Rationally designed anode and gel polymer electrolyte for high-performance zinc-ion hybrid supercapacitors

Abstract

Aqueous zinc ion hybrid supercapacitor (ZIHS) remains a challenge to achieve the practical usage of ZIHS with long service life due to the Zn dendrite growth and side reactions. Herein, a combined strategy is proposed to effectively improve the electrochemical performance of ZIHS devices. It consists of three approaches to engineer gel polymer electrolyte (GPE), protective layer for Zn anode, and redox reaction of catholyte, respectively. The optimal GPE demonstrates a super-high strength of 3.22 MPa and a satisfactory ionic conductivity of 70.9 mS cm−1. The optimal Zn anode coated with a protective layer of sulfonated polyether ether ketone and vermiculite exhibits highly reversible Zn plating/stripping behavior over 1000 h in the symmetric cell with an optimal GPE. The introduction of ZnBr2 with an optimal content can result in a 90% energy density increase at least through Br‾/Br3‾ redox reactions. The resultant ZIHS delivers an energy density of 68.59 Wh kg−1 at a power density of 1677.5 W kg−1, and ultra-long cycling stability with ∼88% capacitance retention after 40,000 cycles at 5 A g−1. It is believed that this strategy could provide a meaningful guide for the design and construction of high-performance ZIHS devices.