Lithiation of Anodic Magnetite−Hematite Nanotubes Formed on Iron

This study represents progress in comprehending the storage of lithium-ion within 1D nanotubes. It achieves this through an analysis of the differential capacity plots (d(Q−Q0) · dE-1), complemented by in situ Raman spectroscopy observations. The surface morphology and cross-section of the specimens were analysed using a Zeiss Sigma 500 field emission scanning electron microscope (SEM) instrument. An accelerating voltage of 1kV was employed to investigate the morphology. The phase present in the anodic films was determined using a Rigaku RINT-2000 X-ray diffractometer with CuKα radiation. To analyse thin films, the grazing incidence XRD mode was utilized to reduce the influence of the substrate material. The anodic iron oxide microelectrode was subjected to electrochemical testing as negative electrodes in a half-cell PAT-cell (EL-cell) within a lithium-ion battery (LIB) setup. In situ Raman spectroscopy measurements were conducted utilizing the In situ Raman ECC-OPTO cell.Mechanistic studies, conducted both in situ and ex-situ, unveiled the quasi-reversible reduction of iron oxide to metallic iron facilitated by the formation of Li2O during electrochemical Li+ insertion.

本研究在理解锂离子在一维纳米管中的存储机制方面取得了进展。该进展通过差分容量曲线（d(Q−Q₀)·dE⁻¹）分析辅以原位拉曼光谱（in situ Raman spectroscopy）观测实现。采用蔡司Sigma 500场发射扫描电子显微镜（field emission scanning electron microscope, SEM）对样品的表面形貌及横截面进行分析，形貌研究采用1kV的加速电压。采用配备CuKα辐射源的理学RINT-2000 X射线衍射仪（X-ray diffractometer, XRD）测定阳极膜中的物相；分析薄膜时，采用掠入射XRD模式以降低基底材料的影响。阳极氧化铁微电极作为锂离子电池（lithium-ion battery, LIB）装置中半电池PAT-cell（EL-cell）的负极进行电化学测试。采用原位拉曼ECC-OPTO电池开展原位拉曼光谱测量。通过原位及非原位（ex-situ）机理研究，揭示了电化学Li⁺嵌入过程中Li₂O的形成促进氧化铁准可逆还原为金属铁的机制。