FI128050B - LAYER THIN FILM PACK AND A METHOD FOR MANUFACTURING A PACK - Google Patents

Abstract

The invention is concerned with a stacked thin-film layered battery pack of the invention and comprises at least a first cell (110a) and a second cell (110b), which are connected in series. Each cell (110a, 110b) comprises an anode part and a cathode part. The battery pack of the invention is mainly characterized in that the cells (110a, 110b) are series-5 connected through a common substrate (1a) between the cells (110a, 110b). The common substrate (1a) has one or more vias with conductive material thereby providing an electrical connection between the cathode part of the first cell (110a) and the anode part of the second cell (110b). The invention is also concerned with a method of manufacturing such a battery pack.

Description

A STACKED THIN-FILM BATTERY PACK AND A METHOD FOR MANUFACTURING SUCH A BATTERY PACK

TECHNICAL FIELD

The invention is concerned with a stacked thin-film battery pack comprising two or more cells, each cell comprising an anode with an anode current collector, a cathode with a cathode current collector, a separator, and electrolyte. The invention is also concerned with a method for manufacturing such a battery pack.

20175594 prh 11 -06- 2018 io BACKGROUND

An electric battery consists of one or more electrochemical cells that convert stored chemical energy into electrical energy and have external connections provided to power electrical devices. Each cell contains a negative electrode, which is called anode, and a positive electrode, which is called a cathode. The basic components of a battery are the electrodes 15 with terminals to connect to an external circuit, a separator to keep the electrodes apart and prevent them from shorting, an electrolyte which carries the charged ions resulting from the chemical reactions taking place at the electrodes and a cover to contain the active chemicals and hold the electrodes in place. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work. All batteries 20 utilize similar procedures to create electricity; however, variations in materials and construction have produced different types of batteries.

One battery type consists of a layered structure, i.e. those called thin-film batteries or just thin batteries. The thin-film batteries, which term in this text is to be understood as “layeredstructured” batteries can be deposited directly onto circuit boards or vice versa. These 25 batteries can be formed into any shape and the layers can be stacked, further reducing space. In a stacked construction of a thin battery, the layers are directly on top of each other.

In thin-film batteries, the cathode can e.g. consist of manganese dioxide and the anode of zinc. The electrolyte can consist of e.g. ammonium chloride and/or zinc chloride dissolved

20175594 prh 11 -06- 2018 in water but is not restricted to these. The zinc is oxidized at the negative anode electrode and the manganese dioxide is reduced at the positive cathode electrode.

The whole thin-film battery usually consist of a substrate, an electrolyte, one or more current collectors, an anode, a cathode, and a separator.

The current collectors are generally designed to extend outwardly from the battery cell in the form of extensions in order to be connected to an external circuit. The current collector material can be conductive carbon ink, carbon film or other material, which is chemically inert but conductive enough for the purpose.

In thin-film batteries, the electroactive materials that the electrodes consist of are io advantageously in the form of a paste on the current collector. The separator in thin-film batteries can e.g. consist of paper.

It is possible to vary the total voltage, current and current in batteries by connecting them in different ways in a circuit, the two simplest ways of these being called series and parallel connection. Components connected in series are connected along a single path, so the 15 same current flows through all the components. Components connected in parallel are connected so that the same voltage is applied to each component.

Batteries in series have the positive end of one battery connected to the negative end of the next battery. Batteries correctly placed in series, positive to negative, will add their output voltages, producing a greater voltage.

Two batteries in parallel need to have a connection between the positive ends of both batteries and another connection between the negative ends of both batteries. When connecting in parallel, the capacity (amp hours) of the two batteries is doubled compared to only one while maintaining the voltage of the individual batteries.

Several methods have been used for connecting the terminals of adjacent cells in a series 25 connection. The terminals maybe soldered together and especially cells of flat type, such as thin-film batteries, maybe connected together merely by physical contact between the surfaces of the opposite electrodes of adjacent cells.

One of the basic requirements for batteries is a low resistance. The lower the resistance, the less restriction the battery encounters in delivering the needed power spikes. This is

20175594 prh 11 -06- 2018 especially important in batteries connected in series since, the total resistance of a battery will be equal to the sum of the internal resistances of the individual cells.

A prior art solution is presented in WO publication WO 01/41232, which discloses an ultrathin assembly construction for energy storage.

SUMMARY OF THE INVENTION

The stacked thin-film layered battery pack of the invention comprises at least a first cell and a second cell, which are connected in series. Each cell comprises an anode part and a cathode part. The battery pack of the invention is mainly characterized in that the cells are io series-connected through a common substrate between the cells. The common substrate has one or more vias with conductive material thereby providing an electrical connection between the cathode part of the first cell and the anode part of the second cell.

The method of the invention for manufacturing a stacked thin-film layered battery pack comprises steps in which a substrate is perforated to have one or more holes. The holes are 15 at least partly filled by printing layers of conducting material on both sides of a first substrate.

A first cell, which comprises a cathode part and an anode part, is formed by printing layers on the first substrate. A second cell, which also comprises a cathode part and an anode part, is formed by printing layers on a second substrate. The cells are combined against each other by placing the first cell on the second cell with the first substrate between the 20 cells. The substrate thereby provides an electrical connection between the cathode part of the first cell and the anode part of the second cell.

The preferably embodiments of the invention have the characteristics of the sub claims.

The electrical connection formed by the conductive material in the via(s) works as one or more conductors through the common substrate, which substrate thereby becomes an intra25 connection part between the cells. The vias are located within the area of cathode collector, preferably at or near the center of that area.

The conductive material is preferably connected to a cathode current collector of one cell and an anode current collector of the other cell, the cathode current collector being connected to the cathode layer of the first cell and the anode current collector being 30 connected to the anode layer of the second cell. Thus, the anode part of the second cell and

20175594 prh 11 -06- 2018 the cathode part of the first cell are connected through the vias in the substrate between the cells. The conductive material forms a coherent silver conductor in the vias between the cells and is advantageously silver or other suitable conducting material.

The layer of conductive material have extension parts for forming an interconnection part 5 that form one or more positive terminals to connect the battery pack to an external electronic device.

The stacked battery of the invention can furthermore be characterized by a combination of a conductive adhesive, partly covering the anode layer, and a non-conductive two-sided adhesive, having an opening for said conductive adhesive and covering the rest of battery io pack area. The surface of the conductive adhesive thereby forms a negative terminal for the battery pack.

The area of the common substrate is smaller than that of the substrate of the second cell so that the two-sided, non-conductive adhesive tape joints and seals the cells by facing the edges of the substrates.

The conductive tape is placed so that it partly covers an anode layer in the first cell in order to work as an anode current collector in the anode part of the first cell. A non-conductive two-sided adhesive tape with an opening is placed so that a part of the surface of the conductive tape is left exposed. In that way, the surface of the conductive tape can be a negative terminal for the battery pack and the uncovered surface of anode layer can form the minus terminal of the battery pack through the conductive tape.

The area of the first substrate, which will be the common substrate is made smaller than that of the second substrate of the second cell in order to joint the cells together by means of the two-sided adhesive in a way that it faces the edges of the substrate of the second cell.

The battery pack has a low resistance thanks to the connections in the middle of the layers 25 of the battery. The fact that the current flows in from the middle of the anode there is a short way for the current to flow everywhere in the battery.

In the following, the invention will be described by means of some preferable embodiments for the inventive battery pack and the manufacturing of such battery pack. It is pointed out that the invention is not restricted to the details of these embodiments.

20175594 prh 11 -06- 2018

TERMS USED

The following terms are used in this text

An electrode is the electroactive species of a battery, wherein electron transfer occurs. An electrode is either an anode (electrode) or a cathode (electrode)

An anode is the negative electrode at which the electrons leave the cell and oxidation occurs

A cathode is the positive electrode at which electrons enter the cell and reduction occurs

A cell is short for an electrochemical cell consisting of two half-cells generating the electrical energy from chemical reactions at the electrodes. One of the half10 cells constitutes an anode part and the other one a cathode part

A current collector is a material that the electrodes in thin film batteries are connected to for providing a conducting path for the electrons to and from the electrodes and that receives electrons from the external circuit

An anode current collector is the current collector associated with the anode

A cathode current collector is the current collector associated with the cathode

An anode part comprises, in this text, an anode current collector, an anode layer and a separator

A cathode part comprises, in this text, a cathode current collector and a cathode layer

A battery comprises at least one cell, having an anode part and a cathode part, electrolyte, a separator, terminals and a cover

A battery pack is a set of at least two individual batteries configured in a series, parallel or a mixture of both

A stacked battery comprises one or more cells directly on top of each other

The intra-connection part is a substrate between the cathode part of one cell and the anode part of a neighboring cell, which substrate comprises (silver) conductors, which are electrically connected through the substrate.

20175594 prh 11 -06- 2018

Interconnection part is the substrate of the second (lower) cell providing means to connect the battery pack to an external (electrical) device.

A substrate is a sheet on which the necessary conductive and / or electrochemical layers are printed or built, typically of polyethylene terephthalate or paper.

FIGURES

Figures 1 - 9 illustrates the steps of an embodiment of the method of the invention for the manufacturing of the inventive battery pack of the invention, wherein

Figures 1 - 3 mainly describe the manufacturing of the cathode parts of the io battery pack of the invention

Figures 4-6 mainly describe the manufacturing of the anode parts of the battery pack of the invention

Figures 7-9 mainly describe the combination of the anode parts and of the cathode parts into a battery pack of the invention

Figure 10 is a perspective side view of the battery pack of the invention (with the layers apart for illustrative purposes)

Figure 11 is a cross-section of the battery pack of the invention (with the cells apart for illustrative purposes

DETAILED DESCRIPTION

Figure 1 illustrates the first steps of a method of the invention for the manufacturing of the inventive battery pack of the invention.

A substrate 1 is provided as the first step of the method of the invention.

Figure 1a shows a substrate 1a, which is folded so that parts of both the bottom side of the 25 substrate and top side of the substrate can be seen.

Figure 1 b shows the top side of a substrate 1 b.

20175594 prh 11 -06- 2018

Cathode parts will be prepared on the substrates 1a, 1b. The manufacturing could also be performed by preparing the cathode parts on a common substrate big enough for this purporse.

The substrates 1a, 1b typically consists of Poly-Ethylene-Terephtalate (PET). The substrate 5 dimensions are selected somewhat bigger than the intended size of the battery to be manufactured. The battery to be manufactured usually has a length of ca 5 - 10 cm and a breadth of ca 2 - 3 cm, such as 7,0 cm and 2,5 cm.

Holes 2 in a row in the middle of the breadth of substrate 1a are provided through the io substrate along a distance in order to arrange for one or more vias, preferably several vias, typically 5-10 vias, for interconnection of batteries. The vias, which are on certain mutual distances, such as ca 0,2 - 0,5 cm, from eachother, provide for an electrical connection between the anode of one cell and the cathode of another cell. Each via is a vertical interconnect access in the electrical connection between the layers of the cells and goes 15 through the plane of the substrate 1 a. The substrate thereby forms an intra-connecting part between the cells. An exact number is not critical even if an improved performance is achieved with a higher number.

Layers of silver ink is printed on both the bottom side and the top side of substrate 1a to form a conductive pattern. Alternatively, carbon C or other suitable conductive material can 20 be used instead of silver.

The printing of the silver layers is performed so that one silver layer is printed as a conductive layer 3c on the bottom side 1 of the substrate 1a on the holes 2. The size and form of the first conductive layer 3c is sufficient so that, as a consequence of the printing of the conductive layer 3c, the holes 2 will at least partly be filled with silver and an oblong layer of 25 silver extending over the holes 2 is formed.

There is furthermore a second conductive layer 3a of silver printed on the other side, i.e. the top side of the substrate 1a over the already filled holes 2. Alternatively, the second conductive layer 3a is printed first, which then would fill the holes 2 first.

Furthermore, there is, as illustrated by figure 1 b, a third conductive layer 3b of silver to be 30 printed on another substrate 1b of the top side of substrate 1b. Substrates 1a and 1b can also be part of the same substrate, whereby the third conductive layer 3b would be printed

20175594 prh 11 -06- 2018 on a distance from the second conductive layer 3a. When we, in this text, say “another substrate”, the expression also covers “another part of the substrate”.

The design of the conductive layers 3a, 3b of silver on the top side of the substrates 1a, 1b (or substrate parts) is for example advantageously a “rake”, these layers 3a, 3b being formed 5 to consist of an extended oblong or rectangular part with transversal arms along the extended part for improved conductivity. In addition, two of the arms of the third conductive layer 3b have extensions to end up as positive terminals 5a, 5b, one of which is for testing purposes.

io Figures 2a and 2b show cathode current collector layers 6a, 6b printed on the second and third printed conductive layers 3a, 3b of silver, respectively. The cathode collector material in the layers 6a, 6b consists of conductive ink, such as carbon ink, in liquid form, and is preferably printed in the form of a patterned layer. Such an ink conducts electricity and can comprise graphite or soot or the like and/or other conductive material. The conductive layers 15 3a, 3b of silver should be completely covered and the design of the patterned and printed layers 6a, 6b is for example in the form of a rectangle and extend over the conductive layers.

Layers 7a and 7b of cathode paste are then printed on the cathode current collector layers 6a and 6b, respectively, which is illustrated by figures 3a and 3b. The cathode paste 20 comprises e.g. manganese dioxide MnCte as the active cathode material and then electrolyte, such as zinc chloride (ZnCL·), that carries the charged ions between the anode and cathode electrodes.

Two cathode units have now been prepared. In this text, and to facilitate the description,

- the first cathode unit is here called the one of the separately manufactured part of the cell, 25 which before combining with the anode unit comprises substrate 1a, the cathode part, which comprises the second conductive layer 3a on the top side of the substrate 1a, the cathode current collector 6a, and the cathode paste layer 7a,

- the second cathode unit is here the one of the separately manufactured part of the cell, which before combining with the anode unit comprises the substrate 1 b, the cathode part consisting of the third conductive layer 3b with the terminal extensions 5a, 5b on the top side of the substrate 1 b, the cathode current collector 6b and the cathode paste layer 7b.

20175594 prh 11 -06- 2018

One or more anode units are separately prepared in parallel with the cathode units by printing anode material, such as anode ink, on a separate substrate or substrates as is illustrated by figures 4a and 4b. The active anode material can be e.g. zinc and the anode material in the whole can contain additional substances, such as conductive carbon, binders 5 and solvents. The substrate(s) 9a, 9b (see figures 4a, 4b) can be made of paper and they act as separators between the electrodes.

The anode material, such as anode ink, is printed as a first anode layer 8a on substrate 9a and as a second anode layer 8b on a second substrate 9b. The substrates 9a and 9b can naturally be parts of the same substrates as well.

io In this stage of preparing the anode units, excess substrate can be cut away in order to manufacture the anode units in pieces to fit the size of the layers of the cathode parts. The substrates 9a, 9b can be cut into suitable sizes before or after the printing of anode paste on them.

The applying of the anode material layers can take place by printing or coating a thin film of 15 anode material paste in a certain pattern on the separator. The printing can be performed by flat bed or rotary screen printing equipment.

Figures 5a and 5b illustrates placing pieces 10a and 10b of conductive material, such as of adhesive tape, on the anode layers 8a and 8b. The adhesive tape can be of isotropic or 20 anisotropic type, but is preferably isotropic. The pieces of conductive material are bigger than the second and third conductive layers of silver 3a and 3b and smaller than the anode layers 8a, 8b. The pieces of conductive material 10a and 10b act as anode current collectors.

The pieces 10a and 10b can be placed before or after the cutting of the anode parts in suitable sizes (before or after removing of excess substrate).

Two anode units have now been prepared. In this text, and to facilitate the description,

- one anode unit is here the one of the separately manufactured parts of the cell, which before combining with the cathode unit comprises the separator 9a, 9b, the anode (ink)

20175594 prh 11 -06- 2018 layer 8a, 8b, and the conductive adhesive tape 10a, 10b placed on the anode layer 8a,

8b.

As illustrated by figures 6a and 6b, the anode units comprising the substrates 9a, 9b and 5 the anode layers 8a and 8b with the pieces of conductive tape 10a, 10b on are then placed on the cathode units.

The dotted lines in figures 6a and 6b indicate in which extent excess substrate will be cut before the combining. The area of the first cell in figure 6a of the remaining substrate of 1a should be smaller than that of substrate 1 b so that a the to-be assembled non-conductive io double-sided adhesive tape 11 can form protective seams for both cells.

There are now two preliminary cells, which will be combined in a later stage. Before combining the first preliminary cell is on the substrate 1a and the second preliminary cell is on substrate 1 b.

In the next step of the manufacturing, excess substrate material is cut off from around the cells 110a and 110b so that the substrate area of cell 110b is slightly larger than that of cell 110a, and the substrate area of cell 110a is slightly larger than the other layers of that cell.

As illustrated by figure 7, the preliminary cells are then combined by placing the first 20 preliminary cell 110a on the second preliminary cell 110b. Excess substrate material 1a is removed from the first preliminary cell optionally before combining.

The combination is performed by placing the preliminary cells on each other so that the conductive layer 3c of silver on the bottom side of the substrate 1a is against and faces the piece of adhesive tape 10b, which piece of adhesive tape 10b partly covers the anode layer 25 8b.

After combining, the conductive layer of silver 3c is considered to belong to the cell 110a and the remaining substrate part 1a (what is left from substrate part 1a after cutting) to belong to both the cell 110a and the cell 110b. Otherwise the first preliminary cell corresponds to the first cell 110a and the second preliminary cell corresponds to the second cell 110b.

Thus,

- cell 110a corresponds to the first preliminary cell + the first conductive layer 3c of silver

- cell 110b corresponds to the second preliminary cell (without the first conductive layer of silver, substrate 1 a belonging to both cells 110a and 110b.

20175594 prh 11 -06- 2018 io As a result, as shown in figure 8, there are now two cells 110a, 110b stacked on each other and connected in series as a result. The first conductive layer 3c of silver is in contact with the second conductive layer 3a of silver via the holes 2 made in substrate 1a, which holes 2 are filled with silver as a result of the printing of the conductive layers on both sides of the substrate 1a.

If the stacked battery pack to be manufactured is connected to a circuit board, the conductive adhesive tape 10a will face the circuit board and work as a minus terminal in such a combination.

The conductive layers 3a, 3c of silver filling also the holes 2 therebetween are thus arranged to constitute a silver conductor that coherently interconnects the cells 110a, 110b.

After combining the preliminary cells into a battery pack, the next step is to apply a nonconductive double-sided adhesive tape 11 on the stacked battery pack as illustrated by figures 8 and 9. Tape 11 is also against the edges of the protruding substrate 1a material by facing the edges of it and by thus sealing the edges of cell 110b and the joint between 25 the cells 110a, 110b and isolating them from each other. There is then no way for the ions in the chemical electrode reactions to transfer via the edges since the double-sided tape 11 secures the joint.

The double-sided tape 11 also works as a medium for connecting electronics physically to the battery. There is an opening in the non-conductive tape 11 so that the anode layer 8a and the conductive tape 10a can be a minus terminal for an external electronic device.

The stacked cells 110a, 110b thus have their own separators, 9a and 9b and share a 5 common substrate 1a.

The refinement of the stacked battery pack of the invention is that the common substrate 1a is the “roof” (or top surface) for one of the cells 110b and simultaneously the “floor” (or bottom surface) for the other cell 110a. In other words, the anode of one cell, i.e. cell 110b, is on the bottom surface 1c of substrate 1a and the cathode of the other cell, i.e. cell 110a, is on io the top surface 1 d of the same substrate 1 a. The vias are realized through the substrate 1 a.

The two cells are thus connected in series effectively. The voltage of such a battery pack is a sum of individual cell voltages, and the capacity is the same as that of a single cell.

20175594 prh 11 -06- 2018

The structure of the stacked battery pack now made can be more illustratively seen in figure 15 10 in cross-section. The preliminary cells are shown separated for illustrative purposes.

The innovative series connection is formed using vias in the substrate 1a, which is between the first conductive layer 3c of the second cell 110b (the lower cell) and the second conductive layer 3a of the first cell 110a (the upper cell).

The two-sided non-conductive adhesive tape 11 extends from the boundaries of the conductive tape 10a, (which works as an anode current collector), over the anode layer 8a, separator 9a, cathode layer 7a, cathode current collector 6a and substrate 1a up to the edges of substrate 1 b. Substrate 1 a has a bigger area than the cell layers above it. in figure 10, tape 11 is shown separated from the cell 110b.

The first conductive layer 3a of silver is on the layers of cell 110b, i.e. the conductive tape

10b working as an anode current collector, anode layer 8b, separator 9b, cathode layer 7b, cathode current collector 6b and the third conductive layer 3b of silver, and substrate 1 b.

In addition, the assembly can be surrounded by an outer cover, which is not shown as the battery is for illustrative purpose presented in cross-section.

Claims (13)

A layered thin film battery pack comprising at least a first cell (110a) and a second cell (110b) connected in series, 5 wherein each cell (110a, 110b) comprises an anode portion and a cathode portion, the cells being connected in series through a common substrate (1a) between the cells (110a, 110b), the common substrate (1a) having one or more vias thereby providing a conductive material an electrical connection between the cathode part of the first cell (110a) and the anode part of the second cell (110b), characterized in that The conductive material in the vias 10 forms a unitary conductor between the cells (110a, 110b) together with the conductive layers (3a, 3c) on both sides of the common substrate (1a), said conductive layers thus communicating with each other through vias filled with conductive material, and in place of the vias The electrode area. Laminated battery pack according to Claim 1, characterized in that the electrical connection formed of the conductive material in the bushings acts as one or more conductors through a common substrate (1a), which substrate (1a) is thus an internal connection part between the cells (110a, 110b). Layered battery pack according to Claim 1 or 2, characterized in that the conductive substance provides an electrical connection between the cathode current collector (6a) of one cell (110a) and the anode current collector (10b) of the other cell (110b), the cathode current collector (6a) being connected first cell (110a) The cathode layer (7a) and the anode current collector (10b) are connected to the anode layer (8b) of the second cell (110b), the anode part of the second cell (1b) and the cathode part of the first cell (110a) being connected through bushings between the cells (110a, 110b). . 30 Laminated battery pack according to one of Claims 1 to 3, characterized in that the conductive material in the bushings, which is silver, forms a uniform silver conductor between the cells (110a, 110b). 20175594 prh 14-06- 2018 Layered battery pack according to Claim 3 or 4, characterized in that the layer (3b) of conductive material has extensions forming one or more positive connectors (5a, 5b) for forming a connecting part and further for connecting the battery pack to an external electrical device. Layered battery pack according to one of Claims 1 to 5, characterized in that the bushings are located in the region of the cathode collector (6a), preferably in the middle of or close to this region. 10 A layered battery pack according to any one of claims 1 to 6, characterized by a combination of a conductive grip (10a) partially covering the anode layer (8a) and a non-conductive double-sided grip (11) having an opening for said conductive grip 15 and which covers the rest of the packaging area so that the surface of the conductive gripper (10a) forms a negative connector of the battery pack. Laminated battery pack according to Claim 7, characterized in that the surface area of the common substrate (1a) is smaller than that of the substrate (1b) of the second cell, so that 20 that the double-sided non-conductive adhesive tape (11) connects and encloses the cells (110a, 11bb) being against the edges of the substrates (1a, 1b). A method of making a layered thin film battery pack, the method comprising: 25 a) piercing the first substrate (1a) so that it enters one or more holes (2), b) printing layers of conductive material on both sides of the first substrate (1a), thus filling the holes (2) at least partially, c) pressing layers on the first substrate (1a) over the first cell 30 (110a) comprising an anode portion and a cathode portion, d) pressing a layer of conductive material on the second substrate (1b), e) pressing layers on the second substrate (1b) to form a second cell (110b) comprising an anode portion and a cathode portion, f) connecting the cells (110a, 110b) against each other by placing the first cell (110a) on top of the second cell (110b) so that the first substrate (1a) remains between the cells (110a, 110b), whereby the first substrate (1a) thus provides electrical connection between the cathode portion of the first cell (110a) and the anode portion of the second cell 5 (110b). Method according to Claim 9, characterized in that the layer (3b) of conductive material is extended so as to provide extensions for forming a connecting part with one or more positive connectors (5a, 5b), whereby the battery pack can be 10 connect to an external electrical device. Method according to Claim 9, characterized in that the holes are pierced in the region of the cathode collector (6a), preferably in the middle of or close to this region. 15 Method according to one of Claims 9 to 11, characterized in that a conductive tape (10a) is applied so as to partially cover the anode layer in the first cell (8a) to act as an anode current collector in the anode part of the first cell, and a non-conductive double-sided conductive tape is applied (11) with an opening leaving a portion of the surface of the conductive tape (10a) exposed so that the conductive The surface of the tape (10a) may be the negative connector of the battery pack and the uncovered surface of the anode layer may form a negative pack of conductor tape (10a) through the conductive tape (10a). A method according to claim 12, characterized in that the surface area of the common substrate (1a) is made smaller than the substrate (1b) of the second cell and the cells (110a, 110b) are connected by means of a double-sided grip (11) so that it is (110b) against the edges of the substrate.