WO2008074352A1

WO2008074352A1 - A method of filling a component with an anhydrous material and a component made by the method

Info

Publication number: WO2008074352A1
Application number: PCT/EP2006/012372
Authority: WO
Inventors: Alexander Bittner; Hans-Fabian Waibel; Manxi Zhu; Yongan Yang; Klaus Kern; Christoph J. Weber
Original assignee: Max-Planck-Gesellschaft Zur Förderung Der Wissenschaften
Priority date: 2006-12-21
Filing date: 2006-12-21
Publication date: 2008-06-26

Abstract

A method of filling at least one component, such as an electrochemical double layer capacitor or a lithium ion battery, having a relatively inaccessible structure in at least one of a porous and non-porous form and encapsulated in a housing with an anhydrous filling material, the method comprising the steps of: a) carrying out an initial drying process in which the encapsulated structure is subjected in a vacuum chamber connectable to an associated vacuum system to vacuum and heating conditions, b) carrying out a further drying process by filling the housing with a chemical drying agent using the vacuum present in the evacuated housing, with the chemical drying agent being adapted to take up residual water physisorbed and/ or chemisorbed on said structure and to volatilize under the prevailing vacuum and heating conditions, c) extracting the chemical drying agent using the vacuum system associated with the vacuum chamber and d) subsequently filling the evacuated housing with an anhydrous filling material fluid under the prevailing vacuum conditions. A component filled in accordance with the method is also claimed.

Description

A Method Of Filling A Component With An Anhydrous Material And A Component Made by The Method

The present invention relates to a method of filling at least one component with an anhydrous filling material, the component having a relatively inaccessible structure in at least one of a porous and non-porous form and encapsulated in a housing and also relates to a component made using the method.

There are various components in the electrical and electronic field which need to be manufactured in such a way that the amount of water con- tained therein is kept very small. For example, electrochemical double layer capacitors (EDLCs) use active carbon fixed on aluminum foils as an electrode material. Two such coated electrode foils are coiled up and mechanically separated from one another by the use of paper. The coils are then inserted into a housing and electrically connected to the base of the housing and to the cover which is mounted in an insulated manner.

Thereafter the capacitors are dried and filled with an electrolyte consisting of an organic solvent and a conductive salt and closed off. Through the use of electrochemically stable electrolytes it is possible to operate EDLCs with an operating voltage of over 2 V per individual cell.

Water residues in the capacitor and in particular in the active carbon due to incomplete drying are very damaging because gases arise through the electrolysis of water which lead to a pronounced mechanical loading of the active carbon coating and may initiate separation of the coating from the aluminum support foil. Through the electrolysis of water (which already takes place from 1.3 V onwards) the internal pressure of the capacitor can increase so that in an extreme case it can lead to the response of an intended point of breakage or of another device for the controlled discharge of a high internal pressure. Furthermore, residual water in the capacitor can interact chemically or electrochemically with the materials used there, for example by a reaction with the conductive salt that is used. This can lead to the formation of very reactive compounds such as for example hydrogen fluoride.

Similar problems can arise in other electrical components such as lithium ion batteries. Examples of patent applications relating to lithium batteries and their constituents can be found in the PCT application published as WO2004/034489 and in the European patent application 04018470.7 (attorney's ref M5489PEP2) the contents of which are incorporated herein by reference. Moreover, there are certain electronic components such as transistors or solar cells which can benefit from being encapsulated in ultra dry form.

The best possible drying of all materials thus leads to a considerable pro- longation of the working life and improvement of the technical data, in particular of the internal resistance and capacity.

It is current practice in the industry with regard to the manufacture of EDLCs to dry the coil inserted into the capacitor housing by vacuum and heat treatment; in some cases drying takes place in an energy and time intensive manner in vacuum at up to 20O⁰C for more than one day. Through the vacuum treatment (as a rule high vacuum) which takes a lot of time very high investments are required. Moreover, it is almost impossible using this method to remove water which is chemisorbed at the carbon surface. The object underlying the present invention is to provide a method for filling components, in particular electrical and electronic components, while taking steps to avoid or remove residual amounts of water therein, in an economical and efficient manner so that their working life and performance is improved and so that they are made safer and more reliable, and indeed in a way which preferably avoids unwanted contamination of the components.

It is also an object of the present invention to provide improved components as a result of the use of the method.

In order to satisfy these objects there is provided, in accordance with the present invention, a method of filling at least one component with an an- hydrous filling material, the component having a relatively inaccessible structure in at least one of a porous and non-porous form and encapsulated in a housing, the method comprising the steps of:

a) carrying out an initial drying process in which the encapsulated structure is subjected in a vacuum chamber connectable to an associated vacuum system to vacuum and heating conditions,

b) carrying out a further drying process by filling the housing with a chemical drying agent using the vacuum present in the evacuated housing, with the chemical drying agent being adapted to take up residual water physisorbed and/ or chemisorbed on said structure and to volatilize under the prevailing vacuum and heating conditions, c) extracting the chemical drying agent using the vacuum system associated with the vacuum chamber and

d) subsequently filling the evacuated housing with an anhydrous filling material fluid under the prevailing vacuum conditions.

The said at least one component is selected from the group comprising electrical components, micromechanical components, mechatronic components and electronic components. The said at least one component is preferably selected from the group comprising supercapacitors, electrochemical double layer capacitors, normal capacitors and lithium batteries.

The methods can be used both for electrodes and also for completely assembled and not yet filled capacitors.

In accordance with a first variant of the method of the invention the chemical drying agent is selected from the group comprising polar and non-polar compounds, short-chain alkanes, chloroalkanes, short-chain alcohols, esters, ethers, ketones, carbonates such as ethylene and propyl- ene carbonate; aromatics such as toluene, gases such as noble gases, nitrogen and hydrogen, carbon monoxide, N_xOy species, oxides of sulphur, aldehydes, alkenes and alkynes.

The chemical drying agent is preferably acetonitrile. This has the particu- lar advantage that, with an electrolyte for a lithium ion battery or EDLC, acetonitrile can also be part of the electrolyte composition so that residues of acetonitrile left in the component after drying thereof do not constitute contaminants. In this connection mention should be made of US patent 6,491,848 and its German equivalent DElOO 46 884Al . These two documents describe a method of pretreating an activated carbon for use as a polarized electrode comprising the steps of: - bringing an activated water-containing carbon for use as a polarized electrode into contact with an organic compound which forms an azeotropic mixture with water, so that the activated carbon is impregnated with the organic compound and

- drying the activated carbon impregnated with the organic compound with heat to remove the azeotropic mixture of the organic compound and the water contained in the activated water containing carbon.

In these prior art references the organic compound can be chosen from the group consisting of pentane, chloroform, diisopropyl ether, carbon tet- rachloride, vinyl acetate, acetonitrile, chlorobenzene, benzene, ethyl acetate, methyl ethyl ketone, 1,4-dioxane and methyl acetate.

In accordance with a second variant of the method of the present invention said chemical drying agent is a supercritical solvent selected from the group comprising: pentane, chloroform, diisopropyl ether, carbon tetrachloride, acetonitrile, chlorobenzene, benzene, ethyl acetate, methyl ethyl ketone, 1, 4-dioxane, methyl acetate, carbon dioxide, carbon monoxide, argon, hydrogen, ammonia gas, nitrogen monoxide, nitrogen, laughing gas (nitrous oxide), nitrogen dioxide, neon, N_xOy species, xenon, methane, ethyne, ethylene, ethane, propane, butane , sulphur dioxide, methanol, ethanol, 1-propanol, 2-propanol, ethyl-methyl ether, acetone, furane, iso- butane, diethyl ether, cyclopentane, 1-pentene, cis-2-pentene, trans-2- pentene, cyclohexane, hexane, toluene, o-xylenes , m-xylene, p-xylene, This variant is based on the concept that such supercritical solvents have not just an affinity for water but also a very low viscosity so that they can penetrate quickly into very small structures and pores of the component and pick up water chemisorbed or physisorbed on the structure, thus leading, on extraction of the supercritical solvent, to a highly efficient removal of water trapped in the component. The extraction by connection to a vacuum source is also highly efficient.

For the sake of completeness it should be pointed out that it is known in connection with the recovery of anhydrous electrolyte from lithium ion batteries, in connection with the recycling of the materials used and the refurbishing of batteries for reuse, to use supercritical carbon dioxide in order to remove residues of electrolyte. For this purpose carbon dioxide is admitted into the batteries and is heated and compressed until the critical region is reached. This process is described in WO03/06105 and in the equivalent US document US2003/0186110. In this way the carbon dioxide extracts even small residues of electrolyte from the battery electrode structure.

Drying with supercritical carbon dioxide is an extensively used method, for example for the drying and cleaning of micro- structured surfaces and porous materials. Thus, it is also known, in connection with the drying and cleaning of micro- structured and nano-structured systems in particular micro- structured surfaces and highly porous materials to pre-treat the materials with solvents of medium of low polarity and then to flush them with supercritical carbon dioxide. Through relaxation carbon dioxide, water and solvent are removed. This process is for example described in WO03/ 070846 and also in the Japanese patents JP 2004327894, JP 2004363440, JP 2004363404 and Taiwanese patent 567289. Supercritical fluids can be used in order to assist the formation of extremely fine structures. This relates for example to the manufacture of electrolyte films for fuel cells, as described in Japanese patent JP 2004119269, and for lithium ion batteries, in which polyether dissolved in the fluid is blown through a fine nozzle against the electrode surface, see for example also Japanese patent JP 2004234982. In order to produce aero gels, supercritical carbon dioxide is used in order to remove solvent from the precursors and thus to obtain an already formed gel scaffold. At the same time eventual shrinkage should be prevented and thus the high porosity guaranteed. This material is used amongst other things as a template for the formation of carbon electrodes for supercapacitors as described by R. W. Pekala, J. Mater. Sci 24 (1989) 3221, in WOO 1/28675 and in US patent 5864923.

In a third variant of the method of the invention the chemical drying agent is a substance reactive with water, e.g. a substance chosen from the group comprising: carbon dioxide (in critical or non- supercritical form), organic anhydrides including acetic acid anhydride (EA) and formic acid-acetic acid anhydride, ethylene oxide, phosgene, sulphur dioxide, sulphur triox- ide, N_xOy species, and thionyl chloride.

Such substances typically comprise molecules with a diameter of <2 nm and preferably less than 1 nm, so that they are also well adapted to penetrate fine structures and pores to remove phsyisorbed or chemisorbed wa- ter at and in such fine structures and pores.

Moreover, in accordance with a fourth variant of the method of the present invention, a solvent of the above named kind (as recited in claim 4) is advantageously used in a mixture with a supercritical solvent, e.g. a super- critical solvent from the selection recited in Table 1 incorporated into the description of Example 2 below.

Moreover, in accordance with a fifth variant of the method of the present invention, a supercritical fluid in accordance with Table 1 can be used to advantage in a mixture with a substance reactive with water in accordance with claim 8.

Finally, the present invention also relates to a component filled in accor- dance with any one of the preceding methods.

Thus, for the purpose of the invention, a series of methods is presented which are based on the use of gases and solvents, partly in the supercritical state, on reactive vapors and on temperature and pressure variations during drying.

The invention will now be described in more detail with reference to examples and the associated drawings in which:

Fig. 1 is a schematic drawing of one possible apparatus which can be used to carry out the method of the present invention,

Fig. 2 is a schematic diagram to explain the various stations used in the apparatus of Fig. 1 to carry out different operations,

Fig. 3 is a perspective illustration of an insert which can be used in the apparatus of Fig. 1 , Fig. 4 is a schematic diagram of the basic layout of a partly disassembled EDLC, this being a component which can be treated in the apparatus of Figs. 1 to 3,

Fig. 5 a possible reaction mechanism of acetic acid anhydride with adsorbed water,

Fig. 6 a possible reaction mechanism of carbon dioxide with adsorbed water.

Turning first of all to Figs. 1, 2 and 3, there can be seen a schematic illustration (not to scale) of an apparatus 10 which can be used for carrying out the method of the invention to fill a component such as an EDLC, of which a schematic drawing is shown in Fig. 4. As can be seen from Fig. 4 an EDLC basically comprises a housing 20 typically in the form of a deep drawn aluminum can or housing 20 having a cylindrical wall 22, a base 24 integral with the cylindrical wall and having a first terminal lug 26. A separate cover 28 having a central terminal lug 30 is provided. The cover 28 is shown removed from the cylindrical housing wall 22 in this embodi- ment to show the internal features of the EDLC, namely the two coiled together electrodes 32, 34 of carbon fixed on aluminum foil which are separated by insulators 36 of paper for example and filled in use with an electrolyte 38.

The one electrode 32 is bonded internally, e.g. by a lead 40 (or directly), to the base 24 and or to the cylindrical wall 22 of the housing and thus electrically connected to the first terminal lug 26. The other electrode 34 is bonded, via a lead 42 (or directly) to the cover 28 and thus to the terminal lug 30 or directly to the terminal lug 30. The cover is sealingly connected to the open end of the cylindrical housing wall 22, e.g. by a crimped con- nection at the crimping flange 44 with an insulator disposed therebetween (not shown) The cover 28 typically has a filling orifice 46 which enables the assembled EDLC to be dried internally and subsequently filled with electrolyte, the orifice then being sealed, e.g. with a plug of synthetic resin.

At the heart of the plant 10 there is a rotatable drum 52 having, in this example, six working stations I -VI, which are uniformly angularly distributed around the central longitudinal axis 54 of the drum. In each working station there is a respective insert 56 of which a perspective view can be seen in Fig. 3. It will be noted that each insert has six cylindrical recesses 58, each intended to receive an EDLC or another component to be filled. The drum 52 can be rotated around the vertical axis of rotation 54 by a stepping motor 60 connected to the drum 52 via an axle 62. At least the stations II, III and IV in Fig. 2 include a heater element 64 making it pos- sible to supply heat to the respective insert 56. The heaters 64 are electrically heated from the power supply 66 which is connected to the respective heaters via leads 68 and a slip ring arrangement 70.

As can best be seen from Fig. 2, EDLCs to be filled in accordance with the method of the invention are first loaded into the respective insert 56 in the loading station I. This can be done either by placing the capacitors individually into respective recesses 58 of the insert 56 or by placing an insert such as 56 with EDLCs present therein into the respective station of the drum 52. Thereafter, the stepping motor 60 is energized, for example un- der the control of a computer adapted to control all aspects of the method (but not shown), to rotate through 60° so that the insert 16 loaded in the loading station I moves to the vacuum station II.

There, the insert together with the six capacitors with fitted coils provided therein can be first flushed with argon from the source 72, which is con- trolled by the valve 74. The argon injected into the EDLC, e.g. by a needle inserted through the filling orifice 46 and emerging from orifice around the needle can either be exhausted to air or recollected via suitable manifolding and a pump for cleaning and reuse. The EDLCs in the station II are subsequently connected via a valve 76 to a vacuum present in a large vacuum chamber 78. The vacuum in the vacuum chamber can be produced in the usual manner by a combination of a turbo pump 80 and a membrane pump 82 evacuating the plenum chamber via a cooling trap 84.

Although not shown in Fig. 1, the vacuum unit comprising the valve 76, the vacuum chamber 78, the turbo pump 80, the membrane pump 82 and the cooling trap 84 can also be connected to the heating station III and to the filling and extraction stations IV and V shown in Fig. 2. This can be done by internal connections or flow passages within the drum (not shown) or alternatively by providing a separate vacuum system for each of the stations II, III, IV, V or for example by using two different vacuum systems, each connected to two of the stations or by some other suitable arrangement.

Once the vacuum has been generated in the vacuum station II, the drum is indexed further using the stepping motor 60 so that the insert previously in the vacuum station II now moves into the heating station III where it is heated by the respective heater 64 to drive off any residual wa- ter capable of being removed by heating and vacuum. Thereafter, the drum 52 is rotated further so that the insert is now located in the filling station IV where one or more chemical agents from pressurized supplies 90, 90' are admitted by respective valves 92, 92' into the area of the respective insert 56 and e.g. via a suitable injector into the partly or fully evacuated capacitors located in the recesses 58. The valves 92, 92' can be controlled by the associated computer (not shown) as can the valves 74 and 76. The chemical drying agent flows into and around the capacitor housings and removes residual water located therein by the processes which will subsequently be described in more detail. The chemical drying agent including the water it has taken up from the capacitor housings and the electrodes and separators provided therein can, for example, be subjected in the filling station IV to heating and pressurization (by the pressure of the supply source or by use of a suitable pump) to place the fluid in a supercritical condition.

Thereafter, the drum 52 can be rotated one step further so that the insert 56 under discussion reaches the extraction station V for the drying agent. This station V is again connected to the vacuum system or to a separate vacuum system permitting the chemical drying agent together with the water it has taken up or reacted with to be removed through the vacuum system. Thereafter, the drum 52 is indexed a further 60° so that the insert reaches the filling station VI still under vacuum. In the filling and sealing station the electrolyte required for the capacitor is injected into the capacitor from the pressurized supply 94 shown in Fig. 1 via the valve 96. The fact that the EDLCs are in an evacuated state when they reach the station VI greatly facilitates the filling thereof and avoids any unwanted bubbles. After withdrawing the electrolyte injection needle from the entrance to the orifice 46, this orifice in the capacitor housing is also sealed, so that the entire EDLC is sealed. Thereafter, the insert with the capacitor is indexed further to the station I where the finished capacitors are removed and fresh housings with electrodes are loaded into the now empty receiving positions of the insert 56. The just described process then repeats using the new insert. Naturally, there is an insert present in each of the stations at all times so that the treatments in each individual station can take place in parallel. It should be noted that this is just one simple example of a possible construction. Many other constructions will be apparent to the person skilled in the art. Moreover, many variants are possible on this basic structure. For example, there could be a different number of stations from six and the operations carried out in each station can be varied as desired. Thus, for example, the heating station III could be combined with the vacuum station II so that a separate heating station is unnecessary.

Moreover, the station IV for the filling of the capacitors with the drying agent could also be used for the extraction of the drying agent following drying, thus saving the need for a separate station V. The filling and sealing station VI could be divided into two separate stations - one for filling and one for sealing the capacitors. Also separate loading and unloading stations can be provided. Moreover, when loading and unloading the inserts 56, it is possible, instead of changing the capacitors present in the inserts, to change the inserts with the capacitors contained therein.

These are only some of the examples of how basic equipment could be var- ied and many others will be readily apparent to the person skilled in the art.

Some examples will now be given of the way the invention is carried out in practice with reference also where appropriate to the accompanying draw- ings. Using the methods described herein an improved drying of the electrode and of the entire capacitor is achieved. The methods relate to the shifting of the absorption equilibrium and can be carried out using five different variants, for which examples will now be given.

Example 1 (Variant 1) This method of treating materials, especially carbon materials, relates to the use of solvents, such as acetonitrile, or any of the other solvents listed in claim 4, which are introduced into the components to be treated, e.g. by injection through a hollow needle on Station IV of the apparatus of Figs. 1 to 3. The method operates by a shift of the adsorption equilibrium. More specifically, through the large excess of the solvent a displacement of the absorbed water arises which is then removed. The equilibrium equation can be formulated as

H₂Oads + LM is LMads + H₂O

r ₊• LM_ads * H₂0 „

Law of mass action: — — = K_aHe

H₂O_ads * LM ^ads

where LMads = adsorbed solvent, H2θ_ads = adsorbed water, Kads = equilibrium constant for adsorption

In accordance with the principle of Le Chatelier the increase of the solvent concentration brings about a reduction of the concentration of the ad- sorbed water. Moreover, the desorption of the water is free of mixing entropy which additionally favors the process energetically.

Apart from acetonitrile other polar and non-polar compounds are also advantageous which are not used as solvents in the electrodes. In particular short-chain alkanes, chloroalkanes, short-chain alcohols, esters, ethers, ketones, carbonates such as ethylene and propylene carbonate; aromatics such as toluene, gases such as noble gases, nitrogen and hydrogen are also suitable. Furthermore, carbon monoxide, N_xOy species, oxides of sulphur, aldehydes, alkenes and alkynes are considered. The solvent with the water dissolved therein is then conveniently removed in station V prior to the filling of the component with the desired anhydrous substance in station VI.

Example 2 (Variant 2)

In this variant, the coil of an EDLC is impregnated with a supercritical solvent such as supercritical carbon dioxide or any one of the further compounds listed in Table 1.

TABLE 1

Substances from the accompanying table 1 are suitable for use for supercritical drying even though the table 1 is not necessarily complete. As described above, mixtures of these substances are also possible.

Again, the drying can take place by injection of the supercritical fluid into the interior of the component through a hollow needle in station IV of the apparatus described in connection with Figs. 1 to 3. This has the advantage that a liquid with extreme creeping capability can penetrate into the highly porous structure of the active carbon electrodes. This method step is concluded within seconds or a few minutes. Supercritical carbon dioxide is non-polar and thus wets graphitic structures better as described by T. Clifford in Fundamentals of Supercritical Fluids, Oxford University Press 1999.

Supercritical carbon dioxide also offers further advantages for drying processes; the extremely small surface tension between the gas and the liquid phase, the high transport coefficients and the characteristics that can be readily controlled by pressure temperature and additives can serve to effectively remove water adsorbed on surface and in pores and/ or to transport them out of the porous structure. Through the large excess of carbon dioxide relative to the adsorbed water, the water content in the extract always remains very low so that no saturation is achieved and also the supercritical characteristics cannot be changed. A re-adsorption is thus very effectively suppressed. The supercritical solvent can again be removed in station V prior to filling the component with the anhydrous electrolyte or other anhydrous medium in station VI by exploiting the vacuum generated in the component in station V and also avoiding unwanted contamination by contact with a moist environment such as ambient air.

As indicated above, Table 1 presents further gases and liquids which are likewise suitable. The method is particularly advantageously carried out with short-chain alkanes, for example pentane, the drying action of which is excellent even at sub-critical conditions and with acetonitrile which does not leave any contamination because it is in any event a component of the finished capacitors. Nitrogen is to be emphasized because relatively low pressures for example >34 bar and room temperature lead to the supercritical state and because it is chemically almost completely inert. Through relaxation and recompression, the dissolved water can be re- moved very simply and the gas can be guided in a circuit if desired.

Example 3 (Variant 2)

This example specifically refers to carbon structures located within the component to be filled, with the treatment being carried out using supercritical CO2. This method has proved to be particularly advantageous because it can easily be carried out and leads to careful treatment of the samples. Moreover, no waste products occur when using CO2, since only CO2 and the carbonic acid which arises in the process remain after the treatment. CO2 requires pressures above 73 atm (7.38 MPa) and simultaneously temperatures above 31⁰C (304 K) to become supercritical (Handbook of Chemistry and Physics 80^th edition 1999-2000). Water is readily soluble in supercritical CO2 and small proportions (up to 10 %) of water change the behavior of the supercritical phase to only a small degree as described by K. Tόdheide and E. U. Franck in Z. Phys. Chem. Neue Folge 37 (1963], 387.

Example 4 (Variant 2)

When using CO2 as a supercritical solvent, the method described with reference to Figs. 1 to 3 does not have to be used. Instead, an autoclave provided with a gas feed and gas discharge line is loaded with the capacitors to be dried and with a previously calculated quantity of dry ice (solid CO2) sufficient to remove all water possibly contained therein. Dry ice has the advantage that it is the readily available as the solid form of carbon dioxide.

The autoclave is then closed (sealed) and is heated up to supercritical temperature. After a certain time the system is cooled down and the gas exhausted. The capacitors are filled with the anhydrous electrolyte and sealed under a carbon dioxide atmosphere. Carbon dioxide is heavier than air and water vapor so that no water can penetrate prior to filling and sealing of the component.

This method can also be used with other supercritical fluids. The autoclave is typically heated to a temperature of ca. 20° K above the critical temperature (i.e. kept at room temperature, when the critical temperature lies below O⁰C) and thereafter the pressure (at least a few % above the critical pressure) is produced by compression of the supplied gas. When advantageous from the point of view of the technology of the plant that is used higher pressures or temperatures can be set. The pressure build-up can take place with the aid of compressors when using the pure substance which is to be converted into the supercritical state. As an alternative to this the pressure build-up can also take place with the aid of compressed gases which flow into the pressure-type reaction chamber.

Example 5 (Variant 3)

As a further new method, reactive drying will be described. In this method, substances reactive with water, for example CO2, and organic anhydrides such as acetic acid anhydride (EA), formic acid-acetic acid anhydride, ethylene oxide, phosgene, sulphur dioxide, sulphur trioxide, N_xOy species, thionyl chloride are used in order to remove water quantitatively and irreversibly. Molecules with a diameter of <2 nm can sensibly be used which are thus in a position of being able to wet macro-pores and meso-pores of the active carbon. The above-named molecules which have a molecular diameter of < 1 nm are however particularly advantageous. They are thus able to wet the active carbon structure right into the micro-pores and meso-pores from which the water residues can only be removed by conventional methods with great effort (temperature, pressure, time) if at all. Again, the substance selected is conveniently injected through a hollow needle into the component in station IV of the apparatus of Figs. 1 to 3 and subsequently removed again by the vacuum system in station V prior to filling with component with anhydrous electrolyte in station VI.

The excess of educt and also the adsorbed reaction products are thus driven out from the capacitor by vacuum/ temperature. With reference to the exemplary reaction of EA with water the method thus proceeds as follows:

x (CH₃CO)₂O + y H₂Oads → 2y CH₃COOH + (x-y) (CH₃CO)₂O Eq. 1 With respect to equation 1 : acetic acid anhydride is relatively non-polar (2 phases can be recognized on mixing with water, acetic acid is dissolved in the anhydride so that only 1 phase remains) whereby the adsorption onto the hydrophobic graphene layers is favored. Water is principally bound to the polar sites (i.e. the functional sites) of the activated carbon. Through the adsorbed reactive acetic acid anhydride molecule it is possible to bind the adjacent water molecules irreversibly as indicated in Fig. 5. Since acetic acid is less polar than water, the desorption from the polar sites is easier. Through complete vaporization of the acetic acid/ acetic acid anhy- dride mixture anhydrous carbon is obtained. pH measurements of the carbon showed that the mixture could be completely removed. A suspension of activated carbon treated in this way did not react acidically.

Example 6 (Variant 3)

This example is similar to the previous one except that CO2 in non- supercritical form is used instead of EA.

For CO2 the following reaction is expected:

x CO2 + y H2θads → y H2CO3 + (x-y) CO2 Eq. 2

With regard to equation 2: CO2 reacts with the adsorbed water molecules and thus weakens the binding of the water to the substrate as indicated in Fig. 6. In this way, the desorption is facilitated and the carbonic acid is completely removed by the vaporization (with the gas flow). By subsequent impregnation of the carbon with the electrolyte the CO2 is driven out completely.

Example 7 (Variant 4) A combination of the above drying methods is used here.

One example relates to the use of a solvent from claim 4 (here acetonitrile AN and an anhydrous substance from claim 8 (here EA).

The following reaction takes place:

x (CH₃CO)₂O + y.H₂Oads —^→ 2y CH₃COOH + (x-y) (CH₃CO)₂O

x = excess components

In this method, small quantities of an anhydrous substance are mixed with the above-described solvents prior to introduction into the compo- nent in station IV, or by simultaneous introduction into the component via respective hollow needles in station IV. This mixture of substances is able to react quantitatively and irreversibly with water in the active carbon structure. The excess of educt and also the reaction products are taken up by the liquid material phase and removed by vacuum/ temperature from the capacitor in station VI. The use of AN as a solvent again has the advantage that it is non-contaminating.

Example 8 (Variant 5)

This example is similar to the last one but here a combination of a substance reactive with water in accordance with claims 7 or 8 is used with a supercritical fluid. Here, the excess of educt and also the reaction products are taken up by the supercritical fluid phase and removed either by vacuum/ temperature or by convection.

The invention is particularly applicable, without restriction, to EDLCs with carbon electrodes but can also be used with EDLCs with non-carbon electrodes, for example EDLCs which use metal oxide electrodes.

Claims

1. A method of filling at least one component having a relatively inaccessible structure in at least one of a porous and non-porous form and encapsulated in a housing with an anhydrous filling material, the method comprising the steps of:

a) carrying out an initial drying process in which the encapsulated structure is subjected in a vacuum chamber connectable to an as- sociated vacuum system to vacuum and heating conditions,

b) carrying out a further drying process by filling the housing with a chemical drying agent using the vacuum present in the evacuated housing, with the chemical drying agent being adapted to take up residual water physisorbed and/or chemisorbed on said structure and to volatilize under the prevailing vacuum and heating condi- - tions,

c) extracting the chemical drying agent using the vacuum system as- sociated with the vacuum chamber and

2. A method in accordance with claim 1 , wherein said at least one component is selected from the group comprising electrical components, micromechanical components, mechatronic components and electronic components.

3. A method in accordance with claim 1 or claim 2, wherein said at least one component is selected from the group comprising superca- pacitors, electrochemical double layer capacitors, normal capacitors and lithium batteries.

4. A method in accordance with any one of the preceding claims wherein the chemical drying agent is selected from the group comprising polar and non-polar compounds, short-chain alkanes, chloro alkanes, short-chain alcohols, esters, ethers, ketones, carbonates such as ethylene and propylene carbonate; aromatics such as toluene, gases such as noble gases, nitrogen and hydrogen, carbon monoxide, N_xOy species, oxides of sulphur, aldehydes, alkenes and alkynes.

5. A method in accordance with any one of the preceding claims wherein the chemical drying agent is acetonitrile.

6. A method in accordance with any one of the preceding claims 1 to 3 wherein said chemical drying agent is a supercritical solvent se- lected from the group comprising: pentane, chloroform, diisopropyl ether, carbon tetrachloride, acetonitrile, chlorobenzene, benzene, ethyl acetate, methyl ethyl ketone, 1, 4-dioxane, methyl acetate, carbon dioxide , carbon monoxide, argon, hydrogen, ammonia gas, nitrogen monoxide, nitrogen, laughing gas (nitrous oxide), nitrogen dioxide, neon, N_xOy species, xenon, methane, ethyne, ethylene, ethane, propane, butane , sulphur dioxide, methanol, ethanol, 1- propanol, 2-propanol, ethyl-methyl ether, acetone, furane, isobu- tane, diethyl ether, cyclopentane, 1-pentene, cis-2-pentene, trans-2- pentene, cyclohexane, hexane, toluene, o-xylene , m-xylene, p- xylene,

7. A method in accordance with any one of the preceding claims wherein said chemical drying agent is a substance reactive with water.

8. A method in accordance with claim 7 wherein said substance is chosen from the group comprising: carbon dioxide, organic anhydrides including acetic acid anhydride (EA) and formic acid-acetic acid anhydride, ethylene oxide, phosgene, sulphur dioxide, sulphur trioxide, N_xOy species, and thionyl chloride.

9. A method in accordance with claim 7 or claim 8 in which said substance comprises molecules with a diameter of <2 nm and preferably less than 1 nm.

10. A method in accordance with claim 6 wherein a solvent in accordance with claim 4 is simultaneously used.

11. A method in accordance with claim 10 wherein the solvent is ace- tonitrile.

12. A method in accordance with claim 11 wherein the chemical drying agent includes (CH3CO)2O and the drying proceeds in accordance with the reaction

x (CH₃CO)₂O + y H₂O₃CiS —^→ 2y CH₃COOH + (x-y) (CH₃CO)₂O

here x signifies excess components and y is a number depending on the amount of water absorbed.

13. A method in accordance with claim 4 and claim 7 wherein a substance reactive with water and a supercritical fluid are simultaneously used as the chemical drying agent.

14. A method in accordance with any one of the preceding claims wherein the component is subsequently filled with a composition containing as ingredient a chemical used as the chemical drying agent.

15. A method in accordance with claim 14 wherein the composition comprises an electrolyte and the chemical drying agent is or comprises acetonitrile.

16. A method of filling a plurality of components having a relatively in- accessible structure in at least one of a porous and non-porous form and encapsulated in a respective housing with an anhydrous filling material, the method comprising the steps of:

a) optionally carrying out an initial drying process in which the encap- sulated structure is subjected in a vacuum chamber connectable to an associated vacuum system to vacuum and heating conditions,

b) carrying out a drying process or a further drying process by placing the housings in an autoclave, filling the autoclave with a chemical drying agent comprising a quantity of a supercritical fluid in sub- critical liquid or solid form,

c) providing an atmosphere of a gas phase of the supercritical fluid in the autoclave, d) heating the autoclave to a temperature above the critical temperature for the supercritical fluid and raising the pressure of the gas phase of the supercritical fluid in the autoclave to a pressure level at which the supercritical fluid is in the supercritical state, either by the supply of further supercritical fluid into the autoclave in thegas phase or by formation of the gas phase by the action of heat on the supercritical fluid in liquid or solid form, with the chemical drying agent in the supercritical state being adapted to take up residual water physisorbed and/ or chemisorbed on said structure and to volatilize under the prevailing vacuum and heating conditions,

e) cooling down the components and exhausting the supercritical fluid, e.g. in the gas phase, and subsequently filling the housings in evacuated form or under a gas atmosphere, e.g. a gas phase of the supercritical fluid, with an anhydrous filling material fluid under the prevailing conditions.

17. A method in accordance with claim 16 wherein the supercritical fluid comprises carbon dioxide.

18. A method in accordance with claim 17 wherein the carbon dioxide is present in the solid form ("dry ice").

19. A component filled in accordance with any one of the preceding methods.