title: Investigation of the Na Intercalation Mechanism into Nanosized V2O5/C Composite Cathode Material for Na-Ion Batteries.
abstract: There is a significant interest to develop high-performance and cost-effective electrode materials for next-generation sodium ion batteries. Herein, we report a facile synthesis method for nanosized V2O5/C composite cathodes and their electrochemical performance as well as energy storage mechanism. The composite exhibits a discharge capacity of 255 mAh g(-1) at a current density of 0.05 C, which surpasses that of previously reported layered oxide materials. Furthermore, the electrode shows good rate capability; discharge capacity of 160 mAh g(-1) at a current density of 1 C. The reaction mechanism of V2O5 upon sodium insertion/extraction is investigated using ex situ X-ray diffraction (XRD) and synchrotron based near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Ex situ XRD result of the fully discharged state reveals the appearance of NaV2O5 as a major phase with minor Na2V2O5 phase. Upon insertion of sodium into the array of parallel ladders of V2O5, it was confirmed that lattice parameter of c is increased by 9.09%, corresponding to the increase in the unit-cell volume of 9.2%. NEXAFS results suggest that the charge compensation during de/sodiation process accompanied by the reversible changes in the oxidation state of vanadium (V(4+) ↔ V(5+)).
authors.affiliation: Center for Energy Convergence Research, Korea Institute of Science and Technology , Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.|Korea University of Science and Technology , 217 Gajeong-ro Yuseong-gu, Daejeon 305-333, Republic of Korea.
authors.forename: Ghulam
authors.initials: G
authors.lastname: Ali
authors.affiliation: Center for Energy Convergence Research, Korea Institute of Science and Technology , Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Center for Energy Convergence Research, Korea Institute of Science and Technology , Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.|Korea University of Science and Technology , 217 Gajeong-ro Yuseong-gu, Daejeon 305-333, Republic of Korea.
authors.forename: Si Hyoung
authors.initials: SH
authors.lastname: Oh
authors.affiliation: Center for Energy Convergence Research, Korea Institute of Science and Technology , Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors.forename: Byung Won
authors.initials: BW
authors.lastname: Cho
authors.affiliation: Department of Energy and Materials Engineering, Dongguk University-Seoul , Seoul 100-715, Republic of Korea.
authors.forename: Kyung-Wan
authors.initials: KW
authors.lastname: Nam
authors.affiliation: Center for Energy Convergence Research, Korea Institute of Science and Technology , Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.|Korea University of Science and Technology , 217 Gajeong-ro Yuseong-gu, Daejeon 305-333, Republic of Korea.
authors.forename: Kyung Yoon
authors.initials: KY
authors.lastname: Chung
keywords: Na-ion batteries; NaV2O5; X-ray diffraction; nanosized V2O5; near-edge X-ray absorption fine structure