Presentation on theme: "Characterization of Battery Failure"— Presentation transcript:
1Characterization of Battery Failure Nitash BalsaraUniversity of California, BerkeleyLawrence Berkeley National LaboratoryIntellectual support:John Newman (Berkeley)Support:Soft Matter EM Program (BES), Lithium sulfur LDRD and Program (BATT, EERE)
3TEM of block copolymer electrolytes PS-b-PEONaPF6Intense 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
4Species identification Principal component analysis (PCA) enables speciation in spite of big fat highly overlapping ugly peaks!Frances Allen, Andy Minor, et al., Ultromicroscopy, 2012
5Lithium Battery - anode at 0.2 V (vs Li/Li+) Li Li+ + e- Li+ currentcollector-anode: Li/graphiteanode at 0.2 V (vs Li/Li+)Li Li+ + e-alkylcarbonates/Li+X-Li+cathode: FePO4cathode at 4 VLi+ + e- + FePO LiFePO4current collector+conductive carbon and binderComponents of electrodes: active particles, electron conductor, ion conductor
6Miracle of lithium battery electrodes conductive carboninactive binderreaction sitesactive particlee-Li+Li+ + e- + FePO LiFePO4Need equal electronic and ionic conductivityelectrolyteComponents 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.
7Time-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: terribleOnce 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.
9Why 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 particlee-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.
10Balsara’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.”
11Lithium-air saves the day Perfect for fundamental studies because…Easy to detect gasses!
12Detect something other than electrons McCloskey et al., JACS 2011electrolyte: carbonate/etherether
17These simulations show clustering that is not limited by box Li2S8
18Work in a real environment XAS measurements of Li2Sx in PEO or SEOWujcik, Velasco-Velez, Cabana, Salmeron, GuoKevin WujcikXAS predictions Li2Sx in tetraglyme (in progress…)Bottom line: No clear distinction between species…
19Principal Component Analysis Juan Velasco VelezEigenvalue IndicatorTruncate at 3Unconstrained PCA analysis gives unphysical underlying spectra.Iterative transformation factor analysis (Marcus)
21Ideal speciation spectroscopy SignalLi2S4Li2S6Li2S2100200500EnergyWaiting for this is not an option…..but developing such tools is!
22Prototype Electrode Project Active particleTabElectron and ion conducting binder(electron side street)C nanotubes(electron highway)Ensure that electron and ion are delivered to particle.contamination
23Characterization 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 particlee-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 PascalAndy Minor, Jinguha Guo, Miquel Salmeron, David Prendergast