Fabrication of Li anode metal via bulk mechanical property analysis

Abstract

Two types of lithium (Li) metals with a different average grain size, i.e., ∼10 μm in orders and above 100 μm, are successfully produced by extrusion process and rapid molding process. The results obtained from nano-indentation tests show that hardness is influenced by grain size, and it decreases with a finer grained structure, which is not the general trend as those of other light-weight pure metals. It is remarkable to observe that these Li metals have a large strain rate dependence (a large m-value) even at room-temperature, irrespective of the grain size. Compared with the Frost-Ashby deformation mechanism map, the dominant deformation mechanism is the dislocation climb. On the contrary, this unusual behavior in the fine-grained Li metal is due to the partial contribution of grain boundary sliding to deformation. This behavior is associated with the enhancement of grain boundary diffusivity and high density of grain boundaries. Concerning the effect of grain size on electrochemical characteristics, similar to the mechanical property, the results obtained from electrodeposition and dissolution tests display that the fine-grained Li metal has much better over-potential of charging and discharging operation as well as voltage response.