Synthesis, characterization and electrochemical studies of LiNi_0·8M_0·2O₂ cathode material for rechargeable lithium batteries

摘要

LiNiO₂ and substituted nickel oxides, LiNi_0·8M_0·2O₂ and LiCo_0·8M_0·2O₂ (M = Mg2+, Ca2+, Ba2+), have been synthesized using simple solid state technique and used as cathode active materials for lithium rechargeable cells. Physical properties of the synthesized products are discussed in the structural (XRD, TEM, SEM with EDAX) and spectroscopic (FTIR) measurements. XRD results show that the compounds are similar to LiNiO₂ in structure. TEM and SEM analyses were used to examine the particle size, nature and morphological aspects of the synthesized oxides. The composition of the materials was explored by EDAX analysis. Electrochemical studies were carried out in the range 3–4·5 V (vs Li metal) using 1 M LiBF₄ in ethylene carbonate/dimethyl carbonate as the electrolyte. The doping involving 20% Mg resulted in a discharge capacity of 185 mAhg−1 at 0·1 mA/cm2 and remained stable even after 25 cycles. Discharge capacity retention for Mg doped lithium nickelate at 25th cycle was noted to be nearly 7% higher than for the undoped material.