MXene (Ti₃C₂T _x ) modified α-Co(OH)₂ battery-type cathode and highly capacitive binder-free Ti₃C₂T _x anode for high-performance electrochemical hybrid capacitor

The layered nanostructure of cobalt hydroxide has received great attention in the field of the electrochemical hybrid capacitor (EHC). However, the poor electrical conductivity and cyclic stability hinder its practical applicability. Surface modification of electrodes is considered one of the effective strategies to improve these properties. In this work, the surface of α-Co(OH)₂ is modified via Ti₃C₂T _x MXene using a simple drop-casting method with different mass loadings and corresponding electrochemical performance is evaluated. The α-Co(OH)₂ surface modified with 0.05 mg cm⁻² Ti₃C₂T _x MXene (CM0.05) shows the maximum specific capacity of 403 C g⁻¹ at the current density of 3 A g⁻¹. The aqueous EHC fabricated with CM0.05 as a positive electrode and two-dimensional (2D) Ti₃C₂T _x MXene nanosheets as a negative electrode outperforms the EHC fabricated with the activated carbon as a negative electrode. The CM0.05//MXene EHC shows the maximum energy density of 44.5 Wh kg⁻¹ at the power density of 2762 W kg⁻¹. This also shows appreciable stability of 72% even after 5000 cycles. The flexible EHC fabricated using polyvinyl alcohol: KOH gel electrolyte demonstrates a superior energy density of 1.17 mWh cm⁻² at the power density of 11.9 mW cm⁻² with a wide operating potential of 1.6 V. Therefore, MXene (Ti₃C₂T _x ) modified α-Co(OH)₂ can be considered as a promising electrode material for flexible EHCs.