High-Energy Density LiNiO2 Core- Li[Ni0.87Co0.065Mn0.065]O2 shell Structured Li[Ni0. 95Co0. 025Mn0. 025]O2 Cathode for Lithium-Ion Batteries

Abstract

A core-shell (CS) structured cathode with a LiNiO2 core and Li[Ni0.87Co0.065Mn0.065]O2 shell, resulting in an average composition of Li[Ni0.95Co0.025Mn0.025]O2, was synthesized via the co-precipitation method. The core material, LiNiO2, designed to maximize the discharge capacity, was protected by a 500-nm-thick encapsulating Li[Ni0.87Co0.065Mn0.065]O2 shell layer to improve the structural stability. The CS cathode delivered an initial discharge capacity of 235.7 mAh g-1 at 0.1 C (18 mA g-1) and 90% of its initial capacity was maintained after 100 cycles at 0.5 C (90 mA g-1), whereas the capacity retention of the LiNiO2 cathode without the protective shell was limited to 74.2% after 100 cycles. The improved cycling stability of the CS cathode was also verified in a full cell test (against graphite anode) in which the cathode also clearly outperformed the LiNiO2 cathode. The improved cycling performance is mainly attributed to stabilization of the inherently reactive LiNiO2 surface by the Ni-depleted protective shell layer. The proposed CS approach allows harnessing of the high capacity of LiNiO2 and other extremely Ni-rich compositions with dramatically improved capacity retention, thus moving closer to satisfying the high energy density and long lifetime requirements for lithium-ion batteries for electric vehicles. References S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett. 2017, 2, 196. H. J. Noh, S. Youn, C. S. Yoon and Y.-K. Sun, J. Power Sources 2013, 233, 121. C. S. Yoon, M. H. Choi, B.-B. Lim, E.-J. Lee, and Y.-K. Sun, J. Electrochem. Soc. 2015, 162, A2483. Y.-K. Sun, S.-T. Myung, M.-H. Kim, J. Parakash, and K. Amine, J. Am. Chem. Soc. 2005, 127, 13411