A high-performance magneto-mechano-triboelectric nanogenerator (MMTEG) is demonstrated for powering a wireless indoor positioning system.

Lead-free antiferroelectric (AFE) ceramics are promising candidates for next-generation pulsed power capacitors. However, their practical deployment remains limited by low recoverable energy density (<em>W_rec</em>), limited dielectric breakdown strength (<em>E_b</em>), and poor efficiency (<em>η</em>), particularly under moderate electric fields. To address these challenges, this study introduces a compositional design strategy that simultaneously engineers both A- and B-sites in AgNbO₃ (AN) perovskite ceramics. Specifically, 20 mol% Ta⁵⁺ is fixed at the B-site while dual A-site substitution with Li⁺ and Nd³⁺ is implemented. This co-doping approach enables a tunable transition from a conventional AFE behavior to a relaxor-antiferroelectric-like (R-AFE-like) state. This evolution is primarily driven by A-site chemical disorder introduced by Li⁺/Nd³⁺ co-doping, which disrupts long-range antiferroelectric ordering and facilitates the formation of nanodomains. In parallel, B-site Ta⁵⁺ substitution contributes by suppressing octahedral tilting and stabilizing the nonpolar phase. The optimized composition, (Ag_1-4xLi_xNd_x)(Nb_0.8Ta_0.2)O₃ at x = 0.03, delivers a remarkable recoverable energy density of 7.2 J/cm³ and an efficiency of 92.3% under a moderate electric field of 327 kV/cm. In addition, this composition demonstrates an excellent <em>W_rec/E_b</em> ratio and capacitor-grade reliability, including strong frequency and thermal stability, as well as ultrafast discharge characteristics (<em>t_0.9</em> ~ 40 ns) with a peak power density of 172 MW/cm³. Overall, this work provides a detailed structure-property-performance framework for designing high-efficiency, high-power, lead-free capacitors by harnessing tunable relaxor-antiferroelectricity.