Characterization of NaxLi0.67+yNi0.33Mn0.67O2 as a positive electrode material for lithium-ion batteries

摘要

The relationship between the charge–discharge properties and crystal structure of Na _( x ) Li _(0.67+ y ) Ni _(0.33) Mn _(0.67) O _(2) (0.010 ≤ x ≤ 0.013, 0.16 ≤ y ≤ 0.20) has been investigated. Li/Na _( x ) Li _(0.67+ y ) Ni _(0.33) Mn _(0.67) O _(2) cells exhibit gradually sloping initial charge and discharge voltage–capacity curves. The initial charge capacity increased from 171 mA h g ~(?1) for thermally-treated Na _(0.15) Li _(0.51) Ni _(0.33) Mn _(0.67) O _(2) to 226 mA h g ~(?1) for Na _(0.010) Li _(0.83) Ni _(0.33) Mn _(0.67) O _(2) with an increase in the Li content. The initial maximum discharge capacity was 252 mA h g ~(?1) in the case of Na _(0.010) Li _(0.83) Ni _(0.33) Mn _(0.67) O _(2) between 4.8 and 2.0 V at a fixed current density of 15 mA g ~(?1) (0.06C) at 25 °C. The predominance of the spinel phase leads to the high initial discharge capacity of Na _(0.010) Li _(0.83) Ni _(0.33) Mn _(0.67) O _(2) . This study shows that chemical lithiation using LiI is effective to improve the electrochemical properties.