Structural characterization of the surface-modified LixNi0.9Co0.1O2 cathode materials by MPO4 coating (M = Al, Ce, SrH, and Fe) for Li-ion cells

Abstract

Structural characterization of surface-modified Lix Ni0.9 Co0.1 O2 cathodes (x=0.3 and 0.15) using an MP O4 coating (M=Al, Ce, SrH, and Fe) were investigated for their potential applications to Li-ion cells. MP O4 nanoparticles that were precipitated from metal nitrate and (N H4) 2 HP O4 in water at pH=10 were coated on the cathodes via mixing and heat treatment at 700°C. The CeP O4 and SrHP O4 -coated Li0.3 Ni0.9 Co0.1 O2 cathodes heat treated at 300°C were mainly made up of the rock-salt phase (Fm3m), while AlP O4 and FeP O4 -coated cathodes showed disordered [Li1-x (Ni,Co)x] 3b [(Ni,Co)y] 3a O2 -type hexagonal structure (R 3- m) with a cation mixing. However, when the x value decreased from 0.3 to 0.15, bare and coated cathodes which had a spinel (Fd3m) or hexagonal structure (R 3- m) at x=0.3 were transformed into a NiO-type rock-salt structure. AlP O4 -coated sample exhibited lowest degree of oxygen generation after 300°C annealing at x=0.15, indicating the highest thermal stability among the bare and coated cathodes.