In situ atomic force microscopy study on lithium deposition on nickel substrates at elevated temperatures

The effects of temperature on lithium deposition and dissolution on Ni substrate were investigated in 1 mol dm(-3) solutions of lithium bis(perfluoroethylsulfonyl)imide [LiN(C2F5SO2)(2)] and lithium trifluoromethanesulfonate (LiCF3SO3) dissolved in propylene carbonate. The cyclability for lithium deposition and dissolution was greatly improved at elevated temperatures of 60 and 80degreesC. The surface morphologies of lithium deposited on Ni substrates at different temperatures were observed by in situ atomic force microscopy (AFM). The surface film formed at room temperature and 40degrees C was inhomogeneous, and large masses of deposits appeared after prolonged deposition (0.3 C cm(-2)). In contrast, closely packed, uniform surface film consisting of particle-like deposits of 100-200 nm diam was formed at 60 and 80degrees C, and no significant morphology changes were observed after prolonged deposition and even after dissolution. It was concluded that the uniformity and self-reparability of the surface film, and an enhanced surface diffusion of lithium atoms suppressed dendritic deposition and improved the cycling characteristics at the elevated temperatures. (C) 2002 The Electrochemical Society.