Progress, Outlook, and Challenges in Lead‐Free Energy‐Storage Ferroelectrics

Abstract For energy‐storage materials, dielectric capacitors exhibit higher power density than fuel cells, Li ion batteries, and super capacitors, giving them potentional for application in hybrid electric vehicles, high‐speed trains, and even spaceplanes. However, their low energy‐storage density (ESD) has limited their commercialization, which has therefore fallen behind the other three named systems to some extent. Because of this, a key factor in the development of dielectric/ferroelectric capacitors is an increase in ESD. Optimizing electrical breakdown strength and dielectric constant are regarded as two promising ways to achieve this. Five‐state dielectric energy‐storage materials are introduced and their respective merits and demerits are summarized. Enormous efforts, including the modification of preparation techniques, have been made to improve energy‐storage performances in the past two decades; the significance of interface engineering is discussed in this context. Energy‐storage density, efficiency, thermal stability with polarization fatigue, and mechanical fatigue are all optimized, demonstrating promising potential for practical applications.