1. TIAX LLC 15 Acorn Park Cambridge, MA 02140-2390 www. TIAXLLC.com © 2006 TIAX LLC David Clatterbuck Jacqueline Ashmore 6/16/08 Presentation to: Math Problems in Industry workshop Reference No.: Modeling battery electrode properties

2. 1 MPI workshop, WPI, 2008 Overview Introduction to TIAX Batteries & electrodes MPI workshop project description

3. 2 MPI workshop, WPI, 2008 Overview Batteries & electrodes Introduction to TIAX MPI workshop project description

4. 3 MPI workshop, WPI, 2008 Ideas & TechnologiesMarket Impact Reach of Research Reach of Companies Hospitals Universities National Labs Corporate R&D Inventors Start-ups Internal laboratories Development tools 150+ technologists Surround technologies StartEnd Implementation Focus Company A Company B Company C Company … TIAX implements innovations, accelerating the transformation of ideas and technologies into significant and sustainable business growth for our clients. Introduction to TIAX Focus

5. 4 MPI workshop, WPI, 2008 We incorporate several important elements into our approach, making TIAX unique in its ability to create value for our clients. Leveraging investments by accessing and incorporating the most appropriate IP from all available sources IP Blending Creating a team that really works—reliably accelerating development while building capabilities Collaboration Integrating deep technical expertise within a multidisciplinary business context Linked Diversity Adapting proven solutions and insights from one industry to resolve issues and create opportunities in another Context Shifting Delivering tangible results using our people, tools, and infrastructure Hands-On Approach: Implementation Focus Introduction to TIAX Approach

6. 5 MPI workshop, WPI, 2008 TIAX is a new, independent company that builds on the 116-year legacy of Arthur D. Little, Inc. Founded in May 2002 by Dr. Kenan Sahin Acquired assets of the ADL Technology & Innovation business Dr. Charles Vest, MIT President Emeritus, chairs our Advisory Board More than 150 scientists, engineers, and technicians, with PhD and MS degrees from top universities More than 40,000ft 2 of laboratory space Extensive ties to research and industry Headquartered in Cambridge, MA, with a West Coast presence in Silicon Valley, CA An ISO 9001-registered and secure facility Introduction to TIAX Overview

7. 6 MPI workshop, WPI, 2008 TIAX advances a century-long track record of breakthrough innovation. Nonflammable motion picture film (sold to Eastman Kodak) Patented technology leads to development of Fiberglas First iso-octane (later adopted as antiknock gas standard) Developed SABRE with IBM Commercialized & patented synthetic penicillin Flavor Profile method Sent five experiments on first moon mission Formulated Slim Fast line of drinks Commercialized scroll technology for automotive applications Developed and sold advanced lithium ion battery technology to major Japanese firm Advanced protective clothing used by industrial & agricultural workers APTAC chemical reactor measures process risk Non-CFC aerosol device TIAX LLC founded (May 2002) Non-toxic foam neutralizes chemical & biological agents 1920’s 40’s 50’s 60’s 70’s 80’s 90’s Today Heat-pump water heater has 60% more efficiency New line of cooking appliances for SubZero/Wolf 2002 Griffin & Little established 1886 Developed reformer technology— enabling fuel-cell vehicles to use gasoline & alternative fuels MIT Holds Controlling Interest Pioneered commercial cryogenics applications, founded HELIX Introduction to TIAX History 1886

8. 7 MPI workshop, WPI, 2008 TIAX’s mission is to help clients create an impact in the market and a difference in people’s lives across four interconnected themes: Health & Wellness Human Safety & Security Lifestyle Comfort & Convenience Energy Efficiency & Sustainability Introduction to TIAX Mission Enhancing people’s safety and security at rest or while performing functions and missions Enabling people be more effective in daily chores and make their time more enjoyable, satisfying and fulfilling New ways to deliver care as well as improve wellness through the air we breath, our food and personal care products Delivering energy/power efficiently, subject to cost effective resource and environmental constraints

9. 8 MPI workshop, WPI, 2008 Overview Introduction to TIAX Batteries & electrodes MPI workshop project description

10. 9 MPI workshop, WPI, 2008 Advanced Li-ion battery technology is one of TIAX’s key market areas TIAX has the largest independent Li-ion battery research group in the US Our research spans the Li-ion field:  cathode, anode, electrolyte, separator, battery safety  modeling, material synthesis, characterization, performance testing Applications: Hybrid electric vehicles (HEVs) – Toyota Prius Plug-in hybrid electric vehicles (PHEVs) – Chevy Volt Batteries & electrodes Li-ion batteries Applications Power ToolsPortable electronics Laptops

11. 10 MPI workshop, WPI, 2008 Microkinetics Transport phenomena Battery engineering Device engineering M O M O C3H7C3H7 H C3H8C3H8 $ ¥ € – Market Model Value - in - Use Model Customer Model New Products & Processes Quantum Chemistry EfEf Batteries & electrodes Modeling Cost model We use a wide range of linked models which span the range from atomistic calculations, to cost models for entire systems. Examples Quantum Chemistry: Designing new cathode materials with improved cycle life (stability). Battery Engineering: Determining the role of internal short circuits in battery safety incidents. Cost Modeling: Evaluating the impact of different cathode materials on the cost of PHEV battery systems.

12. 11 MPI workshop, WPI, 2008 Li–ion batteries must meet a range of performance criteria which vary in importance depending on the application. Energy Density: Total amount of energy that can be stored per unit mass or volume. How long will your laptop run before it must be recharged? Power Density: Maximum rate of energy discharge per unit mass or volume. Low power: laptop, i-pod. High power: power tools. Low-Temperature Energy Density: The amount of energy that can be recovered decreases at low temperatures due to slower charge and mass transfer. Safety: At high temperatures, certain battery components will breakdown and can undergo exothermic reactions. Life: Stability of energy density and power density with repeated cycling is needed for the long life required in many applications. Cost: Must compete with other energy storage technologies. Key Battery Attributes Batteries & electrodes Key Battery Attributes

13. 12 MPI workshop, WPI, 2008 A Li-ion battery is a electrochemical device which converts stored chemical energy directly into electricity. During charging an external voltage source pulls electrons from the cathode through an external circuit to the anode and causes Li-ions to move from the cathode to the anode by transport through an liquid electrolyte. During discharge the processes are reversed. Li-ions move from the anode to the cathode through the electrolyte while electrons flow through the external circuit from the anode to the cathode and produce power. To a large extent, the cathode material limits the performance of current Li-ion batteries LiMO 2 Cathode Graphite Anode +- Li Non-aqueous electrolyte Separator V Li Batteries & electrodes Li-ion battery chemistry/physics

14. 13 MPI workshop, WPI, 2008 More details on the transport of Li-ions. Both the anode and cathode are made from a collection of powder particles which are bonded together into a 3-D porous body (electrode). During discharge, ion transport in the electrode occurs as follows (green line) 1.Li-ion starts in the bulk of a cathode particle. 2.It undergoes solid state diffusion in the particle. 3.At the surface it disassociates from the e - and enters the electrolyte which occupies the pores of the electrode. 4.The ion is transported through the electrolyte (liquid phase diffusion) to the anode. 5.In enters the anode. 6.It undergoes solid state diffusion in the anode. At the same time, the electron must pass through the collection of solid particles to a metal current collector where it can be extracted from the cell and used to power a device (red line). It can not travel in the electrolyte. Batteries & electrodes Li-ion battery chemistry/physics Cathode Current Collector Electrolyte Anode Current Collector 2 1 4 4 4 5 6 3

15. 14 MPI workshop, WPI, 2008 Real electrodes are more complex. Electrodes typically contain high surface area carbon to increase the electrical conductivity between particles. A small amount of polymer binder is used to hold the particles in place. Typical particle size ~10um. Typical electrode thickness 50-75um. Batteries & electrodes Battery Electrodes Cathode Current Collector

16. 15 MPI workshop, WPI, 2008 Real powder particles can have different morphologies and surface roughness. Batteries & electrodes Particle size distribution 10  m 1m1m

17. 16 MPI workshop, WPI, 2008 The internal structure of the electrode plays an important role in the performance of a battery. Energy vs. Power For a given battery chemistry, the energy stored in the battery is proportional to the amount of active materials (i.e. anode + cathode powder). –For a cell of a given size, the higher the packing fraction of the powders, the more energy the battery can store and the longer your device can run before it needs recharging. The power (rate of energy delivery) depends on having sufficient mass and electrical transport throughout the electrodes. In theory, higher power can be achieved with: –smaller particles –higher surface area –larger fraction of porosity (i.e. more electrolyte) –thinner electrodes Careful design of electrodes is required in order to produce electrodes with the desired balance between high power and high energy. Commercial electrode design is currently dominated by empirical experimental approaches. Batteries & electrodes Impact of electrode structure

18. 17 MPI workshop, WPI, 2008 For a given cathode material, you can vary the electrode morphology to gain power at the expense of energy density. Different applications require different combinations of properties (laptop vs. cordless drill). Power and energy from a high-power cell design Batteries & electrodes Property trade-offs

19. 18 MPI workshop, WPI, 2008 Electrodes for cathodes with slow solid state diffusion Some cathode materials suffer from poor kinetics (slow solid state diffusion) Some success has been achieved by using very small cathode particles (~100nm) because the average diffusion distance a Li-ion must travel in the particle is much smaller. However, these nano-powders typically have a low tap density and are difficult to tightly pack due to surface effects. This causes the batteries to have lower energy densities. Selecting a the best particle size will involve a trade-off between energy density and rate behavior. Batteries & electrodes Impact of electrode structure The internal structure of the electrode plays an important role in the performance of a battery.

20. 19 MPI workshop, WPI, 2008 Overview Introduction to TIAX MPI workshop project description Batteries & electrodes

21. 20 MPI workshop, WPI, 2008 TIAX would benefit from algorithms, methods, models, scaling relations, or frameworks to analyze the effect of different particle characteristics on electrode properties. MPI workshop problem description Overview Knowledge of qualitative and/or quantitative relationships between electrode structure and performance will be useful in: –Isolating which features of current electrode structures are critical in achieving good performance, –Predicting improvements to current empirically determined relationships, –Identifying tradeoffs in structural features and performance. The inputs for the problem for the MPI workshop are particle properties; the outputs are electrode properties. TIAX can link the predicted electrode properties to key parameters quantifying electrode performance, such as energy density.

22. 21 MPI workshop, WPI, 2008 The inputs for the problem for this workshop are particle properties. Some particle characteristics to consider might include: –Size of monodisperse spheres –Roughness of monodisperse spheres –Radii of bidisperse spheres –Particle sizes with more realistic distributions of sizes (i.e. Gaussian distribution) –Deviations from sphericity, e.g., ellipsoidal particles MPI workshop problem description Input variables (Zamponi, Nature, 2008)

23. 22 MPI workshop, WPI, 2008 The outputs for the problem for this workshop are electrode properties. MPI workshop problem description Output variables Some electrode properties of interest include: –Packing fraction or void volume –Total surface area –Average path lengths for transport through the individual solid particles to the particle surface –Average path length for diffusion through the void volume from the surface of a particle to the surface of a collection of particles (electrode) of a certain thickness. –Effective cross-sectional area for this type of mass transport. –Average path length to travel through the collection of particles of a certain thickness, if you must travel only through the particles (passing from particle to particle only at points where they meet). Effective cross- sectional area for this type of transport.

24. 23 MPI workshop, WPI, 2008 Determining all of the electrode properties for all possible combinations of particle characteristics is probably not a manageable task! MPI workshop problem description Problem scope It may be useful to consider some of the more complex electrode properties for the case of simple particle size distributions (i.e., monodisperse spheres). For more complex particles, determining the packing fraction may be a sufficiently challenging problem. We would also like to increase our understanding of the literature in this area; any information you can provide on relevant references will be useful. http://www.physics.nyu.edu/~pc86/ packing.html Finally, experiments involving M&Ms may contribute to understanding the packing fraction of different shaped particles.

25. 24 MPI workshop, WPI, 2008 David and Jacquie will be a “tag team” at the workshop part-time. MPI workshop problem description Contact information When we are not here you can reach either of us in the following way: –Jacquiemobile tel. 617 899-8935 –Davidoffice tel. 617 498-6088 (mobile tel. 510 290-0982) We look forward to seeing the results, and thank you in advance for your efforts!