Hierarchical NiCo2S4 nanostructures anchored on nanocarbons and Ti3C2Tx MXene for high-performance flexible solid-state asymmetric supercapacitors

Rational construction of hybrid nanostructures is one of the efficient approaches to designing high-performance and flexible energy devices. However, the achievement of improved electrochemical energy storage performance and low-cost production are challenging aspects for scalable production. Herein, the solid-state flexible asymmetric supercapacitor devices are fabricated by employing MXene (Ti3C2Tx) as negative electrode and composites of spinel NiCo2S4 with nanocarbons (reduced graphene oxide (rGO), multiwalled carbon nanotubes (MWCNT)) and MXene (Ti3C2Tx) as positive electrode prepared by simple hydrothermal method. From the comparative studies, NCS@TCX (NiCo2S4@Ti3C2Tx) composite exhibited a high specific capacitance of 1076 F/g as well as a good capacity value of 591.45 C/g at the current density of 3A/g with 80% of capacitance retention over 5000 cycles. The capacity rate of the NCS@TCX electrode manifests the diffusion-controlled process revealed through detailed kinetic studies. Additionally, comparative supercapacitor performance of NCS and its composites in asymmetric assembly with MXene (Ti3C2Tx) is investigated. The flexible NCS@TCX//TCX solid-state asymmetric device showed excellent electrochemical energy storage performance as compared to other devices that deliver maximum areal energy density of 11.5 mu Wh/cm(2) and power density of 1.24 mW/cm(2) with the areal capacitance of 57.47 mF/cm(2) without compromising on the rate capability (90% over 5000 cycles). Also, the devices demonstrated good mechanical and electrical stability after bending at various angles. Comparatively, the NCS @rGO@MWCNT//TCX device showed outstanding cycling performance (99% over 5000 cycles at 10 mA/cm(2)). Thus, NCS and its nanocarbon and MXene hybrids can be further exploited constructively for the fabrication of high-performance flexible energy storage device applications.

Automated summary

By utilizing MXene (Ti3C2Tx) and composites of spinel NiCo2S4 with nanocarbons (rGO, MWCNT), solid-state flexible asymmetric supercapacitor devices are fabricated, achieving improved electrochemical energy storage performance and low-cost production.