One of the more promising cathode materials for high-energy high-voltage lithium ion batteries (LIBs) are Ni-rich layered cathode materials such as LiNi_xMn_yCo_zO₂ (where _x + _y + _z = 1). Although these cathode materials are attractive from a high capacity standpoint, they commonly suffer from poor structural stability at highly delithiated (charged) states leading to poor electrochemical performance.^1-3 While incorporation of additives into the electrolyte provides one way to improve cycling performance in LIBs, surface coatings are becoming a widely adopted method to improve the cycling performance of high-voltage cathode materials. More widely investigated coating materials include oxide coatings (Al₂O₃, TiO₂, etc.)⁴ while comparatively fewer studies have investigated organic monomer or polymer coatings (PEDOT, polyimide, etc.).⁵ Additionally, the mechanism of the coating interaction with the material is intriguing due to its importance in creating a performance-enhancing coating.

In this work, the surface of LiNi_0.5Mn_0.3Co_0.2O₂ cathode materials were coated with organosilane reagents to investigate their effect on cell electrochemical performance. The impact of the cathode pretreatment, the weight percentage of organosilane used and the functionality of the organosilane used will be presented. Characterization of the organosilane coating using SEM shows a slight morphological change in the cathode surface while EDX and FTIR confirm the presence of a Si-containing coating. Half cells (Li/ LiNi_0.5Mn_0.3Co_0.2O₂) using the organosilane coated cathodes operating in the voltage window of 3.0 - 4.4 V showed similar cycling behavior to that of non-coated material. In conclusion, a new type of organic coating was utilized on Ni-rich cathode materials and this research explores a new type of coating for high voltage cathodes.

References

1)      Son, I. H.; Park, J. H.; Kwon, S.; Mun, J. and Choi, J. W. Chem. Mat. 2015, 27, 7370-7379.

2)      Bak, S.-M.; Hu, E.; Zhou, Y.; Yu, X.; Senanayake, S. D.; Cho, S.-J.; Kim, K.-B.; Chung, K. Y.; Yang, X.-Q. and Nam, K.-W. ACS Appl. Mater. Interfaces 2014, 6, 22594-22601.

3)      Lin, F.; Markus, I. M.; Doeff, M. M.; Xin, H. L. Sci. Rep., 2014, 4, 5694.

4)      Xu, S.; Jacobs, R. M.; Nguyen, H. M.; Hao, S.; Mahanthappa, M.; Wolverton, C.; Morgan, D. J. Mater. Chem. A, 2015, 3, 17248.

5)      Zhang, J.; Lu, Q.; Fang, J.; Wang, J.; Yang, J. and NuLi, Y. ACS Appl. Mater. Interfaces 2014, 6, 17965-17973.