HIGH-DENSITY MICROPOROUS CARBON AND METHOD FOR PREPARING SAME

Abstract

A gelled aqueous polymer composition made from a resin produced by polycondensation of at least: a polyhydroxybenzene R, preferably resorcinol, hexamethylenetetramine HMTA, an anionic polyelectrolyte PA, preferably phytic acid. An aerogel obtained by drying these microparticles, and porous carbon microspheres obtained from the gel microparticles by pyrolysis. A method for producing a polymerised aqueous gel, an aerogel and porous carbon microspheres. Electrodes and electrochemical cell prepared from the porous carbon particles.

Claims

1-20. (canceled)

21. A gelled aqueous polymeric composition based on a resin resulting from the polycondensation of at least the following monomers: a polyhydroxybenzene R, hexamethylenetetramine HMTA, an anionic polyelectrolyte AP with a molar mass of less than or equal to 2000 g/mol.

22. The composition as claimed in claim 21, wherein the polyhydroxybenzene R is resorcinol.

23. The composition as claimed in claim 21, in which the anionic polyelectrolyte comprises nitrogen atoms or phosphorus atoms.

24. The composition as claimed in claim 23, in which the anionic polyelectrolyte is phytic acid HPhy.

25. The composition as claimed in claim 21 in which the anionic polyelectrolyte comprises several carboxylic acid functional groups.

26. The composition as claimed in claim 25, in which the anionic polyelectrolyte is chosen from: citric acid, oxalic acid, fumaric acid, maleic acid, succinic acid, ethylenediaminetetraacetic acid, polyacrylic acids or polymethacrylic acids.

27. The composition as claimed in claim 21, which is in the form of gel microparticles in an aqueous medium.

28. The composition as claimed in claim 21, in which the monomers comprise at least one cationic polyelectrolyte.

29. The composition as claimed in claim 21, in which the AP/HMTA molar ratio is from 0.010 to 0.150.

30. The composition as claimed in claim 21, in which the ratio by weight R/W of the polyhydroxybenzene, to the aqueous medium conforms to:
0.01R/W2.

31. The composition as claimed in claim 21, in which the ratio by weight HMTA/W of the hexamethylenetetramine to the aqueous medium conforms to:
0.01HMTA/W1.

32. The composition as claimed in claim 21, in which the molar ratio R/HMTA of the polyhydroxybenzene, to the HMTA conforms to:
2R/HMTA4.

33. A process for the manufacture of a gelled aqueous polymeric composition as claimed in claim 21, this process comprising the following stages: a) the mixing in an aqueous solvent of the polyhydroxybenzene(s) R and of the hexamethylenetetramine HMTA, so as to form a polycondensate, b) the introduction into the product of stage a) of the anionic polyelectrolyte AP, c) the heating of the mixture of stage b).

34. The process as claimed in claim 33, in which: stage a) is carried out at a temperature ranging from 40 to 80 C., stage c) is carried out at a temperature ranging from 70 to 100 C.

35. The process as claimed in claim 33, in which stage b) comprises the addition of the anionic polyelectrolyte, in the form of an aqueous solution in several goes to the product of stage a).

36. The process as claimed in claim 33, which comprises a stage of addition of a cationic polyelectrolyte between stages b) and c).

37. The process as claimed in claim 33, which comprises a stage of dilution with water of the composition of stage b).

38. The process as claimed in claim 33, wherein the polyhydroxybenzene R is resorcinol.

39. The process as claimed in claim 33 which additionally comprises a stage of drying in an oven to prepare an aerogel.

40. The process as claimed in claim 39 which additionally comprises at least one pyrolysis stage to prepare a porous carbon.

Description

DETAILED DESCRIPTION

[0065] The invention relates to a method for the preparation by the aqueous route of porous organic gel microparticles and of porous carbon microspheres doped with nitrogen and with phosphorus. By virtue of their high specific surface and their high density, these porous carbon microspheres can in particular be used as constituent of electrodes of supercapacitors. The method of the invention makes it possible to avoid the use of carcinogenic precursors, organic solvents or dispersants, it does not comprise a grinding stage and it does not require expensive tooling. By virtue of the high carbon density and of the presence of nitrogen and of phosphorus, it makes it possible to produce supercapacitors, the capacitance per unit volume of which is improved with respect to the prior art, without losing in capacitance per unit weight.

[0066] According to the IUPAC classification, micropores are defined as having a diameter of less than 2 nm, mesopores as having a diameter of 2 to 50 nm and macropores as having a diameter of greater than 50 nm.

[0067] The term microspheres is understood, within the meaning of the present invention, to mean particles, the volume median particle size of which, measured by a laser particle sizer in a liquid medium, is less than or equal to 1 mm.

[0068] The term constituted essentially of is understood to mean, on the subject of a product or of a process, that it is composed of the constituents or of the stages listed. It can optionally comprise other components or stages provided that these do not substantially modify the nature and the properties of the product or of the process under consideration.

[0069] Gelled Aqueous Polymeric Composition:

[0070] This composition is based on a resin resulting from the polycondensation of at least:

[0071] a polyhydroxybenzene R,

[0072] hexamethylenetetramine HMTA,

[0073] an anionic polyelectrolyte, preferably phytic acid HPhy.

[0074] It additionally comprises an aqueous phase.

[0075] The term gel or gelled composition is understood to mean, in a known way, the mixture of a colloidal material and of a liquid, which is formed, spontaneously or under the action of a catalyst, by the flocculation and the coagulation of a colloidal solution. Chemical gels and physical gels are distinguished: the first owe their structure to a chemical reaction and are by definition irreversible, while the second result from a physical interaction between the components and the aggregation between the macromolecular chains is reversible.

[0076] While a condensation reaction of a polyhydroxybenzene, such as resorcinol, with hexamethylenetetramine results in an irreversible monolithic chemical gel, the presence of an anionic polyelectrolyte, in particular phytic acid, in the medium results in the formation of a dispersion of gelled microspheres, that is to say a physical gel, based on microspheres which are themselves formed from a chemical gel.

[0077] Specifically, the inventors have discovered that phytic acid makes it possible, in the presence of polyhydroxybenzene and of hexamethylenetetramine, to form polymeric microparticles.

[0078] The gelled composition of the invention can be dried easily and rapidly by simple oven drying. This oven drying is simple to carry out and less expensive than the drying carried out by solvent exchange or by supercritical CO.sub.2 which is taught in the prior art.

[0079] The composition of the invention retains the strong porosity of the gel subsequent to this oven drying and results in an aerogel having a high density combined with a high specific surface and a high pore volume. The gel according to the invention is mainly microporous, which makes it possible to produce an essentially microporous carbon by pyrolysis of this gel. The electrodes of supercapacitors obtained from this pyrolyzed gel have available a high specific energy and a high capacitance.

[0080] Mention may be made, among the polyhydroxybenzene monomers which can be used in the preparation of the resin of the invention, of: di- or trihydroxybenzenes, advantageously resorcinol (1,3-dihydroxybenzene). It is possible to plan to use several monomers chosen from polyhydroxybenzenes, such as, for example, the mixture of resorcinol with another compound chosen from catechol, hydroquinone or phloroglucinol.

[0081] The anionic polyelectrolytes which can be used in the invention are preferably characterized by a molar mass of less than or equal to 2000 g/mol, advantageously of less than or equal to 1000 g/mol. For example, mention may be made, as anionic polyelectrolytes which can be used in the formation of the resin of the invention, of the chemical compounds carrying one or more functional groups chosen from carboxylic acid, phosphoric acid, phosphonic acid or sulfonic acid functional groups.

[0082] Preferably, anionic polyelectrolytes are chosen from the compounds carrying several functional groups chosen from carboxylic acid and phosphoric acid functional groups.

[0083] Mention is very particularly made, among these anionic polyelectrolytes, of molecules comprising several carboxylic acid functional groups, such as, for example, citric acid, oxalic acid, maleic acid, fumaric acid, succinic acid or ethylenediaminetetraacetic acid (EDTA).

[0084] Mention may also be made of the derivatives of carbohydrate compounds, or monosaccharides, carrying one or more functional groups chosen from the functional groups: carboxylic acid, phosphoric acid or phosphonic acid. In particular, mention may be made, in this category, of phytic acid, oligomers of uronic acids, in particular oligomers of D-glucuronic acid and of D-N-acetylglucosamine, such as hyaluronic acid, oligomers of guluronic acid and of mannuronic acid, such as alginates, oligomers of -D-galacturonic acid (pectin) with a molar mass of less than or equal to 2000 g/mol.

[0085] Mention may also be made of oligomers of vinylphosphonic acid, polyacrylic acids, polymethacrylic acids, with a molar mass of less than or equal to 2000 g/mol.

[0086] According to an advantageous embodiment, the anionic polyelectrolyte is a polyacrylic acid.

[0087] Said anionic polyelectrolytes can be used in the process of the invention in the form of salts, in particular of alkali metal or alkaline earth metal salts. For example, mention may be made of sodium polyacrylates.

[0088] Mention may more particularly be made, among the anionic polyelectrolytes which can be used in the formation of the resin of the invention, of: phytic acid, hyaluronic acid, polyvinylphosphonic acids.

[0089] The polyelectrolyte preferably used is phytic acid, which is also known under the name of myo-inositol hexaphosphoric acid (CAS No. 83-86-3).

[0090] The monomers participating in the formation of the resin of the invention can additionally comprise, optionally, one or more cationic polyelectrolytes, such as, for example, an organic polymer chosen from the group consisting of quaternary ammonium salts, poly(vinylpyridinium chloride), poly(ethyleneimine), poly(vinylpyridine), poly(allylamine hydrochloride), poly(trimethylammonioethyl methacrylate chloride), poly(acrylamide-co-dimethylammonium chloride) and their blends.

[0091] More preferably still, the cationic polyelectrolyte is a salt comprising units resulting from a quaternary ammonium chosen from poly(diallyldimethylammonium halide)s and is preferably poly(diallyldimethylammonium chloride) or poly(diallyldimethylammonium bromide).

[0092] Other monomers than those stated above can participate in the composition of the resin of the invention. Preferably, their content does not represent more than 20% by weight, with respect to the total weight of the main monomers (polyhydroxybenzene, hexamethylenetetramine, anionic polyelectrolyte, optionally cationic polyelectrolyte) participating in the composition of the resin, advantageously not more than 10% by weight, more advantageously still not more than 5% by weight, even better still not more than 1% by weight.

[0093] According to a first preferred alternative form of the invention, the resin comprises:

[0094] one or more polyhydroxybenzenes R, preferably resorcinol,

[0095] hexamethylenetetramine HMTA,

[0096] one or more anionic polyelectrolytes AP, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably phytic acid HPhy,

[0097] and these monomers represent at least 80% by weight, with respect to the total weight of the resin, better still at least 90%, advantageously at least 95% and more preferably still at least 99%.

[0098] More advantageously still, the resin is essentially formed of:

[0099] one or more polyhydroxybenzenes R, preferably resorcinol,

[0100] hexamethylenetetramine HMTA,

[0101] one or more anionic polyelectrolytes AP, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably phytic acid HPhy.

[0102] According to another preferred alternative form of the invention, the resin comprises:

[0103] one or more polyhydroxybenzenes R, preferably resorcinol,

[0104] hexamethylenetetramine HMTA,

[0105] one or more anionic polyelectrolytes AP, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably phytic acid HPhy,

[0106] one or more cationic polyelectrolytes CP,

[0107] and these monomers represent at least 80% by weight, with respect to the total weight of the resin, better still at least 90%, advantageously at least 95% and more preferably still at least 99%.

[0108] More advantageously still, the resin is essentially formed of:

[0109] one or more polyhydroxybenzenes R, preferably resorcinol,

[0110] hexamethylenetetramine HMTA,

[0111] one or more anionic polyelectrolytes AP, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably phytic acid HPhy,

[0112] one or more cationic polyelectrolytes CP.

[0113] Advantageously, in the composition of the invention, the ratio by weight R/W of the polyhydroxybenzene, preferably resorcinol, to the aqueous medium conforms to:

0.01R/W2,

more preferably still:

0.03R/W1.5,

better still:

0.05R/W1.

[0114] Advantageously, in the composition of the invention, the ratio by weight HMTA/W of the hexamethylenetetramine to the aqueous medium conforms to:

0.01HMTA/W1,

more preferably still:

0.03HMTA/W0.5.

[0115] Preferably, the molar ratio R/HMTA of the polyhydroxybenzene, preferably resorcinol, to the HMTA conforms to:

2R/HMTA4,

more preferably still:

2.5R/HMTA3.5.

[0116] Preferably, the molar ratio AP/HMTA of the anionic polyelectrolyte to the hexamethylenetetramine conforms to:

0.010AP/HMTA0.150, [0117] preferably 0.015AP/HMTA0.140, [0118] better still 0.020AP/HMTA0.130.

[0119] Advantageously, the molar ratio HPhy/HMTA conforms to:

0.010HPhy/HMTA0.150, [0120] preferably 0.015HPhy/HMTA0.140, [0121] better still 0.020HPhy/HMTA0.130.

[0122] Advantageously, the ratio by weight of the cationic polyelectrolytes to the polyhydroxybenzene, preferably resorcinol, conforms to:

0CP/R0.5.

[0123] The aqueous phase is essentially formed of water. It can comprise other components, such as, for example, surfactants, which are liable to influence the porosity of the microspheres and of the carbon (in particular anionic surfactants, nonionic surfactants). It can comprise salts. It can comprise acids or bases which will modify the pH and are thus liable to modify the kinetics of the polycondensation reaction.

[0124] Process for the Preparation of the Gelled Aqueous Polymeric Composition

[0125] The gelled aqueous polymeric composition of the invention is obtained by a process which comprises several alternative forms described below.

[0126] This process comprises: [0127] a) the mixing in an aqueous solvent of the polyhydroxybenzene(s) R, preferably resorcinol, and of the hexamethylenetetramine HMTA, so as to form a polycondensate, [0128] b) the introduction into the product of stage a) of the anionic polyelectrolyte AP, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably phytic acid, [0129] c) the heating of the mixture of stage b).

[0130] On conclusion of stage b), a suspension of microspheres is formed which gels during stage c).

[0131] Preferably, this process first of all comprises the preparation of an aqueous solution of the polyhydroxybenzene(s) R, preferably resorcinol, and of an aqueous solution of the hexamethylenetetramine HMTA, the two solutions being mixed in order to form the polycondensate of stage a).

[0132] According to a preferred embodiment of the invention, the anionic polyelectrolyte, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably phytic acid, is prepared in the form of an aqueous composition which is subsequently introduced during stage b) into the polycondensate of stage a).

[0133] Preferably, stage a) is carried out at a temperature ranging from 40 to 80 C.

[0134] Preferably, stage c) is carried out at a temperature ranging from 70 to 100 C.

[0135] According to a first alternative form of the process of the invention, the aqueous solution of anionic polyelectrolyte, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably the aqueous solution of phytic acid, can be introduced in several goes, in particular in two goes, into the product of stage a) with optionally an intermediate storage of the composition of R/HMTA/AP microspheres at low temperature (greater than 0 C. and less than 10 C.).

[0136] According to a second alternative form of the process of the invention, the aqueous solution of anionic polyelectrolyte, advantageously chosen from the compounds with a molar mass of a less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably the aqueous solution of phytic acid, is introduced into the product of stage a) and then, after an optional resting time at low temperature (for example of greater than 0 C. and less than 10 C.), and before stage c), a cationic polyelectrolyte is introduced into the composition of R/HMTA/AP microspheres.

[0137] According to a third alternative form of the process of the invention, the aqueous solution of anionic polyelectrolyte, advantageously chosen from the compounds with a molar mass of less than or equal to 2000 g/mol comprising several functional groups chosen from carboxylic acids and phosphoric acids, preferably the aqueous solution of phytic acid, is introduced into the product of stage a) and then, after an optional resting time at low temperature (for example of greater than 0 C. and less than 10 C.), and before stage c), the composition of R/HMTA/AP microspheres is diluted with water.

[0138] According to the process of the invention, whatever the alternative form followed for the addition of the anionic polyelectrolyte, of the optional cationic electrolyte, of the optional dilution, the composition of microspheres obtained is subsequently subjected to a heating which makes possible a complete polymerization of the R/HMTA/AP system, in particular of the R/HMTA/HPhy system.

[0139] The size of the microspheres and their porosity is controlled as a function of the duration of the heating and of the dilution.

[0140] The doping of the carbon with elements P and N is controlled as a function of the amount of HMTA, of anionic polyelectrolyte, in particular of phytic acid, and optionally of cationic polyelectrolyte.

[0141] Surprisingly, if a cationic polyelectrolyte is introduced into the R/HMTA mixture on conclusion of stage a), a monolithic gel is obtained, whereas the addition of an anionic polyelectrolyte results in a suspension of microspheres.

[0142] Organic Aerogel:

[0143] The drying of the gelled aqueous composition of microspheres results in an organic aerogel in the form of a powder. Such a drying can be carried out in a known way in an oven.

[0144] The aerogel advantageously exhibits a porous structure which is predominantly microporous.

[0145] Carbon-Based Composition:

[0146] A further subject matter of the invention is a carbon-based composition obtained by drying and then pyrolysis of a gelled aqueous composition as described above.

[0147] The aerogel is subjected to a pyrolysis treatment, in a known way, in order to obtain a carbon powder which can be used in the manufacture of electrodes. The pyrolysis is typically carried out at a temperature of greater than or equal to 500 C., better still of greater than or equal to 600 C. The composition of gelled microspheres of the invention retains its porous structure, in particular its microporous structure, through the drying and pyrolysis stages.

[0148] Advantageously, this process can additionally comprise, on conclusion of the pyrolysis stage, a stage of activation of the porous carbon, this stage comprising an impregnation of the porous carbon with a strong sulfur-comprising acid, preferably with an acid in the form of a solution with a pH of less than or equal to 1, and which is, for example, chosen from sulfuric acid, oleum, chlorosulfonic acid and fluorosulfonic acid, as described in the document EP 2 455 356, or nitric acid. Preferably, sulfuric acid H.sub.2SO.sub.4 is used.

[0149] The carbon powder thus obtained exhibits advantageous properties:

[0150] It exhibits a density, measured by the tapped density method, of greater than or equal to 0.38 g/cm.sup.3, better still of greater than or equal to 0.39 g/cm.sup.3 and advantageously of greater than or equal to 0.40 g/cm.sup.3.

[0151] It exhibits a nonzero content of nitrogen and of phosphorus. Advantageously, it exhibits a nitrogen content of greater than or equal to 0.5% by weight, with respect to the total weight of the material, better still of greater than or equal to 1% and advantageously of greater than or equal to 1.5%. Advantageously, it exhibits a phosphorus content of greater than or equal to 0.01% by weight, with respect to the total weight of the material, better still of greater than or equal to 0.02% and advantageously of greater than or equal to 0.03%. According to an alternative form of the invention, the phosphorus content can be greater than 0.1%.

[0152] It exhibits a nonzero content of oxygen. Advantageously, it exhibits an oxygen content which can range up to 25% by weight, with respect to the total weight of the material, preferably from 8 to 17%.

[0153] It exhibits a ratio of the micropore volume, with respect to the sum of the micropore and mesopore volumes, of greater than or equal to 0.70, measured by nitrogen adsorption manometry.

[0154] It exhibits a ratio of the micropore volume, with respect to the mesopore volume, of greater than or equal to 2.20, measured by nitrogen adsorption manometry.

[0155] It exhibits a ratio of the micropore specific surface, with respect to the sum of the micropore specific surface and of the mesopore specific surface, of greater than or equal to 0.80, measured by nitrogen adsorption manometry.

[0156] It exhibits a ratio of the micropore specific surface, with respect to the mesopore specific surface, of greater than or equal to 7.00, measured by nitrogen adsorption manometry.

[0157] Electrodes and Supercapacitors:

[0158] The invention further relates to an electrode comprising a current collector and a layer of active material comprising the porous carbon of the invention.

[0159] In a known way, such an electrode is manufactured by the preparation of an ink comprising the porous carbon of the invention, water and optionally a binder, the deposition of this ink on the current collector, the drying of the ink. For the preparation of the electrode, reference may be made, for example, to the protocols described in the document FR 2 985 598.

[0160] The invention also relates to an electrochemical cell comprising such an electrode.

[0161] An electrode according to the invention can be used to equip a supercapacitor cell by being immersed in an aqueous ionic electrolyte, the electrode covering a metal current collector. Preferably, this electrode exhibits a geometry wound around an axis, for example a substantially cylindrical electrode.

[0162] The microporosity plays an important role in the formation of the electrochemical double layer in such a cell, and the porous carbons of the invention, which are predominantly microporous, make it possible to have available a high specific energy and a high capacitance for these supercapacitor electrodes.

[0163] Experimental Part:

IMaterials and Methods:

[0164] Starting Materials:

TABLE-US-00001 TABLE 1 List of the precursors used Starting materials Supplier Resorcinol Acros Organics Hexamethylenetetramine (HMTA) Sigma-Aldrich Phytic acid (HPhy) Sigma-Aldrich Poly(diallyldimethylammonium chloride) Sigma-Aldrich Citric acid Merck KGaA Ethylenediaminetetraacetic acid (EDTA) Sigma-Aldrich Poly(acrylic acid, sodium salt) solution Sigma-Aldrich (PAA 1200) (*) Poly(acrylic acid) partial sodium salt Sigma-Aldrich solution (PAA 5000) (**) (*) weight-average molecular weight Mw = 1200 (**) weight-average molecular weight Mw = 5000

[0165] Methods of Characterization:

[0166] Characterization by Nitrogen Adsorption Manometry:

[0167] The results presented in table 7 are obtained by nitrogen adsorption manometry at 77K on the Tristar 3020 and Asap 2020 apparatuses from Micromeritics.

[0168] Characterization by Mercury Porosimetry:

[0169] Mercury porosity measurements were carried out on the carbon-based materials (after pyrolysis) using a Poremaster apparatus from Quantachrome.

[0170] Characterization by Volumetric Analysis (Tapped Density):

[0171] The carbon in the powder form is compacted by tapping a cylindrical measuring cylinder containing a known weight of carbon w for 30 min by the Volumeter Type Stay II from Engelsmann (50 Hz). The powder density p is calculated as =w/v, where V is the tapped powder final volume.

[0172] Characterization by Elemental Analysis:

[0173] The content of carbon, hydrogen, oxygen, nitrogen and sulfur was estimated by CHONS elemental analysis. The phosphorus content was measured using the ICP/AES apparatus from SDS Multilab. The nitrogen was also measured by the thermal conductivity according to the MO 240 LA 2008 method of SDS Multilab.

[0174] Electrochemical Characterization:

[0175] Carbon electrodes are produced from the porous carbon particles. For this, binders, conductive fillers, various additives and the porous carbon particles are mixed with water according to the protocol of FR 2 985 598, example 1. The formulation obtained is coated and then crosslinked on a metal collector coated beforehand with an aqueous dispersion from Timcal. Two identical electrodes are placed in series (isolated by a separator) within a measurement cell containing the electrolyte (ex. LiNO.sub.3, 5M) and controlled by a potentiostat/galvanostat via a three-electrode interface. A first electrode corresponds to the working electrode and the second constitutes the counterelectrode and the reference is the calomel electrode.

[0176] For the measurement of the specific capacitance, the system is subjected to charge/discharge cycles at a constant current I of 0.5 A/g of the working electrode (each electrode is in turn a working electrode and a counterelectrode).

[0177] As the potential changes linearly with the charge conveyed, the capacitance C of the electrodes is deduced from the slopes p in the discharge (C=11p).

IISynthesis Protocols:

[0178] The protocols described below are employed using the components presented in table 2.

TABLE-US-00002 TABLE 2 Components of the initial protocol and of the protocols 1a, 2 and 3 and of the counterexamples Ex. 1 Ex. 2 Ex. 3 C. Ex. 1 C. Ex. 2 C. Ex. 3 Resorcinol (R) (g) 116.8 116.8 73.74 116.8 175.21 188.7 Water (W) for dissolving R (g) 116.8 116.8 147.48 116.8 175.21 233.6 Hexamethylenetetramine (HMTA) (g) 49.59 49.59 31.31 49.59 74.36 Water (E) for dissolving HMTA (g) 116.8 116.8 147.48 116.8 175.21 Phytic acid (HPhy) 50% in H.sub.2O (g) 19.46 19.46 6.25- 0 36.87 Formaldehyde 37% (F) in H.sub.2O (g) 281.6 Na.sub.2CO.sub.3 (C) (g) 10.9 Poly(diallyldimethylammonium 29.6 chloride) (P) 35% by weight in H.sub.2O R/W (ratio by weight) 0.29 0.29 0.18 0.29 0.5 1.13 HMTA/W (ratio by weight) 0.12 0.12 0.078 0.12 0.12 R/HMTA (ratio in moles) 3 3 3 3 3 HPhy/HMTA (ratio in moles) 0.042 0.042 0.021- 0 0.126 R/F (ratio in moles) 0.5 R/C (ratio in moles) 174 P/R (ratio in moles) 6 10.sup.4 P/R (ratio by weight) 0.055

[0179] In table 2, for the products employed in the diluted form, the amounts of products correspond to amounts of active material.

[0180] Initial Protocol (Common to All the Examples):

[0181] An organic gel is produced by the polycondensation of polyhydroxybenzene/resorcinol (R) with hexamethylenetetramine (HMTA), with or without addition of phytic acid (HPhy), according to the composition listed in table 2 above.

[0182] In a first step, the resorcinol is first dissolved in distilled water (the concentration can vary, see table 2). The dissolution of the hexamethylenetetramine is also carried out in water, brought to 50 C. by means of an oil bath. After dissolution, the solution of resorcinol in water is poured into the solution of HMTA in water and the temperature of the oil bath is brought to 80 C.

[0183] In a second step, the nonviscous mixture is prepolymerized in a reactor placed in an oil bath at 80 C. for approximately 40 min.

[0184] Protocol 1 (Examples 1a to 1 e):

[0185] Protocol 1.1: This protocol is applied to the mixture resulting from example 1. When the mixture of precursors becomes clear (at 68-71 C., after heating for 40-50 min), inositol hexakisphosphate (phytic acid) is added (19.46 g of aqueous solution of phytic acid with a concentration of 50% by weight) while mixing for 1 min, before cooling it in an ice bath.

[0186] A suspension of HMTA-resorcinol-phytic acid microspheres is obtained, which suspension is subsequently placed in a refrigerator (T=4 C.) for 24 h.

[0187] Protocol 1.2: The suspension of microspheres formed is then diluted in water, either with a polyelectrolyte, poly(diallyldimethylammonium chloride), denoted P in table 3, or with phytic acid, or with water. The mixture obtained is heated at reflux or in a heated oil bath in order to make possible complete polymerization of the HMTA-resorcinol-phytic acid system.

[0188] The experimental conditions related to the dilution and to the heating at reflux are listed in table 3.

[0189] The dispersion is subsequently left standing in order to make possible sedimentation of the HMTA-resorcinol gel or HMTA-resorcinol-phytic acid gel particles.

TABLE-US-00003 TABLE 3 Experimental conditions of protocol 1.2 Exam- Exam- Exam- Exam- Exam- ple 1a ple 1b ple 1c ple 1d ple 1e Concentration by 33 33 33 33 33 weight of the gel (%) in the aqueous solution Concentration by 1.88 1.88 weight of the P in the water (%) Concentration by 1 2 weight of HPhy in the water (%) Temperature of the 15 15 15 15 15 gel during the dilution ( C.) Temperature of the 95 85 85 85 85 water during the dilution ( C.) Temperature of the 98 86-92 86-92 86-92 86-92 mixture at reflux ( C.) in the reactor Reflux/heating time (h) 0.5 2 2 2 2 Stirring rate (rpm) 500 300 300 300 300

[0190] Protocol 2:

[0191] This protocol is applied to the composition of example 2 on conclusion of the initial protocol: When the mixture of precursors becomes clear (at 68-71 C., after heating for 40-50 min), the phytic acid is added (19.46 g of aqueous solution of phytic acid with a concentration of 50% by weight) and the mixture is left heating for a time T ranging from 15 to 120 min in order to obtain large HMTA-resorcinol-phytic acid microspheres which have adsorbed the water of the synthesis. The HMTA-resorcinol-phytic acid paste obtained is subsequently cooled in an ice bath for one hour.

TABLE-US-00004 TABLE 4 Heating conditions of example 2 Example 2a Example 2b Duration of the heating T (min) 15 120

[0192] Protocol 3:

[0193] This protocol is applied to the composition of example 3 on conclusion of the initial protocol: When the mixture of precursors becomes clear (at 68-71 C., after heating for 40-50 min), the dilute phytic acid is added (at varied concentrations set out in table 5) and the mixture is left heating for 2 to 4 h in order to obtain HMTA-resorcinol-phytic acid microspheres which float in the solution. The suspension obtained is subsequently cooled in an ice bath for one hour.

TABLE-US-00005 TABLE 5 Conditions for implementation of protocol 3, examples 3a to 3d Exam- Exam- Exam- Exam- ple 3a ple 3b ple 3c ple 3d Concentration by 50 100 100 100 weight of the initial gel (%) in the aqueous solution HPhy/HMTA ratio 0.042 0.042 0.021 0.126 (mol) Concentration by 50 3.9 2.0 11.1 weight of HPhy in the aqueous solution (%) added to the gel Heating time (min) 240 240 240 240

[0194] Examples 4, 5 and 6 and comparative example 4 are carried out with the same conditions and the same protocol as example 3a, the phytic acid being replaced with the anionic polyelectrolytes listed in table 5a. In these examples, the anionic polyelectrolyte/HMTA molar ratio is 0.042.

TABLE-US-00006 TABLE 5a Choice of the anionic polyelectrolyte in examples 4, 5 and 6 and comparative example 4 Anionic polyelectrolyte Example 4 Citric acid Example 5 Ethylenediaminetetraacetic acid (EDTA) Example 6 Poly(acrylic acid, sodium salt) solution (PAA 1200) Comparative Poly(acrylic acid) partial sodium salt solution (PAA example 4 5000)

[0195] Final Protocol (Common to all the Examples):

[0196] This protocol is applied to all the examples, on conclusion of the synthesis of the suspension of microspheres. If the gel is in a dilute aqueous medium, the supernatant is recovered, in particular by filtration, so as to obtain a wet powder. If the gel is in a saturated aqueous medium, it is recovered directly in the form of a wet powder. The wet powder of HMTA-resorcinol-phytic acid microspheres is placed in an oven at 90 C. for 12 hours. The dried HMTA-resorcinol (counterexample 1) gel or HMTA-resorcinol-phytic acid gel particles are subsequently pyrolyzed at 800 C. under nitrogen in order to make it possible to obtain porous carbon particles. The carbon obtained is activated by impregnation by a 5M sulfuric acid solution for 1 h, followed by a heat treatment under nitrogen at 350 C. for 1 h.

[0197] Protocols of Counter Examples 1 to 3:

[0198] Counter example 1: the same conditions as in example 1 are applied but without phytic acid.

[0199] Counter example 2: example G1 of the patent application FR 3 022 248.

[0200] Counter example 3: synthesis of a pyrolyzed powdered resorcinol-formaldehyde gel according to the protocol of example G1 of WO2015/155419.

IIIResults:

[0201] Characterization by Nitrogen Adsorption Manometry:

[0202] The results of the measurements of the specific surfaces and of the pore volumes by nitrogen adsorption manometry are listed in tables 6 and 6a.

TABLE-US-00007 TABLE 6 Specific surface and pore volume - results of the nitrogen adsorption manometry measurements on the materials studied Ex. 1a Ex. 1b Ex. 2a Ex. 2b Ex. 3a Ex. 3d Ex. 4 Ex. 5 Ex. 6 Specific surface micro + 587 574 605 584 569 605 498 534 838 (m.sup.2 .Math. g.sup.1) meso micro 514 510 540 527 498 521 446 496 773 meso 73 64 65 57 71 84 52 38 65 Micro/micro + meso ratio 0.88 0.89 0.89 0.90 0.88 0.86 0.90 0.93 0.92 Micro/meso ratio 7.04 7.96 8.31 9.24 7.01 6.20 8.6 13.1 11.9 Pore volume micro + 0.26 0.25 0.25 0.24 0.25 0.27 0.22 0.22 0.36 (cm.sup.3 .Math. g.sup.1) meso micro 0.20 0.20 0.21 0.20 0.19 0.20 0.16 0.19 0.25 meso 0.06 0.05 0.04 0.04 0.06 0.07 0.06 0.03 0.11 Micro/micro + meso ratio 0.77 0.8 0.84 0.83 0.76 0.74 0.73 0.86 0.69 Micro/meso ratio 3.3 4.0 5.25 5.0 3.15 2.25 2.67 6.3 2.27

TABLE-US-00008 TABLE 6a Specific surface and pore volume - results of the nitrogen adsorption manometry measurements on the materials studied for the comparative examples C. Ex. 1 C. Ex. 2 C. Ex. 3 C. Ex. 4 Specific surface Micro + 581 600 532 345 (m.sup.2 .Math. g.sup.1) meso micro 558 470 318 meso 82 62 27 Micro/micro + meso ratio 0.93 0.88 0.92 Micro/meso ratio 6.80 7.58 11.8 Pore volume micro + 0.32 0.30 0.27 0.14 (cm.sup.3 .Math. g.sup.1) meso micro 0.21 0.22 0.18 0.12 meso 0.11 0.08 0.09 0.02 Micro/micro + meso ratio 0.65 0.73 0.66 0.86 Micro/meso ratio 1.9 2.75 2.0 6

[0203] It is observed that the materials of the invention exhibit a greater micropore volume/(micropore+mesopore) volume ratio than that of the materials of the prior art.

[0204] It is observed that the materials of the invention exhibit a greater micropore volume/mesopore volume ratio than that of the materials of the prior art.

[0205] Only the material of the prior art represented by counterexample 2 exhibits pore volume parameters comparable to those of the invention. However, this is a monolithic material, whereas the material of the invention is obtained directly in the powder form.

[0206] It is observed that the materials of the invention exhibit a micropore specific surface/(micropore+mesopore) specific surface ratio comparable to that of the materials of the prior art.

[0207] It is observed that the materials of the invention exhibit a micropore specific surface/mesopore specific surface ratio comparable to that of the materials of the prior art.

[0208] Characterization by Mercury Porosimetry:

[0209] The results of the mercury porosity measurements are represented in table 7:

TABLE-US-00009 TABLE 7 Results of the mercury porosimetry measurements on the carbon-based materials Ex. 1b Ex. 2b Ex. 3a C. Ex. 3 Macropore volume (cm.sup.3 .Math. g.sup.1) 1.010 0.491 0.575 0.698 Mesopore volume (cm.sup.3 .Math. g.sup.1) 0.122 0.024 0.071 0.871 Micro/meso ratio 8.28 20.46 8.10 0.80

[0210] It is observed that the macropore volume/mesopore volume ratio is higher in the materials of the invention in comparison with the materials of the prior art.

[0211] Characterization by Volumetric Analysis (Tapped Density):

[0212] The measurement of the tapped density of the pyrolyzed carbons, in the powder form, is reported in table 8.

TABLE-US-00010 TABLE 8 Tapped density of the carbon powders Tapped density (g/cm.sup.3) Ex. 1a 0.41 Ex. 1b 0.40 Ex. 1c 0.40 Ex. 1d 0.39 Ex. 1e 0.40 Ex. 2b 0.58 Ex. 3a 0.46 Ex. 3b 0.55 Ex. 4 0.58 Ex. 5 0.58 Ex. 6 0.64 C. Ex. 1 0.34 C. Ex. 2 Monolith C. Ex. 3 0.34 C. Ex. 4 0.56

[0213] It is observed that the carbon powders of the invention exhibit a density which is very significantly greater than that of the carbons of the prior art. The measurement cannot be applied to the carbon of counterexample 2, which is in the form of a monolith. The carbon of counterexample 4 exhibits a tapped density comparable to that of the carbons of the invention.

[0214] Characterization by Elemental Analysis

[0215] The results of the elemental analysis of the carbon-based materials (after pyrolysis) are presented in table 9:

TABLE-US-00011 TABLE 9 Elemental analysis of the carbon-based materials Ex. 1a Ex. 1b Ex. 1d Ex. 1e Ex. 2b Ex. 3a C. Ex. 1 C. Ex. 2 C (% by weight) 79.03 75 H (% by weight) 1.56 1.4 O (% by weight) 14.37 N (% by weight) 1.74 2.77 2.83 2.70 2.27 2.90 0.7 P (% by weight) 0.22 0.37 0.143 0.101 0.044 0.039 0 0 S (% by weight) 0.003

[0216] It is observed that only the materials of the invention comprise both nitrogen and phosphorus.

[0217] Electrochemical Characterization:

[0218] The results of the measurements of the capacitances per unit weight and per unit volume of the electrodes are presented in table 10.

TABLE-US-00012 TABLE 10 Measurement of the capacitances per unit weight and per unit volume of the electrodes prepared from the carbon- based materials of the invention and of the prior art Capacitance Capacitance Capacitance Capacitance per unit per unit per unit per unit weight weight volume volume cathode anode cathode anode (F/g) (F/g) (F/cm.sup.3) (F/cm.sup.3) Ex. 1a 98 135 66 89 Ex. 1b 96 124 69 89 Ex. 1c 80 128 66 106 Ex. 1d 104 140 78 109 Ex. 1e 104 140 85 115 Ex. 2a 94 129 77 106 Ex. 2b 118 127 97 104 Ex. 3a 114 132 86 99 Ex. 3b 98 140 73 104 Ex. 3c 107 129 85 102 Ex. 3d 103 142 79 109 Ex. 5 99 103 93 97 Ex. 6 102 122 62 74 C. Ex. 1 92 114 46 57 C. Ex. 2 90 108 C. Ex. 3 90 110 45 55 C. Ex. 4 Measurements not able to be carried out

[0219] It is observed that the capacitances per unit weight of the electrodes obtained from the materials of the invention are in the majority of cases greater than those obtained from the materials of the prior art. The capacitances per unit volume of the electrodes obtained from the materials of the invention are, in all cases, very significantly greater than those obtained from the materials of the prior art. The measurements carried out on the electrode prepared from the material of counterexample 4 show that this electrode cannot be used as electrode.