Bioinspired pomegranate-like microflowers confining core-shell binary NixSy nanobeads for efficient supercapacitors exhibiting a durable lifespan exceeding 100 000 cycles

Abstract

Inspired by the structure of pomegranates, an intriguing pomegranate-like microflower (PM-Ni_xS_y) confining core–shell binary nickel sulfide (β-NiS/Ni₃S₄) nanobeads has been constructed for the first time, which contributes to breaking through the bottleneck of poor cycle performance for nickel sulfide-based supercapacitors (SCs). The PM-Ni_xS_y microflowers possess an open nano–micro-structure, in which the core–shell binary Ni_xS_y nanobeads are well confined in the compartment of three-dimensional (3D) graphene flowers, endowing them with robust structural integrity. Profiting from the unique structure, the PM-Ni_xS_y microflowers deliver a high specific capacity of 323.8 mA h g⁻¹ at 2 A g⁻¹ and maintain a capacity retention up to 98.9% even after 100 000 cycles. PM-Ni_xS_y//PG asymmetric supercapacitors (ASCs) are assembled and achieve an attractive energy density of 88 W h kg⁻¹ at a power density of 810 W kg⁻¹. More importantly, 97.6% of the initial capacitance is still retained even after 100 000 cycles at 5 A g⁻¹ for PM-Ni_xS_y//PG ASCs, displaying their unprecedented durable cycling life. On this basis, ASCs can be recharged by sustainable solar energy and repeatedly supply power to various electronics without a decline of electrochemical performance. Therefore, this work presents a facile route to design a pomegranate-like microflower for SCs with durable cycling performance that can be applied to store sustainable energy.