Dr. Natalia Stryzhakova Dr. Yurii Maletin Dr. Sergiy Zelinskiy

1. Methodology for supercapacitor performance measurements Dr. Natalia Stryzhakova Dr. Yurii Maletin Dr. Sergiy Zelinskiy

2. Methodology for supercapacitor performance measurement FreedomCAR Ultracapacitor Test Manual. Idaho National Laboratory Report DOE/NE-ID-11173, September 21, 2004. IEC 62391-2 . Fixed electric double layer capacitors for use in electronic equipment. Part 2. Sectional specification – Electric double layer capacitors for power application. IEC 62576. Electric double layer capacitors for use in hybrid electric vehicles – Test methods for electrical characteristics. A. Burke, M. Miller. Testing of Electrochemical Capacitors: Capacitance, Resistance, Energy Density, and Power Capability. ISEE’Cap09 Conference, Nantes, 2009. A. Burke, M. Miller. Testing of Electrochemical Capacitors: Capacitance, Resistance, Energy Density, and Power Capability. Idaho National Engineering Laboratory Report DOE/ID-10491, October 1994. S. Zhao, F. Wu, L. Yang, L. Gao, A. Burke. A measurement method for determination of dc internal resistance of batteries and supercapacitors. Electrochemistry Communications, 2010, v.12, p.242-245. A. Burke. Testing Large Format Electrochemical Capacitors. Tutorial of ISEECap2011, Poznan, Poland, June 12, 2011. References

3. Methodology for supercapacitor performance measurement • Rated voltage, Ur (V) • Capacitance, C (F) • Internal resistance, R (Ohm) • Specific energy, E (Wh/kg) • Specific power, P (W/kg) • Specific energy vs. Specific power (Ragone plot) • Resistance and capacitance vs. temperature (-40…+70 ºC) • Cycle life • Self discharge • Calendar life (hours) at rated voltage and high temperature (60 ºC) Main characteristics of a supercapacitor unit cell

4. Methodology for supercapacitor performance measurement • Constant current charge/discharge • Capacitance and resistance • Cycle life • Pulse tests to determine resistance • Constant power charge/discharge • Ragone Plot for power densities between 100 and at least 1000 W/kg for the voltage between Ur and ½ Ur. • Test at increasing W/kg until discharge time is less than 5 sec. The charging is often done at constant current with a charge time of at least 30 sec. • Voltage maintenance • Self discharge test • Continuous application of rated voltage at high temperature • Endurance test (calendar lifeestimation) Test procedures

5. Methodology for supercapacitor performance measurement Test procedure: Constant current charge/discharge USABC test procedure Capacitance • Current of 5C corresponds to 12 min discharge • IMAXcan be chosen as the lowest of: (a) the current required to cause an immediate ( <0.1 s) 20 % voltage drop in a fully charged device at 30 ºC, or (b) the current required to discharge the device from UMAXto UMINwithin 2 s. • At least 5 cycles at each current value

6. Methodology for supercapacitor performance measurement Test procedure: Constant current charge/discharge IEC procedure (# 62576) Capacitance Single test to determine the capacitor performance at a single current – so that the efficiency in charge and discharge to be of 95%.

7. Methodology for supercapacitor performance measurement Test procedure: Constant current charge/discharge UC Davis procedure (ITS, Dr.A.Burke) Capacitance 1) The nominal charge/discharge current Incorresponding to nominal power density (200 or 400 W/kg) 2) A set of current values: 0.25, 0.5, 1.0, 2.0, 4.0, 8.0In

8. Methodology for supercapacitor performance measurement Test procedure: Constant current charge/discharge Yunasko procedure Capacitance 1) A set of current values from 0.2Itestto Itest.; Itest 200 A 2) From С = f(I) plot the С0 max capacitance value (extrapolation to zero current) and -dC/dI value (the slope) can be found. NOTE: The -dC/dI slope characterizes the system behavior at high power loads and depends on electrode material and system design.

9. Methodology for supercapacitor performance measurement • Conclusions: • Capacitance value depends on test conditions, though, not dramatically. • Testing current conditions differ significantly: Capacitance 9

10. Methodology for supercapacitor performance measurement Internal resistance • Equivalent Series Resistance (ESR) - the resistance due to all the resistive components within the supercapacitor. • Equivalent Distributed Resistance (EDR) includes ESR and an additional contribution from the chargeredistribution processin the electrode pore matrix due to non-homogeneous electrode structure, the process adding significantly to Joule heating: I2Rt. 10

11. Methodology for supercapacitor performance measurement Test procedure: Constant current method, sampling rate of 10 ms Internal resistance 11

12. Methodology for supercapacitor performance measurement Internal resistance ESR is independent of current value. EDR value depends on testing current 12

13. Methodology for supercapacitor performance measurement Measurements using the voltage recovery after current interruption (Maxwell procedure) Internal resistance 13

14. Methodology for supercapacitor performance measurement Yunasko procedure Internal resistance 14

15. Methodology for supercapacitor performance measurement Pulse procedure (Arbin) Internal resistance Rpulse = Average (Voltage at P2 – Voltage at P3) / (2 I). 15

16. Methodology for supercapacitor performance measurement Comparison of different procedures: Internal resistance Conclusions: Internal resistance measurements involve different time intervals to fix the voltage drop/jump. Resistance values depend on test conditions, in particular, on time interval and testing current chosen. 16

17. Methodology for supercapacitor performance measurement Test procedure: Constant power tests 1) Power values between 200 and at least 1000 W/kg Specific energy and power 2) For each constant power test, the energy is calculated as E = U×I×Δt during charge and discharge. The usable specific energy Em (Wh/kg) The efficiency η: Ragone plot: a plot illustrating Em (or Ev) vsPm (or Pv)

18. Methodology for supercapacitor performance measurement Test procedure: Constant power tests, Ragone plot Specific energy and power

19. Methodology for supercapacitor performance measurement Maximum energy stored - the energy that can be obtained at discharge from the rated voltage to zero: Specific energy and power Available energy - at discharge from the rated voltage Ur to Ur/2

20. Methodology for supercapacitor performance measurement Maximum power (matched impedance power) - the power that can be delivered to the load of the same resistance as a supercapacitor. Specific energy and power Power density according to IEC 62391-2: where U6=0.2U (20%) Ue=0.4U (40%) The power at efficiency η and at discharge from the rated voltage Ur to Ur/2: NOTE: YUNASKO normally uses the η value of 0.95

21. Methodology for supercapacitor performance measurement The time dependence of the capacitor self-dissipation, i.e., the rate of internal processes that cause the capacitor discharge when not connected to a load. Self-discharge test where B is the voltage maintenance rate (%)

22. Methodology for supercapacitor performance measurement Self-discharge test - example where B is the voltage maintenance rate (%)

23. Methodology for supercapacitor performance measurement • Stable performance over more than 100,000 charge/discharge cycles is desired. Constant-current charge and discharge are used. • Typical procedure: • Condition the capacitor at 25 ± 3°C. • Charge the device by a current I chosenso that the voltage reaches Urin 30 s. • Maintain voltage Urof the device for 15 s. • Then discharge the capacitor to Uminwith current I. • Hold the capacitor at Uminfor 50 s. • Repeat cycling. • Devices shall be characterized initially and after 1000; 4000; 10,000; 40,000; 100,000 cycles. • Characterization tests to be performed at each measurement cycle include: • 1. Constant-Current Charge/Discharge (In) • 2. ESR (from constant-current test data) • 3. Constant Power Discharge (200 W/kg, 1000 W/kg) Cycle-life test

24. Methodology for supercapacitor performance measurement Cycle-life test – SC example Cycling a 1200F device between 2.0 and 3.2 V at 60 °C

25. Methodology for supercapacitor performance measurement Cycle-life test – hybrid capacitor example

26. Methodology for supercapacitor performance measurement • Temperature influences the energy that can be stored in a device as well as the power it can deliver. • Typical procedure: • Step 1 - Condition the device at 25±3°C and perform the followed tests: • 1. Constant-Current Charge/Discharge (In) • 2. ESR (from constant-current test data) • 3. Constant Power Discharge (200 W/kg, 1000 W/kg) . • Step 2 - Condition the capacitor at 60 ± 3°C until thermal equilibrium is achieved. Perform the above mentioned tests at this temperature. • Step 3 - Condition the capacitor at -30 ± 3°C until thermal equilibrium is achieved. Perform the above mentioned tests at this temperature . • Step 4 - Condition the capacitor at 25 ± 3°C and repeat the tests listed above. This test data will provide information about the stability of the capacitor under thermal cycling conditions. • Step 5 - Perform a visual inspection of the capacitors to identify any damage or electrolyte leakage caused by the thermal cycle Temperature Performance

27. Methodology for supercapacitor performance measurement Hybrid EDLC Temperature performance

28. Methodology for supercapacitor performance measurement • This procedure characterizes device life properties and performance using an accelerated aging condition. • Typical procedure: • Device properties and performance are measured initially and then periodically throughout the aging period. • Age the capacitors in a suitable oven or environmental chamber maintained at 60 ± 3°C with an applied voltage equal to Ur. • Characterization tests of the devices should be performed at the start of the test sequence and after 250 ± 10, 500 ± 25, 1000 ± 50, and 2000 ± 100 hours. Measurements are made at 25 ± 3°C. • 1. Constant-Current Charge/Discharge (In) • 2. ESR (from constant-current test data) • 3. Constant Power Discharge (200 W/kg, 1000 W/kg) Endurance test

29. Methodology for supercapacitor performance measurement Endurance test

30. Methodology for supercapacitor performance measurement • There is a need to further standardization of test procedures. • The largest uncertainty is related with the resistance measurements. • The effective capacitance of carbon/carbon devices is well-defined from constant current tests, but varies with the voltage range used; it is recommended the voltage range of Vr and Vr/2 to be used. • Further work is needed to define the effective capacitance and resistance of hybrid capacitors. • The energy density should be measured at the constant power discharge; this is especially the case for hybrid capacitors • Definition and determination of maximum power capability of both supercapacitors and lithium batteries remains a very confused issue (A.F. Burke) Conclusions

31. Methodology for supercapacitor performance measurement Acknowledgements Special thanks to my R&D and Design Bureau colleagues: S.Podmogilny, S.Chernukhin, S.Tychina, D. Gromadsky, O.Gozhenko, A.Maletin, D.Drobny, and A.Slezin Our Pilot Plant and Administrative Department: For the great support, diligence and dedication to work YUNASKO investment, technical, scientific and industrial partners: For the great collaboration and support during the projects Many thanks to Dr. Andrew F. Burke (ITS) and Dr. John R. Miller (JME) for their measurements and stimulating discussions Financial support from FP7 Project no. 286210 (Energy Caps) is very much acknowledged

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