Materials under extreme conditions: panel membersPanelists:
Ralph Brodd Andrew Burke
Ranjan Dash John Ferraris
Wesley Henderson Sam Jenekhe
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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
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EDLC and Pseudocapacitive Charge Storage Materials
New strategies are needed to improve power and energy density of charge storage materials
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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
- 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
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EDLC Charge
Storage Materials:
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EDLC Charge Storage Materials
require understanding of pore structure and ion size
influences on charge storage
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
- 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
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Electrolytes for Capacitor Storage
high voltage devices and revolutionary electrode
combinations for capacitive storage;
designed for capacitor storage
- Electronic characteristics of carbon
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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
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Ralph Brodd Patrice Simon
Ranjan Dash John Ferraris*
Potential scientific impact
Identify new strategies in which EDLC materials simultaneously exploit multiple charge storage mechanisms.
Establish nanodimensional spatial control of the interface utilizing tethered functionalized molecular wires.
Understand ion transport across interfaces
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
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technology challenges
New strategies are required to improve both power and energy density of EDLC materials
Materials Synthesis
Designed Architectures
Modeling Input/Output
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
Materials utilizing mixed charge storage
Highly reversible redox-active functionalities on high surface area electrodes
 
  Requires new synthesis methodology
PRD Charge Storage Materials by Design
Electrode materials with controlled pore size and surface area deposited in ordered geometries with intimate contact to current collectors
  Requires new synthesis methodology
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Materials Synthesis
Designed Architectures
Development of new EDLC materials and architectures will dramatically boost:
      Power and Energy!
Samson Jenekhe, sub-Panel lead
New Research Directions
Multifunctional architecture.
Understand fundamental charge-storage mechanisms.
Challenge: Simultaneously maximize both energy density and power density, and enhance lifetime.
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= New opportunities for fundamental
understanding and scientific advances.
immobilized matrix
non-toxic, biodegradable and/or recyclable
Bulk
Interfacial
Fundamental lack of understanding: solvent-salt structure and physical properties.
Bulk Properties
Various conditions (temperature, concentration, …)
Modelling and simulations
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.
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Potential scientific impact
Knowledge will cross-over to battery systems
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
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
Enable high power technologies for load levelling, improve energy efficiency.
Enable novel energy recovery applications, HEVs and PHEVs
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Lawrence Pratt (Los Alamos)
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Pros: Simple formulae, fit to experimental impedance spectra
Cons: No nonlinear dynamics, microstructure, chemistry…
Continuum models (Poisson-Nernst-Planck equations).
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
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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
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
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New multi-scale simulation methods
Prediction of new materials
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Andrew Burke
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
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
Improved understanding of fundamental capacitive energy storage and optimization of a device as a system
Improved material synthesis and processing
Efficient, fast, distributed capacitive energy storage for a wide range of applications
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Increased energy density
Safe failure modes under extreme conditions
Technologies to enable reduced device cost
30 MJ CAPACITOR STORAGE SYSTEM
30 MJ CAPACITOR STORAGE SYSTEM
0
200
400
600
800
1000
1200
1400
AC
CNT
MPC
CAG
C
60
NRC
PANI/AC
PEDT/AC
PIThi
PFDT
PPy
/AC
MPFPT
DAAQ
PAn
/CNT
P3MT
PEDT
PAn
RuO
2
/PAPPA
RuO
2
(sol