Orbital Interaction-Driven Charge Transfer in CoSn(OH)6/Carbon Nanofiber Electrodes for High-Energy Density Hybrid Supercapacitors

Abstract A π–d conjugation-driven CoSn(OH)6@carbon nanofiber (CNF) nano hybrid composite was synthesized and comprehensively investigated for high-performance asymmetric hybrid supercapacitors (AHSs). Structural and chemical characterizations using XRD, Raman, SEM, and XPS confirm the formation of crystalline CoSn(OH)6 uniformly anchored onto a conductive CNF network. Electrochemical analyses in a three-electrode configuration reveal that 20% CNF-added CoSn(OH)6 electrode exhibits a specific charge of 503.2 C/g at 1 A/g. Distribution of relaxation time (DRT) analysis further demonstrates a suppression of charge-transfer resistance and improved ion-accessible surface kinetics. Density functional theory (DFT) calculations show that π–d conjugation between CNFs and CoSn(OH)6, which increases the electronic density of states near the Fermi level, while 1D charge density distribution validates enhanced charge delocalization, and quantum capacitance results show superior intrinsic capacitance of 35.2 μF/cm2 (184.24 F/g) at 0.2 V (Theoretical) for CoSn@CNF. When integrated into a two-electrode AHS device, the CoSn@CNF20//rGO delivers a high energy density of 94.7 Wh/kg and power density of 750 W/kg at 1 A/g, along with 82% capacity retention after 5000 cycles, highlighting its good electrochemical stability. This work establishes π–d conjugation as an effective strategy to improve charge-transfer dynamics in perovskite hydroxide/carbon hybrid electrodes and provides fundamental insights into the electronic interactions that enable the fabrication of next-generation high-energy supercapacitors.