Cyclic performances of HT-LiCo0.8M0.2O2 (M=Al, Ni) powders prepared by the molten salt synthesis method

Single phases of M-substituted lithium cobalt oxides, HT-LiCo 0.8 M 0.2 O 2 (M=Al, Ni), were prepared by molten salt synthesis (MSS) method using coprecipitated Co–M hydroxides in 0.59 LiNO 3 –0.41 LiOH. The prepared powders consisted of well-developed particles with spherical shape and the particle size was around 150 nm in diameter. Among them, HT-LiCo 0.8 Al 0.2 O 2 showed an inferior cyclic performance and a smaller discharge capacity than HT-LiCo 0.8 Ni 0.2 O 2 , even though the former is more structurally stable than the latter. Structural analysis of HT-Li x Co 0.8 Al 0.2 O 2 indicated that the Al substitution, causing an enhanced internal resistance for lithium ion diffusion, is responsible for the capacity fading. In the meanwhile, HT-Li x Co 0.8 Ni 0.2 O 2 with large c layer spacing showed as high as 146 mAh/g at the first cycle and 130 mAh/g at the twentieth cycle.