Optimizing ZnFe2O4 with copper substitution for improved lithium storage performance

The facile sol–gel method is used to synthesize Zn_1-xCu_xFe₂O₄ (0 ≤ x ≤ 0.4) nanoparticles and tested as LIBs anode. The research demonstrated the successful substitution of Zn⁺² with Cu⁺² ions within the cubic spinel framework of ZnFe₂O₄. The average crystalline size of the prepared samples confirmed by XRD ranged from 40.98 to 31.40 nm. FESEM and EDS analyses revealed particle morphologies and elemental distributions, with average particle sizes ranging from 30 to 40 nm. A higher Cu concentration correlates with a lower band gap energy, as indicated by DRS analysis. The incorporation of dopants into ZnFe₂O₄ significantly improves its overall electrical conductivity, leading to enhanced electrochemical performance when utilized as an anode in LIBs. The Zn_1-xCu_xFe₂O₄ (x = 0.2), attains the highest specific surface area of 206.4 m² g⁻¹ and exhibits an average pore size of about 12 nm. The Zn_1-xCu_xFe₂O₄ (x = 0.2) electrode delivered maximum initial charge/discharge specific capacities of 1472.8/1274.5 mAh g⁻¹, resulting in a coulombic efficiency of 86.5 %. In comparison to pure ZnFe₂O₄, which delivered a specific capacity of only 794.7 mAh g⁻¹ after 100 cycles, the Zn_1-xCu_xFe₂O₄ (x = 0.2) electrode demonstrated remarkable cycling stability by maintaining a capacity of 910.1 mAh g⁻¹ at a current density of 0.1 A g⁻¹. Additionally, the electrode exhibited outstanding rate performance characteristics, maintaining a specific capacity of 788.0 mAh g⁻¹ at a high current density of 5.0 A/g. The superior electrochemical results obtained for Zn_1-xCu_xFe₂O₄ (x = 0.2) demonstrate its potential as a high-performance electrode material for battery technology.