Functional carbon dots induced defect configuration entropy strengthening polyanion cathode for ultrafast-charging sodium ion batteries in a wide temperature

The development of fast-charging and wide-temperature sodium-ion batteries (SIBs) is of great significance to all-climate energy storage. However, the gigantic challenge lies in achieving super dynamic performance and stability of cathode materials. Herein, the defect configuration entropy (DCE) is conceptualized in Na3V2(PO4)3/carbon composite (NVP/C) cathode by manipulating heteroatoms and vacancies in the surface carbon layer. It is found that the bonding energy between the carbon layer and NVP interface increases with the DCE. Accompanying, the Na+ migration energy barrier is reduced and the electronic conductivity is enhanced, which are pivotal factors underpinning the low-temperature performance. Furthermore, the increase of DCE engenders the formation of a NaF-rich cathode-electrolyte interface, furnishing support for high-temperature stability. As a result, the DCE-strengthened NVP/carbon composite cathode exhibits a high capacity of ∼88 mAh g−1 at an ultrahigh rate of 200 C (13 s per charge process). Moreover, the superior electrochemical performance in the wide temperature range of −30–60 °C is achieved with 0.101 % capacity decay per cycle at −20 ℃, and 0.0047 % capacity decay per cycle at 60 ℃.