The effects of M (M=Mn,Pr,Sn,Zr) doping on the redox thermodynamics of CeO2 have been investigated using first-principles density-functional theory calculations with the on-site Coulomb interaction taken into account. Two different mechanisms for the O-vacancy formation in doped CeO2 have been clarified. Compared with the case of pure CeO2, the decrease in the O-vacancy formation energy for the Zr-doped CeO2 is mostly caused by the structural distortion, whereas the decrease for Mn-, Pr-, or Sn-doped CeO2 originates from the electronic modification as well as from the structural distortion. It is found that the electronic modification occurs in those dopants whose uttermost atomic orbitals are half or fully occupied by the filling of the excess electrons left by the formation of the O vacancy. Two effects also contribute to concentration dependence of the O-vacancy formation energies for different dopant species.

A facile sol–gel approach combined with a carbon-coating technique via high-temperature thermally decomposing C₂H₂ has been developed for the synthesis of a Li₃V₂(PO₄)₃/C (LVP/C) cathode material employing the biomass of phytic acid as an eco-friendly phosphorus source. The effects of the carbon-coating on the structural, morphological and electrochemical properties of LVP have been investigated. Compared with pristine LVP, the LVP/C composite presents a higher discharge capacity of 127 mA h g⁻¹ at 0.1 C, better rate capability and long-term cyclability in the voltage range of 3.0–4.3 V. Even at a high charge–discharge rate of 5 C, it can still deliver a reversible capacity of 107 mA h g⁻¹ over 400 cycles without obvious fading, demonstrating great potential as a superior cathode material for lithium-ion batteries.