Enlarged interlayer spacing and enhanced capacitive behavior of a carbon anode for superior potassium storage

Potassium-ion batteries (PIBs) hold great potential as an alternative to lithium-ion batteries due to the abundant reserves of potassium and similar redox potentials of K+/K and Li+/Li. Unfortunately, PIBs with carbonaceous electrodes present sluggish kinetics, resulting in unsatisfactory cycling stability and poor rate capability. Herein, we demonstrate that the synergistic effects of the enlarged interlayer spacing and enhanced capacitive behavior induced by the co-doping of nitrogen and sulfur atoms into a carbon structure (NSC) can improve its potassium storage capability. Based on the capacitive contribution calculations, electrochemical impedance spectroscopy, the galvanostatic intermittent titration technique, and density functional theory results, the NSC electrode is found to exhibit favorable electronic conductivity, enhanced capacitive adsorption behavior, and fast K+ ion diffusion kinetics. Additionally, a series of ex situ characterizations demonstrate that NSC exhibits superior structural stability during the (de)potassiation process. As a result, NSC displays a high reversible capacity of 302.8 mAh g(-1) at 0.1 A g(-1) and a stable capacity of 105.2 mAh g(-1) even at 2 A g(-1) after 600 cycles. This work may offer new insight into the effects of the heteroatom doping of carbon materials on their potassium storage properties and facilitate their application in PIBs. (C) 2020 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.