High N-doped hierarchical porous carbon networks with expanded interlayers for efficient sodium storage
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High N-doped hierarchical porous carbon networks with expanded interlayers for efficient sodium storage Dongqin Su1, Man Huang1, Junhao Zhang1 (), Xingmei Guo1, Jiale Chen1, Yanchun Xue1, Aihua Yuan1 (), and Qinghong Kong2 1 2
School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 19 November 2019 / Revised: 26 December 2019 / Accepted: 28 December 2019
ABSTRACT Sodium-ion batteries (SIBs) have been attracting considerable attention as a promising candidate for large-scale energy storage because of the abundance and low-cost of sodium resources. However, lack of appropriate anode materials impedes further applications. Herein, a novel self-template strategy is designed to synthesize uniform flowerlike N-doped hierarchical porous carbon networks (NHPCN) with high content of N (15.31 at.%) assembled by ultrathin nanosheets via a self-synthesized single precursor and subsequent thermal annealing. Relying on the synergetic coordination of benzimidazole and 2-methylimidazole with metal ions to produce a flowerlike network, a self-formed single precursor can be harvested. Due to the structural and compositional advantages, including the high N doping, the expanded interlayer spacing, the ultrathin two-dimensional nano-sized subunits, and the three-dimensional porous network structure, these unique NHPCN flowers deliver ultrahigh reversible capacities of 453.7 mAh·g−1 at 0.1 A·g−1 and 242.5 mAh·g−1 at 1 A·g−1 for 2,500 cycles with exceptional rate capability of 5 A·g−1 with reversible capacities of 201.2 mAh·g−1. The greatly improved sodium storage performance of NHPCN confirms the importance of reasonable engineering and synthesis of hierarchical carbon with unique structures.
KEYWORDS hierarchical porous carbon networks, high N doping, expanded interlayer spacing, anode, sodium-ion batteries
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Introduction
Sodium-ion batteries (SIBs) are widely considered as a prospective alternative energy storage system for lithium-ion batteries (LIBs) based on naturally rich and lower cost of Na [1−4]. Na as the main alkali metal element, which is an adjacent element of lithium, has similar chemical and physical properties, so the existing technology for LIBs could also apply to SIBs systems. However, the high redox potential (−2.71 V) of Na+/Na (Li+/Li, −3.04 V) and slow Na+ migration due to its large radius of 1.02 Å (Li+, 0.76 Å) will evidently affect ion transport kinetics and structural stability during charge/discharge process. Therefore, the direct use of anode materials of LIBs to SIBs usually causes poor electrochemical performance, for instance, insufficient rate performance, poor cycle life, etc. [5−7]. Considering the above issues, various research efforts have been done to let the anode materials match LIBs and SIBs. For example, the previous studies indica
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