Battery technologies involving Li-S chemistry are promising approaches to realize inexpensive and high energy density storage for sustainable energy applications. However, current Li-S batteries still suffer from short life-time due to active material loss through the soluble polysulfide molecules shuttling between battery cathode and anode.[1] We present herein our recent advances in the understanding of the electrochemical reactions at Li-S battery cathode and addressing the shuttle effect by polysulfide trapping. Specifically, an in-operando characterization technique based on optical microscopy is developed to intuitively visualize the selective deposition of sulfur and Li₂S in battery cathodes, and the critical roles of current collectors and additives, including different metals and semiconductors, are demonstrated. Accordingly, innovative cathode architectures are designed to control the oriented deposition and diffusion of sulfur-containing species. In particular, an ultrathin and compact blocking layer of 2D MoS₂ and WS₂ nanoflakes, with a thickness of ca. 15 nm, are deposited on separator through a solution based self-assembly method,[2] which effectively adsorb polysulfide molecules and thus suppress their diffusion to the battery anode. In addition, Li₂S-metal composites and polymer-metal hybrid networks are fabricated as hosts for sulfur cathodes to enable rapid battery charge-discharge processes given the large active surface area and better control of charge (or discharge) product deposition.[3] Combining these two strategies, we report greatly enhanced specific capacity (over 1200 mAh g^-1) and cyclability (over 500 cycles) for the nanostructured sulfur cathodes compared to the conventional carbon-sulfur based cathode, and the routes to further improving high-energy and long-life Li-S battery are discussed.

[1] Seh, Z. W.; Sun, Y.; Zhang, Q.; Cui, Y. Chem. Soc. Rev. 2016, 45, 5605.

[2] Yu, X.; Prévot, M. S.; Guijarro, N.; Sivula, K. Nat. Commun. 2015, 6, 7596.

[3] Zhou, G. M.; Sun, J.; Jin, Y.; Chen, W.; Zu, C. X.; Zhang, R. F.; Qiu, Y. C.; Zhao, J.; Zhuo, D.; Liu, Y. Y.; Tao, X. Y.; Liu, W.; Yan, K.; Lee, H. R.; Cui, Y. Adv. Mater. 2017, 29, 1603366