Co(OH) ₂ Electrode Finds Plenty of Room: Preparation, Structure, and Performance for Electrochemical Energy Storage

The performance of an electrochemical energy system is largely determined by the electrode materials. Ideal electrodes should offer high energy density, high power density, and excellent cyclic stability. Cobalt hydroxide (Co(OH) ₂ ), an electrode that blurs the boundary between batteries and supercapacitors, delivers high energy through battery‐like faradaic reaction, exhibiting excellent rate capability and cyclic stability, as well as characteristics of supercapacitors. However, the correlation between its structure and electrochemical performance remains insufficiently summarized. This review systematically covers the preparation, structure, property, and electrochemical performance of Co(OH) ₂ . Particularly, emphasis lies on how the former three factors influence electrochemical response and performance, and how their modulation can be leveraged to enhance the latter. Concomitantly, it discusses recent advances in developing the relevant supercapacitor devices, gaining insights into energy storage mechanisms by using in situ electrochemical characterization techniques, and nanostructure engineering for optimizing the electrochemical performance of Co(OH) ₂ electrode.