Enhancing the Cycling Stability by Tuning the Chemical Bonding between Phosphorus and Carbon Nanotubes for Potassium-Ion Battery Anodes

Phosphorus/carbon (P/C) composites as promising potassium-ion storage materials have been extensively investigated for its compound superiorities of high specific capacity and favorable electronic conductivity. However, the effects of different chemical bonding states between P and the carbon matrix for potassium-ion storage and cycling performance still need to be investigated. Herein, three P/C composites with different chemical bonding states were successfully fabricated through simply ball-milling red P with carboxylic group carbon nanotubes (CGCNTs), carbon nanotubes (CNTs), and reduced carboxylic group carbon nanotubes (RCGCNTs), respectively. When used as potassium-ion battery (PIB) anodes, the red P and CGCNT (P-CGCNT) composite deliver the most outstanding cycling stability (402.6 mAh g–1 over 110 cycles) with a favorable capacity retention of 68.26% at a current density of 0.1 A g–1, much higher than that of the phosphorus-CNT (P-CNT) composite (297.5 mAh g–1 and 50.40%). Based on the results of X-ray photoelectron spectroscopy and electrochemical performance, we propose that the existence of a carboxyl functional group will be instrumental for the formation of the P–O–C bond. More importantly, when compared with the P–C bond, the P–O–C bond can lead to a higher reversible capacity and a better long-term cycling stability as a result of the more robust bonding energy of the P–O–C bond (585 KJ mol–1) than that of the P–C bond (264 kJ mol–1). This work provides some insights into designing high-performance P anodes for PIBs.