Graphitic nanorings for super-long lifespan lithium-ion capacitors
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Graphitic nanorings for super-long lifespan lithium-ion capacitors Guangchao Li1, Zhoulan Yin1, Yuqing Dai1, Bianzheng You1, Huajun Guo1, Zhixing Wang1, Guochun Yan1, Yong Liu2, and Jiexi Wang1,2 () 1 2
School of Metallurgy and Environment & College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 26 February 2020 / Revised: 1 April 2020 / Accepted: 14 April 2020
ABSTRACT Porous graphitic carbon nanorings (PGCNs) are proposed by smart catalytic graphitization of nano-sized graphene quantum dots (GQDs). The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm, and demonstrate extraordinary mesoporous structure, controllable graphitization degree and highly defective nature. The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process, undergoing the procedure of amorphous carbon, intermediate phase, graphitic carbon nanorings and graphitic carbon nanosheets. Further, the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed. The unique microstructure implies PGCNs a broad prospect for energy storage application. When applied as negative electrode materials in dual-carbon lithium-ion capacitors, high energy density (77.6 Wh·kg−1) and super long lifespan (89.5% retention after 40,000 cycles at 5.0 A·g−1) are obtained. The energy density still maintains at 24.5 Wh·kg−1 even at the power density of 14.1 kW·kg−1, demonstrating excellent rate capability. The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage.
KEYWORDS graphene quantum dots, carbon nanorings, catalytic graphitization, defects, lithium ion capacitors
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Introduction
Benefiting from the abundant nature, chemical stability and structural diversity, carbon-based materials have been widely applied in sensors, imaging, drug delivery, superconducting devices and energy related fields during the past two decades [1–4]. In recent years, carbon nanomaterials bloom into superstars in energy storage and conversion systems, focusing on the convenience provided by nanosized distribution [5, 6]. Interestingly, different types of carbon nanomaterials show multiple properties among zero-dimensional (0D) carbon dots, one-dimensional (1D) carbon nanofibers/nanotubes, two-dimensional (2D) graphene as well as carbon nanosheets, and three-dimensional (3D) carbon foams [7–11]. Carbon dots, associated to a novel member in nano carbon family, have sparked a research climax because of the abundant resource and benignant nature to environment when compared to inorganic dots [12]. Especially, carbon dots have been widely applied in optoelectronic and photodetctors [13]. As another example, car
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