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Abstract
From signal transduction of living cells to oxidation and corrosion of metals, mechanical
stress intimately couples with chemical reactions, regulating these biological and
physiochemical processes. The coupled effect is particularly evident in the electrochemical
lithiation/delithiation cycling of high-capacity electrodes, such as silicon (Si),
where on the one hand lithiation-generated stress mediates lithiation kinetics and
on the other the electrochemical reaction rate regulates stress generation and mechanical
failure of the electrodes. Here we report for the first time the evidence on the controlled
lithiation in germanium nanowires (GeNWs) through external bending. Contrary to the
symmetric core-shell lithiation in free-standing GeNWs, we show bending the GeNWs
breaks the lithiation symmetry, speeding up lithaition at the tensile side while slowing
down at the compressive side of the GeNWs. The bending-induced symmetry breaking of
lithiation in GeNWs is further corroborated by chemomechanical modeling. In the light
of the coupled effect between lithiation kinetics and mechanical stress in the electrochemical
cycling, our findings shed light on strain/stress engineering of durable high-rate
electrodes and energy harvesting through mechanical motion.
[1
]Engineering
Science and Mechanics and Bioengineering, Pennsylvania State University,
University Park, State College, Pennsylvania 16801, United States