Acid-etched halloysite and Co-Ni-B composites for high-performance supercapacitor application

The rational design and optimization of electrode materials can effectively enhance the electrochemical performance of supercapacitors. In this work, by utilizing the microemulsion method to combine the nanoflake-structured Co-Ni-B material with the highly porous hollow tubular structure of acid-etched halloysite (eHal), the stable and porous Co-Ni-B@eHal composites have been successfully synthesized. Simultaneously, the bimetallic composition in Co-Ni-B can offer a wealth of redox reactions, while the eHal tubes provide support and facilitate the ionic transport channels. The optimal electrode exhibits a high specific capacitance of 1534 F g⁻¹ at a current density of 0.5 A g⁻¹ and maintains 99.67 % of its initial specific capacitance at a current density of 20 A g⁻¹, demonstrating excellent rate performance. Furthermore, it shows remarkable cyclic stability, retaining a specific capacitance of approximately 100 % after 60,000 cycles at a current density of 5 A g⁻¹. The assembled Co-Ni-B@eHal-based asymmetric supercapacitor operates at a working voltage of 1.5 V and achieves a maximum energy density of 105.73 W h kg⁻¹ at a power density of 375 W kg⁻¹. These findings offer new insights into the development of bimetallic boride-based nanostructures and clay minerals in the field of electrochemical energy storage.