Electron microscopy investigations of changes in morphology and conductivity of LiFePO4/C electrodes

Roberto Scipioni; Peter S. Jørgensen; Duc The Ngo; Søren B. Simonsen; Zhao Liu; Kyle J. Yakal-Kremski; Hongqian Wang; Johan Hjelm; Poul Norby; Scott A. Barnett; Søren H. Jensen

doi:10.1016/j.jpowsour.2015.12.119

Electron microscopy investigations of changes in morphology and conductivity of LiFePO₄/C electrodes

Roberto Scipioni^*, Peter S. Jørgensen, Duc The Ngo, Søren B. Simonsen, Zhao Liu, Kyle J. Yakal-Kremski, Hongqian Wang, Johan Hjelm, Poul Norby, Scott A. Barnett, Søren H. Jensen

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

53 Scopus citations

Abstract

In this work we study the structural degradation of a laboratory Li-ion battery LiFePO₄/Carbon Black (LFP/CB) cathode by various electron microscopy techniques including low kV Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) 3D tomography. Several changes are observed in FIB/SEM images of fresh and degraded cathodes, including cracks in the LFP particles, secondary disconnected particles, and agglomeration of CB. Low voltage (1 kV) SEM images show that the CB agglomerates have a different brightness than the fresh CB, due to charging effects. This suggests that the electronic conductivity of the CB agglomerates is low compared to that of the fresh CB particles. HRTEM analysis shows that fresh CB particles are quasi crystalline, whereas the LFP/CB interface in the degraded electrode shows amorphous carbon surrounding the LFP particles. The presence of the amorphous carbon is known to impede the electronic conductivity and thereby decreasing percolation in the cathode and reducing the electrode capacity.

Original language	English (US)
Pages (from-to)	259-269
Number of pages	11
Journal	Journal of Power Sources
Volume	307
DOIs	https://doi.org/10.1016/j.jpowsour.2015.12.119
State	Published - Mar 1 2016

Funding

The authors gratefully acknowledge financial support from the Danish strategic research council through the project “Advanced Lifetime Prediction of Battery Energy Storage” (contract no. 0603-00589B ). The authors wish to thank Ebtisam Abdellahi for laboratory assistance and sample preparation. The authors at Northwestern gratefully acknowledge the financial support from the Office of Naval Research Grant # N00014-12-1-0713 .

Keywords

Degradation mechanism
Focused ion beam scanning electron microscopy
Loss in electron percolation
Low accelerating voltage
Three-dimensional analysis of LiFePO/Carbon electrode

ASJC Scopus subject areas

Renewable Energy, Sustainability and the Environment
Energy Engineering and Power Technology
Physical and Theoretical Chemistry
Electrical and Electronic Engineering

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.jpowsour.2015.12.119

Cite this

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title = "Electron microscopy investigations of changes in morphology and conductivity of LiFePO4/C electrodes",

abstract = "In this work we study the structural degradation of a laboratory Li-ion battery LiFePO4/Carbon Black (LFP/CB) cathode by various electron microscopy techniques including low kV Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) 3D tomography. Several changes are observed in FIB/SEM images of fresh and degraded cathodes, including cracks in the LFP particles, secondary disconnected particles, and agglomeration of CB. Low voltage (1 kV) SEM images show that the CB agglomerates have a different brightness than the fresh CB, due to charging effects. This suggests that the electronic conductivity of the CB agglomerates is low compared to that of the fresh CB particles. HRTEM analysis shows that fresh CB particles are quasi crystalline, whereas the LFP/CB interface in the degraded electrode shows amorphous carbon surrounding the LFP particles. The presence of the amorphous carbon is known to impede the electronic conductivity and thereby decreasing percolation in the cathode and reducing the electrode capacity.",

keywords = "Degradation mechanism, Focused ion beam scanning electron microscopy, Loss in electron percolation, Low accelerating voltage, Three-dimensional analysis of LiFePO/Carbon electrode",

author = "Roberto Scipioni and J{\o}rgensen, {Peter S.} and Ngo, {Duc The} and Simonsen, {S{\o}ren B.} and Zhao Liu and Yakal-Kremski, {Kyle J.} and Hongqian Wang and Johan Hjelm and Poul Norby and Barnett, {Scott A.} and Jensen, {S{\o}ren H.}",

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doi = "10.1016/j.jpowsour.2015.12.119",

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AU - Scipioni, Roberto

AU - Jørgensen, Peter S.

AU - Ngo, Duc The

AU - Simonsen, Søren B.

AU - Liu, Zhao

AU - Yakal-Kremski, Kyle J.

AU - Wang, Hongqian

AU - Hjelm, Johan

AU - Norby, Poul

AU - Barnett, Scott A.

AU - Jensen, Søren H.

PY - 2016/3/1

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N2 - In this work we study the structural degradation of a laboratory Li-ion battery LiFePO4/Carbon Black (LFP/CB) cathode by various electron microscopy techniques including low kV Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) 3D tomography. Several changes are observed in FIB/SEM images of fresh and degraded cathodes, including cracks in the LFP particles, secondary disconnected particles, and agglomeration of CB. Low voltage (1 kV) SEM images show that the CB agglomerates have a different brightness than the fresh CB, due to charging effects. This suggests that the electronic conductivity of the CB agglomerates is low compared to that of the fresh CB particles. HRTEM analysis shows that fresh CB particles are quasi crystalline, whereas the LFP/CB interface in the degraded electrode shows amorphous carbon surrounding the LFP particles. The presence of the amorphous carbon is known to impede the electronic conductivity and thereby decreasing percolation in the cathode and reducing the electrode capacity.

AB - In this work we study the structural degradation of a laboratory Li-ion battery LiFePO4/Carbon Black (LFP/CB) cathode by various electron microscopy techniques including low kV Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) 3D tomography. Several changes are observed in FIB/SEM images of fresh and degraded cathodes, including cracks in the LFP particles, secondary disconnected particles, and agglomeration of CB. Low voltage (1 kV) SEM images show that the CB agglomerates have a different brightness than the fresh CB, due to charging effects. This suggests that the electronic conductivity of the CB agglomerates is low compared to that of the fresh CB particles. HRTEM analysis shows that fresh CB particles are quasi crystalline, whereas the LFP/CB interface in the degraded electrode shows amorphous carbon surrounding the LFP particles. The presence of the amorphous carbon is known to impede the electronic conductivity and thereby decreasing percolation in the cathode and reducing the electrode capacity.

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KW - Loss in electron percolation

KW - Low accelerating voltage

KW - Three-dimensional analysis of LiFePO/Carbon electrode

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