Summary

Analyse de défaillance des piles Utilisation de base-Synchrotron microtomographie rayons X durs

Published: August 26, 2015
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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

1. Préparation électrolyte Synthétiser un 240 kg / mol – 260 kg / mol de poly (styrène) – block – poly (oxyde d'éthylène) copolymère (SEO) en utilisant la polymérisation anionique. Effectuer toute la préparation de l'échantillon supplémentaire dans un boîte à gants argon où les niveaux d'eau et d'oxygène sont contrôlés et rester <5 ppm. Dissoudre 0,3 g de polymère dans anhydre N-méthyl-2-pyrrolidone (NMP) avec de lithium sec bis (trifluorométh…

Representative Results

Lorsque les cellules lithium-lithium symétriques décrits ci-dessus sont recyclés à 90 ° C, la réponse en tension ressemble à celui de la figure 1. Finalement, dendrites de lithium se développeront à travers l'électrolyte et provoquer une défaillance de la cellule en court-circuit. Lorsque cela se produit, la réponse de la tension au courant appliqué tombera à 0,00 V. Les dendrites, comme celui montré dans la figure 2 apparaissent dans…

Discussion

Disque microtomographie à rayons X est particulièrement bien adapté pour les échantillons sensibles à l'air, comme de nombreux matériaux électrochimiquement actifs, puisque les rayons X peuvent traverser les matières pochette de protection, permettant l'imagerie facile de l'échantillon sans exposition à l'air. Peut-être la caractéristique la plus précieuse de cette technique d'imagerie est que les rayons X pénétrant permettent à l'utilisateur de voir à l'intérieur de l'?…

Disclosures

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

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Cite This Article
Harry, K. J., Parkinson, D. Y., Balsara, N. P. Failure Analysis of Batteries Using Synchrotron-based Hard X-ray Microtomography. J. Vis. Exp. (102), e53021, doi:10.3791/53021 (2015).

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