Anion Solvation Regulation Enables Long Cycle Stability of Graphite Cathodes,ACS Energy Letters

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Anion Solvation Regulation Enables Long Cycle Stability of Graphite Cathodes
ACS Energy Letters ( IF 19.3 ) Pub Date : 2021-02-12 , DOI: 10.1021/acsenergylett.1c00043
Dandan Yu ₁ , Qiaonan Zhu ₁ , Liwei Cheng ₁ , Shuai Dong ₁ , Xiuhui Zhang ₂ , Hua Wang ₁ , Nianjun Yang ₃

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Graphite is useful as a low-cost and high-voltage cathode of dual-ion batteries (DIBs) to allow anion (de-)intercalation, yet its practical applications are hindered by low Coulombic efficiencies (CEs) and poor cyclability. Meanwhile, the solvation behavior of anions and the impact of solvation on interphase chemistry have not been well clarified. Herein, a fluorinated co-solvent-modified electrolyte is proposed for graphite cathodes in sodium-based DIBs. The introduced composition participates in the solvation of Na⁺ cations and PF₆^̅ anions. The NaF-rich interphase layer formed on the anodes effectively inhibits side reactions with the electrolyte. More importantly, the fluorinated cathode–electrolyte interphase plays significant roles in suppressing electrolyte oxidation decomposition and maintaining the structural integrity of graphite. Consequently, this modified electrolyte endows graphite cathodes with enhanced CEs and long cycle life, and it enables good cycling stability of graphite cathode-based full cells. With this full understanding of anion solvation, this work provides a guideline to design electrolytes for anion-intercalation cathodes.

中文翻译：

阴离子溶剂调节可实现石墨阴极的长周期稳定性

石墨可用作双离子电池（DIB）的低成本高压阴极，以允许阴离子（de-）嵌入，但其实际应用受到低库仑效率（CE）和较差的可循环性的阻碍。同时，还没有很好地阐明阴离子的溶剂化行为以及溶剂化对相化学的影响。在本文中，提出了氟化共溶剂改性的电解质用于钠基DIB中的石墨阴极。以Na的溶剂化所引入的组合物参与⁺阳离子和PF ₆^̅阴离子。在阳极上形成的富NaF相间层有效地抑制了与电解质的副反应。更重要的是，氟化的阴极－电解质中间相在抑制电解质氧化分解和保持石墨的结构完整性方面起着重要作用。因此，该改性电解质赋予石墨阴极增强的CE和长循环寿命，并且它使基于石墨阴极的全电池具有良好的循环稳定性。在对阴离子溶剂化有充分的了解之后，这项工作为设计用于阴离子嵌入阴极的电解质提供了指导。

更新日期：2021-03-12

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