Donggi Ahn

The Effect of AlPO[sub 4]-Coating Layer on the Electrochemical Properties in LiCoO[sub 2] Thin Films

The electrochemical properties of nanoscale Al2O3-coated LiCoO2 thin films were examined as a function of the coating coverage. Al2O3-coated LiCoO2 films showed enhanced cycle-life performance with increasing degree of coating coverage, which was attributed to the suppression of Co dissolution and F− concentration in the electrolyte. Moreover, an Al2O3-coating layer with partial coverage clearly improved the electrochemical properties, even at 60 °C or with a water-contaminated electrolyte. Even though metal-oxide coating on LiCoO2 has been actively investigated, the mechanisms of nanoscale coating have yet to be clearly identified. In this article, surface analysis suggested that the Al2O3-coating layer had transformed to an AlF3∙3H2O layer during cycling, which inhibited the generation of HF by scavenging H2O molecules present in the electrolyte.

Nanostructural Effect of AlPO4-Nanoparticle Coating on the Cycle-Life Performance in LiCoO2 Thin Films

To control the nanostructure of an AlPO 4 -coating layer, nanoparticles with three AlPO 4 phases were synthesized: amorphous, tridymite, and cristobalite phases. These colloids were layered on LiCoO 2 thin films by spin coating, and subsequently annealed at 400°C. The interdiffusion variations at the interface were eliminated by the spin-coating method, while the cycle-life performance of the coated cathode depended on the nanostructure of the AlP04-nanoparticle-coating layer. The LiCoO 2 thin-film cathode coated with amorphous nanoparticles and annealed at 400°C showed the best cycle-life performance, and effectively suppressed the degradation of Li + -diffusion kinetics during cycling.