Ultra-high N-doped open hollow carbon nano-cage with excellent Na+ and K+ storage performances

Abstract

The sodium and potassium ion batteries develop rapidly with the aid of abundant resources and similar electrochemistry with lithium ion batteries, being the promising candidates for the next-generation energy storage devices. Nevertheless, the limited storage capacity of Na+/K+ and poor structural stability become the challenging obstructions for the development of carbon anodes. Herein, we creatively prepared the ultra-high N-doping carbons with open carbon nano-cages morphology. Thanks to the adjustable carbonization conditions, the N-doping level can be precisely controlled. This process leads to abundant defective carbons (HNC-550) with a high N-doping level of 17.03 at%, an edge-N–doped ratio of 92.17 at% and an open hollow structure. As for anodes for sodium ion batteries, the optimized HNC-550 demonstrates a high rate performance of 352.2 mAh/g of 100 mA/g. Based on the cross-linked open channel and outstanding structural stability, the sodium ion batteries also exhibit a superior capacity of 97.5 mAh/g after 2000 cycles at an extremely high current density of 10 A/g. Additionally, potassium ion batteries coupled with HNC-550 deliver excellent K+ storage performance of 293.3 mAh/g under 100 mA/g and unprecedented cyclic stability (merely 0.0068% capacity decay per cycle).