合金型负极材料为锂离子电池提供高容量;然而,它们遭受由循环期间的体积变化引起的粉碎问题。因此,实现这些阳极的循环可逆性对于维持它们的电化学性能是关键的。这里,我们利用原位高分辨率TEM研究了在原子级分辨率下循环过程中SnNP的结构可逆性。我们观察到一个完整的周期后,一个惊人的接近完美的结构可逆性。锂化过程中会发生三步相变,伴随着大量缺陷的产生,晶界,和高达202%的体积膨胀。在随后的脱锂中,体积,形态学,SnNP的结晶度恢复到初始状态。理论计算表明,压缩应力驱动脱锂过程中NPs内产生的空位的去除,因此保持其完整的形态。这项工作表明,在循环过程中去除空位可以有效地提高高容量阳极材料的结构可逆性。
Alloying-type anode materials provide high capacity for lithium-ion batteries; however, they suffer pulverization problems resulting from the volume change during cycling. Realizing the cycling reversibility of these anodes is therefore critical for sustaining their electrochemical performance. Here, we investigate the structural reversibility of Sn NPs during cycling at atomic-level resolution utilizing in situ high-resolution TEM. We observed a surprisingly near-perfect structural reversibility after a complete cycle. A three-step phase transition happens during lithiation, accompanied by the generation of a significant number of defects, grain boundaries, and up to 202% volume expansion. In subsequent delithiation, the volume, morphology, and crystallinity of the Sn NPs were restored to their initial state. Theoretical calculations show that compressive stress drives the removal of vacancies generated within the NPs during delithiation, therefore maintaining their intact morphology. This work demonstrates that removing vacancies during cycling can efficiently improve the structural reversibility of high-capacity anode materials.