Annealing-temperature effect on various cutoff-voltage electrochemical performances in AlPO4-Nanoparticle-Coated LiCoO2

The electrochemical properties of AlPO4-coated LiCoO2 cathodes were found to be superior to those of bare cathodes at various charge-cutoff voltages (4.3, 4.6, and 4.8 V), and depended on the annealing temperature. The AlPO4-coated cathodes annealed at 600 and 700 degreesC retained a discharge capacity of similar to150 mAh/g even with a 4.8 V charge-cutoff voltage (after 46 cycles at 1 C = 140 mA/g). The bare cathode showed zero capacity retention at the same condition after only 20 cycles. The enhanced electrochemical performance and rate capability in the coated cathodes were attributed to the inhibition of structural degradation during cycling. The AlPO4-nanoparticle coating layer on the LiCoO2 effectively suppressed cobalt dissolution and a nonuniform distribution of local strain in the cathode. (C) 2004 The Electrochemical Society.