LPM2021 (The 22nd International Symposium on
Laser Precision Microfabricaton)

MXene in-plane micro-supercapacitor
prepared by laser direct writing
Akira Watanabe*1,, Ashiqur Rahman1,2, Hirotaka Ooi*3
1- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University,
2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
2- Department of Electrical and Electronics Engineering, Faculty of Engineering,
American International University Bangladesh, 408/1, Kuratoli Road, Kuril Dhaka-1229, Bangladesh
3- Japan Material Technologies Corporation, 2-3-4, Nihonbashi-Honcho, Chuo-ku, Tokyo 103-0023, JapanWearable Devices

ICT （Information and Communication Technology）
Smart city
BIG DATA

http://www.mumbrella.asia/2013/08/wearabletechnology-fad-or-the-future/

Small, Lightweight
Portable, Flexible,
Fashionable

http://www.myabcspace.com/wirelesscity/

Energy Storage Devices■ Fast chargeability■ Compatibility with wirelesscharging■ Safety

Various energy storage devices
Capacitor

Supercapacitor

Li ion battery(LIB)

Electric double-layer capacitor(EDLC)

Charge-discharge
mechanism

Charge separation

Adsorption-desorption of ions at
the electrode interface

Redox reactions ofelectrode

Charging time

Several seconds

Several-tens seconds

Several hours

Product life

Limitless

Limitless- 800 times

Electric Double-Layerelectrolyte■ Fast chargeability■ Compatibility with wirelesscharging■ Safety

electrodeelectrodeexternalpower supplyStructure comparison of energy storage devices
In-plane micro-supercapacitor (MSC)■ light weight, thin, flexible■ bending resistance, safety

Conventional supercapacitor(a) Capacitor+ Electrode-Electrode(b) Sandwich-type supercapacitor+ Electrode

Electrochemical double layer
capacitor (EDLC)-Dielectricmaterial

Porous carbon
Separator
Porous carbon

Electrode(c) In-Plane micro-supercapacitor (MSC)+Film-Interdigitatedelectrode
PVA-H2SO4

Energy density （Wh/cm3)

Performance comparison of energy storage devices

1Ideal energy
storage device

Fuel cell

0.1
0.01

Secondarybattery

0.001
0.0001Supercapacitor（Electric doublelayer capacitor）

0.00001

0.000001
0.001

Capacitor
0.01

0.1

110100Power density （W/cm3)

1000

10000

Materials for MSC
Graphite nanomaterials, graphene,carbon nanotube, etc.
• High specific surface areas• Electrochemical stability• High electrical conductivity• High mechanical tolerance
Good candidates forwearable energy storage device

Further improvements of energy storage device are requiredin capacitance, energy density, and power density, etc.

New Material for Innovation

New Material for MSC: MXene Ti3C2Tx
Mxene is a new class of two-dimensional materials
MXenes have a general formula Mn+1XnTx,
where `M' is a transition metal, X is C and/or N,and Tx represent surface functional groups.

Ti3C2Tx
Fig. SEM image of MXene.

T = O, H, F, etc.

Ref.) M. Naguib et al, Adv. Mater., 2011, 23 , 4248
Tej B. Limbu et al., J. Mater. Chem. C, 2020, B, 4722

Exfoliation of titanium
aluminum carbide (Ti3AlC2)
in hydrofluoric acidEtching■ Hydrophilicity
polar groups

MXene supercapacitor in a H2SO4 electrolyte solution■ Pseudo-capacitive characteristics

This work
MXene
all-solid
in-plane MSCRef.) M. Ghidiuet al., Nature, 516, 7881 (2014)

Preparation of MXene in-plane MSC(1) Mixture (1/3 w/w) of Mxene and PA (polyamide) NMP solution (12.8%) was coated on aglass substrate covered by a PI (polyimide) film (50 µm thickness) with a rectangular hole(11.3x6.3 mm).
(2) A MXene/PA (polyamide) composite film was prepared on a glass substrate by peelingoff the PI mask film after drying at 110oC.
(3) The raster scan of CW 445 nm laser beam on the MXene/PA composite film gave a
MXene/laser-induced graphene (LIG) composite film by laser-carbonization of PA binderpolymer.
Film

Surface resistivity （Ω/□）

MXene/PA composite film (1/3 w/w)
before 445 nm laser annealing

3400

MXene/LIG composite film
after 445 nm laser annealing

119Preparation of MXene in-plane MSC(4) Laser ablation usinga fiber laser (1064 nm) galvano-scanner system

11.3x6.3mm(5) Copper tape electrode terminal wereconnected to the MXene/PA with a Ag paste
and then the connected area was covered by PItape.

(6) The interdigitated electrode was covered by PVA (polyvinyl alcohol) – H2SO4 as asolid electrolyte.

Cyclic voltammograms of MXene/LIG in-plane MSC■ Pseudo-capacitive characteristics
of MXene was not clear in the cyclic
voltammograms of a MXene/LIG allsolid in-plane MSC.
5 mV/s
10 mV/s
20 mV/s
50 mV/s
100 mV/s

Areal capacitance

20.9 mF/cm2@ 10 mV/s

■ Laser annealing of PA binder
polymer and carbonization caused
the change of surface structure ofMXene.
Volumetric capacitancePrevious highest laser-induced graphene MSC
prepared by laser carbonization of PI film
16.4 mF/cm2 @ 10 mV/sacbdRef.) J. Cai, C. Lv, A. Watanabe, Nano Energy, 30, 790 (2016).

Galvanostatic charge-discharge (CC) curvesof MXene/LIG in-plane MSC

0.049 mA/cm2
0.097 mA/cm2
0.194 mA/cm20.485 mA/cm2
0.971 mA/cm2Ragone plots of MXene/LIG in-plane MSC
in comparison with other energy storage devices
Li thin Film battery (4V/500µAh)
MXene/LIG MSC

LIG-MSCin aqueous H2SO4Boron-doped
LIG-MSC
LIG-MSCin PVA/H2SO4

Al electrolytic capacitor
3V/300µF

Optical microscope image of MXene/PA composite film

Before laser annealing

After laser annealing

Preparation of MXene/PA/Au in-plane MSC
Without laser annealing(1) Au (120 nm) was sputtered on a glass substrate through a PI mask with a rectangularhole (11.3x6.3 mm).
(2) Mixture of MXene, PA (polyamide,
12.8% NMP sol.), and NMP (2/1/1 weightratio) was coated on the Au layer (120nm) through a PI mask.
(3) A MXene/PA/Au layered film was prepared on a glass substrate by peeling off the PI
mask film after drying at 110oC.
(4) Laser ablation by a fiber laser (1064 nm) - galvano-scanner system
Laser ablation

11.3x6.3mm
Front side of Interdigitatedelectrode (MXene/PA)

Back side of Interdigitatedelectrode (Au)Surface Resistivity

MXene/PA sol.
w/w

Laser annealing

Surfaceresistivity（Ω/□）

Thickness（μm）

1/3-

3400

52.0

1/3

Laser annealing

119

20.4

1/1-

535

52.1

1/1

Laser annealing

1754

21.3

Cracking by laser
annealing

2/1-

1.45

35.1

AuRemarkCyclic voltammograms of MXene/PA/Au in-plane MSC■ Pseudo-capacitive characteristics
were clear in the cyclic voltammogramsof a MXene/PA/Au in-plane MSC.
5 mV/s
10 mV/s
20 mV/s
50 mV/s
100 mV/s■ The capacitance was 5 times higher
than those of MXene/LIG and previous
highest laser-induced graphene MSCs.

Areal capacitance

Volumetric capacitanceMXene/PA/Au

MXene/PA/Au

MXene/LIG

MXene/LIG

116 mF/cm2@ 10 mV/s

33.1 F/cm3@ 10 mV/s

Ragone plots of MXene/PA/Au in-plane MSC
in comparison with other energy storage devices
Li thin Film battery (4V/500µAh)
MXene/PA/Au MSC
MXene/LIG MSC

LIG-MSCin aqueous H2SO4Boron-doped
LIG-MSC
LIG-MSCin PVA/H2SO4

Al electrolytic capacitor
3V/300µF

SummaryAn all-solid-state in-plane micro-surpercapacitor (MSC) was studied byapplying laser direct writing method to a MXene-polyamide (PA)composite film.
The energy density of the MXene/LIG in-plane MSC was remarkably
higher than previously reported laser-induced graphene MSCs.

The capacitance of MXene/PA/Au in-plane MSC was 5 times higher thanthose of MXene/LIG and previous highest laser-induced graphene MSCs.

MXene is a potential candidate material for a high performance all-solidMSC.

Acknowledgements
This work was partially supported by JSPS KAKENHI
Grant Number JP15H04132, JSPS KAKENHI Grant
Number JP19H05356.

Thank you for your attention!