Preparation of NiO / Cobaltite Nanosheets and their Application in Cathode of High-Performance Lithium-Sulfur Batteries

Abstract

Lithium sulfur batteries Li-S Lithium-sulfur (Li-S) batteries are under intense investigation for nearly three decades as one of the most promising energy storage devices due to its high theoretical capacity of 1675 mAh/g and the theoretical high theoretical density of 2567 Wh/kg. Other advantages include natural abundance, low cost and environmental dignity, and the characteristics of long cycling, making sulfur more attractive such as cathode for rechargeable batteries. However, lithium and sulfur batteries are not used in industries due to some critical issues, such as the disintegration of the polysephide during cycling which causes the so-called "shuttle effect" with its associated fast loss of power and the low capacity of Coulomb's efficiency and expansion in the large volume of 80% ~ Generation of sulfur elements to Li2S. In order to achieve the superior electrochemical performance of (Li-S), this thesis focused on addressing the above issues by designing and manufacturing new cathode materials. Transition metal oxides have a great promise as the high-performance electronic cathode material for lithium batteries.In this study, NiO nanosheets on carbon cloth (CC) was prepared via a simple chemical bath method, it is the hierarchy matrix and used as a cathode material for LSBs. And also, the hybrid nanostructure (NiCo2O4) was manufactured via a facile atmospheric and water-based method, and designed as cathode additive for Li-S batteries. The nano structures of CC and NiO/CC composite and also NiCo2O4 were probed using X-ray diffraction (XRD) technique and scanning electron microscope (SEM). Cyclic voltammetry (CV) and galvanostatic charge/discharge measurement were performed on CHI660c electrochemical workstation. The relationship between current and voltage of the working electrode were measured by Cyclic Voltammetry (CV) at different scan rates. The compound (CC / NiO/S) containing sulfur content is 80% by weight. The compound pole provides a high discharge capacity of 1154.8 mAh/g at 0.1C, a specific capacity of 661.9 mAh/g can be obtained, with a low decay rate of 0.07% per cycle over 300 cycles. At the current densities of 0.5, 1, 2, 3, 4 and 5 mA cm2, the specific capacities of 1008.8, 761.6, 596.5, 526.2, 442.2 and 416.9 mAh/g can be achieved, respectively, indicating excellent rate performance. Besides, a capacity of 1004.4 mAh/g is observed when the current density reduces back to 0.5 mA cm2, indicating high reversibility of the NiO/CC/S composite electrode after high-rate cycling. Excellent capabilities and periodic stability arise from many unique functional features of the cathode. Carbon fiber works to improve the transfer of ion / electron with the absorption of expanding size, NiO nanosheets play an important role in limiting the dissolution of polysulfides by chemical bonds with sulfur. And also, electrochemical measurements reveal that the NiCo2O4 electrode exhibits an initial specific capacity of 1399.8 mAh/g at the current density of 0.1C. The mesoporous NiCo2O4 nanoparticles can provide abundant adsorption sites to confine polysulfides and facilitate the ionic transport. This work may provide a promising method for preparing high-performance cathodes of Li-S batteries.