Ultra-high energy storage performance with mitigated polarization saturation in lead-free relaxors

Relaxor ferroelectric ceramics have attracted much attention for storing the electricity generated from clean and renewable energy sources due to their high permittivity and near-zero remnant polarization. The polarization of many relaxor based ceramics tends to saturate at high electric fields, however, which limits their energy storage performance. In this study, a lead-free Sn-modified (Na_0.5Bi_0.5)TiO₃-SrTiO₃ system is investigated, where mitigated polarization saturation is observed with the addition of Sn⁴⁺, as a result of the different electronic configurations between d¹⁰ Sn⁴⁺ and d⁰ Ti⁴⁺. As expected, high energy density of 3.4 J cm^-3 and energy efficiency of 90% are simultaneously achieved in (Na_0.25Bi_0.25Sr_0.5)(Ti_0.8Sn_0.2)O₃ ceramic. In addition, the ceramic exhibits good thermal stability, with the energy storage property variations below 5% over the temperature range of -20 °C to 150 °C, and satisfactory cycling stability with a variation of less than 8% over 10⁵ cycles. All these merits demonstrate that the (Na_0.25Bi_0.25Sr_0.5)(Ti_0.8Sn_0.2)O₃ ceramic has great potential for high power energy storage applications.