02-acs-excluded-blocks

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Abstract chars: 908

Pristine Li-rich layered cathodes, such as Li 1.2 Ni 0.2 Mn0.6 O2 and Li 1.2 Ni 0.1 Mn0.525 -Co0.175 O2 , were identi fi ed to exist in two di ff erent structures: LiMO 2 R 3 m and Li2MO3 C 2/ m phases. Upon 300 cycles of charge/discharge, both phases gradually transform to the spinel structure. The transition from LiMO 2 R 3 m to spinel is accomplished through the migration of transition metal ions to the Li site without breaking down the lattice, leading to the formation of mosaic structured spinel grains within the parent particle. In contrast, transition from Li2MO3 C 2/ m to spinel involves removal of Li þ and O 2 -, which produces large lattice strain and leads to the breakdown of the parent lattice. The newly formed spinel grains show random orientation within the same particle. Cracks and pores were also noticed within some layered nanoparticles after cycling, which is believed to be the

Sections

• Body (475 chars)
• RESULTS AND DISCUSSIONS (15506 chars)
• METHODS (1603 chars)
• CONCLUSIONS (2661 chars)

Low Coverage Blocks

• p1 front_summary coverage=0.034: of cations, and phase stability upon lithium extraction and insertion. Structurally, these layered structures are often composed of the intergrowth of LiMO2 R3m and Li2MO3 C2/m phases.7,13 Nevertheless, it is not clear how each individual phase affects the per-
• p1 front_summary coverage=0.0: reported a nanoscale phase separation caused by the preferential segregation of Ni atoms on the particle surface and bound- aries in the layered lithium nickel manga- nese oxide cathode materials. They further predicted that the formation of the Ni-rich surfac
• p1 front_summary coverage=0.0: i-ion batteries have been widely used as an energy storage device for mod- ern electric devices, grid application, and renewable energy.1
  7 Cathodes with a layered structure such as Li1.2Ni0.2Mn0.6O2 (LNMO) andLi1.2Ni0.1Mn0.525Co0.175O2(LNMCO) can provide much
• p2 scientific_body coverage=0.04: the release of oxygen and Liþ(removal of the Li2O part).2 However, the effect of the removal of the Li2O part on the lattice stability has not been established. The layered-to-spinel transformation has long been postulated as an important factor to account for
• p2 scientific_body coverage=0.01: to Z1.8),18 which is therefore termed as Z-contrast imaging and is chemical sensitive, allowing us to intuitively interpret the atomic structure changes di- rectly. We found that both LNMO and LNMCO layer structured cathodes are a random mixing of LiMO2 R3m an
• p8 back_matter coverage=0.0: Acknowledgment. The research described in this paper is part of the Chemical Imaging Initiative at Pacific North- west National Laboratory (PNNL). It was conducted under the Laboratory Directed Research and Development Program at PNNL, a multiprogram national l
• p8 back_matter coverage=0.0: Supporting Information Available: The Supporting Informa- tion includes STEM image of the prestine LNMCO cathode nano- particles. No cracks are visible in the pristine particles. This material is available free of charge via the Internet at http://pubs.acs.org