Sea-island nanostructured polyvinylidene fluoride/zeolitic imidazolate framework-8 polyelectrolyte for high-performance all-solid-state supercapacitors

All-solid-state supercapacitors with high power density, lightweight and durability have shown enormous potential for sustainable energy applications. However, the insufficient mechanical and electrochemical properties of polyelectrolyte membranes restrict their energy storage performances. Here, we report a sea-island nanostructured polyvinylidene fluoride/zeolitic imidazolate framework-8 (PVDF/ZIF-8) polyelectrolyte with superior mechanical and ionic properties for boosting energy storage performances of the supercapacitors. ZIF-8 nanoparticles with 8% content were dispersed uniformly into PVDF substrate and improved ionic liquid uptake of the membrane (from 42% to 74%) because of its high surface area (764 m²g⁻¹) and porous structure (pore width of 2.1 nm). Meanwhile, plastication effect of ZIF-8 materials improved mechanical properties of the membrane with tensile modulus of 2.88 MPa and break elongation of 11.6%. The PVDF/ZIF-8 based supercapacitors delivered a high specific capacitance of 156 F g−1 at current density of 1 Ag⁻¹ and showed good rate capability at current densities from 1 to 10 Ag⁻¹. The device could keep working over 20000 cycles at 1 Ag⁻¹ with capacitance retention of 91.7%, showing excellent cycling stability and enormous potential for applications. This work sheds light on design of novel polyelectrolyte membranes with high electrochemical and mechanical properties for long life energy storage devices. © 2019 Elsevier B.V.