Supercapacitors store and release energy instantaneously, possess long-term stability and are much safer to handle as compared to batteries. Traditional supercapacitors based on carbonaceous materials work through the electrical double-layer capacitance mechanism that limits their energy density. A significant improvement in energy density can be achieved by use of metal oxide pseudocapacitors. However, their long-term stability is limited due to the volume change that occurs during charging and discharging processes and also unexpected secondary reactions that lead to degradation of the electrode materials. Layer-structured materials are advantageous for supercapacitor applications owing to their ability to host a variety of atoms or ions, large ionic conductivity and high surface area. In particular, ternary or higher-order layered materials provide a unique opportunity to develop stable supercapacitor devices with high specific capacitance values by offering additional redox sites combined with the flexibility of tuning the interlayer distance by substitution. CuSbE2 (E = S or Se) are ternary layered semiconductor materials that are composed of sustainable and less-toxic elements. We report solution-based approaches for the synthesis of mono-, few- and multiple layers of CuSbE2 (E = S or Se) and their systematic study for their use as supercapacitors along with the effect of ionic size of electrolyte ions on the specific capacitance and long-term cycling performance behavior. Electronic structure calculations based on density functional theory predict that with complete surface coverage by electrolyte ions a specific capacitance of over 1160 F/g is achievable using CuSbS2, making it a very attractive layer-structured material for supercapacitor applications. Additionally, the calculations indicate that lithium ions can be intercalated between the van der Waals layers without significantly distorting the CuSbS2 structure, thereby further enhancing the specific capacitance by 85 F/g. Quasi-solid-state flexible supercapacitor devices fabricated using CuSbS2 nanoplates exhibit an aerial capacitance value of 40 mF/cm2 with excellent cyclic stability and no loss of specific capacitance at various bending angles.

Supercapacitors based on CuSbS2 nanoplates

251st National Meeting (2016)

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