Ageing - Energimyndigheten

Report
KTH ROYAL INSTITUTE
OF TECHNOLOGY
Electrochemical Characterization of
Li-ion Batteries for Hybrid Application
Ageing Study
Abdilbari Shifa Mussa, Rakel Wreland Lindström, Mårten Behm, Göran Lindbergh
Li-ion Battery
Works by shuttling lithium
ions between the two
electrodes
-
+
Graphite
Lithiated metal oxides
Lithiated metal oxides:
LCO, LFP, LMO, NMC etc...
Shuttling doesn’t continue
indefinitely without loosing
performance
Electrolyte
Lithium ion battery during charging operation
Adapted from http://www.sigmaaldrich.com/technical-documents/articles/material-matters/u-sdepartment-of0.html
Ageing
Capacity and power fade with time
and use.
Hybrid Electric Vehicle Cycle
Temperature, C-rate, DOD, SOC
are the main factors of ageing
Constant Current Cycle
Life time is a challenge for batteries
in vehicles!!
c)
( Klett et. al, Journal of power sources 257 (2014) 126-137)
How the battery age?
Jens Groot, Main ageing mechanisms in Li-ion battery, 2012
 Complex set of ageing mechanisms due to multiple interactions
 Complementary charcterization techniques and models needed
Electrochemical Characterization
Using electrochemical techniques to observe changes in
parametres affecting the performance with ageing
Charge/Discharge cycling
- Discharge capacity vs cycle number
- Coulombic efficiency (CE)
- Differential voltage (dV/dQ vs Q
plot)
etc...
Potentiostatic test
Charge/Discharge Cycling
Coulombic effciency
CE=
ℎ 
ℎ 
For precise measurement of CE:
the voltage limits, the current,
time and temperature should be
precise
Cost of instrumentation and time
are in perspective
High precision battery cyclers
custom set up in our lab
High precission battery cycler experimental set up
Charge/Discharge Cycling
dV/dQ vs Q
State analysis
Quantitative determination of active
electrode mass and lithium loss
 (+ )  (/)
=



−
Vcell Cell voltage
Vc Cathode half cell voltage
Va Anode half cell voltage
Qc Cathode half cell capacity
Qa Anode half cell capacity
 Cathode Slippage
a Anode Slippage
S= a - c
ma anode active mass (cell)
mc cathode active mass (cell)
  ((−)/)


K.Honkura, ECS Transactions, 13 (19) 61-73 (2008)
Potentiostatic test
How side reaction rate depends on
state of charge (SOC)?
• The cathodic current is an indication of a
continuous reduction at the graphite
probably due to SEI layer development.
•
Generally, lower state of charge gives lower
side reaction rate.
•
The growth of SEI deviates from a parabolic
rate law for higher % SOC.
Summary and Future works
•
•
Ageing of lithium ion battery is a challenge being very
complex.
Need for complementary models and characterization
techniques to determine aging rates and mechanisms.
Future additional works:
• Physics based models for performance prediction and
ageing.
• Electrochemical Impedance Spectroscopy (Model and
Experiment).
Tack för uppmärksamheten!

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