338
W. Pfleging et al.
Fig. 11.21 Processing steps for manufacturing of 3D electrodes: a slurry preparation,
b coating/drying, c calendering and d ultrashort laser structuring
deposited onto a 20 μm thick aluminum foil, which is denoted as current collector.
The coating procedure was carried out using a tape-casting film coater with an integrated heating lid. Subsequently, the electrode sheets were dried for 2 h at elevated
temperatures. All cathodes were calendered for improving the particle-to-particle
contact (Fig. 11.23a) and for realizing a good film adhesion between the NMC
composite material and the current collector. Furthermore, calendering is an essential processing step to increase the volumetric energy density of the entire cell [96].
Within the next step, free-standing micro-pillars were generated with a dimension
of 600 μm × 600 μm by removing the composite material down to the substrate
(Fig. 11.24a). A micromachining workstation (PS450-TO, Optec s.a., Belgium)
equipped with an ultrafast fiber laser (Tangerine, Amplitude Systèmes, France) was
used. The pitch distance was set to 1200 μm. Finally, two types of electrodes (unstructured/laser structured NMC cathodes) were laser cut in circular disks with 12 mm in
diameter. Prior to cell assembly, the electrodes were dried in a vacuum oven for 24 h
at 130 °C. Swagelok
® cell design was applied for the subsequent battery tests.
11.5.2 Post-mortem LIBS Investigation of Lithium
Distribution in NMC Thick Film Electrodes
Unstructured and laser patterned NMC cathodes were characterized post-mortem by
LIBS in order to study the lithium amount at the sample surface at different SoH. For
this purpose, the Swagelok
® cells were electrochemically cycled using the following
testing procedure: In a first approach (electrochemical formation) both Swagelok
®
cells were cycled for three cycles using a C-rate of C/10 in a voltage range of 3.0–
4.2 V. For investigation of lithium distribution in electrodes, which operate at high
electrical currents, the C-rate was increased up to C/2 for 100 cycles. Additionally,
both types of Swagelok
® cells were disassembled in an argon-filled glovebox and the
NMC electrodes were washed two times for each 30 min in fresh dimethylcarbonate.
Finally, an elemental mapping of lithium was carried out for both electrodes in order
to investigate the lithium distribution at different SoH.
The experimental setup of LIBS used in this work is illustrated in Fig. 11.22. LIBS
measurements were performed using a dot matrix with a point-to-point distance of
W. Pfleging et al.
Fig. 11.21 Processing steps for manufacturing of 3D electrodes: a slurry preparation,
b coating/drying, c calendering and d ultrashort laser structuring
deposited onto a 20 μm thick aluminum foil, which is denoted as current collector.
The coating procedure was carried out using a tape-casting film coater with an integrated heating lid. Subsequently, the electrode sheets were dried for 2 h at elevated
temperatures. All cathodes were calendered for improving the particle-to-particle
contact (Fig. 11.23a) and for realizing a good film adhesion between the NMC
composite material and the current collector. Furthermore, calendering is an essential processing step to increase the volumetric energy density of the entire cell [96].
Within the next step, free-standing micro-pillars were generated with a dimension
of 600 μm × 600 μm by removing the composite material down to the substrate
(Fig. 11.24a). A micromachining workstation (PS450-TO, Optec s.a., Belgium)
equipped with an ultrafast fiber laser (Tangerine, Amplitude Systèmes, France) was
used. The pitch distance was set to 1200 μm. Finally, two types of electrodes (unstructured/laser structured NMC cathodes) were laser cut in circular disks with 12 mm in
diameter. Prior to cell assembly, the electrodes were dried in a vacuum oven for 24 h
at 130 °C. Swagelok
® cell design was applied for the subsequent battery tests.
11.5.2 Post-mortem LIBS Investigation of Lithium
Distribution in NMC Thick Film Electrodes
Unstructured and laser patterned NMC cathodes were characterized post-mortem by
LIBS in order to study the lithium amount at the sample surface at different SoH. For
this purpose, the Swagelok
® cells were electrochemically cycled using the following
testing procedure: In a first approach (electrochemical formation) both Swagelok
®
cells were cycled for three cycles using a C-rate of C/10 in a voltage range of 3.0–
4.2 V. For investigation of lithium distribution in electrodes, which operate at high
electrical currents, the C-rate was increased up to C/2 for 100 cycles. Additionally,
both types of Swagelok
® cells were disassembled in an argon-filled glovebox and the
NMC electrodes were washed two times for each 30 min in fresh dimethylcarbonate.
Finally, an elemental mapping of lithium was carried out for both electrodes in order
to investigate the lithium distribution at different SoH.
The experimental setup of LIBS used in this work is illustrated in Fig. 11.22. LIBS
measurements were performed using a dot matrix with a point-to-point distance of