Production of rGO based hybrid composite buckypaper cathodes by using copper oxide polysulfide adsorbent for Li-S batteries

Abstract

Lithium-sulfur batteries are particularly noteworthy for applications requiring large capacity and long battery life. Transition metal oxides have emerged as polar host materials for lithium polysulfides to further modulate the bonding energy with polysulfides and increase the coupling density of the electrodes. Polar metal oxides naturally adsorb polysulfides on their hydrophilic surfaces. In this study, the polysulfide adsorbing ability of CuO against the shuttle effect is utilized. For this purpose, copper(II) oxide (CuO) is used as polysulfide adsorbent and CuO - reduced Graphene Oxide / Sulphur (CuO-rGO/S) hybrid composite buckypaper electrodes are produced as cathodes in Li-S batteries without using binders. In this work, optical, morphological and structural analyzes of composite films were carried out by Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analysis, respectively. After the CR2032 button cell was assembled using the produced cathode materials, cyclic voltammetry (CV), charge-discharge performance tests, rate capability and electrochemical impedance spectroscopy (EIS) analyzes were performed to investigate the Li-S battery capacities. With the CuO-rGO/S hybrid composite cathode containing 2 % CuO, a discharge capacity of 1205 mAh g⁻¹ was obtained in the first cycle. At the end of the 1000 cycles, the discharge capacity of the cathode was achieved as high as 696 mAh g⁻¹. As a result, the battery capacity of rGO/S-based composite electrodes has been improved by taking advantage of CuO added to the cathode structure to adsorb polysulfides.