Johnston-Peck Aaron C, Takeuchi Saya, Bharathi K Kamala, Herzing Andrew A, Bendersky Leonid A
Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
Thin Solid Films. 2018;647. doi: https://doi.org/10.1016/j.tsf.2017.12.006.
Due to the directional dependence of physical properties, it is advantageous to grow and then study materials in specific orientations. Films of battery materials grown in epitaxy offers the possibility to gain new insight into the role of physical structure on electrochemical behaviors. Here we demonstrate the growth, testing, and characterization of monoclinic-phase (space group 2/) Li-Mn-Ni-Co-O epitaxial films. The monoclinic phase is a layered structure and as such lithium diffusion is favored along specific crystallographic directions. Films were grown by pulsed laser deposition onto SrRuO/SrTiO substrates with (001) and (111) orientations. Cyclic voltammetry measured the response of these positive electrode materials, while the film structure was characterized using scanning transmission electron microscopy. A combination of imaging and diffraction identifies the presence of orientational variants. Variants disrupt the orientation anisotropy expected of these layered materials when grown in epitaxy, thereby masking differences in electrochemical behavior as a function of substrate orientation. Learning to control the domain structure now presents itself as a challenge to realize the potential of low symmetry battery materials grown in epitaxy on high symmetry substrates.
由于物理性质的方向依赖性，在特定取向上生长并随后研究材料是有利的。外延生长的电池材料薄膜为深入了解物理结构对电化学行为的作用提供了可能性。在此，我们展示了单斜相（空间群2/）锂锰镍钴氧化物外延薄膜的生长、测试和表征。单斜相是一种层状结构，因此锂沿特定晶体学方向扩散较为有利。通过脉冲激光沉积在具有（001）和（111）取向的SrRuO/SrTiO衬底上生长薄膜。循环伏安法测量了这些正极材料的响应，同时使用扫描透射电子显微镜对薄膜结构进行了表征。成像和衍射相结合确定了取向变体的存在。当外延生长时，变体破坏了这些层状材料预期的取向各向异性，从而掩盖了作为衬底取向函数的电化学行为差异。学会控制畴结构现在成为实现高对称衬底上外延生长的低对称电池材料潜力的一个挑战。
