Tailoring of amorphous vanillin-based benzoxazine polymer as a high-performance electrode for symmetrical supercapacitor

The development of a novel vanillin-based benzoxazine polymer (PBZ) with rich hetero atoms has become more attractive due to its superior mechanical strength, chemical resistance and thermal stability, which can be tailored through a customized structure, achieving high specific capacities, better rate capabilities and high energy densities. In this study, a multifunctionalized vanillin-based benzoxazine polymer with an amorphous phase was successfully synthesized via Mannich condensation reaction. When used as electrode material, the polymer exhibited a notable specific capacitance (Csp) of 373.25 F/g at current density of 1 A/g and demonstrated long-term stability, retaining approximately 95 % of its capacitance over 11,000 galvanostatic charge-discharge (GCD) cycles. Furthermore, a symmetrical supercapacitor was constructed using the PBZ/graphite sheet (GS) electrode, which delivered a capacitance of 44.66 F/g at 1 A/g. It exhibited a high energy density of 89.32 Wh/kg at a power density of 2512.26 W/kg and retained 30.33 Wh/kg even at an elevated power density of 43,687.01 W/kg. The enhanced electrochemical performance of PBZ could be ascribed to multiple contributing factors:(i) the presence of multifunctional groups, which could facilitate intra and inter-molecular hydrogen bonds within the crosslinked network, enhancing the structural integrity; (ii) its exceptional mechanical and thermal stability with minimal volume contraction, significantly improving its recyclability; (iii) its amorphous nature, combined with its high specific surface area of 25.431 m²/g, can increase the number of electrochemically active sites and facilitate ion transport during charge/discharge cycles, enabling faster electron transfer through a short-range order arrangement with a low energy barrier. Herein, we present a budget-conscious preparation route for PBZ electrodes that delivers excellent electrochemical characteristics and prolonged cycling performance.