Superior energy-storage performance in Sn-doped SrTiO3

SrTiO 3 (ST) ceramics exhibit high breakdown strength ( E b ) but suffer from low polarization, limiting their recoverable energy density ( W rec ). Herein, we propose a multivalent Sn dual-site doping strategy to concurrently enhance polarization and E b . The co-occupation of A-sites by Sn 2 + and B-sites by Sn 4+ promotes the formation of polar nanoregions (PNRs) while suppressing deleterious interfacial polarization. This synergistic mechanism yields a substantial maximum polarization of 25 μC/cm 2 and a robust E b of 640 kV/cm in the optimal composition ( x  = 0.02). Consequently, a superior W rec of 6.1 J/cm 3 and a high efficiency ( η ) of 90.58% are achieved. Furthermore, the ceramics demonstrate outstanding pulsed charge-discharge performance, delivering a power density of 125 MW/cm 3 with an ultrafast discharge time of 23.3 ns. This work highlights the critical role of defect engineering and valence state engineering in optimizing the energy storage properties of ST-based ceramics.