LiF-induced in-situ engineering of a dense inorganic SEI for superior lithium storage in black phosphorus anode

Black phosphorus (BP) has been highly regarded as a favourable candidate for fast-charging anode applications owing to its high theoretical capacity and advantageous charge-discharge platform. However, BP faces challenges related to compromised electrochemical performance resulting from an unstable solid-electrolyte interface (SEI) and substantial volumetric expansion. This study proposes the engineering of an inorganic-dense SEI on the surface of BP-C through the strategic incorporation of lithium fluoride (LiF). The presence of LiF in the system preferentially promotes LiPF₆ adsorption from the electrolyte, facilitating the in-situ formation of a lithium-enriched inorganic SEI film on the BP-C particulate surfaces. This strategic formation effectively mitigates subsequent electrolytic decomposition, accommodates volumetric expansion, and substantially improves the rate capability and cycling stability of the system. Consequently, the BP-LiF-C electrode demonstrates high initial coulombic efficiency of 86.8 % and maintains a steady capacity of 926.1 mAh g^-1 over 700 cycles at 2000 mA g^-1. Moreover, when paired with a LiFePO₄ cathode, the full cell exhibits long cycling stability, retaining 98.6 % of its capacity after 500 cycles at 2000 mA g^-1, and performs at high rate. Therefore, utilising LiF to modulate the interfacial architecture of BP-based electrode composites provide notable guidance to enhance energy storage systems.