Comparison of the Reactions Between Li7 / 3Ti5 / 3 O 4 or LiC6 and Nonaqueous Solvents or Electrolytes Using Accelerating Rate Calorimetry

Abstract

The reactions of discharged or discharged mesocarbon microbead with ethylene carbonate/diethyl carbonate (EC/DEC) (1:2 by volume) solvent, 1 M EC/DEC or 0.8 M LiBOB EC/DEC are compared using accelerating rate calorimetry (ARC). We find that (1.5 V vs. Li) shows lower reactivity than (0.05 V vs. Li) in EC/DEC solvent or in -based electrolyte. The reactions between both electrodes and 1 M EC/DEC proceed in a clear stepwise fashion, where first, intercalated lithium reacts with (from the decomposition of to produce LiF, and then, when the is consumed, the remaining lithium reacts with the solvents. The addition of 0.8 M LiBOB to EC/DEC solvent greatly increases the thermal stability of both and X-ray diffraction (XRD) studies show that both and react with EC/DEC or LiBOB EC/DEC to produce at the end of the ARC experiments. XRD studies show that reacts with 1 M EC/DEC to form LiF, and some In fact, even a fresh sample of reacts with 1 M EC/DEC to produce substantial quantities of and LiF, but little heat is evolved during this reaction since the Li in is so tightly bound. The results in this paper suggest that safer lithium-ion cells could be built using negative electrodes than with graphite negative electrodes. © 2004 The Electrochemical Society. All rights reserved.