Synthesis and electrochemical performance of high voltage cycling LiM0.05Co0.95O2 as cathode material for lithium rechargeable cells

Substituted cobalt oxides, LiM0.05Co0.95O2 (M = Mg2+, Al3+, and Ti4+), have been synthesized using solid-state technique and their performance in a 2032-type lithium rechargeable coin cell is reported. The synthesized powders were structurally analyzed using X-ray diffraction (XRD) and the surface morphology evaluated with scanning electron microscopy. XRD patterns indicate that single-phase materials were formed involving Al-doped LiCoO2. Electrochemical studies were carried out in the voltage range 3.5-4.5 V (vs. Li metal) using 1 M LiPF6 in ethylene carbonate/dimethyl carbonate as electrolyte. The doping involving 5% Mg resulted in a charge/discharge capacity of similar to160 mAh/g at C/5 rate and remained stable even after 50 cycles. To the best of our knowledge, this is the first time that such high stable capacities have been obtained involving doped LiCoO2 when cycled up to 4.5 V. (C) 2004 The Electrochemical Society.