摘要
The sodium-pre-intercalated δ-MnO 2 is in-situ grown on carbon nanofiber via a simple, one-step method for the application of asymmetric supercapacitors. The pre-intercalation of Na ions into the layered structure of δ-MnO 2 reduces the crystallinity, beneficial to Na + diffusion into/out the interlayer structure and pseudocapacitive utilization of MnO 2 . This Na x MnO 2 @CNF nanocomposite with desirable pseudo-capacitance from δ-Na x MnO 2 and high electric conductivity from CNF network shows a high specific capacitance of 321 F g −1 at 1 A g −1 with ca. 75.2% capacitance retention from 1 to 32 A g −1 . An ASC cell consisting of this nanocomposite and activated carbon as the positive and negative electrodes can be reversibly charged and discharged to a cell voltage of 2.0 V in 1 M Na 2 SO 4 and 4 mM NaHCO 3 with specific energy and power of 21 Wh kg −1 and 1 kW kg −1 , respectively. This ASC also shows excellent cell capacitance retention (7% decay) in the 2 V, 10,000-cycle stability test, revealing superior performance.