Sodiation Kinetics of Metal Oxide Conversion Electrodes: A Comparative Study with Lithiation.
The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including electrochemical and synchrotron studies, real-time electron microscopy observation, and ab initio molecular dynamics (MD) simulations. We found that a crystalline Na2O reaction layer that was formed at the beginning of sodiation plays an important role in blocking the further transport of sodium ions. In addition, sodiation in NiO exhibits a "shrinking-core" mode that results from a layer-by-layer reaction, as identified by ab initio MD simulations. For lithiation, however, the formation of Li antisite defects significantly distorts the local NiO lattice that facilitates Li insertion, thus enhancing the overall reaction rate. These observations delineate the mechanistic difference between sodiation and lithiation in metal-oxide conversion materials. More importantly, our findings identify the importance of understanding the role of reaction layers on the functioning of electrodes and thus provide critical insights into further optimizing NIB materials through surface engineering.
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Kai
K
He
Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Feng
F
Lin
Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
Yizhou
Y
Zhu
Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States.
Xiqian
X
Yu
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Jing
J
Li
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Ruoqian
R
Lin
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
Dennis
D
Nordlund
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
Tsu-Chien
TC
Weng
Department of Chemistry and Geochemistry, Materials Science Program, Colorado School of Mines , Golden, Colorado 80401, United States.
Ryan M
RM
Richards
Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States.
Xiao-Qing
XQ
Yang
Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Marca M
MM
Doeff
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Eric A
EA
Stach
Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
Yifei
Y
Mo
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Huolin L
HL
Xin
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Dong
D
Su
Sodiation; conversion electrodes; in situ TEM; kinetics; nickel oxides; reaction pathways