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Title: Revealing the reaction mechanisms of Li–O2 batteries using environmental transmission electron microscopy

Abstract

The capacity, Coulombic efficiency, rate, and cyclability of a Li-O2 battery critically depend on the electrode reaction mechanism and the structure/morphology of the reaction product as well as their spatial and temporal evolution1-8, which are all further complicated by the choice of different electrolyte. For the case of aprotic cell, the discharge product, Li2O2, is formed through solution and surface mechanisms9,10, but little is known on the formation mechanism of the perplexing morphology of the reaction product11-15. For the case of Li-O2 battery using solid electrolyte, neither electrode reaction mechanism nor the nature of the reaction production is known. Herein, we reveal the full cycle reaction pathway for Li-O2 batteries and its correlation with the nature of the reaction product. Using an aberration-corrected environmental TEM under oxygen environment, we captured, for the first time, the morphology and phase evolution on the carbon nanotube (CNT) cathode of a working solid-state Li-O2 nano-battery16 and directly correlated these features with electrochemical reaction. We found that the oxygen reduction reaction on CNTs initially produces LiO2, which subsequently evolves to Li2O2 and O2 through disproportionation reaction. Surprisingly it is just the releasing of O2 that inflates the particles to a hollow structure with a Li2Omore » outer surface layer and Li2O2 inner-shell, demonstrating that, in general, accommodation of the released O2 coupled with the Li+ ion diffusion and electron transport paths across both spatial and temporal scales critically governs the morphology of the discharging/charging product in Li-O2 system. We anticipate that the direct observation of Li-O2 reaction mechanisms and their correlation with the morphology of the reaction product set foundation for quantitative understanding/modeling of the electrochemical processes in the Li-O2 system, enabling rational design of both solid-state and aprotic Li-O2 batteries.« less

Authors:
; ORCiD logo; ; ; ORCiD logo;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1371985
Report Number(s):
PNNL-SA-123331
Journal ID: ISSN 1748-3387; 49321; KP1704020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature Nanotechnology; Journal Volume: 12; Journal Issue: 6
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; 36 MATERIALS SCIENCE; 25 ENERGY STORAGE; Environmental Molecular Sciences Laboratory

Citation Formats

Luo, Langli, Liu, Bin, Song, Shidong, Xu, Wu, Zhang, Ji-Guang, and Wang, Chongmin. Revealing the reaction mechanisms of Li–O2 batteries using environmental transmission electron microscopy. United States: N. p., 2017. Web. doi:10.1038/nnano.2017.27.
Luo, Langli, Liu, Bin, Song, Shidong, Xu, Wu, Zhang, Ji-Guang, & Wang, Chongmin. Revealing the reaction mechanisms of Li–O2 batteries using environmental transmission electron microscopy. United States. doi:10.1038/nnano.2017.27.
Luo, Langli, Liu, Bin, Song, Shidong, Xu, Wu, Zhang, Ji-Guang, and Wang, Chongmin. Mon . "Revealing the reaction mechanisms of Li–O2 batteries using environmental transmission electron microscopy". United States. doi:10.1038/nnano.2017.27.
@article{osti_1371985,
title = {Revealing the reaction mechanisms of Li–O2 batteries using environmental transmission electron microscopy},
author = {Luo, Langli and Liu, Bin and Song, Shidong and Xu, Wu and Zhang, Ji-Guang and Wang, Chongmin},
abstractNote = {The capacity, Coulombic efficiency, rate, and cyclability of a Li-O2 battery critically depend on the electrode reaction mechanism and the structure/morphology of the reaction product as well as their spatial and temporal evolution1-8, which are all further complicated by the choice of different electrolyte. For the case of aprotic cell, the discharge product, Li2O2, is formed through solution and surface mechanisms9,10, but little is known on the formation mechanism of the perplexing morphology of the reaction product11-15. For the case of Li-O2 battery using solid electrolyte, neither electrode reaction mechanism nor the nature of the reaction production is known. Herein, we reveal the full cycle reaction pathway for Li-O2 batteries and its correlation with the nature of the reaction product. Using an aberration-corrected environmental TEM under oxygen environment, we captured, for the first time, the morphology and phase evolution on the carbon nanotube (CNT) cathode of a working solid-state Li-O2 nano-battery16 and directly correlated these features with electrochemical reaction. We found that the oxygen reduction reaction on CNTs initially produces LiO2, which subsequently evolves to Li2O2 and O2 through disproportionation reaction. Surprisingly it is just the releasing of O2 that inflates the particles to a hollow structure with a Li2O outer surface layer and Li2O2 inner-shell, demonstrating that, in general, accommodation of the released O2 coupled with the Li+ ion diffusion and electron transport paths across both spatial and temporal scales critically governs the morphology of the discharging/charging product in Li-O2 system. We anticipate that the direct observation of Li-O2 reaction mechanisms and their correlation with the morphology of the reaction product set foundation for quantitative understanding/modeling of the electrochemical processes in the Li-O2 system, enabling rational design of both solid-state and aprotic Li-O2 batteries.},
doi = {10.1038/nnano.2017.27},
journal = {Nature Nanotechnology},
number = 6,
volume = 12,
place = {United States},
year = {Mon Mar 27 00:00:00 EDT 2017},
month = {Mon Mar 27 00:00:00 EDT 2017}
}