Ultra-High Capacity and Cyclability of β-phase Ca0.14V2O5 as a Promising Cathode in Calcium-Ion Batteries |
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Authors: | Samuel Jayaraj Richard Prabakar Amol Bhairuba Ikhe Woon-Bae Park Docheon Ahn Kee-Sun Sohn Myoungho Pyo |
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Affiliation: | 1. Department of Advanced Components and Materials Engineering, Sunchon National University, Chonnam, 57922 Republic of Korea;2. Beamline Department, Pohang Accelerator Laboratory, Pohang, 790-784 Republic of Korea;3. Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, 05006 Republic of Korea |
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Abstract: | Crystalline water-free β-phase Ca0.14V2O5 is reported for the first time as a viable cathode material for calcium-ion batteries (CIBs). In contrast to layered α-V2O5 and δ-CaxV2O5·nH2O, which have limited capacity, the β-phase delivers a reversible capacity of ≈247 mAh g?1, which corresponds to the insertion/extraction of Ca2+ between Ca0.14V2O5 and Ca1.0V2O5. The process of Ca2+ insertion process and the accompanying structural relaxation are theoretically and experimentally verified. The initial insertion of Ca2+ into Ca0.14V2O5 causes a slight shift of oxygen atoms surrounding hepta-coordination sites, creating penta-coordinated sites that are then partially filled up to Ca0.33V2O5. Further insertion occurs through the stepwise occupation of up to 50% of neighboring hexa- and tetra-coordination sites to form Ca0.67V2O5 and Ca1.0V2O5, respectively. The rearrangement of oxygen atoms in Ca0.14V2O5 also minimizes dimensional changes, leading to high cyclic stability during repeated charge/discharge cycles. The remarkable electrochemical performance of full cells containing a Ca0.14V2O5 cathode and a K metal anode in Ca2+/K+ hybrid electrolytes, is also demonstrated, thanks to the inertness of K+ insertion into Ca0.14V2O5 and the absence of calcium plating/stripping. The cyclic stability and high capacity of Ca0.14V2O5 is not compromised in hybrid electrolytes, making it a viable CIB cathode. |
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Keywords: | calcium-ion batteries cyclic stability high capacity vanadium oxide β-phase |
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