Metal–Organic Framework/Polyaniline Nanocomposites for Lightweight Energy Storage

We describe a simple strategy to modify zeolitic imidazolate framework-8 (ZIF-8) using polyaniline (PANI) via a controlled interfacial polymerization method, without using a template, to synthesize ZIF-8/PANI nanocomposites. Our method avoids the agglomeration of ZIF-8/PANI, boosts the utilization of active materials, and exposes more active sites, and hence, it is advantageous to facile electron transfer. Because of its unique hierarchical structure, ZIF-8/PANI has a high surface area (610.8 m2·g–1) and the ZIF-8/PANI electrode exhibited a capacitance value of 395.4 F·g–1 at 0.2 A·g–1, which is the highest among the metal–organic framework (MOF)-based composites reported to date. A solid-state asymmetric supercapacitor (SASC) fabricated with ZIF-8/PANI as the electrode showed good capacitive behavior over a wide potential window from 0 to 2.5 V without nonaqueous electrolytes. It exhibited a specific areal capacitance of 28.1 mF·cm–2 at 0.1 mA·cm–2, which is much higher than the values reported for other MOF-based supercapacitors. The SASC also possessed a high energy density (3.2 μW h·cm–2) and power density (1.1 mW·cm–2), good cycling stability, and flexibility. These characteristics make our ZIF-8/PANI nanocomposite an excellent MOF-based electrode for highly flexible and lightweight energy storage applications.