Cobalt-Free Oxide Cathode Material with Phase Composition Control to High Electrochemical Performance in Li-Ion Batteries

Abstract

Cobalt-free layered oxide cathode material (LiMn0.5Ni0.5O2) was obtained via a two-step synthesis method. Firstly, hydrothermal synthesis of MnOOH with nanorod morphology was achieved and then a co-precipitation process to obtain the LiMn0.5Ni0.5O2 active layered material was performed. Structural and morphological characterization revealed a promising disordered layered structure obtained at 800 °C with improved electrochemical performance. The thermal treatment performed on the active materials resulted in a controlled balance between the monoclinic and rhombohedral phase leading to good phases formation ratio in a cobalt-free layer cathode. It was found that the controlled mixing of structural phases plays an important role in improving the electrochemical performance of the active cathodic layer material, resulting in an adequate balance between high discharge capacity and electrochemical stability during the charge/discharge cycling. The morphological analysis showed two kinds of particles that played a crucial role in the structural stability and electrochemical performance. The active material thermally treated at 800 °C displayed outstanding discharge capacity of 235.05 mAh g−1 at 20 mA g−1 in CCCV (Current Constant-Constant Voltage) mode. While, in CC (Current Constant) mode showed the highest discharge capacity, of 178.95 mAh g−1 at 20 mA g−1 and good capacity retention (87.2% after 100 cycles).