Composition-Driven Structural Evolution in Cobalt–Manganese Glycerates toward Defect-Rich Amorphous Electrodes for High-Performance Battery–Supercapacitor Hybrids

Abstract

The development of electrode materials with efficient charge transfer and abundant active sites remains crucial for high-performance supercapacitors. In this work, cobalt–manganese glycerates with tunable cobalt-to-manganese ratios are synthesized to systematically investigate the relationship between composition, structure, and electrochemical behavior. The incorporation of manganese disrupts the regular growth of cobalt-based glycerates, resulting in amorphous, rough, and defect-rich structures with enhanced surface area and improved electrolyte accessibility. Among all compositions, the optimized bimetallic sample with the highest manganese content exhibits the highest specific capacitance of 1333.6 F/g at 20 mV/s, demonstrating a balanced combination of electrical conductivity and redox activity. Compared with monometallic counterparts, the bimetallic system shows improved charge storage capability due to synergistic electronic interaction and more efficient ion and electron transport. The assembled two-electrode device achieves a potential window of 1.3 V and a maximum energy density of 83 Wh/kg at 325 W/kg. In addition, the device retains 90% of its initial capacitance with nearly 100% Coulombic efficiency after 7500 cycles. These results highlight the importance of composition regulation in glycerate-derived materials, and further improvements may be achieved by optimizing composition and enhancing structural stability.