Ti Assisted the Cation–Anion Redox Balance with the Suppression of the Jahn–Teller Effect of O2-Type Li-Rich Layered Oxide Cathode Materials

Li-rich layered oxide (LRLO) materials are regarded as one of the promising cathode materials for Li-ion batteries (LIBs) because of their high energy density, which benefits from the synergetic redox contribution of both cations and anions. Among these materials, O2-type LRLOs have attracted considerable attention due to the suppression of irreversible cation migration. However, the excessive oxygen redox reaction can lead to significant lattice oxygen loss and mechanical failure, which, in turn, cause capacity fading and voltage decay upon cycling. In this work, the d 0 element Ti-doped LRLO Li 0.72 [Li 0.2 Ni 0.06 Mn 0.62 Ti 0.12 ]O 2 was prepared, which exhibits cation and anion redox balance with the suppression of the Jahn–Teller effect. Electrochemical studies show that Li 0.72 [Li 0.2 Ni 0.06 Mn 0.62 Ti 0.12 ]O 2 achieves a markedly lower voltage decay and long cycling life even at high current density compared to the Ti-free samples. Local structure evolution and charge compensation mechanisms using X-ray absorption spectroscopy and extended X-ray absorption fine structure spectroscopy, as implemented, disclose that they serve to stabilize the anion redox and enhance the local coordination environment. Moreover, the theoretical study combined with electrochemical impedance spectroscopy (EIS) analysis unveiled that Ti substitution can facilitate Li + migration, thus leading to better kinetic properties as well. This study inspires a novel insight into the modulation of the cation–anion redox reaction process and provides an effective method to modify LRLOs toward high-performance LIBs.