Transcript Capacitive Storage Science

Capacitive Storage Science
Chairs: Bruce Dunn and Yury Gogotsi
Panelists:
Michel Armand (France)
Martin Bazant
Ralph Brodd
Andrew Burke
Ranjan Dash
John Ferraris
Wesley Henderson
Sam Jenekhe
Katsumi Kaneko (Japan)
Prashant Kumta
Keryn Lian (Canada)
Jeff Long
John Miller
Katsuhiko Naoi (Japan)
Joel Schindall
Bruno Scrosati (Italy)
Patrice Simon (France)
Henry White
p. 1
Capacitive Storage Science
Supercapacitors bridge between batteries and conventional capacitors
Supercapacitors are able to attain
greater energy densities while still
maintaining the high power density
of conventional capacitors.
Supercapacitors provide versatile
solutions to a variety of emerging
energy applications including
harvesting and regenerating
energy in transportation, industrial
machinery, and storage of wind,
light and vibrational energy. This
is enabled by their sub-second
response time.
*Halper, M.S., & Ellenbogen, J.C., MITRE Nanosystems Group, March 2006
p. 2
Capacitive Storage Science:
technology challenges
 Capacitor Systems and Devices
- Increased energy density
- Longer life cells
- Self-balancing
- Cost
 Electrolytes for Capacitor Storage
30 MJ CAPACITOR STORAGE SYSTEM
Design electrolytes for EC operation: high ionic conductivity;
wide electrochemical window, chemical and thermal stability; non toxic,
biodegradable and/or renewable
 EDLC and Pseudocapacitive Charge Storage Materials
New strategies are needed to improve power and energy density of charge
storage materials
p. 3
Capacitive Storage Science:
current status
 Capacitor Systems and Devices
High specific capacitance (100 F/g) and fast response time (~ 1 sec),
but energy storage (2-10 wh/kg) not sufficient for many apps
Long shelf (10 yr) and cycle (>1M) life
 Electrolytes for Capacitor Storage
Traditional Electrolytes:
- aqueous (KOH, H2SO4) - corrosive, low voltage
- organic (AN or PC and [Et4N][BF4] or [Et3MeN][BF4]) - low
capacitance, toxicity and safety concerns
Ionic Liquid Electrolytes - safer, but viscosity too high, conductivity too low
for capacitor applications; improvements in properties from mixing with
organic solvents
 Theory and Modeling Variety of approaches available – continuum, atomistic,
ab initio; all have advantages and limitations
p. 4
Capacitive Storage Science: current
EDLC Charge
Storage Materials:
Majority of present day
EDLC devices are based
on activated carbon
Specific Capacitance / F g-1
status
1400
1200
RuO2/PAPPA
1000
RuO2(sol-gel)
800
600
400
0
RuO2(ED)
2
RuO2(sol-gel)
RuO2/AC
RuO2/AC
RuO2(ESD)
RuO2/CB
MPC C60 CAG NRC
CNT
200
MnO
MPFPT
PAn/CNT
DAAQ
P3MT
PEDT
AC
PFDT
PAn
PIThi
PPy/AC
PEDT/AC
Carbons
Polymers
Ir0.3Mn0.7
O2
MnO2
NiO/RuO2
NiO
PANI/AC
MnOx
NiO
MnO2
RuO2/CNT
RuO2/AC
RuO2/CXG
RuO2/AC
RuO2/MPC
SnO2 / Fe3O4
Metal Oxides
RuO2
Multifunctional Materials for Pseudocapacitors:
Pseudocapacitive materials generally exhibit higher specific capacitance and
energy density relative to high-surface-area carbon
p. 5
Capacitive Storage Science:
basic-science challenges, opportunities, and needs
 EDLC Charge Storage Materials
- Materials utilizing only double layer storage
require understanding of pore structure and ion size
influences on charge storage
- Identify new strategies in which EDLC materials
exploit both multiple charge storage mechanisms; combine double
layer charging and pseudocapacitance to enhance energy and power densities
 Multifunctional Materials for Pseudocapacitors
- The underlying charge-storage mechanisms
for pseudocapacitive materials are not well understood.
- Opportunities for new directions in
pseudocapacitor materials; single phase and multi-phase;
nanostructure design of novel 3-D electrode architectures
with tailored ion and electronic transport
p. 6
Capacitive Storage Science:
basic-science challenges, opportunities, and needs
 Electrolytes for Capacitor Storage
- Create new electrolyte formulations enabling
high voltage devices and revolutionary electrode
combinations for capacitive storage;
- New salts, new solvents, immobilizing matrices
designed for capacitor storage
 Theory and Modeling
- Structure and dynamics of solvent
and ions in non-polar nanopores.
- Electronic characteristics of carbon
and MOx electrodes.
- Validation against simple model experiments.
p. 7
Capacitive Storage Science:
basic-science challenges, opportunities, and needs
 Capacitor Systems and Devices
Higher volumetric and gravimetric energy density with less than one
second response time: Increased voltage, increased specific capacitance
Improved device safety: Non-toxic, non-flammable electrolyte
Regenerative Energy
Capture using Capacitors:
40% of energy is recovered
p. 8
Capacitive Storage Science:
Materials for Electrical Double Layer Capacitors
Subpanel members
Ralph Brodd
Patrice Simon
Ranjan Dash
John Ferraris*
* Subpanel leader
p. 9
Capacitive Storage Science:
PRD: Charge Storage Materials by Design
Scientific challenges
Identify new strategies in which EDLC
materials simultaneously exploit
multiple charge storage mechanisms.
Summary of research direction
Enhance EDLC materials performance by
creating designed architectures, surface
functionality, tailored porosity, and thin
conformal films, matched synergistically
with appropriate electrolyte systems.
Potential scientific impact
Establish nanodimensional spatial
control of the interface utilizing tethered
functionalized molecular wires.
Understand ion transport across
interfaces
Potential impact on EES
EDLC systems will be rationally designed
to revolutionize their utilization throughout
the energy sector
Develop new EDLC materials and
architectures to dramatically boost energy
and power densities
Anticipate impact in decades
p. 10
Capacitive Storage Science: Materials for
Electrical Double Layer Capacitors
technology challenges
New strategies are required
to improve both power and
energy density of EDLC
materials
 Materials Synthesis
 Designed Architectures
 Modeling Input/Output
p. 11
Capacitive Storage Science:
PRD Charge Storage Materials by Design
Systematic guidelines are currently lacking for
development of improved charge storage materials
Materials utilizing only double layer charge storage
Requires fundamental understanding of pore
structure and “effective” ion size
 Requires new synthesis methodology

p. 12
Capacitive Storage Science:
PRD Charge Storage Materials by Design
Materials utilizing mixed charge storage
 Highly reversible redox-active functionalities on high surface area
electrodes
 Thin dielectric or conducting coatings on ordered high surface
area materials
 Surfaces decorated with nanowires having active functionality
 Requires new synthesis methodology
p. 13
Capacitive Storage Science:
PRD Charge Storage Materials by Design
Materials utilizing synthetic ordered architectures
Electrode materials with controlled
pore size and surface area deposited
in ordered geometries with intimate
contact to current collectors

Requires new synthesis
methodology
p. 14
Capacitive Storage Science:
PRD: Charge Storage Materials by Design
 Materials Synthesis
 Designed Architectures
Development of new EDLC
materials and architectures will
dramatically boost:
Power and Energy!
p. 15
Capacitive Storage Science:
Sub-panel on Materials for Pseudocapacitors and Hybrid
Devices
Samson Jenekhe, sub-Panel lead
Prashant Kumta
Jeffrey Long
Katsuhiko Naoi
John Newman
p. 16
Capacitive Storage Science:
PRD: Multifunctional Materials for Pseudocapacitors and
Hybrid Devices
Motivation: Pseudocapacitors enable energy densities
significantly higher than for double-layer capacitors.
Challenge: Simultaneously maximize both energy
density and power density, and enhance lifetime.
New Research Directions
•Investigation of new materialsbeyond metal oxides
•Multifunctional architecture.
•Rational design of materials and structures.
•Understand fundamental charge-storage mechanisms.
p. 17
Capacitive Storage Science:
Multifunctional Materials for Pseudocapacitors
and Hybrid Devices
New Materials
+
Architectures
Vanadium Nitride, VN nanocrystals
= New opportunities for fundamental
understanding and scientific advances.
p. 18
Capacitive Storage Science:
Electrolyte subpanel members
Keryn Lian*
* Subpanel lead
Bruno Scrosati
Michel Armand
Wesley Henderson
p. 19
Capacitive Storage Science:
technology challenges
Aqueous and non-aqueous electrolytes with the following
properties:
■ immobilized matrix
■ produced from sustainable sources
■ high ionic conductivity
■ chemical and thermal stability
■ large electrochemical stability window (>5V)
■ non-toxic, biodegradable and/or recyclable
■ exceptional performance with long device lifetime
Bulk
Device Performance
Interfacial
p. 20
Capacitive Storage Science:
PRD Topic: Molecular Understanding of Electrolyte
Interactions in Capacitor Science
Fundamental lack of understanding: solvent-salt structure and
physical properties.
 Bulk Properties




Diverse materials (salt, solvent, immobilizing matrices, …)
Various conditions (temperature, concentration, …)
Experimental measurements (phase diagrams, spectroscopy, …)
Modelling and simulations
 Interfacial Effects
 Same approaches to explore interfacial and confined pore interactions
differ from the bulk
 Performance
 Create a fundamental understanding of link between device performance
and bulk/interfacial molecular interactions.
p. 21
Capacitive Storage Science:
PRD Topic: Molecular Understanding of Electrolyte
Interactions in Capacitor Science
Scientific challenges
The ideal electrolyte is an immobilized material
produced from sustainable sources, which has
high ionic conductivity; wide electrochemical,
chemical and thermal stability; and is non toxic,
biodegradable and/or renewable
Summary of research direction
Explore new salts, new solvents, immobilizing
matrices designed for capacitor storage
Examine bulk properties (solvent-salt
interactions), interfacial effects and behavior in
confined spaces using measurements and
modelling
Understand effect of additives and impurities
Potential scientific impact
Potential impact on EES
Understanding the mechanism of charging and
degradation
Enable high power technologies for load
levelling, improve energy efficiency.
New electrolyte formulations enabling
revolutionary novel electrochemical capacitor
devices
Enable novel energy recovery applications,
HEVs and PHEVs
Knowledge will cross-over to battery systems
p. 22
Capacitive Storage Science:
Theory & Modeling sub-panel members
Martin Bazant (MIT), sub-panel lead
Katsumi Kaneko (Chiba University, Japan)
Lawrence Pratt (Los Alamos)
Henry White (University of Utah)
p. 23
Capacitive Storage Science:
current status of modeling
 Equivalent circuit models (transmission-line models)
 Pros: Simple formulae, fit to experimental impedance spectra
 Cons: No nonlinear dynamics, microstructure, chemistry…
 Continuum models (Poisson-Nernst-Planck equations).
 Pros: analytical insight, nonlinear, microstucture
 Cons: point-like ions, mean-field approximation, no chemistry
 Atomistic models (Monte Carlo, molecular dynamics).
 Pros: molecular details, correlations, atomic mechanisms.
 Cons: <10,000 atoms, < 10ns, limited chemical reactions.
 Quantum models (ab initio quantum chemistry and DFT)
 Pros: Mechanisms and chemical reactions from first principles.
 Cons: <100 atoms, <ps, periodic boundary conditions
VERY FEW MODELS HAVE BEEN APPLIED TO SUPERCAPACITORS
p. 24
Capacitive Storage Science:
priority research directions for modeling
 Mathematical theory (beyond equivalent circuits)
 Derivation of nonlinear transmission line models for large voltages
 Modified Poisson-Nernst-Planck equations (steric effects, correlations…)
 Continuum models coupling charging to mechanics, energy dissipation,…
 Physics & chemistry of electrolytes
 Develop accurate models for MD and MC simulations
 Entrance of ions into nanopores -- desolvation energy and kinetics.
 Ion transport, wetting, surface activation, and chemical modification.
 Physics & chemistry of electrode materials
 Electron and ion transport in capacitor electrodes.
 Theory of capacitance of metal oxides and conducting polymers.
 Validation against simple model experiments
 Ordered arrays of monodisperse pores, single carbon nanotubes.
 Spectroscopic and x-ray analysis of ions and solvent in confined spaces
p. 25
Capacitive Storage Science:
Theory and Modeling
Scientific challenges
Summary of research direction
Fundamental understanding
and modeling tools for
supercapacitors across all
length and time scales.
Continuum, atomistic, & quantum models
Potential scientific impact
•Discovery of new physical phenomenananopore behavior, nonlinear dynamics…
•New models at system, microstructure,
molecular, and electronic levels
•New multi-scale simulation methods
Potential impact on EES
• Models for rational design of EES systems
• Prediction of new materials
• Increased power and energy density
• Time scale: decades to centuries
p. 26
Capacitive Storage Science:
Sub-panel members: Capacitive Devices and
Systems
Andrew Burke
John R. Miller
Pat Moseley
Joel Schindall
p. 27
Capacitive Storage Science:
Capacitive devices and systems
Scientific challenges
Develop and use efficient, low cost and
safe capacitive products to efficiently
harvest and recover waste energy in
applications that include electrical grid
storage, renewable solar and wind energy,
transportation, industrial stop-go
machinery, mining, and microstorage of
light, vibration, and motion energy
Potential scientific impact
Improved understanding of fundamental
capacitive energy storage and
optimization of a device as a system
Improved material synthesis and
processing
Summary of research direction
New approaches for higher
specific capacitance :electrode
materials with improved
morophology, uniform
micropores, higher cell voltages,
non-toxic, high conductivity,
electrolytes, and low resistance
separator materials
Potential impact on EES
Efficient, fast, distributed
capacitive energy storage for a
wide range of applications
p. 28
Capacitive Storage Science:
PRDs: Basic science of Capacitive Devices and Systems
 Increased energy density
 Longer life at high voltages and temperatures
 Self-balancing series strings of cells without electronics
 Safe failure modes under extreme conditions
 Technologies to enable reduced device cost
p. 29