Superior Energy Storage Performances Achieved in (Ba, Sr)TiO3-based Bulk Ceramics through Composition Design and Core-shell Structure Engineering

• The comprehensive optimization strategy of discharge curve can serve as the paradigm of conceptual materials. • A balance between W re = 5.92 J/cm 3 and η = 81.7% is gotten in the BSZT-BMN-0.06 ceramic. • The mechanism of core-shell structure enhancing breakdown strength is clarified. • BSZT-BMN-0.06 ceramics owns a fast charge-discharge speed (44 ns) and a high P D of 144 MW/cm 3 . The conventional dielectric ceramics are extensively studied for applications in electronics and pulsed power systems owing to the advantages of high voltage and high power density. However, the inferior energy storage performance is difficult to satisfy the development requirements of integration and lightweight of power electronic devices. The main research efforts have been done to improve the energy storage density by enhancing the electric breakdown strength (BDS) or effective dielectric constant (ΔP/ΔE) due to the contradiction between ΔP/ΔE and BDS. Here, it is proposed to use composition design and microstructural core-shell engineering to surmount this contradiction and thus enhance the energy storage density. The heterogeneous microstructures are introduced through a two-step calcination, and the appearance of this microstructure is related to the destruction of the cooperative diffusion effect of multiple ions. Consequently, 0.93Ba 0.55 Sr 0.45- x Zn x TiO 3 -0.07BiMg 2/3 Nb 1/3 O 3 (BSZT-BMN-x) ceramics with core-shell microstructure prepared by traditional solid-state reaction method exhibits an ultrahigh recoverable energy density of 5.92 J/cm 3 , a superior energy storage efficiency of 81.7% and an outstanding charge-discharge performance (P D = 144 MW/cm 3 , t 0.9 = 44 ns). The experimental results and numerical simulations reveal that the doping of Zn 2+ enhances the potential for off-centering of anions and cations, the core-shell microstructure makes the distribution of electric field to be regulated and the effective path of electric trees is extended to improve the BDS. The present research not only offers a novel paradigm for other material systems to further improve energy storage performance, but also should be generalizable for other functional materials for which a high BDS is required.