Rechargeable lithium batteries with long cycle life and high energy density have great market demand for energy storage systems. The lithium sulfur battery is attracting intense interest because of its theoretical capacity and energy density, which is much higher than that of Lithium ion battery based on intercalation reactions. Moreover, the cathode, sulfur, is highly abundant, low cost and nontoxic. Lithium sulfur battery has been considered as a next-generation energy storage system, especially for large scale applications.[1] The main obstacle to realize the practical use of lithium sulfur battery lies in the rapid capacity fading, which is primarily attributed to the solubility and shuttle of polysulfides generated during charge and discharge.[2] The shuttle of polysulfides between electrodes not only decreases utilization of sulfur, but also greatly corrodes lithium and reduces coulombic efficiency of the cell.

Here, we introduced carbon disulfide (CS₂) as an additive for DOL/DME-based electrolytes. We found that CS₂ is able to form complexes with polysulfides. These complexes are soluble in DOL/DME and can suppress shuttle reactions. In addition, the employ of CS₂ can also passivate the surface of both cathodes and anodes. Improved coulombic efficiency and cycling performance were exhibited in Fig 1.a combined with LiNO₃[3] as binary additives. Fig 1.b presents the morphology of anode after 50 cycles. It's observed that the surface is quite dense and smooth. XPS (Fig 1.c) shows the existence of LiF. This result indicates the ability of CS₂ to passivate the Li metal because of the halides, which can improve Li cycling.[4]   

Fig 1. a. Electrochemical performance of lithium sulfur batteries. b. Morphology of Li anode after 50 cycles with CS₂ and LiNO₃ additives. c. The F 1s XPS spectra of Li anode after 50 cycles with CS₂ and LiNO₃ additives.

References

[1] X.L. Ji, L.F. Nazar, Journal of Materials Chemistry, 20 (2010) 9821-9826.

[2] Y.V. Mikhaylik, J.R. Akridge, J. Electrochem. Soc., 151 (2004) A1969.

[3] D. Aurbach, E. Pollak, R. Elazari, G. Salitra, C.S. Kelley, J. Affinito, J. Electrochem. Soc., 156 (2009) A694.

[4] Y.Y. Lu, Z.Y. Tu, L.A. Archer, Nature Materials, 13 (2014) 961-969.