A strategy for design of non-percolative composites with stable giant dielectric constants and high energy densities

Highlights: • Core-shell Ag@BaTiO₃ particle fillers were self-assembled via simultaneous-hydrolysis decomposition. • Non-percolative BaTiO₃ composites were made from core-shell Ag@BaTiO₃ fillers to address low breakdown strength issues. • Giant ε_r of 51,800, peak ε_r of 84,000, E_b >43 kV cm^–1 and U_e of 4.35 J cm^–3 were achieved in the composites. -- Abstract: Materials with high dielectric constants can be fabricated into electrostatic capacitors for energy storage. Traditional percolative dielectrics such as epoxy/Ag and BaTiO₃/Ni have limited energy densities due to the limited breakdown strengths. Here, a strategy for design of non-percolative composites is reported having stable giant dielectric constants and high breakdown strengths simultaneously, and thus, exhibiting high energy densities. A composite is fabricated by using a core-shell type Ag@BaTiO₃ fillers where the BaTiO₃ shell helps to completely separate the Ag cores with other cores in a sintered BaTiO₃ matrix. The composite possesses a stable giant dielectric constant (ε