Abstract We explored the doping effect of Ge4+ on the Li4Ti5-xGexO12 (x = 0.0 and 0.05) anode material by looking at its electrochemical performance in both Li- and Na-ion batteries. Combined analysis using Rietveld refinement of high-resolution powder diffraction (HRPD) and transmission electron microscopy (TEM) unambiguously identified homogeneous Ge doping into the 16c octahedral Ti site of the Li4Ti5O12 (LTO) cubic spinel structure. This Ge doping leads to a much-reduced particle size, slightly expanded lattice and increased electrical conductivity due to the increased Ti3+ to Ti4+ ratio, these results were verified by HRPD, scanning electron microscopy (SEM), 4-point probe and x-ray photoelectron spectroscopy (XPS) analysis. The Li4Ti4.95Ge0.05O12 (Ge0.05-LTO) electrode shows much-improved capacity, high-rate capability and excellent cycling stability in a Li-half cell compared with an un-doped LTO electrode. This performance improvement is due to the reduced Li+ diffusion path and faster Li+ insertion/extraction kinetics that originate from Ge doping. In addition to these results, when tested as an anode for SIBs, the Ge0.05-LTO electrode exhibits enhanced capacity and cycling stability compared to un-doped LTO electrode, demonstrating its bi-functional, advantageous features in both LIB and SIB systems.

中文翻译：

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Ge掺杂的Li4Ti5-Ge O12（x = 0.05）作为锂离子和钠离子电池的快速充电、长寿命双功能负极材料

摘要 我们通过观察锂离子和钠离子电池的电化学性能，探讨了 Ge4+ 对 Li4Ti5-xGexO12（x = 0.0 和 0.05）负极材料的掺杂效应。使用高分辨率粉末衍射 (HRPD) 和透射电子显微镜 (TEM) 的 Rietveld 精修的组合分析明确地确定了均匀的 Ge 掺杂到 Li4Ti5O12 (LTO) 立方尖晶石结构的 16c 八面体 Ti 位点中。由于 Ti3+ 与 Ti4+ 的比例增加，这种 Ge 掺杂导致颗粒尺寸大大减小、晶格略微扩大和电导率增加，这些结果已通过 HRPD、扫描电子显微镜 (SEM)、4 点探针和 X 射线验证光电子能谱 (XPS) 分析。Li4Ti4.95Ge0.05O12 (Ge0.05-LTO) 电极显示出大大提高的容量，与未掺杂的 LTO 电极相比，Li-半电池具有高倍率能力和优异的循环稳定性。这种性能改进是由于减少了 Li+ 扩散路径以及源自 Ge 掺杂的更快的 Li+ 插入/提取动力学。除了这些结果之外，当作为 SIB 的阳极进行测试时，Ge0.05-LTO 电极与未掺杂的 LTO 电极相比表现出更高的容量和循环稳定性，证明了其在 LIB 和 SIB 系统中的双功能、有利特征。