James Rohan - Electric vehicle battery systems

2,421
-1

Published on

Published in: Business, Technology
1 Comment
2 Likes
Statistics
Notes
No Downloads
Views
Total Views
2,421
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
84
Comments
1
Likes
2
Embeds 0
No embeds

No notes for slide

James Rohan - Electric vehicle battery systems

  1. 1. Materials utilised in lithium batteries. James Rohan Electrochemical Materials & Energy Tyndall National Institute UCC Inaugural IEEE VTS UKRI chapter meeting ITRN 2011 30th August1 www.tyndall.ie
  2. 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 Volts2 www.tyndall.ie
  3. 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 Sanyo3 www.tyndall.ie
  4. 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 area4 www.tyndall.ie Increased Energy
  5. 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 ppm5 www.tyndall.ie
  6. 6. Non-aqueous solvent systems Polar solvents6 www.tyndall.ie
  7. 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-17 www.tyndall.ie
  8. 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 electrolyte8 – Various sizes www.tyndall.ie
  9. 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 binder9 www.tyndall.ie
  10. 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 +210 www.tyndall.ie
  11. 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-111 www.tyndall.ie
  12. 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 +212 www.tyndall.ie
  13. 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.13 www.tyndall.ie
  14. 14. Main challenges Energy Storage Power Cycle output life Safety Cost14 www.tyndall.ie
  15. 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 – Semiconductors15 www.tyndall.ie
  16. 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 factor16 www.tyndall.ie
  17. 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 price17 www.tyndall.ie
  18. 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-118 www.tyndall.ie
  19. 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. 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/cm20 - J.W. Long, B. Dunn, D.R. Rolison and H.S. White, Chem. Rev., 104, (2004) 4463. www.tyndall.ie
  21. 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 structures21 - J.W. Long, B. Dunn, D.R. Rolison and H.S. White, Chem. Rev., 104, (2004) 4463. www.tyndall.ie
  22. 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 scattering22 ITRS Roadmap www.tyndall.ie
  23. 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)23 www.tyndall.ie
  24. 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 capability24 www.tyndall.ie J.P. Maranchi, A.F. Hepp, A.G. Evans, N.T. Nuhfer, P.N. Kumta, J. Electrochem.. Soc. 153 (2006) A1246.
  25. 25. Si nanowires25 www.tyndall.ie
  26. 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.26 www.tyndall.ie
  27. 27. If overoxidised Cu Cu2O Cu2O • If essentially all converted to Cu2O shell • Very poor initial capacity & retention Cu2O + 2Li+ + 2e-  2Cu + Li2O27 Cu core www.tyndall.ie
  28. 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.28 Cu core www.tyndall.ie
  29. 29. New materials29 M. Hasan, Ph.D Thesis, UCC, 2010 www.tyndall.ie
  30. 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) 62130 www.tyndall.ie
  31. 31. Li-Air31 Cho. Adv. Energy Mater. 2011, 1, 34–50 www.tyndall.ie
  32. 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 Plan32 www.tyndall.ie
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×