Sandwich-Structured PC/PVDF-Based Energy Storage Dielectric with Inorganic Doping to Regulate Electric Field Distribution

With the goal of “dual carbon”, China’s clean energy industry has witnessed a rapid development period. As a key component of AC–DC conversion of clean energy, the usage of film capacitors is widespread in many fields such as photovoltaic power generation, wind power generation, and new energy vehicles. Therefore, how to develop film capacitors with high power density is the key to realizing energy savings and low-carbon environmental protection. In this paper, a P-X-P sandwich-structured composite dielectric with polycarbonate (PC) as the outer insulation layer and x wt % TiO₂–PC/polyvinylidene fluoride as the middle polarization layer was designed and prepared by solution calendering and a hot pressing process, and its dielectric properties and insulation performance were optimized synergistically. It was found that when the TiO₂ content of the intermediate layer was increased to 3 wt %, the P-3-P sandwich-structured film obtained outstanding energy storage capacity (U_e ∼ 11.69 J/cm³, η ∼ 93.86%) at a high field strength of 510 kV/mm. At the same time, the P-3-P sandwich-structured film has good charge–discharge characteristics (1.74 μs, 1.01 MW/cm³). It has a rapid pace of energy release and outstanding cycle stability after 50,000 charge–discharge cycles. The P-3-P sandwich-structured film provides excellent possibilities for the construction of high storage capacity film capacitors and could be used to its full potential in the field of film capacitors with high storage of energy.