Electrochemical Stability of LiMF6 ( M = P , As , Sb ) in Tetrahydrofuran and Sulfolane

LiAsF 6 is the current state‐of‐the‐art lithium salt for use in many prototype rechargeable systems. The instability and potential toxicity of LiAsF 6 has led to the search for new lithium salts. To this end, we investigated the electrochemical stability of LiSbF 6 and LiPF 6 in aprotic organic solvents. Electrochemical studies, conductivity measurements, and open‐circuit stability tests were conducted on LiSbF 6 in tetrahydrofuran and sulfolane. Cyclic voltammetric studies of SbF 6 − were compared with those of AsF 6 − and PF 6 − anions. Sb(V) was reduced to Sb(III), and then to Sb(0). AsF 6 − was reduced to AsF 3 , while no reduction of PF 6 − was observed. Reduction products of AsF 6 − and SbF 6 − passivated the glassy carbon electrode, presumably due to LiF precipitation. Peak potentials were observed to shift in the positive direction as a function of concentration. This was accounted for on the basis of a follow‐up chemical reaction.