关键词: 脉冲激光沉积, LiNi_0.5Mn_0.5O₂, 薄膜锂离子电池

Abstract: The all-solid-state thin-film Li-ion batteries with high energy density, power density and temperature stability are the ideal power sources for microelectronic devices. Developing new thin-film cathodes with large specific capacity is the key to their practical applications. The LiNi0.5Mn0.5O2 with a layered structure has a higher reversible capacity and better structural stability compared with traditional LiCoO2 cathode material. In this work, the LiNi0.5Mn0.5O2 thin film cathodes were prepared by pulsed laser deposition. The effects of substrate material and temperature on the microstructure, surface morphology and composition of the thin films were investigated. Rate capability and cycle performance of LiNi0.5Mn0.5O2 thin-film electrodes at different voltage windows were investigated and their correlations with the crystal structure, surface morphology and composition of the thin films are discussed. It was shown that the LiNi0.5Mn0.5O2 thin-film electrodes prepared on the Au substrates exhibited a pure layered phase, while those on the stainless steel substrates exhibited mixed phases, which is due to the severe diffusion between the film and the substrate. The reversible specific capacity of the LiNi0.5Mn0.5O2 thin-film electrode reached 210 mAh?g-1 between 2 and 5 V at a current density of 2 μA?cm-2, which agrees well with literature report. The excellent cycling stability was obtained at a voltage up to 4.7 V, indicating good structural stability of the film also confirmed with the XRD data. However, the relatively low rate capability could be due to the Li/Ni intermixing in the layered structure, while the capacity fade observed when the charge voltage was further increased to 4.9 V could be due to the formation of solid electrolyte interface induced by the electrolyte decomposition at such a high voltage.

Key words: pulsed laser deposition, LiNi0.5Mn0.5O2, thin film Li-ion battery