Constructing sulfur and nitrogen codoped porous carbon with optimized defect-sites and electronic structure promises high performance potassium-ion storage

Abstract

Defective-rich carbon can help to promote effectively the gravimetric potassium storage capability because of the introduced more active sites. Nevertheless, the low reversibility caused by undesirable defects and the deteriorative conductivity limits their cycling stability. Herein, we propose an “order-in-disorder” synergetic engineering strategy by in situ embedding nanographitic in the defective carbon structure to boost the specific capacity and conductivity simultaneously. Meanwhile, porous and hollow carbon architectures built of interconnected carbon skeleton provide a better accommodation for the strains during the charge/discharge process, which effectively maintains the structural integrity to alleviate the capacity fading. With outstanding structural merits, the as-prepared electrode delivers high specific capacities of 328 mAh/g at 0.2 A/g and 161 mAh/g at 4 A/g with an ultralong cycling stability over 2000 cycles at 1 A/g. Density functional theory calculations confirm that the adsorption/diffusion of K+ ions and electronic conductivity of carbon structure can be facilitated synergistically benefitting from N/S codoping. Moreover, in situ Raman and ex situ XPS spectra reveals that the excellent cycling stability mainly originates from the superior phase reversibility and robust structure integrity of as-prepared electrode. Therefore, this work could inspire to rational design and achieve appropriate heteroatom configurations, and provide in-depth understanding of K+ storage mechanism.