Nanostructured Carbons and Additives for Improvement of the Lithium-Sulfur Battery Positive Electrode

Abstract

Large specific gravimetric/volumetric energy density, environmental benignity and safe low working voltage. All of these points have been used to describe the lithium sulfur (Li-S) battery in the past, but often times it is short cycle life and poor capacity retention that is associated with the Li-S battery. In order to realize the full potential of the Li-S battery in society today, many obstacles must be overcome. In a typical Li-S cell with an organic liquid electrolyte sulfur is reduced by lithium during discharge and subsequent lithium polysulfide species (Li2Sx where x, 2 < x < 8) are formed. These species are readily soluble in typical organic electrolytes and can lead to low Coulombic efficiency and most challenging: active mass loss. Through the loss of active mass, rapid capacity fading occurs over long-term cell cycling. Overcoming the loss of active mass and stabilizing cell capacity at high rates is pivotal to the realization of practical Li-S cells. In this thesis, four separate concepts and materials were studied and prepared with the aim to improve the Li-S batteries capacity, cycle life and capacity retention.