ISOC14 Molecular Design of Organic Electrode Active Materials for Aqueous Rechargeable Magnesium-ion Battery Masato Ito (Kyushu Univ.) Sep. 22, 2015@PWTC, Kuala Lumpur
Toward Large-Scale Electricity Storage
Commercial Rechargeable Batteries using s -Block Element Nickel-Metal hydride Lithium-ion Sodium-sulfur (NiMH) (LiB) (NaS) Advantage High power density High energy density Rare-metal free Disadvantage •memory effect •Flammable •High operation temp. •Less conductive •Corrosion of insulator •High cost •Dendritic-Na growth Electrolyte Aqueous Non-aqueous Solid ( β -Al 2 O 3 ) (KOH aq.) (Organic carbonate) Application Hybrid Vehicle Electric Vehicle Power Plant Accident example Nothing •Toko-Takaoka (2011) •PC smoking and fire •TEPCO (2013) •Boeing 787 (2013)
Energy Density = Voltage x Capacity Stability Window of H 2 O Characteristics of Selected Ions 1.5 E (V) vs. NHE theoretical O 2 generation (E = 1.23 – 0.059pH) standard specific 1.0 Clarke ionic radius, electrode volume Number Å (CN6) potential, capacity, V (vs. SHE) Ah/cc 0.5 3 Li 0.006 0.76 -3.045 2.05 Stable Electrochemical Window 0.0 11 Na 2.63 1.02 -2.714 1.13 H 2 generation (E = – 0.059pH) ‐ 0.5 12 Mg 1.93 0.72 -2.356 3.83 ‐ 1.0 13 Al 7.56 0.54 -1.676 8.05 ‐ 1.5 0 2 4 6 8 10 12 14 pH
Aqueous Rechargeable Battery: Historical Background capacity electrolyte cathode anode group (year) (mAh/g) 5 M LiNO 3 aq. LiMn 2 O 4 VO 2 10 Dahn (1994) sat. LiNO 3 aq. LiCoO 2 LiV 3 O 8 55 Wu (2007) 1 M Mg(NO 3 ) 2 aq. LiMn 2 O 4 Pt 42 Munichandraiah (2008) 1 M Li 2 SO 4 aq. LiFePO 4 LiTi 2 (PO 4 ) 3 82 Okada (2008) 1 M Na 2 SO 4 aq. Na 0.44 MnO 2 AC 45 Whitacre (2010) 2 M Na 2 SO 4 aq. Zn NaTi 2 (PO 4 ) 3 121 Okada (2011) 2 M Na 2 SO 4 aq. Na 0.44 MnO 2 NaTi 2 (PO 4 ) 3 42 Okada (2011) 5 M LiNO 3 aq. LiCoO 2 DANTCBI 71 Zhan (2014) 2 M MgSO 4 aq. Zn DAAQ 260 This work (2014) O O O N N N N O O O n 1,4-DAAQ DANTCBI
Molecular Design of New Electrode Active Materials ■ Hexagonal Radialenes : 6-electron redox reaction at maximum X X X X 2e - 2e - 2e - X X X X X X X X X X X X X X 2e - 2e - 2e - X X X X X X X = CR 2 . NR, O oxidation reduction ■ The parent C 6 O 6 molecule can not exist without hydration O HO OH HO OH O O HO OH 8 H 2 O 2 H 2 O HO OH O O HO OH HO OH O Chem. Rev. 1992 , 92 , 1227 Acta Cryst. E, 2005 , 61 , o1393
Hetero[6]radialenes New Candidates for Electrode Active Materials The two contiguous exocyclic double bonds in C 6 O 6 are replaced X 6 = O 4 N 2 X 6 = O 2 N 4 X 6 = N 6 X 6 = O 2 C 4 X 6 = O 2 N 2 C 2 O O N O O N O N O N N O N O N O N N N N N O N N O O O N N N N N N O O O
Experimental Setup and Conditions RE hetero[6]radialene:AB:PTFE = WE composite 70:25:5 (by weight) electrolyte 2 M MgSO 4 aq. Zn wire Ni wire CE Zn metal, 99.9% (Nilaco) RE Ag/AgCl (BAS) CE WE 0.2 mA/cm 2 (constant) ＠ 25 ℃ current density － 0.8 ～ +0.6 V potential range Zn foil Ni mesh WE = working electrode, CE = counter electrode, RE = reference electrode AB = acetylene black (Denki Kagaku), PTFE = poly(tetrafluoroethylene) (Daikin)
Charge/Discharge Profiles ： Diaza-anthraquinone 1.0 1.0 1.0 1st 1st 1st 2nd 2nd 2nd Voltage (V) vs. Ag/AgCl Voltage (V) vs. Ag/AgCl Voltage (V) vs. Ag/AgCl 0.5 0.5 0.5 0.0 0.0 0.0 -0.5 -0.5 -0.5 -1.0 -1.0 -1.0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Capacity (mAh/g) Capacity (mAh/g) Capacity (mAh/g) O O O N N N O O O 1,4-DAAQ • • flat voltage plateau initial capacity decrease • • just above the lower limit significant loss of energy • clean reversible reaction
Pyrazine-substructure 1.0 1.0 1.0 1st 1st 1st 2nd 2nd 2nd Voltage (V) vs. Ag/AgCl Voltage (V) vs. Ag/AgCl Voltage (V) vs. Ag/AgCl 0.5 0.5 0.5 0.0 0.0 0.0 -0.5 -0.5 -0.5 -1.0 -1.0 -1.0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Capacity (mAh/g) Capacity (mAh/g) Capacity (mAh/g) O O O N N N N N N O O O 1,4-DAAQ • flat voltage plateaus • initial capacity decrease
para- vs ortho- Quinone 1.0 1.0 1st 1st 2nd 2nd Voltage (V) vs. Ag/AgCl Voltage (V) vs. Ag/AgCl 0.5 0.5 0.0 0.0 -0.5 -0.5 -1.0 -1.0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Capacity (mAh/g) Capacity (mAh/g) O O N N O N N O 1,4-DAAQ • unattractive potential • initial capacity decrease
Benzene Juncture 1.0 1.0 1st 1st 2nd 2nd Voltage (V) vs. Ag/AgCl Voltage (V) vs. Ag/AgCl 0.5 0.5 0.0 0.0 -0.5 -0.5 -1.0 -1.0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Capacity (mAh/g) Capacity (mAh/g) O O N N N N O O 1,4-DAAQ The benzene ring possibly prevents 1,4-addition of water at the surface.
Structural Change on Electrolysis : ex-situ IR 1 8 0 0 1 6 0 0 1 4 0 0 1 2 0 0 1 0 0 0 1.0 1st ③ Mg extraction 2nd Voltage (V) vs. Ag/AgCl ③ 0.5 ② 0.0 -0.5 ① ① Initial ② Mg insertion -1.0 0 50 100 150 200 250 300 1 8 0 0 1 6 0 0 1 4 0 0 1 2 0 0 1 0 0 0 Capacity (mAh/g) Wavenumber [cm -1 ] e e 260 mA/g: one Mg per one 1,4-DAAQ Mg 2+ O N N O 1,4-DAAQ electrolyte electrode
Summary 1.5 E (V) vs. NHE O 2 generation (E = 1.23 – 0.059pH) 1.0 MgMnSiO 4 0.5 Stable electrochemical window of H 2 O 0.0 O N O H 2 generation (E = – 0.059pH) N ‐ 0.5 O N N ‐ 1.0 O 1,4-DAAQ ‐ 1.5 0 2 4 6 8 10 12 14 pH ■ 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
Acknowledgement Prof. S. Okada （ Kyushu Univ.) K. Chihara （ Tokyo Univ. of Science) K. Nakamoto （ Kyushu Univ.) T. Ikeda （ Kyushu Univ.)
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