Subject of the invention

The invention relates to a flexible electrode developed for use in many areas such as energy storage devices, biosensors, fuel cells, electronic textiles, etc., and the production method of such electrode.

State of the Art

The working principle of devices used in many areas such as energy storage or production, sensors, electronic textiles or automotive industry is based on electrochemical reactions. Examples of such devices include batteries, supercapacitors, fuel cells, biosensors or artificial muscles. With the developing technology, flexible electronic devices have become one of today's active research areas and hard electronic elements have been replaced by flexible materials.

Devices based on electrochemical reactions have three basic components: electrode, electrolyte, and separator. There are separators with flexible structure and electroactive materials used as the electrode, but the substrate of the electrodes used as the current collector are generally not flexible. For example, substrates used in lithium-ion batteries, which are described as current collectors, are copper plates at the negative pole and aluminum plates at the positive pole. The flexibility of these plates is not at the desired level, although they are produced to be very thin.

Nowadays, although mobile phone screens can be produced to be flexible, energy storage systems cannot be produced to be flexible. This is due to the fact that flexible electrodes that can be used in energy storage devices do not have the desired energy or power density, and are disadvantageous in terms of costs. Another example is electrodes used as the biosensor in the human body. Said electrodes must be thin, flexible and suitable for the body curves. The use of non- flexible electrodes leads to injury and movement limitation on the areas where the electrode is in contact with the body.

The production and design of the new generation flexible electronic devices are expensive and laborious. The material that may be used as the electrode in these devices must be flexible, electrically conductive and low cost as well as light and suitable for large-scale production. Therefore, there is a need for flexible electrode current collectors and flexible electrodes with high energy and power density that can be produced easily and at a low cost.

There are studies on flexible electrode production in the art.

In many studies, fabrics containing conductive wires, carbon- based conductive papers, metal sheets have been used as the flexible electrode substrate, however, it has been observed that these materials have low electrochemical performance due to their weight.

CN106725418A can be given as an example of the state of the art. Said document relates to a carbon fabric-based flexible electrode in the field of medical devices, which is developed for collecting electrical signals in the human body. Said electrode mainly comprises a flexible conductive carbon fabric electrode, a flexible support layer and a wire. In producing the electrode of the document, the fabric must be treated at a temperature range of 950 °C-1200 °C for 2 to 3 hours in order to obtain a flexible carbon fabric. The preparation method of said electrode is laborious and its area of use is limited.

CN106898729A can be given as another example of the state of the art. Said document relates to a flexible current collector, and a flexible electrode and battery comprising said flexible current collector. The flexible current collector of the document comprises a textile fabric, and a metal conductive coating wrapping the fibers of the textile fabric. The active substance of the electrode is located on the flexible current collector and/or within the openings of the flexible current collector. The production method of the flexible electrode of the document includes the process steps of applying the active substance to the current collector and drying it in a vacuum oven in the temperature range of 80°C- 120°C. The production of said electrode requires the use of equipment such as a vacuum oven, etc.

It is seen that the electrodes mentioned in these documents of the art do not include any improvements in order to overcome the above-mentioned disadvantages. There is still a need for the development of a current collector and electrode with high energy and power density, which can be produced easily, cost-efficiently and with high efficiency in order to produce flexible electrodes with a wide area of use, and in which these disadvantages are eliminated.

Detailed Description of the invention

The invention relates to a flexible and conductive electrode developed for use in many areas such as energy storage devices including supercapacitors and batteries, sensor technology, electronic textiles, etc., and the production method of such electrode. The purpose of the invention is to produce a flexible electrode with high energy and power density by an easy and cost-efficient method.

The flexible electrode of the invention mainly comprises an adhesive tape, at least one graphite layer on the adhesive tape and a coating layer on said graphite layer, comprising graphene, conductive polymer, metal, alloy, metal oxide, metal hydroxide and/or composites thereof.

In one embodiment of the invention, the coating layer comprises polyaniline, polypyrrole, polythiophene and/or derivatives and/or copolymers thereof as the conductive polymer.

In one embodiment of the invention, the coating layer comprises cobalt, nickel, copper, manganese, ruthenium, iridium or zinc material as the metal.

In one embodiment of the invention, the coating layer comprises an alloy obtained by different combinations of cobalt, nickel, copper, manganese, ruthenium, iridium or zinc metals as the alloy.

In one embodiment of the invention, the coating layer comprises cobalt, nickel, copper, manganese, ruthenium, iridium or zinc-based oxide/hydroxide with different oxidation states as the metal oxides/hydroxides.

In one embodiment of the invention, the coating layer comprises cobalt, nickel, copper, ruthenium, iridium or zinc- based metal sulfide material with different oxidation states. In one embodiment of the invention, the adhesive tape is a flexible tape with one adhesive side.

In one embodiment of the invention, the adhesive tape is a flexible tape with double-sided adhesive.

In one embodiment of the invention, the adhesive tape is a non-flexible adhesive tape.

In one embodiment of the invention, the top of the graphite layer is coated with graphene which is a carbon nanomaterial consisting of hexagonally arranged carbon atoms of one atom thickness. In another embodiment of the invention, it is coated with conductive polymers or metal oxides/hydroxides, which are thicker materials. Thus, conductive and bendable electrodes can be obtained.

The production of the electrode of the invention is based on obtaining a very thin and flexible current collector (substrate) and making different coatings suitable for its intended use.

The production method of the flexible electrode of the invention comprises the steps of; obtaining at least one graphite layer on the tape by means of adhering the adhesive surface of the adhesive tape to the graphite surface and separating them or coating it with a graphite powder of different dimensions, coating the graphite layer with a material comprising conductive graphene, polymer, metal, alloy, metal oxide, metal hydroxide and/or composites thereof.

In one embodiment of the invention, adhering the graphite to the tape is formed during tape production. In the production of the flexible electrode of the invention, graphite which does not have a suitable structure for the production of brittle and flexible electrodes, is made suitable by coating it on flexible tape. Coating the graphite on the adhesive tape enables the tape of 100 micrometers, which is not normally conductive, to become conductive, and flexibility is thus maintained without causing a loss in the flexibility of the tape.

The surface area of the adhesive tape with graphite surface is increased by coating its graphite side, and thus excess ion transition is provided during the electrochemical reaction. For example, if the electrode is to be used in an energy device such as a supercapacitor or battery, the increased surface area of the electrode ensures that the electrode has high energy and power density.

The selection of the material for coating varies according to the intended use of the electrode. For example, if the produced electrode is to be used in a biosensor, the material coated on the graphite has a structure that can react with the molecules or ions to be analyzed.

In one embodiment of the invention, electrodeposition method or chemical precipitation method from a solution, sol-gel, spin coating or spraying method are used to obtain a coating layer on the graphite layer.

In one embodiment of the invention, non-aqueous (ionic liquids, deep eutectic solvents, organic solvents) and aqueous (acidic, basic and salt) solutions may be used as the electrolyte in the preparation of polymers and metal oxide/hydroxide that is to be deposited on the surface of the flexible graphite tape.

In one embodiment of the invention, chemical, electrochemical and/or spraying techniques are used to obtain materials to be coated on the graphite.

The selection of the tape to be used (thickness, width, length, amount of chemicals on its adhesive surface) varies depending on the choice and intended use. In addition, the methods and electrolytes selected when deposited polymers, metal oxides/hydroxides and composites thereof on the flexible graphite-tape surface prepared as the electrode also vary depending on the choice and purpose.

One embodiment of the invention comprises a graphite layer on the adhesive tape and a polyaniline layer on the graphite layer. In this embodiment, the polyaniline layer is obtained on the graphite tape by an electrodeposition method.

Figure-1 of the invention shows a graph of current density and potential data. The graph shows only values from the graphitised tape and the polyaniline coated graphitised tape. When the electrode is immersed in an acetonitrile electrolyte containing 0.1 M LiCICh, a dashed alternating voltammetry graph shown in Figure-1 is obtained between -0.5 V and 0.6V at a scan rate of 50 mV s ^_1 . The tape with the graphite layer that is not coated with polyaniline does not have oxidation and reduction peaks in the LiClCb electrolyte containing acetonitrile, and thus, the straight line data on the graph in Figure-1 is obtained. Figure-2 of the invention shows the specific capacitance at different scan rates of the obtained electrode that consists of the polyaniline coated graphitized tape.

In summary, the invention relates to a flexible electrode comprising an adhesive tape, at least one graphite layer on the adhesive tape and a coating layer on said graphite layer, comprising graphene, conductive polymer, metal, alloy, metal oxide, metal hydroxide and/or composites thereof. The production method of the flexible electrode is also within the scope of protection of the invention.

Thanks to the invention, an electrode with high electrochemical performance (energy density, capacitance) can be produced easily at a low cost. The said electrode is not only light and flexible but also suitable for large-scale production.

Description of the figures

Figure-1 Cycling Voltammetry Graph of an Embodiment of the Invention

Figure-2 Specific Capacitance and Scan Rate Graph of an Embodiment of the Invention