Comparison of AlPO4- and Co3(PO4)2-coated LiNi0.8Co0.2O2 cathode materials for Li-ion battery

Electrochemical and thermal properties of Co-3(PO4)(2)- and AlPO4-coated LiNi0.8Co0.2O2 cathode materials were compared. AIPO(4)-coated LiNi0.8Co0.2O2 cathodes exhibited an original specific capacity of 170.8 mAh g(-1) and had a capacity retention (89.1% of its initial capacity) between 4.35 and 3.0V after 60 cycles at 150mAg(-1). Co-3(PO4)(2)-coated LiNi0.8Co0.2O2 cathodes exhibited an original specific capacity of 177.6 mAh g(-1) and excellent capacity retention (91.8% of its initial capacity), which was attributed to a lithium-reactive Co-3(PO4)(2) coating. The CO3(PO4)(2) coating material could react with LiOH and Li2CO3 impurities during annealing to form an olivine LixCoPO4 phase on the bulk surface, which minimized any side reactions with electrolytes and the dissolution of Ni4+ ions compared to the AIPO(4)-coated cathode. Differential scanning calorimetry results showed CO3(PO4)(2)-coated LiNi0.8Co0.2O2 cathode material had a much improved onset temperature of the oxygen evolution of about 218 degrees C, and a much lower amount of exothermic-heat release compared to the Al PO4-coated sample. (c) 2007 Elsevier Ltd. All rights reserved.