CNFs/S 1-x Se x Composites as Promising Cathode Materials for High-Energy Lithium-Sulfur Batteries
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.144
CNFs/S1-xSex Composites as Promising Cathode Materials for High-Energy Lithium-Sulfur Batteries Gaind P. Pandey, Kobi Jones, Lamartine Meda
Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125
ABSTRACT
High-energy lithium-sulfur (Li-S) batteries still suffer from poor rate capability and short cycle life caused by the polysulfides shuttle and insulating nature of S (and the discharge product, Li2S). Selenium disulfide (SeS2), with a theoretical specific capacity of 1342 mAh g−1, is a promising cathode material as it has better conductivity compared to sulfur. The electrochemical reaction kinetics of CNFs-S/SeS2 composites (denoted as CNFs/S1-xSex, where x ≤ 0.1) are expected to be remarkably improved because of the better conductivity of SeS2 compared to sulfur. Here, a high-performance composite cathode material of CNFs/S1-xSex for novel Li-S batteries is reported. The CNFs/S1-xSex composites combine the higher conductivity and higher density of SeS 2 with high specific capacity of sulfur. The CNFs/S1-xSex electrode shows good initial discharge capacity of ~1050 mAh g−1 at 0.05 C rate with high mass loading of materials (~6-7 mg cm−2 of composites) and > 97% initial coulombic efficiency. The CNFs/S1-xSex electrode shows more than 600 mAh g-1 specific capacity after 50 charge-discharge cycles at 0.5C rate, much higher compared to the CNFs/S cathodes. INTRODUCTION Currently, high energy density is one primary goal for advanced rechargeable batteries to fulfil the rising demand for plug-in hybrid electric vehicles and smart grid community systems [1]. In recent years, lithium-sulfur (Li-S) batteries have been considered among the most promising candidates for next-generation electric energy storage systems due to their high theoretical capacity of 1675 mAh g -1 and energy density of 2600 Wh kg-1, which are the most attractive properties for electrochemical energy storage [2–4]. Extensive research efforts have been devoted to develop Li-S batteries toward practical applications [5–7]. So far, both specific capacity and cycle life of Li–S
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batteries have been significantly improved with various strategies [5-9]. However, most of the good rate and cycling properties are obtained from electrodes with areal mass loading of sulfur less than 2 mg cm−2. In these cases, the overall areal capacities and areal energy densities of the Li-S cells are still much lower than that of commercial Li-ion batteries [1, 7-9]. The high S mass-loaded electrodes for higher areal capacities is predominantly limited by the poor conductivity and low reactivity of S. Compared to sulfur, Se exhibits higher electrical conductivity (Se: 1 × 10 −3 S −1 m vs S: 5 × 10−28 S m−1) and comparable theoretical volumetr
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