Adopting Mixed Sulfur and Selenium Chalcogenides As High Energy Density Copolymer Cathodes in Rechargeable Sodium Metal Systems

Abstract

The ever increasing demand for energy storage has encouraged exploration of battery systems with higher energy density and lower cost than Li-ion batteries.1 This work reveals the very first demonstration of a room temperature, sodium/polymeric mixed-chalcogenide battery. The chemistry is enabled by crosslinking of sulfur and selenium, which maintains the elemental mixture in long chains instead of crystalline rings, for a mechanistically different conversion cathode. Room temperature Li-S batteries, which boast ultra-high energy density (~2600 Wh/kg) and low cost/highly abundant sulfur, are expected to succeed the intercalation Li-ion battery (<400 Wh/kg), but to-date deliver impractical cycle life due to active material dissolution. The novel chain assembly provided by crosslinking prevents this behavior, enabling extensive cycle life.2 Herein the crosslinker type and molecular ratio are modulated for optimal chain length and performance. Furthermore, selenium delivers 20 orders of magnitude greater electrical conductivity than sulfur.3 The atomic ratio of sulfur to selenium is modulated for a balance of electrical conductivity and energy density. Notably, these cathodes are simplistically processed at temperatures below 200 ˚C. The crosslinked, mixed chalcogenide cathodes are paired with metallic sodium anodes, that are 3 orders of magnitude more abundant than lithium metal,1 and exhibit favorable plating behavior in the system-prescribed, ether-based electrolytes.4 This full cell touts a theoretical energy density of ~1000 Wh/kg and effective incorporation of highly abundant raw materials. Hong, X.; Mei, J.; Wen, L.; Tong, Y.; Vasileff, A. J.; Wang, L.; Liang, J.; Sun, Z.; Dou, S. X., Nonlithium Metal–Sulfur Batteries: Steps Toward a Leap. Advanced Materials 0 (0), 1802822.Simmonds, A. G.; Griebel, J. J.; Park, J.; Kim, K. R.; Chung, W. J.; Oleshko, V. P.; Kim, J.; Kim, E. T.; Glass, R. S.; Soles, C. L.; Sung, Y.-E.; Char, K.; Pyun, J., Inverse Vulcanization of Elemental Sulfur to Prepare Polymeric Electrode Materials for Li–S Batteries. ACS Macro Letters 2014, 3 (3), 229-232.Abouimrane, A.; Dambournet, D.; Chapman, K. W.; Chupas, P. J.; Weng, W.; Amine, K., A New Class of Lithium and Sodium Rechargeable Batteries Based on Selenium and Selenium–Sulfur as a Positive Electrode. Journal of the American Chemical Society 2012, 134 (10), 4505-4508.Seh, Z. W.; Sun, J.; Sun, Y.; Cui, Y., A Highly Reversible Room-Temperature Sodium Metal Anode. ACS Central Science 2015, 1 (8), 449-455.