s-Tetrazines as Active Materials for Na-ion Battery
Masaki Furusawa
IMCE, Kyushu University, Okada・Sakaebe・Albrecht Lab.

Introduction■Change of society needs against secondary battery
Secondary battery
marketWeightEnergy density

SafetyCost performance

Structure

Teoretical capasity（mAh/g）

Potential （V）
Discharge / Charge

Diacharge capasity
1st / 2ndRef.

1255

0.18 / 0.5

225 / 105

C. Wang, et al., J. Am. Chem. Soc. 2015, 137, 3124.

2257

1.57, 1.89 / 1.92. 2.18

214 / 207

C. Guo, et al., Chem. Commun. 2015, 51, 10244.

3115

1.8 / 2.0

105 / 89

M. Yao, et al., Sci. Rep. 2014, 4, 3650.

4170

1.2 / 1.4

220 / 170

C. Luo, et al., Angew. Chem. Int. Ed. 2018, 57, 2879.

5586

0.7 / 2.2567 / 520

H. Zhao, et al., Angew. Chem. 2017, 129, 15536.

6221

1.8 / 2.0

222 / -J. Hong, et al., Nat. Commun. 2014, 5, 5335.

enlargement

enlargement

Mobile electronicequipment■Examples of organic electrode materials for Na ion batteries

Large storage system

Automotive battery

Conventional type（C=O）

New redox type■Comparison of Na and Li
Clarkenumber

Cost(carbonate)

Theoreticalcapacity

Ion volume

Na

2.63

150 $/t

1166 mAh/g

6.54 Å3-2.714 VLi

0.006

5000 $/t

3861 mAh/g

3.05 Å3-3.045 VDisadvantage◆Low energy density◆Large ion-volume

Standard electrodepotential (V vs.SHE)
1Advantage◆Multi-electron redox reaction◆Systematic control of host structure

OrganicElectrode

5462➣Redox-active organic compounds will lead to thecreation of new organic secondary batteries andprovide important guidelines for molecular
design as useful electrode materials.

3This Work■Tetrazines

Form stable anion radicals (at the reducing end)

Cyclic π-electron compound stable at r.t.

Easy to synthesize with inexpensive raw materials

High electron affinitys-tetrazins■Cell fabrication■Previous research (Li-ion：D.J. Min et al., ChemSusChem. 2019, 503, 12.)

Spencer
Ni meshChemical stability(DPT is promising)

DCT

DMT

DPT

CMT

Voltage (V vs. Li/Li+)

3.0

GasketSepareter
Working electrode2.5

DPT(114 mAh/g)
2.0

High

Redox potentialLow

050100150Specific Capacity (mAh/g)

Fig. Cyclic voltammetry of s-tetrazines

Counter electrode

1 M LiPF6 (EC:DMC = 1:1 in vol.)Fig. Charge/discharge profile of DPT

Conductivematerial

Acetylene black (AB)Binder

Polytetrafluoroethylene (PTFE)

Workingelectrodes-tetrazines：AB：PTFE＝70：25：5

Counterelectrode

Na metal

DPT①Stabilization of anion
radicals (by pyridine ring)②Control of potential(by substituent effect )Dipyrdyl-tetrazines(113 mAh/g)

Results and Discussion■Charge/discharge characteristics of s-tetrazines
5■Analysis of reaction mechanism : (b) Ex situ XRD spectra of DPT (c) FT-IR spectra of DPT51st2nd

Voltage (V) vs. Na/Na+

32

100

Voltage (V) vs. Na/Na+

4

Electrolyte：1 M NaPF6(EC:DMC = 1:1 in vol.)Voltage range：1.5~2.5 V
Current density：0.2 mA/㎠50
100
Capacity (mAh/g)

32

10150

5544

Voltage (V) vs. Na/Na+

Voltage (V) vs. Na/Na+

43

2

10-50050
Capacity (mAh/g)

100

050
100
Capacity (mAh/g)➣ The 002 diffraction peak observed at 8.8°has➣The new peaks at 1466 cm-1 and 1599

2decreased upon discharging and perfectly disappeared at
the end of the discharge cycle and the 002 peak recovered
after charging the cell that is indicating the reversibility.

cm-1 appeared assigned to discharge but
decreased after charging, indicating thatthe reaction was reversible.

1Conclusion

300

Investigation of the properties of s-tetrazines as electrode materials for Na-ion batteries
50
100
Capacity (mAh/g)

150

The discharge voltage increases by about 0.1 to 0.2 V with thepyridyl groups (compared to DPT)
➣ It is suggested that the voltage can be tuned by introducing asubstituent (electron-withdrawing/-donating) by molecular design.

➣ DPT was operated as electrode materials for Na-ion batteries, and the initial discharge capacity was
about 110 mAh/g (theoretical capacity: 114 mAh/g).The cycle characteristics were not satisfactory, mainly
due to leaching into the electrolyte.
➣ The potential can be changed by the effect of substituents such as pyridyl groups.
➣ s-tetrazines have a flat charge-discharge curve around 2 V (vs. Na), which is attributed to a two-phaseequilibrium reaction, as revealed by X-ray diffraction.

Acknowledgemant
This work was supported by the Elements Strategy Initiative for Catalysts and Batteries (ESICB) project (Grant Number JPMXP0112101003), and Leading Initiative for
Excellent Young Researchers, Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), JSPS KAKENHI Grant No. JP20H00400, JST PRESTO
Grant Number JPMJPR18T2, and Kyushu University Platform of Inter-/Transdisciplinary Energy Research（QPIT）, and Industrial Science Research Promotion Foundation.