Dataset Information

Understanding the Electrochemical Formation and Decomposition of Li₂O₂ and LiOH with Operando X-ray Diffraction.

ABSTRACT: 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 Li₂O₂ and LiOH discharge products, held at least partially responsible for the limited reversibility and poor rate performance, is hard to measure operando under realistic electrochemical conditions. This study uses Rietveld refinement of operando X-ray diffraction data during a complete discharge-charge cycle to reveal the detailed structural evolution of Li₂O₂ and LiOH crystallites in 1,2-dimethoxyethane (DME) and DME/LiI electrolytes, respectively. The anisotropic broadened reflections confirm and quantify the platelet crystallite shape of Li₂O₂ and LiOH and show how the average crystallite shape evolves during discharge and charge. Li₂O₂ is shown to form via a nucleation and growth mechanism, whereas the decomposition appears to start at the smallest Li₂O₂ crystallite 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. Operando X-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.

SUBMITTER: Li Z

PROVIDER: S-EPMC5354633 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Understanding the Electrochemical Formation and Decomposition of Li2O2 and LiOH with Operando X-ray Diffraction.

Li Zhaolong Z Ganapathy Swapna S Xu Yaolin Y Heringa Jouke R JR Zhu Quanyao Q Chen Wen W Wagemaker Marnix M

Chemistry of materials : a publication of the American Chemical Society 20170127 4

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 Li2O2 and LiOH discharge products, held at least partially responsible for the limited reversibility and poor ...[more]

PMID: 28316369

Similar Datasets

Project description:Here, we report that the trimetallic nanosized oxide NiFeMnO4 consists of a mixture of NiO and a strained cubic spinel phase, which is clearly demonstrated by analysis of the pair distribution function (PDF) and synchrotron X-ray data. Such a finding can easily be overlooked by using only inhouse X-ray powder diffraction, leading to inaccurate assumption of the stoichiometry and oxidation states. Such advanced characterization is essential because a homogeneous distribution of the elements is observed in energy-dispersive X-ray spectroscopy maps, giving no hints for a phase separation. Cycling of the sample against Li delivers a high reversible capacity of ≈840 mAh/g in the 50th cycle. Operando X-ray absorption spectroscopy (XAS) experiments indicate that ≈0.8 Li/fu is consumed without detectable changes of the electronic structure. Increasing amounts of Li, Mn3+, and Fe3+ are simultaneously reduced. The disappearance of the pre-edge features in X-ray absorption near-edge spectroscopy indicates movement of these cations from tetrahedral sites to octahedral sites. PDF analysis of the pattern after an uptake of 2 Li/fu evidences that the principal structure can be sufficiently well modeled assuming coexisting NiO, a mixed monoxide, and a small amount of residual spinel phase. Thus, the majority of cations is located on octahedral sites. Furthermore, an improvement of the PDF model is achieved taking into account small amounts of LiOH. The 7Li MAS NMR spectrum of this sample clearly shows the signal of Li in a diamagnetic environment, excluding Li-O-TM bonds. A further increase of the Li content leads to a successive conversion of the cations to nanosized metal particles embedded in a LiOH/Li2O matrix. Ex situ XAS results indicate that Fe can be reversibly reoxidized to Fe3+ during charge whereas Mn does not reach the oxidation state observed in the pristine material. After excessive cycling, reoxidation of metallic Ni is suppressed and contributes to a capacity loss compared with the early discharge/charge cycles.

Dataset Information

Understanding the Electrochemical Formation and Decomposition of Li₂O₂ and LiOH with Operando X-ray Diffraction.

Publications

Understanding the Electrochemical Formation and Decomposition of Li<sub>2</sub>O<sub>2</sub> and LiOH with <i>Operando</i> X-ray Diffraction.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets