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Ageing Investigation of Lithium Ion LiFePO4 Batteries with a Combination of EIS and Structural Analysis

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Delf Kober, Oliver Görke and Julia KowalAgeing Investigation of Lithium Ion LiFePO4Batteries with a Combination of EIS andStructural AnalysisAbstract:Electrochemical impedance spectroscopy (EIS) measurements and post-mortem analyses are used on commercial LiFePO4cells to identify the ageing mecha-nisms and their representation in the impedance spectrum. The cells were cycled upto 1,667 cycles and measured with EIS. At different ageing states two cells were openedand analyzed with X-ray diffraction (XRD) and scanning electron microscope (SEM),one at 0% state of charge (SoC) and one at 100% SoC. First results show slight changesboth in the EIS spectra and in the micro-structure with cycling.Keywords:LiFePO4, ageing, impedance spectroscopy, post-mortem analysis1 IntroductionWithinthescopeofenergysupply,energystorageapplicationsbecomemoreandmoreimportant. Since 25 years rechargeable Li ion batteries have been applied successfullyin portable electric devices. The understanding of the degradation behaviour of singlecomponents and the entire cell is crucial for high-power applications – be mobile ornon-mobile – in terms of economic and safety aspects. Despite of the growing interestand the continuous increasing of publications in this field of research, there remainunanswered questions.One important attribute of a battery is its ageing, which is highly governed bydegradation processes. Ageing determines the lifetime of the battery and is causedby both cycling and storage. Among other influences, ambient temperature (as wellas electrode potential, depth of discharge (DOD) and cycling rate [1]) affects ageing.The structural changes in the active material (oxidation, corrosion, disordering,micro-cracking), SEI formation, chemical decomposition or dissolution and loss ofcontact are some of the main reasons for ageing [2, 3]. They lead to loss of accessiblecapacity and increasing cell impedance. It was found that ageing is more related tothe cathode than to the anode. So the cathode is to a high degree responsible forcapacity fade [4, 5] and to a certain degree also for an increase of impedance, causedbyparticlesizereduction[5].Thedifferentapproachesinliteraturetomodelageingaredealing with the influence of temperature, state of charge (SoC),DOD, U or I(t) andDelf Kober and Oliver Görke,Department of Material Science, Technical University of Berlin, Berlin,GermanyDelf Kober and Julia Kowal,Department of Energy and Automation Technology, Technical Universityof Berlin, Berlin, GermanyDOI 10.1515/9783110449822-002
© 2016 Walter de Gruyter GmbH, Berlin/Munich/Boston

Delf Kober, Oliver Görke and Julia KowalAgeing Investigation of Lithium Ion LiFePO4Batteries with a Combination of EIS andStructural AnalysisAbstract:Electrochemical impedance spectroscopy (EIS) measurements and post-mortem analyses are used on commercial LiFePO4cells to identify the ageing mecha-nisms and their representation in the impedance spectrum. The cells were cycled upto 1,667 cycles and measured with EIS. At different ageing states two cells were openedand analyzed with X-ray diffraction (XRD) and scanning electron microscope (SEM),one at 0% state of charge (SoC) and one at 100% SoC. First results show slight changesboth in the EIS spectra and in the micro-structure with cycling.Keywords:LiFePO4, ageing, impedance spectroscopy, post-mortem analysis1 IntroductionWithinthescopeofenergysupply,energystorageapplicationsbecomemoreandmoreimportant. Since 25 years rechargeable Li ion batteries have been applied successfullyin portable electric devices. The understanding of the degradation behaviour of singlecomponents and the entire cell is crucial for high-power applications – be mobile ornon-mobile – in terms of economic and safety aspects. Despite of the growing interestand the continuous increasing of publications in this field of research, there remainunanswered questions.One important attribute of a battery is its ageing, which is highly governed bydegradation processes. Ageing determines the lifetime of the battery and is causedby both cycling and storage. Among other influences, ambient temperature (as wellas electrode potential, depth of discharge (DOD) and cycling rate [1]) affects ageing.The structural changes in the active material (oxidation, corrosion, disordering,micro-cracking), SEI formation, chemical decomposition or dissolution and loss ofcontact are some of the main reasons for ageing [2, 3]. They lead to loss of accessiblecapacity and increasing cell impedance. It was found that ageing is more related tothe cathode than to the anode. So the cathode is to a high degree responsible forcapacity fade [4, 5] and to a certain degree also for an increase of impedance, causedbyparticlesizereduction[5].Thedifferentapproachesinliteraturetomodelageingaredealing with the influence of temperature, state of charge (SoC),DOD, U or I(t) andDelf Kober and Oliver Görke,Department of Material Science, Technical University of Berlin, Berlin,GermanyDelf Kober and Julia Kowal,Department of Energy and Automation Technology, Technical Universityof Berlin, Berlin, GermanyDOI 10.1515/9783110449822-002
© 2016 Walter de Gruyter GmbH, Berlin/Munich/Boston

Chapters in this book

  1. Frontmatter I
  2. Preface V
  3. Contents VII
  4. Part I: Batteries
  5. State-of-Charge and State-of-Health Estimation of Commercial LiFePO4 Batteries by means of Impedance Spectroscopy 3
  6. Ageing Investigation of Lithium Ion LiFePO4 Batteries with a Combination of EIS and Structural Analysis 19
  7. Streamlining Calculation of the Distribution of Relaxation Times from Time Domain Data 29
  8. Influence of the Anode Graphite Particle Size on the SEI Film Formation in Lithium-Ion Cells 35
  9. Frequency-Dependent Phase Correction for Impedance Measurements 44
  10. On-line State Estimation of Automotive Batteries using In-situ Impedance Spectroscopy 49
  11. Part II: Sensors
  12. Capacitive Measurements for Characterizing Thin Layers of Aqueous Solutions 59
  13. Low-Frequency Dielectric Spectroscopy Approach to Water Content in Winter Premium Diesel Fuel Assessment 73
  14. A Novel Method for Capacitive Determination of the Overall Resistance of an Aqueous Solution 81
  15. Part III: Material Characterization
  16. Nanoscale Electrochemical Characterization of Materials by means of Electrostatic Force and Current Measurements 91
  17. AC Impedance Investigation of Multi-walled Carbon Nanotubes/PEDOT:PSS Nanocomposites Fabricated with Different Sonication Times 105
  18. Part IV: Bioimpedance
  19. From Counting Single Biological Cells to Recovering Photons: The Versatility of Contactless Impedance Sensing 119
  20. Electric Impedance Measurement of Tissue Phantom Materials for Development of Medical Diagnostic Systems 131
  21. Problems Encountered during Inappropriate Use of Commercial Bioimpedance Devices in Novel Applications 138
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