Superior anode performance in lithium-ion batteries with optimized cobalt-doped zinc ferrite

Porous Zn 1-x Co x Fe 2 O 4 (0 ≤ x ≤ 0.2) nanoparticles were successfully prepared via a simple sol–gel synthesis route. X-ray diffraction (XRD) analysis confirms a well-crystallized spinel structure without detectable impurities. Among the samples studied, Zn 0.9 Co 0.1 Fe 2 O 4 exhibited the largest specific surface area and a uniform pore size distribution. Diffuse reflectance spectroscopy (DRS) combined with density functional theory (DFT) calculations demonstrated a significant narrowing of the band gap after Co 2+ incorporation, suggesting improved electronic conductivity. X-ray photoelectron spectroscopy (XPS) analysis showed that Co 2+ is the dominant species, which alters the Fe O bonding environment and promotes charge transfer via synergistic Fe 2+ /Fe 3+ –Co 2+ redox interactions. The Zn 0.9 Co 0.1 Fe 2 O 4 electrode exhibited initial discharge/charge capacities of 1460.2/1185.5 mAh g −1 , with a coulombic efficiency of 81.1%. Following 100 charge–discharge cycles, the electrode preserved a reversible capacity of 970.1 mAh g −1 , achieving a capacity retention of 72.4%. At the higher current density of 5 A g −1 , Zn 0.9 Co 0.1 Fe 2 O 4 electrode exhibited a capacity of 896.2 mAh g −1 , demonstrating excellent rate performance. Electrochemical impedance spectroscopy (EIS) analysis further indicated that the Zn 0.9 Co 0.1 Fe 2 O 4 electrode possesses a lower charge-transfer resistance, reflecting enhanced lithium-ion diffusion and electrical conductivity. The enhanced electrochemical performance results from the optimized Co 2+ substitution, decreased band-gap energy, and synergistic multi-electron redox processes. These features highlight Zn 0.9 Co 0.1 Fe 2 O 4 as a promising and stable anode material for advanced lithium-ion battery (LIBs) applications. • Porous Co-doped ZnFe 2 O 4 spinals synthesized via sol-gel method. • Zn 0.9 Co 0.1 Fe 2 O 4 exhibits 970.1 mAh g −1 capacity at 100 cycles. • Excellent rate performance with 896.2 mAh g −1 at 5 A g −1 current. • High surface area (260.1 m 2 g −1 ) and reduced charge transfer resistance. • Promising anode material for next-generation lithium-ion batteries.