [0045] Heating the aromatic organic precursors
into the melted state with stirring to form precursors in the solid
form. Sometimes, evaporation of byproducts, such as a low molecular
weight alcohol or water, produces foams instead of dense solid. The
precursor is further ground into fine powder or porous particles,
filtered through a sieve if it is necessary.
[0046] The polyimide precursors are preferably condensation
products of aromatic diamines and aromatic tetracarboxylic
dianhydride, or aromatic diamines and tetracarboxylic acids, or
aromatic diamines and ester(s) of tetracarboxylic acids, or
aromatic isocyanates and aromatic tetracarboxylic dianhydride. As
an option, a small amount of polyamine compounds with amine
functionality greater than two takes the place of some of the
aromatic diamine to introduce chemical cross-links to the polyimide
precursors. Therefore, polyimide precursors may possess linear
molecular structure, or a hyper-branched molecular structure, or a
three-dimensional network molecular structure. The synthesis of
polyimide precursors generally proceeds in the synthesis of
poly(amic acids) and then imidization to form polyimide.
[0047] Using the monomers of aromatic amines including diamines and
polyamine compounds and acids or ester(s) of tetracarboxylic acids
the synthesis of polyimide precursors can be carried out according
to any of Procedures 1 to 3. In Procedure 1, the monomers and other
additives are dissolved in a solvent to form a clear solution. The
precursors in the form of fine powders are either a homogeneous
mixture of monomers or a mixture of low molecular weight oligomers
of polyimide and poly(amic acids). In Procedure 2, the monomers and
other additives are dissolved in an organic solvent. The reaction
is carried out with a normal agitation at or above 100.degree. C.,
preferably at or above 150.degree. C., to produce polyimide
precipitate. The polyimide precursors are in the form of either
precipitated powder or gels. The solvent is removed from the
product by distillation, assisted by vacuum if it is necessary. In
Procedure 3, preferably, the esters of tetracarboxylic acids and
aromatic amines are the monomers of choice. The condensation
reaction at molten state of monomers releases phenol or an alcohol
molecule in the gas phase to produce rigid polyimide foams. The
product is further ground to produce polyimide powder.
[0048] Using the monomers of aromatic dianhydride and aromatic
amines including diamines and polyamines the synthesis of polyimide
precursor is carried out according to Procedure 2 in two steps:
synthesis of poly(amic acids) and imidization to form polyimide.
The synthesis of poly(amic acids) is conducted by dissolving
monomers and other additives in an organic solvent at ambient
temperature with a normal agitation for a time period from several
hours to overnight to yield product in the forms of either
precipitated powder or viscous liquid solution or gels. The
imidization of poly(amic acids) to form polyimide is carried out by
either chemical imidization at ambient temperature or thermal
imidization at elevated temperatures.
[0049] The chemical imidization is conducted by addition of
dehydrating agents to poly(amic acids). In the cases of poly(amic
acids) in the form of precipitated powder, preferably, dehydrating
agents are added before the reaction solvent is removed from the
system. In the cases of poly(amic acids) in the form of viscous
solution, the addition of dehydrating agents to poly(amic acids)
solution is carried out in such a way that the reaction at ambient
temperature yields polyimide precipitate. The solvent is removed
from the polyimide precipitate by distillation.
[0050] The dehydrating agents consists of either an acid anhydride
or a mixture of an acid anhydride and an organic base. Preferred
acid anhydrides include acetic anhydride, propionic anhydride,
n-butyric anhydride, benzoic anhydride, and trifluoroacetic
anhydride. Preferred organic bases include optionally substituted
mono-, di-, trialkylamines, and optionally substituted
pyridines.
[0051] The thermal imidization is conducted at elevated
temperatures.
[0052] In the cases of poly(amic acids) in the form of precipitated
powder, the solvent is removed by distillation followed by a
thermal imidization of poly(amic acids) powder at a temperature in
the range of 50.degree. C. to 500.degree. C. preferably in the
range of 100.degree. C. to 400.degree. C. and preferably under
protection of an inert gas, such as nitrogen or argon. In the cases
of poly(amic acids) in the form of viscous liquid solution or gels
the imidization is conducted at elevated temperatures in the range
of 50.degree. C. to 400.degree. C., preferably in the range of
100.degree. C. to 250.degree. C. to produce polyimide in the form
of precipitated powder. The solvent is removed by distillation,
assisted by vacuum if it is necessary.
[0053] Using aromatic dianhydride and aromatic isocyanate including
diisocyanate and polyisocyanate as the organic precursor the
synthesis of polyimide precursors is preferably carried out
according to Procedure 1. In this procedure, the monomers and
additives are admixed at ambient temperature in the presence of
preferably a dipolar aprotic organic solvent. The solvent removal
produces a homogeneous mixture in the powder form.
[0054] Although not exclusive to the other synthetic procedures,
preferably, polyimide precursors are prepared from aromatic
monomers of tetracarboxylic dianhydride, aromatic diamine, and
optionally, a polyamine compound according to Procedure 2 using
thermal imidization method. In this procedure, the reaction of
monomers and other additives are conducted in an organic solvent,
such as dimethylacetamide (DMAc), at ambient temperature with
agitation for a period of time. Temperature of the reaction system
is then raised to the range of 130.degree. C. to 200.degree. C.,
preferably in the range of 150.degree. C. to 180.degree. C. to
produce polyimide as precipitate. The solvent is distilled off to
produce the dried polyimide precursor powder.
[0055] The polybenzimidazole precursors are preferably condensation
products of aromatic tetraamines and aromatic esters of
dicarboxylic acids, or aromatic tetraamines and aromatic
dialdehyde. The synthesis proceeds either in the molten state of
monomers or in the presence of a solvent.
[0056] Using aromatic tetraamine and aromatic dialdehyde as
aromatic monomers the synthesis of polybenzimidazole is carried out
according to Procedure 2 in two-stages: synthesis of
poly(azomethines) as intermediate product in the presence of an
organic solvent and synthesis of poly(benzimidazole). In this
procedure, the reaction of the monomers in an organic solvent is
carried out at temperatures in the range of -30.degree. C. and
ambient temperature to produce poly(azomethines) in the forms of
either precipitated powder or viscous liquid solution. Further
reaction at an elevated temperature in the range of 50.degree. C.
to 350.degree. C., more preferably in the range of 100.degree. C.
to 250.degree. C., converts poly(azomethines) to polybenzimidazole.
The solvent is removed from the system when the product
precipitated from the solution either before or after second stage
reaction at elevated temperatures.
[0057] Using the monomers of aromatic tetraamine and esters of
dicarboxylic acids the synthesis of polybenzimidazole proceeds
preferably according to Procedure 3 in the molten state of the
monomers although not exclusive to the synthesis in the presence of
a solvent. The reactions are conducted at or above melting
temperatures of the monomers with strong agitation and in such
conditions that side products of phenol, or water, or an alcohol in
the gas phase are released from the system to produce the product
in foams. The products are crushed and further ground to produce
polybenzimidazole precursors in the form of porous powder.
[0058] The precursors comprising both polyimide and
polybenzimidazole segments in the molecular structure can be
prepared preferably in the presence of an organic solvent. The
synthesis can be conducted by either synthesizing one precursor of
either polyimide or polybenzimidazole before adding the monomers
for the other precursor to the reaction system. Or the reactions of
polyimide and polybenzimidazole are carried out separately before
combining two reactions into one reaction system. Or two sets of
the monomers are mixed together simultaneously in the same reaction
solution when the reaction conditions are compatible. Yet, such
mixing would be generally prohibited if a relatively large amount
of flexible amide links were introduced to the molecular chain
structure so as to reduce the glass transition temperature of the
material significantly.
[0059] An alternative approach to prepare monolithic porous carbon
disks from precursors comprising both polyimide and
polybenzimidazole is mixing both powders of polyimide and
polybenzimidazole precursors together during the process of
consolidating the powders into a monolith disk.
[0060] As an option, the precursor powders comprising either or
both polyimide and polybenzimidazole are further broken down to
smaller particle size by a shear stress and filtered through a
sieve if it is necessary. The preferred particle size of precursors
for the purpose of compression molding is in the range of 1 .mu.m
to 300 .mu.m, more preferably in the range of 5 .mu.m to 75 .mu.m,
even more preferably in the range of 110 .mu.m to 50 .mu.m.
[0061] As another option, the precursor powder comprising either or
both polyimide and polybenzimidazole in the powder form is further
thermally annealed at elevated temperatures before consolidating
into a disk. The annealing is conducted in a temperature range of
50.degree. C. to 600.degree. C., more preferably in the range of
50.degree. C. to 500.degree. C. for a time period between 20
minutes to 2 hours under vacuum or under protection of argon or
nitrogen atmosphere.
[0062] In a second aspect, the present invention provides processes
for producing porous monolithic disks of transition metal doped
precursors comprising either or both polyimide and
polybenzimidazole as organic precursors for producing transition
metal doped monolithic porous carbon disks which have surface area
at or above 500 m.sup.2/gram, sufficiently high mechanical
strength, and macrocyclic pyridine structure wherein the transition
metal atoms caged or complexed into to provide catalytic
activities.
[0063] In a general procedure, a transition metallic compound in
solution is added to the reaction system or to the dried precursor
powder or to the dried disk precursor. The solvent used for
dissolving the transition metallic compound is preferably the same
solvent as the one for preparing the precursors. Although not
exclusive to the addition of the metallic compounds at any stage or
any step during preparation of the monolith disk including each
synthetic step of the condensation reaction and the consolidation
process, preferably, the transition metallic compounds are added
during the early stages of the procedures. Even more preferably,
the transmission metallic compounds are admixed with the organic
precursors in the presence of an organic solvent before proceeding
with the synthesis of the precursors.
[0064] The solvent removal during the synthesis of the precursors
comprising either or both of polyimide and polybenzimidazole are
conducted by distillation, preferably assisted by vacuum.
[0065] Metals suitable for use in the preparation of metal doped
monolithic porous carbon of this invention are not limited and may
include elemental metals, organometallic compounds, coordination
inorganic compounds, metal salts or any combinations thereof. The
preferred metals include Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Ru, Co, Rh,
Ni, Pd, Pt, Cu, Ag, Zn, Si, Sn, Pb, Sb, Nb, Bi, Hf, Ba, Al, B, P
As, Li and combinations thereof. Exemplary transition metal
compounds include cobalt chloride (CoCl.sub.2), iron chloride
(FeCl.sub.3), nickel chloride (NiCl.sub.2), molybdenum chloride
(MoCl.sub.5), hydrogen hexachloroplatinate hydrate
(H.sub.2PtCl.sub.6*xH.sub.2O), copper chloride (CuCl.sub.2),
tungsten chloride (WCl.sub.6), zirconium chloride (ZrCl.sub.4),
cerium nitrate (Ce(NO.sub.3).sub.3), ruthenium chloride
(RuCl.sub.3) and hafnium chloride (HfCl.sub.4).
[0066] Typically, the transition metallic compound is present in
the precursor in an amount from 0.01% to 20% by weight, or
more.
[0067] In a third aspect, the present invention provides processes
for producing monolithic porous carbon disks which has a rod
density of less than or equal to 1.0 gram/cc comprising: producing
the organic precursors in powders comprising either or both
polyimide and polybenzimidazole; consolidation of the powder into a
monolith under a pressure in the range of 3000 psi to 13000 psi;
and pyrolysis under protection of an inert atmosphere.
[0068] In a fourth aspect, the present invention provides processes
for producing monolithic porous carbon having one or more than one
metals dispersed therein, which has a rod density of less than or
equal to 1.0 gram/cc comprising: powders of transition metal doped
precursors comprising either or both polyimide and
polybenzimidazole; consolidation of the porous precursor powders
into a monolith preferably at ambient temperature under a pressure
in the range of 3000 psi to 13000 psi. and pyrolysis under
protection of an inert atmosphere.
[0069] In a general consolidating procedure, the precursor powders
are evenly placed in a mold or on a supporting substrate such as a
fiber pad, before a sufficiently high compression pressure and a
sufficient holding time are applied to produce a monolith disk with
rod density in the range of 0.4 g/c to 1.0 g/c, preferably 0.6 g/cc
to 0.95 g/cc.
[0070] Pyrolysis of the compressed disks is carried out under
protection of an inert gas atmosphere, such as argon, nitrogen or
carbon dioxide, at a temperature in the range of 600.degree. C. to
3000.degree. C., more preferably 750.degree. C. to 1500.degree. C.
As an option, the inert gas atmosphere may be changed to carbon
dioxide during the pyrolysis, preferably in the later stage of the
pyrolysis, to further activate the pore surface of the monolithic
carbon disk. The heating rate shall be sufficiently slow as to
optimize the properties of the monolithic carbon.
[0071] In fifth aspect, the present invention provides processes
for producing porous carbon-carbon composite with a rod density of
less than or equal to 1.0 gram/cc from the precursors comprising
either or both polyimide or polybenzimidazole and activated carbon
in the forms of powder and fiber comprising: blending the
precursor, carbon, and other additives thoroughly; removing the
solvent in the mixture in cases that a solvent is involved in the
mixture; consolidating the mixture into monolith under pressure
conditions as to produce a homogeneous composition with desired rod
density; and pyrolysis under an inert atmosphere for producing
monolithic porous carbon.
[0072] In a sixth aspect, the present invention provides processes
for producing porous carbon composites incorporating other
additives in addition to the carbon comprising: blending the
organic precursor of this invention, carbon, and other additives
thoroughly; removing the solvent in the mixture in cases that a
solvent is involved during the mixing; consolidating the mixture
into monolith under pressure conditions as to produce a homogeneous
composition with desired rod density; and pyrolysis under an inert
atmosphere for producing monolithic porous carbon.
[0073] Other additives include metallic compounds, silica, carbon
in the forms of powders, fibers, nanotubes, and bulkyballs or
fullerences, graphite, metal oxides and metal carbides, polymeric
resins in either liquid or powder forms, such as commercial
phenolic resins and commercial polyimide resins, and mixtures
thereof.
[0074] The additives can be in the forms of powders, fibers,
flakes, liquids, or porous substrates composed of one or more than
one kind of fibers, membranes, metallic meshes, and foams.
[0075] There are different ways to blend the polyimide precursor,
carbon, and other ingredients together. For example in the cases of
polyimide precursors, one way of blending is to thoroughly mix
polyimide powder with the carbon and other additives. Another way
is to coat viscous solution of poly(amic acid) onto carbon and
other additives before removing the solvent, then converting
poly(amic acids) to polyimides. The present invention is directed
in one aspect to simply mixing the polyimide precursor powder with
the carbon and other additives, but is not intended to be limited
to any particular way of blending the precursor with the carbon as
well as other additives.
[0076] The organic precursors comprising either or both polyimide
and polybenzimidazole suitable for use in the method of making
monolithic porous carbon disks of the present invention can
incorporate other components during the synthesis, such as
imidazopyrrolone, siloxane, silica, epoxy, bismaleimide,
polyetherimide, but have the composition of polyimide and/or
polybenzimidazole preferably greater than or equal to 70% by
weight.
[0077] Preferred aromatic tetracarboxylic dianhydride, or
tetracarboxylic acids, or diester(s) of tetracarboxylic acids
monomers suitable for use in the method of making polyimide
precursors of the present invention include following dianhydride
compounds and their derivatives of tetracarboxylic acids and
dialkyl ester(s) of tetracarboxylic acids: pyromellitic
dianhydride; pyromellitic tetracarboxylic acids, dialkyl ester(s)
of pyromellitic tetracarboxylic acids and aromatic tetracarboxylic
dianhydride or tetracarboxylic acids or esters of the
tetracarboxylic acids including 3,3',4,4'-biphenyltetracarboxylic
acid dianhydride, 3,3',4,4'-benzophenone dianhydride,
2,3,6,7-naphthylene tetracarboxylic acid dianhydrides,
1,4,5,8-naphthalene tetracarboxylic acids, 2,2-bis(3,4-dicarboxy
phenyl) propane acid dianhydride, and combinations thereof.
[0078] When ester(s) are alkyl esters the alkyl group preferably
contains 1 to 5 carbon atoms and is more preferably methyl.
[0079] Preferred aromatic diamine monomers suitable for use in the
methods of making polyimide precursors of the present invention
include 1,4-phenylene diamine, m-phenylene diamine,
4,4'diamino-biphenyl, 4,4' and 3,3'-diaminodiphenylmethanes, 4,4',
and 3,3'-diaminobenzophenones, benzidine, 2,6-diaminopyridine,
2,6-diaminonaphthalene, 1,4-diaminocyclohexane, 2,4 and
2,6-diaminotoluene, and derivatives thereof (i.e.: substituted
diamine having a substituent(s)). The above diamine monomers may be
used alone or as a mixture of two or more of them.
[0080] Preferred polyamine compounds with amine functionality
greater than 2 suitable for use in the methods of making polyimide
precursors of the present invention include
3,3'4,4'-biphenyltetraamine (TAB), 1,2,4,5-benzenetetraamine,
3,3'4,4'-tetraminodiphenyl ether,
3,3'4,4'-tetraminodiphenylmethane, 3,3',4,4'-tetraminobenzophenone,
3,3',4-triaminodiphenyl, 3,3',4-triaminodiphenylmethane,
3,3',4-triaminobenzophenone, 1,2,4-triaminobenzene, their mono-,
di-, tri-, or tetra-acid salts, such as 3,3'4,4'-biphenyltetraamine
tetrahydrochloride, 1,2,4,5-benzenetetraamine tetrahydrochloride,
3,3'4,4'-tetraminodiphenyl ether tetrahydrochloride,
3,3'4,4'-tetraminodiphenylmethane tetrahydrochloride,
3,3',4,4'-tetraminobenzophenone tetrahydrochloride,
3,3',4-triaminodiphenyl trihydrochloride,
3,3',4-triaminodiphenylmethane trihydrochloride,
3,3',4-triaminobenzophenone trihydrochloride, 1,2,4-triaminobenzene
trihydrochloride, melamine, 2,4,6-triaminopyrimidine (TAP). The
acid salts of above compounds usually exist in the form of hydrated
compounds. Any of the above compounds may be used either alone or
as a mixture of two or more of them.
[0081] Preferred polyamine compounds with amine functionality
greater than 2 suitable for use in the methods of making polyimide
precursors composed of a three-dimensional molecular structure of
the present invention also include a polyamine oligomer with the
formula:
##STR00002##
[0082] Preferred aromatic isocyanate monomers suitable for use in
the methods of making polyimide precursors of the present invention
include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate,
4,4'-diphenylmethane diisocyanate. Any of the above compounds may
be used either alone or as a mixture of two or more of them.
[0083] Preferred aromatic dialdehyde monomers suitable for use in
the methods of making polybenzimidazole precursors of the present
invention include isophthalaldehyde, terephthaldicarboxaldehyde,
phthalic dicarboxaldehyde, and 2,6-naphthalenedicarboxaldehyde.
[0084] Preferred monomers of aromatic acids and esters of
dicarboxylic acids suitable for use in the methods of making
polybenzimidazole precursors of the present invention include acids
and esters of isophthalic acid, phthalic acid, terephthalic acid,
1,4-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic
acid. The ester(s) may be alkyl or phenyl esters. When ester(s) are
alkyl esters the alkyl group preferably contains 1 to 5 carbon
atoms and is more preferably methyl.
[0085] Preferred monomers of aromatic tetraamines suitable for use
in the methods of making polybenzimidazole precursors of the
present invention include
3,3',4,4'-tetraminobiphenyl(3,3''-diaminobenzidine);
1,2,4,5-tetraminobenzene; 1,2,5,6-tetraminonaphthalene;
2,3,6,7-tetraminonaphthalene; 3,3',4,4'-tetraminodiphenyl methane;
3,3',4,4'-tetraminodiphenyl ethane;
3,3',4,4'-tetraminodiphenyl-2,2-propane; and combinations thereof.
Preferred reaction solvents for the synthesis of the precursors
comprising either or both polyimide and polybenzimidazole include
N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc),
N,N-dimethyl formamide (DMF), tetrahydrofuran (THF), dimethyl
sulfoxide (DMSO), acetone, methanol, toluene, chlorobenzene,
ethanol, and mixtures thereof.
[0086] The monolithic carbon of this invention is suitable for use
as an electrode material in electrochemical capacitors and related
electrochemical devices. The porous monolithic carbon of the
invention offer the advantage of a monolithic structure, high
density, high surface area, and narrow pore size distribution.
EXAMPLES
Example 1
Synthesis of Polyimide Precursor with Three-Dimensional Molecular
Structure and Carbon Disk Therefrom
[0087] Starting monomers: 3,3'4,4'-biphenyltetraamine (TAB),
1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), and
1,4-phenylenediamine (PPD).
Solvent: N,N-dimethylacetamide (DMAc).
[0088] 1.30 gram (0.012 mole) PPD was dissolved in 40 ml DMAc in a
flask. While stirring, 3.270 gram (0.015 mole) PMDA in the solid
form was added to the reaction system. After PMDA was fully
dissolved, 0.3215 gram (0.0015 mole) TAB was added to the reaction
system. The reaction was carried out at ambient temperature with
mechanical stirring until a very viscous solution, often gel lumps,
were formed. The temperature of the reaction was gradually raised
to 150.degree. C. with strong agitation to produce polyimide in
precipitated powder form. The solvent was distilled off under
vacuum at 50.degree. C. The powders were further broken down and
filtered through a 50 micron-sized sieve.
[0089] By using a hydraulic press, the polyimide powders were
placed in a mold and compressed under pressure of 5000 psi at
ambient temperature to produce a monolithic disk. The monolithic
disk was pyrolyzed at 800.degree. C. for 3 hours under protection
of nitrogen to produce a monolithic carbon disk. The cyclic
voltammetry of the carbon disk at a scan rate of 5 mV/s displayed
the capacitance of the material at 90 F/gram. See FIG. 1.
Example 2
Synthesis of Polyimide Prepolymer with Three-Dimensional Molecular
Structure Doped with 1% Molybdenum by Weight and Carbon Disk
Therefrom
[0090] Starting monomers and additive: 3,3'4,4'-biphenyltetraamine
(TAB), 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA),
1,4-phenylenediamine (PPD), and molybdenum chloride (V)
(MoCl5).
Solvent: N,N-dimethylacetamide (DMAc).
[0091] 1.30 gram (0.012 mole) PPD and 0.135 gram MoCl5 were
dissolved in 40 ml DMAc in a flask. While stirring, 3.270 gram
(0.015 mole) PMDA in the solid form was added to the reaction
system. After PMDA was fully dissolved, 0.3215 gram (0.0015 mole)
TAB was added to the reaction system. The reaction was carried out
at ambient temperature with mechanical stirring until a very
viscous solution, often gel lumps, were formed. The temperature of
the reaction was gradually raised to 150.degree. C. with strong
agitation to produce polyimide/MoCl5 in precipitated powder form.
The solvent was distilled off under vacuum at 50.degree. C. The
powders were further broken down and filtered through a 50
micron-sized sieve.
[0092] The polyimide powders were consolidated at 4500 psi pressure
at ambient temperature to produce a monolithic disk. The monolithic
disk was pyrolyzed at 800.degree. C. for 3 hours under protection
of a nitrogen to produce a monolithic carbon disk. The cyclic
voltammetry of the carbon disk at a scan rate of 5 mV/s displayed
the capacitance of the material at 210 F/gram. See FIG. 2.
Example 3
Synthesis of Polyimide Prepolymer Doped with 1% Molybdenum by
Weight and Carbon Disk Therefrom
[0093] Starting monomers and additive:
1,2,4,5-benzenetetracarboxylic dianhydride (PMDA),
1,4-phenylenediamine (PPD), and molybdenum chloride (V)
(MoCl5).
Solvent: N,N-dimethylacetamide (DMAc).
[0094] 1.622 gram (0.015 mole) PPD and 0.135 gram MoCl5 were
dissolved in 40 ml DMAc in a flask. While stirring, 3.270 gram
(0.015 mole) PMDA in the solid form was added to the reaction
system. The reaction was carried out at ambient temperature with
stirring until a very viscous solution was formed. The reaction
temperature was raised to 150.degree. C. with strong agitation to
produce polyimide/MoCl5 precipitate in precipitated powder form.
The solvent was distilled off under vacuum at 50.degree. C. The
powders were further broken down and filtered through a
5-micron-sized sieve.
[0095] The polyimide powders were consolidated at 4500 psi pressure
at ambient temperature to produce a monolith. Pyrolysis of the
monolith was carried out at 800.degree. C. for 2 hours under a
nitrogen atmosphere and 1 hour under a carbon dioxide atmosphere.
The cyclic voltammetry of the carbon disk at a scan rate of 5 mV/s,
shown in FIG. 3, displayed the capacitance of the material at 200
F/gram.
Example 4
Synthesis of Polyimide Precursor Doped with 1% (by Wt.) Molybdenum
in Acetone and Carbon Disk Therefrom
[0096] Starting monomers and additive: 3,3'4,4'-biphenyltetraamine
(TAB), 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA),
1,4-phenylenediamine (PPD), and molybdenum chloride (V)
(MoCl5).
Solvent: acetone
[0097] 3.270 gram (0.015 mole) PMDA was dissolved in 20 ml acetone.
1.30 gram (0.012 mole) PPD, 0.3215 gram (0.0015 mole) TAB, and
0.135 gram MoCl5 were dissolved in 20 ml acetone in a separate
flask. The PMDA solution was gradually added to PPD/TAB/MoCl5
solution to produce a white precipitate immediately. The solvent
was distilled off and temperature of the product was raised to
150.degree. C. to convert poly(amic acids) to polyimide in powder
form. The powders are further broken down and filtered through a 50
micron-sized sieve.
[0098] The polyimide powder was compressed at 4000 psi pressure at
ambient temperature to produce a monolithic disk. The monolithic
disk was pyrolyzed at 800.degree. C. for 3 hours under protection
of nitrogen to produce a monolithic carbon disk. The cyclic
voltammetry of the carbon disk at a scan rate of 5 mV/s displayed
the capacitance of the material at 100 F/gram.
Example 5
Synthesis of Polyimide Precursor with three-dimensional molecular
Structure Doped with 1% Molybdenum by Weight and Carbon Disk
Therefrom
[0099] Starting monomers and additive: 3,3'4,4'-biphenyltetraamine
(TAB), 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA),
1,4-phenylenediamine (PPD), diaminopyridine, and molybdenum
chloride (V) (MoCl5).
Solvent: N,N-dimethylacetamide (DMAc).
[0100] 1.082 gram (0.01 mole) PPD, 0.218 gram diaminopyridine
(0.002 mole) and 0.135 gram MoCl5 were dissolved in 40 ml DMAc in a
flask. While stirring, 3.270 gram (0.015 mole) PMDA in the solid
form was added to the reaction system. After PMDA was fully
dissolved, 0.3215 gram (0.0015 mole) TAB was added to the reaction
system. The reaction was carried out at ambient temperature with a
normal agitation until a viscous solution was formed. The
temperature of the reaction was raised to 150.degree. C. with
strong agitation to produce polyimide/MoCl5 in precipitated powder
form. The solvent was distilled off under vacuum at 50.degree. C.
The powders were further broken down and filtered through a 50
micron-sized sieve.
[0101] The polyimide powder were compressed at 4000 psi pressure at
ambient temperature to produce a monolithic disk. The monolithic
disk was pyrolyzed at 800.degree. C. for 3 hours under protection
of nitrogen to produce a monolithic carbon disk. The cyclic
voltammetry of the carbon disk at a scan rate of 5 mV/s displayed
the capacitance of the material at 100 F/gram.
Example 6
Synthesis of Polyimide Prepolymer and Porous Carbon Therefrom
[0102] Starting monomers: 1,2,4,5-benzenetetracarboxylic
dianhydride (PMDA), and 1,4-phenylenediamine (PPD).
Solvent: N,N-dimethylacetamide (DMAc).
[0103] 1.622 gram (0.015 mole) PPD was dissolved in 40 ml DMAc in a
flask.
[0104] While stirring, 3.270 gram (0.015 mole) PMDA in the solid
form was added to the reaction system. The reaction was carried out
at ambient temperature with stirring until a very viscous solution
was formed. The reaction temperature was raised to 150.degree. C.
with strong agitation to produce polyimide precipitate. The solvent
was distilled off under vacuum at 50.degree. C. The powders were
further annealed at 300.degree. C. for 30 minutes.
[0105] The polyimide powders were consolidated at 4500 psi pressure
at ambient temperature to produce a monolith. Pyrolysis of the
monolith was carried out at 900.degree. C. for 3 hours under a
nitrogen atmosphere. The cyclic voltammetry of the carbon disk at a
scan rate of 5 mV/s displayed the capacitance of the material at 80
F/gram.
Example 7
Electrode for Supercapacitor
[0106] A supercapacitor was constructed using the carbon prepared
according to Example 3 as electrodes. The electrode dimension was
0.81'' in diameter and 0.012'' in thickness. The prototype
supercapacitor comprises a pair of carbon electrodes sandwiched
between two current collector plates. A microporous separator was
placed between two electrodes. 38% sulfuric acid electrolyte
impregnates the electrodes and the separator before the current
plates were sealed by a thermoplastic edge sealant. The result of
characterization is shown in Table 1.
TABLE-US-00001 TABLE 1 ESR (Ohm) Normalized Capacitance at 1 kHz C
(F) (F/g) (F/cm.sup.3) 0.32 7.58 203 156
Example 8
Synthesis of Polyimide Precursor Doped with 0.5% Molybdenum and
Porous Carbon Therefrom
[0107] Starting monomers and additive:
1,2,4,5-benzenetetracarboxylic dianhydride (PMDA),
1,4-phenylenediamine (PPD), and molybdenum chloride (V)
(MoCl5).
Solvent: tetrahydrofuran (THF).
[0108] 3.270 gram (0.015 mole) PMDA was dissolved in 20 ml THF.
1.62 gram (0.015 mole) PPD, and 0.065 gram MoCl5 were dissolved in
20 ml THF in a separate flask. The PMDA solution was gradually
added to PPD/MoCl5 solution to produce a white precipitate
immediately. The solvent was distilled off. The poly(amic acids)
powder was converted to polyimide by thermally annealed at
300.degree. C. for 30 minutes.
[0109] The polyimide powders were compressed at 4500 psi pressure
at ambient temperature to produce a monolith. The monolith was
pyrolyzed at 900.degree. C. for 3 hours under protection of
nitrogen to produce a monolithic carbon. The cyclic voltammetry of
the carbon disk at a scan rate of 5 mV/s displayed the capacitance
of the material at 150 F/gram.
Example 9a
Preparation of Carbon-Carbon Composite and an Electrochemical
Capacitor Cell Therefrom
[0110] Polyimide precursor: prepared in Example 6. Carbon Black
Powder: commercially available carbon black from a natural source;
Activated Carbon fiber: phenolic resin based carbon fiber.
[0111] 1.58 gram carbon black powder (66%), 0.68 gram polyimide
powder (28%), and 0.14 gram carbon fiber (6%) were blended together
by grinding and mixing 0.5 gram mixture was compressed at 6500 psi
at ambient temperature to produce a monolithic disk about 1 mm
thick and 2.5 cm in diameter. The disk was pyrolyzed at 800.degree.
C. for 3 hours under protection of nitrogen to produce a porous
carbon-carbon composite disk.
[0112] Two carbon-carbon composite disks of 0.78 gram with diameter
of 2.5 cm and thickness of 1.20 mm were used to assemble a
symmetric single cell according to the procedure in Example 3. The
result of characterization is listed in Table 2. A Z'' vs. Z' plot
of impedance data is displayed in FIG. 4.
Example 9b
A Comparative Electrochemical Capacitor Cell Using Carbon Black
Electrodes
[0113] Two carbon disks of 0.77 gram with diameter of 2.5 cm and
thickness of 1.20 mm were prepared from same carbon black powder as
used in Example 9a. The disks were used to assemble a symmetric
single cell according to the procedure in Example 3. The result of
characterization is listed in Table 2. A Z'' vs. Z' plot of
impedance data is displayed in FIG. 4.
TABLE-US-00002 TABLE 2 Normalized ID ESR (Ohm) at 1 kHz C (F) C
(F/g) C-C composite 0.082 30.25 154 (Example 9a) Control carbon
0.101 22.44 116 (Example 9b)
Example 10
Preparation of Carbon-Carbon Composite Doped with 0.85% Molybdenum
and an Electrochemical Capacitor Cell Therefrom
[0114] Polyimide precursor: prepared in Example 1. Carbon Black
Powder: commercially available carbon black from a natural source;
Activated Carbon fiber: phenolic resin based carbon fiber;
Molybdenum chloride (V) (MoCl5).
[0115] 0.06 gram molybdenum chloride was dissolved in 3.0 ml
methanol. 2.6 gram carbon black powder was immersed in Mo/methanol
solution with stirring for overnight before methanol was removed by
distillation.
[0116] 1.24 gram Mo doped carbon black powder (61%), 0.665 gram
polyimide powder (33%), and 0.12 gram activated carbon fiber (6%)
were blended together by grinding and mixing. 0.5 gram mixture was
compressed at 6500 psi at ambient temperature to produce a
monolithic disk about 1 mm thick and 2.5 cm in diameter. The disk
was pyrolyzed at 800.degree. C. for 1.5 hours under protection of
nitrogen and 1.5 hours under carbon dioxide to produce a porous
carbon-carbon composite disk.
[0117] Two carbon-carbon composite disks with diameter of 2.5 cm
and thickness of 1.20 mm were used to assemble a symmetric single
cell according to the procedure in Example 3.
* * * * *