Alexander Johannes Warnecke Degradation Mechanisms in NMC-Based Lithium-Ion Batteries

173 Pages·2017·5.36 MB·English

Alexander Johannes Warnecke
Degradation Mechanisms in NMC-Based
Lithium-Ion Batteries
electrolyte decomposition binder
surface film formation
dissolution structural disorder
conductive additive
re-precipitation micro cracking aluminum corrosion
influence of geometry material ageing lithium plating
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Aachener Beiträge des ISEA Band 105
Degradation Mechanisms in NMC Based
Lithium-Ion Batteries

Von der Fakultät für Elektrotechnik und Informationstechnik
der Rheinisch-Westfälischen Technischen Hochschule Aachen
zur Erlangung des akademischen Grades eines Doktors der
Ingenieurwissenschaften genehmigte Dissertation

vorgelegt von
Diplom-Ingenieur
Alexander Johannes Warnecke
aus Brilon

Berichter:
Universitätsprofessor Dr. rer. nat. Dirk Uwe Sauer
Universitätsprofessor Dr.-Ing. Michael Danzer

Tag der mündlichen Prüfung: 22. September 2017

Diese Dissertation ist auf den Internetseiten
der Hochschulbibliothek online verfügbar.
Alexander Johannes Warnecke

Degradation Mechanisms in NMC Based
Lithium-Ion Batteries
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche
Nationalbibliographie; detailed bibliographic data are available in the Internet at:
http://dnb.d-nb.de.

Electronic version
The electronic version is available online on the institutional repository of RWTH
Aachen University (https://publications.rwth-aachen.de).

D82 (Diss. RWTH Aachen University, 2017)

AACHENER BEITRÄGE DES ISEA
Vol. 105

Editor:
Univ.-Prof. Dr. ir. Rik W. De Doncker
Director of the Institute for Power Electronics and
Electrical Drives (ISEA), RWTH Aachen University

Copyright ISEA and Alexander Johannes Warnecke 2017
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without prior permission of the publisher.

ISSN 1437-675X

Institut für Stromrichtertechnik und Elektrische Antriebe (ISEA)
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Vorwort
Diese Arbeit entstand im Rahmen meiner Tätigkeit als wissenschaftlicher Mitarbeiter
am Institut für Stromrichtertechnik und elektrische Antriebe (ISEA) der RWTH
Aachen, am Lehrstuhl für Elektrochemische Energiewandlung und Speichersystem-
technik von Prof. Dirk Uwe Sauer. Während der fünfeinhalb Jahre am Institut hatte
ich die Möglichkeit, in vielen Themenfeldern der Lithium-Ionen-Batterie zu arbeiten.
Der Start mit Alterungsuntersuchungen und Modellierung hat sich als gute Grundlage
für meine Dissertation herausgestellt. Viel Spaß machte aber auch die Zeit im
Analyselabor, bei der Zerlegung und Untersuchung von Zellen.
Professor Sauer danke ich für Möglichkeit bei ihm im Themenbereich Batterien zu
Promovieren und natürlich für die Betreuung während der gesamten Zeit. Herr
Professor Michael Danzer danke ich sehr für die Übernahme des Korreferats und
seine konstruktiven Anmerkungen zur Arbeit.
Solch eine Arbeit ist nie eine pure Einzelleistung. Allen Kollegen, Studenten und
Projektpartnern aus dieser Zeit möchte ich für jegliche Unterstützung danken, ohne
die dies nicht möglich gewesen wäre.
Die Arbeitsatmosphäre am ISEA ist eine ganz besondere. Neben den hohen
Erwartungen an die Arbeitsleistung kommen Spaß und Miteinander nie zu kurz. Die
Zeit am Institut werde ich sehr vermissen. Madeleine möchte ich danken, dass sie
mich mit Studienarbeit und Diplomarbeit ans Institut geholt hat. Auch in den späteren
Jahren hat sie mich stets als Abteilungsleiterin und Kollegin unterstützt. Die Laborzeit
mit den Kellerkindern wird für mich Unvergesslich bleiben und kann so schnell nicht
übertroffen werden. Zu den Kellerkindern zählen natürlich Kollegen und Studenten.
Spezieller Dank geht an Jens, Meinert und Luke für das fachliche Korrekturlesen.
Auch wenn die Anmerkungen oft viel Arbeit verursacht haben, haben diese die
Qualität der Arbeit gesteigert. Für die Überarbeitung in sprachlicher Hinsicht gilt mein
Dank meinen Schwestern Christina und Annika, sowie wieder Luke.
Zum Schluss möchte ich mich noch meiner Familie und Freunden bedanken. Eure
Unterstützung habt ihr gezeigt, indem es kein Problem war auch mal keine Zeit für
euch zu haben, besonders in den kritischen Phasen der Doktorarbeit.
Aachen, im Oktober 2017 Alexander Warnecke
Introduction and Motivation i

Table of Contents
(cid:883)(cid:484)(cid:3) Introduction and Motivation .................................................................................. 1(cid:3)
(cid:884)(cid:484)(cid:3) Lithium-ion batteries ............................................................................................. 5(cid:3)
(cid:884)(cid:484)(cid:883)(cid:3) Working principle ........................................................................................... 6(cid:3)
(cid:884)(cid:484)(cid:884)(cid:3) Components of a lithium-ion battery .............................................................. 7(cid:3)
(cid:884)(cid:484)(cid:884)(cid:484)(cid:883)(cid:3) Anode ..................................................................................................... 9(cid:3)
(cid:884)(cid:484)(cid:884)(cid:484)(cid:884)(cid:3) Cathode ................................................................................................ 14(cid:3)
(cid:884)(cid:484)(cid:884)(cid:484)(cid:885)(cid:3) Separator .............................................................................................. 18(cid:3)
(cid:884)(cid:484)(cid:884)(cid:484)(cid:886)(cid:3) Electrolyte ............................................................................................. 20(cid:3)
(cid:885)(cid:484)(cid:3) Ageing behavior of NMC-based cells ................................................................. 23(cid:3)
(cid:885)(cid:484)(cid:883)(cid:3) Cell of investigation ..................................................................................... 23(cid:3)
(cid:885)(cid:484)(cid:883)(cid:484)(cid:883)(cid:3) Electrical properties .............................................................................. 24(cid:3)
(cid:885)(cid:484)(cid:884)(cid:3) Initial characterization and post mortem analysis ........................................ 27(cid:3)
(cid:885)(cid:484)(cid:884)(cid:484)(cid:883)(cid:3) Acquiring geometrical data ................................................................... 30(cid:3)
(cid:885)(cid:484)(cid:884)(cid:484)(cid:884)(cid:3) Identification of material composition .................................................... 34(cid:3)
(cid:885)(cid:484)(cid:884)(cid:484)(cid:885)(cid:3) Description of morphology .................................................................... 37(cid:3)
(cid:885)(cid:484)(cid:884)(cid:484)(cid:886)(cid:3) Electrical electrode characteristics ........................................................ 39(cid:3)
(cid:885)(cid:484)(cid:885)(cid:3) Accelerated ageing analysis ........................................................................ 41(cid:3)
(cid:885)(cid:484)(cid:885)(cid:484)(cid:883)(cid:3) Concept of accelerated ageing ............................................................. 41(cid:3)
(cid:885)(cid:484)(cid:885)(cid:484)(cid:884)(cid:3) Ageing behavior in storage conditions .................................................. 42(cid:3)
(cid:885)(cid:484)(cid:885)(cid:484)(cid:885)(cid:3) Ageing behavior in cycling conditions ................................................... 47(cid:3)
(cid:885)(cid:484)(cid:885)(cid:484)(cid:886)(cid:3) Variability in ageing curves ................................................................... 57(cid:3)
(cid:885)(cid:484)(cid:886)(cid:3) Separation of degradation behavior............................................................. 59(cid:3)
(cid:886)(cid:484)(cid:3) Influence of the cell design on degradation ........................................................ 61(cid:3)
(cid:886)(cid:484)(cid:883)(cid:3) Spatial resolved measurements of lithium concentrations ........................... 62(cid:3)
(cid:886)(cid:484)(cid:884)(cid:3) Importance of delivery conditions ................................................................ 64(cid:3)
(cid:886)(cid:484)(cid:885)(cid:3) Influence on calendric ageing ...................................................................... 67(cid:3)
(cid:886)(cid:484)(cid:886)(cid:3) Influence in cycling conditions ..................................................................... 71(cid:3)
(cid:886)(cid:484)(cid:887)(cid:3) Approach for calculation of geometry caused transition .............................. 72(cid:3)
(cid:886)(cid:484)(cid:888)(cid:3) Passive electrode in automotive cells .......................................................... 76(cid:3)
(cid:887)(cid:484)(cid:3) Linearized degradation ....................................................................................... 79(cid:3)
ii Degradation Mechanisms in NMC-Based Lithium-Ion Batteries

(cid:888)(cid:484)(cid:3) Rapid cell break down ........................................................................................ 85(cid:3)
(cid:888)(cid:484)(cid:883)(cid:3) Lithium plating ............................................................................................. 85(cid:3)
(cid:888)(cid:484)(cid:884)(cid:3) Post mortem of cell in the linear degradation phase .................................... 86(cid:3)
(cid:888)(cid:484)(cid:885)(cid:3) Post mortem of cells with break down ......................................................... 87(cid:3)
(cid:888)(cid:484)(cid:886)(cid:3) Model approach for cell break down ............................................................ 89(cid:3)
(cid:889)(cid:484)(cid:3) Ex ante assignment of degradation effect .......................................................... 93(cid:3)
(cid:889)(cid:484)(cid:883)(cid:3) Electrical impedance spectroscopy (EIS) .................................................... 93(cid:3)
(cid:889)(cid:484)(cid:884)(cid:3) Differential voltage analysis (DVA) .............................................................. 94(cid:3)
(cid:890)(cid:484)(cid:3) Dissolution of transition metals .......................................................................... 99(cid:3)
(cid:890)(cid:484)(cid:883)(cid:3) Driver for dissolution of transition-metals ..................................................... 99(cid:3)
(cid:890)(cid:484)(cid:883)(cid:484)(cid:883)(cid:3) Dissolution by HF ................................................................................ 100(cid:3)
(cid:890)(cid:484)(cid:883)(cid:484)(cid:884)(cid:3) Disproportion reaction ......................................................................... 100(cid:3)
(cid:890)(cid:484)(cid:884)(cid:3) Effects of re-deposition on the cathode ..................................................... 101(cid:3)
(cid:890)(cid:484)(cid:885)(cid:3) Impact of material loss on cathode capacity .............................................. 102(cid:3)
(cid:890)(cid:484)(cid:886)(cid:3) Effects at the anode/electrolyte interphase ................................................ 102(cid:3)
(cid:890)(cid:484)(cid:887)(cid:3) Measurement techniques for identification and quantification of dissolved
transition metals .................................................................................................. 103(cid:3)
(cid:890)(cid:484)(cid:888)(cid:3) Impact of stress factors ............................................................................. 105(cid:3)
(cid:890)(cid:484)(cid:888)(cid:484)(cid:883)(cid:3) Influence of temperature and SoC ...................................................... 106(cid:3)
(cid:890)(cid:484)(cid:888)(cid:484)(cid:884)(cid:3) Influence of cycling depth and current rate ......................................... 110(cid:3)
(cid:890)(cid:484)(cid:889)(cid:3) Conclusion for influence of dissolution on overall cell ageing .................... 114(cid:3)
(cid:890)(cid:484)(cid:889)(cid:484)(cid:883)(cid:3) Advice for improved operation strategy in electric vehicles ................. 115(cid:3)
(cid:891)(cid:484)(cid:3) Structural changes ........................................................................................... 117(cid:3)
(cid:891)(cid:484)(cid:883)(cid:3) Ideal and real structure of NMC ................................................................. 117(cid:3)
(cid:891)(cid:484)(cid:884)(cid:3) Identification of crystal structure ................................................................ 119(cid:3)
(cid:891)(cid:484)(cid:885)(cid:3) Structural changes due to lithium insertion and extraction ........................ 120(cid:3)
(cid:891)(cid:484)(cid:886)(cid:3) Structural changes in storage .................................................................... 124(cid:3)
(cid:891)(cid:484)(cid:887)(cid:3) Structural changes by usage ..................................................................... 126(cid:3)
(cid:891)(cid:484)(cid:888)(cid:3) Summary of structural changes ................................................................. 127(cid:3)
(cid:883)(cid:882)(cid:484)(cid:3) Electrolyte decomposition on the cathode .................................................... 129(cid:3)
(cid:883)(cid:882)(cid:484)(cid:883)(cid:3) Gravimetric analysis of the CEI .............................................................. 130(cid:3)
(cid:883)(cid:882)(cid:484)(cid:884)(cid:3) Thermo-gravimetric analysis of the CEI ................................................. 132(cid:3)
Introduction and Motivation iii

(cid:883)(cid:883)(cid:484)(cid:3) Current collector corrosion ............................................................................ 137(cid:3)
(cid:883)(cid:883)(cid:484)(cid:883)(cid:3) Dissolved aluminum ............................................................................... 137(cid:3)
(cid:883)(cid:883)(cid:484)(cid:884)(cid:3) Optical analysis ...................................................................................... 139(cid:3)
(cid:883)(cid:883)(cid:484)(cid:885)(cid:3) Comparison of method ........................................................................... 141(cid:3)
(cid:883)(cid:883)(cid:484)(cid:886)(cid:3) Influence on cell degradation ................................................................. 141(cid:3)
(cid:883)(cid:884)(cid:484)(cid:3) Conclusion and outlook ................................................................................ 143(cid:3)
(cid:883)(cid:885)(cid:484)(cid:3) Bibliography .................................................................................................. 145(cid:3)
(cid:883)(cid:886)(cid:484)(cid:3) Appendix ....................................................................................................... 157(cid:3)
(cid:883)(cid:886)(cid:484)(cid:883)(cid:3) Own Publications ................................................................................... 157(cid:3)
(cid:883)(cid:886)(cid:484)(cid:883)(cid:484)(cid:883)(cid:3) Scientific Journals ............................................................................... 157(cid:3)
(cid:883)(cid:886)(cid:484)(cid:883)(cid:484)(cid:884)(cid:3) Conference Publications ..................................................................... 157(cid:3)
(cid:883)(cid:886)(cid:484)(cid:884)(cid:3) Supervised Thesis .................................................................................. 158(cid:3)
Introduction and Motivation 1

(cid:883)(cid:484) Introduction and Motivation
“Climate change is happening, humans are causing it, and I think this is perhaps the
most serious environmental issue facing us” – Bill Nye “The Science guy”
“We're running the most dangerous experiment in history right now, which is to see
how much carbon dioxide the atmosphere (..). can handle before there is an
environmental catastrophe.” – Elon Musk
The above-stated quotes illustrate that climate change is an important issue on the
agenda of researchers as well as economical world leaders. To stop global warming,
major changes need to occur in the sectors of energy, industry, agriculture, and
transportation. One of the highest impact and widely discussed topics is the
decreased use of fossil energy sources for the transportation sector. At the moment,
petroleum is the main source of energy for transportation with around 95% [1].
Typical combustion engines have improved drastically since the invention in 1883,
but the typical efficiency in today’s vehicles is still low. One way to reduce the usage
of fossil fuels is using electric powered vehicles, where energy comes from high
efficient power plants or even better, from renewable energy. To store the electric
energy in the vehicle, two main techniques are in favor for the next decades:
hydrogen fuel cells and batteries [2]. Self-evidently, both techniques have
advantages and disadvantages. As an example, the refueling of fuel cell vehicles
with liquid hydrogen can be accomplished with fast filling speeds; whereas the
charging of battery powered vehicles ranges from half an hour to several hours. In
contrast, the erratic power demand of vehicles shortens the lifetime of a fuel cell,
which cannot be seen for battery electric vehicles. However, the price and absence
of a hydrogen infrastructure led to a higher market share for battery electric vehicles
(BEV).
Currently lithium-ion batteries are used as an energy storage in BEVs, but as it can
be seen from the high prices for electric vehicles they are not competitive as
compared to vehicles with combustion engines (Tesla Model S 60 starting at
69,019 € [3] vs. BMW 5er starting at 45,200 € [4]). Batteries are the most cost
intensive component of these automobiles [5]. To build affordable electric vehicles,
many manufacturers sell cars with a small battery resulting in lower ranges (around
150 km) [6].
To justify such high investments, the most important and cost intensive component of
a BEV should have an exceptionally long lifetime. However, testing batteries for ten
to twenty years is not possible for manufacturers who aim to stay competitive
concerning the rapid development of new and innovative vehicles. For them it is of
2 Degradation Mechanisms in NMC-Based Lithium-Ion Batteries

crucial importance to understand and gather lifetime results in a rather short period.
Unfortunately, the results of small lab cells differ significantly from that of full cells of
an adequate size and type. The degradation mechanisms seem to change so that
cost-intensive tests of the later cells cannot be omitted. As a result, it is necessary to
find a way to attribute the degradation of commercial lithium-ion batteries to the
results of lab cells, tested in research.
The following thesis is aimed at the ageing of a commercial lithium-ion battery, with a
special focus on the influence of the positive electrode (cathode). A schematic of a
degradation curve for commercial cells is graphically depicted in Figure 1. As one
can see the degradation is split up into three phases starting with a possible
influence of the geometry of the cell and ending with a rapid break down. The linear
graph signifies the material degradation. The focus of this work is on the linear
region. It is intended to associate the three phases with the ongoing degradation
effects, which is done by electrical testing and post mortem analysis.

Figure 1: Schematic overview of the divided ageing regions of Nickel Manganese
Cobalt (NMC)-based lithium-ion battery. After how much capacity loss (X%) the third
phase starts differs for each battery type.
The commercial cell design used for the analysis of the following thesis is a 20 Ah
cell from the Korean manufacturer EIG. With regards to the cathode materials, the
current and most widely used material group was chosen [7]. The material belongs to
a class definite as Layered Transition Metal Oxides. The crystal structure consists of
consecutive layers of oxygen, lithium and the transition metals. The widely used
transition metals are nickel, cobalt, manganese and aluminum. Starting point for
materials with a combination of transition metals was an Li(NiMnCo)O (NMC) with
x y z 2