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

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 Li_yTiP₄ 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.