Boosted lithium storage cycling stability of TiP₂ by in-situ partial self-decomposition and nano-spatial confinement

Abstract

Titanium phosphide (TiP2) is particularly interesting due to its ability to form the stable Li–Ti–P ternary phase. However, TiP2 faces the limitations in cyclic stability due to the volume change occurred by the destruction/recovery of the long-range cubic order Li–Ti–P phase, and unable to deliver high capacity. In this work, we propose the in-situ formation of electrochemically inactive TiP and phosphorus via partial decomposition of TiP2 by ball milling process, achieving a multi-phase TiP2–TiP–P–C composite. On one hand, the decomposition-formed TiP effectively relieve the stress caused by the formation of LixTiP4 and LiP3. On the other hand, another decomposition-formed small-sized phosphorus significantly reduce its volume change during the lithiation/delithiation cycles for the overall capacity. Accordingly, the synthesized multi-phase TiP2–TiP–P–C with the above cooperative effects delivers a high capacity of 836.3 mAh g−1 at 0.2 A g−1 as high-performance Lithium-ion battery anode. In addition, a notable capacity retention of 81.4% is also achieved after 1000 cycles at 5 A g−1. Furthermore, when paired with LiFePO4 cathode in a full cell, the excellent specific capacity, cycling and rate performance can also be obtained. The rational design of TiP2–TiP–P–C will be beneficial towards the future development of metal-phosphide-phosphorous composite as LIB anode.