Lithium-Sulfur Batteries

1 Electrochemical Theory and Physics

Geraint Minton

OXIS Energy, E1 Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK

1.1 Overview of a LiS cell

On discharge, the overall process occurring in a lithium–sulfur (LiS) cell is the reaction of lithium and sulfur to form lithium sulfide, Li₂S, according to the reaction shown in Eq. (1.1).

(1.1)

Although both reactants are present in the cell, its design, shown in Figure 1.1, prevents the reaction from taking place directly. The cell comprises a lithium metal electrode and a mixed carbon/sulfur (C/S) electrode. The latter is composed of a mix of highly porous carbon, which provides both electronic conductivity and an electrochemically active surface; sulfur, which is the active material in this electrode; and binder, which holds the structure together. The two electrodes are divided by a separator material, which stops the active materials from making direct contact and also prevents electrons passing internally between the electrodes. Contact between the active materials in each electrode is made indirectly, via an electrolyte, which is in contact with the lithium electrode and permeates the separator and C/S electrode. The electrolyte is composed of a solvent in which a lithium salt, plus any additives, has been dissolved. Adjacent to the C/S electrode is a current collector material to facilitate the flow ...