Impact of P–O–C bonds on the electrochemical performance of black phosphorus-carbon composites used in sodium-ion batteries

Sodium-ion batteries (SIBs) offer great viability for extensive energy storage due to their abundance, low cost, and excellent safety. In this study, we investigate the relationship between P–O–C bonds content and electrochemical performance of black phosphorus–hard carbon–carbon nanotubes (BP-HC-CNTs) composite anode. A series of composites are prepared via ball milling, in which the relative P–O–C bonds content is modulated by varying the HC to CNTs ratio, and the effect of different relative P–O–C bond contents on the electrochemical performance of the materials is systematically investigated. The findings indicate that tuning the HC to CNTs ratio alters the chemical bonding degree between phosphorus and carbon, specifically the P–O–C bond content, which positively correlates with enhanced electrochemical performance. Notably, the composite with the highest P–O–C content (36 %) exhibits superior performance compared to those with lower bond contents: The specific capacity is approximately 2.9 times higher after 600 cycles at 6.0 A g ⁻¹ , and after 2000 cycles at 15.0 A g ⁻¹ , it is about 5.7 times higher. These results demonstrate excellent rate capability and cycling stability. Therefore, we propose that adjusting the hard carbon/carbon nanotubes ratio effectively regulates P–O–C bonds formation, which is essential for improving interfacial stability and electrochemical kinetics.