Molecular Design of Organic Electrode Active Materials for Aqueous

Rechargeable Magnesium-ion Battery

Masato Ito(Kyushu Univ.)

Sep. 22, 2015@PWTC, Kuala Lumpur

ISOC14

Toward Large-Scale Electricity Storage

Commercial Rechargeable Batteries using s-Block Element

Nickel-Metal hydride(NiMH)

Lithium-ion (LiB)

Sodium-sulfur(NaS)

AdvantageHigh power density High energy density Rare-metal free

Disadvantage •memory effect •Flammable•Less conductive•High cost

•High operation temp.•Corrosion of insulator•Dendritic-Na growth

Electrolyte Aqueous(KOH aq.)

Non-aqueous (Organic carbonate)

Solid(β-Al2O3)

Application Hybrid Vehicle Electric Vehicle Power Plant

Accident example Nothing •PC smoking and fire•Boeing 787 (2013)

•Toko-Takaoka (2011)•TEPCO (2013)

O2 generation (E = 1.23 – 0.059pH)

H2 generation (E = – 0.059pH)

Stable Electrochemical Window

E (V) vs. NHE

‐1.5

‐1.0

‐0.5

0.0

0.5

1.0

1.5

14121086420pH

Stability Window of H2O

Clarke Number

ionic radius,Å (CN6)

standard electrode potential,

V (vs. SHE)

theoretical specific volume

capacity, Ah/cc

3Li 0.006 0.76 -3.045 2.05

11Na 2.63 1.02 -2.714 1.13

12Mg 1.93 0.72 -2.356 3.83

13Al 7.56 0.54 -1.676 8.05

Energy Density = Voltage x Capacity

Characteristics of Selected Ions

Aqueous Rechargeable Battery: Historical Background

electrolyte cathode anode capacity(mAh/g) group (year)

5 M LiNO3 aq. LiMn2O4 VO2 10 Dahn (1994)sat. LiNO3 aq. LiCoO2 LiV3O8 55 Wu (2007)1 M Mg(NO3)2 aq. LiMn2O4 Pt 42 Munichandraiah (2008)1 M Li2SO4 aq. LiFePO4 LiTi2(PO4)3 82 Okada (2008)1 M Na2SO4 aq. Na0.44MnO2 AC 45 Whitacre (2010)2 M Na2SO4 aq. Zn NaTi2(PO4)3 121 Okada (2011)2 M Na2SO4 aq. Na0.44MnO2 NaTi2(PO4)3 42 Okada (2011)5 M LiNO3 aq. LiCoO2 DANTCBI 71 Zhan (2014)2 M MgSO4 aq. Zn DAAQ 260 This work (2014)

NN

O

O

O

On

DANTCBI

O

N

O

N

1,4-DAAQ

reduction oxidation

Chem. Rev. 1992, 92, 1227Acta Cryst. E, 2005, 61, o1393

OHOH

OHOHHO

HOHOHO

HOHO OH

OH

O

O

O

O

O

O

8 H2O 2 H2O

Molecular Design of New Electrode Active Materials

X

X X

X

XX

X

X X

X

XX

X

X X

X

XX

X

X X

X

XX

2e-

2e-

2e-

2e-

2e-

2e-

X = CR2. NR, O

■Hexagonal Radialenes : 6-electron redox reaction at maximum

■The parent C6O6 molecule can not exist without hydration

O

O

N

N

O

O

O

N

N

N

O

N

N

N

N

N

O

O

N

N

N

N

N

N

X6 = O4N2 X6 = O2N4 X6 = N6

O

O

O

O

X6 = O2C4

O

N

N

O

N

N

O

O

X6 = O2N2C2

Hetero[6]radialenesNew Candidates for Electrode Active Materials

The two contiguous exocyclic double bonds in C6O6 are replaced

Experimental Setup and Conditions

CEWE

Ni wire

Ni mesh

RE

Zn foil

Zn wire

WE composite hetero[6]radialene:AB:PTFE = 70:25:5 (by weight)

electrolyte 2 M MgSO4 aq.

CE Zn metal, 99.9% (Nilaco)

RE Ag/AgCl (BAS)

current density 0.2 mA/cm2 (constant)＠25 ℃

potential range －0.8～+0.6 V

WE = working electrode, CE = counter electrode, RE = reference electrodeAB = acetylene black (Denki Kagaku), PTFE = poly(tetrafluoroethylene) (Daikin)

Charge/Discharge Profiles：Diaza-anthraquinone

N

N

O

O

O

O

1,4-DAAQ

N

O

O

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

• flat voltage plateau• just above the lower limit• clean reversible reaction

• initial capacity decrease• significant loss of energy

N

N

O

O

N N

O

O

Pyrazine-substructure

N

N

O

O

1,4-DAAQ

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

• flat voltage plateaus• initial capacity decrease

para- vs ortho-Quinone

N

N

O

O

O

N

N

O

1,4-DAAQ

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

• unattractive potential • initial capacity decrease

Benzene Juncture

N

N

O

O

The benzene ring possibly prevents 1,4-addition of water at the surface.

N

N

O

O

1,4-DAAQ

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

-1.0

-0.5

0.0

0.5

1.0

Vol

tage

(V) v

s. A

g/A

gCl

300250200150100500Capacity (mAh/g)

1st 2nd

Structural Change on Electrolysis : ex-situ IR

-1.0

-0.5

0.0

0.5

1.0V

olta

ge (V

) vs.

Ag/

AgC

l

300250200150100500Capacity (mAh/g)

1st 2nd

①Initial②Mg insertion

③Mg extraction

Wavenumber [cm-1]1800

1800

1600

1600

1400

1400

1200

1200

1000

1000

②

③

①

N

N

O

O

e e

Mg2+

electrodeelectrolyte

260 mA/g: one Mg per one 1,4-DAAQ

1,4-DAAQ

MgMnSiO4

Summary

N

N

O

O

O

N

N

O

1,4-DAAQ

■1,4-DAAQ as a promising electrode material for Mg ion battery■Capacity of 260 mAh/g is largest ever for an aqueous battery■Attractive potential for an anode material■Judicious arrangement of four consecutive exocyclic double bonds

O2 generation (E = 1.23 – 0.059pH)

H2 generation (E = – 0.059pH)

Stable electrochemical window of H2O

E (V) vs. NHE

‐1.5

‐1.0

‐0.5

0.0

0.5

1.0

1.5

14121086420pH

Acknowledgement

Prof. S. Okada（Kyushu Univ.)K. Chihara（Tokyo Univ. of Science)K. Nakamoto （Kyushu Univ.)T. Ikeda （Kyushu Univ.)