Electrochemical properties of Sn-substituted LiMn₂O₄ thin films prepared by radio-frequency magnetron sputtering

The LiMn₂O₄ and LiSn_0.0125Mn _1.975O₄ thin films were grown on Pt/Ti/SiO₂/Si (100) substrate by RF magnetron sputtering. To obtain the structural stability and good cycle performance, deposition parameters, namely working pressure, sputtering gas ratio of Ar and O₂, post-annealing temperature were established. The structure and surface morphology of thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemical properties were estimated by two electrode half-cell test with WBCS 3000 (Wonatech, Korea) at constant current rate of 1 C-rate. The Sn substituted LiMn₂O₄ thin film deposited at 10 mtorr with mixture of argon and oxygen (Ar/O₂ = 3/1) and then annealed at 500 °C in O₂ atmosphere showed good cycle performance. The Sn substituted LiMn₂O₄ thin films showed larger capacity of ~30 μAh/μm-cm² and higher cyclability than LiMn₂O₄ thin films.