First-Principles Studies on the Formation of Oxygen Vacancies in Li2CoSiO4

The existence of oxygen vacancy has a significant effect on the structural and electronic properties of Li2CoSiO4. Herein, the formation energy of an oxygen vacancy (V-O) in Li2CoSiO4 in different oxidation environments is calculated by using a first-principles method. The increased temperature, decreased oxygen partial pressure, and the increased charge state of O vacancy reduce the formation energy of the oxygen vacancy. The presence of V-O is accompanied by a distinct redistribution of the electronic charge densities only around the Co and Si ions next to the O-vacancy site, which shows a very local influence on the host material arising from V-O. Furthermore, the existence of vacancy defects (V-Li1, V-Li2, V-Co and V-Si) in the vicinity of the O vacancy are found to be beneficial to the formation of the O vacancy. The substitutional defects, Mn-Co, and Ni-Co, near the O vacancy are found to increase the formation energy of the oxygen vacancy, however, Fe-Co decreases the formation energy of the O vacancy. (C) 2021 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.