Iron oxides, such as hematite (α-Fe₂O₃), maghemite (γ-Fe₂O₃), and magnetite (Fe₃O₄), have been considered as alternative anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacity, abundant reserves, low cost, and non-toxicity. However, their practical application has been hampered by the large volume expansion, which leads to rapid capacity fading. Nanostructure engineering has been demonstrated to be an effective avenue in tackling the volume variation issue and boosting the electrochemical performances. Herein, recent advances on nanostructure engineering of iron oxides for lithium storage are summarized. These nanostructures include 0D nanoparticles, 1D nanowires/nanorods/ nanofibers/nanotubes, 2D nanoflakes/nanosheets, as well as 3D porous/hollow/hierarchical architectures. The structure- electrochemical performance correlations are also discussed. It is believed that the performance optimization strategies summarized here might be extended to other high-capacity LIB anode materials.

NiCo₂S₄ has attracted worldwide attention in the field of energy storage/conversion. In this paper, we summarize the up-to-date progress on the preparation strategies, the applications as electrode materials for supercapacitors, lithium-ion batteries and dye sensitized solar cells, as well as electrocatalysts for the hydrogen evolution reaction, oxygen reduction reaction and oxygen evolution reaction. We also discuss the strategies to improve the electrochemical performance, and future trends of the NiCo₂S₄-based materials.

Organic electrode materials offer virtually infinite resource availability, cost advantages, and some of the highest specific energy for batteries to satisfy the demand for large-scale energy storage. Among the biggest challenges for the practical applications of batteries based on organic electrodes is the dissolution of organic active materials into the electrolyte, which leads to underwhelming cycling stability. This minireview provides an overview of electrolyte advancements to improve the stability of organic batteries. Research efforts on the control of solvent polarity, electrolyte mobility, and exploration of novel electrolyte systems are highlighted.