Synthesis and Characterization of Complex Framework Material (CFM) Hosts for Li – S Battery

Abstract

Great demand for improvements in battery technology has recently been spurred by the rapidly growing personal electronics and electric vehicle industries. The search for high energy density batteries have reached a limit in lithium intercalation electrodes which have a theoretical capacity of ~250 mAh/g1. Lithium sulfur batteries are a promising alternative to intercalation chemistry batteries, as a sulfur cathode features a theoretical capacity of 1675 mAh/g2. However, the development of lithium sulfur batteries has been impeded by two fundamental issues which are: the low conductivity of sulfur (~10-15 S/cm)3, and the dissolution of polysulfides formed during cycling4. While the conductivity issue can be mitigated by incorporating conductive carbon into the cathode, polysulfide dissolution has proven more challenging to address5 , 6. The formation and dissolution of polysulfides results in the loss of active material from the cathode which culminates in cell failure. Previous attempts to prevent polysulfide dissolution by embedding sulfur into porous carbon structures have been moderately successful. However, the efficiency of these approaches is limited by a lack of control over porosity. To improve on these carbon structures, sulfur hosts with engineered structures and chemical properties should be developed. In this work, lithium sulfur battery cathodes were created using complex framework materials as sulfur hosts. The cathodes were created by solution phase infiltration of sulfur into complex framework materials synthesized by microwave-assisted hydrothermal synthesis. the XRD spectrum and SEM image of one of the CFMs is shown in Figure 1. The cathodes demonstrated impressive electrochemical performance with an initial discharge capacity of ~1620 mAh/g which stabilized at 1100 mAh/g after 100 cycles. Acknowledgement: The authors acknowledge the financial support of DOE grant DE-EE 0006825, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM).