Tuning electrolyte components plays a very important role in improving the sodium storage of hard carbon (HC) anode. Herein, we unprecedentedly synthesize a fluorinated moisture resistant aluminum-centered sodium salt of sodium bis(perfluoropinacolato)aluminate (NaAl[OC(CF)], NaBPPA), which enhances the sodium storage and specific capacity of HC anode when serving as main conducting salt in electrolyte. It is revealed that NaBPPA induces the formation of a mechanically robust and fast Na conducting SEI layer on HC anode. In specific, the NaBPPA-based electrolyte facilitates the enrichment of unique inorganic species (such as NaAlF, NaF, AlF and AlO), which endow the SEI layer with high Young's modulus and fast Na transportation. Thus, the problem of SEI layer dissolution is alleviated and the formation of quasi-metallic Na clusters at low potential plateau region is promoted by using NaBPPA as a main salt in electrolytes. This work reveals the great importance of novel sodium salt anions beyond conventional ones in boosting sodium storage of HC anode.

中文翻译：

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氟化铝钠主导电盐促进硬碳储钠

调整电解质成分对于改善硬碳（HC）阳极的钠存储起着非常重要的作用。在此，我们前所未有地合成了氟化防潮铝中心双(全氟频哪醇)铝酸钠盐(NaAl[OC(CF)]，NaBPPA)，该钠盐在作为主导电盐时增强了HC阳极的钠存储和比容量在电解液中。研究表明，NaBPPA 会诱导在 HC 阳极上形成机械坚固且快速的 Na 导电 SEI 层。具体而言，基于NaBPPA的电解质有利于独特无机物质（如NaAlF、NaF、AlF和Al2O）的富集，从而赋予SEI层高杨氏模量和快速Na传输。因此，通过使用NaBPPA作为电解液中的主要盐，缓解了SEI层溶解的问题，并促进了低电位平台区准金属Na簇的形成。这项工作揭示了新型钠盐阴离子超越传统钠盐阴离子在促进 HC 阳极钠储存方面的重要性。