Pfeifer Kristina, Arnold Stefanie, Becherer Julian, Das Chittaranjan, Maibach Julia, Ehrenberg Helmut, Dsoke Sonia
Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
Helmholtz-Institute Ulm for Electrochemical Energy Storage (HIU), P.O. Box 3640, 76021, Karlsruhe, Germany.
ChemSusChem. 2019 Jul 19;12(14):3312-3319. doi: 10.1002/cssc.201901056. Epub 2019 Jun 11.
Sodium-ion batteries (NIBs) are promising energy-storage devices with advantages such as low cost and highly abundant raw materials. To probe the electrochemical properties of NIBs, sodium metal is most frequently applied as the reference and/or counter electrode in state-of-the-art literature. However, the high reactivity of the sodium metal and its impact on the electrochemical performance is usually neglected. In this study, it is shown that spontaneous reactions of sodium metal with organic electrolytes and the importance of critical interpretation of electrochemical experiments is emphasized. When using sodium-metal half-cells, decomposition products contaminate the electrolyte during the electrochemical measurement and can easily lead to wrong conclusions about the stability of the active materials. The cycling stability is highly affected by these electrolyte contaminations, which is proven by comparing sodium-metal-free cell with sodium-metal-containing cells. Interestingly, a more stable cycling performance of the Li Ti O half-cells can be observed when replacing the Na metal counter and reference electrodes with activated carbon electrodes. This difference is attributed to the altered properties of the electrolyte as a result of contamination and to different surface chemistries.
钠离子电池（NIBs）是很有前景的储能设备，具有低成本和原材料储量丰富等优点。为了探究钠离子电池的电化学性质，在最新的文献中，金属钠最常被用作参比电极和/或对电极。然而，金属钠的高反应活性及其对电化学性能的影响通常被忽视。在本研究中，展示了金属钠与有机电解质的自发反应，并强调了对电化学实验进行批判性解读的重要性。使用钠金属半电池时，在电化学测量过程中分解产物会污染电解质，并且很容易导致对活性材料稳定性得出错误结论。通过比较无钠金属电池和含钠金属电池，证实了循环稳定性受这些电解质污染的影响很大。有趣的是，当用活性炭电极取代钠金属对电极和参比电极时，可以观察到LiTi O半电池具有更稳定的循环性能。这种差异归因于污染导致的电解质性质改变以及不同的表面化学性质。
