Organic active materials for electrochemical energy storage

Abstract

A compound having the structure Red-R-M, wherein: Red is a redox center; R is a bridging group; and M is a monomer giving rise to an electronically conductive polymer, is provided. Also provides are polymers obtained by polymerization of such compounds and uses in electronic devices of such polymers, for example uses in batteries.

Claims

1. A compound comprising a structure Red-R-M, wherein: Red is a redox center; R is a bridging group; and M is a monomer giving rise to an electronically conductive polymer, wherein the redox center contains a group selected from the group consisting of arylenebisimides and indolizines, and wherein the compound has a structure as shown below: ##STR00006##

2. A compound comprising a structure Red-R-M, wherein: Red is a redox center; R is a bridging group; and M is a monomer giving rise to an electronically conductive polymer, wherein the redox center comprises a group selected from the group consisting of indolizines, and wherein the monomer M comprises a group selected from the group consisting of thiophene, pyrrole, paraphenylenvinylene, furan, carbazole, silole, and fluorene.

3. The compound according to claim 2, wherein the compound has the following structure: ##STR00007##

4. The compound according to claim 2, wherein the compound comprises a 3,4-ethylenedioxythiophene (EDOT) group.

5. The compound according to claim 2, wherein the bridge R comprises a linear alkylene chain, a branched alkylene chain, or a glycolic chain, or a combination of functional groups selected from the group consisting of C(O), C(S), OC(O), OC(S), OC(O)O, (CO)O, C(S)O, C(S)S, C(O)NR, and C(S)NR where R is H, alkyl, SO, SO.sub.2, or a combination of any linear alkylic chain or branched alkylic chain or glycolic chain separated by one or more of the said functional groups.

6. A polymer obtained by polymerization of a compound according to claim 2.

7. A method for storing electrochemical energy, comprising transferring charge to the polymer according to claim 6 by charge transfer or by adsorption.

8. A lithium-ion battery comprising the polymer according to claim 6.

9. A lithium-ion battery comprising a polymer obtained by polymerization of a compound comprising a structure Red-R-M, wherein: Red is a redox center; R is a bridging group; and M is a monomer giving rise to an electronically conductive polymer, wherein the redox center comprises a group selected from the group consisting of arylenebisimides.

Description

BRIEF SUMMARY OF THE FIGURES

(1) FIG. 1 is a schematic diagram showing an illustrative example of electroactive polymers with a PEDOT polymeric backbone attached to a redox centre via an alkylene bridge.

(2) FIG. 2 is a schematic drawing of a battery.

(3) FIG. 3 is a schematic view of polymer materials according to the present invention, illustrated for a polymeric backbone based on PEDOT.

(4) FIG. 4 is a schematic view of polymer materials according to the present invention, illustrated for a polymeric backbone based on various monomer types envisaged in the invention.

(5) FIG. 5 illustrates some specific redox centres that may be used in exemplary compounds and polymer materials of the present invention.

(6) FIG. 6 illustrates some specific compounds of the present invention.

(7) FIG. 7 illustrates various redox centres that may be used in compounds and polymer materials of the present invention

(8) FIG. 8 illustrates some specific polymers of the present invention.

(9) FIG. 9 illustrates power delivery of Poly-NPbIM-1, an exemplary polymer material according to the present invention.

(10) FIG. 10 illustrates long-term stability of Poly-NPbIM-1.

DETAILED DESCRIPTION OF THE INVENTION

(11) An important feature of the present invention is in the coupling of a molecule able to store charge to an electrically conductive polymeric backbone.

(12) The structure of the polymer materials of the present invention can be generalized as containing three elements: a polymeric electronically conductive backbone, electrochemically active redox centres and organic bridges linking the other two elements i.e the redox centres to the polymeric electronically conductive backbone. An illustrative and non-limiting example is given in FIG. 3. In this example the polymeric backbone is PEDOT (poly(3,4-ethylenedioxythiophene)) i.e. a polymer derived from a 3,4-ethylenedioxythiophene (EDOT) group. This is a preferred material for the polymeric electronically conductive backbone in the present invention, but other electronically conductive polymers can also be used. As an example, possible polymers could be but are not limited to: polythiophenes, polypyrroles, polyparaphenylenevinylenes, polyfurans, polycarbazoles, polysiloles, polyfluorenes, and copolymers obtained by combining repeating units of the above mentioned homopolymers. Representative structures, as well as an indication of the functionalization site bearing the redox center, are shown in FIG. 4. For example, where the monomer unit contains a nitrogen atom, the latter may be functionalized with, for example, alkyl groups or other types of groups constituting bridging groups in the compounds and polymers of the present invention. In other systems, such as the five-membered ring monomers thiophene, furan, pyrrole and silole, the 3-position of the ring may be used to link through a bridge to a redox centre. For example, monomers containing such a core five-membered ring exist for which the 3-position of the ring is linked to a functional group such as an OH or CO.sub.2H group, which may then be linked to the other parts of the compounds of the invention.

(13) Polymerization of the monomer units may be carried out according to techniques known in the art for such monomers giving rise to electrically conductive polymer backbones. As an example, when polymerizing thiophene monomers, in a typical polymerization process, a suitable oxidizing agent is added, which may in particular give rise to polymers in which hydrogen atoms are removed from thiophene rings as the latter are joined together to produce polymer chains. As a suitable but merely illustrative and non-limiting example of an oxidizing agent that may be used to induce polymerization of thiophene-containing monomers to give electrically conductive polymers, one may cite Baytron-CB-40, which is iron (III) tosylate.

(14) The same type of polymerization protocol may be applied for the polymerization of thiophene, pyrrole, furane and carbazole derivatives shown in FIG. 4. Fluorene, polyparaphenylenevinylene and silole derivatives may be polymerized starting from suitable halogenated and/or organotin and/or organoboron derivatives using either nickel, copper or palladium catalyzed coupling reactions.

(15) Various structures are possible for the bridge R in compounds of the present invention. As an example, the bridge can be made using any linear alkylene chain or branched alkylene chain or glycolic chain (alkylene or branched alkylene chain with one or more CH.sub.2 or CHR or CRR groups being replaced by an oxygen atom, where R and R are alkyl groups) or a combination of them, the alkylene and/or glycolic chain(s) being optionally separated by functional groups selected among the following: CO, CS, O(CO), O(CS), O(CO)O, (CO)O, (CS)O, (CS)S, (CO)NR or (CS)NR wherein R is H or alkyl such as C1-C6 alkyl, SO, SO.sub.2. It is also possible for the bridge to be wholly constituted by such functional groups. In an advantageous embodiment, the minimum number of atoms counted directly along the atomic chain between the redox centre, in particular between the ring atom of a redox centre to which bridging group R is joined on the one hand, and the monomer M, in particular the ring atom of monomer M to which bridging group R is joined on the other hand, is between 1 and 15 atoms, preferably between 3 and 11 atoms, and more preferably between 5 and 9 atoms.

(16) It is also envisaged in embodiments of the present invention that the bridging group may include a divalent aryl, substituted aryl, heteroaryl or substituted heteroaryl group. The substituents on the divalent (hetero)aryl ring may include electron-rich groups, or electron-withdrawing groups such as halogen groups, including fluorine atoms. In the event that the (hetero)aryl ring is bound directly to the redox centre, this may be considered to be part of the redox centre itself.

(17) Two specific illustrative and non-limiting examples of compounds according to the present invention which have ester-type bridge are shown in FIG. 6. These illustrative exemplified compounds show the structure (Redox centre)-[Bridge-EDOT].sub.2. These symmetrical structures, with two monomers M positioned around a central redox centre, appear to provide higher electrochemical stability compared to ones in which there is a single pendant monomer M. Structures of the type (Redox centre)-[Bridge-EDOT].sub.2 therefore constitute a preferred embodiment according to the present invention. However, providing that there is at least one pendant M group, a functioning polymer material of the present invention may be obtained, and thus there may be only one, or three, or more, bridges and conductive monomer groups around the redox centre.

(18) As redox centers, molecules which can be oxidized or reduced reversibly within the potential window of interest for organic batteries may be used. Amongst oxidizable centers are electron rich heterocyclic amines. Among reducible centers are: viologens, violenes, anthraquinones, arylenebisimides, and related compounds. FIG. 7 shows representative examples of the above mentioned structures. In a number of advantageous embodiments, the redox centre contains one or two (most commonly two) nitrogen atoms which may be functionalized with, for example, alkyl groups or other types of groups constituting bridging groups in the compounds and polymers of the present invention.

(19) As mentioned above, in some possible exemplary embodiments of the present invention, a substituted or unsubstituted aryl or heteroaryl ring may be bound directly to the redox centre, for example, bound in particular to a nitrogen atom of the redox centre. The divalent substituted or unsubstituted aryl or heteroaryl ring may then have an effect on the properties of the redox centre, for example the substituents on the divalent (hetero)aryl ring may include electron-rich groups, or electron-withdrawing groups such as halogen groups, including fluorine atoms. In such a case where a (hetero)aryl ring is bound directly to the redox centre, the ring may be conceptually considered to be part of the redox centre itself, rather than considering that the (hetero)aryl ring atoms are part of the bridging group.

(20) Changing redox centers and bridges in compounds in the invention has notably the following two effects: (1) defining the electrochemical potential at which the molecule is active and (2) defining the molecular weight of the material, thus influencing the volumetric and gravimetric energy and power densities. For example adopting Electron-Withdrawing Groups (EWG) will increase the potential, allowing the preparation of materials suitable to be used as positive electrode materials (cathodes).

(21) The polymeric backbone of polymers of the present invention has the primary function to serve as a fast electronic conductor, but it can also store charge either by charge transfer or by adsorption (capacitive behavior). In the present invention, a preferred electrically conductive polymer backbone is PEDOT.

(22) The polymer materials of the present invention may be used in an electrochemical device to store energy (e.g. a battery). The materials may be used as part of a composite electrode. The materials may be used either as a positive electrode material, negative electrode material, or both, separated by a liquid, gel, polymeric or solid electrolyte. An electrolyte allows the passage of ions from one end of the device to the other, and ions may be stored using materials of the invention. At the same time, electrons flow from one end of the battery to the other, the direction of the flow depending if the device is being used to power an external load or if it is being recharged. A current collector will appropriately be used on both sides of the battery to carry the electrical energy. FIG. 2 has an example of a device into which materials of the present invention may be incorporated. The present invention could be used in batteries where the electrolyte contains mono- and divalent cations and anions, both organic and inorganic. The choice of electrolyte can include, but is not limited to, lithium ions, sodium ions, potassium ions, tetrabutylammonium ions, hexafluorophosphate ions, perchlorate ions, tetrafluoroborate ions, bis-trifluoromethanesulfoneimide ions (TFSI). The solvent for the electrolyte will be chosen according to the operation potential of the electrode materials and can contain, but is not limited to, ethylene carbonate, dimethylcarbonate, propylenecarbonate, acetonitrile.

Examples

Monomer Preparation Procedures

(23) A1. Synthesis of INZ-0

(24) ##STR00003##
In an amber glass 50 ml RBF, equipped with CaCl.sub.2 guard tube, chloroacetone (10.34 ml, 11.91 g, 128.7 mmol) was added to a solution of 2-picoline (10.00 g, 107.3 mmol) in 2-butanone (25 ml) followed by KI (641 mg, 3.86 mmol). The mixture was heated to 70 C. for 15 h, cooled to RT and kept under stirring for 12 h. Et.sub.2O (25 ml) was added to the mixture and the obtained suspension was filtered on an Hirsh funnel. The deliquescent dark solid was transferred to a 250 ml RBF and dissolved in 125 ml of water. The solution was kept under stirring and NaHCO.sub.3 was slowly added observing gas evolution. The mixture was steam distilled obtaining a suspension of the pure product in the distillate. The distillate was filtered on an Hirsh funnel and the white solid was dried under reduced pressure at room temperature (8.305 g, 63.3 mmol, yield 59%).
A2. Synthesis of INZ-1

(25) ##STR00004##
Synthesis of 9
Chloroacetone (8.09 g, 87.40 mmol) was dropwise added to a solution of 2-propanolpyridine (10.00 g, 72.89 mmol) in 2-butanone (25 ml). KI (435 mg, 2.62 mmol) was added and the mixture was heated to reflux for 24 h. The mixture was cooled to RT and Et.sub.2O (100 ml) was added. The solvent was decanted and the residue was transferred to a 500 ml RBF. The organic phase was further extracted with 450 ml of water collecting the aqueous phase. Under N.sub.2 atmosphere, NaHCO.sub.3 was slowly added under stirring to the aqueous mixture observing a vigorous gas evolution. The mixture was heated to reflux for 90 min and cooled to RT. The dark mixture was extracted with 5100 ml of Et.sub.2O. The organic phase was collected, washed with brine (50 ml), dried over Na.sub.2SO.sub.4 overnight and evaporated under reduced pressure. The residue was purified by filtration on a silica plug (eluent: CH.sub.2Cl.sub.2/AcOEt 1:1). Product was obtained as a pale yellow oil after solvent evaporation under reduced pressure (4.200 g, 23.97 mmol, yield 33%).

(26) .sup.1H NMR (500 MHz, Acetone-d.sub.6) [ppm]: 7.98 (d, J=7.0 Hz, 1H), 7.31 (d, J=9.0 Hz, 1H), 7.23 (s, 1H), 6.55 (t, J=8.3 Hz, 1H), 6.36 (t, J=6.7 Hz, 1H), 3.68-3.64 (m, 2H), 3.54 (t, J=5.7 Hz, 1H), 2.93 (t, J=7.4 Hz, 2H), 2.25 (s, 3H); .sup.13C NMR (125.7 MHz, Acetone-d.sub.6) [ppm]: 131.52, 125.66, 124.18, 117.47, 116.12, 111.68, 109.77, 109.10, 63.46, 28.73, 10.72.

(27) Synthesis of 10

(28) A mixture of 9 (4.100 g, 23.39 mmol) and Pt/C 10% (4.56 g, 2.34 mmol) in chlorobenzene (220 ml) was stirred at RT in an open 500 ml round bottom flask for 24 h. The mixture was filtered to remove the catalyst washing with chlorobenzene and the filtrate was evaporated under reduced pressure. The residue was purified by chromatography on silica gel (eluent: CH.sub.2Cl.sub.2/AcOEt 2:3), obtaining a clear oil after solvent evaporation under reduced pressure. The residue was triturated with Et.sub.2O (10 ml) obtaining pure product as pale greenish solid (901 mg, 2.58 mmol, yield 22%, m.p.: 148-150 C.).

(29) .sup.1H NMR (500 MHz, Acetone-d.sub.6) [ppm]: 7.51 (d, J=9.0 Hz, 2H), 7.22 (d, J=7.0 Hz, 2H), 6.71 (t, J=7.5 Hz, 2H), 6.44 (t, J=7.1 Hz, 2H), 3.80-3.76 (m, 4H), 3.61 (t, J=5.8 Hz, 2H), 3.06 (t, J=7.1 Hz, 4H), 2.11 (s, 6H); .sup.13C NMR (125.7 MHz, Acetone-d.sub.6) [ppm]: 132.50, 126.13, 123.62, 117.82, 117.07, 112.46, 110.47, 109.60, 63.42, 29.03, 10.46.

(30) Synthesis of INZ-1

(31) Under N.sub.2 atmosphere, MeCN (13 ml) was added to a mixture of 10 (350 mg, 1.004 mmol), 4 (672 mg, 2.35 mmol), DCC (515 mg, 2.49 mmol) and DMAP (27 mg, 0.22 mmol). EDOT derivatives 4 can be obtained by the methods disclosed in Italian patent application TO2011A000830 filed 15 Sep. 2011, sharing common inventors with the present application. The mixture was kept under stirring at RT for 4 days and filtered washing with MeCN. The filtrate was collected, evaporated under reduced pressure and purified by cromatography on silica gel (eluent: CH.sub.2Cl.sub.2/AcOEt 9:1). Product was obtained as a greenish oil after solvent evaporation under reduced pressure at 50 C. (499 mg, 0.564 mmol, yield 56%).

(32) .sup.1H NMR (500 MHz, Acetone-d.sub.6) [ppm]: 7.54 (d, J=9.0 Hz, 2H), 7.26-7.24 (m, 2H), 6.78-6.75 (m, 2H), 6.48-6.44 (m, 6H), 4.37-4.27 (m, 12H), 4.09-4.04 (m, 2H), 3.18 (t, J=7.1 Hz, 4H), 2.40-2.34 (m, 8H), 2.13 (d, J=1.2 Hz, 6H), 1.86 (qui, J=7.3 Hz, 4H).

(33) A3. Synthesis of NPBIM-1

(34) ##STR00005##
Synthesis of 11
Ethanolamine (4.759 g, 77.92 mmol) was dropwise added to a suspension of 1,4,5,8-Naphthalenetetracarboxylic dianhydride (5.226 g, 19.48 mmol) in water (60 ml) and the mixture was heated to 80 C. for 24 h. Mixture was cooled to RT and product was collected by filtration on a Buechner funnel washing with water followed by acetone. Residual solvent was evaporated under reduced pressure at 50 C. obtaining product as a pale brown solid (5.785 g, 17.73 mmol, yield 91%., m.p.: 325 C. (lit. 321-323 C.)).
Synthesis of 12
In a test tube, a mixture of 11 (3.000 g, 9.20 mmol), glutaric anhydride (21.6 g, 184 mmol) and DMAP (112 mg, 0.920 mmol) was heated to 110 C. for 30 min. The mixture was poured in 75 ml of water and acidified adding 1 ml of HCl.sub.(aq.) 37%. The obtained suspension was stirred at RT overnight and filtered on an Hirsh funnel washing with water followed by few ml of EtOH. Product was purified by crystallization from cyclohexanone and residual solvent was evaporated under reduced pressure. Pink solid (3.168 g, 5.44 mmol, yield 59%, m.p.: 220 C.).

(35) .sup.1H NMR (500 MHz, DMSO-d.sub.6) [ppm]: 12.04 (s, 2H), 8.65 (s, 4H), 4.35 (s, 8H), 2.27 (t, J=7.3 Hz, 4H), 2.17 (t, J=7.4 Hz, 4H), 1.65 (qui, J=7.4 Hz, 4H).

(36) Synthesis of NPBIM-1

(37) Acetonitrile (35 ml) was added to a mixture of 12 (3.160 g, 5.42 mmol), EDOT-MeOH (2.33 g, 13.53 mmol), DCC (2.44 mg, 11.82 mmol) and DMAP (89 mg, 0.74 mmol). EDOT-MeOH is a commercial product (Hydroxymethyl EDOT) available from Sigma Aldrich (product reference #687553). The mixture was kept under stirring at RT for 8 days and filtered washing with MeCN. The filtrate was collected and evaporated under reduced pressure. The residue was purified by cromatography on silica gel (eluent: CH.sub.2Cl.sub.2/AcOEt 7:3). Solvent was evaporated under reduced pressure, and the residue was triturated with Et.sub.2O obtaining product as a pale yellow solid (1.304 g, 1.46 mmol, yield 27%, m.p.: 124-125 C.).

(38) .sup.1H NMR (500 MHz, CDCl.sub.3-d.sub.6) d [ppm]: 8.77 (s, 4H), 6.34-6.32 (m, 4H), 4.52-4.50 (m, 4H), 4.48-4.46 (m, 4H), 4.36-4.32 (m, 2H), 4.31-4.24 (m, 4H), 4.21-4.18 (m, 4H), 4.03-3.99 (m, 2H), 2.41 (t, J=7.3 Hz, 4H), 2.34 (t, J=7.2 Hz, 4H), 1.90 (qui, J=7.3 Hz, 4H); .sup.13C NMR (125.7 MHz, CDCl.sub.3-d.sub.6).sub.d [ppm]: 172.90, 172.62, 163.05, 141.23, 141.05, 131.29, 126.98, 126.63, 100.21, 100.11, 71.49, 65.65, 62.37, 61.72, 39.85, 33.01, 32.97, 19.81.

(39) Polymer Preparation Procedures

(40) B1. Polymerization of INZ-0

(41) Under N2 atmosphere, N-methyl-imidazole (1.313 g, 16.00 mmol) and Baytron-CB-40 (21.7 g, 15.2 mmol) were added to a stirred solution of 2-methylindolizine (INZ-0, 1.000 g, 7.62 mmol) in dry MeCN (40 ml). The mixture was heated to reflux for 7.5 h, cooled to RT and kept under stirring for 3 days. The precipitate was collected by filtration as a dark solid. Product was sonicated and filtered twice with MeCN. The same procedure was repeated with MeOH (250 ml). The product was finally filtered and washed with fresh MeOH followed by Et.sub.2O. Residual solvent was removed under reduced pressure at 40 C. Dark solid (1.160 g).

(42) B2. Polymerization of NPBIM-1

(43) Procedure A (Batch P-NPBIM-1B)

(44) Under N.sub.2 atmosphere, anhydrous benzonitrile (5 ml) was added to a mixture of NPBIM-1 (1.000 g, 1.122 mmol) and anhydrous Fe(OTs).sub.3 (2.979 g, 5.231 mmol) in a Schlenk flask. The flask was sealed and heated to 145 C. for 24 h. The mixture was cooled to RT and poured in a cellulose extraction thimble. The solid residue was extracted with MeCN in a Soxhlet apparatus until a colourless extract was obtained. The solid was further extracted with CHCl.sub.3 followed by MeOH. The black solid residue in the thimble was dried under reduced pressure at 50 C. for 12 h and collected (737 mg).
Procedure B (Batch p-NPBIM-2B)
A suspension of NPBIM-1 (735 mg, 0.835 mmol) and anhydrous Fe(OTs).sub.3 (2.189 g, 3.845 mmol) in a mixture of dry CHCl.sub.3 (20 ml) and anhydrous MeCN (10 ml) was reflux for 14 h under N.sub.2 atmosphere. The light yellow mixture turns to green and then to blue. The mixture was cooled to RT and poured in a cellulose extraction thimble. The solid residue was extracted in a Soxhlet apparatus with CHCl.sub.3 followed by MeOH till colourless extracts were obtained. The dark blue solid was collected and residual solvent was removed under reduced pressure at 65 C. (150 mg).
Testing of Compounds and Materials According to the Present Invention

(45) The data in FIG. 9 was obtained in a Li-battery configuration. Poly-NPbIm-1 was used to prepare a composite electrode (72% by weight) along with graphite (SFG6, Timcal, 26% by weight), Carboxymethylcellulose (Sigma, 1%) and Styrene-Butadiene Rubber (Targray, 1%) in water. The resulting slurry was cast on an aluminum foil with a wet thickness of 300 m. The electrode was dried in atmosphere at 80 C. overnight. From the foil, 16 mm diameter circular electrodes were cut and used to build coin cells. The counter electrode in the coin cell was metallic lithium, the separator was glass fiber and the electrolyte was 1M LiClO.sub.4 in Ethylene Carbonate/Dimethylcarbonate 1:1 in weight. The coin cells were tested using a BioLogic VMP3 charge-discharge machine.

(46) The data in FIG. 10 was obtained in a flooded cell where the working electrode was a film of Poly-NPbIm-1 electropolymerized on an aluminum foil. The counter electrode was Pt and the reference electrode was Ag/Ag.sup.+. The electrolyte was Acetonitrile/TBAClO.sub.4, changed later to Acetonitrile/LiClO.sub.4.

(47) Rate Capability

(48) FIG. 9 shows the power delivery of NPbIm-1 upon discharge at 5 different rates. The material was observed to deliver more than 70% of the original capacity (C/10) upon discharge at a current 10 times higher (C).

(49) High Stability

(50) In FIG. 10 the long term stability of NPbIm-1 is shown. The material completed 1000 cycles and retained more than 85% of the original charge.

(51) No Dissolution in Common Li-Ion Battery Electrolyte Solvents

(52) A sample of the material was put in an ethylene carbonate/dimethyl carbonate mixture for 7 days under magnetic stirring. The powder was then filtered and dried. The weight was unchanged. No discoloration of the solvent was observed.

(53) In view of the above results, it therefore appears that at least problems among problems (1), (3) and (4) mentioned above (electronic conductivity, power density, insolubility in Li-ion electrolytes) are solved by the above-exemplified materials according to the present invention.