In-situ introducing TiP₂ nanocrystals in black phosphorus anode to promote high rate-capacity synergy

Abstract

Owing to the high theoretic capacity (2596 mAh g−1) and suitable lithiation potential (～0.7 V vs. Li+/Li), Black phosphorus (BP) is considered as an ideal anode material for the fast-charging lithium-ion batteries. However, BP still faces the large volume change and low Li+ transfer during the charge/discharge. In this work, a facile two-step high-energy ball milling method is developed to synthesis the black phosphorus@TiP2–C (CBP@TiP2–C) nanocomposite for the high-rate performance anode material, in which the conductive nanocrystalline TiP2 is in-situ introduced and uniformly distributed into BP-C matrix. We reveal that the uniformly dispersed TiP2 nanocrystals can enhance the electronic and ionic conductivities of active particles and the electrode reaction kinetics. The lithiation product cubic LiyTiP4 phase is beneficial to release the stress, reduce the Li+ diffusion energy barrier and accelerate the Li+ extraction from LiP3 upon delithiation. Moreover, the contact among different components can be improved by Ti–C and P–C bonds in the CBP@TiP2–C, thus ensuring excellent electric contact within the material and enhancing the structural stability of composites. As a result, the CBP@TiP2–C anode displays a high reversible capacity of 1007.4 mAh g−1 at 10.0 A g−1 and excellent capacity retention of 925.6 mAh g−1 after 500 cycles at 2 A g−1.