Improved Lithium Sulfur Battery Performance through Attaching Nanosilica on the Backside of Nickel Foam

Lithium Sulfur (Li-S) battery has a theoretically high specific capacity of 1675 mAh g-1, which one of the most promising energy source for electric vehicles (EVs), hybrid electric vehicles (HEVs) and energy storage system (ESS). However, Li-S batteries have crucial problem resulting from the polysulfides dissolution which is called ‘Shuttle Effect’. This shuttle effect causes overpotential and lowers its Coulomb efficiency. Also, a loss of active material by dissolution makes capacity fading. So the prevention of the polysulfides dissolution is the main issue of sulfur batteries. To solve the polysulfides dissolution we use nanosilica material on the current collector of cathode. It is reported that nanosilica has a characteristics of absorbing polysulfides. Zhang. et. al reported that they could control the shuttle mechanism by using nanosilica on the separator. However, the polysulfides accumulated on the separator hinder Li ion transport, leading to low capacity values compared to pristine Li-S batteries. In our research, nickel foam based sulfur cathode with silica coated on backside is investigated. Silica on the backside absorbs polysulfides, eventually suppressing the shuttle effect and reducing the quantity of the polysulfides on the separator. As a result, the coulomb efficiency and the capacity of the Li-S battery has increased comparing the uncoated Li-S battery. The examination was conducted by comparing between the pristine and the silica coated sample. Cells were tested at the current densities of 0.1 C rate with limited voltage of 1.8 to 2.8V. The morphology of the samples was observed on a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The structure of the samples was characterized by X-ray diffraction (XRD) spectroscopy. The result was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).

[1] S.S.Zhang, D.T.Tran, Electrochim. Acta, 114, 296 (2013).