Electrochemically induced NiCoSe2@NiOOH/CoOOH heterostructures as multifunctional cathode materials for flexible hybrid zn batteries

Hybrid Zn batteries integrate with the two advantages of Zn-air and alkaline Zn batteries, showing high energy and power density and great environmental adaptability. To achieve better electrochemical and catalytic activity of hybrid Zn batteries, designing multifunctional electrode materials that possess simultaneously high electrical conductivity, fast mass transfer kinetics, and sufficient active sites is essential. Herein, porous NiCoSe2@NiOOH/CoOOH (NCS@NCH) heterostructures, derived from NiCoSe2 (NCS) nanosheets by an in-situ electrochemical phase transformation process, are firstly utilized as multifunctional electrode material for flexible hybrid Zn batteries. During the phase transformation process, the porous nanosheet structure of the highly conductive NCS scaffold can be well maintained and plenty of electroactive sites are formed uniformly, which are beneficial to both faradaic and oxygen reduction/evolution reaction (ORR/OER). Together with sodium polyacrylate (PANa) hydrogel electrolyte, the flexible hybrid battery delivers ultrahigh energy density (944.8 Wh/Kg) and superior cycling life both in a tightly sealed state (capacity retention:105.1% after 4000 cycles) and open-air environment (100 h at 4 mA/cm(2)), indicating its favorable durability and environmental adaptation. This work may bring the flexible hybrid Zn batteries one step forward toward practical applications and stimulate the pullulation of hybrid energy storage and conversion devices by the introduction of multifunctional electrode materials.