Comparison of the Reactivity of NaxC6 and LixC6 with Non-Aqueous Solvents and Electrolytes

The reactivity of sodium inserted nanoporous carbon with ethylene carbonate (EC), diethyl carbonate (DEC), EC:DEC or NaPF6/EC:DEC electrolyte was studied using Accelerating Rate Calorimetry (ARC) and compared to analogous results for Li intercalated graphite. Lithiated graphite is less reactive in LiPF6/EC:DEC than in EC:DEC solvent due to the formation of LiF in the passivating film. By contrast, Na inserted nanoporous carbon is more reactive in NaPF6/EC:DEC than in EC:DEC due to the high thermal stability of NaPF6, which does not react to make NaF, and the preferential solvation of NaPF6 by EC which leads to an increased reaction with the more reactive DEC. This could have important consequences for the safety of Na-ion batteries. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3606364] All rights reserved.