Intrinsically high efficiency sodium metal anode
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tps://doi.org/10.1007/s11426-020-9808-6
SPECIAL TOPIC: Electrocatalysis & Energy Science
Intrinsically high efficiency sodium metal anode 1,2
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Yifang Zhang , Qiuwei Shi , Yiren Zhong & Hailiang Wang 1
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Department of Chemistry and Energy Sciences Institute, Yale University, West Haven, CT 06516, USA; Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, China Received June 1, 2020; accepted June 28, 2020; published online August 18, 2020
Efficient plating/stripping of Na metal is critical to stable operation of any rechargeable Na metal battery. However, it is often overlooked or misunderstood in electrochemical measurements using thick Na electrodes with large excess of Na reserves. Herein, we report two crucial aspects, which have generally been ignored in previous studies, in the development of more practical capacity-controlled Na metal electrodes that can be efficiently cycled at 100% depth. We find that common carbonate electrolytes induce severe side reaction and highly irreversible Na plating/stripping, whereas ether electrolytes without any additive support thick Na metal electrodes operating at a high average Coulombic efficiency of 99.6% for over 300 cycles. We further show that to realize such high efficiency in thin Na metal electrodes, it is necessary to ensure strong adhesion between the thin Na layer and the Cu current collector, which we solve by introducing an Au interlayer. The resulting transferable thin Na metal electrodes enable high-energy-density, high-efficiency and reasonably stable-cycling Na||Na3V2(PO4)3 batteries. sodium metal battery, electrolyte, Coulombic efficiency, deep cycling Citation:
Zhang Y, Shi Q, Zhong Y, Wang H. Intrinsically high efficiency sodium metal anode. Sci China Chem, 2020, 63, https://doi.org/10.1007/s11426-0209808-6
The low cost and high abundance of Na resources has brought Na-based batteries on the front burner of future energy storage technologies [1–4]. Resembling Li metal for Li batteries, Na metal, with its high specific capacity −1 (1,164 mAh g ) and low redox potential (−2.714 V vs. SHE (standard hydrogen electrode)), is the optimal anode material for Na batteries except for its side reaction and dendrite formation tendency causing poor reversibility in electrochemical plating/stripping and hence a short cycle life [5–9]. While many approaches have been taken to improve the stability of Na metal electrodes, most of these studies were based on thick Na electrodes that are shallowly cycled (e.g., 99.9%) to better satisfy application requirements. In conclusion, Na metal electrodes have high CE when operating in ether electrolytes but are highly irreversible in
carbonate electrolytes. Preparation and effective cycling of thin Na metal electrodes with controlled capacities is challenged by the adhesion problem between Na and Cu, which can be solved by introducing an Au interlayer. With this progress, we have reached the 99.5% level of CE, which means
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