BIS(PYRIDINIUM)-NAPHTHALENE DIIMIDE REDOX IONIC COMPOUNDS AS ELECTRODE ACTIVE MATERIALS

Abstract

The invention relates to the use of a bis(pyridinium)-naphthalene diimide redox ionic compound as electrode active material, notably for an aqueous electrolyte battery, to a negative electrode comprising at least said bis(pyridinium)-naphthalene diimide redox ionic compound, to a battery, notably an aqueous electrolyte battery comprising said negative electrode, and to particular bis(pyridinium)-naphthalene diimide redox ionic compounds.

Claims

1. A redox ionic compound, said redox compound configured to be operable as a negative electrode active material, said redox compound comprising: at least one naphthalene diimide unit; and at least one N,N-disubstituted bis(pyridinium) unit.

2. The redox ionic compound according to claim 1, wherein the N,N-disubstituted bis(pyridinium) and naphthalene diimide units are coupled within the redox ionic compound by means of a linker denoted by L.

3. The redox ionic compound according to claim 2, wherein the linker L is a saturated or unsaturated carbon chain, an aromatic carbon chain, or a mixture of a saturated or unsaturated carbon chain and an aromatic carbon chain, the aforementioned carbon chains being optionally fluorinated, and possibly containing one or more heteroatoms, for example one or more oxygen or sulfur atoms, said carbon chains having from 2 to 20 carbon atoms.

4. The redox ionic compound according to claim 1, wherein the redox ionic compound comprises one or more anions A chosen from inorganic anions and organic anions, a representing the valence of the anion, with 1a3.

5. The redox ionic compound according to claim 1, wherein the N,N-disubstituted bis(pyridinium) unit is represented by any one of the chemical formulae (I-a), (I-b) or (I-c) below: ##STR00011## in which the sign * denotes the attachment point of the N,N-disubstituted bis(pyridinium) unit to a naphthalene diimide unit; R represents an end group chosen from an alkyl group, an alkenyl group, an alkynyl group, and an aryl group, said aforementioned groups being optionally substituted by one or more aromatic groups, optionally fluorinated or perfluorinated, said aforementioned groups possibly containing one or more heteroatoms, for example one or more oxygen, sulfur or nitrogen atoms; R.sup.1 and R.sup.2, which are identical or different, represent an alkyl group or a cyano group; and q is such that 0q4.

6. The redox ionic compound according to claim 1, wherein the naphthalene diimide unit is represented by either one of the chemical formulae (II-a) or (II-b) below: ##STR00012## in which the sign ** denotes the attachment point of the naphthalene diimide unit to an N,N-disubstituted bis(pyridinium) unit and R represents an end group chosen from a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, and an aryl group, said aforementioned groups being optionally substituted by one or more aromatic groups, optionally fluorinated or perfluorinated, said aforementioned groups possibly containing one or more heteroatoms, for example one or more oxygen, sulfur or nitrogen atoms.

7. The redox ionic compound according to claim 1, wherein the redox ionic compound comprises at least one ionic compound of formula (III-a) or (III-b) below: ##STR00013## in which R, A, a and L have the same definitions as in claims 2 to 5, p is such that 1p10 000 and n is such that 1n10 000.

8. The redox ionic compound according to claim 1, wherein the redox ionic compound comprises at least one ionic compound of formula (III-a.sub.1) or (III-b.sub.1) below: ##STR00014## in which L is an alkylene group having 3 carbon atoms, 1n3 and A.sup.a is chosen from Cl.sup., TFSI.sup., Br.sup. and one of the mixtures thereof.

9. The redox ionic compound according to claim 1, wherein the redox ionic compound has a theoretical bulk capacity of at least 80 mAh/g.

10. A negative electrode comprising: a composite material including a negative electrode active material, optionally a binder, and optionally an agent that imparts electron conductivity, wherein the negative electrode active material is a redox ionic compound as defined in claim 1.

11. The negative electrode according to claim 10, wherein the composite material includes, relative to the total mass of the composite material: (i) from 55% to 90% by weight of a redox ionic compound as defined in claim 1, (ii) from 0.1% to 10% by weight of a binder, (iii) from 1% to 25% by weight of an agent that imparts electron conductivity, (iv) from 0% to 30% by weight of a salt that imparts ion conductivity, and (v) from 0% to 30% by weight of a solvent within which the salt that imparts ion conductivity used in the negative electrode is soluble.

12. The negative electrode according to claim 10, wherein the agent that imparts electron conductivity is chosen from carbon black, SP carbon, acetylene black, carbon fibres and nanofibres, carbon nanotubes, reduced graphene oxide, graphene oxide, graphite, metal particles and fibres and one of the mixtures thereof.

13. The negative electrode according to claim 10, wherein the binder is chosen from copolymers and homopolymers of ethylene; copolymers and homopolymers of propylene; homopolymers and copolymers of ethylene oxide, of methylene oxide, of propylene oxide, of epichlorohydrin or of allyl glycidyl ether, and mixtures thereof halogenated polymers; polyacrylates; polyalcohols; electron-conducting polymers; polymers of cationic type; biobased binders; and one of the mixtures thereof.

14. The negative electrode according to claim 10, wherein the negative electrode further comprises a current collector which is coated on its surface with said composite material.

15. A battery comprising: a negative electrode, a positive electrode, a porous separator inserted between said positive and negative electrodes, and an aqueous liquid electrolyte impregnating said separator, wherein the negative electrode is as defined in claim 10.

16. The battery according to claim 15, wherein the positive electrode comprises: 1) a composite material including a positive electrode active material chosen from redox organic compounds and hybrid compounds of metal-organic type, optionally an agent that imparts electron conductivity and optionally a binder, said composite material possibly being supported by a current collector, or 2) an oxide, phosphate or sulfate of transition metals or one of the combinations thereof.

17. The battery according to claim 15, wherein the aqueous liquid electrolyte comprises a salt of an alkali metal, of an alkaline-earth metal, of aluminium or of the ammonium ion in water or consists of seawater.

18. A redox ionic compound wherein said redox ionic compound comprises at least one ionic compound of formula (III-a), (III-a.sub.1), (III-b) or (III-b.sub.1) as defined in claim 7, with the exception of the compounds of formula (III-a) for which L is a linear alkylene chain having 2 or 10 carbon atoms.

Description

EXAMPLES

[0140] The raw materials used in the examples are listed below: [0141] carbon black, Carbon super P, TIMCAL, [0142] polytetrafluoroethylene (PTFE), Aldrich, [0143] 1,4,5,8-naphthalenetetracarboxylic anhydride, Aldrich, [0144] triethylamine, Aldrich, [0145] 3-bromopropylamine, Aldrich, [0146] acetic acid, Carlo Erba, [0147] anhydrous dimethylformamide (DMF), Aldrich, [0148] lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Aldrich, [0149] 4,4-bipyridine, Aldrich, [0150] acetonitrile, Carlo Erba, [0151] o-dichlorobenzene, Aldrich, [0152] dimethylaminopyridine (DMAP), Aldrich, [0153] imidazole, Aldrich, [0154] NaClO.sub.4, Aldrich, [0155] MeI, Aldrich, [0156] Mg(ClO.sub.4).sub.2, Aldrich [0157] 4-hydroxy-TEMPO-benzoate, Sigma Aldrich.

[0158] Unless otherwise indicated, all the materials were used as received from the manufacturers.

Example 1

Preparation of the Redox Ionic Compounds 1 and 2

[0159] 1.1 Preparation of the Redox Ionic Compound 1

[0160] The redox ionic compound 1 satisfies the following formula:

##STR00007##

[0161] in which A.sup.a is a mixture of TFSI.sup. and Br.sup., and n is such that 1 n 3.

[0162] 1.072 g of 1,4,5,8-naphthalenetetracarboxylic anhydride were mixed under a nitrogen atmosphere with 3.280 g of 3-bromopropylamine in the presence of 2 ml of triethylamine and 20 ml of acetic acid. The resulting mixture was brought to reflux for 24 h. The intermediate product formed was isolated in the following manner: the precipitate was filtered and washed thoroughly with water and methanol (MeOH) to result in the intermediate product with 77% yield.

[0163] In a sealed tube, 0.5 g of intermediate product formed above was mixed with 0.154 g of 4,4-bipyridine in 10 ml of anhydrous dimethylformamide (DMF), then the resulting mixture was heated at 130 C. for 2 days. After 2 days, 2 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 5 ml of DMF were added to the stirred solution. The mixture was left for another 2 days at 130 C. After cooling to ambient temperature, the brown precipitate was filtered and washed thoroughly with dichloromethane (DCM) to give 0.18 g of the final compound.

[0164] The final addition of LiTFSI may be omitted by leaving the mixture for 4 days at 130 C., by filtering and by washing the precipitate with dichloromethane (DCM). This procedure results in the same amount of redox-active fraction of the compound 1, but with only bromide ions as counter-anions.

[0165] 1.2 Preparation of the Redox Ionic Compound 2

[0166] The redox ionic compound 2 satisfies the following formula:

##STR00008##

[0167] 2 g of 4,4-bipyridine were mixed with 0.280 g of 3-bromopropylamine in the presence of 20 ml of acetonitrile. The resulting mixture was brought to reflux for 1.5 h. The intermediate product formed was isolated in the following manner: the mixture was cooled to ambient temperature, the resulting white precipitates were collected by filtration and dried under vacuum to give an intermediate product in the form of a white solid (yield of 47%).

[0168] 0.213 g of intermediate product formed above was mixed with 0.113 g of 1,4,5,8-naphthalenetetracarboxylic anhydride in 5 ml of o-dichlorobenzene in the presence of 0.064 g of DMAP and 0.077 g of imidazole, then the resulting mixture was heated at 80 C. for 12 h. After cooling, the resulting precipitates were collected by filtration. The red solid collected was dissolved in water (50 ml), then the solution was washed with dichloromethane (DCM) to remove the water-insoluble residues. An excess of powdered sodium perchlorate was added to the separated water layer. A second intermediate product in the form of a white precipitate was collected by filtration and dried under vacuum (yield of 63%).

[0169] A mixture of the second intermediate product formed above (173 mg) and iodomethane (50 l) in acetonitrile (6 ml) was heated at reflux at 90 C. for 24 h. After cooling to ambient temperature, the resulting precipitates were collected by filtration and washed with acetonitrile. The resulting red precipitates were dried under vacuum (yield of 52%).

[0170] 1.3 Preparation of the Redox Ionic Compound 3

[0171] The redox ionic compound 3 satisfies the following formula:

##STR00009##

in which A.sup.a is Cl.sup., and n is such that 1 n 3.

[0172] 50 mg of the redox ionic compound 1 were added and dispersed in a saturated solution of NaCl. The suspension was stirred for 4 days at 50 C. Next, the precipitate obtained was washed several times with water, and dried at 60 C. under vacuum overnight to obtain 40 mg of 3.

Example 2

Electrochemical Performance of the Redox Ionic Compound 1

[0173] 2.1 Preparation of the Negative Electrode

[0174] 25 mg of Ketjen black carbon black and 70 mg of redox ionic compound 1 as prepared in Example 1.1 were mixed by manual co-milling in a mortar. 5 mg of PTFE were then added to this mixture and the resulting mixture was co-milled, which makes it possible to form a film of composite material.

[0175] The film thus obtained was then pressed onto a 316L stainless steel mesh at 5 tonnes/cm.sup.2. The electrode comprised around 10 mg/cm.sup.2 of redox ionic compound 1. The negative electrode had a total thickness of 100 m and comprised an amount of 2 mg approximately of redox ionic compound 1.

[0176] Table 1 below presents the composition by weight of the negative electrode E-1 obtained:

TABLE-US-00001 TABLE 1 Negative Carbon Redox ionic electrode black (%) PTFE (%) compound 1 (%) E-1 25 5 70

[0177] 2.2 Electrochemical tests on cells C.sup.1 and C.sup.2

[0178] The electrochemical tests were carried out under a nitrogen atmosphere in glass cells comprising three electrodes and 10 ml of electrolyte.

[0179] The three electrodes of the cell C.sup.1 were the following: [0180] a working electrode consisting of the negative electrode E-1 as prepared in Example 2.1, [0181] a reference electrode consisting of a calomel electrode (SCE), and [0182] a counter electrode consisting of a mixture of 95% by weight of carbon (Ketjen Black) and 5% by weight of PTFE and having a capacity systematically oversized by a factor of two to four, relative to the working electrode.

[0183] The aqueous liquid electrolyte of the cell C.sup.1 was a 1.25M aqueous solution of Mg(ClO.sub.4).sub.2.

[0184] In the cell, the electrodes are immersed in a large excess of electrolyte and are approximately 1 cm from one another. It is therefore not necessary to use a separator.

[0185] FIG. 1a shows the potential versus SCE (in volts, V) as a function of the specific capacity (in mAh/g) at various currents 0.3 A/g (curve with the black solid line), 0.6 A/g (curve with the large dots), 1.2 A/g (curve with the grey solid line), and 2.4 A/g (curve with the small dots) for the cell C.sup.1.

[0186] FIG. 1b shows the charge capacity (in mAh/g) (bottom curve) and coulombic efficiency (in %) (top curve) as a function of the number of cycles for the cell C.sup.1, when the following cycling protocol denoted by P.sup.1 was carried out: galvanostatic cycling between 0 and 0.75 V with successive sequences of cycles for a current of 0.3 A/g, 0.6 A/g and 1.2 A/g, followed by galvanostatic cycling between 0 and 0.90 V with a sequence of 100 cycles at a current of 2.4 A/g, followed by galvanostatic cycling between 0 and 0.75 V with a sequence of 20 cycles for a current of 0.3 A/g, followed by a period at a constant potential of 0.75 V for one minute.

[0187] FIG. 2 shows the charge capacity (in mAh/g) (bottom curve) and coulombic efficiency (in %) (top curve) as a function of the number of cycles for the cell C.sup.1, when the cycling protocol P.sup.1 as defined above was carried out until the 520.sup.th cycle; followed by a subsequent cycling protocol P.sup.2 carried out until the 1853.sup.rd cycle: galvanostatic cycling between 0 and 0.90 V with successive sequences of 20 cycles for a current of 0.3 A/g, 0.6 A/g and 1.2 A/g, followed by galvanostatic cycling between 0 and 0.90 V with a sequence of 100 cycles at a current of 2.4 A/g, followed by galvanostatic cycling between 0 and 0.75 V with a sequence of 20 cycles for a current of 0.3 A/g, followed by a period at a constant potential of 0.75 V for one minute; followed by a subsequent cycling protocol P.sup.3 carried out until the end: galvanostatic cycling between 0 and 0.85 V with a sequence of 100 cycles at a current of 2.4 A/g.

[0188] A cell C.sup.2 in which the three electrodes were identical to those used for the cell C.sup.1 and the aqueous liquid electrolyte was unfiltered water from the Atlantic Ocean (instead of the 1.25M aqueous solution of Mg(ClO.sub.4).sub.2) was tested.

[0189] FIG. 3 shows the charge capacity (in mAh/g) (top curve) and coulombic efficiency (in %) (bottom curve) as a function of the number of cycles for the cell C.sup.2, when the cycling protocol P.sup.1 as defined above was carried out, except that between the 161.sup.st to 165.sup.th cycles, the current was 0.3 A/g with galvanostatic cycling between 0 and 0.65 V, followed by a period at a constant potential of 0.65 V for one minute.

Example 3

Electrochemical Performance of the Redox Ionic Compound 2

[0190] 3.1 Preparation of the Negative Electrode

[0191] 25 mg of Ketjen black carbon black and 70 mg of redox ionic compound 2 as prepared in Example 1.1 were mixed by manual co-milling in a mortar. 5 mg of PTFE were then added to this mixture and the resulting mixture was co-milled, which makes it possible to form a film of composite material.

[0192] The film thus obtained was then pressed onto a 316L stainless steel mesh at 5 tonnes/cm.sup.2. The electrode comprised around 10 mg/cm.sup.2 of redox ionic compound 2. The negative electrode had a total thickness of 100 m and comprised an amount of 2 mg approximately of redox ionic compound 2.

[0193] Table 2 below presents the composition by weight of the negative electrode E-2 obtained:

TABLE-US-00002 TABLE 2 Negative Carbon Redox ionic electrode black (%) PTFE (%) compound 2 (%) E-2 25 5 70

[0194] 3.2 Electrochemical Tests on Cells C.sup.3, C.sup.A, C.sup.B and C.sup.C

[0195] The electrochemical tests were carried out under a nitrogen atmosphere in glass cells comprising three electrodes and 10 ml of electrolyte.

[0196] The three electrodes of the cell C.sup.3 were the following: [0197] a working electrode consisting of the negative electrode E-2 as prepared in Example 3.1, [0198] a reference electrode consisting of a calomel electrode (SCE), and [0199] a counter electrode consisting of a mixture of 95% by weight of carbon (Ketjen Black) and 5% by weight of PTFE and having a capacity systematically oversized by a factor of two to four, relative to the working electrode.

[0200] The aqueous liquid electrolyte of the cell C.sup.3 was a 2.5M aqueous solution of NaClO.sub.4.

[0201] In the cell, the electrodes are immersed in a large excess of electrolyte and are approximately 1 cm from one another. It is therefore not necessary to use a separator.

[0202] The cell C.sup.3 was compared to cells C.sup.A, C.sup.B and C.sup.C that are not part of the invention, and the features of which are the following, relative to the cell C.sup.3: [0203] the cell C.sup.A comprised a mixture A that is not part of the invention consisting of a 4,4-bipyridine that is N,N-disubstituted by a methyl and a naphthalene diimide that is disubstituted by a methyl, having a 2:1 molar ratio, the mixture A having the following formula:

##STR00010##

[0204] instead of the redox ionic compound 2, [0205] the cell C.sup.B comprised a 4,4-bipyridine N,N-disubstituted by a methyl that is not part of the invention instead of the redox ionic compound 2, and [0206] the cell C.sup.C comprised a naphthalene diimide disubstituted by a methyl that is not part of the invention instead of the redox ionic compound 2.

[0207] The 4,4-bipyridine N,N-disubstituted by a methyl was prepared from the corresponding commercial chlorinated compound (Sigma Aldrich), by dissolving said compound in water and by re-precipitating it in the presence of sodium perchlorate.

[0208] The naphthalene diimide disubstituted by a methyl was prepared according to the process as described in Sci. China Chem., 2012, 55, 10.

[0209] FIG. 4 shows the charge capacity (in mAh/g) (top curve) and coulombic efficiency (in %) (bottom curve) as a function of the number of cycles for the cell C.sup.3, when the cycling protocol P.sup.1 as defined in Example 2.2 was carried out until the 470.sup.th cycle, followed by galvanostatic cycling between 0 and 1.20 V until the 520.sup.th cycle for a current of 2.4 A/g, followed by galvanostatic cycling between 0 and 0.75 V until the 550.sup.th cycle for a current of 0.3 A/g, followed by galvanostatic cycling between 0 and 1.10 V until the 580.sup.th cycle for a current of 1.2 A/g, followed by galvanostatic cycling between 0 and 1.20 V until the end for a current of 2.4 A/g.

[0210] FIG. 5 shows the charge capacity (in mAh/g) as a function of the number of cycles of the cells C.sup.3 (curve with squares), C.sup.A (curve with triangles), C.sup.B (curve with circles) and C.sup.C (curve with crosses), when the following cycling protocol was carried out: galvanostatic cycling between 0 and 0.75 V with successive sequences of 20 cycles for a current of 0.3 A/g, 0.6 A/g and 1.2 A/g, followed by galvanostatic cycling between 0 and 0.90 V with a sequence of 100 cycles at a current of 2.4 A/g, followed by a loop.

[0211] The respective molar proportions of naphthalene diimide and of N,N-disubstituted 4,4-bipyridine in the mixtures A and B were the same as in the redox ionic compound 2.

[0212] As can clearly be seen in FIG. 5, the electrochemical performance is significantly worse when a mixture of two separate compounds, a naphthalene diimide and an N,N-disubstituted 4,4-bipyridine, is used, compared to a redox ionic compound as defined in the invention which comprises both the two aforementioned compounds optionally in the form of repeat units.

Example 4

Battery in Accordance with the Invention

[0213] 4.1 Preparation of the Negative Electrode

[0214] 25 mg of Ketjen black carbon black and 70 mg of redox ionic compound 1 as prepared in Example 1.1 were mixed by manual co-milling in a mortar. 5 mg of PTFE were then added to this mixture and the resulting mixture was co-milled, which makes it possible to form a film of composite material.

[0215] The film thus obtained was then pressed onto a 316L stainless steel mesh at 5 tonnes/cm.sup.2. The electrode comprised around 10 mg/cm.sup.2 of redox ionic compound 1. The negative electrode had a total thickness of 100 m and comprised an amount of 2 mg approximately of redox ionic compound 1.

[0216] Table 3 below presents the composition by weight of the negative electrode E-3 obtained:

TABLE-US-00003 TABLE 3 Negative Carbon Redox ionic electrode black (%) PTFE (%) compound 2 (%) E-3 25 5 70

[0217] 4.2 Preparation of a Battery B-1

[0218] A battery B-1 was prepared by assembling three electrodes under a nitrogen atmosphere at ambient temperature: [0219] the negative electrode E-3 obtained in Example 4.1 above, [0220] a positive electrode consisting of 66% by weight of carbon black and 34% by weight of Prussian blue Fe.sub.7(CN).sub.18, and having a capacity oversized by a factor of four, relative to the negative electrode, [0221] a calomel reference electrode (SCE), and [0222] the aqueous liquid electrolyte was unfiltered water from the Atlantic Ocean.

[0223] In the battery, the positive and negative electrodes are immersed in a large excess of electrolyte and are approximately 1 cm from one another. It is therefore not necessary to use a separator.

[0224] FIG. 6a shows the potential versus SCE (in volts, V) as a function of the discharge capacity (in mAh/g) for the negative electrode (curve with the solid line), for the positive electrode (curve with the crosses), and for the complete battery B-1 (curve with the dotted lines), in the 2.sup.nd cycle for a current of 0.225 A/g (nominal rate of 4 C).

[0225] FIG. 6b shows the charge capacity (in mAh/g) (bottom curve) and coulombic efficiency (in %) (top curve) as a function of the number of cycles for the complete battery B-1, when the cycling protocol P.sup.1 as defined in Example 2.1 was carried out.

[0226] The results of Examples 2-4 show that the redox ionic compounds as used in the invention have good electrochemical performance in terms of capacity, cyclability and efficiency.

Example 5

Battery in Accordance with the Invention

[0227] 5.1 Preparation of the Negative Electrode

[0228] 25 mg of Ketjen black carbon black and 70 mg of redox ionic compound 1 as prepared in Example 1.1 were mixed by manual co-milling in a mortar. 5 mg of PTFE were then added to this mixture and the resulting mixture was co-milled manually, which makes it possible to form a film of composite material.

[0229] The film thus obtained was then cut to the desired size and pressed onto a 316L stainless steel mesh at 5 tonnes/cm.sup.2. The electrode comprised around 10 mg/cm.sup.2 of redox ionic compound 1. The negative electrode had a total thickness of 100 m and comprised an amount of 1 mg approximately of redox ionic compound 1.

[0230] Table 4 below presents the composition by weight of the negative electrode E-4 obtained:

TABLE-US-00004 TABLE 4 Negative Carbon Redox ionic electrode black (%) PTFE (%) compound 1 (%) E-4 25 5 70

[0231] 5.2 Preparation of a Battery B-2

[0232] A batterie B-2 was prepared by assembling three electrodes under nitrogen atmosphere at ambient temperature: [0233] the negative electrode E-4 obtained in Example 5.1 above, [0234] a positive electrode consisting of 25% by weight of carbon black, 5% by weight of PTFE and 70% by weight of 4-hydroxy-TEMPO-benzoate, and having a capacity oversized by a factor of 1, relative to the negative electrode, [0235] a calomel reference electrode (SCE), and [0236] the aqueous liquid electrolyte was a saturated solution of NaClO.sub.4.

[0237] In the battery, the positive and negative electrodes are immersed in a large excess of electrolyte and are approximately 1 cm from one another. It is therefore not necessary to use a separator.

[0238] FIG. 7 shows the charge capacity (in mAh) (top curve) and charge energy (in mW.Math.h) (bottom curve) as a function of the number of cycles for the complete battery B-2 (each of the two electrodes being 1.1 mg approximately), when the voltage of the cell is 1.12 V and the cycling protocol carried out is the following: galvanostatic cycling at a current of 0.075 A/g with a maximum charge voltage of 1.8 V.

Example 6

Electrodes in Accordance with the Invention

[0239] 6.1 Preparation of the Negative Electrode

[0240] 20 mg or 15 mg of Ketjen black carbon black and 75 mg or 80 mg of redox ionic compound 1 as prepared in Example 1.1 were mixed by co-milling using a ball mill sold under the trade name Pulverisette 7 Classic Line by the company Fritsch. 5 mg of PTFE were then added to this mixture and the resulting mixture was co-milled using the ball mill, which makes it possible to form a film of composite material.

[0241] The film thus obtained was then pressed onto a 316L stainless steel mesh at 5 tonnes/cm.sup.2. The electrode comprised around 10 mg/cm.sup.2 of redox ionic compound 1. The negative electrode had a total thickness of 100 m and comprised an amount of 1 mg approximately of redox ionic compound 1.

[0242] Table 5 below presents the composition by weight of the negative electrode E-5 or E-6 obtained:

TABLE-US-00005 TABLE 5 Negative Carbon Redox ionic electrode black (%) PTFE (%) compound (%) E-5 20 5 75 E-6 15 5 80

[0243] 6.2 Electrochemical Tests on Cells C.sup.5, C.sup.6 and C.sup.1

[0244] The electrochemical tests were carried out under a nitrogen atmosphere in glass cells comprising three electrodes and 10 ml of electrolyte.

[0245] The three electrodes of the cell C.sup.5 (respectively of the cell C.sup.6) were the following: [0246] a working electrode consisting of the negative electrode E-5 (respectively of the negative electrode E-6) as prepared in Example 6.1, [0247] a reference electrode consisting of a calomel electrode (SCE), and [0248] a counter electrode consisting of a mixture of 90% by weight of carbon (Ketjen Black) and 10% by weight of PTFE and having a capacity systematically oversized by a factor of two to four, relative to the working electrode.

[0249] The aqueous liquid electrolyte of the cells C.sup.5 and C.sup.6 was a 2.5M solution of NaClO.sub.4.

[0250] FIG. 8 shows the charge capacity (in mAh/g) as a function of the number of cycles for the cell C.sup.1 as defined previously (curve with the crosses), for the cell C.sup.5 (curve with the circles) and for the cell C.sup.6 (curve with the squares) when the following cycling protocol was carried out: galvanostatic cycling with successive looped linkages of two sequences (i) then (ii) then (i): (i) between 0 and 0.75 V with successive sequences of 20 cycles for a current of 0.3 A/g, 0.6 A/g and 1.2 A/g, followed by (ii) between 0 and 0.85 V with a sequence of 100 cycles at a current of 2.4 A/g.

Example 7

Electrodes in Accordance with the Invention

[0251] 7.1 Preparation of the Negative Electrode

[0252] 25 mg of Ketjen black carbon black and 70 mg of redox ionic compound 3 as prepared in Example 1.3 were mixed by manual co-milling in a mortar. 5 mg of PTFE were then added to this mixture and the resulting mixture was co-milled, which makes it possible to form a film of composite material.

[0253] The film thus obtained was then pressed onto a 316L stainless steel mesh at 5 tonnes/cm.sup.2. The electrode comprised around 10 mg/cm.sup.2 of redox ionic compound 3. The negative electrode had a total thickness of 100 m and comprised an amount of 2 mg approximately of redox ionic compound 3.

[0254] Table 6 below presents the composition by weight of the negative electrode E-7 obtained:

TABLE-US-00006 TABLE 6 Negative Carbon Redox ionic electrode black (%) PTFE (%) compound 1 (%) E-7 25 5 70

[0255] 7.2 Electrochemical tests on cells C.sup.7 and C.sup.1

[0256] The electrochemical tests were carried out under a nitrogen atmosphere in glass cells comprising three electrodes and 10 ml of electrolyte.

[0257] The three electrodes of the cell C.sup.7 were the following: [0258] a working electrode consisting of the negative electrode E-7 as prepared in Example 7.1, [0259] a reference electrode consisting of a calomel electrode (SCE), and [0260] a counter electrode consisting of a mixture of 95% by weight of carbon (Ketjen Black) and 5% by weight of PTFE and having a capacity systematically oversized by a factor of two to four, relative to the working electrode.

[0261] The aqueous liquid electrolyte of the cell C.sup.7 was a 2.5M aqueous solution of NaClO.sub.4.

[0262] In the cell, the electrodes are immersed in a large excess of electrolyte and are approximately 1 cm from one another. It is therefore not necessary to use a separator.

[0263] FIG. 9 shows the charge capacity (in mAh/g) as a function of the number of cycles for the cell C.sup.1 as defined previously (curve with the squares), and for the cell C.sup.7 (curve with the circles) when the following cycling protocol was carried out: galvanostatic cycling with successive looped linkages of two sequences (i) then (ii) such that: (i) between 0 and 0.75 V with successive sequences of 20 cycles for a current of 0.3 A/g, 0.6 A/g and 1.2 A/g, followed by (ii) between 0 and 0.85 V with a sequence of 100 cycles at a current of 2.4 A/g.