Morphological and Surface Structural Changes during Electrochemical Cycling in Li-rich Layered Oxides for Next Generation Li-ion Batteries

Conference · Wed Apr 12 00:00:00 EDT 2017

DOI:https://doi.org/10.2172/1770696· OSTI ID:1770696

Zhang, Minghao ^[1]; Liu, Haodong ^[1]; Fang, Chengcheng ^[1]; Meng, Ying Shirley ^[1]

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1. Univ. of California, San Diego, CA

Li-rich layered oxides, either as a solid solution or as a nano-composite of layered Li₂MnO₃ and Li(TM)O₂ (TM=Ni, Co, Mn), draw significant attention as the next-generation cathode materials for high-energy-density Li-ion batteries in electric vehicles. However, there are many issues still unclear, and numerous scientific challenges of these materials that must be overcome to realize their utilization in commercial Li-ion batteries. The first drawback is the irreversible voltage degradation process that limits cycle life. Modified co-precipitation synthesis is introduced to obtain morphology controlled Li-rich material without ammonia addition. This unique design increases meso-structure morphological stability compared with the sample with large secondary particles as proved by Transmission X-ray Microscope. As a result, the voltage decay and capacity loss during long term cycling have been minimized to a large extent. On the other hand, lattice oxygen plays an intriguing role in the electrochemical process of Li-rich material through a reversible redox process as well as an irreversible oxidation with O₂ gas release. To prevent oxygen gas generation, oxygen vacancies have been proposed to form on the surface of the morphology controlled Li-rich layered oxides through the design of a gas-solid interface reaction (GSIR). Dynamic structural changes during the initial two electrochemical cycles of GSIR Li-rich layered oxides are investigated with In operando synchrotron X-ray diffraction (SXRD). Different electrochemical reaction regions dominated by either cations or anions redox are identified in the shifts of the lattice parameters during the first cycle. Changes in lattice parameters, oxygen positions, and microstrain help to explain the lithium de-intercalation mechanism in this class of materials.

• Research Organization: Univ. of California, San Diego, CA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: EE0007744
• OSTI ID: 1770696
• Resource Relation: Conference: Materials Research Society Spring Meeting and Exhibit, Phoenix, AZ (USA), April 20, 2017
• Country of Publication: United States
• Language: English