Superior Temperature Sensing and Capacitive Energy-Storage Performance in Pb-Free Ceramics

The ultrafast charge/discharge rate and high power density (P_D) endow lead-free dielectric energy storage ceramics (LDESCs) with enormous application potential in electric vehicles. However, their low energy storage density and single energy storage performance (ESP) limit their further development and applicability in rugged environments. Here, through the design of vacancy defects and phase structure regulation, Pb-free (Bi_0.5Na_0.5)TiO₃-based ceramics with an optimal composition can achieve a large maximum polarization (>44 µC cm^-2) under a moderate electric field (410 kV cm^-1), resulting in an extremely high recoverable energy storage density (≈6.14 J cm^-3), nearly ideal energy storage efficiency (91.32%), a very short time (≈67 ns) to release 90% of the energy, and a high P_D (243.57 MW cm^-3). More importantly, the energy storage capacities of these ceramics remain stable over a wide temperature range (25-220 °C) and for a wide range of fatigue cycles (1-10⁶). Additionally, the real-time temperature sensing performance with high sensitivity (with a relative sensitivity of up to ≈0.04 K^-1) in the ceramics is developed based on Yb³⁺ and Tm³⁺ codoping, which further supports the potential application of LDESCs to automotive batteries with a temperature monitoring function.