Self-discharge of lithium–sulfur cells using stainless-steel current-collectors

The self-discharge behaviour of Li–S cell, is investigated through changes in the open-circuit voltage (OCV) and discharge capacity with storage time. A fresh Li–S cell experiences 72% sulfur utilization during the first discharge, as based on the theoretical capacity for the formation of Li2S. After 30 days of storage, the OCV has fallen from 2.48 to 2.16 V and the discharge capacity has decreased from 1206 to 924 mAh g−1 (based on sulfur). Analysis of the self-discharged sample by a variety of techniques shows the formation of lithium polysulfides, such as Li2Sn (n ≥ 1) from the reaction of lithium and sulfur, which is related to the corrosion of the stainless current-collector. Stainless steel is not the most appropriate current-collector material for Li–S cells. The extent of self-discharge can be decreased by using a gold-coated current-collector that offers protection against corrosion.