1. Materials utilised in lithium batteries.
James Rohan
Electrochemical Materials & Energy
Tyndall National Institute
UCC
Inaugural IEEE VTS UKRI chapter meeting
ITRN 2011
30th August
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2. Why Lithium?
Li lightest Metal
6.9g – 1 mole of electrons
Pb – 103.5g – 1 M
Li large Voltage gain +
Li /LiMn2O4
+ + + + +
Li /Li Li /C H /H2 Li /LiCoO2 Li /LiMnxNiyCozO4
MnO2/
Mn2O3
-3 -2 -1 0 +1 +2
Volts
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3. Batteries for EV’s
Developments in battery materials processing can be scaled
Car makers have been signing agreements with electronics
companies that have 15 years experience of Li ion technology to
bring the batteries to the automotive market.
Nissan/Renault NEC
Mitsubishi GS Yuasa
Tesla Panasonic
FORD LG Chem
GM LG Chem
Toyota Matsushita (Panasonic)
BMW Samsung/Bosch
VW Sanyo
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4. Rate of discharge
• C rate
– is the current used to fully discharge the battery in 1 hour
• 5 C rate
– is at five times that rate and therefore the capacity
achievable when discharged in 12 mins
• At higher rates generally utilise less of the capacity
• Power vs. Energy
Increased Power
by
increased area
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Increased Energy

5. Lithium metal
• Thermodynamically unstable to aqueous systems
– Li + H2O LiOH + 1/2H2
• Also thermodynamically unstable in non-aqueous
systems but passivates
• Must be handled in low humidity dry room
– Cost
– Most research performed in argon recirculating glovebox
with O2 and H2O < 1 ppm
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6. Non-aqueous solvent systems
Polar solvents
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7. Li salts
• Polar solvents enable dissolution of Li salts with complex
monovalent anions, e.g. LiCl low solubility
– LiClO4
– LiBF4
– LiAsF6
– LiPF6
– LiCF3SO3
– LiN(CF3SO2)2 For higher temperature cells such as polymer based
• Conductivities of these salts in organic solvents ~ 10-2 S cm-1
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8. Polymer Li ion batteries
• Polyethylene oxide electrolytes
– Poor ionic conductivity at rt (10-8 S cm-1)
– But at 60 – 100 oC conduction in amorphous PEO orders of
magnitude higher e.g. 2.5 x 10-4 S cm-1 at 90oC
– Higher T operation requires higher T compatible lithium salts
• LiCF3SO3
• LiN(CF3SO2)2
– Thin film versions
• 25 to 50 m
• Low current
– iR drop across electrolyte maintained low
• Possible to laminate
– Both electrodes and polymer electrolyte
8 – Various sizes
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9. Polymer gel electrolytes
• Using the typical carbonate
electrolytes
• Add a plasticiser polymer ((20%)
– Polyvinylidene fluoride (PVDF)
– Polyacrylonitrile (PAN)
– Polymeylmethacrylate (PMMA)
• Forms a gel
– Like solid polymer electrolyte in terms of
mechanical stability
– But rt operation possible
– Conductivities similar to solvent only
• ~ 0.01 S cm-1
– Functions as separator and electrolyte
• This gel can also be incorporated into
electrodes as binder
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10. Insertion Cathodes
• Electronically conducting framework
• Transition metal ions in mixed valence state
• Insertion of alkali metal ion reduces the framework
– TiIVS2 + Li+ + e- LiTiIIIS2
• Extraction reoxidises the framework
If the reaction does not change the cathode structure
over a useful compositional range it can be used as
an insertion electrode
Li+/LiMn2O4
Li+/Li H+/H2 Li+/LiCoO2
MnO2/
Mn2O3
-3 -2 -1 Volts 0 +1 +2
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11. Cathodes
As more cathodes investigated found that transition metal
oxides intercalate Li at higher potentials
More ionic character in M-O rather than M-S bonds
• LiCoO2
– Expensive, environmental
concerns, • LiFePO4
– Theoretical capacity 273 mAh/g – Inexpensive, abundant,
• Practical capacity 140 mAh/g but environmentally friendly, thermally
excellent cyclability in limited stable
range
– Li diffusion coeff = 10-10 cm2 s-1 – Theoretical capacity 170 mAh/g
– Electronic conductivity = 10-3 S cm-1 – Li diffusion coeff. = 10-14 cm2 s-1
• Cu = 5 x 105 S cm-1 – Electronic conductivity = 10-11 S cm-1
• Graphite = 400 S cm-1 • Carbon coated = 10-5 S cm-1
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12. Insertion anodes
As oxide cathodes introduced
Possibility to use other than Li metal anode and still have a
useable cell voltage
• Carbon investigated
– Cheap, Abundant
– Li++ e- + 6C LiC6
• Capacity (mAh/g) = (96,485/3,600)/72 = 372 mAh/g
• 10X less capacity than Li metal (but no dendrites – safer)
• Sony cell 1991 Li+/LiMn2O4
Li+/Li +
Li /C H+/H2 Li+/LiCoO2
MnO2/
Mn2O3
-3 -2 -1 Volts 0 +1 +2
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13. Planar Li batteries
650 0.65
0.60
Projected
550 0.55
mW h / cm2 (10 m thick)
0.50
W h /litre
450 0.45
2X in 14 0.40
350 years 0.35
0.30
250 0.25
0.20
150 0.15
1991 1994 1997 2000 2003 2006 2008 2011
Year
Li ion batteries
• Since the introduction to mass production in 1991
• Gradual increase in energy density achieved through improvements in
electrode materials.
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14. Main challenges
Energy
Storage
Power Cycle
output life
Safety Cost
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15. Solutions
• Structuring • New materials
– 2D to 3D to 1D – Cathodes
• Advanced oxides
– Core – shell
• Air
• Nanoscale active
region • Sulphur
• New materials – Electrolytes
• Polymer gel
– Anodes combinations
– Metals • Solid state
– Alloys • Ionic liquids
– Semiconductors
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16. Solid state electrolytes
• Typical thin film Li microbattery
• LiCoO2 cathode capacity
• LiPON solid state electrolyte – 100 Ah/cm2
– 10-6 S cm-1 • And volumetric energy density
– 300 Wh/cm2
• Li anode
• But mW/cm2 and mAh/cm2
J.B. Bates , N.J. Dudney, B. Neudecker, desirable
A. Ueda and C.D. Evans, Solid State Ionics,
135, (2000) 33.
• Footprint on Si is a big factor
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17. FP7 Nanofunction & Guardian Angel
• NANOFUNCTION : Beyond CMOS Nano-devices for Adding
Functionalities to CMOS
– ‘More than Moore’ devices (Analogue-RF-sensors-actuators-biochips-
energy harvesters, etc.) for adding functionalities to ICs and Beyond-
CMOS nanostructures (nano-wires, nano-structured materials, etc.)
which could be integrated on CMOS platforms.
– In particular, the interest of these nano-devices for the development of
innovative applications with increased performance in the field of
nano-sensing, energy harvesting & storage, nano-cooling and RF being
investigated
• Micro/nanobattery materials and integration schemes
• Guardian Angels :
– Zero Power devices harvest and store energy from their immediate
surroundings, including light, vibrations and temperature. By
combining these new sources of energy with low-power electronics, to
develop completely autonomous systems at an affordable price
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18. Charge and discharge rate
• Li diffuses in & out of the active material on cycling
– Diffusion times limit the rate capability of the battery
• Time for diffusion in a spherical particle estimated using
– = r2 / D
• Diffusion length example using 10-14 cm2 s-1
– 1 nm = 0.3 s
– 10 nm = 32 s
– 1 m = 316,000 s (88 hrs)
• Small particles desirable and access to good electrical conductor
– LiCoO2= 10-3 S cm-1 to 1 S cm-1
– Graphite = 400 S cm-1
• Cu = 5 x 105 S cm-1
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19. 2D to 3D
Increased Power
by
increased area
• Advantage of smaller length scales is the distance the ions
travel in the solid state electrodes
– where the lithium diffusion is orders of magnitude lower than that
in non-aqueous solvent or polymer gel electrolytes.
19 - J.W. Long, B. Dunn, D.R. Rolison and H.S. White, Chem. Rev., 104, (2004) 4463.
www.tyndall.ie

20. Micro to Nano
Increased Power
by
increased area
• If 5 m radius wires separated from
each other by 10 m
– 222,222 wires / cm2
• Active surface area per unit footprint
– For 500 m long wires
– 35 cm2 surface area
• If the wires were 50 nm diameter
separated by approx 50 nm
– 10 m long
– to get 35 cm2/cm
20 - J.W. Long, B. Dunn, D.R. Rolison and H.S. White, Chem. Rev., 104, (2004) 4463.
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21. Capacity
Increased Energy
• Need to increase the electrode
length to increase storage
capacity
– without decreasing the benefits
of the 3D design
• To do this need good
electronic conductivity in high
aspect ratio structures
21 - J.W. Long, B. Dunn, D.R. Rolison and H.S. White, Chem. Rev., 104, (2004) 4463.
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22. Conductor materials
• Micro/nanoelectronics
– Since 1998 – Cu used as
electrical interconnect
• lowest resistivity of practical
metals
• Resistivities
– Cu = 1.7 cm
– Graphite = 2,500 cm
Sub 100 nm
Even for Cu there are issues due to
sidewall and grain boundary scattering
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ITRS Roadmap www.tyndall.ie

23. Alternative anodes
• Metals • Metal alloys
– Sn (990 mAh/g) • CuSn (400 to 600 mAh/g
• Semiconductors depending on alloy)
– Si (4,200 mAh/g) • Metal oxides
– Ge (1,600 mAh/g) • SnO (500 mAh/g)
• Cu2O (374 mAh/g)
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24. New high capacity anode issues
• Large volume
changes on Li+
insertion
• Isotropic contraction
on Li+ removal
• Leads to cracking
– Loss of electrical
contact
– Loss of useful battery
capacity
– Very poor cycling
capability
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J.P. Maranchi, A.F. Hepp, A.G. Evans, N.T. Nuhfer, P.N. Kumta, J. Electrochem.. Soc. 153 (2006) A1246.

25. Si nanowires
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26. Nanotube growth
• No additives • + typical Cu bath additives
PEG and Cl-
T. Chowdhury, D.P. Casey and J.F. Rohan, Electrochemistry Communications, 11
(2009) 1203-1206, Additive influence on Cu nanotube electrodeposition in anodised
aluminium oxide templates.
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27. If overoxidised
Cu
Cu2O
Cu2O
• If essentially all converted to Cu2O shell
• Very poor initial capacity & retention
Cu2O + 2Li+ + 2e-  2Cu + Li2O
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Cu core
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28. After cycling
• Structural integrity retained
• Changed morphology
Cu2O
shell
M. Hasan, T. Chowdhury and J.F. Rohan, Journal of the
Electrochemical Society. 157, 6 (2010), Nanotubes of core/shell
Cu/Cu2O as anode materials for Li-ion rechargeable batteries.
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Cu core www.tyndall.ie

29. New materials
29 M. Hasan, Ph.D Thesis, UCC, 2010
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30. Ionic liquid electrolytes
• New materials
– Electrolytes
• Polymer gel
combinations
• Solid state
• Ionic liquids
The archetype of ionic liquids
1-ethyl-3-methylimidazolium (EMI) cation
&
N,N- bis(trifluoromethane)sulphonamide (TFSI) anion
Armand et al, Nature Materials, 8 (2009) 621
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31. Li-Air
31 Cho. Adv. Energy Mater. 2011, 1, 34–50
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32. Acknowledgements
Enterprise Ireland for Funding Microbattery research
CFTD/05/IT/317
Nanofunction
Beyond CMOS Nanodevices for Adding Functionalities to CMOS (10/2010 –
9/2013)
EU ICT Network of Excellence, Grant No.257375
Guardian Angels
Guardian Angels for a Smarter Life. (5/2011 – 4/2012)
EU Future and Emerging Technologies (FET) flagship pre-proposal phase,
FP7-ICT-2011-FET-F, Grant No. 285406
Energy storage - Scoping study
Strategic research challenges and opportunities
International Energy Research Centre (IERC), EI & IDA, Grant No. SCR2-019
Funded through the European Commission European Regional Development Fund.
National Development Plan
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