Ziyue Wang,Huan Liu,Yicheng Peng,Jiyang Xie,Chengding Gu,Wanbiao Hu
Enhancing the breakdown strength (Eb) and polarization of the polymer-based composites through improving the effective interface bonding between the inorganic fillers and polymer matrix is always pursued to achieve high electrostatic energy storage performances. Along with this, paraelectric–ferroelectric (P–F) structured bipolymer PMMA-P(VDF-HFP) was copolymerized and blended to maintain the high Eb but reduce the residual polarization, and meanwhile, potassium triniobate (KNb3O8) rods synthesized by a molten salt (KCl and K2SO4) method were surface-modified using a polydopamine (PDA) shell to form fillers for the fabrication of the composite films that were prepared by a solution casting process. The fabricated PDA@KNb3O8/PMMA-P(VDF-HFP) composite film by filling only a tiny amount of PDA@KNb3O8 (1.0 wt %) exhibits a much enhanced dielectric constant (ε ∼ 9) and polarization (Pmax ∼ 6.9) and large Eb (∼600 MV m–1), therefore giving rise to a high energy density of 15.30 J cm–3 combined with a discharge energy efficiency of 65%. The results herein can be comparative and superior to those of many high-energy storage inorganic–polymer systems that may render this system much potential for dielectric energy storage capacitors.
A novel gel polymer electrolyte (GPE) is prepared based on the co-polymerization of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), the blending of the copolymer P(VDF-HFP) with poly(ethyleneoxide) and Poly(methylmethacrylate), and the absorption of liquid electrolyte of lithium hexafluorophosphate (LiPF 6 ) in ethylene carbonate (EC) + dimethyl carbonate (DMC) (1:1 v/v) as the plasticizer . This GPE has more amorphous region, and can accommodate larger amount of liquid electrolyte via its porous structure without leakage, which provide an ionic conductivity of 0.81 mS cm −1 at 25 °C. Furthermore, the GPE possesses a high electrochemical window of 5.0 V (vs. Li/Li + ), superior thermal stability, large Li + transport number and excellent interface stability to Li metal anode . The test cells with the GPE, Li metal anode and LiCoO 2 cathode show a superior cycling stability and rate performance. This GPE is promising to be applied to rechargeable Li batteries with high safety and long cycle life.
Developing solid electrolyte for alkali metal batteries is of important significance. A gel polymer electrolyte (GPE) based on the porous composite polymer membrane formed by blending of PEO , PMMA and P(VDF-HFP) is prepared, and the effects of the addition of nano-sized oxide fillers (Al 2 O 3 , TiO 2 , SiO 2 ) on the characteristics of the composite GPEs are investigated. The composite GPE with filling of SiO 2 has more amorphous region and porous structure which can hold more liquid electrolyte without leakage, so the composite GPE can provide high ionic conductivity at room temperature and large Li + or Na + transport number. Furthermore, the composite GPE possesses a large electrochemical window, superior thermal stability and excellent interfacial stability. The composite GPEs can be applied in a variety of lithium and sodium metal batteries and exhibit superior cycling stability and rate performance.
Paraelectric/ferroelectric bilayer composites are promising candidates for high-performance dielectric capacitors. However, the energy densities of these composites need to be further improved to satisfy the miniaturization of electronic devices. Herein, an Al2O3/P(VDF–HFP) buffer layer is inserted between a paraelectric PMMA layer and a ferroelectric P(VDF–HFP) layer, forming a novel trilayer structure. It is interesting to find that the buffer layer effectively alleviates the huge electric field gap between the P(VDF–HFP) layer and PMMA layer, yielding substantially improved breakdown strengths (>600 kV/mm), which are over 140% that of the bilayer P(VDF–HFP)/PMMA composite (∼425 kV/mm). In addition, the introduction of the buffer layer also results in improved interfacial polarization, hence, the moderately elevated permittivity. Consequently, a high energy density of 10.03 J/cm3, which is about 260% that of the bilayer P(VDF–HFP)/PMMA composite (∼3.9 J/cm3), is achieved at 600 kV/mm. This work offers a facile strategy to achieve dielectric composites with high breakdown strengths, which is illuminating for the design of high-voltage energy-storage capacitors.
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