The cycling behavior and electrochemical characteristics of the sulfur electrode in the lithium/sulfur rechargeable cell were investigated using galvanostatic cycling and cyclic voltammetry. The cycling performance of the sulfur electrode was characterized in different solvents (triglyme, PEGDME 250 and 500). The variations of capacity and capacity fade rate were also measured as a function of the content of sulfur, carbon and binder. The capacity fade rate of the sulfur electrode was lower with a higher molecular weight solvent such as PEGDME 250 or 500. The content of carbon in the sulfur electrode plays an important role in capacity improvement. The best cell cycled for 600 deep cycles above 100 mAh/g of electrode, and 400 cycles above 160 mAh/g of electrode (80% of original capacity) at room temperature. © 2002 The Electrochemical Society. All rights reserved.

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Laboratory-size LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite lithium-ion pouch cells were cycled over 100% DOD at room temperature and 60°C in order to investigate high-temperature degradation mechanisms of this important technology. Capacity fade for the cell was correlated with that for the individual components, using electrochemical analysis of the electrodes and other diagnostic techniques. The high-temperature cell lost 65% of its initial capacity after 140 cycles at 60 o C compared to only 4% loss for the cell cycled at room temperature. Cell ohmic impedance increased significantly with the elevated temperature cycling, resulting in some of loss of capacity at the C/2 rate. However, as determined with slow rate testing of the individual electrodes, the anode retained most of its original capacity, while the cathode lost 65%, even when cycled with a fresh source of lithium.Diagnostic evaluation of cell components including XRD, Raman, CSAFM and suggest capacity loss occurs primarily due to a rise in the impedance of the cathode, especially at the end-of-charge. The impedance rise may be caused in part by a loss of the conductive carbon at the surface of the cathode and/or by an organic film on the surface of the cathode that becomes non-ionically conductive at low lithium content.

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