Sodium-Ion-Based Hybrid Devices

Abstract

The rapid growth of the population and the global economy has significantly increased the demand for energy consumption. To this end, batteries and electrochemical supercapacitors (ESCs) are recognized as the two most important types of electrochemical conversion devices in a matter of advances in energy storage. Therefore, a novel energy storage system has emerged combining the advantages of batteries and supercapacitors, the hybrid capacitors (HCs). Sodium-ion hybrid capacitors (SIHCs) are promising for large-scale electric energy storage benefiting from the low cost and the high abundance of sodium. SIHCs are generally composed of two electrodes for redox reactions: the anode is in battery form and cathode ion sorption in the ESCs. The big challenge for SIHC’s large-scale expansion is the sluggish redox reaction kinetics of the fast-capacitive sorption in the capacitor-type electrode, which fails to match the battery-type electrode. In this regard, SIHCs face a big challenge in reaching high power and energy density, especially lacking suitable battery-type electrodes with fast redox responses. This chapter provides a brief introduction to the charge storage mechanism of the different energy storage systems and the experimental methods for the performance evaluation of SIHC devices. Additionally, insights into the recent studies of SIHCs systems are provided, focusing on materials design, electrochemical performance, and some aspects of the value market. Finally, some challenges and future perspectives on SIHC research are presented.KeywordsSodium-ion hybrid capacitorsSIHCsBattery-type electrodesCapacitive electrodesPseudocapacitanceStorage mechanism