Due to the excessive use of fossil fuel resources and tremendous generation of greenhouse gases, the development of green and sustainable energy resources is urgently demanded in recent years [1,2]. Supercapacitors (SCs) can be used for storing energy harvested from renewable energy resources such as solar, wind and tidal energy, and they have attracted increasing attention because of their high power density and long cyclic stability [3]. Especially, hybrid SCs (HSCs) combine the battery-type electrode with capacitor-type electrode, which achieve the merits from both batteries and capacitors and display enhanced supercapacitive behaviors [4].

Electrode material is a crucial indicator determining the performances of HSCs. Among the developed electrode materials, transition metal (TM) chalcogenides, notably in the form of nanostructures, are particularly attractive due to their high theoretical specific capacity and capacitance, multiple oxidation states and fast charge transfer kinetics [[5], [6], [7], [8]]. Owing to the lower electronegativity and larger atomic size of tellurium (Te), TM tellurides (TMTe) exhibit higher electrical conductivity and electrochemical activity than TM sulfides and TM selenides, which can accommodate more electrolyte ions and improve charge transfer kinetics [6]. Compared with monometal TMTe, bimetal TMTe usually shows better performance thanks to the combined contributions from each transition metal [9]. More importantly, heterogeneous interfaces may be generated during the formation of the bimetal compounds [10], and the introduced heterojunction can greatly promote the reaction kinetics through adjusting interfacial electronic structure, inducing internal electric fields, and accelerating electron transfer [11,12].

Prussian blue analogues (PBA) are an important class of metal-organic frameworks (MOF), which have been intensively used for battery electrodes, hydrogen storage and electrochromic materials thanks to their high specific surface area, unique coordination frameworks and diverse compositions [13,14]. Typical PBA has an open framework structure and a large lattice gap, which can provide large channels and interstices for alkali metal ions with large volumes and result in fast charge kinetics [15,16]. Therefore, heterostructured bimetal TMTe derived from PBA might endow electrode materials with enhanced reaction kinetics. However, PBA in powder form usually has random orientation and is prone to be agglomerated, reducing the specific area and active sites by causing gap spacing shrinkage [17,18]. As a result, the electrochemical performance of PBA is seriously deteriorated. To overcome this obstacle, oriented PBA or PBA derivatives grown on flexible current collectors has been proposed [17]. As a flexible current collector, nickel foam (NF), a three-dimensional (3D) porous material with a zig-zag skeleton, is generally used as the underlying substrate in batteries and SCs due to its low cost, high surface area and high electrical conductivity [19]. Therefore, PBA or PBA derivatives grown on NF may provide sufficient active sites and reduce ion diffusion path, which is favor of both electron transport and electrode/electrolyte contact [19,20].

Herein, heterostructured and multi-dimensional Ni-Co tellurides ((Ni-Co)Te)/NiTe is prepared for HSCs. Ni-Co PBA precursor is first grown in situ on NF through a simple co-precipitation method, which is further converted into cubic structured (Ni-Co)Te through a hydrothermal strategy by anion exchange reactions. Meanwhile, two-dimensional (2D) NiTe nanosheets are also produced during the hydrothermal process by the reaction between Te²⁻ and Ni²⁺. Distinct heterogeneous interfaces between NiTe and CoTe are formed in the resultant (Ni-Co)Te. The unique heterostructured and multi-dimensional structure of (Ni-Co)Te/NiTe endows it with enhanced performances including considerable areal specific capacitance (2390.7 mF cm⁻² at 1 mA cm⁻²) and high capacitance retention (80.3 % after 5000 cycles). Finally, an asymmetric HSC is assembled by using the (Ni-Co)Te/NiTe grown on NF (NF@(Ni-Co)Te/NiTe) as the cathode and activated carbon (AC) supported on NF (NF@AC) as the anode, respectively. The developed HSC shows enhanced reaction kinetics with a maximum energy density of 95.6 Wh kg⁻¹ at the power density of 444.5 W kg⁻¹ as well as high capacitance retention and coulombic efficiency. In addition, the electrochemical properties of the HSC indicate that it combines the merits of Faradaic reaction originated from NF@(Ni-Co)Te/NiTe and capacitive behavior originated from NF@AC.