Cathode–Electrolyte Interphase in a LiTFSI/Tetraglyme Electrolyte Promoting the Cyclability of V2O5,ACS Applied Materials & Interfaces

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Cathode–Electrolyte Interphase in a LiTFSI/Tetraglyme Electrolyte Promoting the Cyclability of V2O5
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-11-20 , DOI: 10.1021/acsami.0c16727
Xu Liu _{1,

2} , Maider Zarrabeitia _{1,

2} , Bingsheng Qin _{1,

2} , Giuseppe Antonio Elia _{1,

2} , Stefano Passerini _{1,

2}

Affiliation

V₂O₅, one of the earliest intercalation-type cathode materials investigated as a Li⁺ host, is characterized by an extremely high theoretical capacity (441 mAh g^–1). However, the fast capacity fading upon cycling in conventional carbonate-based electrolytes is an unresolved issue. Herein, we show that using a LiTFSI/tetraglyme (1:1 in mole ratio) electrolyte yields a highly enhanced cycling ability of V₂O₅ (from 20% capacity retention to 80% after 100 cycles at 50 mA g^–1 within 1.5–4.0 V vs Li⁺/Li). The improved performance mostly originates from the V₂O₅ electrode itself, since refreshing the electrolyte and the lithium electrode of the cycled cells does not help in restoring the V₂O₅ electrode capacity. Electrochemical impedance spectroscopy (EIS), post-mortem scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the origin of the improved electrochemical behavior. The results demonstrate that the enhanced cyclability is a consequence of a thinner but more stable cathode–electrolyte interphase (CEI) layer formed in LiTFSI/tetraglyme with respect to the one occurring in 1 M LiPF₆ in EC/DMC (1:1 in weight ratio, LP30). These results show that the cyclability of V₂O₅ can be effectively improved by simple electrolyte engineering. At the same time, the uncovered mechanism further reveals the vital role of the CEI on the cyclability of V₂O₅, which can be helpful for the performance optimization of vanadium-oxide-based batteries.

中文翻译：

LiTFSI/四甘醇二甲醚电解质中的阴极-电解质界面促进 V2O5 的可循环性

V ₂ O ₅是最早作为 Li ⁺主体研究的插层型正极材料之一，其特点是具有极高的理论容量（441 mAh g ^-1）。然而，在传统的碳酸盐基电解质中循环后容量快速衰减是一个未解决的问题。在此，我们展示了使用 LiTFSI/四甘醇二甲醚（摩尔比为 1:1）电解液可产生高度增强的 V ₂ O ₅循环能力（在 1.5 范围内以 50 mA g ^-1循环 100 次后容量保持率从 20% 提高到 80%）–4.0 V 与 Li ⁺ /Li)。改进的性能主要来自 V ₂ O ₅电极本身，因为刷新循环电池的电解质和锂电极无助于恢复 V ₂ O ₅电极容量。电化学阻抗谱 (EIS)、尸检扫描电子显微镜 (SEM)、能量色散 X 射线 (EDX) 光谱和 X 射线光电子能谱 (XPS) 已被用于研究改善电化学行为的原因。结果表明，与在 EC/DMC 中的 1 M LiPF ₆中（重量为 1:1比率，LP30）。这些结果表明，V ₂ O _{5的循环性}可以通过简单的电解液工程有效改善。同时，揭示的机理进一步揭示了CEI对V ₂ O ₅循环性能的重要作用，有助于优化钒氧化物电池的性能。

更新日期：2020-12-09

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