Underlåtenhet Analys av batterier Använda Synchrotron-baserade Hard röntgen Microtomography
Summary
Synchrotron-based hard X-ray microtomography is used to image the electrochemical growth of dendrites from a lithium metal electrode through a solid polymer electrolyte membrane.
Abstract
Imaging morphological changes that occur during the lifetime of rechargeable batteries is necessary to understand how these devices fail. Since the advent of lithium-ion batteries, researchers have known that the lithium metal anode has the highest theoretical energy density of any anode material. However, rechargeable batteries containing a lithium metal anode are not widely used in consumer products because the growth of lithium dendrites from the anode upon charging of the battery causes premature cell failure by short circuit. Lithium dendrites can also form in commercial lithium-ion batteries with graphite anodes if they are improperly charged. We demonstrate that lithium dendrite growth can be studied using synchrotron-based hard X-ray microtomography. This non-destructive imaging technique allows researchers to study the growth of lithium dendrites, in addition to other morphological changes inside batteries, and subsequently develop methods to extend battery life.
Introduction
Researchers are actively investigating battery chemistries with theoretical energy densities over an order of magnitude larger than traditional lithium-ion batteries.1,2 These high-energy-density batteries will make electric vehicles more competitive with their gasoline-powered counterparts.3 However, these new chemistries have several failure modes that preclude their use in commercial technologies. For example, these battery chemistries require a lithium metal anode to achieve large enhancements in energy density; unfortunately, lithium metal is prone to dendrite growth as lithium ions are reduced at the anode surface during charging.4-9 Additionally, breakage of active particles in the cathode and poor adhesion within the battery can cause cell failure.10
Many modes of battery failure occur on the micrometer scale. However, most battery materials are air sensitive making sample preparation for analysis by electron microscopy and traditional optical microscopy difficult. Synchrotron hard X-ray microtomography allows one to visualize the interior of a battery without disassembly.11-14 Furthermore, the technique produces a three-dimensional (3D) reconstruction of the assembled cell making it easy to find locations of failure.15 Finding robust techniques that enable researchers to develop the scientific understanding required to accurately predict the lifetime of a battery is critical for the design of next generation battery technologies. The procedure discussed herein will specifically demonstrate how one can prepare and image model batteries to study the growth of lithium metal dendrites through solid polymer electrolyte membranes.
Computed tomography (CT) scanning is not a new technique and has been used frequently for failure analysis in industry. Synchrotron-based X-ray microtomography is advantageous because the high brightness and flux of the source allow collection of images with high resolution and good signal to noise in a much shorter amount of time.16 Additionally, one can take advantage of the X-ray energy resolution to image at energies around a chemical species’ absorption edge, causing the components containing that chemical species to be identified.17 It was found that the synchrotron source provides sufficient flux to achieve good contrast between lithium metal and solid polymer electrolyte membranes enabling one to image lithium metal dendrites.15
The study discussed herein uses a high modulus, block copolymer electrolyte membrane.18 These high modulus membranes suppress lithium dendrite growth, lengthening the lifetime of batteries.19,20 However, dendrites still eventually puncture the membrane causing the battery to fail by short-circuit. It is important to understand the nature of dendrite formation and growth in these high modulus electrolyte membranes in order to design strategies to prevent their growth.
Protocol
Representative Results
Discussion
Hard X-ray microtomography is especially well-suited for air-sensitive samples, like many electrochemically active materials, since the X-rays can penetrate through protective pouch material, enabling facile imaging of the sample without exposure to air. Perhaps the most valuable characteristic of this imaging technique is that the penetrating X-rays allow the user to see inside of the sample without destroying it. Most common imaging techniques, like scanning electron microscopy and traditional optical microscopy, can o…
Declarações
The authors have nothing to disclose.
Acknowledgements
Primary funding for the work was provided by the Electron Microscopy of Soft Matter Program from the Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The battery assembly portion of the project was supported by the BATT program from the Vehicle Technologies program, through the Office of Energy Efficiency and Renewable Energy under U.S. DOE Contract DE-AC02-05CH11231. Hard X-ray microtomography experiments were performed at the Advanced Light Source which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Katherine J. Harry was supported by a National Science Foundation Graduate Research Fellowship.
Materials
| Anhydrous N-methyl-2-pyrrolidone | MILLIPORE | MX1396-7 | |
| Lithium bis(trifluoromethane)sulfonamide | MILLIPORE | 8438730010 | |
| Lithium metal | FMC Lithium | None | Lectro Max 100 |
| Pouch material | MTI Corporation | EQ-alf-400-7.5M | |
| Nickel tabs | MTI Corporation | EQ-PLiB-NTA3 |
Referências
- Bruce, P. G., Freunberger, S. A., Hardwick, L. J., Tarascon, J. M. Li-O-2 and Li-S batteries with high energy storage. Nat Mater. 11, 19-29 (2012).
- Balsara, N. P., Newman, J. Comparing the Energy Content of Batteries, Fuels, and Materials. J Chem Educ. 90, 446-452 (2013).
- Girishkumar, G., McCloskey, B., Luntz, A. C., Swanson, S., Wilcke, W. Lithium – Air Battery: Promise and Challenges. J Phys Chem Lett. 1, 2193-2203 (2010).
- Selim, R., Bro, P. Some observations on rechargeable lithium electrodes in a propylene carbonate electrolyte. J Electrochem Soc. 121, 1457-1459 (1974).
- Aurbach, D., Zinigrad, E., Cohen, Y., Teller, H. A short review of failure mechanisms of lithium metal and lithiated graphite anodes in liquid electrolyte solutions. Solid State Ionics. 148, 405-416 (2002).
- Monroe, C., Newman, J. Dendrite Growth in Lithium/Polymer Systems. J Electrochem Soc. 150, A1377 (2003).
- Barton, J. L., Bockris, J. O. The Electrolytic Growth of Dendrites from Ionic Solutions. Proc R Soc Ser A. 268, 485-505 (1962).
- Bhattacharyya, R., et al. In situ NMR observation of the formation of metallic lithium microstructures in lithium batteries. Nat Mater. 9, 504-510 (2010).
- Chandrashekar, S., et al. 7Li MRI of Li batteries reveals location of microstructural lithium. Nat Mater. 11, 311-315 (2012).
- Arora, P., White, R. E., Doyle, M. Capacity fade mechanisms and side reactions in lithium-ion batteries. J Electrochem Soc. 145, 3647-3667 (1998).
- Ebner, M., Marone, F., Stampanoni, M., Wood, V. Visualization and Quantification of Electrochemical and Mechanical Degradation in Li Ion Batteries. Science. 342, 716-720 (2013).
- Qi, Y., Harris, S. J. In Situ Observation of Strains during Lithiation of a Graphite Electrode. J Electrochem Soc. 157, A741-A747 (2010).
- Eastwood, D. S., et al. Three-dimensional characterization of electrodeposited lithium microstructures using synchrotron X-ray phase contrast imaging. Chem Commun. , (2014).
- Shui, J. -. L., et al. Reversibility of anodic lithium in rechargeable lithium–oxygen batteries. Nat commun. 4, (2013).
- Harry, K. J., Hallinan, D. T., Parkinson, D. Y., MacDowell, A. A., Balsara, N. P. Detection of subsurface structures underneath dendrites formed on cycled lithium metal electrodes. Nat Mater. 13, 69-73 (2014).
- Baruchel, J., et al. Advances in synchrotron hard X-ray based imaging. Cr Phys. 9, 624-641 (2008).
- Flannery, B. P., Deckman, H. W., Roberge, W. G., D’Amico, K. L. Three-Dimensional X-ray Microtomography. Science. 237, 1439-1444 (1987).
- Singh, M., et al. Effect of molecular weight on the mechanical and electrical properties of block copolymer electrolytes. Macromolecules. 40, 4578-4585 (2007).
- Monroe, C., Newman, J. The Impact of Elastic Deformation on Deposition Kinetics at Lithium/Polymer Interfaces. J Electrochem Soc. 152, A396-1149 (2005).
- Stone, G. M., et al. Resolution of the Modulus versus Adhesion Dilemma in Solid Polymer Electrolytes for Rechargeable Lithium Metal Batteries. J Electrochem Soc. 159, A222-A227 (2012).
- Panday, A., et al. Effect of Molecular Weight and Salt Concentration on Conductivity of Block Copolymer Electrolytes. Macromolecules. 42, 4632-4637 (2009).
- Schneider, C. A., Rasband, W. S., Eliceiri, K. W. NIH Image to ImageJ: 25 years of image analysis. Nat methods. 9, 671-675 (2012).
- Henke, B. L., Gullikson, E. M., Davis, J. C. X-Ray Interactions – Photoabsorption, Scattering, Transmission and Reflection at E=50-30,000 Ev, Z=1-92 (Vol 54, Pg 181, 1993). Atom Data Nucl Data. 55, 349-349 (1993).
