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
• Silicon
• Tin
• Nanotubes
• Solid Electrolyte
• Ionic Liquids
•LiBOB, LiTFSI
Cathode
• Metal Oxides
• High Voltage
• Iron Phosphate Phosphates
• Mixed Oxides
•Layered Oxides
Source: US DOE
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
Cell Design &Form Factor
Variations in Performance
MCMB
Copper
50 mm
Aluminum
LiCoO2
50 mm
•Coating Thickness
•Binder concentration
•Conductive additives
•Particle surface area
•Cylindrical vs. Prismatic
•Container materials
•Safety components
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.
Multi-Wall
Single 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
2
Review Article in the June 2009 Issue
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
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
Raman Intensity (a.u.)
161
75%
50%
35%
1
2
164
179
181
100
150
200
2
MWCNTs
Raman Shift (cm
-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