Two-Phase Electrochemical Lithiation in Amorphous Silicon
详细信息 查看全文
- 作者：Jiang Wei Wang ; Yu He ; Feifei Fan ; Xiao Hua Liu ; Shuman Xia ; Yang Liu ; C. Thomas Harris ; Hong Li ; Jian Yu Huang ; Scott X. Mao ; Ting Zhu
- 刊名：Nano Letters
- 出版年：2013
- 出版时间：February 13, 2013
- 年：2013
- 卷：13
- 期：2
- 页码：709-715
- 全文大小：421K
- 年卷期：v.13,no.2(February 13, 2013)
- ISSN：1530-6992
文摘
Lithium-ion batteries have revolutionized portable electronics and will be a key to electrifying transport vehicles and delivering renewable electricity. Amorphous silicon (a-Si) is being intensively studied as a high-capacity anode material for next-generation lithium-ion batteries. Its lithiation has been widely thought to occur through a single-phase mechanism with gentle Li profiles, thus offering a significant potential for mitigating pulverization and capacity fade. Here, we discover a surprising two-phase process of electrochemical lithiation in a-Si by using in situ transmission electron microscopy. The lithiation occurs by the movement of a sharp phase boundary between the a-Si reactant and an amorphous LixSi (a-LixSi, x 2.5) product. Such a striking amorphous鈥揳morphous interface exists until the remaining a-Si is consumed. Then a second step of lithiation sets in without a visible interface, resulting in the final product of a-LixSi (x 3.75). We show that the two-phase lithiation can be the fundamental mechanism underpinning the anomalous morphological change of microfabricated a-Si electrodes, i.e., from a disk shape to a dome shape. Our results represent a significant step toward the understanding of the electrochemically driven reaction and degradation in amorphous materials, which is critical to the development of microstructurally stable electrodes for high-performance lithium-ion batteries.