Effect of AlPO4-nanoparticle coating concentration on high-cutoff-voltage electrochemical performances in LiCoO2

AlPO4 coating thickness on LiCoO2 cathodes was controlled in the range on the order of 10-100 nm by changing the AlPO4-nanoparticle concentration in the coating solution. The specific capacity and cycle-life performance of the coated cathodes had a strong correlation with the AlPO4 coating concentration (thickness). The cycle-life performance of the 1.0 wt % AlPO4-coated cathodes had the best cycling stability, showing 149 mAh/g capacity retention with 4.8 V charge cutoff by 50 cycles at 1 C (=140 mA/g) rate after precycles. However, the bare cathode showed zero capacity retention at the same condition after only 20 cycles. As the coating concentration was increased to 3.2 wt %, the amount of Co dissolution into the electrolyte decreased. In contrast, the 1.0 wt % AlPO4-coated cathode showed the best cycling stability, possibly due to the suppression of Li diffusivity decay and the appropriate electronic conduction. (C) 2004 The Electrochemical Society.