Low-Temperature Behavior of Layered and Tunnel-Type Sodium Cathode Materials

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) for low-temperature applications, owing to sodium’s lower desolvation energy compared to lithium. The crystal structure of the cathode active material determines the kinetics and transport properties of the cathode and can have a significant influence on the low temperature operation of SIBs. In this study, the performance of sodium layered (Na 2/3 Fe 1/2 Mn 1/2 O 2 , or NFMO) and channel-type cathodes (Na 0.44 MnO 2 , or NMO) at varying temperatures is investigated through electrochemical cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. NMO, although having a lower initial capacity, demonstrates better capacity retention and more stable charge transfer kinetics at low temperatures. The lattice changes and relatively stable phases correlate with the electrochemical data, suggesting superior performance of channel-type NMO at lower temperatures. This indicates that the channel-type sodium cathode structure is more suitable for applications demanding stable performance at low-temperature conditions.