Technical Field of the Invention

The invention relates to a biocompatible supercapacitor with high energy-power density and ultra-high-performance lifetime, and the production method thereof. The supercapacitor mentioned here comprises a poly(3,4-ethylenedioxythiophene) (PEDOT) carbon felt electrode modified with a coumarin derivative compound.

State of the Art

Wearable technology is technological devices that can be worn by people, and these devices are loaded with smart sensors that monitor human body movements. Examples of wearable electronics include smart watches, wireless headphones, smart glasses, smart clothing, wearable pacemakers, and hearing aids. Wearable technology products, which users always carry with them, are used for health services, location tracking, tracking sports performance, being more organised, staying fit and active, losing weight, and activity tracking. It provides services in areas such as entertainment, education, health, work, information, socialisation, and security. Wearable technology products often sync with a smartphone wirelessly via Wi-Fi, Bluetooth, and mobile internet connection. Users connect to wearable devices with the help of sensors. Wearable devices such as activity trackers are an example of the Internet of Things, since "things" such as electronics, software, sensors, and connection are factors that enable things to exchange data over the Internet. These are devices that connect manufacturers, operators or users without requiring human intervention. By means of advanced material technologies, it is of great importance that these devices can be used efficiently for a long time. By means of this material produced, it is important that the energy is ready to be used, especially in the medical and military fields, when urgent energy is required and where it is desired. For this reason, supercapacitors, which are energy storage systems, are used in said devices Supercapacitors are promising energy storage units to meet the requirements in the field of energy storage with their advantages such as high capacitance values, long chargedischarge life, and low costs. Supercapacitors are very similar to batteries, but unlike the redox systems of batteries, they are systems that allow to store electrical energy by transferring the charge of electrolyte ions to the interlayer at the electrode-electrolyte interface. Supercapacitors are used in applications that require long-term compact energy storage rather than very fast charge/discharge [2],

Supercapacitors comprise an electric double-layer capacitor and a pseudo-capacitor, wherein the electric double-layer capacitor uses positive and negative ions respectively to adsorb on the surface between the electrode and the electrolyte to form a potential difference between the two electrodes, thereby providing energy storage. The pseudocapacitor uses a rapid reversible redox reaction that occurs at and near the electrode surface over a range of potentials to enable energy storage. The supercapacitor is a new energy storage device between a conventional capacitor and a chemical battery, and the energy storage process of the supercapacitor is reversible, so that the supercapacitor can be repeatedly charged and discharged tens of thousands of times. It has the advantages of high capacity, high power density, long cycle life, high charge and discharge efficiency and the like, and features such as instant heavy current discharge, no maintenance, economy, environmental protection, no pollution and so on. As a new energy storage device with environmental protection and excellent performance, the supercapacitor is widely used in various fields [3],

Unlike ordinary capacitors, supercapacitors do not have traditional solid dielectrics, instead they use electrostatic double layer capacitance and electrochemical pseudo capacitance, both of which, with a few differences, contribute to the total capacitance of the capacitor. Electrostatic double-layer capacitors (EDLC) use carbon electrodes or derivatives with an electrostatic double-layer capacitance much higher than the electrochemical pseudo capacitance and allow charge separation in a Helmholtz bilayer at the interface between the surface of a conductive electrode and an electrolyte. Charge separation is in the order of a few angstroms (0.3-0.8 nm) and is much smaller than a conventional capacitor. Electrochemical pseudo capacitors use metal oxide or conductive polymer electrodes with a high amount of electrochemical pseudo capacitance in addition to double-layer capacitance. The so-called capacitance is obtained by Faradaic electron charge transfer by redox reactions, intercalation or electrosorption. In hybrid capacitors, such as a lithium-ion capacitor, electrodes with different properties are used. One of these electrodes mostly exhibits electrostatic capacitance and the other mostly electrochemical capacitance. The electrolyte forms an ionic conductive connection between the two electrodes, which distinguishes them from the electrolyte and the conventional electrolytic capacitors in which a dielectric layer is always present. Supercapacitors are polarised by design with asymmetric electrodes or, for symmetric electrodes, with an applied potential during manufacture [4],

The maximum capacitance value, energy density and cycle life of conventional batteries used in the state of the art are quite low. At the same time, rechargeable Li-ion batteries, which are the conventional batteries used in the state of the art, and supercapacitors, in which ionic liquid electrolytes are used to achieve high energy-power density, comprise expensive chemicals, so the production costs of these batteries are quite high. In addition, the chemicals used in said supercapacitors are toxic and if the batteries leak, these chemicals endanger human health.

The patent no CN105161316B in the state of the art is about a supercapacitor and the preparation method thereof. The current collector may be a self-supporting conductive film such as carbon fibre paper, carbon fibre felt, graphene film, carbon nanotube film, a mixture of one or more of these, or carbon fibre cloth or it may be a mixture of fabric, sponge, paper, plastic film such as polyethylene terephthalate (PET), one or more carbon nanotubes, graphene, and a conductive polymer such as poly(3,4- ethylenedioxythiophene) (PEDOT). Flexible supercapacitors usually use a water-based gel electrolyte, that is, a polymer hydrogel electrolyte. The most commonly used system is a polyvinyl alcohol (PVA) based polymer gel electrolyte, such as polyvinyl alcohol/sulphuric acid (PVA-H2SO4) or (phosphoric acid) H3PO4, hydrochloric acid (HCI), perchloric acid (HCIO4), potassium hydroxide (KOH), sodium hydroxide (NaOH), sodium sulphate (Na2SO4), sodium chloride (NaCI), lithium sulphate (U2SO4), lithium chloride (LiCI), polymer hydrogel electrolyte. PVA-based polymer gel electrolytes, such as PVA- H2SO4 or HsPC , HCI, HCIC , KOH, NaOH, Na ₂ SO4, NaCI, U2SO4, LiCI, polymer hydrogel electrolyte, are expensive chemicals, which increases the production cost of the supercapacitor. In addition, the chemicals mentioned are chemicals that adversely affect human health, and if the capacitor leaks, it will have negative effects on human health.

Patent application WO2017065963A1 in the state of the art relates to the field of supercapacitors or ultracapacitors and more specifically to manufacturing processes for supercapacitor electrodes and cells. Said method comprises impregnating a wet cathode active material mixture from at least one of the two porous surfaces to the first electrically conductive porous layer to form a cathode electrode, wherein the wet cathode active material mixture comprises a cathode active material and an optional conductive additive mixed with a first liquid electrolyte is used. It comprises an anode electrode, a porous separator to form an alkali metal battery. The conductive porous layer here refers to the structure of an interconnection network with high pore volume (>70% or more) and electron conduction pathways. This may be, for example, an end-jointed 2D felt, a web, a woven wire mesh, or the like. Also, supercapacitor cells based on foamed structures may contain poly(3,4-ethylenedioxythiophene) (PEDOT). In addition, the supercapacitor contains electrolyte. Said electrolyte may comprise organic solvents such as acetonitrile, propylene carbonate, tetrahydrofuran, diethyl carbonate, y-butyrolactone and solutes containing alkyl ammonium salts or quaternary ammonium salts such as tetraethylammonium tetrafluoroborate (N(Et)4 BF4) or triethyl (methyl). The production cost of said supercapacitor is high due to the expensiveness of the mentioned chemicals. In addition, these chemicals have negative effects on human health as they are not biocompatible chemicals and are not suitable for use in wearable electronic devices.

Due to the negativities such as Low maximum capacitance value, energy density and cycle life of the energy storage systems or batteries used in wearable electronic devices in the state of the art, the high production costs of the Rechargeable lithium-ion (Li-ion) batteries, which are conventional batteries used in the current art, and supercapacitors, in which ionic liquid electrolytes are used to achieve high energy-power density, since they contain expensive chemicals, toxicity of chemicals used in batteries in the state of the art and the fact that if these batteries leak, these chemicals endanger human health, there is a need to develop a biocompatible supercapacitor with high energy-power density and ultra-high performance lifetime and a method for its production.

Brief Description and Aims of the Invention

In the invention, a biocompatible supercapacitor with high energy-power density and ultra- high-performance lifetime, consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) carbon felt electrode, electrolyte solution and separator strainer modified with coumarin derivative compound, and the production method of this capacitor are described.

The most important aim of the invention is to provide a biocompatible supercapacitor with high energy-power density and ultra-high-performance lifetime for use in wearable electronic devices. PEDOT carbon felt electrode modified with coumarin derivative compound is used in the supercapacitor that is the subject of the invention. In the invention, the presence of electron donating and electron withdrawing groups in different positions of the coumarin-based Schiff base ensures a high degree of conjugation of the supercapacitor and an increase in intramolecular charge transfer; thus, providing a biocompatible supercapacitor with high energy-power density and ultra-high-performance lifetime.

Another aim of the invention is to provide a non-toxic supercapacitor that is harmless for human health for use in wearable electronic devices. In the supercapacitor that is the subject of the invention, physiological 0.5 M-3.0 M sodium chloride (NaCI) aqueous solution is used as electrolyte instead of toxic chemicals such as lithium-ion (Li-ion) and ionic liquid used in other energy storage systems, and energy storage is carried out in this supercapacitor without the need for any chemical electrolyte.

Another aim of the invention is to provide a low-cost supercapacitor for use in wearable electronic devices. In the invention, 0.5-3.0 M NaCI aqueous solution with physiological properties is used as electrolyte instead of expensive chemicals such as Li-ion and ionic liquid used in other energy storage systems. With the invention, energy storage is realised without requiring any chemical electrolyte. Low-cost super capacitor is provided by not using very expensive chemicals and expensive production methods during the production of the supercapacitor.

With the invention, a biocompatible, low-cost, non-toxic supercapacitor that is harmless to human health, with high energy-power density, ultra-high-performance lifetime is provided for use in wearable electronic devices.

Description of Drawings

Figure 1. Schematic representation of the supercapacitor.

Figure 2. Cyclic voltammograms of the supercapacitor at different scan rates.

Figure 3. Galvonastatic charge-discharge (GCD) curves of a supercapacitor at different current density.

Figure 4. Specific capacitance values obtained from cyclic voltammograms of the supercapacitor.

Figure 5. Specific Capacitance values obtained from the galvanostatic charge-discharge (GCD) curves of the supercapacitor.

Figure 6. % capacitance performance results depending on the number of cycles of the supercapacitor.

Figure 7. Graph showing the results of the cell viability test of the electrode of the supercapacitor.

Figure 8. Fourier Transform Infrared Spectroscopy (FTIR) spectrum of poly(3,4- ethylenedioxythiophene) (PEDOT) electrodes.

Figure 9. FTIR spectrum of PEDOT carbon felt (PEDOT/Coumarin-derived) electrodes modified with coumarin-derived compound.

Figure 10. Thermogravimetry (TGA) plot of PEDOT electrodes.

Figure 11. TGA plot of PEDOT/Coumarin derivative electrodes. Figure 12. Scanning electron microscope (SEM) image of PEDOT electrodes.

Figure 13. SEM image of PEDOT/Coumarin derivative electrodes.

Figure 14. Graph of pore volume (cc/g)/width distribution (A) of PEDOT/Coumarin-derived electrodes.

Figure 15. Adsorption isotherm plot of PEDOT/Coumarin derivative electrodes.

Figure 16. Multi-point BET surface area plot of PEDOT/Coumarin derivative electrodes.

Figure 17. Fourier Transform Infra-red (FTIR) spectrum of 7-Hydroxy-4-phenyl-2H- chromen-2-one (C15H10O3) (Compound 1).

Figure 18. Fourier Transform Infra-red (FTIR) spectrum of 7-Hydroxy-2-oxo-4-phenyl-2H- chromene-8-carbaldehyde (C16H10O4) (Compound 2).

Figure 19. Fourier Transform Infra-red (FTIR) spectrum of (S)-Ethyl 2-(((7-hydroxy-2-oxo- 4-phenyl-2H-chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3)

Figure 20. ¹ H-NMR spectrum (CDCI3) of (S)-Ethyl 2-(((7-hydroxy-2-oxo-4-phenyl-2H- chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3)

Figure 21. ¹³ C-NMR spectrum (CDCI3) of (S)-Ethyl 2-(((7-hydroxy-2-oxo-4-phenyl-2H- chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3)

Figure 22. Liquid chromatography (LC-MS, ESI-QTOF) spectrum of (S)-Ethyl 2-(((7- hydroxy-2-oxo-4-phenyl-2H-chromen-8-yl) methylene) amino)-3-(4- hydroxyphenyl) propanoate (C27H23NO6) (Compound 3) combined with electrospray-ionization quadrupole time-of-flight mass spectrometry Description of the References in the Figures

1. Electrode

2. Electrolyte

3. Separator

Detailed Description of the Invention

The invention relates to a biocompatible supercapacitor with high energy-power density and ultra-high-performance lifetime, and the production method thereof. The supercapacitor mentioned here comprises two electrodes (1), an electrolyte (2) and a separator (3).

In the supercapacitor subject to the invention, PEDOT carbon felt (PEDOT/Coumarin derivative) modified with coumarin derivative compound is used as electrode (1), 0.5-3.0 M NaCI aqueous solution as electrolyte (2) and ordinary filter paper as separator (3). Said electrolyte (2) is used by being impregnated with the separator (3). In the supercapacitor, the electrodes (1) are positioned parallel to each other and are connected to each other from the outside in order to carry the current passing through the circuit. The electrolyte (2), on the other hand, is absorbed into the separator (3) and positioned between the parallel electrodes (1) to obtain a supercapacitor. The schematic representation of the supercapacitor is shown in Figure 1.

The production method of the supercapacitor comprises the process steps of; i. Production of two poly(3,4-ethylenedioxythiophene) (PEDOT) carbon felt (PEDOT/Coumarin derivative) electrodes modified with coumarin derivative compound (Compound 3), ii. Absorption of 0.5-3.0 M sodium chloride (NaCI) aqueous solution into the separator (3), iii. Parallel positioning of two poly(3,4-ethylenedioxythiophene) (PEDOT) carbon felt (PEDOT/Coumarin derivative) electrodes modified with 2 coumarin derivative compounds (Compound 3) and connecting these two electrodes from the outside to carry the current passing through the circuit, and iv. Obtaining the supercapacitor by positioning the separator (3) impregnated with 0.5-3.0 M sodium chloride (NaCI) aqueous solution between the electrodes positioned in parallel

The aforementioned carbon felt electrode is produced by hydrothermal method at high temperature in ethanol/distilled water environment, using 3,4-ethylenedioxythiophene monomer, FeCls.F metal salt and (S)-Ethyl 2-(((7-hydroxy-2-oxo-4-phenyl-2H- chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3) which is a coumarin derivative compound. Production method of PEDOT carbon felt electrode (1) modified with coumarin derivative compound comprises the process steps of: i. Synthesising (S)-Ethyl 2-(((7-hydroxy-2-oxo-4-phenyl-2H-chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) compound (Compound 3), ii. washing the carbon felt electrodes in an ultrasonic bath for 30 minutes, in ethanol, acetone and distilled water, respectively, to remove impurities and then drying at room temperature for 24 hours, iii. immersing the dried electrodes are in concentrated nitric acid (HNO3) solution and keeping them at room temperature for 72 hours, iv. washing the carbon felt electrodes kept at room temperature with distilled water until the pH is neutral and drying in an oven at 40 °C for 12 hours, v. adding 3,4-Ethylenedioxythiophene (EDOT), (S)-Ethyl 2-(((7-hydroxy-2-oxo-4- phenyl-2/-/-chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) compound (Compound 3) and ferric chloride hexahydrate (FeCIs. 6H2O) to the 50:50 ethanokwater mixture solution and mixing in an ultrasonic bath at room temperature for 30 minutes, vi. synthesising the prepared solution and the carbon felt electrode in a hydrothermal reactor at 150°C for 12 hours, and vii. following the synthesis, washing the electrodes in a 50:50 ethanol:water mixture solution and drying at 90°C for 12 hours. Here, the amount of EDOT monomer in the reaction medium can range from 0.01 mol/L to 1.0 mol/L. Coumarin derivative can be adjusted to be (S)-Ethyl 2-(((7-hydroxy-2-oxo-4- phenyl-2H-chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3), and the concentration of (C27H23NO6) (Compound 3) can be adjusted between 0.001 mol/L and 0.1 mol/L. The synthesis scheme of said compound (S)-Ethyl 2-(((7-hydroxy-2-oxo-4-phenyl-2H-chromen-8-yl) methylene) amino)-3-(4- hydroxyphenyl) propanoate (C27H23NO6) (Compounds) is shown below: L-tyrosine ethyl

Ph Ph ester

HMTA hydrochloride, glacial acetic acid

HO « O ⁸ a ho ^C ’ urs ¹² HO nhydrous etOH

Compound 1 HCI, reflux, 2 water hours

Compound 2

Synthesis 2

Synthesis 3 Compound 3

The synthesis method of said coumarin derivative compound (S)-Ethyl 2-(((7-hydroxy-2- oxo-4-phenyl-2H-chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3) comprises the process steps of: i. synthesising 7-Hydroxy-4-phenyl-2H-chromen-2-one (C15H10O3) (Compound 1) resorcinol and ethyl benzoylacetate in trifluoroacetic acid (TFA) by interacting with ultrasonic waves (Synthesis 1), ii. then, synthesising 7-Hydroxy-2-oxo-4-phenyl-2H-chromene-8-carbaldehyde (C16H10O4) (Compound 2) by reacting 7-Hydroxy-4-phenyl-2H-chromen-2-one (C15H10O3) (Compound 1) and hexamethylenetetramine in glacial acetic acid (Synthesis 2), followed by iii. synthesising (S)-Ethyl 2-(((7-hydroxy-2-oxo-4-phenyl-2H-chromen-8-yl) methylene) amino)-3-(4-hydroxyphenyl) propanoate (C27H23NO6) (Compound 3) by condensing 7-Hydroxy-2-oxo-4-phenyl-2H-chromene-8-carbaldehyde (C16H10O4) (Compound 2) with L-tyrosine ethyl ester hydrochloride in anhydrous ethanol (Synthesis 3).

TFA mentioned here is used both as a solvent and as a catalyst.

The following electrochemical methods were used to examine the performance of the supercapacitor electrode:

1. Cyclic Voltammetry (CV)

2. Galvanostatic Charge-Discharge (GCD)

3. Electrochemical Impedance Spectroscopy (EIS).

In the system where 0.5 M H2SO4 solution is used as the electrolyte, the potential gap optimisation is made by using the cyclic voltammetry method (CV). After determining the potential range with capacitive properties, the same optimisation was also examined using the Galvanostatic Charge-Discharge Method (GCD). In addition, the cycle life offered by the material and how much of the capacitance can be preserved have been examined. Cell viability test, structural and morphological analyses of the supercapacitor electrode are shown in Figure 7-16. As a result of the cell viability test in Figure 7, the electrode presenting biocompatibility with a value of 81 .2% supports its use in wearable and flexible energy storage systems. When the FTIR spectrum in Figure 9 is examined, it is clearly observed that the PEDOT carbon felt (PEDOT/Coumarin derivative) electrode modified with coumarin-derived compound has structural differences from the PEDOT carbon felt electrode in Figure 8. When the TGA analysis results given in Figure 10 and Figure 11 are examined, it is understood, with the decrease in % mass loss, that the thermal stability of the PEDOT/Coumarin derivative electrode has increased compared to the PEDOT electrode. When the SEM analysis results given in Figure 12 and Figure 13 are examined, it is seen that the modified PEDOT/Coumarin derivative electrode surface has a more granular and porous structure. The increase in the electrode/electrolyte interface interaction with the modification supports the increase in supercapacitor performance. The pore volume (cc/g) and width distribution (A) graph of the PEDOT/Coumarin derivative electrode in Figure 14 is given. As seen in Figure 15, the modified electrode exhibited the characteristic adsorption/desorption isotherm. In Figure 16, the characteristic multi-point BET surface area is obtained with increasing relative pressure.

As seen in Figure 6, the fact that the supercapacitor that is the subject of the invention maintains its capacitance performance of 113.6% even when it is cycled 15000 times shows that this supercapacitor can be used for a long time without being damaged. The positive effect of the supercapacitor on cell viability as a result of cytotoxicity tests can be seen in Figure 7, where the material is biocompatible.

The PEDOT/Coumarin derivative electrodes used in the supercapacitor that is the subject of the invention are compared with the electrodes in the state of the art in terms of maximum capacitance, energy density and cycle life in Table 1. Table 1 presents a comparison of the maximum capacitance and energy density values obtained by using cyclic voltammetry and galvanostatic charge/discharge electrochemical measurement methods of PEDOT-based wearable electrodes in the literature. A value of 672.6 F/g was obtained at a current density of 1 .6 A/g of the supercapacitor, which is the subject of the invention, and when compared with the capacitance values given in Table 1 , it is seen that it is higher than similar studies in the literature. In addition, the supercapacitor has a high energy storage capacity and high-power density compared to other supercapacitors. When the cycle life of the supercapacitor, which is the subject of the invention, is examined, the fact that it maintains the capacitance performance even when the number of cycles is 15000 times and increases the capacitance performance with a value of 113.6% shows that this supercapacitor is superior to other supercapacitors in the literature.

Table 1. Comparison of PEDOT/coumarin derivative electrodes with the electrodes in the state of the art in terms of maximum capacitance, energy density and cycle life.

Electrode Electrolyte Measurement Maximum Energy Cycle Life Ref.

Type Capacitance Density

ProDOT LiBTI/H ₂ O 3-electrodes 175000 [6]

NaCI/F 42 F/g, 50 mV/s - (%75)

33 F/g , 50 mV/s p(EDOTOH) 0.1 M NaCI/ 3-electrodes 71 F/g, 1.3 A/g 12000 [7] agarose 20 Wh/kg (%75)

2-electrodes 75 F/g, 8.47 A/g 4000 (%95)

3D-PEDOT KC 2-electrodes 55.5 F/g, 1.38 - - [8] biohydrogel. A/g.

SWCNTs/PEDOT 1 M H3PO4 3-electrodes 215 F/g, 50 mV/s 5000 (%90) [9]

PVA/ H3PO4 2-electrodes 53 F/g, 1 A/g 6 Wh/kg

SWCNT/PEDOT PVA/H3PO4 2-electrodes 56 F/g, 1 A/g 6 Wh/kg 10000 [12]

(%95)

PEDOT:PSS NaCI /ter 2-electrodes 8.94 F/g, 1 mV/s 1.36 Wh/kg 4000 [13] electrolyte. (%75)

PEDOT/Coumarin 3.0 M NaCI 2-electrodes 672.6 F/g, 1.6 46.7 15000 derivative A/g Wh/kg, (%114) The cytotoxicity tests of the electrode in the supercapacitor were carried out and it was found that it is harmless in biological systems. The biocompatible supercapacitor containing modified PEDOT carbon felt electrode with coumarin derivative compound as electrode (1), 0.5-3.0 M NaCI aqueous solution as electrolyte (2) and ordinary filter paper as separator (3) supports cell viability in the human body with its many features. By means of its chemical structure that does not harm the human body, the biocompatible supercapacitor offers the opportunity to be used in areas where the body needs electrical stimulation, especially in the treatment of diseases that cause death, such as heart failure, increasing the life span and quality of life. Therefore, the supercapacitor of the invention is suitable for use in wearable electronic devices.

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