Patent Application
20200194190
The present invention relates to the field of electrical engineering and, in particular, to the field of electrodes and electrode-based energy storage devices or secondary sources of current such as electrochemical capacitors and supercapacitors also known as ultracapacitors.
The present invention proposes an hybrid electrode coated with a novel redox polymer containing particular dione units such as 4,9-dihydro-S-indaceno[1,2-b:5,6b′]dithiophene-4,9-dione units, several processes for preparing an electrode coated with such a redox polymer and electrode-based energy storage device containing such a coated electrode.
Silicon nanowires (SiNWs), as a novel 1-D nanostructured material, have aroused a great deal of attention in the field of electrochemical double layer capacitors due to their extraordinary properties in terms of high maximal power density (225 mW.cm−2) and long lifespan (millions of cycles) [1]. Additionally, their excellent compatibility with Si based-microelectronic industry has also awakened a special interest in a wide range of technological applications from medicine to aerospace industry.
Within this context, over the past years intensive research activities have been devoted to the development of high performance supercapacitors based on SiNWs [2]. Recently, several strategies have been addressed in this direction, which result mainly from the functionalization of SiNW surface using nanostructured carbonaceous materials (e.g. diamond or porous carbon) [3-5] or pseudocapacitive materials such as transition metal oxides (NiO, MnO2) [6,7], metallic hydroxides (Ni(OH)2) [8] or electroactive conducting polymers (ECPs) (PEDOT, PPy) respectively [9,10].
Precisely, the functionalization of SiNWs by using organic polymers has been also widely investigated in the field of solar cells. Thereby, new hybrid solar cell devices were designed from poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) [11,12], poly(3-hexylthiophene) (P3HT) [13], poly(N-vinylcarbazole) (PVK) [14], poly(2-methoxy-5-(2-ethyhexyl-oxy)-p-phenylenevinylene) (MEH-PPV) [15] deposited onto SiNWs in order to improve the efficiency. This successful strategy allowed to obtain very interesting efficiency values in this domain (˜10%).
From the material perspective, organic polymer-coated SiNWs have emerged as promising hybrid nanostructured materials to be employed as electrodes in electrochemical energy storage and conversion devices. More specifically, supercapacitor and battery devices made of ECP-coated SiNW electrodes exhibited excellent electrochemical performances in terms of specific capacitance, capacity, energy and power densities respectively [9,16]. Despite of extraordinary results reported in the literature concerning this research domain, ECPs present important drawbacks concerning their cycling stability, which is limited to thousands of cycles. Consequently, the use of these hybrid devices is hampered for commercial technological applications. In this regard, the rational design of advanced polymer structures capable to solve this stability issues, results of vital importance.
Within this context, several works dealing with novel conducting redox polymers have been recently reported in the field of energy storage devices. Thus, a new n-dopable polymer poly{[N,N′-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5′-(2,2′ bithiophene)} (P(NDI2OD-T2) or pyrene derivatives were employed as electrodes for battery devices with excellent electrochemical performances at very fast charge-discharge rates and long cycling [17,18]. In this way, other redox polymer complex compounds were addressed for their use in battery [19,20], which are displayed below:
Among different redox polymer structures, quinone polymer electrodes such as poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM), poly(2,5-dihydroxy-1,4-benzoquinonyl sulfide) (PDBS) and poly(anthraquinonyl sulfide) (PAQS) [21] or pyridyl complexes exhibited also enhanced cycling stability with relatively high capacitance in lithium-ion batteries [22].
Over the past years, electrodes made of advanced redox polymer structures have been also investigated for supercapacitor devices. One example corresponds to a novel phenanthridine based bithiophene modified conjugated monomer tert-butyl 3,8-di([2,2′-bithiophen]-5-yl)-6-oxophenanthridine-5(6H)-carboxylat.
As already explained, the use of conventional pseudo-capacitive materials, as for example conducting organic polymers, has emerged as a promising strategy to enhance the capacitive properties in supercapacitors. This improvement of the electrochemical performance is due to the faradaic processes (oxidation-reduction reactions) induced by the polymer coating during the charge-discharge cycles. However, such electroactive conducting polymers (ECPs) exhibit a poor electrochemical stability, which limit their potential to be employed in commercial applications. Therefore, the development of ultra-high performance supercapacitors remains still a big challenge for our society.
From this point of view, the need of finding reliable solutions through the research and design of advanced conjugated polymers will be crucial to accomplish this goal.
As a consequence, the present inventors have sought to provide conjugated polymers useful for coating electrodes and for preparing energy storage devices with improved cycling stability in order to maintain high power and energy density values.
These objects and others are achieved by the invention, which proposes to implement new redox molecules containing 4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione units and that can be polymerized not only onto SiNWs but also onto various nanostructured materials, to provide electroactive organic-inorganic materials with high robustness to be employed in the field of energy storage devices.
Even if 4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione moiety has already been reported for the preparation of alternating copolymers via chemical polymerization reactions for application in bulk-heterojunction solar cells [23], these molecules and corresponding copolymers have never been used for electrochemical energy storage. Indeed in previous reports these molecules cannot be electro-polymerized and their processing is complex.
The present inventors have introduced polymerization groups on each side of 4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione building block and demonstrated that the corresponding alternating copolymers can be prepared easily and deposited on surfaces to create modified electrodes with high robustness. These electrodes have been implemented in energy storage devices providing higher stability upon cycling compared to reference materials in the field as illustrated in the experimental part. From the results presented for bulk-heterojunction solar cells in [23], it was not at all obvious for the one skilled in the art that polymers containing 4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione units used in energy storage devices would imply an improved stability upon cycling. This class of molecules and polymers has never been investigated for electrochemical energy storage.
In addition, it should be noted that the present invention can implement polymers containing 4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione units but also on polymers containing variant units in which at least one thiophene ring has been replaced by a selenophene ring or a furan ring.
Thus, the present invention concerns an electrode comprising:
wherein the redox polymer is of formula (I):
In the field of energy storage devices, “redox polymers” correspond to compounds in which electron transfer occurs mainly due to redox reactions between adjacent fragments of the polymer chain. In other words, these redox polymers are intrinsically electronically conductive polymers that receive electrons by electrochemical reduction (negative doping; n-type doping) or donate electrons by oxidation (positive doping; p-type doping). The doping/dedoping is electrochemically reversible and redox polymers may be used to store and release charge in devices for storing and releasing electrical energy such as batteries and supercapacitors. Redox polymers possess high electrochemical capacitances because the doping/dedoping process involves all the mass and volume of the polymers. In the charged state, they possess high electron conductivities. The doping/dedoping process is rapid and the resistances obtained are low.
“Dione unit” is taken to mean, within the scope of the present invention, the unit of formula (I′):
“Alkyl group” is taken to mean, within the scope of the present invention, a linear, branched or cyclic alkyl group, comprising from 1 to 20 carbon atoms, particularly from 1 to 15 carbon atoms and in particular, from 1 to 10 carbon atoms, which can optionally comprise at least one heteroatom and/or at least one carbon-carbon double bonds or triple bonds, such as, for example, a methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, octyl or nonyl group.
“Arylalkyl group” is taken to mean, within the scope of the present invention, any group derived from an alkyl group as defined above wherein a hydrogen atom is replaced by an aryl group.
“Aryl group” is taken to mean, within the scope of the present invention, any functional group or substituent derived from at least one simple aromatic ring wherein an aromatic ring corresponds to any planar cyclic compound having a delocalized π system in which each atom of the ring comprises a p-orbital, said p-orbitals overlapping themselves. An aryl group comprises one aromatic ring or several aromatic rings identical or different joined or connected by a single bond or by a hydrocarbon group, each ring having from 4 to 20 carbon atoms, particularly from 4 to 14 carbon atoms, in particular, from 4 to 8 carbon atoms and which can optionally comprise at least one heteroatom. As examples of aryl group, phenyl, biphenyl, naphthyl, anthracenyl, cyclopentadienyl, pyrenyl, tetrahydronaphthyl, furanyl, pyrrolyl, thiophenyl, oxazolyl, pyrazolyl, isoquinolinyl, thiazolyl, imidazolyl, triazolyl, pyridinyl, pyranyl, quinolinyl, pyrazinyl and pyrimidinyl groups may be cited. An aryl group can be substituted.
“Alkylaryl group” is taken to mean, within the scope of the present invention, any group derived from an aryl group as defined above wherein a hydrogen atom is replaced by an alkyl group as defined above.
“Substituted alkyl group”, “substituted arylalkyl group”, “substituted aryl group” or “substituted alkylaryl group” are taken to mean, within the scope of the present invention, an alkyl, arylalkyl, aryl or alkylaryl group as defined previously substituted by a group or several groups, identical or different, chosen from a halogen; an amine; a diamine; a carboxyl; a carboxylate; an aldehyde; an ester; an ether; a hydroxyl; a halogen; an aryl optionally substituted as defined previously and particularly such as a phenyl, a benzyl or a naphthyl; an alkyl optionally substituted as defined previously and particularly such as a methyl, an ethyl, a propyl or a hydroxypropyl; an amide; a sulphonyl; a sulphoxide; a sulphonic acid; a sulphonate; an acyl; a vinyl; a hydroxyl; an epoxy; a phosphonate; an isocyanate; a thiol; a glycidoxy; an acryloxy; a thiophene; a furan; a selenophene and salts thereof.
“Heteroatom” is taken to mean, within the scope of the present invention, an atom chosen from the group consisting of nitrogen, oxygen, phosphorous, sulphur, silicon, fluorine, chlorine and bromine.
“Halogen” is taken to mean, within the scope of the present invention, an atom chosen from the group consisting of fluorine, chlorine, iodine and bromine. Advantageously, when a halogen is implemented in the present invention, it is a fluorine or a chlorine.
“Bridging group” is taken to mean, within the scope of the present invention, a hydrocarbon group from 1 to 50 carbon atoms and particularly from 2 to 40 carbon atoms, optionally comprising one heteroatom or several heteroatoms identical or different and/or one or several ethylenic unsaturation(s), said group being optionally substituted. Any bridging group known by one skilled in the art can be implemented within the scope of the present invention. As illustrative examples of bridging groups, one can cite group of formula —O—(CH2)m—O— in which m is 1, 2, 3 or 4; a group of formula —O—(CH2)x—C(CH3)2—(CH2)y—O— in which x and y are identical or different and each independently is selected from the group consisting of 1, 2, 3 and 4, a group of formula —S—(CH2)m—S— in which m is 1, 2, 3 or 4 or group of formula —S—(CH2)x—C(CH3)2—(CH2)y—S— in which x and y are identical or different and each independently is selected from the group consisting of 1, 2, 3 and 4.
Advantageously, in the redox polymer of formula (I), X1 and X2 are identical. Thus (X1,X2) is selected from the group consisting of (S,S), (O,O) and (Se,Se). More particularly, X1 and X2 both represent S.
In the redox polymer of formula (I), advantageous dione units are those in which the groups R1 and R2 are identical and/or the groups R3 and R4 are identical and particularly those in which the groups R1 and R2 both represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted arylalkyl group or an optionally substituted alkylaryl group and/or the groups R3 and R4 both represent a hydrogen.
In particular, in advantageous dione units, the groups R1 and R2 are identical and both represent an optionally substituted alkyl group. In this particular embodiment, the groups R3 and R4 advantageously represent a hydrogen.
Advantageously, in the G1 group and/or the G2 group of formula (II), X3 and X4 are identical. Thus (X3,X4) is selected from the group consisting of (S,S), (O,O) and (Se,Se). More particularly, X3 and X4 both represent S.
As above defined, four alternatives for the G1 (or G2) group of formula (II) exist and are:
The first and the fourth alternatives are preferred.
Advantageously, in the G1 group and/or the G2 group of formula (II) according to the first alternative, R5 and R8 are identical and selected from the group consisting of a hydrogen atom, an optionally substituted alkyl group, an optionally substituted arylalkyl group and an optionally substituted alkylaryl group and/or R6 and R7 are identical and selected from the group consisting of a hydrogen atom, an optionally substituted alkyl group, an optionally substituted arylalkyl group and an optionally substituted alkylaryl group. More particularly, R5 and R8 are identical and represent a hydrogen atom and R6 and R7 are identical and selected from the group consisting of a hydrogen atom, an optionally substituted alkyl group, an optionally substituted arylalkyl group and an optionally substituted alkylaryl group. More particularly, R5 and R8 are identical and represent a hydrogen atom and R6 and R7 are identical and represent an optionally substituted alkyl group.
Advantageously, in the G1 group and/or the G2 group of formula (II) according to the fourth alternative, R5 and R6 form together a bridging group and R7 and R8 form together a bridging group, these bridging groups being identical.
More particularly, in the G1 group and/or the G2 group of formula (II), a is selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; b is selected from the group consisting of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and c is selected from the group consisting of 0, 1, 2, 3, 4 and 5.
In a particular embodiment, in the G1 group and/or the G2 group of formula (II), a and c are identical and selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10, and b is selected from the group consisting of 0, 1, 2, 3, 4 and 5. In a more particular embodiment, in formula (II), a and c both are equal to 1 and b is selected from the group consisting of 0, 1, 2, 3, 4 and 5 and advantageously from the group consisting of 0, 1, 2 and 3. In a still more particular embodiment, in formula (II), a, b and c are all equal to 1.
In a variant embodiment, in the G1 group and/or the G2 group of formula (II), a and c are different and b is selected from the group consisting of 0, 1, 2, 3, 4 and 5. Advantageously, in this variant, a is equal to 1 and c is equal to 0 and b is selected from the group consisting of 0, 1, 2, 3, 4 and 5 and advantageously from the group consisting of 0, 1, 2 and 3. More advantageously, b and c are both equal to 0 and a is equal to 1. In this variant embodiment, R6 represents a hydrogen atom and R5 is selected from the group consisting of a hydrogen atom, an optionally substituted alkyl group, an optionally substituted arylalkyl group and an optionally substituted alkylaryl group and advantageously is an optionally substituted alkyl group.
In a particular embodiment, G1 and G2 are identical in the formula (I) whereby the redox polymer of formula (I) is symmetrical and thus devoid of coupling defects.
As examples of particular redox polymers usable in the present invention, one can cite:
In formulas (III), (III′), (IV), (IV′), (V) and (VI), n is as previously defined.
The redox polymer implemented in the electrode according to the present invention forms a layer that covers the at least one nanostructure present on at least one of the support surfaces. In other words, said polymer coats the nanostructure and is deposited or applied thereon.
Thus, no covalent bond exists between at least one atom of the polymer and at least one atom of the nanostructure in the electrode according to the present invention. More particularly, the interactions between the polymer and the nanostructure in the electrode according to the present invention are non-covalent bonds such as bonds of electrostatic interaction type and/or bonds of hydrogen bridge type.
By “electrostatic bond” is meant an intermolecular interaction between at least two positively or negatively charged groups belonging to either the polymer, or the nanostructure. The expressions “ionic non-covalent bond”, “ionic interaction”, “electrostatic bond” or “electrostatic interaction” are equivalent and can be used interchangeably. In the present invention, this intermolecular interaction is attracting. It involves a negatively charged group of the polymer and a positively charged group of the nanostructure. Alternatively, it involves a positively charged group of the polymer and a negatively charged group of the nanostructure. By “hydrogen non-covalent bond” is meant a bond in which a hydrogen atom bound covalently to an atom A is attracted by an atom B containing a pair of free electrons (:B). This leads to strong polarization of the A-H bond and to electrostatic interactions between H(δ+) and :B. The expression “hydrogen non-covalent bond” is equivalent to the expression “dipole-dipole interaction”.
Advantageously, the layer of redox polymer implemented in the present invention has a thickness below the nanostructure thickness. In particular, the redox polymer layer has a thickness comprised between 1 nm and 20 μm and more particularly between 5 nm and 5 μm. More particularly, the redox polymer layer is conformal and thus closely follows the shape of the nanostructure.
The electrode according to the present invention comprises a support made of a conductor or semiconductor. Any support usually implemented for electrode in the field of energy storage devices can be used within the present invention. This support is a solid substrate which can present different shapes and sizes, according to the device in which the electrode according to the present invention is or will be used. Advantageously, this support has a shape selected from the group consisting of a plaque, a rod, a cylinder, a tube and a wire.
The support of the electrode according to the present invention is made of a semiconductive material, of conductive material or of a material presenting semiconductive areas and conductive areas.
From among the conductive materials advantageously implemented within the scope of the present invention, mention may be made of carbon, metals, noble metals, oxidized metals, transition metals, metal alloys and as particular and non-limiting examples, graphite, glass carbon, iron, copper, brass, nickel, cobalt, zinc, gold, platinum, titanium, steel, stainless steel, fluorine-doped tin oxide (FTO), indium tin oxide (ITO), aluminium-doped zinc oxide (AZO), mixtures thereof and alloys thereof.
The term “semiconductor” or the expression “semiconductive material” is understood to mean an organic or inorganic material that has an electrical conductivity intermediate between metals and insulators. The conductivity properties of a semiconductor are mainly influenced by the charge carriers (electrons or holes) that the semiconductor has. These properties are determined by two particular energy bands known as the valence band (corresponding to the electrons involved in covalent bonds) and the conduction band (corresponding to electrons in an excited state and that are capable of moving within the semiconductor). The “band gap” represents the energy difference between the valence band and the conduction band. The band gap generally does not exceed 3.5 eV for semiconductors, versus 5 eV in materials considered to be insulators. A semiconductor also corresponds, unlike insulators or metals, to a material for which the electrical conductivity can be controlled, to a large extent, by addition of dopants which correspond to foreign elements inserted into the crystal structure of the semiconductor.
From among the semiconductive materials advantageously implemented within the scope of the present invention, mention may be made, as particular and non-limiting examples, of silicon (Si), doped silicon, silicon carbide (SiC), germanium (Ge), gallium (Ga), gallium arsenide (GaAs), gallium nitride (GaN), gallium phosphide (GaP), gallium antimonide (GaSb), indium arsenide (InAs), indium phosphide (InP), indium antimonide (InSb), aluminium phosphide (AlP), aluminium antimonide (AlSb), aluminium sulfide (AlS), lead sulfide (PbS), lead selenide (PbSe), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), magnesium sulfide (MgS), magnesium selenide (MgSe), magnesium telluride (MgTe), calcium sulfide (CaS), calcium selenide (CaSe), calcium telluride (CaTe), strontium sulfide (SrS), strontium selenide (SrSe), strontium telluride (SrTe), barium sulfide (BaS), barium selenide (BaSe), barium telluride (BaTe), binary and ternary metal oxides such as zinc oxide (ZnO), titanium dioxide (TiO2), tin oxide (SnO2) and zinc tin oxide (Zn2SnO4), mixtures thereof and alloys thereof. Particular examples of such alloys are alloys of silicon and germanium in any proportions (SiGe).
In a particular embodiment, the support of the electrode is made of silicon and more advantageously doped silicon.
The electrode according to the present invention comprises at least one nanostructure made of a conductor or semiconductor, on at least one of the support surfaces. One can speak about a nanostructured support. Using a nanostructured support makes it possible to obtain an electrode with high area density and a greatly increased exchange area at the electrode/electrolyte interface.
In the sense of the present invention, by “surface” is meant the outer portion of the support which limits it in any direction. It is possible, for said support to conceptually define different surfaces. The invention applies to any type of surface regardless of its geometry. The latter may be simple, like a perfectly planar surface or complex surface, like a rough surface.
In the sense of the present invention, by “nanostructure” is meant a structure having one or more characteristic dimensions in the range of 0.1 to 100 nm. Advantageously, the nanostructure implemented in the present invention is with a large surface area: there are voids between the nanoelements forming this nanostructure. More particularly, the nanostructure implemented in the present invention in the form of nanotubes, nanowires, nanocones, nanotrees, nanoneedles, nanoparticles, nanoarrays, nanorods, nanospheres, nanosheets or mixtures thereof.
The nanostructure implemented in the present invention can be made of any conductive or semiconductive material as previously defined. Advantageously, this nanostructure is made of silicon and more advantageously doped silicon.
In a particular embodiment of the electrode according to the present invention, the support and the nanostructure are both made of silicon and more advantageously doped silicon. In this embodiment, the nanostructure is advantageously in the form of nanowires. Such nanostructures can either be obtained by chemical growth, electrochemical growth, epitaxial growth or chemical vapor deposition (CVD) or by etching the structures directly into the silicon support. More complex 3D nanostructures such as nanotrees and nanocones can also be obtained using these methods.
The present invention concerns a device for storing and releasing electrical energy comprising at least one electrode as previously defined. Such a device can be a battery, a dielectric capacitor, a supercapacitor or a hybrid system that can act simultaneously as a capacitor or a battery.
In a particular embodiment, the device for storing and releasing electrical energy according to the present invention comprises at least two electrodes as previously defined. These electrodes can be different or identical. Advantageously these electrodes are identical.
In a variant embodiment, the device for storing and releasing electrical energy according to the present invention comprises at least two electrodes, one of which is an electrode according to the present invention and the other of which is different from an electrode according to the present invention. For example, this other electrode can be made of carbon such as, for example, nanotubes, graphene or diamond, advantageously with a large specific surface area i.e. a specific surface area above 1500 m2/g. It can also be made of semiconducting polymers or inorganic semiconducting materials.
An electrochemical supercapacitor usually comprises a hermetically sealed housing filled with an electrolyte, two electrodes placed inside the housing, a separator soaked by an electrolyte, such as a membrane that separates the anode space from the cathode space and special lead terminals coupling the supercapacitor to external electric circuits. An electrochemical capacitor comprises a case, housing electrodes disposed inside the case and an electrolyte that fills the space between the electrodes.
When the device for storing and releasing electrical energy according to the present invention is an electrochemical capacitor or a supercapacitor, the latter is based on the Faradic (battery type) method for storing electrical power. In such a device, the charge/discharge process is accompanied by redox reactions in the layer of redox polymers at the surfaces of the electrodes.
The electrode according to the present invention can be employed as a positive electrode of the device for storing and releasing electrical energy according to the present invention and in particular in the electrochemical capacitor or supercapacitor. The negative electrode can be made by different methods.
In a variant, the electrode according to the present invention can be employed as a negative electrode of the device for storing and releasing electrical energy according to the present invention and in particular in the electrochemical capacitor or supercapacitor. The positive electrode can be made by different methods.
In another variant, the negative electrode and the positive electrode of the device for storing and releasing electrical energy according to the present invention and in particular in the electrochemical capacitor or supercapacitor can consist in two electrodes according to the present invention.
The other elements implemented in the electrochemical capacitor or supercapacitor such as the electrolyte, the case and the separator are well-known to the one skilled in the art. Additional information thereon can be found in the litterature and for example in [20].
The present invention also concerns a method for preparing an electrode as previously defined.
In a particular embodiment of the preparation of an electrode as previously defined, the redox polymer is prepared before being placed onto the nanostructured support of the electrode. Thus this method comprises the steps consisting in:
a) preparing a redox polymer of formula (I) as previously defined, and
b) depositing said redox polymer onto the at least one nanostructure as previously defined present on at least one surface of the support as previously defined.
Any method known by the one skilled in the art for preparing a redox polymer of formula (I) can be implemented at step (a). In this method, it can be used different or identical monomers of formula (VII):
All alternatives and particular embodiments disclosed for the groups G1 and G2 apply to groups G1′ and G2′ mutatis mutandis.
Any monomer of formula (VII) and in particular any symmetrical monomer of formula (VII) in which X1 and X2 represent S and G1′ and G2′ are identical can be prepared from 3,8-dioctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione. This compound is functionalized by two bromine groups whereby 2,7-dibromo-3,8-dioctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione is obtained. The latter can be coupled using the Stille or Suzuki coupling conditions well-known to the one skilled in the art with at least one derivative functionalized by a boronic ester or a stannyl group according to known procedures since these functional groups are known to be effective in palladium-catalyzed couplings. The derivative will be chosen according to the monomer of formula (VII) to be prepared. Some particular procedures are disclosed in the hereinafter experimental description in order to prepare FL136 or FL137. It is obvious that this description can be applied to all redox polymers of formula (I) according to the invention with the necessary adaptations of the processes and means for implementation which can be easily carried out by the one skilled in the art in this technical field.
Various procedures for polymerizing monomers of formula (VII) can be implemented at step (a) of the method according to the present invention. As for illustrative and non-limitative examples, one can cite (i) chemical or electro-chemical oxidizing coupling, for example using ferric chloride (FeCl3), (ii) polycondensation or polyaddition of correctly functionalized derivatives of the monomers of formula (VII), for example, by incorporating bromines in the [alpha] position of the end thiophene, selenophene or furan rings and then by using the Yamamoto coupling conditions, the polymerization taking place by polyaddition in the presence of a “zero valent” nickel complex or (iii) oxidative polymerization as illustrated in the hereinafter experimental description.
Various procedures can also be used to apply the redox polymer of formula (I) obtained at step (a) on the nanostructured support. This procedure is advantageously a liquid route technique that can be selected from the group consisting of sublimation, evaporation, spin-coating, dip-coating, spray-coating, drop casting, painting coating, screen-printing and resist-deposition.
In a variant embodiment of the preparation of an electrode as previously defined, the redox polymer is prepared in presence of the nanostructured support of the electrode. This embodiment makes it possible to obtain an improved impregnation of the nanostructure by the redox polymer. This variant method comprises the steps consisting in:
The electropolymerization implemented during step (b′) of this variant embodiment is a technique well-known by the one skilled in the art. A particular electropolymerization procedure is disclosed in the hereinafter experimental description in order to prepare poly(FL137).
Other characteristics and advantages of the invention can be seen more clearly from the additional description below, given by way of illustrative and non-limiting example and with reference to the accompanying figures.
−1.50 V; reversal potential: 0.50 V.
All reagents and chemicals were purchased from Aldrich or Acros and used as received, except for THF which was distilled over sodium-benzophenone prior to use. Thin layer chromatography was performed on silica gel-coated aluminium plates with a particle size of 2-25 μm and a pore size of 60 Å. Silica from Merck (70-230 mesh) was used for flash chromatography. 5,5-dimethyl-2-(4-octylthien-2-yl)[1,3,2]dioxaborinane and [E-(5-(3-octylthien-2-yl-vinyl)-(3-octylthien-2-yl)]-trimethyltin were prepared according to published procedures [24].
All synthesized products were identified by 1H and 13C NMR spectroscopy, as well as by elemental analysis. NMR spectra were recorded in chloroform-d, or acetone-d6 containing tetramethylsilane (TMS) as internal standard, on a Bruker AC200 spectrometer.
Elemental analyses (C, H, N, and S) were carried out by the Analytical Service of the CNRS (Vernaison, France) or by CRMPO at the University of Rennes 1.
Ultraviolet-visible (UV-vis) absorption spectra were recorded on a HP 8452A spectrometer (wavelength range 190-820 nm).
To a stirred solution of 3-octylthiophene (7.50 g, 38.19 mmol) in 100 mL of freshly distilled THF at −78° C. was added dropwise a solution of n-butyllithium (n-BuLi) (2.5 M, 16.8 mL, 42 mmol). The resulting solution was stirred for 45 min and warmed to −50° C. The mixture was cooled at −78° C. and trimethyltin chloride (8.40 g, 42 mmol) dissolved in 20 mL of THF was added quickly.
The resulting mixture was allowed to warm to room temperature over 80 min and then it was poured into water, extracted with diethyl ether and the organic extracts were washed with saturated aqueous solution of NH4Cl. After drying and filtration, the filtrate was concentrated under reduced pressure to give 13.80 g of organostannane. Due to the high toxicity of organostannane compound, the crude product was merely titrated (90% of purity) by NMR and used without further purification.
1H NMR (200 MHz, CDCl3) δ (ppm): 7.20 (d, J=0.8 Hz, 1 H), 7.01 (d, J=0.8 Hz, 1 H), 2.64 (t, 3J=7.4 Hz, 2 H), 1.62 (tbr, 2 H), 1.35-1.25 (m, 10 H), 0.88 (t, 3J=6.8 Hz, 3 H), 0.35 (s, 9 H).
Diethyl-2,5-dibromo-1,4-benzenedicarboxylate (2.50 g, 6.57 mmol) and 3-octyl-5-trimethylstannylthiophene (7.20 g, 18.94 mmol) were dissolved in anhydrous DMF (75 mL) and the resulting mixture was purged 10 min with Ar.
Separately Pd(OAc)2 (0.15 g, 0.66 mmol) and PPh3 (0.70 g, 2.65 mmol) were placed in 5 mL of freshly distilled THF and stirred 10 min under argon. After the formation of a yellow precipitate, the catalyst was transferred in the DMF solution and the mixture was heated to 100° C. overnight. The mixture was then filtered through celite and DMF was removed under reduced pressure. The crude product was purified by column chromatography (silica gel, hexane/CH2Cl2, 7:3) to afford 3.85 g (98%) of a transparent oil.
1H NMR (200 MHz, CDCl3) δ (ppm): 7.76 (s, 2 H), 6.96 (d, 4J=1.4 Hz, 2 H), 6.91 (d, 4J=1.4 Hz, 2 H), 4.21 (q, 3J=7.1 Hz, 4 H, OCH2), 2.60 (t, 3J=8.0 Hz, 4H), 1.65-1.55 (m, 4 H), 1.45-1.25 (m, 20 H), 1.16 (t, 3J=7.1 Hz, 6 H, OCH2CH3,), 0.92-0.85 (m, 6 H). Elemental analysis, found (calcd): C, 70.51 (70.78); H, 8.19 (8.25).
Elemental analysis, found (calcd): C, 69.35 (69.28); H, 7.50 (7.63).
2,5-bis[4′-octylthien-2′-yl]-1,4-benzenedicarboxylic (1.0 g, 1.80 mmol) was dissolved in 70 mL of anhydrous CH2Cl2 under argon. Then oxalyl chloride (1.80 mL, 20.5 mmol) and 0.40 mL of DMF, were added and the mixture was stirred 12 h at room temperature. The solvent was removed under reduced pressure to obtain the crude 2,5-bis[4′-octylthien-2′-yl]-1,4-benzenedicarboxylic acid dichloride which was used without further purification.
The product was dissolved in 80 mL of anhydrous CH2Cl2 under argon, then cooled to 0° C. and a suspension of AlCl3 (0.72 g, 5.41 mmol) in 80 mL of anhydrous CH2C12 was added dropwise. The mixture was maintained at 0° C. for 30 min and then allowed to warm to room temperature. After stirring 3 h at room temperature, the reaction mixture was poured into ice water and 1 M hydrochloric acid and extracted with chloroform. The organic layer was washed with water, dried over Na2SO4, filtered and concentrated under reduced pressure. Column chromatography (silica gel, hexane/CHCl3, 7:3) afforded 0.78 g of a blue solid (84%).
1H NMR (200 MHz, CDCl3) δ (ppm): 7.18 (s, 2 H), 6.79 (s, 2 H), 2.71 (t, 3J=7.3 Hz, 4 H), 1.69-1.62 (m, 3J=7.3 Hz, 4 H), 1.40-1.26 (m, 20 H), 0.92-0.84 (m, 6 H). 13C NMR (CDC13, 50 MHz): δ (ppm): 189.07 (2C=O), 161.15 (2C), 143.85 (2C), 143.54 (2C), 142.49 (2C), 142.38 (2C), 127.57 (2C), 117.09 (2C), 34.75 (2C), 32.28 (2C), 32.24 (2C), 32.20 (2C), 32.10 (2C), 31.28 (2C), 25.55 (2C), 17.02 (2C). Elemental analysis, found (calcd): C, 73.95 (74.09); H, 7.33 (7.38).
To a solution of 3,8-dioctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione (1.0 g, 1.92 mmol) in 30 mL of CHCl3 and 30 mL of AcOH, was added N-Bromosuccinimide (1,04 g, 2.92 mmol) in small portions over a period of 15 min. The reaction mixture was stirred 10 h at room temperature and then it was poured into water and extracted with CHCl3. The organic layer was washed with NaHCO3 and dried over Na2SO4.
The crude product was concentrated under reduced pressure and precipitated from hexane. The filtrate was washed with methanol and acetone and then dried under vacuum to give 1.26 g of a greenish solid (97%).
1H NMR (200 MHz, C2D2Cl4) δ (ppm): 7.14 (s, 2H), 2.71 (t, 3J=7.0 Hz, 4H), 2.61 (t, 3J=7.3 Hz, 4H), 1.67-1.50 (m, 4H), 1.25-1.10 (m, 20H), 0.95-0.85 (m, 6H). 13C NMR (C2D2C14, 50 MHz): δ (ppm): 185.28 (2C=O), 156.45 (2C), 139.83 (2C), 139.66 (4C), 138.18 (2C), 114.64 (2C), 113.64 (2C), 32.06 (2C), 29.50 (2C), 29.42 (2C), 29.37 (2C), 29.07 (2C), 27.46 (2C), 22.87 (2C), 14.36 (2C).
This product was synthesized starting from 2,7-dibromo-3,8-dioctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione (0.65 g, 0.96 mmol) and 3-octyl-5-trimethylstannylthiophene (2.5 eq) according to the Stille palladium-catalyzed coupling procedure described above.
After usual work up, the product was purified by column chromatography (silica gel, hexane/CHCl3, 7:3) to give 0.62 g (72%) of a green-blue solid.
1H NMR (200 MHz, CDC13) δ (ppm): 7.14 (s, 2H), 6.98 (d, 4J=1.2 Hz, 2H), 6.94 (d br, 2H), 2.85 (t, 3J=6.8 Hz, 4H), 2.61 (t, 3J=7.3 Hz, 4H), 1.75-1.52 (m, 8H), 1.45-1.20 (m, 40H), 0.95-0.80 (m, 12H). 13C NMR (CDCl3, 50 MHz): δ (ppm): 186.57 (2C=O), 155.31 (2C), 143.83 (2C), 140.55 (2C), 140.33 (2C), 139.43 (2C), 136.37 (4C), 134.36 (2C), 127.81 (2C), 120.91 (2C), 114.07 (2C), 31.89 (4C), 30.42 (4C), 29.57 (4C), 29.43 (4C), 29.34 (4C), 29.28 (4C), 22.68 (4C), 14.13 (4C). Elemental analysis, found (calcd): C, 73.85 (74.12); H, 8.14 (8.22); S, 13.95 (14.13).
This product was synthesized starting from 2,7-dibromo-3,8-dioctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione (0.50 g, 0.74 mmol) and [E-(5-(3-octylthien-2-yl-vinyl)-(3-octylthien-2-yl)]-trimethyltin (2.2 eq.) according to the Stille palladium-catalyzed coupling procedure described above. After usual work up, the product was purified by column chromatography (silica gel, hexane/CHCl3, 8:2) to give 0.62 g (63%) of a dark greenish solid.
1H NMR (200 MHz, CDCl3) δ (ppm): 7.12 (s, 2H), 7.09 (d, 3J=5.1 Hz, 2H), 6.96 (s br, 4H), 6.90 (s, 2H), 6.86 (d, 3J=5.1 Hz, 2H), 2.91 (t, 3J=7.4 Hz, 4H), 2.75-2.55 (m, 3J=7.4 Hz, 8H), 1.75-1.50 (m, 12H), 1.45-1.15 (m, 60H), 0.90-0.80 (m, 18H). 13C NMR (CDC13, 50 MHz): δ (ppm): 186.53 (2C=0), 155.05 (2C), 141.29 (2C), 141.21 (2C), 140.73 (2C), 140.41 (2C), 139.38 (2C), 137.18 (2C), 136.53 (2C), 136.27 (2C), 136.07 (2C), 131.56 (2C), 129.89 (2C), 128.69 (2C), 122.96 (2C), 119.86 (2C), 118.53 (2C), 114.02 (2C), 31.90 (6C), 30.93 (2C), 30.82 (2C), 29.89 (2C), 29.63 (2C), 29.47 (2C), 29.44 (2C), 29.39 (4C), 29.34 (2C), 29.33 (2C), 29.29 (4C), 28.46 (2C), 28.39 (2C), 27.16 (2C), 22.69 (6C), 14.13 (6C). Elemental analysis, found (calcd): C, 74.25 (74.83); H, 8.53 (8.52).
Under argon, 3,4-Ethylenedioxythiophene (63 mg, 0.44 mmol) was dissolved in distilled THF (8 mL) then n-BuLi (0.20 mL, 0.49 mmol) was added at −78° C. The solution was stirred for an hour at −50° C. before adding a n-hexane solution of trimethyltin chloride (0.49 mL, 0.49 mmol) at −78° C. The solution was allowed to reach room temperature and stirred for 2 hours. The reaction was quenched with water and the organic phase was extracted with n-hexane, dried on Na2SO4, filtered and concentrated under vacuum. The resulting oil was engaged without any further purification in a Stille coupling with 4-2,7-dibromo-3,8-dioctyl-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione. Under argon, solids stannic, 2,7-dibromo-3,8-dioctyl-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione (100 mg, 0.15 mmol), tris(dibenzylideneacetone)dipalladium (5.4 mg, 6 μmol) and tri(o-tolyl)phosphine (3.6 mg, 12 μmol) were dissolved in anhydrous toluene (8 mL) and refluxed for 14 h. The mixture was then poured into HCl (2 M). The organic phase was extracted with diethyl ether, washed with HCl (2 M), dried over Na2SO4 and concentrated. The crude solid was chromatographed on silica using petroleum ether/CHCl3 1:1 as eluent to afford green solid (118 mg, 0.10 mmol, 70%).
1H NMR (CDCl3, 400 MHz): δ=7.18 (s, 2H), 6.44 (s, 1H), 4.31 (m, 8H), 2.86 (t, J=7.8Hz, 4H), 1.72-1.60 (m, 4H), 1.45-1.20 (m, 24H), 0.90 (t, 1H, J=6.8Hz).
1H NMR (CDC13, 400 MHz): δ=186.66, 156.78, 141.48, 140.54, 139.83, 139.69, 139.04, 137.74, 132.72, 114.09, 99.81, 65.00, 64.46, 31.90, 29.87, 29.62, 29.35, 29.26, 27.33, 22.68, 14.126.
Cyclic voltammetry experiments were performed in an argon glove box, using a one-compartment electrolytic cell with a platinum disk working electrode (7 mm2 surface area), a platinum counter electrode and an Ag/0.01 mol.L−1 AgNO3 reference electrode. The electrolyte consisted of 0.1 mol.L−1 tetrabutylammonium tetrafluoroborate (Bu4NBF4) solution in dichloromethane, to which 2.10−3 mol.L−1 of FL136 or 1.5.10−3 mol.L−1 of FL137 were added. The results of this characterization are presented in
A solution of 145 mg of anhydrous ferric chloride (0.89 mmol) in a mixed solvent consisting of 4 mL of nitromethane and 5 mL of chloroform was added dropwise to a solution of FL136 (200 mg, 0.2204 mmol) in 30 mL of freshly distilled and degassed chloroform. The addition was performed at 0° C. with constant stirring over a period of 90 min. At the end of the addition, the mixture was warmed to 10° C. and was maintained at this temperature for an additional period of 60 min. The reaction mixture was then allowed to warm to room temperature and stirred for 5 h. Subsequently, it was concentrated by pumping under vacuum and then precipitated in 100 mL of methanol. The crude polymer was then dissolved in 50 mL of chloroform and washed four times with a 0.1 M aqueous solution of ammonia (150 mL each time). In the next step the polymer was stirred for 48 h with the same aqueous solution.
As-synthesized polymer usually contains small amounts of dopants of unidentified chemical nature and requires further dedoping. The dedoping was achieved by washing the chloroform solution of the polymer with an EDTA aqueous solution (0.05 M, 200 mL). The polymer was then washed with water twice and acetone and then dried under vacuum to give 185 mg (93%) of a dark powder. The product is then fractionated with a Sohxlet apparatus using chloroform and chlorobenzene.
Size exclusion chromatography analysis of the batch: Mn[kDa eq. PS]=3.7643 kDa eq. PS; Mw[kDa eq. PS]=4.9664 kDa eq. PS; I=Mw/Mn=1.3194; Mw up to[kDa eq. PS]˜20.0 kDa eq. PS.
The same procedure as described above was employed using 200 mg of FL137 and 97 mg of iron chloride. The polymer was obtained as a dark powder (150 mg).
Size exclusion chromatography analysis of the batch: Mn[kDa eq. PS]=3.3648 kDa eq. PS; Mw[kDa eq. PS]=4.1824 kDa eq. PS; I=Mw/Mn=1.2430; Mw up to[kDa eq. PS]˜ 15.0 kDa eq. PS.
Growth of SiNWs : Highly doped SiNWs electrodes with a length of approximately 20 μm and a diameter of 50 nm were grown in a CVD reactor (EasyTube3000 First Nano, a Division of CVD Equipment Corporation) by using the vapor-liquid-solid (VLS) method via gold catalysis on highly doped p-Si(111) substrate using an optimal deposition procedure, which has been previously detailed [25]. Briefly, the SiNWs were grown from a colloidal gold catalyst performed at 600° C., under 6 Torr total pressure, with 40 sccm (standard cubic centimeters) of SiH4, 100 sccm of B2H6 gas (0.2% B2H6 in H2) for p doping, 100 sccm of HCl gas and 700 sccm of H2 as supporting gas.
Electropolymerization of FL137 on SiNWs: FL137 films were electrochemically deposited from a CH2Cl2 solution containing 0.1 M tetrabutylammonium hexafluorophosphate (NBu4PF6) and 1.5 mM FL137 as the monomer using an AUTOLAB PGSTAT 302 N potentiostat-galvanostat. The electropolymerization was conducted in a 3-electrode electrochemical cell. SiNWs was employed as the working electrode, a Pt wire was used as the counter electrode and the nonaqueous Ag/Ag+ reference electrode was composed of a silver wire immersed in a 10 mM silver trifluoromethanesulfonate (AgTf) solution in N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR13 TFSI). The electrochemical deposition of FL137 was carried out by potentiostatic methods using a constant potential (1 V) controlled by the chronocoulometry technique (Total polymerization charge of 20 mC) in an argon-filled glove box with oxygen and water levels less than 1 ppm. After the electrochemical deposition, the electrodes were washed in acetone and dried with a N2 flow before the electrochemical characterization.
Morphological characterization: The morphology of the resulting SiNWs and hybrid SiNWs electrodes was examined by scanning electron microscopy. A Zeiss Ultra 55 scanning microscope operating at an accelerating voltage of 10 kV was used.
Electrochemical characterization: FL137-coated SiNWs electrode was evaluated in a 3-electrode cell configuration using PYR13 TFSI as electrolyte. The hybrid electrode was employed as the working electrode, a Pt wire was used as the counter electrode and the nonaqueous Ag/Ag+ reference electrode was composed of a silver wire immersed in a 10 mM silver trifluoromethanesulfonate (AgTf) solution in PYR13 TFSI.
Performance and configuration of the device: Symmetric micro-supercapacitors were designed from hybrid nanostructured electrodes made of FL137-coated SiNWs as mentioned in the previous section. A homemade two-electrode supercapacitor cell was built by assembling two hybrid nanostructured material-based electrodes (1 cm2) separated by a Whatman glass fiber paper separator soaked with butyl-trimethyl ammonium bis(trifluoromethylsulfonyl)imide (N1114 BTA) as electrolyte. Cyclic voltammetry (CV) and galvanostatic charge-discharge cycles were performed using a multichannel VMP3 potentiostat/galvanostat with Ec-Lab software (Biologic, France). All measurements were carried out using N1114 BTA as electrolyte in an argon-filled glove box with oxygen and water levels less than 1 ppm at room temperature.
Results: The morphology of SiNWs and FL137-coated SiNW electrodes was analyzed by scanning electron microscopy as displayed in
Concerning one of the most important criteria in a supercapacitor, cycling stability, the lifetime of the device was evaluated by applying successive galvanostatic cycles at a high current density of 1 mA.cm−2. Thus, the device was able to retain more than 80% after 25000 complete galvanostatic cycles demonstrating its enormous potential in terms of lifespan (
This cycling stability value was compared with similar systems based on electroactive conducting polymers. Consequently, PEDOT-coated SiNW and PPy-coated Silicon Nanotree supercapacitors reflected a loss of specific capacitance of 20% and 30% after 3,500 and 10,000 charge-discharge cycles respectively [9]. The use of electroactive conducting polymers for supercapacitor devices is limited due to their poor cycling stability (typically a few thousand cycles).
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| Number | Date | Country | Kind |
|---|---|---|---|
| 16306053.6 | Aug 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/070354 | 8/10/2017 | WO | 00 |
