LiNi 0.8Co 0.15Al 0.05O 2 cathode materials prepared by TiO 2 nanoparticle coatings on Ni 0.8Co 0.15Al 0.05(OH) 2 precursors

Abstract

Synthesis, electrochemical, and structural properties of LiNi 0.8Co 0.15Al 0.05O 2 cathodes prepared by TiO 2 nanoparticles coating on a Ni 0.8Co 0.15Al 0.05(OH) 2 precursor have been investigated by the variation of coating concentration and annealing temperature. TiO 2-coated cathodes showed that Ti elements were distributed throughout the particles. Among the coated cathodes, the 0.6 wt% TiO 2-coated cathode prepared by annealing at 750 °C for 20 h exhibited the highest reversible capacity of 176 mAh g −1 and capacity retention of 92% after 40 cycles at a rate of 1 C (=190 mA g −1). On the other hand, an uncoated cathode showed a reversible first discharge capacity of 186 mAh g −1 and the same capacity retention value to the TiO 2-coated sample at a 1 C rate. However, under a 1 C rate cycling at 60 °C for 30 cycles, the uncoated sample showed a reversible capacity of 40 mAh g −1, while a TiO 2-coated one showed 71 mAh g −1. This significant improvement of the coated sample was due to the formation of a possible solid solution between TiO 2 and LiNi 0.8Co 0.15Al 0.05O 2. This effect was more evident upon annealing the charged sample while increasing the annealing temperature, and at 400 °C, the coated one showed a more suppressed formation of the NiO phase from the spinel LiNi 2O 4 phase than the uncoated sample.