Lead-free perovskite (1-x)(K0.48Na0.48Li0.04)Nb0.95Sb0.05O3-x(Bi0.5Na0.5)HfO3 piezoelectric ceramics were prepared by a traditional ceramic fabrication method. An investigation was conducted to assess the effects of (Bi0.5Na0.5)HfO3 content on the crystal structure, microstructure, phase-transition temperatures, and piezoelectric properties of the ceramics. The X-ray diffraction results, combined with the temperature dependence of dielectric properties, revealed that the ceramics experienced a structural transition from an orthorhombic phase to a tetragonal phase with the addition of (Bi0.5Na0.5)HfO3, and a coexistence of orthorhombic and tetragonal phases was identified in the composition range of 0.005x0.015. An obviously improved piezoelectric activity was obtained for the ceramics with compositions near the orthorhombic-tetragonal phase boundary, among which the composition x=0.005 exhibited the maximum values of piezoelectric constant d(33), and planar and thickness electromechanical coupling coefficients (k(p) and k(t)) of 246 pC/N, 0.435, and 0.554, respectively. Furthermore, the Curie temperature of the ceramics was found decreasing with the increase in (Bi0.5Na0.5)HfO3 content, but still maintaining above 300 degrees C for the phase boundary compositions. These results indicate that the ceramics are promising lead-free candidate materials for piezoelectric applications.