Electrified Vehicles for Personal Transportation, the Role of - - PowerPoint PPT Presentation
Electrified Vehicles for Personal Transportation, the Role of Surface Coatings, and the Use of Thin Films for Electrode Characterization GM Mark Verbrugge (speaker) and Xingcheng Xiao University of Kentucky Rutooj Deshpande, Juchuan Li,
Molecular Engineering & Sciences Symposium, University of Washington, WA, 18 September 2012
GM Mark Verbrugge (speaker) and Xingcheng Xiao University of Kentucky Rutooj Deshpande, Juchuan Li, Yang-Tse Cheng
Automotive context Why do LiIon cells fail? The use of thin-film surface coatings to
(particularly life) – positives and negatives
behavior – stress evolution and solute (Li) diffusion Summary
EM ERGING VS. M ATURE M ARKETS – GLOBAL COMP ARISON: 2010
Source: GM Economics & Trade; IMF; U.S . Census Bureau/ Haver Analystics
5 10 15 20
China EU U.S. Japan Brazil India Russia Canada
Vehicle Sales (M)
2005 2009 2010 2011
TOP 10 MARKETS BY NEW VEHICLE SALES IN 2011
China Growth (%)
2% 325% 854%
2011 Sales (M)
Emerging Markets 39.5 Mature Markets 36.5
World Total 76.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1 2 3 4 5 6 7 8 9 1980 1990 2000 2010 2020 2030 Vehicle Parc (Billion) World Population (Billion) World Population Vehicle Parc
PERSONAL MOBILITY MUS T BE REINVENTED FOR THE 21st CENTURY
Data from U.S. Census Bureau and GM Global Market & Industry Analysis Data from U.S. Census Bureau and GM Global Market & Industry Analysis
Future vehicles will use alternative energy sources like bio-fuel, grid electricity, and hydrogen Future vehicles will use alternative energy sources like bio-fuel, grid electricity, and hydrogen
Improved Vehicle Fuel Economy & Emissions Improved Vehicle Fuel Economy & Emissions Displace Petroleum Displace Petroleum Energy Diversity Energy Diversity Hybrid Electric Vehicles (including Plug-In HEV) IC Engine and Transmission Improvements Hydrogen Fuel Cell Petroleum (Conventional & Alternative S
Alternative Fuels (Ethanol, Bio-diesel, CNG, LPG) Hydrogen Electricity (Conventional & Alternative S
Battery Electric Vehicles (E-Rev)
Time Time
Main challenges
& kWh/m3
Starter Motor Electric Auxiliary Pump
~ 0.5 kWh battery
2012 BUICK REGAL 2013 CHEVROLET MALIBU
~ 1 kWh battery
~ 2 kWh battery
The Volt proves electric driving can be spirited
Top Speed – 100 mph
– Torque – 273 lb.-ft.
0-60 mph in less than
– Quarter mile in less than 9 seconds 17 seconds
The Volt proves electric driving can be spirited
Top Speed – 100 mph
– Torque – 273 lb.-ft.
0-60 mph in less than
– Quarter mile in less than 9 seconds 17 seconds
Main challenges
& kWh/m3
16 kWh battery
V Electrochemical reaction Conventional lithium ion
1.35 NiOOH +H2O + e- = Ni(OH)2 + OH 1 Li1-xMO2 + xLi+ + xe = LiMO2 (M: Ni, Co, Mn) 0.4 FePO4 + Li+ + e = LiFePO4 0 H+ + e = 0.5H2 O2 + 2H+ + 2e = 2H2O
Newer lithium ion Lithium ion conventional stability window
~ 2.5 V ~ 3.3 V ~ 4 V ~ 1.35 V ~ 1.2 V
Electrode potentials
By changing an electrode voltage, new electrolytes can be employed with improved stability. For traction applications, conventional lithium ion cells still dominate…lower utilization for improved durability & abuse tolerance.
Very stable potential window, but lower energy density
V Electrochemical reaction Conventional lithium ion
1.35 NiOOH +H2O + e- = Ni(OH)2 + OH 1 Li1-xMO2 + xLi+ + xe = LiMO2 (M: Ni, Co, Mn) 0.4 FePO4 + Li+ + e = LiFePO4 0 H+ + e = 0.5H2 O2 + 2H+ + 2e = 2H2O
Newer lithium ion Lithium ion conventional stability window
~ 2.5 V ~ 3.3 V ~ 4 V ~ 1.35 V ~ 1.2 V
Summary: role of surface layers on + and
Solvent reduction on negative ~0.8 V vs Li Solvent oxidation on Pt ~2.1 V vs Li
1.3 V
Underscores the importance of protective surface coatings, be they formed in situ or ex situ
propagation, etc.) is deleterious to cell life
Li+ + B + e- Li
Formation of the SEI…solvent reduction
(ethylene carbonate)
Example reactions only…many others contribute to the formation of the solid electrolyte layer
147(2000)1695-1702…dimers found to be lowest energy
EC and EC+DEC systems with 1M LiPF6, see C. R. Yang, Y. Y. Wang, C. C. Wan, J. Power Sources, 72(1998)66.
CH2 O C O H2C O
2Li+ + 2e +
Li2CO3 + H2C=CH2 LiCH2CH2(OCOO)Li Inorganic layer Gassing (ethylene) Organic layer [Li(OCOO)CH2]2 + H2C=CH2 Gassing (ethylene) Organic layer [Li(OCOO)CH2]2
Li+ + 2e = Li
Vcell ~ Li ~ ln(SOC) (Calendar life influence)
Synthetic SEI approach, Al2O3 over LixSi
Commercial electrodes, primary vs secondary particles, composition analyses. FIBS analysis of NCM + LiMn2O4
O map F map SEM image S map K map Ni map Co map Mn map
weak x-rays shadowed region weak x-rays shadowed region
C map
NCM:
Li(NixCoyMnz)O2
C map
Synthetic SEI approach, “Al2O3” over LixCO2
The crack spacing is around 5 to 10 microns, comparable to the pattern with 2000 mesh size.
Pattern size 7 x 7 µm2 Gap: 7 µm Pattern size 40 x 40 µm2 Gap: 15 µm Pattern size 17 x 17 µm2 Gap: 10 µm
relaxation?
accommodated? Related Si island works
lowered from 0.5 to 0.01 V
9/24/2012 29
29 29
29
29
In-situ Stress Measurement with MOSS system (Multibeam Optical Stress Sensors)
f in-plane film stress h f film thickness Ms substrate biaxial modulus Hs substrate thickness R substrate radius of curvature
R H M h L d d d R
s s f f 2
6 1 Equation Stoney 2 cos 1 curvature Wafer
Developments from polycrystalline steel strips to single crystal silicon wafers,” Thin Solid Films 517 (2009) 1858–1867.
silicon thin films,” Scripta Materialia 64 (2011) 307–310.
Voltage (V) vs Li/Li+
Continuous Film Patterned Sample 2nd & 3rd Cycle
flow No evidence
Stress recovered
Note stress ordinate scales differ
h = 0.1 m
We seek the minimum crack spacing Lcr that does not allow an extra crack to be formed in between the existing cracks. Below this minimum crack spacing, the stress in the lithiated Si film can not reach its plastic yield stress and therefore no strain localization in the film can take place to form an additional crack.
(Li) final concentration.
dimensionless group…diffusion over kinetic resistance. Short time solution Long time solution
Short time comparison Long time comparison
Acknowledgments
HRL
(now with ARPA-E), Elena Sherman, Souren Soukiazian, John Wang National Science Foundation
Brown University
Gao, Brian Sheldon, Sumit Soni (now at Intel) GM
Balogh, Mei Cai, Xiaosong Huang, Hamid Kia, Anil Sachdev, Curt Wong, Jihui Yang (now at U. Washington)
Summary
– Importance of protective thin films for current and future electrode materials
coatings to 1. enhance lithium ion electrode performance (particularly life) – positives and negatives 2. characterize and understand active material behavior – stress evolution and solute (Li) diffusion