Ni3S2/Ni2O3 heterojunction anchored on N-doped carbon nanosheet aerogels for dual-ion hybrid supercapacitors

As a member of transition metal sulfides, Ni3S2 has been reported as one type of the effective pseudocapacitive electrode materials for supercapacitors, due to its good electrical conductivity and high electrochemical activity. To further improve the energy density of the Ni3S2-based supercapacitors, we propose a novel approach to the Ni3S2/Ni2O3 heterojunction anchored on N-doped carbon nanosheet aerogels (Ni3S2/Ni2O3@N-CNA), which is used as the cathode for Zn-ion hybrid supercapacitors with the dual-ion electrolytes. The Ni3S2/Ni2O3@N-CNA samples can be prepared through the bubble-templated polymerization of pyrrole and the carbonization of the polypyrrole nanosheet hydrogel/Ni2+. The Ni3S2/Ni2O3@N-CNA cathode is immersed into the Li-ion catholyte for Li+ storage, while the Zn foil anode is immersed into the Zn-ion anolyte for Zn2+ storage. Electrochemical kinetic analysis of the dual-ion hybrid supercapacitor indicates its evident capacitance characteristic. Additionally, theoretical calculations reveal that the Ni3S2/Ni2O3 heterojunction can facilitate the adsorption and dehydration of a hydrated Li+ ion to further play a great role in the enhancement of pseudocapacitance. Based on the novel strategy of the alkaline dual-ion electrolytes, this dual-ion hybrid supercapacitor with the high energy density (64.2 Wh kg-1) opens up a new avenue to develop high-performance Zn-ion hybrid supercapacitors.