Abstract:
The invention relates to a supercapacitor with a double electrochemical layer that comprises at least two complexes ( 2, 3 ) and at least one spacer ( 4 ) between the two complexes ( 2, 3 ), the complexes ( 2, 3 ) and the spacer ( 4 ) being spirally wound together in order to form a coiled member ( 10 ), characterized in that it further comprises at least another complex ( 1 ) and at least another spacer ( 4 ), the other complex ( 1 ) and the other spacer ( 4 ) being spirally wound together around the coiled member ( 10 ) in order to form at least one subsequent coiled member ( 20 ), the consecutive coiled members ( 10, 20 ) being separated by an electronic insulation space.

Description:
This is a non-provisional application claiming the benefit of International application number PCT/EP2009/051665 filed Feb. 12, 2009. 
     The present invention relates to the general technical field of supercapacitors, i.e. capacitors with a double electrochemical layer (or EDLC acronym of “Electrochemical Double Layer Capacitor”). 
     GENERAL PRESENTATION OF THE PRIOR ART 
     A supercapacitor is a means for storing energy with which it is possible to obtain a power density and an intermediate energy density between those of dielectric capacitors and batteries. Their discharge time is generally of the order of a few seconds. 
     A supercapacitor conventionally comprises a cylindrical wound element comprising at least two electrodes. Each electrode is made from a mixture of active coal (also called “active material”), of carbon black and polymers. During a so-called extrusion step, a conductive paste is deposited on an aluminium collector which is used as a current collector. Both electrodes are separated by a porous separator in order to avoid short-circuits between both electrodes. During a so-called impregnation step, the supercapacitor is filled with an electrolyte. This electrolyte consists of a salt dissolved in a solvent, generally acetonitrile. This salt is separated into two charged species which are called ions (for example: BF4 −  and TEA + ). 
     The thickness of an electrode is typically 100 μm. The ions have a size of the order of 1/1000 th  of a μm, i.e. 100,000 times smaller than the thickness of the electrode. Active coal (or active material) is an extremely porous material. 
     When a voltage is applied with a DC generator between two electrodes of the supercapacitor, the ions move in the porosity very close to the surface of the coal. The greater the amount of ions present at the surface of coal, the larger is the capacitance. 
     The amount of energy stored in a supercapacitor depends on the voltage applied between both electrodes and on the total capacitance of the supercapacitor. 
     Many investigations have shown that the higher the operating voltage of the supercapacitors, the shorter is the lifetime, because of very large generation of gas in the supercapacitor. 
     This gas generation is related to the decomposition of the material forming the electrolyte, this decomposition being a function of the applied voltage between the electrodes of the supercapacitor. 
     For example, the decomposition voltage of pure acetonitrile is 5.9V. 
     Presently, the reference voltage applied to the electrodes of supercapacitors is 2.7V (see notably WO 9 815 962 which teaches to the person skilled in the art that the voltage of a supercapacitor should be limited in order not to degrade too much the electrolyte). 
     In order to remedy this drawback, it is known how to electrically connect several supercapacitors to each other in order to form a module. This allows an increase in the voltage applied to the module. 
     In order to electrically connect two adjacent supercapacitors, connection means comprising two lids and a strap are used. 
     Each lid is capable of capping a respective supercapacitor so as to be electrically connected to the latter, for example by soldering. 
     Each lid further comprises a connection terminal capable of coming into contact with a through-bore of the strap, so as to electrically connect both adjacent supercapacitors. 
     However, such supercapacitors have drawbacks. 
     Notably, the volume and the mass of two supercapacitors electrically connected through a strap and two lids are significant. 
     Moreover, the manufacturing cost related to the purchase and mounting of the straps and lids for connecting both supercapacitors is significant. 
     Also, the series resistance Rs between two electrically connected supercapacitors—which corresponds to the sum of the resistances of the supercapacitors and of the connection means (strap+lid+solder)—is significant. 
     The general object of the invention is to propose a supercapacitor, the lifetime of which is increased at the reference voltage. 
     Another object of the present invention is to propose a supercapacitor in which gas generation is limited. 
     Another object of the present invention is to propose a supercapacitor capable of supporting a voltage above the reference voltage without undergoing any degradation. 
     PRESENTATION OF THE INVENTION 
     For this purpose, a supercapacitor is provided comprising at least two electrodes and at least one separator between both electrodes, the electrodes and the separator being wound together in turns in order to form a wound element, the supercapacitor further comprising at least one other electrode and at least one other separator, the other electrode and the other separator being wound together in turns around the wound element so as to form at least one consecutive wound element, these successive wound elements being separated by an electronic insulating space. 
     “Complex” designates the association of a current collector and of at least one electrode, the current collector and the electrode having a common electrically conducting surface. 
     “Successive complexes” designate two coplanar complexes (before being wound in turns in order to form a wound element) and separated by an electronic insulating space of width d during their being wound. 
     “Common complex” designates any association of complexes in electronic continuity. 
     The separator(s) extend(s) beyond the electrodes of each complex facing each other but not beyond the collectors of the complexes being used as a connection to the outside. 
     Preferred but non-limiting aspects of the module according to the invention are the following:
         an electrode of the supercapacitor is common to two successive wound elements.   the supercapacitor further comprises at least one second other electrode, the other electrodes and the other separator being wound together in turns around the wound element so as to form the consecutive wound element,   the electronic insulating space is formed by a reinforcement formed with at least one turn of dielectric insulating material,   the electronic insulating space is formed by a distance q separating at least one of the electrodes of the first wound element from at least one electrode of the second wound element,   the distance q should be at least equal to 1 mm,   the separators are continuous so that the supercapacitor includes a single separator common to the different wound elements and acting as a reinforcement between the different wound elements,   the height of each wound element is constant,   the wound elements have different heights,   the wound elements are shifted relatively to each other along their longitudinal axis,   the wound elements are electrically connected through a first conducting lid over the whole of its surface, said lid being positioned on one of the base faces of the wound elements,   the first lid has an indented cross-section,   the first lid substantially extends in a plane,   the wound elements are electrically connected through a second conducting lid over the whole of its surface, said lid being positioned on the other of the base faces of the wound elements so as to connect the wound elements in parallel,   the wound elements are electrically connected through a second conducting lid comprising electrically conducting portions, the conducting portions being separated from each other by electrically insulating portions, each conducting portion respectively being in electric contact with a wound element so as to connect the wound elements in series,   one of the electrically conducting portions is disk-shaped, and the other electrically conducting portions are crown-shaped, the conducting portions being separated from each other by crown-shaped electrically insulating portions,   the second lid globally extends in a plane,   the second lid has an indented cross-section,   each conducting portion is in the shape of a disk portion, the disk portions being separated from each other by radial insulating portions,   the supercapacitor is connected to at least one other supercapacitor of the same type through at least two connecting straps, each connecting strap comprising an electrically conducting portion intended to respectively come into contact with a disk-shaped conducting portion of the lid,   the supercapacitor is electrically connected to another supercapacitor of the same type through at least one connecting strap comprising at least two electrically conducting portions insulated from each other by at least one electrically insulating portion, said conducting portions being intended to respectively come into contact with one conducting portion of the lid,   the connecting strap is substantially flat and in that the lid comprises electrically insulating areas extending at the contact surface between the lid and the strap, the electrically insulating areas being positioned so that each conducting portion of the strap is electrically in contact with a single conducting portion of the lid,   each electrically conducting portion comprises a protruding connection element at the ends of the connecting strap, each protruding element being intended to come into contact with a respective conducting portion of the lid,   the height of the reinforcement is comprised between the height of active material of the first wound element and the total height of said first wound element,   the electrodes of the wound elements are of different width and/or length,   the thicknesses of the electrodes of the wound elements are different   the electrodes of the wound elements are of different natures,   the base of the wound elements orthogonal to the winding axis is of circular shape,   the base of the wound elements orthogonal to the winding axis is of hexagonal shape,   the base of the wound element orthogonal to the winding axis is of triangular shape,   the base of the wound elements orthogonal to the winding axis is of octagonal shape,   the base of the wound elements orthogonal to the winding axis is of rectangular shape,   the angles of the wound elements are non-protruding,   the base of the wound elements orthogonal to the winding axis is of elliptical shape,       

     The invention also relates to a module comprising a casing in which is positioned at least one supercapacitor as described above. 
     Advantageously, the module may both comprise supercapacitors according to the invention and supercapacitors of the prior art, as illustrated in  FIG. 11 . In other words, the module may further comprise a supercapacitor according to the invention, a standard supercapacitor comprising a cylindrical wound element including at least two electrodes and at least one separator wound together in turns in order to form a wound element positioned in a casing and lids intended to close the casing, this standard supercapacitor being electrically connected to a supercapacitor according to the invention via at least one connecting strap. 
    
    
     
       PRESENTATION OF THE FIGURES 
       Other features, objects and advantages of the present invention will further become apparent from the description which follows, which is purely illustrative and non-limiting and should be read with reference to the appended drawings wherein: 
         FIGS. 1   a - 7  illustrate different embodiments of wound elements of a supercapacitor according to the invention, 
         FIGS. 8-13  illustrate different embodiments of lids of the supercapacitor according to the invention, 
         FIGS. 14-16  illustrate different embodiments of a connecting strap for connecting adjacent supercapacitors, 
         FIG. 17  illustrates a supercapacitor of the prior art, 
         FIGS. 18-20  are graphic illustrations illustrating the volume V of a supercapacitor versus the number of wound elements, 
         FIGS. 21-23  are graphic illustrations illustrating the mass m of a supercapacitor versus the number of wound elements, 
         FIGS. 24-28  illustrate different electric circuits which may be made with the supercapacitors according to the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Different embodiments of the supercapacitor according to the invention will now be described with reference to  FIGS. 1-23 . In these different figures, equivalent elements of the supercapacitor bear the same numerical references. 
     With reference to  FIGS. 1   a  and  1   b , a sectional view along a transverse axis of a first embodiment of the supercapacitor is illustrated. 
     The supercapacitor comprises two complexes  2 ,  3  positioned face to face and separated by a separator  4 . 
     The complexes  2 ,  3  and the separator  4  are wound together in turns in order to form a first wound element. 
     The supercapacitor also comprises another complex  1  successive to one  2  of the complexes  2 ,  3  and another separator  4 . The other electrode and the other separator are wound together in turns around the first wound element so as to form at least one second consecutive wound element. 
     The successive complexes  1 ,  2  are spaced apart by a distance q along a direction circumferential to the longitudinal axis of the supercapacitor. 
     Advantageously, the distance q between the successive complexes  1 ,  2  is provided to be sufficient in order to electrically insulate the successive complexes  1 ,  2  from each other. In the embodiment illustrated in  FIG. 1 , the distance q is larger than or equal to 1 millimeter. 
     A distance q of one millimeter is indeed sufficient in order to prevent the electric field generated between both successive complexes  1 ,  2  from being too large, which would risk decomposing the electrolytes under normal conditions of use of the supercapacitor. 
     The complex  3  positioned facing both successive complexes is a so-called “common complex”. 
     With the separators  4 , it is possible to electrically insulate the successive complexes  1 ,  2  of the common complex  3 . One of the separators is positioned between the common complex  3  and the successive complexes  1 ,  2 . The other separator  4  is positioned on the other face of the common complex  3  so that the common complex  3  is located between the separators  4 . 
     Each complex  1 ,  2 ,  3  comprises a current collector  11 ,  21 ,  31  and at least one electrode consisting of active material, the electrode having an electrically conducting face in common with the current collector  11 ,  21 ,  31 . 
     In the embodiment illustrated in  FIGS. 1   a  and  1   b , each complex  1 ,  2 ,  3  comprises two opposite electrodes  12 ,  13 ,  22 ,  23 ,  32 ,  33  on either side of the current collector  11 ,  21 ,  31 . Each electrode  12 ,  13 ,  22 ,  23 ,  32 ,  33  has an electrically conducting surface in common with a respective face of the current collector  11 ,  21 ,  31 . 
     The areas facing the successive and common complexes define two supercapacitor cells, the capacitances of which are determined by their respective lengths. The continuity of the common complex  3  allows both supercapacitor cells to be placed in series. 
     The complexes  1 ,  2 ,  3  and separators  4  respectively consist of one or more superposed sheets. 
     Advantageously, the successive complexes  1 ,  2 , the common complex  3  and the separators  4  are successively wound together in turns, in order to form a consecutive first wound element and second wound element. 
     The proposed solution is less costly than the supercapacitors of the prior art described earlier. Indeed, the number of straps, lids and tubes (used as a housing for the wound elements) in order to electrically connect two supercapacitor cells is less than the number of straps, lids and tubes required for electric connection of several supercapacitors of the prior art. 
     Moreover, the proposed solution above allows a reduction in the series resistance Rs of the system (by the reduction of the number of lids and straps required for connecting the supercapacitor cells as compared with the number of lids and straps required for connecting supercapacitors of the prior art), and a significant increase in the admissible energy per unit volume while optimizing the capacitance. 
     With the supercapacitor described above, it is thus possible to obtain a compact wound structure:
         allowing series and parallel electric connections of supercapacitor cells with identical capacitances C, or of different capacitances C, C′ operating at the same supply voltage Un with the purpose of increasing the global currents and/or voltage of the compact structure,   meeting particular balancing requirements in an application (a triangle or star circuit of supercapacity cells of any capacitances operating at any voltages),   allowing optimization of the energy and power bulk and mass densities of assemblies of supercapacitor cells of identical capacitance C operating at the same voltage Un.       

     Other advantages related to the removal of straps and lids for connecting two supercapacity cells in series/parallel are the following:
         reduction in the volume of the supercapacitor   mass reduction as compared with two supercapacitors of the prior art connected in series,   reduction in the volume of two supercapacitors connected in series/parallel: twice the volume of a supercapacitor of the prior art (obtained by winding together in turns two complexes and a separator) is larger than the volume of a supercapacitor according to the invention (obtained by winding together in turns three complexes and two separators) as illustrated in  FIG. 1 , therefore   increase in the energy and power bulk and mass densities,   non-reduction in the internal free volume as compared with a series association of supercapacitors of the prior art (standards),   gain in time from a manufacturing method point of view (n cells in 1 single supercapacitor) by simplifying the manufacturing method, because of single winding, single impregnation, single heat treatment and single soldering.       

     With reference to  FIG. 2 , another embodiment of the supercapacitor according to the invention is illustrated. 
     The supercapacitor illustrated in  FIG. 2  differs from the supercapacitor illustrated in  FIG. 1  in that it comprises four complexes instead of three. 
     Two first complexes  2 ,  3   a  are positioned face to face. One  2  of both first complexes is positioned between two separators  4 . The first two complexes  2 ,  3   a  and the separators  4  are wound together in turns in order to form a first wound element. 
     Two other complexes  1 ,  3   b  are successive to the first two complexes  2 ,  3   a  and spaced apart (from the first two complexes) by a distance q along a direction circumferential to the supercapacitor. 
     Both complexes  1 ,  3   b  are wound together in turns around the first wound element consisting of the complexes  2 ,  3   a  so as to form at least one second consecutive wound element. 
     In this embodiment, each wound element forms an independent supercapacitor. The series or parallel electric connection of both thereby formed supercapacitors is ensured by the lids  50  as this will be described in more detail in the following. 
     In  FIG. 3  different wound elements  10 ,  20 ,  30  of a supercapacitor according to the invention are illustrated. The successive wound elements  10 ,  20 ,  30  are coaxial with an axis Z. These successive wound elements  10 ,  20 ,  30  are separated by an electronic insulating space. This electronic insulating space allows insulation of the wound elements from each other. 
     According to an alternative embodiment, the electronic insulating space is formed by a distance q separating two successive wound elements. Advantageously, this distance q is provided to be sufficient in order to prevent direct passage of the current between two successive wound elements. For example, the distance q may be greater than one millimeter. 
     According to another alternative embodiment, the electronic insulating space may be formed by a reinforcement  40  formed with at least one turn of dielectric insulating material. The use of a reinforcement for electrically separating two successive wound elements facilitates the making of the supercapacitor. 
     Advantageously, the height of the reinforcement is comprised between the height of active material of the first wound element and the total height of said first wound element. 
     As illustrated in  FIG. 4 , the separators  4  may be continuous so that the supercapacitor includes a single separator  4  common to different wound elements and acting as a reinforcement between the successive wound elements. 
     In the embodiment illustrated in  FIG. 3 , the different wound elements  10 ,  20 ,  30  are of constant height. Moreover, the bases of the different wound elements  10 ,  20 ,  30  are coplanar. With this the winding of the successive wound elements may be facilitated. 
     In other embodiments as illustrated in  FIG. 5 , the successive wound elements  10 ,  20 ,  30  are of different heights, the successive wound elements having a coplanar base. 
     Still in other embodiments, the successive wound elements  10 ,  20 ,  30  are of identical height, but their bases are shifted relatively to each other along their longitudinal axis. Such embodiments are illustrated in  FIGS. 6 and 7 . 
     In the embodiment of  FIG. 6 , the successive wound elements  10 ,  20 ,  30  are fitted into each other. In other words, the successive wound elements are coaxial and stacked around the central wound element  10 . 
     In the embodiment illustrated in  FIG. 7 , the successive wound elements  10 ,  20 ,  30  are shifted relatively to each other so that their bases form a set of indentations along a longitudinal section view. 
     The successive wound elements of the supercapacitor are intended to be connected together or with wound elements of other adjacent supercapacitors via lids  50  and/or straps. 
     The different types of the lids  50  will now be described in more detail, which may be used for connecting together the wound elements of a supercapacitor or of different adjacent supercapacitors. 
     With reference to  FIG. 8 , a first embodiment of a lid  50  is illustrated, allowing electric connection of two wound elements of a same supercapacitor. The lid  50  has an indented cross-section. 
     This first lid embodiment  50  is intended to cap a supercapacitor, the wound elements of which have bases shifted relatively to each other. In order to electrically connect wound elements of identical height non-shifted relatively to each other (such as illustrated in  FIG. 5 ), a lid  50  substantially extending in a plane will be used. 
     Advantageously, the lid  50  is conducting on the whole of its surface, and allows the successive wound elements of a supercapacitor to be placed in electric contact so as to form a common terminal for these wound elements. 
     The other face of the supercapacitor may be capped with a conducting lid  50  over the whole of its surface in order to electrically connect in parallel the successive wound elements of the supercapacitor. 
     The other face of the supercapacitor may also be capped with a lid  50  comprising electrically conducting portions, the conducting portions being separated from each other by electrically insulating portions, each electrically conducting portion being respectively in electric contact with a wound element so as to connect the wound elements in series. 
     Embodiments of lids comprising electrically conducting portions intended to respectively come into electric contact with one of the wound elements are illustrated in  FIGS. 9 and 10 . 
     In the embodiment illustrated in  FIG. 9 , the lid comprises two electrically conducting portions. The first electrically conducting portion S 1  is disk-shaped. The second electrically conducting portion S 2  is crown-shaped. The electrically conducting portions S 1 , S 2  are separated from each other by crown-shaped electrically insulating portions  60 . This lid  50  is intended to cap a supercapacitor comprising two successive wound elements. The first electrically conducting portion S 1  is electrically connected to the central wound element  10  of the supercapacitor. The second electrically conducting portion S 2  is electrically connected to the peripheral wound element  20  of the supercapacitor. 
     In the embodiment illustrated in  FIG. 10 , the lid  50  comprises three electrically conducting portions S 1 , S 2 , S 3 . One of the electrically conducting portions S 1  is disk-shaped. The other electrically conducting portions S 2 , S 3  are crown-shaped. The electrically conducting portions S 1 , S 2 , S 3  are separated from each other by crown-shaped electrically insulating portions  60 . The electrically conducting portions S 1 , S 2 , S 3  are electrically connected to a respective wound element  10 ,  20 ,  30 . This lid  50  is intended to cap a supercapacitor comprising three successive wound elements. 
     Of course, the lid  50  may comprise more than three electrically conducting portions, the number of conducting portions depending on the number of wound elements of the supercapacitor. 
     Depending on the application, the lid  50  may substantially extend in a plane, or have an indented cross-section as illustrated in  FIG. 11 . 
     Moreover, the electrically conducting portions may have other shapes. Lids  50  are illustrated in  FIGS. 12 and 13 , wherein the electrically conducting portions respectively are in the shape of a disk portion. The disk portions are separated from each other by radial insulating portions. 
     In the embodiment illustrated in  FIG. 12 , the lid  50  comprises two electrically conduction portions S 1 , S 2  in the shape of a half-disk. Each portion S 1  (S 2  respectively) is intended to be electrically connected to a respective wound element  10  ( 20  respectively) of the supercapacitor in an area Z 1  (Z 2  respectively) of each portion S 1  (S 2  respectively). This lid  50  is intended to cap a supercapacitor comprising two wound elements. 
     In the embodiment in  FIG. 13 , the lid  50  comprises three electrically conducting portions S 1 , S 2 , S 3  in the shape of a third of a disk. Each portion S 1  (S 2  respectively, S 3  respectively) is electrically connected to a respective wound element  10  ( 20  respectively,  30  respectively) of the supercapacitor at the solders Z 1  (Z 2  respectively, Z 3  respectively). This lid  50  is intended to cap a supercapacitor comprising three wound elements  10 ,  20 ,  30 . 
     Once the supercapacitor is capped with one of the lids  50  described earlier with reference to  FIGS. 9-13 , the supercapacitor may be connected to adjacent supercapacitor(s) by using electrically conducting connecting straps. 
     With reference to  FIG. 14 , an exemplary connecting strap  70  is illustrated. Each connecting strap  70  comprises an electrically conducting portion intended to come into contact respectively with a disk-shaped conducting portion S 1 , S 2 , S 3  of the lid  50  described with reference to  FIG. 13 . 
     More specifically, each strap  70  is substantially flat. The main body of the connecting strap  70  is rectangular. The ends  80  of the strap are of triangular shape. The size and the shape of these ends  80  are provided to be sufficient for coming into contact with a respective conducting portion S 1 , S 2 , S 3  of the lid  50 , without covering the insulating portion separating two conducting portions of the lid  50 . Thus, the connecting straps  70  are insulated from each other. By avoiding the contact between the straps  70 , the electric insulation of the straps  70  are guaranteed so as to avoid a short-circuit. 
     With reference to  FIG. 15 , an alternative connecting strap  70  is illustrated. This connecting strap  70  provides electric connection of two supercapacitors of the type described with reference to  FIGS. 9 and 10 . 
     The connecting strap  70  comprises two (or more than two) electrically conducting portions insulated from each other (respectively the ones from the others) by one (or more) electrically insulating portions. Each electrically conducting portion is respectively intended to come into contact with a conducting portion S 1 , S 2 , S 3  of the lid  50 . Each electrically conducting portion comprises a protruding connecting element  90  at the ends  80  of the connecting strap  70 . Each of these elements which protrude is intended to come into contact with a respective conducting portion S 1 , S 2 , S 3  of the lid  50 . 
     With reference to  FIG. 16 , another embodiment of a connecting strap  70  and of a lid is illustrated. This connecting strap  70  and this lid are adapted to connecting two supercapacitors each comprising three wound elements. Of course, this lid and this strap may comprise more than three electrically conducting portions in the case when the supercapacitors comprise more than three wound elements. 
     The connecting strap  70  is substantially flat. The lid comprises electrically insulating areas extending at the contact surface between the lid and the strap. These electrically insulating areas are positioned so that each conducting portion of the strap is electrically in contact with a single conducting portion of the lid. With this, the wound elements of the thereby connected supercapacitors may be electrically connected two by two. 
     Advantageously, the supercapacitor may be dissymmetrical, i.e. the electrodes of the different complexes may be different in terms of length and/or thickness and/or nature of the material making them up. 
     By working with a dissymmetrical supercapacitor, it is possible to optimize:
         the capacitance of the supercapacitor on the one hand, and   the aging of the supercapacitor on the other hand because of better control of the potential of each electrode.       

     The dissymmetry of the supercapacitor may for example be obtained by varying the thickness of the electrodes of the wound elements, so that the positive and negative electrodes of each wound element have different volumes. 
     The dissymmetry of the supercapacitor may also be obtained by varying the thicknesses and/or lengths of the electrodes of the wound elements. 
     The dissymmetry may also be obtained by varying the nature of the constituents of the electrodes of the wound elements. For example, in an embodiment, the electrodes of a wound element are of identical thickness but are made up of different materials so as to have different faradic densities. 
     The supercapacitors may have different shapes, for example the supercapacitors may be cylindrical. 
     The supercapacitors may also have a hexagonal or triangular, or octagonal, or rectangular shape, or further elliptical shape, orthogonally to the winding axis. With this, the dead volume may be limited between two adjacent supercapacitors. The angles of the wound elements may be non-protruding. 
     General Case Allowing Demonstration in the Gain in Volume on a Co-Wound System 
     As described earlier, the supercapacitor according to the invention allows reduction of the volume associated with the series or parallel electric connection of two supercapacitors as compared with the modules of the prior art. 
     Such a module of the prior art is illustrated in  FIG. 17 . The module comprises two supercapacitors  120 . Each supercapacitor  120  comprises a cylindrical wound element comprising two electrodes and one separator. A portion  180  of the electrodes juts out outwards. The supercapacitors are connected in series by means of a connecting strap  170  and of lids  180 . Each lid  180  caps a respective supercapacitor  120  so as to be electrically connected to the latter at the electrode portion  190  jutting out outwards. Each lid  180  is in contact by soldering with a strap  70 , so as to electrically connect both supercapacitors  120  in series. 
     In order to demonstrate the gain in volume of the supercapacitor according to the invention as compared with the module of the prior art, the following parameters are required: 
     C: capacitance to be obtained (F) 
     ξ: faradic density (F/cm 3 ) 
     h: activated height (cm) 
     H: total height (cm) 
     e: thickness of the wound separator/electrode/collector/electrode/separator/electrode/collector/electrode (cm) 
     Ø int : inner diameter around which begins the winding (Ø int &gt;0) (cm) 
     The output data are the following: 
     k: number of turns 
     Ø ext : outer diameter of a winding of capacitance C comprising k turns (cm) 
     C n : capacitance of n parallel nested windings (F) 
     Ø ext n : Outer Diameter of the Capacitor C n  (Cm) 
     V n : volume of the n-nested capacitor of value C n  (cm 3 ) 
     V: volume of n capacitors of value C in parallel (cm 3 ) 
     Formulae: 
             C   =       ξ   ⁡     (     h   ⁢           ⁢     e   /   2       )       ⁢   π   ⁢           ⁢     k   ⁡     (       ∅   int     +   ke     )                       ∅   ext     =       ∅   int     +     2   ⁢           ⁢   ke                   k   =         -     ∅   int       +         ∅   int   2     +       8   ⁢           ⁢   C       ξπ   ⁢           ⁢   h               2   ⁢           ⁢   e                     ∅   ext     =         ∅   int   2     +       8   ⁢           ⁢   C       ξπ   ⁢           ⁢   h                         C   n     =   nC                 V   n     =         ∅     ext   ⁢           ⁢   n     2     ⁢   H     =       (       ∅   int   2     +       8   ⁢           ⁢   nC       ξπ   ⁢           ⁢   h         )     ⁢   H                   V   =       n   ⁢           ⁢     ∅   ext   2     ⁢   H     =       n   ⁡     (       ∅   int   2     +       8   ⁢           ⁢   C       ξπ   ⁢           ⁢   h         )       ⁢   H             
Numerical Application of the Formulae Established Earlier:
 
     In the following numerical examples, the value of capacitance of each winding is assumed to be identical, which in practice means that windings of larger diameters have smaller thickness than the windings of smaller diameters, the winding length being identical for each capacitor. 
     Numerical Example 1 
     C=600 F ξ=30 F/cm 3  h=8 cm H=10 cm 
     e=0.05 cm Ø int =2.5 cm 
       FIG. 18  shows the volume V of n wound elements associated as a module and the equivalent of a single supercapacitor according to the invention containing n co-wound elements V n . The volumes are expressed in cm 3  (ordinates on the left). %ΔV represents the percent gain between a co-wound element and associated elements (ordinate axis on the right). 
     Numerical Example 2 
     C=2600 F ξ=30 F/cm 3  h=8 cm H=10 cm 
     e=0.05 cm Ø int =2.5 cm 
       FIG. 19  shows the volume V of n wound elements associated as a module and the equivalent of a single supercapacitor according to the invention containing n co-wound elements V n . The volumes are expressed in cm 3  (ordinates on the left). %ΔV represents the percent gain between a co-wound element and associated elements (ordinate axis on the right). 
     Numerical Example 3 
     C=5000 F ξ=30 F/cm 3  h=8 cm H=10 cm 
     e=0.05 cm Ø int =2.5 cm 
       FIG. 20  shows the volume V of n wound elements associated as a module and the equivalent of a single supercapacitor according to the invention containing n co-wound elements V n . The volumes are expressed in cm 3  (ordinates on the left). %ΔV represents the percent gain between a co-wound element and associated elements (ordinate axis on the right).
 
Result:
 
 FIGS. 18 ,  19 ,  20  show that the gain in volume is obtained regardless of the number of co-wound elements and of the initial capacitance used.
 
General Case Allowing Demonstration of the Gain in Mass on a Co-Wound System
 
     As described earlier, with the supercapacitor according to the invention, it is possible to reduce the mass associated with the series or parallel electric connection of two supercapacitors as compared with the modules of the prior art. 
     In order to demonstrate the gain in mass of the supercapacitor according to the invention as compared with the module of the prior art, the following parameters are required: 
     e c : thickness of the lid (cm) 
     e t : thickness of the tube (cm) 
     m u   C : mass of the capacitor C (g) 
     d: specific gravity of the material of the tube and of the lid (g/cm 3 ) 
     The output data are the following: 
     m c   C : mass of the lid of a capacitor of value C (g) 
     m t   C : mass of the tube of a capacitor of value C (g) 
     m: total mass of n capacitors of value C in parallel (g) 
     m n : total mass of the n-nested capacitor of value C n  (g) 
     Formulae:
 
 m   c   C =πØ ext   2   e   c   d  
 
 m   t   C =πØ ext   e   t   Hd  
 
 m=n ( m   u   C +2 m   c   C   +m   t   C )
 
 m   n   =m   u   Cn +2 m   c   Cn   +m   t   Cn  
 
Numerical Application of the Formulae Established Earlier:
 
e c =0.4 cm e t =0.05 cm
 
d (specific gravity of aluminium)=2.7 g/cm 3  
 
m n   600F =75 g m u   2600F =325 g
 
     Numerical Example 1 
     e c =0.4 cm e t =0.05 cm 
     d (specific gravity of aluminium)=2.7 g/cm 3    
     m u   600F =75 g 
       FIG. 21  shows the mass m of n wound elements associated as a module and the equivalent of a single supercapacitor according to the invention containing n co-wound elements m n . The masses are expressed in grams (ordinates on the left). %Δm represents the percent gain in mass between a co-wound element and associated elements (axis of ordinates on the right). 
     Numerical Example 2 
     e c =0.4 cm e t =0.05 cm 
     d (specific gravity of aluminium)=2.7 g/cm 3    
     m u   2600F =325 g 
       FIG. 22  shows the mass m of n wound elements associated as a module and the equivalent of a single supercapacitor according to the invention containing n co-wound elements m n . The masses are expressed in grams (ordinates on the left). %Δm represents the percent gain in mass between a co-wound element and associated elements (axis of ordinates on the right). 
     Numerical Example 3 
     e c =0.4 cm e t =0.05 cm 
     d (specific gravity of aluminium)=2.7 g/cm 3    
     m u   5000F =650 g 
       FIG. 23  shows the mass m of n elements associated as a module and the equivalent of a single supercapacitor according to the invention containing n co-wound elements m n . The masses are expressed in grams (ordinates on the left). %Δm represents the percent gain in mass between a co-wound element and associated elements (axis of ordinates on the right).
 
Result:
 
 FIGS. 21 ,  22 ,  23  show that the gain in mass is obtained regardless of the number of co-wound elements and of the initial capacitance used. This gain in mass does not take into account the consequent gain in terms of extra-element connection technology (connecting straps, lid, etc.) which further increases the obtained gain in terms of mass.
 
     CONCLUSION 
     Regardless of the number of co-wound elements, the simultaneous gain in mass and volume exists relatively to a series or parallel assembly of several wound elements as proposed in the prior art. 
     This novel system therefore corresponds to a significant increase in bulk and mass energy density. 
     It is important to specify that the mass of each electrode, the thickness of the coating, of the collector, the type of carbon and the overall width may be different, as shown by the different descriptive diagrams. 
     Among the examples which we have mentioned, we have taken the simplest cases and they may easily be multiplied over and over again. Regardless of the type of arrangement, the gain in mass and in volume is targeted in an advantageous way. This gain may also be accomplished in terms of voltage, according to arrangements of the type described in  FIG. 8 . 
     Each electrode may be symmetrical (the simplest and generally applied case) relatively to a specific collector so as to double the amount of active material of the thereby formed capacitance and to drastically increase the bulk capacitance of the assembly, and therefore the maximum admissible energy. The case of dissymmetry should not be set aside:
         case of windings with different capacitances in the same element,   case of different active materials (for example porosity of different carbons)   combination of multitrack co-windings, i.e. a supercapacitor, such that it comprises at least two juxtaposed complexes spaced apart by a distance d and at least one common complex facing both juxtaposed complexes and separated from the latter by at least one separator, the separator and the complexes being wound together in turns in order to form a wound element (object of a separate patent application) with the multicoil system, object of the present application.       

     In  FIGS. 24-28  different examples of circuits are illustrated which may be achieved with the supercapacitor according to the invention. 
     With reference to  FIG. 24 , an exemplary circuit is illustrated in which, with the succession of wound elements  10 ,  20 ,  30  (each forming a supercapacitor) connected in series by means of a particular type of lid comprising different conducting and insulating areas, a series electric connection of the different wound elements may be obtained. 
     With reference to  FIG. 25 , another exemplary circuit is illustrated in which each wound element  10 ,  20 ,  30  of a first supercapacitor is connected in series with a wound element  10 ′,  20 ′,  30 ′ of another supercapacitor, the different wound elements of the first supercapacitor being connected in parallel. 
     More specifically, the bases of each supercapacitor are capped with lids (of the type illustrated in  FIG. 10 ) comprising three electrically conducting portions S 1 , S 2 , S 3  (S 1  is disk-shaped and S 2   n  S 3  are crown-shaped) separated from each other by electrically insulating portions  60  (crown-shaped). Both supercapacitors are then stacked so that:
         the central wound element  10  of the first supercapacitor is connected in series with the central wound element  10 ′ of the second supercapacitor   the peripheral wound element  30  of the first supercapacitor is connected in series with the peripheral wound element  30 ′ of the second supercapacitor, and   the intermediate wound element  20  of the first supercapacitor is connected in series with the intermediate wound element  20 ′ of the second supercapacitor.       

     The advantage of this circuit is that the electric connection of both supercapacitors does not require the use of a connecting strap. It is quite obvious that in the case of the electric connection of two adjacent supercapacitors, the same circuit may be achieved by using particular connecting straps (such as the connecting strap illustrated in  FIG. 16 ), as illustrated in  FIG. 26 . 
     With reference to  FIG. 27 , an embodiment is illustrated in which the successive wound elements of a supercapacitor are connected so as to form a star circuit. 
     More specifically, the lower base of the supercapacitor is capped with a conducting lid over the whole of its surface, and the upper base of the supercapacitor is capped with a lid of the type illustrated in  FIG. 13  comprising three disk portions connected to a respective wound element of the supercapacitor. Connecting straps of the type described with reference to  FIG. 14  are used for connecting the wound elements of the supercapacitor to the wound elements of other adjacent supercapacitors. 
     With reference to  FIG. 28 , an exemplary circuit is finally illustrated in which two supercapacitors are electrically connected in series, the wound elements of each supercapacitor being connected in parallel. 
     More specifically, the bases of each supercapacitor are capped with conducting lids over the whole of their surface and are connected through conducting connecting straps over the whole of their surface. 
     The supercapacitors according to the invention therefore allow a large number of electric circuits to be made, much more ergonomically than the supercapacitors of the prior art. 
     The reader will have understood that many modifications may be made to the supercapacitor described earlier without materially departing from the novel teachings and advantages described herein. 
     Therefore, all the modifications of this type are intended to be incorporated within the scope of the supercapacitor as defined in the appended claims. 
     This type of element design may also find all its application for batteries or battery cells of any nature (Li-ion, lithium polymer, Ni—Cd, Ni—MH), or further even for fuel cells. 
     The supercapacitor according to the invention has many advantages:
         for a supercapacitor according to the invention, with bulk energy identical with that of two standard supercapacitors, it is possible to apply a lower voltage and therefore very strongly limit the generation of gas and therefore increase the lifetime in a very advantageous way,   the internal volume of a supercapacitor according to the invention may advantageously be greater, per circuit, than the internal volume of two associated standard supercapacitors. In this case, the lifetime will also be increased.       

     Finally, in a module comprising a plurality of supercapacitors connected to each other, at least half of the series resistance of the module is a connection technology resistance between the coils and the lids. In a module comprising a plurality of supercapacitors according to the invention, the series resistance of the module is strongly reduced, due to the reduction in the number of junctions required between lid and coil as compared with a module comprising a plurality of standard supercapacitors.