<i></i>层状锂化Ni-Co-Mn氧化物中早期Ni介导的表面重构的<i>Operando</i>监测,The Journal of Physical Chemistry C

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层状锂化Ni-Co-Mn氧化物中早期Ni介导的表面重构的Operando监测
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-06-14 00:00:00 , DOI: 10.1021/acs.jpcc.7b02303
Daniel Streich ₁ , Christoph Erk ₂ , Aurelie Guéguen ₁ , Philipp Müller ₂ , Frederick-Francois Chesneau ₂ , Erik J. Berg ₁

Affiliation

富镍层状锂镍钴锰氧化物（NCM）正在成为下一代锂离子电池阴极的最有希望的候选者。但是，由于对导致性能受限的阻抗增长和降低的循环稳定性的过程的不完全了解，阻碍了进步。这些过程通常涉及在阴极表面进行表面重建和O ₂释放，这两者都很难在工作单元中进行监控。我们证明在线电化学质谱法可用于测量在实际相关电势下和在操作电化学条件下，不同Ni含量的NCM释放出的气体。我们发现对于高达4.3 V的阴极电势（vs Li ⁺/ Li）在Ni介导的比电荷增强和寄生表面反应之间几乎没有权衡。但是，在大于4.3 V的电势下，会发生表面重构过程，导致大量CO ₂和O ₂释放，这意味着在首次充电后可能已经形成了几纳米厚的表面重构层。发现镍含量和Ni / Co比值决定了这些表面重建过程的开始，速率和程度。这些结果为镍在控制锂离子层状氧化物的表面稳定性和性能中的作用提供了新颖的见解。

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Operando Monitoring of Early Ni-mediated Surface Reconstruction in Layered Lithiated Ni–Co–Mn Oxides

Nickel-rich layered lithiated Ni–Co–Mn oxides (NCMs) are emerging as the most promising candidates for next-generation Li-ion battery cathodes. Progress, however, is hindered by an incomplete understanding of processes that lead to performance-limiting impedance growth and reduced cycling stability. These processes typically involve surface reconstruction and O₂ release at the cathode surface, both of which are difficult to monitor in the working cell. We demonstrate that online electrochemical mass spectrometry can be used to measure the gas release from NCMs of varying Ni content at practically relevant potentials and under operando electrochemical conditions. We find that for cathode potentials up to 4.3 V (vs Li⁺/Li) there is virtually no trade-off between Ni-mediated specific-charge enhancement and parasitic surface reactions. However, at potentials greater than 4.3 V, surface-reconstruction processes giving rise to substantial CO₂ and O₂ release occur, implying that surface-reconstructed layers a few nanometers thick may form already after the first charge. Ni content and the Ni/Co ratio are found to govern the onset, rate, and extent of these surface-reconstruction processes. These results provide novel insights into the role of Ni in governing the surface stability and performance of Li-ion layered oxides.

更新日期：2017-06-28

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