Film capacitors based on polymer dielectrics

which are able to operate reliably under harsh conditions of electrothermal coupling

are vital components for many areas. However

the interchain force among polymer molecules is weak

which will form defects at its interface with metal electrode and affect the electrical strength and reliability of capacitor. Suppressing the interfacial defects by constructing inorganic buffer coating between polymer and metal becomes an effective approach to improve the overall performance of capacitor. Different fabricating approaches of surface inorganic coating on dielectric film are reviewed

such as physical vapor deposition

chemical vapor deposition

atomic layer deposition

and self-assembly by solution. The pros and cons are illustrated

especially the improvement effect on performance and the feasibility of large-scale application. The coating successfully impedes the charge injection at polymer-electrode interface

leading to the significant enhancement of breakdown strength

charge-discharge efficiency

energy storage density

and high-temperature resistance. The effectiveness of inorganic coatings made from 2D materials with anisotropic structures

compared to nanoparticle coatings

are more pronounced. The analysis on the enhancement mechanism of 2D coating demonstrates that it not only forms barrier to the charge injection along normal direction

but also provides zigzag pathways for the charge dissipation along tangential direction. Besides

the stack of nanosheets enables a defect-free property.