[Energy Storage Materials] 我室杨勇教授发表论文:Tailoring the redox-active transition metal content to enhance cycling stability in cation-disordered rock-salt oxides

发布日期:2021年10月11日   浏览次数:

我室杨勇教授在 Energy Storage Materials 上发表论文:Tailoring the redox-active transition metal content to enhance cycling stability in cation-disordered rock-salt oxides

摘要:Lithium-excess cation-disordered rock-salt oxides (DRXs) are investigated intensively as cathode materials for future lithium-ion batteries combining cationic and anionic redox reactions. However, the lattice oxygen redox can cause severe oxygen release resulting in rapid capacity fading. Here, we investigate a series of xLi2TiO3-(1 - x)LiMnO2 (0 ≤ x ≤1) materials and find that only Li1.2Mn0.4Ti0.4O2 (x = 0.4) and Li1.1Mn0.7Ti0.2O2 (x= 0.2) can form phase-pure DRXs, which both deliver high capacity (> 250 mAh g−1). The newly discovered Li1.1Mn0.7Ti0.2O2 DRX exhibits remarkably high capacity retention of 84.4% after 20 cycles compared to only 60.8% for Li1.2Mn0.4Ti0.4O2. Our result indicates that the irreversible oxygen loss is reduced by raising the Mn content. Theoretical calculations further reveal that increasing the redox-active Mn content from Li1.2Mn0.4Ti0.4O2 to Li1.1Mn0.7Ti0.2O2 causes the orbitals near the Fermi level to change from O 2p non-bonding (Lisingle bondOsingle bondLi unhybridized orbitals) to (Mnsingle bondO)* antibonding bands, exhibiting a high Osingle bondO aggregation barrier, preventing O2 release and resulting in sustained capacity retention. Hence, these new findings demonstrate that regulating oxygen redox by tailoring the redox-active transition metal content is an effective strategy to enhance the cycling stability of DRXs.

文章链接:https://www.sciencedirect.com/science/article/pii/S2405829721004153