Theoretical insight into oxygen vacancy formation in Li1.25Ni0.5Mn0.25O2 cathode material

Abstract

Here, we have studied the thermodynamic stability of lattice oxygen in Li-rich Co-free cathode material Li1.25Ni0.5Mn0.25O2 using first-principles calculations. It is found that the oxygen at O2 coordination is more likely to be released in Li-rich cathode Li1.25Ni0.5Mn0.25O2, and the stability of oxygen is closely related to temperature and oxygen partial pressure. The Li1.25Ni0.5Mn0.25O2 cathode will spontaneously form O-vacancies above 842 K. When the oxygen partial pressure increases to 22 atm, the lattice oxygen is stable even at 1000 K. The presence of O-vacancy will cause more localized charges, and Ni-ions will also undergo a reduction reaction in the electrode. This theoretical study gives new insight about the thermodynamic stability of lattice oxygen and will help to suppress the formation of O-vacancy in Li-rich cathode materials, paving the way for developing Li-rich cathode materials for next-generation Li-ion batteries.