Silicon nanowires for rechargeable li ion batteries
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Silicon Nanowires for Rechargeable Li-Ion Batteries. Onur Ergen , Brian Lambson , Anthony Yeh EE C235, Spring 2009. Overview. Battery Technology Landscape Battery Basics Lithium Ion Battery State of the Art Silicon Nanowire Anode Why Silicon Nanowires? Experimental Results

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Silicon Nanowires for Rechargeable Li-Ion Batteries

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Silicon nanowires for rechargeable li ion batteries

Silicon Nanowires for Rechargeable Li-Ion Batteries

OnurErgen, Brian Lambson, Anthony Yeh

EE C235, Spring 2009


Overview

Overview

  • Battery Technology Landscape

    • Battery Basics

    • Lithium Ion Battery

    • State of the Art

  • Silicon Nanowire Anode

    • Why Silicon Nanowires?

    • Experimental Results

    • Technical Comparison

  • Economic Perspective

    • Market Analysis

    • Future Outlook

    • Conclusion


Battery technology landscape

Battery Technology Landscape

Battery Basics

Lithium Ion Battery

State of the Art


Motivation batteries and life

Motivation: Batteries and Life

Nanowire Batteries


How does a battery work

How does a battery work?


History of batteries

History of Batteries


Lithium ion batteries

Lithium-ion Batteries

  • How do Li-ion batteries work?

  • Battery Parameters

    • Energy density: cathode and anode

      • E (Wh) = voltage x capacity

    • Power density: ion intercalation and electron transport

    • Cycle life: strain relaxation

  • Advantages of Li-ion batteries

    • High cell voltage

    • Superior energy and power density

    • High cycling stability

    • Low self-discharge

    • No memory or lazy battery effect

    • 100% depth of discharge possible

J.-M. Tarascon& M. Armand. Nature. 414, 359 (2001).


What we have in daily technology

What we have in daily technology


How can we improve from here

How can we improve from here?

  • Using silicon nanowires as anode

    • Energy capacity

    • Peak power

    • Endurance

    • Manufacture cost


Silicon nanowire anode

Silicon Nanowire Anode

Why Silicon Nanowires?

Experimental Results

Technical Comparison


Silicon an optimal anode material

Silicon: an optimal anode material

  • Graphite energy density: 372 mA h/g

  • Silicon energy density: 4200 mA h/g

  • C6LiC6

  • SiLi4.4Si


Why haven t we been using si anodes

Why haven’t we been using Si anodes?

Lithiation of silicon has one major problem – it is accompanied by a 400% volume increase!

Chan et. al, Nature Nanotech, 2007


Solution silicon nanowires

Solution: Silicon Nanowires

  • 10 x energy density of current anodes

  • Structurally stable after many cycles

Chan et. al, Nature Nanotech, 2007


Experimental technique

Experimental Technique

  • NW growth on stainless steel by vapor-liquid-solid (VLS) technique

    • Crystalline Si

    • Core-shell (core = crystalline Si, shell = amorphous Si)

  • Test current-voltage characteristics over many charge/discharge cycles using cyclic voltammetry

C

Li metal

V

Electrolyte

Si NW on

Stainless steel


Experimental results

Experimental Results

Charge and discharge capacity per cycle

Chan et. al., Nature Nanotech, 2007


Experimental results1

Experimental Results

Charge and discharge capacity per cycle

Dramatic (~10x) improvement in charging capacity over graphite!

Chan et. al., Nature Nanotech, 2007


Experimental results2

Experimental Results

Charge and discharge capacity per cycle

No decrease in capacity beyond first charge cycle!

Chan et. al., Nature Nanotech, 2007


Experimental results3

Experimental Results

Core-shell nanowires may improve performance after first cycle

Cui et. al., Nano Letters, 2009


Experimental results4

Experimental Results

Core-shell nanowires may improve performance after first cycle

Amorphous shell thickness as a function of growth time

Crystalline core thickness

Cui et. al., Nano Letters, 2009


Experimental results5

Experimental Results

Study of reaction dynamics:

Near capacity charging at high reaction rates

Chan et. al., Nature Nanotech, 2007


Experimental results6

Experimental Results

Study of reaction dynamics:

Near capacity charging at high reaction rates

Graphite

Even one hour cycle time is much better than a fully charged graphite anode!

Chan et. al., Nature Nanotech, 2007


Technological comparison

Technological Comparison

Fuel Cells:

Smithsonian Institution, 2008

Li-ion batteries have proved optimal for most mobile electronics and competitive for hybrid and electric vehicles


Technological comparison1

Technological Comparison

Supercapacitors:

Maxwell Technologies, 2009

Li-ion batteries have proved optimal for most mobile electronics and competitive for hybrid and electric vehicles


Technological comparison2

Technological Comparison

Piezoelectric nanogenerators:

Wang, ZL, Adv. Funct. Mater., 2008

Li-ion batteries have proved optimal for most mobile electronics and competitive for hybrid and electric vehicles


Technological comparison3

Technological Comparison

  • Energy and power density

    • Only fuel cells and batteries can be primary power supply

    • Among those, Si NW batteries are optimal

  • Lifetime and efficiency

    • Batteries last about as long as typical electronic components

    • Energy efficiency of electrochemical devices is generally high

Li-ion batteries have proved optimal for most mobile electronics and competitive for hybrid and electric vehicles


Economic perspective

Economic Perspective

Market Analysis

Future Outlook

Conclusion


Portable electronics

Portable Electronics

Lighter Phones

Longer-lasting Laptops

More powerful PDAs

P. Agnolucci, “Economics and market prospects of portable fuel cells”


Hybrid electric vehicles

Hybrid/Electric Vehicles

  • Emerging market for H/EV batteries

  • Batteries are the main roadblock

    • Energy density (range)

    • Power density (acceleration)

  • Li-ion poised to be biggest contender

http://www.chemetalllithium.com/index.php?id=56


Competing technologies

Competing Technologies

  • Other battery technologies

    • NiMH

    • NiCd

    • other Li-ion

  • Fuel cells

    • 5/8/09 (CNET News) – “DOE to slash fuel cell vehicle research”

      • “[...] many years from being practical.”

    • Portable fuel cells

  • Supercapacitors

    • <30 Wh/kg

    • Li-ion: <160 Wh/kg

P. Agnolucci, “Economics and market prospects of portable fuel cells”


Economics of nanowire batteries

Economics of Nanowire Batteries

  • Silicon is abundant and cheap

    • Leverage extensive silicon production infrastructure

  • Don’t need high purity (expensive) Si

  • Nanowire growth substrate is also current collector

    • Leads to simpler/easier battery design/manufacture (one step synthesis)

    • Nanowire growth is mature and scalable technique

    • J.-G. Zhang et al., “Large-Scale Production of Si-Nanowires for Lithium Ion Battery Applications” (Pacific Northwest National Laboratory)

    • 9 sq. mi. factory = batteries for 100,000 cars/day

GM-Volt.com, “Interview with Dr. Cui, Inventor of Silicon Nanowire Lithium-ion Battery Breakthrough”

K. Peng et al., "Silicon nanowires for rechargeable lithium-ion battery anodes," Applied Physics Letters, 2008


Capacity issues

Capacity Issues

Can you really get 10x?

Si nanowire anode ~3541 Ah/kg

Adjust anode/cathode mass ratio

  • Cathode materials

    • Lithium Cobalt Oxide

    • Lithium Iron Phosphate

J.-M. Tarascon, M. Armand, "Issues and challenges facing rechargeable lithium batteries"


Lifetime issues

Lifetime Issues

  • Initial capacity loss after first cycle (17%)

    • Cause still unknown?

  • Capacity stable at ~3500 Ah/kg for 20 cycles

    • Can’t yet maintain theoretical 4200 Ah/kg

  • Crystalline-Amorphous Core-Shell Nanowires (2009)

    • Energy Density: ~1000 Ah/kg (3x)

      • 90% retention, 100 cycles

    • Power Density: ~6800 A/kg (20x)

Y. Cui, “High-performance lithium battery anodes using silicon nanowires”

Y. Cui, “Crystalline-Amorphous Core-Shell Silicon Nanowires for High Capacity and High Current Battery Electrodes”


Conclusion

Conclusion

  • Summary

    • Motivation

    • Technology landscape

    • Silicon nanowire battery advantages

    • Market

    • Prospects

  • Time to market

    • ~5 years (Cui)


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