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.