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ACS Appl Mater Interfaces. 2018 Jul 18;10(28):23842-23850. doi: 10.1021/acsami.8b06399. Epub 2018 Jul 9.

Accelerated Evolution of Surface Chemistry Determined by Temperature and Cycling History in Nickel-Rich Layered Cathode Materials.

Author information

1
Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , United States.
2
Department of Geosciences , Virginia Tech , Blacksburg , Virginia 24061 , United States.
3
Center for Functional Nanomaterials , Brookhaven National Laboratory , Upton , New York 11973 , United States.
4
Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Menlo Park , California 94035 , United States.

Abstract

Nickel-rich layered cathode materials have the potential to enable cheaper and higher energy lithium ion batteries. However, these materials face major challenges (e.g., surface reconstruction, microcracking, potential oxygen evolution) that can hinder the safety and cycle life of lithium ion batteries. Many studies of nickel-rich materials have focused on ways to improve performance. Understanding the effects of temperature and cycling on the chemical and structural transformations is essential to assess the performance and suitability of these materials for practical battery applications. The present study is focused on the spectroscopic analysis of surface changes within a strong performing LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material. We found that surface chemical and structural transformations (e.g., gradient metal reduction, oxygen loss, reconstruction, dissolution) occurred quicker and deeper than expected at higher temperatures. Even at lower temperatures, the degradation occurred rapidly and eventually matched the degradation at high temperatures. Despite these transformations, our performance results showed that a better performing nickel-rich NMC is possible. Establishing relationships between the atomic, structural, chemical, and physical properties of cathode materials and their behavior during cycling, as we have done here for NMC811, opens the possibility of developing lithium ion batteries with higher performance and longer life. Finally, our study also suggests that a separate, systematic, and elaborate study of surface chemistry is necessary for each NMC composition and electrolyte environment.

KEYWORDS:

layered oxide cathode; nickel rich; phase transformation; surface chemistry; temperature

PMID:
29920072
DOI:
10.1021/acsami.8b06399

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