Experimental realization of nitrogen doping into LiFePO₄ films has been carried out by reactive sputtering on graphite substrates without any carbon additive. LiFePO_xN_y films were deposited under various N₂/Ar flow ratios followed by thermal annealing under Ar/H₂ gas mixture. The amounts of nitrogen doping increased with the N₂/Ar flow ratios. Enhanced Li-N signals were recorded by Fourier transform infrared spectroscopy, where Nitrogen substitutes for Oxygen at LiO₆ octahedral structure in LiFePO₄. The binding energy bands of the double and triple coordinated N-P bonds were found and the triple bond became predominant with increased nitrogen doping as characterized by X-ray photoelectron spectroscopy (XPS). With nitrogen doping, Fe²⁺ remained unchanged, whereas Fe-O defects in FeO₈ octahedron increased. Nitrogen doping has effectively elevated the conductivity of the films to the order of 10⁴ S/cm, and also reduced the electrochemical impedance. The charge-discharge tests show that capacity of 140 mAh/g at 0.2 C can be obtained with appropriate nitrogen doping. Even at a current rate of 10 C, the optimized LiFePO_xN_y film can delivered a capacity of 100 mAh/g. The LiFePO_xN_y films were charged-discharged for 100 cycles at 1C, and 97 % of capacity retention can be achieved for most films.