通过XPS了解富锂镍钴钴层氧化物阴极上的电极/电解质界面层,ACS Applied Materials & Interfaces

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通过XPS了解富锂镍钴钴层氧化物阴极上的电极/电解质界面层
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2019-11-08 , DOI: 10.1021/acsami.9b14389
Maral Hekmatfar _{1,

2} , Arefeh Kazzazi _{1,

2} , Gebrekidan Gebresilassie Eshetu _{1,

2} , Ivana Hasa _{1,

2} , Stefano Passerini _{1,

2}

Affiliation

层状富含锂的锰酸钴钴镍合金（LR-NMC）代表了用于高能量密度锂离子电池的最有希望的阴极材料之一。交付的非凡能力源于阳离子和阴离子氧化还原工艺的结合。但是，后者会导致氧气释放，从而触发结构退化和电极/电解质界面（EEI）不稳定性，从而阻碍了LR-NMC在实际应用中的使用。在这项工作中，我们研究了LR-NMC的表面化学及其在不同条件下的演变，以进一步了解EEI发生的过程。X射线光电子能谱研究表明，一旦形成了该层的有机成分，它便会独立于所施加的更高的截止电压而保持稳定，同时发生无机物的连续生长以及氧气的释放。在锂化和去锂化的LR-NMC表面上执行的结果表明，在高电压下形成的EEI层不稳定，并经历了部分分解。此外，三（五氟苯基）硼烷电解质添加剂同时防止过量的LiF形成并改变EEI层的化学组成。后者的特点是聚（环氧乙烷）低聚物种类和锂含量较高。三（五氟苯基）硼烷电解质添加剂可同时防止形成过量的LiF，并改变EEI层的化学成分。后者的特点是聚环氧乙烷低聚物种类和锂含量较高。三（五氟苯基）硼烷电解质添加剂可同时防止形成过量的LiF，并改变EEI层的化学成分。后者的特点是聚（环氧乙烷）低聚物种类和锂含量较高。_x PO_y F_z的形成。此外，不能排除EEI层中含硼化合物的存在，这也可能是EEI层厚度增加的原因。最后，在升高的温度下快速的动力学加剧了盐的分解，这导致形成了EEI，该EEI的LiF越来越浓。

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Understanding the Electrode/Electrolyte Interface Layer on the Li-Rich Nickel Manganese Cobalt Layered Oxide Cathode by XPS

Layered lithium-rich nickel manganese cobalt oxide (LR-NMC) represents one of the most promising cathode materials for application in high energy density lithium-ion batteries. The extraordinary capacity delivered derives from a combination of both cationic and anionic redox processes. However, the latter ones lead to oxygen evolution which triggers structural degradation and electrode/electrolyte interface (EEI) instability that hinders the use of LR-NMC in practical application. In this work, we investigate the surface chemistry of LR-NMC and its evolution upon different conditions to give further insights into the processes occurring at the EEI. X-ray photoelectron spectroscopy studies reveal that once the organic component of the layer is formed, it remains stable independently on the higher cutoff voltage applied, while continuous growth of inorganics along with oxygen evolution occurs. The results performed on lithiated and delithiated LR-NMC surfaces indicate an instability of the EEI layer formed at high voltages, which undergoes a partial decomposition. Furthermore, the tris(pentafluorophenyl)borane electrolyte additive simultaneously prevents excess LiF formation and changes the chemical composition of the EEI layer. The latter is characterized by a higher amount of poly(ethylene oxide) oligomer species and Li_xPO_yF_z formation. In addition, the presence of boron-containing compounds in the EEI layer cannot be excluded, which may be also responsible of the increased thickness of the EEI layer. Finally, fast kinetics at elevated temperatures exacerbate the salt decomposition which results in the formation of an EEI which is thicker and richer in LiF.

更新日期：2019-11-11

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