doi: 10.1149/1.32767362010, Volume 13, Issue 3, Pages A22-A24.Electrochem. Solid-State Lett.

Yang Dai, Yixiao Zhang, Lei Gao, Guofeng Xu and Jingying Xie A Sodium Ion Based Organic Radical Battery

serviceEmail alerting

click heretop right corner of the article or Receive free email alerts when new articles cite this article - sign up in the box at the

http://esl.ecsdl.org/subscriptions go to: Electrochemical and Solid-State LettersTo subscribe to

© 2009 ECS - The Electrochemical Society

www.esltbd.org address. Redistribution subject to ECS license or copyright; see 128.59.62.83Downloaded on 2013-03-07 to IP

Electrochemical and Solid-State Letters, 13 3 A22-A24 2010A22

A Sodium Ion Based Organic Radical BatteryYang Dai,a,b Yixiao Zhang,a Lei Gao,a Guofeng Xu,c and Jingying Xiea,*,z

aResearch and Development Center of Electrochemistry, Shanghai Institute of Space Power Sources,Shanghai 200233, ChinabLaboratory of Radio Frequency and Energy Microsystem Technology, Shanghai Institute of Microsystemand Information Technology, Chinese Academy of Sciences, Shanghai 200050, ChinacKey Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences, Shanghai 200032, China

A sodium ion based organic radical battery has been developed using a polynorbornene derivative radical polymer as the cathodeactive material. The electrochemical performances of the battery are preliminarily investigated, showing the cyclability of thebattery. The battery delivers a discharge capacity of 75 mAh g−1 at the 1st cycle and a capacity retention of 48 mAh g−1 at the50th cycle.© 2009 The Electrochemical Society. DOI: 10.1149/1.3276736 All rights reserved.

Manuscript submitted October 20, 2009; revised manuscript received December 2, 2009. Published December 29, 2009.

1099-0062/2009/133/A22/3/$28.00 © The Electrochemical Society

Organic radical batteries ORBs are emerging as high rate ca-pable, designable, environment friendly, and promising powersources. An ORB is composed of at least one of its electrodes basedon the radical polymer or the organic radical as the active material.The first article about ORBs was by Nakahara et al. in 2002.1,2 InRef. 1, a lithium-ion based ORB was introduced, employing ap-type radical polymer poly2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate PTMA cathode and a lithium metal anode. Sincethen, a variety of p-type radical polymers, such as polyacetylene,polyethers, and polynorbornene derivatives, was developed as thepotential cathode materials. Most recently, an n-type anode activematerial, polystyrene derivative radical polymer for the all-organicbattery has been reported.3-9 However, most of the articles on ORBsare limited to the lithium-ion based system. In fact, based on thesimilar electrochemical mechanism, the sodium ion or magnesiumion based systems might be applied to the ORB.

Recently, based on the successful development of lithium-ionbatteries, several researchers developed the sodium ion batteries,which are promising substitutes for lithium-ion batteries in variousapplication areas.10 Some materials, such as NaxCoO2,11

NaxMnO2,12 NaxTiS2, NaxTaS2,13 NaVPO4F, NaV1−xCrxPO4F,14

and sulfur composite material,10 have been widely investigated asthe potential electrode active materials. However, most of the pre-viously reported sodium ion batteries are based on the sodium inter-calation mechanism.

In this article, a sodium ion based ORB is assembled, employingthe polynorbornene derivative radical polymer as the cathode activematerial. The charging process of the battery corresponds to theone-electron oxidation of the stable nitroxide radicals to the oxoam-monium cations per repeating unit of the radical polymer at thecathode with the electrolyte anions providing the counter-charge.Sodium ions present in the electrolyte salt are reduced to metal,which is plated at the anode. Upon discharge, the reverse processesoccur.3-9 Its electrochemical mechanism is quite different from thepreviously reported sodium ion batteries.10-14 The electrochemicalperformances of the battery are preliminarily investigated.

Experimental

Polynorbornene-2,3-endo,exo-COO-4-TEMPO2 was synthe-sized according to Suga et al.6 Mn = 64,312 and Mw/Mn = 1.4.Polymer 30 mg and 10 mg of a binder powder polyvinylidenefluoride resin, Kureha Chemical Co. were dissolved in the pres-ence of N-methyl-2-pyrrolidone to form a solution, and then thesolution was mixed with 60 mg of a carbon fiber vapor growth

* Electrochemical Society Active Member.z E-mail: jyxie@mail.sim.ac.cn

address. Redistribu128.59.62.83Downloaded on 2013-03-07 to IP

carbon fiber VGCF, Showa Denko Co. with vigorous stirring. Theresulting black clay was spread onto an aluminum plate and dried invacuum at 333 K.

The cathode sheet 14 mm, separator Celgard 2300, andsodium metal anode were encapsulated into 2016-type coin cellswith 1 M NaClO4 J&K Chemical Co. ethylene carbonate EC-dimethyl carbonate DMC v/v 1:1, Guotaihuarong Chemical Co.electrolyte.

A potentiostat system Princeton Applied Research 273A inter-faced with Solartron SI 1260 was used for the cyclic voltammo-gram and ac impedance measurements. The measurement was car-ried out using a coin cell with a sodium foil as the counter andreference electrode. The ac impedance measurements were per-formed over the frequency range of 0.1 Hz–100 kHz with an ampli-tude of 5 mV at 298 K.

The charge–discharge and cycling properties of the ORBs wereevaluated on a battery measurement system Land CT2001A Wu-han at room temperature.

Results and Discussion

Figure 1 is the scanning electron microscope SEM image of theradical polymer/VGCF composite electrode. It could be seen that thepolymer covers the surface of the carbon fiber conducting networkuniformly.

Figure 2 presents the successive cyclic voltammetric CV curvesof the cathode electrode measured in 1 M NaClO4 EC-DMC v/v1:1 electrolytes. The initial cycle is quite different from the follow-ing ones, exhibiting a couple of asymmetric redox peaks. It shows asharp anodic peak at 3.42 V vs Na+/Na, which is much larger than

Figure 1. SEM image of the radical polymer/VGCF composite electrodeHitachi S4700.

www.esltbd.orgtion subject to ECS license or copyright; see

A23Electrochemical and Solid-State Letters, 13 3 A22-A24 2010 A23

the cathodic peak at 3.38 V vs Na+/Na. This phenomenon may bedue to the electrolyte decomposition or surface filming on the so-dium electrode.15 The following cycles are almost overlapped, indi-cating a quite symmetric redox couple and narrow peak-to-peakseparations similar to the previous articles based on the lithium-ionsystem, suggesting that the reaction is reversible.6

The charge and discharge profiles of the sodium ion based ORBare shown in Fig. 3. The battery exhibited an open-circuit voltageOCV of 1.92 V at room temperature. The initial charging processshows a high and irreversible charge capacity of 296 mAh g−1,with a plateau of 3.44 V vs Na+/Na. However, only 75 mAh g−1 ofthe initial discharge capacity can be obtained, revealing a very lowcoulombic efficiency of 25%. A similar case could be seen from theprevious article of the NaxC6/NaClO4/NaxCoO2 battery.16 So far, thereason is not so clear, which might be due to the electrolyte decom-position or the passive filming on the surface of the anodeelectrode.17 After that, the second cycle delivers a discharge capacityof 73 mAh g−1 with a coulombic efficiency of 63%.

Compared to the results of the lithium-ion based ORB using thesame cathode active material the discharge capacity is about100 mAh g−1 at the same current density, the performance in thesodium ion based system is poor. Many reasons are responsible forthis, and the main reason could be attributed to the poor conductivethick passive film. The inset picture of Fig. 3 is the dischargecapacity–retention curve of the sodium ion based ORB. Only 64.5%

2.0 2.5 3.0 3.5 4.0-0.1

0.0

0.1

0.2

0.3

3rd

2nd

1st

Currentdensity(mA)

Voltage ( vs. Na+/Na)

Figure 2. CV curves first to third of the radical polymer cathode in 1 MNaClO4 EC-DMC electrolyte. Scan rate of 0.1 mV s−1 and voltage rangeof 1.8–4 V vs Na+/Na.

0 50 100 150 200 250 3002.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

0 10 20 30 40 5001020304050607080

Dischargecapacity(mAhg-1 )

Cycle number

1st, 2nd and 3rd

Voltage(Vvs.Na+/Na)

Capacity (mAh g-1)

Figure 3. Charge–discharge profiles of the sodium ion based ORB at roomtemperature. Inset: Discharge capacity–retention curve. Current density of50 mA g−1 and voltage range of 2–4 V vs Na+/Na.

address. Redistribu128.59.62.83Downloaded on 2013-03-07 to IP

of its initial discharge capacity can be retained after cycling for 50times. After cycling, the batteries were disassembled in the argon-filled box. A thick black moss covers the surface of the anode andsome black particles, clinging to the separator. That may be due tothe formation of the sodium dendrite, negatively affecting the elec-trochemical performances, especially the cyclic performance.10,16 Ifthe sodium metal anode and the electrolyte were replaced by thehard carbon anode and the polymer electrolyte, respectively,16,17 theproblem could be minimized.

To better understand the electrochemical behavior of the sodiumion based ORB, the ac impedance spectra were obtained before andafter cycling for 50 times. Figure 4 presents the ac impedance spec-tra of the battery in the state of OCV. Similar to the spectra of theLi/PTMA cell,2 typical semicircle impedance spectra are observed,exhibiting the real-axis intercepts at a high frequency region corre-sponding to the bulk electrolyte resistance Re and at a low fre-quency region corresponding to the electrode/electrolyte interfaceresistance Rf. After the 50 charge–discharge cycles, the Rf valueconsiderably increased, which could be attributed to the formationof a poorly conductive passive film on the anode surface and apartial loss of the electroactivity through electrochemical degrada-tion of the radical polymer.18

In summary, by employing a radical polymer as the cathode ac-tive material, we constructed a sodium ion based ORB. The batterydelivers a maximum initial discharge capacity of 75 mAh g−1 at thecurrent density of 50 mA g−1 and a discharge capacity retention of64.5% after 50 cycles. Detailed studies will be done in the nearfuture. Considering the diversity of the radical polymers, our re-search adds a class of potential cathode materials to the sodium ionbattery and enlarges the electrochemical systems of ORB.

Shanghai Institute of Space Power Sources assisted in meeting the pub-lication costs of this article.

References1. K. Nakahara, S. Iwasa, M. Satoh, Y. Morioka, J. Iriyama, M. Suguro, and E.

Hasegawa, Chem. Phys. Lett., 359, 351 2002.2. J. K. Kim, G. Cheruvally, J. Choi, J. Ahn, S. H. Lee, D. S. Choi, and C. E. Song,

Solid State Ionics, 178, 1546 2007.3. K. Oyaizu and H. Nishide, Adv. Mater., 21, 2339 2009.4. K. Nakahara, J. Iriyama, S. Iwasa, M. Suguro, M. Satoh, and E. J. Cairns, J. Power

Sources, 165, 398 2007.5. T. Suga, H. Ohshiro, S. Sugita, K. Oyaizu, and H. Nishide, Adv. Mater., 21, 1627

2009.6. T. Suga, H. Konishi, and H. Nishide, Chem. Commun. (Cambridge), 2007, 1730.7. T. Katsumata, J. Qu, M. Shiotsuki, M. Satoh, J. Wada, J. Igarashi, K. Mizoguchi,

and T. Masuda, Macromolecules, 41, 1175 2008.8. T. Katsumata, M. Satoh, J. Wada, M. Shiotsuki, F. Sanda, and T. Masuda, Macro-

mol. Rapid Commun., 27, 1206 2006.9. S. H. Lee, J.-K. Kim, G. Cheruvally, J.-W. Choi, J.-H. Ahn, G. S. Chauhan, and C.

E. Song, J. Power Sources, 184, 503 2008.

0 50 100 150 200 250 300 350 4000

-50

-100

-150

-200

-250

-300

Z"(Ω)

Z'(Ω)

before cyclingafter cycling

Figure 4. Electrochemical impedance spectra of the sodium ion cell beforeand after cycling vs OCV.

www.esltbd.orgtion subject to ECS license or copyright; see

A24 Electrochemical and Solid-State Letters, 13 3 A22-A24 2010A24

10. J. Wang, J. Yang, Y. Nuli, and R. Holze, Electrochem. Commun., 9, 31 2007.11. L. W. Shacklette, T. R. Jow, and L. Townsend, J. Electrochem. Soc., 135, 2669

1988.12. M. M. Doeff, M. Y. Peng, Y. Ma, and L. C. De Jonghe, J. Electrochem. Soc., 141,

L145 1994.13. M. S. Whittingham, Prog. Solid State Chem., 12, 41 1978.14. H. Zhuo, X. Wang, A. Tang, Z. Liu, S. Gamboab, and P. J. Sebastian, J. Power

Sources, 160, 698 2006.

address. Redistribu128.59.62.83Downloaded on 2013-03-07 to IP

15. Y. Nuli, J. Yang, J. Wang, and Y. Li, J. Phys. Chem. C, In press.16. R. Alcántara, J. M. Jimenez-Mateos, P. Lavela, and J. L. Tirado, Electrochem.

Commun., 3, 639 2001.17. C. Zhang, S. Gamble, D. Ainsworth, A. M. Z. Slawin, Y. G. Andreev, and P. G.

Bruce, Nature Mater., 8, 580 2009.18. S. R. Sivakkumar, D. R. MacFarlane, M. Forsyth, and D. Kim, J. Electrochem.

Soc., 154, A834 2007.

www.esltbd.orgtion subject to ECS license or copyright; see