Rational core-shell design of novel Ni-Co bimetallic MOF@PBA and Al x V 2 O 5 @C as positive and negative electrode materials for high-performance aqueous Zn-ion hybrid supercapacitors

Abstract

Aqueous Zn-ion hybrid supercapacitors (ZIHSCs) represent a viable energy-storage technology for power-oriented applications, combining long cycle life with intrinsic safety, low cost, and environmental compatibility. However, their practical development is often hindered by kinetic mismatch between capacitive and battery-type electrodes in conventional asymmetric configurations. In this work, we demonstrate the feasibility of a core–shell electrode design strategy that enables improved kinetic compatibility by integrating complementary Faradaic and capacitive charge-storage mechanisms within each electrode of a ZIHSC. The positive electrode (NCBMOF@PBA) is designed with a new pseudocapacitive nickel, cobalt bimetallic metal–organic framework (NCBMOF) core and a Faradaic Prussian blue analogue (PBA) shell, combining fast redox reactions with stable Zn2+-storage behaviour. The negative electrode employs a Faradaic Al-doped vanadate (AlxV2O5/AlVO) core encapsulated by a capacitive carbon shell (AlVO@C), which enhances electronic conductivity, buffers volume changes and facilitates charge-transfer processes. This complementary core–shell configuration serves as a model system to mitigate electrode-level kinetic imbalance and improve active-material utilization. An aqueous ZIHSC assembled with NCBMOF@PBA//AlVO@C electrodes and a 1 M ZnSO4–silica gel electrolyte exhibits stable charge–storage behaviour within a 0–1.8 V operating window. Representative electrochemical performance includes a capacitance of 450 F g-1 at 1 A g-1, an energy density of 203 Wh kg-1 at 900 W kg-1, a power density of 9000 W kg-1 at 158 Wh kg-1. These results validate the proposed core–shell design concept and highlight its potential as a generalizable electrode-engineering approach for advancing aqueous ZIHSCs.