Polymer nanocomposites with high-dielectric-constant ceramic fillers have been supposed to a positive candidate for electrostatic capacitors owing to their higher energy density. Herein, the P(VDF-HFP)/BST (poly(vinylidene fluoride-hexafluoropropylene)/Ba 0.6 Sr 0.4 TiO 3 ) nanocomposites films were carefully prepared by layer-by-layer electrospinning, hot-pressing, and quenching processes. In an effort to overcome this challenge that the decrease in breakdown strength due to the high load of ceramic nanoparticles, self-assembly phase-transitioned lysozyme (PTL) is utilized to modify BST ( m BST) to improve interface conditions and layered gradient structure is designed to reduce charge injection at the electrode/films respectively. Studying its microstructure and electrical properties found the gradient structure can simultaneously weaken interface defects and improve energy storage performance. Consequently, a remarkable energy density (13.1 J/cm 3 @450 MV/m) has been obtained compared to that of pure polymer films (5.7 J/cm 3 ). This work presents an attractive approach to enhancing the energy storage properties of polymer nanocomposites by surface modification and structure modulation.
Dielectric capacitors with high dielectric constant and energy density are of great importance for electronic devices. Barium titanate(BaTiO 3 ) have been widely explored for polymer-based dielectric composites owning to its ultrahigh dielectric constant and commercial availability. However, due to the large difference of dielectric constant between BaTiO 3 and polymer matrix , the interface becomes fragile under electric field, which is not conducive for the improvement in breakdown strength and energy storage density . Herein, a flower like barium titanate/nickel hydroxide(BTO/Ni(OH) 2 ) core-shell structured filler has been fabricated to provide a novel approach to modify the interface between BTO and P(VDF-HFP) matrix for dielectric polymer composites . Ni(OH) 2 nanoflakes have grown in-situ on the surface of hydroxylated BaTiO 3 particles to form the flower like core-shell assemblies via hydrothermal reaction . Then, these synthetic BTO/Ni(OH) 2 particles with specific flower-like core-shell structure can be uniformly dispersed in P(VDF-HFP) without any additional surface modification due to their surface –OH groups. Meanwhile, Ni(OH) 2 shell triggered beta phase of P(VDF-HFP) near core-shell filler based on the interfacial interaction between Ni(OH) 2 and P(VDF-HFP). Thus, the intensity of the local electric field can be gradually reduced due to the formation of a dielectric constant gradient. Besides, these Ni(OH) 2 nanoflakes shell are able to cut down the local electric field and prevent the growth of electrical trees on the surface of BaTiO 3 during breakdown process. When the composite filler content is 10 wt%, the dielectric constant and breakdown strength increases to 14.8 and 330 kV/mm from 11 to 260 kV/mm, respectively. And the calculated energy density is 7.13 J/cm 3 , which is 1.5 times that of 10 wt% BTO/P(VDF-HFP) composite film . This study provides a novel shell material Ni(OH) 2 for the preparation of BTO core-shell structure filler, which has good compatibility with polymer substrates .
The performance of thin lithium metal anodes is affected due to issues that weaken the electrode-electrolyte interphase. In this work, a coating layer serving as a Li + traffic controller based on hexadecyl trimethyl ammonium bis(trifluoromethanesulphonyl)imide ([CTA][TFSI]) and poly (vinylidene difluoride co-hexafluoropropylene) (P(VDF-HFP)) is used to stabilize the thin lithium metal interface. The CTA + ions in the coating layer can effectively regulate the distribution of Li + concentration to promote uniform deposition of lithium. The anion of [CTA][TFSI] can optimize solid electrolyte interphase (SEI) with inorganic-rich components, which improve the ionic conductivity and reaction kinetics. Furthermore, the flexible polymer skeleton can fortify the fragile SEI, facilitating the consistent operation of the battery. Due to these improvements, a thin Li metal anode (4 mAh cm −2 ) with a coating layer in a Li||Li symmetric cell demonstrates a lifespan of 600 h at 1 mA cm −2 and 1 mAh cm −2 . Notably, full cells with an ultra-low negative electrode/positive electrode = 1 (N/P = 1) demonstrate a stable performance over 200 cycles and 90 cycles at 0.5C and 1C (1C = 170 mA g −1 ), respectively.
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