Rechargeable Lithium Sulfur Battery

Abstract

In this paper, the structural change of the sulfur cathode during the electrochemical reaction of a lithium sulfur battery employing 0.5 M LiCF 3 SO 3 -tetra͑ethylene glycol͒ dimethyl ether ͑TEGDME͒ was studied by means of scanning electron microscopy ͑SEM͒, X-ray diffraction ͑XRD͒, and wave dispersive spectroscopy ͑WDS͒. The discharge process of the lithium sulfur cell could be divided in the first discharge region ͑2.4-2.1 V͒ where the reduction of elemental sulfur to form soluble polysulfides and further reduction of the soluble polysulfide occur, and the second discharge region ͑2.1-1.5 V͒ where the soluble polysulfides are reduced to form a nonuniform Li 2 S solid film covered over the carbon matrix. It was also found that the charge of lithium sulfur cell leads to the conversion from Li 2 S to the soluble polysulfide, resulting in the removal of Li 2 S layer formed on carbon matrix. However, the oxidization of the soluble polysulfide to solid sulfur hardly occurs and few Li 2 S are left on carbon matrix even at 100% depth of charge.

Li2S nano spheres anchored to single-layered graphene as a high-performance cathode material for lithium/sulfur cells

“…Two discharge plateaus in the range of 2.4-2.1 V and 2.1-1.7 V, respectively, were observed, which are related to the stepwise reactions between Li 2 S and solid S 8 molecules [8]. The second discharge plateau was more sensitive to the discharge C rate [55], consequently, all the cathodes revealed decreased utilization of sulfur and increased overpotentials as the discharge C-rate increased. Both the #8 and #5-Li 2 S/G@C could undergo reversible redox reactions at higher C rates, however, #8-Li 2 S/G@C showed the lowest charge and discharge overpotentials at each C rate and exhibited a stable plateau even at the high C rate of 2 C, demonstrating a remarkable electronic conductivity and the lowest energy loss associated with charge/discharge overpotentials owing to the combination of the highly conductive graphene substrate and the carbon coating.…”

“…3a, even though good capacities can be obtained with #3, #5 and #8-Li 2 S/G@C cathodes at 0.2 C, the specific capacity of the #3 and #5-Li 2 S/G@C composite cathodes dramatically decreased as the discharge rate increased. This capacity loss with increased rates is directly associated with the conductivity of the cathodes [55]. In contrast, the #8-Li 2 S/G@C cathode showed the best rate capability and delivered specific capacities of 1029.8 mA h g À 1 of Li 2 S (1472 mA h g À 1 of S), 831.6 mA h g À 1 of Li 2 S (1189 mA/ h g À 1 of S), 769 mA h g À 1 of Li 2 S (1099 mA h g À 1 of S) and 672.8 mA h g À 1 of Li 2 S (962 mA h g À 1 of S) at charge/discharge rates of 0.2 C, 0.5 C, 1.0 C and 2.0 C (1.0 C ¼1166 mA h g À 1 Li 2 S), respectively.…”

Lithium/Sulfur Secondary Batteries: A Review

“…The structural changes of sulfur cathode during the charge-discharge process of a Li/S cell employing a liquid electrolyte (0.5 M LiCF 3 SO 3 in TEGDME) have been investigated in detail by Cheon et al using SEM, XRD and wave dispersive spectroscopy (WDS) [14]. The cathode morphology examination at different depths of discharge has shown a significant change in morphology at the end of the lower (2.1 V) plateau.…”

“…The influence of sulfur cathode thickness (varied as 15, 30 and 60 µm) on the discharge capacity of Li/ S cell was investigated by Cheon et al [14]. It was observed that an increase in thickness resulted in a decrease in sulfur utilization at all current rates, as a result of the thicker insulative layer of sulfur.…”

Optimization of S/Mno2 Composite Cathode Material for Lithium Sulfur Batteries

“…The rechargeable lithium-sulfur (Li-S) battery has attracted immense assiduity in the last several years [4][5][6] owing to its high energy density (theoretically 2567 Wh/kg) and high theoretical specific capacity (1675 mAh/g). It exhibits higher specific capacity and specific energy (with lithium anode) than any other known cathode active materials [7,8] . In addition to, sulfur is abundant in nature, inexpensive and environmental harmless.…”