Research progress of NiFe2O4 electrode materials in supercapacitors: Preparation, modification, structural regulation, and future challenges

Supercapacitors have attracted extensive research attention in the fields of materials science, new devices, and new energy due to their better temperature characteristics, rapid charge-discharge rates, environmental friendliness, and ultra-long cycle life. NiFe₂O₄, as a pseudocapacitive electrode material with a spinel structure, has shown enormous potential as an electrode material for supercapacitors due to its low cost, high abundance, and better electrochemical performance. This paper systematically reviews various preparation methods of NiFe₂O₄ electrode materials, including but not limited to hydrothermal method, solvothermal method, electrospinning technique, sol-gel method, chemical bath deposition (CBD), co-precipitation method, and continuous ion layer adsorption reaction. Strategies for carbon material modification of NiFe₂O₄ electrodes using graphene and its derivatives, carbon nanotubes, porous carbon, and activated carbon are thoroughly discussed. Furthermore, the paper elaborates on structural regulation methods of NiFe₂O₄ and its composite materials, comprehensively analyzing different structural design strategies such as heterojunction structure, core-shell structure, hollow structure, dendritic structure, and layered structure, and their effects on material performance. In particular, a detailed analysis of the pore size distribution and specific surface area (SSA) characteristics of porous materials is conducted, and the specific impact mechanisms of pore size and SSA on electrochemical performance are summarized. The paper also focuses on the latest research progress in preparing asymmetric supercapacitors (ASCs) using NiFe₂O₄ electrode materials and comprehensively discusses the challenges faced by NiFe₂O₄ electrode materials and possible future development directions. Through this series of comprehensive analyses, the aim is to provide a solid theoretical foundation and practical guidance for the application of NiFe₂O₄ electrode materials in the field of supercapacitors.