Exploring the effects of temperature-driven phase transition on supercapacitive performance of cobalt diselenide

Recently, doping-induced phase transition of cobalt diselenide have been explored extensively for applications in the electrocatalysis, lithium-ion batteries, and sodium-ion batteries, however, there are very few works on understanding of the relationship between phase transition and supercapacitor performance up to now. Herein, we report a temperature-driven phase transformation strategy to synthesize metastable orthorhombic o-CoSe2 and stable c-CoSe2 by the thermal induced in-situ reaction of cobalt precursor and selenium powder. The o-CoSe2 shows a higher specific capacity (244.2 mAh g(- 1) at 1.0 A g(-1)), while c-CoSe2 shows a better cycling stability (103.0% capacity retention after 2000 cycles at 10.0 A g(-1)). Combing density functional theory (DFT) calculations and experimental results, we explain the unique effects of phase structure on supercapacitive perfor-mance. Furthermore, a hybrid supercapacitor of o-CoSe2//AC delivers a high energy density of 79.1 Wh kg(-1) at a power density of 850.0 W kg(-1), which suggests the prospects of practical application as energy storage device. Our work provides useful guidance for the design of cobalt diselenide based materials for supercapacitors.

Automated summary

A temperature-driven phase transformation strategy was used to synthesize metastable o-CoSe2 and stable c-CoSe2, which showed higher specific capacity and better cycling stability respectively. The unique effects of phase structure on supercapacitive performance were explained through density functional theory calculations and experimental results, providing useful guidance for the design of cobalt diselenide based materials for supercapacitors.