Si‐Doping Mediated Phase Control from β‐ to γ‐Form Li3VO4 toward Smoothing Li Insertion/Extraction

Abstract

AbstractThe γ phase Li3VO4 which possesses higher ionic conductivity is more preferable for lithium ion batteries, but it is only stable at high temperature and would convert to low temperature β phase spontaneously when cooling down. Here, the phase control of Li3VO4 to stabilize its γ phase in room temperature is successfully mediated by introducing proper Si‐doping, and for the first time the electrochemical performances of γ‐Li3VO4 is investigated. It is found that pure γ‐Li3VO4 can be obtained in a doping ratio of x = 0.05–0.15 in Li3+xV1−xSixO4 with addition of excess Li source in synthesis design. The doping mechanism and the energy changes are investigated in detail by using the first principle calculations, it reveals that an interstitial Li+ is formed with doping of Si4+ in Li3VO4 to balance the system charge. When served as an anode, the Si‐doped γ‐Li3VO4 shows much smoothed Li+ insertion/extraction and enhanced cycle stability with only a single pair of redox peaks, which behaves much different with the complex multicouples of redox peaks in typical β‐Li3VO4. These changes in electrochemical performances implies that γ‐Li3VO4 can effectively accommodate Li+ in an easier and more facile way and relieved structure stress during the charge/discharge process.