Mechanical Robustness Two-Dimensional Silicon Phosphide Flake Anodes for Lithium Ion Batteries
Hailin Shen, Yu Huang, Ronghui Hao, Yukai Chang, Zhongtao Ma, Bingkun Guo, Peng Wang, Hangsheng Yang, J.P. Cheng, Qianqian Li, Hongtao Wang, Zhongyuan Liu, Anmin Nie
Abstract
Silicon phosphide (SiP) has attracted a great deal of attention in the field of energy storage because of its unique properties of stable semiconducting two-dimensional structure and promising theoretical capacity of 3120 mA h g–1 for lithium ion batteries (LIBs) anodes. Especially, the thickness is reduced down to the nanoscale, the physical and chemical properties will be largely changed. Here, we investigate the electrochemical performance of few-layer SiP nanoflakes, successfully exfoliated by a mechanical method. These few-layer SiP nanoflakes exhibit better electrical conductivity, faster charge transfer kinetics, and lower resistance than bulk SiP, leading to the enhancement of fast chargeability and long cyclability of LIBs. In situ transmission electron microscopy reveals that reversible phase transformation occurred in the dynamic lithiation/delithiation process; a series of new phases are formed sequentially, that is, amorphous Li3P, LixSi (x ≤ 3.75), and polycrystal SiP, accompanied by an area expansion of ∼233% for an individual SiP nanoflake in the lithiation process. Meanwhile, a high initial discharge/charge capacity of 862/737 mA h g–1 can be achieved experimentally by adjusting the electrode component ratios, and an almost 460 mA h g–1 capacity retention can be maintained after 100 cycles. This work contributes to the development of novel materials of few-layer SiP as next-generation anodes in LIBs.