镁电池电极材料方面取得重要进展

   近日，由Technical University的Peter Strasser和Sorbonne Universités 的Damien Dambournet、Jiwei Ma课题组合作，在镁电池电极材料方面取得重要进展，相关成果以“Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO2”发表在Nature Materials 上。镁电池由于具有安全性好、价格便宜、比容量高等优点，受到越来越多的重视。然而由于Mg2+离子极性强，缺少合适的嵌镁材料。传统的锐钛矿型TiO2在镁电池中表现出较低的嵌镁活性。该工作通过对TiO2进行F-掺杂，大量引入阳离子空位作为Mg2+嵌入的活性位点，大大提高了TiO2的储镁能力。当阳离子空位占有率为22%时，首圈放电容量可以达到165 mAh g-1，并可稳定在155 mAh g-1。此外，该材料对Al3+的嵌入也表现出很高的电化学活性。文章结合理论计算与实验证明，Mg2+在电化学过程中确实嵌入了阳离子空位中。该工作为提高镁电池电极材料的电化学性能提供了一种新的设计思路。

Reference: Koketsu, T. et al. Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO2. Nat Mater, doi:10.1038/nmat4976 (2017).

a, High-resolution Cs-corrected TEM image of a Ti O1.12F0.40(OH)0.48 nanoparticle. b, Atomic-resolution image of anatase crystal (space group I41/amd) oriented along the [001] axis. c, Coloured high-resolution TEM image with a profile plot of a line of atoms (white rectangle), which exhibit a clear intensity variation both of atomic columns and dark patches in between. d,e, Calculated high-resolution TEM images of anatase structure oriented along the [001] axis using MactempasX-2 software with an average Ti occupancy of 78%: uniform (d) and random (e) distribution. The calculated image in e exhibits features similar to those observed in the experimental high-resolution image, which demonstrates the irregularity of the Ti occupancy in the structure. f, Galvanostatic discharge–charge curves for TiO2 and vacancy-containing anatase versus Mg. Cells were cycled under 20 mA g−1 in the potential range 0.05–2.3 V versus Mg2+/Mg (the electrochemical stability of the electrolyte solution was determined by cyclic voltammetry shown in Supplementary Fig. 2). g, Galvanostatic discharge–charge curves for TiO2 and vacancy-containing anatase versus Al. Cells were cycled under 20 mA g−1 in the potential range 0.01–1.8 V versus Al3+/Al (the electrochemical stability of the electrolyte solution was determined by cyclic voltammetry shown in Supplementary Fig. 3).

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