Production of a nickel hydroxide-based supercapacitor electrode material functionalised by high-energy x-ray irradiation

Abstract

The invention relates to a nickel hydroxide (f-Ni(OH)2)-based electrode material functionalised by surface modification using a high-energy X-ray irradiation method, and to a production method of this material. In addition, the invention describes the usability of this electrode material modified using high-energy X-rays as a high-performance electrode in supercapacitor applications.

Description

[0001] PRODUCTION OF A NICKEL HYDROXIDE-BASED SUPERCAPACITOR ELECTRODE MATERIAL FUNCTIONALISED BY HIGH-ENERGY X-RAY IRRADIATION

[0002] Technical Field of the Invention

[0003] The invention relates to a nickel hydroxide (f-Ni(OH)2)-based electrode material functionalised by surface modification through a high-energy X-ray irradiation method, and to a production method thereof. In addition, the invention describes the usability of the electrode material modified by the high-energy X-ray irradiation method as high-performance electrodes in supercapacitor applications.

[0004] State of the Art

[0005] The demand for energy is rapidly increasing day by day, particularly due to the growing importance of renewable energy sources and the limited reserves of fossil fuels. Portable electronic devices, electric vehicles, and energy grids, which have become indispensable elements of modem life, increase the need for energy storage systems with higher performance [1], In this respect, the development of systems having high energy density, power density, and long cycle life has become a critical requirement [2], Supercapacitors, which attract attention due to their high charge-discharge rates, long cycle lives, and environmentally friendly structures, hold an important position among the systems capable of meeting these needs [3], However, for commercial applications, improving cycle life and cycle efficiency and increasing energy densities constitute a major necessity [4],

[0006] In the performance of supercapacitors, the electrode material used plays a decisive role [5], The surface area, electrical conductivity properties, and redox activity of the electrode material directly affect the energy storage capacities and cyclic stability of supercapacitors [6], As electrode materials, carbon-based materials, metal oxides, and conductive polymers are generally used [7], In particular, metal oxides are extensively investigated in this field due to their high specific capacitance values and good redox activity [8], Among metal oxides, nickel hydroxide (Ni(OH)2), with a high theoreticalcapacitance value (2082 F g-1), comes to the forefront due to both its economic and electroactive properties [9], Although high redox activity, low cost, and easy production methods are among the prominent features of this material, low ionic conductivity, limited cycle stability, and structural degradation are the main factors limiting the performance of Ni(OH)2-based electrodes

[0010] , In order to eliminate these deficiencies, studies aimed at improving the surface properties of Ni(OH)2and stabilising its crystal structure are ongoing

[0011] , In the literature, various methods such as chemical vapour deposition (CVD), hydrothermal synthesis, electrochemical deposition, and composite formation with carbon-based materials have been proposed for these improvements [9,10], However, these methods have disadvantages such as complex production processes, long processing times, high costs, and limited applicability on an industrial scale.

[0007] Due to the limitations and insufficiencies of the solutions in the state of the art, arising from reasons such as the complexity of the Ni(OH)2electrode production methods used, the requirement for long processing times, high costs, and limited industrial-scale applicability, it has become necessary to make an improvement in the field of electrode material production methods.

[0008] Brief Description and Aims of the Invention

[0009] The invention relates to the production of nickel hydroxide (f-Ni(OH)2) structures functionalised by a high-energy X-ray irradiation method and to a method for producing supercapacitor electrode materials from these structures.

[0010] One aim of the invention is to obtain a Ni(OH)2-based electrode having a wide range of applications. In the invention, by developing supercapacitors with high cycle stability, long lifetime, and high efficiency, use can be achieved particularly in microelectronic devices, sensor systems, and short-term energy storage applications where low energy density is required but high cycle stability and fast charge-discharge capability are critical. The development of next-generation supercapacitors providing long charge-discharge cycle life and efficiency makes a significant contribution to the future of energy storage technologies. In this respect, the invention introduces an important innovation for sustainability- and efficiency-oriented applications in the energy sector.Another aim of the invention is to obtain a Ni(OH)2-based electrode with increased energy storage capacity. High-energy X-ray irradiation increases the surface area, thereby enhancing the efficiency of redox reactions. This improves the fast chargedischarge capability of supercapacitors while raising cycle efficiency to high levels such as 99.2%. Accordingly, a sustainable and highly efficient solution is provided for energy storage technologies.

[0011] Additionally, in the invention, it is aimed to obtain a Ni(OH)2-based electrode having a long cycle life. By stabilising the crystal structure through the X-ray irradiation technique, the mechanical and chemical durability of the material is increased. In this way, high stability with minimal loss in capacitance value is achieved even after 5,000 cycles. This significantly extends the lifetime of energy storage systems.

[0012] Furthermore, an aim of the invention is to obtain a Ni(OH)2-based electrode that is simple and applicable on an industrial scale. Instead of complex processes such as chemical vapour deposition (CVD) or hydrothermal synthesis, effective surface modifications are performed in a short time using the X-ray irradiation technique. Thus, production costs are reduced and industrial applications are facilitated.

[0013] Description of the Figures

[0014] Figure 1. X-ray Diffraction (XRD) analysis results

[0015] Figure 2. Raman spectra

[0016] Figure 3. FTIR analysis results

[0017] Figure 4. Cyclic voltammetry (CV) curves of Ni(OH)2and f-Ni(OH)2electrodes (a: Ni(OH)2, b: f-Ni(OH)2)

[0018] Figure 5. Galvanostatic charge-discharge (GCD) curves of Ni(OH)2and f-Ni(OH)2electrodes (a: f-Ni(OH)2, b: Ni(OH)2)

[0019] Figure 6. Nyquist curves obtained by electrochemical impedance spectroscopy (EIS) analysis of Ni(OH)2and f-Ni(OH)2electrodes (a: Ni(OH)2, b: f-Ni(OH)2)

[0020] Figure 7. Cycle stability results of the f-Ni(OH)2electrodeDetailed Description of the Invention

[0021] The invention relates to a method for producing nickel (II) hydroxide (f-Ni(OH)2) electrodes functionalised using high-energy X-rays. The production method that is the subject of the invention comprises the process steps of;

[0022] a. placing 1.0-2.0 grams of nickel (II) hydroxide Ni(OH)2powder in a petri dish as a homogeneous layer having a thickness of at most 1 mm,

[0023] b. exposing the prepared sample to X-rays having an energy of 10-15 MV at a distance of 100-150 cm from the radiation source, at a dose rate of 1000-1200 MU / rnin, and at a total dose of 10-20 Gy,

[0024] c. mixing the f-Ni(OH)2obtained after irradiation with carbon black and polyvinylidene fluoride compounds, and

[0025] d. converting the obtained powder mixture into pellets by applying a pressure of 12,000-15,000 psi.

[0026] An embodiment of the production method that is the subject of the invention comprises the process steps of;

[0027] a. placing 1.5 grams of nickel (II) hydroxide Ni(OH)2powder in a petri dish as a homogeneous layer having a thickness of at most 1 mm,

[0028] b. exposing the prepared sample to X-rays having an energy of 15 MV at a distance of 100 cm from the radiation source, at a dose rate of 1000 MU / rnin, and at a total dose of 10-20 Gy,

[0029] c. weighing and mixing the f-Ni(OH)2obtained after irradiation with carbon black and polyvinylidene fluoride compounds at a mass ratio of 5:3:1 , and

[0030] d. converting the obtained powder mixture into pellets by applying a pressure of 15,000 psi.

[0031] The invention relates to the production of nickel hydroxide (f-Ni(OH)2) structures functionalised by high-energy X-rays and to a method for producing supercapacitor electrode materials from these structures. The production method that is the subject of the invention relates to the fact that high-energy X-rays cause improvements in the physicochemical and electrochemical properties of the material as a result of Compton scattering interaction with the material. The electrode material that is the subject of theinvention is nickel hydroxide (f-Ni(OH)2) functionalised by high-energy X-rays. The supercapacitor electrode that is the subject of the invention is an f-Ni(OH)2electrode having a long charge-discharge cycle life and high cycle efficiency.

[0032] By using the nickel hydroxide (f-Ni(OH)2) structures functionalised by high-energy X-ray irradiation as supercapacitor electrode materials, significant increases have been achieved in specific capacitance, cycle life, and cycle efficiency values compared to unmodified Ni(OH)2. In particular, as a result of the irradiation process with high-energy X-rays, the formation of new redox-active regions on the surface and the increase in surface roughness have improved the electrochemical performance of the electrode that is the subject of the invention. f-Ni(OH)2electrodes have exhibited up to 40% higher specific capacitance values compared to unmodified Ni(OH)2electrodes. In addition, the electrode that is the subject of the invention has exhibited high performance in charge-discharge stability owing to crystal structure stabilisation formed as a result of irradiation, increased redox activity, and improved ionic conductivity. It has been determined that the f-Ni(OH)2electrode that is the subject of the invention offers advanced advantages in energy storage technologies compared to existing systems due to its low internal resistance values.

[0033] The physicochemical characterisations of the f-Ni(OH)2and unmodified Ni(OH)2structures that are the subject of the invention were carried out by ICP-MS, XRD, Raman, and FTIR analyses.

[0034] The ICP-MS analysis results of the f-Ni(OH)2and unmodified Ni(OH)2structures that are the subject of the invention are shown in Table 1. These results show that there is general stability in the main isotope compositions and that only minimal differences are observed in the percentage distributions. While the main isotopes Ni-58, Ni-60, Ni-61, and Ni-62 constitute more than 98% of the total nickel content, no significant change is observed in the distribution of these isotopes after modification. For example, while the Ni-58 ratio decreases from 25.34% to 25.30%, the Ni-62 ratio shows a slight increase from 24.61% to 24.65%. This demonstrates that the high-energy X-ray irradiation method provides a modification on the material surface while preserving the isotopic stability and bulk structure of the main isotopes.

[0035] A significant decrease has also been observed in the amounts of Ni-59 and Ni-63 isotopes detected at low levels in the Ni(OH)2structure. While Ni-59 and Ni-63 were atlevels of 10.38 ppb and 24.96 ppb, respectively, in the unmodified sample, these values decreased to 1.69 ppb and 2.90 ppb, respectively, in the functionalised sample. Since the proportions of these isotopes within the total nickel content are at negligible levels, their effect on the electrochemical performance of the material is expected to be limited. The preservation of high proportions of the main isotopes (Ni-58, Ni-60, Ni-61 , and Ni-62) demonstrates that the energy storage performance of the material is independent of the presence of these rare isotopes and confirms the effectiveness of the surface modification.

[0036] The fact that the Ni-59 and Ni-63 isotopes are present at low percentages or further decrease after irradiation does not create a negative effect on the overall performance of the material. This is because these isotopes do not have a decisive role in surface chemistry or redox mechanisms. On the contrary, increasing the number of active redox regions and improving the surface area through irradiation have enhanced the specific capacitance and stability performance of the material.

[0037] Table 1. ICP-MS analysis results of Ni(OH)2orf-Ni(OH)2structures

[0038] Isotopes Ni(OH)2(ppb) % f-Ni(OH)2(ppb) %

[0039] 196,323.1825 34i85,21T66 25.30

[0040] i gi 737 22 24 75

[0041] 180,843'97 24.70 ................177 146 66 24 19186.994.17 24 13

[0042] Ni-62 190,671.81 24.61 180,461.58 24.65 Ni-63 24.96 0.003 2.90

[0043] Ni-64 8,945.40 1.17 8,433.27 1.15

[0044]

[0045] The XRD analysis of the f-Ni(OH)2and unmodified Ni(OH)2structures that are the subject of the invention is shown in Figure 1. The XRD spectra show that the production method that is the subject of the invention modifies the surface properties of the material while preserving and stabilising the fundamental crystal structure. The positions of the diffraction peaks are consistent with the typical crystal structure of Ni(OH)2and are located at around 26 = 18°, 37°, and 60° [21 ,22], This shows that the irradiation process provides surface-level modification without damaging the main structure of the material. In accordance with the literature, these peaks are associatedwith the (001), (100), (101), and (110) planes and support the purity of the structure [21 ,22], The absence of any shift in the peak positions proves that the integrity of the crystal structure is preserved and that the changes occurring at the surface do not affect the internal structure of the material.

[0046] In the f-Ni(OH)2that is the subject of the invention, a slight decrease in peak intensity and an increase in peak broadening indicate the formation of amorphous structures or nanoscale disorder on the surface. These disorders may increase the surface area, thereby enhancing the efficiency of redox reactions and contributing positively to the electrochemical performance of the material. Nevertheless, the complete preservation of the intensity of the main peaks reveals that these surface-level changes do not disrupt the crystalline structure of the material and that a more stable surface arrangement has been obtained through the irradiation process. This surface stabilisation has made a significant contribution to the cycle stability of the material, enabling superior performance such as 99.2% capacity stability after 5,000 cycles. The production method that is the subject of the invention has transformed the surface crystal structure of the material into a lower-energy, stable form. This surface rearrangement has led to the formation of new pathways facilitating ion transfer and new redox-active regions. When compared with other modification methods of Ni(OH)2reported in the literature, the XRD results obtained within the scope of this invention demonstrate that the irradiation process both provides effective surface modification and stabilises the crystal structure.

[0047] The Raman spectra of the f-Ni(OH)2and unmodified Ni(OH)2structures that are the subject of the invention are shown in Figure 2. Both materials exhibit peaks consistent with the typical Raman spectrum of Ni(OH)2reported in the literature

[0021] , The distinct peak at 2922 cm-1, observed in both samples, belongs to hydroxyl (OH-) groups and demonstrates that the fundamental structure of the material is not disrupted after irradiation. This finding indicates that the irradiation provides a surface-focused modification and preserves the overall chemical integrity of the material.

[0048] A new peak appearing at around 2850 cm-1in the f-Ni(OH)2that is the subject of the invention indicates chemical changes occurring on the material surface after irradiation. This peak shows similarity to peaks reported in the literature at positions close to the A2u vibrational mode of |3-Ni(OD)2

[0021] , The new peak around 2850 cm-1demonstrates that the method that is the subject of the invention optimises energy storage performance through surface modifications. The new peak may have formed as a result of the rearrangement of hydroxyl groups or localised modifications on the surface. This may indicate an increase in the number of redox-active regions on the material surface. Such chemical changes occurring on the surface are key factors that enhance the electrochemical performance of the material.

[0049] The positions and intensities of the other peaks observed in the Raman spectra are largely similar between the unmodified and functionalised samples. This indicates that the irradiation process affects only the surface properties while not altering the fundamental crystal structure. Apart from the formation of the new peak, the preservation of the structural integrity of the material confirms that a high-performance and durable electrode material suitable for energy storage applications has been obtained.

[0050] In addition, it is observed that the chemical changes occurring on the surface after functionalisation contribute positively to the energy storage capacity.

[0051] The FTIR (Fourier Transform Infrared) spectroscopy analysis results of the f-Ni(OH)2and unmodified Ni(OH)2structures that are the subject of the invention are shown in Figure 3 and were examined in order to evaluate the chemical changes caused by the irradiation process on the material surface. In both spectra, peaks at around 635 cm-1, 1360 cm-1, and 1600 cm-1are noteworthy. These peaks are consistent with the typical vibrational modes of the Ni(OH)2structure reported in the literature. While the peak at 635 cm-1is attributed to vibrations of the nickel-oxygen (Ni-O) bond, the peaks at around 1360 cm-1and 1600 cm-1represent deformation modes of hydroxyl (OH-) groups on the surface. These results show that the production method that is the subject of the invention does not alter the fundamental chemical structure of the material and preserves the basic presence of OH” groups [23,24],

[0052] In the FTIR spectrum of the f-Ni(OH)2structure that is the subject of the invention, a distinct shift and an intensity difference are observed at high wavenumbers (3297 cm-1and 3307 cm-1). These peaks are attributed to stretching vibrations of hydroxyl groups. Unlike the peak observed at 3283 cm-1in unmodified Ni(OH)2, these shifts in f-N i(OH)2indicate that the bonding energies of hydroxyl groups on the surface change during the irradiation process and that the surface chemistry is rearranged. In the literature, suchwavenumber shifts are known to be associated with the strengthening of hydrogen bonds or the formation of new bonding structures on the surface. This explains how the irradiation process enhances the electrochemical performance of the material by increasing surface roughness and the density of redox-active regions.

[0053] The effects of the production method that is the subject of the invention on the material are more clearly understood through the new peaks observed at around 3307 cm-1in f-Ni(OH)2. These peaks may have formed as a result of the rearrangement of different types of hydroxyl groups or nickel-hydroxyl (Ni-OH) bonds on the surface. In the literature, such peaks have been reported to indicate an increased ion adsorption capacity on the surface and more effective redox mechanisms [23,24], The emergence of these new chemical features in the FTIR spectrum supports that the irradiation process increases the energy storage capacity by modifying functional groups on the surface.

[0054] The electrochemical performance of the electrodes that are the subject of the invention was evaluated in a standard three-electrode electrochemical cell using a saturated calomel electrode (SCE) as the reference electrode, a platinum wire as the counter electrode, and pellet electrodes prepared as the working electrodes, in a 1.0 M Na2SO4electrolyte environment. The electrochemical performance of the electrodes was tested by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques using an IVIUMSTAT A06061 potentiostat-galvanostat system. CV measurements were carried out in the voltage range of -1.0 V to 1.0 V at potential scan rates ranging from 1.0 mV s’1to 100.0 mV s’1. GCD tests were performed at current densities ranging from 1.0 mA cm-2to 5.0 mA cm'2. The cycle stability of the electrodes was evaluated by the CV method over 5,000 consecutive cycles at a potential scan rate of 100.0 mV s"1, and a capacitive stability of 99.2% was determined. Using the obtained data, specific capacitance (Cs; mF crrr2) and cycle stability (%) values were calculated. The analysis results showed that the f-Ni(OH)2electrodes functionalised by high-energy X-ray irradiation exhibited higher specific capacitance compared to unmodified Ni(OH)2electrodes and also provided stable performance with a long cycle life.

[0055] The CV voltammograms obtained by the cyclic voltammetry technique for unmodified Ni(OH)2and f-Ni(OH)2electrodes in a 1.0 M Na2SO4electrolyte environment atpotential scan rates ranging from 1 mV s'1to 100 mV s'1are shown in Figures 4a and 4b, respectively. The CV curves of the unmodified Ni(OH)2electrode presented in Figure 4a exhibit low redox activity and limited capacitive behaviour. In the curves, the current density remains at low levels at all scan rates. This indicates that the redoxactive regions on the surface of the unmodified electrode are limited and that the surface area is insufficient for capacitive energy storage. Especially at high scan rates such as 100 mV s’1, the current density decreases significantly, and it is understood that ion transfer is restricted due to the limited number of redox-active regions. In addition, the lack of symmetry of the curves along the potential axis indicates that the redox reactions are kinetically weak and that the electrochemical stability of the material remains at a low level.

[0056] The CV curves of the f-Ni(OH)2electrode that is the subject of the invention (Figure 4b) exhibited a much higher electrochemical performance compared to the unmodified electrode. Owing to the redox-active regions formed on the surface by high-energy X-ray modification, a significant increase in current density was achieved. Particularly at low scan rates such as 1.0 mV s"1, the f-Ni(OH)2electrodes facilitated the diffusion of ions to the surface and exhibited more effective energy storage behaviour. Even at high scan rates, the curves preserved their symmetric shape and demonstrated that the electrochemical reactions were kinetically supported. This situation is associated with an increase in the number of redox-active regions and the optimisation of ion transfer pathways.

[0057] The CV curves of the functionalised electrodes exhibited a more stable and consistent capacitive behaviour compared to the unmodified electrodes. This demonstrates that the modifications performed on the material surface by the high-energy X-ray irradiation method not only increase the surface area but also stabilise the crystal structure and improve ion transfer mechanisms. In Table 2, specific capacitance (Cs,CV; mF crrr2) values calculated on the basis of electrode surface area from the CV curves obtained at potential scan rates ranging from 1 mV s'1to 100 mV s'1in a 1.0 M Na2SO4electrolyte environment for the f-Ni(OH)2and unmodified Ni(OH)2electrodes that are the subject of the invention are presented. Due to the increase in the number of redox-active regions on the surface of f-N i(OH)2and the improvement in ion transfer capacity, the specific capacitance values of the f-Ni(OH)2electrodes show a marked increase at all scan rates compared to the unmodified Ni(OH)2electrodes. In particular, at a low scan rate (1.0 mV s'1), the specific capacitance of the f-Ni(OH)2electrode was measured as 671.2 mF cm'2and exhibited approximately 41% higher performance compared to the unmodified electrode. This superiority continued at high scan rates, confirming the improvement in ion transfer mechanisms of f-Ni(OH)2and the positive effect of surface modification on energy storage capacity. The f-Ni(OH)2electrodes that are the subject of the invention provide a significant advantage in energy storage applications by exhibiting superior electrochemical properties such as high current density, stable electrochemical performance over a wide range of scan rates, and symmetric pseudocapacitive behaviour. These results clearly demonstrate that the irradiation method is an effective approach for improving the electrochemical performance of metal hydroxide materials such as Ni(OH)2. Surface modification not only increases specific capacitance but also optimises the long cycle stability and kinetic behaviours of the electrode, thereby maximising supercapacitor performance. This demonstrates that the invention offers an innovative solution in energy storage technologies.

[0058] Table 2. Specific capacitance (Cs,CV; mF cm-2) values calculated using data obtained by the cyclic voltammetry technique for the f-Ni(OH)2and unmodified Ni(OH)2electrodes that are the subject of the invention in a 1.0 M Na2SO4electrolyte environment

[0059] Specific capacitance (Cs,cv;mF.cnr2) Electrode 1.0 mV.s_10 mV.S' 20 mV.s_50 mV.S' 100 mV.s_

[0060] 1 1 1 1 1 Ni(OH)2474.7 89.1 56.3 34.3 25.45 f- Ni(OH)2671.2 203.7 129.6 72.3 45.7

[0061] The GCD curves obtained by the galvanostatic charge-discharge technique for the f-Ni(OH)2and unmodified Ni(OH)2electrodes obtained by the preparation method that is the subject of the invention, in a 1.0 M Na2SO4electrolyte environment at current densities ranging from 1.0 mA cm'2to 5.0 mA cm'2, are shown in Figures 5a and 5b, respectively. The specific capacitance values calculated using the data obtained by theGCD technique were normalised with respect to the electrode surface area (Cs,GCD; mF cm-2) and are presented in Table 3.

[0062] Table 3. Specific capacitance (Cs,GCD; mF cm-2) values calculated using data obtained by the GCD technique for the f-Ni(OH)2and unmodified Ni(OH)2electrodes that are the subject of the invention in a 1.0 M Na2SO4electrolyte environment

[0063] Specific capacitance (CS,GCD;mF.crrr2) Electrode 1.0 2.0 3.0 4.0 5.0 mA.cnr2mV.crrr2mV.cnr2mV.cnr2mV.cnr2

[0064] 502.1 237.2 108.8 57.4 Ni(OH)21002'5

[0065] f-Ni(OH)21253.5 530.3 322.7 180.8 89.0

[0066] The galvanostatic charge-discharge (GCD) curves of the unmodified Ni(OH)2electrode exhibit a pronounced limitation in energy storage capacity. At low current densities (1.0 mA cm'2), the charge and discharge processes display a long-duration energy storage performance. However, as the current density increases, the chargedischarge curves become increasingly asymmetric, revealing the kinetic limitations of the material. The humps observed in the curves indicate the presence of limited redox -active regions on the Ni(OH)2surface and the low kinetic efficiency of the faradaic reactions occurring in these regions. Due to the lack of surface modification, the energy density and charge-discharge stability of the material are significantly constrained. The GCD curves of the f-Ni(OH)2electrode that is the subject of the invention exhibit markedly higher energy storage capacity and stability compared to the unmodified Ni(OH)2electrodes. At low current density (1.0 mA cm-2), the charge and discharge processes continue for a longer duration compared to the unmodified electrode. This is associated with the increase in surface area and the improvement in ion transfer capacity of f-Ni(OH)2. Even when the current density is increased (for example, 5.0 mA- cm-2), the curves maintain their symmetric shape and demonstrate that the energy storage capacity is more stable.

[0067] Hump-like features are observed in the GCD curves for both electrodes. However, these humps exhibit a more pronounced and longer-lasting energy storage behaviourin the f-Ni(OH)2electrodes. These humps indicate the effectiveness of faradaic reactions on the surface and the presence of pseudocapacitive behaviour. In the unmodified electrodes, the humps occur over a shorter duration and with lower intensity due to lower energy density and limited redox-active regions. The more pronounced humps in the functionalised electrodes are associated with the new redoxactive regions formed on the material surface by X-ray modification. This modification has increased the kinetic efficiency of the redox reactions of Ni(OH)2and improved the energy storage capacity.

[0068] The Nyquist curves of the unmodified Ni(OH)2electrode and the f-Ni(OH)2electrode that is the subject of the invention are presented in Figures 6a and 6b, respectively. The curve obtained for the unmodified Ni(OH)2electrode has a larger semicircular region, indicating that the redox reactions on the electrode surface are kinetically limited. The width of the semicircle indicates that the charge transfer resistance (Ret) is quite high at 32.50 and that the redox-active regions on the surface are insufficient. In addition, the solution resistance (Rs) being measured as 18.4 0 reveals that the contact resistance between the electrode and the electrolyte is higher and that ionic conductivity is limited. This situation is a factor that adversely affects the energy storage performance of unmodified Ni(OH)2electrodes.

[0069] The Nyquist curve of the f-Ni(OH)2electrode that is the subject of the invention (Figure 6b) has a smaller semicircular region. The decrease in the solution resistance (Rs) to 13.0 0 demonstrates an increase in ion transfer capacity at the electrode-electrolyte interface and reveals the effectiveness of the surface modification. The increase in surface area and the optimisation of ion transfer pathways in these electrodes functionalised by high-energy X-ray irradiation have accelerated the redox reactions and enabled the attainment of higher capacitance values. These results clearly demonstrate that the production method that is the subject of the invention significantly improves electrochemical performance.

[0070] In order to examine the cycle stability and efficiency of the f-Ni(OH)2electrode that is the subject of the invention, the CV curves obtained over 5,000 consecutive CV cycles at a potential scan rate of 500 mV s'1in a 1 M Na2SO4electrolyte solution, and the cycle efficiency values calculated via these curves, are shown in Figure 7. Both the capacity stability and the cycle performance of the electrode demonstrate the superiorperformance of the material obtained by the production method that is the subject of the invention.

[0071] The cycle efficiency (%) shown in Figure 7 refers to the retention ratio of the specific capacitance compared to its initial value over the number of cycles. The f-Ni(OH)2electrode exhibited approximately 99.2% cycle efficiency after 5,000 consecutive CV cycles. This demonstrates that the redox-active regions of the material do not undergo chemical or mechanical degradation over the long cycle duration and operate with high stability. In addition, the minimal decrease observed in the capacitance value indicates that the surface roughness and ion transfer capacity obtained after irradiation support the stability of the material.

[0072] The negligible difference between the 1st cycle and the 5,000th cycle in the CV curves proves that the electrode operates without losing effectiveness in its redox reactions. This indicates that the new redox-active regions and surface chemistry formed on the material surface by the production method that is the subject of the invention maintain their stability throughout the cycling process. The symmetry of the curves and the stability of the changes in current density emphasise that the electrode preserves both its kinetic and capacitive properties over long-term performance.

[0073] As a result, the f-N i(OH)2electrodes that are the subject of the invention demonstrate high cycle stability and capacitive behaviour, thereby proving to be strong candidates for supercapacitor applications. The performance of the electrode offers superior stability and energy storage capacity compared to electrodes obtained by other modification methods reported in the literature. This invention provides an innovative solution for energy storage systems requiring long cycle life and high performance.References

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Claims

CLAIMS1. A method for producing nickel (II) hydroxide (f-Ni(OH)2) electrodes functionalised using high-energy X-rays, comprising the process steps of;a. placing 1.0-2.0 grams of nickel (II) hydroxide Ni(OH)2powder in a petri dish as a homogeneous layer having a thickness of at most 1 mm,b. exposing the prepared sample to X-rays having an energy of 10-15 MV at a distance of 100-150 cm from the radiation source, at a dose rate of 1000- 1200 MU / rnin, and at a total dose of 10-20 Gy,c. mixing the f-Ni(OH)2obtained after irradiation with carbon black and polyvinylidene fluoride compounds, andd. converting the obtained powder mixture into pellets by applying a pressure of 12,000-15,000 psi.

2. A method for producing functionalised nickel (II) hydroxide (f-Ni(OH)2) electrodes according to Claim 1 , comprising the process steps of;a. placing 1.5 grams of nickel (II) hydroxide Ni(OH)2powder in a petri dish as a homogeneous layer having a thickness of at most 1 mm,b. exposing the prepared sample to X-rays having an energy of 15 MV at a distance of 100 cm from the radiation source, at a dose rate of 1000 MU / rnin, and at a total dose of 10-20 Gy,c. weighing and mixing the f-Ni(OH)2obtained after irradiation with carbon black and polyvinylidene fluoride compounds at a mass ratio of 5:3:1 , and d. converting the obtained powder mixture into pellets by applying a pressure of 15,000 psi.

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