Enhanced capacity of Lithium-Sulfur batteries using functional amorphous carbon coated separators

MARÍA ROJAS; M. L. PARA; DANIEL BARRACO; GUILLERMINA L. LUQUE

Bologna

Congreso; 9th Annual Meeting of the International Society of Electrochemistry; 2018

Currently, Lithium batteries present the most promising solution for energy storage in many applications, from electronic devices to electrical vehicles and electrical network power storage. Among the new battery technologies, Lithium-Sulfur batteries are attractive because since they have high capacity (1675 mAh g-1), high energy density, high efficiency and long life cycles. [1] However, they present some disadvantages such as low conductivity of sulfur, volume changes during lithiation / delitiation and generation of polysulfides (PS) during cycling, leading to the reduction of active material, the decreasing in the coulombic efficiency, and deterioration of cycling performance. The aim of the present work is to modified commercial separator with carbon material in order to optimize the performance and durability of Lithium-Sulfur batteries. The problem is approached from an experimental and theoretical point of view in a coordinated manner. The separator was modified with amorphous Carbon (Super P Timcal) treated with different acid and basic protocols, to generate functional groups that can trap PS, improving life battery. Coin cell were used to made every experiment, using LiTFSI 0.5 M and LiNO3 0.25M in 1,2-dimethoxyethane(DME)/1,3dioxolane (DOL) 1:1. The new materials were studied applying different experimental techniques in order to obtain structural information such as particle size, morphology, crystalline structure, chemical composition, and roughness, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetry and adsorption isotherms. Additionally, the electrochemical behavior of the cathodes obtained were characterized by charge-discharge cycles, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Simultaneously computational calculations were carried out within the electronic density functional theory (DFT) of the same carbonaceous structures with different functional groups to study their interaction with long-chain polysulfides, using the SIESTA code. The different experimental and computational characterizations allow understanding the interaction between PS and treated amorphous carbon.