Selenium disulfide (SeS₂)-based composites have received much attention as a promising cathode material for high-energy lithium metal batteries due to their higher theoretical capacity (1342 mAh g⁻¹) than that (675 mAh g⁻¹) of selenium and a less significant shuttle effect than that of sulfur.^[1] However, the biggest challenges faced by Li/SeS₂ batteries are (1) the development of high-performance cathodes that can maintain the functional interface during cycling and (2) the identification of suitable electrolytes that can allow good cyclability without the degradation of lithium metal anodes. It has been reported that an ionic liquid, N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, i.e. Py₁₄TFSI, can be used as co-solvent in ether-based electrolytes to form high-quality protection layer on lithium metal.^[2] In this study, an effective strategy for developing high-performance Li/SeS₂ batteries is introduced via a synergistic enhancement comprising the effective cathode design and the lithium anode protection in Py₁₄TFSI containing electrolytes. We found that the hierarchical SeS₂@carbon nanocomposites, confirmed by X-ray nano-computed tomography, facilitated Li-ion transportation and enhanced the electrochemical utilization of SeS₂, enabling the improved rate capability of Li/SeS₂ battery. Furthermore, the systematic studies on the morphological change as well as the electrochemical stability of lithium anode indicate that Py₁₄TFSI-LiNO_3­-containing electrolytes could effectively suppress the shuttle effect and protect lithium metal by forming a stable and LiF-dominated solid-electrolyte-interphase layer, leading to much improved Coulombic efficiency and cyclability of Li/SeS₂ batteries. These results underscore a synergistic approach toward the development of high-energy Li/SeS₂ batteries with long cycle life.

[1] a) A. Abouimrane, D. Dambournet, K. W. Chapman, P. J. Chupas, W. Weng, K. Amine, J. Am. Chem. Soc. 2012, 134, 4505-4508; b) Y. Cui, A. Abouimrane, J. Lu, T. Bolin, Y. Ren, W. Weng, C. Sun, V. A. Maroni, S. M. Heald, K. Amine, J. Am. Chem. Soc. 2013, 135, 8047-8056.

[2] J. Zheng, M. Gu, H. Chen, P. Meduri, M. H. Engelhard, J.-G. Zhang, J. Liu, J. Xiao, Journal of Materials Chemistry A 2013, 1, 8464.