Sulphur-modified monolithic porous carbon-based material, process for the preparation thereof and uses thereof in the storage and release of energy
A subject-matter of the invention is a novel process for the preparation of sulphur-modified monolithic porous carbon-based materials by impregnation with a strong sulphur-based acid, the materials capable of being obtained according to this process and the use of these materials with improved supercapacitance properties to produce electrodes intended for energy storage systems. Electrodes composed of sulphur-modified monolithic porous carbon-based materials according to the invention and lithium batteries and supercapacitors having such electrodes also form part of the invention.
1. Process for the preparation of a sulphur-modified monolithic porous carbon-based material, comprising at least the following stages:
(i) drying of a gel comprising at least one hydrophilic polymer of polyhydroxybenzene/formaldehyde type,
(ii) pyrolysis of the material obtained during stage (i),
(iii) impregnation of the material resulting from stage (ii) with a strong sulphur-based acid,
(iv) heat treatment at a temperature of between 300 and 500° C., of the sulphur-modified material obtained at the end of stage (iii),
the said process not comprising a hydrogenation stage.
2. Process according to claim 1 , wherein said gel additionally comprises at least one latex.
3. Process according to claim 2 , wherein said latex is a nitrogen-based latex, preferably chosen from nitrile rubbers.
4. Process according to claim 1 , wherein the stage (i) of drying is carried out either by exchange of solvents and then drying in a supercritical CO2 medium, or by convective drying under a gas stream or in a climate-controlled chamber at a controlled degree of humidity, or by lyophilization.
5. Process according to claim 1 , wherein the stage (ii) of pyrolysis is carried out under a nitrogen atmosphere according to the following protocol:
a slow rise in temperature, at a rate of between 1 and 5° C./min, up to a temperature of 400-500° C., it being possible for this temperature to be maintained for an approximate period of time of one hour, followed by
a faster rise in temperature, at a rate of between 5 and 20° C./min, up to a temperature of 800-1500° C., it being possible for this temperature to be maintained for an approximate period of time of two hours.
6. Process according to claim 1 , wherein the strong sulphur-based acid is an acid based on sulphur which is provided in the form of a solution of pH<1.
7. Process according to claim 1 , wherein the strong sulphur-based acid is chosen from sulphuric acid, oleum, chlorosulphonic acid and fluorosulphonic acid.
8. Process according to claim 1 , wherein the said strong sulphur-based acid is a sulphuric acid solution having a concentration of between 0.5M and saturation, and preferably between 1M and saturation.
9. Process according to claim 1 , wherein the stage (iv) of heat treatment is carried out for a period of time of between 1 minute and 12 hours, and preferably of less than or equal to 2 hours.