Post on 02-Sep-2021
transcript
Progress of Biochar Supercapacitors
Junhua Jiang
1st Midwest Biochar Conference June 14, 2013
Acknowledgement
Management team and staff at the ISTC (Nancy Holm, Ed Delso, Xinying Wang, John Scott, et al.)
Illinois Hazardous Waste Research Fund Dr. Lei Zhang and Prof. Frank Chen at the University of South
Carolina
Staff at the Beckman Institute, the Frederick Seitz Materials Research Laboratory, and the Illinois State Geological Survey of the UIUC
Supercapacitor Applications
Traditional market • Electronics: camera, flashlights, PC
cards, portable media players, and automated meter reading equipment
• Telecom and others: Complementing
batteries (uninterruptible power supplies, handle short interruptions)
Emerging market
• Transportation (electric vehicles, buses, aerospace)
• Energy storage
Supercapacitor Energy Storage
Energy storage-conversion Ragone plot Efficiency-lifetime properties
Industry Outlook
2005 2010 2015 20200
2
4
6
US$bn
0.20.5
1.2
5.0
14% CAGR
21% CAGR
33% CAGR
Source: Daiwa forecast
Due to its fast charge-discharge capability (power density), we expect ultracapacitor use to rise along with batteries for future EV and ESS applications.
New materials are being
developed that should lead to the energy density of ultracapacitors increasing.
We forecast the ultracapacitor
market to expand tenfold, from US$0.5bn in 2010 to US$5.0bn by 2020.
CAGR: Compound annual growth rate
Cost Breakdown
Production cost 50%
15%
10%
25% Packaging
Separator
Electrolyte
Electrode
Material cost
Cost is the key market consideration and barrier for mass adoption.
Materials account for a large portion of overall costs compared to other storage
technologies.
Electrodes account for a significant portion of the materials.
Biochar electrode
Human hair
Potential low cost $0.1/kg vs $5/kg for activated carbon
Low carbon footprint Highly developed surface
area (~400 m2 g-1)
Excellent chemical and electrochemical stability
High conductivity High utilization of
surface area
Biochar Electrode
High-Carbon Zero-Ash Biochar
E / KeV
Element Wt % At % K-Ratio
C K 97.64 98.22 0.9637
O K 2.36 1.78 0.0071
Total 100 100
Electrical Conductivity
Sample Conductivity / S cm-1
Biochar 1.0 ~ 50
Vulcan 3 38.0
Vulcan 6 26.2
Black pearls 880 32.0
Black pearls 1300 34.1
Black pearls 2000 7.0
Sterling V 21.2
Graphite 300
t / oC
Porous model
Macropores (> 50 nm)
Mesopores (2 ~ 50 nm)
Micropores (< 2nm)
X-ray Computed Tomography of Corn Cob Biochar
nm diameter pore
nm thickness wall Wood-ring
Chaff
Woody Ring
Pith
CT of Corn Cob Pith
Softwood Biochar
Hardwood Biochar
Original Biochar Supercapacitor
-0.750 -0.500 -0.250 0 0.250 0.500 0.750-3-0.125x10
-3-0.100x10
-3-0.075x10
-3-0.050x10
-3-0.025x10
0
-30.025x10
-30.050x10
-30.075x10
-30.100x10
-30.125x10
E / V
I /
A
5000 scans
Typical supercapacitor responses
Fast charge-discharge bahavior
Good lifetime
Low environmental impact
Low cost
However, specific capacitance is low (10~20 F g-1)
200 mV s-1
Pseudocapacitance
Activity of O-groups
E
I
De
crease
in activity
Activation of Biochar
Black: Untreated
Red: HNO3-treated
-0.500-0.250 0 0.250 0.500 0.750 1.000 1.250-2-0.100x10
-2-0.075x10
-2-0.050x10
-2-0.025x10
0
-20.025x10
-20.050x10
-20.075x10
E / V
I /
A
Current-potential curve
Untreated
HNO3-treated
0 50.0 100.0 150.0 200.0 250.0 300.0-0.500
-0.250
0
0.250
0.500
0.750
1.000
1.250
t / s
E /
V
Constant current charge-discharge
0.5 A g-1
Raman and FTIR Patterns
0 1000 2000 3000 4000
ID/I
G=1.05
ID/I
G=1.18
D+G
D*
G
D
Inte
nsit
y / a
.u.
Wavenumber / cm-1
Untreated
HNO3-treated
Capacity of Biochar in Aqueous Electrolyte
Electrode material Specific capacitance
(F g-1) BET Surface area
(m2 g-1)
Activated Biochar 100 to 300 300~400
Carbon black 100 to 300 1000~2000
Activated carbon 100 to 400 1000~3000
Mesoporous carbon 100 to 200 1500~2500
Reduced graphene oxide 150 to 250 2000~3000
Multiwall carbon nanotube 100 to 150 500~1000
Single-wall carbon nanotube 100 to 200 1500~2000
Source: Zhang & Zhao, ChemSusChem, 5 (2012) 818-841.
Electrolyte Dependence
Solvent Or salt
Anode potential limit / V
Cathode potential limit / V
Potential window /
V
Water -0.20 1.2 1.4
Acetonitrile -2.8 3.3 6.1
Propylene carbonate
-3.0 3.6 6.6
TEABF4 -3.0 3.65 6.65
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5-0.005
-0.004
-0.003
-0.002
-0.001
0.000
0.001
0.002
0.003
0.004
0.005
0.5 M H2SO
4
BMIBF4
1 M KOH
Cu
rre
nr
/ A
Potential / V
1.4 V
2.7 V
*Potential vs SCE.
Source: Aurbach et al, Nonaqueous electrochemistry,
Marcel, 1999
Maximum energy stored
Emax = CV2/2 (V: cell operating voltage)
Specific Capacity of Biochar in non-Aqueous Electrolyte
Electrode material Specific
capacitance (F g-1)
Surface area (m2 g-1)
Biochar in TEABF4 75 400
Biochar in TEAPF6 35 400
Biochar in TBAPF6 30 400
Activated carbon TEABF4 90 to 140 1000 to 1400
Mesoporous carbon in TEABF4 70 to 160 1500 to 2000
Graphene in TEABF4 100 ~3000
Carbon nanotube in TEABF4 80 to 110 ~2000
Source: J. Zhang & X. Zhao, ChemSusChem 5 (2012) 818-841.
Charge Transport Model
0 25 50 75 100 125 150 175 2000
25
50
75
100
125
150
175
200
Z' / ohm
-Z'' / o
hm
AC impedance spectra
R1
Q1
C
ZW R2
Zw: Warburg transport resistance
Medium
BC Cathode
-
-
-
Charged Discharged
Medium
BC Cathode
-
-
-
-
- -
-
-
Charge transport within a single pore
Conclusions
Biochars have finger-print microstructures inherited their corresponding biomass precursors;
Low ash even zero-ash high carbon bichars can be prepared from wood feedstocks;
Biochar supercapacitors have demonstrated promising capacity and durability which are comparable to those of using advanced carbon materials, especially in aqueous media;
Surface activation of biochars substantially increases their capacitance and degree of surface utilization;
Woody biochars with developed surface area, good conductivity, electrochemical stability, and interesting pore network will be promising energy and environmental materials.