Sulfidation of NiFe-layered double hydroxides as novel negative electrodes for supercapacitors with enhanced performance

The discovery and design of new negative electrodes play an essential role in the development of high-performance asymmetric supercapacitors (ASCs). In this work, we report a sulfidation of NiFe-layered double hydroxides (NiFe-LDHS) fabricated through vulcanizing NiFe-LDH via a hydrothermal method, with enhanced electrochemical performance serving as a negative electrode for ASCs. The sulfidation treatment significantly improves the electrical conductivity and reduces the diffusion resistance of the electrode. Electrochemical tests show that the NiFe-LDHS exhibits much higher area specific capacitance (992 mF cm−2 at 2 mA cm−2) and better cycling stability (64.5% of the initial capacity after 2000 cycles at 4 mA cm−2), compared with the pristine NiFe-LDH. ASCs which are configurated by using NiFe-LDHS as the negative electrodes and Ni(OH)2 as the positive electrodes, deliver high energy density of 39.9 Wh kg−1 at a power density of 211.4 W kg−1 and remain 13.5 Wh kg−1 at a high power density of 2114 W kg−1.