Electrochemical Properties of Lithiated Silicon/Sulfur Battery

The lithium sulfur battery has much higher specific capacity of 1675 mAh/g and energy density of 2600 Wh/kg than conventional lithium ion battery [1]. However, the lithium sulfur battery is difficult to commercialize because a lithium metal used as anode has dendrite growth and explosiveness. Traditional graphite anodes that are applicable for rechargeable Li-ion batteries may not be suitable for rechargeable sulfur batteries since they have low capacity and poor passivation in ethereal solutions. Therefore alternative anodes for sulfur cathode are required. Silicon anode material, which exhibits very high specific capacity of 4200 mAh/g (for a stoichiometry of Li_4.4Si) is one of the most attractive candidates for Li-ion batteries [2, 3]. Combining pre-lithiated silicon anode with sulfur cathode may promote the commercialization. However, both sulfur cathode and silicon anode have drawbacks. The most serious drawback in sulfur cathode that the capacity is rapidly decreased with cycling, because the lithium polysulfide, an intermediate product in the sulfur redox reaction is readily dissolved out into the electrolyte during cycling. Silicon as an anode material is hampered by its large volume expansion (>300%), causing pulverization, loss of electrical contact and consequently early capacity fading. Therefore, various approaches to solve such problems have been suggested [4].

In this work, we suggest an advanced lithium metal free, pre-lithiated silicon-sulfur battery. In our previous research, carbon mesh was inserted between the sulfur cathode and the separator [5]. Sulfur cathode with carbon mesh was inhibited polysulfide dissolved in an electrolyte and was enhanced a utilization of sulfur. In the silicon anode, carbon coating on silicon surface has been conducted. Silicon properties such as electrical conductivity and Li-ion conductivity can be enhanced by carbon coating. Prior to use in the silicon/sulfur battery, the silicon was lithiated by direct contact with a lithium metal in a 1M LiTFSI solution with 1, 2-dimethoxyethane (DME) and 1, 3-dioxolane (DOL) at volume ratio of 1:1. The results show that lithiated silicon-sulfur battery exhibits increased capacity and good cyclability.

[1] Y. Yang, M. T. McDowell, A. Jackson, J. J. Cha, S. S. Hong and Y. Cui, Nano let., 10 (2010) 1486-1491.

[2] N. Liu, L. Hu, M. T. McDowell, A. Jackson and Y. Cui, Acs Nano, 5 (2011) 6487-6493

[3] I. Hong, B. Scrosati, F. Croce, Solid State Ionics, 232 (2013) 24-28

[4] M. Green, E. Fielder, B. Scrosati, M. Wachtler, J. S. Moreno, Electrochemical and Solid-State Letters, 6 (2003) A75-A79

[5] T. G. Jeong, Y. H. Moon, H. H. Chun, H. S. Kim, B. W. Cho and Y. T. Kim, Chem. Commun., 49 (2013) 11107-11109