Improving Cycling Stability of Vanadium Sulfide (VS4) as a Li Battery Cathode Material Using a Localized High-Concentration Carbonate-Based Electrolyte,ACS Applied Energy Materials

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Improving Cycling Stability of Vanadium Sulfide (VS4) as a Li Battery Cathode Material Using a Localized High-Concentration Carbonate-Based Electrolyte
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2021-11-09 , DOI: 10.1021/acsaem.1c02312
Yuta Maeyoshi ₁ , Kazuki Yoshii ₁ , Masahiro Shikano ₁ , Hikari Sakaebe ₁

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Vanadium sulfide (VS₄) is a promising cathode material for rechargeable Li batteries because it exhibits high capacity and can address the problematic dissolution of lithium polysulfides and the low electrical conductivity of sulfur cathodes. However, VS₄ cathodes suffer from low Coulombic efficiency and fast capacity fading during battery cycling. Here, we report a localized high-concentration electrolyte comprising lithium bis(fluorosulfonyl)imide (LiFSI), ethylene carbonate (EC), propylene carbonate (PC), and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE), which not only stabilizes Li metal anodes but also improves the Coulombic efficiency and cycling stability of the cathode. Further, we propose that the dissolution of V is one of the reasons for the poor cycling stability of VS₄. The localized high-concentration electrolyte has a local coordination structure similar to the high-concentration LiFSI/EC:PC electrolyte, which suppresses the dissolution of V from VS₄ during discharge/charge cycling. Spectroscopic analysis revealed that a LiF-rich layer is formed on the surface of VS₄ in the electrolyte, which also should prevent the dissolution of V from the cathode and the decomposition of the solvents. Our findings suggest that the limited dissolution of V from VS₄ and the LiF-rich cathode–electrolyte interphase layer inhibit the degradation of the cathode, resulting in the improved cycling stability in the electrolyte. This concept of electrolyte design will pave the way for developing high-energy-density Li|transition metal sulfide batteries with stable performance.

中文翻译：

使用局部高浓度碳酸盐基电解质提高硫化钒 (VS4) 作为锂电池正极材料的循环稳定性

硫化钒（VS ₄）是一种很有前途的可充电锂电池正极材料，因为它具有高容量，可以解决多硫化锂的溶解问题和硫正极的低电导率问题。然而，VS ₄正极在电池循环过程中库仑效率低，容量衰减快。在这里，我们报告了一种局部高浓度电解质，包括双（氟磺酰基）亚胺锂 (LiFSI)、碳酸亚乙酯 (EC)、碳酸亚丙酯 (PC) 和 1,1,2,2-四氟乙基 2,2,3,3 -四氟丙基醚（HFE），它不仅可以稳定锂金属负极，还可以提高正极的库仑效率和循环稳定性。此外，我们提出 V 的溶解是 VS ₄循环稳定性差的原因之一。局部高浓度电解质具有类似于高浓度 LiFSI/EC:PC 电解质的局部配位结构，可抑制 V 从 VS _{4 中}溶解在放电/充电循环期间。光谱分析表明，电解液中VS ₄表面形成了富LiF层，这也应防止V从阴极溶解和溶剂分解。我们的研究结果表明，VS ₄中 V 的有限溶解和富含 LiF 的正极-电解质界面层抑制了正极的降解，从而提高了电解质的循环稳定性。这种电解液设计理念将为开发性能稳定的高能量密度锂|过渡金属硫化物电池铺平道路。

更新日期：2021-12-27

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