Studies of electrode materials for lithium and sodium metal batteries

There is a need for higher capacity batteries to address the increasing energy demand for electric vehicles and portable technologies. With more than ten times the capacity of current graphite anodes, Li metal is an ideal replacement; however, it suffers from safety and efficiency problems that have so far prevented it from being commercialized. In particular, Li metal has a tendency to form dendritic structures during electrodeposition, which not only present a high surface area leading to excess electrolyte consumption, but may also cause short circuit leading to thermal runaway and battery fires. The causes for dendrite nucleation on metallic Li are numerous and complex making determination of an exact cause for dendrite growth difficult. In this work, the mechanisms for dendrite growth are examined by exploring the relationship between the anode chemistry, topography, and solid electrolyte interphase. Based on the findings, mitigation techniques are proposed and tested; specifically, the used of artificial coatings to homogenize Li electrodeposition on Li metal anodes. While Li may be an ideal anode in terms of its capacity and redox potential, from a practical standpoint it is geographically limited and therefore less desirable for commercial production. Sodium is less expensive and more abundant than Li making it a potential alternative for high capacity batteries. High capacity cathodes are needed to pair with Na anodes, and S is an ideal candidate. However, similar to Li-S batteries, Na-S batteries experience rapid capacity fade due to polysulfide shuttling. The final portion of this work explores a sulfur equivalent cathode material, MoS [subscript 5.6], with the aim of creating a high-capacity, stable Na-S battery.