Şarj Edilebilir Li-İyon Piller İçin Karbon Esaslı Li2CuP2O7 Katot Elektrotlarının Geliştirilmesi ve Elektrokimyasal Performanslarının İncelenmesi

Abstract

Lithium-ion batteries are widely used in various fields, from the healthcare sector to the defense industry, transportation, and communication, and their demand is constantly increasing. Among the primary objectives of this master's thesis work is to enhance the electrochemical performance of the Li2CuP2O7 cathode active electrode material, which can be produced at a lower cost as an alternative to high-cost lithium-based advanced commercial cathode materials used in the growing Li-ion battery sector. Concerning this objective, cathode electrodes prepared using high electrical conductivity various graphene sources have been compared for the first time in this study regarding their charge-discharge capacities and cycle lifetimes. The cathode electrodes, prepared with graphene, graphene oxide, reduced graphene oxide, carbon black and a 1:1 mixture of carbon black and graphene as conductivity sources, were characterized in detail, including the analysis of the graphene derivatives and Li2CuP2O7 material using various techniques such as Raman Spectroscopy, X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), as well as Brunauer-Emmett-Teller (BET) measurements for surface area and porosity. The electrochemical performance of carbon sources was carried out using techniques such as cyclic voltammetry (CV), chronoamperometry (galvanostatic charge-discharge), and electrochemical impedance spectroscopy (EIS). CV and EIS results support significant electron transfer and Li+ diffusion differences among different carbon sources. In this study, it is indicated that the surface area of the conductivity agent carbon source has a significant impact on the capacity of active electrode materials used in lithium-ion batteries. When ranking the performance of the cathode electrodes based on the first cycle discharge values at a current density of 20 mA/g, the order is as follows: graphene oxide (372 mAh/g) > a mixture of carbon and graphene (228 mAh/g) > graphene (196 mAh/g) > carbon black (177 mAh/g) > reduced graphene oxide (25 mAh/g). Similarly, at a current density of 30 mA/g for the first cycle discharge values: graphene oxide (374 mAh/g) > graphene (266 mAh/g) > a mixture of carbon and graphene (84 mAh/g) > reduced graphene oxide (74 mAh/g) > carbon black (26 mAh/g). The obtained results indicate that using different carbon sources as cathode electrode materials in Li-ion batteries could significantly contribute to energy-focused technologies.