Spinel-structured ZnMn2O4 has attracted considerable attention as a promising material for supercapacitors and other secondary energy storage devices due to its environmental friendliness, low toxicity, and decent electrochemical performance. However, its practical application is hindered by intrinsic drawbacks such as low electrical conductivity and manganese dissolution from the crystal lattice. In the present study, these limitations are addressed by partially substituting Mn with Fe to form Zn(Mn2-xFex)O4 (where x = 0.4, 0.8, 1.2, or 1.6). This material was synthesized via a hydrothermal method and subsequently fabricated into electrodes for use in hybrid supercapacitor devices. Electrochemical analysis using a three-electrode system revealed that Zn(Mn1.2Fe0.8)O4 has the highest specific capacitance of 374 F/g at a current density of 0.1 A/g, with a b-value of 0.811, thereby indicating a highly capacitive-dominant energy storage mechanism. When applied in a full hybrid supercapacitor device, the system achieved a specific capacitance of 121.44 F/g at 0.1 A/g, and retained 70 % of its capacitance after 1,000 charge-discharge cycles at 1 A/g. These results demonstrate the potential of Zn(Mn2-xFex)O4 as a viable electrode material for high-performance hybrid supercapacitors.

Abstract
1. Introduction
2. Experimental Procedure
    2.1. Materials
    2.2. Synthesis of the Zn(Mn2-xFex)O4 powders
    2.3. Fabrication of the ZMFO cathodes and supercapacitorcells
    2.4. Characterization
3. Results and Discussion
    3.1. Characterization of the ZMFO powders
    3.2. The electrochemical properties of the ZMFO
4. Conclusion
Acknowledgement
References
Author Information

• Hyeon-Uk Ko(Department of Nano & Advanced Material Engineering, Kyungpook National University, Sangju 37224, Republic of Korea)
• Sang-Shik Park(Department of Nano & Advanced Material Engineering, Kyungpook National University, Sangju 37224, Republic of Korea, Advanced Battery Research Center, Kyungpook National University, Sangju 37224, Republic of Korea) Corresponding author