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Energy storage performance of Na0.5K0.5NbO3-P(VDF-TrFE) lead-free composite films


The lead-free Na0.5K0.5NbO3-Poly(vinylidene fluoride-trifluoroethylene) (KNN-P(VDF-TrFE)) composite films were prepared by sol-spin coating method. The KNN film was annealed at 700 °C for 3 min with the P(VDF-TrFE) film annealed then at 160 °C for 2 h. The ferroelectric and energy storage properties of composite films were also investigated. The energy storage density of the composite films reached 7.58 J/cm3, and the efficiency was 52%. In addition, the KNN-P(VDF-TrFE) composite films showed weak leakage behavior.

(a) Schematic diagram of the composite films. (b) P-E hysteresis loops of KNN-P(VDF-TrFE) composite films with different film layers and concentration of P(VDF-TrFE) at 1 kHz, the annealing process was 160 °C for 2 hours. “K/0.02 P × 1” means “KNN-1 layer of P(VDF-TrFE) composite films, and the solution is 0.02 g/ml”. (c) Leakage current density of composite films at 1000 kV/cm.


  • The P(VDF-TrFE) (Poly(vinylidene fluoride-trifluoroethylene)) films were annealed at different temperatures and characterized by Integrated Ferroelectric Measurement System and then get the storage density of 3.30 J/cm3 at the η = 33%.

  • The 2-2 KNN-P(VDF-TrFE) composite films were prepared to get high energy storage density for the first time.

  • The ferroelectric and energy storage performance of KNN-P(VDF-TrFE) composite films were studied and the storage density can reach 7.58 J/cm3 at the η = 52%.

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This work was financially supported by the National Natural Science Foundation of China (Grant No. 51372055, 51621091).

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Correspondence to Wen Wang.

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Liu, Y., Diao, Z., Zhao, C. et al. Energy storage performance of Na0.5K0.5NbO3-P(VDF-TrFE) lead-free composite films. J Sol-Gel Sci Technol 93, 608–614 (2020). https://doi.org/10.1007/s10971-019-05105-0

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  • Energy storage
  • Na0.5K0.5NbO3(KNN)
  • Poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))
  • Composite films