Among currently available energy storage (ES) devices, dielectric capacitors are optimal systems owing to their having the highest power density, high operating voltages, and a long lifetime. Standard high-performance ferroelectric-based ES devices are formed of complex-composition perovskites and require precision, high-temperature thin-film fabrication. The discovery of ferroelectricity in doped HfO₂ in 2011 at the nanoscale was potentially game-changing for many modern technologies, such as field effect transistors, non-volatile memory, and ferroelectric tunnel junctions. This is because HfO₂ is a well-established material in the semiconductor industry, where it is used as a gate dielectric. On the other hand, (pseudo)binary HfO₂ and ZrO₂-based materials have received much less attention for ES capacitors, even though antiferroelectric HfO₂ and ZrO₂-based thin films show strong promise. This Focus Review summarizes the current status of conventional polymer and perovskite ferroic-based ES. It then discusses recent developments in, and proposes new directions for, antiferroelectric and ferroelectric group IV oxides, namely HfO₂ and ZrO₂-based thin films.

High energy density of 54.3 J cm ⁻³ with an efficiency of 51.3% was obtained for the ZrO ₂ film capacitors with 2 nm-thick HAO insert layer.