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Polysulfide Trapping Agent (PTA) Coated Directly Doped Sulfur Architectures (DDSA) – New Platforms for High Capacity Li – S Batteries

Thursday, 5 October 2017: 11:50
National Harbor 8 (Gaylord National Resort and Convention Center)
P. Murugavel Shanthi (University of Pittsburgh), P. Jampani (Department of Bioengineering, University of Pittsburgh), B. Gattu (Dept of Chemical Engineering, University of Pittsburgh), and P. N. Kumta (Department of Bioengineering, University of Pittsburgh)
Increasing demands for high energy and high power storage systems for use in electric vehicles and electronic devices has made it imperative to develop high performance rechargeable batteries. This stringent need has attracted widespread attention worldwide. Lithium – sulfur (Li – S) batteries has been consequently, extensively studied recently as a potential rechargeable electrochemical power sources due to its high theoretical capacity (1672 Ah kg−1 sulfur)1 and high energy density (2500 Wh kg−1 sulfur)2 based on the complete reduction of elemental sulfur to form the end product of lithium sulfide (Li2S).

However, commercialization pathway for Li – S batteries is still fraught with high self – discharge and the short cycle life problems of the Li – S rechargeable system. These limitations are largely related to the poor ionic and electronic conductivity of elemental sulfur3, formation of a series of sulfur reduction intermediates during discharge (Li2Sx, x > 2)4, 5 that are highly soluble in organic electrolyte and the high reactivity of the dissolved polysulfides with the Li anode4.

Several approaches including the use of a conductive additive6, encasing sulfur into conductive porous host materials7 and replacing the organic electrolyte with a polymer electrolyte8 has been shown to improve the performance by improving the ionic conductivity of sulfur and reducing polysulfide dissolution by avoiding direct contact with the liquid electrolyte. However, despite these advances, complete prevention of polysulfide dissolution has not yet been accomplished due to lack of fundamental understanding about the mechanism of polysulfide dissolution.

In this work, directly doped sulfur architectures (DDSA) with sulfur loadings greater than 16mg/cm2 were created using simple electrochemical techniques. The cathodes were studied chemically and electrochemically to understand the mechanism of polysulfide dissolution in these structures. The DDSA electrodes are then coated with a polysulfide trapping agent (PTA) to chemically prevent the dissolution of polysulfide species. These PTA coated DDSA showed a high initial capacity of 1305 mAhg-1 with stable performance of 1208 mAhg-1 for over 30 cycles (Figure 1). Mechanism of polysulfide dissolution by PTA will be presented and discussed.