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Exploring the Role of an Electrolyte Additive in Suppressing Surface Reconstruction of a Ni-Rich NMC Cathode at Ultrahigh Voltage via Enhanced In Situ and Operando Characterization Methods
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2024-02-09 , DOI: 10.1021/acsami.3c15670
Huidong Dai 1 , Luisa Gomes 1 , Derrick Maxwell 2 , Somayeh Zamani 3 , Kevin Yang 2 , Dianne Atienza 3 , Nilesh Dale 3 , Sanjeev Mukerjee 1
Affiliation  

Vinylene carbonate (VC) is a widely used electrolyte additive in lithium-ion batteries for enhanced solid electrolyte interphase formation on the anode side. However, the cathode electrolyte interphase (CEI) formation with VC has received a lot less attention. This study presents a comprehensive investigation employing advanced in situ/operando-based Raman and X-ray absorption spectroscopy (XAS) to explore the effect of electrolyte composition on the CEI formation and suppression of surface reconstruction of LixNiyMnzCo1–yzO2 (NMC) cathodes. A novel chemical pathway via VC polymerization is proposed based on experimental results. In situ Raman spectra revealed a new peak at 995 cm–1, indicating the presence of C–O semi-carbonates resulting from the radical polymerization of VC. Operando Raman analysis unveiled the formation of NiO at 490 cm–1 in the baseline system under ultrahigh voltage (up to 5.2 V). However, this peak was conspicuously absent in the VC electrolyte, signifying the effectiveness of VC in suppressing surface reconstruction. Further investigation was carried out utilizing in situ XAS compared X-ray absorption near edge structure spectra from cells of 3 and 20 cycles in both electrolytes at different operating voltages. The observed shift at the Ni K-edge confirmed a more substantial reduction of Ni in the baseline electrolyte compared to that in the VC electrolyte, thus indicating less CEI protection in the former. A sophisticated extended X-ray absorption fine structure analysis quantitatively confirmed the effective suppression of rock-salt formation with the VC electrolyte during the charging process, consistent with the operando Raman results. The in situ XAS results thus provided additional support for the key findings of this study, establishing the crucial role of VC polymerization in enhancing CEI stability and mitigating surface reconstruction on NMC cathodes. This work clarifies the relationship between the enhanced CEI layer and NMC degradation and inspires rational electrolyte design for long-cycling NMC cathodes.

中文翻译:


通过增强的原位和操作表征方法探索电解质添加剂在超高电压下抑制富镍 NMC 阴极表面重构的作用



碳酸亚乙烯酯 (VC) 是锂离子电池中广泛使用的电解质添加剂,用于增强阳极侧固体电解质界面的形成。然而,与 VC 形成的阴极电解质中间相 (CEI) 却很少受到关注。本研究采用先进的基于原位/操作的拉曼和 X 射线吸收光谱 (XAS) 进行全面研究,探讨电解质成分对 CEI 形成和抑制 Li x Ni y Mn z Co 1–表面重构的影响yz O 2 (NMC) 阴极。根据实验结果,提出了一种通过 VC 聚合的新化学途径。原位拉曼光谱显示在 995 cm –1处有一个新峰,表明存在由 VC 自由基聚合产生的 C-O 半碳酸酯。 Operando 拉曼分析揭示了超高电压(高达 5.2 V)下基线系统中 490 cm –1处 NiO 的形成。然而,该峰在 VC 电解液中明显缺失,表明 VC 在抑制表面重构方面的有效性。利用原位 XAS 进行了进一步的研究,比较了不同工作电压下两种电解质中 3 次和 20 次循环的电池的 X 射线吸收近边缘结构光谱。在 Ni K 边缘观察到的变化证实了与 VC 电解质相比,基线电解质中 Ni 的减少量更大,因此表明前者的 CEI 保护较少。 复杂的扩展 X 射线吸收精细结构分析定量证实了 VC 电解质在充电过程中有效抑制岩盐形成,与操作拉曼结果一致。因此,原位 XAS 结果为本研究的主要发现提供了额外的支持,确定了 VC 聚合在增强 CEI 稳定性和减轻 NMC 阴极表面重建方面的关键作用。这项工作阐明了增强型 CEI 层与 NMC 降解之间的关系,并启发了长循环 NMC 正极的合理电解质设计。
更新日期:2024-02-09
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