Electronic structures and electrochemical properties of LiPF6−n(CF3)n

We evaluated (1) thermal and electrochemical stability and (2) ion-dissociation ability of PF6−n(CF3)n− anions by computational method. The thermal stability order by ΔΔE (anion) is PF4(CF3)2−>PF5(CF3)−>PF3(CF3)3−>PF6−. The ion-dissociation ability order by ΔΔE (Li salts) is LiPF3(CF3)3>LiPF4(CF3)2>LiPF5(CF3)>LiPF6. The conductivity of electrolyte solution with LiPF4(CF3)2 (3.9 mS/cm) was a little lower than that of LiPF6 (4.4 mS/cm) in 0.1 mol/l Li salt/PC:DME electrolyte, while the oxidation potential of LiPF4(CF3)2 in PC was higher than that of LiPF6. The LiPF4(CF3)2-cell showed better cycle characteristics than LiPF6-cell.