The effect of Al(OH)3 coating on the Li[Li0.2Ni0.2Mn0.6]O2 cathode material for lithium secondary battery

Layered LiLi_0.2Ni_0.2Mn_0.6]O₂ powder was modified by coating its surface with amorphous Al(OH)₃. Energy dispersive spectroscopy (EDS) showed that nano-sized Al(OH)₃ powders were homogeneously dispersed in the parent LiLi_0.2Ni_0.2Mn_0.6]O₂ powders. Al(OH)₃ coated LiLi_0.2Ni_0.2Mn_0.6]O₂ exhibited an greater retention capacity at higher rates compared to uncoated LiLi_0.2Ni_0.2Mn_0.6]O₂. The low area specific impedance (ASI) value of the Al(OH)₃ is the major factor for its higher rate performance. The 1.4 wt.% Al(OH)₃ coated sample had an impedance of 41 Ω cm² while uncoated LiLi_0.2Ni_0.2Mn_0.6]O₂ had a 57 Ω cm² at 30-80% state of charge. Electrochemical impedance spectroscopy (EIS) also showed that the Al(OH)₃ coated sample had a lower charge transfer resistance (R_ct) than the uncoated sample. Differential scanning calorimetry (DSC) analysis showed that Al(OH)₃ coating improved the thermal stability. Al(OH)₃ coating increased the onset temperature of thermal decomposition and reduced the amount of heat for the exothermic peak.