A multi-interface CoNi-SP/C heterostructure for quasi-solid-state hybrid supercapacitors with a graphene oxide-containing hydrogel electrolyte

Abstract

Reasonable construction of multi-phase hybrid materials with strong interfacial interaction and unique architecture remains intriguing yet challenging to exploit metal–organic framework (MOF) derivatives in the field of energy storage. Herein, a hollow multivariate hybrid with polyphase interfaces and hierarchical porosity (CoNi-SP/C) is prepared via a one-step sulfurization/phosphorization transformation approach. Such hollow heterospheres with porous walls possess abundant diffusion channels and well-regulated electronic and interfacial structures, which guarantees rapid redox kinetics and efficient charge storage. Therefore, the prepared CoNi-SP/C with high-density redox centers presents a superb capacity of 760.6 C g⁻¹ at 1 A g⁻¹ and an excellent rate behavior with 426 C g⁻¹ at 20 A g⁻¹, and shows better pseudocapacitive activity than its parent material (CoNi-MOF) and other derived counterparts (CoNi–P/C and CoNi–S/C). What's more, a novel hydrogel-based electrolyte with excellent ionic conductivity (6.9 S m⁻¹) for fast charge transfer and a network-like highway for efficient ion migration is successfully accomplished. Thanks to these ideal properties, the as-obtained quasi-solid-state hybrid supercapacitor enables a maximum energy density up to 55.6 W h kg⁻¹ to be achieved at a power density of 941.2 W kg⁻¹, and a long cycle life of 10 000 cycles at 4 A g⁻¹ with a low capacity loss of 8.2%. The protocol by integrating an efficient MOF derivative and hydrogel electrolyte affords a good opportunity for building surface reaction-dominated energy storage devices with high performance.