School of Materials Science and Engineering, Center for Innovative Fuel Cell and Battery Technologies, Georgia Institute of Technology , 771 Ferst Drive, Atlanta, Georgia 30332-0245, United States.
Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology , 901 Atlantic Drive, Atlanta, Georgia 30332-0400, United States.
J Am Chem Soc. 2017 May 24;139(20):7071-7081. doi: 10.1021/jacs.7b03141. Epub 2017 May 12.
While T-NbO has been frequently reported to display an exceptionally fast rate of Li-ion storage (similar to a capacitor), the detailed mechanism of the energy storage process is yet to be unraveled. Here we report our findings in probing the nature of the ultrafast Li-ion storage in T-NbO using both experimental and computational approaches. Experimentally, we used in operando Raman spectroscopy performed on a well-designed model cell to systematically characterize the dynamic evolution of vibrational band groups of T-NbO upon insertion and extraction of Li ions during repeated cycling. Theoretically, our model shows that Li ions are located at the loosely packed 4g atomic layers and prefer to form bridging coordination with the oxygens in the densely packed 4h atomic layers. The atomic arrangement of T-NbO determines the unique Li-ion diffusion path topologies, which allow direct Li-ion transport between bridging sites with very low steric hindrance. The proposed model was validated by computational and experimental vibrational analyses. A comprehensive comparison between T-NbO and other important intercalation-type Li-ion battery materials reveals the key structural features that lead to the exceptionally fast kinetics of T-NbO and the cruciality of atomic arrangements for designing a new generation of Li-ion conduction and storage materials.
虽然 T-NbO 经常被报道具有极快的锂离子存储速度（类似于电容器），但其储能过程的详细机制尚未被揭示。在这里，我们使用实验和计算方法报告了我们在探测 T-NbO 中超快速锂离子存储的本质方面的发现。在实验中，我们使用在精心设计的模型电池上进行的原位拉曼光谱学，系统地表征了在重复循环过程中插入和提取锂离子时 T-NbO 的振动带组的动态演变。从理论上讲，我们的模型表明，锂离子位于松散堆积的 4g 原子层中，并且倾向于与密集堆积的 4h 原子层中的氧形成桥接配位。T-NbO 的原子排列决定了独特的锂离子扩散路径拓扑结构，允许在具有非常低空间位阻的桥接位点之间直接传输锂离子。所提出的模型通过计算和实验振动分析得到了验证。对 T-NbO 和其他重要的嵌入型锂离子电池材料进行的全面比较揭示了导致 T-NbO 具有极快动力学的关键结构特征，以及原子排列对于设计新一代锂离子传导和存储材料的重要性。
