NM03.05.04 Oral Presentation @ 2017 Fall MRS Meeting, Boston, MA, United States.

1. 1D Vanadium Oxide Nanowires:
Experimental Synthesis and Investigation of the
Electrochemical Behaviors for Energy Storage
Dr. Tianyu LIU
Yat Li Lab
Department of Chemistry and Biochemistry
University of California, Santa Cruz
11/2017
NM03.05.04

2. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Experimental Results and An Observation
 Further Investigations
 Summary

3. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Experimental Results and An Observation
 Further Investigations
 Summary

4. Supercapacitors
Electrochemical energy storage devices
ChargingTime
LiuT. et al., J. Mater. Chem.A, 2017, 5, 17705-17733
< 1s to ~100 s
~ hours
(Supercapacitors)
(Batteries)
vs.

5. Capacitance
𝐂𝐚𝐩𝐚𝐜𝐢𝐭𝐚𝐧𝐜𝐞(𝐅) =
Capacity (C)
Potential Window (V)
A measure of the
amount of charge (energy) stored
 A figure-of-merit of electrode materials for supercapacitors

6. Capacitance
Mechanisms
Electrical Double
Layer Capacitance
Pseudo-
capacitance
Activated Carbon,
CNT, Graphene etc.
Conjugated polymers,
metal oxides etc.
ES04.11.03
Wed, 8:45 am – 9:00 am
Hynes, Level 3, Ballroom A

7. Vanadium Pentoxide (V2O5)
Pseudocapacitance (in LiCl aqueous electrolyte)
V2O5 + 𝑥Li+
+ 𝑥𝑒−
↔ LixV2O5
VO5High charge storage capability
Ease of fabrication
Inexpensiveness
One-dimensional morphology
+
-
Current Collector
 Utilization efficiency
 Ion diffusion

8. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Stability Results and A Discovery
 In-depth Investigations
 Summary

9. The story begins with...
Structure Degradation
Instability
Li+
Peel off
 Soft substrates

10. The story begins with...
Chemical Dissolution
Instability
V2O5
H2VO4
-
HVO4
2-
Water Soluble V5+

11. The story begins with...
Chemical Dissolution
Instability
V2O5 VO2
H2VO4
-
HVO4
2-
V5+
V4+
Yu et al., Adv. Funct. Mater., 2015, 25, 3534-3540
Water Soluble

12. Instable
Vanadium Pentoxide
Stable
Soft substrates
Mixed valence states

13. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Experimental Results and An Observation
 Further Investigations
 Summary

14. Exfoliated Carbon Cloth
Commercialized
Carbon Cloth (CC)
0.5 M KNO3
1.9 V, 3 h
50 mL N2H4 (H2O)
50 oC, 1 h
Exfoliated Carbon Cloth
(ECC)
O
V
O
O
O
O
V
O
O
O
ECCCC

15. Introduction of Mixed-Valence States
b c
-1.5 V ~ 1.4 V, 50 cycles, 50 mV/s
0.1 M VOSO4, 0.2 M NH4OAc
-1.5 V, 1 min
a
2 μm
VOx
RVOx
ECC ECC/RVOx

16. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Experimental Results and An Observation
 Further Investigations
 Summary

17. Cycling Stability Performance
4 μm 200 nm
4 μm 200 nm
4 μm 200 nm

18. Cycling Stability Performance
?
?
Activation

19. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Experimental Results and An Observation
 Further Investigations
 Summary

20. Uptake of structural water
Investigation

21. Investigation
Uptake of structural water
Electrochemical Impedance
Spectroscopy (EIS)
Slope ∝(Diffusion
Resistance)-1

22. Outline
 Background of Supercapacitors
 Motivation –Vanadium Oxide
 Our Strategy
 Experimental Results and An Observation
 Further Investigations
 Summary

23. Summary
Pseudo-capacitive
Materials
1D Vanadium
Pentoxide
Uptake of
Structural Water
200 nm
Instability
Activation?

24. Acknowledgements
Prof. Yat Li Group, UCSC Dr. Yu Song

25. ES04.11.03
8:45 am – 9:00 am, 11/29
Hynes Level 3, Ballroom A
Carbon Aerogels with Multiscale Pores for
Supercapacitors
You are more than welcome to attend: