Peapod-Like Structured B/N Co-Doped Carbon Nanotube Array Encapsulating MP (M = Fe, Co, and Ni) Nanoparticles for...

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 MP@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 MP 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/Co₂P@BNCNT, and Ni₂P@BNCNT electrodes, respectively. Especially, after 1000 cycles at 2.0 A g^-1, the CoP/Co₂P@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.