Search

Summary: The carbon layer acting as a conductive medium is beneficial to overcoming the comparatively inferior electronic conductivity of Na3V2(PO4)3. Based on this, Na3V2(PO4)3/C composites with diverse ratios of citric acid are synthetized via rheological phase reaction way in this work. The consequences display that the Na3V2(PO4)3/C‐1.5 composite brings a higher initial discharge capacity of 113.2 mAh g−1 at a current rate of 1 C with coulombic efficiency above 99% during all cycles. The discharge capacity retains at 117.6 mAh g−1 at the 100th cycle. Even at the high current densities of 5 C and 10 C, the composite also shows superior cycling performance with negligible capacity fading. Its discharge capacities decline from 97 to 92.6 mAh g−1 at 5 C and from 85.3 to 83.7 mAh g−1 at 10 C. These remarkable outcomes arise from its preferable morphology with suitable carbon coating because both excess and skimpy carbon seriously affect the microstructure and electrochemical properties of Na3V2(PO4)3/C composites. [ABSTRACT FROM AUTHOR]

Summary: Polyaniline‐derived N‐doped carbon‐composited Na3V2(PO4)3 (NVP@NC) are synthesized by a rheological phase reaction followed by calcination. The NVP@NC composite displays improved cycling and rate properties. Its discharge capacity remains 118.7 mAh g−1 at the 400th cycle at 0.3 C. It also obtains invertible capacities of 93.7 and 91.1 mAh g−1 at 5 and 10 C after 1000 cycles, with capacity retention rates of 92.7% and 98.4%, respectively. These enhanced results due to the N‐doped carbon layer (NC), which restrains the expansion and deformation of the crystal structure, reduce the transport length of sodium ion and electrons and improves the electroconductibility of NVP. [ABSTRACT FROM AUTHOR]

Summary: Graphene‐wrapped poly 2,5‐dihydroxy‐1,4‐benzoquinone‐3,6‐methylene (PDBM) nanocomposites with three‐dimensional nanoflower structures have been successfully prepared through the ultrasonic exfoliation and reassembly process in methanol. Compact distribution of graphene into the nanocomposite has established a three‐dimensional conductive network, which contributes to improved properties on discharge capacity and cycle performance. Composite with 20 wt% graphene was proved the best ratio when used in sodium‐ion batteries. Its initial discharge capacity can achieve 210 at 30 mA g−1. After 100 cycles, the capacity is stable at 121 mAh g−1. The composite featuring highly conductive channels and multidimensional electron transport pathway is synthesized by an easy ultrasonic way, which may be applied in large scales for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]