Sodium-ion batteries (SIBs) is a promising technology for next-generation energy storage. However, their performance is limited at low temperatures due to the inferior bulk and interfacial resistance of current electrolytes. Here we present a systematic study to evaluate carboxylate ester-based electrolytes for SIB applications, due to their favorable properties (i.e., low melting point, low viscosity and high dielectric constant). The effects of salt, concentration and solvent molecular structure were systematically examined and compared with those of carbonate-based electrolytes. By combining electrochemical tests with spectroscopic characterization, the performance of selective carboxylate ester-based electrolytes in hard carbon/Na and Na₃V₂(PO₄)₃/Na half-cells was evaluated. We found carboxylates enable high electrolyte conductivities, especially at low temperatures. However, carboxylates alone are inadequate to form a stable interphase due to their high reactivity, which can be addressed by choosing a suitable anion and facilitating anion-rich Na⁺ solvation by increasing salt concentration. Fundamental knowledge on the chemistry–property–performance correlation of this new family of electrolytes was obtained, and their benefits and pitfalls were thoroughly discussed. These discoveries and knowledge will shed light on the potential of carboxylate ester-based electrolytes and provide the foundation for further electrolyte engineering.

中文翻译：

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钠离子电池用羧酸酯基电解质


钠离子电池（SIB）是一种很有前景的下一代储能技术。然而，由于当前电解质的体电阻和界面电阻较差，它们在低温下的性能受到限制。在这里，我们提出了一项系统研究，以评估用于 SIB 应用的羧酸酯基电解质，因为它们具有良好的特性（即低熔点、低粘度和高介电常数）。系统地检查了盐、浓度和溶剂分子结构的影响，并与碳酸酯基电解质进行了比较。通过将电化学测试与光谱表征相结合，选择性羧酸酯基电解质在硬碳/Na和Na ₃ V ₂ (PO ₄ ) 中的性能< b3> /Na半电池进行了评估。我们发现羧酸盐可以实现高电解质电导率，尤其是在低温下。然而，由于其高反应性，单独的羧酸盐不足以形成稳定的界面，这可以通过选择合适的阴离子并通过增加盐浓度促进富含阴离子的Na ⁺ 溶剂化来解决。获得了关于这一新电解质家族的化学-性质-性能相关性的基础知识，并深入讨论了它们的优点和缺陷。这些发现和知识将揭示羧酸酯基电解质的潜力，并为进一步的电解质工程奠定基础。