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연정석,박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Nigrogen-doped Honeycomb-like Structure Carbon are synthesised through the facile hydrothermal carbonisation of a lignin precursor, subsequent KOH activation, and a post-doping process. The asobtained n-hC exhibits a large surface area and pore volume, as well as a high N content. The n-hC is used as a S-hosting material with mass loading of 64.1 wt% through the in situ redox reaction of Na2S2O3. The S@n-hC achieves a high initial discharge capacity of 1295.5 mAh g-1 at 0.1C and retains 647.2 mAh g-1 after 600 cycles, with a low capacity decay of 0.08% per cycle and show excellent cycling stability The strong confinement of S in the N-doped micropores leads to the electrochemical and thermal stabilisation of S, providing different redox environments. The facile and reversible redox kinetics of the S@n-hC are confirmed by the Nyquist plots as well as by the prominent cyclic voltammetry and galvanostatic charge/discharge profiles.
activated n-doped porous carbon derived from Lignin for Lithium-sulfur batteries
연정석,박소현,박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
A activated nitrogen-doped honeycomb-shape porous carbon (n-hC ) is successfully synthesized through a facile hydrothermal carbonization of lignin precursor, subsequent KOH activation, and N-doping process. The as-obtained n-hC shows large surface area and pore volume and N composition (3.47%) . The n-hC is then used as hosting matrix with a sulfur loading of 64.1wt% (n-hC@S) through in-situ redox reaction of Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> with HCl. This n-hC@S composite achieves a high initial discharge capacity of 1295.5 mAh g<sup>-1</sup> at 0.1C, while preserving 938.6 mAh g<sup>-1</sup> over 300 cycles with a low capacity decay of 0.08% per cycle. The excellent electrochemical performance of n-hC@S is attributed to the synergistic effect of porous honeycomb structure and N-incorporation, which can effectively prevent the diffusion of sulfur from the host material by physical barrier and strong chemical adsorption between n-hC and sulfur.
Graphene/sulfur composite cathode material with high capacity and cycling stability
연정석,박호석 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Lithium-sulfur batteries are receiving enormous interest because of its high theoretical capacity. (1,675mAhg-1) However, their commerciali-zation still hindered by several issues, including short cycle life, low cycling and high self-discharge rate. Moreover, due to the low electrical conductivity and polysulfide dissolution (Li2S2 and Li2S), sulfur-based electrodes are limited its specific discharge capacity. Herein, we report a facile synthesis method for preparing reduced graphene oxide composites containing high sulfur content (up to 80%). With this strategy, we are used to homogeneously mixed the aqueous dispersed sulfur and the GO solution. And then electrode synthesis by using Spray method. Consequently, the electrode shows an initial capacity of 1211mAhg-1 and can retain a reversible capacity of 946mAhg-1 after 100 charge/discharge cycles at 0.1C and the strong covalent bonds between sulfur and rGO that enable to improve efficiency during charge/discharge.
박호석,연정석,윤솔,박재민 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
The hierarchical architecturing and hybridization of iron oxide is very important for achieving multifunctional capability that makes it possible for practical applications. In particular, hierarchical architecturing of graphene/iron oxide hybrids in a three-dimensionally manner is expected to become an innovative chemical approach for full potential of respective functionality.
MOF-Nafion separator preventing polysulfide shuttle effect in Li-S batteries
김선화,연정석,박호석 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
High order lithium polysulfide dissolves in electrolyte and it moves from cathode to anode in lithium-sulfur(Li-S) batteries. This shuttle effect causes the loss of active sulfur and it makes the electrochemical performances of cell decreased. It is most critical issue to enhance the Li-S battery performance. Here, we present a simple strategy to block the shuttle effect using metal-organic framework(MOF) and Nafion coated battery separator. -SO3 group in MOF and Nafion push the negatively charged polysulfide, but positively charged lithium ion can be permitted to pass. This functionalized -SO3 group also help to improve the ionic conductivity. This NOF-Nafion coated separator for Li-S batteries shows a low capacity decay(0.079% per cycle within 250 cycles).
윤솔,연정석,박재민,박호석 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
The hierarchical architecturing and hybridization of iron oxide is very important for achieving multifunctional capability that makes it possible for practical applications. In particular, hierarchical structure constructed by graphene nanosheets and iron nanoparticles takes advantages of 3D interconnected structure in terms of a large accessible area, fast mass and ion transport, and structural integrity. In this study, hierarchically structured reduced graphene oxide (hrGO)/α-Fe2O3 nanobox hybrids (hrGO/α-Fe NBhs) are synthesized via a hydrothermal self-assembly process. The 3D porous structure of hrGO/α-Fe NBhs is constructed, while α-Fe2O3 nanoboxs (NBs) in a proximate contact with the hrGO surface are simultaneously nucleated and grown during a hydrothermal treatment. The discrete α- Fe2O3 NBs are uniformly distributed on the surface of the hrGO/α-Fe and confined in the 3D architecture, thereby inhibiting the restacking of rGO layers and maximizing their functionalities.