Na₃V₂(PO₄)₂F₃ is recognized as a promising cathode for high energy density sodium-ion batteries due to its high average potential of ∼3.95 V (vs Na/Na⁺). A high-voltage-resistant electrolyte is of high importance due to the long duration of 4.2 V (vs Na/Na⁺) when improving cyclability. Herein, a targeted electrolyte containing additives with two –C≡N groups like succinonitrile has been designed. In this design, one –C≡N group is accessible to the solvation sheath and enables the other –C≡N in dinitrile being exposed and subsequently squeezed into the electric double layer. Then, the squeezed –C≡N group is prone to a preferential adsorption on the electrode surface prior to the exposed –CH₂/–CH₃ in Na⁺-solvent and oxidized to construct a stable and electrically insulating interface enriched CN^–/NCO^–/Na₃N. The Na₃V₂(PO₄)₂F₃-based sodium-ion batteries within a high-voltage of 2–4.3 V (vs Na/Na⁺) can accordingly achieve an excellent cycling stability (e.g., 95.07% reversible capacity at 1 C for 1,5-dicyanopentane and 98.4% at 2 C and 93.0% reversible capacity at 5 C for succinonitrile after 1000 cycles). This work proposes a new way to design high-voltage electrolytes for high energy density sodium-ion batteries.

中文翻译：

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含双 –C=N 基团的电解质设计可实现高压 Na3V2(PO4)2F3 钠离子电池

Na ₃ V ₂ (PO ₄ ) ₂ F _{3因其平均电势高达~3.95 V（相对于Na/Na} ⁺）而被认为是高能量密度钠离子电池的有前途的阴极。由于 4.2 V（相对于 Na/Na ⁺）的持续时间较长，因此在提高循环性能时，耐高压电解质非常重要。在此，设计了一种含有具有两个 –CeqN 基团（如丁二腈）的添加剂的目标电解质。在该设计中，一个 –C=N 基团可接近溶剂化鞘层，并使二腈中的另一个 –C=N 基团暴露并随后被挤压到双电层中。然后，在Na ^{+溶剂中暴露的-CH} ₂ /-CH ₃之前，挤压的-CeqN基团倾向于优先吸附在电极表面上并被氧化，构建稳定且电绝缘的富含CN ^- /NCO的界面^– /Na ₃ N。Na ₃ V ₂ (PO ₄ ) ₂ F ₃基钠离子电池在2-4.3 V（相对于Na/Na ⁺）的高电压下可以相应地实现优异的循环稳定性（例如1000 个循环后，1,5-二氰基戊烷在 1 C 时可逆容量为 95.07%，在 2 C 时可逆容量为 98.4%，丁二腈在 5 C 时可逆容量为 93.0%。这项工作提出了一种设计高能量密度钠离子电池高压电解质的新方法。