title: Kinetic Phase Evolution of Spinel Cobalt Oxide during Lithiation.
abstract: Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalation reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. This work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.|Department of Materials Science and Engineering, Stony Brook University , Stony Brook, New York 11720, United States.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: He
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Qingping
authors.initials: Q
authors.lastname: Meng
authors.affiliation: John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Sooyeon
authors.initials: S
authors.lastname: Hwang
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Ke
authors.initials: K
authors.lastname: Sun
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Hong
authors.initials: H
authors.lastname: Gan
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Yimei
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Mo
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Stach
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Dong
authors.initials: D
authors.lastname: Su
keywords: Co3O4 nanoparticles; in situ TEM; lithium-ion battery