Construction of NiCoZnS materials with controllable morphology for high-performance supercapacitors

A facile two-step hydrothermal approach with post-sulfurization treatment was put forward to construct the mixed transition metal sulfide (NiCoZnS) with a high electrochemical performance. The different morphologies of NiCoZnS materials were successfully fabricated by adjusted the Ni/Co molar ratio of the NiCoZn(OH)F precursor. Moreover, the in-situ phase transformation from the NiCoZn(OH)F phase to Zn0.76Co0.24S and NiCo2S4 phases and lattice defects via the S2− ion-exchange were determined by XRD, TEM and XPS techniques, which improved electric conductivity and interfacial active sites of the NiCoZnS, and so promoted the reaction kinetics. Significantly, the urchin-like NiCoZnS1/1 prepared at the Ni/Co molar ratio of 1.0 exhibited promising electrochemical performances with high capacitance and excellent cycling stability. Furthermore, the asymmetric device (NiCoZnS//AC) using NiCoZnS1/1 as the positive electrode had excellent supercapacitor performances with an energy density of 57.8 Wh·kg–1 at a power density of 750 W·kg–1 as well as a long cycle life (79.2% capacity retention after 10000 cycles), indicating the potential application in high-performance supercapacitors.

Binary vanadium pentoxide carbon-graphene foam composites derived from dark red hibiscus sabdariffa for advanced asymmetric supercapacitor

The development of advanced electrode materials derived from biomass for the next generation of energy storage devices, such as supercapacitors with high specific energy and specific power coupled with a good cycle stability, is required to meet the high demand for electric vehicles and portable devices. In this study, sustainable binary vanadium pentoxide carbon-graphene foam composites (V 2 O 5 @C-R 2 HS/GF) were synthesized using a solvothermal method. The X-ray diffraction, Raman and FTIR techniques were used to study the structural properties of the composites (V 2 O 5 @C-R 2 HS/20 mg GF and V 2 O 5 @C-R 2 HS/40 mg GF). The SEM micrographs displayed an accordion-like morphology resulting from the graphene foam-modified V 2 O 5 @C-R 2 HS composite. The V 2 O 5 @C-R 2 HS, V 2 O 5 @C-R 2 HS/20 mg GF and V 2 O 5 @C-R 2 HS/40 mg GF composites were evaluated in a three-electrode configuration using 6 M potassium hydroxide (KOH) as an aqueous electrolyte. Furthermore, a two-electrode device was carried out by fabricating an asymmetric device (V 2 O 5 @C-R 2 HS/GF//AC) where V 2 O 5 @C-R 2 HS/20 mg GF was used as a positive electrode and activated carbon (AC) as a negative electrode at a cell voltage of 1.6 V in 6 M KOH. The V 2 O 5 @C-R 2 HS/GF//AC showed a high specific energy and specific power values of 55 W h kg −1 and 707 W kg −1 , respectively, at a specific current of 1 A g −1 . The asymmetric device presented a good stability test showing 99% capacity retention up to 10 000 cycles and was confirmed by the floating time up to 150 h with specific energy increasing 23.6% after the first 10 h. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)’.

Realizing high performance flexible supercapacitors by electrode modification

We prepare hybrid structured NiCo2S4@PPy nanoarchitectures by a hydrothermal method and subsequent electrodeposition process. The assembled asymmetric device presents an energy density of 59.59 W h kg−1 at 1404.04 W kg−1.

Scalable construction of heteroatom-doped and hierarchical core–shell MnO2 nanoflakes on mesoporous carbon for high performance supercapacitor devices

Combining interfacial methods and mesoporous carbon channels, an asymmetric device, using N,S-codoped mesoporous carbon and a MnO2@MC-30 core shell composite, is assembled with high energy, power densities and outstanding cycling stability.

A rational design of nanoporous Cu–Co–Ni–P nanotube arrays and CoFe2Se4 nanosheet arrays for flexible solid-state asymmetric devices

A facile method was developed to synthesize nanoporous Cu–Co–Ni–P nanotube arrays and hierarchical CoFe2Se4 nanosheet arrays for a flexible asymmetric device.