DEGRADATION MECHANISM DUE TO DECOMPOSITION OF ORGANIC ELECTROLYTE IN LI MOS2 CELLS DURING LONG CYCLING/

The degradation mechanism due to the decomposition of organic electrol ytes during charge and discharge cycling of Li/MoS2 cells has been inv estigated. The gas products of the electrolyte decomposition during lo ng cycling were measured by gas chromatography (GC), and the changes o f electrolyte composition was measured by gas chromatography/mass spec trometry (GC/MS). The gases were produced through two types of electro lyte decomposition: the electrochemical reaction, which was dependent on the charge and discharge voltage, and the chemical reaction, which was independent of the discharge voltage. This decomposition of electr olytes occurred under a discharge voltage lower than 1.4 V. The operat ing conditions with a lower discharge rate and a deeper depth of disch arge (D.O.D.) accelerated the electrochemical decomposition. The rate of gas production by chemical decomposition, which is independent of t he discharge condition, was estimated to be about 0.1 ml/h. (C) 1998 E lsevier Science S.A.