Choudhury Snehashis, Wei Shuya, Ozhabes Yalcin, Gunceler Deniz, Zachman Michael J, Tu Zhengyuan, Shin Jung Hwan, Nath Pooja, Agrawal Akanksha, Kourkoutis Lena F, Arias Tomas A, Archer Lynden A
School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14853, USA.
Department of Physics, Cornell University, Ithaca, NY, 14853, USA.
Nat Commun. 2017 Oct 12;8(1):898. doi: 10.1038/s41467-017-00742-x.
Secondary batteries based on earth-abundant sodium metal anodes are desirable for both stationary and portable electrical energy storage. Room-temperature sodium metal batteries are impractical today because morphological instability during recharge drives rough, dendritic electrodeposition. Chemical instability of liquid electrolytes also leads to premature cell failure as a result of parasitic reactions with the anode. Here we use joint density-functional theoretical analysis to show that the surface diffusion barrier for sodium ion transport is a sensitive function of the chemistry of solid-electrolyte interphase. In particular, we find that a sodium bromide interphase presents an exceptionally low energy barrier to ion transport, comparable to that of metallic magnesium. We evaluate this prediction by means of electrochemical measurements and direct visualization studies. These experiments reveal an approximately three-fold reduction in activation energy for ion transport at a sodium bromide interphase. Direct visualization of sodium electrodeposition confirms large improvements in stability of sodium deposition at sodium bromide-rich interphases.The chemistry at the interface between electrolyte and electrode plays a critical role in determining battery performance. Here, the authors show that a NaBr enriched solid-electrolyte interphase can lower the surface diffusion barrier for sodium ions, enabling stable electrodeposition.
基于储量丰富的钠金属负极的二次电池对于固定式和便携式电能存储都很理想。如今室温钠金属电池并不实用，因为充电过程中的形态不稳定性会导致粗糙的树枝状电沉积。液态电解质的化学不稳定性也会由于与负极发生寄生反应而导致电池过早失效。在此，我们使用联合密度泛函理论分析表明，钠离子传输的表面扩散势垒是固体电解质界面化学性质的敏感函数。特别是，我们发现溴化钠界面呈现出异常低的离子传输能垒，与金属镁相当。我们通过电化学测量和直接可视化研究来评估这一预测。这些实验表明，在溴化钠界面处离子传输的活化能降低了约三倍。钠电沉积的直接可视化证实了在富含溴化钠的界面处钠沉积稳定性有了大幅提高。电解质与电极之间界面处的化学性质在决定电池性能方面起着关键作用。在此，作者表明富含溴化钠的固体电解质界面可以降低钠离子的表面扩散势垒，实现稳定的电沉积。
