Electrochemical behavior of a thin film of LiFe0.5Mn1.5O4 spinel deposited on a Pt substrate electrode in nonaqueous medium of LiBF4 in ethylene carbonate/dimethyl carbonate (EC/DMC) solution was investigated using cyclic voltammetric technique. In addition, the chemical diffusion coefficients of Li+ at different states of charge (different electrode potentials) in the system under investigation were estimated using chronoamperometric technique. The charge/discharge characterization of the lithium secondary cell employing this 5V cathode material shows an acceptable electrochemical performance with high-voltage and specific capacity. The disadvantage of the material was related to significant capacity fades at elevated temperature. It was demonstrated that the capacity fading in this electrolyte solution is significantly lesser than common electrolyte solutions, e.g. LiPF6. In addition, an approach viz. surface modification of the spinel with aluminum oxide was utilized to reduce the capacity fade at elevated temperatures. The sources for the appearance of such capacity fades appearing at both 4 and 5V performance of the cathode material were discussed.