Polyaniline modified bimetallic hydroxide/ZIF composites as electrode materials for supercapacitors with high capacity and high stability

Abstract

Metal-organic framework materials (MOFs) are widely used in electrochemical energy storage due to their abundant active sites and high redox activity. Especially in the field of supercapacitors, the porous structure of MOFs makes them the most promising candidates for composite electrode materials due to their vast specific surface area. However, the poor chemical stability of MOFs in alkaline electrolytes limits their application. Constructing and improving the stability of metal-organic backbone materials through rational structural design is the key to enhancing the electrochemical performance of capacitors. In this paper, the stability of ZIF-67 was enhanced by the complexing with bimetallic hydroxide (CoMn-LDH), and the conductivity is further enhanced by the mixing of polyaniline (PANI) to form a ``network structure'' morphology. As a result, the composite electrode material has a specific capacity of 1048 F g−1 at 1 A g−1 with a good cycle life (80.5 % capacity retention for 5000 cycles). The specific capacity of the CoMn-LDH/ZIF-67/PANI//AC asymmetric supercapacitor (ASC) was 164 F g−1 at 1 A g−1 in the voltage range of 0–1.5 V. The maximum energy density of the ASC was 51.25 Wh kg−1 at a power density of 2250 W kg−1. In addition, excellent cycling stability (71.2 % capacitance retention after 5000 cycles) was delivered.