Y. Maletin , N. Stryzhakova , S. Zelinskiy , S. Chernukhin , D . Tretyakov , S. Tychina

Y. Maletin, N. Stryzhakova, S. Zelinskiy, S. Chernukhin, D. Tretyakov, S. Tychina

How Electrochemical Science Can Improve the EDLC Performance

AABC Europe 2013, Strasbourg, June 24-28

Presentation outline

1. Yunasko key targets2. CV and galvanostatic measurements3. Impedance measurements (EIS)4. In-pore diffusion measurements5. Recent test results: unit cells and modules6. Company development

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Why SC’s sometimes look like the Cinderella of energy storage market?

1. Billions were invested in Li-ion batteries over the last few decades resulting in a huge advance of this technology.

2. SC technology was developing rather slowly and was deemed to be rather complicated and expensive for many applications.

Hence, Yunasko approach: 3. SC’s must demonstrate by far the best

performance in areas where they can compete with batteries or complement them.

4. Low cost and commercially available components should preferably be used.

Cell design for 3-electrode measurements

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CV: scanning the electrode potential to (+)

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• 0V corresponds to the equilibrium potential• scan rate: 10 mV/s

NOTE: potential range with Faraday processes cannot be used for long

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CV curves: A - 3-electrode cell B - SC prototype


A

B

2.43.1


Charge accumulated in (-) or (+) potential range

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Hybrid cell: CC charge-discharge curves

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40 50 60 70 80 90 100 110 120-10

010203040506070

DC=2.7V AC= 5mV Freq --> 0.1Hz to 10 kHz

1- poor2- typical3- optimized

SC design:

Impedance spectroscopy (Nyquist plots)

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2

3

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1

9

10

100 101 102 103 104

0.6

0.7

0.8

0.9

1.0

frequency, Hz

R, O

hm. c

m2

-10

-5

0

5

10

15

C, F

/cc


Impedance spectroscopy (capacitance and resistance vs. frequency)

rAl-C ≤ 0.01 (in Yunasko technology)

rC ~ 0.05

Thus: rEl ~ 0.75

“pore resistance” ~ 0.6

SC resistivity (in W.cm2)

total ~ 0.8

Though: rEl-in-bulk ~ 0.15 (electrode+separator thickness)

Yunasko approach to reduce R and RC

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TEM image of carbon powder

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Slit-shaped pores or just shear cracks of graphene layers


Why the in-pore electrolyte mobility is slow?

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• Pore width is mostly within 1 ÷ 3 nm (is comparable with the Debye length).

• There is no potential gradient in narrow pores, and therefore, diffusion is the only driving force for ions to move. (Y.Maletin et al., 7th EDLC Seminar, FL, Dec.1997)

• Diffusion can be slow due to strong interaction between the charged electrolyte species and conductive pore walls.


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Correlation of in-pore diffusion coefficients with EDLC resistance

Diffusion coefficients of Fc+ cations in various NP carbons (Rotating Disc Electrode measurements, see: A.J.Bard, L.R.Faulkner; Electrochemical

Methods. Fundamentals and Applications (2nd ed.); Wiley, 2001, p.335 )

NOTE: in bulk solution

Deff = 10.1×10-10 m2/s


Test results

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a) Also tested in ITS, UC Davis, CA; b) Also tested in JME, Cleveland, OH;c) Also tested in Wayne State University, Detroit, MI;d) Equipped with a proprietary voltage balancing system (patent pending).


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Recent Yunasko EDLC modules


15 V, 200 F:max working voltage 16.2 V max surge voltage 18.0 V dc pulse resistance 0.5 mΩmass 2.5 kg

equipped with a proprietary voltage balancing system and temperature sensor

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Yunasko competitive advantage: low heat generation

Continuous cycling the module over 8 hours

basic city duty cycle

ΔT:cells in the centre

cells at the edge


Time, s

V

A, charge

A, discharge

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Ragone plot: EDLC vs hybrid devices

1000 100000

5

10

15

20

25

30

35

40

Spec

ific

ener

gy, W

h/kg

Specific power, W/kg

Hybrid 2.7-1.35 V Hybrid 2.7-2.0 V Supercapacitor 650F 2.7-1.35 V


As tested in ITS, UC Davis, CA

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Hybrid cell: cycle life(charge/discharge between 2.7 and 1.35 V)


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Hybrid cell: temperature/rate performance

-40 -20 0 20 40 600

20

40

60

80

10050 0C25 0C

Dis

char

ge c

apac

ity, %

t, 0C

1 C 20 C 50 C

-30 0C


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Company background and prospects

Principal researchers participate in various supercapacitor projects since 1989

YUNASKO Ltd: registered in the UK since 2010

Subsidiaries:YUNASKO-Ukraine: R&D, design bureau and pilot plant since 2010YUNASKO-Latvia: industrial scale production will start in 2014


R&D team: breakthrough story

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Conclusions1. Electrochemical methods are a powerful

instrument to show a way to SC improvements.2. Yunasko technology* enables to significantly

reduce SC resistance and to achieve the power density up to 100 kW/kg.

3. Yunasko hybrid devices* demonstrate by far larger energy and power density than competing hybrids.

4. First industrial scale production will soon be launched.

5. Yunasko is open to cooperation with investors and industrial partners.

* US and EU patents pending

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Acknowledgements

Many thanks to Dr. Andrew Burke (ITS) and Prof. John R. Miller (JME) for stimulating discussions and valuable help in testing

Special thanks to Dekarta Capital Fund for investing in the Yunasko project

Participation in EU FP7 Energy Caps projectis very much acknowledged

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THANKS FOR YOUR ATTENTION! Please visit us at: www.yunasko.com

E-mail: [email protected]

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Y. Maletin , N. Stryzhakova , S. Zelinskiy , S. Chernukhin , D . Tretyakov , S. Tychina

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