1. CESE November 13, 2009 Jai Prakash Center for Electrochemical Science and Engineering Department of Chemical and Biological Engineering Illinois Institute of Technology Electrochemical and thermal characterization of Li-ion batteries Electrochemical and thermal characterization of Li-ion batteries

2. CESE November 13, 2009 Li-ion cell reactions Oxide 1  m Metal oxide cathode LiMO 2 Graphite anode LiPF6/EC,DMC High volumetric energy/power densities

3. CESE November 13, 2009 Limitations of Li-ion cells  High power performance  Cell impedance)  Cycle life  Cell impedance  Thermal safety  Structural stability of delithiated oxide  Cell impedance produces heat  Cost

4. CESE November 13, 2009 Typical Changes in Li-ion Cell EIS with Time Impedance rise is associated with interfacial arc Most of the impedance is attributed to the positive electrode

5. CESE November 13, 2009 (003) reflections are weak or absent in oxide surface layers 5 nm Surface Film ~ 5-10 nm HR-TEM of cycled oxide particles LiNiO 2 -typeLi x Ni 1-x O-type

6. CESE November 13, 2009 Electrochemical Model Approach  Porous electrode model  Solid electrolyte interface (SEI) and interfacial oxide film included in the model  Diffusion through the electrolyte, SEI film, interfacial oxide, and bulk oxide considered  Butler-Volmer relation used for electrochemical reaction  AC impedance model constructed for Li-ion cell

7. CESE November 13, 2009 Governing equations for the AC impedance model  Linear perturbation complex analysis complex analysis  Numerical solution of a set of coupled differential equations  Kinetic impedance and lithium diffusion in active particles

8. CESE November 13, 2009 Simulation and prediction for the positive electrode

9. CESE November 13, 2009 Safety Concerns of Li-ion Batteries

10. CESE November 13, 2009 Thermal runaway produces fire in Li-ion cells Peter Roth (Sandia National Lab) 18650 Li-ion cell

11. CESE November 13, 2009 Understanding Thermal Runaway in Li-ion Cells: A Fire Triangle

12. CESE November 13, 2009 In-situ studies of thermal effects in Li-ion cells during normal cycling using IMC CurrentC/20C/10C/5C/1 Q anode mJ.cm -2 615427-74 Q cathode mJ.cm -2 -84-93-110-214 ChargeDischarge

13. CESE November 13, 2009 DSC features of Mag-10 anode at various SOC SEI decomposition

14. CESE November 13, 2009 Enthalpy vs. the amount of intercalated lithium in the secondary SEI film formation 1600 J/g for Mag-10 The formation of a secondary SEI film consumes about 0.37 Li

15. CESE November 13, 2009 DSC and XRD of DSC and XRD of LiNi 0.8 Co 0.15 Al 0.5 O 2 cathode at various SOC

16. CESE November 13, 2009 Thermal studies of Li 0.36 Ni 0.8 Co 0.15 Al 0.05 O 2 (CDL) With and Without Electrolyte using ARC Flash point of EC: 150 o C SHR dramatically increased from 150 o C is due to the combustion of the electolyte with released O 2 from delithiated cathode

17. CESE November 13, 2009 A conceptual road map for the thermal runaway in Li-ion cells Stable SEI films

18. CESE November 13, 2009 Approaches to improve thermal safety of Li-ion cells  Use of additives to form stable SEI film »Stable SEI film decomposes at higher temperature »Avoids the secondary SEI formation »Delay the initiation of thermal runaway  Thermally stable cathodes »Stable spinel oxides »Core-shell cathodes (Hanyang university)  Nonflammable electrolytes »Flame retardant additives »Nonflammable solvents

19. CESE November 13, 2009 Effects of VC, VEC and LiBOB additives on the thermal behavior of anode

20. CESE November 13, 2009 Electrolyte modification: FR additives

21. CESE November 13, 2009 Core-Shell approach to improve thermal safety 50 o C delay ARC DSC Li[Ni 0.5 Mn 0.5 ]O 2 LiNi 0.8 Co 0.1 Mn 0.1 O 2

22. CESE November 13, 2009 Acknowledgments  Dr. Evren Gunen  Dr. H. Bang  Dr. Hui Yang  Dr. C. Lee  Dr. D. Dess (ANL)  Dr. K. Amine (ANL)  Prof. Y. K. Sun (Hanyang U., S. Korea