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Seung Bok Lee,Ramkumar Balasubramaniam 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-
Ternary metal oxides Fe2O3 and MgFe2O4 have attracted considerable attention as lithium anode materialsowing to their high theoretical capacities, environmental friendliness, and low cost; however, theirrapid capacity decay and large volume expansion inhibit their lithium storage performance. Herein, wesynthesize hybrid MgFe2O4/Fe2O3 hollow microspheres (MFO/FO-HS) hydrothermally, via the polyolreaction of ethylene glycol, followed by calcination at different temperatures. The surface morphologywas tuned by adjusting the calcination temperature, assisted by inward and outward Ostwald ripening. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetricanalysis were performed to investigate the physio-chemical properties of the prepared samples. Thesample calcined at 450 C exhibited an excellent electrochemical performance and retained a reversiblecapacity of 1390 mAh g1 after 160 cycles, indicating the significant role of calcination temperature intuning the structural and electrochemical properties of anode materials. The double-shelled hollowmicrospheres inhibit rapid capacity decay and prevent severe volume expansion during the electrochemicalprocess. This work opens new paths toward constructing an electrode material with a high electrochemicalperformance.
공민경,( Thangavel Ranjith ),김소영,( Hari Vignesh Ramasamy ),박주연,( Balasubramaniam Ramkumar ),김현재,정강현,이윤성 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
We have developed a new high performing sodium hybrid capacitor (NHC) using sodium super ionic conductor NaTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> grown on graphene sheets (GNTP) and capacitor type carbon electrode in an organic electrolyte. The hybrid device works on two charge storage reactions that occurs simultaneously, sodium ion intercalation/deintercalation into GNTP, providing high energy, and adsorption/desorption of anion over the pores of carbon provides high power. A high energy density of 80 Wh kg<sup>-1</sup> has been achieved at a specific power of Additionally, the hybrid capacitor retains 32 Wh kg<sup>-1</sup> of energy at high specific power of 8 kW kg<sup>-1</sup>, outperforming lithium hybrid capacitors. An outstanding stability of 90% has been achieved even after 75,000 cycles. The combination of high energy at high power along with high stability emerge them as a suitable candidate for next generation high power devices.
Surface modification using atomic layer deposition for developing high voltage sodium layered oxides
공민경,( Hari Vignesh Ramasamy ),( Thangavel Ranjith ),김소영,박주연,( Balasubramaniam Ramkumar ),이윤성 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Here, we present a comprehensive study on the influence of ultrathin metal oxide coating for developing high voltage sodium layered oxides using Atomic Layer Deposition (ALD). Detailed structural, morphological, and electrochemical investigations were carried out using X-ray diffraction, cyclic voltammetry, and galvanostatic charge-discharge measurements. The ALD modified electrode exhibits exceptional stability of above 80% for 100 cycles within a 2.0-4.5V window, and outperforms several other Mn-based cathodes for SIBs. Our work presents new insights for designing structurally stable cathode for Sodium Ion Batteries (SIBs).