Sulfidation of NiMn-Layered Double Hydroxides/Graphene Oxide Composites toward Supercapacitor Electrodes with Enhanced Performance

Supercapacitors can deliver high-power density and long cycle stability, but the limited energy density due to poor electronic and ionic conductivity of the supercapacitor electrode has been a bottleneck in many applications. A strategy to prepare microflower-like NiMn-layered double hydroxides (LDH) with sulfidation is delineated to reduce the charge transfer resistance of supercapacitor electrode and realize faster reversible redox reactions with notably enhanced specific capacitance. The incorporation of graphite oxide (GO) in NiMn LDH during sulfidation leads to simultaneous reduction of GO with enhanced conductivity, lessened defects, and doping of S into the graphitic structure. Cycling stability of the sulfidized composite electrode is enhanced due to the alleviation of phase transformation during electrochemical cycling test. As a result, this sulfidation product of LDH/GO (or LDHGOS) can reach a high-specific capacitance of 2246.63 F g^-1 at a current density of 1 A g^-1, and a capacitance of 1670.83 F g^-1 is retained at a high-current density of 10 A g^-1, exhibiting an outstanding capacitance and rate performance. The cycling retention of the LDHGOS electrode is also extended to ≈ 67% after 1500 cycles compared to only ≈44% of the pristine NiMn LDH.