Post on 22-Feb-2016
description
transcript
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
2
How Electrochemical Science Can Improve the EDLC Performance
3
How Electrochemical Science Can Improve the EDLC Performance
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
4
How Electrochemical Science Can Improve the EDLC Performance
CV: scanning the electrode potential to (+)
5
How Electrochemical Science Can Improve the EDLC Performance
• 0V corresponds to the equilibrium potential• scan rate: 10 mV/s
NOTE: potential range with Faraday processes cannot be used for long
6
CV curves: A - 3-electrode cell B - SC prototype
How Electrochemical Science Can Improve the EDLC Performance
A
B
2.43.1
How Electrochemical Science Can Improve the EDLC Performance
Charge accumulated in (-) or (+) potential range
7
Hybrid cell: CC charge-discharge curves
8
How Electrochemical Science Can Improve the EDLC Performance
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)
1
2
3
23
How Electrochemical Science Can Improve the EDLC Performance
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
How Electrochemical Science Can Improve the EDLC Performance
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
11
How Electrochemical Science Can Improve the EDLC Performance
TEM image of carbon powder
12
Slit-shaped pores or just shear cracks of graphene layers
How Electrochemical Science Can Improve the EDLC Performance
Why the in-pore electrolyte mobility is slow?
13
• 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.
How Electrochemical Science Can Improve the EDLC Performance
14
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
How Electrochemical Science Can Improve the EDLC Performance
Test results
15
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).
How Electrochemical Science Can Improve the EDLC Performance
16
Recent Yunasko EDLC modules
How Electrochemical Science Can Improve the EDLC Performance
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
17
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
How Electrochemical Science Can Improve the EDLC Performance
Time, s
V
A, charge
A, discharge
18
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
How Electrochemical Science Can Improve the EDLC Performance
As tested in ITS, UC Davis, CA
19
Hybrid cell: cycle life(charge/discharge between 2.7 and 1.35 V)
How Electrochemical Science Can Improve the EDLC Performance
20
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
How Electrochemical Science Can Improve the EDLC Performance
21
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
How Electrochemical Science Can Improve the EDLC Performance
R&D team: breakthrough story
22
How Electrochemical Science Can Improve the EDLC Performance
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
23
How Electrochemical Science Can Improve the EDLC Performance
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
24
How Electrochemical Science Can Improve the EDLC Performance
THANKS FOR YOUR ATTENTION! Please visit us at: www.yunasko.com
E-mail: ymaletin@yunasko.com
25