Mechanical Properties of Lithiated Tin for Lithium Ion Battery Applications.

Abstract

Sn, in comparison to graphite, has three times higher capacity as an anode material for Li ion batteries. Compared to Si, another potential anode candidate, Sn is compliant and ductile in nature, thus expected to readily relax the Li diffusion induced stresses. In this study, numerical modeling of the Sn micropillar showed that the maximum elastic tensile hoop stresses with 1 μm diameter Sn micropillar decreases from 1 GPa to 200 MPa when Sn is allowed to plastically deform, and further reduced to 0.45 MPa when creep relaxation is activated. In addition, the critical size to prevent fracture is calculated to be ~5.3 μm for C/10 charging rate, that is significantly larger than that of Si at the same conditions. Inspired by the simulations, Sn anode was prepared via electrodeposition with a sputter deposited thin Cr adhesion layer. EDS and XRD analysis were used for compositional and structural characterization and of Sn thin film. Nanoindentations were carried out pre and post lithiation of the battery with two cyclic voltammetry sweep cycles between 0 and 3V at a scan rate of 1 mV/s. New method of nanoindentations where the specimen is immersed in the mineral oil to avoid oxidation of lithiated Sn. Fully lithiated Sn exhibited hardness of 480 MPa, and modulus values of 32 GPa, from non-lithiated Sn’s hardness of 690 MPa and modulus values of 56 GPa.