1. Characterization of Battery Failure
Nitash Balsara
University of California, Berkeley
Lawrence Berkeley National Laboratory
Intellectual support:
John Newman (Berkeley)
Support:
Soft Matter EM Program (BES), Lithium sulfur LDRD and Program (BATT, EERE)

2. Ideal speciation spectroscopy
PS-b-PEO
NaPF6 PS
PEO
salt
Energy
Signal
100
200
500 PS
PEO
Salt

3. TEM of block copolymer electrolytes
PS-b-PEO
NaPF6
Intense plasmon peak is sensitive to the material’s chemical structure.
One big fat broad peak regardless of chemical details.
Typically, we record a series of EFTEM images from 5-60eV in 1eV steps using a 5eV energy slit.
EFTEM SI datasets analyzed by Principle Component Analysis

4. Species identification
Principal component analysis (PCA) enables speciation in spite of big fat highly overlapping ugly peaks!
Frances Allen, Andy Minor, et al., Ultromicroscopy, 2012

5. Lithium Battery - anode at 0.2 V (vs Li/Li+) Li Li+ + e- Li+
current
collector -
anode: Li/graphite
anode at 0.2 V (vs Li/Li+)
Li Li+ + e-
alkyl
carbonates/
Li+X-
Li+
cathode: FePO4
cathode at 4 V
Li+ + e- + FePO LiFePO4
current collector +
conductive carbon and binder
Components of electrodes: active particles, electron conductor, ion conductor

6. Miracle of lithium battery electrodes
conductive carbon
inactive binder
reaction sites
active particle e-
Li+
Li+ + e- + FePO LiFePO4
Need equal electronic and ionic conductivity
electrolyte
Components of electrodes: active particles, electron conductor, ion conductor.
Every active particle needs to have access to electron and ion conducting pathways at all times!
It is a miracle that any electrode works.

7. Time-honored Approach
Synthesize a new cathode or anode material.
Make a full cell (not half cell with excess lithium).
Make sure that the cathodes are thick enough to be commercially viable.
Count electrons coming in and out of the battery.
Measure voltage.
Usual result: terrible
Once in a while: result better than terrible base line  Publish!
Advantage: If it works you can go directly to the market.
Disadvantage: You might be throwing out a perfectly good material. Perhaps the binder failed.

8. Example of approach

9. Why did the miracle not happen?
What if the binder was not holding the structure together?
What if the electrons were reacting with the electrolyte?
What if ionic pathways were blocked?
What if the electronic pathways were blocked?
What if the top half of the cell is working fine but the bottom half is not?
PIs who go through the pains of establishing a new synthesis route may no be great cell builders.
active particle e-
Li+
JCESR desperately needs a facile lab to answer these questions.
We cannot afford to throw out good active materials.
The prototyping and characterization group has an opportunity to create such an infrastructure.

10. Balsara’s Version of the Time-honored Approach
Synthesize a polymer binder.
Make a full cell (not half cell with excess lithium).
Make sure that the cathodes are thick enough to be commercially viable.
Count electrons coming in and out of the battery.
Measure voltage.
Usual result.
Joke: Balsara drops his keys in front of his home and the area around the door is pitch-dark. An hour later a neighbor drives by and sees Balsara searching for something on the street near lamppost. “What’s up?” he asks. “Looking for my keys”. “Why are you searching here?” he asks. “Because there is light here and I can see.”

11. Lithium-air saves the day
Perfect for fundamental studies because…
Easy to detect gasses!

12. Detect something other than electrons
McCloskey et al., JACS 2011
electrolyte: carbonate/ether
ether

13. - - - - - - Li-S needs miracles + + + + + +
Sulfur
Lithium - + + - - + - + + - - +
Quoting Venkat: Milk-to-cheese-to-milk-…

14. Ideal speciation spectroscopy
Signal
Li2S4
Li2S6
Li2S2
100
200
500
Energy

15. Work in a pristine environment (computer)
Simulation of Li2Sx and S8 dissolution in tetraglyme (oligomeric PEO)
Tod Pascal
Tod Pascal and David Prendergast

16. Simulations show clustering
Li2S6

17. These simulations show clustering that is not limited by box
Li2S8

18. Work in a real environment
XAS measurements of Li2Sx in PEO or SEO
Wujcik, Velasco-Velez, Cabana, Salmeron, Guo
Kevin Wujcik
XAS predictions Li2Sx in tetraglyme (in progress…)
Bottom line: No clear distinction between species…

19. Principal Component Analysis
Juan Velasco Velez
Eigenvalue Indicator
Truncate at 3
Unconstrained PCA analysis gives unphysical underlying spectra.
Iterative transformation factor analysis (Marcus)

20. Theory vs Experiment

21. Ideal speciation spectroscopy
Signal
Li2S4
Li2S6
Li2S2
100
200
500
Energy
Waiting for this is not an option…..but developing such tools is!

22. Prototype Electrode Project
Active particle
Tab
Electron and ion conducting binder
(electron side street)
C nanotubes
(electron highway)
Ensure that electron and ion are delivered to particle.
contamination

23. Characterization Task: Make the miracle happen.
Respect the intuition of Stan Wittinghams of the day. (You cannot convince me to work on binder for Sn5Fe.)
We must work under our lampposts. Need to find lampposts near the key.
Make sure we do not discard gem.
Get your hands dirty and help the synthetic folks succeed.
Concerted deployment of tools: theory, experiment, statistics.
active particle e-
Li+
Nobody can afford to throw out good active materials.
JCESR prototyping and characterization groups have an opportunity to create the necessary infrastructure.
Credit: Frances Allen, Kevin Wujcik, Juan Velasco Velez, Tod Pascal
Andy Minor, Jinguha Guo, Miquel Salmeron, David Prendergast