Elucidation of Parasitic Reaction Mechanisms at Interfaces in Na–O 2 Batteries
Elucidation of Parasitic Reaction Mechanisms at Interfaces in Na–O 2 Batteries
复制标题
Na-O 2 电池界面寄生反应机制的阐明
DOI：
10.1021/acs.chemmater.3c00850
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发表时间：
2023
影响因子：
8.6
通讯作者：
Greeley, Jeffrey
中科院分区：
文献类型：
--
作者：
Von Gunten, Alex;Velinkar, Kunal;Nikolla, Eranda;Greeley, Jeffrey
含钠电池有潜力解决正在进行的增强型储能设备开发中面临的许多挑战。钠价格低廉，储量丰富，尤其是非质子na - o2电池，其重量能量密度显著超过锂离子电池。然而，较差的功能细胞寿命是na - o2细胞发育的一个重大障碍，与nao2放电产物有关的寄生副反应导致细胞性能迅速下降。假设这些寄生反应通过两个主要途径发生：(i)在电池空转期间nao2有害溶解到电解质中；（ii） nao2在近表面区域歧化，在阴极上形成富na物质（Na1+xO2）。为了制定实际的策略来抑制这些过程，反过来，发展基本的，分子水平的机制理解是必不可少的。在这篇论文中，通过耦合密度泛函理论计算和实验观察来研究nao2放电产物的表面化学，从而阐明了这种机理的见解。首先，构建了一系列初始表面相图，确定了实际操作条件下nao2表面的结构，从而确定了表面配位与表面能之间的反比关系。接下来，对确定的表面末端进行分子表面溶解分析，进一步证明了表面能与溶解热力学势垒之间的反比关系。最后，对nao2放电产物上氧化钠薄膜形成的热力学进行了研究，结果表明，在高放电过电位下，在近表面区域形成观察到的富na物质是电化学还原反应，而不是固有的化学歧化反应。根据这些见解，我们建议未来的研究可能会产生实际的设计变化，以提高na - o2电池的稳定性和延长其使用寿命。
Sodium-containing batteries have the potential to address many of the challenges faced in the ongoing development of enhanced energy storage devices. Sodium is inexpensive and earth abundant, and aprotic Na–O2batteries, in particular, have gravimetric energy densities significantly exceeding those of Li-ion devices. However, poor functional cell lifespans present a significant obstacle to the development of Na–O2cells, with parasitic side reactions involving the NaO2discharge products, leading to a rapid decline in cell performance. These parasitic reactions are hypothesized to occur through two main pathways: (i) deleterious dissolution of NaO2into the electrolyte during periods of cell idling and (ii) disproportionation of NaO2in the near-surface region to form Na-rich species (Na1+xO2) on the cathode. To formulate practical strategies to suppress these processes, in turn, the development of fundamental, molecular-level mechanistic understanding is essential. In this contribution, such mechanistic insights are elucidated by coupling density functional theory calculations with experimental observations to study the surface chemistry of the NaO2discharge product. First, a series ofab initiosurface phase diagrams are constructed to determine the structure of the NaO2surfaces under realistic operating conditions, whereby an inverse relationship between surface coordination and surface energy is determined. Next, a molecular surface dissolution analysis is performed for the identified surface terminations, demonstrating a further inverse relationship between surface energy and the thermodynamic barrier for dissolution. Finally, a study of the thermodynamics of thin-film formation of sodium oxides over the NaO2discharge product is carried out and suggests that an electrochemical reduction reaction, rather than an inherent chemical disproportionation, forms the observed Na-rich species in the near-surface region under high discharge overpotentials. From these insights, we suggest future studies that may yield practical design changes to improve stability and extend the lifespan of Na–O2batteries.