AbstractDielectric capacitors with high energy storage performance are highly desired for next-generation advanced high/pulsed power capacitors that demand miniaturization and integration. However, the poor energy-storage density that results from the low breakdown strength, has been the major challenge for practical applications of dielectric capacitors. Herein, we propose a heterovalent-doping-enabled atom-displacement fluctuation strategy for the design of low-atom-displacements regions in the antiferroelectric matrix to achieve the increase in breakdown strength and enhancement of the energy-storage density for AgNbO₃-based multilayer capacitors. An ultrahigh breakdown strength ~1450 kV·cm⁻¹ is realized in the Sm_0.05Ag_0.85Nb_0.7Ta_0.3O₃ multilayer capacitors, especially with an ultrahigh U_rec ~14 J·cm⁻³, excellent η ~ 85% and P_D,max ~ 102.84 MW·cm⁻³, manifesting a breakthrough in the comprehensive energy storage performance for lead-free antiferroelectric capacitors. This work offers a good paradigm for improving the energy storage properties of antiferroelectric multilayer capacitors to meet the demanding requirements of advanced energy storage applications.