Ping Jiang-Bo, Feng Qi-Kun, Zhang Yong-Xin, Wang Xin-Jie, Huang Lei, Zhong Shao-Long, Dang Zhi-Min
State Key Laboratory of Power System, Department of Electrical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China.
Nanomicro Lett. 2023 Jun 8;15(1):154. doi: 10.1007/s40820-023-01121-6.
The further electrification of various fields in production and daily life makes it a topic worthy of exploration to improve the performance of capacitors for a long time, including thin-film capacitors. The discharge energy density of thin-film capacitors that serves as one of the important types directly depends on electric field strength and the dielectric constant of the insulation material. However, it has long been a great challenge to improve the breakdown strength and dielectric constant simultaneously. Considering that boron nitride nanosheets (BNNS) possess superior insulation and thermal conductivity owing to wide band gap and 2-dimensional structure, a bilayer polymer film is prepared via coating BNNS by solution casting on surface of polyethylene terephthalate (PET) films. By revealing the bandgap and insulating behavior with UV absorption spectrum, leakage current, and finite element calculation, it is manifested that nanocoating contributes to enhance the bandgap of polymer films, thereby suppressing the charge injection by redirecting their transport from electrodes. Worthy to note that an ultrahigh breakdown field strength (~ 736 MV m), an excellent discharge energy density (~ 8.77 J cm) and a prominent charge-discharge efficiency (~ 96.51%) are achieved concurrently, which is ascribed to the contribution of BNNS ultrathin layer. In addition, the modified PET films also have superior comprehensive performance at high temperatures (~ 120 °C). The materials and methods here selected are easily accessible and facile, which are suitable for large-scale roll-to-roll process production, and are of certain significance to explore the methods about film modification suitable for commercial promotion.
生产和日常生活中各个领域的进一步电气化使得长期提高电容器（包括薄膜电容器）的性能成为一个值得探索的课题。作为重要类型之一的薄膜电容器的放电能量密度直接取决于电场强度和绝缘材料的介电常数。然而，同时提高击穿强度和介电常数长期以来一直是一个巨大的挑战。考虑到氮化硼纳米片（BNNS）由于宽带隙和二维结构而具有优异的绝缘性和导热性，通过溶液浇铸在聚对苯二甲酸乙二酯（PET）薄膜表面涂覆BNNS制备了双层聚合物薄膜。通过用紫外吸收光谱、漏电流和有限元计算揭示带隙和绝缘行为，表明纳米涂层有助于提高聚合物薄膜的带隙，从而通过改变电荷从电极的传输来抑制电荷注入。值得注意的是，同时实现了超高的击穿场强（约736 MV m）、优异的放电能量密度（约8.77 J cm）和显著的充放电效率（约96.51%），这归因于BNNS超薄层的贡献。此外，改性后的PET薄膜在高温（约120°C）下也具有优异的综合性能。这里选择的材料和方法易于获得且简便，适用于大规模卷对卷工艺生产，对于探索适合商业推广的薄膜改性方法具有一定意义。
