The low-temperature performance of sodium-ion batteries featuring Cs+/ Zn2+co-doped Prussian blue analogues as cathode materials

Iron-based Prussian blue analogues (Fe-PB) are considered to be one of the most promising cathode materials for sodium-ion batteries (SIB) due to their open skeleton structure and strong redox activity. However, their large ion radius might lead to stress and structural degradation, resulting in worse rate performance and cycle stability, especially at low temperatures. In this work, a Cs+/Zn2+ co-doping strategy is proposed to increase the performance at low temperature of -20 degrees C for the first time. The doped Cs+/Zn2+ ions have a vital role in lowering interstitial water content in PBA, resulting in improved diffusion dynamics of Na+ ions and greatly enhancing cyclic stability at temperature as low as -20 degrees C. The half cells made from PBA with an optimized Cs+/Zn2+ concentration exhibited excellent performance, retaining 79.63 % of the capacity after 5400 cycles at a low temperature of -20 degrees C and a current density of 5C. The results indicate that the Cs+/Zn2+ co-doped Fe-PB cathode material shows extraordinary performance at low temperature, which holds significant practical importance for promoting low-temperature SIB technology.