EC-Lab – Application Note #58
07/2016
Battery cycling with reference electrodes using the PAT-cell test cell
I – INTRODUCTION
Until recently, to study both the positive and
the negative electrode of batteries, resea-
rchers investigated half-cells. It is now
becoming increasingly common to study a
battery with a reference electrode. [1-2] With B
this configuration, researchers can obtain
information simultaneously from both
electrodes.
To achieve this goal, researchers need advan-
ced testing cells along with advanced poten-
tiostats/galvanostats. Because of the
outstanding reliability of the built-in lithium
metal reference electrode, the PAT-Cell is the
ideal test cell for long-term 3-electrode
experiments on Li-ion battery systems. In this
device, the user can build an experiment cell
and test the materials of the cathode and
anode electrode. The Bio-Logic potentio-
stat/galvanostat is a perfect match for
controlling this type of experiment, as it is
capable of monitoring the half-cell voltages
while controlling the full cell voltage. In this
note, in order to show the benefits of the PAT-
Cell equipped with reference electrode, we
describe a typical cycling experiment of a Figure 1: A) Experimental set-up with the PAT-Cell
lithium-ion battery. This comprises of a NMC docked into the PAT-Single-Stand (in the red
rectangle) connected to the VSP potentiostat. B)
(Nickel Manganese Cobalt) cathode and a Exploded view of the PAT-Cell.
graphite anode (both with a capacity of
~2 mA.h.cm-2, purchased from CCI) in a
conventional LiPF6 based electrolyte EC-Lab® software provides several powerful
(1 molL in Ethylen Carbonate/ DiMethyl-
-1
GCPL techniques which can be used for
Carbonate 1:1 with 2% Vinylen Carbonate, battery cycling with Constant Current/
BASF). Constant Voltage (CC/CV) including sophi-
sticated Galvanostatic Intermittent Titration
II – EXPERIMENTAL SET-UP Techniques (GITT). GCPL is the acronym for
Fig. 1 depicts the PAT-Cell docked into the Galvanostatic Cycling with Potential Limi-
PAT-Single-Stand [4], and connected to the tation. The GCPL techniques differ in several
Bio-Logic VSP potentiostat galvanostat. options such as the available step end
A conditions and the potential control modes
used. Differences between GCPL techniques
are explained in the Technical Note #30 [5].
In this experiment, we have applied the GCPL6
technique, which allows control of the full cell
voltage between the NMC cathode (socket 1
Bio-Logic Science Instruments, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, FRANCE
Tel: +33 476 98 68 31 – Fax: +33 476 98 69 09 www.bio-logic.net
1
EC-Lab – Application Note #58
07/2016
at the PAT-Single-Stand) and the graphite with SP-200, SP-240, SP-300, VSP-300 and
anode (socket 2). At the same time, the GCPL6 VMP-300 instruments.
technique records the two half-cell voltages Figure 3 shows a screenshot of the GCPL6
and the voltage of the full cell: settings, the second of four overall sequences.
• The voltage between NMC and the lithium
reference (sockets 1S and R of the PAT-Single-
Stand). This variable is named EWE in EC-Lab®.
• The voltage between graphite and the
reference (socket 2S and R of the PAT-Single-
Stand). This variable is named ECE in EC-Lab®.
• The voltage between the positive and the
negative electrode. This variable is named
ECELL in EC-Lab®.
Figure 2: Configuration for a battery with a reference
electrode.
NOTE:
During the CV period, the voltage of the cell is
Figure 3: Sequence 1 of the GCPL6 setting.
controlled between the positive and the
negative (and not between the positive elec-
Note that, in the Advanced Settings tab of the
trode and the reference as per standard
GCPL6 technique, ECE is ticked by default.
potentiostat mode).
The GCPL6 technique is available in SP-50, SP-
150, VSP, VMP3 and MPG-2 instruments.
Because of this specific regulation mode du-
ring the CV step, the GCPL6 cannot be linked
with potentio technique. To perform an EIS
measurement, it should be linked to GEIS
Figure 4: ECE ticked in the Advanced Setting tab.
techniques.
It is possible to record the two half-cell III – CYCLING DISCUSSION
voltages and the voltage of the full cell also Figure 5 shows the voltage and current
profiles of the overall experiment. The cut-off
Bio-Logic Science Instruments, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, FRANCE
Tel: +33 476 98 68 31 – Fax: +33 476 98 69 09 www.bio-logic.net
2
EC-Lab – Application Note #58
07/2016
cell voltages were changed from 2.5/4.2 V When increasing the cut-off cell voltage from
during the initial cycle to 2.5/4.5 V in the 2nd 4.2 to 4.5 V, the graphite electrode can no
cycle, 1.0/4.5 V in the 3rd cycle, 0.0/4.5 V in the longer accommodate all the lithium released
4th cycle, and 2.5/4.5 V in the last cycle. from the cathode. As a consequence, the
Throughout the experiment, the magnitude of graphite potential drops to 0 V. Plating occurs.
the current was set to 1 mA, corresponding to The graphite electrode is no longer able to
a rate of approximately 0.2 C during the initial accommodate the lithium released from the
cycle. cathode. Accordingly, plating of Li metal takes
Ewe vs. time #
Cycles-NCM-Graphite.mpr
Ece vs. time Ecell vs. time <I> vs. time place, as can be seen from the drop of the
4,5
4
1
0,8
negative half-cell voltage to 0 V.
Cycles-NCM-Graphite.mpr
0,6 Ewe vs. time # Ece vs. time Ecell vs. time <I> vs. time
3,5
0,4 4,5 1
3
0,2 4 0,8
<I>/mA
Ewe/V
2,5
0 0,6
3,5
2
-0,2 0,4
3
1,5
0,2
<I>/mA
-0,4
Ewe/V
2,5
1 0
-0,6
2
0,5 -0,8 -0,2
1,5
0 -1 -0,4
0 50 100 1
time/h -0,6
Figure 5: Voltage and current profiles of the overall 0,5 -0,8
experiment. The blue line corresponds to the positive
0 -1
10 12 14 16 18 20 22 24 26
time/h
half-cell voltage, the red line to the negative half-cell
voltage, and the green line to the full cell voltage. Figure 7: Voltages evolution during second cycle.
III - 3 THIRD AND FOURTH CYCLE (BETWEEN
III - 1 FIRST CYCLE (BETWEEN 2.5 AND 4.2 V)
0.0 AND 4.5 V)
The following graphs are merely details of
During the third cycle, the lower cut-off
Fig. 5.
voltage was decreased to 1.0 V, in order to see
Fig. 6 shows the evolution of the negative half-
the effects of deep discharge. Discharge to
cell voltage during the formation cycle. One
below 2.5 V cell voltage is considered to
can clearly observe the staging plateaus of
potentially damage the Li-ion battery because
graphite. At the end of discharge, the graphite
the copper current collector of the anode may
was still not fully lithiated.
Ew e vs. time
Cycles-NCM-Graphite.m pr
Ece vs. time Ecell vs. time <I> vs. time #
start to corrode at potentials above 3 V vs. Li.
1
1 In this experiment, at a cut-off voltage of 1.0
0.9
0.8
V the graphite potential does not exceed 1.6 V
vs. Li (Fig. 8). Even when lowering the cell
0.8
0.6
0.7
voltage to 0 V in the subsequent cycle (Fig. 9),
0.4
0.6
0.2
the graphite potential stays well below 3 V vs.
Voltages/V
0.5
I/mA
0.4
-0.2 Li.
0.3
-0.4 Cycles-NCM-Graphite.mpr
Ewe vs. time # Ece vs. time Ecell vs. time <I> vs. time
0.2
-0.6 4,5 1
0.1
4 0,8
-0.8
0,6
0 3,5
-1
0 2 4 6 8 10 0,4
time/h 3
Figure 6: Evolution of the graphite half-cell voltage
0,2
<I>/mA
Ewe/V
2,5
0
during first lithiation. The cut-off of the cell voltage 2
-0,2
was set to 4.2 V. 1,5
-0,4
1
-0,6
0,5 -0,8
III - 2 SECOND CYCLE (BETWEEN 2.5 AND 0
26 28 30 32 34 36 38 40
-1
4.5 V) time/h
The condition changed after increasing the Figure 8: Voltages evolution during third cycle.
upper cut-off voltage to 4.5 V, see Fig. 7.
Bio-Logic Science Instruments, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, FRANCE
Tel: +33 476 98 68 31 – Fax: +33 476 98 69 09 www.bio-logic.net
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EC-Lab – Application Note #58
07/2016
Cycles-NCM-Graphite.mpr
Ewe vs. time # Ece vs. time Ecell vs. time <I> vs. time
4,5 1
0,8
120
4
0,6
3,5
0,4
3 100
0,2
<I>/mA
Ewe/V
2,5
0
2
-0,2
80
1,5
-Im(Z)/Ohm
-0,4
1
-0,6
0,5 -0,8 60
0 -1
40 42 44 46 48 50 52 54
time/h
40
Figure 9: Voltages evolution during the fourth cycle.
III - 4 FIFTH CYCLE (BETWEEN 2.5 AND 4.5 V)
20
Figure 10 depicts the last cycle of the
0
experiment, again with the more regular cut- 0 50 100
off cell voltages of 2.5 and 4.5 V. The battery Re(Z)/Ohm
Figure 11: EIS data on NMC battery equipped with
did survive the two deep discharge cycles. The reference electrode.
situation may change, however, when conti-
nuously cycling the battery, as the evolution Data files can be found in :
of the absolute electrode potentials depends C:\Users\xxx\Documents\EC-
on the ratio of the two half-cell capacities. If Lab\Data\Samples\Battery\AN58 folder
the capacity loss of the graphite exceeds that
of the NMC electrode, then the graphite elec-
trode will continuously rise and eventually REFERENCES
exceed the stability limit of the copper current 1) M Dolle, F. Orsini, A. S. Gozdz, and J.-M.
collector. Tarascon, J. Electrochem. Soc., 148, (2001)
Ewe vs. time #
Cycles-NCM-Graphite.mpr
Ece vs. time Ecell vs. time <I> vs. time
A851.
2) M. Klett, J. A. Gilbert, S. E. Trask, Bryant
4,5 1
4 0,8
3,5
0,6
J. Polzin, A. N. Jansen, D. W. Dees, and D. P.
Abraham, J. Electrochem. Soc., 163, 6 (2016)
0,4
3
0,2
<I>/mA
Ewe/V
A875.
2,5
0
2
3) B. Le Gorrec, C. Montella, R. Yazami, J.
-0,2
1,5
-0,4
1
-0,6
Power Sources 97-97 (2001) 83.
4) More information on the cells are available
0,5 -0,8
0 -1
54 56 58 60 62
time/h
64 66 68 70
on the web.
Figure 10: Voltages evolution during the last cycle. 5) Technical Note #30 “Which GCPL tech-
nique is the most appropriate for my measu-
IV – CONCLUSION rement?”
This application note shows how to set up an
experiment involving a battery with a Revised in 08/2019
reference electrode and how to take
advantage of this configuration combining an
advanced test cell and cycler. This note is
focused on the cycling aspect. Notably, with
the same set-up described here, it is possible
to measure the half and full cell impedances
of the battery as well (Fig. 11). This topic will
be addressed in a separate application note.
Bio-Logic Science Instruments, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, FRANCE
Tel: +33 476 98 68 31 – Fax: +33 476 98 69 09 www.bio-logic.net
4
