Li(Al 1-z Zn z ) alloys as anode materials for rechargeable Li-ion batteries
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G. Dmytriv and V. Pavlyuk Department of Inorganic Chemistry, Ivan Franko Lviv National University, 79005 Lviv, Ukraine
S. Oswald and J. Eckertb) IFW Dresden, Institute for Complex Materials, 01069 Dresden, Germany
H. Trill and H. Eckert Institute for Physical Chemistry, Westfa¨lische Wilhelms-Universita¨t Mu¨nster, 48149 Mu¨nster, Germany
H. Pauly Technische Universita¨t Darmstadt, Materials Science, 64287 Darmstadt, Germany
H. Ehrenberg IFW Dresden, Institute for Complex Materials, 01069 Dresden, Germany (Received 15 December 2009; accepted 26 March 2010)
The cycling behavior of anode materials based on alloys from the Li(Al1–zZnz) continuous solid solution has been studied. The performance of the most promising composition Li(Al0.8Zn0.2) was tested in half-cells against metallic Li with three different electrolytes and in full Li-ion cells against a V2O5 cathode. The underlying structure evolution during cycling and the most relevant fatigue mechanisms are elucidated by x-ray diffraction, nuclear magnetic resonance, and x-ray photoelectron spectroscopy, and reveal a loss of mobile Li due to the ongoing formation of solid electrolyte interfaces. An enhanced stability for Li(Al1–zZnz) electrodes with z0.2 results from a peculiar microstructure due to the demixing of Al and Zn in the Li-poor state and their intermixing in the Li-rich state. I. INTRODUCTION
Li-ion batteries for the application as an energy storage system in electrical vehicles (EV) or hybrid electrical vehicles (HEV) need to provide high charge–discharge currents and high specific capacities. Graphite-based anodes are well established, but (i) suffer from reactions with the electrolyte at elevated temperatures; (ii) are limited in the specific capacity below 372 mAh/g, corresponding to one Li per 6 C; and (iii) lithium dendrites can be deposited on graphite surfaces, especially at low temperatures and high charge rates. Such dendrites may form filaments that can locally shortcut the cell. Local overheat can trigger a disastrous thermal runaway due to the low melting point of Li.1 The theoretical capacities of the intermetallic anodes are much higher than that of a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www. mrs.org/jmr_policy DOI: 10.1557/JMR.2010.0191 1492
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J. Mater. Res., Vol. 25, No. 8, Aug 2010 Downloaded: 11 Mar 2015
graphite, and they are more chemically and thermally stable. The most serious disadvantage of intermetallic alloys is their limited cycle stability. Substantial volume changes during insertion-deinsertion of lithium cause large mechanical strain, which in combination with the brittleness of these materials results in a disintegration of the electrode and therefore reduces the performance parameters and electrode lifetime. To overcome this challenge several strategies are
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