Nanostructured Li2S鈥揅 Composites as Cathode Material for High-Energy Lithium/Sulfur Batteries

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• 作者：Kunpeng Cai ; Min-Kyu Song ; Elton J. Cairns ; Yuegang Zhang
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：December 12, 2012
• 年：2012
• 卷：12
• 期：12
• 页码：6474-6479
• 全文大小：404K
• 年卷期：v.12,no.12(December 12, 2012)
• ISSN：1530-6992

文摘

With a theoretical capacity of 1166 mA路h路g^鈥?, lithium sulfide (Li₂S) has received much attention as a promising cathode material for high specific energy lithium/sulfur cells. However, the insulating nature of Li₂S prevents the achievement of high utilization (or high capacity) and good rate capability. Various efforts have been made to ameliorate this problem by improving the contact between Li₂S and electronic conductors. In the literature, however, a relatively high capacity was only obtained with the Li₂S content below 50 wt %; therefore, the estimated cell specific energy values are often below 350 W路h路kg^鈥?, which is insufficient to meet the ever-increasing requirements of newly emerging technologies. Here, we report a cost-effective way of preparing nanostructured Li₂S-carbon composite cathodes by high-energy dry ball milling of commercially available micrometer-sized Li₂S powder together with carbon additives. A simple but effective electrochemical activation process was used to dramatically improve the utilization and reversibility of the Li₂S鈥揅 electrodes, which was confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. We further improved the cycling stability of the Li₂S鈥揅 electrodes by adding multiwalled carbon nanotubes to the nanocomposites. With a very high specific capacity of 1144 mA路h路g^鈥? (98% of the theoretical value) obtained at a high Li₂S content (67.5 wt %), the estimated specific energy of our cell was 610 W路h路kg^鈥?, which is the highest demonstrated so far for the Li/Li₂S cells. The cells also maintained good rate capability and improved cycle life. With further improvement in capacity retention, nanostructured Li₂S鈥揅 composite cathodes may offer a significant opportunity for the development of rechargeable cells with a much higher specific energy.

Keywords:

Energy storage; lithium/sulfur batteries; lithium sulfide (Li₂S); cathodes; high specific energy; electrochemical activation