Abstract

The coupling between lithiation reaction of silicon and the considerable volume change has been widely recognized as an adverse effect which hinders the practical application of silicon-based lithium-ion batteries. Here we theoretically demonstrate a novel class of nanoscale electrochemically-driven silicon actuators, in virtue of the “unfavorable” gigantic volume expansion engendered by lithiation. Two representative design prototypes are reported, namely, a nano-sized flat-film silicon actuator and a nanowire silicon actuator. Our thermodynamic analysis establishes the operation condition of the actuators by identifying the electrochemical driving force and mechanical resistance due to lithiation-induced stress. We show that the nano-actuator exhibits an extremely low driving voltage about 1 V and an extremely high strain of actuation up to 300%, which goes far beyond the features of most common actuator materials. Given a mechanical load, the flat-film silicon actuator features a constant actuation strain and the nanowire actuator can provide tunable actuation strain. The results from the study offer quantitative guidance to the design of the novel silicon-based nano-actuators.

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