Molecule-assisted modulation of the high-valence Co3+ in 3D honeycomb-like CoxSy networks for high-performance solid-state asymmetric supercapacitors

Abstract

Modulating the oxidation states of transition metal species has been regarded as a promising strategy to tune the redox activity and achieve more active sites in electrode materials. In this work, a unique three-dimensional (3D) honeycomb-like cobalt sulfide (CoxSy) network organized by cross-linked nanosheets (CoxSy-T NSs) was prepared via a simple triethanolamine (TEOA)-assisted self-templating strategy. Interestingly, it has been found for the first time that the introduction of TEOA in the reaction effectively increases the ratio of high-valence Co3+ in the final product. Benefiting from the synergetic effect of the tailored high-valence Co3+ with the 3D network structure, the CoxSy-T NS electrode exhibits a maximum specific capacity of 351 mAhg−1 (2635 F g−1) at 5 A g−1 as well as excellent cycling stability. Furthermore, with the solid-state asymmetric supercapacitor (ASC) constructed based on the CoxSy-T NSs and activated carbon (AC) electrodes, a high energy density up to 81.62 W h kg−1 has been achieved at the power density of 0.81 kW kg−1 and 96.2% capacitance is preserved after 7000 cycles, indicating robust cycling stability. This result high lights the simple approach of simultaneously tailoring high valence metal species and constructing 3D network structure toward high performance electrode materials for energy sto rage and conversion.