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Nanomaterial approaches to enhance lithium ion batteries

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth July 17th, 2009

Brian J. Landi

Assistant Professor of Chemical Engineering and Sustainability NanoPower Research Laboratories (NPRL) Golisano Institute for Sustainability (GIS) Rochester Institute of Technology [email protected]

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Rechargeable Batteries

Recent Economic Trends (source: Aarkstore Enterprise)

· Rechargeable batteries, also known as storage batteries, are a continuing strong market, with worldwide sales of $36 billion in 2008. The rechargeable battery market will rise to $51 billion by 2013. · In the US, lead-acid battery technology continues to head rechargeable battery sales with a rechargeable battery market share of 79% in 2008. · The portable rechargeable battery market, of which lithium-ion has a 75% share, is the fastest growing segment of the rechargeable battery market, showing world market growth of 20% in 2008.

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Advantages of Lithium Ion

Portable Energy Challenge: Energy demand exceeds supply

· Increase Energy Density (carry more) · Fast Recharge (refill often)

· Device Energy Efficiency (use wisely)

Advantages of Lithium Ion

·Higher Energy and Power Density ·Higher Cell Voltage (2 to 3X over Ni-X) ·High charge rates available ·Low Self discharge rate (1-5%/month) ·Chemistry is form factor dependent (flexible design) ·Life can exceed tens of thousands cycles

Side note: ZPower has reported that Silver Zinc technology has higher energy density than Li ion

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Energy Density vs. Power Density

· Energy (J or Wh) is the ability to do work (currency) · Power (J/s or W) is the rate energy is consumed (spending) · Power/Energy ratio relates to battery application Lithium ion batteries are generally optimized either for high energy (e.g. for the consumer laptop or cellphone market where longer runtimes are a premium) or for high power (e.g. for the power tool or hybrid vehicle market where brief, high power pulses are a premium).

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Demands for Rechargeable Batteries

Consumer Electronics Grid and Renewable Energy Storage

Altairnano and A123 Systems have independently developed 2MW power units for demonstration of utility-grade energy storage as a replacement for lead acid batteries.

Automotive HEV: PHEV: EV: P/E = >15 P/E = 3-10 P/E = <3

Source: US DOE

Industry Considerations -Battery size (energy density) -Number of units -Cell form factorsfe management

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Considerations for Vehicles

· Battery Size and Cost (today: $1000+/kWh) HEV:1-2 kWh, PHEV: 5-15 kWh, EV: 40+ kWh · Safety ­ battery abuse from overcharge, physical damage, or high temperature; high voltage (300-400 V) concerns · Policy Incentives ­ if economics are only driver, then it directly competes with oil:

Electric vehicle with a $10,000 battery requires oil to exceed $125/barrel to equal 5 year total cost of ownership in a Volkswagen Golf 1.6 driven 15,000 km annually ­ source: Boston Consulting

· Model for ownership ­ buy electric vehicle, lease electric vehicle, or battery exchange (better place model) · Manufacturing and battery design

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Battery Manufacturing...for Vehicles

Today...18650 cells

~3.3 Billion cells in 2008

The Tesla Roadster battery pack (53 KWh-375 V) is comprised of about 6800 18650 cells; pack has a mass of about 450kg. Source: Tesla Motors

Global Investment in Manufacturing

In the near future...

Battery design for safety, performance, and end-of-life

· United States: American Recovery and Reinvestment Act of 2009 authorized $2 billion in grants for manufacturers of advanced battery systems and components · Germany: Lithium Ion Battery 2015 $650M for 1M PHEV cars by 2020 · Japan: Next Generation Vehicle Battery Program · China: National High Tech R&D Program

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Mechanism and Components of Li+

Components Anode ­ (negative) ­ active material, binder, substrate, additives

Cathode ­ (positive) ­ active material, binder, substrate, additives

Electrolyte ­ Lithium salt in mixed carbonate solvents; additives for overcharge, SEI regulation

Separator - porous polyolefin

Solid-Electrolyte Interface (SEI) is a surface film that generally establishes between an electrode and electrolyte and serves as a passivation layer to allow diffusion of Li+ but restricts additional solvent reduction

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Active Materials Comparison

Electrode Capacity: set by intrinsic materials properties and method of fabrication (i.e. coating thickness, active material loading, etc.) Battery voltage: set by anode/cathode materials and is derived from the electrochemical potential difference

Li4Ti5O12 has a lithium ion potential of 1.5 V vs. Li/Li+ for intercalation

Battery Energy Density (Wh): is the product of capacity (Ah) and average voltage (V) the discharge profile is critical

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Li+ Battery Development

There are many possible combinations of active materials for the anode, cathode, and electrolyte that are used in commercial lithium ion batteries ­ each combination will affect performance (i.e. voltage, energy density, cyclability, etc.)

Anode · Graphite ·MCMBs ·Li4Ti5O12 Electrolyte · LiPF6 · Carbonates · Additives Cathode · Metal Oxides · High Voltage · Iron Phosphate Phosphates · Mixed Oxides ·Layered Oxides

Source: US DOE

· Silicon · Tin · Nanotubes · Solid Electrolyte · Ionic Liquids ·LiBOB, LiTFSI

Variation in relative constituents will alter performance and energy density (by mass and volume)

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Challenges with Li+ Today

Fabrication &Processing

MCMB Copper Aluminum LiCoO2 50 mm ·Cylindrical vs. Prismatic ·Container materials ·Safety components 50 mm

Cell Design &Form Factor

Variations in Performance

·Coating Thickness ·Binder concentration ·Conductive additives ·Particle surface area

Reality: Manufacturing Design affects Energy Density, Power Density, Cost, Cyclability, Safety... Outcome: Some batteries are good for certain applications, others are not...

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Properties of Nanomaterials

Imitating Nature

Enhancement of light collection on the cornea of a night-flying moth

1 mm

Source: Vukusic and Sambles, 2003

Nanomaterials can have unique quantum confinement properties that are particle size dependent

Physical · Surface area/interfacial energy from high surface to volume ratio · van der Waals forces

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Advantages of Nano in Lithium Ion

· Small particle size decreases electron diffusion parameters (benefit: high rate capability; detriment: need for percolation to current collector) · High surface area allows active material to absorb lithium ions more effectively (benefit: higher capacity; deteriment: increased SEI) · Small particle size may accommodate crystalline expansion of lattice (benefit: improved cyclability; detriment: lattice crystallinity) · Nanotubes and nanowires can enhance electrical percolation and mechanical properties by entanglement

Doped LiFePO4 = 165 mAh/g*

Altairnano nano-Li titanate Electrovaya SuperPolymer®

Nanomaterials offer the potential to create a unique lithium ion battery with both high energy and power density

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Recent Nanomaterial Research

Silicon and Germanium Nanowires LiMn2O4 Nanowires

Capacity >1000 mAh/g Directed growth

Higher Rate capability over conventional materials

Potential Limitation: conventional slurry on metal current collector

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Carbon Nanotubes

Carbon nanotubes can be envisioned as a rolled up graphene sheet into a seamless cylinder. The role-up vector will determine the so-called `chirality' of the single wall carbon nanotube, which relates to whether the structure will be metallic or semiconducting.

Single Wall

Multi-Wall

Single Wall Bundle

· · · ·

High conductivity Nanoscale porosity Electrochemical and thermal stability High tensile strength/Young's modulus

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Carbon Nanotubes for Li+ batteries

Overview of potential uses

1

CNTs can be used as a conductive additive material which increases capacity, improves cyclability, enhances rate capability and mechanical toughness due to percolation network CNTs can be fabricated into freestanding electrodes - Anode ­ lithium ion storage · Predicted LiC2 = 1116 mAh/g, · 3X improvement over graphite maximum of LiC6 =372 mAh/g - Active material support for ultra high capacity semiconductors and electrical percolation pathways

2

Review Article in the June 2009 Issue

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Free-Standing Carbon Nanotubes Electrodes

CNT Advantages Increased specific capacity Zero voltage SOC Increased DOD High temperature ­ no binder Comparable C-rates Flexible Geometries Semiconductor Support

CNT free-standing electrodes offer a constant capacity as a function of thickness which can dramatically improve the usable electrode capacity in a full battery, particularly in a high power battery design.

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Battery Capacity Improvements

Si-SWCNTs

145% SWCNTs

161 164

1 2

75%

Raman Intensity (a.u.)

179 181

50% 35%

100 150 200 MWCNTs Shift (cm2 Raman

-1

(a)

(b)

5 nm

CNT free-standing electrodes have the potential to more than double the state-of-the-art battery capacity with proper design and density.

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Challenges going forward

Nanomaterial Challenges

· Ongoing technical research is necessary · Manufacturing/Costs are not available or competitive · Purification of materials requires technical expertise and energy intensive · Lack of knowledge for environmental and health risks

Bulk Powder Paper

Lithium Ion Challenges

· August 2006, Sony recalled all battery packs sold to Dell over a multi-year period · March 2008, LG Chemical experienced a factory fire · Concern for battery safety (e.g. electrolyte flammability) · Environmental effects of constituent materials

Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth

Acknowledgements

Dr. Ryne P. Raffaelle Dr. Cory D. Cress Matt Ganter

Roberta DiLeo Chris Schauerman Jack Alvarenga

U.S. Government

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