Li+-locked domain effect for breaking the temperature stability bottleneck in thermal-detection high-entropy energy storage ceramics

Conventional brain pacemakers rely on electrochemical batteries, which suffer from leakage, performance degradation, and neurotoxicity, posing serious safety risks. Ceramic-based pulse generators with ultra-fast discharge, high-temperature stability, and self-diagnostic capability offer a promising alternative. However, most dielectric ceramics lose their polarization activity at elevated temperatures. To address this challenge, we introduce a high-entropy composition design that induces a Li-locked domain effect in the ceramic system (1-x)[0.9(Bi0.47Na0.47Yb0.03Tm0.01)TiO3−0.1LiTaO3]−0.06(Ba0.3Sr0.7)(Sn0.5Hf0.5)O3. We demonstrate that Li+-enriched regions lock polar nanodomains, preserving them even at 300 °C. This mechanism yields a recoverable energy density of 11.43 J·cm−3, an efficiency of 84.67%, and excellent temperature stability (Δη/η < 0.3% up to 320 °C). Moreover, Yb3+/Tm3+ co-doping enables anomalous thermal enhancement of photoluminescence and precise temperature monitoring. Remarkably, the experimentally measured temperature sensing deviation is only ±0.23 K. The integration of stable energy storage and optical self-diagnosis provides a new paradigm for ceramic-based brain pacemaker pulse generators with early warning capability, pointing toward a possible solution to the intrinsic safety limitations of conventional battery-powered devices. Dielectric energy-storage ceramics lose polarization at high temperatures, limiting harsh-environment use. Here, the authors show a Li+- locked domain effect in high-entropy BNT-based ceramics, achieving Wrec = 11.43 J cm−3, η = 84.67%, Δη/η < 0.3% up to 320 °C, with self-diagnostic thermometry.