Understanding Origin of Voltage Hysteresis in Conversion Reaction for Na Rechargeable Batteries: The Case of Cobalt Oxides

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• 作者：Haegyeom Kim ; Hyunchul Kim ; Hyungsub Kim ; Jinsoo Kim ; Gabin Yoon ; Kyungmi Lim ; Won-Sub Yoon and Kisuk Kang
• 刊名：Advanced Functional Materials
• 出版年：2016
• 出版时间：July 25, 2016
• 年：2016
• 卷：26
• 期：28
• 页码：5042-5050
• 全文大小：4803K
• ISSN：1616-3028

文摘

Conversion reaction electrodes offer a high specific capacity in rechargeable batteries by utilizing wider valence states of transition metals than conventional intercalation-based electrodes and have thus been intensively studied in recent years as potential electrode materials for high-energy-density rechargeable batteries. However, several issues related to conversion reactions remain poorly understood, including the polarization or hysteresis during charge/discharge processes. Herein, Co₃O₄ in Na cells is taken as an example to understand the aforementioned properties. The large hysteresis in charge/discharge profiles is revealed to be due to different electrochemical reaction paths associated with respective charge and discharge processes, which is attributed to the mobility gap among inter-diffusing species in a metal oxide compound during de/sodiation. Furthermore, a Co₃O₄–graphene nanoplatelet hybrid material is demonstrated to be a promising anode for Na rechargeable batteries, delivering a capacity of 756 mAh g⁻¹ with a good reversibility and an energy density of 96 Wh kg⁻¹ (based on the total electrode weight) when combined with a recently reported Na₄Fe₃(PO₄)₂(P₂O₇) cathode.