Rechargeable Lithium Sulfur Battery II. Rate Capability and Cycle Characteristics

TLDR: In this article, the authors investigated the rate capability and cycle characteristics of a lithium sulfur battery and found that the second discharge region where solid Li 2 S is formed on the surface of the carbon matrix in the cathode was highly sensitive to cathode thickness and discharge rate.

Abstract: This paper reports on the investigation of rate capability and cycle characteristics of a lithium sulfur battery. The second discharge region where solid Li 2 S is formed on the surface of the carbon matrix in the cathode was highly sensitive to cathode thickness and discharge rate. The scanning electron microscope (SEM) observation suggests that thick Li 2 S layer formed at the surface of the cathode causes the diminution of the second discharge region at high discharge rate. Upon repeated cycle, the delocalization of the surface Li 2 S layer happened, however, the irreversible Li 2 S gradually increased with cycle as evidence by (SEM) and wave dispersive spectroscopy measurements, causing capacity fade. The formation of the irreversible Li 2 S was more significant for higher rates of discharge. It is believed that the destruction of the carbon matrix by stress generated during the localized deposition of Li 2 S is responsible for the formation of irreversible Li 2 S.