cross-cutting science: panel members andrew gewirth* daniel nocera* christian amatore (france) greg...

Cross-Cutting Science: Panel Members

Andrew Gewirth*Daniel Nocera*Christian Amatore (France)Greg Baker Larry Curtiss Marten denBoer

John Harb Royce Murray Reginald Penner Hrvoje Petek Daniel Scherson Ralph White

* Panel co-lead

Ideal electrical energy storage device requires improvements in:

Safety – Capacity – Lifetime – Cost

Crosscutting Themes Emerge in areas of:

Interfaces, Electrolytes, Charge and Discharge, Materials, Architectures

Develop new tools and concepts in synthesis, measurement, computation

Leverage recent developments in other areas of chemistry and physics

Cross-Cutting Science: Overview

Potential scientific impact Potential impact on EES

Summary of research directionScientific challenges

PRD1: Probing Energy Storage Chemistry and Physics at all Time and Length Scales

• Develop and implement techniques to monitor, with spatial resolution from atomic to mesoscopic and temporal resolution down to fs, changes in structure and composition including - in-situ spectroscopy- microscopy- scattering

• Fundamental understanding of the thermodynamic, reaction kinetics, and transport aspects of systems displaying ionic mobility and charge transfer

• Determine structural and dynamical changes that occur in energy storage devices during charge and discharge as function of cycle life and other variables.

• Develop model experiments of irreducible complexity which:- are amenable to theoretical study- isolate key aspects of device operation

• RADICALLY NEW batteries and electrochemical capacitors can be designed with a microscopic understanding of the mechanisms underlying device performance and failure

Cross-Cutting Science: Basic Science Challenges, Opportunities, and

Needs

Develop “irreducibly complex” experimental model systems, with relevance to these elementary processes, which are simple enough to be amenable to theoretical analysis

The development and implementation of experimental techniques with time resolution down to fs and spatial resolution to the atomic scale

• Will permit a microscopic understanding of elementary events associated with electrochemical energy storage, at interfaces and in bulk phases, to enable improvements in the performance of actual devices

• Crucial to achieving this understanding is spectroscopy, microscopy, and scattering, both photon- and particle-based (neutrons)

• Potential control at electrochemical interfaces cannot be achieved in micron-sized electrodes at times shorter than 100 ns, much slower than the time resolution of the probes. Nanoparticle ensembles will allow much faster electrochemical response.

• Monitor, down to fs resolution, elementary interfacial events (concerted electron and ion transfer) and bulk events (ion transport within lattice)

• Image, in real time and with nm resolution, charge transport in electrodes and devices, including evolution of fronts and moving boundaries in single particles

• Monitor, in situ, during charge, discharge and cycling:

– structure, morphology and composition of the SEI

– electrolyte composition


Needs

active particles

binder

carbon

current collector

• Challenge: Electrochemical energy storage requires complex multicomponent systems.

• Opportunity: Use high flux neutron beams (at the new Spallation Neutron Source, Oak Ridge) to distinguish the structure and dynamics of individual components in complex systems by exploiting the neutron scattering length differences of 6Li and 7Li, and 1H and 2H.


Needs

Modulate contrast between specific componentsModulate contrast between specific components



PRD2: Efficacy of Structure in Energy Storage

• Use theory and experiment in conjunction with well-defined structures to elucidate fundamental materials properties

• Design, synthesize, and optimize architectures for improved energy storage

• Develop multifunctional materials that are, e.g., self-healing, self-regulating, failure-tolerant, impurity-sequestering, sustainable

• A fundamental understanding of the relationship between structure and function for energy storage materials

• New materials for energy storage

• New methods for synthesizing and optimizing energy storage materials

Understand the fundamental relationships between structure and energy storage properties:

• Is nano more than small?

• What are the critical spatio/temporal scales?

• Can novel architectures transcend capacity, power, and lifetime barriers?

• Transformational capacity, power and lifetime improvement

• SUSTAINABLE, SAFE, AND ABUSE-TOLERANT materials

Transcend capacity, power, and lifetime barriers by:

Designing and synthesizing novel architectures.

Developing multifunctional components to eliminate dead weight.

Engineering robust, abuse-tolerant systems.

Utilizing safe and sustainable materials and processes.

K. Naoi, U.S. DOE Workshop on Basic Energy Needs for Energy Storage, Bethesda, MD, April 1-5, 2007.

Cross-Cutting Science: Technology Challenges

ion

Tantalizing results highlight the potential of diminished scale and scale control in materials properties

Anomalous increases in carbon capacitances at pore sizes < 1 nmChmiola et al., Science, 2006, 313 1760

Cross-Cutting Science: Current Status

Carbon nanohorns enable tunable capacitances

Sub-1 nm pores are associated with higher than expected capacitances for porous carbons

Carbon SWNTs improve the performance of both supercapacitor and battery electrodes

Nanocrystalline metal oxides improve performance of battery cathodes

Multifunctional materials

Self-assembly

Autonomic healing of polymer compositesWhite et al., Nature, 2001, 409, 794

Joe Hupp et al.http://chemgroups.northwestern.edu/hupp/research2.html

New and exciting technologies that will have a role in energy storage:


• Use theory and experiment in conjunction with well-defined structures to elucidate fundamental materials properties

• Design, synthesize, and optimize architectures for improved energy storage

• Develop multifunctional materials that are, e.g., self-healing, self-regulating, failure-tolerant, impurity-sequestering, sustainable

Pellin et al., Catal.Lett. 102 (2005) 127

Cross-Cutting Science: Research Needs



PRD3: Charge Transfer and Transport in Energy Storage

• Characterizing the dynamical structure of interfaces

• Tailoring the potential landscape of interfaces (electronic and nuclear)

• Designing efficient transport channels to reacting sites

• Optimization of charge transfer through coupling of electron and nuclear motions

• Activated healing of interfaces

• Correlation of stochastic electronic and nuclear structures and electron transfer on the nanoscale

• Molecular scale structure/electrical potential probes

• Electron transfer dynamics at atomically and molecularly tailored interfaces

• Supramolecular and surfactant design for transport channels and healing interfaces

• Understanding of nanoscale electrochemical processes on the femto/pico timescale

• Many-body and collective dynamics in charge transfer

• Charge transfer of nanoscale materials• Strategies for tailoring interfacial free-energy

• New material design concepts (interface, electrolyte, additive) for efficient and high capacity storage

• LONGER LIFE in energy storage devices and enhancement through self-healing design

Probing of and controlling interfaces on the fundamental nanometer spatial scales and femto/pico second time scale of electron/nuclear dynamics

3D mapping of interfacial molecular and atomic structure and electrostatic potentials at interfaces and in transport channels

Sensitive methods of measuring electron transfer rates at interfaces

Time-resolved imaging and scanning electron and optical microscopy with chemical contrast

Tailoring nanometer scale electrode environment for optimal transport to the reactive sites


• Mechanistic characterization of electron transfer rates in the >10–6 s regime at electrochemical interfaces

• Interfacial charge transport measurements on well-defined single crystal and polycrystalline interfaces on fs time scale

• Homogeneous and heterogeneous electron/ion solvation on 10–14 - 100 s time scale

• Potential dependent spectroscopic characterization with <100 nm spatial resolution by micro Raman, near-field optical, X-ray methods

1500 1550 1600 1650 1700

0

800

1600

2400

3200

4000

4800

5600

0.215V - 0.157V

Inte

nsity

Raman Shift (cm-1)

Micro-Raman spectra of single 30 m flake of graphite vs. applied potential


• Pseudo-homogenous - ion+solvation shell (spectator interface; diffusive dynamics)

• Strongly heterogeneous - Strong chemical reorganization at the surface (active interface; ballistic dynamics)

Vertical transition

Solvated state

1 ML CH3OH (50% dissociated) on TiO2

Experimental and theoretical understanding of the molecular scale interfacial electron transfer under weak and strong coupling conditions:


Needs

• Design of optimal electronic coupling - electrode material, electrode surface processing, morphology, surfactant effects, nanostructure wavefunction design, matching of electrolyte/surface interactions (direct or through a molecular or ionic mediator)

• Develop concepts for spontaneous or activated reactive site rejuvenation

• Elucidation of rare, deleterious processes that lead to cumulative failure

Marcus parabolas

Electron tunneling


Needs

Schenter, Garrett, Truhlar, JPC B 2001



PRD 4: Innovation in Electrical Energy Storage Electrolytes

• Innovative design and syntheses to obtain strong ionic solvation, yet weak ion-ion inter-action, high fluidity, controlled thermodynamics

• Ionic, multi-ionic, and redox liquids, screened anions, ions linked by conducting segments to extend the space charge region, and hard and soft additives

• Target electrode interactions with highly concentrated ionic phases

• Replace battery electrolytes, which are currently liquid based with safety and reactivity issues

• Conductivity of polymer electrolytes is low, need to be increased dramatically

• New electrolytes needed for capacitors to support increased charge transfer rates

• New tools for synthesis, delineation of structure-property rules, and measurement

• RELIABLE AND SAFE BATTERIES AND CAPACITORS with high capacities and operating ranges

• A MULTIDISCIPLINARY research infra-structure to address energy materials research

• New battery and capacitor electrodes can be explored with advances in electrolytes

• Delineation of ion-ion and ion-solvent interactions will lead to greater understanding of crowded double layers


Liquid electrolytes

• Provide the needed high conductivity for electrochemical capacitors but can have safety and containment issues

• Have voltage windows that limit the device performance range

• Contain electrolyte impurities that lead to degradation in performance

Need new electrolytes with high ionic conductivity, low fluidity, easily purified

Low nucleophilicity and electrophilicity - unreactive in both electron transfer and acid-base chemistry

Electrolytes can be the weak link limiting innovations in electrode materials, and associated power and power density


"Solid" electrolytes

• Difficult to combine the electrolyte and electrode separator functions in a single material

• Modeling provides a recipe for high conductivity - polymers with low glass transition temperatures - but low Tg polymers have poor mechanical properties

• Two-phase materials provide a partial solution - favorable mechanical properties, but with the electrochemical characteristics and problems of low molecular weight liquid electrolytes ( electrolyte decomposition, flammability, ...)

New approaches to electrolyte design are needed that go beyond incremental improvements

• Design rules for salts with weak ion-ion interactions (ion-pairing)

– match a large delocalized charge, with asymmetrical ions that are steric misfits with one another (known examples of weakly coordinating anions include BARF and carboranes)

• Novel ion structures, such as a short electronically conducting entity bearing numerous ionic groupings

– contact of this soluble electrolyte with the electrode and charging of the conductor may extend the double layer thickness and thereby the capacitance


Needs

BF3C

F3C

CF3F3C

CF3

CF3

CF3F3C

BARF

electrical conductor

Design and synthesis of new salts for electrolytes:liquid electrolytes, polymer electrolytes, and ionic liquids

• Wide of unexplored structural diversity available

• Improvements needed in fluidity, ionic conductivity, and better detailing of actual potential limits, ...

• Need investigation of response of the double layer structure to high ion concentrations, detection of ion-ion interactions, and the dynamics of changes in solvation

• Redox-labeled versions of these materials are possible reversible fuel cell materials.


Needs

N CH3N

S O

OS

O CF3

OCF3

PP13 TFSI

N

N

CH3BF4

EM - B

Molten salts offer high ion concentrations, low volatility and good temperature tolerance = SAFETY, and useful potential windows

• Nanoparticle composites that exploit the interstitial space in ensembles of high surface area nanoparticles and provide conductive channels for ion transport.

• Design smart materials that respond to moderate temperature excursions within batteries, polymer layers while selectively removing lithium dendrites, or restore conductive pathways in composite electrode structures - potentially dramatic improvement in device reliability, lifetime and SAFETY


Needs

M+

anode

cathode

"dendrite mower"

Solid electrolytes…need REVOLUTIONARY rather than evolutionary change



PRD5: Multi-Scale Computations for EES

• Need theoretical tools to explore physical and chemical processes occurring over the full range of length and time scales

• To understand complex phenomena, molecules, and materials

• Connect experiment and theory to guide and interpret experiment and assist in the design of molecules, materials, and systems

• Novel material discovery with required properties

• New multiscale modeling techniques for designing energy storage systems

• Theory and modeling will guide and understand the development of the next generation of storage devices

• OPTIMIZE AND MODERNIZE electrical-energy-storage systems

• Multi-scale modeling: improved integration of length and time scales

• Virtual design of materials

• Modeling of sustainability and life cycle

• Validation of theoretical methods with experiment on model systems

• Merging of new theoretical methodologies to explore the complexity of physical and chemical processes occurring over the full range of length and time scales

• Multi-scale modeling for the virtual design of materials with user defined properties

• Computer simulation for prediction of sustainability, risk, and life cycle analysis

Three cross-cutting challenges for computation simulations required for making REVOLUTIONARY breakthroughs in battery and

capacitor research


• Intensive collaboration with characterization scientists, e.g., neutrons, x-rays, electrons, and spectroscopy

• Validation with experiment on model systems to assure reliability of computational simulations.

• High-performance computing

• Resources to train a new generation of scientists in fundamental research on electrical energy storage systems

Formation and destruction of water monolayer on RuO2 surface from theory and experiment


Enabling support required to successfully address computer modeling challenges

• Density functional calculations can generally handle up to hundreds of atoms for calculations of energetics and structure

• Classical molecular dynamics can handle millions of atoms and provide information on thermodynamics, structure, and transport properties

• Finite element and continuum modeling of long timescales of interest in prediction of lifetime, based on mechanisms of degradation


Examples of current status of theoretical methodology

Need to integrate new computational techniques, which operate on different time scales

• Modeling of kinetics and dynamics of phase transformations in electrode materials and electrolytes

• High-throughput virtual screening of materials and devices for batteries and capacitors

• Design and construction of materials with desired electrical storage properties using multiscale modeling

• Understanding charge transfer and transport in electrical storage materials

• Integrating modeling of nanoscale and macroscale effects


Needs

Predicted T-distribution in multi-electrode Li+ pouch cell

MD simulation of LiClO4/PEO polymer electrolyte

Predicted Li ion position in Li4V3O8