Electrochemical Performance of Pure Sn and Sn/Ti Composite Thin Film Cathodes for Lithium Ion Battery

Pure thin film, Sn/Ti, Sn/C composite thin film cathodes were prepared by magnetron sputtering technology. Electrochemical performance of these thin film cathodes for lithium ion battery has been investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic charge and discharge, and cyclic voltammetry. For the pure tin thin film, the relationship between the 1st cycle capacity lost and SEI capacity was studied. And the reason of SEI capacity evolution versus deposition time was explained, where the 1st cycle capacity lost and cycle performance both decrease as the deposition time grown. For the composite thin film, the addition of Ti made the flat potential plateaus of lithium ion battery into a slop curve, but effectively improves the cycle performance. Although it caused some tin inactive to lithium ion.

I. Introduction

Lithium-ion batteries (LIBs) are currently considered leading candidates for hybrid, plug-in hybrid and complete electric vehicles. LIBs are also attracting attention for possible utility applications. For such practical usages, safe, environment-friendly and inexpensive LIBs are urgently demanded. However, the current commercial graphite anode with low theoretical capacity (372mAhg⁻¹)^[1] is unable to meet the ever-increasing demand for the applications of electric vehicles and large-scale energy storage systems. Therefore, it is imperative to develop alternative anode materials with higher specific capacity and superior cycle stability in order to meet industrialization production requirements. Metallic tin (Sn) is considered as one of the promising alternative anode materials for LIBs due to its high theoretical specific capacity (994mAhg⁻¹) and environmentally benign nature ^{[2], [3]}. Unfortunately, the practical application of tin anode material is seriously hampered by its gigantic volume expansion (~300%) during lithiation and delithiation process, leading to pulverization of the electrode active materials and unstable solid electrolyte interphase (SEI) growth, eventually, resulting in deteriorating structures and poor cycle life ^[4]–[9].