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 NaPF 6 /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 LiPF 6 /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 NaPF 6 /EC:DEC than in EC:DEC due to the high thermal stability of NaPF 6 , which does not react to make NaF, and the preferential solvation of NaPF 6 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.