Peapod-Like Structured B/N Co-Doped Carbon Nanotube Array Encapsulating M_xP_y (M = Fe, Co, and Ni) Nanoparticles for High-Rate Potassium Storage

Abstract

Potassium-ion batteries (PIBs) have become the desirable alternatives for lithium-ion batteries (LIBs) originating from abundant reserves and appropriate redox potential, while the considerable radius size of K + leading to poor reaction kinetics and huge volume expansion limits the practical application of PIBs. Hybridization of transition-metal phosphides and carbon substrates can effectively optimize the obstacles of poor conductivity, sluggish kinetics, and huge volume variation. Thus, the peapod-like structural M x P y @BNCNTs (M = Fe, Co, and Ni) composites as anode materials for PIBs were synthesized through a facile strategy. Notably, the unique architecture of B/N codoped carbon nanotube array as fast ion/electron transfer pathways effectively improves the electronic conductivity of composites. The M x P y nanoparticles (NPs) are encapsulated in BNCNTs with an amorphous carbon layer (5−10 nm), which discernibly alleviate the volume changes during potassiation/depotassiation. In conclusion, the composites show a commendable cycling performance, possessing reversible capacities of 111, 152, and 122 mA h g −1 after 1000 cycles at 1.0 A g −1 with a negligible capacity loss for FeP@BNCNT, CoP/Co 2 P@BNCNT, and Ni 2 P@BNCNT electrodes, respectively. Especially, after 1000 cycles at 2.0 A g −1 , the CoP/Co 2 P@BNCNT electrode still possesses a capacity of 87.9 mA h g −1 , demonstrating excellent rate performance and long-term life. This work may offer an innovative and viable route to construct a stable architecture for solving the issue of poor stability of TMP-based anodes at a high current density.

Recent advances in rational design for high-performance potassium-ion batteries

“…The electrochemical conversion reaction of PIBs is based on the occurrence of redox reactions, allowing metal compounds to undergo multivalent redox reversible reactions and deliver potentially large capacities. 338,525–527 This electrochemical reaction involves the complete reduction of transition metal in the host material to its metallic state. When the metal is an electrochemically active metal (such as Bi, Sb, etc.…”