Enhanced energy storage density and discharge efficiency in potassium sodium niobite-based ceramics prepared using a new scheme

The development of lead-free ceramics with high recoverable energy density (W-rec) and high energy storage efficiency (eta) is of great significance to the current energy situation. In this work, a new scheme was proposed to improve the W-rec and eta of potassium sodium niobate ((K, Na)NbO3, abbreviated as KNN) lead-free ceramics. Doping El 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 (P-max). So the K1-3xBixNa0.5NbO3-1 mol%CuO ceramics was proposed to improve the W-rec of lead-free ceramics. A large W-rec (2.89 J/cm 3 ) and dielectric breakdown strength (DBS) (300 kV/cm with a thickness of 0.2 mm) were achieved for K-0.14 Bi0.12Na0.5NbO3-1 mol%CuO ceramics. The high W ren was supposed to benefit from low remnant polarization (P-r), high Ps and DBS of ceramics. In addition, a large eta (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.