Improvement of cycle performance of carbon-sulfur composite cathode materials for Li-S battery.

Abstract

Recently, there has been intense interest in the spherical structures due to their advantage of good surface permeability and accessibility, low density, and high mechanical stability. Additionally, mesoporous carbons with large surface area are proved to be an important class of functional materials for their super performance compared with other carbon materials. A lithium superbattery exploiting a high performances mesoporous hard carbon spherules-sulfur cathode and a stable, highly conducting electrolyte is reported. The results demonstrate that the battery cycles with very high capacity, i.e. of the order of 750 mAh g-1 (S) with excellent retention during cycling. In addition, by exploiting the high conductivity of our selected electrolyte, the battery performs very well also at low temperature, i.e. delivering a capacity of 500 mAh g-1 (S) at 0 oC for over 170 charge-discharge cycle. We believe that these results, to our knowledge not commonly achieved in the past, may substantially contribute to the progress of the lithium-sulfur battery technology. Furthermore, in this work we disclose a new, lithium metal-free, silicon-sulfur, lithium ion battery based on a high-rate sulfur-carbon composite cathode, formed by trapping sulfur in highly porous and hard carbon spherules, combined with a lithiated silicon-carbon nanocomposite anode, separated by a glycol-based electrolyte. This 2 V battery shows an average specific capacity of 300 mAh g-1 (S), a long cycle life, an expected low cost and high safety. Due to these properties, this new battery is expected to be a very valid power source for efficient electric vehicles.