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

Structural characterization of surface-modified LixNi0.9Co0.1O2 cathodes (x=0.3 and 0.15) using an MPO4 coating (M=Al, Ce, SrH, and Fe) were investigated for their potential applications to Li-ion cells. MPO4 nanoparticles that were precipitated from metal nitrate and (NH4)(2)HPO4 in water at pH=10 were coated on the cathodes via mixing and heat treatment at 700 degrees C. The CePO4 and SrHPO4-coated Li0.3Ni0.9Co0.1O2 cathodes heat treated at 300 degrees C were mainly made up of the rock-salt phase (Fm3m), while AlPO4 and FePO4-coated cathodes showed disordered [Li1-x(Ni,Co)(x)](3b)[(Ni,Co)(y)](3a)O-2-type hexagonal structure (R (3) over barm) 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) over barm) at x=0.3 were transformed into a NiO-type rock-salt structure. AlPO4-coated sample exhibited lowest degree of oxygen generation after 300 degrees C annealing at x=0.15, indicating the highest thermal stability among the bare and coated cathodes.