Precise synthesis of N-doped graphitic carbon via chemical vapor deposition to unravel the dopant functions on potassium
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ege of Energy, Soochow Institute for Energy and Materials InnovationS (SIEMIS), Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou 215006, China 2 Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China § Yu Zhao and Zhongti Sun contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 25 September 2020 / Accepted: 18 October 2020
ABSTRACT Nitrogen doped carbon is a burgeoning anode candidate for potassium-ion battery (PIBs) owing to its outstanding attributes. It is imperative to grasp further insight into specific effects of different nitrogen dopants in carbon anode toward advanced K-ion storage. However, the prevailing fabrication method is plagued by the fact that considerable variations in the total N-doping concentration occur in the course of regulating the type of nitrogen dopants, incapable of distinguishing the certain roles of them under similar conditions. Herein, throughout the precise preparation of high edge-N doped carbon (HENC) and high graphitic-N doped carbon (HGNC) harnessing basically identical N-doping levels (5.78 at.% for HENC; 5.07 at.% for HGNC) via chemical vapor deposition route, the effects of edge-N and graphitic-N in the carbon anode on K-ion storage are revisited, offering guidance into the design of low-cost and high-performance PIB systems.
KEYWORDS nitrogen doping, carbon anode, potassium storage, adsorption, voltage
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Introduction
The merit of abundant potassium resources has triggered growing research endeavors of potassium-ion battery (PIBs) [1]. The key to realizing reliable PIBs lies in developing highperformance electrodes, especially the anodes. In comparison with emerging anode material candidates (metals, transitional metal chalcogenides, etc.) [2–5], carbonaceous nanostructures offer inimitable advantages in terms of cost-effectiveness and environmental friendliness. Graphite [6, 7], soft carbon [8, 9], hard carbon [10, 11] and few-layer graphene [12] are all prevailing nowadays. The storage of K+ by the latter three listed is governed by a hybridization of ion-intercalation and ion-adsorption mechanism [13]. Considering that the larger radius of K+ (1.38 Å vs. 0.68 Å for Li+) is highly likely to give rise to sluggish kinetics and high irreversibility of the intercalation, enhancing the adsorption of K+ on the surface of carbons has rendered as an effective solution to improve anode performance [14]. In this regard, atomic modulation via introducing nitrogen atoms into carbon frameworks has garnered emerging attraction to promote the adsorption dominated charge storage. In normal scenarios, there exist three configurations of nitrogen species within the carbon lattice: pyridinic N (Py-N) bonding with two C atoms at edges or defects, pyrrolic N (Pr-N) bonding into the five-membered carbon ring and gra
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