Toward high-end lead-free ceramics for energy storage: Na0.5Bi0.5TiO3-based relaxor ferroelectrics with simultaneously enhanced energy density and efficiency

The utilization of relaxor ferroelectrics is thought to be a feasible approach to enhance energy storage performance due to the low remnant polarizations and slim hysteresis. Herein, environment-friendly (1- x )(Bi 0.5 Na 0.5 )TiO 3 - x Sr(Ti 0.5 Zr 0.5 )O 3 bulk ceramics have been developed, where the synergistic effect of enhanced relaxor-ferroelectricty and grain refinement with increasing x value boosts excellent energy storage performance, with impressive energy density ( W rec ) of 4.2 J cm -3 accompanied by satisfactory energy efficiency ( η ) of 75.1%. Together with high thermal stability of the energy storage density of 2.0-2.1 J cm -3 (with minimal variation of ≤ ±5%) over 25-150 o C at 150.0 kV cm -1 due to the enhancement of thermal insensitivity, which is evidenced by simulation based on thermal conduction model. Additionally, an extraordinary fast discharge rate ( t 0.9 ) of 54.6 ns and a high power density ( P d ) of 35.4 MW cm -3 can be achieved in the x = 0.20 ceramic sample. This discovery provides new opportunities to lead-free dielectric materials with high energy density and efficiency for capactive electrical energy storage. • A relaxor-ferroelectric (Bi 0.5 Na 0.5 )TiO 3 -Sr(Ti 0.5 Zr 0.5 )O 3 ceramics have been designed to achieve a high W rec of 4.20 J·cm -3 . • The (Bi 0.5 Na 0.5 )TiO 3 -Sr(Ti 0.5 Zr 0.5 )O 3 ceramics delivered highly insensitivity to both temperature and frequency in energy storage properties. • The underlying mechanism of thermal stability in electrical properties has been uncovered based on thermal conduction model. • Ultra-fast discharge rate and ultra-high power density can be achieved.