High-pressure and high-temperature synthesis of black phosphorus-graphite anode material for lithium-ion batteries

Phosphorus-based materials with a high theoretical specific capacity and a fast charge-discharge rate are considered as promising anode materials for high energy density lithium-ion batteries (LIBs). Red phosphorus (RP) and black phosphorus (BP) are two main allotropes to be used as anode materials. However, huge volume expansion during charge-discharge processes hinders the application of RP and BP in LIBs. Composites of phosphorus and carbon-based materials have been extensively fabricated to withstand volume expansion of phosphorus and improve cycle performance. Here, composites of BP and graphite (BP-G) with three P-G mass ratios (8 : 2, 7 : 3, and 6 : 4) have been synthesized by a facile and scalable high-pressure and high-temperature (HPHT) method using RP and graphite composites (RP-G) prepared by ball milling as precursors. Their microstructure and bonding configurations have been analyzed by various characterization techniques. Among three RP-G composites, 7RP-3G exhibits the most excellent cycling stability, a high reversible capacity of 1331 mAh/g after 200 cycles at a current density of 0.78 A/g. However, RP-G composites show poor stability at high current densities. Among three BP-G composites, 6BP-4G shows the best cycle stability at high current densities, a reversible capacity of 634.6 mAh/g after 500 cycles at a current density of 2.6 A/g. Although, the reversible specific capacities of BP-G composites after long cycles are lower than those of RP-G, BP-G composites show more stable cycle performance than RP-G, especially at high current densities. The present work illustrates a direct and facile method to synthesize BP-G composites, and sheds light to explore new synthetic route of BP-based composites.