Catalytic effect of nanostructured CeO2 coating on the electrochemical performance of Li(Li,Ni,Mn,Co)O2

Abstract

CeO2 coatings (1.0, 3.5 and 5.0 mass%) have been obtained at the surface of 150–200 nm Li[Li0.13Ni0.2Mn0.47Co0.2]O2 (LLNMC) particles. According to TEM and STEM-EDX data, at 1% CeO2, the coating consists of 20–60 nm spherical ceria particles, while at 5%, their size is increased to 150–200 nm. The reversible electrochemical capacity of the coated samples is larger than for bare LLNMC, especially at higher discharge rates. The maximum capacity is observed for the 1% CeO2-coated sample (235 mAh g−1 at U = 2.0–4.8 V). It is essential that the extra capacity of CeO2-coated samples is appeared since the first cycles and, hence, could not be attributed to the protection of LLNMC from the electrochemical degradation by CeO2. The cyclic voltammetry curves of the 1% coated sample demonstrate a considerable effect at U = 4.2–4.6 V that could be associated with redox processes in the oxygen sublattice of LLNMC. Taking into account a significant activation of the oxygen species at the surface of ceria nanoparticles, the observed capacity increase of LLNMC could be affiliated with the catalytic effect of CeO2 on the oxidation of lattice oxygen in LLNMC rather than the protecting effect of ceria particles.