Optimizing performance of supercapacitors via PVDF gel electrochemical separators Travis G. Martin1, Amir Reza Aref2, Dr. Ramakhrisnan Rajagopalan2,

Bellwood-Antis Middle School1, Department of Engineering Sciences2, Materials Research Institute

Research Experiences for Teachers and Young Scholars in Advanced Self-Powered Systems of Integrated Sensors and Technologies

(ASSIST)

The ASSIST RET and Young Scholar programs are funded by NSF nanosystems engineering research center grant EEC 1160483.

Batteries vs. Supercapacitors

Though low in energy, supercapacitors offersignificantly higher power densities. (1)(2)(3)

Charge times are significantly faster than batteries,often less than 1 second. (1)(2)(3)

Life cycle is exponentially longer than commercialbatteries. (1)(2)(3)

(1) Simon, Patrice and Gogosti, Yury and Dunn, Bruce. Where Do Batteries End and Supercapacitors Begin? (2014) Science Magazine, vol. 343 (n 6176). Pp 1210-1211. ISSN 0036-8075

(2) Simon, Patrice and Gogosti, Yury. Materials for electrochemical capacitors. (2008) Nature, vol. 7. Nov 2008. (3) US Defense Logistics Agency(4) Hun Lee, Meltem Yanilmaz, Ozan Toprakci, Kun Fu and Xiangwu Zhang A review of recent developments in

membrane separators for rechargeable lithium-ion batteries. (2014) Energy Environ. Sci., vol. 7, 3857(5) A .Aref, J. Chou, S. Berbano, R. Rajagopalan, C. Randall. Development of high energy density electrochemical

capacitor for energy harvesting application. (2015) ASSIST Research Update Poster(6) Feng Zang, Xilan Ma, Chuanbao Cai, Jili Li, Youqi Zhu Poly(vinylidene fluoride)/SiO2 composite membranes

prepared by electrospinning and their excellent properties for nonwoven separators for lithium-ion batteries. Journal of Power Sources.(2014). Vol. 251, 423- 431

*Diagonals represent charge time

Present Research

Polymer Solution

Pore Development

Vacuum Dry

Cast

Study FindingsRationale

Additives, such as SiO2, may improve durability. (6) Breath-Figure method may be altered to improve exposure

of polymer to humidity (i.e. increase air current flow)

Dr. Rajagopalan and his lab colleagues (Amir, Miriam, REUs) Dr. Mathew Johnson, Dr. Annemarie Ward, Kathleen Hill, & Amanda Smith (CSATS); Lori Piper & Kelly Forrest (RETs), Hannah Schuster & Ben Martin (Young Scholars)

Separator Synthesis-Breath Figure Method

Structure-Thickness

Supercapacitor Design Limitations

Optimal Synthesized Separator

Further Research

References

Acknowledgements

Composition- Polymer Solution [ ]

9mL:1mL

12mL:1.5mL

12mL:2mL

Synthesized vs. Commercial Separator

0 10 20 30 40 50 60

1

1.5

2

ETH

ANO

L (M

L)

Polymer Solution Concentration

Porosity

Electrolyte Uptake= %/10 for formatting purposes

Separator Polymer Porosity (%) Electrolyte Uptake (%)

Ionic Conductivity (S/cm)

PVDF (Experimental-9mL Acetone/1mL Ethanol) 60 1,024 2.09 x 10-3

PVDF (Commercial) 72* 420.86* 7.47x10-3 **

b

b

p

p

b

b

mm

m

ρρ

ρε

+=

Electrolyte Uptake omitted due to folding of polymer

0

10

20

30

40

50

60

0

20

40

60

80

100

120

140

160

180

5 10 15

PORO

SITY

(%)

ELEC

TRO

LYTE

UPT

AKE

(%)

THICKNESS (RELATIVE)

Polymer Thickness

Electrolyte Uptake Porosity

*Tested in lab **Highest in literature (6)

SEM Image

Commercial Polymer remains superior in performance.

1. Electrode ion uptake2. Electrolyte affinity for electrodes3. Ability of separator to perform ion exchange

between electrodes.

Optimal Polymer [ ] = 9mL Acetone:1mL Ethanol Optimal Polymer Thickness = 15 µm

FOCUS: Supercapacitor Separator1. Improve supercapacitor performance by optimizing

separator composition and structure.2. Develop polymer superior to commercially available

separator. Separator Performance Indicators:

- Porosity (Allows ion exchange)- Electrolyte Uptake - Ionic Conductivity

Acetone: EthanolPVDF (1g) +PVDF= Polyvinylidene fluoride

5, 10, 15 µm