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

Layered Li[Li0.2Ni0.2Mn0.6]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 Li[Li0.2Ni0.2Mn0.6]O2 powders. Al(OH)3 coated Li[Li0.2Ni0.2Mn0.6]O2 exhibited an greater retention capacity at higher rates compared to uncoated Li[Li0.2Ni0.2Mn0.6]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 Li[Li0.2Ni0.2Mn0.6]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 (Rct) 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.