Browsing by Subject "organopolysulfide"

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    Bis(aryl) Tetrasulfides as Cathode Materials for Rechargeable Lithium Batteries
    (Wiley, 2017) Guo, Wei; Wawrzyniakowski, Zachary D.; Cerda, Matthew M.; Bhargav, Amruth; Pluth, Michael D.; Ma, Ying; Fu, Yongzhu; Department of Mechanical Engineering, School of Engineering and Technology
    An organotetrasulfide consists of a linear chain of four sulfur atoms that could accept up to 6 e− in reduction reactions, thus providing a promising high-capacity electrode material. Herein, we study three bis(aryl) tetrasulfides as cathode materials in lithium batteries. Each tetrasulfide exhibits two major voltage regions in the discharge. The high voltage slope region is governed by the formation of persulfides and thiolates, and the low voltage plateau region is due to the formation of Li2S2/Li2S. Based on theoretical calculations and spectroscopic analysis, three reduction reaction processes are revealed, and the discharge products are identified. Lithium half cells with tetrasulfide catholytes deliver high specific capacities over 200 cycles. The effects of the functional groups on the electrochemical characteristics of tetrasulfides are investigated, which provides guidance for developing optimum aryl polysulfides as cathode materials for high energy lithium batteries.
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    A Class of Organopolysulfides As Liquid Cathode Materials for High-Energy-Density Lithium Batteries
    (ACS, 2018) Bhargav, Amruth; Bell, Michaela Elaine; Karty, Jonathan; Cui, Yi; Fu, Yongzhu; Mechanical Engineering, School of Engineering and Technology
    Sulfur-based cathodes are promising to enable high-energy-density lithium–sulfur batteries; however, elemental sulfur as active material faces several challenges, including undesirable volume change (∼80%) when completely reduced and high dependence on liquid electrolyte wherein an electrolyte/sulfur ratio >10 μL mg–1 is required for high material utilization. These limit the attainable energy densities of these batteries. Herein, we introduce a new class of phenyl polysulfides C6H5SxC6H5 (4 ≤ x ≤ 6) as liquid cathode materials synthesized in a facile and scalable route to mitigate these setbacks. These polysulfides possess sufficiently high theoretical specific capacities, specific energies, and energy densities. Spectroscopic techniques verify their chemical composition and computation shows that the volume change when reduced is about 37%. Lithium half-cell testing shows that phenyl hexasulfide (C6H5S6C6H5) can provide a specific capacity of 650 mAh g–1 and capacity retention of 80% through 500 cycles at 1C rate along with superlative performance up to 10C. Furthermore, 1302 Wh kg–1 and 1720 Wh L–1 are achievable at a low electrolyte/active material ratio, i.e., 3 μL mg–1. This work adds new members to the cathode family for Li–S batteries, reduces the gap between the theoretical and practical energy densities of batteries, and provides a new direction for the development of alternative high-capacity cathode materials.