supercapacitors technical and physical basics of edlc
TRANSCRIPT
APEC 2019 in AnaheimCapacitor Workshop PSMA
SupercapacitorsTechnical and Physical Basics of EDLC
RenΓ© KalbitzProduct Manager Supercapacitor
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RenΓ© KalbitzProduct Manager, SupercapacitorseiCap / eiRis Capacitors and Resistors Division
β’ Experience inβ’ application-oriented researchβ’ development of organic electronics, β’ polymer analysis
β’ Responsible for Supercapacitors
Background:
+49 7942945 3501
www.we-online.com
Short Introduction of Todayβs Presenter
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Classification of Capacitors
Physical Processes
Model Parameters and Performance
Charge, Discharge and frequency behavior
Physical limitations of capacitance
Agenda
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Tradename / Synonyms:
4
Classification of Capacitors
APowerCap, BestCap, BoostCap, CAP-XX, EVerCAP, DynaCap, Goldcap, HY-CAP,
SuperCap, PAS Capacitor, PowerStor, PseudoCap, Ultracapacitor, Ultracap, ENYCAP, β¦
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Types of Supercapacitors, based on design of electrodes:
Double-layer capacitorsβ Electrodes: carbon or carbon derivatives
Pseudocapacitorsβ Electrodes: oxides or conducting polymers (high
faradaic pseudocapacitance) Hybrid capacitors
β Electrodes: special electrodes with significant double-layer capacitance and pseudocapacitance
5
Classification of Capacitors
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Batteries
β’ High energy capacityβ’ Constant voltage dependence
β’ low power outputβ’ low life expectancy (β 1000 cycles)β’ long charging time (hours)
Supercaps
β’ fast charging and discharging (min β sec)β’ high life cycle (β 500,000 cycles)β’ high power output
β’ β ππππ times higher than Li-ion battery
β’ low energy capacity β’ β 30 times lower than Li-ion battery
β’ linear voltage dependence
Supercaps vs. Batteries and Caps
Capacitors
β’ fast charging and discharging (βͺ sec)
β’ high life timeβ’ high operating voltagesβ’ high power output
β’ low energy capacity
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Discharged State:1) no voltage is applied to electrodes2) anions and cations are in close
vicinity to each other3) Movement of anions and cations
governed by electrostatic interaction and diffusion processes
Amp-Meter
Neg Pos0
A-+
electrolyte
Energy Storage - Charge Separation
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Charging:1) voltage between plates (i.e.
electric field) is applied2) electric field βtearsβ charges
apart3) movement of the charges
causes a current, provided by the voltage source
Amp-Meter
Neg Pos0
A-+
Energy Storage - Charge Separation
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A
-+ +-
Amp-Meter
Neg Pos0
Fully charged:1) anions and cations reach
interface/electrode2) Reorientation of charges comes
to hold3) Each anion/cation is mirrored
by a opposing positive/negative charge at the electrode
mirror-chargeEnergy Storage - Charge Separation
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A
-+ +-
Amp-Meter
Neg Pos0
Open circuit:1) Each anion/cation is balanced by an
equal amount of mirror charge at the interface
2) Anions and cations reside a the interface
3) Charges can be stored at interface for a long time
Energy Storage - Charge Separation
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A
-+ +-
Amp-Meter
Neg Pos0
Discharge process:1) circuit is closed 2) potential difference between the plates,
causes electrical current at a certain voltage
3) Anion/cations βlooseβ their mirror charge, leading to charge movement
4) The quicker the anions/cations can be released, the larger the current
Energy Storage - Charge Separation
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AAmp-Meter
Neg Pos0
-+
Discharged State:1) no voltage is applied to electrodes2) anions and cations are again in
close vicinity to each other3) movement of anions and cations
governed by electrostatic interaction and diffusion processes
Energy Storage - Charge Separation
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Structure of EDLCH
elmholtz (double) layer:
β’Ionic charge is balanced by m
irror-charge
ππ+ π π
π π
π π
π π
ππβ
++
+ +
+
+
---
--
-- +
+ + + + + + + + +
+ + + + + + + + +
Electrolytic System:β’ Ammonium salt with
counter ion
β’ Acetonitrile Pore / Capillary
separator paper
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Structure of EDLCs
+
+++
+
++
---
----
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++
+ +
+
+
---
--
-- +
Physical Processes and Parameters
πΆπΆ+ πΆπΆβ
π π ππβπ π ππ+
π π π π
1πΆπΆ+
+1πΆπΆβ
=1ππ
π π π π ~ πΉπΉπ¬π¬π¬π¬πΉπΉ
π π π π + π π ππ+ + π π ππβ ~ πΉπΉπ³π³π³π³π³π³π³π³
ππ πΉπΉπ¬π¬π¬π¬πΉπΉ
πΉπΉπ³π³π³π³π³π³π³π³
equivalent circuit equivalent circuit
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Parameter and Performance
πͺπͺ πΉπΉπ¬π¬π¬π¬πΉπΉ
π π πΏπΏπΏπΏπΏπΏπΏπΏ
Basic Parameters:β’ πΌπΌππ, Rated Voltage:
β is not determined by the equivalent circuit but by electrochemistry (Decomposition Voltage)β Non-Aqueous Electrolyte (typ.):
β 2 ππ β¦ 3ππβ Aqueous Electrolyte (typ.):
β 1.5 ππ
β’ πͺπͺ, Capacitance: β’ πΉπΉπ¬π¬π¬π¬πΉπΉ, ESR:
β’ πΉπΉπ³π³π³π³π³π³π³π³, Leakage: β Influence on charge storing
capabilities (π π πΏπΏπΏπΏπΏπΏπΏπΏ β 10 kΞ©β¦ 1 MΞ©)
Performance Parameters:β’ Energy storage capacity:
πΈπΈ =12
Γ πͺπͺ Γ πΌπΌππππ
β’ Maximum Power output:
πππππΏπΏππ =πΌπΌππππ
4 πΉπΉπ¬π¬π¬π¬πΉπΉβ’ Characteristic R-C Time:ππ = πΉπΉπ¬π¬π¬π¬πΉπΉ Γ πͺπͺ
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πππ π
Time (sec)
Volta
ge(V
)
Charge Rest/Self Discharge
~πΌπΌπΏπΏπΏπΏπΏπΏπΏπΏ
Discharge
CapacitorBattery
Charge and Discharge Behavior
Time (sec)
Cur
rent
(A)
ππ =πΌπΌππβπͺπͺ
Γ π‘π‘
πΌπΌπππππ π πΌπΌππβ
πΌπΌππβ,πππππ π ~1
π π πΈπΈπΈπΈπ π
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Source: Wikipedia: βhttps://en.wikipedia.org/wiki/Dielectric_spectroscopyβ
Dielectric (impedance) spectroscopy:β’ βmeasuresβ polarizability of a medium as
a function of frequency
Impedance Spectra
Range of interest: 1 mHz β¦ 1 MHz
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Impedance Spectra
Fit results:πΉπΉπ¬π¬π¬π¬πΉπΉ = 0.011 Ξ©,ππ = 50.3 F
πͺπͺ β ππππππ
12ππ πΉπΉπ¬π¬π¬π¬πΉπΉπͺπͺ
β 0.29π»π»π»π»
πΉπΉπ¬π¬π¬π¬πΉπΉ β 7 mΞ©
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Physical Limitations of Capacitance
Source: Activated carbon based electrodes in commercial supercapacitors and their performance, V. Obreja et al., International Review of Electrical Engineering (2010)
πΆπΆππ
~π΄π΄ππ
πΆπΆ: capacitanceππ: mass of a.c.π΄π΄: specific area of a.c.
Specific surface area of a. c.:π΄π΄β = π΄π΄
ππm2
g
Specific capacitance of a. c.:πΆπΆβ = πΆπΆ
ππFg
m [g] π΄π΄β m2
g π΄π΄ [m2] πΆπΆβ Fg πΆπΆ [F]
Comm.2.2
500 1120 24 54Micro. 935 2095 142 318Micro. 2312 5179 113 253
Example of calulation: 50F EDLC contains β 2.2 g a. c.
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Pore Accessibility:
Source: Supercapacitors Materials, Systems and Applications, ed. F. Beguin et al., WILEY-VCH (2013)
Physical Limitations of Capacitance
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β’ fast charging and discharging (min β sec)β’ high power output
β’ β 10 times higher than Li-ion battery
β’ low energy capacity β’ β 30 times lower than Li-ion battery
β’ linear voltage dependenceβ’ low operating voltage
Parameters β Device Properties
ππ = πΉπΉπ¬π¬π¬π¬πΉπΉ Γ πͺπͺ βlow πΉπΉπ¬π¬π¬π¬πΉπΉ β
charges are only stored at the interface β
ELDC are capacitors βπππ«π« < Decomposition Voltage β
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Thank you for your attention.
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Additional Slides / Take Outs.
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πΈπΈ = 12
Γ πΆπΆ Γ ππππ2 ,
Parameter and PerformanceSp
ecifi
c Po
wer
, ππ ππ
ππππ
πππππππππππΏπΏ
[W/l]
Specific Energy, πΈπΈπππππππππππΏπΏ
[W/l]
Fuel cell
Batteries
Super-capacitors
Capacitors
ππ(πΈπΈ) =2
π π πΈπΈπΈπΈπ π Γ πΆπΆπΈπΈπΉπΉπ¬π¬π¬π¬πΉπΉ Γ πͺπͺ determines power
for a given energy capacity
πͺπͺ and πΌπΌππ determine the energy capacity
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πΏπΏπ³π³ = ππ Γ π³π³π¬π¬π¬π¬π³π³
πΏπΏπͺπͺ = βππ
ππ Γ πͺπͺ
οΏ½ππ = πΉπΉπ¬π¬π¬π¬πΉπΉ + πππΏπΏπ³π³ + πππΏπΏπͺπͺ
β’ inductive reactance (neglectable)
β’ impedance
β’ electrical model is equal to that for MLCC, ELKOs, β¦
β’ capacitive reactance
no influence on frequency dependence
Impedance Spectra
πͺπͺ πΉπΉπ¬π¬π¬π¬πΉπΉ
π π πΏπΏπΏπΏπΏπΏπΏπΏ
π³π³π¬π¬π¬π¬π³π³
π·π·π·π· = tan(πΏπΏ)
ππβππ
ππ Γ πͺπͺ
πΉπΉπ¬π¬π¬π¬πΉπΉ
πΏπΏ
ππ Γ π³π³π¬π¬π¬π¬π³π³
πΌπΌππ
π π π π 0
οΏ½ππ =1
jπποΏ½πͺπͺοΏ½πͺπͺ =
πͺπͺ1 + ππ πΉπΉπ¬π¬π¬π¬πΉπΉ πͺπͺ 2 β ππ
πππͺπͺ2πΉπΉπ¬π¬π¬π¬πΉπΉ1 + πππΉπΉπ¬π¬π¬π¬πΉπΉ πͺπͺ 2
ππ = 2ππππ, β1 = ππ