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Just Accepted ACS Nano: Behavior of Germanium and Silicon Nanowire Anodes with Ionic Liquid Electrolytes

26Behavior of Germanium and Silicon Nanowire Anodes with Ionic Liquid Electrolytes

Helmholtz Institute Ulm, Karlsruhe Institute of Technology, Helmholtzstrasse 11, 89081 Ulm, Germany
Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany
§ Materials and Surface Science Institute and the Department of Chemical and Environmental Sciences, University of Limerick, V94 T9PX Limerick, Ireland
ENEA, Italian National Agency for New Technology, Energy and Sustainable Economic Development, Materials and Physicochemical Processes Laboratory, Via Anguillarese 301, 00123 Rome, Italy
ACS Nano, 2017, 11 (6), pp 5933–5943
DOI: 10.1021/acsnano.7b01705
Publication Date (Web): May 22, 2017
Copyright © 2017 American Chemical Society
The electrochemical behavior of binder-free, germanium and silicon nanowires as high-capacity anode materials for lithium-ion battery systems is investigated in an ionic liquid electrolyte. Cyclic voltammetry, cycling tests, and impedance spectroscopy reveal a highly reversible lithium alloying/dealloying process, as well as promising compatibility between the Ge and Si materials and the electrolyte components. Reversible capacities of 1400 and 2200 mA h g–1 are delivered by the Ge and Si anodes, respectively, matching the values exhibited in conventional organic solutions. Furthermore, impressive extended cycling performance is obtained in comparison to previous research on Li alloying anodes in ionic liquids, with capacity retention overcoming 50% for Si after 500 cycles and 67% for Ge after 1000 cycles, at a current rate of 0.5C. This stable long-term cycling arises due to the ability of the electrolyte formulation to promote the transformation of the nanowires into durable porous network structures of Ge or Si nanoligaments, which can withstand the extreme volume changes associated with lithiation/delithiation. Remarkable capacity is exhibited also by composite Ge and Si nanowire electrodes. Preliminary tests with lithium cobalt oxide cathodes clearly demonstrate the feasibility of Ge and Si nanowires in full batteries.