Defect Sites-Rich Porous Carbon with Pseudocapacitive Behaviors as an Ultrafast and Long-Term Cycling Anode for Sodium-Ion Batteries.

Room-temperature sodium-ion batteries have been regarded as promising candidates for grid-scale energy storage due to their low cost and the wide distribution of sodium sources. The main scientific challenge for their practical application is to develop suitable anodes with long-term cycling stability and high rate capacity. Here, novel hierarchical three-dimensional porous carbon materials are synthesized through an in situ template carbonization process. Electrochemical examination demonstrates that carbonization temperature is a key factor that affects Na+-ion-storage performance, owing to the consequent differences in surface area, pore volume, and degree of crystallinity. The sample obtained at 600 °C delivers the best sodium-storage performance, including long-term cycling stability (15 000 cycles) and high rate capacity (126 mAh g-1 at 20 A g-1). Pseudocapacitive behavior in the Na+-ion-storage process has been confirmed and studied via cyclic voltammetry. Full cells based on the porous carbon anode and Na3V2(PO4)3-C cathode also deliver good cycling stability (400 cycles). Porous carbon, combining the merits of high energy density and extraordinary pseudocapacitive behavior after cycling stability, can be a promising replacement for battery/supercapacitors hybrid and suggest a design strategy for new energy-storage materials.