The development of lead-free ceramics with high recoverable energy density (Wrec) and high energy storage efficiency (η) is of great significance to the current energy situation. In this work, a new scheme was proposed to improve the Wrec and η of potassium sodium niobate ((K, Na)NbO3, abbreviated as KNN) lead-free ceramics. Doping Bi elements in KNN ceramics to form a second phase (K2BiNb5O15) can reduce the grain size and form Schottky-like contact. Meanwhile, the hybridization between the Bi 6p and O 2p orbitals can enhance the maximum polarization (Pmax). So the K1-3xBixNa0.5NbO3-1 mol%CuO ceramics was proposed to improve the Wrec of lead-free ceramics. A large Wrec (2.89 J/cm3) and dielectric breakdown strength (DBS) (300 kV/cm with a thickness of 0.2 mm) were achieved for K0.14Bi0.12Na0.5NbO3-1 mol%CuO ceramics. The high Wrec was supposed to benefit from low remnant polarization (Pr), high Ps and DBS of ceramics. In addition, a large η (80%) was simultaneously achieved for K1-3xBixNa0.5NbO3-1 mol%CuO ceramics, which is superior to mostly reported lead-free bulk ceramics. The results show that K1-3xBixNa0.5NbO3-1 mol%CuO ceramics have a good application prospect in the field of energy storage, and provide a new scheme for the preparation of lead-free ceramics with high energy storage density and high conversion efficiency.