Understanding the Electrochemical Formation and Decomposition of Li2O2and LiOH withOperandoX-ray Diffraction.
The lithium air, or Li-O2, battery system is a promising electrochemical energy storage system because of its very high theoretical specific energy, as required by automotive applications. Fundamental research has resulted in much progress in mitigating detrimental (electro)chemical processes; however, the detailed structural evolution of the crystalline Li2O2and LiOH discharge products, held at least partially responsible for the limited reversibility and poor rate performance, is hard to measureoperandounder realistic electrochemical conditions. This study uses Rietveld refinement ofoperandoX-ray diffraction data during a complete discharge-charge cycle to reveal the detailed structural evolution of Li2O2and LiOH crystallites in 1,2-dimethoxyethane (DME) and DME/LiI electrolytes, respectively. The anisotropic broadened reflections confirm and quantify the platelet crystallite shape of Li2O2and LiOH and show how the average crystallite shape evolves during discharge and charge. Li2O2is shown to form via a nucleation and growth mechanism, whereas the decomposition appears to start at the smallest Li2O2crystallite sizes because of their larger exposed surface. In the presence of LiI, platelet LiOH crystallites are formed by a particle-by-particle nucleation and growth process, and at the end of discharge, H2O depletion is suggested to result in substoichiometric Li(OH)1-x, which appears to be preferentially decomposed during charging.OperandoX-ray diffraction proves the cyclic formation and decomposition of the LiOH crystallites in the presence of LiI over multiple cycles, and the structural evolution provides key information for understanding and improving these highly relevant electrochemical systems.
Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands; State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, P. R. China.
Zhaolong
Z
Li
Department of Radiation Science and Technology, Delft University of Technology , Mekelweg 15, 2629JB Delft, The Netherlands.
Swapna
S
Ganapathy
Department of Radiation Science and Technology, Delft University of Technology , Mekelweg 15, 2629JB Delft, The Netherlands.
Yaolin
Y
Xu
Department of Radiation Science and Technology, Delft University of Technology , Mekelweg 15, 2629JB Delft, The Netherlands.
Jouke R
JR
Heringa
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology , Wuhan 430070, P. R. China.
Quanyao
Q
Zhu
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology , Wuhan 430070, P. R. China.
Wen
W
Chen
Department of Radiation Science and Technology, Delft University of Technology , Mekelweg 15, 2629JB Delft, The Netherlands.
Marnix
M
Wagemaker