Low Temperature Crystalized LiNi0.5Mn1.5O4 Cathode Thin Films by Excimer Laser for Flexible Thin Film Batteries

Abstract

The requirement of flexible and stretchable all-solid-state thin film lithium batteries have been steady increased as rapid development of flexible electronic devices such as smart cards, bio sensors, and roll-up displays. In order to satisfy the requirements, using the conventional polymer substrate is necessary for inexpensive and light weight battery. However, the cathode thin film, which is a critical component of thin film battery, certainly needs to be crystallized by high temperature annealing process because of the hindrance of solid-state lithium diffusion from any imperfections in the crystal. Eventually, the polymer substrate goes through sudden changes because of its poor resistance to high temperature, so a new direction of crystallization should be considered. Here, we demonstrated all-solid-state flexible thin film lithium battery using LiNi0.5Mn1.5O4 cathode thin film, LIPON electrolyte, and Li metal anode thin film on polyimide (PI) substrate. The deposited cathode thin films were crystallized by the excimer laser annealing instead of high temperature annealing, so that the PI substrate was not damaged. Structural properties of the thin films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties were measured using WBC3000 battery cycler and impedance analyzer. The results of this study shows the applicability of well-crystallized cathode film at low temperature, and it will be an important method in flexible devices.