284455 Dendrite Suppression in Lithium Batteries Using Block Copolymer Electrolyte
Electric vehicles are desirable for decreasing petroleum dependence and leveraging renewable electricity sources.1 Battery cost, specific capacity, and lifetime are key factors in making electric vehicles commercially competitive.2 An order of magnitude improvement in specific capacity is possible by changing the negative electrode from graphite to lithium metal. However, lithium does not plate evenly, and eventually dendrite structures cause failure by electrically shorting the battery electrodes. Modeling results demonstrate that dendrites can be blocked by a rigid separator.3 Similarly, experiments show a dependence of cell lifetime on block copolymer electrolyte modulus in lithium half cells. At the same modulus, block copolymer electrolyte lifetime is 10 times longer than homopolymer electrolyte.4 This suggests that electrolyte nanostructure can suppress dendrite formation.
In this work, we studied dendrite failure in batteries and half cells composed of block copolymer electrolyte. The electrolyte consists of lithium bis(trifluoromethane)sulfonimide salt dissolved in a polystyrene-b-poly(ethylene oxide) block copolymer. The battery electrodes are separated by the block copolymer electrolyte. The negative electrode is lithium metal. The positive electrode is heterogeneous. It consists of lithium iron phosphate active material, carbon black for electron conduction and block copolymer electrolyte, which also acts as binder. The performance and lifetime of these batteries will be presented. Special attention will be paid to the effect of electrolyte thickness and the contrast between batteries and half cells.
1. Handbook of batteries. 3rd ed. ed.; McGraw-Hill: New York, 2002; p 37.4.
2. Howell, D., Progress Report for Energy Storage Research and Development. U.S., D. o. E., Ed. Office of Vehicle Technologies: Washington, D.C., 2008.
3. Monroe, C.; Newman, J., The impact of elastic deformation on deposition kinetics at lithium/polymer interfaces. Journal of the Electrochemical Society 2005, 152 (2), A396-A404.
4. Stone, G. M.; Mullin, S. A.; Teran, A. A.; Hallinan, D. T., Jr.; Minor, A. M.; Hexemer, A.; Balsara, N. P., Resolution of the Modulus versus Adhesion Dilemma in Solid Polymer Electrolytes for Rechargeable Lithium Metal Batteries. Journal of the Electrochemical Society 2012, 159 (3), A222-A227.
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