Herein, ammonium manganese tri-fluoride (NH4MnF3) nanoparticles (similar to 20-80 nm) were synthesized via easy, non-sophisticated and environment friendly reverse micro-emulsion method for the first time. Two type i.e. sintered and non-sintered NH4MnF3 nanoparticles were prepared with different ratio by changing water to surfactant percentage while keeping the temperature constant at 22 degrees C. The structural, morphological and optical properties of as-prepared nanoparticles were investigated by x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV-vis spectroscopy and Fourier-Transform infrared (FTIR) spectroscopy. The electrochemical performances were measured by using cyclic voltammetry and the result shows that after sintering the performance are significantly improved up to similar to 0.079 mA g(-1). We hope, our approach will opens up a new opportunity for such materials in energy storage devices.