Exceptional elevated temperature performance of high voltage spinel cathodes are realized by LiFePO4 coating in a single-step process at 600°C under Ar flow. First, the single-phase spinel LiNi0.5Mn1.5O4 is prepared via sol-gel route by optimizing the adipic acid concentration (0 - 1mol.). Then, the high performing spinel phase (0.7mol. adipic acid treated) is subjected to LiFePO4 modification by conventional two-step coating procedure with various coating concentrations (1-3wt.%). Single-step LiFePO4 coating procedure also performed at 550°C under Ar atmosphere for the comparison. Although LiFePO4 modified LiNi0.5Mn1.5O4 delivered appreciable performance in elevated temperature (55°C), but it is not sufficient for the practical applications. Therefore, fine tuning of the LiFePO4 (1wt.%) formation temperature (500-600°C) have been varied to achieve excellent electrochemical profiles at elevated temperature conditions. The presence of thin LiFePO4 have been confirmed by high resolution TEM studies and supported well with EDAX measurements.