Revealing Anisotropic Spinel Formation on Pristine Li- and Mn-Rich Layered Oxide Surface and Its Impact on Cathode Performance

Revealing Anisotropic Spinel Formation on Pristine Li- and Mn-Rich Layered Oxide Surface and Its Impact on Cathode Performance

TitleRevealing Anisotropic Spinel Formation on Pristine Li- and Mn-Rich Layered Oxide Surface and Its Impact on Cathode Performance
Publication TypeJournal Article
Year of Publication2017
AuthorsSaravanan Kuppan, Alpesh Khushalcha Shukla, Daniel Membreno, Dennis Nordlund, Guoying Chen
JournalAdvanced Energy Materials
Volume7
Issue11
Pagination1602010
Date Published06/2017
Abstract

Surface properties of cathode particles play important roles in the transport of ions and electrons and they may ultimately dominate cathode's performance and stability in lithium‐ion batteries. Through the use of carefully prepared Li1.2Ni0.13Mn0.54Co0.13O2 crystal samples with six distinct morphologies, surface transition‐metal redox activities and crystal structural transformation are investigated as a function of surface area and surface crystalline orientation. Complementary depth‐profiled core‐level spectroscopy, namely, X‐ray absorption spectroscopy, electron energy loss spectroscopy, and atomic‐resolution scanning transmission electron microscopy, are applied in the study, presenting a fine example of combining advanced diagnostic techniques with a well‐defined model system of battery materials. The present study reports the following findings: (1) a thin layer of defective spinel with reduced transition metals, similar to what is reported on cycled conventional secondary particles in the literature, is found on pristine oxide surface even before cycling, and (2) surface crystal structure and chemical composition of both pristine and cycled particles are facet dependent. Oxide structural and cycling stabilities improve with maximum expression of surface facets stable against transition‐metal reduction. The intricate relationships among morphology, surface reactivity and structural transformation, electrochemical performance, and stability of the cathode materials are revealed.

DOI10.1002/aenm.201602010
Short TitleAdv. Energy Mater.
Refereed DesignationRefereed