Chemical composition regulation to enhance the energy storage property of the lead-free relaxor ferroelectric

As a critical research direction in dielectric energy storage applications, achieving a synergistic balance between a high breakdown strength and high polarization remains a significant challenge for lead-free relaxor ferroelectrics. In this work, we proposed a rational chemical design strategy by simultaneously doping A- and B-site ions into classical BaTiO₃ ferroelectrics, breaking the long-range ordered polarization, increasing maximum polarization (<em>P</em>_m), reducing remnant &nbsp;polarization (<em>P</em>_r), and improving breakdown strength (<em>E</em>_b). An ultrahigh recoverable energy storage density (<em>W</em>_rec) of 15.3 J cm^-3, accompanied by a high energy storage efficiency (<em>η</em>) of 82.4% was achieved at 1150 kV cm^-1finally. Impedance spectroscopy and microstructure analyses reveal enhanced activation energies for both grains and grain boundaries, as well as multiphase coexistence and formation of polar nanoregions. It collectively contributes to an elevated breakdown strength while maintaining robust polarization. This study presents a promising pathway to achieve advanced energy storage performance in lead-free dielectric systems.